Geological and Petrophysical Characterization of the Ferron Sandstone for 3-D Simulation of a Fluvial-Deltaic Reservoir

Energy Technology Data Exchange (ETDEWEB)

Chidsey, Jr, Thomas C.

2001-10-31

The objective of the Ferron Sandstone project was to develop a comprehensive, interdisciplinary, quantitative characterization f fluvial-deltaic reservoir to allow realistic interwell and reservoir-scale models to be developed for improved oil-field development in similar reservoirs world-wide. Quantitative geological and petrophysical information on the Cretaceous Ferron Sandstone in east-central Utah was collected. Both new and existing data was integrated into a three-dimensional model of spatial variations in porosity, storativity, and tensorial rock permeability at a scale appropriate for inter-well to regional-scale reservoir simulation. Simulation results could improve reservoir management through proper infill and extension drilling strategies, reduction of economic risks, increased recovery from existing oil fields, and more reliable reserve calculations.

Mid-Cretaceous aeolian desert systems in the Yunlong area of the Lanping Basin, China: Implications for palaeoatmosphere dynamics and paleoclimatic change in East Asia

Science.gov (United States)

Li, Gaojie; Wu, Chihua; Rodríguez-López, Juan Pedro; Yi, Haisheng; Xia, Guoqing; Wagreich, Michael

2018-02-01

The mid-Cretaceous constitutes a period of worldwide atmospheric and oceanic change associated with slower thermohaline circulation and ocean anoxic events, possible polar glaciations and by a changing climate pattern becoming controlled by a zonal planetary wind system and an equatorial humid belt. During the mid-Cretaceous, the subtropical high-pressure arid climate belt of the planetary wind system controlled the palaeolatitude distribution of humid belts in Asia as well as the spatial distribution of rain belts over the massive continental blocks at mid-low latitudes in the southern and northern hemispheres. Additionally, the orographic effect of the Andean-type active continental margin in East Asia hindered the transportation of ocean moisture to inland regions. With rising temperatures and palaeoatmospheric conditions dominated by high pressure systems, desert climate environments expanded at the inland areas of East Asia including those accumulated in the mid-Cretaceous of the Simao Basin, the Sichuan Basin, and the Thailand's Khorat Basin, and leading the Late Cretaceous erg systems in the Xinjiang Basin and Jianghan Basin. This manuscript presents evidences that allow to reinterpret previously considered water-laid sediments to be accumulated as windblown deposits forming part of extensive erg (sandy desert) systems. Using a multidisciplinary approach including petrological, sedimentological and architectural observations, the mid-Cretaceous (Albian-Turonian) Nanxin Formation from the Yunlong region of Lanping Basin, formerly considered to aqueous deposits is here interpreted as representing aeolian deposits, showing local aeolian-fluvial interaction deposits. The palaeowind directions obtained from the analysis of aeolian dune cross-beddings indicates that inland deserts were compatible with a high-pressure cell (HPC) existing in the mid-low latitudes of East Asia during the mid-Cretaceous. Compared with the Early Cretaceous, the mid-Cretaceous had

Fluvial Apophenia

Science.gov (United States)

Coulthard, Tom; Armitage, John

2017-04-01

Apophenia describes the experience of seeing meaningful patterns or connections in random or meaningless data. Francis Bacon was one of the first to identify its role as a "human understanding is of its own nature prone to suppose the existence of more order and regularity in the world than it finds". Examples include pareidolia (seeing shapes in random patterns), gamblers fallacy (feeling past events alter probability), confirmation bias (bias to supporting a hypothesis rather than disproving), and he clustering illusion (an inability to recognise actual random data, instead believing there are patterns). Increasingly, researchers use records of past floods stored in sedimentary archives to make inferences about past environments, and to describe how climate and flooding may have changed. However, it is a seductive conclusion, to infer that drivers of landscape change can lead to changes in fluvial behaviour. Using past studies and computer simulations of river morphodynamics we explore how meaningful the link between drivers and fluvial changes is. Simple linear numerical models would suggest a direct relation between cause and effect, despite the potential for thresholds, phase changes, time-lags and damping. However, a comparatively small increase in model complexity (e.g. the Stream Power law) introducing non-linear behaviour and Increasing the complexity further can lead to the generation of time-dependent outputs despite constant forcing. We will use this range of findings to explore how apophenia may manifest itself in studies of fluvial systems, what this can mean and how we can try to account for it. Whilst discussed in the context of fluvial systems the concepts and inferences from this presentation are highly relevant to many other studies/disciplines.

Fluvial systems and their sedimentary models

Directory of Open Access Journals (Sweden)

Dragomir Skabeme

1995-12-01

Full Text Available The Slovenian géomorphologie and sedimentologie terminology for fluvial depositional environments is not established yet. Therefore a classification and the proposal for Slovenian names of fluvial sedimentary and erosional forms and influences controlling them are discussed. Attention is given to the problems of recognition of sedimentary environments in sedimentary rocks, and to fluvial sedimentary models.

The Gediz River fluvial archive

NARCIS (Netherlands)

Maddy, D.; Veldkamp, A.; Demir, T.; Gorp, van W.; Wijbrans, J.R.; Hinsbergen, van D.J.J.; Dekkers, M.J.; Schreve, D.; Schoorl, J.M.; Scaife, R.

2017-01-01

The Gediz River, one of the principal rivers of Western Anatolia, has an extensive Pleistocene fluvial archive that potentially offers a unique window into fluvial system behaviour on the western margins of Asia during the Quaternary. In this paper we review our work on the Quaternary Gediz River

Formation of topographically inverted fluvial deposits on Earth and Mars

Science.gov (United States)

Hayden, A.; Lamb, M. P.; Fischer, W. W.; Ewing, R. C.; McElroy, B. J.

2016-12-01

Sinuous ridges interpreted as exhumed river deposits (so-called "inverted channels") are common features on Mars that show promise for quantifying ancient martian surface hydrology. Morphological similarity of these inverted channels to river channels led to a "landscape inversion hypothesis" in which the geometries of ridges and ridge networks accurately reflect the geometries of the paleo-river channels and networks. An alternative "deposit inversion hypothesis" proposes that ridges represent eroded fluvial channel-belt deposits with channel-body geometries that may differ significantly from those of the rivers that built the deposit. To investigate these hypotheses we studied the sedimentology and morphology of inverted channels in Jurassic and Cretaceous outcrops in Utah and the Aeolis Dorsa region of Mars. Ridges in Utah extend for hundreds of meters, are tens of meters wide, and stand up to 30 meters above the surrounding plain. A thick ribbon-geometry sandstone or conglomerate body caps overbank mudstone, paleosols, and thin crevasse-splay sandstone beds. Caprock beds consist of stacked dune- to bar-scale trough cross sets, mud intraclasts, and in cases scroll bars indicating meandering. In plan view, ridge networks bifurcate; however, crosscutting relationships show that distinct sandstone channel bodies at distinct stratigraphic levels intersect at these junctions. Ridge-forming sandstone bodies have been narrowed from their original dimensions by cliff retreat and bisected by modern fluvial erosion and mass wasting. We therefore interpret the sinuous ridges in Utah as eroded remnants of channel-belt sandstone bodies formed by laterally migrating and avulsing rivers rather than channel fills - consistent with deposit inversion. If the sinuous ridges in Aeolis Dorsa also formed by deposit inversion, river widths previously interpreted under the landscape inversion hypothesis are overestimated by up to a factor of 10 and discharges by up to a factor of 100.

Predicting interwell heterogeneity in fluvial-deltaic reservoirs: Outcrop observations and applications of progressive facies variation through a depositional cycle

Energy Technology Data Exchange (ETDEWEB)

Knox, P.R.; Barton, M.D. [Univ. of Texas, Austin, TX (United States)

1997-08-01

Nearly 11 billion barrels of mobile oil remain in known domestic fluvial-deltaic reservoirs despite their mature status. A large percentage of this strategic resource is in danger of permanent loss through premature abandonment. Detailed reservoir characterization studies that integrate advanced technologies in geology, geophysics, and engineering are needed to identify remaining resources that can be targeted by near-term recovery methods, resulting in increased production and the postponement of abandonment. The first and most critical step of advanced characterization studies is the identification of reservoir architecture. However, existing subsurface information, primarily well logs, provides insufficient lateral resolution to identify low-permeability boundaries that exist between wells and compartmentalize the reservoir. Methods to predict lateral variability in fluvial-deltaic reservoirs have been developed on the basis of outcrop studies and incorporate identification of depositional setting and position within a depositional cycle. The position of a reservoir within the framework of a depositional cycle is critical. Outcrop studies of the Cretaceous Ferron Sandstone of Utah have demonstrated that the architecture and internal heterogeneity of sandstones deposited within a given depositional setting (for example, delta front) vary greatly depending upon whether they were deposited in the early, progradational part of a cycle or the late, retrogradational part of a cycle. The application of techniques similar to those used by this study in other fluvial-deltaic reservoirs will help to estimate the amount and style of remaining potential in mature reservoirs through a quicklook evaluation, allowing operators to focus characterization efforts on reservoirs that have the greatest potential to yield additional resources.

Cretaceous Crocodyliforms from the Sahara

Directory of Open Access Journals (Sweden)

Paul Sereno

2009-11-01

Full Text Available Diverse crocodyliforms have been discovered in recent years in Cretaceous rocks on southern landmasses formerly composing Gondwana.  We report here on six species from the Sahara with an array of trophic adaptations that significantly deepen our current understanding of African crocodyliform diversity during the Cretaceous period.  We describe two of these species (Anatosuchus minor, Araripesuchus wegeneri from nearly complete skulls and partial articulated skeletons from the Lower Cretaceous Elrhaz Formation (Aptian-Albian of Niger. The remaining four species (Araripesuchus rattoides sp. n., Kaprosuchus saharicus gen. n. sp. n., Laganosuchus thaumastos gen. n. sp. n., Laganosuchus maghrebensis gen. n. sp. n. come from contemporaneous Upper Cretaceous formations (Cenomanian in Niger and Morocco.

Evaluating controls on fluvial sand-body clustering in the Ferris Formation (Cretaceous/Paleogene, Wyoming, USA)

Science.gov (United States)

Hajek, E. A.; Heller, P.

2009-12-01

A primary goal of sedimentary geologists is to interpret past tectonic, climatic, and eustatic conditions from the stratigraphic record. Stratigraphic changes in alluvial-basin fills are routinely interpreted as the result of past tectonic movements or changes in climate or sea level. Recent physical and numerical models have shown that sedimentary systems can exhibit self-organization on basin-filling time scales, suggesting that structured stratigraphic patterns can form spontaneously rather than as the result of changing boundary conditions. The Ferris Formation (Upper Cretaceous/Paleogene, Hanna Basin, Wyoming) exhibits stratigraphic organization where clusters of closely-spaced channel deposits are separated from other clusters by intervals dominated by overbank material. In order to evaluate the role of basinal controls on deposition and ascertain the potential for self-organization in this ancient deposit, the spatial patterns of key channel properties (including sand-body dimensions, paleoflow depth, maximum clast size, paleocurrent direction, and sediment provenance) are analyzed. Overall the study area lacks strong trends sand-body properties through the stratigraphic succession and in cluster groups. Consequently there is no indication that the stratigraphic pattern observed in the Ferris Formation was driven by systematic changes in climate or tectonics.

Fluvial geomorphology on Earth-like planetary surfaces: A review.

Science.gov (United States)

Baker, Victor R; Hamilton, Christopher W; Burr, Devon M; Gulick, Virginia C; Komatsu, Goro; Luo, Wei; Rice, James W; Rodriguez, J A P

2015-09-15

Morphological evidence for ancient channelized flows (fluvial and fluvial-like landforms) exists on the surfaces of all of the inner planets and on some of the satellites of the Solar System. In some cases, the relevant fluid flows are related to a planetary evolution that involves the global cycling of a volatile component (water for Earth and Mars; methane for Saturn's moon Titan). In other cases, as on Mercury, Venus, Earth's moon, and Jupiter's moon Io, the flows were of highly fluid lava. The discovery, in 1972, of what are now known to be fluvial channels and valleys on Mars sparked a major controversy over the role of water in shaping the surface of that planet. The recognition of the fluvial character of these features has opened unresolved fundamental questions about the geological history of water on Mars, including the presence of an ancient ocean and the operation of a hydrological cycle during the earliest phases of planetary history. Other fundamental questions posed by fluvial and fluvial-like features on planetary bodies include the possible erosive action of large-scale outpourings of very fluid lavas, such as those that may have produced the remarkable canali forms on Venus; the ability of exotic fluids, such as methane, to create fluvial-like landforms, as observed on Saturn's moon, Titan; and the nature of sedimentation and erosion under different conditions of planetary surface gravity. Planetary fluvial geomorphology also illustrates fundamental epistemological and methodological issues, including the role of analogy in geomorphological/geological inquiry.

Titan's fluvial valleys: Morphology, distribution, and spectral properties

Science.gov (United States)

Langhans, M.H.; Jaumann, R.; Stephan, K.; Brown, R.H.; Buratti, B.J.; Clark, R.N.; Baines, K.H.; Nicholson, P.D.; Lorenz, R.D.; Soderblom, L.A.; Soderblom, J.M.; Sotin, Christophe; Barnes, J.W.; Nelson, R.

2012-01-01

Titan's fluvial channels have been investigated based on data obtained by the Synthetic Aperture Radar (SAR) instrument and the Visible and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft. In this paper, a database of fluvial features is created based on radar-SAR data aiming to unveil the distribution and the morphologic and spectral characteristics of valleys on Titan on a global scale. It will also study the spatial relations between fluvial valleys and Titan's geologic units and spectral surface units which have become accessible thanks to Cassini-VIMS data. Several distinct morphologic types of fluvial valleys can be discerned by SAR-images. Dendritic valley networks appear to have much in common with terrestrial dendritic systems owing to a hierarchical and tree-shaped arrangement of the tributaries which is indicative of an origin from precipitation. Dry valleys constitute another class of valleys resembling terrestrial wadis, an indication of episodic and strong flow events. Other valley types, such as putative canyons, cannot be correlated with rainfall based on their morphology alone, since it cannot be ruled out that they may have originated from volcanic/tectonic action or groundwater sapping. Highly developed and complex fluvial networks with channel lengths of up to 1200 km and widths of up to 10 km are concentrated only at a few locations whereas single valleys are scattered over all latitudes. Fluvial valleys are frequently found in mountainous areas. Some terrains, such as equatorial dune fields and undifferentiated plains at mid-latitudes, are almost entirely free of valleys. Spectrally, fluvial terrains are often characterized by a high reflectance in each of Titan's atmospheric windows, as most of them are located on Titan's bright 'continents'. Nevertheless, valleys are spatially associated with a surface unit appearing blue due to its higher reflection at 1.3??m in a VIMS false color RGB composite with R: 1.59/1.27??m, G: 2

Vision for a worldwide fluvial-sediment information network

Science.gov (United States)

Gray, J.R.; Osterkamp, W.R.

2007-01-01

The nations of the world suffer both from the deleterious effects of some natural and human-altered fluxes of fluvial sediment and a lack of consistent and reliable information on the temporal and spatial occurrence of fluvial sediments. Decades ago, this difficulty was unavoidable due to a lack of understanding of the magnitude and scope of environmental influences exerted by fluvial sediment coupled with a dearth of tools for monitoring and studying the data. Such is no longer the case.

Lithofacies control in detrital zircon provenance studies: Insights from the Cretaceous Methow basin, southern Canadian Cordillera

Science.gov (United States)

DeGraaff-Surpless, K.; Mahoney, J.B.; Wooden, J.L.; McWilliams, M.O.

2003-01-01

High-frequency sampling for detrital zircon analysis can provide a detailed record of fine-scale basin evolution by revealing the temporal and spatial variability of detrital zircon ages within clastic sedimentary successions. This investigation employed detailed sampling of two sedimentary successions in the Methow/Methow-Tyaughton basin of the southern Canadian Cordillera to characterize the heterogeneity of detrital zircon signatures within single lithofacies and assess the applicability of detrital zircon analysis in distinguishing fine-scale provenance changes not apparent in lithologic analysis of the strata. The Methow/Methow-Tyaughton basin contains two distinct stratigraphic sequences of middle Albian to Santonian clastic sedimentary rocks: submarine-fan deposits of the Harts Pass Formation/Jackass Mountain Group and fluvial deposits of the Winthrop Formation. Although both stratigraphic sequences displayed consistent ranges in detrital zircon ages on a broad scale, detailed sampling within each succession revealed heterogeneity in the detrital zircon age distributions that was systematic and predictable in the turbidite succession but unpredictable in the fluvial succession. These results suggest that a high-density sampling approach permits interpretation of finescale changes within a lithologically uniform turbiditic sedimentary succession, but heterogeneity within fluvial systems may be too large and unpredictable to permit accurate fine-scale characterization of the evolution of source regions. The robust composite detrital zircon age signature developed for these two successions permits comparison of the Methow/Methow-Tyaughton basin age signature with known plutonic source-rock ages from major plutonic belts throughout the Cretaceous North American margin. The Methow/Methow-Tyaughton basin detrital zircon age signature matches best with source regions in the southern Canadian Cordillera, requiring that the basin developed in close proximity to the

Island life in the Cretaceous - faunal composition, biogeography, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelago

OpenAIRE

Csiki Sava,Zoltan; Buffetaut,Eric; Ősi,Attila; Pereda-Suberbiola,Xabier; Brusatte,Stephen

2015-01-01

Abstract The Late Cretaceous was a time of tremendous global change, as the final stages of the Age of Dinosaurs were shaped by climate and sea level fluctuations and witness to marked paleogeographic and faunal changes, before the end-Cretaceous bolide impact. The terrestrial fossil record of Late Cretaceous Europe is becoming increasingly better understood, based largely on intensive fieldwork over the past two decades, promising new insights into latest Cretaceous faunal evolution. We revi...

A fluvial mercury budget for Lake Ontario.

Science.gov (United States)

Denkenberger, Joseph S; Driscoll, Charles T; Mason, Edward; Branfireun, Brian; Warnock, Ashley

2014-06-03

Watershed mercury (Hg) flux was calculated for ten inflowing rivers and the outlet for Lake Ontario using empirical measurements from two independent field-sampling programs. Total Hg (THg) flux for nine study watersheds that directly drain into the lake ranged from 0.2 kg/yr to 13 kg/yr, with the dominant fluvial THg load from the Niagara River at 154 kg/yr. THg loss at the outlet (St. Lawrence River) was 68 kg/yr and has declined approximately 40% over the past decade. Fluvial Hg inputs largely (62%) occur in the dissolved fraction and are similar to estimates of atmospheric Hg inputs. Fluvial mass balances suggest strong in-lake retention of particulate Hg inputs (99%), compared to dissolved total Hg (45%) and methyl Hg (22%) fractions. Wetland land cover is a good predictor of methyl Hg yield for Lake Ontario watersheds. Sediment deposition studies, coupled atmospheric and fluvial Hg fluxes, and a comparison of this work with previous measurements indicate that Lake Ontario is a net sink of Hg inputs and not at steady state likely because of recent decreases in point source inputs and atmospheric Hg deposition.

Dinosaurs and the Cretaceous Terrestrial Revolution

Science.gov (United States)

Lloyd, Graeme T; Davis, Katie E; Pisani, Davide; Tarver, James E; Ruta, Marcello; Sakamoto, Manabu; Hone, David W.E; Jennings, Rachel; Benton, Michael J

2008-01-01

The observed diversity of dinosaurs reached its highest peak during the mid- and Late Cretaceous, the 50 Myr that preceded their extinction, and yet this explosion of dinosaur diversity may be explained largely by sampling bias. It has long been debated whether dinosaurs were part of the Cretaceous Terrestrial Revolution (KTR), from 125–80 Myr ago, when flowering plants, herbivorous and social insects, squamates, birds and mammals all underwent a rapid expansion. Although an apparent explosion of dinosaur diversity occurred in the mid-Cretaceous, coinciding with the emergence of new groups (e.g. neoceratopsians, ankylosaurid ankylosaurs, hadrosaurids and pachycephalosaurs), results from the first quantitative study of diversification applied to a new supertree of dinosaurs show that this apparent burst in dinosaurian diversity in the last 18 Myr of the Cretaceous is a sampling artefact. Indeed, major diversification shifts occurred largely in the first one-third of the group's history. Despite the appearance of new clades of medium to large herbivores and carnivores later in dinosaur history, these new originations do not correspond to significant diversification shifts. Instead, the overall geometry of the Cretaceous part of the dinosaur tree does not depart from the null hypothesis of an equal rates model of lineage branching. Furthermore, we conclude that dinosaurs did not experience a progressive decline at the end of the Cretaceous, nor was their evolution driven directly by the KTR. PMID:18647715

Coalbed methane potential of the Upper Cretaceous Mesaverde and Meeteetse formations, Wind River Reservation, Wyoming

Science.gov (United States)

Johnson, R.C.; Clark, A.C.; Barker, C.E.; Crysdale, B.L.; Higley, D.K.; Szmajter, R.J.; Finn, T.M.

1993-01-01

The environments of deposition of the uppermost part of the Cody Shale and the Mesaverde and Meeteetse Formations of Late Cretaceous age were studied on outcrop in the Shotgun Butte area in the north-central part of the Wind River Reservation. A shoreface sandstone occurs in the lower part of the Mesaverde Formation at all localities studied, and is directly overlain by a coaly interval. Repetitive coarsening-upward cycles of mudstone, siltstone, and sandstone occur in the 200 ft interval of the upper part of the Cody Shale below the shoreface sandstone. These Cody sandstones are typically hummocky cross stratified with symmetrical ripples near the top, indicating that they are largely storm surge deposits that were later reworked. Channel-form sandstones from 10 to 20 ft thick, with abundant locally derived clayey clasts, occur in a 75 ft thick interval below the shoreface at one locality. These unusual sandstones are largely confined to a narrow area of the outcrop and grade laterally into more typical storm surge deposits. They may be unusually large storm surge channels created when high-energy flow conditions were localized to a limited area of the shelf.The Mesaverde Formation above the shoreface sandstone is divided into a middle member and the Teapot Sandstone Member. The lower part of the middle member is everywhere coaly. Erosional-based sandstones in this coaly interval are highly variable in thickness and architecture. Thin, single channel sandstone bodies were deposited by moderate to high sinuosity streams, and thick, multistory channel sandstone bodies were deposited by rapidly switching fluvial channel systems that remained relatively stationary for extended periods of time. The architecture of the fluvial channel sandstones in the overlying noncoaly interval appears to be highly variable as well, with complex multistory sandstones occurring at different stratigraphic levels at different localities. This distribution may be explained by long term

Turkana Grits - a Cretaceous braided alluvial system in northern Kenya

Energy Technology Data Exchange (ETDEWEB)

Handford, C.R.

1987-05-01

Rather spotty but excellent exposures of the Cretaceous-age Turkana Grits occur near the western shore of Lake Turkana, northern Kenya. These very coarse to pebbly arkosic sandstones and sandy conglomerates were derived from and rest unconformably upon Precambrian metamorphic basement; they are overlain by late Tertiary basaltic flows that comprise much of the volcanics in the East African Rift Zone. The formation ranges up to 2000 ft thick in the Laburr Range. Several outcrops contain sauropod, crocodile, and tortoise remains as well as abundant trunks of petrified wood (Dryoxylon). Five major facies make up the Turkana Grits and record a major episode of continental fluvial deposition in basins flanked by Precambrian basement. Facies 1 is crudely stratified, cobble and boulder conglomerate (clast-supported); Facies 2 is crudely stratified pebble-cobble conglomerate and pebbly sandstone; Facies 3 is trough cross-bedded, very coarse sandstones containing fossils wood and vertebrate remains; Facies 4 is crudely stratified to massive sandstones with ironstone nodules; and Facies 5 is red, purple, and gray mudstone and mud shale with carbonate nodules. Facies 1 through 3 record deposition in proximal to medial braided-stream channel, longitudinal bar and dune complexes. Facies 4 is a lowland, hydromorphic paleosol, and Facies 5 represents overbank and abandoned channel-fill sedimentation in an alluvial plain.

Field migration rates of tidal meanders recapitulate fluvial morphodynamics

Science.gov (United States)

Finotello, Alvise; Lanzoni, Stefano; Ghinassi, Massimiliano; Marani, Marco; Rinaldo, Andrea; D'Alpaos, Andrea

2018-02-01

The majority of tidal channels display marked meandering features. Despite their importance in oil-reservoir formation and tidal landscape morphology, questions remain on whether tidal-meander dynamics could be understood in terms of fluvial processes and theory. Key differences suggest otherwise, like the periodic reversal of landscape-forming tidal flows and the widely accepted empirical notion that tidal meanders are stable landscape features, in stark contrast with their migrating fluvial counterparts. On the contrary, here we show that, once properly normalized, observed migration rates of tidal and fluvial meanders are remarkably similar. Key to normalization is the role of tidal channel width that responds to the strong spatial gradients of landscape-forming flow rates and tidal prisms. We find that migration dynamics of tidal meanders agree with nonlinear theories for river meander evolution. Our results challenge the conventional view of tidal channels as stable landscape features and suggest that meandering tidal channels recapitulate many fluvial counterparts owing to large gradients of tidal prisms across meander wavelengths.

Heavy mineral delineation of the Cretaceous, Paleocene, and Eocene stratigraphic sections at the Savannah River Site, Upper Coastal Plain of South Carolina

International Nuclear Information System (INIS)

Cathcart, E.M.; Sargent, K.A.

1994-01-01

The Upper Atlantic Coastal Plain of South Carolina consists of a fluvial-deltaic and shallow marine complex of unconsolidated sediments overlying the crystalline basement rocks of the North American continent. Because of the lateral and vertical variability of these sediments, stratigraphic boundaries have been difficult to distinguish. Portions of the Cretaceous, Paleocene, and eocene stratigraphic sections from cores recovered during the construction of two monitoring wells at the Savannah River Site were studied to determine if heavy mineral suites could be utilized to distinguish boundaries. The stratigraphic sections include: the Late Cretaceous Middendorf, Black Creek, and Steel Creek Formations, the Paleocene Snapp Formation, the late Paleocene-Early Eocene Fourmile Branch Formation, and the Early Eocene Congaree formation. In previous studies composite samples were taken over 2.5 ft. intervals along the cores and processed using a heavy liquid for heavy mineral recovery. During this study, heavy mineral distributions were determined by binocular microscope and the mineral identifications confirmed by x-ray diffraction analysis of hand-picked samples. The heavy mineral concentration data and grain size data were then compared to the stratigraphic boundary positions determined by other workers using more classical methods. These comparisons were used to establish the utility of this method for delineating the stratigraphic boundaries in the area of study

Anatomy and dimensions of fluvial crevasse-splay deposits: Examples from the Cretaceous Castlegate Sandstone and Neslen Formation, Utah, U.S.A.

Science.gov (United States)

Burns, C. E.; Mountney, N. P.; Hodgson, D. M.; Colombera, L.

2017-04-01

Crevasse-splay deposits form a volumetrically significant component of many fluvial overbank successions (up to 90% in some successions).Yet the relationships between the morphological form of accumulated splay bodies and their internal facies composition remains poorly documented from ancient successions. This work quantifies lithofacies distributions and dimensions of exhumed crevasse-splay architectural elements in the Campanian Castlegate Sandstone and Neslen Formation, Mesaverde Group, Utah, USA, to develop a depositional model. Fluvial crevasse-splay bodies thin from 2.1 m (average) to 0.8 m (average) and fine from a coarsest recorded grain size of lower-fine sand to fine silt away from major trunk channel bodies. Internally, the preserved deposits of splays comprise laterally and vertically variable sandstone and siltstone facies associations: proximal parts are dominated by sharp and erosional-based sandstone-prone units, which may be structureless or may comprise primary current lineation on beds and erosional gutter casts; medial parts comprise sets of climbing-ripple strata and small scale deformed beds; distal parts comprise sets of lower-stage plane beds and complex styles of lateral grading into fine-grained floodbasin siltstones and coals. Lithofacies arrangements are used to establish the following: (i) recognition criteria for crevasse-splay elements; (ii) criteria for the differentiation between distal parts of crevasse-splay bodies and floodplain fines; and (iii) empirical relationships with which to establish the extent (ca. 500 m long by 1000 m wide) and overall semi-elliptical planform shape of crevasse-splay bodies. These relationships have been established by high-resolution stratigraphic correlation and palaeocurrent analysis to identify outcrop orientation with respect to splay orientation. This permits lateral changes in crevasse-splay facies architecture to be resolved. Facies models describing the sedimentology and architecture of

Early cretaceous dinosaurs from the sahara.

Science.gov (United States)

Sereno, P C; Wilson, J A; Larsson, H C; Dutheil, D B; Sues, H D

1994-10-14

A major question in Mesozoic biogeography is how the land-based dinosaurian radiation responded to fragmentation of Pangaea. A rich fossil record has been uncovered on northern continents that spans the Cretaceous, when continental isolation reached its peak. In contrast, dinosaur remains on southern continents are scarce. The discovery of dinosaurian skeletons from Lower Cretaceous beds in the southern Sahara shows that several lineages of tetanuran theropods and broad-toothed sauropods had a cosmopolitan distribution across Pangaea before the onset of continental fragmentation. The distinct dinosaurian faunas of Africa, South America, and Asiamerica arose during the Cretaceous by differential survival of once widespread lineages on land masses that were becoming increasingly isolated from one another.

The contribution of bank and surface sediments to fluvial sediment ...

African Journals Online (AJOL)

The contribution of bank and surface sediments to fluvial sediment transport of the Pra River. ... the relative contribution of surface and bank sediments to the fluvial sediment transport. ... EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT

New Australian sauropods shed light on Cretaceous dinosaur palaeobiogeography

Science.gov (United States)

Poropat, Stephen F.; Mannion, Philip D.; Upchurch, Paul; Hocknull, Scott A.; Kear, Benjamin P.; Kundrát, Martin; Tischler, Travis R.; Sloan, Trish; Sinapius, George H. K.; Elliott, Judy A.; Elliott, David A.

2016-01-01

Australian dinosaurs have played a rare but controversial role in the debate surrounding the effect of Gondwanan break-up on Cretaceous dinosaur distribution. Major spatiotemporal gaps in the Gondwanan Cretaceous fossil record, coupled with taxon incompleteness, have hindered research on this effect, especially in Australia. Here we report on two new sauropod specimens from the early Late Cretaceous of Queensland, Australia, that have important implications for Cretaceous dinosaur palaeobiogeography. Savannasaurus elliottorum gen. et sp. nov. comprises one of the most complete Cretaceous sauropod skeletons ever found in Australia, whereas a new specimen of Diamantinasaurus matildae includes the first ever cranial remains of an Australian sauropod. The results of a new phylogenetic analysis, in which both Savannasaurus and Diamantinasaurus are recovered within Titanosauria, were used as the basis for a quantitative palaeobiogeographical analysis of macronarian sauropods. Titanosaurs achieved a worldwide distribution by at least 125 million years ago, suggesting that mid-Cretaceous Australian sauropods represent remnants of clades which were widespread during the Early Cretaceous. These lineages would have entered Australasia via dispersal from South America, presumably across Antarctica. High latitude sauropod dispersal might have been facilitated by Albian–Turonian warming that lifted a palaeoclimatic dispersal barrier between Antarctica and South America. PMID:27763598

Lower Cretaceous Puez key-section in the Dolomites - towards the mid-Cretaceous super-greenhouse

Science.gov (United States)

Lukeneder, A.; Halásová, E.; Rehákova, D.; Józsa, Š.; Soták, J.; Kroh, A.; Jovane, L.; Florindo, F.; Sprovieri, M.; Giorgioni, M.; Lukeneder, S.

2012-04-01

Investigations on different fossil groups in addition to isotopic, paleomagnetic and geochemical analysis are combined to extract the Early Cretaceous history of environmental changes, as displayed by the sea level and climate changes. Results on biostratigraphy are integrated with other dating methods as magnetostraigraphy, correlation and cyclostratigraphy. The main investigation topics of the submitted project within the above-described framework are the biostratigraphic (Lukeneder and Aspmair, 2006, 2012), palaeoecological (Lukeneder, 2008, 2012), palaeobiogeographic, lithostratigraphic (Lukeneder, 2010, 2011), cyclostratigraphic and magnetostratigraphic development of the Early Cretaceous in the Puez area. The main sections occur in expanded outcrops located on the southern margin of the Puez Plateau, within the area of the Puez-Geisler Natural Park, in the northern part of the Dolomites (South Tyrol, North Italy). The cephalopod, microfossil and nannofossil faunas and floras from the marly limestones to marls here indicates Hauterivian to Albian/Cenomanian age. Oxygen isotope values from the Lower Cretaceous Puez Formation show a decreasing trend throughout the log, from -1.5‰ in the Hauterivian to -4.5‰ in the Albian/Cenomanian. The decreasing values mirror an increasing trend in palaeotemperatures from ~ 15-18°C in the Hauterivian up to ~25-30 °C in the Albian/Cenomanian. The trend probably indicates the positive shift in temperature induced by the well known Mid Cretaceous Ocean warming (e.g., Super-Greenhouse). The cooperative project (FWF project P20018-N10; 22 international scientists): An integrative high resolution project. Macro- and microfossils, isotopes, litho-, cyclo-, magneto-and biostratigraphy as tools for investigating the Lower Cretaceous within the Dolomites (Southern Alps, Northern Italy) -The Puez area as a new key region of the Tethyan Realm), is on the way since 2008 by the Natural History Museum in Vienna and the 'Naturmuseum S�

Fluvial to Lacustrine Facies Transitions in Gale Crater, Mars

Science.gov (United States)

Sumner, Dawn Y.; Williams, Rebecca M. E.; Schieber, Juergen; Palucis, Marisa C.; Oehler, Dorothy Z.; Mangold, Nicolas; Kah, Linda C.; Gupta, Sanjeev; Grotzinger, John P.; Grant, John A., III;

Field migration rates of tidal meanders recapitulate fluvial morphodynamics.

Science.gov (United States)

Finotello, Alvise; Lanzoni, Stefano; Ghinassi, Massimiliano; Marani, Marco; Rinaldo, Andrea; D'Alpaos, Andrea

2018-02-13

The majority of tidal channels display marked meandering features. Despite their importance in oil-reservoir formation and tidal landscape morphology, questions remain on whether tidal-meander dynamics could be understood in terms of fluvial processes and theory. Key differences suggest otherwise, like the periodic reversal of landscape-forming tidal flows and the widely accepted empirical notion that tidal meanders are stable landscape features, in stark contrast with their migrating fluvial counterparts. On the contrary, here we show that, once properly normalized, observed migration rates of tidal and fluvial meanders are remarkably similar. Key to normalization is the role of tidal channel width that responds to the strong spatial gradients of landscape-forming flow rates and tidal prisms. We find that migration dynamics of tidal meanders agree with nonlinear theories for river meander evolution. Our results challenge the conventional view of tidal channels as stable landscape features and suggest that meandering tidal channels recapitulate many fluvial counterparts owing to large gradients of tidal prisms across meander wavelengths. Copyright © 2018 the Author(s). Published by PNAS.

Fluvial hydrology and geomorphology of Monsoon-dominated Indian rivers

Directory of Open Access Journals (Sweden)

Vishwas S. Kale

2005-11-01

Full Text Available The Indian rivers are dominantly monsoon rainfed. As a result, their regime characteristics are dictated by the spatio-temporal variations in the monsoon rainfall. Although the rivers carry out most of the geomorphic work during 4-5 months of the monsoon season, the nature and magnitude of response to variations in the discharge and sediment load varies with the basin size and relief characteristics. Large monsoon floods play a role of great importance on all the rivers. This paper describes the hydrological and geomorphological characteristics of the two major fluvial systems of the Indian region, namely the Himalayan fluvial system and the Peninsular fluvial system. Large number of studies published so far indicate that there are noteworthy differences between the two river systems, with respect to river hydrology, channel morphology, sediment load and behaviour. The nature of alterations in the fluvial system due to increased human interference is also briefly mentioned. This short review demonstrates that there is immense variety of rivers in India. This makes India one of the best places to study rivers and their forms and processes.

Cretaceous paleogeography and depositional cycles of western South America

Science.gov (United States)

Macellari, C. E.

The western margin of South America was encroached upon by a series of marine advances that increased in extent from the Early Cretaceous to a maximum in the early Late Cretaceous for northern South America (Venezuela to Peru). In southern South America, however, the area covered by the marine advances decreased from a maximum in the Early Cretaceous to a minimum during mid-Cretaceous time, followed by a widespread advance at the end of the period. A series of unconformity-bounded depositional cycles was recognized in these sequences: five cycles in northern South America, and six (but not exactly equivalent) cycles in the Cretaceous back-arc basins of southern South America (Neuquén and Austral, or Magallanes, Basins). Both widespread anoxic facies and maximum flooding of the continent in northern South America coincide in general terms with recognized global trends, but this is not the case in southern South America. Here, anoxic facies are restricted to the Lower Cretaceous and seem to be controlled by local aspects of the basin evolution and configuration. The contrasts observed between northern and southern South America can be explained by differences in tectonic setting and evolution. To the north, sediments were deposited around the tectonically stable Guayana-Brazilian Massifs, and thus registered global "signals" such as anoxic events and major eustatic changes. The southern portion of the continent, on the contrary, developed in an active tectonic setting. Here, the mid-Cretaceous Peruvian Orogeny overprinted, to a large extent, world-wide trends and only the earliest and latest Cretaceous conform to global depositional patterns.

Cretaceous Vertebrate Tracksites - Korean Cretaceous Dinosaur Coast World Heritage Nomination Site

Science.gov (United States)

Huh, M.; Woo, K. S.; Lim, J. D.; Paik, I. S.

2009-04-01

South Korea is one of the best known regions in the world for Cretaceous fossil footprints, which are also world-renowned. Korea has produced more scientifically named bird tracks (ichnotaxa) than any other region in the world. It has also produced the world's largest pterosaur tracks. Dinosaur tracksites also have the highest frequency of vertebrate track-bearing levels currently known in any stratigraphic sequence. Among the areas that have the best track records, and the greatest scientific significance with best documentation, Korea ranks very highly. Objective analysis of important individual tracksites and tracksite regions must be based on multiple criteria including: size of site, number of tracks, trackways and track bearing levels, number of valid named ichnotaxa including types, number of scientific publications, quality of preservation. The unique and distinctive dinosaur tracksites are known as one of the world's most important dinosaur track localities. In particular, the dinosaur track sites in southern coastal area of Korea are very unique. In the sites, we have excavated over 10,000 dinosaur tracks. The Hwasun sites show diverse gaits with unusual walking patterns and postures in some tracks. The pterosaur tracks are the most immense in the world. The longest pterosaur trackway yet known from any track sites suggests that pterosaurs were competent terrestrial locomotors. This ichnofauna contains the first pterosaur tracks reported from Asia. The Haenam Uhangri pterosaur assigns to a new genus Haenamichnus which accomodates the new ichnospecies, Haenamichnus uhangriensis. At least 12 track types have been reported from the Haman and Jindong Formations (probably late Lower Cretaceous). These include the types of bird tracks assigned to Koreanornis, Jindongornipes, Ignotornis and Goseongornipes. In addition the bird tracks Hwangsanipes, Uhangrichnus, the pterosaur track Haenamichnus and the dinosaur tracks, Brontopodus, Caririchnium, Minisauripus and

Late Jurassic – early Cretaceous inversion of rift structures, and linkage of petroleum system elements across post-rift unconformity, U.S. Chukchi Shelf, arctic Alaska

Science.gov (United States)

Houseknecht, David W.; Connors, Christopher D.

2015-01-01

Basin evolution of the U.S. Chukchi shelf involved multiple phases, including Late Devonian–Permian rifting, Permian–Early Jurassic sagging, Late Jurassic–Neocomian inversion, and Cretaceous–Cenozoic foreland-basin development. The focus of ongoing exploration is a petroleum system that includes sag-phase source rocks; inversion-phase reservoir rocks; structure spanning the rift, sag, and inversion phases; and hydrocarbon generation during the foreland-basin phase.

40Ar/39Ar dating of the Late Cretaceous

International Nuclear Information System (INIS)

Gaylor, Jonathan

2013-01-01

As part of the wider European GTS Next project, I propose new constraints on the ages of the Late Cretaceous, derived from a multitude of geochronological techniques, and successful stratigraphic interpretations from Canada and Japan. In the Western Canada Sedimentary Basin, we propose a new constraint on the age of the K/Pg boundary in the Red Deer River section (Alberta, Canada). We were able to cyclo-stratigraphically tune sediments in a non-marine, fluvial environment utilising high-resolution proxy records suggesting a 11-12 precession related cyclicity. Assuming the 40 Ar/ 39 Ar method is inter-calibrated with the cyclo-stratigraphy, the apparent age for C29r suggests that the K/Pg boundary falls between eccentricity maxima and minima, yielding an age of the C29r between 65.89 ± 0.08 and 66.30 ± 0.08 Ma. Assuming that the bundle containing the coal horizon represents a precession cycle, the K/Pg boundary is within the analytical uncertainty of the youngest zircon population achieving a revised age for the K/Pg boundary as 65.75 ± 0.06 Ma. The Campanian - Maastrichtian boundary is preserved in the sedimentary succession of the Horseshoe Canyon Formation and has been placed 8 m below Coal nr. 10. Cyclo-stratigraphic studies show that the formation of these depositional sequences (alternations) of all scales are influenced directly by sea-level changes due to precession but more dominated by eccentricity cycles proved in the cyclo-stratigraphic framework and is mainly controlled by sand horizons, which have been related by auto-cyclicity in a dynamic sedimentary setting. Our work shows that the Campanian - Maastrichtian boundary in the Western Canada Sedimentary Basin coincides with 2.5 eccentricity cycles above the youngest zircon age population at the bottom of the section and 4.9 Myr before the Cretaceous - Palaeogene boundary (K/Pg), and thus corresponds to an absolute age of 70.65 ± 0.09 Ma producing an 1.4 Myr younger age than recent published ages

Unsteady Landscapes: Climatic and Tectonic Controls on Fluvial Terrace Formation

Science.gov (United States)

Clubb, F. J.; Mudd, S. M.

2017-12-01

Fluvial terraces are common landforms throughout mountainous regions which represent abandoned remnants of active river systems and their floodplains. The formation of these landforms points to a fundamental unsteadiness in the incision rate of the fluvial network, providing important information on channel response to climatic, tectonic, and base-level forcing, sediment storage and dynamics within mountainous systems, and the relative importance of lateral and vertical incision rates. In his 1877 Report on the Geology of the Henry Mountains, G.K. Gilbert suggested that strath terraces may form due to climatically-driven increase in sediment supply, causing armouring of the channel bed and hindering vertical incision. An alternative hypothesis suggests that strath terraces may be preserved through progressive tectonic uplift or base-level fall. These different formation mechanisms should result in varying distribution of terrace elevations along channels: if terraces are formed through climate-driven variations in sediment supply, we might expect that terrace elevations would be random, whereas progressive fluvial incision should result in a series of terraces with a systematic elevation pattern. Here we test alternative hypotheses for strath terrace formation using a new method for objectively and rapidly identifying terrace surfaces from digital elevation models (DEMs) over large spatial scales. Our new method identifies fluvial terraces using their gradient and elevation compared to the modern channel, thresholds of which are statistically calculated from the DEM and do not need to be set manually by the user. We use this method to extract fluvial terraces for every major river along the coast of California, and quantify their distribution and elevation along the fluvial long profile. Our results show that there is no systematic pattern in terrace elevations despite a well-constrained spatial variation in uplift rates, suggesting that terraces in this region do

Chapter 5. Assessment of undiscovered conventional oil and gas resources-Lower Cretaceous Travis Peak and Hosston formations, Jurassic Smackover interior salt basins total petroleum system, in the East Texas basin and Louisiana-Mississippi salt basins provinces.

Science.gov (United States)

Dyman, T.S.; Condon, S.M.

2006-01-01

The Lower Cretaceous Travis Peak Formation of east Texas and southern Arkansas (and the correlative Hosston Formation of Louisiana and Mississippi) is a basinward-thickening wedge of terrigenous clastic sedimentary rocks that underlies the northern Gulf of Mexico Basin from east Texas across northern Louisiana to southern Mississippi. Clastic detritus was derived from two main fluvial-deltaic depocenters, one in northeastern Texas and the other extending from southeastern Mississippi northwestward into northeastern Louisiana. Across the main hydrocarbon-productive trend in east Texas and northern Louisiana, the Travis Peak and Hosston Formations are about 2,000 ft thick.

Fluvial deposits as an archive of early human activity: Progress during the 20 years of the Fluvial Archives Group

Science.gov (United States)

Chauhan, Parth R.; Bridgland, David R.; Moncel, Marie-Hélène; Antoine, Pierre; Bahain, Jean-Jacques; Briant, Rebecca; Cunha, Pedro P.; Despriée, Jackie; Limondin-Lozouet, Nicole; Locht, Jean-Luc; Martins, Antonio A.; Schreve, Danielle C.; Shaw, Andrew D.; Voinchet, Pierre; Westaway, Rob; White, Mark J.; White, Tom S.

2017-06-01

Fluvial sedimentary archives are important repositories for Lower and Middle Palaeolithic artefacts throughout the 'Old World', especially in Europe, where the beginning of their study coincided with the realisation that early humans were of great antiquity. Now that many river terrace sequences can be reliably dated and correlated with the globally valid marine isotope record, potentially useful patterns can be recognized in the distribution of the find-spots of the artefacts that constitute the large collections that were assembled during the years of manual gravel extraction. This paper reviews the advances during the past two decades in knowledge of hominin occupation based on artefact occurrences in fluvial contexts, in Europe, Asia and Africa. As such it is an update of a comparable review in 2007, at the end of IGCP Project no. 449, which had instigated the compilation of fluvial records from around the world during 2000-2004, under the auspices of the Fluvial Archives Group. An overarching finding is the confirmation of the well-established view that in Europe there is a demarcation between handaxe making in the west and flake-core industries in the east, although on a wider scale that pattern is undermined by the increased numbers of Lower Palaeolithic bifaces now recognized in East Asia. It is also apparent that, although it seems to have appeared at different places and at different times in the later Lower Palaeolithic, the arrival of Levallois technology as a global phenomenon was similarly timed across the area occupied by Middle Pleistocene hominins, at around 0.3 Ma.

Martian Fluvial Conglomerates at Gale Crater

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Williams, R. M. E.; Grotzinger, J. P.; Dietrich, W. E.; Gupta, S.; Sumner, D. Y.; Wiens, R. C.; Mangold, N.; Malin, M. C.; Edgett, K. S.; Maurice, S.; Forni, O.; Gasnault, O.; Ollila, A.; Newsom, H. E.; Dromart, G.; Palucis, M. C.; Yingst, R. A.; Anderson, R. B.; Herkenhoff, K. E.; Le Mouélic, S.; Goetz, W.; Madsen, M. B.; Koefoed, A.; Jensen, J. K.; Bridges, J. C.; Schwenzer, S. P.; Lewis, K. W.; Stack, K. M.; Rubin, D.; Kah, L. C.; Bell, J. F.; Farmer, J. D.; Sullivan, R.; Van Beek, T.; Blaney, D. L.; Pariser, O.; Deen, R. G.; Kemppinen, Osku; Bridges, Nathan; Johnson, Jeffrey R.; Minitti, Michelle; Cremers, David; Edgar, Lauren; Godber, Austin; Wadhwa, Meenakshi; Wellington, Danika; McEwan, Ian; Newman, Claire; Richardson, Mark; Charpentier, Antoine; Peret, Laurent; King, Penelope; Blank, Jennifer; Weigle, Gerald; Schmidt, Mariek; Li, Shuai; Milliken, Ralph; Robertson, Kevin; Sun, Vivian; Baker, Michael; Edwards, Christopher; Ehlmann, Bethany; Farley, Kenneth; Griffes, Jennifer; Miller, Hayden; Newcombe, Megan; Pilorget, Cedric; Rice, Melissa; Siebach, Kirsten; Stolper, Edward; Brunet, Claude; Hipkin, Victoria; Léveillé, Richard; Marchand, Geneviève; Sobrón Sánchez, Pablo; Favot, Laurent; Cody, George; Steele, Andrew; Flückiger, Lorenzo; Lees, David; Nefian, Ara; Martin, Mildred; Gailhanou, Marc; Westall, Frances; Israël, Guy; Agard, Christophe; Baroukh, Julien; Donny, Christophe; Gaboriaud, Alain; Guillemot, Philippe; Lafaille, Vivian; Lorigny, Eric; Paillet, Alexis; Pérez, René; Saccoccio, Muriel; Yana, Charles; Aparicio, Carlos Armiens; Caride Rodríguez, Javier; Carrasco Blázquez, Isaías; Gómez Gómez, Felipe; Elvira, Javier Gómez; Hettrich, Sebastian; Lepinette Malvitte, Alain; Marín Jiménez, Mercedes; Frías, Jesús Martínez; Soler, Javier Martín; Torres, F. Javier Martín; Molina Jurado, Antonio; Sotomayor, Luis Mora; Muñoz Caro, Guillermo; Navarro López, Sara; González, Verónica Peinado; García, Jorge Pla; Rodriguez Manfredi, José Antonio; Planelló, Julio José Romeral; Alejandra Sans Fuentes, Sara; Sebastian Martinez, Eduardo; Torres Redondo, Josefina; O'Callaghan, Roser Urqui; Zorzano Mier, María-Paz; Chipera, Steve; Lacour, Jean-Luc; Mauchien, Patrick; Sirven, Jean-Baptiste; Manning, Heidi; Fairén, Alberto; Hayes, Alexander; Joseph, Jonathan; Squyres, Steven; Thomas, Peter; Dupont, Audrey; Lundberg, Angela; Melikechi, Noureddine; Mezzacappa, Alissa; DeMarines, Julia; Grinspoon, David; Reitz, Günther; Prats, Benito; Atlaskin, Evgeny; Genzer, Maria; Harri, Ari-Matti; Haukka, Harri; Kahanpää, Henrik; Kauhanen, Janne; Paton, Mark; Polkko, Jouni; Schmidt, Walter; Siili, Tero; Fabre, Cécile; Wray, James; Wilhelm, Mary Beth; Poitrasson, Franck; Patel, Kiran; Gorevan, Stephen; Indyk, Stephen; Paulsen, Gale; Bish, David; Schieber, Juergen; Gondet, Brigitte; Langevin, Yves; Geffroy, Claude; Baratoux, David; Berger, Gilles; Cros, Alain; Uston, Claude d.; Lasue, Jérémie; Lee, Qiu-Mei; Meslin, Pierre-Yves; Pallier, Etienne; Parot, Yann; Pinet, Patrick; Schröder, Susanne; Toplis, Mike; Lewin, Éric; Brunner, Will; Heydari, Ezat; Achilles, Cherie; Oehler, Dorothy; Sutter, Brad; Cabane, Michel; Coscia, David; Szopa, Cyril; Robert, François; Sautter, Violaine; Nachon, Marion; Buch, Arnaud; Stalport, Fabien; Coll, Patrice; François, Pascaline; Raulin, François; Teinturier, Samuel; Cameron, James; Clegg, Sam; Cousin, Agnès; DeLapp, Dorothea; Dingler, Robert; Jackson, Ryan Steele; Johnstone, Stephen; Lanza, Nina; Little, Cynthia; Nelson, Tony; Williams, Richard B.; Jones, Andrea; Kirkland, Laurel; Treiman, Allan; Baker, Burt; Cantor, Bruce; Caplinger, Michael; Davis, Scott; Duston, Brian; Fay, Donald; Hardgrove, Craig; Harker, David; Herrera, Paul; Jensen, Elsa; Kennedy, Megan R.; Krezoski, Gillian; Krysak, Daniel; Lipkaman, Leslie; McCartney, Elaina; McNair, Sean; Nixon, Brian; Posiolova, Liliya; Ravine, Michael; Salamon, Andrew; Saper, Lee; Stoiber, Kevin; Supulver, Kimberley; Van Beek, Jason; Zimdar, Robert; French, Katherine Louise; Iagnemma, Karl; Miller, Kristen; Summons, Roger; Goesmann, Fred; Hviid, Stubbe; Johnson, Micah; Lefavor, Matthew; Lyness, Eric; Breves, Elly; Dyar, M. Darby; Fassett, Caleb; Blake, David F.; Bristow, Thomas; DesMarais, David; Edwards, Laurence; Haberle, Robert; Hoehler, Tori; Hollingsworth, Jeff; Kahre, Melinda; Keely, Leslie; McKay, Christopher; Bleacher, Lora; Brinckerhoff, William; Choi, David; Conrad, Pamela; Dworkin, Jason P.; Eigenbrode, Jennifer; Floyd, Melissa; Freissinet, Caroline; Garvin, James; Glavin, Daniel; Harpold, Daniel; Mahaffy, Paul; Martin, David K.; McAdam, Amy; Pavlov, Alexander; Raaen, Eric; Smith, Michael D.; Stern, Jennifer; Tan, Florence; Trainer, Melissa; Meyer, Michael; Posner, Arik; Voytek, Mary; Anderson, Robert C.; Aubrey, Andrew; Beegle, Luther W.; Behar, Alberto; Brinza, David; Calef, Fred; Christensen, Lance; Crisp, Joy A.; DeFlores, Lauren; Feldman, Jason; Feldman, Sabrina; Flesch, Gregory; Hurowitz, Joel; Jun, Insoo; Keymeulen, Didier; Maki, Justin; Mischna, Michael; Morookian, John Michael; Parker, Timothy; Pavri, Betina; Schoppers, Marcel; Sengstacken, Aaron; Simmonds, John J.; Spanovich, Nicole; de la Torre Juarez, Manuel; Vasavada, Ashwin R.; Webster, Christopher R.; Yen, Albert; Archer, Paul Douglas; Cucinotta, Francis; Jones, John H.; Ming, Douglas; Morris, Richard V.; Niles, Paul; Rampe, Elizabeth; Nolan, Thomas; Fisk, Martin; Radziemski, Leon; Barraclough, Bruce; Bender, Steve; Berman, Daniel; Dobrea, Eldar Noe; Tokar, Robert; Vaniman, David; Leshin, Laurie; Cleghorn, Timothy; Huntress, Wesley; Manhès, Gérard; Hudgins, Judy; Olson, Timothy; Stewart, Noel; Sarrazin, Philippe; Grant, John; Vicenzi, Edward; Wilson, Sharon A.; Bullock, Mark; Ehresmann, Bent; Hamilton, Victoria; Hassler, Donald; Peterson, Joseph; Rafkin, Scot; Zeitlin, Cary; Fedosov, Fedor; Golovin, Dmitry; Karpushkina, Natalya; Kozyrev, Alexander; Litvak, Maxim; Malakhov, Alexey; Mitrofanov, Igor; Mokrousov, Maxim; Nikiforov, Sergey; Prokhorov, Vasily; Sanin, Anton; Tretyakov, Vladislav; Varenikov, Alexey; Vostrukhin, Andrey; Kuzmin, Ruslan; Clark, Benton; Wolff, Michael; McLennan, Scott; Botta, Oliver; Drake, Darrell; Bean, Keri; Lemmon, Mark; Lee, Ella Mae; Sucharski, Robert; Hernández, Miguel Ángel de Pablo; Blanco Ávalos, Juan José; Ramos, Miguel; Kim, Myung-Hee; Malespin, Charles; Plante, Ianik; Muller, Jan-Peter; González, Rafael Navarro; Ewing, Ryan; Boynton, William; Downs, Robert; Fitzgibbon, Mike; Harshman, Karl; Morrison, Shaunna; Kortmann, Onno; Williams, Amy; Lugmair, Günter; Wilson, Michael A.; Jakosky, Bruce; Zunic, Tonci Balic; Frydenvang, Jens; Kinch, Kjartan; Stipp, Susan Louise Svane; Boyd, Nick; Campbell, John L.; Gellert, Ralf; Perrett, Glynis; Pradler, Irina; VanBommel, Scott; Jacob, Samantha; Owen, Tobias; Rowland, Scott; Savijärvi, Hannu; Boehm, Eckart; Böttcher, Stephan; Burmeister, Sönke; Guo, Jingnan; Köhler, Jan; García, César Martín; Mellin, Reinhold Mueller; Schweingruber, Robert Wimmer; McConnochie, Timothy; Benna, Mehdi; Franz, Heather; Bower, Hannah; Brunner, Anna; Blau, Hannah; Boucher, Thomas; Carmosino, Marco; Atreya, Sushil; Elliott, Harvey; Halleaux, Douglas; Rennó, Nilton; Wong, Michael; Pepin, Robert; Elliott, Beverley; Spray, John; Thompson, Lucy; Gordon, Suzanne; Williams, Joshua; Vasconcelos, Paulo; Bentz, Jennifer; Nealson, Kenneth; Popa, Radu; Moersch, Jeffrey; Tate, Christopher; Day, Mackenzie; Kocurek, Gary; Hallet, Bernard; Sletten, Ronald; Francis, Raymond; McCullough, Emily; Cloutis, Ed; ten Kate, Inge Loes; Arvidson, Raymond; Fraeman, Abigail; Scholes, Daniel; Slavney, Susan; Stein, Thomas; Ward, Jennifer; Berger, Jeffrey; Moores, John E.

2013-05-01

Observations by the Mars Science Laboratory Mast Camera (Mastcam) in Gale crater reveal isolated outcrops of cemented pebbles (2 to 40 millimeters in diameter) and sand grains with textures typical of fluvial sedimentary conglomerates. Rounded pebbles in the conglomerates indicate substantial fluvial abrasion. ChemCam emission spectra at one outcrop show a predominantly feldspathic composition, consistent with minimal aqueous alteration of sediments. Sediment was mobilized in ancient water flows that likely exceeded the threshold conditions (depth 0.03 to 0.9 meter, average velocity 0.20 to 0.75 meter per second) required to transport the pebbles. Climate conditions at the time sediment was transported must have differed substantially from the cold, hyper-arid modern environment to permit aqueous flows across several kilometers.

The origin and early evolution of metatherian mammals: the Cretaceous record

Directory of Open Access Journals (Sweden)

Thomas E. Williamson

2014-12-01

Full Text Available Metatherians, which comprise marsupials and their closest fossil relatives, were one of the most dominant clades of mammals during the Cretaceous and are the most diverse clade of living mammals after Placentalia. Our understanding of this group has increased greatly over the past 20 years, with the discovery of new specimens and the application of new analytical tools. Here we provide a review of the phylogenetic relationships of metatherians with respect to other mammals, discuss the taxonomic definition and diagnosis of Metatheria, outline the Cretaceous history of major metatherian clades, describe the paleobiology, biogeography, and macroevolution of Cretaceous metatherians, and provide a physical and climatic background of Cretaceous metatherian faunas. Metatherians are a clade of boreosphendian mammals that must have originated by the Late Jurassic, but the first unequivocal metatherian fossil is from the Early Cretaceous of Asia. Metatherians have the distinctive tightly interlocking occlusal molar pattern of tribosphenic mammals, but differ from Eutheria in their dental formula and tooth replacement pattern, which may be related to the metatherian reproductive process which includes an extended period of lactation followed by birth of extremely altricial young. Metatherians were widespread over Laurasia during the Cretaceous, with members present in Asia, Europe, and North America by the early Late Cretaceous. In particular, they were taxonomically and morphologically diverse and relatively abundant in the Late Cretaceous of western North America, where they have been used to examine patterns of biogeography, macroevolution, diversification, and extinction through the Late Cretaceous and across the Cretaceous-Paleogene (K-Pg boundary. Metatherian diversification patterns suggest that they were not strongly affected by a Cretaceous Terrestrial Revolution, but they clearly underwent a severe extinction across the K-Pg boundary.

Utilization of alternatives fuels in a fluvial convoy; Utilizacao de combustiveis alternativos em um comboio fluvial

Energy Technology Data Exchange (ETDEWEB)

Padovezi, Carlos D; Giraldo, Arnaldo

1987-12-31

This work presents the results of tests performed with ethanol and methanol in a fluvial convoy in Tiete river, Sao Paulo State - Southeast Brazil. It also outlines a comparison and evaluation methodology. 9 figs., 3 tabs.

Utilization of alternatives fuels in a fluvial convoy; Utilizacao de combustiveis alternativos em um comboio fluvial

Energy Technology Data Exchange (ETDEWEB)

Padovezi, Carlos D.; Giraldo, Arnaldo

1986-12-31

This work presents the results of tests performed with ethanol and methanol in a fluvial convoy in Tiete river, Sao Paulo State - Southeast Brazil. It also outlines a comparison and evaluation methodology. 9 figs., 3 tabs.

Landform Evolution Modeling of Specific Fluvially Eroded Physiographic Units on Titan

Science.gov (United States)

Moore, J. M.; Howard, A. D.; Schenk, P. M.

2015-01-01

Several recent studies have proposed certain terrain types (i.e., physiographic units) on Titan thought to be formed by fluvial processes acting on local uplands of bedrock or in some cases sediment. We have earlier used our landform evolution models to make general comparisons between Titan and other ice world landscapes (principally those of the Galilean satellites) that we have modeled the action of fluvial processes. Here we give examples of specific landscapes that, subsequent to modeled fluvial work acting on the surfaces, produce landscapes which resemble mapped terrain types on Titan.

Riparian shrub metal concentrations and growth in amended fluvial mine tailings

Science.gov (United States)

Fluvial mine tailing deposition has caused extensive riparian damage throughout the western United States. Willows are often used for fluvial mine tailing revegetation, but some species accumulate excessive metal concentrations which could be detrimental to browsers. In a greenhouse experiment, gr...

Dinosaur morphological diversity and the end-Cretaceous extinction.

Science.gov (United States)

Brusatte, Stephen L; Butler, Richard J; Prieto-Márquez, Albert; Norell, Mark A

2012-05-01

The extinction of non-avian dinosaurs 65 million years ago is a perpetual topic of fascination, and lasting debate has focused on whether dinosaur biodiversity was in decline before end-Cretaceous volcanism and bolide impact. Here we calculate the morphological disparity (anatomical variability) exhibited by seven major dinosaur subgroups during the latest Cretaceous, at both global and regional scales. Our results demonstrate both geographic and clade-specific heterogeneity. Large-bodied bulk-feeding herbivores (ceratopsids and hadrosauroids) and some North American taxa declined in disparity during the final two stages of the Cretaceous, whereas carnivorous dinosaurs, mid-sized herbivores, and some Asian taxa did not. Late Cretaceous dinosaur evolution, therefore, was complex: there was no universal biodiversity trend and the intensively studied North American record may reveal primarily local patterns. At least some dinosaur groups, however, did endure long-term declines in morphological variability before their extinction.

Morphology of fluvial levee series along a river under human influence, Maros River, Hungary

Science.gov (United States)

Kiss, Tímea; Balogh, Márton; Fiala, Károly; Sipos, György

2018-02-01

The development and morphometry of fluvial levees reflect the connection between channel and overbank processes, which can be altered by various human activities. The aims of this study are to investigate the morphology and spatial characteristics of fluvial levees and evaluate the role of some local- and catchment-scale human activities on their medium-term (150 years) development. This study applies LiDAR data along a 53-km-long reach of the Maros River in Hungary. Six fluvial levee types are identified based on the beginning and end of their evolution. These levee types were generated by local nineteenth century channel regulation works (cutoffs) and mid-twentieth century channel narrowing, which was caused by gravel mining and water impoundment in the upstream sections. However, other human activities also influenced the development of active fluvial levees because their horizontal evolution could have been limited by embanked flood-protection levees or the widening of low-lying floodplain benches that were generated by channel narrowing. Additionally, revetment constructions influenced their vertical parameters as higher fluvial levees developed along the fixed banks. Generally, the older active fluvial levees are wider, while the younger active levees are narrower with steeper slopes but not always lower. On the low-lying floodplain levels (benches), the youngest fluvial levees evolved quite rapidly and consist of coarser material. Currently, only 9.8- to 38-year return-period floods could cover the fluvial levees, contributing to their evolution. This fact and the development of fluvial levee series with two-three members reflect a gradual decoupling of the channel from the floodplain.

Stratigraphy and Facies of Cretaceous Schrader Bluff and Prince Creek Formations in Colville River Bluffs, North Slope, Alaska

Science.gov (United States)

Flores, Romeo M.; Myers, Mark D.; Houseknecht, David W.; Stricker, Gary D.; Brizzolara, Donald W.; Ryherd, Timothy J.; Takahashi, Kenneth I.

2007-01-01

Stratigraphic and sedimentologic studies of facies of the Upper Cretaceous rocks along the Colville River Bluffs in the west-central North Slope of Alaska identified barrier shoreface deposits consisting of vertically stacked, coarsening-upward parasequences in the Schrader Bluff Formation. This vertical stack of parasequence deposits represents progradational sequences that were affected by shoaling and deepening cycles caused by fluctuations of sea level. Further, the vertical stack may have served to stabilize accumulation of voluminous coal deposits in the Prince Creek Formation, which formed braided, high-sinuosity meandering, anastomosed, and low-sinuosity meandering fluvial channels and related flood plain deposits. The erosional contact at the top of the uppermost coarsening-upward sequence, however, suggests a significant drop of base level (relative sea level) that permitted a semiregional subaerial unconformity to develop at the contact between the Schrader Bluff and Prince Creek Formations. This drop of relative sea level may have been followed by a relative sea-level rise to accommodate coal deposition directly above the unconformity. This rise was followed by a second drop of relative sea level, with formation of incised valley topography as much as 75 ft deep and an equivalent surface of a major marine erosion or mass wasting, or both, either of which can be traced from the Colville River Bluffs basinward to the subsurface in the west-central North Slope. The Prince Creek fluvial deposits represent late Campanian to late Maastrichtian depositional environments that were affected by these base level changes influenced by tectonism, basin subsidence, and sea-level fluctuations.

Heavy mineral analyses as a powerful tool in fluvial geomorphology

Science.gov (United States)

von Suchodoletz, Hans; Gärtner, Andreas; Faust, Dominik

2014-05-01

The Marneuli depression is a tectonic sub-basin of the Transcaucasian depression in eastern Georgia, filled with several decametres of fluvial, lacustrine and aeolian Quaternary sediments. In order to reconstruct past landscape evolution of the region we studied Late Quaternary fluvial sediments found along several rivers that flow through that depression. Whereas Holocene river sediments could generally easily be assigned to corresponding rivers, this was not always the case for older fluvial sediments. For this reason, we studied the heavy mineral contents of five recent rivers and of four sedimentary deposits of potential precursors. A total of 4088 analysed heavy mineral grains enabled us to set up the characteristic heavy mineral distribution pattern for each sample. Using these data, we were able to reconstruct the most likely source areas of the Late Pleistocene fluvial sediments and to link them with the catchment areas of recent rivers. This allowed us to identify and to substantiate significant Late Quaternary river diversions that could at least partly be assigned to ongoing tectonic processes.

Tribosphenic mammal from the North American Early Cretaceous.

Science.gov (United States)

Cifelli, R L

1999-09-23

The main groups of living mammals, marsupials and eutherians, are presumed to have diverged in the Early Cretaceous, but their early history and biogeography are poorly understood. Dental remains have suggested that the eutherians may have originated in Asia, spreading to North America in the Late Cretaceous, where an endemic radiation of marsupials was already well underway. Here I describe a new tribosphenic mammal (a mammal with lower molar heels that are three-cusped and basined) from the Early Cretaceous of North America, based on an unusually complete specimen. The new taxon bears characteristics (molarized last premolar, reduction to three molars) otherwise known only for Eutheria among the tribosphenic mammals. Morphometric analysis and character comparisons show, however, that its molar structure is primitive (and thus phylogenetically uninformative), emphasizing the need for caution in interpretation of isolated teeth. The new mammal is approximately contemporaneous with the oldest known Eutheria from Asia. If it is a eutherian, as is indicated by the available evidence, then this group was far more widely distributed in the Early Cretaceous than previously appreciated. An early presence of Eutheria in North America offers a potential source for the continent's Late Cretaceous radiations, which have, in part, proven difficult to relate to contemporary taxa in Asia.

Invertebrate ichnofossils and rhizoliths associated with rhizomorphs from the Marília Formation (Echaporã Member), Bauru Group, Upper Cretaceous, Brazil

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Mineiro, Adriano Santos; Santucci, Rodrigo Miloni; da Rocha, Dulce Maria Sucena; de Andrade, Marco Brandalise; Nava, William Roberto

2017-12-01

The Marília Formation (Bauru Group, Upper Cretaceous, Brazil) has furnished a large array of vertebrate fossils. However, its ichnological and botanical contents are poorly explored to date. Here we report findings of invertebrate trace fossils (Beaconites isp., Skolithos isp., and Taenidium barretti), rhizoliths associated with rhizomorphs with preserved hyphae, and fossil roots from the Echaporã Member, Marília Formation, São Paulo State, Brazil. The association of trace fossils suggest they can be regarded to the Scoyenia Ichnofacies. The rhizoliths indicate that at least two types of herbaceous/arbustive plants inhabited the area, one of them living in the vadose zone and the other one with roots closer to the water table, under arid/semiarid conditions. Sedimentological analyses suggest the studied outcrop comprises fluvial deposits, with predominance of sand bars that underwent different and relatively long periods of subaerial exposure.

Fluvial response to the last Holocene rapid climate change in the Northwestern Mediterranean coastlands

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Degeai, Jean-Philippe; Devillers, Benoît; Blanchemanche, Philippe; Dezileau, Laurent; Oueslati, Hamza; Tillier, Margaux; Bohbot, Hervé

2017-05-01

The variability of fluvial activity in the Northwestern Mediterranean coastal lowlands and its relationship with modes of climate change were analysed from the late 9th to the 18th centuries CE. Geochemical analyses were undertaken from a lagoonal sequence and surrounding sediments in order to track the fluvial inputs into the lagoon. An index based on the K/S and Rb/S ratios was used to evidence the main periods of fluvial activity. This index reveals that the Medieval Climate Anomaly (MCA) was a drier period characterized by a lower fluvial activity, while the Little Ice Age (LIA) was a wetter period with an increase of the river dynamics. Three periods of higher than average fluvial activity were evidenced at the end of the first millennium CE (ca. 900-950 cal yr CE), in the first half of the second millennium CE (ca. 1150-1550 cal yr CE), and during the 1600s-1700s CE (ca. 1650-1800 cal yr CE). The comparison of these fluvial periods with other records of riverine or lacustrine floods in Spain, Italy, and South of France seems to indicate a general increase in fluvial and flood patterns in the Northwestern Mediterranean in response to the climate change from the MCA to the LIA, although some episodes of flooding are not found in all records. Besides, the phases of higher than average fluvial dynamics are in good agreement with the North Atlantic cold events evidenced from records of ice-rafted debris. The evolution of fluvial activity in the Northwestern Mediterranean coastlands during the last millennium could have been driven by atmospheric and oceanic circulation patterns.

Geomorphic Unit Tool (GUT): Applications of Fluvial Mapping

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Kramer, N.; Bangen, S. G.; Wheaton, J. M.; Bouwes, N.; Wall, E.; Saunders, C.; Bennett, S.; Fortney, S.

2017-12-01

Geomorphic units are the building blocks of rivers and represent distinct habitat patches for many fluvial organisms. We present the Geomorphic Unit Toolkit (GUT), a flexible GIS geomorphic unit mapping tool, to generate maps of fluvial landforms from topography. GUT applies attributes to landforms based on flow stage (Tier 1), topographic signatures (Tier 2), geomorphic characteristics (Tier 3) and patch characteristics (Tier 4) to derive attributed maps at the level of detail required by analysts. We hypothesize that if more rigorous and consistent geomorphic mapping is conducted, better correlations between physical habitat units and ecohydraulic model results will be obtained compared to past work. Using output from GUT for coarse bed tributary streams in the Columbia River Basin, we explore relationships between salmonid habitat and geomorphic spatial metrics. We also highlight case studies of how GUT can be used to showcase geomorphic impact from large wood restoration efforts. Provided high resolution topography exists, this tool can be used to quickly assess changes in fluvial geomorphology in watersheds impacted by human activities.

Definition of Greater Gulf Basin Lower Cretaceous and Upper Cretaceous Lower Cenomanian Shale Gas Assessment Unit, United States Gulf of Mexico Basin Onshore and State Waters

Science.gov (United States)

Dennen, Kristin O.; Hackley, Paul C.

2012-01-01

An assessment unit (AU) for undiscovered continuous “shale” gas in Lower Cretaceous (Aptian and Albian) and basal Upper Cretaceous (lower Cenomanian) rocks in the USA onshore Gulf of Mexico coastal plain recently was defined by the U.S. Geological Survey (USGS). The AU is part of the Upper Jurassic-Cretaceous-Tertiary Composite Total Petroleum System (TPS) of the Gulf of Mexico Basin. Definition of the AU was conducted as part of the 2010 USGS assessment of undiscovered hydrocarbon resources in Gulf Coast Mesozoic stratigraphic intervals. The purpose of defining the Greater Gulf Basin Lower Cretaceous Shale Gas AU was to propose a hypothetical AU in the Cretaceous part of the Gulf Coast TPS in which there might be continuous “shale” gas, but the AU was not quantitatively assessed by the USGS in 2010.

Modeling plan-form deltaic response to changes in fluvial sediment supply

NARCIS (Netherlands)

Nienhuis, J.H.; Ashton, A.D.; Roos, Pieter C.; Hulscher, Suzanne J.M.H.; Giosan, L.; Kranenburg, W.M.; Horstman, E.M.; Wijnberg, K.M.

2012-01-01

This study focuses on the effects of changes in fluvial sediment supply on the plan-form shape of wave-dominated deltas. We apply a one-line numerical shoreline model to calculate shoreline evolution after (I) elimination and (II) time-periodic variation of fluvial input. Model results suggest four

Shaler: in situ analysis of a fluvial sedimentary deposit on Mars

Science.gov (United States)

Edgar, Lauren; Gupta, Sanjeev; Rubin, David M.; Lewis, Kevin W.; Kocurek, Gary A.; Anderson, Ryan; Bell, James F.; Dromart, Gilles; Edgett, Kenneth S.; Grotzinger, John P.; Hardgrove, Craig; Kah, Linda C.; LeVeille, Richard A.; Malin, Michael C.; Mangold, Nicholas; Milliken, Ralph E.; Minitti, Michelle; Palucis, Marisa C.; Rice, Melissa; Rowland, Scott K.; Schieber, Juergen; Stack, Kathryn M.; Sumner, Dawn Y.; Wiens, Roger C.; Williams, Rebecca M.E.; Williams, Amy J.

2018-01-01

This paper characterizes the detailed sedimentology of a fluvial sandbody on Mars for the first time, and interprets its depositional processes and palaeoenvironmental setting. Despite numerous orbital observations of fluvial landforms on the surface of Mars, ground-based characterization of the sedimentology of such fluvial deposits has not previously been possible. Results from the NASA Mars Science Laboratory Curiosity rover provide an opportunity to reconstruct at fine scale the sedimentary architecture and palaeomorphology of a fluvial environment on Mars. This work describes the grain size, texture, and sedimentary facies of the Shaler outcrop, reconstructs the bedding architecture, and analyses cross-stratification to determine palaeocurrents. On the basis of bedset geometry and inclination, grain-size distribution, and bedform migration direction, this study concludes that the Shaler outcrop likely records the accretion of a fluvial barform. The majority of the outcrop consists of large-scale trough cross-bedding of coarse sand and granules. Palaeocurrent analyses and bedform reconstruction indicate that the beds were deposited by bedforms that migrated towards the northeast, across the surface of a bar that migrated southeast. Stacked cosets of dune cross-bedding suggest aggradation of multiple bedforms, which provides evidence for short periods of sustained flow during Shaler deposition. However, local evidence for aeolian reworking and the presence of potential desiccation cracks within the outcrop suggests that fluvial deposition may have been intermittent. The uppermost strata at Shaler are distinct in terms of texture and chemistry, and are inferred to record deposition from a different sediment dispersal system with a contrasting provenance. The outcrop as a whole is a testament to the availability of liquid water on the surface of Mars in its early history.

Contemporary Conceptual Approaches in Fluvial Geomorphology

Directory of Open Access Journals (Sweden)

Mônica dos Santos Marçal

2016-06-01

Full Text Available Contemporary fluvial geomorphology faces challenging questions, especially as it goes by understanding the Late Holocene/Anthropocene period, which has repercussions today and are intrinsically important to understand the human river disturbance. Given the scale that physical rates operate in complex river systems, two conceptual paths were developed to analyze the spatial and temporal organization. The network view emphasizes controls on catchment-scale and a reach approach focuses on discontinuity and local controls. Fluvial geomorphology has seek to understand the organization of complex river systems from the integrated view of the continuity and discontinuity paradigm. This integrated approach has stimulated within the geomorphology, the emergence of new theoretical-methodological instruments. It is recognized that rivers management is an ongoing process, part of the socio-cultural development, which refers to both a social movement and scientific exercise.

Protracted fluvial recovery from medieval earthquakes, Pokhara, Nepal

Science.gov (United States)

Stolle, Amelie; Bernhardt, Anne; Schwanghart, Wolfgang; Andermann, Christoff; Schönfeldt, Elisabeth; Seidemann, Jan; Adhikari, Basanta R.; Merchel, Silke; Rugel, Georg; Fort, Monique; Korup, Oliver

2016-04-01

River response to strong earthquake shaking in mountainous terrain often entails the flushing of sediments delivered by widespread co-seismic landsliding. Detailed mass-balance studies following major earthquakes in China, Taiwan, and New Zealand suggest fluvial recovery times ranging from several years to decades. We report a detailed chronology of earthquake-induced valley fills in the Pokhara region of western-central Nepal, and demonstrate that rivers continue to adjust to several large medieval earthquakes to the present day, thus challenging the notion of transient fluvial response to seismic disturbance. The Pokhara valley features one of the largest and most extensively dated sedimentary records of earthquake-triggered sedimentation in the Himalayas, and independently augments paleo-seismological archives obtained mainly from fault trenches and historic documents. New radiocarbon dates from the catastrophically deposited Pokhara Formation document multiple phases of extremely high geomorphic activity between ˜700 and ˜1700 AD, preserved in thick sequences of alternating fluvial conglomerates, massive mud and silt beds, and cohesive debris-flow deposits. These dated fan-marginal slackwater sediments indicate pronounced sediment pulses in the wake of at least three large medieval earthquakes in ˜1100, 1255, and 1344 AD. We combine these dates with digital elevation models, geological maps, differential GPS data, and sediment logs to estimate the extent of these three pulses that are characterized by sedimentation rates of ˜200 mm yr-1 and peak rates as high as 1,000 mm yr-1. Some 5.5 to 9 km3 of material infilled the pre-existing topography, and is now prone to ongoing fluvial dissection along major canyons. Contemporary river incision into the Pokhara Formation is rapid (120-170 mm yr-1), triggering widespread bank erosion, channel changes, and very high sediment yields of the order of 103 to 105 t km-2 yr-1, that by far outweigh bedrock denudation rates

Murgabskaya Oblast, a promising gas region of Central Asia

Energy Technology Data Exchange (ETDEWEB)

Amanniyazov, K.N.; Abdyyev, A.A.

1981-01-01

Gas fields of the Murgabskiy region are multiple-bed. The industrial gas content is associated with the sandy-terrigenous formations of the Shatlyk productive level of the lower Goterivskiy stage. The gas formation is anticlinal, occasionally floating. A map is compiled for the dispersal of the Shatlyk level which isolates the lithological composition, thickness, zones of dispersal of sandstone, etc. A description is provided for the map plan of the Shatlyk level. Alternation of sandy-argillaceous and carbonate rocks created favorable prerequisites for the development in the deposits of the Neocomian of lithological-physical pairs of ''collectors-mantles'', the basis for trap formation in structures and zones of lithological substitution. Within the Murgabskiy region, the greatest outlook for discovering new gas fields is confined to the Shatlyk level. It is associated with the central part of the Murgabskiy Basin where major deposits have already been discovered. A group of structures in the eastern submersion of the Kopetdag trough at the junction of the Murgabskiy Basin is important. The structures at the junction of East Kopetdag and the Murgabskiy Basin may be promising. The outlook for possible gas is associated with deposits of the lower cretaceous and Sharaplinksiy level. The main task must be comprehensive in investigation of the suprasaline apt-Neocomian and Kimmeridgian-Tithonian deposits as possible multiple-bed gas and oil containing masses.

Modeling Long-Term Fluvial Incision : Shall we Care for the Details of Short-Term Fluvial Dynamics?

Science.gov (United States)

Lague, D.; Davy, P.

2008-12-01

Fluvial incision laws used in numerical models of coupled climate, erosion and tectonics systems are mainly based on the family of stream power laws for which the rate of local erosion E is a power function of the topographic slope S and the local mean discharge Q : E = K Qm Sn. The exponents m and n are generally taken as (0.35, 0.7) or (0.5, 1), and K is chosen such that the predicted topographic elevation given the prevailing rates of precipitation and tectonics stay within realistic values. The resulting topographies are reasonably realistic, and the coupled system dynamics behaves somehow as expected : more precipitation induces increased erosion and localization of the deformation. Yet, if we now focus on smaller scale fluvial dynamics (the reach scale), recent advances have suggested that discharge variability, channel width dynamics or sediment flux effects may play a significant role in controlling incision rates. These are not factored in the simple stream power law model. In this work, we study how these short- term details propagate into long-term incision dynamics within the framework of surface/tectonics coupled numerical models. To upscale the short term dynamics to geological timescales, we use a numerical model of a trapezoidal river in which vertical and lateral incision processes are computed from fluid shear stress at a daily timescale, sediment transport and protection effects are factored in, as well as a variable discharge. We show that the stream power law model might still be a valid model but that as soon as realistic effects are included such as a threshold for sediment transport, variable discharge and dynamic width the resulting exponents m and n can be as high as 2 and 4. This high non-linearity has a profound consequence on the sensitivity of fluvial relief to incision rate. We also show that additional complexity does not systematically translates into more non-linear behaviour. For instance, considering only a dynamical width

Novel insect leaf-mining after the end-Cretaceous extinction and the demise of cretaceous leaf miners, Great Plains, USA.

Directory of Open Access Journals (Sweden)

Michael P Donovan

Full Text Available Plant and associated insect-damage diversity in the western U.S.A. decreased significantly at the Cretaceous-Paleogene (K-Pg boundary and remained low until the late Paleocene. However, the Mexican Hat locality (ca. 65 Ma in southeastern Montana, with a typical, low-diversity flora, uniquely exhibits high damage diversity on nearly all its host plants, when compared to all known local and regional early Paleocene sites. The same plant species show minimal damage elsewhere during the early Paleocene. We asked whether the high insect damage diversity at Mexican Hat was more likely related to the survival of Cretaceous insects from refugia or to an influx of novel Paleocene taxa. We compared damage on 1073 leaf fossils from Mexican Hat to over 9000 terminal Cretaceous leaf fossils from the Hell Creek Formation of nearby southwestern North Dakota and to over 9000 Paleocene leaf fossils from the Fort Union Formation in North Dakota, Montana, and Wyoming. We described the entire insect-feeding ichnofauna at Mexican Hat and focused our analysis on leaf mines because they are typically host-specialized and preserve a number of diagnostic morphological characters. Nine mine damage types attributable to three of the four orders of leaf-mining insects are found at Mexican Hat, six of them so far unique to the site. We found no evidence linking any of the diverse Hell Creek mines with those found at Mexican Hat, nor for the survival of any Cretaceous leaf miners over the K-Pg boundary regionally, even on well-sampled, surviving plant families. Overall, our results strongly relate the high damage diversity on the depauperate Mexican Hat flora to an influx of novel insect herbivores during the early Paleocene, possibly caused by a transient warming event and range expansion, and indicate drastic extinction rather than survivorship of Cretaceous insect taxa from refugia.

Novel insect leaf-mining after the end-Cretaceous extinction and the demise of cretaceous leaf miners, Great Plains, USA.

Science.gov (United States)

Donovan, Michael P; Wilf, Peter; Labandeira, Conrad C; Johnson, Kirk R; Peppe, Daniel J

2014-01-01

Plant and associated insect-damage diversity in the western U.S.A. decreased significantly at the Cretaceous-Paleogene (K-Pg) boundary and remained low until the late Paleocene. However, the Mexican Hat locality (ca. 65 Ma) in southeastern Montana, with a typical, low-diversity flora, uniquely exhibits high damage diversity on nearly all its host plants, when compared to all known local and regional early Paleocene sites. The same plant species show minimal damage elsewhere during the early Paleocene. We asked whether the high insect damage diversity at Mexican Hat was more likely related to the survival of Cretaceous insects from refugia or to an influx of novel Paleocene taxa. We compared damage on 1073 leaf fossils from Mexican Hat to over 9000 terminal Cretaceous leaf fossils from the Hell Creek Formation of nearby southwestern North Dakota and to over 9000 Paleocene leaf fossils from the Fort Union Formation in North Dakota, Montana, and Wyoming. We described the entire insect-feeding ichnofauna at Mexican Hat and focused our analysis on leaf mines because they are typically host-specialized and preserve a number of diagnostic morphological characters. Nine mine damage types attributable to three of the four orders of leaf-mining insects are found at Mexican Hat, six of them so far unique to the site. We found no evidence linking any of the diverse Hell Creek mines with those found at Mexican Hat, nor for the survival of any Cretaceous leaf miners over the K-Pg boundary regionally, even on well-sampled, surviving plant families. Overall, our results strongly relate the high damage diversity on the depauperate Mexican Hat flora to an influx of novel insect herbivores during the early Paleocene, possibly caused by a transient warming event and range expansion, and indicate drastic extinction rather than survivorship of Cretaceous insect taxa from refugia.

Cretacic tectonics in Uruguay

International Nuclear Information System (INIS)

Gomez Rifas, C.

2012-01-01

This work is about Cretacic tectonics in Uruguay, this formation is characterized by high level cortex because the basament is cratonized since Middle Devonian. There were formed two main grabens such as Santa Lucia and Mirim-Pelotas which are filled with basalt and sediments.

Experimental investigation of fluvial dike breaching due to flow overtopping

Science.gov (United States)

El Kadi Abderrezzak, K.; Rifai, I.; Erpicum, S.; Archambeau, P.; Violeau, D.; Pirotton, M.; Dewals, B.

2017-12-01

The failure of fluvial dikes (levees) often leads to devastating floods that cause loss of life and damages to public infrastructure. Overtopping flows have been recognized as one of the most frequent cause of dike erosion and breaching. Fluvial dike breaching is different from frontal dike (embankments) breaching, because of specific geometry and boundary conditions. The current knowledge on the physical processes underpinning fluvial dike failure due to overtopping remains limited. In addition, there is a lack of a continuous monitoring of the 3D breach formation, limiting the analysis of the key mechanisms governing the breach development and the validation of conceptual or physically-based models. Laboratory tests on breach growth in homogeneous, non-cohesive sandy fluvial dikes due to flow overtopping have been performed. Two experimental setups have been constructed, permitting the investigation of various hydraulic and geometric parameters. Each experimental setup includes a main channel, separated from a floodplain by a dike. A rectangular initial notch is cut in the crest to initiate dike breaching. The breach development is monitored continuously using a specific developed laser profilometry technique. The observations have shown that the breach develops in two stages: first the breach deepens and widens with the breach centerline being gradually shifted toward the downstream side of the main channel. This behavior underlines the influence of the flow momentum component parallel to the dike crest. Second, the dike geometry upstream of the breach stops evolving and the breach widening continues only toward the downstream side of the main channel. The breach evolution has been found strongly affected by the flow conditions (i.e. inflow discharge in the main channel, downstream boundary condition) and floodplain confinement. The findings of this work shed light on key mechanisms of fluvial dike breaching, which differ substantially from those of dam

Characterizing fluvial heavy metal pollutions under different rainfall conditions: Implication for aquatic environment protection.

Science.gov (United States)

Zhang, Lixun; Zhao, Bo; Xu, Gang; Guan, Yuntao

2018-09-01

Globally, fluvial heavy metal (HM) pollution has recently become an increasingly severe problem. However, few studies have investigated the variational characteristics of fluvial HMs after rain over long periods (≥1 year). The Dakan River in Xili Reservoir watershed (China) was selected as a case study to investigate pollution levels, influencing factors, and sources of HMs under different rainfall conditions during 2015 and 2016. Fluvial HMs showed evident spatiotemporal variations attributable to the coupled effects of pollution generation and rainfall diffusion. Fluvial HM concentrations were significantly associated with rainfall characteristics (e.g., rainfall intensity, rainfall amount, and antecedent dry period) and river flow, which influenced the generation and the transmission of fluvial HMs in various ways. Moreover, this interrelationship depended considerably on the HM type and particle size distribution. Mn, Pb, Cr, and Ni were major contributors to high values of the comprehensive pollution index; therefore, they should be afforded special attention. Additionally, quantitative source apportionment of fluvial HMs was conducted by combining principal component analysis with multiple linear regression and chemical mass balance models to obtain comprehensive source profiles. Finally, an environment-friendly control strategy coupling "source elimination" and "transport barriers" was proposed for aquatic environment protection. Copyright © 2018 Elsevier B.V. All rights reserved.

Signatures of Late Pleistocene fluvial incision in an Alpine landscape

Science.gov (United States)

Leith, Kerry; Fox, Matthew; Moore, Jeffrey R.

2018-02-01

Uncertainty regarding the relative efficacy of fluvial and glacial erosion has hindered attempts to quantitatively analyse the Pleistocene evolution of alpine landscapes. Here we show that the morphology of major tributaries of the Rhone River, Switzerland, is consistent with that predicted for a landscape shaped primarily by multiple phases of fluvial incision following a period of intense glacial erosion after the mid-Pleistocene transition (∼0.7 Ma). This is despite major ice sheets reoccupying the region during cold intervals since the mid-Pleistocene. We use high-resolution LiDAR data to identify a series of convex reaches within the long-profiles of 18 tributary channels. We propose these reaches represent knickpoints, which developed as regional uplift raised tributary bedrock channels above the local fluvial baselevel during glacial intervals, and migrated upstream as the fluvial system was re-established during interglacial periods. Using a combination of integral long-profile analysis and stream-power modelling, we find that the locations of ∼80% of knickpoints in our study region are consistent with that predicted for a fluvial origin, while the mean residual error over ∼100 km of modelled channels is just 26.3 m. Breaks in cross-valley profiles project toward the elevation of former end-of-interglacial channel elevations, supporting our model results. Calculated long-term uplift rates are within ∼15% of present-day measurements, while modelled rates of bedrock incision range from ∼1 mm/yr for low gradient reaches between knickpoints to ∼6-10 mm/yr close to retreating knickpoints, typical of observed rates in alpine settings. Together, our results reveal approximately 800 m of regional uplift, river incision, and hillslope erosion in the lower half of each tributary catchment since 0.7 Ma.

Faunal turnover of marine tetrapods during the Jurassic-Cretaceous transition.

Science.gov (United States)

Benson, Roger B J; Druckenmiller, Patrick S

2014-02-01

Marine and terrestrial animals show a mosaic of lineage extinctions and diversifications during the Jurassic-Cretaceous transition. However, despite its potential importance in shaping animal evolution, few palaeontological studies have focussed on this interval and the possible climate and biotic drivers of its faunal turnover. In consequence evolutionary patterns in most groups are poorly understood. We use a new, large morphological dataset to examine patterns of lineage diversity and disparity (variety of form) in the marine tetrapod clade Plesiosauria, and compare these patterns with those of other organisms. Although seven plesiosaurian lineages have been hypothesised as crossing the Jurassic-Cretaceous boundary, our most parsimonious topology suggests the number was only three. The robust recovery of a novel group including most Cretaceous plesiosauroids (Xenopsaria, new clade) is instrumental in this result. Substantial plesiosaurian turnover occurred during the Jurassic-Cretaceous boundary interval, including the loss of substantial pliosaurid, and cryptoclidid diversity and disparity, followed by the radiation of Xenopsaria during the Early Cretaceous. Possible physical drivers of this turnover include climatic fluctuations that influenced oceanic productivity and diversity: Late Jurassic climates were characterised by widespread global monsoonal conditions and increased nutrient flux into the opening Atlantic-Tethys, resulting in eutrophication and a highly productive, but taxonomically depauperate, plankton. Latest Jurassic and Early Cretaceous climates were more arid, resulting in oligotrophic ocean conditions and high taxonomic diversity of radiolarians, calcareous nannoplankton and possibly ammonoids. However, the observation of discordant extinction patterns in other marine tetrapod groups such as ichthyosaurs and marine crocodylomorphs suggests that clade-specific factors may have been more important than overarching extrinsic drivers of faunal

Aeolian and fluvial processes in dryland regions: the need for integrated studies

Science.gov (United States)

Belnap, Jayne; Munson, Seth M.; Field, Jason P.

2011-01-01

Aeolian and fluvial processes play a fundamental role in dryland regions of the world and have important environmental and ecological consequences from local to global scales. Although both processes operate over similar spatial and temporal scales and are likely strongly coupled in many dryland systems, aeolian and fluvial processes have traditionally been studied separately, making it difficult to assess their relative importance in drylands, as well as their potential for synergistic interaction. Land degradation by accelerated wind and water erosion is a major problem throughout the world's drylands, and although recent studies suggest that these processes likely interact across broad spatial and temporal scales to amplify the transport of soil resources from and within drylands, many researchers and land managers continue to view them as separate and unrelated processes. Here, we illustrate how aeolian and fluvial sediment transport is coupled at multiple spatial and temporal scales and highlight the need for these interrelated processes to be studied from a more integrated perspective that crosses traditional disciplinary boundaries. Special attention is given to how the growing threat of climate change and land-use disturbance will influence linkages between aeolian and fluvial processes in the future. We also present emerging directions for interdisciplinary needs within the aeolian and fluvial research communities that call for better integration across a broad range of traditional disciplines such as ecology, biogeochemistry, agronomy, and soil conservation.

Late Cretaceous vicariance in Gondwanan amphibians.

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Ines Van Bocxlaer

Full Text Available Overseas dispersals are often invoked when Southern Hemisphere terrestrial and freshwater organism phylogenies do not fit the sequence or timing of Gondwana fragmentation. We used dispersal-vicariance analyses and molecular timetrees to show that two species-rich frog groups, Microhylidae and Natatanura, display congruent patterns of spatial and temporal diversification among Gondwanan plates in the Late Cretaceous, long after the presumed major tectonic break-up events. Because amphibians are notoriously salt-intolerant, these analogies are best explained by simultaneous vicariance, rather than by oceanic dispersal. Hence our results imply Late Cretaceous connections between most adjacent Gondwanan landmasses, an essential concept for biogeographic and palaeomap reconstructions.

Sediment dynamics in the Rhine catchment : Quantification of fluvial response to climate change and human impact

NARCIS (Netherlands)

Erkens, G.

2009-01-01

Fluvial systems are strongly responsive to changes in climate and land use — but take their time to show it. Accurate prediction of the timing and degree of future fluvial response requires comprehensive understanding of fluvial response in the past. This PhD-thesis studied the response of the river

GOEMORFOLOGIA FLUVIAL DA BACIA HIDROGRÁFICA DO RIO DE ONDAS

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Ossifleres Silva Damasceno

2011-10-01

Full Text Available Os estudos de Geomorfologia Fluvial para analise de Bacias Hidrográficas vêm tendo nos últimos tempos grande importância, tanto para se conhecer as características de determinadas bacias como para se planejar o uso de tais recursos. Neste sentido, este trabalho foi efetuado no intuito de somar aos estudos anteriormente executados nessa bacia, levantando algumas características geomorfológicas, o uso e ocupação atual. Palavras-chaves: geomorfologia fluvial, hidrografia, agricultura irrigada.

Surficial geological tools in fluvial geomorphology: Chapter 2

Science.gov (United States)

Jacobson, Robert B.; O'Connor, James E.; Oguchi, Takashi

2016-01-01

Increasingly, environmental scientists are being asked to develop an understanding of how rivers and streams have been altered by environmental stresses, whether rivers are subject to physical or chemical hazards, how they can be restored, and how they will respond to future environmental change. These questions present substantive challenges to the discipline of fluvial geomorphology, especially since decades of geomorphologic research have demonstrated the general complexity of fluvial systems. It follows from the concept of complex response that synoptic and short-term historical views of rivers will often give misleading understanding of future behavior. Nevertheless, broadly trained geomorphologists can address questions involving complex natural systems by drawing from a tool box that commonly includes the principles and methods of geology, hydrology, hydraulics, engineering, and ecology.

Rates of morphological evolution are heterogeneous in Early Cretaceous birds

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Lloyd, Graeme T.

2016-01-01

The Early Cretaceous is a critical interval in the early history of birds. Exceptional fossils indicate that important evolutionary novelties such as a pygostyle and a keeled sternum had already arisen in Early Cretaceous taxa, bridging much of the morphological gap between Archaeopteryx and crown birds. However, detailed features of basal bird evolution remain obscure because of both the small sample of fossil taxa previously considered and a lack of quantitative studies assessing rates of morphological evolution. Here we apply a recently available phylogenetic method and associated sensitivity tests to a large data matrix of morphological characters to quantify rates of morphological evolution in Early Cretaceous birds. Our results reveal that although rates were highly heterogeneous between different Early Cretaceous avian lineages, consistent patterns of significantly high or low rates were harder to pinpoint. Nevertheless, evidence for accelerated evolutionary rates is strongest at the point when Ornithuromorpha (the clade comprises all extant birds and descendants from their most recent common ancestors) split from Enantiornithes (a diverse clade that went extinct at the end-Cretaceous), consistent with the hypothesis that this key split opened up new niches and ultimately led to greater diversity for these two dominant clades of Mesozoic birds. PMID:27053742

Fluvial system response to Late Devensian (Weichselian) aridity, Baston, Lincolnshire, England

Science.gov (United States)

Briant, Rebecca M.; Coope, G. Russell; Preece, Richard C.; Keen, David H.; Boreham, Steve; Griffiths, Huw I.; Seddon, Mary B.; Gibbard, Philip L.

2004-07-01

Little is known about the impact of Late Devensian (Weichselian) aridity on lowland British landscapes, largely because they lack the widespread coversand deposits of the adjacent continent. The concentration of large interformational ice-wedge casts in the upper part of many Devensian fluvial sequences suggests that fluvial activity may have decreased considerably during this time. The development of optically stimulated luminescence (OSL) dating enables this period of ice-wedge cast formation to be constrained for the first time in eastern England, where a marked horizon of ice-wedge casts is found between two distinctive dateable facies associations. Contrasts between this horizon and adjacent sediments show clear changes in environment and fluvial system behaviour in response to changing water supply, in line with palaeontological evidence. In addition to providing chronological control on the period of ice-wedge formation, the study shows good agreement of the radiocarbon and OSL dating techniques during the Middle and Late Devensian, with direct comparison of these techniques beyond 15 000 yr for the first time in Britain. It is suggested that aridity during the Late Devensian forced a significant decrease in fluvial activity compared with preceding and following periods, initiating a system with low peak flows and widespread permafrost development. Copyright

Lacustrine-fluvial interactions in Australia's Riverine Plains

Science.gov (United States)

Kemp, Justine; Pietsch, Timothy; Gontz, Allen; Olley, Jon

2017-06-01

Climatic forcing of fluvial systems has been a pre-occupation of geomorphological studies in Australia since the 1940s. In the Riverine Plain, southeastern Australia, the stable tectonic setting and absence of glaciation have combined to produce sediment loads that are amongst the lowest in the world. Surficial sediments and landforms exceed 140,000 yr in age, and geomorphological change recorded in the fluvial, fluvio-lacustrine and aeolian features have provided a well-studied record of Quaternary environmental change over the last glacial cycle. The region includes the Willandra Lakes, whose distinctive lunette lakes preserve a history of water-level variations and ecological change that is the cornerstone of Australian Quaternary chronostratigraphy. The lunette sediments also contain an ancient record of human occupation that includes the earliest human fossils yet found on the Australian continent. To date, the lake-level and palaeochannel records in the Lachlan-Willandra system have not been fully integrated, making it difficult to establish the regional significance of hydrological change. Here, we compare the Willandra Lakes environmental record with the morphology and location of fluvial systems in the lower Lachlan. An ancient channel belt of the Lachlan, Willandra Creek, acted as the main feeder channel to Willandra Lakes before channel avulsion caused the lakes to dry out in the late Pleistocene. Electromagnetic surveys, geomorphological and sedimentary evidence are used to reconstruct the evolution of the first new channel belt following the avulsion. Single grain optical dating of floodplain sediments indicates that sedimentation in the new Middle Billabong Palaeochannel had commenced before 18.4 ± 1.1 ka. A second avulsion shifted its upper reaches to the location of the present Lachlan River by 16.2 ± 0.9 ka. The timing of these events is consistent with palaeohydrological records reconstructed from Willandra Lakes and with the record of

The Gediz River fluvial archive : A benchmark for Quaternary research in Western Anatolia

NARCIS (Netherlands)

Maddy, D.; Veldkamp, A.; Demir, T.; van Gorp, W.; Wijbrans, J.R.; van Hinsbergen, D.J.J.; Dekkers, M.J.; Schreve, D.; Schoorl, J.M.; Scaife, R.; Stemerdink, C.; van der Schriek, T.; Bridgland, D.R.; Aytaç, A.S.

2017-01-01

The Gediz River, one of the principal rivers of Western Anatolia, has an extensive Pleistocene fluvial archive that potentially offers a unique window into fluvial system behaviour on the western margins of Asia during the Quaternary. In this paper we review our work on the Quaternary Gediz River

Evidence of anthropogenic tipping points in fluvial dynamics in Europe

Science.gov (United States)

Notebaert, Bastiaan; Broothaerts, Nils; Verstraeten, Gert

2018-05-01

In this study the occurrence of thresholds in fluvial style changes during the Holocene are discussed for three different catchments: the Dijle and Amblève catchments (Belgium) and the Valdaine Region (France). We consider tipping points to be a specific type of threshold, defined as relatively rapid and irreversible changes in the system. Field data demonstrate that fluvial style has varied in all three catchments over time, and that different tipping points can be identified. An increase in sediment load as a result of human induced soil erosion lead to a permanent change in the Dijle floodplains from a forested peaty marsh towards open landscape with clastic deposition and a well-defined river channel. In the Valdaine catchment, an increase in coarse sediment load, caused by increased erosion in the mountainous upper catchment, altered the floodplains from a meandering pattern to a braided pattern. Other changes in fluvial style appeared to be reversible. Rivers in the Valdaine were prone to different aggradation and incision phases due to changes in peak water discharge and sediment delivery, but the impact was too low for these changes to be irreversible. Likewise the Dijle River has recently be prone to an incision phase due to a clear water effect, and also this change is expected to be reversible. Finally, the Amblève River did not undergo major changes in style during the last 2000 to 5000 years, even though floodplain sedimentation rates increased tenfold during the last 600 years. Overall, these examples demonstrate how changes in fluvial style depend on the crossing of thresholds in sediment supply and water discharge. Although changes in these controlling parameters are caused by anthropogenic land use changes, the link between those land use changes and changes in fluvial style is not linear. This is due to the temporal variability in landscape connectivity and sediment transport and the non-linear relationship between land use intensity and soil

A basal thunnosaurian from Iraq reveals disparate phylogenetic origins for Cretaceous ichthyosaurs

Science.gov (United States)

Fischer, Valentin; Appleby, Robert M.; Naish, Darren; Liston, Jeff; Riding, James B.; Brindley, Stephen; Godefroit, Pascal

2013-01-01

Cretaceous ichthyosaurs have typically been considered a small, homogeneous assemblage sharing a common Late Jurassic ancestor. Their low diversity and disparity have been interpreted as indicative of a decline leading to their Cenomanian extinction. We describe the first post-Triassic ichthyosaur from the Middle East, Malawania anachronus gen. et sp. nov. from the Early Cretaceous of Iraq, and re-evaluate the evolutionary history of parvipelvian ichthyosaurs via phylogenetic and cladogenesis rate analyses. Malawania represents a basal grade in thunnosaurian evolution that arose during a major Late Triassic radiation event and was previously thought to have gone extinct during the Early Jurassic. Its pectoral morphology appears surprisingly archaic, retaining a forefin architecture similar to that of its Early Jurassic relatives. After the initial latest Triassic radiation of early thunnosaurians, two subsequent large radiations produced lineages with Cretaceous representatives, but the radiation events themselves are pre-Cretaceous. Cretaceous ichthyosaurs therefore include distantly related lineages, with contrasting evolutionary histories, and appear more diverse and disparate than previously supposed. PMID:23676653

NEW ABELISAURID MATERIAL FROM THE UPPER CRETACEOUS (CENOMANIAN OF MOROCCO

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SIMONE D'ORAZI PORCHETTI

2011-11-01

Full Text Available Fragmentary cranial bones of dinosaur origin have been recently recovered from the Kem Kem beds (Upper Cretaceous, Cenomanian of Morocco. They include two incompletely preserved maxillary bones evidencing diagnostic features of abelisaurid theropods. These new finds provide further evidence of Abelisauridae in the Late Cretaceous of Morocco. 

The mid-Cretaceous super plume, carbon dioxide, and global warming

Science.gov (United States)

Caldeira, Ken; Rampino, Michael R.

1991-01-01

Carbon-dioxide releases associated with a mid-Cretaceous super plume and the emplacement of the Ontong-Java Plateau have been suggested as a principal cause of the mid-Cretaceous global warming. A carbonate-silicate cycle model is developed to quantify the possible climatic effects of these CO2 releases, utilizing four different formulations for the rate of silicate-rock weathering as a function of atmospheric CO2. CO2 emissions resulting from super-plume tectonics could have produced atmospheric CO2 levels from 3.7 to 14.7 times the modern preindustrial value of 285 ppm. Based on the temperature sensitivity to CO2 increases used in the weathering-rate formulations, this would cause a global warming of from 2.8 to 7.7 C over today's glogal mean temperature. Altered continental positions and higher sea level may have been contributed about 4.8 C to mid-Cretaceous warming. Thus, the combined effects of paleogeographic changes and super-plume related CO2 emissions could be in the range of 7.6 to 12.5 C, within the 6 to 14 C range previously estimated for mid-Cretaceous warming. CO2 releases from oceanic plateaus alone are unlikely to have been directly responsible for more than 20 percent of the mid-Cretaceous increase in atmospheric CO2.

Geological aspects of paleoseismicity and archaeosismology in the fluvial alluvial Rimac valley

OpenAIRE

Jacay, Javier

2017-01-01

The sedimentary fill of the Rimac River fluvial-alluvial plain (Upper Miocene-Quaternary) consists of a thick sequence of unconsolidated material that corresponds to fluvial deposits. A record of seismotectonic activity is presentedin the sedimentary levels of fine facie within numerous paleoseismic structures such as contoured layers, pseudonodules, load figures, and material injections. Additionally, wall inclination and collapse, as well as displacement and partialfracturing, and pavement ...

Natural radionuclide behaviour in the fluvial environment

International Nuclear Information System (INIS)

Murray, A.S.; Olley, J.M.; Wallbrink, P.J.

1992-01-01

Variable concentrations of uranium and thorium series nuclides and 7 Be have been measured in soils and sediments. Strong correlations between 226 Ra and thorium series nuclides were found in sediments but not in soils. Laboratory measurements suggest the correlations arise from particle size and density dependent transport, and transport-related abrasion of iron oxide coatings. These correlations are characteristic of the sampled location, and provide a method for identifying the source areas which dominate the fluvial nuclide flux, and by implication, the associated sediment flux. Cosmogenic 7 Be (half-life 53 d) also contributes to nuclide fluxes. Over an 18 month period, individual rainstorms increased the 7 Be soil inventory by 10% on average. Dry precipitation contributed less than 10% to the total. Most 7 Be was retained within the top few millimetres of soil. It is deduced that 7 Be presence in fluvial sediments indicates a significant surface source contribution to the overall nuclide and sediment flux. (author)

Molecular fossils in Cretaceous condensate from western India

Science.gov (United States)

Bhattacharya, Sharmila; Dutta, Suryendu; Dutta, Ratul

2014-06-01

The present study reports the biomarker distribution of condensate belonging to the early Cretaceous time frame using gas chromatography-mass spectrometry (GC-MS). The early Cretaceous palaeoenvironment was inscribed into these molecular fossils which reflected the source and conditions of deposition of the condensate. The saturate fraction of the condensate is characterized by normal alkanes ranging from n-C9 to n-C29 (CPI-1.13), cycloalkanes and C14 and C15 sesquiterpanes. The aromatic fraction comprises of naphthalene, phenanthrene, their methylated derivatives and cyclohexylbenzenes. Isohexylalkylnaphthalenes, a product of rearrangement process of terpenoids, is detected in the condensate. Several aromatic sesquiterpenoids and diterpenoids have been recorded. Dihydro- ar-curcumene, cadalene and ionene form the assemblage of sesquiterpenoids which are indicative of higher plant input. Aromatic diterpenoid fraction comprises of simonellite and retene. These compounds are also indicative of higher plants, particularly conifer source which had been a predominant flora during the Cretaceous time.

A Field Exercise in Fluvial Sediment Transport.

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Tharp, Thomas M.

1983-01-01

Describes an investigation which introduces the mathematical principles of stream hydraulics and fluvial sediment in a practical context. The investigation has four stages: defining hydrology of the stream; defining channel hydraulics in a study reach; measuring grain size; and calculating transportable grain size and comparing measure stream-bed…

Cretaceous – Paleogene boundary Fish Clay at Højerup (Stevns Klint, Denmark: Zn, Pb and REE in kerogen

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MILOS G. DJORDJEVIC

2008-04-01

Full Text Available Geochemical analyses of Zn, Pb and rare earth elements (La, Ce, Nd, Sm, Eu, Tb, Yb and Lu in the kerogen of the black marl at the Cretaceous – Paleogene boundary Fish Clay at Højerup were performed. Substantial proportions of the Zn, Pb and rare earths were probably contained in terrestrial humic substances (the kerogen precursor arriving at the marine sedimentary site. This is in accord with a previous hypothesis that kerogen is mainly derived from humic acids of an oxic soil in of the adjacent coastal areas of eastern Denmark. It is also suggested that humics enriched in Zn, Pb and rare earth elements were transported mainly through fluvial transport into the deposition site of the Fish Clay. Local weathering/leaching of the impact–eject fallout on the land surface and local terrestrial rocks by impact-induced? acid surface waters perhaps played an important role in providing Zn, Pb and rare earths to these humic substances. Apparently, chondritic and non-chondritic Zn originated from the impact fallout; Pb and rare earth elements were most likely sourced by exposed rocks in the coastal areas of eastern Denmark.

Highly specialized mammalian skulls from the Late Cretaceous of South America.

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Rougier, Guillermo W; Apesteguía, Sebastián; Gaetano, Leandro C

2011-11-02

Dryolestoids are an extinct mammalian group belonging to the lineage leading to modern marsupials and placentals. Dryolestoids are known by teeth and jaws from the Jurassic period of North America and Europe, but they thrived in South America up to the end of the Mesozoic era and survived to the beginnings of the Cenozoic. Isolated teeth and jaws from the latest Cretaceous of South America provide mounting evidence that, at least in western Gondwana, dryolestoids developed into strongly endemic groups by the Late Cretaceous. However, the lack of pre-Late Cretaceous dryolestoid remains made study of their origin and early diversification intractable. Here we describe the first mammalian remains from the early Late Cretaceous of South America, including two partial skulls and jaws of a derived dryolestoid showing dental and cranial features unknown among any other group of Mesozoic mammals, such as single-rooted molars preceded by double-rooted premolars, combined with a very long muzzle, exceedingly long canines and evidence of highly specialized masticatory musculature. On one hand, the new mammal shares derived features of dryolestoids with forms from the Jurassic of Laurasia, whereas on the other hand, it is very specialized and highlights the endemic, diverse dryolestoid fauna from the Cretaceous of South America. Our specimens include only the second mammalian skull known for the Cretaceous of Gondwana, bridging a previous 60-million-year gap in the fossil record, and document the whole cranial morphology of a dryolestoid, revealing an unsuspected morphological and ecological diversity for non-tribosphenic mammals.

Late Cretaceous seasonal ocean variability from the Arctic.

Science.gov (United States)

Davies, Andrew; Kemp, Alan E S; Pike, Jennifer

2009-07-09

The modern Arctic Ocean is regarded as a barometer of global change and amplifier of global warming and therefore records of past Arctic change are critical for palaeoclimate reconstruction. Little is known of the state of the Arctic Ocean in the greenhouse period of the Late Cretaceous epoch (65-99 million years ago), yet records from such times may yield important clues to Arctic Ocean behaviour in near-future warmer climates. Here we present a seasonally resolved Cretaceous sedimentary record from the Alpha ridge of the Arctic Ocean. This palaeo-sediment trap provides new insight into the workings of the Cretaceous marine biological carbon pump. Seasonal primary production was dominated by diatom algae but was not related to upwelling as was previously hypothesized. Rather, production occurred within a stratified water column, involving specially adapted species in blooms resembling those of the modern North Pacific subtropical gyre, or those indicated for the Mediterranean sapropels. With increased CO(2) levels and warming currently driving increased stratification in the global ocean, this style of production that is adapted to stratification may become more widespread. Our evidence for seasonal diatom production and flux testify to an ice-free summer, but thin accumulations of terrigenous sediment within the diatom ooze are consistent with the presence of intermittent sea ice in the winter, supporting a wide body of evidence for low temperatures in the Late Cretaceous Arctic Ocean, rather than recent suggestions of a 15 degrees C mean annual temperature at this time.

The mid-Cretaceous North Atlantic nutrient trap: black shales and OAEs

NARCIS (Netherlands)

Trabucho Alexandre, J.; Tuenter, E.; Henstra, G.A.; Zwan, C.J. van der; Wal, R.S.W. van de; Dijkstra, H.A.; Boer, P.L. de

2010-01-01

Organic-rich sediments are the salient marine sedimentation product in the mid-Cretaceous of the ocean basins formed in the Mesozoic. Oceanic anoxic events (OAEs) are discrete and particularly organic-rich intervals within these mid-Cretaceous organic-rich sequences and are defined by pronounced

Palynological and iridium anomalies at Cretaceous-Tertiary boundary, south-central Saskatchewan

Science.gov (United States)

Nichols, D.J.; Jarzen, D.M.; Orth, C.J.; Oliver, P.Q.

1986-01-01

The Cretaceous-Tertiary boundary in south-central Saskatchewan is marked by coincident anomalies in abundance of iridium and fern spores at the extinction level of a suite of Cretaceous pollen taxa. Evidence of disruption of the terrestrial flora includes the fern-spore abundance anomaly and local extinction of as much as 30 percent of angiosperm species. The reorganized earliest Tertiary flora is made up largely of surviving species that assumed new roles of dominance. Persistence of climatically sensitive taxa across the boundary indicates that if paleoclimate was altered by the terminal Cretaceous event, it returned quickly to the pre-event condition.

Tyrant dinosaur evolution tracks the rise and fall of Late Cretaceous oceans.

Science.gov (United States)

Loewen, Mark A; Irmis, Randall B; Sertich, Joseph J W; Currie, Philip J; Sampson, Scott D

2013-01-01

The Late Cretaceous (∼95-66 million years ago) western North American landmass of Laramidia displayed heightened non-marine vertebrate diversity and intracontinental regionalism relative to other latest Cretaceous Laurasian ecosystems. Processes generating these patterns during this interval remain poorly understood despite their presumed role in the diversification of many clades. Tyrannosauridae, a clade of large-bodied theropod dinosaurs restricted to the Late Cretaceous of Laramidia and Asia, represents an ideal group for investigating Laramidian patterns of evolution. We use new tyrannosaurid discoveries from Utah--including a new taxon which represents the geologically oldest member of the clade--to investigate the evolution and biogeography of Tyrannosauridae. These data suggest a Laramidian origin for Tyrannosauridae, and implicate sea-level related controls in the isolation, diversification, and dispersal of this and many other Late Cretaceous vertebrate clades.

Fluvial facies reservoir productivity prediction method based on principal component analysis and artificial neural network

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Pengyu Gao

2016-03-01

Full Text Available It is difficult to forecast the well productivity because of the complexity of vertical and horizontal developments in fluvial facies reservoir. This paper proposes a method based on Principal Component Analysis and Artificial Neural Network to predict well productivity of fluvial facies reservoir. The method summarizes the statistical reservoir factors and engineering factors that affect the well productivity, extracts information by applying the principal component analysis method and approximates arbitrary functions of the neural network to realize an accurate and efficient prediction on the fluvial facies reservoir well productivity. This method provides an effective way for forecasting the productivity of fluvial facies reservoir which is affected by multi-factors and complex mechanism. The study result shows that this method is a practical, effective, accurate and indirect productivity forecast method and is suitable for field application.

Gold-bearing fluvial and associated tidal marine sediments of Proterozoic age in the Mporokoso Basin, northern Zambia

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Andrews-Speed, C. P.

1986-07-01

The structurally defined Mporokoso Basin contains up to 5000 m of continental and marine clastic sediments and minor silicic volcanics which together form the Mporokoso Group. These rocks overlie unconformably a basement of silicic-intermediate igneous rocks and accumulated within the interval 1830-1130 Ma. This sedimentological study was restricted to the eastern end of the basin and was part of an assessment of the potential for palaeoplacer gold in the Mporokoso Group. At the base of the Mporokoso Group, the Mbala Formation consists of 1000-1500 m of purple sandstones and conglomerates deposited in a braided-stream system overlain by 500-1000 m of mature quartz arenites deposited in a tidal marine setting. A general coarsening-upward trend exists within the fluvial sediments. Sandy, distal braided-stream facies passes upwards into more proximal conglomeratic facies. In proximal sections, poorly sorted conglomerates form the top of the coarsening-up sequence which is 500-700 m thick. The overlying fluvial sediments fine upwards. The tidal marine sandstones at the top of the Mbala Formation resulted from reworking of fluvial sediments during a marine transgression. Well-exposed sections with fluvial conglomerates were studied in detail. Individual conglomerate bodies form sheets extending for hundreds of metres downstream and at least one hundred metres across stream, with little sign of deep scouring or channelling. They are generally matrix-supported. The whole fluvial sequence is characterised by a paucity of mud or silt. These conglomerates were deposited by large velocity, sheet flows of water which transported a bed-load of pebbles and sand. Most fine material settling out from suspension was eroded by the next flow. The great lateral and vertical extent and the uniformity of the fluvial sediments suggest that the sediments accumulated over an unconfined alluvial plain and that the tectonic evolution of the source area was relatively continuous and not

Late Cretaceous restructuring of terrestrial communities facilitated the end-Cretaceous mass extinction in North America.

Science.gov (United States)

Mitchell, Jonathan S; Roopnarine, Peter D; Angielczyk, Kenneth D

2012-11-13

The sudden environmental catastrophe in the wake of the end-Cretaceous asteroid impact had drastic effects that rippled through animal communities. To explore how these effects may have been exacerbated by prior ecological changes, we used a food-web model to simulate the effects of primary productivity disruptions, such as those predicted to result from an asteroid impact, on ten Campanian and seven Maastrichtian terrestrial localities in North America. Our analysis documents that a shift in trophic structure between Campanian and Maastrichtian communities in North America led Maastrichtian communities to experience more secondary extinction at lower levels of primary production shutdown and possess a lower collapse threshold than Campanian communities. Of particular note is the fact that changes in dinosaur richness had a negative impact on the robustness of Maastrichtian ecosystems against environmental perturbations. Therefore, earlier ecological restructuring may have exacerbated the impact and severity of the end-Cretaceous extinction, at least in North America.

Detailed measured sections, cross sections, and paleogeographic reconstructions of the upper cretaceous and lower tertiary nonmarine interval, Wind River Basin, Wyoming: Chapter 10 in Petroleum systems and geologic assessment of oil and gas resources in the Wind River Basin Province, Wyoming

Science.gov (United States)

Johnson, Ronald C.

2007-01-01

Cretaceous Cody Shale was being eroded off a rising Owl Creek Mountains in latest Cretaceous time. The Paleocene Fort Union Formation unconformably overlies older units but with only slight angular discordance around much of the margins of the Wind River Basin. Pre-Fort Union erosion was most pronounced toward the Wind River Range to the southwest, where the Fort Union ultimately overlies strata as old as the upper part of the Cretaceous Cody Shale. The unconformity appears to die out toward the basin center. Coal-forming mires developed throughout the western part of the basin near the beginning of the Paleocene. River systems entering the basin from the Wind River Range to the southwest and the Granite Mountains to the south produced areas of sandy fluvial deposition along mountain fronts. A major river system appears to have entered the basin from about the same spot along the Wind River Range throughout much of the Paleocene, probably because it became incised and could not migrate laterally. The muddy floodplain facies that developed along the deep basin trough during latest Cretaceous time, expanded during the early part of the Paleocene. Coal-forming mires that characterize part of the lower Fort Union Formation reached maximum extent near the beginning of the late Paleocene and just prior to the initial transgression of Lake Waltman. From the time of initial flooding, Lake Waltman expanded rapidly, drowning the coal-forming mires in the central part of the basin and spreading to near basin margins. Outcrop studies along the south margin of the basin document that once maximum transgression was reached, the lake was rapidly pushed basinward and replaced by fluvial environments.

La géoarchéologie fluviale

Directory of Open Access Journals (Sweden)

Gilles Arnaud-Fassetta

2008-03-01

Full Text Available Les recherches des hydrogéomorphologues ont des applications nombreuses dans le vaste champ des sciences géoarchéologiques. Elles fournissent des réponses précises sur la façon dont l’environnement des anciens lieux de passage et de vie humaine a évolué. Le propos n’est pas seulement de définir les causes des grands changements environnementaux, mais aussi de juger de la vulnérabilité sociétale face aux contraintes hydroclimatiques. Pour cela, les méthodes d’étude doivent nécessairement prendre en compte les trois facettes de la géomorphologie fluviale : la paléohydrographie, la paléohydrologie et la paléohydraulique. La pertinence de cette approche est montrée en milieu rural et urbain dans les plaines deltaïques du Rhône (France du Sud et de l’Isonzo (Italie du Nord.Current research led by hydrogeomorphologists has numerous applications in the vast field of geoarchaeological sciences. It brings precise answers on environmental characteristics around the ancient places of passage and human life. The goal is not only to define the causes of global environmental changes, but also to precise the links between river dynamics and human societies in terms of fluvial risk. Therefore, the studied methods should simultaneously take into account the three facets of the fluvial geomorphology, i.e., the palaeohydrography, the palaeohydrology, and the palaeohydraulics. The pertinence of this combinatorial approach is deduced from the work of the author led both in rural and urban areas of the deltaic plains of the Rhône (South of France and Isonzo (northern Italy rivers.

Fluvial processes and channel morphometry of the upper Orashi ...

African Journals Online (AJOL)

Fluvial processes and channel morphometry of the upper Orashi basin in ... of channel equilibrium between morphology and hydrology, the Orashi channel is not well ... Drainage basins, watershed morphology, morphometric analysis, Nigeria ...

Fluvial Channel Networks as Analogs for the Ridge-Forming Unit, Sinus Meridiani, Mars

Science.gov (United States)

Wilkinson, M. J.; du Bois, J. B.

2010-01-01

Fluvial models have been generally discounted as analogs for the younger layered rock units of Sinus Meridiani. A fluvial model based on the large fluvial fan provides a possibly close analog for various features of the sinuous ridges of the etched, ridge-forming unit (RFU) in particular. The close spacing of the RFU ridges, their apparently chaotic orientations, and their organization in dense networks all appear unlike classical stream channel patterns. However, drainage patterns on large fluvial fans low-angle, fluvial aggradational features, 100s of km long, documented worldwide by us provide parallels. Some large fan characteristics resemble those of classical floodplains, but many differences have been demonstrated. One major distinction relevant to the RFU is that channel landscapes of large fans can dominate large areas (1.2 million km2 in one S. American study area). We compare channel morphologies on large fans in the southern Sahara Desert with ridge patterns in Sinus Meridiani (fig 1). Stream channels are the dominant landform on large terrestrial fans: they may equate to the ubiquitous, sinuous, elongated ridges of the RFU that cover areas region wide. Networks of convergent/divergent and crossing channels may equate to similar features in the ridge networks. Downslope divergence is absent in channels of terrestrial upland erosional landscapes (fig. 1, left), whereas it is common to both large fans (fig. 1, center) and RFU ridge patterns (fig 1, right downslope defined as the regional NW slope of Sinus Meridiani). RFU ridge orientation, judged from those areas apparently devoid of impact crater control, is broadly parallel with the regional slope (arrow, fig. 1, right), as is mean orientation of major channels on large fans (arrow, fig. 1, center). High densities per unit area characterize fan channels and martian ridges reaching an order of magnitude higher than those in uplands just upstream of the terrestrial study areas fig. 1. In concert with

Ridge Orientations of the Ridge-Forming Unit, Sinus Meridiani, Mars-A Fluvial Explanation

Science.gov (United States)

Wilkinson, M. Justin; Herridge, A.

2013-01-01

Imagery and MOLA data were used in an analysis of the ridge-forming rock unit (RFU) exposed in Sinus Meridiani (SM). This unit shows parallels at different scales with fluvial sedimentary bodies. We propose the terrestrial megafan as the prime analog for the RFU, and likely for other members of the layered units. Megafans are partial cones of fluvial sediment, with radii up to hundreds of km. Although recent reviews of hypotheses for the RFU units exclude fluvial hypotheses [1], inverted ridges in the deserts of Oman have been suggested as putative analogs for some ridges [2], apparently without appreciating The wider context in which these ridges have formed is a series of megafans [3], a relatively unappreciated geomorphic feature. It has been argued that these units conform to the megafan model at the regional, subregional and local scales [4]. At the regional scale suites of terrestrial megafans are known to cover large areas at the foot of uplands on all continents - a close parallel with the setting of the Meridiani sediments at the foot of the southern uplands of Mars, with its incised fluvial systems leading down the regional NW slope [2, 3] towards the sedimentary units. At the subregional scale the layering and internal discontinuities of the Meridiani rocks are consistent, inter alia, with stacked fluvial units [4]. Although poorly recognized as such, the prime geomorphic environment in which stream channel networks cover large areas, without intervening hillslopes, is the megafan [see e.g. 4]. Single megafans can reach 200,000 km2 [5]. Megafans thus supply an analog for areas where channel-like ridges (as a palimpsest of a prior landscape) cover the intercrater plains of Meridiani [6]. At the local, or river-reach scale, the numerous sinuous features of the RFU are suggestive of fluvial channels. Cross-cutting relationships, a common feature of channels on terrestrial megafans, are ubiquitous. Desert megafans show cemented paleo-channels as inverted

Early Cretaceous greenhouse pumped higher taxa diversification in spiders.

Science.gov (United States)

Shao, Lili; Li, Shuqiang

2018-05-24

The Cretaceous experienced one of the most remarkable greenhouse periods in geological history. During this time, ecosystem reorganizations significantly impacted the diversification of many groups of organisms. The rise of angiosperms marked a major biome turnover. Notwithstanding, relatively little remains known about how the Cretaceous global ecosystem impacted the evolution of spiders, which constitute one of the most abundant groups of predators. Herein, we evaluate the transcriptomes of 91 taxa representing more than half of the spider families. We add 23 newly sequenced taxa to the existing database to obtain a robust phylogenomic assessment. Phylogenetic reconstructions using different datasets and methods obtain novel placements of some groups, especially in the Synspermiata and the group having a retrolateral tibial apophysis (RTA). Molecular analyses indicate an expansion of the RTA clade at the Early Cretaceous with a hunting predatory strategy shift. Fossil analyses show a 7-fold increase of diversification rate at the same period, but this likely owes to the first occurrences spider in amber deposits. Additional analyses of fossil abundance show an accumulation of spider lineages in the Early Cretaceous. We speculate that the establishment of a warm greenhouse climate pumped the diversification of spiders, in particular among webless forms tracking the abundance of insect prey. Our study offers a new pathway for future investigations of spider phylogeny and diversification. Copyright © 2018. Published by Elsevier Inc.

A model of plant strategies in fluvial hydrosystems

NARCIS (Netherlands)

Bornette, G.; Tabacchi, E.; Hupp, C.; Puijalon, S.; Rostan, J.C.

2008-01-01

1. We propose a model of plant strategies in temperate fluvial hydrosystems that considers the hydraulic and geomorphic features that control plant recruitment, establishment and growth in river floodplains. 2. The model describes first how the disturbance gradient and the grain-size of the river

The origin of dose distributions in fluvial sediments, and the prospect of dating single grains from fluvial deposits using optically stimulated luminescence

International Nuclear Information System (INIS)

Olley, J.M.; Caitcheon, G.G.; Roberts, R.G.

1999-01-01

We examine the causes of the asymmetric distributions of dose observed from measurements of the optically stimulated luminescence emitted by small aliquots of fluvial quartz, and deduce that the asymmetry arises as a result of samples being composed of a mix of mainly well bleached grains with grains that were effectively unbleached at the time of deposition. We demonstrate that the shapes of the dose distributions can be used to assess the likelihood that aliquots consist only of grains that were well-bleached at the time of deposition. The more asymmetric the distribution, the greater the probability that the aliquots with the lowest dose most closely represent the true burial dose. Single grains with differing doses are present in each of the samples examined, and the population with the lowest dose gives an optical age consistent with the expected burial age. This result implies that the beta-dose heterogeneity in these deposits is small, and that the effects of micro-dosimetric variations on optical dating of individual grains are not significant for these samples. We demonstrate that single-grain dating of fluvial material is possible and practicable using standard Risoe optical dating equipment, and we conclude that application of a new regenerative-dose protocol to single grains of quartz, using the lowest dose population to estimate the burial dose, is the best available means of obtaining reliable luminescence ages for heterogeneously bleached fluvial sediments

A geologic approach to field methods in fluvial geomorphology

Science.gov (United States)

Fitzpatrick, Faith A.; Thornbush, Mary J; Allen, Casey D; Fitzpatrick, Faith A.

2014-01-01

A geologic approach to field methods in fluvial geomorphology is useful for understanding causes and consequences of past, present, and possible future perturbations in river behavior and floodplain dynamics. Field methods include characterizing river planform and morphology changes and floodplain sedimentary sequences over long periods of time along a longitudinal river continuum. Techniques include topographic and bathymetric surveying of fluvial landforms in valley bottoms and describing floodplain sedimentary sequences through coring, trenching, and examining pits and exposures. Historical sediment budgets that include floodplain sedimentary records can characterize past and present sources and sinks of sediment along a longitudinal river continuum. Describing paleochannels and floodplain vertical accretion deposits, estimating long-term sedimentation rates, and constructing historical sediment budgets can assist in management of aquatic resources, habitat, sedimentation, and flooding issues.

Birth and death of the Late Cretaceous ``La Luna Sea'', and origin of the Tres Esquinas phosphorites

Science.gov (United States)

Erlich, R. N.; Macsotay I., O.; Nederbragt, A. J.; Lorente, M. Antonieta

2000-05-01

Deposition of organic carbon-rich intervals of the La Luna and Navay formations of northwestern Venezuela was governed by the development of key paleobathymetric barriers (Santa Marta and Santander massifs, Paraguana Block, and ancestral Mérida Andes). These enhanced the development of anoxia in the "La Luna Sea" by causing poor circulation and limited ventilation. Anoxia was also promoted by high evaporation and low precipitation rates (high salinity bottom water), and high levels of marine algal productivity (high organic matter flux). Nutrient supply was augmented by infrequent fluvial sources. Bottom water oxygen levels increased from the Late Santonian through the end of the Cretaceous. Ventilation of anoxic bottom waters may have been enhanced by more frequent or intense seasonal upwelling (caused by higher wind stress) and catastrophic overturn, as well as the removal of a key paleobathymetric barrier. Common byproducts of overturn events were massive phytoplankton blooms, which produced red tides. Fish and marine reptile bone beds within the Tres Esquinas Member (La Luna Formation) are attributed to massive mortality during these events, and are correlative with similar Campanian units in eastern Colombia. During the Maastrichtian, increasing ventilation, combined with siliciclastic dilution, ultimately produced sediments with lower total organic carbon (TOC) content.

Stratigraphy and structural setting of Upper Cretaceous Frontier Formation, western Centennial Mountains, southwestern Montana and southeastern Idaho

Science.gov (United States)

Dyman, T.S.; Tysdal, R.G.; Perry, W.J.; Nichols, D.J.; Obradovich, J.D.

2008-01-01

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

Implications from Sedimentary records in Fluvial Terraces for Geomorphological Evolution in the Puli Basin, Taiwan

NARCIS (Netherlands)

Tseng, C.H.; Wenske, D.; Böse, M.; Reimann, T.; Lüthgens, C.; Frechen, Manfred

2013-01-01

Fluvial terraces play an important role for research on previous geomorphic processes as their sediments can record various sedimentation stages. In the mountains of central Taiwan, however, the formation time of sediments in the Puli Basin is still unclear. In this study, we investigate the fluvial

Combined fluvial and pluvial urban flood hazard analysis: concept development and application to Can Tho city, Mekong Delta, Vietnam

Science.gov (United States)

Apel, Heiko; Martínez Trepat, Oriol; Nghia Hung, Nguyen; Thi Chinh, Do; Merz, Bruno; Viet Dung, Nguyen

2016-04-01

Many urban areas experience both fluvial and pluvial floods, because locations next to rivers are preferred settlement areas and the predominantly sealed urban surface prevents infiltration and facilitates surface inundation. The latter problem is enhanced in cities with insufficient or non-existent sewer systems. While there are a number of approaches to analyse either a fluvial or pluvial flood hazard, studies of a combined fluvial and pluvial flood hazard are hardly available. Thus this study aims to analyse a fluvial and a pluvial flood hazard individually, but also to develop a method for the analysis of a combined pluvial and fluvial flood hazard. This combined fluvial-pluvial flood hazard analysis is performed taking Can Tho city, the largest city in the Vietnamese part of the Mekong Delta, as an example. In this tropical environment the annual monsoon triggered floods of the Mekong River, which can coincide with heavy local convective precipitation events, causing both fluvial and pluvial flooding at the same time. The fluvial flood hazard was estimated with a copula-based bivariate extreme value statistic for the gauge Kratie at the upper boundary of the Mekong Delta and a large-scale hydrodynamic model of the Mekong Delta. This provided the boundaries for 2-dimensional hydrodynamic inundation simulation for Can Tho city. The pluvial hazard was estimated by a peak-over-threshold frequency estimation based on local rain gauge data and a stochastic rainstorm generator. Inundation for all flood scenarios was simulated by a 2-dimensional hydrodynamic model implemented on a Graphics Processing Unit (GPU) for time-efficient flood propagation modelling. The combined fluvial-pluvial flood scenarios were derived by adding rainstorms to the fluvial flood events during the highest fluvial water levels. The probabilities of occurrence of the combined events were determined assuming independence of the two flood types and taking the seasonality and probability of

Ephemeral-fluvial sediments as potential hydrocarbon reservoirs. Vol. 1: Sedimentology

Energy Technology Data Exchange (ETDEWEB)

Taylor, K.S.

1994-12-31

Although reservoirs formed from ephemeral-fluvial sandstones have previously been considered relatively simple, unresolved problems of sandbody correlation and production anomalies demonstrate the need for improved understanding of their internal complexity. Outcropping ephemeral-fluvial systems have been studied in order to determine the main features and processes occurring in sand-rich ephemeral systems and to identify which features will be of importance in a hydrocarbon reservoir. The Lower Jurassic Upper Moenave and Kayenta Formations of south-eastern Utah and northern Arizona comprise series of stacked, sand-dominated sheet-like palaeochannels suggestive of low sinuosity, braided systems. Low subsidence rates and rapid lateral migration rates enabled channels to significantly modify their widths during high discharge. (author)

From nappe stacking to exhumation: Cretaceous tectonics in the Apuseni Mountains (Romania)

Science.gov (United States)

Reiser, Martin Kaspar; Schuster, Ralf; Spikings, Richard; Tropper, Peter; Fügenschuh, Bernhard

2017-03-01

New Ar-Ar muscovite and Rb-Sr biotite age data in combination with structural analyses from the Apuseni Mountains provide new constraints on the timing and kinematics of deformation during the Cretaceous. Time-temperature paths from the structurally highest basement nappe of the Apuseni Mountains in combination with sedimentary data indicate exhumation and a position close to the surface after the Late Jurassic emplacement of the South Apuseni Ophiolites. Early Cretaceous Ar-Ar muscovite ages from structurally lower parts in the Biharia Nappe System (Dacia Mega-Unit) show cooling from medium-grade conditions. NE-SW-trending stretching lineation and associated kinematic indicators of this deformation phase (D1) are overprinted by top-NW-directed thrusting during D2. An Albian to Turonian age (110-90 Ma) is proposed for the main deformation (D2) that formed the present-day geometry of the nappe stack and led to a pervasive retrograde greenschist-facies overprint. Thermochronological and structural data from the Bihor Unit (Tisza Mega-Unit) allowed to establish E-directed differential exhumation during Early-Late Cretaceous times (D3.1). Brittle detachment faulting (D3.2) and the deposition of syn-extensional sediments indicate general uplift and partial surface exposure during the Late Cretaceous. Brittle conditions persist during the latest Cretaceous compressional overprint (D4).

Cretaceous rocks of the Western Interior basin

International Nuclear Information System (INIS)

Molenaar, C.M.; Rice, D.D.

1988-01-01

The Cretaceous rocks of the conterminous United States are discussed in this chapter. Depositional facies and lithology are reviewed along with economic resources. The economic resources include coal, hydrocarbons, and uranium

Small theropod teeth from the Late Cretaceous of the San Juan Basin, northwestern New Mexico and their implications for understanding latest Cretaceous dinosaur evolution.

Science.gov (United States)

Williamson, Thomas E; Brusatte, Stephen L

2014-01-01

Studying the evolution and biogeographic distribution of dinosaurs during the latest Cretaceous is critical for better understanding the end-Cretaceous extinction event that killed off all non-avian dinosaurs. Western North America contains among the best records of Late Cretaceous terrestrial vertebrates in the world, but is biased against small-bodied dinosaurs. Isolated teeth are the primary evidence for understanding the diversity and evolution of small-bodied theropod dinosaurs during the Late Cretaceous, but few such specimens have been well documented from outside of the northern Rockies, making it difficult to assess Late Cretaceous dinosaur diversity and biogeographic patterns. We describe small theropod teeth from the San Juan Basin of northwestern New Mexico. These specimens were collected from strata spanning Santonian - Maastrichtian. We grouped isolated theropod teeth into several morphotypes, which we assigned to higher-level theropod clades based on possession of phylogenetic synapomorphies. We then used principal components analysis and discriminant function analyses to gauge whether the San Juan Basin teeth overlap with, or are quantitatively distinct from, similar tooth morphotypes from other geographic areas. The San Juan Basin contains a diverse record of small theropods. Late Campanian assemblages differ from approximately coeval assemblages of the northern Rockies in being less diverse with only rare representatives of troodontids and a Dromaeosaurus-like taxon. We also provide evidence that erect and recurved morphs of a Richardoestesia-like taxon represent a single heterodont species. A late Maastrichtian assemblage is dominated by a distinct troodontid. The differences between northern and southern faunas based on isolated theropod teeth provide evidence for provinciality in the late Campanian and the late Maastrichtian of North America. However, there is no indication that major components of small-bodied theropod diversity were lost

Global effects of agriculture on fluvial dissolved organic matter

DEFF Research Database (Denmark)

Graeber, Daniel; Boëchat, Iola; Encina, Francisco

2015-01-01

Agricultural land covers approximately 40% of Earth’s land surface and affects hydromorphological, biogeochemical and ecological characteristics of fluvial networks. In the northern temperate region, agriculture also strongly affects the amount and molecular composition of dissolved organic matter...

Pseudoclypeina? crnogorica Radoičić, 1972: Stratigraphic revision and taxonomic note on a little known dasycladalean alga from Montenegro

Directory of Open Access Journals (Sweden)

Radoičić Rajka

2013-01-01

Full Text Available Pseudoclypeina? crnogorica was first described in 1972 from the Lower, Cretaceous limestone of the Njegoš Mt. area, Montenegro, Dinaric Carbonate Platform. It differs from other species of the genus Pseudoclypeina by its calcification pattern, the shape and relative length of the first and second order laterals, and by the presence in the type-material (a thin section containing the holotype of sections standing for the sterile portion of the thallus. This is why in this paper, the generic name is left in open nomenclature. On this occasion the species, whose presence is also reported from southern Iran, is re-described and better illustrated, based on material originating from other outcrops in Montenegro. The stratigraphic position is reviewed as well. Pseudoclypeina? crnogorica occurs in shallow water inner platform facies of early Neocomian age, along with Selliporella neocomiensis.

Fluvial processes on Mars: Erosion and sedimentation

Science.gov (United States)

Squyres, Steven W.

1988-01-01

One of the most important discoveries of the Mariner 9 and Viking missions to Mars was evidence of change of the Martian surface by the action of liquid water. From the standpoint of a Mars Rover/Sample Return Mission, fluvial activity on Mars is important in two ways: (1) channel formation has deeply eroded the Martian crust, providing access to relatively undisturbed subsurface units; and (2) much of the material eroded from channels may have been deposited in standing bodies of liquid water. The most striking fluvial erosion features on Mars are the outflow channels. A second type of channel apparently caused by flow of liquid water is the valley systems. These are similar to terrestial drainage systems. The sedimentary deposits of outflow channels are often difficult to identfy. No obvious deposits such as deltaic accumulations are visible in Viking images. Another set of deposits that may be water lain and that date approx. from the epoch of outflow channels are the layered deposits in the Valles Marineris. From the standpoint of a Mars Rover/Sample Return mission, the problem with all of these water-lain sediments is their age, or rather the lack of it.

Shallow magnetic inclinations in the Cretaceous Valle Group, Baja California: remagnetization, compaction, or terrane translation?

Science.gov (United States)

Smith, Douglas P.; Busby, Cathy J.

1993-10-01

Paleomagnetic data from Albian to Turonian sedimentary rocks on Cedros Island, Mexico (28.2° N, 115.2° W) support the interpretation that Cretaceous rocks of western Baja California have moved farther northward than the 3° of latitude assignable to Neogene oblique rifting in the Gulf of California. Averaged Cretaceous paleomagnetic results from Cedros Island support 20 ± 10° of northward displacement and 14 ± 7° of clockwise rotation with respect to cratonic North America. Positive field stability tests from the Vizcaino terrane substantiate a mid-Cretaceous age for the high-temperature characteristic remanent magnetization in mid-Cretaceous strata. Therefore coincidence of characteristic magnetization directions and the expected Quaternary axial dipole direction is not due to post mid-Cretaceous remagnetization. A slump test performed on internally coherent, intrabasinal slump blocks within a paleontologically dated olistostrome demonstrates a mid-Cretaceous age of magnetization in the Valle Group. The in situ high-temperature natural remanent magnetization directions markedly diverge from the expected Quaternary axial dipole, indicating that the characteristic, high-temperature magnetization was acquired prior to intrabasinal slumping. Early acquisition of the characteristic magnetization is also supported by a regional attitude test involving three localities in coherent mid-Cretaceous Valle Group strata. Paleomagnetic inclinations in mudstone are not different from those in sandstone, indicating that burial compaction did not bias the results toward shallow inclinations in the Vizcaino terrane.

Fluvial geomorphology: where do we go from here?

Science.gov (United States)

Smith, Derald G.

1993-07-01

The evolution of geomorphology and in particular, fluvial geomorphology, is at a crossroads. Currently, the discipline is dismally organized, without focus or direction, and is practised by individualists who rarely collaborate in numbers significant enough to generate major research initiatives. If the discipline is to mature and to prosper, we must make some very difficult decisions that will require major changes in our ways of thinking and operating. Either the field stays in its current operational mode and becomes a backwater science, or it moves forward and adopts the ways of the more competitive sectors of the earth and biosciences. For the discipline to evolve, fluvial geomorphologists must first organize an association within North America or at the international level. The 3rd International Geomorphology Conference may be a start, but within that organization we must develop our own divisional and/or regional organizations. Within the Quaternary geology/geomorphology divisions of the Geological Socieity of America (GSA), Association of American Geographers (AAG), American Geophysical Union (AGU) and British Geomorphology Research Group (BGRG) the voice of fluvial geomorphology is lost in a sea of diverse and competitive interests, though there is reason for hope resulting from some recent initiatives. In Canada, we have no national geomorphology organization per se; our closest organization is Canqua (Canadian Quaternary Association). Next, fluvial researchers must collaborate, by whatever means, to develop "scientific critical mass" in order to generate ideas and long-range goals of modest and major scientific importance. These projects will help secure major research funding without which, research opportunities will diminish and initiating major new research will become nearly impossible. Currently, we are being surpassed by the glaciologists, remote sensors, ecologists, oceanographers, climatologists-atmospheric researchers and some Quaternary

Diverse dinosaur-dominated ichnofaunas from the Potomac Group (Lower Cretaceous) Maryland

Science.gov (United States)

Stanford, Ray; Lockley, Martin G.; Weems, Robert E.

2007-01-01

Until recently fossil footprints were virtually unknown from the Cretaceous of the eastern United States. The discovery of about 300 footprints in iron-rich siliciclastic facies of the Patuxent Formation (Potomac Group) of Aptian age is undoubtedly one of the most significant Early Cretaceous track discoveries since the Paluxy track discoveries in Texas in the 1930s. The Patuxent tracks include theropod, sauropod, ankylosaur and ornithopod dinosaur footprints, pterosaur tracks, and miscellaneous mammal and other vertebrate ichnites that collectively suggest a diversity of about 14 morphotypes. This is about twice the previous maximum estimate for any known Early Cretaceous vertebrate ichnofauna. Among the more distinctive forms are excellent examples of hypsilophodontid tracks and a surprisingly large mammal footprint. A remarkable feature of the Patuxent track assemblage is the high proportion of small tracks indicative of hatchlings, independently verified by the discovery of a hatchling-sized dinosaur. Such evidence suggests the proximity of nest sites. The preservation of such small tracks is very rare in the Cretaceous track record, and indeed throughout most of the Mesozoic.This unusual preservation not only provides us with a window into a diverse Early Cretaceous ecosystem, but it also suggests the potential of such facies to provide ichnological bonanzas. A remarkable feature of the assemblage is that it consists largely of reworked nodules and clasts that may have previously been reworked within the Patuxent Formation. Such unusual contexts of preservation should provide intriguing research opportunities for sedimentologists interested in the diagenesis and taphonomy of a unique track-bearing facies.

Explosive Radiation of Malpighiales Supports a Mid-Cretaceous Origin of Modern Tropical Rain Forests

OpenAIRE

Wurdack, Kenneth J.; Jaramillo, Carlos A.; Davis, Charles; Webb, Campbell O.; Donoghue, Michael J.

2005-01-01

Fossil data have been interpreted as indicating that Late Cretaceous tropical forests were open and dry adapted and that modern closed-canopy rain forest did not originate until after the Cretaceous-Tertiary (K/T) boundary. However, some mid-Cretaceous leaf floras have been interpreted as rain forest. Molecular divergence-time estimates within the clade Malpighiales, which constitute a large percentage of species in the shaded, shrub, and small tree layer in tropical rain forests worldwide, p...

Fluvial archives, a valuable record of vertical crustal deformation

Science.gov (United States)

Demoulin, A.; Mather, A.; Whittaker, A.

2017-06-01

The study of drainage network response to uplift is important not only for understanding river system dynamics and associated channel properties and fluvial landforms, but also for identifying the nature of crustal deformation and its history. In recent decades, geomorphic analysis of rivers has proved powerful in elucidating the tectonic evolution of actively uplifting and eroding orogens. Here, we review the main recent developments that have improved and expanded qualitative and quantitative information about vertical tectonic motions (the effects of horizontal deformation are not addressed). Channel long profiles have received considerable attention in the literature, and we briefly introduce basic aspects of the behaviour of bedrock rivers from field and numerical modelling perspectives, before describing the various metrics that have been proposed to identify the information on crustal deformation contained within their steady-state characteristics. Then, we review the literature dealing with the transient response of rivers to tectonic perturbation, through the production of knickpoints propagating through the drainage network. Inverse modelling of river profiles for uplift in time and space is also shown to be very effective in reconstructing regional tectonic histories. Finally, we present a synthetic morphometric approach for deducing the tectonic record of fluvial landscapes. As well as the erosional imprint of tectonic forcing, sedimentary deposits, such as fluvial terrace staircases, are also considered as a classical component of tectonic geomorphology. We show that these studies have recently benefited from rapid advances in dating techniques, allowing more reliable reconstruction of incision histories and estimation of incision rates. The combination of progress in the understanding of transient river profiles and larger, more rigorous data sets of terrace ages has led to improved understanding of river erosion and the implications for terrace

Model Projections of Future Fluvial Sediment Delivery to Major Deltas Under Environmental Change

Science.gov (United States)

Darby, S. E.; Dunn, F.; Nicholls, R. J.; Cohen, S.; Zarfl, C.

2017-12-01

Deltas are important hot spots for climate change impacts on which over half a billion people live worldwide. Most of the world's deltas are sinking as a result of natural and anthropogenic subsidence and due to eustatic sea level rise. The ability to predict rates of delta aggradation is therefore critical to assessments of the extent to which sedimentation can potentially offset sea level rise, but our ability to make such predictions is severely hindered by a lack of insight into future trends of the fluvial sediment load supplied to their deltas by feeder watersheds. To address this gap we investigate fluvial sediment fluxes under future environmental change for a selection (47) of the world's major river deltas. Specifically, we employed the numerical model WBMsed to project future variations in mean annual fluvial sediment loads under a range of environmental change scenarios that account for changes in climate, socio-economics and dam construction. Our projections indicate a clear decrease (by 34 to 41% on average, depending on the specific scenario) in future fluvial sediment supply to most of the 47 deltas. These reductions in sediment delivery are driven primarily by anthropogenic disturbances, with reservoir construction being the most influential factor globally. Our results indicate the importance of developing new management strategies for reservoir construction and operation.

Paleomagnetism of the Cretaceous Galula Formation and implications for vertebrate evolution

Science.gov (United States)

Widlansky, Sarah J.; Clyde, William C.; O'Connor, Patrick M.; Roberts, Eric M.; Stevens, Nancy J.

2018-03-01

This study uses magnetostratigraphy to help constrain the age of the paleontologically important Galula Formation (Rukwa Rift Basin, southwestern Tanzania). The formation preserves a Cretaceous vertebrate fauna, including saurischian dinosaurs, a putative gondwanatherian mammal, and notosuchian crocodyliforms. With better dating, the Galula Formation and its fossils help fill a temporal gap in our understanding of vertebrate evolution in continental Africa, enabling better evaluation of competing paleobiogeographic hypotheses concerning faunal exchange throughout Gondwana during the Cretaceous. Paleomagnetic samples for this study were collected from the Namba (higher in section) and Mtuka (lower in section) members of the Galula Formation and underwent stepwise thermal demagnetization. All samples displayed a strong normal magnetic polarity overprint, and maximum unblocking temperatures at approximately 690 °C. Three short reversed intervals were identified in the Namba Member, whereas the Mtuka Member lacked any clear reversals. Given the relatively limited existing age constraints, one interpretation correlates the Namba Member to Chron C32. An alternative correlation assigns reversals in the Namba Member to recently proposed short reversals near the end of the Cretaceous Normal Superchron (Chron C34), a time that is traditionally interpreted as having stable normal polarity. The lack of reversals in the Mtuka Member supports deposition within Chron C34. These data suggest that the Namba Member is no older than Late Cretaceous (Cenomanian-Campanian), with the Mtuka Member less well constrained to the middle Cretaceous (Aptian-Cenomanian). The paleomagnetic results are supported by the application of fold and reversal tests for paleomagnetic stability, and paleomagnetic poles for the Namba (246.4°/77.9°, α95 5.9°) and Mtuka (217.1°/72.2°, α95 11.1°) members closely matching the apparent polar wander path for Africa during the Late Cretaceous. These

Influence of fluvial sandstone architecture on geothermal energy production

NARCIS (Netherlands)

Willems, C.J.L.; Maghami Nick, Hamidreza M.; Weltje, G.J.; Donselaar, M.E.; Bruhn, D.F.

2015-01-01

Fluvial sandstone reservoirs composed of stacked meander belts are considered as potential geothermal resources in the Netherlands. Net-to-gross, orientation and stacking pattern of the channel belts is of major importance for the connectivity between the injection and production well in such

Reservoirs as hotspots of fluvial carbon cycling in peatland catchments.

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Stimson, A G; Allott, T E H; Boult, S; Evans, M G

2017-02-15

Inland water bodies are recognised as dynamic sites of carbon processing, and lakes and reservoirs draining peatland soils are particularly important, due to the potential for high carbon inputs combined with long water residence times. A carbon budget is presented here for a water supply reservoir (catchment area~9km 2 ) draining an area of heavily eroded upland peat in the South Pennines, UK. It encompasses a two year dataset and quantifies reservoir dissolved organic carbon (DOC), particulate organic carbon (POC) and aqueous carbon dioxide (CO 2 (aq)) inputs and outputs. The budget shows the reservoir to be a hotspot of fluvial carbon cycling, as with high levels of POC influx it acts as a net sink of fluvial carbon and has the potential for significant gaseous carbon export. The reservoir alternates between acting as a producer and consumer of DOC (a pattern linked to rainfall and temperature) which provides evidence for transformations between different carbon species. In particular, the budget data accompanied by 14 C (radiocarbon) analyses provide evidence that POC-DOC transformations are a key process, occurring at rates which could represent at least ~10% of the fluvial carbon sink. To enable informed catchment management further research is needed to produce carbon cycle models more applicable to these environments, and on the implications of high POC levels for DOC composition. Copyright © 2016 Elsevier B.V. All rights reserved.

Variability in fluvial geomorphic response to anthropogenic disturbance

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Verstraeten, Gert; Broothaerts, Nils; Van Loo, Maarten; Notebaert, Bastiaan; D'Haen, Koen; Dusar, Bert; De Brue, Hanne

2017-10-01

Humans have greatly impacted the processes and intensities of erosion, sediment transport and storage since the introduction of agriculture. In many regions around the world, accelerated floodplain sedimentation can be related to increases in human pressure on the environment. However, the relation between the intensity of anthropogenic disturbance and the magnitude of change in fluvial sediment dynamics is not straightforward and often non-linear. Here, we review a number of case studies from contrasting environmental settings in the European loess belt, the Eastern Mediterranean mountain ranges and the eastern USA. Detailed field-based sediment archive studies and sediment budgets covering time periods ranging from 200 to over 5000 year, as well as the use of pollen and sediment provenance techniques, show that no overarching concept of changes in floodplain sedimentation following anthropogenic disturbance can be established. Slope-channel (dis)connectivity controls the existence of thresholds or tipping points that need to be crossed before significant changes in downstream sediment dynamics are recorded following human impact. This coupling can be related to characteristics of human pressure such as its duration, intensity and spatial patterns, but also to the geomorphic and tectonic setting. Furthermore, internal feedback mechanisms, such as those between erosion and soil thickness, further complicate the story. All these factors controlling the propagation of sediment from eroding hillslopes to river channels vary between regions. Hence, only unique patterns of fluvial geomorphic response can be identified. As a result, unravelling the human impact from current-day sediment archives and predicting the impact of future human disturbances on fluvial sediment dynamics remain a major challenge. This has important implications for interpreting contemporary sediment yields as well as downstream sediment records in large floodplains, deltas and the marine

SISTEMA FLUVIAL E PLANEJAMENTO LOCAL NO SEMIÁRIDO

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Jonas Otaviano Praça de Souza

2012-01-01

Full Text Available El presente estudio analiza un sistema fluvial semiárido y sus características físicas, centrándose en los procesos geomorfológicos y las formas resultantes, sino también en las relaciones con las actividades humanas, con el fin de utilizar dichos datos en la planificación local. La encuesta se llevó a cabo en el municipio de Belém do São Francisco, en Pernambuco, mesorregión del São Francisco en la cuenca del arroyo Mulungu, lugar expuesto a un clima semi-árido con lluvias de verano, y la cobertura del suelo con un predominio de la caatinga arbustiva abierta. Se tomó como procedimiento metodológico la cartografía geomorfológica a diferentes escalas y con diferentes énfasis, para evaluar la relación jerárquica entre los distintos compartimentos, sustratos geológicos y formas de uso de la tierra. De la información espacial obtenida en los distintos niveles de la cartografía detallada del sistema fluvial, se realizó una evaluación ambiental de la zona, teniendo como base la dinámica erosiva/deposicional a lo largo del canal y su relación con sus bancos. Se concluyó que las formas de acumulación en la llanura aluvial exhiben controles de origen antropogénico, vinculados a los tipos tradicionales de uso del suelo en la cuenca. Estos controles, como la construcción de represas a lo largo del canal, actúan cambiando a los procesos de creación de nuevas morfologías de depósito en el sistema fluvial, que a su vez comienzan a redefinir los tipos usos de la zona.

Combined fluvial and pluvial urban flood hazard analysis: method development and application to Can Tho City, Mekong Delta, Vietnam

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Apel, H.; Trepat, O. M.; Hung, N. N.; Chinh, D. T.; Merz, B.; Dung, N. V.

2015-08-01

Many urban areas experience both fluvial and pluvial floods, because locations next to rivers are preferred settlement areas, and the predominantly sealed urban surface prevents infiltration and facilitates surface inundation. The latter problem is enhanced in cities with insufficient or non-existent sewer systems. While there are a number of approaches to analyse either fluvial or pluvial flood hazard, studies of combined fluvial and pluvial flood hazard are hardly available. Thus this study aims at the analysis of fluvial and pluvial flood hazard individually, but also at developing a method for the analysis of combined pluvial and fluvial flood hazard. This combined fluvial-pluvial flood hazard analysis is performed taking Can Tho city, the largest city in the Vietnamese part of the Mekong Delta, as example. In this tropical environment the annual monsoon triggered floods of the Mekong River can coincide with heavy local convective precipitation events causing both fluvial and pluvial flooding at the same time. Fluvial flood hazard was estimated with a copula based bivariate extreme value statistic for the gauge Kratie at the upper boundary of the Mekong Delta and a large-scale hydrodynamic model of the Mekong Delta. This provided the boundaries for 2-dimensional hydrodynamic inundation simulation for Can Tho city. Pluvial hazard was estimated by a peak-over-threshold frequency estimation based on local rain gauge data, and a stochastic rain storm generator. Inundation was simulated by a 2-dimensional hydrodynamic model implemented on a Graphical Processor Unit (GPU) for time-efficient flood propagation modelling. All hazards - fluvial, pluvial and combined - were accompanied by an uncertainty estimation considering the natural variability of the flood events. This resulted in probabilistic flood hazard maps showing the maximum inundation depths for a selected set of probabilities of occurrence, with maps showing the expectation (median) and the uncertainty by

Marine reptiles from the Late Cretaceous of northern Patagonia

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Gasparini, Z.; Casadio, S.; Fernández, M.; Salgado, L.

2001-04-01

During the Campanian-Maastrichtian, Patagonia was flooded by the Atlantic and reduced to an archipelago. Several localities of northern Patagonia have yielded marine reptiles. Analysis of several assemblages suggests that the diversity and abundance of pelagic marine reptiles in northern Patagonia was higher by the end of the Cretaceous than previously thought. Several plesiosaurids, including Aristonectes parvidens and the polycotylid Sulcusuchus, and the first remains of mosasaurinae have been found. The Cretaceous marine reptile record from South America is scanty. Nevertheless, materials described here suggest that Tethyan and Weddelian forms converged in northern Patagonia, as seen with invertebrates.

Suspended sediment transport trough a large fluvial-tidal channel network

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Wright, Scott A.; Morgan-King, Tara L.

2015-01-01

The confluence of the Sacramento and San Joaquin Rivers, CA, forms a large network of interconnected channels, referred to as the Sacramento-San Joaquin Delta (the Delta). The Delta comprises the transition zone from the fluvial influences of the upstream rivers and tidal influences of San Francisco Bay downstream. Formerly an extensive tidal marsh, the hydrodynamics and geomorphology of Delta have been substantially modified by humans to support agriculture, navigation, and water supply. These modifications, including construction of new channels, diking and draining of tidal wetlands, dredging of navigation channels, and the operation of large pumping facilities for distribution of freshwater from the Delta to other parts of the state, have had a dramatic impact on the physical and ecological processes within the Delta. To better understand the current physical processes, and their linkages to ecological processes, the USGS maintains an extensive network of flow, sediment, and water quality gages in the Delta. Flow gaging is accomplished through use of the index-velocity method, and sediment monitoring uses turbidity as a surrogate for suspended-sediment concentration. Herein, we present analyses of the transport and dispersal of suspended sediment through the complex network of channels in the Delta. The primary source of sediment to the Delta is the Sacramento River, which delivers pulses of sediment primarily during winter and spring runoff events. Upon reaching the Delta, the sediment pulses move through the fluvial-tidal transition while also encountering numerous channel junctions as the Sacramento River branches into several distributary channels. The monitoring network allows us to track these pulses through the network and document the dominant transport pathways for suspended sediment. Further, the flow gaging allows for an assessment of the relative effects of advection (the fluvial signal) and dispersion (from the tides) on the sediment pulses as they

Sedimentary Record of the Back-Arc Basins of South-Central Mexico: an Evolution from Extensional Basin to Carbonate Platform.

Science.gov (United States)

Sierra-Rojas, M. I.; Molina-Garza, R. S.; Lawton, T. F.

2015-12-01

The Lower Cretaceous depositional systems of southwestern Oaxaquia, in south-central Mexico, were controlled by tectonic processes related to the instauration of a continental arc and the accretion of the Guerrero arc to mainland Mexico. The Atzompa Formation refers to a succession of conglomerate, sandstone, siltstone, and limestone that crop out in southwestern Mexico with Early Cretaceous fauna and detrital zircon maximum depositional ages. The sedimentary record shows a transition from early fluvial/alluvial to shallow marine depositional environments. The first stage corresponds to juvenile fluvial/alluvial setting followed by a deep lacustrine depositional environment, suggesting the early stages of an extensional basin. The second stage is characterized by anabranched deposits of axial fluvial systems flowing to the NE-SE, showing deposition during a period of rapid subsidence. The third and final stage is made of tidal deposits followed, in turn, by abrupt marine flooding of the basin and development of a Barremian-Aptian carbonate ramp. We interpret the Tentzo basin as a response to crustal extension in a back-arc setting, with high rates of sedimentation in the early stages of the basin (3-4 mm/m.y), slower rates during the development of starved fluvial to tidal systems and carbonate ramps, and at the top of the Atzompa Formation an abrupt deepening of the basin due to flexural subsidence related to terrane docking and attendant thrusting to the west. These events were recorded in the back-arc region of a continental convergent margin (Zicapa arc) where syn-sedimentary magmatism is indicated by Early Cretaceous detrital and volcanic clasts from alluvial fan facies west of the basin. Finally, and as a response to the accretion of the Guerrero superterrane to Oaxaquia during the Aptian, a carbonate platform facing toward the Gulf of Mexico was established in central to eastern Oaxaquia.

Mapping Variability in the Medusae Fossae Formation: Yardang Morphologies, Fluvial Reworking, and Crater Depth to Diameter Ratios

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Khuller, A. R.; Kerber, L.

2017-12-01

The Medusae Fossae Formation (MFF) is a voluminous, fine-grained deposit thought to be of pyroclastic origin. While it contains widespread, well-preserved inverted fluvial features, its pervasive cover of dust means that little is known about its composition, and indirect means must be used to characterize its material properties. This project aims to correlate fluvial features in the Western MFF with other indicators of material strength: yardang morphology and crater depth-to-diameter ratios. For this work, Context Camera (CTX) images were used to map features of fluvial origin (inverted channels, sinuous ridges, alluvial fans). The presence of rounded, meso-yardangs in close proximity to fluvial features was also mapped. Crater depth-diameter (d/D) ratios (for craters 1-512km) were analyzed using a global Mars crater database (Robbins and Hynek, 2012) as a proxy for material strength. Approximately 1400 fluvial segments were mapped, with the most populous cluster located in Aeolis and Zephyria Plana. Rounded meso-yardangs were found to be common in areas that also have fluvial features. In agreement with previous work (Barlow, 1993), MFF craters were found to have a greater d/D ratio (0.0523) than the global mean (0.0511). Ratios between MFF lobes differ significantly, providing insight into the heterogeneity of induration within the formation. The deepest craters are found in Eumenides Dorsum and the shallowest in Aeolis Planum, consistent with a greater degree of induration and reworking in the western part of the formation where the fluvial features and "salt-playa" meso-yardangs are found. It also suggests that Eumenides, which is the tallest MFF outcrop, could also be the least compacted. The presence of long, complex, and sometimes overlapping branching networks imply multiple relative episodes of channel formation. Rounded meso-yardangs, which are associated with salt playa surfaces on Earth, provide additional evidence for the presence of liquid water

A new genus and species of enantiornithine bird from the Early Cretaceous of Brazil

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Ismar de Souza Carvalho

Full Text Available The fossil record of birds in Gondwana is almost restricted to the Late Cretaceous. Herein we describe a new fossil from the Araripe Basin, Cratoavis cearensis nov. gen et sp., composed of an articulated skeleton with feathers attached to the wings and surrounding the body. The present discovery considerably extends the temporal record of the Enantiornithes birds at South America to the Early Cretaceous. For the first time, an almost complete and articulated skeleton of an Early Cretaceous bird from South America is documented.

Larger miliolids of the Late Cretaceous and Paleogene seen through space and time

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Vlasta Ćosović

2002-12-01

Full Text Available Spatial and temporal occurrences of the larger (complex miliolids are discussed to give more light on biostratigraphy and paleobiogeographic provinces distribution. Seven generaand 47 species from the Late Cretaceous to Oligocene inhabited shallow marine settings in the Indo-Pacific, Tethyan and Caribbean regions. Of all genera only four (Idalina, Periloculina, Pseudolacazina, Lacazina widespread throughout Tethys in theLate Cretaceous and Paleogene. Single occurrence of Lacazina was recorded further to east (Moluccas. By now the Late Cretaceous genus Adrahentina is known only from the Spain. The newcomer’s Eocene genera were Fabularia and Lacazinella. Fabularia reachedhigh diversity in species term in the Central and Western Tethys and occured as unique genus in Caribbean realm, too. Conversely, during the same period, Lacazinella spread over the southern border of Neo-Tethys reaching New Guinea.On the Adriatic – Dinaric Carbonate Platform, larger miliolids occurred from the Late Cretaceous to Cuisian, having the same biostratigraphically trends and distribution as contemporaneous larger miliolids from the Tethys.

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

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

1997-01-01

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

Volcanogenic Fluvial-Lacustrine Environments in Iceland and Their Utility for Identifying Past Habitability on Mars

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Claire Cousins

2015-02-01

Full Text Available The search for once-habitable locations on Mars is increasingly focused on environments dominated by fluvial and lacustrine processes, such as those investigated by the Mars Science Laboratory Curiosity rover. The availability of liquid water coupled with the potential longevity of such systems renders these localities prime targets for the future exploration of Martian biosignatures. Fluvial-lacustrine environments associated with basaltic volcanism are highly relevant to Mars, but their terrestrial counterparts have been largely overlooked as a field analogue. Such environments are common in Iceland, where basaltic volcanism interacts with glacial ice and surface snow to produce large volumes of meltwater within an otherwise cold and dry environment. This meltwater can be stored to create subglacial, englacial, and proglacial lakes, or be released as catastrophic floods and proglacial fluvial systems. Sedimentary deposits produced by the resulting fluvial-lacustrine activity are extensive, with lithologies dominated by basaltic minerals, low-temperature alteration assemblages (e.g., smectite clays, calcite, and amorphous, poorly crystalline phases (basaltic glass, palagonite, nanophase iron oxides. This paper reviews examples of these environments, including their sedimentary deposits and microbiology, within the context of utilising these localities for future Mars analogue studies and instrument testing.

Volcanogenic fluvial-lacustrine environments in iceland and their utility for identifying past habitability on Mars.

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Cousins, Claire

2015-02-16

The search for once-habitable locations on Mars is increasingly focused on environments dominated by fluvial and lacustrine processes, such as those investigated by the Mars Science Laboratory Curiosity rover. The availability of liquid water coupled with the potential longevity of such systems renders these localities prime targets for the future exploration of Martian biosignatures. Fluvial-lacustrine environments associated with basaltic volcanism are highly relevant to Mars, but their terrestrial counterparts have been largely overlooked as a field analogue. Such environments are common in Iceland, where basaltic volcanism interacts with glacial ice and surface snow to produce large volumes of meltwater within an otherwise cold and dry environment. This meltwater can be stored to create subglacial, englacial, and proglacial lakes, or be released as catastrophic floods and proglacial fluvial systems. Sedimentary deposits produced by the resulting fluvial-lacustrine activity are extensive, with lithologies dominated by basaltic minerals, low-temperature alteration assemblages (e.g., smectite clays, calcite), and amorphous, poorly crystalline phases (basaltic glass, palagonite, nanophase iron oxides). This paper reviews examples of these environments, including their sedimentary deposits and microbiology, within the context of utilising these localities for future Mars analogue studies and instrument testing.

Lamellaptychi from the Lower Cretaceous of south-east Spain (Murcia and Jaen provinces)

Czech Academy of Sciences Publication Activity Database

Vašíček, Zdeněk; Company, M.; Měchová, L.

2015-01-01

Roč. 276, č. 3 (2015), s. 335-351 ISSN 0077-7749 Institutional support: RVO:68145535 Keywords : Lower Cretaceous * aptychi * ammonite zonation * Betic Cordillera Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.719, year: 2015 http://cretaceous.ru/files/pub/temp3/vasicek_et_al_2015_lamellaptychi.pdf

Evidence of reworked Cretaceous fossils and their bearing on the existence of Tertiary dinosaurs

Energy Technology Data Exchange (ETDEWEB)

Eaton, J.G. (Museum of Northern Arizona, Flagstaff (USA)); Kirkland, J.I. (Univ. of Nebraska, Lincoln (USA)); Doi, K. (Univ. of Colorado, Boulder (USA))

1989-06-01

The Paleocene Shotgun fauna of Wyoming includes marine sharks as well as mammals. It has been suggested that the sharks were introduced from the Cannonball Sea. It is more likely that these sharks were reworked from a Cretaceous rock sequence that included both marine and terrestrial deposits as there is a mixture of marine and freshwater taxa. These taxa have not been recorded elsewhere after the Cretaceous and are not known from the Cannonball Formation. Early Eocene localities at Raven Ridge, Utah, similarly contain teeth of Cretaceous marine and freshwater fish, dinosaurs, and Eocene mammals. The Cretaceous teeth are well preserved, variably abraded, and serve to cast doubts on criteria recently used to claim that dinosaur teeth recovered from the Paleocene of Montana are not reworked. Another Eocene locality in the San Juan Basin has produced an Eocene mammalian fauna with diverse Cretaceous marine sharks. Neither the nature of preservation nor the degree of abrasion could be used to distinguish reworked from contemporaneous material. The mixed environments represented by the fish taxa and recognition of the extensive pre-Tertiary extinction of both marine and freshwater fish were employed to recognize reworked specimens.

Study on detailed geological modelling for fluvial sandstone reservoir in Daqing oil field

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Zhao Hanqing; Fu Zhiguo; Lu Xiaoguang [Institute of Petroleum Exploration and Development, Daqing (China)

1997-08-01

Guided by the sedimentation theory and knowledge of modern and ancient fluvial deposition and utilizing the abundant information of sedimentary series, microfacies type and petrophysical parameters from well logging curves of close spaced thousands of wells located in a large area. A new method for establishing detailed sedimentation and permeability distribution models for fluvial reservoirs have been developed successfully. This study aimed at the geometry and internal architecture of sandbodies, in accordance to their hierarchical levels of heterogeneity and building up sedimentation and permeability distribution models of fluvial reservoirs, describing the reservoir heterogeneity on the light of the river sedimentary rules. The results and methods obtained in outcrop and modem sedimentation studies have successfully supported the study. Taking advantage of this method, the major producing layers (PI{sub 1-2}), which have been considered as heterogeneous and thick fluvial reservoirs extending widely in lateral are researched in detail. These layers are subdivided into single sedimentary units vertically and the microfacies are identified horizontally. Furthermore, a complex system is recognized according to their hierarchical levels from large to small, meander belt, single channel sandbody, meander scroll, point bar, and lateral accretion bodies of point bar. The achieved results improved the description of areal distribution of point bar sandbodies, provide an accurate and detailed framework model for establishing high resolution predicting model. By using geostatistic technique, it also plays an important role in searching for enriched zone of residual oil distribution.

Variables and potential models for the bleaching of luminescence signals in fluvial environments

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Gray, Harrison J.; Mahan, Shannon

2015-01-01

Luminescence dating of fluvial sediments rests on the assumption that sufficient sunlight is available to remove a previously obtained signal in a process deemed bleaching. However, luminescence signals obtained from sediment in the active channels of rivers often contain residual signals. This paper explores and attempts to build theoretical models for the bleaching of luminescence signals in fluvial settings. We present two models, one for sediment transported in an episodic manner, such as flood-driven washes in arid environments, and one for sediment transported in a continuous manner, such as in large continental scale rivers. The episodic flow model assumes that the majority of sediment is bleached while exposed to sunlight at the near surface between flood events and predicts a power-law decay in luminescence signal with downstream transport distance. The continuous flow model is developed by combining the Beer–Lambert law for the attenuation of light through a water column with a general-order kinetics equation to produce an equation with the form of a double negative exponential. The inflection point of this equation is compared with the sediment concentration from a Rouse profile to derive a non-dimensional number capable of assessing the likely extent of bleaching for a given set of luminescence and fluvial parameters. Although these models are theoretically based and not yet necessarily applicable to real-world fluvial systems, we introduce these ideas to stimulate discussion and encourage the development of comprehensive bleaching models with predictive power.

A complete skull of an early cretaceous sauropod and the evolution of advanced titanosaurians.

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Hussam Zaher

Full Text Available Advanced titanosaurian sauropods, such as nemegtosaurids and saltasaurids, were diverse and one of the most important groups of herbivores in the terrestrial biotas of the Late Cretaceous. However, little is known about their rise and diversification prior to the Late Cretaceous. Furthermore, the evolution of their highly-modified skull anatomy has been largely hindered by the scarcity of well-preserved cranial remains. A new sauropod dinosaur from the Early Cretaceous of Brazil represents the earliest advanced titanosaurian known to date, demonstrating that the initial diversification of advanced titanosaurians was well under way at least 30 million years before their known radiation in the latest Cretaceous. The new taxon also preserves the most complete skull among titanosaurians, further revealing that their low and elongated diplodocid-like skull morphology appeared much earlier than previously thought.

A multi-scale approach of fluvial biogeomorphic dynamics using photogrammetry.

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Hortobágyi, Borbála; Corenblit, Dov; Vautier, Franck; Steiger, Johannes; Roussel, Erwan; Burkart, Andreas; Peiry, Jean-Luc

2017-11-01

Over the last twenty years, significant technical advances turned photogrammetry into a relevant tool for the integrated analysis of biogeomorphic cross-scale interactions within vegetated fluvial corridors, which will largely contribute to the development and improvement of self-sustainable river restoration efforts. Here, we propose a cost-effective, easily reproducible approach based on stereophotogrammetry and Structure from Motion (SfM) technique to study feedbacks between fluvial geomorphology and riparian vegetation at different nested spatiotemporal scales. We combined different photogrammetric methods and thus were able to investigate biogeomorphic feedbacks at all three spatial scales (i.e., corridor, alluvial bar and micro-site) and at three different temporal scales, i.e., present, recent past and long term evolution on a diversified riparian landscape mosaic. We evaluate the performance and the limits of photogrammetric methods by targeting a set of fundamental parameters necessary to study biogeomorphic feedbacks at each of the three nested spatial scales and, when possible, propose appropriate solutions. The RMSE varies between 0.01 and 2 m depending on spatial scale and photogrammetric methods. Despite some remaining difficulties to properly apply them with current technologies under all circumstances in fluvial biogeomorphic studies, e.g. the detection of vegetation density or landform topography under a dense vegetation canopy, we suggest that photogrammetry is a promising instrument for the quantification of biogeomorphic feedbacks at nested spatial scales within river systems and for developing appropriate river management tools and strategies. Copyright © 2016 Elsevier Ltd. All rights reserved.

Environmental changes in the central Po Plain (northern Italy) due to fluvial modifications and anthropogenic activities

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Marchetti, Mauro

2002-05-01

The fluvial environment of the central Po Plain, the largest plain in Italy, is discussed in this paper. Bounded by the mountain chains of the Alps and the Apennines, this plain is a link between the Mediterranean environment and the cultural and continental influences of both western and eastern Europe. In the past decades, economic development has been responsible for many changes in the fluvial environment of the area. This paper discusses the changes in fluvial dynamics that started from Late Pleistocene and Early Holocene due to distinct climatic changes. The discussion is based on geomorphological, pedological, and archaeological evidences and radiocarbon dating. In the northern foothills, Late Pleistocene palaeochannels indicate several cases of underfit streams among the northern tributaries of the River Po. On the other hand, on the southern side of the Po Plain, no geomorphological evidence of similar discharge reduction has been found. Here, stratigraphic sections, together with archaeological remains buried under the fluvial deposits, show a reduction in the size of fluvial sediments after the 10th millennium BC. During the Holocene, fluvial sedimentation became finer, and was characterised by minor fluctuations in the rate of deposition, probably related to short and less intense climatic fluctuations. Given the high rate of population growth and the development of human activities since the Neolithic Age, human influence on fluvial dynamics, especially since the Roman Age, prevailed over other factors (i.e., climate, tectonics, vegetation, etc.). During the Holocene, the most important changes in the Po Plain were not modifications in water discharge but in sediment. From the 1st to 3rd Century AD, land grants to war veterans caused almost complete deforestation, generalised soil erosion, and maximum progradation of the River Po delta. At present, land abandonment in the mountainous region has led to reafforestation. Artificial channel control in the

Analytically based forward and inverse models of fluvial landscape evolution during temporally continuous climatic and tectonic variations

Science.gov (United States)

Goren, Liran; Petit, Carole

2017-04-01

Fluvial channels respond to changing tectonic and climatic conditions by adjusting their patterns of erosion and relief. It is therefore expected that by examining these patterns, we can infer the tectonic and climatic conditions that shaped the channels. However, the potential interference between climatic and tectonic signals complicates this inference. Within the framework of the stream power model that describes incision rate of mountainous bedrock rivers, climate variability has two effects: it influences the erosive power of the river, causing local slope change, and it changes the fluvial response time that controls the rate at which tectonically and climatically induced slope breaks are communicated upstream. Because of this dual role, the fluvial response time during continuous climate change has so far been elusive, which hinders our understanding of environmental signal propagation and preservation in the fluvial topography. An analytic solution of the stream power model during general tectonic and climatic histories gives rise to a new definition of the fluvial response time. The analytic solution offers accurate predictions for landscape evolution that are hard to achieve with classical numerical schemes and thus can be used to validate and evaluate the accuracy of numerical landscape evolution models. The analytic solution together with the new definition of the fluvial response time allow inferring either the tectonic history or the climatic history from river long profiles by using simple linear inversion schemes. Analytic study of landscape evolution during periodic climate change reveals that high frequency (10-100 kyr) climatic oscillations with respect to the response time, such as Milankovitch cycles, are not expected to leave significant fingerprints in the upstream reaches of fluvial channels. Linear inversion schemes are applied to the Tinee river tributaries in the southern French Alps, where tributary long profiles are used to recover the

New ophthalmosaurid ichthyosaurs from the European Lower Cretaceous demonstrate extensive ichthyosaur survival across the Jurassic-Cretaceous boundary.

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Valentin Fischer

Full Text Available BACKGROUND: Ichthyosauria is a diverse clade of marine amniotes that spanned most of the Mesozoic. Until recently, most authors interpreted the fossil record as showing that three major extinction events affected this group during its history: one during the latest Triassic, one at the Jurassic-Cretaceous boundary (JCB, and one (resulting in total extinction at the Cenomanian-Turonian boundary. The JCB was believed to eradicate most of the peculiar morphotypes found in the Late Jurassic, in favor of apparently less specialized forms in the Cretaceous. However, the record of ichthyosaurs from the Berriasian-Barremian interval is extremely limited, and the effects of the end-Jurassic extinction event on ichthyosaurs remains poorly understood. METHODOLOGY/PRINCIPAL FINDINGS: Based on new material from the Hauterivian of England and Germany and on abundant material from the Cambridge Greensand Formation, we name a new ophthalmosaurid, Acamptonectes densus gen. et sp. nov. This taxon shares numerous features with Ophthalmosaurus, a genus now restricted to the Callovian-Berriasian interval. Our phylogenetic analysis indicates that Ophthalmosauridae diverged early in its history into two markedly distinct clades, Ophthalmosaurinae and Platypterygiinae, both of which cross the JCB and persist to the late Albian at least. To evaluate the effect of the JCB extinction event on ichthyosaurs, we calculated cladogenesis, extinction, and survival rates for each stage of the Oxfordian-Barremian interval, under different scenarios. The extinction rate during the JCB never surpasses the background extinction rate for the Oxfordian-Barremian interval and the JCB records one of the highest survival rates of the interval. CONCLUSIONS/SIGNIFICANCE: There is currently no evidence that ichthyosaurs were affected by the JCB extinction event, in contrast to many other marine groups. Ophthalmosaurid ichthyosaurs remained diverse from their rapid radiation in the Middle

New Ophthalmosaurid Ichthyosaurs from the European Lower Cretaceous Demonstrate Extensive Ichthyosaur Survival across the Jurassic–Cretaceous Boundary

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Fischer, Valentin; Maisch, Michael W.; Naish, Darren; Kosma, Ralf; Liston, Jeff; Joger, Ulrich; Krüger, Fritz J.; Pérez, Judith Pardo; Tainsh, Jessica

2012-01-01

Background Ichthyosauria is a diverse clade of marine amniotes that spanned most of the Mesozoic. Until recently, most authors interpreted the fossil record as showing that three major extinction events affected this group during its history: one during the latest Triassic, one at the Jurassic–Cretaceous boundary (JCB), and one (resulting in total extinction) at the Cenomanian-Turonian boundary. The JCB was believed to eradicate most of the peculiar morphotypes found in the Late Jurassic, in favor of apparently less specialized forms in the Cretaceous. However, the record of ichthyosaurs from the Berriasian–Barremian interval is extremely limited, and the effects of the end-Jurassic extinction event on ichthyosaurs remains poorly understood. Methodology/Principal Findings Based on new material from the Hauterivian of England and Germany and on abundant material from the Cambridge Greensand Formation, we name a new ophthalmosaurid, Acamptonectes densus gen. et sp. nov. This taxon shares numerous features with Ophthalmosaurus, a genus now restricted to the Callovian–Berriasian interval. Our phylogenetic analysis indicates that Ophthalmosauridae diverged early in its history into two markedly distinct clades, Ophthalmosaurinae and Platypterygiinae, both of which cross the JCB and persist to the late Albian at least. To evaluate the effect of the JCB extinction event on ichthyosaurs, we calculated cladogenesis, extinction, and survival rates for each stage of the Oxfordian–Barremian interval, under different scenarios. The extinction rate during the JCB never surpasses the background extinction rate for the Oxfordian–Barremian interval and the JCB records one of the highest survival rates of the interval. Conclusions/Significance There is currently no evidence that ichthyosaurs were affected by the JCB extinction event, in contrast to many other marine groups. Ophthalmosaurid ichthyosaurs remained diverse from their rapid radiation in the Middle Jurassic to

Integrated geophysical and geological study and petroleum appraisal of Cretaceous plays in the Western Gulf of Gabes, Tunisia

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Dkhaili, Noomen; Bey, Saloua; El Abed, Mahmoud; Gasmi, Mohamed; Inoubli, Mohamed Hedi

2015-09-01

An integrated study of available seismic and calibrated wells has been conducted in order to ascertain the structural development and petroleum potential of the Cretaceous Formations of the Western Gulf of Gabes. This study has resulted in an understanding of the controls of deep seated Tethyan tectonic lineaments by analysis of the Cretaceous deposits distribution. Three main unconformities have been identified in this area, unconformity U1 between the Jurassic and Cretaceous series, unconformity U2 separating Early from Late Cretaceous and known as the Austrian unconformity and the major unconformity U3 separating Cretaceous from Tertiary series. The seismic analysis and interpretation have confirmed the existence of several features dominated by an NE-SW extensive tectonic regime evidenced by deep listric faults, asymmetric horst and graben and tilted blocks structures. Indeed, the structural mapping of these unconformities, displays the presence of dominant NW-SE fault system (N140 to N160) bounding a large number of moderate sized basins. A strong inversion event related to the unconformity U3 can be demonstrated by the mapping of the unconformities consequence of the succession of several tectonic manifestations during the Cretaceous and post-Cretaceous periods. These tectonic events have resulted in the development of structural and stratigraphic traps further to the porosity and permeability enhancement of Cretaceous reservoirs.

Does deposition depth control the OSL bleaching of fluvial sediment?

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Cunningham, A. C.; Wallinga, J.; Hobo, N.; Versendaal, A. J.; Makaske, B.; Middelkoop, H.

2014-01-01

The Optically Stimulated Luminescence (OSL) signal from fluvial sediment often contains a remnant from the previous deposition cycle, leading to a partially bleached equivalent-dose distribution. Although identification of the burial dose is of primary concern, the degree of bleaching could

Stability of Fluvial and Gravity-flow Antidunes

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Fedele, J. J.; Hoyal, D. C. J. D.; Demko, T. M.

2017-12-01

Antidunes develop as a consequence of interface (free surface) deformation and sediment transport feedback in supercritical flows. Fluvial (open-channel flow) antidunes have been studied extensively in the laboratory and the field, and recognized in ancient sedimentary deposits. Experiments on gravity flow (turbidity and density currents) antidunes indicate that they are more stable and long-lived than their fluvial counterpart but the mechanism controlling this stability is poorly understood. Sea floor bathymetric and subsurface data suggest that large-scale, antidune-like sediment waves are extremely common in deep-water, found in a wide range of settings and sediment characteristics. While most of these large features have been interpreted as cyclic steps, the term has been most likely overused due to the lack of recognition criteria and basic understanding on the differences between antidunes and cyclic steps formed under gravity flows. In principle, cyclic steps should be more common in confined or channel-lobe transition settings where flows tend to be more energetic or focused, while antidunes should prevail in regions of less confinement, under sheet-like or expanding flows. Using published, fluvial stable-antidune data, we show that the simplified 1D, mechanical-energy based analysis of flow over a localized fixed obstacle (Long, 1954; Baines, 1995; Kubo and Yokokawa, 2001) is inaccurate for representing flow over antidunes and their stability. Instead, a more detailed analysis of a flow along a long-wavelength (in relation to flow thickness) wavy bed that also considers the interactions between flow and sediment transport is used to infer conditions of antidune stability and the breaking of surface waves. In particular, the position of the surface wave crest in relation to the bedform crest, along with the role of average flow velocity, surface velocity, and surface wave celerity appear relevant in determining antidune instability. The analysis is

High-resolution leaf-fossil record spanning the Cretaceous/Tertiary boundary

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Johnson, K.R.; Nichols, D.J.; Attrep, M.; Orth, C.J.

1989-01-01

THEORIES that explain the extinctions characterizing the Cretaceous/Tertiary (K/T) boundary1-3 need to be tested by analyses of thoroughly sampled biotas. Palynological studies are the primary means for stratigraphic placement of the terrestrial boundary and for estimates of plant extinction4-12, but have not been combined with quantitative analyses of fossil leaves (megaflora). Megafloral studies complement palynology by representing local floras with assemblages capable of high taxonomic resolution13, but have previously lacked the sample size and stratigraphic spacing needed to resolve latest Cretaceous floral history5,14-18. We have now combined megafloral data from a 100-m-thick composite K/T boundary section in North Dakota with detailed palynological analysis. Here the boundary is marked by a 30% palynofloral extinction coincident with iridium and shocked-mineral anomalies and lies ???2 m above the highest dinosaur remains. The megaflora undergoes a 79% turnover across the boundary, and smaller changes 17- and 25-m below it. This pattern is consistent with latest Cretaceous climatic warming preceding a bolide impact. ?? 1989 Nature Publishing Group.

Nove interpretacije fluvialnih sedimentov na krasu = New interpretations of fluvial sediments from the Kras

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Andrej Mihevc

2007-01-01

Full Text Available Important unroofed caves with fluvial sediments from Divaški kras, Matarsko podoljePodgorski kras are presented. Extend of the phenomena and relation to the existingand karst surface and geomorphological meaning of them are described. Sedimentsthem were analysed and dated with different methods. The largest age of the sedimentfound in the unroofed cave excavated in Črnotiče quarry. In the cave wall fossil remainsstygobiont Marifugia cavatica were covered by 3.2-4.1 Ma old fluvial sediments.

Precambrian fluvial deposits: Enigmatic palaeohydrological data from the c. 2 1.9 Ga Waterberg Group, South Africa

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Eriksson, Patrick G.; Bumby, Adam J.; Brümer, Jacobus J.; van der Neut, Markus

2006-08-01

Precambrian fluvial systems, lacking the influence of rooted vegetation, probably were characterised by flashy surface runoff, low bank stability, broad channels with abundant bedload, and faster rates of channel migration; consequently, a braided fluvial style is generally accepted. Pre-vegetational braided river systems, active under highly variable palaeoclimatic conditions, may have been more widespread than are modern, ephemeral dry-land braided systems. Aeolian deflation of fine fluvial detritus does not appear to have been prevalent. With the onset of large cratons by the Neoarchaean-Palaeoproterozoic, very large, perennial braided river systems became typical. The c. 2.06-1.88 Ga Waterberg Group, preserved within a Main and a smaller Middelburg basin on the Kaapvaal craton, was deposited largely by alluvial/braided-fluvial and subordinate palaeo-desert environments, within fault-bounded, possibly pull-apart type depositories. Palaeohydrological data obtained from earlier work in the Middelburg basin (Wilgerivier Formation) are compared to such data derived from the correlated Blouberg Formation, situated along the NE margin of the Main basin. Within the preserved Blouberg depository, palaeohydrological parameters estimated from clast size and cross-bed set thickness data, exhibit rational changes in their values, either in a down-palaeocurrent direction, or from inferred basin margin to palaeo-basin centre. In both the Wilgerivier and Blouberg Formations, calculated palaeoslope values (derived from two separate formulae) plot within the gap separating typical alluvial fan gradients from those which characterise rivers (cf. [Blair, T.C., McPherson, J.G., 1994. Alluvial fans and their natural distinction from rivers based on morphology, hydraulic processes, sedimentary processes, and facies assemblages. J. Sediment. Res. A64, 450-489.]). Although it may be argued that such data support possibly unique fluvial styles within the Precambrian, perhaps related to

Fluvial landscape development in the southwestern Kalahari during the Holocene - Chronology and provenance of fluvial deposits in the Molopo Canyon

DEFF Research Database (Denmark)

Ramisch, Arne; Bens, Oliver; Buylaert, Jan-Pieter

2017-01-01

are sparse and often discontinuous. Hence, little is known about Holocene environmental change in this region. This study focuses on reconstructing paleoenvironmental change from the timing and provenance of fluvial deposits located within the Molopo Canyon, which connects the southern Kalahari drainage...... to the deposition of alluvial fills. These results suggest that the southern Kalahari Drainage remained endorheic and therefore disconnected from the Orange River throughout the Holocene....

Paleoenvironments of the Jurassic and Cretaceous Oceans: Selected Highlights

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Ogg, J. G.

2007-12-01

There are many themes contributing to the sedimentation history of the Mesozoic oceans. This overview briefly examines the roles of the carbonate compensation depth (CCD) and the associated levels of atmospheric carbon dioxide, of the evolution of marine calcareous microplankton, of major transgressive and regressive trends, and of super-plume eruptions. Initiation of Atlantic seafloor spreading in the Middle Jurassic coincided with an elevated carbonate compensation depth (CCD) in the Pacific-Tethys mega-ocean. Organic-rich sediments that would become the oil wealth of regions from Saudi Arabia to the North Sea were deposited during a continued rise in CCD during the Oxfordian-early Kimmeridgian, which suggests a possible increase in carbon dioxide release by oceanic volcanic activity. Deep-sea deposits in near-equatorial settings are dominated by siliceous shales or cherts, which reflect the productivity of siliceous microfossils in the tropical surface waters. The end-Jurassic explosion in productivity by calcareous microplankton contributed to the lowering of the CCD and onset of the chalk ("creta") deposits that characterize the Tithonian and lower Cretaceous in all ocean basins. During the mid-Cretaceous, the eruption of enormous Pacific igneous provinces (Ontong Java Plateau and coeval edifices) increased carbon dioxide levels. The resulting rise in CCD terminated chalk deposition in the deep sea. The excess carbon was progressively removed in widespread black-shale deposits in the Atlantic basins and other regions - another major episode of oil source rock. A major long-term transgression during middle and late Cretaceous was accompanied by extensive chalk deposition on continental shelves and seaways while the oceanic CCD remained elevated. Pacific guyots document major oscillations (sequences) of global sea level superimposed on this broad highstand. The Cretaceous closed with a progressive sea-level regression and lowering of the CCD that again enabled

Late Cenozoic fluvial successions in northern and western India: an overview and synthesis

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Sinha, R.; Kumar, R.; Sinha, S.; Tandon, S. K.; Gibling, M. R.

2007-11-01

Late Cenozoic fluvial successions are widespread in India. They include the deposits of the Siwalik basin which represent the accumulations of the ancient river systems of the Himalayan foreland basin. Palaeomagnetic studies reveal that fluvial architecture and styles of deposition were controlled by Himalayan tectonics as well as by major climatic fluctuations during the long (∼13 Ma) span of formation. The Indo-Gangetic plains form the world's most extensive Quaternary alluvial plains, and display spatially variable controls on sedimentation: Himalayan tectonics in the frontal parts, climate in the middle reaches, and eustasy in the lower reaches close to the Ganga-Brahmaputra delta. Climatic effects were mediated by strong fluctuations in the SW Indian Monsoon, and Himalayan rivers occupy deep valleys in the western Ganga plains where stream power is high, cut in part during early Holocene monsoon intensification; the broad interfluves record the simultaneous aggradation of plains-fed rivers since ∼100 ka. The eastward increase in precipitation across the Ganga Plains results in rivers with low stream power and a very high sediment flux, resulting in an aggradational mode and little incision. The river deposits of semi-arid to arid western India form important archives of Quaternary climate change through their intercalation with the eolian deposits of the Thar Desert. Although the synthesis documents strong variability-both spatial and temporal-in fluvial stratigraphy, climatic events such as the decline in precipitation during the Last Glacial Maximum and monsoon intensification in the early Holocene have influenced fluvial dynamics throughout the region.

"The Waters of Meridiani" - Further Support for a Fluvial Interpretation of the Ridged, Layered Units

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Wilkinson, Justin; Kreslavsky, Misha

2009-01-01

A relatively unknown terrestrial fluvial environment, the mesoscale megafan, provides analogs for various Martian landscapes, including the etched unit (etched unit, Unite E of Arvidson et al., 2003; ridge-forming unit R of Edgett, 2005) of the Sinus Meridiani region on Mars. A global survey of Earth shows that megafans are very large partial cones of dominantly fluvial sediment with radii on the order of hundreds of km, and very low slopes. Responsible fluvial processes are sufficiently different from those of classical arid alluvial fans and deltas that it is useful to class megafans as separate features. The megafan model calls into question two commonly held ideas. 1. Earth examples prove that topographic basins per se are unnecessary for the accumulation of large sedimentary bodies. 2. River channels are by no means restricted to valleys (Meridiani sediments are termed a "valley-ed volume" of Edgett). These perspectives reveal unexpected parallels with features at Meridiani-several channel-like features that are widespread, mostly as ridges inverted by eolian erosion; channel networks covering thousands of sq km, especially on intercrater plains; and regional relationships of sediment bodies situated immediately downstream of highland masses. These all suggest that fluvial explanations are at least part of the Meridiani story.

Beaver ponds' impact on fluvial processes (Beskid Niski Mts., SE Poland).

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Giriat, Dorota; Gorczyca, Elżbieta; Sobucki, Mateusz

2016-02-15

Beaver (Castor sp.) can change the riverine environment through dam-building and other activities. The European beaver (Castor fiber) was extirpated in Poland by the nineteenth century, but populations are again present as a result of reintroductions that began in 1974. The goal of this paper is to assess the impact of beaver activity on montane fluvial system development by identifying and analysing changes in channel and valley morphology following expansion of beaver into a 7.5 km-long headwater reach of the upper Wisłoka River in southeast Poland. We document the distribution of beaver in the reach, the change in river profile, sedimentation type and storage in beaver ponds, and assess how beaver dams and ponds have altered channel and valley bottom morphology. The upper Wisłoka River fluvial system underwent a series of anthropogenic disturbances during the last few centuries. The rapid spread of C. fiber in the upper Wisłoka River valley was promoted by the valley's morphology, including a low-gradient channel and silty-sand deposits in the valley bottom. At the time of our survey (2011), beaver ponds occupied 17% of the length of the study reach channel. Two types of beaver dams were noted: in-channel dams and valley-wide dams. The primary effect of dams, investigated in an intensively studied 300-m long subreach (Radocyna Pond), was a change in the longitudinal profile from smooth to stepped, a local reduction of the water surface slope, and an increase in the variability of both the thalweg profile and surface water depths. We estimate the current rate of sedimentation in beaver ponds to be about 14 cm per year. A three-stage scheme of fluvial processes in the longitudinal and transverse profile of the river channel is proposed. C. fiber reintroduction may be considered as another important stage of the upper Wisłoka fluvial system development. Copyright © 2015 Elsevier B.V. All rights reserved.

Fluvial sediment inputs to upland gravel bed rivers draining forested catchments: potential ecological impacts

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S. D. Marks

1997-01-01

Full Text Available As identified by the detailed long-term monitoring networks at Plynlimon, increased sediment supply to upland fluvial systems is often associated with forestry land-use and practice. Literature is reviewed, in the light of recent results from Plynlimon sediment studies, to enable identification of the potential ecological impacts of fluvial particulate inputs to upland gravel bed rivers draining forested catchments similar to the headwaters of the River Severn. Both sediment transport and deposition can have significant impacts upon aquatic vertebrates, invertebrates and plants.

The Late Cretaceous frog Gobiates from Central Asia: its evolutionary status and possible phylogenetic relationships

Czech Academy of Sciences Publication Activity Database

Roček, Zbyněk

2008-01-01

Roč. 29, č. 4 (2008), s. 577-591 ISSN 0195-6671 Institutional research plan: CEZ:AV0Z30130516 Keywords : Amphibia * Anura * Gobiatidae * Cretaceous * Cretaceous (Mongolia) Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.938, year: 2008

Dose response of artificial irradiation of fluvial sediment sample for ESR dating

International Nuclear Information System (INIS)

Liu Chunru; Yin Gongming; Gao Lu; Li Jianping; Han Fei; Lin Min

2011-01-01

ESR dating samples need be irradiated to obtain dose response curve and the equivalent dose. The artificial dose rate is about 1 x 10 -1 -1 x 10 2 Gy/min, whereas the natural dose rate is about 3 Gy/ka. Therefore, one must be sure whether the much higher artificial dose rate is suitable for the ESR dating study. In this paper, we use different artificial dose rate to irradiate the same fluvial sample and measure the quartz Al centre ESR signal under the same conditions. The dose response curves are compared, in an attempt to gain a preliminary knowledge on that problem and build a good foundation for our ESR dating studies on fluvial samples. (authors)

Hydrodynamic and sedimentological controls governing formation of fluvial levees

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Johnston, G. H.; Edmonds, D. A.; David, S. R.; Czuba, J. A.

2017-12-01

Fluvial levees are familiar features found on the margins of river channels, yet we know little about what controls their presence, height, and shape. These attributes of levees are important because they control sediment transfer from channel to floodplain and flooding patterns along a river system. Despite the familiarity and importance of levees, there is a surprising lack of basic geomorphic data on fluvial levees. Because of this we seek to understand: 1) where along rivers do levees tend to occur?; 2) what geomorphic and hydrodynamic variables control cross-sectional shape of levees? We address these questions by extracting levee shape from LiDAR data and by collecting hydrodynamic and sedimentological data from reaches of the Tippecanoe River, the White River, and the Muscatatuck River, Indiana, USA. Fluvial levees are extracted from a 1.5-m resolution LiDAR bare surface model and compared to hydrological, sedimentological, and geomorphological data from USGS stream gages. We digitized banklines and extracted levee cross-sections to calculate levee slope, taper, height, e-folding length, and e-folding width. To answer the research questions, we performed a multivariable regression between the independent variables—channel geometry, sediment grain size and concentration, flooding conditions, and slope—and the dependent levee variables. We find considerable variation in levee presence and shape in our field data. On the Muscatatuck River levees occur on 30% of the banks compared to 10% on the White River. Moreover, levees on the Muscatatuck are on average 3 times wider than the White River. This is consistent with the observation that the Muscatatuck is finer-grained compared to the White River and points to sedimentology being an important control on levee geomorphology. Future work includes building a morphodynamic model to understand how different hydrodynamic and geomorphic conditions control levee geometry.

Two depositional models for Pliocene coastal plain fluvial systems, Goliad Formation, south Texas Gulf Coastal plain

International Nuclear Information System (INIS)

Hoel, H.D.; Galloway, W.E.

1983-01-01

The Goliad Formation consists of four depositional systems-the Realitos and Mathis bed-load fluvial systems in the southwest and the Cuero and Eagle Lake mixed-load fluvial systems in the northeast. Five facies are recognized in the Realitos and Mathis bed-load fluvial systems: (1) primary channel-fill facies, (2) chaotic flood channel-fill facies, (3) complex splay facies, (4) flood plain facies, and (5) playa facies. A model for Realitos-Mathis depositional environments shows arid-climate braided stream complexes with extremely coarse sediment load, highly variable discharge, and marked channel instability. Broad, shallow, straight to slightly sinuous primary channels were flanked by wide flood channels. Flood channels passed laterally into broad, low-relief flood plains. Small playas occupied topographic lows near large channel axes. Three facies are recognized in the Cuero and Eagle Lake mixed-load fluvial systems: (1) channel-fill facies, (2) crevasse splay facies, and (3) flood plain facies. A model for Cuero-Eagle Lake depositional environments shows coarse-grained meander belts in a semi-arid climate. Slightly to moderately sinuous meandering streams were flanked by low, poorly developed natural levees. Crevasse splays were common, but tended to be broad and ill-defined. Extensive, low-relief flood plains occupied interaxial areas. The model proposed for the Realitos and Mathis fluvial systems may aid in recognition of analogous ancient depositional systems. In addition, since facies characteristics exercise broad controls on Goliad uranium mineralization, the proposed depositional models aid in defining target zones for Goliad uranium exploration

Salmon habitat use, tidal-fluvial estuary - Columbia River Estuary Tidal Habitats

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National Oceanic and Atmospheric Administration, Department of Commerce — The goal of the tidal-fluvial estuary study is to determine the estuary's contribution to the spatial structure and life history diversity of Columbia River salmon...

A new Early Cretaceous eutherian mammal from the Sasayama Group, Hyogo, Japan.

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Kusuhashi, Nao; Tsutsumi, Yukiyasu; Saegusa, Haruo; Horie, Kenji; Ikeda, Tadahiro; Yokoyama, Kazumi; Shiraishi, Kazuyuki

2013-05-22

We here describe a new Early Cretaceous (early Albian) eutherian mammal, Sasayamamylos kawaii gen. et sp. nov., from the 'Lower Formation' of the Sasayama Group, Hyogo Prefecture, Japan. Sasayamamylos kawaii is characterized by a robust dentary, a distinct angle on the ventral margin of the dentary at the posterior end of the mandibular symphysis, a lower dental formula of 3-4 : 1 : 4 : 3, a robust lower canine, a non-molariform lower ultimate premolar, and a secondarily reduced entoconid on the molars. To date, S. kawaii is the earliest known eutherian mammal possessing only four premolars, which demonstrates that the reduction in the premolar count in eutherians started in the late Early Cretaceous. The occurrence of S. kawaii implies that the relatively rapid diversification of eutherians in the mid-Cretaceous had already started by the early Albian.

Rib fracture in Prognathodon saturator (Mosasauridae, Late Cretaceous)

NARCIS (Netherlands)

Schulp, Anne S.; Walenkamp, G. H I M; Hofman, P.A.M.; Rothschild, B. M.; Jagt, J. W M

2004-01-01

Two unusual bumps occur on the internal surface of a rib of the marine reptile Prognathodon saturator from the Upper Cretaceous (Maastrichtian) of Maastricht, The Netherlands. These bumps are interpreted as stress fractures, possibly related to agonistic behaviour.

Reconstructing paleo-discharge from geometries of fluvial sinuous ridges on Earth and Mars

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Hayden, A.; Lamb, M. P.; Mohrig, D. C.; Williams, R. M. E.; Myrow, P.; Ewing, R. C.; Cardenas, B. T.; Findlay, C. P., III

2017-12-01

Sinuous, branching networks of topographic ridges resembling river networks are common across Mars, and show promise for quantifying ancient martian surface hydrology. There are two leading formation mechanisms for ridges with a fluvial origin. Inverted channels are ridges that represent casts (e.g., due to lava fill) of relict river channel topography, whereas exhumed channel deposits are eroded remnants of a more extensive fluvial deposit, such as a channel belt. The inverted channel model is often assumed on Mars; however, we currently lack the ability to distinguish these ridge formation mechanisms, motivating the need for Earth-analog study. To address this issue, we studied the extensive networks of sinuous ridges in the Ebro basin of northeast Spain. The Ebro ridges stand 3-15 meters above the surrounding plains and are capped by a cliff-forming sandstone unit 3-10 meters thick and 20-50 meters in breadth. The caprock sandstone bodies contain bar-scale cross stratification, point-bar deposits, levee deposits, and lenses of mudstone, indicating that these are channel-belt deposits, rather than casts of channels formed from lateral channel migration, avulsion and reoccupation. In plan view, ridges form segments branching outward to the north resembling a distributary network; however, crosscutting relationships indicate that ridges cross at different stratigraphic levels. Thus, the apparent network in planview reflects non-uniform exhumation of channel-belt deposits from multiple stratigraphic positions, rather than an inverted coeval river network. As compared to the inverted channel model, exhumed fluvial deposits indicate persistent fluvial activity over geologic timescales, indicating the potential for long-lived surface water on ancient Mars.

Anguilles estuariennes et fluviales : apports de l'otolithométrie

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MOUNAIX B.

1994-10-01

La zonation de l'otolithe, interprétée par rapport à la croissance des poissons, décrit deux écotypes dans la population d'anguilles de la Vilaine : un écotype fluvial dont la croissance est perturbée et ralentie, et un écotype estuarien dont la croissance est plus régulière. Cette partition de la population est cohérente avec les caractéristiques environnementales des deux milieux. Elle pourrait par ailleurs constituer un indice de l'impact des aménagements des bassins versants sur la croissance, la durée du cycle biologique et la dynamique des populations d'anguilles. Il apparaît alors nécessaire de considérer séparément les sous-unités estuariennes et fluviales des stocks d'anguilles des bassins versants de la Vilaine et de la Loire, en particulier pour étudier la diminution des abondances.

Dinosaur trackways from the early Late Cretaceous of western Cameroon

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Martin, Jeremy E.; Menkem, Elie Fosso; Djomeni, Adrien; Fowe, Paul Gustave; Ntamak-Nida, Marie-Joseph

2017-10-01

Dinosaur trackways have rarely been reported in Cretaceous strata across the African continent. To the exception of ichnological occurrences in Morocco, Tunisia, Niger and Cameroon, our knowledge on the composition of Cretaceous dinosaur faunas mostly relies on skeletal evidence. For the first time, we document several dinosaur trackways from the Cretaceous of the Mamfe Basin in western Cameroon. Small and medium-size tridactyl footprints as well as numerous large circular footprints are present on a single horizon showing mudcracks and ripple marks. The age of the locality is considered Cenomanian-Turonian and if confirmed, this ichnological assemblage could be younger than the dinosaur footprints reported from northern Cameroon, and coeval with or younger than skeletal remains reported from the Saharan region. These trackways were left in an adjacent subsiding basin along the southern shore of the Benue Trough during a time of high-sea stand when the Trans-Saharan Seaway was already disconnecting West Africa from the rest of the continent. We predict that other similar track sites may be occurring along the margin of the Benue Trough and may eventually permit to test hypotheses related to provincialism among African dinosaur faunas.

Late Holocene lowland fluvial archives and geoarchaeology : Utrecht's case study of Rhine river abandonment under Roman and Medieval settlement

NARCIS (Netherlands)

van Dinter, M.; Cohen, K.M.; Hoek, W.Z.; Stouthamer, E.; Jansma, E.; Middelkoop, H.

2017-01-01

Fluvial lowlands have become attractive human settling areas all around the world over the last few millennia. Because rivers kept changing their course and networks due to avulsion, the sedimentary sequences in these areas are archives of both fluvial geomorphological and archaeological

Pre- and post-remediation characterization of acid-generating fluvial tailings material

Science.gov (United States)

Smith, Kathleen S.; Walton-Day, Katherine; Hoal, Karin O.; Driscoll, Rhonda L.; Pietersen, K.

2012-01-01

The upper Arkansas River south of Leadville, Colorado, USA, contains deposits of fluvial tailings from historical mining operations in the Leadville area. These deposits are potential non-point sources of acid and metal contamination to surface- and groundwater systems. We are investigating a site that recently underwent in situ remediation treatment with lime, fertilizer, and compost. Pre- and post-remediation fluvial tailings material was collected from a variety of depths to examine changes in mineralogy, acid generation, and extractable nutrients. Results indicate sufficient nutrient availability in the post-remediation near-surface material, but pyrite and acid generation persist below the depth of lime and fertilizer addition. Mineralogical characterization performed using semi-quantitative X-ray diffraction and quantitative SEM-based micro-mineralogy (Mineral Liberation Analysis, MLA) reveal formation of gypsum, jarosite, and complex coatings surrounding mineral grains in post-remediation samples.

Introduction to the special issue on discontinuity of fluvial systems

Science.gov (United States)

Burchsted, Denise; Daniels, Melinda; Wohl, Ellen E.

2014-01-01

Fluvial systems include natural and human-created barriers that modify local base level; as such, these discontinuities alter the longitudinal flux of water and sediment by storing, releasing, or changing the flow path of those materials. Even in the absence of distinct barriers, fluvial systems are typically discontinuous and patchy. The size of fluvial discontinuities ranges across scales from 100 m, such as riffles, to 104 m, such as lava dams or major landslides. The frequency of occurrence appears to be inversely related to size, with creation and failure of the small features, such as beaver dams, occurring on a time scale of 100 to 101 years and a frequency of occurrence at scales as low as 101 m. In contrast, larger scale discontinuities, such as lava dams, can last for time scales up to 105 years and have a frequency of occurrence of approximately 104 m. The heterogeneity generated by features is an essential part of river networks and should be considered as part of river management. Therefore, we suggest that "natural" dams are a useful analog for human dams when evaluating options for river restoration. This collection of papers on the studies of natural dams includes bedrock barriers, log jams and beaver dams. The collection also addresses the discontinuity generated by a floodplain — in the absence of an obvious barrier in the channel — and tools for evaluation of riverbed heterogeneity. It is completed with a study of impact of human dams on floodplain sedimentation. These papers will help geomorphologists and river managers understand the factors that control river heterogeneity across scales and around the world.

A laser profilometry technique for monitoring fluvial dike breaching in laboratory experiments

Science.gov (United States)

Dewals, Benjamin; Rifai, Ismail; Erpicum, Sébastien; Archambeau, Pierre; Violeau, Damien; Pirotton, Michel; El kadi Abderrezzak, Kamal

2017-04-01

A challenging aspect for experimental modelling of fluvial dike breaching is the continuous monitoring of the transient breach geometry. In dam breaching cases induced by flow overtopping over the whole breach crest (plane erosion), a side view through a glass wall is sufficient to monitor the breach formation. This approach can be extended for 3D dam breach tests (spatial erosion) if the glass wall is located along the breach centreline. In contrast, using a side view does not apply for monitoring fluvial dike breaching, because the breach is not symmetric in this case. We present a non-intrusive, high resolution technique to record the breach development in experimental models of fluvial dikes by means of a laser profilometry (Rifai et al. 2016). Most methods used for monitoring dam and dike breaching involve the projection of a pattern (fringes, grid) on the dam or dike body and the analysis of its deformation on images recorded during the breaching (e.g., Pickert et al. 2011, Frank and Hager 2014). A major limitation of these methods stems from reflection on the water surface, particularly in the vicinity of the breach where the free surface is irregular and rippled. This issue was addressed by Spinewine et al. (2004), who used a single laser sheet so that reflections on the water surface were strongly limited and did not hamper the accurate processing of each image. We have developed a similar laser profilometry technique tailored for laboratory experiments on fluvial dike breaching. The setup is simple and relatively low cost. It consists of a digital video camera (resolution of 1920 × 1080 pixels at 60 frames per second) and a swiping red diode 30 mW laser that enables the projection of a laser sheet over the dike body. The 2D image coordinates of each deformed laser profile incident on the dike are transformed into 3D object coordinates using the Direct Linear Transformation (DLT) algorithm. All 3D object coordinates computed over a swiping cycle of the

Coal depositional models in some tertiary and cretaceous coal fields in the US western interior

Energy Technology Data Exchange (ETDEWEB)

Flores, R M

1979-12-01

Detailed stratigraphic and sedimentological studies of the Tertiary Tongue River Member of the Fort Union Formation in the Powder River Basin, Wyoming, and the Cretaceous Blackhawk Formation and Star Point Sandstone in the Wasatch Plateau, Utah, indicate that the depositional environments of coal played a major role in controlling coal thickness, lateral continuity, potential minability, and type of floor and roof rocks. The potentially minable, thick coal beds of the Tongue River Member were primarily formed in long-lived floodbasin backswamps of upper alluvial plain environment. Avulsion of meandering fluvial channels contributed to the erratic lateral extent of coals in this environment. Laterally extensive coals formed in floodbasin backswamps of a lower alluvial plain environment; however, interruption by overbank and crevasse-splay sedimentation produced highly split and merging coal beds. Lacustrine sedimentation common to the lower alluvial plain, similar to the lake-covered lower alluvial valley of the Atchafalaya River Basin, is related to a high-constructive delta. In contrast to these alluvial coals are the deltaic coal deposits of the Blackhawk Formation. The formation consists of three coal populations: upper delta plain, lower delta plain, and back-barrier. Coals of the lower delta plain are thick and laterally extensive, in contrast to those of the upper delta plain and back-barrier, which contain abundant, very thin and laterally discontinuous carbonaceous shale partings. The reworking of the delta-front sediments of the Star Point Sandstone suggests that the Blackhawk-Star Point delta was a high-destructive system. 1 figure, 1 table.

Examining fluvial fish range loss with SDMs

Science.gov (United States)

Taylor, Andrew T.; Papeş, Monica; Long, James M.

2018-01-01

Fluvial fishes face increased imperilment from anthropogenic activities, but the specific factors contributing most to range declines are often poorly understood. For example, the range of the fluvial‐specialist shoal bass (Micropterus cataractae) continues to decrease, yet how perceived threats have contributed to range loss is largely unknown. We used species distribution models to determine which factors contributed most to shoal bass range loss. We estimated a potential distribution based on natural abiotic factors and a series of currently occupied distributions that incorporated variables characterizing land cover, non‐native species, and river fragmentation intensity (no fragmentation, dams only, and dams and large impoundments). We allowed interspecific relationships between non‐native congeners and shoal bass to vary across fragmentation intensities. Results from the potential distribution model estimated shoal bass presence throughout much of their native basin, whereas models of currently occupied distribution showed that range loss increased as fragmentation intensified. Response curves from models of currently occupied distribution indicated a potential interaction between fragmentation intensity and the relationship between shoal bass and non‐native congeners, wherein non‐natives may be favored at the highest fragmentation intensity. Response curves also suggested that >100 km of interconnected, free‐flowing stream fragments were necessary to support shoal bass presence. Model evaluation, including an independent validation, suggested that models had favorable predictive and discriminative abilities. Similar approaches that use readily available, diverse, geospatial data sets may deliver insights into the biology and conservation needs of other fluvial species facing similar threats.

Deciphering Fluvial-Capture-Induced Erosional Patterns at the Continental Scale on the Iberian Peninsula

Science.gov (United States)

Anton, L.; Munoz Martin, A.; De Vicente, G.; Finnegan, N. J.

2017-12-01

The process of river incision into bedrock dictates the landscape response to changes in climate and bedrock uplift in most unglaciated settings. Hence, understanding processes of river incision into bedrock and their topographic signatures are a basic goal of geomorphology. Formerly closed drainage basins provide an exceptional setting for the quantification of long term fluvial dissection and landscape change, making them valuable natural laboratories. Internally drained basins are peculiar because they trap all the sediment eroded within the watershed; as closed systems they do not respond to the base level of the global ocean and deposition is the dominant process. In that context, the opening of an outward drainage involves a sudden lowering of the base level, which is transmitted upstream along fluvial channels in the form of erosional waves, leading to high incision and denudation rates within the intrabasinal areas. Through digital topographic analysis and paleolandscape reconstruction based on relict deposits and landscapes on the Iberian Peninsula, we quantify the volume of sediments eroded from formerly internally drained basins since capture. Mapping of fluvial dissection patterns reveals how, and how far, regional waves of incision have propagated upstream. In our analysis, erosional patterns are consistent with the progressive establishment of an outward drainage system, providing a relative capture chronology for the different studied basins. Divide migration inferred from chi maps supports the interpretations based on fluvial dissection patterns and volumes, providing clues on how landscaped changed and how drainage integration occurred within the studied watersheds. [Funded by S2013/MAE-2739 and CGL2014-59516].

Heterogeneity in a Suburban River Network: Understanding the Impact of Fluvial Wetlands on Dissolved Oxygen and Metabolism in Headwater Streams

Science.gov (United States)

Cain, J. S.; Wollheim, W. M.; Sheehan, K.; Lightbody, A.

2014-12-01

Low dissolved oxygen content in rivers threatens fish populations, aquatic organisms, and the health of entire ecosystems. River systems with high fluvial wetland abundance and organic matter, may result in high metabolism that in conjunction with low re-aeration rates, lead to low oxygen conditions. Increasing abundance of beaver ponds in many areas may exacerbate this phenomenon. This research aims to understand the impact of fluvial wetlands, including beaver ponds, on dissolved oxygen (D.O.) and metabolism throughout the headwaters of the Ipswich R. watershed, MA, USA. In several fluvial wetland dominated systems, we measured diel D.O. and metabolism in the upstream inflow, the surface water transient storage zones of fluvial wetland sidepools, and at the outflow to understand how the wetlands modify dissolved oxygen. D.O. was also measured longitudinally along entire surface water flow paths (x-y km long) to determine how low levels of D.O. propagate downstream. Nutrient samples were also collected to understand how their behavior was related to D.O. behavior. Results show that D.O. in fluvial wetlands has large swings with periods of very low D.O. at night. D.O. swings were also seen in downstream outflow, though lagged and somewhat attenuated. Flow conditions affect the level of inundation and the subsequent effects of fluvial wetlands on main channel D.O.. Understanding the D.O. behavior throughout river systems has important implications for the ability of river systems to remove anthropogenic nitrogen.

Experimental insights into organic carbon oxidation potential during fluvial transport without floodplain storage

Science.gov (United States)

Scheingross, J. S.; Hovius, N.; Sachse, D.; Vieth-Hillebrand, A.; Turowski, J. M.; Hilton, R. G.

2016-12-01

Over geologic timescales, the exchange of organic carbon (OC) between the atmosphere, rock, and biosphere is thought to be a major control on global climate. CO2 flux estimates from oxidation of rock-derived OC and sequestration of biospheric OC during fluvial transit from source to sink are approximately the same order of magnitude or larger than those from silicate weathering. Despite field data showing loss of OC moving downstream in lowland rivers, it is unclear if losses occur primarily during active fluvial transport within the river, where OC is in continual motion within an aerated environment, or during longer periods when OC is temporarily stored in river floodplains which may be anoxic. This represents a major knowledge gap, as the unknown location of OC oxidation (i.e., river vs. floodplain) limits our ability to develop process-based models that can be employed to predict OC losses, constrain carbon budgets, and unravel links between climate, tectonics, and erosion. To fill this gap, we investigated the potential for OC oxidation in laboratory experiments simulating fluvial transport without floodplain storage. Mixtures of OC-rich and siliciclastic sediment were transported for distances of 2000 km in annular flumes while making time-series measurements of sediment TOC and water DOC concentrations. Initial results for transport of OC-rich soil show increasing DOC with transport distance to levels that represent a transfer of 2% of the total OC from the solid to the dissolved phase; however, we observed no detectable change in the solid-phase TOC. Similar results were obtained in a control experiment with identical sediment in still water. These preliminary results suggest minimal OC oxidation within our experiment, and, to the extent that such experiments represent natural transport through river systems, are consistent with the hypothesis that OC losses may occur primarily during floodplain storage rather than fluvial transport.

A diverse ant fauna from the mid-cretaceous of Myanmar (Hymenoptera: Formicidae.

Directory of Open Access Journals (Sweden)

Phillip Barden

Full Text Available A new collection of 24 wingless ant specimens from mid-Cretaceous Burmese amber (Albian-Cenomanian, 99 Ma comprises nine new species belonging to the genus Sphecomyrmodes Engel and Grimaldi. Described taxa vary considerably with regard to total size, head and body proportion, cuticular sculpturing, and petiole structure while all species are unified by a distinct shared character. The assemblage represents the largest known diversification of closely related Cretaceous ants with respect to species number. These stem-group ants exhibit some characteristics previously known only from their extant counterparts along with presumed plesiomorphic morphology. Consequently, their morphology may inform hypotheses relating to basal relationships and general patterns of ant evolution. These and other uncovered Cretaceous species indicate that stem-group ants are not simply wasp-like, transitional formicids, but rather a group of considerable adaptive diversity, exhibiting innovations analogous to what crown-group ants would echo 100 million years later.

Rhinochelys amaberti Moret (1935, a protostegid turtle from the Early Cretaceous of France

Directory of Open Access Journals (Sweden)

Isaure Scavezzoni

2018-04-01

Full Text Available Modern marine turtles (chelonioids are the remnants of an ancient radiation that roots in the Cretaceous. The oldest members of that radiation are first recorded from the Early Cretaceous and a series of species are known from the Albian-Cenomanian interval, many of which have been allocated to the widespread but poorly defined genus Rhinochelys, possibly concealing the diversity and the evolution of early marine turtles. In order to better understand the radiation of chelonioids, we redescribe the holotype and assess the taxonomy of Rhinochelys amaberti Moret (1935 (UJF-ID.11167 from the Late Albian (Stoliczkaia dispar Zone of the Vallon de la Fauge (Isère, France. We also make preliminary assessments of the phylogenetic relationships of Chelonioidea using two updated datasets that widely sample Cretaceous taxa, especially Rhinochelys. Rhinochelys amaberti is a valid taxon that is supported by eight autapomorphies; an emended diagnosisis proposed. Our phylogenetic analyses suggest that Rhinochelys could be polyphyletic, but constraining it as a monophyletic entity does not produce trees that are significantly less parsimonious. Moreover, support values and stratigraphic congruence indexes are fairly low for the recovered typologies, suggesting that missing data still strongly affect our understanding of the Cretaceous diversification of sea turtles.

Arctic black shale formation during Cretaceous Oceanic Anoxic Event 2

DEFF Research Database (Denmark)

Lenniger, Marc; Nøhr-Hansen, Henrik; Hills, Len V.

2014-01-01

The Late Cretaceous Oceanic Anoxic Event 2 (OAE2) represents a major perturbation of the global carbon cycle caused by the widespread deposition of organic-rich black shales. Although the paleoceanographic response and the spatial extent of bottom-water anoxia in low and mid-paleolatitudes are re......The Late Cretaceous Oceanic Anoxic Event 2 (OAE2) represents a major perturbation of the global carbon cycle caused by the widespread deposition of organic-rich black shales. Although the paleoceanographic response and the spatial extent of bottom-water anoxia in low and mid...... caused massive organic-carbon burial on the Arctic shelf in general, with important implications for hydrocarbon source-rock distribution in the Arctic region....

National Uranium Resource Evaluation: Newcastle Quadrangle, Wyoming and South Dakota

International Nuclear Information System (INIS)

Santos, E.S.; Robinson, K.; Geer, K.A.; Blattspieler, J.G.

1982-09-01

Uranium resources of the Newcastle 1 0 x2 0 Quadrangle, Wyoming and South Dakota were evaluated to a depth of 1500 m (5000 ft) using available surface and subsurface geologic information. Many of the uranium occurrences reported in the literature and in reports of the US Atomic Energy Commission were located, sampled and described. Areas of anomalous radioactivity, interpreted from an aerial radiometric survey, were outlined. Areas favorable for uranium deposits in the subsurface were evaluated using gamma-ray logs. Based on surface and subsurface data, two areas have been delineated which are underlain by rocks deemed favorable as hosts for uranium deposits. One of these is underlain by rocks that contain fluvial arkosic facies in the Wasatch and Fort Union Formations of Tertiary age; the other is underlain by rocks containing fluvial quartzose sandstone facies of the Inyan Kara Group of Early Cretaceous age. Unfavorable environments characterize all rock units of Tertiary age above the Wasatch Formation, all rock units of Cretaceous age above the Inyan Kara Group, and most rock units of Mesozoic and Paleozoic age below the Inyan Kara Group. Unfavorable environments characterize all rock units of Cretaceous age above the Inyan Kara Group, and all rock units of Mesozoic and Paleozoic age below the Inyan Kara Group

National Uranium Resource Evaluation: Newcastle Quadrangle, Wyoming and South Dakota

Energy Technology Data Exchange (ETDEWEB)

Santos, E S; Robinson, K; Geer, K A; Blattspieler, J G

1982-09-01

Uranium resources of the Newcastle 1/sup 0/x2/sup 0/ Quadrangle, Wyoming and South Dakota were evaluated to a depth of 1500 m (5000 ft) using available surface and subsurface geologic information. Many of the uranium occurrences reported in the literature and in reports of the US Atomic Energy Commission were located, sampled and described. Areas of anomalous radioactivity, interpreted from an aerial radiometric survey, were outlined. Areas favorable for uranium deposits in the subsurface were evaluated using gamma-ray logs. Based on surface and subsurface data, two areas have been delineated which are underlain by rocks deemed favorable as hosts for uranium deposits. One of these is underlain by rocks that contain fluvial arkosic facies in the Wasatch and Fort Union Formations of Tertiary age; the other is underlain by rocks containing fluvial quartzose sandstone facies of the Inyan Kara Group of Early Cretaceous age. Unfavorable environments characterize all rock units of Tertiary age above the Wasatch Formation, all rock units of Cretaceous age above the Inyan Kara Group, and most rock units of Mesozoic and Paleozoic age below the Inyan Kara Group. Unfavorable environments characterize all rock units of Cretaceous age above the Inyan Kara Group, and all rock units of Mesozoic and Paleozoic age below the Inyan Kara Group.

Source rock potential of middle cretaceous rocks in Southwestern Montana

Science.gov (United States)

Dyman, T.S.; Palacas, J.G.; Tysdal, R.G.; Perry, W.J.; Pawlewicz, M.J.

1996-01-01

The middle Cretaceous in southwestern Montana is composed of a marine and nonmarine succession of predominantly clastic rocks that were deposited along the western margin of the Western Interior Seaway. In places, middle Cretaceous rocks contain appreciable total organic carbon (TOC), such as 5.59% for the Mowry Shale and 8.11% for the Frontier Formation in the Madison Range. Most samples, however, exhibit less than 1.0% TOC. The genetic or hydrocarbon potential (S1+S2) of all the samples analyzed, except one, yield less than 1 mg HC/g rock, strongly indicating poor potential for generating commercial amounts of hydrocarbons. Out of 51 samples analyzed, only one (a Thermopolis Shale sample from the Snowcrest Range) showed a moderate petroleum potential of 3.1 mg HC/g rock. Most of the middle Cretaceous samples are thermally immature to marginally mature, with vitrinite reflectance ranging from about 0.4 to 0.6% Ro. Maturity is high in the Pioneer Mountains, where vitrinite reflectance averages 3.4% Ro, and at Big Sky Montana, where vitrinite reflectance averages 2.5% Ro. At both localities, high Ro values are due to local heat sources, such as the Pioneer batholith in the Pioneer Mountains.

New Mid-Cretaceous (Latest Albian) Dinosaurs from Winton, Queensland, Australia

Science.gov (United States)

Hocknull, Scott A.; White, Matt A.; Tischler, Travis R.; Cook, Alex G.; Calleja, Naomi D.; Sloan, Trish; Elliott, David A.

2009-01-01

Background Australia's dinosaurian fossil record is exceptionally poor compared to that of other similar-sized continents. Most taxa are known from fragmentary isolated remains with uncertain taxonomic and phylogenetic placement. A better understanding of the Australian dinosaurian record is crucial to understanding the global palaeobiogeography of dinosaurian groups, including groups previously considered to have had Gondwanan origins, such as the titanosaurs and carcharodontosaurids. Methodology/Principal Findings We describe three new dinosaurs from the late Early Cretaceous (latest Albian) Winton Formation of eastern Australia, including; Wintonotitan wattsi gen. et sp. nov., a basal titanosauriform; Diamantinasaurus matildae gen. et sp. nov., a derived lithostrotian titanosaur; and Australovenator wintonensis gen. et sp. nov., an allosauroid. We compare an isolated astragalus from the Early Cretaceous of southern Australia; formerly identified as Allosaurus sp., and conclude that it most-likely represents Australovenator sp. Conclusion/Significance The occurrence of Australovenator from the Aptian to latest Albian confirms the presence in Australia of allosauroids basal to the Carcharodontosauridae. These new taxa, along with the fragmentary remains of other taxa, indicate a diverse Early Cretaceous sauropod and theropod fauna in Australia, including plesiomorphic forms (e.g. Wintonotitan and Australovenator) and more derived forms (e.g. Diamantinasaurus). PMID:19584929

New Mid-Cretaceous (latest Albian dinosaurs fromWinton, Queensland, Australia.

Directory of Open Access Journals (Sweden)

Scott A Hocknull

Full Text Available BACKGROUND: Australia's dinosaurian fossil record is exceptionally poor compared to that of other similar-sized continents. Most taxa are known from fragmentary isolated remains with uncertain taxonomic and phylogenetic placement. A better understanding of the Australian dinosaurian record is crucial to understanding the global palaeobiogeography of dinosaurian groups, including groups previously considered to have had Gondwanan origins, such as the titanosaurs and carcharodontosaurids. METHODOLOGY/PRINCIPAL FINDINGS: We describe three new dinosaurs from the late Early Cretaceous (latest Albian Winton Formation of eastern Australia, including; Wintonotitan wattsi gen. et sp. nov., a basal titanosauriform; Diamantinasaurus matildae gen. et sp. nov., a derived lithostrotian titanosaur; and Australovenator wintonensis gen. et sp. nov., an allosauroid. We compare an isolated astragalus from the Early Cretaceous of southern Australia; formerly identified as Allosaurus sp., and conclude that it most-likely represents Australovenator sp. CONCLUSION/SIGNIFICANCE: The occurrence of Australovenator from the Aptian to latest Albian confirms the presence in Australia of allosauroids basal to the Carcharodontosauridae. These new taxa, along with the fragmentary remains of other taxa, indicate a diverse Early Cretaceous sauropod and theropod fauna in Australia, including plesiomorphic forms (e.g. Wintonotitan and Australovenator and more derived forms (e.g. Diamantinasaurus.

Utilization of ancient permafrost carbon in headwaters of Arctic fluvial networks

NARCIS (Netherlands)

Mann, Paul J.; Eglinton, Timothy I.; McIntyre, Cameron P.; Zimov, Nikita; Davydova, Anna; Vonk, Jorien E.; Holmes, Robert M.; Spencer, Robert G M

2015-01-01

Northern high-latitude rivers are major conduits of carbon from land to coastal seas and the Arctic Ocean. Arctic warming is promoting terrestrial permafrost thaw and shifting hydrologic flowpaths, leading to fluvial mobilization of ancient carbon stores. Here we describe 14 C and 13 C

When do plants modify fluvial processes? Plant-hydraulic interactions under variable flow and sediment supply rates

Science.gov (United States)

Manners, Rebecca B.; Wilcox, Andrew C.; Kui, Li; Lightbody, Anne F.; Stella, John C.; Sklar, Leonard S.

2015-02-01

Flow and sediment regimes shape alluvial river channels; yet the influence of these abiotic drivers can be strongly mediated by biotic factors such as the size and density of riparian vegetation. We present results from an experiment designed to identify when plants control fluvial processes and to investigate the sensitivity of fluvial processes to changes in plant characteristics versus changes in flow rate or sediment supply. Live seedlings of two species with distinct morphologies, tamarisk (Tamarix spp.) and cottonwood (Populus fremontii), were placed in different configurations in a mobile sand-bed flume. We measured the hydraulic and sediment flux responses of the channel at different flow rates and sediment supply conditions representing equilibrium (sediment supply = transport rate) and deficit (sediment supply plant species and configuration. Species-specific traits controlled the hydraulic response: compared to cottonwood, which has a more tree-like morphology, the shrubby morphology of tamarisk resulted in less pronation and greater reductions in near-bed velocities, Reynolds stress, and sediment flux rates. Under sediment-deficit conditions, on the other hand, abiotic factors dampened the effect of variations in plant characteristics on the hydraulic response. We identified scenarios for which the highest stem-density patch, independent of abiotic factors, dominated the fluvial response. These results provide insight into how and when plants influence fluvial processes in natural systems.

Fluvial organic carbon losses from oil palm plantations on tropical peat, Sarawak, Southeast Asia

Science.gov (United States)

Cook, Sarah; Page, Susan; Evans, Chris; Whelan, Mick; Gauci, Vincent; Lip Khoon, Kho

2017-04-01

Tropical peatlands are valuable stores of carbon. However, tropical peat swamp forests (TPSFs) in Southeast Asia have increasingly been converted to other land-uses. For example, more than 25% of TPSFs are now under oil palm plantations. This conversion - requiring felling and burning of trees and drainage of the peat - can enhance carbon mineralization, dissolved organic carbon (DOC) losses and can contribute significantly to global anthropogenic greenhouse gas emissions, changing these natural carbon sinks into carbon sources. At present, relatively few scientifically sound studies provide dependable estimates of gaseous and fluvial carbon losses from oil palm plantations or from drained tropical peat in general. Here we present an annual (54 week) estimate of the export of dissolved and particulate organic carbon in water draining two oil palm estates and nearby stands of TPSF in Sarawak, Malaysia, subjected to varying degrees of past anthropogenic disturbance. Spectrophotometric techniques including SUVA254 (Specific Ultra-Violet Absorption) were used to gain insight into the aromaticity and subsequent bioavailability of the exported DOC. Water draining plantation and deforested land had a higher proportion of labile carbon compared to water draining forested areas. Preliminary data suggest a total fluvial DOC flux from plantations of ca. 190 g C m-2 year-1; nearly three times estimates from intact TPSFs (63 g C m-2 year-1). DOC accounted for between 86 % - 94 % of the total organic carbon lost (most of which was bioavailable). Wit et al. (2015) estimates that an average of 53 % of peat-derived DOC is decomposed and emitted as CO2, on a monthly basis. Based on these estimates our data suggests an additional 101 g CO2 m-2 may be emitted indirectly from fluvial organic carbon in degraded TPSFs per year. Overall, these findings emphasize the importance of including fluvial organic carbon fluxes when quantifying the impact of anthropogenic disturbance on the

The Brahmaputra River: a stratigraphic analysis of Holocene avulsion and fluvial valley reoccupation history

Science.gov (United States)

Hartzog, T. R.; Goodbred, S. L.

2011-12-01

The Brahmaputra River, one of the world's largest braided streams, is a major component of commerce, agriculture, and transportation in India and Bangladesh. Hence any significant change in course, morphology, or behavior would be likely to influence the regional culture and economy that relies on this major river system. The history of such changes is recorded in the stratigraphy deposited by the Brahmaputra River during the Holocene. Here we present stratigraphic analysis of sediment samples from the boring of 41 tube wells over a 120 km transect in the upper Bengal Basin of northern Bangladesh. The transect crosses both the modern fluvial valley and an abandoned fluvial valley about 60 km downstream of a major avulsion node. Although the modern Brahmaputra does not transport gravel, gravel strata are common below 20 m with fluvial sand deposits dominating most of the stratigraphy. Furthermore, the stratigraphy preserves very few floodplain mud strata below the modern floodplain mud cap. These preliminary findings will be assessed to determine their importance in defining past channel migration, avulsion frequency, and the reoccupation of abandoned fluvial valleys. Understanding the avulsion and valley reoccupation history of the Brahmaputra River is important to assess the risk involved with developing agriculture, business, and infrastructure on the banks of modern and abandoned channels. Based on the correlation of stratigraphy and digital surface elevation data, we hypothesize that the towns of Jamalpur and Sherpur in northern Bangladesh were once major ports on the Brahmaputra River even though they now lie on the banks of small underfit stream channels. If Jamalpur and Sherpur represent the outer extent of the Brahmaputra River braid-belt before the last major avulsion, these cities and any communities developed in the abandoned braid-belt assume a high risk of devastation if the next major avulsion reoccupies this fluvial valley. It is important to

Fluvial biogeomorphology in the Anthropocene: Managing rivers and managing landscapes.

Science.gov (United States)

Viles, Heather

2015-04-01

Biogeomorphology considers the many, and often complex, interactions between ecological and geomorphological processes. The concept of the Anthropocene deserves greater attention by scientists working on biogeomorphology, as will be demonstrated in this talk though a focus on fluvial environments. Rivers and river systems have been the subject of long-term human interference and management across the world, often in the form of direct manipulation of biogeomorphic interactions. Up to the present three broadly-defined phases of the Anthropocene can be identified - the Palaeoanthropocene, the Industrial Revolution and the Great Acceleration. Each of these broad phases of the Anthropocene has different implications for fluvial biogeomorphology and river management. The nature and dynamics of tufa-depositing systems provide good examples of the differing Anthropocene situations and will be focused on in this talk. We may now be entering a fourth phase of the Anthropocene called 'Earth system stewardship'. In terms of better understanding and managing the biogeomorphic interactions within rivers in such a phase, an improved conceptualisation of the Anthropocene and the complex web of interactions between human, ecological and geomorphological processes is needed.

Cretaceous magmatism in North-Eastern India and Gondwanaland ...

Indian Academy of Sciences (India)

jsray

Cretaceous magmatism of NEI: Major Objectives. • Age and duration of Sylhet Traps and its connection to Kerguelene hotspot and Gondwanaland breakup? • Age of carbonatite magmatism associated with the traps? • Relationship of basaltic-carbonatite magmatism with. Aptian (~116 Ma) Mass Extinction event? • Nature of ...

Sedimentary basin analysis and petroleum potential of the Cretaceous and Tertiary strata in Korea.

Energy Technology Data Exchange (ETDEWEB)

Son, Jin-Dam; Kwak, Young-Hoon; Bong, Pil-Yoon [Korea Institute of Geology Mining and Materials, Taejon (KR)] (and others)

1999-12-01

Since 1992 sedimentary basin analysis to assess petroleum potential of the Cretaceous and Tertiary strata in the Korean onshore and continental shelf have been carried out. The Cretaceous non-marine strata mainly occupy the Gyeongsang Basin in southeastern part of the Korean Peninsula and small basins such as Haenam and Gyeokpo depressions in western coastal areas. The Tertiary strata are mostly distributed in Domi, Cheju, Socotra subbasins, and Okinawa Trough in the South Continental Shelf, and Kunsan and Heuksan basins in the West. The basin evolution and petroleum potential for each basins are characterized as follow. The Cretaceous Gyeongsang sediments were deposited in three subbasins including Milyang, Euisung and Yongyang subbasins. The black shales in Nakdong and Jinju formations are interpreted to contain abundant organic matter during the deposition, thermal maturity reaching up to the zone of dry gas formation. Because porosity and permeability are too low, the sandstones can act as a tight gas reservoir rather than conventional oil and gas reservoir. The latest Cretaceous strata of Haenam and Kyeokpo depressions in western coastal area are correlated into the Yuchon Volcanic Group of the Gyeongsang Basin. Petroleum potential of the Early Cretaceous basin in the West Continental Shelf could be relatively high in terms of sedimentary basin filled with thick lacustrine sediments. The Kunsan basin in the West Continental Shelf originated in the Early Cretaceous time expanded during the Paleocene time followed by regional erosion at the end of Paleocene on which Neogene sediment have been accumulated. The Paleocene-Eocene sublacustrine shales may play an major role as a source and cap rocks. South Continental Shelf Basin is subdivided by Cheju subbasin in the center, Socotra Subbasin to the west, Domi Subbasin to the northeast and Okinawa Trough to the East. The potential hydrocarbon traps associated with anticline, titled fault blocks, fault, unconformity

Using Stable Isotope Geochemistry to Determine Changing Paleohydrology and Diagenetic Alteration in the Late Cretaceous Kaiparowits Formation, UT USA

Science.gov (United States)

Yamamura, Daigo

The Western Interior Basin of the North America preserves one of the best sedimentary and paleontological records of the Cretaceous in the world. The Upper Cretaceous Kaiparowits Formation is a rapidly deposited fluvial sequence and preserves one of the most complete terrestrial fossil record of the North America. Such a unique deposit provides an opportunity to investigate the interaction between the physical environment and ecology. In an effort to decipher such interaction, stable isotope composition of cements in sedimentary rocks, concretions and vertebrate fossils were analyzed. Despite the difference in facies and sedimentary architecture, the isotope composition does not change significantly at 110 m from the base of the formation. Among the well-preserved cement samples, stable isotope composition indicates a significant hydrologic change within the informal Middle unit; a 6.37‰ depletion in delta13C and 3.30‰ enrichment in delta 18O occurs at 300 m above the base of the formation. The isotope values indicate that the sandstone cements below 300 m were precipitated in a mixing zone between marine and terrestrial groundwater, whereas the cements in upper units were precipitated in a terrestrial groundwater. Despite the difference in physical appearance (i.e. color and shape), the isotopic compositions of cements in concretions are similar to well-cemented sandstone bodies in similar stratigraphic positions. Isotope compositions of the host rock are similar to that of mudrock and weathered sandstone, suggesting the origin of cementing fluids for the sandstone and concretions were the same indicating that: 1) the concretions were formed in shallow groundwater and not related to the groundwater migration, or 2) all cements in upper Kaiparowits Formation are precipitated or altered during later stage groundwater migration. Average delta18Oc from each taxon show the same trend as the delta18Op stratigraphic change, suggesting delta18Oc is still useful as a

Highly derived eutherian mammals from the earliest Cretaceous of southern Britain

Directory of Open Access Journals (Sweden)

Steven C. Sweetman

2017-11-01

Full Text Available Eutherian mammals (Placentalia and all mammals phylogenetically closer to placentals than to marsupials comprise the vast majority of extant Mammalia. Among these there is a phenomenal range of forms and sizes, but the origins of crown group placentals are obscure. They lie within the generally tiny mammals of the Mesozoic, represented for the most part by isolated teeth and jaws, and there is strongly conflicting evidence from phenomic and molecular data as to the date of origin of both Eutheria and Placentalia. The oldest purported eutherians are Juramaia from the Upper Jurassic of China, and Eomaia and Acristatherium from the Lower Cretaceous, also of China. Based on dental characters and analyses of other morphological and molecular data, doubt has recently been cast on the eutherian affinities of the Chinese taxa and consequently on the date of emergence of Eutheria. Until now, the only tribosphenic mammal recorded from the earliest Cretaceous (Berriasian Purbeck Group of Britain was the stem tribosphenidan Tribactonodon. Here we document two new tribosphenic mammals from the Purbeck Group, Durlstotherium gen. nov. and Durlstodon gen. nov., showing highly derived eutherian molar characters that support the early emergence of this clade, prior to the Cretaceous.

A diplodocid sauropod survivor from the early cretaceous of South America.

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Pablo A Gallina

Full Text Available Diplodocids are by far the most emblematic sauropod dinosaurs. They are part of Diplodocoidea, a vast clade whose other members are well-known from Jurassic and Cretaceous strata in Africa, Europe, North and South America. However, Diplodocids were never certainly recognized from the Cretaceous or in any other southern land mass besides Africa. Here we report a new sauropod, Leikupal laticauda gen. et sp. nov., from the early Lower Cretaceous (Bajada Colorada Formation of Neuquén Province, Patagonia, Argentina. This taxon differs from any other sauropod by the presence of anterior caudal transverse process extremely developed with lateroventral expansions reinforced by robust dorsal and ventral bars, very robust centroprezygapophyseal lamina in anterior caudal vertebra and paired pneumatic fossae on the postzygapophyses in anterior-most caudal vertebra. The phylogenetic analyses support its position not only within Diplodocidae but also as a member of Diplodocinae, clustering together with the African form Tornieria, pushing the origin of Diplodocoidea to the Middle Jurassic or even earlier. The new discovery represents the first record of a diplodocid for South America and the stratigraphically youngest record of this clade anywhere.

Tratamiento de los espacios fluviales urbanos andaluces en la planificación territorial y sectorial

Directory of Open Access Journals (Sweden)

David González Rojas

2017-01-01

Full Text Available La recuperación y conservación de los espacios fluviales urbanos debe insertarse dentro de los procesos de planificación territorial y sectorial. El presente trabajo analiza la evolución y las transformaciones de los espacios fluviales urbanos en Andalucía durante las últimas décadas, a través del análisis de los distintos planes. Para el estudio de las relaciones entre el planeamiento territorial y sectorial y los espacios fluviales urbanos se ha realizado una recopilación de los documentos actualmente aprobados o en tramitación. En el artículo se destacan los avances durante el periodo estudiado, pero también las inercias, resistencias y nuevos problemas asociados. El esfuerzo realizado para la ordenación de los ríos a su paso por las ciudades no ha tenido su reflejo en los resultados obtenidos, siendo las interrelaciones entre la gestión del agua y del territorio (regional, subregional y municipal una cuestión no resuelta.

Optimizing sampling strategy for radiocarbon dating of Holocene fluvial systems in a vertically aggrading setting

International Nuclear Information System (INIS)

Toernqvist, T.E.; Dijk, G.J. Van

1993-01-01

The authors address the question of how to determine the period of activity (sedimentation) of fossil (Holocene) fluvial systems in vertically aggrading environments. The available data base consists of almost 100 14 C ages from the Rhine-Meuse delta. Radiocarbon samples from the tops of lithostratigraphically correlative organic beds underneath overbank deposits (sample type 1) yield consistent ages, indicating a synchronous onset of overbank deposition over distances of at least up to 20 km along channel belts. Similarly, 14 C ages from the base of organic residual channel fills (sample type 3) generally indicate a clear termination of within-channel sedimentation. In contrast, 14 C ages from the base of organic beds overlying overbank deposits (sample type 2), commonly assumed to represent the end of fluvial sedimentation, show a large scatter reaching up to 1000 14 C years. It is concluded that a combination of sample types 1 and 3 generally yields a satisfactory delimitation of the period of activity of a fossil fluvial system. 30 refs., 11 figs., 4 tabs

A new dinosaur ichnotaxon from the Lower Cretaceous Patuxent Formation of Maryland and Virginia

Science.gov (United States)

Stanford, Ray; Weems, Robert E.; Lockley, Martin G.

2004-01-01

In recent years, numerous dinosaur footprints have been discovered on bedding surfaces within the Lower Cretaceous Patuxent Formation of Maryland and Virginia. Among these, distinctive small tracks that display a combination of small manus with five digit impressions and a relatively much larger pes with four toe impressions evidently were made by animals belonging to the ornithischian family Hypsilophodontidae. These tracks differ from any ornithischian ichnotaxon previously described. We here name them Hypsiloichnus marylandicus and provide a description of their diagnostic characteristics. Although hypsilophodontid skeletal remains have not been found in the Patuxent, their skeletal remains are known from Lower Cretaceous strata of similar age in both western North America and Europe. Therefore, it is not surprising to find that an Early Cretaceous representative of this family also existed in eastern North America.

Paleomagnetic tests for tectonic reconstructions of the Late Jurassic-Early Cretaceous Woyla Group, Sumatra

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Advokaat, Eldert; Bongers, Mayke; van Hinsbergen, Douwe; Rudyawan, Alfend; Marshal, Edo

2017-04-01

SE Asia consists of multiple continental blocks, volcanic arcs and suture zones representing remnants of closing ocean basins. The core of this mainland is called Sundaland, and was formed by accretion of continental and arc fragments during the Paleozoic and Mesozoic. The former positions of these blocks are still uncertain but reconstructions based on tectonostratigraphic, palaeobiogeographic, geological and palaeomagnetic studies indicate the continental terranes separated from the eastern margin of Gondwana. During the mid-Cretaceous, more continental and arc fragments accreted to Sundaland, including the intra-oceanic Woyla Arc now exposed on Sumatra. These continental fragments were derived from Australia, but the former position of the Woyla Arc is unconstrained. Interpretations on the former position of the Woyla Arc fall in two end-member groups. The first group interprets the Woyla Arc to be separated from West Sumatra by a small back-arc basin. This back arc basin opened in the Late Jurassic, and closed mid-Cretaceous, when the Woyla Arc collided with West Sumatra. The other group interprets the Woyla Arc to be derived from Gondwana, at a position close to the northern margin of Greater India in the Late Jurassic. Subsequently the Woyla Arc moved northwards and collided with West Sumatra in the mid-Cretaceous. Since these scenarios predict very different plate kinematic evolutions for the Neotethyan realm, we here aim to place paleomagnetic constraints on paleolatitudinal evolution of the Woyla Arc. The Woyla Arc consists mainly of basaltic to andesitic volcanics and dykes, and volcaniclastic shales and sandstones. Associated limestones with volcanic debris are interpreted as fringing reefs. This assemblage is interpreted as remnants of an Early Cretaceous intra-oceanic arc. West Sumatra exposes granites, surrounded by quartz sandstones, shales and volcanic tuffs. These sediments are in part metamorphosed. This assemblage is interpreted as a Jurassic

Fluvial-aeolian interactions in sediment routing and sedimentary signal buffering: an example from the Indus Basin and Thar Desert

Science.gov (United States)

East, Amy E.; Clift, Peter D.; Carter, Andrew; Alizai, Anwar; VanLaningham, Sam

2015-01-01

Sediment production and its subsequent preservation in the marine stratigraphic record offshore of large rivers are linked by complex sediment-transfer systems. To interpret the stratigraphic record it is critical to understand how environmental signals transfer from sedimentary source regions to depositional sinks, and in particular to understand the role of buffering in obscuring climatic or tectonic signals. In dryland regions, signal buffering can include sediment cycling through linked fluvial and eolian systems. We investigate sediment-routing connectivity between the Indus River and the Thar Desert, where fluvial and eolian systems exchanged sediment over large spatial scales (hundreds of kilometers). Summer monsoon winds recycle sediment from the lower Indus River and delta northeastward, i.e., downwind and upstream, into the desert. Far-field eolian recycling of Indus sediment is important enough to control sediment provenance at the downwind end of the desert substantially, although the proportion of Indus sediment of various ages varies regionally within the desert; dune sands in the northwestern Thar Desert resemble the Late Holocene–Recent Indus delta, requiring short transport and reworking times. On smaller spatial scales (1–10 m) along fluvial channels in the northern Thar Desert, there is also stratigraphic evidence of fluvial and eolian sediment reworking from local rivers. In terms of sediment volume, we estimate that the Thar Desert could be a more substantial sedimentary store than all other known buffer regions in the Indus basin combined. Thus, since the mid-Holocene, when the desert expanded as the summer monsoon rainfall decreased, fluvial-eolian recycling has been an important but little recognized process buffering sediment flux to the ocean. Similar fluvial-eolian connectivity likely also affects sediment routing and signal transfer in other dryland regions globally.

Fluvial particle characterization using artificial neural network and spectral image processing

Science.gov (United States)

Shrestha, Bim Prasad; Gautam, Bijaya; Nagata, Masateru

2008-03-01

Sand, chemical waste, microbes and other solid materials flowing with the water bodies are of great significance to us as they cause substantial impact to different sectors including drinking water management, hydropower generation, irrigation, aquatic life preservation and various other socio-ecological factors. Such particles can't completely be avoided due to the high cost of construction and maintenance of the waste-treatment methods. A detailed understanding of solid particles in surface water system can have benefit in effective, economic, environmental and social management of water resources. This paper describes an automated system of fluvial particle characterization based on spectral image processing that lead to the development of devices for monitoring flowing particles in river. Previous research in coherent field has shown that it is possible to automatically classify shapes and sizes of solid particles ranging from 300-400 μm using artificial neural networks (ANN) and image processing. Computer facilitated with hyper spectral and multi spectral images using ANN can further classify fluvial materials into organic, inorganic, biodegradable, bio non degradable and microbes. This makes the method attractive for real time monitoring of particles, sand and microorganism in water bodies at strategic locations. Continuous monitoring can be used to determine the effect of socio-economic activities in upstream rivers, or to monitor solid waste disposal from treatment plants and industries or to monitor erosive characteristic of sand and its contribution to degradation of efficiency of hydropower plant or to identify microorganism, calculate their population and study the impact of their presence. Such system can also be used to characterize fluvial particles for planning effective utilization of water resources in micro-mega hydropower plant, irrigation, aquatic life preservation etc.

Palaeomagnetism of lower cretaceous tuffs from Yukon-Kuskokwim delta region, western Alaska

Science.gov (United States)

Globerman, B.R.; Coe, R.S.; Hoare, J.M.; Decker, J.

1983-01-01

During the past decade, the prescient arguments1-3 for the allochthoneity of large portions of southern Alaska have been corroborated by detailed geological and palaeomagnetic studies in south-central Alaska 4-9 the Alaska Peninsula10, Kodiak Island11,12 and the Prince William Sound area13 (Fig. 1). These investigations have demonstrated sizeable northward displacements for rocks of late Palaeozoic, Mesozoic, and early Tertiary age in those regions, with northward motion at times culminating in collision of the allochthonous terranes against the backstop of 'nuclear' Alaska14,15. A fundamental question is which parts of Alaska underwent significantly less latitudinal translation relative to the 'stable' North American continent, thereby serving as the 'accretionary nucleus' into which the displaced 'microplates'16 were eventually incorporated17,18? Here we present new palaeomagnetic results from tuffs and associated volcaniclastic rocks of early Cretaceous age from the Yukon-Kuskokwin delta region in western Alaska. These rocks were probably overprinted during the Cretaceous long normal polarity interval, although a remagnetization event as recent as Palaeocene cannot be ruled out. This overprint direction is not appreciably discordant from the expected late Cretaceous direction for cratonal North America. The implied absence of appreciable northward displacement for this region is consistent with the general late Mesozoic-early Tertiary tectonic pattern for Alaska, based on more definitive studies: little to no poleward displacement for central Alaska, though substantially more northward drift for the 'southern Alaska terranes' (comprising Alaska Peninsula, Kodiak Island, Prince William Sound area, and Matunuska Valley) since late Cretaceous to Palaeocene time. ?? 1983 Nature Publishing Group.

Insights into organic carbon oxidation potential during fluvial transport from laboratory and field experiments

Science.gov (United States)

Scheingross, J. S.; Dellinger, M.; Eglinton, T. I.; Fuchs, M. C.; Golombek, N.; Hilton, R. G.; Hovius, N.; Lupker, M.; Repasch, M. N.; Sachse, D.; Turowski, J. M.; Vieth-Hillebrand, A.; Wittmann, H.

2017-12-01

Over geologic timescales, the exchange of organic carbon (OC) between the atmosphere, hydropshere, biosphere and geosphere can be a major control on atmospheric carbon dioxide concentrations. The carbon fluxes from the oxidation of rock-derived OC (a CO2 source) and erosion, transport, and burial of biospheric OC (a potential CO2 sink) during fluvial transit are approximately the same order of magnitude or larger than those from silicate weathering. Despite field data showing increasing oxidation of OC moving downstream in lowland rivers, it is unclear if losses occur primarily during active fluvial transport, where OC is in continual motion within an aerated river, or during periods of temporary storage in river floodplains which may be anoxic. The unknown location of OC oxidation (i.e., river vs. floodplain) limits our ability to mechanistically link geochemical and geomorphic processes which are required to develop models capable of predicting OC losses, constrain carbon budgets, and unravel links between climate, tectonics, and erosion. To fill this knowledge gap, we investigated OC oxidation in controlled laboratory experiments and a simplified field setting. We performed experiments in annular flumes that simulate fluvial transport without floodplain storage, allowing mixtures of OC-rich and siliciclastic sediment to be transported for distances of 1000 km. Preliminary experiments exploring both rock-derived and biospheric OC sources show minimal OC oxidation during active river transport, consistent with the idea that the majority of OC loss occurs during transient floodplain storage. These results are also consistent with new field data collected in the Rio Bermejo, Argentina, a lowland river traversing 800 km with no tributary inputs, where aged floodplain deposits have 3 to 10 times lower OC concentrations compared to modern river sediments. Together our field data and experiments support the hypothesis that oxidation of OC occurs primarily during

The end-Cretaceous in the southwestern Tethys (Elles, Tunisia)

DEFF Research Database (Denmark)

Thibault, Nicolas Rudolph; Galbrun, Bruno; Gardin, Silvia

2016-01-01

An integrated study of magnetic mass susceptibility (MS), bulk stable isotopes and calcareous nannofossil paleoecological changes is undertaken on the late Maastrichtian of the Elles section, Tunisia, spanning the last ca. 1 Myr of the Cretaceous. A cyclostratigraphic analysis reveals the presenc...

Explosive radiation of Malpighiales supports a mid-cretaceous origin of modern tropical rain forests.

Science.gov (United States)

Davis, Charles C; Webb, Campbell O; Wurdack, Kenneth J; Jaramillo, Carlos A; Donoghue, Michael J

2005-03-01

Fossil data have been interpreted as indicating that Late Cretaceous tropical forests were open and dry adapted and that modern closed-canopy rain forest did not originate until after the Cretaceous-Tertiary (K/T) boundary. However, some mid-Cretaceous leaf floras have been interpreted as rain forest. Molecular divergence-time estimates within the clade Malpighiales, which constitute a large percentage of species in the shaded, shrub, and small tree layer in tropical rain forests worldwide, provide new tests of these hypotheses. We estimate that all 28 major lineages (i.e., traditionally recognized families) within this clade originated in tropical rain forest well before the Tertiary, mostly during the Albian and Cenomanian (112-94 Ma). Their rapid rise in the mid-Cretaceous may have resulted from the origin of adaptations to survive and reproduce under a closed forest canopy. This pattern may also be paralleled by other similarly diverse lineages and supports fossil indications that closed-canopy tropical rain forests existed well before the K/T boundary. This case illustrates that dated phylogenies can provide an important new source of evidence bearing on the timing of major environmental changes, which may be especially useful when fossil evidence is limited or controversial.

Exhumation History Of Brasilian Highlands After Late Cretaceous Alcaline Magmatism

Science.gov (United States)

Doranti Tiritan, Carolina; Hackspacher, Peter Christian; Carina Siqueira Ribeiro, Marli; Glasmacher, Ulrich Anton; Françoso de Godoy, Daniel

2017-04-01

The southeast Brazilian margin recorded a long history of tectonic and magmatic events after the Gondwana continent break up. The drifting of the South American Platform over a thermal anomaly generated a series of alkaline intrusions that are distributed from the interior to the coast from west to east. Several exhumation events are recorded on the region and we are providing insights on the landscape evolution of the region since Late Cretaceous, comparing low temperature thermochronology results from two alkaline intrusions regions. Poços de Caldas Alkaline Massif (PCAM), is lied in the interior, 300km from the coastline, covering over 800km2 intruding the Precambrian basement around 83Ma, nepheline syenites, phonolites and tinguaites intruded in a continuous and rapid sequence lasting between 1 to 2 Ma. São Sebastião Island (SSI) on the other hand is located at the coast, 200 km southeast of São Paulo. It is characterized by an intrusion in Precambrian/Brazilian orogen and intruded by Early Cretaceous sub-alkaline basic and acid dykes, as well as by Late Cretaceous alkaline stocks (syenites) and dykes (basanite to phonolite). Will be presenting the apatite fission track (AFT) and (U-Th)/He results that shows the main difference between the areas is that PCAM region register older history then the coastal area of SSI, where thermal history starts register cooling event after the South Atlantic rifting process, while in the PCAM area register a previous history, since Carboniferous. The results are giving support to studies that indicate the development of the relief in Brazil being strongly influenced by the local and regional tectonic movements and the lithological and structural settings. The landscape at the Late Cretaceous was witness of heating process between 90 and 60Ma due the intense uplift of South American Platform. The elevation of the isotherms is associated with the mantellic plumes and the crustal thickness that caused thermal anomalies due

A nearly modern amphibious bird from the Early Cretaceous of northwestern China.

Science.gov (United States)

You, Hai-Lu; Lamanna, Matthew C; Harris, Jerald D; Chiappe, Luis M; O'connor, Jingmai; Ji, Shu-An; Lü, Jun-Chang; Yuan, Chong-Xi; Li, Da-Qing; Zhang, Xing; Lacovara, Kenneth J; Dodson, Peter; Ji, Qiang

2006-06-16

Three-dimensional specimens of the volant fossil bird Gansus yumenensis from the Early Cretaceous Xiagou Formation of northwestern China demonstrate that this taxon possesses advanced anatomical features previously known only in Late Cretaceous and Cenozoic ornithuran birds. Phylogenetic analysis recovers Gansus within the Ornithurae, making it the oldest known member of the clade. The Xiagou Formation preserves the oldest known ornithuromorph-dominated avian assemblage. The anatomy of Gansus, like that of other non-neornithean (nonmodern) ornithuran birds, indicates specialization for an amphibious life-style, supporting the hypothesis that modern birds originated in aquatic or littoral niches.

Extended Late-Cretaceous Magnetostratigraphy of the James Ross Basin Island, Antarctica

Science.gov (United States)

Chaffee, T. M.; Mitchell, R.; Slotznick, S. P.; Buz, J.; Biasi, J.; O'Rourke, J.; Sousa, F.; Flannery, D.; Fu, R. R.; Kirschvink, J. L.

2017-12-01

Sediments in the James Ross Island Basin (JRB) in the West Antarctic Peninsula contain one of the world's highest-resolution records of the late Cretaceous period, including the end-Cretaceous (K-Pg) mass extinction event. However, the geological record of this region has been poorly studied, limited in the past only to the relative dating of local fossils. Recent studies of this region have provided only low-resolution data, with gaps of greater than 0.5 million years between samples where no data was collected. A high-resolution magnetostratigraphic sampling and analysis is necessary in order to accurately determine the age of the JRB sediments and connect them to the global time record. During the 2016 field season in Antarctica, our team collected nearly 1,300 sample cores from JRB sediments using a diamond-tipped, gasoline powered coring drill. Drill sites were densely clustered across bedding in order to obtain a high-resolution record of magnetostratigraphy, permitting the recognition of distinct, high-resolution units of time (group of over 300 of these samples from the Brandy Bay area which constrain the end of the Cretaceous Superchron (C34N) and the C34N/C34R reversal and allow us to investigate the presence of geomagnetic excursions before the end of superchron. These samples span in age from the top of C34N to the mid-Maastrichtian. We also test the Late Cretaceous True Polar Wander (TPW) hypothesis. Current theories on the global extent of TPW are not substantiated by any data sets that confirm the presence and similarity of the effect across multiple continents. Evidence of a rapid TPW oscillation in Antarctica can be correlated with other samples from the North American continent currently under study to provide evidence for the theory of global, short-timescale TPW.

A fast, parallel algorithm to solve the basic fluvial erosion/transport equations

Science.gov (United States)

Braun, J.

2012-04-01

Quantitative models of landform evolution are commonly based on the solution of a set of equations representing the processes of fluvial erosion, transport and deposition, which leads to predict the geometry of a river channel network and its evolution through time. The river network is often regarded as the backbone of any surface processes model (SPM) that might include other physical processes acting at a range of spatial and temporal scales along hill slopes. The basic laws of fluvial erosion requires the computation of local (slope) and non-local (drainage area) quantities at every point of a given landscape, a computationally expensive operation which limits the resolution of most SPMs. I present here an algorithm to compute the various components required in the parameterization of fluvial erosion (and transport) and thus solve the basic fluvial geomorphic equation, that is very efficient because it is O(n) (the number of required arithmetic operations is linearly proportional to the number of nodes defining the landscape), and is fully parallelizable (the computation cost decreases in a direct inverse proportion to the number of processors used to solve the problem). The algorithm is ideally suited for use on latest multi-core processors. Using this new technique, geomorphic problems can be solved at an unprecedented resolution (typically of the order of 10,000 X 10,000 nodes) while keeping the computational cost reasonable (order 1 sec per time step). Furthermore, I will show that the algorithm is applicable to any regular or irregular representation of the landform, and is such that the temporal evolution of the landform can be discretized by a fully implicit time-marching algorithm, making it unconditionally stable. I will demonstrate that such an efficient algorithm is ideally suited to produce a fully predictive SPM that links observationally based parameterizations of small-scale processes to the evolution of large-scale features of the landscapes on

Late Cretaceous and Cenozoic exhumation history of the Malay Peninsula

Science.gov (United States)

François, Thomas; Daanen, Twan; Matenco, Liviu; Willingshofer, Ernst; van der Wal, Jorien

2015-04-01

The evolution of Peninsular Malaysia up to the collisional period in the Triassic is well described but the evolution since the collision between Indochina and the Sukhothai Arc in Triassic times is less well described in the literature. The processes affecting Peninsular Malaysia during the Jurassic up to current day times have to explain the emplacement multiple intrusions (the Stong Complex, and the Kemahang granite), the Jurassic/Cretaceous onland basins, the Cenozoic offshore basins, and the asymmetric extension, which caused the exhumation of Taku Schists dome. The orogenic period in Permo-Triassic times, which also formed the Bentong-Raub suture zone, resulted in thickening of the continental crust of current day Peninsular Malaysia due to the collision of the Indochina continental block and the Sukhothai Arc, and is related to the subduction of oceanic crust once present between these continental blocks. The Jurassic/Cretaceous is a period of extension, resulting in the onland Jurassic/Cretaceous basins, synchronous melting of the crust, resulting in the emplacement Stong Complex and the Kemahang granite and thinning of the continental crust on the scale of the Peninsular, followed by uplift of the Peninsular. Different models can explain these observations: continental root removal, oceanic slab detachment, or slab delamination. These models all describe the melting of the lower crust due to asthenospheric upwelling, resulting in uplift and subsequent extension either due to mantle convective movements or gravitational instabilities related to uplift. The Cenozoic period is dominated by extension and rapid exhumation in the area as documented by low temperature thermocrological ages The extension in this period is most likely related to the subduction, which resumed at 45 Ma, of the Australian plate beneath the Eurasian plate after it terminated in Cretaceous times due to the collision of an Australian microcontinental fragment with the Sunda margin in the

Patterns of larval development in Cretaceous pipid frogs

Czech Academy of Sciences Publication Activity Database

Roček, Zbyněk; van Dijk, E.

2006-01-01

Roč. 51, č. 1 (2006), s. 111-126 ISSN 0567-7920 R&D Projects: GA AV ČR IAA3013206 Institutional research plan: CEZ:AV0Z30130516 Keywords : Anura * Pipidae * Cretaceous Subject RIV: EG - Zoology Impact factor: 1.076, year: 2006 http://app.pan.pl/archive/published/app51/app51-111.pdf

Excursions in fluvial (dis)continuity

Science.gov (United States)

Grant, Gordon E.; O'Connor, James E.; Safran, Elizabeth

2017-01-01

Lurking below the twin concepts of connectivity and disconnectivity are their first, and in some ways, richer cousins: continuity and discontinuity. In this paper we explore how continuity and discontinuity represent fundamental and complementary perspectives in fluvial geomorphology, and how these perspectives inform and underlie our conceptions of connectivity in landscapes and rivers. We examine the historical roots of continuum and discontinuum thinking, and how much of our understanding of geomorphology rests on contrasting views of continuity and discontinuity. By continuum thinking we refer to a conception of geomorphic processes as well as geomorphic features that are expressed along continuous gradients without abrupt changes, transitions, or thresholds. Balance of forces, graded streams, and hydraulic geometry are all examples of this perspective. The continuum view has played a prominent role in diverse disciplinary fields, including ecology, paleontology, and evolutionary biology, in large part because it allows us to treat complex phenomena as orderly progressions and invoke or assume equilibrium processes that introduce order and prediction into our sciences.In contrast the discontinuous view is a distinct though complementary conceptual framework that incorporates non-uniform, non-progressive, and non-equilibrium thinking into understanding geomorphic processes and landscapes. We distinguish and discuss examples of three different ways in which discontinuous thinking can be expressed: 1) discontinuous spatial arrangements or singular events; 2) specific process domains generally associated with thresholds, either intrinsic or extrinsic; and 3) physical dynamics or changes in state, again often threshold-linked. In moving beyond the continuous perspective, a fertile set of ideas comes into focus: thresholds, non-equilibrium states, heterogeneity, catastrophe. The range of phenomena that is thereby opened up to scientific exploration similarly expands

Evidence of cretaceous to recent West African intertropical vegetation from continental sediment spore-pollen analysis

Science.gov (United States)

Salard-Cheboldaeff, M.; Dejax, J.

The succession of spore-pollen assemblages during the Cretaceous and Tertiary, as defined in each of the basin from Senegal to Angola, gives the possibility to consider the intertropical African flora evolution for the past 120 M.a. During the Early Cretaceous, xeric-adapted gymnosperms and various ferns were predominant the flora which nevertheless comprises previously unknown early angiosperm pollen. During the Middle Cretaceous, gymnospers were gradually replaced by angiosperms; these became more and more abundant, along with the diversification of new genera and species. During the Paleocene, the radiation of the monocotyledons (mainly that of the palm-trees) as well as a greater diversification among the dicotyledons and ferms are noteworthy. Since gymnosperms had almost disappeared by the Eocene, the diversification of the dicotyledons went on until the neogene, when all extinct pollen types are already present. These important modifications of the vegetation reflect evolutionary trends as well as climatic changes during the Cretaceous: the climate, firstly hot, dry and perhaps arid, did probably induced salt deposition, and later became gradually more humid under oceanic influences which arose in connection with the Gondwana break-up.

Evidence for global cooling in the Late Cretaceous

Science.gov (United States)

Linnert, Christian; Robinson, Stuart A.; Lees, Jackie A.; Bown, Paul R.; Pérez-Rodríguez, Irene; Petrizzo, Maria Rose; Falzoni, Francesca; Littler, Kate; Arz, José Antonio; Russell, Ernest E.

2014-01-01

The Late Cretaceous ‘greenhouse’ world witnessed a transition from one of the warmest climates of the past 140 million years to cooler conditions, yet still without significant continental ice. Low-latitude sea surface temperature (SST) records are a vital piece of evidence required to unravel the cause of Late Cretaceous cooling, but high-quality data remain illusive. Here, using an organic geochemical palaeothermometer (TEX86), we present a record of SSTs for the Campanian–Maastrichtian interval (~83–66 Ma) from hemipelagic sediments deposited on the western North Atlantic shelf. Our record reveals that the North Atlantic at 35 °N was relatively warm in the earliest Campanian, with maximum SSTs of ~35 °C, but experienced significant cooling (~7 °C) after this to <~28 °C during the Maastrichtian. The overall stratigraphic trend is remarkably similar to records of high-latitude SSTs and bottom-water temperatures, suggesting that the cooling pattern was global rather than regional and, therefore, driven predominantly by declining atmospheric pCO2 levels. PMID:24937202

Late Cretaceous neosuchian crocodiles from the Sultanate of Oman

NARCIS (Netherlands)

Buscalioni, Angela D.; Schulp, Anne S.; Jagt, John W M; Hanna, Samir S.; Hartman, Axel Frans

Two apparently new crocodilian taxa from the Late Cretaceous (Late Campanian-Maastrichtian) Al-Khod Conglomerate of the Sultanate of Oman are described. The fragmentary state of preservation precludes formal naming, yet enables comparisons to be made with other taxa. One is a short-snouted

Large Fluvial Fans: Aspects of the Attribute Array

Science.gov (United States)

Wilkinson, Justin M.

2015-01-01

In arguing for a strict definition of the alluvial fan (coarse-grained with radii less than10 km, in mountain-front settings), Blair and McPherson (1994) proposed that there is no meaningful difference between large fluvial fans (LFF) and floodplains, because the building blocks of both are channel-levee-overbank deposits. Sediment bodies at the LFF scale (greater than 100 km long, fan-shaped in planform), are relatively unstudied although greater than 160 are now identified globally. The following perspectives suggest that the significance of LFF needs to be reconsidered.

Early Cretaceous paleomagnetic results from Marie Byrd Land, West Antarctica: Implications for the Weddellia collage of crustal blocks

Science.gov (United States)

Divenere, Vic; Kent, Dennis V.; Dalziel, Ian W. D.

1995-05-01

A new approximately 117 Ma paleomagnetic pole has been defined from the study of volcanic and plutonic rocks from the eastern portion Marie Byrd Land (MBL). The new pole (185.6 deg E/56.8 deg S, A(sub 95) = 8.7 deg) implies that the eastern portion of MBL was an integral part of Weddellia, which included the ancestral Antarctic Peninsula, Thurston Island, and Ellsworth-Whitmore Mountains blocks of West Antarctica. This pole is generally similar to a approximately 125 Ma pole from Thurston Island. Both poles call for major clockwise rotation and poleward motion of eastern MBL and Thurston Island between the Early Cretaceous (125-117 Ma) and the mid-Cretaceous (110-100 Ma). We propose that in the Early Cretaceous, eastern MBL and the Eastern Province of New Zealand were part of a continuous active Pacific margin of Gondwana, connecting with the Antarctic Peninsula, and distinct from western MBL, the Western Province of New Zealand, and North Victoria Land. These western terranes are thought to have accreted to Gondwana in the Devonian. Eastern MBL and the Eastern Province of New Zealand amalgamated with western MBL and the Western Province of New Zealand by the mid-Cretaceous. Major Early Cretaceous motions of the Weddellia blocks postdate the estimated initiation of seafloor spreading in the Weddell Sea and therefore may be the result of plate reorganization during the Cretaceous Quiet Zone.

Methane in the Northern West Siberian Basin. Generation, dynamics of the reservoirs and exchange with the atmosphere

International Nuclear Information System (INIS)

Cramer, B.

1997-07-01

Based on compositional data and isotope geochemistry natural gas in northern West Siberia can be divided into three groups. These are: natural gas in Jurassic rocks, natural gas in Neocomian rocks and natural gas from the Aptian to Cenomanian Pokur Formation. Natural gas in Jurassic rocks was generated thermogenically from rocks of the Jurassic Tyumen Formation. Natural gas in Neocomian rocks is also of thermogenic origin, possibly being generated from the organic matter of Lower Cretaceous sediments. The largest accumulation of natural gas occurs in sandstone reservoirs in the Pokur Formation. This gas can be described as a mixture between thermogenic gas from deeper strata and isotopically light almost pure methane. 98.6% of this gas consists of methane with an unusual isotope signature of -51.2 permille. It is not possible to explain the existence of this methane with established concepts of gas generation. A new model was developed to examine the possibility of a thermogenic origin of the isotopically light methane in early mature rocks of the Pokur Formation. Based on pyrolysis experiments and reaction kinetic calculations the model enables the simulation of stable carbon isotope ratios of hydrocarbon components in natural gas. The temperature dependent kinetic isotope fractionation is defined by a difference in the activation energies of 12 C-and 13 C-methane generation. The application of the new method to two coaly sandstones of the Pokur Formation results in a good correspondence between modelled carbon isotope ratios of δ 13 C values of methane in the reservoirs. The mass of methane thermogenically generated within the Pokur Formation under the gas field structures, however, is not sufficient to explain the mass of accumulated methane. (orig./SR) [de

ENSO-Type Signals Recorded in the Late Cretaceous Laminated Sediments of Songliao Basin, Northeast China

Science.gov (United States)

Yu, E.; Wang, C.; Hinnov, L. A.; Wu, H.

2014-12-01

The quasi-periodic, ca. 2-7 year El Niño Southern Oscillation (ENSO) phenomenon globally influences the inter-annual variability of temperature and precipitation. Global warming may increase the frequency of extreme ENSO events. Although the Cretaceous plate tectonic configuration was different from today, the sedimentary record suggests that ENSO-type oscillations had existed at the time of Cretaceous greenhouse conditions. Cored Cretaceous lacustrine sediments from the Songliao Basin in Northeast China (SK-1 cores from the International Continental Drilling Program) potentially offer a partially varved record of Cretaceous paleoclimate. Fourteen polished thin sections from the depth interval 1096.12-1096.53 m with an age of 84.4 Ma were analyzed by optical and scanning electron microscopy (SEM). ImageJ software was applied to extract gray scale curves from optical images at pixel resolution. We tracked minimum values of the gray scale curves to estimate the thickness of each lamina. Five sedimentary structures were recognized: flaser bedding, wavy bedding, lenticular bedding, horizontal bedding, and massive layers. The mean layer thicknesses with different sedimentary structures range from 116 to 162mm, very close to the mean sedimentation rate estimated for this sampled interval, 135mm/year, indicating that the layers bounded by pure clay lamina with the minimum gray values are varves. SEM images indicate that a varve is composed, in succession, of one lamina rich in coarse silt, one lamina rich in fine silt, one clay-rich lamina with some silt, and one clay-rich lamina. This suggests that a Cretaceous year featured four distinct depositional seasons, two of which were rainy and the others were lacking precipitation. Spectral analysis of extended intervals of the tuned gray scale curve indicates the presence of inter-annual periodicities of 2.2-2.7 yr, 3.5-6.1 year, and 10.1-14.5 year consistent with those of modern ENSO cycles and solar cycles, as well as

The mid-cretaceous water bearer: Isotope mass balance quantification of the Albian hydrologic cycle

Science.gov (United States)

Ufnar, David F.; Gonzalez, Luis A.; Ludvigson, Greg A.; Brenner, Richard L.; Witzke, B.J.

2002-01-01

A latitudinal gradient in meteoric ??18O compositions compiled from paleosol sphaerosiderites throughout the Cretaceous Western Interior Basin (KWIB) (34-75??N paleolatitude) exhibits a steeper, more depleted trend than modern (predicted) values (3.0??? [34??N latitude] to 9.7??? [75??N] lighter). Furthermore, the sphaerosiderite meteoric ??18O latitudinal gradient is significantly steeper and more depleted (5.8??? [34??N] to 13.8??? [75??N] lighter) than a predicted gradient for the warm mid-Cretaceous using modern empirical temperature-??18O precipitation relationships. We have suggested that the steeper and more depleted (relative to the modern theoretical gradient) meteoric sphaerosiderite ??18O latitudinal gradient resulted from increased air mass rainout effects in coastal areas of the KWIB during the mid-Cretaceous. The sphaerosiderite isotopic data have been used to constrain a mass balance model of the hydrologic cycle in the northern hemisphere and to quantify precipitation rates of the equable 'greenhouse' Albian Stage in the KWIB. The mass balance model tracks the evolving isotopic composition of an air mass and its precipitation, and is driven by latitudinal temperature gradients. Our simulations indicate that significant increases in Albian precipitation (34-52%) and evaporation fluxes (76-96%) are required to reproduce the difference between modern and Albian meteoric siderite ??18O latitudinal gradients. Calculations of precipitation rates from model outputs suggest mid-high latitude precipitation rates greatly exceeded modern rates (156-220% greater in mid latitudes [2600-3300 mm/yr], 99% greater at high latitudes [550 mm/yr]). The calculated precipitation rates are significantly different from the precipitation rates predicted by some recent general circulation models (GCMs) for the warm Cretaceous, particularly in the mid to high latitudes. Our mass balance model by no means replaces GCMs. However, it is a simple and effective means of obtaining

Gateways and Water Mass Mixing in the Late Cretaceous North Atlantic

Science.gov (United States)

Asgharian Rostami, M.; Martin, E. E.; MacLeod, K. G.; Poulsen, C. J.; Vande Guchte, A.; Haynes, S.

2017-12-01

Regions of intermediate/deep water formation and water-mass mixing in the North Atlantic are poorly defined for the Late Cretaceous, a time of gateway evolution and cooler conditions following the Mid Cretaceous greenhouse. Improved proxy data combined with modeling efforts are required to effectively evaluate the relationship between CO2, paleogeography, and circulation during this cooler interval. We analyzed and compiled latest Cretaceous (79 - 66 Ma) ɛNd and δ13C records from seven bathyal (paleodepths 0.2 - 2 km) and eight abyssal (paleodepths > 2 km) sites in the North Atlantic. Data suggest local downwelling of Northern Component Water (NCW; ɛNd -9.5 and δ13C 1.7 ‰) is the primary source of intermediate/deep water masses in the basin. As this water flows southward and ages, δ13C values decrease and ɛNd values increase; however, additional chemical changes at several sites require mixing with contributions from several additional water masses. Lower ɛNd ( -10) and higher δ13C ( 1.9 ‰) values in the deep NW part of the basin indicate proximal contributions from a region draining old continental crust, potentially representing deep convection following opening of the Labrador Sea. In the deep NE Iberian Basin, higher ɛNd ( -7) and lower δ13C ( 0.8 ‰) during the Campanian suggest mixing with a Tethyan source (ɛNd -7 and δ13C 0.1 ‰) whose importance decreased with restriction of that gateway in the Maastrichtian. Data from bathyal sites suggest additional mixing. In the SE Cape Verde region, observed ɛNd variations from -10 in the Campanian to -13 and -12 in the early and late Maastrichtian, respectively, may record variations in output rates of Tethyan and/or NCW sources and Demerara Bottom Water (ɛNd -16), a proposed warm saline intermediate water mass formed in shallow, equatorial seas. Pacific inflow through the Caribbean gateway impacts intermediate sites at Blake Nose (ɛNd values -8), particularly the shallowest site during the late

Press/Pulse: Explaining selective terrestrial extinctions at the Cretaceous/Palaeogene boundary

Science.gov (United States)

Arens, Nan Crystal

2010-05-01

Single-cause mass extinction scenarios require extreme conditions to generate sufficiently strong kill mechanisms. Such dire effects are commonly at odds with the taxonomic selectivity that characterizes most extinction events. In response, some researchers have proposed that the interaction of a variety of factors typify episodes of elevated extinction. Previous work (Arens & West 2008 Paleobiology 34:456-471) has shown that a combination of press and pulse disturbances increases the probability of elevated extinction. The press/pulse contrast is borrowed from community ecology, where researchers have long recognized that the ecological response to long-term stress differs from that of an instantaneous catastrophe. Scaled to the macroevolutionary level, press disturbances alter community composition by placing multigenerational stress on populations. Press disturbances do not necessarily cause mortality, but reduce population size by a variety of mechanisms such as curtailed reproduction. Pulse disturbances are sudden catastrophic events that cause extensive mortality. Either press or pulse disturbances of sufficient magnitude can cause extinction, however elevated extinction occurs more commonly during the coincidence of lower-magnitude press and pulse events. The Cretaceous/Palaeogene (K/P) extinction is one of the best examples of a press/pulse extinction. Deccan Trap volcanism, which straddled the K/P boundary, altered atmospheric composition and climate. This episodic volcanism likely contributed to the climate instability observed in terrestrial ecosystems and exerted press stress. Pulse disturbance was produced by bolide impact, which punctuated the end of the Cretaceous. The press/pulse mechanism also more effectively explains selectivity in terrestrial vertebrate and plant extinctions at the K/P boundary than do single-mechanisms scenarios. For example, why do environmentally sensitive vertebrates such as amphibians experience no extinction? And why do

Pleistocene-Holocene sedimentation of Solimões-Amazon fluvial system between the tributaries Negro and Madeira, Central Amazon

Directory of Open Access Journals (Sweden)

Eliezer Senna Gonçalves Júnior

Full Text Available ABSTRACT: In the scope of Solimões-Amazon fluvial system between the Negro and Madeira tributaries, three levels of Quaternary fluvial terraces overlie the Alter do Chão and Novo Remanso formations further than 100 km southward its current main channel. Smooth undulated topography presenting low drainages density formed by sparse secondary plain channels and rounded lakes characterizes these deposits. Internally, they show point bars morphology constituted by intercalated layers of mud (silt and clay and sand forming an inclined heterolithic stratification. The asymmetric distribution of fluvial terraces allied to the records of old scroll-bars features and paleochannels in many extensions of the Solimões River suggests the predominance of a meander pattern between 240 to 6 kyears. On the other hand, the development of the current anabranching pattern took place in the last six kyears due to the Holocene sea-level rise, besides the action of neotectonics and rainforest establishment related to the increase of humidity in Amazonia.

A new ‘superassemblage’ model explaining proximal-to-distal and lateral facies changes in fluvial environments, based on the Proterozoic Sanjauli Formation (Lesser Himalaya, India

Directory of Open Access Journals (Sweden)

Ananya Mukhopadhyay

2016-09-01

Full Text Available Facies analysis of fluvial deposits of the Proterozoic Sanjauli Formation in the Lesser Himalaya was combined with an architectural analysis. On this basis, a model was developed that may be applied to other fluvial systems as well, whether old or recent. The new model, which might be considered as an assemblage of previous models, explains lateral variations in architecture and facies but is not in all respects consistent with the standard fluvial models. The Sanjauli fluvial model is unique in that it deals with lateral facies variations due to shifts of the base-level along with fluctuations in accommodation space owing to changes in palaeoclimate.

Assessing the Effects of Climate on Global Fluvial Discharge Variability

Science.gov (United States)

Hansford, M. R.; Plink-Bjorklund, P.

2017-12-01

Plink-Bjorklund (2015) established the link between precipitation seasonality and river discharge variability in the monsoon domain and subtropical rivers (see also Leier et al, 2005; Fielding et al., 2009), resulting in distinct morphodynamic processes and a sedimentary record distinct from perennial precipitation zone in tropical rainforest zone and mid latitudes. This study further develops our understanding of discharge variability using a modern global river database created with data from the Global Runoff Data Centre (GRDC). The database consists of daily discharge for 595 river stations and examines them using a series of discharge variability indexes (DVI) on different temporal scales to examine how discharge variability occurs in river systems around the globe. These indexes examine discharge of individual days and monthly averages that allows for comparison of river systems against each other, regardless of size of the river. Comparing river discharge patterns in seven climate zones (arid, cold, humid subtropics, monsoonal, polar, rainforest, and temperate) based off the Koppen-Geiger climate classifications reveals a first order climatic control on discharge patterns and correspondingly sediment transport. Four groupings of discharge patterns emerge when coming climate zones and DVI: persistent, moderate, seasonal, and erratic. This dataset has incredible predictive power about the nature of discharge in fluvial systems around the world. These seasonal effects on surface water supply affects river morphodynamics and sedimentation on a wide timeframe, ranging from large single events to an inter-annual or even decadal timeframe. The resulting sedimentary deposits lead to differences in fluvial architecture on a range of depositional scales from sedimentary structures and bedforms to channel complex systems. These differences are important to accurately model for several reasons, ranging from stratigraphic and paleoenviromental reconstructions to more

Low ecological disparity in Early Cretaceous birds

Science.gov (United States)

Mitchell, Jonathan S.; Makovicky, Peter J.

2014-01-01

Ecological divergence is thought to be coupled with evolutionary radiations, yet the strength of this coupling is unclear. When birds diversified ecologically has received much less attention than their hotly debated crown divergence time. Here, we quantify how accurately skeletal morphology can predict ecology in living and extinct birds, and show that the earliest known assemblage of birds (= pygostylians) from the Jehol Biota (≈ 125 Ma) was substantially impoverished ecologically. The Jehol avifauna has few representatives of highly preservable ecomorphs (e.g. aquatic forms) and a notable lack of ecomorphological overlap with the pterosaur assemblage (e.g. no large or aerially foraging pygostylians). Comparisons of the Jehol functional diversity with modern and subfossil avian assemblages show that taphonomic bias alone cannot explain the ecomorphological impoverishment. However, evolutionary simulations suggest that the constrained ecological diversity of the Early Cretaceous pygostylians is consistent with what is expected from a relatively young radiation. Regardless of the proximate biological explanation, the anomalously low functional diversity of the Jehol birds is evidence both for ecological vacancies in Cretaceous ecosystems, which were subsequently filled by the radiation of crown Aves, and for discordance between taxonomic richness and ecological diversity in the best-known Mesozoic ecosystem. PMID:24870044

Sedimentary environments and hydrocarbon potential of cretaceous rocks of indus basin, Pakistan

International Nuclear Information System (INIS)

Sheikh, S.A.; Naseem, S.

1999-01-01

Cretaceous rocks of Indus Basin of Pakistan are dominated by clastics with subordinate limestone towards the top. These rocks represent shelf facies and were deposited in deltaic to reducing marine conditions at variable depths. Indications of a silled basin with restricted circulation are also present. Cretaceous fine clastics/carbonates have good source and reservoir qualities. Variable geothermal gradients in different parts of basin have placed these rocks at different maturity levels; i.e. from oil to condensate and to gas. The potential of these rocks has been proved by several oil and gas discoveries particularly in the Central and Southern provinces of Indus Basin. (author)

Reservoir architecture and tough gas reservoir potential of fluvial crevasse-splay deposits

NARCIS (Netherlands)

Van Toorenenburg, K.A.; Donselaar, M.E.; Weltje, G.J.

2015-01-01

Unconventional tough gas reservoirs in low-net-to-gross fluvial stratigraphic intervals may constitute a secondary source of fossil energy to prolong the gas supply in the future. To date, however, production from these thin-bedded, fine-grained reservoirs has been hampered by the economic risks

A sequence of events across the Cretaceous-Tertiary boundary

NARCIS (Netherlands)

Smit, J.; Romein, A.J.T.

1985-01-01

The lithological and biological sequence of events across the Cretaceous-Tertiary (K/T), as developed in thick and complete landbased sections and termed the standard K/T event sequence, is also found in many DSDP cores from all over the globe. Microtektite-like spherules have been found in

Extreme Changes in Stream Geomorphic Conditions induced by Fluvial Scour in Bridges

Science.gov (United States)

Özcan, O.; Ozcan, O.

2016-12-01

The numerous complexities associated with bridge scour have caused scour to be one of the most active topics of stream geomorphic research. The assessment of local scouring mechanism around bridge piers provides information for decision-making regarding the pile footing design, predicting the safety of bridges under critical scoured conditions, and as a result, may help prevent unnecessary loses. In the study, bridge design plans and HEC-RAS modeling were used for the assessment of changes in stream geomorphic conditions. The derived fluvial scour depths were compared with the field measurements and the empirical formula which is based on stream flow discharge rate, streambed condition and shape of river. Preliminary results revealed that bridge damage resulting from the flood event in 2003 induced substantial scour around bridge piles. Afterwards, significant stream bed change was observed under the influence of fluvial scour in another flood occurred in 2009. Consequently, geomorphic conditions of the stream bed should be considered in the structural design of the bridges.

Carbonate deposition and salt diapirism during the Cretaceous in the Persian Gulf, offshore Iran

OpenAIRE

U. P. Baaske; M. Mutti; F. Baioni; R. Buonaguro; G. Bertozzi; M. A. Naini; C. M. Krawczyk; P. Kukla; R. Littke; H. Stollhofen; D. Schwarzer;  

2004-01-01

The Cretaceous deposits in the Persian Gulf area are part of one of the largest hydrocarbon systems in the world. The stratigraphic evolution of the northern part of the Gulf is, however, poorly constrained. Seismic data from offshore Iran reveal that the shallow water deposition is marked by topographic features like the NNE-SSW trending Qatar-Fars-Arch and salt-related structures (diapirs and salt walls) of smaller scale. These structures were active during the Cretaceous. To examine the ef...

Results of radiocarbon dating of Holocene fluvial sediments from Northeastern Bohemia

International Nuclear Information System (INIS)

Silar, J.; Zeman, A.

1989-01-01

Samples of wood and charcoal from the latest Holocene fluvial sediments under the lowest surface of alluvial plains were dated by radiocarbon in order to check paleomagnetic data at four sites in northeastern Bohemia. The results are presented as funcorrected 14 C ages and dendrochronologically corrected ages. Two samples were recent. 4 figs., 1 tab., 3 refs

National Uranium Resource Evaluation: Manhattan Quadrangle, Kansas

International Nuclear Information System (INIS)

Fair, C.L.; Smit, D.E.

1982-08-01

Surface reconnaissance and detailed subsurface studies were conducted in the Manhattan Quadrangle, Kansas, to evaluate uranium favorability using National Uranium Resource Evaluation criteria. These studies were designed in part to follow up airborne radiometric and hydrogeochemical and stream-sediment surveys. More than 600 well records were examined in the subsurface phase of the study. Results of these investigations indicate environments favorable for channel-controlled peneconcordant sandstone uranium deposits in Cretaceous rocks and for Wyoming roll-type deposits in Pennsylvanian sandstones. The Cretaceous sandstone environments exhibit such favorable characteristics as a bottom unconformity, high bed load, braided fluvial channels, large-scale cross-bedding, and one anomalous outcrop. The Pennsylvanian sandstone environments exhibit such favorable characteristics as arkosic cross-bedded sandstones, included pyrite and organic debris, interbedded shales, and gamma-ray log anomalies. Environments considered unfavorable for uranium deposits are limestone and dolomite environments, marine black shale environments, evaporative precipitate environments, and some fluvial sandstone environments. Environments considered unevaluated because not enough data were available include Precambrian plutonic, metamorphic, and sedimentary rocks, even though a large number of thin sections were available for study

Astronomical calibration of the Maastrichtian (Late Cretaceous)

DEFF Research Database (Denmark)

Husson, Dorothée; Galbrun, Bruno; Laskar, Jacques

2011-01-01

/Pg boundary, considering the uncertainty of the long-term variation of the 405 ka eccentricity cycle. The first proposal provides a Cretaceous/Paleogene boundary age of 65.59 ± 0.07 Ma and the second an age of 66 ± 0.07 Ma, which is coherent with the most recent radio-isotopic datings. Magnetochron boundaries...... and the Campanian/Maastrichtian boundary are dated relative to these numerical ages of the K/Pg boundary....

Climatic implications of correlated upper Pleistocene glacial and fluvial deposits on the Cinca and Gallego rivers, NE Spain

Energy Technology Data Exchange (ETDEWEB)

Lewis, Claudia J [Los Alamos National Laboratory; Mcdonald, Eric [NON LANL; Sancho, Carlos [NON LANL; Pena, Jose- Luis [NON LANL

2008-01-01

We correlate Upper Pleistocene glacial and fluvial deposits of the Cinca and Gallego River valleys (south central Pyrenees and Ebro basin, Spain) using geomorphic position, luminescence dates, and time-related trends in soil development. The ages obtained from glacial deposits indicate glacial periods at 85 {+-} 5 ka, 64 {+-} 11 ka, and 36 {+-} 3 ka (from glacial till) and 20 {+-} 3 ka (from loess). The fluvial drainage system, fed by glaciers in the headwaters, developed extensive terrace systems in the Cinca River valley at 178 {+-} 21 ka, 97 {+-} 16 ka, 61 {+-} 4 ka, 47 {+-} 4 ka, and 11 {+-} 1 ka, and in the Gallego River valley at 151 {+-} 11 ka, 68 {+-} 7 ka, and 45 {+-} 3 ka. The times of maximum geomorphic activity related to cold phases coincide with Late Pleistocene marine isotope stages and heinrich events. The maximum extent of glaciers during the last glacial occurred at 64 {+-} 11 ka, and the terraces correlated with this glacial phase are the most extensive in both the Cinca (61 {+-} 4 ka) and Gallego (68 {+-} 7 ka) valleys, indicating a strong increase in fluvial discharge and availability of sediments related to the transition to deglaciation. The global Last Glacial Maximum is scarcely represented in the south central Pyrenees owing to dominantly dry conditions at that time. Precipitation must be controlled by the position of the Iberian Peninsula with respect to the North Atlantic atmospheric circulation system. The glacial systems and the associated fluvial dynamic seem sensitive to (1) global climate changes controlled by insolation, (2) North Atlantic thermohaline circulation influenced by freshwater pulses into the North Atlantic, and (3) anomalies in atmospheric circulation in the North Atlantic controlling precipitation on the Iberian peninsula. The model of glacial and fluvial evolution during the Late Pleistocene in northern Spain could be extrapolated to other glaciated mountainous areas in southern Europe.

Reflexiones y enfoques en la conservación y restauración de ríos: georrestauración y pensamiento fluvial

OpenAIRE

Horacio, Jesús

2015-01-01

En los últimos años las sociedades más avanzadas se comienzan a replantear los principios y métodos aplicados para la gestión de los ríos. Este cambio de tendencia en la forma de pensar acerca de nuestro patrimonio fluvial es lo que se denomina en este trabajo: pensamiento fluvial. Este pensamiento implica derrocar ideas incompletas o erróneas sobre qué es un río y aceptarlo como un sistema natural dinámico. Pero el pensamiento fluvial invita también a discutir sobre la forma de conservar y r...

Chemical Remagnetization of Jurassic Carbonates and a Primary Paleolatitude of Lower Cretaceous Volcaniclastic Rocks of the Tibetan Himalaya

Science.gov (United States)

Huang, W.; Van Hinsbergen, D. J. J.; Dekkers, M. J.; Garzanti, E.; Dupont Nivet, G.; Lippert, P. C.; Li, X.; Maffione, M.; Langereis, C. G.; Hu, X.; Guo, Z.; Kapp, P. A.

2014-12-01

Paleolatitudes for the Tibetan Himalaya Zone based on paleomagnetic inclinations provide kinematic constraints of the passive northern Indian margin and the extent of 'Greater India' before the India-Asia collision. Here, we present a paleomagnetic investigation of the Jurassic (carbonates) to Lower Cretaceous (volcaniclastic rocks) Wölong section of the Tibetan Himalaya in the Everest region. The carbonates yield positive fold tests, suggesting that the remanent magnetizations have a pre-folding origin. However, detailed paleomagnetic analyses, rock magnetic tests, end-member modeling of acquisition curves of isothermal remanent magnetization, and petrographic studies reveal that the magnetic carrier of the Jurassic carbonates is authigenic magnetite, whereas the dominant magnetic carrier of the Lower Cretaceous volcaniclastic rocks is detrital magnetite. We conclude that the Jurassic carbonates were remagnetized, whereas the Lower Cretaceous volcaniclastics retain a primary remanence. We hypothesize that remagnetization of the Jurassic carbonates was probably caused by the oxidation of early diagenetic pyrite to magnetite within the time interval at ~86-84 Ma during the latest Cretaceous Normal Superchron and earliest deposition of Cretaceous oceanic red beds in the Tibetan Himalaya. The remagnetization of the limestones prevents determining the size of 'Greater India' during Jurassic time. Instead, a paleolatitude of the Tibetan Himalaya of 23.8±2.1° S at ~86-84 Ma is suggested. This value is lower than the expected paleolatitude of India from apparent polar wander path (APWP). The volcaniclastic rocks with the primary remanence, however, yielded a Lower Cretaceous paleolatitude of Tibetan Himalaya of 55.5±3° S, fitting well with the APWP of India.

Late Cretaceous origin of the rice tribe provides evidence for early diversification in Poaceae.

Science.gov (United States)

Prasad, V; Strömberg, C A E; Leaché, A D; Samant, B; Patnaik, R; Tang, L; Mohabey, D M; Ge, S; Sahni, A

2011-09-20

Rice and its relatives are a focal point in agricultural and evolutionary science, but a paucity of fossils has obscured their deep-time history. Previously described cuticles with silica bodies (phytoliths) from the Late Cretaceous period (67-65 Ma) of India indicate that, by the latest Cretaceous, the grass family (Poaceae) consisted of members of the modern subclades PACMAD (Panicoideae-Aristidoideae-Chloridoideae-Micrairoideae-Arundinoideae-Danthonioideae) and BEP (Bambusoideae-Ehrhartoideae-Pooideae), including a taxon with proposed affinities to Ehrhartoideae. Here we describe additional fossils and show that, based on phylogenetic analyses that combine molecular genetic data and epidermal and phytolith features across Poaceae, these can be assigned to the rice tribe, Oryzeae, of grass subfamily Ehrhartoideae. The new Oryzeae fossils suggest substantial diversification within Ehrhartoideae by the Late Cretaceous, pushing back the time of origin of Poaceae as a whole. These results, therefore, necessitate a re-evaluation of current models for grass evolution and palaeobiogeography.

Palaeoenvironments and facies on a progressively flooded rocky island (Upper Cenomanian – Lower Turonian, Bohemian Cretaceous Basin)

Czech Academy of Sciences Publication Activity Database

Žítt, Jiří; Vodrážka, R.; Hradecká, L.; Svobodová, Marcela

2010-01-01

Roč. 179, - (2010), s. 223-234 ISSN 1802-6842 Institutional research plan: CEZ:AV0Z30130516 Keywords : Cretaceous island * weathering * geomorphology * sedimentary environments * biostratigraphy * Upper Cenomanian-Lower Turonian * Bohemian Cretaceous Basin Subject RIV: DB - Geology ; Mineralogy http://www.nm.cz/publikace/archiv-en.php?id=1&rok=179&f_=Show

Soil development on loess overlying Cretaceous sediments and Devonian limestones

Czech Academy of Sciences Publication Activity Database

Žigová, Anna; Šťastný, Martin

2015-01-01

Roč. 12, č. 3 (2015), s. 267-278 ISSN 1214-9705 Institutional support: RVO:67985831 Keywords : loess * Cretaceous and Devonian rocks * mineral composition * soil development * Luvic Chernozem * Albic Luvisol Subject RIV: DF - Soil Science Impact factor: 0.561, year: 2015

Fluvial geomorphology and aquatic-to-terrestrial Hg export are weakly coupled in small urban streams of Columbus, Ohio

Science.gov (United States)

Sullivan, S. Mažeika P.; Boaz, Lindsey E.; Hossler, Katie

2016-04-01

Although mercury (Hg) contamination is common in stream ecosystems, mechanisms governing bioavailability and bioaccumulation in fluvial systems remain poorly resolved as compared to lentic systems. In particular, streams in urbanized catchments are subject to fluvial geomorphic alterations that may contribute to Hg distribution, bioaccumulation, and export across the aquatic-to-terrestrial boundary. In 12 streams of urban Columbus, Ohio, we investigated the influence of fluvial geomorphic characteristics related to channel geometry, streamflow, and sediment size and distribution on (1) Hg concentrations in sediment and body burdens in benthic larval and adult emergent aquatic insects and (2) aquatic-to-terrestrial contaminant transfer to common riparian spiders of the families Pisauridae and Tetragnathidae via changes in aquatic insect Hg body burdens as well as in aquatic insect density and community composition. Hydrogeomorphic characteristics were weakly related to Hg body burdens in emergent insects (channel geometry) and tetragnathid spiders (streamflow), but not to Hg concentrations in sediment or benthic insects. Streamflow characteristics were also related to emergent insect density, while wider channels were associated with benthic insect community shifts toward smaller-bodied and more tolerant taxa (e.g., Chironomidae). Thus, our results provide initial evidence that fluvial geomorphology may influence aquatic-to-terrestrial contaminant Hg transfer through the collective effects on emergent insect body burdens as well as on aquatic insect community composition and abundance.

Late Cretaceous paleosols as paleoclimate proxies of high-latitude Southern Hemisphere: Mata Amarilla Formation, Patagonia, Argentina

Science.gov (United States)

Varela, Augusto N.; Raigemborn, M. Sol; Richiano, Sebastián; White, Tim; Poiré, Daniel G.; Lizzoli, Sabrina

2018-01-01

Although there is general consensus that a global greenhouse climate characterized the mid-Cretaceous, details of the climate state of the mid-Cretaceous Southern Hemisphere are less clearly understood. In particular, continental paleoclimate reconstructions are scarce and exclusively derived from paleontological records. Using paleosol-derived climofunction studies of the mid- to Upper Cretaceous Mata Amarilla Formation, southern Patagonia, Argentina, we present a reconstruction of the mid-Cretaceous climate of southern South America. Our results indicate that at 60° south paleolatitude during the Cenomanian-Santonian stages, the climate was subtropical temperate-warm (12 °C ± 2.1 °C) and humid (1404 ± 108 mm/yr) with marked rainfall seasonality. These results are consistent with both previous estimations from the fossil floras of the Mata Amarilla Formation and other units of the Southern Hemisphere, and with the previous observations of the displacement of tropical and subtropical floras towards the poles in both hemispheres. The data presented here show a more marked seasonality and slightly lower mean annual precipitation and mean annual temperature values than those recorded at the same paleolatitudes in the Northern Hemisphere.

Fluvial incision by the Qingyijiang River on the northern fringe of Mt. Huangshan, eastern China: Responses to weakening of the East Asian summer monsoon

Science.gov (United States)

Hu, Chunsheng; Liu, Shaochen; Hu, Chenqi; Xu, Guanglai; Zhou, Yingqiu

2017-12-01

This paper focuses on climatic and tectonic controls to determine their relative importance to the Quaternary fluvial incision by the Qingyijiang River, eastern China. The Qingyijiang, which is one of longest tributaries of the lower Yangtze River, drains the northern piedmont of Mt. Huangshan. A field survey focused on three natural sections of the Qingyijiang in the Jingxian basin, where a well-preserved sequence of one alluvial platform (P) and three fluvial terraces (T3, T2, and T1) is presented. The heights of the platform and the terraces above river level are 65, 40, 20, and 7 m respectively. In this study, electron spin resonance (ESR), optical stimulated luminescence (OSL), and palaeomagnetic dating were applied to reconstruct the fluvial incision history of the Qingyijiang and evaluate the possible influence of tectonic uplift and/or climate change on the fluvial incision. The main results show that (1) the ages of P, T3, T2, and T1 were determined to be ∼ 1300, ∼ 900, ∼ 600, and ∼ 1.5 ka respectively, corresponding to four incision events in the Qingyijiang; (2) the East Asian summer monsoon (EASM) experienced four significant weakening events at 1300, 900, 600, and ∼ 1.5 ka, according to previous research. Correspondingly, we propose that four significant increased periods of regional precipitation occurred at 1300, 900, 600, and ∼ 1.5 ka in the study area because of the negative correlation between the intensity of the EASM and regional precipitation from 1960 to 2012; and (3) fluvial incision by the Qingyijiang arose as a result of the weakening of the EASM in combination with tectonic uplift, determined by matching fluvial incision history of the Qingyijiang with tectonic movement and EASM change. In addition, the weakening of the EASM climatically triggered fluvial incision by the Qingyijiang. This study supports the conclusion that major fluvial incision has been climatically triggered; however, it also suggests that the mechanism of

The reservoir properties of the upper Cretaceous productive deposits at the Pravoberezhnoe field. Kollektornyye svoystva verkhnemelovykh produktivnykh otlozheniy mestorozhdeniya Pravobeiezhnoye

Energy Technology Data Exchange (ETDEWEB)

Merkulov, A.V.; Yengibarov, V.N.

1984-01-01

Based on a set of various studies, an evaluation of the type of upper Cretaceous reservoir in the Pravoberezhnoe field is given. Compared to other fields in the Chechen Ingush Autonomous Soviet Socialist Republic, the upper Cretaceous productive deposits at this field are characterized by poorer reservoir properties. The set of all data indicates that the upper Cretaceous reservoir is analogous to reservoirs of equal age in existing fields in this republic and are cavernous fissured type.

Geologic models and evaluation of undiscovered conventional and continuous oil and gas resources: Upper Cretaceous Austin Chalk

Science.gov (United States)

Pearson, Krystal

2012-01-01

The Upper Cretaceous Austin Chalk forms a low-permeability, onshore Gulf of Mexico reservoir that produces oil and gas from major fractures oriented parallel to the underlying Lower Cretaceous shelf edge. Horizontal drilling links these fracture systems to create an interconnected network that drains the reservoir. Field and well locations along the production trend are controlled by fracture networks. Highly fractured chalk is present along both regional and local fault zones. Fractures are also genetically linked to movement of the underlying Jurassic Louann Salt with tensile fractures forming downdip of salt-related structures creating the most effective reservoirs. Undiscovered accumulations should also be associated with structure-controlled fracture systems because much of the Austin that overlies the Lower Cretaceous shelf edge remains unexplored. The Upper Cretaceous Eagle Ford Shale is the primary source rock for Austin Chalk hydrocarbons. This transgressive marine shale varies in thickness and lithology across the study area and contains both oil- and gas-prone kerogen. The Eagle Ford began generating oil and gas in the early Miocene, and vertical migration through fractures was sufficient to charge the Austin reservoirs.

Phosphorus and nitrogen loading depths in fluvial sediments following manure spill simulations

Science.gov (United States)

Manure spills that enter streams can devastate the aquatic ecosystem. The depth of nitrogen (N) and phosphorus (P) loading in fluvial sediments following a manure spill have not been documented. Thus, the objectives of this study were (i) to determine the depth of N and P contamination as a result o...

Middle Moscovian climate of eastern equatorial Pangea recorded in paleosols and fluvial architecture

Czech Academy of Sciences Publication Activity Database

Opluštil, S.; Lojka, R.; Rosenau, N.A.; Strnad, L.; Sýkorová, Ivana

2015-01-01

Roč. 440, DEC (2015), s. 328-352 ISSN 0031-0182 Institutional support: RVO:67985891 Keywords : Carboniferous paleoclimate * fluvial architectures * paleosols * geochemistry Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.525, year: 2015 http://www.sciencedirect.com/science/article/pii/S0031018215004939

Terpenoid composition and botanical affinity of Cretaceous resins from India and Myanmar

Energy Technology Data Exchange (ETDEWEB)

Dutta, Suryendu; Mallick, Monalisa [Department of Earth Sciences, Indian Institute of Technology-Bombay (India); Kumar, Kishor [Wadia Institute of Himalayan Geology, Uttarakhand (India); Mann, Ulrich [Forschungzentrum Juelich (Germany). Institut fuer Chemie und Dynamik der Geosphaere; Greenwood, Paul F. [John De Laeter Mass Spectrometry and WA Biogeochemistry Centres (M090), University of Western Australia, Crawley (Australia)

2011-01-01

Fossil resins from the Cretaceous sediments of Meghalaya, India and Kachin, Myanmar (Burma) were analysed using Curie point pyrolysis-gas chromatography-mass spectrometry and thermochemolysis gas chromatography-mass spectrometry to help elucidate their botanical source. The major pyrolysis products and methyl-esterified thermochemolysis products of both the resins were abietane and labdane type diterpenoids with minor amount of sesquiterpenoids. The thermochemolysis products also included methyl-16,17-dinor callitrisate, methyl-16,17-dinor dehydroabietate and methyl-8-pimaren-18-oate - the latter two from just the Myanmarese resin. The exclusive presence of both labdane and abietane diterpenoids and the lack of phenolic terpenoids may suggest that the studied Cretaceous resins were derived from Pinaceae (pine family) conifers. (author)

High temporal resolution in situ measurement of the effective particle size characteristics of fluvial suspended sediment.

Science.gov (United States)

Williams, N D; Walling, D E; Leeks, G J L

2007-03-01

This paper reports the use of a LISST-100 device to monitor the effective particle size characteristics of suspended sediment in situ, and at a quasi-continuous temporal resolution. The study site was located on the River Exe at Thorverton, Devon, UK. This device has not previously been utilized in studies of fluvial suspended sediment at the storm event scale, and existing studies of suspended sediment dynamics have not involved such a high temporal resolution for extended periods. An evaluation of the field performance of the instrument is presented, with respect to innovative data collection and analysis techniques. It was found that trends in the effective particle size distribution (EPSD) and degree of flocculation of suspended sediment at the study site were highly complex, and showed significant short-term variability that has not previously been documented in the fluvial environment. The collection of detailed records of EPSD facilitated interpretation of the dynamic evolution of the size characteristics of suspended sediment, in relation to its likely source and delivery and flocculation mechanisms. The influence of measurement frequency is considered in terms of its implications for future studies of the particle size of fluvial suspended sediment employing in situ data acquisition.

Calcium isotopes offer clues on resource partitioning among Cretaceous predatory dinosaurs.

Science.gov (United States)

Hassler, A; Martin, J E; Amiot, R; Tacail, T; Godet, F Arnaud; Allain, R; Balter, V

2018-04-11

Large predators are overabundant in mid-Cretaceous continental dinosaur assemblages of North Africa. Such unbalanced ecosystem structure involves, among predatory dinosaurs, typical abelisaurid or carcharodontosaurid theropods co-occurring with long-snouted spinosaurids of debated ecology. Here, we report calcium (Ca) isotope values from tooth enamel (expressed as δ 44/42 Ca) to investigate resource partitioning in mid-Cretaceous assemblages from Niger (Gadoufaoua) and Morocco (Kem Kem Beds). In both assemblages, spinosaurids display a distinct isotopic signature, the most negative in our dataset. This distinct taxonomic clustering in Ca isotope values observed between spinosaurids and other predators provides unambiguous evidence for niche partitioning at the top of the trophic chains: spinosaurids foraged on aquatic environments while abelisaurid and carcharodontosaurid theropods relied almost exclusively on terrestrial resources. © 2018 The Author(s).

Biostratigraphy of the Cretaceous/Tertiary boundary in the Sirwan Valley (Sulaimani Region, Kurdistan, NE Iraq)

Science.gov (United States)

Sharbazheri, Khalid Mahmood; Ghafor, Imad Mahmood; Muhammed, Qahtan Ahmad

2009-10-01

The Cretaceous/Tertiary (K/T) boundary sequence, which crops out in the studied area is located within the High Folded Zone, in the Sirwan Valley, northeastern Iraq. These units mainly consist of flysch and flysch-type successions of thick clastic beds of Tanjero/Kolosh Formations. A detailed lithostratigraphic study is achieved on the outcropping uppermost part of the Upper Cretaceous successions (upper part of Tanjero Formation) and the lowermost part of the Kolosh Formation. On the basis of the identified planktonic foraminiferal assemblages, five biozones are recorded from the uppermost part of Tanjero Formation and four biozones from the lower part of the Kolosh Formation (Lower Paleocene) in the Sirwan section. The biostratigraphic correlations based on planktonic foraminiferal zonations showed a comparison between the biostratigraphic zones established in this study and other equivalents of the commonly used planktonic zonal scheme around the Cretaceous/Tertiary boundary in and outside Iraq.

A Late Pleistocene linear dune dam record of aeolian-fluvial dynamics at the fringes of the northwestern Negev dunefield

Science.gov (United States)

Roskin, Joel; Bookman, Revital; Friesem, David; Vardi, Jacob

2017-04-01

The paper presents a late Pleistocene aeolian-fluvial record within a linear dune-like structure that partway served as a dune dam. Situated along the southern fringe of the northwestern Negev desert dunefield (Israel) the structure's morphology, orientation, and some of its stratigraphic units partly resemble adjacent west-east extending vegetated linear dunes. Uneven levels of light-colored, fine-grained fluvial deposits (LFFDs) extend to the north and south from the flanks of the studied structure. Abundant Epipalaeolithic sites line the fringes of the LFFDs. The LFFD microstructures of fine graded bedding and clay blocky peds indicate sorting and shrinking of saturated clays in transitional environments between low energy flows to shallow standing water formed by dunes damming a mid-sized drainage system. The structure's architecture of interchanging units of sand with LFFDs indicates interchanging dominances between aeolian sand incursion and winter floods. Sand mobilization associated with powerful winds during the Heinrich 1 event led to dune damming downstream of the structure and within the structure to in-situ sand deposition, partial fluvial erosion, reworking of the sand, and LFFD deposition. Increased sand deposition led to structure growth and blockage of its drainage system that in turn accumulated LFFD units up stream of the structure. Extrapolation of current local fluvial sediment yields indicate that LFFD accretion up to the structure's brim occurred over a short period of several decades. Thin layers of Geometric Kebaran (c. 17.5-14.5 ka cal BP) to Harifian (12-11 ka BP) artifacts within the structure's surface indicates intermittent, repetitive, and short term camping utilizing adjacent water along a timespan of 4-6 kyr. The finds directly imply that the NW Negev LFFDs formed in dune-dammed water bodies which themselves were formed following events of vegetated linear dune elongation. LFFD accumulation persisted as a result of dune dam

Time scales of critical events around the Cretaceous-Paleogene boundary

NARCIS (Netherlands)

Renne, P.R.; Deino, A.L.; Hilgen, F.J.; Kuiper, K.F.; Mark, D.F.; Mitchell III, W.S.; Morgan, L.; Mundil, R.; Smit, J.

2013-01-01

Mass extinctions manifest in Earth's geologic record were turning points in biotic evolution. We present 40Ar/39Ar data that establish synchrony between the Cretaceous-Paleogene boundary and associated mass extinctions with the Chicxulub bolide impact to within 32,000 years. Perturbation of the

Extraterrestrial cause for the Cretaceous-Tertiary extinction

International Nuclear Information System (INIS)

Alvarez, L.W.; Alvarez, W.; Asaro, F.; Michel, H.V.

1980-01-01

Platinum metals are depleted in the earth's crust relative to their cosmic abundance; concentrations of these elements in deep-sea sediments may thus indicate influxes of extraterrestrial material. Deep-sea limestones exposed in Italy, Denmark, and New Zealand show iridium increases of about 30, 160, and 20 times, respectively, above the background level at precisely the time of the Cretaceous-Tertiary extinctions, 65 million years ago. Reasons are given to indicate that this iridium is of extraterrestrial origin, but did not come from a nearby supernova. A hypothesis is suggested which accounts for the extinctions and the iridium observations. Impact of a large earth-crossing asteroid would inject about 60 times the object's mass into the atmosphere as pulverized rock; a fraction of this dust would stay in the stratosphere for several years and be distributed worldwide. The resulting darkness would suppress photosynthesis, and the expected biological consequences match quite closely the extinctions observed in the paleontological record. One prediction of this hypothesis has been verified: the chemical composition of the boundary clay, which is thought to come from the stratospheric dust, is markedly different from that of clay mixed with the Cretaceous and Tertiary limestones, which are chemically similar to each other. Four different independent estimates of the diameter of the asteroid give values that lie in the range 10 +- 4 kilometers

Integrated stratigraphy of the Jurassic-Cretaceous sequences of the Kurovice Quarry, Outer Western Carpathians: correlations and tectonic implications

Czech Academy of Sciences Publication Activity Database

Pruner, Petr; Schnabl, Petr; Čížková, Kristýna; Elbra, Tiiu; Kdýr, Šimon; Svobodová, Andrea; Reháková, D.

2017-01-01

Roč. 120 (2017), s. 216-216 ISSN 1017-8880. [International Symposium on the Cretaceous /10./. 21.08.2017-26.08.2017, Vienna] R&D Projects: GA ČR(CZ) GA16-09979S Institutional support: RVO:67985831 Keywords : stratigraphy * Jurassic-Cretaceous sequences * Western Carpathians Subject RIV: DB - Geology ; Mineralogy

Transport and redistribution of Chernobyl fallout radionuclides by fluvial processes: some preliminary evidence

International Nuclear Information System (INIS)

Walling, D.E.; Bradley, S.B.

1988-01-01

Several measurements of 137 Cs concentrations in suspended sediment transported by the River Severn during the post-Chernobyl period and in recent channel and floodplain deposits along the river emphasise the potential significance of fluvial processes in the transport and concentration of fallout radionuclides. (author)

The impact of disturbance on the dynamics of fluvial processes in mountain landscapes

Czech Academy of Sciences Publication Activity Database

Langhammer, J.; Hartvich, Filip; Kliment, Z.; Jeníček, M.; Bernsteinová (Kaiglová), J.; Vlček, L.; Su, Y.; Štych, P.; Miřijovský, J.

2015-01-01

Roč. 21, č. 1 (2015), s. 105-116 ISSN 1211-7420 Institutional support: RVO:67985891 Keywords : runoff * fluvial dynamics * forest disturbance * climate change * Bohemian Forest Subject RIV: DE - Earth Magnetism, Geodesy, Geography http://www.npsumava.cz/gallery/31/9345-sg_21_1_langhammeretal.pdf

Modelling the impact of regional uplift and local tectonics on fluvial terrace preservation.

NARCIS (Netherlands)

Viveen, W.; Schoorl, J.M.; Veldkamp, A.; Balen, van R.T.

2014-01-01

A terrace formation model (TERRACE) combined with a longitudinal river profile model (FLUVER) was used to simulate fluvial terrace formation and preservation in the northwest Iberian lower Miño River basin under the influence of three tectonic conditions; namely regional vertical uplift, local basin

Effects of Wildfire on Fluvial Sediment Regime through Perturbations in Dry-Ravel

Science.gov (United States)

Florsheim, J. L.; Chin, A.; Kinoshita, A. M.; Nourbakhshbeidokhti, S.; Storesund, R.; Keller, E. A.

2015-12-01

In steep chaparral ecosystems with Mediterranean climate, dry ravel is a natural process resulting from wildfire disturbance that supplies sediment to fluvial systems. When dense chaparral vegetation burns, sediment accumulated on steep hillslopes is released for dry-season transport (dry ravel) down steep hillslopes during or soon after the wildfire. Results of a field study in southern California's Transverse Ranges illustrate the effect of wildfire on fluvial sediment regime in an unregulated chaparral system. Big Sycamore Canyon in the steep Santa Monica Mountains burned during the May 2013 Springs Fire and experienced one small sediment-transporting stormflow during the following winter. We conducted pre- and post-storm field campaigns during the fall and winter following the fire to quantify the effect of wildfire on the fluvial sediment regime. We utilized a sediment mass balance approach in which: 1) sediment supply, consisting primarily of dry ravel-derived deposits composed of relatively fine grained-sediment, was measured in the upstream basin and in the hillslope-channel margin adjacent to the study reach; 2) changes in storage in the study reach were quantified by analyzing the difference between pre- and post-storm channel topography derived from Terrestrial LiDAR Scanning (TLS) and field surveys; and 3) transport from the study reach was estimated as the difference between supply and change in storage where uncertainty is estimated using calculated sediment transport as a comparison. Results demonstrate channel deposition caused by changes in the short-term post-wildfire sediment regime. The increased sediment supply and storage are associated with significant changes in morphology, channel bed-material characteristics, and ecology. These results suggest that dry-ravel processes are an important factor to consider in post-wildfire sediment management.

Facies architecture and high resolution sequence stratigraphy of an aeolian, fluvial and shallow marine system in the Pennsylvanian Piauí Formation, Parnaíba Basin, Brazil

Science.gov (United States)

Vieira, Lucas Valadares; Scherer, Claiton Marlon dos Santos

2017-07-01

The Pennsylvanian Piauí Formation records the deposition of aeolian, fluvial and shallow marine systems accumulated in the cratonic sag Parnaíba basin. Characterization of the facies associations and sequence stratigraphic framework was done by detailed description and logging of outcrops. Six facies associations were recognized: aeolian dunes and interdunes, aeolian sandsheets, fluvial channels, tidally-influenced fluvial channels, shoreface and shoreface-shelf transition. Through correlation of stratigraphic surfaces, the facies associations were organized in system tracts, which formed eight high frequency depositional sequences, bounded by subaerial unconformities. These sequences are composed of a lowstand system tract (LST), that is aeolian-dominated or fluvial-dominated, a transgressive system tract (TST) that is formed by tidally-influenced fluvial channels and/or shoreface and shoreface-shelf transition deposits with retrogradational stacking, and a highstand system tract (HST), which is formed by shoreface-shelf transition and shoreface deposits with progradational stacking. Two low frequency cycles were determined by observing the stacking of the high frequency cycles. The Lower Sequence is characterized by aeolian deposits of the LST and an aggradational base followed by a progressive transgression, defining a general TST. The Upper Sequence is characterized by fluvial deposits and interfluve pedogenesis concurring with the aeolian deposits of the LST and records a subtle regression followed by transgression. The main control on sedimentation in the Piauí Formation was glacioeustasy, which was responsible for the changes in relative sea level. Even though, climate changes were associated with glacioeustatic phases and influenced the aeolian and fluvial deposition.

Resolving the Timing of Events Around the Cretaceous-Paleogene Boundary

Science.gov (United States)

Sprain, Courtney Jean

Despite decades of study, the exact cause of the Cretaceous-Paleogene boundary (KPB) mass extinction remains contentious. Hypothesized scenarios center around two main environmental perturbations: voluminous (>10 6 km3) volcanic eruptions from the Deccan Traps in modern-day India, and the large impact recorded by the Chicxulub crater. The impact hypothesis has gained broad support, bolstered by the discoveries of iridium anomalies, shocked quartz, and spherules at the KPB worldwide, which are contemporaneous with the Chicxulub impact structure. However, evidence for protracted extinctions, particularly in non-marine settings, and paleoenvironmental change associated with climatic swings before the KPB, challenge the notion that the impact was the sole cause of the KPB mass extinction. Despite forty years of study, the relative importance of each of these events is unclear, and one key inhibitor is insufficient resolution of existing geochronology. In this dissertation, I present work developing a high-precision global chronologic framework for the KPB that outlines the temporal sequence of biotic changes (both within the terrestrial and marine realms), climatic changes, and proposed perturbations (i.e. impact, volcanic eruptions) using 40Ar/39Ar geochronology and paleomagnetism. This work is focused on two major areas of study: 1) refining the timing and tempo of terrestrial ecosystem change around the KPB, and 2) calibrating the geomagnetic polarity timescale, and particularly the timing and duration of magnetic polarity chron C29r (the KPB falls about halfway into C29r). First I develop a high-precision chronostratigraphic framework for fluvial sediments within the Hell Creek region, in NE Montana, which is one of the best-studied terrestrial KPB sections worldwide. For this work I dated 15 tephra deposits with +/- 30 ka precision using 40Ar/ 39Ar geochronology, ranging in time from 300 ka before the KPB to 1 Ma after. By tying these results to paleontological

Causes and consequences of short-term sea-level changes in the Cretaceous green- and "hothouse": Topics and context of IGCP Project 609

Science.gov (United States)

Sames, Benjamin; Wagreich, Michael

2015-04-01

In contrast to the well-understood process of glacial eustasy, controlled mainly by waxing and waning of continental ice sheets, significant short-term, i.e. 10s kyr to a few myr (3rd to 4th order cycles) sea-level changes during the Cretaceous major greenhouse episode remain enigmatic. Such cyclic changes are often explained by the presence of ephemeral ice sheets even during the hottest greenhouse phases ("hothouse periods"), such as the mid-Cretaceous. Though Cretaceous global eustasy involves processes like brief glacial episodes (glacio-eustasy) for which evidence was given - at least for the Early Cretaceous and the late Late Cretaceous - other mechanisms have to be taken into consideration for the "hothouse periods" during which continental ice shields are highly improbable, like the storage and release of groundwater (termed "limno-eustasy" or "aquifer-eustasy"), the possible effect and magnitude of which might have been highly underestimated. Investigation of the timing, the causes, and the consequences of significant short-term (i.e. mainly kyr to 100s of kyr) sea-level changes during the last major greenhouse episode of Earth history, the Cretaceous, is the ultimate goal of the UNESCO IGCP (International Geoscience Programme) project number 609 "Climate-environmental deteriorations during greenhouse phases: Causes and consequences of short-term Cretaceous sea-level changes" (2013-2017; http://www.univie.ac.at/igcp609/). This also comprises the global versus regional correlation and extent of the sequences, their cyclicities, as well as the processes and triggering mechanisms for these, and marine to non-marine correlations. Recent refinements of the geological time scale have made major advances for the Cretaceous to yield a resolution comparable to that of younger Earth history. It is now for the first time possible to correlate and date short-term Cretaceous sea-level records with a resolution appropriate for their detailed analysis. Recognized

Dental Disparity and Ecological Stability in Bird-like Dinosaurs prior to the End-Cretaceous Mass Extinction.

Science.gov (United States)

Larson, Derek W; Brown, Caleb M; Evans, David C

2016-05-23

The causes, rate, and selectivity of the end-Cretaceous mass extinction continue to be highly debated [1-5]. Extinction patterns in small, feathered maniraptoran dinosaurs (including birds) are important for understanding extant biodiversity and present an enigma considering the survival of crown group birds (Neornithes) and the extinction of their close kin across the end-Cretaceous boundary [6]. Because of the patchy Cretaceous fossil record of small maniraptorans [7-12], this important transition has not been closely examined in this group. Here, we test the hypothesis that morphological disparity in bird-like dinosaurs was decreasing leading up to the end-Cretaceous mass extinction, as has been hypothesized in some dinosaurs [13, 14]. To test this, we examined tooth morphology, an ecological indicator in fossil reptiles [15-19], from over 3,100 maniraptoran teeth from four groups (Troodontidae, Dromaeosauridae, Richardoestesia, and cf. Aves) across the last 18 million years of the Cretaceous. We demonstrate that tooth disparity, a proxy for variation in feeding ecology, shows no significant decline leading up to the extinction event within any of the groups. Tooth morphospace occupation also remains static over this time interval except for increased size during the early Maastrichtian. Our data provide strong support that extinction within this group occurred suddenly after a prolonged period of ecological stability. To explain this sudden extinction of toothed maniraptorans and the survival of Neornithes, we propose that diet may have been an extinction filter and suggest that granivory associated with an edentulous beak was a key ecological trait in the survival of some lineages. Copyright © 2016 Elsevier Ltd. All rights reserved.

Noble metals in cretaceous/tertiary sediments from El Kef

International Nuclear Information System (INIS)

Kuslys, M.; Kraehenbuehl, U.

1983-01-01

Sediments from El Kef, Tunisia, were analysed by RNAA for Au, Ir and Os. All three elements show a 10-20 fold enrichment at the Cretaceous/Tertiary boundary. This enrichment must be the result of the addition of material with a high concentration of noble metals. It is plausible that this exotic material has an extra-terrestrial origin. (orig.)

Noble metals in Cretaceous/Tertiary sediments from El Kef

International Nuclear Information System (INIS)

Kuslys, M.; Kraehenbuehl, U.

1983-01-01

Sediments from El Kef, Tunisia, were analysed by RNAA for Au, Ir and Os. All three elements show a 10-20 fold enrichment at the Cretaceous/Tertiary boundary. This enrichment must be the result of the addition of material with a high concentration of noble metals. It is plausible that this exotic material has an extraterrestrial origin. (orig.)

Calibrating Late Cretaceous Terrestrial Cyclostratigraphy with High-precision U-Pb Zircon Geochronology: Qingshankou Formation of the Songliao Basin, China

Science.gov (United States)

Wang, T.; Ramezani, J.; Wang, C.

2015-12-01

A continuous succession of Late Cretaceous lacustrine strata has been recovered from the SK-I south (SK-Is) and SKI north (SK-In) boreholes in the long-lived Cretaceous Songliao Basin in Northeast China. Establishing a high-resolution chronostratigraphic framework is a prerequisite for integrating the Songliao record with the global marine Cretaceous. We present high-precision U-Pb zircon geochronology by the chemical abrasion isotope dilution thermal-ionization mass spectrometry method from multiple bentonite core samples from the Late Cretaceous Qingshankou Formation in order to assess the astrochronological model for the Songliao Basin cyclostratigraphy. Our results from the SK-Is core present major improvements in precision and accuracy over the previously published geochronology and allow a cycle-level calibration of the cyclostratigraphy. The resulting choronostratigraphy suggest a good first-order agreement between the radioisotope geochronology and the established astrochronological time scale over the corresponding interval. The dated bentonite beds near the 1780 m depth straddle a prominent oil shale layer of the Qingshankou Formation, which records a basin-wide lake anoxic event (LAE1), providing a direct age constraint for the LAE1. The latter appears to coincide in time with the Late Cretaceous (Turonian) global sea level change event Tu4 presently constrained at 91.8 Ma.

Fluvial organic carbon flux from an eroding peatland catchment, southern Pennines, UK

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R. R. Pawson

2008-03-01

Full Text Available This study investigates for the first time the relative importance of dissolved organic carbon (DOC and particulate organic carbon (POC in the fluvial carbon flux from an actively eroding peatland catchment in the southern Pennines, UK. Event scale variability in DOC and POC was examined and the annual flux of fluvial organic carbon was estimated for the catchment. At the event scale, both DOC and POC were found to increase with discharge, with event based POC export accounting for 95% of flux in only 8% of the time. On an annual cycle, exports of 35.14 t organic carbon (OC are estimated from the catchment, which represents an areal value of 92.47 g C m⁻² a⁻¹. POC was the most significant form of organic carbon export, accounting for 80% of the estimated flux. This suggests that more research is required on both the fate of POC and the rates of POC export in eroding peatland catchments.

The Amazonian Craton and its influence on past fluvial systems (Mesozoic-Cenozoic, Amazonia)

NARCIS (Netherlands)

Hoorn, C.; Roddaz, M.; Dino, R.; Soares, E.; Uba, C.; Ochoa-Lozano, D.; Mapes, R.; Hoorn, C.; Wesselingh, F.P.

2010-01-01

The Amazonian Craton is an old geological feature of Archaean/Proterozoic age that has determined the character of fluvial systems in Amazonia throughout most of its past. This situation radically changed during the Cenozoic, when uplift of the Andes reshaped the relief and drainage patterns of

Sedimentary Provenance Constraints on the Middle Jurassic to Late Cretaceous Paleogeography of the Sichuan Basin, SW China

Science.gov (United States)

Li, Y.; He, D.; Li, D.; Lu, R.

2017-12-01

Sedimentary provenance of the Middle Jurassic to Late Cretaceous sediments in the Sichuan Basin is constrained by sandstone petrology and detrital zircon U-Pb geochronology, which provides critical insights into mid-late Mesozoic paleogeographic evolution of the Sichuan Basin. Petrographic analyses of 22 sandstone samples indicate moderate to high mature sediments and are primarily derived from cratonic or recycled sources. U-Pb age data for the Middle Jurassic to Late Cretaceous detrital zircons generally show populations at 130-200, 200-330, 400-490, 680-890, 1730-1960, and 2360-2600 Ma, with up-section variations. The Middle Jurassic sediments contain a relatively high density of 1.85 and 2.5 Ga zircons and a low density of the 800 Ma zircons, which are consistent with derivation mainly from the Songpan-Ganzi terrane and the South Qinling belt, and secondarily from the Western Jiangnan Orogen. The Late Jurassic and Early Cretaceous sedimentation with a scattered age distribution shared common multiple-source to sink systems that were predominantly draining towards the south and southeast, but increasingly drained southward, and were later disrupted by a synchronous northeastward drainage capture. Late Cretaceous sediments have a distinct reduction in Block.

New Mesoscale Fluvial Landscapes - Seismic Geomorphology and Exploration

Science.gov (United States)

Wilkinson, M. J.

2013-01-01

Megafans (100-600 km radius) are very large alluvial fans that cover significant areas on most continents, the surprising finding of recent global surveys. The number of such fans and patterns of sedimentation on them provides new mesoscale architectures that can now be applied on continental fluvial depositional systems, and therefore on. Megafan-scale reconstructions underground as yet have not been attempted. Seismic surveys offer new possibilities in identifying the following prospective situations at potentially unsuspected locations: (i) sand concentrations points, (ii) sand-mud continuums at the mesoscale, (iii) paleo-valley forms in these generally unvalleyed landscapes, (iv) stratigraphic traps, and (v) structural traps.

Transport and deposition of plutonium-contaminated sediments by fluvial processes, Los Alamos Canyon, New Mexico

International Nuclear Information System (INIS)

Graf, W.L.

1996-01-01

Between 1945 and 1952 the development of nuclear weapons at Los Alamos National Laboratory, New Mexico, resulted in the disposal of plutonium into the alluvium of nearby Acid and (to a lesser degree) DP Canyons. The purpose of this paper is to explore the connection between the disposal sites and the main river, a 20 km link formed by the fluvial system of Acid, Pueblo, DP, and Los Alamos Canyons. Empirical data from 15 yr of annual sediment sampling throughout the canyon system has produced 458 observations of plutonium concentration in fluvial sediments. These data show that, overall, mean plutonium concentrations in fluvial sediment decline from 10,000 fCi/g near the disposal area to 100 fCi/g at the confluence of the canyon system and the Rio Grande. Simulations using a computer model for water, sediment, and plutonium routing in the canyon system show that discharges as large as the 25 yr event would fail to develop enough transport capacity to completely remove the contaminated sediments from Pueblo Canyon. Lesser flows would move some materials to the Rio Grande by remobilization of stored sediments. The simulations also show that the deposits and their contaminants have a predictable geography because they occur where stream power is low, hydraulic resistance is high, and the geologic and/or geomorphic conditions provide enough space for storage. 38 refs., 13 figs., 1 tab

A critical transition in leaf evolution facilitated the Cretaceous angiosperm revolution

NARCIS (Netherlands)

Boer, H.J. de; Eppinga, M.B.; Wassen, M.J.; Dekker, S.C.

2012-01-01

The revolutionary rise of broad-leaved (flowering) angiosperm plant species during the Cretaceous initiated a global ecological transformation towards modern biodiversity. Still, the mechanisms involved in this angiosperm radiation remain enigmatic. Here we show that the period of rapid

Re-evaluating luminescence burial doses and bleaching of fluvial deposits using Bayesian computational statistics.

NARCIS (Netherlands)

Cunningham, A.C.; Wallinga, J.; Versendaal, Alice; Makaske, A.; Middelkoop, H.; Hobo, N.

2015-01-01

The optically stimulated luminescence (OSL) signal from fluvial sediment often contains a remnant from the previous deposition cycle, leading to a partially bleached equivalent-dose distribution. Although identification of the burial dose is of primary concern, the degree of bleaching could

Re-evaluating luminescence burial doses and bleaching of fluvial deposits using Bayesian computational statistics

NARCIS (Netherlands)

Cunningham, A. C.; Wallinga, J.; Hobo, N.; Versendaal, A. J.; Makaske, B.; Middelkoop, H.

2015-01-01

The optically stimulated luminescence (OSL) signal from fluvial sediment often contains a remnant from the previous deposition cycle, leading to a partially bleached equivalent-dose distribution. Although identification of the burial dose is of primary concern, the degree of bleaching could

Late cretaceous aquatic plant world in Patagonia, Argentina.

Directory of Open Access Journals (Sweden)

N Rubén Cúneo

Full Text Available In this contribution, we describe latest Cretaceous aquatic plant communities from the La Colonia Formation, Patagonia, Argentina, based on their taxonomic components and paleoecological attributes. The La Colonia Formation is a geological unit deposited during a Maastrichtian-Danian transgressive episode of the South Atlantic Ocean. This event resulted in the deposition of a series of fine-grained sediments associated with lagoon systems occurring along irregular coastal plains in northern Patagonia. These deposits preserved a diverse biota, including aquatic and terrestrial plants and animals. The aquatic macrophytes can be broadly divided into two groups: free-floating and rooted, the latter with emergent or floating leaves. Free-floating macrophytes include ferns in Salviniaceae (Azolla and Paleoazolla and a monocot (Araceae. Floating microphytes include green algae (Botryoccocus, Pediastrum and Zygnemataceae. Among the rooted components, marsileaceous water ferns (including Regnellidium and an extinct form and the eudicot angiosperm Nelumbo (Nelumbonaceae are the dominant groups. Terrestrial plants occurring in the vegetation surrounding the lagoons include monocots (palms and Typhaceae, ferns with affinities to Dicksoniaceae, conifers, and dicots. A reconstruction of the aquatic plant paleocommuniy is provided based on the distribution of the fossils along a freshwater horizon within the La Colonia Formation. This contribution constitutes the first reconstruction of a Cretaceous aquatic habitat for southern South America.

Late Cretaceous Aquatic Plant World in Patagonia, Argentina

Science.gov (United States)

Cúneo, N. Rubén; Gandolfo, María A.; Zamaloa, María C.; Hermsen, Elizabeth

2014-01-01

In this contribution, we describe latest Cretaceous aquatic plant communities from the La Colonia Formation, Patagonia, Argentina, based on their taxonomic components and paleoecological attributes. The La Colonia Formation is a geological unit deposited during a Maastrichtian-Danian transgressive episode of the South Atlantic Ocean. This event resulted in the deposition of a series of fine-grained sediments associated with lagoon systems occurring along irregular coastal plains in northern Patagonia. These deposits preserved a diverse biota, including aquatic and terrestrial plants and animals. The aquatic macrophytes can be broadly divided into two groups: free-floating and rooted, the latter with emergent or floating leaves. Free-floating macrophytes include ferns in Salviniaceae (Azolla and Paleoazolla) and a monocot (Araceae). Floating microphytes include green algae (Botryoccocus, Pediastrum and Zygnemataceae). Among the rooted components, marsileaceous water ferns (including Regnellidium and an extinct form) and the eudicot angiosperm Nelumbo (Nelumbonaceae) are the dominant groups. Terrestrial plants occurring in the vegetation surrounding the lagoons include monocots (palms and Typhaceae), ferns with affinities to Dicksoniaceae, conifers, and dicots. A reconstruction of the aquatic plant paleocommuniy is provided based on the distribution of the fossils along a freshwater horizon within the La Colonia Formation. This contribution constitutes the first reconstruction of a Cretaceous aquatic habitat for southern South America. PMID:25148081

Thyasirid bivalves from Cretaceous and Paleogene cold seeps

Directory of Open Access Journals (Sweden)

Krzysztof Hryniewicz

2017-11-01

Full Text Available We present a systematic study of thyasirid bivalves from Cretaceous to Oligocene seep carbonates worldwide. Eleven species of thyasirid bivalves are identified belonging to three genera: Conchocele, Maorithyas, and Thyasira. Two species are new: Maorithyas humptulipsensis sp. nov. from middle Eocene seep carbonates in the Humptulips Formation, Washington State, USA, and Conchocele kiritachiensis sp. nov. from the late Eocene seep deposit at Kiritachi, Hokkaido, Japan. Two new combinations are provided: Conchocele townsendi (White, 1890 from Maastrichtian strata of the James Ross Basin, Antarctica, and Maorithyas folgeri (Wagner and Schilling, 1923 from Oligocene rocks from California, USA. Three species are left in open nomenclature. We show that thyasirids have Mesozoic origins and appear at seeps before appearing in “normal” marine environments. These data are interpreted as a record of seep origination of thyasirids, and their subsequent dispersal to non-seep environments. We discuss the age of origination of thyasirids in the context of the origin of the modern deep sea fauna and conclude that thyasirids could have deep sea origins. This hypothesis is supported by the observed lack of influence of the Cretaceous and Paleogene Oceanic Anoxic Events on the main evolutionary lineages of the thyasirids, as seen in several other members of the deep sea fauna.

Lower Cretaceous Source Rock and its Implication for the Gulf of Guinea Petroleum System

International Nuclear Information System (INIS)

Frost, B.R.; Griffith, R.C.

2002-01-01

Current petroleum system models for the Gulf of Guinea propose Tertiary-age deltaic organic material as the principal source for the hydrocarbons found there. Although previous workers recognized numerous difficulties and inconsistencies, no alternative model has been resented to adequately explain the complete petroleum system. We propose that the principal source rock for the Gulf of Guinea system occurs in upper lower Cretaceous-age shales at the rift-drift transition. Tertiary loading and the consequent maturation of this lower Cretaceous source rock can explain the controls on tap formation, reservoir distribution and hydrocarbon types found in the Gulf of Guinea

Controls on the deposition and preservation of the Cretaceous Mowry Shale and Frontier Formation and equivalents, Rocky Mountain region, Colorado, Utah, and Wyoming

Science.gov (United States)

Kirschbaum, Mark A.; Mercier, Tracey J.

2013-01-01

Regional variations in thickness and facies of clastic sediments are controlled by geographic location within a foreland basin. Preservation of facies is dependent on the original accommodation space available during deposition and ultimately by tectonic modification of the foreland in its postthrusting stages. The preservation of facies within the foreland basin and during the modification stage affects the kinds of hydrocarbon reservoirs that are present. This is the case for the Cretaceous Mowry Shale and Frontier Formation and equivalent strata in the Rocky Mountain region of Colorado, Utah, and Wyoming. Biostratigraphically constrained isopach maps of three intervals within these formations provide a control on eustatic variations in sea level, which allow depositional patterns across dip and along strike to be interpreted in terms of relationship to thrust progression and depositional topography. The most highly subsiding parts of the Rocky Mountain foreland basin, near the fold and thrust belt to the west, typically contain a low number of coarse-grained sandstone channels but limited sandstone reservoirs. However, where subsidence is greater than sediment supply, the foredeep contains stacked deltaic sandstones, coal, and preserved transgressive marine shales in mainly conformable successions. The main exploration play in this area is currently coalbed gas, but the enhanced coal thickness combined with a Mowry marine shale source rock indicates that a low-permeability, basin-centered play may exist somewhere along strike in a deep part of the basin. In the slower subsiding parts of the foreland basin, marginal marine and fluvial sandstones are amalgamated and compartmentalized by unconformities, providing conditions for the development of stratigraphic and combination traps, especially in areas of repeated reactivation. Areas of medium accommodation in the most distal parts of the foreland contain isolated marginal marine shoreface and deltaic sandstones

Evolution of anuran assemblages in the Late Cretaceous of Utah, USA

Czech Academy of Sciences Publication Activity Database

Roček, Zbyněk; Eaton, J. G.; Gardner, J.; Přikryl, Tomáš

2010-01-01

Roč. 90, č. 4 (2010), s. 341-393 ISSN 1867-1594 R&D Projects: GA MŠk ME08066 Institutional research plan: CEZ:AV0Z30130516 Keywords : Anura * evolution * Late Cretaceous * fossil frogs * stratigraphy * Utah Subject RIV: EG - Zoology

Study on fine geological modelling of the fluvial sandstone reservoir in Daqing oilfield

Energy Technology Data Exchange (ETDEWEB)

Zhoa Han-Qing [Daqing Research Institute, Helongjiang (China)

1997-08-01

These paper aims at developing a method for fine reservoir description in maturing oilfields by using close spaced well logging data. The main productive reservoirs in Daqing oilfield is a set of large fluvial-deltaic deposits in the Songliao Lake Basin, characterized by multi-layers and serious heterogeneities. Various fluvial channel sandstone reservoirs cover a fairly important proportion of reserves. After a long period of water flooding, most of them have turned into high water cut layers, but there are considerable residual reserves within them, which are difficult to find and tap. Making fine reservoir description and developing sound a geological model is essential for tapping residual oil and enhancing oil recovery. The principal reason for relative lower precision of predicting model developed by using geostatistics is incomplete recognition of complex distribution of fluvial reservoirs and their internal architecture`s. Tasking advantage of limited outcrop data from other regions (suppose no outcrop data available in oilfield) can only provide the knowledge of subtle changing of reservoir parameters and internal architecture. For the specific geometry distribution and internal architecture of subsurface reservoirs (such as in produced regions) can be gained only from continuous infilling logging well data available from studied areas. For developing a geological model, we think the first important thing is to characterize sandbodies geometries and their general architecture`s, which are the framework of models, and then the slight changing of interwell parameters and internal architecture`s, which are the contents and cells of the model. An excellent model should possess both of them, but the geometry is the key to model, because it controls the contents and cells distribution within a model.

On the Application of an Enthalpy Method to the Evolution of Fluvial Deltas Under Sea-Level Changes

Science.gov (United States)

Anderson, W.; Lorenzo-Trueba, J.; Voller, V. R.

2017-12-01

Fluvial deltas are composites of two primary sedimentary environments: a depositional fluvial region and an offshore region. The fluvial region is defined by two geomorphic moving boundaries: an alluvial-bedrock transition (ABT), which separates the sediment prism from the non-erodible bedrock basement, and the shoreline (SH), where the delta meets the ocean. The trajectories of these boundaries in time and space define the evolution of the shape of the sedimentary prism, and are often used as stratigraphic indicators, particularly in seismic studies, of changes in relative sea level and the identification of stratigraphic sequences. In order to better understand the relative role of sea-level variations, tectonics, and sediment supply on the evolution of these boundaries, we develop a forward stratigraphic model that captures the dynamic behavior of the fluvial surface and treats the SH and ABT as moving boundaries (i.e., internal boundaries whose location must be determined as part of the solution to the overall morphological evolution problem). This forward model extends a numerical technique from heat transfer (i.e., enthalpy method), previously applied to the evolution of sedimentary basins, to account for sea-level changes. The mathematics of the approach are verified by comparing predictions from the numerical model with both existing and newly developed closed form analytical solutions. Model results support previous work, which suggests that the migration of the ABT can respond very differently to the sea-level signal. This response depends on factors such as sediment supply and delta length, which can vary greatly between basins. These results can have important implications for the reconstruction of past sea-level changes from the stratigraphic record of sedimentary basins.

Assessing Potential Algal Blooms in a Shallow Fluvial Lake by Combining Hydrodynamic Modelling and Remote-Sensed Images

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Monica Pinardi

2015-04-01

Full Text Available Shallow fluvial lakes are dynamic ecosystems shaped by physical and biological factors and characterized by the coexistence of phytoplankton and macrophytes. Due to multiple interplaying factors, understanding the distribution of phytoplankton in fluvial lakes is a complex but fundamental issue, in the context of increasing eutrophication, climate change, and multiple water uses. We analyze the distribution of phytoplankton by combining remotely sensed maps of chlorophyll-a with a hydrodynamic model in a dammed fluvial lake (Mantua Superior Lake, Northern Italy. The numerical simulation of different conditions shows that the main hydrodynamic effects which influence algal distribution are related to the combined effect of advection due to wind forces and local currents, as well as to the presence of large gyres which induce recirculation and stagnation regions, favoring phytoplankton accumulation. Therefore, the general characters of the phytoplankton horizontal patchiness can be inferred from the results of the hydrodynamic model. Conversely, hyperspectral remote-sensing products can be used to validate this model, as they provide chlorophyll-a distribution maps. The integration of ecological, hydraulic, and remote-sensing techniques may therefore help the monitoring and protection of inland water quality, with important improvements in management actions by policy makers.

The Hunt for Pristine Cretaceous Astronomical Rhythms at Demerara Rise (Cenomanian-Coniacian)

Science.gov (United States)

Ma, C.; Meyers, S. R.

2014-12-01

Rhythmic Upper Cretaceous strata from Demerara Rise (ODP leg 207) preserve a strong astronomical signature, and this attribute has facilitated the development of continuous astrochronologies to refine the geologic time scale and calibrate Late Cretaceous biogeochemical events. While the mere identification of astronomical rhythms is a crucial first step in many deep-time paleoceanographic investigations, accurate evaluation of often subtle amplitude and frequency modulations are required to: (1) robustly constrain the linkage between climate and sedimentation, and (2) evaluate the plausibility of different theoretical astrodynamical models. The availability of a wide range of geophysical, lithologic and geochemical data from multiple sites drilled at Demerara Rise - when coupled with recent innovations in the statistical analysis of cyclostratigraphic data - provides an opportunity to hunt for the most pristine record of Cretaceous astronomical rhythms at a tropical Atlantic location. To do so, a statistical metric is developed to evaluate the "internal" consistency of hypothesized astronomical rhythms observed in each data set, particularly with regard to the expected astronomical amplitude modulations. In this presentation, we focus on how the new analysis yields refinements to the existing astrochronologies, provides constraints on the linkages between climate and sedimentation (including the deposition of organic carbon-rich sediments at Demerara Rise), and allows a quantitative evaluation of the continuity of deposition across sites at multiple temporal scales.

Early cretaceous zircon SHRIMP U-Pb age of the trachyte and its significances of the Gan-Hang belt

International Nuclear Information System (INIS)

Liu Feiyu; Wu Jianhua; Liu Shuai

2009-01-01

The Shixi basin was located at Gan-Hang tectonic volcanic uranium deposit of rock-magma belt which belong to a part of the Mesozoic volcanic rocks in the northeastern of China. The appearance of the trachyte in Shixi basin have the majoy elements characteristic of the shoshonite series volcanic rocks. To determine the geological age of trachyte have very important significance on the geodynamics research and the study on the cause of uranium mineralization. The zircons of the trachyte have clear ring and high Th/U ratio which belong to the typical magmatic zircons. The zircon SHRIMP U-Pb dating resules show that 14points' age range is very smaller is 132-144 Ma and the weighted average age is (137.00±0.94)Ma which represents the diagenetic age of volcanic rocks. Accronding to the latest International Stratigraphic Chart the boundary of Jurassic and Cretaceous is (145.4±4.0)Ma. So the trachyte of Shixi Group belong to early Cretaceous. The large-scale acidic volcanic activity occurred in the Early Cretaceous in Southeastern China, and the Volcanic uranium deposit of Gan-Hang tectonic belt relate to Alkali metasomatism Uranium mineralization also occurred in the Early Cretaceous (120-130 Ma). The determined of trachyte in Shixi Group in the Early Cretaceous show that the acidic volcanic activity have connection with magma activity and the early Uranium mineralization consistent with the Alkali magma activity. (authors)

Late Cretaceous extension and exhumation of the Stong Complex and Taku Schist, NE Peninsular Malaysia

Science.gov (United States)

François, Thomas; Afiq Md, Muhammad; Matenco, Liviu; Willingshofer, Ernst; Fatt Ng, Tham; Iskandar Taib, N.; Kamal Shuib, Mustaffa

2017-04-01

Dismembering large continental areas by post-orogenic extension requires favourable geodynamic conditions and frequently occurs along pre-existing suture zones or nappe contacts as exemplified by the Stong Complex and Taku Schist of northern Peninsular Malaysia. For this particular case we have employed a field and microstructural kinematic study combined with low temperature thermo-chronology to analyse the tectonic and exhumation history. The results show that the late Palaeozoic - Triassic Indosinian orogeny created successive phases of burial related metamorphism, shearing and contractional deformation. This orogenic structure was then dismembered during a Cretaceous thermal event that culminated in the formation of a large scale late Santonian - early Maastrichtian extensional detachment, genetically associated with crustal melting, the emplacement of syn-kinematic plutons and widespread migmatisation. The emplacement of these magmatic rocks led to an array of simultaneously formed structures that document deformation conditions over a wide temperature range, represented by amphibolite-facies mylonites and more brittle structures, such as cataclastic zones and normal faults that formed during exhumation in the footwall of the detachment. The formation of this detachment and a first phase of Late Cretaceous cooling was followed by renewed Eocene - Oligocene exhumation evidenced from our apatite fission track ages. We infer that an initial Cretaceous thermal anomaly was responsible for the formation of an extensional gneiss dome associated with simple shear and normal fault rotation. These Cretaceous processes played a critical role in the establishment of the presently observed crustal structure of Peninsular Malaysia.

Trace element patterns at a non-marine cretaceous-tertiary boundary

Science.gov (United States)

Gilmore, J.S.; Knight, J.D.; Orth, C.J.; Pillmore, C.L.; Tschudy, R.H.

1984-01-01

At the fossil-pollen-defined Cretaceous-Tertiary boundary in the Raton Basin of New Mexico and Colorado, an iridium abundance anomaly and excess scandium, titanium, and chromium are associated with a thin ash or dust fallout bed (now kaolinitic clay) that was preserved in freshwater coal swamps. ?? 1984 Nature Publishing Group.

Origin of Cretaceous phosphorites from the onshore of Tamil Nadu ...

Indian Academy of Sciences (India)

Cretaceous phosphorites occur as light brown to yellow- ish brown or white nodules in Karai Shale of the Uttatur Group in the onshore Cauvery basin. Nodules exhibit phosphatic nucleus encrusted by a chalky shell of carbonate. The nucleus of the nodules consists of light and dark coloured laminae, phosphate ...

Analysis of Fluvial Bed Sediments Along the Apalachicola River, Florida through Field Reconnaissance Studies

Science.gov (United States)

Passeri, D.; Hagen, S. C.; Daranpob, A.; Smar, D. E.

2011-12-01

River competence is an important parameter in understanding sediment transport in fluvial systems. Competence is defined as the measure of a stream's ability to transport a certain maximum grain size of sediment. Studies have shown that bed sediment particle size in rivers and streams tends to vary spatially along the direction of stream flow. Over a river section several reaches long, variability of sediment particle sizes can be seen, often becoming finer downstream. This phenomenon is attributed to mechanisms such as local control of stream gradient, coarse tributary sediment supply or particle breakdown. Average particle size may also be smaller in tributary sections of rivers due to river morphology. The relationship between river mean velocity and particle size that can be transported has also been explored. The Hjulstrom curve classifies this relationship by relating particle size to velocity, dividing the regions of sedimentation, transportation, and erosion. The curve can also be used to find values such as the critical erosion velocity (the velocity required to transport particles of various sizes in suspension) and settling velocity (the velocity at which particles of a given size become too heavy to be transported and fall out of suspension, consequently causing deposition). The purpose of this research is to explore the principles of river competence through field reconnaissance collection and laboratory analysis of fluvial sediment core samples along the Apalachicola River, FL and its distributaries. Sediment core samples were collected in the wetlands and estuarine regions of the Apalachicola River. Sieve and hydrometer analyses were performed to determine the spatial distribution of particle sizes along the river. An existing high resolution hydrodynamic model of the study domain was used to simulate tides and generate river velocities. The Hjulstrom curve and the generated river velocities were used to define whether sediment was being transported

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

Science.gov (United States)

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

2017-08-01

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.

Rapid fluvial incision of a late Holocene lava flow: Insights from LiDAR, alluvial stratigraphy, and numerical modeling

Science.gov (United States)

Sweeney, Kristin; Roering, Joshua J.

2016-01-01

Volcanic eruptions fundamentally alter landscapes, paving over channels, decimating biota, and emplacing fresh, unweathered material. The fluvial incision of blocky lava flows is a geomorphic puzzle. First, high surface permeability and lack of sediment should preclude geomorphically effective surface runoff and dissection. Furthermore, past work has demonstrated the importance of extreme floods in driving incision via column toppling and plucking in columnar basalt, but it is unclear how incision occurs in systems where surface blocks are readily mobile. We examine rapid fluvial incision of the Collier lava flow, an andesitic Holocene lava flow in the High Cascades of Oregon. Since lava flow emplacement ∼1600 yr ago, White Branch Creek has incised bedrock gorges up to 8 m deep into the coherent core of the lava flow and deposited >0.2 km3 of sediment on the lava flow surface. Field observation points to a bimodal discharge regime in the channel, with evidence for both annual snowmelt runoff and outburst floods from Collier glacier, as well as historical evidence of vigorous glacial meltwater. To determine the range of discharge events capable of incision in White Branch Creek, we used a mechanistic model of fluvial abrasion. We show that the observed incision implies that moderate flows are capable of both initiating channel formation and sustaining incision. Our results have implications for the evolution of volcanic systems worldwide, where glaciation and/or mass wasting may accelerate fluvial processes by providing large amounts of sediment to otherwise porous, sediment-starved landscapes.

Evidence of Egg Diversity in Squamate Evolution from Cretaceous Anguimorph Embryos

Czech Academy of Sciences Publication Activity Database

Fernandez, V.; Buffetaut, E.; Suteethorn, V.; Rage, J. C.; Tafforeau, P.; Kundrát, Martin

2015-01-01

Roč. 10, č. 7 (2015), e0128610 E-ISSN 1932-6203 R&D Projects: GA ČR(CZ) GAP302/12/1207 Institutional support: RVO:67985823 Keywords : squamates * egg * fossils * cretaceous Subject RIV: EA - Cell Biology Impact factor: 3.057, year: 2015

Applying fluvial geomorphology to river channel management: Background for progress towards a palaeohydrology protocol

Science.gov (United States)

Gregory, K. J.; Benito, G.; Downs, P. W.

2008-06-01

Significant developments have been achieved in applicable and applied fluvial geomorphology as shown in publications of the last three decades, analyzed as the basis for using results of studies of environmental change as a basis for management. The range of types of publications and of activities are more pertinent to river channel management as a result of concern with sustainability, global climate change, environmental ethics, ecosystem health concepts and public participation. Possible applications, with particular reference to river channel changes, include those concerned with form and process, assessment of channel change, urbanization, channelization, extractive industries, impact of engineering works, historical changes in land use, and restoration with specific examples illustrated in Table 1. In order to achieve general significance for fluvial geomorphology, more theory and extension by modelling methods is needed, and examples related to morphology and process characteristics, integrated approaches, and changes of the fluvial system are collected in Table 2. The ways in which potential applications are communicated to decision-makers range from applicable outputs including publications ranging from review papers, book chapters, and books, to applied outputs which include interdisciplinary problem solving, educational outreach, and direct involvement, with examples summarized in Table 3. On the basis of results gained from investigations covering periods longer than continuous records, a protocol embracing palaeohydrological inputs for application to river channel management is illustrated and developed as a synopsis version (Table 4), demonstrating how conclusions from geomorphological research can be expressed in a format which can be considered by managers.

Tamarix, hydrology and fluvial geomorphology: Chapter 7

Science.gov (United States)

Auerbach, Daniel A.; Merritt, David M.; Shafroth, Patrick B.; Sher, Anna A; Quigley, Martin F.

2013-01-01

This chapter explores the impact of hydrology and fluvial geomorphology on the distribution and abundance of Tamarix as well as the reciprocal effects of Tamarix on hydrologic and geomorphic conditions. It examines whether flow-regime alteration favors Tamarix establishment over native species, and how Tamarix stands modify processes involved in the narrowing of river channels and the formation of floodplains. It begins with an overview of the basic geomorphic and hydrologic character of rivers in the western United States before analyzing how this setting has contributed to the regional success of Tamarix. It then considers the influence of Tamarix on the hydrogeomorphic form and function of rivers and concludes by discussing how a changing climate, vegetation management, and continued water-resource development affect the future role of Tamarix in these ecosystems.

A method of fingerprinting the sources of fluvial sediment using environmental radionuclides. A case study of Tsuzura river watershed

International Nuclear Information System (INIS)

Mizugaki, Shigeru; Onda, Yuichi; Fukuyama, Taijiro; Koga, Satoko; Hiramatsu, Shinya

2006-01-01

To study the fluvial sediment sources in forested watershed in Shikoku Island, Japan, the concentration of Cs-137 and Pb-210 ex and U decay series radionuclides were analyzed. The study area in the midstream of Shimanto River basin, located 700 km southwest of Tokyo. The 0.33 km 2 area watershed ranges in elevation from 170 m to 560 m above sea level. The soil sampling was conducted in hillslopes in various locations such as landslide scar, soil surface in unmanaged Hinoki (Chamacecyparis obtusa) plantation and unsealed forest road, and detailed sampling in the stream bed and bank was also conducted in several tributaries. Time-integrated suspended sediment sampler was adopted to obtain enough volume of sample to determine the radionuclides. The activities of Cs-137, Pb-210, Pb-214 and Bi-214 of soils and fluvial sediments were determined by gamma-ray spectrometry. Correction for the effect of particle size distribution and organic matter content on the radionuclides were conducted to compare the radionuclides concentration between the soils of potential suspended sediment sources and fluvial sediments. It was found that there were significant differences of Cs-137 and Pb-210 ex concentration between forest floor or runoff sediment and forest road or stream bank. The Cs-137 and Pb-210 ex concentration of suspended sediment varied among them, suggesting the possibility of fingerprinting the sources of fluvial sediment by Cs-137 and Pb-210 ex . (author)

Stable carbon isotope analysis of fluvial sediment fluxes over two contrasting C(4) -C(3) semi-arid vegetation transitions.

Science.gov (United States)

Puttock, Alan; Dungait, Jennifer A J; Bol, Roland; Dixon, Elizabeth R; Macleod, Christopher J A; Brazier, Richard E

2012-10-30

Globally, many drylands are experiencing the encroachment of woody vegetation into grasslands. These changes in ecosystem structure and processes can result in increased sediment and nutrient fluxes due to fluvial erosion. As these changes are often accompanied by a shift from C(4) to C(3) vegetation with characteristic δ(13) C values, stable isotope analysis provides a promising mechanism for tracing these fluxes. Input vegetation, surface sediment and fluvially eroded sediment samples were collected across two contrasting C(4) -C(3) dryland vegetation transitions in New Mexico, USA. Isotope ratio mass spectrometric analyses were performed using a Carlo Erba NA2000 analyser interfaced to a SerCon 20-22 isotope ratio mass spectrometer to determine bulk δ(13) C values. Stable isotope analyses of contemporary input vegetation and surface sediments over the monitored transitions showed significant differences (p fluvially eroded sediment from each of the sites, with no significant variation between surface sediment and eroded sediment values. The significant differences in bulk δ(13) C values between sites were dependent on vegetation input. Importantly, these values were robustly expressed in fluvially eroded sediments, suggesting that stable isotope analysis is suitable for tracing sediment fluxes. Due to the prevalent nature of these dryland vegetation transitions in the USA and globally, further development of stable isotope ratio mass spectrometry has provided a valuable tool for enhanced understanding of functional changes in these ecosystems. Copyright © 2012 John Wiley & Sons, Ltd.

Influencia de tres tipos de vegetación riberena en el control de la erosión fluvial en Pantanos de Centla, México

NARCIS (Netherlands)

Sepúlveda, A.; Geissen, V.; Ochoa-Gaona, S.; Jarquin-Sanchez, A.; Hernandez de la Cruz, S.; Zamora-Cornelio, L.F.

2009-01-01

Influence of three types of riparian vegetation on fluvial erosion control in Pantanos de Centla, Mexico. Wetlands constitute very important ecological areas. The aim of this study was to quantify the soil losses due to fluvial erosion from 2006 to 2008 in two riverbanks under three types of vegetal

Stratigraphy of Guichon Formation (lower cretaceous) in litoral basin, Uruguay

International Nuclear Information System (INIS)

Goso, C.; Perea, D.; Perinotto, J.

1999-01-01

This report is about the stratigraphic al analysis of the Guichon Formation (lower cretaceous, litoral basin in Uruguay). The facies association is represented by conglomerates mainly fine sandstones and mud stones wi ch is interpreted as an alluvial system. A regional palaeogeography and a new geochronological alternative are established for this formation. (author).

New fossil ants in French Cretaceous amber (Hymenoptera: Formicidae)

Science.gov (United States)

Perrichot, Vincent; Nel, André; Néraudeau, Didier; Lacau, Sébastien; Guyot, Thierry

2008-02-01

Recent studies on the ant phylogeny are mainly based on the molecular analyses of extant subfamilies and do not include the extinct, only Cretaceous subfamily Sphecomyrminae. However, the latter is of major importance for ant relationships, as it is considered the most basal subfamily. Therefore, each new discovery of a Mesozoic ant is of high interest for improving our understanding of their early history and basal relationships. In this paper, a new sphecomyrmine ant, allied to the Burmese amber genus Haidomyrmex, is described from mid-Cretaceous amber of France as Haidomyrmodes mammuthus gen. and sp. n. The diagnosis of the tribe Haidomyrmecini is emended based on the new type material, which includes a gyne (alate female) and two incomplete workers. The genus Sphecomyrmodes, hitherto known by a single species from Burmese amber, is also reported and a new species described as S. occidentalis sp. n. after two workers remarkably preserved in a single piece of Early Cenomanian French amber. The new fossils provide additional information on early ant diversity and relationships and demonstrate that the monophyly of the Sphecomyrminae, as currently defined, is still weakly supported.

Climate evolution during the Pleniglacial and Late Glacial as recorded in quartz grain morphoscopy of fluvial to aeolian successions of the European Sand Belt

Directory of Open Access Journals (Sweden)

Woronko Barbara

2015-06-01

Full Text Available We present results of research into fluvial to aeolian successions at four sites in the foreland of the Last Glacial Maximum, i.e., the central part of the “European Sand Belt”. These sites include dune fields on higher-lying river terraces and alluvial fans. Sediments were subjected to detailed lithofacies analyses and sampling for morphoscopic assessment of quartz grains. Based on these results, three units were identified in the sedimentary succession: fluvial, fluvio-aeolian and aeolian. Material with traces of aeolian origin predominate in these sediments and this enabled conclusions on the activity of aeolian processes during the Pleniglacial and Late Glacial, and the source of sediment supply to be drawn. Aeolian processes played a major role in the deposition of the lower portions of the fluvial and fluvio-aeolian units. Aeolian material in the fluvial unit stems from aeolian accumulation of fluvial sediments within the valley as well as particles transported by wind from beyond the valley. The fluvio-aeolian unit is composed mainly of fluvial sediments that were subject to multiple redeposition, and long-term, intensive processing in an aeolian environment. In spite of the asynchronous onset of deposition of the fluvio-aeolian unit, it is characterised by the greatest homogeneity of structural and textural characteristics. Although the aeolian unit was laid down simultaneously, it is typified by the widest range of variation in quartz morphoscopic traits. It reflects local factors, mainly the origin of the source material, rather than climate. The duration of dune-formation processes was too short to be reflected in the morphoscopy of quartz grains.

Preliminary magnetostratigraphy and environmental magnetism of the Lower Cretaceous from the Italian Dolomites

Science.gov (United States)

Savian, J. F.; Jovane, L.; Florindo, F.; Lukeneder, A.

2011-12-01

The Lower Cretaceous (~146 to 100 Ma) represents an enigmatic time interval for paleoclimatic, paleogeography and paleomagnetic evolution of the Earth's history. The climatic changes include global oceanic anoxic events (OAEs), biotic changes, global excursions of carbon and strontium isotopes, rises in eustatic sea level and paleotemperature. Paleoceanography was marked by a rapid rate of ocean spreading in the Atlantic. The opening of the Atlantic Ocean was wide enough to allow significant circulation of masses of waters across the equator. This period is furthermore important for the oceanographic events occurring at the base of the Aptian (Selli Level). This period also present one of the most intriguing geomagnetic events: the long normal Cretaceous superchron, lasted for almost 40 million years. We study here the lower Cretaceous deposits of the Puez section in the Dolomites (northern Italy) which represents a continuous section during this period. The samples collected represent marine sedimentary materials of the Biancone and Puez formations. The Puez section consists essentially of green-grey to red limestones and calcareous marls. We present preliminary results of integrated magnetostratigraphic analysis, including a detailed lithostratigraphy and environmental magnetism. We recognize magnetic behavior that are relative to normal polarity (the normal Cretaceous superchron), with a short reverse interval that might represent the M-1r event. We also recognize a series of normal and reverse polarities (below the normal Cretaceous superchron) which can be referred to the magnetozones M1/M5. The environmental magnetic data consists of magnetic susceptibility (χ), natural remanent magnetization (NRM), anhysteretic remanent magnetization (ARM), isothermal remanent magnetization (IRM) at 900 mT and backfield isothermal remanent magnetization (BIRM) at 100 mT and 300 mT. Derived parameters, such as S-ratio (S300=BIRM300/IRM900) and hard isothermal remanent

The last dinosaurs of Brazil: The Bauru Group and its implications for the end-Cretaceous mass extinction

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STEPHEN L. BRUSATTE

Full Text Available ABSTRACT The non-avian dinosaurs died out at the end of the Cretaceous, ~66 million years ago, after an asteroid impact. The prevailing hypothesis is that the effects of the impact suddenly killed the dinosaurs, but the poor fossil record of latest Cretaceous (Campanian-Maastrichtian dinosaurs from outside Laurasia (and even more particularly, North America makes it difficult to test specific extinction scenarios. Over the past few decades, a wealth of new discoveries from the Bauru Group of Brazil has revealed a unique window into the evolution of terminal Cretaceous dinosaurs from the southern continents. We review this record and demonstrate that there was a diversity of dinosaurs, of varying body sizes, diets, and ecological roles, that survived to the very end of the Cretaceous (Maastrichtian: 72-66 million years ago in Brazil, including a core fauna of titanosaurian sauropods and abelisaurid and carcharodontosaurid theropods, along with a variety of small-to-mid-sized theropods. We argue that this pattern best fits the hypothesis that southern dinosaurs, like their northern counterparts, were still diversifying and occupying prominent roles in their ecosystems before the asteroid suddenly caused their extinction. However, this hypothesis remains to be tested with more refined paleontological and geochronological data, and we give suggestions for future work.

The last dinosaurs of Brazil: The Bauru Group and its implications for the end-Cretaceous mass extinction.

Science.gov (United States)

Brusatte, Stephen L; Candeiro, Carlos R A; Simbras, Felipe M

2017-01-01

The non-avian dinosaurs died out at the end of the Cretaceous, ~66 million years ago, after an asteroid impact. The prevailing hypothesis is that the effects of the impact suddenly killed the dinosaurs, but the poor fossil record of latest Cretaceous (Campanian-Maastrichtian) dinosaurs from outside Laurasia (and even more particularly, North America) makes it difficult to test specific extinction scenarios. Over the past few decades, a wealth of new discoveries from the Bauru Group of Brazil has revealed a unique window into the evolution of terminal Cretaceous dinosaurs from the southern continents. We review this record and demonstrate that there was a diversity of dinosaurs, of varying body sizes, diets, and ecological roles, that survived to the very end of the Cretaceous (Maastrichtian: 72-66 million years ago) in Brazil, including a core fauna of titanosaurian sauropods and abelisaurid and carcharodontosaurid theropods, along with a variety of small-to-mid-sized theropods. We argue that this pattern best fits the hypothesis that southern dinosaurs, like their northern counterparts, were still diversifying and occupying prominent roles in their ecosystems before the asteroid suddenly caused their extinction. However, this hypothesis remains to be tested with more refined paleontological and geochronological data, and we give suggestions for future work.

Chronology of fluvial terrace sequences for large Atlantic rivers in the Iberian Peninsula (Upper Tagus and Duero drainage basins, Central Spain)

Science.gov (United States)

Silva, Pablo G.; Roquero, Elvira; López-Recio, Mario; Huerta, Pedro; Martínez-Graña, Antonio M.

2017-06-01

This work analyses the chronology of fluvial terrace sequences of the two most important fluvial basins from central Spain draining to the Atlantic Ocean (Upper Tagus and Duero drainage basins). Both basins evolved under similar Mediterranean climatic conditions throughout the Pleistocene and present comparable number of fluvial terraces (16-17) after excluding the higher terrace levels of the Tagus (T1-T5) entrenched in the Raña surface. These higher ;rañizo terraces; was formed in response to fan-head trenching in this high alluvial piedmont (+220 m) and therefore not properly controlled by Quaternary fluvial downcutting. The study accomplishes the implementation of multiple regression analyses for terrace height-age relationships. To transform relative terrace heights above the present river thalwegs (i.e. +100 m) in numerical ages a ;height-age transference function; has been developed on the basis of preliminary statistical geochronological approaches proposed for Central Spain. The resultant height-age transference function gather 73 published geochronological data for terrace sequences, featuring a 3rd Order Polynomial Function (R2 0.90). This function describes the overall trend of valley downcutting for the last c. 2.3 Ma in Central Spain and is used to assign numerical ages to terrace levels at different relative elevation.

Arsenic and fluvial biofilms: biogeochemistry, toxicity and biotic interactions

OpenAIRE

Barral Fraga, Laura

2017-01-01

Basándonos en los conocimientos actuales sobre la ecotoxicología del biofilm y la biogeoquímica del arsénico en ecosistemas dulceacuícolas, esta tesis estudió, bajo concentraciones ambientales realistas, i) el papel de los biofilms bentónicos en la biodisponibilidad y destoxificación del arsénico, ii) los efectos tóxicos del arsénico sobre la estructura y función de los biofilms bentónicos fluviales, prestando especial atención a las respuestas de las diatomeas, y iii) la interacción entre es...

A New Sail-Backed Styracosternan (Dinosauria: Ornithopoda) from the Early Cretaceous of Morella, Spain.

Science.gov (United States)

Gasulla, José Miguel; Escaso, Fernando; Narváez, Iván; Ortega, Francisco; Sanz, José Luis

2015-01-01

A new styracosternan ornithopod genus and species is here described based on a partial postcranial skeleton and an associated dentary tooth of a single specimen from the Arcillas de Morella Formation (Early Cretaceous, late Barremian) at the Morella locality, (Castellón, Spain). Morelladon beltrani gen. et sp. nov. is diagnosed by eight autapomorphic features. The set of autapomorphies includes: very elongated and vertical neural spines of the dorsal vertebrae, midline keel on ventral surface of the second to fourth sacral vertebrae restricted to the anterior half of the centrum, a posterodorsally inclined medial ridge on the postacetabular process of the ilium that meets its dorsal margin and distal end of the straight ischial shaft laterally expanded, among others. Phylogenetic analyses reveal that the new Iberian form is more closely related to its synchronic and sympatric contemporary European taxa Iguanodon bernissartensis and Mantellisaurus atherfieldensis, known from Western Europe, than to other Early Cretaceous Iberian styracosternans (Delapparentia turolensis and Proa valdearinnoensis). The recognition of Morelladon beltrani gen. et sp. nov. indicates that the Iberian Peninsula was home to a highly diverse medium to large bodied styracosternan assemblage during the Early Cretaceous.

Stratigraphy, provenance, and diagenesis of the Cretaceous Horse Range Formation, east Otago, New Zealand

International Nuclear Information System (INIS)

Mitchell, M.; Craw, D.; Landis, C.A.; Frew, R.

2009-01-01

The Horse Range Formation is a structurally controlled late Early Cretaceous to early Late Cretaceous nonmarine unit in east Otago, South Island, New Zealand, containing immature lithic debris. Clasts are generally rounded, with only minor subangular material. The formation contains clasts derived from two principal basement sources: schist and greywacke. Schist debris is most abundant at the base of the described section, and this material is dominated (>60%) by quartz from the greenschist facies core of the Otago Schist belt. Conglomerates with >70% greywacke clasts constitute most of the upper part of the Horse Range Formation. These greywacke conglomerates have a matrix of sand derived mainly from schist. A 60 m thick wedge of quartz-rich, locally carbonaceous sand occurs interlayered with greywacke conglomerates. The Horse Range Formation rests on sub-greenschist facies semischist, which forms only a small proportion ( 18 O SMOW near +24 permil and δ 13 C PDB near -2 permil, and was partly dissolved and redeposited from the immature basement debris (metamorphic calcite) and partly introduced from overlying Late Cretaceous and Teriary marine sediments by groundwater. (author). 43 refs., 11 figs., 1 tab.

Possible markers of the Jurassic/Cretaceous boundary in the Mediterranean Tethys: A review and state of art

Directory of Open Access Journals (Sweden)

Jozef Michalík

2011-10-01

Full Text Available During the last decades, several integrated studies of Tethyan Jurassic/Cretaceous boundary sections from different countries were published with the objective to indicate problems for the selection of biological, chemical or physical markers suitable for identification of the Jurassic/Cretaceous boundary – the only system boundary within the Phanerozoic still not fixed by GSSP. Drawing the boundary between the Jurassic and Cretaceous systems is a matter of global scale discussions. The problem of proposing possible J/K boundary stratotypes results from lack of a global index fossils, global sea level drop, paleogeographic changes causing development of isolated facies areas, as well as from the effect of Late Cimmerian Orogeny. This contribution summarizes and comments data on J/K boundary interval obtained from several important Tethyan sections and shows still existing problems and discrepancies in its determination.

Hadrosauroid dinosaurs from the Late Cretaceous of the Sultanate of Oman

NARCIS (Netherlands)

Buffetaut, Eric; Hartman, Axel Frans; Al-Kindi, Mohammed; Schulp, Anne S.

2015-01-01

Fragmentary post-cranial remains (femora, tibia, vertebrae) of ornithischian dinosaurs from the Late Cretaceous of the Sultanate of Oman are described and referred to hadrosauroids. The specimens come from the Al-Khod Conglomerate, of latest Campanian to Maastrichtian age, in the north-eastern part

A Late Cretaceous theropod caudal vertebra from the Sultanate of Oman

NARCIS (Netherlands)

Schulp, Anne S.; Hanna, Samir S.; Hartman, Axel Frans; Jagt, John W M

2000-01-01

A caudal vertebra collected from conglomerates of the Al-Khod Formation (Late Cretaceous) in the Al-Khod area, Sultanate of Oman, is assigned to a medium-sized theropod dinosaur. The Al-Khod discovery represents one of the very few dinosaur records from the Middle East.

Contribution of radioactive tracers to sediment transport study in fluvial flows

International Nuclear Information System (INIS)

Wilson Junior, G.

1995-01-01

The uses of radioactive tracers in sediment transport studies are presented in this report to evidence the importance of: Open channel researches, to describe field applications in waterways; Simultaneous utilization of classical methods and radiotracer techniques, in fluvial and estuarine environments; Development of radiotracers techniques applied in dynamic sedimentology. The report illustrated with some experiments carried out in Brazil and France, in open channel and natural flows. (author). 5 refs, 4 figs

Gully annealing by fluvially-sourced Aeolian sand: remote sensing investigations of connectivity along the Fluvial-Aeolian-hillslope continuum on the Colorado River

Science.gov (United States)

Sankey, Joel B.; East, Amy E.; Collins, Brian D.; Caster, Joshua J.

2015-01-01

Processes contributing to development of ephemeral gully channels are of great importance to landscapes worldwide, and particularly in dryland regions where soil loss and land degradation from gully erosion pose long-term, land-management problems. Whereas gully formation has been relatively well studied, much less is known of the processes that anneal gullies and impede their growth. This work investigates gully annealing by aeolian sediment, along the Colorado River downstream of Glen Canyon Dam in Glen, Marble, and Grand Canyons, Arizona, USA (Figure 1). In this segment of the Colorado River, gully erosion potentially affects the stability and preservation of archaeological sites that are located within valley margins. Gully erosion occurs as a function of ephemeral, rainfall-induced overland flow associated with intense episodes of seasonal precipitation. Measurements of sediment transport and topographic change have demonstrated that fluvial sand in some locations is transported inland and upslope by aeolian processes to areas affected by gully erosion, and aeolian sediment activity can be locally effective at counteracting gully erosion (Draut, 2012; Collins and others, 2009, 2012; Sankey and Draut, 2014). The degree to which specific locations are affected by upslope wind redistribution of sand from active channel sandbars to higher elevation valley margins is termed “connectivity”. Connectivity is controlled spatially throughout the river by (1) the presence of upwind sources of fluvial sand within the contemporary active river channel (e.g., sandbars), and (2) bio-physical barriers that include vegetation and topography that might impede aeolian sediment transport. The primary hypothesis of this work is that high degrees of connectivity lead to less gullying potential.

Cretaceous sedimentology of the Barmer Basin, Rajasthan, India

OpenAIRE

Beaumont, Hazel

2017-01-01

The Barmer Basin, western India, is a well-known and prospected petroleum system. However, the Lower Cretaceous Ghaggar-Hakra Formation has not been recognised as basin fill and not documented prior to this study. The formation outcrops in rotational fault blocks at the Sarnoo Hills and surrounding areas, on the eastern Barmer Basin margin. The thesis here describes and analyses the nature and evolution of the formation at both outcrop and within the subsurface, producing facies and depositio...

The first reported ceratopsid dinosaur from eastern North America (Owl Creek Formation, Upper Cretaceous, Mississippi, USA).

Science.gov (United States)

Farke, Andrew A; Phillips, George E

2017-01-01

Ceratopsids ("horned dinosaurs") are known from western North America and Asia, a distribution reflecting an inferred subaerial link between the two landmasses during the Late Cretaceous. However, this clade was previously unknown from eastern North America, presumably due to limited outcrop of the appropriate age and depositional environment as well as the separation of eastern and western North America by the Western Interior Seaway during much of the Late Cretaceous. A dentary tooth from the Owl Creek Formation (late Maastrichtian) of Union County, Mississippi, represents the first reported occurrence of Ceratopsidae from eastern North America. This tooth shows a combination of features typical of Ceratopsidae, including a double root and a prominent, blade-like carina. Based on the age of the fossil, we hypothesize that it is consistent with a dispersal of ceratopsids into eastern North America during the very latest Cretaceous, presumably after the two halves of North America were reunited following the retreat of the Western Interior Seaway.

The first reported ceratopsid dinosaur from eastern North America (Owl Creek Formation, Upper Cretaceous, Mississippi, USA

Directory of Open Access Journals (Sweden)

Andrew A. Farke

2017-05-01

Full Text Available Ceratopsids (“horned dinosaurs” are known from western North America and Asia, a distribution reflecting an inferred subaerial link between the two landmasses during the Late Cretaceous. However, this clade was previously unknown from eastern North America, presumably due to limited outcrop of the appropriate age and depositional environment as well as the separation of eastern and western North America by the Western Interior Seaway during much of the Late Cretaceous. A dentary tooth from the Owl Creek Formation (late Maastrichtian of Union County, Mississippi, represents the first reported occurrence of Ceratopsidae from eastern North America. This tooth shows a combination of features typical of Ceratopsidae, including a double root and a prominent, blade-like carina. Based on the age of the fossil, we hypothesize that it is consistent with a dispersal of ceratopsids into eastern North America during the very latest Cretaceous, presumably after the two halves of North America were reunited following the retreat of the Western Interior Seaway.

National Uranium Resource Evaluation: Hutchinson Quadrangle, Kansas

International Nuclear Information System (INIS)

Fair, C.L.; Smit, D.E.; Gundersen, J.N.

1982-08-01

Surface reconnaissance and detailed subsurface studies were done within the Hutchinson Quadrangle, Kansas, to evaluate uranium favorability in accordance with National Uranium Resource Evaluation criteria. These studies were designed in part to follow up prior airborne radiometric, hydrogeochemical, and stream-sediment surveys. Over 4305 well records were examined in the subsurface phase of this study. The results of these investigations indicate environments favorable for channel-controlled peneconcordant sandstone deposits in rocks of Cretaceous age and for Wyoming and Texas roll-type deposits in sandstones of Pennsylvanian age. The Cretaceous sandstone environments exhibit favorable characteristics such as a bottom unconformity; high bedload; braided, fluvial channels; large-scale cross-bedding; and an anomalous outcrop. The Pennsylvanian sandstone environments exhibit favorable characteristics such as arkosic cross-bedded sandstones, included pyrite and organic debris, interbedded shales, and gamma-ray log anomalies. Environments considered unfavorable for uranium deposits are limestone and dolomite environments, marine black shale environments, evaporative precipitate environments, and some fluvial sandstone environments. Environments considered unevaluated due to insufficient data include Precambrian plutonic, metamorphic, and sedimentary rocks, even though a large number of thin sections were available for study

Fluvial diffluence episodes reflected in the Pleistocene tufa deposits of the River Piedra (Iberian Range, NE Spain)

Science.gov (United States)

Vázquez-Urbez, M.; Pardo, G.; Arenas, C.; Sancho, C.

2011-01-01

The Pleistocene deposits of the valley of the River Piedra (NE Spain) are represented by thick tufas with small amounts of detrital material; the development of these deposits correlates with marine isotopic stages 9, 7, 6, and 5. The sedimentary scenario in which they formed mostly corresponded to stepped fluvial systems with barrage-cascade and associated dammed areas separated by low gradient fluvial stretches. Mapping and determining the sedimentology and chronology of these deposits distinguished two main episodes of fluvial diffluence that originated as a result of the temporary blockage of the river — a consequence of the vertical growth of tufa barrages in the main channel. In both episodes, water spilt out toward a secondary course from areas upstream of barrages where the water level surpassed the height of the divide between the main and secondary course. As a consequence, extensive and distinct tufa deposits with very varied facies formed over a gently inclined area toward and, indeed, within the secondary course. The hydrology of this secondary course was episodic, fed only by surface water. The two diffluence episodes detected occurred during MIS 7 and 7-6 and were interrupted by incision events, reflected by detrital deposits at the base of each tufa sedimentation stage in the main channel. Incision, which caused the breakage of the barrages, allowed water to again flow through the main channel. No evidence of diffluence was seen in any younger (MIS 5 to present-day) tufa deposits. The proposed diffluence model might help explain other carbonate fluvial systems in which (1) tufas appear in areas with no permanent water supply, and (2) tufas are absent over extensive areas despite conditions favourable to their formation.

Ecological impact of the end-Cretaceous extinction on lamniform sharks.

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Rachel A Belben

Full Text Available Lamniform sharks are apex marine predators undergoing dramatic local and regional decline worldwide, with consequences for marine ecosystems that are difficult to predict. Through their long history, lamniform sharks have faced widespread extinction, and understanding those 'natural experiments' may help constrain predictions, placing the current crisis in evolutionary context. Here we show, using novel morphometric analyses of fossil shark teeth, that the end-Cretaceous extinction of many sharks had major ecological consequences. Post-extinction ecosystems supported lower diversity and disparity of lamniforms, and were dominated by significantly smaller sharks with slimmer, smoother and less robust teeth. Tooth shape is intimately associated with ecology, feeding and prey type, and by integrating data from extant sharks we show that latest Cretaceous sharks occupied similar niches to modern lamniforms, implying similar ecosystem structure and function. By comparison, species in the depauperate post-extinction community occupied niches most similar to those of juvenile sand tigers (Carcharias taurus. Our data show that quantitative tooth morphometrics can distinguish lamniform sharks due to dietary differences, providing critical insights into ecological consequences of past extinction episodes.

Ecological impact of the end-Cretaceous extinction on lamniform sharks.

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Belben, Rachel A; Underwood, Charlie J; Johanson, Zerina; Twitchett, Richard J

2017-01-01

Lamniform sharks are apex marine predators undergoing dramatic local and regional decline worldwide, with consequences for marine ecosystems that are difficult to predict. Through their long history, lamniform sharks have faced widespread extinction, and understanding those 'natural experiments' may help constrain predictions, placing the current crisis in evolutionary context. Here we show, using novel morphometric analyses of fossil shark teeth, that the end-Cretaceous extinction of many sharks had major ecological consequences. Post-extinction ecosystems supported lower diversity and disparity of lamniforms, and were dominated by significantly smaller sharks with slimmer, smoother and less robust teeth. Tooth shape is intimately associated with ecology, feeding and prey type, and by integrating data from extant sharks we show that latest Cretaceous sharks occupied similar niches to modern lamniforms, implying similar ecosystem structure and function. By comparison, species in the depauperate post-extinction community occupied niches most similar to those of juvenile sand tigers (Carcharias taurus). Our data show that quantitative tooth morphometrics can distinguish lamniform sharks due to dietary differences, providing critical insights into ecological consequences of past extinction episodes.

Mountain building triggered late cretaceous North American megaherbivore dinosaur radiation.

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Terry A Gates

Full Text Available Prior studies of Mesozoic biodiversity document a diversity peak for dinosaur species in the Campanian stage of the Late Cretaceous, yet have failed to provide explicit causal mechanisms. We provide evidence that a marked increase in North American dinosaur biodiversity can be attributed to dynamic orogenic episodes within the Western Interior Basin (WIB. Detailed fossil occurrences document an association between the shift from Sevier-style, latitudinally arrayed basins to smaller Laramide-style, longitudinally arrayed basins and a well substantiated decreased geographic range/increased taxonomic diversity of megaherbivorous dinosaur species. Dispersal-vicariance analysis demonstrates that the nearly identical biogeographic histories of the megaherbivorous dinosaur clades Ceratopsidae and Hadrosauridae are attributable to rapid diversification events within restricted basins and that isolation events are contemporaneous with known tectonic activity in the region. SymmeTREE analysis indicates that megaherbivorous dinosaur clades exhibited significant variation in diversification rates throughout the Late Cretaceous. Phylogenetic divergence estimates of fossil clades offer a new lower boundary on Laramide surficial deformation that precedes estimates based on sedimentological data alone.

Mountain building triggered late cretaceous North American megaherbivore dinosaur radiation.

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Gates, Terry A; Prieto-Márquez, Albert; Zanno, Lindsay E

2012-01-01

Prior studies of Mesozoic biodiversity document a diversity peak for dinosaur species in the Campanian stage of the Late Cretaceous, yet have failed to provide explicit causal mechanisms. We provide evidence that a marked increase in North American dinosaur biodiversity can be attributed to dynamic orogenic episodes within the Western Interior Basin (WIB). Detailed fossil occurrences document an association between the shift from Sevier-style, latitudinally arrayed basins to smaller Laramide-style, longitudinally arrayed basins and a well substantiated decreased geographic range/increased taxonomic diversity of megaherbivorous dinosaur species. Dispersal-vicariance analysis demonstrates that the nearly identical biogeographic histories of the megaherbivorous dinosaur clades Ceratopsidae and Hadrosauridae are attributable to rapid diversification events within restricted basins and that isolation events are contemporaneous with known tectonic activity in the region. SymmeTREE analysis indicates that megaherbivorous dinosaur clades exhibited significant variation in diversification rates throughout the Late Cretaceous. Phylogenetic divergence estimates of fossil clades offer a new lower boundary on Laramide surficial deformation that precedes estimates based on sedimentological data alone.

Inversion of the Erlian Basin (NE China) in the early Late Cretaceous: Implications for the collision of the Okhotomorsk Block with East Asia

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Guo, Zhi-Xin; Shi, Yuan-Peng; Yang, Yong-Tai; Jiang, Shuan-Qi; Li, Lin-Bo; Zhao, Zhi-Gang

2018-04-01

A significant transition in tectonic regime from extension to compression occurred throughout East Asia during the mid-Cretaceous and has stimulated much attention. However, the timing and driving mechanisms of the transition remain disputed. The Erlian Basin, a giant late Mesozoic intracontinental petroliferous basin located in the Inner Mongolia, Northeast China, contains important sedimentary and structural records related to the mid-Cretaceous compressional event. The stratigraphical, sedimentological and structural analyses reveal that a NW-SE compressional inversion occurred in the Erlian Basin between the depositions of the Lower Cretaceous Saihan and Upper Cretaceous Erlian formations, causing intense folding of the Saihan Formation and underlying strata, and the northwestward migration of the depocenters of the Erlian Formation. Based on the newly obtained detrital zircon U-Pb data and previously published paleomagnetism- and fossil-based ages, the Saihan and Erlian formations are suggested as latest Aptian-Albian and post-early Cenomanian in age, respectively, implying that the inversion in the Erlian Basin occurred in the early Late Cretaceous (Cenomanian time). Apatite fission-track thermochronological data record an early Late Cretaceous cooling/exhuming event in the basin, corresponding well with the aforementioned sedimentary, structural and chronological analyses. Combining with the tectono-sedimentary evolutions of the neighboring basins of the Erlian Basin, we suggest that the early Late Cretaceous inversional event in the Erlian Basin and the large scale tectonic transition in East Asia shared the common driving mechanism, probably resulting from the Okhotomorsk Block-East Asia collisional event at about 100-89 Ma.

Characterizing Feedbacks Between Environmental Forcing and Sediment Characteristics in Fluvial and Coastal Systems

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Feehan, S.; Ruggiero, P.; Hempel, L. A.; Anderson, D. L.; Cohn, N.

2016-12-01

Characterizing Feedbacks Between Environmental Forcing and Sediment Characteristics in Fluvial and Coastal Systems American Geophysical Union, 2016 Fall Meeting: San Francisco, CA Authors: Scott Feehan, Peter Ruggiero, Laura Hempel, and Dylan Anderson Linking transport processes and sediment characteristics within different environments along the source to sink continuum provides critical insight into the dominant feedbacks between grain size distributions and morphological evolution. This research is focused on evaluating differences in sediment size distributions across both fluvial and coastal environments in the U.S. Pacific Northwest. The Cascades' high relief is characterized by diverse flow regimes with high peak/flashy flows and sub-threshold flows occurring in relative proximity and one of the most energetic wave climates in the world. Combining analyses of both fluvial and coastal environments provides a broader understanding of the dominant forces driving differences between each system's grain size distributions, sediment transport processes, and resultant evolution. We consider sediment samples taken during a large-scale flume experiment that simulated floods representative of both high/flashy peak flows analogous to runoff dominated rivers and sub-threshold flows, analogous to spring-fed rivers. High discharge flows resulted in narrower grain size distributions while low flows where less skewed. Relative sediment size showed clear dependence on distance from source and the environments' dominant fluid motion. Grain size distributions and sediment transport rates were also quantified in both wave dominated nearshore and aeolian dominated backshore portions of Long Beach Peninsula, Washington during SEDEX2, the Sandbar-aEolian-Dune EXchange Experiment of summer 2016. The distributions showed spatial patterns in mean grain size, skewness, and kurtosis dependent on the dominant sediment transport process. The feedback between these grain size

Latest Cretaceous climatic and environmental change in the South Atlantic region

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Woelders, L.; Vellekoop, J.; Kroon, D.; Smit, J.; Casadío, S.; Prámparo, M. B.; Dinarès-Turell, J.; Peterse, F.; Sluijs, A.; Lenaerts, J.T.M.; Speijer, R. P.

Latest Maastrichtian climate change caused by Deccan volcanism has been invoked as a cause of mass extinction at the Cretaceous-Paleogene (K-Pg) boundary (~66.0 Ma). Yet late Maastrichtian climate and ecological changes are poorly documented, in particular on the Southern Hemisphere. Here we present

Latest Cretaceous climatic and environmental change in the South Atlantic region

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Woelders, L.; Vellekoop, J.; Kroon, D.; Smit, J.; Casadío, S.; Prámparo, M. B.; Dinarès-Turell, J.; Peterse, F.; Sluijs, A.; Lenaerts, J. T.M.; Speijer, R. P.

2017-01-01

Latest Maastrichtian climate change caused by Deccan volcanism has been invoked as a cause of mass extinction at the Cretaceous-Paleogene (K-Pg) boundary (~66.0 Ma). Yet late Maastrichtian climate and ecological changes are poorly documented, in particular on the Southern Hemisphere. Here we present

Quantifying bleaching for zero-age fluvial sediment: A Bayesian approach

International Nuclear Information System (INIS)

Cunningham, Alastair C.; Evans, Mary; Knight, Jasper

2015-01-01

Luminescence dating of sediment requires the sand grains to have been exposed to sunlight prior to their most recent burial. Under fluvial transport, the amount of sunlight exposure may not always be sufficient to reset the luminescence signal, a phenomenon known as ‘partial bleaching'. The extent of bleaching is dependent on a combination of geomorphic, sedimentological and fluvial processes. If bleaching can be quantified, and the relationship with these processes understood, it could potentially be used as a new environmental proxy for changes in the dynamics of river systems. Here, we use a recently developed statistical model to evaluate the extent of bleaching, by inferring the proportion of well-bleached grains in the small-aliquot population. We sampled low-flow and flood deposits at a single site on the River Sabie, South Africa. We show that the low-flow sediment is almost perfectly bleached (>80% of grains well bleached), while sediment at flood elevations is partially bleached (20–70 % of grains well bleached). The degree of bleaching may show a relationship with flood magnitude as defined by elevation above normal river level, and we speculate on the causes of variability in bleaching between flood samples. - Highlights: • We sampled modern river sediment from low-flow and flood elevations. • The unbleached OSL dose was measured. • Bayesian methods can estimate the proportion of well-bleached grains. • Low-flow sediments are well bleached; flood deposits are poorly bleached.

Glacial vs. Interglacial Period Contrasts in Midlatitude Fluvial Systems, with Examples from Western Europe and the Texas Coastal Plain

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Blum, M.

2001-12-01

Mixed bedrock-alluvial valleys are the conveyor belts for sediment delivery to passive continental margins. Mapping, stratigraphic and sedimentologic investigations, and development of geochronological frameworks for large midlatitude rivers of this type, in Western Europe and the Texas Coastal Plain, provide for evaluation of fluvial responses to climate change over the last glacial-interglacial period, and the foundations for future quantitative evaluation of long profile evolution, changes through time in flood magnitude, and changes in storage and flux of sediments. This paper focuses on two issues. First, glacial vs. interglacial period fluvial systems are fundamentally different in terms of channel geometry, depositional style, and patterns of sediment storage. Glacial-period systems were dominated by coarse-grained channel belts (braided channels in Europe, large-wavelength meandering in Texas), and lacked fine-grained flood-plain deposits, whereas Holocene units, especially those of late Holocene age, contain appreciable thicknesses of flood-plain facies. Hence, extreme overbank flooding was not significant during the long glacial period, most flood events were contained within bankfull channel perimeters, and fine sediments were bypassed through the system to marine basins. By contrast, extreme overbank floods have been increasingly important during the relatively short Holocene, and a significant volume of fine sediment is sequestered in flood-plain settings. Second, glacial vs. interglacial systems exhibit different amplitudes and frequencies of fluvial adjustment to climate change. High-amplitude but low-frequency adjustments characterized the long glacial period, with 2-3 extended periods of lateral migration and sediment storage puncuated by episodes of valley incision. Low-amplitude but high-frequency adjustments have been more typical of the short Holocene, when there has been little net valley incision or net changes in sediment storage, but

The microfauna assemblages as indicators of paleoenvironmental changes in the Miocene fluvial- lacustrine cycles (NE Duero Basin, Spain

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A. Herrero-Hernández

2016-11-01

Full Text Available The siliclastic and carbonate deposits are interbedded in the Villadiego area (Miocene, NE Duero Basin. They have been subdivided into two high-rank depositional sequences: DDS and CDS. The sedimentary analysis of these units and the study of the microfauna content, mainly ostracods, led to the identification of lacustrine-fluvial interaction systems. The sedimentary characteristics reveal the existence of fluvial systems of gravel, flood plains and lacustrine systems that were interconnected and intimately related in north-south direction. In the sedimentological analysis, thirteen types of fluvial and lacustrine lithofacies and six genetic facies associations were recognized. The top of DDS is the result of lake level risings. The CDS shows a deepening-shallowing cycle. The ostracod micropaleontological analysis of the sediments have been studied, with the aim of reconstructing the palaeoenvironmental evolution of this area. These microfauna assemblages integrated with the analysis of the sedimentary facies allowed to conclude the existence of lakes with a water-bearing level of few tens of meters. A change in the chemical conditions of the waters, which evolved from oligohaline and carbonated to mesohaline and sulphated is concluded.

Evidence for an early land use in the Rhône delta (Mediterranean France) as recorded by late Holocene fluvial paleoenvironments (1640-100 BC)

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Arnaud-Fassetta, Gilles; De Beaulieu, Jacques-Louis; Suc, Jean-Pierre; Provansal, Mireille; Williamson, David; Leveau, Philippe; Aloïsi, Jean-Claude; Gadel, François; Giresse, Pierre; Oberlin, Christine; Duzer, Danièle

The overall objective of this paper is to describe the late Holocene (1640-100 BC) sedimentary and biological evolution of the Rhône-delta-plain, to interpret the sedimentary facies and palynofacies as the result of the effects of fluvial dynamic fluctuations and relative sea level change and to evaluate the paleohydrological constraints in the development of the land use and settlements of the Camargue. Focus is made on the upper part of V III core drilled on NE of the Vaccarès lagoon. By combining sedimentology, palynology, magnetic susceptibility and archeological data, this study allowed to identify the superposition of three types of paleo-environments (marsh, fluvial floodplain, levee/crevasse splay). This sequence indicates a gradual extension of fluvial environments between the end of the second millennium BC and the 1st century BC. The variability of fluvial dynamic is evident during this period with important flood events which contrast with periods of low flow. Pollen record can be a good marker of the fluvial dynamic variability. The expression of the riparian tree pollen grains in the coarser floodplain deposits could correspond to increased fluvial influence and probably to erosion of riverbank during flood events. The local plants are associated to the low energy sedimentary environments. Focuses are made on the relations between the evolution of the environment and land use. The development of the cereal culture in the floodplain of the Rhône delta has been demonstrated between 1640-1410 and 100 BC. The last alluviation of the Rhône perturbs the research of the archaeological sites in the central part of the delta but the existence of the rural villages from the first part of the first millennium BC is highly possible.

Fluvial wood function downstream of beaver versus man-made dams in headwater streams in Massachusetts, USA

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David, G. C.; DeVito, L. F.; Munz, K. T.; Lisius, G.

2014-12-01

Fluvial wood is an essential component of stream ecosystems by providing habitat, increasing accumulation of organic matter, and increasing the processing of nutrients and other materials. However, years of channel alterations in Massachusetts have resulted in low wood loads despite the afforestation that has occurred since the early 1900s. Streams have also been impacted by a large density of dams, built during industrialization, and reduction of the beaver population. Beavers were reintroduced to Massachusetts in the 1940s and they have since migrated throughout the state. Beaver dams impound water, which traps sediment and results in the development of complex channel patterns and more ecologically productive and diverse habitats than those found adjacent to man-made dams. To develop better management practices for dam removal it is essential that we understand the geomorphic and ecologic function of wood in these channels and the interconnections with floodplain dynamics and stream water chemistry. We investigate the connections among fluvial wood, channel morphology, floodplain soil moisture dynamics, and stream water chemistry in six watersheds in Massachusetts that have been impacted by either beaver or man-made dams. We hypothesize that wood load will be significantly higher below beaver dams, subsequently altering channel morphology, water chemistry, and floodplain soil moisture. Reaches are surveyed up- and downstream of each type of dam to better understand the impact dams have on the fluvial system. Surveys include a longitudinal profile, paired with dissolved oxygen and ammonium measurements, cross-section and fluvial wood surveys, hydraulic measurements, and floodplain soil moisture mapping. We found that dissolved oxygen mirrored the channel morphology, but did not vary significantly between reaches. Wood loads were significantly larger downstream of beaver dams, which resulted in significant changes to the ammonium levels. Floodplain soil moisture

Discovery of a new stonefly genus with three new species from mid-Cretaceous Burmese amber (Plecoptera: Perlidae).

Science.gov (United States)

Chen, Zhi-Teng; Wang, Bo; Du, Yu-Zhou

2018-02-11

A new fossil stonefly genus of the subfamily Acroneuriinae Klapálek, 1914 (Plecoptera: Perlidae), Largusoperla gen. nov. is reported based on three well-preserved specimens in mid-Cretaceous amber from northern Myanmar. Three new species of this new genus, L. acus sp. nov, L. flata sp. nov and L. arcus sp. nov. are described and illustrated. This is the first report of stonefly specimens from mid-Cretaceous Burmese amber. The taxonomic placement of the new genus is discussed.

Earth history. U-Pb geochronology of the Deccan Traps and relation to the end-Cretaceous mass extinction.

Science.gov (United States)

Schoene, Blair; Samperton, Kyle M; Eddy, Michael P; Keller, Gerta; Adatte, Thierry; Bowring, Samuel A; Khadri, Syed F R; Gertsch, Brian

2015-01-09

The Chicxulub asteroid impact (Mexico) and the eruption of the massive Deccan volcanic province (India) are two proposed causes of the end-Cretaceous mass extinction, which includes the demise of nonavian dinosaurs. Despite widespread acceptance of the impact hypothesis, the lack of a high-resolution eruption timeline for the Deccan basalts has prevented full assessment of their relationship to the mass extinction. Here we apply uranium-lead (U-Pb) zircon geochronology to Deccan rocks and show that the main phase of eruptions initiated ~250,000 years before the Cretaceous-Paleogene boundary and that >1.1 million cubic kilometers of basalt erupted in ~750,000 years. Our results are consistent with the hypothesis that the Deccan Traps contributed to the latest Cretaceous environmental change and biologic turnover that culminated in the marine and terrestrial mass extinctions. Copyright © 2015, American Association for the Advancement of Science.

Construction of the seawater 87Sr/86Sr curve for the Cenozoic and Cretaceous: supporting data

International Nuclear Information System (INIS)

Koepnick, R.B.; Burke, W.H.; Denison, R.E.; Hetherington, E.A.; Nelson, H.F.; Otto, J.B.; Waite, L.E.

1985-01-01

We present the data used to construct the Cenozoic and Cretaceous portion of the Phanerozoic curve of seawater 87 Sr/ 86 Sr that had been given in summary form by W.H. Burke and coworkers. All Cenozoic samples (128) and 22 Cretaceous samples are foram-nannofossil oozes and limestones from DSDP cores distributed among 13 sites in the Atlantic, Pacific and Indian Oceans, and the Caribbean Sea. Non-DSDP Cretaceous samples (126) include limestone, anhydrite and phosphate samples from North America, Europe and Asia. Determination of the 87 Sr/ 86 Sr value of seawater at particular times in the past is based on comparison of ratios derived from coeval marine samples from widely separated geographic areas. The general configuration of the Cenozoic and Cretaceous curve appears to be strongly influenced by the history of plate interactions and sea-floor spreading. Specific rises and falls in the 87 Sr/ 86 Sr of seawater, however, may be caused by a variety of factors such as variation in lithologic composition of the crust exposed to weathering, configuration and topographic relief of continents, volcanic activity, rate of sea-floor spreading, extent of continental inundation by epeiric seas, and variations in both climate and paleo-oceanographic conditions. Many or all of these factors are probably related to global tectonic processes, yet their combined effect on the temporal variation of seawater 87 Sr/ 86 Sr can complicate a direct plate-tectonic interpretation for portions of the seawater curve. (Auth.)

AN APPROACH TO PROVENANCE, TECTONIC AND REDOX CONDITIONS OF JURASSIC-CRETACEOUS AKKUYU FORMATION, CENTRAL TAURIDS, TURKEY

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Ali SARI

2012-06-01

Full Text Available - Late Jurassic-Early Cretaceous Akkuyu formation was deposited in a marine carbonate platform in Central Tarurids. The organic material of the unit is composed of Type III kerogen which is woody material transported from the land. Late Jurassic- Early Cretaceous is an important period which great anoxic events in deep sea bottom occurred due to the primary organic productivity in global sea surface. Use of several trace elements values (Ni, V, U, Cr, Co, Th revealed that Late Jurassic-Early Cretaceous Akkuyu formation shows oxic, disoxic and anoxic paleoredox conditions. In this period the primary productivity was considerably high. Examination of specimen derived from Akkuyu formation revealed that there exists a very good positive relationship between the major oxides of Al2O3, SiO2, Fe2O3, TiO2, and K2O. These combinations of major oxides indicate a detrital origin of source rock. Chemical weathering evaluations of Central Taurids in the Jurassic-Cretaceous period indicated moderate and strong weathering of source rock. K2O/Na2O versus SiO2; SiO2/Al2O3 versus K2O/Na2O; Al2O3/ SiO2 versus Fe2O3 + MgO ve TiO2 versus Fe2O3 + MgO diagrams indicated that Akkuyu formation was deposited along active and/or passive continental margin and derived from basalt and basalt+granite mixed rocks.

Mechanosensory based orienting behaviors in fluvial and lacustrine populations of mottled sculpin (Cottus bairdi)

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Sheryl Coombs; Gary D. Grossman

2006-01-01

We compared prey-orienting and rheotactic behaviors in a fluvial (Coweeta Creek) and lacustrine (Lake Michigan) population of mottled sculpin. Blinded sculpin from both populations exhibited unconditioned, mechanosensory based rheotaxis to low velocity flows. Whereas Lake Michigan sculpin generally showed increasing levels of positive rheotaxis to increasing velocities...

Calculation of paleohydraulic parameters of a fluvial system under spatially variable subsidence, of the Ericson sandstone, South western Wyoming

Science.gov (United States)

Snyder, H.; Leva-Lopez, J.

2017-12-01

During the late Campanian age in North America fluvial systems drained the highlands of the Sevier orogenic belt and travelled east towards the Western Interior Seaway. One of such systems deposited the Canyon Creek Member (CCM) of the Ericson Formation in south-western Wyoming. At this time the fluvial system was being partially controlled by laterally variable subsidence caused by incipient Laramide uplifts. These uplifts rather than real topographic features were only areas of reduced subsidence at the time of deposition of the CCM. Surface expression at that time must have been minimum, only minute changes in slope and accommodation. Outcrops around these Laramide structures, in particular both flanks of the Rock Springs Uplift, the western side of the Rawlins uplift and the north flank of the Uinta Mountains, have been sampled to study the petrography, grain size, roundness and sorting of the CCM, which along with the cross-bed thickness and bar thickness allowed calculation of the hydraulic parameters of the rivers that deposited the CCM. This study reveals how the fluvial system evolved and responded to the very small changes in subsidence and slope. Furthermore, the petrography will shed light on the provenance of these sandstones and on the relative importance of Sevier sources versus Laramide sources. This work is framed in a larger study that shows how incipient Laramide structural highs modified the behavior, style and architecture of the fluvial system, affecting its thickness, facies characteristics and net-to-gross both down-dip and along strike across the basin.

Detrital shadows: estuarine food web connectivity depends on fluvial influence and consumer feeding mode.

Science.gov (United States)

Howe, Emily; Simenstad, Charles A; Ogston, Andrea

2017-10-01

We measured the influence of landscape setting on estuarine food web connectivity in five macrotidal Pacific Northwest estuaries across a gradient of freshwater influence. We used stable isotopes (δ 13 C, δ 15 N, δ 34 S) in combination with a Bayesian mixing model to trace primary producer contributions to suspension- and deposit-feeding bivalve consumers (Mytilus trossulus and Macoma nasuta) transplanted into three estuarine vegetation zones: emergent marsh, mudflat, and eelgrass. Eelgrass includes both Japanese eelgrass (Zostera japonica) and native eelgrass (Zostera marina). Fluvial discharge and consumer feeding mode strongly influenced the strength and spatial scale of observed food web linkages, while season played a secondary role. Mussels displayed strong cross-ecosystem connectivity in all estuaries, with decreasing marine influence in the more fluvial estuaries. Mussel diets indicated homogenization of detrital sources within the water column of each estuary. In contrast, the diets of benthic deposit-feeding clams indicated stronger compartmentalization in food web connectivity, especially in the largest river delta where clam diets were trophically disconnected from marsh sources of detritus. This suggests detritus deposition is patchy across space, and less homogenous than the suspended detritus pool. In addition to fluvial setting, other estuary-specific environmental drivers, such as marsh area or particle transport speed, influenced the degree of food web linkages across space and time, often accounting for unexpected patterns in food web connectivity. Transformations of the estuarine landscape that alter river hydrology or availability of detritus sources can thus potentially disrupt natural food web connectivity at the landscape scale, especially for sedentary organisms, which cannot track their food sources through space. © 2017 by the Ecological Society of America.

Preliminary vitrinite and bitumen reflectance, total organic carbon, and pyrolysis data for samples from Upper and Lower Cretaceous strata, Maverick Basin, south Texas

Science.gov (United States)

Hackley, Paul C.; Dennen, Kristin O.; Gesserman, Rachel M.; Ridgley, Jennie L.

2009-01-01

The Lower Cretaceous Pearsall Formation, a regionally occurring limestone and shale interval of 500-600-ft maximum thickness (Rose, 1986), is being evaluated as part of an ongoing U.S. Geological Survey (USGS) assessment of undiscovered hydrocarbon resources in onshore Lower Cretaceous strata of the northern Gulf of Mexico. The purpose of this report is to release preliminary vitrinite and bitumen reflectance, total organic carbon, and pyrolysis data for Pearsall Formation, Glen Rose Formation, Hosston Formation, Austin Group, and Eagle Ford Group samples from the Maverick Basin in south Texas in order to aid in the characterization of these strata in this area. The preliminary nature of this report and the data contained herein reflect that the assessment and characterization of these samples is a work currently in progress. Pearsall Formation subdivisions are, in ascending stratigraphic order, the Pine Island Shale, James Limestone, and Bexar Shale Members (Loucks, 2002). The Lower Cretaceous Glen Rose Formation is also part of the USGS Lower Cretaceous assessment and produces oil in the Maverick Basin (Loucks and Kerans, 2003). The Hosston Formation was assessed by the USGS for undiscovered oil and gas resources in 2006 (Dyman and Condon, 2006), but not in south Texas. The Upper Cretaceous Austin Group is being assessed as part of the USGS assessment of undiscovered hydrocarbon resources in the Upper Cretaceous strata of the northern Gulf of Mexico and, along with the Upper Cretaceous Eagle Ford Group, is considered to be an important source rock in the Smackover-Austin-Eagleford Total Petroleum System (Condon and Dyman, 2006). Both the Austin Group and the Eagle Ford Group are present in the Maverick Basin in south Texas (Rose, 1986).

Revisiting geochemical methods of distinguishing natural concentrations and pollution by risk elements in fluvial sediments

Czech Academy of Sciences Publication Activity Database

Matys Grygar, Tomáš; Popelka, J.

2016-01-01

Roč. 170, NOV (2016), s. 39-57 ISSN 0375-6742 R&D Projects: GA ČR(CZ) GA15-00340S Institutional support: RVO:61388980 Keywords : Enrichment * Fluvial sediments * Heavy metals Subject RIV: DD - Geochemistry Impact factor: 2.464, year: 2016

Large-scale coastal and fluvial models constrain the late Holocene evolution of the Ebro Delta

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J. H. Nienhuis

2017-09-01

Full Text Available The distinctive plan-view shape of the Ebro Delta coast reveals a rich morphologic history. The degree to which the form and depositional history of the Ebro and other deltas represent autogenic (internal dynamics or allogenic (external forcing remains a prominent challenge for paleo-environmental reconstructions. Here we use simple coastal and fluvial morphodynamic models to quantify paleo-environmental changes affecting the Ebro Delta over the late Holocene. Our findings show that these models are able to broadly reproduce the Ebro Delta morphology, with simple fluvial and wave climate histories. Based on numerical model experiments and the preserved and modern shape of the Ebro Delta plain, we estimate that a phase of rapid shoreline progradation began approximately 2100 years BP, requiring approximately a doubling in coarse-grained fluvial sediment supply to the delta. River profile simulations suggest that an instantaneous and sustained increase in coarse-grained sediment supply to the delta requires a combined increase in both flood discharge and sediment supply from the drainage basin. The persistence of rapid delta progradation throughout the last 2100 years suggests an anthropogenic control on sediment supply and flood intensity. Using proxy records of the North Atlantic Oscillation, we do not find evidence that changes in wave climate aided this delta expansion. Our findings highlight how scenario-based investigations of deltaic systems using simple models can assist first-order quantitative paleo-environmental reconstructions, elucidating the effects of past human influence and climate change, and allowing a better understanding of the future of deltaic landforms.

Kinematics of Late Cretaceous subduction initiation in the Neo-Tethys Ocean reconstructed from ophiolites of Turkey, Cyprus, and Syria

Science.gov (United States)

Maffione, Marco; van Hinsbergen, Douwe J. J.; de Gelder, Giovanni I. N. O.; van der Goes, Freek C.; Morris, Antony

2017-05-01

Formation of new subduction zones represents one of the cornerstones of plate tectonics, yet both the kinematics and geodynamics governing this process remain enigmatic. A major subduction initiation event occurred in the Late Cretaceous, within the Neo-Tethys Ocean between Gondwana and Eurasia. Suprasubduction zone ophiolites (i.e., emerged fragments of ancient oceanic lithosphere formed at suprasubduction spreading centers) were generated during this subduction event and are today distributed in the eastern Mediterranean region along three E-W trending ophiolitic belts. Several models have been proposed to explain the formation of these ophiolites and the evolution of the associated intra-Neo-Tethyan subduction zone. Here we present new paleospreading directions from six Upper Cretaceous ophiolites of Turkey, Cyprus, and Syria, calculated by using new and published paleomagnetic data from sheeted dyke complexes. Our results show that NNE-SSW subduction zones were formed within the Neo-Tethys during the Late Cretaceous, which we propose were part of a major step-shaped subduction system composed of NNE-SSW and WNW-ESE segments. We infer that this subduction system developed within old (Triassic?) lithosphere, along fracture zones and perpendicular weakness zones, since the Neo-Tethyan spreading ridge formed during Gondwana fragmentation would have already been subducted at the Pontides subduction zone by the Late Cretaceous. Our new results provide an alternative kinematic model of Cretaceous Neo-Tethyan subduction initiation and call for future research on the mechanisms of subduction inception within old (and cold) lithosphere and the formation of metamorphic soles below suprasubduction zone ophiolites in the absence of nearby spreading ridges.

Quantitative reconstruction of cross-sectional dimensions and hydrological parameters of gravelly fluvial channels developed in a forearc basin setting under a temperate climatic condition, central Japan

Science.gov (United States)

Shibata, Kenichiro; Adhiperdana, Billy G.; Ito, Makoto

2018-01-01

Reconstructions of the dimensions and hydrological features of ancient fluvial channels, such as bankfull depth, bankfull width, and water discharges, have used empirical equations developed from compiled data-sets, mainly from modern meandering rivers, in various tectonic and climatic settings. However, the application of the proposed empirical equations to an ancient fluvial succession should be carefully examined with respect to the tectonic and climatic settings of the objective deposits. In this study, we developed empirical relationships among the mean bankfull channel depth, bankfull channel depth, drainage area, bankfull channel width, mean discharge, and bankfull discharge using data from 24 observation sites of modern gravelly rivers in the Kanto region, central Japan. Some of the equations among these parameters are different from those proposed by previous studies. The discrepancies are considered to reflect tectonic and climatic settings of the present river systems, which are characterized by relatively steeper valley slope, active supply of volcaniclastic sediments, and seasonal precipitation in the Kanto region. The empirical relationships derived from the present study can be applied to modern and ancient gravelly fluvial channels with multiple and alternate bars, developed in convergent margin settings under a temperate climatic condition. The developed empirical equations were applied to a transgressive gravelly fluvial succession of the Paleogene Iwaki Formation, Northeast Japan as a case study. Stratigraphic thicknesses of bar deposits were used for estimation of the bankfull channel depth. In addition, some other geomorphological and hydrological parameters were calculated using the empirical equations developed by the present study. The results indicate that the Iwaki Formation fluvial deposits were formed by a fluvial system that was represented by the dimensions and discharges of channels similar to those of the middle to lower reaches of

External controls on Quaternary fluvial incision and terrace formation at the Segre River, Southern Pyrenees

NARCIS (Netherlands)

Stange, K.M.; van Balen, R.T.; Vandenberghe, J.; Peña, J.L.; Sancho, C.

2013-01-01

Focusing on climatic- and structural (tectonic) controls, we aim to determine their relative importance for the (Pliocene to Quaternary) fluvial landscape evolution in the Southern Pyrenees foreland. We investigate the Segre River, which is one of the major streams of the Southern Pyrenees that

Arquitectura fluvial de las «Areniscas del río Arandilla». Triásico de Molina de Aragón (Guadalajara

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Sánchez-Moya, Y.

1989-08-01

Full Text Available The outstanding outcrops of Upper Buntsandstein sediments (Middle Triassic in Molina de Aragón (Guadalajara area, allow a detailed study of their characteristics and their associations which are described here. The fluvial architecture of the section indicates four main depositional episodes. The two lowest episodes were laid down by a fluvial system characterized by frequent channel shifting, low sinuosity and wide shallow channels. The drainage basin was controlled by highly seasonal discharge. The middle episode evolved into a more distal systems, with smaller higher sinuosity channels and fine overbank deposits. The uppermost episode is related to an increase of slope in the basin. That increase is probably related to tectonic movements recorded in this area. An attempt has been made to correlate the above events to the global sea level fluctuations (Haq et al., 1987. So, the low stage that have been stated occurred during Early Anisian can be tentatively correlated with the uppermost episode in Areniscas del río Arandilla.Los excelentes afloramientos de la parte superior del Buntsandstein (Triásico medio en Molina de Aragón (Guadalajara, han permitido llevar a cabo un análisis sedimentológico detallado de las facies fluviales y de su arquitectura. Se han distinguido doce diferentes facies cuyas características y asociaciones se describen en este trabajo. La evolución fluvial indica la existencia de cuatro episodios deposicionales. Los dos episodios inferiores son característicos de un sistema fluvial con canales de baja sinuosidad, inestables, de gran amplitud y poca profundidad. El drenaje de la cuenca estaba controlado por importantes descargas estacionales. El episodio intermedio es el resultado de la evolución del sistema hacia facies más distales. En esta etapa los canales son de menor tamaño, la sinuosidad es mayor y existe un mayor porcentaje de depósitos de granulometría fina relacionados con la llanura de inundaci

Geologic assessment of undiscovered oil and gas resources—Lower Cretaceous Albian to Upper Cretaceous Cenomanian carbonate rocks of the Fredericksburg and Washita Groups, United States Gulf of Mexico Coastal Plain and State Waters

Science.gov (United States)

Swanson, Sharon M.; Enomoto, Catherine B.; Dennen, Kristin O.; Valentine, Brett J.; Cahan, Steven M.

2017-02-10

In 2010, the U.S. Geological Survey (USGS) assessed Lower Cretaceous Albian to Upper Cretaceous Cenomanian carbonate rocks of the Fredericksburg and Washita Groups and their equivalent units for technically recoverable, undiscovered hydrocarbon resources underlying onshore lands and State Waters of the Gulf Coast region of the United States. This assessment was based on a geologic model that incorporates the Upper Jurassic-Cretaceous-Tertiary Composite Total Petroleum System (TPS) of the Gulf of Mexico basin; the TPS was defined previously by the USGS assessment team in the assessment of undiscovered hydrocarbon resources in Tertiary strata of the Gulf Coast region in 2007. One conventional assessment unit (AU), which extends from south Texas to the Florida panhandle, was defined: the Fredericksburg-Buda Carbonate Platform-Reef Gas and Oil AU. The assessed stratigraphic interval includes the Edwards Limestone of the Fredericksburg Group and the Georgetown and Buda Limestones of the Washita Group. The following factors were evaluated to define the AU and estimate oil and gas resources: potential source rocks, hydrocarbon migration, reservoir porosity and permeability, traps and seals, structural features, paleoenvironments (back-reef lagoon, reef, and fore-reef environments), and the potential for water washing of hydrocarbons near outcrop areas.In Texas and Louisiana, the downdip boundary of the AU was defined as a line that extends 10 miles downdip of the Lower Cretaceous shelf margin to include potential reef-talus hydrocarbon reservoirs. In Mississippi, Alabama, and the panhandle area of Florida, where the Lower Cretaceous shelf margin extends offshore, the downdip boundary was defined by the offshore boundary of State Waters. Updip boundaries of the AU were drawn based on the updip extent of carbonate rocks within the assessed interval, the presence of basin-margin fault zones, and the presence of producing wells. Other factors evaluated were the middle

New tyrannosaur from the mid-Cretaceous of Uzbekistan clarifies evolution of giant body sizes and advanced senses in tyrant dinosaurs.

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Brusatte, Stephen L; Averianov, Alexander; Sues, Hans-Dieter; Muir, Amy; Butler, Ian B

2016-03-29

Tyrannosaurids--the familiar group of carnivorous dinosaurs including Tyrannosaurus and Albertosaurus--were the apex predators in continental ecosystems in Asia and North America during the latest Cretaceous (ca. 80-66 million years ago). Their colossal sizes and keen senses are considered key to their evolutionary and ecological success, but little is known about how these features developed as tyrannosaurids evolved from smaller basal tyrannosauroids that first appeared in the fossil record in the Middle Jurassic (ca. 170 million years ago). This is largely because of a frustrating 20+ million-year gap in the mid-Cretaceous fossil record, when tyrannosauroids transitioned from small-bodied hunters to gigantic apex predators but from which no diagnostic specimens are known. We describe the first distinct tyrannosauroid species from this gap, based on a highly derived braincase and a variety of other skeletal elements from the Turonian (ca. 90-92 million years ago) of Uzbekistan. This taxon is phylogenetically intermediate between the oldest basal tyrannosauroids and the latest Cretaceous forms. It had yet to develop the giant size and extensive cranial pneumaticity of T. rex and kin but does possess the highly derived brain and inner ear characteristic of the latest Cretaceous species. Tyrannosauroids apparently developed huge size rapidly during the latest Cretaceous, and their success in the top predator role may have been enabled by their brain and keen senses that first evolved at smaller body size.

New tyrannosaur from the mid-Cretaceous of Uzbekistan clarifies evolution of giant body sizes and advanced senses in tyrant dinosaurs

Science.gov (United States)

Brusatte, Stephen L.; Averianov, Alexander; Sues, Hans-Dieter; Muir, Amy; Butler, Ian B.

2016-03-01

Tyrannosaurids-the familiar group of carnivorous dinosaurs including Tyrannosaurus and Albertosaurus-were the apex predators in continental ecosystems in Asia and North America during the latest Cretaceous (ca. 80-66 million years ago). Their colossal sizes and keen senses are considered key to their evolutionary and ecological success, but little is known about how these features developed as tyrannosaurids evolved from smaller basal tyrannosauroids that first appeared in the fossil record in the Middle Jurassic (ca. 170 million years ago). This is largely because of a frustrating 20+ million-year gap in the mid-Cretaceous fossil record, when tyrannosauroids transitioned from small-bodied hunters to gigantic apex predators but from which no diagnostic specimens are known. We describe the first distinct tyrannosauroid species from this gap, based on a highly derived braincase and a variety of other skeletal elements from the Turonian (ca. 90-92 million years ago) of Uzbekistan. This taxon is phylogenetically intermediate between the oldest basal tyrannosauroids and the latest Cretaceous forms. It had yet to develop the giant size and extensive cranial pneumaticity of T. rex and kin but does possess the highly derived brain and inner ear characteristic of the latest Cretaceous species. Tyrannosauroids apparently developed huge size rapidly during the latest Cretaceous, and their success in the top predator role may have been enabled by their brain and keen senses that first evolved at smaller body size.

Pemaknaan Filsafati Kearifan Lokal untuk Adaptasi Masyarakat terhadap Ancaman Bencana Marin dan Fluvial di Lingkungan Kepesisiran

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S Sunarto

2011-07-01

Full Text Available The purpose of this research was to study the philosophical meaning of local wisdom that developed in the communities in the coastal environment, particularly in the eastern coast of Central Java. The method used for this philosophical meaning using the approach of geomorphological hermeneutics and disaster semiotics. The results of this research indicate that identified local wisdom in the form of cultural semiotics and faunal semiotics to anticipate the hazards of climate change as marine hazard and fluvial hazard. Cultural semiotics found in the form of advice that still need to be interpreted with a geomorphological hermeneutics approach order to use it to adapt to the coastal environment against marine hazard. The cultural semiotics has a geomorphological philosophical meaning as natural cycle that leads to dynamic equilibrium, not the philosophical meaning that leads to the view of anthropocentrism. In addition, also found cultural semiotics of “Dina Rèntèng” based on the philosophical views of ecocentrism. The cultural semiotics is used in society to adapt to the fluvial hazard. Faunal semiotics found in the form of anomalous crab behavior as a form of adaptation due to its response to environmental condition. The faunal semiotics has been used as a guide for the community to adapt to the fluvial hazard. Because of the local wisdom is loaded with philosophical meaning, it can be metatourism assets, so it can convert harm into benefit.

Geoarchaeology, the four dimensional (4D) fluvial matrix and climatic causality

Science.gov (United States)

Brown, A. G.

2008-10-01

Geoarchaeology is the application of geological and geomorphological techniques to archaeology and the study of the interactions of hominins with the natural environment at a variety of temporal and spatial scales. Geoarchaeology in the UK over the last twenty years has flourished largely because it has gone beyond technological and scientific applications. Over the same period our ability to reconstruct the 3-dimensional stratigraphy of fluvial deposits and the matrix of fluvial sites has increased dramatically because of a number of technological advances. These have included the use of LiDAR (laser imaging) and radar to produce high-resolution digital surface models, the use of geophysics, particularly ground penetrating radar and electrical resistivity, to produce sediment depth models, and the use of GIS and data visualisation techniques to manipulate and display the data. These techniques along with more systematic and detailed sedimentological recording of exposed sections have allowed the construction of more precise 3-dimensional (volumetric) models of the matrix of artefacts within fluvial deposits. Additionally a revolution in dating techniques, particularly direct sediment dating by luminescence methods, has enabled the creation of 4-dimensional models of the creation and preservation of these sites. These 4-dimensional models have the ability to provide far more information about the processes of site creation, preservation and even destruction, and also allow the integration of these processes with independent data sources concerning cultural evolution and climatic change. All improvements in the precision of dating fluvial deposits have archaeological importance in our need to translate events from a sequential or geological timeframe to human timescales. This allows geoarchaeology to make a more direct contribution to cultural history through the recognition of agency at the individual or group level. This data can then form a component of

Palynology of uppermost Jurassic and lowermost Cretaceous strata in the Eastern Netherlands

NARCIS (Netherlands)

Burger, D.

1965-01-01

The present investigation is a systematical treatment of the sporomorphs from strata at the Jurassic-Cretaceous boundary in the eastern Netherlands Twente area, and an attempt to apply palynology to detailed stratigraphical study, by making use of quantitative pollen analyses. The rock samples used

Traces of a large crocodylian from the Lower Cretaceous Sousa Formation, Brazil

DEFF Research Database (Denmark)

Campos, Herbert B.N.; da Silva, Rafael C.; Milàn, Jesper

2010-01-01

Body imprints and tracks attributed to large crocodylians from the Lower Cretaceous Sousa Formation of Brazil are described and interpreted as having been produced in a subaqueous environment. In addition to the crocodylian tracks, the assemblage also comprises isolated tracks from medium-sized t...

Similarities and differences in the ilia of Late Cretaceous anurans and urodeles

Czech Academy of Sciences Publication Activity Database

Roček, Zbyněk; Gardner, J. D.; Eaton, J. G.; Přikryl, Tomáš

2012-01-01

Roč. 183, č. 6 (2012), s. 529-535 ISSN 0037-9409 R&D Projects: GA MŠk ME08066 Institutional support: RVO:67985831 Keywords : Anura * Cretaceous * Ilium * North America * Postcranial skeleton * Urodela Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.182, year: 2012

Cretaceous origin and repeated tertiary diversification of the redefined butterflies.

Science.gov (United States)

Heikkilä, Maria; Kaila, Lauri; Mutanen, Marko; Peña, Carlos; Wahlberg, Niklas

2012-03-22

Although the taxonomy of the ca 18 000 species of butterflies and skippers is well known, the family-level relationships are still debated. Here, we present, to our knowledge, the most comprehensive phylogenetic analysis of the superfamilies Papilionoidea, Hesperioidea and Hedyloidea to date based on morphological and molecular data. We reconstructed their phylogenetic relationships using parsimony and Bayesian approaches. We estimated times and rates of diversification along lineages in order to reconstruct their evolutionary history. Our results suggest that the butterflies, as traditionally understood, are paraphyletic, with Papilionidae being the sister-group to Hesperioidea, Hedyloidea and all other butterflies. Hence, the families in the current three superfamilies should be placed in a single superfamily Papilionoidea. In addition, we find that Hedylidae is sister to Hesperiidae, and this novel relationship is supported by two morphological characters. The families diverged in the Early Cretaceous but diversified after the Cretaceous-Palaeogene event. The diversification of butterflies is characterized by a slow speciation rate in the lineage leading to Baronia brevicornis, a period of stasis by the skippers after divergence and a burst of diversification in the lineages leading to Nymphalidae, Riodinidae and Lycaenidae.

Allogenic controls on the fluvial architecture and fossil preservation of the Upper Triassic Ischigualasto Formation, NW Argentina

Science.gov (United States)

Colombi, Carina E.; Limarino, Carlos O.; Alcober, Oscar A.

2017-12-01

The Upper Triassic Ischigualasto Formation in NW Argentina was deposited in a fluvial system during the synrift filling of the extensional Ischigualasto-Villa Unión Basin. The expansive exposures of the fluvial architecture and paleosols provide a framework to reconstruct the paleoenvironmental evolution of this basin during the Upper Triassic using continental sequence stratigraphy. The Ischigualasto Formation deposition can be divided into seven sequential sedimentary stages: the 1) Bypass stage; 2) Confined low-accommodation stage; 3) Confined high accommodation stage; 4) Unstable-accommodation stage; 5) Unconfined high-accommodation stage; 6) Unconfined low-accommodation stage; and finally, 7) Unconfined high-accommodation stage. The sedimentary evolution of the Ischigualasto Formation was driven by different allogenic controls such as rises and falls in lake levels, local tectonism, subsidence, volcanism, and climate, which also produced modifications of the equilibrium profile of the fluvial systems. All of these factors result in different accommodations in central and flank areas of the basin, which led to different architectural configurations of channels and floodplains. Allogenic processes affected not only the sequence stratigraphy of the basin but also the vertebrate and plant taphocenosis. Therefore, the sequence stratigraphy can be used not only as a predictive tool related to fossil occurrence but also to understand the taphonomic history of the basin at each temporal interval.

Avulsion and its implications for fluvial-deltaic architecture: insights from the Holocene Rhine-Meuse delta

NARCIS (Netherlands)

Stouthamer, E.; Cohen, K.M.; Gouw, M.J.P.

2010-01-01

Avulsion is a key process in the formation of fluvial-deltaic successions and a primary control on deltaic architecture. It determines the distribution of sediment and water and hence which location in the delta receives clastic sedimentation for what time. This makes the avulsion process an

Avulsion and its implications for fluvial-deltaic architecture: insights from the Holocene Rhine-Meuse delta

NARCIS (Netherlands)

Stouthamer, E.; Cohen, K.M.; Gouw, M.J.P.

2010-01-01

Avulsion is a principal process in the formation of fluvial-deltaic successions and a primary control on deltaic architecture. It determines the distribution of sediment and water and hence influences which location in the delta receives clastic sedimentation in what amounts for what time. It also

Evolution of tertiary intermontane fluvial system of Powder River Basin, Wyoming and Montana

International Nuclear Information System (INIS)

Flores, R.M.; Ethridge, F.G.

1985-01-01

Exploration and development of economic coal and uranium deposits of the Tertiary Fort Union and Wasatch Formations provided data related to the evolution of depositional systems in the Powder River Basin. In ascending order, the Paleocene Fort Union Formation consists of the Tullock, Lebo, and Tongue River Members. The overlying Eocene Wasatch Formation consists of the conglomeratic Kingsbury and Moncrief Members and laterally equivalent finer grained deposits. Evolution of fluvial deposition in the basin was determined from sandstone percent maps. A high proportion of sandstones in the Tullock Member and combined Tongue River Member and Wasatch Formation formed in interconnected east-west and north-south belts. The east-west belts represent alluvial fans, as well as braided and meandering tributary streams. The north-south belts reflect meandering and anastomosing trunk streams fed by basin margin tributaries. The sandstones of the Lebo Shale show east-west trends and represent deposits of fluvio-deltaic systems that filled a western, closed-lacustrine basin. The lake in this basin may have formed during localized subsidence along the Buffalo deep fault. These contrasting styles of fluvial deposition were largely controlled by extrabasinal and intrabasinal tectonics associated with Laramide orogeny

Post Cretaceous cooling trend documented in the gastropods (Turritella Sp.) from the Cenozoic startigraphic successions of India

Science.gov (United States)

Banerjee, Y.; Ghosh, P.; Halder, K.; Malarkodi, N.; Pathak, P.

2017-12-01

The aftermath of the Himalyan orogeny and subsequent cooling is documented in the deep sea sedimentary record from the Oceanic realm (1). Here we attempt to reconstruct the temperature pattern based on marine gastropods i.e. Turritella sp. which became abundant during the post Cretaceous period and have successfully been used for the reconstruction of climate by measuring the stable isotopic composition (2,3,4). Well preserved specimens of Cretaceous Turritella from the Rajamundry Infratrappean beds and those from the Miocene, Holocene succession of Kutch, western India were analysed along with specimen from the modern time scale (also from Kutch). The Cretaceous, early to mid Miocene, early Holocene and modern shells recorded δ13C variability from 0.36 to 4.94‰, -1.83 to -4.83‰, -3.26 to 0.40‰, -1.47 to -4.70‰ respectively suggesting drop in the productivity during mid Miocene and subsequent period of rapid growth. The Variability in terms of δ18O ranges from -2.28 to -4.99‰, -2.66 to -7.06‰, -2.86 to 0.96‰, -1.05 to -3.23‰ for the Cretaceous, early to mid Miocene, early Holocene and modern shells respectively. Corbula sp. collected from the same strata with that of the early to mid Holocene Turritella showed a similar δ13C and δ18O values denoting similar environmental condition during deposition. Absence of any significant correlation between δ13C vs δ18O support equilibrium precipitation of shell growth bands. We used Epstein oxygen isotope thermometry to derive temperature from the oxygen isotope of carbonate and adopted water isotopic composition (1‰ for the Cretaceous and -0.7‰ for the Miocene) from the literature. Our observation captured an overall cooling trend from the Cretaceous to the Holocene time period (especially in between mid Miocene to Holocene) and a subsequent warming trend in modern time. Validation with other thermometry method will be displayed at the time of presentation. References: [1] Zachos et al., 2001

High geomagnetic intensity during the mid-Cretaceous from Thellier analyses of single plagioclase crystals.

Science.gov (United States)

Tarduno, J A; Cottrell, R D; Smirnov, A V

2001-03-02

Recent numerical simulations have yielded the most efficient geodynamo, having the largest dipole intensity when reversal frequency is low. Reliable paleointensity data are limited but heretofore have suggested that reversal frequency and paleointensity are decoupled. We report data from 56 Thellier-Thellier experiments on plagioclase crystals separated from basalts of the Rajmahal Traps (113 to 116 million years old) of India that formed during the Cretaceous Normal Polarity Superchron. These data suggest a time-averaged paleomagnetic dipole moment of 12.5 +/- 1.4 x 10(22) amperes per square meter, three times greater than mean Cenozoic and Early Cretaceous-Late Jurassic dipole moments when geomagnetic reversals were frequent. This result supports a correlation between intervals of low reversal frequency and high geomagnetic field strength.

High diversity in cretaceous ichthyosaurs from Europe prior to their extinction.

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Valentin Fischer

Full Text Available BACKGROUND: Ichthyosaurs are reptiles that inhabited the marine realm during most of the Mesozoic. Their Cretaceous representatives have traditionally been considered as the last survivors of a group declining since the Jurassic. Recently, however, an unexpected diversity has been described in Upper Jurassic-Lower Cretaceous deposits, but is widely spread across time and space, giving small clues on the adaptive potential and ecosystem control of the last ichthyosaurs. The famous but little studied English Gault Formation and 'greensands' deposits (the Upper Greensand Formation and the Cambridge Greensand Member of the Lower Chalk Formation offer an unprecedented opportunity to investigate this topic, containing thousands of ichthyosaur remains spanning the Early-Late Cretaceous boundary. METHODOLOGY/PRINCIPAL FINDINGS: To assess the diversity of the ichthyosaur assemblage from these sedimentary bodies, we recognized morphotypes within each type of bones. We grouped these morphotypes together, when possible, by using articulated specimens from the same formations and from new localities in the Vocontian Basin (France; a revised taxonomic scheme is proposed. We recognize the following taxa in the 'greensands': the platypterygiines 'Platypterygius' sp. and Sisteronia seeleyi gen. et sp. nov., indeterminate ophthalmosaurines and the rare incertae sedis Cetarthrosaurus walkeri. The taxonomic diversity of late Albian ichthyosaurs now matches that of older, well-known intervals such as the Toarcian or the Tithonian. Contrasting tooth shapes and wear patterns suggest that these ichthyosaurs colonized three distinct feeding guilds, despite the presence of numerous plesiosaur taxa. CONCLUSION/SIGNIFICANCE: Western Europe was a diversity hot-spot for ichthyosaurs a few million years prior to their final extinction. By contrast, the low diversity in Australia and U.S.A. suggests strong geographical disparities in the diversity pattern of Albian

Glaciers et évolution climatique dans les Andes boliviennes. Glacier de Zongo et glacier de Chacaltaya Cordillère Royale, 16°S

Directory of Open Access Journals (Sweden)

1995-01-01

Full Text Available SEDIMENTOLOGY OF THE HUANCANE FORMATION (NEOCOMIAN OF THE CUSCO REGION AND ITS RELATION TO SEA LEVEL VARIATIONS. The Huancane formation (Neocomian of the Cusco region is mainly composed of quartz sandstones which are deposited in fluvial environments. The facies recognized are organized in a vertical sequence: fluvial sheet sandstones, oxidized or eroded surface, the shale facies of alluvial plain and unusual limestone facies of possible marine origin. These vertical facies sequences show that eustatic sea level variations controlled the fluvial sedimentation. The rivers came from the NE and were fed by the erosion of the Brazilian Shield. The sedimentation developed above the boundary of the SW edge of the Eastern basin, and the Cusco-Puno Swell which had locale horst and grabens inherited from pre-neocomian relief. GLACIARES Y EVOLUCIÓN CLIMÁTICA EN LOS ANDES BOLIVIANOS GLACIAR DE ZONGO Y GLACIAR DE CHACALTAYA, CORDILLERA REAL, 16°S. Por su sensibilidad y su plazo de respuesta breve, el glaciar es de un gran interés para analizar la evolución y la variabilidad actuales del clima entre los trópicos. Se presentan los métodos de determinación del balance de masas y del balance hidrológico, con una frecuencia de mediciones mensual. Los resultados recogidos durante tres años (1991-1994 muestran una grande variabilidad. Ésta es controlada sobre todo por la extensión del periodo de precipitaciones en medio de la temporada cálida que dura más o menos 6 meses. Los eventos ENSO (El Niño Southern Oscillation son asociados a balances netamente negativos, lo que es demostrado por la respuesta del glaciar al episodio de 1991-1992 y por la reconstrucción de los balances efectuados en base a los datos hidrológicos durante los dos últimos decenios. El retroceso acelerado de los glaciares tropicales desde los años 1980 es vinculado a la vez a una sucesión de eventos ENSO y al recalentamiento atmosférico. GLACIERS AND CLIMATIC EVOLUTION IN

Geochemical evolution of Cenozoic-Cretaceous magmatism and its relation to tectonic setting, southwestern Idaho, U.S.A

International Nuclear Information System (INIS)

Norman, M.D.; Leeman, W.P.

1989-01-01

Magmatism in the western United States spanned a change in tectonic setting from Mesozoic and early Tertiary plate convergence to middle and late Tertiary crustal extension. This paper presents new major element, trace element, and isotopic (Sr, Nd, Pb) data on a diverse suite of Cretaceous to Neogene igneous rocks from the Owyhee area of southwestern Idaho to evaluate possible relationships between the evolving tectonic regime and temporal changes in igneous activity. The oldest studied rocks are Cretaceous granitic intrusives that probably formed by large-scale mixing of Precambrian crust with subduction-related magmas. Silicic Eocene tuffs are also rich in crustal components, but have isotopic compositions unlike the Cretaceous intrusives. These data require at least two crustal sources that may correspond to domains of significantly different age (Archean vs. Proterozoic). The oldest mafic lavas in the study area are Oligocene andesites and basalts compositionally similar to subduction-related magmas derived from asthenospheric mantle and erupted through thick continental crust. Direct crustal involvement during oligocene time was limited to minor interaction with the mafic magmas. Miocene activity produced bimodal basalt-rhyolite suites and minor volumes of hybrid lavas. Compositions of Miocene basalts demonstrate the decline of subduction-related processes, and increased involvement of subcontinental lithospheric mantle as a magma source. Crustally-derived Miocene rhyolites have isotopic compositions similar to those of the Cretaceous granitic rocks but trace element abundances more typical of within-plate magmas. (orig./WB)

Distribution of uranium and thorium in sediments and plants from a granitic fluvial area

International Nuclear Information System (INIS)

Vargas, M.J.; Tome, F.V.; Sanchez, A.M.; Vazquez, M.T.C.; Murillo, J.L.G.

1997-01-01

A study of the presence of natural uranium and thorium isotopes in sediments and plants belonging to a granitic fluvial region of the Ortigas river (west of Spain) has been carried out. The existence of two uranium mines in the neighbourhood of the sampled sites and the granitic characteristics of the zone produce significant concentrations of natural radionuclides. Temporal and spatial variations of uranium and thorium concentrations and the activity ratios 234 U/ 238 U, 228 Th/ 232 Th and Th/U were studied to better understand the mobilization mechanisms such as leaching and transport at play in the studied system. These determinations were made using alpha-particle spectrometry with silicon detectors. The measurements were also compared with the results previously found for waters of this fluvial area. Uranium in sediments showed variations due to changes in rainfall, but thorium content was nearly constant. Uranium and thorium concentrations in plants were lower after rainfall. Incorporation of uranium into the plants seemed to be mainly from water, whereas incorporation of thorium seemed to be from both sediments and water. (Author)

Modelling sediment dynamics due to hillslope-river interactions : incorporating fluvial behaviour in landscape evolution model LAPSUS

NARCIS (Netherlands)

Baartman, Jantiene E. M.; van Gorp, Wouter; Temme, Arnaud J. A. M.; Schoorl, Jeroen M.

Landscape evolution models (LEMs) simulate the three-dimensional development of landscapes over time. Different LEMs have different foci, e.g. erosional behaviour, river dynamics, the fluvial domain, hillslopes or a combination. LEM LAPSUS is a relatively simple cellular model operating on

Fluvial fluxes from the Magdalena River into Cartagena Bay, Caribbean Colombia: Trends, future scenarios, and connections with upstream human impacts

Science.gov (United States)

Restrepo, Juan D.; Escobar, Rogger; Tosic, Marko

2018-02-01

Fluxes of continental runoff and sediments as well as downstream deposition of eroded soils have severely altered the structure and function of fluvial and deltaic-estuarine ecosystems. The Magdalena River, the main contributor of continental fluxes into the Caribbean Sea, delivers important amounts of water and sediments into Cartagena Bay, a major estuarine system in northern Colombia. Until now, trends in fluvial fluxes into the bay, as well as the relationship between these tendencies in fluvial inputs and associated upstream changes in the Magdalena catchment, have not been studied. Here we explore the interannual trends of water discharge and sediment load flowing from the Magdalena River-Canal del Dique system into Cartagena Bay during the last three decades, forecast future scenarios of fluxes into the bay, and discuss possible connections between observed trends in fluvial inputs and trends in human intervention in the Magdalena River basin. Significant upward trends in annual runoff and sediment load during the mid-1980s, 1990s, and post-2000 are observed in the Magdalena and in the Canal del Dique flowing into Cartagena Bay. During the last decade, Magdalena streamflow and sediment load experienced increases of 24% and 33%, respectively, compared to the pre-2000 year period. Meanwhile, the Canal del Dique witnessed increases in water discharge and sediment load of 28% and 48%, respectively. During 26 y of monitoring, the Canal del Dique has discharged 177 Mt of sediment to the coastal zone, of which 52 Mt was discharged into Cartagena Bay. Currently, the Canal drains 6.5% and transports 5.1% of the Magdalena water discharge and sediment load. By 2020, water discharge and sediment flux from the Canal del Dique flowing to the coastal zone will witness increments of 164% and 260%, respectively. Consequently, sediment fluxes into Cartagena Bay will witness increments as high as 8.2 Mt y- 1 or 317%. Further analyses of upstream sediment load series for 21

A large Cretaceous theropod from Patagonia, Argentina, and the evolution of carcharodontosaurids

Science.gov (United States)

Novas, Fernando E.; Valais, Silvina; Vickers-Rich, Pat; Rich, Tom

2005-05-01

The Cretaceous Carcharodontosauridae is the latest clade of carnosaurs, including the largest predatory dinosaurs yet recorded. Albeit spectacular for their size, the skeletal anatomy of these theropods remains poorly-known, and their diversity was until recently restricted to two Cenomanian species: the highly derived Giganotosaurus carolinii, from southern South America, and the incompletely known Carcharodontosaurus saharicus, from northern Africa. Here we describe an older and basal member of the group, Tyrannotitan chubutensis gen. et sp. nov., from Aptian strata of Patagonia, Argentina. The new taxon gives new insights into the systematics and evolution of carcharodontosaurids and offers a better understanding of the evolution of Southern theropod faunas. We suggest that carcharodontosaurids radiated in Gondwana sharing with spinosaurids the role of top-predators until their extinction in Cenomanian Turonian times. During this interval, the diplodocoid sauropods and giant titanosaurians went extinct (probably as part of a global-scale crisis), and the smaller abelisaurid theropods took dominance, reigning until the end of the Cretaceous. Electronic Supplementary Material is available.

Eocene and not Cretaceous origin of spider wasps: Fossil evidence from amber

Directory of Open Access Journals (Sweden)

Juanita Rodriguez

2016-02-01

Full Text Available Spider wasps had long been proposed to originate in the mid-Cretaceous based on the Burmese amber fossil Bryopompilus interfector Engel and Grimaldi, 2006. We performed a morphological examination of this fossil and determined it does not belong to Pompilidae or any other described hymenopteran family. Instead, we place it in the new family Bryopompilidae. The oldest verifiable member of the Pompilidae is from Baltic amber, which suggests the family probably originated in the Eocene, not in the mid-Cretaceous as previously proposed. The origin of spider wasps appears to be correlated with an increase in spider familial diversity in the Cenozoic. We also we add two genera to the extinct pompilid fauna: Tainopompilus gen. nov., and Paleogenia gen. nov., and describe three new species of fossil spider wasps: Anoplius planeta sp. nov., from Dominican amber (Burdigalian to Langhian; Paleogenia wahisi sp. nov., from Baltic amber (Lutetian to Priabonian; and Tainopompilus argentum sp. nov, from Dominican amber (Chattian to Langhian.

Estuary-wide genetic stock distribution and salmon habitat use, tidal-fluvial estuary - Columbia River Estuary Tidal Habitats

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The goal of the tidal-fluvial estuary study is to determine the estuary's contribution to the spatial structure and life history diversity of Columbia River salmon...

Depositional environments and oil potential of Jurassic/Cretaceous source rocks within the Seychelles microcontinent

Energy Technology Data Exchange (ETDEWEB)

Plummer, P.S.; Joseph, P.R.; Samson, P.J. [Seychelles National Oil Co., Mahe (Seychelles)

1998-12-31

The Seychelles microcontinent became isolated between the Somali, Mascarene and Arabian basins of the Indian Ocean as a result of the Mesozoic fragmentation of Gondwana. Major rifting events occurred during the Triassic-Middle Jurassic and Late Cretaceous (Cenomanian-Santonian and Maastrichtian) during which shaly source rock facies accumulated in principally marginal marine/deltaic environments. Between these times, post-rift passive margin deposition within restricted to open marine environments produced shaly source rocks during late Middle Jurasic-Early Cretaceous, Campanian-Maastrichtian and Paleocene times. Recent geochemical analysis of cuttings from the Seagull Shoals-1 well has identified an oil-prone liptinitic (Type II) coaly shale within early Middle Jurassic abandoned deltaic deposits. This coaly source rock is regionally developed, having also been identified in the Majunja and Morondava basins of Madagascar. Oil-prone Type II organic matter has also been identified in the Owen Bank A-1 well within restricted marine shales of late Middle Jurassic age. These shales are part of a thick post-rift source rock sequence that extends into the Early Cretaceous and is in part correlative with the proven Late Jurassic Uarandab Shale of Somalia. Analysis of Campanian marine shales from Reith Bank-1 well identified significant dilution of total organic carbon content in composite, compared to picked, well cuttings samples. This finding supports a published inference that these post-rift shales have source rock potential. (author)

Cretaceous plutonic rocks in the Donner Lake-Cisco Grove area, northern Sierra Nevada, California

Science.gov (United States)

Kulow, Matthew J.; Hanson, Richard E.; Girty, Gary H.; Girty, Melissa S.; Harwood, David S.

1998-01-01

The northernmost occurrences of extensive, glaciated exposures of the Sierra Nevada batholith occur in the Donner Lake-Cisco Grove area of the northern Sierra Nevada. The plutonic rocks in this area, which are termed here the Castle Valley plutonic assemblage, crop out over an area of 225 km2 and for the most part are shown as a single undifferentiated mass on previously published geological maps. In the present work, the plutonic assemblage is divided into eight separate intrusive units or lithodemes, two of which each consist of two separate plutons. Compositions are dominantly granodiorite and tonalite, but diorite and granite form small plutons in places. Spectacular examples of comb layering and orbicular texture occur in the diorites. U-Pb zircon ages have been obtained for all but one of the main units and range from ~120 to 114 Ma, indicating that the entire assemblage was emplaced in a narrow time frame in the Early Cretaceous. This is consistent with abundant field evidence that many of the individual phases were intruded penecontemporaneously. The timing of emplacement correlates with onset of major Cretaceous plutonism in the main part of the Sierra Nevada batholith farther south. The emplacement ages also are similar to isotopic ages for gold-quartz mineralization in the Sierran foothills west of the study area, suggesting a direct genetic relationship between the voluminous Early Cretaceous plutonism and hydrothermal gold mineralization.

The phosphorus content of fluvial sediment in rural and industrialized river basins.

Science.gov (United States)

Owens, Philip N; Walling, Desmond E

2002-02-01

The phosphorus content of fluvial sediment (suspended sediment and the sediment) has been examined in contrasting rural (moorland and agricultural) and industrialized catchments in Yorkshire, UK. The River Swale drains a rural catchment with no major urban and industrial areas, and the total phosphorus (TP) content of fluvial sediment is generally within the range 500-1,500 microg g(-1). There is little evidence of any major downstream increase in TP content. In contrast, fluvial sediment from the industrialized catchments of the Rivers Aire and Calder exhibits both higher levels of TP content and marked downstream increases, with values of TP content ranging from 7,000 microg g(-1) at downstream sites. These elevated levels reflect P inputs from point sources, such as sewage treatment works (STWs) and combined sewer overflows. The influence of STWs is further demonstrated by the downstream increase in the inorganic P/organic P ratio from 4 in the lower reaches. Comparison of the P content of suspended sediment with that of the sediment and both discharge and suspended sediment concentration, reflecting changes in sediment and P sources during high flow events. Spatial variations in the P contents of the sediment evidence a similar pattern as those for suspended sediment, with relatively low levels of TP in the River Swale and elevated levels in the middle and downstream reaches of the Rivers Aire and Calder. The PP concentrations associated with floodplain and channel bed sediment are, however, lower than equivalent values for suspended sediment, and this primarily reflects the differences in the particle size composition between the three types of sediments. Rates of floodplain deposition and the amounts of fine-grained sediment stored in the river channels are relatively high, and suggest that such environments may represent important sinks for PP. Based on the sediment samples collected from the study basins, a simple four-fold classification which relates the

Curstal evolution and sedimentation history of the Bay of Bengal since the cretaceous

Digital Repository Service at National Institute of Oceanography (India)

Rao, D.G.; Krishna, K.S.; Sar, D.

on three latitudinal profiles) in the Bay of Bengal. The trend of the fracture zones, the locations of the magnetic chron 34, and the Cretaceous Magnetic Quiet Zone suggest that Greater India separated from Antarctica after a period of transform motion...

Recycling of Amazonian detrital zircons in the Mixteco terrane, southern Mexico: Paleogeographic implications during Jurassic-Early Cretaceous and Paleogene times

Science.gov (United States)

Silva-Romo, Gilberto; Mendoza-Rosales, Claudia Cristina; Campos-Madrigal, Emiliano; Morales-Yáñez, Axél; de la Torre-González, Alam Israel; Nápoles-Valenzuela, Juan Ivan

2018-04-01

In the northeastern Mixteco terrane of southern Mexico, in the Ixcaquixtla-Atzumba region, the recycling of Amazonian detrital zircons records the paleogeography during the Mesozoic period in the context of the breakup of Pangea, a phenomenon that disarticulated the Sanozama-La Mora paleo-river. The clastic units of southern Mexico in the Ayuquila, Otlaltepec and Zapotitlán Mesozoic basins, as well as in the Atzumba Cenozoic basin, are characterized by detrital zircon contents with ages specific to the Amazonian craton, ranging between 3040 and 1278 Ma. The presence of zircons of Amazonian affinity suggests a provenance by recycling from carrier units such as the La Mora Formation or the Ayú Complex. In the area, the Ayú and Acatlán complexes form the Cosoltepec block, a paleogeographic element that during Early Cretaceous time acted as the divide between the slopes of the paleo-Gulf of Mexico and the paleo-Pacific Ocean. The sedimentological characteristics of the Jurassic-Cenozoic clastic successions in the Ixcaquixtla-Atzumba region denote relatively short transport in braided fluvial systems and alluvial fans. In this way, several basins are recognized around the Cosoltepec block. At the southeastern edge of the Cosoltepec block, the Ayuquila and Tecomazúchil formations accumulated in the Ayuquila continental basin on the paleo-Pacific Ocean slope. On the other hand, within the paleo-Gulf of Mexico slope, in the Otlaltepec continental basin, the Piedra Hueca and the Otlaltepec formations accumulated. The upper member of the Santa Lucía Formation accumulated in a transitional environment on the southwestern shoulder of the Zapotitlán basin, as well as on the paleo-Gulf of Mexico slope. In the Ayuquila basin, a marine transgression is recognized that advanced from south to north during the Late Jurassic. At the northeastern edge of the Cosoltepec block, we propose that the Santa Lucía formation attests to a transgression from the paleo-Gulf of Mexico

A Triassic to Cretaceous Sundaland-Pacific subduction margin in West Sarawak, Borneo

Science.gov (United States)

Breitfeld, H. Tim; Hall, Robert; Galin, Thomson; Forster, Margaret A.; BouDagher-Fadel, Marcelle K.

2017-01-01

Metamorphic rocks in West Sarawak are poorly exposed and studied. They were previously assumed to be pre-Carboniferous basement but had never been dated. New 40Ar/39Ar ages from white mica in quartz-mica schists reveal metamorphism between c. 216 to 220 Ma. The metamorphic rocks are associated with Triassic acid and basic igneous rocks, which indicate widespread magmatism. New U-Pb dating of zircons from the Jagoi Granodiorite indicates Triassic magmatism at c. 208 Ma and c. 240 Ma. U-Pb dating of zircons from volcaniclastic sediments of the Sadong and Kuching Formations confirms contemporaneous volcanism. The magmatic activity is interpreted to represent a Triassic subduction margin in westernmost West Sarawak with sediments deposited in a forearc basin derived from the magmatic arc at the Sundaland-Pacific margin. West Sarawak and NW Kalimantan are underlain by continental crust that was already part of Sundaland or accreted to Sundaland in the Triassic. One metabasite sample, also previously assumed to be pre-Carboniferous basement, yielded Early Cretaceous 40Ar/39Ar ages. They are interpreted to indicate resumption of subduction which led to deposition of volcaniclastic sediments and widespread magmatism. U-Pb ages from detrital zircons in the Cretaceous Pedawan Formation are similar to those from the Schwaner granites of NW Kalimantan, and the Pedawan Formation is interpreted as part of a Cretaceous forearc basin containing material eroded from a magmatic arc that extended from Vietnam to west Borneo. The youngest U-Pb ages from zircons in a tuff layer from the uppermost part of the Pedawan Formation indicate that volcanic activity continued until c. 86 to 88 Ma when subduction terminated.

Micropaleontology and palaeoclimate during the early Cretaceous in the Lishu depression, Songliao basin, Northeast China

Directory of Open Access Journals (Sweden)

Wei Yan

2017-01-01

Full Text Available Diverse and abundant microfossils, such as palynomorphs, algae and Ostracoda, were collected from lower Cretaceous strata of Lishu depression, located in southeastern Songliao basin, and were identified and classified in order to provide relevant, detailed records for paleoclimate research. The early Cretaceous vegetation and climate of southeastern Songliao basin have been inferred from the analysis of palynomorph genera, algae and Ostracoda of the LS1 and SW110 wells. The lower Cretaceous strata include, in ascending stratigraphic order, the Shahezi, Yingcheng and Denglouku formations. Palynological assemblages for each formation, based on biostratigraphic and statistical analyses, provide an assessment of their longitudinal variations. During deposition of the Shahezi Formation, the climate was mid-subtropical. Vegetation consisted of coniferous forest and herbage. During deposition of the Yingcheng Formation, the climate was south Asian tropical. Vegetation consisted mainly of coniferous forest and herbal shrub. In addition, fresh and saline non-marine water dominated the lacustrine setting during deposition of these formations. Deposition of the Denglouku Formation, however, occurred under a hot and dry tropical climate. The vegetation was mostly coniferous forest and lake waters became saline. Palaeoclimate variation is correlated by the lake level change and the development of sedimentary facies. Palaeoclimate contribute to the formation of hydrocarbon source rocks and reservoir.

Geology of pre-Dakota uranium geochemical cell, sec. 13, T. 16 N., R. 17 W., Church Rock area, McKinley County

International Nuclear Information System (INIS)

Peterson, R.J.

1980-01-01

Exploration drilling on sec. 13, T. 16 N., R. 17 W., McKinley County, New Mexico, has defined uranium deposits within the Westwater Canyon Member of the Morrison Formation (Jurassic). Elongate, tabular, redistributed deposits were formed peripherally along the zones of highest transmissivity of the northeast-trending Westwater Canyon fluvial system by a Jurassic-Cretaceous geochemical cell. Strongly reducing conditions, which existed locally in the channel-margin areas owing to the presence of organic materials, were the primary ore control. Evidence that this major redistribution process took place in pre-Dakota time is the bleaching of the Westwater Canyon Sandstone by Dakota swamps is superimposed on older oxidation, and the primary mineralization above the Jurassic-Cretaceous water table was not affected by the geochemical-cell redistribution process

Progress in Late Cretaceous planktonic foraminiferal stable isotope paleoecology and implications for paleoceanographic reconstructions

Science.gov (United States)

Petrizzo, Maria Rose; Falzoni, Francesca; Huber, Brian T.; MacLeod, Kenneth G.

2015-04-01

Paleoecological preferences proposed for Cretaceous planktonic foraminiferal taxa have traditionally been based on morphological analogies with depth-stratified modern species, on biofacies comparison in continental margin and deepwater settings, and limited oxygen and carbon stable isotope data. These studies concluded that large-sized, keeled and heavily calcified planktonic foraminifera generally lived at deeper levels in the surface waters than small-sized, thinner-walled non-keeled species. Stable isotope data have been used to infer information on paleotemperature, paleoceanography and paleoproductivity of ancient oceans and constrain biological paleo-activities (i.e. photosymbiosis and respiration) of fossil species. These studies have suggested that the depth-distribution model based on analogy with modern taxa might not be fully applicable for Cretaceous species, and found particularly 13C-enriched values in some Maastrichtian multiserial taxa that have been related to the activity of photosymbionts. We have collected about 1500 δ18O and δ13C species-specific analyses on glassy preserved planktonic foraminifera from Tanzania (Tanzania Drilling Project TDP sites 23, 28 and 32) and well-preserved planktonic foraminifera from other mid-low latitude localities (Shatsky Rise, northwestern Pacific Ocean, ODP Leg 198 Hole 1210B; Exmouth Plateau, eastern Indian Ocean, ODP Leg 122, Hole 762C; Eratosthenes Seamount, eastern Mediterranean, ODP Leg 160, Hole 967E; Blake Nose, central Atlantic Ocean, ODP Leg 171B, holes 1050C and 1052E) to investigate Late Cretaceous species paleoecological preferences, life strategies and depth distribution in the surface water column. Our results indicates that several large-sized (> 500 μm) double-keeled species belonging to the genera Dicarinella, Marginotruncana and Contusotruncana, generally interpreted as deep to thermocline dwellers, instead occupied shallow/warm layers of the water column, whilst not all biserial species

The Pliocene initiation and Early Pleistocene volcanic disruption of the palaeo-Gediz fluvial system, Western Turkey

NARCIS (Netherlands)

Maddy, D.; Demir, T.; Bridgland, D.R.; Veldkamp, A.; Stemerdink, C.; Schriek, van der T.; Schreve, D.

2007-01-01

In this paper, we report our latest observations concerning a Pliocene and Early Pleistocene record from Western Turkey. The sedimentary sequence described comprises the fluvial deposits of an Early Pleistocene palaeo-Gediz river system and its tributaries prior to the onset of volcanism around Kula

Buried late Pleistocene fluvial channels on the inner continental shelf off Vengurla, west coast of India

Digital Repository Service at National Institute of Oceanography (India)

SubbaRaju, L.V.; Krishna, K.S.; Chaubey, A.K.

with sediments. Cross sectional dimensions between 15 to 100 m width and 2 to 6 m depth suggest a fluvial origin of the channels. These buried channels appear to mark former positions of rivers flowing from the nearby coast and debouching into the Arabian Sea...

Estuarine abandoned channel sedimentation rates record peak fluvial discharge magnitudes

Science.gov (United States)

Gray, A. B.; Pasternack, G. B.; Watson, E. B.

2018-04-01

Fluvial sediment deposits can provide useful records of integrated watershed expressions including flood event magnitudes. However, floodplain and estuarine sediment deposits evolve through the interaction of watershed/marine sediment supply and transport characteristics with the local depositional environment. Thus extraction of watershed scale signals depends upon accounting for local scale effects on sediment deposition rates and character. This study presents an examination of the balance of fluvial sediment dynamics and local scale hydro-geomorphic controls on alluviation of an abandoned channel in the Salinas River Lagoon, CA. A set of three sediment cores contained discrete flood deposits that corresponded to the largest flood events over the period of accretion from 1969 to 2007. Sedimentation rates scaled with peak flood discharge and event scale sediment flux, but were not influenced by longer scale hydro-meteorological activities such as annual precipitation and water yield. Furthermore, the particle size distributions of flood deposits showed no relationship to event magnitudes. Both the responsiveness of sedimentation and unresponsiveness of particle size distributions to hydro-sedimentological event magnitudes appear to be controlled by aspects of local geomorphology that influence the connectivity of the abandoned channel to the Salinas River mainstem. Well-developed upstream plug bar formation precluded the entrainment of coarser bedload into the abandoned channel, while Salinas River mouth conditions (open/closed) in conjunction with tidal and storm surge conditions may play a role in influencing the delivery of coarser suspended load fractions. Channel adjacent sediment deposition can be valuable records of hydro-meteorological and sedimentological regimes, but local depositional settings may dominate the character of short term (interdecadal) signatures.

First complete sauropod dinosaur skull from the Cretaceous of the Americas and the evolution of sauropod dentition.

Science.gov (United States)

Chure, Daniel; Britt, Brooks B; Whitlock, John A; Wilson, Jeffrey A

2010-04-01

Sauropod dinosaur bones are common in Mesozoic terrestrial sediments, but sauropod skulls are exceedingly rare--cranial materials are known for less than one third of sauropod genera and even fewer are known from complete skulls. Here we describe the first complete sauropod skull from the Cretaceous of the Americas, Abydosaurus mcintoshi, n. gen., n. sp., known from 104.46 +/- 0.95 Ma (megannum) sediments from Dinosaur National Monument, USA. Abydosaurus shares close ancestry with Brachiosaurus, which appeared in the fossil record ca. 45 million years earlier and had substantially broader teeth. A survey of tooth shape in sauropodomorphs demonstrates that sauropods evolved broad crowns during the Early Jurassic but did not evolve narrow crowns until the Late Jurassic, when they occupied their greatest range of crown breadths. During the Cretaceous, brachiosaurids and other lineages independently underwent a marked diminution in tooth breadth, and before the latest Cretaceous broad-crowned sauropods were extinct on all continental landmasses. Differential survival and diversification of narrow-crowned sauropods in the Late Cretaceous appears to be a directed trend that was not correlated with changes in plant diversity or abundance, but may signal a shift towards elevated tooth replacement rates and high-wear dentition. Sauropods lacked many of the complex herbivorous adaptations present within contemporaneous ornithischian herbivores, such as beaks, cheeks, kinesis, and heterodonty. The spartan design of sauropod skulls may be related to their remarkably small size--sauropod skulls account for only 1/200th of total body volume compared to 1/30th body volume in ornithopod dinosaurs.

Late Cretaceous extension and exhumation of the Stong and Taku magmatic and metamorphic complexes, NE Peninsular Malaysia

Science.gov (United States)

François, T.; Md Ali, M. A.; Matenco, L.; Willingshofer, E.; Ng, T. F.; Taib, N. I.; Shuib, M. K.

2017-08-01

Fragmentation of large continental areas by post-orogenic extension requires favourable geodynamic conditions and frequently occurs along pre-existing suture zones or nappe contacts, as exemplified by the Stong and Taku magmatic and metamorphic complexes of northern Peninsular Malaysia. For this case, we have employed a field and microstructural kinematic study combined with low temperature thermo-chronology to analyse the tectonic and exhumation history. The results show that the Late Palaeozoic - Triassic Indosinian orogeny created successive phases of burial related metamorphism, shearing and contractional deformation. This orogenic structure was subsequently dismembered during a Cretaceous thermal event that culminated in the formation of a large scale Late Santonian - Early Maastrichtian extensional detachment, genetically associated with crustal melting, the emplacement of syn-kinematic plutons and widespread migmatisation. The emplacement of these magmatic rocks led to an array of simultaneously formed structures that document deformation conditions over a wide temperature range, represented by amphibolite- and greenschist- facies mylonites and as well as brittle structures, such as cataclastic zones and normal faults that formed during exhumation in the footwall of the detachment. The formation of this detachment and a first phase of Late Cretaceous cooling was followed by renewed Eocene - Oligocene exhumation, as evidenced from our fission track ages. We infer that an initial Cretaceous thermal anomaly was responsible for the formation of an extensional gneiss dome associated with simple shear and rotation of normal faults. These Cretaceous processes played a critical role in the establishment of the presently observed crustal structure of Peninsular Malaysia.

Impact of phenomenological theory of turbulence on pragmatic approach to fluvial hydraulics

Science.gov (United States)

Ali, Sk Zeeshan; Dey, Subhasish

2018-04-01

The phenomenological theory of turbulence (PTT) remains a long-standing and fascinating theory in turbulence research. In this review article, we highlight the state-of-the-science of the impact of the PTT on the pragmatic approach to fluvial hydraulics, explored over recent decades, discussing the salient and the subtle roles that the turbulence plays in governing many physical processes. To acquire a theoretical explanation of this pragmatic approach necessitates an intuitive thought that can bring together the background mechanisms of all the physical processes under one law—a thought that is capable of finding their inextricable links with the turbulent energy spectrum. We begin here with emphasizing the spectral and the co-spectral origin of the well-recognized laws of the wall, the resistance equation, and the turbulence intensities by portraying the typical momentum transfer mechanism of eddies in a turbulent flow. Next, we focus on the scaling laws of key fluvial processes derived from the perspective of the PTT, enlightening their physical insight and ability to judge how far the so-called empirical formulas can be used with confidence. The PTT has been able to disclose the origin of several primeval empirical formulas that have been used over many years without having any theoretical clarification and confirmation. Finally, we make an effort to describe some unsolved issues to be resolved as a future scope of research.

A Cretaceous origin for fire adaptations in the Cape flora.

Science.gov (United States)

He, Tianhua; Lamont, Byron B; Manning, John

2016-10-05

Fire has had a profound effect on the evolution of worldwide biotas. The Cape Floristic Region is one of the world's most species-rich regions, yet it is highly prone to recurrent fires and fire-adapted species contribute strongly to the overall flora. It is hypothesized that the current fire regimes in the Cape could be as old as 6-8 million years (My), while indirect evidence indicates that the onset of fire could have reached 18 million years ago (Ma). Here, we trace the origin of fire-dependent traits in two monocot families that are significant elements in the fire-prone Cape flora. Our analysis shows that fire-stimulated flowering originated in the Cape Haemodoraceae 81 Ma, while fire-stimulated germination arose in the African Restionaceae at least 70 Ma, implying that wildfires have been a significant force in the evolution of the Cape flora at least 60 My earlier than previous estimates. Our results provide strong evidence for the presence of fire adaptations in the Cape from the Cretaceous, leading to the extraordinary persistence of a fire-adapted flora in this biodiversity hotspot, and giving support to the hypothesis that Cretaceous fire was a global phenomenon that shaped the evolution of terrestrial floras.

Middle Jurassic - Early Cretaceous rifting of the Danish Central Graben

Energy Technology Data Exchange (ETDEWEB)

Moeller, J.J.; Rasmussen, E.S.

1998-12-01

During the Jurassic-early Cretaceous, the Danish Central Graben developed as a N-S to NNW-SSE trending Graben bounded by the Ringkoebing-Fyn High towards the east and the Mid North Sea High towards the west. The Graben consists of a system of half-Grabens and evolved by fault-controlled subsidence; three main rift pulses have been recognized. The first pulse ranged from the Callovian to the early Oxfordian, the second pulse was initiated in the latest Late Kimmeridgian and Early Volgian, and the third and final pulse occurred within the Valanginian in the Early Cretaceous. The first pulse was characterized by subsidence along N-S trending faults. During the second pulse, in early Volgian times, subsidence was concentrated along new NNW-SSE trending faults and the main depocentre shifted westward, being most marked within the Tail End Graben, the Arne-Elin Graben, and the Feda Graben. This tectonic event was accompanied by the accumulation of a relatively thick sediment load resulting in the development of salt diapers, especially within the Salt Dome Province. The third tectonic pulse was essentially a reactivation of the NNW-SSE trending structures. This tectonic pulse also shows clear evidence of combined fault-controlled subsidence and salt movements. (EG) 12 figs.; 45 refs.

15N/14N variations in Cretaceous Atlantic sedimentary sequences: implication for past changes in marine nitrogen biogeochemistry

Science.gov (United States)

Rau, G.H.; Arthur, M.A.; Dean, W.E.

1987-01-01

At two locations in the Atlantic Ocean (DSDP Sites 367 and 530) early to middle Cretaceous organic-carbon-rich beds ("black shales") were found to have significantly lower ??15N values (lower 15N/14N ratios) than adjacent organic-carbon-poor beds (white limestones or green claystones). While these lithologies are of marine origin, the black strata in particular have ??15N values that are significantly lower than those previously found in the marine sediment record and most contemporary marine nitrogen pools. In contrast, black, organic-carbon-rich beds at a third site (DSDP Site 603) contain predominantly terrestrial organic matter and have C- and N-isotopic compositions similar to organic matter of modern terrestrial origin. The recurring 15N depletion in the marine-derived Cretaceous sequences prove that the nitrogen they contain is the end result of an episodic and atypical biogeochemistry. Existing isotopic and other data indicate that the low 15N relative abundance is the consequence of pelagic rather than post-depositional processes. Reduced ocean circulation, increased denitrification, and, hence, reduced euphotic zone nitrate availability may have led to Cretaceous phytoplankton assemblages that were periodically dominated by N2-fixing blue-green algae, a possible source of this sediment 15N-depletion. Lack of parallel isotopic shifts in Cretaceous terrestrially-derived nitrogen (Site 603) argues that the above change in nitrogen cycling during this period did not extend beyond the marine environment. ?? 1987.

Intense acidic volcanism at the Cretaceous-Tertiary boundary

International Nuclear Information System (INIS)

Javoy, M.; Courtillot, V.

1989-01-01

A 87 Sr/ 86 Sr spike in seawater strontium with amplitude 2 x 10 -4 and duration of order 2 Ma is superimposed on longer-term variations at the Cretaceous-Tertiary boundary. The anomaly has been attributed to increased continental runoff due either to meteorite impact-related acid rain or sea-level regression. We speculate here that the spike could have resulted from intense, explosive acid volcanism preceding the development of the Deccan traps. A good model, both in tectonic position and geochemical characteristics, for these as yet elusive acidic products is provided by granites in the Seychelles Islands and particularly Mahe. (orig.)

Reworked Middle Jurassic sandstones as a marker for Upper Cretaceous basin inversion in Central Europe—a case study for the U-Pb detrital zircon record of the Upper Cretaceous Schmilka section and their implication for the sedimentary cover of the Lausitz Block (Saxony, Germany)

Science.gov (United States)

Hofmann, Mandy; Voigt, Thomas; Bittner, Lucas; Gärtner, Andreas; Zieger, Johannes; Linnemann, Ulf

2018-04-01

The Saxonian-Bohemian Cretaceous Basin (Elbsandsteingebirge, E Germany and Czech Republic, Elbtal Group) comprises Upper Cretaceous sedimentary rocks from Upper Cenomanian to Santonian age. These sandstones were deposited in a narrow strait of the sea linking the northern Boreal shelf to the southern Tethyan areas. They were situated between the West Sudetic Island in the north and the Mid-European Island in the south. As known by former studies (e.g. Tröger, Geologie 6/7:717-730, 1964; Tröger, Geologie von Sachsen, Schweizerbart, 311-358, 2008; Voigt and Tröger, Proceedings of the 4th International Cretaceous Symposium, 275-290, 1996; Voigt, Dissertation, TU Bergakademie Freiberg, 1-130, 1995; Voigt, Zeitschrift der geologischen Wissenschaften 37(1-2): 15-39, 2009; Wilmsen et al., Freiberger Forschungshefte C540: 27-45, 2011) the main sedimentary input came from the north (Lausitz Block, southern West-Sudetic Island). A section of Turonian to Coniacian sandstones was sampled in the Elbsandsteingebirge near Schmilka (Elbtal Group, Saxony, Germany). The samples were analysed for their U-Pb age record of detrital zircon using LA-ICP-MS techniques. The results show main age clusters typical for the Bohemian Massif (local material) and are interpreted to reflect the erosion of uniform quartz-dominated sediments and basement rocks. Surprisingly, these rocks lack an expected Upper Proterozoic to Lower Palaeozoic age peak, which would be typical for the basement of the adjacent Lausitz Block (c. 540-c. 560 Ma). Therefore, the Lausitz Block basement must have been covered by younger sediments that acted as source rocks during deposition of the Elbtal Group. The sandstones of the Elbe valley (Elbtal Group, Schmilka section) represent the re-deposited sedimentary cover of the Lausitz Block in inverse order. This cover comprised Permian, Triassic, Jurassic and Lower Cretaceous deposits, which are eroded already today and cannot be investigated. Within the samples of the

Human impact on fluvial regimes and sediment flux during the Holocene: review and future research agenda

NARCIS (Netherlands)

Hoffmann, T.; Thorndycraft, V.R.; Brown, A.G.; Coulthard, T.J.; Damnati, B.; Kale, V.S.; Middelkoop, H.; Notebaert, B.; Walling, D.E.

2010-01-01

There is a long history of human–riverine interactions throughout the period of agriculture that in some regions of the world started several thousand years ago. These interactions have altered rivers to human dominated systems with often negative impacts on fluvial environments. To achieve a good

Depositional record of an avulsive fluvial system controlled by peat compaction (Neogene, Most Basin, Czech Republic)

Czech Academy of Sciences Publication Activity Database

Rajchl, M.; Uličný, David

2005-01-01

Roč. 52, č. 3 (2005), s. 601-625 ISSN 0037-0746 R&D Projects: GA ČR GA205/01/0629 Institutional research plan: CEZ:AV0Z30120515 Keywords : avulsion * Eger Graben * fluvial channels Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.876, year: 2005

A conceptual connectivity framework for understanding geomorphic change in human-impacted fluvial systems

Science.gov (United States)

Pöppl, Ronald; Keesstra, Saskia; Maroulis, Jerry

2017-04-01

Human-induced landscape change is difficult to predict due to the complexity inherent in both geomorphic and social systems as well as due to emerging coupling relationships between them. To better understand system complexity and system response to change, connectivity has become an important research paradigm within various disciplines including geomorphology, hydrology and ecology. With the proposed conceptual connectivity framework on geomorphic change in human-impacted fluvial systems a cautionary note is flagged regarding the need (i) to include and to systematically conceptualise the role of different types of human agency in altering connectivity relationships in geomorphic systems and (ii) to integrate notions of human-environment interactions to connectivity concepts in geomorphology to better explain causes and trajectories of landscape change. Underpinned by case study examples, the presented conceptual framework is able to explain how geomorphic response of fluvial systems to human disturbance is determined by system-specific boundary conditions (incl. system history, related legacy effects and lag times), vegetation dynamics and human-induced functional relationships (i.e. feedback mechanisms) between the different spatial dimensions of connectivity. It is further demonstrated how changes in social systems can trigger a process-response feedback loop between social and geomorphic systems that further governs the trajectory of landscape change in coupled human-geomorphic systems.

MODELLING LANDSCAPE MORPHODYNAMICS BY TERRESTRIAL PHOTOGRAMMETRY: AN APPLICATION TO BEACH AND FLUVIAL SYSTEMS

Directory of Open Access Journals (Sweden)

E. Sánchez-García

2016-06-01

Full Text Available Beach and fluvial systems are highly dynamic environments, being constantly modified by the action of different natural and anthropic phenomena. To understand their behaviour and to support a sustainable management of these fragile environments, it is very important to have access to cost-effective tools. These methods should be supported on cutting-edge technologies that allow monitoring the dynamics of the natural systems with high periodicity and repeatability at different temporal and spatial scales instead the tedious and expensive field-work that has been carried out up to date. The work herein presented analyses the potential of terrestrial photogrammetry to describe beach morphology. Data processing and generation of high resolution 3D point clouds and derived DEMs is supported by the commercial Agisoft PhotoScan. Model validation is done by comparison of the differences in the elevation among the photogrammetric point cloud and the GPS data along different beach profiles. Results obtained denote the potential that the photogrammetry 3D modelling has to monitor morphological changes and natural events getting differences between 6 and 25 cm. Furthermore, the usefulness of these techniques to control the layout of a fluvial system is tested by the performance of some modeling essays in a hydraulic pilot channel.

The Jurassic-Cretaceous basaltic magmatism of the Oued El-Abid syncline (High Atlas, Morocco): Physical volcanology, geochemistry and geodynamic implications

Science.gov (United States)

Bensalah, Mohamed Khalil; Youbi, Nasrrddine; Mata, João; Madeira, José; Martins, Línia; El Hachimi, Hind; Bertrand, Hervé; Marzoli, Andrea; Bellieni, Giuliano; Doblas, Miguel; Font, Eric; Medina, Fida; Mahmoudi, Abdelkader; Beraâouz, El Hassane; Miranda, Rui; Verati, Chrystèle; De Min, Angelo; Ben Abbou, Mohamed; Zayane, Rachid

2013-05-01

Basaltic lava flows, dykes and sills, interbedded within red clastic continental sedimentary sequences (the so called "Couches Rouges") are widespread in the Oued El-Abid syncline. They represent the best candidates to study the Jurassic-Cretaceous magmatism in the Moroccan High Atlas. The volcanic successions were formed during two pulses of volcanic activity, represented by the Middle to Upper Jurassic basaltic sequence B1 (1-4 eruptions) and the Lower Cretaceous basaltic sequence B2 (three eruptions). Whether belonging to the B1 or B2, the lava flows present morphology and internal structures typical of inflated pahoehoe. Our geochemical data show that, at least for Jurassic magmatism, the dykes, and sills cannot be considered as strictly representing the feeders of the sampled lava flows. The Middle to Upper Jurassic pulse is moderately alkaline in character, while the Lower Cretaceous one is transitional. Crustal contamination plays a minor role in the petrogenesis of these magmas, which were generated by variable partial melting degrees of a garnet-bearing mantle source. Magmatism location was controlled by pre-existing Hercynian fault systems reactivated during a Middle to Upper Jurassic-Cretaceous rifting event. The associated lithospheric stretching induced melting, by adiabatic decompression, of enriched low-solidus infra-lithospheric domains.

Hadrosauroid Dinosaurs from the Late Cretaceous of the Sultanate of Oman.

Directory of Open Access Journals (Sweden)

Eric Buffetaut

Full Text Available Fragmentary post-cranial remains (femora, tibia, vertebrae of ornithischian dinosaurs from the Late Cretaceous of the Sultanate of Oman are described and referred to hadrosauroids. The specimens come from the Al-Khod Conglomerate, of latest Campanian to Maastrichtian age, in the north-eastern part of the country. Although the fragmentary condition of the fossils precludes a precise identification, various characters, including the shape of the fourth trochanter of the femur and the morphology of its distal end, support an attribution to hadrosauroids. With the possible exception of a possible phalanx from Angola, this group of ornithopod dinosaurs, which apparently originated in Laurasia, was hitherto unreported from the Afro-Arabian plate. From a paleobiogeographical point of view, the presence of hadrosauroids in Oman in all likelihood is a result of trans-Tethys dispersal from Asia or Europe, probably by way of islands in the Tethys shown on all recent paleogeographical maps of that area. Whether hadrosauroids were widespread on the Afro-Arabian landmass in the latest Cretaceous, or where restricted to the « Oman island » shown on some paleogeographical maps, remains to be determined.

Hadrosauroid Dinosaurs from the Late Cretaceous of the Sultanate of Oman.

Science.gov (United States)

Buffetaut, Eric; Hartman, Axel-Frans; Al-Kindi, Mohammed; Schulp, Anne S

2015-01-01

Fragmentary post-cranial remains (femora, tibia, vertebrae) of ornithischian dinosaurs from the Late Cretaceous of the Sultanate of Oman are described and referred to hadrosauroids. The specimens come from the Al-Khod Conglomerate, of latest Campanian to Maastrichtian age, in the north-eastern part of the country. Although the fragmentary condition of the fossils precludes a precise identification, various characters, including the shape of the fourth trochanter of the femur and the morphology of its distal end, support an attribution to hadrosauroids. With the possible exception of a possible phalanx from Angola, this group of ornithopod dinosaurs, which apparently originated in Laurasia, was hitherto unreported from the Afro-Arabian plate. From a paleobiogeographical point of view, the presence of hadrosauroids in Oman in all likelihood is a result of trans-Tethys dispersal from Asia or Europe, probably by way of islands in the Tethys shown on all recent paleogeographical maps of that area. Whether hadrosauroids were widespread on the Afro-Arabian landmass in the latest Cretaceous, or where restricted to the « Oman island » shown on some paleogeographical maps, remains to be determined.

Tectonics and stratigraphy of the East Brazil Rift system: an overview

Science.gov (United States)

Hung Kiang Chang; Kowsmann, Renato Oscar; Figueiredo, Antonio Manuel Ferreira; Bender, AndréAdriano

1992-10-01

The East Brazilian Rift system (Ebris) constitutes the northern segment of the South Atlantic rift system which developed during the Mesozoic breakup of South America and Africa. Following crustal separation in the Late Aptian, it evolved into a passive continental margin. Along the continental margin six basins are recognized, while three onshore basins form part of an aborted rift. Three continental syn-rift stratigraphic sequences are recognized, spanning Jurassic to Barremian times. The Jurassic (Syn-rift I) and Neocomian (Syn-rift II) phases were most active in the interior rift basins. During the Barremian (Syn-rift III), rift subsidence rates were twice as large as during the Neocomian (Syn-rift II), both in the interior rift and in the marginal rift segments, indicating that rift axis did not migrate from the interior to the marginal setting. Rift magmatism was centered on the southern EBRIS and peaked between 130 and 120 Ma during syn-rift phase II. Rift phase III was followed by a transitional marine, evaporitic megasequence of Aptian age, which directly overlies the rift unconformity and a marine drift megasequence which spans Albian to Recent times. During the Late Cretaceous, sedimentation rates responded to first-order eustatic sea-level fluctuations. Tertiary accelerated sedimentation rates can be related to local clastic supply which filled in spaces inherited from previous starved conditions. Between 60 and 40 Ma, post-rift magmatism, centered on the Abrolhos and Royal Charlotte banks, is probably related to development of a hot spot associated with the Vitória-Trindade Seamount Chain. Although crossing three distinct Precambrian tectono-thermal provinces, ranging from Archean through Late Proterozoic, rift structures follow a general NE trend, subparallel to the principal basement fabric. A NW-SE oriented stress field appears to be compatible with both Neocomian and Barremian phases of crustal extension. Profiles transverse to the rift axis

Cretaceous origin of dogwoods: an anatomically preserved Cornus (Cornaceae fruit from the Campanian of Vancouver Island

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Brian A. Atkinson

2016-12-01

Full Text Available Background Cornaceae consists of 58 species, all within the genus Cornus. The Cenozoic record of Cornus is extensive and well documented. Molecular divergence-time studies suggest that crown-group Cornus may have originated by the Late Cretaceous. However, there has been no formal report of Cornus from Cretaceous deposits. Here, we characterize a permineralized fossil fruit assignable to Cornus subg. Cornus from the Upper Cretaceous (Campanian Shelter Point locality of Vancouver Island, British Columbia, Canada. Methods Serial sections of the specimen were made using the cellulose acetate peel technique. Peels were mounted onto microscope slides and studied by light microscopy. Results The fossil fruit consists of a tri-locular woody endocarp with dorsal germination valves. The locules are sub-triangular to ellipsoidal in transverse section and are separated by thin septa. Endocarp tissue consists of elongated and isodiametric sclereids and secretory cavities. Internal vascular tissue was not observed, but is interpreted to have been located along the outer periphery of the septa for some length, common in many cornalean taxa. There is one seed in each locule, one of which was found to have endosperm and a dicotyledonous embryo. Discussion Woody endocarps with germination valves, without central vascular bundles, and with one seed per locule are characteristic of several families within the order Cornales. The interpreted vascular pattern and presence of secretory cavities indicates that the fossil fruit is assignable to Cornus subg. Cornus. Comparative analysis suggests that the fossil is most similar to Cornus piggae, a species described from the Paleocene of North Dakota. This fossil is the first evidence of crown-group Cornaceae from the Cretaceous and sheds light on both the plesiomorphic fruit characters and the timing of the initial diversification of the family and basal asterid lineage, Cornales.

On the connectivity anisotropy in fluvial Hot Sedimentary Aquifers and its influence on geothermal doublet performance

DEFF Research Database (Denmark)

Willems, Cees J.L.; Nick, Hamid; Donselaar, Marinus E.

2017-01-01

This study finds that the geothermal doublet layout with respect to the paleo flow direction in fluvial sedimentary reservoirs could significantly affect pump energy losses. These losses can be reduced by up to 10% if a doublet well pair is oriented parallel to the paleo flow trend compared...

Fluvial response to Holocene volcanic damming and breaching in the Gediz and Geren rivers, western Turkey

NARCIS (Netherlands)

van Gorp, W.; Veldkamp, A.; Temme, A.J.A.M.; Maddy, D; Demir, T.; Schriek van der, T.; Reimann, T.; Wallinga, J.; Wijbrans, J.R.; Schoorl, J.M.

2013-01-01

This study discusses the complex late Holocene evolution of the Gediz River north of Kula, western Turkey, when a basaltic lava flow dammed and filled this river valley. Age control was obtained using established and novel feldspar luminescence techniques on fluvial sands below and on top of the

Fluvial response to abrupt global warming at the Palaeocene/Eocene boundary.

Science.gov (United States)

Foreman, Brady Z; Heller, Paul L; Clementz, Mark T

2012-11-01

Climate strongly affects the production of sediment from mountain catchments as well as its transport and deposition within adjacent sedimentary basins. However, identifying climatic influences on basin stratigraphy is complicated by nonlinearities, feedback loops, lag times, buffering and convergence among processes within the sediment routeing system. The Palaeocene/Eocene thermal maximum (PETM) arguably represents the most abrupt and dramatic instance of global warming in the Cenozoic era and has been proposed to be a geologic analogue for anthropogenic climate change. Here we evaluate the fluvial response in western Colorado to the PETM. Concomitant with the carbon isotope excursion marking the PETM we document a basin-wide shift to thick, multistoried, sheets of sandstone characterized by variable channel dimensions, dominance of upper flow regime sedimentary structures, and prevalent crevasse splay deposits. This progradation of coarse-grained lithofacies matches model predictions for rapid increases in sediment flux and discharge, instigated by regional vegetation overturn and enhanced monsoon precipitation. Yet the change in fluvial deposition persisted long after the approximately 200,000-year-long PETM with its increased carbon dioxide levels in the atmosphere, emphasizing the strong role the protracted transmission of catchment responses to distant depositional systems has in constructing large-scale basin stratigraphy. Our results, combined with evidence for increased dissolved loads and terrestrial clay export to world oceans, indicate that the transient hyper-greenhouse climate of the PETM may represent a major geomorphic 'system-clearing event', involving a global mobilization of dissolved and solid sediment loads on Earth's surface.

The asteroid genus Haccourtaster (Echinodermata, Goniasteridae) in the Bohemian Cretaceous Basin, Czech Republic

Czech Academy of Sciences Publication Activity Database

Žítt, Jiří

2005-01-01

Roč. 26, č. 2 (2005), s. 225-237 ISSN 0195-6671 R&D Projects: GA ČR(CZ) GA206/01/1580 Institutional research plan: CEZ:AV0Z30130516 Keywords : Cretaceous * Asteroidea * New species Subject RIV: EG - Zoology Impact factor: 0.981, year: 2005

Debris-carrying camouflage among diverse lineages of Cretaceous insects.

Science.gov (United States)

Wang, Bo; Xia, Fangyuan; Engel, Michael S; Perrichot, Vincent; Shi, Gongle; Zhang, Haichun; Chen, Jun; Jarzembowski, Edmund A; Wappler, Torsten; Rust, Jes

2016-06-01

Insects have evolved diverse methods of camouflage that have played an important role in their evolutionary success. Debris-carrying, a behavior of actively harvesting and carrying exogenous materials, is among the most fascinating and complex behaviors because it requires not only an ability to recognize, collect, and carry materials but also evolutionary adaptations in related morphological characteristics. However, the fossil record of such behavior is extremely scarce, and only a single Mesozoic example from Spanish amber has been recorded; therefore, little is known about the early evolution of this complicated behavior and its underlying anatomy. We report a diverse insect assemblage of exceptionally preserved debris carriers from Cretaceous Burmese, French, and Lebanese ambers, including the earliest known chrysopoid larvae (green lacewings), myrmeleontoid larvae (split-footed lacewings and owlflies), and reduviids (assassin bugs). These ancient insects used a variety of debris material, including insect exoskeletons, sand grains, soil dust, leaf trichomes of gleicheniacean ferns, wood fibers, and other vegetal debris. They convergently evolved their debris-carrying behavior through multiple pathways, which expressed a high degree of evolutionary plasticity. We demonstrate that the behavioral repertoire, which is associated with considerable morphological adaptations, was already widespread among insects by at least the Mid-Cretaceous. Together with the previously known Spanish specimen, these fossils are the oldest direct evidence of camouflaging behavior in the fossil record. Our findings provide a novel insight into early evolution of camouflage in insects and ancient ecological associations among plants and insects.

Terrestrial catastrophe caused by cometary impact at the end of Cretaceous

Science.gov (United States)

Hsü, Kenneth J.

1980-05-01

Evidence is presented indicating that the extinction, at the end of the Cretaceous, of large terrestrial animals was caused by atmospheric heating during a cometary impact and that the extinction of calcareous marine plankton was a consequence of poisoning by cyanide released by the fallen comet and of a catastrophic rise in calcite-compensation depth in the oceans after the detoxification of the cyanide.

Tidal Simulations of an Incised-Valley Fluvial System with a Physics-Based Geologic Model

Science.gov (United States)

Ghayour, K.; Sun, T.

2012-12-01

Physics-based geologic modeling approaches use fluid flow in conjunction with sediment transport and deposition models to devise evolutionary geologic models that focus on underlying physical processes and attempt to resolve them at pertinent spatial and temporal scales. Physics-based models are particularly useful when the evolution of a depositional system is driven by the interplay of autogenic processes and their response to allogenic controls. This interplay can potentially create complex reservoir architectures with high permeability sedimentary bodies bounded by a hierarchy of shales that can effectively impede flow in the subsurface. The complex stratigraphy of tide-influenced fluvial systems is an example of such co-existing and interacting environments of deposition. The focus of this talk is a novel formulation of boundary conditions for hydrodynamics-driven models of sedimentary systems. In tidal simulations, a time-accurate boundary treatment is essential for proper imposition of tidal forcing and fluvial inlet conditions where the flow may be reversed at times within a tidal cycle. As such, the boundary treatment at the inlet has to accommodate for a smooth transition from inflow to outflow and vice-versa without creating numerical artifacts. Our numerical experimentations showed that boundary condition treatments based on a local (frozen) one-dimensional approach along the boundary normal which does not account for the variation of flow quantities in the tangential direction often lead to unsatisfactory results corrupted by numerical artifacts. In this talk, we propose a new boundary treatment that retains all spatial and temporal terms in the model and as such is capable to account for nonlinearities and sharp variations of model variables near boundaries. The proposed approach borrows heavily from the idea set forth by J. Sesterhenn1 for compressible Navier-Stokes equations. The methodology is successfully applied to a tide-influenced incised

Lower Cretaceous smarl turbidites of the Argo Abyssal Plain, Indian Ocean

Science.gov (United States)

Dumoulin, Julie A.; Stewart, Sondra K.; Kennett, Diana; Mazzullo, Elsa K.

1992-01-01

Sediments recovered during Ocean Drilling Program (ODP) Leg 123 from the Argo Abyssal Plain (AAP) consist largely of turbidites derived from the adjacent Australian continental margin. The oldest abundant turbidites are Valanginian-Aptian in age and have a mixed (smarl) composition; they contain subequal amounts of calcareous and siliceous biogenic components, as well as clay and lesser quartz. Most are thin-bedded, fine sand to mud-sized, and best described by Stow and Piper's model (1984) for fine-grained biogenic turbidites. Thicker (to 3 m), coarser-grained (medium-to-coarse sand-sized) turbidites fit Bouma's model (1962) for sandy turbidites; these generally are base-cut-out (BCDE, BDE) sequences, with B-division parallel lamination as the dominant structure. Parallel laminae most commonly concentrate quartz and/or calcispheres vs. lithic clasts or clay, but distinctive millimeter to centimeter-thick, radiolarian-rich laminae occur in both fine and coarse-grained Valanginian-Hauterivian turbidites.AAP turbidites were derived from relatively deep parts of the continental margin (outer shelf, slope, or rise) that lay below the photic zone, but above the calcite compensation depth (CCD). Biogenic components are largely pelagic (calcispheres, foraminifers, radiolarians, nannofossils); lesser benthic foraminifers are characteristic of deep-water (abyssal to bathyal) environments. Abundant nonbiogenic components are mostly clay and clay clasts; smectite is the dominant clay species, and indicates a volcanogenic provenance, most likely the Triassic-Jurassic volcanic suite exposed along the northern Exmouth Plateau.Lower Cretaceous smarl turbidites were generated during eustatic lowstands and may have reached the abyssal plain via Swan Canyon, a submarine canyon thought to have formed during the Late Jurassic. In contrast to younger AAP turbidites, however, Lower Cretaceous turbidites are relatively fine-grained and do not contain notably older reworked fossils. Early

Paleolatitudes of the Tibetan Himalaya from primary and secondary magnetizations of Jurassic to Lower Cretaceous sedimentary rocks

Science.gov (United States)

Huang, Wentao; van Hinsbergen, Douwe J. J.; Dekkers, Mark J.; Garzanti, Eduardo; Dupont-Nivet, Guillaume; Lippert, Peter C.; Li, Xiaochun; Maffione, Marco; Langereis, Cor G.; Hu, Xiumian; Guo, Zhaojie; Kapp, Paul

2015-01-01

The Tibetan Himalaya represents the northernmost continental unit of the Indian plate that collided with Asia in the Cenozoic. Paleomagnetic studies on the Tibetan Himalaya can help constrain the dimension and paleogeography of "Greater India," the Indian plate lithosphere that subducted and underthrusted below Asia after initial collision. Here we present a paleomagnetic investigation of a Jurassic (limestones) and Lower Cretaceous (volcaniclastic sandstones) section of the Tibetan Himalaya. The limestones yielded positive fold test, showing a prefolding origin of the isolated remanent magnetizations. Detailed paleomagnetic analyses, rock magnetic tests, end-member modeling of acquisition curves of isothermal remanent magnetization, and petrographic investigation reveal that the magnetic carrier of the Jurassic limestones is authigenic magnetite, whereas the dominant magnetic carrier of the Lower Cretaceous volcaniclastic sandstones is detrital magnetite. Our observations lead us to conclude that the Jurassic limestones record a prefolding remagnetization, whereas the Lower Cretaceous volcaniclastic sandstones retain a primary remanence. The volcaniclastic sandstones yield an Early Cretaceous paleolatitude of 55.5°S [52.5°S, 58.6°S] for the Tibetan Himalaya, suggesting it was part of the Indian continent at that time. The size of "Greater India" during Jurassic time cannot be estimated from these limestones. Instead, a paleolatitude of the Tibetan Himalaya of 23.8°S [21.8°S, 26.1°S] during the remagnetization process is suggested. It is likely that the remagnetization, caused by the oxidation of early diagenetic pyrite to magnetite, was induced during 103-83 or 77-67 Ma. The inferred paleolatitudes at these two time intervals imply very different tectonic consequences for the Tibetan Himalaya.

Cross-stratified Wood: Enigmatic Woody Debris Deposits in Warm-Polar Fluvial Sediments (Pliocene Beaufort Formation, Nunavut)

Science.gov (United States)

Davies, N. S.; Gosse, J. C.; Rybczynski, N.

2012-04-01

Woody debris has been an important sediment component and a significant geomorphic agent in pristine fluvial systems since the Devonian. In recent years a large volume of research has focussed on various aspects of the importance of woody debris within the fluvial realm; from the evolutionary significance of fossil wood accumulations in the rock record to studies of the biogeomorphological and ecological importance of woody debris in modern rivers. In this presentation we describe cross-stratified woody debris deposits comprising organic detritus from a boreal-type treeline forest that included species of pine, birch, poplar, alder, spruce, eastern cedar, and larch, in both shrub and tree form. The cross-stratified wood is an enigmatic subset of fine woody debris which, to our knowledge, has never before been described from either the global stratigraphic record or modern fluvial environments. The deposits we describe are located within the Pliocene Beaufort Formation on Meighen Island, Nunavut, Canada, at a latitude of 80°N, and are compared with other cross-stratified woody debris deposits that have been noted elsewhere in the Pliocene of the Canadian Arctic. We make the robust observation that these deposits appear to be geographically and stratigraphically restricted to polar latitudes from a period of warm climatic conditions during the Pliocene (15-20 °C warmer mean annual temperature than the present day). In this regard it is possible to speculate that the transport of large amounts of woody debris as bedload is potentially a unique feature of forested high latitude rivers. Such bedload deposition requires a large amount of woody debris with a greater density than the fluid transporting it. The softwood composition of the debris suggests that this was most likely attained by saturation and subsequent entrainment of extensive accumulations of deadwood, promoted by unusually high rates of tree mortality and low rates of bacterial decomposition arising from

Tectonostratigraphic reconstruction Cretaceous volcano-sedimentary in the northwestern Andes: from extensional tectonics to arc accretion.

Science.gov (United States)

Zapata, S.; Patino, A. M.; Cardona, A.; Mejia, D.; Leon, S.; Jaramillo, J. S.; Valencia, V.; Parra, M.; Hincapie, S.

2014-12-01

Active continental margins characterized by continuous convergence experienced overimposed tectonic configurations that allowed the formation of volcanic arcs, back arc basins, transtensional divergent tectonics or the accretion of exotic volcanic terranes. Such record, particularly the extensional phases, can be partially destroyed and obscure by multiple deformational events, the accretion of exotic terranes and strike slip fragmentation along the margin. The tectonic evolution of the northern Andes during the Mesozoic is the result of post Pangea extension followed by the installation of a long-lived Jurassic volcanic arc (209 - 136 ma) that apparently stops between 136 Ma and 110 Ma. The Quebradagrande Complex has been define as a single Lower Cretaceous volcano-sedimentary unit exposed in the western flank of the Central Cordillera of the Colombian Andes that growth after the Late Jurassic to Early Cretaceous magmatic hiatus. The origin of this unit have been related either to an oceanic volcanic arc or a marginal basin environment. The existence of such contrasting models reflect the regional perspective followed in published studies and the paucity of detail analysis of the volcano-sedimentary sequences.We integrate multiple approaches including structural mapping, stratigraphy, geochemistry, U-Pb provenance and geochronology to improve the understanding of this unit and track the earlier phases of accumulation that are mask on the overimposed tectonic history. Our preliminary results suggest the existence of different volcano-sedimentary units that accumulated between 100 Ma and 82 Ma.The older Lower Cretaceous sequences was deposited over Triassic metamorphic continental crust and include a upward basin deepening record characterized by thick fan delta conglomerates, followed by distal turbidites and a syn-sedimentary volcanic record at 100 ma. The other sequence include a 85 - 82 Ma fringing arc that was also formed close to the continental margin or

Proximal Cretaceous-Tertiary boundary impact deposits in the Caribbean

Science.gov (United States)

Hildebrand, Alan R.; Boynton, Willam V.

1990-01-01

Trace element, isotopic, and mineralogic studies indicate that the proposed impact at the Cretaceous-Tertiary boundary occurred in an ocean basin, although a minor component of continental material is required. The size and abundance of shocked minerals and the restricted geographic occurrence of the ejecta layer and impact-wave deposits suggest an impact between the Americas. Coarse boundary sediments at sites 151 and 153 in the Colombian Basin and 5- to 450-meter-thick boundary sediments in Cuba may be deposits of a giant wave produced by a nearby oceanic impact.

Fluvial sediment transport in a glacier-fed high-mountain river (Riffler Bach, Austrian Alps)

Science.gov (United States)

Morche, David; Weber, Martin; Faust, Matthias; Schuchardt, Anne; Baewert, Henning

2017-04-01

High-alpine environments are strongly affected by glacier retreat since the Little Ice Age (LIA). Due to ongoing climate change the hydrology of proglacial rivers is also influenced. It is expected that the growing proportions of snow melt and rainfall events will change runoff characteristics of proglacial rivers. Additionally, the importance of paraglacial sediment sources in recently deglaciating glacier forefields is increasing, while the role of glacial erosion is declining. Thus complex environmental conditions leading to a complex pattern of fluvial sediment transport in partly glaciated catchments of the European Alps. Under the umbrella of the joint PROSA-project the fluvial sediment transport of the river Riffler Bach (Kaunertal, Tyrol, Austria) was studied in 3 consecutive ablation seasons in order to quantify sediment yields. In June 2012 a probe for water level and an automatic water sampler (AWS) were installed at the outlet of the catchment (20km2). In order to calculate annual stage-discharge-relations by the rating-curve approach, discharge (Q) was repeatedly measured with current meters and by salt dilution. Concurrent to the discharge measurements bed load was collected using a portable Helley-Smith sampler. Bed load samples were weighted and sieved in the laboratory to gain annual bed load rating curves and grain size distributions. In total 564 (2012: 154, 2013: 209, 2014: 201) water samples were collected and subsequently filtered to quantify suspended sediment concentrations (SSC). Q-SSC-relations were calculated for single flood events due to the high variability of suspended sediment transport. The results show a high inter- and intra-annual variability of solid fluvial sediment transport, which can be explained by the characteristics of suspended sediment transport. Only 13 of 22 event-based Q-SSC-relations show causal dependency. In 2012, during a period with multiple pluvial-induced peak discharges most sediment was transported. On the

Characterization of organic matter in dusts and fluvial sediments from exposed areas of dowtown Prague, Czech Republic

Czech Academy of Sciences Publication Activity Database

Sýkorová, Ivana; Havelcová, Martina; Trejtnarová, Hana; Matysová, Petra; Vašíček, Michal; Suchý, V.; Kříbek, B.

2009-01-01

Roč. 80, č. 2 (2009), s. 69-86 ISSN 0166-5162 R&D Projects: GA AV ČR IAA300460804 Institutional research plan: CEZ:AV0Z30460519 Keywords : dust * fluvial sediment * carbonaceous particles Subject RIV: DD - Geochemistry Impact factor: 1.924, year: 2009

Middel Pleistocene to Holocene fluvial terrace development and uplift-driven valley incision in the SE Carpathians, Romania

NARCIS (Netherlands)

Necea, D.; Fielitz, W.; Andriessen, P.A.M.; Dinu, C.

2013-01-01

This study reveals that in the SE Carpathians terrace development and fluvial incision during the Middle Pleistocene-Holocene are predominantly controlled by tectonic uplift as shown by terrace distributions and uplift amounts and rates. The work focuses on a transect from the internal nappes and

The clasts of Cretaceous marls in the conglomerates of the Konradsheim Formation (Pöchlau quarry, Gresten Klippen Zone, Austria)

Science.gov (United States)

Ślączka, Andrzej; Gasiñski, M. Adam; Bąk, Marta; Wessely, Godfrid

2009-04-01

Investigations were carried out on foraminiferids and radiolaria from redeposited clasts within the conglomerates of the Konradsheim Formation (Gresten Klippen Zone) in the area of the Pöchlau hill, east of Maria Neustift. These shales and marls are of Middle to Late Jurassic and Early Cretaceous age. In the latter clasts, foraminiferal assemblages with Tritaxia ex gr. gaultina as well as radiolaria species Angulobracchia portmanni Baumgartner, Dictyomitra communis (Squinabol), Hiscocapsa asseni (Tan), Pseudodictyomitra lodogaensis Pessagno, Pseudoeucyrtis hanni (Tan), Rhopalosyringium fossile (Squinabol) were found. In one block from the uppermost part of the sequence there is an assemblage with Caudammina (H) gigantea, Rotalipora appenninica and Globotruncana bulloides. However, the brecciated character of this block and occurrence near a fault suggest that it was probably wedged into the conglomerates of the Konradsheim Formation during tectonic movements. In pelitic siliceous limestones below the Konradsheim Limestone radiolarian assemblages of Middle Callovian to Early Tithonian age were found. They enable correlation with the Scheibbsbach Formation. In a marly sequence, above the conglomeratic limestone, the foraminiferal assemblages contain taxa from mid-Cretaceous up to Paleocene. The present biostratigraphic investigation confirmed the previous stratigraphic assignments and imply clearly that the sedimentation of deposits similar to the Konradsheim Formation also occurred at the end of the Early Cretaceous and deposition of conglomeratic limestones within the Gresten Klippen Zone, and especially within the Konradsheim Formation, was repeated several times during the Late Jurassic and Early Cretaceous.

Genetic stratigraphy of Coniacian deltaic deposits of the northwestern part of the Bohemian Cretaceous Basin

Czech Academy of Sciences Publication Activity Database

Nádaskay, R.; Uličný, David

2014-01-01

Roč. 165, č. 4 (2014), s. 547-575 ISSN 1860-1804 Institutional support: RVO:67985530 Keywords : genetic stratigraphy * well log * Bohemian Cretaceous Basin Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.569, year: 2014

Assessment of spatiotemporal variations in the fluvial wash-load component in the 21st century with regard to GCM climate change scenarios

International Nuclear Information System (INIS)

Mouri, Goro

2015-01-01

For stream water, in which a relationship exists between wash-load concentration and discharge, an estimate of fine-sediment delivery may be obtained from a traditional fluvial wash-load rating curve. Here, we demonstrate that the remaining wash-load material load can be estimated from a traditional empirical principle on a nationwide scale. The traditional technique was applied to stream water for the whole of Japan. Four typical GCMs were selected from the Coupled Model Intercomparison Project Phase 5 (CMIP5) ensemble to provide the driving fields for the following regional climate models to assess the wash-load component based on rating curves: the Model for Interdisciplinary Research on Climate (MIROC), the Meteorological Research Institute Atmospheric General Circulation Model (MRI-GCM), the Hadley Centre Global Environment Model (HadGEM) and the Geophysical Fluid Dynamics Laboratory (GFDL) climate model. The simulations consisted of an ensemble, including multiple physics configurations and different Representative Concentration Pathways (RCP2.6, RCP4.5 and RCP8.5), which was used to produce monthly datasets for the whole country of Japan. The impacts of future climate changes on fluvial wash load in Japanese stream water were based on the balance of changes in hydrological factors. The annual and seasonal variations of the fluvial wash load were assessed from the result of the ensemble analysis in consideration of the Greenhouse Gas (GHG) emission scenarios. The determined results for the amount of wash load increase range from approximately 20 to 110% in the 2040s, especially along part of the Pacific Ocean and the Sea of Japan regions. In the 2090s, the amount of wash load is projected to increase by more than 50% over the whole of Japan. The assessment indicates that seasonal variation is particularly important because the rainy and typhoon seasons, which include extreme events, are the dominant seasons. Because fluvial wash-load-component turbidity

Assessment of spatiotemporal variations in the fluvial wash-load component in the 21st century with regard to GCM climate change scenarios

Energy Technology Data Exchange (ETDEWEB)

Mouri, Goro, E-mail: mouri@rainbow.iis.u-tokyo.ac.jp

2015-11-15

For stream water, in which a relationship exists between wash-load concentration and discharge, an estimate of fine-sediment delivery may be obtained from a traditional fluvial wash-load rating curve. Here, we demonstrate that the remaining wash-load material load can be estimated from a traditional empirical principle on a nationwide scale. The traditional technique was applied to stream water for the whole of Japan. Four typical GCMs were selected from the Coupled Model Intercomparison Project Phase 5 (CMIP5) ensemble to provide the driving fields for the following regional climate models to assess the wash-load component based on rating curves: the Model for Interdisciplinary Research on Climate (MIROC), the Meteorological Research Institute Atmospheric General Circulation Model (MRI-GCM), the Hadley Centre Global Environment Model (HadGEM) and the Geophysical Fluid Dynamics Laboratory (GFDL) climate model. The simulations consisted of an ensemble, including multiple physics configurations and different Representative Concentration Pathways (RCP2.6, RCP4.5 and RCP8.5), which was used to produce monthly datasets for the whole country of Japan. The impacts of future climate changes on fluvial wash load in Japanese stream water were based on the balance of changes in hydrological factors. The annual and seasonal variations of the fluvial wash load were assessed from the result of the ensemble analysis in consideration of the Greenhouse Gas (GHG) emission scenarios. The determined results for the amount of wash load increase range from approximately 20 to 110% in the 2040s, especially along part of the Pacific Ocean and the Sea of Japan regions. In the 2090s, the amount of wash load is projected to increase by more than 50% over the whole of Japan. The assessment indicates that seasonal variation is particularly important because the rainy and typhoon seasons, which include extreme events, are the dominant seasons. Because fluvial wash-load-component turbidity

Total petroleum systems of the Pelagian Province, Tunisia, Libya, Italy, and Malta; the Bou Dabbous, Tertiary and Jurassic-Cretaceous composite

Science.gov (United States)

Klett, T.R.

2001-01-01

Undiscovered conventional oil and gas resources were assessed within total petroleum systems of the Pelagian Province (2048) as part of the U.S. Geological Survey World Petroleum Assessment 2000. The Pelagian Province is located mainly in eastern Tunisia and northwestern Libya. Small portions of the province extend into Malta and offshore Italy. Although several petroleum systems may exist, only two ?composite? total petroleum systems were identified. Each total petroleum system comprises a single assessment unit. These total petroleum systems are called the Bou Dabbous?Tertiary and Jurassic-Cretaceous Composite, named after the source-rock intervals and reservoir-rock ages. The main source rocks include mudstone of the Eocene Bou Dabbous Formation; Cretaceous Bahloul, Lower Fahdene, and M?Cherga Formations; and Jurassic Nara Formation. Known reservoirs are in carbonate rocks and sandstone intervals throughout the Upper Jurassic, Cretaceous, and Tertiary sections. Traps for known accumulations include fault blocks, low-amplitude anticlines, high-amplitude anticlines associated with reverse faults, wrench fault structures, and stratigraphic traps. The estimated means of the undiscovered conventional petroleum volumes in total petroleum systems of the Pelagian Province are as follows: [MMBO, million barrels of oil; BCFG, billion cubic feet of gas; MMBNGL, million barrels of natural gas liquids] Total Petroleum System MMBO BCFG MMBNGL Bou Dabbous?Tertiary 667 2,746 64 Jurassic-Cretaceous Composite 403 2,280 27

The trace fossil Lepidenteron lewesiensis (Mantell, 1822) from the Upper Cretaceous of southern Poland

Science.gov (United States)

Jurkowska, Agata; Uchman, Alfred

2013-12-01

Jurkowska, A. and Uchman, A. 2013. The trace fossil Lepidenteron lewesiensis (Mantell, 1822) from the Upper Cretaceous of southern Poland. Acta Geologica Polonica, 63(4), 611-623. Warszawa. Lepidenteron lewesiensis (Mantell, 1822) is an unbranched trace fossil lined with small fish scales and bones, without a constructed wall. It is characteristic of the Upper Cretaceous epicontinental, mostly marly sediments in Europe. In the Miechow Segment of the Szczecin-Miechow Synclinorium in southern Poland, it occurs in the Upper Campanian-Lower Maastrichtian deeper shelf sediments, which were deposited below wave base and are characterized by total bioturbation and a trace fossil assemblage comprising Planolites, Palaeophycus, Thalassinoides , Trichichnus, Phycosiphon, Zoophycos and Helicodromites that is typical of the transition from the distal Cruziana to the Zoophycos ichnofacies. L. lewesiensis was produced by a burrowing predator or scavenger of fishes. The tracemaker candidates could be eunicid polychaetes or anguillid fishes.

Evidence for Cretaceous-Paleogene boundary bolide "impact winter" conditions from New Jersey, USA

NARCIS (Netherlands)

Vellekoop, J.; Esmeray-Senlet, S.; Miller, K.G.; Browning, J.V.; Sluijs, A.|info:eu-repo/dai/nl/311474748; van de Schootbrugge, B.|info:eu-repo/dai/nl/376758562; Sinninghe Damsté, J.S.|info:eu-repo/dai/nl/07401370X; Brinkhuis, H.|info:eu-repo/dai/nl/095046097

2016-01-01

Abrupt and short-lived “impact winter” conditions have commonly been implicated as the main mechanism leading to the mass extinction at the Cretaceous-Paleogene (K-Pg) boundary (ca. 66 Ma), marking the end of the reign of the non-avian dinosaurs. However, so far only limited evidence has been

Geocronología de los yacimientos achelenses de Pinedo y Cien Fanegas (Valle del Tajo) e implicaciones en la evolución fluvial en el entorno de Toledo (España)

DEFF Research Database (Denmark)

López-Recio, M.; Silva, P. G.; Roquero, E.

2015-01-01

This study presents the first geochronological data from several research projects focused on the chronostratigraphy of the Tagus fluvial terraces in the environs of Toledo city (Central Spain). The research is centered on Middle to Late Pleistocene fluvial terraces with palaeontological and Ache...

The contribution of the young Cretaceous Caribbean Oceanic Plateau to the genesis of late Cretaceous arc magmatism in the Cordillera Occidental of Ecuador

Science.gov (United States)

Allibon, J.; Monjoie, P.; Lapierre, H.; Jaillard, E.; Bussy, F.; Bosch, D.; Senebier, F.

2008-12-01

The eastern part of the Cordillera Occidental of Ecuador comprises thick buoyant oceanic plateaus associated with island-arc tholeiites and subduction-related calc-alkaline series, accreted to the Ecuadorian Continental Margin from Late Cretaceous to Eocene times. One of these plateau sequences, the Guaranda Oceanic Plateau is considered as remnant of the Caribbean-Colombian Oceanic Province (CCOP) accreted to the Ecuadorian Margin in the Maastrichtien. Samples studied in this paper were taken from four cross-sections through two arc-sequences in the northern part of the Cordillera Occidental of Ecuador, dated as (Río Cala) or ascribed to (Macuchi) the Late Cretaceous and one arc-like sequence in the Chogòn-Colonche Cordillera (Las Orquídeas). These three island-arcs can clearly be identified and rest conformably on the CCOP. In all four localities, basalts with abundant large clinopyroxene phenocrysts can be found, mimicking a picritic or ankaramitic facies. This mineralogical particularity, although not uncommon in island arc lavas, hints at a contribution of the CCOP in the genesis of these island arc rocks. The complete petrological and geochemical study of these rocks reveals that some have a primitive island-arc nature (MgO values range from 6 to 11 wt.%). Studied samples display marked Nb, Ta and Ti negative anomalies relative to the adjacent elements in the spidergrams characteristic of subduction-related magmatism. These rocks are LREE-enriched and their clinopyroxenes show a tholeiitic affinity (FeO T-TiO 2 enrichment and CaO depletion from core to rim within a single crystal). The four sampled cross-sections through the island-arc sequences display homogeneous initial Nd, and Pb isotope ratios that suggest a unique mantellic source for these rocks resulting from the mixing of three components: an East-Pacific MORB end-member, an enriched pelagic sediment component, and a HIMU component carried by the CCOP. Indeed, the ankaramite and Mg

Aptian sedimentation in the Recôncavo-Tucano-Jatobá Rift System and its tectonic and paleogeographic significance

Science.gov (United States)

Freitas, Bernardo T.; Almeida, Renato P.; Carrera, Simone C.; Figueiredo, Felipe T.; Turra, Bruno B.; Varejão, Filipe G.; Assine, Mario L.

2017-12-01

This study, based on detailed sedimentologic and stratigraphic analysis of the Aptian succession preserved in the Recôncavo-Tucano-Jatobá Rift System (RTJ), present new elements for biostratigraphic correlation and paleogeographic reconstruction in the mid-Cretaceous South Atlantic realm, supporting novel interpretations on the tectonic and sedimentary evolution related to the W-Gondwana breakup. The Aptian sedimentary succession in the RTJ has been referred to as Marizal Formation, and interpreted as post-rift deposits. Detailed sedimentologic and stratigraphic studies of these deposits enabled the recognition and individualization of two distinctive sedimentary units that can be traced in the entire RTJ. These units are here described and named Banzaê and Cícero Dantas members of the Marizal Formation. Their contact is locally marked by the fossiliferous successions of the here proposed Amargosa Bed, lying at the top of the Banzaê Member. Both members of the Marizal Formation record large river systems captured by the Tucano Basin with the local development of eolian dune fields and fault-bounded alluvial fans. The Amargosa Bed represents a regional-scale base level change preserved between the Aptian fluvial successions along the RTJ. Hence, the studied sedimentary record presents important implications for the timing and direction of marine ingressions affecting NE-Brazil interior basins during the Aptian. A remarkable contrast in preserved fluvial architecture between the Banzaê Member, characterized by connected channel bodies, and the Cícero Dantas Member, characterized by isolated channel bodies within overbank fines, is here reported. The main interpreted control for the observed contrast in fluvial stratigraphy is sedimentary yield variation. The interval is also subject to the interpretation of a regional shift in the mechanism responsible for the subsidence of the basins formed during the Cretaceous break-up of the Central South Atlantic. This

Compound simulation of fluvial floods and storm surges in a global coupled river-coast flood model: Model development and its application to 2007 Cyclone Sidr in Bangladesh

Science.gov (United States)

Ikeuchi, Hiroaki; Hirabayashi, Yukiko; Yamazaki, Dai; Muis, Sanne; Ward, Philip J.; Winsemius, Hessel C.; Verlaan, Martin; Kanae, Shinjiro

2017-08-01

Water-related disasters, such as fluvial floods and cyclonic storm surges, are a major concern in the world's mega-delta regions. Furthermore, the simultaneous occurrence of extreme discharges from rivers and storm surges could exacerbate flood risk, compared to when they occur separately. Hence, it is of great importance to assess the compound risks of fluvial and coastal floods at a large scale, including mega-deltas. However, most studies on compound fluvial and coastal flooding have been limited to relatively small scales, and global-scale or large-scale studies have not yet addressed both of them. The objectives of this study are twofold: to develop a global coupled river-coast flood model; and to conduct a simulation of compound fluvial flooding and storm surges in Asian mega-delta regions. A state-of-the-art global river routing model was modified to represent the influence of dynamic sea surface levels on river discharges and water levels. We conducted the experiments by coupling a river model with a global tide and surge reanalysis data set. Results show that water levels in deltas and estuaries are greatly affected by the interaction between river discharge, ocean tides and storm surges. The effects of storm surges on fluvial flooding are further examined from a regional perspective, focusing on the case of Cyclone Sidr in the Ganges-Brahmaputra-Meghna Delta in 2007. Modeled results demonstrate that a >3 m storm surge propagated more than 200 km inland along rivers. We show that the performance of global river routing models can be improved by including sea level dynamics.

Crocodilian Nest in a Late Cretaceous Sauropod Hatchery from the Type Lameta Ghat Locality, Jabalpur, India.

Directory of Open Access Journals (Sweden)

Rahul Srivastava

Full Text Available The well-known Late Cretaceous Lameta Ghat locality (Jabalpur, India provides a window of opportunity to study a large stable, near shore sandy beach, which was widely used by sauropod dinosaurs as a hatchery. In this paper, we revisit the eggs and eggshell fragments previously assigned to lizards from this locality and reassign them to crocodylomorphs. Several features point to a crocodilian affinity, including a subspherical to ellipsoidal shape, smooth, uneven external surface, discrete trapezoid shaped shell units with wide top and narrow base, basal knobs and wedge shaped crystallites showing typical inverted triangular extinction under crossed nicols. The crocodylomorph eggshell material presented in this paper adds to the skeletal data of these most probably Cretaceous-Eocene dryosaurid crocodiles.

Teeth of embryonic or hatchling sauropods from the Berriasian (Early Cretaceous of Cherves-de-Cognac, France

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Paul M. Barrett

2016-08-01

Full Text Available The Cherves-de-Cognac site (Charente, France has yielded a diverse continental microvertebrate fauna of Berriasian (earliest Cretaceous age. Dinosaur remains are rare, but include three teeth that are referrable to an indeterminate sauropod, which might represent either a titanosauriform, a non-titanosauriform macronarian or a non-neosauropod. The small size of these teeth (with a maximum length of 3 mm, as preserved and the almost complete absence of emanel wrinkling suggests that they pertained to embryonic or hatchling individuals. The Cherves-de-Cognac sauropod represents a rare occurrence of sauropod embryos/hatchlings, a new sauropod record from the poorly-known terrestrial Berriasian and another possible instance of the persistence of non-diplodocoid, non-titanosauriform sauropods into the Cretaceous.

Reconstructing Early Pleistocene (1.3 Ma) terrestrial environmental change in western Anatolia: Did it drive fluvial terrace formation?

NARCIS (Netherlands)

Veldkamp, A.; Candy, I.; Jongmans, A.G.; Maddy, D.; Demir, T.; Schoorl, J.M.; Schreve, D.; Stemerdink, C.; Schriek, van der T.

2015-01-01

A terrestrial environmental reconstruction of an Early Pleistocene landscape from western Anatolia is presented. The basis of this reconstruction is a sedimentary stack comprising fluvial and colluvial slope deposits. Contained within this stack is a sequence comprising two massive laminar calcretes

Sediment Transport Dynamic in a Meandering Fluvial System: Case Study of Chini River

Science.gov (United States)

Nazir, M. H. M.; Awang, S.; Shaaban, A. J.; Yahaya, N. K. E. M.; Jusoh, A. M.; Arumugam, M. A. R. M. A.; Ghani, A. A.

2016-07-01

Sedimentation in river reduces the flood carrying capacity which lead to the increasing of inundation area in the river basin. Basic sediment transport can predict the fluvial processes in natural rivers and stream through modeling approaches. However, the sediment transport dynamic in a small meandering and low-lying fluvial system is considered scarce in Malaysia. The aim of this study was to analyze the current riverbed erosion and sedimentation scenarios along the Chini River, Pekan, Pahang. The present study revealed that silt and clay has potentially been eroded several parts of the river. Sinuosity index (1.98) indicates that Chini River is very unstable and continuous erosion process in waterways has increase the riverbank instability due to the meandering factors. The riverbed erosional and depositional process in the Chini River is a sluggish process since the lake reduces the flow velocity and causes the deposited particles into the silt and clay soil at the bed of the lake. Besides, the bed layer of the lake comprised of cohesive silt and clayey composition that tend to attach the larger grain size of sediment. The present study estimated the total sediment accumulated along the Chini River is 1.72 ton. The HEC-RAS was employed in the simulations and in general the model performed well, once all parameters were set within their effective ranges.

La Pérdida de Espacios Fluviales en Andalucía (1956-2007. Una Aproximación Escalar.

Directory of Open Access Journals (Sweden)

David González-Rojas

2017-12-01

Full Text Available Desde mediados del siglo pasado, los espacios fluviales andaluces han conocido un acelerado proceso de degradación. En el presente artículo se realiza una aproximación histórica y multiescalar de la distribución de estos espacios a partir de los mapas de usos y coberturas vegetales. A escala regional, se evidencia que Andalucía ha perdido una décima parte de los espacios fluviales en seis décadas. En segundo lugar, se analiza, a escala local, dos casos paradigmáticos (río Guadalmina y río Guadalquivir y extensibles al resto del territorio. El esfuerzo realizado para la ordenación de los ríos no ha tenido su reflejo en los resultados obtenidos, siendo las interrelaciones entre la gestión del agua y del territorio (regional, subregional y municipal una cuestión no resuelta.

Late Cenomanian - Early Turonian Hardgrounds and nearshore Depositional Environments (Bohemian Cretaceous Basin)

Czech Academy of Sciences Publication Activity Database

Žítt, Jiří; Bosák, Pavel; Hradecká, L.; Svobodová, Marcela

Colloque sur le Cénomanien/Colloquium on the Cenomanian Stage, - (2001), s. 105-107 ISSN 0766-5946. [Colloque sur le Cénomanien/Colloquium on the Cenomanian Stage. Rouen, 20.10.2001-21.10.2001] R&D Projects: GA ČR GA205/99/1315 Institutional research plan: CEZ:AV0Z3013912 Keywords : Upper Cretaceous * Hardgrounds Subject RIV: DB - Geology ; Mineralogy

Petrological-geochemical characteristics of coarse-grained clastic sedimentary rocks of Quantou Formation, Cretaceous in Songliao basin and their geological significance

International Nuclear Information System (INIS)

Wang Gan; Zhang Bangtong

2005-01-01

Clastic sedimentary rocks of Quantou Formation, Cretaceous in Qing-an area, Songliao basin are mainly composed of sandstone, mudstone and siltstone. The petrological-chemical analysis of clastic sedimentary rocks from Quantou Formation, Cretaceous indicates that their lithology mainly consists of arkose, shale and minor rock debris sandstone and greywacke by chemical classification of bulk elements. REE distribution pattern displays the apparent enrichment of LREE and negative anomaly of Eu and is similar to that of NASC and PAAS. The ratio of trace-element in sedimentary rocks to that of upper crust shows gentle character. All the above features indicate that these sedimentary rocks were slowly deposited under weakly active tectonic setting. They are sediments typical for passive continental margin and active continental margin. It is suggested that material source of clastic sediments of Quantou Formation, Cretaceous in Qing-an area, Songliao basin was originated from Hercynian granite of Zhangguangchai Mountain, and the granite was originated from upper crust. (authors)

Review of the Upper Jurassic-Lower Cretaceous stratigraphy in Western Cameros basin, Northern Spain

DEFF Research Database (Denmark)

Vidal, Maria del Pilar Clemente

2010-01-01

The Upper Jurassic-Lower Cretaceous stratigraphy of the Cameros basin has been reviewed. In Western Cameros the stratigraphic sections are condensed but they have a parallel development with the basin depocentre and the same groups have been identified. The Tera Group consists of two formations: ...

The evolution of a colluvial hollow to a fluvial channel with periodic steps following two transformational disturbances: A wildfire and a historic flood

Science.gov (United States)

Rengers, Francis K.; McGuire, Luke; Ebel, Brian A.; Tucker, G. E.

2018-01-01

The transition of a colluvial hollow to a fluvial channel with discrete steps was observed after two landscape-scale disturbances. The first disturbance, a high-severity wildfire, changed the catchment hydrology to favor overland flow, which incised a colluvial hollow, creating a channel in the same location. This incised channel became armored with cobbles and boulders following repeated post-wildfire overland flow events. Three years after the fire, a record rainstorm produced regional flooding and generated sufficient fluvial erosion and sorting to produce a fluvial channel with periodically spaced steps. An analysis of the step spacing shows that after the flood, newly formed steps retained a similar spacing to the topographic roughness spacing in the original colluvial hollow (prior to channelization). This suggests that despite a distinct change in channel form roughness and bedform morphology, the endogenous roughness periodicity was conserved. Variations in sediment erodibility helped to create the emergent steps as the largest particles ( >D84) remained immobile, becoming step features, and downstream soil was easily winnowed away.

The evolution of a colluvial hollow to a fluvial channel with periodic steps following two transformational disturbances: A wildfire and a historic flood

Science.gov (United States)

Rengers, F. K.; McGuire, L. A.; Ebel, B. A.; Tucker, G. E.

2018-05-01

The transition of a colluvial hollow to a fluvial channel with discrete steps was observed after two landscape-scale disturbances. The first disturbance, a high-severity wildfire, changed the catchment hydrology to favor overland flow, which incised a colluvial hollow, creating a channel in the same location. This incised channel became armored with cobbles and boulders following repeated post-wildfire overland flow events. Three years after the fire, a record rainstorm produced regional flooding and generated sufficient fluvial erosion and sorting to produce a fluvial channel with periodically spaced steps. An analysis of the step spacing shows that after the flood, newly formed steps retained a similar spacing to the topographic roughness spacing in the original colluvial hollow (prior to channelization). This suggests that despite a distinct change in channel form roughness and bedform morphology, the endogenous roughness periodicity was conserved. Variations in sediment erodibility helped to create the emergent steps as the largest particles (>D84) remained immobile, becoming step features, and downstream soil was easily winnowed away.

Evidence of population resistance to extreme low flows in a fluvial-dependent fish species

Science.gov (United States)

Katz, Rachel A.; Freeman, Mary C.

2015-01-01

Extreme low streamflows are natural disturbances to aquatic populations. Species in naturally intermittent streams display adaptations that enhance persistence during extreme events; however, the fate of populations in perennial streams during unprecedented low-flow periods is not well-understood. Biota requiring swift-flowing habitats may be especially vulnerable to flow reductions. We estimated the abundance and local survival of a native fluvial-dependent fish species (Etheostoma inscriptum) across 5 years encompassing historic low flows in a sixth-order southeastern USA perennial river. Based on capturemark-recapture data, the study shoal may have acted as a refuge during severe drought, with increased young-of-the-year (YOY) recruitment and occasionally high adult immigration. Contrary to expectations, summer and autumn survival rates (30 days) were not strongly depressed during low-flow periods, despite 25%-80% reductions in monthly discharge. Instead, YOY survival increased with lower minimum discharge and in response to small rain events that increased low-flow variability. Age-1+ fish showed the opposite pattern, with survival decreasing in response to increasing low-flow variability. Results from this population dynamics study of a small fish in a perennial river suggest that fluvial-dependent species can be resistant to extreme flow reductions through enhanced YOY recruitment and high survival

Oxygen isotopes from biogenic apatites suggest widespread endothermy in Cretaceous dinosaurs

Science.gov (United States)

Amiot, Romain; Lécuyer, Christophe; Buffetaut, Eric; Escarguel, Gilles; Fluteau, Frédéric; Martineau, François

2006-06-01

The much debated question of dinosaur thermophysiology has not yet been conclusively solved despite numerous attempts. We used the temperature-dependent oxygen isotope fractionation between vertebrate body water (δ 18O body water) and phosphatic tissues (δ 18O p) to compare the thermophysiology of dinosaurs with that of non-dinosaurian ectothermic reptiles. Present-day δ 18O p values of vertebrate apatites show that ectotherms have higher δ 18O p values than endotherms at high latitudes due to their lower body temperature, and conversely lower δ 18O p values than endotherms at low latitudes. Using a data set of 80 new and 49 published δ 18O p values, we observed similar and systematic differences in δ 18O p values (Δ 18O) between four groups of Cretaceous dinosaurs (theropods, sauropods, ornithopods and ceratopsians) and associated fresh water crocodiles and turtles. Expressed in terms of body temperatures ( Tb), these Δ 18O values indicate that dinosaurs maintained rather constant Tb in the range of endotherms whatever ambient temperatures were. This implies that high metabolic rates were widespread among Cretaceous dinosaurs belonging to widely different taxonomic groups and suggest that endothermy may be a synapomorphy of dinosaurs, or may have been acquired convergently in the studied taxa.

EVOLUTION. A four-legged snake from the Early Cretaceous of Gondwana.

Science.gov (United States)

Martill, David M; Tischlinger, Helmut; Longrich, Nicholas R

2015-07-24

Snakes are a remarkably diverse and successful group today, but their evolutionary origins are obscure. The discovery of snakes with two legs has shed light on the transition from lizards to snakes, but no snake has been described with four limbs, and the ecology of early snakes is poorly known. We describe a four-limbed snake from the Early Cretaceous (Aptian) Crato Formation of Brazil. The snake has a serpentiform body plan with an elongate trunk, short tail, and large ventral scales suggesting characteristic serpentine locomotion, yet retains small prehensile limbs. Skull and body proportions as well as reduced neural spines indicate fossorial adaptation, suggesting that snakes evolved from burrowing rather than marine ancestors. Hooked teeth, an intramandibular joint, a flexible spine capable of constricting prey, and the presence of vertebrate remains in the guts indicate that this species preyed on vertebrates and that snakes made the transition to carnivory early in their history. The structure of the limbs suggests that they were adapted for grasping, either to seize prey or as claspers during mating. Together with a diverse fauna of basal snakes from the Cretaceous of South America, Africa, and India, this snake suggests that crown Serpentes originated in Gondwana. Copyright © 2015, American Association for the Advancement of Science.

Diversification of Rosaceae since the Late Cretaceous based on plastid phylogenomics.

Science.gov (United States)

Zhang, Shu-Dong; Jin, Jian-Jun; Chen, Si-Yun; Chase, Mark W; Soltis, Douglas E; Li, Hong-Tao; Yang, Jun-Bo; Li, De-Zhu; Yi, Ting-Shuang

2017-05-01

Phylogenetic relationships in Rosaceae have long been problematic because of frequent hybridisation, apomixis and presumed rapid radiation, and their historical diversification has not been clarified. With 87 genera representing all subfamilies and tribes of Rosaceae and six of the other eight families of Rosales (outgroups), we analysed 130 newly sequenced plastomes together with 12 from GenBank in an attempt to reconstruct deep relationships and reveal temporal diversification of this family. Our results highlight the importance of improving sequence alignment and the use of appropriate substitution models in plastid phylogenomics. Three subfamilies and 16 tribes (as previously delimited) were strongly supported as monophyletic, and their relationships were fully resolved and strongly supported at most nodes. Rosaceae were estimated to have originated during the Late Cretaceous with evidence for rapid diversification events during several geological periods. The major lineages rapidly diversified in warm and wet habits during the Late Cretaceous, and the rapid diversification of genera from the early Oligocene onwards occurred in colder and drier environments. Plastid phylogenomics offers new and important insights into deep phylogenetic relationships and the diversification history of Rosaceae. The robust phylogenetic backbone and time estimates we provide establish a framework for future comparative studies on rosaceous evolution. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Ecomorphological selectivity among marine teleost fishes during the end-Cretaceous extinction.

Science.gov (United States)

Friedman, Matt

2009-03-31

Despite the attention focused on mass extinction events in the fossil record, patterns of extinction in the dominant group of marine vertebrates-fishes-remain largely unexplored. Here, I demonstrate ecomorphological selectivity among marine teleost fishes during the end-Cretaceous extinction, based on a genus-level dataset that accounts for lineages predicted on the basis of phylogeny but not yet sampled in the fossil record. Two ecologically relevant anatomical features are considered: body size and jaw-closing lever ratio. Extinction intensity is higher for taxa with large body sizes and jaws consistent with speed (rather than force) transmission; resampling tests indicate that victims represent a nonrandom subset of taxa present in the final stage of the Cretaceous. Logistic regressions of the raw data reveal that this nonrandom distribution stems primarily from the larger body sizes of victims relative to survivors. Jaw mechanics are also a significant factor for most dataset partitions but are always less important than body size. When data are corrected for phylogenetic nonindependence, jaw mechanics show a significant correlation with extinction risk, but body size does not. Many modern large-bodied, predatory taxa currently suffering from overexploitation, such billfishes and tunas, first occur in the Paleocene, when they appear to have filled the functional space vacated by some extinction victims.

Caracterización estacional del hábitat fluvial del río Erro (Navarra

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P.M. Leunda, R. Miranda, M.C. Escala

2004-01-01

Full Text Available Se presenta la descripción de catorce tramos representativos del río Erro (Navarra a partir de la caracterización del hábitat fluvial llevada a cabo en invierno, verano y otoño de 2002. Para este estudio se han considerado parámetros tanto del hábitat físico (profundidad, anchura del cauce, pendiente de las orillas, velocidad del agua, tipo de sustrato, vegetación acuática y sombreado como físico-químicos del agua (temperatura, pH, conductividad, sólicos disueltos y oxigeno disuelto. El análisis de las caracteristicas del rio Erro permite considerar su estado general como bueno, aunque se detecta la presencia de un tramo sensible aguas abajo de la localidad de Erro. Si bien este tramo sensible presenta niveles de conservación aceptables, es susceptible de deteriorarse si no de adoptan las medidas oportunas para su conservación. Se sugiere su inclusión en el Lugar de Interés Comunitario (Red Natura 2000 de Navarra de los "Sistemas Fluviales de lis Ríos Irati, Urrobi y Erro".

Milankovitch cyclicity in the paleotropical, fluvial, Late Triassic age strata recovered by the Colorado Plateau Coring Project (CPCP)

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Olsen, P. E.; Mundil, R.; Kent, D.; Rasmussen, C.

2017-12-01

Two questions addressed by the CPCP are: 1) is Milankovitch-paced climate cyclicity recorded in the fluvial Late Triassic age Chinle Formation ( 227-202 Ma); and 2) do geochronological data from the Chinle support the Newark-Hartford astrochronological polarity time scale (1) (APTS). To these ends we examined the upper 157 m (stratigraphic thickness) of Petrified Forest National Park core 1A (Owl Rock, Petrified Forest, and upper Sonsela members), consisting mostly of massive red paleosols and less important fluvial sandstones. A linear age model tied to new U-Pb zircon CA ID-TIMS dates from core 1A, consistent with published data from outcrop (2), yields a duration of about 5 Myr for this interval. Magnetic susceptibility variations, interpreted as reflecting penecontemporaneous soil and sandstone redox conditions, show a clear 12 m cycle corresponding to a 400 kyr cycle based on Fourier analysis in both core and hole. Similar cyclicity is apparent in spectrophotometric data, largely reflecting hematite variability. Weak, higher frequency cycles are present consistent with 100 kyr variability. There is no interpretable 20 kyr signal. Such cyclicity is not an anticipated direct effect of Milankvitch insolation variations, but must reflect non-linear integration of variability that changes dramatically at the eccentricity-scale, brought about by the sedimentary and climate systems. Our results support a direct 405 kyr-level correlation between the fluvial medial Chinle and lacustrine Newark Basin section (middle Passaic Formation), consistent with new and published (3) paleomagnetic polarity stratigraphy from the Chinle, showing that the Milankovitch eccentricity cycles are recorded in lower accumulation rate fluvial systems. Our results also independently support the continuity of the Newark Basin section and corroborate the Newark-Hartford APTS, not allowing for a multi-million year hiatus in the Passaic Formation, as has been asserted (4). We anticipate further

Fluvial sedimentology of a major uranium-bearing sandstone - A study of the Westwater Canyon member of the Morrison Formation, San Juan Basin, New Mexico

International Nuclear Information System (INIS)

Turner-Peterson, C.E.

1986-01-01

The Westwater Canyon Member of the Morrison Formation, the main ore-bearing sandstone in the San Juan basin, consists of a sequence of vertically stacked braided stream deposits. Three fluvial units within the sequence can be delineated in the basin. Volcanic pebbles are abundant in the middle fluvial unit, in a zone that forms a crude time line. A pronounced thickening of sandstone in the Westwater Canyon Member north of Gallup, once believed to be the apex of a large alluvial fan, is now thought to merely reflect a greater accumulation of sediment in response to downwarping of the basin in that area. Provenance studies suggest that highlands that contributed detritus to Westwater Canyon streams were located several hundred kilometers to the west and southwest of the San Juan basin, and thus fan apices would also have been several hundred kilometers upstream. The fluvial units recognized in the basin may well be coalesced distal fan deposits, but are probably best interpreted as vertically stacked braided steam sequences. Facies changes in fine-grained interbeds of the Westwater Canyon probably have greater significance in terms of localizing ore than any special attribute of the fluvial sandstones themselves. Uranium ore generally occurs in sandstones that are interbedded with greenish-gray lacustrine mudstones. Pore waters that were expelled from these mudstones are thought to have been the source of the pore-filling organic matter (humate) associated with primary uranium ore in nearby sandstones

Reconstructing late quaternary fluvial process controls in the upper aller valley (north Germany) by means of numerical modeling

NARCIS (Netherlands)

Veldkamp, A.; Berg, van den M.; Dijke, van J.J.; Berg van Saparoea, van den R.M.

2002-01-01

The morpho-genetic evolution of the upper Aller valley (Weser basin, North Germany) was reconstructed using geological and geomorphologic data integrated within a numerical process model framework (FLUVER-2). The current relief was shaped by Pre-Elsterian fluvial processes, Elsterian and Saalian ice

Reconstructing Late Quaternary fluvial process controls in the upper Aller Valley (North Germany) by means of numerical modeling

NARCIS (Netherlands)

Veldkamp, A.; Berg, M.W. van den; Dijke, J.J. van; Berg van den; Saparoea, R.M. van

2002-01-01

The morpho-genetic evolution of the upper Aller valley (Weser basin, North Germany) was reconstructed using geological and geomorphologic data integrated within a numerical process model framework (FLUVER-2). The current relief was shaped by Pre-Elsterian fluvial processes, Elsterian and Saalian ice

Étude préliminaire de recrutement fluvial de l'anguille

Directory of Open Access Journals (Sweden)

LEGAULT A.

1994-10-01

La passe piège représente la seule voie de franchissement de l'obstacle. L'évaluation des captures permet d'estimer le taux de recrutement du bassin versant pour l'année 1992. Il s'établit à 561 individus par km2 de bassin versant. L'évaluation annuelle de ce taux pourrait être utilisée afin de suivre la dynamique du stock à l'échelle du bassin versant. Ces évaluations, conduites à l'échelle de l'aire de répartition européenne de l'anguille, pourraient permettre d'établir le recrutement fluvial annuel et ses fluctuations.

A molecular genetic time scale demonstrates Cretaceous origins and multiple diversification rate shifts within the order Galliformes (Aves).

Science.gov (United States)

Stein, R Will; Brown, Joseph W; Mooers, Arne Ø

2015-11-01

The phylogeny of Galliformes (landfowl) has been studied extensively; however, the associated chronologies have been criticized recently due to misplaced or misidentified fossil calibrations. As a consequence, it is unclear whether any crown-group lineages arose in the Cretaceous and survived the Cretaceous-Paleogene (K-Pg; 65.5 Ma) mass extinction. Using Bayesian phylogenetic inference on an alignment spanning 14,539 bp of mitochondrial and nuclear DNA sequence data, four fossil calibrations, and a combination of uncorrelated lognormally distributed relaxed-clock and strict-clock models, we inferred a time-calibrated molecular phylogeny for 225 of the 291 extant Galliform taxa. These analyses suggest that crown Galliformes diversified in the Cretaceous and that three-stem lineages survived the K-Pg mass extinction. Ideally, characterizing the tempo and mode of diversification involves a taxonomically complete phylogenetic hypothesis. We used simple constraint structures to incorporate 66 data-deficient taxa and inferred the first taxon-complete phylogenetic hypothesis for the Galliformes. Diversification analyses conducted on 10,000 timetrees sampled from the posterior distribution of candidate trees show that the evolutionary history of the Galliformes is best explained by a rate-shift model including 1-3 clade-specific increases in diversification rate. We further show that the tempo and mode of diversification in the Galliformes conforms to a three-pulse model, with three-stem lineages arising in the Cretaceous and inter and intrafamilial diversification occurring after the K-Pg mass extinction, in the Paleocene-Eocene (65.5-33.9 Ma) or in association with the Eocene-Oligocene transition (33.9 Ma). Copyright © 2015 Elsevier Inc. All rights reserved.

A new species of Cretalamna sensu stricto (Lamniformes, Otodontidae) from the Late Cretaceous (Santonian-Campanian) of Alabama, USA

Science.gov (United States)

Ehret, Dana J.

2018-01-01

Decades of collecting from exposures of the Upper Cretaceous Tombigbee Sand Member of the Eutaw Formation and Mooreville Chalk in Alabama, USA has produced large numbers of isolated Cretalamna (sensu stricto) teeth. Many of these teeth had formerly been assigned to the extinct Late Cretaceous shark Cretalamna appendiculata (Agassiz, 1843), a taxon that is now considered largely restricted to the Turonian of Europe. Recent studies have shed light on the diversity of Late Cretaceous Cretalamna (s.s.) taxa, and here we recognize a new species from Alabama, Cretalamna bryanti. The teeth of C. bryanti sp. nov. appear aligned with the members of the Cretalamna borealis species group, but can be distinguished from these other species by a combination of the following: anterior teeth with a more pronounced and triangular lingual root protuberance, broader triangular cusp, and a taller root relative to the height of the crown; anteriorly situated lateroposterior teeth have a distally inclined or hooked main cusp and more than one pair of lateral cusplets; and lateroposterior teeth have a strong distally hooked main cusp and a root that is largely symmetrical in basal view. At present, C. bryanti sp. nov. is stratigraphically confined to the Santonian/Campanian Dicarinella asymetrica Sigal, 1952 and Globotruncanita elevata Brotzen, 1934 Planktonic Foraminiferal Zones within the Tombigbee Sand Member of the Eutaw Formation and Mooreville Chalk, and teeth have been collected from only four counties in central and western Alabama. The recognition of C. bryanti sp. nov. in Alabama adds to our knowledge on the diversity and distribution of Late Cretaceous otodontids in the region. PMID:29333348

A new species of Cretalamna sensu stricto (Lamniformes, Otodontidae from the Late Cretaceous (Santonian-Campanian of Alabama, USA

Directory of Open Access Journals (Sweden)

Jun A. Ebersole

2018-01-01

Full Text Available Decades of collecting from exposures of the Upper Cretaceous Tombigbee Sand Member of the Eutaw Formation and Mooreville Chalk in Alabama, USA has produced large numbers of isolated Cretalamna (sensu stricto teeth. Many of these teeth had formerly been assigned to the extinct Late Cretaceous shark Cretalamna appendiculata (Agassiz, 1843, a taxon that is now considered largely restricted to the Turonian of Europe. Recent studies have shed light on the diversity of Late Cretaceous Cretalamna (s.s. taxa, and here we recognize a new species from Alabama, Cretalamna bryanti. The teeth of C. bryanti sp. nov. appear aligned with the members of the Cretalamna borealis species group, but can be distinguished from these other species by a combination of the following: anterior teeth with a more pronounced and triangular lingual root protuberance, broader triangular cusp, and a taller root relative to the height of the crown; anteriorly situated lateroposterior teeth have a distally inclined or hooked main cusp and more than one pair of lateral cusplets; and lateroposterior teeth have a strong distally hooked main cusp and a root that is largely symmetrical in basal view. At present, C. bryanti sp. nov. is stratigraphically confined to the Santonian/Campanian Dicarinella asymetrica Sigal, 1952 and Globotruncanita elevata Brotzen, 1934 Planktonic Foraminiferal Zones within the Tombigbee Sand Member of the Eutaw Formation and Mooreville Chalk, and teeth have been collected from only four counties in central and western Alabama. The recognition of C. bryanti sp. nov. in Alabama adds to our knowledge on the diversity and distribution of Late Cretaceous otodontids in the region.

Calibration of the Late Cretaceous to Paleocene geomagnetic polarity and astrochronological time scales: new results from high-precision U-Pb geochronology

Science.gov (United States)

Ramezani, Jahandar; Clyde, William; Wang, Tiantian; Johnson, Kirk; Bowring, Samuel

2016-04-01

Reversals in the Earth's magnetic polarity are geologically abrupt events of global magnitude that makes them ideal timelines for stratigraphic correlation across a variety of depositional environments, especially where diagnostic marine fossils are absent. Accurate and precise calibration of the Geomagnetic Polarity Timescale (GPTS) is thus essential to the reconstruction of Earth history and to resolving the mode and tempo of biotic and environmental change in deep time. The Late Cretaceous - Paleocene GPTS is of particular interest as it encompasses a critical period of Earth history marked by the Cretaceous greenhouse climate, the peak of dinosaur diversity, the end-Cretaceous mass extinction and its paleoecological aftermaths. Absolute calibration of the GPTS has been traditionally based on sea-floor spreading magnetic anomaly profiles combined with local magnetostratigraphic sequences for which a numerical age model could be established by interpolation between an often limited number of 40Ar/39Ar dates from intercalated volcanic ash deposits. Although the Neogene part of the GPTS has been adequately calibrated using cyclostratigraphy-based, astrochronological schemes, the application of these approaches to pre-Neogene parts of the timescale has been complicated given the uncertainties of the orbital models and the chaotic behavior of the solar system this far back in time. Here we present refined chronostratigraphic frameworks based on high-precision U-Pb geochronology of ash beds from the Western Interior Basin of North America and the Songliao Basin of Northeast China that places tight temporal constraints on the Late Cretaceous to Paleocene GPTS, either directly or by testing their astrochronological underpinnings. Further application of high-precision radioisotope geochronology and calibrated astrochronology promises a complete and robust Cretaceous-Paleogene GPTS, entirely independent of sea-floor magnetic anomaly profiles.

Fossil mega- and microflora from the Březno Beds s.s. (Bohemian Cretaceous Basin, Coniacian)

Czech Academy of Sciences Publication Activity Database

Halamski, A. T.; Kvaček, J.; Svobodová, Marcela

2018-01-01

Roč. 253, June 2018 (2018), s. 123-138 ISSN 0034-6667 Institutional support: RVO:67985831 Keywords : fossil plant * Cretaceous * taxonomy * paleobotany * Coniacian * Czech Republic Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Paleontology Impact factor: 1.817, year: 2016

A Late Cretaceous diversification of Asian oviraptorid dinosaurs: evidence from a new species preserved in an unusual posture

Science.gov (United States)

Lü, Junchang; Chen, Rongjun; Brusatte, Stephen L.; Zhu, Yangxiao; Shen, Caizhi

2016-11-01

Oviraptorosaurs are a bizarre group of bird-like theropod dinosaurs, the derived forms of which have shortened, toothless skulls, and which diverged from close relatives by developing peculiar feeding adaptations. Although once among the most mysterious of dinosaurs, oviraptorosaurs are becoming better understood with the discovery of many new fossils in Asia and North America. The Ganzhou area of southern China is emerging as a hotspot of oviraptorosaur discoveries, as over the past half decade five new monotypic genera have been found in the latest Cretaceous (Maastrichtian) deposits of this region. We here report a sixth diagnostic oviraptorosaur from Ganzhou, Tongtianlong limosus gen. et sp. nov., represented by a remarkably well-preserved specimen in an unusual splayed-limb and raised-head posture. Tongtianlong is a derived oviraptorid oviraptorosaur, differentiated from other species by its unique dome-like skull roof, highly convex premaxilla, and other features of the skull. The large number of oviraptorosaurs from Ganzhou, which often differ in cranial morphologies related to feeding, document an evolutionary radiation of these dinosaurs during the very latest Cretaceous of Asia, which helped establish one of the last diverse dinosaur faunas before the end-Cretaceous extinction.

Paleomagnetism of Jurassic and Cretaceous rocks in central Patagonia: a key to constrain the timing of rotations during the breakup of southwestern Gondwana?

Science.gov (United States)

Geuna, Silvana E.; Somoza, Rubén; Vizán, Haroldo; Figari, Eduardo G.; Rinaldi, Carlos A.

2000-08-01

A paleomagnetic study in Jurassic and Cretaceous rocks from the Cañadón Asfalto basin, central Patagonia, indicates the occurrence of about 25-30° clockwise rotation in Upper Jurassic-lowermost Cretaceous rocks, whereas the overlying mid-Cretaceous rocks do not show evidence of rotation. This constrains the tectonic rotation to be related to a major regional unconformity in Patagonia, which in turn seems to be close in time with the early opening of the South Atlantic Ocean. The sense and probably the timing of this rotation are similar to those of other paleomagnetically detected rotations in different areas of southwestern Gondwana, suggesting a possible relationship between these and major tectonic processes related with fragmentation of the supercontinent. On the other hand, the mid-Cretaceous rocks in the region yield a paleopole located at Lat. 87° South, Long. 159° East, A95=3.8°. This pole position is consistent with coeval high-quality paleopoles of other plates when transferred to South American coordinates, implying it is an accurate determination of the Aptian (circa 116 Ma) geomagnetic field in South America.

The bivalve Anopaea (Inoceramidae) from the Upper Jurassic-lowermost Cretaceous of Mexico

Science.gov (United States)

Zell, Patrick; Crame, J. Alistair; Stinnesbeck, Wolfgang; Beckmann, Seija

2015-07-01

In Mexico, the Upper Jurassic to lowermost Cretaceous La Casita and coeval La Caja and La Pimienta formations are well-known for their abundant and well-preserved marine vertebrates and invertebrates. The latter include conspicuous inoceramid bivalves of the genus Anopaea not formally described previously from Mexico. Anopaea bassei (Lecolle de Cantú, 1967), Anopaea cf. stoliczkai (Holdhaus, 1913), Anopaea cf. callistoensis Crame and Kelly, 1995 and Anopaea sp. are rare constituents in distinctive Tithonian-lower Berriasian levels of the La Caja Formation and one Tithonian horizon of the La Pimienta Formation. Anopaea bassei was previously documented from the Tithonian of central Mexico and Cuba, while most other members of Anopaea described here are only known from southern high latitudes. The Mexican assemblage also includes taxa which closely resemble Anopaea stoliczkai from the Tithonian of India, Indonesia and the Antarctic Peninsula, and Anopaea callistoensis from the late Tithonian to ?early Berriasian of the Antarctic Peninsula. Our new data expand the palaeogeographical distribution of the high latitude Anopaea to the Gulf of Mexico region and substantiate faunal exchange, in the Late Jurassic-earliest Cretaceous, between Mexico and the Antarctic Realm.

Modern mammal origins: evolutionary grades in the Early Cretaceous of North America.

Science.gov (United States)

Jacobs, L L; Winkler, D A; Murry, P A

1989-07-01

Major groups of modern mammals have their origins in the Mesozoic Era, yet the mammalian fossil record is generally poor for that time interval. Fundamental morphological changes that led to modern mammals are often represented by small samples of isolated teeth. Fortunately, functional wear facets on teeth allow prediction of the morphology of occluding teeth that may be unrepresented by fossils. A major step in mammalian evolution occurred in the Early Cretaceous with the evolution of tribosphenic molars, which characterize marsupials and placentals, the two most abundant and diverse extant groups of mammals. A tooth from the Early Cretaceous (110 million years before present) of Texas tests previous predictions (based on lower molars) of the morphology of upper molars in early tribosphenic dentitions. The lingual cusp (protocone) is primitively without shear facets, as expected, but the cheek side of the tooth is derived (advanced) in having distinctive cusps along the margin. The tooth, although distressingly inadequate to define many features of the organism, demonstrates unexpected morphological diversity at a strategic stage of mammalian evolution and falsifies previous claims of the earliest occurrence of true marsupials.

Geochemical evaluation of marginal basins in the south of Bahia state, Brazil

International Nuclear Information System (INIS)

Gaglianone, P.C.; Trindade, L.A.F.; Nascimento, M.M. do

1987-01-01

Geochemical analyses were performed on more than 700 rock samples and 4 oil samples, from Mucuri, Cumuruxatiba and Jequitinhonha basins, offshore Bahia state, Brazil. The methods employed in this study includes the evaluation of organic carbon contents, Rock-Eval pyrolysis, vitrinite reflectance, carbon isotopes, assessment of oils and extrats by liquid and gas chromatography and gas chromatography - spectrometry. Three main source rock systems have been identified in offshore Bahia: the Mucuri shales from Rio da Serra and Aratu Stages lower Neocomian related to a lacustrine fresh water environment; the Jiquia shales (Upper Neocomian) deposited in a lacustrine saline water environment, and the Alagoas Shales related to an evaporitic environment of Aptian age. (author) [pt

Cenozoic to Cretaceous paleomagnetic dataset from Egypt: New data, review and global analysis

Science.gov (United States)

Perrin, Mireille; Saleh, Ahmed

2018-04-01

Different phases of igneous activity took place in Egypt during the Mesozoic and the Cenozoic and oriented samples were collected from three Cenozoic localities (Baharya oasis in the Western Desert, Abu Had in the Eastern Desert and Quseir along the Red Sea coast), and four Cretaceous localities (Toshki & Abu Simbel south of Aswan, and Shalaten & Abu Shihat along the Red Sea coast). Rock magnetic properties of the samples indicate magnetite and titanomagnetite as the main carrier of the remanent magnetization. Following stepwise demagnetization, characteristic remanent directions were identified only for 62% of the samples, a fairly low rate for that type of samples, and 8 new paleomagnetic poles were calculated. All our Cenozoic poles fall clearly off Master Polar Wander Paths proposed for South Africa. Therefore, all paleomagnetic results, previously published for Egypt, were compiled from Cretaceous to Quaternary. The published poles largely overlap, blurring the Egyptian Apparent Polar Wander Path. A new analysis at the site level was then carried out. Only poles having a kappa larger than 50 were selected, and new pole positions were calculated by area and by epoch, when at least 3 sites were available. Even though the selection drastically reduced the number of considered poles, it allows definition of a reliable Cenozoic apparent polar wander trend for Egypt that differs from the South African Master Polar Wander Path by about 10-15 °. If the Cretaceous igneous poles are in good agreement with the rest of the African data, the sedimentary poles plot close to the Cenozoic portion of the South African Master Polar Wander Path, a discrepancy that could be related either to inclination flattening and/or error on age and/or remagnetization in the Cenozoic.

Astronomically Forced Hydrology of the Late Cretaceous Sub-tropical Potosí Basin, Bolivia

Science.gov (United States)

Tasistro-Hart, A.; Maloof, A. C.; Schoene, B.; Eddy, M. P.

2017-12-01

Orbital forcings paced the ice ages of the Pleistocene, demonstrating that periodic variations in the latitudinal distribution of insolation amplified by ice-albedo feedbacks can guide global climate. How these forcings operate in the hot-houses that span most of the planet's history, however, is unknown. The lacustrine El Molino formation of the late Cretaceous-early Paleogene Potosí Basin in present-day Bolivia contains carbonate-mud parasequences that record fluctuating hydrological conditions from 73 to 63 Ma. This study presents the first cyclostratigraphic analysis using high-resolution drone-derived imagery and 3D elevation models, combined with conventional stratigraphic measurements and magnetic susceptibility data. The drone-derived data are integrated over the entire outcrop at two field areas using a novel application of stratigraphic potential field modeling that increases signal-to-noise ratios prior to spectral analysis. We demonstrate that these parasequences exhibit significant periodicities consistent with eccentricity (400 and 100 kyr), obliquity (50 kyr, 40 kyr, and 29 kyr), precession (17-23 kyr), and semi-precession (9-11 kyr). New U-Pb ID-TIMS zircon ages from intercalacted ash beds corroborate the interpreted sedimentation rates at two sites, indicating that the Potosí Basin contains evidence for hot-house astronomical forcing of sub-tropical lacustrine hydrology. Global climate simulations of late Cretaceous orbital end-member configurations demonstrate precessional-eccentricity and obliquity driven modulation of basin hydrology. In model simulations, the forcings drive long-term shifts in the location of the intertropical convergence zone, changing precipitation along the northern extent of the Potosí Basin's catchment area. This study is the first to demonstrate orbital forcing of a lacustrine system during the Maastrichtian and could ultimately contribute to a precise age for the Cretaceous-Paleogene boundary.

Mantle dynamics and Cretaceous magmatism in east-central China: Insight from teleseismic tomograms

Science.gov (United States)

Jiang, Guoming; Zhang, Guibin; Zhao, Dapeng; Lü, Qingtian; Li, Hongyi; Li, Xinfu

2015-11-01

Both the rich mineralization in the Lower Yangtze Block (LYB) and the post-collisional mafic rocks in the Dabie Orogen (DBO) are closely related to the Cretaceous magmatism in east-central China. Various geodynamic models have been proposed for explaining the mechanism of the Cretaceous magmatism, but these models are controversial and even contradictory with each other, especially on the mechanism of adakites. A unified geodynamic model is required for explaining the magmatism in east-central China, in particular, the spatial and temporal correlations of magmatic activity in the DBO and that in the LYB. For this purpose, we apply teleseismic tomography to study P-wave velocity structure down to 800 km depth beneath east-central China. A modified multiple-channel cross-correlation method is used to collect 28,805 high-quality P-wave arrival-time data from seismograms of distant earthquakes recorded by permanent seismic stations and our temporary stations in the study region. To remove the influence of crustal heterogeneity on the mantle tomography, we used the CRUST1.0 model to correct the teleseismic relative residuals. Our tomography revealed distinct high-velocity (high-V) anomalies beneath the DBO and two flanks of the LYB, and low-velocity (low-V) anomalies above the high-V zones. Combining our tomographic images with previous geological, geochemical and geophysical results, we infer that these high-V and low-V anomalies reflect the detached lithosphere and upwelling asthenospheric materials, respectively, which are associated with the Late Mesozoic dynamic process and the Cretaceous magmatism. We propose a double-slab subduction model that a ridge subduction yielded the adakitic rocks in the LYB during 150-135 Ma and the subsequent Pacific Plate subduction played a crucial role in not only the formation of igneous rocks in the LYB but also remelting of the subducted South China Block beneath the DBO during 135-101 Ma.

Phytolith analysis in fluvial quaternary sediment (San Salvador and Palmar formation) Uruguay river and Argentina eastern

International Nuclear Information System (INIS)

Patterer, N.; Passeggi, E.; Zucol, A.; Brea, M.; Krohling, D.

2012-01-01

This work is about two microfossils fluvial units deposited by the Uruguay river during the Quaternary. These are San Salvador and Palmar formation (Plio-Pleistocene - Upper Pleistocene).The Palmar formation is a band of 4-15 km along the right bank of the Uruguay river outcropping from the eastern provinces of Corrientes and Entre Rios, to Concepcion del Uruguay

Early and late cretaceous magmatism from Sao Sebastiao island (SE-Brazil): geochemistry and petrology

International Nuclear Information System (INIS)

Bellieni, G.; Cavazzini, G.; Montes-Lauar, C.R.; Melfi, A.J.; Pacca, I.G.; De Min, A.; Piccirillo, E.M.

1990-01-01

The Sao Sebastiao island (236 km 2 ), located along the coast of the Sao Paulo State (Southern Brazil), is characterized by precambrian granitic affected by the Brasiliano tectonic-metamorphic cycle. This crystalline basement is intruded by Early Cretaceous (EC) sub alkaline basic and acid dykes, as well as by Late Cretaceous (LC) alkaline stocks (syenites) and dykes (basanite to phonolite). Geochemical, Sr-isotopic and mineral chemistry data point out that: EC-dykes reveal a basic-acid bimodal character, similar to that of the 'coeval' Parana basin flood volcanics; the acid dykes correspond, in composition, to the acid volcanics of the northern Parana basin: the EC-dykes can represent the eastern extension of the inland Santos-Rio de Janeiro dyke swarm, and LC alkaline stocks and dykes constitute distinct groups, characterized by different Sr-isotope initial ratios (syenites: av. 0.7052 and basanites + tephrites = av. 0.7045), which indicate that they are related to different time-integrated mantle source materials. (author)

Molecular evidence of keratin and melanosomes in feathers of the Early Cretaceous bird Eoconfuciusornis.

Science.gov (United States)

Pan, Yanhong; Zheng, Wenxia; Moyer, Alison E; O'Connor, Jingmai K; Wang, Min; Zheng, Xiaoting; Wang, Xiaoli; Schroeter, Elena R; Zhou, Zhonghe; Schweitzer, Mary H

2016-12-06

Microbodies associated with feathers of both nonavian dinosaurs and early birds were first identified as bacteria but have been reinterpreted as melanosomes. Whereas melanosomes in modern feathers are always surrounded by and embedded in keratin, melanosomes embedded in keratin in fossils has not been demonstrated. Here we provide multiple independent molecular analyses of both microbodies and the associated matrix recovered from feathers of a new specimen of the basal bird Eoconfuciusornis from the Early Cretaceous Jehol Biota of China. Our work represents the oldest ultrastructural and immunological recognition of avian beta-keratin from an Early Cretaceous (∼130-Ma) bird. We apply immunogold to identify protein epitopes at high resolution, by localizing antibody-antigen complexes to specific fossil ultrastructures. Retention of original keratinous proteins in the matrix surrounding electron-opaque microbodies supports their assignment as melanosomes and adds to the criteria employable to distinguish melanosomes from microbial bodies. Our work sheds new light on molecular preservation within normally labile tissues preserved in fossils.

Lower Cretaceous Luscar group (revised) of the northern and north-central foothills of Alberta

Energy Technology Data Exchange (ETDEWEB)

Langenberg, C W; McMechan, M E

1985-03-01

Lower Cretaceous coal-bearing strata exposed in the northern and north-central foothills of Alberta form part of a predominantly nonmarine succession that extends from Montana to northeastern British Columbia. The Luscar Group (revised) forms the sequence of coal bearing Lower Cretaceous strata that disconformably overlies marine and nonmarine strata of the Nikanassin Formation or Minnes Group and disconformably underlies marine shales of the Blackstone or Shaftesbury formations. It includes a thin, basal conglomerate, a predominantly nonmarine sandstone and shale unit that locally contains coal; a marine shale and sandstone unit, and an upper nonmarine sandstone and shale unit that contains thick commercial coal seams. These units form the Cadomin, Gladstone, Moosebar and Gates formations, respectively. The Luscar Group is exposed from Kakwa River to Clearwater River in the Foothills of Alberta. It represents a slight modification, by the inclusion of the thin basal conglomerate, from the previous usage of the term Luscar in the northern Foothills of Alberta. 25 references.

Seawater strontium isotopes, acid rain, and the Cretaceous-Tertiary boundary

Science.gov (United States)

Macdougall, J. D.

1988-01-01

A large bolide impact at the end of the Cretaceous would have produced significant amounts of nitrogen oxides by shock heating of the atmosphere. The resulting acid precipitation would have increased continental weathering greatly and could be an explanation for the observed high ratio of strontium-87 to strontium-86 in seawater at about this time, due to the dissolution of large amounts of strontium from the continental crust. Spikes to high values in the seawater strontium isotope record at other times may reflect similar episodes.

Relevance of the Paraná River hydrology on the fluvial water quality of the Delta Biosphere Reserve.

Science.gov (United States)

Puig, Alba; Olguín Salinas, Héctor F; Borús, Juan A

2016-06-01

The increasing frequency of extreme events in large rivers may affect not only their flow, but also their water quality. In the present study, spatial and temporal changes in fluvial physico-chemical variables were analyzed in a mega-river delta during two extreme hydrological years (La Niña-El Niño) and related to potential explanatory factors. Basic water variables were evaluated in situ at 13 points (distant 2-35 km from each other) in watercourses of the Delta Biosphere Reserve (890 km(2)) in the Lower Paraná River (Argentina) in nine surveys (October 2008-July 2010) without meteorological tides. Samples for laboratory analyses were collected from each main river. Multivariate tests by permutations were applied. The period studied was influenced by a drought, within a long period dominated by low flows combined with dry weather and wildfires, and a large (10 years of recurrence) and prolonged (7 months) flood. The hydrological phase, followed by the season and the hydrological year (according to the ENSO event) were the principal explanatory factors of the main water quality changes, whereas the drainage sub-basin and the fluvial environment (river or stream) were secondary explanatory factors. During the drought period, conductivity, turbidity, and associated variables (e.g., major ions, silicon, and iron concentrations) were maximal, whereas real color was minimal. In the overbanking flood phase, pH and dissolved oxygen concentration were minimal, whereas real color was maximal. Dissolved oxygen saturation was also low in the receding flood phase and total major ion load doubled after the arrival of the overbanking stage. The water quality of these watercourses may be affected by the combination of several influences, such as the Paraná River flow, the pulses with sediments and solutes from the Bermejo River, the export of the Delta floodplain properties mainly by the flood, the season, and the saline tributaries to the Lower Paraná River. The high

Sedimentary history and economic geology of San Juan Basin, New Mexico and Colorado

International Nuclear Information System (INIS)

Peterson, J.A.; LeLeit, A.J.; Spencer, C.W.; Ullrich, R.A.

1981-01-01

The San Juan Basin contains up to 15,000 ft of sedimentary rocks ranging in age from Cambrian to Recent. The earliest development of the area as a sedimentary basin or trough apparently took place in Pennsylvanian time, and the basin was maintained, with changing rates of subsidence and filling, through the remainder of geologic time. During the Early Paleozoic, sedimentation was dominated by marine transgressions across the northwestern flank of the regional Transcontinental Arch. The Late Paleozoic history was strongly influenced by tectonism related to development of the Ancestral Rocky Mountains Uplifts and associated downwarping. The Early Mesozoic is characterized by fluvial and eolian environments, interrupted periodically by thin marine transgressive deposits of nearshore redbeds. The final Mesozoic event was the widespread Late Cretaceous marine transgression which deposited a thick cyclic sequence of marine gray shale and sandstone, with interbedded coal. Late Tertiary regional uplift and resulting volcanism were accompanied by a regional dissection of the area by stream systems that evolved into the present drainage pattern of superposed streams. The sedimentary history is directly related to the occurrence of economic deposits in the basin. Major reserves of petroleum and gas are in Cretaceous and Pennsylvanian rocks, coal in Cretaceous, and uranium in Jurassic and Cretaceous. Abstract only

Implications of sedimentological studies for environmental pollution assessment and management: Examples from fluvial systems in North Queensland and Western Australia

Science.gov (United States)

Eyre, Bradley; McConchie, David

1993-05-01

Sedimentology is of increasing importance in environmental research, particularly environmental pollution studies, where past trends in environmental processes need to be combined with data on present conditions to predict likely future changes—the past and present as a key to the future. Two examples are used to illustrate the role of sedimentology in assessing the influence of major processes on the transport, accumulation, deposition and modification of contaminants in fluvial/estuarine systems and in developing environmental management plans. Example 1 shows that when assessing nutrient behaviour in fluvial/estuarine depositional settings, it is important to examine the partitioning of phosphorus between grain size fractions to evaluate the sedimentological processes which control the dispersion and trapping of these contaminants. Example 2 shows that in studies of anthropogenic metal inputs to modern depositional settings, lateral and stratigraphic trends in sediment texture and mineralogy should be examined, in addition to trends in metal loads and evaluation of the prevailing physical, chemical and biological processes that may influence metal mobility and dispersion. Clearly, basic sedimentological data should form part of any assessment of potentially contaminated sites and part of investigations into the dispersion and trapping of contaminants in fluvial systems. These data are also required for rational environmental management to ensure that planning decisions are compatible with natural environmental constraints.

DOS SISTEMAS AMBIENTAIS AO SISTEMA FLUVIAL – UMA REVISÃO DE CONCEITOS

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Jonas Otaviano Praça de Souza

2013-10-01

Full Text Available Tentando consolidar as noções de totalidade, a geografia física passa a utilizar a noção de sistemas dinâmicos, não lineares e de comportamento caótico. Deste modo, a abordagem sistêmica/complexa apresenta-se como meio de compreensão do mundo natural, assim possibilitando a previsão de mudanças, avaliação dos sistemas ambientais, distúrbios e limiares do sistema. Nota-se, assim, a importância dos estudos processuais para o gerenciamento de recursos hídricos, tornando imprescindíveis estudos sistêmicos que analisem os diversos elementos importantes para a análise dos recursos hídricos, dentre eles as questões processuais. Deste modo, a necessidade de se trabalhar o gerenciamento integrado de recursos hídricos, enquadrado na perspectiva sistêmica, solidificou a bacia hidrográfica e/ou bacia de drenagem como recorte espacial sistêmico. Delimitada a área pode-se compreender a bacia hidrográfica como um Sistema Fluvial, conceituado por Schumm (1977, que é analisado a partir da zona fonte de sedimentos, da rede de transporte e dos sítios de deposição. Esses elementos não são espacialmente excludentes, interagindo entre si, além de apresentar escalas diferenciadas. Para o estudo do sistema fluvial é necessário levar em consideração quatro conceitos: uniformidade dos processos, limiares de mudança, evolução da paisagem e respostas complexas.

The formation of the Late Cretaceous Xishan Sn-W deposit, South China: Geochronological and geochemical perspectives

Science.gov (United States)

Zhang, Lipeng; Zhang, Rongqing; Hu, Yongbin; Liang, Jinlong; Ouyang, Zhixia; He, Junjie; Chen, Yuxiao; Guo, Jia; Sun, Weidong

2017-10-01

The Xishan Sn-W deposit is spatially related to K-feldspar granites in the Yangchun basin, western Guangdong Province, South China. LA-ICP-MS zircon U-Pb dating for the Xishan pluton defines an emplacement age of 79 Ma (78.1 ± 0.9 Ma; 79.0 ± 1.2 Ma; 79.3 ± 0.8 Ma), consistent with the mineralization age of the Xishan Sn-W deposit constrained by molybdenite Re-Os isochron age (79.4 ± 4.5 Ma) and LA-ICP-MS cassiterite U-Pb ages (78.1 ± 0.9 Ma and 79.0 ± 1.2 Ma) for the cassiterite-quartz vein. These indicate a close genetic relationship between the granite and Sn-W mineralization. The Xishan K-feldspar granites have geochemical characteristics of A-type granites, e.g., high total alkali (Na2O + K2O = 7.88-10.07 wt.%), high Ga/Al ratios (10000*Ga/Al > 2.6) and high Zr + Nb + Ce + Y concentrations (> 350 ppm). They are further classified as A2-type granites. The whole-rock isotopic compositions of K-feldspar granites (initial 87Sr/86Sr = 0.705256-0.706181; εNd(t) = - 5.4 to - 4.8) and zircon εHf(t) values (- 7.8 to 2.0) suggest a mixed magma source. The low zircon Ce4 +/Ce3 + ratios (12-88) of K-feldspar granites suggest low oxygen fugacities, which is key for enrichment of tin in primary magmas. The K-feldspar granites have experienced strong differentiation as indicated by their high Rb/Sr and K/Rb ratios, and low Nb/Ta and Zr/Hf ratios, which play an important role in ore-forming element transportation and concentration. A-type granite characteristics of the Xishan pluton show that it formed in an extensional environment. The high F and low Cl characteristics of the K-feldspar granite are most probably attributed to slab rollback. In the Late Cretaceous, the Xishan Sn-W deposit was located near the interaction of the circum-Pacific and the Tethys tectonic realms. Late Cretaceous Sn-W deposits, including the Xishan deposit, form an EW-trending belt from Guangdong to Yunnan Province in South China. This belt is in accordance with the direction of the Neo

Volcanic or Fluvial Channels on Ascraeus Mons: Focus on the Source Area of Sinuous Channels on the Southeast Rift Apron

Science.gov (United States)

Signorella, J. D.; de Wet, A. P.; Bleacher, J. E.; Collins, A.; Schierl, Z. P.; Schwans, B.

2012-03-01

This study focuses on the source area of sinuous channels on the southeast rift apron on Ascraeus Mons, Mars and attempts to understand whether the channels were formed through volcanic or fluvial processes.

Evidence for subduction-related magmatism during the Cretaceous and Cenozoic in Myanmar

Science.gov (United States)

Sevastjanova, Inga; Sagi, David Adam; Webb, Peter; Masterton, Sheona; Hill, Catherine; Davies, Clare

2017-04-01

Myanmar's complex geological history, numerous controversies around its tectonic evolution and the presence of prospective hydrocarbon basins make it a key area of interest for geologists. Understanding whether a passive or an active margin existed in the region during the Cenozoic is particularly important for the production of accurate basin models; active Cenozoic subduction would imply that hydrocarbon basins in the forearc experienced extension due to slab rollback. The geology of Myanmar was influenced by the regional tectonics associated with the Cretaceous and Cenozoic closure of the Neotethys Ocean. During this time, India travelled rapidly from Gondwana to Asia at speeds up to 20 cm/yr. To accommodate the north-eastward motion of India, the Neotethys Ocean was consumed at the subduction zone along the southern margin of Eurasia. Based on our Global Plate Model, this subduction zone can reasonably be expected to extend for the entire width of the Neotethys Ocean as far as Myanmar and Southeast Asia at their eastern extent. Moreover, a) Cretaceous volcanism onshore Myanmar, b) the middle Cenozoic arc-related extension in the Present Day eastern Andaman Sea and c) the late Cenozoic uplift of the Indo-Burman Ranges are all contemporaneous with the subduction ages predicted by the global plate motions. However, because of the geological complexity of the area, additional evidence would augment interpretations that are based on structural data. In an attempt to reduce the uncertainty in the existing interpretations, we have compiled published zircon geochronological data from detrital and igneous rocks in the region. We have used published zircon U-Pb ages and, where available, published Hf isotope data and CL images (core/rim) in order to distinguish 'juvenile' mantle-derived zircons from those of reworked crustal origin. The compilation shows that Upper Cretaceous and Cenozoic zircons, which are interpreted to have a volcanic provenance, are common across the

Bolide impact and long- and short term environmental change across the cretaceous-paleogene boundary

NARCIS (Netherlands)

Vellekoop, J.

2015-01-01

The Cretaceous-Paleogene (K-Pg) boundary mass extinction, ~66 million years ago, was one of the most devastating events in the history of life, marking the end of the dinosaur era. This mass extinction event is now widely acknowledged to be related to the global environmental consequences of the

Tectonics and Volcanism During the Cretaceous Normal Superchron Seafloor in the Western Pacific Ocean

Science.gov (United States)

O'Brien, E.

2017-12-01

We have conducted an integration study on the origin and evolution of the tectonics and volcanism of seafloor in the Western Pacific Ocean that took place during the Cretaceous Normal Superchron (CNS) where sparse data has so far precluded detailed investigation. We have compiled the latest satellite-based gravity, gravity gradient, and magnetic grids (EMAG2 v.3) for this region. These crustal-scale high-resolution grids suggest that the CNS seafloor contains fossilized lithospheric morphology possibly attributed to the interaction between Cretaceous supervolcanism activity and Mid-Cretaceous Pacific mid ocean ridge systems that have continuously expanded the Pacific Plate. We recognize previously identified fossilized microplates west of the Magellan Rise, short-lived abandoned propagating rifts and fracture zones, all of which show significant rotation of seafloor fabric. In addition to these large scale observations, we have also compiled marine geological information from previously drilled cores and new data from a Kongsberg Topas PS18 Parametric Sub-Bottom Profiler collected on a transect from Honolulu, Hawaii to Apra, Guam acquired during research cruise SKQ2014S2. In particular, the narrow beam and high bandwidth signal of the Topas PS18 sub-bottom profiler provides sonar data of the seabed with a resolution and depth penetration that is unprecedented compared with previously available surveys in the region. A preliminary assessment of this high resolution Topas data allows us to better characterize sub-seafloor sediment properties and identify features, including the Upper Transparent Layer with identifiable pelagic clay and porcelanite-chert reflectors as well as tectonic features such as the westernmost tip of the Waghenaer Fracture Zone.

The Rise of Flowering Plants and Land Surface Physics: The Cretaceous and Eocene Were Different

Science.gov (United States)

Upchurch, G. R.; Feild, T.

2010-12-01

The Cretaceous and Eocene have served as the poster children of past greenhouse climates. One difference between the two time periods is that angiosperms (flowering plants) underwent a major diversification and rise to dominance during the mid-Cretaceous to Paleocene. Flowering plants differ from all other living and fossil plants in having significantly higher rates of transpiration and photosynthesis, which in modern leaves correlate with the density of venation (Dv), a feature that can be measured directly from fossils. This increase in Dv, coupled with an increase in the abundance of angiosperms, is thought to have had major impact on the climate system. This is, in part, because transpiration plays an important role in determining the ratio of sensible to latent heat flux from the land surface and in determining precipitation rate in regions such as the equatorial rainforest. Analysis of Dv in fossil leaves indicates two phases of increase in transpiration rate for angiosperms during the Cretaceous-Paleocene. The oldest known angiosperms (Aptian-early Albian) have a low Dv characteristic of extant and fossil ferns and gymnosperms. At this time angiosperms are low-stature plants of minor importance in terms of relative abundance and diversity (ferns, and maximum Dv reaches levels characteristic of many trees from the temperate zone. This first phase coincides with the first local dominance of angiosperms, the first occurrence of moderate to large angiosperm trees (up to 1 m in diameter) , and the first common occurrence of angiosperms in the Arctic. The second phase of Dv increase occurs during the Maastrichtian to Paleocene, where average Dv reaches levels characteristic of modern tropical forests and maximum Dv reaches the level found in highly productive modern vegetation. This second phase coincides with the rise to dominance of angiosperms in regional vegetation, a corresponding decline of conifers and ferns, and the modernization of hydraulic architecture

TRANSITION FROM CARBONATE PLATFORM TO PELAGIC DEPOSITION (MID JURASSIC- LATE CRETACEOUS, VOURINOS MASSIF, NORTHERN GREECE

Directory of Open Access Journals (Sweden)

NICOLAOS CARRAS

2004-03-01

Full Text Available A Jurassic- Cretaceous carbonate succession crops out along the Zyghosti Rema, Kozani (Northern Greece. The substratum consists of the ophiolitic succession of the Vourinos Massif (Pelagonian Domain: serpentinites tectonically overlain by basalts, with thin lenses of radiolarian cherts of middle Bathonian age. The contact with the overlying Jurassic limestones is tectonic. Eight informal units have been distinguished within the Mesozoic limestones, from the base upwards. (A bioclastic, intraclastic and oolitic packstone (Callovian- Oxfordian. (B bioclastic packstone and coral boundstone (Oxfordian . (C bioclastic and oncoidal wackestone with Clypeina jurassica (Oxfordian- Upper Kimmeridgian. (D (Upper Kimmeridgian- Portlandian: oncoidal packstone and rudstone (facies D1; intraclastic and bioclastic grainstone and packstone (facies D2; neptunian dykes with intraclastic and bioclastic wackestone and packstone filling (facies D3; neptunian dykes with Fe-Mn rich laterite filling and with pink silty filling of early Late Cretaceous age. An unconformity surface, due to emersion and erosion of the platform during the latest Jurassic- Early Cretaceous, is overlain by (E intraclastic, bioclastic packstone and grainstone (Cenomanian. (F massive body of debrites with coral, echinoderm, algae and rudist large clasts (facies F1 (Cenomanian; turbiditic beds of bioclastic, intraclastic and lithoclastic rudstone and grainstone (facies F2. (G thin bedded bioclastic mudstone and wackestone with planktonic foraminifers and radiolarians, alternating with turbiditic beds of bioclastic, intraclastic packstone and rudstone and with conglomeratic levels and slumped beds of the previous turbidites (upper Santonian- lower Campanian. (H: bioclastic packstone with planktonic foraminifers (facies H1 (lower Campanian - ?Maastrichtian; amalgamated turbiditic beds of bioclastic wackestone and packstone with planktonic foraminifers (facies H2; turbiditic beds of bioclastic

Severity of ocean acidification following the end-Cretaceous asteroid impact.

Science.gov (United States)

Tyrrell, Toby; Merico, Agostino; Armstrong McKay, David Ian

2015-05-26

Most paleo-episodes of ocean acidification (OA) were either too slow or too small to be instructive in predicting near-future impacts. The end-Cretaceous event (66 Mya) is intriguing in this regard, both because of its rapid onset and also because many pelagic calcifying species (including 100% of ammonites and more than 90% of calcareous nannoplankton and foraminifera) went extinct at this time. Here we evaluate whether extinction-level OA could feasibly have been produced by the asteroid impact. Carbon cycle box models were used to estimate OA consequences of (i) vaporization of up to 60 × 10(15) mol of sulfur from gypsum rocks at the point of impact; (ii) generation of up to 5 × 10(15) mol of NOx by the impact pressure wave and other sources; (iii) release of up to 6,500 Pg C as CO2 from vaporization of carbonate rocks, wildfires, and soil carbon decay; and (iv) ocean overturn bringing high-CO2 water to the surface. We find that the acidification produced by most processes is too weak to explain calcifier extinctions. Sulfuric acid additions could have made the surface ocean extremely undersaturated (Ωcalcite ocean very rapidly (over a few days) and if the quantity added was at the top end of literature estimates. We therefore conclude that severe ocean acidification might have been, but most likely was not, responsible for the great extinctions of planktonic calcifiers and ammonites at the end of the Cretaceous.

Vertebrate assemblages from the early Late Cretaceous of southeastern Morocco: An overview

Science.gov (United States)

Cavin, L.; Tong, H.; Boudad, L.; Meister, C.; Piuz, A.; Tabouelle, J.; Aarab, M.; Amiot, R.; Buffetaut, E.; Dyke, G.; Hua, S.; Le Loeuff, J.

2010-07-01

Fossils of vertebrates have been found in great abundance in the continental and marine early Late Cretaceous sediments of Southeastern Morocco for more than 50 years. About 80 vertebrate taxa have so far been recorded from this region, many of which were recognised and diagnosed for the first time based on specimens recovered from these sediments. In this paper, we use published data together with new field data to present an updated overview of Moroccan early Late Cretaceous vertebrate assemblages. The Cretaceous series we have studied encompasses three Formations, the Ifezouane and Aoufous Formations, which are continental and deltaic in origin and are often grouped under the name "Kem Kem beds", and the Akrabou Formation which is marine in origin. New field observations allow us to place four recognised vertebrate clusters, corresponding to one compound assemblage and three assemblages, within a general temporal framework. In particular, two ammonite bioevents characterise the lower part of the Upper Cenomanian ( Calycoceras guerangeri Zone) at the base of the Akrabou Formation and the upper part of the Lower Turonian ( Mammites nodosoides Zone), that may extend into the Middle Turonian within the Akrabou Formation, and allow for more accurate dating of the marine sequence in the study area. We are not yet able to distinguish a specific assemblage that characterises the Ifezouane Formation when compared to the similar Aoufous Formation, and as a result we regard the oldest of the four vertebrate "assemblages" in this region to be the compound assemblage of the "Kem Kem beds". This well-known vertebrate assemblage comprises a mixture of terrestrial (and aerial), freshwater and brackish vertebrates. The archosaur component of this fauna appears to show an intriguingly high proportion of large-bodied carnivorous taxa, which may indicate a peculiar trophic chain, although collecting biases alter this palaeontological signal. A small and restricted assemblage, the

Neutron activation analysis in geochemical characterization of Jurassic-Cretaceous sedimentary rocks from the Nordvik Peninsula

Czech Academy of Sciences Publication Activity Database

Mizera, Jiří; Řanda, Zdeněk; Košťák, M.

2010-01-01

Roč. 284, č. 1 (2010), s. 211-219 ISSN 0236-5731 Institutional research plan: CEZ:AV0Z10480505 Keywords : Jurassic-Cretaceous boundary * Nordvik Peninsula * Iridium anomaly Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 0.777, year: 2010

A hydro-geochemical study of Nahr-Ibrahim catchment area: Fluvial metal transport

International Nuclear Information System (INIS)

Korfali, Samira

2004-01-01

Author.Metals enter water bodies geological weathering, soil erosion, industrial and domestic waste discharges, as well as atmospheric deposition. The metal content in sediments is a reflection of the nature of their background whether of geologic and/or anthropogenic origin. The depositional process of metals in sediment are controlled by river discharge, turbulence of river, morphology and river geometry, as well as the geochemical phases of sediment and soils. Thus a study of metal content in river and /or metal transport with a water body should include a hydrological study of the river, types of minerals in sediment and soil, sediment and soil textures, and metal speciation in the different geochemical phases of sediment, bank and soils. A contaminated flood plain is a temporary storage system for pollutants and an understanding of soil-sediment-interactions is important prerequisite for modeling fluvial pollutant transport. The determination of metal speciation in sediment and soil chemical fraction can provide information on the way in which these metals are bound to sediment and soil, their mobilization potential, bioavailability and possible mechanism of fluvial pollutant transport. Sequential extraction techniques yielding operationally defined chemical pools have been used by many workers to examine the partitioning of metals among the various geochemical phases of sediment or soil. The sequential extraction method specifies metals in sediment fractions as: exchangeable, specifically sorbed, easily reducible, moderately reducible, organic, residual. Previously, I have conducted a study on speciation of metals (Fe, Mn, Zn, Cu, Pb and Cd) in the dry season bed-load sediments only at five sites 13 km stretch upstream from the mouth of Nahr Ibrahim. The reported data revealed that the specifically sorbed sediment fraction was the prime fraction for deposition of Mn, Z, CU, Pb and Cd metals in sediments. X-ray diffraction analysis of bed sediments showed

Early Cretaceous ribbed aptychi - a proposal for a new systematic classification

Czech Academy of Sciences Publication Activity Database

Měchová, L.; Vašíček, Zdeněk; Houša, Václav

2010-01-01

Roč. 85, č. 2 (2010), s. 219-274 ISSN 1214-1119 Institutional research plan: CEZ:AV0Z30860518; CEZ:AV0Z30130516 Keywords : Late Jurassic * J/K boundary * Early Cretaceous * aptychi Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.202, year: 2010 http://apps.isiknowledge.com/full_record.do?product=WOS&search_mode=GeneralSearch&qid=6&SID=Z1P9aiFnKb7Ka2PiKmk&page=1&doc=2

Temporal correlation of fluvial and alluvial sequences in the Makran Range, SE-Iran

Science.gov (United States)

Kober, F.; Zeilinger, G.; Ivy-Ochs, S.; Dolati, A.; Smit, J.; Burg, J.-P.; Bahroudi, A.; Kubik, P. W.; Baur, H.; Wieler, R.; Haghipour, N.

2009-04-01

The Makran region of southeastern Iran is an active accretionary wedge with a partially subaerial component. New investigations have revealed a rather complex geodynamic evolution of the Makran active accretionary wedge that is not yet fully understood in its entity. Ongoing convergence between the Arabian and Eurasian plates and tectonic activity since the late Mesozoic has extended all trough the Quaternary. We focus here on fluvial and alluvial sequences in tectonically separated basins that have been deposited probably in the Pliocene/Quaternary, based on stratigraphic classification in official geological maps, in order to understand the climatic and tectonic forces occurring during the ongoing accretionary wegde formation. Specifically, we investigate the influence of Quaternary climate variations (Pleistocene cold period, monsoonal variations) on erosional and depositional processes in the (semi)arid Makran as well as local and regional tectonic forces in the Coastal and Central Makran Range region. Necessary for such an analysis is a temporal calibration of alluvial and fluvial terrace sequences that will allow an inter-basin correlation. We utilize the exposure age dating method using terrestrial cosmogenic nuclides (TCN) due to the lack of otherwise datatable material in the arid Makran region. Limited radiocarbon data are only available for marine terraces (wave-cut platforms). Our preliminary 21Ne and 10Be TCN-ages of amalgamated clast samples from (un)deformed terrace and alluvial sequences range from ~250 ky to present day (modern wash). These ages agree in relative terms with sequences previously assigned by other investigations through correlation of Quaternary sequences from Central and Western Iran regions. However, our minimum ages suggest that all age sequences are of middle to late Pleistocene age, compared to Pliocene age estimates previously assigned for the oldest units. Although often suggested, a genetical relation and connection of those

Regional Contamination of Moravia (South-Eastern Czech Republic): Temporal Shift of Pb and Zn Loading in Fluvial Sediments

Czech Academy of Sciences Publication Activity Database

Matys Grygar, Tomáš; Sedláček, J.; Bábek, O.; Nováková, Tereza; Strnad, L.; Mihaljevič, M.

2012-01-01

Roč. 223, č. 2 (2012), s. 739-753 ISSN 0049-6979 R&D Projects: GA AV ČR IAAX00130801 Institutional research plan: CEZ:AV0Z40320502 Keywords : fluvial sediments * Pb * Zn * regional contamination Subject RIV: DD - Geochemistry Impact factor: 1.748, year: 2012

An inventory of published and unpublished fluvial-sediment data for California, 1956-70

Science.gov (United States)

Porterfield, George

1972-01-01

This inventory was prepared to provide a convenient reference to published and unpublished fluvial-sediment data for water years 1956-70, and updates substantially previous inventories. Sediment stations are listed in downstream order, and an alphabetical list of stations is also included. Figure 1 shows the approximate location of sediment stations in California. Most of the fluvial-sediment data in California were collected by the U.S. Geological Survey, under cooperative agreements with the following Federal, State, and local agencies: California Department of Water Resources, California Department of Navigation and Ocean Development, California Department of Fish and Game, Bolinas Harbor District, Monterey County Flood Control and Water Conservation District, Orange County Flood Control District, Riverside County Flood Control and Water Conservation District, San Diego County Department of Sanitation and Flood Control, San Luis Obispo County, San Mateo County, Santa Clara County Flood Control and Water District, Santa Cruz County Flood Control and Water Conservation District, Santa Cruz, city of, University of California, Ventura County Flood Control District, Forest Service, U.S. Department of Agriculture, Soil Conservation Service, U.S. Department of Agriculture, Corps of Engineers, U.S. Army, Bureau of Reclamation, U.S. Department of the Interior, National Park Service, U.S. Department of the Interior. This report was prepared by the Geological Survey under the general supervision of R. Stanley Lord, district chief in charge of water-resources investigations in California.

Floodplain forest succession reveals fluvial processes: A hydrogeomorphic model for temperate riparian woodlands.

Science.gov (United States)

Egger, Gregory; Politti, Emilio; Lautsch, Erwin; Benjankar, Rohan; Gill, Karen M; Rood, Stewart B

2015-09-15

River valley floodplains are physically-dynamic environments where fluvial processes determine habitat gradients for riparian vegetation. These zones support trees and shrubs whose life stages are adapted to specific habitat types and consequently forest composition and successional stage reflect the underlying hydrogeomorphic processes and history. In this study we investigated woodland vegetation composition, successional stage and habitat properties, and compared these with physically-based indicators of hydraulic processes. We thus sought to develop a hydrogeomorphic model to evaluate riparian woodland condition based on the spatial mosaic of successional phases of the floodplain forest. The study investigated free-flowing and dam-impacted reaches of the Kootenai and Flathead Rivers, in Idaho and Montana, USA and British Columbia, Canada. The analyses revealed strong correspondence between vegetation assessments and metrics of fluvial processes indicating morphodynamics (erosion and shear stress), inundation and depth to groundwater. The results indicated that common successional stages generally occupied similar hydraulic environments along the different river segments. Comparison of the spatial patterns between the free-flowing and regulated reaches revealed greater deviation from the natural condition for the braided channel segment than for the meandering segment. This demonstrates the utility of the hydrogeomorphic approach and suggests that riparian woodlands along braided channels could have lower resilience than those along meandering channels and might be more vulnerable to influences such as from river damming or climate change. Copyright © 2015 Elsevier Ltd. All rights reserved.

High resolution stratigraphy of the Jurassic-Cretaceous boundary interval in the Gresten Klippenbelt (Austria)

Czech Academy of Sciences Publication Activity Database

Lukeneder, A.; Halásová, E.; Kroh, A.; Mayrhofer, S.; Pruner, Petr; Reháková, D.; Schnabl, Petr; Sprovieri, M.; Wagreich, M.

2010-01-01

Roč. 61, č. 5 (2010), s. 365-381 ISSN 1335-0552 R&D Projects: GA ČR GA205/07/1365 Institutional research plan: CEZ:AV0Z30130516 Keywords : Jurassic/Cretaceous boundary * Penninic Ocean, * paleoecology * paleogeography * environmental changes Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.909, year: 2010

Evidence for Cretaceous-Paleogene boundary bolide “impact winter” conditions from New Jersey, USA

NARCIS (Netherlands)

Vellekoop, J.; Esmeray-Senlet, S.; Miller, K.G.; Browning, J.V.; Sluijs, A.; van de Schootbrugge, B.; Sinninghe Damsté, J.S.; Brinkhuis, H.

2016-01-01

Abrupt and short-lived “impact winter” conditions have commonly been implicated as the main mechanism leading to the mass extinction at the Cretaceous-Paleogene (K-Pg) boundary (ca. 66 Ma), marking the end of the reign of the non-avian dinosaurs. However, so far only limited evidence has been

Arctic deltaic lake sediments as recorders of fluvial organic matter deposition

Directory of Open Access Journals (Sweden)

Jorien E Vonk

2016-08-01

Full Text Available Arctic deltas are dynamic and vulnerable regions that play a key role in land-ocean interactions and the global carbon cycle. Delta lakes may provide valuable historical records of the quality and quantity of fluvial fluxes, parameters that are challenging to investigate in these remote regions. Here we study lakes from across the Mackenzie Delta, Arctic Canada, that receive fluvial sediments from the Mackenzie River when spring flood water levels rise above natural levees. We compare downcore lake sediments with suspended sediments collected during the spring flood, using bulk (% organic carbon, % total nitrogen, 13C, 14C and molecular organic geochemistry (lignin, leaf waxes. High-resolution age models (137Cs, 210Pb of downcore lake sediment records (n=11 along with lamina counting on high-resolution radiographs show sediment deposition frequencies ranging between annually to every 15 years. Down-core geochemical variability in a representative delta lake sediment core is consistent with historical variability in spring flood hydrology (variability in peak discharge, ice jamming, peak water levels. Comparison with earlier published Mackenzie River depth profiles shows that (i lake sediments reflect the riverine surface suspended load, and (ii hydrodynamic sorting patterns related to spring flood characteristics are reflected in the lake sediments. Bulk and molecular geochemistry of suspended particulate matter from the spring flood peak and lake sediments are relatively similar showing a mixture of modern higher-plant derived material, older terrestrial permafrost material, and old rock-derived material. This suggests that deltaic lake sedimentary records hold great promise as recorders of past (century-scale riverine fluxes and may prove instrumental in shedding light on past behaviour of arctic rivers, as well as how they respond to a changing climate.

Late Jurassic-Early Cretaceous continental convergence and intracontinental orogenesis in East Asia: A synthesis of the Yanshan Revolution

Science.gov (United States)

Dong, Shuwen; Zhang, Yueqiao; Zhang, Fuqin; Cui, Jianjun; Chen, Xuanhua; Zhang, Shuanhong; Miao, Laicheng; Li, Jianhua; Shi, Wei; Li, Zhenhong; Huang, Shiqi; Li, Hailong

2015-12-01

The basic tectonic framework of continental East Asia was produced by a series of nearly contemporaneous orogenic events in the late Middle Jurassic to Early Cretaceous. Commonly, the Late Mesozoic orogenic processes were characterized by continent-continent collision, large-scale thrusting, strike-slip faulting and intense crustal shortening, crustal thickening, regional anatexis and metamorphism, followed by large-scale lithospheric extension, rifting and magmatism. To better understand the geological processes, this paper reviews and synthesizes existing multi-disciplinary geologic data related to sedimentation, tectonics, magmatism, metamorphism and geochemistry, and proposes a two-stage tectono-thermal evolutionary history of East Asia during the late Middle Jurassic to Early Cretaceous (ca. 170-120 Ma). In the first stage, three orogenic belts along the continental margins were formed coevally at ca. 170-135 Ma, i.e., the north Mongol-Okhotsk orogen, the east paleo-Pacific coastal orogen, and the west Bangong-Nujiang orogen. Tectonism related to the coastal orogen caused extensive intracontinental folding and thrusting that resulted in a depositional hiatus in the Late Jurassic, as well as crustal anatexis that generated syn-kinematic granites, adakites and migmatites. The lithosphere of the East Asian continent was thickened, reaching a maximum during the latest Jurassic or the earliest Cretaceous. In the second stage (ca. 135-120 Ma), delamination of the thickened lithosphere resulted in a remarkable (>120 km) lithospheric thinning and the development of mantle-derived magmatism, mineralization, metamorphic core complexes and rift basins. The Middle Jurassic-Early Cretaceous subduction of oceanic plates (paleo-Pacific, meso-Tethys, and Mongol-Okhotsk) and continent-continent collision (e.g. Lhasa and Qiangtang) along the East Asian continental margins produced broad coastal and intracontinental orogens. These significant tectonic activities, marked by