Sample records for stratigraphy seismic stratigraphy

  1. Seismic stratigraphy of the Bahamas

    Ladd, J.W.; Sheridan, R.E.


    Seismic reflection profiles from the Straits of Florida, Northwest Providence Channel, Tongue of the Ocean, and Exuma Sound reveal a seismic stratigraphy characterized by a series of prograding Upper Cretaceous and Tertiary seismic sequences with seismic velocities generally less than 4 km/sec overlying a Lower Cretaceous section of low-amplitude reflections which are more nearly horizontal than the overlying prograding clinoforms and have seismic velocities greater than 5 km/sec. The prograding units are detrital shallow-water carbonates shed from nearby carbonate banks into deep intrabank basins that were established in the Late Cretaceous. The Lower Cretaceous units are probably shallow-water carbonate banks that were drowned in the middle Cretaceous but which, during the Early Cretaceous, extended from Florida throughout the Bahamas region. The seismic reflection profiles reveal a sharp angular unconformity at 5-sec two-way traveltime in northwest Tongue of the Ocean, suggesting a rift-drift unconformity and deposition on thinned continental crust. No such unconformity is seen in central and southeast Tongue of the Ocean or in Exuma Sound, suggesting that these areas are built on oceanic crust.

  2. Elastic-Wavefield Seismic Stratigraphy: A New Seismic Imaging Technology

    Bob A. Hardage; Milo M. Backus; Michael V. DeAngelo; Sergey Fomel; Khaled Fouad; Robert J. Graebner; Paul E. Murray; Randy Remington; Diana Sava


    The purpose of our research has been to develop and demonstrate a seismic technology that will provide the oil and gas industry a better methodology for understanding reservoir and seal architectures and for improving interpretations of hydrocarbon systems. Our research goal was to expand the valuable science of seismic stratigraphy beyond the constraints of compressional (P-P) seismic data by using all modes (P-P, P-SV, SH-SH, SV-SV, SV-P) of a seismic elastic wavefield to define depositional sequences and facies. Our objective was to demonstrate that one or more modes of an elastic wavefield may image stratal surfaces across some stratigraphic intervals that are not seen by companion wave modes and thus provide different, but equally valid, information regarding depositional sequences and sedimentary facies within that interval. We use the term elastic wavefield stratigraphy to describe the methodology we use to integrate seismic sequences and seismic facies from all modes of an elastic wavefield into a seismic interpretation. We interpreted both onshore and marine multicomponent seismic surveys to select the data examples that we use to document the principles of elastic wavefield stratigraphy. We have also used examples from published papers that illustrate some concepts better than did the multicomponent seismic data that were available for our analysis. In each interpretation study, we used rock physics modeling to explain how and why certain geological conditions caused differences in P and S reflectivities that resulted in P-wave seismic sequences and facies being different from depth-equivalent S-wave sequences and facies across the targets we studied.



    <正>20111095 Chen Rong(Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu 610059,China);Li Yong Sequence Stratigraphy of Neogene in the Northern Slope of the Chengning Uplift(Journal of Stratigraphy,ISSN0253-4959,CN32-1187/P,34(2),2010,p.179-186,7 illus.,1 table,9 refs.)Key words:Neogene Period,stratigraphic framework,Huanghua Depression According to the tectonic evolutionary history and stratigraphic and depositional characteristics,and based on drill cores,cutting logs,well logs and high-resolution 3-D seismic data,sequences

  4. Seismic stratigraphy and sedimentary architecture of the Chalk Group in south-west Denmark

    Larsen, Connie; Ineson, Jon; Boldreel, Lars Ole


    The article focuses on a study undertaken by the Chalk Group on the western onshore region of the Danish Basin in Eastern Denmark related on the seismic stratigraphy and sedimentary architecture of the region. The study is undertaken through subdividing the northern North German Basin and the south...

  5. Modeling of the Sedimentary Interbedded Basalt Stratigraphy for the Idaho National Laboratory Probabilistic Seismic Hazard Analysis

    Suzette Payne


    This report summarizes how the effects of the sedimentary interbedded basalt stratigraphy were modeled in the probabilistic seismic hazard analysis (PSHA) of the Idaho National Laboratory (INL). Drill holes indicate the bedrock beneath INL facilities is composed of about 1.1 km of alternating layers of basalt rock and loosely consolidated sediments. Alternating layers of hard rock and “soft” loose sediments tend to attenuate seismic energy greater than uniform rock due to scattering and damping. The INL PSHA incorporated the effects of the sedimentary interbedded basalt stratigraphy by developing site-specific shear (S) wave velocity profiles. The profiles were used in the PSHA to model the near-surface site response by developing site-specific stochastic attenuation relationships.

  6. Modeling of the Sedimentary Interbedded Basalt Stratigraphy for the Idaho National Laboratory Probabilistic Seismic Hazard Analysis

    Suzette Payne


    This report summarizes how the effects of the sedimentary interbedded basalt stratigraphy were modeled in the probabilistic seismic hazard analysis (PSHA) of the Idaho National Laboratory (INL). Drill holes indicate the bedrock beneath INL facilities is composed of about 1.1 km of alternating layers of basalt rock and loosely consolidated sediments. Alternating layers of hard rock and “soft” loose sediments tend to attenuate seismic energy greater than uniform rock due to scattering and damping. The INL PSHA incorporated the effects of the sedimentary interbedded basalt stratigraphy by developing site-specific shear (S) wave velocity profiles. The profiles were used in the PSHA to model the near-surface site response by developing site-specific stochastic attenuation relationships.



    <正>20122559 Chen Fangwen ( College of Earth Sciences,Northeast Petroleum University,Daqing 163318,China );Lu Shuangfang High-Resolution Sequence Stratigraphy and Sedimentary Characteristics of the Fuyu Oil-Bearin Layers in the Wangfu Depression ( Journal of Stratigraphy,ISSN0253-4959,CN32-1187 / P,35 ( 4 ), 2011,p.368-374,3illus.,14refs. ) Key words:Cretaceous,high resolution sequence stratigraphy,Songliao Plain



    <正>20142287Cao Changqun(State Key Laboratory of Paleobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,CAS,Nanjing 210008,China);Zhang Mingyuan The Permian Capitanian Stratigraphy at the Rencunping Section,Sangzhi County of Hunan Province and Its Environmental Implications

  9. Integrating sequence stratigraphy and rock-physics to interpret seismic amplitudes and predict reservoir quality

    Dutta, Tanima

    This dissertation focuses on the link between seismic amplitudes and reservoir properties. Prediction of reservoir properties, such as sorting, sand/shale ratio, and cement-volume from seismic amplitudes improves by integrating knowledge from multiple disciplines. The key contribution of this dissertation is to improve the prediction of reservoir properties by integrating sequence stratigraphy and rock physics. Sequence stratigraphy has been successfully used for qualitative interpretation of seismic amplitudes to predict reservoir properties. Rock physics modeling allows quantitative interpretation of seismic amplitudes. However, often there is uncertainty about selecting geologically appropriate rock physics model and its input parameters, away from the wells. In the present dissertation, we exploit the predictive power of sequence stratigraphy to extract the spatial trends of sedimentological parameters that control seismic amplitudes. These spatial trends of sedimentological parameters can serve as valuable constraints in rock physics modeling, especially away from the wells. Consequently, rock physics modeling, integrated with the trends from sequence stratigraphy, become useful for interpreting observed seismic amplitudes away from the wells in terms of underlying sedimentological parameters. We illustrate this methodology using a comprehensive dataset from channelized turbidite systems, deposited in minibasin settings in the offshore Equatorial Guinea, West Africa. First, we present a practical recipe for using closed-form expressions of effective medium models to predict seismic velocities in unconsolidated sandstones. We use an effective medium model that combines perfectly rough and smooth grains (the extended Walton model), and use that model to derive coordination number, porosity, and pressure relations for P and S wave velocities from experimental data. Our recipe provides reasonable fits to other experimental and borehole data, and specifically

  10. Seismic stratigraphy, some examples from Indian Ocean, interpretation of reflection data in interactive mode

    Krishna, K.S.

    are correlated to bio- and litho- stratigraphic results of ODP Leg 116 sites for the purpose of assigning ages to them. The oldest and youngest unconformities have ages of late Miocene (7.5- 8.0 Ma) and late Pleistocene (0.8 Ma). The middle one would appear... unconformities at different geological ages. Hiatus This is most frequently used term in seismic stratigraphy. A hiatus is the total interval of geologic time that is not represented by strata at a specific position along a...

  11. Seismic stratigraphy of the Heuksan mud belt in the southeastern Yellow Sea, Korea

    Lee, Gwang-Soo; Yoo, Dong Geun; Bae, Sung Ho; Min, Gun-Hong; Kim, Seong-Pil; Choi, Hunsoo


    To establish the seismic stratigraphy of the Heuksan mud belt (HMB) and reconstruct its depositional history, approximately 1,600 km of high-resolution seismic data were newly obtained using chirp acoustic sub-bottom profiler, sparker, and air-gun seismic systems. Based on seismic stratigraphic analysis, the HMB can be divided into three major seismic units (I, II, and III, from top to bottom) and four subunits (II-a, II-b, III-a, and III-b) overlying transgressive sands, pre-last glacial maximum (LGM) deposits, and the acoustic basement. Each unit and subunit show different seismic facies and geometry, being clearly separated from each other by bounding surfaces formed since the LGM. The spatial distribution, thicknesses and volumes of the seismic units were determined and plotted to document the sequential formation of the HMB. The correlation between deep drill core data (HMB-101, HMB-102, HMB-103, YSDP-101, and YSDP-102) and the seismic data suggests that subunits III-b and III-a were formed by the continuous accumulation of fine-grained sediment with partial sandy sediment in an estuarine/deltaic environment during the early to middle transgressive stage, accompanied by landward migration of the shoreline. Subunits II-b and II-a were probably formed by re-deposition of large volumes of sediment eroded from unit III during the middle transgressive to early highstand stage. Unit I is interpreted as the most recent mud deposit representing the highstand systems tract when sea-level rise terminated. The careful definition of seismic units and their interpretation proposed in this study, on the basis of the large and partly new seismic dataset covering the entire HMB together with deep drill core data, have been instrumental in reconstructing the depositional environment and formation mechanisms of the HMB.



    <正>20102510 Cai Xiongfei(Faculty of Earth Sciences,China University of Geosciences,Wuhan 430074,China);Wei Qirong New Progress in Research on Stratigraphy of the Middle Eastern Kunlun Orogenic Belt(Resources Survey & Environment,ISSN1671-4814,CN32-1640/N,30(4),2009,p.243-254,5 illus.,3 tables,24 refs.)Key words:stratigraphy,Kunlun MountainsThe middle Eastern Kunlun is a popular area with a great attraction in basic geologic researches of the Kunlun orogenic



    <正>20050893 Chen Ming (Institute of Sedimentary, Chengdu University of Technology, Chengdu, Sichuan); Xu Xiaosong Study on Outcrop Sequence Stratigraphy of the Lower - Middle Ordovician Strata in Keping, Tarim Basin, Xinjiang, China (Acta Sedimentologica Sinica, ISSN1000-0550, CN62 -1038/P, 22(1), 2004, p. 110-116, 4 illus. , 15 refs. )



    <正>20131120 A.Averianov (Zoological Institute , Russian Academy of Sciences , Universitetskaya nab.1 , Saint Petersburg 199034 , Russia); H.-D.Sues Correlation of Late Cretaceous Continental Vertebrate Assemblages in Middle and Central Asia (Journal of Stratigraphy , ISSN0253-4959 , CN32-1187/P , 36 (2), 2012 , p.462-485



    <正>20090393 Cai Xiongfei (Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China); Wei Qirong Stratigraphic Sequence of Oceanic Islands and Palinspastic Reconstruction of the Wanbaogou Group-Complex in the Eastern Kunlun Orogenic Belt (Journal of Stratigraphy, ISSN0253-4959, CN32-1187/P, 31(2), 2007, p.117-125, 9 illus., 14 refs.)



    20152571 Bai Ping(Guizhou Academy of Geologic Survey,Guiyang 550005,China);Xiao Jiafei Sequence Stratigraphy and Sedimentary Environment of Early Cambrian in ZunyiDafang Area of Northwest Guizhou Province(Guizhou Geology,ISSN1000-5943,CN52-1059/P,31(4),2014,p.291-296,272,3



    <正> 20070428 Liu Wenye (Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029) Application of Wavelet Analysis in High-Resolution Sequence Stratigraphic Division (Journal of Geomechanics, ISSN1006-6616, CN11-3672/P, 12(1), 2006, p.64-70, 4 illus., 12 refs.) Key words: sequence stratigraphy, wavelet transform



    20151119Cui Zhengke(No.1 Marine Geological Investigation Party,Shanghai Offshore Petroleum Bureau,SINOPEC,Shanghai201208,China);Yang Wenda Late Quaternary Sequence Stratigraphy and Sedimentary Environment of East China Sea Continental Shelf(Marine Geology&Quaternary; Geology,ISSN0256-1492,CN37-1117/P,34(4),

  19. Subtle traps prediction using sequence stratigraphy and 3D seismic technology: A case study from Qikou depression in Huanghua basin

    MAO Ning-bo; DAI Ta-gen; PENG Sheng-lin


    Forecasting subtle traps by sequence stratigraphy and 3D seismic data is a sensitive topic in hydrocarbon exploration. Research on subtle traps by geophysical data is the most popular and difficult. Based on the sufficiently drilling data, log data, core data and 3D seismic data, sediment sequence of Qikou depression, Huanghua basin was partitioned by using sequence stratigraphy theory. Each sediment sequence system mode was built. Sediment faces of subtle traps were pointed out. Dominating factors forming subtle traps were analyzed. Sandstone seismic rock physics and its response were studied in Tertiary System. Sandstone geophysical response and elastic modulus vary laws with pressure, temperature, porosity, depth were built. Experimental result and practice shows that it is possible using seismic information forecasting subtle traps. Integrated using geology, log, drilling data, special seismic processing technique, interpretation technique, high precision horizon calibration technique, 3D seismic visualizing interpretation, seismic coherence analysis, attribute analysis, logging-constrained inversion, time frequency analysis, subtle trapsobject is identified and interpreted. Finally, advantage object of subtle trap in this area was determined. Bottomland sand stratigraphic and lithologic reservoirs in Qinan slope zone have been founded by means of high resolution 3D seismic data field technique, high resolution 3D seismic data processing technique and seismic wave impendence inversion technique.

  20. Seismic stratigraphy and cenozoic evolution of the mesetan moroccan atlantic continental shelf

    Le Roy, Pascal; Sahabi, Mohamed; Lahsini, Salim; Mehdi, Khalid; Zourarah, Bendehhou


    A recent high-resolution seismic survey of the El Jadida continental shelf allows the characterization of the Cenozoic evolution of the Northern Atlantic Moroccan Shelf, which belongs to the Western Meseta structural domain. Seismic stratigraphy indicates a subdivision of the Cenozoic deposits into four sequences (Sca1 to Sca4) restricted to the northern portion of the shelf. Chronostratigraphic identification of the sequences shows that principal deposits correspond to Upper Miocene deposits overlying the Cenomanian carbonate platform. Quaternary deposits are restricted to the lowstand sedimentary wedge extending below a water depth of 130 m and to the last highstand system tract corresponding to the Oum Er Rbia prodelta. Cenozoic evolution of the continental shelf was controlled by a combination of pluvial/interpluvial stages and eustatic fluctuations, but also by local tectonics. Terrigenous sediments built up the Oum Er Rbia prodelta during the estimated time interval 6-2 ka coinciding with stabilisation of high sea level and pluvial stage. Tectonic deformations occurred mainly during the Upper Miocene and accentuated shelf subsidence through reactivation of inherited N20°/N40° and N140° faults in response to the Europe/Africa collision. Some of the N140° faulting zones are still active during the Quaternary. Currently subsidence has ceased and a broad uplift of the greater part of the continental shelf probably occurs.



    <正>20072053 Bao Qingzhon(Shenyang Institute of Geology and Mineral Resources,China Geological Survey,Shenyang,Liaoning 110032,China);Zhang Changjie Carboniferous-Permian Marine Lithostratigraphy and Sequence Stratigraphy in Xi Ujimqin Qi,Southeastern Inner Mongolia,China(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,25(5),2006,p.572-579,4 illus.,2 tables,26 refs.,with English abstract)



    <正>20141624 Cai Xiongfei(Key Laboratory of Geobiology and Environmental Geology,Ministry of Education,China University of Geosciences,Wuhan 430074,China);Yang Jie A Restudy of the Upper Sinian Zhengmuguan and Tuerkeng Formations in the Helan Mountains(Journal of Stratigraphy,ISSN0253-4959CN32-1187/P,37(3),2013,p.377-386,5 illus.,2 tables,10 refs.)

  3. Mechanical stratigraphy and normal faulting

    Ferrill, David A.; Morris, Alan P.; McGinnis, Ronald N.; Smart, Kevin J.; Wigginton, Sarah S.; Hill, Nicola J.


    Mechanical stratigraphy encompasses the mechanical properties, thicknesses, and interface properties of rock units. Although mechanical stratigraphy often relates directly to lithostratigraphy, lithologic description alone does not adequately describe mechanical behavior. Analyses of normal faults with displacements of millimeters to 10's of kilometers in mechanically layered rocks reveal that mechanical stratigraphy influences nucleation, failure mode, fault geometry, displacement gradient, displacement distribution, fault core and damage zone characteristics, and fault zone deformation processes. The relationship between normal faulting and mechanical stratigraphy can be used either to predict structural style using knowledge of mechanical stratigraphy, or conversely to interpret mechanical stratigraphy based on characterization of the structural style. This review paper explores a range of mechanical stratigraphic controls on normal faulting illustrated by natural and modeled examples.

  4. Pennsylvanian Subsurface Sequence Stratigraphy Based on 3D Seismic and Wireline Data in Western Osage County, Oklahoma

    West, Alexander

    The Pennsylvanian System in the Mid-Continent United States has been studied for nearly a century. In north central Oklahoma, the Pennsylvanian is primarily composed of cyclothems. These cyclothems are sequences of alternating carbonate, clastic, and shale members. Because of this, these zones can be difficult to differentiate. This project provides valuable insight into better understanding the Pennsylvanian System in western Osage County, Oklahoma. The scope of this project is to perform a subsurface study to produce a detailed interpretation of the depositional history and stratigraphy of Pennsylvanian sequences in western Osage County. This study features 3D seismic and well log investigations that will be used together for local and regional subsurface interpretations. The seismic surveys used in the project are the Wild Creek and Gray Horse 3D surveys in western Osage County. The well logs, digital and raster, provide respectable well control for western Osage County. Together, interpretations from the seismic data and well logs will be used to provide a better understanding of the subsurface stratigraphy and depositional history of Pennsylvanian sequences in western Osage County, Oklahoma.

  5. Seismic stratigraphy of rift basins: techniques, methods and its application in the Reconcavo Basin; Sismoestratigrafia de bacias rifte: tecnicas, metodos e sua aplicacao na Bacia do Reconcavo

    Kuchle, Juliano [Universidade Federal do Rio Grande do Sul (UFRGS). Inst. de Geociencias. Programa de Pos-Graduacao em Geociencias (Brazil)], e-mail:; Scherer, Claiton Marlon dos Santos [Universidade Federal do Rio Grande do Sul (UFRGS). Inst. de Geociencias. Dept. de Paleontologia e Estratigrafia (Brazil)], e-mail:


    This paper aims a proposal of interpretation and seismic stratigraphy systematic mapping of rift basins based on genetic concepts, as offered by the basic development of the Sequence Stratigraphy - the temporal interpretation of units based on concepts derived from variables and observable in depositional trends. So, rift basins are controlled by specifically variables and its relationships, which results in theoretical evolutional models. Those theoretical models are detailed as depositional trends denominated stacking patterns. Thus, from the stacking patterns, it is able to establish the inverse way analysis, picturing evolutional models and controlling variables. The main objective of this paper is the migration of the genetic tectonic-stratigraphic model of rift basins to the seismic platform, supported by the key-concepts of the seismic stratigraphy. This analysis is based on the recognition of seismic stratigraphic units which composes the tectonic system tracts - basic units of the framework, and these system tracts are formed by specific stacking patterns for each portion of the half Graben. As those stacking patterns reflect changes in the accommodation, stratigraphic surfaces and strata termination patterns are established. Therefore, a whole conceptual basis of seismic stratigraphy recognition and mapping is proposed, as well as a time determination of evolutional models in chronostratigraphic diagrams (Wheeler charts), to supply a useful tectonic-stratigraphic framework to hydrocarbon exploration. (author)

  6. Workshop on quantitative dynamic stratigraphy

    Cross, T.A.


    This document discusses the development of quantitative simulation models for the investigation of geologic systems. The selection of variables, model verification, evaluation, and future directions in quantitative dynamic stratigraphy (QDS) models are detailed. Interdisciplinary applications, integration, implementation, and transfer of QDS are also discussed. (FI)

  7. Stratigraphy of the crater Copernicus

    Paquette, R.


    The stratigraphy of copernicus based on its olivine absorption bands is presented. Earth based spectral data are used to develop models that also employ cratering mechanics to devise theories for Copernican geomorphology. General geologic information, spectral information, upper and lower stratigraphic units and a chart for model comparison are included in the stratigraphic analysis.

  8. Investigations on alluvial deposits through borehole stratigraphy, radiocarbon dating and passive seismic technique (Carnic Alps, NE Italy)

    Viero, Alessia; Marchi, Lorenzo; Cavalli, Marco; Crema, Stefano; Fontana, Alessandro; Mozzi, Paolo; Venturini, Corrado


    their extent and the maximum depths. Two passive seismic campaigns were carried out near the borehole site and along the But valley at different elevations. The aim was to investigate the depth of the buried bedrock and therefore to indirectly characterize the thickness of alluvial deposits. We calibrated the fundamental frequency of each site by constraining average shear velocity of the alluvial sediments close to the borehole site with known stratigraphy. Eight HVSR (Horizontal to Vertical Spectral Ratio, Nakamura, 1989) were carried out, and thus a first sketch of the buried valley floor along a longitudinal profile of about 5 km was depicted. The values of the derived bedrock depth allow to quantify the differences in thickness between the alluvial deposits and the Moscardo Torrent fan deposits. This information helps to address the contribution of the debris-flow processes in damming the upper But River during the last five centuries. The results confirm the role of debris-flow deposits from the Moscardo Torrent in shaping the morphology of the valley floor of But River and show suitability of an integrated approach, encompassing log stratigraphy, geophysical surveys and analysis of historical documents, for gaining insights on the evolution of alpine valleys. Reference Nakamura, Y., 1989. A method for dynamic characteristic estimation of subsurface using microtremor on the ground surface. Quarterly Report of Railway Technical Research Institute, 30(1): 25-33.

  9. Global stratigraphy. [of planet Mars

    Tanaka, Kenneth L.; Scott, David H.; Greeley, Ronald


    Attention is given to recent major advances in the definition and documentation of Martian stratigraphy and geology. Mariner 9 provided the images for the first global geologic mapping program, resulting in the recognition of the major geologic processes that have operated on the planet, and in the definition of the three major chronostratigraphic divisions: the Noachian, Hesperian, and Amazonian Systems. Viking Orbiter images permitted the recognition of additional geologic units and the formal naming of many formations. Epochs are assigned absolute ages based on the densities of superposed craters and crater-flux models. Recommendations are made with regard to future areas of study, namely, crustal stratigraphy and structure, the highland-lowland boundary, the Tharsis Rise, Valles Marineris, channels and valley networks, and possible Martian oceans, lakes, and ponds.

  10. Seismic and sequence stratigraphy of the central western continental margin of India: late-Quaternary evolution

    Karisiddaiah, S.M.; Veerayya, M.; Vora, K.H.

    Seismic and sequence stratigraphic architecture of the central western continental margin of India (between Coondapur and south of Mangalore) has been investigated with shallow seismic data. Seismic stratigraphic analysis defined nine seismic units...

  11. Stratigraphic relationships between the Colombian, Sinú Offshore and Sinú-San Jacinto basins based on seismic stratigraphy

    Esteban Alfaro

    Full Text Available There are diverse controversial and contradictory models about the geological history of the Caribbean region. Some issues such as the origin of the Caribbean plate, the nature of basement of the Caribbean basins and the regional tectonics, have been in discussion during decades. There are disperse and punctual studies across the Caribbean. Application of seismic stratigraphy in regional seismic lines across the Colombian, Sinú Offshore and Sinú-San Jacinto basins suggests a stratigraphic continuity between these regions. A chronostratigraphic chart of the Colombian and Sinú Offshore basins based on stratal terminations and seismic facies was proposed. Seven stratigraphic stages were identified in the Colombian, Sinú Offshore and Sinú-San Jacinto basins, which, also, have been recognized across the Caribbean region. First stratigraphic stage was characterized by continental to restricted marine deposition during a Triassic/Jurassic rifting. Second, third and fourth stages correspond with deposition of a wide carbonate platform in the Cretaceous, sandy carbonate platform during the Paleocene and carbonate and coarse-grained fluvial sedimentation during the Eocene, respectively. Another stage was characterized by rising of base level and deep-water deposition (turbidites and pelagic/hemipelagic sediments during the Oligocene. The Early to Middle Miocene was characterized by shallow marine to fluvial sedimentation during falling base level, which was controlled by episodic events of tectonic inversion. During the Late Miocene to recent, the sedimentation consisted of terrigenous coarse-grained deposits. Stratigraphic relationships between these zones, suggest a shared geological history between the Caribbean and northern South America. The geologic continuity founded in this study is easily explained by the model of an in situ origin for the Caribbean plate.

  12. Regional seismic stratigraphy and controls on the Quaternary evolution of the Cape Hatteras region of the Atlantic passive margin, USA

    Mallinson, D.J.; Culver, S.J.; Riggs, S.R.; Thieler, E.R.; Foster, D.; Wehmiller, J.; Farrell, K.M.; Pierson, J.


    Seismic and core data, combined with amino acid racemization and strontium-isotope age data, enable the definition of the Quaternary stratigraphic framework and recognition of geologic controls on the development of the modern coastal system of North Carolina, U.S.A. Seven regionally continuous high amplitude reflections are defined which bound six seismic stratigraphic units consisting of multiple regionally discontinuous depositional sequences and parasequence sets, and enable an understanding of the evolution of this margin. Data reveal the progressive eastward progradation and aggradation of the Quaternary shelf. The early Pleistocene inner shelf occurs at a depth of ca. 20-40 m beneath the western part of the modern estuarine system (Pamlico Sound). A mid- to outer shelf lowstand terrace (also early Pleistocene) with shelf sand ridge deposits comprising parasequence sets within a transgressive systems tract, occurs at a deeper level (ca. 45-70 m) beneath the modern barrier island system (the Outer Banks) and northern Pamlico Sound. Seismic and foraminiferal paleoenvironmental data from cores indicate the occurrence of lowstand strandplain shoreline deposits on the early to middle Pleistocene shelf. Middle to late Pleistocene deposits occur above a prominent unconformity and marine flooding surface that truncates underlying units, and contain numerous filled fluvial valleys that are incised into the early and middle Pleistocene deposits. The stratigraphic framework suggests margin progradation and aggradation modified by an increase in the magnitude of sea-level fluctuations during the middle to late Pleistocene, expressed as falling stage, lowstand, transgressive and highstand systems tracts. Thick stratigraphic sequences occur within the middle Pleistocene section, suggesting the occurrence of high capacity fluvial point sources debouching into the area from the west and north. Furthermore, the antecedent topography plays a significant role in the evolution

  13. Seismic stratigraphy of sedimentary cover in Amerasian Basin based on the results of Russian High Arctic expeditions

    Poselov, Viktor; Kireev, Artem; Smirnov, Oleg; Butsenko, Viktor; Zholondz, Sergey; Savin, Vasily


    Massive amount of multichannel seismic (MCS) data were obtained by Russian High Arct ic expeditions "Arctica-2011", "Acrtica-2012" and "Arctica-2014". More than 40 MCS lines are located in the Amerasian basin and help to substantiate the seismic stratigraphy model of its sedimentary cover. The proposed seismic stratigraphy model was successively determined for the Cenozoic and pre-Cenozoic parts of the sedimentary section and was based on correlation of the Russian MCS data and seismic data documented by boreholes. Cenozoic part of the sedimentary cover is based on correlation of the Russian MCS data and AWI91090 section calibrated by ACEX-2004 boreholes on the Lomonosov Ridge. Two major unconformities are traced. The upper regional unconformity (RU) is associated with a major pre-Miocene hiatus. Another major hiatus is recorded in the borehole section between the Campanian and the Upper Paleocene units. It is recognized as the post-Campanian unconformity (pCU) in the seismic sections. Formation of the regional unconformities is associated with a fundamental change in depositional environment. Formation of RU was initiated by opening of the Fram Strait gateway at the Paleogene/Neogene boundary. Post-Campanian unconformity is linked with the initial stage of the Eurasian Basin opening between the Cretaceous and the Paleogene. Cenozoic sedimentary units are continuously traced from the East-Siberian and Chukchi sea shelves across the transit zone to the Amerasian basin. Paleogene unit (between pCU and RU) is formed under the neritic depositional environment and it is characterized by an extremely small thickness on the Lomonosov Ridge (less than 200 m), on the Mendeleev Rise and in the Podvodnikov Basin (not more than 300-400 m). Neogene unit (above RU) consists of hemipelagic deposits and occupies the essential part of thickness of the Cenozoic section in Podvodnikov and Makarov Basins. Interval velocities in the Paleogene unit vary within 2.8-3.2 km/s, in the

  14. Mapping the productive sands of Lower Goru Formation by using seismic stratigraphy and rock physical studies in Sawan area, southern Pakistan: A case study

    Munir, K.


    This study has been conducted in the Sawan gas field located in southern Pakistan. The aim of the study is to map the productive sands of the Lower Goru Formation of the study area. Rock physics parameters (bulk modulus, Poisson\\'s ratio) are analysed after a detailed sequence stratigraphic study. Sequence stratigraphy helps to comprehend the depositional model of sand and shale. Conformity has been established between seismic stratigraphy and the pattern achieved from rock physics investigations, which further helped in the identification of gas saturation zones for the reservoir. Rheological studies have been done to map the shear strain occurring in the area. This involves the contouring of shear strain values throughout the area under consideration. Contour maps give a picture of shear strain over the Lower Goru Formation. The identified and the productive zones are described by sands, high reflection strengths, rock physical anomalous areas and low shear strain.

  15. The Cenozoic geological evolution of the Central and Northern North Sea based on seismic sequence stratigraphy

    Jordt, Henrik


    This thesis represents scientific results from seismic sequence stratigraphic investigations. These investigations and results are integrated into an ongoing mineralogical study of the Cenozoic deposits. the main results from this mineralogical study are presented and discussed. The seismic investigations have provided boundary conditions for a forward modelling study of the Cenozoic depositional history. Results from the forward modelling are presented as they emphasise the influence of tectonics on sequence development. The tectonic motions described were important for the formation of the large oil and gas fields in the North Sea.

  16. Seismic Stratigraphy of Pleistocene Deltaic Deposits in Bahía Blanca Estuary, Argentina



    Full Text Available The Bahía Blanca estuary (Argentina has a morphological configuration resulting from hydrological and sedimentary processes related to Late Quaternary sea level changes. This estuarine system occupies a large coastal plain with a dense net of tidal channels, low-altitude islands and large intertidal flats. Little is known about the sedimentary units of the marine subbottom. Therefore, a stratigraphical analysis of the northern coast of Bahía Blanca estuary was carried out using high resolution seismic (3.5 kHz in order to: i define Quaternary sequences, ii describe sedimentary structures, and iii determine the paleoenvironmental conditions of sedimentation. The seismic stratigraphic data collected and their correlation with drilling lithological data show five seismic sequences (S1, S2, S3, S4 and S5, of which S1-S2 were found to be associated with a continental paleoenvironment of Miocene-Pleistocene age. Sequences S3 and S4, whose lithology and seismic facies (paleochannel structures and prograding reflection configurations, were defined on these materials, to evidence the development of an ancient deltaic environment which was part of a large Pleistocene drainage system. The S5 sequence was formed during the Holocene transgressive-regressive process and complete the seismostratigraphic column defined in the present study.

  17. Seismic stratigraphy and structure of the area to the southeast of the trobriand platform

    Francis, G.; Lock, J.; Okuda, Y.


    The area to the southeast of the Trobriand Platform contains an easterly continuation of the Oligocene to Quaternary Cape Vogel Basin (CVB). Within this area, three major seismic sequences are recognized: sea bed-A, A B, and B D. The latter sequence occurs within a depocenter with approximately 3,200 m of sediment. The A B and B D sequences were faulted and gently folded in Late Miocene times. To the south and southeast of this depocenter the CVB has been truncated by the Pliocene opening of the Woodlark Basin, an active westward-propagating spreading system.

  18. Environmental History of Southern Patagonia Unraveled by Seismic Stratigraphy and Sediment Cores of Laguna Potrok Aike

    Anselmetti, F. S.; Ariztegui, D.; de Batist, M.; Gebhardt, C.; Haberzettl, T.; Niessen, F.; Ohlendorf, C.; Zolitschka, B.


    Laguna Potrok Aike, located in Southernmost Patagonia (Argentina, 52°S) is a maar lake and likely provides the only continental Southern Patagonian archive that covers a long and continuous interval of several glacial- to-interglacial cycles. In the context of a proposed ICDP-drilling initiative (see Zolitschka et al., this session), several site surveys have been undertaken that characterize in detail the shallow subsurface of the lake. A variety of environmental changes are identified based on seismic stratigraphic analyses of a dense grid of high- resolution data. Long sediment cores recovered the material to date and calibrate these changes providing a chronology of events. The paleoenvironmental history reflects the complex interplay between variations in the hydrologic cycle, wind regime, and volcanic/tectonic activity. Laguna Potrok Aike is the largest and deepest lake (maximum depth 100 m) in the Pali Aike Volcanic Field. It is steeply-rimmed, circular in shape with a diameter of 3 km and surrounded subaerially by a series of paleoshorelines, reflecting its sensitivity to changes in the evaporation/precipitation ratio. Seismic subsurface data indicate a basinwide erosional unconformity, that consistently occurs on the shoulder of the lake down to a depth of -35 m (below modern lake level) marking the lowest lake level during the Late Glacial-to-Holocene times. Cores that penetrate this unconformity comprise MIS3-dated sediments (45 ka) 3.5 m below the unconformity that were deposited during high lake levels. These cores also provide an age of 6800 cal BP for the transgressional sediments burying the unconformity. This middle Holocene transgression following the maximum lake level lowstand marks the onset of a stepwise increase in moisture, as shown by a series of buried paleoshorelines that were formed during at least five lake level stillstands between the depths of -32 and -12 m. No indications point towards an intermittent lake level lowering, so that

  19. Stratigraphy of a proposed wind farm site southeast of Block Island: Utilization of borehole samples, downhole logging, and seismic profiles

    Sheldon, Dane P. H.

    Seismic stratigraphy, sedimentology, lithostratigraphy, downhole geophysical logging, mineralogy, and palynology were used to study and interpret the upper 70 meters of the inner continental shelf sediments within a proposed wind farm site located approximately two to three nautical miles to the southeast of Block Island, Rhode Island. Core samples and downhole logging collected from borings drilled for geotechnical purposes at proposed wind turbine sites along with seismic surveys in the surrounding area provide the data for this study. Cretaceous coastal plain sediments that consist of non-marine to marine sand, silt, and clay are found overlying bedrock at a contact depth beyond the sampling depth of this study. The upper Cretaceous sediments sampled in borings are correlated with the Magothy/Matawan formations described regionally from New Jersey to Nantucket. An unconformity formed through sub-aerial, fluvial, marine, and glacial erosion marks the upper strata of the Cretaceous sediments separating them from the overlying deposits. The majority of Quaternary deposits overlying the unconformity represent the advance, pulsing, and retreat of the Laurentide ice sheet that reached its southern terminus in the area of Block Island approximately 25,000 to 21,000 years before present. The sequence consists of a basal glacial till overlain by sediments deposited by meltwater environments ranging from deltaic to proglacial lakefloor. A late Pleistocene to early Holocene unconformity marks the top of the glacial sequence and was formed after glacial retreat through fluvial and subaerial erosion/deposition. Overlying the glacial sequence are sediments deposited during the late Pleistocene and Holocene consisting of interbedded gravel, sand, silt, and clay. Sampling of these sediments was limited and surficial reflectors in seismic profiles were masked due to a hard bottom return. However, two depositional periods are interpreted as representing fluvial and estuarine

  20. The northern Caribbean plate boundary in the Jamaica Passage: Structure and seismic stratigraphy

    Corbeau, J.; Rolandone, F.; Leroy, S.; Mercier de Lépinay, B.; Meyer, B.; Ellouz-Zimmermann, N.; Momplaisir, R.


    Multibeam bathymetry data and multichannel seismic reflection profiles have been collected at the end of 2012 along the Enriquillo-Plantain-Garden Fault Zone (EPGFZ) in the Jamaica Passage, between Jamaica and Hispaniola. Analysis of the data set reveals the tectonic evolution and the stratigraphic complexity of the northern Caribbean boundary. Stratigraphic correlations with previous marine and on land studies are proposed to place the identified seismic sequences in their regional tectonic history. Two distinct crustal domains are interpreted. Typical stratigraphic sequences for the rifted blocks of the Eastern Cayman Trough margin are identified in five basins of the Jamaica Passage, highlighting the eastward limit of the Cayman Trough margin. These inherited basins are deformed and folded during a first phase of compression that could correspond to the regional tectonic rearrangement recorded in the early Miocene (about 20 Ma). A distinct crustal domain that we propose to relate to the Carib Beds (Caribbean typical reflectors A″, B″ and V) is identified in the southern part of the Jamaica Passage, indicating that the Caribbean Large Igneous Province could extend up to the extreme northeast part of the Lower Nicaragua Rise. The left-lateral EPGFZ currently cuts across two pre-existing basins, the Morant and Matley basins. During the activity of the EPGFZ, these basins are deformed and folded indicating a second phase of compression. In contrast, the Navassa basin, located in the middle of the Jamaica Passage, results from the strike-slip motion of the EPGFZ and is interpreted as an asymmetrical basin bordered by the EPGFZ only on its northern side.

  1. Würmian deglaciation of western Lake Geneva (Switzerland) based on seismic stratigraphy

    Fiore, Julien; Girardclos, Stéphanie; Pugin, André; Gorin, Georges; Wildi, Walter


    Western Lake Geneva (le Petit-Lac) was filled during the Quaternary over a major erosion surface truncating the cemented, folded and thrusted Tertiary sediments of the foreland Alpine basin. The carving of the lake occurred during Quaternary glaciations with ice originating from the Rhone valley catchment basin flowing in two branches oriented SW and NE over the Swiss Plateau. Lake Geneva is situated on the South-Western branch of this paleo ice-cap. For the first time, a dense grid of high-resolution seismic profiles (airgun 5-inch 3, airgun 1-inch 3 and echosounder) has imaged the whole Quaternary sequence, providing a paleoenvironmental interpretation and a detailed reconstruction of the Rhone glacier retreat stages during glacial events that led to the formation of western Lake Geneva. The Quaternary sequence filling up the bedrock valley is exceptionally thick with up to 220 m of deposits and consists of glacial, glacio-lacustrine and lacustrine sediments. Fourteen seismic units have been defined (units U1-U14). Unit U1 represents the remnants of glacial deposits older than the last glacial cycle, preserved in the deepest part of the lake and in secondary bedrock valleys. Unit U2 represents gravel and sands deposited by meltwater circulation at the bottom of the glacial valley. Unit U3 is a thick, stratified unit marking the beginning of the deglaciation, when the Rhone glacier became thinner and buoyant and allowed the formation of a subglacial lake. Younger glacial units (units U4, U5, U7, U9, U11) are acoustically chaotic sediments deposited subglacially under the water table (undermelt tills), while the glacier was thinning. These glacial units are bounded by synform erosion surfaces corresponding to readvances of the glacier. The transition from a glacial to a glacio-lacustrine environment started with the appearance of a marginal esker-fan system (unit U6). Esker formation was followed by a small advance-retreat cycle leading to the deposition of unit U7

  2. Cement stratigraphy: Image probes of cathodoluminescent facies.

    Vuillemin, Aurèle; Ndiaye, Mapathe; Martini, Rossana; Davaud, Eric Jean


    Cement stratigraphy of carbonates aims to establish the chronology of processes involved in the rock diagenesis. Regional cement stratigraphy allows correlations and understanding of the petrological heterogeneities in reservoirs and aquifers, but is a long and rigorous approach. This article exposes a methodology of image analysis that facilitates the spatial correlation of diagenetic events in carbonate rocks. Based on the statistical comparison of signals extracted from the red spectrum em...

  3. Seismic-sequence stratigraphy and geologic structure of the Floridan aquifer system near "Boulder Zone" deep wells in Miami-Dade County, Florida

    Cunningham, Kevin J.


    The U.S. Geological Survey, in cooperation with the Miami-Dade Water and Sewer Department, acquired, processed, and interpreted seismic-reflection data near the North and South District “Boulder Zone” Well Fields to determine if geologic factors may contribute to the upward migration of injected effluent into that upper part of the Floridan aquifer system designated by the U.S. Environmental Protection Agency as an underground source of drinking water. The depth of the Boulder Zone at the North and South District “Boulder Zone” Well Fields ranges from about 2,750 to 3,300 feet below land surface (ft bls), whereas overlying permeable zones used as alternative drinking water supply range in depth from about 825 to 1,580 ft bls at the North and South District “Boulder Zone” Well Fields. Seismic-sequence stratigraphy and geologic structures imaged on seismic-reflection profiles created for the study describe the part of the Floridan aquifer system overlying and within the Boulder Zone. Features of the Floridan aquifer system underlying the Boulder Zone were not studied because seismic-reflection profiles acquired near the North and South District “Boulder Zone” Well Fields lacked adequate resolution at such depths.

  4. The orbital record in stratigraphy

    Fischer, Alfred G.


    , and (2) presence of abundant microfossils yields close ties to geochronology. A tantalizing possibility that stratigraphy may yield a record of orbital signals unrelated to climate has turned up in magnetic studies of our Cretaceous core. Magnetic secular variations here carry a strong 39 ka periodicity, corresponding to the theoretical obliquity period of that time - Does the obliquity cycle perhaps have some direct influence on the magnetic field?

  5. Some fundamenltal problems in outcrop sequence stratigraphy



    Some fundamental problems in outcrop sequence stratigraphy are discussed, and the following ideas are obtained: (i) Detailed sedimentary facies analysis and study on stacking pattern of parasequences, careful and accurate study of biostratigraphy, and stratigraphical correlation of different facies areas are the essential conditions for proper identification of sequences. (ii) The first flooding surface may be an ideal sequence boundary in outcrop sequence stratigraphy, where the most distinct palaeontological and sedimentary changes take place and make the surface readily recognizable in outcrop. (iii) The distribution in space, specially in different facies belts, is regarded as an important criterion for defining and recognizing the various orders of sequences. The third-order sequence is probably global in nature , which may be discerned in various depositional facies belts at least on one continental margin, and can be correlated over long distances, sometimes worldwide. (iv) The first flooding surf

  6. Integrated well log and 2-D seismic data interpretation to image the subsurface stratigraphy and structure in north-eastern Bornu (Chad) basin

    Isyaku, Aminu A.; Rust, Derek; Teeuw, Richard; Whitworth, Malcolm


    Structural and stratigraphic mapping within the Bornu Basin in north east Nigeria was commonly carried out using traditional field geological methods. However, such traditional approaches remain inadequate in the semi-arid region characterised by topographically flat areas and lack of continuous bedrock outcrops that are mostly concealed beneath sand cover. Previous studies in the north-eastern part of the basin carried out using ditch cuttings from few wells and disconnected seismic data were largely inadequate and the resulting stratigraphic analyses were more often generalised. This paper presents an integrated structural and stratigraphic study of the basin using combined subsurface geophysical datasets. A Combined Log Pattern (CLP) method is a well log analysis, which utilises various well log data including gamma ray, resistivity, bulk density and sonic logs to identify lithology and stratigraphic boundaries of subsurface formations. This method is applied to constrain the subsurface stratigraphy of the north-eastern part of the Bornu Basin bordering the Lake Chad. In addition to qualitative combined well log analysis, the time-depth relationship of the sonic log and seismic data was quantitatively determined by tying a well with an intersecting seismic section to validate the stratigraphic facies horizons identified. Four well log facies and their environments of deposition were characterised from the combined well log analysis of the different log types. It is discovered that the Cretaceous basement structural features controlled the deposition of overlying formations in the basin. Without intact core data, the shallower wells were discovered to have bottomed over subsurface horst features while deeper wells penetrated into the basal facies contained mainly within the grabens. Main subsurface structural lineaments in the area include NW-SE, NE-SW and NNW-SSE trending faults, which mainly formed the horst and graben features. Some stratigraphic formations

  7. New insights into the structure and stratigraphy of the Swedish sector of the Baltic Sea sedimentary Basin from vintage 2D marine seismic data

    Sopher, Daniel; Juhlin, Christopher; Erlström, Mikael


    A large dataset originally acquired by the Swedish Oil Prospecting CO. (OPAB) between 1970 and 1990 including 2D marine seismic data, well log data, core data and seismic interpretations has recently been made available by the Swedish Geological Survey (SGU). In this study this dataset has been used to produce a set of regional geoseismic sections across the Swedish sector of the Baltic Sea. Regional depth structure maps detailing the deep structure of the basin produced from previous interpretations are also presented. The Baltic Sea Basin is an intra-cratonic basin located in northern Europe. The Swedish sector of the basin is characterised primarily by two structural elements, the Hanö Bay Basin and the Baltic Syneclise. The largest of these, the Baltic Syneclise, is a large synclinal depression formed during the Caledonian Orogeny. The Hanö Bay Basin was formed during the Mesozoic due to subsidence along the Christiansø Fault Zone. The Swedish sector of the Baltic Sea Basin is primarily characterised by a sequence of shallow marine Cambrian sediments overlain by a relatively thin succession of Ordovician marine limestone and marls; these are in turn overlain by a thick layer of marl, siltstone and claystone deposited during the Silurian. Mesozoic sediments are found in the Hanö Bay and outer Hanö Bay area. These were deposited in areas of local subsidence, associated with transtensional tectonics prevalent within and adjacent to the Tornquist Zone, during the Late Carboniferous/Early Permian. Block faulting occurring throughout the Mesozoic also affected sedimentation patterns in the area. In this study a sparse grid of marine seismic reflection profiles have been reprocessed across the Swedish sector of the Baltic Sea Basin. These have been interpreted based on the available well data and synthetic seismograms. Several regional seismic profiles were constructed which detail the major structural elements and basin stratigraphy across the Swedish sector. A

  8. Imaging continental shelf shallow stratigraphy by using different high-resolution seismic sources: an example from the Calabro-Tyrrhenian margin (Mediterranean Sea

    Eleonora Martorelli


    Full Text Available High-resolution seismic reflection profiles of the Calabro-Tyrrhenian continental shelf were collected using different seismic sources (Sub-Bottom Profiler, Uniboom, Sparker 0.5-1-4.5 kJ. Noticeable differences and results were obtained both from a geophysical and geological-interpretative point of view. The availability of different sources permitted the definition of the most suitable seismostratigraphic characterization in terms of resolution, penetration and acoustic facies. Very high resolution stratigraphy was defined through profiles produced by different seismic systems used in parallel. This permitted the application of sequence-stratigraphy concepts with the reconstruction of a thick postglacial depositional sequence, formed by a transgressive and a high-stand systems tract. The thickness distribution of postglacial deposits reveals that the main depocenter (55-65 m is located offshore of the Coastal Range, along a stretch of coast supplied by several small and seasonal streams ("fiumare" and characterized by the lack of a coastal plain. This suggests the greater efficiency of sediment supply and bypass in this area relatively to sectors located offshore of the main rivers. The transgressive systems tract, usually thin or nearly absent, is particularly well developed (up to 33 m and is composed of up to three parasequences with a retrogradational stacking pattern. The high-stand systems tract, up to 30 m thick, is made up of two parasequences and has a quite regular geometry and acoustic facies.Perfis de reflexão sísmica de alta resolução da plataforma continental tirreniana de Calabro foram obtidos utilizando-se recursos sísmicos diversos (Perfilador de Sub-superfície, Uniboom, Sparker 0.5-1-4.5 kJ. Diferenças evidentes foram encontradas sob o ponto de vista geofísico e geológico-interpretativo. A disponibilidade de diferentes fontes permitiu a definição de uma caracterização sismo-estratigráfica mais acurada em termos

  9. Integrating sequence stratigraphy and seismic attributes for quantitative reservoir characterization: A case study of a Pliocene reservoir, Campeche Sound, Mexico

    Mendez-Hernandez, Efrain

    An integrated workflow including analysis of seismic, core, well log and biostratigraphic data was developed and conducted to both construct a reliable geologic model and characterize a Pliocene gas reservoir which overlies the Cantarell field in the Campeche Sound, southern Gulf of Mexico. In 2003, the offshore exploratory Utan #1 well was drilled to investigate the gas potential of the Pliocene sequence. The well provided successful results from facies characterized by thin mixed siliciclastic-carbonate beds contained within a faulted rollover anticline. Campeche Sound is the most prolific Mexican oil producing province where the best fields are Mesozoic-Paleocene carbonates in structural traps. Therefore, little exploration has been focused on the overlying late Tertiary and more siliciclastic section, representing a gap in the knowledge of this part of the basin where new expectations arise for non-associated gas entrapments in a traditionally oil-producing province. Based upon development of a sequence stratigraphic framework, a new play analysis is developed where the reservoirs are identified as retrogradational shoreface parasequences sitting atop third-order sequence boundaries. Basic and advanced seismic attributes contribute to the stratigraphic interpretation and gas detection. Seismic inversion for reflectivity allowed better identification of key stratigraphic surfaces. Modeled Type-I AVO and a dimmed spectral decomposition response following structural contours provide reliability to gas discrimination and reservoir delineation. The seismic attributes will require additional support to be valuable as reservoir quality predictors. Because biogenic methane and thin sheet reservoirs define the rock-fluid system, development may be uneconomic. However, the trapped gas could be reinjected at deeper depths to improve recovery efficiency of oil in the Cantarell field. The knowledge gained from this research is an important contribution to the petroleum

  10. Deriving a framework for the hydrocarbon potential offshore Namibia: An ideal case for using seismic and sequence stratigraphy?

    Bagguley, J.G.; Prosser, S.D. [Oxford Brookes Univ. (United Kingdom)


    The passive continental margin offshore Namibia remains one of the few relatively unexplored, frontier areas for hydrocarbon exploration. The availability of 14,300km of speculative, non-exclusive seismic reflection dam has provided the opportunity to build up a sequence stratigraphic framework for this margin, with a view to hydrocarbon play analysis and prediction. The high seismic resolution of the data allows the definition of a number of megasequences. each representing a major phase of basin evolution. The post-rift prograding wedge (MS50) can be divided into a lower MS50a (Aptian - Masianchtian) and an upper MS50b (Ternary) unit. Internally these units are composed of a number of T/R cycles. Isopach maps for MS50a and MS50b have been constructed. The information from these can be supplemented by river system and drainage basin analysis to gain some insight into the type of sediment expected to be deposited offshore at different times during the evolution of the margin. A number of different features can be identified from the data which can help place the post-rift units into a sequence stratigraphic framework. Channel forms and slump-related features are observed which may form in response to relative sea level changes or tectonic triggering. The seismic expressions of these features enables the causative process to be determined. By constructing geohistory curves using a basin modelling program, the structural and stratigraphic evolution of the Namibian margin may be further elucidated. Such geohistories pinpoint the location of possible source rock horizons which, when fed back into the sequence stratigraphic framework, may aid the prediction of potential hydrocarbon plays.

  11. Cenozoic Circulation History of the North Atlantic Ocean From Seismic Stratigraphy of the Newfoundland Ridge Drift Complex

    Boyle, P. R.; Romans, B.; Norris, R. D.; Tucholke, B. E.; Swift, S. A.; Sexton, P. F.


    In the North Atlantic Ocean, contour-following bottom currents have eroded regional unconformities and deposited contourite drifts that exceed two km in thickness and extend for 100s of km. The character of deep-water masses that are conveyed through ocean basins by such currents influence global heat transfer and ocean-atmosphere partitioning of CO2. The Newfoundland Ridge Drift Complex lies directly under the modern Deep Western Boundary Current southeast of Newfoundland, close to the site of overturning in the northwest Atlantic Ocean and at the intersection of the warm Gulf Stream and cool Labrador surface currents. To the south are regions of the western North Atlantic basin that are influenced by southern- as well as northern-sourced bottom waters. Here, we document the evolution of North Atlantic deep-water circulation by seismic-stratigraphic analysis of the long-lived and areally extensive Newfoundland Ridge Drift Complex. IODP Expedition 342 boreholes provide age control on seismic units, allowing sedimentation patterns to be placed in a temporal framework. We find three major phases of sedimentation: pre-contourite drift (~115-50 Ma), active contourite drift (~50-2.6 Ma), and late-contourite drift (~2.6-0 Ma). Bottom-current-controlled deposition of terrigenous-rich sediment began at ~50 Ma, which correlates to the onset of a long-term global cooling trend. A further change in deep circulation near the Eocene-Oligocene transition (~30 Ma) is indicated by more focused drift sedimentation with greatly increased accumulation rates and stratal architecture dominated by mud waves. At ~2.6 Ma to present the axis of drift accumulation shifted markedly towards shallower water depths, corresponding with the onset of Northern Hemisphere ice sheets. We discuss how these reorganizations of deep circulation correlate with results of other North Atlantic seismic stratigraphic studies to the north and south.

  12. Computer techniques to aid the interpretation of salt bodies and stratigraphy in three-dimensional seismic volumes

    Hammon, William S., III

    The life cycle of a seismic data volume can be broken into three parts: acquisition, processing, and interpretation. Accomplishing each of these steps requires the application of a different set of skills and techniques to accomplish. Of the three, data acquisition and processing are the most expensive steps to perform. Data acquisition is a time and equipment intensive operation. Processing the seismic data, after acquisition, is a computationally very expensive procedure; usually performed on very large computer clusters. However, the most time consuming of these steps is the interpretation of the seismic data. Arguably, this is also the least optimized part of the volume life cycle, as certain aspects of interpretation are still performed largely by hand. Efficiency gains are ongoing in the fields of seismic acquisition and processing (especially migration). Initial steps have also been made in the semi-automation of interpretation, but much work remains to be done. Semi-automatic interpretation holds the greatest promise for quickly improving the value of the seismic volume acquisition and utilization cycle. This dissertation concentrates on the development of new techniques to aid the human interpreter in their interpretation of 3D seismic volumes. The ability to both accelerate and improve interpretation of geology in a data volume is a significant goal for increasing the value realized from a given data set. Particular attention is given to two of the more intractable problems in seismic data interpretation: salt-body delineation, and the interpretation of stratigraphic features. The difficulties inherent in each task are different, but both tasks are quite time consuming when performed largely by hand. This dissertation is comprised of five parts. Part 1 describes Voxel Density, a novel volume processing technique that can be used to filter, or improve the contrast in a data set. This technique uses the local persistence of features in the data set to

  13. Stratigraphy and dissolution of the Rustler Formation

    Bachman, G.O.


    The Rustler Formation is the uppermost evaporite-bearing unit in the Permian Ochoan series in southeastern New Mexico. It rests on the Salado Formation which includes the salt beds where the mined facility for the Waste Isolation Pilot Plant (WIPP) is being constructed. An understanding of the physical stratigraphy of the Rustler Formation is pertinent to studies of the WIPP site because some portions of the Rustler are water-bearing and may provide paths for circulating waters to come into contact with, and dissolve, evaporites within the Ochoan sequence. Knowledge of the processes, magnitude, and history of evaporite dissolution in the vicinity of the WIPP site is important to an evaluation of the integrity of the site. 2 refs., 2 figs.

  14. Strontium isotope stratigraphy of the Pelotas Basin

    Zerfass, Geise de Santana dos Anjos, E-mail: [Petroleo Brasileiro S.A. (PETROBRAS/CENPES/PDGEO/BPA), Rio de Janeiro, RJ (Brazil). Centro de Pesquisas e Desenvolvimento Leopoldo Americo Miguez de Mello; Chemale Junior, Farid, E-mail: [Universidade de Brasilia (UnB), DF (Brazil). Instituto de Geociencias; Moura, Candido Augusto Veloso, E-mail: [Universidade Federal do Para (UFPA), Belem, PA (Brazil). Centro de Geociencias. Dept. de Geoquimica e Petrologia; Costa, Karen Badaraco, E-mail: [Instituto Oceanografico, Sao Paulo, SP (Brazil); Kawashita, Koji, E-mail: [Unversidade de Sao Paulo (USP), SP (Brazil). Centro de Pesquisas Geocronologicas


    Strontium isotope data were obtained from foraminifera shells of the Pelotas Basin Tertiary deposits to facilitate the refinement of the chronostratigraphic framework of this section. This represents the first approach to the acquisition of numerical ages for these strata. Strontium isotope stratigraphy allowed the identification of eight depositional hiatuses in the Eocene-Pliocene section, here classified as disconformities and a condensed section. The reconnaissance of depositional gaps based on confident age assignments represents an important advance considering the remarkably low chronostratigraphic resolution in the Cenozoic section of the Pelotas Basin. The recognition of hiatuses that match hiatuses is based on biostratigraphic data, as well as on global events. Furthermore, a substantial increase in the sedimentation rate of the upper Miocene section was identified. Paleotemperature and productivity trends were identified based on oxygen and carbon isotope data from the Oligocene-Miocene section, which are coherent with worldwide events, indicating the environmental conditions during sedimentation. (author)

  15. Rootless tephra stratigraphy and emplacement processes

    Hamilton, Christopher W.; Fitch, Erin P.; Fagents, Sarah A.; Thordarson, Thorvaldur


    Volcanic rootless cones are the products of thermohydraulic explosions involving rapid heat transfer from active lava (fuel) to external sources of water (coolant). Rootless eruptions are attributed to molten fuel-coolant interactions (MFCIs), but previous studies have not performed systematic investigations of rootless tephrostratigraphy and grain-size distributions to establish a baseline for evaluating relationships between environmental factors, MFCI efficiency, fragmentation, and patterns of tephra dispersal. This study examines a 13.55-m-thick vertical section through an archetypal rootless tephra sequence, which includes a rhythmic succession of 28 bed pairs. Each bed pair is interpreted to be the result of a discrete explosion cycle, with fine-grained basal material emplaced dominantly as tephra fall during an energetic opening phase, followed by the deposition of coarser-grained material mainly as ballistic ejecta during a weaker coda phase. Nine additional layers are interleaved throughout the stratigraphy and are interpreted to be dilute pyroclastic density current (PDC) deposits. Overall, the stratigraphy divides into four units: unit 1 contains the largest number of sediment-rich PDC deposits, units 2 and 3 are dominated by a rhythmic succession of bed pairs, and unit 4 includes welded layers. This pattern is consistent with a general decrease in MFCI efficiency due to the depletion of locally available coolant (i.e., groundwater or wet sediments). Changing conduit/vent geometries, mixing conditions, coolant and melt temperatures, and/or coolant impurities may also have affected MFCI efficiency, but the rhythmic nature of the bed pairs implies a periodic explosion process, which can be explained by temporary increases in the water-to-lava mass ratio during cycles of groundwater recharge.

  16. Stratigraphy and Evolution of Delta Channel Deposits, Jezero Crater, Mars

    Goudge, T. A.; Mohrig, D.; Cardenas, B. T.; Hughes, C. M.; Fassett, C. I.


    The Jezero impact crater hosted an open-basin lake that was active during the valley network forming era on early Mars. This basin contains a well exposed delta deposit at the mouth of the western inlet valley. The fluvial stratigraphy of this deposit provides a record of the channels that built the delta over time. Here we describe observations of the stratigraphy of the channel deposits of the Jezero western delta to help reconstruct its evolution.

  17. 50 years of snow stratigraphy observations

    Johansson, C.; Pohjola, V.; Jonasson, C.; Challagan, T. V.


    With start in autumn 1961 the Abisko Scientific Research Station (ASRS) located in the Swedish sub Arctic has performed snow stratigraphy observations, resulting in a unique 50 year long time series of data. The data set contains grain size, snow layer hardness, grain compactness and snow layer dryness, observed every second week during the winter season. In general snow and snow cover are important factors for the global radiation budget, and the earth's climate. On a more local scale the layered snowpack creates a relatively mild microclimate for Arctic plants and animals, and it also determines the water content of the snowpack (snow water equivalent) important for e.g. hydrological applications. Analysis of the snow stratigraphy data, divided into three consecutive time periods, show that there has been a change in the last time period. The variable most affected is the snow layer hardness, which shows an increase in hardness of the snowpack. The number of observations with a very hard snow layer/ice at ground level increased three-fold between the first two time periods and the last time period. The thickness of the bottom layer in the snowpack is also highly affected. There has been a 60% increase in layers thinner than 10 cm in the last time period, resulting in a mean reduction in the thickness of the bottom layer from 14 cm to 11 cm. Hence the living conditions for plants and animals at the ground surface have been highly changed. The changes in the snowpack are correlated to an increased mean winter air temperature. Thus, continued increasing, or temperatures within the same ranges as in the last time period, is likely to create harder snow condition in the future. These changes are likely to affect animals that live under the snow such as lemmings and voles or animals that graze sub-Arctic vegetation in winter (e.g. reindeer that would potentially require increased supplementary feeding that incurs financial costs to Sami reindeer herders). Any decrease

  18. Logging Data High-Resolution Sequence Stratigraphy

    Li Hongqi; Xie Yinfu; Sun Zhongchun; Luo Xingping


    The recognition and contrast of bed sets in parasequence is difficult in terrestrial basin high-resolution sequence stratigraphy. This study puts forward new methods for the boundary identification and contrast of bed sets on the basis of manifold logging data. The formation of calcareous interbeds, shale resistivity differences and the relation of reservoir resistivity to altitude are considered on the basis of log curve morphological characteristics, core observation, cast thin section, X-ray diffraction and scanning electron microscopy. The results show that the thickness of calcareous interbeds is between 0.5 m and 2 m, increasing on weathering crusts and faults. Calcareous interbeds occur at the bottom of Reservoir resistivity increases with altitude. Calcareous interbeds may be a symbol of recognition for the boundary of bed sets and isochronous contrast bed sets, and shale resistivity differences may confirm the stack relation and connectivity of bed sets. Based on this, a high-rcsolution chronostratigraphic framework of Xi-1 segment in Shinan area, Junggar basin is presented, and the connectivity of bed sets and oil-water contact is confirmed. In this chronostratigraphic framework, the growth order, stack mode and space shape of bed sets are qualitatively and quantitatively described.

  19. Eolian event stratigraphy - A conceptual framework

    Kocurek, G.; Havholm, K.G. (Univ. of Texas, Austin (United States))


    A basis for eolian event stratigraphy is to distill the impact of events into fundamental processes and products. For accumulation (net deposit through time) to occur, the sediment budget must be positive. If the sediment budget becomes neutral or negative, accumulation ceases and a bypass or erosional super bounding surface, respectively, forms capping the genetic unit. Within the three types of eolian systems (dry, wet, stabilized), the mechanisms of accumulation and super-surface formation differ. In the dry system, accumulation occurs because of areal deceleration of sand-carrying winds. Because of dune-interdune flow conditions, accumulation begins when interdune flats are closed, requiring sand supply, time, and conditions for dune growth at the expense of interdune flats. In the wet system, accumulation of dune and interdune deposits occurs by trapping with a rising water table. Accumulations vary with the nature of the water table rise, proportion of dunes and interdune flats, and interdune topography. In the stabilized system, accumulation occurs with rapid stabilization of elements of active eolian systems; super surfaces form when the causes of stabilization cease. The eolian rock record consists of preserved accumulations and super surfaces. Accumulation space is distinct from preservation space. Preservation space is made by subsidence and water table rise. Without preservation space, an unconformity results. The dominance of subsidence versus water table rise is reflected in dry and wet accumulations respectively, such as the Jurassic Navajo and Entrada sandstones.

  20. Refining the Bengal Fan stratigraphy - A first correlation of IODP Expedition 354 results and seismic data from the Bay of Bengal

    Schwenk, Tilmann; Spiess, Volkhard; Bergmann, Fenna; France-Lanord, Christian; Klaus, Adam


    The Bengal Fan covers the floor of the entire Bay of Bengal from the continental margins of India and Bangladesh to the sediment-filled Sunda Trench off Myanmar and the Andaman Islands, and along the west side of the Ninetyeast Ridge. The deposition and progradation of the Bengal Fan started in the Eocene after the collision of India with Asia resulting in the build-up of the Himalaya and the formation of a large proto-Bay of Bengal. Continued convergence of the Indian and Australian plates with the Southeast Asian plate reduced the size of the bay and focused the source of turbidites finally into the present Bengal Basin, Bangladesh shelf, and the shelf canyon "Swatch of no Ground". Today, the Bengal Fan is mainly fed by the sediment load of the Ganges and Brahmaputra rivers, which drain the Himalayas at its southern and northern slope, respectively, and deliver their load to the delta in the Bengal Basin, to the Bengal Shelf and to the deep sea fan. Thus the Bengal Fan is a suitable recorder to study interactions among the growth of the Himalaya and Tibet, the development of the Asian monsoon, and processes affecting the carbon cycle and global climate. Because sedimentation in the Bengal Fan responds to both, climate and tectonic processes, its terrigenous sediment records the past evolution of both the Himalaya and regional climate. This evolution is also expressed in the stratigraphy of the fan in terms of unconformities and key horizons, average sedimentation rates as a function of distance from the basement ridges at 85°E and 90°E and the presence or absence of channel-levee systems. The histories of the Himalaya/Tibetan system and the Asian monsoon require sampling different periods of time with different levels of precision. Therefore IODP Expedition 354 drilled in February-March 2015 a seven site, 320 km-long transect across the Bengal Fan at 8°N. This strategy has been chosen because sediment transport took place by turbidity currents following

  1. Basin deconstruction-construction: Seeking thermal-tectonic consistency through the integration of geochemical thermal indicators and seismic fault mechanical stratigraphy ​- Example from Faras Field, North Western Desert, Egypt

    Pigott, John D.; Abouelresh, Mohamed O.


    To construct a model of a sedimentary basin's thermal tectonic history is first to deconstruct it: taking apart its geological elements, searching for its initial conditions, and then to reassemble the elements in the temporal order that the basin is assumed to have evolved. Two inherent difficulties implicit to the analysis are that most organic thermal indicators are cumulative, irreversible and a function of both temperature and time and the non-uniqueness of crustal strain histories which complicates tectonic interpretations. If the initial conditions (e.g. starting maturity of the reactants and initial crustal temperature) can be specified and the boundary conditions incrementally designated from changes in the lithospheric heat engine owing to stratigraphic structural constraints, then the number of pathways for the temporal evolution of a basin is greatly reduced. For this investigation, model input uncertainties are reduced through seeking a solution that iteratively integrates the geologically constrained tectonic subsidence, geochemically constrained thermal indicators, and geophysically constrained fault mechanical stratigraphy. The Faras oilfield in the Abu Gharadig Basin, North Western Desert, Egypt, provides an investigative example of such a basin's deconstructive procedure. Multiple episodes of crustal extension and shortening are apparent in the tectonic subsidence analyses which are constrained from the fault mechanical stratigraphy interpreted from reflection seismic profiles. The model was iterated with different thermal boundary conditions until outputs best fit the geochemical observations. In so doing, the thermal iterations demonstrate that general relationship that basin heat flow increases decrease vertical model maturity gradients, increases in surface temperatures shift vertical maturity gradients linearly to higher values, increases in sediment conductivities lower vertical maturities with depth, and the addition of "ghost" layers

  2. Workshop on quantitative dynamic stratigraphy. Final conference report

    Cross, T.A.


    This document discusses the development of quantitative simulation models for the investigation of geologic systems. The selection of variables, model verification, evaluation, and future directions in quantitative dynamic stratigraphy (QDS) models are detailed. Interdisciplinary applications, integration, implementation, and transfer of QDS are also discussed. (FI)

  3. Sino-German Cooperation on Stratigraphy, Vegetation and Climatic Development

    Sun Ge; Volker Mosbrugger


    @@ The research project between the Nanjing Institute of Geology and Paleontology, CAS (NIGPAS), the Research Center of Paleontology, Jilin University, the Geological Survey No.1, Xinjiang and the Institute of Geology, University of Tübingen deals with the Mesozoic biota and stratigraphy of the Junggar Basin, located in the Xinjiang Autonomous Uygur Region in Northwest China.

  4. Stratigraphy of the type Maastrichtian – a synthesis

    Jagt, J.W.M.; Jagt-Yazykova, E.A.


    A synthesis of the stratigraphy of the Maastrichtian Stage in its extended type area, that is, southern Limburg (the Netherlands), and adjacent Belgian and German territories, is presented with a brief historical overview. Quarrying activities at the large quarry complex of ENCI-HeidelbergCement

  5. Late Carboniferous to Late Permian carbon isotope stratigraphy

    Buggisch, Werner; Krainer, Karl; Schaffhauser, Maria


    An integrated study of the litho-, bio-, and isotope stratigraphy of carbonates in the Southern Alps was undertaken in order to better constrain δ13C variations during the Late Carboniferous to Late Permian. The presented high resolution isotope curves are based on 1299 δ13Ccarb and 396 δ13Corg a...

  6. Reading and Abstracting Journal Articles in Sedimentology and Stratigraphy.

    Conrad, Susan Howes


    An assignment centered on reading journal articles and writing abstracts is an effective way to improve student reading and writing skills in sedimentology and stratigraphy laboratories. Each student reads two articles and writes informative abstracts from the author's point of view. (PR)

  7. Stratigraphy of the type Maastrichtian – a synthesis

    Jagt, J.W.M.; Jagt-Yazykova, E.A.


    A synthesis of the stratigraphy of the Maastrichtian Stage in its extended type area, that is, southern Limburg (the Netherlands), and adjacent Belgian and German territories, is presented with a brief historical overview. Quarrying activities at the large quarry complex of ENCI-HeidelbergCement Gro

  8. Stratigraphy of the type Maastrichtian – a synthesis

    Jagt, J.W.M.; Jagt-Yazykova, E.A.


    A synthesis of the stratigraphy of the Maastrichtian Stage in its extended type area, that is, southern Limburg (the Netherlands), and adjacent Belgian and German territories, is presented with a brief historical overview. Quarrying activities at the large quarry complex of ENCI-HeidelbergCement Gro

  9. West Antarctic Ice Sheet Grounding-Line Positions in the Whales Deep Paleo-Ice-Stream Trough of Eastern Ross Sea Inferred From New Multibeam bBathymetry and Seismic Stratigraphy

    Bart, P. J.; DeCesare, M.; McGlannan, A. J.; Krogmeier, B.; Danielson, M.


    Regional dip-oriented seismic lines and a large-area (2500 km2) multibeam bathymetric survey were acquired during expedition NBP1502B in the Whales Deep paleo-ice-stream trough of eastern Ross Sea. This outer-shelf trough is the downstream continuation of the Bindschadler Ice Stream. The new data provide a more detailed 3D view of the time-transgressive erosional and depositional seafloor features formed during West Antarctic Ice Sheet (WAIS) advance and retreat than was possible to reconstruct with previous reconnaissance-level multibeam and seismic data. The multibeam survey also provides the opportunity to conduct a more detailed analysis of core sedimentology and stratigraphy (McGlannan et al.) that can ultimately be used to investigate grounding-event chronology (DeCesare et al.). The geophysical data show that the WAIS occupied at least four grounding-line positions as it retreated 40 km from the shelf edge to the middle shelf. After the fourth grounding event at the middle shelf, grounded ice retreated abruptly by >200 km to an area/zone south of the modern calving front - where it may have pinned at Roosevelt Island.

  10. East Greenland Caledonides: stratigraphy, structure and geochronology: Lower Palaeozoic stratigraphy of the East Greenland Caledonides

    Smith, M. Paul


    Full Text Available The Lower Palaeozoic stratigraphy of the East Greenland Caledonides, from the fjord region of North-East Greenland northwards to Kronprins Christian Land, is reviewed and a number of new lithostratigraphical units are proposed. The Slottet Formation (new is a Lower Cambrian quartzite unit, containing Skolithos burrows, that is present in the Målebjerg and Eleonore Sø tectonic windows, in the nunatak region of North-East Greenland. The unit is the source of common and often-reported glacial erratic boulders containing Skolithos that are distributed throughout the fjord region. The Målebjerg Formation (new overlies the Slottet Formation in the tectonic windows, and comprises limestones and dolostones of assumed Cambrian–Ordovician age. The Lower Palaeozoic succession of the fjord region of East Greenland (dominantly limestones and dolostones is formally placed in the Kong Oscar Fjord Group (new. Amendments are proposed for several existing units in the Kronprins Christian Land and Lambert Land areas, where they occur in autochthonous, parautochthonous and allochthonous settings.

  11. Absolute chronology and stratigraphy of Lepenski Vir

    Borić Dušan


    radiometric dates from Lepenski Vir 21 made by the conventional 14C dating of charcoal and 8 AMS dates made on animal (3 dates and human bones (5 dates. There is also a series of 20 new AMS dates made on human bones from Lepenski Vir. The last group of dates has not been published with all the contextual details and are of limited use in our analyses of absolute chronology and stratigraphy of Lepenski Vir. New dates are listed in Table 1. From 32 dated contexts from Lepenski Vir, 27 contexts are stratigraphically related to trapezoidal buildings while 5 dates are connected with the area outside of buildings. From those contexts related to trapezoidal structures, 24 contexts are dated with animal and 3 with human bones. The emphasis on the dating of animal bones is connected with problems of precision when dating samples made on human and dog bones due to the reservoir effect and the deposition of 'old' carbon. Dated remains of animal and human bones originate from the following types of stratigraphic contexts a beneath building floors, i.e. stratigraphically the oldest contexts in the settlement (2 dates (Fig. 2; b between two superposed floors of trapezoidal buildings as 'sealed' contexts (8 dates (Fig. 3; c lying directly on top of the floors of trapezoidal buildings but not overlapped by a later floor (17 dates (Fig. 3; d outside of trapezoidal buildings, found in contexts such as pits, domed ovens, and burials, or in contexts that can be attributed to the occupation layer only (6 dates (Fig. 4. The new dates indicate a very long duration of the Mesolithic period, from around 9400 to around 7500 cal BC (Fig. 2, 23. These early dates are concentrated in two particular periods that may point to two separate phases within these two millennia, with settlement discontinuities. It remains possible that there were many more occupation episodes that these dates do not encompass, and more AMS dates may indicate whether these two groupings with three dates per grouping are

  12. Sequence stratigraphy of the Orange basin, western offshore South Africa

    Muntingh, A. (SOEKOR Ltd., Parow (South Africa))


    A seismic/sequence-stratigraphic framework for the siliciclastic fluvial to deepwater Cretaceous strata of the Orange basin has been constructed. Sequence-stratigraphic concepts developed by Exxon were used to interpret 10,000 km of seismic data and logs from 31 exploration boreholes within an area of 90,000 km{sup 2}. The sequence stratigraphy of the western margin exhibits 34 cyclical depositional sequences interpreted to document the response of the passive margin to cyclical changes in relative sea-level from Mid-Aptian to Late Maastrichtian times. All but one of the sequence boundaries are type 1 unconformities displaying intense erosion on the shelf and interpreted to develop during periods of rapid fall in relative sea-level. Basin-wide sequence boundaries (type 1 and 2 unconformities) were correlated with the third-order cycles of Exxon's global cycle chart utilizing SOEKOR's paleontological dating of a limited number of marine condensed sections. Higher-order cycles are recognized and best developed along the flanks of the structural arches where lower subsidence rates permitted impact of higher frequency cycles. Component depositional systems tracts inferred to have resulted from changes in relative sea level were interpreted and paleogeographic maps were constructed outlining incised valley systems on the shelf, shelf edge canyons, prograding wedges, basin floor fan, and slope fan systems. Distal marine shales and marine condensed sections provide both seal and hydrocarbon source. The chronostratigraphic and depositional framework being used to predict prospective play areas for hydrocarbon exploration on the western offshore of South Africa is also applicable to the Namibian offshore.

  13. Chicxulub Post-Impact Sedimentary Sequence: Integrated Borehole Paleogene Carbonate Stratigraphy

    Fucugauchi, J. U.; Perez-Cruz, L. L.; Escobar-Sanchez, E.; Ortega-Nieto, A.; Velasco-Villarreal, M.


    terrestrial, marine and aerogeophysical surveys. We use the marine seismic sections for correlation of the geophysical logs and borehole stratigraphy, allowing lateral correlation across the crater and further constraining the sequence stratigraphy, platform evolution and impact effects.

  14. Ordered hierarchy versus scale invariance in sequence stratigraphy

    Schlager, Wolfgang


    Sequence stratigraphy has been applied in a wide range of scales of time and space, from decimeter-thick layers formed within hours to kilometer-thick basin fills formed during hundreds of millions of years. The traditional approach to practice sequence stratigraphy in this wide range of scales is to subdivide the sediment piles into an ordered hierarchy of sequence cycles of different duration and different architecture. An alternative are scale-invariant models with fractal characteristics. Published data confirm two predictions of the ordered-hierarchy model: sequences of very short duration (200 × 106 years) are symmetrical transgressive-regressive cycles. However, the sequence record in the range of 1 × 104-200 × 106 years, the principal domain of sequence stratigraphy, shows a rather irregular succession of sequences with variable symmetry and bounded by flooding surfaces or exposure surfaces. For these time scales, scale-invariant models are a good first approximation, particularly because the evidence for scale-invariance and randomness in the stratigraphic record is strong: Frequency spectra of sea-level change as well as rates of sedimentation and rates of accommodation change plotted against length of observation span show basic trends indistinguishable from random walk. These trends, combined with scale-invariant sequence models may be the most efficient tools for across-the-board predictions on sequences and for locating islands of order in the sequence record.

  15. Division of high resolution sequence stratigraphy units with wavelet transform of logs in Dagang Oilfield


    Division of high resolution sequence stratigraphy units based on wavelet transform of logging data is found to be good at identifying subtle cycles of geological process in Kongnan area of Dagang Oilfield. The analysis of multi-scales gyre of formation with 1-D continuous Dmey wavelet transform of log curve (GR) and 1-D discrete Daubechies wavelet transform of log curve (Rt) all make the division of sequence interfaces more objective and precise, which avoids the artificial influence with core analysis and the uncertainty with seismic data and core analysis.

  16. Studies in stratology: the physics of stratigraphy

    Thorne, J.A.


    In this study the author infers the nature of thermo-mechanical processes of basin evolution and, secondarily, eustatic sea-level changes from study of borehole stratigraphic logs and regional seismic sections in the North Sea basin, and the Baltimore Canyon trough. Through nature numerical modelling, it is shown that the combination of thermal contraction of the lithosphere, flexure and slowly varying global changes in sea-level can account for the overall stratigraphic features of the U.S. Atlantic continental margin which include tectonically-controlled Jurassic onlap and eustatitically controlled onlap and offlap in the Tertiary. The modeling results indicate: (1) during times of minimal continental ice cover changes in relative rate of sea-level are generally sufficient to cause unconformities, except in old, slowly subsiding margins; (2) seismic and biostratigraphic resolution is commonly too poor to identify sequences bounded by short-lived uncomformities (less than 5-10 my); (3) sequence boundaries should be best defined on margin slopes or in regions of active tectonic tilting. A variety of stratigraphic and geophysical maps of the North Sea basin are used: (1) tectonic subsidence for 10 time/stratigraphic units: (2) predicted and observed sediment overpressure; (3) geographic variation of compaction parameters; (4) fault extension; (5) salt movement; (6) free-air gravity; (7) heat flow and (8) predicted and observed oil maturation. Quantitative analysis of the first of these, tectonic subsidence, provides a means of determining the basin flexural rigidity through time, acceleration and deceleration of subsidence, and the development and reactivation of basin structural trends. Appendices include an extensive Fortran code for quantitative basin modelling.

  17. Continental margin sedimentation: from sediment transport to sequence stratigraphy

    Nittrouer, Charles A.; Austin, James A.; Field, Michael E.; Kravitz, Joseph H.; Syvitski, James P.M.; Wiberg, Patricia L.; Nittrouer, Charles A.; Austin, James A.; Field, Michael E.; Kravitz, Joseph H.; Syvitski, James P. M.; Wiberg, Patricia L.


    This volume on continental margin sedimentation brings together an expert editorial and contributor team to create a state-of-the-art resource. Taking a global perspective, the book spans a range of timescales and content, ranging from how oceans transport particles, to how thick rock sequences are formed on continental margins. - Summarizes and integrates our understanding of sedimentary processes and strata associated with fluvial dispersal systems on continental shelves and slopes - Explores timescales ranging from particle transport at one extreme, to deep burial at the other - Insights are presented for margins in general, and with focus on a tectonically active margin (northern California) and a passive margin (New Jersey), enabling detailed examination of the intricate relationships between a wide suite of sedimentary processes and their preserved stratigraphy - Includes observational studies which document the processes and strata found on particular margins, in addition to numerical models and laboratory experimentation, which provide a quantitative basis for extrapolation in time and space of insights about continental-margin sedimentation - Provides a research resource for scientists studying modern and ancient margins, and an educational text for advanced students in sedimentology and stratigraphy

  18. The structure and stratigraphy of the sedimentary succession in the Swedish sector of the Baltic Basin: New insights from vintage 2D marine seismic data

    Sopher, Daniel; Erlström, Mikael; Bell, Nicholas; Juhlin, Christopher


    We present five interpreted regional seismic profiles, describing the full sedimentary sequence across the Swedish sector of the Baltic Sea. The data for the study are part of an extensive and largely unpublished 2D seismic dataset acquired between 1970 and 1990 by the Swedish Oil Prospecting Company (OPAB). The Baltic Basin is an intracratonic basin located in northern Europe. Most of the Swedish sector of the basin constitutes the NW flank of a broad synclinal depression, the Baltic Basin. In the SW of the Swedish sector lies the Hanö Bay Basin, formed by subsidence associated with inversion of the Tornquist Zone during the Late Cretaceous. The geological history presented here is broadly consistent with previously published works. We observe an area between the Hanö Bay and the Baltic Basin where the Palaeozoic strata has been affected by transpression and subsequent inversion, associated with the Tornquist Zone during the late Carboniferous-Early Permian and Late Cretaceous, respectively. We propose that the Christiansø High was a structural low during the Late Jurassic, which was later inverted in the Late Cretaceous. We suggest that a fan shaped feature in the seismic data, adjacent to the Christiansø Fault within the Hanö Bay Basin, represents rapidly deposited, coarse-grained sediments eroded from the inverted Christiansø High during the Late Cretaceous. We identify a number of faults within the deeper part of the Baltic Basin, which we also interpret to be transpressional in nature, formed during the Caledonian Orogeny in the Late Silurian-Early Devonian. East of Gotland a number of sedimentary structures consisting of Silurian carbonate reefs and Ordovician carbonate mounds, as well as a large Quaternary glacial feature are observed. Finally, we use the seismic interpretation to infer the structural and stratigraphic history of the Baltic and Hanö Bay basins within the Swedish sector.

  19. Near coast sedimentary stratigraphy as a proxy for climatic instability

    McLivenny, J.


    Several studies have indicated a link between climatic deterioration and dune stability (Wilson 2002, Issar 2003, Dawson et al 2004). The frequency and magnitude of storms have been cited as a key variable in the stability of large dune systems. For the stratigraphy of dune systems to act as a regional climatic proxy there must be a good regional relationship between known climatic events and regionally correlated stratigraphic changes. Dunnet Bay in Caithness, Northern Scotland was chosen as a study site to look at the relationship between dune stability and climatic change during the late Holocene in Northern Scotland. Dunnet Bay was chosen for its physical attributes which make it an excellent natural sediment trap. Tucked in between headlands which act as barriers to long-shore transport the predominant movement of sediment there is straight onshore, with only minor amounts being lost to the sea. The immediate back-dune stratigraphy, colloquially known as "links", provided evidence of peat formation and dune stability. Stratigraphy was mapped using traditional field techniques and ground penetrating radar. The cores consisted mostly of massive layers of sand interleaved with peat. Sand layers were dated with optically stimulated luminescence (OSL) and interpreted as reflecting high wind energy regimes transporting sand inland. Peat layers were C14 dated and taken as representing climatic stability. Stratigraphy was mapped using hand auguring, percussion coring, and open sections. Ground penetrating radar was also used to look at the continuity of key layers. OSL dating in two open sections showed dates obtained from the first section (1790 AD ±70, 53 BC ± 100, 300 BC ± 100, 400 BC ± 100) mapped to the top of the second section (1800 AD ± 100, 1500 BC ± 200, 2900 BC ± 300) which was consistent with stratigraphy increasing sediment thickness towards the centre of the bay. The results were consistent with acquired C14 dates from selected peat layers. Taken

  20. Sequence stratigraphy as a scientific enterprise: the evolution and persistence of conflicting paradigms

    Miall, Andrew D.; Miall, Charlene E.


    In the 1970s, seismic stratigraphy represented a new paradigm in geological thought. The development of new techniques for analyzing seismic-reflection data constituted a "crisis," as conceptualized by T.S. Kuhn, and stimulated a revolution in stratigraphy. We analyze here a specific subset of the new ideas, that pertaining to the concept of global-eustasy and the global cycle chart published by Vail et al. [Vail, P.R., Mitchum, R.M., Jr., Todd, R.G., Widmier, J.M., Thompson, S., III, Sangree, J.B., Bubb, J.N., Hatlelid, W.G., 1977. Seismic stratigraphy and global changes of sea-level. In: Payton, C.E. (Ed.), Seismic Stratigraphy—Applications to Hydrocarbon Exploration, Am. Assoc. Pet. Geol. Mem. 26, pp. 49-212.] The global-eustasy model posed two challenges to the "normal science" of stratigraphy then underway: (1) that sequence stratigraphy, as exemplified by the global cycle chart, constitutes a superior standard of geologic time to that assembled from conventional chronostratigraphic evidence, and (2) that stratigraphic processes are dominated by the effects of eustasy, to the exclusion of other allogenic mechanisms, including tectonism. While many stratigraphers now doubt the universal validity of the model of global-eustasy, what we term the global-eustasy paradigm, a group of sequence researchers led by Vail still adheres to it, and the two conceptual approaches have evolved into two conflicting paradigms. Those who assert that there are multiple processes generating stratigraphic sequences (possibly including eustatic processes) are adherents of what we term the complexity paradigm. Followers of this paradigm argue that tests of the global cycle chart amount to little more than circular reasoning. A new body of work documenting the European sequence record was published in 1998 by de Graciansky et al. These workers largely follow the global-eustasy paradigm. Citation and textual analysis of this work indicates that they have not responded to any of the




    Full Text Available The objective of this work is to analyze the Miocene depositional units of the southern side of the Volterra Basin (Tuscany, Italy utilizing outcrop and seismic data and to establish the major events that led to their formation. Four depositional units have been recognized: Unit 1 is characterized by marine sediments of late Serravallian-early Tortonian age; Unit 2 is characterized by fluvio-lacustrine and brackish deposits of late Tortonian-early Messinian age; Unit 3 is characterized by marine deposits of early Messinian age; Unit 4 is characterized by the lacustrine deposits ("Lago-mare" facies of late Messinian age. The deposition of these four units is associated with an extensional tectonic regime that has been active in Tuscany since the late Tortonian. This regime generated half graben type structures in which deposition occurred. The recognized unconformities between the units are mainly related to uplift as a consequence of the extensional tectonic regime.    

  2. A study of the distribution, structure and seismic stratigraphy of syn-breakup and post-breakup sediments in the Faroe sector of the Faroe-Shetland Basin

    Olavsdottir, Jana

    Emplacement of the Cenozoic sediments in the Faroese sector of the Faroe-Shetland Basin appear to be controlled by decelerating thermal subsidence of the basin, and local uplift of sediment source areas. However, the actual distribution of sediments appears to be controlled by re-activation of ol......Emplacement of the Cenozoic sediments in the Faroese sector of the Faroe-Shetland Basin appear to be controlled by decelerating thermal subsidence of the basin, and local uplift of sediment source areas. However, the actual distribution of sediments appears to be controlled by re...... is a potential tool understanding deviations from “normal” thermal subsidence and for predicting the prospectivity in syn- and post-rift succession in the Faroe-Shetland Basin. On top of the basalt in the Faroe-Shetland Basin there is deposited up to 3.5 km thick sedimentary package, which led into the basin...... from different directions. With interpretations of 2-D and 3-D reflection seismic data of the post-basalt package it is shown which adjacent areas the various sub-sedimentary packages comes from and where they are located in the basin at specific time intervals. The adjacent areas to the Faroe-Shetland...

  3. Hyperspectral Analysis of Paleoseismic Trench Stratigraphy: Toward Improving the Recognition and Documentation of Past Earthquakes

    Ragona, D. E.; Minster, B.; Fialko, Y.; Rockwell, T.


    We are conducting a pilot project to use hyperspectral imagery to assist in the recognition and documentation of paleoseismic events in trench exposures. Recent advances in hyperspectral imagery suggest that stratigraphy can be analyzed in much the same way as Aviris imagery of Earth's surface. In principle, hyperspectral images may be able to elucidate and record otherwise-poor stratigraphy in some exposures, thereby improving the information that can be gleaned from a paleoseismic site. This technique may also eliminate some problems in interpretation of the earthquake history of a site by illuminating details of the stratigraphy and structure that are not apparent to the human eye, such as unique unit correlations across complicated fault ruptures. The trench site chosen for this study is located at Hog Lake in the Anza seismic gap along the San Jacinto Fault in southern California. The site was selected because of its detailed, well defined stratigraphy. The method adopted was to obtain a 50 cm side square matrix of samples that could be used to generate a low-resolution image of the sampled area, in the sense that each sample represents a single pixel. The samples were collected 2.5 cm apart in a square matrix of 20x20 samples. Each of the 400 samples collected are stored into PVC or metallic cylinders of 3/4" or 1/2" diameter. All samples were spectrally analyzed at JPL using a FieldSpec Pro instrument that measure radiation in the 350-2,500 nm wavelength window. Five measurements of each sample were performed, along with measurements of the radiation reflected by a reference surface (Spectralon), under natural light and clear sky conditions. The data obtained was then processed to obtain reflectance spectra for all samples. Principal Component Analysis was used to create a pixilated image from the three dominant components. That image shows promising similarity with the standard digital picture of the sampled trench wall. However, large random measurement

  4. Late Eocene impact microspherules - Stratigraphy, age and geochemistry

    Keller, G.; D'Hondt, S. L.; Orth, C. J.; Gilmore, J. S.; Oliver, P. Q.; Shoemaker, E. M.; Molina, E.


    The stratigraphy, faunal changes, and geochemistry of deep-sea sediments associated with late Eocene microtektite and microspherule layers are reported. Microprobe analyses of major element compositions of microspherules show that, although there is some compositional overlap in all three late Eocene layers as well as with the Pleistocene Australasian and Ivory Coast microtektites, each microspherule population has characteristic compositional features. All three microspherule layers are associated with decreased carbonate, possibly due to a sudden productivity change, increased dissolution as a result of sea-level and climate fluctuations, or impact events. A discovery of microtektites in the Gl. cerroazulensis Zone off the New Jersey coast extends the North American strewn field from the Caribbean to the northwest Atlantic.

  5. Sediment Flux from Stratigraphy: Insights from 300 Ma Sedimentary Archives

    Romans, B.; Mason, C. C.; Eriksson, K. A.


    Tectonic or climate signals that originate in net-erosional catchments are transmitted down-system as sediment. The accumulation of that sediment in net-depositional regions and preservation as stratigraphy can be accessed and used to reconstruct signal generation and propagation. Studies of modern to millennial rates in deep-time sedimentary archives do not yet exist. Here, we use the extraordinary tidal rhythmite deposits of the Pride Shale in the Appalachian Basin as a high-resolution chronometer to constrain the duration of basin filling. We then use the scale of fluvial channel bodies in the underlying and overlying units combined with climate-specific empirical relationships derived from modern systems to estimate the size of the paleo-catchment. The resultant estimates of sediment yield allow calculation of denudation rates for a system in which the catchment has long-since eroded.

  6. Evolution of a high-latitude sediment drift inside a glacially-carved trough based on high-resolution seismic stratigraphy (Kveithola, NW Barents Sea)

    Rebesco, Michele; Özmaral, Asli; Urgeles, Roger; Accettella, Daniela; Lucchi, Renata G.; Rüther, Denise; Winsborrow, Monica; Llopart, Jaume; Caburlotto, Andrea; Lantzsch, Hendrik; Hanebuth, Till J. J.


    Kveithola is a glacially-carved, E-W trending trough located in the NW Barents Sea, an epicontinental shelf sea of the Arctic Ocean located off northern Norway and Russia. A set of confined sediment drifts (the "Kveithola Drift") is located in the inner part of the trough. In general, drift deposits are commonly characterized by high lateral continuity, restricted occurrence of hiatuses and relatively high accumulation rates, and thus represent excellent repositories of paleo-environmental information. We provide for the first time a detailed morphological and seismostratigraphic insight into this sediment drift, which is further supported by some preliminary lithological and sedimentological analyses. The complex morphology of the drift, imaged by combining all available multibeam data, includes a main and a minor drift body, two drift lenses in the outer part of the trough, more or less connected drift patches in the innermost part and small perched sediment patches in a structurally-controlled channel to the north. The seismic (PARASOUND) data show that the main and minor drift bodies are mainly well-stratified, characterized by sub-parallel reflections of moderate to high amplitude and good lateral continuity. The reflectors show an abrupt pinch-out on the northern edge where a distinct moat is present, and a gradual tapering to the south. Internally we identify the base of the drift and four internal horizons, which we correlate throughout the drift. Two units display high amplitude reflectors, marked lensoidal character and restricted lateral extent, suggesting the occurrence of more energetic sedimentary conditions. Facies typical for contourite deposition are found in the sediment cores, with strongly bioturbated sediments and abundant silty/sandy mottles that contain shell fragments. These characteristics, along with the morphological and seismic information, suggest a strong control by a bottom current flowing along the moat on the northern edge of the

  7. Structure and Stratigraphy of the Rift Basins in the Northern Gulf of California: Results from Analysis of Seismic Reflection and Borehole Data.

    Martín, A.; González, M.; Helenes, J.; García, J.; Aragón, M.; Carreño, A.


    The northern Gulf of California contains two parallel, north-south trending rift basin systems separated by a basement-high. The interpretation of several exploration wells, and ~4500 km of seismic reflection data from PEMEX (Mexican national oil company) indicate that the tectonically active basins to the west (Wagner- Consag and Upper Delfin basins) may have initiated synchronously with the now abandoned Tiburón- Tepoca-Altar basins to the east in the Sonora margin. In both basin systems the lower sequence (A) is marine mudstone-siltstone, has parallel reflectors and a largely uniform thickness that reaches up to1.5 km, and gradually pinches out toward the lateral margins. This suggests that the unit was deposited prior to their segmentation by transtensional faulting. Marine microfossils from borehole samples from sequence A in the Tiburón and Consag basins indicates middle Miocene (>11.2 Ma) proto-Gulf conditions. Sequence B conformably overlies sequence A, and is characterized by up to 2 km growth strata with a fanning geometry that show a clear genetic relationship to the major transtensional faults that control the segmentation of the two basin systems. Sequence C in the Tiburón and Tepoca basins is comparatively thin (<800 m) and includes several unconformities, but is much less affected by faulting. In contrast, sequence C in the active Wagner, Consag and Upper Delfin basin is a much thicker (up to 2 km) growth sequence with abundant volcanic intrusions. Marked variations in sequence C in the different basin systems clearly demonstrate a major westward shift of deformation and subsidence at this time. The modern depocenter in Wagner-Consag basins is controlled by the Consag and Wagner faults, which trend parallel to the north ~20 km apart, and show opposite normal offset. These two faults merge at an oblique angle (70°-50°, respectively) into the Cerro Prieto transform fault to the north and likely accommodate an important amount of dextral shear. To

  8. Pyloniid stratigraphy - A new tool to date tropical radiolarian ooze from the central tropical Indian Ocean

    Gupta, S.M.

    of 25 modern radiolarian groups in surface sediments and monsoonal surface salinity from the central Indian Ocean is analyzed. Among them, Pyloniids exhibit the potential to serve in the same way as the C. davisiana stratigraphy. Down-core (temporal...

  9. Carboniferous-Permian sedimentology and stratigraphy of the Nordfjorden High and Loppa Spur, Arctic Norway

    Ahlborn, Morten

    Abstract (shortened) Facies analysis of Late Paleozoic warm-water carbonates, were conducted in order to investigate the depositional evolution, cyclicity, internal architecture and sequence stratigraphy of the upper Gipsdalen Group carbonate platform on the Nordfjorden High in central Spitsberge...

  10. The INTIMATE event stratigraphy and recommendations for its use

    Rasmussen, Sune O.


    The North Atlantic INTIMATE (INtegration of Ice-core, MArine and TErrestrial records) group has previously recommended an Event Stratigraphy approach for the synchronisation of records of the Last Termination using the Greenland ice core records as the regional stratotypes. A key element of these protocols has been the formal definition of numbered Greenland Stadials (GS) and Greenland Interstadials (GI) within the past glacial period as the Greenland expressions of the characteristic Dansgaard-Oeschger events that represent cold and warm phases of the North Atlantic region, respectively. Using a recent synchronization of the NGRIP, GRIP, and GISP2 ice cores that allows the parallel analysis of all three records on a common time scale, we here present an extension of the GS/GI stratigraphic template to the entire glacial period. In addition to the well-known sequence of Dansgaard-Oeschger events that were first defined and numbered in the ice core records more than two decades ago, a number of short-lived climatic oscillations have been identified in the three synchronized records. Some of these events have been observed in other studies, but we here propose a consistent scheme for discriminating and naming all the significant climatic events of the last glacial period that are represented in the Greenland ice cores. In addition to presenting the updated event stratigraphy, we make a series of recommendations on how to refer to these periods in a way that promotes unambiguous comparison and correlation between different proxy records, providing a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations. The work presented is a part of a manuscript under review for publication in Quaternary Science Reviews. Author team: S.O. Rasmussen, M. Bigler, S.P.E. Blockley, T. Blunier, S.L. Buchardt, H.B. Clausen, I. Cvijanovic, D. Dahl-Jensen, S.J. Johnsen, H. Fischer, V. Gkinis, M. Guillevic, W.Z. Hoek, J.J. Lowe, J. Pedro, T

  11. CRISM Analyses of Noachian Stratigraphy in Argyre Basin

    Buczkowski, D.; Murchie, S.; Seelos, F.; Malaret, E.; Hash, C.; CRISM Team


    The Argyre basin is a >1500 km, well preserved impact basin in the southern highlands of Mars and the geologic units associated with the basin are mostly Noachian in age (Scott and Tanaka, 1986). Thus, Argyre is an ideal location to characterize the stratigraphy of ancient highland rocks. We analyzed 72-channel CRISM multispectral data that had been map projected to 256 ppd into 40 5-degree map tiles. The data were corrected for illumination by dividing by the cosine of the solar incidence angle. A multiplicative correction for atmospheric gas absorption was applied (Bibring et al., 2005). Spectrally distinct regions were identified by calculating summary parameters (Pelkey et al., 2007); spectra of key areas were examined in detail. A scarp is roughly associated with a contact between the Hpl3 and Npld units in NW Argyre. At the top of the scarp (unit Hpl3) CRISM has detected an olivine signature associated with a depression. Phyllosilicates have been identified extending laterally along the scarp, related to unit Npld (dissected impact breccias). Below the phyllosilicates are found deposits of high-Ca pyroxene hugging scarps in unit Npld. High-Ca pyroxene is also identified in unit Npl1 (undissected impact breccias), at the same stratigraphic level of the Npld pyroxenes. A high-standing knob in Npl1 has a phyllosilicate signature. CRISM investigations also support previous studies by OMEGA, which identified olivine and pyroxene in north Argyre (Gondet et al., 2007). A correlation appears between the low-Ca pyroxene/olivine exposures and the hills of unit Nplh, the oldest geologic unit in Argyre interpreted as uplifted by tectonism during the formation of the impact basin (Scott and Tanaka, 1986). We suggest that as a group these deposits reveal the stratigraphy of the Noachian crust in this region. At the bottom of the stratigraphic column are olivine and low-Ca pyroxene associated with uplifted ancient rocks (unit Nplh). Above these deposits are high

  12. Applied Sequence Stratigraphy in Nonmarine Basin of China


    This paper presents a preliminary summary of the applied sequence stratigraphy in nonmarine basins in China. The geological and geophysical data show that the nonmarine sequences mainly resulted from both allocyclic and autocyclic processes where the most important factors were isolated tectonics and climate. However, the environmental factor should have been crucial. The depositionai base level served as the sea level in the marine environment, while the water table, lake level and fluvial equilibrium were profiled in a terrigenous environment. This accommodation varied periodically with the base level, resulting in the formation of a series of depositional sequences in terms of genesis and space. Basically, the base level of the inner continent was not affected by the changes in the relative sea level. But there would have been some relations between the changes in the relative sea level and that in the continental base level during eustacy flooding. However, a small time lag existed between the changes in the marine basin and the inner continent basin, The lake basin is smaller than the marine basin,but its velocity of sediment supply is greater than that of the marine basin. Therefore, the number of nonmarine sequences is greater than that of marine ones in the same period. It is important to recognize the system tracts for the study of high-precision or high-resolution sequence stratigraphy, especially to analyze the Iow-stand systems tract with its depositional system. The sequence boundary is genetically characterized by subaerial exposure, stratigraphic truncation and subaqueous erosion. The deposition analysis of Zhanhua depression reveals 5 sequence architectures: alluvial-fluvial/lacustrine architecture,transitional architecture formed between haline (mesohaline) lake and fresh lake, marine duration-deep lacustrine architecture, half deep lacustrine-ramp architecture and fluvial-alluvial plain architecture.During the major development of the nonmarine

  13. cyclostratigraphy, sequence stratigraphy and organic matter accumulation mechanism

    Cong, F.; Li, J.


    The first member of Maokou Formation of Sichuan basin is composed of well preserved carbonate ramp couplets of limestone and marlstone/shale. It acts as one of the potential shale gas source rock, and is suitable for time-series analysis. We conducted time-series analysis to identify high-frequency sequences, reconstruct high-resolution sedimentation rate, estimate detailed primary productivity for the first time in the study intervals and discuss organic matter accumulation mechanism of source rock under sequence stratigraphic framework.Using the theory of cyclostratigraphy and sequence stratigraphy, the high-frequency sequences of one outcrop profile and one drilling well are identified. Two third-order sequences and eight fourth-order sequences are distinguished on outcrop profile based on the cycle stacking patterns. For drilling well, sequence boundary and four system tracts is distinguished by "integrated prediction error filter analysis" (INPEFA) of Gamma-ray logging data, and eight fourth-order sequences is identified by 405ka long eccentricity curve in depth domain which is quantified and filtered by integrated analysis of MTM spectral analysis, evolutive harmonic analysis (EHA), evolutive average spectral misfit (eASM) and band-pass filtering. It suggests that high-frequency sequences correlate well with Milankovitch orbital signals recorded in sediments, and it is applicable to use cyclostratigraphy theory in dividing high-frequency(4-6 orders) sequence stratigraphy.High-resolution sedimentation rate is reconstructed through the study interval by tracking the highly statistically significant short eccentricity component (123ka) revealed by EHA. Based on sedimentation rate, measured TOC and density data, the burial flux, delivery flux and primary productivity of organic carbon was estimated. By integrating redox proxies, we can discuss the controls on organic matter accumulation by primary production and preservation under the high-resolution sequence

  14. Contribution to the stratigraphy of the onshore Paraiba Basin, Brazil

    Rossetti, Dilce F.; Valeriano, Marcio M., E-mail: [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Divisao de Sensoriamento Remoto; Goes, Ana M.; Brito-Neves, Benjamim B. [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Inst. de Geociencias; Bezerra, Francisco H.R.; Ochoa, Felipe L. [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Centro de Ciencias Exatas e da Terra. Departamento de Geologia


    Several publications have contributed to improve the stratigraphy of the Paraiba Basin in northeastern Brazil. However, the characterization and distribution of sedimentary units in onshore areas of this basin are still incomplete, despite their significance for reconstructing the tectono- sedimentary evolution of the South American passive margin. This work provides new information to differentiate among lithologically similar strata, otherwise entirely unrelated in time. This approach included morphological, sedimentological and stratigraphic descriptions based on surface and sub-surface data integrated with remote sensing, optically stimulated luminescence dating, U+Th/He dating of weathered goethite, and heavy mineral analysis. Based on this study, it was possible to show that Cretaceous units are constrained to the eastern part of the onshore Paraiba Basin. Except for a few outcrops of carbonatic-rocks nearby the modern coastline, deposits of this age are not exposed to the surface in the study area. Instead, the sedimentary cover throughout the basin is constituted by mineralogically and chronologically distinctive deposits, inserted in the Barreiras Formation and mostly in the Post-Barreiras Sediments, of early/middle Miocene and Late Pleistocene-Holocene ages, respectively. The data presented in this work support tectonic deformation as a factor of great relevance to the distribution of the sedimentary units of the Paraiba Basin. (author)

  15. Alaskan Peninsula Cenozoic stratigraphy: stratigraphic sequences and current research

    Allison, R.C.; Armentrout, J.M.


    Geology of the Alaska Peninsula-Island Arc and Continental Margin, by C.A. Burk, is the principal reference for stratigraphic studies on the Alaska Peninsula. Burk mapped the Phanerozoic stratigraphy and provided a geologic history and structural interpretation of the area between Wide Bay and Unimak Island. Cenozoic rocks were mapped as three unconformity-bounded sequences. Recognition of specific formations was difficult due to similarity of lithofacies, isolated outcrops, rapid facies changes, and alteration and burial by young volcanics. Consequently, megafossil assemblages were relied upon to facilitate correlations between study areas. The three unconformity-bounded Cenozoic sequences are: (1) the Paleogene Beaver Bay Group consisting of three formations: the dominantly nonmarine Tolstoi Formation, the dominantly marine Stepovak Formation, and the volcanic Meshik Formation. Current work suggests these units are at least in part coeval facies of late Paleocene through Oligocene age. (2) The Neogene Bear Lake Formation consisting of the lower Unga Conglomerate Member and an unnamed upper member. Rapid facies changes and incorrect reports of fossil occurrence have resulted in confusion of stratigraphic relationships within this sequence of middle to late Miocene age. (3) A late Neogene informally defined upper sequence consisting of interbedded marginal marine, coastal-plain, and volcanic facies. Current work suggests this sequence is Pliocene through Pleistocene in age.

  16. Carbonate fracture stratigraphy: An integrated outcrop and 2D discrete element modelling study

    Spence, Guy; Finch, Emma


    Constraining fracture stratigraphy is important as natural fractures control primary fluid flow in low matrix permeability naturally fractured carbonate hydrocarbon reservoirs. Away from the influence of folds and faults, stratigraphic controls are known to be the major control on fracture networks. The fracture stratigraphy of carbonate nodular-chert rhythmite successions are investigated using a Discrete Element Modelling (DEM) technique and validated against observations from outcrops. Comparisons are made to the naturally fractured carbonates of the Eocene Thebes Formation exposed in the west central Sinai of Egypt, which form reservoir rocks in the nearby East Ras Budran Field. DEM allows mechanical stratigraphy to be defined as the starting conditions from which forward numerical modelling can generate fracture stratigraphy. DEM can incorporate both stratigraphic and lateral heterogeneity, and enable mechanical and fracture stratigraphy to be characterised separately. Stratally bound stratified chert nodules below bedding surfaces generate closely spaced lateral heterogeneity in physical properties at stratigraphic mechanical interfaces. This generates extra complexity in natural fracture networks in addition to that caused by bed thickness and lithological physical properties. A series of representative geologically appropriate synthetic mechanical stratigraphic models were tested. Fracture networks generated in 15 DEM experiments designed to isolate and constrain the effects of nodular chert rhythmites on carbonate fracture stratigraphy are presented. The discrete element media used to model the elastic strengths of rocks contain 72,866 individual elements. Mechanical stratigraphies and the fracture networks generated are placed in a sequence stratigraphic framework. Nodular chert rhythmite successions are shown to be a distinct type of naturally fractured carbonate reservoir. Qualitative stratigraphic rules for predicting the distribution, lengths, spacing

  17. Study on quaternary stratigraphy and environmental changes in South Sea, Korea

    Chang, Jeong-Hae; Lee, Chi-Won; Kim, Sung-Pil [Korea Institute of Geology Mining and Materials, Taejon (KR)] (and others)


    According to interpretation of seismic profiles crossing the drilled sites, there are five sequences, namely Unit I, Unit II, Unit III, Unit IV and Unit V from bottom, separable by a reflector with good lateral continuity. If we apply the conception of sequential stratigraphy to the sea level fluctuation caused depositional processes, based on the results of seismic profiles, it will be possible to figure out the late Quaternary depositional processes in the context of sea level changes. According to the sedimentological and seismic stratigraphic analysis, most of SSDP sites showed transgression and regression sequences. Chemical analyses of elements for the sediment samples of SSDP-102 core exhibit the geochemical factors which may influenced the sedimentary environments of the study area. The lower-most sedimentary sequence Unit III can be interpreted as an environment which was influenced dominantly by stronger chemical weathering under a semi-fresh water environment. Based on predominance of carbonate-originated Ca in the homogeneous mud sequence, a high productive surface water along with transgression may have controlled the upper-most sedimentary sequence Unit I. Scatter diagram represents oxygen and carbon isotopic values of benthic foraminifera (Asterorotalia concinna) which is analyzed. All 61 points has value between +1 and -1. If isotopic values of selected benthic foraminifera are equilibrium with surrounding values. These distributions indicate transitional between coastal environment affected by fresh water and open marine environment. (author). 24 refs., 8 tabs., 25 figs.

  18. Identifying Fracture Types and Relative Ages Using Fluid Inclusion Stratigraphy

    Dilley, Lorie M.; Norman, David; Owens, Lara


    Enhanced Geothermal Systems (EGS) are designed to recover heat from the subsurface by mechanically creating fractures in subsurface rocks. Understanding the life cycle of a fracture in a geothermal system is fundamental to the development of techniques for creating fractures. Recognizing the stage of a fracture, whether it is currently open and transmitting fluids; if it recently has closed; or if it is an ancient fracture would assist in targeting areas for further fracture stimulation. Identifying dense fracture areas as well as large open fractures from small fracture systems will also assist in fracture stimulation selection. Geothermal systems are constantly generating fractures, and fluids and gases passing through rocks in these systems leave small fluid and gas samples trapped in healed microfractures. Fluid inclusions trapped in minerals as the fractures heal are characteristic of the fluids that formed them, and this signature can be seen in fluid inclusion gas analysis. Our hypothesis is that fractures over their life cycle have different chemical signatures that we can see in fluid inclusion gas analysis and by using the new method of fluid inclusion stratigraphy (FIS) the different stages of fractures, along with an estimate of fracture size can be identified during the well drilling process. We have shown with this study that it is possible to identify fracture locations using FIS and that different fractures have different chemical signatures however that signature is somewhat dependent upon rock type. Open, active fractures correlate with increase concentrations of CO2, N2, Ar, and to a lesser extent H2O. These fractures would be targets for further enhancement. The usefulness of this method is that it is low cost alternative to current well logging techniques and can be done as a well is being drilled.

  19. Hydrated mineral stratigraphy of Ius Chasma, Valles Marineris

    Roach, L.H.; Mustard, J.F.; Swayze, G.; Milliken, R.E.; Bishop, J.L.; Murchie, S.L.; Lichtenberg, K.


    New high-resolution spectral and morphologic imaging of deposits on walls and floor of Ius Chasma extend previous geomorphic mapping, and permit a new interpretation of aqueous processes that occurred during the development of Valles Marineris. We identify hydrated mineralogy based on visible-near infrared (VNIR) absorptions. We map the extents of these units with CRISM spectral data as well as morphologies in CTX and HiRISE imagery. Three cross-sections across Ius Chasma illustrate the interpreted mineral stratigraphy. Multiple episodes formed and transported hydrated minerals within Ius Chasma. Polyhydrated sulfate and kieserite are found within a closed basin at the lowest elevations in the chasma. They may have been precipitates in a closed basin or diagenetically altered after deposition. Fluvial or aeolian processes then deposited layered Fe/Mg smectite and hydrated silicate on the chasma floor, postdating the sulfates. The smectite apparently was weathered out of Noachian-age wallrock and transported to the depositional sites. The overlying hydrated silicate is interpreted to be an acid-leached phyllosilicate transformed from the underlying smectite unit, or a smectite/jarosite mixture. The finely layered smectite and massive hydrated silicate units have an erosional unconformity between them, that marks a change in surface water chemistry. Landslides transported large blocks of wallrock, some altered to contain Fe/Mg smectite, to the chasma floor. After the last episode of normal faulting and subsequent landslides, opal was transported short distances into the chasma from a few m-thick light-toned layer near the top of the wallrock, by sapping channels in Louros Valles. Alternatively, the material was transported into the chasma and then altered to opal. The superposition of different types of hydrated minerals and the different fluvial morphologies of the units containing them indicate sequential, distinct aqueous environments, characterized by alkaline

  20. Research on the bio-stratigraphy. Stratigraphy and paleontology of the Cretaceous sedimentary strata in the Youngdong basin

    Choi, Sung Ja; Kim, Yoo Bong; Kim, Bok Chul [Korea Institute of Geology Mining and Materials, Taejon (Korea, Republic of)


    The Youngdong Basin developed at the eastern margin of the Okcheon Orogenic Belt is in contact with the Yongnam Massif by the Youngdong Fault. This study deals with tectonic setting, sedimentological, pale-ontological study of the Youngdong Basin. Concerned with the formation of the basin, left lateral movement of the Ogdong and Youngdong faults gave a major role for the development of the Youngdong Basin. The Youngdong Basin is tectonically subdivided into three parts (north, center, and south) on the basis of bedding form line and fracture patterns. Sedimentological study is concentrated in the southern part of the basin in order to establish stratigraphy in this area. The Mangyeri Formation is characterized by the deposit of debris flow and hyper-concentrated flow deposits developed at the steep gradient fan-delta slope and on alluvial fan along the southern basin margin. On the other hand, the formation in northern part of the basin is deposited in alluvial fan and braided rivers. The Gadongri Formation is mostly deposited by the process of turbidity current and density under current in lacustrine environment, and the Dongjongri Formation comprises alluvial fan and braided river sediments which mostly deposited by debris flow, hyper-concentrated flood flow, sheet flood and stream flow. For paleontology, ostracodes and charophytes are yielded from the Gadongri, Dongjongri and Sonyoudong formations. On the basis of fossils, the Dongjongri formation is correlated with the Iljig Formation of the Euisung basin, the Sonyoudong formation is correlated with the Songnaedong and Geonchunri formations of the Milyang basin. Consequently, the Mangyeri and Gadongri formations are correlated with the Sindong Group, the Dongjongri and Sonyoudong formations are correlated with the Hayang Group. (author). 47 refs., 5 tabs.

  1. The role of sequence stratigraphy in 3-D characterization of carbonate reservoirs

    Tinker, S.W.; Brondos, M.D.; Brinton, L. [Marathon Oil Co., Littleton, CO (United States)


    The product of 3-D reservoir characterization is a 3-D reservoir model. The integrity of the 3-D reservoir model is largely a function of the stratigraphic framework. Interpreting the correct stratigraphic framework for a subsurface reservoir is the most difficult and creative part of the 3-D modeling process. Sequence- and seismic-stratigraphic interpretation provide the best stratigraphic framework for 3-D reservoir modeling. Depositional sequences are comprised of many petrophysically-distinct lithofacies regions. If each lithofacies region was uniform and homogeneous, it would be reasonable to use a lithofacies ({open_quote}layer-cake{close_quote}) framework interpretation to distribute data in a 3-D model. However, lithofacies are typically time- transgressive, and often internally heterogeneous because geologic processes such as siliciclastic sediment deposition, sediment bypass, hardground formation, variable diagenesis, and facies shifts occur along depositional time surfaces on carbonate platforms. Therefore, a sequence stratigraphic framework interpretation, in which stratal geometries are honored, is better for controlling the distribution of petrophysical data in 3-D. The role that sequence stratigraphy plays in the 3-D characterization of carbonate reservoirs will be presented using two outcrop and four subsurface studies from the Paleozoic. The outcrop examples illustrate the important distinction between lithostratigraphic and sequence stratigraphic correlation, and the subsurface examples illustrate the process of quantification, integration, reduction, and analysis of geological, petrophysical, seismic, and engineering data. The concepts and techniques can be applied to carbonate reservoirs of any age.

  2. The role of sequence stratigraphy in 3-D characterization of carbonate reservoirs

    Tinker, S.W.; Brondos, M.D.; Brinton, L. (Marathon Oil Co., Littleton, CO (United States))


    The product of 3-D reservoir characterization is a 3-D reservoir model. The integrity of the 3-D reservoir model is largely a function of the stratigraphic framework. Interpreting the correct stratigraphic framework for a subsurface reservoir is the most difficult and creative part of the 3-D modeling process. Sequence- and seismic-stratigraphic interpretation provide the best stratigraphic framework for 3-D reservoir modeling. Depositional sequences are comprised of many petrophysically-distinct lithofacies regions. If each lithofacies region was uniform and homogeneous, it would be reasonable to use a lithofacies ([open quote]layer-cake[close quote]) framework interpretation to distribute data in a 3-D model. However, lithofacies are typically time- transgressive, and often internally heterogeneous because geologic processes such as siliciclastic sediment deposition, sediment bypass, hardground formation, variable diagenesis, and facies shifts occur along depositional time surfaces on carbonate platforms. Therefore, a sequence stratigraphic framework interpretation, in which stratal geometries are honored, is better for controlling the distribution of petrophysical data in 3-D. The role that sequence stratigraphy plays in the 3-D characterization of carbonate reservoirs will be presented using two outcrop and four subsurface studies from the Paleozoic. The outcrop examples illustrate the important distinction between lithostratigraphic and sequence stratigraphic correlation, and the subsurface examples illustrate the process of quantification, integration, reduction, and analysis of geological, petrophysical, seismic, and engineering data. The concepts and techniques can be applied to carbonate reservoirs of any age.




    Full Text Available The Permian sequence of the Transcaucasia, which comprises the Davaly, Asni, Gnishik, Arpa, Khachik, and Akhura Formations, is described. A precise dating of the formations based on the analysis of fusulinid assemblages is also provided. The Davaly Formation corresponds to the Bolorian Stage of the Lower Permian (Cisuralian; the Asni Formation corresponds to the Kubergandian Stage, and to the lower half of the Murgabian Stage of the Middle Permian (Guadalupian; the Gnishik Formation corresponds approximately to the upper half of the Murgabian Stage; and the Arpa and Khachik Formations represent the entire Midian Stage of the Middle Permian. Only the uppermost Chanakhchy Beds of the Khachik Formation are referred to the upper series of the Permian (Lopingian, based on the latest proposal of the International Subcommission on Permian Stratigraphy concerning series boundaries. The Akhura Formation encompasses the Dzhulfian and Dorashamian Stages of the Upper Permian. Refined correlations between the Permian sequence of the Transcaucasia and the most complete Permian sequences of the Tethyan region (Central Iran, southestern Pamirs, South China, Japan are presented. The transgressive overlapping of the Permian deposits is recorded in these areas, similar to the Transcaucasia. Although the transgression began during the Bolorian, it reached the widest extent in the Kubergandian and therefore, in most sections the transgressive series begins with deposits of Kubergandian age. The Middle and Upper Permian deposits of the Transcaucasia, Iran, and southern Turkey belonged to a single carbonate platform. Similar extensive carbonate platforms are recorded in the southern parts of Afghanistan and China. A change in the sedimentary regime was recorded in all these platforms at the boundary between the Guadalupian and Lopingian epochs. The Guadalupian time was marked by the intensive accumulation of biolitithic and detrital limestones produced by benthic

  4. Stratigraphy and palaeoclimate of Spitsbergen, Svalbard, during the Early Cretaceous

    Vickers, Madeleine; Price, Gregory; Watkinson, Matthew; FitzPatrick, Meriel; Jerrett, Rhodri


    During the Early Cretaceous, Spitsbergen was located at a palaeolatitude of ~60°N. Abundant fossil wood derived from conifer forests, dinosaur trackways, enigmatic deposits such as glendonites, and stable isotope data from the Early Cretaceous formations of Spitsbergen suggest that the climate at that time was much more dynamic than the traditional view of "invariant greenhouse" conditions on Earth. The Early Cretaceous succession in central Spitsbergen comprises a regressive-transgressive mega-cycle. This is made up of the deep water to wave-dominated, Berriasian-Hauterivian Rurikfjellet Formation; the deltaic, Barremian Helvetiafjellet Formation; and the coastal to deep water, Aptian-Albian Carolinefjellet Formation. An erosion surface marks the base of the Helvetiafjellet Formation. Two regions with excellently exposed Early Cretaceous strata were chosen for study in this project: the Festningen section, on the north-western side of Isfjorden; and outcrops found along Adventdalen, near Longyearbyen, ~40km northeast of Festningen. We present the data collected in July 2015 from the Adventdalen area, and compare and correlate it with sedimentological and geochemical data collected from the Festningen succession in 2014. The Festningen section records a full sequence from the Berriasian to the Aptian, whereas the Longyearbyen sections record Aptian-Albian deposition. We use carbon isotope stratigraphy to constrain the Barremian-Aptian boundary in the previously only indirectly-dated Helvetiafjellet Formation, and to identify other major global climatic and carbon cycle perturbations in the Early Cretaceous. We are thus able to correlate this succession with other successions globally. We combine this δ13C(terrestrial) data with sedimentological and petrological data to elucidate the origins of enigmatic glendonites found in both regions. Glendonites are thought to be associated with cold-water (and therefore also cold-climate) conditions, although their mode of

  5. Three-dimensional modelling of thrust-controlled foreland basin stratigraphy

    Clevis, Q. (Quintijn)


    In this thesis a tectono-sedimentary forward model has been presented, devised to simulate sediment erosion and deposition in a coupled drainage basin - foreland system, as well as accumulating a three-dimensional stratigraphy. The aim of the research was to investigate which features recorded in th

  6. Geochemical-Sequence Stratigraphy and Its Application Prospects in Lake Basins

    李美俊; 纪云龙; 胡礼国


    As a useful approach for hydrocarbon exploration, the sequence stratigraphy has been commonly accepted. The concepts of sequence and parasequence provide a state-of-the-artframework for studying the distribution and characters of depositional system, and analyzing the occurrence, distribution, characteristics of source, reservoir and seal-play elements. The newly-de-veloped geochemical-sequence stratigraphy focuses mainly on the occurrence, distribution and characters of source rocks and reservoir hydrocarbons within a chronostratigraphic framework.Integrated with sequence stratigraphy, geochemistry can be used to study the source rock potential within a sequence stratigraphic framework and to describe the characteristics of hydrocarbons accumulated in reservoirs, which were predicted by way of sequence stratigraphy. The concept of geochemical-sequence stratigraphy was proposed by Peters et al. (2000). Constructing a reliable sequence stratigraphic framework is the basis of geochemical-sequence stratigraphic study although it is not the main goal. High-resolution biomarker analysis is critical to the construction of a geochemical-sequence stratigraphic model. The geochemical-stratigraphic study involves mainly: ( 1 ) the distribution and geochemical characteristics of source rocks within a sequence chronostratigraphic framework; (2) the geochemical features of source rocks with relative sea (lake)-level change; (3) to predict if these reservoirs bear hydrocarbons and their geochemical features; (4) to be used to construct the time-stratigraphic framework. This paper also summarizes the lake basin types, and introduces their facies associations, source potential and organic geochemical features. At the end, the authors offer some suggestions about how to carry out geo chemical-sequence stratigraphic study in lacustrine strata.

  7. A stratigraphy fieldtrip for people with visual impairment

    Gomez-Heras, Miguel; Gonzalez-Acebron, Laura; Muñoz-Garcia, Belen; Garcia-Frank, Alejandra; Fesharaki, Omid


    This communication presents how a stratigraphy fieldtrip adapted to people with visual impairment was prepared and carried out. This fieldtrip aimed to promote scientific knowledge on Earth sciences to people with visual impairment and to inspire Earth scientists to take into account the needs of people with disabilities when designing public engagement activities. To do this, the theme chosen for the fieldtrip was the importance of sedimentary rocks shaping the Earth and what information can one extract from observing sedimentary structures. The Triassic outcrops of Riba de Santiuste (Guadalajara, Spain) were observed during this fieldtrip. The expected learning outcomes were: a) understanding what are sedimentary rocks, how they are formed and how they fold and crop out, b) knowing what is a sedimentary structure and recognising some of them and c) be able to make inferences of the sedimentary environment from certain sedimentary structures. The fieldtrip was prepared, through the NGO "Science without Barriers" together with the Madrid delegation of the National Association for Spanish Blind People (ONCE-Madrid). ONCE-Madrid was responsible of advertising this activity as a part of their yearly cultural program to its affiliate. A preparatory fieldtrip was carried out to test the teaching methodology and to make an appropriate risk assessment. This was made together with the responsible of the Culture Area of ONCE-Madrid and two blind people. The involvement of end-users in the preparation of activities is in the core of the European Disability Forum motto: "Nothing about us without us". A crucial aspect of the site was accessibility. In terms of perambulatory accessibility of outcrops the site is excellent and suitable to some extent for end-users regardless of their physical fitness. The fieldtrip itself took place on October 15th 2016 and 30 people with and without visual disability attended. In addition to overall observations and explanations of strata and

  8. Stratigraphy and structure of the western Kentucky fluorspar district

    Trace, R.D.; Amos, D.H.


    The western Kentucky fluorspar district is part of the larger Illinois-Kentucky fluorspar district, the largest producer of fluorspar in the United States. This report is based largely on data gathered from 1960 to 1974 during the U.S. Geological Survey-Kentucky Geological Survey cooperative geologic mapping program of Kentucky. It deals chiefly with the stratigraphy and structure of the district and, to a lesser extent, with the fluorspar-zinc-lead-barite deposits. Sedimentary rocks exposed in the district range in age from Early Mississippian (Osagean) to Quaternary. Most rocks exposed at the surface are Mississippian in age; two-thirds are marine fossiliferous limestones, and the remainder are shales, siltstones, and sandstones. Osagean deep-water marine silty limestone and chert are present at the surface in the southwestern corner of the district. Meramecian marine limestone is exposed at the surface in about half the area. Chesterian marine and fluvial to fluviodeltaic clastic sedimentary rocks and marine limestone underlie about one-third of the area. The total sequence of Mississippian rocks is about 3,000 ft thick. Pennsylvanian rocks are dominantly fluvial clastic sedimentary rocks that change upward into younger fluviodeltaic strata. Pennsylvanian strata of Morrowan and Atokan age are locally thicker than 600 ft along the eastern and southeastern margin and in the major grabens of the district where they have been preserved from erosion. Cretaceous and Tertiary sediments of the Mississippi embayment truncate Paleozoic formations in and near the southwestern corner of the district and are preserved mostly as erosional outliers. The deposits are Gulfian nonmarine gravels, sands, and clays as much as 170 ft thick and upper Pliocene fluvial continental deposits as thick as 45 ft. Pleistocene loess deposits mantle the upland surface of the district, and Quaternary fluvial and fluviolacustrine deposits are common and widespread along the Ohio and Cumberland

  9. Geology and Stratigraphy of Four Candidate Pyroclastic Deposits on Mercury

    Weinauer, Julia; Hiesinger, Harald; Bauch, Karin; Preusker, Frank


    The MESSENGER (Mercury Surface, Space Environment, Geochemistry, and Ranging) spacecraft [1] to Mercury revealed numerous new findings, including the discovery of potential pyroclastic deposits [2-9]. Besides impact cratering, volcanic processes, including the deposition of pyroclastic materials are among the most important processes to shape the surface of a planet. Volcanic processes allow us to study the thermal evolution of the planet, and impacts provide insights into the composition of the crust, and possible the mantle. In this study we focus on four specific examples of potential pyroclastic deposits: Lermontov NE (-48.15°E, 15.80°), Lermontov SE (-49.08°E, 15.04°), Glinka (-112.42°E, 15.01°), and Unnamed crater 7 (88.20°E, 32.40°). For our investigation we used data of the Mercury Dual Imaging System (MDIS) [10]. In particular we studied narrow-angle Camera (NAC) images with a resolution of 25-100 m/pixel and wide-angle camera (WAC) images with a resolution of about 170-250 m/pixel. Our data set is complemented by Digital Terrain Models (DTM) based on photogrammetric analyses of stereo images [11]. The objectives of this study are to investigate the geologic context of the pyroclastic deposits, to map their morphological/compositional sub-units in detail, to derive volume estimates for these deposits, to study their eruption conditions, and to derive information on the timing of the emplacement of these units. In addition, absolute model ages are determined to develop a stratigraphy of the mapped units Several morphologic features were observed in association with the pyroclastic deposits, including lobate scarps, melt pools, and large irregular depressions, as well as small-scale irregularly shaped, shallow, rimless depressions, i.e., hollows [2]. In Lermontov, the large irregular depressions that can be plausibly interpreted as vent structures [6,7] occur within a roughly circular depression of about 50 km in diameter, located in the center of

  10. Pre-glacial, Early Glacial, and Ice Sheet Stratigraphy Cored During NBP1402, Sabrina Coast, East Antarctic Margin

    Domack, E. W.; Gulick, S. P. S.; Fernandez-Vasquez, R. A.; Frederick, B.; Lavoie, C.; Leventer, A.; Shevenell, A.; Saustrup, S., Sr.; Bohaty, S. M.; Sangiorgi, F.


    Western Wilkes Land provides an unusual setting with regard to passive margin subsidence and exposure of Cenozoic sedimentary units across the continental shelf, due to the unique rift to drift history off of the Australian-Antarctic Discordance and subsequent deep glacial erosion of the evolved continental shelf. The first factor has provided extensive accommodation space for the preservation of stratigraphic sequences that in turn represent critical periods in the climate evolution of Antarctica. Glacial erosion has then provided access to this stratigraphy that is usually inaccessible to all but deep drilling programs. Such stratigraphies are well exposed to within cm of the seafloor off the Sabrina Coast. Cruise NBP1402 investigated this region via a combination of multi-channel seismic imaging and innovative, strategic coring. The geophysical data imaged the geologic evolution of the margin, which exhibits a continuum from non-glacial, partly glaciated, to fully glaciated depo- and erosional systems. Based on the seismic stratigraphy, we collected dredges and one barrel Jumbo Piston Cores (JPCs) across areas of outcropping strata imaged seismically, a unique strategy that allowed us to identify and sample specific reflectors. The stratigraphically deepest coring targeted sections for which the seismic character suggested a pre-glacial context, with non-glaciated continental margin sequences including deltas. Coring recovered dark organic rich siltstones and sandy mudstones, and a large concretion whose center contained a cm-sized plant fossil. In addition, the sediments contain a fossil snail. These fossils provide a glimpse into the pre-glacial terrestrial environment in Antarctica. Overlying this section, coring recovered similar dark siltstones with a 20 cm thick horizon with abundant large angular clasts of variable lithology, interpreted to be ice-rafted debris and indicative of early glacial ice in Antarctica. Finally, JPCs targeting a younger part of

  11. Refined stratigraphy and its paleogeographic implication of the Mungyeong Group (Cambrian-Ordovician), Korea

    Kim, Inhye; Kwon, Yoojin; Kwon, Yikyun


    The Mungyeong Group is a typical lower Paleozoic carbonate-dominated succession regarded as a lithologic subunit of the Joseon Supergroup in the mid-eastern part of the Korean peninsula. This succession was strongly affected by a series of diagenetic processes and tectonic deformation, so it is not easy to realize its sedimentary fabric and structure on outcrops. In addition, due to rare occurrence of fossils, its biostratigraphic information has been restricted. As a result, this group has exposed a lot of debates on its stratigraphy and consequently has failed to establish stratigraphy until now. Through the detailed outcrop description and geologic mapping, this study recognized two lithologically-distinct basin fills (western Gaeun and eastern Hogye basins) suggesting a refined lithostratigraphic framework on the group. The Gaeun basin is filled by the mixed carbonate-siliciclastic succession (Gaeun Subgroup) of the Mungyeong Group, comprising six lithologic formations: Gurangri, Maseong, Hanaeri, Seokgyori, Jeongri and Dotan formation in ascending order. The basal Gurangri Formation is the siliciclastic-dominated unit, containing abundant lower Paleozoic trilobite fossils, conformably overlain by other carbonate-dominated successions characterized by repetitions of limestone and marlstone with intercalations of dolostone beds. On the other hand, the Hogye Subgroup occurs in the eastern basin, divided into five lithostatigraphic units: Gadori, Seonamri, Urori, Yugok and Byeolamri formations in ascending order. This subgroup consists mainly of severely deformed limestone and dolostone successions, intercalated with shale beds. In the Hogye Subgroup, the basal siliciclastic-dominated succession (like as the Gurangri Formation in the Gaeun Subgroup) is not present. This study reveals that the Gaeun and Hogye subgroups in the Mungyeong Group have a distinctive lithology and stratigraphy with each other and compared with the adjacent Yeongweol and Taebaek groups

  12. Late Pleistocene Stratigraphy and Palaeobotany of the Isles of Scilly

    Scourse, J. D.


    A re-evaluation of the Pleistocene stratigraphy of the Isles of Scilly has enabled the formal definition of eight lithostratigraphic units of member status grouped into two formations. A chronology of events has been provided by radiocarbon (14C) determinations, optical and thermoluminescene (TL) dates. Intersite correlations have been strengthened by palynology, which has aided palaeoenvironmental reconstruction. The defined units have been incorporated into two lithostratigraphic models, one for the `northern' (glacial) Scillies and one for the `southern' (extra-glacial) Scillies. Raised beach sediments of the Watermill Sands and Gravel in the southern Scillies are overlain by the Porthloo Breccia, a unit of soliflucted material derived exclusively from the weathering of local granite. Organic sequences at Carn Morval, Watermill Cove, Porth Askin, Porth Seal and Bread and Cheese Cove occur within the Porthloo Breccia, and are interpreted as the infillings of ponds associated with active solifluction. Radiocarbon determinations from these organic sediments are critical because they pre-date units associated with a glacial event. The 14C determinations indicate deposition of the organic material between 34500-800+885 (Q-2410) and 21500-800+890 (Q-2358) years BP and provide a maximum age for the glacial event and the first radiometric dates for the coastal `head' sediments of southwest England. The pollen assemblages from these organic sites all record open grassland vegetation, and represent the earliest vegetational record for the Scillies. High Pinus values are interpreted as evidence of climatic deterioration. In the southern Scillies, the Porthloo Breccia is overlain by the Old Man Sandloess, a coarse aeolian silt with subdominant fine sand, TL-dated to 18600-3700+3700 years (QTL-ld and lf; Wintle 1981) and optically dated to 20000-7000+7000 and 26000-9000+10000 years (two samples; 738al and 741al; Smith et al. 1990). This material occurs in a variety of facies

  13. Effect of explicit representation of detailed stratigraphy on brine and gas flow at the Waste Isolation Pilot Plant

    Christian-Frear, T.L.; Webb, S.W. [Sandia National Labs., Albuquerque, NM (United States). Geohydrology Dept.


    Stratigraphic units of the Salado Formation at the Waste Isolation Pilot Plant (WIPP) disposal room horizon includes various layers of halite, polyhalitic halite, argillaceous halite, clay, and anhydrite. Current models, including those used in the WIPP Performance Assessment calculations, employ a ``composite stratigraphy`` approach in modeling. This study was initiated to evaluate the impact that an explicit representation of detailed stratigraphy around the repository may have on fluid flow compared to the simplified ``composite stratigraphy`` models currently employed. Sensitivity of model results to intrinsic permeability anisotropy, interbed fracturing, two-phase characteristic curves, and gas-generation rates were studied. The results of this study indicate that explicit representation of the stratigraphy maintains higher pressures and does not allow as much fluid to leave the disposal room as compared to the ``composite stratigraphy`` approach. However, the differences are relatively small. Gas migration distances are also different between the two approaches. However, for the two cases in which explicit layering results were considerably different than the composite model (anisotropic and vapor-limited), the gas-migration distances for both models were negligible. For the cases in which gas migration distances were considerable, van Genuchten/Parker and interbed fracture, the differences between the two models were fairly insignificant. Overall, this study suggests that explicit representation of the stratigraphy in the WIPP PA models is not required for the parameter variations modeled if ``global quantities`` (e.g., disposal room pressures, net brine and gas flux into and out of disposal rooms) are the only concern.

  14. Progress in the stratigraphy and geochronology of the Shuidonggou site,Ningxia,North China

    LIU DeCheng; WANG XuLong; GAO Xing; XIA ZhengKai; PEI ShuWen; CHEN FuYou; WANG HuiMing


    In the past years we carried out further stratigraphy division in field and it is found that rich stone artifacts can be found in fluvial-shallow lake-alluvial sediments on the terrace Ⅱ of Biangou River,in Shuidonggou site,Ningxia and they are SDG1,2 and 7.More luminescence and AMS 14C dating in laboratory show that Paleolithic culture develops during the Upper Paleolithic period with ages of 35-20 ka.The Paleolithic culture of SDG 1 is a little earlier than that of SDG 2 similar to SDG 7.The sandy sediments on terrace Ⅱ of Biangou River deposits in the past 72-18 ka,corresponding to Last Glacial.SDG2 has a stable sedimentary environment,resulting in the continuous stratigraphy,thickest deposits and rich environment and culture information,which can be regarded as the important and classic paleoanthropological section of Late Pleistocene in this region.

  15. Great earthquakes along the Western United States continental margin: implications for hazards, stratigraphy and turbidite lithology

    C. H. Nelson


    Full Text Available We summarize the importance of great earthquakes (Mw ≳ 8 for hazards, stratigraphy of basin floors, and turbidite lithology along the active tectonic continental margins of the Cascadia subduction zone and the northern San Andreas Transform Fault by utilizing studies of swath bathymetry visual core descriptions, grain size analysis, X-ray radiographs and physical properties. Recurrence times of Holocene turbidites as proxies for earthquakes on the Cascadia and northern California margins are analyzed using two methods: (1 radiometric dating (14C method, and (2 relative dating, using hemipelagic sediment thickness and sedimentation rates (H method. The H method provides (1 the best estimate of minimum recurrence times, which are the most important for seismic hazards risk analysis, and (2 the most complete dataset of recurrence times, which shows a normal distribution pattern for paleoseismic turbidite frequencies. We observe that, on these tectonically active continental margins, during the sea-level highstand of Holocene time, triggering of turbidity currents is controlled dominantly by earthquakes, and paleoseismic turbidites have an average recurrence time of ~550 yr in northern Cascadia Basin and ~200 yr along northern California margin. The minimum recurrence times for great earthquakes are approximately 300 yr for the Cascadia subduction zone and 130 yr for the northern San Andreas Fault, which indicates both fault systems are in (Cascadia or very close (San Andreas to the early window for another great earthquake.

    On active tectonic margins with great earthquakes, the volumes of mass transport deposits (MTDs are limited on basin floors along the margins. The maximum run-out distances of MTD sheets across abyssal-basin floors along active margins are an order of magnitude less (~100 km than on passive margins (~1000 km. The great earthquakes along the Cascadia and northern California margins

  16. Sequence stratigraphy of the Kingak Shale (Jurassic-Lower Cretaceous), National Petroleum Reserve in Alaska

    Houseknecht, D.W.; Bird, K.J.


    Beaufortian strata (Jurassic-Lower Cretaceous) in the National Petroleum Reserve in Alaska (NPRA) are a focus of exploration since the 1994 discovery of the nearby Alpine oil field (>400 MMBO). These strata include the Kingak Shale, a succession of depositional sequences influenced by rift opening of the Arctic Ocean Basin. Interpretation of sequence stratigraphy and depositional facies from a regional two-dimensional seismic grid and well data allows the definition of four sequence sets that each displays unique stratal geometries and thickness trends across NPRA. A Lower to Middle Jurassic sequence set includes numerous transgressive-regressive sequences that collectively built a clastic shelf in north-central NPRA. Along the south-facing, lobate shelf margin, condensed shales in transgressive systems tracts downlap and coalesce into a basinal condensed section that is likely an important hydrocarbon source rock. An Oxfordian-Kimmeridgian sequence set, deposited during pulses of uplift on the Barrow arch, includes multiple transgressive-regressive sequences that locally contain well-winnowed, shoreface sandstones at the base of transgressive systems tracts. These shoreface sandstones and overlying shales, deposited during maximum flooding, form stratigraphic traps that are the main objective of exploration in the Alpine play in NPRA. A Valanginian sequence set includes at least two transgressive-regressive sequences that display relatively distal characteristics, suggesting high relative sea level. An important exception is the presence of a basal transgressive systems tract that locally contains shoreface sandstones of reservoir quality. A Hauterivian sequence set includes two transgressive-regressive sequences that constitute a shelf-margin wedge developed as the result of tectonic uplift along the Barrow arch during rift opening of the Arctic Ocean Basin. This sequence set displays stratal geometries suggesting incision and synsedimentary collapse of the shelf

  17. Changes in Stratigraphy Across the Lake Ojibway Basin, Implications for Lake Drainage Record

    Stroup, J. S.; Lowell, T. V.; Breckenridge, A.


    Changes in Stratigraphy Across the Lake Ojibway Basin, Implications for Lake Drainage Record Lake Ojibway's formation, sedimentation and drainage history was influenced by the retreat of the Laurentide ice sheet. Eleven Lake cores were taken from a geographic area ranging from the Cochran area in central Ontario 240km south east into western Québec to establish a varve chronology to help assess the timing of its final drainage as it is implicated in the 8200 yr event. Differences in stratigraphy have been found across the basin. In three sites interior to the Cochran re-advance limit (Paulen, 2001) the stratigraphy is: a till unit, at the bottom, grades into an ice proximal varve unit which thins upward and gives way to a pellet unit of fine grained silts and clays above which a finely laminated sediment becomes massive. Outside the Cochran re- advance limit the sequence is: an ice proximal varve unit containing contorted sections above which disturbed sediments become finely laminated or massive until a contact with darker organic "modern" sediments. A sudden drainage event across the entire basin should leave a distinct signature. The new cores east of the Cochran re-advance act as a test and allow the generation of two new hypotheses: (1) the finely laminated to massive units common in both sets of cores below the darker organics is the drainage stratigraphy or (2) the finely laminated to massive units are the post drainage signature representing the settling out after drainage, making the contact between the varved glacial sediments and the finely laminated sediments the drainage signature. This data may also place the Cochran re-advance closer to the drainage event because the stratigraphy between regions is similar above. It is possible that the Cochran could have been the triggering mechanism for the drainage event. If true, it could have ramifications for the size of the basin and geometry of the ice sheet, putting the ice margin further south and making

  18. Upper crustal mechanical stratigraphy and the evolution of thrust wedges: insights from sandbox analogue experiments

    Milazzo, Flavio; Storti, Fabrizio; Nestola, Yago; Cavozzi, Cristian; Magistroni, Corrado; Meda, Marco; Salvi, Francesca


    Crustal mechanical stratigraphy i.e. alternating mechanically weaker and stronger layers within the crust, plays a key role in determining how contractional deformations are accommodated at convergent plate boundaries. In the upper crust, evaporites typically provide preferential décollement layers for fault localization and foreland ward propagation, thus significantly influencing evolution of thrust-fold belts in terms of mechanical balance, geometries, and chronological sequences of faulting. Evaporites occur at the base of many passive margin successions that underwent positive inversion within orogenic systems. They typically produce salient geometries in deformation fronts, as in the Jura in the Northern Alps, the Salakh Arch in the Oman Mountains, or the Ainsa oblique thrust-fold belt in the Spanish Pyrenees. Evaporites frequently occur also in foredeep deposits, as in the Apennines, the Pyrenees, the Zagros etc. causing development of additional structural complexity. Low-friction décollement layers also occur within sedimentary successions involved in thrust-fold belts and they contribute to the development of staircase fault trajectories. The role of décollement layers in thrust wedge evolution has been investigated in many experimental works, particularly by sandbox analogue experiments that have demonstrated the impact of basal weak layers on many first order features of thrust wedges, including the dominant fold vergence, the timing of fault activity, and the critical taper. Some experiments also investigated on the effects of weak layers within accreting sedimentary successions, showing how this triggers kinematic decoupling of the stratigraphy above and below the décollements, thus enhancing disharmonic deformation. However, at present a systematic experimental study of the deformation modes of an upper crustal mechanical stratigraphy consisting of both low-friction and viscous décollement layers is still missing in the specific literature. In

  19. Eo-Ulrichian to Neo-Ulrichian views: The renaissance of "layer-cake stratigraphy"

    Brett, Carlton E.; McLaughlin, P.I.; Baird, G.C.


    Classical notions of "layer-cake stratigraphy" have been denigrated as representing an antiquated "Neptunian" view of the geologic record with the American paleontologist-stratigrapher E.O. Ulrich vilified as its quintessential advocate. Some of the extreme "layer-cake" interpretations of E.O. Ulrich are demonstrably incorrect, especially where applied in marginal marine and terrestrial settings. However, close scrutiny of Ulrich's work suggests that the bulk was correct and demonstrated considerable insight for the time. Subsequent development of facies concepts revolutionized geologists' view of time-space relationships in stratigraphy, but rather than focusing on facies patterns within the established stratigraphic (layer-cake) frameworks many geologists in North America came to view strata as parts of diachronous facies mosaics. Recent advances in the development of event and sequence stratigraphic paradigms are beginning to swing the pendulum back the other way. Possible causes of "layer-cake" patterns are numerous and varied, including: (1) parallelism of depositional strike and outcrop belts, especially in foreland basins, (2) very widespread environmental belts developed in low-relief cratonic areas, (3) time-averaging homogenizes facies to a limited extent, resulting in a very subtle signature of lateral change, (4) condensed beds (hardgrounds, bone beds, ironstones, etc.) often form in responses to extrabasinal forces, thus they cross-cut facies, and (5) large events (i.e. hurricanes, floods, tsunamis, eruptions, etc.) are "over represented" in the rock record. A revised ("Neo-Ulrichian") layer-cake paradigm carries many of the original correct empirical observations of pattern, noted by Ulrich, recast in terms of event and sequence stratigraphy.

  20. Regional stratigraphy and petroleum potential, Ghadames basin, Algeria

    Emme, J.J. (Anadarko Algeria Corp., Houston, TX (United States)); Sunderland, B.L. (Anadarko Petroleum Corp., Houston, TX (United States))


    The Ghadames basin in east-central Algeria extends over 65,000 km{sup 2} (25,000 mi{sup 2}), of which 90% is covered by dunes of the eastern Erg. This intracratonic basin consists of up to 6000 m (20,000 ft) of dominantly clastic Paleozoic through Mesozoic strata. The Ghadames basin is part of a larger, composite basin complex (Ilizzi-Ghadames-Triassic basins) where Paleozoic strata have been truncated during a Hercynian erosional event and subsequently overlain by a northward-thickening wedge of Mesozoic sediments. Major reservoir rocks include Triassic sandstones that produce oil, gas, and condensate in the western Ghadames basin, Siluro-Devonian sandstones that produce mostly oil in the shallower Ilizzi basin to the south, and Cambro-Ordovician orthoquartzites that produce oil at Hassi Messaoud to the northwest. Organic shales of the Silurian and Middle-Upper Devonian are considered primary source rocks. Paleozoic shales and Triassic evaporite/red bed sequences act as seals for hydrocarbon accumulations. The central Ghadames basin is underexplored, with less than one wildcat well/1700 km{sup 2} (one well/420,000 ac). Recent Devonian and Triassic oil discoveries below 3500 m (11,500 ft) indicate that deep oil potential exists. Exploration to date has concentrated on structural traps. Subcrop and facies trends indicate that potential for giant stratigraphic or combination traps exists for both Siluro-Devonian and Triassic intervals. Modern seismic acquisition and processing techniques in high dune areas can be used to successfully identify critical unconformity-bound sequences with significant stratigraphic trap potential. Advances in seismic and drilling technology combined with creative exploration should result in major petroleum discoveries in the Ghadames basin.

  1. Evidence of miocene crustal shortening in the North Qilian Shan from cenozoic stratigraphy of the Western Hexi Corridor, Gansu Province, China

    Bovet, P.M.; Ritts, B.D.; Gehrels, G.; Abbink, A.O.; Darby, B.; Hourigan, J.


    New sedimentologic, stratigraphie, and compositional data from the Paleogene-Neogene stratigraphie succession exposed in the northwest Hexi Corridor and within the North Qilian Shan, provide evidence to suggest that crustal shortening in the North Qilian Shan fold-thrust belt initiated during die Mi

  2. The role of antecedent drainage networks and isolated normal fault propagation on basin stratigraphy

    Finch, E.; Brocklehurst, S. H.; Gawthorpe, R.


    The stratigraphy of an extensional basin reflects a history of fault activity, erosion, drainage network evolution, and sediment transport and deposition. Here a three-dimensional numerical model of erosion and clastic sedimentation is applied to investigate the effect of displacement on a normal fault to the distribution of deposition in an extensional basin. Material is eroded from the hinterland through a stream-power incision law and deposited in the basin using a modified diffusion algorithm. Experiments are implemented for 3Ma, in which the initial 1Ma are used to permit a drainage network to evolve to a topographic steady state. This system is then perturbed by the introduction of a propagating isolated normal fault at varying displacement rates (1.0m/kyr - 2.0m/kyr) to demonstrate the influence of fault propagation on drainage capture, network re-organisation, sediment routing and deposition. Faster displacement rates and smaller antecedent drainage networks cause footwall-derived deltas to be cut-off more rapidly from the hinterland source area. Drainage networks are re-organised such that sediment is then transported around the fault tips into axially sourced deltas. Sediments may continue to be deposited in the hanging wall at the fault centre, but this material has not been sourced directly from the adjacent footwall, even though the stratigraphic architecture might suggest that this is the case. Drainage networks are modified by drainage reversals in the antecedent channels, and the development of areas of abandoned/trapped drainage. These changes in sediment supply due to network re-organisation are also reflected in the basin stratigraphy, with rapid back-stepping of deltas when the source is removed in the adjacent footwall. Later incision and headward erosion of the footwall channels may cause re-capture of earlier channels, while network re-organisation may also cause depositional in-filling of earlier channels. The drainage divide shifts

  3. Rim Structure, Stratigraphy, and Aqueous Alteration Exposures Along Opportunity Rover's Traverse of the Noachian Endeavour Crater

    Crumpler, L.S.; Arvidson, R. E.; Golombek, M.; Grant, J. A.; Jolliff, B. L.; Mittlefehldt, D. W.


    The Mars Exploration Rover Opportunity has traversed 10.2 kilometers along segments of the west rim of the 22-kilometer-diameter Noachian Endeavour impact crater as of sol 4608 (01/09/17). The stratigraphy, attitude of units, lithology, and degradation state of bedrock outcrops exposed on the crater rim have been examined in situ and placed in geologic context. Structures within the rim and differences in physical properties of the identified lithologies have played important roles in localizing outcrops bearing evidence of aqueous alteration.

  4. Apollo 16 stratigraphy - The ANT hills, the Cayley Plains, and a pre-Imbrian regolith

    Taylor, G. J.; Drake, M. J.; Hallam, M. E.; Marvin, U. B.; Wood, J. A.


    A total of 645 particles in the 1 to 2 mm size range has been classified in the Apollo 16 soil samples 60602,3, 61242,7, 66042,4, 67602,13, and 69942,13. Five major categories of lithic fragments recognized in these samples include (1) an anorthositic/noritic/troctolitic, or ANT suite, (2) light-matrix breccias, (3) poikiloblastic noritic/anorthositic fragments, (4) spinel-troctolites, and (5) feldspathic basalts. The petrography and phase chemistry of the lithic fragments are discussed along with results of the fragment census and the stratigraphy of the Apollo 16 site.

  5. A Re-appraisal of the Stratigraphy, Palaeontology and Dating of Cow Cave, Chudleigh, Devon, England

    Simons Jim W.


    Cow Cave is an important Quaternary paleontological site in Chudleigh Gorge, Devon, UK., now known to have a sequence of cave-earths and stalagmite floors that range in age from Upper Middle Pleistocene (~MIS 7 interglacial) through to the Holocene (Flandrian) and the present day. Excavations in 1927-1934, and again in 1962-3, have provided a rich fauna, with some artefacts. Here, the stratigraphy of the deposits is now more fully described and the faunal remains are considered in their strat...

  6. Sequence stratigraphy and depositional systems in the Paleogene, Liaodong Bay

    Ji Hancheng


    Based on drilling and seismic data,the Paleogene developed in Liaodong Bay can be divided into five third-order sequences bounded by six sequence boundaries.Through analyzing depositional systems in each sequence in detail,the Es-3 time was defined as fast rifting.During the deposition of the Es-3 member,the lake basin was continuous along the N-S direction but compartmentalized along the E-W direction by several N-S trending faults.Deposition was dominated by steep slope fans and fan deltas.The time of Es-2 and Es-1 was stable settling.The lake basin expanded substantially.The fan delta system and braided fluvial system were developed.Carbonate and clastic deposits were formed on the Liaoxi (west Liaohe) Rise.The time of Ed-3 time was again fast rifting.During this time,shale was deposited.In the time of Es-2,tectonic movement weakened.The basin was higher in the west and north,and lower in the east and south.A series of delta depositionai systems were developed and smallscale slumping turbidite fans were present in semi-deep lake to deep lake.In the time of Ed-1,tectonic movement stopped.Flood plain deposition occurred.Finally the paper presents the characteristics of evolution and distribution of depositional systems both vertically and horizontally.

  7. Integrated stratigraphy and paleoenvironmental reconstruction for the Late Cretaceous Danish chalk based on the Stevns-2 core

    Boussaha, Myriam; Thibault, Nicolas Rudolph; Stemmerik, Lars

    An integrated stratigraphy of the Stevns-2 core located in eastern Denmark is hereby presented based on calcareous nannofossil biostratigraphy and carbon isotope stratigraphy. Carbon and oxygen isotope have been performed on 419 bulk samples. Calcareous nannofossil biostratigraphy has been applied...... in order to provide an age-model for Stevns-2. While using this age-model, differences in the sedimentation rates of Stevns-1 and Stevns-2 borehole are nicely expressed, although the two sites are only 8 km apart from each other. The mechanisms responsible for these changes are under investigation...

  8. Coastal barrier stratigraphy for Holocene high-resolution sea-level reconstruction

    Costas, Susana; Ferreira, Óscar; Plomaritis, Theocharis A.; Leorri, Eduardo


    The uncertainties surrounding present and future sea-level rise have revived the debate around sea-level changes through the deglaciation and mid- to late Holocene, from which arises a need for high-quality reconstructions of regional sea level. Here, we explore the stratigraphy of a sandy barrier to identify the best sea-level indicators and provide a new sea-level reconstruction for the central Portuguese coast over the past 6.5 ka. The selected indicators represent morphological features extracted from coastal barrier stratigraphy, beach berm and dune-beach contact. These features were mapped from high-resolution ground penetrating radar images of the subsurface and transformed into sea-level indicators through comparison with modern analogs and a chronology based on optically stimulated luminescence ages. Our reconstructions document a continuous but slow sea-level rise after 6.5 ka with an accumulated change in elevation of about 2 m. In the context of SW Europe, our results show good agreement with previous studies, including the Tagus isostatic model, with minor discrepancies that demand further improvement of regional models. This work reinforces the potential of barrier indicators to accurately reconstruct high-resolution mid- to late Holocene sea-level changes through simple approaches.

  9. Stratigraphy, geomorphology, geochemistry and hazard implications of the Nejapa Volcanic Field, western Managua, Nicaragua

    Avellán, Denis Ramón; Macías, José Luis; Pardo, Natalia; Scolamacchia, Teresa; Rodriguez, Dionisio


    The Nejapa Volcanic Field (NVF) is located on the western outskirts of Managua, Nicaragua. It consists of at least 30 volcanic structures emplaced along the N-S Nejapa fault, which represents the western active edge of the Managua Graben. The study area covers the central and southern parts of the volcanic field. We document the basic geomorphology, stratigraphy, chemistry and evolution of 17 monogenetic volcanic structures: Ticomo (A, B, C, D and E); Altos de Ticomo; Nejapa; San Patricio; Nejapa-Norte; Motastepe; El Hormigón; La Embajada; Asososca; Satélite; Refinería; and Cuesta El Plomo (A and B). Stratigraphy aided by radiocarbon dating suggests that 23 eruptions have occurred in the area during the past ~ 34,000 years. Fifteen of these eruptions originated in the volcanic field between ~ 28,500 and 2,130 yr BP with recurrence intervals varying from 400 to 7,000 yr. Most of these eruptions were phreatomagmatic with minor strombolian and fissural lava flow events. A future eruption along the fault might be of a phreatomagmatic type posing a serious threat to the more than 500,000 inhabitants in western Managua.

  10. Automated grid generation from models of complex geologic structure and stratigraphy

    Gable, C.; Trease, H.; Cherry, T.


    The construction of computational grids which accurately reflect complex geologic structure and stratigraphy for flow and transport models poses a formidable task. With an understanding of stratigraphy, material properties and boundary and initial conditions, the task of incorporating this data into a numerical model can be difficult and time consuming. Most GIS tools for representing complex geologic volumes and surfaces are not designed for producing optimal grids for flow and transport computation. We have developed a tool, GEOMESH, for generating finite element grids that maintain the geometric integrity of input volumes, surfaces, and geologic data and produce an optimal (Delaunay) tetrahedral grid that can be used for flow and transport computations. GEOMESH also satisfies the constraint that the geometric coupling coefficients of the grid are positive for all elements. GEOMESH generates grids for two dimensional cross sections, three dimensional regional models, represents faults and fractures, and has the capability of including finer grids representing tunnels and well bores into grids. GEOMESH also permits adaptive grid refinement in three dimensions. The tools to glue, merge and insert grids together demonstrate how complex grids can be built from simpler pieces. The resulting grid can be utilized by unstructured finite element or integrated finite difference computational physics codes.

  11. Stratigraphy of the north polar layered deposits of Mars from high-resolution topography

    Becerra, Patricio; Byrne, Shane; Sori, Michael M.; Sutton, Sarah; Herkenhoff, Kenneth E.


    The stratigraphy of the layered deposits of the polar regions of Mars is theorized to contain a record of recent climate change linked to insolation changes driven by variations in the planet's orbital and rotational parameters. In order to confidently link stratigraphic signals to insolation periodicities, a description of the stratigraphy is required based on quantities that directly relate to intrinsic properties of the layers. We use stereo Digital Terrain Models (DTMs) from the High Resolution Imaging Science Experiment (HiRISE) to derive a characteristic of North Polar Layered Deposits (NPLD) strata that can be correlated over large distances: the topographic protrusion of layers exposed in troughs, which is a proxy for the layers’ resistance to erosion. Using a combination of image analysis and a signal-matching algorithm to correlate continuous depth-protrusion signals taken from DTMs at different locations, we construct a stratigraphic column that describes the upper ~500 m of at least 7% of the area of the NPLD, and find accumulation rates that vary by factors of up to two. We find that, when coupled with observations of exposed layers in orbital images, the topographic expression of the strata is consistently continuous through large distances in the top 300 – 500 m of the NPLD, suggesting it is better related to intrinsic layer properties than brightness alone.

  12. The structures, stratigraphy and evolution of the Gulf of Corinth rift, Greece

    Taylor, Brian; Weiss, Jonathan R.; Goodliffe, Andrew M.; Sachpazi, Maria; Laigle, Mireille; Hirn, Alfred


    A multichannel seismic and bathymetry survey of the central and eastern Gulf of Corinth (GoC), Greece, reveals the offshore fault geometry, seismic stratigraphy and basin evolution of one of Earths most active continental rift systems. Active, right-stepping, en-echelon, north-dipping border faults trend ESE along the southern Gulf margin, significantly overlapping along strike. The basement offsets of three (Akrata-Derveni, Sithas and Xylocastro) are linked. The faults are biplanar to listric: typically intermediate angle (˜35° in the centre and 45-48° in the east) near the surface but decreasing in dip and/or intersecting a low- or shallow-angle (15-20° in the centre and 19-30° in the east) curvi-planar reflector in the basement. Major S-dipping border faults were active along the northern margin of the central Gulf early in the rift history, and remain active in the western Gulf and in the subsidiary Gulf of Lechaio, but unlike the southern border faults, are without major footwall uplift. Much of the eastern rift has a classic half-graben architecture whereas the central rift has a more symmetric w- or u-shape. The narrower and shallower western Gulf that transects the >40-km-thick crust of the Hellenides is associated with a wider distribution of overlapping high-angle normal faults that were formerly active on the Peloponnesus Peninsula. The easternmost sector includes the subsidiary Gulfs of Lechaio and Alkyonides, with major faults and basement structures trending NE, E-W and NW. The basement faults that control the rift architecture formed early in the rift history, with little evidence (other than the Vrachonisida fault along the northern margin) in the marine data for plan view evolution by subsequent fault linkage. Several have maximum offsets near one end. Crestal collapse graben formed where the hanging wall has pulled off the steeper onto the shallower downdip segment of the Derveni Fault. The dominant strikes of the Corinth rift faults

  13. Yucatan Subsurface Stratigraphy from Geophysical Data, Well Logs and Core Analyses in the Chicxulub Impact Crater and Implications for Target Heterogeneities

    Canales, I.; Fucugauchi, J. U.; Perez-Cruz, L. L.; Camargo, A. Z.; Perez-Cruz, G.


    Asymmetries in the geophysical signature of Chicxulub crater are being evaluated to investigate on effects of impact angle and trajectory and pre-existing target structural controls for final crater form. Early studies interpreted asymmetries in the gravity anomaly in the offshore sector to propose oblique either northwest- and northeast-directed trajectories. An oblique impact was correlated to the global ejecta distribution and enhanced environmental disturbance. In contrast, recent studies using marine seismic data and computer modeling have shown that crater asymmetries correlate with pre-existing undulations of the Cretaceous continental shelf, suggesting a structural control of target heterogeneities. Documentation of Yucatan subsurface stratigraphy has been limited by lack of outcrops of pre-Paleogene rocks. The extensive cover of platform carbonate rocks has not been affected by faulting or deformation and with no rivers cutting the carbonates, information comes mainly from the drilling programs and geophysical surveys. Here we revisit the subsurface stratigraphy in the crater area from the well log data and cores retrieved in the drilling projects and marine seismic reflection profiles. Other source of information being exploited comes from the impact breccias, which contain a sampling of disrupted target sequences, including crystalline basement and Mesozoic sediments. We analyze gravity and seismic data from the various exploration surveys, including multiple Pemex profiles in the platform and the Chicxulub experiments. Analyses of well log data and seismic profiles identify contacts for Lower Cretaceous, Cretaceous/Jurassic and K/Pg boundaries. Results show that the Cretaceous continental shelf was shallower on the south and southwest than on the east, with emerged areas in Quintana Roo and Belize. Mesozoic and upper Paleozoic sediments show variable thickness, possibly reflecting the crystalline basement regional structure. Paleozoic and Precambrian

  14. Sequence Stratigraphy of the Dakota Sandstone, Eastern San Juan Basin, New Mexico, and its Relationship to Reservoir Compartmentalization

    Varney, Peter J.


    This research established the Dakota-outcrop sequence stratigraphy in part of the eastern San Juan Basin, New Mexico, and relates reservoir quality lithologies in depositional sequences to structure and reservoir compartmentalization in the South Lindrith Field area. The result was a predictive tool that will help guide further exploration and development.

  15. Upper Campanian–Maastrichtian nannofossil biostratigraphy and high-resolution carbon-isotope stratigraphy of the Danish Basin

    Thibault, Nicolas Rudolph; Harlou, Rikke; Schovsbo, Niels


    High-resolution carbon isotope stratigraphy of the upper Campanian – Maastrichtian is recorded in the Boreal Realm from a total of 1968 bulk chalk samples of the Stevns-1 core, eastern Denmark. Isotopic trends are calibrated by calcareous nannofossil bio-events and are correlated with a lower-res...

  16. Subsurface stratigraphy and structure of A/M area at the Savannah River Site, Aiken County, South Carolina

    Fallaw, W.C.; Sims, W.R.; Haselow, J.S.


    This report is a study of the stratigraphy and structure of the A/M Area Hazardous Waste Management Facility Post-Closure Care Permit process on the Savannah River Site. The data from the lithologic and geophysical logs of 93 wells is the basis of this analysis.

  17. Subsurface stratigraphy and structure of A/M area at the Savannah River Site, Aiken County, South Carolina. Final report

    Fallaw, W.C.; Sims, W.R.; Haselow, J.S.


    This report is a study of the stratigraphy and structure of the A/M Area Hazardous Waste Management Facility Post-Closure Care Permit process on the Savannah River Site. The data from the lithologic and geophysical logs of 93 wells is the basis of this analysis.

  18. High-resolution sequence stratigraphy of fluvio-deltaic systems: Prospects of system-wide chronostratigraphic correlation

    Dalman, R.A.F.; Weltje, G.J.; Karamitopoulos, P.


    A basin-scale numerical model with a sub-grid parameterization of fluvio–deltaic processes and stratigraphy was used to study the relation between alluvial sedimentation and marine deltaic deposition under conditions of time-invariant forcing. The experiments show that delta evolution is governed by

  19. Analyses of Sequence Stratigraphy and Environments across Permian-Triassic Boundary in Liaotian, Northwestern Jiangxi Province


    Based on the study of lithology, sedimentology and paleontology at the Permian-Triassic boundary in Liaotian, Northwestern Jiangxi Province, the sequence stratigraphy and depositional environments across the boundary are reconstructed. The top part of the Upper Permian Changxing Formation is composed of very thick-bedded light-colored dolomitic limestone formed in high deposition rate on carbonate ramp, which indacates a transgression systems tract (TST). The Lower Triassic Qinglong Formation shows continuous deposition with the underlying Upper Permian. The lower member of Qinglong Formation consists of calcareous shale, shelly limestome and dolomitic limestone with abundant bivalves (Claraia sp. )and trace fossils (Chondrites). The calcareous shale at the bottom of Lower Triassic indicates a calm deep water environment to form the condensed section (CS). The shelly limestome and dolomitic limestone with shell fossils, intraclast, algal ooide show clean but turbulent environment of carbonate ramp, which produce the deposition of highstand systems tract (TST).

  20. Significance of ichnofossils to genetic stratigraphy--Examples from the Cretaceous of Alberta, Canada


    Trace fossils represent both sedimentological and paleontological entities, representing a unique blending of potential environmental indicators in the rock record. Trace fossils and trace fossil suites can be employed effectively to aid in the recognition of various discontinuity types and to assist in their genetic interpretation. Ichnology may be employed to resolve surfaces of stratigraphic significance in two main ways: 1) through the identification of discontinuities using substrate-controlled ichnofacies, and 2) through careful analysis of vertical softground (penecontemporaneous) ichnologic successions (analogous to facies successions). Ichnological analysis is a valuable tool in genetic stratigraphic studies. Integrating the data derived from substrate-controlled ichnofacies with paleoecological data from vertical ichnologic successions greatly enhances the recognition and interpretation of a wide variety of stratigraphic surfaces. When this is coupled with conventional facies analysis and sequence stratigraphy, a powerful approach to the interpretation of the rock record is generated.

  1. Reinterpretation of the stratigraphy and structure of the Rancho Las Norias area, central Sonora, Mexico

    Page, W.R.; Harris, A.G.; Poole, F.G.; Repetski, J.E.


    New geologic mapping and fossil data in the vicinity of Rancho Las Norias, 30 km east of Hermosillo, Sonora, Mexico, show that rocks previously mapped as Precambrian instead are Paleozoic. Previous geologic maps of the Rancho Las Norias area show northeast-directed, southwest-dipping reverse or thrust faults deforming both Precambrian and Paleozoic rocks. The revised stratigraphy requires reinterpretation of some of these faults as high-angle normal or oblique-slip faults and the elimination of other faults. We agree with earlier geologic map interpretations that compressional structures have affected the Paleozoic rocks in the area, but our mapping suggests that the direction of compression is from southeast to northwest. Published by Elsevier Ltd.

  2. Ice stratigraphy at the Pakitsoq ice margin, West Greenland, derived from gas records

    Schaefer, H.; Petrenko, V. V.; Brook, E. J.;


    Horizontal ice-core sites, where ancient ice is exposed at the glacier surface, offer unique opportunities for paleo-studies of trace components requiring large sample volumes. Following previous work at the Pakitsoq ice margin in West Greenland, we use a combination of geochemical parameters...... measured in the ice matrix (delta O-18(ice)) and air occlusions (delta O-18(atm), delta N-15 of N-2 and methane concentration) to date ice layers from specific climatic intervals. The data presented here expand our understanding of the stratigraphy and three-dimensional structure of ice layers outcropping...... at Pakitsoq. Sections containing ice from every distinct climatic interval during Termination I, including Last Glacial Maximum, Bolling/Allerod, Younger Dryas and the early Holocene, are identified. In the early Holocene, we find evidence for climatic fluctuations similar to signals found in deep ice cores...

  3. Soil Stratigraphy from Three Pleistocene Archaeological Sites of the Middle Ter River Valley, Catalonia, Spain

    Sayantani NEOGI


    Full Text Available This dissertation summarizes the stratigraphic description of three Pleistocene archaeological sites inthe middle Ter river valley. A long history of archaeological research in this region suggests thepossibility of developing contextual studies. This work is basically an investigation of two soilformation processes from the deep soil horizons of the Mediterranean region: clay illuviation andcarbonatation. This approach has been developed by soil micromorphology, a technique well suitedfor this type of record, supplemented by fundamental field descriptions and basic cartography of the geomorphological terraces of the middle Ter river valley. The soil stratigraphy of archaeological sites and Pleistocene landscapes opens the opportunity to investigate a complex subject of study. The soils and paleosols are a source of information for palaeoecology and human occupations. It has been attempted here only to lay the groundwork for the interpretation of genetic factors pointing to the classification of soils.

  4. Holocene stratigraphy and vegetation history in the Scoresby Sund area, East Greenland

    Funder, Svend Visby


    areas, and a 'poor' heath dominated by the high arctic Salix Arctica and Cassiope tetragona expanded. These two species, which are now extremely common, apparently did not grow in the area until c. 6000 yrBP. In lakes in the coastal area minerogenic sedimentation at c. 2800 yr BP, reflecting the general......The Holocene stratigraphy in Scoresby Sund is based on climatic change as reflected by fluctuations in fjord and valley glaciers, immigration and extinction of marine molluscs, and the vegetation history recorded in pollen diagrams from five lakes. The histories are dated by C-14, and indirectly...... into the area, and in the period until 5000 yr BP dense dwarf shrub heath grew in areaS where it is now absent. In the fjords the subarctic Mytilus edulis and Pecten islandica lived, suggesting a climate warmer than the present. From c. 5000 yr BP the dense dwarf shrub heath began to disappear in the coastal...

  5. A Re-appraisal of the Stratigraphy, Palaeontology and Dating of Cow Cave, Chudleigh, Devon, England

    Simons Jim W.


    Full Text Available Cow Cave is an important Quaternary paleontological site in Chudleigh Gorge, Devon, UK., now known to have a sequence of cave-earths and stalagmite floors that range in age from Upper Middle Pleistocene (~MIS 7 interglacial through to the Holocene (Flandrian and the present day. Excavations in 1927-1934, and again in 1962-3, have provided a rich fauna, with some artefacts. Here, the stratigraphy of the deposits is now more fully described and the faunal remains are considered in their stratigraphical contexts. Data supporting the existence of former cave entrances are presented along with an analysis of the processes of sedimentation and taphonomy with their climatic interpretations. Based on recent U-Th dating of a critical Stalagmite horizon, a chronology of the mid-Pleistocene to Holocene sequence is discussed. Finally, further excavation in Cow Cave and nearby sites is recommended.

  6. Banding in Mount Sharp, Gale Crater: Stratigraphy, Strandlines, or Buttress Unconformities?

    Parker, T. J.; Dietrich, W. E.; Palucis, M. C.; Calef, F. J., III; Newsom, H. E.


    Banding along the lower flanks of Mount Sharp has generally been interpreted to indicate stratigraphy within the mound that dips gently outward from it. Many of these bands define prominent terraces that can be traced nearly to closure around the mound, potentially providing chronostratigraphic markers. However, comparing orbital imagery and digital elevation models with ground-based views from Curiosity's Mastcam suggests much of the banding might indicate buttress unconformities of now-largely-deflated plains units and/or paleolake strandlines that may not extend into the subsurface. Resistant horizons that parallel the upper surface of the mound can be identified in several erosional pits and along flanks of many of the butte "foothills" of Mt Sharp. These surfaces suggest that Mt Sharp was emplaced as a mound that may have been a few percent larger than the modern remnant, but that likely never extended across Gale crater and over the surrounding highland terrains. Other geomorphic surfaces - e.g., the fan-shaped feature at the mouth of the science target canyon - suggest paleo stratigraphic surfaces that dip outward at an angle steeper than the banding. The banding continues across these resistant horizons and other geomorphic surfaces without interruption, supporting the inference that it is overprinted onto dipping stratigraphy within Mt Sharp. Previously, we have identified at least three lake levels associated with major valley network fans/deltas debouching into Gale through the crater's rim. It may be possible to correlate these with specific bands or terraces along the outer margin of Mount Sharp, enabling volume estimates and relative timing of lake levels within the crater to be addressed.

  7. Observations of stratigraphy and volcanism from guinevere and sedna planitiae, venus

    Copp, Duncan L.


    Detailed mapping, using recently acquired full resolution photo-products and synthetic stereo data from the Magellan spacecraft, is used to investigate the stratigraphy and formation of landforms observed on Venus. The research focuses on two large contiguous plains, Guinevere and Sedna Planitiae. It has been suggested that distinct volcanic and deformational processes have operated throughout Venus within specific time periods. For example tesserae are considered to have only formed relatively early on in the visible venusian rock record. New observations of volcanic landforms within Guinevere and Sedna Planitia support a non-directional stratigraphy. Contrary to earlier models for the evolution of coronae, those in the study area have had a protracted history. Both Idem-Kuva and Heng-o display multiple phases of annulus formation (previously thought to occur during a specific stage of corona formation). Furthermore, annulus formation and rim topography formation do not necessarily coincide in space and time, as seen at Idem-Kuva, indicating that both large and small-scale deformational processes at coronae can be protracted. The amount and style of volcanism associated with the coronae studied here varies considerably. Predicted early stage volcanism is not observed at Idem-Kuva, Nissaba or Silvia Coronae, while Benten Corona shows multiple phases of volcanism which decrease in volume over time. A study of Sif and Gula Montes shows the two large shield volcanoes have a different overall morphology, summit structure and associated flow fields. Sif Mons is approximately circular in plan view, with a prominent summit caldera, with morphologically varying flow fields. In contrast, Gula Mons in elongate in plan view, surmounted by a rift joining two modified calderas, and is surrounded by more sinuous flows. Using terrestrial volcanoes as analogies, especially Mt. Etna, it is shown that the morphological differences between the two volcanoes may be a consequence of

  8. Stratigraphy of Pyroclastic Deposits of EL Aguajito Caldera, Baja California Sur, MÉXICO

    Osorio Ocampo, L. S.; Macias, J. L.; García Sánchez, L.; Pola, A.; Saucedo, R.; Sánchez, J. M.; Avellán, D. R.; Cardona, S.; Reyes-Agustín, G.; Arce, J. L.


    El Aguajito caldera is located in the State of Baja California Sur, it comprises an area of 450 km2 and sits within the Santa Rosalía Basin which is controlled by NE-SW extensional structures and the NW-SE Cimarron Fault that transects the caldera structure. The oldest rocks are ~90 Ma granodiorites covered by an Oligocene-Miocene volcano-sedimentary sequence, the Miocene Santa Lucia Formation and La Esperanza basalt. Pliocene volcanism is represented by La Reforma caldera, El Aguajito caldera, and the Tres Vírgenes Volcanic complex. This study focuses on the cartography and stratigraphy of area in order to understand the evolution of the volcanic system. The stratigraphy from base to top consists of a series of shallow marine sediments (fossiliferous sandstones) covered by a thick sequence of ignimbrites and pyroclastic flows interbedded with volcaniclastic deposits (Gloria and El Infierno Formations). On top of these deposits is El Aguajito caldera, it consists of a 2 m thick pumice fallout followed by an ignimbrite with three transitional lithofacies: a ≤30-m thick light-pink pyroclastic flow enriched in pumice at the base that gradually becomes enrich in lithics towards the top with the occurrence of degasing pipes. On top rests a 15 m-thick light-purple ignimbrite slightly welded with fiammes and a sequence of pumiceous pyroclastic flows and fallouts. These deposits have been associate to the caldera formation with a collapse diameter of ~8 km marked by rhyolitic domes exposed along a ring collapse crowned the sequence as well as NW-SE aligned rhyolitic domes parallel to the seashore. This cartography allowed to present a preliminary new geological map with four stratigraphic units recognized so far, that were emplaced under subaerial conditions beginning with a Plinian column followed by the emplacement of El Aguajito ignimbrite with its subsequent caldera collapse and finally the extrusion of resurgent domes.

  9. Shallow Stratigraphy of Valsequillo Basin From Electrical Resistivity Soundings, Gravity and Magnetics

    Trigo-Huesca, A.; Tellez-Garcia, E.; Ortega-Nieto, A.; Mayo-Reyes, J.; Lopez-Aguirre, D.; Perez-Cruz, L.; Gogichaishvili, A.; Urrutia-Fucugauchi, J.


    The recent study by Gonzalez et al. (2006) on the occurrence of apparent human and animal footprints on the Xalnene ash that outcrops in the Valsequillo Basin has attracted attention to the region of central Mexico, within the context of the early human migration in the Americas. OSL dating of interlayered baked lake sediments gave dates around 40 ka, supporting an early human presence in central Mexico. Xalnene ash was dated by Renne et al. (2005) giving an Ar/Ar date of 1.3 Ma, questioning a human origin for the footprints. Paleomagnetic and rock magnetic data on the Xalnene ash and Toluquilla volcano lavas have been discussed in terms of the correlation to the C1r.2r chron (about 1.07 to 1.77 Ma) and the old Ar/Ar date or the Laschamp geomagnetic excursion and the younger OSL dates. These studies have highlighted the interest on the stratigraphy of the volcanic and sedimentary sequence of the Valsequillo Basin. Here, we present initial results from electrical resistivity soundings, gravity and magnetics in the areas covered by the Xalnene ash and the nearby Toluquilla volcano. The geophysical models are interpreted in terms of the shallow stratigraphy of the volcanic and lacustrine sediment units. The electrical resistivity soundings identify several layers in the shallow 8-20 m, beneath the area with the apparent footprints and the slope of Toluquilla volcano, and permit imaging of these shallow units. Geophysical models for the Toluquilla volcano and surrounding zones allow deeper investigation and incorporate several units mapped in past studies, particularly the Xalnene ash, upper/lower lacustrine sequences, lahars, Caulapan tuffs and sediments, and Balsas Group sedimentary rocks.

  10. 3-D visualisation of palaeoseismic trench stratigraphy and trench logging using terrestrial remote sensing and GPR - a multiparametric interpretation

    Schneiderwind, Sascha; Mason, Jack; Wiatr, Thomas; Papanikolaou, Ioannis; Reicherter, Klaus


    Two normal faults on the island of Crete and mainland Greece were studied to test an innovative workflow with the goal of obtaining a more objective palaeoseismic trench log, and a 3-D view of the sedimentary architecture within the trench walls. Sedimentary feature geometries in palaeoseismic trenches are related to palaeoearthquake magnitudes which are used in seismic hazard assessments. If the geometry of these sedimentary features can be more representatively measured, seismic hazard assessments can be improved. In this study more representative measurements of sedimentary features are achieved by combining classical palaeoseismic trenching techniques with multispectral approaches. A conventional trench log was firstly compared to results of ISO (iterative self-organising) cluster analysis of a true colour photomosaic representing the spectrum of visible light. Photomosaic acquisition disadvantages (e.g. illumination) were addressed by complementing the data set with active near-infrared backscatter signal image from t-LiDAR measurements. The multispectral analysis shows that distinct layers can be identified and it compares well with the conventional trench log. According to this, a distinction of adjacent stratigraphic units was enabled by their particular multispectral composition signature. Based on the trench log, a 3-D interpretation of attached 2-D ground-penetrating radar (GPR) profiles collected on the vertical trench wall was then possible. This is highly beneficial for measuring representative layer thicknesses, displacements, and geometries at depth within the trench wall. Thus, misinterpretation due to cutting effects is minimised. This manuscript combines multiparametric approaches and shows (i) how a 3-D visualisation of palaeoseismic trench stratigraphy and logging can be accomplished by combining t-LiDAR and GPR techniques, and (ii) how a multispectral digital analysis can offer additional advantages to interpret palaeoseismic and stratigraphic

  11. Improved understanding of Diatom stratigraphy in a varved sediment through a sediment trap, lake monitoring and a catchment study

    Maier, D. B.


    Biological sediment remains reflect past lake surrounding conditions. Potential drivers of change in the biological sediment proxy can be environmental contributors like weather and temperature changes as well as man-made such as developments in agriculture and forestry. However we don't know how these different factors contribute to the biological sediment signal. Here we are monitoring a boreal lake with a varved sediment to understand how the biological signal of diatom remains is formed in the annually layered sediment. We compare the diatom stratigraphy with a sequential sediment trap. For a deeper understanding of the underlying mechanisms we look at three full years of bi-weekly monitoring of physical, chemical and biological parameters and 15 years of water stratification data. We seek to link the monitored in-lake processes with the yearly environmental characteristics. The diatom sediment stratigraphy of the two most abundant species Asterionella formosa and Fragilaria delicatissima indicates three periods with a contrasting trend for both species from 1975 until 2014. In the first period Asterionella formosa is almost not abundant spanning one decade (1975-1985), reaching elevated abundance with a decreasing trend in period 2 over the following 17 years to be followed by a tripling of Asterionella fromosa remains in the sediment during the third period. The opposite trend is found for Fragilaria delicatissima. Linking the recorded data with the corresponding sediment stratigraphy allows us to distinguish between weather changes and catchment disturbances as potential drivers for changes in a sedimentary diatom signal.

  12. Late Pleistocene Holocene stratigraphy and radiocarbon dating of La Malinche volcano, Central Mexico

    Castro-Govea, Renato; Siebe, Claus


    Previous studies of La Malinche identified and radiocarbon dated several volcanic layers, the youngest of which yielded an age of ca. 7.5 ka. An additional ash fallout layer that crops out at high altitudes was considered the most recent deposit, with an estimated age of 6 ka. In the present work 38 new radiocarbon ages are presented. From these, several date the young ash fallout layer and lie around 3.1 ka. With the aid of these dates a new and comprehensive stratigraphy documenting the Late Pleistocene-Holocene eruptive history of La Malinche is presented. The stratigraphy indicates two main stages of volcanic activity: Pre-Malinche and Malinche. The first undoubtedly comprises the major part of the eruptive history, but its deposits are largely covered by the products of the latter stage, on which this study is focused. The Malinche stage was subdivided into three eruptive periods. Period 1 started with the emplacement of the Huamantla Pumice more than 45 ka ago. This deposit consists of a thick pumice fallout overlain by pyroclastic flow deposits. Subsequently, several episodes of construction and collapse of summit domes occurred. The oldest dome was dated at ca. 45 ka. Period 2 started 21.5 ka ago with the Malinche Pumice I, a widespread pumice fallout covering the entire slopes of the volcano. Pyroclastic flows and lahars related to this eruption were channeled along deep barrancas and reached considerable distances. Deposits produced by partial sector collapse and dated at ca. 20.9 ka, and a pumice-and-ash flow deposit dated at 15.9 ka were also generated during this period. The last period started with the eruption of the Malinche Pumice II, a distinctive fallout deposit overlain by ash flow deposits on the NE slope of the volcano. The age of this pumice layer is estimated between 12 and 9 ka. Formation of block-and-ash flows, lahars and pumice-and-ash flows followed during this period, and peaked in a most intensive episode that was dated at 7.5 ka

  13. Quantifiable effectiveness of experimental scaling of river- and delta morphodynamics and stratigraphy

    Kleinhans, Maarten G.; van Dijk, Wout M.; van de Lageweg, Wietse I.; Hoyal, David C. J. D.; Markies, Henk; van Maarseveen, Marcel; Roosendaal, Chris; van Weesep, Wendell; van Breemen, Dimitri; Hoendervoogt, Remko; Cheshier, Nathan


    Laboratory experiments to simulate landscapes and stratigraphy often suffer from scale effects, because reducing length- and time scales leads to different behaviour of water and sediment. Classically, scaling proceeded from dimensional analysis of the equations of motion and sediment transport, and minor concessions, such as vertical length scale distortion, led to acceptable results. In the past decade many experiments were done that seriously violated these scaling rules, but nevertheless produced significant and insightful results that resemble the real world in quantifiable ways. Here we focus on self-formed fluvial channels and channel patterns in experiments. The objectives of this paper are 1) to identify what aspects of scaling considerations are most important for experiments that simulate morphodynamics and stratigraphy of rivers and deltas, 2) to establish a design strategy for experiments based on a combination of relaxed classical scale rules, theory of bars and meanders, and small-scale experiments focussed at specific processes. We present a number of small laboratory setups and protocols that we use to rapidly quantify erosional and depositional types of forms and dynamics that develop in the landscape experiments as a function of detailed properties, such as effective material strength, and to assess potential scale effects. Most importantly, the width-to-depth ratio of channels determines the bar pattern and meandering tendency. The strength of floodplain material determines these channel dimensions, and theory predicts that laboratory rivers should have 1.5 times larger width-to-depth ratios for the same bar pattern. We show how floodplain formation can be controlled by adding silt-sized silicaflour, bentonite, Medicago sativa (alfalfa) or Partially Hydrolyzed PolyAcrylamide (a synthetic polymer) to poorly sorted sediment. The experiments demonstrate that there is a narrow range of conditions between no mobility of bed or banks, and too much

  14. OSL dating of Glacial Sediments from New Zealand and Olympic Mountains: Using Stratigraphy to our Advantage

    Rittenour, T. M.; Thackray, G. D.; Shulmeister, J.


    Optically stimulated luminescence (OSL) dating provides an age estimate for the last time sediment was exposed to light. In glacial environments solar resetting of the luminescence signal prior to deposition is not assured and can lead to significant age overestimates. Sediments derived from glacial settings also commonly have other deleterious properties such as weak quartz luminescence signals, feldspar contamination and high levels of electron thermal transfer. Despite these potential problems, OSL commonly provides the only means to date glacial deposits due to limited material for radiocarbon and/or surface exposure dating, discrepancies between the age of a landform and the targeted underlying sediment, or deposit age beyond the range for radiocarbon. As part of a larger project to reconstruct MIS 3/4 glacial chronologies, OSL samples were collected from the Rangitata and Clutha River basins along the eastern Southern Alps, New Zealand and from the Hoh and Queets River basins, western Olympic Mountains, Washington USA. Samples for quartz OSL dating were collected from carefully selected shallow-water and well-sorted facies of glaciofluvial and glaciolacustrine sediments to select sediments most likely to have been exposed to light prior to deposition. OSL dating is preferred over other dating methods in the study areas because evidence for multiple pre-LGM glaciations is commonly preserved as buried and over-run packages of diamicton, outwash and lacustrine sediment, excluding application of surface-exposure techniques. Further, where the sediments are in fact associated with surficial landforms, detailed description of the underlying stratigraphy permits interpretation of the glacial processes at work and thus provides a more thorough understanding of the relevance of the ages to the advance. Results indicate that while some samples contain evidence for partial bleaching, most show symmetric equivalent dose distributions, and ages are in stratigraphic order

  15. A Subsurface Soil Composition and Physical Properties Experiment to Address Mars Regolith Stratigraphy

    Richter, L.; Sims, M.; Economou, T.; Stoker, C.; Wright, I.; Tokano, T.


    Previous in-situ measurements of soil-like materials on the surface of Mars, in particular during the on-going Mars Exploration Rover missions, have shown complex relationships between composition, exposure to the surface environment, texture, and local rocks. In particular, a diversity in both compositional and physical properties could be established that is interpreted to be diagnostic of the complex geologic history of the martian surface layer. Physical and chemical properties vary laterally and vertically, providing insight into the composition of rocks from which soils derive, and environmental conditions that led to soil formation. They are central to understanding whether habitable environments existed on Mars in the distant past. An instrument the Mole for Soil Compositional Studies and Sampling (MOCSS) - is proposed to allow repeated access to subsurface regolith on Mars to depths of up to 1.5 meters for in-situ measurements of elemental composition and of physical and thermophysical properties, as well as for subsurface sample acquisition. MOCSS is based on the compact PLUTO (PLanetary Underground TOol) Mole system developed for the Beagle 2 lander and incorporates a small X-ray fluorescence spectrometer within the Mole which is a new development. Overall MOCSS mass is approximately 1.4 kilograms. Taken together, the MOCSS science data support to decipher the geologic history at the landing site as compositional and textural stratigraphy if they exist - can be detected at a number of places if the MOCSS were accommodated on a rover such as MSL. Based on uncovered stratigraphy, the regional sequence of depositional and erosional styles can be constrained which has an impact on understanding the ancient history of the Martian near-surface layer, considering estimates of Mars soil production rates of 0.5... 1.0 meters per billion years on the one hand and Mole subsurface access capability of approximately 1.5 meters. An overview of the MOCSS, XRS

  16. Preliminary Physical Stratigraphy and Geophysical Data From the USGS Dixon Core, Onslow County, North Carolina

    Seefelt, Ellen L.; Gonzalez, Wilma Aleman B.; Self-Trail, Jean M.; Weems, Robert E.; Edwards, Lucy E.; Pierce, Herbert A.; Durand, Colleen T.


    In October through November 2006, scientists from the U. S. Geological Survey (USGS) Eastern Region Earth Surface Processes Team (EESPT) and the Raleigh (N.C.) Water Science Center (WSC), in cooperation with the North Carolina Geological Survey (NCGS) and the Onslow County Water and Sewer Authority (ONWASA), drilled a stratigraphic test hole and well in Onslow County, N.C. The Dixon corehole was cored on ONWASA water utility property north of the town of Dixon, N.C., in the Sneads Ferry 7.5-minute quadrangle at latitude 34deg33'35' N, longitude 77deg26'54' W (decimal degrees 34.559722 and -77.448333). The site elevation is 66.0 feet (ft) above mean sea level as determined using a Paulin precision altimeter. The corehole attained a total depth of 1,010 ft and was continuously cored by the USGS EESPT drilling crew. A groundwater monitoring well was installed in the screened interval between 234 and 254 ft below land surface. The section cored at this site includes Upper Cretaceous, Paleogene, and Neogene sediments. The Dixon core is stored at the NCGS Coastal Plain core storage facility in Raleigh. The Dixon corehole is the fourth and last in a series of planned North Carolina benchmark coreholes drilled by the USGS Coastal Carolina Project. These coreholes explore the physical stratigraphy, facies, and thickness of Cretaceous, Paleogene, and Neogene Coastal Plain sediments in North Carolina. Correlations of lithologies, facies, and sequence stratigraphy can be made with the Hope Plantation corehole, N.C., near Windsor in Bertie County (Weems and others, 2007); the Elizabethtown corehole, near Elizabethtown, N.C., in Bladen County (Self-Trail and others, 2004b); the Smith Elementary School corehole, near Cove City, N.C., in Craven County (Harris and Self-Trail, 2006; Crocetti, 2007); the Kure Beach corehole, near Wilmington, N.C., in New Hanover County (Self-Trail and others, 2004a); the Esso#1, Esso #2, Mobil #1, and Mobil #2 cores in Albermarle and Pamlico Sounds

  17. 'Combined reflectance stratigraphy' - subdivision of loess successions by diffuse reflectance spectrometry (DRS)

    Szeberényi, Jozsef; Bradak-Hayashi, Balázs; Kiss, Klaudia; Kovács, József; Varga, György; Balázs, Réka; Szalai, Zoltán; Viczián, István


    The different varieties of loess (and intercalated paleosol layers) together constitute one of the most widespread terrestrial sediments, which was deposited, altered, and redeposited in the course of the changing climatic conditions of the Pleistocene. To reveal more information about Pleistocene climate cycles and/or environments the detailed lithostratigraphical subdivision and classification of the loess variations and paleosols are necessary. Beside the numerous method such as various field measurements, semi-quantitative tests and laboratory investigations, diffuse reflectance spectroscopy (DRS) is one of the well applied method on loess/paleosol sequences. Generally, DRS has been used to separate the detrital and pedogenic mineral component of the loess sections by the hematite/goethite ratio. DRS also has been applied as a joint method of various environmental magnetic investigations such as magnetic susceptibility- and isothermal remanent magnetization measurements. In our study the so-called "combined reflectance stratigraphy method" were developed. At First, complex mathematical method was applied to compare the results of the spectral reflectance measurements. One of the most preferred multivariate methods is cluster analysis. Its scope is to group and compare the loess variations and paleosol based on the similarity and common properties of their reflectance curves. In the Second, beside the basic subdivision of the profiles by the different reflectance curves of the layers, the most characteristic wavelength section of the reflectance curve was determined. This sections played the most important role during the classification of the different materials of the section. The reflectance value of individual samples, belonged to the characteristic wavelength were depicted in the function of depth and well correlated with other proxies like grain size distribution and magnetic susceptibility data. The results of the correlation showed the significance of

  18. Origins and Asteroid Main-Belt Stratigraphy for H-, L-, LL-Chondrite Meteorites

    Binzel, Richard; DeMeo, Francesca; Burbine, Thomas; Polishook, David; Birlan, Mirel


    We trace the origins of ordinary chondrite meteorites to their main-belt sources using their (presumably) larger counterparts observable as near-Earth asteroids (NEAs). We find the ordinary chondrite stratigraphy in the main belt to be LL, H, L (increasing distance from the Sun). We derive this result using spectral information from more than 1000 near-Earth asteroids [1]. Our methodology is to correlate each NEA's main-belt source region [2] with its modeled mineralogy [3]. We find LL chondrites predominantly originate from the inner edge of the asteroid belt (nu6 region at 2.1 AU), H chondrites from the 3:1 resonance region (2.5 AU), and the L chondrites from the outer belt 5:2 resonance region (2.8 AU). Each of these source regions has been cited by previous researchers [e.g. 4, 5, 6], but this work uses an independent methodology that simultaneously solves for the LL, H, L stratigraphy. We seek feedback from the planetary origins and meteoritical communities on the viability or implications of this stratrigraphy.Methodology: Spectroscopic and taxonomic data are from the NASA IRTF MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS) [1]. For each near-Earth asteroid, we use the Bottke source model [2] to assign a probability that the object is derived from five different main-belt source regions. For each spectrum, we apply the Shkuratov model [3] for radiative transfer within compositional mixing to derive estimates for the ol / (ol+px) ratio (and its uncertainty). The Bottke source region model [2] and the Shkuratov mineralogic model [3] each deliver a probability distribution. For each NEA, we convolve its source region probability distribution with its meteorite class distribution to yield a likelihood for where that class originates. Acknowledgements: This work supported by the National Science Foundation Grant 0907766 and NASA Grant NNX10AG27G.References: [1] Binzel et al. (2005), LPSC XXXVI, 36.1817. [2] Bottke et al. (2002). Icarus 156, 399. [3

  19. Influence of near-surface stratigraphy on coastal landslides at Sleeping Bear Dunes National Lakeshore, Lake Michigan, USA

    Barnhardt, W.A.; Jaffe, B.E.; Kayen, R.E.; Cochrane, G.R.


    Lake-level change and landslides are primary controls on the development of coastal environments along the coast of northeastern Lake Michigan. The late Quaternary geology of Sleeping Bear Dunes National Lakeshore was examined with high-resolution seismic reflection profiles, ground-penetrating radar (GPR), and boreholes. Based on sequence-stratigraphic principles, this study recognizes ten stratigraphic units and three major unconformities that were formed by late Pleistocene glaciation and postglacial lake-level changes. Locally high sediment supply, and reworking by two regressions and a transgression have produced a complex stratigraphy that is prone to episodic failure. In 1995, a large landslide deposited approximately 1 million m3 of sediment on the lake floor. The highly deformed landslide deposits, up to 18 m thick, extend 3-4 km offshore and unconformably overlie well-stratified glacial and lacustrine sediment. The landslide-prone bluff is underlain by channel-fill deposits that are oriented nearly perpendicular to the shoreline. The paleochannels are at least 10 m deep and 400 m wide and probably represent stream incision during a lake-level lowstand about 10.3 ka B.P. The channels filled with sediment during the subsequent transgression and lake-level highstand, which climaxed about 4.5 ka B.P. As lake level fell from the highstand, the formation of beach ridges and sand dunes sealed off the channel and isolated a small inland lake (Glen Lake), which lies 5 m above the level of Lake Michigan and may be a source of piped groundwater. Our hypothesis is that the paleochannels act as conduits for pore water flow, and thereby locally reduce soil strength and promote slope failure.

  20. Geology and Stratigraphy of the East and West Firing Areas Lawrence Livermore National Laboratory Site 300

    Ehman, K D


    The purpose of this project is to gain a better understanding of the stratigraphy and geologic structure of the East and West Firing Areas, at Lawrence Livermore National Laboratory Site 300 (Figure 1). This analysis is designed to help better delineate hydrostratigraphic units (HSUs) in order to enhance the understanding of the fate and transport of contaminants in the subsurface. Specific objectives of the investigation include: (1) Evaluation of the stratigraphic relationships between the units that contain tritium in ground water that originates from Pit 7 and the Building 850 area in the vicinity of Doall Ravine; (2) The correlation of these units across the Elk Ravine Fault Zone; and (3) The correlation of these units between the Building 865, Pit 1, Pit 2, and Building 812 areas. These issues were raised by regulators at the Regional Water Quality Control Board in the review of the Pit 7 RI/FS (Taffet and others, 2005). The results of this investigation will assist Lawrence Livermore National Laboratory (LLNL) hydrogeologists to conduct work in a more focused and cost-effective manner. This document is submitted to fulfill contract obligations for subcontract B539658.

  1. Magnetic polarity stratigraphy of the Siwalik sequence in Nurpur area, NW Himalaya, India

    M Venkateshwarlu


    Magnetic polarity stratigraphy studies were carried out on Jabbar Khad section of Nurpur area, Kangra District, Himachal Pradesh, India. Oriented block samples were collected at 202 sites with 3–5 samples per site from a 2350-m thick continuous sedimentary sequence consisting of sandstone–mudstone alternating beds. Specimens were subjected to thermal demagnetization (100–700°C) after measuring their natural remanent magnetization (NRM). Palaeolatitudes of virtual geomagnetic pole (VGP) from each site were calculated from the acquired characteristic remanent magnetization (ChRM) directions. The observed remanence carrier could be haematite. Magnetic polarity scale (MPS) was erected. This MPS is correlated with the standard geomagnetic polarity time scale (GPTS) of Lourens et al. (2004). The MPS readily matched from chron C2An.1n to chron C4n.2n, therefore assigning an age 8.20–2.60 Ma to the middle and upper Siwalik sections at Nurpur. The rate of sedimentation in middle Siwalik is 29 mm/yr and upper Siwalik is 59 mm/yr.

  2. Depositional architecture and sequence stratigraphy of Pleistocene coarse-grained deltas along the Ligurian coast (Italy)

    A Ciampalini; M Firpo


    This study aims to develop a better understanding of the stratigraphy of the southern side of the Maritime Alps and of the Ligurian Sea during the Plio-Pleistocene. Five stratigraphic sections were measured and studied in the Segno River valley (Liguria, Italy). These sections are composed of Lower to Middle Pleistocene marine and continental deposits. Based on detailed mapping and sedimentological analysis, 12 marine and deltaic facies were identified. These facies were grouped into facies associations. Two allostratigraphic units were recognized, namely U1 and U2 from oldest to youngest. The lower unit (U1) represents the evolution of a coarse-grained delta developed in a valley or embayment. Within the deltaic sequence, transgressive and highstand systems tracts were recognized. The coarsening/shallowing upward trend observed within the sections suggests that the delta prograded rapidly in the landward portion of the canyon adjacent to the paleo-river outlet. The upper boundary of U1 is represented by a subaerial unconformity overlain by U2, which is composed of sediments deposited by several alluvial fan systems.

  3. Use of the Bochum proton microprobe in isotope stratigraphy and paleoceanographic

    Bruhn, F.; Bruckschen, P.; Korte, C. [Ruhr-University, Bochum (Germany). Institute fuer Geologie; Meijer, J. [Ruhr-Univ., Bochum (Germany). Inst. fuer Physik mit Ionenstrahlen; Veizer, J. [Ruhr-University Bochum (Germany). Institute fuer Geologie]|[Ottawa-Carleton Univ., Ottawa, ON (Canada)


    Over the past five years, the proton microprobe at Bochum (Germany) has been used as a trace element tool in the context of isotope stratigraphy and paleoceanographic studies. The Sr, O, and C isotopic composition of some biogenic material (e.g. calcitic brachiopod shells, phosphatic conodonts) is widely accepted to mirror, under favourable conditions, the isotopic composition of the coeval sea water. The latter, in turn, is a function of a variety of global processes, such as climatic change, volcanic activity, plate tectonics or circulation of ocean water. Thus, on the basis of the isotopic properties of fossil shell material, isotope curves can be constructed that reflect variations in the above factors over the entire Phanerozoic. However, as a consequence of the long time elapsed since deposition of the fossils, they are prone to chemical and isotopic alteration and may thus yield equivocal or even irrelevant information if no care is taken to monitor the degree of their diagenetic alteration. Trace element composition of the fossil material, combined with cathodoluminescence investigations, is one of the most frequently utilized tools to assess the diagenetic quality of the samples. Beam current was in the range of a few nA, resulting in charges of 1-10 {mu}C for a single measurement. Detection limits for point analyses were between 10 and 30 ppm for Mn, Fe, Sr, but considerably higher for rare earth elements. Accuracy around 10% for a number of elements analysed is reported. 8 refs., 2 figs.

  4. The stratigraphy and evolution of lower Mount Sharp from spectral, morphological, and thermophysical orbital data sets

    Fraeman, A. A.; Ehlmann, B. L.; Arvidson, R. E.; Edwards, C. S.; Grotzinger, J. P.; Milliken, R. E.; Quinn, D. P.; Rice, M. S.


    We have developed a refined geologic map and stratigraphy for lower Mount Sharp using coordinated analyses of new spectral, thermophysical, and morphologic orbital data products. The Mount Sharp group consists of seven relatively planar units delineated by differences in texture, mineralogy, and thermophysical properties. These units are (1-3) three spatially adjacent units in the Murray formation which contain a variety of secondary phases and are distinguishable by thermal inertia and albedo differences, (4) a phyllosilicate-bearing unit, (5) a hematite-capped ridge unit, (6) a unit associated with material having a strongly sloped spectral signature at visible near-infrared wavelengths, and (7) a layered sulfate unit. The Siccar Point group consists of the Stimson formation and two additional units that unconformably overlie the Mount Sharp group. All Siccar Point group units are distinguished by higher thermal inertia values and record a period of substantial deposition and exhumation that followed the deposition and exhumation of the Mount Sharp group. Several spatially extensive silica deposits associated with veins and fractures show that late-stage silica enrichment within lower Mount Sharp was pervasive. At least two laterally extensive hematitic deposits are present at different stratigraphic intervals, and both are geometrically conformable with lower Mount Sharp strata. The occurrence of hematite at multiple stratigraphic horizons suggests redox interfaces were widespread in space and/or in time, and future measurements by the Mars Science Laboratory Curiosity rover will provide further insights into the depositional settings of these and other mineral phases.

  5. DNA Stratigraphy reveals Holocene Haptophyte Population Dynamics and Sources of Alkenones at the Species Level

    Coolen, M. J. L.


    Lipid biomarkers provide information on the ancient microbiota of aquatic systems and, hence, can be used to reconstruct the palaeoenvironment. However, these biomarkers are often not very specific. The ultimate biomarkers would be ribosomal RNA (rRNA) genes, which are widely applied in phylogenetic studies. However, it was generally thought that DNA is rapidly degraded soon after burial within sediments. Using advanced molecular biological techniques we showed that DNA of planktonic photosynthetic bacteria and algae as well as zooplankton survived degradation in Holocene anoxic, sulfidic sediments of the permanently stratified, saline Ace Lake (Vestfold Hills, Antarctica). Alkenones were predominant biomarkers in the sediment layers and their source organisms (haptophytes) were identified based on the analysis of fossil 18S rRNA genes. The quantitative comparison of the individual 18S rRNA genes and the various alkenones allowed for the first time the identification of fossil organisms and their biomarkers at the species level. It was shown that all six identified haptophyte phylotypes are closer related to the alkenone-producing haptophyte genus Isochrysis than to the genera Emiliania and Gephyrocapsa. Subtle changes in the alkenone and alkenoate composition correlated with changes in the quantitative phylotype composition of haptophytes. Implications for alkenone stratigraphy will be discussed.

  6. Stratigraphy of the Descartes region /Apollo 16/ - Implications for the origin of samples

    Head, J. W.


    Analysis of terrain in the Apollo 16 Descartes landing region shows a series of features that form a stratigraphic sequence which dominates the history and petrogenesis at the site. An ancient 150-km diam crater centered on the Apollo 16 site is one of the earliest recognizable major structures. Nectaris ejecta was concentrated in a regional low at the base of the back slope of the Nectaris basin to form the Descartes Mountains. Subsequently, a 60-km diam crater formed in the Descartes Mountains centered about 25 km to the west of the site. This crater dominates the geology and petrogenetic history of the site. Stone and Smoky Mountains represent the degraded terraced crater walls, and the dark matrix breccias and metaclastic rocks derived from North and South Ray craters represent floor fallback breccias from this cratering event. The interpretation is developed that the stratigraphy of the Cayley and Descartes, and thus the historical record of the Apollo 16 region, documents the complex interaction of deposits and morphology of local and regional impact cratering events. Large local 60- to 150-km diam craters have had a dramatic and previously unrecognized effect on the history and petrology of the Apollo 16 site.

  7. Criteria for defining and recognizing the various orders of sequences in outcrop sequence stratigraphy

    WANG Xunlian


    The regional distribution in different depositional facies belts is here regarded as an important criterion for defining and recognizing the various orders of sequences. The third-order sequence is possibly global in nature, which may be discerned in different depositional facies belts in one continental margin and can be correlated over long distances, sometimes even worldwide. Commonly, correlation of subsequence (fourth-order sequence with time interval of 0.5-1.5 Ma) is difficult in different facies belts, although some of them may also be worldwide in distribution. A subsequence should be able to discern and correlate within at least one facies belt.The higher-order sequences, including microsequence (fifth-order sequence) and minisequence (sixth-order sequence), are regional or local in distribution. They may reflect the longer and shorter Milankovitch cycles respectively. Sequence and subsequence are usually recognizable in different facies belts, while microsequence and minisequence may be distinguished only in shallow marine deposits, but not in slope and basin facies deposits. A brief discussion is made on the essential conditions for correct identification of sequences, useful methods of study, and problems meriting special attention in outcrop sequence stratigraphy.

  8. Neogene biogenic sediments of onshore Peru: part I, sedimentology and stratigraphy

    Marty, R.C.; Dunbar, R.B.; Baker, P.


    The Sechura (approx.6/sup 0/S) and Pisco (approx.14/sup 0/S) Basins of onshore Peru contain Miocene diatom and phosphate rich sediments which sharply contrast with underlying clastics. In the Sechura Basin the Miocene clastic Mancora, Heath and Montera Formations are overlain by the Zapallal Formation which grades upwards from a weakly biogenic base into fairly pure diatomites (biogenic silica >20%) and ore grade phosphorite (P/sub 2/O/sub 5/>20%). Biogeneic content decreases in the eastern basin as clastic content increases. The base of the Zapallal Formation has been dated at between 12.2 and 14.0 mybp using radiolaria correlated to magnetic stratigraphy by Theyer, et al (1978), and the phosphatic section yields dates of between 8.0 and 11.2 my. In the Pisco Basin the Eocene clastic Paracas Formation is overlain unconformably by the Miocene Pisco Formation which contains a basal sequence of cross-bedded clastics, tuffs, and partially recrystallized diatomites; a phosphorite bearing middle sequence; and a diatom rich top. Current direction from the cross beds of the basal Pisco Formation indicate a generally southerly transport direction but with considerable directional variability. This may be related to the Peru under-current which shows highly variable strength and direction near 15/sup 0/S.

  9. Yucatán subsurface stratigraphy: Implications and constraints for the Chicxulub impact

    Ward, W. C.; Keller, G.; Stinnesbeck, W.; Adatte, T.


    Much of the discussion about the effects of an end-of-Cretaceous impact by a large extraterrestrial body in northwestern Yucatán has been done in the context of limited and partly erroneous published data on the Mesozoic stratigraphy of that area. Reexamination of cores and geophysical logs taken in several Pemex wells has produced improved lithologic and biostratigraphic correlation of the Jurassic to Maastrichtian section across the northern Yucatán peninsula. These data suggest that major disturbance of strata by an impact would have been confined to within about 100 km of the proposed impact center near Chicxulub. The only unusual lithologic unit is polymict breccia, which apparently was penetrated at or near the top of the Cretaceous section in all the deep wells of northern Yucatán. This breccia in Pemex wells Yucatán 1, 2, 4, 5A, and 6 is composed predominantly of detrital dolomite, limestone, and anhydrite clasts set in dolomitized carbonate mud matrix, which contains upper Maastrichtian foraminifers. These constituents, mixed with fragments of altered glass or melt rock, shocked quartz and feldspar, and basement rock, suggest an impact as the most likely origin for the breccia. The timing of brecciation is poorly constrained by biostratigraphic data. There is some evidence, however, that the breccia unit is overlain by about 18 m of uppermost Maastrichtian marls, suggesting an impact before the Cretaceous-Tertiary boundary. In addition, there may have been more than one episode of breccia deposition.

  10. Stratigraphy and mineralogy of a carbonate-hosted gold deposit: Kings Mountain gold mine, NC

    Supplee, J.; Lapoint, D.; Feiss, P.G.


    The Kings Mountain Gold Mine, Cleveland Company, North Carolina, is unique in the Appalachians in that it is carbonate-hosted, with a distinctive ore mineralogy. The mine stratigraphy is upright, younging east to west. The basal unit is a volcanic to subvolcanic chlorite, feldspar, quartz-eye porphyry, cut by a silicic porphyry, interpreted as a shallow level intrusion. Above and gradational to the chloritic porphyry, unless separated by the intrusive silicic porphyry, is a sericitic, quartz-eye porphyry, probably a metatuff. A north-thinning, graphite schists is above the sericitic porphyry. Carbonates overlie the graphite schist except to the north where they are above the sericitic porphyry. The carbonates consist of basal and upper sequences separated by a sericite, quartz-eye schists (metatuff) which is capped by a chlorite-sericite-graphite schist. Mineralization occurs within each carbonate sequence. This is overlain by interbedded chlorite and graphite schists with two horizons of exhalative iron formation (I.F.). Above the I.F. is a thick sequence of sericitic chlorite schists (turbidites). The mineralized carbonates are pervasively silicified with a disseminated assemblage of pyrite, pyrrhotite, sphalerite, chalcopyrite, galena, gold, altaite (PbTe), tetrahedrite, and pyrargyrite in quartz and dolomite +/- fluorite gangue. We suggest that the mineralization is associated with hydrothermal activity during emplacement of the silicic porphyry and following carbonate diagenesis. Mineralization was syn- or post-depositional with respect to the I.F.


    黄思静; 石和; 刘洁; 沈立成


    锶同位素地层学(SIS)根据地质历史中的任何时间全球范围内海水的锶同位素组成都是均一的、海水87Sr/86Sr比值随时间变化这一基本原理,利用代表原始海水的海相碳酸盐(以及磷酸盐和硫酸盐)的87Sr/86Sr比值确定海相地层的年代,研究海平面变化、造山运动、古气候等全球事件,在地层学、沉积学、石油地质学和矿床学等领域中有着广泛的应用前景。锶同位素地层学已在世界范围内得到地质学家的普遍关注,并已获得迅速的发展,国内的有关研究则刚刚起步。锶同位素地层学研究的难点主要在于对样品成岩蚀变的控制和分析技术上,同时还需要有良好的地层学研究基础,在样品选择上应充分考虑其原始组分的抗成岩蚀变能力。锶同位素地层学的研究需要地层学家、沉积学家和地球化学家的共同努力。%Strontium isotope stratigraphy relies on the fundamental principle that the marine strontium is isotopically homogenous world-wide at any tim e and the 87Sr/86Sr ratio of strontium in seawater of geological history has varied through time. By means of the 87Sr/86Sr rati o of marine carbonate (also phosphate and sulphate) which should record the orig inal composition of sea water, we can date the marine sediments, research global events, such as history of basin subside, sea level change,orogenic events and palaeoclimate variation. The applied expectation of strontium isotope stratigra phy would be very extensive on stratigraphy, sedimentology, petroleum geology a nd economic geology, which has attained considerable development internationally . However strontium isotope stratigraphy is still in its infancy in China. The f ocus of strontium isotope stratigraphy is the influence of diagenesis and techno logy of measurement of 87Sr/86Sr ratio. Meantime, strontium isot ope stratigraphy also needs the support of stratigraphy. The ability of anti

  12. Neogene oxygen isotopic stratigraphy, ODP Site 1148,northern South China Sea

    ZHAO; Quanhong


    [1]Miller, K. G., Fairbank, R. G., Mountain, G. S., Tertiary oxygen isotope synthesis, sea level history, and continental mar gin erosion, Paleoceanogr., 1987, 2(1): 1-19.[2]Savin, S. M., Keller, G., Douglas, R. G. et al., Miocene benthic foraminiferal isotopic records: A synthesis, Mar. Micro paleont., 1981, 6: 423-450.[3]Jian Zhimin, Chen Minben, Lin Huiling et al., Stepwise paleoceanographic changes during the last deglaciation in the southern South China Sea: the records of isotopes and microfossils, Science in China, Ser. D, 1998, 41 (2): 187-124.[4]Jian Zhimin, Stable isotopic evidences of the glacial deep water properties in the South China Sea, Science in China, Ser.D, 1998, 41(4): 337-344.[5]Zhao Quanhong, Wang Pinxian, Progress in Quaternary paleoceanography of the South China Sea: A review, Quaternary Sciences (in Chinese with English abstract), 1999, 6: 481-501.[6]Woodruff, F., Douglas, R. G., Response of deep-sea benthic Foraminifera to Miocene paleoclimatic events, DSDP Site 289,Mar. Micropaleont., 1981, 6: 617-632.[7]Kennett, J. P., Miocene to early Pliocene oxygen and carbon isotope stratigraphy of the Southwest Pacific, DSDP Leg 90,in Init. Rep. DSDP (eds. Kennett, J. P., von der Borch, C. C.), 1986, 90(pt.2):1383-1411.[8]Vincent, E., Killingley, J. S., Oxygen and carbon isotope record for the Early and Middle Miocene in the central equatorial Pacific (Leg 85) and paleoceanographic implications, in Init. Rep. DSDP (eds. Mayer, L., Theyer, F., Barron, A. J. et al.),1985, 85: 749-769.[9]Woodruff, F., Savin, S. M., Abel, L., Miocene benthic foraminifer oxygen and carbon isotopes, Site 709, Indian Ocean, in Proc. ODP Sci. Res. (eds. Duncan, R. A., Backman, J., Peterson, L. C. et al.), 1990, 115:519-528.[10]Vincent, E., Berger, W. H., Carbon dioxide and polar cooling in the Miocene: The Monterey hypothesis, AGU, Washing ton, D.C., Geophys. Monogr., 1985, 32: 455-468.[11]Miller, K. G., Wright, J. D., Fairbanks

  13. Tectono-Stratigraphy of the Seeps on the Guaymas Basin at the Sonora Margin, Gulf of California, Mexico

    Figueroa Albornoz, L. J.; Mortera-Gutierrez, C. A.; Bandy, W. L.; Escobar-Briones, E. G.; Godfroy, A.; Fouquet, Y.


    Recently several hydrothermal and gas seeps systems has been located precisely at the Sonora margin within the Guaymas Basin (GB), Gulf of California. Since late 1970's , several marine studies had reported two main hydrothermal systems in the Guaymas Rift (one at the Northern Rift, and other at the Southern Rift) and a cold seeps system at the Satellite Basin in the Sonora-margin lower edge. During the campaign BIG10, onboard the IFREMER vessel, NO L'Atalante, the EM122 echo-sounder log more than 30,000 water column acoustic images, which allows us to create a data base of the bubble plumes active systems on the northern part of the GB and the Sonora Margin. These plumes are the expression on the water column of an active seeps site during the cruise time. These images document the presence of the cold seep activity around the scarp of the Guaymas Transform Fault (GTF), and within the Satellite Basin. Few active plumes are first located off-axis, on both sides of the Northern Rift. Although it is not observed any plume within NR. Sub-bottom profiles and bathymetric data logged during the campaign GUAYRIV10, onboard the UNAM vessel, BO EL PUMA, are analyzed to determine the shallow tectonic-stratigraphy of GB near the Sonora Margin. We analyze 17 high-resolution seismic profiles (13 with NE-SW strike and 3 with NW-SE strike). From this data set, the continental shelf stratigraphy at the Sonora Margin tilts toward the slope, showing 3 low angle unconformities due to tectonics and slope angle changes. The strata slope changes angle up to 60°. However, the constant trans-tension shear along the GTF causes gravitation instability on the slope, generating a few submarine landslides close to the Northern Rift, and the rotation of blocks, tilting toward the shelf. To the north, the GTF splits in two fault escarpments, forming a narrow pull-apart basin, known as Satellite Basin. The submarine canyon from the Sonora River flows through the Satellite Basin into the GB

  14. Sequence stratigraphy and systems tract development of the Latemar platform, Middle Triassic of the dolomites: Outcrop calibration keyed by cycle stacking patterns

    Goldhammer, R.K.; Dunn, P.A. (Exxon Production Research Co., Houston, TX (United States)); Harris, M.T. (Univ. of Wisconsin, Milwaukee (United States)); Hardie, L.A. (Johns Hopkins Univ., Baltimore, MD (United States))


    The Middle Triassic Latemar platform provides a seismic-scale outcrop example of an intact carbonate shelf-to-basin transition, ideal for integrating sequence stratigraphy with facies and cyclic stratigraphy. This subcircular, high-relief buildup records two third-order accommodation sequences within the platform interior: the lower Ladinian sequence and the upper Ladinian sequence. Sequence L1 developed atop a widespread, low-relief Middle Anisian carbonate bank (60 m thick). Underlying subtidal bank cycles thin upward into the basal, subaerial sequence boundary (type 1) reflecting decreasing third-order accommodation; above it, platform-interior facies of sequence L1 retrograde. This results in superimposition of Ladinian basinal and foreslope facies atop the underlying, horizontal, shallow-water bank along its periphery. The transgressive (TST) and highstand systems tract (HST) of sequence L1 (as well as L2) are marked by long-term, systematic vertical facies changes and variation in stacking patterns of aggradational high-frequency, 20 kyr cycles within the platform interior. The maximum flooding surface (MFS) is a marine hardground surface displaying evidence of very slow sedimentation and is the platform expression of the condensed section. A type 2 SB caps sequence L1, marked by an interval of vertically superimposed thin subaerial tepees; beneath this, high-frequency cycles are thinning-upward, and above they are thickening-upward. Only the transgressive systems tract of sequence L2 is preserved at the Latemar owing to late Ladinian-Early Carnian volcanism and tectonism which terminated carbonate platform deposition.

  15. The shallow stratigraphy and sand resources offshore of the Mississippi Barrier Islands

    Twichell, David; Pendleton, Elizabeth A.; Baldwin, Wayne; Foster, David; Flocks, James; Kelso, Kyle; DeWitt, Nancy; Pfeiffer, William; Forde, Arnell; Krick, Jason; Baehr, John


    Coastal Mississippi is protected by a series of barrier islands ranging in length from 10-25 kilometers that are less than 2 kilometers wide. The majority of these islands comprise the Gulf Islands National Seashore (GUIS), an ecologically diverse shoreline that provides habitat for wildlife including migratory birds and endangered animals. The majority of GUIS is submerged, and aquatic environments include dynamic tidal inlets, ebb-tide deltas, and seagrass beds. The islands are in a state of decline, with land areas severely reduced during the past century by storms, sea-level rise, and human alteration. Morton (2008) estimates that since the mid-1800s up to 64 percent of island surface area has been lost. Heavy damage was inflicted in 2005 by Hurricane Katrina, which passed by as a Category 3 storm and battered the islands with winds of more than 160 kilometers per hour and a storm surge up to 9 meters. Since 2007, the U.S. Geological Survey (USGS), in collaboration with the National Park Service, has been mapping the seafloor and substrate around the islands as part of the USGS Northern Gulf of Mexico Ecosystem Change and Hazard Susceptibility project. The purpose of these investigations is to characterize the near-surface stratigraphy and identify the influence it may have on island evolution and fate. In 2009, this effort provided the basis for a collaborative effort with the U.S. Army Corps of Engineers (USACE) to expand the investigation outside of GUIS boundaries as part of the Mississippi Coastal Improvement Project (MsCIP). The MsCIP program consists of structural, nonstructural, and environmental project elements to restore portions of coastal Mississippi and GUIS affected by storm impact. The project includes the placement of sand along the islands, both on the present beaches and within the littoral zone, to mitigate shoreline erosion and breaching. This action requires the location and assessment of offshore sand or sediment deposits that can provide

  16. Volcanic stratigraphy of intermediate to acidic rocks in southern Paraná Magmatic Province, Brazil

    Liza Angélica Polo


    Full Text Available This article presents the first map in detail scale for an area covered by Palmas type volcanic rocks in the south border of the eocretaceous Paraná Magmatic Province, south Brazil. The study of the structural features coupled with petrography and geochemistry made it possible to separate these rocks into three main volcanic sequences and recognize their stratigraphy. The older Caxias do Sul sequence rests directly over the first low-Ti basalt flows (Gramado type, and corresponds to the stacking of lobated lava flows, laminar flows and lava domes, mostly emitted as continuous eruptions; only the latest eruptions are intercalated with thin sandstone deposits. These rocks have dacitic composition (~ 68 wt% SiO2 with microphenocrysts of plagioclase and subordinate pyroxenes and Ti-magnetite immersed in glassy or devitrified matrix. A second volcanic sequence, named Barros Cassal, is composed of several lava flows of basaltic andesite, andesitic and dacitic composition (~ 54; ~ 57 and ~ 63 wt% SiO2 , respectively, with microphenocrysts of plagioclase, pyroxenes and Ti-magnetite. The frequent intercalation of sandstone between the flows attests to the intermittent behaviour of this event. The upper sequence, Santa Maria, is made up of more silica-rich (~ 70 wt% SiO2 rocks occurring as laminar flows, lobated flows and lava-domes. These rocks have rhyolitic composition with microphenocrysts of plagioclase and Ti-magnetite set in a glassy or devitrified matrix with microlites. The structures and textures of all three silicic sequences favor the interpretation that they had a predominantly effusive character, which is thought to be a reflection of the remarkably high temperatures of the lavas (~ 1,000 ºC.

  17. The Sr-isotopic stratigraphy of the Northern Limb of the Bushveld Complex, South Africa

    Mangwegape, Mpho; Roelofse, Frederick; Mock, Timothy; Carlson, Richard W.


    We present a compilation of Sr-isotopic data obtained on plagioclase from 27 samples covering the entire stratigraphy of the Northern Limb of the Bushveld Complex as determined by LA-MC-ICPMS. The lower parts of the Main Zone in the Northern Limb are characterised by significant variations in Sr-isotopic compositions (87Sr/86Sr ˜0.7087 ± 0.0005 (1-σ)) coupled with very limited differentiation as exemplified by plagioclase An%, suggesting construction of the lower Main Zone through the repeated influx of magmas. Fairly constant Sr-isotopic compositions of plagioclase within the Upper and upper Main Zones (87Sr/86Sr ˜0.7073 ± 0.0003) coupled with a broad normal differentiation trend are suggestive of fractionation processes being the dominant factor in the petrogenesis of these zones. The present results argue against the laterally extensive troctolite horizon of the Northern Limb having a Critical Zone parentage or being the direct equivalent of the Pyroxenite Marker in the Northern Limb. It may, however, be an analogue of the Pyroxenite Marker in that it occurs at the approximate level where the last voluminuous influx of magma into the Northern Limb is inferred to have taken place. The nature of the magmas that gave rise to the lower parts of the Main Zone in the Northern Limb deserves further investigation in light of the fact that plagioclase here shows considerable variation both within and between individual co-existing plagioclase crystals that may point to the intrusion of crystal mushes as opposed to aphyric liquids.

  18. Investigating the stratigraphy of Mare Imbrium flow emplacement with Earth-based radar

    Morgan, G. A.; Campbell, B. A.; Campbell, D. B.; Hawke, B. R.


    The lunar maria are the product of extensive basaltic volcanism that flooded widespread portions of the Moon's surface. Constraining mare volcanic history therefore provides a window into the endogenic processes responsible for shaping the Moon. Due to the low magma viscosity and the associated thin nature of lava units, the majority of mare surface structures are masked and subdued by impact regolith. Subtle individual mare flow morphologies, coupled with spatial limitations in the use of crater size distributions to distinguish surface units close in age, restrict our understanding of mare stratigraphy. Earth-based 70 cm wavelength (P band) radar can reveal features beneath the regolith and highlight very subtle changes in the ilmenite content of the flows, providing a unique means to map mare units. Here we map volcanic units in Mare Imbrium using high-resolution (200 m/pixel), Earth-based P band data. Situated within the heat-producing potassium, rare earth element, and phosphorus terrane, Mare Imbrium experienced some of the most long-lived (and recent) lunar volcanism, and its surface exhibits a significant diversity of basaltic chemistry. Our investigation identifies at least four distinct stages of volcanic activity, originating from multiple sources within Imbrium. The most recent of these stages comprises extensive, yet relatively thin volcanic flow units that left remnant kipukas of older mare material distributed across much of the basin. From a future mission perspective, it may be possible to collect samples expressing a wide range in age from small areas of Mare Imbrium. Our map also places important constraints on the interpretation of the Chang'e-3 Lunar Penetrating Radar measurements.




    Three wells, PB-1, PB-2, and PB-3, were drilled in 2003 at the Nopal I uranium deposit as part of a natural analogue study to evaluate radionuclide transport processes. The wells penetrate through the Tertiary volcanic section down to the Cretaceous limestone basement, and intersect the top of the regional aquifer system. The PB-1 well, drilled immediately adjacent to the Nopal I ore body, was cored to a depth of 250 m, thus providing an opportunity to document the local stratigraphy. The uppermost unit encountered in the PB-1 well is the Nopal Formation, a densely welded, crystal-rich rhyolitic ash-flow tuff. The cored section is highly altered and devitrified, with kaolinite, quartz, chlorite, and montmorillonite replacing feldspars and much of the groundmass. Breccia zones within the tuff contain fracture fillings of hematite, limonite, and goethite. A zone of intense clay alteration encountered in the depth interval 17.45-22.30 m was interpreted to represent the basal vitrophyre of this unit. Underlying the basal vitrophyre is the Coloradas Formation, which consists of a welded, lithic-rich rhyolitic ash-flow tuff. The cored section of this unit has undergone devitrification and oxidation, and has a similar alteration mineralogy to that observed in the Nopal tuff. The Nopal I ore body is restricted to a brecciated zone that intersects these two volcanic units. A sharp contact between the Coloradas tuff and the underlying Pozos Formation was observed at a depth of 136.38 m. The Pozos Formation in the PB-1 core consists of interbedded, poorly sorted sandstone and conglomerate layers. The conglomeratic clasts consist of subangular to subrounded fragments of volcanic rocks, limestone, and chert. Thin (2-6 m) intervals of intercalated pumiceous tuffs were observed within this unit. The contact between the Pozos Formation and the underlying Cretaceous limestone basement was observed at a depth of 244.4 m.

  20. Late Quaternary stratigraphy and sedimentation patterns in the western Arctic Ocean

    Polyak, L.; Bischof, J.; Ortiz, J.D.; Darby, D.A.; Channell, J.E.T.; Xuan, C.; Kaufman, D.S.; Lovlie, R.; Schneider, D.A.; Eberl, D.D.; Adler, R.E.; Council, E.A.


    Sediment cores from the western Arctic Ocean obtained on the 2005 HOTRAX and some earlier expeditions have been analyzed to develop a stratigraphic correlation from the Alaskan Chukchi margin to the Northwind and Mendeleev-Alpha ridges. The correlation was primarily based on terrigenous sediment composition that is not affected by diagenetic processes as strongly as the biogenic component, and paleomagnetic inclination records. Chronostratigraphic control was provided by 14C dating and amino-acid racemization ages, as well as correlation to earlier established Arctic Ocean stratigraphies. Distribution of sedimentary units across the western Arctic indicates that sedimentation rates decrease from tens of centimeters per kyr on the Alaskan margin to a few centimeters on the southern ends of Northwind and Mendeleev ridges and just a few millimeters on the ridges in the interior of the Amerasia basin. This sedimentation pattern suggests that Late Quaternary sediment transport and deposition, except for turbidites at the basin bottom, were generally controlled by ice concentration (and thus melt-out rate) and transportation distance from sources, with local variances related to subsurface currents. In the long term, most sediment was probably delivered to the core sites by icebergs during glacial periods, with a significant contribution from sea ice. During glacial maxima very fine-grained sediment was deposited with sedimentation rates greatly reduced away from the margins to a hiatus of several kyr duration as shown for the Last Glacial Maximum. This sedimentary environment was possibly related to a very solid ice cover and reduced melt-out over a large part of the western Arctic Ocean.

  1. Determination of the historical variation of the trophic state in lakes using sediment stratigraphies

    G. Olli


    Full Text Available Biogenic silica (BSi and phosphorous (P accumulation were investigated in sediment cores from Karlskärsviken, a bay of Lake Mälaren. The aim was to make use of BSi and P relations in sediment stratigraphies in order to investigate the historical nutrient trophy in a near shore lake environment since the Middle Ages, with focus on industrial times, and to evaluate anthropogenic influences on the bay's trophic state. The BSi accumulation in the sediments is a better indicator of former nutrient pelagic trophy than P accumulation in sediments and for this reason a BSi inferred P (BSi-P water concentration is calculated. This method enables the determination of the background total phosphorous (TP concentration (which is related to the reference conditions in the investigated bay; this background TP is determined equal to 0.020–0.022 mg L−1. There is an increasing trend of BSi-P concentration in the bay since the Middle Ages to the present, about 0.025 mg L−1, with a small decrease in the inner bay section during the last decades. The P accumulation rate is not found to have changed since the 1960s and 1970s, which indicates that the P loading to Karlskärsviken has not decreased. In Karlskärsviken, the shallow inner section of the bay, where the water quality is dominated by loading from the bay catchment area, is less nutritious than the water in the outer section, which is influenced by the main streams from the western part of Lake Mälaren.

  2. The sedimentary sequence recovered from the Voka outcrops, northeastern Estonia: implications for late Pleistocene stratigraphy

    Miidel, Avo


    Full Text Available New palaeoenvironmental and geological data, which may be integrated with the results from the neighbouring regions, were collected from two well-exposed continuous outcrops in the vicinity of Voka village, northeastern Estonia. These outcrops, situated in a klint depression – klint bay –, show an about 22 m thick stacked sequence of sandy to clayey subaqueous deposits. This succession of water-lain sediments documents the response to climate change during the late Pleistocene. On the basis of grain size characteristics, sedimentological structures, and luminescence chronostratigraphical data, the sequence is subdivided into two main units – A and B. Optical dating of 18 samples from the upper unit A shows that the unit is of middle Järva (= middle Weichselian age (marine isotope stage (MIS 3. Representative pollen spectra derived from 45 samples from the pollen-bearing part of unit A provide convincing evidence of noticeable changes in vegetation and climate in NE Estonia during the time period from 39 to 33 kyr BP, within which two intervals of severe climate and two relatively milder ones have been recognized. Preliminary data from the underlying unit B indicate that deposits of the last interglacial sensu lato and those of early pleniglacial age correlating with MIS 5 and MIS 4, respectively, occur here as well. Thus, the data obtained during the present study show unambiguously that in contrast with the expectations, the greater part of the late Pleistocene sequence is represented in the Voka section. No evidence was found for glacial activity during the late Pleistocene period predating the last glacial maximum. The use of the Voka event stratigraphy as a template facilitates search for correlative horizons in the neighbouring regions.

  3. Synthetic stratigraphy of epicontinental seas: a carbonate sedimentation model and its applications in sea level studies

    Cisne, J.L.; Gildner, R.F.


    Carbonates from the central parts of epicontinental seas are ideal strata for detailed study of eustatic sea level change. On the basis of sedimentation model in which carbonate accumulation rate is directly proportional to water depth, we developed synthetic stratigraphies for sea level histories expected for post-glacial transgression and for constant and sinusoidally fluctuating ocean ridge volume increase. These histories give distinctly different trends for water depth as a function of stratigraphic position in the sections' bathymetric curves. In general, water depth is proportional to the rate of sea level rise. Depth-dependent sedimentation leads to a time lag between sea level fluctuation and corresponding depth fluctuation which, as examples show, can approach 10/sup 6/ years for depth fluctuations of even a few meters--a fundamental consideration for reconstructing sea level curves, time-correlating sections by bathymetric curves, and relating water depth on continents to ocean ridge volume. Bathymetric curves based on gradient analysis of fossil assemblages (coenocorrelation curves) for American Middle Ordovician sections approximate patterns expected for sinusoidally increasing sea level. The model's predictions are tested in an ''artificial experiment'' that takes advantage of differential subsidence between the craton's middle and its edge to make a difference in the bathymetric histories of sections that otherwise record the same sea level history. The depth dependence in sedimentation was that above wave base net accumulation per year was very roughly 3 x 10/sup -6/ of the water depth.

  4. Simulating the effects of hyperpycnal events on the stratigraphy of Poverty Shelf, New Zealand

    Hutton, E. W.; Kettner, A. J.; Kubo, Y.; Gomez, B.; Syvitski, J. P.


    The hydrologic-transport model, HydroTrend indicates that suspended sediment discharge of the Waipaoa River, New Zealand increased from 2.3 to 15 Mt/y over the last 3000 years. Prior to the arrival of European colonists in the nineteenth century A.D., volcanic eruptions, natural fires and severe storms controlled erosion rates within the basin. Since then, clearing of much of the indigenous forest for sheep farming has caused suspended sediment discharge of the Waipaoa to increase by 850%. HydroTrend simulations indicate the Waipaoa was not able to generate hyperpycnal discharges before the arrival of European colonists. However, because of deforestation in the headwaters, suspended sediment concentrations of the Waipaoa are now able to exceed 40 kg/m3 during large flood events. The river density of these events is great enough to cause the manner by which sediment is transported from the river to change from a surface plume to a hyperpycnal plume. Although these hyperpycnal events are rare (recurrence intervals greater than 2 years), simulations suggest these events carry approximately one fifth of the total sediment load. Observational data of hyperpycnal flows are scarce as they often only occur during extreme weather events. Given the proper boundary conditions, these events have the potential to transport large amounts of sediment over the sheltered Poverty Bay shelf, and into the deep ocean. For this study, we have used HydroTrend results as input to the basin filling model, sedflux (coupled with the hyperpycnal plume model, sakura), to investigate the impact of these hyperpycnal events on the stratigraphy of the Poverty Bay shelf. We note that while some flood events generate hyperpycnal flows that are able to bypass the shelf, others are unable to ignite and deposit the bulk of their sediment on the shelf.

  5. Sediment yield model implementation based on check dam infill stratigraphy in a semiarid Mediterranean catchment

    G. Bussi


    Full Text Available Soil loss and sediment transport in Mediterranean areas are driven by complex non-linear processes which have been only partially understood. Distributed models can be very helpful tools for understanding the catchment-scale phenomena which lead to soil erosion and sediment transport. In this study, a modelling approach is proposed to reproduce and evaluate erosion and sediment yield processes in a Mediterranean catchment (Rambla del Poyo, Valencia, Spain. Due to the lack of sediment transport records for model calibration and validation, a detailed description of the alluvial stratigraphy infilling a check dam that drains a 12.9 km2 sub-catchment was used as indirect information of sediment yield data. These dam infill sediments showed evidences of at least 15 depositional events (floods over the time period 1990–2009. The TETIS model, a distributed conceptual hydrological and sediment model, was coupled to the Sediment Trap Efficiency for Small Ponds (STEP model for reproducing reservoir retention, and it was calibrated and validated using the sedimentation volume estimated for the depositional units associated with discrete runoff events. The results show relatively low net erosion rates compared to other Mediterranean catchments (0.136 Mg ha−1 yr−1, probably due to the extensive outcrops of limestone bedrock, thin soils and rather homogeneous vegetation cover. The simulated sediment production and transport rates offer model satisfactory results, further supported by in-site palaeohydrological evidences and spatial validation using additional check dams, showing the great potential of the presented data assimilation methodology for the quantitative analysis of sediment dynamics in ungauged Mediterranean basins.

  6. Usbnd Pb detrital zircon ages from some Neoproterozoic successions of Uruguay: Provenance, stratigraphy and tectonic evolution

    Pecoits, Ernesto; Aubet, Natalie R.; Heaman, Larry M.; Philippot, Pascal; Rosière, Carlos A.; Veroslavsky, Gerardo; Konhauser, Kurt O.


    The Neoproterozoic volcano-sedimentary successions of Uruguay have been the subject of several sedimentologic, chrono-stratigraphic and tectonic interpretation studies. Recent studies have shown, however, that the stratigraphy, age and tectonic evolution of these units remain uncertain. Here we use new Usbnd Pb detrital zircon ages, combined with previously published geochronologic and stratigraphic data in order to provide more precise temporal constraints on their depositional age and to establish a more solid framework for the stratigraphic and tectonic evolution of these units. The sequence of events begins with a period of tectonic quiescence and deposition of extensive mixed siliciclastic-carbonate sedimentary successions. This is followed by the development of small fault-bounded siliciclastic and volcaniclastic basins and the emplacement of voluminous granites associated with episodic terrane accretion. According to our model, the Arroyo del Soldado Group and the Piedras de Afilar Formation were deposited sometime between ∼1000 and 650 Ma, and represent passive continental margin deposits of the Nico Pérez and Piedra Alta terranes, respectively. In contrast, the Ediacaran San Carlos (Dionisio terranes, and the herein defined Edén Terrane. The Edén and the Nico Pérez terranes likely accreted at ∼650-620 Ma (Edén Accretionary Event), followed by their accretion to the Piedra Alta Terrane at ∼620-600 Ma (Piedra Alta Accretionary Event), and culminating with the accretion of the Cuchilla Dionisio Terrane at ∼600-560 Ma (Cuchilla Dionisio Accretionary Event). Although existing models consider all the Ediacaran granites as a result of a single orogenic event, recently published age constraints point to the existence of at least two distinct stages of granite generation, which are spatially and temporally associated with the Edén and Cuchilla Dionisio accretionary events.

  7. Soil stratigraphy of charcoal kiln remains (CKR) in the Litchfield Hills, CT, USA

    Raab, Thomas; Hirsch, Florian; Ouimet, Will; Dethier, David


    Charcoal kiln relicts (CKRs) are small anthropogenic landforms that are often found in historic mining areas. CKRs have not been a big research topic yet but mainly were studied as by-products of archaeological excavations. In the last years newly available and very accurate Digital Elevation Models (DEMs) based on high-resolution Airborne Laser Scanning (ALS) data have been used to identify these archaeological remains. In addition, findings of several thousands CKRs in the North German Lowland have increased the awareness that historical charcoal production may significantly contribute to Late Holocene landscape change. Besides the archaeological aspect of CKRs, potential impacts of charcoal burning on the ecology of modern soil landscapes and ecosystem processes must be considered. A relatively high density of CKRs is found in the Litchfield Hills nearby the town of West Cornwall, Litchfield County, CT, USA. The CKRs are especially well preserved on slopes of the tributary valleys of the Housatonic River and form little, circular ramparts with diameters normally less than ten meters. First, rough field surveys in Litchfield County in spring 2015 have suggested differences between soils inside and outside the CKR. Soils on the CKR seem to have relatively deep humus-rich and charcoal containing topsoils whereas the topsoils outside the CKR appear typically thinner and less rich in humus. More thorough investigations have been started in autumn 2015 to prove the hypothesis that properties, distribution and development of soils are controlled by archaeological remains of historical charcoal burning. We present preliminary results from our field studies conducted in October 2015. The stratigraphy and the extent of the 26 CKRs were studied using a sedimentological-pedological approach by coring and trenching. Our results indicate that in Litchfield County the CKRs were used twice and in quick succession. Before the second reuse, the rim of the platform was stabilized

  8. A new high-resolution Holocene tephra stratigraphy in eastern Iceland: Improving the Icelandic and North Atlantic tephrochronology

    Gudmundsdóttir, Esther Ruth; Larsen, Gudrún; Björck, Svante; Ingólfsson, Ólafur; Striberger, Johan


    A new and improved Holocene tephra stratigraphy and tephrochronological framework for eastern and northern Iceland is presented. Investigations of a sediment sequence from Lake Lögurinn have revealed a comprehensive tephra record spanning the last 10.200 years. A total of 157 tephra layers have been identified, whereof 149 tephra layers have been correlated to its source volcanic system using geochemistry, stratigraphy and age. Fifteen layers have chemical composition of two affinities that possibly represent two very closely spaced eruptions. Thus, these 157 tephra layers are believed to represent 172 explosive eruptions. Nineteen tephra marker layers have been identified in the Lake Lögurinn record (G1922, A1875, V1477, V1410, H1636, K1625, Ö1362, G1354, K1262, V874, Hrafnkatla, Sn-1, Grákolla, HY, H3, H4, HÖ, LL1755 and Reitsvík-8 tephra markers). New potential tephra markers are the silicic Askja L (∼9400 cal BP), the low titanium basalt layers, LL 1774 (∼10.150 cal BP) and LL 1755 (∼9990 cal BP), assigned to Veidivötn-Bárdarbunga and the tephra layers, LL 1527.8 (∼7850 cal BP), LL 911.2 (∼2370 cal BP), LL 908.4 (∼2350 cal BP), LL 781.9 (∼1930 cal BP), LL 644.4 (∼1480 cal BP), not yet correlated to a source volcanic system. A silicic tephra marker layer, Reitsvík 8, correlated to the Fosen tephra in Norway has been identified in Lake Lögurinn. The Lake Lögurinn tephra record has been connected and integrated with the Icelandic terrestrial tephrochronology and stratigraphy through 102 tephra layers, the marine tephra stratigraphy through 39 layers and overseas through 9 tephra layers. This record is the first high-resolution tephra stratigraphical and chronological framework for the Holocene in eastern Iceland as well as the most detailed and continuous record, and has considerable potential to serve as a key section or a stratotype for the Holocene in eastern Iceland and the North Atlantic.

  9. Why stratigraphy and sedimentology in shales are important : an example from the Woodford Shale, Permian Basin, west Texas

    Harris, N.B. [Alberta Univ., Edmonton, AB (Canada); Colorado School of Mines, Boulder, CO (United States); Hemmesch, N.T.; Mnich, C.A. [Colorado School of Mines, Boulder, CO (United States). Geology and Geological Engineering; Aoudia, K.; Miskimins, J. [Colorado School of Mines, Boulder, CO (United States). Dept. of Petroleum Engineering


    This presentation explained why stratigraphy and sedimentology in shales are important. The presentation provided an example from the Woodford Shale, Permian Basin, located in western Texas. Several illustrations were presented to demonstrate a stratigraphic sequence in black shale. Other topics that were discussed included geologic settings; paleogeography; silled basins; motivation for rock properties research; and factor analysis results. It was concluded that sequence stratigraphic analyses in black shales requires an integrated, multidisciplinary approach. The presentation showed that third and fourth order stratigraphic cycles are indicated by the repetition of exotic beds whose composition vary regionally. tabs., figs.

  10. A History of Repeated Failures: Stratigraphy of the Currituck and Cape Fear Slide Complexes on the Central U.S. Atlantic Margin

    Hill, J. C.; Brothers, D. S.; Ten Brink, U. S.


    The Currituck and Cape Fear Slide complexes, offshore of North Carolina, are two of the largest (>150 km3) submarine slope failure provinces on the U.S. Atlantic margin. Detailed stratigraphy of these slides and the surrounding regions is derived from a combination of high-resolution sparker multichannel seismic (MCS) data collected by the USGS in 2012, airgun MCS collected as part of the NSF GeoPRISMs Community Seismic Experiment in 2014 & legacy industry airgun MCS data collected in 1970s and 80s. Both the Currituck and Cape Fear Slide complexes are located in regions with high sediment input that resulted in the development of a broad, low gradient (Fear Slide, the Quaternary section upslope of a large salt diapir displays evidence of possible downslope creep folding within strata that downlap onto a possible buried failure plane. While submarine slope failure along this portion of the margin has long been linked with hydrate dissociation and/or salt tectonics, features that are pervasive along the margin, our new stratigraphic analyses suggest that antecedent margin physiography and sediment loading may be critical factors in determining the locations of large-scale slope failures.

  11. Magmatism, sedimentation and stratigraphy of the northern region of the Santos Basin; Magmatismo, sedimentacao e estratigrafia da porcao norte da Bacia de Santos

    Moreira, Jobel Lourenco Pinheiro [PETROBRAS S.A., Rio de de Janeiro, RJ (Brazil). E e P. Grupo de Interpretacao Exploratoria da Bacia de Santos], E-mail:; Esteves, Carlos Augusto; Rodrigues, Jose Joaquim Goncalves; Vasconcelos, Claudemir Severiano de


    The Santos Basin, passive margin basin, had its sedimentary history disrupted by intra and extra-basinal tectonic activity that took place during the Eocene and Santonian-Campanian. Many authors have identified these events; however this matter still deserves an integrated study including basement and basin areas. Recent Ar/Ar geochronological data from intrusive and extrusive rocks in the Santos basin have identified two events precisely at 82 {+-} 1 Ma and 48,9 Ma. Among the depositional sequences individualized from seismic and well data in the Santos Basin, the K90 depositional sequence - of Santonian- Campanian age - is the best example to investigate magmatism, sedimentation and stratigraphy. Substantial volcanic building, intrusive and extrusive rocks can be observed in this sequence and have a strong impact on in the mineralogical and sedimentary composition of the siliciclastic deposits (sandstones and shales). Subaerial and subaqueous volcanisms are well identified and its characteristics are described herein in terms of seismic facies, log facies and lithofacies. Siliciclastic depositional systems from the transgressive tract (shallow marine) and from lowstand (deep marine) of this sequence are lithic arkosean sandstones, composed mainly by quartz, Kfeldspar, plagioclase and fragments of igneous rocks. An intensive diagenetic chloritization, probably due to the presence of ferromagnesian minerals, has a strong impact on the reservoir quality. (author)

  12. Conodonts, stratigraphy, and relative sea-level changes of the tribes hill formation (lower ordovician, east-central New York)

    Landing, E.D.; Westrop, S.R.; Knox, L.A.


    Tremadocian onlap is recorded by the Tribes Hill Formation. The formation is a lower Lower Ordovician (upper conodont Fauna B Interval(?)- Rossodus manitouensis Zone) depositional sequence that unconformably overlies the Upper Cambrian Little Falls Formation. Depositional environments and stratigraphy indicate that the Tribes Hill was deposited on a wave-, not tide-, dominated shelf and that a uniform, 'layer-cake' stratigraphy is present. The deepening-shoaling sequence of the Tribes Hill includes the: 1) Sprakers Member (new; peritidal carbonate and overlying tempestite limestone and shale); 2) Van Wie Member (new; subtidal shale and limestone); 3) Wolf Hollow Member (revised; massive carbonates with thrombolitic cap); and 4) Canyon Road Member (new; glauconitic limestone and overlying evaporitic dolostone). The shoaling half-cycle of the Tribes Hill is older than a shoaling event in western Newfoundland, and suggests epeirogenic factors in earliest Ordovician sea-level change in east Laurentia. Conodont and trilobite biofacies track lithofacies, and Rossodus manitouensis Zone conodonts and Bellefontia Biofacies trilobites appear in the distal, middle Tribes Hill Formation. Twenty-four conodont species are illustrated. Ansella? protoserrata new species, lapetognathus sprakersi new species, Leukorhinion ambonodes new genus and species, and Laurentoscandodus new genus are described.

  13. Stratigraphy and paleontology of Lower Permian rocks north of Cananea, northern Sonora, Mexico

    Blodgett, R.B.; Moore, T.E.; Gray, F.


    Sonora and confirms the presence of North American cratonal stratigraphy in the northern part of the state of Sonora, Mexico. Published by Elsevier Science Ltd.

  14. Chemo- and palyno-stratigraphy of the Permian-Triassic transition in the Boreal region

    van Soelen, Els; Planke, Sverre; Svensen, Henrik; Twitchett, Richard; Polozov, Alexander; Kürschner, Wolfram


    Late Permian and early Triassic sediments from Boreal regions are studied using palynological and organic geochemical tools. We present preliminary results from two sites: a Norwegian site which is represented by a 100-m long borehole core and outcrops from Deltadalen on Spitsbergen, and a Russian site which is represented by outcrops and short cores collected near Norilsk in northern Siberia. The main goals of the project are to improve the stratigraphy and to study the environmental changes at high resolution. There is a growing scientific consensus that end Permian biotic crisis was linked to the Siberian Traps Large Igneous Province (LIP) event. However, direct evidence for a stratigraphic correlation of the marine and terrestrial extinction events, with the volcanic successions in the Siberian basin, is rather limited. The Permian-Triassic boundary successions in the Arctic are crucial for direct correlation eastwards to the Siberian Traps. The magnitude and timing of a carbon isotope excursion near the Permian-Triassic boundary is an important stratigraphical tool that may help to unravel the sequence of the events happening during this important period. Preliminary results from the Deltadalen core near the base of the Vikinghøgda Formation show shifts in δ13C from -24.5 to -32.7‰ in the interval expected to span the Permian/Triassic boundary. New Rock-Eval pyrolysis data will shed further light on the origin of the organic matter (e.g. marine versus terrestrial) and may help to understand how much of the δ13C signal can be explained by changes in organic matter source and how much may be attributed to a global change in the carbon isotope signature. Furthermore, compound specific isotope analysis will be done on terrestrial derived lipids (long chain n-alkanes) to reconstruct changes in atmospheric carbon isotopes. In addition to chemostratigraphy, the palynological record will be used for biostratigraphical studies at both Deltadalen and Norilsk

  15. Chemo-stratigraphy in the Murray Formation Using ChemCam

    Blaney, D. L.; Anderson, R. B.; Bridges, N.; Bridges, J.; Calef, F. J., III; Clegg, S. M.; Le Deit, L.; Fisk, M. R.; Forni, O.; Gasnault, O.; Kah, L. C.; Kronyak, R. E.; Lanza, N.; Lasue, J.; Mangold, N.; Maurice, S.; Milliken, R.; Ming, D. W.; Nachon, M.; Newsom, H. E.; Rapin, W.; Stack, K.; Sumner, D. Y.; Wiens, R. C.


    Curiosity has completed a detailed chemo-stratigraphy analysis at the Pahrump exposure of the Murray formation. In total >570 chemical measurements and supporting remote micro images to classify texturally were collected. Chemical trends with both stratigraphic position and with texture were evaluated. From these data emerges a complex aqueous history where sediments have interacted with fluids with variable chemistry in distinct episodes. The ChemCam data collected at the nearby "Garden City" (GC) vein complex provides constraints on the chemical evolution of the Pahrump. GC is thought be stratigraphically above the Pahrump outcrop. Fluids producing the veins likely also migrated through the Pahrump sediments. Multiple episodes of fluids are evident at GC, forming distinct Ca sulfate, F-rich, enhanced MgO, and FeO-rich veins. These different fluid chemistries could be the result of distinct fluids migrating through the section from a distance with a pre-established chemical signature, fluids locally evolved from water rock interactions, or both. Texturally rocks have been classified into two distinct categories: fine grained or as cross-bedded sandstones. The sandstones have significantly lower SiO2, Al2O3, and K2O and higher FeO, and CaO. Fine grained rocks have further been sub-classified as resistant and recessive with other textural features such as laminations and pits noted.The strongest chemical trend in the fine-grained sandstones shows enhancements in MgO and FeO in erosion-resistant materials compared to fine grained recessive units, suggesting that increased abundance of Mg- and/or iron-rich cements may provide additional strength. The MgO and FeO variations with texture are independent of stratigraphic locations (e.g resistant material at both the bottom and top of the outcrop both are enhanced in MgO and FeO). The presence of the GC MgO and FeO rich veins provides additional evidence for fluids rich in these elements were present in the outcrop. Other

  16. Integrated stratigraphy of the Cenomanian-Turonian boundary interval: improving understanding of Oceanic Anoxic Events

    Jarvis, Ian


    implicates rising atmospheric pCO2 linked to volcanic outgassing as a major forcing mechanism for palaeoclimate warming and palaeoceanographic change accompanying OAE2. New marine 187Os/188Os isotope stratigraphy further reveals the interaction of volcanism and ocean circulation during OAE2, and provides a further chemostratigraphic tool. Li isotope (δ 7Li) data may be interpreted as evidence that increased silicate weathering promoted by rising pCO2 acted as both a forcing and negative feedback mechanism driving OAE2 history. Neodymium and sulphur isotopes offer further insights into interactions between global biogeochemical cycles and ocean circulation changes.

  17. Cenozoic Carbonate Stratigraphy of the Yucatan Shelf, Southern Gulf of Mexico

    Ortega-Nieto, A.; Urrutia-Fucugauchi, J.


    The Yucatan shelf in the southern Gulf of Mexico has developed as a large shallow ramp shelf, tectonically stable that preserves a continuous sedimentary record for the Late Mesozoic and Cenozoic. We present the preliminary results of a study involving well stratigraphy, X-ray diffraction and petrography of the Cenozoic sequence sampled in the UNAM-5, UNAM-6 and UNAM-7 exploratory boreholes drilled in the southwestern and southern sectors of the Yucatan state. The boreholes were drilled as part of the Chicxulub Drilling Project aimed to investigate the formation and characteristics of the large crater, formed by an asteroid impact at the Cretaceous/Paleogene (K/Pg) boundary. Our study aims to investigate the stratigraphic relations, textural changes and characteristics of the sedimentary units, to identify events associated with the evolution of the platform during the Cenozoic. We constructed detailed stratigraphic columns for the three borehole cores and prepared samples collected across the stratigraphic section for petrography and clay analyses. The petrographic studies were made at different depths above the K/Pg boundary to recognize textural variations, the identification of dolomite was made by the method of staining thin sections, and the dolomite fabrics were analyzed to identify the nature and shape of their crystal boundaries. The method of X-ray diffraction was used to identify clay types. The three boreholes cross the K/Pg boundary at different depths. The stratigraphic column is formed, from bottom to top, of a limestone sequence with evaporites nodules, little contents of benthic foraminifera, scarce planktic foraminifera and oogonia fossils suggesting internal lagoonal environments that vary to outer lagoon. This sequence is underlain by limestones with different degrees of dolomitization that in many cases present poorly preserved microfossil contents. Above this sequence, there is a clay bed identified as palygorskita, which has a variable




    Full Text Available Defined as a piggyback basin, the Plio-Pleistocene Sant'Arcangelo basin is one of the more recent onshore sedimentary basin of the Southern Apennines. Extensive field studies allow to reinterpret the whole stratigraphy of the basin in a more simple and significant way. Five unconformity-bounded units ("groups" have been recognised : The (1 Catarozzo Group (late Pliocene unconformably overlies pre-Miocene units, and it is composed of a flood-dominated fan-delta marine (C1 and restricted-marine (C2 systems bounded by a sharp contact with a total thickness up to 650 meters. The (2 Aliano Group (late Pliocene - early Pleistocene includes an up to 1,400 meters thick succession of flood-dominated fan-delta systems, with facies ranging from poorly organised alluvial conglomerates in the west to massive marine mudstones in the east. Two sub-units have been recognised, bounded by a regional unconformity, which shows an abrupt passage from marine (A1 to restricted-marine (A2 conditions. The (3 Tursi Group (early-middle Pleistocene reaches a thickness of 500 meters. It is composed of two sub-units, corresponding to alluvial fan (T1 and fan-delta (T2 systems. The alluvial facies of T2 (conglomerates outcrop extensively in the Sant'Arcangelo basin, with equivalent flood-dominated shelfal sandstone lobes broadly developed in the Tursi area (Metaponto basin. The (4 Profico and (5 Montalbano Jonico groups (middle Pleistocene are partially time equivalents, and were developed in both sides of the Valsinni structure, which divided an early, broader Sant'Arcangelo basin into two sub-basins, the present "Sant'Arcangelo" and "Metaponto" basins. The Profico Group has a thickness of up to 300 m and consists of lacustrine strata overlying in angular unconformity the Tursi Allogroup in the "Sant'Arcangelo basin". The Montalbano Jonico Group on the other hand is made up of up to 300 m of fine-grained marine strata unconformably overlying the Tursi Group in the "Metaponto

  19. Stratigraphy of the central parts of the Palaeoproterozoic Tampere Schist Belt, southern Finland: review and revision

    Kähkönen, Y.


    Full Text Available The arc-type Palaeoproterozoic volcanic-sedimentary Tampere Schist Belt (TSB, close to the centre of the Svecofennian Orogen, comprises an E-W-striking major synform in its central parts. This paper presents a review of stratigraphy and proposes a revision of stratigraphic nomenclature of the central TSB. The stratigraphic columns differ from each other in different parts of the belt, and along-strike as well as limb-to-limb correlations are often problematic. However, certain generalizations are possible to make. The pillow-basalt-bearing Haveri formation with EMORB, not arc-type, affinities is the lowermost unit in the northern limb, and it is overlain by the turbidites of the Osara formation. The Haveri formation is regarded as the oldest unit of the TSB and it was evidently related to extension of Palaeoproterozoic crust before ca. 1.91 Ga. The Myllyniemi formation, characterized by mid-fan turbidites, is the lowermost unit in the southern limb. The Myllyniemi turbidites are thought to be broadly coeval with the Osara turbidites, and they were evidently deposited before the emplacement of the 1.904 Ga subaerial dacite- and andesite-rich Koskuenjärvi formation of the northern limb. The turbidites of the Myllyniemi formation and those of the overlying Tuuliniemi formation show a general fining-upward trend. On the other hand, the proportion of arc-type volcanic rocks increases above the Myllyniemi formation and this evolution is accentuated by the growth of the ca. 1.89 Ga Pulesjärvi-Kolunkylä complex of volcanic and sedimentary rocks that was in part subaerial. The subaqueous pyro-/volcaniclastic intermediate rocks among the turbidites of the southern limb possibly contain units coeval with the Koskuenjärvi formation. The 1.889 Ga Takamaa formation, rich in mafic volcanics, was formed after deposition of the sedimentary rocks (e.g. the Veittijärvi conglomerate of the Pulesjärvi-Kolunkylä complex. The subaerial to shallow-water volcanic

  20. Improved understanding of Diatom stratigraphy in a varved sediment through lake monitoring and sediment trap data

    Maier, Dominique Beatrice; Bigler, Christian


    Biological remains in lake sediments reflect past conditions in the lake itself and within its catchment. However, it is difficult to disentangle to which extent the environmental drivers are natural (e.g. population dynamics, climate) or human-induced (e.g. agriculture, forestry). Therefore, comprehensive lake monitoring is crucial to understand taphonomy and sediment formation, and enhances the value of the paleolimnological archive. In this study, we analyze survey data of a varved lake in northern Sweden (Nylandssjön, Nordingrå) with special focus on the diatom record. Different monitoring components are combined, i.e. (1) bi-weekly data of chemical parameters (chlorophyll a, nutrients) covering the period from 2012 to 2015, (2) physical parameters (temperature, oxygen, ice-cover) covering the period from 2000-2015, (3) high-resolution data from a sequential sediment trap covering the period from 2000-2015 and (4) annually resolved diatom data from the sediment varves. Early and intense spring mixing in 2012 translates into a short but vertically pervasive chlorophyll a band which is simultaneously recorded in the sequential trap with a high diatom peak (500 000 valves cm2 d-1). The years 2013 and 2014 show higher chlorophyll a concentrations in the water column, but diatoms do not form a peak flux (>100 000 diatoms cm2 d-1) at any time in the sediment trap, probably due to stratification patterns. The trap record from 2012 indicates a spring bloom dominating the sediment signal, but this is not repeated in 2013 and 2014. Future analyses will be directed towards linking the monitored in-lake processes to annually or even seasonally resolved environmental characteristics. The multiplicity of potential ecological and environmental drivers led us to reverse our analytical view by starting with the diatom stratigraphy in the varved sediment, continuing through the data from sediment trap and water column into the lake catchment to identify deviations (timing

  1. Late Holocene stratigraphy of the Tetimpa archaeological sites, northeast flank of Popocatepetl volcano, central Mexico

    Panfil, M.S.; Gardner, T.W.; Hirth, K.G.


    1400 yr B.P. The archaeology and lacustrine stratigraphy of the Tetimpa area help constrain the timing of the Plinian phase of eruptive sequence I to ca. 2100 yr B.P. and suggest that the pumice-fall eruptions of eruptive sequence II took place in at least two intervals between ca. 1350 and ca. 1200 yr B.P.

  2. Insights into the stratigraphy of Mars' northern plains from impact crater mineralogy

    Pan, Lu; Ehlmann, Bethany; Carter, John; Ernst, Carolyn; CRISM Team


    , leaving few detections of mafic or hydrated minerals. Detailed mapping using high-resolution imagery over regions of interest will continue to bring insights into the regional stratigraphy and possible geologic or aqueous processes involved.

  3. Late Pleistocene-Holocene alluvial stratigraphy of southern Baja California, Mexico

    Antinao, José Luis; McDonald, Eric; Rhodes, Edward J.; Brown, Nathan; Barrera, Wendy; Gosse, John C.; Zimmermann, Susan


    A late Pleistocene to Holocene alluvial stratigraphy has been established for the basins of La Paz and San José del Cabo, in the southern tip of the Baja California peninsula, Mexico. Six discrete alluvial units (Qt1 through Qt6) were differentiated across the region using a combination of geomorphologic mapping, sedimentological analysis, and soil development. These criteria were supported using radiocarbon, optically stimulated luminescence and cosmogenic depth-profile geochronology. Major aggradation started shortly after ∼70 ka (Qt2), and buildup of the main depositional units ended at ∼10 ka (Qt4). After deposition of Qt4, increasing regional incision of older units and the progressive development of a channelized alluvial landscape coincide with deposition of Qt5 and Qt6 units in a second, incisional phase. All units consist of multiple 1-3 m thick alluvial packages deposited as upper-flow stage beds that represent individual storms. Main aggradational units (Qt2-Qt4) occurred across broad (>2 km) channels in the form of sheetflood deposition while incisional stage deposits are confined to channels of ∼0.5-2 km width. Continuous deposition inside the thicker (>10 m) pre-Qt5 units is demonstrated by closely spaced dates in vertical profiles. In a few places, disconformities between these major units are nevertheless evident and indicated by partly eroded buried soils. The described units feature sedimentological traits similar to historical deposits formed by large tropical cyclone events, but also include characteristics of upper-regime flow sedimentation not shown by historical sediments, like long (>10 m) wavelength antidunes and transverse ribs. We interpret the whole sequence as indicating discrete periods during the late Pleistocene and Holocene when climatic conditions allowed larger and more frequent tropical cyclone events than those observed historically. These discrete periods are associated with times when insolation at the tropics was

  4. Stratigraphy and geochronlogy of the Guarinos greenstone belt, Goiás, Brazil

    Hardy Jost


    Full Text Available The Guarinos greenstone belt is one of the three low metamorphic grade supracrustal rocks assemblage rimmed by orthogneissesof Central Brazil’s Archean Block northern limits. The investigation of the stratigraphy of those greenstone beltsstarted by the end of 1970’s and underwent improvements during the years as a result of detailed geological mapping. Thelatest and accepted stratigraphic model for the Guarinos greenstone belt refers its supracrustal rocks under the GuarinosGroup, which is subdivided into the Serra do Cotovelo (metakomatiites, Serra Azul (metabasalts, São Patricinho (maficmetaturbidites, Aimbé (BIF and Cabaçal (carbonaceous phyllites and impure metarenites formations. Detailed geologicmapping (1:10,000 and drill-cores during an exploration program by Yamana Desenvolvimento Mineral S.A. in the areaallowed a better definition of the metasedimentary package of the Cabaçal Formation, which is here formally proposed tobe subdivided into a Lower Member of carbonaceous phyllites with basalt lava flows and gondite lenses interlayers, anIntermediate Member of gondite, iron formation, metachert and massive barite lenses, and an Upper Member of carbonaceous phyllites with minor metachert lenses. The impure metarenites, formerly considered as part of the Cabaçal Formation, are proposedunder the Mata Preta Formation, which is laterally interfingered with the Cabaçal Formation. U-Pb LA-ICP-MS geochronologicaldata of detrital zircon grains from the São Patricinho mafic metaturbidites and the impure metarenites of the Mata Preta formationsindicate that the major source-area of the clastic load had a Siderian to Rhyacian age, with minor contribution from Archean rocks.From the rock assemblage of both units and their contact relationships it is concluded that the basin stage they represent evolved duringthe world-wide Anoxic Oceanic Event (AOE that took place during the 2.2 to 2.06 Ga, represented by the carbonaceous phyllites ofthe

  5. Stratigraphy, mineralogy, and origin of layered deposits inside Terby crater, Mars

    Ansan, V.; Loizeau, D.; Mangold, N.; Le Mouélic, S.; Carter, J.; Poulet, F.; Dromart, G.; Lucas, A.; Bibring, J.-P.; Gendrin, A.; Gondet, B.; Langevin, Y.; Masson, Ph.; Murchie, S.; Mustard, J. F.; Neukum, G.


    , attesting to late fluvial processes dated as late Early to early Late Hesperian. After this late fluvial episode, the Terby impact crater was submitted to aeolian processes and permanent cold conditions with viscous flow features. Therefore, the Terby crater displays, in a single location, geologic features that characterize the three main periods of time on Mars, with the presence of one of the thickest sub-aqueous fan deposits reported on Mars. The filling of Terby impact crater is thus one potential "reference geologic cross-section" for Mars stratigraphy.

  6. Magnetic Anomaly Modeling of Volcanic Structure and Stratigraphy - Socorro Island, Eastern Pacific Ocean

    Urrutia-Fucugauchi, Jaime; Escorza-Reyes, Marisol; Pavon-Moreno, Julio; Perez-Cruz, Ligia; Sanchez-Zamora, Osvaldo


    Results of a magnetic survey of the volcanic structure of Socorro Island in the Revillagigedo Archipielago are presented. Socorro is part of a group of seamounts and oceanic islands built by volcanic activity at the northern end of the Mathematician ridge and intersection with the Clarion and Rivera fracture zones. Subaerial volcanic activity is characterized by alkaline and peralkaline compositions, marked by pre-, syn- and post-caldera phases of the Evermann volcano, and the Holocene mafic activity of the Lomas Coloradas. The magnetic survey conducted in the central-southern sector of the island permits to investigate the volcanic structure and subsurface stratigraphy. Regional fields for second- and third-degree polynomials show a magnetic low over the caldera, positive anomalies above the pre-caldera deposits and intermediate amplitude anomalies over Lomas Coloradas. Residual fields delineate the structural rim of the caldera, anomaly trends for the pre- and post-caldera deposits and a broad anomaly over Lomas Coloradas. Regional-residual anomalies, first vertical derivative, analytical upward and downward continuations, and forward four-layer modeling are used to construct the geophysical models. Rock magnetic properties were analyzed on samples collected at 24 different sites. Magnetic susceptibility showed wide range of variation from ~10 to ~500 10-3 SI, corresponding to the different lithologies from trachytes and glass-rich tuffs to alkali basalts. Data have been divided into groups with low, intermediate and high values. Rock magnetic analyses indicate that magnetite and titanomagnetites are the main magnetization carriers. Magnetic hysteresis loops indicate low coercivity minerals, with high saturation and remanent magnetizations and PSD domain states. Magnetic susceptibility versus temperature curves show irreversible behavior with Curie temperatures around 560-575 C, suggesting magnetite and Ti-poor titanomagnetites. Paleomagnetic directions

  7. Isotope stratigraphy of cenozoic carbonate sequences of Brazilian Northern coast; Estratigrafia isotopica de sequencias carbonaticas cenozoicas da Costa Norte do Brasil

    Rodrigues, Rene; Takaki, Tikae [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas


    Study of sedimentary rocks formation process on the Northern coast of Brazil, its stratigraphy characteristic, methodology of dating process to determine rocks age and correlation with carbonates sequences of Atlantic ocean (North and South) are presented. Results of analysed samples, isotopics studies, its dating, and comparative studies with samples analyzed in other sites are also discussed. 3 figs., 19 refs

  8. Alluvial flash-flood stratigraphy of a large dryland river: the Luni River, Thar Desert, Western India

    Carling, Paul; Leclair, Suzanne; Robinson, Ruth


    Detailed descriptions of the fluvial architecture of large dryland rivers are few, which hinders the understanding of stratigraphic development in aggradational settings. The aim of this study was to obtain new generic insight of the fluvial dynamics and resultant stratigraphy of such a river. The novelty of this investigation is that an unusually extensive and deep section across a major active dryland river was logged and the dated stratigraphy related to the behaviour of the discharge regimen. The results should help improve understanding of the stratigraphic development in modern dryland rivers and in characterizing oil, gas and groundwater reservoirs in the dryland geological record more generally. The Luni River is the largest river in the Thar desert, India, but yet details of the channel stratigraphy are sparse. Discharges can reach 14,000 m3s-1 but the bed is dry most of the year. GPS positioning and mm-resolution surveys within a 700m long, 5m deep trench enabled logging and photography of the strata associations, dated using optically-stimulated luminescence (OSL). The deposits consist of planar, sandy, upper-stage plane bed lamination and low-angle stratification, sandwiching less-frequent dune trough cross-sets. Mud clasts are abundant at any elevation. Water-ripple cross-sets or silt-clay layers occur rarely, usually near the top of sections. Aeolian dune cross-sets also appear sparsely at higher elevations. Consequently, the majority of preserved strata are due to supercritical flows. Localized deep scour causes massive collapse and soft-sediment deformation. Scour holes are infilled by rapidly-deposited massive sands adjacent to older bedded-deposits. Within bedform phase diagrams, estimated hydraulic parameters indicate a dominance of the upper-stage plane bed state, but the presence of dune cross-sets is also related to the flood hydrograph. Repeated deep scour results in units of deposition of different OSL ages (50 to 500 years BP) found at

  9. The Absolute Dating Potential of Proximal-Distal Tephra Correlations in an Aegean Marine Stratigraphy (Core LC21).

    Satow, Christopher; Lowe, John; Rohling, Eelco; Blockley, Simon; Menzies, Martin; Grant, Katharine; Smith, Vicki; Tomlinson, Emma


    Quaternary marine stratigraphies frequently suffer from poor absolute age control. Radiocarbon dating is intuitively the most appropriate technique for most marine stratigraphies, but its application is limited to the last 50ka or so by the decay rate of carbon. There are also uncertainties related to reservoir effects and the calibration of radiocarbon time to real time. However, precise dating and correlation of marine cores is essential to understand the timing and spatial relationships of the valuable environmental records they preserve. Here we demonstrate the potential of both visible and "invisible" micro-tephra layers to precisely date an important marine environmental record (Core LC21 from the Southern Aegean Sea). This is done by geochemically correlating the distal marine tephra layers to proximal volcanic deposits from Italy, Greece and Turkey. We use both Major Element (EPMA- Oxford Archaeology) and Trace Element (LA-ICP-MS, Royal Holloway Earth Sciences) analyses on individual tephra shards to determine the source of the tephra, and to make the correlations to explosive eruptive events. The most precise date (14C, 39Ar:40Ar or U-Th) from the event's proximal deposit is then imported into the equivalent distal tephra found in the marine core. Many of these distal "micro-tephras" were previously undetected by standard core logging techniques such as visual stratigraphy or scanning XRF. The extent and potential application of these tephras is now being realised. This study will provide the first direct (same core) and independent, absolute chronological markers for sapropels S3, S4 and S5, three major anoxic events found in the Eastern Mediterranean. In addition, the major and trace element geochemistry will be used to robustly correlate three marine cores spanning the Mediterranean. This work forms the Marine Tephrostratigraphy component (Work Package 5) of the UK Natural Environment Research Council (NERC) consortium project "RESET" (Response of

  10. Chemical Signatures of and Precursors to Fractures Using Fluid Inclusion Stratigraphy

    Lorie M. Dilley


    Enhanced Geothermal Systems (EGS) are designed to recover heat from the subsurface by mechanically creating fractures in subsurface rocks. Open or recently closed fractures would be more susceptible to enhancing the permeability of the system. Identifying dense fracture areas as well as large open fractures from small fracture systems will assist in fracture stimulation site selection. Geothermal systems are constantly generating fractures (Moore, Morrow et al. 1987), and fluids and gases passing through rocks in these systems leave small fluid and gas samples trapped in healed microfractures. These fluid inclusions are faithful records of pore fluid chemistry. Fluid inclusions trapped in minerals as the fractures heal are characteristic of the fluids that formed them, and this signature can be seen in fluid inclusion gas analysis. This report presents the results of the project to determine fracture locations by the chemical signatures from gas analysis of fluid inclusions. With this project we hope to test our assumptions that gas chemistry can distinguish if the fractures are open and bearing production fluids or represent prior active fractures and whether there are chemical signs of open fracture systems in the wall rock above the fracture. Fluid Inclusion Stratigraphy (FIS) is a method developed for the geothermal industry which applies the mass quantification of fluid inclusion gas data from drill cuttings and applying known gas ratios and compositions to determine depth profiles of fluid barriers in a modern geothermal system (Dilley, 2009; Dilley et al., 2005; Norman et al., 2005). Identifying key gas signatures associated with fractures for isolating geothermal fluid production is the latest advancement in the application of FIS to geothermal systems (Dilley and Norman, 2005; Dilley and Norman, 2007). Our hypothesis is that peaks in FIS data are related to location of fractures. Previous work (DOE Grant DE-FG36-06GO16057) has indicated differences in the

  11. Sedimentology and sequence stratigraphy of Lower Shihezi Formation in Shenguhao area, northern Ordos basin, China

    Chen, Lin; Lu, Yongchao; Lin, Zi


    The structural location of Shenguhao area locates at the transition zone of Yimeng uplift and Yishan slope of northern Ordos basin, China. The study area is in erosion condition until Late Carboniferous and has deposited Taiyuan Formation (C2t), Shanxi Formation (P1s), Lower Shihezi Formation (P1x), Upper Shihezi Formation (P2s) and Shiqianfeng Formation (P2sh) in succession during Late Paleozoic, which mainly develops transition facies and alluvial plain facies. The fluvial sandstone of Lower Shihezi Formation is the major target layer of gas exploration and development in this area. This study is based on the interpretation of 38 wells and 113 sesmic reflection profiles. Three significant lithofacies were identified with sedimentological analysis of cores from the Shenguhao area: fluvial conglomerates, fluvial sandstone and floodplain mudstone, which represent fluvial depositional environment. Based on sequence stratigraphy methodology, well log patterns and lithofacies analysis, Lower Shihezi Formation can be divided into four depositional sequence cycles (1-4) bounded by fluvial scouring erosional surfaces. Each sequence succession shows the trend of base level rising and overall performs fining-upward feature, which characterized by coarsening-upward lower to upper fluvial sandstone and floodplain mudstone. In ascending order, sequence 1 records the transition from the underlying braided river delta plain fine-grained sediments of Shanxi Formation into the overlying fluvial sandstone of Lower Shihezi Formation and develops scouring erosional unconformity at the base, representing a regression. Sequence 1 consists of a package of progradting thick layer of amalgamated fluvial sandstone at the lower part passing into aggrading thin layer of floodplain mudstone at the upper part, suggesting that accommodation growing rate is gradually greater than deposition supply rate under the background of base level gradual increase. Sequence 2 and 3 record similar

  12. Stratigraphy of the PB-1 well, Nopal I uranium deposit, Sierra Pena Blanca, Chihuahua, Mexico

    Dobson, P.; Fayek, M.; Goodell, P.; Ghezzehei, T.; Melchor, F.; Murrell, M.; Oliver, R.; Reyes-Cortes, I.A.; de la Garza, R.; Simmons, A.


    The Nopal I site in the Pena Blanca uranium district has a number of geologic and hydrologic similarities to the proposed high-level radioactive waste repository at Yucca Mountain, making it a useful analogue to evaluate process models for radionuclide transport. The PB-1 well was drilled in 2003 at the Nopal I uranium deposit as part of a DOE-sponsored natural analogue study to constrain processes affecting radionuclide transport. The well penetrates through the Tertiary volcanic section down to Cretaceous limestone and intersects the regional aquifer system. The well, drilled along the margin of the Nopal I ore body, was continuously cored to a depth of 250 m, thus providing an opportunity to document the local stratigraphy. Detailed observations of these units were afforded through petrographic description and rock-property measurements of the core, together with geophysical logs of the well. The uppermost unit encountered in the PB-1 well is the Nopal Formation, a densely welded, crystal-rich, rhyolitic ash-flow tuff. This cored section is highly altered and devitrified, with kaolinite, quartz, chlorite, and montmorillonite replacing feldspars and much of the groundmass. Breccia zones within the tuff contain fracture fillings of hematite, limonite, goethite, jarosite, and opal. A zone of intense clay alteration encountered in the depth interval 17.45-22.30 m was interpreted to represent the basal vitrophyre of this unit. Underlying the Nopal Formation is the Coloradas Formation, which consists of a welded lithic-rich rhyolitic ash-flow tuff. The cored section of this unit has undergone devitrification and oxidation, and has a similar alteration mineralogy to that observed in the Nopal tuff. A sharp contact between the Coloradas tuff and the underlying Pozos Formation was observed at a depth of 136.38 m. The Pozos Formation consists of poorly sorted conglomerate containing clasts of subangular to subrounded fragments of volcanic rocks, limestone, and chert

  13. Contribution to the stratigraphy of the onshore Paraíba Basin, Brazil

    Dilce F. Rossetti


    Full Text Available Several publications have contributed to improve the stratigraphy of the Paraíba Basin in northeastern Brazil. However, the characterization and distribution of sedimentary units in onshore areas of this basin are still incomplete, despite their significance for reconstructing the tectono-sedimentary evolution of the South American passive margin. This work provides new information to differentiate among lithologically similar strata, otherwise entirely unrelated in time. This approach included morphological, sedimentological and stratigraphic descriptions based on surface and sub-surface data integrated with remote sensing, optically stimulated luminescence dating, U+Th/He dating of weathered goethite, and heavy mineral analysis. Based on this study, it was possible to show that Cretaceous units are constrained to the eastern part of the onshore Paraíba Basin. Except for a few outcrops of carbonatic rocks nearby the modern coastline, deposits of this age are not exposed to the surface in the study area. Instead, the sedimentary cover throughout the basin is constituted by mineralogically and chronologically distinctive deposits, inserted in the Barreiras Formation and mostly in the Post-Barreiras Sediments, of early/middle Miocene and Late Pleistocene-Holocene ages, respectively. The data presented in this work support tectonic deformation as a factor of great relevance to the distribution of the sedimentary units of the Paraíba Basin.Várias publicações têm contribuído para melhorar a estratigrafia da Bacia Paraíba no nordeste do Brasil. Entretanto, a caracterização e distribuição das unidades sedimentares em áreas continentais desta bacia são ainda incompletas, apesar de sua importância para reconstruir a evolução tectono-sedimentar da margem passiva sulamericana. Este trabalho fornece novas informações para diferenciar entre estratos litologicamente similares que, por outro lado, não são relacionados no tempo. Esta

  14. Tephro- and chemo-stratigraphy of the Vulcanello Peninsula (Vulcano, Aeolian Islands)

    Rosi, M.; Fusillo, R.; di Traglia, F.; Pistolesi, M.; Todman, A.; Menzies, M. A.


    New stratigraphic studies of the Vulcanello Peninsula have been used to better define the small-scale evolution of this young (1000 AD and 325±100 BP) volcanic center and to re-investigate the last 1000 years of volcanic history for the Island of Vulcano (Aeolian Islands, Southern Italy). Vulcanello Peninsula is the northern-most part of the Island of Vulcano. It comprises a shoshonitic lava platform and a volcanic edifice made up of three overlying cones, which are shoshonitic to trachytic in composition. Volcanic activity in this area was coeval with the recent eruptions of the La Fossa Cone, the present-day active center of the island. Our goal is to constrain the recent volcanic development of this mafic volcano and to focus on the historic eruptive activity of the two other recent or active centres in the southern Aeolian Islands, Mt. Pilato (Island of Lipari) and La Fossa Cone. In order to do so, we reconstructed the stratigraphical setting of the proximal deposits of the three Vulcanello cones, through the investigation of 25 outcrops. We analyzed the stratigraphy of the tephra blankets deposited on the lava platform, studying 10 trenches. Our intention is to integrate morphological, textural and chemical data in order to correlate these deposits with the Vulcanello, La Fossa Cone or Mt Pilato. LA-MC-ICPMS (RHUL) analysis of juvenile clasts is underway in order to investigate the evolution of the Vulcanello juvenile clasts. In addition 14C dating is planned on selected organic matter from the volcanostratigraphic sections. Our preliminary data for the Vulcanello proximal deposits suggest that each of the three cones experienced several eruptions, with a wide spectrum of eruptive styles and a diversity of chemistry. The oldest cone (Vulcanello I) is characterised by four different eruptions separated by minor unconformities or reworking material indicative of little or not time breaks in the eruptive cycle. The eruptions shift from Violent Strombolian to

  15. Stratigraphy of Upper Cretaceous-Palaeogene sequences in the southern and eastern Menderes Massif (western Turkey)

    Özer, Sacit; Sözbilir, Hasan; Özkar, İzver; Toker, Vedia; Sari, Bilal


    The stratigraphy of the uppermost levels of the Menderes Massif is controversial and within its details lie vital constraints to the tectonic evolution of south-western Turkey. Our primary study was carried out in four reference areas along the southern and eastern Menderes Massif. These areas lie in the upper part of the Menderes metamorphic cover and have a clear stratigraphic relationship and contain datable fossils. The first one, in the Akbük-Milas area, is located south-east of Bafa Lake where the Milas, then Kızılağaç and Kazıklı formations are well exposed. There, the Milas formation grades upwards into the Kızılağaç formation. The contact between the Kızılağaç and the overlying Kazıklı formation is not clearly seen but is interpreted as an unconformity. The Milas and Kızılağaç formations are also found north of Muğla, in the region of Yatağan and Kavaklıdere. In these areas, the Milas formation consists of schists and conformably overlying platform-type, emery and rudist-bearing marbles. Rudists form the main palaeontological data from which a Santonian-Campanian age is indicated. The Kızılağaç formation is characterized by reddish-greyish pelagic marbles with marly-pelitic interlayers and coarsening up debris flow deposits. Pelagic marbles within the formation contain planktonic foraminifera and nanoplankton of late Campanian to late Maastrichtian age. The Kazıklı formation is of flysch type and includes carbonate blocks. Planktonic foraminifera of Middle Palaeocene age are present in carbonate lenses within the formation. In the Serinhisar-Tavas area, Mesozoic platform-type marbles (Yılanlı formation) belonging to the cover series of the Menderes Massif exhibit an imbricated internal structure. Two rudist levels can be distinguished in the uppermost part of the formation: the first indicates a middle-late Cenomanian age and the upper one is Santonian to Campanian in age. These marbles are unconformably covered by the

  16. Carbonate Sequence Stratigraphy of a Back-Arc Basin: A Case Study of the Qom Formation in the Kashan Area, Central Iran

    XU Guoqiang; ZHANG Shaonan; LI Zhongdong; SONG Lailiang; LIU Huimin


    The Qom Formation comprises Oligo-Miocene deposits from a marine succession distributed in the Central Basin of Iran. It is composed of five members designated as A-F. Little previous work exists on the sequence stratigraphy. Based on an integrated study of sequence stratigraphy with outcrop data, wells and regional seismic profiles, the Qom Formation is interpreted as a carbonate succession deposited in a mid-Tertiary back-arc basin. There are two second-order sequences (designated as SS1 and SS2) and five third-order sequences (designated as S1-S5). Five distinct systems tracts including transgressive, highstand, forced regressive, slope margin and lowstand have been recognized. The relationship between the sequences and lithologic sub-units has been collated and defined (S1 to S5 individually corresponding to A-C1, C2-C4, D-E, the lower and upper portions of F); a relative sea level change curve and the sequence stratigraphic framework have been established and described in detail. The coincidence of relative sea level change between that of the determined back-arc basin and the world indicates that the sedimentary cycles of the Qom Formation are mainly controlled by eustatic cycles. The variable combination of the systems tracts and special tectonic-depositional setting causally underpin multiple sequence stratigraphic framework styles seen in the carbonates of the back-arc basin revealing: (1) a continental margin basin that developed some form of barrier, characterized by the development of multiple cycles of carbonate-evaporites; (2) a flat carbonate ramp, which occurred on the southern shelf formed by the lack of clastic supply from nearby magmatic islands plus mixed siliciclastics and carbonates that occurred on the northern shelf due to a sufficient clastics supply from the land; and (3) a forced regressive stratigraphic stacking pattern that occured on the southern shelf and in basin lows due to the uplifting of the southern shelf. Thick and widespread

  17. Depositional sequence stratigraphy and architecture of the cretaceous ferron sandstone: Implications for coal and coalbed methane resources - A field excursion

    Garrison, J.R.; Van Den, Bergh; Barker, C.E.; Tabet, D.E.


    This Field Excursion will visit outcrops of the fluvial-deltaic Upper Cretaceous (Turonian) Ferron Sandstone Member of the Mancos Shale, known as the Last Chance delta or Upper Ferron Sandstone. This field guide and the field stops will outline the architecture and depositional sequence stratigraphy of the Upper Ferron Sandstone clastic wedge and explore the stratigraphic positions and compositions of major coal zones. The implications of the architecture and stratigraphy of the Ferron fluvial-deltaic complex for coal and coalbed methane resources will be discussed. Early works suggested that the southwesterly derived deltaic deposits of the the upper Ferron Sandstone clastic wedge were a Type-2 third-order depositional sequence, informally called the Ferron Sequence. These works suggested that the Ferron Sequence is separated by a type-2 sequence boundary from the underlying 3rd-order Hyatti Sequence, which has its sediment source from the northwest. Within the 3rd-order depositional sequence, the deltaic events of the Ferron clastic wedge, recognized as parasequence sets, appear to be stacked into progradational, aggradational, and retrogradational patterns reflecting a generally decreasing sediment supply during an overall slow sea-level rise. The architecture of both near-marine facies and non-marine fluvial facies exhibit well defined trends in response to this decrease in available sediment. Recent studies have concluded that, unless coincident with a depositional sequence boundary, regionally extensive coal zones occur at the tops of the parasequence sets within the Ferron clastic wedge. These coal zones consist of coal seams and their laterally equivalent fissile carbonaceous shales, mudstones, and siltstones, paleosols, and flood plain mudstones. Although the compositions of coal zones vary along depositional dip, the presence of these laterally extensive stratigraphic horizons, above parasequence sets, provides a means of correlating and defining the tops

  18. Small-scale disturbances in the stratigraphy of the NEEM ice core: observations and numerical model simulations

    Jansen, D.; Llorens, M.-G.; Westhoff, J.; Steinbach, F.; Kipfstuhl, S.; Bons, P. D.; Griera, A.; Weikusat, I.


    Disturbances on the centimetre scale in the stratigraphy of the North Greenland Eemian Ice Drilling (NEEM) ice core (North Greenland) can be mapped by an optical line scanner as long as the ice has visual layering, such as, for example, cloudy bands. Different focal depths allow, to a certain extent, a three-dimensional view of the structures. In this study we present a detailed analysis of the visible folds, discuss their characteristics and frequency, and present examples of typical fold structures. We also analyse the structures with regard to the deformation boundary conditions under which they formed. The structures evolve from gentle waves at about 1500 m to overturned z folds with increasing depth. Occasionally, the folding causes significant thickening of layers. Their similar fold shape indicates that they are passive features and are probably not initiated by rheology differences between alternating layers. Layering is heavily disturbed and tracing of single layers is no longer possible below a depth of 2160 m. C axes orientation distributions for the corresponding core sections were analysed, where available, in addition to visual stratigraphy. The data show axial-plane parallel strings of grains with c axis orientations that deviate from that of the matrix, which shows a single maximum fabric at the depth where the folding occurs. Numerical modelling of crystal viscoplastic deformation and dynamic recrystallisation was used to improve the understanding of the formation of the observed structures during deformation. The modelling reproduces the development of bands of grains with a tilted-lattice orientation relative to the single maximum fabric of the matrix, and also the associated local deformation. We conclude from these results that the observed folding can be explained by formation of these tilted-lattice bands.

  19. The stratigraphy of cretaceous mudstones in the eastern Fuegian Andes: new data from body and trace fossils

    Eduardo B. Olivero


    Full Text Available The stratigraphy of Cretaceous marine mudstones in the Fuegian Andes, roughly equivalent to Charles Darwin's clay-slate formation, remains a still unsolved problem. Previous records of Albian, Turonian-Coniacian, and Santonian-Campanian bivalves are combined with new findings of the Late Albian inoceramid Inoceramus anglicus Woods, and the Maastrichtian ammonites Diplomoceras sp., Anagaudryceras sp., Maorites densicostatus (Kilian and Reboul, Maorites sp., and Pachydiscus (Neodesmoceras sp. to further constrain the Cretaceous stratigraphy of the eastern Fuegian Andes. In addition, new records of distinctive trace fossils and ichnofabric are meaningful for stratigraphic division and delineation of paleoenvironmental settings in these Cretaceous mudstones. The Lower Cretaceous ichnoassemblage of Chondrites targioni (Brongniart and Zoophycos isp. is consistent with the inferred slope-volcaniclastic apron settings of the Yahgan Formation; Nereites missouriensis (Weller reflects distal basin plain depositional settings for the Beauvoir Formation. In the Upper Cretaceous, the "Estratos de Buen Suceso" record the earliest extensively bioturbated horizons, reflecting prolonged well-oxygenated bottom conditions. In the Bahía Thetis Formation, organic-rich, channel margin or distal basin slaty mudstones record the last occurrence of inoceramid bivalves in the Austral Basin; the generalized absence of trace fossils is consistent with dysoxic bottom conditions. The thoroughly bioturbated Policarpo Formation, records a marked change in paleoceanographic conditions. The strong contrast in the intensity of bioturbation between the Upper Campanian-Maastrichtian Bahía Thetis Formation, almost devoid of trace fossils, and the highly bioturbated Maastrichtian-Danian Policarpo Formation reflects a change from dysoxic-anoxic to well ventilated conditions, probably associated with a cooling trend of bottom waters in the austral deep oceans.

  20. Relationship between regional changes of soil physical properties and volcanic stratigraphy on the southern slope of Batur volcano in the island of Bali, Indonesia

    Tanaka, T.; Sunarta, N.


    The present paper shows the relationship between the regional changes of soil physical properties and the volcanic stratigraphy on the southern slope of Batur volcano in the island of Bali, Indonesia, from the hydrogeological point of view based on the data obtained from field observations and laboratory experiments. The Bali soils data showed marked differences in regional distribution and their characteristics are closely correlated to the distribution of the volcanic stratigraphy derived from the Batur volcanic activities with the eruption about 23,700 years ago. On the basis of these data, the hydrogeological situation of the slope are presented schematically and groundwater flow regimes on the slope, such as recharge and discharge areas, are also classified according to the hydrogeological information. These classifications of groundwater flow regimes are useful to consider the occurrence of hydrological phenomena such as springs and paddy field distributions observed on the slope.

  1. Introduction to the decisions of the International Subcommission on Devonian Stratigraphy%介绍国际泥盆纪地层委员会的几个决定



    @@ 国际泥盆纪地层委员会(Subcommission on Devonian Stratigraphy,简称SDS)是国际地层委员会下属分会中最活跃的分会之一.在它的领导下,于1972年通过了志留-泥盆系界线的决定,在世界上建立了第一个界线层型.

  2. Geomorphology, facies architecture, and high-resolution, non-marine sequence stratigraphy in avulsion deposits, Cumberland Marshes, Saskatchewan

    Farrell, K. M.


    This paper demonstrates field relationships between landforms, facies, and high-resolution sequences in avulsion deposits. It defines the building blocks of a prograding avulsion sequence from a high-resolution sequence stratigraphy perspective, proposes concepts in non-marine sequence stratigraphy and flood basin evolution, and defines the continental equivalent to a parasequence. The geomorphic features investigated include a distributary channel and its levee, the Stage I crevasse splay of Smith et al. (Sedimentology, vol. 36 (1989) 1), and the local backswamp. Levees and splays have been poorly studied in the past, and three-dimensional (3D) studies are rare. In this study, stratigraphy is defined from the finest scale upward and facies are mapped in 3D. Genetically related successions are identified by defining a hierarchy of bounding surfaces. The genesis, architecture, geometry, and connectivity of facies are explored in 3D. The approach used here reveals that avulsion deposits are comparable in process, landform, facies, bounding surfaces, and scale to interdistributary bayfill, i.e. delta lobe deposits. Even a simple Stage I splay is a complex landform, composed of several geomorphic components, several facies and many depositional events. As in bayfill, an alluvial ridge forms as the feeder crevasse and its levees advance basinward through their own distributary mouth bar deposits to form a Stage I splay. This produces a shoestring-shaped concentration of disconnected sandbodies that is flanked by wings of heterolithic strata, that join beneath the terminal mouth bar. The proposed results challenge current paradigms. Defining a crevasse splay as a discrete sandbody potentially ignores 70% of the landform's volume. An individual sandbody is likely only a small part of a crevasse splay complex. The thickest sandbody is a terminal, channel associated feature, not a sheet that thins in the direction of propagation. The three stage model of splay evolution

  3. Stratigraphy of amethyst geode-bearing lavas and fault-block structures of the Entre Rios mining district, Paraná volcanic province, southern Brazil



    Full Text Available The Entre Rios mining district produces a large volume of amethyst geodes in underground mines and is part of the world class deposits in the Paraná volcanic province of South America. Two producing basalt flows are numbered 4 and 5 in the lava stratigraphy. A total of seven basalt flows and one rhyodacite flow are present in the district. At the base of the stratigraphy, beginning at the Chapecó river bed, two basalt flows are Esmeralda, low-Ti type. The third flow in the sequence is a rhyodacite, Chapecó type, Guarapuava subtype. Above the rhyodacite flow, four basalt flows are Pitanga, high-Ti type including the two mineralized flows; only the topmost basalt in the stratigraphy is a Paranapanema, intermediate-Ti type. Each individual flow is uniquely identified from its geochemical and gamma-spectrometric properties. The study of several sections in the district allowed for the identification of a fault-block structure. Blocks are elongated NW and the block on the west side of the fault was downthrown. This important structural characterization of the mining district will have significant consequences in the search for new amethyst geode deposits and in the understanding of the evolution of the Paraná volcanic province.

  4. High-Resolution Magnetic Susceptibility Stratigraphy Spanning Late Devonian Global Change from a New Scientific Drillcore in Canning Basin, Northwest Australia

    Diamond, M. R.; Raub, T. D.; Kirschvink, J. L.; Playton, T. E.; Hocking, R. M.; Haines, P.; Tulipani, S.


    New shallow scientific drillcore has been recovered through the Frasnian-Famennian extinction boundary in northwest Australia’s Canning Basin. Previous work in the McWhae Ridge outcrop belt has identified patterns of turnover in trilobites and other fauna, change from sponge- and coral-dominated reefs to post-extinction microbial-dominated reefs, apparent sea level changes, and carbon isotopic evidence of late Devonian crisis. Continuous magnetic susceptibility (MS) stratigraphy yields highly structured oscillations spanning ~42 m of reef-slope carbonate. These oscillations appear to identify late Frasnian “Kellwasser” events and they may record sedimentary response to orbital variations, establishing a high-resolution relative chronostratigraphy of late Devonian global change. Magnetic susceptibility stratigraphy has been proposed as a generally useful chronometer for late Devonian time. Most of fifteen published MS stratigraphies crossing the Frasnian-Famennian boundary appear to share major excursions with the new McWhae Ridge result. Although upland tectonism in Canning Basin may be a caveat to straightforward eustatic interpretation of magnetic susceptibility variations, we suggest the higher-resolution and fresh drillcore context of this result prioritizes it as a standard for Frasnian-Famennian magnetic susceptibility variation.

  5. Carbon isotope stratigraphy and palynology of an eastern Tethyan Cretaceous-Paleogene boundary section from Sumbar, Turkmenistan

    Gilmour, I.; Pearce, C. A.; Jolley, D.; Sephton, M. A.; Widdowson, M.; Gilmour, M. A.


    A number of marine sequences across the K/Pg boundary have been identified that offer reasonably continuous records and relatively high sedimentation rates, most notably those near Tethyan continental margins. However, few Eastern Tethys K/Pg localities have been studied compared to the well-known North African and Southern European sites. Here we present a high-resolution stable carbon isotope and palynological record of a 2m thick section across the K/Pg boundary from the eastern Tethys at Sumbar in Turkmenistan (38°28'N, 56°14'E). The stratigraphy and inorganic geochemistry of the section used in this study, SM-4, has been described in detail by [1]. A moderately diverse series of palynofloras were recovered from the samples spanning the K/Pg boundary with a late Maastrichtian assemblage comparable to that described from Tunisia [2]. Above the K/Pg boundary a dinocyst assemblage dominated by Areoligera is observed, reinforcing the similarity with Tunisia, that we interpret as representing a marine transgression by eutrophic water masses with the levels of Areoligera decreasing up section with a decline in nutrient availability. Carbon isotope stratigraphy of bulk carbonate and bulk organic matter reveal correlated negative carbon isotope excursions (CIEs) across the K/Pg boundary. The extent of the CIE and the concomitant drop in carbonate content parallels that observed for bulk and fine fraction carbonate isotopic analyses from other K/Pg sections. The negative CIE of bulk organic matter is similar in magnitude to CIEs for organic matter that have been observed at only a few other marine K/Pg sections. In contrast, the marked CIE observed in bulk organic matter is not evident in the carbon isotopic compositions of algal lipids. We interpret this as a geochemical signature of post-K/Pg algal blooms. Recent analysis identified the K/Pg boundary in the Boltysh meteorite crater sediment fill and reported evidence of a marine incursion into the crater during the

  6. Elemental geochemistry and strontium-isotope stratigraphy of Cenomanian to Santonian neritic carbonates in the Zagros Basin, Iran

    Navidtalab, Amin; Rahimpour-Bonab, Hossain; Huck, Stefan; Heimhofer, Ulrich


    A Neo-Tethyan upper Cenomanian-Santonian neritic carbonate ramp succession (Sarvak and Ilam formations), drilled in the Zagros Basin in southwest Iran, was investigated via detailed sedimentology, microfacies analysis, elemental geochemistry and Sr-isotope stratigraphy (SIS). The succession contains two exposure surfaces, which are known as the CT-ES and mT-ES (Cenomanian-Turonian and middle Turonian, respectively), and associated prominent negative carbon-isotope excursions that represent important regional stratigraphic marker horizons. Precise knowledge about the onset of platform exposure and the duration of the exposure-related hiatus, however, is currently lacking due to a rather low-resolved shallow-water biostratigraphic framework and a bulk carbonate carbon-isotope pattern that clearly differs from global Late Cretaceous reference curves. Therefore, the existing bio-chemostratigraphic framework was complemented by bulk carbonate strontium-isotope stratigraphy (SIS). As bulk carbonate material is in particular prone to diagenetic alteration, a careful selection of least altered samples has been carried out by means of elemental geochemistry and petrography. In contrast to what could be expected, the meteoric alteration of limestones beneath both exposure surfaces is not clearly expressed by increasing iron and manganese and coeval decreasing strontium contents. On the contrary, the impact of meteoric diagenesis is well illustrated via pronounced increases in Rb concentrations and concomitant prominent positive shifts to radiogenic strontium-isotope values, an observation that clearly reflects the decay of continentally derived 87Rb into 87Sr. Rubidium corrected strontium-isotope values place the CT-ES around the Cenomanian-Turonian boundary and point to an exposure duration of less than 0.4 Myr. This rather short-term CT-ES related hiatus is supported by petrographic evidence, which indicates a youth karstification stage of strata beneath the CT

  7. 3-D visualisation of palaeoseismic trench stratigraphy and trench logging using terrestrial remote sensing and GPR - combining techniques towards an objective multiparametric interpretation

    Schneiderwind, S.; Mason, J.; Wiatr, T.; Papanikolaou, I.; Reicherter, K.


    Two normal faults on the Island of Crete and mainland Greece were studied to create and test an innovative workflow to make palaeoseismic trench logging more objective, and visualise the sedimentary architecture within the trench wall in 3-D. This is achieved by combining classical palaeoseismic trenching techniques with multispectral approaches. A conventional trench log was firstly compared to results of iso cluster analysis of a true colour photomosaic representing the spectrum of visible light. Passive data collection disadvantages (e.g. illumination) were addressed by complementing the dataset with active near-infrared backscatter signal image from t-LiDAR measurements. The multispectral analysis shows that distinct layers can be identified and it compares well with the conventional trench log. According to this, a distinction of adjacent stratigraphic units was enabled by their particular multispectral composition signature. Based on the trench log, a 3-D-interpretation of GPR data collected on the vertical trench wall was then possible. This is highly beneficial for measuring representative layer thicknesses, displacements and geometries at depth within the trench wall. Thus, misinterpretation due to cutting effects is minimised. Sedimentary feature geometries related to earthquake magnitude can be used to improve the accuracy of seismic hazard assessments. Therefore, this manuscript combines multiparametric approaches and shows: (i) how a 3-D visualisation of palaeoseismic trench stratigraphy and logging can be accomplished by combining t-LiDAR and GRP techniques, and (ii) how a multispectral digital analysis can offer additional advantages and a higher objectivity in the interpretation of palaeoseismic and stratigraphic information. The multispectral datasets are stored allowing unbiased input for future (re-)investigations.

  8. 3-D visualisation of palaeoseismic trench stratigraphy and trench logging using terrestrial remote sensing and GPR – combining techniques towards an objective multiparametric interpretation

    S. Schneiderwind


    Full Text Available Two normal faults on the Island of Crete and mainland Greece were studied to create and test an innovative workflow to make palaeoseismic trench logging more objective, and visualise the sedimentary architecture within the trench wall in 3-D. This is achieved by combining classical palaeoseismic trenching techniques with multispectral approaches. A conventional trench log was firstly compared to results of iso cluster analysis of a true colour photomosaic representing the spectrum of visible light. Passive data collection disadvantages (e.g. illumination were addressed by complementing the dataset with active near-infrared backscatter signal image from t-LiDAR measurements. The multispectral analysis shows that distinct layers can be identified and it compares well with the conventional trench log. According to this, a distinction of adjacent stratigraphic units was enabled by their particular multispectral composition signature. Based on the trench log, a 3-D-interpretation of GPR data collected on the vertical trench wall was then possible. This is highly beneficial for measuring representative layer thicknesses, displacements and geometries at depth within the trench wall. Thus, misinterpretation due to cutting effects is minimised. Sedimentary feature geometries related to earthquake magnitude can be used to improve the accuracy of seismic hazard assessments. Therefore, this manuscript combines multiparametric approaches and shows: (i how a 3-D visualisation of palaeoseismic trench stratigraphy and logging can be accomplished by combining t-LiDAR and GRP techniques, and (ii how a multispectral digital analysis can offer additional advantages and a higher objectivity in the interpretation of palaeoseismic and stratigraphic information. The multispectral datasets are stored allowing unbiased input for future (re-investigations.

  9. Multi-scale petrophysical and geomechanical characterization of full core from the Groningen Field to understand mechanical stratigraphy and compaction behavior

    van Eijs, Rob; Hol, Sander; Marcelis, Fons; Ishmukhametova, Gulfiia; van der Linden, Arjan; Zuiderwijk, Pedro; Makurat, Axel


    The Groningen gas field in The Netherlands is one of the largest onshore gas reserves known. Advancing production from the field has resulted in field-scale deformation with surface subsidence and accompanied local seismicity. Part of the deformation is associated with compaction of the Permian reservoir. While depletion-induced reservoir compaction is expected to be controlled locally by grain-scale physical mechanisms such as sub-critical cracking or particle re-arrangement and intergranular pressure solution creep, understanding of the intra-reservoir variability of these mechanisms is still limited, though crucial for predicting the coupling between production, rock deformation, and surface effects. To aid an improved understanding of fundamental processes and scaling effects, approximately 200 meters of core over the reservoir section was taken from a well in the Groningen Field, drilled in July 2015 close to the village of Zeerijp. Using this material, we have performed detailed laboratory investigations and will continue to do so in significant numbers, to compare the results obtained with well- and field-scale observations. In this contribution, we present several exemplary mechanical data sets for the reservoir and caprock, and compare these data with well-scale petrophysical and mechanical information, notably sonic, scratch and visual geological details with the aim to arrive at a multi-scale description of petrophysical and geomechanical rock properties. Our first comparison reveals a strong contrast in compressibility and strength between the reservoir and caprock, as well as a contribution of inelastic strain to the total strain response of the tested rock samples. We will discuss the observed mechanical stratigraphy in considering regional and field scale deformation patterns.

  10. Sequence Stratigraphy and Sedimentary Facies of Lower Oligocene Yacheng Formation in Deepwater Area of Qiongdongnan Basin, Northern South China Sea:Implications for Coal-Bearing Source Rocks

    Jinfeng Ren; Hua Wang; Ming Sun; Huajun Gan; Guangzeng Song; Zhipeng Sun


    For unveiling coal-bearing source rocks in terrestrial-marine transitional sequences, the sequence stratigraphic framework and sedimentary facies of Lower Oligocene Yacheng Formation of Qiongdongnan Basin were investigated using seismic profiles, complemented by well bores and cores. Three third-order sequences are identified on the basis of unconformities on basin margins and cor-relative conformities in the basin center, namely SQYC3, SQYC2 and SQYC1 from bottom to top. Coal measure in Yacheng Formation of Qiongdongnan Basin were deposited within a range of facies asso-ciations from delta plain/tidal zone to neritic sea, and three types of favourable sedimentary facies as-sociations for coal measure were established within the sequence stratigraphic framework, including braided delta plain and alluvial fan, lagoon and tidal flat, and fan delta and coastal plain facies associa-tions. Results shown that, in the third-order sequences, coal accumulation in landward areas (such as delta plain) of the study area predominantly correlates with the early transgressive systems tract (TST) to middle highstand systems tract (HST), while in seaward areas (such as tidal flat-lagoon) it correlates with the early TST and middle HST. The most potential coal-bearing source rocks formed where the accommodation creation rate (Ra) and the peat-accumulation rate (Rp) could reach a state of balance, which varied among different sedimentary settings. Furthermore, intense tectonic subsidence and fre-quent alternative marine-continental changes of Yacheng Formation during the middle rift stage were the main reasons why the coal beds shown the characteristics of multi-beds, thin single-bed, and rapidly lateral changes. The proposed sedimentary facies associations may aid in predicting distribution of coal-bearing source rocks. This study also demonstrates that controlling factors analysis using sequence stratigraphy and sedimentology may serve as an effective approach for coal

  11. Oxygen isotope stratigraphy and events in the northern South China Sea during the last 6 million years


    Based on the stable isotopic analysis of more than 1000 samples of planktonic and benthic foraminifers from ODP Site 1148 in the northern South China Sea (SCS), the oxygen iso tope stratigraphy has been applied to the last 3 million years for the first time in the SCS. Further more, the paleoceanographic changes in the northern SCS during the last 6 million years have been unraveled. The benthic foraminiferaδl8O record shows that before ~3.1 Ma the SCS was much more influenced by the warm intermediate water of the Pacific. The remarkable decrease in the deepwater temperature of the SCS during the period of 3.1-2.5 Ma demonstrates the forma tion of the Northern Hemisphere ice-sheet. However, the several sea surface temperature (SST)reductions during the early and middle Pliocene, reflected by the planktonic foraminiferal δ18O,might be related to the ice-sheet growth in the Antarctic region. Only those stepwise and irreversi ble SST reductions during the period of ~2.2-0.9 Ma could be related to the formation and growth of the Northern Hemisphere ice-sheet.

  12. Correlation of near-surface stratigraphy and physical properties of clayey sediments from Chalco Basin, Mexico, using Ground Penetrating Radar

    Carreón-Freyre, Dora; Cerca, Mariano; Hernández-Marín, Martín.


    Detailed measurements of water content, liquid and plastic limits, electric conductivity, grain-size distribution, specific gravity, and compressibility were performed on the upper 7 m of the lacustrine sequence from the Chalco Basin, Valley of Mexico. Eight stratigraphic units consisting of alternating layers of clay, silt, sand, and gravel of volcanic origin are described for this sequence. The analysis of contrasts in the physical properties permitted to identify potential reflectors of radar waves: (i) change in the electrical conductivity at 0.4 m depth; (ii) increment in the clay and water content at 0.8 m depth; (iii) bimodal behavior of the water content at 1.3 m depth; (iv) increment in the sand content and decrease in water content at 2.6 m depth; and (v) the presence of a pyroclastic unit at 3.7 m depth. Radargrams with frequencies of 900 and 300 MHz were collected on a grid of profiles covering the study area. Correlation of radargrams with the reference section permitted the spatial interpolation of variations in the physical properties and the near-surface stratigraphy. Contrary to the expected in these clayey sediments, electric contrast enhanced by variations in water content and grain size permitted the recording of the near-surface sedimentary structures. Distinctive radar signatures were identified between reflectors. Furthermore, lateral discontinuities of the reflectors and their vertical displacements permitted the identification of deformational features within the sequence.

  13. Late Paleocene–early Eocene carbon isotope stratigraphy from a near-terrestrial tropical section and antiquity of Indian mammals

    A Samanta; A Sarkar; M K Bera; Jyotsana Rai; S S Rathore


    Late Paleocene to early Eocene (∼56 to 51 Ma) interval is characterized by five distinct transient warming (hyperthermal) events (Paleocene–Eocene thermal maximum (PETM), H1/ETM2/ELMO, H2, I1 and I2) in a super greenhouse globe associated with negative carbon isotope excursions (CIEs). Although well-documented marine records exist at different latitudes, terrestrial PETM sections are rare. In particular, almost no terrestrial records of either the PETM or early Eocene hyperthermals (EEHs) are yet available from the tropics. Further, evolution of modern order of mammals near the PETM has been recorded in many northern continents; however, the response of mammals in the tropics to these warming events is unknown. A tropical terrestrial record of these hyperthermal/CIE events, encompassing the earliest modern order mammal bearing horizon from India, can therefore be vital in understanding climatic and biotic evolution during the earliest Cenozoic time. Here, for the first time, we report high resolution carbon isotope (13C) stratigraphy, nannofossil, and Sr isotope ratio of marine fossil carbonate from the Cambay Shale Formation of Western India. The record shows complete preservation of all the above CIE events, including the PETM, hitherto unknown from the equatorial terrestrial records. 13C chemostratigraphy further suggests that at least the present early Eocene mammal-bearing horizon, recently discovered at Vastan, does not support the `out of India' hypothesis of earliest appearance of modern mammals and subsequent dispersal to the Holarctic continents.

  14. Late Paleocene-early Eocene carbon isotope stratigraphy from a near-terrestrial tropical section and antiquity of Indian mammals

    Samanta, A.; Sarkar, A.; Bera, M. K.; Rai, Jyotsana; Rathore, S. S.


    Late Paleocene to early Eocene (~56 to 51 Ma) interval is characterized by five distinct transient warming (hyperthermal) events (Paleocene-Eocene thermal maximum (PETM), H1/ETM2/ELMO, H2, I1 and I2) in a super greenhouse globe associated with negative carbon isotope excursions (CIEs). Although well-documented marine records exist at different latitudes, terrestrial PETM sections are rare. In particular, almost no terrestrial records of either the PETM or early Eocene hyperthermals (EEHs) are yet available from the tropics. Further, evolution of modern order of mammals near the PETM has been recorded in many northern continents; however, the response of mammals in the tropics to these warming events is unknown. A tropical terrestrial record of these hyperthermal/CIE events, encompassing the earliest modern order mammal bearing horizon from India, can therefore be vital in understanding climatic and biotic evolution during the earliest Cenozoic time. Here, for the first time, we report high resolution carbon isotope ( δ 13C) stratigraphy, nannofossil, and Sr isotope ratio of marine fossil carbonate from the Cambay Shale Formation of Western India. The record shows complete preservation of all the above CIE events, including the PETM, hitherto unknown from the equatorial terrestrial records. δ 13C chemostratigraphy further suggests that at least the present early Eocene mammal-bearing horizon, recently discovered at Vastan, does not support the `out of India' hypothesis of earliest appearance of modern mammals and subsequent dispersal to the Holarctic continents.

  15. Stratigraphy, sedimentology, paleontology, and paleomagnetism of Pliocene-early Pleistocene lacustrine deposits in two cores from western Utah

    Thompson, R.S.; Oviatt, Charles G.; Roberts, A.P.; Buchner, J.; Kelsey, R.; Bracht, C.J.; Forester, R.M.; Bradbury, J.P.


    The paleoclimatic history of western Utah is being investigated as part of the USGS Global Change and Climate History Program studies of long-term climatic changes in the western United States. The initial objective of the study is to document the environmental conditions during the mid-Pliocene period of warmer-than-modern global climates (the focus of the USGS Pliocene Research, Interpretation, and Synoptic Mapping [PRISM] project). The investigation also seeks to determine how and when these conditions gave way to the late Quaternary pattern of climatic variations (in which short periods of very moist climates have been separated by long periods of arid conditions). This is a collaborative project involving specialists from the USGS, Kansas State University, and the University of California-Davis in paleontology (Thompson, Buchner, Forester, Bradbury), stratigraphy and sedimentology (Oviatt, Kelsey, Bracht), and paleomagnetism and environmental magnetism (Roberts). The data presented herein represent preliminary findings of the analyses of two cores of Pliocene and early Pleistocene sediments from the eastern Great Basin.

  16. Depositional environments and sequence stratigraphy of the Bahram Formation (middleelate Devonian) in north of Kerman, south-central Iran

    Afshin Hashmie; Ali Rostamnejad; Fariba Nikbakht; Mansour Ghorbanie; Peyman Rezaie; Hossien Gholamalian


    This study is focused on sedimentary environments, facies distribution, and sequence stratigraphy. The facies and sequence stratigraphic analyses of the Bahram Formation (middleelate Devonian) in south-central Iran are based on two measured stratigraphic sections in the southern Tabas block. The Bah-ram Formation overlies red sandstones Padeha Formation in sections Hutk and Sardar and is overlain by Carboniferous carbonate deposits of Hutk Formation paraconformably, with a thickness of 354 and 386 m respectively. Mixed siliciclastic and carbonate sediments are present in this succession. The field observations and laboratory studies were used to identify 14 micro/petrofacies, which can be grouped into 5 depositional environments: shore, tidal flat, lagoon, shoal and shallow open marine. A mixed carbonate-detrital shallow shelf is suggested for the depositional environment of the Bahram Formation which deepens to the east (Sardar section) and thins in southern locations (Hutk section). Three 3rd-order cyclic siliciclastic and carbonate sequences in the Bahram Formation and one sequence shared with the overlying joint with Hutk Formation are identified, on the basis of shallowing upward patterns in the micro/pertofacies.

  17. A luminescence dating study of the sediment stratigraphy of the Lajia Ruins in the upper Yellow River valley, China

    Zhang, Yuzhu; Huang, Chun Chang; Pang, Jiangli; Zhou, Yali; Zha, Xiaochun; Wang, Longsheng; Zhou, Liang; Guo, Yongqiang; Wang, Leibin


    Pedo-sedimentological fieldwork were carried out in the Lajia Ruins within the Guanting Basin along the upper Yellow River valley. In the eolian loess-soil sections on the second river terrace in the Lajia Ruins, we find that the land of the Qijia Culture (4.20-3.95 ka BP) are fractured by several sets of earthquake fissures. A conglomerated red clay covers the ground of the Qijia Culture and also fills in the earthquake fissures. The clay was deposited by enormous mudflows in association with catastrophic earthquakes and rainstorms. The aim of this study is to provide a luminescence chronology of the sediment stratigraphy of the Lajia Ruins. Eight samples were taken from an eolian loess-soil section (Xialajia section) in the ruins for optically stimulated luminescence (OSL) dating. The OSL ages are in stratigraphic order and range from (31.94 ± 1.99) ka to (0.76 ± 0.02) ka. Combined OSL and 14C ages with additional stratigraphic correlations, a chronological framework is established. We conclude that: (1) the second terrace of the upper part of Yellow River formed 35.00 ka ago, which was followed by the accumulation of the eolian loess-soil section; and (2) the eolian loess-soil section is composed of the Malan Loess of the late last glacial (MIS-2) and Holocene loess-soil sequences.

  18. Sedimentary environment, diagenesis and sequence stratigraphy of Sarvak Formation in Abteymour Oilfield in Western part of the Dezful embayment

    H., Mehrabi,


    Full Text Available Sarvak Formation (Late Albian-Middle Turonian is one of the important reservoir units after Asmari (Oligo-Miocene in southwest Iran that host an important hydrocarbon reserves in this region. Due to facies and environmental variations as well as complex diagenetic history, its reservoir properties show intense complexity and heterogeneity. To understand these imposed heterogeneities a comprehensive reservoir study including facies analysis, diagenetic study and sequence stratigraphy are carried out. According to facies analysis study, carbonates of the Sarvakformation deposited in a homoclinal ramp-type platform. Low diversity of determined microfacies as well as mud-dominated facies in this field, indicating of a leeward ramp. Main diagenetic processes affected carbonates of this unit are extensive dissolution (in two step: eogenetic and telogenetic, dolomitization (in two ways: mixing zone and stylolite related, cementation (include meteoric, shallow and deep burial cements, micritization, mechanical and chemical compaction (stylolitization, dedolomitization, silicification, pyritization, recrystallization and fracturing. Paragenetic sequence of diagenetic events of this formation above and below Cenomanian-Turonian boundary showed two different histories for these two parts. Three 3rd ordered are recognized in sequence stratigraphic within the Sarvak Formation belong to Middle Cenomanian to Middle Turonian time span. Examining facies distribution patterns and diagenetic events in a sequence stratigraphic framework indicate close relationships and predictability of diagenetic alterations.



    The characteristics of the Triassic sequences developed in the Lower Yangtze area display some great changes in both environment and climate. The change of environment was a transition from marine to continent via alternating environments. The change of climate was a transition from tropic (torrid) to warm and wet climate via subtropic dry climate. The type variations of the sequences were from the marine sequences to the continental sequences, corresponding to the changes of environments and climates.Sequence 1 is a type Ⅱ of sequence of mixed clastic and carbonate sediments; sequence 2 is a type Ⅰ of sequence of carbonate platform; sequence 3 is a type Ⅰ of sequence of carbonate tidal flat-salt lagoon,sequence 4 is a type Ⅱ of sequence of lacustrine within marine layers, and sequence 5 is a sequence of lacustrine-swamp. The development, distribution and preservation of those sequences reveal the tectonic controls and their changes in the background. The collision between the Yangtze plate and the North China plate was a great geological event in the geological history, but the timing of the collision is still disputed.However, the characteristics of Triassic sequence stratigraphy and sea level changes in the Lower Yangtze area responded to this coliision. The collision started at the beginning of middle Triassic and the great regression in the Lower Yangtze area started 22Ma earlier than those in the world. The tectonic conditions occurred before and during the collision controlled the development of sequences and type changes.

  20. Carbon isotope stratigraphy, magnetostratigraphy, and 40Ar/39Ar age of the Cretaceous South Atlantic coast, Namibe Basin, Angola

    Strganac, Christopher; Salminen, Johanna; Jacobs, Louis L.; Polcyn, Michael J.; Ferguson, Kurt M.; Mateus, Octávio; Schulp, Anne S.; Morais, Maria Luísa; Tavares, Tatiana da Silva; Gonçalves, António Olímpio


    We present the δ13C and paleomagnetic stratigraphy for marine strata at the coast of southern Angola, anchored by an intercalated basalt with a whole rock 40Ar/39Ar radiometric age of 84.6 ± 1.5 Ma, being consistent with both invertebrate and vertebrate biostratigraphy. This is the first African stable carbon isotope record correlated to significant events in the global carbon record spanning the Late Cenomanian to Early Maastrichtian. A positive ∼3‰ excursion seen in bivalve shells below the basalt indicates the Cenomanian-Turonian Boundary Event at 93.9 Ma, during Oceanic Anoxic Event 2. Additional excursions above the basalt are correlated to patterns globally, including a negative ∼3‰ excursion near the top of the section interpreted as part of the Campanian-Maastrichtian Boundary Events. The age of the basalt ties the studied Bentiaba section to a pulse of Late Cretaceous magmatic activity around the South Atlantic and significant tectonic activity, including rotation, of the African continent.

  1. Anthropogenic versus climatic control in a high-resolution 1500-year chironomid stratigraphy from a southwestern Greenland lake

    Millet, Laurent; Massa, Charly; Bichet, Vincent; Frossard, Victor; Belle, Simon; Gauthier, Emilie


    We performed a high-resolution study of chironomid assemblages in a sediment core retrieved from Lake Igaliku in southern Greenland. The well-dated core is located within the former Norse Eastern Settlement and covered the last 1500 yr. The comparison of chironomid stratigraphy (PCA axis scores) with instrumental temperature data, land use history and organic matter in the sediment over the last 140 yr suggested that the primary changes in chironomid fauna in 1988 ± 2 yr were driven by the shift to modern agriculture in the catchment. This unprecedented change in chironomid fauna was most likely triggered by a shift in in-lake processes. Within the instrumental period, subtle variations in the chironomid assemblages that occurred before 1988 ± 2 yr were significantly correlated with summer temperatures even in times of traditional extensive sheep farming in the catchment. The relevance of the chironomid-derived climate signal over the last 1500 yr was supported by its good concordance with previous studies in west Greenland and in the Arctic. The chironomid assemblage therefore appeared to be a valuable proxy for climate changes within the Norse colony area. Synchronous changes in Norse diet and chironomid-reconstructed climate give new insights into the interplay of Norse society with climate.




    Full Text Available The biochronological setting proposed for the Plio-Pleistocene large mammal faunas of the Italian peninsula is based on the definition of faunal units (FUs and mammal ages (MAs. Many evidences suggest that a multidisciplinary approach could enable us to better understand the actual meaning of a given faunal assemblage taking into account sedimentological and physical stratigraphic studies of the sedimentary successions in which local mammal faunas occur. The Pleistocene deposits of the Roman Basin can be considered a significant model to test this integrated approach. The detailed study of this sedimentary succession, in terms of facies analysis and sequence stratigraphy, sets some physical and temporal constrains to the occurrence of faunal complexes because the allocyclic control (climate and eustatic variations on both landscape and stratigraphical evolution can affect the association type of mammal faunas. A correlation scheme between the Roman Pleistocene sequence-stratigraphic units and the mammal biochrons has been proposed; this approach constitutes a first tentative to connect the mammal fauna remains to the sedimentary processes which are responsible of their transport, stock and potential preservation in the depositional environments and to collocate this fauna in the systems tracts of the fourth-order depositional sequences recognised in the local Roman Basin Pleistocene succession.

  3. Gastropoda-Bivalvia Fauna And Neogene-Quaternary Stratigraphy of the Southwest of Dardanelles (Çanakkale-NWAnatolia)

    Kapan, Sevinç; Kabasakal, Sinem


    Gastropoda-Bivalvia Fauna And Neogene-Quaternary Stratigraphy of the Southwest of Dardanelles (Çanakkale-NWAnatolia) Sevinç KAPAN, Sinem KABASAKAL, Çanakkale Onsekiz Mart University, Engineering Faculty, Geological Engineering Department In this study, paleontology and stratigraphy of Neogene and Quaternary units around south of the Dardanelles have been examined using Gastropoda and Bivalvia fauna. In the investigation area, the base of the sediments that belongs to Neogene, consist of the volcanics which are formed with basalts, andesites and tuff. Neogene begins unconformity with basal conglomerate which are formed with basalt and tuff gravels. The measurable thickness of the Neogene sediments is approximately 200meters in total. First fossiliferius level which consist of Lymnocardium (Euxinicardium) nobile Sabba has showed similarities with the Pontian (Late Miocene) fauna of the Eastern Paratethys. The existence of Melanopsis and Psidium species indicate that the basin has been brackish water feeding by fresh water in the Early Pliocene. Theodoxus fluviatilis (Linne), Theodoxus (Calvertia) aff. imbricata Brusina, Theodoxus (Calvertia) licherdopoli scriptus (Stefanescu), Viviparus mammatus (Stefanescu), Valvata (Valavata) sulekiana Brusina, Valvata (Cincinna) crusitensis Fontannes, Hydrobia cf grandis Cobalcescu, Hydrobia ventrosa Monfort, Melanopsis (Melanopsis) cf. bergeroni Stefanescu, , Melanopsis (Melanopsis) sandbergeri rumana Tournouer, Melanopsis (Canthidomus) hybostoma anili Taner, Melanopsis (Canthidomus) hybostoma amaradica Fontannes, Melanopsis (Canthidomus) lanceolata Neumayr, Amphimelania fossariformis (Tournouer), Melanoides tuberculata monolithica (Bukowski), Radix (Radix) peregra (Müller), Planorbarius thiollierei (Michaud), Potamida (Potamida) craiovensis craiovensis (Tournouer), Potamida (Potamida) berbestiensis (Fontannes), Unio pristinus davilai Porumbaru, Unio subexquisitus Jatzko, Anadonta zmaji

  4. Stratigraphy and reservoir quality of the turbidite deposits, western sag, Bohai bay, China P.R.

    Rotimi, Oluwatosin J.; Ako, Bankole D.; Zhenli, Wang


    Stratigraphic and subtle reservoirs such as pinchouts, sand lenses and unconformities have been discovered in Bohai basin. These reservoirs occur in sub-basins and sag structures called depressions. A prolific depression is the Liaohe depression that has been filled with rapidly changing mixed alluvial fan deposit of the Cenozoic age. Attempts made at recovering residual hydrocarbon from the subtle reservoir have necessitated the re-evaluation of available data to characterize and model the prolific Shahejie Formation turbidite deposit occurring as pinchouts and sand lenses for hydrocarbon assessment, reservoir quality and possible recovery through enhanced methods. Methods employed covered well logs analysis, clustering analysis for electrofacies and fuzzy logic analysis to predict missing log sections. Stratigraphic and structural analysis was done on SEGY 3D seismic volume after seismic to well tie. Stochastic simulation was done on both discrete and continuous upscaled data. This made it possible to correctly locate and laterally track identified reservoir formation on seismic data. Petrophysical parameters such as porosity and permeability were modeled with result of clustering analysis. Result shows that electrofacies converged on 2 rock classes. The area is characterized by the presence of interbeded sand-shale blanket formations serving as reservoir and seal bodies. The reservoir quality of the formations as seen on the petrophysical analysis done is replicated in simulation volume results. Reservoir rocks have porosity between 0.1 and 0.25, permeability between 1 and 2mD and hydrocarbon saturation as high as 89%. Lithofacies are observed to be laterally inconsistent, sub-parallel to dipping and occurring as porous and permeable continuous beds or pinchouts hosting hydrocarbon. The stochastic stratigraphic model depicts rock units in associations that are synsedimentary. The prevalent configuration gotten from the model gave an insight into exploring and

  5. Dominant events in the northern Danube Basin palaeogeography – a tool for specification of the Upper Miocene and Pliocene stratigraphy

    Peter Joniak


    Full Text Available Late Neogene palaeogeography and geodynamics of the Danube Basin is characterized by wide rifting of the back arc basin, its gradual infill, followed by the Pliocene uplift and denudation. Basin development is well recorded in its sedimentary succession, where three 3rd order sequence stratigraphy cycles were documented. DB1 cycle comprising the Lower and Middle Pannonian sediments (A – E zones sensu Papp, 1951 deposited in time span 11.6 – (9.7? 8.9 Ma is represented in Slovakia by the Ivanka and Beladice formations, in Hungary (where the formations are defined as appearance of sedimentary facies in time and space the equivalents are: deepwater setting marls, clays and sandy turbidites of the Endrőd and Szolnok formations, towards overlying strata by deposits of the basin palaeoslope or delta-slope represented by the Algyő Formation and the final shallow water setting deposits of marches, lagoons, coastal and delta plain built up by clays, sands with coal seams, represented by the Újfalu Formation. DB2 cycle comprises the Upper Pannonian sediments of the Danube Basin (F, G & H zones sensu Papp, 1951 deposited in time span (9.7? 8.9 – 6.3? Ma and is represented by the uppermost part of the Beladice and Volkovce formations, in Hungary by the Zagyva Formation. Sedimentary environment can be characterized as alluvial – with wide range of facies – from fluvial, deltaic, ephemeral lake to marches and dry land deposits. DB3 cycle comprises the Pliocene sediments of the Danube Basin Slovak part represented by the Kolárovo Formation, dated 4.1? – 2.6 Ma. The formation was deposited in fluvial to lake, and alluvial environment.

  6. Geologic Mapping of the Lunar South Pole, Quadrangle LQ-30: Volcanic History and Stratigraphy of Schroedinger Basin

    Mest, S. C.; Berman, D. C.; Petro, N. E.


    In this study we use recent images and topographic data to map the geology and geomorphology of the lunar South Pole quadrangle (LQ-30) at 1:2.5M scale [1-4] in accordance with the Lunar Geologic Mapping Program. Mapping of LQ-30 began during Mest's postdoctoral appointment and has continued under the PG&G Program, from which funding became available in February 2009. Preliminary map-ping and analyses have been done using base materials compiled by Mest, but properly mosaicked and spatially registered base materials are being compiled by the USGS and should be received by the end of June 2009. The overall objective of this research is to constrain the geologic evolution of the lunar South Pole (LQ-30: 60deg -90deg S, 0deg - +/-180deg ) with specific emphasis on evaluation of a) the regional effects of basin formation on the structure and composition of the crust and b) the spatial distribution of ejecta, in particular resulting from formation of the South Pole-Aitken (SPA) basin and other large basins. Key scientific objectives include: 1) Constraining the geologic history of the lunar South Pole and examining the spatial and temporal variability of geologic processes within the map area. 2) Constraining the vertical and lateral structure of the lunar regolith and crust, assessing the distribution of impact-generated materials, and determining the timing and effects of major basin-forming impacts on crustal structure and stratigraphy in the map area. And 3) assessing the distribution of resources (e.g., H, Fe, Th) and their relationships with surface materials.

  7. Facies analysis and sequence stratigraphy of the Asmari Formation in the northern area of Dezful Embayment, south-west Iran

    Fateme Zabihi Zoeram


    Full Text Available This paper concerns the sequence stratigraphy of the Oligocene (Rupelian–Chattian–Early Miocene (Burdigalian Asmari Formation based on microfacies analysis of the sediments in the Ghale Nar Oilfield, central area of Zagros fold-thrust belt. Fourteen facies types typical for upward shallowing trend from open marine (MF 1–3, to shoal (MF 4-5, semi-restricted and restricted lagoon (MF 6–12 and finally to near-shore lagoon (MF 13-14 depositional environments were identified. Based on the environmental interpretations, we reconstructed a homoclinal ramp mainly represented by its inner and middle sectors. Facies types MF 4–14 are characterized by the occurrence of large and small porcelaneous benthic foraminifera representing a shallow-water setting of an inner ramp influenced by wave and tide processes. MF1 (Pabdeh Formation, and 2 -3 with planktonic, large and small hyaline benthic foraminifera represent between FWWB and SWB. Four third-order depositional sequences were recognized. In this study, in order to better correlate the identified sequences with pre-defined sequences of the Asmari Formation in the Dezful Embayment and the Izeh zone that are chronologically well-defined, we use their number instead of their name. Sequence 2 mainly consists of an open marine environment in the base, followed by semi-restricted to restricted lagoonal facies. Sequences 36 are characterized by semi-restricted to restricted lagoonal facies. Moreover, the regional relative sea-level change curves correlate well with the global sea-level change curves.

  8. The archaeology, chronology and stratigraphy of Madjedbebe (Malakunanja II): A site in northern Australia with early occupation.

    Clarkson, Chris; Smith, Mike; Marwick, Ben; Fullagar, Richard; Wallis, Lynley A; Faulkner, Patrick; Manne, Tiina; Hayes, Elspeth; Roberts, Richard G; Jacobs, Zenobia; Carah, Xavier; Lowe, Kelsey M; Matthews, Jacqueline; Florin, S Anna


    Published ages of >50 ka for occupation at Madjedbebe (Malakunanja II) in Australia's north have kept the site prominent in discussions about the colonisation of Sahul. The site also contains one of the largest stone artefact assemblages in Sahul for this early period. However, the stone artefacts and other important archaeological components of the site have never been described in detail, leading to persistent doubts about its stratigraphic integrity. We report on our analysis of the stone artefacts and faunal and other materials recovered during the 1989 excavations, as well as the stratigraphy and depositional history recorded by the original excavators. We demonstrate that the technology and raw materials of the early assemblage are distinctive from those in the overlying layers. Silcrete and quartzite artefacts are common in the early assemblage, which also includes edge-ground axe fragments and ground haematite. The lower flaked stone assemblage is distinctive, comprising a mix of long convergent flakes, some radial flakes with faceted platforms, and many small thin silcrete flakes that we interpret as thinning flakes. Residue and use-wear analysis indicate occasional grinding of haematite and woodworking, as well as frequent abrading of platform edges on thinning flakes. We conclude that previous claims of extensive displacement of artefacts and post-depositional disturbance may have been overstated. The stone artefacts and stratigraphic details support previous claims for human occupation 50-60 ka and show that human occupation during this time differed from later periods. We discuss the implications of these new data for understanding the first human colonisation of Sahul.

  9. Northward extension of Carolina slate belt stratigraphy and structure, South-Central Virginia: Results from geologic mapping

    Hackley, P.C.; Peper, J.D.; Burton, W.C.; Horton, J.W.


    Geologic mapping in south-central Virginia demonstrates that the stratigraphy and structure of the Carolina slate belt extend northward across a steep thermal gradient into upper amphibolite-facies correlative gneiss and schist. The Neoproterozoic greenschist-facies Hyco, Aaron, and Virgilina Formations were traced northward from their type localities near Virgilina, Virginia, along a simple, upright, northeast-trending isoclinal syncline. This syncline is called the Dryburg syncline and is a northern extension of the more complex Virgilina synclinorium. Progressively higher-grade equivalents of the Hyco and Aaron Formations were mapped northward along the axial trace of the refolded and westwardly-overturned Dryburg syncline through the Keysville and Green Bay 7.5-minute quadrangles, and across the northern end of the Carolina slate belt as interpreted on previous geologic maps. Hyco rocks, including felsic metatuff, metawacke, and amphibolite, become gneisses upgrade with areas of local anatexis and the segregation of granitic melt into leucosomes with biotite selvages. Phyllite of the Aaron Formation becomes garnet-bearing mica schist. Aaron Formation rocks disconformably overlie the primarily felsic volcanic and volcaniclastic rocks of the Hyco Formation as evidenced by repeated truncation of internal contacts within the Hyco on both limbs of the Dryburg syncline at the Aaron-Hyco contact. East-northeast-trending isograds, defined successively by the first appearance of garnet, then kyanite ?? staurolite in sufficiently aluminous rocks, are superposed on the stratigraphic units and synclinal structure at moderate to high angles to strike. The textural distinction between gneisses and identifiable sedimentary structures occurs near the kyanite ?? staurolite-in isograd. Development of the steep thermal gradient and regional penetrative fabric is interpreted to result from emplacement of the Goochland terrane adjacent to the northern end of the slate belt during

  10. Revisiting the Ceara Rise, equatorial Atlantic Ocean: isotope stratigraphy of ODP Leg 154 from 0 to 5 Ma

    R. H. Wilkens


    Full Text Available Isotope stratigraphy has become the method of choice for investigating both past ocean temperatures and global ice volume. Lisiecki and Raymo (2005 published a stacked record of 57 globally distributed benthic δ18O records versus age (LR04 stack. In this study LR04 is compared to high-resolution records collected at all of the sites drilled during ODP Leg 154 on the Ceara Rise, in the western equatorial Atlantic Ocean. Newly developed software is used to check data splices of the Ceara Rise sites and better align out-of-splice data with in-splice data. Core images recovered from core table photos are depth and age scaled and greatly assist in the data analysis. The entire splices of ODP sites 925, 926, 927, 928 and 929 were reviewed. Most changes were minor although several were large enough to affect age models based on orbital tuning. A Ceara Rise composite record of benthic δ18O is out of sync with LR04 between 1.80 and 1.90 Ma, where LR04 exhibits two maxima but Ceara Rise data contain only one. The interval between 4.0 and 4.5 Ma in the Ceara Rise compilation is decidedly different from LR04, reflecting both the low amplitude of the signal over this interval and the limited amount of data available for the LR04 stack. A regional difference in benthic δ18O of 0.2 ‰ relative to LR04 was found. Independent tuning of Site 926 images and physical property data to the Laskar et al. (2004 orbital solution and integration of available benthic stable isotope data from the Ceara Rise provides a new regional reference section for the equatorial Atlantic covering the last 5 million years.

  11. Sites without stratigraphy: Devesa do Rei, a cultual site in Galician late Prehistory and the Iron Age?

    Aboal Fernández, Roberto


    Full Text Available In this text we explore a singular site that offers a series of important novelties, both in terms of its discontinuous pattern of use in different periods (covering a lengthy period from the Neolithic to the Iron Age, and its apparent use for ritual purposes in all of them, as well as the possible identification of a funerary structure from the Galician Iron Age. At the same time, this work is proposed as a case for study that makes it possible to define a procedure to reconstruct the sequence and function of open sites from Late Prehistory in Galicia characterized by a lack of vertical stratigraphy. This problem is solved by combining different analytical techniques, all based on a record of high quality excavation that makes use of analyses of material culture, radiocarbon dating, distribution patterns, as well as soil and sediment analysis.

    Se estudia en este texto un yacimiento singular que ofrece importantes novedades, tanto por su reocupación discontinua en épocas distintas (con una secuencia amplia que cubre desde el Neolítico a la Edad del Hierro, como por su aparente funcionalidad ritual en todas ellas, y la posible identificación de una estructura funeraria de la Edad del Hierro de Galicia. Al mismo tiempo, este trabajo se plantea como caso de estudio que permite definir un procedimiento para reconstituir la secuencia y función de yacimientos abiertos de la Prehistoria Reciente de Galicia caracterizados por no presentar estratigrafía vertical. Este problema se solventa con el entrecruzamiento de diferentes técnicas de análisis basadas todas ellas en un registro de excavación de calidad que se sirve de análisis de cultura material, radiocarbónicos, distributivos, sedimentológicos y edafológicos.

  12. Lunar Impact Basins: Stratigraphy, Sequence and Ages from Superposed Impact Crater Populations Measured from Lunar Orbiter Laser Altimeter (LOLA) Data

    Fassett, C. I.; Head, J. W.; Kadish, S. J.; Mazarico, E.; Neumann, G. A.; Smith, D. E.; Zuber, M. T.


    Impact basin formation is a fundamental process in the evolution of the Moon and records the history of impactors in the early solar system. In order to assess the stratigraphy, sequence, and ages of impact basins and the impactor population as a function of time, we have used topography from the Lunar Orbiter Laser Altimeter (LOLA) on the Lunar Reconnaissance Orbiter (LRO) to measure the superposed impact crater size-frequency distributions for 30 lunar basins (D = 300 km). These data generally support the widely used Wilhelms sequence of lunar basins, although we find significantly higher densities of superposed craters on many lunar basins than derived by Wilhelms (50% higher densities). Our data also provide new insight into the timing of the transition between distinct crater populations characteristic of ancient and young lunar terrains. The transition from a lunar impact flux dominated by Population 1 to Population 2 occurred before the mid-Nectarian. This is before the end of the period of rapid cratering, and potentially before the end of the hypothesized Late Heavy Bombardment. LOLA-derived crater densities also suggest that many Pre-Nectarian basins, such as South Pole-Aitken, have been cratered to saturation equilibrium. Finally, both crater counts and stratigraphic observations based on LOLA data are applicable to specific basin stratigraphic problems of interest; for example, using these data, we suggest that Serenitatis is older than Nectaris, and Humboldtianum is younger than Crisium. Sample return missions to specific basins can anchor these measurements to a Pre-Imbrian absolute chronology.

  13. Ordovician ocean plate stratigraphy and thrust duplexes of the Ballantrae Complex, SW Scotland: Implications for the pelagic deposition rate and forearc accretion in the closing Iapetus Ocean

    Fujisaki, Wataru; Asanuma, Hisashi; Suzuki, Kazue; Sawaki, Yusuke; Sakata, Shuhei; Hirata, Takafumi; Maruyama, Shigenori; Windley, Brian F.


    The Ballantrae Complex (at Bennane Lea in SW Scotland) contains important ocean plate stratigraphy (basalt, chert, mudstone, sandstone) in an accretionary prism that is associated with a classic Ordovician ophiolite. We used the ocean plate stratigraphy to sub-divide the prism into 11 tectonic units. To determine the depositional age of bedded cherts, zircons were separated from 9 tuff beds from 6 different units. All the tuffs have early to middle Ordovician ages, even though their present positions are mutually distant. These ages are consistent with microfossil records of radiolaria and graptolites. The stratigraphic-structural relationships demonstrate that the ocean plate stratigraphy has been repeated by bedding-parallel thrusts; this is typical of a modern accretionary duplex. We calculated the sedimentation rate of Early to Middle Ordovician bedded cherts at Bennane Lea on the basis of U-Pb zircon ages obtained from several tuff beds; the data indicate that the depositional rate (0.6-3 m/myr) was as slow as that of Mesozoic-Cenozoic equivalents defined by radiolaria. The age spectra of detrital zircons from Ballantrae sandstones show prominent single peaks at ca. 467 and 478 Ma, and a lack of Precambrian zircons. Integration of our new zircon ages with published isotopic data and palaeo-geographic maps indicates that the sandstones were deposited near an intra-oceanic arc and far from any continent containing Precambrian rocks. The pelagic-to-clastic sediments at Bennane Lea were deposited in the closing Iapetus Ocean from ca. 477 Ma to ca. 464 Ma, when they were accreted with the intra-oceanic arc of Ballantrae.

  14. Shallow sequence stratigraphy of the inner shelf deposits off the southeastern coast of Korea (Korea Strait)

    Yoo, Dong-Geun; Sunwoo, Don [Korea Institute of Geoscience and Mineral Resources, Taejeon(Korea)


    High-resolution seismic profiles on the inner shelf off the southeastern coast of Korea reveal that late Quaternary deposits consist of three sedimentary units (A upper, B middle and C lower) accumulated after the last glacial period. The upper unit (A) above the maximum flooding surface is the highstand systems tract formed during the recent highstand of sea level. The middle and lower units (B and C) represent the transgressive systems tract related to shoreface retreat during the post-glacial transgression. The middle unit (B) above the ravinement surface forms a thin veneer of transgressive sands, while lower unit (C) overlying the sequence boundary represents the transgressive estuarine deposits accumulated in the late stage of Holocene transgression. (author). 19 refs., 6 figs.

  15. A natural fiber composite in a pelagic limestone-chert sequence. The importance of mechanical stratigraphy for fracture type development in carbonate anticlines.

    Petracchini, Lorenzo; Antonellini, Marco; Scrocca, Davide; Billi, Andrea


    Thrust fault-related folds in carbonate rocks are characterized by deformation accommodated by different kinds of structures, such as joints, faults, pressure solution seams (PSSs), and deformation bands, which may form at various stages during the folding process. Defining the distribution, orientation, and the type of fold-related structures and understanding the relationships between folding and fracturing is significant both for theoretical and practical purposes. Furthermore, as the deformation related to the folding process influences fluid flow through rocks, identifying the types of structures formed during folding is as important as predicting their geometries. To unravel the relationship between mechanical stratigraphy and folding process, the well-exposed Cingoli anticline (Northern Apennines), has been studied in detail. The Upper Cretaceous-Middle Eocene stratigraphy of the Cingoli anticline is characterized by a pelagic multilayer made up of fine-grained pelagic limestones and, marly limestones, in places alternated with thin continuous chert layers. The presence of several outcrops located in different structural positions of the anticline makes the Cingoli anticline an excellent natural laboratory to investigate relationships between folding, fracturing, and mechanical stratigraphy relative to the structural setting of the fold. The field data collected show that high angle to bedding PSSs, which formed before tilting and during the first stage of folding, are not homogeneously distributed in the pelagic limestones. Generally, high angle to bedding PSSs form in the marly pelagic limestones and they have been observed in several outcrops and in different structural positions except where the marly limestones are inter-bedded with stiffer chert layers. In order to analyse theoretically what observed in the field, we compared the deformation of limestones and chert layers with the deformation acting on fiber composites. In the mechanics of materials

  16. The chrono-stratigraphie sequense of asturian castros: (8th century BC-2nd century AD

    Villa Valdés, Ángel


    Full Text Available A synthesis is presented of the current state of knowledge of castros in Western Asturias according to the archaeological evidence -stratigraphy, typological studies, and absolute dates-, supporting the hypothesis that pre-Roman fortified settlements existed in Asturias with long occupation sequence.

    Se ofrece una síntesis del estado de la cuestión en el área occidental de la provincia que avala con datos arqueológicos -estratigrafías, estudio de materiales y dataciones absolutas-, la existencia en Asturias de poblados fortificados con larga secuencia de ocupación prerromana.

  17. Depth and stratigraphy of Quaternary deposits. Preliminary site description Laxemar subarea - version 1.2

    Nyman, Helena [SWECO Position AB, Stockholm (Sweden)


    This report aims at describing the modelled Quaternary deposits (QD) depth according to six layers with different geological and hydrological properties in the Simpevarp regional model area. The program used in the modelling of QD depths is the GeoEditor, which is an ArcView3.3-extension. The input data used in the model consist of 102 boreholes and 328 observation points. As input is also a large number of observation points interpreted from geophysical investigations used; 1,087 points based on refraction seismic measurements (distributed in 31 profiles), 22 points from electrical soundings (VES) and 19,237 points from seismic and sediment echo sounding data. The outer part of the area has a low data density. Some of the used points are generally not very deep and do not describe the actual bedrock elevation. They do, however, describe the minimum QD depth at each location. A detailed topographical Digital Elevation Model (DEM), the maps of Quaternary deposits and outcrops were also used. The model is based on a three-layer-principle where each layer can be given similar properties. The uppermost layer, Z1, has been influenced by the impact from surface processes, e.g. roots and biological activity. The bottom layer, Z3, is characterized by contact with the bedrock and is corresponding to a till layer. The middle layer, Z2, is corresponding to a clay layer and assumed to have different hydraulic qualities than Z1 and Z3. Besides those layers, another three layers are also modelled; M1 corresponds to a peat layer, M2 answers to a glaciofluvial sediment layer and M3 corresponds to a layer with artificial fill. All layers can have thickness zero. The resulting model clearly shows the valleys with thicker depths of QD, surrounded by areas with thinner or no depths. The esker near Faarbo (Tunaaasen) is also distinctly marked in the south-western area. The northern and central part of the model area are characterized by numerous bedrock outcrops. The maximum depth of

  18. Base- level Chang and Sequence Stratigraphy of Lishu Fault Lacustrine Basin

    Wang Simin; Liu Zhaojun; Liu Kui


    Base - level is a kind of surface which controls sedimentation and erosion. So, it can be concluded that it is baselevel change that controls the formation and internal structure of a sequence. A single cycle of base- level change can generate four sets of different stacking patterns. They are two sets of aggradation, one progradation and one retrogradation, which affects the features of the internal structure of a sequence. Lishu fault subsidence of Songliao basin is a typical half - graben lacustrine basin. Comprehensive base - level change analysis indicates that six base - level cycles and their related six sequences can be recognized between T4 and T5 seismic reflection surface. The contemporaneous fault is the main controlling factor of the fault lacustrine basin. There are obvious differences exist in the composition of sedimentary systems and all systems tracts between its steep slope (the side that basin control fault existed) and flat slope. Except highstand systems tract is composed of fan delta - lacustrine system, lowstand systems tract, transgressive systems tract and regressive systems tract are all made up of fan delta - underwater fan- lacustrine sedimentary systems in the side of steep slope.

  19. Stratigraphy, depositional rates, and other DSDP Leg 96 conclusions: Mississippi fan

    Coleman, J.M.; Bouma, A.H.


    The Quaternary Mississippi fan consists of at least seven seismically mappable fan lobes. Eight sites were drilled into the youngest fan lobe during DSDP Leg 96. The Holocene (Ericson Zone Z) is capped by a marly foraminiferal ooze. Assuming an age of 12,000 yr for the Holocene/Pleistocene boundary, a minimum accumulation rate of 3-30 cm/1000 yr (1-12 in/1000 yr) is computed for the Holocene. The youngest fan lobe was deposited during the upper part of Ericson Zone Y (late Wisconsin glacial, 12,000-85,000 y.B.P.). Deposition rates for the Y Zone are extremely high for the middle fan sites, averaging 12 m/1000 yr (39 ft/1000 yr). Lower fan accumulation rates are 7 m/1000 yr (23 ft/1000 yr) for the channel sites and 6 m/1000 yr (20 ft/1000 yr) for the channel-mouth depositional lobes. These rates are not corrected for compaction. Foraminifera are scarce; the occurrence of shallow-water benthic species indicates a displaced inner and middle neritic origin for the sediments. Drilling on the youngest fan lobe shows that most of the silts and sands were transported through the upper and middle fan channel onto the lower fan, producing a 6 to 10-km (4 to 6-mi) wide, 135-m (443-ft) thick aggradational channel deposit. Much of the fine-grained sediment spilled out of the channel onto the adjacent overbank areas, constructing broad marginal plain. The channels on the lower fans are smaller and shift position frequently. Channel-mount depositional lobes are constructed at the end of the active channels and are composed of more than 50% net sand.

  20. Cenozoic stratigraphy on the north of Saigo bay, southern part of Oki-Dogo island, southwest Japan. Oki-Dogo, Saigo wan hoppo no shinseikai so jo

    Yamasaki, H. (Hiroshima Univ., Hiroshima (Japan). Faculty of Science)


    The Cenozoic strata, overlying the Oki Metamorphics, are widely distributed on the north of Saigo Bay, the Oki-Dogo Island, Southwest Japan. They are divided into the following seven stratigraphic units in ascending order: the Tokibariyama Formation, the Kori Formation, the Kumi Formation, the Oki Trachyte-Ryolite, the Togo Gravel Bed, the Saigo Basalt, and the Nijiyama Gravel Bed. The geology and the stratigraphy of the area reveal two horizons of basaltic rocks, i.e. the early Mioceno Togo Basalt Member within the Kori Formation and the Quaternary Saigo Basalt which has been thought to be the oldest alkaline volcanics, the Saigo Basalt Group.'' The stratigraphically defined two basaltic rocks also display different petrological and geochemical characteristics. Early Miocene basic volcanic activities, late early Miocene transgression, subsequent middle Miocene rapid subsidence, and late Miocene uplifts were the major geological events in the island during the Miocene Epoch. The Miocene stratigraphy and timing of the geological events such as transgression and subsidence suggests that the geological history of the Oki-Dogo Island is very much similar to that of the western margin of the Yamato Basin. 33 refs., 12 figs., 2 tabs.

  1. Geology and stratigraphy of the San Lorenzo Tezonco deep well and its correlation to surrounding ranges, Mexico Basin

    Arce, J. L.; Layer, P. W.; Morales-Casique, E.; Benowitz, J.


    The San Lorenzo Tezonco deep well stratigraphy records intense episodic volcanic activity in the Mexico Basin and surroundings during the past 20 Ma. The 2008-m deep lithological column is dominated by volcanic material, either as lava flows or pyroclastic deposits (97%), and only the upper most 70 m are composed of lacustrine deposits (3%). Based on geochronology and geochemistry, the lower part of the drill core is represented by rocks correlating to the Tepoztlán Formation (876-2008 m deep) that vary in composition from basaltic-andesite to rhyolite, and ages ranging from 13 to 21.2 Ma. On the surface this formation outcrops near the towns of Malinalco and Tepoztlán, ~43 km south of the deep well. Between depths of 581 and 875 m, volcanic rocks were recovered and are interpreted as lavas from the Sierra de las Cruces that vary in composition from andesite to dacite and range in age from 0.9 Ma to 5 Ma. Additionally, we documented rocks belonging to the Xochitepec Formation, outcropping around Xochimilco, in the Mexico City, with ages ranging from 1.2 and 1.7 Ma, in contrast with the Oligocene age proposed in previous works for these rocks. These new ages plus the chemical composition data, allow us to correlate the Xochitepec rocks with Sierra de las Cruces. Upward in the drill core (510-580 m) there are andesitic rocks that correlate with the 0.25 Ma Cerro de la Estrella volcanic center. The last volcanic package found in the well is correlated to the Santa Catarina basaltic andesites (70-120 m) that are younger than 0.25 Ma, and probably Holocene. Lacustrine deposits crown the stratigraphic column of the drill core with ages probably younger than 34 ka. The San Lorenzo Tezonco well is in a graben-like structure that was filled with more than 1900 m of volcanic products, suggesting that volcanism were intense in the Miocene to the Recent, and the south drainage of the Mexico Basin was closed probably in the early Pleistocene.

  2. Preliminary Physical Stratigraphy and Geophysical Data of the USGS Hope Plantation Core (BE-110), Bertie County, North Carolina

    Weems, Robert E.; Seefelt, Ellen L.; Wrege, Beth M.; Self-Trail, Jean M.; Prowell, David C.; Durand, Colleen; Cobbs, Eugene F.; McKinney, Kevin C.


    physical stratigraphy, facies, thickness, and hydrogeology of the Tertiary and Cretaceous Coastal Plain sediments of North Carolina.

  3. Miocene Bahean stratigraphy in the Longzhong Basin,northern central China and its implications in environmental change

    LI; Jijun; ZHANG; Jun; SONG; Chunhui; ZHAO; Zhijun; ZHANG; Yong; WANG; Xiuxi; ZHANG; Jianming; CUI; Qiaoyu


    Fossil mammal-riched Neogene strata are widely distributed in the southeast corner of the huge Longzhong Basin at Tianshui,Gansu Province,northern central China.Hipparion weihoense,a typical member of late Middle Miocene Bahean stage,was recently excavated at Yaodian along a well-exposed outcrop.Owing to the importance of the Bahean stage in the mammalian evolution and its potential for environmental change,we suggested a name of Yaodian Formation for the stratigraphy,which is correlated to the Bahe Formation at Lantian,Shaanxi.High resolution paleomagnetic dating of the section shows that the Yaodian Formation covers the period between 11.67 Ma and 7.43 Ma,with the site bearing Hipparion weihoense being estimated at about 10.54-10.30 Ma,providing first magnetostratigraphic chronology for the Bahean Stage.The Yaodian Formation consists of fluvial channel deposits (11.67-10.40 Ma) at the bottom,floodplain deposits in the middle (10.40-9.23 Ma) and shallow lake sediments at the top (9.23-7.43 Ma).This upward fining sequence suggests that the relief in nearby mountain ranges such as West Qinling to the south and Huajia Ling to the north was greatly reduced after long-term denudation,fluvial transport capacity was low,and finally the drainage system was disintegrated,replaced with broad-shallow lakes in which only fine sediments like mud and marlite were deposited,indicating an old stage of development of a planation surface.A remarkable shift in ecology and climatic environment was found at 7.4-7.7 Ma when paleoclimate changed from early warm humid to late dry as indicated by sedimentary facies changed from early shallow lake sequence to late eolian red clays and a former coniferous-deciduous mixed forest was replaced by grassland,leading to great growth of Hipparion Fauna of Baodean stage in the region.Therefore,it is estimated that the present high relief of Qinling and drainage pattern did not come into being until Late Pliocene in response to intensive

  4. Evidence For Regional-scale Alteration Fronts On Mars: Extent, Stratigraphy, And Mineralogy Of Phyllosilicates Around Mawrth Vallis.

    Noe Dobrea, Eldar Z.; Bishop, J. L.; McKeown, N. K.; Fu, R.; Rossi, C.; Swayze, G.; Michalski, J. R.; Poulet, F.; Bibring, J.; Mustard, J. F.; Mustard, J. F.; Arvidson, R.; Morris, R. V.; Murchie, S.; Murchie, S.; Malaret, E.; Hash, C.; CRISM Team


    The largest exposure of phyllosilicates on Mars occurs on the highland plains around Mawrth Vallis. This exposure is known to extend almost continuously for about 300 km southward from the edge of the dichotomy boundary, covering an area greater than 200 x 300 km over an elevation range of 2000 m ([1],[2],[3],[4]). At least three different types of hydrated phyllosilicates (Fe/Mg- and Al-phyllosilicates), as well as examples of hydrated silica (e.g., opal-A, hydrated glass), have been identified in OMEGA and CRISM data[1]. These hydrated units are generally associated with layered, indurated light-toned outcrops with complex spatial and stratigraphic relationships, and are unconformably overlain by a darker, indurated, more heavily cratered unit[3]. Recent studies of the light-toned layered units show a mineralogical stratigraphy: the Fe/Mg phyllosilicate-bearing units are overlaying by the Al-phyllosilicate-bearing units, which are in turn overlain by a dark-toned, spectrally unremarkable capping unit ([4],[5],[6]). We have used CRISM, CTX, and HiRISE data to perform a regional study of the distribution of phyllosilicates in the Arabia Terra region, and have found that the same assemblages of hydrous minerals and stratigraphic relationships observed around Mawrth Vallis occur in many erosional windows throughout a 1000x1000 km region, regardless of elevation. The distribution and observed mineralogical relationships suggests that these secondary minerals were not deposited in a basin, but may rather be the product of alteration of primary minerals to Fe/Mg phyllosilicates with subsequent near-surface leaching to Al-bearing phyllosilicates and hydrated silica phases in hydrothermal, pedogenic, or diagenetic settings. [1] Poulet et al. (2005) Nature 438, 632-627 [2] Noe Dobrea and Michalski (2006) AGU Fall 2006, #P23D-0091 [3] Michalski and Noe Dobrea(2007) Geology,35, pp. 951-954 [4] Loizeau D. et al. (2007) JGR, 112 (E8) [5] Bishop et al. (2008) Science , in press

  5. Stratigraphy, sedimentology, and geothermal reservoir potential of the volcaniclastic Cura-Mallín succession at Lonquimay, Chile

    Pedroza, Viviana; Le Roux, Jacobus P.; Gutiérrez, Néstor M.; Vicencio, Vladimir E.


    The Tolhuaca Volcano near Lonquimay in south-central Chile has been the subject of several studies due to its geothermal manifestations, but little is known about the stratigraphy and reservoir potential of the Cura-Mallín Formation forming its basement. Field work and U-Pb dating of detrital zircons allow us to redefine this succession as the Cura-Mallín Group, consisting of the volcano-sedimentary Guapitrío Formation, sedimentary Río Pedregoso Formation, and volcano-sedimentary Mitrauquén Formation. The Río Pedregoso Formation can be subdivided into three formal units, namely the Quilmahue Member, Rucañanco Member, and Bío-Bío Member. The base of the Quilmahue Member interfingers laterally with the base of the Guapitrío Formation, for which a previous K/Ar date of 22.0 ± 0.9 Ma was apparently discarded by the original authors. However, this date is consistent with the stratigraphic position of the Quilmahue Member and new zircon dates from the overlying units, also coinciding with the initiation of an extensional phase in the Bíobío-Aluminé Basin. Deposition of the Quilmahue Member continued throughout the early Miocene, as confirmed by dates of 17.5 Ma reported by previous authors and 16.5 Ma obtained in this study. The Rucañanco Member was deposited during the Serravalian around 12.6 Ma, whereas the Bío-Bío Member was dated at the Serravalian-Tortonian limit (11.6 Ma). Although all three members were deposited in a fluvio-lacustrine environment, they were dominated respectively by flood plains with crevasse splays, lake margins with distributary mouth bars and Gilbert-type deltas, and distal braided and meandering rivers. Whereas the Quilmahue Member was deposited during basin extension, the Rucañanco Member was formed during a period of basin inversion and compression. Temporary tectonic quiescence during deposition of the Bío-Bío Member allowed denudation of the landscape, but around 9.5 Ma tectonism was renewed again during deposition of

  6. Character of Terrestrial Sequence Stratigraphy and Depositional System in Incised Valley, Outcrop Area of Karamay Oilfield, Junggar Basin, China

    Jiao Yangquan; Yan Jiaxin; Li Sitian; Yang Ruiqi; Lang Fengjiang; Yang Shengke


    In the Karamay oilfield located on the northwestern margin of Junggar basin, Xinjiang, China, a large area of the Karamay Formation is exposed at outcrop in the northeast of the oilfield, a consequence of thrusting. The Middle Triassic Karamay Formation in the outcrop area is a type of terrestrial third-order sequence, bounded by two easily recognizable sequence boundaries: a regional surface of angular unconformity (SB1) at the base and a regional unconformity (SB2) at the top. Within the Karamay Formation, two lacustrine expansion events can be recognized and be used to identify both the initial and the maximum lacustrine flooding surfaces. The two lacustrine flooding surfaces serve as references for the classification of this third-order sequence-Karamay Formation into the following three sedimentary successions: a lower lowstand systems tract (LST), a middle lacustrine-expanding systems tract (EST), and an upper highstand systems tract (HST). Different systems tracts are composed of different depositional system assemblages. In this paper, each depositional system is described in detail. The lowstand systems tract in the study area is characterized by incised valleys. At the base and on the margin of the incised valleys occur alluvial fan depositional systems, and in the upper and distal parts of the alluvial fan, low-sinuosity river depositional systems. The lacustrine-expanding systems tract consists of a lacustrine depositional system and a lacustrine delta depositional system, overlying the lower incised valley fills. The highstand systems tract is filled by a widespread lacustrine braided delta depositional system. The analysis of sequence stratigraphy in this paper serves the description of the spatial distribution of the reservoir. The depositional system analysis serves the description of the reservoir types. Field investigations of oil sandstone and oil seepage show that the Karamay Formation is composed of several types of reservoirs. However, two

  7. Glacial sequence stratigraphy reveal the Weichselian glacial history of the SE sector of the Eurasian Ice Sheet

    Räsänen, Matti


    Reconstructions of the last Weichselian glacial cycle 117,000-11,700 years (kyr) ago propose that S Finland, adjacent Russia and the Baltic countries in the SE sector of the Eurasian Ice Sheet (EIS), were glaciated during the Middle Weichselian time [marine isotope stage (MIS) 4, 71-57 kyr ago] and that this glaciation was preceded in S Finland by an Early Weichselian interstadial (MIS 5c, 105-93 kyr ago) with pine forest. Here glacial sequence stratigraphy (Powell and Cooper 2002) is applied to isolated Late Pleistocene onshore outcrop sections in S Finland. The analysed sedimentary records have traditionally been investigated, interpreted and published separately by different authors without an attempt to a methodologically more systematic survey. By putting new field data and old observations into a regional sequence stratigraphic framework it is shown how previously unnoticed regularities can be found in the lithofacies and fossil successions. It is shown that the proposed Middle Weichselian glaciation or the pine dominated interstadial did not take place at all (Räsänen et al. 2015). The one Late Weichselian glaciation (MIS 2, 29-11 kyr ago) at the SE sector of EIS was preceded in S Finland by a nearly 90 kyr long still poorly known non-glacial period, featuring tundra with permafrost and probably birch forest. The new Middle Weichselian paleoenvironmental scenario revises the configuration and hydrology of the S part of EIS and gives new setting for the evolution of Scandinavian biota. References Powell, R. D., and Cooper, J. M., 2002, A glacial sequence stratigraphic model for temperate, glaciated continental shelves, in Dowdeswell, J. A., and Cofaig, C. Ó. eds., Glacier-Influenced Sedimentation on High-Latitude Continental Margins: The Geological Society of London, London, Geological Society London, Special Publication v. 203, p. 215-244. Räsänen, M.E., Huitti, J.V., Bhattarai, S. Harvey, J. and Huttunen, S. 2015, The SE sector of the Middle

  8. Final Pleistocene and Early Holocene at Sitio do Meio, Piauí, Brazil: Stratigraphy and comparison with Pedra Furada

    Giulia Aimola


    Full Text Available English: Sitio do Meio, in southern Piaui, Brazil, is the second rock shelter presenting fully Pleistocene dates and artefacts after Pedra Furada.  Despite the anthropogenic origin of Pedra Furada artefacts has been questioned, SDM has better chances to be accepted by the scientific community because of the absence of the most relevant stone breaking agents in this kind of site, i.e. waterfalls. This paper presents a critical revision of the history of excavations (1980-2000, stratigraphy, chronology, and the archaeological content of the site (sector 2. At least 98 stone tools have been identified and described, all of them being older than 12,500 BP, i.e. belonging to the Upper Pleistocenic phase of Pedra Furada 3, as defined in the close reference site. The lithic industry of Serra Talhada phase (lower Holocene is also presented and compared with paleoindian sites of North-Eastern and Central Brazil.French:Le Sitio do meio, dans le  Piaui méridional (Brésil est le deuxième abri sous roche de la région ayant livré des dates pléistocènes en dehors du site de la Pedra Furada. L'article présente une révision critique des fouilles (1980-2000, la chronostratigraphie et le contenu archéologique du secteur 2. Une centaine d'outils lithiques sont décrits, ils sont plus anciens de 12,5 ka BP  et correspondent à la phase Pléistocène Pedra Furada 3 définie dans le site éponyme de référence. On présente aussi l' industrie lithique de la phase Serra Talhada (Holocène  ancien en la comparant aux industries paléoindiennes du Nord-Est et du centre du Brésil.

  9. Paleoenvironmental conditions and strontium isotope stratigraphy in the Paleogene Gafsa Basin (Tunisia) deduced from geochemical analyses of phosphatic fossils

    Kocsis, László; Ounis, Anouar; Chaabani, Fredj; Salah, Neili Mohamed


    Fossil shark teeth and coprolites from three major phosphorite occurrences in the Gafsa Basin (southwestern Tunisia) were investigated for their geochemical compositions to improve local stratigraphy and to better assess paleoenvironmental conditions. 87Sr/86Sr isotope ratios of shark teeth from the Early Maastrichtian El Haria Formation and from the Early Eocene Métlaoui s.s. Formation yielded Sr isotope ages of 68 ± 1 and 47.9 ± 1.3 Ma, respectively, which accord with the expected stratigraphic positions of these sediments. Conversely, shark teeth from the Paleocene-Eocene Chouabine Formation have large variation in Sr isotope ratios even within individual layers. After statistical treatment and then elimination of certain outlier samples, three age-models are proposed and discussed. The most reasonable solution includes three subsequent Sr ages of 61.8 ± 2.2 Ma, 57.2 ± 1.8 and 54.6 ± 1.6 for layer IX, layers VIII-V and layers IV-0, respectively. Three scenarios are discussed for explanation of the presence of the outliers: (1) diagenesis, (2) re-working and (3) locally controlled seawater Sr isotope ratio. The most plausible account for the higher 87Sr/86Sr ratios relative to the global ocean in some fossils is enhanced intrabasinal re-working due to low sea level. Conversely, the sample with lower 87Sr/86Sr than the global seawater may link to diagenesis or to seawater influenced by weathering of Late Cretaceous marine carbonates, which latter is supported by model calculation as well. The ɛNd values of these fossils are very similar to those reported for Paleogene and Late Cretaceous Tethyan seawater and are compatible with the above interpretations. The relatively low oxygen isotope values in shark teeth from the topmost phosphate bed of the Chouabine Formation, together with the Sr isotope results, point toward recovering better connections with the open sea. These δ18O data reflect elevated ambient temperature, which may link to the Early Eocene

  10. Sedimentology and High Resolution Sequence Stratigraphy of the Middle Jurassic Dhruma Formation Carbonates Outcrops in the Central Saudi Arabia

    Yousif, Ibrahim; Abdullatif, Osman; Makkawi, Mohammed; Abdulghani, Waleed


    This study investigates the microfacies and sequence stratigraphic frame work of the Middle Jurassic Dhruma Formation in outcrops in central Saudi Arabia. The study contributes to the efforts to understand and enhance local and regional stratigraphic relationship and correlation of the Jurassic carbonate sequences and their significance to reservoir description and prediction in the subsurcae. The study describes and characterizes the sedimentology, microfacies and the stratigraphy of Dhruma Formation from outcrop sections having a total thickness of 70 m. Detailed microfacies and high-resolution stratigraphical analysis were carried out to determine microfacies, cyclicity, sequences and staking pattern. The study revealed ten lithofacies namely: oolitic grainstone,bioclastic oolitic grainstone, oolitic grapestone, bioclastic grainstone,foraminiferal packstone, echinoderm packstone, peloidal packstone to grainstone,skeletal wackestone to packstone, mudstone, and marlstone.These lithofacies were grouped into five lithofacies associations that deposited on a carbonate ramp setting. The depositional environment ranging from low energy lagoonal setting to high-energy shoals and banks to low energy outer ramp setting. Five high-resolution composite sequences have been defined and each sequence is composed at the bottom of intercalated mudstone/wackestone that passing up into grainstone lithofacies.The composite sequences range in thickness from 7 to 15 m, while the parasequences range from 0.5 to 1.5 m. The composite sequences extend laterally for a distance of more than 350 m. The overall composite section shows a shallowing upward succession of the 4th to the 5th order high-resolution sequences.The dominant lithofacies are the grainy ones, which constitute 30%, 50% and 80% of the studied sections. Furthermore, the parasequences thickness and their bio-components are increasing towards the top. The muddy lithofacies intensively affected the vertical continuity of the

  11. Late Quaternary Incisions and Related Shallow Subsurface Stratigraphy on the New Jersey Mid-Outer Shelf: Preliminary Results from Ultra-High Resolution Chirp Sonar Images - Part II

    Fulthorpe, C. S.; Goff, J. A.; Austin, J. A.; Gulick, S. P.; Nordfjord, S.


    High-resolution (1-15 kHz), shallow-penetration (~50 m), deep-towed chirp seismic profiles were collected on the New Jersey mid- and outer-shelf in August-September 2001 (R/V Endeavor cruise 359) in support of ONR's Geoclutter program. Geoclutter goals are to understand and predict acoustic scattering from the seafloor and the shallow sub-seafloor in order to distinguish man-made objects from naturally occurring features ("geological clutter") on sonar returns. The 2001 chirp survey focused on previously identified buried channels, of presumed fluvial origin, which may contribute to geoclutter. These channels are inferred to have formed during the sea-level lowstand of the last glacial maximum, and their fill likely constitutes a high-resolution record of the latest transgression. This survey represents the most comprehensive mapping to date of shallowly buried fluvial channels in a continental shelf setting. To allow robust mapping of channel systems, the survey maintained dense seismic profile spacings, mainly 200-900 m, but with some at 50 m. We focus on the southern portion of the survey area, where three channel systems are identified within an 8.6 x 10.2 km grid. The northernmost of these lies sufficiently within the survey area to be mapped in detail. Its channels are mainly V-shaped, up to 350 m wide and 12 m deep. Present water depth is ~80 m and channel flanks are truncated by the seafloor, except in a small area where an overlying unconformity truncating channel flanks is preserved. Some channels are truncated by erosional seafloor scour pits, mapped earlier with high-resolution multibeam data. Channel fill stratigraphy indicates multiple stages of incision and filling. Interfluves comprise up to ~20 m of a seismically transparent facies overlying stratified sediment. Grab samples contain medium-to-coarse sands, but such surficial sediments may not be entirely representative of the transparent facies. The contact with the stratified sediment is irregular

  12. Variable scale channel avulsion history using fan architecture and stratigraphy, and sediment provenance of Sutlej-Yamuna fans in northwest Gangetic plains during Late Quaternary

    Singh, Ajit; Gupta, Sanjeev; Sinha, Rajiv; Densmore, Alexander; Buylaert, Jan-Pieter; Carter, Andrew; Van-Dijk, Wout M.; Joshi, Suneel; Nayak, Nibedita; Mason, Philippa J.; Kumar, Dewashish; Mondal, Setbandhu; Murray, Andrew; Rai, Shiv P.; Shekhar, Shashank


    Channel avulsion during fan development controls distribution and deposition of channel sandbodies and hence alluvial architecture of a fan system. Variable scale spatio-temporal information of fluvial responses to past climate changes is stored in these channel sandbodies. Further these channel sandbodies form fluvial aquifers in alluvial fans and therefore understanding of alluvial architecture and stratigraphy of a fan is crucial for development of groundwater management strategies. In this study we used multiple approaches to map subsurface fluvial aquifer architecture and alluvial stratigraphy, and to estimate sediment provenance using U-Pb dating of detrital zircon grains of Sutlej-Yamuna fan system in northwest India. Satellite imagery based geomorphic mapping shows two large fan system with interfan area. The fan surfaces show presence of major and minor paleochannels. 2D resistivity tomography along several transects across fan surfaces shows distinct layers with contrasting resistivity values. These geo-electric facies corresponds to presence of channel sandbodies beneath surface signature of paleochannels and finer floodplain deposits useful to demarcate lateral extent of subsurface channel sandbodies. A more detailed subsurface stratigraphy using ~50m deep sediment cores and their luminescence ages from across fan surface shows presence of multi-storey sandbodies (MSB) separated by floodplain fines. Within the MSB, individual channel deposits are identified by presence of channel scour surfaces located at coarse sand overlying fine sand layer. Depositional ages of MSB's ranges from ~81 ka (late MIS5) to ~15 ka (MIS2) with major depositional break during MIS3 in parts of the fans. Sediment aggradation rate varies laterally across fan surface as well as vertically down the depth with an average rate of 0.54 mm/year. Fluvial channel persistence for studied time interval (about last 81 ka BP) shows major depositional breaks (and possible incision) at ~41 ka



    <正>20082513 Chen Guocheng(State Key Labo- ratory of Marine Geology,Tongji University, Shanghai 200092,China);Zheng Hongbo Sedimentary Records of Volcanic Activities in the South China Sea over the Past 480 ka (Marine Geology & Quaternary Geology, ISSN0256—1492,CN37—1117/P,27(4), 2007,p.69—76,4 illus.,1 table,25 refs., with English abstract) Key words:sedimentary sequence,South China Sea



    20151823 Cai Xiyao(Petroleum Exploration and Production Research Institute,SINOPEC,Beijing100083,China);Dou Liwei Classification and Correlation of Cambrian in Eastern Tarim Basin(Petroleum Geology&Experiment;,ISSN1001-6112,CN32-1151/TE,36(5),2014,p.539-545,3illus.,1table,



    <正>20041544 Chen Xiaohong (Faculty of Earth Sciences, China University of Geosciences, Wuhan, Hubei); Wang Xiaofeng Elaborate Biostratigraphic Subdivision and Correlation of the Basal Da wan Stage (Middle Ordovi-cian) in Yangtze Platform, China (Acta Palaeontologica Sinica, ISSN 0001 - 6616, CN32-1188/Q, 42(3), 2003, p. 317-327, 4 illus. , 1 plate, 1 table, 34 refs. )



    20160442Bai Jianke(Xi’an Center of China Geological Survey,Xi’an 710054,China);Chen Junlu The Timing of Opening and Closure of the Mayile Oceanic Basin:Evidence from the Angular Unconformity between the Middle De-



    <正>20081118 Bai Long(Guizhou Academy of Geology Surveying,Guiyang 550005,Guizhou,China);Shi Yuanhua Discovery of Permian Strata and Its Significance in the Mayidang Area,Yiwu County,Xinjiang(Guizhou Geology,ISSN1000-5943,CN52-1059/P,24(2),2007,p.134-137,141,3 illus.,9 refs.)Key words:Upper Permian,XinjiangIn the survey of regional geology and minera



    <正>20131708 Cai Xiyao(Research Institute of Exploration&Production,SINOPEC,Beijing100083,China);Jin Xianmei The Stratigraphic Classification and Correlation of Jurassic in Caohu Depression,Tarim Basin(Xinjiang Geology,ISSN1000-8845,CN65-1092/P,30(3),2012,p.287-291,2illus.,1table,10refs.)



    <正>20112482 Bai Ping (Guizhou Academy of Geologic Survey,Guiyang 550005,China); Xiao Jiafei Sediment and Stratum Succession Characteristic of the Last Stage of Late Triassic and Middle Jurassic in Northwest Gui



    <正>20091797 Cao Shenghua(Faculty of Earth Science,China University of Geosciences,Wuhan 430074,China);Xiao Xiaolin Renew-Establishment of the Jurassic Mugagangri Groups and Its Geological Significance on the Western Side of the Bangong Co-Nujiang Junction Zone(Acta Sedimentologica Sinica,ISSN1000-0550,CN62-1038/P,26(4),2008,p.559-564,4 illus.,1 table,7 refs.)Key words:Jurassic,Qinghai-Tibetan PlateauMugagangri Groups is a suite of flysch-flyschoid elastic deposits,and is Early-Middle Jurassic abyssal sedimentary,which is widespread in the western side of the Bangong



    <正>20132580 Cai Xiyao(Research Institute of Petroleum Exploration and Development,SINOPEC,Beijing 100083,China);Wei Ling Stratigraphic Classification and Correlation of Triassic in Shuntuoguole Area,Tarim Basin(Xinjiang Petroleum Geology,ISSN1001-3873,CN65-1107/TE,33(3),2012,p.327-330,1illus.,1table,7refs.)Key words:Triassic,stratigraphic



    <正>20140358Cao Jie(Oil&Gas Survey,China Geological Survey,Beijing 100029,China);Zhang Yongsheng Further Study of Transgression in Eastern Heilongjiang Basins in the Early Cretaceous:A Case Study of JD7 Well in Jixi Basin(Acta Geoscientica Sinica,ISSN1006-3021,CN11-3474/P,34(1),2013,p.103-110,3illus.,20refs.)Key words:Lower Cretaceous,transgression,Heilongjiang Province



    <正>20111878 Cao Jie(Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China);Zhang Yongsheng Mineralogical Evidences and Significance of Transgression Event in the Cretaceous Basins of Eastern Heilongjiang Province,China(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,29(7),2010,p.1024-1030,8 illus.,2 tables,18 refs.)Key words:Lower Cretaceous,transgression,Heilongjiang ProvinceThe evidences of marine fossils show that multiple different scales of transgression events have occurred in the Cretaceous basins of eastern Heilongjiang Pro



    <正>20042202 Chen Gang (Department of Geology, Northwest University, Xi’an, Shaanxi); Zhao Zhongyuan Natural of Pre-Mesozoic Tectono-Lithostratigraphic Units of North -Huaiyang Belt and Implication for Tectonic Evolution (Journal of Northwest University (Natural Science Edition), ISSN 1000-274X, CN61-1072/N, 33(5), 2003, p. 595 -598, 1 table, 14 refs. )



    <正>20080430 An Zhisheng(Institute of Earth Environment,Chinese Academy of Sciences,Xi’an 710075);Zhang Peizhen Changes of the Monsoon-Arid Environment in China and Growth of the Tibetan Plateau since Miocene(Quaternary Sciences,ISSN1001-7410,CN11-2708/P,26(5),2006,p.678-693,6 illus.,1 table,158 refs.)



    20161152Bai Jianke(Xi’an Center of China Geological Survey,Xi’an 710054,China);Li Zhipei Tectonic Environment of Western Tianshan during the Early Carboniferous:Sedimentary and Stratigraphical Evidence from the Bottom of the Dahalajunshan Formation(Acta Sedimentologica Sinica,ISSN1000-0550,



    20150369Cai Xiongfei(State Key Laboratory of Biological and Environmental Geology,Faculty of Earth Sciences,China University of Geosciences,Wuhan 430074,China);He Wenjian New Advances in the Study of the Cambrian in Helan Mountains(Resources Survey&Environment;,ISSN1671-4814,CN32-1640/N,35(1),2014,p.12-18,2illus.,4tables,25refs.)Key words:Cambrian,Helan Mountains The Early Cambrian Suyukou Formation of the Helan Mountain is formed of the alluvial fan deposit including mixed sands and gravels with unequigranular texture,the Wudao-



    <正>20040593 A Chengye (Qinghao Institute of Geological Survey, Xinjing, Qinghai); Wang Yizhi Disintegration of the Wanbaogou Group and Discovery of Early Cambrian Strata in the Eastern Kunlun Area, Xinjiang, China (Geology in China, ISSN 1000 -3657, CN11-1167/P, 30(2), 2003, p. 199 - 206, 6 illus. , 2 tables, 15 refs. , with English abstract)



    <正>20091185 Duan Jianxiang(Institute of Geologic Survey of Jilin Province,Changchun 130061,China);Liu Jingbo Characteristics of Yaojia Formation Petrostratigraphy and Sedimentary Environment in the Songnen Basin in the Fuyu,Yushu Areas(Jilin Geology, ISSN1001-2427,CN22-1099/P,27



    <正>20101833 Cao Ke (State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Beijing 100083,China);Wang Meng Constraints of Sedimentary Records on Cretaceous Paleoclimate Simulation in China Mainland (Earth Science Frontiers,ISSN1005-2321,CN11-3370/P,16(5),2009,p.29-36,3 illus.,1 table,41 refs.)



    <正>20072731 Dong Yecai(School of Earth Sciences and Mapping Engineering,East China Institute of Technology,Fuzhou 344000,Jiangxi);Wu Jianhua New Understanding and Signification on Lithostratigraphic Classification in Sanbaishan Basin,South Jiangxi Province(Jiangsu Geology,ISSN1003-6474,CN32-1258/P,30(4),2006,p.254-260,5 illus.,2 tables,10 refs.)Key words:lithostratigraphy,stratigraphic classification,Jiangxi Province



    <正>20071228 Bao Zhidong(China University of Petroleum,Beijing 102200);Jin Zhijun Sea -Level Fluctuation of the Tarim Area in the Early Paleozoic Respondence from Geochem- istry and Karst(Acta Geologica Sinica,ISSN 0001-5717,CN11-1951/P,80(3),2006, p.366-373,5 illus.,1 table,15 refs.,with English abstract) Key words:Lower Palaeozoic,sea-level changes,Tarim Basin



    <正>20140985Chen Liang(Post-Doctoral Research Station of Mining Engineering,School of Nuclear Resources and Nuclear Fuel Engineering,University of South China,Heng-yang 421001,China);Huang Wei Composition of Major and Correlated Elements with Organic Matters and Paleoclimatic Implication for Lower Paleogene Sediments in Sanshui Basin



    <正>20110406 Bai Xianzhou(College of Applied Nuclear Technology and Automation Engineering,Chengdu University of Technology,Chengdu 610059,China);He Mingyou On the Geochemical Characteristics,Provenance and Paleoweathering(Geoscience,ISSN1000-8527,CN11-2035/P,24(1),2010,p.151-157,5 illus.,3 tables,22 refs.)Key words:Triassic,Sichuan Province Through a comprehensive study on the major elements,trace elements and rar

  15. Carbon isotope stratigraphy of an ancient (Ordovician) Bahamian-type carbonate platform: Implications for preservation of global seawater trends

    Saltzman, M.; Leslie, S. A.; Edwards, C. T.; Diamond, C. W.; Trigg, C. R.; Sedlacek, A. R.


    Carbon isotope stratigraphy has a unique role in the interpretation of Earth history as one of the few geochemical proxies that have been widely applied throughout the geologic time scale, from the Precambrian to the Recent, as both a global correlation tool and proxy for the carbon cycle. However, in addition to consideration of the role of diagenesis, numerous studies have raised awareness of the fact that C-isotope trends derived from ancient carbonate platforms may not be representative of dissolved inorganic carbon from a well-mixed global ocean reservoir. Furthermore, the larger carbon isotopic fractionation in the formation of aragonite versus calcite from seawater must be taken into account. All three of these variables (diagenesis, water mass residence time, % aragonite) may change in response to sea level, producing trends in C-isotopes on ancient carbonate platforms that are unrelated to the global carbon cycle. Global carbon cycle fluxes may also have a cause-effect relationship with sea level changes, further complicating interpretations of stratigraphic trends in carbon isotopes from ancient platform environments. Studies of C-isotopes in modern carbonate platform settings such as the Great Bahama Bank (GBB) provide important analogues in addressing whether or not ancient platforms are likely to preserve a record of carbon cycling in the global ocean. Swart et al. (2009) found that waters of the GBB had generally the same or elevated values (ranging from +0.5‰ to +2.5‰) compared to the global oceans, interpreted as reflecting differential photosynthetic fractionation and precipitation of calcium carbonate (which lowers pH and converts bicarbonate into 12-C enriched carbon dioxide, leaving residual bicarbonate heavier). Carbonate sediments of the GBB have elevated C-isotopes, not only because of the high C-isotope composition of the overlying waters, but also due to the greater fractionation associated with precipitation of aragonite versus calcite

  16. After a century-Revised Paleogene coal stratigraphy, correlation, and deposition, Powder River Basin, Wyoming and Montana

    Flores, Romeo M.; Spear, Brianne D.; Kinney, Scott A.; Purchase, Peter A.; Gallagher, Craig M.


    The stratigraphy, correlation, mapping, and depositional history of coal-bearing strata in the Paleogene Fort Union and Wasatch Formations in the Powder River Basin were mainly based on measurement and description of outcrops during the early 20th century. Subsequently, the quality and quantity of data improved with (1) exploration and development of oil, gas, and coal during the middle 20th century and (2) the onset of coalbed methane (CBM) development during the late 20th and early 21st centuries that resulted in the drilling of more than 26,000 closely spaced wells with accompanying geophysical logs. The closeness of the data control points, which average 0.5 mi (805 m) apart, made for better accuracy in the subsurface delineation and correlation of coal beds that greatly facilitated the construction of regional stratigraphic cross sections and the assessment of resources. The drillhole data show that coal beds previously mapped as merged coal zones, such as the Wyodak coal zone in the Wyoming part of the Powder River Basin, gradually thinned into several discontinuous beds and sequentially split into as many as 7 hierarchical orders westward and northward. The thinning and splitting of coal beds in these directions were accompanied by as much as a ten-fold increase in the thicknesses of sandstone-dominated intervals within the Wyodak coal zone. This probably resulted from thrust loading by the eastern front of the Bighorn uplift accompanied by vertical displacement along lineaments that caused subsidence of the western axial part of the Powder River Basin during Laramide deformation in Late Cretaceous and early Tertiary time. Accommodation space was thereby created for synsedimentary alluvial infilling that controlled thickening, thinning, splitting, pinching out, and areal distribution of coal beds. Equally important was differential subsidence between this main accommodation space and adjoining areas, which influenced the overlapping, for example, of the

  17. From Cycles to Sequences: Sequence Stratigraphy and Relative Sea Level Change for the Late Cambrian of the North China Platform

    MEI Mingxiang; MA Yongsheng; DENG Jun; CHEN Huijun


    -order sequences is marked by "shallow ramp-tidal flat"; the sequence boundaries are characterized by exposure punctuated surfaces. According to the changes for the third-order sequences from the north to the south, a regular sequencestratigraphic framework can be established. From cycles to sequences, the study of sequence stratigraphy from litho-facies successions to sedimentary-facies successions exposes that as follows: meter-scale cycles that are used as the basic working unit actually are litho-facies successions formed by the mechanism of a punctuated aggradational cycle, and thirdorder sequences that are constituted by regularly vertical stacking patterns of meter-scale cycles are marked by sedimentary-facies successions. On the basis of the changing curve of water depth at each section, the curve of the relative third-order sea level changes in the late Cambrian of the North China Platform can be integrated qualitatively from changing curve of water depth. The correlation of Late Cambrian long-term sea level changes between North China and North America demonstrates that there are not only similarities but also differences, reflecting control of long-term sea level changes both by global eustacy and by regional factors.

  18. Basin Evolution and Exhumation of the Xigaze Forearc, Southern Tibet: Insight from Sedimentology, Stratigraphy, and Geo-Thermochronology

    Orme, D. A.; Carrapa, B.; Abbey, A. L.; Kapp, P. A.; Ding, L.


    Forearc basins are important data archives for understanding continental dynamics because they preserve the tectono-erosional record of continental margins before collision. This study focuses on the Cretaceous-Eocene Xigaze forearc basin in southern Tibet, which is exposed along ~600 km of the Indus-Yarlung Suture Zone between the Indian craton to the south and the Asian Lhasa terrane to the north. From late Cretaceous to early Cenozoic time, subduction of Neo-Tethyan oceanic crust beneath the southern margin of Asia accommodated the northward motion of the Indian craton and formed the Xigaze forearc basin. Following collision with India in the early Cenozoic, the basin transitioned from predominantly marine to non-marine sedimentation and was subsequently uplifted to a mean elevation of 5000 m. How this transition occurred remains unresolved. This study's overall objective is to decipher forearc-basin and Indo-Asia continental-margin development from field sedimentology and stratigraphy, and detrital geo-thermochronology. We present new stratigraphic sections, totaling 8 km thick, from a previously unexplored ~60 km segment of the Xigaze forearc, ~50 km north-northwest of Saga. These sections are quite different from those known farther east. Sedimentary facies of mid-Cretaceous to early Eocene deposits indicate a shoaling-upward trend consistent with other ancient forearc basins (e.g., Great Valley forearc, California). Middle to late Cretaceous deposits indicate a variety of facies and depositional environments along strike in the study area. Facies include distal marine turbidites, shelf limestones, estuarine siliciclastics, and brown paleosols. In contrast, Eocene depositional environments are transitional from nearshore marine to pericontinental. Facies consist of dirty limestones, packstones, and wackestones, interbedded with terrigenous conglomerates and red-green paleosols. Eocene fauna include abundant foraminifera such as Nummulites-Discocyclina and

  19. Hydrothermal zebra dolomite in the Great Basin, Nevada--attributes and relation to Paleozoic stratigraphy, tectonics, and ore deposits

    Diehl, S.F.; Hofstra, A.H.; Koenig, A.E.; Emsbo, P.; Christiansen, W.; Johnson, Chad


    In other parts of the world, previous workers have shown that sparry dolomite in carbonate rocks may be produced by the generation and movement of hot basinal brines in response to arid paleoclimates and tectonism, and that some of these brines served as the transport medium for metals fixed in Mississippi Valley-type (MVT) and sedimentary exhalative (Sedex) deposits of Zn, Pb, Ag, Au, or barite. Numerous occurrences of hydrothermal zebra dolomite (HZD), comprised of alternating layers of dark replacement and light void-filling sparry or saddle dolomite, are present in Paleozoic platform and slope carbonate rocks on the eastern side of the Great Basin physiographic province. Locally, it is associated with mineral deposits of barite, Ag-Pb-Zn, and Au. In this paper the spatial distribution of HZD occurrences, their stratigraphic position, morphological characteristics, textures and zoning, and chemical and stable isotopic compositions were determined to improve understanding of their age, origin, and relation to dolostone, ore deposits, and the tectonic evolution of the Great Basin. In northern and central Nevada, HZD is coeval and cogenetic with Late Devonian and Early Mississippian Sedex Au, Zn, and barite deposits and may be related to Late Ordovician Sedex barite deposits. In southern Nevada and southwest California, it is cogenetic with small MVT Ag-Pb-Zn deposits in rocks as young as Early Mississippian. Over Paleozoic time, the Great Basin was at equatorial paleolatitudes with episodes of arid paleoclimates. Several occurrences of HZD are crosscut by Mesozoic or Cenozoic intrusions, and some host younger pluton-related polymetallic replacement and Carlin-type gold deposits. The distribution of HZD in space (carbonate platform, margin, and slope) and stratigraphy (Late Neoproterozoic Ediacaran-Mississippian) roughly parallels that of dolostone and both are prevalent in Devonian strata. Stratabound HZD is best developed in Ediacaran and Cambrian units, whereas

  20. Sequence Stratigraphy of Jurassic in Turpan-Hami Basin%吐哈盆地侏罗系层序地层学研究

    沈守文; 彭大钧; 颜其彬; 黄先律; 李志军


    吐哈盆地侏罗系是一个盆地充填层序(一级层序),包括4个构造层序(二级层序),分别与侏罗纪湖盆的4个演化阶段(稳定沉降阶段、短期收缩阶段、扩张阶段和萎缩阶段)相对应,其中又分为13个(三级)层序。与海相地层不同的是,本区识别出了4种层序边界类型(A型、B型、C型和D型),其对应的层序本文分别称之为冲积层序、淹没层序、类Ⅰ型层序和类Ⅱ型层序。冲积层序形成于构造剧烈抬升时的盆地萎缩阶段,淹没层序形成于构造沉降迅速时的盆地扩张阶段。%Fourteen sequence boundaries showing onlap or erosional truncation are recognize d in the seismic sections of the Jurassic Turpan-Hami basin.The two major bound a ries (at the top and bottom of the Jurassic deposits)are regional unconformities extending beyond the basin.Three intermediate ones (between 3re and 4 th section of Xishanyao Fm.Qikeai Fm.and Sanjianfeng Fm.and Kalaza Fm.and Qigu Fm.) are unconformities spaning most of the basin.The remaining nine sequence boundaries are local unconformities.The Jurassic sedimentary strata in Turpan-Hami basin i s a basin-fill sequence (1st order)including four tectonic sequences(2n d order) and thirteen depositional sequences(3rd order).The four tectonic sequences are bound with the four evolutionary stages(stable subsidence,short- time contraction,expansion,and uplift desiccation)of the lake basin.   According to classic sequence stratigraphy,there are two types of sequences and sequence boundaries in passive continental margins with a shelf and slope.The ty pes of depositional sequences in terrestrial basin,however,are not the same as t hose from a passive continental margin.Four types of sequence boundaries(type A, B,C,and D)are identified in the basin.A type A boundary is formed at the desicca t ion stage of the lake basin caused by strong tectonic uplift.The sequence above the type A boundary is

  1. 川南地区石宝矿段龙潭组层序地层研究%sequence stratigraphy of the Longtan formation in the Shibao ore block of South Sichuan

    刘安然; 巫晓兵; 胡俊仁


    Upper Permian Longtan Formation coal-bearing strata in southern Sichuan region is characterized by the depth and thickness variation .Guided by the theories and methods of the Sedimentary petrology and sequence stratigraphy ,through consolidated results of previous studies ,the authors divided the Upper Permian Longtan Formation in the Shibao ore block of South Sichuan into 3 long-term sequence (LSC1-LSC3) and many medium-term sequences through comprehensive study of outcrops ,coring ,logging and seismic data . According to the identified four kinds of sequence boundary and its manifestations substances , including regional unconformity , fluvial erosion surface , lithology , lithofacies conversion surface and maximum flooding surface ,the long-term base-level cycles in each cycle of the material change and mechanism of coal accumulation has been described .By multi-well sequence stratigraphy contrast , isochronous stratigraphic framework has been established that has important implications for coalbed methane exploration and mine development work Shibao ore block .%针对川南地区上二叠统龙潭组煤系地层埋深和厚度变化大的特点,以沉积岩石学、层序地层学的理论方法为指导,综合前人研究成果,通过对石宝矿段内上二叠统龙潭组野外露头、钻井岩芯和物探测井资料的研究,识别出区域不整合面、河流冲刷侵蚀面、岩性、岩相转换面和最大海泛面4种层序界面及其物质表现形式,并将其划分为3个长期基准面旋回层序(LSC1-LSC3)和若干中期基准面旋回层序。运用等时对比法,进行连井层序地层对比,建立了等时地层格架。根据基准面旋回升降趋势对各长期旋回层序内物质变化规律和成煤机制进行了系统的描述。认为对石宝矿段的煤层气勘探开发工作具有重要意义。

  2. Synchronisation of palaeoenvironmental records over the last 60,000 years, and an extended INTIMATE event stratigraphy to 48,000 b2k

    Blockley, S.P.E.; Lane, C.S.; Hardiman, M.


    article of this INTIMATE special issue we introduce some of the recent achievements of the INTIMATE community and discuss the challenges associated with extending the INTIMATE approach back in time, focussing in particular on the chronological problems inherent in comparing different proxy records......The INTIMATE protocol for the correlation of marine ice core and terrestrial records is here updated, reflecting recent developments in palaeoclimate research. Originally focussed on Last Glacial to Interglacial Transition (LGIT: 22,000-11,500 years B.P.), the INTIMATE group has now extended its...... study period back to 60,000 years. As a first step, the INTIMATE event stratigraphy has now been extended to include 8000-48,000 b2k based on a combined NGRIP and GRIP isotope profile against a GICC05 chronology and key tephra horizons from Iceland and continental European volcanic sources. In this lead...

  3. Stratigraphy, Sequence, and Crater Populations of Lunar Impact Basins from Lunar Orbiter Laser Altimeter (LOLA) Data: Implications for the Late Heavy Bombardment

    Fassett, C. I.; Head, J. W.; Kadish, S. J.; Mazarico, E.; Neumann, G. A.; Smith, D. E.; Zuber, M. T.


    New measurements of the topography of the Moon from the Lunar Orbiter Laser Altimeter (LOLA)[1] provide an excellent base-map for analyzing the large crater population (D.20 km)of the lunar surface [2, 3]. We have recently used this data to calculate crater size-frequency distributions (CSFD) for 30 lunar impact basins, which have implications for their stratigraphy and sequence. These data provide an avenue for assessing the timing of the transitions between distinct crater populations characteristic of ancient and young lunar terrains, which has been linked to the late heavy bombardment (LHB). We also use LOLA data to re-examine relative stratigraphic relationships between key lunar basins.

  4. Sequence stratigraphy and depositional environments of the Sarmatian sediments in the NW part of the Vienna Basin: Moravian Central Depression, Czech Republic

    Bohuslava Sopková


    Full Text Available The study is focused on the development of the Sarmatian sedimentary record in the NW Vienna Basin, Moravian Central Depression. To identify key surfaces, the principles of sequence stratigraphy and electrosequence analysis were used together with the well logs and well cores data as well as data obtained from final reports. The identified sequence boundaries (SB and surfaces (ts, mfs divide the Sarmatian sediments into sequences of the relative base level change of the third and fourth order. Except the third order cycle related to Haq's TB 2.6 cycle, which includes the whole Sarmatian stage, two individual cycles of higher order were revealed in the sedimentary record for the Moravian Central Depression. Their occurrence was also proved in Austrian as well as in Slovak part of the Vienna Basin, what points to their interregional character.

  5. The Relationship between Litho-Sequential Stratigraphy, Chemostratigraphy of Khuff Carbonates: Implication for Facies and Paleoenvironmental Recognition and Correlation, Central Saudi Arabia

    Abdullatif, Osman; Abdlmutalib, Ammar; Ahmed, Jarrah; Abdelgadir, Mohamed; Adam, Ammar


    The Permian-Triassic Khuff Formation carbonate reservoirs (and equivalents) in the Middle East are estimated to contain about 15-20 % of the world's gas reserves. Excellently exposed outcropping Khuff strata in central Saudi Arabia provide good outcrop equivalents to the Khuff Formation in the subsurface. The Khuff Formation is composed of five members and from bottom to top are Ash Shiqqah, Huqayl, Duhaysan, Midnab and Khartam members. The Carbonates lithofacies dominate with minor terrestrial clastics, and the paleoenvironments vary from terrestrial, sabkha, tidal-intertidal and open marine environments. This study investigates the relationship between lithostratigraphy, sequence stratigraphy and chemostratigraphy by integration of both field and laboratory sedimentological and chemical elements data. The vertical chemical elements profiles along the Khuff members show variations in their chemical elements content with the variation in lithofacies types, staking pattern, depositional and stratigraphic pattern. The chemostratigraphic distribution of the chemical elements also showed variation within and between the Khuff members. There is a general agreement between chemostratigraphic analyses based on vertical profiles and binary cross plots. The Khuff members and their stratigraphic boundaries can be differentiated based on their chemostratigraphic signatures. Moreover, the lithofacies and depositional paleoenvironmental of different Khuff members can be identified based on their chemical element contents. Chemostratigraphic zones or clusters are markedly established indicating different lithofacies and depositional paleoenvironments. Terrestrial, channel, lacustrine, shoreline to open marine carbonate lithofacies, as building blocks of sequence stratigraphy, all may be distinguished based on their chemical signatures. These outcrop analog results might be of significance to lithofacies, paleoenvironmental, stratigraphic identification, classification and

  6. Regional-scale stratigraphy of surface units in Tyrrhena and Iapygia Terrae, Mars: insights into highland crustal evolution and alteration history

    Rogers, A. Deanne; Fergason, Robin L.


    The compositional, thermophysical and geologic characteristics of surface units in Iapygia and Tyrrhena Terra (60°E-100°E, 0°-30°S) provide new insights into the compositional stratigraphy of the region. Intercrater plains are dominated by two surface units. The older unit (unit 1) is deficient in olivine and more degraded and likely consists of a mixture of impact, volcanic and sedimentary materials. The younger unit (unit 2) is enriched in olivine, exhibits a resistant morphology and higher thermal inertia, and likely represents volcanic infilling of plains. Units 1 and 2 bear a strong resemblance to those previously mapped in Mare Serpentis, a section of highlands crust located northwest of Hellas Basin. Thus, the two major intercrater plains units are even more widespread than previously thought and therefore likely constitute important components of Mars' highland stratigraphy. Many craters in the region contain high thermal inertia deposits (unit 3) that are compositionally identical to unit 2. These may have formed via volcanic infilling or may represent sedimentary materials that have been eroded from crater walls and lithified. Less common units include olivine and/or pyroxene-rich massifs and crater central peaks. These are primarily found within Hellas Basin rim units and may represent mantle materials brought toward the surface during the Hellas impact. Putative chloride deposits are primarily associated with olivine-deficient surfaces (unit 1) that may be heavily degraded occurrences of unit 2. The observations raise a variety of questions related to Martian crustal evolution and alteration that may have more widespread implications outside the study region.

  7. Regional-scale stratigraphy of surface units in Tyrrhena and Iapygia Terrae, Mars: Insights into highland crustal evolution and alteration history

    Rogers, A. Deanne; Fergason, Robin L.


    The compositional, thermophysical and geologic characteristics of surface units in Iapygia and Tyrrhena Terra (60°E-100°E, 0°-30°S) provide new insights into the compositional stratigraphy of the region. Intercrater plains are dominated by two surface units. The older unit (unit 1) is deficient in olivine and more degraded and likely consists of a mixture of impact, volcanic and sedimentary materials. The younger unit (unit 2) is enriched in olivine, exhibits a resistant morphology and higher thermal inertia, and likely represents volcanic infilling of plains. Units 1 and 2 bear a strong resemblance to those previously mapped in Mare Serpentis, a section of highlands crust located northwest of Hellas Basin. Thus, the two major intercrater plains units are even more widespread than previously thought and therefore likely constitute important components of Mars' highland stratigraphy. Many craters in the region contain high thermal inertia deposits (unit 3) that are compositionally identical to unit 2. These may have formed via volcanic infilling or may represent sedimentary materials that have been eroded from crater walls and lithified. Less common units include olivine and/or pyroxene-rich massifs and crater central peaks. These are primarily found within Hellas Basin rim units and may represent mantle materials brought toward the surface during the Hellas impact. Putative chloride deposits are primarily associated with olivine-deficient surfaces (unit 1) that may be heavily degraded occurrences of unit 2. The observations raise a variety of questions related to Martian crustal evolution and alteration that may have more widespread implications outside the study region.

  8. Preliminary stratigraphy and facies analysis of the Upper Cretaceous Kaguyak Formation, including a brief summary of newly discovered oil stain, upper Alaska Peninsula

    Wartes, Marwan A.; Decker, Paul L.; Stanley, Richard G.; Herriott, Trystan M.; Helmold, Kenneth P.; Gillis, Robert J.


    The Alaska Division of Geological and Geophysical Surveys has an ongoing program aimed at evaluating the Mesozoic forearc stratigraphy, structure, and petroleum systems of lower Cook Inlet. Most of our field studies have focused on the Jurassic component of the petroleum system (this report). However, in late July and early August of 2012, we initiated a study of the stratigraphy and reservoir potential of the Upper Cretaceous Kaguyak Formation. The Kaguyak Formation is locally well exposed on the upper Alaska Peninsula (fig. 25) and was named by Keller and Reiser (1959) for a sequence of interbedded siltstone and sandstone of upper Campanian to Maastrichtian age that they estimated to be 1,450 m thick.Subsequent work by Detterman and Miller (1985) examined 900 m of section and interpreted the unit as the record of a prograding submarine fan.This interpretation of deep-water deposition contrasts with other Upper Cretaceous rocks exposed along the Alaska Peninsula and lower Cook Inlet that are generally described as nonmarine to shallow marine (Detterman and others, 1996; LePain and others, 2012).Based on foraminifera and palynomorphs from the COST No. 1 well, Magoon (1986) concluded that the Upper Cretaceous rocks were deposited in a variety of water depths and environments ranging from upper bathyal to nonmarine. During our recent fieldwork west and south of Fourpeaked Mountain, we similarly encountered markedly varying lithofacies in the Kaguyak Formation (fig. 25), and we also found oil-stained rocks that are consistent with the existence of an active petroleum system in Upper Cretaceous rocks on the upper Alaska Peninsula and in lower Cook Inlet. These field observations are summarized below.

  9. Late Quaternary seismic sequence stratigraphy of the Gulf of Kachchh, northwest of India

    Michael, L.; Rao, D.G.; Krishna, K.S.; Vora, K.H.

    along the northwest coast of India), lies between the mainland of Kachchh in the north and the Saurashtra/Kathiawar peninsula in the south and is open to the Arabian Sea in the west (Figure 1). The nonhostile conditions, high 3-6 knots tidal currents... (Figure 2) and the macrotidal (semidiurnal with ~ 6 m maximum wave heights) regime of the gulf are unfavourable for conducting any underwater investigations in the area, and thus understanding of the geologic structure and origin of the gulf is elusive...

  10. Seismic stratigraphy of Ongole-Paradip continental shelf, east coast of India

    Murthy, K.S.R.

    outer-shelf from Pudimadaka in the south to Kalingapatnam in the north and is overlain by the unconsolidated sediments further south and north. The exposed palaeoshelf, particularly over the outer-shelf off Visakhapatnam is capped by calcareous reefs...

  11. Oxygen isotope stratigraphy and events in the northern South China Sea during the last 6 million years

    JIAN; Zhimin


    [1]Clemens, S. C., Murry, D. W., Prell, W. L., Nonstationary phase of the Plio-Pleistocene Asian monsoon, Science, 1996,274: 943.[2]Ruddiman, W. F., Raymo, M. E., Northern Hemisphere climatic regimes during the past 3 Ma: Possible tectonic connec tions, Philos. Trans. R. Soc. London, Ser. B, 1988, 318: 411.[3]Shackleton, N. J., Hall, M. A., Pate, D., Pliocene stable isotope stratigraphy of ODP site 846, Proc. Ocean Drill Program Sci. Results, 1995, 138: 337.[4]Tiedeman, R., Sarnthein, M., Shackleton, N. J., Astronomic timescale for the Pliocene Atlantic δ18O and dust flux records of Ocean Drilling Program site 659, Paleoceanography, 1994, 9(4): 619.[5]Jian, Z., Stable isotopic evidences of the glacial deep water properties in the South China Sea, Science in China, Ser D,1998, 41(4): 337.[6]Wang, P., Western Pacific in glacial cycles: Seasonality in marginal seas and variability of Warm Pool, Science in China,SerD, 1998,41(1): 35.[7]Jian, Z., Wang, P., Chen, M. P. et al., Foraminiferal response to major Pleistocene paleoceanographic changes in the south ern South China Sea, Paleoceanography, 2000, 15(2): 229.[8]Jian, Z., Quantitative analysis of paleoenvironment in the northwestern shelf of South China Sea based on cutting samples (in Chinese with English abstract), Acta Palaeontologica Sinica, 1993, 32(5): 550.[9]Wang, P., Prell, W., Blum, P., Proceedings ofthe Ocean Drilling Program, Initial Reports Volume 184, College Station:Ocean Drilling Program, 2000.[10]Fairbanks, R. G., Sverdlove, M., Free, R. et al., Vertical distribution and isotopic fractionation of living planktonic fo raminifera from the Panama Basin, Nature, 1982, 298: 841.[11]Imbrie, J., Hays, J. D., Martinson, D. G. et al., The orbital theory of Pleistocene climate: Support from a revised chronol ogy of the marine o18O record, in Milankovitch and Climate (eds. Berger, A., Imbrie, J.), Norwell: D Riedel, 1984, 269-305.[12]Shackleton, N. J., Berger, A

  12. Stratigraphy of the Roraima Supergroup along the Brazil-Guyana border in the Guiana shield, Northern Amazonian Craton - results of the Brazil-Guyana Geology and Geodiversity Mapping Project

    Reis,Nelson Joaquim; Nadeau, Serge; Fraga,Leda Maria; BETIOLLO, Leandro Menezes; Faraco,Maria Telma Lins; Reece,Jimmy; Lachhman,Deokumar; Ault,Randy


    ABSTRACT: The Geological and Geodiversity Mapping binational program along the Brazil-Guyana border zone allowed reviewing and integrating the stratigraphy and nomenclature of the Roraima Supergroup along the Pakaraima Sedimentary Block present in northeastern Brazil and western Guyana. The area mapped corresponds to a buffer zone of approximately 25 km in width on both sides of the border, of a region extending along the Maú-Ireng River between Mount Roraima (the triple-border region) and Mu...

  13. From the valley floor to the peaks: Stratigraphy and landscape evolution of the Alpine Lateglacial in the Kitzbühel Alps (Tyrol, Austria)

    Dippenaar, Elijah; Reitner, Jürgen


    Our understanding of Alpine landscape evolution and more specifically, chronology of glacier activity during the Alpine Lateglacial (ALG; c. 19 - 11.7 ka) i.e. the timespan between the Würmian Pleniglacial (= Alpine Last Glacial Maximum; AlpLGM) and the beginning of the Holocene, is based on the evidence of only few areas in the Alps. In order to get a better understanding of glaciation and palaeoclimate during this phase, N-S and E-W transects are needed. The Kitzbühel Alps, which are currently not glaciated, span an area of 1700km2 and have peaks that reach c. 2400m a.s.l. They lie at the center of the Eastern Alps on the northern rim, which is more humid than the relatively dry central parts. A modern geological investigation of the ALG record is missing in the Kitzbühel Alps. In order to overcome this gap of knowledge and to gain a more complete understanding of the ALG landscape development, a pioneering study has been performed in the area of Langer Grund Valley, a tributary valley of the Kelchsau Valley. This was done through detailed field mapping, thereby describing the shape and sediment composition of Quaternary morphological features, such as moraines, landslides and rock glacier deposits. Sedimentary evidence of one short glacial advance and two glacial stadials were identified. In chronological order they were named the: Frommbach advance, the Arnbach (glacier) halt and the Küharn halt. Where possible, palaeoglaciers were constructed using ArcGIS. With the palaeoglaciers, equlibrium line altitudes (ELA) were calculated and compared to ELA values of known glacial stadials in an attempt to correlate the relative local stratigraphy to the Lateglacial stratigraphy. Four methods to calculate ELAs were used; Maximum Elevation of Lateral Moraines (MELM), Toe to Headwall Altitude Ratio (THAR), Area x Altitude (AA) and Accumulation Area Ratio (AAR). Furthermore, the glacial sedimentary sequence of the study area was compared to that of the Gschnitz Valley

  14. Roles of calcareous nannofossil in petroleum exploration. Its usefulness for biostratigraphy, sequence stratigraphy and paleoceanography; Sekiyu tanko ni okeru sekitanshitsu nanno kaseki no yakuwari. Sono seiso jogaku, sequence so jogaku oyobi kokaiyogakuteki yukosei

    Hiramatsu, C. [Japan Petroleum Exploration Corp., Musashino, Tokyo (Japan)


    Conventionally, stratigraphy of oil field area of East-northern Japan Sea side was decided and used by foraminifer fossils. Foraminifer fossils analysis has various types of benefits not only from the aspect of rich in data, easy available of data at the exploration site, promptness, formation sequence decision but also from the point of view of wider application area such as estimation of paleo-environment using bottom species and so forth, and even at present, it covers the most important position in the fine fossil analysis of well samples. Research of calcareous nannofossil of East-northern coast region of the Japan Sea has been promoted rapidly since the beginning of 1980`s, and its effectiveness for the detail determination of stratigraphy age has been stressed. According to this research findings, quaternary section will be possible with contrast of about 10,000 order by using calcareous nannofossil base. In this report, simple introduction of the application of calcareous nannofossil stratigraphy to oil exploration in the same region together with the role of calcareous nannofossil in the oil exploration, are described. 29 refs., 8 figs.

  15. Integrated stratigraphy of the Smirra Coring: a new reference sedimentary record for the early Paleogene from the Umbria-Marche Basin (Northern Apennines, Italy)

    Turtù, Antonio; Lauretano, Vittoria; Catanzariti, Rita; Galeotti, Simone; Lanci, Luca; Moretti, Matteo; Lourens, Lucas J.


    The early Paleogene represents a critical time interval in Earth's history characterized by prolonged greenhouse conditions, culminating in a series of extreme global warming events (i.e. hyperthermals), as well as large uncertainties in the Geological Time Scale. Therefore new, high-resolution, geological records are crucial in providing novel constraints on these topics. The Paleogene Umbria-Marche sections of the Northern Apennines (Italy) have shown to be suitable for integrated stratigraphy allowing regional-to-global correlations and environmental reconstructions across this time interval. Among several well-known sections, a new sedimentary record is provided by the Smirra Coring, which recovered an undisturbed sequence of rocks (~120 m from 4 overlapping holes) spanning the upper Scaglia Fms. (early Paleocene - middle Eocene) of the Umbria-Marche pelagic succession. Here we present a new, high-resolution, integrated stratigraphic framework (magnetostratigraphy, calcareous nannofossil biostratigraphy, physical properties, calibrated XRF core scanning and cyclostratigraphy) of the ~93 m composite section drilled in Smirra Holes 1 and 2. The succession extends almost continuously, with modest tectonic disturbance affecting its lowermost part with minor faulting. The resulting magnetic stratigraphy defines a succession of normal and reversed polarity magnetozones. The correlation of the paleomagnetic polarity sequence with the latest Geomagnetic Polarity Timescales (GPTSs; e.g. CK95, GTS 2004 and 2012), also constrained through nannofossil biostratigraphy, shows that the section spans the late Paleocene - middle Eocene from chrons C21n (~46 Ma) to C26r (~60 Ma). The overall sedimentation rates computed at Smirra are fully comparable with those from coeval sections from the Umbria-Marche Basin, ranging from ~10 m/Ma, between chrons C21n and C22n, to ~6 m/Ma, between chrons C22r and the base of the section. However, the sedimentation rates vary considerably

  16. Floodplain deposits, channel changes and riverbank stratigraphy of the Mekong River area at the 14th-Century city of Chiang Saen, Northern Thailand

    Wood, Spencer H.; Ziegler, Alan D.; Bundarnsin, Tharaporn


    Riverbank stratigraphy and paleochannel patterns of the Mekong River at Chiang Saen provide a geoarchaeological framework to explore for evidence of Neolithic, Bronze-age, AD 5th Century Yonok and AD 14-16th Century Lan Na Cultures. Typical bank stratigraphy charted on the Thailand side is imbricate cobble gravel overlain by 5-10 m of reddish-brown sandy silt. The silt section is composed chiefly of 1/2 to 2-m thick layers of massive silt without paleosols interpreted as near-channel floodplain and gently-inclined levee deposits laid down by episodic, infrequent, large floods. The surface soil is dark-brown clay loam (pottery shards and charcoal of Lan Na time. Brick ruins of 14-16th Century Buddhist temples are crumbling into the river at Chiang Saen Noi, and formerly did so at Chiang Saen until banks were stabilized by rock walls. Bank retreat from river erosion has been > 20 m since Lan Na time, and has exposed a silt-filled moat. A radiocarbon age of 1475 cal yr AD was obtained from charcoal at the bottom of the moat, beneath 5.6 m of silt. Lag material from erosion of the silt banks contains Neolithic and Bronze Age artifacts out of stratigraphic context, as well as ceramics and bricks of Lan Na age. These artifacts as well Neolithic artifacts obtained from a 1972 excavation near the mouth of the Kham River indicate long human habitation of this riverbank area. In northern Thailand the Mekong is mostly in a bedrock canyon, but shifting topography along the active strike-slip Mae Chan fault has formed the upstream 2-5-km wide floodplain at Chiang Saen, and downstream has diverted the river into a broad S-shaped loop in the otherwise straight course of the river. A 1.7-Ma basalt within the bedrock channel 45-km downstream of Chiang Saen indicates little vertical incision by the river. Satellite images show former channels in the Chiang Saen area, meander-point-bar scrolls (radii of curvature > 1.2 km), and floodplain edges as arcuate cuts of similar curvature

  17. New insights into the painting stratigraphy of L'Homme blesse by Gustave Courbet combining scanning macro-XRF and confocal micro-XRF

    Reiche, Ina [Staatliche Museen zu Berlin-Preussischer Kulturbesitz, Rathgen-Forschungslabor, Berlin (Germany); Laboratoire d' Archeologie Moleculaire et Structurale, Sorbonne Universites, Univ. Paris 06, CNRS, UMR 8220, Paris (France); Eveno, Myriam; Pichon, Laurent; Laval, Eric; Mottin, Bruno [Centre de Recherche et de Restauration des Musees de France (C2RMF), Paris (France); Mueller, Katharina [Laboratoire d' Archeologie Moleculaire et Structurale, Sorbonne Universites, Univ. Paris 06, CNRS, UMR 8220, Paris (France); Calligaro, Thomas [Centre de Recherche et de Restauration des Musees de France (C2RMF), Paris (France); PSL Research University, Chimie ParisTech-CNRS, Institut de Recherche Chimie Paris, Paris (France); Mysak, Erin [Centre de Recherche et de Restauration des Musees de France (C2RMF), Paris (France); Yale University, Institute for the Preservation of Cultural Heritage, New Haven, CT (United States)


    The painting L'Homme blesse by Gustave Courbet kept at the Musee d'Orsay in Paris has been recently studied by X-ray radiography, SEM-EDX observation of paint cross sections and confocal micro-X-ray fluorescence analyses (CXRF) at locations where the cross section samples were taken. This study allowed the establishment of the paint palette used by Courbet for the three paint compositions. Eight or more paint layers could be evidenced. In the view of the complexity of this painting, further analyses using two-dimensional scanning macro-X-ray fluorescence imaging (MA-XRF) providing chemical images corresponding to the superimposition of all detectable paint layers were employed. This method is combined with CXRF for depth-resolved paint layer analysis. Large elemental maps of Hg, Cu, As, Fe, Zn, Cr, Ba, Pb and Ca were obtained by MA-XRF on the painting and are discussed in combination with depth profiles obtained by CXRF on strategic points where three painting compositions overlap. The order of three successive compositions of this painting were determined in this study. This work also highlights the benefits of using complementary imaging methods to obtain a complete three-dimensional vision of the chemistry and stratigraphy of paintings. (orig.)

  18. Stratigraphy and paleogeographic significance of a Late Pennsylvanian to Early Permian channeled slope sequence in the Darwin Basin, southern Darwin Hills, east-central California

    Stevens, Calvin H.; Stone, Paul; Magginetti, Robert T.; Ritter, Scott M.


    The complex stratigraphy of late Paleozoic rocks in the southern Darwin Hills consists of regionally extensive Mississippian and Early to Middle Pennsylvanian rocks overlain by latest Pennsylvanian to Early Permian rocks, herein called the Darwin Hills sequence. Deposition of this latter sequence marked the beginning of the Darwin Basin. In Mississippian time, a carbonate platform prograded westward over slightly older slope deposits. In the Late Mississippian this platform was exposed to erosion and siliciclastic sediments were deposited. In Early to Middle Pennsylvanian time the area subsided, forming a west-facing ramp that was subjected to deformation and erosion in Middle or early Late Pennsylvanian time. Later this area was tilted westward and deep-water sediments were deposited on this slope. In latest Pennsylvanian to earliest Permian time, a major channel was cut through the older Pennsylvanian rocks and into the Upper Mississippian strata. This channel was gradually filled with increasingly finer grained, deep-water sediment as the area evolved into a basin floor by Early Permian (Sakmarian) time. Expansion of the Darwin Basin in Artinskian time led to a second phase of deposition represented by strata of the regionally extensive Darwin Canyon Formation. The geology in this small area thus documents tectonic events occurring during the early development of the Darwin Basin.

  19. Field-trip guide to the vents, dikes, stratigraphy, and structure of the Columbia River Basalt Group, eastern Oregon and southeastern Washington

    Camp, Victor E; Reidel, Stephen P.; Ross, Martin E.; Brown, Richard J.; Self, Stephen


    The Columbia River Basalt Group covers an area of more than 210,000 km2 with an estimated volume of 210,000 km3. As the youngest continental flood-basalt province on Earth (16.7–5.5 Ma), it is well preserved, with a coherent and detailed stratigraphy exposed in the deep canyonlands of eastern Oregon and southeastern Washington. The Columbia River flood-basalt province is often cited as a model for the study of similar provinces worldwide.This field-trip guide explores the main source region of the Columbia River Basalt Group and is written for trip participants attending the 2017 International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) Scientific Assembly in Portland, Oregon, USA. The first part of the guide provides an overview of the geologic features common in the Columbia River flood-basalt province and the stratigraphic terminology used in the Columbia River Basalt Group. The accompanying road log examines the stratigraphic evolution, eruption history, and structure of the province through a field examination of the lavas, dikes, and pyroclastic rocks of the Columbia River Basalt Group.

  20. Insights into complex layered ejecta emplacement and subsurface stratigraphy in Chryse Planitia, Mars, through an analysis of THEMIS brightness temperature data

    Jones, Eriita; Caprarelli, Graziella; Osinski, Gordon R.


    Layered ejecta craters on Mars have been interpreted to indicate the presence of volatiles in the substrate, making them important targets for the investigation of sites of astrobiological significance. If the ejecta are associated with the presence of water in the substratum, specific surface grain size trends are expected. In this study we explore the distribution of grain sizes in the layered ejecta of impact craters located in Chryse Planitia, using Thermal Emission Imaging System (THEMIS) thermal infrared data. Ejecta grain size trends, in conjunction with ejecta mobility and lobateness values, are applied to assess the degree of surface flow of the ejecta, and in turn to constrain the plausible volatile abundance, cohesion, and fine particle content of the target materials. Craters with a larger fraction of small grain sizes in their ejecta showed greater ejecta mobility and lobateness, consistent with a water-rich and/or a low-cohesion target. Craters displaying decreasing grain size with increasing radius had smaller diameters and lower ejecta mobility and lobateness, indicating only a minimal component of surface ejecta flow. Ejecta grain size trends varied with crater diameter, from which the presence of vertical compositional stratigraphy in Chryse Planitia is inferred and interpreted. Our observations are synthesized into a number of plausible geologic scenarios for Chryse Planitia.

  1. Crystal Stratigraphy of Two Basalts from Apollo 16: Unique Crystallization of Picritic Basalt 606063,10-16 and Very-Low-Titanium Basalt 65703,9-13

    Donohue, P. H.; Neal, C. R.; Stevens, R. E.; Zeigler, R. A.


    A geochemical survey of Apollo 16 regolith fragments found five basaltic samples from among hundreds of 2-4 mm regolith fragments of the Apollo 16 site. These included a high-Ti vitrophyric basalt (60603,10-16) and one very-low-titanium (VLT) crystalline basalt (65703,9-13). Apollo 16 was the only highlands sample return mission distant from the maria (approx. 200 km). Identification of basaltic samples at the site not from the ancient regolith breccia indicates input of material via lateral transport by post-basin impacts. The presence of basaltic rocklets and glass at the site is not unprecedented and is required to satisfy mass-balance constraints of regolith compositions. However, preliminary characterization of olivine and plagioclase crystal size distributions indicated the sample textures were distinct from other known mare basalts, and instead had affinities to impact melt textures. Impact melt textures can appear qualitatively similar to pristine basalts, and quantitative analysis is required to distinguish between the two in thin section. The crystal stratigraphy method is a powerful tool in studying of igneous systems, utilizing geochemical analyses across minerals and textural analyses of phases. In particular, trace element signatures can aid in determining the ultimate origin of these samples and variations document subtle changes occurring during their petrogenesis.

  2. Stratigraphy and Ar/Ar geochronology of the Miocene lignite-bearing Tunçbilek-Domaniç Basin, western Anatolia

    Helvacı, C.; Ersoy, E. Y.; Billor, M. Z.


    The Tunçbilek-Domaniç Basin is one of the Neogene basins containing economic coal deposits in western Anatolia, Turkey. The basin fill represents fluvial to lacustrine sedimentary units which are interlayered with volcanic rocks with bimodal composition. In order to reveal the stratigraphy and the exact ages of the basin fill and coal deposits, and to explore the tectonic evolution of the basin, we present new field data and Ar/Ar age data from the volcanic units. The field studies and the age data indicate that the whole basin fills were deposited between ~23 and ~19 Ma (Aquitanian-Early Burdigalian) without any unconformity. Taking into account the ages of the coal-bearing sedimentary units in the other Neogene basins in the region, it is concluded that most of the economic coal deposits in the western Anatolia were formed during Aquitanian. The field studies also show that the deposition of the sedimentary units in the basin was controlled by the NE-SW-trending strike- to oblique-slip normal faults. In a regional scale, tectonic evolution of the Tunçbilek-Domaniç Basin is linked to the differential stretching in the hanging wall of the southerly located, a crustal-scale low-angle detachment fault (the Simav detachment fault) that controlled the Early Miocene exhumation of the Menderes Extensional Core Complex.

  3. Sequence Stratigraphy of lower zones of Asmari Formation in Marun Oilfield by using of microfacies analysis, isolith maps and γ- Ray log

    Ahmad Mirmarghabi


    Full Text Available The Oligo- Miocene Asmari Formation is one of the most important reservoir units of the Marun Oilfield in Dezful Embayment SW Iran, deposited in Zagros foreland basin. The goal of this study is to interpret depositional environment and sequence stratigraphy of lower zones of the Asmari Formation in Well No.281, 342 and 312in Marun Oilfield based on changes in the shape of γ- Ray, isolith maps and microfacies properties. Accordingly, identification of 9 carbonate microfacies and 2 siliciclastic petrofacies were identified that are deposited in four depositional environment including open marine, barrier, lagoon and tidal flat in a homoclinal ramp (consisting of outer, middle and inner ramp. Also, based on the shape of γ- Ray log, There sediment were deposited in marine environment. In open marine and barrier environments, The shape of γ- Ray log is serrated bell-shaped, serrated funnel-shaped, left bow-shaped, serrated shape and right boxcar shape, Whole in the beach environment it is cylinder and funnel shape and in lagoon and tidal flat environment can be seen on right bow to cylinder-shaped. Based on the isolith maps, sandstone of lower zones of the Asmari Formation in Marun Oilfield expanded by deltaic system along the southwestern margin of the basin and influenced by changes in sea level constantly. Sequence stratigraphic analysis led to identification of three third- order (DS1, DS2 and DS3 depositional sequences.

  4. Sedimentology and Sequence Stratigraphy of the Lower Cretaceous Fortress Mountain and Torok Formations Exposed Along the Siksikpuk River, North-Central Alaska

    Houseknecht, David W.; Schenk, Christopher J.; Wartes, Marwan A.


    An exposure of the Lower Cretaceous Fortress Mountain and Torok Formations along the Siksikpuk River in north-central Alaska provides a rare opportunity to observe the stratigraphic contact between these two formations and to interpret the depositional facies and sequence stratigraphy of the exposed strata. The Fortress Mountain Formation at the base of the measured section includes braided-fluvial and coastal-plain facies deposited in a lowstand-systems tract, and an overlying succession of mostly shallow marine facies deposited in the basal part of a transgressive-systems tract. The overlying Torok Formation includes a thick, upward-deepening succession of marine-shelf to marine-slope facies deposited in the upper part of the transgressive-systems tract. The upper part of the section includes marine-slope and incised-slope-channel turbidite deposits of the Torok Formation, interpreted as a highstand-systems tract. Consideration of the balance between accommodation and sediment flux inferred from the sequence-stratigraphic analysis suggests that both tectonics and eustasy may have influenced deposition of the lowstand-systems and transgressive-systems tracts. In contrast, the highstand-systems tract may have been primarily influenced by progradation of a regional sediment-dispersal system and by subsidence induced by sediment loading.

  5. Investigating the stratigraphy and palaeoenvironments for a suite of newly discovered mid-Cretaceous vertebrate fossil-localities in the Winton Formation, Queensland, Australia

    Tucker, Ryan T.; Roberts, Eric M.; Darlington, Vikie; Salisbury, Steven W.


    The Winton Formation of central Queensland is recognized as a quintessential source of mid-Cretaceous terrestrial faunas and floras in Australia. However, sedimentological investigations linking fossil assemblages and palaeoenvironments across this unit remain limited. The intent of this study was to interpret depositional environments and improve stratigraphic correlations between multiple fossil localities within the preserved Winton Formation in the Eromanga Basin, including Isisford, Lark Quarry, and Bladensburg National Park. Twenty-three facies and six repeated facies associations were documented, indicating a mosaic of marginal marine to inland alluvial depositional environments. These developed synchronously with the final regression of the Eromanga Seaway from central Australia during the late Albian-early Turonian. Investigations of regional- and local-scale structural features and outcrop, core and well analysis were combined with detrital zircon provenance signatures to help correlate stratigraphy and vertebrate faunas across the basin. Significant palaeoenvironmental differences exist between the lower and upper portions of the preserved Winton Formation, warranting informal subdivisions; a lower tidally influenced fluvial-deltaic member and an upper inland alluvial member. This work further demonstrates that the Isisford fauna is part of the lower member of the preserved Winton Formation; whereas, fossil localities around Winton, including Lark Quarry and Bladensburg National Park, are part of the upper member of the Winton Formation. These results permit a more meaningful framework for both regional and global comparisons of the Winton flora and fauna.

  6. Orbitally-driven evolution of Lake Turkana (Turkana Depression, Kenya, EARS) between 1.95 and 1.72 Ma: A sequence stratigraphy perspective

    Nutz, Alexis; Schuster, Mathieu; Boës, Xavier; Rubino, Jean-Loup


    Lakes act as major archives for continental paleoenvironments, particularly when the evolution of lake levels over time serves as a guide for understanding regional paleohydrology and paleoclimate. In this paper, two sections from the Nachukui Formation (Turkana Depression, East African Rift System) provide a complete record of lake level variability and then paleohydrology for Lake Turkana between 1.95 and 1.72 Ma. This period corresponds to a key time during which important human evolutionary and technological innovations have occurred in East Africa and in the Turkana area. Based on sedimentary facies and sequence analyses on coastal deposits, one long-term regressive-transgressive cycle is identified between 1.95 and 1.72 Ma. Superimposed on this trend, five higher-frequency cycles of lake level change are identified between 1.87 and 1.76 Ma. Origins of these periodicities are attributed to orbital forcings. The extents of bathymetry change and shoreline migration during these periods are explored, suggesting that the period between 1.87 and 1.76 Ma was relatively dry and that climate experienced a relatively low variability. This finding differs strongly from most of the previous paleoenvironmental investigations in the region that argue high climate variability during a relatively wet period. This work emphasizes the importance of using sequence stratigraphy for analyzing lacustrine deposits.

  7. Paleoclimatical significance of the paleosol levels occurring in the Miocene-Pleistocene stratigraphy of the Manonga-Wembere Valley inCentral Tanzania



    Micromorphological characteristics of four paleosol levels of the Manonga - Wembere deposits in Central Tanzania indicate periods of wetter climate in the Pliocene than at present. The stratigraphy of the studied section shows a series of lacustrine calcareous clay sediments alternating with gravel, sand and silt. The sediments are believed to have been deposited in the Manonga - Wembere paleolake environment. Paleosols intercalate these sediments and were formed when stable landscapes developed on former lake beds during regression periods. Micromorphological features of the paleosols indicate strong clay illuviation of red to yellow typic clay coating and some Fe-Mn hydoxide hypocoatings in voids and channels. The groundmass consists of either an accumulation of bioturbated yellow to red clay coating fragments or an argillic red to yellow groundmass of clay mass. Such an illuviation and its associated groundmass is comparable to intense clay illuviation fronts that are found in present-day calcareous sediments of warm and wet climates. The paleosol levels therefore represent wetter climatic conditions than today in the area during the Lower Pliocene.

  8. Hierarchy of sedimentary discontinuity surfaces and condensed beds from the middle Paleozoic of eastern North America: Implications for cratonic sequence stratigraphy

    McLaughlin, P.I.; Brett, Carlton E.; Wilson, M.A.


    Sedimentological analyses of middle Paleozoic epeiric sea successions in North America suggest a hierarchy of discontinuity surfaces and condensed beds of increasing complexity. Simple firmgrounds and hardgrounds, which are comparatively ephemeral features, form the base of the hierarchy. Composite hardgrounds, reworked concretions, authigenic mineral crusts and monomictic intraformational conglomerates indicate more complex histories. Polymictic intraformational conglomerates, ironstones and phosphorites form the most complex discontinuity surfaces and condensed beds. Complexity of discontinuities is closely linked to depositional environments duration of sediment starvation and degree of reworking which in turn show a relationship to stratigraphic cyclicity. A model of cratonic sequence stratigraphy is generated by combining data on the complexity and lateral distribution of discontinuities in the context of facies successions. Lowstand, early transgressive and late transgressive systems tracts are representative of sea-level rise. Early and late transgressive systems tracts are separated by the maximum starvation surface (typically a polymictic intraformational conglomerate or condensed phosphorite), deposited during the peak rate of sea-level rise. Conversely the maximum flooding surface, representing the highest stand of sea level, is marked by little to no break in sedimentation. The highstand and falling stage systems tracts are deposited during relative sea-level fall. They are separated by the forced-regression surface, a thin discontinuity surface or condensed bed developed during the most rapid rate of sea-level fall. The lowest stand of sea level is marked by the sequence boundary. In subaerially exposed areas it is occasionally modified as a rockground or composite hardground.

  9. Shallow stratigraphy and gas-charged sediments in the inner shelf off Redi, west coast of India

    Subbaraju, L.V.

    palaeochannel running across the region in ENE-WSW direction. Shallow seismic surveys indicate a pseudo escapment of more than 7 m deep between 12-14 m water depths. Eastern part (11-14 m) of the escarpment indicate the existence of gas-charged sediments (silty...

  10. Paleomagnetism of the Stanislaus Group, CA reveals revised stratigraphy, Walker Lane kinematics, and radio-isotopic constraints on C5 magnetic subchrons

    Pluhar, C. J.; Wright, T. J.; Fischer, C. P.; Busby, C. J.


    Paleomagnetic study of the c.a. 9.2-10.3 Ma Stanislaus Group of intercalated latite (trachyandesite) lavas, ignimbrites and accessory sediments at three localities in Mono county California reveals: 1) a detailed, revised stratigraphy for the Stanislaus group, 2) kinematic constraints on the part of the Walker Lane since Stanislaus group emplacement, and 3) two age-constrained magnetic subchrons during chron C5N recorded by latites that had previously only been identified in seafloor magnetic anomalies. The revised stratigraphy results from detailed magnetostratigraphy combined with previous 40Ar/39Ar geochronologic constraints and stratigraphic studies. We find the lowermost unit, Table Mountain Latite, to consist of 23 or more individual lava flows falling into 5 magnetic (mostly normal) polarity zones, indicating that these rocks span at least 40,000 years of geologic time, based on the expected duration of magnetic reversals. Overlying Table Mountain Latite is the reversed-polarity Tollhouse Flat member of the Eureka Valley Tuff as described by previous authors. In the Sweetwater Roadless Area, thought to be proximal to the Stanislaus eruptive center, latite lava of both normal and reversed polarity are emplaced ontop of the Tollhouse Flat Member. Normal-polarity By Day member and normal-polarity Upper Member lie at very top of entire sequence. We find no field evidence for the normal polarity Dardanelle Formation latite flow at the top of the Group as had been previously reported by other workers. Instead, the Dardanelle formation member likely corresponds to the latite lava(s) between the By Day and Tollhouse Flat Eureka Valley Tuff. Based on previous 40Ar/39Ar dating, the two reversed zones within our magnetostratigraphy correspond to two of the proposed reversed subchrons/excursions during chron C5N. Direct dating of these reversed units may lead to future improvements to the magnetic polarity timescale for C5N. Our paleomagnetic results from three study

  11. Integrating bio-, chemo- and sequence stratigraphy of the Late Ordovician, Early Katian: A connection between onshore and offshore facies using carbon isotope analysis: Kentucky, Ohio, USA

    Young, Allison; Brett, Carlton; McLaughlin, Patrick


    A common problem in stratigraphic correlation is the difficulty of bridging shallow water shelf carbonates and down ramp shale-rich facies. This issue is well exemplified by the Upper Ordovician (lower Katian) Lexington Limestone of Kentucky, USA and adjacent dark shale facies in the deeper water Sebree Trough, an elongate, narrow bathymetric low abruptly north of the outcrop belt in the Ohio subsurface. Chronostratigraphic schemes for this interval have been proposed on the basis of conodont and graptolite biostratigraphy, mapping of event beds, and sequence stratigraphy through facies analysis. The relation of the siliciclastic rich offshore records of the "Point Pleasant-Utica" interval, well known to drillers because of its oil and gas potential, with the up-ramp shallow water carbonate dominated equivalents of the Lexington Formation is complicated by convoluted nomenclature, a major, abrupt change in facies, and disparity in the availability and completeness of records. Current genetic models of organic rich shale intervals, such as the Point Pleasant-Utica interval, are still lacking in detail, and will greatly benefit from detailed correlation with shallow water settings where more is understood about paleoclimatic conditions. In order to understand the development and evolution of this Late Ordovician Laurentian basin, it is important to understand the age relationships of depositional processes occurring at a range of depths, particularly in the less well studied epeiric sea setting of the "Point Pleasant-Utica" interval of Ohio and partial lateral equivalent, Lexington Formation of central Kentucky. The outcrop area of central Kentucky, exposed by the later uplift of the Cincinnati Arch, hosts numerous world-class exposures of the Lexington Formation, nearly all of which are representative of the highly fossiliferous, shallow-water marine platform carbonates. These successions display well differentiated depositional sequences, with sharp facies offsets

  12. A re-evaluation of the stratigraphy and sedimentology of the Day Point Formation (Chazy Group): A new look at old reefs

    Falkenberg, J.; Mehrtens, C.J. (Vermont Univ., Burlington, VT (United States). Dept. of Geology)


    The Day Point Formation (Chazy Group, Middle Ordovician) outcrops in the Champlain Valley of New York and Vermont. The stratigraphy of the Day Point Formation is complex, containing lithologic sequences that are unique at different localities around the Champlain Valley. The formation exhibits complex lateral interfingering of seven lithofacies: (1) Highly bioturbated sandstone with symmetrical and bifurcating ripples. (2) Bioturbated, brachiopod rich, wackestone facies. (3) Planar cross-bedded, interlayered sand and sandy packstone. (4) Interlayered sand and shale grading into sand and limestone layers. (5) Grainstone which, at some localities, contains mound-shaped bryozoan reefs, at other localities thin non-reefal sheet-like layers are present. The grainstone also has planar laminated and cross stratified beds. (6) Fine-grained, calcareous sandstone with planar and herringbone cross bedding, which in places contains small bryozoan reefs and thin sheet-reefs. (7) Planar cross bedded packstone containing bryozoan reefs and thin sheet-like non-reefal layers. The thin reefal layers are found where the mound-shaped reefs are absent. The sand units are found only in the lower portion of the Day Point Formation. The bryozoan reefs and non-reefal layers are associated with the sand beds in the lower portion of the Day Point Formation, and either live within the sand or on top of it. The bryozoans that form the non-reefal layers, found in the limestones, are contained within thin layers of sand. In contrast, no sand is found in the upper section of the Day Point Formation, yet the bryozoan reefs flourish.

  13. Volcanic Event Recurrence Rate Model (VERRM): Incorporating Radiometric Ages, Volcanic Stratigraphy and Paleomagnetic Data into a Monte Carlo Simulation to Estimate Uncertainty in Recurrence Rate through Time

    Wilson, J. A.; Richardson, J. A.


    Traditional methods used to calculate recurrence rate of volcanism, such as linear regression, maximum likelihood and Weibull-Poisson distributions, are effective at estimating recurrence rate and confidence level, but these methods are unable to estimate uncertainty in recurrence rate through time. We propose a new model for estimating recurrence rate and uncertainty, Volcanic Event Recurrence Rate Model. VERRM is an algorithm that incorporates radiometric ages, volcanic stratigraphy and paleomagnetic data into a Monte Carlo simulation, generating acceptable ages for each event. Each model run is used to calculate recurrence rate using a moving average window. These rates are binned into discrete time intervals and plotted using the 5th, 50th and 95th percentiles. We present recurrence rates from Cima Volcanic Field (CA), Yucca Mountain (NV) and Arsia Mons (Mars). Results from Cima Volcanic Field illustrate how several K-Ar ages with large uncertainties obscure three well documented volcanic episodes. Yucca Mountain results are similar to published rates and illustrate the use of using the same radiometric age for multiple events in a spatially defined cluster. Arsia Mons results show a clear waxing/waning of volcanism through time. VERRM output may be used for a spatio-temporal model or to plot uncertainty in quantifiable parameters such as eruption volume or geochemistry. Alternatively, the algorithm may be reworked to constrain geomagnetic chrons. VERRM is implemented in Python 2.7 and takes advantage of NumPy, SciPy and matplotlib libraries for optimization and quality plotting presentation. A typical Monte Carlo simulation of 40 volcanic events takes a few minutes to couple hours to complete, depending on the bin size used to assign ages.

  14. Stratigraphy and sedimentology of a basement-onlapping shallow marine sandstone succession, the Charcot Bugt Formation, Middle-Upper Jurassic, East Greenland

    Larsen, M.; Piasecki, S. [Geological Survey of Denmark and Greenland, Copenhagen (Denmark)]. Geocenter; Surlyk, F. [Univ. of Copenhagen, Copenhagen (Denmark)]. Geological Inst.


    A rocky shore developed in early Middle Jurassic times by transgression of the crystalline basement in Milne'Land at the western margin of the East Greenland rift basin. The basement is onlapped by shallow marine sandstones of the Charcot Bugt Formation, locally with a thin fluvial unit at the base. The topography of the onlap surface suggests that a relative sea-level rise of at least 300 m took place in Early Bathonian - Middle Oxfordian times. The sea-level rise was punctuated by relative stillstands and falls during which progradation of the shoreline took place. Palynological data tied to the Boreal ammonite stratigraphy have greatly improved time resolution within the Charcot Bugt Formation, and the Jurassic succession in Milne Land can now be understood in terms of genetically-related depositional systems with a proximal to distal decrease in grain size. The sequence stratigraphic interpretation suggests that translation of the depositional systems governed by relative sea-level changes resulted in stacking of sandstone-dominated falling stage deposits in the Bastern, basinwards parts of Milne Land, whereas thick, remarkably coarsegrained transgressive systems tract deposits formed along the western basin margin. The bulk of the Charcot Bugt Formation consists of stacked sandstone-dominated shoreface units that prograded during highstands. The overall aggradational to backstepping stacking pattem recognised in the Charcot Bugt Formation is comparable to that in the contemporaneous Pelion Formation of the Jameson Land Basin and in correlative units of the mid-Norway shelf and the Northern North Sea. We suggest that the long-term evolution of the depositional systems may have been controlled by long-term eustatic rise acting in concert with relative sea-level changes reflecting regionally contemporaneous phases of rift initiation, dimax and gradual cessation of rifting. (au)

  15. A Major Unconformity Between Permian and Triassic Strata at Cape Kekurnoi, Alaska Peninsula: Old and New Observations on Stratigraphy and Hydrocarbon Potential

    Blodgett, Robert B.; Sralla, Bryan


    A major angular unconformity separates carbonates and shales of the Upper Triassic Kamishak Formation from an underlying unnamed sequence of Permian agglomerate, volcaniclastic rocks (sandstone), and limestone near Puale Bay on the Alaska Peninsula. For the first time, we photographically document the angular unconformity in outcrop, as clearly exposed in a seacliff ~1.3 mi (2.1 km) west of Cape Kekurnoi in the Karluk C?4 and C?5 1:63,360-scale quadrangles. This unconformity is also documented by examination of core chips, ditch cuttings, and (or) open-hole electrical logs in two deep oil-and-gas-exploration wells (Humble Oil & Refining Co.?s Bear Creek No. 1 and Standard Oil Co. of California?s Grammer No. 1) drilled along the Alaska Peninsula southwest of Puale Bay. A third well (Richfield Oil Corp.?s Wide Bay Unit No. 1), south of and structurally on trend with the other two wells, probed deeply into the Paleozoic basement, but Triassic strata are absent, owing to either a major unconformity or a large fault. Here we briefly review current and newly acquired data on Permian and Triassic rocks of the Puale Bay-Becharof Lake-Wide Bay area on the basis of an examination of surface and subsurface materials. The resulting reinterpretation of the Permian and Triassic stratigraphy has important economic ramifications for oil and gas exploration on the Alaska Peninsula and in the Cook Inlet basin. We also present a history of petroleum exploration targeting Upper Triassic reservoirs in the region.

  16. 成因层序地层学的回顾与展望%Looking back and ahead on Genetic Sequence Stratigraphy



    Genetic sequence stratigraphy on the basis of genetic stratigraphic sequence proposed by Galloway (1989) is aparadigm of Exxon's depositional sequence model. A genetic stratigraphic sequence is the sedimentary product of adepositional episode. The sequence consists of three important components: offlap components, onlap or transgres-sive components, and top and base bounding surfaces reflecting maximum marine flooding. The model of genetic stratigraphic sequence is firstly capplied to the northwest Gulf of Mexico Cenozoic basin,U.S.A. Galloway (1989) recognized nine genetic stratigraphic sequences for the Cenozoic strata of the basin. Theextrabasinal fluvial systems and associated depocenters shift significantly from a genetic stratigraphic sequence tothe following sequence. Within each genetic stratigraphic sequence, the paleogeography remains comparatively sta-ble, but depositional styles and patterns between offlap components and onlap or transgressive components changeas relative sea level changes. Galloway (1990) studied the relationship among Paleogene depositional episodes, genetic stratigraphic se-quences, and sediment accumulation rates NW Gulf of Mexico basin. He found that the genetic stratigraphic se-quences record episodes of high supply, punctuated by intervals of low supply and consequent transgressive floodingof the basin margin. Within sequences, depositional rates vary with position relative to the contemporaneous shelfmargin, with depositional system, and between subbasins. Liu and Galloway (1997) studied Tertiary sedimentsupply to the North Sea basin. They concluded that all episodes of Tertiary sedimen supply correlate to source-terrain tectonic pulses. The history of changing source - area relief and resulting topographic grades and relatedchanges in sediment yield into the basin was a principal control on North Sea Cenozoic sequence development. The precepts of genetic sequence stratigraphy were developed from the study of marine basins

  17. Lithology and late postglacial stratigraphy of bottom sediments in isolated basins of the White Sea coast exemplified by a small lake in the Chupa settlement area (Northern Karelia)

    Korsakova, O. P.; Kolka, V. V.; Tolstobrova, A. N.; Lavrova, N. B.; Tolstobrov, D. S.; Shelekhova, T. S.


    The complex lithological, geochemical, geochronological, and micropaleontological (diatoms, spores, pollen) investigations of stratified bottom sediments that constitute facies-variable sedimentary sequences in a small isolated lake located near the upper limit of the sea on the White Sea coast made it possible to define lithostratigraphic units (LSU) forming the complete sedimentary succession in deep parts of isolated basins. It is shown that stratigraphy of heterogeneous sequences is determined by two regional transgressive-regressive cycles in relative sea level fluctuations: alternating late Glacial and Holocene transgressions and regressions. The lower part of a clastogenic clayey-sandy-silty sequence successively composed of freshwater (LSU 1) and brackish-water (LSU 2) sediments of the ice-marginal basins and marine postglacial facies (LSU 3) was formed during the late Glacial glacioeustatic marine transgression. Its upper part formed in different isolated basins at different stages of the Holocene is represented depending on its altimetric position on the coastal slope by costal marine sediments (LSU 4) and facies of the partly isolated inlet (LSU 5). The organogenic sapropelic sequence, which overlies sediments of the marine basin and partly isolated bay, corresponds to lithostratigraphic units represented by Holocene sediments accumulated in the meromictic lake (LSU 6), onshore freshwater basin (LSU 7), and freshwater basin with elevated water mineralization (LSU 8) deposited during maximum development of Holocene transgression and lacustrine sediments (LSU 9) formed in coastal environments during terminal phases of the Holocene. The defined lithostratigraphic units differ from each other in lithological, micropaleontological, and geochemical features reflected in structural and textural properties of their sediments, their composition, inclusions, and composition of paleophytocoenoses and diatom assemblages.

  18. Study on Sequence Stratigraphy of Zhujiang and Zhuhai Formations, Zhu Ⅲ Subbasin, Pearl River Mouth Basin, South China Sea


    The early Miocene in the Zhu Ⅲ subbasin, the Pearl River Mouth basin, includes two formations—Zhujiang and Zhuhai. There are 8 third-order sequences, S1, S2, S3, S4, S5, S6, S7 and S8 from the bottom of Zhuhai to the top of Zhujiang in these two formations. There are only one transgressive systems tract (TST) and one highstand systems tract (HST) in each sequence because the whole Zhu Ⅲ subbasin was located updip the shelf break during sequence deposition. The boundaries and maximum flooding surfaces (mfs) are in good response to both gamma and acoustic log curves in the study area. In seismic profile 1249, sediments obviously onlap over the unconformity (SB0, the bottom of Zhuhai Fm), SB1 and SB2, but obviously over only SB2 in seismic profile 1283 since the well-developed faults in the subbasin. The sand bodies with high porosity and permeability for petroleum migration and accumulation had been reworked by tidal currents before their burial. Hence, the tidal influenced parasequence sets occur both in TST and HST. Through detailed analysis, the sand bodies in TST are more favorable for petroleum to migrate and accumulate than those in HST.

  19. Stratigraphy of two conjugate margins (Gulf of Lion and West Sardinia): modeling of vertical movements and sediment budgets

    Leroux, Estelle; Gorini, Christian; Aslanian, Daniel; Rabineau, Marina; Blanpied, Christian; Rubino, Jean-Loup; Robin, Cécile; Granjeon, Didier; Taillepierre, Rachel


    The post-rift (~20-0 Ma) vertical movements of the Provence Basin (West Mediterranean) are quantified on its both conjugate (the Gulf of Lion and the West Sardinia) margins. This work is based on the stratigraphic study of sedimentary markers using a large 3D grid of seismic data, correlations with existing drillings and refraction data. The post-rift subsidence is measured by the direct use of sedimentary geometries analysed in 3D [Gorini et al., 2015; Rabineau et al., 2014] and validated by numerical stratigraphic modelling. Three domains were found: on the platform (1) and slope (2), the subsidence takes the form of a seaward tilting with different amplitudes, whereas the deep basin (3) subsides purely vertically [Leroux et al., 2015a]. These domains correspond to the deeper crustal domains respectively highlighted by wide angle seismic data. The continental crust (1) and the thinned continental crust (2) are tilted, whereas the intermediate crust, identified as lower continental exhumed crust [Moulin et al., 2015, Afhilado et al., 2015] (3) sagged. The post-break-up subsidence re-uses the initial hinge lines of the rifting phase. This striking correlation between surface geologic processes and deep earth dynamic processes emphasizes that the sedimentary record and sedimentary markers is a window into deep geodynamic processes and dynamic topography. Pliocene-Pleistocene seismic markers enabled high resolution quantification of sediment budgets over the past 6 Myr [Leroux et al., in press]. Sediment budget history is here completed on the Miocene interval. Thus, the controlling factors (climate, tectonics and eustasy) are discussed. Afilhado, A., Moulin, M., Aslanian, D., Schnürle, P., Klingelhoefer, F., Nouzé, H., Rabineau, M., Leroux, E. & Beslier, M.-O. (2015). Deep crustal structure across a young 1 passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment) - II. Sardinia's margin. Bull. Soc. géol. France, 186, ILP Spec. issue, 4

  20. Ground-motion amplification at the Colle di Roio ridge, central Italy: a combined effect of stratigraphy and topography

    Hailemikael, S.; Lenti, L.; Martino, S.; Paciello, A.; Rossi, D.; Mugnozza, G. Scarascia


    Following the Mw 6.3 L'Aquila Earthquake of 2009 April 6, the Colle di Roio village, central Italy, suffered severe building damages. The village is located on top of an elongated carbonate ridge characterized by a complex subsurface structure, a condition prone to seismic amplification due to topographic and stratigraphic effects. We address the role of the subsurface structure and topography in the ground-motion amplification observed at the ridge top. To characterize the subsurface structure of the ridge we performed geological investigations and ambient vibration measurements in single-station as well as 2-D-array configuration. Geological investigations pointed out that the ridge top is characterized by the presence of fractured rock material as a consequence of its anticlinal fold structure. Horizontal-to-vertical spectral ratio (HVSR) processing of ambient vibration records showed a broad peak in the HVSR functions in the frequency range 4-6 Hz and 2-D-array data demonstrated that locally the subsurface structure at the ridge top cannot be considered homogeneous. In summer 2009, we further installed one accelerometric station on the ridge top to experimentally evaluate the site amplification. By means of HVSR analysis of a sample of 18 weak-motion records (H/V), we found that ground-motion amplification occurs in a narrow frequency range centred around 4 Hz with mean ratio amplitude of 6. We also analysed the dependence of seismic amplification on the azimuth by calculating H/V ratios for horizontal components rotated into a range of azimuths. This analysis showed that the higher level of horizontal amplification occurs in the direction perpendicular to the ridge trending direction. With the aim of evaluating the contribution of the topography and the local subsurface structure on the observed seismic amplification, we performed 2-D finite-difference modelling of wave propagation through the ridge, adopting both homogeneous and heterogeneous models. We were

  1. Sedimentology and sequence stratigraphy of the Cretaceous Nanushuk, Seabee, and Tuluvak formations exposed on Umiat Mountain, north-central Alaska

    Houseknecht, David W.; Schenk, Christopher J.


    Upper Cretaceous strata of the upper part of the Nanushuk Formation, the Seabee Formation, and the lower part of the Tuluvak Formation are exposed along the Colville River on the east flank of Umiat Mountain in north-central Alaska. The Ninuluk sandstone, which is the uppermost unit of the Nanushuk Formation, displays a vertical succession of facies indicative of deposition in an upward-deepening estuarine through shoreface setting. A marine-flooding surface lies between the Ninuluk sandstone and organic-rich shale of the basal part of the Seabee Formation. The Ninuluk sandstone and the lower part of the Seabee Formation are interpreted as components of a transgressive-systems tract. The lowest, well-exposed strata in the Seabee Formation are a succession of shoreface sandstone beds in the middle of the formation. Integration of outcrop information and the Umiat No. 11 well log suggests that this sandstone succession rests on a sequence boundary and is capped by a marine-flooding surface. The sandstone succession is interpreted as a lowstand-systems tract. The upper part of the Seabee Formation includes a thick interval of organic-rich shale deposited in a dysaerobic offshore environment, and the gradational Seabee-Tuluvak contact is a coarsening-upward shale-to-sandstone succession deposited in a prodelta/delta-front environment. The observation that the upper part of the Seabee Formation correlates with seismic clinoforms suggests that dysaerobic conditions extended well up onto the prodelta slope during intervals of transgression and highstand. Correlation of the Umiat Mountain outcrop section with well logs and seismic data suggests that sequence boundaries and lowstand shoreface deposits may be common in the Seabee Formation and that wave action may have been important in transporting sand to the paleoshelf margin. These conclusions may contribute to an enhanced understanding of sand distribution in prospective lowstand turbidite deposits in the subsurface of

  2. Conclusions of the Ad-hoc Review Committee (ARC) on the International Commission on Stratigraphy (ICS) of the International Union of Geological Sciences (IUGS) (Paris, 7-8 November 2005)


    @@ Background Following the recommendations of the IUGS Strategic Planning Committee (2000) and IUGS Strategic Action Plan (2001)to appoint Ad-hoc Review Committees (ARCs) to hold reviewsof all IUGS-funded scientific activities on a regular basis, theIUGS Executive Committee decided at its last meeting in Vilnius, Lithuania (March 2005) that an ARC should be convened toreview the IUGS International Commission on. Stratigraphy(ICS). ICS has been part of IUGS since 1965, and the last reviewof ICS by the IUGS was in 1995.

  3. Tentative revision of the global Pliocene-Pleistocene sequences based on the sequence stratigraphy in the Gulf of Mexico

    Wornardt, W.W. Jr. (Micro-Strat, Inc., Houston, TX (United States) Rice Univ., Houston, TX (United States)); Vail, P.R. (Rice Univ., Houston, TX (United States))


    The Pliocene-Pleistocene sequence chronostratigraphy presented in this paper is based on a vast amount of data obtained from more than 100 wells drilled over the past eight years in the south additions and deep-water areas in offshore Texas and Louisiana, Gulf of Mexico. This high-resolution biostratigraphic data base consists of individual checklist with the abundance, diversity, occurrences, and ranges of planktonic and benthic foraminifers and calcareous nannofossils plotted against depth. The benthic foraminifers have been interpreted largely for their paleobathymetric significance and result in a water-depth curve for each well studied. These wells have been further calibrated by having a portion of the study wells tied to sequence stratigraphic interpretations of seismic record sections through a two-way-time log or synthetic seismogram. The Pliocene and Pleistocene is tentatively divided into 14 fourth-order sequences from 3.0 to 0 Ma and three third-order cycles from 5.5 to 3.0 Ma. Each of the cycles is bounded by a sequence boundary and has an age-dateable maximum flooding surface. Depending on location, each sequence may have lowstand, transgressive, and highstand systems tracts within the basin. The age (Ma) of the sequence boundaries are third-order, 5.5, 4.2, 3.8, fourth-order, 3.0, 2.6, 2.4, 1.86, 1.4., 1.0, 0.82, 0.72, 0.62, 0.52, 0.42., 0.32, 0.22, 0.12, and 0.02. Within these sequence boundaries are the 5.0, 4.0, 3.4, 2.7, 2.45, 2.0, 1.47, 1.3, 0.92, 0.76, 0.66, 0.56, 0.46, 0.36, 0.26, 0.16, and 0.06 Ma maximum flooding surfaces, respectively. All of the condensed sections associated with the maximum flooding surfaces, systems tract boundaries, and sequences boundaries in the Pliocene-Pleistocene can be recognized and traced on well logs and seismic record sections in the offshore Texas and Louisiana areas.

  4. From stratigraphy to (inferred) processes: development of the late Pleistocene Po Delta clinothems at millennial to centennial scales

    Pellegrini, Claudio; Asioli, Alessandra; Drexler, Tina; Bohacs, Kevin; Sweet, Michael; Maselli, Vittorio; Gamberi, Fabiano; Rovere, Marzia; Dalla Valle, Giacomo; Trincardi, Fabio


    The 350-m thick succession of the late-Pleistocene Po River Lowstand Delta (PRLD) deposited in just 17 k.y. encompassing the Last Glacial Maximum and contains stratal architecture at a physical scale commonly attributed to much longer time intervals, with complex, systematically varying internal clinothem characteristics. We document clinothem characteristics, stacking patterns, and controls through the integration of seismic-reflection data with sediment attributes, micropaleontology, regional climate, eustacy, and high-resolution age control on the PRLD. Within the PRLD, three clinothem types are characterized by distinctive topset geometry, shelf-edge and onlap-point trajectory, internal seismic facies, and interpreted bottomset deposits: Type A) moderate topset aggradation, ascending shelf-edge trajectories, and thin mass-transport bottomset deposits; Type B) eroded topset, descending shelf-edge trajectories, and bottomset distributary channel-lobe complexes; and Type C) maximal topset aggradation, ascending shelf-edge trajectories, and draped concordant bottomsets. Measured sediment accumulation rates suggest that Type A and C clinothems experienced reduced sediment bypass and delivery to the basin, whereas, Type B clinothems were associated with short intervals of increased sediment export from the shelf to deep water and development of distributary channel-lobe complexes. This interpretation is supported by micropaleontological analyses that highlight increased delivery of sediment and fresh water to the basin during the progradation of Type B clinothems, as suggested by the reduced occurrence of Cassidulina laevigata carinata and the peak abundance of Nonion spp. Each clinothem formed in a very short interval, from 0.4 to 4.7 k.y., contemporaneous with significant eustatic and climate changes. While changes in stacking patterns at these temporal scales have previously been observed in modern deltaic clinothems, the significance of our study is that we have

  5. Continental Shelf Morphology and Stratigraphy Offshore San Onofre, CA: The Interplay Between Rates of Eustatic Change and Sediment Supply

    Klotsko, Shannon; Driscoll, Neal W.; Kent, Graham; Brothers, Daniel


    New high-resolution CHIRP seismic data acquired offshore San Onofre, southern California reveal that shelf sediment distribution and thickness are primarily controlled by eustatic sea level rise and sediment supply. Throughout the majority of the study region, a prominent abrasion platform and associated shoreline cutoff are observed in the subsurface from ~ 72 to 53 m below present sea level. These erosional features appear to have formed between Melt Water Pulse 1A and Melt Water Pulse 1B, when the rate of sea-level rise was lower. There are three distinct sedimentary units mapped above a regional angular unconformity interpreted to be the Holocene transgressive surface in the seismic data. Unit I, the deepest unit, is interpreted as a lag deposit that infills a topographic low associated with an abrasion platform. Unit I thins seaward by downlap and pinches out landward against the shoreline cutoff. Unit II is a mid-shelf lag deposit formed from shallower eroded material and thins seaward by downlap and landward by onlap. The youngest, Unit III, is interpreted to represent modern sediment deposition. Faults in the study area do not appear to offset the transgressive surface. The Newport Inglewood/Rose Canyon fault system is active in other regions to the south (e.g., La Jolla) where it offsets the transgressive surface and creates seafloor relief. Several shoals observed along the transgressive surface could record minor deformation due to fault activity in the study area. Nevertheless, our preferred interpretation is that the shoals are regions more resistant to erosion during marine transgression. The Cristianitos fault zone also causes a shoaling of the transgressive surface. This may be from resistant antecedent topography due to an early phase of compression on the fault. The Cristianitos fault zone was previously defined as a down-to-the-north normal fault, but the folding and faulting architecture imaged in the CHIRP data are more consistent with a

  6. Stratigraphy of the Archean western Superior Province from P- and S-wave receiver functions: Further evidence for tectonic accretion?

    Angus, D. A.; Kendall, J.-M.; Wilson, D. C.; White, D. J.; Sol, S.; Thomson, C. J.


    The Archean western Superior Province in Canada represents the nucleus of the North American continent whose origin has been speculated to be the result of widespread crustal accretion some 2.7 Ga ago. In this paper, crustal and upper-mantle seismic discontinuities beneath the western Superior Province of the Canadian shield are imaged with teleseismic P-to-S and S-to-P converted phases using the receiver function method. Three crustal discontinuities are observed: the Moho, ranging in depth between 38 and 47 km and dipping to the south; and two intra-crustal discontinuities having depths of approximately 15 and 30 km. The crustal discontinuities undulate laterally and often lose continuity, possibly indicating an imbricated structure and/or regions of velocity gradients. In the shallow lithosphere, a positive discontinuity is imaged at approximately 65 km depth and is consistent with earlier refraction and wide-angle reflection results. Additionally, two zones of negative receiver function amplitudes at 55 km depth are observed and are coincident with a region of anomalous tomographic low P- and S-wave velocities as well as a zone of high electrical conductivity. The images for the crust and shallow upper-mantle, when integrated with previous geophysical studies, are consistent with ideas of continental root formation due to imbrication of Archean subducted material and accretion of island arcs observed in surface geology.

  7. Proximal pyroclastic deposits from the 1989-1990 eruption of Redoubt Volcano, Alaska - stratigraphy, distribution, and physical characteristics

    Gardner, C.A.; Neal, C.A.; Waitt, R.B.; Janda, R.J.


    More than 20 eruptive events during the 1989-1990 eruption of Redoubt Volcano emplaced a complex sequence of lithic pyroclastic-flow, -surge, -fall, ice-diamict, and lahar deposits mainly on the north side of the volcano. The deposits record the changing eruption dynamics from initial gas-rich vent-clearing explosions to episodic gas-poor lava-dome extrusions and failures. The repeated dome failures produced lithic pyroclastic flows that mixed with snow and glacial ice to generate lahars that were channelled off Drift glacier into the Drift River valley. Some of the dome failures occurred without precursory seismic warning and appeared to result solely from gravitational instability. Material from the disrupted lava domes avalanched down a steep, partly ice-filled canyon incised on the north flank of the volcano and came to rest on the heavily crevassed surface of the piedmont lobe of Drift glacier. Most dome-collapse events resulted in single, monolithologic, massive to reversely graded, medium- to coarse-grained, sandy pyroclastic-flow deposits containing abundant dense dome clasts. These deposits vary in thickness, grain size, and texture depending on distance from the vent and local topography; deposits are finer and better sorted down flow, thinner and finer on hummocks, and thicker and coarser where ponded in channels cut through the glacial ice. The initial vent-clearing explosions emplaced unusual deposits of glacial ice, snow, and rock in a frozen matrix on the north and south flanks of the volcano. Similar deposits were described at Nevado del Ruiz, Columbia and have probably been emplaced at other snow-and-ice-clad volcanoes, but poor preservation makes them difficult to recognize in the geologic record. In a like fashion, most deposits from the 1989-1990 eruption of Redoubt Volcano may be difficult to recognize and interpret in the future because they were emplaced in an environment where glacio-fluvial processes dominate and quickly obscure the primary

  8. Stratigraphy and structural setting of Upper Cretaceous Frontier Formation, western Centennial Mountains, southwestern Montana and southeastern Idaho

    Dyman, T.S.; Tysdal, R.G.; Perry, W.J.; Nichols, D.J.; Obradovich, J.D.


    Stratigraphic, sedimentologic, and palynologic data were used to correlate the Frontier Formation of the western Centennial Mountains with time-equivalent rocks in the Lima Peaks area and other nearby areas in southwestern Montana. The stratigraphic interval studied is in the middle and upper parts (but not uppermost) of the formation based on a comparison of sandstone petrography, palynologic age data, and our interpretation of the structure using a seismic line along the frontal zone of the Centennial Mountains and the adjacent Centennial Valley. The Frontier Formation is comprised of sandstone, siltstone, mudstone, limestone, and silty shale in fluvial and coastal depositional settings. A distinctive characteristic of these strata in the western Centennial Mountains is the absence of conglomerate and conglomeratic sandstone beds. Absence of conglomerate beds may be due to lateral facies changes associated with fluvial systems, a distal fining of grain size, and the absence of both uppermost and lower Frontier rocks in the study area. Palynostratigraphic data indicate a Coniacian age for the Frontier Formation in the western Centennial Mountains. These data are supported by a geochronologic age from the middle part of the Frontier at Lima Peaks indicating a possible late Coniacian-early Santonian age (86.25 ?? 0.38 Ma) for the middle Frontier there. The Frontier Formation in the western Centennial Mountains is comparable in age and thickness to part of the Frontier at Lima Peaks. These rocks represent one of the thickest known sequences of Frontier strata in the Rocky Mountain region. Deposition was from about 95 to 86 Ma (middle Cenomanian to at least early Santonian), during which time, shoreface sandstone of the Telegraph Creek Formation and marine shale of the Cody Shale were deposited to the east in the area now occupied by the Madison Range in southwestern Montana. Frontier strata in the western Centennial Mountains are structurally isolated from other

  9. Toward a three-dimensional vision of the different compositions and the stratigraphy of the painting L'Homme blesse by G. Courbet: coupling SEM-EDX and confocal micro-XRF

    Reiche, Ina [Universite Paris 06 - Sorbonne Universites, Laboratoire d' Archeologie Moleculaire et Structurale, UMR 8220 CNRS UPMC, Paris (France); National Museums in Berlin-Prussian Cultural Heritage Foundation, Rathgen Research Laboratory, Berlin (Germany); Mueller, Katharina [Universite Paris 06 - Sorbonne Universites, Laboratoire d' Archeologie Moleculaire et Structurale, UMR 8220 CNRS UPMC, Paris (France); Mysak, Erin [Centre de Recherche et de Restauration des Musees de France (C2RMF), Paris (France); Harvard Art Museums, Straus Center for Conservation and Technical Studies, Cambridge, MA (United States); Yale University, Institute for the Preservation of Cultural Heritage, New Haven, CT (United States); Eveno, Myriam; Mottin, Bruno [Centre de Recherche et de Restauration des Musees de France (C2RMF), Paris (France)


    Examination of Gustave Courbet's L'Homme blesse (Musee d'Orsay, Paris), a painting with three successive compositions on a single canvas, was undertaken with scanning electron microscopy coupled with an energy-dispersive X-ray analyzing system (SEM-EDX) on cross sections taken in the 1970s at the Laboratoire de Recherche de Musees de France, Paris and confocal X-ray fluorescence spectroscopy (CXRF) analysis adjacent to the sample locations of the three previously removed cross sections. Recent developments of in situ techniques such as CXRF have enabled investigation of the chemical composition of complicated paint layering without sampling. Here, we compare depth profiling by CXRF analysis with SEM-EDX data from cross sections with the goal of understanding how well CXRF data represent such a complicated paint stratigraphy. Beyond suggesting the paint palettes for Courbet's three compositions, this new data provide insight into the complex paint layer stratigraphy of eight or more layers and serve as the basis for interpreting further analyses by scanning XRF and CXRF of additional areas of interest on the painting. Data from these additional locations will be discussed in a forthcoming paper. (orig.)

  10. Stratigraphy of the Basalt Flows of the Formação Serra Geral (Ribeirão Preto - SP Based on Physical Geology, Petrography and Geochemistry

    Amélia João Fernandes


    Full Text Available The study of the physical geology and geochemistry of the basalts of Ribeirão Preto was part of a hydrogeologicalresearch that aimed at investigating the recharge of the Guarani Aquifer System (SAG through the basalts of the SerraGeral Aquifer (ASG, a project shortly named FRATASG. In addition to hydrogeological methods, the research demandeda detailed geological investigation, which is essential for the elaboration of conceptual models of groundwater circulationin complex aquifers, as is the case of the fractured basalts of the ASG. Thus, the study encompassed field work for thedescription of the macroscopic aspects and relationships among the basalts and the underlying sandstones, as well as, rocksampling and petrographic and chemical analysis. Furthermore, the use of lithologic logs of five wells drilled in FRATASG project was essential for the establishment of the subsurface basalt stratigraphy. The study concluded that, in Bonfim Paulista region,there are four basalt floods, namely B1, B2, B3 and B4. The B4 occurrence is very restricted as it was largely eroded. B1 and B2average thicknesses are 45 and 60 m, respectively. All four basalts are of sheet-like lobe types and were probably emplaced by inflation,B1 being the one that presents more evidence in that respect. B1 presents a thick vesicular top and, as well as B2, can show more thanone vesicular layer at the top. Columnar joints were observed in B2 and B3 and are more remarkable in B3, where a lower colonnadetier (B3-C is overlain by an entablature layer (B3-E. B3 is the thickest flow (75 to 105 m and contains irregular and roughly roundpatches of hydraulic breccia in B3-C or along sub-horizontal fractures that allow the circulation of fluids (groundwater at the present. The chemical composition of B3 is homogeneous and very different from B1 and B2 with regard to several oxides (Al2O3, P2O5, Fe2O3, TiO2 e MgO and trace elements (Ni, Zn, Cu, Y. B1 is very different from B2 with regard

  11. Sequence stratigraphy, organic petrology and chemistry applied to the upper and lower coal seams in the Candiota Coalfield, Parana Basin, RS, Brazil

    Oliveira, J.S. de; Kalkreuth, W. [Instituto de Geociencias, UFRGS, Porto Alegre (Brazil)


    The Permian age coal seams in the Candiota Coalfield represent the largest coal deposit of the country. Currently two seams are mined, called ''Camada Candiota Superior'' and ''Camada Candiota Inferior''. The other coal seams of the coalfield, seams S1-S9 (upper seams) and I1-I5 (lower seams) have as yet not been exploited. The objective of this paper is to perform a detailed sequence stratigraphic, petrologic and chemical study of the upper and lower coal seams, thereby generating data for assisting in the development and better use of the coal-bearing interval. The methodology includes application of the concepts of sequence stratigraphy, which includes the lithological interpretation of the core to establish the depositional environments and genetic correlation between facies associations to define parasequences and bounding surfaces; coal petrology (analysis of the reflectance of vitrinite, determination of the petrographic composition of the coals by maceral analyses), and chemical analyses such as sulphur determination, proximate analyses (ash, moisture, volatile matter, and fixed carbon), and elemental analyses. Three main depositional systems were so far identified: alluvial fan, fluvial system, lagoonal estuary system. This study shows that coal development was controlled by accommodation/accumulation rates, with coal seams with greater thickness and lateral continuity being formed within the transgressive systems tract (lagoonal depositional system) of parasequence 2 (PS2), indicating that the accumulation rates of the peat and distribution of the coal seams were controlled by stratigraphic setting. Vitrinite reflectances for the upper and lower coal seams are indicative of subbituminous rank (Rrandom = 0.36-0.47%), with evidence that anomalously low reflectance values are related to high mineral-matter contents. Maceral composition is highly variable, with some coal seams being extremely rich in inertinite (up to

  12. Insights into the October-November 2010 Gunung Merapi eruption (Central Java, Indonesia) from the stratigraphy, volume and characteristics of its pyroclastic deposits

    Cronin, Shane J.; Lube, Gert; Dayudi, Devi S.; Sumarti, Sri; Subrandiyo, S.; Surono


    The 2010 eruption of Merapi was the second most deadly in the historic record of this volcano, claiming over 380 lives. By relating the observations of this eruption with detailed examination of deposit distribution, stratigraphy and sedimentology, a reconstruction of the properties of the pyroclastic density currents (PDCs) is presented, including the valley controlled block-and-ash flows (BAFs) and widespread, energetic pyroclastic surges. The distribution, volume and mobility characteristics of all types of PDC during the eruption sequence show evidence for levels of intensity unseen since the large-scale 1872 and 1930 eruption phases, especially during the climactic events of October 26 and November 5. Many tephra falls interbedded with PDC units show that most dome-collapse events occurred along with and between explosive vulcanian eruptions. The 2010 eruption produced very long-runout BAFs, reaching 16.1 km in the Kali Gendol on November 5. This runout could be explained by its large-volume (20 million m3), around 10 times that of previous Merapi BAFs during the last 130 years. Major avulsion of these dense BAFs to form overbank deposits became more common through the eruptive sequence as the valley was progressively filled with successive PDC deposits. Spreading avulsed BAFs were a particular hazard downstream of ~ 10 km where the landscape is less dissected. Less clear, however, is why pyroclastic surges extended up to 10 km from the vent on November 5 and > 6.4 km on October 26. These expanded much farther from BAF margins (~ 2 km) than ever seen before at Merapi. In one location they were decoupled from valley-centered BAFs with high momentum, traveling initially laterally across steep valley systems, before draining downslope. At this site, on the western side of the upper Gendol at around 3 km from source, surge decoupling was apparently exacerbated by upstream collision and deflection of high-flux, hot and gas-rich BAFs against the cliffs of Gunung

  13. Geologic map and upper Paleozoic stratigraphy of the Marble Canyon area, Cottonwood Canyon quadrangle, Death Valley National Park, Inyo County, California

    Stone, Paul; Stevens, Calvin H.; Belasky, Paul; Montañez, Isabel P.; Martin, Lauren G.; Wardlaw, Bruce R.; Sandberg, Charles A.; Wan, Elmira; Olson, Holly A.; Priest, Susan S.


    This geologic map and pamphlet focus on the stratigraphy, depositional history, and paleogeographic significance of upper Paleozoic rocks exposed in the Marble Canyon area in Death Valley National Park, California. Bedrock exposed in this area is composed of Mississippian to lower Permian (Cisuralian) marine sedimentary rocks and the Jurassic Hunter Mountain Quartz Monzonite. These units are overlain by Tertiary and Quaternary nonmarine sedimentary deposits that include a previously unrecognized tuff to which we tentatively assign an age of late middle Miocene (~12 Ma) based on tephrochronologic analysis, in addition to the previously recognized Pliocene tuff of Mesquite Spring. Mississippian and Pennsylvanian rocks in the Marble Canyon area represent deposition on the western continental shelf of North America. Mississippian limestone units in the area (Tin Mountain, Stone Canyon, and Santa Rosa Hills Limestones) accumulated on the outer part of a broad carbonate platform that extended southwest across Nevada into east-central California. Carbonate sedimentation was interrupted by a major eustatic sea-level fall that has been interpreted to record the onset of late Paleozoic glaciation in southern Gondwana. Following a brief period of Late Mississippian clastic sedimentation (Indian Springs Formation), a rise in eustatic sea level led to establishment of a new carbonate platform that covered most of the area previously occupied by the Mississippian platform. The Pennsylvanian Bird Spring Formation at Marble Canyon makes up the outer platform component of ten third-order (1 to 5 m.y. duration) stratigraphic sequences recently defined for the regional platform succession. The regional paleogeography was fundamentally changed by major tectonic activity along the continental margin beginning in middle early Permian time. As a result, the Pennsylvanian carbonate shelf at Marble Canyon subsided and was disconformably overlain by lower Permian units (Osborne Canyon and

  14. Ice-Atmosphere Interactions on the Devon Ice Cap, Canada: The Effects of Climate Warming on Surface Energy Balance, Melting, and Firn Stratigraphy

    Gascon, Gabrielle

    In order to better constrain the magnitude of projected sea-level rise from Canadian Arctic glaciers during the 21st century warming, it is critical to understand the environmental mechanisms that enhance surface warming and melt, and how the projected increase in surface melt will translate into increased runoff. Between 2004 and 2010, a 4 °C increase in mean air summer temperature, and a 6.1 day yr-1 increase in melt season duration were observed on the Devon Ice Cap, Nunavut. At the same time, a combination of strengthening of the 500 hPa ridge over the Arctic in June-July, and more frequent south-westerly low-pressure systems in August after 2005 created atmospheric conditions that contributed to an increase in the surface energy balance of the ice cap. At 1400m elevation, these changes led to a doubling of the available melt energy and surface melt between 2007 and 2010. Currently, refreezing of meltwater in firn buffers the relationship between increased surface melt and runoff. Between 2007 and 2012, increased meltwater percolation and infiltration ice formation associated with high surface melt rates modified the stratigraphy of firn in the ice cap's accumulation area very substantially. Growth of a 0.5-4.5 m thick ice layer that filled much of the pore volume of the upper part of the firn reduced vertical percolation of meltwater into deeper parts of the firn. This progressively limited the water storage potential of the firn reservoir, and likely caused a significant increase in surface runoff. An evaluation of the snowpack model Crocus against ground observations for the period 2004-2012 showed that, although the model simulated observed density/depth profiles relatively well at all sites, its representation of heterogeneous percolation as a homogeneous process created conditions that favoured excessive near-surface freezing. At the same time, Crocus's parameterization of the permeability of ice layers forced meltwater to percolate through them

  15. The Middle Jurassic basinal deposits of the Surmeh Formation in the Central Zagros Mountains, southwest Iran: Facies, sequence stratigraphy, and controls

    Lasemi, Y.; Jalilian, A.H.


    The lower part of the Lower to Upper Jurassic Surmeh Formation consists of a succession of shallow marine carbonates (Toarcian-Aalenian) overlain by a deep marine basinal succession (Aalenian-Bajocian) that grades upward to Middle to Upper Jurassic platform carbonates. The termination of shallow marine carbonate deposition of the lower part of the Surmeh Formation and the establishment of deep marine sedimentation indicate a change in the style of sedimentation in the Neotethys passive margin of southwest Iran during the Middle Jurassic. To evaluate the reasons for this change and to assess the basin configuration during the Middle Jurassic, this study focuses on facies analysis and sequence stratigraphy of the basinal deposits (pelagic and calciturbidite facies) of the Surmeh Formation, referred here as 'lower shaley unit' in the Central Zagros region. The upper Aalenian-Bajocian 'lower shaley unit' overlies, with an abrupt contact, the Toarcian-lower Aalenian platform carbonates. It consists of pelagic (calcareous shale and limestone) and calciturbidite facies grading to upper Bajocian-Bathonian platform carbonates. Calciturbidite deposits in the 'lower shaley unit' consist of various graded grainstone to lime mudstone facies containing mixed deep marine fauna and platform-derived material. These facies include quartz-bearing lithoclast/intraclast grainstone to lime mudstone, bioclast/ooid/peloid intraclast grainstone, ooid grainstone to packstone, and lime wackestone to mudstone. The calciturbidite layers are erosive-based and commonly exhibit graded bedding, incomplete Bouma turbidite sequence, flute casts, and load casts. They consist chiefly of platform-derived materials including ooids, intraclasts/lithoclasts, peloids, echinoderms, brachiopods, bivalves, and open-ocean biota, such as planktonic bivalves, crinoids, coccoliths, foraminifers, and sponge spicules. The 'lower shaley unit' constitutes the late transgressive and the main part of the highstand

  16. Estratigrafía del Valle de Luracatao (Valle Calchaquí, Noroeste Argentino: nueva propuesta Stratigraphy of Luracato Valley (Calchaquí Valley, Norwestern Argentina: New proposal

    Patricio Augusto Payrola Bosio


    (Balbuena and Santa Barbara Subgroups stages. Then and superimposed to the rift, broad foreland basin was generated. The Payogastilla Group represents the Andean synorogenic filling in the Calchaquí Valley; its base records the Paleogene deformation and inversion tectonics of this zone of the Eastern Cordillera. The Luracatao valley (western branch of the Calchaquí Valley preserves a thick sedimentary sequence designed as the Luracatao Formation of possible Oligocene age in previous regional maps. This paper presents a redefinition of the stratigraphy of the Luracatao valley based on field works of regional scale, stratigraphic logs and detailed structural mapping. The analyses of sedimentary facies and facies association and the identification of stratigraphic unconformities allow identifying the units of the Santa Bárbara Subgroup (Mealla Formation, Maíz Gordo Formation and Lumbrera Formation and of the Payogastilla Group (Quebrada de los Colorados Formation among the levels previously assigned to the Luracatao Formation. Special importance has the identification of an unconformity between Santa Bárbara Subgroup and Quebrada de los Colorados Formation that integrated to paleontological data allow us interpret this unconformity as the record of the first Cenozoic deformation events. Based on the redefinition of the Luracatao Valley stratigraphic column, this paper proposes to replace the Luracatao Formation by the respective units identified.

  17. New considerations on the stratigraphy and environmental context of the oldest (2.34 Ma) Lokalalei archaeological site complex of the Nachukui Formation, West Turkana, northern Kenya Rift

    Tiercelin, Jean-Jacques; Schuster, Mathieu; Roche, Hélène; Brugal, Jean-Philippe; Thuo, Peter; Prat, Sandrine; Harmand, Sonia; Davtian, Gourguen; Barrat, Jean-Alix; Bohn, Marcel


    At the northwest end of the Lake Turkana Basin (northern Kenya Rift), intensive fieldwork conducted on the Plio-Pleistocene fluvio-lacustrine Nachukui Formation by the National Museums of Kenya and the West Turkana Archaeological Project (WTAP), led to the discovery of more than 50 archaeological sites aged between 2.4 and 0.7 Ma. Among them is the Lokalalei archaeological site complex, which includes the two oldest archaeological sites (2.34 Ma) found in the Kenyan segment of the East African Rift System. The environmental background of the two sites was described as a succession of ephemeral streams with floodplain palaeosols in which the archaeological sites are situated, bordering the western bank of a large axial meandering river flowing southward. The Lokalalei 1 (LA1) and Lokalalei 2C (LA2C) archaeological sites are of extreme importance in terms of knowledge of hominins' knapping activities. The stratigraphic position of the LA1 and LA2C sites as well as implications on the technical differences between the two sites have been successively discussed by Roche et al. (1999), Brown and Gathogo (2002), and Delagnes and Roche (2005). In terms of stratigraphic position, Lokalalei 2C was estimated to be slightly higher in the section (i.e. younger) than Lokalalei 1. An alternative stratigraphic correlation was proposed by Brown and Gathogo (2002), who suggested that LA2C site should have been approximately 100,000 years younger than LA1. New considerations on the stratigraphy and environmental context of the Lokalalei sites have been developed following controversy on the stratigraphic position and time interval between the LA1 and LA2C sites. High-resolution lithostratigraphic work based on bed-to-bed field correlations, facies sedimentology and tephra geochemistry confirms that the LA2C site is slightly higher in the section than the LA1 site by about 11.20 m. This represents a time interval of ˜74,000 years based on an assumed sedimentation rate of 152 mm

  18. Study of Sequence Stratigraphy on Mesoprotozoic and Cambrian Stratum in Northern Henan Province%豫北地区中元古界-寒武系层序地层研究



    豫北地区中元古界-寒武系岩层出露广泛,露头良好,层位稳定,沉积构造发育。是层序地层研究的理想区域。通过剖面基本层序研究、沉积相研究及区域追索进行了层序地层划分的探讨。共识别出二个I型(SB1)层序界面和12个Ⅱ型(SB2)层序界面,识别出2个超序(Ⅱ级层序,编号Ⅱ1-Ⅱ3)及15个层序(Ⅲ级层序,编号Ⅲ1-Ⅲ15)。%The Mesoprotozoic and Cambrian stratum were preserved well in Northern region of Henan Province, and the outcrops are in good condition to be researched. The sequence of these stratum is very steady and the sedimentary structures are typical for study. So, Northern region of Henan Province is a ideal research area for sequence stratigraphy. Through the research of section, sedimentary facies and regional survey, this paper made a discussion on the basic sequence stratigraphy. Two type I Sedimentary sequence interface (SB1) and twelve type ⅡSedimentary sequence interface (SB2) are found and two super sequence (Ⅱ level sequence and titled Ⅱ1- Ⅱ2) and fifteen sequence (Ⅲ level sequence and titled Ⅲ1- Ⅲ 15 ) are identified .

  19. Advances through collaboration: sharing seismic reflection data via the Antarctic Seismic Data Library System for Cooperative Research (SDLS)

    Wardell, N.; Childs, J. R.; Cooper, A. K.


    The Antarctic Seismic Data Library System for Cooperative Research (SDLS) has served for the past 16 years under the auspices of the Antarctic Treaty (ATCM Recommendation XVI-12) as a role model for collaboration and equitable sharing of Antarctic multichannel seismic reflection (MCS) data for geoscience studies. During this period, collaboration in MCS studies has advanced deciphering the seismic stratigraphy and structure of Antarctica’s continental margin more rapidly than previously. MCS data compilations provided the geologic framework for scientific drilling at several Antarctic locations and for high-resolution seismic and sampling studies to decipher Cenozoic depositional paleoenvironments. The SDLS successes come from cooperation of National Antarctic Programs and individual investigators in “on-time” submissions of their MCS data. Most do, but some do not. The SDLS community has an International Polar Year (IPY) goal of all overdue MCS data being sent to the SDLS by end of IPY. The community science objective is to compile all Antarctic MCS data to derive a unified seismic stratigraphy for the continental margin – a stratigraphy to be used with drilling data to derive Cenozoic circum-Antarctic paleobathymetry maps and local-to-regional scale paleoenvironmental histories.

  20. New seismic attributes and methodology for automated stratigraphic, structural, and reservoir analysis

    Randen, Trygve; Reymond, Benoit; Sjulstad, Hans Ivar; Soenneland, Lars


    Seismic stratigraphy represents an attractive framework for interpretation of 3-D data. This presentation is an introduction to a set of primitives that will enable guided interpretation of seismic signals in the framework of seismic stratigraphy. A method capable of automatic detection of terminations is proposed. The new procedure can be run on the entire seismic volume or it may be restricted to a limited time interval and detects terminations in an unguided manner without prior interpretation. The density of terminations can be computed. The procedure may alternatively be guided by pre-existing interpretation, e.g. detecting terminations onto an interpreted horizon. In such a case, the density of terminations will be a new surface attribute. 6 refs., 3 figs.

  1. Sequence Stratigraphy Characteristics and Filling Evolution Models of Paleogene in Baiju Sag, Subei Basin%苏北盆地白驹凹陷古近系层序地层特征及充填演化模式

    魏祥峰; 张廷山; 黄静; 梁兴; 姚秋昌; 汤兴友


    根据陆相断陷盆地层序界面在电测曲线和地震剖面上的识别标志、岩石类型组合特点以及古生物资料等方面的特征,在苏北盆地白驹凹陷古近系共识别出6个层序界面,划分出1个超层序组、2个超层序、5个三级层序,其中SQ1、SQ2~SQ4分别为断陷Ⅰ幕初始断陷、断陷-坳陷转化阶段的湖泊层序,SQ5为断陷Ⅲ幕断陷收敛阶段的河流层序.根据盆地幕式构造演化、气候条件以及物源供给的条件不同,建立了初始断陷阶段、断陷-坳陷转换阶段和断陷收敛阶段3种层序地层充填模式,认为不同构造演化阶段的充填序列、体系域构成和砂体发育存在显著的差异.初步分析了不同层序充填演化模式与油气的关系,认为断陷Ⅰ幕的断陷-坳陷转换阶段的充填层序低位体系域和高位体系域砂体与湖侵体系域优质烃源岩配置关系最好,成藏条件最优越.%Based on the identification features of stratigraphic sequences of the continental faulted basin along electric logging curves and seismic profiles as well as the characteristics of lithologic combination and palaeontological data, the authors identified six Paleogene sequence boundaries in Baiju sag of Subei basin and divided the Paleogene into one super sequence group, two super sequences, and five sequences. SQ1 and SQ2-SQ4 are lacustrine sequences developed in the initial faulting phase and faulting-depression stage of faulting episode I, while SQ5 is the fluvial sequence developed in the faulting convergence stage of faulting episode III. Based on the episodic tectonic evolution, different climate conditions and suppy of sediments for the basin in each evolution phase, the authors established three kinds of sequence stratigraphy filling evolution models composed of initial faulting phase, faulting-depression stage and faulting convergence stage. It is thought that differenttectono-evolutionary stages have significantly different

  2. Benthic foraminifera across the K/Pg boundary in the Brazos River area (Texas) and Stevns Klint (Denmark): sequence stratigraphy, sea level change and extinctions.

    Hart, Malcolm; Smart, Christopher; Searle, Sarah; Feist, Sean; Leighton, Andrew; Price, Gregory; Twitchett, Richard


    sea floor into the range of storm wave base and that this is what is indicated by the "Event Bed". There are a number of water-depth changes in the famous Stevns Klint succession in Denmark, although the majority of the benthic taxa are different. All belong to the normal Chalk Sea assemblage of North West Europe. The planktic assemblage in Denmark is limited and there are no aragonitic taxa (preservation problems). Benthic foraminifera are rare, though generally more abundant in the chalks immediately below the K/T boundary. Work on material from Denmark and the Brazos River successions is on-going including a more detailed assessment of the various morphogroups represented. The presence of an unusual "foraminiferal sand" within the lowermost Paleocene of the Cottonmouth Creek succession has yet to be fully described and its presence is not fully understood (environmental control or re-deposition?). A sequence stratigraphical interpretation of the successions in Texas and Denmark has shown parallel changes in sea level (of the same magnitude in both areas) that are coincident with the major lithological changes. The most significant feature is a fall in sea level some tens of thousands of years before the K/Pg boundary. Cushman, J. A. 1946. Upper Cretaceous Foraminifera of the Gulf Coastal Region of the United States and adjacent areas. U. S. Geological Survey, Professional Paper, 206, 1 - 241. Gale, A. S. 2006. The Cretaceous-Palaeogene boundary on the Brazos River, Falls County, Texas: is there evidence for impact-induced tsunami sedimentation? Proceedings of the Geologists' Association, London, 117, 173 - 185. Keller, G., Abramovich, S., Berner, Z. & Adatte, T. 2009. Biotic effects of the Chicxulub Impact, K-T catastrophe and sea level change in Texas. Palaegeography, Palaeoclimatology, Palaeoecology, 271, 52 - 68. Yancey, T. E. 1996. Stratigraphy and depositional environments of the Cretaceous-Tertiary Boundary Complex and Basal Paleocene section, Brazos River

  3. Revised Stratigraphy of The Nallıhan-Dudaş (Beypazarı) Area and Significance of the Campanian-Maastrichtian Reef Occurrences Based on the Foraminiferal and Rudist Data

    Görmüş, Muhittin; Sami Us, Muhammed; Özer, Sacit; Tekin, Erdoǧan; Akpınar, Serap; Kabakcı, Büşra


    Transgressive to regressive succession of the Cretaceous Period and Cretaceous Paleogene boundary from the Nallıhan-Beypazarı area have significant data to interpret the past geological history of northwestern Turkey. In the literature, main scientific differences are seen on the formation/lithodem names, their ages, contact relations and environmental interpretations. In the study, a revision has been made for a proper stratigraphy of the area. For the revised stratigraphy, the obtained results from our field and laboratory works and the literature information were used. The following stratigraphy were established from basement to top: the Permo-Triassic aged Sekli metamorphics, Jurassic to lower Cretaceous Soǧukçam formation, Campanian to Maastrichtian aged Dereköy Group-Haremiköy conglomerates, Çeǧiköy reefs, Nardin formation (Seben formation), Taraklı formation; the Paleogene aged Kızılçay group including Kızılbayır formation, Karaköy volcanoclastics, Selvipınar limestone, the Miocene-Pliocene terrestrial sediments, Çoraklar formation, Hırka formation, Akpınar formation, Çayırhan formation, Teke volkanics, Bozbelen formation, Kirmir formation. The main unconformities are between Jura and Campanian, Maastrichtian and Paleogene, Eocene and Miocene times. Among the geological units, the Çeǧiköy reefs having rich rudist fauna overlie the Haremiköy conglomerates in both sides at the north-Yeşilyurt village and at the south-Gökçeöz village. Another outcrop, Emincik is between two mentioned villages. Biohermal reefs mainly includes very rich rudists up to 40 centimetres in size around the Yeşilköy such as: Pironaea polystyla, Vaccinites loftusi, Hippurites sublaevis. Larger foraminifera Orbitoides medius, O. apiculatus, Siderolites calcitrapoides, Pseodosiderolites vidali are also common in the fore reef areas. Around the Gökçeöz at the south part, the identified rudists are as follows: Vaccinites sp., Hippurites aff. sublaevis

  4. Comment on “Stratigraphy, petrography and dispersion of the lower Permian syn-eruptive deposits in the Viar Basin, Spain” by S. Sierra, C. Moreno and E. Pascual [Sedimentary Geology 217 (2009) 1-29

    Wagner, R. H.; Mayoral, E.


    Comments are provided on a published paper on "Lower Permian" strata in SW Spain [S. Sierra, C. Moreno and E. Pascual, Stratigraphy, petrography and dispersion of the lower Permian syn-eruptive deposits in the Viar Basin, Spain, Sedimentary Geology 217 (2009) 1-29], which failed to take into account up-to-date information on this most southerly occurrence in western Europe. This generally lacustrine basin commenced with valley fill deposits in a deeply incised palaeotopography and contains mainly red beds with two basaltic intervals and a major acidic volcanic episode linked to a nearby volcanic centre to the Northeast. The stratigraphic succession shows southeasterly onlap. Although a syn-sedimentary fault has been postulated on the NE basin margin, the field evidence disproves this notion as well as the assumption that this "Early Permian" basin would have been controlled by a rejuvenated Ossa-Morena/South Portuguese boundary fault. In fact, this basin lies within the (former) area of Ossa-Morena.

  5. Stratigraphy and eruption ages of deposits at the southeast side of Nishiyama volcano, Hachijo island during the last 2,500 years; Hachijojima, Nishiyama kazan nantoroku ni okeru saikin 2,500 nenkan no funshutsubutsu no sojo to funka nendai

    Sugihara, S.; Shimada, S. [Meiji University, Tokyo (Japan)


    The Nishiyama volcano of the Hachijo island is a stratovolcano whose volcanic activity started approximately 10,000 years ago. Among the lateral volcanos surrounding the cone-shaped mountain, there is a Kandoyama tuff cone formed by a phreatomagmatic eruption at the southeastern base of the Nishiyama volcano. It is known that Kandoyama`s latest eruption is not older than 4,000 years. In this report, the stratigraphy of eruptive deposits and the types of eruptions involving Nishiyama after Kandoyama formation are clarified. Also, the history of Nishiyama` eruption is discussed, for which a study is made about the stratigraphic relationship between its eruption and the results of {sup 14}C dating or the eruption remainders, corresponding terrestrial episodes recorded in ancient literature usable for eruption dating, etc. The conclusion is summarized below. The eruptive deposits are to be supposedly dated at a period after the completion of caldera aggradation. At the southeastern base of Nishiyama, the eruption of 1605 is to immediately follow the eruption of approximately 1,100 years ago, and no eruption so active as to cause the outflow of lava is noticed therebetween. It is inferred that the Nishiyama volcano erupts once in a period of 300-700 years. 44 refs., 11 figs., 2 tabs.

  6. Stratigraphy of sequences and heterogeneity of the fluvio-deltaic of the Sao Sebastiao formation, Reconcavo basin; Estratigrafia de sequencias e heterogeneidade dos reservatorios fluvio-deltaicos da formacao Sao Sebastiao, bacia do Reconcavo

    Bongiolo, Daniela Elias [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Inst. de Geociencias. Curso de Pos-graduacao em Estratigrafia]. E-mail:; Scherer, Claiton Marlon dos Santos [Grande do Sul Univ., Porto Alegre, RS (Brazil). Inst. de Geociencias]. E-mail:


    This work applies the sequence stratigraphy concepts in the faciological analysis based on the individualization of the boundary surfaces and the architectural elements, with the aim to work out prediction models for the permeability changes of the oil reservoir from fluvial-deltaic Sao Sebastiao Formation, Reconcavo Basin. The descriptions of drill holes and outcrops related to the studied interval allow to recognize three complete 4th order sequences, all of that limited by erosive surfaces. The best oil reservoirs are related to fluvial sandstones deposited during the low stand system tract and to deltaic sandstones from the lower portion of the transgressive system tract. The main sealers of the oil reservoir are the maximum flooding surfaces. The fluvial oil reservoirs are homogeneous, however the deltaic ones have a good lateral continuity, but a lower vertical connectivity in the sand bodies. The vertical and lateral inter finger of the D A and S B elements control the flow units in fluvial systems. In deltaic systems, the reservoir homogeneity depends on the relation between deltaic front and pro delta deposits. (author)

  7. Description of Cretaceous Sedimentary Sequence of the Second and Third Member of the Qingshankou Formation Recovered by CCSD-SK-Is Borehole in Songliao Basin: Lithostratigraphy, Sedimentary Facies and Cyclic Stratigraphy

    Wang, Pujun; Gao, Youfeng; Cheng, Rihui; Wang, Guodong; Wu, Heyong; Wan, Xiaoqiao; Yang, Gansheng; Wang, Zhongxing

    The second and third member of the Qingshankou Formation recovered by CCSD-SK-Is borehole (China Cretaceous Continental Scientific Drilling-SongkeI-the south borehole) is 415.61 m long and 100% of cores recovery. The age of the member corresponds approximately to the Coniacian. The sequence and process of lithology-lithofacies and cyclic stratigraphy were revealed by a detailed core description. 12 rock types and 2 kinds of sedimentary subfacies including semi-deep lake and shallow lake were recognized from the drilling core of the second and third member of the Qingshankou Formation. 10 sedimentary microfacies are present, including dolomite, marl, limestone, oil shale, semi-deep lake turbidite, volcanic ash, seismite, semi-deep lake mudstone, shallow lake mudstone, and shallow lake turbidite microfacies. The second and third member of the Qingshankou Formation represents 422 meter-scale cycles (sixth-order cycle), 130 fifth-order cycles, 21 fourth-order cycles, and one third-order cycles. The special lithologies, such as mudstone, seismite, dolomite, volcanic ash, and so on are important to researches on source rocks and lacustrine event sediments.

  8. New seismo-stratigraphic data of the Volturno Basin (northern Campania, Tyrrhenian margin, southern Italy: implications for tectono-stratigraphy of the Campania and Latium sedimentary basins

    Ennio Marsella


    Full Text Available A geological section of the Volturno Basin (northern Campania, continental margin, Italy has been constructed based on new multi-channel seismic data, to show the stratigraphic relationships between the filling in the Quaternary basin and the Meso-Cenozoic acoustic basement. The new seismic sections presented here outline the underlying structures of the basin and their relationships to the filling in the Quaternary basin. Deep exploration wells in Campania and Latium on the Tyrrhenian margin have gathered litho-stratigraphic and commercial multi-channel seismic data that can be used for better integration of the geological data for the area under study. The trending of the seismic units is controlled by the Massico Structural High, which forms the boundary of the Volturno Basin towards the north-west. This produces a geometry that is characteristic of a fan complex, with NE-SW trending. This qualitative calibration of the seismic sequences that fill the sedimentary basin was carried out through the litho-stratigraphic data of the «Castelvolturno 2» well, which highlights the pyroclastic layers and conglomeratic strata of the lagoon and delta environments as they evolve upwards towards marine sediments. Seismo-stratigraphic analysis shows the complex depositional geometries of the filling in the Volturno Basin, which overlie the Meso-Cenozoic carbonatic basement and the related flysch deposits. Coupled with regional geological evidence, the data interpretation here suggests that the Volturno Basin represents a half-graben structure that is characterized by down-thrown blocks along normal faults.

  9. 高分辨率层序地层学在河流相油田开发中的应用%Application of High-resolution Sequence Stratigraphy of Fluvial Facies in Development of Oilfield

    胡光义; 陈飞; 孙立春; 范廷恩; 赵春明; 吴胜和


    Fluvial sandbody is one of the most important hydrocarbon reservoirs in China.Using of high-resolution sequence stratigraphy in fluvial facies in development of oilfield is very important to the Guidance of fluvail sandbod Subdivision and Correlation.There are complex factors,including fluvial facies autocyclicity sediment,the effect of sedimentary surface,channel pattern and sandbody architecture,and the orders of base-level cycles,which resulted in the difficulty to define subdivision and correlation.According to the theory and approach of high-resolution sequence stratigraphy,combining with fluvial facies model,lithofacies and facies sequence and association,and key surface correlation,reservoir fluid correlation and channel erosion and fill,fluvial reservoir subdivision and comparison have been carried out.Provided a clue and methods on the fluvial facies subdivision and correlation in development of oilfield of intermediary and later stage,in order to be helpful to product and develop of oilfield.In Minghuazhen Formation Bohai Q Oilfield,It has achieved good results in the practical application.%河流相是我国陆相盆地重要的油气储集层系类型之一,开发阶段应用高分辨率层序地层学进行河流相高精度小层划分,对于指导河道砂体的精细划分对比有重要意义.由于受到河流相地层自旋回沉积、沉积间歇面的作用、河型和砂体叠置样式的变化以及基准面旋回的级次的划分等复杂因素的影响,在开发阶段进行高精度层序对比时,难度更大.运用高分辨率层序地层学原理和方法,综合分析河流相模式的特点,充分利用河流相岩相、相序的组合特征随空容纳空间规律性变化,结合各种关键面的约束控制、油水界面在小层内部空间的分布位置以及河道的切割充填作用,进行精细河流相小层划分对比.旨在摸索一套油田开发中后期河流相高精度层序划分的思路和方法,以指导油田

  10. The complex influences of back-barrier deposition, substrate slope and underlying stratigraphy in barrier island response to sea-level rise: Insights from the Virginia Barrier Islands, Mid-Atlantic Bight, U.S.A.

    Brenner, Owen T.; Moore, Laura J.; Murray, A. Brad


    To understand the relative importance of back barrier environment, substrate slope and underlying stratigraphy in determining barrier island response to RSLR (relative sea-level rise), we use a morphological-behavior model (GEOMBEST) to conduct a series of sensitivity experiments, based on late-Holocene hindcast simulations of an island in the U.S. mid-Atlantic Bight (Metompkin Island, VA) having both salt marsh and lagoonal back-barrier environments, and we draw comparisons between these results and future simulations (2000-2100 AD) of island response to RSLR. Sensitivity analyses indicate that, as a whole, the island is highly sensitive to factors that reduce overall sand availability (i.e., high sand-loss rates and substrates containing little sand). Results also indicate that for all predicted future RSLR scenarios tested, islands having high substrate sand proportions (if allowed to migrate freely) will likely remain subaerial for centuries because of sufficient substrate sand supply and elevation to assist in keeping islands above sea level. Simulation results also lead to basic insights regarding the interactions among substrate slope, back-barrier deposition and island migration rates. In contrast to previous studies, which suggest that changes in substrate slope directly affect the island migration trajectory, we find that-in the presence of back-barrier deposition-the connection between substrate slope and island behavior is modulated (i.e., variability in migration rates is dampened) by changes in back-barrier width. These interactions-which tend to produce changes in shoreface sand content-lead to a negative feedback when the back-barrier deposit contains less sand than the underlying layer, resulting in a stable back-barrier width. Alternatively, a positive feedback arises when the back-barrier deposit contains more sand than the underlying layer, resulting in either back-barrier disappearance or perpetual widening.

  11. Geochemical correlation and 40Ar/39Ar dating of the Kern River ash bed and related tephra layers: Implications for the stratigraphy of petroleum-bearing formations in the San Joaquin Valley, California

    Baron, D.; Negrini, R.M.; Golob, E.M.; Miller, D.; Sarna-Wojcicki, A.; Fleck, R.J.; Hacker, B.; Erendi, A.


    The Kern River ash (KRA) bed is a prominent tephra layer separating the K and G sands in the upper part of the Kern River Formation, a major petroleum-bearing formation in the southern San Joaquin Valley (SSJV) of California. The minimum age of the Kern River Formation was based on the tentative major-element correlation with the Bishop Tuff, a 0.759??0.002 Ma volcanic tephra layer erupted from the Long Valley Caldera. We report a 6.12??0.05 Ma 40Ar/39Ar date for the KRA, updated major-element correlations, trace-element correlations of the KRA and geochemically similar tephra, and a 6.0??0.2 Ma 40Ar/39Ar age for a tephra layer from the Volcano Hills/Silver Peak eruptive center in Nevada. Both major and trace-element correlations show that despite the similarity to the Bishop Tuff, the KRA correlates most closely with tephra from the Volcano Hills/Silver Peak eruptive center. This geochemical correlation is supported by the radiometric dates which are consistent with a correlation of the KRA to the Volcano Hills/Silver Peak center but not to the Bishop Tuff. The 6.12??0.05 Ma age for the KRA and the 6.0??0.2 Ma age for the tephra layer from the Volcano Hills/Silver Peak eruptive center suggest that the upper age of the Kern River Formation is over 5 Ma older than previously thought. Re-interpreted stratigraphy of the SSJV based on the new, significantly older age for the Kern River Formation opens up new opportunities for petroleum exploration in the SSJV and places better constraints on the tectonostratigraphic development of the SSJV. ?? 2007 Elsevier Ltd and INQUA.




    Full Text Available The Gelasian succession of the Capodarso area (Enna-Caltanissetta basin, Sicily, Italy consists of an offlapping stack of cycles composed of siliciclastic units passing to carbonate heterozoan, clino-stratified wedges, developed from a growing positive tectonic structure. Identification of a number of facies tracts, based on sedimentary facies, biofacies and taphofacies, provided important information about the differentiation and characterisation of systems tracts and key stratal surfaces of sequence stratigraphy. The bulk of carbonate wedges are interpreted as representing the rapid falling-stage progradation of distally steepened ramps. The inferred highest rate of carbonate production during forced regressions was concomitant with active downramp resedimentation by storm-driven downwelling flows, leading to storing of most carbonate sediment on the ramp slope as clino-beds of the prograding bodies. Comparison of the Capodarso ramps with other icehouse carbonate ramps, with particular regard to the Mediterranean Plio-Pleistocene, provides clues for defining some common features. These are inferred to include: (1 brief, rapid episodes of progradation concomitant with orbitally-forced sea-level changes, resulting in limited ramp width; (2 preferential fostering of growth and downramp resedimentation of heterozoan carbonates during glacial hemicycles marked by enhanced atmospheric and marine circulation; (3 building out from positive features of entirely submerged distally-steepened ramps with storm-wave-graded profile and distinctive clinoforms; (4 ramp stacks generally consisting of mixed clastic-carbonate sequences showing an ordered spectrum of distinct frequencies; (5 rapid, continuous changes in environmental parameters, leading to the short-lived persistence of faunal communities, climax communities generally having insufficient time to form. 

  13. Stratigraphy, Structure, and Geologic and Coastal Hazards in the Peñuelas to Salinas Area, Southern Puerto Rico: A Compendium of Published Literature

    Rodríguez-Martínez, Jesús


    The Puerto Rico Electrical Power Authority has proposed construction of a pipeline to convey natural gas from the municipio of Pe?uelas to the Aguirre thermoelectric power plant in the municipio of Salinas in southern Puerto Rico. To ensure that the geologic conditions along the possible routes do not represent a threat to the physical integrity of the natural gas pipeline, and thus comply with State and Federal regulations, the Puerto Rico Electrical Power Authority requested the U.S. Geological Survey to provide a synthesis of published literature of the geology of the coastal plain in the Pe?uelas to Salinas area. The study area is located in part of the Southern Coastal Plain of Puerto Rico. In the area that extends from the municipio of Pe?uelas eastward to the Laguna de las Salinas at Ponce, a distance of about 5 miles, the study area is underlain by middle Tertiary carbonate units. Eastward from the Laguna de las Salinas to the pipeline terminus at the Aguirre power plant in Salinas, a distance of about 30 miles, the terrain is underlain by fan-delta deposits of Quaternary age. The carbonate units and the fan-delta deposits are underlain by early Tertiary and older-age volcaniclastics with subordinate sedimentary rocks and lavas. The Great Southern Puerto Rico Fault Zone is the principal geologic structural feature in southern Puerto Rico. At present, the Great Southern Puerto Rico Fault Zone is considered largely quiescent, although it apparently is associated with minor earthquakes. There is no evidence of terrestrial, late Quaternary faulting within the Pe?uelas to Salinas area. Seismic activity in this area mostly originates from extension zones of more distal shallow sources such as Mona Canyon to the northwest and the Anegada Trough northeast of the island of Puerto Rico. The magnitude of completeness of earthquakes in the study area ranges from 2.0 to 2.5. The seismic density for the southern coast including the study area is about 0.128 earthquakes

  14. A Geophysical Study in Grand Teton National Park and Vicinity, Teton County, Wyoming: With Sections on Stratigraphy and Structure and Precambrian Rocks

    Behrendt, John Charles; Tibbetts, Benton L.; Bonini, William E.; Lavin, Peter M.; Love, J.D.; Reed, John C.


    An integrated geophysical study - comprising gravity, seismic refraction, and aeromagnetic surveys - was made of a 4,600-km2 area in Grand Teton National Park and vicinity, Wyoming, for the purpose of obtaining a better understanding of the structural relationships in the region. The Teton range is largely comprised of Precambrian crystalline rocks and layered metasedimentary gneiss, but it also includes granitic gneiss, hornblende-plagioclase gneiss, granodiorite, and pegmatite and diabase dikes. Elsewhere, the sedimentary section is thick. The presence of each system except Silurian provides a chronological history of most structures. Uplift of the Teton-Gros Ventre area began in the Late Cretaceous; most of the uplift occurred after middle Eocene time. Additional uplift of the Teton Range and downfaulting of Jackson Hole began in the late Pliocene and continues to the present. Bouguer anomalies range from -185 mgal over Precambrian rocks of the Teton Range to -240 mgal over low-density Tertiary and Cretaceous sedimentary rocks of Jackson Hole. The Teton fault (at the west edge of Jackson Hole), as shown by steep gravity gradients and seismic-refraction data, trends north-northeast away from the front of the Teton Range in the area of Jackson Lake. The Teton fault either is shallowly inclined in the Jenny Lake area, or it consists of a series of fault steps in the fault zone; it is approximately vertical in the Arizona Creek area. Seismic-refraction data can be fitted well by a three-layer gravity model with velocities of 2.45 km per sec for the Tertiary and Cretaceous rocks above the Cloverly Formation, 3.9 km per sec for the lower Mesozoic rocks, and 6.1 km per sec for the Paleozoic (limestone and dolomite) and Precambrian rocks. Gravity models computed along two seismic profiles are in good agreement (sigma=+- 2 mgal) if density contrasts with the assumed 2.67 g per cm2 Paleozoic and Precambrian rocks are assumed to be -0.35 and -0.10 g per cm2 for the 2

  15. Late Quaternary Incisions and Related Shallow Subsurface Stratigraphy on the New Jersey Mid-Outer Shelf: Preliminary Results from Ultra-High Resolution Chirp Sonar Images - Part I

    Nordfjord, S.; Gulick, S. P.; Austin, J. A.; Goff, J. A.; Fulthorpe, C. S.


    ONR's Geoclutter program is a multi-year initiative to investigate systematic relationships between geologic phenomena and discrete acoustic signals ("geoclutter"). The New Jersey middle and outer shelf is the natural laboratory for Geoclutter because of the abundance of surficial geologic structures, including complex dendritic networks of fluvial (?) channels shallowly buried below the seafloor. Their geophysical characterization includes collection of high resolution seismic data in August-September 2001, using a deep-towed chirp sonar aboard the R/V Endeavor. These data image the upper ~30 m of sediments at ~2 m horizontal resolution and ~10 cm vertical resolution. Track spacing is typically 200 m. This resolution allows us to resolve subsurface structures in greater detail and over a wider range of spatial scales than previous imaging efforts using boomer sources. We present preliminary results from the central portion of the survey, a ~20x30 km area covering two separate dendritic systems. Principal drainage axes of buried channels are oriented NW to SE. Multiple incisions include cut-and-fill morphologies that characterize the channel fills, suggesting a complicated history since the last eustatic lowstand, ~20-22 ka. Both flat-lying and chaotic reflections are imaged within the fills, suggesting that infilling occurred episodically, in response to high-order relative base-level variations, and under fluctuating energy conditions. Channel-fills are often capped with a thin veneer of sand deposited after channel-filling; this has been confirmed by recent grab sampling geoclutter aboard R/V Cape Henlopen. These sediments appear to have been deposited during the last glacio-eustatic cycle (~100 kyr). A regionally important seismic reflector mappable throughout the middle to outer shelf, "R", has been interpreted as an erosional surface created during the last regression. This hypothesis is supported by the few age constraints currently available (AMS Carbon-14

  16. Multi-waveform classification for seismic facies analysis

    Song, Chengyun; Liu, Zhining; Wang, Yaojun; Li, Xingming; Hu, Guangmin


    Seismic facies analysis provides an effective way to delineate the heterogeneity and compartments within a reservoir. Traditional method is using the single waveform to classify the seismic facies, which does not consider the stratigraphy continuity, and the final facies map may affect by noise. Therefore, by defining waveforms in a 3D window as multi-waveform, we developed a new seismic facies analysis algorithm represented as multi-waveform classification (MWFC) that combines the multilinear subspace learning with self-organizing map (SOM) clustering techniques. In addition, we utilize multi-window dip search algorithm to extract multi-waveform, which reduce the uncertainty of facies maps in the boundaries. Testing the proposed method on synthetic data with different S/N, we confirm that our MWFC approach is more robust to noise than the conventional waveform classification (WFC) method. The real seismic data application on F3 block in Netherlands proves our approach is an effective tool for seismic facies analysis.

  17. A new 0.9 Ma oxygen isotope stratigraphy for a shallow-water sedimentary transect across three IODP 317 sites in the Canterbury Bight of southwest Pacific Ocean

    Ding, Xuan; Wu, YingYing


    Sedimentary records in shallow-water environment provide unique opportunity to further our understanding on the regional relative sea level changes in relation to global climate change. Here we present a new 0.9 Ma oxygen isotope stratigraphy for a shallow-water sedimentary transect across three IODP 317 sites in the Canterbury Bight of southwest Pacific Ocean. The three sites are located on the eastern margin of the South Island of New Zealand, including a continental slope site, IODP317-U1352 and two continental shelf sites, IODP317-U1354 and IODP317-U1351. We first generated high resolution benthic foraminifers (Nonionella flemingi) δ18O records for the three sites and a planktonic (Globigerina bulloides) record for the U1352B. An initial chronological framework for the benthic δ18O record of the U1352B was constructed using 8 accelerator mass spectrometry (AMS) radiocarbon dates and 4 biostratigraphic events. Then a refined age model was established by correlating the U1352B benthic δ18O record with the EDC δD record on the AICC2012 time-scale, and the LR04 benthic δ18O stack. Although the U1354B and U1351B have lower sedimentation rates, their benthic δ18O records correlate well with that of U1352B. In order to ensure the accuracy of the chronostratigraphic framework established, we also analyzed the characteristics of sedimentary grain size and the planktonic and benthic δ18O values. In accord with the adjacent sites, the results show that the melt of Southern Alps glaciers due to the warming climate during MIS 11 and 5.5 led to the increased fresh water delivery, with massive terrigenous deposit; and the warm SST during the MIS7 is related with the STF migration, which led to strong current activity, with coarser grain size. Meanwhile, records of benthic δ18O, sedimentation rate and content of >63μm coarse fraction of site U1352 all indicate the MIS 20 was indeed a colder interval compared to subsequent glacial times.

  18. The Stratigraphy and Lithofacies of the Paleoproterozoic Volcaniclastic Sequences in the Cape Three Points Area- Akodda section of the Southern in Ashanti Belt in the Birimian of southwest Ghana

    Yoshimaru, S.; Kiyokawa, S.; Ito, T.; Ikehara, M.; Nyame, F. K.; Tetteh, G. M.


    The Paleoproterozoic Era is thought to have experienced one of the most significant changes in earth's environment during earth history. Early continents started to diverge and collide accompanied by first major oxidation of the atmosphere-oceanic system known as the Great Oxidation Environment (GOE). Due to their well-preserved oceanic sedimentary sequences, Paleoproterozoic belts are usually good targets for studies on the history of earth's past environment. In addition, these belts provide great help to understand the nature of the Paleoproterozoic deeper oceanic environments. Birimian greenstone belt in southwestern Ghana is likely to have made up of subduction of oceanic basin to form a volcanic island arc. Birimian rocks are separated by nonconformity from the Tarkwaian Group which is a younger paleoplacer deposit (Perrouty et al., 2012). The Birimian is made up of island-arc volcanic rocks; foreland basin made up of shale, sandstone, quartzite and turbidities derived from 2.17 Ga granite intrusions during Birimian volcanism. In this study, we focused on the coastal area around Cape Three Points at the southernmost part of the Ashanti (Axim-Konongo) belt in Ghana. In the eastern part of the area, excellently preserved Paleoprotorozoic deeper oceanic sedimentary sequences extensively outcrop for over 4km stretch. This volcano-sedimentary sequence has been affected by greenschist facies metamorphism. Structurally, this region preserves S1 cleavage and asymmetrical synform with west vergence and S0 younging to the east. Provisional stratigraphy is very continuous up to more than 2000m thick and, in addition, suggests at least four different fining upward sequences in the area to the east and west of Atwepo, west of Kwetakora and Akodda. These sub-sequences are mainly composed of volcaniclasitc, sandstone, black shale and rare volcanics such as pillow basalt or massive volcanic lava. In other words, this continuous sequence suggests distal submarine

  19. Origin, growth history and glacial-interglacial responses of a cold-water coral mound in NE Atlantic: Results from O-isotope and Sr-isotope stratigraphy in IODP Expedition 307

    Sakai, S.; Kano, A.; Abe, K.; Browning, E.; Scientific Party, I.


    Cold-water corals may cover as a large area as the better-known warm-water corals forming shallow reefs, and they occur in a variety of forms and settings, from small isolated colonies or patch reefs to giant mound structures such as those found west of Ireland. In May 2005, IODP Expedition 307 sailed to Challenger Mound, which is one of thousands of cold-water coral mounds in Porcupine Seabight, 150 km offshore of southwestern Ireland, and recovered the first complete section through to the base of a modern cold-water coral mound which is composed of up to 155 m of unlithified coral-bearing (Lophelia pertusa) sediments. The coral-bearing sediments lie on an angular unconformable surface above the lower-middle Miocene glauconitic siltstones and sandstones. Mound growth could have been continuous, and the repeated 10-m-scale alternations in lithology between lighter- colored calcareous layers (interglacials) and darker-colored clayey layers (glacials) could be essentially related to the glacial-interglacial cycles, which supported by correspondence of the two curves of O-isotopes of planktic foraminifers and natural Gamma radiation. O-isotope results of planktic foraminifers show cold-water coral L. pertusa, which are organisms sensitive to environmental change, were able to maintain a cold-water coral mound community (e.g. temperature remained above 4°C) under the latest Pliocene-Pleistocene glacial- interglacial changes. Sr-isotopic stratigraphy revealed that the section is divided into two growth stages at 23.6 mbsf, and mound of the first stage started growing on the mid-Miocene basement around 2.6 Ma, when Northern Hemisphere glaciation was intensified. The mound growth reached a maximum rate (24 cm/ky) around 2.0Ma, and ceased at 1.7Ma. The second stage (1.0-0.5 Ma) shows a lower growth rate (5 cm/ky). Corals require zooplanktons that tend to condense in density gradient of ~800 m deep developed between Eastern North Atlantic Water (ENAW) and the underlying

  20. Explosive and Phreatomagmatic Activity from San Salvador Volcanic Complex (El Salvador) and Their Effects on El Cambio Archaeological Site: a Review of the Last 3000 yrs. Based on Volcanic Stratigraphy Data

    Ferrés, D.; Delgado, H.; Pullinger, C.; Castillo, R.; Chávez, H. I.


    El Cambio archeological site (ECAS; Zapotitán Valley), 4 km NW from the San Salvador Volcanic Complex comprises 3000 yrs. of pyroclastic record. Sheets (1983) identified different levels rich in cultural remains intercalated within the volcanic deposits, indicating that different prehistoric settings were affected by San Salvador volcano eruptions, and giving information on the reoccupation frequency in the area. Accordingly, ECAS was occupied since the Late Pre-Classic period until before the last plinian eruption of Ilopango Caldera (425AD) reference, that originated the Tierra Blanca Joven (TBJ), pyroclastic deposits generally used as key-layer in stratigraphic reconstructions. Within the next two centuries, there is no evidence of human occupation at ECAS until the end of Late Classic which was a period of maximum splendor in the valley. During this time the area was affected by at least 3 eruptions from the San Salvador volcanic complex that produced the: Laguna Caldera volcanic fall deposits (which affected Joya de Cerén archeological site in 625AD), "Talpetate" surge deposits or Toba de San Andrés (600-900AD), and fall deposits of El Playón volcano (1658). We report new data on volcanic stratigraphy and archeological history including the following: a) the phreatomagmatic nature of eruptions that affected the area, the new excavations allowed the detailed study of surge deposits indicating magma-water interaction at Laguna Caldera and El Playón, previously considered strombolian eruptions; b)document the occupation of ECAS during Middle Pre-Classic period, new surge deposits below TBJ have been identified (with Middle Pre-Classic artifacts and pottery), that had not been documented before, extending the historic record up to 3000 yrs. BP. and c) detailed study of the "Talpetate" deposits, this sequence consists of fall, pyroclastic flow and surge deposits, present in the rim and slopes of San Salvador Volcano, which can be correlated with surge deposits

  1. Cenozoic stratigraphy of the Sahara, Northern Africa

    Swezey, Christopher S.


    This paper presents an overview of the Cenozoic stratigraphic record in the Sahara, and shows that the strata display some remarkably similar characteristics across much of the region. In fact, some lithologies of certain ages are exceptionally widespread and persistent, and many of the changes from one lithology to another appear to have been relatively synchronous across the Sahara. The general stratigraphic succession is that of a transition from early Cenozoic carbonate strata to late Cenozoic siliciclastic strata. This transition in lithology coincides with a long-term eustatic fall in sea level since the middle Cretaceous and with a global climate transition from a Late Cretaceous–Early Eocene “warm mode” to a Late Eocene–Quaternary “cool mode”. Much of the shorter-term stratigraphic variability in the Sahara (and even the regional unconformities) also can be correlated with specific changes in sea level, climate, and tectonic activity during the Cenozoic. Specifically, Paleocene and Eocene carbonate strata and phosphate are suggestive of a warm and humid climate, whereas latest Eocene evaporitic strata (and an end-Eocene regional unconformity) are correlated with a eustatic fall in sea level, the build-up of ice in Antarctica, and the appearance of relatively arid climates in the Sahara. The absence of Oligocene strata throughout much of the Sahara is attributed to the effects of generally low eustatic sea level during the Oligocene and tectonic uplift in certain areas during the Late Eocene and Oligocene. Miocene sandstone and conglomerate are attributed to the effects of continued tectonic uplift around the Sahara, generally low eustatic sea level, and enough rainfall to support the development of extensive fluvial systems. Middle–Upper Miocene carbonate strata accumulated in northern Libya in response to a eustatic rise in sea level, whereas Upper Miocene mudstone accumulated along the south side of the Atlas Mountains because uplift of the mountains blocked fluvial access to the Mediterranean Sea. Uppermost Miocene evaporites (and an end-Miocene regional unconformity) in the northern Sahara are correlated with the Messinian desiccation of the Mediterranean Sea. Abundant and widespread Pliocene paleosols are attributed to the onset of relatively arid climate conditions and (or) greater variability of climate conditions, and the appearance of persistent and widespread eolian sediments in the Sahara is coincident with the major glaciation in the northern hemisphere during the Pliocene.

  2. Sedimentary environments: processes, facies, and stratigraphy

    Reading, H. G; Reading, Harold G


    ... and chemical systems, 6 2.1.2 Climate, 7 2.1.3 Tectonic movements and subsidence, 11 2.1.4 Sea-level changes, 11 2.1.5 Milankovitch processes and orbital forcing, 14 2.1.6 Intrinsic sedimentary processes,...

  3. Hafnium isotope stratigraphy of ferromanganese crusts

    Lee, D.-C.; Halliday, A.N.; Hein, J.R.; Burton, K.W.; Christensen, J.N.; Gunther, D.


    A Cenozoic record of hafnium isotopic compositions of central Pacific deep water has been obtained from two ferromanganese crusts. The crusts are separated by more than 3000 kilometers but display similar secular variations. Significant fluctuations in hafnium isotopic composition occurred in the Eocene and Oligocene, possibly related to direct advection from the Indian and Atlantic oceans. Hafnium isotopic compositions have remained approximately uniform for the past 20 million years, probably reflecting increased isolation of the central Pacific. The mechanisms responsible for the increase in 87Sr/86Sr in seawater through the Cenozoic apparently had no effect on central Pacific deep-water hafnium.




    Full Text Available The diversity curve of Permian fusulinid genera shows two peaks corresponding to the Asselian-Sakmarian and Midian times. The minimal generic diversity is recorded in the late Bolorian. The most significant extinction events occurred at the end of the Midian (71% of all genera, Bolorian (48%, Asselian (27% and Sakmarian (23% ages. The fusulinid assemblage was most notably changed by the appearance of new genera (52% of the total number in the Kubergandian age. These data  identify two main stages (Asselian-Bolorian and Kubergandian-Dorashamian and four second-order stages (Asselian-Sakmarian, Yakhtashian-Bolorian, Kubergandian-Midian, and Dzhulfian-Dorashamian in the Permian history of fusulinids. The main stages correspond to two Permian series of the East European scale, which can be considered as subsystems named Cisuralian and Tethysian, respectively. The latter are subdivided into the Uralian, Darvasian, Yanghsingian and Lopingian series which correspond to the second-order stages. The scale suggested does not contradict the traditional two-member subdivision and has an advantage over the accepted global three-member chronostratigraphic scale because the series suggested are more proportional to each other in scope and reflect natural evolutionary processes of the marine biota. In addition, the application of the global scale to the Tethyan sequences is hampered by a limited number of criteria used in the drawing of series and stage boundaries, as evidenced by the existing different views on the position of the lower Guadalupian boundary in the Tethyan sections. 

  5. Geochemical Stratigraphy of Southern Parana' Lava Piles

    Marzoli, A.; De Min, A.; Marques, L. S.; Nardy, A.; Chiaradia, M.


    Basaltic lava flows of the Paranà Large Igneous Province exhibit significant regional and stratigraphic geochemical variations. While the most notable difference concerns the dominance of low-Ti (TiO2 Esmeralda low-Ti basalts (these latter being present both towards the base and the top of the sequence) in Paranà State, while in Santa Caterina State Gramado flows are interlayered with Urubici-type high-Ti basalts. The interlayering of distinct basaltic magma type requires near-synchronous eruption of chemically strongly different magma types generated from clearly heterogeneous mantle sources and erupted through separated magma plumbing systems, without apparent interaction (mixing) among the distinct basalts. In conclusion, the relative timing of low- and high-Ti magma types seems to be much more complicated than previously thought, as for example Esmeralda or Pitanga basalts, previously considered as quite late and postdating Gramado basalts, are indeed synchronous with them.

  6. Strontium-isotope stratigraphy of Enewetak Atoll

    Ludwig, K. R.; Halley, Robert B.; Simmons, Kathleen R.; Peterman, Zell E.


    87Sr/86Sr ratios determined for samples from a 350 m core of Neogene lagoonal, shallow-water limestones from Enewetak Atoll display a remarkably informative trend. Like the recently published data for Deep Sea Drilling Project (DSDP) carbonates, 87Sr/86Sr at Enewetak increases monotonically but not smoothly from the early Miocene to the Pleistocene. The data show intervals of little or no change in 87Sr/86Sr, punctuated by sharp transitions to lower values toward greater core depths. The sharp transitions correlate with observed solution disconformities caused by periods of subaerial erosion, whereas the intervals of little or no change in 87Sr/86Sr correspond to intervals of rapid accumulation of shallow-water carbonate sediments. When converted to numerical ages using the published DSDP 590B trend, the best-resolved time breaks are at 282 m (12.3 to 18.2 Ma missing) and 121.6 m (3.0 to 5.3 Ma missing) below the lagoon floor. At Enewetak, Sr isotopes offer a stratigraphic resolution for these shallow-marine Neogene carbonates comparable to that of nannofossil zonation in deep-sea carbonates (0.3-3 m.y.). In addition, the correlation of times of Sr-isotope breaks at Enewetak with times of rapid Sr-isotope change in the DSDP 590B samples confirms the importance off sea-level changes in the evolution of global-marine Sr isotopes and shows that the Sr-isotope response to sea-level falls is rapid.

  7. Quaternary glacial stratigraphy and chronology of Mexico

    White, Sidney E.

    The volcano Iztaccihuatl in central Mexico was glaciated twice during the middle Pleistocene, once probably in pre-Illinoian (or pre-Bull Lake) time, and once in late Illinoian (or Bull Lake) time. Glaciation during the late Pleistocene was restricted to the late Wisconsin (or Pinedale). A maximum advance and one readvance are recorded in the early part, and one readvance in the latter part. Three or four small neoglacial advances occurred during the Holocene. Two other volcanoes nearby, Ajusco and Malinche, have a partial record of late Pleistocene and Holocene glaciations. Three others, Popocatépetl, Pico de Orizaba, and Nevado de Toluca, have a full Holocene record of three to five glacial advances during Neoglaciation.

  8. Strontium-isotope stratigraphy of Enewetak Atoll

    Ludwig, K. R.; Halley, R. B.; Simmons, K. R.; Peterman, Z. E.


    87Sr/86Sr ratios determined for samples from a 350 m core of Neogene lagoonal, shallow-water limestones from Enewetak Atoll display a remarkably informative trend. Like the recently published data for Deep Sea Drilling Project (DSDP) carbonates, 87Sr/86Sr at Enewetak increases monotonically but not smoothly from the early Miocene to the Pleistocene. The data show intervals of little or no change in 87Sr/86Sr, punctuated by sharp transitions to lower values toward greater core depths. The sharp transitions correlate with observed solution disconformities caused by periods of subaerial erosion, whereas the intervals of little or no change in 87Sr/86Sr correspond to intervals of rapid accumulation of shallow-water carbonate sediments. When converted to numerical ages using the published DSDP 590B trend, the best-resolved time breaks are at 282 m (12.3 to 18.2 Ma missing) and 121.6 m (3.0 to 5.3 Ma missing) below the lagoon floor. At Enewetak, Sr isotopes offer a stratigraphic resolution for these shallow-marine Neogene carbonates comparable to that of nannofossil zonation in deep-sea carbonates (0.3-3 m.y.). In addition, the correlation of times of Sr-isotope breaks at Enewetak with times of rapid Sr-isotope change in the DSDP 590B samples confirms the importance off sea-level changes in the evolution of global-marine Sr isotopes and shows that the Sr-isotope response to sea-level falls is rapid.

  9. Quaternary stratigraphy and palaeogeography of Poland

    Marks, Leszek; Dzierżek, Jan; Janiszewski, Robert; Kaczorowski, Jarosław; Lindner, Leszek; Majecka, Aleksandra; Makos, Michał; Szymanek, Marcin; Tołoczko-Pasek, Anna; Woronko, Barbara


    Though the stratigraphical and palaeogeographical framework of the Quaternary in Poland is still to be completed, several crucial points have been confirmed recently. The preglacial series, accepted for years as belonging to the Lower Pleistocene, is undoubtedly of Early Pliocene age, with a huge hiatus above almost until the uppermost Lower Pleistocene. The earliest glaciation in Poland (Nidanian) occurred at about 900 ka BP when the ice sheet reached the mid-southern part of the country. The following Podlasian Interglacial embraced the Brunhes/Matuyama boundary in the middle, in a similar fashion to the corresponding Cromerian Complex in Western Europe. The late Early and early Middle Pleistocene interglacials in Poland comprised 2-3 optima each, whereas every one of the younger interglacials was characterised by a single optimum only. The Late Vistulian ice sheet was most extensive in the western part of Poland (Leszno Phase) whereas the younger Poznań Phase was more extensive in the central and eastern part of the country. This was due to the varied distance from the glaciation center in Scandinavia, making the ice sheet margin reach a terminal position in different times. Palaeoclimatological research in the Tatra Mountains has provided new evidence for the atmospheric circulation over Europe. During cold phases of the Pleistocene in Poland a continental climate extended further westwards, quite the opposite that occurring during warmer intervals.

  10. Prediction of calcite Cement Distribution in Shallow Marine Sandstone Reservoirs using Seismic Data

    Bakke, N.E.


    This doctoral thesis investigates how calcite cemented layers can be detected by reflection seismic data and how seismic data combined with other methods can be used to predict lateral variation in calcite cementation in shallow marine sandstone reservoirs. Focus is on the geophysical aspects. Sequence stratigraphy and stochastic modelling aspects are only covered superficially. Possible sources of calcite in shallow marine sandstone are grouped into internal and external sources depending on their location relative to the presently cemented rock. Well data and seismic data from the Troll Field in the Norwegian North Sea have been analysed. Tuning amplitudes from stacks of thin calcite cemented layers are analysed. Tuning effects are constructive or destructive interference of pulses resulting from two or more closely spaced reflectors. The zero-offset tuning amplitude is shown to depend on calcite content in the stack and vertical stack size. The relationship is found by regression analysis based on extensive seismic modelling. The results are used to predict calcite distribution in a synthetic and a real data example. It is found that describing calcite cemented beds in shallow marine sandstone reservoirs is not a deterministic problem. Hence seismic inversion and sequence stratigraphy interpretation of well data have been combined in a probabilistic approach to produce models of calcite cemented barriers constrained by a maximum amount of information. It is concluded that seismic data can provide valuable information on distribution of calcite cemented beds in reservoirs where the background sandstones are relatively homogeneous. 63 refs., 78 figs., 10 tabs.

  11. 湖北恩施硒富集区中二叠世孤峰组露头层序地层研究%Sequence stratigraphy of Middle Permian Gufeng Formation from selenium-rich area in Enshi, Southwestern Hubei

    石先滨; 翁茂芝; 罗红; 许露露; 龚志愚; 赵雪松; 段先锋


    -type sequence boundary, and two types of Three-grade Sequence Interface(SQ1,SQ2)was subdivided. Through comparison analysis, sequence-internal structures and types of basic sequence with transgressions of the area was obvious difference, and the sedimentation paleogeographic feature was formed in shallow water in the southern side and deep water in northern side. Through analysis of the coupling relationship of se-quence stratigraphy and selenium anomaly, high selenium anomalous character was discovered near Ⅱ-type sequence boundary in Gufeng Formation, that the new prospecting criteria was established.

  12. Estratigrafía y petrología del sector noreste de sierra de Apas. Provincia del Chubut Stratigraphy and petrology of the Northeastern sector of Sierra de Apas. Chubut Province

    M. Remesal


    where five effusive facies were recognized within the volcanic pile. The lowermost unit is represented by phenochryst-poor dark trachytes which classsify as trachytes and benmoreites. The dark trachytes are overlain either by light trachytes or by pyroclastic flows. The former are porphyritic rocks clasiffied as comendites and yielded an age of 19 ± 2 Ma. The pyroclastic flows are mainly pumiceous, of trachyandesite composition; both petrography and chemical features suggest a genetic link with the light trachytes.An exogene dome is represented by the Cerro Colorado, composed of a peralkaline rhyolite (comendite which yielded an age of 24 ± 1 Ma. The uppermost effusive unit is represented by basaltic lava flows which are found resting upon either the light trachytes or the pyroclastic flows. Basaltic rocks may be grouped into porphyric and aphyric. On the basis of their chemical composition, the latter are transitional olivine basalts, whereas the former may be further divided in alkaline olivine basalts and hawaiites. Both stratigraphy and chemical data suggest that the described volcanic pile is the result of at least two evolutionary stages. One of them includes the basalts, light trachytes, pyroclastic flows and comendites which display an evolutionary trend likely resulting from fractional crystallization. The oldest dark trachytes would belong to another evolutionary stage.

  13. 贵州平塘甘寨剖面二叠系茅口组沉积特征与层序地层%Sedimentary characteristics and sequence stratigraphy of the Permian Maokou Formation in the Ganzhai section, Pingtang, Guizhou

    李刚; 侯明才; 林良彪; 王文楷


    According to the sedimentological methods, the present paper deals, in detail, with the sedimentary characteristics and sequence stratigraphy of the Permian Maokou Formation in the Ganzhai section, Pingtang,Guizhou. The rock types of the Maokou Formation mainly consist of sparry-micritic bioclastic limestone, biogenic limestone, micritic limestone, intrasparite, siliceous rocks, nodular limestone and cherty limestone. The fossil types in the Formation comprise ostracods, gastropods, brachiopods, trilobites, algae, echinoderms, fusulinids,corals and crinoids. The lithology and fossils cited above indicate the open carbonate platform sedimentary environment of the Permian Maokou Formation. Three third-order sequences have been distinguished, including PSQ1 , PSQ2 and PSQ3 , all of which are built up of the transgressive ( TST) and highstand ( HST) systems tracts.The development of these sequences may be controlled by the sea-level changes. The sequence boundaries P2q/PSQ1, PSQ1/PSQ2 and PSQ2/PSQ3 represent lithologic-lithofacies transform surfaces. The sequence boundary P3l/PSQ3 exhibits a tectonic unconformity due to the influence of the Dongwu movement during the latest Maokouan.%本文应用沉积学手段对贵州平塘甘寨剖面中二叠统茅口组进行详细的沉积特征和层序地层的研究.研究结果显示,茅口组主要的岩石类型有亮晶-微晶生屑灰岩、生物灰岩、微晶灰岩、亮晶内碎屑灰岩、硅质岩、瘤状厌岩和含燧石灰岩等,茅口组生物种类有介形虫、腹足、腕足、三叶虫、藻类、棘屑、蜒、珊瑚、海百合茎等.岩石学特征和生物组合指示,平塘甘寨地区中二叠统茅口组为开阔碳酸盐台地沉积环境,包括台内滩和滩间两个业相.茅口组可划分出3个Ⅲ级层序PSQ1、PSQ2和PSQ3,均由海侵体系域(TST)与高水位体系域(HST)两部分组成.层序发育受到了海平面升降变化控制,层序之间的界面Pq/PSQ1、PSQ1/PSQ2、PSQ2/PSQ3

  14. Estratigrafía y centros eruptivos de la region de Pairique, Puna jujeña Stratigraphy and eruptive centers of the Pairique region, Puna Jujeña

    P.J. Caffe


    the study area, was previously interpreted as the oldest caldera structure related to Cenozoic volcanism in the broad Altiplano-Puna Volcanic Complex (APVC region. In this work we characterise the stratigraphy of the Pairique area, in order to distinguish the products of the postulated caldera collapse from those originated in other centers. Based on lithological attributes, as well as geographical and chronostratigraphical distribution, we suggest that only a few units recognised in this area are related to the Pairique ring structure. There is no conclusive evidence to propose a caldera collapse along the latter. Therefore, Pairique is re-defined as a volcanic complex, i.e. a center that experienced persistent volcanic activity during a long span of time, from >11.5 to 10.3 Ma. Its eruptive model will be established when more structural and volcanological data are available. This work also identifies three other source areas for several volcanic rocks which were previously thought as related to the Pairique structure: the Nevado Torona-San Pedro compound volcano, the Lina volcanic complex and the Pairique Grande dome complex. Similar to the "inner arc" of Perú-Bolivia, volcanic rocks in the Pairique region show distinct compositional features, in which calcalkaline basaltic andesite to dacite units coexisted with felsic lithologies of peraluminous (cordierite- or garnet-bearing affinities.

  15. CPT site characterization for seismic hazards in the New Madrid seismic zone

    Liao, T.; Mayne, P.W.; Tuttle, M.P.; Schweig, E.S.; Van Arsdale, R.B.


    A series of cone penetration tests (CPTs) were conducted in the vicinity of the New Madrid seismic zone in central USA for quantifying seismic hazards, obtaining geotechnical soil properties, and conducting studies at liquefaction sites related to the 1811-1812 and prehistoric New Madrid earthquakes. The seismic piezocone provides four independent measurements for delineating the stratigraphy, liquefaction potential, and site amplification parameters. At the same location, two independent assessments of soil liquefaction susceptibility can be made using both the normalized tip resistance (qc1N) and shear wave velocity (Vs1). In lieu of traditional deterministic approaches, the CPT data can be processed using probability curves to assess the level and likelihood of future liquefaction occurrence. ?? 2002 Elsevier Science Ltd. All rights reserved.

  16. Toward Linking Seabed Stratigraphy and Nested Seismic Datasets in STRATAFORM: Finalizing Plans for Long Coring and Synthesizing Existing Physical Property Data


    field test of the GLAD800 coring rig and its DURIP-funded active heave compensation system needs to be made and an additional planning meeting...sampled. 3) In November 2001, I participated with Mountain and Austin in a successful test of the GLAD800 active heave compensation system on the RV

  17. The Sequence Stratigraphy of Neogene Shizigou Formation of North Slope in Sanhu Depression and the Prediction of Potential Targets%三湖坳陷北斜坡新近系狮子沟组层序地层特征及有利勘探目标预测

    芮华松; 关平


    伊深1井在柴达木盆地三湖地区新近系狮子沟组试气获得工业气流,指示新近系狮子沟组中可能存在生物气。为突破柴达木盆地一直局限于第四系寻找生物气的局面,拓宽生物气的勘探领域,采用钻/测井、地震及米兰科维奇旋回相结合的方法,对三湖坳陷北斜坡新近系狮子沟组进行高分辨率层序地层学研究。狮子沟组相当于一个三级层序(长期基准面旋回),在狮子沟组可识别出6个层序界面,进而划分出5个四级层序(中期基准面旋回)。每个层序内部可进一步划分为基准面上升半旋回和基准面下降半旋回。层序Ⅲ(Sq3)基准面上升半旋回时期发育的三角洲前缘砂体尖灭及砂岩透镜体圈闭是进一步勘探的有利目标。%Yishen-1 well has obtained commercial gas flow in the Neogene Shizigou Formation.Results show that the Sanhu area of the Neogene Shizigou Formation has biogenic gas,but the study of the Neogene in Sanhu area is very poor and lack of drilling targets.In order to make a breakthrough of the situation to find biogenic gas in the Quaternary and widen the biogenic gas exploration field,this paper combined drilling/logging,seismic and Milankovitch cycles to study the high resolution sequence stratigraphy of the Neogene in Sanhu depression,Qaidam basin.Results show that Shizigou Formation equals to a Ⅲ sequence(long-term datum plane cycles).Six sequence boundaries can be further identified and divided into five Ⅳ sequence(medium-term datum plane cycles) in Shizigou Formation.Each sequence can be further divided into half cycle of increasing and half cycle of descending.The delta front sandstone thinning out and sand lens trap which develop in half cycle of increasing period of Sequence III(sq3) are favorable target for further exploration.

  18. Expanding Conventional Seismic Stratigrphy into the Multicomponent Seismic Domain

    Innocent Aluka


    Multicomponent seismic data are composed of three independent vector-based seismic wave modes. These wave modes are, compressional mode (P), and shear modes SV and SH. The three modes are generated using three orthogonal source-displacement vectors and then recorded using three orthogonal vector sensors. The components travel through the earth at differing velocities and directions. The velocities of SH and SV as they travel through the subsurface differ by only a few percent, but the velocities of SV and SH (Vs) are appreciably lower than the P-wave velocity (Vp). The velocity ratio Vp/Vs varies by an order of magnitude in the earth from a value of 15 to 1.5 depending on the degree of sedimentary lithification. The data used in this study were acquired by nine-component (9C) vertical seismic profile (VSP), using three orthogonal vector sources. The 9C vertical seismic profile is capable of generating P-wave mode and the fundamental S-wave mode (SH-SH and SV-SV) directly at the source station and permits the basic components of elastic wavefield (P, SH-SH and SV-SV) to be separated from one another for the purposes of imaging. Analysis and interpretations of data from the study area show that incident full-elastic seismic wavefield is capable of reflecting four different wave modes, P, SH , SV and C which can be utilized to fully understand the architecture and heterogeneities of geologic sequences. The conventional seismic stratigraphy utilizes only reflected P-wave modes. The notation SH mode is the same as SH-SH; SV mode means SV-SV and C mode which is a converted shear wave is a special SV mode and is the same as P-SV. These four wave modes image unique geologic stratigraphy and facies and at the same time reflect independent stratal surfaces because of the unique orientation of their particle-displacement vectors. As a result of the distinct orientation of individual mode's particle-displacement vector, one mode may react to a critical subsurface sequence

  19. Accelerometer Sensor Specifications to Predict Hydrocarbon Using Passive Seismic Technique

    M. H. Md Khir


    Full Text Available The ambient seismic ground noise has been investigated in several surveys worldwide in the last 10 years to verify the correlation between observed seismic energy anomalies at the surface and the presence of hydrocarbon reserves beneath. This is due to the premise that anomalies provide information about the geology and potential presence of hydrocarbon. However a technology gap manifested in nonoptimal detection of seismic signals of interest is observed. This is due to the fact that available sensors are not designed on the basis of passive seismic signal attributes and mainly in terms of amplitude and bandwidth. This is because of that fact that passive seismic acquisition requires greater instrumentation sensitivity, noise immunity, and bandwidth, with active seismic acquisition, where vibratory or impulsive sources were utilized to receive reflections through geophones. Therefore, in the case of passive seismic acquisition, it is necessary to select the best monitoring equipment for its success or failure. Hence, concerning sensors performance, this paper highlights the technological gap and motivates developing dedicated sensors for optimal solution at lower frequencies. Thus, the improved passive seismic recording helps in oil and gas industry to perform better fracture mapping and identify more appropriate stratigraphy at low frequencies.

  20. Galicia Bank ocean-continent transition zone: New seismic reflection constraints

    Dean, S. L.; Sawyer, D. S.; Morgan, J. K.


    The West Iberia continental margin is a type locale for magma-poor rifting, and studies there have been instrumental in changing the classical view of the ocean-continent transition (OCT) from a discrete boundary juxtaposing continental and oceanic crust, into a more complicated zone of varying width that can include exhumed mantle. This study examines two new seismic lines in the Galicia Bank area extending west of the Peridotite Ridge, showing high resolution images of five new ridges. These ridges could be hyperextended continental crust, exhumed continental mantle, or rough ultra-slow spreading oceanic crust. There are no tilted fault blocks with pre-syn rift stratigraphy that would indicate continental crust. There are also no faults indicating mid-ocean spreading with seismic layer stratigraphy indicating normal oceanic crust. The ridges have no coherent internal seismic structure, and some resemble the topographic profile of the Peridotite Ridge. Therefore, it is likely the western ridges are also mainly composed of serpentinized mantle. These western ridges are also similar to small oceanic core complexes observed along the active part of the Mid-Atlantic Ridge, which also contain exhumed serpentinized mantle. This implies that there is a gradual transition within our study area from continental extension to seafloor spreading. Exhumation of continental mantle results in the formation of peridotite ridges, then transitions to episodic volcanism, which produces local thin basaltic crust, and exhumation of oceanic core complexes. Asymmetric processes during initial rifting and spreading result in contrasting structures on the two resulting margins.

  1. 从旋回的有序叠加形式到层序的识别和划分:层序地层学进展之三%From vertical stacking pattern of cycles to discerning and division of sequences: The third advance in sequence stratigraphy



    表了层序地层学的第3个重要进展.%In the conceptual system of the Exxon sequence stratigraphy, stratal units bounded by unconformities and their correlative conformities are defined as the depositional sequence. The depositional sequence is made up of systems tract, and the systems tract is composed of many parasequences or parasequence sets. In term of the sequence stratigraphic model that is based on the coastal sedimentology, the parasequence can be defined as a relative conformity succession of strata that is bounded by flooding surface; Further, the flooding surface, that is used as the bound surface of parasequence, is defined as a stratigraphic surface that divides the older strata from the young strata through which exists an abrupt rapid deepening of water depth. Thus, there is no universalism for the flooding surface that can be used as the bound surface of parasequence, which leads to the lacking of the integrality for parasequence. The term of the parasequence has subsequently been modified as high-frequency sequence by Exxon scientists, but this term that is lack of integrality has widely been used up to the present. In the same time or the time that is earlier than that of the Exxon age for sequence stratigraphy, the sedimentary cycle that is made up of lithofacies successions had been described by geologists, such as Lofer Cyclothem. This similar type of cyclic sedimentary records has been further defined as meter-scale cycle, and the meter-scale cycle has been interpreted as the product of autocyclic depositional process (the puncatuated aggradational cyclic mechanism; the PAC mechanism) which is controlled by allocyclic mechanism; Further, the allocyclic mechanism was explained as high frequency sea level change that is genetically related to the volume change of sea water due to the increasing and decreasing of ice cap in the polar region resulting from the Milankovitch cycle. These meter-scale cycles with thickness from several centimetem to several meters

  2. 准噶尔盆地东部地区八道湾组层序地层及油气勘探有利区带预测%Sequence Stratigraphy and Prediction of Favorable Zones for Hydrocarbon Exploration of Badaowan Formation in Eastern Junggar Basin

    王哲; 金振奎; 付晶; 郭守波


    Dishuiquan Area is located in slope area of Kalameili Mountain in the eastern Junggar Basin; at the south are Wucaiwan Depression and Dongdaohaizi Depression; at the west is Dishuiquan Depression.By using of the theory and method of sequence stratigraphy and sedimentology and the data of seismic,well drilling,well logging and core,the authors establish the sequence stratigraphic framework and divide sedimentary facies of Jurassic Badaowan Formation in the Dishuiquan Area.The sequence of Badaowan Formation is one and half,including 5 system tracts divided by two FFS,two MFS and the stable core inner J1 b3.The whole experiences the process of retrogradation,progradation and then retrogradation again.Multilevel topographic breaks developed in the Dishuiquan Area in the early Jurassic.Superimposing patterns of system tracts are lowstand system tract,lacustrine transgressive system track and highstand system tract.As is mentioned above,JSB1 is the bottom boundary of the sequence and JSB2 as the top boundary.We divide the middle and lower part with the lower up part of Badaowan Formation into one sequence,from up to down,including lowstand system tract,lacustrine transgressive system track and highstand system tract.Its upper part of the lowstand system tract and lacustrine transgressive system track together with the lower member of Sangonghe Formation of highstand system tract make up another sequence.The Badaowan Group is the first lake influx lake retreat cycle after the late Triassic tectonic uplift,which has the vertical sequence of bottom-up development of coarse to fine to coarse complete cycle,and the sedimentary facies perform for the evolution of river-lake-delta.The tectonic activity of Badaowan depositional period is relatively stable,accompanied with regional sublacustrine concussion,and the climate is wet warm.Influenced by ancient water system in the eastern part of the Junggar Basin,the study area constitutes the sedimentary system with east

  3. Étude haute résolution de la distribution et de la granulométrie des constituants organiques sédimentaires dans le Kimméridgien Tithonien du Boulonnais (Nord de la France). Application à l'analyse séquentielleSedimentary organic matter, accumulation and grain-size in the Kimmeridgian Tithonian of the Boulonnais area (Northern France). Application to sequence stratigraphy.

    Bialkowski, Anne; Tribovillard, Nicolas-Pierre; Vergès, Elisabeth; Deconinck, Jean-François


    The sedimentary organic matter from the Kimmeridgian-Tithonian marlstones of the Boulonnais area is studied through a petrographic, geochemical and a grain-size distribution approach. The abundance of the orange amorphous organic matter (AOM) correlates well with the geochemical parameters and intense sulfurisation reactions could explain its preservation, with a relative iron shortage. This may imply strong surface-water productivity linked to sea-level highstands and a possible decrease in sedimentation rate. The OM grain-size parameters correlate with sea-level variations and the orange AOM distribution in the Argiles de Châtillon formation. This relation could be helpful for the comprehension of the sequential stratigraphy.

  4. The stratigraphy of cretaceous mudstones in the eastern Fuegian Andes: new data from body and trace fossils Estratigrafía de las fangolitas del Cretácico en los Andes Fueguinos orientales: Nuevos datos de cuerpos y trazas fósiles

    Eduardo B. Olivero


    Full Text Available The stratigraphy of Cretaceous marine mudstones in the Fuegian Andes, roughly equivalent to Charles Darwin's clay-slate formation, remains a still unsolved problem. Previous records of Albian, Turonian-Coniacian, and Santonian-Campanian bivalves are combined with new findings of the Late Albian inoceramid Inoceramus anglicus Woods, and the Maastrichtian ammonites Diplomoceras sp., Anagaudryceras sp., Maorites densicostatus (Kilian and Reboul, Maorites sp., and Pachydiscus (Neodesmoceras sp. to further constrain the Cretaceous stratigraphy of the eastern Fuegian Andes. In addition, new records of distinctive trace fossils and ichnofabric are meaningful for stratigraphic division and delineation of paleoenvironmental settings in these Cretaceous mudstones. The Lower Cretaceous ichnoassemblage of Chondrites targioni (Brongniart and Zoophycos isp. is consistent with the inferred slope-volcaniclastic apron settings of the Yahgan Formation; Nereites missouriensis (Weller reflects distal basin plain depositional settings for the Beauvoir Formation. In the Upper Cretaceous, the "Estratos de Buen Suceso" record the earliest extensively bioturbated horizons, reflecting prolonged well-oxygenated bottom conditions. In the Bahía Thetis Formation, organic-rich, channel margin or distal basin slaty mudstones record the last occurrence of inoceramid bivalves in the Austral Basin; the generalized absence of trace fossils is consistent with dysoxic bottom conditions. The thoroughly bioturbated Policarpo Formation, records a marked change in paleoceanographic conditions. The strong contrast in the intensity of bioturbation between the Upper Campanian-Maastrichtian Bahía Thetis Formation, almost devoid of trace fossils, and the highly bioturbated Maastrichtian-Danian Policarpo Formation reflects a change from dysoxic-anoxic to well ventilated conditions, probably associated with a cooling trend of bottom waters in the austral deep oceans.En los Andes Fueguinos la

  5. Sequence stratigraphy of the last filling phase of an intra continental rift: a model based on the Lower Barremian of the Reconcavo Basin; Estratigrafia de sequencias da fase final de preenchimento de um rifte intracontinental: um modelo com base no Barremiano Inferior da Bacia do Reconcavo

    Santos, Clovis Francisco [PETROBRAS S.A., Campos dos Goytacases, RJ (Brazil). E e P.], E-mail:


    The sedimentary deposits of the Buracica Stage (Lower Barremian) of the Reconcavo Basin are characterized by a cyclic succession of fluvial, deltaic and lacustrine sediments, included in the Sao Sebastiao Formation. Outcrop, core and well log studies supported the proposal of a model that explains the architecture of the stratigraphic sequences and its subdivision in six third order sequences and twenty fourth order sequences. The lowstand lake-level systems tract (LLST) is characterized by a broad fluviodeltaic progradation, whereas the transgressive lake-level systems tract (TLST) is characterized by a retrogradational architecture, mainly in the distal areas of the basin. An aggradational pattern can occur in the proximal areas, where the sedimentation rate equals the rate of creation of accommodation space. The high stand lake level systems tract (HLST) is predominantly characterized by a lacustrine pelitic sedimentation, which is a continuation of the sedimentation of the TLST pelites. The broad deltaic progradation anticipated by the Sequence Stratigraphy for the high stand systems tract of the marine sequences does not apply to the studied interval. The forced-regression systems tract (FRST) is represented by thin sandstone beds. The identification of this systems tract is hard since its deposits can be easily eroded. In the proposed model, the sequence boundaries are erosive surfaces produced during falling lake-level periods, which are climatically controlled. The position of transgressive and maximum flooding surfaces are related to the rate of coarse-grained sediment influx, which is dependent upon the water influx. The sequences are deposited and preserved by the accommodation space created by subsidence. (author)

  6. The Early Gulf of Mexico as a Subaerial Basin Below Sea Level (SABSEL) Basin. Evidence from Stratigraphy and Facies of Luanne salt, Norphlet sandstone and Smackover Brown Dense Formations.

    Cassidy, M. M.


    Many workers recognize that large salt deposits form in post-rift sag basins which were subaerial and susceptible to rapid flooding from adjacent oceansl. I have termed these basins "subaerial basins below sea level" or "SABSEL" basins. A key marker of SABSEL basins are terrestrial sediments immediately overlain by deepwater sediments with no transition. Desert deposits -including Aeolian dunes- are preserved in the adiabatically heated depression. Dunes are not eroded by transgressing seas but are drowned by rising water as in a bath tub. They maintain their shape. Deepwater marine black shales or limestones drape the dunes. The Southern North sea is an example. Above the original marine shale over the dunes are evaporites. Winds descending into the basin were heated by adiabatic compression providing the very hot air need to allow survival of potassium salts. A similar situation was probably active during the Messinian salinity crisis in the Mediterranean basin, and the opening of the South Atlantic. In the Gulf of Mexico (GOM) a desert is on the Louann salt. Here the sea invaded the lows first to deposit the salt overlying tilted fault blocks of the opening basin, as in the Afar Triangle of Africa. In the GOM entry to the west fed in sea water, then closed. The Norphlet desert formed. Streams carried sands to the basin to be spread by winds where they willed, not limited to sand entry areas. Upon deposition their original weight depressed the salt. Seismic shows depressions in the salt but the dunes are high at the top Norphlet, forming distinctive small "eyes" at the top salt. The 600 foot dunes are draped by deep water dolomitic finely laminated organic rich black/ brown shale, the Brown Dense Facies of the Smackover formation. The lack of reworking of the dunes found by detailed seismic is distinctive of deposition in a SABSEL basin. The overlap of terrestrial sediments by deep water deposition is good evidence of sudden flooding. In summary this vertical

  7. Interlobate esker architecture and related hydrogeological features derived from a combination of high-resolution reflection seismics and refraction tomography, Virttaankangas, southwest Finland

    Maries, Georgiana; Ahokangas, Elina; Mäkinen, Joni; Pasanen, Antti; Malehmir, Alireza


    A novel high-resolution (2-4 m source and receiver spacing) reflection and refraction seismic survey was carried out for aquifer characterization and to confirm the existing depositional model of the interlobate esker of Virttaankangas, which is part of the Säkylänharju-Virttaankangas glaciofluvial esker-chain complex in southwest Finland. The interlobate esker complex hosting the managed aquifer recharge (MAR) plant is the source of the entire water supply for the city of Turku and its surrounding municipalities. An accurate delineation of the aquifer is therefore critical for long-term MAR planning and sustainable use of the esker resources. Moreover, an additional target was to resolve the poorly known stratigraphy of the 70-100-m-thick glacial deposits overlying a zone of fractured bedrock. Bedrock surface as well as fracture zones were confirmed through combined reflection seismic and refraction tomography results and further validated against existing borehole information. The high-resolution seismic data proved successful in accurately delineating the esker cores and revealing complex stratigraphy from fan lobes to kettle holes, providing valuable information for potential new pumping wells. This study illustrates the potential of geophysical methods for fast and cost-effective esker studies, in particular the digital-based landstreamer and its combination with geophone-based wireless recorders, where the cover sediments are reasonably thick.

  8. Interlobate esker architecture and related hydrogeological features derived from a combination of high-resolution reflection seismics and refraction tomography, Virttaankangas, southwest Finland

    Maries, Georgiana; Ahokangas, Elina; Mäkinen, Joni; Pasanen, Antti; Malehmir, Alireza


    A novel high-resolution (2-4 m source and receiver spacing) reflection and refraction seismic survey was carried out for aquifer characterization and to confirm the existing depositional model of the interlobate esker of Virttaankangas, which is part of the Säkylänharju-Virttaankangas glaciofluvial esker-chain complex in southwest Finland. The interlobate esker complex hosting the managed aquifer recharge (MAR) plant is the source of the entire water supply for the city of Turku and its surrounding municipalities. An accurate delineation of the aquifer is therefore critical for long-term MAR planning and sustainable use of the esker resources. Moreover, an additional target was to resolve the poorly known stratigraphy of the 70-100-m-thick glacial deposits overlying a zone of fractured bedrock. Bedrock surface as well as fracture zones were confirmed through combined reflection seismic and refraction tomography results and further validated against existing borehole information. The high-resolution seismic data proved successful in accurately delineating the esker cores and revealing complex stratigraphy from fan lobes to kettle holes, providing valuable information for potential new pumping wells. This study illustrates the potential of geophysical methods for fast and cost-effective esker studies, in particular the digital-based landstreamer and its combination with geophone-based wireless recorders, where the cover sediments are reasonably thick.

  9. Miocene uplift of the NE Greenland margin linked to plate tectonics: Seismic evidence from the Greenland Fracture Zone, NE Atlantic

    Døssing Andreasen, Arne; Japsen, Peter; Watts, Anthony B.


    Tectonic models predict that, following breakup, rift margins undergo only decaying thermal subsidence during their post-rift evolution. However, post-breakup stratigraphy beneath the NE Atlantic shelves shows evidence of regional-scale unconformities, commonly cited as outer margin responses to ...... by plate tectonic forces, induced perhaps by a change in the Iceland plume (a hot pulse) and/or by changes in intra-plate stresses related to global tectonics.......Tectonic models predict that, following breakup, rift margins undergo only decaying thermal subsidence during their post-rift evolution. However, post-breakup stratigraphy beneath the NE Atlantic shelves shows evidence of regional-scale unconformities, commonly cited as outer margin responses...... to inner margin episodic uplift, including the formation of coastal mountains. The origin of these events remains enigmatic. We present a seismic reflection study from the Greenland Fracture Zone – East Greenland Ridge (GFZ-EGR) and the NE Greenland shelf. We document a regional intra-Miocene seismic...

  10. Study of the elementary composition and stratigraphy layers of pigments in statues of polychromed wood using a portable system of EDXRF; Estudo da composicao elementar e estratigrafia das camadas de pigmentos em estatuas de madeira policromada usando um sistema portatil de EDXRF

    Blonski, Maria Selia


    recuperated more recently, it was verified the absence of Au and a great amount of Cu. On the other hand, the analysis of the intensities ratios of the lines K{sub {alpha}}/K{sub {beta}} or L{sub {alpha}}/L{sub {beta}} in the measured areas allowed to explore the possibility to measure the stratigraphy of the layers of the pigments. (author)

  11. A High-Sensitivity Broad-Band Seismic Sensor for Shallow Seismic Sounding of the Lunar Regolith

    Pike, W. Thomas; Standley, Ian M.; Banerdt, W. Bruce


    The recently undertaken Space Exploration Initiative has prompted a renewed interest in techniques for characterizing the surface and shallow subsurface (0-10s of meters depth) of the Moon. There are several reasons for this: First, there is an intrinsic scientific interest in the subsurface structure. For example the stratigraphy, depth to bedrock, density/porosity, and block size distribution all have implications for the formation of, and geological processes affecting the surface, such as sequential crater ejecta deposition, impact gardening, and seismic settling. In some permanently shadowed craters there may be ice deposits just below the surface. Second, the geotechnical properties of the lunar surface layers are of keen interest to future mission planners. Regolith thickness, strength, density, grain size and compaction will affect construction of exploration infrastructure in terms of foundation strength and stability, ease of excavation, radiation shielding effectiveness, as well as raw material handling and processing techniques for resource extraction.

  12. Astor Pass Seismic Surveys Preliminary Report

    Louie, John [UNR; Pullammanappallil, Satish [Optim; Faulds, James; Eisses, Amy; Kell, Annie; Frary, Roxanna; Kent, Graham


    In collaboration with the Pyramid Lake Paiute Tribe (PLPT), the University of Nevada, Reno (UNR) and Optim re-processed, or collected and processed, over 24 miles of 2d seismic-reflection data near the northwest corner of Pyramid Lake, Nevada. The network of 2d land surveys achieved a near-3d density at the Astor Pass geothermal prospect that the PLPT drilled during Nov. 2010 to Feb. 2011. The Bureau of Indian Affairs funded additional seismic work around the Lake, and an extensive, detailed single-channel marine survey producing more than 300 miles of section, imaging more than 120 ft below the Lake bottom. Optim’s land data collection utilized multiple heavy vibrators and recorded over 200 channels live, providing a state-of-the-art reflection-refraction data set. After advanced seismic analysis including first-arrival velocity optimization and prestack depth migration, the 2d sections show clear fault-plane reflections, in some areas as deep as 4000 ft, tying to distinct terminations of the mostly volcanic stratigraphy. Some lines achieved velocity control to 3000 ft depth; all lines show reflections and terminations to 5000 ft depth. Three separate sets of normal faults appear in an initial interpretation of fault reflections and stratigraphic terminations, after loading the data into the OpendTect 3d seismic visualization system. Each preliminary fault set includes a continuous trace more than 3000 ft long, and a swarm of short fault strands. The three preliminary normal-fault sets strike northerly with westward dip, northwesterly with northeast dip, and easterly with north dip. An intersection of all three fault systems documented in the seismic sections at the end of Phase I helped to locate the APS-2 and APS-3 slimholes. The seismic sections do not show the faults connected to the Astor Pass tufa spire, suggesting that we have imaged mostly Tertiary-aged faults. We hypothesize that the Recent, active faults that produced the tufa through hotspring

  13. 2D Seismic Reflection Data across Central Illinois

    Smith, Valerie; Leetaru, Hannes


    In a continuing collaboration with the Midwest Geologic Sequestration Consortium (MGSC) on the Evaluation of the Carbon Sequestration Potential of the Cambro-Ordovician Strata of the Illinois and Michigan Basins project, Schlumberger Carbon Services and WesternGeco acquired two-dimensional (2D) seismic data in the Illinois Basin. This work included the design, acquisition and processing of approximately 125 miles of (2D) seismic reflection surveys running west to east in the central Illinois Basin. Schlumberger Carbon Services and WesternGeco oversaw the management of the field operations (including a pre-shoot planning, mobilization, acquisition and de-mobilization of the field personnel and equipment), procurement of the necessary permits to conduct the survey, post-shoot closure, processing of the raw data, and provided expert consultation as needed in the interpretation of the delivered product. Three 2D seismic lines were acquired across central Illinois during November and December 2010 and January 2011. Traversing the Illinois Basin, this 2D seismic survey was designed to image the stratigraphy of the Cambro-Ordovician sections and also to discern the basement topography. Prior to this survey, there were no regionally extensive 2D seismic data spanning this section of the Illinois Basin. Between the NW side of Morgan County and northwestern border of Douglas County, these seismic lines ran through very rural portions of the state. Starting in Morgan County, Line 101 was the longest at 93 miles in length and ended NE of Decatur, Illinois. Line 501 ran W-E from the Illinois Basin – Decatur Project (IBDP) site to northwestern Douglas County and was 25 miles in length. Line 601 was the shortest and ran N-S past the IBDP site and connected lines 101 and 501. All three lines are correlated to well logs at the IBDP site. Originally processed in 2011, the 2D seismic profiles exhibited a degradation of signal quality below ~400 millisecond (ms) which made

  14. Late Devonian conodonts and event stratigraphy in northwestern Algerian Sahara

    Mahboubi, Abdessamed; Gatovsky, Yury


    Conodonts recovered from the Late Devonian South Marhouma section comprise 5 genera with 31 species (3 undetermined). The fauna establishes the presence of MN Zones 5, undifferentiated 6/7, 8/10 for the Middle Frasnian, the MN Zones 11, 12, 13 for the Upper Frasnian as well as the Early through Late triangularis Zones in the basal Famennian. The outcropping lithological succession is one of mostly nodular calcilutites alternating with numerous marly and shaly deposits, which, in the lower and upper part, comprise several dysoxic dark shale intervals. Among these the Upper Kellwasser horizon can be precisely dated and as such the presence of the terminal Frasnian Kellwasser Event is recognized for the first time in Algeria. Both the Middlesex and Rhinestreet Events cannot yet be precisely located, but supposedly occur among the dark shale horizons in the lower part of the section. However, their assignment to a precise level has so far not been established. Though poor in conodont abundance the South Marhouma section provides first evidence of the presence of several Montagne Noire conodont zones within the so far widely unstudied Frasnian of the Ougarta Chain. As such it is considered representative for the northwestern Algerian Saoura region.

  15. Shallow stratigraphy and paleolandscapes offshore from the Northern Channel Islands

    Maloney, J. M.; Braje, T.; Gusick, A. E.; Ho, B.; Ball, D.


    New high-resolution Chirp and sidescan sonar data collected on the shelf offshore from the Northern Channel Islands image patterns of sediment distribution since the last glacial maximum (LGM), extensive faulting and deformation, and submerged paleolandscapes that may contain archaeological resources. During the last glacial maximum, the four Northern Channel Islands in the Southern California Bight formed an extensive landmass known as Santarosae. Sea-level transgression since the LGM has inundated over 70% of Santarosae, submerging the shelf around the modern islands. The islands are traversed by numerous faults that extend offshore and marine terraces are observed both onshore and offshore. This area is an ideal landscape to investigate the relationships between sediment supply, eustasy, and tectonics in controlling sediment distribution on continental shelves. Furthermore, the presence of Paleocoastal archaeological sites on the islands suggests that similar sites may be present on the submerged shelf. The new data reveal faulting and deformation associated with the Santa Rosa and Santa Cruz fault zones. Both faults offset acoustic horizons below a regional unconformity interpreted as the transgressive surface. Sediment thickness is variable above the transgressive surface and bedform spatial patterns imaged in the sidescan sonar do not appear to correlate with sediment thickness or depth. In Chirp data, we interpret several filled paleochannels extending across the shelf, some of which appear fault controlled. Along with possible estuarine deposits imaged near the modern submarine canyon, these paleolandforms would have been important resources for people living on Santarosae and may contain archaeological resources. Overall, these data elucidate effects of sea level transgression and patterns of sediment distribution on islands located along an active margin.

  16. Huygens Crater: Insights into Noachian Volcanism, Stratigraphy, and Aqueous Processes

    Ackiss, S. E.; Wray, J. J.; Seelos, K. D.; Niles, P. B.


    Huygens crater is a well preserved peak ring structure on Mars centered at 13.5 deg S, 55.5 deg E in the Noachian highlands between Terras Tyrrhena and Sabaea near the NW rim of Hellas basin. With a diameter of approximately 470 km, it uplifted and exhumed pre-Noachian crustal materials from depths greater than 25 km, penetrating below the thick, ubiquitous layer of Hellas ejecta. In addition, Huygens served as a basin for subsequent aqueous activity, including erosion/deposition by fluvial valley networks and subsurface alteration that is now exposed by smaller impacts. Younger mafic-bearing plains that partially cover the basin floor and surrounding intercrater areas were likely emplaced by later volcanism.

  17. Permian stratigraphy and correlation of Northeast China: A review

    Shen, S.-Z.; Zhang, H.; Shang, Q. H.; Li, W.-Z.


    Palaeontological, lithostratigraphical data from the Permian strata and correlation of the Permian successions for different tectonic units in Northeast China are reviewed and summarized in this paper. Permian strata in Northeast China are dominated by brachiopods, fusulinoideans and land plants, with limited ammonoids, conodonts and bivalves. The Cisuralian (Early Permian) in the northern margin of the North China Block and in the Manchuride Belt is composed mostly of marine massive limestone with the characteristic Pseudoschwagerina Zone in the Asselian and Sakmarian and the Misellina claudiae Zone in the Kungurian. The Cisuralian in the Xing'an Block and the northeastern part of Inner Mongolia is dominated by huge terrestrial deposits with fossil plants. The Guadalupian (Middle Permian) in the Manchuride, Altaid and Yanbian Belts are characterized by bi-temperate Roadian or early Wordian Monodiexodina fauna and the late Wordian-Capitanian Codonofusiella- Schwagerina or Neoschwagerina- Yabeina faunas, the mixed brachiopod faunas between the Boreal/antitropical and the Palaeoequatorial Cathaysian forms, the Roadian or early Wordian solitary coral faunas, and the late Wordian-Capitanian compound Waagenophyllum- Wentzelella fauna. The Nadanhada Terrane contains some exotic limestone blocks with a typical Cathaysian Neoschwagerina- Yabeina fauna in a Late Jurassic-Early Cretaceous mélange, which is related to Mesozoic subduction in the western Circum-Pacific region. The Lopingian (Late Permian) in Northeast China is mostly characterized by terrestrial molasse deposits with a mixed flora between the Boreal Angaran and the palaeoequatorial Cathaysian Provinces, indicating the final closure of the Palaeo-Asian Ocean.

  18. New age findings on the stratigraphy of the Keban metamorphites

    Ali KAYA


    Full Text Available Keban metamorphic rocks, located in Eastern Taurides, consist of platforms type carbonate and clastic rocks, regionally metamorphosed in greenschist facies. The age of the Keban metamorphites was based on two fossil findings (Glomospira and Ammodiscus family which of the microorganism species were not detected and they were observed in only one location in Zeryandere, Permian aged estimated. The other formations of the metamorphic sequence were correlated with it. The age for the Keban metamorphites has been proposed as Permo-Triassic/Permo-Carboniferous up to now. All geological evaluations of the region were based on these ages. For the first time in this study, trace fossils (vermes trace like Planolites, Rhizocorallium and Thalassinoides have been observed extensively. These fossils were detected on the layer surfaces of the Gogodere stratified dolomitic-crystallized limestone which is a member of Nimri formation, represents the medium level of the Keban metamorphites. The limestone levels include these trace fossils correspond to a typical “vermicular limestone facies”, representing Early-Middle Triassic (Scythian-Anisian in Taurides. Allochthonous Keban metamorphic rocks consist of several nappes which overlaid by the others. There are three nappes in the study area; the lower nappe is constitute Early Triassic-Jurassic Nimri formation, the middle nappe is constitute Late Devonian Keban marbles and Delimehmet formation and the upper nappe is Early Carboniferous Süleymanlı formation. Also metabasic intercalations consisting green metadiabases pre-Triassic aged are observed in the middle and upper nappes. The regional correlations propose that the Keban metamorphites are equivalent of the Bolkardağı Union.

  19. Terreneuvian stratigraphy and faunas from the Anabar Uplift, Siberia

    Artem Kouchinsky


    Full Text Available Assemblages of mineralized skeletal fossils are described from limestone rocks of the lower Cambrian Nemakit-Daldyn, Medvezhya, Kugda-Yuryakh, Manykay, and lower Emyaksin formations exposed on the western and eastern flanks of the Anabar Uplift of the northern Siberian Platform. The skeletal fossil assemblages consist mainly of anabaritids, molluscs, and hyoliths, and also contain other taxa such as Blastulospongia, Chancelloria, Fomitchella, Hyolithellus, Platysolenites, Protohertzina, and Tianzhushanella. The first tianzhushanellids from Siberia, including Tianzhushanella tolli sp. nov., are described. The morphological variation of Protohertzina anabarica and Anabarites trisulcatus from their type locality is documented. Prominent longitudinal keels in the anabaritid Selindeochrea tripartita are demonstrated. Among the earliest molluscs from the Nemakit-Daldyn Formation, Purella and Yunnanopleura are interpreted as shelly parts of the same species. Fibrous microstructure of the outer layer and a wrinkled inner layer of mineralised cuticle in the organophosphatic sclerites of Fomitchella are reported. A siliceous composition of the globular fossil Blastulospongia is reported herein and a possible protistan affinity similar to Platysolenites is discussed. New carbon isotope data facilitate correlation both across the Anabar Uplift and with the Terreneuvian Series of the IUGS chronostratigraphical scheme for the Cambrian System. The base of Cambrian Stage 2 is provisionally placed herein within the Fortunian‒Cambrian Stage 2 transitional interval bracketed by the lowest appearance of Watsonella crosbyi and by a slightly higher horizon at the peak of carbon isotope excursion Iʹ from western flank of the Anabar Uplift. Correlation across the Siberian Platform of the fossiliferous Medvezhya and lower Emyaksin formations showing δ13Ccarb excursion Iʹ with the upper Sukharikha Formation containing excursion 5p and upper Ust’-Yudoma Formation containing excursion I is supported herein.

  20. Late Pleistocene stratigraphy of a carbonate platform margin, Exumas, Bahamas

    Aalto, K. R.; Dill, Robert F.


    Detailed field studies of the southern Exuma Cays on the eastern margin of the Great Bahama Bank show a complex history of late Pleistocene island construction. Pleistocene rocks include island core eolianites, overlain at island margins by fossil patch reefs and reef sands, which in turn are overlain by, and/or grade laterally into, talus breccia cones derived from the erosion of island core eolianite at paleo-seacliffs situated at approximately 5-6 m above present mean high tide. Laminated pedogenic calcrete widely caps Pleistocene rocks. Minor zones of penetrative subsurface calcretization, developed in association with root growth, occur along permeable horizons, including: contacts between talus units or crossbed sets, along tension joints, and (possibly) at the Pleistocene reef-eolianite contact. Among Pleistocene eolianite samples studied in thin-section, the relative proportions of ooids-intraclasts+grapestones-skeletal grains-peloids are approximately 48:39:6:7. Marginal to the Exuma Sound and on the Brigantine Cays, a greater proportion of ooids have peloidal nuclei and cortices with numerous laminae, which may reflect ooid derivation from shelf margin and broad platform interior regions that were characterized by high wave energy during ooid formation. Between these two areas, ooids are more commonly superficial and have cortices with few laminae and nuclei composed of subrounded micrite or pelmicrite intraclasts. Such ooid nuclei are most likely derived from storm erosion of partially cemented seafloor muds. Some skeletal-rich eolianite in this region may reflect local sediment input from platform margin reefs, or may be part of an older(?) stratigraphic unit.

  1. The Role of Anthropogenic Stratigraphy in River Restoration Projects

    Evans, J. E.; Webb, L. D.


    As part of a river restoration project and removal of a low-head dam on the Ottawa River (northwestern Ohio and southeastern Michigan) in 2007, a longer-term project was initiated to assess anthropogenic changes of the Ottawa River fluvial system. A composite stratigraphic section 4.5 m in length was constructed by stratigraphic correlation from three trenches up to 2.5 m in depth and 14 vibracores up to 2.5 m in length, all within a small region (system over time: (1) prior to approximately 5 Ka, the river system was transporting mineral-rich sediment and formed meandering point-bar sequences approximately 1.5 m thick; (2) between approximately 5 Ka and 200 YBP, the river system was transporting organic-rich sediment (i.e., blackwater stream) bordered by riparian wetlands accumulating peat (part of the regional "Great Black Swamp" discovered by settlers from eastern North America); (3) between approximately 200 YBP and the early 1960s the river system was transporting mineral-rich sediment (i.e., brownwater stream), probably sourced from extensive land clearance for agriculture, which backfilled and overtopped the previous riparian wetlands and produced an series of thin channel fills interpreted as rapidly shifting avulsional channels; (4) since the early 1960s, sediment supply has exceeded sediment conveyance capacity, leading to vertical aggradation of approximately 1.7 m, creating the fill-terrace morphology evident today; and (5) overlapping with the previous stage, channel incision and lateral channel migration has produced a fluvial system dominated by bank erosion, logjams due to tree fall, and degraded substrate with fluvial pavements. Stage 4 is interpreted as a time-specific (1950s-1960s) sediment pulse related to extensive urbanization of the lower drainage basin, while the partly overlapping stage 6 is interpreted as fluvial reworking of intrabasinal storage of legacy sediment under conditions of lower sediment input (reforested suburban housing developments) but higher water inputs (increasingly urbanized stormwater networks). Regarding river restoration, it is clear that most of the modern fluvial system is a recent and highly manipulated system that may not be sustainable.

  2. Greenland Snow Pit and Core Stratigraphy (Analog and Digital Formats)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set is comprised of scientific field study notebooks from geologist Carl S. Benson describing his traverses of Greenland from 1952 to 1955. The notebooks...

  3. Late Cenozoic structure and stratigraphy of south-central Washington

    Reidel, S.P. [Westinghouse Hanford Co., Richland, WA (United States)]|[Washington State Univ., Pullman, WA (United States). Dept. of Geology; Campbell, N.P. [Yakima Valley Coll., WA (United States); Fecht, K.R.; Lindsey, K.A. [Westinghouse Hanford Co., Richland, WA (United States)


    The structural framework of the Columbia Basin began developing before Columbia River Basalt Group (CRBG) volcanism. Prior to 17.5 Ma, the eastern part of the basin was a relatively stable area, with a basement of Paleozoic and older crystalline rock. The western part was an area of subsidence in which large volumes of sediment and volcanic rocks accumulated. Concurrent with eruption of the CRBG, anticlinal ridges of the Yakima Fold Belt (YFB) were growing under north-south compression. Topographic expression of these features was later masked by the large volume of CRBG basalt flowing west from fissures in the eastern Columbia Basin. The folds continued to develop after cessation of volcanism, leading to as much as 1,000 m of structural relief in the past 10 million years. Post-CRBG evolution of the Columbia Basin is recorded principally in folding and faulting in the YFB and sediments deposited in the basins. The accompanying tectonism resulted in lateral migration of major depositional systems into subsiding structural lows. Although known late Cenozoic faults are on anticlinal ridges, earthquake focal mechanisms and contemporary strain measurements indicate most stress release is occurring in the synclinal areas under north-south compression. There is no obvious correlation between focal mechanisms for earthquakes whose foci are in the CRBG and the location of known faults. High in situ stress values help to explain the occurrence of microseismicity in the Columbia Basin but not the pattern. Microseismicity appears to occur in unaltered fresh basalt. Faulted basalt associated with the YFB is highly brecciated and commonly altered to clay. The high stress, abundance of ground water in confined aquifers of the CRBG, and altered basalt in fault zones suggest that the frontal faults on the anticlinal ridges probably have some aseismic deformation. 85 refs.

  4. Shorter contributions to stratigraphy and structural geology, 1979



    PART A: A system of anticlines lies along the trend of the sinuous course of the Colorado River for a distance of 97 km in the central Grand Canyon. Similar anticlines occur in some perennially wet side canyons. The anticlines are most abundant and well developed along northeast-trending reaches of the main canyon where it is floored by the Cambrian Muav Limestone. Dips of the folded strata are as great as 60?, and the folding locally extends more than 250 m from the river. Low-angle thrust faults in the limbs of the anticlines parallel the river and have formed in response to folding of the comparatively brittle carbonate strata. High-angle reverse kink bands, along which rocks are displaced up toward the river, also parallel the anticlines and have develop2d in response to the upward bulging of the canyon floor. The river anticlines are an unloading phenomenon. They result from lateral squeezing toward the river of saturated shaly parts of the Muav Limestone and underlying Bright Angel Shale. The driving mechanism for the deformation is a stress gradient that results from a difference in lithostatic load between the heavily loaded rocks under the 650-m-high canyon walls and the unloaded canyon floor. Saturation appears to weaken the shaly rocks sufficiently to allow deformation to take place. River anticlines are not present in the eastern Grand Canyon, where the Cambrian rocks also occur at river level. Their absence is explained by a lack of shaly rocks that could flow when saturated. PART B: The current interest in contemporary tectonic processes in the Eastern United States is turning up abundant evidence of crustal movements in late geologic time. Topographic analysis of the highland areas from the southern Blue Ridge to the Adirondack Mountains indicates that most of the landforms owe their origin to erosion of rocks of different resistance rather than to tectonic processes. Most areas of high relief and high altitude have been formed on resistant rocks. The Cambrian and Ordovician belt, containing mostly shale and carbonate rock, on the other hand, forms an extensive lowland from Alabama to the Canadian border and girdles the Adirondack Mountains. Differences in altitude can be explained by the presence of resistant rocks outside the belt; these resistant rocks form local base levels on the streams that drain the belt. A few areas may have undergone local uplift at a higher rate than areas nearby--for example, the Piedmont region northwest of Chesapeake Bay. Most estimates of erosion rates, based on the load transported by streams and of uplift rates, based on removal during a known period of time, are of the same order of magnitude, averaging almost 4x 10^-2 millimeters per year. Rates of uplift, based on study of tilted Pleistocene beaches and repeated geodetic traverses, are at least an order of magnitude higher for comparable areas. Tectonic uplift of the highlands has been slow and involves mostly warping or tilting on a large scale. Erosion rates keep up with or exceed the rate of uplift and have been sufficient to mask evidence of faulting or other differential movements. The high rates of uplift that are inferred on tilted water planes in the glaciated regions or that are measured by differences in repeated geodetic traverses cannot have been sustained for long periods of time. PART C: The Hanson Creek Formation southwest of Eureka, Nev., in the Bellevue Peak Quadrangle is composed of three lithostratigraphic members: (1) a basal dark-gray dolomite, (2) a middle silty thin- to thick-bedded, locally nodular, dark-gray, light-yellow-mottled limestone topped by light-gray dolomite, and (3) an upper dark-gray dolomite, which is herein named the Combs Canyon Dolomite Member. Detailed geologic mapping and accompanying fossil collecting prove that the same lithostratigraphic and biostratigraphic sequence is present in the Mountain Boy Range and 11 km to the south near Wood Cone Peak. Minor differences in




    .... The Davaly Formation corresponds to the Bolorian Stage of the Lower Permian (Cisuralian); the Asni Formation corresponds to the Kubergandian Stage, and to the lower half of the Murgabian Stage of the Middle Permian (Guadalupian...

  6. Petrology and stratigraphy of Paleogene nonmarine sandstones, Cascade Range, Washington

    Frizzell, Virgil A.


    The Cascade Range of Washington north of 47? latitude is composed of probable Paleozoic and Mesozoic metamorphic rocks and Mesozoic and Tertiary plutonic rocks. Several Paleogene nonmarine arkosic sandstone units fringe and in part occur within the complex crystalline core. The early to middle Eocene Chuckanut Formation is present on the west side of the crystalline core in the western foothills of the Cascades. The early to middle Eocene Swauk Formation partially encircles the Mt. Stuart massif of the central Cascades. In the western foothills of the Cascades, between the main body of Chuckanut Formation near Bellingham and the main outcrop area of the Swauk Formation south of Mt. Stuart, many smaller bodies of arkosic sandstone have variously been referred to either the Swauk or Chuckanut Formations. The early Eocene Manastash Formation occurs locally in an area south of the Yakima River. The middle to late Eocene Chumstick Formation is mostly confined to the Chiwaukum graben within the crystalline core and is separated from the Swauk Formation on the southwest by the Leavenworth Fault. The Oligocene Wenatchee Formation unconformably over lies the Chumstick Formation near Wenatchee. The middle to late Eocene Roslyn Formation crops out north of the Yakima River and is underlain by the Teanaway Basalt which separates the Roslyn from the older Swauk Formation. The middle Eocene to early Oligocene Naches Formation forms a north-trending body that crosses the Yakima River and is in fault contact with both the Swauk and Manastash Formations. The middle to late Eocene Puget Group underlies the Quaternary deposits of the Puget Lowland southeast of Seattle on the western flank of the Cascades. The various formations are all composed predominantly of fine- to medium-grained sandstones with lesser amounts of interbedded shale, conglomerate and coal. Compositionally, the units are predominantly either feldspathic or litho-feldspathic subquartzose sandstones. Volcanic rocks are important constituents of the Puget Group, the Chumstick and Naches Formations, and the isolated arkosic bodies. The three older units, however, contain relatively less volcanic lithics to total lithics than do younger units, indicating perhaps the initiation of more widespread volcanic activity in middle Eocene time. Ratios of framework grain parameters show that the terrestrial sandstone units were derived from a mixed plutonic and tectonic source terrane of continental block tectonic provenance with an overprint of magmatic arc provenance. Modal analysis was performed on samples from the various sedimentary units to establish petrologic compositions, and to provide data with which to compare the different units and discuss clast provenance and tectonic regimen. Although the arkosic sandstones have generally uniform framework clast compositions, minor yet significant differences do exist between the units. Basal or basement-onlap portions of the units in particular are locally derived and differ markedly from the overall compositions of the individual units. Many coincidences of composition, age, structure, and bedrock indicate that the Chuckanut and Swauk may have originally been deposited as a single unit that since has been offset approximately 160 kilometers by right lateral strike slip motion starting about 48 Ma. If this hypothetical offset did occur, then major movement on the Straight Creek Fault is bracketed between about 48 Ma and Oligocene time.

  7. One-Centimeter Stratigraphy in Foraminiferal Ooze: Theory and Practice.


    fine fraction, nozno(z) varies somewhat in parallel with s0=S0 (z). In other words, just as It is difficult to make inferences about paleoclimate ...without accounting for dissolution, it its difficult to make inferences about dissolution without accounting for paleoclimate . As we saw In Chapter 2...the volume of CO2 evolved when a small sample (ə g) is dissolved in, say, 3H HC1. A comparison of the earlier analysis of ERDC 79 (run by Dave Ripley

  8. Stratigraphy of Reforma Caldera, Baja California Sur, Mexico

    García Sánchez, L.; Macias, J. L.; Osorio, L. S.; Pola, A.; Avellán, D. R.; Arce, J. L.; Saucedo, R.; Sánchez, J. M.; García-Tenorio, F.; Cisneros, G.; Reyes-Agustín, G.; Cardona, S.; Jimenez, A.


    The Reforma caldera is located at ~35 km to the northwest of Santa Rosalía in the central part of the Baja California peninsula. It has 10 km in diameter and a maximum height of 1200 masl in the center and between 100 and 500 masl in its slopes. Reforma is within a tectonic zone affected by two fault systems: A NW-SE normal fault system linked to the opening of the Gulf of California, and a NNW-SSE and NW-SE strike-slip fault system associated with an active Riedel system. Reforma was built upon Cretaceous granites that outcrop at the caldera center, Miocene to Pliocene volcano-sedimentary rocks of the Comondú group, and Miocene marine sediments of the Santa Rosalía basin. On top of these rocks outcrop at least four submarine to subaerial ignimbrites interbedded with marine fossiliferous beds and the lower Pleistocene deposits associated to the Reforma caldera. These deposits are formed by a ignimbrite that shifts to different lithofacies that change gradually their welding, here dubbed basal, transitional, intermediate, and upper (all of then enriched in black fiammes), followed by a pumice-rich, white fiammes, and vitrophyre lithofacies, which are distributed around the 9 km wide caldera and have been associated to the caldera formation episode. Deposits related to post-caldera volcanism are andesite-basaltic lava flows erupted along the caldera rim through localized feeding dikes and andesitic and rhyolitic domes, and scoria cinder cones exposed inside and outside the caldera. On top of these deposits rest the middle Pleistocene Aguajito caldera deposits.

  9. Cretaceous stratigraphy and biostratigraphy, Sierra Blanca basin, southeastern New Mexico

    Lucas, S.G. (New Mexico Museum of Natural History, Albuquerque, NM (United States)); Anderson, O.R. (New Mexico Bureau of Mines Mineral Resources, Socorro, NM (United States))


    The Sierra Blanca basin of Otero and Lincoln counties, New Mexico contains a Lower (upper Albian)-Upper (Santonian) Cretaceous section of marine and nonmarine strata as much as 700 m thick which represent the upper part of a regressive cycle followed by two transgressive-regressive deposition cycles. The lower 55 m of the Cretaceous section are the same tripartite Dakota Group units recognized in Guadalupe and San Miguel counties: basal Mesa Rica Sandstone (late Albian), medial Pajarito formation (late Albian) and upper Romeroville sandstone (earliest Cenomanian). The Mesa Rica and Pajarito represent a regression and are overlain disconformably by the transgressive Romeroville sandstone. Overlying transgressive marine clastics and minor carbonates of the Mancos Shale are as much as 73 m thick and include the early Turonian Greenhorn Limestone. The overlying Tres Hermanos formation (up to 91 m thick) consists of the (ascending order) Atarque sandstone and the Carthage and Fite Ranch sandstone members. These strata represent a mid-Turonian regression in response to regional tectonism (Atarque and Carthage), followed by a transgression (Fite Ranch sandstone) that ended in the deposition of the D-Cross Tongue of the Mancos Shale and Fort Hays Member of the Niobrara Formation during the late Turonian. The subsequent regression began with the Coniacian Gallup Sandstone (55 m) followed by coal-bearing Crevasse Canyon Formation (up to 244 m thick). The Coniacian-Santonian Crevasse Canyon Formation, the youngest Cretaceous unit in the basin, is disconformably overlain by middle Eocene conglomerates and red-bed siliciclastics of the Cub Mountain formation. Dakota Group age determinations in the Sierra Blanca basin are those of well-dated sections to the north, but ammonites and inoceramid bivalves from the Sierra Blanca basin provide precise age control for Cenomanian-Santonian marine and marginal marine strata and palynology and megafossil plants for nonmarine strata.

  10. The Diatom Stratigraphy of Rawapening Lake, Implying Eutrophication History

    Tri Retnaningsih Soeprobowati


    Full Text Available Problem statement: The use of diatoms to reconstruct past ecological conditions in lakes is well established. Diatoms are microscopic algae that forms siliceous frustules which allow them to preserve well in sediments. Rawapening Lake is one of 15 Indonesian lakes identified as 2010-2014 National Priority Lakes. Naturally, Rawapening is a tectono-volcanic lake. In the early 1900s, the sole outlet of the lake, Tuntang River, was impounded for hydroelectricity, irrigation and fisheries. Since then Rawapening had become a semi natural lake. The main problem of Rawapening Lake is blooming of water hyacinth that reduce lake function. This research was conducted in order to reconstruct the nutrient history of Rawapening Lake, Java. Approach: Sediment samples were taken from four sites and were sliced every 0.5 cm for diatom analysis and bulked across 2-5 cm for 210Pb radiometric dating of sediment. Diatom analysis consisted of three steps: the digestion process to separate the diatoms from the sediment; preparation and mounting of diatom residues onto slides and identification-enumeration. Results: The diatom-inferred condition of Rawapening Lake may be divided into four phases represented by zone 1 (1967-1974, zone 2 (1974-1983, zone 3 (1984-1990 and zone 4 (1990-2008. The predominance of Synedra from 1967 to present indicates that Rawapening Lake has been fresh and meso-eutrophic throughout. Zone 1 is also characterized by Fragilaria capucina Desm, Luticola goeppertiana (Bleisch Mann, Mayamae atomus (Kutzing Lange-Bertalot, Navicula radiosa Kutzing, Nitzschia palea (Kutzing W. Smith and in one site, Tryblionella apiculata Gregory, that reflect eutrophic, but clear waters. An increase in epiphytic Gomphonema spp. in zone 2 marks an increase in aquatic macrophyte plants, perhaps in response to high nutrient levels. This change is followed promptly by an increase in acidophilous Eunotia spp. reflecting high organic production. A transition to a diatom community dominated by planktonic forms occurs c. 1983. This community was initially dominated by more clear water, oligotrophic species such as Discostella stelligera (Cleve and Grunow Houk and Klee and Aulacoseira distans (Ehrenberg Simonsen, but transitions in 1990 to one dominated by A. granulata (Ehrenberg Simonsen and ultimately Aulacoseira ambigua (Grunow Simonsen. This is interpreted as a shift to a turbid water phase that has advantaged phytoplankton, at the expense of benthic or epiphytic taxa that require clear water. Conclusion: The dominance of A. granulate (Ehrenberg Simonsen since the 1990s indicates the lake experienced hypertrophic conditions with pH > 9. A high proportion of the taxa in Rawa Pening sediments are not represented in the European data set, so the development of data set of tropical lakes is recommended to provide stronger inferences in local settings.

  11. Mars - Stratigraphy and gravimetry of Olympus Mons and its aureole

    Hiller, K. H.; Neukum, G. P. O.; Janle, P.; Guest, J. E.; Lopes, R. M. C.


    The relative ages of the major geologic units on and around Olympus Mons are considered, together with an interpretation of the gravity anomaly found for this area. The crater data for this investigation have been acquired and interpreted according to the method outlined by Neukum and Hiller (1981). After careful geological mapping, craters clearly identified as impacts are measured and counted. Crater frequency values per sq km for craters greater than or equal to 1 km ('crater retention ages') are read from the individual counts by fitting the Martian cumulative crater production size-frequency distribution to the individual counts. In addition to age dating, the problem of the origin and nature of the aureole materials using gravity data is addressed. This is done by determining whether the line-of-sight gravity extending from Olympus Mons to the northwestern part of the aureole can be explained by the aureole masses alone or whether additional high-density intrusive masses must be assumed in the aureola area.

  12. Quaternary alluvial stratigraphy and palaeoclimatic reconstruction at the Thar margin

    Jain, M.; Tandon, S.K.


    Quaternary alluvial record at the Thar desert margin has been examined using the exposed succession along Mahudi, Sabarmati river, Western India. Different alluvial facies, their associations and granulometry have been studied for palaeoenvironmental reconstruction. Clay mineral indices smectite/...

  13. Stratigraphy of the Krš Gradac section (SW Serbia

    Radoičić Rajka


    Full Text Available In the Krš Gradac section (near to Sjenica, SW Serbia, a transition of a carbonate platform to basin facies are outcropped: Norian-lower Liassic shallow-water carbonates, middle Liassic-lower Dogger Ammonitico Rosso facies, and upper Bathonian into lowermost Cretaceous deep-water radiolarites in which the carbonate graded bed and mass flow layer are intercalated. The presence of a lower Dogger condensed sequence with the Bajocian protoglobigerinid event was hitherto not evidenced. It is documented that components of a graded bed are of extrabasinal (upper Triassic-lower Tithonian carbonate platform sediments and intrabasinal (radiolarite, meta-andesite origin, indicating a tectonic event not older than the early Tithonian. This tectonic event caused the fracturing of the carbonate platform, also partly basinal area. Consequently, the age of the graded bed is not older than the lower Tithonian. In the uppermost radiolaritic sediments in the Krš Gradac section (?middle-upper Tithonian-lowermost Cretaceous, a mass flow layer appears, which contains clasts of intrabasinal origin - different radiolarites, siliceous radiolarian argillites (some of which are unconsolidated with washed radiolarians and sponge spicules in a ferruginous sediment, sandstone grains, etc. The mass flow event is estimated as Berriasian. In the Krš Gradac radiolarite succession, the authors recognized two deep-water formations, an older one, upper Bathonian-lower Tithonian, between hardground (Dogger and a graded bed, and a younger formation, which started with a graded bed. This formation, according to its stratigraphic position, corresponds to ?middle-upper Tithonian-lowermost Cretaceous.

  14. Geoethical Audit of Himalayan Stratigraphy: A Current Insight from India

    Deep Ahluwalia, Arun


    Focus of this presentation is to illustrate how learned societies and an eminent academy fellow can unfortunately become a pressure group. It is a very unfair and unbecoming even perhaps more than HIMALAYAN HOAX perpetrated by V. J. Gupta two decades back for over 25 years where he fooled journals, funding agencies and about 120 co-authors. Unless corrected, our learned societies and academies may continue degenerate even more. If this can happen today in the biggest democracy of the world with rule of law and freedom of press, what may happen in other set ups across our planet. The ill conceived and highly misleading book HIMALAYAN FOSSIL FRAUD recently published from PSI, Lucknow University, gives some vital but also unfortunately partial, selective and falsified historical and scientific perspectives of the Himalayan Hoax. This book is a standing testimony of a geoethical failure of individuals and of a learned society who published it without checking facts. Lot of personal testimonies and experiences can be added by the presenter. Some INSA Fellows are today like a cooperative society for cover ups and dirty politicking. The nexus within INSA Fellows to mutually protect each other and gratify at public cost is transparent but ignored for fear and power of their huge clout. Mistakes are allowed in science but science ethics does not allow silence once a fraud is known. If one is such a celebrated VIP like Ashok Sahni and D. M. Banerjee highly rewarded and awarded by so many, it becomes mandatory to maintain highest ethical standards and appear to be doing so. Our eminent INSA Fellows and learned society PSI are making themselves look like a mafia. This is neither ethics nor science. It is pure reckless money making and petty politicking by big guns to save their own skin. Very unfortunate indeed for Lucknow University, Lucknow where PSI is based and the retired teachers manning it are staying put for a life time endlessly getting self elected. Ever lowering ethical standards in learned societies of India and Indian National Science Academy stand exposed thanks to this historic revisit.




    Full Text Available The ammonite successions of Turkmenistan, particularly those of the Greater Balkhan and Tuarkyr areas, are considered references for the Aptian Stage. Six sections across the uppermost Barremian - basal Upper Aptian interval were studied in the Tuarkyr desert in October 1997,and ammonites and bivalves were collected. Data are compared with those from a section sampled by a Russian team in 1959. The stratigraphic distribution of the faunas in the sections is discontinuous, as the fossiliferous levels intercalate with terrigenous sediments. The ammonite faunas, at least in the intervals sampled, show low diversity and are dominated by the genus Deshayesites in the lower Aptian and the genus Epicheloniceras, associated with the less common Caspianites, in the basal upper Aptian. The Turkmenistan sections contain species present also in the Caucasus, England, Germany, France and Switzerland, indicating that the Turkmenian faunas reflect impoverishement rather than geographic isolation. The chronologic equivalence between the Turkmenian Epicheloniceras subnodosocostatum Zone and the Epicheloniceras martinioides Zone in England seems questionable because the Epicheloniceras-bearing beds of the Tuarkyr correspond to the upper part of the E. martinioides Zone, i. e. the Epicheloniceras buxtorfi Subzone. The bivalve fauna consists mainly of pteriids, Exogyrinae oysters and trigoniids. These groups undoubtedly indicate a very shallow, fairly warm and fully marine environment, typical of the Tethyan Lower Cretaceous. The heterodonts are too rare to give further bathymetric indications. None of the taxa indicate deep burrowing and all are assumed to be ?? littoral. The bivalve fauna shows strong affinities with that of the English Lower Greensand. 

  16. Seismic Studies of Paleo-Pockmarks on the Chatham Rise, New Zealand

    Smith, A. E.; Pecher, I. A.; Davy, B. W.; Coffin, R. B.; Rose, P. S.


    This study investigates buried pockmark features on the Chatham Rise through the analysis and interpretation of 2D seismic and Parasound data. The main objectives of this research are to establish what caused the formation of buried pockmarks on the Chatham Rise and to determine when the pockmarks were formed. The study area is located on the Western Chatham Rise, near the Canterbury Shelf off the East Coast of New Zealand. The pockmark fields were revealed through multibeam bathymetry data collected from surveys during the past 20 years. Previously, the pockmarks on the Chatham Rise were thought to have been produced by the release of methane through gas hydrate dissociation. However, recent geochemical investigations showed no indication of methane in the sediment cores. Current hypotheses for the formation of the pockmarks include groundwater fluid flow and the release of CO2 modulated by CO2 hydrates. We present the results of the spatial analysis of the pockmarks on the Western Chatham Rise and whether there are any links between the location of pockmark formation and regional geology. The structures of the pockmarks were investigated to determine how the features were formed. The spatial configuration of the pockmarks were analysed vertically for stacking and laterally for potential ties to specific horizons, particularly horizons associated with Milankovitch order climate cycles. Results show stacking and clustering of pockmarks around specific horizons and a depth window in the upper sediment in which pockmarks are formed. 2D seismic data was interpreted to build a regional geology model, through relative stratigraphy from intersecting seismic lines through the survey area. This improves the current understanding of the stratigraphy along the Chatham Rise and Canterbury Shelf areas and places the pockmark field in a regional geologic context.

  17. "大洋板块地层"的重建与意义——以藏南仲巴地区为例%The reconstruction of oceanic plate stratigraphy and its impli-cations:A case study of Zhongba area, southern Tibet

    魏玉帅; 李亚林; 陈曦; 王成善; 李祥辉; 李鑫; 钟瀚涏


    混杂岩是古增生楔存在的标志之一,一般由枕状玄武岩、灰岩、放射虫硅质岩、硅质页岩、砂岩等混乱无序组成.目前"大洋板块地层"(OPS)运用放射虫地层学方法对混乱的增生楔断片进行重建取得了良好效果,并清晰地展示了大洋板块俯冲和洋底物质连续增生的历史.在西藏仲巴地区填图过程中,结合放射虫年代学分析鉴定结果,以OPS重建的思路和理论作为指导,重建了仲巴地区混杂岩的大洋板块地层,并恢复了该区域特提斯洋在洋中脊大洋板块增生至消亡的岩石序列,自下而上分别为侏罗纪海山玄武岩、海山覆盖物侏罗系—白垩系碳酸盐岩、海山周围沉积的侏罗系—白垩系放射虫硅质岩和硅质页岩,以及海沟附近的白垩系陆源碎屑岩等,为特提斯洋大洋板块俯冲的方向、持续时间和古大地构造环境提供了信息.%Mélange generally consists of such chaotic blocks as pillow lava, limestones, radiolarian cherts, siliceous shales and sand-stones, which tectonically contact with each other. Mélange serves as a piece of evidence of the accretionary prism (AP) related to the subduction zones. Recently, by using radiolarian biostratigraphy, the theory of ocean plate stratigraphy (OPS) is referred to as an ap-proach to the accretionary process of these blocks. In order to reconstruct the process of subduction and successive accretion of ocean floor material of Neo-tethys, the authors used the theory to mapping the accretionary prism related to the Yalung Zangbo suture zone in Zhongba area, southern Tibet. The OPS of AP in Zhongba area consists of Jurassic basalt of sea mountain, Jurassic-Creta-ceous reefs on the sea mountain, the pelagic sediments such as siliceous shales and radiolarian cherts and the Cretaceous terrigenous clasts close to the trough. This study provides new information on the direction, duration and the tectonic settings of the subduction of the Neo

  18. Seismic Structural Setting of Western Farallon Basin, Southern Gulf of California, Mexico.

    Pinero-Lajas, D.; Gonzalez-Fernandez, A.; Lopez-Martinez, M.; Lonsdale, P.


    Data from a number of high resolution 2D multichannel seismic (MCS) lines were used to investigate the structure and stratigraphy of the western Farallon basin in the southern Gulf of California. A Generator-Injector air gun provided a clean seismic source shooting each 12 s at a velocity of 6 kts. Each signal was recorded during 6- 8 s, at a sampling interval of 1 ms, by a 600 m long digital streamer with 48 channels and a spacing of 12.5 m. The MCS system was installed aboard CICESE's (Centro de Investigacion Cientifica y de Educacion Superior de Ensenada) 28 m research vessel Francisco de Ulloa. MCS data were conventionally processed, to obtain post- stack time-migrated seismic sections. The MCS seismic sections show a very detailed image of the sub-bottom structure up to 2-3 s two-way travel time (aprox. 2 km). We present detailed images of faulting based on the high resolution and quality of these data. Our results show distributed faulting with many active and inactive faults. Our study also constrains the depth to basement near the southern Baja California eastern coast. The acoustic basement appears as a continuous feature in the western part of the study area and can be correlated with some granite outcrops located in the southern Gulf of California islands. To the East, near the center of the Farallon basin, the acoustic basement changes, it is more discontinuous, and the seismic sections show a number of diffracted waves.

  19. Seismic stability of the Duwamish River Delta, Seattle, Washington

    Kayen, Robert E.; Barnhardt, Walter A.


    The delta front of the Duwamish River valley near Elliott Bay and Harbor Island is founded on young Holocene deposits shaped by sea-level rise, episodic volcanism, and seismicity. These river-mouth deposits are highly susceptible to seismic soil liquefaction and are potentially prone to submarine landsliding and disintegrative flow failure. A highly developed commercial-industrial corridor, extending from the City of Kent to the Elliott Bay/Harbor Island marine terminal facilities, is founded on the young Holocene deposits of the Duwamish River valley. The deposits of this Holocene delta have been shaped not only by relative sea-level rise but also by episodic volcanism and seismicity. Ground-penetrating radar (GPR), cores, in situ testing, and outcrops are being used to examine the delta stratigraphy and to infer how these deposits will respond to future volcanic eruptions and earthquakes in the region. A geotechnical investigation of these river-mouth deposits indicates high initial liquefaction susceptibility during earthquakes, and possibly the potential for unlimited-strain disintegrative flow failure of the delta front.

  20. Micropaleontology of selected wells and seismic shot holes, northern Alaska

    Mickey, Michael B.; Haga, Hideyo; Bird, Kenneth J.


    This report provides micropaleontologic data (foraminifera, pollen, spores, and microplankton) and interpretations of the rocks penetrated by 49 wells and 3,134 seismic shot holes distributed among 73 seismic lines (figs. 1, 2; table 1). All shot holes and 30 wells are located within the National Petroleum Reserve in Alaska (NPRA); the remaining 19 wells are located adjacent to the NPRA. The biostratigraphic zonation scheme, stratigraphy, and geologic ages followed in this study are summarized in figure 3. This update brings paleontologic analyses performed at various times over several decades to a current, unified set of interpretations that benefit from the evolution of northern Alaska biostratigraphic understanding developed during the past 33-years by Mickey and Haga. For each well, paleontologic information includes microfossil distribution charts, data spreadsheets, diversity graphs, and interpretive reports describing age and environments of deposition. Three biostratigraphic well-correlation sections that relate Chukchi Sea wells to onshore northwestern NPRA wells are also included. For all analyzed seismic shot hole samples, foraminiferal age and environmental interpretations are provided; palynological interpretations are provided only for those shot hole samples collected and analyzed after 1976, a little less than half of the total number of samples.

  1. 高分辨率层序地层划分在陆相油藏剩余油分布研究中的应用——以克拉玛依油田一东区克拉玛依组为例%Application of high resolution sequence stratigraphy on remaining oil distribution of continental reservoirs: case of Karamay formation of east Karamay oilfield

    刘岩; 丁晓琪; 李学伟


    Because China has some of the most water-flooded oilfield in world, stable oil production relies on controlling water injection and increasing oil recovery. The sandstone stacked styles, heterogeneity, geometry of reservoirs can be studied by high resolution sequence stratigraphy with a kind of new vision, which closely links remaining oil distribution and extends new method for studying remaining oil distribution. This paper studies base level changing laws of different cycles based on detailed research of sedimentary mi-cro-facies of Karamay formation, then the short base level cycles of Karamay formation can be divided into 2 main classes and 12 small classes. The middle base level cycles control the development of short base level cycles, so the Karamay formation can be divided into 3 middle cycles and 14 short cycles, then the isochronous stratigraphic framework are built. The short base level cycles which are located in the middle base level cycles have different remaining oil distribution in isochronous stratigraphic framework. The result shows that the detailed sedimentary work is the base for studying sequence stratigraphy. The reservoirs that are deposited in the high accommodation can have good isochronous and low intraformational heterogeneity, so, the remaining oil distribute in thin, small, nonproduc-ing or low degree of water flooded area. Meanwhile, the reservoir that is distributed in low accommodation can have poor isochronous and high intraformational heterogeneity, and which are composed of noncontemporaneous deposit, so, the remaining oil is distributed in low permeable reservoirs in form of lens.%克拉玛依油田经过半个世纪注水开发,已进入开发后期,提高采收率的关键是明确剩余油的分布规律.在对研究区克拉玛依组沉积相研究的基础上,分析了不同类型剖面结构代表的基准面变化规律,将该组的短期基准面旋回划分为2大类12个小类.短期基准面旋回的规律性变化

  2. Probabilistic stability evaluation and seismic triggering scenarios of submerged slopes in Lake Zurich (Switzerland)

    Strupler, M.; Hilbe, M.; Anselmetti, F. S.; Kopf, A. J.; Fleischmann, T.; Strasser, M.


    Subaqueous landslides and their consequences, such as tsunamis, can cause serious damage to offshore infrastructure and coastal communities. Stability analyses of submerged slopes are therefore crucial, yet complex steps for hazard assessment, as many geotechnical and morphological factors need to be considered. Typically, deterministic models with data from a few sampling locations are used for the evaluation of slope stabilities, as high efforts are required to ensure high spatial data coverage. This study presents a simple but flexible approach for the probabilistic stability assessment of subaqueous slopes that takes into account the spatial variability of geotechnical data. The study area ( 2 km2) in Lake Zurich (northern Switzerland) shows three distinct subaquatic landslides with well-defined headscarps, translation areas (i.e. the zone where translational sliding occurred) and mass transport deposits. The ages of the landslides are known ( 2,210 and 640 cal. yr BP, and 1918 AD), and their triggers have been assigned to different mechanisms by previous studies. A combination of geophysical, geotechnical, and sedimentological methods served to analyse the subaquatic slope in great spatial detail: 3.5 kHz pinger seismic reflection data and a 300 kHz multibeam bathymetric dataset (1 m grid) were used for the detection of landslide features and for the layout of a coring and an in situ cone penetration testing campaign. The assignment of geotechnical data to lithological units enabled the construction of a sediment-mechanical stratigraphy that consists of four units, each with characteristic profiles of bulk density and shear strength. The thickness of each mechanical unit can be flexibly adapted to the local lithological unit thicknesses identified from sediment cores and seismic reflection profiles correlated to sediment cores. The sediment-mechanical stratigraphy was used as input for a Monte Carlo simulated limit-equilibrium model on an infinite slope for

  3. Probabilistic stability evaluation and seismic triggering scenarios of submerged slopes in Lake Zurich (Switzerland)

    Strupler, M.; Hilbe, M.; Anselmetti, F. S.; Kopf, A. J.; Fleischmann, T.; Strasser, M.


    Subaqueous landslides and their consequences, such as tsunamis, can cause serious damage to offshore infrastructure and coastal communities. Stability analyses of submerged slopes are therefore crucial, yet complex steps for hazard assessment, as many geotechnical and morphological factors need to be considered. Typically, deterministic models with data from a few sampling locations are used for the evaluation of slope stabilities, as high efforts are required to ensure high spatial data coverage. This study presents a simple but flexible approach for the probabilistic stability assessment of subaqueous slopes that takes into account the spatial variability of geotechnical data. The study area ( 2 km2) in Lake Zurich (northern Switzerland) shows three distinct subaquatic landslides with well-defined headscarps, translation areas (i.e. the zone where translational sliding occurred) and mass transport deposits. The ages of the landslides are known ( 2,210 and 640 cal. yr BP, and 1918 AD), and their triggers have been assigned to different mechanisms by previous studies. A combination of geophysical, geotechnical, and sedimentological methods served to analyse the subaquatic slope in great spatial detail: 3.5 kHz pinger seismic reflection data and a 300 kHz multibeam bathymetric dataset (1 m grid) were used for the detection of landslide features and for the layout of a coring and an in situ cone penetration testing campaign. The assignment of geotechnical data to lithological units enabled the construction of a sediment-mechanical stratigraphy that consists of four units, each with characteristic profiles of bulk density and shear strength. The thickness of each mechanical unit can be flexibly adapted to the local lithological unit thicknesses identified from sediment cores and seismic reflection profiles correlated to sediment cores. The sediment-mechanical stratigraphy was used as input for a Monte Carlo simulated limit-equilibrium model on an infinite slope for

  4. The seismic property of reef flat in the Changxing-Feixianguan Formation, Northwest Sichuan Province, China

    LIU Shu; TANG Jianming; GUO Xusheng; ZHAO Shuang


    The development of a carbonate reservoir is dominated by its primary sedimentary environment. Gener-ally, a good reservoir must be the oolite of a bank or bioclas-tics of an organic reef in a marginal mesa, which must deposit on the slope of the mesa. Therefore, the analyses of sequence stratigraphy are the key for predicting the presence of carbonate reservoirs. A typical sequence pattern can be seen in the Puguang gas field. As an independent lithologicalbody, the mechanical property of a reef flat is very different from the surrounding rock, causing stress to concentrate.Stress centralization will, in turn, cause a lot of fractures and faults to develop, and ultimately, result in a gas chimney,which is a seismic smear zone beneath or above the reef flat.Known gas fields, such as the Puguang gas field, also possess gas chimneys. Sequence stratigraphy patterns in the marginal mesa and gas chimney near the reservoir are very obvious in all known fields in southeast and east Sichuan Province.By analyzing the seismic features of all known gas fields, a model to predict carbonate reservoirs has been set up. Using this prediction model, we have found that there is a typical reef flat of the marginal mesa in the Malubei structure of Tongnanba structural belts whose sequence stratigraphy pat-tern is very much like that of the Puguang gas field; and in the Cangxi-Jiulongshan structure, there is another reef flat which is symmetrical to the Malubei reef The Cangxi reef flat pos-sesses the largest platform edge shallow facies domestically found, and has a typical prograding sequence. Its gas chimney is very obvious too. Because the Cangxi reef flat is in the very vicinity of the hydrocarbon kitchen and the depression is much bigger than that of the Puguang gas fields, we predict that there may be a gigascopic gas field in Cangxi County.There may also be a large gas field in the Malubei structure.

  5. A Fiber-Optic Borehole Seismic Vector Sensor System for Geothermal Site Characterization and Monitoring

    Paulsson, Bjorn N.P. [Paulsson, Inc.; Thornburg, Jon A [Paulsson, Inc.; He, Ruiqing [Paulsson, Inc.


    Seismic techniques are the dominant geophysical techniques for the characterization of subsurface structures and stratigraphy. The seismic techniques also dominate the monitoring and mapping of reservoir injection and production processes. Borehole seismology, of all the seismic techniques, despite its current shortcomings, has been shown to provide the highest resolution characterization and most precise monitoring results because it generates higher signal to noise ratio and higher frequency data than surface seismic techniques. The operational environments for borehole seismic instruments are however much more demanding than for surface seismic instruments making both the instruments and the installation much more expensive. The current state-of-the-art borehole seismic instruments have not been robust enough for long term monitoring compounding the problems with expensive instruments and installations. Furthermore, they have also not been able to record the large bandwidth data available in boreholes or having the sensitivity allowing them to record small high frequency micro seismic events with high vector fidelity. To reliably achieve high resolution characterization and long term monitoring of Enhanced Geothermal Systems (EGS) sites a new generation of borehole seismic instruments must therefore be developed and deployed. To address the critical site characterization and monitoring needs for EGS programs, US Department of Energy (DOE) funded Paulsson, Inc. in 2010 to develop a fiber optic based ultra-large bandwidth clamped borehole seismic vector array capable of deploying up to one thousand 3C sensor pods suitable for deployment into ultra-high temperature and high pressure boreholes. Tests of the fiber optic seismic vector sensors developed on the DOE funding have shown that the new borehole seismic sensor technology is capable of generating outstanding high vector fidelity data with extremely large bandwidth: 0.01 – 6,000 Hz. Field tests have shown

  6. Drilling fractured gas sweet spots using new 3D seismic interpretation methods

    Reeves, J.J. [GeoSpectrum Inc., Midland, TX (United States)


    This presentation outlined new drilling and mapping techniques designed by GeoSpectrum Inc. for coalbed methane and shale gas resource development. A technology using Azimuth dependent seismic processing with a pre-stack time migration and interval velocity was presented. A petrophysical analysis technique was used to analyze effective porosity, clay content, gas saturation, and fracture density and image logs. Seismic mapping and interpretation services offered by the company included collocated co-kriging; isopach; coherency and channel stratigraphy; clay content; acoustic impedance and seismic inversion; interval velocity anisotropy and fracture density; and AVO attributes and gas detection. Regional maps of areas used to demonstrate the technologies included base maps of Dakota gas production as well as a Greenhorn-Burro Canyon type log. Lower Dakota seismic lineaments with borehole breakout rose diagrams were provided along with details of production trends. Production data and AVO modelling case studies were included, as well as details of rating classifications and recent drilling results. refs., tabs., figs.

  7. Volcanic stratigraphy and evidence of magma mixing in the Quaternary Payún Matrú volcano, andean backarc in western Argentina Estratigrafía volcánica y evidencia de mezcla de magmas en el volcán Payún Matrú del Cuaternario, en el retroarco andino de Argentina occidental

    Irene R Hernando


    work, petrography, and major element geochemistry and 87Sr/86Sr isotopic ratios. For the first time a detailed map of the Payún Matrú Volcanic Field and its volcanic stratigraphy, primarily based on field observations, are presented.El Campo Volcánico Payún Matrú está localizado en la Provincia Basáltica Payenia, en el retroarco reciente al oeste de Argentina (35°S-38°S. Esta provincia es más joven que 5 Ma, y la mayor parte de su actividad volcánica tuvo lugar desde hace 2 Ma. El Campo Volcánico Payún Matrú contiene dos volcanes compuestos, el Payún Matrú y el Payún Liso, así como dos campos basálticos en una franja E-W, ubicados al este y oeste del Payún Matrú. El Payún Matrú es el volcán más grande de este campo volcánico, y consiste en un edificio en forma de escudo con una caldera circular en su cúspide de 8 km de diámetro. La composición de ambos volcanes compuestos es alcalina y predominantemente traquítica, con menor participación de lavas intermedias. Los campos basálticos consisten en basaltos y traquibasaltos, con clinopiroxeno y abundante olivina como fenocristales, presentes también en la pasta. En la etapa pre-caldera del Payún Matrú y en algunas lavas post-caldera son comunes las texturas que indican procesos de mezcla de magmas, 'mixing' y 'mingling', como plagioclasas cribadas en panal de abejas junto con otras limpias, biotitas reemplazadas por minerales anhidros y la presencia de dos pastas con una relación fluido-fluido. Las lavas post-caldera tardías son traquíticas, con fenocristales limpios de sanidina y sin texturas de desequilibrio. Una característica destacable del Campo Volcánico Payún Matrú es el hecho de que la caldera está rodeada por campos basálticos en su base, mientras que no se han producido erupciones de basaltos en la zona de la caldera. Proponemos que la ausencia de lavas basálticas en el volcán Payún Matrú se debe a la presencia de una cámara magmática por debajo del mismo, y a que

  8. Volcano-estratigrafía y tectónica del Valle Central Occidentaly las estribaciones de los Montes del Aguacate a lo largo de la ruta 27, Costa Rica Volcano-stratigraphy and tectonics of the Western Central Valley and Montes del Aguacate along road 27, Costa Rica

    Hernán Porras


    existencia de algunos altos estructurales, se podría explicar por un sistema de corrimientos con componente de rumbo.Route 27, known as Ciudad Colón-Caldera Highway, offers excellent geological sections showing much of the volcanic and sub-volcanic stratigraphy of the western part of the Central Valley and the Aguacate Mountains foothills. Here a volcaniclastic succession correlated with the Grifo Alto Formation (Pliocene is exposed. It consists of lavas, breccias and epivolcanic deposits (hyperconcetrated fluvial and debris avalanches deposits that locally show strong propilitic alteration. In some places the succession is slightly to moderately tilted, faulted and cut by dykes. A series of old debris avalanche deposits is also present, related to the volcanic activity in the Aguacate Mountains. Locally, a series of monomictic mesobreccias units is exposed consisting of glassy andesitic blocks in a vitro-crystalline matrix ash interpreted as block and ash-flow deposits, which is probably coeval with the volcanic Monteverde Formation (Lower Pleistocene. At least, 4 units of debris flow/debris avalanche deposits are associated with Nuestro Amo Formation. At the upper part of the succession, several porphyrytic andesitic lava-flows, correlated to the Lower Colima Formation are followed by ignimbrites of the Puente de Mulas and Tiribí Formations, of middle Pleistocene age, containing hyperconcentrated fluvial-ignimbrite deposits with decreasing thicknesses. A propagation fold deforms these ignimbrites, indicating the existence of a thin-skinned type overthrust with a SW vergency, which was active since, at least, the middle Pleistocene. The tilting of the rocks exposed along Route 27, the type of fracturing/faulting and folding, and the existence of some structural highs, is well explained with the thrust faulting model proposed in this article.

  9. Estratigrafía y paleontología del Cenozoico marino del Gran Bajo y Salinas del Gualicho, Argentina, y descripción de 17 especies nuevas Stratigraphy and Paleontology of the marine Cenozoic from the Gran Bajo and Salinas del Gualicho , Argentina and description of 17 new species

    Valeria A Reichler


    .The stratigraphy of the Gran Bajo del Gualicho Formation is explained by the identification of the new Saladar and Arrióla Members. The molluscan fauna comprises 38 genera and 44 species, 17 of which are new: Anadara australis sp. nov, Cubitostrea delrioi sp. nov., Amusium rorii sp. nov, Zygochlamys rizzoloi sp. nov,Pododesmus (Monia atlántica sp. nov, Tawera canalei sp. nov,Dosinia (Dosinia salarensis sp. nov., 'Spirocolpuá adapicis sp. nov., Torcula magna sp. nov, Magnatica hansi sp. nov, Eudolium lissiei sp. nov, Sconsia magdai sp. nov, Chicoreus (Chicoreus guadalupei sp. nov., Penion patagonensis sp. nov., Mitra (Fusimitra carlosi sp. nov, Austroimbricaria brugnii sp. nov. y Polystira cingula sp. nov. The NVG (Nodipecten sp.-Venericor abasolensis- Glycymerita camaronesia Molluscan Assemblage in the Saladar Member nov. indicates an age of late Early Miocene-earliest Middle Miocene. The Saladar Member correlates with the upper section of the Chenque Formation and with the Venericorbeanng horizons of the Gaiman and Vaca Mahuida formations. The fauna of this member constitutes another evidence with respect to the weather stripes stated for Patagonia since the Late Oligocene-Early Mocene. The assemblage recorded in the Arrióla Member nov. indicates the probable presence of the Aequipecten parenensis Zone and a stratigraphic relationship with the Puerto Madryn Formation of a Late Mocene age, extending the covered área along the Valdesian Province to the Salinas del Gualicho. The fauna of the Saladar Member shows more affmity with that in the Monte León and Chenque formations, while the fauna in the Arrióla Member shares more resemblance with the Paraná and Puerto Madryn formations. The Chilean Navidad and Guadal formations have 30% and 10% of genus in common with fauna of the Saladar Member, respectively.

  10. El Cenozoico del alto río Teno, Cordillera Principal, Chile central: estratigrafía, plutonismo y su relación con estructuras profundas The Cenozoic of the upper Teno River, Cordillera Principal, Central Chile: stratigraphy, plutonism and their relation with deep structures

    José Piquer


    ío, focalizando el ascenso de los intrusivos mencionados.The Cenozoic geologic evolution of the central part of the Cordillera Principal at ~35°S, is intimately related to the geodynamic evolution of deep crustal structures, which during different stages contra lled the deposition of volcanosedimentary sequences, and the ascent and emplacement of epizonal intrusions. Newly defined stratigraphy around these structures confirms the Cenozoic age of a group of pyroclastic and sedimentary rocks, which conformably underlie andesitic lavas of the Abanico Formation (assigned to the Late Eocene-Early to Middle Miocene. Intrusive rocks correspond to four main phases (from oldest to youngest: diorite, granodiorite, rhyo-dacitic and dacitic porphyry, which oceurs in a North-South trending belt. The granodiorite was dated at 7.8+0.4 Ma (K-Ar in biotite. Rhyo-dacitic porphyries, considered as a marginal lithodeme of the granodiorite, yielded 7.9+0.4 Ma (K-Ar in plagioclase phenocrysts. Two main structures of regional importance were observed: the El Fierro thrust, and, towards the west, the Infiernillo-Los Cipreses Fault System. In the characterization of the latter, magnetic modeling of cross-sections were analyzed as a complement to the geologic information. The ascent of the different intrusive phases mentioned before, is interpreted as being controlled by the Infiernillo-Los Cipreses Fault System. This structure, as well as the El Fierro thrust, acted as a basin-margin normal fault during the Late Eocene-Mddle Mocene, contralling the deposition of the Abanico Formation. These faults were reactivated as reverse faults during an episode of major tectonic contraction and magmatic-induced high fluid pressure in the Late Mocene, focusing the ascent of the intrusive bodies.

  11. Reflection seismic imaging of shallow aquifers in Milano (northern Italy)

    Francese, R.; Zaja, A.; Giudici, M.; Schmitt, D.


    A high resolution P-wave seismic reflection survey was conducted in the Lambro park within the city of Milano (northern Italy). The objective of the survey was to image structure and stratigraphy of shallow late tertiary and quaternary deposits. This information is necessary to develop a comprehensive 3D hydrological model of the fresh water aquifers where the municipality drilled several production wells. The expected complexity of the acoustic framework and the urban environment with its complications created a challenging test site for the reflection technique. The aquifer system was targeted with a 2-D high resolution seismic reflection survey to outline its vertical and lateral dimensions to a depth of 150-200 m and to estimate some petrophysical properties of the depositional units. A 0.8-km CMP seismic line, with 1-m station spacing, was deployed to collect reflection data. The recording geometry was a 240-channel split spread array, with 6-m shot separation, resulting in a maximum of 20-fold dataset. A single 40-Hz geophone at each station location detected the incoming signals. Field records exhibit clear reflections although the signal to noise ratio is poor because of strong surface waves and severe disturbances from the nearby highway. Optimized FK and KL transforms were used to attenuate these coherent noises and to enhance the primary reflections from the main horizons. The data analysis was also assisted by forward modeling to guide the selection of the processing parameters. The seismic data have a good correlation thourhgout the section and most of the acoustic units show flat bedding. The boundaries of the three major depositional units are clearly resolved by the seismic images. The stacked section clearly indicates that reflection technique provides a powerful method to characterize aquifers, even in a very noisy environment like the urban areas.

  12. Mechanical and chemical processes affecting the chalk during burial, insights from combined reflection seismics, well data and field work

    Moreau, Julien; Boussaha, Myriam; Thibault, Nicolas Rudolph


    and cores analyses, respectively.However, few sites allow to combine all the different scale of observation for chalk diagenesis. Onshore and offshore high resolution seismics, two fully cored >350 m wells with wireline logging tools and very high quality exposures from a coastal cliff and a quarry form...... works have been performed with astronomical calibration based on stable isotope stratigraphy, wireline logs as well as several palaeontological proxies and detailed sedimentological analysis. Since a couple of decades, a specific kind of fractures has been described in the Chalk of Denmark, the so......-called hairline fractures. They have recently been interpreted as compaction bands associated with the pore collapse of the chalk. We have observed these fractures on the field and on the cores in specific intervals. At depth, these fractures are in genetic relation with the formation of some stylolithes...


    吴时国; 黄孝健


    Seismic stratigraphic analysis of 150 km of high-resolution seismic profiles (G E OPULSE and 3.5 kHz) obtained along the muddy coast off Taishan, Guangdong pr ovided valuable information on the offshore Quaternary stratigraphy, tectonics, sedimentary evol ution, and environmental and engineering geology of this area.The following late Quaternary stratigraphic sequences were mapped. (1) Pleistoce ne alluvial silty sand and shallow marine clay; (2) coarse fluvial channel sand; (3 ) nearshore and bay clayey sediments. The incision of fluvial channels occurred in two stages: duri ng the Late Pleistocene and at the beginning of the Holocene. The Pleistocene fluvial channe ls have been filled by coarse sand overlain by more than 10 m of late Pleistocene clay and 20-30 m o f Holocene clay.The coastal area is dissected by two major fault systems: the first group strike s ENE-WSW and controls the evolution of the adjacent Quaternary basin, while the second one tr ends NNE-SSW. These fault systems must be taken into account in any coastal engineering consid erations. In addition, both granitic and metamorphic basements were recognized.

  14. Paleoseismic potential of sublacustrine landslide records in a high-seismicity setting (south-central Alaska)

    Praet, Nore; Moernaut, Jasper; Van Daele, Maarten; Boes, Evelien; Haeussler, Peter J.; Strupler, Michael; Schmidt, Sabine; Loso, Michael G.; De Batist, Marc


    Sublacustrine landslide stratigraphy is considered useful for quantitative paleoseismology in low-seismicity settings. However, as the recharging of underwater slopes with sediments is one of the factors that governs the recurrence of slope failures, it is not clear if landslide deposits can provide continuous paleoseismic records in settings of frequent strong shaking. To test this, we selected three lakes in south-central Alaska that experienced a strong historical megathrust earthquake (the 1964 Mw9.2 Great Alaska Earthquake) and exhibit high sedimentation rates in their main basins (0.2 cm yr-1 -1.0 cm yr-1). We present high-resolution reflection seismic data (3.5 kHz) and radionuclide data from sediment cores in order to investigate factors that control the establishment of a reliable landslide record. Seismic stratigraphy analysis reveals the presence of several landslide deposits in the lacustrine sedimentary infill. Most of these landslide deposits can be attributed to specific landslide events, as multiple landslide deposits sourced from different lacustrine slopes occur on a single stratigraphic horizon. We identify numerous events in the lakes: Eklutna Lake proximal basin (14 events), Eklutna Lake distal basin (8 events), Skilak Lake (7 events) and Kenai Lake (7 events). The most recent event in each basin corresponds to the historic 1964 megathrust earthquake. All events are characterized by multiple landslide deposits, which hints at a regional trigger mechanism, such as an earthquake (the synchronicity criterion). This means that the landslide record in each basin represents a record of past seismic events. Based on extrapolation of sedimentation rates derived from radionuclide dating, we roughly estimate a mean recurrence interval in the Eklutna Lake proximal basin, Eklutna Lake distal basin, Skilak Lake and Kenai Lake, at ~ 250 yrs, ~ 450 yrs, ~ 900 yrs and ~ 450 yrs, respectively. This distinct difference in recording can be explained by variations

  15. Improving the Monitoring, Verification, and Accounting of CO{sub 2} Sequestered in Geologic Systems with Multicomponent Seismic Technology and Rock Physics Modeling

    Alkan, Engin; DeAngelo, Michael; Hardage, Bob; Sava, Diana; Sullivan, Charlotte; Wagner, Donald


    Research done in this study showed that P-SV seismic data provide better spatial resolution of geologic targets at our Appalachian Basin study area than do P-P data. This finding is important because the latter data (P-P) are the principal seismic data used to evaluate rock systems considered for CO{sub 2} sequestration. The increase in P-SV{sub 1} resolution over P-P resolution was particularly significant, with P-SV{sub 1} wavelengths being approximately 40-percent shorter than P-P wavelengths. CO{sub 2} sequestration projects across the Appalachian Basin should take advantage of the increased resolution provided by converted-shear seismic modes relative to P-wave seismic data. In addition to S-wave data providing better resolution of geologic targets, we found S-wave images described reservoir heterogeneities that P-P data could not see. Specifically, a channel-like anomaly was imaged in a key porous sandstone interval by P-SV{sub 1} data, and no indication of the feature existed in P-P data. If any stratigraphic unit is considered for CO{sub 2} storage purposes, it is important to know all heterogeneities internal to the unit to understand reservoir compartmentalization. We conclude it is essential that multicomponent seismic data be used to evaluate all potential reservoir targets whenever a CO{sub 2} storage effort is considered, particularly when sequestration efforts are initiated in the Appalachian Basin. Significant differences were observed between P-wave sequences and S- wave sequences in data windows corresponding to the Oriskany Sandstone, a popular unit considered for CO{sub 2} sequestration. This example demonstrates that S-wave sequences and facies often differ from P-wave sequences and facies and is a principle we have observed in every multicomponent seismic interpretation our research laboratory has done. As a result, we now emphasis elastic wavefield seismic stratigraphy in our reservoir characterization studies, which is a science based on the

  16. Local Wave Propagation in the Kachchh Basin, India: Synergy With the New Madrid Seismic Zone

    Langston, C. A.; Kang, D.; Bodin, P.; Horton, S.


    Aftershocks of the Mw7.6 Bhuj earthquake are used to infer velocity structure and the nature of wave propagation within the Kachchh Basin, India. The data were collected from a joint MAEC/ISTAR deployment of seismographs within 3 weeks of the main event and from existing broadband stations in the region under the India Meteorological Department. Waveforms are available from events that span the entire thickness of the crust and display a variety of wave propagation effects due to low-velocity near-surface site structure and larger structure of the Mesozoic Kachchh basin. These effects include near-site, high frequency reverberations in P and S waves, Sp and Ps mode conversions, PL waves within the Mesozoic basin, basin S multiples, and surface waves. Surface wave group velocity dispersion yields estimates of basin shear wave velocity, and when coupled to analysis of large observed Sp conversions, give a migrated image of stratigraphy within the Banni plains that agrees favorably with published stratigraphy. Identification of basin structure effects allows constraints to be placed on aftershock source depths that are needed in evaluating standard earthquake locations. Structure models are used to construct Green's functions for determining source parameters through waveform modeling. Although stations of the aftershock network were situated on a variety of sites that varied from consolidated Mesozoic bedrock to unconsolidated recent sediments, all stations show major wave propagation effects due to basin fill that must be included in source parameter estimation. These effects seen in India have many similarities to wave propagation effects observed within the Mississippi embayment from microearthquakes in the New Madrid Seismic Zone (NMSZ) of the central U.S. Joint waveform studies are motivating new ways of understanding wave propagation and source processes within both areas.

  17. A Cenozoic tectono-sedimentary model of the Tainan Basin, the South China Sea: evidence from a multi-channel seismic profile

    Wei-wei DING; Jia-biao LI; Ming-bi LI; Xue-lin QIU; Yin-xia FANG; Yong TANG


    The Tainan Basin is one of the set of Cenozoic extensional basins along northern margin of the South China Sea that experienced extension and subsequently thermal subsidence. The Tainan Basin is close to the Taiwan Arc-Trench System and straddles a transition zone between oceanic and continental crust. A new regional multi-channel seismic profile (973-01) across the region of NE South China Sea is introduced in this paper. In seismic stratigraphy and structural geology, a model of Cenozoic tectono-sedimentation of the Tainan Basin is established. The results show that three stages can be suggested in Tainan Basin; In Stage A (Oligocene (?)-Lower Miocene) the stratigraphy shows restricted rifting, indicating crustal extension. Terrestrial sediments mostly filled the faulted sags of the North Depression on the continental shelf~ Structural highs, including the Central Uplift, blocked material transportation to the South Depression in abyssal basin. In Stage B the Tainan Basin (Middle-Upper Miocene) exhibits a broad subsidence resulting from the post-tiffing thermal cooling. The faulted-sags in North Depression had been filled up. Terrestrial materials were transported over the structural highs and deposited directly in the South Depression through submarine gullies or canyons. This sedimentation resulted in a crucial change in the slope to a modern shape. In Stage C (Latesl Miocene-Recent) a phase change from extension to compression took place due to the orogeny caused by the overthrusting of the Luzon volcanic arc. Many inverse structures, such as thrusts, fault bend folds, and a regional unconformity were formed. Forland basin began developing.


    Gudrun DAXNER-H(O)CK; Demchig BADAMGARAV; Margarita ERBAJEVA


    The Oligocene sedimentary sequence of the Taatsiin Gol and Taatsiin Tsagaan Nuur area is of unique stratigraphic importance:here,the exposed sediments of the Hsanda Gol and the Loh Formations display multiple fossil horizons and interbedded basah layers.In the frame of a Mongolian-Austrian pro-ject,289 fossil taxa(11 Gastropoda,2 Amphibia,9 Reptilia and 267 Mammalia)were collected from 85 fossil horizons of 33 sections/fossil sites of the study area.The taxa were identified by an interna-tional team of specialists.This contribution presents comprehensive mammal lists of all localities.By integrating the new data on large and small mammals,the Mongolian informal biozones A,B,C,C1 were updated.40Ar/39Ar-datings provide at least two groups of basalt ages,the Early Oligocene ba-salt I group around 31.5 Ma and the Late Oligocene basalt II group around 28 Ma.They serve as chronological tie points in the Oligocene mammalian stratigraphy.From the Early to the Late Oligocene the mammal associations underwent remarkable changes involving a ignificant decrease of species numbers in the Late Oligocene.This trend was most strik-ing in creodont,carnivore and ruminant communities.%Taatsiin Col和Taatsiin Tsagaan Nuur地区的渐新世沉积序列具有重要的地层学意义:这里出露的三达河组和Loh组沉积含有多个化石层和玄武岩夹层.在蒙古-奥地利合作项目中,从研究区域的33个剖面/化石地点的85个化石层中采集了289种化石(11种腹足类、2种两柄类、9种爬行类和267种哺乳类).本文提供了所有地点的完整哺乳动物清单,并结合大、小哺乳动物的新资料,对蒙古非正式的生物带A,B,C和Cl进行了更新.40Ar/39Ar测年给出了至少两组玄武岩年龄:早渐新世玄武岩Ⅰ组大约31.5 Ma,晚渐新世玄武岩Ⅱ组大约28 Ma.它们可以用作渐新世哺乳动物地层学的年代校正点.从早渐新世至晚渐新世,哺乳动物群发生了显著的变化,包括晚渐新世种

  19. Episodic Sediment Failure in Northern Flemish Pass, Eastern Canadian Margin: Interplay of Seismicity, Contour Current Winnowing, and Excess Pore Pressures

    Piper, D.


    Episodic sediment failures are recognised on continental slopes around Flemish Pass and Orphan Basin from multibeam bathymetry, seismic reflection profiles and piston cores. Seismic stratigraphy is tied to published long cores with O-isotope data back to before MIS 6 and carbonate rich Heinrich layers in places produce marker reflections in high-resolution sparker profiles. Heinrich layers, radiocarbon dates and peaks in diatom abundance provide core chronology. Slope sedimentation was strongly influenced by the Labrador Current and the silty muds show architecture characteristic of contourites. Variation in Labrador Current strength is known from the sortable silt proxy over the past 125 ka. Large slope failures were mapped from seismic reflection profiles and their age estimated from seismic stratigraphy (3-5 ka resolution) and in some cases refined from cores (1-3 ka resolution). Large slope failures occurred apparently synchronously over margin lengths of 50-350 km. Such failures were earthquake triggered: other mechanisms for producing laterally extensive synchronous failure do not apply. Triaxial shear measurements show a Su/σ' ratio of typical slope sediment of 0.48, implying considerable stability. However, some silty muds have Atterberg limits that suggest susceptibility to liquefaction under cyclic loading, particularly in Holocene deposits and by analogy those of past full interglacials. Basal failure planes of some large failures correspond with either the last interglacial or the MIS 6 glacial maximum. Comparison with seismological models suggests that the observed slope failures represent earthquakes ranging from Mw ~5.6 to ~7.6. Mean recurrence interval of M = 7 earthquakes at any point on the margin is estimated at 30 ka from seismological models and 40 ka from the sediment failure record. In northern Flemish Pass, a spatial cluster of several failures over 30 ka preceded by a long interval with no failures suggests that some other mechanism has

  20. Characterizing an unconventional reservoir with conventional seismic data: A case study using seismic inversion for the Vaca Muerta Formation, Neuquen Basin, Argentina

    Fernandez-Concheso, Jorge E.

    Reservoir characterization for unconventional shale plays ideally requires multi-component, wide-azimuth, long-offset surface seismic data. These data are generally not available, especially in exploration or pre-development stages. Furthermore, it is common to have only a few wells over a large area, along with non-existent or scarce microseismic, engineering and production data. This thesis presents a methodology and workflow to deal with these circumstances of limited data availability. By using a narrow-azimuth, regional P-wave seismic volume and integrating it with wireline logs, cuttings and PLT data, the variability in the geomechanical properties of the Vaca Muerta Formation in Argentina's Neuquen Basin, and their relationships with lithology, stress state and total organic content, were analyzed. Post-stack and pre-stack inversions were performed on the seismic volume. The un- certainties inherent from limited well control in the estimation of elastic properties were investigated using blind well testing. Sensitivity and error analysis was conducted on post-stack vs pre-stack derived P-impedance, the choice of the inversion algorithm (model-based vs sparse-spike) and the definition of the low frequency model (simple kriging model vs complex model derived from multi-attribute stepwise regression) were examined. Also, the use of isotropic AVA equations to approximate the anisotropic (VTI) behaviour of the reservoir was evaluated, using estimates of Thomsen parameters and simple AVA modelling. The integration of the inversion results with the petrophysical analysis and the mechanical stratigraphy work by Bishop (2015), suggests that the rock composition has the largest influence on the geomechanical behaviour of the reservoir. Overpressure is also a major driving factor in that it controls changes in elastic properties. Bishop's cluster analysis was used to identify good quality rock classes. The probabilistic interpretation of these rock classes from seismic

  1. Applicability of time-lapse refraction seismic tomography for the detection of ground ice degradation

    C. Hilbich


    Full Text Available The ice content of the subsurface is a major factor controlling the natural hazard potential of permafrost degradation in alpine terrain. Monitoring of changes in ground ice content is therefore similarly important as temperature monitoring in mountain permafrost. Although electrical resistivity tomography monitoring (ERTM has proved to be a valuable tool for the observation of ground ice degradation, results are often ambiguous or contaminated by inversion artefacts. In theory, the P-wave velocity of seismic waves is similarly sensitive to phase changes between unfrozen water and ice. Provided that the general conditions (lithology, stratigraphy, state of weathering, pore space remain unchanged over the observation period, temporal changes in the observed travel times of repeated seismic measurements should indicate changes in the ice and water content within the pores and fractures of the subsurface material. In this paper, the applicability of refraction seismic tomography monitoring (RSTM as an independent and complementary method to ERTM is analysed for two test sites in the Swiss Alps. The development and validation of an appropriate RSTM approach involves a the comparison of time-lapse seismograms and analysis of reproducibility of the seismic signal, b the analysis of time-lapse travel time curves with respect to shifts in travel times and changes in P-wave velocities, and c the comparison of inverted tomograms including the quantification of velocity changes. Results show a high potential of the RSTM approach concerning the detection of altered subsurface conditions caused by freezing and thawing processes. For velocity changes on the order of 3000 m/s even an unambiguous identification of significant ground ice loss is possible.

  2. Time-lapse refraction seismic tomography for the detection of ground ice degradation

    C. Hilbich


    Full Text Available The ice content of the subsurface is a major factor controlling the natural hazard potential of permafrost degradation in alpine terrain. Monitoring of changes in ice content is therefore similarly important as temperature monitoring in mountain permafrost. Although electrical resistivity tomography monitoring (ERTM proved to be a valuable tool for the observation of ice degradation, results are often ambiguous or contaminated by inversion artefacts. In theory, the sensitivity of P-wave velocity of seismic waves to phase changes between unfrozen water and ice is similar to the sensitivity of electric resistivity. Provided that the general conditions (lithology, stratigraphy, state of weathering, pore space remain unchanged over the observation period, temporal changes in the observed travel times of repeated seismic measurements should indicate changes in the ice and water content within the pores and fractures of the subsurface material. In this paper, a time-lapse refraction seismic tomography (TLST approach is applied as an independent method to ERTM at two test sites in the Swiss Alps. The approach was tested and validated based on a the comparison of time-lapse seismograms and analysis of reproducibility of the seismic signal, b the analysis of time-lapse travel time curves with respect to shifts in travel times and changes in P-wave velocities, and c the comparison of inverted tomograms including the quantification of velocity changes. Results show a high potential of the TLST approach concerning the detection of altered subsurface conditions caused by freezing and thawing processes. For velocity changes on the order of 3000 m/s even an unambiguous identification of significant ice loss is possible.

  3. Quantitative Analogue Experimental Sequence Stratigraphy : Modelling landscape evolution and sequence stratigraphy of river-shelf sedimentary systems by quantitative analogue experiments

    Heijst, Maximiliaan Wilhelmus Ignatius Maria van


    This thesis reports a series of flume tank experiments that were conducted to model the stratigraphic evolution of river-delta systems. Chapter 1 introduces the river-delta sedimentary system that is subject of modelling. The chapter also includes an overview of previous research and the summary and

  4. Chronostratigraphic relations of Neogene formations of the Great Hungarian Plain based on interpretation of seismic and paleomagnetic data

    Pogacsas, G.; Lakatos, L.; Simon, E.; Vakaros, G.; Varkonyi, L.; Varnai, P. (Geofizikai, Budapest (Hungary)); Jambor, A.; Hamor, T.; Lantos, M. (Magyar Allami Foeldtani Intezet, Budapest (Hungary)); Mattick, R.E. (Geological Survey, Reston, VA (USA)); Elston, D.P. (Geological Survey, Flagstaff, AZ (USA))


    This cooperative study by Hungarian and American geologists and geophysicists, demonstrates the power of the combination of modern paleomagnetic techniques and seismic profiling in working out the stratigraphy of a basin, with only limited paleontologic and isotopic control. Indirect evidence suggests that lake levels in the Pannonian inland sea (a remnant of the Paratethys), although isolated from the world's oceans, were affected by eustatic sea-level changes. Four hiatuses identified by seismic profiles near the northern margin of the Pannonian Basin and inferred to represent non-deposition between 11.5 and 10.5, 7.9 and 7.6, 6.8 and 5.7, 5.4 and 4.6 million years ago. Comparing these hiatuses with the eustatic sea level change curves the accordance is close and systematic. This indicates that the sea level of the Pannonian Inland Sea that became gradually isolated from the world oceans fluctuated in the same phase as global sea level. The hiatus between 6.8 and 5.7 Ma is tentatively correlated with the Messinian global stage during which time evaporite deposition in the Mediterranean was widespread--the so-called Messinian salinity crisis.

  5. Multicomponent seismic methods for characterizing gas hydrate occurrences and systems in deep-water Gulf of Mexico

    Haines, Seth S.; Lee, Myung W.; Collett, Timothy S.; Hardage, Bob A.


    In-situ characterization and quantification of natural gas hydrate occurrences remain critical research directions, whether for energy resource, drilling hazard, or climate-related studies. Marine multicomponent seismic data provide the full seismic wavefield including partial redundancy, and provide a promising set of approaches for gas hydrate characterization. Numerous authors have demonstrated the possibilities of multicomponent data at study sites around the world. We expand on this work by investigating the utility of very densely spaced (10’s of meters) multicomponent receivers (ocean-bottom cables, OBC, or ocean-bottom seismometers, OBS) for gas hydrate studies in the Gulf of Mexico and elsewhere. Advanced processing techniques provide high-resolution compressional-wave (PP) and converted shearwave (PS) reflection images of shallow stratigraphy, as well as P-wave and S-wave velocity estimates at each receiver position. Reflection impedance estimates can help constrain velocity and density, and thus gas hydrate saturation. Further constraint on velocity can be determined through identification of the critical angle and associated phase reversal in both PP and PS wideangle data. We demonstrate these concepts with examples from OBC data from the northeast Green Canyon area and numerically simulated OBS data that are based on properties of known gas hydrate occurrences in the southeast (deeper water) Green Canyon area. These multicomponent data capabilities can provide a wealth of characterization and quantification information that is difficult to obtain with other geophysical methods.

  6. Terrane Boundary Geophysical Signatures in Northwest Panay, Philippines: Results from Gravity, Seismic Refraction and Electrical Resistivity Investigations

    Jillian Aira S. Gabo


    Full Text Available Northwest Panay consists of two terranes that form part of the Central Philippine collision zone: Buruanga Peninsula and Antique Range. The Buruanga Peninsula consists of a Jurassic chert-clastic-limestone sequence, typical of oceanic plate stratigraphy of the Palawan Micro-continental Block. The Antique Range is characterized by Antique Ophiolite Complex peridotites and Miocene volcanic and clastic rocks, representing obducted oceanic crust that serves as the oceanic leading edge of the collision with the Philippine Mobile Belt. The Nabas Fault is identified as the boundary between the two terranes. This study employed the gravity method to characterize the Northwest Panay subsurface structure. Results indicate higher Bouguer anomaly values for Buruanga Peninsula than those for Antique Range, separated by a sudden decrease in gravity values toward the east-southeast (ESE direction. Forward gravity data modeling indicates the presence of an underlying basaltic subducted slab in the Buruanga Peninsula. Furthermore, the Nabas Fault is characterized as an east-dipping thrust structure formed by Buruanga Peninsula basement leading edge subduction beneath Antique Range. Additional geophysical constraints were provided by shallow seismic refraction and electrical resistivity surveys. Results from both methods delineated the shallow subsurface signature of the Nabas Fault buried beneath alluvium deposits. The gravity, seismic refraction and electrical resistivity methods were consistent in identifying the Nabas Fault as the terrane boundary between the Buruanga Peninsula and the Antique Range. The three geophysical methods helped constrain the subsurface configuration in Northwest Panay.

  7. Sand Resources of Southern Lake Erie, Conneaut to Toledo, Ohio - A Seismic Reflection and Vibracore Study.