The Mesozoic rift basins of eastern North America: Potential reservoir or Explorationist's folly

Energy Technology Data Exchange (ETDEWEB)

Pyron, A.

1991-08-01

Mesozoic rift basins are found on the East Coast of North America from Georgia to Nova Scotia. The basins formed as a result of extensional activity associated with the breakup of Pangaea. The internal geometry of the basins includes a depositional sequence ranging from coarse fanglomerates to fine-grained siltstones and argillites. Since these Mesozoic rift basins were first studied, they have not been considered to be likely spots for hydrocarbon accumulations. Recently, geologists have reconsidered these Mesozoic basins and have developed a more synergistic approach that suggests that many of these rift basins might be suitable targets for exploration. By analogy, these Mesozoic basins are correlative to similar basins in northwestern Africa, where significant reserved of oil and natural gas have been developed. The similarity between the productive basins in northwestern Africa and the Mesozoic basins of North America and their proximity to major markets provides sufficient rationale to further investigate these basins.

Petroleum systems in rift basins – a collective approach in South-east Asian basins.

NARCIS (Netherlands)

Doust, H.; Sumner, D.

2007-01-01

This paper synthesizes some of the main conclusions reached in a recent regional review of the Tertiary basins of Southeast Asia, carried out by Shell. Four distinctive types of petroleum systems, correlating with the four main stages of basin evolution (early to late syn-rift and early to late

Crustal structure and rift tectonics across the Cauvery–Palar basin ...

Indian Academy of Sciences (India)

The Cauvery–Palar basin is a major peri-cratonic rift basin located along the Eastern Continental. Margin of India ..... density P(k) of a magnetized body having infinite extensions in the .... aly data must be brought down to the sea level through ...

Tectono-stratigraphy of the Lower Cretaceous Syn-rift Succession in Bongor Basin, Chad: Insights into Structural Controls on Sedimentary Infill of a Continental Rift

Science.gov (United States)

Chen, C.; Ji, Y.; Wei, X.; An, F.; Li, D.; Zhu, R.

2017-12-01

In a rift basin, the dispersal and deposition of sediments is significantly influenced by the paleo-topography, which is highly controlled by the evolution and interaction of normal faults in different scales. To figure out the impact of faults evolution and topographic elements towards sedimentary fillings, we investigated the Lower Cretaceous syn-rift package in Bongor Basin, south of Chad Republic. Constrained with 2D and 3D seismic data, core data and logging information, a sequence stratigraphy architecture and a variety of depositional systems are recognized, including fan delta, braided delta, sub-lacustrine fan and lacustrine system. We also studied the spatial distribution and temporal evolution of clastic depositional systems of the syn-rift complex, and valuable insights into structural controls of sequence architectures and depositional systems are provided. During the evolution of rift basin, marginal structures such as relay ramps and strike-slipping boundary transfer fault are major elements that influence the main sediments influx points. Release faults in the hanging-wall could form a differential evolution pattern for accommodation, and effect the deposition systems in the early stage of rift evolution. Oblique crossing-faults, minor faults that develop on the erosional uplift in the interior foot-wall, would cut the uplifts and provide faulted-through paths for the over-filled sediments in the accommodation space, making it possible to develop sedimentary systems towards the center of basin during the early stage of rift evolution, although the origins of such minor faults still need further discussion. The results of this research indicate that different types of fault interactions have a fundamental control on patterns of sediment dispersal during early stage of rift basins.

Modeling the Sedimentary Infill of Lakes in the East African Rift: A Case Study of Multiple versus Single Rift Basin Segments

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Zhang, C.; Scholz, C. A.

2016-12-01

The sedimentary basins in the East African Rift are considered excellent modern examples for investigating sedimentary infilling and evolution of extensional systems. Some lakes in the western branch of the rift have formed within single-segment systems, and include Lake Albert and Lake Edward. The largest and oldest lakes developed within multi-segment systems, and these include Lake Tanganyika and Lake Malawi. This research aims to explore processes of erosion and sedimentary infilling of the catchment area in single-segment rift (SSR) and multi-segment rift (MSR) systems. We consider different conditions of regional precipitation and evaporation, and assess the resulting facies architecture through forward modeling, using state-of-the-art commercial basin modeling software. Dionisos is a three-dimensional numerical stratigraphic forward modeling software program, which simulates basin-scale sediment transport based on empirical water- and gravity-driven diffusion equations. It was classically used to quantify the sedimentary architecture and basin infilling of both marine siliciclastic and carbonate environments. However, we apply this approach to continental rift basin environments. In this research, two scenarios are developed, one for a MSR and the other for a SSR. The modeled systems simulate the ratio of drainage area and lake surface area observed in modern Lake Tanganyika and Lake Albert, which are examples of MSRs and SSRs, respectively. The main parameters, such as maximum subsidence rate, water- and gravity-driven diffusion coefficients, rainfall, and evaporation, are approximated using these real-world examples. The results of 5 million year model runs with 50,000 year time steps show that MSRs are characterized by a deep water lake with relatively modest sediment accumulation, while the SSRs are characterized by a nearly overfilled lake with shallow water depths and thick sediment accumulation. The preliminary modeling results conform to the features

Initiation and evolution of the Oligo-Miocene rift basins of southwestern Europe: Contribution of deep seismic reflection profiling

Science.gov (United States)

Bois, C.

1993-11-01

Southwestern European Oligo-Miocene rift basins have recently been investigated by deep seismic reflection profiling. The study of these data, together with other geophysical and geological data, shows that the rifts, which run from the Rhinegraben to the western Mediterranean, do not form a single clearcut system. The N-trending rifts (Rhinegraben, Bresse and Limagne) were developed on a cold and rigid lithosphere affected by the Alpine collision. The NE-trending rifts (southeastern France, Gulf of Lions and Valencia Trough) were formed slightly later in a backarc basin associated with an active segment of the European-Iberian plate that was heated, affected by widespread calcalkaline volcanism and probably weakened. All the southwestern European rifts and basins together may, however, be related to a common heritage represented by the boundary between the European-Iberian and African-Apulian plates that was created in the Jurassic with the initiation of the Tethys Ocean. The present features of the southwestern European Oligo-Miocène rift basins may be explained by a combination of three geodynamic mechanisms: mechanical stretching of the lithosphere, active mantle uplifting, and subordinate lithospheric flexuring. All the rifts were probably initiated by passive stretching. A systematic discrepancy between stretching derived from fault analysis and attenuation of the crust has been observed in all the rifts. This suggests that these rifts were subsequently reworked by one or several active mantle upwelling events associated with late shoulder uplift, asthenosphere upwelling and anomalous P-wave velocities in the lowermost crust and the uppermost mantle. Crustal attenuation may have been achieved by mantle intrusion, metamorphism of the deep crust and/or its delamination. Some of the rifts were affected by lithospheric flexuring. Combinations, in various proportions, of a small number of geodynamic mechanisms probably controlled many basins in the world. This

Early evolution of the southern margin of the Neuquén Basin, Argentina: Tectono-stratigraphic implications for rift evolution and exploration of hydrocarbon plays

Science.gov (United States)

D'Elia, Leandro; Bilmes, Andrés; Franzese, Juan R.; Veiga, Gonzalo D.; Hernández, Mariano; Muravchik, Martín

2015-12-01

Long-lived rift basins are characterized by a complex structural and tectonic evolution. They present significant lateral and vertical stratigraphic variations that determine diverse basin-patterns at different timing, scale and location. These issues cause difficulties to establish facies models, correlations and stratal stacking patterns of the fault-related stratigraphy, specially when exploration of hydrocarbon plays proceeds on the subsurface of a basin. The present case study corresponds to the rift-successions of the Neuquén Basin. This basin formed in response to continental extension that took place at the western margin of Gondwana during the Late Triassic-Early Jurassic. A tectono-stratigraphic analysis of the initial successions of the southern part of the Neuquén Basin was carried out. Three syn-rift sequences were determined. These syn-rift sequences were located in different extensional depocentres during the rifting phases. The specific periods of rifting show distinctly different structural and stratigraphic styles: from non-volcanic to volcanic successions and/or from continental to marine sedimentation. The results were compared with surface and subsurface interpretations performed for other depocentres of the basin, devising an integrated rifting scheme for the whole basin. The more accepted tectono-stratigraphic scheme that assumes the deposits of the first marine transgression (Cuyo Cycle) as indicative of the onset of a post-rift phase is reconsidered. In the southern part of the basin, the marine deposits (lower Cuyo Cycle) were integrated into the syn-rift phase, implying the existence of different tectonic signatures for Cuyo Cycle along the basin. The rift climax becomes younger from north to south along the basin. The post-rift initiation followed the diachronic ending of the main syn-rift phase throughout the Neuquén Basin. Thus, initiation of the post-rift stage started in the north and proceeded towards the south, constituting a

Signature recognition for rift structures of different sediment strata in ordos basin

International Nuclear Information System (INIS)

Zhao Xigang

2006-10-01

The rift structure weak information of high Bouguer gravity anomaly data among different Sediment strata are extracted By the horizontal gradient Maximum modulus, the wavelet variation, stripped gravity anomaly of basement and interfaces above/under researched layer, image processing method. So the linear rift structures of different Sediment strata are recognized on data images, such as Cretaceous, Jurassic, Triassic, Permian and Carboniferous, Ordovician System. Development rifts of different Sediment strata occur in stereo structure with quasi-uniform spacing, the rift density of above Sediment stratum is more than lower in different Sediment strata, but the north rift density of the same Sediment stratum is less than south's. It is useful to study rift structure and co-explore for oil, gas, coal and uranium resources in Ordos Basin. (authors)

Spatial and Temporal Strain Distribution Along the Central Red Sea Rift - A Study of the Hamd-Jizil Basin in Saudi Arabia

Science.gov (United States)

Szymanski, E.; Stockli, D.; Johnson, P.; Kattan, F. H.; Al Shamari, A.

2006-12-01

Numerous models exploring the rupturing modes and mechanisms of continental lithosphere are based on geological evidence from the Red Sea/Gulf of Suez rift system. Individually, the Red Sea basin is the prototype for many models of orthogonal continental rifting. Despite being a classic example of continental extension, many temporal and spatial strain distribution aspects, as well as the dynamic evolution of the rift architecture of the Red Sea, remain poorly constrained. Critical data come mostly from the Gulf of Suez and the Egyptian and Yemeni margins of the Red Sea; the rift flanks in Sudan and Saudi Arabia have remained largely unstudied, leaving a large information gap along the central portions of the rift system. Improving continental lithosphere rupture models requires an absolute understanding of the timing and magnitude of strain partitioning along the full rift flank. This study focuses on the development of extensional structures, syn- extensional sedimentary deposits, and rift-related Tertiary basaltic volcanism along the central flank of the rift system in Saudi Arabia. Geo- and thermochronometric techniques are used to elucidate the evolution of inboard and outboard strain markers manifested by structurally-controlled extensional basins that parallel the trend of the main Red Sea rift. Constraints on the dynamics of rift flank deformation are achieved through the collection of thermochronometric transects that traverse both the entire Arabian shield and individual normal faults that bound inland basins. Preliminary results show inland basins as asymmetric half-grabens filled by tilted Cenozoic sedimentary strata and separated by exhumed basement fault blocks. The most prominent extensional basin is the NW-trending Hamd-Jizil basin, located north of Madinah, measuring ~200 km along strike and up to 20 km in width. The Hamd-Jizil basin is structurally characterized by two half-grabens exposing a series of syn-rift siliciclastic sedimentary sections

Lateral variations in foreland flexure of a rifted continental margin: The Aquitaine Basin (SW France)

Science.gov (United States)

Angrand, P.; Ford, M.; Watts, A. B.

2017-12-01

We study the effects of the inherited Aptian to Cenomanian rift on crustal rheology and evolution of the Late Cretaceous to Neogene flexural Aquitaine foreland basin, northern Pyrenees. We use surface and subsurface geological data to define the crustal geometry and the post-rift thermal subsidence, and Bouguer gravity anomalies and flexural modeling to study the lateral variation of the elastic thickness, flexure of the European plate and controlling loads. The Aquitaine foreland can be divided along-strike into three sectors. The eastern foreland is un-rifted and is associated with a simple flexural subsidence. The central sector is affected by crustal stretching and the observed foreland base is modeled by combining topographic and buried loads, with post-rift thermal subsidence. In the western sector the foreland basin geometry is mainly controlled by post-rift thermal subsidence. These three sectors are separated by major lineaments, which affect both crustal and foreland geometry. These lineaments seem to be part of a larger structural pattern that includes the Toulouse and Pamplona Faults. The European foreland shows lateral variations in flexural behavior: the relative role of surface and sub-surface (i.e., buried) loading varies along-strike and the elastic thickness values decrease from the north-east to the south-west where the plate is the most stretched. We suggest that foreland basins are influenced by the thermal state of the underlying lithosphere if it was initiated soon after rifting and that thermal cooling can contribute significantly to subsidence.

Chemical stratigraphy of Grande Ronde Basalt, Pasco Basin, south-central Washington

International Nuclear Information System (INIS)

Long, P.E.; Ledgerwood, R.K.; Myers, C.W.; Reidel, S.P.; Landon, R.D.; Hooper, P.R.

1980-02-01

Grande Ronde Basalt in the Pasco Basin, south-central Washington, can be subdivided into three chemical types and two chemical subtypes based on x-ray fluorescence major element analysis of samples from seven deep core holes and three surface sections. These chemical types are: (1) high-Mg Grande Ronde chemical type; (2) low-Mg Grande Ronde chemical type; (3) low-K (very high-Mg.) Grande Ronde chemical type; and (4) Umtanum Grande Ronde chemical subtype. A possible fifth subdivision is the McCoy Canyon Grande Ronde chemical subtype. The Umtanum and the McCoy Canyon subtypes are both single flows which belong to the low Mg and high-Mg chemical types, respectively. These subdivisions are all distinguished on a plot of MgO versus TiO 2 and/or MgO versus P 2 O 5 , but other major and minor elements, as well as trace elements, also reflect consistent chemical differences between the chemical types. Identification of these chemical types in the Pasco Basin subsurface shows that the high-Mg and low-Mg chemical types are ubiquitous, but the low-K chemical type is limited to the central, southern, and eastern parts of the basin. The Umtanum chemical subtype is present throughout the Pasco Basin subsurface, although it thins in the northeastern part of the basin and is apparently absent from surface exposures 40 kilometers (25 miles) north of the basin. The McCoy Canyon chemical subtype is also present throughout the basin

Evidence for Strong Controls from Preexisting Structures on Border Fault Development and Basin Evolution in the Malawi Rift from 3D Lacustrine Refraction Data

Science.gov (United States)

Accardo, N. J.; Shillington, D. J.; Gaherty, J. B.; Scholz, C. A.; Ebinger, C.; Nyblade, A.; McCartney, T.; Chindandali, P. R. N.; Kamihanda, G.; Ferdinand-Wambura, R.

2017-12-01

A long-standing debate surrounds controls on the development and ultimately abandonment of basin bounding border faults. The Malawi Rift in the the Western Branch of the East African Rift System presents an ideal location to investigate normal fault development. The rift is composed of a series of half graben basins bound by large border faults, which cross several terranes and pre-existing features. To delineate rift basin structure, we undertook 3D first arrival tomography across the North and Central basins of the Malawi Rift based on seismic refraction data acquired in Lake Malawi. The resulting 3D velocity model allows for the first-ever mapping of 3D basin structure in the Western Branch of the EAR. We estimate fault displacement profiles along the two border faults and find that each accommodated 7.2 km of throw. Previous modeling studies suggest that given the significant lengths (>140 km) and throws of these faults, they may be nearing their maximum dimensions or may have already been abandoned. While both faults accommodate similar throws, their lengths differ by 40 km, likely due to the influence of both preexisting basement fabric and large-scale preexisting structures crossing the rift. Over 4 km of sediment exists where the border faults overlap in the accommodation zone indicating that these faults likely established their lengths early. Portions of both basins contain packages of sediment with anomalously fast velocities (> 4 km/s), which we interpret to represent sediment packages from prior rifting episodes. In the Central Basin, this preexisting sediment traces along the inferred offshore continuation of the Karoo-aged Ruhuhu Basin that intersects Lake Malawi at the junction between the North and Central basins. This feature may have influenced the length of the border fault bounding the Central Basin. In the North Basin, the preexisting sediment is thicker ( 4 km) and likely represents the offshore continuation of a series of preexisting rift

Tectonic Implications of Changes in the Paleogene Paleodrainage Network in the West-Central Part of the San Luis Basin, Northern Rio Grande Rift, New Mexico and Colorado, USA

Science.gov (United States)

Thompson, R. A.; Turner, K. J.; Cosca, M. A.; Drenth, B.

2016-12-01

The San Luis Basin is the largest of extensional basins in the northern Rio Grande rift (>11,400 km2). The modern basin configuration is the result of Neogene deformation that has been the focus of numerous studies. In contrast, Paleogene extensional deformation is relatively little studied owing to a fragmentary or poorly exposed stratigraphic record in most areas. However, volcanic and volcaniclastic deposits exposed along the western margin of the basin provide the spatial and temporal framework for interpretation of paleodrainage patterns that changed in direct response to Oligocene basin subsidence and the migration of centers of Tertiary volcanism. The early Oligocene (34 to 30 Ma) drainage pattern that originated in the volcanic highlands of the San Juan Mountains flowed south into the northern Tusas Mountains. A structural and topographic high composed of Proterozoic rocks in the Tusas Mountains directed flow to the southeast at least as late as 29 Ma, as ash-flow tuffs sourced in the southeast San Juan Mountains are restricted to the north side of the paleohigh. Construction of volcanic highlands in the San Luis Hills between 30 and 28.5 Ma provided an abundant source of volcanic debris that combined with volcanic detritus sourced in the southeast San Juan Mountains and was deposited (Los Pinos Formation) throughout the northern Tusas Mountains progressively onlapping the paleotopographic high. By 29 Ma, subsidence of the Las Mesitas graben, a structural sub-basin, between the San Luis Hills and the southeast San Juan and northern Tusas Mountains is reflected by thick deposits of Los Pinos Formation beneath 26.5 Ma basalts. Regional tectonism responsible for the formation of the graben may have also lowered the topographic and structural high in the Tusas Mountains, which allowed development of a southwest-flowing paleodrainage that likely flowed onto the Colorado Plateau. Tholeiitic basalt flows erupted in the San Luis Hills at 25.8 Ma, that presently cap

Geophysical evidence of pre-sag rifting and post-rifting fault reactivation in the Parnaíba basin, Brazil

OpenAIRE

de Castro, David Lopes; Bezerra, Francisco Hilário; Fuck, Reinhardt Adolfo; Vidotti, Roberta Mary

2016-01-01

This study investigated the rifting mechanism that preceded the prolonged subsidence of the Paleozoic Parnaíba basin in Brazil and shed light on the tectonic evolution of this large cratonic basin in the South American platform. From the analysis of aeromagnetic, aerogravity, seismic reflection and borehole data, we concluded the following: (1) large pseudo-gravity and gravity lows mimic graben structures but are associated with linear supracrustal strips in the basement. (2...

Rift systems of the Russian Eastern Arctic shelf and Arctic deep water basins: link between geological history and geodynamics

Directory of Open Access Journals (Sweden)

A. M. Nikishin

2017-01-01

Full Text Available In our study, we have developed a new tectonic scheme of the Arctic Ocean, which is based mainly on seismic profiles obtained in the Arctic-2011, Arctic-2012 and Arctic-2014 Projects implemented in Russia. Having interpreted many seismic profiles, we propose a new seismic stratigraphy of the Arctic Ocean. Our main conclusions are drawn from the interpretation of the seismic profiles and the analysis of the regional geological data. The results of our study show that rift systems within the Laptev, the East Siberian and the Chukchi Seas were formed not earlier than Aptian. The geological structure of the Eurasian, Podvodnikov, Toll and Makarov Basins is described in this paper. Having synthesized all the available data on the study area, we propose the following model of the geological history of the Arctic Ocean: 1. The Canada Basin formed till the Aptian (probably, during Hauterivian-Barremian time. 2. During the Aptian-Albian, large-scale tectonic and magmatic events took place, including plume magmatism in the area of the De Long Islands, Mendeleev Ridge and other regions. Continental rifting started after the completion of the Verkhoyansk-Chukotka orogenу, and rifting occurred on the shelf of the Laptev, East Siberian, North Chukchi and South Chukchi basins, and the Chukchi Plateau; simultaneously, continental rifting started in the Podvodnikov and Toll basins. 3. Perhaps the Late Cretaceous rifting continued in the Podvodnikov and Toll basins. 4. At the end of the Late Cretaceous and Paleocene, the Makarov basin was formed by rifting, although local spreading of oceanic crust during its formation cannot be excluded. 5. The Eurasian Basin started to open in the Early Eocene. We, of course, accept that our model of the geological history of the Arctic Ocean, being preliminary and debatable, may need further refining. In this paper, we have shown a link between the continental rift systems on the shelf and the formation history of the Arctic

Structure of the la VELA Offshore Basin, Western Venezuela: AN Obliquely-Opening Rift Basin Within the South America-Caribbean Strike-Slip Plate Boundary

Science.gov (United States)

Blanco, J. M.; Mann, P.

2015-12-01

Bathymetric, gravity and magnetic maps show that the east-west trend of the Cretaceous Great Arc of the Caribbean in the Leeward Antilles islands is transected by an en echelon series of obliquely-sheared rift basins that show right-lateral offsets ranging from 20 to 40 km. The basins are 75-100 km in length and 20-30 km in width and are composed of sub-parallel, oblique slip normal faults that define deep, bathymetric channels that bound the larger islands of the Leeward Antilles including Aruba, Curacao and Bonaire. A single basin of similar orientation and structure, the Urumaco basin, is present to the southwest in the Gulf of Venezuela. We mapped structures and sedimentation in the La Vela rift basin using a 3D seismic data volume recorded down to 6 seconds TWT. The basin can be mapped from the Falcon coast where it is correlative with the right-lateral Adicora fault mapped onshore, and its submarine extension. To the southeast of the 3D survey area, previous workers have mapped a 70-km-wide zone of northeast-striking, oblique, right-lateral faults, some with apparent right-lateral offsets of the coastline. On seismic data, the faults vary in dip from 45 to 60 degrees and exhibit maximum vertical offsets of 600 m. The La Vela and other obliquely-opening rifts accommodate right-lateral shear with linkages to intervening, east-west-striking right-lateral faults like the Adicora. The zone of oblique rifts is restricted to the trend of the Great Arc of the Caribbean and may reflect the susceptiblity of this granitic basement to active shearing. The age of onset for the basins known from previous studies on the Leeward Antilles is early Miocene. As most of these faults occur offshore their potential to generate damaging earthquakes in the densely populated Leeward Antilles is not known.

Oppositely directed pairs of propagating rifts in back-arc basins: Double saloon door seafloor spreading during subduction rollback

Science.gov (United States)

Martin, A. K.

2006-06-01

When a continent breaks up into two plates, which then separate from each other about a rotation pole, it can be shown that if initial movement is taken up by lithospheric extension, asthenospheric breakthrough and oceanic accretion propagate toward the pole of rotation. Such a propagating rift model is then applied to an embryonic centrally located rift which evolves into two rifts propagating in opposite directions. The resultant rhombic shape of the modeled basin, initially underlain entirely by thinned continental crust, is very similar to the Oligocene to Burdigalian back-arc evolution of the Valencia Trough and the Liguro-Provencal Basin in the western Mediterranean. Existing well and seismic stratigraphic data confirm that a rift did initiate in the Gulf of Lion and propagated southwest into the Valencia Trough. Similarly, seismic refraction, gravity, and heat flow data demonstrate that maximum extension within the Valencia Trough/Liguro-Provencal Basin occurred in an axial position close to the North Balearic Fracture Zone. The same model of oppositely propagating rifts, when applied to the Burdigalian/Langhian episode of back-arc oceanic accretion within the Liguro-Provencal and Algerian basins, predicts a number of features which are borne out by existing geological and geophysical, particularly magnetic data. These include the orientation of subparallel magnetic anomalies, presumed to be seafloor spreading isochrons, in both basins; concave-to-the-west fracture zones southwest of the North Balearic Fracture Zone, and concave-to-the-east fracture zones to its northeast; a spherical triangular area of NW oriented seafloor spreading isochrons southwest of Sardinia; the greater NW extension of the central (youngest?) magnetic anomaly within this triangular area, in agreement with the model-predicted northwestward propagation of a rift in this zone; successively more central (younger) magnetic anomalies abutting thinned continental crust nearer to the pole of

Carbon Sequestration Potential in Mesozoic Rift Basins Offshore the US East Coast: Teaching Old Seismic Data New Tricks

Science.gov (United States)

Fortin, W.; Goldberg, D.; Hutchinson, D. R.; Slagle, A. L.

2017-12-01

Motivated by rising atmospheric CO2 levels and recent developments in sequestration and seismic processing technologies, studies addressing the feasibility of offshore carbon sequestration are ongoing. The subsurface off the US east coast offers a few potential storage reservoirs including sedimentary layers as well as buried Mesozoic rift basins. Marine seismic reflection data first identified these features in the 1970s and are now being revisited as potential sequestration reservoirs. The rift basins are of particular interest as storage reservoirs for CO2 in light of recent work showing the efficacy of mineralizing injected carbon in basaltic formations. The use of these data presents unique challenges, particularly due to their vintage. However, new data processing capabilities and seismic prestack waveform inversion techniques elevate the potential of the legacy data. Using state of the art processing techniques we identify previously un-imaged rift basins off the US east coast between Delaware and Massachusetts and update mapping related to the areal and volumetric extent of basaltic fill. Applying prestack waveform inversion to the reprocessed seismic data, we show that each rift basin has different basaltic properties and thereby distinct utilities as carbon storage reservoirs.

The early-stage structural evolution of the Barmer Basin rift, Rajasthan, northwest India

OpenAIRE

Bladon, Andrew John

2015-01-01

The structural evolution of the Barmer Basin and the context of the rift within the northwest Indian region are poorly understood, despite being a prolific hydrocarbon province. In this work an integrated basin analysis is presented covering the outcrop-, seismic-, and lithosphere-scales. The early-stage structural evolution and the origin of poorly understood structural complications in the Barmer Basin subsurface are assessed. Subsequently, the findings are placed within the wider context o...

Analysis of the pre-rift/rifte transition interval (Serraria and Barra de Itiuba formations) from the Sergipe-Alagoas basin; Analise da secao de transicao pre-rifte/rifte (formacoes Serraria e Barra de Itiuba) da Bacia Sergipe-Alagoas

Energy Technology Data Exchange (ETDEWEB)

Barreiro, C.B.; Mizusaki, A.M.P. [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil)]. E-mail: camilita@terra.com.br; ana.misuzaki@ufrgs.br; Garcia, A.J.V. [Universidade do Vale do Rio dos Sinos (UNISINOS), Sao Leopoldo, RS (Brazil)]. E-mail: garcia@euler.unisinos.br

2003-07-01

The pre-rift/rift transition is represented by the Serraria and Barra de Itiuba formations. This interval was analyzed through qualitative and quantitative descriptions of cores, electric log analysis and studies of outcropping sections. The integration of surface and subsurface data allowed the stratigraphic characterization of sandstone bodies in the pre-rift/rift. These sandstones bodies were deposited by fluvial braided, lacustrine and deltaic systems (delta plain, delta front and pro delta). The sedimentary deposits characterized in the Serraria Formation are of channel, flooding of the fluvial system and eolic. The upper interval of this formation is characterized by to coarse medium-grained sandstones identified as the Caioba Sandstone. The Barra de Itiuba Formation contains lake, pro delta, frontal bar, distributary mouth, crevasse and distributary channel deposits. The sandstone units were specifically characterized in terms of their potential reservoir quality, and they were characterized the reservoirs R1 (good to medium quality) and Caioba (good quality) from the pre-rift phase, and reservoirs R2 (medium quality) and R3 (medium to good quality) from the rift phase. The reservoirs from pre-rift phase phase show the better reservoirs quality potential of the pre-rift/rift transition in the Sergipe-Alagoas Basin. (author)

The crustal characteristics at syn- and/or post-rifting in eastern Shikoku basin by seismic reflection survey

Science.gov (United States)

Yamashita, M.; Takahashi, N.; Kodaira, S.; Takizawa, K.; No, T.; Miura, S.; Kaneda, Y.

2008-12-01

Imaging of the arc-backarc transition zone is important in relation to the backarc opening process. Shikoku Basin locates between the Kyushu-Palau Ridge and the Izu-Ogasawara Arc, which is an important area to reveal the opening evolution of the backarc basins as a part of the growth process of the Philippine Sea. The Shikoku Basin was in the backarc rifting and spreading stage during about 30-15 Ma (e.g. Okino et al., 1994). High P-wave velocity lower crust is identified in arc-backarc transition zone by refraction survey using OBSs (Takahashi et al., 2007). Japan Agency for Marine-Earth Science and Technology (JAMSTEC) carried out multi-channel seismic reflection (MCS) survey using 12,000 cu.in. air gun and 5 km streamer with 204 ch hydrophones in the Izu-Ogasawara region since 2004. We extracted and mapped the crustal characteristics from poststack and prestack depth migrated profiles. According to obtained profiles, the deformation structure with share component is recognized in arc-backarc transition zone, which located eastern side of Shikoku Basin from Zenisu Ridge to about 500 km south. The maximum width of this deformation zone is about 100 km. The relative displacement of horizon is little; however, it is strongly deformed from upper crust beneath seafloor. This deformation zone indicates the post- rifting activity in east side of Shikoku Basin. On the other hand, some knolls are indicated along the en- echelon arrangement from Izu-Ogasawara arc. Ishizuka et al. (2003) reported post-rifting volcanism with Miocene age in en-echelon arrangement. A part of these knolls are estimated to penetrate at syn-rifting and/or post-rifting stage in backarc opening. By comparing the both side of arc-backarc transition zone, we elucidate syn- and post-rifting effect in Shikoku Basin. We also carried out high density MCS surveys in Shikoku Basin in order to IODP proposal site for reconstruction of magmatic processes since Oligocene in rear arc. In this survey, we use new

Tectonoestratigraphic and Thermal Models of the Tiburon and Wagner Basins, northern Gulf of California Rift System

Science.gov (United States)

Contreras, J.; Ramirez Zerpa, N. A.; Negrete-Aranda, R.

2014-12-01

The northern Gulf of California Rift System consist sofa series faults that accommodate both normal and strike-slip motion. The faults formed a series of half-greens filled with more than 7 km of siliciclastic suc­cessions. Here, we present tectonostratigraphic and heat flow models for the Tiburón basin, in the southern part of the system, and the Wag­ner basin in the north. The models are constrained by two-dimensional seis­mic lines and by two deep boreholes drilled by PEMEX­-PEP. Analysis of the seismic lines and models' results show that: (i) subsidence of the basins is controlled by high-angle normal faults and by flow of the lower crust, (ii) basins share a common history, and (iii) there are significant differences in the way brittle strain was partitioned in the basins, a feature frequently observed in rift basins. On one hand, the bounding faults of the Tiburón basin have a nested geometry and became active following a west-to-east sequence of activation. The Tiburon half-graben was formed by two pulses of fault activity. One took place during the protogulf extensional phase in the Miocene and the other during the opening of Gulf of California in the Pleistocene. On the other hand, the Wagner basin is the result of two fault generations. During the late-to middle Miocene, the west-dipping Cerro Prieto and San Felipe faults formed a domino array. Then, during the Pleistocene the Consag and Wagner faults dissected the hanging-wall of the Cerro Prieto fault forming the modern Wagner basin. Thermal modeling of the deep borehole temperatures suggests that the heat flow in these basins in the order of 110 mW/m2 which is in agreement with superficial heat flow measurements in the northern Gulf of California Rift System.

Seismic Anisotropy Beneath the Eastern Flank of the Rio Grande Rift

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Benton, N. W.; Pulliam, J.

2015-12-01

Shear wave splitting was measured across the eastern flank of the Rio Grande Rift (RGR) to investigate mechanisms of upper mantle anisotropy. Earthquakes recorded at epicentral distances of 90°-130° from EarthScope Transportable Array (TA) and SIEDCAR (SC) broadband seismic stations were examined comprehensively, via the Matlab program "Splitlab", to determine whether SKS and SKKS phases indicated anisotropic properties. Splitlab allows waveforms to be rotated, filtered, and windowed interactively and splitting measurements are made on a user-specified waveform segment via three independent methods simultaneously. To improve signal-to-noise and improve reliability, we stacked the error surfaces that resulted from grid searches in the measurements for each station location. Fast polarization directions near the Rio Grande Rift tend to be sub-parallel to the RGR but then change to angles that are consistent with North America's average plate motion, to the east. The surface erosional depression of the Pecos Valley coincides with fast polarization directions that are aligned in a more northerly direction than their neighbors, whereas the topographic high to the east coincides with an easterly change of the fast axis.The area above a mantle high velocity anomaly discovered separately via seismic tomography which may indicate thickened lithosphere, corresponds to unusually large delay times and fast polarization directions that are more closely aligned to a north-south orientation. The area of southeastern New Mexico that falls between the mantle fast anomaly and the Great Plains craton displays dramatically smaller delay times, as well as changes in fast axis directions toward the northeast. Changes in fast axis directions may indicate flow around the mantle anomaly; small delay times could indicate vertical or attenuated flow.

Rift architecture and evolution: The Sirt Basin, Libya: The influence of basement fabrics and oblique tectonics

Science.gov (United States)

Abdunaser, K. M.; McCaffrey, K. J. W.

2014-12-01

The Cretaceous-Tertiary northwest-trending Sirt Basin system, Libya, is a rift/sag basin formed on Pan-African to Paleozoic-aged basement of North Africa. In this study, we investigate the rift-basin architecture and tectonic framework of the western Sirt Basin. Using remote sensed data, supported by borehole data from about 300 deep wells and surface geologic maps, we constructed geological cross sections and surface geology maps. Indication of the relative timing of structures and movement along faults has been determined where possible. Direction statistics for all the interpreted linear features acquired in the study area were calculated and given as a total distribution and then the totals are broken down by the major basin elements of the area. Hundreds of lineaments were recognized. Their lengths, range between a hundred meters up to hundreds of kilometers and the longest of the dominant trends are between N35W-N55W and between N55E-N65E which coincides with Sirt Basin structures. The produced rose diagrams reveal that the majority of the surface linear features in the region have four preferred orientations: N40-50W in the Zallah Trough, N45-55W in the Dur al Abd Trough, N35-55W in the Az Zahrah-Al Hufrah Platform, and in contrast in the Waddan Uplift a N55-65E trend. We recognize six lithostratigraphic sequences (phases) in the area's stratigraphic framework. A Pre-graben (Pre-rift) initiation stage involved the Pre-Cretaceous sediments formed before the main Sirt Basin subsidence. Then followed a Cretaceous to Eocene graben-fill stage that can divided into four structurally-active and structurally-inactive periods, and finally a terminal continental siliciclastics-rich package representing the post-rift stage of the development in post-Eocene time. In general five major fault systems dissect and divide the study area into geomorphological elevated blocks and depressions. Most of the oil fields present in the study area are associated with structural hinge

Aulacogens, the Donets Basin (Eastern Ukraine, Southwestern Russia, and the new classification of rifts: Towards a proper terminology

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Ruban Dmitry A.

2012-01-01

Full Text Available Some intra-cratonic basins are traditionally called “aulacogens”. This term has persisted in the geoscience literature since its invention by Soviet geologists in the mid-20th century before the triumph of the plate tectonics, but its meaning has evolved. Attempts to change its meaning from descriptive to genetic have led to a broad spectrum of opinions on the definition of aulacogens. Some specialists related them to continental rifts, while others have restricted aulacogens to the only particular rift systems or peculiar stages in the evolution of young cratons. The Donets Basin is a typical aulacogen stretching across the southern margin of the East European Craton. A brief review of present knowledge of this basin shows that its nature is rather incompatible with the present understanding of aulacogens. Instead, the new classification of rifts offers a more precise terminology for its exact characteristics. It is suggested that the term “aulacogen” should only be restricted to those basins for which it has been applied historically.

Deciphering Past and Present Tectonics of the Rio Grande Rift in New Mexico Utilizing Apatite Fission Track Thermochronology, Geochronology, Quaternary Faulting, and Cross-Section Restoration

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Ricketts, J. W.; Karlstrom, K. E.; Kelley, S. A.; Priewisch, A.; Crossey, L. J.; Asmerom, Y.; Polyak, V.; Selmi, M.

2011-12-01

The Rio Grande rift provides an excellent laboratory for understanding styles and processes of extensional tectonics, and their driving forces. We apply apatite fission track (AFT) thermochronology, geochronology, fracture analysis, and cross-section restoration to decipher past and present tectonics of the Rio Grande rift. AFT data has been compiled from rift flank uplifts along the Rio Grande rift in an attempt to recognize long wavelength spatial and temporal patterns. AFT ages record time of cooling of rocks below ~110°C and, when cooling is due to exhumation, age elevation traverses can record upward advection of rocks through paleo 110°C isotherms. The relatively passive sides of half-grabens (e.g. Manzanos and Santa Fe Range) preserve Laramide AFT ages ranging from 45-70 Ma, indicating they were cooled during the Laramide Orogeny and have remained cooler than 110°C since then. Rift flanks on the tectonically active sides of half-grabens, (e.g. Sierra Ladrones, Sandias, Taos Range, and Sierra Blanca) have AFT ages that range from 35 Ma to history and its mechanisms. AFT data at Ladron Peak, an active rift flank along the western margin of the Rio Grande rift in central New Mexico, indicates that it was rapidly unroofed between 20-10 Ma. Preliminary apatite helium data gives a similar age vs. elevation trend, but apatites have highly radiogenically damaged lattices and hence have corrected closure temperatures tens of degrees higher than AFT ages. The style of faulting at Ladron Peak is unusual because it is bounded by the anomalously low-angle (~15°) Jeter fault. In order to understand the evolution of faulting in this region, a balanced cross-section was constructed and restored to its pre-rift geometry. Our working hypothesis is that the low angle of the Jeter fault is most adequately explained by a rolling hinge model, where isostatic uplift causes progressive rotation of an initially steep (~60°) normal fault to shallower dips. Thirty km north of

Syn-Rift Systems of East Godavari Sub Basin: Its Evolution and Hydrocarbon Prospectivity

Science.gov (United States)

Dash, J., Jr.; Zaman, B.

2014-12-01

Krishna Godavari (K.G.) basin is a passive margin basin developed along the Eastern coast of India. This basin has a polyhistoric evolution with multiple rift systems. Rift basin exploration has provided the oil and gas industry with almost one third of discovered global hydrocarbon resources. Understanding synrift sequences, their evolution, depositional styles and hydrocarbon prospectivity has become important with recent discovery of the wells, G-4-6,YS-AF and KG-8 in the K.G. offshore basin. The East Godavari subbasin is a hydrocarbon producing basin from synrift and pre-rift sediments, and hence this was selected as the study area for this research. The study has been carried out by utilizing data of around 58 wells (w1-w58) drilled in the study area 25 of which are hydrocarbon bearing with organic thickness varying from 200 m to 600 m. Age data generated by palaentology and palynology studies have been utilized for calibration of key well logs to differentiate between formations within prerift and synrift sediments. The electrologs of wells like resistivity, gamma ray, neutron, density and sonic logs have been utilized for correlation of different formations in all the drilled wells. The individual thicknesses of sand, shale and coal in the formations have been calculated and tabulated. For Golapalli formation, the isopach and isolith maps were generated which revealed that there were four depocentres with input from the north direction. Schematic geological cross sections were prepared using the well data and seismic data to understand the facies variation across the basin. The sedimentological and petrophysical analysis reports and electro log suites were referred to decipher the environment of deposition, the reservoir characteristics, and play types. The geochemical reports [w4 (Tmax)= 455-468 °C; w1 (Tmax) = 467-514 °C; w4(VRO)= 0.65-0.85; w1(VRO)= 0.83-1.13] revealed the source facies, its maturation and migration timings i.e. the petroleum systems

Grande Ronde Basin Supplementation Program; Lostine River, 2000 Annual Report.

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Onjukka, Sam T. (Oregon Department of Fish and Wildlife, Portland, OR); Harbeck, Jim (Nez Perce Tribe, Department of Fisheries Resource Management, Enterprise, OR)

2003-03-01

The Northwest Power Planning Council (NPPC) identified supplementation as a high priority to achieve its goal of increasing runs of anadromous fish in the Columbia Basin. Supplementation activities in the Lostine River and associated monitoring and evaluation conducted by the Nez Perce Tribe relate directly to the needs addressed in the Columbia River Basin Fish and Wildlife Program (NPPC 1994). Measure 7.4L.1 of the Program mandates that appropriate research accompany any proposed supplementation. In addition, measure 7.3B.2 of the Program stresses the need for evaluating supplementation projects to assess their ability to increase production. Finally, Section 7.4D.3 encourages the study of hatchery rearing and release strategies to improve survival and adaptation of cultured fish. In 1997, Oregon Department of Fisheries and Wildlife (ODFW) requested a modification of Permit 1011 to allow the take of adult spring chinook salmon. In 1998, the Nez Perce Tribe also requested a permit specific to activities on Lostine River. The permit was issued in 2000. A special condition in the permits required the development of a long term management plan for the spring chinook salmon of the Grande Ronde Basin. The Nez Perce Tribe, ODFW, and the Confederated Tribes of the Umatilla Indian Reservation (CTUIR) completed a formal long range plan entitled ''Grande Ronde Basin Endemic Spring Chinook Salmon Supplementation Program''. The program proposes to increase the survival of spring chinook salmon in the Grand Ronde Basin through hatchery intervention. Adult salmon from the Lostine River, Catherine Creek, and the Upper Grande Ronde River are used for a conventional supplementation program in the basin. The Nez Perce program currently operates under the ESA Section 10 Permit 1149.

Grande Ronde Basin Supplementation Program; Lostine River, 2001 Annual Report.

Energy Technology Data Exchange (ETDEWEB)

Onjukka, Sam T. (Oregon Department of Fish and Wildlife, Portland, OR); Harbeck, Jim (Nez Perce Tribe, Department of Fisheries Resource Management, Enterprise, OR)

2003-03-01

The Northwest Power Planning Council (NPPC) identified supplementation as a high priority to achieve its goal of increasing runs of anadromous fish in the Columbia Basin. Supplementation activities in the Lostine River and associated monitoring and evaluation conducted by the Nez Perce Tribe relate directly to the needs addressed in the Columbia River Basin Fish and Wildlife Program (NPPC 1994). Measure 7.4L.1 of the Program mandates that appropriate research accompany any proposed supplementation. In addition, measure 7.3B.2 of the Program stresses the need for evaluating supplementation projects to assess their ability to increase production. Finally, Section 7.4D.3 encourages the study of hatchery rearing and release strategies to improve survival and adaptation of cultured fish. In 1997, Oregon Department of Fisheries and Wildlife (ODFW) requested a modification of Permit 1011 to allow the take of adult spring chinook salmon. In 1998, the Nez Perce Tribe also requested a permit specific to activities on Lostine River. The permit was issued in 2000. A special condition in the permits required the development of a long term management plan for the spring chinook salmon of the Grande Ronde Basin. The Nez Perce Tribe, ODFW, and the Confederated Tribes of the Umatilla Indian Reservation (CTUIR) completed a formal long range plan entitled ''Grande Ronde Basin Endemic Spring Chinook Salmon Supplementation Program''. The program proposes to increase the survival of spring chinook salmon in the Grand Ronde Basin through hatchery intervention. Adult salmon from the Lostine River, Catherine Creek, and the Upper Grande Ronde River are used for a conventional supplementation program in the basin. The Nez Perce program currently operates under the ESA Section 10 Permit 1149.

Magnetotelluric data collected near geophysically logged boreholes in the Espa?ola and Middle Rio Grande basins, New Mexico

Science.gov (United States)

Williams, Jackie M.; Rodriguez, Brian D.

2006-01-01

The Santa Fe region is growing rapidly. The Santa Fe Group aquifer in the Espa?ola Basin is the main source of municipal water for the region, and water shortfalls could have serious consequences. Future growth and land management in the region depend on accurate assessment and protection of the region's ground-water resources. An important issue in managing the ground-water resources is a better understanding of the hydrogeology of the Tertiary Santa Fe Group. The Santa Fe Group includes the sedimentary deposits that fill the Rio Grande rift and contain the principal ground-water aquifers. The U.S. Geological Survey (USGS) is conducting a series of multidisciplinary studies of the Espa?ola Basin in northern New Mexico. Detailed geologic mapping, high-resolution airborne magnetic surveys, electromagnetic surveys, and hydrologic, lithologic, and hydro-geochemical data are being used to better understand the aquifer systems. Magnetotelluric (MT) surveys were completed as part of these studies. The primary purpose of the MT surveys was to map changes in electrical resistivity with depth that are related to differences in various rock types that help control the properties of aquifers in the region. Resistivity modeling of the MT data can be used to investigate buried structures related to the basic geologic framework of the study area. The purpose of this report is to release MT sounding data collected near geophysically logged boreholes in the study area, including the nearby Middle Rio Grande Basin. This MT data can be used in subsequent resistivity modeling. No interpretation of the data is included in this report.

Combining hydrologic and groundwater modelling to characterize a regional aquifer system within a rift setting (Gidabo River Basin, Main Ethiopian Rift)

Science.gov (United States)

Birk, Steffen; Mechal, Abraham; Wagner, Thomas; Dietzel, Martin; Leis, Albrecht; Winkler, Gerfried; Mogessie, Aberra

2016-04-01

The development of groundwater resources within the Ethiopian Rift is complicated by the strong physiographic contrasts between the rift floor and the highland and by the manifold hydrogeological setting composed of volcanic rocks of different type and age that are intersected by numerous faults. Hydrogeochemical and isotope data from various regions within the Ethiopian Rift suggest that the aquifers within the semi-arid rift floor receive a significant contribution of groundwater flow from the humid highland. For example, the major ion composition of groundwater samples from Gidabo River Basin (3302 km²) in the southern part of the Main Ethiopian Rift reveals a mixing trend from the highland toward the rift floor; moreover, the stable isotopes of water, deuterium and O-18, of the rift-floor samples indicate a component recharged in the highland. This work aims to assess if the hydrological and hydrogeological data available for Gidabo River Basin is consistent with these findings and to characterize the regional aquifer system within the rift setting. For this purpose, a two-step approach is employed: First, the semi-distributed hydrological model SWAT is used to obtain an estimate of the spatial and temporal distribution of groundwater recharge within the watershed; second, the numerical groundwater flow model MODFLOW is employed to infer aquifer properties and groundwater flow components. The hydrological model was calibrated and validated using discharge data from three stream gauging stations within the watershed (Mechal et al., Journal of Hydrology: Regional Studies, 2015, doi:10.1016/j.ejrh.2015.09.001). The resulting recharge distribution exhibits a strong decrease from the highland, where the mean annual recharge amounts to several hundred millimetres, to the rift floor, where annual recharge largely is around 100 mm and below. Using this recharge distribution as input, a two-dimensional steady-state groundwater flow model was calibrated to hydraulic

Lithospheric rheological heterogeneity across an intraplate rift basin (Linfen Basin, North China) constrained from magnetotelluric data: Implications for seismicity and rift evolution

Science.gov (United States)

Yin, Yaotian; Jin, Sheng; Wei, Wenbo; Ye, Gaofeng; Jing, Jian'en; Zhang, Letian; Dong, Hao; Xie, Chengliang; Liang, Hongda

2017-10-01

We take the Linfen Basin, which is the most active segment of the Cenozoic intraplate Shanxi Rift, as an example, showing how to use magnetotelluric data to constrain lithospheric rheological heterogeneities of intraplate tectonic zones. Electrical resistivity models, combined with previous rheological numerical simulation, show a good correlation between resistivity and rheological strength, indicating the mechanisms of enhanced conductivity could also be reasons of reduced viscosity. The crust beneath the Linfen Basin shows overall stratified features in both electrical resistivity and rheology. The uppermost crustal conductive layer is dominated by friction sliding-type brittle fracturing. The high-resistivity mid-crust is inferred to be high-viscosity metamorphic basement being intersected by deep fault. The plastic lower crust show significantly high-conductivity feature. Seismicity appears to be controlled by crustal rheological heterogeneity. Micro-earthquakes mainly distribute at the brittle-ductile transition zones as indicated by high- to low-resistivity interfaces or the high pore pressure fault zones while the epicenters of two giant destructive historical earthquakes occur within the high-resistivity and therefore high-strength blocks near the inferred rheological interfaces. The lithosphere-scale lateral rheological heterogeneity along the profile can also be illustrated. The crust and upper mantle beneath the Ordos Block, Lüliang Mountains and Taihang Mountains are of high rheological strength as indicated by large-scale high-resistivity zones while a significant high-conductivity, lithosphere-scale weak zone exists beneath the eastern margin of the Linfen Basin. According to previous geodynamic modeling works, we suggest that this kind of lateral rheological heterogeneity may play an essential role for providing driving force for the formation and evolution of the Shanxi Rift, regional lithospheric deformation and earthquake activities under the

Grande Ronde Basin Fish Habitat Enhancement Project : 1998 Annual Report.

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McGowan, Vance R.; Powell, Russ M.

1999-05-01

The primary goal of ''The Grande Ronde Basin Fish Habitat Improvement Project'' is to access, create, improve, protect, and restore reparian and instream habitat for anadromous salmonids, thereby maximizing opportunities for natural fish production within the basin.

Concentration of strain in a marginal rift zone of the Japan backarc during post-rift compression

Science.gov (United States)

Sato, H.; Ishiyama, T.; Kato, N.; Abe, S.; Shiraishi, K.; Inaba, M.; Kurashimo, E.; Iwasaki, T.; Van Horne, A.; No, T.; Sato, T.; Kodaira, S.; Matsubara, M.; Takeda, T.; Abe, S.; Kodaira, C.

2015-12-01

Late Cenozoic deformation zones in Japan may be divided into two types: (1) arc-arc collision zones like those of Izu and the Hokkaido axial zone, and (2) reactivated back-arc marginal rift (BMR) systems. A BMR develops during a secondary rifting event that follows the opening of a back-arc basin. It forms close to the volcanic front and distant from the spreading center of the basin. In Japan, a BMR system developed along the Sea of Japan coast following the opening of the Japan Sea. The BMR appears to be the weakest, most deformable part of the arc back-arc system. When active rifting in the marginal basins ended, thermal subsidence, and then mechanical subsidence related to the onset of a compressional stress regime, allowed deposition of up to 5 km of post-rift, deep-marine to fluvial sedimentation. Continued compression produced fault-related folds in the post-rift sediments, in thin-skin style deformation. Shortening reached a maximum in the BMR system compared to other parts of the back-arc, suggesting that it is the weakest part of the entire system. We examined the structure of the BMR system using active source seismic investigation and earthquake tomography. The velocity structure beneath the marginal rift basin shows higher P-wave velocity in the upper mantle/lower crust which suggests significant mafic intrusion and thinning of the upper continental crust. The syn-rift mafic intrusive forms a convex shape, and the boundary between the pre-rift crust and the mafic intrusive dips outward. In the post-rift compressional stress regime, the boundary of the mafic body reactivated as a reverse fault, forming a large-scale wedge thrust and causing further subsidence of the rift basin. The driver of the intense shortening event along the Sea of Japan coast in SW Japan was the arrival of a buoyant young (15 Ma) Shikoku basin at the Nankai Trough. Subduction stalled and the backarc was compressed. As the buoyant basin cooled, subduction resumed, and the rate of

PRELIMINARY PALEOMAGNETIC RESULTS FROM OUTFLOW EOCENE-OLIGOCENE ASH FLOW TUFFS FROM THE WESTERN MARGIN OF THE SAN LUIS BASIN: IMPLICATION FOR THE KINEMATIC EVOLUTION OF THE RIO GRANDE RIFT

Science.gov (United States)

Mason, S. N.; Geissman, J. W.; Sussman, A. J.

2009-12-01

In the Rio Grande rift (RGR), a late Cenozoic continental rift from central Colorado to southern New Mexico, hanging wall margins typically contain en echelon normal fault systems with intervening areas of typically complex structure, called relay zones. Relay zones transfer displacement through complex strain patterns and eventual linkage of faults and hold clues as to how fault zones initiate and grow. The western margin of the RGR at the latitude of the San Luis basin (SLB) exposes laterally continuous Eocene-Oligocene volcanic rocks, well-correlated by 40Ar/39Ar data, and well-preserved rift structures. Ash flow tuffs are usually excellent recorders of the instantaneous geomagnetic field and five ash flow tuffs (ca. 32.3 to 27.3 Ma; including the Saguache Creek, La Jara Canyon, Masonic Park, Fish Canyon, and Carpenter Ridge tuffs) have been sampled in spatial detail along west to east transects of the eastern San Juan volcanic field to the westernmost margin of the RGR at the SLB. Data obtained from our sampling approach will yield a comprehensive definition of relative vertical-axis rotations across the area and will be used to assess the timing of RGR fault linkages. Preliminary paleomagnetic data from the Masonic Park tuff (ca. 28.2 Ma) suggest up to ~17° clockwise rotation between sample locations on the Colorado Plateau and locations to the east, nearest the western margin of the RGR. Preliminary data from the Fish Canyon tuff (ca. 27.8 Ma) show a ~12° clockwise rotation. The relative clockwise vertical-axis rotation of sampling sites in both ash flow tuffs nearest the RGR margin suggests that relay zone development with attending vertical-axis rotation played an important role in the opening of the northern RGR. Our data set is not sufficiently robust at present to test the hypothesis that rotation was taking place concurrently with eruption of these large-volume ash flow tuffs in the early Oligocene, but it is a possibility and if so, the RGR at the

Syn-sedimentary tectonics and facies analysis in a rift setting: Cretaceous Dalmiapuram Formation, Cauvery Basin, SE India

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Nivedita Chakraborty

2018-04-01

Full Text Available The Cretaceous (Albian–Cenomanian Dalmiapuram Formation is one of the economically significant constituents in the hydrocarbon-producing Cauvery rift basin, SE India that opened up during the Late Jurassic–Early Cretaceous Gondwanaland fragmentation. The fossil-rich Dalmiapuram Formation, exposed at Ariyalur within the Pondicherry sub-basin of Cauvery Basin, rests in most places directly on the Archean basement and locally on the Lower Cretaceous (Barremian–Aptian Basal Siliciclastic Formation. In the Dalmiapuram Formation, a facies association of tectonically-disturbed phase is sandwiched between two drastically quieter phases. The early syn-rift facies association (FA 1, records the first carbonate marine transgression within the basin, comprising a bar–lagoon system with occasionally storms affecting along the shore and a sheet-like non-recurrent biomicritic limestone bed on the shallow shelf that laterally grades into pyrite–glauconite-bearing dark-colored shale in the deeper shelf. Spectacular breccias together with varied kinds of mass-flow products comprise the syn-rift facies association (FA 2. While the breccias occur at the basin margin area, the latter extend in the deeper inland sea. Clast composition of the coarse clastics includes large, even block-sized limestone fragments and small fragments of granite and sandstone from the basement. Marl beds of quieter intervals between tectonic pulses occur in alternation with them. Faulted basal contact of the formation, and small grabens filled by multiple mass-flow packages bear the clear signature of the syntectonic activity localized contortions, slump folds, and pillow beds associated with mega slump/slide planes and joints, which corroborates this contention further. This phase of tectonic intervention is followed by another relatively quieter phase and accommodates the late syn-rift facies association (FA 3. A tidal bar–interbar shelf depositional system allowed a

Drowning unconformity of lacustrine rift basins: A case study from the Dongying Sag in Bohai Bay Basin, China

Science.gov (United States)

Chen, R.; Fan, J.

2015-12-01

The concept of drowning unconformity of lacustrine rift basins was proposed in this paper. This paper utilized 3D seismic data, well-log and the principles methods associated with structural geology, sedimentology and geochemistry, to analyze the drowning unconformity and discuss the origins of drowning unconformity in Dongying Sag in Bohai Bay Basin.Researching on it is not only important for a better understanding of tectonic evolution, palaeogeography and sedimentation of hydrocarbon source rocks, but also a vital guiding significance for the exploration of beach-bar sandstone reservoirs and shale oil.1. The concept of drowning unconformity of lacustrine rift basins is defined. With the consequences of rapid tectonic subsidence in basin, the sharp rise of lake-level and the increased rate of accommodation(A) in basin exceeded the rate of sediment supply(S),namely A>>S, the basin suddenly transformed into deep-water settings from shallow-water settings with sudden change of sediment transport and sediment dispersal patterns. 2.The sequence surface between Sha4 and Sha3 Member of Shahejie Formation is the drowning unconformity(43.5Ma). There are the sedimentary association of the reefs in shallow lacustrine, beach-bar sandstones and glutenite fan bodies under the surface. By contrast, there are the sedimentary association of deep-lake oil shales and shales over the surface. The drowning unconformity in Dongying Sag is a tectonic revolution surface which is changed from extensional tectonics to transtensional tectonics and it is also the surface of discontinuity from shallow lacustrine to deep lacustrine. The responses to sudden changes appeared in the parameters of geophysics, geochemistry and paleontology. 3. With the penetration of India into Asia plate in NNE trending,the subduction zones of Pacific Plate retreated. It caused the rapid downwelling of asthenospheric mantle, followed by the extensive drowning unconformity.

Tectonic characteristics and structural styles of a continental rifted basin: Revelation from deep seismic reflection profiles

Directory of Open Access Journals (Sweden)

Yuan Li

2016-09-01

Full Text Available The Fushan Depression is a half-graben rifted sub-basin located in the southeast of the Beibuwan Basin, South China Sea. The Paleogene Liushagang sequence is the main hydrocarbon-bearing stratigraphic unit in the sub-basin. Using three-dimensional (3-D seismic data and logging data over the sub-basin, we analyzed structural styles and sedimentary characteristics of the Liushagang sequence. Five types of structural styles were defined: ancient horst, traditional slope, flexure slope-break, faulted slope-break and multiple-stage faults slope, and interpretations for positions, background and development formations of each structural style were discussed. Structural framework across the sub-basin reveals that the most remarkable tectonic setting is represented by the central transfer zone (CTZ which divides the sub-basin into two independent depressions, and two kinds of sequence architectures are summarized: (i the western multi-stage faults slope; (ii the eastern flexure slope break belt. Combined with regional stress field of the Fushan Depression, we got plane combinations of the faults, and finally built up plan distribution maps of structural system for main sequence. Also, we discussed the controlling factors mainly focused on subsidence history and background tectonic activities such as volcanic activity and earthquakes. The analysis of structural styles and tectonic evolution provides strong theoretical support for future prospecting in the Fushan sub-basin and other similar rifted basins of the Beibuwan Basin in South China Sea.

Evolution of basin architecture in an incipient continental rift: the Cenozoic Most Basin, Eger Graben (Central Europe)

Czech Academy of Sciences Publication Activity Database

Rajchl, M.; Uličný, David; Grygar, R.; Mach, K.

2009-01-01

Roč. 21, č. 3 (2009), s. 269-294 ISSN 0950-091X R&D Projects: GA AV ČR IAA3012705; GA ČR GA205/01/0629; GA ČR(CZ) GA205/06/1823 Institutional research plan: CEZ:AV0Z30120515 Keywords : Cenozoic Most Basin * continental rift * Eger Graben Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.161, year: 2009

Middle Rio Grande Basin Research Report 2008

Science.gov (United States)

Deborah M. Finch; Catherine Dold

2008-01-01

An ecosystem is rarely static. A natural system composed of plants, animals, and microorganisms interacting with an area's physical factors, an ecosystem is always fluctuating and evolving. But sometimes, often at the hands of humans, ecosystems change too much. Such is the case with many of the ecosystems of the Middle Rio Grande Basin of New Mexico.

Along strike behavior of the Tizi n' Firest fault during the Lower Jurassic rifting (Central High Atlas Carbonate basin, Morocco)

Science.gov (United States)

Sarih, S.; Quiquerez, A.; Allemand, P.; Garcia, J. P.; El Hariri, K.

2018-03-01

The purpose of this study is to document the along-strike early syn-rift history of the Lower Jurassic Carbonate basin of the Central High Atlas (Morocco) by combining sedimentological observations and high-resolution biostratigraphy. Six sections, each from the Sinemurian to the Upper Pliensbachian, were investigated along a 75 km-long transect at the hanging wall of a major fault of the Lower Jurassic Basin (i.e. the Tizi n' Firest fault). Depositional geometries of the early syn-rift deposits were reconstructed from the correlation between eight main timelines dated by biochronological markers for a time span covering about 6 Ma. Depocentre migration was examined and accommodation rates were calculated at the sub-zone timescale to discuss the along-strike-fault behavior of the Lower Jurassic basin formation. The early stages of extension are marked by contrasted along-strike variations in depositional geometry thickness, depocentre migration and accommodation rates, leading to the growth of three independent sub-basins (i.e. western, central, and eastern), ranging in size from 30 to 50 km, and displaying three contrasted tectono-sedimentary histories. Our results suggest that, during the early rifting phase, tectonic activity was not a continuous and progressive process evolving towards a rift climax stage, but rather a series of acceleration periods that alternated with periods of much reduced activity. The length of active fault segments is estimated at about 15-20 km, with a lifespan of a few ammonite sub-zones (> 2-3 Ma).

Grande Ronde Basin Spring Chinook Salmon Captive Broodstock Program, 1995-2002 Summary Report.

Energy Technology Data Exchange (ETDEWEB)

Hoffnagle, Timothy; Carmichael, Richard; Noll, William

2003-12-01

The Grande Ronde Basin once supported large runs of chinook salmon Oncorhynchus tshawytscha and estimated peak escapements in excess of 10,000 occurred as recently as the late 1950's (U.S. Army Corps of Engineers 1975). Natural escapement declines in the Grande Ronde Basin have been severe and parallel those of other Snake River populations. Reduced productivity has primarily been attributed to increased mortality associated with downstream and upstream migration past eight dams and reservoirs in the Snake and Columbia rivers. Reduced spawner numbers, combined with human manipulation of previously important spawning and rearing habitat in the Grande Ronde Basin, have resulted in decreased spawning distribution and population fragmentation of chinook salmon in the Grande Ronde Basin (Figure 1; Table 1). Escapement of spring/summer chinook salmon in the Snake River basin included 1,799 adults in 1995, less than half of the previous record low of 3,913 adults in 1994. Catherine Creek, Grande Ronde River and Lostine River were historically three of the most productive populations in the Grande Ronde Basin (Carmichael and Boyce 1986). However, productivity of these populations has been poor for recent brood years. Escapement (based on total redd counts) in Catherine Creek and Grande Ronde and Lostine rivers dropped to alarmingly low levels in 1994 and 1995. A total of 11, 3 and 16 redds were observed in 1994 in Catherine Creek, upper Grande Ronde River and Lostine River, respectively, and 14, 6 and 11 redds were observed in those same streams in 1995. In contrast, the maximum number of redds observed in the past was 505 in Catherine Creek (1971), 304 in the Grande Ronde River (1968) and 261 in 1956 in the Lostine River (Tranquilli et al 2003). Redd counts for index count areas (a standardized portion of the total stream) have also decreased dramatically for most Grande Ronde Basin streams from 1964-2002, dropping to as low as 37 redds in the 119.5 km in the index

Geology of Santa Rita Coal Basin, Rio Grande do Sul, Brazil

Energy Technology Data Exchange (ETDEWEB)

Correa da Silva, Z.C.; Bortoluzzi, C.A.; Cazzulo-Klepzig, M.; Dias-Fabricio, M.E.; Guerra-Sommer, M.; Marques-Toigo, M.; Paim, P.S.G.; Piccoli, A.E.M.; Silva Filho, B.C.

1984-04-01

Data on the sedimentology, stratigraphy, palynology, coal petrography and geochemistry of the Santa Rita Coal Basin, Rio Grande do Sul, Brazil, are presented. The investigations were carried out on samples obtained from drill cores of the sedimentary rocks of Tubarao Supergroup, Lower Permian of Parana Basin. (25 refs.)

Mid-Continent Rift: Rift, LIP, or Both?

Science.gov (United States)

Stein, C. A.; Stein, S. A.; Kley, J.; Hindle, D.; Keller, G. R., Jr.

2014-12-01

North America's Midcontinent Rift (MCR) is traditionally considered to have formed by midplate extension and volcanism ~1.1 Ga that ended due to compression from the Grenville orogeny, the ~1.3 - ~0.98 Ga assembly of Amazonia (Precambrian northeast South America), Laurentia (Precambrian North America), and other continents into the supercontinent of Rodinia. We find that a more plausible scenario is that it formed as part of the rifting of Amazonia from Laurentia and became inactive once seafloor spreading was established. The MCR has aspects both of a continental rift - a segmented linear depression filled with sedimentary and igneous rocks - and a large igneous province (LIP). Comparison of areas and volumes for a range of continental LIPS shows that the MCR volcanic rocks are significantly thicker than the others. The MCR flood basalts have steeper dips and thicker overlying sediments than other continental flood basalts, and were deposited in a subsiding basin after most extension ended, indicating that they are better viewed as post-rift than syn-rift rocks. Hence we view the MCR as a LIP deposited in crust weakened by rifting, and thus first a rift and then a LIP.

Anatomy of a rift system: Triassic-Jurassic basins of eastern North America

Energy Technology Data Exchange (ETDEWEB)

Schlische, R.W. (Rutgers Univ., New Brunswick, NJ (United States)); Olsen, P.E. (Columbia Univ., Palisades, NY (United States))

1991-03-01

Basins containing the early Mesozoic Newark Supergroup formed during the incipient rifting of Pangaea. The basins are characterized by the following: (1) The border fault systems (BFS) represent reactivated older faults. (2) A regionally persistent northwest-southeast to west-northeast-east-southeast extension direction reactivated northeast- to north-striking structures as predominantly normal dip-slip faults. (3) The half-grabens are lozenge-shaped basins in which subsidence-fault slip was greatest at or near the center of the BFS and decreased to zero toward either end. (4) Transverse folds in the hanging walls immediately adjacent to the BFS formed as a result of higher-frequency variations in subsidence. (5) Subsidence also decreased in a direction perpendicular to the BFS. (6) Intrabasinal faults are overwhelmingly synthetic and predominantly post-depositional. (7) Younger strata progressively onlap prerift rocks of the hanging wall block; this indicates that the basins grew both in width and length as they filled. (8) In all basins initial sedimentation was fluvial, reflecting an oversupply of sediment with respect to basin capacity. (9) Sediments were derived largely from the hanging wall block, which sloped toward the basin, and from streams that entered the basin axially; a direct footwall source was minor, owing to footwall uplift. (10) In strike-slip-dominated basins, subsidence was considerably less than in dip-slip basins, and mosaics of strike- and dip-slip faults are common.

Neoproterozoic stratigraphic framework of the Tarim Craton in NW China: Implications for rift evolution

Science.gov (United States)

Wu, Lin; Guan, Shuwei; Zhang, Shuichang; Yang, Haijun; Jin, Jiuqiang; Zhang, Xiaodan; Zhang, Chunyu

2018-06-01

The Tarim Craton is overlain by thick Neoproterozoic sedimentary successions in rift tectonic setting. This study examines the latest outcrop, seismic, and drilling core data with the objective of investigating the regional stratigraphy to deeply recognize the evolution of rifting in the craton. Cryogenian to Lower Ediacaran successions are mainly composed of clastic rocks with thicknesses of 2000-3000 m, and the Upper Ediacaran successions are composed of carbonate rocks with thicknesses of 500-800 m. The rift basins and stratigraphic zones are divided into northern and southern parts by a central paleo-uplift. The northern rift basin extends through the northern Tarim Craton in an E-W direction with two depocenters (Aksu and Kuruktag). The southern rift basin is oriented NE-SW. There are three or four phases of tillites in the northern zone, while there are two in the southern zone. Given the north-south difference of the stratigraphic framework, the northern rift basin initiated at ca. 740 Ma and the southern rift basin initiated at ca. 780 Ma. During the Cryogenian and Ediacaran, the northern and southern rift basins were separated by the central paleo-uplift, finally connecting with each other in the early Cambrian. Tectonic deformation in the Late Ediacaran led to the formation of a parallel unconformity in the rift basins and an angular unconformity in the central paleo-uplift. The Neoproterozoic rift basins continued to affect the distribution of Lower Cambrian hydrocarbon source rocks. The north-south distribution and evolution of the rift basins in the Tarim Craton have implications for reconstructions of the Rodinia supercontinent.

Generation of continental rifts, basins, and swells by lithosphere instabilities

Science.gov (United States)

Fourel, Loïc.; Milelli, Laura; Jaupart, Claude; Limare, Angela

2013-06-01

Continents may be affected simultaneously by rifting, uplift, volcanic activity, and basin formation in several different locations, suggesting a common driving mechanism that is intrinsic to continents. We describe a new type of convective instability at the base of the lithosphere that leads to a remarkable spatial pattern at the scale of an entire continent. We carried out fluid mechanics laboratory experiments on buoyant blocks of finite size that became unstable due to cooling from above. Dynamical behavior depends on three dimensionless numbers, a Rayleigh number for the unstable block, a buoyancy number that scales the intrinsic density contrast to the thermal one, and the aspect ratio of the block. Within the block, instability develops in two different ways in an outer annulus and in an interior region. In the outer annulus, upwellings and downwellings take the form of periodically spaced radial spokes. The interior region hosts the more familiar convective pattern of polygonal cells. In geological conditions, such instabilities should manifest themselves as linear rifts striking at a right angle to the continent-ocean boundary and an array of domal uplifts, volcanic swells, and basins in the continental interior. Simple scaling laws for the dimensions and spacings of the convective structures are derived. For the subcontinental lithospheric mantle, these dimensions take values in the 500-1000 km range, close to geological examples. The large intrinsic buoyancy of Archean lithospheric roots prevents this type of instability, which explains why the widespread volcanic activity that currently affects Western Africa is confined to post-Archean domains.

The effect of tectonic evolution on lacustrine syn-rift sediment patters in Qikou Sag, Bohaiwan Basin, eastern China

Science.gov (United States)

Liao, Y.; Wang, H.; Xu, W.

2013-12-01

Normal fault arrays and associated relay ramps between two overlapping en-echelon normal faults are well known to control the deposition and distribution of sediments in alluvial, fluvial and deltaic systems in rift settings. The influence of transfer zones or relay ramps on sediment routes and dispersal patterns in subaqueous (deeper marine/lacustrine), however, is barely studied and hence less clear. Previous experimental studies indicate that subaqueous relay ramps may act as sediment transportation pathways if certain conditions are available. In this study, we integrate detailed structural and stratigraphic analysis with three-dimensional seismic data and limited well log data from the Qikou Sag to examine the tectonic evolution and the syn-rift sediment patterns response to fault growth and linkage in an active rift setting. Qikou Sag is located at the center of Huanghua Depression, Bohaiwan Basin of eastern China. Structurally, it is a typical continental rift basin characterized by a linked system of two NEE-SWW-striking half-grabens and one E-W-striking graben. Qikou sag is filled with Eocene-Oligocene syn-rift sediments and Miocene to Quaternary post-rift sediments. The Eocene-Oligocene rifting stage can be divided into early rifting period (43-36.5 Ma, the third member and second member of Shahejie Formation, Es3 and Es2), stable rifting period (36.5-29Ma, the first member of Shaehejie Formation, Es1) and fault-depressed diversionary period (29-24.6Ma, the Dongying Formation, Ed). This study focus on the early syn-rift, the third and second member of Shehejie Formation, which is mostly dark-grey mudstone interbedded with fine to coarse-grained sandstone deposited by large-scale turbidity currents in deep-lake. In particular, we use a combination of thickness variability and facies distributions, onlap patterns within a high-resolution sequence stratigraphic framework, integrated with structural geometry, fault activity and subsidence history analysis to

Quantifying the Forcing Factors Responsible for the Tectono-Geomorphological Evolution of Neogene Rift Basins, Baja California

Science.gov (United States)

El-Sobky, H. F.; Dorobek, S. L.

2005-12-01

The Gulf of California and its surrounding land areas provide a classic example of recently rifted continental lithosphere, where back-arc stretching of a continental volcanic arc has culminated in the ongoing seafloor spreading that characterizes the present-day axis of the gulf. The recent tectonic history of eastern Baja California, which includes most of the land area eastward of the main drainage divide that extends north-south along the length of the peninsula, has been dominated by oblique rifting that began at about 5 Ma. Thus, extensional tectonics, bedrock lithology, long-term climatic changes, and evolving surface processes have controlled the tectono-geomorphological evolution of the eastern part of the peninsula since 5 Ma. No previous studies, however, examined the effect of these combined factors on the current tectono-geomorphological characteristics of eastern Baja California. We assume that although long-term climate may have changed along the peninsula over the last several million years, precipitation amounts are likely to have changed in a similar way along the entire length of the peninsula, regardless of the long-term climatic trend. This suggests that climatic variation can be largely ruled out as an explanation for the geomorphologic variability between basins. In an attempt to quantify the factors that affected the geomorphologic development along the eastern side of Baja California, thirty-four drainage basins were extracted from a 15-m-resolution absolute digital elevation model (DEM). The stacked-vector method was applied to utilize the different terrain attributes (e.g., hillshaded relief, aspect, slope, etc.) for supervised classification of bedrock lithologies using object-oriented techniques. Stream-length gradient indices were then measured for the main stream in each of the basins. Bedrock lithologies and alluvium were plotted along the stream profiles to identify any relationship between lithology, structure, and stream gradient

78 FR 16569 - Iowa Pacific Holdings, LLC, Permian Basin Railways, and San Luis & Rio Grande Railroad-Corporate...

Science.gov (United States)

2013-03-15

... DEPARTMENT OF TRANSPORTATION Surface Transportation Board [Docket No. FD 35721] Iowa Pacific Holdings, LLC, Permian Basin Railways, and San Luis & Rio Grande Railroad--Corporate Family Transaction... subsidiaries Permian Basin Railways (PBR) and San Luis & Rio Grande Railroad (SLRG), and Massachusetts Coastal...

Simulations of Precipitation Variability over the Upper Rio Grande Basin

International Nuclear Information System (INIS)

Costigan, Keeley R.; Bossert, James E.; Langley, David L.

1997-10-01

In this research, we study Albuquerque's water and how it may be affected by changes in the regional climate, as manifested by variations in Rio Grande water levels. To do this, we rely on the use of coupled atmospheric, runoff, and ground water models. Preliminary work on the project has focused on uncoupled simulations of the aquifer beneath Albuquerque and winter precipitation simulations of the upper Rio Grande Basin. The latter is discussed in this paper

Record of a Statherian rift-sag basin in the Central Espinhaço Range: Facies characterization and geochronology

Science.gov (United States)

Costa, Alice Fernanda de Oliveira; Danderfer, André; Bersan, Samuel Moreira

2018-03-01

Several rift-related sequences and volcanic-plutonic associations of Statherian age occur within the São Francisco block. One succession within the sedimentary record, the Terra Vermelha Group, defines one of the evolutionary stages of the Espinhaço basin in the Central Espinhaço Range. As a result of stratigraphic analyses and supported by U-Pb zircon geochronological data, the evolution of this unit has been characterized. To more effectively delimit its upper depositional interval, the sequence of this unit, which is represented by the Pau d'Arco Formation, was also studied. The sedimentary signature of the Terra Vermelha Group suggests the infilling of an intracontinental rift associated with alluvial fans as well as lacustrine and eolian environments with associated volcanism. The basal succession represented by the Cavoada do Buraco Formation mainly consists of conglomerates with interlayered sandstones and subordinate banded iron formations. Detrital zircon obtained from this unit reveals ages of 1710 ± 21 Ma. The upper succession, represented by the Espigão Formation, records aeolian sandstones with volcanic activity at the top. A volcanic rock dated at 1758 ± 4 Ma was interpreted as the timing of volcanism in this basin. The eolian deposits recorded within the Pau d'Arco Formation were caused by a renewal of the sequence, which represent a stage of post-rift thermal subsidence. The maximum age of sedimentation for this unit is 1675 ± 22 Ma. The basin-infill patterns and Statherian ages suggest a direct link with the first rifting event within the São Francisco block, which was responsible for the deposition of the Espinhaço Supergroup.

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

Change in tectonic force inferred from basin subsidence: Implications for the dynamical aspects of back-arc rifting in the western Mediterranean

NARCIS (Netherlands)

Yamasaki, T.; Stephenson, R.A.

2009-01-01

A method has been developed that allows temporal changes in tectonic force during rift basin formation to be inferred from observed tectonic subsidence curves and has been applied to the Gulf of Lions (the Provençal Basin) and the Valencia Trough in order to gain some understanding of the dynamical

Grande Ronde Basin Fish Habitat Enhancement Project : 2000 Annual Report.

Energy Technology Data Exchange (ETDEWEB)

McGowan, Vance R.; Powell, Russ M.; Stennfeld, Scott P.

2001-04-01

On July 1, 1984 the Bonneville Power Administration and the Oregon Department of Fish and Wildlife entered into an agreement to initiate fish habitat enhancement work in the Joseph Creek subbasin of the Grande Ronde River Basin in northeast Oregon. In July of 1985 the Upper and Middle Grande Ronde River, and Catherine Creek subbasins were included in the intergovernmental contract, and on March 1, 1996 the Wallowa River subbasin was added. The primary goal of ''The Grande Ronde Basin Fish Habitat Enhancement Project'' is to access, create, improve, protect, and restore riparian and instream habitat for anadromous salmonids, thereby maximizing opportunities for natural fish production within the basin. This project provided for implementation of Program Measure 703 (C)(1), Action Item 4.2 of the Northwest Power Planning Council's Columbia River Basin Fish and Wildlife Program (NPPC, 1987), and continues to be implemented as offsite mitigation for mainstem fishery losses caused by the Columbia River hydro-electric system. All work conducted by the Oregon Department of Fish and Wildlife is on private lands and therefore requires that considerable time be spent developing rapport with landowners to gain acceptance of, and continued cooperation with this program throughout 10-15 year lease periods. This project calls for passive regeneration of habitat, using riparian enclosure fencing as the primary method to restore degraded streams to a normative condition. Active remediation techniques using plantings, off-site water developments, site-specific instream structures, or whole channel alterations are also utilized where applicable. Individual projects contribute to and complement ecosystem and basin-wide watershed restoration efforts that are underway by state, federal, and tribal agencies, and local watershed councils. Work undertaken during 2000 included: (1) Implementing 2 new projects in the Grande Ronde drainage, and retrofitting one old

Orogenic structural inheritance and rifted passive margin formation

Science.gov (United States)

Salazar Mora, Claudio A.; Huismans, Ritske S.

2016-04-01

Structural inheritance is related to mechanical weaknesses in the lithosphere due to previous tectonic events, e.g. rifting, subduction and collision. The North and South Atlantic rifted passive margins that formed during the breakup of Western Gondwana, are parallel to the older Caledonide and the Brasiliano-Pan-African orogenic belts. In the South Atlantic, 'old' mantle lithospheric fabric resulting from crystallographic preferred orientation of olivine is suggested to play a role during rifted margin formation (Tommasi and Vauchez, 2001). Magnetometric and gravimetric mapping of onshore structures in the Camamu and Almada basins suggest that extensional faults are controlled by two different directions of inherited older Brasiliano structures in the upper lithosphere (Ferreira et al., 2009). In the South Atlantic Campos Basin, 3D seismic data indicate that inherited basement structures provide a first order control on basin structure (Fetter, 2009). Here we investigate the role of structural inheritance on the formation of rifted passive margins with high-resolution 2D thermo-mechanical numerical experiments. The numerical domain is 1200 km long and 600 km deep and represents the lithosphere and the sublithospheric mantle. Model experiments were carried out by creating self-consistent orogenic inheritance where a first phase of orogen formation is followed by extension. We focus in particular on the role of varying amount of orogenic shortening, crustal rheology, contrasting styles of orogen formation on rifted margin style, and the time delay between orogeny and subsequent rifted passive formation. Model results are compared to contrasting structural styles of rifted passive margin formation as observed in the South Atlantic. Ferreira, T.S., Caixeta, J.M., Lima, F.D., 2009. Basement control in Camamu and Almada rift basins. Boletim de Geociências da Petrobrás 17, 69-88. Fetter, M., 2009. The role of basement tectonic reactivation on the structural evolution

Metallogeny of the Paramillos de Uspallata Pb-Zn-Ag vein deposit in the Cuyo Rift Basin, Argentina

Science.gov (United States)

Rubinstein, Nora A.; Carrasquero, Silvia I.; Gómez, Anabel L. R.; Ricchetti, Ana P. Orellano; D'Annunzio, María C.

2018-05-01

The Paramillos de Uspallata deposit, previously considered as genetically linked to a Miocene porphyry deposit, is located in the Mesozoic Cuyo Basin, which was formed during the beginning of the break-up of Gondwana. In the present study, both previous information and new geological, mineralogical, and isotopic data allowed outlining a new descriptive model for this deposit. Stratigraphic and structural controls allowed considering this deposit as contemporaneous with the Mesozoic rifting, with the mineralization resulting from a Pb-Zn stage followed by an Ag-Cu-Pb stage. The hydrothermal fluids were found to have low temperature and low to moderate salinity, and to result from the mixing between metamorphic and meteoric fluids, with the lead sourced by the igneous Paleozoic basement and the sulfur partly derived from a magmatic source. These characteristics allow describing Paramillos de Uspallata as Pb-Zn-Ag veins hosted in clastic sedimentary sequences genetically linked to a rift basin and redefining it as detachment-related mineralization.

The Lower Triassic Sorkh Shale Formation of the Tabas Block, east central Iran: Succesion of a failed-rift basin at the Paleotethys margin

Science.gov (United States)

Lasemi, Y.; Ghomashi, M.; Amin-Rasouli, H.; Kheradmand, A.

2008-01-01

The Lower Triassic Sorkh Shale Formation is a dominantly red colored marginal marine succession deposited in the north-south trending Tabas Basin of east central Iran. It is correlated with the unconformity-bounded lower limestone member of the Elika Formation of the Alborz Mountains of northern Iran. The Sorkh Shale is bounded by the pre-Triassic and post-Lower Triassic interregional unconformities and consists mainly of carbonates, sandstones, and evaporites with shale being a minor constituent. Detailed facies analysis of the Sorkh Shale Formation resulted in recognition of several genetically linked peritidal facies that are grouped into restricted subtidal, carbonate tidal flat, siliciclastic tidal flat, coastal plain and continental evaporite facies associations. These were deposited in a low energy, storm-dominated inner-ramp setting with a very gentle slope that fringed the Tabas Block of east central Iran and passed northward (present-day coordinates) into deeper water facies of the Paleotethys passive margin of northern Cimmerian Continent. Numerous carbonate storm beds containing well-rounded intraclasts, ooids and bioclasts of mixed fauna are present in the Sorkh Shale Formation of the northern Tabas Basin. The constituents of the storm beds are absent in the fair weather peritidal facies of the Sorkh Shale Formation, but are present throughout the lower limestone member of the Elika Formation. The Tabas Block, a part of the Cimmerian continent in east central Iran, is a rift basin that developed during Early Ordovician-Silurian Paleotethys rifting. Facies and sequence stratigraphic analyses of the Sorkh Shale Formation has revealed additional evidence supporting the Tabas Block as a failed rift basin related to the Paleotethys passive margin. Absence of constituents of the storm beds in the fair weather peritidal facies of the Sorkh Shale Formation, presence of the constituents of the storm beds in the fair weather facies of the Elika Formation (the

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.

Subsidence transition during the post-rift stage of the Dongpu Sag, Bohai Bay Basin, NE China: A new geodynamic model

Science.gov (United States)

Xu, Han; Wang, Xin-Wen; Yan, Dan-Ping; Qiu, Liang

2018-06-01

The Dongpu Sag, located in the Bohai Bay Basin, NE China, is a Cenozoic continental rift basin. The post-rift evolution of the Dongpu Sag is associated with the development of petroleum reservoirs and has implications for Neogene-Quaternary basin evolution along the eastern margin of Eurasia. To determine the nature and origin of post-rift subsidence in the Dongpu Sag, we apply backstripping, modified strain-rate inversion, and revised finite extension modelling techniques, using data from 14 real and synthetic wells that are intersected by three seismic lines. Our results reveal discrepancies by subsidence based on backstripping of well data (the observed subsidence) minus that predicted by modified strain-rate inversion and revised finite extension modelling (the predicted subsidence). During the Miocene, the observed subsidence was smaller than the predicted subsidence, leaving negative discrepancies referred to here as "insufficient subsidence" ranging from -343 to -96 m. In contrast, during the Pliocene-Quaternary the observed subsidence was greater than the predicted subsidence by +123 to +407 m, which left positive discrepancies referred to as "over-sufficient subsidence". Therefore, we infer a transition from insufficient to over-sufficient subsidence during the post-rift stage. Normal faulting that started at ca. 5.3 Ma is estimated to have produced only ∼20% of the over-sufficient subsidence. Therefore, the remaining over-sufficient subsidence, as well as the preceding insufficient subsidence and the transition between the two, were likely controlled by lithosphere processes. We propose a new tectonic model in which variations in the conditions (e.g. rate, direction, and angle) associated with subduction of the Pacific plate resulted in a change of heat flow decreasing from a linear to a curvilinear pattern, leading to a transition from insufficient to over-sufficient subsidence.

Ethiopian Central Rift Valley basin hydrologic modelling using HEC-HMS and ArcSWAT

Science.gov (United States)

Pascual-Ferrer, Jordi; Candela, Lucila; Pérez-Foguet, Agustí

2013-04-01

An Integrated Water Resources Management (IWRM) shall be applied to achieve a sustainable development, to increase population incomes without affecting lives of those who are highly dependent on the environment. First step should be to understand water dynamics at basin level, starting by modeling the basin water resources. For model implementation, a large number of data and parameters are required, but those are not always available, especially in some developing countries where different sources may have different data, there is lack of information on data collection, etc. The Ethiopian Central Rift Valley (CRV) is an endorheic basin covering an area of approximately 10,000 km2. For the period 1996-2005, the average annual volume of rainfall accounted for 9.1 Mm3, and evapotranspiration for 8 Mm3 (Jansen et al., 2007). From the environmental point of view, basin ecosystems are endangered due to human activities. Also, poverty is widespread all over the basin, with population mainly living from agriculture on a subsistence economy. Hence, there is an urgent need to set an IWRM, but datasets required for water dynamics simulation are not too reliable. In order to reduce uncertainty of numerical simulation, two semi-distributed open software hydrologic models were implemented: HEC-HMS and ArcSWAT. HEC-HMS was developed by the United States Army Corps of Engineers (USACoE) Hydrologic Engineering Center (HEC) to run precipitation-runoff simulations for a variety of applications in dendritic watershed systems. ArcSWAT includes the SWAT (Soil and Water Assessment Tool, Arnold et al., 1998) model developed for the USDA Agricultural Research Service into ArcGIS (ESRI®). SWAT was developed to assess the impact of land management practices on large complex watersheds with varying soils, land use and management conditions over long periods of time (Neitsch et al., 2005). According to this, ArcSWAT would be the best option for IWRM implementation in the basin. However

Tectonic inheritance and continental rift architecture: Numerical and analogue models of the East African Rift System.

NARCIS (Netherlands)

Corti, G.; van Wijk, J.W.; Cloetingh, S.A.P.L.; Morley, C.

2007-01-01

The western branch of the East African Rift is composed of an arcuate succession of elongate asymmetric basins, which differ in terms of interaction geometry, fault architecture and kinematics, and patterns of uplift/subsidence and erosion/sedimentation. The basins are located within Proterozoic

Tectonic inheritance in the development of the Kivu - north Tanganyika rift segment of the East African Rift System: role of pre-existing structures of Precambrian to early Palaeozoic origin.

Science.gov (United States)

Delvaux, Damien; Fiama Bondo, Silvanos; Ganza Bamulezi, Gloire

2017-04-01

The present architecture of the junction between the Kivu rift basin and the north Tanganyika rift basin is that of a typical accommodation zone trough the Ruzizi depression. However, this structure appeared only late in the development of the Western branch of the East African Rift System and is the result of a strong control by pre-existing structures of Precambrian to early Palaeozoic origin. In the frame of a seismic hazard assessment of the Kivu rift region, we (Delvaux et al., 2016) constructed homogeneous geological, structural and neotectonic maps cross the five countries of this region, mapped the pre-rift, early rift and Late Quaternary faults and compiled the existing knowledge on thermal springs (assumed to be diagnostic of current tectonic activity along faults). We also produced also a new catalogue of historical and instrumental seismicity and defined the seismotectonic characteristics (stress field, depth of faulting) using published focal mechanism data. Rifting in this region started at about 11 Ma by initial doming and extensive fissural basaltic volcanism along normal faults sub-parallel to the axis of the future rift valley, as a consequence of the divergence between the Nubia and the Victoria plate. In a later stage, starting around 8-7 Ma, extension localized along a series of major border faults individualizing the subsiding tectonic basins from the uplifting rift shoulders, while lava evolved towards alkali basaltic composition until 2.6 Ma. During this stage, initial Kivu rift valley was extending linearly in a SSW direction, much further than its the actual termination at Bukavu, into the Mwenga-Kamituga graben, up to Namoya. The SW extremity of this graben was linked via a long oblique transfer zone to the central part of Lake Tanganyika, itself reactivating an older ductile-brittle shear zone. In the late Quaternary-early Holocene, volcanism migrated towards the center of the basin, with the development of the Virunga volcanic massif

Rift magmatism on the Eurasia basin margin: U–Pb baddeleyite ages of alkaline dyke swarms in North Greenland

DEFF Research Database (Denmark)

Thórarinsson, Sigurjón B.; Söderlund, Ulf; Døssing, Arne

2015-01-01

The opening of the Arctic Ocean involved multiple stages of continental rifting and intrusion of extensive dyke swarms. To trace tectonomagmatic processes of the High Arctic, we present the first U–Pb ages for alkaline dyke swarms of North Greenland. Concordia ages of 80.8 ± 0.6 and 82.1 ± 1.5 Ma...... indicate that north–south and east–west dykes are coeval. The north–south dykes reflect initial east–west rifting that led to break-up along the Gakkel Ridge and formation of the Eurasia Basin. The east–west dykes reflect local variations in the stress field associated with reactivated Palaeozoic faults...

Grande Ronde Basin Fish Habitat Enhancement Project : 2007 Annual Report.

Energy Technology Data Exchange (ETDEWEB)

McGowan, Vance R.; Morton, Winston H.

2008-12-30

On July 1, 1984 the Bonneville Power Administration and the Oregon Department of Fish and Wildlife entered into an intergovernmental contract to initiate fish habitat enhancement work in the Joseph Creek subbasin of the Grande Ronde River Basin in northeast Oregon. In 1985 the Upper and Middle Grande Ronde River, and Catherine Creek subbasins were included in the contract, and in 1996 the Wallowa River subbasin was added. The primary goal of 'The Grande Ronde Basin Fish Habitat Enhancement Project' is to create, protect, and restore riparian and instream habitat for anadromous salmonids, thereby maximizing opportunities for natural fish production within the basin. This project provided for implementation of Program Measure 703 (C)(1), Action Item 4.2 of the Northwest Power Planning Council's Columbia River Basin Fish and Wildlife Program (NPPC, 1987), and continues to be implemented as offsite mitigation for mainstem fishery losses caused by the Columbia River hydro-electric system. All work conducted by the Oregon Department of Fish and Wildlife and partners is on private lands and therefore requires that considerable time be spent developing rapport with landowners to gain acceptance of, and continued cooperation with this program throughout 10-15 year lease periods. Both passive and active restoration treatment techniques are used. Passive regeneration of habitat, using riparian exclosure fencing and alternate water sources are the primary method to restore degraded streams when restoration can be achieved primarily through changes in management. Active restoration techniques using plantings, bioengineering, site-specific instream structures, or whole stream channel alterations are utilized when streams are more severely degraded and not likely to recover in a reasonable timeframe. Individual projects contribute to and complement ecosystem and basin-wide watershed restoration efforts that are underway by state, federal, and tribal agencies, and

Comparative Riftology: Insights into the Evolution of Passive Continental Margins and Continental Rifts from the Failed Midcontinent Rift (MCR)

Science.gov (United States)

Elling, R. P.; Stein, C. A.; Stein, S.; Kley, J.; Keller, G. R.; Wysession, M. E.

2017-12-01

Continental rifts evolve to seafloor spreading and are preserved in passive margins, or fail and remain as fossil features in continents. Rifts at different stages give insight into these evolutionary paths. Of particular interest is the evolution of volcanic passive margins, which are characterized by seaward dipping reflectors, volcanic rocks yielding magnetic anomalies landward of the oldest spreading anomalies, and are underlain by high-velocity lower crustal bodies. How and when these features form remains unclear. Insights are given by the Midcontinent Rift (MCR), which began to form during the 1.1 Ga rifting of Amazonia from Laurentia, but failed when seafloor spreading was established elsewhere. MCR volcanics are much thicker than other continental flood basalts, due to deposition in a narrow rift rather than a broad region, giving a rift's geometry but a LIP's magma volume. The MCR provides a snapshot of the deposition of a thick and highly magnetized volcanic section during rifting. Surface exposures and reflection seismic data near Lake Superior show a rift basin filled by inward-dipping flood basalt layers. Had the rift evolved to seafloor spreading, the basin would have split into two sets of volcanics with opposite-facing SDRs, each with a magnetic anomaly. Because the rift formed as a series of alternating half-grabens, structural asymmetries between conjugate margins would have naturally occurred had it gone to completion. Hence the MCR implies that many passive margin features form prior to seafloor spreading. Massive inversion of the MCR long after it failed has provided a much clearer picture of its structure compared to failed rifts with lesser degrees of inversion. Seismic imaging as well as gravity and magnetic modeling provide important insight into the effects of inversion on failed rifts. The MCR provides an end member for the evolution of actively extending rifts, characterized by upwelling mantle and negative gravity anomalies, to failed

Sedimentology and paleoenvironments of a new fossiliferous late Miocene-Pliocene sedimentary succession in the Rukwa Rift Basin, Tanzania

Science.gov (United States)

Mtelela, Cassy; Roberts, Eric M.; Hilbert-Wolf, Hannah L.; Downie, Robert; Hendrix, Marc S.; O'Connor, Patrick M.; Stevens, Nancy J.

2017-05-01

This paper presents a detailed sedimentologic investigation of a newly identified, fossiliferous Late Neogene sedimentary succession in the Rukwa Rift Basin, southwestern Tanzania. This synrift deposit is a rare and significant new example of a fossiliferous succession of this age in the Western Branch of East Africa Rift System. The unit, informally termed the lower Lake Beds succession, is late Miocene to Pliocene in age based on cross-cutting relationships, preliminary biostratigraphy, and U-Pb geochronology. An angular unconformity separates the lower Lake Beds from underlying Cretaceous and Oligocene strata. Deposition was controlled by rapid generation of accommodation space and increased sediment supply associated with late Cenozoic tectonic reactivation of the Rukwa Rift and synchronous initiation of the Rungwe Volcanic Centre. The lower Lake Beds, which have thus far only been identified in three localities throughout the Rukwa Rift Basin, are characterized by two discrete lithologic members (herein A and B). The lower Member A is a volcanic-rich succession composed mostly of devitrified volcanic tuffs, and volcaniclastic mudstones and sandstones with minor conglomerates. The upper Member B is a siliciclastic-dominated succession of conglomerates, sandstones, mudstones and minor volcanic tuffs. Detailed facies analysis of the lower Lake Beds reveals various distinctive depositional environments that can be grouped into three categories: 1) alluvial fan; 2) fluvial channel; and 3) flood basin environments, characterized by volcanoclastic-filled lakes and ponds, abandoned channel-fills and pedogenically modified floodplains. Member A represents a shallow lacustrine setting filled by tuffaceous sediments, which grade up into a system of alluvial fans and high-energy, proximal gravel-bed braided rivers. An unconformity marks the contact between the two members. Member B shows an upward transition from a high-energy, gravel-bed braided river system to a sandy

Magnetostratigraphy of the Grande Ronde Basalt Pasco Basin, Washington

International Nuclear Information System (INIS)

Packer, D.R.; Petty, M.H.

1979-01-01

The paleomagnetic measurements of samples from the holes sampled have shown that there are four magnetic correlation lines, between adjacent flows in holes that have distinctly different mean stratigraphic inclinations, and two magnetic polarity boundaries that can be used for magnetic correlation in the Grande Ronde Basalt in the Pasco Basin. The results of paleomagnetic measurements of samples from the Wanapum Basalt and Saddle Mountains Basalt indicate that the potential for magnetostratigraphic correlation in these sequences is also good

Tectonic setting and uplift analysis of the Pangani rift basin in northern Tanzania using apatite fission track thermochronology

International Nuclear Information System (INIS)

Mbede, E.I.

2001-01-01

Thirty four new Apatite Fission Track (AFT) ages and 32 track length distributions from samples of basement rocks flanking the Pangani rift, East African Rift System (EARS) are presented, in an attempt to elucidate the uplift and erosion of the rift flanks. The ages fall in the range of 207±15 to 48±4 Ma, spanning from Early Jurassic to Early Tertiary. These ages are much younger than the last thermal event in the Mozambique belt that form the basement complex and are interpreted to represent the most recent tectonic events. Track length (TL) distributions suggest that uplift and erosion of the rift flanks are related to three different tectonic events, which are also recorded by the sedimentary units within the adjacent coastal basins. These included the Triassic/Early Jurassic, Late Cretaceous and Early Tertiary tectonic events. Erosion and isostatic rebound have modified the tectonically induced topographic patterns and the highly elevated plateaus flanking the Pangani rift represent an erosional surface referred to as the 'Gondwana surface' of eastern and central Africa. T he present AFT data suggest that initial exhumation of the 'Gondwana surface' from temperatures above 383.15 K to temperatures less than 333.15 K, in this area, took place during Early Jurassic times, but the final sub-aerial exposure of the surface did not take place until Early Tertiary. (author)

Correlation of Plio Pleistocene Tephra in Ethiopian and Kenyan rift basins: Temporal calibration of geological features and hominid fossil records

Science.gov (United States)

WoldeGabriel, Giday; Hart, William K.; Katoh, Shigehiro; Beyene, Yonas; Suwa, Gen

2005-10-01

The 200-m-thick fossiliferous Konso Formation and overlying terrace deposits, which crop out at the end of the southern sector of the Main Ethiopian Rift (MER), contain more than 30 distal tephra layers. Local and regional tephra correlations of more than 20 tephra units were established using major and trace element data of discrete and purified bulk glass samples within the Konso study area. Eleven correlative marker tuffs were recognized in stratigraphic sections of both the Konso Formation and the Omo-Turkana Basin sediments in southern Ethiopia and northern Kenya. The Turoha, Hope, Ivory, Bright White, and Boleshe Tuffs in the Konso Formation, and the Upper White Tuff in the overlying terrace deposits are securely correlated with the KBS, Akait, Lokapetamoi, Chari, Lower Nariokotome, and Silbo Tuffs of the Omo-Turkana Basin, using least mobile major elements (CaO, Fe 2O 3*, and TiO 2) and geochronology. Preliminary correlations are also suggested between the Konso Formation distal tephra and proximal units of the Quaternary caldera-forming silicic centers in the central sector of the MER. The strongly peralkaline tuffs of the Konso Formation are compositionally similar to proximal eruptions mostly located along the Quaternary axial rift zone of the southern, central, and northern sectors of the MER. The tephra correlation provides information about the temporal and spatial features of the volcanic and tectonic processes recorded in the evolving basins. Thickness and sedimentation rate were determined for both the Konso Formation and the Omo-Turkana Basin sections, measured between the Turoha (=KBS; 1.91 ± 0.03 Ma) and the Bright White (=Chari; 1.40 ± 0.02 Ma) Tuffs. Although the lithostratigraphic sequence at the Konso study area is younger, sedimentation rate within the Konso Formation was comparable to that of the Koobi Fora Formation, higher in the Nachukui Formation, and lower in the Shungura Formation. Local and regional differences in thickness and

Grande Ronde Basin Fish Habitat Enhancement Project, Annual Report 2002-2003.

Energy Technology Data Exchange (ETDEWEB)

McGowan, Vance

2003-08-01

On July 1, 1984 the Bonneville Power Administration and the Oregon Department of Fish and Wildlife entered into an agreement to initiate fish habitat enhancement work in the Joseph Creek subbasin of the Grande Ronde River Basin in northeast Oregon. In July of 1985 the Upper and Middle Grande Ronde River, and Catherine Creek subbasins were included in the intergovernmental contract, and on March 1, 1996 the Wallowa River subbasin was added. The primary goal of 'The Grande Ronde Basin Fish Habitat Enhancement Project' is to create, protect, and restore riparian and instream habitat for anadromous salmonids, thereby maximizing opportunities for natural fish production within the basin. This project provided for implementation of Program Measure 703 (C)(1), Action Item 4.2 of the Northwest Power Planning Council's Columbia River Basin Fish and Wildlife Program (NPPC, 1987), and continues to be implemented as offsite mitigation for mainstem fishery losses caused by the Columbia River hydro-electric system. All work conducted by the Oregon Department of Fish and Wildlife is on private lands and therefore requires that considerable time be spent developing rapport with landowners to gain acceptance of, and continued cooperation with this program throughout 10-15 year lease periods. This project calls for passive regeneration of habitat, using riparian exclosure fencing as the primary method to restore degraded streams to a normative condition. Active remediation techniques using plantings, off-site water developments, site-specific instream structures, or whole channel alterations are also utilized where applicable. Individual projects contribute to and complement ecosystem and basin-wide watershed restoration efforts that are underway by state, federal, and tribal agencies, and local watershed councils. Work undertaken during 2002 included: (1) Implementing 1 new fencing project in the Wallowa subbasin that will protect an additional 0.95 miles of stream

Escape tectonism in the Gulf of Thailand: Paleogene left-lateral pull-apart rifting in the Vietnamese part of the Malay Basin

DEFF Research Database (Denmark)

Fyhn, Michael B.W.; Boldreel, Lars Ole; Nielsen, Lars H

2010-01-01

The Malay Basin represents one of the largest rift basins of SE Asia. Based on a comprehensive 2-D seismic database tied to wells covering mainly Vietnamese acreage, the evolution of the Vietnamese part of the basin is outlined and a new tectonic model is proposed for the development of the basin....... The Vietnamese part of the Malay Basin comprises a large and deep Paleogene pull-apart basin formed through Middle or Late Eocene to Oligocene left-lateral strike-slip along NNW-trending fault zones. The Tho Chu Fault Zone constitutes a significant Paleogene left-lateral strike-slip zone most likely associated......–Strending faults in the central part of the basin. However, the lack of inversion in Vietnamese territory only seems to merit a few kilometers of dextral inversion....

The Role of Rift Obliquity in Formation of the Gulf of California

Science.gov (United States)

Bennett, Scott Edmund Kelsey

The Gulf of California illustrates how highly oblique rift geometries, where transform faults are kinematically linked to large-offset normal faults in adjacent pull-apart basins, enhance the ability of continental lithosphere to rupture and, ultimately, hasten the formation of new oceanic basins. The Gulf of California rift has accommodated oblique divergence of the Pacific and North America tectonic plates in northwestern Mexico since Miocene time. Due to its infancy, the rifted margins of the Gulf of California preserve a rare onshore record of early continental break-up processes from which to investigate the role of rift obliquity in strain localization. Using new high-precision paleomagnetic vectors from tectonically stable sites in north-central Baja California, I compile a paleomagnetic transect of Miocene ignimbrites across northern Baja California and Sonora that reveals the timing and distribution of dextral shear associated with inception of this oblique rift. I integrate detailed geologic mapping, basin analysis, and geochronology of pre-rift and syn-rift volcanic units to determine the timing of fault activity on Isla Tiburon, a proximal onshore exposure of the rifted North America margin, adjacent to the axis of the Gulf of California. The onset of strike-slip faulting on Isla Tiburon, ca. 8 - 7 Ma, was synchronous with the onset of transform faulting along a significant length of the nascent plate boundary within the rift. This tectonic transition coincides with a clockwise azimuthal shift in Pacific-North America relative motion that increased rift obliquity. I constrain the earliest marine conditions on southwest Isla Tiburon to ca. 6.4 - 6.0 Ma, coincident with a regional latest Miocene marine incursion in the northern proto-Gulf of California. This event likely flooded a narrow, incipient topographic depression along a ˜650 km-long portion of the latest Miocene plate boundary and corresponds in time and space with formation of a newly

Sedimentology and Reservoir Characteristics of Early Cretaceous Fluvio-Deltaic and Lacustrine Deposits, Upper Abu Gabra Formation, Sufyan Sub-basin, Muglad Rift Basin, Sudan

Science.gov (United States)

Yassin, Mohamed; Abdullatif, Osman; Hariri, Mustafa

2017-04-01

Sufyan Sub-basin is an East-West trending Sub-basin located in the northwestern part of the Muglad Basin (Sudan), in the eastern extension of the West and Central Africa Rift System (WCARS). The Early Cretaceous Abu Gabra Formation considered as the main source rock in the Muglad Basin. In Sufyan Sub-basin the Early Cretaceous Upper Abu Gabra Formation is the main oil-producing reservoir. It is dominated by sandstone and shales deposited in fluvio-deltaic and lacustrine environment during the first rift cycle in the basin. Depositional and post-depositional processes highly influenced the reservoir quality and architecture. This study investigates different scales of reservoir heterogeneities from macro to micro scale. Subsurface facies analysis was analyzed based on the description of six conventional cores from two wells. Approaches include well log analysis, thin sections and scanning electron microscope (SEM) investigations, grain-size, and X-ray diffraction (XRD) analysis of the Abu Gabra sandstone. The cores and well logs analyses revealed six lithofacies representing fluvio-deltaic and lacustrine depositional environment. The sandstone is medium to coarse-grained, poorly to moderately sorted and sub-angular to subrounded, Sub-feldspathic arenite to quartz arenite. On macro-scale, reservoir quality varies within Abu Gabra reservoir where it shows progressive coarsening upward tendencies with different degrees of connectivity. The upper part of the reservoir showed well connected and amalgamated sandstone bodies, the middle to lower parts, however, have moderate to low sandstone bodies' connectivity and amalgamation. On micro-scale, sandstone reservoir quality is directly affected by textures and diagenesis.The XRD and SEM analyses show that kaolinite and chlorite clay are the common clay minerals in the studied samples. Clay matrix and quartz overgrowth have significantly reduced the reservoir porosity and permeability, while the dissolution of feldspars

The East African rift system

Science.gov (United States)

Chorowicz, Jean

2005-10-01

This overview paper considers the East African rift system (EARS) as an intra-continental ridge system, comprising an axial rift. It describes the structural organization in three branches, the overall morphology, lithospheric cross-sections, the morphotectonics, the main tectonic features—with emphasis on the tension fractures—and volcanism in its relationships with the tectonics. The most characteristic features in the EARS are narrow elongate zones of thinned continental lithosphere related to asthenospheric intrusions in the upper mantle. This hidden part of the rift structure is expressed on the surface by thermal uplift of the rift shoulders. The graben valleys and basins are organized over a major failure in the lithospheric mantle, and in the crust comprise a major border fault, linked in depth to a low angle detachment fault, inducing asymmetric roll-over pattern, eventually accompanied by smaller normal faulting and tilted blocks. Considering the kinematics, divergent movements caused the continent to split along lines of preexisting lithospheric weaknesses marked by ancient tectonic patterns that focus the extensional strain. The hypothesis favored here is SE-ward relative divergent drifting of a not yet well individualized Somalian plate, a model in agreement with the existence of NW-striking transform and transfer zones. The East African rift system comprises a unique succession of graben basins linked and segmented by intracontinental transform, transfer and accommodation zones. In an attempt to make a point on the rift system evolution through time and space, it is clear that the role of plume impacts is determinant. The main phenomenon is formation of domes related to plume effect, weakening the lithosphere and, long after, failure inducing focused upper mantle thinning, asthenospheric intrusion and related thermal uplift of shoulders. The plume that had formed first at around 30 Ma was not in the Afar but likely in Lake Tana region (Ethiopia

Polyphased rifting to post-breakup evolution of the Coral Sea region, Papua New Guinea

Science.gov (United States)

Bulois, Cédric; Pubellier, Manuel; Chamot-Rooke, Nicolas; Delescluse, Matthias

2016-04-01

The Coral Sea Basin, offshore Papua New Guinea, is generally described as a rift propagator that opened through the Australian craton during the Late Cretaceous. Rifting was later followed by spreading activity during Palaeocene to lowermost Eocene times and basin inversion during the Cenozoic. Herein, we specifically describe the extensional structures and show that the area has actually a much longer history that dates back from the Late Palaeozoic. A special focus is made on the northern margin of the Coral Sea Basin along which subsurface and HD topographic data were recently acquired. Extension took place discontinuously from the Late Palaeozoic to the Lower Cenozoic through several rift megacycles that include extensional pulses and relaxation episodes. The first rift megacycle (R1), poorly documented, occurred during the Triassic along an old Permo-Triassic, NS-trending structural fabric. Evidence of Permo-Triassic features is principally observed in the western part of the Coral Sea near the Tasman Line, a major lithospheric discontinuity that marks the eastern limit of the underlying Australian craton in Papua New Guinea. This early Triassic framework was reactivated during a Jurassic rifting stage (R2), resulting in small (~10/20km) tilted basins bounded by major NS, NE-SW and EW normal faults. Extension formed a large basin, floored by oceanic crust that might have connected with the Tethys Ocean. The Owen Stanley Oceanic Basin containing deep-marine sediments now obducted in the Ocean Stanley Thrust Belt are likely to represent this oceanic terrane. Both R1 and R2 megacycles shaped the geometry of the Jurassic Australian margin. A third Cretaceous extensional megacycle (R3) only reactivated the largest faults, cutting through the midst of this early stretched continental margin. It formed wider, poorly tilted basins and terminated with the onset of the Coral Sea seafloor spreading from Danian to Ypresian times (61.8 to 53.4 Myr). Then, the overall

Lower Crustal Seismicity, Volatiles, and Evolving Strain Fields During the Initial Stages of Cratonic Rifting

Science.gov (United States)

Lambert, C.; Muirhead, J.; Ebinger, C. J.; Tiberi, C.; Roecker, S. W.; Ferdinand-Wambura, R.; Kianji, G.; Mulibo, G. D.

2014-12-01

The volcanically active East African rift system in southern Kenya and northern Tanzania transects thick cratonic lithosphere, and comprises several basins characterized by deep crustal seismicity. The US-French-Tanzania-Kenya CRAFTI project aims to understand the role of magma and volatile movement during the initiation and evolution of rifting in cratonic lithosphere. Our 38-station broadband network spans all or parts of fault-bounded rift segments, enabling comparison of lithospheric structure, fault kinematics, and seismogenic layer thickness with age and proximity to the deeply rooted Archaen craton. Seismicity levels are high in all basins, but we find profound differences in seismogenic layer thickness along the length of the rift. Seismicity in the Manyara basin occurs almost exclusively within the lower crust, and in spatial clusters that have been active since 1990. In contrast, seismicity in the ~ 5 My older Magadi basin is localized in the upper crust, and the long border fault bounding the west side of the basin is seismically inactive. Between these two basins lies the Natron rift segment, which shows seismicity between ~ 20 and ~2 km depth, and high concentrations at Oldoinyo Lengai and Gelai volcanoes. Older volcanoes on the uplifted western flank (e.g., Ngorongoro) experience swarms of activity, suggesting that active magmatism and degassing are widespread. Focal mechanisms of the frequent earthquakes recorded across the array are spatially variable, and indicate a stress field strongly influenced by (1) Holocene volcanoes, (2) mechanical interactions between adjacent rift basins, and (3) a far-field ESE-WNW extensional stress regime. We explore the spatial correlation between zones of intense degassing along fault systems and seismicity, and examine the influence of high gas pressures on lower and upper crustal seismicity in this youthful cratonic rift zone.

The tectonic evolution of the southeastern Terceira Rift/São Miguel region (Azores)

Science.gov (United States)

Weiß, B. J.; Hübscher, C.; Lüdmann, T.

2015-07-01

The eastern Azores Archipelago with São Miguel being the dominant subaerial structure is located at the intersection of an oceanic rift (Terceira Rift) with a major transform fault (Gloria Fault) representing the westernmost part of the Nubian-Eurasian plate boundary. The evolution of islands, bathymetric highs and basin margins involves strong volcanism, but the controlling geodynamic and tectonic processes are currently under debate. In order to study this evolution, multibeam bathymetry and marine seismic reflection data were collected to image faults and stratigraphy. The basins of the southeastern Terceira Rift are rift valleys whose southwestern and northeastern margins are defined by few major normal faults and several minor normal faults, respectively. Since São Miguel in between the rift valleys shows an unusual W-E orientation, it is supposed to be located on a leaky transform. South of the island and separated by a N120° trending graben system, the Monacco Bank represents a N160° oriented flat topped volcanic ridge dominated by tilted fault blocks. Up to six seismic units are interpreted for each basin. Although volcanic ridges hamper a direct linking of depositional strata between the rift and adjacent basins, the individual seismic stratigraphic units have distinct characteristics. Using these units to provide a consistent relative chrono-stratigraphic scheme for the entire study area, we suggest that the evolution of the southeastern Terceira Rift occurred in two stages. Considering age constrains from previous studies, we conclude that N140° structures developed orthogonal to the SW-NE direction of plate-tectonic extension before ~ 10 Ma. The N160° trending volcanic ridges and faults developed later as the plate tectonic spreading direction changed to WSW-ENE. Hence, the evolution of the southeastern Terceira Rift domain is predominantly controlled by plate kinematics and lithospheric stress forming a kind of a re-organized rift system.

Annual suspended sediment and trace element fluxes in the Mississippi, Columbia, Colorado, and Rio Grande drainage basins

Science.gov (United States)

Horowitz, A.J.; Elrick, K.A.; Smith, J.J.

2001-01-01

Suspended sediment, sediment-associated, total trace element, phosphorus (P), and total organic carbon (TOC) fluxes were determined for the Mississippi, Columbia, Rio Grande, and Colorado Basins for the study period (the 1996, 1997, and 1998 water years) as part of the US Geological Survey's redesigned National Stream Quality Accounting Network (NASQAN) programme. The majority (??? 70%) of Cu, Zn, Cr, Ni, Ba, P, As, Fe, Mn, and Al are transported in association with suspended sediment; Sr transport seems dominated by the dissolved phase, whereas the transport of Li and TOC seems to be divided equally between both phases. Average dissolved trace element levels are markedly lower than reported during the original NASQAN programme; this seems due to the use of 'clean' sampling, processing, and analytical techniques rather than to improvements in water quality. Partitioning between sediment and water for Ag, Pb, Cd, Cr, Co, V, Be, As, Sb, Hg, and Ti could not be estimated due to a lack of detectable dissolved concentrations in most samples. Elevated suspended sediment-associated Zn levels were detected in the Ohio River Basin and elevated Hg levels were detected in the Tennessee River, the former may affect the mainstem Mississippi River, whereas the latter probably do not. Sediment-associated concentrations of Ag, Cu, Pb, Zn, Cd, Cr, Co, Ba, Mo, Sb, Hg, and Fe are markedly elevated in the upper Columbia Basin, and appear to be detectable (Zn, Cd) as far downstream as the middle of the basin. These elevated concentrations seem to result from mining and/or mining-related activities. Consistently detectable concentrations of dissolved Se were found only in the Colorado River Basin. Calculated average annual suspended sediment fluxes at the mouths of the Mississippi and Rio Grande Basins were below, whereas those for the Columbia and Colorado Basins were above previously published annual values. Downstream suspended sediment-associated and total trace element fluxes

Regional tectonic framework of the Pranhita Godavari basin, India

Science.gov (United States)

Biswas, S. K.

2003-03-01

The Pranhita-Godavari Gondwana rift (PGR) has a co-genetic relationship with Permo-Triassic reactivation of the Narmada-Son Geofracture (NSG). The Satpura Gondwana basin represents the terminal depocentre against the NSG, which restricted the northwestward propagation of the PGR. The NE-SW tensional stress responsible for the NW-SE trending PGR could not propagate beyond the ramp formed by uplift along the NSG and transformed kinetically into an ENE directed horizontal shear along the NSG, inducing large scale strike-slip movements. The latter dynamics were responsible for ENE extension of the Satpura rift as a pull-apart basin. The PGR extends up to the present east coast of India, where it is apparently terminated by the NE-SW trending Bapatla ridge along the Eastern Ghat Rift (EGR). The subsurface data, however, shows that the PGR extends across the Bapatla ridge and continues beneath the Cretaceous-Tertiary sediments of the Krishna-Godavari basin (KG) in the EGR. Thus, the Permo-Triassic PGR appears to have continued in the Indo-Antarctic plate before the Cretaceous break up. The EGR, during break up of the continents, cuts across the PGR and the KG basin was superimposed on it. The PGR site is located on a paleo-suture between the Dharwar and Bastar proto-cratons. The master faults developed bordering the rift, and the intra-rift higher order faults followed the pre-existing fabric. The transverse transfer zones manifested as basement ridges, divide the rift into segments of tectono-sedimentary domains. The major domains are the Chintalapudi, Godavari, and Chandrapur sub-basins, each of which subsided differentially. The central Godavari sub-basin subsided most and shows maximum structural complexity and sediment accommodation. The rifting started with initial half-graben faulting along the northeastern master fault and expanded by successive half graben faulting. This gave rise to intra-basinal horsts and grabens, which exercised control on the syn-rift

Long wavelength magnetic anomalies over continental rifts in cratonic region

Science.gov (United States)

Friedman, S. A.; Persaud, P.; Ferre, E. C.; Martín-Hernández, F.; Feinberg, J. M.

2017-12-01

New collections of unaltered mantle xenoliths shed light on potential upper mantle contributions to long wavelength magnetic anomalies (LWMA) in continental rifts in cratonic / shield areas. The new material originates from the East African Rift (Tanzania), the Rio Grande Rift (U.S.A.), the Rhine Rift (Germany), and the West Antarctic Rift (Antarctica). The xenoliths sample the uppermost ( 0.2 or Fe geotherms (>60ºC/km) that are characteristic of rifted regions preclude any contribution to LWMA at depths >10 km. Hence, only upper basalts and hypovolcanic mafic sills would constitute potential magnetic sources. In contrast, the margins of these rifted regions consist of refractory cratonic domains, often characterized by oxidized sublithospheric mantle that host significant concentrations of primary magnetite. The higher NRMs of these peridotites (up to 15 A/m, Qn > 2.5) combined with much lower geotherms (as low as 15ºC/km) allows for a 5 to 10 km layer of uppermost mantle to potentially contribute to LWMA. Assuming that Qn values in rift margins are also gradient across the rift would primarily reflect thermal equilibration over time.

Active intra-basin faulting in the Northern Basin of Lake Malawi from seismic reflection data

Science.gov (United States)

Shillington, D. J.; Chindandali, P. R. N.; Scholz, C. A.; Ebinger, C. J.; Onyango, E. A.; Peterson, K.; Gaherty, J. B.; Nyblade, A.; Accardo, N. J.; McCartney, T.; Oliva, S. J.; Kamihanda, G.; Ferdinand, R.; Salima, J.; Mruma, A. H.

2016-12-01

Many questions remain about the development and evolution of fault systems in weakly extended rifts, including the relative roles of border faults and intra-basin faults, and segmentation at various scales. The northern Lake Malawi (Nyasa) rift in the East African Rift System is an early stage rift exhibiting pronounced tectonic segmentation, which is defined by 100-km-long border faults. The basins also contain a series of intrabasinal faults and associated synrift sediments. The occurrence of the 2009 Karonga Earthquake Sequence on one of these intrabasinal faults indicates that some of them are active. Here we present new multichannel seismic reflection data from the Northern Basin of the Malawi Rift collected in 2015 as a part of the SEGMeNT (Study of Extension and maGmatism in Malawi aNd Tanzania) project. This rift basin is bound on its east side by the west-dipping Livingstone border fault. Over 650 km of seismic reflection profiles were acquired in the Northern Basin using a 500 to 1540 cu in air gun array and a 1200- to 1500-m seismic streamer. Dip lines image a series of north-south oriented west-dipping intra-basin faults and basement reflections up to 5 s twtt near the border fault. Cumulative offsets on intra-basin faults decrease to the west. The largest intra-basin fault has a vertical displacement of >2 s two-way travel time, indicating that it has accommodated significant total extension. Some of these intra-basin faults offset the lake bottom and the youngest sediments by up to 50 s twtt ( 37 m), demonstrating they are still active. The two largest intra-basin faults exhibit the largest offsets of young sediments and also correspond to the area of highest seismicity based on analysis of seismic data from the 89-station SEGMeNT onshore/offshore network (see Peterson et al, this session). Fault patterns in MCS profiles vary along the basin, suggesting a smaller scale of segmentation of faults within the basin; these variations in fault patterns

Landsat Evapotranspiration for Historical Field-scale Water Use (1984-2015) in the Upper Rio Grande River Basin

Science.gov (United States)

Senay, G. B.; Schauer, M.; Singh, R. K.; Friedrichs, M.

2017-12-01

Field-scale water use maps derived from evapotranspiration (ET) can characterize water use patterns and the impacts of water management decisions. This project generated historical (1984-2015) Landsat-based ET maps for the entire Upper Rio Grande basin which makes this one of the largest regions in the United States with remotely sensed historical ET at Landsat resolution. More than 10,000 Landsat images spanning 32 years were processed using the Operational Simplified Surface Energy Balance (SSEBop) model which integrates weather data and remotely sensed images to estimate monthly and annual ET. Time-series analysis focused on three water-intensive study areas within the basin: the San Luis Valley in Colorado, irrigated fields along the Rio Grande River near Albuquerque, NM, and irrigated fields near Las Cruces, NM. Preliminary analysis suggests land use changes result in declining water use in irrigated areas of the basin which corresponds with increases in land surface temperatures. Time-series analysis of water use patterns at multiple temporal and spatial scales demonstrates the impact of water management decisions on the availability of water in the basin. Comparisons with cropland data from the USDA (NASS CDL) demonstrate how water use for particular crop types changes over time in response to land use changes and shifts in water management. This study illustrates a useful application of "Big Data" earth observation science for quantifying impacts of climate and land use changes on water availability within the United States as well as applications in planning water resource allocation, managing water rights, and sustaining agricultural production in the Upper Rio Grande basin.

Analysis of gravity anomalies in the Ulleung Basin (East Sea/Sea of Japan) and its implications for the crustal structure of rift-dominated back-arc basin

Science.gov (United States)

Kim, Yoon-Mi; Lee, Sang-Mook

2018-01-01

The Ulleung Basin (UB), one of three major basins in the East Sea/Sea of Japan, is considered to represent a continental-rifting end-member of back-arc basin system, but is much less understood compared to the nearby Yamato Basin (YB) and Japan Basin (JB). This study examines the gravity anomalies of the UB since the variation in crustal thickness can provide important insights on the mode of extension during basin opening. Our analysis shows that the Moho depth (from the sea surface) varies from 16 km at the basin center to 22 km at the edges. However, within the central part of the basin, the crustal thickness (not including sediment) is more or less the same (10-12 km), by varying only about 10-20% of the total thickness, contrary to the previous suggestions. Our finding of anomalous but uniformly thick crust is consistent with the recent seismic results from the YB (14 km on average). A mantle residual gravity anomaly high (∼20 mGal) exists in the northeastern part of the UB. This feature is interpreted as the location of maximum extension (slightly thinner crust by ∼1 km). Together with another moderate gravity high to the southwest, the two anomalies form a NNE-SSW line, which corresponds to the direction of the major tectonic structures of the Korean Peninsula. We argue that the a massive magmatic emplacement took place extensively in the lower crust of the UB during the opening, significantly increasing its overall thickness to almost twice as that of the JB where a mid-ocean-ridge style seafloor spreading occurred. Two important post-opening processes took place after the formation of uniformly thick crust: post-rift volcanic intrusions in the north, especially in its northeast sections but had little effect on the residual gravity anomaly itself, and the deflection of crust in response to differential sediment loading towards the south, producing the median high in the basement in response to the flexural bending. We also conducted a simple test to

Possible Different Rifting Mechanisms Between South and North Part of the Fenhe-Weihe Rift Zone Revealed by Shear Velocity Structures

Science.gov (United States)

Ai, S.; Zheng, Y.

2017-12-01

As an active intraplate continental rift, FWR plays an important role in accommodating the trans-tension in the Trans North China Craton (TNCO). Velocity field derived from GPS measurements reveals that the northern part of FWR is still under extension in N105°E direction at a rate of 4±2 mm/yr [Shen et al., 2000]. Actually, the FWR has been the most seismically active region in NCC. Bouguer gravity profile and seismic sounding lines [Xu and Ma, 1992] revealed a 2-3 km uplift of Moho depth beneath Taiyuan basin and 5-6 km beneath the Southwestern rift zone, those geophysical observations give clues to the un-evenly upwelling of the asthenosphere beneath the rift system and the different rifting process of the FWR. Therefore, studying the extension process of FWR is meaningful to understanding the NCC geodynamics associated with rifting tectonism. Using vertical continuous waveforms recorded during 2014 from CEarray, we construct a reliable and detailed 3-D crustal and uppermost mantle S-wave velocity structure of FWR, using a Bayesian Monte-Carlo method to jointly interpret teleseismic P-wave receiver functions and Rayleigh wave dispersions [Shen et al., 2013]. In the upmost crust, FWR appear as awful low velocity anomaly zone (LVZ), while the Taihang and Lvliang mountain ranges are imaged as strong high velocity anomaly zones(HVZ). In the middle crust, the low velocity zones still keep their LVZ features Additionally, nearly the whole FWR appears as a linearly LVZ line separating Taihang Uplift and Lvliang Uplift, except beneath Shilingguan and Linshi blocks that separate the Xinxian, Taiyuan and Linfen Basins, consisting with the high seismicity there. The velocity of the lower crust beneath Taiyuan and Weihe Basin are relatively higher than the rest rift regions, we interpret them as the limited mafic underplating beneath the TNCO. From the lower crust to upper mantle, the Datong volcanic zone display robust low velocity features, though the lowest velocity

Asymmetric lithosphere as the cause of rifting and magmatism in the Permo-Carboniferous Oslo Graben, in Permo-Carboniferous Rifting and Magmatism in Europe.

NARCIS (Netherlands)

Pascal Candas, C.; Cloetingh, S.A.P.L.; Davies, G.R.

2004-01-01

Compared to other Permo-Carboniferous rift basins of NW Europe, the Oslo Graben has two distinct characteristics. First, it initiated inside cold and stable Precambrian lithosphere, whereas most Permo-Carboniferous basins developed in weaker Phanerozoic lithosphere, and second, it is characterized

Fylla Bank: structure and evolution of a normal-to-shear rifted margin in the northern Labrador Sea

DEFF Research Database (Denmark)

Døssing, Arne

2011-01-01

‐strike discontinuities in oceanic crust in the Labrador Sea to define margin segmentation in southern West Greenland, including the borders of Fylla Bank. A structural‐kinematic model presented here thus suggests that the Cretaceous–Cenozoic poly‐phase rifting to some extent was controlled by pre‐existing crustal fabric......, the Bank may be compared with the Demerara Plateau, part of the French Guinea‐Northeast Brazil continental margin. Seismic reflection interpretations presented in this study show that Fylla Bank is situated above an extensive basin complex, herein referred to as Fylla Structural Complex, which contains...... an up to 5‐km‐thick Cretaceous–Cenozoic sedimentary succession above an inferred pre‐Cretaceous basement. Seismic mapping of basement structures show that the complex is dominated by NNW‐/NW‐striking rift basins in its southern part and NNE‐striking rift basins in its northern part. The rift basins...

The geology and hydrocarbon possibilities of the Triassic-Jurassic Fundy Basin, eastern Canada

Energy Technology Data Exchange (ETDEWEB)

Wade, J.A.; Fensome, R.A. [Geological Survey of Canada, Dartmouth, NS (Canada). Atlantic Geoscience Centre; Brown, D.E. [Canada-Nova Scotia Offshore Petroleum Board, Halifax, NS (Canada)

1997-09-01

The development of the Mesozoic sedimentary basins beneath the waters of the eastern coast of North America was discussed. These basins have been linked to the rifting of the central part of Pangaea during Mid and Late Triassic time that ended in the formation of a series of grabens extending from Florida to The Grand Banks of Newfoundland, one of them being the Bay of Fundy Basin which is about 16,500 square kilometres in size. Onshore and offshore geologic mapping and seismic interpretations have shown their age range to be from the Mid Triassic Anisian or Ladinian to Mid Jurassic. Up to 12 km of Mesozoic rocks were deposited in the basin with up to 9 km still present. The depositional history of the area was described. The two areas with greatest hydrocarbon potential are the Bay of Fundy and the Chignecto subbasins.

Proterozoic structure, cambrian rifting, and younger faulting as revealed by a regional seismic reflection network in the Southern Illinois Basin

Science.gov (United States)

Potter, C.J.; Drahovzal, James A.; Sargent, M.L.; McBride, J.H.

1997-01-01

Four high-quality seismic reflection profiles through the southern Illinois Basin, totaling 245 km in length, provide an excellent regional subsurface stratigraphic and structural framework for evaluation of seismic risk, hydrocarbon occurrence, and other regional geologic studies. These data provide extensive subsurface information on the geometry of the intersection of the Cambrian Reelfoot and Rough Creek rifts, on extensive Proterozoic reflection sequences, and on structures (including the Fluorspar Area Fault Complex and Hicks Dome) that underlie a transitional area between the well-defined New Madrid seismic zone (to the southwest) and a more diffuse area of seismicity in the southern Illinois Basin. Our principal interpretations from these data are listed here in order of geologic age, from oldest to youngest: 1. Prominent Proterozoic layering, possibly equivalent to Proterozoic (???1 Ga) Middle Run Formation clastic strata and underlying (1.3-1.5 Ga) volcanic rocks of the East Continent rift basin, has been strongly deformed, probably as part of the Grenville foreland fold and thrust belt. 2. A well-defined angular unconformity is seen in many places between Proterozoic and Cambrian strata; a post-Grenville Proterozoic sequence is also apparent locally, directly beneath the base of the Cambrian. 3. We infer a major reversal in Cambrian rift polarity (accommodation zone) in the Rough Creek Graben in western Kentucky. 4. Seismic facies analysis suggests the presence of basin-floor fan complexes at and near the base of the Cambrian interval and within parts of a Proterozoic post-Grenville sequence in several parts of the Rough Creek Graben. 5. There is an abrupt pinchout of the Mount Simon Sandstone against crystalline basement beneath the Dale Dome (near the Texaco no. 1 Cuppy well, Hamilton County) in southeastern Illinois, and a more gradual Mount Simon pinchout to the southeast. 6. Where crossed by the seismic reflection line in southeast Illinois, some

Replacement of benthic communities in two Neoproterozoic-Cambrian subtropical-to-temperate rift basins, High Atlas and Anti-Atlas, Morocco

Science.gov (United States)

Clausen, Sébastien; Álvaro, J. Javier; Zamora, Samuel

2014-10-01

The ‘Cambrian explosion’ is often introduced as a major shift in benthic marine communities with a coeval decline of microbial consortia related to the diversification of metazoans and development of bioturbation (‘Agronomic Revolution’). Successive community replacements have been reported along with ecosystem diversification and increase in guild complexity from Neoproterozoic to Cambrian times. This process is recorded worldwide but with regional diachroneities, some of them directly controlled by the geodynamic conditions of sedimentary basins. The southern High Atlas and Anti-Atlas of Morocco record development of two rifts, Tonian (?) - early Cryogenian and latest Ediacarian-Cambrian in age, separated by the onset of the Pan-African Orogeny. This tectonically controlled, regional geodynamic change played a primary control on pattern and timing of benthic ecosystem replacements. Benthic communities include microbial consortia, archaeocyathan-thromboid reefal complexes, chancelloriid-echinoderm-sponge meadows, and deeper offshore echinoderm-dominated communities. Microbial consortia appeared in deeper parts of the Tonian (?) - early Cryogenian fluvio-deltaic progradational rift sequences, lacustrine environments of the Ediacaran Volcanic Atlasic Chain (Ouarzazate Supergroup) and the Ediacaran-Cambrian boundary interval, characterized by the peritidal-dominated Tifnout Member (Adoudou Formation). They persisted and were largely significant until Cambrian Age 3, as previous restricted marine conditions precluded the immigration of shelly metazoans in the relatively shallow epeiric parts of the Cambrian Atlas Rift. Successive Cambrian benthic communities were replaced as a result of distinct hydrodynamic and substrate conditions, which allow identification of biotic (e.g., antagonistic relationships between microbial consortia and echinoderms, and taphonomic feedback patterns in chancelloriid-echinoderm-sponge meadows) and abiotic (e.g., rifting

3D Numerical Rift Modeling with Application to the East African Rift System

Science.gov (United States)

Glerum, A.; Brune, S.; Naliboff, J.

2017-12-01

As key components of plate tectonics, continental rifting and the formation of passive margins have been extensively studied with both analogue models and numerical techniques. Only recently however, technical advances have enabled numerical investigations into rift evolution in three dimensions, as is actually required for including those processes that cause rift-parallel variability, such as structural inheritance and oblique extension (Brune 2016). We use the massively parallel finite element code ASPECT (Kronbichler et al. 2012; Heister et al. 2017) to investigate rift evolution. ASPECT's adaptive mesh refinement enables us to focus resolution on the regions of interest (i.e. the rift center), while leaving other areas such as the asthenospheric mantle at coarse resolution, leading to kilometer-scale local mesh resolution in 3D. Furthermore, we implemented plastic and viscous strain weakening of the nonlinear viscoplastic rheology required to develop asymmetric rift geometries (e.g. Huismans and Beaumont 2003). Additionally created plugins to ASPECT allow us to specify initial temperature and composition conditions based on geophysical data (e.g. LITHO1.0, Pasyanos et al. 2014) or to prescribe more general along-strike variation in the initial strain seeding the rift. Employing the above functionality, we construct regional models of the East African Rift System (EARS), the world's largest currently active rift. As the EARS is characterized by both orthogonal and oblique rift sections, multi-phase extension histories as well as magmatic and a-magmatic branches (e.g. Chorowicz 2005; Ebinger and Scholz 2011), it constitutes an extensive natural laboratory for our research into the 3D nature of continental rifting. References:Brune, S. (2016), in Plate boundaries and natural hazards, AGU Geophysical Monograph 219, J. C. Duarte and W. P. Schellart (Eds.). Chorowicz, J. (2005). J. Afr. Earth Sci., 43, 379-410. Ebinger, C. and Scholz, C. A. (2011), in Tectonics of

The Grand Challenge of Basin-Scale Groundwater Quality Management Modelling

Science.gov (United States)

Fogg, G. E.

2017-12-01

The last 50+ years of agricultural, urban and industrial land and water use practices have accelerated the degradation of groundwater quality in the upper portions of many major aquifer systems upon which much of the world relies for water supply. In the deepest and most extensive systems (e.g., sedimentary basins) that typically have the largest groundwater production rates and hold fresh groundwaters on decadal to millennial time scales, most of the groundwater is not yet contaminated. Predicting the long-term future groundwater quality in such basins is a grand scientific challenge. Moreover, determining what changes in land and water use practices would avert future, irreversible degradation of these massive freshwater stores is a grand challenge both scientifically and societally. It is naïve to think that the problem can be solved by eliminating or reducing enough of the contaminant sources, for human exploitation of land and water resources will likely always result in some contamination. The key lies in both reducing the contaminant sources and more proactively managing recharge in terms of both quantity and quality, such that the net influx of contaminants is sufficiently moderate and appropriately distributed in space and time to reverse ongoing groundwater quality degradation. Just as sustainable groundwater quantity management is greatly facilitated with groundwater flow management models, sustainable groundwater quality management will require the use of groundwater quality management models. This is a new genre of hydrologic models do not yet exist, partly because of the lack of modeling tools and the supporting research to model non-reactive as well as reactive transport on large space and time scales. It is essential that the contaminant hydrogeology community, which has heretofore focused almost entirely on point-source plume-scale problems, direct it's efforts toward the development of process-based transport modeling tools and analyses capable

Constraining Basin Depth and Fault Displacement in the Malombe Basin Using Potential Field Methods

Science.gov (United States)

Beresh, S. C. M.; Elifritz, E. A.; Méndez, K.; Johnson, S.; Mynatt, W. G.; Mayle, M.; Atekwana, E. A.; Laó-Dávila, D. A.; Chindandali, P. R. N.; Chisenga, C.; Gondwe, S.; Mkumbwa, M.; Kalaguluka, D.; Kalindekafe, L.; Salima, J.

2017-12-01

The Malombe Basin is part of the Malawi Rift which forms the southern part of the Western Branch of the East African Rift System. At its southern end, the Malawi Rift bifurcates into the Bilila-Mtakataka and Chirobwe-Ntcheu fault systems and the Lake Malombe Rift Basin around the Shire Horst, a competent block under the Nankumba Peninsula. The Malombe Basin is approximately 70km from north to south and 35km at its widest point from east to west, bounded by reversing-polarity border faults. We aim to constrain the depth of the basin to better understand displacement of each border fault. Our work utilizes two east-west gravity profiles across the basin coupled with Source Parameter Imaging (SPI) derived from a high-resolution aeromagnetic survey. The first gravity profile was done across the northern portion of the basin and the second across the southern portion. Gravity and magnetic data will be used to constrain basement depths and the thickness of the sedimentary cover. Additionally, Shuttle Radar Topography Mission (SRTM) data is used to understand the topographic expression of the fault scarps. Estimates for minimum displacement of the border faults on either side of the basin were made by adding the elevation of the scarps to the deepest SPI basement estimates at the basin borders. Our preliminary results using SPI and SRTM data show a minimum displacement of approximately 1.3km for the western border fault; the minimum displacement for the eastern border fault is 740m. However, SPI merely shows the depth to the first significantly magnetic layer in the subsurface, which may or may not be the actual basement layer. Gravimetric readings are based on subsurface density and thus circumvent issues arising from magnetic layers located above the basement; therefore expected results for our work will be to constrain more accurate basin depth by integrating the gravity profiles. Through more accurate basement depth estimates we also gain more accurate displacement

ALVIN-SeaBeam studies of the Sumisu Rift, Izu-Bonin arc

Science.gov (United States)

Taylor, B.; Brown, G.; Fryer, P.; Gill, J. B.; Hochstaedter, A. G.; Hotta, H.; Langmuir, C. H.; Leinen, M.; Nishimura, A.; Urabe, T.

1990-10-01

Bimodal volcanism, normal faulting, rapid sedimentation, and hydrothermal circulation characterize the rifting of the Izu-Bonin arc at 31°N. Analysis of the zigzag pattern, in plan view, of the normal faults that bound Sumisu Rift indicates that the extension direction (080° ± 10°) is orthogonal to the regional trend of the volcanic front. Normal faults divide the rift into an inner rift on the arc side, which is the locus for maximum subsidence and sedimentation, and an outer rift further west. Transfer zones that link opposing master faults and/or rift flank uplifts further subdivide the rift into three segments along strike. Volcanism is concentrated along the ENE-trending transfer zone which separates the northern and central rift segments. The differential motion across the zone is accommodated by interdigitating north-trending normal faults rather than by ENE-trending oblique-slip faults. Volcanism in the outer rift has built 50-700 m high edifices without summit craters whereas in the inner rift it has formed two multi-vent en echelon ridges (the largest is 600 m high and 16 km long). The volcanism is dominantly basaltic, with compositions reflecting mantle sources little influenced by arc components. An elongate rhyolite dome and low-temperature hydrothermal deposits occur at the en echelon step in the larger ridge, which is located at the intersection of the transfer zone with the inner rift. The chimneys, veins, and crusts are composed of silica, barite and iron oxide, and are of similar composition to the ferruginous chert that mantles the Kuroko deposits. A 1.2-km transect of seven ALVIN heat flow measurements at 30°48.5'N showed that the inner-rift-bounding faults may serve as water recharge zones, but that they are not necessarily areas of focussed hydrothermal outflow, which instead occurs through the thick basin sediments. The rift basin and arc margin sediments are probably dominated by permeable rhyolitic pumice and ash erupted from submarine

Volcanism in the Sumisu Rift. Pt. 2

International Nuclear Information System (INIS)

Hochstaedter, A.G.; Gill, J.B.; Morris, J.D.

1990-01-01

A bimodal suite of volcanic rocks collected from the Sumisu Rift by ALVIN provide present day example of the first magmatic products of arc rifting during the initiation of back-arc spreading. The trace element and isotopic composition of these rocks, which are contemporaneous with island arc tholeiite lavas of the Izu-Ogasawara arc 20 km to the east, differ from those of arc rocks and N-MORB in their relative incorporation of both subduction-related and non-subduction-related components. Subduction-related components, i.e., those that distinguish volcanic arc basalts from N-MORB, are less pronounced in rift lavas than in arc lavas. Alkali and alkaline earth to high field strength element and REE ratios as well as 87 Sr/ 86 Sr are intermediate between those of N-MORB and Izu arc lavas and indicate that Sumisu Rift basalts are similar to BABB erupted in other, more mature back-arc basins. These results show that back-arc basins may begin their magmatic evolution with BABB rather than more arc-like lavas. Evidence of non-subduction related components remains after the effects of subduction related components are removed or accounted for. Compared to the arc, higher HFSE and REE concentrations, contrasting REE patterns, and ≤ε Nd in the rift reflect derivation of rift lavas from more enriched components. Although SR basalt resembles E-MORB in many trace element ratios, it is referred to as BABB because low concentrations of Nb are similar to those in volcanic arcs and H 2 O/REE and H 2 O/K 2 O exceed those of E-MORB. Differences in HREE pattern and ε Nd require that the E-MORB characteristics result from source heterogeneities and not lower degrees of melting. Enriched mantle beneath the rift may reflect enriched blobs entrained in a more depleted matrix, or injection of new, more enriched mantle. High 208 Pb/ 204 Pb and moderate 207 Pb/ 204 Pb ratios with respect to Pacific MORB also reflect ancient mantle enrichment. (orig.)

Mesozoic lithofacies palaeogeography and petroleum prospectivity in North Carnarvon Basin, Australia

Directory of Open Access Journals (Sweden)

Tao Chongzhi

2013-01-01

Full Text Available The North Carnarvon Basin, which lies in the North West Shelf of Australia, is highly rich in gas resources. As a typical passive marginal basin, it experienced the pre-rifting, early rifting, main rifting, late rifting, post-rifting sagging and passive margin stages. The basin was mainly filled with thick Mesozoic-Cenozoic sediments, of which the Mesozoic hosts the principal source, reservoir and seal intervals. Mesozoic palaeogeography has an important control on the oil and gas distribution. Triassic gas-prone source rocks of deltaic origin determine the high endowment of natural gases in the North Carnarvon Basin. The more restricted distribution of oil accumulations is controlled by oil source rocks in the Upper Jurassic Dingo Claystone. The Muderong Shale deposited in the Early Cretaceous marine transgression provides the effective regional seal for the underlying oil and gas reservoirs.

Deep Production Well for Geothermal Direct-Use Heating of A Large Commercial Greenhouse, Radium Springs, Rio Grande Rift, New Mexico; FINAL

International Nuclear Information System (INIS)

James C. Witcher

2002-01-01

Expansion of a large commercial geothermally-heated greenhouse is underway and requires additional geothermal fluid production. This report discusses the results of a cost-shared U.S. Department of Energy (DOE) and A.R. Masson, Inc. drilling project designed to construct a highly productive geothermal production well for expansion of the large commercial greenhouse at Radium Springs. The well should eliminate the potential for future thermal breakthrough from existing injection wells and the inducement of inflow from shallow cold water aquifers by geothermal production drawdown in the shallow reservoir. An 800 feet deep production well, Masson 36, was drilled on a US Bureau of Land Management (BLM) Geothermal Lease NM-3479 at Radium Springs adjacent to the A. R. Masson Radium Springs Farm commercial greenhouse 15 miles north of Las Cruces in Dona Ana County, New Mexico just west of Interstate 25 near the east bank of the Rio Grande. The area is in the Rio Grande rift, a tectonically-active region with high heat flow, and is one of the major geothermal provinces in the western United State

Probable existence of a Gondwana transcontinental rift system in western India: Implications in hydrocarbon exploration in Kutch and Saurashtra offshore: A GIS-based approach

Science.gov (United States)

Mazumder, S.; Tep, Blecy; Pangtey, K. K. S.; Das, K. K.; Mitra, D. S.

2017-08-01

The Gondwanaland assembly rifted dominantly during Late Carboniferous-Early Permian forming several intracratonic rift basins. These rifts were subsequently filled with a thick sequence of continental clastic sediments with minor marine intercalations in early phase. In western part of India, these sediments are recorded in enclaves of Bikaner-Nagaur and Jaisalmer basins in Rajasthan. Facies correlatives of these sediments are observed in a number of basins that were earlier thought to be associated with the western part of India. The present work is a GIS based approach to reconnect those basins to their position during rifting and reconstruct the tectono-sedimentary environment at that time range. The study indicates a rift system spanning from Arabian plate in the north and extending to southern part of Africa that passes through Indus basin, western part of India and Madagascar, and existed from Late Carboniferous to Early Jurassic. Extensions related to the opening of Neo-Tethys led to the formation of a number of cross trends in the rift systems that acted as barriers to marine transgressions from the north as well as disrupted the earlier continuous longitudinal drainage systems. The axis of this rift system is envisaged to pass through present day offshore Kutch and Saurashtra and implies a thick deposit of Late Carboniferous to Early Jurassic sediments in these areas. Based on analogy with other basins associated with this rift system, these sediments may be targeted for hydrocarbon exploration.

The temporal and spatial distribution of upper crustal faulting and magmatism in the south Lake Turkana rift, East Africa

Science.gov (United States)

Muirhead, J.; Scholz, C. A.

2017-12-01

During continental breakup extension is accommodated in the upper crust largely through dike intrusion and normal faulting. The Eastern branch of the East African Rift arguably represents the premier example of active continental breakup in the presence magma. Constraining how faulting is distributed in both time and space in these regions is challenging, yet can elucidate how extensional strain localizes within basins as rifting progresses to sea-floor spreading. Studies of active rifts, such as the Turkana Rift, reveal important links between faulting and active magmatic processes. We utilized over 1100 km of high-resolution Compressed High Intensity Radar Pulse (CHIRP) 2D seismic reflection data, integrated with a suite of radiocarbon-dated sediment cores (3 in total), to constrain a 17,000 year history of fault activity in south Lake Turkana. Here, a set of N-S-striking intra-rift faults exhibit time-averaged slip-rates as high as 1.6 mm/yr, with the highest slip-rates occurring along faults within 3 km of the rift axis. Results show that strain has localized into a zone of intra-rift faults along the rift axis, forming an approximately 20 km-wide graben in central parts of the basin. Subsurface structural mapping and fault throw profile analyses reveal increasing basin subsidence and fault-related strain as this faulted graben approaches a volcanic island in the center of the basin (South Island). The long-axis of this island trends north-south, and it contains a number of elongate cones that support recent emplacement of N-S-striking dike intrusions, which parallel recently active intra-rift faults. Overall, these observations suggest strain localization into intra-rift faults in the rift center is likely a product of both volcanic loading and the mechanical and thermal effects of diking along the rift axis. These results support the establishment of magmatic segmentation in southern Lake Turkana, and highlight the importance of magmatism for focusing upper

Constraints Imposed by Rift Inheritance on the Compressional Reactivation of a Hyperextended Margin: Mapping Rift Domains in the North Iberian Margin and in the Cantabrian Mountains

Science.gov (United States)

Cadenas, P.; Fernández-Viejo, G.; Pulgar, J. A.; Tugend, J.; Manatschal, G.; Minshull, T. A.

2018-03-01

The Alpine Pyrenean-Cantabrian orogen developed along the plate boundary between Iberia and Europe, involving the inversion of Mesozoic hyperextended basins along the southern Biscay margin. Thus, this margin represents a natural laboratory to analyze the control of structural rift inheritance on the compressional reactivation of a continental margin. With the aim to identify former rift domains and investigate their role during the subsequent compression, we performed a structural analysis of the central and western North Iberian margin, based on the interpretation of seismic reflection profiles and local constraints from drill-hole data. Seismic interpretations and published seismic velocity models enabled the development of crustal thickness maps that helped to constrain further the offshore and onshore segmentation. Based on all these constraints, we present a rift domain map across the central and western North Iberian margin, as far as the adjacent western Cantabrian Mountains. Furthermore, we provide a first-order description of the margin segmentation resulting from its polyphase tectonic evolution. The most striking result is the presence of a hyperthinned domain (e.g., Asturian Basin) along the central continental platform that is bounded to the north by the Le Danois High, interpreted as a rift-related continental block separating two distinctive hyperextended domains. From the analysis of the rift domain map and the distribution of reactivation structures, we conclude that the landward limit of the necking domain and the hyperextended domains, respectively, guide and localize the compressional overprint. The Le Danois block acted as a local buttress, conditioning the inversion of the Asturian Basin.

A shifting rift—Geophysical insights into the evolution of Rio Grande rift margins and the Embudo transfer zone near Taos, New Mexico

Science.gov (United States)

Grauch, V.J.S.; Bauer, Paul W.; Drenth, Benjamin J.; Kelson, Keith I.

2017-01-01

We present a detailed example of how a subbasin develops adjacent to a transfer zone in the Rio Grande rift. The Embudo transfer zone in the Rio Grande rift is considered one of the classic examples and has been used as the inspiration for several theoretical models. Despite this attention, the history of its development into a major rift structure is poorly known along its northern extent near Taos, New Mexico. Geologic evidence for all but its young rift history is concealed under Quaternary cover. We focus on understanding the pre-Quaternary evidence that is in the subsurface by integrating diverse pieces of geologic and geophysical information. As a result, we present a substantively new understanding of the tectonic configuration and evolution of the northern extent of the Embudo fault and its adjacent subbasin.We integrate geophysical, borehole, and geologic information to interpret the subsurface configuration of the rift margins formed by the Embudo and Sangre de Cristo faults and the geometry of the subbasin within the Taos embayment. Key features interpreted include (1) an imperfect D-shaped subbasin that slopes to the east and southeast, with the deepest point ∼2 km below the valley floor located northwest of Taos at ∼36° 26′N latitude and 105° 37′W longitude; (2) a concealed Embudo fault system that extends as much as 7 km wider than is mapped at the surface, wherein fault strands disrupt or truncate flows of Pliocene Servilleta Basalt and step down into the subbasin with a minimum of 1.8 km of vertical displacement; and (3) a similar, wider than expected (5–7 km) zone of stepped, west-down normal faults associated with the Sangre de Cristo range front fault.From the geophysical interpretations and subsurface models, we infer relations between faulting and flows of Pliocene Servilleta Basalt and older, buried basaltic rocks that, combined with geologic mapping, suggest a revised rift history involving shifts in the locus of fault activity as

Physical Processes Contributing To Small-scale Vertical Movements During Changing Inplane Stresses In Rift Basins and At Passive Continental Margins

Science.gov (United States)

Paulsen, G. E.; Nielsen, S. B.; Hansen, D. L.

The vertical movements during a regional stress reversal in a rifted basin or on a passive continental margin are examined using a numerical 2D thermo-mechanical finite element model with a visco-elastic-plastic rheology. Three different physical mechanisms are recognized in small-scale vertical movements at small inplane force variations: elastic dilatation, elastic flexure, and permanent deformation. Their rela- tive importance depend on the applied force, the duration of the force, and the thermal structure of the lithosphere. Elastic material dilatation occurs whenever the stress state changes. A reversal from extension to compression therefore immediately leads to elastic dilatation, and re- sults in an overall subsidence of the entire profile. Simultaneously with dilatation the lithosphere reacts with flexure. The significance of the flexural component strongly depends on the thermal structure of the lithosphere. The polarity and amplitude of the flexure depends on the initial (before compression) loading of the lithosphere. Gener- ally, the flexural effects lead to subsidence of the overdeep in the landward part of the basin and a small amount of uplift at the basin flanks. The amplitudes of the flexural response are small and comparable with the amplitudes of the elastic dilatation. With continuing compression permanent deformation and lithospheric thickening becomes increasingly important. Ultimately, the thickened part of the lithosphere stands out as an inverted zone. The amount of permanent deformation is directly connected with the size and duration of the applied force, but even a relatively small force leads to inversion tectonics in the landward part of the basin. The conclusions are: 1) small stress induced vertical movements in rift basins and at passive continental margins are the result of a complex interaction of at least three different processes, 2) the total sediment loaded amplitudes resulting from these pro- cesses are small (2-300 m) for

Geology and geologic history of the Moscow-Pullman basin, Idaho and Washington, from late Grande Ronde to late Saddle Mountains time

Science.gov (United States)

Bush, John H; Garwood, Dean L; Dunlap, Pamela

2016-01-01

The Moscow-Pullman basin, located on the eastern margin of the Columbia River flood basalt province, consists of a subsurface mosaic of interlayered Miocene sediments and lava flows of the Imnaha, Grande Ronde, Wanapum, and Saddle Mountains Basalts of the Columbia River Basalt Group. This sequence is ~1800 ft (550 m) thick in the east around Moscow, Idaho, and exceeds 2300 ft (700 m) in the west at Pullman, Washington. Most flows entered from the west into a topographic low, partially surrounded by steep mountainous terrain. These flows caused a rapid rise in base level and deposition of immature sediments. This field guide focuses on the upper Grande Ronde Basalt, Wanapum Basalt, and sediments of the Latah Formation.Late Grande Ronde flows terminated midway into the basin to begin the formation of a topographic high that now separates a thick sediment wedge of the Vantage Member to the east of the high from a thin layer to the west. Disrupted by lava flows, streams were pushed from a west-flowing direction to a north-northwest orientation and drained the basin through a gap between steptoes toward Palouse, Washington. Emplacement of the Roza flow of the Wanapum Basalt against the western side of the topographic high was instrumental in this process, plugging west-flowing drainages and increasing deposition of Vantage sediments east of the high. The overlying basalt of Lolo covered both the Roza flow and Vantage sediments, blocking all drainages, and was in turn covered by sediments interlayered with local Saddle Mountains Basalt flows. Reestablishment of west-flowing drainages has been slow.The uppermost Grande Ronde, the Vantage, and the Wanapum contain what is known as the upper aquifer. The water supply is controlled, in part, by thickness, composition, and distribution of the Vantage sediments. A buried channel of the Vantage likely connects the upper aquifer to Palouse, Washington, outside the basin. This field guide locates outcrops; relates them to

Quantitative analysis of the tectonic subsidence in the Potiguar Basin (NE Brazil)

Science.gov (United States)

Lopes, Juliana A. G.; de Castro, David L.; Bertotti, Giovanni

2018-06-01

The Potiguar Basin, located in the Brazilian Equatorial Margin, evolved from a complex rifting process implemented during the Atlantic Ocean opening in the Jurassic/Cretaceous. Different driving mechanisms were responsible for the onset of an aborted onshore rift and an offshore rift that initiated crustal rupture and the formation of a continental transform margin. Therefore, we applied the backstripping method to quantify the tectonic subsidence during the rift and post-rift phases of Potiguar Basin formation and to analyze the spatial variation of subsidence during the two successive and distinct tectonic events responsible for the basin evolution. The parameters required to apply this methodology were extracted from 2D seismic lines and exploratory well data. The tectonic subsidence curves present periods with moderate subsidence rates (up to 300 m/My), which correspond to the evolution of the onshore Potiguar Rift (∼141 to 128 Ma). From 128-118 Ma, the tectonic subsidence curves show no subsidence in the onshore Potiguar Basin, whereas subsidence occurred at high rates (over 300 m/My) in the offshore rift. The post-rift phase began ca. 118 Ma (Aptian), when the tectonic subsidence drastically slowed to less than 35 m/My, probably related to thermal relaxation. The tectonic subsidence rates in the various sectors of the Potiguar Rift, during the different rift phases, indicate that more intense faulting occurred in the southern portion of the onshore rift, along the main border faults, and in the southeastern portion of the offshore rift. During the post-rift phase, the tectonic subsidence rates increased from the onshore portion towards the offshore portion until the continental slope. The highest rates of post-rift subsidence (up to 35 m/My) are concentrated in the central region of the offshore portion and may be related to lithospheric processes related to the continental crust rupture and oceanic seafloor spreading. The variation in subsidence rates and

Recognized Multiple Rifts of the Neoproterozoic in the Initiation of the Tarim Craton (NW China) and Their Tectonic Implications

Science.gov (United States)

He, B.; Jiao, C.; Huang, T.; Zhou, X.; Cai, Z.; Cao, Z.; Jiang, Z.; Cui, J.; Yu, Z.; Chen, W.

2017-12-01

The Tarim Basin is the largest, oil-bearing and superimposed basin in the northwest of China. The development and tectonic property of the initial Tarim basin have been acutely disputed and remain enigmatic. Urgently need to reveal the origin and formation dynamics of the Tarim Carton and evaluate the potential of the deep energy resources. However, covered by vast desert and huge-thickness sedimentary strata, suffered by multiple tectonic movements, seismic data with low signal- to- noise ratio in the deep are the critical difficulties. We analyse 4 field outcrops, 18 wells, 27 reprocessed seismic reflection profiles with high SNR across the basin and many ancillary ones and aeromagnetic data. We find about 20 normal fault-controlled rift depressions of the Cryogenian and Ediacaran scattered in the Tarim basin, which developed on the Precambrian metamorphic and crystalline basements and covered by the epeiric sea and basin facies sediments of the Lower Cambrian. The structural styles of the rifts are mainly half grabens, symmetrical troughs and horst-grabens. The regional differences exist obviously in spatial and temporal. The WNW-ESE-trending faults occur in the central part and northern of the basin and the NE, and the NEE-trending faults occur in the southern parts, which response with the anomaly of aeromagnetic. Some main faults of the Ediacaran inherited from the Cryogenian and some occurred newly, the more rifting depressions occurred during the Ediacaran. The extensional NNW-SSE-oriented and NNE-SSW-oriented paleostress field occurred simultaneously during rifting, and accompanied with the clockwise shearing. According to the activities of syn-sedimentary faults, magmatic events and sediments, the tectonic properties of the rifts are different depending on their locations in the Tarim craton. The rifting phases mainly occurred from 780 Ma to 615 Ma. The formation of rifts were associated with the opening of the South Tianshan Ocean and the South Altun

A bottom-driven mechanism for distributed faulting: Insights from the Gulf of California Rift

Science.gov (United States)

Persaud, P.; Tan, E.; Choi, E.; Contreras, J.; Lavier, L. L.

2017-12-01

findings motivate a suite of 3D models of the early plate boundary evolution in the Gulf, and highlight the importance of local stress field perturbations as a mechanism for broadening the deformation zone in other regions such as the Basin and Range, Rio Grande Rift and Malawi Rift.

Hydrocarbon resource potential of the Bornu basin northeastern ...

African Journals Online (AJOL)

Global Journal of Geological Sciences ... In the Bornu Basin which belongs to the West African Rift Subsystem (WARS) two potential petroleum systems are suggested. “Lower ... “Upper Cretaceous Petroleum System” – is the phase II rift sediments in the Bornu Basin which comprise mainly shallow marine to paralic shales,

Controls of inherited lithospheric heterogeneity on rift linkage: Numerical and analog models of interaction between the Kenyan and Ethiopian rifts across the Turkana depression

Science.gov (United States)

Brune, Sascha; Corti, Giacomo; Ranalli, Giorgio

2017-09-01

Inherited rheological structures in the lithosphere are expected to have large impact on the architecture of continental rifts. The Turkana depression in the East African Rift connects the Main Ethiopian Rift to the north with the Kenya rift in the south. This region is characterized by a NW-SE trending band of thinned crust inherited from a Mesozoic rifting event, which is cutting the present-day N-S rift trend at high angle. In striking contrast to the narrow rifts in Ethiopia and Kenya, extension in the Turkana region is accommodated in subparallel deformation domains that are laterally distributed over several hundred kilometers. We present both analog experiments and numerical models that reproduce the along-axis transition from narrow rifting in Ethiopia and Kenya to a distributed deformation within the Turkana depression. Similarly to natural observations, our models show that the Ethiopian and Kenyan rifts bend away from each other within the Turkana region, thus forming a right-lateral step over and avoiding a direct link to form a continuous N-S depression. The models reveal five potential types of rift linkage across the preexisting basin: three types where rifts bend away from the inherited structure connecting via a (1) wide or (2) narrow rift or by (3) forming a rotating microplate, (4) a type where rifts bend towards it, and (5) straight rift linkage. The fact that linkage type 1 is realized in the Turkana region provides new insights on the rheological configuration of the Mesozoic rift system at the onset of the recent rift episode.

The age of the Tunas formation in the Sauce Grande basin-Ventana foldbelt (Argentina): Implications for the Permian evolution of the southwestern margin of Gondwana

Science.gov (United States)

López-Gamundí, Oscar; Fildani, Andrea; Weislogel, Amy; Rossello, Eduardo

2013-08-01

New SHRIMP radiogenic isotope dating on zircons in tuffs (280.8 ± 1.9 Ma) confirms the Early Permian (Artinskian) age of the uppermost section of the Tunas Formation. Tuff-rich levels in the Tunas Formation are exposed in the Ventana foldbelt of central Argentina; they are part of a deltaic to fluvial section corresponding to the late overfilled stage of the Late Paleozoic Sauce Grande foreland basin. Recent SHRIMP dating of zircons from the basal Choiyoi volcanics exposed in western Argentina yielded an age of 281.4 ± 2.5 Ma (Rocha-Campos et al., 2011). The new data for the Tunas tuffs suggest that the volcanism present in the Sauce Grande basin can be considered as the distal equivalent of the earliest episodes of the Choiyoi volcanism of western Argentina. From the palaeoclimatic viewpoint the new Tunas SHRIMP age confirms that by early Artinskian glacial conditions ceased in the Sauce Grande basin and, probably, in adajacent basins in western Gondwana.

LATE CREATACEOUS-CENOZOIC SEDIMENTS OF THE BAIKAL RIFT BASIN AND CHANGING NATURAL CONDITIONS

Directory of Open Access Journals (Sweden)

Viktor D. Mats

2010-01-01

Full Text Available The late Cretaceous-Cenozoic sediments of fossil soils and weathering crusts of the Baikal rift have been subject to long-term studies. Based on our research results, it is possible to distinguish the following litho-stratigraphic complexes which are related to particular stages of the rift development: the late Cretaceous–early Oligocene (crypto-rift Arheo-baikalian, the late Oligocene–early Pliocene (ecto-rift early orogenic Pra-baikalian, and the late Pliocene-Quaternary (ecto-rift late orogenic Pra-baikalian – Baikalian complexes. Changes of weathering modes (Cretaceous-quarter, soil formation (Miocene-quarter and differences of precipitation by vertical and lateral stratigraphy are analysed with regard to specific features of climate, tectonics and facial conditions of sedimentation. Tectonic phases are defined in the Cenozoic period of the Pribaikalie.

Three-dimensional geologic model of the southeastern Espanola Basin, Santa Fe County, New Mexico

Science.gov (United States)

Pantea, Michael P.; Hudson, Mark R.; Grauch, V.J.S.; Minor, Scott A.

2011-01-01

This multimedia model and report show and describe digital three-dimensional faulted surfaces and volumes of lithologic units that confine and constrain the basin-fill aquifers within the Espanola Basin of north-central New Mexico. These aquifers are the primary groundwater resource for the cities of Santa Fe and Espanola, six Pueblo nations, and the surrounding areas. The model presented in this report is a synthesis of geologic information that includes (1) aeromagnetic and gravity data and seismic cross sections; (2) lithologic descriptions, interpretations, and geophysical logs from selected drill holes; (3) geologic maps, geologic cross sections, and interpretations; and (4) mapped faults and interpreted faults from geophysical data. Modeled faults individually or collectively affect the continuity of the rocks that contain the basin aquifers; they also help define the form of this rift basin. Structure, trend, and dip data not previously published were added; these structures are derived from interpretations of geophysical information and recent field observations. Where possible, data were compared and validated and reflect the complex relations of structures in this part of the Rio Grande rift. This interactive geologic framework model can be used as a tool to visually explore and study geologic structures within the Espanola Basin, to show the connectivity of geologic units of high and low permeability between and across faults, and to show approximate dips of the lithologic units. The viewing software can be used to display other data and information, such as drill-hole data, within this geologic framework model in three-dimensional space.

Using Temperature Forecasts to Improve Seasonal Streamflow Forecasts in the Colorado and Rio Grande Basins

Science.gov (United States)

Lehner, F.; Wood, A.; Llewellyn, D.; Blatchford, D. B.; Goodbody, A. G.; Pappenberger, F.

2017-12-01

Recent studies have documented the influence of increasing temperature on streamflow across the American West, including snow-melt driven rivers such as the Colorado or Rio Grande. At the same time, some basins are reporting decreasing skill in seasonal streamflow forecasts, termed water supply forecasts (WSFs), over the recent decade. While the skill in seasonal precipitation forecasts from dynamical models remains low, their skill in predicting seasonal temperature variations could potentially be harvested for WSFs to account for non-stationarity in regional temperatures. Here, we investigate whether WSF skill can be improved by incorporating seasonal temperature forecasts from dynamical forecasting models (from the North American Multi Model Ensemble and the European Centre for Medium-Range Weather Forecast System 4) into traditional statistical forecast models. We find improved streamflow forecast skill relative to traditional WSF approaches in a majority of headwater locations in the Colorado and Rio Grande basins. Incorporation of temperature into WSFs thus provides a promising avenue to increase the robustness of current forecasting techniques in the face of continued regional warming.

Rift systems in the southern North Atlantic: why did some fail and others not?

Science.gov (United States)

Nirrengarten, M.; Manatschal, G.; Tugend, J.; Kusznir, N. J.; Sauter, D.

2017-12-01

Orphan, Rockall, Porcupine, Parentis and Pyrenean Basins are failed rift systems surrounding the southern North Atlantic Ocean. The failure or succeessing of a rift system is intimately linked to the question of what controls lithospheric breakup and what keeps oceanic spreading alive. Extension rates and the thermal structure are usually the main parameters invoked. However, between the rifts that succeeded and those that failed, the relative control and relative importance of these parameters is not clear. Cessation of driving forces, strain hardening or competition between concurrent rifts are hypotheses often used to explain rift failure. In this work, we aim to analyze the influence of far field forces on the abandon of rift systems in the southern North Atlantic domain using plate kinematic modeling. A new reconstruction approach that integrates the spatio-temporal evolution of rifted basins has been developed. The plate modeling is based on the definition, mapping and restoration of rift domains using 3D gravity inversions methods that provide crustal thickness maps. The kinematic description of each rift system enables us to discuss the local rift evolution relative to the far field kinematic framework. The resulting model shows a strong segmentation of the different rift systems during extreme crustal thinning that are crosscut by V-shape propagators linked to the exhumation of mantle and emplacement of first oceanic crust. The northward propagating lithospheric breakup of the southern North Atlantic may be partly triggered and channeled by extreme lithospheric thinning. However, at Aptian-Albian time, the northward propagating lithospheric breakup diverts and is partitioned along a transtensional system resulting in the abandon of the Orphan and Rockall basins. The change in the propagation direction may be related to a local strain weakening along existing/inherited transfer zones and/or, alternatively, to a more global plate reorganization. The

Shallow velocity structure above the Socorro Magma Body from ambient noise tomography using the large-N Sevilleta array, central Rio Grande Rift, New Mexico

Science.gov (United States)

Worthington, L. L.; Ranasinghe, N. R.; Schmandt, B.; Jiang, C.; Finlay, T. S.; Bilek, S. L.; Aster, R. C.

2017-12-01

The Socorro Magma Body (SMB) is one of the largest recognized active mid-crustal magma intrusions globally. Inflation of the SMB drives sporadically seismogenic uplift at rates of up to of few millimeters per year. We examine the upper crustal structure of the northern section of the SMB region using ambient noise seismic data collected from the Sevilleta Array and New Mexico Tech (NMT) seismic network to constrain basin structure and identify possible upper crustal heterogeneities caused by heat flow and/or fluid or magma migration to shallower depths. The Sevilleta Array comprised 801 vertical-component Nodal seismic stations with 10-Hz seismometers deployed within the Sevilleta National Wildlife Refuge in the central Rio Grande rift north of Socorro, New Mexico, for a period of 12 days during February 2015. Five short period seismic stations from the NMT network located south of the Sevilleta array are also used to improve the raypath coverage outside the Sevilleta array. Inter-station ambient noise cross-correlations were computed from all available 20-minute time windows and stacked to obtain estimates of the vertical component Green's function. Clear fundamental mode Rayleigh wave energy is observed from 3 to 6 s period. Beamforming indicates prominent noise sources from the southwest, near Baja California, and the southeast, in the Gulf of Mexico. The frequency-time analysis method was implemented to measure fundamental mode Rayleigh wave phase velocities and the resulting inter-station travel times were inverted to obtain 2-D phase velocity maps. One-dimensional sensitivity kernels indicate that the Rayleigh wave phase velocity maps are sensitive to a depth interval of 1 to 8 km, depending on wave period. The maps show (up to 40%) variations in phase velocity within the Sevilleta Array, with the largest variations found for periods of 5-6 seconds. Holocene to upper Pleistocene, alluvial sediments found in the Socorro Basin consistently show lower phase

Grande Ronde Basin Chinook Salmon Captive Brood and Conventional Supplementation Programs, 2002 Annual Report.

Energy Technology Data Exchange (ETDEWEB)

Carmichael, Richard W. (Oregon Department of Fish and Wildlife, La Grande, OR)

2003-07-01

Endangered Species Permit Number 1011 (formerly Permit No. 973) authorizes ODFW to take listed spring chinook salmon juveniles from Catherine Creek (CC), Lostine River (LR) and Grande Ronde River (GR) for research and enhancement purposes. Modification 2 of this permit authorizes ODFW to take adults for spawning and the production and release of smolts for the Captive and Conventional broodstock programs. This report satisfies the requirement that an annual report be submitted. Herein we report on activities conducted and provide cursory data analyses for the Grande Ronde spring chinook salmon Captive and Conventional broodstock projects from 1 January-31 December 2002. The Grande Ronde Basin Spring Chinook Salmon Captive Broodstock Project is designed to rapidly increase numbers of salmon in stocks that are in imminent danger of extirpation. Parr are captured in Catherine Creek, upper Grande Ronde River and Lostine River and reared to adulthood in captivity. Upon maturation, they are spawned (within stocks) and their progeny reared to smoltification before being released into the natal stream of their parents. This program is co-managed by ODFW, National Marine Fisheries Service, the Nez Perce Tribe and Confederated Tribes of the Umatilla Indian Reservation.

Style and timing of salt tectonics in the Dniepr-Donets Basin (Ukraine): implications for triggering and driving mechanisms of salt movement in sedimentary basins.

NARCIS (Netherlands)

Stovba, S.M.; Stephenson, R.A.

2003-01-01

The Ukrainian Dniepr-Donets Basin (DDB) is a Late Palaeozoic intracratonic rift basin, with sedimentary thicknesses up to 19 km, displaying the effects of salt tectonics during its entire history of formation, from Late Devonian rifting to the Tertiary. Hundreds of concordant and discordant salt

Petroleum prospectivity of the onshore Gaspe and offshore Anticosti Basins, eastern Canada

International Nuclear Information System (INIS)

Durling, P.; Martel, T.; Waldron, J.W.F.

1998-01-01

The development of oil and gas reserves on the Scotian Shelf and the Grand Banks of Newfoundland has sparked a renewed interest in the onshore Gaspe-Connecticut Valley Synclinorium (GCVS) and the offshore Anticosti Basin. The geologic history of each basin was described and some of the geological relationships that suggest the presence of hydrocarbon resources in the area were reviewed. The Anticosti Basin developed in a rift and open marine shelf environment during the early Cambrian period. Petroleum exploration in the Basin began in the early 1960s when Imperial Oil collected 435 km of single channel seismic reflection data - enough to identify several drilling locations. Eight wells were drilled on the island which resulted in a number of shows of oil and gas. The GCVS was developed within the Appalachian Orogen and is comprised of fine grained siliciclastic turbidites. The structural geology of the GCVS is more complicated than the Anticosti Basin. Petroleum exploration in the GCVS has, for the most part, been in the eastern part of the Gaspe Peninsula where one producing well is located. The central part is mainly unexplored for petroleum resources

Research and management of soil, plant, animal, and human resources in the Middle Rio Grande Basin

Science.gov (United States)

Deborah M. Finch

1996-01-01

The Rocky Mountain Forest and Range Experiment Station initiated a research program in 1994 called. "Ecology, diversity, and sustainability of soil, plant, animal, and human resources of the Rio Grande Basin". This program is funded by an Ecosystem Management grant from Forest Service Research. Its mission focuses on the development and application of new...

SALT LAKES OF THE AFRICAN RIFT SYSTEM: A VALUABLE ...

African Journals Online (AJOL)

dell

rift lake locations fitting the description. “endorheic” (closed) ... updating, as well as harness the scholarship ... Ionic concentrations are location and season .... Progress and effects of weathering of Lake Natron Basin rock formations; a hill in.

The Jurassic of Denmark and Greenland: key elements in the reconstruction of the North Atlantic Jurassic rift system

Directory of Open Access Journals (Sweden)

Surlyk, Finn

2003-10-01

Full Text Available The Jurassic succession of Denmark is largely confined to the subsurface with the exception of exposures on the island of Bornholm in the Baltic Sea. In East Greenland, in contrast, the Jurassic is extensively exposed. Comparison of basin evolution in the two regions, which now occur on two separate plates, thus relies on highly different datasets. It is possible nevertheless to construct an integrated picture allowing testing of hypotheses concerning basin evolution, regional uplift, onset and climax of rifting, relative versus eustatic sea-level changes and sequence stratigraphic subdivision and correlation. On a smaller scale, it is possible to compare the signatures of sequence stratigraphic surfaces as seen on well logs, in cores and at outcrop and of sequences recognised and defined on the basis of very different data types. Breakdown of the successions into tectonostratigraphic megasequences highlights the high degree of similarity in overall basin evolution and tectonic style. An important difference, however, lies in the timing. Major events such as late Early - Middle Jurassic uplift, followed by onset of rifting, basin reorganisation and rift climax were delayed in East Greenland relative to the Danish region. This has important implications both for regional reconstructions of the rift system and for the understanding and testing of classical sequence stratigraphic concepts involving eustatic versus tectonic controls of basin evolution and stratigraphy.

Fluids circulation during the Miocene rifting of the Penedès half-graben, NE Iberian Peninsula

Science.gov (United States)

Baqués, Vinyet; Travé, Anna; Cantarero, Irene

2013-04-01

The Penedès half-graben, located in the north-western part of the Mediterranean, is a NE-SW oriented basin generated during the Miocene rifting. This graben is bounded to the northwest by the SE-dipping Vallès-Penedès fault, which places the Mesozoic rocks in contact with the Miocene basin-fill. The basin is filled with an up to 4 km thick succession of sediments divided into three lithostratigraphic units. From base to top: (1) a lower continental complex, (2) a continental to marine complex and (3) an upper continental complex. These units are covered by Pliocene deposits which onlap a Messinian regional erosive surface. The structural features within the Penedès half-graben allow defining three deformational phases during the Miocene rifting. The first, during the syn-rift, two successive stages of NE-SW normal faults were formed. The second, during the early post-rift, one stage of NE-SW normal faults and one minor compression phase with a dextral directional developed. The third, during the late post-rift, two successive stages of N-S trending extensional fractures (faults and joints) and one minor compression with a sinistral component developed. The fractures related to the syn-rift stage acted as conduits for meteoric fluids both, in the phreatic and in the vadose zone. During the early post-rift, Fe2+- rich fluids precipitated oxides along the NE-SW fault planes. The dextral directional faults served as conduits for meteoric fluids which reequilibrated totally the marine Miocene host rocks under the phreatic environment. The late post-rift stage was characterized by marine fluids upflowing through the N-S fractures, probably derived from the Miocene marine interval, which mixed with meteoric fluids producing dolomitization. The second set of N-S fractures served as conduits for meteoric fluids characterised by δ13C-depleted soil-derived CO2 attributed to precipitation in the vadose zone. The change from phreatic to vadose meteoric environment and the

Preliminary Geologic Map of the Vermejo Peak area, Colfax and Taos Counties, New Mexico and Las Animas and Costilla Counties, Colorado

Science.gov (United States)

Fridrich, Christopher J.; Shroba, Ralph R.; Pillmore, Charles L.; Hudson, Adam M.

2009-01-01

This geologic map covers four 7.5-minute quadrangles-The Wall, NM-CO (New Mexico-Colorado), Vermejo Park, NM-CO, Ash Mountain, NM, and Van Bremmer Park, NM. The study area straddles the boundary between the eastern flank of the Sangre de Cristo Mountains and the western margin of the Raton Basin, with about two-thirds of the map area in the basin. The Raton Basin is a foreland basin that formed immediately eastward of the Sangre de Cristo Mountains during their initial uplift, in the Late Cretaceous through early Eocene Laramide orogeny. Subsequently, these mountains have been extensively modified during formation of the Rio Grande rift, from late Oligocene to present. The map area is within that part of the Sangre de Cristo Mountains that is called the Culebra Range. Additionally, the map covers small parts of the Devil's Park graben and the Valle Vidal half-graben, in the northwestern and southwestern parts of the map area, respectively. These two grabens are small intermontaine basins, that are satellitic to the main local basin of the Rio Grande rift, the San Luis Basin, that are an outlying, early- formed part of the rift, and that separate the Culebra Range from the Taos Range, to the southwest.

Origin of marginal basins of the NW Pacific and their plate tectonic reconstructions

Science.gov (United States)

Xu, Junyuan; Ben-Avraham, Zvi; Kelty, Tom; Yu, Ho-Shing

2014-03-01

Geometry of basins can indicate their tectonic origin whether they are small or large. The basins of Bohai Gulf, South China Sea, East China Sea, Japan Sea, Andaman Sea, Okhotsk Sea and Bering Sea have typical geometry of dextral pull-apart. The Java, Makassar, Celebes and Sulu Seas basins together with grabens in Borneo also comprise a local dextral, transform-margin type basin system similar to the central and southern parts of the Shanxi Basin in geometry. The overall configuration of the Philippine Sea resembles a typical sinistral transpressional "pop-up" structure. These marginal basins except the Philippine Sea basin generally have similar (or compatible) rift history in the Cenozoic, but there do be some differences in the rifting history between major basins or their sub-basins due to local differences in tectonic settings. Rifting kinematics of each of these marginal basins can be explained by dextral pull-apart or transtension. These marginal basins except the Philippine Sea basin constitute a gigantic linked, dextral pull-apart basin system.

Rifting an Archaean Craton: Insights from Seismic Anisotropy Patterns in E. Africa

Science.gov (United States)

Ebinger, C. J.; Tiberi, C.; Currie, C. A.; van Wijk, J.; Albaric, J.

2016-12-01

Few places worldwide offer opportunities to study active deformation of deeply-keeled cratonic lithosphere. The magma-rich Eastern rift transects the eastern edge of the Archaean Tanzania craton in northeastern Tanzania, which has been affected by a large-scale mantle upwelling. Abundant xenolith locales offer constraints on mantle age, composition, and physical properties. Our aim is to evaluate models for magmatic fluid-alteration (metasomatism) and deformation of mantle lithosphere along the edge of cratons by considering spatial variations in the direction and magnitude of seismic anisotropy, which is strongly influenced by mantle flow patterns along lithosphere-asthenosphere topography, fluid-filled cracks (e.g., dikes), and pre-existing mantle lithosphere strain fabrics. Waveforms of teleseismic earthquakes (SKS, SKKS) recorded on the 39-station CRAFTI-CoLiBREA broadband array in southern Kenya and northern Tanzania are used to determine the azimuth and amount of shear-wave splitting accrued as seismic waves pass through the uppermost mantle and lithosphere at the craton edge. Lower crustal earthquakes enable evaluation of seismic anisotropy throughout the crust along the rift flanks and beneath the heavily intruded Magadi and Natron basins, and the weakly intruded Manyara basin. Our results and those of earlier studies show a consistent N50E splitting direction within the craton, with delay times of ca. 1.5 s, and similar direction east of the rift in thinner Pan-African lithosphere. Stations within the rift zone are rotated to a N15-35E splitting, with the largest delay times of 2.5 s at the margin of the heavily intruded Magadi basin. The short length scale of variations and rift-parallel splitting directions are similar to patterns in the Main Ethiopian rift attributed to melt-filled cracks or oriented pockets rising from the base of the lithosphere. The widespread evidence for mantle metasomatism and magma intrusion to mid-crustal levels suggests that

STRATIGRAPHIC EVOLUTION, PALEOENVIRONMENTS AND HYDROCARBON POTENTIALS OF THE BENUE/DAHOMEY BASINS, NIGERIAN AND POTIGUAR/CEARA BASINS, NE BRAZIL

International Nuclear Information System (INIS)

Akande, S.O; Adekeye, O.A.; Oj, O.J; Erdtmann, B.D.; Koutsokous, E.I.

2004-01-01

The stratigraphy, facies relationship and paleoenvironment of selected West African and the Brazillian rift basins permit the recognition of at least two major petroleum systems apart from the prolific Niger Delta petroleum system. The Lower Cretaceous fluivio-lacustrine petroleum system and Upper Cretaceous to Lower Tertiary, marine dominated petroleum system. Our combined studies of the stratigraphic, structural framework, paleoenvironment and time-space relationships of the petroleum systems in the Benue/Dahomey and the Potiguar/Ceara basins indicated that rifting and subsequent drifting during the opening of the South Atlantic controlled subsidence, sediment deposition and facies associations in individual basins. Whereas in the Potiguar/Ceara basins, the best developed source rocks are within the Neomacin-Aptian fluvio- lacustrine sequence of the Pendencia and Alagamar Formations which generated reserved hydrocarbon in the Acu Formation, empirical evidence for this petroleum system in the contiguous Benue/Dahomey basins are only based on the geochemical characteristics of the lower parts of the Bima Formation and the Abeokuta Group. In contrast, the Upper Cretaceous-Lower Tertiary marine petroleum system, which is constrained by poor development of reservoirs in the Potiguar/Ceara basin is productive in the Benue/Dahomey basins where source rocks, reservoir and sealing facies occur at this interval. Considering the recent hydrocarbon discoveries of the East Niger basin, the Doba (southern Chad), the Muglad basin (southern Sudan) sourced from the fluvio-lacustrine rift sequences, we suggest that this petroleum system needs more detailed exploration and has some potentials in the Benue/Dahomey frontier basins

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

Science.gov (United States)

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

2008-12-01

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

Active Magmatic Underplating in Western Eger Rift, Central Europe

Science.gov (United States)

Hrubcová, Pavla; Geissler, Wolfram H.; Bräuer, Karin; Vavryčuk, Václav; Tomek, Čestmír.; Kämpf, Horst

2017-12-01

The Eger Rift is an active element of the European Cenozoic Rift System associated with intense Cenozoic intraplate alkaline volcanism and system of sedimentary basins. The intracontinental Cheb Basin at its western part displays geodynamic activity with fluid emanations, persistent seismicity, Cenozoic volcanism, and neotectonic crustal movements at the intersections of major intraplate faults. In this paper, we study detailed geometry of the crust/mantle boundary and its possible origin in the western Eger Rift. We review existing seismic and seismological studies, provide new interpretation of the reflection profile 9HR, and supplement it by new results from local seismicity. We identify significant lateral variations of the high-velocity lower crust and relate them to the distribution and chemical status of mantle-derived fluids and to xenolith studies from corresponding depths. New interpretation based on combined seismic and isotope study points to a local-scale magmatic emplacement at the base of the continental crust within a new rift environment. This concept of magmatic underplating is supported by detecting two types of the lower crust: a high-velocity lower crust with pronounced reflectivity and a high-velocity reflection-free lower crust. The character of the underplated material enables to differentiate timing and tectonic setting of two episodes with different times of origin of underplating events. The lower crust with high reflectivity evidences magmatic underplating west of the Eger Rift of the Late Variscan age. The reflection-free lower crust together with a strong reflector at its top at depths of 28-30 km forms a magma body indicating magmatic underplating of the late Cenozoic (middle and upper Miocene) to recent. Spatial and temporal relations to recent geodynamic processes suggest active magmatic underplating in the intracontinental setting.

Relations between tectonics and sedimentation along the Eastern Sardinian margin (Western Tyrrhenian Sea) : from rifting to reactivation

Science.gov (United States)

Gaullier, Virginie; Chanier, Frank; Vendeville, Bruno; Lymer, Gaël; Maillard, Agnès; Thinon, Isabelle; Lofi, Johanna; Sage, Françoise; Giresse, Pierre; Bassetti, Maria-Angela

2014-05-01

The offshore-onshore project "METYSS-METYSAR" aims at better understand the Miocene-Pliocene relationships between crustal tectonics, salt tectonics, and sedimentation along the Eastern Sardinian margin, Western Tyrrhenian Sea. In this key-area, the Tyrrhenian back-arc basin underwent recent rifting (9-5 Ma), pro parte coeval with the Messinian Salinity Crisis (MSC, 5.96-5.33 Ma), sea-floor spreading starting during Pliocene times. Thereby, the Tyrrhenian basin and the Eastern Sardinian margin are excellent candidates for studying the mechanisms of extreme lithospheric stretching and thinning, the role of pre-existing structural fabric during and after rifting, and the reactivation of a passive margin and the associated deformation and sedimentation patterns during the MSC. We looked at the respective contributions of crustal and salt tectonics in quantifying vertical and horizontal movements, using especially the seismic markers of the MSC. Overall, we delineate the history of rifting and tectonic reactivation in the area. The distribution maps respectively of the Messinian Erosion Surface and of Messinian units (Upper Unit and Mobile Unit) show that a rifted basin already existed by Messinian time. This reveals a major pre-MSC rifting across the entire domain. Because salt tectonics can create fan-shaped geometries in sediments, syn-rift deposits have to be carefully re-examined in order to decipher the effects of crustal tectonics (rifting) and thin-skinned salt tectonics. Our data surprisingly show that there are no clues for Messinian syn-rift sediments along the East-Sardinia Basin and Cornaglia Terrace, hence no evidence for rifting after Late Tortonian times. Nevertheless, widespread deformation occurred during the Pliocene and can only be attributed to post-rift reactivation. This reactivation is characterized not only by normal faulting but also by contractional structures. Some Pliocene vertical movements caused localized gravity gliding of the mobile

Asymmetric rifting, breakup and magmatism across conjugate margin pairs: insights from Newfoundland to Ireland

Science.gov (United States)

Peace, Alexander L.; Welford, J. Kim; Foulger, Gillian R.; McCaffrey, Ken J. W.

2017-04-01

Continental extension, subsequent rifting and eventual breakup result in the development of passive margins with transitional crust between extended continental crust and newly created oceanic crust. Globally, passive margins are typically classified as either magma-rich or magma-poor. Despite this simple classification, magma-poor margins like the West Orphan Basin, offshore Newfoundland, do exhibit some evidence of localized magmatism, as magmatism to some extent invariably accompanies all continental breakup. For example, on the Newfoundland margin, a small volcanic province has been interpreted near the termination of the Charlie Gibbs Fracture Zone, whereas on the conjugate Irish margin within the Rockall Basin, magmatism appears to be more widespread and has been documented both in the north and in the south. The broader region over which volcanism has been identified on the Irish margin is suggestive of magmatic asymmetry across this conjugate margin pair and this may have direct implications for the mechanisms governing the nature of rifting and breakup. Possible causes of the magmatic asymmetry include asymmetric rifting (simple shear), post-breakup thermal anomalies in the mantle, or pre-existing compositional zones in the crust that predispose one of the margins to more melting than its conjugate. A greater understanding of the mechanisms leading to conjugate margin asymmetry will enhance our fundamental understanding of rifting processes and will also reduce hydrocarbon exploration risk by better characterizing the structural and thermal evolution of hydrocarbon bearing basins on magma-poor margins where evidence of localized magmatism exists. Here, the latest results of a conjugate margin study of the Newfoundland-Ireland pair utilizing seismic interpretation integrated with other geological and geophysical datasets are presented. Our analysis has begun to reveal the nature and timing of rift-related magmatism and the degree to which magmatic asymmetry

Is the Gop rift oceanic? A reevaluation of the Seychelles-India conjugate margins

Science.gov (United States)

Guan, Huixin; Werner, Philippe; Geoffroy, Laurent

2016-04-01

Recent studies reevaluated the timing and evolution of the breakup process between the Seychelles continental ridge and India, and the relationship between this evolution and mantle melting associated with the Deccan Igneous Province1,2,3. Those studies, mainly based on gravity and seismic refraction surveys, point that the oceanic domain located between the Seychelles and the Laxmi Ridge (here designed as the Carlsberg Basin) is the youngest oceanic domain between India and the Seychelles. To the East of the Laxmi Ridge, the aborted Gop Rift is considered as an older highly magmatic extensional continental system with magmatism, breakup and oceanic spreading being coeval with or even predating the emplacement of the major pulse of the Deccan trapps. This interpretation on the oceanic nature of the Gop Rift conflicts with other extensive surveys based on magnetic and seismic reflection data4 which suggest that the Gop Rift is an extended syn-magmatic continental domain. In our work based (a) on the existing data, (b) on new deep-seismic reflection surveys (already published by Misra5) down to the Moho and underlying mantle and (c) on new concepts on the geometry of volcanic passive margins, we propose a distinct interpretation of the Seychelles-India system. As proposed by former authors6,7, the Indian margin suffered some continental stretching and thinning before the onset of the Deccan traps during the Mesozoic. Thus continental crust thickness cannot be used easily as a proxy of syn-magmatic stretching-thinning processes or even to infer the presence or not of oceanic-type crust based, solely, on crustal thickness. However, some remarkable features appear on some of the deep penetration seismic lines we studied. We illustrate that the whole Seychelles/India system, before the opening of the present-day "Carlsberg Basin" may simply be regarded as a pair of sub-symmetric conjugate volcanic passive margins (VPMs) with inner and outer SDR wedges dipping towards the

sRecovery Act: Geologic Characterization of the South Georgia Rift Basin for Source Proximal CO₂ Storage

Energy Technology Data Exchange (ETDEWEB)

Waddell, Michael [South Carolina Research Foundation, Columbia, SC (United States)

2015-02-10

This study focuses on evaluating the feasibility and suitability of using the Jurassic/Triassic (J/TR) sediments of the South Georgia Rift basin (SGR) for CO₂ storage in southern South Carolina and southern Georgia The SGR basin in South Carolina (SC), prior to this project, was one of the least understood rift basin along the east coast of the U.S. In the SC part of the basin there was only one well (Norris Lightsey #1) the penetrated into J/TR. Because of the scarcity of data, a scaled approach used to evaluate the feasibility of storing CO₂ in the SGR basin. In the SGR basin, 240 km (~149 mi) of 2-D seismic and 2.6 km2 3-D (1 mi2) seismic data was collected, process, and interpreted in SC. In southern Georgia 81.3 km (~50.5 mi) consisting of two 2-D seismic lines were acquired, process, and interpreted. Seismic analysis revealed that the SGR basin in SC has had a very complex structural history resulting the J/TR section being highly faulted. The seismic data is southern Georgia suggest SGR basin has not gone through a complex structural history as the study area in SC. The project drilled one characterization borehole (Rizer # 1) in SC. The Rizer #1 was drilled but due to geologic problems, the project team was only able to drill to 1890 meters (6200 feet) instead of the proposed final depth 2744 meters (9002 feet). The drilling goals outlined in the original scope of work were not met. The project was only able to obtain 18 meters (59 feet) of conventional core and 106 rotary sidewall cores. All the conventional core and sidewall cores were in sandstone. We were unable to core any potential igneous caprock. Petrographic analysis of the conventional core and sidewall cores determined that the average porosity of the sedimentary material was 3.4% and the average permeability was 0.065 millidarcy. Compaction and diagenetic studies of the samples determined there would not be any porosity or permeability at depth in SC. In Georgia there

Two-Dimensional Numerical Modeling of Intracontinental Extension: A Case Study Of the Baikal Rift Formation

DEFF Research Database (Denmark)

Yang, H.; Chemia, Zurab; Artemieva, Irina

The Baikal Rift zone (BRZ) is a narrow ( 10 km) active intra-continental basin, located at the boundary between the Amurian and Eurasian Plates. Although the BRZ is one of the major tectonically active rift zones in the world andit has been a subject of numerous geological...... on topography,basin depth, the structure of the crust, lithosphere thickness, and the location of major tectonic faults. Our goal is to determine the physical models that reproduce reasonably well the ob-served deformation patterns of the BRZ.We perform a systematic analysis of the pa-rameter space in order...

Thermomechanical Controls on the Success and Failure of Continental Rift Systems

Science.gov (United States)

Brune, S.

2017-12-01

Studies of long-term continental rift evolution are often biased towards rifts that succeed in breaking the continent like the North Atlantic, South China Sea, or South Atlantic rifts. However there are many prominent rift systems on Earth where activity stopped before the formation of a new ocean basin such as the North Sea, the West and Central African Rifts, or the West Antarctic Rift System. The factors controlling the success and failure of rifts can be divided in two groups: (1) Intrinsic processes - for instance frictional weakening, lithospheric thinning, shear heating or the strain-dependent growth of rift strength by replacing weak crust with strong mantle. (2) External processes - such as a change of plate divergence rate, the waning of a far-field driving force, or the arrival of a mantle plume. Here I use numerical and analytical modeling to investigate the role of these processes for the success and failure of rift systems. These models show that a change of plate divergence rate under constant force extension is controlled by the non-linearity of lithospheric materials. For successful rifts, a strong increase in divergence velocity can be expected to take place within few million years, a prediction that agrees with independent plate tectonic reconstructions of major Mesozoic and Cenozoic ocean-forming rift systems. Another model prediction is that oblique rifting is mechanically favored over orthogonal rifting, which means that simultaneous deformation within neighboring rift systems of different obliquity and otherwise identical properties will lead to success and failure of the more and less oblique rift, respectively. This can be exemplified by the Cretaceous activity within the Equatorial Atlantic and the West African Rifts that lead to the formation of a highly oblique oceanic spreading center and the failure of the West African Rift System. While in nature the circumstances of rift success or failure may be manifold, simplified numerical and

Basin Analysis and Petroleum System Characterisation of Western Bredasdorp Basin, Southern Offshore of South Africa: Insights from a 3d Crust-Scale Basin Model - (Phase 1)

Science.gov (United States)

Sonibare, W. A.; Scheck-Wenderoth, M.; Sippel, J.; Mikeš, D.

2012-04-01

In recent years, construction of 3D geological models and their subsequent upscaling for reservoir simulation has become an important tool within the oil industry for managing hydrocarbon reservoirs and increasing recovery rate. Incorporating petroleum system elements (i.e. source, reservoir and trap) into these models is a relatively new concept that seems very promising to play/prospect risk assessment and reservoir characterisation alike. However, yet to be fully integrated into this multi-disciplinary modelling approach are the qualitative and quantitative impacts of crust-scale basin dynamics on the observed basin-fill architecture and geometries. The focus of this study i.e. Western Bredasdorp Basin constitutes the extreme western section of the larger Bredasdorp sub-basin, which is the westernmost depocentre of the four southern Africa offshore sub-basins (others being Pletmos, Gamtoos and Algoa). These basins, which appear to be initiated by volcanically influenced continental rifting and break-up related to passive margin evolution (during the Mid-Late Jurassic to latest Valanginian), remain previously unstudied for crust-scale basin margin evolution, and particularly in terms of relating deep crustal processes to depo-system reconstruction and petroleum system evolution. Seismic interpretation of 42 2D seismic-reflection profiles forms the basis for maps of 6 stratigraphic horizons which record the syn-rift to post-rift (i.e. early drift and late drift to present-day seafloor) successions. In addition to this established seismic markers, high quality seismic profiles have shown evidence for a pre-rift sequence (i.e. older than Late Jurassic >130 Ma). The first goal of this study is the construction of a 3D gravity-constrained, crust-scale basin model from integration of seismics, well data and cores. This basin model is constructed using GMS (in-house GFZ Geo-Modelling Software) while testing its consistency with the gravity field is performed using IGMAS

Chukchi Borderland | Crustal Complex of the Amerasia Basin, Arctic Ocean

Science.gov (United States)

Ilhan, I.; Coakley, B.; Houseknecht, D. W.

2017-12-01

In the Arctic Ocean, Chukchi Borderland separates the North Chukchi shelf and Toll deep basins to the west and Canada deep basin to the east. Existing plate reconstructions have attempted to restore this north-striking, fragments of the continental crust to all margins of the Amerasia Basin based on sparse geologic and geophysical measurements. Regional multi-channel seismic reflection and potential field geophysics, and geologic data indicate it is a high standing continental block, requiring special accommodation to create a restorable model of the formation of the Amerasia Basin. The Borderland is composed of the Chukchi Plateau, Northwind Basin, and Northwind Ridge divided by mostly north striking normal faults. These offset the basement and bound a sequence of syn-tectonic sediments. Equivalent strata are, locally, uplifted, deformed and eroded. Seaward dipping reflectors (SDRs) are observed in the juncture between the North Chukchi, Toll basins, and southern Chukchi Plateau underlying a regional angular unconformity. This reveals that this rifted margin was associated with volcanism. An inferred condensed section, which is believed to be Hauterivian-Aptian in age, synchronous with the composite pebble shale and gamma-ray zone of the Alaska North Slope forms the basal sediments in the North Chukchi Basin. Approximately 15 km of post-rift strata onlap the condensed section, SDRs and, in part, the wedge sequence on the Chukchi Plateau from west to east, thinning to the north. These post-Aptian sediments imply that the rifted margin subsided no later than the earliest Cretaceous, providing a plausible time constraint for the inferred pre-Cretaceous rifting in this region. The recognition of SDRs and Hauterivian—Aptian condensed section, and continuity of the Early—Late Cretaceous post-rift strata along the margins of the Borderland, strike variations of the normal faults, absence of observable deformation along the Northwind Escarpment substantially constrain

Magma-poor vs. magma-rich continental rifting and breakup in the Labrador Sea

Science.gov (United States)

Gouiza, M.; Paton, D.

2017-12-01

Magma-poor and magma-rich rifted margins show distinct structural and stratigraphic geometries during the rift to breakup period. In magma-poor margins, crustal stretching is accommodated mainly by brittle faulting and the formation of wide rift basins shaped by numerous graben and half-graben structures. Continental breakup and oceanic crust accretion are often preceded by a localised phase of (hyper-) extension where the upper mantle is embrittled, serpentinized, and exhumed to the surface. In magma-rich margins, the rift basin is narrow and extension is accompanied by a large magmatic supply. Continental breakup and oceanic crust accretion is preceded by the emplacement of a thick volcanic crust juxtaposing and underplating a moderately thinned continental crust. Both magma-poor and magma-rich rifting occur in response to lithospheric extension but the driving forces and processes are believed to be different. In the former extension is assumed to be driven by plate boundary forces, while in the latter extension is supposed to be controlled by sublithospheric mantle dynamics. However, this view fails in explaining observations from many Atlantic conjugate margins where magma-poor and magma-rich segments alternate in a relatively abrupt fashion. This is the case of the Labrador margin where the northern segment shows major magmatic supply during most of the syn-rift phase which culminate in the emplacement of a thick volcanic crust in the transitional domain along with high density bodies underplating the thinned continental crust; while the southern segment is characterized mainly by brittle extension, mantle seprentinization and exhumation prior to continental breakup. In this work, we use seismic and potential field data to describe the crustal and structural architectures of the Labrador margin, and investigate the tectonic and mechanical processes of rifting that may have controlled the magmatic supply in the different segments of the margin.

Subsidence history, crustal structure and evolution of the Nogal Rift, Northern Somalia

Science.gov (United States)

Ali, M. Y.; Watts, A. B.

2013-12-01

Seismic reflection profile, gravity anomaly, and biostratigraphic data from deep exploration wells have been used to determine the tectonic subsidence, structure and evolution of the Nogal basin, Northern Somalia, one of a number of ENE-WSW trending early Mesozoic rifts that formed prior to opening of the Gulf of Aden. Backstripping of biostratigraphic data at the Nogal-1 and Kali-1 wells provides new constraints on the age of rifting, and the amount of crustal and mantle extension. The tectonic subsidence and uplift history at the wells can be generally explained as a consequence of two, possibly three, major rifting events. The first event initiated in the Late Jurassic (~156 Ma) and lasted for ~10 Myr. We interpret the rift as a late stage event associated with the break-up of Gondwana and the separation of Africa and Madagascar. The second event initiated in the Late Cretaceous (~80 Ma) and lasted for ~20 Myr. This event probably correlates with a rapid increase in spreading rate on the ridges separating the African and Indian and African and Antarctica plates and a contemporaneous slowing down of Africa's plate motion. The backstripped tectonic subsidence data can be explained by a multi-rift extensional model with a stretching factor, β, in the range 1.17-1.38. The third and most recent event occurred in the Oligocene (~32 Ma) and lasted for ~10 Myr. This rift only developed at the centre of the basin close to Nogal-1 well, and is related to the opening of the Gulf of Aden. The amount of crustal thinning inferred at the Kali-1 well is consistent with the results of Process-Oriented Gravity and Flexure (POGM) modelling, assuming an elastic thickness of ~30 km. The thinning at the Nogal-1 well, however, is greater by ~ 7 km than predicted suggesting that the basin may be locally underplated by magmatic material. Irrespective, POGM suggests the transition between thick crust beneath Northern Somalia to thin crust beneath the Indian Ocean forms a ~500 km wide

Besshi-type mineral systems in the Palaeoproterozoic Bryah Rift-Basin, Capricorn Orogen, Western Australia: Implications for tectonic setting and geodynamic evolution

Directory of Open Access Journals (Sweden)

Franco Pirajno

2016-05-01

Full Text Available In this contribution we use VMS mineral systems in the Bryah rift-basin to constrain the tectonic setting of the widespread mafic and ultramafic magmatism that characterises the rift-basin in question. Two distinct, but temporally closely associated, lithostratigraphic sequences, Narracoota and Karalundi Formations, are discussed. The Karalundi Formation is the main host of VMS mineral systems in the region. The Karalundi Formation consists of turbiditic and immature clastic sediments, which are locally intercalated with basaltic hyaloclastites, dolerites and banded jaspilites. We propose that the basaltic hyaloclastites, dolerites and clastics and jaspilites rocks, form a distinct unit of the Karalundi Formation, named Noonyereena Member. The VMS mineral systems occur near the north-east trending Jenkin Fault and comprise the giant and world-class DeGrussa and the Red Bore deposits. The nature of these deposits and their intimate association with terrigenous clastic rocks and dominantly marine mafic volcanic and subvolcanic rocks, as well as the common development of peperitic margins, are considered indicative of a Besshi-type environment, similar to that of present-day Gulf of California. Our Re-Os age data from a primary pyrite yielded a mean model age of 2012 ± 48 Ma, which coincides (within error with recent published Re-Os data (Hawke et al., 2015 and confirms the timing of the proposed geodynamic evolution. We propose a geodynamic model that attempts to explain the presence of the Narracoota and Karalundi Formations as the result of mantle plume activity, which began with early uplift of continental crust with intraplate volcanism, followed by early stages of rifting with the deposition of the Karalundi Formation (and Noonyereena Member, which led to the formation of Besshi-type VMS deposits. With on-going mantle plume activity and early stages of continental separation, an oceanic plateau was formed and is now represented by mafic

NW Africa post-rift tectonics: fieldwork constraints from an "unfitting" anticline in west Morocco

Science.gov (United States)

Fernández-Blanco, David; Gouiza, Mohamed

2015-04-01

The evolution of the Moroccan Atlantic rifted margin is marked by a period of abnormal and excessive early post-rift subsidence during the Late Jurassic-Early Cretaceous affecting the proximal coastal basins, the continental shelf and the distal deep basins, which acted coevally to km-scale uplift and erosion of large domains to the east. The tectonics of the uplift event are still unclear, as it took place 30 to 50 Myr after lithospheric breakup between Morocco and Nova Scotia and prior to the Atlas/Alpine contraction, which gave rise to the Atlas and the Rif mountain belts. The Essaouira-Haha basin, located on the coastal plain of the Atlantic rifted margin of Morocco, and bounded by two uplifted Paleozoic basement highs (i.e. the Massif Ancien of Marrakech, to the east, and the Jebilet, to the northeast), is an ideal location to investigate the tectonic processes that might have triggered these vertical movements. Although most of the deformation observed in the basin is classically attributed to Upper Cretaceous halokinesis and Neogene Atlas contraction, recent works have shown the existence of contractional structures. We carry out a structural analysis of the Jbel Amsittene Anticline, located in the middle of the Essaouira-Haha basin to investigate the tectonics of its formation and its relationship with the above-mentioned exhumation. We show structural field data along several cross-sections transecting the anticline, and characterize a salt-cored fault propagation fold verging north, with a Triassic salt acting as a detachment plane. Regional kinematic indicators and structures show overall NNW-SSE to NNE-SSW shortening and active tectonics during the postrift phase, as indicated by syn-tectonic wedges seen for the Late Jurassic to Early Cretaceous period. These facts discard the "salt-drives-tectonics" theory to let "tectonic-drives-salt" one to rise, and point to factors other than small-cell mantle convection acting during the evolution of the Moroccan

Backward modelling of the subsidence evolution of the Colorado Basin, offshore Argentina and its relation to the evolution of the conjugate Orange Basin, offshore SW Africa

Science.gov (United States)

Dressel, Ingo; Scheck-Wenderoth, Magdalena; Cacace, Mauro

2017-10-01

In this study we focus on reconstructing the post-rift subsidence evolution of the Colorado Basin, offshore Argentina. We make use of detailed structural information about its present-day configuration of the sedimentary infill and the crystalline crust. This information is used as input in a backward modelling approach which relies on the assumption of local isostasy to reconstruct the amount of subsidence as induced by the sedimentary load through different time stages. We also attempt a quantification of the thermal effects on the subsidence as induced by the rifting, here included by following the uniform stretching model of lithosphere thinning and exponentially cooling through time. Based on the available information about the present-day geological state of the system, our modelling results indicate a rather continuous post-rift subsidence for the Colorado Basin, and give no significant evidence of any noticeable uplift phase. In a second stage, we compare the post-rift evolution of the Colorado Basin with the subsidence evolution as constrained for its conjugate SW African passive margin, the Orange Basin. Despite these two basins formed almost coevally and therefore in a similar large scale geodynamic context, their post-rift subsidence histories differ. Based on this result, we discuss causative tectonic processes likely to provide an explanation to the observed differences. We therefore conclude that it is most probable that additional tectonic components, other than the ridge-push from the spreading of the South Atlantic Ocean, are required to explain the observed differences in the subsidence of the two basins along the conjugate passive margins. Such additional tectonic components might be related to a dynamic mantle component in the form of either plume activity (Africa) or a subducting slab and the presence of an ongoing compressional stress system as revealed for different areas in South America.

Compressional reactivation of hyperextended domains on a rifted margin: a requirement for a reappraisal of traditional restoration procedures?

Science.gov (United States)

Cadenas Martínez, P.; Fernandez Viejo, G.; Pulgar, J. A.

2017-12-01

The North Iberian margin is an inverted hyperextended rifted margin that preserves the initial stages of compressional reactivation. Rift inheritance conditioned in a determinant way the contractional reactivation. The underthrusting of the hyperextended distal domains beneath the platform and the formation of an accretionary wedge at the toe of the slope focused most of the compression. The underthrusting gave place to the formation of a crustal root and the uplifting of the Cantabrian Mountains onshore. Meanwhile, the main rift basins within the continental platform were slightly inverted. Plate kinematic reconstructions and palinspatic restorations have provided different shortening values. Thereby, the amount of shortening linked with the Cenozoic compression is still unclear and a matter of debate on this area.In this work, we present a full cross-section at the central part of the North Iberian margin developed from the restoration of a high quality depth migrated seismic profile running from the continental platform to the Biscay abyssal plain. A shortening calculation gives an estimate of about 1 km within the Asturian Basin, in the continental platform, while in the accretionary wedge at the bottom of the slope, shortening values ranges between 12 km and 15 km. The limited values estimated within the Asturian Basin support the mild inversion observed within this basin, which preserves most of the extensional imprint. Within the abyssal plain, shortening values differ from previous estimations and cannot account for a high amount of compression in the upper crust. Deformation of the hyperextended crust and the exhumed mantle domains inherited from the rifting processes would have accommodated most of the compression. Restoration of these domains seems to be the key to decipher the structure and the tectonic evolution of the reactivated rifted margin but cannot be solved accurately using traditional restoration methods. This leads to a reappraisal of the

Metasomatism and the Weakening of Cratons: A Mechanism to Rift Cratons

Science.gov (United States)

Wenker, Stefanie; Beaumont, Christopher

2016-04-01

depends on the timing of extension, with respect to metasomatism. The key effect is the associated increase in temperature which must have time to reach peak values in the initially cold and strongest, uppermost mantle lithosphere. However, it remains true that the model cratons mostly remain strong and only rift when subjected to intensive metasomatism. This may explain why so many cratons have survived and only a few have rifted. An additional effect is that the craton surface subsides isostatically to balance the increasing density of craton mantle lithosphere where it is moderately metasomatized. We suggest that this is the mechanism that forms intracratonic basins. If correct, subsidence and subsequent uplift of intracratonic basins, and cratonic rifting constitute evidence of progressive metasomatism of cratonic mantle lithosphere.

Fish research project -- Oregon: Investigations into the early life history of naturally produced spring chinook salmon in the Grande Ronde River Basin. Annual progress report, 1 September 1995--31 August 1996

International Nuclear Information System (INIS)

Jonasson, B.C.; Carmichael, R.W.; Keefe, M.

1997-09-01

Historically, the Grande Ronde River produced an abundance of salmonids including stocks of spring, summer and fall chinook salmon, sockeye salmon, coho salmon, and summer steelhead. During the past century, numerous factors have caused the reduction of salmon stocks such that only sustainable stocks of spring chinook salmon and summer steelhead remain. The sizes of spring chinook salmon populations in the Grande Ronde River basin also have been declining steadily and are substantially depressed from estimates of historic levels. In addition to a decline in population abundance, a reduction of spring chinook salmon spawning distribution is evident in the Grande Ronde River basin. Numerous factors are thought to contribute to the decline of spring chinook salmon in the Snake River and its tributaries. These factors include passage problems and increased mortality of juvenile and adult migrants at mainstem Columbia and Snake river dams, overharvest, and habitat degradation associated with timber, agricultural, and land development practices. This study was designed to describe aspects of the life history strategies exhibited by spring chinook salmon in the Grande Ronde River basin. During the past year the focus was on rearing and migration patterns of juveniles in the upper Grande Ronde River and Catherine Creek. The study design included three objectives: (1) document the annual in-basin migration patterns for spring chinook salmon juveniles in the upper Grande Ronde River and Catherine Creek, including the abundance of migrants, migration timing and duration; (2) estimate and compare smolt survival indices to mainstem Columbia and Snake river dams for fall and spring migrating spring chinook salmon; and (3) determine summer and winter habitat utilization and preference of juvenile spring chinook salmon in the upper Grande Ronde River and Catherine Creek

Latest Miocene-earliest Pliocene evolution of the ancestral Rio Grande at the Española-San Luis Basin boundary, northern New Mexico

Science.gov (United States)

Daniel J. Koning,; Aby, Scott B.; Grauch, V. J.; Matthew J. Zimmerer,

2016-01-01

We use stratigraphic relations, paleoflow data, and 40Ar/39Ar dating to interpret net aggradation, punctuated by at least two minor incisional events, along part of the upper ancestral Rio Grande fluvial system between 5.5 and 4.5 Ma (in northern New Mexico). The studied fluvial deposits, which we informally call the Sandlin unit of the Santa Fe Group, overlie a structural high between the San Luis and Española Basins. The Sandlin unit was deposited by two merging, west- to southwest-flowing, ancestral Rio Grande tributaries respectively sourced in the central Taos Mountains and southern Taos Mountains-northeastern Picuris Mountains. The river confluence progressively shifted southwestward (downstream) with time, and the integrated river (ancestral Rio Grande) flowed southwards into the Española Basin to merge with the ancestral Rio Chama. Just prior to the end of the Miocene, this fluvial system was incised in the southern part of the study area (resulting in an approximately 4–7 km wide paleovalley), and had sufficient competency to transport cobbles and boulders. Sometime between emplacement of two basalt flows dated at 5.54± 0.38 Ma and 4.82±0.20 Ma (groundmass 40Ar/39Ar ages), this fluvial system deposited 10–12 m of sandier sediment (lower Sandlin subunit) preserved in the northern part of this paleovalley. The fluvial system widened between 4.82±0.20 and 4.50±0.07 Ma, depositing coarse sand and fine gravel up to 14 km north of the present-day Rio Grande. This 10–25 m-thick sediment package (upper Sandlin unit) buried earlier south- to southeast-trending paleovalleys (500–800 m wide) inferred from aeromagnetic data. Two brief incisional events are recognized. The first was caused by the 4.82±0.20 Ma basalt flow impounding south-flowing paleodrainages, and the second occurred shortly after emplacement of a 4.69±0.09 Ma basalt flow in the northern study area. Drivers responsible for Sandlin unit aggradation may include climate

How sedimentation affects rift segment interaction during oblique extension: a 4D analogue modelling study

Science.gov (United States)

Zwaan, Frank; Schreurs, Guido; Adam, Jürgen

2017-04-01

During the early stages of rifting, rift segments may form along non-continuous and/or offset pre-existing weaknesses. It is important to understand how these initial rift segments interact and connect to form a continuous rift system. Previous modelling of rift interaction structures has shown the dominant influence of oblique extension, promoting rift segment linkage (e.g. Zwaan et al., 2016) and eventual continent break-up (Brune et al., 2012). However, these studies did not incorporate sedimentation, which can have important implications for rift evolution (e.g. Bialas and Buck, 2009). Here we present a series of analogue model experiments investigating the influence of sedimentation on rift interaction structures under oblique extension conditions. Our set-up involves a base of compressed foam and plexiglass that forces distributed extension in the overlying analogue materials when the model sidewalls move apart. A sand layer simulates the brittle upper crust and a viscous sand/silicone mixture the ductile lower crust. One of the underlying base plates can move laterally allowing oblique extension. Right-stepping offset and disconnected lines of silicone (seeds) on top of the basal viscous serve as inherited structures since the strong sand cover is locally thinner. We apply syn-rift sediments by filling in the developing rift and transfer zone basins with sand at fixed time steps. Models are run either with sedimentation or without to allow comparison. The first results suggest that the gross structures are similar with or without sedimentation. As seen by Zwaan et al. (2016), dextral oblique extension promotes rift linkage because rift propagation aligns itself perpendicular to the extension direction. This causes the rift segments to grow towards each other and to establish a continuous rift structure. However, the structures within the rift segments show quite different behaviour when sedimentation is applied. The extra sediment loading in the rift basin

Alboran Basin, southern Spain - Part I: Geomorphology

Energy Technology Data Exchange (ETDEWEB)

Munoz, A. [Secretaria General de Pesca Maritima, Corazon de Maria, 8, 28002 Madrid (Spain); Ballesteros, M.; Rivera, J.; Acosta, J. [Instituto Espanol de Oceanografia, Corazon de Maria, 8, 28002 Madrid (Spain); Montoya, I. [Universidad Juan Carlos I, Campus de Mostoles, Madrid (Spain); Uchupi, E. [Woods Hole Oceanographic Institution, Woods Hole, MA 02543 (United States)

2008-01-15

Bathymetric, 3D relief and shaded relief maps created from multibeam echo-sounding data image the morphology of the Alboran Basin, a structural low along the east-west-trending Eurasian-African plates boundary. Topographic features in the basin are the consequence of volcanism associated with Miocene rifting, rift and post-rift sedimentation, and recent faulting resulting from the convergence of the African-Eurasian plates. Pleistiocene glacially induced regressions/transgressions when the sea level dropped to about 150 m below its present level gas seeps and bottom currents. Recent faulting and the Pleistocene transgressions/regressions led to mass-wasting, formation of turbidity currents and canyon erosion on the basin's slopes. Recent fault traces at the base of the northern basin slope have also served as passageways for thermogenic methane, the oxidation of which by bacteria led to the formation of carbonate mounds along the fault intercepts on the sea floor. Expulsion of thermogenic or biogenic gas has led to the formation of pockmarks; erosion by bottom currents has resulted in the formation of moats around seamounts and erosion of the seafloor of the Alboran Ridge and kept the southern edge of the 36 10'N high sediment free. (author)

Post-Pan-African tectonic evolution of South Malawi in relation to the Karroo and recent East African rift systems

Science.gov (United States)

Castaing, C.

1991-05-01

Structural studies conducted in the Lengwe and Mwabvi Karroo basins and in the basement in South Malawi, using regional maps and published data extended to cover Southeast Africa, serve to propose a series of geodynamic reconstructions which reveal the persistence of an extensional tectonic regime, the minimum stress σ3 of which has varied through time. The period of Karroo rifting and the tholeiitic and alkaline magmatism which terminated it, were controlled by NW-SE extension, which resulted in the creation of roughly NE-SW troughs articulated by the Tanganyika-Malawi and Zambesi pre-transform systems. These were NW-SE sinistral-slip systems with directions of movement dipping slightly to the Southeast, which enabled the Mwanza fault to play an important role in the evolution of the Karroo basins of the Shire Valley. The Cretaceous was a transition period between the Karroo rifting and the formation of the Recent East African Rift System. Extension was NE-SW, with some evidence for a local compressional episode in the Lengwe basin. Beginning in the Cenozoic, the extension once more became NW-SE and controlled the evolution in transtension of the Recent East African Rift System. This history highlights the major role of transverse faults systems dominated by strike-slip motion in the evolution and perpetuation of the continental rift systems. These faults are of a greater geological persistence than the normal faults bounding the grabens, especially when they are located on major basement anisotropies.

Sr isotope stratigraphy of some Rupelian carbonated laminites from the Limagne Basin: influence of seawater in the rift of the French Massif central?

International Nuclear Information System (INIS)

Briot, D.; Poidevin, J.L.

1998-01-01

87 Sr/ 86 Sr ratios of biogenic and abiotic calcites Upper Rupelian sediments in the Limagne rift (French Massif Central) define a smooth and regular negative correlation with time interrupted by repetitive sharp peaks; the progressive drop in isotopic ratio can be explained by the geological evolution of the river basin through time. Negative peaks are explained by synsedimentary volcanism, repeated marine incursions, or leaching of ancient evaporites. Comparison with available paleontologic data does not favour the volcanic explanation, but rather the influence of Rupelian marine waters. (authors)

Sediment budget and tectonic evolution of the Meuse catchment in the Ardennes and the Roer Valley Rift System

NARCIS (Netherlands)

Balen, R.T. van; Houtgast, R.F.; Wateren, F.M. van der; Berghe, J. van den; Bogaart, P.W.

2000-01-01

The Meuse river system is located in the northeastern part of the Paris Basin, the Ardennes, and the Roer Valley Rift System (RVRS). The Meuse river system developed during the uplift of the Ardennes since the Eocene and it was affected by renewed rifting of the RVRS starting in the Late Oligocene.

Sediment budget and tectonic evolution of the Meuse catchment in the Ardennes and the Roer Valley Rift System.

NARCIS (Netherlands)

van Balen, R.T.; Houtgast, R.F.; van der Wateren, F.M.; Vandenberghe, J.; Bogaart, P.W.

2000-01-01

The Meuse river system is located in the northeastern part of the Paris Basin, the Ardennes, and the Roer Valley Rift System (RVRS). The Meuse river system developed during the uplift of the Ardennes since the Eocene and it was affected by renewed rifting of the RVRS starting in the Late Oligocene.

Mesozoic tectonics of the Otway Basin region: The legacy of Gondwana and the active Pacific margin: a review and ongoing research

Energy Technology Data Exchange (ETDEWEB)

Hill, K.A. [Monash Univ., Clayton, VIC (Australia). Department of Earth Sciences; Finlayson, D.M. [Australian Geological Survey Organisation, Canberra, ACT (Australia); Hill, K.C. [La Trobe Univ., Bundoora, VIC (Australia). School of Earth Sciences; Cooper, G.T. [Monash Univ., Clayton, VIC (Australia). Department of Earth Sciences

1995-12-31

Recent plate tectonic models for SE Australia and the formerly contiguous parts of Gondwana are reviewed in this paper in order to assess the Mesozoic evolution of the Otway Basin. Research around the Otway Basin is summarised to demonstrate how the application of new technology can address some of the outstanding questions regarding the Basin`s evolution on local to lithospheric scales. The geometry and geology of Australia`s southern margin are compared with Atlantic rift-drift margins to provide analogues for tectonics and hydrocarbon exploration in the Otway Basin. At least two stages of rifting were found to be evident in the Cretaceous and in the deep structure of the Otway basin. These are Early Cretaceous rifting which is manifested in numerous half-graben and accommodation zones, and Late Cretaceous rifting in the deep seismic data seaward of the Tartwaup, Timboon and Sorell fault zones. Major offsets of the spreading axis during break up, at the Tasman and Spencer Fracture Zones were probably controlled by the location of Paleozoic terrace boundaries. The Tasman Fracture System was reactivated during break-up, with considerable uplift and denudation of the Bass failed rift to the east, which controlled Otway Basin facies distribution. Paleozoic structures also had a significant effect in determining the half graben orientations within a general N-S extensional regime during early Cretaceous rifting. The late Cretaceous second stage of rifting, seaward of the Tartwaup, Timboon and Sorell fault zones, left stable failed rift margin to the north, but the attenuated lithosphere of the Otway-Sorell microplate to the south records repeated extension that led to continental separation and may be part of an Antarctic upper plate. 1 table. 16 figs., 4 photos., refs.

Present-day Opening of the Natron Rift: Tectonic and Magmatic Processes at Work

Science.gov (United States)

Calais, E.; Dalaison, M.; Saria, E.; Doubre, C.; Masson, F.

2017-12-01

The young Natron basin (system, is an important locale to study the initial stage of continental rifting. It was the locus of a rarely observed tectono-magmatic event in July 2007, with slow slip on an intra-basin normal fault followed by a 10 km-long dike intrusion underneath the Gelai shield volcano. Here we report on a series of GPS observations over a 20-site network spanning the basin, measured repeatedly since 2013. We observe a long wavelength ( 200 km wide) extension with a horizontal rate of about 2 mm/yr, consistent with recentlty published regional kinematic models, and a velocity gradient centered on the west-bounding fault of the Natron basin. Initial models show that the data is best fit by a normal fault dipping 60 degrees to the east and slipping at a rate of 6 mm/yr. Superimposed on this long wavelength extension, we observe a smaller scale ( 30 km wide) extensional signal in the middle of the basin, roughly coincident with the location of the Gelai volcano, which was the locale of the 2007 seismic-magmatic crisis. We investigate the relative importance of tectonic faulting, post-diking relaxation following the 2007 intrusion (as observed for instance in Afar or Iceland after similar events), and melt recharge of the intra-basin magmatic system in present-day extension across this young segment of the East African Rift.

Infrastructure Improvements for Snowmelt Runoff Forecasting and Assessments of Climate Change Impacts on Water Supplies in the Rio Grande Basin

Science.gov (United States)

Rango, A.; Steele, C. M.; Demouche, L.

2009-12-01

In the Southwest US, the southern Rocky Mountains provide a significant orographic barrier to prevailing moisture-laden Westerly winds, which results in snow accumulation and melt, both vitally important to the region’s water resources. The inherent variability of meteorological conditions in the Southwest, during both snowpack buildup and depletion, requires improved spatially-distributed data. The population of ground-based networks (SNOTEL, SCAN, and weather stations) is sparse and does not satisfactorily represent the variability of snow accumulation and melt. Remote sensing can be used to supplement data from ground networks, but the most frequently available remotely sensed product with the highest temporal and spatial resolution, namely snow cover, only provides areal data and not snow volume. Fortunately, the Snowmelt Runoff Model(SRM), which was developed in mountainous regions of the world, including the Rio Grande basin, accepts snow covered area as one of its major input variables along with temperature and precipitation. With the growing awareness of atmospheric warming and the southerly location of Southwest watersheds, it has become apparent that the effects of climate change will be especially important for Southwestern water users. The NSF-funded EPSCoR project “Climate Change Impacts on New Mexico’s Mountain Sources of Water” (started in 2009) has focused on improving hydrometeorological measurements, developing basin-wide and sub-basin snow cover mapping methods, generating snowmelt runoff simulations, forecasts, and long-term climate change assessments, and informing the public of the results through outreach and educational activities. Five new SNOTEL and four new SCAN sites are being installed in 2009-2010 and 12 existing basic SNOTEL sites are being upgraded. In addition, 30 automated precipitation gages are being added to New Mexico measurement networks. The first phase of snow mapping and modeling has focused on four sub basins

Discussion on final rifting evolution and breakup : insights from the Mid Norwegian - North East Greenland rifted system

Science.gov (United States)

Peron-Pinvidic, Gwenn; Terje Osmundsen, Per

2016-04-01

In terms of rifted margin studies, the characteristics of the distal and outer domains are among the today's most debated questions. The architecture and composition of deep margins are rarely well constrained and hence little understood. Except from in a handful number of cases (eg. Iberia-Newfoundland, Southern Australia, Red Sea), basement samples are not available to decipher between the various interpretations allowed by geophysical models. No consensus has been reached on the basement composition, tectonic structures, sedimentary geometries or magmatic content. The result is that non-unique end-member interpretations and models are still proposed in the literature. So, although these domains mark the connection between continents and oceans, and thus correspond to unique stages in the Earth's lithospheric life cycle, their spatial and temporal evolution are still unresolved. The Norwegian-Greenland Sea rift system represents an exceptional laboratory to work on questions related to rifting, rifted margin formation and sedimentary basin evolution. It has been extensively studied for decades by both the academic and the industry communities. The proven and expected oil and gas potentials led to the methodical acquisition of world-class geophysical datasets, which permit the detailed research and thorough testing of concepts at local and regional scales. This contribution is issued from a three years project funded by ExxonMobil aiming at better understanding the crustal-scale nature and evolution of the Norwegian-Greenland Sea. The idea was to take advantage of the data availability on this specific rift system to investigate further the full crustal conjugate scale history of rifting, confronting the various available datasets. In this contribution, we will review the possible structural and sedimentary geometries of the distal margin, and their connection to the oceanic domain. We will discuss the definition of 'breakup' and introduce a first order conceptual

Remote sensing studies and morphotectonic investigations in an arid rift setting, Baja California, Mexico

Science.gov (United States)

El-Sobky, Hesham Farouk

The Gulf of California and its surrounding land areas provide a classic example of recently rifted continental lithosphere. The recent tectonic history of eastern Baja California has been dominated by oblique rifting that began at ˜12 Ma. Thus, extensional tectonics, bedrock lithology, long-term climatic changes, and evolving surface processes have controlled the tectono-geomorphological evolution of the eastern part of the peninsula since that time. In this study, digital elevation data from the Shuttle Radar Topography Mission (SRTM) from Baja California were corrected and enhanced by replacing artifacts with real values that were derived using a series of geostatistical techniques. The next step was to generate accurate thematic geologic maps with high resolution (15-m) for the entire eastern coast of Baja California. The main approach that we used to clearly represent all the lithological units in the investigated area was objectoriented classification based on fuzzy logic theory. The area of study was divided into twenty-two blocks; each was classified independently on the basis of its own defined membership function. Overall accuracies were 89.6%, indicating that this approach was highly recommended over the most conventional classification techniques. The third step of this study was to assess the factors that affected the geomorphologic development along the eastern side of Baja California, where thirty-four drainage basins were extracted from a 15-m-resolution absolute digital elevation model (DEM). Thirty morphometric parameters were extracted; these parameters were then reduced using principal component analysis (PCA). Cluster analysis classification defined four major groups of basins. We extracted stream length-gradient indices, which highlight the differential rock uplift that has occurred along fault escarpments bounding the basins. Also, steepness and concavity indices were extracted for bedrock channels within the thirty-four drainage basins. The

Water-level data for the Albuquerque Basin and adjacent areas, central New Mexico, period of record through September 30, 2015

Science.gov (United States)

Beman, Joseph E.; Bryant, Christina F.

2016-10-27

The Albuquerque Basin, located in central New Mexico, is about 100 miles long and 25–40 miles wide. The basin is hydrologically defined as the extent of consolidated and unconsolidated deposits of Tertiary and Quaternary age that encompasses the structural Rio Grande Rift between San Acacia to the south and Cochiti Lake to the north. Drinking-water supplies throughout the basin were obtained solely from groundwater resources until December 2008, when the Albuquerque Bernalillo County Water Utility Authority (ABCWUA) began treatment and distribution of surface water from the Rio Grande through the San Juan-Chama Drinking Water Project. A 20-percent population increase in the basin from 1990 to 2000 and a 22-percent population increase from 2000 to 2010 may have resulted in an increased demand for water in areas within the basin.An initial network of wells was established by the U.S. Geological Survey (USGS) in cooperation with the City of Albuquerque from April 1982 through September 1983 to monitor changes in groundwater levels throughout the Albuquerque Basin. In 1983, this network consisted of 6 wells with analog-to-digital recorders and 27 wells where water levels were measured monthly. The network currently (2015) consists of 124 wells and piezometers. (A piezometer is a specialized well open to a specific depth in the aquifer, often of small diameter and nested with other piezometers open to different depths.) The USGS, in cooperation with the ABCWUA, currently (2015) measures and reports water levels from the 124 wells and piezometers in the network; this report presents water-level data collected by USGS personnel at those 124 sites through water year 2015 (October 1, 2014, through September 30, 2015).

Fault-magma interactions during early continental rifting: Seismicity of the Magadi-Natron-Manyara basins, Africa

Science.gov (United States)

Weinstein, A.; Oliva, S. J.; Ebinger, C. J.; Roecker, S.; Tiberi, C.; Aman, M.; Lambert, C.; Witkin, E.; Albaric, J.; Gautier, S.; Peyrat, S.; Muirhead, J. D.; Muzuka, A. N. N.; Mulibo, G.; Kianji, G.; Ferdinand-Wambura, R.; Msabi, M.; Rodzianko, A.; Hadfield, R.; Illsley-Kemp, F.; Fischer, T. P.

2017-10-01

Although magmatism may occur during the earliest stages of continental rifting, its role in strain accommodation remains weakly constrained by largely 2-D studies. We analyze seismicity data from a 13 month, 39-station broadband seismic array to determine the role of magma intrusion on state-of-stress and strain localization, and their along-strike variations. Precise earthquake locations using cluster analyses and a new 3-D velocity model reveal lower crustal earthquakes beneath the central basins and along projections of steep border faults that degas CO2. Seismicity forms several disks interpreted as sills at 6-10 km below a monogenetic cone field. The sills overlie a lower crustal magma chamber that may feed eruptions at Oldoinyo Lengai volcano. After determining a new ML scaling relation, we determine a b-value of 0.87 ± 0.03. Focal mechanisms for 65 earthquakes, and 13 from a catalogue prior to our array reveal an along-axis stress rotation of ˜60° in the magmatically active zone. New and prior mechanisms show predominantly normal slip along steep nodal planes, with extension directions ˜N90°E north and south of an active volcanic chain consistent with geodetic data, and ˜N150°E in the volcanic chain. The stress rotation facilitates strain transfer from border fault systems, the locus of early-stage deformation, to the zone of magma intrusion in the central rift. Our seismic, structural, and geochemistry results indicate that frequent lower crustal earthquakes are promoted by elevated pore pressures from volatile degassing along border faults, and hydraulic fracture around the margins of magma bodies. Results indicate that earthquakes are largely driven by stress state around inflating magma bodies.

Evaluating the State of Water Management in the Rio Grande/Bravo Basin

Science.gov (United States)

Ortiz Partida, Jose Pablo; Sandoval-Solis, Samuel; Diaz Gomez, Romina

2017-04-01

Water resource modeling tools have been developed for many different regions and sub-basins of the Rio Grande/Bravo (RGB). Each of these tools has specific objectives, whether it is to explore drought mitigation alternatives, conflict resolution, climate change evaluation, tradeoff and economic synergies, water allocation, reservoir operations, or collaborative planning. However, there has not been an effort to integrate different available tools, or to link models developed for specific reaches into a more holistic watershed decision-support tool. This project outlines promising next steps to meet long-term goals of improved decision support tools and modeling. We identify, describe, and synthesize water resources management practices in the RGB basin and available water resources models and decision support tools that represent the RGB and the distribution of water for human and environmental uses. The extent body of water resources modeling is examined from a perspective of environmental water needs and water resources management and thereby allows subsequent prioritization of future research and monitoring needs for the development of river system modeling tools. This work communicates the state of the RGB science to diverse stakeholders, researchers, and decision-makers. The products of this project represent a planning tool to support an integrated water resources management framework to maximize economic and social welfare without compromising vital ecosystems.

Thermochronological evidence for polyphase post-rift reactivation in SE Brazil

Science.gov (United States)

Cogné, N.; Gallagher, K.; Cobbold, P. R.; Riccomini, C.

2012-04-01

area cooled and uplifted during the Neogene. The synchronicity of the cooling phases with tectonic pulses in the Andes and in NE Brazil, as well as the tectonic setting of the Tertiary basins (Cogné et al., submitted) lead us to attribute these phases to a plate-wide compressive stress, which reactivated inherited structures during the Late Cretaceous and Tertiary. The relief of the margin is therefore due, more to polyphase post-rift reactivation and uplift, than to rifting itself. - Cobbold, P.R., Meisling, K.E., Mount, V.S., 2001. Reactivation of an obliquely rifted margin, Campos and Santos Basins, Southeastern Brazil. AAPG Bulletin 85, 1925-1944. - Cogné, N., Gallagher, K., Cobbold, P.R., 2011. Post-rift reactivation of the onshore margin of southeast Brazil: Evidence from apatite (U-Th)/He and fission-track data. Earth and Planetary Science Letters 309, 118-130. - Cogné, N., Cobbold, P.R., Riccomini, C., Gallagher, K. Tectonic setting of the Taubaté basin (southeastern Brazil): insights from regional seismic profiles and outcrop data. Submitted to Journal of South American Earth Sciences.

The Red Sea and Gulf of Aden Basins

Science.gov (United States)

Bosworth, William; Huchon, Philippe; McClay, Ken

2005-10-01

We here summarize the evolution of the greater Red Sea-Gulf of Aden rift system, which includes the Gulfs of Suez and Aqaba, the Red Sea and Gulf of Aden marine basins and their continental margins, and the Afar region. Plume related basaltic trap volcanism began in Ethiopia, NE Sudan (Derudeb), and SW Yemen at ˜31 Ma, followed by rhyolitic volcanism at ˜30 Ma. Volcanism thereafter spread northward to Harrats Sirat, Hadan, Ishara-Khirsat, and Ar Rahat in western Saudi Arabia. This early magmatism occurred without significant extension, and continued to ˜25 Ma. Much of the Red Sea and Gulf of Aden region was at or near sea level at this time. Starting between ˜29.9 and 28.7 Ma, marine syn-tectonic sediments were deposited on continental crust in the central Gulf of Aden. At the same time the Horn of Africa became emergent. By ˜27.5-23.8 Ma a small rift basin was forming in the Eritrean Red Sea. At approximately the same time (˜25 Ma), extension and rifting commenced within Afar itself. At ˜24 Ma, a new phase of volcanism, principally basaltic dikes but also layered gabbro and granophyre bodies, appeared nearly synchronously throughout the entire Red Sea, from Afar and Yemen to northern Egypt. This second phase of magmatism was accompanied in the Red Sea by strong rift-normal extension and deposition of syn-tectonic sediments, mostly of marine and marginal marine affinity. Sedimentary facies were laterally heterogeneous, being comprised of inter-fingering siliciclastics, evaporite, and carbonate. Throughout the Red Sea, the principal phase of rift shoulder uplift and rapid syn-rift subsidence followed shortly thereafter at ˜20 Ma. Water depths increased dramatically and sedimentation changed to predominantly Globigerina-rich marl and deepwater limestone. Within a few million years of its initiation in the mid-Oligocene the Gulf of Aden continental rift linked the Owen fracture zone (oceanic crust) with the Afar plume. The principal driving force for extension

Proterozoic rifting and major unconformities in Rajasthan, and their implications for uranium mineralisation

International Nuclear Information System (INIS)

Sinha-Roy, S.

2004-01-01

Evolution of the Precambrian terrain in Rajasthan has taken place via crustal consolidation of the basement at ca. 2.9 Ga, its cratonisation at ca. 2.5 Ga, through protracted tectonostratigraphic evolution of the Proterozoic cover sequences, following repeated rifting and Wilson cycles in the Aravalli and Delhi foldbelts. Consequently, the Proterozoic rift basins are characterised by growth faults and pull-aparts, and multitier volcanose dimentary sequences that contain a number of unconformities and stratigraphic breaks. The Archaean basement of the Mewar terrain that witnessed end-Archaean K-magmatism and ductile shearing, led to the creation of a possible uranium province, namely uranium enriched basement. This province acted as the source of remobilised uranium and its concentration at suitable multilevel structural and stratigraphic traps within the Proterozoic rift basins to give rise to unconformity-related syngenetic uranium mineralisation. Late Neoproterozoic to Pan-African tectonothermal reworking of the basement rocks produced fracture zones and caused Na-metasomatism giving rise to albitite-related uranium mineralisation. Based on an analysis of Proterozoic rift kinematics and lithofacies characteristics, five possible uranium-enriched stratigraphic horizons have been identified in the Aravalli and its equivalent sequences as well as in the North Delhi foldbelt sequences. From a regional synthesis, ten possible uranium metallogenic events, spanning ca. 2.5-0.5 Ga, are recognised in Rajasthan. These uranium events have predictive value for delineation of target areas for exploration. (author)

The transition from diffuse to focused extension: Modeled evolution of the West Antarctic Rift system

Science.gov (United States)

Huerta, Audrey D.; Harry, Dennis L.

2007-03-01

Two distinct stages of extension are recognized in the West Antarctic Rift system (WARS). During the first stage, beginning in the Late Cretaceous, extension was broadly distributed throughout much of West Antarctica. A second stage of extension in the late Paleogene was focused primarily in the Victoria Land Basin, near the boundary with the East Antarctic craton. The transition to focused extension was roughly coeval with volcanic activity and strike-slip faulting in the adjacent Transantarctic Mountains. This spatial and temporal correspondence suggests that the transition in extensional style could be the result of a change in plate motions or impingement of a plume. Here we use finite element models to study the processes and conditions responsible for the two-stage evolution of rifting in the WARS. Model results indicate that the transition from a prolonged period of broadly distributed extension to a later period of focused rifting did not require a change in the regional stress regime (changes in plate motion), or deep mantle thermal state (impingement of a plume). Instead, we attribute the transition from diffuse to focused extension to an early stage dominated by the initially weak accreted lithosphere of West Antarctica, and a later stage that concentrated around a secondary weakness located at the boundary between the juvenile West Antarctica lithosphere and Precambrian East Antarctic craton. The modeled transition in extension from the initially weak West Antarctica region to the secondary weakness at the West Antarctic-East Antarctic boundary is precipitated by strengthening of the West Antarctica lithosphere during syn-extensional thinning and cooling. The modeled syn-extensional strengthening of the WARS lithosphere promotes a wide-rift mode of extension between 105 and ˜ 65 Ma. By ˜ 65 Ma most of the extending WARS region becomes stronger than the area immediately adjacent to the East Antarctic craton and extension becomes concentrated near the

The Red Sea Basin Province: Sudr-Nubia(!) and Maqna(!) Petroleum Systems

Science.gov (United States)

Lindquist, Sandra J.

1999-01-01

The Sudr-Nubia(!) oil-prone total petroleum system dominates the densely explored Gulf of Suez part of the rifted Red Sea Basin Province. Upper Cretaceous to Eocene source rocks, primarily the Senonian Sudr Formation, are organic-rich, areally uniform marine carbonates that have generated known ultimate recoverable reserves exceeding 11 BBOE. The name Nubia is used for sandstone reservoirs with a wide range of poorly constrained, pre-rift geologic ages ranging from Early Paleozoic to Early Cretaceous. Syn- and post-rift Tertiary reservoirs, especially the Kareem Formation, also contain significant reserves. Partly overlapping Sudr-Nubia(!) is the areally larger and geochemically distinct, oil-and-gas-prone Maqna(!) total petroleum system within the southern Gulf of Suez basin and the sparsely explored remaining Red Sea basin. Known ultimate recoverable reserves are 50-100 MMBOE and more than 900 MMBOE, respectively, in those areas. Both the source and reservoir rocks in this petroleum system are Tertiary, dominantly Miocene, in age. Maqna(!) has the greater potential for future resource development.

Vazões máximas e mínimas para bacias hidrográficas da região alto Rio Grande, MG Maximum and minimum discharges for Alto Rio Grande region basins, Minas Gerais state, Brazil

Directory of Open Access Journals (Sweden)

Carlos Rogério de Mello

2010-04-01

Full Text Available Vazões máximas são grandezas hidrológicas aplicadas a projetos de obras hidráulicas e vazões mínimas são utilizadas para a avaliação das disponibilidades hídricas em bacias hidrográficas e comportamento do escoamento subterrâneo. Neste estudo, objetivou-se à construção de intervalos de confiança estatísticos para vazões máximas e mínimas diárias anuais e sua relação com as características fisiográficas das 6 maiores bacias hidrográficas da região Alto Rio Grande à montante da represa da UHE-Camargos/CEMIG. As distribuições de probabilidades Gumbel e Gama foram aplicadas, respectivamente, para séries históricas de vazões máximas e mínimas, utilizando os estimadores de Máxima Verossimilhança. Os intervalos de confiança constituem-se em uma importante ferramenta para o melhor entendimento e estimativa das vazões, sendo influenciado pelas características geológicas das bacias. Com base nos mesmos, verificou-se que a região Alto Rio Grande possui duas áreas distintas: a primeira, abrangendo as bacias Aiuruoca, Carvalhos e Bom Jardim, que apresentaram as maiores vazões máximas e mínimas, significando potencialidade para cheias mais significativas e maiores disponibilidades hídricas; a segunda, associada às bacias F. Laranjeiras, Madre de Deus e Andrelândia, que apresentaram as menores disponibilidades hídricas.Maximum discharges are applied to hydraulic structure design and minimum discharges are used to characterize water availability in hydrographic basins and subterranean flow. This study is aimed at estimating the confidence statistical intervals for maximum and minimum annual discharges and their relationship wih the physical characteristics of basins in the Alto Rio Grande Region, State of Minas Gerais. The study was developed for the six (6 greatest Alto Rio Grande Region basins at upstream of the UHE-Camargos/CEMIG reservoir. Gumbel and Gama probability distribution models were applied to the

Geologic implications of gas hydrates in the offshore of India: Krishna-Godavari Basin, Mahanadi Basin, Andaman Sea, Kerala-Konkan Basin

Digital Repository Service at National Institute of Oceanography (India)

Kumar, P.; Collett, T.S.; Boswell, R.; Cochran, J.R.; Lall, M.; Mazumdar, A.; Ramana, M.V.; Ramprasad, T.; Riedel, M.; Sain, K.; Sathe, A.V.; Vishwanath, K.; Yadav, U.S.

history of the Mahanadi Basin is similar to that of the Krishna-Godavari Basin. The Late Jurassic rift structures along the eastern margin of India cut across older NW-SE-trending Permian-Triassic Gondwana grabens including the Mahanadi and Pranhita...-Godavari grabens (Sastri et al., 1981). The Mahanadi graben appears to have a continuation in Antarctica as the Lambert graben (Federov et al., 1982). These structures served to delineate the fluvial drainage system throughout the evolution of the margin...

Deep structure of Porcupine Basin and nature of the Porcupine Median Ridge from seismic refraction tomography

Science.gov (United States)

Watremez, L.; Chen, C.; Prada, M.; Minshull, T. A.; O'Reilly, B.; Reston, T. J.; Wagner, G.; Gaw, V.; Klaeschen, D.; Shannon, P.

2015-12-01

The Porcupine Basin is a narrow V-shaped failed rifted basin located offshore SW Ireland. It is of Permo-Triassic to Cenozoic age, with the main rifting phase in the Late Jurassic to Early Cretaceous. Porcupine Basin is a key study area to learn about the processes of continental extension and to understand the thermal history of this rifted basin. Previous studies show increasing stretching factors, from less than 1.5 to the North to more than 6 to the South. A ridge feature, the Porcupine Median Ridge, has been identified in the middle of the southernmost part of the basin. During the last three decades, this ridge has been successively interpreted as a volcanic structure, a diapir of partially serpentinized mantle, or a block of continental crust. Its nature still remains debated today. In this study, we use arrival times from refractions and wide-angle reflections in the sedimentary, crustal and mantle layers to image the crustal structure of the thinnest part of the basin, the geometry of the continental thinning from margin to margin, and the Porcupine Median Ridge. The final velocity model is then compared with coincident seismic reflection data. We show that (1) the basin is asymmetric, (2) P-wave velocities in the uppermost mantle are lower than expected for unaltered peridotites, implying upper-mantle serpentinisation, (3) the nature of Porcupine Median Ridge is probably volcanic, and (4) the amount of thinning is greater than shown in previous studies. We discuss the thermal implications of these results for the evolution of this rift system and the processes leading to the formation of failed rifts. This project is funded by the Irish Shelf Petroleum Studies Group (ISPSG) of the Irish Petroleum Infrastructure Programme Group 4.

A study of tectonic activity in the Basin-Range Province and on the San Andreas Fault. No. 2: Lithospheric structure, seismicity, and contemporary deformation of the United States Cordillera

Science.gov (United States)

Smith, R. B.

1986-01-01

The structural evolution of the U.S. Cordillera has been influenced by a variety of tectonic mechanisms including passive margin rifting and sedimentation; arc volcanism; accretion of exotic terranes; intraplate magmatism; and folding and faulting associated with compression and extension processes that have profoundly influenced the lithospheric structure. As a result the Cordilleran crust is laterally inhomogeneous across its 2000 km east-west breadth. It is thin along the West Coast where it has close oceanic affinities. The crust thickens eastward beneath the Sierra Nevada, then thins beneath the Basin-Range. Crustal thickening continues eastward beneath the Colorado Plateau, the Rocky Mountains, and the Great Plains. The total lithospheric thickness attains 65 km in the Basin-Range and increases eastward beneath the Colorado Plateau. The upper-crust, including the crystalline basement of the Cordillera, has P sub G velocities of 6 km/s in the Basin-Range and Rio Grande Rift. Lower P sub G velocities of 5.4 to 5.7 km/s are associated with the youthful Yellowstone, Valles and Long Valley calderas and the Franciscan assemblage of the western coastal margin. Averaged crustal velocity reflects integrated tectonic evolution of the crust-thick silicic bodies, velocity reversals, and a thin crust produce low averaged velocities that are characteristic of a highly attenuated and thermally deformed crust.

Species diversity and distribution of freshwater crabs (Decapoda: Pseudothelphusidae inhabiting the basin of the Rio Grande de Térraba, Pacific slope of Costa Rica

Directory of Open Access Journals (Sweden)

Luis Rólier Lara

2013-09-01

Full Text Available During the last decades, knowledge on biodiversity of freshwater decapods has increased considerably; however, information about ecology of these crustaceans is scarce. Currently, the freshwater decapod fauna of Costa Rica is comprised by representatives of three families (Caridea: Palaemonidae and Atyidae; Brachyura: Pseudothelphusidae. The present study aims to describe the species diversity and distribution of freshwater crabs inhabiting the basin of the Rio Grande de Térraba, Pacific slope of Costa Rica, where the Instituto Costarricense de Electricidad (ICE plans to implement one of the largest damming projects in the region. Samples were collected in 39 locations at an altitude ranging from 20 to 1,225 m. Sampling was carried out during several months in 2007, 2009 and 2010. We collected a total of 661 crabs, comprising eight species of Pseudothelphusidae of three genera, representing 53% of the 15 pseudothelphusid crab species currently recorded from Costa Rica. The most common species was Ptychophallus paraxanthusi followed by P. tristani. Freshwater crabs were more frequently encountered in the middle-low region of the basin (between 311 and 600 m and less frequently in the medium-high basin (between 601 and 1,225 m. Ptychophallus paraxanthusi showed the widest distribution and was collected in altitudes ranging from 20 to 700 m. The Rio Grande de Térraba region can be considered as a relatively small, but highly diverse system. Therefore, any alteration of the basin of Rio Grande de Térraba, and especially the possible construction of a hydroelectric power plant, needs to be carefully analyzed to mitigate the damaging effects of this project on the freshwater crabs. More ecological information about freshwater crabs from Costa Rica and the Central American region are needed to reach a first reasonable overview on the ecological role of these decapods in freshwater systems.

Consumptive Water Use Analysis of Upper Rio Grande Basin in Southern Colorado.

Science.gov (United States)

Dubinsky, Jonathan; Karunanithi, Arunprakash T

2017-04-18

Water resource management and governance at the river basin scale is critical for the sustainable development of rural agrarian regions in the West. This research applies a consumptive water use analysis, inspired by the Water Footprint methodology, to the Upper Rio Grande Basin (RGB) in south central Colorado. The region is characterized by water stress, high dessert conditions, declining land health, and a depleting water table. We utilize region specific data and models to analyze the consumptive water use of RGB. The study reveals that, on an average, RGB experiences three months of water shortage per year due to the unsustainable extraction of groundwater (GW). Our results show that agriculture accounts for 77% of overall water consumption and it relies heavily on an aquifer (about 50% of agricultural consumption) that is being depleted over time. We find that, even though potato cultivation provides the most efficient conversion of groundwater resources into economic value (m 3 GW/$) in this region, it relies predominantly (81%) on the aquifer for its water supply. However, cattle, another important agricultural commodity produced in the region, provides good economic value but also relies significantly less on the aquifer (30%) for water needs. The results from this paper are timely to the RGB community, which is currently in the process of developing strategies for sustainable water management.

Diversity and distribution Patterns of the infralittoral green macroalgae from Potiguar basin, Rio Grande do Norte, Northeastern Brazil

OpenAIRE

Cocentino,Adilma de Lourdes Montenegro; Fujii,Mutue Toyota; Reis,Thiago Nogueira de Vasconcelos; Guimarães-Barros,Nathalia Cristina; Rocha,Marcia de França; Neumann-Leitão,Sigrid

2010-01-01

Diversity and distribution pattern of the infralittoral green macroalgae at Potiguar basin, Rio Grande do Norte, Northeastern Brazil were analyzed from material collected at depths varying from 2 to 100 m. Collections were carried out with two types of dredges during four campaigns: July 2002, May and November 2003 and May 2004 at 43 stations. Chlorophyta is represented by 54 species, five varieties and three forms. The most representative family is Caulerpaceae, and the most diverse genus is...

Littoral sedimentation of rift lakes: an illustrated overview from the modern to Pliocene Lake Turkana (East African Rift System, Kenya)

Science.gov (United States)

Schuster, Mathieu; Nutz, Alexis

2015-04-01

Existing depositional models for rift lakes can be summarized as clastics transported by axial and lateral rivers, then distributed by fan-deltas and/or deltas into a standing water body which is dominated by settling of fine particles, and experiencing occasional coarser underflows. Even if known from paleolakes and modern lakes, reworking of clastics by alongshore drift, waves and storms are rarely considered in depositional models. However, if we consider the lake Turkana Basin (East African Rift System, Kenya) it is obvious that this vision is incomplete. Three representative time slices are considered here: the modern Lake Turkana, the Megalake Turkana which developed thanks to the African Humid Period (Holocene), and the Plio-Pleistocene highstand episodes of paleolake Turkana (Nachukui, Shungura and Koobi Fora Formations, Omo Group). First, remarkable clastic morphosedimentary structures such as beach ridges, spits, washover fans, lagoons, or wave-dominated deltas are very well developed along the shoreline of modern lake Turkana, suggesting strong hydrodynamics responsible for a major reworking of the fluvial-derived clastics all along the littoral zone (longshore and cross-shore transport) of the lake. Similarly, past hydrodynamics are recorded from prominent raised beach ridges and spits, well-preserved all around the lake, above its present water-level (~360 m asl) and up to ~455 m. These large-scale clastic morphosedimentary structures also record the maximum extent of Megalake Turkana during the African Humid Period, as well as its subsequent regression forced by the end of the Holocene climatic optimum. Several hundreds of meters of fluvial-deltaic-lacustrine deposits spanning the Pliocene-Pleistocene are exposed in the Turkana basin thanks to tectonic faulting. These deposits are world famous for their paleontological and archeological content that documents the very early story of Mankind. They also preserve several paleolake highstand episodes with

Active Deformation of Malawi Rift's North Basin Hinge Zone Modulated by Reactivation of Preexisting Precambrian Shear Zone Fabric

Science.gov (United States)

Kolawole, F.; Atekwana, E. A.; Laó-Dávila, D. A.; Abdelsalam, M. G.; Chindandali, P. R.; Salima, J.; Kalindekafe, L.

2018-03-01

We integrated temporal aeromagnetic data and recent earthquake data to address the long-standing question on the role of preexisting Precambrian structures in modulating strain accommodation and subsequent ruptures leading to seismic events within the East African Rift System. We used aeromagnetic data to elucidate the relationship between the locations of the 2009 Mw 6.0 Karonga, Malawi, earthquake surface ruptures and buried basement faults along the hinge zone of the half-graben comprising the North Basin of the Malawi Rift. Through the application of derivative filters and depth-to-magnetic-source modeling, we identified and constrained the trend of the Precambrian metamorphic fabrics and correlated them to the three-dimensional structure of buried basement faults. Our results reveal an unprecedented detail of the basement fabric dominated by high-frequency WNW to NW trending magnetic lineaments associated with the Precambrian Mughese Shear Zone fabric. The high-frequency magnetic lineaments are superimposed by lower frequency NNW trending magnetic lineaments associated with possible Cenozoic faults. Surface ruptures associated with the 2009 Mw 6.0 Karonga earthquake swarm aligned with one of the NNW-trending magnetic lineaments defining a normal fault that is characterized by right-stepping segments along its northern half and coalesced segments on its southern half. Fault geometries, regional kinematics, and spatial distribution of seismicity suggest that seismogenic faults reactivated the basement fabric found along the half-graben hinge zone. We suggest that focusing of strain accommodation and seismicity along the half-graben hinge zone is facilitated and modulated by the presence of the basement fabric.

Chemostratigraphy of Late Cretaceous deltaic and marine sedimentary rocks from high northern palaeolatitudes in the Nuussuaq Basin, West Greenland

DEFF Research Database (Denmark)

Lenniger, Marc; Pedersen, Gunver Krarup; Bjerrum, Christian J.

The Nuussuaq Basin in the Baffin Bay area in West Greenland formed as a result of the opening of the Labrador Sea in Late Mesozoic to Early Cenozoic times. The first rifting and the development of the Nuussuaq Basin took place during the Early Cretaceous and was followed by a second rifting phase...

Cenozoic foreland basins of Central Andes: a preliminary provenance U-Pb zircon analysis of sedimentary sequences of Calchaqui Valley

International Nuclear Information System (INIS)

Oliveira, Alisson Lopes; Hauser, Natalia; Pimentel, Marcio Martins; Matteini, Massimo; Coira, Beatriz; Alonso, Ricardo; Barrientos, Andrea

2015-01-01

The Eocene of northwestern Argentina records complex basin and structural evolution, including continental sedimentation of the post-rift Salta Basin and the beginning of the Andean uplift and foreland system evolution. This illuminates a significant period of evolutionary history of this and surrounding basins in northwestern Argentina. U-Pb zircon analyses by LA-ICP-MS for three formations representing post-rift to foreland stages allowed interpretation about provenance terrains. The Lumbrera Formation, representing the post-rift stage, shows bimodal sources with a main zircon population around 462 Ma, and a second population around 1023 Ma. The Los Colorados and Angastaco Formations representing the sedimentation in a foreland basin, show a unimodal source around 490 Ma, and 517 Ma respectively. Zircons younger than 50 Ma were not identified during this study. (author)

Cenozoic foreland basins of Central Andes: a preliminary provenance U-Pb zircon analysis of sedimentary sequences of Calchaqui Valley

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Alisson Lopes; Hauser, Natalia; Pimentel, Marcio Martins; Matteini, Massimo, E-mail: alisson_oliveira@hotmail.com [Universidade de Brasilia (UnB), DF (Brazil). Laboratorio de Geocronologia; Galli, Claudia Ines [Faculdad de Ingenieria, Universidad Nacional de Jujuy (Argentina); Coira, Beatriz [CIT Jujuy, CONICET. Instituto de Geologia y Mineria (Argentina); Alonso, Ricardo; Barrientos, Andrea [Instituto CEGA, CONICET. Universidad Nacional de Salta (Argentina)

2015-07-01

The Eocene of northwestern Argentina records complex basin and structural evolution, including continental sedimentation of the post-rift Salta Basin and the beginning of the Andean uplift and foreland system evolution. This illuminates a significant period of evolutionary history of this and surrounding basins in northwestern Argentina. U-Pb zircon analyses by LA-ICP-MS for three formations representing post-rift to foreland stages allowed interpretation about provenance terrains. The Lumbrera Formation, representing the post-rift stage, shows bimodal sources with a main zircon population around 462 Ma, and a second population around 1023 Ma. The Los Colorados and Angastaco Formations representing the sedimentation in a foreland basin, show a unimodal source around 490 Ma, and 517 Ma respectively. Zircons younger than 50 Ma were not identified during this study. (author)

Structural Framework and Architecture of the Paleoproterozoic Bryah and Padbury Basins from Integrated Potential Field and Geological Datasets: Towards an Understanding of the Basin Evolution

Science.gov (United States)

Nigro R A Ramos, L.; Aitken, A.; Occhipinti, S.; Lindsay, M.

2017-12-01

The Bryah and Padbury Basins were developed along the northern margin of the Yilgarn Craton, in the southern portion of the Capricorn Orogen, which represents a Proterozoic tectonic zone that bounds the Yilgarn and Pilbara Cratons in Western Australia. These basins have been previously interpreted as developing in a rift, back-arc, and retro-arc foreland basins. Recent studies suggest that the Bryah Basin was deposited in a rift setting, while the overlying Padbury Basin evolved in a pro-foreland basin during the collision of the Yilgarn Craton and the Pilboyne block (formed by the Pilbara Craton and the Glenburgh Terrane), occurring in the Glenburgh Orogeny (2005-1960 Ma). This study focuses on characterizing the architecture and structural framework of the Bryah and Padbury Basins through analysis of geophysical and geological datasets, in order to better understand the different stages of the basins evolution. Gravity and magnetic data were used to define the main tectonic units and lithological boundaries, and to delineate major discontinuities in the upper and lower crust, as well as anomalies through a combination of map view interpretation and forward modelling. Geological mapping and drill core observations were linked with the geophysical interpretations. Fourteen magnetic domains are distinguished within the basins, while four main domains based on the Bouguer Anomaly are recognized. The highest gravity amplitude is related with an anomaly trending EW/NE-SW, which is coincident with the voluminous mafic rocks of the Bryah Basin, and may indicate the presence of an approximately 5km thick package of higher density mafic rocks. Magnetic depth estimations also indicate deep magnetic sources up to approximately 4,45km. These results can help to elucidate processes that occurred during the precursor rift of the early stages of the Bryah Basin, add information in relation to the basement control on sedimentation, allow the characterization of the varying

Extreme Mesozoic crustal thinning in the Eastern Iberia margin: The example of the Columbrets Basin (Valencia Trough)

Science.gov (United States)

Mohn, G.; Etheve, N.; Frizon de Lamotte, D.; Roca, E.; Tugend, J.; Gómez-Romeu, J.

2017-12-01

Eastern Iberia preserves a complex succession of Mesozoic rifts partly or completely inverted during the Late Cretaceous and Cenozoic in relation with Africa-Eurasia convergence. Notably, the Valencia Trough, classically viewed as part of the Cenozoic West Mediterranean basins, preserves in its southwestern part a thick Mesozoic succession (locally »10km thick) over a highly thinned continental basement (locally only »3,5km thick). This sub-basin referred to as the Columbrets Basin, represents a Late Jurassic-Early Cretaceous hyper-extended rift basin weakly overprinted by subsequent events. Its initial configuration is well preserved allowing us to unravel its 3D architecture and tectono-stratigraphic evolution in the frame of the Mesozoic evolution of eastern Iberia. The Columbrets Basin benefits from an extensive dataset combining high resolution reflection seismic profiles, drill holes, refraction seismic data and Expanding Spread Profiles. Its Mesozoic architecture is controlled by interactions between extensional deformation and halokinesis involving the Upper Triassic salt. The thick uppermost Triassic to Cretaceous succession describes a general synclinal shape, progressively stretched and dismembered towards the basin borders. The SE-border of the basin is characterized by a large extensional detachment fault acting at crustal scale and interacting locally with the Upper Triassic décollement. This extensional structure accommodates the exhumation of the continental basement and part of the crustal thinning. Eventually our results highlight the complex interaction between extreme crustal thinning and occurrence of a pre-rift salt level for the deformation style and tectono-stratigraphic evolution of hyper-extended rift basins.

New structural/tectonical model and its implication on hydrological thinking and groundwater management - the Lake Tiberias, Jordan Rift Valley

Science.gov (United States)

Inbar, Nimrod; Magri, Fabien; Yellin-Dror, Annat; Rosenthal, Eliahu; Möller, Peter; Siebert, Christian; Guttman, Josef

2014-05-01

Lake Tiberias is a fresh water lake located at the Kinneret basin which is approximately 30 km long and 10 km wide. It comprises a link in the chain of pull-apart basins that characterizes the structure of the conspicuous Jordan Rift Valley (JRV). The basin surface is about 200 m below mean sea level (msl) and basin-fill attains a thickness of up to 8 km. Until recently, studies focused mainly on the upper strata of basin fill. Consequently, a complete three dimensional geological model, including clear view of the tectonic framework at the Kinneret Basin was incomplete. This situation imposes great difficulty in understanding the local hydrological system and as consequence enforce constrains on groundwater management of the regional aquifers that flows towards the lake. A recently proposed structural/tectonical model (Inbar, 2012) enables revaluation of several geohydrological aspects at Sea of Galilee and its surroundings and a new hydrological model based on those findings aims to clarify those aspects with relation to groundwater management. The deep-seated stratigraphical units were seismically studied at the Kinnarot Valley (southern part of Kinneret basin) where sufficient information is available (Inbar, 2012). This study shows the subsidence and northwestward tilting of the basin floor (pre-rift formations) and the flow of thick Late Miocene salt accumulation accordingly. Furthermore, shallower seismic data, collected at the lake itself, shows a suspected salt dome close to the western boundary fault of the basin (Resnikov et al., 2004). Salt flow is now suggested to be a substantial factor in the tectonic play. At the lake surroundings there are several springs and boreholes where brine immerges from an estimated depth of about 2-3 kilometers. Significant differences in brine characteristics raised questions regarding the location of brine traps, flow mechanism and the mixture process between the fresh water and the brine. However, the effect of the

Latest Miocene transtensional rifting of northeast Isla Tiburón, eastern margin of the Gulf of California

Science.gov (United States)

Bennett, Scott E. K.; Oskin, Michael E.; Iriondo, Alexander

2017-11-01

Details about the timing and kinematics of rifting are crucial to understand the conditions that led to strain localization, continental rupture, and formation of the Gulf of California ocean basin. We integrate detailed geologic and structural mapping, basin analysis, and geochronology to characterize transtensional rifting on northeastern Isla Tiburón, a proximal onshore exposure of the rifted North America margin, adjacent to the axis of the Gulf of California. Slip on the Kunkaak normal fault tilted its hanging wall down-to-the-east 70° and formed the non-marine Tecomate basin, deposited across a 20° angular unconformity. From 7.1-6.4 Ma, the hanging wall tilted at 35 ± 5°/Myr, while non-marine sandstone and conglomerate accumulated at 1.4 ± 0.2 mm/yr. At least 1.8 ± 0.1 km of sediments and pyroclastic deposits accumulated in the Tecomate basin concurrent with clockwise vertical-axis block rotation and 2.8 km of total dip-slip motion on the Kunkaak fault. Linear extrapolation of tilting and sedimentation rates suggests that faulting and basin deposition initiated 7.6-7.4 Ma, but an older history involving initially slower rates is permissible. The Kunkaak fault and Tecomate basin are truncated by NW-striking, dextral-oblique structures, including the Yawassag fault, which accrued > 8 km of post-6.4 Ma dextral displacement. The Coastal Sonora fault zone on mainland Sonora, which accrued several tens of kilometers of late Miocene dextral offset, continues to the northwest, across northeastern Isla Tiburón and offshore into the Gulf of California. The establishment of rapid, latest Miocene transtension in the Coastal Sonora fault zone was synchronous with the 8-7 Ma onset of transform faulting and basin formation along the nascent Pacific-North America plate boundary throughout northwestern Mexico and southern California. Plate boundary strain localized into this Gulf of California shear zone, a narrow transtensional belt that subsequently hosted the

A Physical Assessment of the Opportunities for Improved Management of the Water Resources of the Bi-National Rio Grande/Rio Bravo Basin

Science.gov (United States)

Aparicio, J.; McKinney, D.; Valdes, J.; Guitron, A.; Thomas, G.

2007-05-01

The hydro-physical opportunities for expanding the beneficial uses of the fixed water supply in the Rio Grande/Bravo Basin to better satisfy an array of water management goals are examined. These include making agriculture more resilient to periodic conditions of drought, improving the reliability of supplies to cities and towns, and restoring lost environmental functions in the river system. This is a comprehensive, outcome-neutral, model- based planning exercise performed by some 20 technical, primarily non-governmental institutions from both countries, aimed at proposing strategies that can reduce future conflicts over water throughout the entire basin. The second track consists in generating a set of future water management scenarios that respond to the needs and objectives of the basin stakeholders in each segment and each country. An array of scenarios for improved water management has been developed for the lower Rio Grande/Rio Bravo basin in Texas and the Mexican state of Tamaulipas. Another set under development will focus on the Rio Conchos and the El Paso/Juarez region. Eventually, scenarios will be generated such that will comprehend the entire basin on both sides of the border. These scenarios are the product of consultations with agricultural water districts, governmental organizations and environmental NGOs. They include strategies for reducing the physical losses of water in the system, conservation transfers, improvements in the operations of the Mexican and international reservoirs, improvements in environmental flow conditions, improvements in reliability of water supplies, and drought coping strategies.These scenarios will be evaluated for hydrologic feasibility by the basin-wide model and the gaming exercises. Modeling is necessary to understand how these options will affect the entire system and how they can be crafted to maximize the benefits and avoid unintended or uncompensated effects. The scenarios that have the potential to provide large

ACADEMICIAN N.A. LOGATCHEV AND HIS SCIENTIFIC SCHOOL: CONTRUBITION TO STUDIES OF THE CENOZOIC CONTINENTAL RIFTING

Directory of Open Access Journals (Sweden)

Sergey V. Rasskazov

2010-01-01

Full Text Available N.A. Florensov and N.A. Logatchev pioneered development of fundamental concepts of the structure and evolution of the Baikal system of rift basins. At the turn to the 21st century, in view of the wide availability of scientific research data on the Cenozoic continental rift zones located in Eurasia, Africa and North America, and taking into account the application of new research methods and options to process and analyze huge amounts of geological and geophysical data, a priority was comprehensive modeling of rifting from its origin to the current period of time. This scientific challenge was addressed by the research team under the leadership of N.A. Logachev.

The Volcanic Myths of the Red Sea - Temporal Relationship Between Magmatism and Rifting

Science.gov (United States)

Stockli, D. F.; Bosworth, W.

2017-12-01

The Cenozoic Red Sea is one of the premier examples of continental rifting and active break-up. It has been cited as an example for both prototypical volcanic, pure shear rift systems with limited crustal stretching as well as magma-poor simple-shear rifting and highly asymmetric rift margins characterized by low-angle normal faults. In light of voluminous Oligocene continental flood basalts in the Afar/Ethiopian region, the Red Sea has often been viewed as a typical volcanic rift, despite evidence for asymmetric extension and hyperextended crust (Zabargad Island). An in-depth analysis of the timing, spatial distribution, and nature of Red Sea volcanism and its relationship to late Cenozoic extensional faulting should shed light on some of the misconceptions. The Eocene appearance of the East African super-plume was not accompanied by any recognized significant extensional faulting or rift-basin formation. The first phase of volcanism more closely associated with the Red Sea occurred in northern Ethiopia and western Yemen at 31-30 Ma and was synchronous with the onset of continental extension in the Gulf of Aden. Early Oligocene volcanism has also been documented in southern and central Saudi Arabia and southern Sudan. However, this voluminous Oligocene volcanism entirely predates Red Sea extensional faulting and rift formation. Marking the onset of Red Sea rifting, widespread, spatially synchronous intrusion of basaltic dikes occurred at 24-21 Ma along the entire Red Sea-Gulf of Suez rift and continuing into northern Egypt. While the initiation of lithospheric extension in the central and northern and central Red Sea and Gulf of Suez was accompanied by only sparse basaltic volcanism and possible underplating, the main phase of rifting in the Miocene Red Sea/Gulf of Suez completely lacks any significant rift-related volcanism, suggesting plate-boundary forces probably drove overall separation of Arabia from Africa. During progressive rifting, there is also no

Some aspects of the role of rift inheritance on Alpine-type orogens

Science.gov (United States)

Tugend, Julie; Manatschal, Gianreto; Mohn, Geoffroy; Chevrot, Sébastien

2017-04-01

Processes commonly recognized as fundamental for the formation of collisional orogens include oceanic subduction, arc-continent and continent-continent collision. As collisional belts result from the closure of oceanic basins and subsequent inversion of former rifted margins, their formation and evolution may also in theory be closely interlinked with the initial architecture of the former rifted margins. This assumption is indeed more likely to be applicable in the case of Alpine-type orogens, mainly controlled by mechanical processes and mostly devoid of arc-related magmatism. More and more studies from present-day magma-poor rifted margins illustrate the complex evolution of hyperextended domains (i.e. severely thinned continental crust (images across the Pyrenees (PYROPE) and the Alps (CIFALPS) reveal a surprisingly comparable present-day overall crustal and lithospheric structure. Based on the comparison between the two orogens we discuss: (1) the nature and depth of decoupling levels inherited from hyperextension; (2) the implications for restorations and interpretations of orogenic roots (former hyperextended domains vs. lower crust only); and (3) the nature and major role of buttresses in controlling the final stage of collisional processes. Eventually, we discuss the variability of the role of rift-inheritance in building Alpine-type orogens. The Pyrenees seem to represent one extreme, where rift-inheritance is important at different stages of collisional processes. In contrast, in the Alps the role of rift-inheritance is subtler, likely because of its more complex and polyphase compressional deformation history.

Web application to access U.S. Army Corps of Engineers Civil Works and Restoration Projects information for the Rio Grande Basin, southern Colorado, New Mexico, and Texas

Science.gov (United States)

Archuleta, Christy-Ann M.; Eames, Deanna R.

2009-01-01

The Rio Grande Civil Works and Restoration Projects Web Application, developed by the U.S. Geological Survey in cooperation with the U.S. Army Corps of Engineers (USACE) Albuquerque District, is designed to provide publicly available information through the Internet about civil works and restoration projects in the Rio Grande Basin. Since 1942, USACE Albuquerque District responsibilities have included building facilities for the U.S. Army and U.S. Air Force, providing flood protection, supplying water for power and public recreation, participating in fire remediation, protecting and restoring wetlands and other natural resources, and supporting other government agencies with engineering, contracting, and project management services. In the process of conducting this vast array of engineering work, the need arose for easily tracking the locations of and providing information about projects to stakeholders and the public. This fact sheet introduces a Web application developed to enable users to visualize locations and search for information about USACE (and some other Federal, State, and local) projects in the Rio Grande Basin in southern Colorado, New Mexico, and Texas.

Research of the Rio Grande Ecosystem Management Program

Science.gov (United States)

Deborah M. Finch

2000-01-01

This paper describes the mission, objectives, and preliminary results of the Middle Rio Grande Ecosystem Management Research Program managed at the Rocky Mountain Research Station's Albuquerque laboratory. This program was initiated in 1994 to address growing pressures to effectively manage the limited resources of the middle Rio Grande Basin. The program is...

Mechanism of crustal extension in the Laxmi Basin, Arabian Sea

Directory of Open Access Journals (Sweden)

Anju Pandey

2015-11-01

Full Text Available Continental rifting and magmatism has been extensively studied worldwide as it is believed that continental rifting, break up of continents and associated magmatism lead to genesis of new oceanic crust. However, various regions of the world show that these processes may lead to genesis of other types of crust than the oceanic crust. Laxmi Basin in the western continental margin of the India is one such region with an enigmatic crust. Due to its extreme strategic significance for the palaeogeographic reconstruction of continents during Cretaceous continental breakup of India, this basin has attracted various workers for more than two decades. However, still the issue of nature of crust in the basin remains controversial. In this contribution, in order to identify nature of crust, mechanism of continental extension in the Laxmi Basin has been studied for the first time through newly acquired seismic data from the basin. Here, we propose a plausible mechanism of crustal extension in the Laxmi Basin which eventually constrains the nature of crust of the Laxmi Basin. We have demonstrated that the crust in the Laxmi Basin can be categorised in two zones of stretched and transitional crust. In the stretched zone several fault bounded horst and graben structures are identified which preserve syn- and post-rift sediments along with different periods of hiatus in sedimentations as unconformities. These faults are identified as listric faults in the upper crust which sole out in the detachment faults. Detachment faults decouples the upper brittle and lower ductile crust. The transitional crust is identified as heavily intruded by sills and basaltic volcanic which were emplaced due to melting of subcontinental mantle (SCM after hyper-stretching of crust and serpentinisation of the SCM. Panikkar Ridge is proposed to be one such basaltic volcanic body derived from melting of lower part of the SCM.

Origin and structural evolution of the Cenozoic Rift System of Southeastern Brazil; Origem e evolucao estrutural do Sistema de Riftes Cenozoicos do Sudeste do Brasil

Energy Technology Data Exchange (ETDEWEB)

Zalan, Pedro Victor [PETROBRAS S.A., Salvador, BA (Brazil). E e P. Gerencia de Gestao de Projetos Exploratorios], E-mail: zalan@petrobras.com.br; Oliveira, Joao Alberto Bach de

2005-05-15

The southeastern region of Brazil did not constitute a typical passive margin as one would expect from the premises of Plate Tectonics. After 25 m.y. that rifting (134-114 Ma) ceased an uplift of epeirogenic nature of the continental crust started in response to the drifting of the South American Plate over a thermal anomaly (Trindade hot spot). This Late Cretaceous (89-65 Ma) uplift was accompanied by intense alkaline (over non-extended crust) and basaltic (over thinned crust) magmatism. A marked absence of tectonism, however, also characterized this event. The resulting highlands extended over 300 000 km{sup 2} (Cretaceous Serra do Mar), and they were the main source area for coniacian-maastrichtian sediments of the Santos, Campos and Parana Basins. By the end of the rising (exactly at the K/T boundary) a widespread erosional surface had developed (Japi Surface) and leveled the top of the highlands at around 2 000 m (in relation to present-day sea level). This mega-plateau was adjacent to the subsiding Santos and Campos Basins and created an isostatically unstable situation. Gravitational collapse began around 7 m.y. after K/T, towards the depocenters of the basins. From Late Paleocene to Early Miocene (58-20 Ma) the continental crust broke and collapsed into a series of grabens, thus forming corridors (rifts) parallel to the current coastline. The ancient eastern edge of the Cretaceous Serra do Mar coincided with the current cretaceous hinge line of the Santos and Campos Basins. The topographic remnants of the mega-plateau nowadays form the highest parts of the Mantiqueira and Serra do Mar Ranges, modified by elastic rebound and tilting of the fault blocks. (author)

The Sidi Ifni transect across the rifted margin of Morocco (Central Atlantic): Vertical movements constrained by low-temperature thermochronology

Science.gov (United States)

Charton, Rémi; Bertotti, Giovanni; Arantegui, Angel; Bulot, Luc

2018-05-01

The occurrence of km-scale exhumations during syn- and post-rift stages has been documented along Atlantic continental margins, which are also characterised by basins undergoing substantial subsidence. The relationship between the exhuming and subsiding domains is poorly understood. In this study, we reconstruct the evolution of a 50 km long transect across the Moroccan rifted margin from the western Anti-Atlas to the Atlantic basin offshore the city of Sidi Ifni. Low-temperature thermochronology data from the Sidi Ifni area document a ca. 8 km exhumation between the Permian and the Early/Middle Jurassic. The related erosion fed sediments to the subsiding Mesozoic basin to the NW. Basement rocks along the transect were subsequently buried by 1-2 km between the Late Jurassic and the Early Cretaceous. From late Early/Late Cretaceous onwards, rocks present along the transect were exhumed to their present-day position.

Potential field studies of the central San Luis Basin and San Juan Mountains, Colorado and New Mexico, and southern and western Afghanistan

Science.gov (United States)

Drenth, Benjamin John

This dissertation includes three separate chapters, each demonstrating the interpretive utility of potential field (gravity and magnetic) geophysical datasets at various scales and in various geologic environments. The locations of these studies are the central San Luis Basin of Colorado and New Mexico, the San Juan Mountains of southwestern Colorado, and southern and western Afghanistan. The San Luis Basin is the northernmost of the major basins that make up the Rio Grande rift, and interpretation of gravity and aeromagnetic data reveals patterns of rifting, rift-sediment thicknesses, distribution of pre-rift volcanic and sedimentary rocks, and distribution of syn-rift volcanic rocks. Syn-rift Santa Fe Group sediments have a maximum thickness of ˜2 km in the Sanchez graben near the eastern margin of the basin along the central Sangre de Cristo fault zone. Under the Costilla Plains, thickness of these sediments is estimated to reach ˜1.3 km. The Santa Fe Group sediments also reach a thickness of nearly 1 km within the Monte Vista graben near the western basin margin along the San Juan Mountains. A narrow, north-south-trending structural high beneath San Pedro Mesa separates the graben from the structural depression beneath the Costilla Plains. Aeromagnetic anomalies are interpreted to mainly reflect variations of remanent magnetic polarity and burial depth of the 5.3-3.7 Ma Servilleta basalt of the Taos Plateau volcanic field. Magnetic-source depth estimates indicate patterns of subsidence following eruption of the basalt and show that the Sanchez graben has been the site of maximum subsidence. One of the largest and most pronounced gravity lows in North America lies over the rugged San Juan Mountains in southwestern Colorado. A buried, low-density silicic batholith related to an Oligocene volcanic field coincident with the San Juan Mountains has been the accepted interpretation of the source of the gravity low since the 1970s. However, this interpretation was

Melo carboniferous basin

International Nuclear Information System (INIS)

Flossdarf, A.

1988-01-01

This report is about of the Melo carboniferous basin which limits are: in the South the large and high Tupambae hill, in the west the Paraiso hill and the river mountains, in the North Yaguaron river basin to Candidata in Rio Grande del Sur in Brazil.

Orphan Basin crustal structure from a dense wide-angle seismic profile - Tomographic inversion

Science.gov (United States)

Watremez, Louise; Lau, K. W. Helen; Nedimović, Mladen R.; Louden, Keith E.; Karner, Garry D.

2014-05-01

Orphan Basin is located on the eastern margin of Canada, offshore of Newfoundland and East of Flemish Cap. It is an aborted continental rift formed by multiple episodes of rifting. The crustal structure across the basin has been determined by an earlier refraction study using 15 instruments on a 550 km long line. It shows that the continental crust was extended over an unusually wide region but did not break apart. The crustal structure of the basin thus documents stages in the formation of a magma-poor rifted margin up to crustal breakup. The OBWAVE (Orphan Basin Wide-Angle Velocity Experiment) survey was carried out to image crustal structures across the basin and better understand the processes of formation of this margin. The spacing of the 89 recording stations varies from 3 to 5 km along this 500-km-long line, which was acquired along a pre-existing reflection line. The highest resolution section corresponds to the part of the profile where the crust was expected to be the thinnest. We present the results from a joint tomography inversion of first and Moho reflected arrival times. The high data density allows us to define crustal structures with greater detail than for typical studies and to improve the understanding of the processes leading to the extreme stretching of continental crust. The final model was computed following a detailed parametric study to determine the optimal parameters controlling the ray-tracing and the inversion processes. The final model shows very good resolution. In particular, Monte Carlo standard deviations of crustal velocities and Moho depths are generally Orphan Basin is the result of rifting of a non-homogeneous Avalon terrane where the lower crust is primarily ductile.

The Brazilian marginal basins: current state of knowledge; As bacias marginais brasileiras: estagio atual de conhecimento

Energy Technology Data Exchange (ETDEWEB)

Ponte, Francisco Celso; Asmus, Haroldo Erwin

2004-11-01

Based on distinctive stratigraphic and/or structural characteristics, the brazilian continental margin can be divided into two main provinces : (1)The southeastern-eastern province, extending from the Pelotas to the Recife - Joao Pessoa Basin, presents a tensional tectonic style of Late Jurassic - Early Cretaceous age, paralleling the structural alignments of the Precambrian basement, except in the northeastern segment where the Mesozoic faults of the Recife - Joao Pessoa Basin cut across the east west basement directions. The basin-fill, Upper Jurassic through Recent, consists, where complete, of three stratigraphic sequences, each of a distinct depositional environment: (a) a lower clastic non-marine sequence; (b) a middle evaporitic sequence, and (c) an upper clastic paralic and open marine sequence. (2)The northern province, extending from the Potiguar Basin to the Amazon Submarine Basin, displays both tensional and compressional tectonic styles of Upper Jurassic (?) to Upper Cretaceous age either paralleling or cutting transversally the basement alignments. The stratigraphic column differs from the southeastern - eastern province in lacking the Lower Cretaceous evaporitic rocks. The integration of the stratigraphic and structural data allows one to determine in the eastern Brazilian marginal basins the main evolutionary stages of a typical pull-apart continental margin: a continental pre-rift and rift stage, an evaporitic proto-ocean stage, and a normal open ocean stage. In the northern province it is possible to infer a continental rift valley stage, a marine transform - movement stage and an open ocean stage. The relationship between the rift valley and transform movement stages is not clear. (author)

Madbi Amran/Qishn total petroleum system of the Ma'Rib-Al Jawf/Shabwah, and Masila-Jeza basins, Yemen

Science.gov (United States)

Ahlbrandt, Thomas S.

2002-01-01

Since the first discovery of petroleum in Yemen in 1984, several recent advances have been made in the understanding of that countrys geologic history and petroleum systems. The total petroleum resource endowment for the combined petroleum provinces within Yemen, as estimated in the recent U.S. Geological Survey world assessment, ranks 51st in the world, exclusive of the United States, at 9.8 BBOE, which includes cumulative production and remaining reserves, as well as a mean estimate of undiscovered resources. Such undiscovered petroleum resources are about 2.7 billion barrels of oil, 17 trillion cubic feet (2.8 billion barrels of oil equivalent) of natural gas and 1 billion barrels of natural gas liquids. A single total petroleum system, the Jurassic Madbi Amran/Qishn, dominates petroleum generation and production; it was formed in response to a Late Jurassic rifting event related to the separation of the Arabian Peninsula from the Gondwana supercontinent. This rifting resulted in the development of two petroleum-bearing sedimentary basins: (1) the western MaRibAl Jawf / Shabwah basin, and (2) the eastern Masila-Jeza basin. In both basins, petroleum source rocks of the Jurassic (Kimmeridgian) Madbi Formation generated hydrocarbons during Late Cretaceous time that migrated, mostly vertically, into Jurassic and Cretaceous reservoirs. In the western MaRibAl Jawf / Shabwah basin, the petroleum system is largely confined to syn-rift deposits, with reservoirs ranging from deep-water turbidites to continental clastics buried beneath a thick Upper Jurassic (Tithonian) salt. The salt initially deformed in Early Cretaceous time, and continued halokinesis resulted in salt diapirism and associated salt withdrawal during extension. The eastern Masila-Jeza basin contained similar early syn-rift deposits but received less clastic sediment during the Jurassic; however, no salt formed because the basin remained open to ocean circulation in the Late Jurassic. Thus, Madbi Formation

Inward migration of faulting during continental rifting: Effects of pre-existing lithospheric structure and extension rate

NARCIS (Netherlands)

Corti, G.; Ranalli, G.; Agostini, A.; Sokoutis, D.

Lithospheric-scale analogue models are used to analyse the parameters controlling the typical evolution of deformation during continental narrow rifting, characterized by early activation of large boundary faults and basin subsidence, followed by localization of tectonic activity in internal faults

Kinematic and thermal evolution of the Moroccan rifted continental margin: Doukkala-High Atlas Transect

NARCIS (Netherlands)

Gouiza, M.; Bertotti, G.V.; Hafid, M.; Cloetingh, S.A.P.L.

2010-01-01

The Atlantic passive margin of Morocco developed during Mesozoic times in association with the opening of the Central Atlantic and the Alpine Tethys. Extensional basins formed along the future continental margin and in the Atlas rift system. In Alpine times, this system was inverted to form the High

Salinity Trends in the Upper Colorado River Basin Upstream From the Grand Valley Salinity Control Unit, Colorado, 1986-2003

Science.gov (United States)

Leib, Kenneth J.; Bauch, Nancy J.

2008-01-01

In 1974, the Colorado River Basin Salinity Control Act was passed into law. This law was enacted to address concerns regarding the salinity content of the Colorado River. The law authorized various construction projects in selected areas or 'units' of the Colorado River Basin intended to reduce the salinity load in the Colorado River. One such area was the Grand Valley Salinity Control Unit in western Colorado. The U. S. Geological Survey has done extensive studies and research in the Grand Valley Salinity Control Unit that provide information to aid the U.S. Bureau of Reclamation and the Natural Resources Conservation Service in determining where salinity-control work may provide the best results, and to what extent salinity-control work was effective in reducing salinity concentrations and loads in the Colorado River. Previous studies have indicated that salinity concentrations and loads have been decreasing downstream from the Grand Valley Salinity Control Unit, and that the decreases are likely the result of salinity control work in these areas. Several of these reports; however, also document decreasing salinity loads upstream from the Grand Valley Salinity Control Unit. This finding was important because only a small amount of salinity-control work was being done in areas upstream from the Grand Valley Salinity Control Unit at the time the findings were reported (late 1990?s). As a result of those previous findings, the U.S. Bureau of Reclamation entered into a cooperative agreement with the U.S. Geological Survey to investigate salinity trends in selected areas bracketing the Grand Valley Salinity Control Unit and regions upstream from the Grand Valley Salinity Control Unit. The results of the study indicate that salinity loads were decreasing upstream from the Grand Valley Salinity Control Unit from 1986 through 2003, but the rates of decrease have slowed during the last 10 years. The average rate of decrease in salinity load upstream from the Grand Valley

Using Detrital Zircon Geochronology to Constrain Paleogene Provenance and Its Relationship to Rifting in the Zhu 1 Depression, Pearl River Mouth Basin, South China Sea

Science.gov (United States)

Wang, Wei; Ye, Jiaren; Bidgoli, Tandis; Yang, Xianghua; Shi, Hesheng; Shu, Yu

2017-11-01

Paleogene syn-rift successions in the South China Sea are poorly understood and systematic provenance analysis, which could provide clues to their history, is lacking. Here we report 409 new concordant U-Pb ages from detrital zircons separated from the Paleogene Wenchang, Enping, and Zhuhai formations in the Zhu 1 depression, Pearl River Mouth Basin. The new data, combined with the published age data from the region, document changes in the provenance of syn-rift successions. Detrital zircons from the Eocene Wenchang Formation are unimodal, with Jurassic-Cretaceous (180-80 Ma) ages making up >80% of grains. The ages are consistent with the geochronology of intrabasinal highs, dominated by igneous rocks emplaced during the Yanshanian orogeny, and suggest local provenance. By contrast, detrital zircons from the upper Eocene to lower Oligocene Enping Formation form three well-recognized age-clusters, with peaks at 150, 254, and 438 Ma that match documented tectonomagmatism in South China Block (SCB). Combined with increasing numbers of Precambrian zircons, the data suggest increasing influence of regional provenance of the SCB. Similar age peaks are also recognized from the limited number of zircons analyzed from the upper Oligocene Zhuhai Formation and comparability with modern shelf and river sediment indicates the unit was mainly sourced from the SCB and likely transported by a paleo-Pearl River. We infer that the change in provenance, from local uplifts within the Zhu 1 to the SCB, is related to distinct phases of PRMB rift development; however, later changes are best explained by SCB drainage evolution.

On abrupt transpression to transtension transition in the South Baikal rift system (Tunka - South Baikal segment)

Science.gov (United States)

Sankov, Vladimir; Parfeevets, Anna; Lukhnev, Andrey; Miroshnitchenko, Andrey; Ashurkov, Sergey; Sankov, Alexey; Usynin, Leonid; Eskin, Alexander; Bryzhak, Evgeny

2013-04-01

This work addresses to relation of transpression and extension stress-strain conditions in intracontinental rift system. In our investigation we use a new structural, shallow geophysics, GPS geodetic data and paleostress reconstructions. The surroundings of southern tip of Siberian platform is the region of three Late Cenozoic structures conjugation: sublatitudinal Obruchev fault (OF) controlling the northern boundary of the South Baikal basin, NW trending Main Sayan fault (MSF) as the strike-slip boundary between Siberian platform and East Sayan block and WNW trending eastern segment of Tunka fault (TF) as part of the Tunka basins system northern boundary. A new evidences of superposition of compression and extension fault structures were revealed near the southern extremity of Baikal lake. We've find a very close vicinity of Late Pleistocene - Holocene strike-slip, thrust and normal faulting in the MSF and OF junction zone. The on-land Holocene normal faulting can be considered as secondary fault paragenesis within the main strike-slip zone (Sankov et al., 2009). Active strike-slip, thrust and reverse faulting characterize the MSF and TF junction zone. The transpression conditions are replaced very sharply by transtension and extension ones in eastern direction from zone of structures conjugation - the active normal faulting is dominated within the South Baikal basin. The Bystraya rift basin located in the west shows the tectonic inversion since Middle Pleistocene as a result of the strike-slip movements partitioning between TF and MSF and inset of edition compression stress. The active strike-slip and intrabasin extension conditions are dominated father to the west in Tunka basin. The results of our GPS measurements show the present day convergence and east movements of Khamar-Daban block and eastern Tunka basins relative to Siberian platform along MSF and TF with NE-SW shortening domination. The clear NW-SE divergence across Baikal basin is documented. Holocene

Hydrochemical tracers in the middle Rio Grande Basin, USA: 1. Conceptualization of groundwater flow

Science.gov (United States)

Plummer, L. Niel; Bexfield, Laura M.; Anderholm, Scott K.; Sanford, Ward E.; Busenberg, Eurybiades

Chemical and isotopic data for groundwater from throughout the Middle Rio Grande Basin, central New Mexico, USA, were used to identify and map groundwater flow from 12 sources of water to the basin, evaluate radiocarbon ages, and refine the conceptual model of the Santa Fe Group aquifer system. Hydrochemical zones, representing groundwater flow over thousands to tens of thousands of years, can be traced over large distances through the primarily siliciclastic aquifer system. The locations of the hydrochemical zones mostly reflect the ``modern'' predevelopment hydraulic-head distribution, but are inconsistent with a trough in predevelopment water levels in the west-central part of the basin, indicating that this trough is a transient rather than a long-term feature of the aquifer system. Radiocarbon ages adjusted for geochemical reactions, mixing, and evapotranspiration/dilution processes in the aquifer system were nearly identical to the unadjusted radiocarbon ages, and ranged from modern to more than 30 ka. Age gradients from piezometer nests ranged from 0.1 to 2 year cm-1 and indicate a recharge rate of about 3 cm year-1 for recharge along the eastern mountain front and infiltration from the Rio Grande near Albuquerque. There has been appreciably less recharge along the eastern mountain front north and south of Albuquerque. Des données sur les éléments chimiques et les isotopes présents dans l'eau souterraine prélevée à divers endroits dans le bassin moyen du Rio Grande, au centre du Nouveau-Mexique (É-U), ont permis de déterminer l'existence et l'étendue de douze sources d'eau régionales dans le bassin, d'évaluer les âges radiocarbones et de raffiner le modèle conceptuel du système aquifère du groupe de Santa Fe. Des zones hydro-chimiques qui représentent l'écoulement de l'eau souterraine depuis des dizaines de milliers d'années peuvent être suivies sur de longues distances à travers l'aquifère principalement siliclastique. La position des

Strength reversal in Europe's intraplate lithosphere: transition of basin inversion to lithospheric folding.

NARCIS (Netherlands)

Cloetingh, S.A.P.L.; Wees van, J.D.

2005-01-01

An intriguing paradox in European tectonics is that present intracontinental seismicity seems to be broadly distributed, whereas past deformation was restricted to sedimentary basin areas. These basins were created by repeated Mesozoic rifting and later affected by pervasive Late Cretaceous-early

Thermo chronology by fission tracks of the conjugated rift margins of the Liguro-Provencal basin: Corsica and the Maures-Tanneron Massif

International Nuclear Information System (INIS)

Jakni, B.

2000-01-01

We have employed apatite fission-track (AFT) thermo-chronology on granitic and metamorphic samples taken from Corsican and Maures-Tanneron basement rocks as well as alpine 'schistes lustres' units in Corsica, in order to constrain the cooling histories and the tectonic evolution of the Liguro-Provencal basin margins. The AFT data indicate that: -) the Tanneron massif (AFT ages 145- 150 My) appears to record the earliest cooling history, reflecting thermal relaxation related to opening of the Tethys; -) the Maures basement (AFT ages 20-25 My) clearly records a thermo- tectonic evolution associated with Liguro-Provencal rifting; -) the island of Corsica, which was the main focus of this work and which shows a complex geomorphology and a poly-phased tectonic evolution. shows a remarkable zoning in the distribution of AFT ages, reflecting the signature of at least two post-Oligocene thermal events. Those events are related to the opening of Liguro-Provencal basin (20-25 My) in the west, and exhumation of the Hercynian basement related to Tyrrhenian extension (12- 16 My) in the east. In the east-Tenda shear zone, which forms the contact between the alpine units and Hercynian basement in northern Corsica, our results indicate that the Tenda Massif was being exhumed from about 21 Ma onwards. (author)

Rifting in heterogeneous lithosphere inferences from numerical modeling of the northern North Sea and the Oslo Graben.

NARCIS (Netherlands)

Pascal Candas, C.; Cloetingh, S.A.P.L.

2002-01-01

Permian rifting and magmatism are widely documented across NW Europe. The different Permian basins often display contrasting structural styles and evolved in lithospheric domains with contrasting past evolution and contrasting thermotectonic ages. In particular, the Oslo Graben and the northern

[Grand Banks activity : updates and opportunities

International Nuclear Information System (INIS)

Bruce, G.

1998-01-01

An overview of the exploration and on-going activities by the petroleum industry on the Grand Banks of Newfoundland was presented. The two offshore oil developments underway are Hibernia and Terra Nova, both located in the Jeanne d'Arc Basin. Current production from Hibernia is 68,000 bopd, expected to rise to 130,000 bopd in 1999. The Terra Nova Field is still under development. Total recoverable reserves from the 17 discoveries made in the Jeanne d'Arc Basin are estimated at 1.6 billion barrels of oil and 4 trillion cubic feet of gas. Industry participants in the area include Amoco, Petro-Canada, Mobil, Chevron, Husky and Norsk Hydro. Petro-Canada believes the Grand Banks represent one of the best opportunities for oil anywhere in the world. There are currently 21 exploration licenses held on the Grand Banks. Major attractions of the area include the large reserve potential, the relatively low finding costs, the size of the pools being discovered, improvements in offshore technology that have substantially lowered development costs, and a profit-sensitive generic royalty regime that ensures reasonable rates of return for investors. figs

Relationships between crustal structure and extension in the Basin and Range Province and East Africa

Energy Technology Data Exchange (ETDEWEB)

Keller, G R [University of Oklahoma, School of Geology and Geophysics, Norman, Oklahoma, 73019 (United States)], E-mail: grkeller@ou.edu

2008-07-01

The Basin and Range Province of the western United States and northern Mexico is often cited as a classic example of a wide rift. It is also a region where metamorphic core complexes such as the ones observed in the Aegean region are observed. On the other hand, the eastern arm (Kenya rift) of the East African rift is considered to be the classic example of a continental rift, which is by some definitions narrow. In this paper, these two features are briefly compared in terms of crustal structure and associated manifestations of extension.

Petroleum systems and hydrocarbon accumulation models in the Santos Basin, SP, Brazil; Sistemas petroliferos e modelos de acumulacao de hidrocarbonetos na Bacia de Santos

Energy Technology Data Exchange (ETDEWEB)

Chang, Hung Kiang; Assine, Mario Luis; Correa, Fernando Santos; Tinen, Julio Setsuo [Universidade Estadual Paulista (UNESP), Rio Claro, SP (Brazil). Lab. de Estudos de Bacias]. E-mails: chang@rc.unesp.br; assine@rc.unesp.br; fscorrea@rc.unesp.br; jstinen@rc.unesp.br; Vidal, Alexandre Campane; Koike, Luzia [Universidade Estadual de Campinas (UNICAMP), Campinas, SP (Brazil). Centro de Estudos de Petroleo]. E-mails: vidal@ige.unicamp.br; luzia@iqm.unicamp.br

2008-07-01

The Santos Basin was formed by rifting process during Mesozoic Afro-American separation. Sediment accumulation initiated with fluvial-lacustrine deposits, passing to evaporitic stage until reaching marginal basin stages. The analysis of hydrocarbon potential of Santos Basin identified two petroleum systems: Guaratiba-Guaruja and Itajai-Acu-Ilhabela. The Guaratiba Formation is less known in the Santos Basin because of small number of wells that have penetrated the rift section. By comparison with Campos Basin, hydrocarbons are of saline lacustrine origin deposited in Aptian age. Analogous to Campos Basin the major source rock is of saline-lacustrine origin, which has been confirmed from geochemical analyses of oil samples recovered from the various fields. These analyses also identified marine source rock contribution, indicating the Itajai-Acu source rock went through oil-window, particularly in structural lows generated by halokynesis. Models of hydrocarbon accumulation consider Guaratiba Formacao as the major source rock for shallow carbonate reservoirs of Guaruja Formacao and for late Albian to Miocene turbidites, as well as siliciclastic and carbonate reservoirs of the rift phase. Migration occurs along salt window and through carrier-beds. The seal rock is composed of shales and limestones intercalated with reservoir facies of the post-rift section and by thick evaporites overlying rift section, especially in the deeper water. In the shallow portion, shale inter-tongued with reservoir rocks is the main seal rock. The hydrocarbon generation and expulsion in the central-north portion of the basin is caused by overburden of a thick Senonian section. Traps can be structural (rollovers and turtle), stratigraphic (pinch-outs) and mixed origins (pinch-outs of turbidites against salt domes). (author)

Implementation of MAR within the Rio Grande Basin of Central New Mexico, USA

Science.gov (United States)

Marley, Robert; Blandford, T. Neil; Ewing, Amy; Webb, Larry; Yuhas, Katherine

2014-05-01

The U.S. Bureau of Reclamation has identified the Rio Grande basin within Central New Mexico as one of several regions where water supplies are over-allocated and future conflicts over the inadequate resource are highly likely. Local water providers have consistently identified managed aquifer recharge (MAR) as an important tool to provide conjunctive management of surface-water, groundwater, and reclaimed water sources in order to extend the useful life of existing water sources. However, MAR projects have been slow to take root partly due to rigorous demonstration requirements, groundwater quality protection concerns, and ongoing water right uncertainties. At first glance the several thousand meters of unconsolidated basin-fill sediments hosting the regional aquifer appear to provide an ideal environment for the subsurface storage of surplus water. However, the basin has a complex structural and depositional history that impacts the siting and overall effectiveness of MAR systems. Several recharge projects are now in various stages of implementation and are overcoming site specific challenges including source water and ambient groundwater compatibility, low-permeability sediments and compartmentalization of the aquifer by extensive faulting, well clogging, and overall water quality management. This presentation will highlight ongoing efforts of these water providers to develop full-scale recharge facilities. The performance of natural in-channel infiltration, engineered infiltration galleries, and direct injection systems designed to introduce from 500 to 5,000 mega-liters per annum to target intervals present from 150 to 600 meters below ground surface will be described. Source waters for recharge operations include inter-basin transferred surface water and highly treated reclaimed water sources requiring from minor to extensive treatment pre-recharge and post-recovery. Operational complexities have raised concerns related to long-term operation and maintenance

Fracture patterns of the drainage basin of Wadi Dahab in relation to tectonic-landscape evolution of the Gulf of Aqaba - Dead Sea transform fault

Science.gov (United States)

Shalaby, Ahmed

2017-10-01

Crustal rifting of the Arabian-Nubian Shield and formation of the Afro-Arabian rifts since the Miocene resulted in uplifting and subsequent terrain evolution of Sinai landscapes; including drainage systems and fault scarps. Geomorphic evolution of these landscapes in relation to tectonic evolution of the Afro-Arabian rifts is the prime target of this study. The fracture patterns and landscape evolution of the Wadi Dahab drainage basin (WDDB), in which its landscape is modeled by the tectonic evolution of the Gulf of Aqaba-Dead Sea transform fault, are investigated as a case study of landscape modifications of tectonically-controlled drainage systems. The early developed drainage system of the WDDB was achieved when the Sinai terrain subaerially emerged in post Eocene and initiation of the Afro-Arabian rifts in the Oligo-Miocene. Conjugate shear fractures, parallel to trends of the Afro-Arabian rifts, are synthesized with tensional fracture arrays to adapt some of inland basins, which represent the early destination of the Sinai drainage systems as paleolakes trapping alluvial sediments. Once the Gulf of Aqaba rift basin attains its deeps through sinistral movements on the Gulf of Aqaba-Dead Sea transform fault in the Pleistocene and the consequent rise of the Southern Sinai mountainous peaks, relief potential energy is significantly maintained through time so that it forced the Pleistocene runoffs to flow via drainage systems externally into the Gulf of Aqaba. Hence the older alluvial sediments are (1) carved within the paleolakes by a new generation of drainage systems; followed up through an erosional surface by sandy- to silty-based younger alluvium; and (2) brought on footslopes of fault scarps reviving the early developed scarps and inselbergs. These features argue for crustal uplifting of Sinai landscapes syn-rifting of the Gulf of Aqaba rift basin. Oblique orientation of the Red Sea-Gulf of Suez rift relative to the WNW-trending Precambrian Najd faults; and

Is the Proterozoic Ladoga Rift (SE Baltic Shield) a rift?

DEFF Research Database (Denmark)

Artemieva, Irina; Shulgin, Alexey

2015-01-01

, and geophysical characteristics typical of continental rifts in general and demonstrate that, except for magmatic and, perhaps, some gravity signature, the Lake Ladoga region lacks any other rift features. We also compare the geophysical data from the Lake Ladoga region with similar in age Midcontinent and Valday...... interpreted as an intracratonic Ladoga rift (graben). We question the validity of this geodynamic interpretation by analyzing regional geophysical data (crustal structure, heat flow, Bouguer gravity anomalies, magnetic anomalies, and mantle Vs velocities). We provide a complete list of tectonic, magmatic...... rifts, and provide alternative explanations for Mesoproterozoic geodynamic evolution of the southern Baltic Shield. We propose that Mesoproterozoic mafic intrusions in southern Fennoscandia may be associated with a complex deformation pattern during reconfiguration of (a part of) Nuna (Columbia...

Lithofacies paleogeography and sedimentary model of Sinian Dengying Fm in the Sichuan Basin

Directory of Open Access Journals (Sweden)

Jingao Zhou

2017-05-01

Full Text Available For predicting the distribution of favorable reservoir facies belts of the super-large ancient Anyue carbonate gas field in the Sichuan Basin, through an analysis of structure and lithofacies paleogeography, the lithofacies paleogeography and sedimentary model of the Sinian Dengying Fm was reconstructed based on the field outcrop, drilling and seismic data. As a result, achievements are made in four aspects. First, the basin and its periphery resided in an extensional tectonic setting in the Sinian. Intense extension led to the formation of the Deyang–Anyue intra-platform rift. The Sichuan Basin was divided into the palaeo-geographic pattern of “two uplifts and four sags”. The “two uplifts” evolved into the platform, and the “four sags” evolved into the slope-basin environment. Second, in the depositional stage of the Deng 2 Member, some favorable reservoir belts developed, such as bioherm-shoal at the continental margin, bioherm-shoal at the rift margin, and bioherm-shoal in the platform. The bioherm-shoal at rift margin developed along both sides of the Deyang–Anyue rift, in a U-shape, with a width of about 5–40 km and a length of about 500 km. It connected with the platform margin belt at the continental margin to the west in the Shifang area, and to the north near Guangyuan area. Third, in the depositional stage of the Deng 4 Member, when the lithofacies paleogeographic features in the Deng 2 Member remained, the platform margin belt at the rift margin evolved into two parts in the east and the west as a result of the continuous southward extensional faulting of the Deyang–Anyue rift until it finally crossed the basin from north to south. The eastern platform margin belt was located in the Guangyuan–Yanting–Anyue–Luzhou area, showing NS distribution with a length of about 450 km and a width of about 4–50 km. The western platform margin belt mainly developed in the Dujiangyan�

Morphostructural evidence for Recent/active extension in Central Tanzania beyond the southern termination of the Kenya Rift.

Science.gov (United States)

Le Gall, B.; Rolet, J.; Gernigon, L.; Ebinger, C.; Gloaguen, R.

2003-04-01

The southern tip zone of the Kenya Rift on the eastern branch of the East African System is usually thought to occur in the so-called North Tanzanian Divergence. In this region, the narrow (50 km-wide) axial graben of southern Kenya splays southwards, via a major EW-trending volcanic lineament, into a 200 km-wide broad rifted zone with three separate arms of normal faulting and tilted fault blocks (Eyasi, Manyara and Pangani arms from W to E). Remote sensing analysis from Central Tanzania demonstrates that rift morphology exists over an area lying 400 km beyond the southern termination of the Kenya Rift. The most prominent rift structures are observed in the Kilombero region and consist of a 100 km-wide range of uplifted basement blocks fringed to the west by an E-facing half-graben inferred to reach depths of 6-8 km from aeromagnetic dataset. Physiographic features (fault scarps), and river drainage anomalies suggest that the present-day rift pattern in the Kilombero extensional province principally results from Recent/Neogene deformation. That assumption is also supported by the seismogenic character of a number of faults. The Kilombero half-graben is superimposed upon an earlier rift system, Karoo in age, which is totally overprinted and is only evidenced from its sedimentary infill. On the other hand, the nature and thickness of the inferred Neogene synrift section is still unknown. The Kilombero rifted zone is assumed to connect northwards into the central rift arm (Manyara) of the South Kenya Rift via a seismically active transverse fault zone that follows ductile fabrics within the Mozambican crystalline basement. The proposed rift model implies that incipient rifting propagates hroughout the cold and strong crust/lithosphere of Central Tanzania along Proterozoic (N140=B0E) basement weakness zones and earlier Karoo (NS)rift structures. A second belt of Recent-active linked fault/basins also extends further East from the Pangani rift arm to the offshore

Plate Speed-up and Deceleration during Continental Rifting: Insights from Global 2D Mantle Convection Models.

Science.gov (United States)

Brune, S.; Ulvrova, M.; Williams, S.

2017-12-01

The surface of the Earth is divided into a jigsaw of tectonic plates, some carrrying continents that disperse and aggregate through time, forming transient supercontinents like Pangea and Rodinia. Here, we study continental rifting using large-scale numerical simulations with self-consistent evolution of plate boundaries, where continental break-up emerges spontaneously due to slab pull, basal drag and trench suction forces.We use the StagYY convection code employing a visco-plastic rheology in a spherical annulus geometry. We consider an incompressible mantle under the Boussinesq approximation that is basally and internally heated.We show that continental separation follows a characteristic evolution with three distinctive phases: (1) A pre-rift phase that typically lasts for several hundreds of millions of years with tectonic quiescence in the suture and extensional stresses that are slowly building up. (2) A rift phase that further divides into a slow rift period of several tens of millions of years where stresses continuously increase followed by a rift acceleration period featuring an abrupt stress drop within several millions of years. The speed-up takes place before lithospheric break-up and therefore affects the structural architecture of the rifted margins. (3) The drifting phase with initially high divergence rates persists over tens of millions of years until the system adjust to new conditions and the spreading typically slows down.By illustrating the geodynamic connection between subduction dynamics and rift evolution, our results allow new interpretations of plate tectonic reconstructions. Rift acceleration within the second phase of rifting is compensated by enhanced convergence rates at subduction zones. This model outcome predicts enhanced subduction velocities, e.g. between North America and the Farallon plate during Central Atlantic rifting 200 My ago, or closure of potential back-arc basins such as in the proto-Andean ranges of South America

Oil and gas in the Ogaden Basin, Ethiopia

Energy Technology Data Exchange (ETDEWEB)

Du Toit, S.R.; Kurdy, S. [Alconsult International, Calgary, AB (Canada); Asfaw, S.H.; Gessesse, A.A. [Petroleum Operations Dept., Ministry of Mines and Energy, Addis Ababa (Ethiopia)

1997-09-01

To date, many of the 47 exploration and development wells drilled in the Ogaden Basin in Ethiopia have exhibited natural oil seeps and oil and gas shows. The Calub gas field and the Hilala oil field occurs in the central part of the 350,000 sq. km. basin. The various units within the basin consist of continental sediments, a regional organic-rich interval close to the Permo-Triassic boundary, organic-rich marine sediments and carbonates. The Ogaden Basin is dissected by several faults that are related to the Ethiopian Rift and may form a component of traps in the Calub-Hilala area.

Palaeoseismicity in relation to basin tectonics as revealed from soft ...

Indian Academy of Sciences (India)

belts acted as zones of rift propagation, and reac- tivation of palaeo-sutures and ... to Jurassic-aged riftogenic continental basins filled ... led to a half-graben geometry with accumulation of greater ... basin margin are thought to have been active dur- ...... Petrol. 22. 83–96. Kundu A and Goswami B 2008 A note on seismic evi-.

Formation and inversion of transtensional basins in the western part of the Lachlan Fold Belt, Australia, with emphasis on the Cobar Basin

Science.gov (United States)

Glen, R. A.

The Palaeozoic history of the western part of the Lachlan Fold Belt in New South Wales was dominated by strike-slip tectonics. In the latest Silurian to late Early Devonian, an area of crust >25,000 km 2 lying west of the Gilmore Suture underwent regional sinistral transtension, leading to the development of intracratonic successor basins, troughs and flanking shelves. The volcaniclastic deep-water Mount Hope Trough and Rast Trough, the siliciclastic Cobar Basin and the volcanic-rich Canbelego-Mineral Hill Belt of the Kopyje Shelf all were initiated around the Siluro-Devonian boundary. They all show clear evidence of having evolved by both active syn-rift processes and passive later post-rift (sag-phase) processes. Active syn-rift faulting is best documented for the Cobar Basin and Mount Hope Trough. In the former case, the synchronous activity on several fault sets suggests that the basin formed by sinistral transtension in response to a direction of maximum extension oriented NE-SW. Structures formed during inversion of the Cobar Basin and Canbelego-Mineral Hill Belt indicate closure under a dextral transpressive strain regime, with a far-field direction of maximum shortening oriented NE-SW. In the Cobar Basin, shortening was partitioned into two structural zones. A high-strain zone in the east was developed into a positive half-flower structure by re-activation of early faults and by formation of short-cut thrusts, some with strike-slip movement, above an inferred steep strike-slip fault. Intense subvertical cleavage, a steep extension lineation and variably plunging folds are also present. A lower-strain zone to the west developed by syn-depositional faults being activated as thrusts soling into a gently dipping detachment. A subvertical cleavage and steep extension lineation are locally present, and variably plunging folds are common. Whereas Siluro-Devonian basin-opening appeared to be synchronous in the western part of the fold belt, the different period of

Deltaic Depositional Systems, Evolution Characteristics, and Petroleum Potential, Palaeogene Sub-Basin, South China Sea

Science.gov (United States)

Li, Yuan; Wang, Hua; Zhang, Guotao

2015-04-01

Deltaic depositional systems are detailed characterized by morphology and facies in a Palaeogene continental sub-basin of Beibuwan Basin, South China Sea. Based on examination of 435 m of conventional cores from 30 wells, three major types of deltaic facies have been recognized: delta, beach and shoreface. Morphology and facies asymmetry between the down-drift and the up-drift sides present a typical asymmetric delta system:1) the down-rift, sourced primarily by the feeding river, are influenced by mixed river and wave processes. Deposits on this side are muddy and consist of barrier, bar, bay-fill, and bayhead delta facies with variable bioturbation intensity; 2)the up-rift, in contrast, is sourced by a second sediment source and typically consists of laterally continuous sandy beach and shoreface facies. Finally, two fundamentally different depositional models are established and reflect a different style of sequence stratigraphic patterns: 1) Multiple-stage faults slopes developed in the down-rift side feed fine grained sediment into two stages channelized front deltaic system; 2) Flexure slope break of the up-rift side, combining with deeper gradual slopes, conversely, feed coarser grained sediment from larger drainages into sandy beach and shoreface systems. Such a distinction has well explained the differentiation of the proven hydrocarbon reserves because the up-rift consists of well-sorted, mature, and laterally continuous homogeneous beach-shoreface reservoirs, whereas the down-rift, in contrast, is muddier and consists of less continuous, less mature, heterolithic reservoirs. The Delta asymmetry concepts and models don't only challenge the traditional definition of deltas in Fushan sub-basin, but also provides strong theoretical support for the future exploration. This process-based model may be applicable to many deep-water settings and provides a framework within which to interpret the stratigraphic and spatial distribution of these complex deposits.

Geochemical constraints on the petrogenesis of the pyroclastic rocks in Abakaliki basin (Lower Benue Rift), Southeastern Nigeria

Science.gov (United States)

Chukwu, Anthony; Obiora, Smart C.

2018-05-01

The pyroclastic rocks in the Cretaceous Abakaliki basin occur mostly as oval-shaped bodies, consisting of lithic/lava and vitric fragments. They are commonly characterized by parallel and cross laminations, as well contain xenoliths of shale, mudstone and siltstones from the older Asu River Group of Albian age. The rocks are basic to ultrabasic in composition, comprising altered alkali basalts, altered tuffs, minor lapillistones and agglomerates. The mineral compositions are characterized mainly by laths of calcic plagioclase, pyroxene (altered), altered olivines and opaques. Calcite, zeolite and quartz represent the secondary mineral constituents. Geochemically, two groups of volcaniclastic rocks, are distinguished: alkaline and tholeiitic rocks, both represented by fresh and altered rock samples. The older alkali basalts occur within the core of the Abakaliki anticlinorium while the younger tholeiites occur towards the periphery. Though most of the rocks are moderate to highly altered [Loss on ignition (LOI, 3.43-22.07 wt. %)], the use of immobile trace element such as Nb, Zr, Y, Hf, Ti, Ta and REEs reflect asthenospheric mantle source compositions. The rocks are enriched in incompatible elements and REEs (∑REE = 87.98-281.0 ppm for alkaline and 69.45-287.99 ppm for tholeiites). The ratios of La/Ybn are higher in the alkaline rocks ranging from 7.69 to 31.55 compared to the tholeiitic rocks which range from 4.4 to 16.89 and indicating the presence of garnet-bearing lherzolite in the source mantle. The spidergrams and REEs patterns along with Zr/Nb, Ba/Nb, Rb/Nb ratios suggest that the rocks were generated by a mantle plume from partial melting of mixed enriched mantle sources (HIMU, EMI and EMII) similar to the rocks of the south Atlantic Ocean such as St. Helena (alkaline rocks) and Ascension rocks (tholeiitic rocks). The rocks were formed in a within-plate setting of the intra-continental rift type similar to other igneous rocks in the Benue Rift and are not

Hydro-meteorological trends in the Gidabo catchment of the Rift Valley Lakes Basin of Ethiopia

Science.gov (United States)

Belihu, Mamuye; Abate, Brook; Tekleab, Sirak; Bewket, Woldeamlak

2018-04-01

The global and regional variability and changes of climate and stream flows are likely to have significant influence on water resource availability. The magnitude and impacts of climate variability and change differs spatially and temporally. This study examines the long term hydroclimatic changes, analyses of the hydro-climate variability and detect whether there exist significant trend or not in the Gidabo catchment, rift valley lakes basin of Ethiopia. Precipitation, temperature and stream flow time series data were used in monthly, seasonal and annual time scales. The precipitation and temperature data span is between 1982 and 2014 and that of stream flow is between 1976 and 2006. To detect trends the analysis were done by using Mann Kendal (MK), Sen's graphical method and to detect change point using the Pettit test. The comparison of trend analysis between MK trend test and Sen graphical method results depict mostly similar pattern. The annual rainfall trends exhibited a significant decrease by about 12 mm per year in the upstream, which is largely driven by the significant decrease in the peak season rainfall. The Pettit test revealed that the years 1997 and 2007 were the change points. It is noted that the rise of temperature over a catchment might have decreased the availability of soil moisture which resulted in less runoff. The temperature analyses also revealed that the catchment was getting warmer; particularly in the upstream. The minimum temperature trend showed a significant increase about 0.08°c per annum. There is generally a decreasing trend in stream flow. The monthly stream flow also exhibited a decreasing trend in February, March and September. The decline in annual and seasonal rainfall and the increase in temperature lead to more evaporation and directly affecting the stream flow negatively. This trend compounded with the growth of population and increasing demand for irrigation water exacerbates the competing demand for water resources. It

Mantle temperature as a control on the time scale of thermal evolution of extensional basins

DEFF Research Database (Denmark)

Petersen, Kenni Dinesen; Armitage, J.J.; Nielsen, S.B.

2015-01-01

Abstract Extension of the lithosphere, the thermo-mechanical boundary layer above the convecting mantle, is followed by cooling and subsidence. The timescale of oceanic basin subsidence is ∼100 Myr whereas basins of the continental interior often subside continuously for more than 200 Myr after...... rifting. Using numerical modelling, we show how these diverse rifting scenarios are unified when accounting for varying mantle potential temperature. At a temperature of 1300 °C, cooling is plate-like with nearly exponential subsidence as observed in oceanic basins. At 1200 °C, subsidence is almost linear...... and continues for more than 800 Myr. The longevity of basin subsidence in the continental interior can therefore be explained by variation of mantle temperature. An additional cause of the longevity of subsidence is related to the equilibrium thickness of the lithosphere which is increased by the local...

Basalt stratigraphy - Pasco Basin

International Nuclear Information System (INIS)

Waters, A.C.; Myers, C.W.; Brown, D.J.; Ledgerwood, R.K.

1979-10-01

The geologic history of the Pasco Basin is sketched. Study of the stratigraphy of the area involved a number of techniques including major-element chemistry, paleomagnetic investigations, borehole logging, and other geophysical survey methods. Grande Ronde basalt accumulation in the Pasco Basin is described. An illustrative log response is shown. 1 figure

Hydrochemical tracers in the middle Rio Grande Basin, USA: 2. Calibration of a groundwater-flow model

Science.gov (United States)

Sanford, Ward E.; Plummer, L. Niel; McAda, Douglas P.; Bexfield, Laura M.; Anderholm, Scott K.

The calibration of a groundwater model with the aid of hydrochemical data has demonstrated that low recharge rates in the Middle Rio Grande Basin may be responsible for a groundwater trough in the center of the basin and for a substantial amount of Rio Grande water in the regional flow system. Earlier models of the basin had difficulty reproducing these features without any hydrochemical data to constrain the rates and distribution of recharge. The objective of this study was to use the large quantity of available hydrochemical data to help calibrate the model parameters, including the recharge rates. The model was constructed using the US Geological Survey's software MODFLOW, MODPATH, and UCODE, and calibrated using 14C activities and the positions of certain flow zones defined by the hydrochemical data. Parameter estimation was performed using a combination of nonlinear regression techniques and a manual search for the minimum difference between field and simulated observations. The calibrated recharge values were substantially smaller than those used in previous models. Results from a 30,000-year transient simulation suggest that recharge was at a maximum about 20,000 years ago and at a minimum about 10,000 years ago. Le calibrage d'un modèle hydrogéologique avec l'aide de données hydrochimiques a démontré que la recharge relativement faible dans le Grand Bassin du Middle Rio est vraisemblablement responsable d'une dépression des eaux souterraines dans le centre du bassin et de la présence d'une quantité substantielle d'eau du Rio Grande dans l'aquifère du Groupe de Santa Fe. Les modèles antérieurs avaient des difficultés à reproduire ses conclusions sans l'aide de données hydrochimiques pour contraindre les taux et la distribution de la recharge. L'objectif de cette étude était d'utiliser une grande quantité de données hydrochimiques permettant de calibrer les paramètres du modèle, et notamment les taux de recharge. Le modèle a �

Studies of geology and hydrology in the Basin and Range province, southwestern United States, for isolation of high-level radioactive waste: characterization of the Rio Grande Region, New Mexico, and Texas

International Nuclear Information System (INIS)

Bedinger, M.S.; Sargent, Kenneth A.; Langer, William H.

1989-01-01

The Rio Grande region, New Mexico and Texas, includes most of the area east of the Rio Grande to the Sacramento Mountains. The region encompasses two large basins, the Jornada del Muerto and Tularosa basins, and the intervening San Andres Mountains. The valley surfaces generally have altitudes from 600 to 1,500 meters, and the mountain ranges generally have altitudes from 1,500 to 2,400 meters. About one-half the area is underlain by basin fill. Sedimentary rocks that crop out in the Rio Grande region range in age from Precambrian to Holocene. The oldest Precambrian rocks are metamorphosed and intruded by plutons. Paleozoic rocks are primarily carbonates, with argillaceous beds in the older Paleozoic units. Clastic and gypsum are in greater abundance in younger Paleozoic units of Pennsylvanian and Permian age. The Mesozoic rocks primarily are clastic rocks with some limestone. Cenozoic rocks consist of sequences of conglomerate, sandstone, mudstone, and siltstone, derived from adjacent mountain masses, interbedded with basalt and andesite flows and silicic tuffs. Early to middle Tertiary volcanic and tectonic processes resulted in the implacement of plutonic bodies; volcanic activity continued into the Quaternary. Media considered to have potential for isolation of high-level radioactive waste include intrusive rocks, ash-flow tuff, and basaltic lava flows. Laharic and mudflow breccia and argillaceous beds also may be potential host rocks. These and other rocks may be potential media in areas where the unsaturated zone is thick. Quaternary faults are more common in the southern one-half of the region than in the northern one-half. Range-bounding faults with evidence of Quaternary movement extend northward into the central part of the region. Volcanic activity in the northern part of the region includes basalt flows of Quaternary age. Historical crustal uplift and seismicity have occurred in the vicinity of Socorro, New Mexico. The region is bordered on the west by

Water-quality assessment of the Lower Grand River Basin, Missouri and Iowa, USA, in support of integrated conservation practices

Science.gov (United States)

Wilkison, Donald H.; Armstrong, Daniel J.

2016-01-01

The effectiveness of agricultural conservation programmes to adequately reduce nutrient exports to receiving streams and to help limit downstream hypoxia issues remains a concern. Quantifying programme success can be difficult given that short-term basin changes may be masked by long-term water-quality shifts. We evaluated nutrient export at stream sites in the 44 months that followed a period of increased, integrated conservation implementation within the Lower Grand River Basin. These short-term responses were then compared with export that occurred in the main stem and adjacent rivers in northern Missouri over a 22-year period to better contextualize any recent changes. Results indicate that short-term (October 2010 through May 2014) total nitrogen (TN) concentrations in the Grand River were 20% less than the long-term average, and total phosphorus (TP) concentrations were 23% less. Nutrient reductions in the short term were primarily the result of the less-than-average precipitation and, consequently, streamflow that was 36% below normal. Therefore, nutrient concentrations measured in tributary streams were likely less than normal during the implementation period. Northern Missouri streamflow-normalized TN concentrations remained relatively flat or declined over the period 1991 through 2013 likely because available sources of nitrogen, determined as the sum of commercial fertilizers, available animal manures and atmospheric inputs, were typically less than crop requirement for much of that time frame. Conversely, flow-normalized stream TP concentrations increased over the past 22 years in northern Missouri streams, likely in response to many years of phosphorus inputs in excess of crop requirements. Stream nutrient changes were most pronounced during periods that coincided with the major tillage, planting and growth phases of row crops and increased streamflow. Nutrient reduction strategies targeted at the period February through June would likely have the

Material Exchange and Migration between Pore Fluids and Sandstones during Diagenetic Processes in Rift Basins: A Case Study Based on Analysis of Diagenetic Products in Dongying Sag, Bohai Bay Basin, East China

Directory of Open Access Journals (Sweden)

W. Meng

2018-01-01

Full Text Available The exchange and migration of basin materials that are carried by pore fluids are the essence of diagenesis, which can alter physical properties of clastic rocks as well as control formation and distribution of favorable reservoirs of petroliferous basins. Diagenetic products and pore fluids, resulting from migration and exchange of basin materials, can be used to deduce those processes. In this study, 300 core samples from 46 wells were collected for preparation of casting thin sections, SEM, BSE, EDS, inclusion analysis, and isotope analysis in Dongying Sag, Bohai Bay Basin, East China. Combined with geochemical characteristics of pore fluids and geological background of the study area, the source and exchange mechanisms of materials in the pore fluids of rift basins were discussed. It was revealed that the material exchange of pore fluids could be divided into five stages. The first stage was the evaporation concentration stage during which mainly Ca2+, Mg2+, and CO32- precipitated as high-Mg calcites. Then came the shale compaction stage, when mainly Ca2+ and CO32- from shale compaction water precipitated as calcites. The third stage was the carboxylic acid dissolution stage featured by predominant dissolution of plagioclases, during which Ca2+ and Na+ entered pore fluids, and Si and Al also entered pore fluids and then migrated as clathrates, ultimately precipitating as kaolinites. The fourth stage was the organic CO2 stage, mainly characterized by the kaolinization of K-feldspar as well as dissolution of metamorphic lithic fragments and carbon cements. During this stage, K+, Fe2+, Mg2+, Ca2+, HCO3-, and CO32- entered pore fluids. The fifth stage was the alkaline fluid stage, during which the cementation of ferro-carbonates and ankerites as well as illitization or chloritization of kaolinites prevailed, leading to the precipitation of K+, Fe2+, Mg2+, Ca2+, and CO32- from pore fluids.

Initial opening of the Eurasian Basin, Arctic Ocean

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Kai Berglar

2016-10-01

Full Text Available Analysis of the transition from the NE Yermak Plateau into the oceanic Eurasian Basin sheds light on the Paleocene formation of this Arctic basin. Newly acquired multichannel seismic data with a 3600 m long streamer shot during ice-free conditions enables the interpretation of crustal structures. Evidence is provided that no major compressional deformation affected the NE Yermak Plateau. The seismic data reveal that the margin is around 80 km wide and consists of rotated fault blocks, major listric normal faults, and half-grabens filled with syn-rift sediments. Taking into account published magnetic and gravimetric data, this setting is interpreted as a rifted continental margin, implying that the NE Yermak Plateau is of continental origin. The transition from the Yermak Plateau to the oceanic Eurasian Basin might be located at a prominent basement high, probably formed by exhumed mantle. In contrast to the Yermak Plateau margin, the North Barents Sea continental margin shows a steep continental slope with a relatively abrupt transition to the oceanic domain. Based on one composite seismic line, it is speculated that the initial opening direction of the Eurasian Basin in the Arctic Ocean was highly oblique to the present day seafloor spreading direction.

Gravity study of the Central African Rift system: a model of continental disruption 2. The Darfur domal uplift and associated Cainozoic volcanism

Science.gov (United States)

Bermingham, P. M.; Fairhead, J. D.; Stuart, G. W.

1983-05-01

Gravity studies of the Darfur uplift, Western Sudan, show it to be associated with a circular negative Bouguer anomaly, 50 mGal in amplitude and 700 km across. A three-dimensional model interpretation of the Darfur anomaly, using constraints deduced from geophysical studies of similar but more evolved Kenya and Ethiopia domes, suggests either a low-density laccolithic body at mid-lithospheric depth (~ 60 km) or a thinned lithosphere with emplacement at high level of low-density asthenospheric material. The regional setting of the Darfur uplift is described in terms of it being an integral part of the Central African Rift System which is shown to be broadly equivalent to the early to middle Miocene stage in the development of the Afro-Arabian Rift System. Comparisons between these rift systems suggest that extensional tectonics and passive rifting, resulting in the subsiding sedimentary rift basins associated with the Ngaoundere, Abu Gabra, Red Sea and Gulf of Aden rifts, are more typical of the early stage development of passive continental margins than the active domal uplift and development of rifted features associated with the Darfur, Kenya and Ethiopia domes.

Carboniferous rifted arcs leading to an archipelago of multiple arcs in the Beishan-Tianshan orogenic collages (NW China)

Science.gov (United States)

Tian, Zhonghua; Xiao, Wenjiao; Windley, Brian F.; Zhang, Ji'en; Zhang, Zhiyong; Song, Dongfang

2017-10-01

The Beishan and East Tianshan Orogenic Collages in the southernmost Central Asian Orogenic Belt (CAOB) record the final stages of evolution of the Paleo-Asian Ocean. These collages and their constituent arcs have an important significance for resolving current controversies regarding their tectonic setting and age, consequent accretionary history of the southern CAOB, and the closure time of the Paleo-Asian Ocean. In this paper, we present our work on the southern Mazongshan arc and the northern Hongyanjing Basin in the Beishan Orogenic Collage (BOC), and our comparison with the Bogda arc and associated basins in the East Tianshan Orogenic Collage. Field relationships indicate that the Pochengshan fault defines the boundary between the arc and basin in the BOC. Volcanic rocks including basalts and rhyolites in the Mazongshan arc have bimodal calc-alkaline characteristics, an enrichment in large ion lithophile elements such as Rb, Ba, and Pb and depletion in high field-strength elements (e.g., Nb and Ta), which were probably developed in a subduction-related tectonic setting. We suggest that these bimodal calc-alkaline volcanic rocks formed in rifted arcs instead of post-orogenic rifts with mantle plume inputs. By making detailed geochemical comparisons between the Mazongshan arc and the Bogda arc to the west, we further propose that they are similar and both formed in arc rifts, and helped generate a Carboniferous archipelago of multiple arcs in the southern Paleo-Asian Ocean. These data and ideas enable us to postulate a new model for the tectonic evolution of the southern CAOB.

Grande Ronde Basin Spring Chinook Salmon Captive Broodstock Program, 2008 Annual Report.

Energy Technology Data Exchange (ETDEWEB)

Hoffnagle, Timothy L.; Hair, Donald; Gee, Sally

2009-03-31

The Grande Ronde Basin Spring Chinook Salmon Captive Broodstock Program is designed to rapidly increase numbers of Chinook salmon in stocks that are in imminent danger of extirpation in Catherine Creek (CC), Lostine River (LR) and upper Grande Ronde River (GR). Natural parr are captured and reared to adulthood in captivity, spawned (within stocks) and their progeny reared to smoltification before being released into the natal stream of their parents. This program is co-managed by ODFW, National Marine Fisheries Service, Nez Perce Tribe and Confederated Tribes of the Umatilla Indian Reservation. Presmolt rearing was initially conducted at Lookingglass Fish Hatchery (LFH) but parr collected in 2003 and later were reared at Wallowa Fish Hatchery (WFH). Post-smolt rearing is conducted at Bonneville Fish Hatchery (BOH - freshwater) and at Manchester Research Station (MRS - saltwater). The CC and LR programs are being terminated, as these populations have achieved the goal of a consistent return of 150 naturally spawning adults, so the 2005 brood year was the last brood year collected for theses populations. The Grande Ronde River program continued with 300 fish collected each year. Currently, we are attempting to collect 150 natural parr and incorporate 150 parr collected as eggs from females with low ELISA levels from the upper Grande Ronde River Conventional Hatchery Program. This is part of a comparison of two methods of obtaining fish for a captive broodstock program: natural fish vs. those spawned in captivity. In August 2007, we collected 152 parr (BY 2006) from the upper Grande Ronde River and also have 155 Grande Ronde River parr (BY 2006) that were hatched from eyed eggs at LFH. During 2008, we were unable to collect natural parr from the upper Grande Ronde River. Therefore, we obtained 300 fish from low ELISA females from the upper Grande Ronde River Conventional Program. In October 2008 we obtained 170 eyed eggs from the upper Grande Ronde river Conventional

Basin characterization and determination of hydraulic connectivity of mega basins using integrated methods: (The case of Baro-Akobo and mega watershed beyond)

Science.gov (United States)

Alemayehu, Taye; Kebede, Tesfaye; Liu, Lanbo

2018-01-01

Despite being the longest river and the fourth in drainage area, Nile River has the lowest discharge per unit areas among the top ten rivers of the world. Understanding the hydrologic significance of the regional litho-stratigraphy and structures help to better understand the hydrodynamics. This work is aimed at characterizing the Baro-Akobo-Sobbat sub-basin of Nile and determine trans-basin flows. Integrated method is used to characterize the basin and determine the Baro-Akobo-Sobbat sub-basin's relationship with African Mesozoic Rifts. Oil and water well drilling logs; aeromagnetic, gravity and vertical electrical sounding data; and various study reports are used to establish regional lithostratigraphic correlations and determine trans-regional hydrogeological connectivity. A total of 633 samples collected from wells, springs, rivers, lakes, swamps and rain water are analysed for their chemical, stable isotopes, tritium and radon properties. The Baro-Akobo river basin is commonly presumed to have good groundwater potential, particularly in its lowland plain. However, it has poor exploitable groundwater potential and recharge rate due to the extensive clay cover, limited retention capacity and the loss of the bulk of the groundwaters through regional geological structures to the deep seated continental sediments; presumably reaching the hydraulically connected African Mesozoic Rifts; mainly Melut and Muglad. The deep underground northward flows, along Nile River is, presumably, retarded by Central African Shear Zone in the Sudan.

Mammal assemblage of the agroecosystem constituents of the Várzea River Basin, Rio Grande do Sul, Brazil doi: 10.5007/2175-7925.2010v23n4p91

Directory of Open Access Journals (Sweden)

Felipe Bortolotto Peters

2010-01-01

Full Text Available We provide recent information on the richness of mammals along the agroecosystems of the Rio da Várzea Basin, Rio Grande do Sul, Brazil. We used different fi eld techniques to confi rm the occurrence of 46 mammal species in this area. Nine species are threatened in at least one of the three "red lists" at state, national and global levels. Adding the up-to-date results obtained in the fi eld to available data, mainly for conservation units, we present a richness of 85 species recorded for the basin. This number represents about 50% of mammals documented for Rio Grande do Sul state. The results suggest the importance of maintaining protected areas in altered regions, confi rming the relevance of inventories of local fauna as a fi rst approach to specifi c studies addressed to distribution, systematics, cytogenetics, physiology, population and community ecology.

Polyphased Inversions of an Intracontinental Rift: Case Study of the Marrakech High Atlas, Morocco

Science.gov (United States)

Leprêtre, R.; Missenard, Y.; Barbarand, J.; Gautheron, C.; Jouvie, I.; Saddiqi, O.

2018-03-01

The High and Middle Atlas intraplate belts in Morocco correspond to Mesozoic rifted basins inverted during the Cenozoic during Africa/Eurasia convergence. The Marrakech High Atlas lies at a key location between Atlantic and Tethyan influences during the Mesozoic rifting phase but represents today high reliefs. Age and style of deformation and the mechanisms underlying the Cenozoic inversion are nevertheless still debated. To solve this issue, we produced new low-temperature thermochronology data (fission track and [U-Th]/He on apatite). Two cross sections were investigated in the western and eastern Marrakech High Atlas. Results of inverse modeling allow recognizing five cooling events attributed to erosion since Early Jurassic. Apart from a first erosional event from Middle/Late Jurassic to Early Cretaceous, four stages can be related to the convergence processes between Africa and Europe since the Late Cretaceous. Our data and thermal modeling results suggest that the inversion processes are guided at first order by the fault network inherited from the rifting episodes. The sedimentary cover and the Neogene lithospheric thinning produced a significant thermal weakening that facilitated the inversion of this ancient rift. Our data show that the Marrakech High Atlas has been behaving as a giant pop-up since the beginning of Cenozoic inversion stages.

Meso and microscopic characterization of deformation bands in porous sandstones: an example on the Paleozoic, Pre- and Sin-rift sequences of the Araripe Basin, Northeast of Brazil; Caracterizacao meso e microscopica de bandas de deformacao em arenitos porosos: um exemplo nas tectonossequencias Paleozoica, Pre- e Sin-rifte da Bacia do Araripe, Nordeste do Brasil

Energy Technology Data Exchange (ETDEWEB)

Araujo Neto, Joao Marculino de; Silva, Fernando Cesar Alves da; Sa, Emanuel Ferraz Jardim de [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Programa de Pos-Graduacao em Geodinamica e Geofisica], e-mails: jota_ex2@hotmail.com, fernando@geologia.ufrn.br, emanuel@ccet.ufrn.br

2012-04-15

Deformation bands are narrow tabular volumes developed in porous sandstones. Although these structures are a product of brittle deformation, they may have internally a continuous displacement gradient. When granular cataclasis is the dominant deformation mechanism, the initial properties of their host rocks (i.e., porosity and permeability) can change significantly. The deformation bands in sandstones from the pre- and syn-rift of the Araripe Basin were studied in meso and microscale in order to classify them and to understand the deformation mechanisms involved during their nucleation and development. Their geometric-spatial, kinematic, and rheological criteria allowed establishing relations between the origin of deformation bands and lithification of their host rocks. Additionally, some inferences on their influence to the fluid flow in the reservoir-scale were outlined. Moreover, the study of deformation bands contributed to the understanding of the tectonic evolution of the studied basin. Accordingly, the study of deformation bands can support research on local and regional aspects of the tectonosedimentary evolution of sedimentary basins. (author)

Tectonic-stratigraphic evolution of Cumuruxatiba Basin - Brazil; Evolucao tectono-estratigrafica da Bacia de Cumuruxatiba

Energy Technology Data Exchange (ETDEWEB)

Lobato, Gustavo; Fernandes, Flavio L.; Silva, Eric Zagotto; Ferreira Neto, Walter Dias [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE). Lab. de Modelagem Multidisciplinar de Bacias Sedimentares; Ribeiro, Juliana [Agencia Nacional do Petroleo, Gas Natural e Biocombustiveis (ANP), Brasilia, DF (Brazil)

2008-07-01

In recent years, the exploratory interest on Cumuruxatiba Basin has been inconstant, with modest discoveries of oil. Aiming to deepen the geological knowledge of the basin and in order to attract the interest of oil companies, the ANP (National Agency of Petroleum, Natural Gas and Biofuels) signed contract with COPPE/UFRJ for carrying out an analysis basin project. The project was developed by the Basin Analysis Multidisciplinary Modeling Laboratory (Lab2M/UFRJ) in the period 2006/2007, and was with the main objective outline the main structural and seismo-stratigraphic features of the basin, and in an integrated and multidisciplinary way, build a model of its sedimentation and tectono-stratigraphic evolution. This paper presents the results of the regional seismic mapping, aided by well and potential methods data. The stratigraphic succession the basin has been divided into genetic units (UN-B, UN-C e UN-D) corresponding to second order depositional sequences, they are: UN-B, corresponding by a rift and sag-rift siliciclastic deposits, plus the Aptian evaporitic deposits; UN-C, characterized by carbonatic deposits, and shelf related sediments; and UN-D, corresponding by a final transgressive (siliciclastic) - regressive (mix) cycle, between Cenomanian and actual days. (author)

Crop intensification options and trade-offs with the water balance in the Central Rift Valley of Ethiopia

NARCIS (Netherlands)

Debas, Mezegebu

2016-01-01

The Central Rift Valley (CRV) of Ethiopia is a closed basin for which claims on land and water have strongly increased over the past decade resulting in over-exploitation of the resources. A clear symptom is the declining trend in the water level of the terminal Lake Abyata. The actual

Spatial analysis from remotely sensed observations of Congo basin of East African high Land to drain water using gravity for sustainable management of low laying Chad basin of Central Africa

OpenAIRE

B. Modu; B. Herbert

2014-01-01

The Chad basin which covers an area of about 2.4 million kilometer square is one of the largest drainage basins in Africa in the centre of Lake Chad .This basin was formed as a result of rifting and drifting episode, as such it has no outlet to the oceans or seas. It contains large area of desert from the north to the west. The basin covers in part seven countries such as Chad, Nigeria, Central African Republic, Cameroun, Niger, Sudan and Algeria. It is named Chad basin because 43.9%...

The evolution of shallow crustal structures in early rift-transform interaction: a case study in the northern Gulf of California.

Science.gov (United States)

Farangitakis, Georgios-Pavlos; van Hunen, Jeroen; Kalnins, Lara M.; Persaud, Patricia; McCaffrey, Kenneth J. W.

2017-04-01

The Gulf of California represents a young oblique rift/transtensional plate boundary in which all of the transform faults are actively shearing the crust, separated by active rift segments. Previous workers have shown that in the northern Gulf of California, the relative plate motion between the Pacific and North American plates is distributed between: a) the Cerro Prieto Fault (CPF) in the NE b) the Ballenas Transform Fault (BTF) in the SW and c) a pull-apart structure located between these two faults consisting of a number of extensional basins (the Wagner, Consag, and Upper and Lower Delfin basins). A plate boundary relocation at approximately 2 Ma, continued to separate Isla Angel de la Guarda from the Baja California peninsula and created the 200x70 km2 NE-SW pull-apart structure located northeast of the BTF. Here we use seismic stratigraphy analysis of the UL9905 high resolution reflection seismic dataset acquired by the Lamont-Doherty Earth Observatory, Caltech, and the Centro de Investigación Científica y de Educación Superior de Ensenada to build on previous structural interpretations and seek to further understand the processes that formed the structural and sedimentary architecture of the pull-apart basin in the northern Gulf of California. We examine the formation of depositional and deformation structures in relation to the regional tectonics to provide insight into the development of structural patterns and related seismic-stratigraphic features in young rift-transform interactions. Using bathymetric data, characteristic seismic-stratigraphic packages, and seismic evidence of faulting, we confirm the existence of three major structural domains in the northern Gulf of California and examine the interaction of the seismic stratigraphy and tectonic processes in each zone. The first and most distinctive is an abrupt NE-SW 28x5 km2 depression on the seabed of the Lower Delfin Basin. This is aligned orthogonally to the BTF, is situated at its northern

Thermal history of the Krishna-Godavari basin, India: Constraints from apatite fission track thermochronology and organic maturity data

Science.gov (United States)

Sahu, Himansu S.; Raab, Matthias J.; Kohn, Barry P.; Gleadow, Andrew J. W.; Bal, Kiron D.

2013-09-01

The Krishna-Godavari (KG) basin, a passive margin Late Carboniferous to Holocene basin along the rifted east coast of India, includes the deltaic and inter-deltaic regions of the Krishna and Godavari rivers onshore and extends into the offshore. It is one of India's premier hydrocarbon-bearing basins. In an attempt to better understand the thermal history of the basin, apatite fission track (AFT) data has been obtained from six exploration wells (five onshore and one offshore). AFT thermal history models as well as other thermal indicators e.g. vitrinite reflectance (VR), Rock-Eval Tmax data reveal that the host rocks are currently at their maximum post-depositional temperatures and that any possible heating related to small-scale tectonism or rifting episodes in the basin bears little significance on the maturation of the sediments. In the case of one borehole (M-1) however, the organic maturity data reveals a period of Oligocene cooling across an unconformity when ∼1000 m of section was eroded due to falling sea-level. This information offers the potential for improved basin modeling of the KG basin.

ODP Leg 210 Drills the Newfoundland Margin in the Newfoundland-Iberia Non-Volcanic Rift

Science.gov (United States)

Tucholke, B. E.; Sibuet, J.

2003-12-01

The final leg of the Ocean Drilling Project (Leg 210, July-September 2003) was devoted to studying the history of rifting and post-rift sedimentation in the Newfoundland-Iberia rift. For the first time, drilling was conducted in the Newfoundland Basin along a transect conjugate to previous drill sites on the Iberia margin (Legs 149 and 173) to obtain data on a complete `non-volcanic' rift system. The prime site during this leg (Site 1276) was drilled in the transition zone between known continental crust and known oceanic crust at chrons M3 and younger. Extensive geophysical work and deep-sea drilling have shown that this transition-zone crust on the conjugate Iberia margin is exhumed continental mantle that is strongly serpentinized in its upper part. Transition-zone crust on the Newfoundland side, however, is typically a kilometer or more shallower and has much smoother topography, and seismic refraction data suggest that the crust may be thin (about 4 km) oceanic crust. A major goal of Site 1276 was to investigate these differences by sampling basement and a strong, basinwide reflection (U) overlying basement. Site 1276 was cored from 800 to 1737 m below seafloor with excellent recovery (avg. 85%), bottoming in two alkaline diabase sills >10 m thick that are estimated to be 100-200 meters above basement. The sills have sedimentary contacts that show extensive hydrothermal metamorphism. Associated sediment structural features indicate that the sills were intruded at shallow levels within highly porous sediments. The upper sill likely is at the level of the U reflection, which correlates with lower Albian - uppermost Aptian(?) fine- to coarse-grained gravity-flow deposits. Overlying lower Albian to lower Oligocene sediments record paleoceanographic conditions similar to those on the Iberia margin and in the main North Atlantic basin, including deposition of `black shales'; however, they show an extensive component of gravity-flow deposits throughout.

CTUIR Grande Ronde River Watershed Restoration Program McCoy Creek/McIntyre Creek Road Crossing, 1995-1999 Progress Report.

Energy Technology Data Exchange (ETDEWEB)

Childs, Allen B.

2000-08-01

The Confederated Tribes of the Umatilla Indian Reservation (CTUIR) and Bonneville Power Administration (BPA) entered into a contract agreement beginning in 1996 to fund watershed restoration and enhancement actions and contribute to recovery of fish and wildlife resources and water quality in the Grande Ronde River Basin. The CTUIR's habitat program is closely coordinated with the Grande Ronde Model Watershed Program and multiple agencies and organizations within the basin. The CTUIR has focused during the past 4 years in the upper portions of the Grande Ronde Subbasin (upstream of LaGrande, Oregon) on several major project areas in the Meadow, McCoy, and McIntyre Creek watersheds and along the mainstem Grande Ronde River. This Annual Report provides an overview of individual projects and accomplishments.

Post-rift magmatism in the Pearl River Mouth Basin, northern South China Sea

Science.gov (United States)

Xu, H.; Zhao, F.; Xia, S.; Sun, J.; Fan, C.

2017-12-01

Multi-beam, 2D seismic reflection and borehole data reveal that post-rift magmatism are widespread in the northern margin of South China Sea. A large-scale volcanic complex was identified at water depths of 500 to 3000 m, covering an area of ca. 8000 km2. This volcanic complex includes seamounts, igneous sills, dykes and intruded volcanic bodies. Combining data from exploration wells BY7-1 and BY2 with published seismic stratigraphic data, we can highlight multiple extrusive events from the Early Oligocene to Early Miocene, reflecting progressive continental breakup in the South China Sea. Most intruded magma through the continental crust also uplifted sediments up to the T6 unconformity. Given the evidence in this work that Early Miocene magmatic bodies were developed above or along faults, we suggest that post-rift magmatism in the northern margin of the South China Sea was largely controlled by the faults. Reactivation events in the faults are suggested to have generated preferential vertical pathways for the ascent of magma within a context of progressive continental breakup and thinned continental crust, as the South China Sea was being formed.

Extension of the Parana Basin to offshore Brazil: Implications for coalbed methane evaluation

Energy Technology Data Exchange (ETDEWEB)

Holz, M.; Kalkreuth, W.; Rolim, S.B.A. [Universidade Federal do Rio Grande do Sul, Porto Alegre (Brazil)

2010-05-15

Coalbed methane (CBM) is a worldwide exploration target of the petroleum industry. In Brazil, the most important coal-bearing succession is associated with the Permian Rio Bonito Formation of the Parana Basin. The gas-prone areas are located at the southeastern margin of the Parana Basin and possibly in the offshore region of the northern part of the Pelotas Basin. Coalfields end abruptly at the present day shoreline, a result of rifting of Gondwana and the evolution of the South Atlantic Ocean. All geologic indicators suggest that in pre-rift times the coal seams extended further eastwards, probably now lying deeply buried below the sedimentary succession of the Pelotas Basin. The present paper discusses structural, stratigraphic, seismic and aeromagenetic data that support the preservation of continental crust beneath ocean sediment. If the coal beds had similar lateral extent to known onshore coals, and coal beds extended across the projected extension of the Parana basin, and there was a conservative 5 m of cumulative coal thickness, then a potential methane volume can be estimated for this newly inferred resource. Average onshore coal gas content is 32 scf/ton (1.00 m(3)/ton). If this is similar in the offshore coal deposits, then the hypothetical methane volume in the offshore area could be in excess of 1.9 x 10(12) scf (56 x 10(9) m(3)). Metamorphism from dikes associated with rifting are potential complicating factors in these deposits, and since no borehole reaching the deep-lying strata in the offshore area are available, this is a hypothetical gas resource with a certain level of uncertainty which should be tested in the future by drilling a deep borehole.

Data collection for cooperative water resources modeling in the Lower Rio Grande Basin, Fort Quitman to the Gulf of Mexico.

Energy Technology Data Exchange (ETDEWEB)

Passell, Howard David; Pallachula, Kiran (GRAM, Inc., Albuquerque, NM); Tidwell, Vincent Carroll; Villalobos, Joshua (Texas A& M University); Piccinni, Giovanni (Texas A& M University); Brainard, James Robert; Gerik, Thomas (Texas A& M University); Morrison, Wendy (Texas A& M University); Serrat-Capdevila, Aleix (University of Arizona); Valdes, Juan (University of Arizona); Sheng, Zhuping (Texas A& M University); Lovato, Rene (Instituto Mexicano de Tecnologia del Agua); Guitron, Alberto (Instituto Mexicano de Tecnologia del Agua); Ennis, Martha Lee; Aparicio, Javier (Instituto Mexicano de Tecnologia del Agua); Newman, Gretchen Carr (GRAM, Inc., Albuquerque, NM); Michelsen, Ari M. (Texas A& M University)

2004-10-01

Water resource scarcity around the world is driving the need for the development of simulation models that can assist in water resources management. Transboundary water resources are receiving special attention because of the potential for conflict over scarce shared water resources. The Rio Grande/Rio Bravo along the U.S./Mexican border is an example of a scarce, transboundary water resource over which conflict has already begun. The data collection and modeling effort described in this report aims at developing methods for international collaboration, data collection, data integration and modeling for simulating geographically large and diverse international watersheds, with a special focus on the Rio Grande/Rio Bravo. This report describes the basin, and the data collected. This data collection effort was spatially aggregated across five reaches consisting of Fort Quitman to Presidio, the Rio Conchos, Presidio to Amistad Dam, Amistad Dam to Falcon Dam, and Falcon Dam to the Gulf of Mexico. This report represents a nine-month effort made in FY04, during which time the model was not completed.

High resolution 2D numerical models from rift to break-up: Crustal hyper-extension, Margin asymmetry, Sequential faulting

Science.gov (United States)

Brune, Sascha; Heine, Christian; Pérez-Gussinyé, Marta; Sobolev, Stephan

2013-04-01

Numerical modelling is a powerful tool to integrate a multitude of geological and geophysical data while addressing fundamental questions of passive margin formation such as the occurrence of crustal hyper-extension, (a-)symmetries between conjugate margin pairs, and the sometimes significant structural differences between adjacent margin segments. This study utilises knowledge gathered from two key examples of non-magmatic, asymmetric, conjugate margin pairs, i.e. Iberia-New Foundland and Southern Africa-Brazil, where many published seismic lines provide solid knowledge on individual margin geometry. While both margins involve crustal hyper-extension, it is much more pronounced in the South Atlantic. We investigate the evolution of these two margin pairs by carefully constraining our models with detailed plate kinematic history, laboratory-based rheology, and melt fraction evaluation of mantle upwelling. Our experiments are consistent with observed fault patterns, crustal thickness, and basin stratigraphy. We conduct 2D thermomechanical rift models using the finite element code SLIM3D that operates with nonlinear stress- and temperature-dependent elasto-visco-plastic rheology, with parameters provided by laboratory experiments on major crustal and upper mantle rocks. In our models we also calculate the melt fraction within the upwelling asthenosphere, which allows us to control whether the model indeed corresponds to the non-magmatic margin type or not. Our modelling highlights two processes as fundamental for the formation of hyper-extension and margin asymmetry at non-magmatic margins: (1) Strain hardening in the rift center due to cooling of upwelling mantle material (2) The formation of a weak crustal domain adjacent to the rift center caused by localized viscous strain softening and heat transfer from the mantle. Simultaneous activity of both processes promotes lateral rift migration in a continuous way that generates a wide layer of hyper-extended crust on

Giant seismites and megablock uplift in the East African Rift: evidence for Late Pleistocene large magnitude earthquakes.

Science.gov (United States)

Hilbert-Wolf, Hannah Louise; Roberts, Eric M

2015-01-01

In lieu of comprehensive instrumental seismic monitoring, short historical records, and limited fault trench investigations for many seismically active areas, the sedimentary record provides important archives of seismicity in the form of preserved horizons of soft-sediment deformation features, termed seismites. Here we report on extensive seismites in the Late Quaternary-Recent (≤ ~ 28,000 years BP) alluvial and lacustrine strata of the Rukwa Rift Basin, a segment of the Western Branch of the East African Rift System. We document examples of the most highly deformed sediments in shallow, subsurface strata close to the regional capital of Mbeya, Tanzania. This includes a remarkable, clastic 'megablock complex' that preserves remobilized sediment below vertically displaced blocks of intact strata (megablocks), some in excess of 20 m-wide. Documentation of these seismites expands the database of seismogenic sedimentary structures, and attests to large magnitude, Late Pleistocene-Recent earthquakes along the Western Branch of the East African Rift System. Understanding how seismicity deforms near-surface sediments is critical for predicting and preparing for modern seismic hazards, especially along the East African Rift and other tectonically active, developing regions.

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

Science.gov (United States)

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

2013-05-01

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

The response of deltaic systems to climatic and hydrological changes in Daihai Lake rift basin, Inner Mongolia, northern China

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Yu Xinghe

2013-01-01

Full Text Available Delta systems are ubiquitous around lacustrine rift basins. Its peripheral geometry, progradation structures and sedimentary successions were controlled by both tectonic settings and climatic changes. Peripheral geometry of a delta was strongly influenced by depositional gradients which formed the fan-shape delta on the steep slopes and developed the lobe-shape delta on the gentle slopes. Due to the discharge feed rivers can change rapidly driven by climatic variations, and the nearshore area of deltas display considerable facies variability. The rise of annual rainfall, which suggests the rivers feeding deltas are continuous, and result in distributary mouth bars that are prevalent in the front of deltas since the down-slope flows are greater than the along-slope currents. On the contrary, when the annual rainfall decreases and evaporation increases, the rivers only can feed deltas ephemerally. If the along-slope currents were in a dominant position, the distal bars were deposited. Progradation structure and sedimentary successions of deltas were controlled by the gradients of slopes. On gentle depositional slopes, shingle foreset beds predominate with fine sediments and small-scale sedimentary structures or vice versa.

Tectonic implications of Mesozoic magmatism to initiation of Cenozoic basin development within the passive South China Sea margin

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Mai, Hue Anh; Chan, Yu Lu; Yeh, Meng Wan; Lee, Tung Yi

2018-04-01

The South China Sea (SCS) is one of the classical example of a non-volcanic passive margin situated within three tectonic plates of the Eurasian, Indo-Australian and Philippine Sea plate. The development of SCS resulted from interaction of various types of plate boundaries, and complex tectonic assemblage of micro blocks and accretionary prisms. Numerous models were proposed for the formation of SCS, yet none can fully satisfy different aspects of tectonic forces. Temporal and geographical reconstruction of Cretaceous and Cenozoic magmatism with the isochrones of major basins was conducted. Our reconstruction indicated the SE margin of Asia had gone through two crustal thinning events. The sites for rifting development are controlled by localized thermal weakening of magmatism. NW-SE extension setting during Late Cretaceous revealed by magmatism distribution and sedimentary basins allow us to allocate the retreated subduction of Pacific plate to the cause of first crustal thinning event. A magmatic gap between 75 and 65 Ma prior to the initiation of first basin rifting suggested a significant modification of geodynamic setting occurred. The Tainan basin, Pearl River Mouth basin, and Liyue basins started to develop since 65 Ma where the youngest Late Cretaceous magmatism concentrated. Sporadic bimodal volcanism between 65 and 40 Ma indicates further continental extension prior to the opening of SCS. The E-W extension of Malay basin and West Natuna began since late Eocene followed by N-S rifting of SCS as Neotethys subducted. The SCS ridge developed between Pearl River Mouth basin and Liyue basin where 40 Ma volcanic activities concentrated. The interaction of two continental stretching events by Pacific followed by Neotethys subduction with localized magmatic thermal weakening is the cause for the non-volcanic nature of SCS.

Panel - Rio Grande restoration: Future directions

Science.gov (United States)

Deborah M. Finch; Pete V. Domenici; Jeffrey. C. Whitney; Steve Harris; Brian Shields; Clifford S. Crawford

1996-01-01

The purpose of this panel was to discuss historical and current changes to the Rio Grande system, focusing on the middle Basin, and to present and review different individual, organizational, and political perspectives on the future of the system. Invitations were made to panelists based on their past and current interests and activities pertaining to restoration of...

Extensional basin evolution in the presence of small-scale convection

DEFF Research Database (Denmark)

Petersen, Kenni Dinesen; Nielsen, S.B.; Clausen, O.R.

2011-01-01

-steady-state. Extension of the convecting equilibrium model causes the formation of rifts or continental margins which, posterior to extension, cools and subsides as predicted by the plate model. However, in contrast to the plate model, the ascended asthenosphere is not instantaneously decoupled from the convecting upper...... mantle below, and cooling is thus not entirely conductive above the former base of the lithosphere. This causes significantly protracted cooling and subsidence.We show that our model features improved consistency with subsidence data from several rifted margins and intracontinental basins. Furthermore...

Magmatic and non-magmatic history of the Tyrrhenain backarc Basin: new constraints from geophysical and geological data

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Prada, Manel; Sallares, Valenti; Ranero, Cesar R.; Zitellini, Nevio; Grevemeyer, Ingo

2016-04-01

The Western Mediterranean region is represented by a system of backarc basins associated to slab rollback and retreat of subduction fronts. The onset of formation of these basins took place in the Oligocene with the opening of the Valencia Through, the Liguro-Provençal and the Algero-Balearic basins, and subsequently, by the formation of the Alboran and Tyrrhenian basins during the early Tortonian. The opening of these basins involved rifting that in some regions evolved until continental break up, that is the case of the Liguro-Provençal, Algero-Balearic, and Tyrrhenian basins. Previous geophysical works in the first two basins revealed a rifted continental crust that transitions to oceanic crust along a region where the basement nature is not clearly defined. In contrast, in the Tyrrhenian Basin, recent analysis of new geophysical and geological data shows a rifted continental crust that transitions along a magmatic-type crust to a region where the mantle is exhumed and locally intruded by basalts. This basement configuration is at odds with current knowledge of rift systems and implies rapid variations of strain and magma production. To understand these processes and their implications on lithospheric backarc extension we first need to constrain in space and time these observations by further analysis of geophysical and geological data. Here we present two analyses; the first one is focused on the spatial variability of magmatism along the Cornaglia Terrace axis, where magmatic-type crust has been previously interpreted. The comparison of three different seismic refraction transects, acquired across the basin axis from North to South, allows to infer that the highest magmatic activity occurred beneath the central and most extended region of the terrace; while it was less important in the North and almost non-existent in the South. The second analysis focuses on the presence of exhumed mantle in the deepest region of the Tyrrhenian, previously interpreted by

Strike-slip tectonics during rift linkage

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Pagli, C.; Yun, S. H.; Ebinger, C.; Keir, D.; Wang, H.

2017-12-01

The kinematics of triple junction linkage and the initiation of transforms in magmatic rifts remain debated. Strain patterns from the Afar triple junction provide tests of current models of how rifts grow to link in area of incipient oceanic spreading. Here we present a combined analysis of seismicity, InSAR and GPS derived strain rate maps to reveal that the plate boundary deformation in Afar is accommodated primarily by extensional tectonics in the Red Sea and Gulf of Aden rifts, and does not require large rotations about vertical axes (bookshelf faulting). Additionally, models of stress changes and seismicity induced by recent dykes in one sector of the Afar triple junction provide poor fit to the observed strike-slip earthquakes. Instead we explain these patterns as rift-perpendicular shearing at the tips of spreading rifts where extensional strains terminate against less stretched lithosphere. Our results demonstrate that rift-perpendicular strike-slip faulting between rift segments achieves plate boundary linkage during incipient seafloor spreading.

Continentward-dipping detachment fault system and asymmetric rift structure of the Baiyun Sag, northern South China Sea

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Zhou, Zhichao; Mei, Lianfu; Liu, Jun; Zheng, Jinyun; Chen, Liang; Hao, Shihao

2018-02-01

The rift architecture and deep crustal structure of the distal margin at the mid-northern margin of the South China Sea have been previously investigated by using deep seismic reflection profiles. However, one fundamental recurring problem in the debate is the extensional fault system and rift structure of the hyperextended rift basins (Baiyun Sag and Liwan Sag) within the distal margin because of the limited amount of seismic data. Based on new 3D seismic survey data and 2D seismic reflection profiles, we observe an array of fault blocks in the Baiyun Sag, which were tilted towards the ocean by extensional faulting. The extensional faults consistently dip towards the continent. Beneath the tilted fault blocks and extensional faults, a low-angle, high-amplitude and continuous reflection has been interpreted as the master detachment surface that controls the extension process. During rifting, the continentward-dipping normal faults evolved in a sequence from south to north, generating the asymmetric rift structure of the Baiyun Sag. The Baiyun Sag is separated from the oceanic domain by a series of structural highs that were uplifted by magmatic activity in response to the continental breakup at 33 Ma and a ridge jump to the south at 26-24 Ma. Therefore, we propose that magmatism played a significant role in the continental extension and final breakup in the South China Sea.

The regional structure of the Red Sea Rift revised

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Augustin, Nico; van der Zwan, Froukje M.; Devey, Colin W.; Brandsdóttir, Bryndís

2017-04-01

The Red Sea Rift has, for decades, been considered a text book example of how young ocean basins form and mature. Nevertheless, most studies of submarine processes in the Red Sea were previously based on sparse data (mostly obtained between the late 1960's and 1980's) collected at very low resolution. This low resolution, combined with large gaps between individual datasets, required large interpolations when developing geological models. Thus, these models generally considered the Red Sea Rift a special case of young ocean basement formation, dividing it from North to South into three zones: a continental thinning zone, a "transition zone" and a fully developed spreading zone. All these zones are imagined, in most of the models, to be separated by large transform faults, potentially starting and ending on the African and Arabian continental shields. However, no consensus between models e.g. about the locations (or even the existence) of major faults, the nature of the transition zone or the extent of oceanic crust in the Red Sea Rift has been reached. Recently, high resolution bathymetry revealed detailed seafloor morphology as never seen before from the Red Sea, very comparable to other (ultra)slow spreading mid-ocean ridges such as the Gakkel Ridge, the Mid-Atlantic Ridge and SW-Indian Ridge, changing the overall picture of the Red Sea significantly. New discoveries about the extent, movement and physical properties of submarine salt deposits led to the Red Sea Rift being linked to the young Aptian-age South Atlantic. Extensive crosscutting transform faults are not evident in the modern bathymetry data, neither in teleseismic nor vertical gravity gradient data and comparisons to Gakkel Ridge and the SW-Indian Ridge suggest that the Red Sea is much simpler in terms of structural geology than was previously thought. Complicated tectonic models do not appear necessary and there appears to be large areas of oceanic crust under the Red Sea salt blankets. Based on

Role of Transtension in Rifting at the Pacific-North America Plate Boundary

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Stock, J. M.

2011-12-01

Transtensional plate motion can be accommodated either in a localized zone of transtensional rifting or over a broader region. Broader zones of deformation can be classified either as diffuse deformation or strain partitioning (one or more major strike-slip shear zones geographically offset from a region of a extensional faulting). The Pacific-North America plate boundary in southwestern North America was transtensional during much of its history and has exhibited the full range of these behaviors at different spatial scales and in different locations, as recorded by fault motions and paleomagnetic rotations. Here we focus on the northern Gulf of California part of the plate boundary (Upper and Lower Delfin basin segments), which has been in a zone of transtensional Pacific-North America plate boundary motion ever since the middle Miocene demise of adjacent Farallon-derived microplates. Prior to the middle Miocene, during the time of microplate activity, this sector of North America experienced basin-and-range normal faults (core complexes) in Sonora. However there is no evidence of continued extensional faulting nor of a Gulf-related topographic depression until after ca 12 Ma when a major ignimbrite (Tuff of San Felipe/ Ignimbrite of Hermosillo) was deposited across the entire region of the future Gulf of California rift in this sector. After 12 Ma, faults disrupted this marker bed in eastern Baja California and western Sonora, and some major NNW-striking right-lateral faults are inferred to have developed near the Sonoran coast causing offset of some of the volcanic facies. However, there are major tectonic rotations of the volcanic rocks in NE Baja California between 12 and 6 Ma, suggesting that the plate boundary motion was still occurring over a broad region. By contrast, after about 6 Ma, diminished rotations in latest Miocene and Pliocene volcanic rocks, as well as fault slip histories, show that plate boundary deformation became localized to a narrower

Extension parallel to the rift zone during segmented fault growth: application to the evolution of the NE Atlantic

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A. Bubeck

2017-11-01

Full Text Available The mechanical interaction of propagating normal faults is known to influence the linkage geometry of first-order faults, and the development of second-order faults and fractures, which transfer displacement within relay zones. Here we use natural examples of growth faults from two active volcanic rift zones (Koa`e, island of Hawai`i, and Krafla, northern Iceland to illustrate the importance of horizontal-plane extension (heave gradients, and associated vertical axis rotations, in evolving continental rift systems. Second-order extension and extensional-shear faults within the relay zones variably resolve components of regional extension, and components of extension and/or shortening parallel to the rift zone, to accommodate the inherently three-dimensional (3-D strains associated with relay zone development and rotation. Such a configuration involves volume increase, which is accommodated at the surface by open fractures; in the subsurface this may be accommodated by veins or dikes oriented obliquely and normal to the rift axis. To consider the scalability of the effects of relay zone rotations, we compare the geometry and kinematics of fault and fracture sets in the Koa`e and Krafla rift zones with data from exhumed contemporaneous fault and dike systems developed within a > 5×104 km2 relay system that developed during formation of the NE Atlantic margins. Based on the findings presented here we propose a new conceptual model for the evolution of segmented continental rift basins on the NE Atlantic margins.

Development of Semi-distributed ecohydrological model in the Rio Grande De Manati River Basin, Puerto Rico

Science.gov (United States)

Setegn, S. G.; Ortiz, J.; Melendez, J.; Barreto, M.; Torres-Perez, J. L.; Guild, L. S.

2015-12-01

There are limited studies in Puerto Rico that shows the water resources availability and variability with respect to changing climates and land use. The main goal of the HICE-PR (Human Impacts to Coastal Ecosystems in Puerto Rico (HICE-PR): the Río Loco Watershed (southwest coast PR) project which was funded by NASA is to evaluate the impacts of land use/land cover changes on the quality and extent of coastal and marine ecosystems (CMEs) in two priority watersheds in Puerto Rico (Manatí and Guánica).The main objective of this study is to set up a physically based spatially distributed hydrological model, Soil and Water Assessment Tool (SWAT) for the analysis of hydrological processes in the Rio Grande de Manati river basin. SWAT (soil and water assessment tool) is a spatially distributed watershed model developed to predict the impact of land management practices on water, sediment and agricultural chemical yields in large complex watersheds. For efficient use of distributed models for hydrological and scenario analysis, it is important that these models pass through a careful calibration and uncertainty analysis. The model was calibrated and validated using Sequential Uncertainty Fitting (SUFI-2) calibration and uncertainty analysis algorithms. The model evaluation statistics for streamflows prediction shows that there is a good agreement between the measured and simulated flows that was verified by coefficients of determination and Nash Sutcliffe efficiency greater than 0.5. Keywords: Hydrological Modeling; SWAT; SUFI-2; Rio Grande De Manati; Puerto Rico

Young rift kinematics in the Tadjoura rift, western Gulf of Aden, Republic of Djibouti

Science.gov (United States)

Daoud, Mohamed A.; Le Gall, Bernard; Maury, René C.; Rolet, JoëL.; Huchon, Philippe; Guillou, Hervé

2011-02-01

The Tadjoura rift forms the westernmost edge of the westerly propagating Sheba ridge, between Arabia and Somalia, as it enters into the Afar depression. From structural and remote sensing data sets, the Tadjoura rift is interpreted as an asymmetrical south facing half-graben, about 40 km wide, dominated by a large boundary fault zone to the north. It is partially filled up by the 1-3 Myr old Gulf Basalts which onlapped the older Somali Basalts along its shallower southern flexural margin. The major and trace element analysis of 78 young onshore lavas allows us to distinguish and map four distinct basaltic types, namely the Gulf, Somali, Goumarre, and Hayyabley Basalts. These results, together with radiometric age data, lead us to propose a revised volcano-stratigraphic sketch of the two exposed Tadjoura rift margins and to discriminate and date several distinct fault networks of this oblique rift. Morphological and statistical analyses of onshore extensional fault populations show marked changes in structural styles along-strike, in a direction parallel to the rift axis. These major fault disturbances are assigned to the arrest of axial fault tip propagation against preexisting discontinuities in the NS-oriented Arta transverse zone. According to our model, the sinistral jump of rifting into the Asal-Ghoubbet rift segment results from structural inheritance, in contrast with the en échelon or transform mechanism of propagation that prevailed along the entire length of the Gulf of Aden extensional system.

Contrasted continental rifting via plume-craton interaction: Applications to Central East African Rift

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Alexander Koptev

2016-03-01

Full Text Available The East African Rift system (EARS provides a unique system with the juxtaposition of two contrasting yet simultaneously formed rift branches, the eastern, magma-rich, and the western, magma-poor, on either sides of the old thick Tanzanian craton embedded in a younger lithosphere. Data on the pre-rift, syn-rift and post-rift far-field volcanic and tectonic activity show that the EARS formed in the context of the interaction between a deep mantle plume and a horizontally and vertically heterogeneous lithosphere under far-field tectonic extension. We bring quantitative insights into this evolution by implementing high-resolution 3D thermo-mechanical numerical deformation models of a lithosphere of realistic rheology. The models focus on the central part of the EARS. We explore scenarios of plume-lithosphere interaction with plumes of various size and initial position rising beneath a tectonically pre-stretched lithosphere. We test the impact of the inherited rheological discontinuities (suture zones along the craton borders, of the rheological structure, of lithosphere plate thickness variations, and of physical and mechanical contrasts between the craton and the embedding lithosphere. Our experiments indicate that the ascending plume material is deflected by the cratonic keel and preferentially channeled along one of its sides, leading to the formation of a large rift zone along the eastern side of the craton, with significant magmatic activity and substantial melt amount derived from the mantle plume material. We show that the observed asymmetry of the central EARS, with coeval amagmatic (western and magmatic (eastern branches, can be explained by the splitting of warm material rising from a broad plume head whose initial position is slightly shifted to the eastern side of the craton. In that case, neither a mechanical weakness of the contact between the craton and the embedding lithosphere nor the presence of second plume are required to

Cyclicity recorded in the provenance sandstones in the sedimentary in fill of the Cameros basin (N. Spain)

Energy Technology Data Exchange (ETDEWEB)

Gonzalez-Acebron, L.; Arribas, J.; Omodeo-Sale, S.; Arribas, E.; Le Pera, E.; Mas, R.; Lopez-Elorza, M.; Fernandez-Diaz, P. R.

2013-06-01

The intra plate Cameros rift basin in the north of Spain was formed came into being between the Tithonian and the Early Albian and contains 9 000 m of mostly continental sediments. This basin is a good example of cyclicity of different depositional sequences (DSs) in sedimentary environments, which show clear repetition in their sandstone composition (petrofacies) and diagenetic patterns. The DSs are arranged in two mega sequences (MSs) separated by a tectonic unconformity. A similar vertical sandstone compositional evolution, subdivided into two stages that repeat cyclically, has been recognised in both MSs: the first comprises quartzo-sedimentolithic petrofacies and the second is made up of several quartzo-feldspathic petrofacies. This was caused by a progression from the recycling of the pre-rift sedimentary cover to the erosion of the mainly plutonic and metamorphic crystalline basement. These changes in the erosion of the different source areas were conditioned by the tectonics of the basin. Furthermore, the original sandstone framework composition conditioned the diagenetic pattern of the two stages: quartzo-sedimentolithic sandstones containing large amounts of very pervasive carbonate cement that reduce their original porosity considerably, and quartzo-feldspathic petrofacies with a rigid framework that maintained the original pores during burial diagenesis. This compositional and diagenetic pattern is probably applicable to other non-volcanic rifted basins, depending upon the original amount of carbonate rock fragments present. (Author)

SYN-RIFT SANDSTONЕS: THE FEATURES OF BULK CHEMICAL COMPOSITIONS, AND POSITIONS ON PALEOGEODYNAMIC DISCRIMINANT DIAGRAMS

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A. V. Maslov

2018-01-01

Full Text Available From the early 1980s, the data on the bulk chemical composition of sandstones and mudstones are actively involved for interpretation of the paleogeodynamic settings for sedimentary sequences. Discriminant diagrams such as K2O/Na2O–SiO2/Al2O3 [Maynard et al., 1982], (Fe2O3*+MgO–K2O/Na2O and others [Bhatia, 1983], SiO2–K2O/Na2O [Roser, Korsch, 1986], (K2O+Na2O–SiO2/20–(TiO2+Fe2O3+MgO [Kroonenberg, 1994] etc., are now widely used in regional investigations to classify terrigenous rocks from several paleogeodynamic settings (passive and active continental margins, oceanic and continental volcanic arcs etc. with a certain ‘percentage of consistency’. The first diagrams DF1–DF2 for syn-rift compositions were published in the early 2010s [Verma, Armstrong-Altrin, 2013]. This article analyzes the bulk chemical compositions of syn-rift sandstones from intracratonic rifts and rifts formed during the break-up of the Columbia and Gondwana supercontinents, rifts within volcanic arcs and related to the collapse of collision orogens (for example, Permian sandstones of the Malužiná formation, Western Carpathians, Slovakia. Our database includes the Neoproterozoic Uinta Mountain Group (USA, the Cretaceous Omdurman formation of the Khartoum Basin (Sudan, the siliciclastic deposits of the Kalahari Basin (East African rift zone, the sandstones of the Vindhyan Supergroup (India, the Neoproterozoic Ui Group of the Uchur-Maya region (Southeast Siberia, the Meso-Neoproterozoic Banxi Group (Southern China, the Mesoproterozoic Belt-Purcell Supergroup (USA, the Oronto and Bayfield Groups of the Midcontinent (USA, as well as the sandstones of the Upper Precambrian Ai and Mashak formations, and the metasedimentary rocks of the Arsha Group (Southern Urals. The article examines: (1 the position of the syn-rift sandstone compositions (fields on the log(SiO2/Al2O3–log(Na2O/K2O classification diagram and the F1–F2 diagram, which gives the possible

Space-based monitoring of land-use/land-cover in the Upper Rio Grande Basin: An opportunity for understanding urbanization trends in a water-scarce transboundary river basin.

Science.gov (United States)

Mubako, S. T.; Hargrove, W. L.; Heyman, J. M.; Reyes, C. S.

2016-12-01

Urbanization is an area of growing interest in assessing the impact of human activities on water resources in arid regions. Remote sensing techniques provide an opportunity to analyze land cover change over time, and are useful in monitoring areas undergoing rapid urban growth. This case study for the water-scarce Upper Rio Grande River Basin uses a supervised classification algorithm to quantify the rate and evaluate the pattern of urban sprawl. A focus is made on the fast growing El-Paso-Juarez metropolitan area on the US-Mexico border and the City of Las Cruces in New Mexico, areas where environmental challenges and loss of agricultural and native land to urban development are major concerns. Preliminary results show that the land cover is dominantly native with some significant agriculture along the Rio Grande River valley. Urban development across the whole study area expanded from just under 3 percent in 1990, to more than 11 percent in 2015. The urban expansion is occurring mainly around the major urban areas of El Paso, Ciudad Juarez, and Las Cruces, although there is visible growth of smaller urban settlements scattered along the Rio Grande River valley during the same analysis period. The proportion of native land cover fluctuates slightly depending on how much land is under crops each analysis year, but there is a decreasing agricultural land cover trend suggesting that land from this sector is being lost to urban development. This analysis can be useful in planning to protect the environment, preparing for growth in infrastructure such as schools, increased traffic demands, and monitoring availability of resources such as groundwater as the urban population grows.

Which Fault Orientations Occur during Oblique Rifting? Combining Analog and Numerical 3d Models with Observations from the Gulf of Aden

Science.gov (United States)

Autin, J.; Brune, S.

2013-12-01

-orthogonal faults. The fault pattern agrees very well with the analog and numerical model results, except for the displacement-orthogonal fault orientation of the initial rift stage. This orientation, however, coincides with the trend of inherited Mesozoic basins indicating the overprinting influence of structural inheritance.

Trap architecture of the Early Cretaceous Sarir Sandstone in the eastern Sirt Basin, Libya

Energy Technology Data Exchange (ETDEWEB)

Gras, R. [Schlumberger GeoQuest, Cedex (France); Thusu, B. [Arabian Gulf Oil Company, Benghazi (Libyan Arab Jamahiriya)

1998-12-31

The Sarir Sandstone is the principal reservoir for oil accumulations in the eastern Sirt Basin in Libya. The main phase of the rifting in this area took place in the Late Jurassic-Early Cretaceous, during which time the Sarir Sandstone was deposited as a non-marine, intra-continental clastic syn-rift sequence. Although successfully explored from 1959 onwards, the prolific eastern Sirt Basin is in a relatively immature stage of exploration regarding wildcat drilling and 3D seismic data acquisition. The most recent phase of exploration, utilizing 3D seismic techniques, revealed a complex structural development. The trap geometries are often related to E-W trending, basement-controlled fault systems, oblique to the NNW-SSE Sirt Basin trend. The fault systems were active during the Sarir Sandstone deposition, giving rise to structural as well as combined structural-traps. An increased understanding of trap architecture has led to both re-evaluation of older fields and new discoveries. (author)

Structuring of The Jurassic Basin of Chott in Gabes region (Southern Tunisia) associated to the Liassic rifting from geophysical and well data

Science.gov (United States)

Hassine, Mouna; Abbes, Chedly; Azaiez, Hajer; Gabtni, Hakim; Bouzid, Wajih

2016-04-01

The graben system of El Hamma, west of Gabes in Tunisia, corresponds to a pull apart basin developed in an extensive relay zone between two principal shear corridors (PSC) with a dextral sliding of N110-120 average direction. These PSC corresponds to two segments of the south-Atlasic shear corridor of NW-SE direction, which extends from Chott El Hodna in Algeria, to the NW, to the Libyan Djeferra to the SE (M.Hassine and al., 2015; M.Hassine and al., work in progress). This work aims to define the basin structuring during the Jurassic, especially from the Upper Lias during the Liassic rifting. For this, we performed seismic, gravity and well data analysis. Several wells situated in this basin and on its edges, which totally or partly crossed the Jurassic series which were described by several authors (J. Bonnefous, 1972 ; M. Soussi, 2002, 2004). These series corresponds to the Nara formation (PF Burollet, 1956) elevated to a group rank by M. Soussi (2003). It consists of two carbonate units separated by a marl-carbonate and sandstone member, dated successively of lower Lias (Hettangian- lower Pliensbachian.), Toarcian to Callovian and Upper Callovian-Tithonian. The correlation of this Jurassic formations along a North-South transect shows, from the South to the North, a significant variation in facies and thickness of the Jurassic series especially from the Upper Lias. Two resistant moles appears to the Northern and Southern edges of the pull-apart basin of El Hamma. The trend reversal of the lateral evolution of this series take place on the border NW-SE faults of the basin (PSC). The analysis of several seismic lines calibrated to well data, reveals a differentiated structuring inside the pull-apart basin itself, associated on the one hand, to the play of the N160 and N130-140 direction fault network which structure the basin in horsts and grabens of second order ( M. Hassine and al., 2015); and on the other hand, to the rise of the upper Triassic evaporates

Stochastic velocity inversion of seismic reflection/refraction traveltime data for rift structure of the southwest Barents Sea

DEFF Research Database (Denmark)

Clark, Stephen A.; Faleide, Jan Inge; Hauser, Juerg

2013-01-01

reflection profiles. We utilize layer-based raytracing in a Markov Chain Monte Carlo (MCMC) inversion to determine a probabilistic velocity model constraining the sedimentary rocks, crystalline crust, and uppermost mantle in a complex tectonic regime. The profile images a wide range of crustal types and ages...... with the amount of overlap derived from published plate reconstructions. Local β factors approach 3, where Bjørnøya Basin reaches a depth of more than 13 km. Volcanics, carbonates, salt, diagenesis and metamorphism make deep sedimentary basin fill difficult to distinguish from original, pre-rift crystalline crust...

Burial and thermal history simulation of the Abu Rudeis-Sidri oil field, Gulf of Suez-Egypt: A 1D basin modeling study

Science.gov (United States)

Awadalla, Ahmed; Hegab, Omar A.; Ahmed, Mohammed A.; Hassan, Saad

2018-02-01

An integrated 1D model on seven wells has been performed to simulate the multi-tectonic phases and multiple thermal regimes in the Abu Rudeis-Sidri oilfield. Concordance between measured and calculated present-day temperatures is achieved with present-day heat flows in the range of 42-55 mW/m2. Reconstruction of the thermal and burial histories provides information on the paleotemperature profiles, the timing of thermal activation as well as the effect of the Oligo-Miocene rifting phases and its associated magmatic activity. The burial histories show the pre-rift subsidence was progressive but modest, whereas the syn-rift was more rapid (contemporaneous with the main rifting phases and basin formation). Finally, the early post-rift thermal subsidence was slow to moderate in contrast to the late post-rift thermal subsidence which was moderate to rapid. The simulated paleo heat flow illustrates a steady state for the pre-rift phase and non-steady state (transient) for syn-rift and postrift phases. Three geothermal regimes are recognized, each of which is associated with a specific geological domain. 1) A lower geothermal regime reflects the impact of stable tectonics (pre-rift). 2) The higher temperature distribution reflects the syn-rift high depositional rate as well as the impact of stretching and thinning (rifting phases) of the lithosphere. 3) A local higher geothermal pulse owing to the magmatic activity during the Oligo-Miocene time (ARM-1 and Sidri-7 wells). Paleoheat flow values of 100mW/m2 (Oligo-Miocene rifting phase) increased to 120mW/m2 (Miocene rifting phase) and lesser magnitude of 80mW/m2 (Mio- Pliocene reactivation phase) have been specified. These affected the thermal regime and temperature distribution by causing perturbations in subsurface temperatures. A decline in the background value of 60mW/m2 owing to conductive cooling has been assigned. The blanketing effect caused by low thermal conductivity of the basin-fill sediments has been simulated

Rift Structure in Eastern Papua New Guinea From the Joint Inversion of Receiver Functions and Seismic Noise

Science.gov (United States)

Abers, G. A.; Obrebski, M. J.; Jin, G.; Eilon, Z.

2014-12-01

The recent CDPapua seismic array in the active D'Entrecasteaux-Woodlark Rift provides insights into how continental crust accommodates large extension. Here, >100 km of extension has occurred in the last 4-6 Ma, exhuming rocks from 100 km depth. To better understand the modes of deformation of the crust, we analyze shear wave velocity (Vs) distribution for a set of temporary land and ocean bottom broadband stations. We resolve the depth of the main velocity contrasts using receiver function (RF) analysis, alleviating the intrinsic trade-off between depth and velocity intrinsic by joint inversion with dispersion constraints (10 - 100 s) from earthquake surface waves and ambient noise. A transdimensional Bayesian scheme explores the model space (Vs in each layer, number of interfaces and their respective depths), minimizing the number of layers required to fit the observations given their noise level. Preliminary results suggest that the Moho is sharp in most places, with a depth of 28-38 km and 20-27 km below the Papuan Peninsula and the highly-extended D'Entracasteaux Islands, respectively. The mid-lower crust of these regions appears to be similar and consistent with felsic compositions, 3.25≤Vs≤3.5 km/s, and may represent the Owen-Stanley Metamorphic Belt or underlying continental rocks. A fast layer (3.75≤Vs≤4 km/s) is observed below the Papuan Peninsula in the 20-30 km depth range and may indicate more mafic lower crust. In contrast, faster velocities between 10 and 20km depth are modeled below the Goodenough Basin (3.75≤Vs≤4 km/s) and the Trobriand Basin (3.5≤Vs≤3.75 km/s) where rocks of the Papuan Ultramafic Belt have been suggested, although these results partly depend upon complicated signals from ocean-bottom seismometers. Well-located seismicity shows that active fault systems generally follow the boundaries between regions of different crustal velocity structure. Overall these results confirm a continental velocity structure for the

Along-axis crustal structure of the Porcupine Basin from seismic refraction data modelling

Science.gov (United States)

Prada, Manel; Watremez, Louise; Chen, Chen; O'Reilly, Brian; Minshull, Tim; Reston, Tim; Wagner, Gerlind; Gaws, Viola; Klaschen, Dirk; Shannon, Patrick

2016-04-01

The Porcupine Basin is a tongue-shaped offshore basin SW of Ireland that formed during the opening of the North Atlantic Ocean. Its history of development involved several rifting and subsidence phases during the Late Paleozoic and Cenozoic, with a particular major rift phase occurring in Late Jurassic-Early Cretaceous times. Previous work, focused on subsidence analysis, showed that stretching factors (β) in the northern part of the basin are 6. However, recent studies based on seismic reflection and refraction profiles concluded that β in places along the basin axis were significantly higher, and suggested the presence of major crustal faulting and uppermost mantle serpentinization in the basin. Constraining β and the processes related to the formation of the basin will provide insights into aspects such as the tectonic response to lithospheric extension and the thermal evolution of the basin. Here we present the tomography results of five wide-angle seismic (WAS) profiles acquired across and along the basin axis. We used a travel time inversion method to model the WAS data and obtain P-wave velocity (Vp) models of the crust and uppermost mantle, together with the geometry of the main geological interfaces along each of these lines. Coincident seismic reflection profiles to each WAS line were also used to integrate the tectonic structure with the Vp model. These results improved constrains on the location of the base of the crust and allow to estimate maximum β (βmax) along each profile. The analysis shows that βmax values in the northern part of the basin are 5-6 times larger than estimates based on subsidence analysis. Towards the south, βmax increases up to 10, but then rapidly decreases to 3.3 southwards. These values are well within the range of crustal extension at which the crust becomes entirely brittle at magma-poor margins allowing the formation of major crustal faulting and serpentinization of the mantle. In agreement with this observation, Vp

Probabilistic Water Availability Prediction in the Rio Grande Basin using Large-scale Circulation Indices as Precursor

Science.gov (United States)

Khedun, C. P.; Mishra, A. K.; Giardino, J. R.; Singh, V. P.

2011-12-01

Hydrometeorological conditions, and therefore water availability, is affected by large-scale circulation indices. In the Rio Grande, which is a transboundary basin shared between the United States and Mexico, the Pacific Decadal Oscillation (PDO) and El Niño Southern Oscillation (ENSO) influence local hydrological conditions. Different sub-regions of the basin exhibit varying degrees of correlation, but in general, an increase (decrease) in runoff during El Niños (La Niñas) is noted. Positive PDO enhances the effect of El Niño and dampens the negative effect of La Niña, and when it is in its neutral/transition phase, La Niña dominates climatic conditions and reduces water availability. Further, lags of up to 3 months have been found between ENSO and precipitation in the basin. We hypothesize that (1) a trivariate statistical relationship can be established between the two climate indices and water availability, and (2) the relationship can be used to predict water availability based on projected PDO and ENSO conditions. We use copula to establish the dependence between climate indices and water availability. Water availability is generated from Noah land surface model (LSM), forced with the North American Land Data Assimilation System Phase 2 (NLDAS-2). The model is run within NASA GSFC's Land Information System. LSM generated runoff gives a more realistic picture of available surface water as it is not affected by anthropogenic changes, such as the construction of dams, diversions, and other land use land cover changes, which may obscure climatic influences. Marginals from climate indices and runoff are from different distribution families, thus conventional functional forms of multivariate frequency distributions cannot be employed. Copulas offer a viable alternative as marginals from different families can be combined into a joint distribution. Uncertainties in the statistical relationship can be determined and the statistical model can be used for

Contrasted continental rifting via plume-craton interaction : Applications to Central East African Rift

NARCIS (Netherlands)

Koptev, Alexander; Burov, Evgueni; Calais, Eric; Leroy, Sylvie; Gerya, Taras; Guillou-Frottier, Laurent; Cloetingh, Sierd

The East African Rift system (EARS) provides a unique system with the juxtaposition of two contrasting yet simultaneously formed rift branches, the eastern, magma-rich, and the western, magma-poor, on either sides of the old thick Tanzanian craton embedded in a younger lithosphere. Data on the

The Jurassic of Denmark and Greenland: The Jurassic of East Greenland: a sedimentary record of thermal subsidence, onset and culmination of rifting

Directory of Open Access Journals (Sweden)

Surlyk, Finn

2003-10-01

Full Text Available The Late Palaeozoic – Mesozoic extensional basin complex of East Greenland contains a record of deposition during a period of Rhaetian – Early Bajocian thermal subsidence, the onset of riftingin the Late Bajocian, its growth during the Bathonian–Kimmeridgian, culmination of rifting in the Volgian – Early Ryazanian, and waning in the Late Ryazanian – Hauterivian. The area was centred over a palaeolatitude of about 45°N in the Rhaetian and drifted northwards to about 50°N in the Hauterivian. A major climate change from arid to humid subtropical conditions took place at the Norian–Rhaetian transition. Deposition was in addition governed by a long-term sea-level rise with highstands in the Toarcian–Aalenian, latest Callovian and Kimmeridgian, and lowstands in the latest Bajocian – earliest Bathonian, Middle Oxfordian and Volgian.The Rhaetian – Lower Bajocian succession is considered the upper part of a megasequence, termed J1, with its base in the upper Lower Triassic, whereas the Upper Bajocian – Hauterivian succession forms a complete, syn-rift megasequence, termed J2. The southern part of the basin complex in Jameson Land contains a relatively complete Rhaetian–Ryazanian succession and underwent only minor tilting during Middle Jurassic – earliest Cretaceous rifting. Rhaetian – Lower Jurassic deposits are absent north of Jameson Land and this region was fragmented into strongly tilted fault blocks during the protracted rift event. The syn-rift successions of the two areas accordingly show different long-term trends in sedimentary facies. In the southern area, the J2 syn-rift megasequence forms a symmetrical regressive–transgressive–regressive cycle, whereas the J2 megasequence in the northern area shows an asymmetrical, stepwise deepening trend.A total of eight tectonostratigraphic sequences are recognised in the Rhaetian–Hauterivian interval. They reflect major changes in basin configuration, drainage systems

Faunal migration into the Late Permian Zechstein Basin

DEFF Research Database (Denmark)

Sørensen, Anne Mehlin; Håkansson, Eckart; Stemmerik, Lars

2007-01-01

Late Permian bryozoans from the Wegener Halvø, Ravnefjeld and Schuchert Formations in East Greenland have been investigated. 14 genera are recognised.      Integration of the new bryozoan data from the Upper Permian of East Greenland with data on the distribution of Permian bryozoans along...... the northern margin of Pangea is used to test hypotheses concerning Late Palaeozoic evolution of the North Atlantic region. During the Permian, the Atlantic rift system formed a seaway between Norway and Greenland from the boreal Barents Shelf to the warm and arid Zechstein Basin. This seaway is considered...... to be the only marine connection to the Zechstein Basin and therefore the only possible migration route for bryozoans to enter the basin. The distribution of Permian bryozoans is largely in keeping with such a connection from the cool Barents Shelf past the East Greenland Basin to the warm Zechstein Basin...

3D crustal model of the US and Canada East Coast rifted margin

Science.gov (United States)

Dowla, N.; Bird, D. E.; Murphy, M. A.

2017-12-01

We integrate seismic reflection and refraction data with gravity and magnetic data to generate a continent-scale 3D crustal model of the US and Canada East Coast, extending north from the Straits of Florida to Newfoundland, and east from the Appalachian Mountains to the Central Atlantic Ocean. The model includes five layers separated by four horizons: sea surface, topography, crystalline basement, and Moho. We tested magnetic depth-to-source techniques to improve the basement morphology, from published sources, beneath the continental Triassic rift basins and outboard to the Jurassic ocean floor. A laterally varying density grid was then produced for the resultant sedimentary rock layer thickness based on an exponential decay function that approximates sedimentary compaction. Using constant density values for the remaining layers, we calculated an isostatically compensated Moho. The following structural inversion results of the Moho, controlled by seismic refraction depths, advances our understanding of rift-to-drift crustal geometries, and provides a regional context for additional studies.

Development of aqueous fluids with bentonite clay for drilling of onshore oil wells; Conceitos, feicoes diagnosticas e exemplos sismicos de dobras associadas a falhas distensionais na secao rifte das bacias de Campos e Santos

Energy Technology Data Exchange (ETDEWEB)

Araujo, Mario Neto Cavalcanti de; Silva, Paulo Cezar Santarem da; Matos, Gabriel Correa de [PETROBRAS SA. (CENPES/PETROBRAS), Rio de Janeiro, RJ (Brazil). Centro de Pesquisas e Desenvolvimento Leopoldo A. Miguez de Mello. Gerencia de Geologia Estrutural e Geotectonica], Emails: marioaraujo@petrobras.com.br, paulosantarem@petrobras.com.br, gabriel.matos@petrobras.com.br; Lima, Rodrigo Dias [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). E e P. Gerencia de Interpretacao das Bacias da Costa Sudeste], Email: rodrigolima@petrobras.com.br

2008-11-15

With the exception of the salt-related rollover folds of the Brazilian Continental Margin, folds are not features commonly associated with extensional faults. N-S-trending folds are common features in the hanging wall or above the termination of normal basement faults of the pre, syn and post-rift sequences of the Campos and Santos basins. Regional compression, differential compaction and local transpression are interpreted as the main reasons to explain the formation of folds in the Brazilian margin. However, they can also be formed as a result of the interplay among kinematics, amount of slip and geometry of faults. Two main types of fault-related folds are strongly influenced by geometry and kinematics: fault-bend folds and fault-propagation folds. Fault-bend folds are flexures formed as a result of dip changes of the fault plane. The folds are formed by the collapse of the hanging wall block as it passes over the top of bends in the fault plane. Fault-propagation folds form when movement of basement faults propagates deformation above their tip into a stratified rift and/or post-rift sequence. In this case, the movement of the buried normal fault produces folding in the overlying rocks, without expressive rupture of the beds. Movement along these folds can be accompanied by flexural slip mechanisms, allowing their lateral migration away from the fault plane and the formation of fold swarms like those in the Campos and Santos basins. The strong geometrical relationships of fault-bend and fault-propagation folds not only facilitate the predictive interpretation of these structures in seismic sections, but also allow measurement of stretching, reservoir quality predictions and fracture intensity estimates. In the Campos and Santos basins, regional scale fault-bend and fault-propagation folds might be responsible for the structural control of basement highs and depressions, distribution and migration of depo centers, and location of fractured zones. Fold swarms

Constraining the dynamic response of subcontinental lithospheric mantle to rifting using Re-Os model ages in the Western Ross Sea, Antarctica

Science.gov (United States)

Doherty, C.; Class, C.; Goldstein, S. L.; Shirey, S. B.; Martin, A. P.; Cooper, A. F.; Berg, J. H.; Gamble, J. A.

2012-12-01

In order to understand the dynamic response of the subcontinental lithospheric mantle (SCLM) to rifting, it is important to be able to distinguish the geochemical signatures of SCLM vs. asthenosphere. Recent work demonstrates that unradiogenic Os isotope ratios can indicate old depletion events in the convecting upper mantle (e.g. Rudnick & Walker, 2009), and allow us to make these distinctions. Thus, if SCLM can be traced across a rifted margin, its fate during rifting can be established. The Western Ross Sea provides favorable conditions to test the dynamic response of SCLM to rifting. Re-Os measurements from 8 locations extending from the rift shoulder to 200 km into the rift basin reveal 187Os/188Os ranging from 0.1056 at Foster Crater on the shoulder, to 0.1265 on Ross Island within the rift. While individual sample model ages vary widely throughout the margin, 'aluminochron' ages (Reisberg & Lorand, 1995) reveal a narrower range of lithospheric stabilization ages. Franklin Island and Sulfur Cones show a range of Re-depletion ages (603-1522 Ma and 436-1497 Ma) but aluminochrons yield Paleoproterozoic stabilization ages of 1680 Ma and 1789 Ma, respectively. These ages coincide with U-Pb zircon ages from Transantarctic Mountain (TAM) crustal rocks, in support of SCLM stabilization at the time of crust formation along the central TAM. The Paleoproterozoic stabilization age recorded at Franklin Island is especially significant, since it lies 200km off of the rift shoulder. The similar ages beneath the rift shoulder and within the rift suggests stretched SCLM reaches into the rift and thus precludes replacement by asthenospheric mantle. The persistence of thinned Paleoproterozoic SCLM into the rifted zone in WARS suggests that it represents a 'type I' margin of Huismans and Beaumont (2011), which is characterized by crustal breakup before loss of lithospheric mantle. The Archean Re-depletion age of 3.2 Ga observed on the rift shoulder suggests that cratonic

Reinterpretation of the tectonics and formation of the Pernambuco Plateau Basin, NE Brazil.

Science.gov (United States)

Hoggett, Murray; Jones, Stephen M.; Dunkley Jones, Tom; Reston, Timothy; Barbosa, Antonio; Biondo, Vanessa; Mort, Haydon P.

2017-04-01

The continental margin from Alagoas to Natal represents arguably the most frontier region for exploration on the Brazillian margin. High quality seismic data was not collected in the region for many decades as it was believed that only a few kilometers of sediment existed, and thus there was no exploration potential. Here we present the results of work done as part of an IODP virtual site survey. The work has resulted in a total reinterpretation of the basin structure and tectonics, including finding sediment filled half grabens holding up to 8km thick stratigraphic sections. The two deepest grabens likely represent rift jumps during breakup, which may imply different age sediments in the different grabens. The basin is also found to contain a sizable salt accumulation, previously uninterpreted due to hard overlying carbonates hampering seismic imaging. This salt can be seen to have been highly mobile in the past, and has developed into kilometer scale diapirs flanked by typical rollover anticlines. For the first time we show the basin has all the elements needed for a working petroleum system, with the exception a source rock - which cannot be speculated on further as the basin is undrilled. However source rock sequences are present in the Alagoas basin to the south, and recent released seep data show evidence for both biogeneic and thermogenic seeps over the plateau basin, which could also signal source rock presence. We present seismic and potential fields data, including forward potential fields models and seismically derived crustal stretching and thinning estimates, to show that the half grabens terminate abruptly at the latitude of the Pernambuco Shear Zone, a major crustal scale Precambrian shear zone. Onshore boreholes, well away from the deep seismically imaged half grabens offshore, find crystalline basement to drop away rapidly across the shearzone, revealing a third graben to terminate at the shear zone. We interpret this as that the preexisting

Systematic heat flow measurements across the Wagner Basin, northern Gulf of California

Science.gov (United States)

Neumann, Florian; Negrete-Aranda, Raquel; Harris, Robert N.; Contreras, Juan; Sclater, John G.; González-Fernández, Antonio

2017-12-01

A primary control on the geodynamics of rifting is the thermal regime. To better understand the geodynamics of rifting in the northern Gulf of California we systematically measured heat-flow across the Wagner Basin, a tectonically active basin that lies near the southern terminus of the Cerro Prieto fault. The heat flow profile is 40 km long, has a nominal measurement spacing of ∼1 km, and is collocated with a seismic reflection profile. Heat flow measurements were made with a 6.5-m violin-bow probe. Although heat flow data were collected in shallow water, where there are significant temporal variations in bottom water temperature, we use CTD data collected over many years to correct our measurements to yield accurate values of heat flow. After correction for bottom water temperature, the mean and standard deviation of heat flow across the western, central, and eastern parts of the basin are 220 ± 60, 99 ± 14, 889 ± 419 mW m-2, respectively. Corrections for sedimentation would increase measured heat flow across the central part of basin by 40 to 60%. We interpret the relatively high heat flow and large variability on the western and eastern flanks in terms of upward fluid flow at depth below the seafloor, whereas the lower and more consistent values across the central part of the basin are suggestive of conductive heat transfer. Moreover, heat flow across the central basin is consistent with gabbroic underplating at a depth of 15 km and suggests that continental rupture here has not gone to completion.

Post-rift deformation of the Red Sea Arabian margin

Science.gov (United States)

Zanoni, Davide; Schettino, Antonio; Pierantoni, Pietro Paolo; Rasul, Najeeb

2017-04-01

systems that locally are associated with metre-thick reverse fault zones. Along the analysed faults there is evidence of tectonic reworking. Relict kinematic indicators or the sense of asymmetry of sigmoidal Miocene dykes may suggest that a former sinistral movement was locally accommodated by these faults. This evidence of inversion of strike-slip movement associated with reverse structures, mostly found at the inland endings of these lineaments, suggests an inversion tectonics that could be related to the progressive and recent oceanisation of rift segments. Schettino A., Macchiavelli C., Pierantoni P.P., Zanoni D. & Rasul N. 2016. Recent kinematics of the tectonic plates surrounding the Red Sea and Gulf of Aden. Geophysical Journal International, 207, 457-480. Schlische R.W., Withjack M.O. & Olsen P.E., 2003. Relative timing of CAMP, rifting, continental breakup, and basin inversion: tectonic significance, in The Central Atlantic Magmatic Province: Insights from Fragments of Pangea, eds Hames W., Mchone J.G., Renne P. & Ruppel C., American Geophysical Union, 33-59.

Geology and hydrocarbon potential of the Hartford-Deerfield Basin, Connecticut and Massachusetts

Science.gov (United States)

Coleman, James

2016-01-01

The Hartford-Deerfield basin, a Late Triassic to Early Jurassic rift basin located in central Connecticut and Massachusetts, is the northernmost basin of the onshore Mesozoic rift basins in the eastern United States. The presence of asphaltic petroleum in outcrops indicates that at least one active petroleum system has existed within the basin. However, to-date oil and gas wells have not been drilled in the basin to test any type of petroleum trap. There are good to excellent quality source rocks (up to 3.8% present day total organic carbon) within the Jurassic East Berlin and Portland formations. While these source rock intervals are fairly extensive and at peak oil to peak gas stages of maturity, individual source rock beds are relatively thin (typically less than 1 m) based solely on outcrop observations. Potential reservoir rocks within the Hartford-Deerfield basin are arkosic conglomerates, pebbly sandstones, and finer grained sandstones, shales, siltstones, and fractured igneous rocks of the Triassic New Haven and Jurassic East Berlin and Portland formations (and possibly other units). Sandstone porosity data from 75 samples range from less than 1% to 21%, with a mean of 5%. Permeability is equally low, except around joints, fractures, and faults. Seals are likely to be unfractured intra-formational shales and tight igneous bodies. Maturation, generation, and expulsion likely occurred during the late synrift period (Early Jurassic) accentuated by an increase in local geothermal gradient, igneous intrusions, and hydrothermal fluid circulation. Migration pathways were likely along syn- and postrift faults and fracture zones. Petroleum resources, if present, are probably unconventional (continuous) accumulations as conventionally accumulated petroleum is likely not present in significant volumes.

Geology and hydrocarbon potential of the Dead Sea Rift Basins of Israel and Jordan

Science.gov (United States)

Coleman, James; ten Brink, Uri S.

2016-01-01

Following its middle Miocene inception, numerous basins of varying lengths and depths developed along the Dead Sea fault zone, a large continental transform plate boundary. The modern day left-lateral fault zone has an accumulated left-lateral offset of 105 to 110 km (65 to 68 mi). The deepest basin along the fault zone, the Lake Lisan or Dead Sea basin, reaches depths of 7.5 to 8.5 km (24,500 ft to 28,000 ft), and shows evidence of hydrocarbons. The basins are compartmentalized by normal faulting associated with rapid basin subsidence and, where present, domal uplift accompanying synrift salt withdrawal.

Transtensional Rifting in the Late Proto-Gulf of California Near Bahía Kino, Sonora, México

Science.gov (United States)

Bennett, S. E.; Oskin, M. E.; Dorsey, R. J.

2009-12-01

We investigate the role of obliquity in continental rupture from the example of the Gulf of California rift. Focused transtensional strain adjacent to strike-slip faults, ubiquitous in oblique rifts, may act as a catalyst for lithospheric rupture. To test this hypothesis we completed detailed structural mapping, fault kinematic analysis, basin analysis, and paleomagnetism of pre- and syn-rift volcanic and sedimentary rocks exposed in coastal Sonora, near Bahía Kino, México. This area is host to the NW-striking, dextral Sacrificio and Bahía Kino faults onshore that are likely linked to the offshore De Mar transform fault that accommodated Gulf opening. Three fault-bounded sedimentary basins formed unconformably above the 12.50 ± 0.08 Ma Tuff of San Felipe. The 6.53 ± 0.18 Ma Tuff of Cerro Tordillo and the 6.39 ± 0.02 Ma Tuffs of Mesa Cuadrada are interbedded in the lower part of the non-marine basin fill. In one of these basins, we used these tuff markers to calibrate a sedimentation rate of 1.2 ± 0.2 mm/yr and a tilting rate of 0.12 ± 0.02 °/kyr. These rapid rates suggest transtensional strain and related basin subsidence initiated ca. 6.6 Ma, near the end of proto-Gulf time. Paleomagnetism of the Tuff of San Felipe and Tuffs of Mesa Cuadrada in coastal Sonora show variable amounts of clockwise vertical-axis rotation when compared to paleomagnetic reference sites in Baja California. Fault blocks in the central and southern parts of the study area are rotated counter-clockwise 15° to clockwise 35°. Strike-slip faults in this area accommodate up to 10 km of slip. In contrast, ~53° of clockwise rotation occurred in the northern part of the study area, where strike-slip faults are absent. In this northern area, transtensional deformation occurred primarily by block rotation and ~6 km of normal slip on the low-angle (5-15°) Punta Chueca fault. After correcting for variable amounts of rotation, fault blocks display a consistent tilt down to the ENE. Pre-rift

Syn-rift unconformities punctuating the lower-middle Cambrian transition in the Atlas Rift, Morocco

Science.gov (United States)

Álvaro, J. Javier; Ezzouhairi, Hassan; Clausen, Sébastien; Ribeiro, M. Luisa; Solá, Rita

2015-04-01

The Cambrian Tamdroust and Bab n'Ali Volcanic Complexes represent two magmatic episodes developed in the latest Ediacaran-Cambrian Atlas Rift of Morocco. Their rifting pulses were accompanied by accumulation of volcanosedimentary edifices (dominated by effusive lava flows in the former and explosive acidic aprons in the latter) associated with active tilting and uplift. Sealing of their peneplaned horst-and-graben palaeotopographies led to the onset of distinct onlapping geometries and angular discordances capping eroded basements ranging from the Ediacaran Ouarzazate Supergroup to the Cambrian Asrir Formation. Previous interpretations of these discordances as pull-apart or compressive events are revised here and reinterpreted in an extensional (rifting) context associated with active volcanism. The record of erosive unconformities, stratigraphic gaps, condensed beds and onlapping patterns across the traditional "lower-middle Cambrian" (or Cambrian Series 2-3) transition of the Atlas Rift must be taken into consideration for global chronostratigraphic correlation based on their trilobite content.

Más allá del valle del Rift: la evidencia arqueológica del Plio-Pleistoceno fuera de África Oriental

Directory of Open Access Journals (Sweden)

Ignacio de la TORRE SÁINZ

2009-12-01

Full Text Available RESUMEN: La mayor parte de los trabajos sobre la arqueología del Plio-Pleistoceno en Africa se centran en la evidencia del valle del Rift. Allí existen extensas columnas crono-estratigráficas que permiten contextualizar de forma fiable los conjuntos arqueo-paleontológicos y reconstruir así la secuencia evolutiva de nuestro género. Se suele obviar de esa forma la evidencia del resto de África, donde existen grandes áreas sedimentarias muy poco conocidas desde un punto de vista arqueológico. En este trabajo se reflexionará sobre el registro arqueológico plio-pleistocénico en las zonas alejadas del valle del Rift, y se tratará de reconstruir cómo fue la primera colonización del continente africano.ABSTRACT: Most of the works about the African Plio-Pleistocene are focused on the Rift Valley evidence. In this area there are long chrono-stratigraphical columns that build reliable contexts for the archaeo-paleontological sites, providing the reconstruction of the evolutionary sequence of our Genus. Evidence on the rest of Africa, where there are poor-known sedimentary areas from an archaeological point of view, is usually dismissed. In this work we will reflect on the Plio-Pleistocene record beyond the Rift Valley, trying to reconstruct the first settlement of the African continent.

Numerical modeling of the late Cenozoic geomorphic evolution of Grand Canyon, Arizona

Science.gov (United States)

Pelletier, J. D.

2008-12-01

The late Cenozoic geomorphic evolution of Grand Canyon has been influenced by three primary tectonic and drainage adjustment events. First, incision into the Paleozoic strata of the southwestern margin of the Colorado Plateau began at 16 Ma in response to relief production along the Grand Wash Fault. Second, the ancestral Upper Colorado River reversed drainage and became integrated with the Lower Colorado River basin through Grand Canyon between 5.5 and 6 Ma. Third, the Colorado River was influenced by Plio- Quaternary normal faulting along the Hurricane and Toroweap Faults. Despite the relatively firm constraints available on the timing of these events, the geomorphic evolution of Grand Canyon is still not well constrained and many questions remain. For example, was there a deeply-incised gorge in western Grand Canyon before Colorado River integration? How and where was the Colorado River integrated? How have incision rates varied in space and time? In this paper, I describe the results of a numerical modeling study designed to address these questions. The model integrates the stream power model for bedrock channel erosion with cliff retreat and the flexural-isostatic response to erosion. The model honors the structural geology of the Grand Canyon region, including the variable erodibility of rocks in the Colorado Plateau and the occurrence of Plio-Quaternary normal faulting along the Hurricane-Toroweap Fault system. We present the results of two models designed to bracket the possible drainage architectures of the southwestern margin of the Colorado Plateau in Miocene time. In the first model, we assume a 13,000 km2 drainage basin primarily sourced from the Hualapai and Coconino Plateaux. The results of this model indicate that relief production along the Grand Wash fault initiated the formation of a large (700 m) knickpoint that migrated headward at a rate of 15 km/Myr prior to drainage integration at 6 Ma to form a deep gorge in western Grand Canyon. This model

Study of southern CHAONAN sag lower continental slope basin deposition character in Northern South China Sea

Science.gov (United States)

Tang, Y.

2009-12-01

Northern South China Sea Margin locates in Eurasian plate,Indian-Australia plate,Pacific Plates.The South China Sea had underwent a complicated tectonic evolution in Cenozoic.During rifting,the continental shelf and slope forms a series of Cenozoic sedimentary basins,including Qiongdongnan basin,Pearl River Mouth basin,Taixinan basin.These basins fill in thick Cenozoic fluviolacustrine facies,transitional facies,marine facies,abyssal facies sediment,recording the evolution history of South China Sea Margin rifting and ocean basin extending.The studies of tectonics and deposition of depression in the Southern Chaonan Sag of lower continental slope in the Norther South China Sea were dealt with,based on the sequence stratigraphy and depositional facies interpretation of seismic profiles acquired by cruises of“China and Germany Joint Study on Marine Geosciences in the South China Sea”and“The formation,evolution and key issues of important resources in China marginal sea",and combining with ODP 1148 cole and LW33-1-1 well.The free-air gravity anomaly of the break up of the continental and ocean appears comparatively low negative anomaly traps which extended in EW,it is the reflection of passive margin gravitational effect.Bouguer gravity anomaly is comparatively low which is gradient zone extended NE-SW.Magnetic anomaly lies in Magnetic Quiet Zone at the Northern Continental Margin of the South China Sea.The Cenozoic sediments of lower continental slope in Southern Chaonan Sag can be divided into five stratum interface:SB5.5,SB10.5,SB16.5,SB23.8 and Hg,their ages are of Pliocene-Quaternary,late Miocene,middle Miocene,early Miocene,paleogene.The tectonic evolution of low continental slope depressions can be divided into rifting,rifting-depression transitional and depression stages,while their depositional environments change from river to shallow marine and abyssa1,which results in different topography in different stages.The topographic evolvement in the study

The Toarcian Bathonian succession of the Antsiranana Basin (NW Madagascar): Facies analysis and tectono-sedimentary history in the development of the East Africa-Madagascar conjugate margins

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Papini, Mauro; Benvenuti, Marco

2008-04-01

The latest Early to Middle Jurassic succession of the Antsiranana Basin (NW Madagascar) records the complex transition from the continental rifting of Gondwana to the drifting of Madagascar-India from East Africa. The Madagascan Late Paleozoic-Mesozoic successions have been included in several paleogeographic and geodynamic models explaining the evolution of the Gondwana margins. Nevertheless, in some cases, as for the Toarcian-Bathonian deposits of the Antsiranana Basin, no significant stratigraphic revision has been carried out since the early 1970s. New field surveys allow reconsidering the stratigraphic and structural context and the palaeoenvironmental meaning of Toarcian-Bathonian successions occurring in different parts of the basin. These successions rest on the Triassic-Early Jurassic Isalo Sandstone which records pre-breakup rift events with a dominantly fluvial deposition. This situation is similar to other continental rift basins of Gondwana. After a regional Toarcian transgression the different portions of the Antsiranana Basin were characterized by significantly diversified and coeval depositional environments. The basin can be subdivided in a SW and NE part separated by a NW-SE trending structural high. In the SW part of the basin (Ampasindava sub-basin) the so-called "Jurassique paralique" [Rerat, J.C., 1964. Note sur les variations de faciès des sèries jurassiques du nord de Madagascar. Comptes Rendus Semaine gèologique, Tananarive, pp. 15-22] or " Facies Mixtes de la Presqu'ile de Ampasindava" [Besairie, H., Collignon, M., 1972. Géologie de Madagascar; I. Les terrains sédimentaires. Annales Géologiques de Madagascar, 35, 1-463], a 1500 m thick prevalently terrigenous deposit, has been subdivided into four units. They document the long-lasting development of coastal-deltaic systems in a highly subsiding area. In the NE portion of the basin (Ankarana-Analamera sub-basin), a coeval mixed carbonate-terrigenous succession subdivided in five units

Deepening, and repairing, the metabolic rift.

Science.gov (United States)

Schneider, Mindi; McMichael, Philip

2010-01-01

This paper critically assesses the metabolic rift as a social, ecological, and historical concept describing the disruption of natural cycles and processes and ruptures in material human-nature relations under capitalism. As a social concept, the metabolic rift presumes that metabolism is understood in relation to the labour process. This conception, however, privileges the organisation of labour to the exclusion of the practice of labour, which we argue challenges its utility for analysing contemporary socio-environmental crises. As an ecological concept, the metabolic rift is based on outmoded understandings of (agro) ecosystems and inadequately describes relations and interactions between labour and ecological processes. Historically, the metabolic rift is integral to debates about the definitions and relations of capitalism, industrialism, and modernity as historical concepts. At the same time, it gives rise to an epistemic rift, insofar as the separation of the natural and social worlds comes to be expressed in social thought and critical theory, which have one-sidedly focused on the social. We argue that a reunification of the social and the ecological, in historical practice and in historical thought, is the key to repairing the metabolic rift, both conceptually and practically. The food sovereignty movement in this respect is exemplary.

Angola: source rock control for Lower Congo Coastal and Kwanza Basin petroleum systems

Energy Technology Data Exchange (ETDEWEB)

Burwood, R. [Fina Exploration Ltd, Epsom (United Kingdom)

1999-07-01

The purpose of this paper is to provide an overview of petroleum occurrence and provenance for the 1000 km West African Atlantic Margin from Cabinda to mid-Angola. Over this margin the Lower Congo Coastal and Kwanza provinces cumulatively account for reserves of c. 6 gigabarrels oil recoverable (GBOR). These are dominantly reservoired in Pinda carbonate traps of the former basin. However, with production from a range of aggradational wedge, carbonate platform and pre-salt reservoirs, a diversity in oil character presupposes complex hydrocarbon habitats charged by multiple sourcing. Each of these two major Atlantic margin salt basins constitutes a different, source rock driven, hydrocarbon habitat. As classic passive margin pull-apart basins, Early Cretaceous initiated rift events (Pre-rift, Syn-rift I, II, etc.) evolved into the drift phase opening of the southern Atlantic. A striking feature of this progression was widespread evaporite deposition of the Aptian Loeme salt. This separates two distinct sedimentary and tectonic domains of the Pre- and Post-Salt. The core Lower Congo Coastal habitat is dominated by the Pre-Salt Bucomazi Formation sourced 'poly' petroleum system. These lacustrine, often super-rich, sediments reveal considerable organofacies variation between their basin fill (Syn-rift I) and sheet drape (Syn-rift II) development, accounting for the compositional diversity in their progenic petroleums. Of crucial impact is a cognate diversity in their kerogen kinetic behaviour. This controls the conditions and timing of generation and realization of charge potential. With the Lower Congo Coastal habitat extending southwards towards the Ambriz Spur, the Bucomazi facies proper appears restricted to the northern and deeper proto-lake trend. Over the more weakly subsident margins such troughs host inferior sheet drape potential. Elswhere, Upper Cretaceous-Palaeogene marine clastic Iabe Formation sourced petroleum systems are hydrocarbon productive

Identification, mapping, and analysis of possible evidences of active petroleum systems in the Colorado Basin, offshore Argentina, South America

Science.gov (United States)

Loegering, Markus; Anka, Zahie; Rodriguez, Jorge; Marchal, Denis; di Primio, Rolando; Vallejo, Eduardo; Kohler, Guillermina; Pangaro, Francisco

2010-05-01

The analysis of a dense 2D seismic reflection dataset and 12 exploration wells data, allowed us to reconstruct the geological evolution of the Colorado Basin, offshore Argentina. We identified and mapped the major syn- and post-rift seismic sequences, and their boundaries such as unconformities and regional seismic markers, present on the continental shelf and slope (water depths from 50 to 1800 m) of the Colorado Basin. Seismic-to-well log correlations, as well as integration with biostratigraphic data provided a chrono-stratigraphic framework for the interpreted horizons. The construction of isochronal (twt) maps provided a 3D spatial visualisation of the stratigraphic relationship among the sequences. The maps show a change in configuration from the break-up unconformity (130 Ma) to the present-day seafloor. The break-up unconformity displays a central EW-elongated graben which prevails on the overlying sequences up to the Miocene. The EW Colorado basin turns NW-SE towards the East, going perpendicular to the present-day continental margin (oriented NE-SW). The strong obliquity of the basin orientation related to the direction corresponding to the opening of the South Atlantic (NE-SW) suggests a structural control from the pre-rift basement on the rift and post-rift sequences. Starting from the break-up unconformity, the history of basin filling is illustrated up to the flat seafloor. The basin sag phase is represented by the sequences deposited between the break-up unconformity and the Colorado discontinuity (Aptian to Campanian). The Campanian to Eocene successions are more or less parallel- layered suggesting sequence aggradation. The distribution of liquid/gas hydrocarbon-leakage features (i.e. gas chimneys, mud volcanoes, and seabed pockmarks) should allow the definition of potential migration pathways. In this sense, a systematic mapping of these paleo- and present-day features observed in the seismic profiles has been performed and their distribution was

Exploration potential of Paraiba and Natal platform basins, NE Brazil; Potencial exploratorio das bacias da Paraiba e da plataforma de Natal, NE do Brazil

Energy Technology Data Exchange (ETDEWEB)

Barbosa, Jose A. [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil); Lima Filho, Mario; Neumann, Virginio H. [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Geologia; Maranhao Neto, Jose Carneiro; Araujo, Joao A.A. [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Programa de Pos Graduacao em Geociencias

2008-07-01

The portion of Brazilian continental margin located between the Pernambuco Shear Zone (ZCPE) and Touros High, enclosing Natal Platform and Paraiba basin, NE Brazil, presents a thin sedimentary cover represented by Neo- Cretaceous deposits, over an elevated basement. In this zone the narrow platform ends abruptly against the ocean plate, forming a scarped slope. This area corresponds to the Transverse zone of Northeast Brazil (TZN) limited by two extensive transcurrent E-W shear zones that acted as accommodation zones for the strain produced by the advance of the southern and northern rift branches. During the Aptian, the rift suffered a NE deflection and contoured the Borborema Province and the TZN. The resistance of this block to the rift advance generated a prominent and elevated region into the Atlantic gulf which resulted in the absence of rift deposition over the Brazilian margin and its deviation to the African side. The model suggested by this paper denominates this area as the 'exception zone' of the Brazilian margin, which possess a poor petroliferous potential and need to be separated from the sector corresponding to the Pernambuco basin, located to south of ZCPE, representing the last piece of margin before the rift deflection and possessing an important petroliferous potential. (author)

Dealing with variability in water availability: the case of the Verde Grande River basin, Brazil

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B. Collischonn

2014-09-01

Full Text Available This paper presents a water resources management strategy developed by the Brazilian National Water Agency (ANA to cope with the conflicts between water users in the Verde Grande River basin, located at the southern border of the Brazilian semi-arid region. The basin is dominated by water-demanding fruit irrigation agriculture, which has grown significantly and without adequate water use control, over the last 30 years. The current water demand for irrigation exceeds water availability (understood as a 95 % percentile of the flow duration curve in a ratio of three to one, meaning that downstream water users are experiencing more frequent water shortages than upstream ones. The management strategy implemented in 2008 has the objective of equalizing risk for all water users and consists of a set of rules designed to restrict water withdrawals according to current river water level (indicative of water availability and water demand. Under that rule, larger farmers have proportionally larger reductions in water use, preserving small subsistence irrigators. Moreover, dry season streamflow is forecasted at strategic points by the end of every rainy season, providing evaluation of shortage risk. Thus, water users are informed about the forecasts and corresponding restrictions well in advance, allowing for anticipated planning of irrigated areas and practices. In order to enforce restriction rules, water meters were installed in all larger water users and inefficient farmers were obligated to improve their irrigation systems’ performance. Finally, increases in irrigated area are only allowed in the case of annual crops and during months of higher water availability (November to June. The strategy differs from convectional approached based only on water use priority and has been successful in dealing with natural variability of water availability, allowing more water to be used in wet years and managing risk in an isonomic manner during dry years.

Polyphase Rifting and Breakup of the Central Mozambique Margin

Science.gov (United States)

Senkans, Andrew; Leroy, Sylvie; d'Acremont, Elia; Castilla, Raymi

2017-04-01

The breakup of the Gondwana supercontinent resulted in the formation of the Central Mozambique passive margin as Africa and Antarctica were separated during the mid-Jurassic period. The identification of magnetic anomalies in the Mozambique Basin and Riiser Larsen Sea means that post-oceanisation plate kinematics are well-constrained. Unresolved questions remain, however, regarding the initial fit, continental breakup process, and the first relative movements of Africa and Antarctica. This study uses high quality multi-channel seismic reflection profiles in an effort to identify the major crustal domains in the Angoche and Beira regions of the Central Mozambique margin. This work is part of the integrated pluri-disciplinary PAMELA project*. Our results show that the Central Mozambique passive margin is characterised by intense but localised magmatic activity, evidenced by the existence of seaward dipping reflectors (SDR) in the Angoche region, as well as magmatic sills and volcanoclastic material which mark the Beira High. The Angoche region is defined by a faulted upper-continental crust, with the possible exhumation of lower crustal material forming an extended ocean-continent transition (OCT). The profiles studied across the Beira high reveal an offshore continental fragment, which is overlain by a pre-rift sedimentary unit likely to belong to the Karoo Group. Faulting of the crust and overlying sedimentary unit reveals that the Beira High has recorded several phases of deformation. The combination of our seismic interpretation with existing geophysical and geological results have allowed us to propose a breakup model which supports the idea that the Central Mozambique margin was affected by polyphase rifting. The analysis of both along-dip and along-strike profiles shows that the Beira High initially experienced extension in a direction approximately parallel to the Mozambique coastline onshore of the Beira High. Our results suggest that the Beira High results

Intraplate seismicity along the Gedi Fault in Kachchh rift basin of western India

Science.gov (United States)

Joshi, Vishwa; Rastogi, B. K.; Kumar, Santosh

2017-11-01

The Kachchh rift basin is located on the western continental margin of India and has a history of experiencing large to moderate intraplate earthquakes with M ≥ 5. During the past two centuries, two large earthquakes of Mw 7.8 (1819) and Mw 7.7 (2001) have occurred in the Kachchh region, the latter with an epicenter near Bhuj. The aftershock activity of the 2001 Bhuj earthquake is still ongoing with migration of seismicity. Initially, epicenters migrated towards the east and northeast within the Kachchh region but, since 2007, it has also migrated to the south. The triggered faults are mostly within 100 km and some up to 200 km distance from the epicentral area of the mainshock. Most of these faults are trending in E-W direction, and some are transverse. It was noticed that some faults generate earthquakes down to the Moho depth whereas some faults show earthquake activity within the upper crustal volume. The Gedi Fault, situated about 50 km northeast of the 2001 mainshock epicenter, triggered the largest earthquake of Mw 5.6 in 2006. We have carried out detailed seismological studies to evaluate the seismic potential of the Gedi Fault. We have relocated 331 earthquakes by HypoDD to improve upon location errors. Further, the relocated events are used to estimate the b value, p value, and fractal correlation dimension Dc of the fault zone. The present study indicates that all the events along the Gedi Fault are shallow in nature, with focal depths less than 20 km. The estimated b value shows that the Gedi aftershock sequence could be classified as Mogi's type 2 sequence, and the p value suggests a relatively slow decay of aftershocks. The fault plane solutions of some selected events of Mw > 3.5 are examined, and activeness of the Gedi Fault is assessed from the results of active fault studies as well as GPS and InSAR results. All these results are critically examined to evaluate the material properties and seismic potential of the Gedi Fault that may be useful

Cambrian–early Ordovician volcanism across the South Armorican and Occitan domains of the Variscan Belt in France: Continental break-up and rifting of the northern Gondwana margin

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André Pouclet

2017-01-01

Full Text Available The Cambrian–lower Ordovician volcanic units of the South Armorican and Occitan domains are analysed in a tectonostratigraphic survey of the French Variscan Belt. The South Armorican lavas consist of continental tholeiites in middle Cambrian–Furongian sequences related to continental break-up. A significant volcanic activity occurred in the Tremadocian, dominated by crustal melted rhyolitic lavas and initial rifting tholeiites. The Occitan lavas are distributed into five volcanic phases: (1 basal Cambrian rhyolites, (2 upper lower Cambrian Mg-rich tholeiites close to N-MORBs but crustal contaminated, (3 upper lower–middle Cambrian continental tholeiites, (4 Tremadocian rhyolites, and (5 upper lower Ordovician initial rift tholeiites. A rifting event linked to asthenosphere upwelling took place in the late early Cambrian but did not evolve. It renewed in the Tremadocian with abundant crustal melting due to underplating of mixed asthenospheric and lithospheric magmas. This main tectono-magmatic continental rift is termed the “Tremadocian Tectonic Belt” underlined by a chain of rhyolitic volcanoes from Occitan and South Armorican domains to Central Iberia. It evolved with the setting of syn-rift coarse siliciclastic deposits overlain by post-rift deep water shales in a suite of sedimentary basins that forecasted the South Armorican–Medio-European Ocean as a part of the Palaeotethys Ocean.

CO2 degassing in the Hartoušov mofette area, western Eger Rift, imaged by CO2 mapping and geoelectrical and gravity surveys

Czech Academy of Sciences Publication Activity Database

Nickschick, T.; Kämpf, H.; Flechsig, C.; Mrlina, Jan; Heinicke, J.

2015-01-01

Roč. 104, č. 8 (2015), s. 2107-2129 ISSN 1437-3254 R&D Projects: GA MŠk LM2010008 Institutional support: RVO:67985530 Keywords : Eger Rift * Cheb Basin * magmatic CO2 * CO2 gas flux studies * geoelectrics * gravity Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 2.133, year: 2015

The major tectonic boundaries of the Northern Red Sea rift, Egypt derived from geophysical data analysis

Science.gov (United States)

Saleh, Salah; Pamukçu, Oya; Brimich, Ladislav

2017-09-01

In the present study, we have attempted to map the plate boundary between Arabia and Africa at the Northern Red Sea rift region including the Suez rift, Gulf of Aqaba-Dead Sea transform and southeastern Mediterranean region by using gravity data analysis. In the boundary analysis method which was used; low-pass filtered gravity anomalies of the Northern Red Sea rift region were computed. Different crustal types and thicknesses, sediment thicknesses and different heat flow anomalies were evaluated. According to the results, there are six subzones (crustal blocks) separated from each other by tectonic plate boundaries and/or lineaments. It seems that these tectonic boundaries reveal complex structural lineaments, which are mostly influenced by a predominant set of NNW-SSE to NW-SE trending lineaments bordering the Red Sea and Suez rift regions. On the other side, the E-W and N-S to NNE-SSW trended lineaments bordering the South-eastern Mediterranean, Northern Sinai and Aqaba-Dead Sea transform regions, respectively. The analysis of the low pass filtered Bouguer anomaly maps reveals that the positive regional anomaly over both the Red Sea rift and South-eastern Mediterranean basin subzones are considered to be caused by the high density of the oceanic crust and/or the anomalous upper mantle structures beneath these regions whereas, the broad medium anomalies along the western half of Central Sinai with the Suez rift and the Eastern Desert subzones are attributed to low-density sediments of the Suez rift and/or the thick upper continental crustal thickness below these zones. There are observable negative anomalies over the Northern Arabia subzone, particularly in the areas covered by Cenozoic volcanics. These negative anomalies may be attributed to both the low densities of the surface volcanics and/or to a very thick upper continental crust. On the contrary, the negative anomaly which belongs to the Gulf of Aqaba-Dead Sea transform zone is due to crustal thickening

Coulomb Stress Change and Seismic Hazard of Rift Zones in Southern Tibet after the 2015 Mw7.8 Nepal Earthquake and Its Mw7.3 Aftershock

Science.gov (United States)

Dai, Z.; Zha, X.; Lu, Z.

2015-12-01

In southern Tibet (30~34N, 80~95E), many north-trending rifts, such as Yadong-Gulu and Lunggar rifts, are characterized by internally drained graben or half-graben basins bounded by active normal faults. Some developed rifts have become a portion of important transportation lines in Tibet, China. Since 1976, eighty-seven >Mw5.0 earthquakes have happened in the rift regions, and fifty-five events have normal faulting focal mechanisms according to the GCMT catalog. These rifts and normal faults are associated with both the EW-trending extension of the southern Tibet and the convergence between Indian and Tibet. The 2015 Mw7.8 Nepal great earthquake and its Mw7.3 aftershock occurred at the main Himalayan Thrust zone and caused tremendous damages in Kathmandu region. Those earthquakes will lead to significant viscoelastic deformation and stress changes in the southern Tibet in the future. To evaluate the seismic hazard in the active rift regions in southern Tibet, we modeled the slip distribution of the 2015 Nepal great earthquakes using the InSAR displacement field from the ALOS-2 satellite SAR data, and calculated the Coulomb failure stress (CFS) on these active normal faults in the rift zones. Because the estimated CFS depends on the geometrical parameters of receiver faults, it is necessary to get the accurate fault parameters in the rift zones. Some historical earthquakes have been studied using the field data, teleseismic data and InSAR observations, but results are in not agreement with each other. In this study, we revaluated the geometrical parameters of seismogenic faults occurred in the rift zones using some high-quality coseismic InSAR observations and teleseismic body-wave data. Finally, we will evaluate the seismic hazard in the rift zones according to the value of the estimated CFS and aftershock distribution.

Aeromagnetic anomalies over faulted strata

Science.gov (United States)

Grauch, V.J.S.; Hudson, Mark R.

2011-01-01

High-resolution aeromagnetic surveys are now an industry standard and they commonly detect anomalies that are attributed to faults within sedimentary basins. However, detailed studies identifying geologic sources of magnetic anomalies in sedimentary environments are rare in the literature. Opportunities to study these sources have come from well-exposed sedimentary basins of the Rio Grande rift in New Mexico and Colorado. High-resolution aeromagnetic data from these areas reveal numerous, curvilinear, low-amplitude (2–15 nT at 100-m terrain clearance) anomalies that consistently correspond to intrasedimentary normal faults (Figure 1). Detailed geophysical and rock-property studies provide evidence for the magnetic sources at several exposures of these faults in the central Rio Grande rift (summarized in Grauch and Hudson, 2007, and Hudson et al., 2008). A key result is that the aeromagnetic anomalies arise from the juxtaposition of magnetically differing strata at the faults as opposed to chemical processes acting at the fault zone. The studies also provide (1) guidelines for understanding and estimating the geophysical parameters controlling aeromagnetic anomalies at faulted strata (Grauch and Hudson), and (2) observations on key geologic factors that are favorable for developing similar sedimentary sources of aeromagnetic anomalies elsewhere (Hudson et al.).

Tectonic-stratigraphic evolution of Espirito Santo Basin - Brazil; Evolucao tectono-estratigrafica da Bacia do Espirito Santo

Energy Technology Data Exchange (ETDEWEB)

Silva, Eric Zagotto; Fernandes, Flavio L.; Lobato, Gustavo; Ferreira Neto, Walter Dias [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE). Lab. de Modelagem de Bacias (LAB2M); Petersohn, Eliane [Agencia Nacional do Petroleo, Gas Natural e Biocombustiveis (ANP), Brasilia, DF (Brazil)

2008-07-01

This paper documents the analysis of seismic data of the Espirito Santo basin obtained during the project realized through partnership between COPPE/UFRJ/Lab2M with the Agencia Nacional do Petroleo, Gas Natural e Biocombustiveis (ANP) during 2006 and 2007. The major objective of the seismic data interpretation in the project was to define the main structural and stratigraphic features in order to build a sedimentation model and a tectonic-stratigraphic evolution model of the Espirito Santo basin. Thus, the sedimentary package has been divided into eight genetic units (UN), grouped into five third order stratigraphic sequences, namely: UN-B, represented by siliciclastics rocks of the rift stage and evaporitic sag-rift stage, deposited during the Aptian; UN-C, which represents the carbonatic rocks deposited in a marine environment, and siliciclastics rocks located in the proximal portions during the Albian; and UN-D, represented by sediments, composed mainly by pelites, deposited in between the Cenomanian and Recent, and includes the Eocene volcanic event, which one changed the sedimentation pattern of the basin. (author)

Análise Multitemporal da Cobertura Florestal da Microbacia do Arroio Grande, Santa Maria, RS Multitemporal Analysis of Forest Cover in the Arroio Grande Small Hydrological Basin, Santa Maria, RS

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Joel Juliano Kleinpaul

2011-03-01

Full Text Available

Sedimentological and paleoenvironmental constraints of the Statherian and Stenian Espinhaço rift system, Brazil.

OpenAIRE

Santos, Marcelo Nascimento dos; Chemale Júnior, Farid; Dussin, Ivo Antonio; Martins, Maximiliano de Souza; Assis, Tiago A. R.; Jelinek, Andréa Ritter; Guadagnin, Felipe; Armstrong, Richard

2013-01-01

The Espinhaço Basin in eastern Brazil contains depositional sequences developed in the São Francisco paleoplate and its margins. Detailed mapping was conducted and combined with U–Pb detrital zircon dating to determine the sedimentological-stratigraphic framework, provenance and minimum and maximum ages of the syn-rift-deposits. The two cycles have minimum ages of 1192 and 923 Ma and maximum ages of 1785 and 1685 Ma. The first depositional cycle, represented by the Bandeirinha and São João da...

Surface deformation in volcanic rift zones

Science.gov (United States)

Pollard, D.D.; Delaney, P.T.; Duffield, W.A.; Endo, E.T.; Okamura, A.T.

1983-01-01

The principal conduits for magma transport within rift zones of basaltic volcanoes are steeply dipping dikes, some of which feed fissure eruptions. Elastic displacements accompanying a single dike emplacement elevate the flanks of the rift relative to a central depression. Concomitant normal faulting may transform the depression into a graben thus accentuating the topographic features of the rift. If eruption occurs the characteristic ridge-trough-ridge displacement profile changes to a single ridge, centered at the fissure, and the erupted lava alters the local topography. A well-developed rift zone owes its structure and topography to the integrated effects of many magmatic rifting events. To investigate this process we compute the elastic displacements and stresses in a homogeneous, two-dimensional half-space driven by a pressurized crack that may breach the surface. A derivative graphical method permits one to estimate the three geometric parameters of the dike (height, inclination, and depth-to-center) and the mechanical parameter (driving pressure/rock stiffness) from a smoothly varying displacement profile. Direct comparison of measured and theoretical profiles may be used to estimate these parameters even if inelastic deformation, notably normal faulting, creates discontinuities in the profile. Geological structures (open cracks, normal faults, buckles, and thrust faults) form because of stresses induced by dike emplacement and fissure eruption. Theoretical stress states associated with dilation of a pressurized crack are used to interpret the distribution and orientation of these structures and their role in rift formation. ?? 1983.

Evidence for cross rift structural controls on deformation and seismicity at a continental rift caldera

Science.gov (United States)

Lloyd, Ryan; Biggs, Juliet; Wilks, Matthew; Nowacki, Andy; Kendall, J.-Michael; Ayele, Atalay; Lewi, Elias; Eysteinsson, Hjálmar

2018-04-01

In continental rifts structural heterogeneities, such as pre-existing faults and foliations, are thought to influence shallow crustal processes, particularly the formation of rift faults, magma reservoirs and surface volcanism. We focus on the Corbetti caldera, in the southern central Main Ethiopian Rift. We measure the surface deformation between 22nd June 2007 and 25th March 2009 using ALOS and ENVISAT SAR interferograms and observe a semi-circular pattern of deformation bounded by a sharp linear feature cross-cutting the caldera, coincident with the caldera long axis. The signal reverses in sign but is not seasonal: from June to December 2007 the region south of this structure moves upwards 3 cm relative to the north, while from December 2007 until November 2008 it subsides by 2 cm. Comparison of data taken from two different satellite look directions show that the displacement is primarily vertical. We discuss potential mechanisms and conclude that this deformation is associated with pressure changes within a shallow (statistically consistent with this fault structure, indicating that the fault has also controlled the migration of magma from a reservoir to the surface over tens of thousands of years. Spatial patterns of seismicity are consistent with a cross-rift structure that extents outside the caldera and to a depth of ∼30 km, and patterns of seismic anisotropy suggests stress partitioning occurs across the structure. We discuss the possible nature of this structure, and conclude that it is most likely associated with the Goba-Bonga lineament, which cross-cuts and pre-dates the current rift. Our observations show that pre-rift structures play an important role in magma transport and shallow hydrothermal processes, and therefore they should not be neglected when discussing these processes.

Speculative petroleum systems of the Punta del Este Basin (offshore Uruguay

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Ethel Morales

Full Text Available ABSTRACT: The Uruguayan continental margin was generated as the result of the breakup of Gondwana and, later, the opening of the South Atlantic Ocean, which began in the Jurassic. Three major areas of Meso-Cenozoic sedimentation are located in the Uruguayan offshore: the Punta del Este Basin, the southernmost sector of the Pelotas Basin and the Oriental del Plata Basin. These basins share the classical stages of tectono-sedimentary evolution of the other Atlantic basins, including the prerift (Paleozoic, rift (Jurassic-Early Cretaceous, transition (Barremian-Aptian and postrift (Aptian-present phases. Based on the analysis of basin evolution through seismic sections and well data as well as on the establishment of analogies with productive Atlantic basins, four speculative petroleum systems are proposed for the Punta del Este Basin: 1 Marine petroleum system of the prerift stage: Devonian/Permian-Devonian/Permian(?, 2 Lacustrine petroleum system of the synrift stage: Neocomian-Neocomian(?, 3 Marine petroleum system of the Cretaceous postrift: Aptian-Late Cretaceous(?, 4 Marine petroleum system of the Cenozoic postrift: Paleocene-Paleogene/Neogene(?.

Geomorphic Response to Spatial and Temporal Tectonic uplift on the Kenya Rift of East African Rift System

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Xue, L.; Abdelsalam, M. G.

2017-12-01

Tectonic uplifts of the shoulders of the East Africa Rift System (EARS) have significant impact on the geological record by reorganizing drainage systems, increasing sediment supply, and changing climate and biogeography. Recent studies in geochronology, geomorphology and geophysics have provided some understanding of the timing of tectonic uplift and its distribution pattern of the (EARS). We do not know how the vertical motion is localized along the rift axis and the relative roles of upwelling of magma and rift extensional processes play in tectonic uplift history. This work presents detailed morphometric study of the fluvial landscape response to the tectonic uplift and climate shifting of the Kenya Rift shoulders in order to reconstruct their incision history, with special attention to timing, location, and intensity of uplift episodes. This work compiles the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) and Sentinel-2A data, summarized previous 39Ar-40Ar and thermochronology data, and calculates long-term incision rate and geomorphic proxies (normalized steepness and chi-integral) along the Kenya Rift. It also models the age of tectonic/climatic events by using knickpoint celerity model and R/SR integrative approach. It found that the maximum long-term incision rates of 300 mm/kyr to be at the central Kenya Rift, possibly related to the mantle-driven process and rapid tectonic uplift. The geomorphic proxies indicate southward decreasing pattern of the short-term incision rate, possibly related to the migration of the mantle plume.

Genesis of copper-lead mineralization in the regionally zoned Agnigundala Sulfide Belt, Cuddapah Basin, Andhra Pradesh, India

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Bhattacharya, H. N.; Bandyopadhyay, Sandip

2018-03-01

Shallow marine sandstone-shale-carbonate sedimentary rocks of the Paleoproterozoic northern Cuddapah basin host copper (Nallakonda deposit), copper-lead (Dhukonda deposit), and lead mineralization (Bandalamottu deposit) which together constitute the Agnigundala Sulfide Belt. The Cu sulfide mineralization in sandstone is both stratabound and disseminated, and Pb sulfide mineralization occurs as stratabound fracture filling veins and/or replacement veins within dolomite. Systematic mineralogical and sulfur, carbon, and oxygen isotope studies of the three deposits indicate a common ore-fluid that deposited copper at Nallakonda, copper-lead at Dhukonda, and lead at Bandalamottu under progressive cooling during migration through sediments. The ore-fluid was of low temperature (water sulfate produced sulfide for ore deposition. It is envisaged that basal red-bed and evaporite-bearing rift-related continental to shallow marine sediments might have acted as the source for the metals. Rift-related faults developed during sedimentation in the basin might have punctured the ore-fluid pool in the lower sedimentary succession and also acted as conduits for their upward migration. The ore-bearing horizons have participated in deformations during basin inversion without any recognizable remobilization.

Residual basins

International Nuclear Information System (INIS)

D'Elboux, C.V.; Paiva, I.B.

1980-01-01

Exploration for uranium carried out over a major portion of the Rio Grande do Sul Shield has revealed a number of small residual basins developed along glacially eroded channels of pre-Permian age. Mineralization of uranium occurs in two distinct sedimentary units. The lower unit consists of rhythmites overlain by a sequence of black shales, siltstones and coal seams, while the upper one is dominated by sandstones of probable fluvial origin. (Author) [pt

Lithospheric structure along wide-angle seismic profile GEORIFT 2013 in Pripyat-Dnieper-Donets Basin (Belarus and Ukraine)

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Starostenko, V.; Janik, T.; Yegorova, T.; Czuba, W.; Środa, P.; Lysynchuk, D.; Aizberg, R.; Garetsky, R.; Karataev, G.; Gribik, Y.; Farfuliak, L.; Kolomiyets, K.; Omelchenko, V.; Komminaho, K.; Tiira, T.; Gryn, D.; Guterch, A.; Legostaeva, O.; Thybo, H.; Tolkunov, A.

2018-03-01

The GEORIFT 2013 (GR'13) WARR (wide-angle reflection and refraction) experiment was carried out in 2013 in the territory of Belarus and Ukraine with broad international co-operation. The aim of the work is to study basin architecture and deep structure of the Pripyat-Dnieper-Donets Basin (PDDB), which is the deepest and best studied Palaeozoic rift basin in Europe. The PDDB is located in the southern part of the East European Craton (EEC) and crosses Sarmatia—one of the three segments of the EEC. The PDDB was formed by Late Devonian rifting associated with domal basement uplift and magmatism. The GR'13 extends in NW-SE direction along the PDDB strike and crosses the Pripyat Trough (PT) and Dnieper Graben (DG) separated by the Bragin Uplift (BU) of the basement. The field acquisition along the GR'13 (of 670 km total length) involved 14 shots and recorders deployed every ˜2.2 km for several shot points. The good quality of the data, with first arrivals visible up to 670 km for several shot points, allowed for construction of a velocity model extending to 80 km depth using ray-tracing modelling. The thickness of the sediments (Vp < 6.0 km s-1) varies from 1-4 km in the PT, to ˜5 km in the NW part of the DG, to 10-13 km in the SE part of the profile. Below the DG, at ˜330-530 km distance, we observed an upwarping of the lower crust (with Vp of ˜7.1 km s-1) to ˜25 km depth that represents a rift pillow or mantle underplate. The Moho shallows southeastwards from ˜47 km in the PT to 40-38 km in the DG with mantle velocities of 8.35 and ˜8.25 km s-1 in the PT and DG, respectively. A near-horizontal mantle discontinuity was found beneath BU (a transition zone from the PT to the DG) at the depth of 50-47 km. It dips to the depth of ˜60 km at distances of 360-405 km, similar to the intersecting EUROBRIDGE'97 profile. The crust and upper mantle structure on the GR'13 may reflect varying intensity of rifting in the PDDB from a passive stage in the PT to active rifting

Identification of multiple detrital sources for Otway Supergroup sedimentary rocks: implications for basin models and chronostratigraphic correlations

International Nuclear Information System (INIS)

Mitchell, M.M.

1997-01-01

Correlation of apatite chlorine content (wt%) with apatite fission track age (Ma) from Lower Cretaceous Otway Supergroup sediments at present-day low temperatures, allows identification of two characteristic detrital source regions. Apatites from eroded Palaeozoic basement terrains yield low Cl content (generally 0.5 wt%) and syndepositional fission track ages. Where post-depositional thermal annealing ( > 70 degree C) has significantly reduced the fission track age, provenance information is preserved in the apatite Cl composition alone. In the Otway Supergroup, evidence for contemporaneous volcanism was found in both the Eumeralla Formation (Albian-Aptian), and Crayfish Group (Aptian-Berriasian) in samples located towards the central rift, where less sandy facies dominate. Results suggest that Crayfish Group sediments deposited along the northern margin of the basin were predominantly derived from eroding basement material, while the section located towards the central rift contains a greater proportion of volcanogenic detritus. Evidence from this study suggests that volcanogenic detritus was a distal sediment source throughout the entire early rift phase, prior to the main influx of arc-related volcanogenic material during deposition of the Eumeralla Formation. As diagenesis of volcanogenic sediments significantly reduces porosity and permeability of the sandstones, reservoir quality and petroleum potential may be significantly reduced in the Crayfish Group in deeper parts of the basin where a greater proportion of volcanogenic detritus is suggested. The results presented here provide important information regarding Lower Cretaceous Otway Basin stratigraphy and clearly indicate that this methodology may have wider application. (authors)

Constraining the Thermal History of the Midcontinent Rift System with Clumped Isotopes and Organic Thermal Maturity Indices

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Gallagher, T. M.; Sheldon, N. D.; Mauk, J. L.; Gueneli, N.; Brocks, J. J.

2015-12-01

The Mesoproterozoic (~1.1 Ga) North American Midcontinent Rift System (MRS) has been of widespread interest to researchers studying its economic mineral deposits, continental rifting processes, and the evolution of early terrestrial life and environments. For their age, the MRS rocks are well preserved and have not been deeply buried, yet a thorough understanding of the regional thermal history is necessary to constrain the processes that emplaced the mineral deposits and how post-burial alteration may have affected various paleo-records. To understand the thermal history of the MRS better, this study presents carbonate clumped isotope (Δ47) temperatures from deposits on the north and south sides of the rift. Due to the age of these deposits and known post-depositional processes, uncertainties exist about whether the clumped isotope signature has been reset. To test this, three generations of calcite were analyzed from the Nonesuch Fm. from the White Pine mine in Michigan including: sedimentary limestone beds, early diagenetic carbonate nodules, and hydrothermal calcite veins associated with the emplacement of copper mineralization. Clumped isotope temperatures from the White Pine mine range from 84 to 131°C, with a hydrothermal vein producing the hottest temperature. The clumped isotope temperature range for samples throughout the rift expands to 41-134°C. The hottest temperatures are associated with areas of known copper mineralization, whereas the coolest temperatures are found on the northern arm of the rift in Minnesota, far from known basin-bounding faults. Our hottest temperatures are broadly consistent with preexisting maximum thermal temperature estimates based on clay mineralogy, fluid inclusions, and organic geochemistry data. Clumped isotope results will also be compared to new hydrocarbon maturity data from the Nonesuch Fm., which suggest that bitumen maturities consistently fall within the early oil window across Michigan and Wisconsin.

Godavari rift and its extension towards the east coast of India

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Mishra, D. C.; Gupta, S. B.; Venkatarayudu, M.

1989-09-01

The Godavari basin is divided into three parts namely Godavari-Pranhita, Chintalapudi, and coastal sub-basins. The Godavari-Pranhita sub-basin, located northwest of the Mailaram basement "high", depicts the characteristics of a half graben. The maximum thickness of the Gondwana sediments in this part is approximately 7.5 km. The gravity "highs" along the shoulders and inside the basin around Chinnur are interpreted as subsurface mass excesses along the Moho and within the crust. The Chinnur "high" in the centre of the basin probably represents a remanence of the arial doming characterizing the rift valleys. The Chintalapudi basin is bounded by the Mailaram "high" and the coastal fault towards the south. This part of the basin has faulted margins on both the sides as indicated by sharp gradients in the Bouguer anomaly with 3.0 km of sediments in the central part and associated mass excesses along the Moho and the shoulders suggesting it to be a full graben. The development of this full graben in this region alone is probably constrained by the deep faults on all four sides. The boundary faults defining these sub-basins, the shoulder "highs" and the transverse Mailaram "high" are still associated with occasional seismic activity suggesting some neo-tectonic adjustments along them. The coastal basin, though striking NE-SW, depicts the Gondwana structural trends (NW-SE) in the total magnetic intensity map of the region in alignment with the boundary faults of the Chintalapudi sub-basin to the north. The prominent structures in this coastal part are a depression of approximately 4.5 km and a coastal ridge at a depth of 2-2.5 km as interpreted from the magnetic data for a susceptibility of 0.009 CGS units. The northwest part of the magnetic map of the coastal basin depicts more short-wavelength shallow anomalies which provide compatible tectonics for a remanent direction of magnetization with azimuth equal to 140° and inclination +60°. This direction of magnetization

Syn-rift unconformities punctuating the lower-middle Cambrian transition in the Atlas Rift, Morocco

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Álvaro, J. Javier; Ezzouhairi, Hassan; Clausen, Sébastien; Ribeiro, Maria Luísa; Solá, Ana Rita

2015-01-01

The Cambrian Tamdroust and Bab n’Ali Volcanic Complexes represent two magmatic episodes developed in the latest Ediacaran–Cambrian Atlas Rift of Morocco. Their rifting pulses were accompanied by accumulation of volcanosedimentary edifices (dominated by effusive lava flows in the former and explosive acidic aprons in the latter) associated with active tilting and uplift. Sealing of their peneplaned horst-and-graben palaeotopographies led to the onset of distinct onlapping geometrie...

Neotethyan rifting-related ore occurrences: study of an accretionary mélange complex (Darnó Unit, NE Hungary

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Kiss Gabriella B.

2016-02-01

Full Text Available The geology of the NE Hungarian Darnó Unit is rather complicated, as it is composed mostly of a Jurassic accretionary mélange complex, according to the most recent investigations. The magmatic and sedimentary rock blocks of the mélange represent products of different evolutionary stages of the Neotethys; including Permian and Triassic sedimentary rocks of marine rifting related origin, Triassic pillow basalt of advanced rifting related origin and Jurassic pillow basalt originated in back-arc-basin environment. This small unit contains a copper-gold occurrence in the Permian marly-clayey limestone, an iron enrichment in the Triassic sedimentary succession, a copper-silver ore occurrence in Triassic pillow basalts and a copper ore indication, occurring both in the Triassic and Jurassic pillow basalts. The present study deals with the Cu(-Ag occurrence in the Triassic basalt and the Fe occurrence in the Triassic sedimentary succession. The former shows significant similarities with the Michigan-type mineralizations, while the latter has typical characteristics of the Fe-SEDEX deposits. All the above localities fit well into the new geological model of the investigated area. The mineralizations represent the different evolutionary stages of the Neotethyan rifting and an epigenetic, Alpine metamorphism-related process and their recent, spatially close position is the result of the accretionary mélange formation. Thus, the Darnó Unit represents a perfect natural laboratory for studying and understanding the characteristic features of several different rifting related ore forming processes.

Kanda fault: A major seismogenic element west of the Rukwa Rift (Tanzania, East Africa)

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Vittori, Eutizio; Delvaux, Damien; Kervyn, François

1997-09-01

The NW-SE trending Rukwa Rift, part of the East African Rift System, links the approximately N-S oriented Tanganyika and Nyassa (Malawi) depressions. The rift has a complex half-graben structure, generally interpreted as the result of normal and strike-slip faulting. Morphological and structural data (e.g. fault scarps, faceted spurs, tilting of Quaternary continental deposits, volcanism, seismicity) indicate Late Quaternary activity within the rift. In 1910 an earthquake of M = 7.4 (historically the largest felt in Africa) struck the Rukwa region. The epicentre was located near the Kanda fault, which affects the Ufipa plateau, separating the Rukwa depression from the south-Tanganyika basin. The geomorphic expression of the Kanda fault is a prominent fresh-looking scarp more than 180 km long, from Tunduma to north of Sumbawanga, that strikes roughly NW-SE, and dips constantly northeast. No evidence for horizontal slip was observed. Generally, the active faulting affects a very narrow zone, and is only locally distributed over several subparallel scarps. The height of the scarp progressively decreases towards the northwest, from about 40-50 m to a few metres north of Sumbawanga. Faulted lacustrine deposits exposed in a road cut near Kaengesa were dated as 8340 ± 700 and 13 600 ± 1240 radiocarbon years. These low-energy deposits now hang more than 15 m above the present-day valley floor, suggesting rapid uplift during the Holocene. Due to its high rate of activity in very recent times, the Kanda Fault could have produced the 1910 earthquake. Detailed paleoseismological studies are used to characterize its recent history. In addition, the seismic hazard posed by this fault, which crosses the fast growing town of Sumbawanga, must be seriously considered in urban planning.

Dykes and structures of the NE rift of Tenerife, Canary Islands: a record of stabilisation and destabilisation of ocean island rift zones

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Delcamp, A.; Troll, V. R.; van Wyk de Vries, B.; Carracedo, J. C.; Petronis, M. S.; Pérez-Torrado, F. J.; Deegan, F. M.

2012-07-01

Many oceanic island rift zones are associated with lateral sector collapses, and several models have been proposed to explain this link. The North-East Rift Zone (NERZ) of Tenerife Island, Spain offers an opportunity to explore this relationship, as three successive collapses are located on both sides of the rift. We have carried out a systematic and detailed mapping campaign on the rift zone, including analysis of about 400 dykes. We recorded dyke morphology, thickness, composition, internal textural features and orientation to provide a catalogue of the characteristics of rift zone dykes. Dykes were intruded along the rift, but also radiate from several nodes along the rift and form en échelon sets along the walls of collapse scars. A striking characteristic of the dykes along the collapse scars is that they dip away from rift or embayment axes and are oblique to the collapse walls. This dyke pattern is consistent with the lateral spreading of the sectors long before the collapse events. The slump sides would create the necessary strike-slip movement to promote en échelon dyke patterns. The spreading flank would probably involve a basal decollement. Lateral flank spreading could have been generated by the intense intrusive activity along the rift but sectorial spreading in turn focused intrusive activity and allowed the development of deep intra-volcanic intrusive complexes. With continued magma supply, spreading caused temporary stabilisation of the rift by reducing slopes and relaxing stress. However, as magmatic intrusion persisted, a critical point was reached, beyond which further intrusion led to large-scale flank failure and sector collapse. During the early stages of growth, the rift could have been influenced by regional stress/strain fields and by pre-existing oceanic structures, but its later and mature development probably depended largely on the local volcanic and magmatic stress/strain fields that are effectively controlled by the rift zone growth

The role of inheritance in structuring hyperextended rift systems

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Manatschal, Gianreto; Lavier, Luc; Chenin, Pauline

2015-04-01

A long-standing question in Earth Sciences is related to the importance of inheritance in controlling tectonic processes. In contrast to physical processes that are generally applicable, assessing the role of inheritance suffers from two major problems: firstly, it is difficult to appraise without having insights into the history of a geological system; and secondly all inherited features are not reactivated during subsequent deformation phases. Therefore, the aim of our presentation is to give some conceptual framework about how inheritance may control the architecture and evolution of hyperextended rift systems. We use the term inheritance to refer to the difference between an "ideal" layer-cake type lithosphere and a "real" lithosphere containing heterogeneities and we define 3 types of inheritance, namely structural, compositional and thermal inheritance. Moreover, we assume that the evolution of hyperextended rift systems reflects the interplay between their inheritance (innate/"genetic code") and the physical processes at play (acquired/external factors). Thus, by observing the architecture and evolution of hyperextended rift systems and integrating the physical processes, one my get hints on what may have been the original inheritance of a system. Using this approach, we focus on 3 well-studied rift systems that are the Alpine Tethys, Pyrenean-Bay of Biscay and Iberia-Newfoundland rift systems. For the studied examples we can show that: 1) strain localization on a local scale and during early stages of rifting is controlled by inherited structures and weaknesses 2) the architecture of the necking zone seems to be influenced by the distribution and importance of ductile layers during decoupled deformation and is consequently controlled by the thermal structure and/or the inherited composition of the curst 3) the location of breakup in the 3 examples is not significantly controlled by the inherited structures 4) inherited mantle composition and rift

Factors influencing seismic wave attenuation in the lithosphere in continental rift zones

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А. А. Dobrynina

2017-01-01

Full Text Available Attenuation of seismic waves in the crust and the upper mantle has been studied in three global rift systems: the Baikal rift system (Eurasia, the North Tanzanian divergence zone (Africa and the Basin and Range Province (North America. Using the records of direct and coda waves of regional earthquakes, the single scattering theory [Aki, Chouet, 1975], the hybrid model from [Zeng, 1991] and the approach described in [Wennerberg, 1993], we estimated the seismic quality factor (QC, frequency parameter (n, attenuation coefficient (δ, and total attenuation (QT. In addition, we evaluated the contributions of two components into total attenuation: intrinsic attenuation (Qi, and scattering attenuation (Qsc. Values of QC are strongly dependent on the frequency within the range of 0.2–16 Hz, as well as on the length of the coda processing window. The observed increase of QC with larger lengths of the coda processing window can be interpreted as a decrease in attenuation with increasing depth. Having compared the depth variations in the attenuation coefficient (δ and the frequency (n with the velocity structures of the studied regions, we conclude that seismic wave attenuation changes at the velocity boundaries in the medium. Moreover, the comparison results show that the estimated variations in the attenuation parameters with increasing depth are considerably dependent on utilized velocity models of the medium. Lateral variations in attenuation of seismic waves correlate with the geological and geophysical characteristics of the regions, and attenuation is primarily dependent on the regional seismic activity and regional heat flow. The geological inhomogeneities of the medium and the age of crust consolidation are secondary factors. Our estimations of intrinsic attenuation (Qi and scattering attenuation (Qsc show that in all the three studied regions, intrinsic attenuation is the major contributor to total attenuation. Our study shows that the

a Microgravity Survey to Determine the Extent of AN Andesitic Sill that Intrudes across the Rio Grande River Basin, Rio Grande Rift Valley, Sunland Park, New Mexico

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Baker, L. A.; Shinagel, S.; Villalobos, J. I.; Avila, V.; Montana, C. J.; Kaip, G.

2012-12-01

In Sunland Park, NM, there is an andesite outcrop near the bank of the Rio Grande (called the River Andesite) which does not match the surrounding sedimentary deposition. Studies of the River Andesite by Garcia (1970) indicate the outcrop is petrologically similar to the Muleros Andesite of Mt. Cristo Rey located several km to the south. A limited GPR and magnetic survey conducted by UTEP students in 2008 suggested the River Andesite was part of a dike, although Garcia mapped smaller outcrops of andesite ~300 m west of the river that may be part of the same body. We have recently (June 2012) found large andesite boulders that may be the outcrops Garcia mapped, although it is uncertain whether these boulders are in-situ. We initially collected microgravity and magnetic data in a small region near the river outcrop in December 2011 to determine the extent of the outcrop. Our preliminary modeling of these data showed the river outcrop appeared to merge with a more extensive igneous body at depth. Ground conductivity data collected near the river outcrop in March 2012 suggested that the outcrop impacts groundwater flow and sediment deposition adjacent to the river. From May through July 2012 we have been collecting additional microgravity data on a grid with 100-200 m spacing extending ~ 500 m from both sides of the river outcrop to better determine the extent of the buried andesite body. We also plan to conduct GPR and magnetic surveys near the recently discovered andesite boulders to determine if these are truly in-situ and part of the same igneous body as the river outcrop. Our eventual goal is to determine how extensive the andesite unit is and how it may impact groundwater flow and flooding in this area of growing urbanization.

Grand Bank seabed and shallow subsurface geology in relation to subsea engineering design

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Sonnichsen, G.V.; King, E.L. [Natural Resources Canada, Dartmouth, NS (Canada). Geological Survey of Canada

2005-07-01

An overview of the surficial and subseabed geology of the northeastern section of the Newfoundland Grand Banks was presented with particular reference to the Jeanne d'Arc Basin. The stratigraphy of the upper 100 metres below seafloor has been interpreted from high-resolution seismic reflection data, surficial sediment samples and geotechnical borehole data. This paper described the character and strength properties of nearby seabed sediments and addressed the issue of seabed scour by icebergs, which is the main process threatening subsea facilities. Other potential geohazards such as shallow gas, buried channels and sediment mobility are not considered to be major barriers to offshore development in the Jeanne d'Arc Basin. However, drifting icebergs with large drafts often impact the seabed, producing either linear furrows or circular pits. The constraints to subsea design and construction were identified. It was noted that regional geological characterization is needed to help select the location for offshore platforms as well as routes for excavating trenches for subsea installations for offshore hydrocarbon development. Updated regional surficial and near-seabed stratigraphy is needed to predict foundation conditions beyond ground truth from isolated geotechnical borehole investigations. This paper described the Grand Banks regional setting, regional geology, near-surface sediment in the northeastern Grand Banks, and Quaternary sediments in the northeastern Grand Banks with reference to the Grand Banks Drift, Adolphus Sand, and the Grand Banks Sand and Gravel Formation. Risk assessments have shown that well heads and manifolds should be installed below the seabed in order to avoid damage by seabed-scouring icebergs and that the design scour depth should be re-examined for future subsea development. It was suggested that more emphasis on gathering multibeam bathymetric data and repetitive mapping of the seabed will better define scour risk. 57 refs., 3

An integrated geological and geophysical study of the Uinta Mountains, Utah, Colorado and a geophysical study on Tamarix in the Rio Grande River basin, West Texas

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Khatun, Salma

2008-07-01

comprehensive picture of the structures in the study area. These models show that the Uinta uplift is a single sedimentary block with numerous thrust faults on the northern and southern flanks of the uplift. These models also reveal the fact that the thickness of the crust is quite variable in the study area. This is also supported by the crustal thickness map constructed for this study from seismic and receiver function information. Magnetic maps show that the Proterozoic sedimentary package known as Uinta Mountain Group extends into the Basin and Range and indicates its link with the ancient rift margin in the Western United States. Findings of this research are correlated to earlier studies and placed in a broader context. Finally an analogy is made between the Uinta aulacogen, the Southern Oklahoma aulacogen and the Dniepr-Donets aulacogen in Ukraine. This discussion focuses light on the mechanism that led to the Uinta's development from a failed rift to an uplift. Part two of this research examined the effect of saltcedar (Tamarix sp) on water and soil properties in the Rio Grande River valley in West Texas. Tamarix is a woody phreatophyte (water-loving plant) common in riparian habitats. The presence of Tamarix in a river system raises concerns about its effect on water quality because it can increase the salinity of water and surrounding soil and it reduces stream flow. Geophysical electrical techniques were used to track soil salinity and moisture changes caused by Tamarix, as well as to determine how soil salinity and moisture properties are altered when Tamarix is eradicated from the region. These techniques allowed more rapid in-situ assessment of the soil properties than the conventional method of removing soil and water samples for analysis. This study was focused on the influence of Tamarix on soil properties and hydrology at the subsurface at four sites in the Rio Bosque Wetlands Park, El Paso, Texas Two sites had flourishing Tamarix and two others were areas

Sedimentary structure and tectonic setting of the abyssal basins adjoining the southeast part of the Ontong Java Plateau, western Pacific Ocean

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Shimizu, S.; Masato, N.; Miura, S.; Suetsugu, D.

2017-12-01

Ontong Java Plateau(OJP) in the western Pacific Ocean is one of the largest oceanic plateau in the world. Radioactive ages of drilling samples indicate that the most part of the OJP was emplaced about 122 Ma (Mahoney et al., 1993). Taylor (2006) proposed that the OJP formed as a single large volcanic province together with the Manihiki and Hikurangi plateaus. OJP is surrounding by East Mariana, Pigafetta, Nauru, Ellice, Stewart, and Lyra basins. The East Mariana and Pigafetta basins were formed at the Pacific-Izanagi ridge and the Nauru basin was formed at Pacific-Phoenix ridges (Nakanishi et al., 1992). The tectonic history of the Ellice, Stewart, and Lyra basins is still unknown because of lack of magnetic anomaly lineations. Tectonic setting during the OJP formation is thus a matter of controversy. To expose the tectonic setting of the Ellice, Stewart, and Lyra basins, we conducted the Multi-Channel Seismic (MCS) survey in the basins during the research cruise by R/V Mirai of JAMSTEC in 2014. We present our preliminary results of the MCS survey in the Stewart basin(SB) and Ellice Basin(EB). After the regular data processing, we compared the seismic facies of MCS profile with DSDP Site 288 and ODP Site 1184 to assign ages to seismic reflectors. Our processing exposed several remarkable structures in the basins. The graben structures deformed only the igneous basement in the northwestern and northeastern and southwestern margins of the SB. This suggests the graben structures were formed before sedimentary layer deposited. Taylor (2006) proposed that the basin was formed by the NW-SE rifting during the separation of OJP and Manihiki Plateau around 120 Ma. Neal (1997) proposed that the NE-SW rifting formed the basin around 80 Ma. Our study supports the rifting model proposed by Neal et al. (1997) because the displacement of graben in northeastern and southwestern margins of the SB is larger than that in northwestern of the SB. We found several igneous diapirs in the

Sedimentary facies and depositional environments of early Mesozoic Newark Supergroup basins, eastern North America

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Smoot, J.P.

1991-01-01

south where coal beds are preserved, and more arid in the north where evaporites and eolian deposits are common. Fluctuations in paleoclimate that caused lake levels to rise and fall in hydrologically closed basins are preserved as lacustrine cycles of various scales, including major shifts in the Late Triassic from a wet Carnian to an arid Norian. In contrast, fluvial deposits were mainly formed in response to the tectonic evolution of the basins, but to some extent also reflect climatic changes. The Newark Supergroup illustrates the complexity of rift-basin sedimentation and the problems that may arise from using a single modern analog for sedimentary deposition spanning millions of years. It also shows that a tremendous wealth of depositional, climatic, and tectonic information is preserved in ancient rift-basin deposits which can be recovered if the depositional processes of modern rift-basin deposits are understood. ?? 1991.

Cenozoic sedimentation in the Mumbai Offshore Basin: Implications for tectonic evolution of the western continental margin of India

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Nair, Nisha; Pandey, Dhananjai K.

2018-02-01

Interpretation of multichannel seismic reflection data along the Mumbai Offshore Basin (MOB) revealed the tectonic processes that led to the development of sedimentary basins during Cenozoic evolution. Structural interpretation along three selected MCS profiles from MOB revealed seven major sedimentary sequences (∼3.0 s TWT, thick) and the associated complex fault patterns. These stratigraphic sequences are interpreted to host detritus of syn- to post rift events during rift-drift process. The acoustic basement appeared to be faulted with interspaced intrusive bodies. The sections also depicted the presence of slumping of sediments, subsidence, marginal basins, rollover anticlines, mud diapirs etc accompanied by normal to thrust faults related to recent tectonics. Presence of upthrusts in the slope region marks the locations of local compression during collision. Forward gravity modeling constrained with results from seismic and drill results, revealed that the crustal structure beneath the MOB has undergone an extensional type tectonics intruded with intrusive bodies. Results from the seismo-gravity modeling in association with litholog data from drilled wells from the western continental margin of India (WCMI) are presented here.

Tectonic evolution of the Paranoá basin: New evidence from gravimetric and stratigraphic data

Science.gov (United States)

Martins-Ferreira, Marco Antonio Caçador; Campos, José Eloi Guimarães; Von Huelsen, Monica Giannoccaro

2018-06-01

Field gravimetric and stratigraphic surveys were conducted with the aim to constraint the mechanisms responsible for the initiation of the Stenian-Tonian Paranoá basin, central Brazil, a subject not yet studied in detail. The Paranoá Group crops out in the external zone of the Brasília Belt, a Neoproterozoic orogen in the western margin of the São Francisco Craton. Detailed geological mapping confirmed the existence of a regional scale fault that controlled sedimentation of the Paranoá Group during the deposition of its basal formations, revealing important details about basin initiation and early evolution. Gravimetric modeling indicates the existence of paleorift structures beneath the Paranoá sequence in the study area. Results from both stratigraphic and gravimetric surveys show strong evidence of mechanical subsidence by faulting during basin initiation. Unsorted, angular, clasts cut by quartz veins and brecciated boulders present in the basal conglomerate, support this hypothesis. Basin initiation faults coincide with deeper paleorift faults and are thus interpreted as reactivations of the older Statherian Araí Rift. The reactivations favored an initial regime of mechanical subsidence, dominated by the development of epirogenic arches subsiding at different rates. Apart from faulting activity, the post-basal sequence presents no evidence of rift environment in the strict sense. Besides, the great lateral continuity and relatively constant thickness of facies, indicate that an initial mechanic subsidence rapidly gave way to flexural subsidence during subsequent stages of basin evolution. The Paranoá Group do not present reliable characteristics that would allow its strict classification as a passive margin. Its main stratigraphic characteristics, tectonic location and basement architecture, indicate that the Paranoá Group was deposited in a cratonic margin basin, and may have been either connected to a passive margin basin at times of sea level rise

Crustal layering and gravity highs in the Midcontinent of North America - implications for the formation of the Illinois Basin

Science.gov (United States)

Gilbert, H. J.; Boschelli, J.; Pavlis, G. L.; Hamburger, M. W.; Marshak, S.; Chen, C.; Yang, X.; DeLucia, M. S.; Larson, T. H.; Rupp, J.

2017-12-01

The emerging picture of crustal and lithospheric structure beneath the North American cratonic platform resulting from recent increases in the resolution of seismic studies is revealing a scale of complexity and heterogeneity not previously recognized. Examples of novel images of the lithosphere allowed by this increased sampling come from the results of the OIINK project, an EarthScope FlexArray experiment. OIINK data provides new insight into tectonic relationships among the Reelfoot Rift, Ozark Plateau, Rough Creek Graben, and Illinois Basin. Making use of ambient-noise tomography from data recorded by the OIINK Array and surrounding stations we produced a new shear-wave velocity model of the region. This model indicates detailed variations in crustal wavespeeds align with the regional tectonic features. Beyond corroborating previous observations of high-speed material in the mid- to lower crust of the southern Illinois Basin, this new model demonstrates that these anomalous velocities extend continuously from the Reelfoot, beneath the Mississippi Embayment, into southern Indiana. This model also includes a separate area characterized by a similarly thickened layer of increased velocities in the middle and lower crust beneath the LaSalle Deformation Belt, a north-south band of faults and folds that runs along the axis of the Illinois Basin. At depths of about 20 km, the top of these areas of thickened high-velocity crust align with a midcrustal discontinuity identified by receiver functions. Additionally, the lateral extent of these structures correlates with regions of increased Bouguer gravity. If the high-velocity structures contain high-density material, this configuration provides an explanation for the source of these positive gravity anomalies. These observations support a model in which Late Proterozoic rifting beneath the region of the Illinois Basin provided an opportunity for high-density material to enter the crust as residuum from melt extraction

Wildlife Mitigation and Restoration for Grand Coulee Dam: Blue Creek Project, Phase 1.

Energy Technology Data Exchange (ETDEWEB)

Merker, Christopher

1993-04-01

This report is a recommendation from the Spokane Tribe to the Northwest Power Planning Council (NPPC) for partial mitigation for the extensive wildlife and wildlife habitat losses on the Spokane Indian Reservation caused by the construction of Grand Coulee Dam. NPPC`s interim wildlife goal over the next 7 years for the Columbia hydropower system, is to protect, mitigate and enhance approximately 35% basin wide of the lost habitat units. Grand Coulee Dam had the greatest habitat losses of any Dams of the Wildlife Rule.

Groundwater fluoride enrichment in an active rift setting: Central Kenya Rift case study

Energy Technology Data Exchange (ETDEWEB)

Olaka, Lydia A., E-mail: lydiaolaka@gmail.com [Department of Geology, University of Nairobi, P.O Box 30197, Nairobi (Kenya); Wilke, Franziska D.H. [Geoforschungs Zentrum, Telegrafenberg, 14473 Potsdam (Germany); Olago, Daniel O.; Odada, Eric O. [Department of Geology, University of Nairobi, P.O Box 30197, Nairobi (Kenya); Mulch, Andreas [Senckenberg Biodiversity and Climate Research Centre, Senckenberganlage 25, 60325 Frankfurt (Germany); Institut für Geowissenschaften, Goethe Universität Frankfurt, Altenhöferallee 1, 60438 Frankfurt (Germany); Musolff, Andreas [UFZ-Helmholtz-Centre for Environmental Research, Department of Hydrogeology, Permoserstr. 15, 04318 Leipzig (Germany)

2016-03-01

Groundwater is used extensively in the Central Kenya Rift for domestic and agricultural demands. In these active rift settings groundwater can exhibit high fluoride levels. In order to address water security and reduce human exposure to high fluoride in drinking water, knowledge of the source and geochemical processes of enrichment are required. A study was therefore carried out within the Naivasha catchment (Kenya) to understand the genesis, enrichment and seasonal variations of fluoride in the groundwater. Rocks, rain, surface and groundwater sources were sampled for hydrogeochemical and isotopic investigations, the data was statistically and geospatially analyzed. Water sources have variable fluoride concentrations between 0.02–75 mg/L. 73% exceed the health limit (1.5 mg/L) in both dry and wet seasons. F{sup −} concentrations in rivers are lower (0.2–9.2 mg/L) than groundwater (0.09 to 43.6 mg/L) while saline lake waters have the highest concentrations (0.27–75 mg/L). The higher values are confined to elevations below 2000 masl. Oxygen (δ{sup 18}O) and hydrogen (δD) isotopic values range from − 6.2 to + 5.8‰ and − 31.3 to + 33.3‰, respectively, they are also highly variable in the rift floor where they attain maximum values. Fluoride base levels in the precursor vitreous volcanic rocks are higher (between 3750–6000 ppm) in minerals such as cordierite and muscovite while secondary minerals like illite and kaolinite have lower remnant fluoride (< 1000 ppm). Thus, geochemical F{sup −} enrichment in regional groundwater is mainly due to a) rock alteration, i.e. through long residence times and natural discharge and/or enhanced leakages of deep seated geothermal water reservoirs, b) secondary concentration fortification of natural reservoirs through evaporation, through reduced recharge and/or enhanced abstraction and c) through additional enrichment of fluoride after volcanic emissions. The findings are useful to help improve water management

Frequency and sources of basin floor turbidites in alfonso basin, Gulf of California, Mexico: Products of slope failures

Science.gov (United States)

Gonzalez-Yajimovich, Oscar E.; Gorsline, Donn S.; Douglas, Robert G.

2007-07-01

Alfonso Basin is a small margin basin formed by extensional tectonics in the actively rifting, seismically active Gulf of California. The basin is centered at 24°40' N and 110° 38' W, and is a closed depression (maximum depth 420 m) with an effective sill depth of about 320 m (deepest sill), a width of 20 km and length of 25 km. Basin floor area below a depth of 350 m is about 260 km 2. The climate is arid to semiarid but was wetter during the early (ca. 10,000-7000 Calendar years Before Present [BP]) and middle Holocene (ca. 7000-4000 Cal. Years BP). Basin-wide turbidity currents reach the floor of Alfonso Basin at centennial to millennial intervals. The peninsular drainages tributary to the basin are small and have maximum flood discharges of the order of 10 4m 3. The basin-floor turbidites thicker than 1 cm have volumes of the order of 10 6m 3 to 10 8m 3 and require a much larger source. The largest turbidite seen in our cores is ca. 1 m thick in the central basin floor and was deposited 4900 Calendar Years Before Present (BP). Two smaller major events occurred about 1500 and 2800 Cal. Years BP. Seismicity over the past century of record shows a clustering of larger epicenters along faults forming the eastern Gulf side of Alfonso Basin. In that period there have been four earthquakes with magnitudes above 7.0 but all are distant from the basin. Frequency of such earthquakes in the basin vicinity is probably millennial. It is concluded that the basin-wide turbidites thicker than 1 cm must be generated by slope failures on the eastern side of the basin at roughly millennial intervals. The thin flood turbidites have a peninsular source at centennial frequencies.

Rift-drift transition in the Dangerous Grounds, South China Sea

Science.gov (United States)

Peng, Xi; Shen, Chuanbo; Mei, Lianfu; Zhao, Zhigang; Xie, Xiaojun

2018-04-01

The South China Sea (SCS) has a long record of rifting before and after subsequent seafloor spreading, affecting the wide continent of the Dangerous Grounds, and its scissor-shape opening manner results in the rifting structures that vary along this margin. Some 2000 km of regional multichannel seismic data combined with borehole and dredge data are interpreted to analyze the multistage rifting process, structural architecture and dynamic evolution across the entire Dangerous Grounds. Key sequence boundaries above the Cenozoic basement are identified and classified into the breakup unconformity and the rift end unconformity, which consist of the rift-related unconformities. Reflector T70 in the east of the Dangerous Grounds represents the breakup unconformity, which is likely corresponding to the spreading of the East Subbasin. T60 formed on the top of carbonate platform is time equivalent to the spreading of the Southwest Subbasin, marking the breakup unconformity of the central Dangerous Grounds. The termination of the spreading of the SCS is manifested by the rift end unconformity of T50 in the southwest and the final rift occurring in the northwest of the Dangerous Grounds is postponed to the rift end unconformity of T40. On the basis of the stratigraphic and structural analysis, distinct segments in the structural architecture of the syn-rift units and the ages of rift-drift transition show obvious change from the proximal zone to the distal zone. Three domains, which are the Reed Bank-Palawan Rift domain, the Dangerous Grounds Central Detachment domain and Nam Con Son Exhumation domain, reflect the propagation of the margin rifting developed initially by grabens formed by high angle faults, then large half-grabens controlled by listric faults and detachments and finally rotated fault blocks in the hyper-extended upper crust associated with missing lower crust or exhumed mantle revealing a migration and stepwise rifting process in the south margin of the SCS.

THE BAIKAL RIFT: PLIOCENE (MIOCENE – QUATERNARY EPISODE OR PRODUCT OF EXTENDED DEVELOPMENT SINCE THE LATE CRETACEOUS UNDER VARIOUS TECTONIC FACTORS. A REVIEW

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V. D. Mats

2015-01-01

Full Text Available The article reviews three typical concepts concerning the age of the Baikal rift (BR which development is still underway: 5 Ma (the BR development start in the Late Pliocene, 30 Ma (Miocene or Oligocene, and 60–70 Ma (the Late Cretaceous. Under the concept of the young BR age (Pliocene–Quaternary [Artyushkov, 1993; Nikolaev et al., 1985; Buslov, 2012], according to E.V. Artyushkov, BR is not a rift, but a graben due to the fact that the pre‐Pliocene structure of BR does not contain any elements that would be indicative of tensile stresses. However, field studies reported in [Lamakin, 1968; Ufimtsev, 1993; Zonenshain et al., 1995; Mats, 1993, 2012; Mats et al., 2001] have revealed that extension structures, such as tilted blocks and listric faults, are abundant in the Baikal basin (BB, and thus do not supportE.V. Artyushkov’s argumentation. The opinion that BR is young is shared by M.M. Buslov [2012]; he refers to studies of  Central Asia and states that only the Pliocene‐Quaternary structure of BB is a rift, while the oldest Cenozoic structures (Upper Cretaceous – Miocene are just fragments of the large Cenozoic Predbaikalsky submontane trough (PBT which are not related to the rift. However, the coeval Cenozoic lithological compositions, thicknesses of sediment layers and types of tectonic structures in PBT and BB have nothing in common. Across the area separating PBT and BB, there are no sediments or structures to justify a concept that BR and PBT may be viewed as composing a single region with uniform structures and formations. The idea of the Pliocene‐Quaternary age of BR should be rejected as it contradicts with the latest geological and geophysical data. Seismic profiling in BB has revealed the syn‐rift sedimentary bed which thickness exceeds 7.5 km. Results of drilling through the 600‐metre sedimentary sequence of Lake Baikal suggest the age of 8.4 Ma [Horiuchi et al., 2004], but M.M. Buslov believes

What's next? Lesser explored basins : offshore Newfoundland and Labrador

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Wright, J.A. [Memorial Univ. of Newfoundland, St. John' s, NL (Canada). Dept. of Earth Sciences

2005-07-01

A review of the sedimentary basins of Atlantic Canada was presented with particular focus on offshore basins in the southern Grand Banks, the Gulf of St. Lawrence and the Labrador Shelf. The exploration history and petroleum geology of the South Whale Basin in southern Grand Banks was discussed with reference to salt diapirism, salt tectonism and gas prone source rocks. Early exploration of the Anticosti and Magdalen Basins, 2 basins in the Gulf of St. Lawrence, revealed a proven petroleum system. However, there has been very limited modern exploration in the area. A detailed geologic review of Appalachian Ordovician carbonate producers was also presented. The early exploration phase of the Labrador Shelf from 1975 to 1982 confirmed a petroleum system. However, the discoveries offered poor economics due to the high cost of recovery. Five gas discoveries in the Hopedale Basin in Labrador were made in the early 1970s, with an estimated development threshold of 6 to 7 Tcf marketable gas reserves. A new outlook for the Labrador Shelf has been provided due to new and extensive seismic data, multiple play concepts, gas takeaway systems such as marine CNG, and strong economics for more than 8 Tcf of gas reserves. It was concluded that 3 new basins with proven petroleum systems in Atlantic Canada are both accessible and close to markets. figs.

Some geodynamic aspects of the Krishna-Godavari basin, east coast of India

Science.gov (United States)

Murthy, K. S. R.; Subrahmanyam, A. S.; Lakshminarayana, S.; Chandrasekhar, D. V.; Rao, T. C. S.

1995-06-01

Detailed analysis of magnetic data of the Krishna-Godavari offshore basin provides new information on the evolution of this basin since the breakup of Peninsular India in the late Jurassic from the erstwhile Gondwanaland. The results establish the offshore extension of two major onshore cross trends viz, the Chintalapudi and Avanigadda cross trends (CCT and ACT). While the onshore basin is characterized by NE-SW ridges and depressions, the offshore basin is divided essentially into three segments by these two NW-SE cross trends. The Ocean-Continent Boundary (OCB), located at the foot of the continental slope of this region, appears to be the seaward limit of these two cross trends. An isolated source of high magnetic intensity (a hot spot?) is identified near the OCB of Machilipatnam, confined between the two cross trends. The Pranhita Godavari Gondwana graben, located north of CCT, extends into the offshore along two faulted cross trends, viz, the CCT and the newly identified Yanam cross trend. The weak magnetic signature associated with this graben at greater depths in the offshore is probably due to flexural subsidence. Preliminary reconstruction of the evolutionary stages of this basin suggests that the hot spot (Marion ?) with its trace located at the OCB represents the earliest stage of the breakup of east coast of India in the late Jurassic (126 Ma), although the relation between this hotspot and the two cross trends on either side remains unresolved. The breakup was associated with rift phase volcanism, as evidenced by the inferred dyke intrusions in the Nizampatnam bay in the southern part of the basin. The Pranhita Godavari Gondwana graben formed due to this split, pull apart and the subsequent downwarping of the eastern continental margin, appears to be much deeper and wider in the offshore. The NE-SW ridges (Tanuku, Kaza and Bapatla) and the depressions (East and West Godavari and Krishna) of the onshore basin are a consequence of the post-rift vertical

Impact of rheological layering on rift asymmetry

Science.gov (United States)

Jaquet, Yoann; Schmalholz, Stefan M.; Duretz, Thibault

2015-04-01

Although numerous models of rift formation have been proposed, what triggers asymmetry of rifted margins remains unclear. Parametrized material softening is often employed to induce asymmetric fault patterns in numerical models. Here, we use thermo-mechanical finite element models that allow softening via thermal weakening. We investigate the importance of lithosphere rheology and mechanical layering on rift morphology. The numerical code is based on the MILAMIN solver and uses the Triangle mesh generator. Our model configuration consists of a visco-elasto-platic layered lithosphere comprising either (1) only one brittle-ductile transition (in the mantle) or (2) three brittle-ductile transitions (one in the upper crust, one in the lower crust and one in the mantle). We perform then two sets of simulations characterized by low and high extensional strain rates (5*10-15 s-1, 2*10-14 s-1). The results show that the extension of a lithosphere comprising only one brittle-ductile transition produces a symmetric 'neck' type rift. The upper and lower crusts are thinned until the lithospheric mantle is exhumed to the seafloor. A lithosphere containing three brittle-ductile transitions favors strain localization. Shear zones at different horizontal locations and generated in the brittle levels of the lithosphere get connected by the weak ductile layers. The results suggest that rheological layering of the lithosphere can be a reason for the generation of asymmetric rifting and subsequent rift morphology.

Geometry and evolution of low-angle normal faults (LANF) within a Cenozoic high-angle rift system, Thailand: Implications for sedimentology and the mechanisms of LANF development

Science.gov (United States)

Morley, Chris K.

2009-10-01

At least eight examples of large (5-35 km heave), low-angle normal faults (LANFs, 20°-30° dip) occur in the Cenozoic rift basins of Thailand and laterally pass into high-angle extensional fault systems. Three large-displacement LANFs are found in late Oligocene-Miocene onshore rift basins (Suphan Buri, Phitsanulok, and Chiang Mai basins), they have (1) developed contemporaneous with, or after the onset of, high-angle extension, (2) acted as paths for magma and associated fluids, and (3) impacted sedimentation patterns. Displacement on low-angle faults appears to be episodic, marked by onset of lacustrine conditions followed by axial progradation of deltaic systems that infilled the lakes during periods of low or no displacement. The Chiang Mai LANF is a low-angle (15°-25°), high-displacement (15-35 km heave), ESE dipping LANF immediately east of the late early Miocene Doi Inthanon and Doi Suthep metamorphic core complexes. Early Cenozoic transpressional crustal thickening followed by the northward motion of India coupled with Burma relative to east Burma and Thailand (˜40-30 Ma) caused migmatization and gneiss dome uplift in the late Oligocene of the core complex region, followed by LANF activity. LANF displacement lasted 4-6 Ma during the early Miocene and possibly transported a late Oligocene-early Miocene high-angle rift system 35 km east. Other LANFs in Thailand have lower displacements and no associated metamorphic core complexes. The three LANFs were initiated as low-angle faults, not by isostatic rotation of high-angle faults. The low-angle dips appear to follow preexisting low-angle fabrics (thrusts, shear zones, and other low-angle ductile foliations) predominantly developed during Late Paleozoic and early Paleogene episodes of thrusting and folding.

Linking the tectonic evolution with fluid history in magma-poor rifted margins: tracking mantle- and continental crust-related fluids

Science.gov (United States)

Pinto, V. H. G.; Manatschal, G.; Karpoff, A. M.

2014-12-01

The thinning of the crust and the exhumation of subcontinental mantle is accompanied by a series of extensional detachment faults. Exhumation of mantle and crustal rocks is intimately related to percolation of fluids along detachment faults leading to changes in mineralogy and chemistry of the mantle, crustal and sedimentary rocks. Field observation, analytical methods, refraction/reflection and well-core data, allowed us to investigate the role of fluids in the Iberian margin and former Alpine Tethys distal margins and the Pyrenees rifted system. In the continental crust, fluid-rock interaction leads to saussuritization that produces Si and Ca enriched fluids found in forms of veins along the fault zone. In the zone of exhumed mantle, large amounts of water are absorbed in the first 5-6 km of serpentinized mantle, which has the counter-effect of depleting the mantle of elements (e.g., Si, Ca, Mg, Fe, Mn, Ni and Cr) forming mantle-related fluids. Using Cr-Ni-V and Fe-Mn as tracers, we show that in the distal margin, mantle-related fluids used detachment faults as pathways and interacted with the overlying crust, the sedimentary basin and the seawater, while further inward parts of the margin, continental crust-related fluids enriched in Si and Ca impregnated the fault zone and may have affected the sedimentary basin. The overall observations and results enable us to show when, where and how these interactions occurred during the formation of the rifted margin. In a first stage, continental crust-related fluids dominated the rifted systems. During the second stage, mantle-related fluids affected the overlying syn-tectonic sediments through direct migration along detachment faults at the future distal margin. In a third stage, these fluids reached the seafloor, "polluted" the seawater and were absorbed by post-tectonic sediments. We conclude that a significant amount of serpentinization occurred underneath the thinned continental crust, that the mantle-related fluids

On the role of mantle depletion and small-scale convection in post rift basin evolution (Invited)

Science.gov (United States)

Petersen, K.; Nielsen, S. B.

2013-12-01

Subsidence and heat flow evolution of the oceanic lithosphere appears to be consistent with the conductive cooling of a ~100 km plate overlying asthenospheric mantle of constant entropy. The physical mechanism behind plate-like subsidence has been suggested to be the result of small-scale convective instabilities which transport heat energy to the base of the lithosphere and cause an eventual departure from half space-like cooling by inhibiting subsidence of old ocean floor and causing an asymptotic surface heat flow of ~50 mW/m^2. Here, we conduct a number of numerical thermo-mechanical experiments of oceanic lithosphere cooling for different models of temperature- and pressure-dependent viscosity. We show that uniform (P, T-dependent) mantle viscosity cannot both explain half space-like subsidence for young (50 mW/m^2) surface heat flow which is observed above old (>100 Myr) lithosphere. The latter requires vigorous sub lithospheric convection which would lead to early (~1Myr) onset of convective instability at shallow depth (paradox, we employ models which account for the density decrease and viscosity increase due to depletion during mid-ocean ridge melting. We demonstrate that the presence of a mantle restite layer within the lithosphere hinders convection at shallow depth and therefore promotes plate-like cooling. A systematic parameter search among 280 different numerical experiments indicates that models with 60-80 km depletion thickness minimize misfit with subsidence and heat flow data. This is consistent with existing petrological models of mid-ocean ridge melting. Our models further indicate that the post-rift subsidence pattern where little or no melting occurred during extension (e.g. non-volcanic margins and continental rifts) may differ from typical oceanic plate-like subsidence by occurring at a nearly constant rate rather than at an exponentially decaying rate. Model comparison with subsidence histories inferred from backstripping analysis implies

Fault kinematics and tectonic stress in the seismically active Manyara Dodoma Rift segment in Central Tanzania Implications for the East African Rift

Science.gov (United States)

Macheyeki, Athanas S.; Delvaux, Damien; De Batist, Marc; Mruma, Abdulkarim

2008-07-01

The Eastern Branch of the East African Rift System is well known in Ethiopia (Main Ethiopian Rift) and Kenya (Kenya or Gregory Rift) and is usually considered to fade away southwards in the North Tanzanian Divergence, where it splits into the Eyasi, Manyara and Pangani segments. Further towards the south, rift structures are more weakly expressed and this area has not attracted much attention since the mapping and exploratory works of the 1950s. In November 4, 2002, an earthquake of magnitude Mb = 5.5 struck Dodoma, the capital city of Tanzania. Analysis of modern digital relief, seismological and geological data reveals that ongoing tectonic deformation is presently affecting a broad N-S trending belt, extending southward from the North Tanzanian Divergence to the region of Dodoma, forming the proposed "Manyara-Dodoma Rift segment". North of Arusha-Ngorongoro line, the rift is confined to a narrow belt (Natron graben in Tanzania) and south of it, it broadens into a wide deformation zone which includes both the Eyasi and Manyara grabens. The two-stage rifting model proposed for Kenya and North Tanzania also applies to the Manyara-Dodoma Rift segment. In a first stage, large, well-expressed topographic and volcanogenic structures were initiated in the Natron, Eyasi and Manyara grabens during the Late Miocene to Pliocene. From the Middle Pleistocene onwards, deformations related to the second rifting stage propagated southwards to the Dodoma region. These young structures have still limited morphological expressions compared to the structures formed during the first stage. However, they appear to be tectonically active as shown by the high concentration of moderate earthquakes into earthquake swarms, the distribution of He-bearing thermal springs, the morphological freshness of the fault scarps, and the presence of open surface fractures. Fault kinematic and paleostress analysis of geological fault data in basement rocks along the active fault lines show that recent

Seismicity of the Earth 1900-2013 East African Rift

Science.gov (United States)

Hayes, Gavin P.; Jones, Eric S.; Stadler, Timothy J.; Barnhart, William D.; McNamara, Daniel E.; Benz, Harley M.; Furlong, Kevin P.; Villaseñor, Antonio; Hayes, Gavin P.; Jones, Eric S.; Stadler, Timothy J.; Barnhart, William D.; McNamara, Daniel E.; Benz, Harley M.; Furlong, Kevin P.; Villaseñor, Antonio

2014-01-01

The East African Rift system (EARS) is a 3,000-km-long Cenozoic age continental rift extending from the Afar triple junction, between the horn of Africa and the Middle East, to western Mozambique. Sectors of active extension occur from the Indian Ocean, west to Botswana and the Democratic Republic of the Congo (DRC). It is the only rift system in the world that is active on a continent-wide scale, providing geologists with a view of how continental rifts develop over time into oceanic spreading centers like the Mid-Atlantic Ridge.

Geologic map and cross sections of the Embudo Fault Zone in the Southern Taos Valley, Taos County, New Mexico

Science.gov (United States)

Bauer, Paul W.; Kelson, Keith I.; Grauch, V.J.S.; Drenth, Benjamin J.; Johnson, Peggy S.; Aby, Scott B.; Felix, Brigitte

2016-01-01

The southern Taos Valley encompasses the physiographic and geologic transition zone between the Picuris Mountains and the San Luis Basin of the Rio Grande rift. The Embudo fault zone is the rift transfer structure that has accommodated the kinematic disparities between the San Luis Basin and the Española Basin during Neogene rift extension. The eastern terminus of the transfer zone coincides with the intersection of four major fault zones (Embudo, Sangre de Cristo, Los Cordovas, and Picuris-Pecos), resulting in an area of extreme geologic and hydrogeologic complexities in both the basin-fill deposits and the bedrock. Although sections of the Embudo fault zone are locally exposed in the bedrock of the Picuris Mountains and in the late Cenozoic sedimentary units along the top of the Picuris piedmont, the full proportions of the fault zone have remained elusive due to a pervasive cover of Quaternary surficial deposits. We combined insights derived from the latest geologic mapping of the area with deep borehole data and high-resolution aeromagnetic and gravity models to develop a detailed stratigraphic/structural model of the rift basin in the southern Taos Valley area. The four fault systems in the study area overlap in various ways in time and space. Our geologic model states that the Picuris-Pecos fault system exists in the basement rocks (Picuris formation and older units) of the rift, where it is progressively down dropped and offset to the west by each Embudo fault strand between the Picuris Mountains and the Rio Pueblo de Taos. In this model, the Miranda graben exists in the subsurface as a series of offset basement blocks between the Ponce de Leon neighborhood and the Rio Pueblo de Taos. In the study area, the Embudo faults are pervasive structures between the Picuris Mountains and the Rio Pueblo de Taos, affecting all geologic units that are older than the Quaternary surficial deposits. The Los Cordovas faults are thought to represent the late Tertiary to

Analysis of ancient-river systems by 3D seismic time-slice technique: A case study in northeast Malay Basin, offshore Terengganu, Malaysia

Energy Technology Data Exchange (ETDEWEB)

Sulaiman, Noorzamzarina; Hamzah, Umar; Samsudin, Abdul Rahim [Geology Programme, School of Environmental and Natural Resource Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia)

2014-09-03

Fluvial sandstones constitute one of the major clastic petroleum reservoir types in many sedimentary basins around the world. This study is based on the analysis of high-resolution, shallow (seabed to 500 m depth) 3D seismic data which generated three-dimensional (3D) time slices that provide exceptional imaging of the geometry, dimension and temporal and spatial distribution of fluvial channels. The study area is in the northeast of Malay Basin about 280 km to the east of Terengganu offshore. The Malay Basin comprises a thick (> 8 km), rift to post-rift Oligo-Miocene to Pliocene basin-fill. The youngest (Miocene to Pliocene), post-rift succession is dominated by a thick (1–5 km), cyclic succession of coastal plain and coastal deposits, which accumulated in a humid-tropical climatic setting. This study focuses on the Pleistocene to Recent (500 m thick) succession, which comprises a range of seismic facies analysis of the two-dimensional (2D) seismic sections, mainly reflecting changes in fluvial channel style and river architecture. The succession has been divided into four seismic units (Unit S1-S4), bounded by basin-wide strata surfaces. Two types of boundaries have been identified: 1) a boundary that is defined by a regionally-extensive erosion surface at the base of a prominent incised valley (S3 and S4); 2) a sequence boundary that is defined by more weakly-incised, straight and low-sinuosity channels which is interpreted as low-stand alluvial bypass channel systems (S1 and S2). Each unit displays a predictable vertical change of the channel pattern and scale, with wide low-sinuosity channels at the base passing gradationally upwards into narrow high-sinuosity channels at the top. The wide variation in channel style and size is interpreted to be controlled mainly by the sea-level fluctuations on the widely flat Sunda land Platform.

Analysis of ancient-river systems by 3D seismic time-slice technique: A case study in northeast Malay Basin, offshore Terengganu, Malaysia

Science.gov (United States)

Sulaiman, Noorzamzarina; Hamzah, Umar; Samsudin, Abdul Rahim

2014-09-01

Fluvial sandstones constitute one of the major clastic petroleum reservoir types in many sedimentary basins around the world. This study is based on the analysis of high-resolution, shallow (seabed to 500 m depth) 3D seismic data which generated three-dimensional (3D) time slices that provide exceptional imaging of the geometry, dimension and temporal and spatial distribution of fluvial channels. The study area is in the northeast of Malay Basin about 280 km to the east of Terengganu offshore. The Malay Basin comprises a thick (> 8 km), rift to post-rift Oligo-Miocene to Pliocene basin-fill. The youngest (Miocene to Pliocene), post-rift succession is dominated by a thick (1-5 km), cyclic succession of coastal plain and coastal deposits, which accumulated in a humid-tropical climatic setting. This study focuses on the Pleistocene to Recent (500 m thick) succession, which comprises a range of seismic facies analysis of the two-dimensional (2D) seismic sections, mainly reflecting changes in fluvial channel style and river architecture. The succession has been divided into four seismic units (Unit S1-S4), bounded by basin-wide strata surfaces. Two types of boundaries have been identified: 1) a boundary that is defined by a regionally-extensive erosion surface at the base of a prominent incised valley (S3 and S4); 2) a sequence boundary that is defined by more weakly-incised, straight and low-sinuosity channels which is interpreted as low-stand alluvial bypass channel systems (S1 and S2). Each unit displays a predictable vertical change of the channel pattern and scale, with wide low-sinuosity channels at the base passing gradationally upwards into narrow high-sinuosity channels at the top. The wide variation in channel style and size is interpreted to be controlled mainly by the sea-level fluctuations on the widely flat Sunda land Platform.

Analysis of ancient-river systems by 3D seismic time-slice technique: A case study in northeast Malay Basin, offshore Terengganu, Malaysia

International Nuclear Information System (INIS)

Sulaiman, Noorzamzarina; Hamzah, Umar; Samsudin, Abdul Rahim

2014-01-01

Fluvial sandstones constitute one of the major clastic petroleum reservoir types in many sedimentary basins around the world. This study is based on the analysis of high-resolution, shallow (seabed to 500 m depth) 3D seismic data which generated three-dimensional (3D) time slices that provide exceptional imaging of the geometry, dimension and temporal and spatial distribution of fluvial channels. The study area is in the northeast of Malay Basin about 280 km to the east of Terengganu offshore. The Malay Basin comprises a thick (> 8 km), rift to post-rift Oligo-Miocene to Pliocene basin-fill. The youngest (Miocene to Pliocene), post-rift succession is dominated by a thick (1–5 km), cyclic succession of coastal plain and coastal deposits, which accumulated in a humid-tropical climatic setting. This study focuses on the Pleistocene to Recent (500 m thick) succession, which comprises a range of seismic facies analysis of the two-dimensional (2D) seismic sections, mainly reflecting changes in fluvial channel style and river architecture. The succession has been divided into four seismic units (Unit S1-S4), bounded by basin-wide strata surfaces. Two types of boundaries have been identified: 1) a boundary that is defined by a regionally-extensive erosion surface at the base of a prominent incised valley (S3 and S4); 2) a sequence boundary that is defined by more weakly-incised, straight and low-sinuosity channels which is interpreted as low-stand alluvial bypass channel systems (S1 and S2). Each unit displays a predictable vertical change of the channel pattern and scale, with wide low-sinuosity channels at the base passing gradationally upwards into narrow high-sinuosity channels at the top. The wide variation in channel style and size is interpreted to be controlled mainly by the sea-level fluctuations on the widely flat Sunda land Platform

Seismic stratigraphy and regional unconformity analysis of Chukchi Sea Basins

Science.gov (United States)

Agasheva, Mariia; Karpov, Yury; Stoupakova, Antonina; Suslova, Anna

2017-04-01

Russian Chukchi Sea Shelf one of petroleum potential province and still one of the most uninvestigated area. North and Sough Chukchi Trough that separated by Wrangel-Hearld Arch have different origin. The main challenge is stratigraphic sequences determination that filled North and South Chukchi basins. The joint tectonic evolution of the territory as Canada basin opening and Brooks Range-Wrangel Herald orogenic events enable to expect the analogous stratigraphy sequences in Russian Part. Analysis of 2D seismic data of Russian and American Chukchi Sea represent the major seismic reflectance that traced throughout the basins. Referring to this data North Chukchi basin includes four seismic stratigraphic sequences - Franklian (pre-Mississippian), Ellesmirian (Upper Devonian-Jurassic), Beaufortian (Jurassic-Lower Cretaceous) and Brookian (Lower Cretaceous-Cenozoic), as it is in North Slope Alaska [1]. South Chukchi basin has different tectonic nature, representing only Franclian basement and Brookian sequences. Sedimentary cover of North Chukchi basins starts with Ellesmirian sequence it is marked by bright reflector that separates from chaotic folded Franklian sequence. Lower Ellesmirian sequence fills of grabens that formed during upper Devonian rifting. Devonian extension event was initiated as a result of Post-Caledonian orogenic collapse, terminating with the opening of Arctic oceans. Beaufortian sequence is distinguished in Colville basin and Hanna Trough by seismically defined clinoforms. Paleozoic and Mesozoic strata are eroded by regional Lower Cretaceous Unconformity (LCU) linked with Canada basin opening. LCU is defined at seismic by angular unconformity, tracing at most arctic basins. Lower Cretaceous erosion and uplift event are of Hauterivian to Aptian age in Brooks Range and the Loppa High uplift refer to the early Barremian. The Lower Cretaceous clinoform complex downlaps to LCU horizon and filling North Chukchi basin (as in Colville basin Alska

Petrological Constraints on Melt Generation Beneath the Asal Rift (Djibouti)

Science.gov (United States)

Pinzuti, P.; Humler, E.; Manighetti, I.; Gaudemer, Y.; Bézos, A.

2010-12-01

The temporal evolution of the mantle melting processes in the Asal Rift is evaluated from the chemical composition of 95 lava flows sampled along 10 km of the rift axis and 8 km off-axis (that is for the last 650 ky). The major element composition and the trace element ratios of aphyric basalts across the Asal Rift show a symmetric pattern relative to the rift axis and preserved a clear signal of mantle melting depth variations. FeO, Fe8.0, Sm/YbN and Zr/Y increase, whereas SiO2 and Lu/HfN decrease from the rift axis to the rift shoulders. These variations are qualitatively consistent with a shallower melting beneath the rift axis than off-axis and the data show that the melting regime is inconsistent with a passive upwelling model. In order to quantify the depth range and extent of melting, we invert Na8.0 and Fe8.0 contents of basalts based on a pure active upwelling model. Beneath the rift axis, melting paths are shallow, from 60 to 30 km. These melting paths are consistent with adiabatic melting in normal-temperature asthenosphere, beneath an extensively thinned mantle lithosphere. In contrast, melting on the rift shoulders occurred beneath a thick mantle lithosphere and required mantle solidus temperature 180°C hotter than normal (melting paths from 110 to 75 km). The calculated rate of lithospheric thinning is high (6.0 cm yr-1) and could explain the survival of a metastable garnet within the mantle at depth shallower than 90 km beneath the modern Asal Rift.

Diverse Eruptions at Approximately 2,200 Years B.P. on the Great Rift, Idaho: Inferences for Magma Dynamics Along Volcanic Rift Zones

Science.gov (United States)

Hughes, S. S.; Nawotniak, S. E. Kobs; Borg, C.; Mallonee, H. C.; Purcell, S.; Neish, C.; Garry, W. B.; Haberle, C. W.; Lim, D. S. S.; Heldmann, J. L.

2016-01-01

Compositionally and morphologically diverse lava flows erupted on the Great Rift of Idaho approximately 2.2 ka (kilo-annum, 1000 years ago) during a volcanic "flare-up" of activity following an approximately 2 ky (kiloyear, 1000 years) hiatus in eruptions. Volcanism at Craters of the Moon (COTM), Wapi and Kings Bowl lava fields around this time included primitive and evolved compositions, separated over 75 kilometers along the approximately 85 kilometers-long rift, with striking variability in lava flow emplacement mechanisms and surface morphologies. Although the temporal associations may be coincidental, the system provides a planetary analog to better understand magma dynamics along rift systems, including that associated with lunar floor-fractured craters. This study aims to help bridge the knowledge gap between ancient rift volcanism evident on the Moon and other terrestrial planets, and active rift volcanism, e.g., at Hawai'i and Iceland.

Transient cracks and triple junctions induced by Cocos-Nazca propagating rift

Science.gov (United States)

Schouten, H.; Smith, D. K.; Zhu, W.; Montesi, L. G.; Mitchell, G. A.; Cann, J. R.

2009-12-01

The Galapagos triple junction is a ridge-ridge-ridge triple junction where the Cocos, Nazca, and Pacific plates meet around the Galapagos microplate (GMP). On the Cocos plate, north of the large gore that marks the propagating Cocos-Nazca (C-N) Rift, a 250-km-long and 50-km-wide band of NW-SE-trending cracks crosscuts the N-S-trending abyssal hills of the East Pacific Rise (EPR). These appear as a succession of minor rifts, accommodating some NE-SW extension of EPR-generated seafloor. The rifts successively intersected the EPR in triple junctions at distances of 50-100 km north of the tip of the C-N Rift. We proposed a simple crack interaction model to explain the location of the transient rifts and their junction with the EPR. The model predicts that crack locations are controlled by the stress perturbation along the EPR, induced by the dominant C-N Rift, and scaled by the distance of its tip to the EPR (Schouten et al., 2008). The model also predicts that tensile stresses are symmetric about the C-N Rift and thus, similar cracks should have occurred south of the C-N Rift prior to formation of the GMP about 1 Ma. There were no data at the time to test this prediction. In early 2009 (AT 15-41), we mapped an area on the Nazca plate south of the C-N rift out to 4 Ma. The new bathymetric data confirm the existence of a distinctive pattern of cracks south of the southern C-N gore that mirrors the pattern on the Cocos plate until about 1 Ma, and lends support to the crack interaction model. The envelope of the symmetric cracking pattern indicates that the distance between the C-N Rift tip and the EPR varied between 40 and 65 km during this time (1-4 Ma). The breakdown of the symmetry at 1 Ma accurately dates the onset of a southern plate boundary of the GMP, now Dietz Deep Rift. At present, the southern rift boundary of the GMP joins the EPR with a steep-sided, 80 km long ridge. This ridge releases the stress perturbation otherwise induced along the EPR by elastic

Stress and slip partitioning during oblique rifting: comparison between data from the Main Ethiopian Rift and laboratory experiments

Science.gov (United States)

Corti, G.; Philippon, M.; Sani, F.; Keir, D.

2012-04-01

Oblique rifting in the central and northern Main Ethiopian Rift (MER) has resulted in a complex structural pattern characterized by two differently oriented fault systems: a set of NE-SW-trending boundary faults and a system of roughly NNE-SSW-oriented fault swarms affecting the rift floor (Wonji faults). Boundary faults formed oblique to the regional extension vector, likely as a result of the oblique reactivation of a pre-existing deep-seated rheological anisotropy, whereas internal Wonji faults developed sub-orthogonal to the stretching direction. Previous works have successfully reconciled this rift architecture and fault distribution with the long-term plate kinematics; however, at a more local scale, fault-slip and earthquake data reveal significant variations in the orientation the minimum principal stress and related fault-slip direction across the rift valley. Whereas fault measurements indicate a roughly N95°E extension on the axial Wonji faults, a N105°E to N110°E directed minimum principal stress is observed along boundary faults. Both fault-slip data and analysis of seismicity indicate a roughly pure dip-slip motion on the boundary faults, despite their orientation (oblique to the regional extension vector) should result in an oblique displacement. To shed light on the process driving the variability of data derived from fault-slip (and seismicity) analysis we present crustal-scale analogue models of oblique rifting, deformed in a large-capacity centrifuge by using materials and boundary conditions described in several previous modeling works. As in these previous works, the experiments show the diachronous activation of two fault systems, boundary and internal, whose pattern strikingly resemble that observed in previous lithospheric-scale modeling, as well as that described in the MER. Internal faults arrange in two different, en-echelon segments connected by a transfer zone where strike-slip displacement dominates. Whereas internal faults develop

Sedimentological reservoir characteristics of the Paleocene fluvial/lacustrine Yabus Sandstone, Melut Basin, Sudan

Science.gov (United States)

Mahgoub, M. I.; Padmanabhan, E.; Abdullatif, O. M.

2016-11-01

Melut Basin in Sudan is regionally linked to the Mesozoic-Cenozoic Central and Western African Rift System (CWARS). The Paleocene Yabus Formation is the main oil producing reservoir in the basin. It is dominated by channel sandstone and shales deposited in fluvial/lacustrine environment during the third phase of rifting in the basin. Different scales of sedimentological heterogeneities influenced reservoir quality and architecture. The cores and well logs analyses revealed seven lithofacies representing fluvial, deltaic and lacustrine depositional environments. The sandstone is medium to coarse-grained, poorly to moderately-sorted and sub-angular to sub-rounded, arkosic-subarkosic to sublitharenite. On the basin scale, the Yabus Formation showed variation in sandstone bodies, thickness, geometry and architecture. On macro-scale, reservoir quality varies vertically and laterally within Yabus Sandstone where it shows progressive fining upward tendencies with different degrees of connectivity. The lower part of the reservoir showed well-connected and amalgamated sandstone bodies, the middle to the upper parts, however, have moderate to low sandstone bodies' connectivity and amalgamation. On micro-scale, sandstone reservoir quality is directly affected by textures and diagenetic changes such as compaction, cementation, alteration, dissolution and kaolinite clays pore fill and coat all have significantly reduced the reservoir porosity and permeability. The estimated porosity in Yabus Formation ranges from 2 to 20% with an average of 12%; while permeability varies from 200 to 500 mD and up to 1 Darcy. The understanding of different scales of sedimentological reservoir heterogeneities might contribute to better reservoir quality prediction, architecture, consequently enhancing development and productivity.

The Jurassic of Denmark and Greenland: Shallow marine syn-rift sedimentation: Middle Jurassic Pelion Formation, Jameson Land, East Greenland

Directory of Open Access Journals (Sweden)

Engkilde, Michael

2003-10-01

Full Text Available The Middle Jurassic Pelion Formation – Fossilbjerget Formation couplet of Jameson Land, East Greenland, is a well-exposed example of the Middle Jurassic inshore–offshore successions characteristicof the rifted seaways in the Northwest European – North Atlantic region. Early Jurassic deposition took place under relatively quiet tectonic conditions following Late Permian – earliest Triassic and Early Triassic rift phases and the Lower Jurassic stratal package shows an overall layer-cake geometry. A long-term extensional phase was initiated in Middle Jurassic (Late Bajocian time, culminated in the Late Jurassic (Kimmeridgian–Volgian, and petered out in the earliest Cretaceous (Valanginian. The Upper Bajocian – Middle Callovian early-rift succession comprises shallow marine sandstones of the Pelion Formation and correlative offshore siltstones of theFossilbjerget Formation. Deposition was initiated by southwards progradation of shallow marine sands of the Pelion Formation in the Late Bajocian followed by major backstepping in Bathonian–Callovian times and drowning of the sandy depositional system in the Middle–Late Callovian. Six facies associations are recognised in the Pelion–Fossilbjerget couplet, representing estuarine, shoreface, offshore transition zone and offshore environments. The north–southtrendingaxis of the Jameson Land Basin had a low inclination, and deposition was sensitive to even small changes in relative sea level which caused the shorelines to advance or retreat over tens to several hundreds of kilometres. Eight composite sequences, termed P1–P8, are recognised and are subdivided into a total of 28 depositional sequences. The duration of the two orders of sequences was about 1–2 Ma and 360,000 years, respectively. The Upper Bajocian P1–2 sequencesinclude the most basinally positioned shallow marine sandstones, deposited during major sealevel lowstands. The lowstands were terminated by significant marine

Environmental evolution of the Rio Grande drainage basin and Nasca region (Peru) in 2003-2007 using ENVISAT ASAR and ASTER time series

Science.gov (United States)

Cigna, Francesca; Tapete, Deodato; Lasaponara, Rosa; Masini, Nicola

2013-04-01

Recent palaeo-environmental studies and remote sensing investigations demonstrated that the Rio Grande drainage basin in Southern Peru is a still evolving landscape, and impacts due to its changes have implications for the preservation of both the natural and cultural features of the Nasca region, well-known for the evidences of the ancient Paracas and Nasca Civilizations, who flourished from the 4th century BC to the 6th century AD. To image the modifications occurred in the last decade, we exploited the entire 4year-long stack of ENVISAT ASAR C-band archive imagery available over the region, which was provided by the European Space Agency (ESA) via the Cat-1 project 11073. The latter supports the activities of the Italian mission of heritage Conservation and Archaeogeophysics (ITACA), which directly involve researchers from the Institute for Archaeological and Monumental Heritage (IBAM) and the Institute of Methodologies for Environmental Analysis (IMAA), National Research Council (CNR) of Italy. With the aim of reconstructing the temporal evolution of the Rio Grande drainage basin and its effects and implications for the heritage of the region, we processed 8 ASAR Image Mode IS2 scenes acquired in descending mode between 04/02/2003 and 15/11/2005 and 5 images in ascending mode between 24/07/2005 and 11/11/2007, and focused on SAR backscattering information, amplitude change detection methods and extraction of ASAR-derived time series of the backscattering coefficient over target areas of interest. The ASAR 2003-2007 analysis was coupled and integrated with NDVI-based soil moisture and vegetation change assessment performed by using ASTER multi-spectral data acquired during the same time frame of the ASAR stacks, on 30/05/2003, 01/06/2004 and 10/06/2007. The research was performed both at the regional scale over the entire Rio Grande drainage basin, with particular focus on its tributaries Rio Ingenio, Rio Nazca and Rio Taruga, and at the local scale over the

First record of Arapaima gigas (Schinz, 1822) (Teleostei: Osteoglossomorpha), the "pirarucu", in the upper Paraná River basin, Southeast Brazil

OpenAIRE

Carvalho, Fernando; Casatti, Lilian; Manzotti, Angelo; Ravazzi, Délcero

2015-01-01

Arapaima gigas (Schinz), the "pirarucu", is one of largest freshwater fish of the Neotropical region, naturally occurring in the Amazon, Essequibo, and Orinoco river basins. Herein, it is first recorded from the Grande River, in the upper Paraná River basin. This record is based on the finding of one dead specimen on the left margin of the Grande River, and in situ observation of juveniles and adults in the river.

Molecular Rift: Virtual Reality for Drug Designers.

Science.gov (United States)

Norrby, Magnus; Grebner, Christoph; Eriksson, Joakim; Boström, Jonas

2015-11-23

Recent advances in interaction design have created new ways to use computers. One example is the ability to create enhanced 3D environments that simulate physical presence in the real world--a virtual reality. This is relevant to drug discovery since molecular models are frequently used to obtain deeper understandings of, say, ligand-protein complexes. We have developed a tool (Molecular Rift), which creates a virtual reality environment steered with hand movements. Oculus Rift, a head-mounted display, is used to create the virtual settings. The program is controlled by gesture-recognition, using the gaming sensor MS Kinect v2, eliminating the need for standard input devices. The Open Babel toolkit was integrated to provide access to powerful cheminformatics functions. Molecular Rift was developed with a focus on usability, including iterative test-group evaluations. We conclude with reflections on virtual reality's future capabilities in chemistry and education. Molecular Rift is open source and can be downloaded from GitHub.

The modest seismicity of the northern Red Sea rift

Science.gov (United States)

Mitchell, Neil C.; Stewart, Ian C. F.

2018-05-01

Inferring tectonic movements from earthquakes (`seismotectonics') relies on earthquakes faithfully recording tectonic motions. In the northern half of the Red Sea, however, events of magnitude 5.0 and above are almost entirely absent from global catalogues, even though GPS and other plate motion data suggest that the basin is actively rifting at ˜10 mm yr-1. Seismic moments computed here from event magnitudes contributed to the International Seismology Centre (ISC) suggest that the moment release rate is more than an order of magnitude smaller than for the southern Red Sea and for the Southwest Indian Ridge (SWIR), which is spreading at a comparable rate to the central Red Sea and is more remote from recording stations. A smaller moment release rate in the northern Red Sea might be anticipated from its smaller spreading rate, but seismic coupling coefficients, which account for spreading rate variations, are also one order of magnitude smaller than for the other two areas. We explore potential explanations for this apparently reduced seismicity. The northern Red Sea is almost continuously covered with thick evaporites and overlying Plio-Pleistocene sediments. These deposits may have reduced the thickness of the seismogenic layer, for example, by elevating lithosphere temperatures by a thermal blanketing effect or by leading to excess pore fluid pressures that reduce effective stress. The presence of subdued seismicity here implies that tectonic movements can in places be poorly recorded by earthquake data and requires that alternative data be sought when investigating the active tectonics of sedimented rifts in particular.

The NE Rift of Tenerife: towards a model on the origin and evolution of ocean island rifts; La dorsal NE de Tenerife: hacia un modelo del origen y evolucion de los rifts de islas oceanicas

Energy Technology Data Exchange (ETDEWEB)

Carracedo, J. C.; Guillou, H.; Rodriguez Badiola, E.; Perez-Torrado, F. J.; Rodriguez Gonzalez, A.; Peris, R.; Troll, V.; Wiesmaier, S.; Delcamp, A.; Fernandez-Turiel, J. L.

2009-07-01

The NE Rift of Tenerife is an excellent example of a persistent, recurrent rift, providing important evidence of the origin and dynamics of these major volcanic features. The rift developed in three successive, intense and relatively short eruptive stages (a few hundred ka), separated by longer periods of quiescence or reduced activity: A Miocene stage (7266 {+-}156 ka), apparently extending the central Miocene shield of Tenerife towards the Anaga massif; an Upper Pliocene stage (2710{+-} 58 ka) and the latest stage, with the main eruptive phase in the Pleistocene. Detailed geological (GIS) mapping, geomagnetic reversal mapping and stratigraphic correlation, and radioisotopic (K/Ar) dating of volcanic formations allowed the reconstruction of the latest period of rift activity. In the early phases of this stage the majority of the eruptions grouped tightly along the axis of the rift and show reverse polarity (corresponding to the Matuyama chron). Dykes are of normal and reverse polarities. In the final phase of activity, eruptions are more disperse and lavas and dykes are consistently of normal polarity (Brunhes chron). Volcanic units of normal polarity crossed by dykes of normal and reverse polarities yield ages apparently compatible with normal subchrons (M-B Precursor and Jaramillo) in the Upper Matuyama chron. Three lateral collapses successively mass-wasted the rift: The Micheque collapse, completely concealed by subsequent nested volcanism, and the Guimar and La Orotava collapses, that are only partially filled. Time occurrence of collapses in the NE rift apparently coincides with glacial stages, suggesting that giant landslides may be finally triggered by sea level chan-ges during glaciations. Pre-collapse and nested volcanism is predominantly basaltic, except in the Micheque collapse, where magmas evolved towards intermediate and felsic (trachytic) compositions. Rifts in the Canary Islands are long-lasting, recurrent features, probably related to primordial

Structural geology of the Rub' Al-Khali Basin, Saudi Arabia

Science.gov (United States)

Stewart, S. A.

2016-10-01

The Rub' Al-Khali basin lies below a Quaternary sand sea, and the structural evolution from the Late Precambrian to Neogene is known only from reflection seismic, gravity, and magnetic data, and wells. Gravity and magnetic data show north-south and northwest-southeast trends, matching mapped Precambrian faults. The deepest structures imaged on reflection seismic data are undrilled Precambrian rifts filled with layered strata at depths up to 13 km. The distribution of Ediacaran-Cambrian Ara/Hormuz mobile salt is restricted to an embayment in the eastern Rub' Al-Khali. The Precambrian rifts show local inversion and were peneplained at base Phanerozoic. A broad crustal-scale fold (Qatar Arch) developed in the Carboniferous and amplified in the Late Triassic, separating subbasins in the west and east Rub' Al-Khali. A phase of kilometer-scale folding occurred in the Late Cretaceous, coeval with thrusting and ophiolite obduction in eastern Oman. These folds trend predominantly north-south, oblique to the northwesterly shortening direction, and occasionally have steep fault zones close to their axial surfaces. The trend and location of these folds closely matches the Precambrian lineaments identified in this study, demonstrating preferential reactivation of basement structures. Compression along the Zagros suture reactivated these folds in the Neogene, this time the result of highly oblique, north-northeast to south-southwest shortening. Cretaceous-Tertiary fold style is interpreted as transpression with minor strain partitioning. Permian, Jurassic, and Eocene evaporite horizons played no role in the structural evolution of the basin, but the Eocene evaporites caused widespread kilometer-scale dissolution collapse structures in the basin center.

Miocene block uplift and basin formation in the Patagonian foreland: The Gastre Basin, Argentina

Science.gov (United States)

Bilmes, A.; D'Elia, L.; Franzese, J. R.; Veiga, G. D.; Hernández, M.

2013-08-01

The intraplate fault-block mountains and intermontane deposits of the Gastre Basin, which are recorded more than 550 km east of the Andean trench in central Patagonia, Argentina, are analyzed. The Gastre Basin is one of the largest Patagonian intermontane basins, limited by uplifted blocks strongly oblique to the Andean chain. It was originated by reverse faulting and inversion of pre-existing normal faults associated with a Mesozoic rift basin and defined by older crustal heterogeneities. The deformational event occurred during the middle Miocene, related to a short contractional episode (16.1-14.86 Ma), probably in response to an eastward migration of the Andean fold and thrust belt. During Pliocene to Quaternary times, neither younger fault-block uplifts nor reconfigurations of the basin occurred. Similarities between the study area and other parts of the Patagonian foreland - such as the presence of Miocene reverse or inversion tectonics, as well as the accommodation of the Miocene sedimentary successions - suggest that the Gastre Basin is part of a major late early to middle Miocene broken foreland system (i.e. the Patagonian broken foreland) that exhumed discrete fault-block mountains and generated contemporary basins along more than 950 km parallel to the Andean trench (i.e. between 40°00' and 48°00' south latitude). Based on recent studies on the southern Andean Margin, this continental-scale contractional episode may be the result of a flat-slab subduction segment. Nevertheless, such a hypothesis is very difficult to support when analyzing such a large flat subduction segment along the entire Patagonian trench. This suggests the need to consider alternative flat-slab trigger mechanisms or other factors in the generation of broken foreland systems.

Geothermal potential on Kirtland Air Force Base lands, Bernalillo County, New Mexico

Science.gov (United States)

Grant, P. R., Jr.

1981-10-01

Public policy expressed in a number of national directives in recent years stresses the conservation of conventional fuel supplies, a switch to alternative fuels, and the application of advanced energy technologies at federal installations. Natural gas currently furnishes 85 to 95 percent of the average 94 x 1,000,000 Btu/hr energy requirements for space heating and cooling at Kirtland Air Force Base. Studies of alternatives to the use of natural gas at the base include examination of the geothermal option. Four of North America's major physiographic provinces coalesce in central New Mexico on or near Kirtland AFB. Their junction is identified throughout much of this region by a tectonic depression occupied by the Rio Grande that is structurally complex, stratigraphically and hydrologically unique, and coincides with geologically recent volcanic centers. This trough, the Rio Grande rift, has been identified as a major geothermal resource area. The western part of Kirtland AFB is in the Albuquerque Basin segment of the Rio Grande rift. Extensive sampling and geochemical analysis of groundwater in and near the base disclosed no significant geothermal parameters. However, structural conditions and current hydrologics regimes strongly suggest that thermal waters would be masked by near surface, low temperature meteoric water originating as rain and snowfall in the nearby mountains.

A new perspective on evolution of the Baikal Rift

Directory of Open Access Journals (Sweden)

Victor D. Mats

2011-07-01

The three-stage model of the rift history does not rule out the previous division into two major stages but rather extends its limits back into time as far as the Maastrichtian. Our model is consistent with geological, stratigraphic, structural, and geophysical data and provides further insights into the understanding of rifting in the Baikal region in particular and continental rifting in general.

The thermal history of the Karoo Moatize-Minjova Basin, Tete Province, Mozambique: An integrated vitrinite reflectance and apatite fission track thermochronology study

Science.gov (United States)

Fernandes, Paulo; Cogné, Nathan; Chew, David M.; Rodrigues, Bruno; Jorge, Raul C. G. S.; Marques, João; Jamal, Daud; Vasconcelos, Lopo

2015-12-01

The Moatize-Minjova Basin is a Karoo-aged rift basin located in the Tete Province of central Mozambique along the present-day Zambezi River valley. In this basin the Permian Moatize and Matinde formations consist of interbedded carbonaceous mudstones and sandstones with coal seams. The thermal history has been determined using rock samples from two coal exploration boreholes (ca. 500 m depth) to constrain the burial and exhumation history of the basin. Organic maturation levels were determined using vitrinite reflectance and spore fluorescence/colour. Ages and rates of tectonic uplift and denudation have been assessed by apatite fission track analysis. The thermal history was modelled by inverse modelling of the fission track and vitrinite reflectance data. The Moatize Formation attained a coal rank of bituminous coals with low to medium volatiles (1.3-1.7%Rr). Organic maturation levels increase in a linear fashion downhole in the two boreholes, indicating that burial was the main process controlling peak temperature maturation. Calculated palaeogeothermal gradients range from 59 °C/km to 40 °C/km. According to the models, peak burial temperatures were attained shortly (3-10 Ma) after deposition. Apatite fission track ages [146 to 84 Ma (Cretaceous)] are younger than the stratigraphic age. Thermal modelling indicates two episodes of cooling and exhumation: a first period of rapid cooling between 240 and 230 Ma (Middle - Upper Triassic boundary) implying 2500-3000 m of denudation; and a second period, also of rapid cooling, from 6 Ma (late Miocene) onwards implying 1000-1500 m of denudation. The first episode is related to the main compressional deformation event within the Cape Fold Belt in South Africa, which transferred stress northwards on pre-existing transtensional fault systems within the Karoo rift basins, causing tectonic inversion and uplift. During the Mesozoic and most of the Cenozoic the basin is characterized by very slow cooling. The second period

Imaging rifting at the lithospheric scale in the northern East African Rift using S-to-P receiver functions

Science.gov (United States)

Lavayssiere, A.; Rychert, C.; Harmon, N.; Keir, D.; Hammond, J. O. S.; Kendall, J. M.; Leroy, S. D.; Doubre, C.

2017-12-01

The lithosphere is modified during rifting by a combination of mechanical stretching, heating and potentially partial melt. We image the crust and upper mantle discontinuity structure beneath the northern East African Rift System (EARS), a unique tectonically active continental rift exposing along strike the transition from continental rifting in the Main Ethiopian rift (MER) to incipient seafloor spreading in Afar and the Red Sea. S-to-P receiver functions from 182 stations across the northern EARS were generated from 3688 high quality waveforms using a multitaper technique and then migrated to depth using a regional velocity model. Waveform modelling of data stacked in large conversion point bins confirms the depth and strength of imaged discontinuities. We image the Moho at 29.6±4.7 km depth beneath the Ethiopian plateaux with a variability in depth that is possibly due to lower crustal intrusions. The crust is 27.3±3.9 km thick in the MER and thinner in northern Afar, 17.5±0.7 km. The model requires a 3±1.2% reduction in shear velocity with increasing depth at 68.5±1.5 km beneath the Ethiopian plateaux, consistent with the lithosphere-asthenosphere boundary (LAB). We do not resolve a LAB beneath Afar and the MER. This is likely associated with partial melt near the base of the lithosphere, reducing the velocity contrast between the melt-intruded lithosphere and the partially molten asthenosphere. We identify a 4.5±0.7% increase in velocity with depth at 91±3 km beneath the MER. This change in velocity is consistent with the onset of melting found by previous receiver functions and petrology studies. Our results provide independent constraints on the depth of melt production in the asthenosphere and suggest melt percolation through the base of the lithosphere beneath the northernmost East African rift.

Hydrothermal Petroleum in Active Continental Rift: Lake Chapala, Western Mexico, Initial Results.

Science.gov (United States)

Zarate-del Valle, P. F.; Simoneit, B. R.; Ramirez-Sanchez, H. U.

2003-12-01

Lake Chapala in western Mexico is located partially in the Citala Rift, which belongs to the well-known neotectonic Jalisco continental triple junction. The region is characterized by active volcanism (Ceboruco, Volcan de Fuego), tectonic (1995 earthquake, M=8, 40-50 mm to SW) and hydrothermal (San Juan Cosala & Villa Corona spas and La Calera sinter deposit) activities. Hydrothermal petroleum has been described in active continental rift (East African Rift) and marine spreading zones (Guaymas Basin, Gulf of California). In 1868 the Mexican local press reported that manifestations of bitumen were appearing in front of the Columba Cap on the mid south shore of Lake Chapala. This bitumen is linked to the lake bottom and when the water level decreases sufficiently it is possible to access these tar bodies as islands. Because of these manifestations the Mexican oil company (PEMEX) drilled an exploration well (2,348m) at Tizapan El Alto without success. Hydrothermal activity is evident in the tar island zone as three in-shore thermal springs (26.8 m depth, 48.5° C, pH 7.8 and oriented N-S). The preliminary analyses by GC-MS of the tar from these islands indicate hydrothermal petroleum derived from lake sedimentary organic matter, generated at low temperatures (150° -200° C). The tars contain no n-alkanes, no PAH or other aromatics, but a major UCM of branched and cyclic hydrocarbons and mature biomarkers derived from lacustrine biota. The biomarkers consist of mainly 17α (H),21β (H)-hopanes ranging from C27 to C34 (no C28), gammacerane, tricyclic terpanes (C20-C26), carotane and its cracking products, and drimanes (C14-C16). The biomarker composition indicates an organic matter source from bacteria and algae, typical of lacustrine ecosystems. 14C dating of samples from two tar islands yielded ages exceeding 40 kyrs, i.e., old carbon from hydrothermal/tectonic remobilization of bitumen from deeper horizons to the surface. The occurrence of hydrothermal petroleum in

Rift propagation at craton margin.: Distribution of faulting and volcanism in the North Tanzanian Divergence (East Africa) during Neogene times

Science.gov (United States)

Le Gall, B.; Nonnotte, P.; Rolet, J.; Benoit, M.; Guillou, H.; Mousseau-Nonnotte, M.; Albaric, J.; Deverchère, J.

2008-02-01

A revised kinematic model is proposed for the Neogene tectono-magmatic development of the North Tanzanian Divergence where the axial valley in S Kenya splits southwards into a wide diverging pattern of block faulting in association with the disappearance of volcanism. Propagation of rifting along the S Kenya proto-rift during the last 8 Ma is first assumed to have operated by linkage of discrete magmatic cells as far S as the Ngorongoro-Kilimanjaro transverse volcanic belt that follows the margin of cratonic blocks in N Tanzania. Strain is believed to have nucleated throughout the thermally-weakened lithosphere in the transverse volcanic belt that might have later linked the S Kenya and N Tanzania rift segments with marked structural changes along-strike. The North Tanzanian Divergence is now regarded as a two-armed rift pattern involving: (1) a wide domain of tilted fault blocks to the W (Mbulu) that encompasses the Eyasi and Manyara fault systems, in direct continuation with the Natron northern trough. The reactivation of basement fabrics in the cold and intact Precambrian lithosphere in the Mbulu domain resulted in an oblique rift pattern that contrasts with the orthogonal extension that prevailed in the Magadi-Natron trough above a more attenuated lithosphere. (2) To the E, the Pangani horst-like range is thought to be a younger (< 1 Ma) structure that formed in response to the relocation of extension S of the Kilimanjaro magmatic center. A significant contrast in the mechanical behaviour of the stretched lithosphere in the North Tanzanian diverging rift is assumed to have occurred on both sides of the Masai cratonic block with a mid-crustal decoupling level to the W where asymmetrical fault-basin patterns are dominant (Magadi-Natron and Mbulu), whereas a component of dynamical uplift is suspected to have caused the topographic elevation of the Pangani range in relation with possible far-travelled mantle melts produced at depth further N.

Summary Report for Bureau of Fisheries Stream Habitat Surveys : Umatilla, Tucannon, Asotin, and Grande Ronde River Basins, 1934-1942, Final Report.

Energy Technology Data Exchange (ETDEWEB)

McIntosh, Bruce A.; Clark, Sharon E.; Sedell, James R.

1995-01-01

This document contains summary reports of stream habitat surveys, conducted in the Umatilla and Grande Ronde River basins, by the Bureau of Fisheries (BOF, now National Marine Fisheries Service) from 1938-1942. These surveys were part of a larger project to survey streams in the Columbia River basin that provided, or had provided, spawning and rearing habitat for salmon and steelhead (Rich, 1948). The purpose of the survey was, as described by Rich, 'to determine the present condition of the various tributaries with respect to their availability and usefulness for the migration, breeding, and rearing of migratory fishes'. Current estimates of the loss of anadromous fish habitat in the Columbia River Basin are based on a series of reports published from 1949-1952 by the U.S. Fish and Wildlife Service. The reports were brief, qualitative accounts of over 5000 miles of stream surveys conducted by the BOF from 1934-1946 (Bryant, 1949; Bryant and Parkhurst, 1950; Parkhurst, 1950a-c; Parkhurst et al 1950). Despite their brevity, these BOF reports have formed the basis for estimating fish habitat losses and conditions in the Columbia River Basin (Fulton, 1968, 1970; Thompson, 1976; NPPC, 1986). Recently, the field notebooks from the BOF surveys were discovered. The data is now archived and stored in the Forest Science DataBank at Oregon State University (Stafford et al., 1984; 1988). These records are the earliest and most comprehensive documentation available of the condition and extent of anadromous fish habitat before hydropower development in the Columbia River Basin. They provide the baseline data for quantifying changes and setting a benchmark for future restoration of anadromous fish habitat throughout the Basin. The summaries contained in this book are exact replicates of the originals. Due to discrepancies between the field data and the summaries, the database should be used to assess pool and substrate conditions. This data is available from the

Timing of the volcanism of the southern Kivu province: Implications for the evolution of the western branch of the East African rift system

International Nuclear Information System (INIS)

Pasteels, P.

1989-01-01

New K-Ar datings of a large rock sampling from the South Kivu volcanic province (Zaire, Rwanda, Burundi) are reported. No ages older than 10 Ma have been obtained. This result contrasts with older assumptions and puts severe constraints on the relations between volcanism and rift evolution. From 10 to 7.5 Ma tholeiitic volcanism predominates corresponding to an episode of fissural eruptions; from 7.5 to 5 Ma alkali basalts and their differentiates are mainly erupted in localized rifts. A culmination of activity occurs between 6.0 and 5.5 Ma ago. Pleistocene alkalic volcanism is restricted to localized areas. The transition from tholeiites to alkali-basaltic volcanism dated around 7.5 Ma would correspond to a major rifting phase which corresponds with the initiation of Lake Kivu Basin formation. The distribution of tholeiitic rocks in the central part of the rift, and predominantly alkalic rocks along the western active border fault, strengthens the idea that the former are associated with tension, the latter with vertical, possibly also strike-slip movements. Volcanism in the Western Rift is restricted to areas where tension occurs in a zone which is located between two zones of strike-slip. In the South Kivu area normal faults intersect strike-slip faults and this seems to have determined the location of volcanic activity. Magma formation is considered to be related with shear heating combined with adiabatic decompression in ascending diapirs. This implies heating at the lithosphere-asthenosphere boundary as a result of extension. Generation of tholeiitic or alkalic magmas is connected with the variable ascent velocity of mantle diapirs or with variable shear heating along the shear zone. Changes in both magma composition and intensity of volcanic activity with time are considered to be related to major phases of rift evolution. (orig.)

Lithospheric-scale centrifuge models of pull-apart basins

Science.gov (United States)

Corti, Giacomo; Dooley, Tim P.

2015-11-01

We present here the results of the first lithospheric-scale centrifuge models of pull-apart basins. The experiments simulate relative displacement of two lithospheric blocks along two offset master faults, with the presence of a weak zone in the offset area localising deformation during strike-slip displacement. Reproducing the entire lithosphere-asthenosphere system provides boundary conditions that are more realistic than the horizontal detachment in traditional 1 g experiments and thus provide a better approximation of the dynamic evolution of natural pull-apart basins. Model results show that local extension in the pull-apart basins is accommodated through development of oblique-slip faulting at the basin margins and cross-basin faults obliquely cutting the rift depression. As observed in previous modelling studies, our centrifuge experiments suggest that the angle of offset between the master fault segments is one of the most important parameters controlling the architecture of pull-apart basins: the basins are lozenge shaped in the case of underlapping master faults, lazy-Z shaped in case of neutral offset and rhomboidal shaped for overlapping master faults. Model cross sections show significant along-strike variations in basin morphology, with transition from narrow V- and U-shaped grabens to a more symmetric, boxlike geometry passing from the basin terminations to the basin centre; a flip in the dominance of the sidewall faults from one end of the basin to the other is observed in all models. These geometries are also typical of 1 g models and characterise several pull-apart basins worldwide. Our models show that the complex faulting in the upper brittle layer corresponds at depth to strong thinning of the ductile layer in the weak zone; a rise of the base of the lithosphere occurs beneath the basin, and maximum lithospheric thinning roughly corresponds to the areas of maximum surface subsidence (i.e., the basin depocentre).

Large-scale variation in lithospheric structure along and across the Kenya rift

Science.gov (United States)

Prodehl, C.; Mechie, J.; Kaminski, W.; Fuchs, K.; Grosse, C.; Hoffmann, H.; Stangl, R.; Stellrecht, R.; Khan, M.A.; Maguire, Peter K.H.; Kirk, W.; Keller, Gordon R.; Githui, A.; Baker, M.; Mooney, W.; Criley, E.; Luetgert, J.; Jacob, B.; Thybo, H.; Demartin, M.; Scarascia, S.; Hirn, A.; Bowman, J.R.; Nyambok, I.; Gaciri, S.; Patel, J.; Dindi, E.; Griffiths, D.H.; King, R.F.; Mussett, A.E.; Braile, L.W.; Thompson, G.; Olsen, K.; Harder, S.; Vees, R.; Gajewski, D.; Schulte, A.; Obel, J.; Mwango, F.; Mukinya, J.; Riaroh, D.

1991-01-01

The Kenya rift is one of the classic examples of a continental rift zone: models for its evolution range from extension of the lithosphere by pure shear1, through extension by simple shear2, to diapiric upwelling of an asthenolith3. Following a pilot study in 19854, the present work involved the shooting of three seismic refraction and wide-angle reflection profiles along the axis, across the margins, and on the northeastern flank of the rift (Fig. 1). These lines were intended to reconcile the different crustal thickness estimates for the northern and southern parts of the rift4-6 and to reveal the structure across the rift, including that beneath the flanks. The data, presented here, reveal significant lateral variations in structure both along and across the rift. The crust thins along the rift axis from 35 km in the south to 20 km in the north; there are abrupt changes in Mono depth and uppermost-mantle seismic velocity across the rift margins, and crustal thickening across the boundary between the Archaean craton and PanAfrican orogenic belt immediately west of the rift. These results suggest that thickened crust may have controlled the rift's location, that there is a decrease in extension from north to south, and that the upper mantle immediately beneath the rift may contain reservoirs of magma generated at greater depth.

Thermodynamic, geophysical and rheological modeling of the lithosphere underneath the North Atlantic Porcupine Basin (Ireland).

Science.gov (United States)

Botter, C. D.; Prada, M.; Fullea, J.

2017-12-01

The Porcupine is a North-South oriented basin located southwest of Ireland, along the North Atlantic continental margin, formed by several rifting episodes during Late Carboniferous to Early Cretaceous. The sedimentary cover is underlined by a very thin continental crust in the center of the basin (10 in the South. In spite of the abundant literature, most of the oil and gas exploration in the Porcupine Basin has been targeting its northern part and is mostly restricted to relatively shallow depths, giving a restrained overview of the basin structure. Therefore, studying the thermodynamic and composition of the deep and broader structures is needed to understand the processes linked to the formation and the symmetry signature of the basin. Here, we model the present-day thermal and compositional structure of the continental crust and lithospheric mantle underneath the Porcupine basin using gravity, seismic, heat flow and elevation data. We use an integrated geophysical-petrological framework where most relevant rock properties (density, seismic velocities) are determined as a function of temperature, pressure and composition. Our modelling approach solves simultaneously the heat transfer, thermodynamic, geopotential, seismic and isostasy equations, and fit the results to all available geophysical and petrological observables (LitMod software). In this work we have implemented a module to compute self-consistently a laterally variable lithospheric elastic thickness based on mineral physics rheological laws (yield strength envelopes over the 3D volume). An appropriate understanding of local and flexural isostatic behavior of the basin is essential to unravel its tectonic history (i.e. stretching factors, subsidence etc.). Our Porcupine basin 3D model is defined by four lithological layers, representing properties from post- and syn-rift sequences to the lithospheric mantle. The computed yield strength envelopes are representative of hyperextended lithosphere and

Structural heritage, reactivation and distribution of fault and fracture network in a rifting context: Case study of the western shoulder of the Upper Rhine Graben

Science.gov (United States)

Bertrand, Lionel; Jusseaume, Jessie; Géraud, Yves; Diraison, Marc; Damy, Pierre-Clément; Navelot, Vivien; Haffen, Sébastien

2018-03-01

In fractured reservoirs in the basement of extensional basins, fault and fracture parameters like density, spacing and length distribution are key properties for modelling and prediction of reservoir properties and fluids flow. As only large faults are detectable using basin-scale geophysical investigations, these fine-scale parameters need to be inferred from faults and fractures in analogous rocks at the outcrop. In this study, we use the western shoulder of the Upper Rhine Graben as an outcropping analogue of several deep borehole projects in the basement of the graben. Geological regional data, DTM (Digital Terrain Model) mapping and outcrop studies with scanlines are used to determine the spatial arrangement of the faults from the regional to the reservoir scale. The data shows that: 1) The fault network can be hierarchized in three different orders of scale and structural blocks with a characteristic structuration. This is consistent with other basement rocks studies in other rifting system allowing the extrapolation of the important parameters for modelling. 2) In the structural blocks, the fracture network linked to the faults is linked to the interplay between rock facies variation linked to the rock emplacement and the rifting event.

Proterozoic orogenic belts and rifting of Indian cratons: Geophysical constraints

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D.C. Mishra

2014-01-01

Full Text Available The Aravalli–Delhi and Satpura Mobile Belts (ADMB and SMB and the Eastern Ghat Mobile Belt (EGMB in India form major Proterozoic mobile belts with adjoining cratons and contemporary basins. The most convincing features of the ADMB and the SMB have been the crustal layers dipping from both sides in opposite directions, crustal thickening (∼45 km and high density and high conductivity rocks in upper/lower crust associated with faults/thrusts. These observations indicate convergence while domal type reflectors in the lower crust suggest an extensional rifting phase. In case of the SMB, even the remnant of the subducting slab characterized by high conductive and low density slab in lithospheric mantle up to ∼120 km across the Purna–Godavari river faults has been traced which may be caused by fluids due to metamorphism. Subduction related intrusives of the SMB south of it and the ADMB west of it suggest N–S and E–W directed convergence and subduction during Meso–Neoproterozoic convergence. The simultaneous E–W convergence between the Bundelkhand craton and Marwar craton (Western Rajasthan across the ADMB and the N–S convergence between the Bundelkhand craton and the Bhandara and Dharwar cratons across the SMB suggest that the forces of convergence might have been in a NE–SW direction with E–W and N–S components in the two cases, respectively. This explains the arcuate shaped collision zone of the ADMB and the SMB which are connected in their western part. The Eastern Ghat Mobile Belt (EGMB also shows signatures of E–W directed Meso–Neoproterozoic convergence with East Antarctica similar to ADMB in north India. Foreland basins such as Vindhyan (ADMB–SMB, and Kurnool (EGMB Supergroups of rocks were formed during this convergence. Older rocks such as Aravalli (ADMB, Mahakoshal–Bijawar (SMB, and Cuddapah (EGMB Supergroups of rocks with several basic/ultrabasic intrusives along these mobile belts, plausibly formed during

Mantle Flow Across the Baikal Rift Constrained With Integrated Seismic Measurements

Science.gov (United States)

Lebedev, S.; Meier, T.; van der Hilst, R. D.

2005-12-01

The Baikal Rift is located at the boundary of the stable Siberian Craton and deforming central Mongolia. The origin of the late Cenozoic rifting and volcanism are debated, as is the mantle flow beneath the rift zone. Here we combine new evidence from azimuthally-anisotropic upper-mantle tomography and from a radially-anisotropic inversion of interstation surface-wave dispersion curves with previously published shear-wave-splitting measurements of azimuthal anisotropy across the rift (Gao et al. 1994). While our tomographic model maps isotropic and anisotropic shear-velocity heterogeneity globally, the inversion of interstation phase-velocity measurements produces a single, radially-anisotropic, shear-velocity profile that averages from the rift to 500 km SE of it. The precision and the broad band (8-340 s) of the Rayleigh and Love wave curves ensures high accuracy of the profile. Tomography and shear-wave splitting both give a NW-SE fast direction (perpendicular to the rift) in the vicinity of the rift, changing towards W-E a few hundred kilometers from it. Previously, this has been interpreted as evidence for mantle flow similar to that beneath mid-ocean ridges, with deeper vertical flow directly beneath the rift also proposed. Our radially anisotropic profile, however, shows that while strong anisotropy with SH waves faster than SV waves is present in the thin lithosphere and upper asthenosphere beneath and SE of the rift, no anisotropy is required below 110 km. The tomographic model shows thick cratonic lithosphere north of the rift. These observations suggest that instead of a flow diverging from the rift axis in NW and SE directions, the most likely pattern is the asthenospheric flow in SE direction from beneath the Siberian lithosphere and across the rift. Possible driving forces of the flow are large-scale lithospheric deformation in East Asia and the draining of asthenosphere at W-Pacific subduction zones; a plume beneath the Siberian craton also cannot be

Fault-Magma Interactions during Early Continental Rifting: Seismicity of the Magadi-Natron-Manyara basins, Africa

Science.gov (United States)

Weinstein, A.; Oliva, S. J.; Ebinger, C.; Aman, M.; Lambert, C.; Roecker, S. W.; Tiberi, C.; Muirhead, J.

2017-12-01

Although magmatism may occur during the earliest stages of continental rifting, its role in strain accommodation remains weakly constrained by largely 2D studies. We analyze seismicity data from a 13-month, 39-station broadband seismic array to determine the role of magma intrusion on state-of-stress and strain localization, and their along-strike variations. Precise earthquake locations using cluster analyses and a new 3D velocity model reveal lower crustal earthquakes along projections of steep border faults that degas CO2. Seismicity forms several disks interpreted as sills at 6-10 km below a monogenetic cone field. The sills overlie a lower crustal magma chamber that may feed eruptions at Oldoinyo Lengai volcano. After determining a new ML scaling relation, we determine a b-value of 0.87 ± 0.03. Focal mechanisms for 66 earthquakes, and a longer time period of relocated earthquakes from global arrays reveal an along-axis stress rotation of 50 o ( N150 oE) in the magmatically active zone. Using Kostrov summation of local and teleseismic mechanisms, we find opening directions of N122ºE and N92ºE north and south of the magmatically active zone. The stress rotation facilitates strain transfer from border fault systems, the locus of early stage deformation, to the zone of magma intrusion in the central rift. Our seismic, structural, and geochemistry results indicate that frequent lower crustal earthquakes are promoted by elevated pore pressures from volatile degassing along border faults, and hydraulic fracture around the margins of magma bodies. Earthquakes are largely driven by stress state around inflating magma bodies, and more dike intrusions with surface faulting, eruptions, and earthquakes are expected.

Origin of the Eastern Mediterranean: Neo-Tethys Rifting Along a Cryptic Cadomian Suture with Afro-Arabia

Science.gov (United States)

Avigad, D.; Abbo, A.; Gerdes, A.

2016-12-01

The East Mediterranean is a land-locked basin, a remnant of Neo-Tethys. It was formed in the Permo-Triassic as a result of the drift of the Tauride block from the Afro-Arabian margin of Gondwana. Herein we show that rather than being a genuine Afro-Arabia crustal fragment, the Tauride block is underlain by a Late Neoproterozoic Cadomian basement, which differs significantly from the Neoproterozoic "Pan-African" basement of NE Africa from which it was detached. Resembling other Cadomian terranes of Western Europe, the Tauride basement is chiefly a greywacke succession deposited in a mid to late Ediacaran back-arc basin formed on the periphery of Afro-Arabia, above the southward subducting proto-Tethys. The back-arc region was deformed and metamorphosed to various degrees and intruded by latest Ediacaran-Cambrian granites and volcanics during the Cadomian orogeny. Unlike the protracted (ca .300 m.y.) Neoproterozoic crustal evolution recorded in Afro-Arabia, the Cadomian basement of the Taurides evolved briefly, over ca. 50 m.y. We show that the entire cycle of sedimentation, metamorphism and magmatism in the Tauribe basement took place in the late Ediacaran-Cambrian and lagged after Neoproterozoic Pan-African orogeny and igneous activity in Afro-Arabia. The Cadomian orogeny had accreted the Taurides, and adjoining peri-Gandwana Cadomian terranes, with an already-consolidated Afro-Arabian continent. Permo-Triassic rifting of the East Mediterranean occurred close to the transition between these two domains. Rifting has thus been inherited from, and superimposed on late Ediacaran structures formed in front of the current Afro-Arabia margin of Gondwana during Cadomian orogeny. The boundary between the Cadomian edifice and the Pan-African crust of Afro-Arabia appears to lie nowadays on the southern margin of the Mediterranean, extending from Morocco in the west to Arabia in the east. Hence, the continental margin of the East Mediterranean, including in the Levant basin

Progress on the palynostratigraphy of the Permian strata in Rio Grande do Sul State, Paraná Basin, Brazil

Directory of Open Access Journals (Sweden)

Souza Paulo A.

2005-01-01

Full Text Available A review of published papers and results of analysis of new material have allowed improvements on the palynostratigraphy of the Permian strata of the Paraná Basin in Rio Grande do Sul State. Based on first and last occurrences of certain species of pollen taxa, two palynozones are formalized, these are the Vittatina costabilis and Lueckisporites virkkiae Interval Zones, in ascending order. The Vittatina costabilis Interval Zone is subdivided into two units, in ascending order the Protohaploxypinus goraiensis and the Hamiapollenites karrooensis Subzones, and is recognized from the glacial (Itararé Group and post-glacial sequence (Rio Bonito Formation and the base of the Palermo Formation. The Lueckisporites virkkiae Interval Zone occurs from the uppermost Rio Bonito Formation, through the Palermo and Irati formations, and into the Serra Alta and Teresina formations. The main characteristics and reference sections are established, as well as additional criteria to recognize biostratigraphical units, in accordance with the International Stratigraphic Guide. Palynostratigraphical correlation suggests that the Vittatina costabilis Zone concerns the Early Permian (early Cisuralian, while the Lueckisporites virkkiae is regarded as late Early Permian to early Middle Permian (late Cisularian to early Guadalupian.

Estimation of age of Dali-Ganis rifting and associated volcanic activity, Venus

Science.gov (United States)

Basilevsky, A. T.

1993-01-01

This paper deals with the estimation of age for the Dali and Ganis Chasma rift zones and their associated volcanism based on photogeologic analysis of stratigraphic relations of rift-associated features with impact craters which have associated features indicative of their age. The features are radar-dark and parabolic, and they are believed to be mantles of debris derived from fallout of the craters' ejecta. They are thought to be among the youngest features on the Venusian surface, so their 'parent' craters must also be very young, evidently among the youngest 10 percent of Venus' crater population. Dali Chasma and Ganis Chasma are a part of a system of rift zones contained within eastern Aphrodite and Atla Regio which is a significant component of Venus tectonics. The rifts of this system are fracture belts which dissect typical Venusian plains with rare islands of tessera terrain. The rift zone system consists of several segments following each other (Diane, Dali, Ganis) and forming the major rift zone line, about 10,000 km long, which has junctions with several other rift zones, including Parga Chasma Rift. The junctions are usually locations of rift-associated volcanism in the form of volcanic edifices (Maat and Ozza Montes) or plain-forming flows flooding some areas within the rift zones and the adjacent plains.

Oblique rift opening revealed by reoccurring magma injection in central Iceland

KAUST Repository

Ruch, Joel; Wang, Teng; Xu, Wenbin; Hensch, Martin; Jonsson, Sigurjon

2016-01-01

-field deformation has rarely been captured, hindering progress in understanding rifting mechanisms and evolution. Here we show new evidence of oblique rift opening during a rifting event influenced by pre-existing fractures and two centuries of extension deficit

Images of the East Africa Rift System from the Joint Inversion of Body Waves, Surface Waves, and Gravity: Investigating the Role of Magma in Early-Stage Continental Rifting