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1

76 FR 25331 - Williston Basin Interstate Pipeline Company; Notice of Request Under Blanket Authorization  

Science.gov (United States)

...CP82-487-000, et al.,\\1\\ for the construction and operation of mainline natural gas compression facilities located at the Charbonneau Compressor Station in McKenzie County, North Dakota. Specifically, Williston Basin proposes to install one new...

2011-05-04

2

Williston Basin pipeline solutions : continuous change, continuous growth  

Energy Technology Data Exchange (ETDEWEB)

The Bakken shale formation in the Williston Basin has the potential to produce 4.3 billion bbls of oil. Carbon dioxide (CO{sub 2}) sequestration is now being successfully used to develop the shale in the 25 per cent area of the Bakken within the province of Saskatchewan. Sequestration projects in the region are also increasing in capacity. Incremental production in Saskatchewan and Manitoba has increased from 150 barrels per day in 2003 to approximately 225 barrels per day in December 2008. Facility upgrades have recently been completed at the Midale, Steelman, Alida and EIP Mainline units. Capacity expansions and new gathering systems are also planned. Further expansion is planned to address bottlenecks and meet projected volume growth in the future. It was concluded that the capacity expansions will include new natural gas and oil pipelines as well as booster stations. tabs., figs.

Taylor, P. [Enbridge Pipelines Inc., Estevan, SK (Canada)

2009-07-01

3

Proceedings of the 13. Williston Basin petroleum conference  

International Nuclear Information System (INIS)

This conference provided a forum for the exchange of ideas and technologies that have resulted in more efficient oil drilling and production methods in the Williston Basin, which plays a significant role in the economies of Saskatchewan, Manitoba, North and South Dakota and Montana. Various enhanced recovery methods were discussed, as well as new surveying techniques. Well construction, new technologies in injection, swelling packer and artificial lift systems were reviewed. Various fracturing options were examined. Updates on oil and gas activities were presented, along with new policies and legislation aimed at increasing productivity in the oil and gas industry. Thirty-nine papers were presented at this conference, 17 of which have been catalogued separately for inclusion in this database. (author)

4

Integrated analysis of the Bakken petroleum system, U.S. Williston Basin  

Energy Technology Data Exchange (ETDEWEB)

The Williston Basin covers an area of several hundred thousand square miles across North and South Dakota, Montana, Manitoba and Saskatchewan. The basin is structurally simple with the thickest sediments occurring in the centre and the thinnest sediments occurring close to its edges. The general stratigraphy of the Williston Basin was illustrated, and the stratigraphic units were used to build isopach grids in a newly developed commercial 3-dimensional basin-modeling tool known as PetroMod 3D. The Lake Devonian-Early Mississippian Bakken Formation is a prolific oil source rock in the Williston Basin. The sandstones, siltstones and fractured shales source rocks are sealed from effective reservoirs. Recent horizontal drilling activity and improvements in completion technology have resulted in the production of high oil volumes from the Middle Bakken in Richland County, Montana. Annual Bakken production in North Dakota and Montana rose from 800,000 bbls in 2000 to 8.4 MMBO in 2004. In this study, PetroMod 3D was used to create a multidimensional digital illustration of the Williston Basin. The purpose was to use migration simulation to determine the potential of the Middle Bakken play and its role in other parts of the basin. The 3-D modelling allowed for a rapid assessment and sensitivity analysis of the regional Bakken hydrocarbon system. It demonstrated that Bakken shale source rocks have generated high volumes of oil, of which nearly 100 BBO are trapped in the Middle Bakken clastic member in the portion of the Williston Basin that lies in the United States. These values do not depend on changes in source-rock and thermal parameters, an important factor when evaluating the future potential in the play. 11 refs., 12 figs.

Flannery, J. [Tethys Geoscience LLC, Houston, TX (United States)

2006-07-01

5

Evaluation of injection-well risk management in the Williston basin  

International Nuclear Information System (INIS)

This paper reports on a study of subsurface water-injection operations in the Williston geologic basin which demonstrated the practicality of incorporating risk management procedures into the regulation of underground injection control (UIC) programs. A realistic model of a computerized data base was developed to assess the maximum quantifiable risk that water from injection wells would reach an underground source of drinking water (USDW). In the Williston basin, the upper-bound probability of injection water escaping the wellbore and reaching a USDW is seven chances in 1 million well-years where surface casings cover the drinking-water aquifers. Where surface casings do not cover the USDW's, the probability is six chances in 1,000 well-years

6

Brine contamination to aquatic resources from oil and gas development in the Williston Basin, United States  

Science.gov (United States)

The Williston Basin, which includes parts of Montana, North Dakota, and South Dakota in the United States and the provinces of Manitoba and Saskatchewan in Canada, has been a leading domestic oil and gas producing region for more than one-half a century. Currently, there are renewed efforts to develop oil and gas resources from deep geologic formations, spurred by advances in recovery technologies and economic incentives associated with the price of oil. Domestic oil and gas production has many economic benefits and provides a means for the United States to fulfill a part of domestic energy demands; however, environmental hazards can be associated with this type of energy production in the Williston Basin, particularly to aquatic resources (surface water and shallow groundwater) by extremely saline water, or brine, which is produced with oil and gas. The primary source of concern is the migration of brine from buried reserve pits that were used to store produced water during recovery operations; however, there also are considerable risks of brine release from pipeline failures, poor infrastructure construction, and flow-back water from hydraulic fracturing associated with modern oilfield operations. During 2008, a multidisciplinary (biology, geology, water) team of U.S. Geological Survey researchers was assembled to investigate potential energy production effects in the Williston Basin. Researchers from the U.S. Geological Survey participated in field tours and met with representatives from county, State, tribal, and Federal agencies to identify information needs and focus research objectives. Common questions from agency personnel, especially those from the U.S. Fish and Wildlife Service, were “are the brine plumes (plumes of brine-contaminated groundwater) from abandoned oil wells affecting wetlands on Waterfowl Production Areas and National Wildlife Refuges?” and “are newer wells related to Bakken and Three Forks development different than the older, abandoned wells (in terms of potential for affecting aquatic resources)?” Of special concern were the wetland habitats of the ecologically important Prairie Pothole Region, which overlays a part of the Williston Basin and is recognized for the production of a majority of North America’s migratory waterfowl. On the basis of the concerns raised by on-the-ground land managers, as well as findings from previous research, a comprehensive study was developed with the following goals: summarize existing information pertaining to oil and gas production and aquatic resources in the Williston Basin; assess brine plume migration from new and previously studied sites in the Prairie Pothole Region; perform a regional, spatial evaluation of oil and gas production activities and aquatic resources; assess the potential for brine contamination to wetlands and streams; and hold a decision analysis workshop with key stakeholders to discuss issues pertaining to oil and gas production and environmental effects and to identify information gaps and research needs. This report represents an initial, multidisciplinary evaluation of measured and potential environmental effects associated with oil and gas production in the Williston Basin and Prairie Pothole Region. Throughout this report there are reviews of current knowledge, and discussions relating to data gaps and research needs. On the basis of the information presented, future research needs include: regional geophysical and water-quality assessments to establish baselines for current conditions and estimate the extent of previous brine contamination, investigations into the direct effects of brine to biotic communities, and evaluations to identify the most effective techniques to mitigate brine contamination.

Gleason, Robert A.; Contributions by Chesley-Preston, Tara L.; Coleman, James L.; Haines, Seth S.; Jenni, Karen E.; Nieman, Timothy L.; Peterman, Zell E.; van der Burg, Max Post; Preston, Todd M.; Smith, Bruce D.; Tangen, Brian A.; Thamke, Joanna N.

2014-01-01

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Examination of brine contamination risk to aquatic resources from petroleum development in the Williston Basin  

Science.gov (United States)

U.S. Geological Survey scientists and cooperating partners are examining the potential risk to aquatic resources (for example, wetlands, streams) by contamination from saline waters (brine) produced by petroleum development in the Williston Basin of Montana, North Dakota, and South Dakota. The primary goals of this study are to provide a science-based approach to assess potential risk of brine contamination to aquatic systems and to help focus limited monitoring and mitigation resources on the areas of greatest need. These goals will be accomplished through field investigations that quantify brine movement and risk assessments using remotely-sensed and other spatial datasets.

Gleason, Robert A.; Thamke, Joanna N.; Smith, Bruce D.; Tangen, Brian A.; Chesley-Preston, Tara; Preston, Todd M.

2011-01-01

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Assessment of Undiscovered Oil and Gas Resources of the Williston Basin Province of North Dakota, Montana, and South Dakota, 2008  

Science.gov (United States)

Using a geology-based assessment method, the U.S. Geological Survey estimated mean undiscovered volumes of 3.8 billion barrels of undiscovered oil, 3.7 trillion cubic feet of associated/dissolved natural gas, and 0.2 billion barrels of undiscovered natural gas liquids in the Williston Basin Province, North Dakota, Montana, and South Dakota.

Anna, Lawrence O.; Pollastro, Richard M.; Gaswirth, Stephanie B.; Lewan, Michael D.; Lillis, Paul G.; Roberts, Laura N.R.; Schenk, Christopher J.; Charpentier, Ronald R.; Cook, Troy A.; Klett, Timothy R.

2008-01-01

9

Risk assessment of brine contamination to aquatic resources from energy development in glacial drift deposits: Williston Basin, USA.  

Science.gov (United States)

Contamination to aquatic resources from co-produced water (brine) associated with energy development has been documented in the northeastern portion of the Williston Basin; an area mantled by glacial drift. The presence and magnitude of brine contamination can be determined using the contamination index (CI) value from water samples. Recently, the U.S. Geological Survey published a section (~2.59km(2)) level risk assessment of brine contamination to aquatic resources for Sheridan County, Montana, using oilfield and hydrogeological parameters. Our goal was to improve the Sheridan County assessment (SCA) and evaluate the use of this new Williston Basin assessment (WBA) across 31 counties mantled by glacial drift in the Williston Basin. To determine if the WBA model improved the SCA model, results from both assessments were compared to CI values from 37 surface and groundwater samples collected to evaluate the SCA. The WBA (R(2)=0.65) outperformed the SCA (R(2)=0.52) indicating improved model performance. Applicability across the Williston Basin was evaluated by comparing WBA results to CI values from 123 surface water samples collected from 97 sections. Based on the WBA, the majority (83.5%) of sections lacked an oil well and had minimal risk. Sections with one or more oil wells comprised low (8.4%), moderate (6.5%), or high (1.7%) risk areas. The percentage of contaminated water samples, percentage of sections with at least one contaminated sample, and the average CI value of contaminated samples increased from low to high risk indicating applicability across the Williston Basin. Furthermore, the WBA performed better compared to only the contaminated samples (R(2)=0.62) versus all samples (R(2)=0.38). This demonstrates that the WBA was successful at identifying sections, but not individual aquatic resources, with an increased risk of contamination; therefore, WBA results can prioritize future sampling within areas of increased risk. PMID:25468531

Preston, Todd M; Chesley-Preston, Tara L

2015-03-01

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Ordovician petroleum source rocks and aspects of hydrocarbon generation in Canadian portion of Williston basin  

Energy Technology Data Exchange (ETDEWEB)

Accumulation of rich petroleum source rocks - starved bituminous mudrocks in both the Winnipeg Formation (Middle Ordovician) and Bighorn Group (Upper Ordovician) - is controlled by cyclical deepening events with a frequency of approximately 2 m.y. Tectonics control both this frequency and the location of starved subbasins of source rock accumulation. Deepening cycles initiated starvation of offshore portions of the inner detrital and medial carbonate facies belts. Persistence of starved offshore settings was aided by marginal onlap and strandline migration in the inner detrital facies belt, and by low carbonate productivity in the medial carbonate facies belt. Low carbonate productivity was accompanied by high rates of planktonic productivity. Periodic anoxia, as a consequence of high rates of planktonic organic productivity accompanying wind-driven equatorial upwellings, is the preferred mechanism for suppressing carbonate productivity within the epeiric sea. The planktonic, although problematic, form Gloecapsamorpha prisca Zalesskey 1917 is the main contributing organism to source rock alginites. A long-ranging alga (Cambrian to Silurian), it forms kukersites in Middle and Upper Ordovician rocks of the Williston basin as a consequence of environmental controls - starvation and periodic anoxia. Source rocks composed of this organic matter type generate oils of distinctive composition at relatively high levels of thermal maturity (transformation ratio = 10% at 0.78% R/sub o/). In the Canadian portion of the Williston basin, such levels of thermal maturity occur at present depths greater than 2950 m within a region of geothermal gradient anomalies associated with the Nesson anticline. Approximately 193 million bbl (30.7 x 10/sup 6/ m/sup 3/) of oil has been expelled into secondary migration pathways from thermally mature source rocks in the Canadian portion of the basin.

Osadetz, K.G.; Snowdon, L.R.

1988-07-01

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Williston Basin architecture and hydrocarbon potential in eastern Saskatchewan and western Manitoba  

Energy Technology Data Exchange (ETDEWEB)

This presentation describes the stratigraphy of an area in eastern Saskatchewan and western Manitoba that is being considered for the Weyburn CO{sub 2} Monitoring and Storage Project. This multi-disciplinary project examines the feasibility of storing anthropogenic carbon dioxide in the Williston Basin. The project involves a Targeted Geoscience Initiative (TGI) which includes mapping the Phanerozoic succession over a 200 square km area centred around the Weyburn Pool and extending to the United States. Subsurface mapping is also part of the strategy that envisions the eventual mapping of all significant Phanerozoic units throughout Saskatchewan. Results of the mapping study are available as a computer-generated regional isopach map for the geological formations in Saskatchewan. 3 refs., 2 figs.

Kreis, K.; Beauchamp, B. [Geological Survey of Canada, Calgary, AB (Canada); Bezys, R. [Manitoba Geological Survey, Winnipeg, MB (Canada); Martiniuk, C. [Manitoba Industry, Economic Development and Mines, Winnipeg, MB (Canada); Whittaker, S. [Saskatchewan Industry and Resources, Regina, SK (Canada)

2004-07-01

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Improved recovery demonstration for Williston basin carbonates. Annual report, June 10, 1994--June 9, 1995  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this project is to demonstrate targeted infill and extension drilling opportunities, better determinations of oil-in-place, methods for improved completion efficiency and the suitability of waterflooding in Red River and Ratcliffe shallow-shelf carbonate reservoirs in the Williston Basin, Montana, North Dakota and South Dakota. Improved reservoir characterization utilizing three-dimensional and multi-component seismic are being investigated for identification of structural and stratigraphic reservoir compartments. These seismic characterization tools are integrated with geological and engineering studies. Improved completion efficiency is being tested with extended-reach jetting lance and other ultra-short-radius lateral technologies. Improved completion efficiency, additional wells at closer spacing and better estimates of oil in place will result in additional oil recovery by primary and enhanced recovery processes.

Sippel, M.; Zinke, S.; Magruder, G.; Eby, D.

1995-09-01

13

Study of the geothermal production potential in the Williston Basin, North Dakota  

Energy Technology Data Exchange (ETDEWEB)

Preliminary studies of geothermal production potential for the North Dakota portion of the Williston Basin have been carried out. Reservoir data such as formation depth, subsurface temperatures, and water quality were reviewed for geothermal brine production predictions. This study, in addition, provides important information about net pay thickness, porosity, volume of geothermal water available, and productivity index for future geothermal direct-use development. Preliminary results show that the Inyan Kara Formation of the Dakota Group is the most favorable geothermal resource in terms of water quality and productivity. The Madison, Duperow, and Red River Formations are deeper formations but because of their low permeability and great depth, the potential flow rates from these three formations are considerably less than those of the Inyan Kara Formation. Also, poor water quality and low porosity will make those formations less favorable for geothermal direct-use development.

Chu, Min H.

1991-09-10

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Improved recovery demonstration for Williston Basin carbonates. Quarterly report, January 1, 1995--March 31, 1995  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this project is to demonstrate targeted infill and extension drilling opportunities, better determinations of oil-in-place, methods for improved completion efficiency and the suitability of waterflooding in certain shallow-shelf carbonate reservoirs in the Williston Basin, Montana, North Dakota and South Dakota. Cores from five Red River wells in the Bowman-Harding study area have been examined and described in detail; contracts have been awarded for a 3-D survey in Bowman Co., ND and a 2D, multi-component survey in Richland Co.; extended-time pressure buildup data have been analyzed from two wells which are candidates for jetting-lance completion workovers; a 20-day injectivity test has been completed in the Red River (upper member); a jetting-lance completion program has commenced with one job completed and three more scheduled during April; and reservoir data from three key Red River fields in the Bowman-Harding study area has been researched and accumulated for inclusion in the TORIS database and technology transfer activities.

Carrell, L.A.; Nautiyal, C.

1995-05-01

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Conceptual model of the uppermost principal aquifer systems in the Williston and Powder River structural basins, United States and Canada  

Science.gov (United States)

The three uppermost principal aquifer systems of the Northern Great Plains—the glacial, lower Tertiary, and Upper Cretaceous aquifer systems—are described in this report and provide water for irrigation, mining, public and domestic supply, livestock, and industrial uses. These aquifer systems primarily are present in two nationally important fossil-fuelproducing areas: the Williston and Powder River structural basins in the United States and Canada. The glacial aquifer system is contained within glacial deposits that overlie the lower Tertiary and Upper Cretaceous aquifer systems in the northeastern part of the Williston structural basin. Productive sand and gravel aquifers exist within this aquifer system. The Upper Cretaceous aquifer system is contained within bedrock lithostratigraphic units as deep as 2,850 and 8,500 feet below land surface in the Williston and Powder River structural basins, respectively. Petroleum extraction from much deeper formations, such as the Bakken Formation, is rapidly increasing because of recently improved hydraulic fracturing methods that require large volumes of relatively freshwater from shallow aquifers or surface water. Extraction of coalbed natural gas from within the lower Tertiary aquifer system requires removal of large volumes of groundwater to allow degasification. Recognizing the importance of understanding water resources in these energy-rich basins, the U.S. Geological Survey (USGS) Groundwater Resources Program (http://water.usgs.gov/ogw/gwrp/) began a groundwater study of the Williston and Powder River structural basins in 2011 to quantify this groundwater resource, the results of which are described in this report. The overall objective of this study was to characterize, quantify, and provide an improved conceptual understanding of the three uppermost and principal aquifer systems in energy-resource areas of the Northern Great Plains to assist in groundwater-resource management for multiple uses. The study area includes parts of Montana, North Dakota, South Dakota, and Wyoming in the United States and Manitoba and Saskatchewan in Canada. The glacial aquifer system is contained within glacial drift consisting primarily of till, with smaller amounts of glacial outwash sand and gravel deposits. The lower Tertiary and Upper Cretaceous aquifer systems are contained within several formations of the Tertiary and Cretaceous geologic systems, which are hydraulically separated from underlying aquifers by a basal confining unit. The lower Tertiary and Upper Cretaceous aquifer systems each were divided into three hydrogeologic units that correspond to one or more lithostratigraphic units. The period prior to 1960 is defined as the predevelopment period when little groundwater was extracted. From 1960 through 1990, numerous flowing wells were installed near the Yellowstone, Little Missouri and Knife Rivers, resulting in local groundwater declines. Recently developed technologies for the extraction of petroleum resources, which largely have been applied in the study area since about 2005, require millions of gallons of water for construction of each well, with additional water needed for long-term operation; therefore, the potential for an increase in groundwater extraction is high. In this study, groundwater recharge and discharge components were estimated for the period 1981–2005. Groundwater recharge primarily occurs from infiltration of rainfall and snowmelt (precipitation recharge) and infiltration of streams into the ground (stream infiltration). Total estimated recharge to the Williston and Powder River control volumes is 4,560 and 1,500 cubic feet per second, respectively. Estimated precipitation recharge is 26 and 15 percent of total recharge for the Williston and Powder River control volumes, respectively. Estimated stream infiltration is 71 and 80 percent of total recharge for the Williston and Powder River control volumes, respectively. Groundwater discharge primarily is to streams and springs and is estimated to be about 97 and 92 percent of total discharge for the W

Long, Andrew J.; Aurand, Katherine R.; Bednar, Jennifer M.; Davis, Kyle W.; McKaskey, Jonathan D.R.G.; Thamke, Joanna N.

2014-01-01

16

77 FR 37036 - Williston Basin Interstate Pipeline Company; Notice of Request Under Blanket Authorization  

Science.gov (United States)

...Commission's Regulations under the Natural Gas Act (NGA) as amended and Williston...the acquisition and operation of natural gas facilities in Sheridan County...Wyoming and modification of underground storage facilities at its Baker...

2012-06-20

17

Long-term solute transport through thick Cretaceous shale in the Williston Basin Canada using naturally-occurring tracer profiles  

International Nuclear Information System (INIS)

Document available in abstract form only. The hydrogeologic evolution of sedimentary basins is generally determined from hydraulic and chemical data collected from aquifers. Hydraulic and chemical data from aquitards, which constitute a much greater volume of basins than aquifers and provide important controls on water and solute transport in the basins, are generally not collected nor studied. In this study we characterized the paleo-groundwater flow and solute transport controls through a vertical section of Cretaceous sediments in the Williston Basin, Canada located near Esterhazy, Saskatchewan. It consists of 384 m of thick argillaceous sediment (aquitard) overlying 93 m of heterogeneous calcareous silt, shale and sandstone (Mannville Fm.; aquifer). Paleo-hydrologic conditions were determined by interpreting high-resolution depth profiles of natural tracers of water isotopes (?18O and (?2H) and Cl- measured on (1) continuous core samples through the aquitard, upper aquifer, and thin Quaternary sediments, (2) water samples collected from monitoring wells installed in the aquifer and the Quaternary sediments, and (3) water samples collected from mine shaft inflows to 900 m below ground. 1D numerical transport modeling reproduced the measured profiles and yielded valuable information on the large-scale and long-term transport behavior in both the Cretaceous aquitard and the Basin. In the modeling, the shapes of the tracer profiles was explaineapes of the tracer profiles was explained by diffusion with paleo-events identified from the modeling including the introduction of fresher water into the aquifer possibly from the onset of glaciation (activation of the lower boundary) about 1 Ma ago and the impact of the most recent deglaciation about 10 ka ago (activation of the upper boundary). These findings show that the hydrogeologic conditions in deep, extensive basins, such as the Williston Basin, cannot be assumed to be static over geologic time. (authors)

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Investigation of relationships between linears, total and hazy areas, and petroleum production in the Williston Basin: An ERTS approach  

Science.gov (United States)

The author has identified the following significant results. ERTS-1 imagery in a variety of formats was used to locate linear, tonal, and hazy features and to relate them to areas of hydrocarbon production in the Williston Basin of North Dakota, eastern Montana, and northern South Dakota. Derivative maps of rectilinear, curvilinear, tonal, and hazy features were made using standard laboratory techniques. Mapping of rectilinears on both bands 5 and 7 over the entire region indicated the presence of a northeast-southwest and a northwest-southeast regional trend which is indicative of the bedrock fracture pattern in the basin. Curved lines generally bound areas of unique tone, maps of tonal patterns repeat many of the boundaries seen on curvilinear maps. Tones were best analyzed on spring and fall imagery in the Williston Basin. It is postulated that hazy areas are caused by atmospheric phenomena. The ability to use ERTS imagery as an exploration tool was examined where petroleum and gas are presently produced (Bottineau Field, Nesson and Antelope anticlines, Redwing Creek, and Cedar Creek anticline). It is determined that some tonal and linear features coincide with location of present production in Redwing and Cedar Creeks. In the remaining cases, targets could not be sufficiently well defined to justify this method.

Erickson, J. M.; Street, J. S. (principal investigators); Munsell, C. J.; Obrien, D. E.

1975-01-01

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The Amaranth Formation of the Williston Basin: Paleomagnetic, Petrologic and Geochemical studies  

Science.gov (United States)

Major debate continues to exist concerning the time of deposition of the Amaranth Formation in the Williston Basin of North America, with postulated ages of Pennsylvanian, Permian, Triassic, Lower and Middle Jurassic. A multidisciplinary study of the lower member of the Amaranth Formation was conducted in six wells in Manitoba. The lower Amaranth red beds are composed of red carbonate-rich and carbonate-poor interbedded sandstones/siltstones/shales containing dolomite and anhydrite and lacking diagnostic fossils. Preliminary analysis of the oxygen and carbon isotope values measured for replacive and cement dolomite show variations related to particular lithologies that can be correlated to the types of dolomite present in the rocks. The siliciclastic sections are dominated by detrital, zoned dolomite that has recrystallized rims, whereas in the more carbonate-rich and evaporitic samples with little to no clastic content, replacive matrix dolomite is the dominant phase. Dolomite samples from the siliciclastic sections are characterized by relatively depleted carbon and oxygen isotope values, the dolomite matrix samples have relatively enriched oxygen and carbon isotope values and a few samples containing replacement matrix dolomite with minor clastic input have intermediate isotope values. These variations reflect primary and diagenetic overprints. Hematite is the major magnetization carrier, with occasional softer magnetic minerals such as magnetite. Optical microscopy revealed the existence of two types of hematite: detrital specular hematite and very fine red pigment hematite. The paleomagnetic data reveals at least three episodes of magnetization. The most pervasive magnetization, B, was formed during the Permian-Carboniferous Kiaman Reverse Superchron. An isolated magnetization in a couple of wells, C, suggests a remagnetization event that happened sometime between mid-Jurassic and Neogene, possibly resulting from a localized oxidizing fluid flow event. The oldest magnetization, D, was acquired sometime between mid-Devonian and Pennsylvanian, but it is usually poorly defined and is not common within the studied samples. B and D are both carried in both specular and pigmentary hematite and are candidates for a primary magnetization preserved in the lower Amaranth samples. The paleomagnetic data presented in this study indicate that the lower Amaranth member red beds are certainly older than early- to mid-Jurassic, and probably even older than Triassic. Our results suggest that these sediments were deposited either in Pennsylvanian or during the Permian-Carboniferous Kiaman Reverse Superchron.

Szabo, E.; Cioppa, M. T.; Al-Aasm, I.

2008-12-01

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Williston Basin Project (targeted geoscience initiative 2): summary report on Mesozoic stratigraphy, mapping and hydrocarbon assessment, southwestern Manitoba  

Energy Technology Data Exchange (ETDEWEB)

This paper described the geological setting of the Williston Basin in southwestern Manitoba, with particular reference to the Paleozoic, Mesozoic and Cenozoic strata from basement to outcrop. Data from more than 9000 drillholes were used to create of series of structural and isopach maps. The regional isopachs were then reviewed along with structural features to determine stratigraphic relationships and to interpret the tectonics of the region. The paper described the major potential hydrocarbon reservoirs and play types for the Mesozoic formations in Manitoba. Rock-Eval geochemistry results were included for certain Cretaceous units in order to determine major potential hydrocarbon reservoirs and play types for the Mesozoic formations in Manitoba. The sequence of rocks are mainly sand, silt and shale with occasional limestone units. It was concluded that the Mesozoic succession has excellent economic potential. The Cretaceous Swan River Formation and Newcastle Member of the Ashville Formation are the best targets for oil, and the Upper Ashville, Favel and Carlile formations and the Pierre Shale are the best targets for shallow, unconventional shale gas. 78 refs., 3 figs., 1 appendix.

Nicolas, M.P.B.

2009-07-01

 
 
 
 
21

Comparing vertical profiles of natural tracers in the Williston Basin to estimate the onset of deep aquifer activation  

Science.gov (United States)

high-resolution depth profiles of different naturally occurring environmental tracers in aquitards should yield consistent and perhaps complementary information about solute transport mechanisms and the timing of major hydrogeological and climatological events. This study evaluated whether deep, continuous profiles of aquitard pore water chloride concentration could provide further insight into the paleohydrology of the Williston Basin, Canada, than possible using high-resolution depth profiles of stable H/O isotopes of water (?18O, ?2H). Pore water samples were obtained from extracts of cores taken over 392 m of the thick Cretaceous shale aquitard. Water samples were also collected from wells installed in the underlying regional sandy aquifer (Mannville Group; 93 m thick) and from seepage inflows into potash mine shafts (to 825 m below ground). Numerical modeling of the 1-D vertical Cl- profile supported diffusion dominated solute transport in the shales. The modeling also showed a similar time frame for development of the Cl- profile prior to activation of the aquifer as determined from the ?18O profile (20-25 Ma); however, it provided a significantly longer and potentially better-constrained time frame for evolution of the profile during the activation phase of the aquifer (0.5-1 Ma). The dominant paleoevent reflected in present-day profiles of both tracers is the introduction of glaciogenic meteoric water to the Mannville aquifer underlying the shale during the Pleistocene. The source area of this water remains to be determined.

Hendry, M. Jim; Harrington, Glenn A.

2014-08-01

22

Geology of the Fox Hills Formation (late Cretaceous) in the Williston Basin of North Dakota, with reference to uranium potential. Report of investigation No. 55  

International Nuclear Information System (INIS)

The Fox Hills Formation is a marine and brackish sequence of primarily medium and fine clastics within the Late Cretaceous Montana Group. In the Williston basin of North Dakota, four members (in ascending order) are recognized: Trail City, Timber Lake, Iron Lightning (with Bullhead and Colgate lithofacies), and Linton. The Fox Hills conformably overlies the Pierre Shale and conformably and disconformably underlies and interfingers with the Hell Creek Formation; it occurs in about the western two-thirds of the state. The geology of the Fox Hills Formation in North Dakota, and the stratigraphy of which is based on previous surface information and recent subsurface data, are summarized, and its potential for uranium is evaluated

23

A new species of Ischyodus (Chondrichthyes: Holocephali: Callorhynchidae) from Upper Maastrichtian Shallow marine facies of the Fox Hills and Hell Creek Formations, Williston basin, North Dakota, USA  

Science.gov (United States)

A new species of chimaeroid, Ischyodus rayhaasi sp. nov., is described based primarily upon the number and configuration of tritors on palatine and mandibular tooth plates. This new species is named in honour of Mr Raymond Haas. Fossils of I. rayhaasi have been recovered from the Upper Maastrichtian Fox Hills Formation and the Breien Member and an unnamed member of the Hell Creek Formation at sites in south-central North Dakota and north-central South Dakota, USA. Ischyodus rayhaasi inhabited shallow marine waters in the central part of the Western Interior Seaway during the latest Cretaceous. Apparently it was also present in similar habitats at that time in the Volga region of Russia. Ischyodus rayhaasi is the youngest Cretaceous species Ischyodus known to exist before the Cretaceous/Tertiary extinction, and the species apparently did not survive that event. It was replaced by Ischyodus dolloi, which is found in the Paleocene Cannonball Formation of the Williston Basin region of North Dakota and is widely distributed elsewhere. ?? The Palaeontological Association.

Hoganson, J.W.; Erickson, J.M.

2005-01-01

24

Manitoba Williston Basin activity update  

Energy Technology Data Exchange (ETDEWEB)

This presentation described the drilling activity in Manitoba from 1998 to 2002 with particular emphasis on horizontal well drilling and production by geologic formation, including the Bakken, Lodgepole and the Lower Amaranth Formations. A total of 97 wells were drilled in Manitoba in 2002. The most active drillers were EOG Resources Canada with a total of 34 wells. Tundra Oil and Gas was close behind with 28 wells, followed by Chevron Canada Resources with 21 wells. Horizontal drilling had a major impact in Manitoba between 1998-2002, representing 30 per cent of drilling activity focused on the Waskada, Virden and Daly fields. Expansion activity throughout the province contributed to the overall increase in oil production for four consecutive years. Annual production reached 650.7 10{sup 3}m{sup 3} in 2001. Manitoba's top 5 producers are Chevron Canada Resources, Tundra Oil and Gas, EOG Resources Canada, Canadian Natural Resources and NCE Petrofund. Together, they account for 89 per cent of Manitoba's production. This paper also described some of the initiatives that Manitoba's Department of Industry, Trade and Mines has taken to improve oil and gas regulations through proposed amendments to the Oil and Gas Act, a review of the Manitoba Drilling Incentive Program, battery re-permitting, and a strategy for managing orphaned wells. 3 figs.

Fox, J. [Manitoba Industry, Trade and Mines, Winnipeg, MB (Canada)

2003-07-01

25

Seismic evidence of tectonic stresses; Implications for basin reconstruction:  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Stress and strain are two important rheological parameters that have impacts on basin development and dynamics. The dynamic evolution of a basin depends on the spatial and temporal changes in the stresses. How to determine the reference state of stress within a sedimentary basin and the magnitude of the forces at the plate boundaries, which produce an important part of these stress fields, have been two of the most important questions in basin research for the past few decades. The stress his...

Tigrek, S.

2004-01-01

26

Quantitative subsidence analysis of the Western Canada foreland basin with implications for short-term facies changes  

Science.gov (United States)

This paper presents a quantitative study of Jurassic-Lower Tertiary basement subsidence in the Western Canada foreland basin, corrected for local sediment loading and paleobathymetrical changes. Subsidence patterns have been investigated for the effects of erosion induced uplift by means of analytical estimations. It is demonstrated that phases of rapid basin shallowing may be related to periods of dominant erosion of the Cordilleran fold-and-thrust belt, leading to 200-20 m flexural uplift of the lithosphere within distances of 300 km of the belt. The amount of sediment that has been derived from the orogenic belt in such a period, can be sufficient for a shelf edge progradation of at least 300 km Myr -1. The history of the Western Canada foreland basin has been subdivided in five stages, 200-154.7 Ma (sI), 154.7-124.5 Ma (sII), 124.5-104 Ma (sIII), 104-77.7 Ma (sIV), and 77.7-60 Ma (sV), recording polyphase lateral and temporal changes in the loading history. The subdivision between stage I and stages II-V is based on a transition from significant vertical motions in the Williston basin in the southeast and minor sedimentation to the west during sI, to continued vertical motions in the Williston basin and major subsidence and sediment accumulation to the west during sII-sV. This major change forms the expression of the transition from passive to convergent margin conditions (cf. Davies and Poulton, 1986). The sII-sIII transition is marked by the expansion of the area of tectonic activity towards the north due to a large scale plate reorganization (cf. Chamberlain and Lambert, 1985). Stage IV is characterized by generally continuous subsidence with deposition of shales, interrupted by phases of rapid uplift with deposition of sandy shallow water units, while the subsequent stage V is defined by similar tectonic processes, but sedimentation conditions changed from mainly shale accumulation to mainly sand accumulation. These latter two stages probably reflect lateral and temporal changes in the rate of progradation of the accretionary wedge.

Peper, Tim

1993-11-01

27

Implication of drainage basin parameters of a tropical river basin of South India  

Science.gov (United States)

Drainage morphometry provides quantitative description of the drainage system which is an important aspect of the characterisation of watersheds. Chalakudi River is one of the important rivers of the South India which has attracted attention of many environmental scientists recently because of the proposed Athirapally Hydel Project across the river. SRTM (Shuttle Radar Topographic Mission) data were used for preparing DEM (Digital Elevation Model), Aspect Map and Slope Map. Geographical Information System (GIS) was used for the evaluation of linear, areal and relief aspects of morphometric parameters. The study reveals that the terrain exhibits dentritic and trellis pattern of drainage. The Chalakudi River Basin has a total area of 1,448.73 km2 and is designated as seventh-order basin. The drainage density of the basin is estimated as 2.54 and the lower-order streams mostly dominate the basin. The high basin relief indicates high runoff and sediment transport. The elongation ratio of the Chalakudi Basin is estimated as 0.48 and indicates that the shape of the basin is elongated. The development of stream segments in the basin area is more or less effected by rainfall. Relief ratio indicates that the discharge capability of watershed is very high and the groundwater potential is meagre. The low value of drainage density in spite of mountainous relief indicates that the area is covered by dense vegetation and resistant rocks permeated by fractures and joints. These studies are helpful in watershed development planning and wise utilization of natural resources.

Babu, K. J.; Sreekumar, S.; Aslam, Arish

2014-07-01

28

3-D basin modelling of the Paris Basin: diagenetic and hydrogeologic implications  

International Nuclear Information System (INIS)

A 3-D basin model of the Paris basin is presented in order to simulate through geological times fluid, heat and solute fluxes. This study emphasizes: i) the contribution of basin models to the quantitative hydrodynamic understanding of behaviour of the basin over geological times; ii) the additional use of Atmospheric General Circulation model (AGCM) to provide palaeo-climatic boundaries for a coupled flow and mass transfer modelling, constrained by geochemical and isotopic tracers and; iii) the integration of different types of data (qualitative and quantitative) to better constrain the simulations. Firstly, in a genetic way, basin model is used to reproduce geological, physical and chemical processes occurring in the course of the 248 My evolution of the Paris basin that ought to explain the present-day hydraulic properties at the regional scale. As basin codes try to reproduce some of these phenomena, they should be able to give a plausible idea of the regional-scale permeability distribution of the multi-layered system, of the pre-industrial hydrodynamic conditions within the aquifers and of the diagenesis timing and type of hydrodynamic processes involved. Secondly, climate records archived in the Paris basin groundwater suggest that climate and morphological features have an impact on the hydrogeological processes, particularly during the last 5 My. An Atmospheric General Circulation model is used with a refined spatial resolution centred on the Paris basin to rresolution centred on the Paris basin to reproduce the climate for the present, the Last Glacial Maximum (21 ky) and the middle Pliocene (3 My). These climates will be prescribed, through forcing functions to the hydrological code with the main objective of understanding the way aquifers and aquitards react under different climate conditions, the period and the duration of these effects. Finally, the Paris basin has been studied for a number of years by different scientific communities, thus a large amount of data has been collected. By integrating all these actors in a same research program (PNRH.99/35-01/44: 'Paris basin modelling') we were able to draw a more comprehensive view of the Paris basin evolution. At each step of the work, meetings and discussions were conducted to assess the validity of the data and quality of the results. Thus work is still in progress, the basin model results will be first emphasized in this short paper, and while the hydro-climatologic modelling will be presented as a perspective for future work. (author)

29

Tritium concentrations in the Yukon River Basin and their implications  

International Nuclear Information System (INIS)

The tritium transient, produced by atmospheric nuclear weapons testing in the 1950s and 1960s, has been used to determine timescales for large-scale hydrologic processes such as the movement of water through river basins. A long-term tritium data base is available from downstream stations on the Yukon River from 1961 to the present. This data has been analyzed using a lumped-sum parameter model to obtain estimates of fraction of base flow and timescales for flow of water through the basin. The data shows that 63% of the water exported by the Yukon River has been retained in the basin less than a year. The average residence time for the older water is approximately 17 years. (author)

30

New aerogeophysical study of the Eurasia Basin and Lomonosov Ridge: Implications for basin development  

DEFF Research Database (Denmark)

In 1998 and 1999, new aerogeophysical surveys of the Arctic Ocean's Eurasia Basin produced the first collocated gravity and magnetic measurements over the western half of the basin. These data increase the density and extend the coverage of the U.S. Navy acromagnetic data from the 1970s. The new data reveal prominent bends in the isochrons that provide solid geometrical constraints for plate reconstructions. Tentative identification of anomaly 25 in the Eurasia Basin links early basin opening to spreading in the Labrador Sea before the locus of spreading in the North Atlantic shifted to the Norwegian-Greenland Sea. With the opening of the Labrador Sea, Greenland began similar to200 km of northward movement relative to North America and eventually collided with Svalbard, Ellesmere Island, and the nascent Eurasia ocean basin. Both gravity and magnetic data sets reconstructed to times prior to chron 13 show a prominent linear anomaly oriented orthogonal to the spreading center and immediately north of the YermakPlateau and Morris Jesup Rise. This anomaly may mark the locus of shortening and possibly subduction as Greenland collided with the nascent Eurasia Basin and impinged upon the southern Gakkel Ridge. This collision may have contributed to vollcanism on the Morris Jesup Rise. By chron 13, Greenland had ended its northward motion and had become fixed to North America, and the plateau north of Greenland had rifted apart to become the Morris Jesup Rise and the Yermak Plateau.

Brozena, J.M.; Childers, V.A.

2003-01-01

31

AEROBIC DENITRIFICATION: IMPLICATIONS FOR THE MOM RIVER BASIN  

Science.gov (United States)

Each year about 1.6 million metric tons of nitrogen, mostly from agriculture, is discharged from the lower Mississippi/Atchafalaya River Basin into the Gulf of Mexico, and each spring this excess nitrogen fuels the formation of a huge hypoxic zone in the Gulf. In the Mississippi...

32

Geochemical characterization of Parana Basin volcanic rocks: petrogenetic implications  

International Nuclear Information System (INIS)

A detailed study of the geochemical characteristics of Parana Basin volcanic rocks is presented. The results are based on the analyses of major and trace elements of 158 samples. Ninety three of these volcanic samples belong to 8 flow sequences from Rio Grande do Sul and Santa Catarina States. The remaining sixty five samples are distributed over the entire basin. In order to study the influence of crustal contamination processes in changing chemical characteristics of the volcanic rocks, 47 samples representative of the crystalline basement of the southern and southeastern Parana Basin were also analysed. Several petrogenetic models were tested to explain the compocional variability of the volcanic rocks, in particular those of southern region. The results obtained sugest an assimilation-fractional crystallization process as viable to explain the differences of both the chemical characteristics and Sr isotope initial ratios observed in basic and intermediate rocks. A model involving melting processes of basic material, trapped at the base of the crust, with composition similar to low and high TiO2 basalts appears to be a possibility to originate the Palmas and Chapeco acid melts, respectively. The study of ''uncontaminated'' or poorly contaminated low TiO2 basic rocks from the southern, central and northern regions shows the existence of significant differences in the geochemical charactetistics according to their geographical occurrence. A similar geochemical diversity is also observed in high TiO2 basalts and Chapeco volcanics. Differences in incompatible element ratios between low and high TiO2 ''uncontaminated'' or poorly contaminated basalts suggest that they could have been produced by different degrees of melting in a garnet peridotite source. Geochemical and isotopic (Sr and Nd) data also support the view that basalts from northern and southern regions of Parana Basin originated from mantle source with different composition. (author)

33

GRAIL Gravity Observations of Peak-Ring Basins on the Moon: Implications for Basin Formation  

Science.gov (United States)

Reassessment of the formation of peak-ring basins on the Moon using image and altimetry data from the Lunar Reconnaissance Orbiter has yielded a number of morphometric properties of these basin types that are helping to constrain the processes leading to their formation and the formation of larger multi-ring basins [1,2]. These analyses demonstrate the importance of the volume and depth of impact melting in modifying the interior morphology of large impact craters. At the onset diameter of peak-ring basins, the depth of the basin's melted zone approaches the depth of the transient crater, creating a strengthless interior melt cavity that facilitates gravitational collapse of the transient crater. The melt cavity suppresses central peak formation, and peak rings are formed outward from the melt zone boundary by the interaction of deep-seated rotational faults in the collapsing wall of the transient crater and huge vertical uplifts in the central portions of the basin. The final configuration of the peak-ring basin has a kilometers-thick slab of cooled residual impact melt resting on an uplifted mantle plug with little or no unmelted crustal material. Highly faulted and fractured, dilatant and possibly thickened crust should occur below and outward from the peak ring due to inward and upward translation of collapsed transient crater rim material. As a result of this configuration, the gravity structure should reflect an anomalously high density, uplifted impact melt plus mantle zone spatially confined to within the peak ring. Surrounding this should be a highly fractured, low density zone of possibly thickened crust. Bouguer gravity anomalies derived from Gravity Recovery and Interior Laboratoy (GRAIL) gravity data and Lunar Orbiter Laser Altimeter (LOLA) altimetry data show spatial patterns that are consistent with those predicted by the formation model briefly outlined above. Nearly all 17 peak-ring basins that have been cataloged on the Moon show positive Bouguer gravity anomalies that are spatially confined within the peak ring. The magnitudes of the anomalies are variable, but appear to be less prominent in the smallest peak-ring basins. These observations are consistent with enhanced crustal densities resulting from thinned crust and extreme uplift of the interior melt zone and mantle below. In many of the basins, the annulus between the peak ring and rim crest shows a Bouguer gravity anomaly that is reduced relative to crust exterior to the rim crest. This is consistent with low density, highly faulted and fractured, dilatant crust resulting from the collapse of the transient cavity and formation of the peak ring. The peak rings show gravity anomalies intermediate between the positive central anomaly and reduced gravity annulus, suggesting that peak rings form at the boundary of the uplifted melt plus mantle plug and the zone of highly fractured or thickened crust. Further quantification of the gravity anomalies and comparisons with the predicted density and crustal structure below peak-ring basins will help to better constrain the preliminary observations presented here. References: [1] Baker et al. (2011) Icarus, 214, 377-393. [2] Baker, D.M.H. et al. (2012) J. Geophys. Res., 117, E00H16.

Baker, D. M.; Head, J. W.; Neumann, G. A.; Smith, D. E.; Zuber, M. T.

2012-12-01

34

Widespread Late Paleozoic remagnetization of the Great Basin miogeocline: Implications for Basin and Range tectonism  

Energy Technology Data Exchange (ETDEWEB)

In the eastern and southern Great Basin, heterogeneous, shallow-water miogeocline carbonate rocks give a shallow inclination, south to southeast-directed characteristic magnetization residing in magnetite. The magnetization, found in the Desert Range of southern Nevada, the Egan Range of east-central Nevada, and the House Range of western utah, is interpreted to be secondary. It was acquired after (1) local, soft compaction, because directions of magnetization are not dispersed by macroscopic compaction of stylolites and fine carbonate laminations, of up to 25[degree], wrapping around chert masses, and (2) local karst brecciation, as conglomerate tests are negative. The uniform reversed polarity in addition to the direction of the magnetization is interpreted to suggest a late Paleozoic time of remagnetization, in the Kiaman superchron. The authors interpret the secondary magnetization to be of chemical origin, and speculate that it was acquired in response to cratonward fluid migration initiated by Antler contraction. In the Egan Range, about 4 km of Paleozoic strata have been remagnetized. That this secondary but ancient late Paleozoic magnetization has survived subsequent events is significant for interpreting Mesozoic and Cenozoic processes. First, on a regional scale, the Paleozoic miogeocline never experienced burial temperatures greater than about 300 C during mesozoic contraction. Second, because the secondary magnetization can be referenced to the paleohorizontal, it may prove to be an important passive marker for assessing vertical axis rotation related to, first, Mesozoic thrusting, and, second, Cenozoic extension. This is currently being tested.

Geissman, J.W. (Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Earth and Planetary Sciences); Gillett, S.L. (Univ. of Nevada, Reno, NV (United States). Mackay School of Mines); Bartley, J.M. (Univ. of Utah, Salt Lake City, UT (United States). Dept. of Geology and Geophysics)

1992-01-01

35

Waterford Formation in the south-eastern Karoo: Implications for basin development  

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English Abstract in english Extensive research on the rocks of the Karoo Supergroup has shown that this sequence, which contains an unsurpassed record of Permian-Jurassic tetrapods, records a largely unbroken stratigraphic succession from 300 Ma to 180 Ma. This Gondwanan succession was deposited in a changing environmental set [...] ting reflecting glacial marine through deltaic to fluvial and aeolian desert conditions. The contact between the Ecca and Beaufort Groups (at the top of the Waterford Formation of the Ecca Group) in the southern and western Karoo represents a change in depositional environment from a subaqueous to a subaerial delta plain. By contrast, the Waterford Formation has not yet been recognised in the south-eastern Karoo Basin, which might imply that a major unconformity is present between the Fort Brown Formation of the Ecca Group, deposited in a prodelta environment, and the overlying fluvially deposited Koonap Formation of the Beaufort Group. From careful documentation of lithofacies and sedimentological data, it can be demonstrated that the Waterford Formation is indeed present in the south-eastern part of the basin and that no major unconformity is present - a fact that has implications for the mapping of Karoo rocks in the Eastern Cape Province of South Africa, for understanding the depositional environment of 'reptilian' fossils from the lowermost Beaufort in this part of the Karoo basin, and for basin development models.

Bruce S, Rubidge; P. John, Hancox; Richard, Mason.

36

Quantification of Exhumation from Sonic Velocity Data, Cooper Basin, Australia, and Implications for Hydrocarbon Exploration  

Science.gov (United States)

Exhumation (defined as rock uplift minus surface uplift) in the Cooper Basin of South Australia and Queensland has been quantified using the compaction methodology. The sonic log, which is strongly controlled by the amount of porosity, is an appropriate indicator of compaction, and hence is used for quantifying exhumation from compaction. The traditional way of estimating exhumation based on the degree of overcompaction of a single shale unit has been modified and five units ranging in age from Permian to Triassic have been analysed. The results reveal that exhumation increases eastwards from the South Australia into the Queensland sector of the basin. The results show that exhumation in Late Triassic - Early Jurassic times, after the Cooper Basin deposition, seems to be 200-400 m higher than exhumation in Late Cretaceous - Tertiary times, after the Eromanga Basin deposition. This study has major implications for hydrocarbon exploration. Maturation of source rocks will be greater for any given geothermal history if exhumation is incorporated in maturation modelling. Exhumation values can also be used to improve porosity predictions of reservoir units in undrilled targets.

Mavromatidis, Angelos

2006-05-01

37

Irrigation efficiency and water-policy implications for river-basin resilience  

Directory of Open Access Journals (Sweden)

Full Text Available Rising demand for food, fiber, and biofuels drives expanding irrigation withdrawals from surface- and groundwater. Irrigation efficiency and water savings have become watchwords in response to climate-induced hydrological variability, increasing freshwater demand for other uses including ecosystem water needs, and low economic productivity of irrigation compared to most other uses. We identify three classes of unintended consequences, presented here as paradoxes. Ever-tighter cycling of water has been shown to increase resource use, an example of the efficiency paradox. In the absence of effective policy to constrain irrigated-area expansion using "saved water", efficiency can aggravate scarcity, deteriorate resource quality, and impair river-basin resilience through loss of flexibility and redundancy. Water scarcity and salinity effects in the lower reaches of basins (symptomatic of the scale paradox may partly be offset over the short-term through groundwater pumping or increasing surface water storage capacity. However, declining ecological flows and increasing salinity have important implications for riparian and estuarine ecosystems and for non-irrigation human uses of water including urban supply and energy generation, examples of the sectoral paradox. This paper briefly examines policy frameworks in three regional contexts with broadly similar climatic and water-resource conditions – central Chile, southwestern US, and south-central Spain – where irrigation efficiency directly influences basin resilience. The comparison leads to more generic insights on water policy in relation to irrigation efficiency and emerging or overdue needs for environmental protection.

C. A. Scott

2013-07-01

38

Irrigation efficiency and water-policy implications for river basin resilience  

Science.gov (United States)

Rising demand for food, fiber, and biofuels drives expanding irrigation withdrawals from surface water and groundwater. Irrigation efficiency and water savings have become watchwords in response to climate-induced hydrological variability, increasing freshwater demand for other uses including ecosystem water needs, and low economic productivity of irrigation compared to most other uses. We identify three classes of unintended consequences, presented here as paradoxes. Ever-tighter cycling of water has been shown to increase resource use, an example of the efficiency paradox. In the absence of effective policy to constrain irrigated-area expansion using "saved water", efficiency can aggravate scarcity, deteriorate resource quality, and impair river basin resilience through loss of flexibility and redundancy. Water scarcity and salinity effects in the lower reaches of basins (symptomatic of the scale paradox) may partly be offset over the short-term through groundwater pumping or increasing surface water storage capacity. However, declining ecological flows and increasing salinity have important implications for riparian and estuarine ecosystems and for non-irrigation human uses of water including urban supply and energy generation, examples of the sectoral paradox. This paper briefly considers three regional contexts with broadly similar climatic and water-resource conditions - central Chile, southwestern US, and south-central Spain - where irrigation efficiency directly influences basin resilience. The comparison leads to more generic insights on water policy in relation to irrigation efficiency and emerging or overdue needs for environmental protection.

Scott, C. A.; Vicuña, S.; Blanco-Gutiérrez, I.; Meza, F.; Varela-Ortega, C.

2014-04-01

39

Structural and Sedimentological Development of Pahrump Basin, Southern Nevada with Implications for Seismic Hazards  

Science.gov (United States)

The purpose of this study is to (1) document potentially active faults and estimate possible earthquake magnitudes, (2) document and analyze sedimentation in a basin controlled by strike-slip and oblique faults, and (3) consider implications on regional development using Pahrump Valley, southern Nevada as a case study. The 2.5 million people living within the region would be significantly impacted by a major earthquake generated in the Valley. With an ever increasing population, the need for evaluation of seismic risk is becoming more important for land use planning in southern Nevada. Using data analysis of well logs, geophysical measurements, surface data from air photos, maps, and field observations, it is possible to document the 3D architecture of the basin-fill sediments and basin structure through abrupt changes in sedimentary facies. 3D modeling of the lithology and depositional environments of shallow basin fill improves the understanding of fault location, type, offset, and surface rupture length. Pahrump Valley is flanked by two documented Neogene (Quaternary) fault systems. The west side is dominated by the Stateline Fault zone, which is a continuous NW-striking right-lateral strike-slip fault zone extending 200 km from Mesquite Valley to Amargosa Valley, Nevada. In Pahrump Valley no fault scarp is present. The eastern side is bordered by the West Spring Mountains fault, which is a N-striking W-dipping normal fault with a right-lateral oblique component. The fault has a large scarp which is visible along the northeastern and east-central Valley border and smaller discontinuous scarps in the south. The 11-km-long central segment contains scarps up to 9.4 m high. On the basis of scarp profiles, the youngest event is estimated to be Pleistocene or early Holocene in age with a maximum fault displacement estimated at 1.8-2.0 m, which suggests an event of M 6.9. 3D basin models, derived from well log lithology, depict the locations of fault surfaces by showing abrupt changes in units and unit offsets among multiple wells. The lithologic data augmented with surface investigations and seismic data show a depositional environment dominated by alluvial deposits of coarse material (gravel and sand) and playa sediments (clay and soils) that interfinger. The playa sediments in the west valley exhibit right-lateral displacement of 10 km consistent with the Stateline fault zone.

Carter, J.; Taylor, W. J.; Luke, B.

2008-12-01

40

Finding the boundary between evolutionary basins of attraction, and implications for Wright's fitness landscape analogy  

International Nuclear Information System (INIS)

In 1932 Wright introduced the notion of the fitness landscape. By analogy with a physical landscape, whose gradient predicts a rolling marble's spatial trajectory, the contours of the fitness landscape are meant to predict an evolving population's genetic trajectory. Wright's chief interest was in the possibility that mutational interactions might frustrate natural selection, giving rise to multiple maxima on the fitness landscape. Here we study a dynamical system over the state space defined by allele frequencies and linkage disequilibria between alleles. We first analytically locate the saddle between basins of attraction in infinite-sized populations evolving under the influence of selection and recombination for the simplest two-locus case. We further show numerically that the boundary between basins is approximately linear with respect to linkage disequilibrium, though not allele frequency. We also employ this framework to develop novel perspectives on two venerable results for single-peaked fitness landscapes. Finally we sought the potential function whose contours would predict evolutionary trajectories through this state space. Importantly not every dynamical system can be described by a potential function, and the present problem is provably one such case. Thus in the parlance of Wright's analogy, in locating the floor of the fitness valley we have lost the landscape, and this conclusion is not limited to our choice of parameterization, nor of problem. This result motivates us to carefully review the formal implications and requirements of this widely used analogy

 
 
 
 
41

The Thrace basin in the Rhodope province of NE Greece — A tertiary supradetachment basin and its geodynamic implications  

Science.gov (United States)

Detailed tectonic analysis and geological mapping on the Tertiary molassic and volcanosedimentary rocks of the Thrace basin in northeastern Greece, allowed us to reconstruct the structural evolution of the basin and its geotectonic setting, as well as the orientation of the regional paleostress field. Sedimentation was linked with a calc-alkaline and locally shoshonitic magmatism associated with the Tertiary syn- to late-orogenic extension in the Rhodope province. We interpret the molassic Tertiary Greek part of the Thrace basin as a supradetachment basin associated with sedimentary and volcanic infilling. Five (5) deformational events (T1 to T5) have been distinguished during basin evolution from Eocene to Quaternary time. T1 is related to a low angle normal detachment fault zone with a top to the SW to SSW sense of movement and initial basin subsidence during Middle-Late Eocene to Oligocene time, simultaneously with uplift and exhumation of the footwall Rhodope metamorphic rocks. Stacking and crustal thickening in the more external parts of the Hellenic orogenic belt have taken place during the same time. T2 evolved during Oligocene-Miocene time. It was characterized by transpressional tectonics and formation of large strike slip faults and extensional fractures, as well as conjugate thrust faults and folds with N-NW or S-SE sense of movement. During Miocene-Pliocene time the third T3 event took place. It was responsible for the high-angle normal faults, dismembering the Eocene-Oligocene molassic basin into Neogene grabens. The T4 event affected the Neogene sediments of the basin with minor reverse strike-slip faults, as well as normal faults. The following T5 event is related to large normal active faults. They coincided with the active tectonics of the study area defined by the earthquake focal mechanisms.

Kilias, Adamantios; Falalakis, George; Sfeikos, Aristides; Papadimitriou, Eleftheria; Vamvaka, Agni; Gkarlaouni, Chara

2013-06-01

42

Geologic Influences on Downstream Fining in the Clearwater River Basin, Western Washington State: Implications for Transient Landscapes  

Science.gov (United States)

Grain size exerts a primary control on river longitudinal profile concavity and thus has important implications for bedrock incision and the feedbacks between hillslope and fluvial processes in both steady-state and transient landscapes. In the Clearwater River basin, Olympic Peninsula, western Washington state, a setting where flux steady-state conditions have been argued, we propose that downstream fining and the downstream development of bimodality in the grain size distribution is primarily attributed to variable weathering and hillslope processes throughout the basin in addition to differential grain size reduction in the channel. The grain size data showing the downstream fining trend have been collected from three sites on each of six lateral alluvial bars in the Clearwater trunk channel. Volumetric grain size analyses separated into the three major rock types found in the Clearwater, siltstone, sandstone and conglomerate, indicates that siltstones are preferentially broken down during transport despite equal recruitment of all rock types along the river continuum. The source, although underlain by relatively uniform greywacke sandstone, siltstone, and shale, is found to be delivering texturally different material to the channel as a function of mean relief, which for the Clearwater, is tightly coupled to the rate of rock uplift. Weathering-resistant sandstone cobbles, primarily derived from the upper basin, therefore dominate the coarse grain size fractions at the river mouth. The potential implications of the geologic control of downstream fining on the estimation of basin-wide erosion rates from 10Be inventories of alluvial sediment are profound. For basins that exhibit a grain size dependency of 10Be concentrations, differential grain size reduction works to dilute or concentrate quartz grains (in which 10Be is generated) differently in each grain size fraction. Whereas this problem is minimized in the Clearwater basin, where sandstones are more or less uniformly distributed throughout the catchment, these results stress the importance of understanding geologic context and geomorphic processes in interpreting concentrations of cosmogenic nuclides in alluvial sediment.

Belmont, P.; Pazzaglia, F. J.

2005-12-01

43

Carbon dioxide generation from coals in Taranaki Basin, New Zealand: implications for petroleum migration in southeast Asian Tertiary basins  

Energy Technology Data Exchange (ETDEWEB)

Elevated CO{sub 2} levels in gas accumulations within the onshore area of the Taranaki Basin can be quantitatively accounted for by decarboxylation of vitrinite-rich Tertiary coals over the lignite to early high-volatile bituminous coal-rank range. The highest levels are found within sandstone reservoirs vertically adjacent to Eocene coal seams that have realized approximately 50% of their CO{sub 2} generative potential. The gas exists as a supercritical fluid under reservoir conditions and appears to be generated in significant amounts, comparable to liquid hydrocarbons. CO{sub 2} may aid oil expulsion from coals directly when intense CO{sub 2} generation coincides with major oil generation, or indirectly by creating pressure-induced microfractures during the relatively rapid generation of large amounts of CO{sub 2} prior to the main phase of oil generation. For these effects to be realized, the rate of CO{sub 2} production relative to removal is considered critical, and favorable conditions are probably restricted to basins that have experienced relatively rapid heating. In this respect, the Taranaki Basin provides a model for CO{sub 2} evolution in many southeast Asian Tertiary basins.

Killops, S.D.; Allis, R.G.; Funnell, R.H. [Institute of Geological and Nuclear Sciences Limited, Lower Hutt (New Zealand)

1996-04-01

44

The Tertiary South-Altiplano-Basin (Bolivia): Sedimentology and Tectonic Implications  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Tertiary sediments of the Southern-Altiplano-Basin, Bolivia, were analised and a basin model was developed. The basin witnessed variation in sediment accumulation, with the central part containing 7500 m and the eastern part up to 4500 m thick cenozoic sediments. These sediments are classified in the El Molino, Santa Lucía, Cayara, Potoco, San Vicente and Chocaya formations. Above the El Molino Formation Tertiary continental sediments were accumulated in the Basin. In the Paleoce...

Silva Gonza?lez, Patricio

2010-01-01

45

Williston Reservoir: Site preparation and post-flood cleanup  

International Nuclear Information System (INIS)

Williston Reservoir is the second largest in Canada and ranks ninth on the world scale. It was formed by the construction of the W.A.C. Bennet Dam and is the most important hydroelectric storage reservoir and largest body of fresh water in British Columbia. Site preparation for the reservoir began in 1962, with pre-flood clearing involving salvage of merchantable timber, handfalling, machine downing, burning of slash and burial. Post-flood cleanup included timber salvage, bailing and burning debris, tractor piling and burning, crane piling in shallows, underwater cutting, and hand cutting during low drawdown. Various types of floating debris have presented problems for recreational use, log booming and transport, waterways and aviation. Protection of the spillway is accomplished with a floating boom upstream of the channel. Administration, funding, forest clearance, salvage methods, clearing standards, wood volumes, project costs, environmental concerns, and future priorities are discussed. 5 figs., 2 tabs

46

(U-Th)/He apatite ages from the Taranaki basin, New Zealand implications for cooling and denudation in the Pliocene  

International Nuclear Information System (INIS)

Full text: The Taranaki basin, located in central-western New Zealand, contains a predominantly terrigenous Late Cretaceous to Holocene terrestrial to marine succession, generally 3-5 km thick and with an estimated maximum thickness of 8 km. This basin is of particular interest because it provides most of New Zealand's commercial hydrocarbon discoveries. Previously published apatite fission track analysis of four well sections in the Taranaki basin indicated that in the southern part cooling from elevated paleotemperatures was effected by the initiation of Late Miocene uplift and erosion ranging from 1-3 km of section (Kamp and Green, 1990). However, the timing of when the denudation ended is poorly defined, being constrained by poorly dated Quaternary sediments overlying mid Miocene deposits. (U-Th)/He apatite age analysis has been applied initially to samples from one well section (1 Fresne) in the southern part of the Taranaki basin. The ages indicate cooling below 75 deg C occurred in the upper section in the early Pliocene, whereas deeper samples record progressively younger ages as they currently reside in the He partial retention zone (40-85 deg C; Wolf et al., 1998). This interpretation is based on the assumption that the samples have resided at the current down hole temperatures since the Pliocene. These data possibly imply that cooling and denudation of the 1 Fresne well section extended beyond the end of the Late Miocene and into the Pliocene. This work is ocene and into the Pliocene. This work is to be extended to other well sections in the basin that intersect other inversion structures. The implications of this work for the hydrocarbon prospectivity of the basin is that it better defines the timing of the formation of the potential trapping structures in relation to the timing of maturation. Copyright (1999) Geological Society of Australia

47

Tectonosedimentary evolution of the Crotone basin, Italy: Implications for Calabrian Arc geodynamics  

Energy Technology Data Exchange (ETDEWEB)

Analysis of outcrop, well, and offshore seismic data has allowed the Neogene tectonosedimentary evolution of an Ionian Sea satellite basin to be outlined. The Crotone basin contains a series of postorogenic sediments deposited since Serravallian time atop a complex nappe system emplaced in the early Miocene. The basin's evolution can be considered predominantly one of distension in a fore-arc setting punctuated by compressional events. The earliest sediments (middle-late Miocene) consist of conglomerates, marls, and evaporites infilling a rapidly subsiding basin. A basin-wide Messinian unconformity and associated intraformational folding mark the close of this sedimentary cycle. Reestablishment of marine conditions in the early Pliocene is documented by sediments which show a distinct color banding and apparent rhythmicity, which may represent the basin margin to lowermost Pliocene marl/limestone rhythmic couplets present in southern Calabria. A bounding unconformity surface of middle Pliocene age (3.0 Ma), which corresponds to a major northwest-southeast compressional event, closes this depositional sequence. The basin depocenter shifted markedly toward the southeast, and both chaotic and strong subparallel reflector seismic facies of wide-ranging thicknesses fill the depositional topography created during this tectonic episode. Basin subsidence decreases dramatically in the late Pliocene and cessates in response to basin margin uplift in the early Pleistocene. The chronostratigraphic hierarchy of these depositional sequences allows them to constrain the deformational history of the basin. In addition, similar depositional hierarchies in adjacent basins (i.e., Paola, Cefalu, and Tyrrhenian Sea) allow them to tie the stratigraphy and evolution of the Crotone basin to the geodynamic evolution of the Calabrian arc system.

Smale, J.L. (Univ. of South Carolina, Columbia (USA)); Rio, D. (Univ. of Padova (Italy)); Thunell, R.C. (Univ. of South Carolina, Columbia (USA))

1990-05-01

48

Watershed Characteristics and Their Implication for Hydrologic Response in the Upper Sokoto Basin, Nigeria  

Directory of Open Access Journals (Sweden)

Full Text Available Most African river basins lack flow data, a condition which has affected river basin operations. Flood is a common occurrence on the Sokoto basin but poor data base has affected various research efforts and flood mitigation attempts in the basin. This present study will study basin variables using a GIS approach with a few to gaining insights to the flood potentials of Sokoto basin. Shuttle Radar Topographic Mission (SRTM image covering 5o-7o E and 12 o to 14oN was used in this study. The analysis was carried out using the Integrated Land and Water Information System (ILWIS and ArcGIS environments. Sinks were removed from the STRM, and the flow direction map was generated as an input for drainage extraction, river ordering and basin catchment extraction. Drainage network overlay was carried out on the generated hill-shade map and on a portion of SPOT image covering the Upper Sokoto catchment for visual analysis. Altogether, 44 basin variables were generated with a view to appraising flood and water resource management in the basin. The results showed that the Upper Sokoto basin is an alluvial catchment; located in a relatively low lying area where high level of deposition is experienced. It is sinuous in nature, circular in shape and compact. These characteristics coupled with the relatively high volume of precipitated water of 14,511,439,620 m³/year are indications that the basin has high flood potential. The paper recommends construction of levees to protect farmlands, efficient reservoir operation and sustainable watershed management for the purpose of environmental management in the Sokoto basin.

Ifabiyi Ifatokun Paul

2012-05-01

49

Nodal basin recurrence following lymph node dissection for melanoma: implications for adjuvant radiotherapy  

International Nuclear Information System (INIS)

Purpose: To analyze patterns of failure in malignant melanoma patients with lymph node involvement who underwent complete lymph node dissection (LND) of the nodal basin. To determine prognostic factors predictive of local recurrence in the lymph node basin in order to select patients who may benefit from adjuvant radiotherapy. Methods and Materials: A retrospective analysis of 338 patients undergoing complete LND for melanoma between 1970 and 1996 who had pathologically involved lymph nodes was performed. Mean follow-up from the time of LND was 54 months (range: 12-306 months). Lymph node basins dissected included the neck (56 patients), axilla (160 patients), and groin (122 patients). Two hundred fifty-three patients (75%) underwent therapeutic LND for clinically involved nodes, while 85 patients (25%) had elective dissections. Forty-four percent of patients received adjuvant systemic therapy. No patients received adjuvant radiotherapy to the lymph node basin. Results: Overall and disease-specific survival for all patients at 10 years was 30% and 36%, respectively. Overall nodal basin recurrence was 30% at 10 years. Mean time to nodal basin recurrence was 12 months (range: 2-78 months). Site of nodal involvement was prognostic with 43%, 28%, and 23% nodal basin recurrence at 10 years with cervical, axillary, and inguinal involvement, respectively (p = 0.008). Extracapsular extension (ECE) led to a 10-year nodal basin failure rate of 63% vs. 23% without ECE (p 10 nodes involved (p 0.0001). There was no significant difference in nodal basin control in patients with synchronous or metachronous lymph node metastases, nor in patients receiving or not receiving adjuvant systemic therapy. Nodal basin failure was predictive of distant metastasis with 87% of patients with nodal basin recurrence developing distant disease compared to 54% of patients without nodal failure (p 3 positive lymph nodes, clinically involved nodes, or any node larger than 3 cm. Patients with these risk factors should be considered for adjuvant radiotherapy to the lymph node basin to reduce the incidence of nodal basin recurrence. Patients with nodal basin failure are at higher risk of developing distant metastases

50

Mesozoic history of the Fairway-Aotea Basin: Implications for the early stages of Gondwana fragmentation  

Science.gov (United States)

The Fairway Ridge is a buried continental structure that separates the Fairway Basin from the New Caledonia Basin. The proposed Cretaceous age of the Fairway Basin has remained highly hypothetical to date. Deep offshore petroleum exploration wells revealed well-dated Mesozoic carbonaceous sedimentary rocks in the Taranaki Basin at the southern end of the Aotea Basin. In this paper we use geophysical data to confirm the continuity of the 2000 km long Fairway-Aotea Basin connecting New Caledonia to New Zealand and prove its early Late Cretaceous age. Analysis of seismic reflection profiles together with newly compiled gravity and magnetic maps reveals Late Cretaceous NE-SW trending lineaments projecting northeastward from major Tasman Sea fracture zones and the Bellona Trough, which demonstrate that the opening of the Fairway-Aotea Basin predates the opening of the Tasman Sea. This result combined with observations of the Mesozoic regional geology suggests that the Lord Howe, Fairway, and Norfolk ridges are part of a remnant late Early Cretaceous continental arc, which was fragmented into three pieces by the late Early to early Late Cretaceous. This event might be contemporaneous with a plate motion change between the Gondwana and Pacific plates and/or the arrival of the Hikurangi plateau in the subduction zone around 105 Ma, which caused the cessation of subduction along this plate boundary. We interpret either of those two events as being possible trigger events for the post-Early Cretaceous fragmentation of the eastern Gondwana margin in a slab retreat process.

Collot, J.; Herzer, R.; Lafoy, Y.; GéLi, L.

2009-12-01

51

Present-day stress-field in the Cooper basin of Australia: implications for petroleum exploration  

Science.gov (United States)

The Cooper Basin is located in centre part of the Australian continent, 5000km away from the nearest plate boundary. This Late Carboniferous to Middle Triassic basin is the largest onshore sedimentary basin producing oil and gas in Australia - mostly by fraccing tight reservoirs. Thus, an extensive database is available for studying the in-situ stress field in the basin. Previous studies have shown a significant variability if the stress field across the basin. However, the development of the mostly tight prospects require a good understanding of the structure of the reservoirs, mechanical properties of the stratigraphy, fracture geometry and density, in-situ stress field and fracture stimulation strategies in order to maximise the production This study provides new in-situ stress data from borehole breakouts and drilling-induced tensile fractures, along with a description of the fractures present along the well trajectory. The geometry of the natural fault and fracture network is interpreted from 3D seismic data, and compared to the well data. Finally, we performed a series of numeric simulation to test the fault and fracture stability in the present-day stress field. These data and our interpretation are used to evaluate the geomechanical properties of the Cooper Basin. This method is reproducible to other oil-bearing basins around the world, but is also applicable to the development of engineered geothermal reservoir or evaluation of carbon dioxide storage site.

Backé, G.; King, R.

2010-12-01

52

Implications of spatial and temporal evolutions of thermal parameters in basin modelling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper presents the Paris Basin numerical modelling at a high sequential resolution scale (1–5 my). Simulations were carried out from the computation of thermal gradients and conductivities varying with the burial of genetic units. Geologic heating rates are also calculated throughout the burial of the stratigraphic sequences. Thermal energies are then deduced. The Paris Basin is well known for its hydrocarbon potential in Liassic sediments. This study is focused on an east–west cross...

Amir, L.; Martinez, Luis; Disnar, Jean-robert; Michels, R.; Vigneresse, J. L.; Robin, C.; Guillocheau, F.

2008-01-01

53

Water temperature of streams in the Cook Inlet basin, Alaska, and implications of climate change  

Science.gov (United States)

Water-temperature data from 32 sites in the Cook Inlet Basin, south-central Alaska, indicate various trends that depend on watershed characteristics. Basins with 25 percent or more of their area consisting of glaciers have the coldest water temperatures during the open-water season, mid-May to mid-October. Streams and rivers that drain lowlands have the warmest water temperatures. A model that uses air temperature as input to predict water temperature as output was utilized to simulate future trends in water temperature based on increased air temperatures due to climate warming. Based on the Nash-Sutcliffe coefficient, the model produced acceptable results for 27 sites. For basins with more than 25 percent glacial coverage, the model was not as accurate. Results indicate that 15 sites had a predicted water-temperature change of 3 degrees Celsius or more, a magnitude of change that is considered significant for the incidence of disease in fish populations.

Kyle, Rebecca E.; Brabets, Timothy P.

2001-01-01

54

Implications of climate change for water resources in the Great Lakes basin  

International Nuclear Information System (INIS)

Several authors have suggested the following impacts of global warming for the Great Lakes region. The average annual warming is predicted by one model to be ca 4.5 degree C, slightly more in winter and slightly less in summer. Annual precipitation is projected to increase by ca 8% for points in the central and western basin, but to decrease by 3-6% for the eastern basin. Basin snowpack could be reduced by up to 100% and the snow season shortened by 2-4 weeks, resulting in a reduction of more than 50% in available soil moisture. Buoyancy-driven turnovers of the water column on four of the six lakes may not occur at all. Presently the phenomena occurs twice per year on all the lakes. Ice formation would be greatly reduced. Maximum ice cover may decline from 72-0% for Lake Superior, 38-0% for Lake Michigan, 65-0% for Lake Huron, 90-50% for Lake Erie and 33-0% for Lake Ontario. Net basin supplies would be reduced probably in the range 15-25% below the current mean value. Possible responses include integrated studies and research, better and continually updated information, assessment of public policies in the U.S. and Canada, enhanced private planning efforts, and increased global cooperation

55

Eustatic implications of late Miocene depositional sequences in the Melilla Basin, northeastern Morocco  

Science.gov (United States)

The age (˜5.78 Ma or lower chron C3r) of the major drawdown of the Paleo-Mediterranean Sea during the Messinian Salinity Crisis has been established by combining results from stratigraphy, paleontology, magnetostratigraphy, and argon dating for a late Miocene sedimentary succession in the Melilla Basin, NE Morocco. This event is inferred from a marine-to-continental series of carbonate and siliciclastic rocks that record the end of Messinian marine deposition in the Melilla Basin and presumably marks the final isolation of the Paleo-Mediterranean Sea. The evidence from the Melilla Basin is approximately coeval with an increase in benthic foraminiferal ?18O values from a deep-marine section in the Bou Regreg valley, NW Morocco (Hodell et al., 1994). This increase suggests that a glacio-eustatic lowering of sea level, at least, contributed to the final closure of the Mediterranean during the Messinian Salinity Crisis. The marine-to-continental succession onlaps a carbonate complex that contains evidence for multiple relative sea-level changes leading up to the main drawdown. From bottom to top, the carbonate complex is composed of: (1) an onlapping ramp; (2) a prograding bioclastic platform; (3) a prograding and, locally, downstepping Porites-reef complex; and (4) a topography-draping sequence composed of grainstones, Porites reefs, and stromatolites (terminal carbonate complex of Esteban, 1979). The transgressive ramp correlates to relatively low values of benthic foraminiferal ?18O values from a Tortonian-to-lower Messinian section at Bou Regreg (Hodell et al., 1994). This correlation indicates, at least in part, a link between rising sea level and a reduction in global ice volume during deposition of the ramp. A major fall in relative sea level (˜60 m) occurred near the demise of the reef complex during chron C3n.1n at 5.95 ± 0.10 Ma. This signals the initiation of drawdown and changing environmental conditions in the Melilla Basin (a marginal basin), and perhaps the entire Paleo-Mediterranean Sea. A megabreccia interpreted as forming by solution collapse of evaporites on the basin margin of the reef complex occurs at the base of the terminal carbonate complex. Updip, a major subaerial unconformity separates the reef complex and terminal carbonate complex. Evaporite deposition likely occurred during this exposure event and has been dated at 5.82 ± 0.02 Ma near the base of chron C3r. We contend that these evaporites, restricted to the shallow Melilla Basin, are related to the continuation of the initial stage of the major drawdown of the Paleo-Mediterranean Sea.

Cunningham, Kevin J.; Benson, Richard H.; Rakic-El Bied, Kruna; McKenna, Larry W.

1997-01-01

56

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

2010-05-15

57

Tertiary basin development and tectonic implications, Whipple detachment system, Colorado River extensional corridor, California and Arizona  

Science.gov (United States)

This paper reports on geologic mapping, stratigraphic and structural observations, and radiometric dating of Miocene deposits of the Whipple detachment system, Colorado River extensional corridor of California and Arizona. From these data, four regions are distinguished in the study area that correspond to four Miocene depositional basins. It is shown that these basins developed in about the same positions, relative to each other and to volcanic sources, as they occupy at present. They formed in the early Miocene from a segmentation of the upper crust into blocks bounded by high-angle faults that trended both parallel and perpendicular to the direction of extension and which were terminated at middle crustal depths by a low-angle detachment fault.

Nielson, J. E.; Beratan, K. K.

1990-01-01

58

Oxygen utilization rates in the Nansen Basin, Arctic Ocean: implications for new production  

Science.gov (United States)

In situ consumption of oxygen is balanced by ventilation if the observed distribution of dissolved oxygen below the euphotic zone is in steady state. Apparent oxygen utilization rates (AOURs) can be estimated from the observed oxygen distribution if the waters of the upper layers can be dated. It has been shown previously that tritium/ 3 He ages can be used, together with observed oxygen concentrations, to estimate AOURs for waters with ages of several months to several decades. This method is applied to data obtained from the Nansen Basin, Arctic Ocean, during the 1987 cruise of F.S. Polarstern. New production is estimated by depth integration of AOURs calculated for several isopycnals to be 19±5 g C m -2 year -1 for the southern part and 3±2 g C m -2 year -1 for the northern part of the Nansen Basin section. The results are discussed and compared with previous estimates based on different methods.

Zheng, Yan; Schlosser, Peter; Swift, James H.; Jones, E. P.

1997-12-01

59

Ordovician conodonts from the Mithaka Formation (Georgina Basin, Australia). Regional and paleobiogeographical implications  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The systematic analysis of conodonts from the previously unstudied Mithaka Formation (Georgina Basin) yielded 1366 identifiable elements, representing 25 species and 21 genera. One new species was recovered and identified, Triangulodus mithakensis n. sp. Four other new species are described in open nomenclature as Bergstroemognathus? n. sp. A, ?Periodon n. sp. A, Phragmodus n. sp. A and Taoqupognathus n. sp. A. The Mithaka Fm fauna shows similarity with conodonts from several previous Austral...

Kuhn, T. S.

2005-01-01

60

Basin-scale hydrodynamics in a Mediterranean reservoir. Implications for the phytoplankton dynamics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Physical processes determine, to a large degree, the ecological response of a reservoir to inflows, outflows and meteorological forcing. This PhD thesis therefore aims to give an assessment of the main physical mechanisms governing Mediterranean reservoirs. The main basin-scale hydrodynamical processes are the generation of seiches and the gravity currents generated by the river inflow. The periodicity of the wind forcing makes that the reservoir responses as a forced harmonic damped oscillat...

Vidal Hurtado, Javier

2007-01-01

 
 
 
 
61

Spatial and temporal variations in precipitation in the Upper Indus Basin, global teleconnections and hydrological implications  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Most of the flow in the River Indus from its upper mountain basin is derived from melting snow and glaciers. Climatic variability and change of both precipitation and energy inputs will, therefore, affect rural livelihoods at both a local and a regional scale through effects on summer runoff in the River Indus. Spatial variation in precipitation has been investigated by correlation and regression analysis of long-period records. There is a strong positive correlation between winter ...

Archer, D. R.; Fowler, H. J.

2004-01-01

62

Implications of transient deformation in the northern Basin and Range, western United States  

Science.gov (United States)

deformation events observed in Global Positioning System (GPS) data from the Basin and Range extensional province may illuminate qualitatively similar transient events observed in subduction zones and other tectonic environments. We model GPS time series at 22 sites using a combination of hyperbolic tangent function analysis and elastic load deformation estimated from climatological data. We identify two transient events, ~2000.4 and ~2004.4, with roughly similar timing and displacement to those described previously by other researchers. The first few years of GPS observations, adopted as a reference state in earlier studies, are found to be anomalous. Our results differ from previous studies in two respects. First, a significant component of northward transient motion occurs during both events, despite a reversal of sign in east component motion. Second, sites move coherently in the eastern as well as the western Basin and Range. Surface mass loading, the largest source of transient stress forcing in the region, exhibits no evidence of a simple relationship to the deformation transients. Prior studies inferred slip on a single megadetachment at the Moho, but that hypothesis assumes negligible ductile deformation of the lower crust and a dry olivine rheology for the uppermost mantle. Recent measurements of crustal quartz abundance and effective elastic thickness suggest both assumptions are unlikely. Basin and Range transients can be reconciled with the frictional slip mechanism widely accepted for subduction zone transients provided that slip is occurring on discontiguous detachment surfaces at midcrustal depths.

Chamoli, Ashutosh; Lowry, Anthony R.; Jeppson, Tamara N.

2014-05-01

63

Globally synchronous compressional pulses in extensional basins: Implications for hydrocarbon exploration  

Energy Technology Data Exchange (ETDEWEB)

Hydrocarbon plays in the Bass, Gippsland, Otway and Taranaki Basins have been described in terms of sediment-fill geometry, hydrocarbon shows and compressional or folding events. The aim of this paper is to document pulses of compression in extensional basins and to relate these events to global tectonics, to subtle trap definition on seismic data and to the seal-breach problem which affects field size in many basins. The first part of the paper describes the current state of stress and strain in the Australian continent. Using several seismic lines from three areas with a triangular distribution relative to the centre of the continent there is indication that the same compressional stress state has occurred at least 14 times since the Late Triassic. The second part of the paper uses the same method on a data set from Australia, Northwest Europe and central Americas to establish global synchroniety of the compressional pulses and compares the implied tectonics with `plate tectonics`. There were 15 globally synchronous compressional pulses identified since the Mid Triassic. In general it appears that periods of high expansion occurred in the Late Eocene/Early Oligocene and coincided with the largest sea level falls. The recognition of subtle structures associated with occasionally quite minor compressional pulses, will assist evaluation of the often destructive sealing effects of faults which have alternated between seals and conduits for hydrocarbons. 24 figs., 1 photo., 35 refs.

Davidson, J.K. [Petrecon Australia, Hobart, TAS (Australia)

1995-12-31

64

Spatial and temporal variations in precipitation in the Upper Indus Basin, global teleconnections and hydrological implications  

Directory of Open Access Journals (Sweden)

Full Text Available Most of the flow in the River Indus from its upper mountain basin is derived from melting snow and glaciers. Climatic variability and change of both precipitation and energy inputs will, therefore, affect rural livelihoods at both a local and a regional scale through effects on summer runoff in the River Indus. Spatial variation in precipitation has been investigated by correlation and regression analysis of long-period records. There is a strong positive correlation between winter precipitation at stations over the entire region, so that, for practical forecasting of summer runoff in some basins, a single valley-floor precipitation station can be used In contrast, spatial relationships in seasonal precipitation are weaker in summer and sometimes significantly negative between stations north and south of the Himalayan divide. Although analysis of long datasets of precipitation from 1895 shows no significant trend, from 1961–1999 there are statistically significant increases in winter, in summer and in the annual precipitation at several stations. Preliminary analysis has identified a significant positive correlation between the winter North Atlantic Oscillation (NAO and winter precipitation in the Karakoram and a negative correlation between NAO and summer rainfall at some stations. Keywords: upper Indus basin, climate change, time series analysis, spatial correlation, teleconnections

D.R. Archer

2004-01-01

65

Comparison of diagenetic fluids in the proterozoic thelon and Athabasca Basins, Canada: implications for protracted fluid histories in stable intracratonic basins  

International Nuclear Information System (INIS)

The Paleoproterozoic Thelon Basin, located on the border between Nunavut and the Northwest Territories of Canada, is a contemporaneous analog of the uranium-rich Paleoproterozoic Athabasca Basin in Canada. Early diagenesis resulted in precipitation of extensive hematite on the surfaces of detrital quartz grains throughout the Thelon Formation and minor hydroxy-phosphate in veins locally. Continued diagenesis then resulted in syntaxial quartz cementation of detrital quartz at 130 degrees C from fluids having ca. 17 wt.% equivalent NaCl, similar to the Athabasca Basin. Cementation of this type is most pronounced in fine-grained sequences in the Thelon Basin. A period of extensive desilicification during continued burial was followed by formation, at ca. 200 degrees C, of peak-diagenetic illite having Ar-Ar ages of ca. 1400-1690 Ma in the Thelon Formation. This illite was associated with fluids with ?l8O and ?D values of ca. 6%o and -50%o,respectively, similar to those during peak diagenesis of the Athabasca Basin. Although the timing, salinity, and isotopic composition of the peak-diagenetic fluids in the Thelon and Athabasca Basins are similar, the peak-diagenetic mineral assemblage in the Athabasca Formation is dickite and illite, with minor dravite and goyasite rather than simply illite. Consequently, the fluids at peak diagenesis, which in the Athabasca Basin are synchronous with formation of world-class unconformity-type uranium deposits, had differentity-type uranium deposits, had different compositions in each basin. Post-peak diagenesis in the Thelon Basin was quite distinct from that in the Athabasca Basin in that illite was replaced in the central portion of the basin by K-feldspar and then sudoite, which crystallized from saline brines at ca. 1000 Ma and 100 degrees C. Evidence for later infiltration of these brines is absent in the Athabasca Basin, although uranium mobilization at ca. 900 Ma from fluids having the same characteristics as those at peak diagenesis was pronounced in the Athabasca Basin. Recent incursion of meteoric waters along reactivated structures into the Athabasca Basin has variably affected hydrous and uraniferous minerals, but evidence for this is lacking in the Thelon Basin. The Thelon Basin reflects less intensive fluid-rock interaction in its early history than that recorded in the basal units of the Athabasca Basin. (author)

66

Multi-Seam Well Completion Technology: Implications for Powder River Basin Coalbed Methane Production  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this study is to evaluate the potential benefits of applying multiseam [well] completion (MSC) technology to the massive stack of low-rank coals in the Powder River Basin. As part of this, the study objectives are: Estimate how much additional CBM resource would become accessible and technically recoverable--compared to the current practice of drilling one well to drain a single coal seam; Determine whether there are economic benefits associated with MSC technology utilization (assuming its widespread, successful application) and if so, quantify the gains; Briefly examine why past attempts by Powder River Basin CBM operators to use MSC technology have been relatively unsuccessful; Provide the underpinnings to a decision whether a MSC technology development and/or demonstration effort is warranted by DOE. To a great extent, this assessment builds on the previously published study (DOE, 2002), which contains many of the key references that underlie this analysis. It is available on the U.S. Department of Energy, National Energy technology Laboratory, Strategic Center for Natural Gas website (www.netl.doe.gov/scng). It is suggested that readers obtain a copy of the original study to complement the current report.

Office of Fossil Energy; National Energy Technology Laboratory

2003-09-01

67

Leaiid conchostracans from the uppermost Permian strata of the Paraná Basin, Brazil: Chronostratigraphic and paleobiogeographic implications  

Science.gov (United States)

Conchostracan fossils are abundant and relatively diversified in the Rio do Rasto Formation (Passa Dois Group, Paraná Basin, southern Brazil), but leaiids (' Leaia pruvosti' [Reed, F.R.C., 1929. Novos Phyllopodos Fósseis do Brasil. Boletim do Serviço Geológico e Mineralógico do Brasil 34, 2-16]) were previously found at only one locality of the formation in the northern Santa Catarina State. New specimens of the Family Leaiidae, collected from two outcrops in central Paraná State near the top of the formation, stimulated a revision of related taxa. Both the new and the previously known leaiids are herein assigned to Hemicycloleaia mitchelli [Etheridge Jr., R., 1892. On Leaia mitchelli Etheridge. Proceedings of the Linnean Society of New South Wales 7, 307-310] based on the presence of three carinae and subovate shape. This species was originally recorded in the upper Tatarian (Wuchiapingian, Late Permian) of Sydney Basin, eastern Australia and therefore corroborates the interpretation that the leaiid bearing strata of the Rio do Rasto Formation cannot be younger than Permian. H. mitchelli possibly was one of the most widespread, eurytopic and conservative Late Paleozoic conchostracans of Gondwana (although records from Africa, India and Antarctica must still be confirmed) and it was also found in the Tatarian of Russia. The sudden disappearance of leaiids after their apparent success is consistent with the hypothesis about the biotic crisis around the Permo-Triassic boundary.

Ferreira-Oliveira, Luis Gustavo; Rohn, Rosemarie

2010-03-01

68

Implication of biomarkers signatures of the Ulleung Basin, East Sea, during the Pleistocene  

Science.gov (United States)

In this study, the molecular distribution of the n-alkanes, alkenone and C/N ratio and ?13C of bulk sediment were used to assess changes in organic matter (OM) source and transport which could be related with paleoclimate change. The proxy records corresponding to the Pleistocene have been obtained from the well-studied the Ulleung Basin Gas Hydrate Expedition 2 (UBGH2) site 11 in the Ulleung Basin, East Sea. The distribution of carbon preference index (CPI) of n-alkane encountered in this study confirmed the importance of terrestrial OM in the marine sediment. Alkenone has been widely applied for sea surface temperature (SST) reconstruction. The data results show that CPI values generally increase with decreasing paleo-SST. Plot of C/N ratio versus ?13C shows a predominance of marine algae origin in the study area. It may indicate that the minimum CPI in warm period is related with the contribution of probably enhanced biodegradation, while the maximum CPI value in cold period result from restrain of OM input associated with sea level lowering. It is likely that the vertical variations of the biomarkers signature reflect the shifts in sedimentary environment and transportation related with change of ocean currents and sea level during the Pleistocene period.

Choi, Jiyoung; Lee, Kyung Eun; Kim, Ji-Hoon; Bahk, Jang-Jun; Yoo, Dong-Geun

2014-05-01

69

Shear wave splitting observations and implications on stress regimes in the Los Angeles basin, California  

Science.gov (United States)

A systematic analysis of three-component seismograms recorded at 15 stations from earthquakes occurring at depths of 5 to 18 km beneath the Los Angeles basin and adjacent areas during the period between 1988 and 1994 shows 20 to 160 ms shear wave splitting. Shallow events exhibit little splitting, while deeper events show progressively greater splitting with depth. The preferred polarization direction of the fast shear wave is nearly N-S, consistent with the direction of the regional maximum horizontal compressive stress but independent of the azimuth between the event and station. We interpret that the shear wave splitting is caused by fluid-filled crustal microcracks and macrofractures aligned in the N-S direction. The shear wave splitting observations of 2.8 to 7.8 ms/km can be explained in terms of an anisotropic crust containing vertical cracks with the apparent crack density of 0.023-0.08. On a regional basis, the crack density may vary from station to station, but we find that the apparent crack density in the strike-slip region of the Newport-Inglewood fault and the Whittier fault is higher than in the reverse-thrusting Santa Monica Mountains and Palos Verdes Hills. No systematic change of shear wave splitting in the Los Angeles basin is found in this study.

Li, Yong-Gang

1996-06-01

70

Seed banks and their implications of rivers with different trophic levels in Chaohu Lake Basin, China.  

Science.gov (United States)

The seed banks of three rivers, with different trophic levels in Chaohu Lake Basin, China, were investigated to explore the dynamics of seed bank under the pressure of eutrophication. A total of 60 species from 25 family 43 genera were identified from the seed banks of the three rivers. In the eutrophic Paihe River, the species richness and mean seed density were the highest, followed by the oligotrophic Hangbuhe River and the hypereutrophic Nanfeihe River. Various compositions of three functional group assemblage of hydro-ecotypes were found in different rivers. The dominant and endemic species were aquatic, wetland, and terrestrial species in Hangbuhe River, Paihe River, and Nanfeihe River, respectively. The shift trend of seed bank in three rivers probably presented past vegetation dynamics under the trophic process in the rivers of Chaohu Lake Basin. Seed bank in the river bed might be quickly assessed by its trophic level. Additionally, it might imply that the seed bank with more aquatic species in the oligotrophic river would be a potential seed resource for vegetation restoration of severely degraded river ecosystems. PMID:25178861

Cui, Naxin; Wu, Juan; Zhong, Fei; Yang, Lihua; Xiang, Dongfang; Cheng, Shuiping; Zhou, Qi

2015-02-01

71

Study of the Ouarzazate basin structure by seismic reflection: hydrogeological implications  

Directory of Open Access Journals (Sweden)

Full Text Available A large number of seismic reflection lines have been carried out in the Ouarzazate basin by the oil industry. The present study is concerned with the interpretation of a part of these data in order to characterize the structure of the Eocene aquifer system. The reflector corresponding to the base of this system, made up of sandstone and limestone, was first identified then digitized on each time-migrated seismic section. An isochrone map of this reflector was realized. The analysis of this map shows that the area under study is subdivided into two structurally contrasted domains. The first, the northern one, is intensively deformed; while the second, the southern one, is slightly folded. The results of this study provide a better understanding of the deep geological structure of the Ouarzazate basin. This allows us to better comprehend the functioning of the Eocene aquifer system, and to rationalize the future potential underground water exploration in the Ouarzazate basin.

Les campagnes d’exploration pétrolière menées dans le bassin d’Ouarzazate ont permis l’acquisition d’une importante base de données de sismique réflexion. La présente étude concerne l’interprétation d’une partie de ces données dans l’objectif de caractériser la tectonique de l’Eocène et la structure de son système aquifère. Dans un premier temps, le réflecteur correspondant à la base de cet étage, représenté de grès et de calcaires, a été identifié, puis numérisé sur les différentes sections sismiques migrées-temps; ce qui nous a permis d’en établir une carte d’isochrones. Celle-ci montre que le secteur étudié est subdivisé en deux domaines très contrastés d’un point de vue structural. Le premier, septentrional, est affecté par une structuration intense de direction atlasique, tandis que le second, méridional, est faiblement plissé. Les résultats de la présente étude permettent une meilleure connaissance de la structure profonde du bassin d’Ouarzazate. Ceci permet de mieux appréhender le fonctionnement du système aquifère éocène et de rationaliser les futures campagnes de reconnaissance des eaux souterraines susceptibles d’être menées dans le bassin d’Ouarzazate.

Jaffal, M.

2009-12-01

72

Spatial and seasonal responses of precipitation in the Ganges and Brahmaputra river basins to ENSO and Indian Ocean dipole modes: implications for flooding and drought  

Science.gov (United States)

We evaluated the spatial and temporal responses of precipitation in the basins as modulated by the El Niño Southern Oscillation (ENSO) and Indian Ocean (IO) dipole modes using observed precipitation records at 43 stations across the Ganges and Brahmaputra basins from 1982 to 2010. Daily observed precipitation records were extracted from Global Surface Summary of the Day dataset and spatial and monthly anomalies were computed. The anomalies were averaged for the years influenced by climate modes combinations. Occurrences of El Niño alone significantly reduced (60% and 88% of baseline in the Ganges and Brahmaputra basins respectively) precipitation during the monsoon months in the northwestern and central Ganges basin and across the Brahmaputra basin. In contrast, co-occurrence of La Niña and a positive IO dipole mode significantly enhanced (135% and 160% of baseline respectively) precipitation across both basins. During the co-occurrence of neutral phases in both climate modes (occurring 13 out of 28 yr), precipitation remained below average to average in the agriculturally extensive areas of Haryana, Uttar Pradesh, Bihar, eastern Nepal, and the Rajshahi district in Bangladesh in the Ganges basin and northern Bangladesh, Meghalaya, Assam, and Arunachal Pradesh in the Brahmaputra basin. This pattern implies that a regular water deficit is likely in these areas with implications for the agricultural sector due to its reliance of consistent rainfall for successful production. Major flooding and drought occurred as a consequence of the interactive effects of the ENSO and IO dipole models, with the sole exception of extreme precipitation and flooding during El Niño events. This observational analysis will facilitate well informed decision making in minimizing natural hazard risks and climate impacts on agriculture, and supports development of strategies ensuring optimized use of water resources in best management practice under changing climate.

Pervez, Md Shahriar; Henebry, Geoffry M.

2014-01-01

73

Spatial and seasonal responses of precipitation in the Ganges and Brahmaputra river basins to ENSO and Indian Ocean dipole modes: implications for flooding and drought  

Science.gov (United States)

We evaluated the spatial and temporal responses of precipitation in the basins as modulated by the El Niño Southern Oscillation (ENSO) and Indian Ocean (IO) dipole modes using observed precipitation records at 43 stations across the Ganges and Brahmaputra basins from 1982 to 2010. Daily observed precipitation records were extracted from Global Surface Summary of the Day dataset and spatial and monthly anomalies were computed. The anomalies were averaged for the years influenced by climate modes combinations. Occurrences of El Niño alone significantly reduced (60% and 88% of baseline in the Ganges and Brahmaputra basins, respectively) precipitation during the monsoon months in the northwestern and central Ganges basin and across the Brahmaputra basin. In contrast, co-occurrence of La Niña and a positive IO dipole mode significantly enhanced (135% and 160% of baseline, respectively) precipitation across both basins. During the co-occurrence of neutral phases in both climate modes (occurring 13 out of 28 yr), precipitation remained below average to average in the agriculturally extensive areas of Haryana, Uttar Pradesh, Bihar, eastern Nepal, and the Rajshahi district in Bangladesh in the Ganges basin and northern Bangladesh, Meghalaya, Assam, and Arunachal Pradesh in the Brahmaputra basin. This pattern implies that a regular water deficit is likely in these areas with implications for the agriculture sector due to its reliance on consistent rainfall for successful production. Major flooding and drought occurred as a consequence of the interactive effects of the ENSO and IO dipole modes, with the sole exception of extreme precipitation and flooding during El Niño events. This observational analysis will facilitate well informed decision making in minimizing natural hazard risks and climate impacts on agriculture, and supports development of strategies ensuring optimized use of water resources in best management practice under changing climate.

Pervez, M. S.; Henebry, G. M.

2014-02-01

74

Basin-scale patterns of subglacial sediment mobility: Implications for glaciological inversion modelling  

Science.gov (United States)

Patterns of glacial bedforms and their internal sediments are described from the Omagh Basin, north-central Ireland. Here, drumlins and ribbed moraines were variously formed, preserved and remoulded during several late Devensian ice flow stages, and their patterns can be used as input into glaciological inversion models. More detailed examination of the morphology and internal sediments of these bedforms shows a complex pattern of reworking driven by local-scale basal thermal and hydrological regime. Sediment lithofacies associations and patterns of erratic carriage can be used to better evaluate ice-bed conditions and basal processes than bedforms alone. The sedimentary evidence suggests that bedforms were unlikely to have been formed during a single glacial episode, as is implicit in glaciological inversion models, and more likely formed during several episodes that cannot be resolved by crosscutting or superimposed bedform relationships alone.

Knight, Jasper

2010-12-01

75

Detection and Extent of Ancient, Buried Mare Deposits in South Pole-Aitken Basin (SPA):Implications for Robotic Sampling  

Science.gov (United States)

The origin of the large mafic anomaly associated with the interior of the South Pole-Aitken Basin has been inferred to be largely the result of iron-rich lower crustal/upper mantle material exposed at the surface and/or a combination of ancient mare basalts covered by younger crater/basin ejecta (cryptomare) interspersed with younger basalts [1-3]. However, the relative influence of either source is poorly constrained, due in part to the unknown abundance of cryptomare within SPA. Early geologic mapping of the interior of SPA identified several plains units, thought to represent basin ejecta deposits [4, 5]. Newer remotely sensed VIS-NIR wavelength data suggested the presence of more extensive deposits of ancient, buried basalts [2, 3, 6]. Mare basalts, when mantled by non-local, low-FeO material may appear to be non-mare plains units [7, 8]. Within SPA, because the regional basement material is inherently enriched in FeO, the mantling material imparts a dark, FeO-enriched, signature. In a survey of rock types within SPA, Pieters et al. [3] identified such a plains unit south of the Apollo Basin with a surface that is both dark and that contains an FeO-rich spectral signature. However, several small craters in the plains unit expose underlying basaltic materials or cryptomaria in this extensive (>75,000 km2), ancient (~3.89 Ga) unit [6, 9]. The positive identification and characterization of cryptomaria within SPA are facilitated by high-spatial and spectral resolution data from recent orbital missions (e.g., Kaguya, Chandrayaan-1, LRO). Hyperspectral data from the Moon Mineralogy Mapper and Multiband Imager for SPA show the presence of two primary mafic materials; a high-Ca pyroxene (gabbroic) signature is pervasive across the center of the basin and a noritic signature is present across the rest of SPA. High spatial resolution (10-0.5 m) images from the Kaguya Terrain Camera and LRO Narrow Angle Camera facilitate surface age dating and morphologic assessment of possible cryptomare units. We will assess the distribution of the gabbroic region using these above datasets to determine what relation, if any, this unit has to surrounding cryptomare and plains units. The definitive identification of cryptomare units has important implications for the selection of appropriate landing sites to sample SPA-derived impact-melt [10]. [1] Head, J. W., et al., (1993) JGR, 98, 17,149-117,181. [2] Yingst, R. A. and J. W. Head, (1999) JGR, 104, 18957-18979. [3] Pieters, C. M., et al., (2001) JGR, 106, 28001-28022. [4] Stuart-Alexander, D. E., (1978) Geologic map of the central far side of the Moon, I-1047. [5] Wilhelms, D. E., et al., (1979) Geologic map of the South side of the Moon, I-1162. [6] Petro, N., et al., (2010) GSA SP: Recent Advances in Lunar Stratigraphy, In Press. [7] Head, J. W., III and L. Wilson, (1992) GCA, 56, 2155-2175. [8] Schultz, P. H. and P. D. Spudis, (1979) Proc. Lunar Sci. Conf., 10, 2899-2918. [9] Haruyama, J., et al., (2009) Science, 323, 905-908. [10] Jolliff, B., et al., (2010) These proceedings.

Petro, N. E.; Jolliff, B. L.; Gaddis, L. R.; Pieters, C. M.

2010-12-01

76

Thickness of Proximal Ejecta from the Orientale Basin from Lunar Orbiter Laser Altimeter (LOLA) Data: Implications for Multi-Ring Basin Formation  

Science.gov (United States)

Quantifying the ejecta distribution around large lunar basins is important to understanding the origin of basin rings, the volume of the transient cavity, the depth of sampling, and the nature of the basin formation processes. We have used newly obtained altimetry data of the Moon from the Lunar Orbiter Laser Altimeter (LOLA) instrument to estimate the thickness of ejecta in the region surrounding the Orientale impact basin, the youngest and best preserved large basin on the Moon. Our measurements yield ejecta thicknesses of approx.2900 m near the Cordillera Mountains, the topographic rim of Orientale, decaying to approx.1 km in thickness at a range of 215 km. These measurements imply a volume of ejecta in the region from the Cordillera ring to a radial range of one basin diameter of approx.2.9 x 10(exp 6)cu km and permit the derivation of an ejecta-thickness decay model, which can be compared with estimates for the volume of excavation and the size of the transient cavity. These data are consistent with the Outer Rook Mountains as the approximate location of the transient cavity s rim crest and suggest a volume of approx.4.8 x 10(exp 6)cu km for the total amount of basin ejecta exterior to this location.

Fassett, Caleb I.a; Head, James W.; Smith, David E.; Zuber, Maria T.; Neumann, Gregory A.

2011-01-01

77

River network and watershed morphology analysis with potential implications towards basin classification  

Science.gov (United States)

Generally, the investigation of river network composition and watersheds morphology (fluvial geomorphology), constituting one of the key patterns of land surface, is a fundamental question of Earth Sciences. Recent ideas in this research field are the equilibrium and optimal, in the sense of minimum energy expenditure, river network evolution under constant or slowly varying conditions (Rodriguez-Iturbe, Rinaldo, 1997). It follows to such network behavior as self-similarity, self-affinity and self-organization. That is to say, under relatively stable conditions the river systems tend to some "good composed" form and vice-versa. Lately appearing global free available detailed DEM covers involve new possibilities in this research field. We develop new methodology and program package for river network structure and watershed morphology detailed analysis on the base of ArcMap tools. Different characteristics of river network (e.g. ordering, coefficients of Horton's laws, Shannon entropy, fractal dimension) and basin morphology (e.g. diagrams of average elevation, slope, width and energy index against distance to outlet along streams) could be calculated to find a good indicators of intensity and non-equilibrium of watershed evolution. Watersheds are non-conservative systems in which energy is dissipated by transporting water and sediment in geomorphic adjustment of the slopes and channels. The problem of estimating the amount of energy expenditure associated with overcoming surface and system resistance is extremely complicated to solve. A simplification on a river network scale is to consider energy expenditure to be primarily associated with friction of the fluid. We propose a new technique to analyze the catchment landforms based on so-called "energy function" that is a distribution of total energy index against distance from outlet. As potential energy of water on the hillslopes is transformed into kinetic energy of the flowing fluid-sediment mixture in the runoff process, the energy is dissipated from the system. The rate of energy dissipation is defined as the work that a fluid element needs to perform to overcome friction at the unit area. Appling the product of local slope and watershed area, i.e. calculating the total energy index at the different distance from outlet, one gets the watershed "energy function" E(x). Application results indicate that the proposed method could be used for watersheds classification, regionalization and paleoreconstructions. NASA-SRTM DEM of 3" resolution has been employed to analyze the 24 watersheds within Amur River Basin with area 20-70 thousand km2 (7-8 order). The study was carried out, in particular, to assess the limitation of SRTM DEM data, especially in flat terrains. The study also revealed that some of regularities investigated are described satisfactorily by well-known simplest model of drainage networks, so-called Peano's basin.

Bugaets, Andrey; Gartsman, Boris; Bugaets, Nadezhda

2013-04-01

78

Fracturing of doleritic intrusions and associated contact zones: Implications for fluid flow in volcanic basins  

Science.gov (United States)

Igneous intrusions act as both carriers and barriers to subsurface fluid flow and are therefore expected to significantly influence the distribution and migration of groundwater and hydrocarbons in volcanic basins. Given the low matrix permeability of igneous rocks, the effective permeability in- and around intrusions is intimately linked to the characteristics of their associated fracture networks. Natural fracturing is caused by numerous processes including magma cooling, thermal contraction, magma emplacement and mechanical disturbance of the host rock. Fracturing may be locally enhanced along intrusion-host rock interfaces, at dyke-sill junctions, or at the base of curving sills, thereby potentially enhancing permeability associated with these features. In order to improve our understanding of fractures associated with intrusive bodies emplaced in sedimentary host rocks, we have investigated a series of outcrops from the Karoo Basin of the Eastern Cape province of South Africa, where the siliciclastic Burgersdorp Formation has been intruded by various intrusions (thin dykes, mid-sized sheet intrusions and thick sills) belonging to the Karoo dolerite. We present a quantified analysis of fracturing in- and around these igneous intrusions based on five outcrops at three individual study sites, utilizing a combination of field data, high-resolution lidar virtual outcrop models and image processing. Our results show a significant difference between the three sites in terms of fracture orientation. The observed differences can be attributed to contrasting intrusion geometries, outcrop geometry (for lidar data) and tectonic setting. Two main fracture sets were identified in the dolerite at two of the sites, oriented parallel and perpendicular to the contact respectively. Fracture spacing was consistent between the three sites, and exhibits a higher degree of variation in the dolerites compared to the host rock. At one of the study sites, fracture frequency in the surrounding host rock increases slightly toward the intrusion at approximately 3 m from the contact. We conclude by presenting a conceptual fluid flow model, showing permeability enhancement and a high potential for fluid flow-channeling along the intrusion-host rock interfaces.

Senger, Kim; Buckley, Simon J.; Chevallier, Luc; Fagereng, Åke; Galland, Olivier; Kurz, Tobias H.; Ogata, Kei; Planke, Sverre; Tveranger, Jan

2015-02-01

79

Microbial hydrocarbon gases in the Witwatersrand Basin, South Africa: Implications for the deep biosphere  

Science.gov (United States)

In this study, compositions and ? 13C and ? 2H isotopic values of hydrocarbon gases from 5 mines in the Witwatersrand basin, South Africa, support the widespread occurrence of microbially produced methane in millions of years-old fissure waters. The presence of microbial methane is, to a large extent, controlled by the geologic formations in which the gases are found. Samples from the Witwatersand Supergroup have the largest microbial component based on ? 13C and ? 2H signatures and CH 4/C 2+ values. Based on mixing between a microbial CH 4 component and a more 13C-enriched and 2H-depleted C 2+-rich end member, conservative estimates of the % contribution of microbial CH 4 to the gas samples range from >90% microbial CH 4 at Beatrix, Masimong, and Merriespruit, to between 5 and 80% microbial CH 4 at Evander, and origin for this 13C-enriched end member. Alternatively, the potential for an abiogenic origin similar to hydrocarbon gases produced by water-rock interaction at other Precambrian Shield mines is discussed. Microbial methane is predominantly found in paleo-meteoric fissure waters with ? 18O and ? 2H values that fall on the meteoric waterline, and have temperatures between 30 to 40°C. In contrast, fissure waters with a larger component of nonmicrobial hydrocarbon gases show a trend towards more enriched ? 18O and ? 2H values that fall well above the meteoric waterline, and temperatures of 45 to 60°C. The enrichment in 18O and 2H in these samples, and their high salinity, are similar to the isotopic and compositional characteristics of saline groundwaters and brines produced by water-rock interaction at Precambrian Shield sites elsewhere. The reported 100 Ma ages of fissure waters from the Witwatersrand and Ventersdorp formations suggest that these microbial hydrocarbon gases are the product of in situ methanogenic communities in the deep subsurface of the Witswaterand basin. Small subunit ribosomal RNA genes were amplified using archaeal-specific primer sets from DNA extracts derived from several of these waters. Fissure waters with a high proportion of microbial methane also contained sequences resembling those of known methanogens.

Ward, J. A.; Slater, G. F.; Moser, D. P.; Lin, L.-H.; Lacrampe-Couloume, G.; Bonin, A. S.; Davidson, M.; Hall, J. A.; Mislowack, B.; Bellamy, R. E. S.; Onstott, T. C.; Sherwood Lollar, B.

2004-08-01

80

Localized Stress Perturbations in the Northern Newark Basin: Implications for Induced Seismicity and Carbon Sequestration  

Science.gov (United States)

Induced seismicity has emerged as one of the primary concerns for large-volume underground injections, such as wastewater disposal and carbon sequestration. In order to mitigate potential seismic risks, detailed knowledge of reservoir geometry, occurrence of faults and fractures, and the distribution of in situ stresses is required to predict the effect of pore pressure increase on formation stability. We present a detailed analysis of in situ stress distribution at a potential carbon sequestration site in the northern Newark basin, and then consider fault and fracture stability under injection conditions taking into account the effects of localized stress perturbations, formation anisotropy and poroelasticity. The study utilizes borehole geophysical data obtained in a 2-km-deep well drilled into Triassic lacustrine sediments in Rockland County, NY. A complex pattern of local variations in the stress field with depth and at multiple scales is revealed by borehole breakouts, including: (i) gradual counter-clockwise rotation of horizontal stress orientation and decrease in relative magnitude with depth, (ii) pronounced rotations of the principal horizontal stresses at two depths, ~800 m and ~1200 m, and (iii) small-scale departures from mean orientation at the scale of meters to tens of meters. Localized stress drop near active faults may explain these observations. Seismic profiling in the vicinity of the borehole and along dip and strike of basin sediments suggests the presence of crosscutting, and potentially active, fault zones but their geometry cannot be accurately resolved. Borehole image data from the site indicates the presence of numerous fractures with increasing density over depth that roughly form two sets: high-angle fractures striking NE-SW and sub-horizontal fractures dipping NW. We perform iterative dislocation modeling for various fault orientations and slip distances to match the observed stress distribution in the borehole. Both intersecting and non-intersecting faults are modeled. Uncertainties introduced by unknown compressive rock strength and heterogeneous lithology are addressed using multivariate statistical analysis of the acquired log data, including elastic wave anisotropy. Our preliminary results suggest that shallow reservoirs ( 1.2 km) may allow injection with up to 15 MPa pore pressure increase before the effective stress reaches the failure limit on critical faults.

Zakharova, N. V.; Goldberg, D.

2013-12-01

 
 
 
 
81

Hydrothermal speleogenesis in the Eastern Basin and Range Province - Implications for Petroleum and precious-metal exploration  

Energy Technology Data Exchange (ETDEWEB)

Previous investigations based on geometric and textural and analysis have shown that most caverns in the eastern Basin and Range province were excavated not by cool, descending, meteoric waters at or above the water table, but by ascending, moderate-temperature hydrothermal fluids. This conclusion, borne out by fluid-inclusion studies, has important implications for both petroleum and precious-metal exploration in the region. Cavernous porosity has been reported in some of the area's carbonate-hosted oil reservoirs, such as the geothermally active Grant Canyon field in Railroad Valley, as well as in massive carbonates directly beneath some Carlin-type, sediment-hosted gold deposits. Moreover, at virtually all such deposits, hydrothermal carbonate-dissolution (Decalcifcation) is known to be an important porosity-inducing process. Rather than being accidental components of these oil and gold occurrences, the authors contend that such caverns may have formed in the same hydrothermal systems ultimately responsible for petroleum entrapment and precious-metal ultimately responsible for petroleum entrapment and precious-metal mineralization. The fluids that excavated the caverns must have been at least mildly acidic. Carbonic acid is the traditionally cited cavern solvent, but organic and sulfur-based acids thermally generated from regionally prevalent hydrocarbon source rocks, such as the Mississippian Chainman Shale, are equally likely as agents of dissolution. The authors suggest that thermal waters charged with these acids locally may have created or enhanced not only caverns, but migration pathways and depositional sites for gold and oil alike.

Green, D.J.; Hulen, J.B. (Univ. of Utah Research Institute, Salt Lake City, UT (United States))

1993-08-01

82

Crop yields response to water pressures in the Ebro basin in Spain: risk and water policy implications  

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Full Text Available The increasing pressure on water systems in the Mediterranean enhances existing water conflicts and threatens water supply for agriculture. In this context, one of the main priorities for agricultural research and public policy is the adaptation of crop yields to water pressures. This paper focuses on the evaluation of hydrological risk and water policy implications for food production. Our methodological approach includes four steps. For the first step, we estimate the impacts of rainfall and irrigation water on crop yields. However, this study is not limited to general crop production functions since it also considers the linkages between those economic and biophysical aspects which may have an important effect on crop productivity. We use statistical models of yield response to address how hydrological variables affect the yield of the main Mediterranean crops in the Ebro river basin. In the second step, this study takes into consideration the effects of those interactions and analyzes gross value added sensitivity to crop production changes. We then use Montecarlo simulations to characterize crop yield risk to water variability. Finally we evaluate some policy scenarios with irrigated area adjustments that could cope in a context of increased water scarcity. A substantial decrease in irrigated land, of up to 30% of total, results in only moderate losses of crop productivity. The response is crop and region specific and may serve to prioritise adaptation strategies.

S. Quiroga

2011-02-01

83

Risk of water scarcity and water policy implications for crop production in the Ebro Basin in Spain  

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Full Text Available The increasing pressure on water systems in the Mediterranean enhances existing water conflicts and threatens water supply for agriculture. In this context, one of the main priorities for agricultural research and public policy is the adaptation of crop yields to water pressures. This paper focuses on the evaluation of hydrological risk and water policy implications for food production. Our methodological approach includes four steps. For the first step, we estimate the impacts of rainfall and irrigation water on crop yields. However, this study is not limited to general crop production functions since it also considers the linkages between those economic and biophysical aspects which may have an important effect on crop productivity. We use statistical models of yield response to address how hydrological variables affect the yield of the main Mediterranean crops in the Ebro River Basin. In the second step, this study takes into consideration the effects of those interactions and analyzes gross value added sensitivity to crop production changes. We then use Montecarlo simulations to characterize crop yield risk to water variability. Finally we evaluate some policy scenarios with irrigated area adjustments that could cope in a context of increased water scarcity. A substantial decrease in irrigated land, of up to 30% of total, results in only moderate losses of crop productivity. The response is crop and region specific and may serve to prioritise adaptation strategies.

S. Quiroga

2010-08-01

84

Surface texture analysis of southern Tuli Basin sediments: Implications for Limpopo Valley geoarchaeological contexts  

Science.gov (United States)

The Hackthorne 1 site (southern Tuli Basin, South Africa) is situated on a sand-covered plateau adjacent to the Limpopo River Valley. Although the site is well known for its Stone Age archaeology, the past environmental contexts (particularly sedimentological/geomorphological) are not well known. We examine the Hackthorne sand grain surface textures, so as to provide some insight on the site specific and regional depositional history. Quartz sands at Hackthorne were collected from surface sands and from underlying weathered calcrete. SEM analysis was performed on sand grains, through which several mechanical and chemical microtextures were identified. Microtextures typical of fluvial environments were found only on grains derived from the plateau calcrete host sediment, whilst the surface sands exhibited only textures associated with aeolian environments. The results indicate that the calcrete host sediment is composed of alluvium, and that the surface sands mantling the Hackthorne Plateau are not deflated from the alluvial deposits in the Limpopo Valley, but may rather be derived from distant aeolian sources. The deposition of aeolian sands is consistent with OSL dates which place sand deposition, or remobilization, at 23 and 15 kya, periods in southern Africa associated with increased aridity.

Le Baron, Joel C.; Grab, Stefan W.; Kuman, Kathleen

2011-03-01

85

A 250,000-year climatic record from great basin vein calcite: Implications for Milankovitch theory  

Science.gov (United States)

A continuous record of oxygen-18 (??18O) variations in the continental hydrosphere during the middle-to-late Pleistocene has been obtained from a uranium-series dated calcitic vein in the southern Great Basin. The vein was deposited from ground water that moved through Devils Hole - an open fault zone at Ash Meadows, Nevada - between 50 and 310 ka (thousand years ago). The configuration of the ??18O versus time curve closely resembles the marine and Antarctic ice core (Vostok) ??18O curves; however, the U-Th dates indicate that the last interglacial stage (marine oxygen isotope stage 5) began before 147 ?? 3 ka, at least 17,000 years earlier than indicated by the marine ??18O record and 7,000 years earlier than indicated by the less well dated Antarctic ??18O record. This discrepancy and other differences in the timing of key climatic events suggest that the indirectly dated marine ??18O chronology may need revision and that orbital forcing may not be the principal cause of the Pleistocene ice ages.

Winograd, I.J.; Szabo, B. J.; Coplen, T.B.; Riggs, A.C.

1988-01-01

86

The potential for convection and implications for geothermal energy in the Perth Basin, Western Australia  

Science.gov (United States)

Convection of groundwater in aquifers can create areas of anomalously high temperature at shallow depths which could be exploited for geothermal energy. Temperature measurements in the Perth Basin (Western Australia) reveal thermal patterns that are consistent with convection in the Yarragadee Aquifer. This observation is supported by Rayleigh number calculations, which show that convection is possible within the range of aquifer thickness, geothermal gradient, salinity gradient and permeability encountered in the Yarragadee Aquifer, assuming that the aquifer can be treated as a homogeneous anisotropic layer. Numerical simulations of convection in a simplified model of the Yarragadee Aquifer show that: (1) the spacing of convective upwellings can be predicted from aquifer thickness and permeability anisotropy; (2) convective upwellings may be circular or elongate in plan view; (3) convective upwellings create significant temperature enhancements relative to the conductive profile; (4) convective flow rates are similar to regional groundwater flow rates; and (5) convection homogenises salinity within the aquifer. Further work is required to constrain the average horizontal and vertical permeability of the Yarragadee Aquifer, to assess the validity of treating the aquifer as a homogeneous anisotropic layer, and to determine the impact of realistic aquifer geometry and advection on convection.

Sheldon, Heather A.; Florio, Brendan; Trefry, Michael G.; Reid, Lynn B.; Ricard, Ludovic P.; Ghori, K. Ameed R.

2012-11-01

87

Geochemistry of Lower Cretaceous strata of northern Priverkhoyansk Foreland Basin (NE SIBERIA): implications for provenance  

Science.gov (United States)

The study area is located in the lower reaches of the Lena R., in between Chekurovka and Chucha Capes. The Lower Cretaceous clastic rocks of the northern part of the Priverkhoyansk foreland basin adjacent to the front of the Verkhoyansk fold-and-thrust belt have been studied. The Lower Cretaceous sections are composed of marine and fluvial terrigenous rocks. Marine deposits are represented by alternating sandstones and siltstones, while continental ones by alternating thick sandstones units (up to 400 m) and shale units with subordinate sandstones beds. The thickness of studied strata varies from 800-1900 m. The whole-rock geochemical analyses were done for 121 samples The geochemical study show: 1) uniform, persistent chemical composition close to that of acid igneous rocks; 2) low TiO2 content; 3) low MgO and FeO* values; 4) prevalence of FeO over Fe2O3 ; 5) high alkalies content with prevailing Na2O; 6) positive correlation between TiO2 and FeO* contents and negative correlation between Na2 O+K2 O and FeO* values. The data point to the same source of sediments both for marine and fluvial deposits with prevailing felsic rocks in provenance area. This research was supported by RFBR grants 14-05-31298, 13-05-00700, 13-05-00943 research grant of Saint Petersburg State University and Grant of President of Russia for Young Scientist MK-2902.2013.5.

Vasiliev, Dmitry; Ershova, Victoria; Ivensen, Galina; Prokopiev, Andrei

2014-05-01

88

Peace/Williston fish and wildlife compensation program: 1992-1993 public compensation report  

International Nuclear Information System (INIS)

The Peace/Williston Fish and Wildlife Compensation Program is a joint initiative by British Columbia Hydro and the provincial environment ministry to enhance and protect fish and wildlife resources and their habitat in the Williston watershed affected by the construction of the WAC Bennett and Peace Canyon dams on the Peace River. The interest from a fund of $11 million, established by BC Hydro in 1988, is used to maintain the compensation programs. Public input to the ongoing fish and wildlife programs is provided by a public consultation program. To date, the Peace/Williston compensation program has undertaken 93 projects to either conserve or enhance fish and wildlife through habitat improvement and protection. A summary is presented of the activities undertaken by the public consultation program in 1992/93 and public attitudes toward the consultation program. Activities undertaken in the fish and wildlife enhancement program are summarized in appendices. Fisheries programs included stocking, stream fertilization, small lake surveys, preparation of a side channel in Carbon Creek for multi-species spawning, and creation of an artificial spring at Windy Point for spawning purposes. Wildlife programs included channel clearance and vegetation supply improvements to enhance muskrat and beaver habitat; radio monitoring of sheep and elk; studying the feasibility of transplanting elk herds; and purchase of critical ungulate winter habitat lands. 13 figs., 4 tabshabitat lands. 13 figs., 4 tabs

89

Paleogene Larger Benthic Foraminiferal Stratigraphy and Facies distribution: implications for tectonostratigraphic evolution of the Kohat Basin, Potwar Basin and the Trans Indus Ranges (TIR) northwest Pakistan  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Thick Paleogene sequences occur in the southern deformed fold and thrust belt of the Himalayas. In this thesis I describe detailed litho- and biostratigraphy from ten key stratigraphic sections in the Kohat Basin, the Potwar Basin and the Trans Indus Ranges (TIR). These stratigraphies combined with microfacies analysis resulted in a new interpretation of the tectono-stratigraphic history of the area, which is dominated by India-Asia collision but where eustatatic effects can al...

Ahmad, Sajjad

2011-01-01

90

Differentiation of the South Pole-Aitken basin impact melt sheet: Implications for lunar exploration  

Science.gov (United States)

modeled the differentiation of the South Pole-Aitken (SPA) impact melt sheet to determine whether noritic lithologies observed within SPA formed as a result of the impact. Results indicate differentiation of SPA impact melt can produce noritic layers that may accommodate observed surface compositions but only in specific scenarios. One of nine modeled impact melt compositions yielded layers of noritic materials that account for observations of noritic lithologies at depths of ~6 km. In this scenario, impact occurred before a hypothesized lunar magma ocean cumulate overturn. The 50 km deep melt sheet would have formed an insulating quenched layer at the surface before differentiating. The uppermost differentiated layers in this scenario have FeO and TiO2 contents consistent with orbital observations if they were subsequently mixed with the uppermost quenched melt layer and with less FeO- and TiO2-enriched materials such as ejecta emplaced during younger impacts. These results verify that noritic lithologies observed within SPA could have formed as a direct result of the impact. Therefore, locations within SPA that contain noritic materials represent potential destinations for collecting samples that can be analyzed to determine the age of the SPA impact. Potential destinations include central peaks of Bhabha, Bose, Finsen, and Antoniadi craters, as well as walls of Leibnitz and Schrödinger basins. Additionally, potential remnants of the uppermost quenched melt may be preserved in gabbroic material exposed in "Mafic Mound." Exploring and sampling these locations can constrain the absolute age of SPA, a task that ranks among the highest priorities in lunar science.

Hurwitz, Debra M.; Kring, David A.

2014-06-01

91

Stratigraphic distribution of macerals and biomarkers in the Donets Basin: Implications for paleoecology, paleoclimatology and eustacy  

International Nuclear Information System (INIS)

More than one hundred and thirty coal seams and coaly layers occur in the Donets Basin (Donbas). Twenty-eight (52 samples) of them, ranging in age from Serpukhovian (Late Mississipian) to Gzhelian (Late Pennsylvanian), 33 clastics and three limestones were studied in terms of maceral composition, sulphur contents, and biomarker distribution. Diterpanes are used to estimate the contribution of different groups of plants and the height of the water table in the swamp; hopanes are a measure of bacterial activity in the peat; and steranes indicate the relative input of wood and algae. Stratigraphic trends in these parameters are discussed in relation to paleoenvironment, climatic changes, and eustacy. A tropical climate prevailed in the Donbas from Serpukhovian to Kasimovian times. Nevertheless, periods with drier and wetter conditions can be distinguished based on maceral and biomarker data. Relatively dry conditions are observed during Serpukhovian and Vereian times, whereas wetter climates with a maximum of coal deposition occurred during the (late) Bashkirian, most of the Moscovian, and the earliest Kasimovian. No economic coal seams are hosted in upper Kasimovian and Gzhelian deposits, a result of a change to an arid climate. Our data also suggest climatic changes during sequences of different order. For the second-order, third-order, and fourth-order sequences, relatively dry or wet conditions occurred during coal deposition in the lowstand systems tract, an interme in the lowstand systems tract, an intermediate climate during the transgressive systems tract and the maximum flooding, and a wet climate during the highstand systems tract. The results for high frequency sequences support the Cecil's paleoclimatic model: an intermediate paleoclimate during LST (sandstone and levee siltstone), a wet climate during early TST (coal), and a dry climate during late TST (limestone), MFS (claystone), and HST (deltaic siltstone). Coals deposited during maximum flooding periods are more enriched in C27 steranes derived from algae, and contain lower proportions of C29 steranes derived from the wood of higher plants. (author)

92

Morphology of the Frontal fault zone, southwest Oklahoma: Implications for deformation and deposition in the Wichita uplift and Anadarko basin  

Science.gov (United States)

Structural fabrics along the northern margin of the Wichita uplift, southwestern Oklahoma, are compared with depositional patterns in the adjacent Anadarko basin. The Frontal fault zone, the structural transition between the uplift and basin, is divisible into three segments that reflect the partitioning of deformation along the northern margin of the uplift. Variations in Pennsylvanian isopach patterns within the Anadarko basin suggest changing conditions of tectonic loading along the basin's southern margin. Anomalously thin sections of syntectonic rocks in the deep basin are interpreted to have been deposited on the crests of growing anticlines.

McConnell, David A.; Goydas, Michael J.; Smith, Graham N.; Chitwood, John P.

1990-07-01

93

Assessing the implications of baseline climate uncertainty on simulated water yield within the Himalayan Beas river basin in NW India  

Science.gov (United States)

Understanding the impacts of the changing water cycle on future water resources and society is one of the most important issues surrounding anthropogenic climate change, especially in regions with limited adaptive capacity or highly water-dependent economies. One such region is the north western Himalayan region of India, where supplementary irrigation is used in the non-monsoon seasons and where over 90% of the population are reliant on agriculture for their livelihoods. This paper focuses on the transboundary 12,560km2 Beas catchment in Himachal Pradesh, which is one of the case study catchments of the Mitigating the Impacts of Climate Change in Indian agriculture (MICCI) project of the UK NERC Changing Water Cycle Programme. However, understanding of the impacts of changes in the water cycle in such regions is dependent on the quality of available observational climate datasets- a challenge given the relative paucity of ground-based observations in mountainous terrains. River flows in the Beas, which support both irrigation and hydropower, are highly seasonal, being dependent on the Indian Monsoon augmented by seasonal snow and ice melt from the Himalayas. This paper describes the uncertainty in simulating water yield in the Beas catchment, using the HySim hydrological model, associated with the use of a diverse range of public domain and governmental observed and derived precipitation and evapo-transpiration datasets (including gridded ground-based data from the Indian Meteorological Department; TRMM, NCEP Climate Forecast System Reanalysis (CFSR) and the APHRODITE project). For example, basin annual average precipitation (2000-07) ranges from 1476 mm/yr (CFSR), 2093mm/yr (APHRODITE) to 2357 mm/yr (TRMM), whilst basin annual average reference evapotranspiration ranges from 1320 mm/yr (with a minimum to maximum sub-basin range of 136-4680 mm/yr) using the Priestley Taylor to 2296 mm/yr (190-6954 mm/yr) with Penman-Monteith. The selection of datasets affects baseline hydrological model performance with, for example, calibration Nash-Sutcliffe Efficiencies ranging from 0.56 to 0.68 across the precipitation datasets (using CFSR data to derive evapotranspiration) for the river Beas. To evaluate the potential impact of such uncertainty on assessments of future water yield, we further describe the application of a scenario-neutral modelling framework using IPPC AR4 ranges of temperature and precipitation changes to the baseline datasets to assess the differences in their response surfaces. The results show that the uncertainty in the driving hydroclimatological variables, associated with the choice of underlying observational dataset and the choice of evopo-transpiration method, translates into significant temporal and spatial uncertainty in simulated baseline and future water yield with significant implications for our ability to project changes in the water cycle in such sensitive regions.

Holman, I.; Remesan, R.; Adeloye, A.; Ojha, C. S.

2013-12-01

94

Late Quaternary tectonics in the inner Northern Apennines (Siena Basin, southern Tuscany, Italy) and their seismotectonic implication  

Science.gov (United States)

Defining the most recent Quaternary tectonics represents a challenging task for neotectonic, palaeoseismological and seismotectonic studies. This paper focuses on an integrated approach to reconstructing the latest Quaternary deformation affecting the northern part of the Siena Basin (inner Northern Apennines, i.e., southern Tuscany, Italy) near the town of Siena, and to discuss the seismological implications. Field work and structural and stratigraphic analyses, coupled with the interpretation of reflection seismic lines, have been combined to define the geometry, kinematics and age of mesoscopic to map-scale faults which have affected the mainly Quaternary continental and Pliocene marine deposits. The resulting dataset describes a tectonic setting characterized by coeval SW- and NW-trending transtensional and normal faults, respectively, dissecting alluvial sediments younger than 23.9 ± 0.23 ka. Seismic interpretation sheds light on the geometrical setting of the faults at deeper levels, down to 1-2 km, and provides support for the presence of a wide brittle shear zone defined by conjugated fault segments, locally giving rise to an asymmetrical negative flower-like structure. Faults and their damage zones have controlled (and still control) the discharge of gas vents (mainly CO2 and H2S) and hydrothermal circulation (which deposits travertine) since at least 23.216 ± 0.124 ka. The resulting complete data set provides support for our description of the Neogene-Quaternary tectonics which were active until the late Quaternary, providing additional information about the seismotectonic framework of an area characterized by low seismicity and generally low-magnitude earthquakes (M < 4), but having experienced significant seismic events over the last few centuries.

Brogi, Andrea; Capezzuoli, Enrico; Martini, Ivan; Picozzi, Matteo; Sandrelli, Fabio

2014-05-01

95

Organofacies and kerogen tranformation kinetics: Implications for hydrocarbon generation in the Bucomazi Formation, lower Congo coastal basin  

Energy Technology Data Exchange (ETDEWEB)

Deposited under lacustrine conditions during the rift-phase opening of the southern Atlantic, the lower Congo Bucomazi Formation is a highly productive source rock sequence. Reaching considerable thickness (1.8 km), a heterogeneous organofacies reflects both rapid accumulation and changing conditions during Early Cretaceous Barremian sedimentation. As a component of organofacies, low resolution studies showed kerogen kinetic parameters (Ea/A) varied widely according to the gross paleoenvironmental conditions prevailing during deposition. As a a general trend, refractory (type I, higher Ea) kerogens of the [open quotes]basin fill[close quotes] Organic Rich Zone (ORZ) give way to more labile (type II, lower Ea) assemblages in the up-section [open quotes]sheet drape[close quotes] sediments. At higher resolution, a considerable fine structure in Ea fluctuation, presumably reflecting micropaleoenvironment control, becomes evident. Using Ea values assembled for the Bucomazi type section, subsidence modeling for a Ponta Vermelha depocenter section showed a wide disparity in behavior. Being more representative of the sheet-drape episode, type II assemblages matured earlier, at lesser overburdens, and provided the initial hydrocarbon charge. For the ORZ assemblages, the dominant type I component was of retarded maturation, only becoming productive at commensurately greater overburdens. Cumulatively, these events merge to provide an extended period of hydrocarbon generation with implications for production of aggregate oils of varied emplacement histories. Significantly, the net effect of the observed Ea contrast results in the less prolific (but more labile) uppermost Bucomazi assuming a more important charging role than the ORZ of superior source richness. The latter can only realize its full potential under the greatest overburdens attainable in the most subsident depocenters.

Burwood, R.; Fortems, G.; Mycke, B.; Paulet, J.; De Witte, S.M. (Petrofina S.A., Brussels (Belgium))

1993-09-01

96

Hydrocarbon Potentials, Thermal and Burial History in Herwa-1 Well from the Nigerian Sector of the Chad Basin: An Implication of 1-D Basin Modeling Study  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This research study attempt to evaluate the hydrocarbon potentials, thermal and burial history and the timing of hydrocarbon generation in Herwa-1 well within the Nigerian Sector of the Chad basin. Organic geochemical study of some ditch cuttings samples from Herwa-1 well and a One-dimensional basin modeling study was carried out. The result of the geochemical analysis revealed a moderate to good TOC greater than 0.5wt% in Fika and Gongila formation, the Hydrogen Index (HI) ranges from 150-30...

Abubakar Mijinyawa; Bhattacharya, S. K.; Moumouni, A.; Mijinyawa, S.; Ibad Mohammad

2013-01-01

97

Implications of paleomagnetic results from the Permian Rodez basin for the late Variscan tectonics in the southern French massif Central.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A paleomagnetic study has been carried out on three sedimentary formations of the Permian Rodez basin in the southern France. Two of them yield paleomagnetic poles of Saxonian and Thuringian age showing counterclockwise rotation of moderate amplitude, during or after the Thuringian deposition. For the French Massif Central, contrary to its stable southern (Lodève basin) and eastern (Largentière basin) borders, on its southwestern border, in a large area including the Rodez, Saint-Affrique a...

Diego-orozco, Arturo; Chen, Yan; Henry, Bernard; Becq-giraudon, Jean-franc?ois

2002-01-01

98

Enriched back-arc basin basalts from the northern Mariana Through: Implications for the magmatic evolution of back-arc basins  

Energy Technology Data Exchange (ETDEWEB)

The composition of basalts erupted at the earliest stages in the evolution of back-arc basin permit unique insights into the composition and structure of the sub-arc mantle. We report major and trace element chemical data and O-, Sr-, Nd-, and Pb-isotopic analyses for basalts recovered from four dredge hauls and one ALVIN dive in the northern Mariana Trough near 22deg N. The petrography and major element chemistry of these basalts (MTB-22) are similar to tholeiites from the widest part of the Trough, near 18deg N (MTB-18), except that MTB-22 have slightly more K{sub 2}O and slightly less TiO{sub 2}. The trace element data exhibit a very strong arc signature in MTB-22, including elevated K, Rb, Sr, Ba, and LREE contents; relatively low K/Ba and high Ba/La and Sr/Nd. The Sr- and Nd-isotopic data plot in a field displaced from that of MTB-18 towards Mariana arc lavas, and the Pb-isotopic composition of MTB-22 is indistinguishable from Mariana arc lavas and much more homogeneous than MTB-18. Mixing of 50-90% Mariana arc component with a MORB component is hypothesized. We cannot determine whether this resulted from physical mixing of arc mantle and MORB mantle, or whether the arc component is introduced by metasomatism of MORB-like mantle by fluids released from the subducted lithosphere. The strong arc signature in back-arc melts from the Mariana Trough at 22deg N, where the back-arc basin is narrow, supports general models for back-arc basin evolution whereby early back-arc basin basalts have a strong arc component which diminishes in importante relative to MORB as the back-arc basin widens. (orig.).

Stern, R.J.; Lin Pingnan (Center for Lithospheric Studies, Texas Univ., Dallas, Richardson (USA)); Morris, J.D. (Dept. of Terrestrial Magnetism, Carnegie Institution, Washington, DC (USA)); Jackson, M.C.; Fryer, P. (Hawaii Inst. of Geophysics, Hawaii Univ., Honolulu (USA)); Bloomer, S.H. (Dept. of Geology, Boston Univ., MA (USA)); Ito, Emi (Dept. of Geology and Geophysics, Minnesota Univ., Minneapolis (USA))

1990-10-01

99

Tectono-stratigraphy of the Neogene basins in Western Turkey: Implications for tectonic evolution of the Aegean Extended Region  

Science.gov (United States)

The western part of the Aegean region includes several Neogene basins containing volcano-sedimentary successions. The Neogene basins, located along the northern Menderes Extensional Metamorphic Complex (MEMC) were developed during the Miocene as supra-detachment basins. They contain two distinct volcano-sedimentary successions, separated by a regional unconformity. The basins located to the west of the MEMC were developed as strike-slip basins and contain volcanic and sedimentary units getting younger from NE to SW with no remarkable unconformity. Available paleomagnetic studies in the Aegean Region suggest to us that, the basins to the west of the MEMC were developed in response to southward clockwise rotational roll-back of the Aegean subduction zone. The eastern margin of this rotational deformation is characterized on the surface by a large strike-slip zone, which is known as ?zmir-Bal?kesir Transfer Zone (?BTZ). The sedimentary successions in the basins along the northern MEMC do not show southward younging and are interpreted to be developed in response to exhumation of the MEMC. During the Pliocene to Quaternary, ~ E-W-trending grabens such as the Gediz (Ala?ehir), Büyük and Küçük Menderes Grabens were developed in response to tectonic escape accompanying the slab-roll back process. These grabens truncate the MEMC basins. During this time, strike-slip deformation and associated sedimentation continued along the ?BTZ.

Ersoy, E. Y.; Çemen, ?.; Helvac?, C.; Billor, Z.

2014-11-01

100

The structural evolution of the Ghadames and Illizi basins during the Paleozoic, Mesozoic and Cenozoic: Petroleum implications  

Energy Technology Data Exchange (ETDEWEB)

The Ghadames and Illizi basins cover the majority of the eastern Sahara of Algeria. Geologicaly, this part of the Central Saharan platform has been influenced by a series of structural arches and {open_quotes}moles{close_quotes} (continental highs) which controlled sedimentation and structure through geologic time. These features, resulting from and having been affected by nine major tectonic phases ranging from pre-Cambrian to Tertiary, completely bound the Ghadames and Illizi Basins. During the Paleozoic both basins formed one continuous depositional entity with the Ghadames basin being the distal portion of the continental sag basin where facies and thickness variations are observed over large distances. It is during the Mesozoic-Cenozoic that the Ghadames basin starts to evolve differently from the Illizi Basin. Eustatic low-stand periods resulted in continental deposition yielding the major petroleum-bearing reservoir horizons (Cambrian, Ordovician, Siluro-Devonian and Carboniferous). High-stand periods corresponds to the major marine transgressions covering the majority of the Saharan platform. These transgressions deposited the principal source rock intervals of the Silurian and Middle to Upper Devonian. The main reservoirs of the Mesozoic and Cenozoic are Triassic sandstone sequences which are covered by a thick evaporite succession forming a super-seal. Structurally, the principal phases affecting this sequence are the extensional events related to the breakup of Pangea and the Alpine compressional events. The Ghadames and Illizi basins, therefore, have been controlled by a polphase tectonic history influenced by Pan African brittle basement fracturing which resulted in complex structures localized along the major basin bounding trends as well as several subsidiary trends within the basin. These trends, as demonstrated with key seismic data, have been found to contain the majority of hydrocarbons trapped.

Gauthier, F.J. [Anadarko Petroleum Corp., Houston, TX (United States); Boudjema, A. [Somatrach, Algiers (Algeria); Lounis, R. [Anadarko Algeria Corp., Houston, TX (United States)

1995-08-01

 
 
 
 
101

Late-Quaternary morphodynamics of Ejina Basin, Inner Mongolia, China: Quantification of neotectonic subsidence and palaeohydrological implications  

Science.gov (United States)

From space, the Ejina Basin (Gaxun Nur Basin) - enclosed by the Tibetan Plateau in the south and the Gobi -Tien Shan in the north - appears as the world's second largest inland delta of approx. 28,000 km2. Today, the crescent-shaped series of terminal lakes (Gaxun Nur, Sogo Nur and Juyanze) represent the endorheic erosion base for the Black River (Hei River) drainage system originating in the Qilian Mountains (>5,000 m asl.). The up to 300 m thick Quaternary basin fill of lacustrine and alluvial origin was deposited during the last approx. 250,000 yrs. Gobi gravel plains protecting Late Pleistocene fine sediments against deflation cover most parts of the basin. They are considered to be a unique sequence within the sediment stratigraphy of the entire basin. The slightly convex-shaped surface of the western basin resembles the prograding formation of an alluvial fan with clear evidence of local subsidence to the north and west, as indicated by the concave shaped surface there. However, the recent terminal lake basins at the northern margin of Ejina Basin are structurally related to tectonic pull-apart basins that were active since Late Pleistocene. The rhomb-shaped Gaxun Nur basin is the most distinct pull-apart feature indicating a left-lateral strike-slip movement parallel to the continental Gobi-Tien-Shan Fault in the north. New radiocarbon dates of lacustrine sediments within a fossil cliff at the southern shore support the estimated subsidence rate of >0.8m per kyr (Hartmann et al. 2011) after the Last Glacial Maximum (LGM). The more trapezoid fault system of the Juyanze pull-apart basin exhibits a more manifold set of tectonically induced geomorphological features. Whereas Hartmannn et al. (2011) assumed a W-E-striking fault by comparing dating inversions along yardangs of lacustrince chalks that host seismites. A nearby new railway construction pit revealed a normal fault that affected the lake sediments that are 35±1 kyr BP in age. The most impressive set of features related to young tectonic subsidence in Ejina basin resembles inverted channels south of western Juyanze. Radiocarbon dates of lacustrine sediments below the gravel cover suggest a reversal of surface gradient, conservation and dissection of gravel beds by subsidence that most likely occurred after 13.6 kyr BP. The continuation of the S-N-striking strike-slip-duplex of the Gurinai structure separates Juyanze in two basins by an impressive >20 m emerging cliff formed within remains of an isolated large alluvial fan. This fan should have been active after approx. 18 kyr BP. Hence, a synopsis of at least 65 radiocarbon dates of lacustrine sediments from the margins and centres of the sub-basins suggests four times higher subsidence rates from the north-western (0.8 m/kyr) to the north-eastern (2-3.6 m/kyr) margin of Ejina Basin. Considering the flat and spatially uncertain water divide to the depression of Wentugaole (and its continuation to the northwest), it seems likely that the basin has lost its endorheic character at least once. Hence, the morphology of basin margins of this large intermontane foreland basin shows up with tectonically active margins and sensitive water divides. Reference: Hartmann, K., Wünnemann, B., Hölz, S., Kraetschell, A., Zhang, H. (2011): Neotectonic constraints on the Gaxun Nur inland basin in north-central China, derived from remote sensing, geomorphology and geophysical analyses. - In: Gloaguen, R. & Ratschbacher, L. (eds.): Growth and Collapse of the Tibetan Plateau. - Geological Society of London Special Publications 353: 221-233.

Hartmann, Kai; Wünnemann, Bernd; Reicherter, Klaus; Rudersdorf, Andreas; Blaauw, Maarten; Diekmann, Bernhard; Bölscher, Judith; Lu, Huayu

2014-05-01

102

Regional patterns of magnetite authigenesis in the Appalachian Basin: Implications for the mechanism of Late Paleozoic remagnetization  

Science.gov (United States)

We report paleomagnetic and rock magnetic data from sedimentary carbonates of the Appalachian Basin that have implications for the mechanism of widespread late Paleozoic remagnetization in this rock type. Sampling was accomplished mostly along two across-basin transects, one in Devonian carbonates of New York State and the other in Ordovician and Mississippian carbonates of Tennessee and Alabama. Paleomagnetic investigations of the New York Devonian carbonates along a transect from Albany to Buffalo indicate that these rocks were completely remagnetized in Alleghenian time. Rock magnetic studies show that magnetite concentration varies in a regular fashion along the transect with a local maximum near Syracuse and decreasing gradually to the east and west. This pattern shows a striking correlation with the degree of diagenetic alteration of clay minerals in a Devonian bentonite horizon which took place during Alleghenian time. We conclude that most of the magnetite present in these carbonates is of authigenic origin and that clay mineral alteration and magnetite authigenesis were coeval, late Paleozoic events that were controlled by the same diagenetic factors. Thermoviscous remagnetization processes cannot be ruled out in this setting in light of the observed degree of thermal maturity. However, our results suggest that chemical factors played a critical role in remagnetization since they allow us to infer that magnetite authigenesis and remagnetization are about the same age. We propose a geochemical model for magnetite authigenesis wherein the iron is derived from detrital smectites during diagenetic illitization, which is triggered by the introduction of potassium-rich brines. Results from the Tennessee transect from Nashville to Chattanooga show a very different pattern. Paleomagnetic studies indicate that late Paleozoic remagnetization has affected Ordovician carbonates of the Nashville Dome. Paleozoic carbonates in the overthrust belt near Chattanooga also carry the late Paleozoic remagnetization. However, Mississippian carbonates between the dome and the overthrust belt are very weakly magnetized and show no evidence for late Paleozoic remagnetization. Samples show only a present field magnetization or, at one locality in northwestern Alabama, a dual-polarity magnetization of probable Mississippian age. Rock magnetic studies indicate that higher concentrations of magnetite are present in the remagnetized rocks of the Nashville Dome and the overthrust belt than in the nonremagnetized Mississippian carbonates. We therefore conclude that magnetite authigenesis and remagnetization are related events in this setting and that the remagnetization must be due to chemical processes. The presence of a remagnetization "shadow" in the younger rocks now exposed between the fold-thrust belt and the flexural arch is attributed to westward flow of magnetite-forming aqueous fluids through deep, sub-Carboniferous aquifers during Alleghenian time. Upward migration of the fluids through the Mississippian carbonates may have been prevented by the Devono-Mississippian Chattanooga Shale, an impermeable stratum that is present throughout the region.

McCabe, Chad; Jackson, Michael; Saffer, Barbara

1989-08-01

103

Eocene to Miocene back-arc basin basalts and associated island arc tholeiites from northern Sulawesi (Indonesia): Implications for the geodynamic evolution of the Celebes basin  

International Nuclear Information System (INIS)

Eocene BABB basalts intruded by tholeiitic and calk-alkalic island arc magmatic rocks are reported from the north arm of Sulawesi (Indonesia). Age and geochemical similarities between these basalts and those drilled in the Celebes Sea indicate this North Sulawesi volcanic arc was built on the same oceanic crust. The 25 deg late Neogene clockwise rotation of the north arm of Sulawesi following its collision with fragments of Australia (Sula, Buton) is not sufficient to explain the asymmetrical magnetic anomalies in the Celebes basin. The North Sulawesi island arc could be interpreted as having progressively retreated northward on its own Celebes sea back arc basin, during an episode of Palaeogene-early Neogene tectonic erosion along the trench. (authors)

104

Hydrocarbon Potentials, Thermal and Burial History in Herwa-1 Well from the Nigerian Sector of the Chad Basin: An Implication of 1-D Basin Modeling Study  

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Full Text Available This research study attempt to evaluate the hydrocarbon potentials, thermal and burial history and the timing of hydrocarbon generation in Herwa-1 well within the Nigerian Sector of the Chad basin. Organic geochemical study of some ditch cuttings samples from Herwa-1 well and a One-dimensional basin modeling study was carried out. The result of the geochemical analysis revealed a moderate to good TOC greater than 0.5wt% in Fika and Gongila formation, the Hydrogen Index (HI ranges from 150-300 (mgHC/g and the Tmax values falls within the range of greater than or equal to 430°C. The hydrocarbon potentials in Herwa-1 well was further supported with the values of S1+S2 which is greater than or equal to 2 mg/g of rock in almost all the samples, suggesting a good hydrocarbon potentials. The 1-D basin model was constructed for Herwa-1 well in order to assess the burial history and thermal maturity of the potential source rocks in the Nigerian sector of the Chad basin. The modeling results indicate that maximum burial occurred in the late Miocene and suggesting erosion might have been the cause of the thinning of the Tertiary sediments in the present time. The calibration of Vitrinite reflectance against Temperature revealed the present day heat flow to be at 60 mW/m2 and Paleo heat flow falls within the range of 68 mW/m2. However, it is also revealed that Oil Window begins at (0.60-1.30% VRr at the depth of (2000-3000 m in the middle Cretaceous and the Gas Window start during the late Cretaceous to Tertiary with a value of (1.3-2.5% VRr at a depth greater than (3500 m.

Abubakar Mijinyawa

2013-06-01

105

Diversity of Manota Williston (Diptera, Mycetophilidae) in Ulu Temburong National Park, Brunei  

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A total of 15 species of Manota Williston, 1896 are recorded from Brunei, based on the investigations in 2013-2014. Thirteen species are recorded from Ulu Temburong National Park and three species from the Universiti Brunei Darussalam Campus in Tungku. Six species are described as new to science: Manota belalongensis sp. n., M. kaspraki sp. n., M. macrothrix sp. n., M. megachaeta sp. n. and M. pileata sp.n. from Ulu Temburong, and M. ricina sp. n. from Tungku. New records of the following spe...

S?evc?i?k, Jan; Hippa, Heikki; Abdul Wahab, Rodzay

2014-01-01

106

Ultramorphological features of the egg of Telmatoscopus albipunctatus (Williston) (Diptera, Psychodidae)  

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Full Text Available SciELO Brazil | Language: English Abstract in portuguese Aspectos ultramorfológicos do ovo de Telmatoscopus albipunctatus (Williston) (Diptera, Psychodidae). As moscas da família Psychodidae, também conhecidas como moscas de banheiro, são de importância médica e veterinária. Informações gerais sobre ciclo de vida e hábitos do adulto são facilmente encontr [...] adas, mas pouco se sabe sobre a morfologia do ovo. Dessa forma, neste estudo, a ultramofologia do ovo de Telmatoscopus albipunctatus (Williston, 1893) foi analisada por microscopia eletrônica de varredura com o objetivo de descrever sua estrutura, provendo importantes dados para futuras comparações entre moscas de diferentes espécies e gêneros. O aspecto geral do ovo de T. albipunctatus é similar a outros Psychodidae, medindo aproximadamente 0.4 mm de comprimento e 0.1 mm de largura. Entretanto, baseado nas esculturas contínuas e descontínuas do exocórion, as quais podem ser espécie-específicas, podemos inferir que os ovos de T. albipunctatus podem sobreviver sob condições de muita umidade ou seca, dificultando o controle da espécie. Nossos resultados ressaltam a importância do uso da microscopia eletrônica como uma ferramenta no estudo dos padrões do exocórion. A morfologia externa do ovo de T. albipunctatus pode ser usada como base para futuros estudos e como ferramenta para comparação de diferentes espécies de moscas do gênero Psychodidae. Abstract in english Ultramorphological features of the egg of Telmatoscopus albipunctatus (Williston) (Diptera, Psychodidae). Psychodidae flies, also known as sewage, sand and filter flies are important for medical and veterinary purposes. General information about life cycle and adult habits is available, but few spec [...] ies are known about the egg morphology. Therefore, in this study, the egg ultramorphology of Telmatoscopus albipunctatus (Williston, 1893) was analyzed by scanning electron microscopy to describe its structure, generating data for further comparison between different fly species and genera. General aspects of T. albipunctatus egg are similar to other Psychodidae; egg measuring approximately 0.4 mm in length and 0.1 mm in width. However, based on the continuous and discontinuous longitudinal ridge sculptures observed on the exochorion, which can be species-specific, we can infer that T. albipunctatus eggs can survive under dry or moist conditions, making their control much more difficult. Our data emphasize the advantages of the electron microscope approach in the study of the exochorion patterns. Eggshell morphology of T. albipunctatus can be used as basis for further studies and as a tool to compare different species of Psychodidae flies.

Thalita, Rocha; José Augusto de Oliveira, David; Flávio Henrique, Caetano.

2011-06-01

107

Heterogeneity in aerosol characteristics over the Indo-Gangetic Basin: Implications to the radiative forcing in the Himalayan region  

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The Indo-Gangetic Basin (IGB) is located in the northern part of India and surrounded by the unique topography with the Himalaya to the north, moderate hills to the south, Thar Desert and Arabian Sea in the west, and Bay of Bengal in the east. Aerosols over the IGB region are highly associated with the emissions from various anthropogenic and natural sources (mostly during the pre-monsoon period), resulting in a large spatial heterogeneity in its distribution, in term of loading and type/composition. Due to combined effects of the IGB topography and the Himalayan orography, these aerosols are lifted up quite often to the high-altitudes and may impact the cryosphere and radiation budget of the climatically sensitive region of the Himalayas. The impact of aerosols on radiation budget were studied at Manora Peak, one of the sparsely inhibited high-altitude stations in the Indian Himalayan foothills, during the period from February 2006-May 2008, and their implications have been addressed in the present study. In the absence of measured aerosol optical properties (crucial for radiative forcing estimations), measured aerosol chemical composition at Manora Peak were used in an aerosol optical model to obtain crucial optical properties of aerosols such as aerosol optical depth (AOD), single scattering albedo (SSA) etc. The monthly and seasonal variability of these optical properties were studied extensively over the station. The AOD was found to be varied from 0.04 to 0.45 during the course of study period and showed a slight increasing trend, mostly during the summer in each year, suggesting the relative influence of transported dust aerosols over the station. The SSA was found to be varied from 0.74 to 0.88, with slightly decreasing trend, suggested the enhancement in absorbing aerosols (dust/BC) over the region. The absorption Ångström exponent (AAE) was also estimated and ranged from 0.72 to 1.40, with higher magnitude (>1.0) during the summer, indicating the dominance of mixed aerosols over the region. Additional observations provide an evidence of the presence of strongly absorbing aerosols over the Himalayan region, derived from the variety of sources, which may affect the strength of Himalayan glaciers, monsoon circulation and precipitation over the Indian region. Further, these derived aerosol optical parameters were used in a radiative transfer model to estimate the associated radiative forcing to understand their possible impacts over the region and will be discussed during the conference.

Srivastava, A. K.; Ram, K.; Sarin, M. M.; Tiwari, S.

2012-12-01

108

Hydrological Controls of Riverine Ecosystems of the Napo River (Amazon Basin): Implications for the Management and Conservation of Biodiversity  

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Scientific understanding of neotropical floodplains comes mainly from work on large rivers with predictable seasonal flooding regimes. Less studied rivers and floodplains on the Andean-Amazon interface are distinct in their hydrology, with more erratic flow regimes, and thus ecological roles of floodplain inundation differ in those ecosystems. Multiple and unpredictable flooding events control inundation of floodplains, with important implications for fish and wildlife, plant communities, and human activities. Wetlands along the river corridor exist across a continuum from strong river control to influence only by local waters, with the latter often lying on floodplain paleoterraces. The goal of this study was to understand the hydrological interactions and habitat diversity of the Napo River, a major Amazon tributary that originates in the Andes and drains exceptionally biodiverse Andean foreland plains. This river system is envisioned by developers as an industrial waterway that would require hydrological alterations and affect floodplain ecosystems. Water level regimes of the Napo River and its associated environments were assessed using networks of data loggers that recorded time under water across transects extending inland from the river across more than 100 sites and for up to 5 years. These networks also included rising stage samplers that collected flood water samples for determination of their origin (i.e., Andean rivers vs. local waters) based on hydrochemical composition. In addition, this work entails a classification of aquatic environments of the Napo Basin using an object-oriented remote sensing approach to simultaneously analyze optical and radar satellite imagery and digital elevation models to better assess the extent and diversity of flooded environments. We found out a continuum of hydrological regimes and aquatic habitats along the Napo River floodplains that are linked to the river hydrology in different degrees. Overall, environments that are proximal or that have high hydrological connectivity are riverine controlled versus systems that are distal or that have less or no connectivity that rely on rainwater or local runoff as a source of flooding. Outcomes of this research gave us insight on the extent and diversity of aquatic habitats of the Napo River, the role that the river has on their ecohydrology, the potential effects of different hydrologic scenarios on these ecosystems, and the management measures that need to be considered to support conservation in the region.

Celi, J. E.; Hamilton, S. K.

2013-12-01

109

Sr-Nd-Hf-Pb isotope geochemistry of basaltic rocks from the Cretaceous Gyeongsang Basin, South Korea: Implications for basin formation  

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To better understand the formative mechanism of the Cretaceous Gyeongsang Basin in South Korea, we determined the geochemical compositions of Early Cretaceous syntectonic basaltic rocks intercalated with basin sedimentary assemblages. Two distinct compositional groups appeared: tholeiitic to calc-alkaline basalts from the Yeongyang sub-basin and high-K to shoshonitic basaltic trachyandesites from the Jinju and Uiseong sub-basins. All collected samples exhibit patterns of light rare earth element enrichment and chondrite-normalized (La/Yb)N ratios ranging from 2.4 to 23.6. In a primitive-mantle-normalized spidergram, the samples show distinctive negative anomalies in Nb, Ta, and Ti and a positive anomaly in Pb. The basalts exhibit no or a weak positive U anomaly in a spidergram, but the basaltic trachyandesites show a negative U anomaly. The basalts have highly radiogenic Sr [(87Sr/86Sr)i = 0.70722-0.71145], slightly negative ?Nd, positive ?Hf [(?Nd)i = -2.7 to 0.0; (?Hf)i = +2.9 to +6.4], and radiogenic Pb isotopic compositions [(206Pb/204Pb)i = 18.20-19.19; (207Pb/204Pb)i = 15.60-15.77; (208Pb/204Pb)i = 38.38-39.11]. The basaltic trachyandesites are characterized by radiogenic Sr [(87Sr/86Sr)i = 0.70576-0.71119] and unradiogenic Nd, Hf, and Pb isotopic compositions [(?Nd)i = -14.0 to -1.4; (?Hf)i = -17.9 to +3.7; (206Pb/204Pb)i = 17.83-18.25; (207Pb/204Pb)i = 15.57-15.63; (208Pb/204Pb)i = 38.20-38.70]. The 'crust-like' signatures, such as negative Nb-Ta anomalies, elevated Sr isotopic compositions, and negative ?Nd(t) and ?Hf(t) values, of the basaltic trachyandesites resemble the geochemistry of Early Cretaceous mafic volcanic rocks from the southern portion of the eastern North China Craton. Considering the lower-crust-like low U/Pb and high Th/U ratios and the unradiogenic Pb isotopic compositions, the basaltic trachyandesites are considered to be derived from lithospheric mantle modified by interaction with melts that originated from foundered eclogite. Basaltic volcanism in the Yeongyang sub-basin is coeval with the basaltic trachyandesite magmatism, but it exhibits an elevated 87Sr/86Sr ratio at a given 143Nd/144Nd and highly radiogenic Pb isotopic compositions, which imply an origin from an enriched but heterogeneous lithospheric mantle source. Melts from subducted altered oceanic basalt and pelagic sediments are considered to be the most likely source for the metasomatism. An extensional tectonic regime induced by highly oblique subduction of the Izanagi Plate beneath the eastern Asian margin during the Early Cretaceous might have triggered the opening of the Gyeongsang Basin. Lithospheric thinning and the resultant thermal effect of asthenospheric upwelling could have caused melting of the metasomatized lithospheric mantle, producing the Early Cretaceous basaltic volcanism in the Gyeongsang Basin.

Choi, S.; Kwon, S.; Lee, D.

2013-12-01

110

Maximum horizontal stress orientations in the Cooper Basin, Australia: implications for plate-scale tectonics and local stress sources  

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Borehole breakouts and drilling-induced tensile fractures (DITFs) were interpreted in 61 wells in the Cooper Basin indicating an average maximum horizontal stress orientation of 101°N. A total of 890 borehole breakouts and 608 DITFs were interpreted in the Cooper Basin. The approximately east-west maximum horizontal stress orientation is consistent over much of the basin, except in the Patchawarra Trough where maximum horizontal stress rotates to a northwest-southeast orientation. This rotation in maximum horizontal stress orientation is consistent with in situ stress data to the northwest of the Cooper Basin. The stress field in the Cooper Basin appears to mark the apex of a major horseshoe-shaped rotation in maximum horizontal stress direction across central eastern Australia. Finite element modelling of the in situ stress field of the Indo-Australian Plate (IAP) using a range of plate-scale tectonic forces is able to match the regional maximum horizontal stress orientation over most of Australia reasonably well, including the mean east-west maximum horizontal stress orientation in the Cooper Basin. However, plate boundary-scale modelling does not adequately match the horseshoe-shaped stress rotation across central eastern Australia. The average east-west maximum horizontal stress orientation in the Cooper Basin indicates that stresses from tensional forces acting along the Tonga-Kermadec subduction zone are not transmitted into the interior of the Australian plate. The majority of the tensional forces associated with the Tonga-Kermadec subduction zone are most likely accommodated along the numerous spreading centres within the Lau-Havre backarc basin. A number of more localized stress anomalies have also been identified. These cannot be explained by plate-scale tectonic forces and are possibly a result of geological structure and/or density contrasts locally perturbing the stress field.

Reynolds, Scott D.; Mildren, Scott D.; Hillis, Richard R.; Meyer, Jeremy J.; Flottmann, Thomas

2005-01-01

111

3D structural restoration of halokinesis in the central portion in the Santos Basin. Implications for the Petroleum Systems  

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The present thesis consists in a real complex case study of halotectonic deformation in the central portion of the Santos Basin passive margin, investigating the complex interactions between deformation and sedimentation and evaluating its impacts on the petroleum systems.Seismic data set and exploration wells were input to the study, which cover an area where halokinetics affect the active petroleum systems. The thickest depocenter of the Santos basin is partially in the study area. The sedi...

Melo Garcia, Savio Francis

2012-01-01

112

Palynology and age of the Early Oligocene units in Cardak-Tokca Basin, Southwest Anatolia: Paleoecological implications  

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In this study, the lignite bearing sediments of Cardak-Tokca basin exposed in southwest Anatolia, were palynologically examined. A well preserved and diverse palynomorph assemblage indicating an Early Oligocene age was recovered from the Hayrettin and Tokca formations. The palynomorph assemblage is dominated by Pinus, Sparganiaceae, Juglandaceae and diverse tricolpate and tricolporate pollen. In addition a few species of marine dinoflagellate cysts were encountered as well. The Early Oligocene age is based primarily on the presence of stratigraphic markers such as: Boehlensipollis hohli, Slowakipollis hippophaeoides, Aglaoreidia cyclops, Dicolpopollis kockeli, Compositoipollenites rhizophorus ssp. burghasungensis, Mediocolpopollis compactus ssp. ellenhausensis, Pentapollenites pentangulus, Subtriporopollenites simplex and Intratriporopollenites instructus. Palynological data indicate a humid subtropical climatic conditions during the deposition of the Cardak-Tokca sediments. Ecological analysis of the palynomorph assemblage identifies several paleo-associations of montana, lowland and slope, swamp and water-edge and freshwater aquatic elements. In this study, Cardak-Tokca, Cankiri-Corum, Thrace and southwest Anatolian molasse basins (Kale-Tavas and Denizli) were correlated in accordance with their palynostratigraphic content and the results show that the deposition took place during the Early Oligocene in the Cardak-Tokca basin. This basin is older than Thrace basin and southwest Anatolian molasse basins (Kale-Tavas and Denizli molasse) which were deposited during the Late Oligocene-Early Miocene.

Akkiraz, M.S.; Akgun, F. [Dokuz Eylul University, Izmir (Turkey)

2005-06-01

113

Study of the Ouarzazate basin structure by seismic reflection: hydrogeological implications; Etude de la structure du bassin d'Ouarzazate par sismique reflexion: Implications hydrogeologiques  

Energy Technology Data Exchange (ETDEWEB)

A large number of seismic reflection lines have been carried out in the Ouarzazate basin by the oil industry. The present study is concerned with the interpretation of a part of these data in order to characterize the structure of the Eocene aquifer system. The reflector corresponding to the base of this system, made up of sandstone and limestone, was first identified then digitized on each time-migrated seismic section. An isochrone map of this reflector was realized. The analysis of this map shows that the area under study is subdivided into two structurally contrasted domains. The first, the northern one, is intensively deformed; while the second, the southern one, is slightly folded. The results of this study provide a better understanding of the deep geological structure of the Ouarzazate basin. This allows us to better comprehend the functioning of the Eocene aquifer system, and to rationalize the future potential underground water exploration in the Ouarzazate basin. (Author) 16 refs.

Boummane, Kh.; Jaffal, M.; Kchikach, A.

2009-07-01

114

Magnetostratigraphy of the Neogene Chaka basin and its implications for mountain building processes in the north-eastern Tibetan Plateau  

Science.gov (United States)

Magnetostratigraphy of sedimentary rock deposited in the Chaka basin (north-eastern Tibetan Plateau) indicates a late Miocene onset of basin formation and subsequent development of the adjacent Qinghai Nan Shan. Sedimentation in the basin initiated at ~11Ma. In the lower part of the basin fill, a coarsening-upward sequence starting at ~9Ma, as well as rapid sedimentation rates, and northward paleocurrents, are consistent with continued growth of the Ela Shan to the south. In the upper section, several lines of evidence suggest that thrust faulting and topographic development of the Qinghai Nan Shan began at ~6.1Ma. Paleocurrent indicators, preserved in the basin in the proximal footwall of the Qinghai Nan Shan, show a change from northward to southward flow between 6.5 and 3.8Ma. At the same location, sediment derived from the Qinghai Nan Shan appears at 6.1Ma. Finally, the initiation of progressively shallowing dips observed in deformed basin strata and a change to pebbly, fluvial deposits at 6.1Ma provide a minimum age for the onset of slip on the thrust fault that dips north-east beneath the Qinghai Nan Shan. We interpret a decrease in sediment accumulation rates since ~6Ma to indicate a reduction in Chaka basin accommodation space due to active faulting and folding along the Qinghai Nan Shan and incorporation of the basin into the wedge-top depozone. Declination anomalies indicate the beginning of counter-clockwise rotation since 6.1Ma, which we associate with local deformation, not regional block rotation. The emergence of the Qinghai Nan Shan near the end of the Miocene Epoch partitioned the once contiguous Chaka-Gonghe and Qinghai basin complex. In a regional framework, our study adds to a growing body of evidence that points to widespread initiation and/or reactivation of fault networks during the late Miocene across the north-eastern Tibetan Plateau. ?? 2011 The Authors. Basin Research ?? 2011 Blackwell Publishing Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists.

Zhang, H.-P.; Craddock, W.H.; Lease, R.O.; Wang, W.-T.; Yuan, D.-Y.; Zhang, P.-Z.; Molnar, P.; Zheng, D.-W.; Zheng, W.-J.

2012-01-01

115

Implications of Spatial Variability in Heat Flow for Geothermal Resource Evaluation in Large Foreland Basins: The Case of the Western Canada Sedimentary Basin  

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Full Text Available Heat flow and geothermal gradient of the sedimentary succession of the Western Canada Sedimentary Basin (WCSB are mapped based on a large thermal database. Heat flow in the deep part of the basin varies from 30 mW/m2 in the south to high 100 mW/m2 in the north. As permeable strata are required for a successful geothermal application, the most important aquifers are discussed and evaluated. Regional temperature distribution within different aquifers is mapped for the first time, enabling a delineation of the most promising areas based on thermal field and aquifer properties. Results of previous regional studies on the geothermal potential of the WCSB are newly evaluated and discussed. In parts of the WCSB temperatures as high as 100–210 °C exist at depths of 3–5 km. Fluids from deep aquifers in these “hot” regions of the WCSB could be used in geothermal power plants to produce electricity. The geothermal resources of the shallower parts of the WCSB (>2 km could be used for warm water provision (>50 °C or district heating (>70 °C in urban areas.

Simon Weides

2014-04-01

116

Thermal regime of the Great Basin and its implications for enhanced geothermal systems and off-grid power  

Science.gov (United States)

The Basin and Range Province of the Western United States covers most of Nevada and parts of adjoining states. It was formed by east-west tectonic extension that occurred mostly between 50 and 10 Ma, but which still is active in some areas. The northern Basin and Range, also known as the Great Basin, is higher in elevation, has higher regional heat flow and is more tectonically active than the southern Basin and Range which encompasses the Mojave and Sonoran Deserts. The Great Basin terrane contains the largest number of geothermal power plants in the United States, although most electrical production is at The Geysers and in the Salton Trough. Installed capacities of electrical power plants in the Great Basin vary from 1 to 260 MWe. Productivity is limited largely by permeability, relatively small productive reservoir volumes, available water, market conditions and the availability of transmission lines. Accessible, in-place heat is not a limiting condition for geothermal systems in the Great Basin. In many areas, economic temperatures (>120°C) can be found at economically drillable depths making it an appropriate region for implementation of the concept of "Enhanced Geothermal Systems" (EGS). An incremental approach to EGS would involve increasing the productivity and longevity of existing hydrothermal systems. Those geothermal projects that have an existing power plant and transmission facilities are the most attractive EGS candidates. Sites that were not developed owing to marginal size, lack of intrinsic permeability, and distance to existing electrical grid lines are also worthy of consideration for off-grid power production in geographically isolated markets such as ranches, farms, mines, and smelters.

Sass, John H.; Walters, Mark A.

1999-01-01

117

Evolution of faulting and volcanism in a back-arc basin and its implications for subduction processes  

Science.gov (United States)

The formation of the Taranaki Basin, an active volcanic back-arc rift situated in the continental Australian Plate, is related to subduction of the Pacific Plate along the Hikurangi margin. The Taranaki Basin contains an almost complete Miocene-Recent sedimentary record of the evolution of faulting and submarine andesitic volcanoes in the back-arc. Detailed study of extensive regional seismic reflection and coastal outcrop data sets yields valuable information about the extent to which back-arc rifting and reverse faulting have been controlled by the evolution of the Hikurangi margin subduction. Normal faulting and andesitic volcanism commenced in the northern part of the basin at ˜12 and ˜16 Ma, respectively, and were synchronous with contraction in the southern part of the basin. The rift, contractional faults and folds, and volcanism migrated southward during the last 12 Ma. Southward migration of faulting was episodic and geologically instantaneous with 100-150 km increases in the length of the rift at ˜12-8 and ˜4 Ma. From ˜4 Ma, displacement rates in the northern basin slowed and ceased at ˜2 Ma. The death of normal faults in the northern Taranaki Basin together with sympathetic variations in the timing of faulting and the overlapping rift geometries between the Taranaki Basin and the Central Volcanic Region are attributed to displacement transfer between the two rift systems. Southward migration of andesitic volcanism, rifting, and contractional deformation are consistent with clockwise rotation of the subduction margin associated with slab rollback coupled with southward motion of the southern termination of subduction and mantle corner flow.

Giba, M.; Nicol, A.; Walsh, J. J.

2010-08-01

118

Paleocene-Eocene potential source rocks in the Avengco Basin, Tibet: Organic geochemical characteristics and their implication for the paleoenvironment  

Science.gov (United States)

The Avengco Basin is located in the western part of the Tibetan Plateau and is similar to the Nima Basin in the central part of the plateau and the Lunpola Basin in the eastern part in terms of sedimentary characteristics and tectonic settings, which are well known to provide a good source rock potential. However, the organic geochemical characteristics of the Paleocene-Eocene potential source rocks in the Avengco Basin have been under debate. Thirty-four marl and mudstone outcrop samples of the Niubao Formation in the Avengco Basin were collected and subjected to the following analyses: total organic carbon (TOC), Rock-Eval pyrolysis, stable carbon isotopes of kerogen, gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Here, we present the results indicating the organic matter of the upper Niubao Formation is mainly composed of Type II kerogen with a mixed source, which is dominated by algae. However, the lower Niubao Formation has the less oil-prone Type II-III kerogen, and the sources of the organic matter are mainly terrestrial plants with less plankton. In addition, the samples are thermally immature to marginally mature. The Niubao Formation was deposited in an anoxic-oxic environment which was brackish with an imperceptible stratified water column. The upper Niubao Formation has a medium to good hydrocarbon-generating potential. However, the lower Niubao Formation has a zero to poor hydrocarbon-generating potential.

Han, Zhongpeng; Xu, Ming; Li, Yalin; Wei, Yushuai; Wang, Chengshan

2014-10-01

119

Multi-Model CIMP5 projected impacts of increased greenhouse gases on the Niger basin and implications for hydropower production  

Science.gov (United States)

Climate change could potentially have large impacts on water availability in West Africa and the predictions are accrued with high uncertainties in this region. Countries in the Niger River basin (West Africa) plan the investment of 200 million in the installation of an additional 400MW of hydropower in the nearest future, adding to the existing 685MW. With the impacts of climate change in the basin already occurring, there is a need for comprehending the influence of future hydro-climatic changes on water resources and hydro-power generation in the basin. This study uses a hydrological model to simulate river flow under present and future conditions and evaluates the impacts of potential changes on electricity production of the largest hydroelectric dam (Kainji) in the Niger Basin. The Kainji reservoir produces 25 per cent of the current energy needs of Nigeria and was subject to large fluctuations in energy production as a result of variable inflow and operational reasons. Inflow into the reservoir was simulated using hydroclimatic data from a set of 7 regional climate models (RCM) with two emission scenarios from the CORDEX-Africa regional downscaling experiment, driven with CMIP5 data. Based on observations of inflow, water level in the reservoir, and energy production we developed a simple hydroelectricity production model to simulate future energy production for the reservoir. Results suggest increases in river flow for the majority of RCM data as a result of increases in precipitation in the headwaters of the basin around 2050 and slightly decreasing trends for low emission scenarios by the end of the century. Despite this consistent increase, shifts in timing of river flow can challenge the reliable production of energy. This analysis could help assess the planning of hydropower schemes in the basin for a sustainable production of hydroelectricity in the future.

Oyerinde, Ganiyu; Wisser, Dominik

2014-05-01

120

High levels of mercury contamination in multiple media of the Carson River drainage basin of Nevada: implications for risk assessment.  

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Approximately 5.5 x 109 g (4.0 x 105) of mercury was discharged into the Carson River Drainage Basin of west-central Nevada during processing of the gold- and silver-rich Comstock ore in the late 1800s. For the past 13 decades, mercury has been redistributed throughout 500 km2 of the basin, and concentrations are some of the highest reported values in North America. This article documents the concentrations of mercury in the air, water, and substrate at both contaminated and noncontaminated s...

Gustin, M. S.; Taylor, G. E.; Leonard, T. L.

1994-01-01

 
 
 
 
121

SHRIMP zircon age of the high aeromagnetic anomaly zone in central Tarim Basin and its geological implications  

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In order to get the correct isotopic age, SHRIMP U-Pb zircon date of Precambrian hornblende granite in Well TD2, located in the central aeromagnetic belt in the eastern of the Tarim basin, was carried out. The result showed a dependable age of 1908.2 ± 8.6 Ma, which demonstrated that the granite pluton is the result of the magmatic activity in early Palaeoproterozoic. It is indicated that the central aeromagnetic belt across Tarim basin, divided it into north and south block, is formed befor...

Chengze Zhang; Yanlong Xu; Tailai Qu; Zhiyong Chen; Guanghui Wu

2011-01-01

122

Implications for Fault and Basin Geometry in the Central California Coast Ranges from Preliminary Gravity and Magnetic Data  

Science.gov (United States)

Preliminary aeromagnetic and newly processed gravity data help define block-bounding faults and deep sedimentary basins in the central California Coast Ranges, ranging from the Hosgri fault east to the San Andreas fault and from Monterey Bay south to Pt. Conception. Interpretation of these data results in an improved framework for seismic hazard and groundwater studies. Aeromagnetic data include a new survey with a flight-line spacing of 800 m at a nominal 300 m above ground and covering 15,000 km2. More than 11,500 gravity measurements, reprocessed with terrain corrections calculated from 30-m DEMs, form a roughly 2-km grid over most of the study area. Combined potential-field data and existing geologic mapping, delineate major fault-bounded blocks in the central California Coast Ranges. Main block-bounding faults from west to east include the San Gregorio- Hosgri, San Luis-Willmar-Santa Maria River-Little Pine, Oceanic-West Huasna, Nacimiento, Rinconada-South Cuyama, San Juan-Chimineas-Morales, and San Andreas faults. Most of these faults have evidence of Quaternary activity. Gravity gradients indicate that the reach of the San Andreas fault bounding the Gabilan Range and the northern extension of the Rinconada fault bounding the Santa Lucia Range dip steeply southwestward and have a reverse component of slip. Magnetic and microseismicity data suggest that the northern reach of the Hosgri fault dips eastward. The potential-field data also delineate several deep sedimentary basins, such as the 3-4 km deep Cuyama basin, the Santa Maria basin, and several basins along and possibly offset by the Rinconada fault. Gravity data show that the main west-northwest-striking faults bounding the Cuyama basin dip away from the basin, indicating compression adjacent to the big bend in the San Andreas fault. Prominent gravity and magnetic highs northeast of the San Andreas fault immediately east of Cuyama Valley suggest that there the San Andreas fault dips southwest. Such dip information is important for estimating shaking potential of scenario earthquakes and for calculating geodetic deformation whereas basin shapes and fault locations are critical components for groundwater flow modeling.

Langenheim, V. E.; Jachens, R. C.; Graymer, R. W.; Wentworth, C. M.

2008-12-01

123

Projected Imbalances between Labor Supply and Labor Demand in the Caribbean Basin: Implications for Future Migration to the United States.  

Science.gov (United States)

This paper examines the economic push factors encouraging migration from the Caribbean Basin to the United States, as part of an assessment of the effectiveness of the Immigration Reform and Control Act of 1986. The basic assumption is that much of the migration is motivated by a desire to improve economic circumstances, and that the…

Espenshade, Thomas J.

124

Diet and environment of a mid-Pliocene fauna in the Zanda Basin (western Himalaya): Paleo-elevation implications  

Science.gov (United States)

A mid-Pliocene fauna (3.1-4.0 Ma) was recently discovered in the Zanda Basin in western Himalaya, at an elevation of about 4200 m above sea level. These fossil materials provide a unique window for examining the linkage among tectonic, climatic and biotic changes. Here we report the initial results from isotopic analyses of this fauna and of modern herbivores in the Zanda Basin. The ?13C values of enamel samples from modern wild Tibetan ass, horse, cow and goat from the Zanda Basin are -9.1±2.1%, which indicate a diet comprising predominantly of C3 plants and are consistent with the current dominance of C3 vegetation in the area. The enamel-?13C values of the fossil horse, rhino, deer, and bovid are -9.6±0.8%, indicating that these ancient mammals, like modern herbivores in the area, fed primarily on C3 vegetation and lived in an environment dominated by C3 plants. The enamel-?18O values of mid-Pliocene obligate drinkers (i.e., horse and rhino) are lower than those of their modern counterpart, most likely indicating a shift in climate to much drier conditions after ~3-4 Ma. Preliminary paleo-temperature estimates derived from a fossil-based temperature proxy as well as the "clumped isotope" thermometer for the mid-Pliocene Zanda Basin, although somewhat equivocal, are close to the present-day mean annual temperature in the area, suggesting that the paleo-elevation of the Zanda Basin in the mid-Pliocene was similar to its present-day elevation.

Wang, Y.; Xu, Y.; Khawaja, S. N.; Wang, X.; Passey, B. H.; Zhang, C.; Li, Q.; Tseng, Z. J.; Takeuchi, G.; Deng, T.; Xie, G.

2011-12-01

125

Franciscan olistoliths in Upper Cretaceous conglomerate deposits, Western Transverse Ranges, California: Implications for basin morphology and tectonic history  

Energy Technology Data Exchange (ETDEWEB)

Compositional analyses reveal that Upper Cretaceous sediments exposed in the Western Transverse Ranges of CA were deposited in submarine fan systems in a forearc basin. Point count data suggest a magmatic arc/recycled orogen as the dominant provenance for these sediments. Paleocurrent measurements from conglomerates in these sediments yield a northerly transport direction. Removal of ca. 90[degree] of clockwise rotation and 70 km of right-lateral slip restore this section to a position west of the San Diego area. The forearc basin would have had a N-S orientation, with the bulk of sediments supplied by the Peninsular Ranges to the east. Evidence of the erosion of the accretionary wedge is provided by the presence of large, internally stratified olistoliths of Franciscan material interbedded with and surrounded by upper Cretaceous conglomerate. Petrographic, quantitative SEM, and microprobe analyses indicate the presence of diagnostic Franciscan mineralogy, including glaucophane, riebeckite, lawsonite, and serpentine. Olistoclasts of chert, jadeitic graywacke, serpentine, and blueschist are found intermixed with the conglomerates in close association with the olistoliths. This association provides strong field evidence that recirculation of melange material within the subduction zone was active and well-established by late Cretaceous time. Inferences regarding the forearc system morphology can be drawn from these observations. The occurrence of coarse, easterly-derived conglomerates surrounded by large, stratified, but sheared, westerly-derived Franciscan debris, suggests a narrow, relatively steep-sided basin. Paleocurrent measurements gave no indication of axial transport within the basin. This morphology suggests that, in late Cretaceous time, the forearc basin was youthful, with a narrow arc-trench gap. Thus, relative convergence rates between the North American and Pacific plates were possibly slower than Tertiary convergence rates.

Reed, W.E.; Campbell, M.D. (Univ. of California, Los Angeles, CA (United States). Dept. of Earth and Space Sciences)

1993-04-01

126

Origin of diverse geochemical signatures in igneous rocks from the West Philippine Basin: Implications for tectonic models  

Science.gov (United States)

The West Philippine Basin (WPB), formed by seafloor spreading between 60 and 35 Ma, provides an excellent case study of relationships between basin tectonics and magma chemistry. At 48 Ma, the Izu-Bonin-Mariana (IBM) arc formed along the basin edge, orthogonal to the active spreading center; thus, WPB development is a key issue for this Margins Subduction Factory focus area. WPB basalts from the main spreading stage are normal to enriched mid-ocean ridge basalt (MORB) with an Indian Ocean MORB isotopic signature. Basalts from the Benham Rise and locations near the western Central Basin Spreading Center (CBSC) at 50-35 Ma are geochemically identical to oceanic island basalts. Late-stage CBSC basalts (35-26 Ma) are isotopically like main spreading-stage MORB, with widely varying and decoupled trace element enrichments. Based on basalt geochemistry, the WPB could be a trapped fragment of ancient Indian/Tethyan ocean ridge, as proposed in some models for the initiation of the IBM arc, or it could be a back-arc basin, provided plate configurations allowed replenishment of sub-Indian Ocean asthenosphere. Ocean island basalts were formed by decompression melting of an enriched source beneath the western CBSC, mixing with normal MORB sources to form enriched MORB. This was a transitory feature (15 Ma) related to spreading, rather than a deep-seated plume, and probably did not affect the early IBM arc. Magma formed in small, deep-seated batches as the extension waned. That CBSC activity continued for 22 Ma after the initiation of the IBM arc indicates that forces related to an additional subduction system influenced the WPB.

Hickey-Vargas, Rosemary; Savov, Ivan P.; Bizimis, Michael; Ishii, Teruaki; Fujioka, Kantaro

127

Genetic mixed-stock analysis of lake-run brown trout Salmo trutta fishery catches in the Inari Basin, northern Finland: implications for conservation and management.  

Science.gov (United States)

Genetic mixed-stock analysis (MSA) of wild lake-run brown trout Salmo trutta fishery catches (n?=?665) from the Inari Basin (northern Finland) between 2006 and 2008 was carried out using a previously characterized baseline with 30 populations (n?=?813) and 13 microsatellite loci. Altogether, 12 populations contributed significantly to mixed-stock fisheries, with the Ivalojoki system being the major contributor (70%) to the total catch. When catches were analysed regionally, geographically nearby populations were the main contributors to the local catches, indicating that a large proportion of S. trutta occupy lacustrine areas near the natal river mouth rather than dispersing throughout the lake. Similarly, far upstream populations contributed insignificantly to catches. These findings have important implications for the conservation and sustainable fishery management of the Inari system. PMID:23991877

Swatdipong, A; Vasemägi, A; Niva, T; Koljonen, M-L; Primmer, C R

2013-09-01

128

SHRIMP zircon age of the high aeromagnetic anomaly zone in central Tarim Basin and its geological implications  

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Full Text Available In order to get the correct isotopic age, SHRIMP U-Pb zircon date of Precambrian hornblende granite in Well TD2, located in the central aeromagnetic belt in the eastern of the Tarim basin, was carried out. The result showed a dependable age of 1908.2 ± 8.6 Ma, which demonstrated that the granite pluton is the result of the magmatic activity in early Palaeoproterozoic. It is indicated that the central aeromagnetic belt across Tarim basin, divided it into north and south block, is formed before Neoproterozoic by a large scale tectonothermal events based on the seismic and drilling date. The Tarim continent may have different age and type basements formed the united crystalline basement in Precambrian. This result has yielded new intraplate evidence to constrain the relation between the Tarim plate and the Colombia supercontinent.

Chengze Zhang

2011-12-01

129

Investigation of Climate Change Impact on Water Resources for an Alpine Basin in Northern Italy: Implications for Evapotranspiration Modeling Complexity  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Assessing the future effects of climate change on water availability requires an understanding of how precipitation and evapotranspiration rates will respond to changes in atmospheric forcing. Use of simplified hydrological models is required beacause of lack of meteorological forcings with the high space and time resolutions required to model hydrological processes in mountains river basins, and the necessity of reducing the computational costs. The main objective of this study was to quanti...

Ravazzani, Giovanni; Ghilardi, Matteo; Mendlik, Thomas; Gobiet, Andreas; Corbari, Chiara; Mancini, Marco

2014-01-01

130

Mechanical stratification of autochthonous salt: Implications from basin-scale numerical models of rifted margin salt tectonics  

Science.gov (United States)

Deformation of salt and sediments owing to the flow of weak evaporites is a common phenomenon in sedimentary basins worldwide, and the resulting structures and thermal regimes have a significant impact on hydrocarbon exploration. Evaporite sequences ('salt') of significant thickness (e.g., >1km) are typically deposited in many cycles of seawater inundation and evaporation in restricted basins resulting in layered autochthonous evaporite packages. However, analogue and numerical models of salt tectonics typically treat salt as a homogeneous viscous material, often with properties of halite, the weakest evaporite. In this study, we present results of two-dimensional plane-strain numerical experiments designed to illustrate the effects of variable evaporite viscosity and embedded frictional-plastic ('brittle') sediment layers on the style of salt flow and associated deformation of the sedimentary overburden. Evaporite viscosity is a first-order control on salt flow rate and the style of overburden deformation. Near-complete evacuation of low-viscosity salt occurs beneath expulsion basins, whereas significant salt is trapped when viscosity is high. Embedded frictional-plastic sediment layers (with finite yield strength) partition salt flow and develop transient contractional structures (folds, thrust faults, and folded faults) in a seaward salt-squeeze flow regime. Multiple internal sediment layers reduce the overall seaward salt flow during sediment aggradation, leaving more salt behind to be re-mobilized during subsequent progradation. This produces more seaward extensive allochthonous salt sheets. If there is a density difference between the embedded layers and the surrounding salt, then the embedded layers 'fractionate' during deformation and either float to the surface or sink to the bottom (depending on density), creating a thick zone of pure halite. Such a process of 'buoyancy fractionation' may partially explain the apparent paradox of layered salt in autochthonous salt basins and thick packages of pure halite in allochthonous salt sheets.

Ings, Steven; Albertz, Markus

2014-05-01

131

Lithofacies and depositional environments of the Cambrian Mount Simon Sandstone in the northern Illinois Basin: Implications for CO2 sequestration  

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Deep saline reservoirs have become a target of increased study with the development of the practice of geological CO2 sequestration. Within the Illinois Basin, the Upper Cambrian Mount Simon Sandstone is being evaluated as a potential reservoir for injected CO2. Because of the depth at which the formation occurs and limited economic interest in the unit it has been only minimally investigated. Previous detailed depositional facies analyses were performed only at local scales or at localities ...

Fischietto, Nicholas E.

2009-01-01

132

Hydrologic impacts of climate change on the Nile River basin: Implications of the 2007 IPCC climate scenarios  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We assess the potential impacts of climate change on the hydrology and water resources of the Nile River basin using a macroscale hydrology model. Model inputs are bias corrected and spatially downscaled 21st Century simulations from 11 General Circulation Models (GCMs) and two global emissions scenarios (A2 and B1) archived from the 2007 IPCC Fourth Assessment Report (AR4). While all GCMs agree with respect to the direction of 21st Century temperature changes, there is considerable variabili...

Beyene, T.; Lettenmaier, D. P.; Kabat, P.

2010-01-01

133

Basin Testing of Wave Energy Converters in Trondheim: Investigation of Mooring Loads and Implications for Wider Research  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper describes the physical model testing of an array of wave energy devices undertaken in the NTNU (Norwegian University of Science and Technology) Trondheim basin between 8 and 20 October 2008 funded under the EU Hydralabs III initiative, and provides an analysis of the extreme mooring loads. Tests were completed at 1/20 scale on a single oscillating water column device and on close-packed arrays of three and five devices following calibration of instrumentation and the wave and curre...

Vladimir Krivtsov; Brian Linfoot

2014-01-01

134

Stable Isotopes In Fossil Mammals, Fish and Shells From Kunlun Pass Basin, Tibetan Plateau: Paleoclimatic and paleoelevation implications  

Science.gov (United States)

Stable carbon and oxygen isotope analyses of both terrestrial and aquatic fossils reveal a drastic change in habitat and hydrological regime in the Kunlun Pass Basin on the northern Tibetan Plateau since the late Pliocene. The ?13C values of both serial and bulk enamel samples from fossil herbivore teeth suggest that C4 grasses (i.e., warm climate grasses) were likely present in local ecosystems at the end of the Pliocene, around 2.0-2.5 Ma. The carbon isotopic variations among different species indicate mix habitats, including grasslands and wooded grasslands, occupied and partitioned by different species, consistent with palynological evidence. The anti-correlation between ?13C and ?18O values observed in the fossil teeth suggests that summer monsoons were a major source of moisture for the area in the late Pliocene. The more negative enamel-?18O values of large herbivores in the late Pliocene suggest that paleo-meteoric water then was more depleted in 18O compared to the present-day meteoric water in the basin. The most likely cause for this ?18O shift in tooth enamel or water after the late Pliocene is a drastic change in the regional hydrological cycle (e.g., change in source and rainout history of atmospheric moisture or atmospheric circulation pattern, increasing aridity, and etc.) possibly due to tectonic and climate change. Our carbon and oxygen isotope data, in conjunction with geological/fossil evidence, suggest that the Kunlun Pass Basin had a much warmer and wetter climate in the late Pliocene, quite different from today's rock desert and cold steppe environments. The paleo-temperature estimates based on the ?18O values of fossil bones and paleo- meteoric water, if valid, would imply that the present-day high elevation of the basin was established after 2-3 Ma.

Wang, Y.; Wang, X.; Xu, Y.; Zhang, C.; Li, Q.; Tseng, Z.; Takeuchi, G.; Deng, T.

2008-05-01

135

Structural evolution of the southwestern margin of the Ulleung Basin, East Sea (Japan Sea) and tectonic implications  

Science.gov (United States)

Structural mapping and restoration of depth-converted seismic profiles from the southwestern Ulleung Basin in the East Sea (Japan Sea) back-arc basin reveal the structural evolution of the area since the Middle Miocene. The back-arc closure began in the earliest Middle Miocene (ca. 15 Ma) and caused compressional deformation that has propagated southwestward from the Dolgorae to the Gorae structures and further to the unnamed inversion structure immediately adjacent to SE Korea. The accelerated convergence of the young (< 20 Ma) and hot Shikoku Basin lithosphere into SW Japan at the culmination (15 Ma) of the regional plate reorganization induced flat subduction along the Nankai Trough. Strong interplate coupling due to the flat subduction probably led to tectonic switching from back-arc opening to back-arc closure in the Middle Miocene. The NE-SW trending Dolgorae structures indicate NW-SE or N-S compression, orthogonal to the direction of convergence along SW Japan, whereas the younger, NW-SE trending Gorae V structure indicates NE-SW or E-W compression. We propose that this apparently abrupt change in stress regime is due to the eastward-movement of the Amur plate that began in the Pliocene.

Lee, Gwang H.; Yoon, Youngho; Nam, Byong H.; Lim, Heonhak; Kim, Young-Seog; Kim, Han J.; Lee, Keumsuk

2011-04-01

136

Observations on sediment sources in the Lower Athabasca River basin: implications of natural hydrocarbons inputs from oil sands deposits  

International Nuclear Information System (INIS)

Government, industry and public concern exists over the environmental consequences of the development of the oil sand deposits in the McMurray Formation in the lower Athabasca River basin, Alberta. The impact of this development is unclear and is undergoing investigation. Investigations to date have focussed on the nature of the effluent produced by the extraction industry and its effect on biotic systems, and on the spatial distribution of hydrocarbon contaminants associated with deposited fluvial sediments. Natural hydrocarbon outcrops may be responsible for observed biomarker responses in areas not exposed to industrial effluent. Given this source of hydrocarbons and doubt concerning its environmental impact, it is difficult to ascertain the impact of oil extraction activities within a fluvial system. A study was conducted to determine the nature and extent of natural hydrocarbon releases within the context of the sediment regime of the lower Athabasca River basin. A description is included of observations from the field and a context is set up for assessing sediment-bound hydrocarbon contaminants in the lower Athabasca River basin. Abstract only included

137

Information from geology: Implications for soil formation and rehabilitation in the post coal mining environment, Bowen Basin, Australia  

International Nuclear Information System (INIS)

The coal mining industry is likely to disturb as much as 60,000 ha of the Bowen Basin up to the year 2000. While comprising only a small proportion of the approximately 32,000 km2 of the Bowen Basin, this considerable area will eventually need to be rehabilitated by creating appropriate land forms with a stabilizing and self-sustaining cover of vegetation. The job of restoring the disturbed area will fall to the practitioners of rehabilitation science. This paper briefly outlines the actual and potential significance of geological information to rehabilitation practice in the open-cut coal mining industry of the Bowen Basin. It focuses particularly on the problems of soil formation and the consequent limitations to ecosystem development due to the nature of the overburden materials and the environment. Lastly, it describes some of the distinctive features of the mine-soils of the area. Geological information can assist in the identification, classification, description and behaviour of post-mining materials. Potential inputs are not restricted to these and there is scope for wider inputs to management of the mining environment although the interface with biology requires further development. (author). 4 figs., 31 refs

138

Detrital Zircon U-Pb Ages From Northern Alaska and Northern Canada: Implications for Opening of the Canada Basin  

Science.gov (United States)

Detrital zircons from five Paleozoic and Mesozoic sandstones from the Brooks Range and North Slope of Alaska, and two Triassic sandstones from the Sverdrup Basin in northern Canada were dated using SHRIMP and laser ablation ICPMS geochronology. In Alaska, dated samples from allochthonous strata of the Brooks Range include the northern and southern lithofacies of the Devonian and(or) Mississippian Kanayut Conglomerate near the Trans-Alaska Pipeline and the Valanginian Tingmerkpuk Sandstone in the western Brooks Range. Also dated are zircons from autochthonous strata of the North Slope foreland, including the Lower Triassic Ivishak Sandstone in the Sadlerochit Mountains and a Hauterivian sandstone from the Jurassic and Lower Cretaceous Kingak Shale in the Tunalik well. In Canada, dated samples are from the Lower Triassic Bjorne Formation and the Upper Triassic Pat Bay Formation on the southeastern and northern margins of the Sverdrup Basin, respectively. The two Valanginian samples from Alaska and the Bjorne Formation in Canada yielded generally similar results dominated by 1.0 to 2.0 Ga zircons, with lower Paleozoic (especially 420 to 450 Ma) and less abundant Archean zircons. Samples from the Triassic Ivishak and Pat Bay Formations also are similar, but are dominated by 530 to 570 Ma zircons with less abundant older zircons. The two samples of Kanayut Conglomerate, in contrast, are dominated by 430 to 400 Ma zircons and yielded only minor amounts of Proterozoic zircons. The similarities between the Sverdrup Basin and northern Alaska samples suggest they were derived from similar source areas and lend support to models that call for opening of the Canada Basin by counterclockwise rotation of northern Alaska and Chukotka in the Early Cretaceous. Moreover, the Alaskan samples, all derived from generally northerly source areas, may indicate that unroofing in the source area progressed from strata rich in 450 to 400 Ma zircons in the Devonian to rocks yielding abundant Proterozoic and Archean zircons in the Early Cretaceous deposits. This pattern is consistent with the unroofing sequence interpreted from Nd isotopic data from the Sverdrup Basin by Patchett and others (2004, J. Geology, p. 39 to 57), who concluded that detritus from 450 to 350 Ma tectonism in the Caledonian and Ellesmerian orogens covered Arctic Canada until it was progressively removed in the Mesozoic.

Moore, T. E.; Miller, E. L.; Embry, A.; Aleinikoff, J. N.; Gehrels, G. E.

2004-12-01

139

The Rock Paintings of Williston : an interpretative study of rock art, rituals and the landscape in which they are created  

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The Williston district in Northern Cape, offers an exciting and new contribution to the rich world of rock art in South Africa. The paintings found here are solely geometric finger paintings, with a variety of different images and motifs. There are possible connections between these paintings and the initiation ceremonies of the Khoekhoen, once pejoratively known as the Hottentots. The main motif and link between the rock art and these rituals, is the so-called ‘apron motif’. These i...

Hykkerud, Martin Kristoffer

2006-01-01

140

The Rock Paintings of Williston :an interpretative study of rock art, rituals and the landscape in which they are created  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Williston district in Northern Cape, offers an exciting and new contribution to the rich world of rock art in South Africa. The paintings found here are solely geometric finger paintings, with a variety of different images and motifs. There are possible connections between these paintings and the initiation ceremonies of the Khoekhoen, once pejoratively known as the Hottentots. The main motif and link between the rock art and these rituals, is the so-called ‘apron motif’. These imag...

Hykkerud, Martin Kristoffer

2006-01-01

 
 
 
 
141

Minerals and trace elements in silcretes of the Sado basin (Alentejo, southern Portugal) and implications for silcrete formation  

Science.gov (United States)

Soils in the eastern part of the Sado basin (southern Portugal) are often characterized by massive cementations caused by silica. The thickness and massive character of these silcretes led to the hypothesis that accumulation of silica took place not only vertically within a soil profile, but also by enrichment through lateral water and element flow into the Sado basin. The aims of the study reported here were: 1) to characterize the cementing agent with regard to its mineralogy; 2) to test the hypothesis that silification was enhanced through lateral silica transport from the adjacent Alto Alentejo into the Sado basin. Aim 1) was achieved by scratching silica coatings from ped surfaces of the silicified soil horizons and cleaning them manually in the lab under a binocular microscope. After careful smashing with a mortar, density separation by sodium polytungstate solution was applied to remove any remaining mineral grains from the silica samples. The cleaned silica samples were then subjected to XRD and SEM in combination with EDS. Aim 2) was attained by using trace element contents of predominant rock types of the Alto Alentejo and of the silcretes in the Sado basin for identifying lateral pathways of water and silica in the landscape. Ten rock samples from the assumed source area of silica were combusted by fusion melt, and their contents of Ba, Co, Cs, Nb, Pb, Rb, Sr, Y and Zr were analyzed by ICP-MS. The same elements were analyzed in NaOH extracts of the cemented soil horizons in the Sado basin. The X-ray diagrams of the silica coatings show the expected broad hump of amorphous silica. In addition, quartz, kaolinite, and surprisingly high amounts of halloysite are identified, the latter reflecting conditions of intensive weathering and pedogenesis during the formation of the silica coatings. This intensive soil formation and hence silification most likely took place during Pliocene. Greater age is impossible, because the silification took place in Pliocene sediments; later, on the other hand, the climate became cooler, hence intensity of pedogenesis should have decreased. It is assumed that halloysite was preserved over such long period of time, because it was occluded in the silica mass. The micromorphology of the coatings under the SEM includes laminar coverings, banded and alveolar structures. EDS analysis shows that the coatings consist mainly of silicon; in addition they contain aluminum and some also have minor amounts of iron. Trace element contents of the rock samples and silcretes enabled tracing lateral silica flows from the Alto Alentejo into the Sado basin. Some rock samples and silcretes contained considerable amounts of Barium. Even barite crystals were observed in the silica coatings under the SEM. Acknowledgement The authors thank Beate Podtschaske for her valuable help in the laboratory and the German Research Foundation DFG for financial support (project STA 146/45-3).

Sauer, Daniela; Kullmann, Sarah; Zarei, Mehdi; Stahr, Karl

2014-05-01

142

Seismic constraints on a large mafic intrusion with implications for the subsidence mechanism of the Danish Basin  

DEFF Research Database (Denmark)

Seismic refraction data from the ESTRID-1 profile are used for seismic velocity modeling along the strike of a large mafic intrusion in the Norwegian-Danish Basin, central Denmark. The P wave velocity structure identifies a ~8 km thick sedimentary succession with velocities between 1.8 and 5.7 km/s. The top basement is defined by a step to vp = 6.2 km/s. In the middle to lower crust a high-velocity body (vp > 6.7 km/s), with its top located at about 10-12 km depth, is interpreted as a high-velocity and high-density gabbroic intrusion of Permian age. This high-velocity body explains the large (~50 mGal) positive gravity anomaly known as Silkeborg Gravity High. The intrusion has a minimum volume of 40,000 km3, which implies that the magma influx and the consequent cooling of the lithosphere from high temperature could have had profound effects on the subsidence of the Danish Basin, in particular because the magma probably intruded during only a few events and other similar structures cover much of the basin. Ananomalously high velocity gradient (from 7.0 km/s in the middle crust to 7.7 km/s at 30-32 km depth) in the central part of the intrusion coincides with an interval without Moho reflections, indicative of a gradual transition zone between the crust and the mantle. This feature may show the location of the feeder dykes of the intrusion.

Sandrin, Alessandro; Thybo, Hans

2008-01-01

143

Hypoxia tolerance of introduced Nile perch: Implications for survival of indigenous fishes in the Lake Victoria basin  

Science.gov (United States)

The introduction of predatory Nile perch (Lates niloticus) into the Lake Victoria basin coincided with a dramatic decline in fish diversity. However, remnant populations of indigenous fishes persist in lagoons and satellite lakes separated from the main lakes by extensive areas of swamp, while other indigenous species find refuge in ecotonal areas at edges of marginal swamps in the main lakes. Low-oxygen conditions in these wetlands may physiologically stress Nile perch and therefore minimize its interaction with prey species. This study examined the low-oxygen tolerance of Nile perch collected from Lake Nabugabo, Uganda, by documenting behavioural and physiological strategies that relate to oxygen uptake. In response to hypoxia, Nile perch used aquatic surface respiration (ASR) at the air-water interface, ventilating their gills with water from the surface. However, several lines of evidence suggest that Nile perch in Lake Nabugabo are inefficient at ASR and relatively intolerant of low oxygen conditions. These include high thresholds for ASR relative to other indigenous fishes of the Lake Victoria basin, no decrease in gill ventilation rate with the onset of ASR, a faster time to loss of equilibrium in hypoxic conditions than other species from the region, and a high critical oxygen tension (24 mm Hg).

Schofield, P.J.; Chapman, L.J.

2000-01-01

144

Hot spot volcanic tracks and their implications for south American plate motion, Campos basin (Rio de Janeiro state), Brazil  

Science.gov (United States)

The spatial and temporal arrangement of volcanism produced by hot spots potentially can reveal the history of lithosphere plate drift. From the age of these igneous bodies, it is possible to estimate not only the drift speed of plates but also the timing of eventual route changes. This article concentrates on the apparent link between both the Poços de Caldas-Cabo Frio alkaline rocks alignment (Rio de Janeiro state) and the Vitória-Trindade chain (situated on the oceanic crust adjacent to Espírito Santo state, Brazil) to a single fixed hot spot. On the basis of geological, geomorphological, and geochronological evidence, the authors propose that the South American continent may have experienced a clockwise rotation during the Eocene, which resulted in the relative displacement of hot spot volcanic manifestations from Cabo Frio (Rio de Janeiro state) to the western border of the Vitória-Trindade chain. At this time, several tectonic, sedimentary, and magmatic events took place that were capable of causing the inferred Eocene displacement. It is worth noting the coincidence between the northeastern trend of the oil fields of the Campos basin and the suggested path of the basin as it moved over the hot spot.

Filho, Antonio Thomaz; Cesero, Pedro de; Mizusaki, Ana Maria; Leão, Joana Gisbert

2005-03-01

145

A regional ocean circulation model for the mid-Cretaceous North Atlantic Basin: implications for black shale formation  

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Full Text Available High concentrations of organic matter accumulated in marine sediments during Oceanic Anoxic Events (OAEs in the Cretaceous. Model studies examining these events invariably make use of global ocean circulation models. In this study, a regional model for the North Atlantic Basin during OAE2 at the Cenomanian-Turonian boundary has been developed. A first order check of the results has been performed by comparison with the results of a recent global Cenomanian CCSM3 run, from which boundary and initial conditions were obtained. The regional model is able to maintain tracer patterns and to produce velocity patterns similar to the global model. The sensitivity of the basin tracer and circulation patterns to changes in the geometry of the connections with the global ocean is examined with three experiments with different bathymetries near the sponges. Different geometries turn out to have little effect on tracer distribution, but do affect circulation and upwelling patterns. The regional model is also used to test the hypothesis that ocean circulation may have been behind the deposition of black shales during OAEs. Three scenarios are tested which are thought to represent pre-OAE, OAE and post-OAE situations. Model results confirm that Pacific intermediate inflow together with coastal upwelling could have enhanced primary production during OAE2. A low sea level in the pre-OAE scenario could have inhibited large scale black shale formation, as could have the opening of the Equatorial Atlantic Seaway in the post-OAE scenario.

R. P. M. Topper

2011-03-01

146

Geochemistry of Neogene sedimentary rocks from Borneo Basin, Malaysia: implications on paleo-weathering, provenance and tectonic setting  

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Multi-element geochemistry and mineralogy are used to characterize the chemical composition, degree of paleo-weathering, provenance and tectonic settingsof the Neogene sedimentary rocks of Borneo Basin from east Malaysia. The sedimentary rocks are classified as extremely weathered sandstones (i.e. wacke, arkose, litharenite, Fe-sandstone and quartz arenite). Higher values of both weathering indices of alteration (i.e. CIA>83 and PIA>89) suggest that the sandstones have undergone extreme chemical weathering. Absence of any feldspar in the mineralogical analysis indicates its degradation during the weathering. Except for the quartz arenite, all other sandstones are characterized by post-depositional K-metasomatism and zircon enrichment through sediment recycling. The geochemical characteristics suggest a mixed-nature provenance for the sandstones with contribution coming from both felsic and mafic igneous rocks. Enriched Cr in quartz arenite and Fe-sandstone are related to contribution from ophiolite or fractionation of Cr-bearing minerals. The inferred tectonic settings are variable and suggest a complex nature of tectonic environment in the basin.

Ramasmay, N.; Roy, P.; MP, J.; Rufino, L.; Franz, L. K.; Viswanathan, P. M.

2013-05-01

147

Investigation of climate change impact on water resources for an Alpine basin in northern Italy: implications for evapotranspiration modeling complexity.  

Science.gov (United States)

Assessing the future effects of climate change on water availability requires an understanding of how precipitation and evapotranspiration rates will respond to changes in atmospheric forcing. Use of simplified hydrological models is required because of lack of meteorological forcings with the high space and time resolutions required to model hydrological processes in mountains river basins, and the necessity of reducing the computational costs. The main objective of this study was to quantify the differences between a simplified hydrological model, which uses only precipitation and temperature to compute the hydrological balance when simulating the impact of climate change, and an enhanced version of the model, which solves the energy balance to compute the actual evapotranspiration. For the meteorological forcing of future scenario, at-site bias-corrected time series based on two regional climate models were used. A quantile-based error-correction approach was used to downscale the regional climate model simulations to a point scale and to reduce its error characteristics. The study shows that a simple temperature-based approach for computing the evapotranspiration is sufficiently accurate for performing hydrological impact investigations of climate change for the Alpine river basin which was studied. PMID:25285917

Ravazzani, Giovanni; Ghilardi, Matteo; Mendlik, Thomas; Gobiet, Andreas; Corbari, Chiara; Mancini, Marco

2014-01-01

148

Crop yields response to water pressures in the Ebro basin in Spain: risk and water policy implications  

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The increasing pressure on water systems in the Mediterranean enhances existing water conflicts and threatens water supply for agriculture. In this context, one of the main priorities for agricultural research and public policy is the adaptation of crop yields to water pressures. This paper focuses on the evaluation of hydrological risk and water policy implications for food production. Our methodological approach includes four steps. For the first step, we estimate the impacts of rainfall an...

Quiroga, S.; Ferna?ndez-haddad, Z.; Iglesias, A.

2011-01-01

149

Risk of water scarcity and water policy implications for crop production in the Ebro Basin in Spain  

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The increasing pressure on water systems in the Mediterranean enhances existing water conflicts and threatens water supply for agriculture. In this context, one of the main priorities for agricultural research and public policy is the adaptation of crop yields to water pressures. This paper focuses on the evaluation of hydrological risk and water policy implications for food production. Our methodological approach includes four steps. For the first step, we estimate the impacts of rain...

Quiroga, S.; Ferna?ndez-haddad, Z.; Iglesias, A.

2010-01-01

150

Miocene stratigraphy and depositional framework of northeastern Maracaibo Basin, Venezuela: Implications for reservoir heterogeneity prediction in tectonically-active settings  

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Lateral and vertical changes in regime variables have a direct impact on the nature and distribution of macroscopic reservoir heterogeneity in tectonically-active basins. This relationship was tested in a clastic Miocene interval of the northeastern region of the Maracaibo Basin, Venezuela, by the integration and analysis of a comprehensive subsurface dataset. Four unconformity-bounded sequences record changes in accommodation, sediment supply, and sediment dispersal directions. These shifts were controlled by the uplift of the Sierra de Perija and by the marine connection between the Maracaibo and Falcon basins. The oldest sequence corresponds to the Early Miocene La Rosa Formation, which represents the episode of greatest increase in the regime ratio. After experiencing the maximum flooding event of the Neogene, accommodation space was filled by a mixed wave- and tide-influenced system of deltas and prograding shorelines that were fed from the west. Waterflooding in these reservoirs has been successful despite the compartmentalization and increased heterogeneity produced by rapid marine flooding of the deltaic pulses. Increased uplift and erosion of the sediment source areas shifted the regime ratio to supply dominated, causing a major fall in relative sea level and the development of a network of southwest- to northeast-oriented fluvially incised valleys. This event separates the La Rosa Formation from a younger sequence of highly heterogeneous tide-dominated estuarine deposits, overlain by tidal flats and tide-dominated deltaic sediments, that characterize the Lagunillas Inferior member of the Lagunillas Formation. The stratigraphic relationships and sedimentary fill of these incised valleys explain the complex nature of the LL-03/LL-05 reservoir boundary to the southeast of the study area. Continuing tectonic activity resulted in yet another significant drop in relative sea level, recorded by the abrupt onset of southeasterly flowing, mixed-load rivers, in the upper section of the Lagunillas Inferior Member. These deposits form the shelf-equivalent lowstand systems tract of the next younger sequence, which also includes the Laguna Member. A significant potential for targeting uncontacted and bypassed hydrocarbons exists in these reservoirs. Waterflooding has been relatively successful, but differences in directional permeability may be encountered across the fluvial entrenchment surfaces.

Guzman Espinal, Jose Ignacio

1999-11-01

151

Tree-Ring Extension of Precipitation Variability for Eastern Nevada: Implications for Drought Analysis in the Great Basin Region, USA  

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In the Great Basin of North America, ecotonal environments characterized as lower forest border sites are ideally suited for tree-ring reconstructions of hydroclimatic variability. A network of 22 tree-ring chronologies, some longer than 800 years, from single-leaf pinyon (Pinus monophylla) tree-ring samples for eastern Nevada, in the central Great Basin of North America was used to analyze long-term precipitation variability. The period in common among all tree-ring chronologies, i.e. 1650-1976, was used to reconstruct October-May total precipitation using the Line of Organic Correlation (LOC) method. Individual site reconstructions were then combined using spatio-temporal kriging to produce annual maps of drought on a 12x12 km grid. Hydro-climatic episodes were numerically identified and modeled using their duration, magnitude, and peak, to estimate the likelihood of severe and sustained drought in this region. According to a numerical scoring rule explained in detail by Biondi et al. 2008, the most remarkable episode in the entire reconstruction was the early 1900s pluvial, followed by the late 1800s drought. The 1930s 'Dust Bowl' drought was in 8th position, making it one of the more remarkable episodes in the past few centuries. This result is consistent with other studies that show how regional drought severity varies going from western to eastern Nevada, and directly addresses the needs of water managers with respect to planning for 'worst case' scenarios of drought duration and magnitude. For instance, it is possible to analyze which geographical areas and hydrographic basins are more likely to be impacted during the most extreme droughts, at the annual (see Figure) or multiannual timescale. In the semi-arid western USA, multi-century long dendroclimatic records with km-scale spatial resolution can therefore provide water managers with a quantitative evaluation of climate episodes well beyond the envelope of instrumental records, thereby increasing the ability to design management practices for single watersheds with the objective to achieve drought resiliency.

Biondi, F.; Strachan, S. D.

2011-12-01

152

Modeling fluid flow in sedimentary basins with sill intrusions: Implications for hydrothermal venting and global climate change  

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In recent years, the emplacement of Large Igneous Provinces (LIPs) has been closely linked with past climate variations and mass extinctions. The hypothesis is that organic matter present within contact aureole of the surrounding sedimentary rock such as shale undergoes thermal maturation and releases greenhouse gases such as methane and carbon dioxide due to the emplacement of hot igneous bodies. These gases are then vented into the atmosphere through hydrothermal pipe structures resulting in climate change. Although, basin-scale estimates of potential methane generation show that these processes alone could trigger global incidents, the rates at which these gases are released into the atmosphere and the transport mechanism are quantitatively unknown. We use a 2D, hybrid FEM/FVM model that solves for fully compressible fluid flow to quantify the thermogenic release of methane and to evaluate flow patterns within these systems. In addition, methane transport within the system is tracked enabling us to constrain the rate of release of methane from the basin surface. The important outcomes of this study are: (1) the location of hydrothermal vents is directly controlled by the flow pattern, even in systems with no vigorous convection, without the explicit need for explosive degassing and/or boiling effects. The merging of fluid flow from the bottom and top edges of the sill result in hydrothermal plumes positioned at the lateral edges of the sill and is consistent with geological observations. (2) Methane generation potential in systems with fluid flow does not significantly differ from that estimated in diffusive systems, e.g. 2200 to 3350 Gt CH4 can be potentially generated within the Vøring and Møre basins with a sediment TOC content of 5 wt% and varying permeability structure. On the other hand, methane venting at the surface occurs in three distinct stages and can last for hundreds of thousands of years. Also, not all of the methane reaches the surface as some may still be trapped beneath an impermeable sill. (3) The model results demonstrate that although the total quantity of methane that may be potentially generated within the contact aureole may have indeed influenced past climate variations, the rate at which this methane is released into the atmosphere is too slow to trigger, by itself, the negative ?13C excursions observed in the fossil record over short time scales (< 10,000 years). For e.g., the PETM is associated with the formation of the North Atlantic igneous province and is characterized by a ?13C incursion of -2 to -3‰ over 10,000 years. The model results demonstrate that with a TOC content of 5 wt%, ~2200 Gt of methane is released within 10,000 years from the Vøring and Møre basins and results in a ?13C excursion of only -1.2‰. It is, therefore, likely that methane from organic cracking in sediments during sill intrusion in conjunction with other processes such as volcanic degassing and the destabilization of sub-surface methane hydrate is responsible for such short term catastrophic climate change.

Iyer, K. H.; Rupke, L.

2013-12-01

153

Note on the distribution of crustaceans in floodplain ponds in the Ciuc Basin (Romania and implications foe habitat restoration  

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Full Text Available In the Ciuc Basin, Olt river was regulated and the old riverbed was filled in the late 1970s and early 1980s. There are few published data on the habitat changes caused by these works. I studied the distribution of two large branchiopods (Chirocephalus shadini and Lynceus brachyurus and a calanoid copepod (Hemidiaptomus amblyodon in ponds of riverbed and non-riverbed origin. I found that these species occur more frequently in non-riverbed ponds and the density of C. shadini was 3.6 times larger on average in non-riverbed ponds than in riverbed ponds. I conclude that these organisms could be used as indicators in reconstituting the small-scale habitat structure of the floodplain before the river regulation.

DEMETER László

2006-09-01

154

Variable gas saturation in coalbed methane reservoirs of the Black Warrior Basin: Implications for exploration and production  

Energy Technology Data Exchange (ETDEWEB)

Gas saturation is highly variable in Carboniferous coalbed methane reservoirs of the Black Warrior Basin (USA), and diverse geologic data derived from more than three decades of exploration and development provides insight into the origin of this variability and the consequences for production performance. Coalbed methane is produced from numerous thin ({proportional_to} 0.3 to < 4 m) coal seams that are distributed through 700 to 1200 m of stratigraphic section. Gas content tends to increase with depth, and gas saturation typically ranges from < 10 to > 95%. Importantly, this range of variation is commonly developed among closely spaced seams within the same well. Exploration has to date been successful where coal seams are in the thermogenic gas window. Geochemical evidence indicates that thermogenic gases have been altered by subsurface water movement and may have been augmented with late-stage biogenic gases, particularly in areas affected by fresh-water recharge. Adsorption isotherms of coal samples in the Black Warrior Basin typically have Langmuir volume between 15 and 30 cm{sup 3}/g and Langmuir pressure between 2 and 6 MPa. Both Langmuir pressure and Langmuir volume correlate significantly with coal rank. In deep, normally pressured coal beds where reservoir pressure is substantially above Langmuir pressure, even a small degree of undersaturation can necessitate prolonged dewatering before a large reservoir volume can reach the critical desorption pressure. Permeability, moreover, decreases exponentially with depth, which can make dewatering coal seams deeper than 800 m difficult. Where reservoir pressure is relatively low, however, isotherm geometry indicates that significantly undersaturated reservoirs can be near the critical desorption pressure. Consequently, areas of underpressure favor high gas production along with minimal water production. (author)

Pashin, Jack C. [Geological Survey of Alabama, P.O. Box 869999, Tuscaloosa, AL 35486-6999 (United States)

2010-06-01

155

Magnetostratigraphy of the Late Cretaceous to Eocene Sverdrup Basin: Implications for heterochroneity, deformation, and rotations in the Canadian Arctic archipelago  

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The temporal and spatial patterns of sedimentation in the Sverdrup Basin provide clues to how deformation in the Canadian Arctic accommodated Late Cretaceous-Eocene relative motion between Greenland and North America. Although the sediments contain a rich assemblage of mammal and megafloral fossils, dating of the sequence has been controversial. Some work suggests a dramatic faunal and floral heterochroneity with species appearing in the Arctic 2-18 m.y. prior to their appearance at lower latitudes. To obtain a chronostratigraphic framework for these sediments, a 2.6-km section of the Eureka Sound Group and Kanguk Formation on western Axel Heiberg Island was sampled for magnetostratigraphy. After removal of a pervasive modern field overprint with thermal and alternating field demagnetization, a characteristic remanent magnetization (ChRM) is isolated. Despite high directional dispersion, the ChRMs form 11 distinct polarity intervals which can be correlated to chrons 34 to 24r. This correlation indicates that some of these sediments are ˜10 m.y. younger than thought previously, reducing the need for large-scale heterochroneity. Sedimentation rates derived from the magnetostratigraphy suggest that an increase in basin subsidence is recorded near the middle of the section sampled. A similar pattern has been reported from the Eureka Sound Group exposed on Ellesmere Island. We interpret this increased sedimentation as a response to crustal flexure caused by lithospheric loading during the middle Paleocene (C26r). The loading may be related to a blind thrust system to the west of Axel Heiberg Island that marks compression between North America and Greenland driven by rapid seafloor spreading in the Labrador Sea. The new data, together with prior results, indicate that most of the Cretaceous Canadian Arctic archipelago has undergone a counterclockwise vertical axis rotation. The new data are more consistent with this rotation being related to events during chron 26r, rather than marking block rotations associated with the terminal Eocene phases of Eurekan deformation.

Tarduno, John A.; Cottrell, Rory D.; Wilkison, Sarah L.

1997-01-01

156

Sensitivity analysis of a sediment dynamics model applied in a Mediterranean river basin: Global change and management implications.  

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Climate change and land-use change are major factors influencing sediment dynamics. Models can be used to better understand sediment production and retention by the landscape, although their interpretation is limited by large uncertainties, including model parameter uncertainties. The uncertainties related to parameter selection may be significant and need to be quantified to improve model interpretation for watershed management. In this study, we performed a sensitivity analysis of the InVEST (Integrated Valuation of Environmental Services and Tradeoffs) sediment retention model in order to determine which model parameters had the greatest influence on model outputs, and therefore require special attention during calibration. The estimation of the sediment loads in this model is based on the Universal Soil Loss Equation (USLE). The sensitivity analysis was performed in the Llobregat basin (NE Iberian Peninsula) for exported and retained sediment, which support two different ecosystem service benefits (avoided reservoir sedimentation and improved water quality). Our analysis identified the model parameters related to the natural environment as the most influential for sediment export and retention. Accordingly, small changes in variables such as the magnitude and frequency of extreme rainfall events could cause major changes in sediment dynamics, demonstrating the sensitivity of these dynamics to climate change in Mediterranean basins. Parameters directly related to human activities and decisions (such as cover management factor, C) were also influential, especially for sediment exported. The importance of these human-related parameters in the sediment export process suggests that mitigation measures have the potential to at least partially ameliorate climate-change driven changes in sediment exportation. PMID:25302447

Sánchez-Canales, M; López-Benito, A; Acuña, V; Ziv, G; Hamel, P; Chaplin-Kramer, R; Elorza, F J

2015-01-01

157

Distribution of sulfur and pyrite in coal seams from Kutai Basin (East Kalimantan, Indonesia): Implications for paleoenvironmental conditions  

Energy Technology Data Exchange (ETDEWEB)

Thirteen Miocene coal samples from three active open pit and underground coal mines in the Kutai Basin (East Kalimantan, Indonesia) were collected. According to our microscopical and geochemical investigations, coal samples from Sebulu and Centra Busang coal mines yield high sulfur and pyrite contents as compared to the Embalut coal mine. The latter being characterized by very low sulfur (< 1%) and pyrite contents. The ash, mineral, total sulfur, iron (Fe) and pyrite contents of most of the coal samples from the Sebulu and Centra Busang coal mines are high and positively related in these samples. Low contents of ash, mineral, total sulfur, iron (Fe) and pyrite have been found only in sample TNT-32 from Centra Busang coal mine. Pyrite was the only sulfur form that we could recognize under reflected light microscope (oil immersion). Pyrite occurred in the coal as framboidal, euhedral, massive, anhedral and epigenetic pyrite in cleats/fractures. High concentration of pyrite argues for the availability of iron (Fe) in the coal samples. Most coal samples from the Embalut coal mine show lower sulfur (< 1 wt.%) and pyrite contents as found within Centra Busang and Sebulu coals. One exception is the coal sample KTD-38 from Embalut mine with total sulfur content of 1.41 wt.%. The rich ash, mineral, sulfur and pyrite contents of coals in the Kutai Basin (especially Centra Busang and Sebulu coals) can be related to the volcanic activity (Nyaan volcanic) during Tertiary whereby aeolian material was transported to the mire during or after the peatification process. Moreover, the adjacent early Tertiary deep marine sediment, mafic igneous rocks and melange in the center of Kalimantan Island might have provided mineral to the coal by uplift and erosion. The inorganic matter in the mire might also originate from the ground and surface water from the highland of central Kalimantan. (author)

Widodo, Sri [Department of Mining Engineering, Moslem University of Indonesia, Jln. Urip Sumoharjo, Makassar (Indonesia); Oschmann, Wolfgang [Institute of Geosciece, J.W. Goethe-University, Altenhoeferallee 1, D-60438 Frankfurt a.M. (Germany); Bechtel, Achim; Sachsenhofer, Reinhard F. [Department of Applied Geoscience and Geophysics, University of Leoben, Peter-Tunner-Str.5, A-8700 Leoben (Austria); Anggayana, Komang [Department of Mining Engineering, Bandung Institute of Technology, Jln. Ganesa 10, I-40132 Bandung (Indonesia); Puettmann, Wilhelm [Institute of Atmospheric and Environmental Sciences, Dapartment of Analytical Enviromental Chemistry, J.W. Goethe-University, Altenhoeferallee 1, D-60438 Frankfurt a.M. (Germany)

2010-03-01

158

Secondary gas emissions during coal desorption, Marathon Grassim Oskolkoff-1 Well, Cook Inlet Basin, Alaska: Implications for resource assessment  

Science.gov (United States)

Cuttings samples of sub-bituminous humic coals from the Oligocene to Pliocene Tyonek Formation, Cook Inlet Basin, Alaska show secondary gas emissions whose geochemistry is consistent with renewed microbial methanogenesis during canister desorption. The renewed methanogenesis was noted after initial desorption measurements had ceased and a canister had an air and desorbed gas mixture backflow into the canister during a measurement. About a week after this event, a secondary emission of gas began and continued for over two years. The desorbed gas volume reached a new maximum, increasing the total from 3.3 to 4.9 litres, some 48% above the pre-contamination total volume. The gases released during desorption show a shift in the isotopic signature over time of methane from ??13CCH4 of -53.60 ??? and ??DCH4 of -312.60 ??? at the first day to ??13CCH4 of -57.06 ??? and ??DCH4 of -375.80 ??? after 809 days, when the experiment was arbitrarily stopped and the canister opened to study the coal. These isotopic data, interpreted using a Bernard Diagram, indicate a shift from a mixed thermogenic and biogenic source typical of natural gases in the coals and conventional gas reservoirs of the Cook Inlet Basin to a likely biogenic acetate-fermentation methane source. However, the appearance of CO2 during the renewed gas emissions with a ??13CCO2 of +26.08 to +21.72 ???, interpreted using the carbon isotope fractions found for acetate fermentation and CO2 reduction between CO2 and CH4 by Jenden and Kaplan (1986), indicates a biogenic CO2-reduction pathway may also be operative during renewed gas emission. Adding nutrients to the coal cuttings and canister water and culturing the microbial consortia under anaerobic conditions led to additional methane-rich gas generation in the laboratory. After this anaerobic culturing, ultraviolet microscopy showed that canister water contained common, fluorescent, rod-like microbes comparable to Methanobacterium sp. Scanning electron microscope investigations of the coal matrix showed several morphological types of microbes, including rod, cocci and spherical forms attached to the coal surface. These microbes apparently represent at least a portion of the microbial consortia needed to depolymerize coal, as well as to generate the observed secondary methane emission from the canister. The introduction of 48% more methane from secondary sources has a major impact on coal-bed methane resource assessments and also in determining the true, in-situ degree of methane saturation in coal-beds using isotherms. Canister and isotherm measurements that show "supersaturation" of methane may actually be the result of additional gases generated during secondary methanogenesis.

Barker, C.E.; Dallegge, T.

2006-01-01

159

Revised age of proximal deposits in the Zagros foreland basin and implications for Cenozoic evolution of the High Zagros  

Science.gov (United States)

The regionally extensive, coarse-grained Bakhtiyari Formation represents the youngest synorogenic fill in the Zagros foreland basin of Iran. The Bakhtiyari is present throughout the Zagros fold-thrust belt and consists of conglomerate with subordinate sandstone and marl. The formation is up to 3000 m thick and was deposited in foredeep and wedge-top depocenters flanked by fold-thrust structures. Although the Bakhtiyari concordantly overlies Miocene deposits in foreland regions, an angular unconformity above tilted Paleozoic to Miocene rocks is expressed in the hinterland (High Zagros). The Bakhtiyari Formation has been widely considered to be a regional sheet of Pliocene-Pleistocene conglomerate deposited during and after major late Miocene-Pliocene shortening. It is further believed that rapid fold growth and Bakhtiyari deposition commenced simultaneously across the fold-thrust belt, with limited migration from hinterland (NE) to foreland (SW). Thus, the Bakhtiyari is generally interpreted as an unmistakable time indicator for shortening and surface uplift across the Zagros. However, new structural and stratigraphic data show that the most-proximal Bakhtiyari exposures, in the High Zagros south of Shahr-kord, were deposited during the early Miocene and probably Oligocene. In this locality, a coarse-grained Bakhtiyari succession several hundred meters thick contains gray marl, limestone, and sandstone with diagnostic marine pelecypod, gastropod, coral, and coralline algae fossils. Foraminiferal and palynological species indicate deposition during early Miocene time. However, the lower Miocene marine interval lies in angular unconformity above ~ 150 m of Bakhtiyari conglomerate that, in turn, unconformably caps an Oligocene marine sequence. These relationships attest to syndepositional deformation and suggest that the oldest Bakhtiyari conglomerate could be Oligocene in age. The new age information constrains the timing of initial foreland-basin development and proximal Bakhtiyari deposition in the Zagros hinterland. These findings reveal that structural evolution of the High Zagros was underway by early Miocene and probably Oligocene time, earlier than commonly envisioned. The age of the Bakhtiyari Formation in the High Zagros contrasts significantly with the Pliocene-Quaternary Bakhtiyari deposits near the modern deformation front, suggesting a long-term (> 20 Myr) advance of deformation toward the foreland.

Fakhari, Mohammad D.; Axen, Gary J.; Horton, Brian K.; Hassanzadeh, Jamshid; Amini, Abdolhossein

2008-04-01

160

The population structure of Glossina fuscipes fuscipes in the Lake Victoria basin in Uganda: implications for vector control  

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Full Text Available Abstract Background Glossina fuscipes fuscipes is the primary vector of trypanosomiasis in humans and livestock in Uganda. The Lake Victoria basin has been targeted for tsetse eradication using a rolling carpet initiative, from west to east, with four operational blocks (3 in Uganda and 1 in Kenya, under a Pan-African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC. We screened tsetse flies from the three Ugandan PATTEC blocks for genetic diversity at 15 microsatellite loci from continental and offshore populations to provide empirical data to support this initiative. Methods We collected tsetse samples from 11 sites across the Lake Victoria basin in Uganda. We performed genetic analyses on 409 of the collected tsetse flies and added data collected for 278 individuals in a previous study. The flies were screened across 15 microsatellite loci and the resulting data were used to assess the temporal stability of populations, to analyze patterns of genetic exchange and structuring, to estimate dispersal rates and evaluate the sex bias in dispersal, as well as to estimate demographic parameters (NE and NC. Results We found that tsetse populations in this region were stable over 4-16 generations and belong to 4 genetic clusters. Two genetic clusters (1 and 2 corresponded approximately to PATTEC blocks 1 and 2, while the other two (3 and 4 fell within PATTEC block 3. Island populations grouped into the same genetic clusters as neighboring mainland sites, suggesting presence of gene flow between these sites. There was no evidence of the stretch of water separating islands from the mainland forming a significant barrier to dispersal. Dispersal rates ranged from 2.5?km per generation in cluster 1 to 14?km per generation in clusters 3 and 4. We found evidence of male-biased dispersal. Few breeders are successfully dispersing over large distances. Effective population size estimates were low (33–310 individuals, while census size estimates ranged from 1200 (cluster 1 to 4100 (clusters 3 and 4. We present here a novel technique that adapts an existing census size estimation method to sampling without replacement, the scheme used in sampling tsetse flies. Conclusion Our study suggests that different control strategies should be implemented for the three PATTEC blocks and that, given the high potential for re-invasion from island sites, mainland and offshore sites in each block should be targeted at the same time.

Hyseni Chaz

2012-10-01

 
 
 
 
161

Tectono-Sedimentary evolution and geochronology of the Middle Miocene Altinapa Basin, and implications for the Late Cenozoic uplift history of the Taurides, southern Turkey  

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The Tauride range in southern Turkey is flanked and overlain by Neogene sedimentary basins. To the south and on top of the high range, these basins are mainly marine, whereas poorly studied intramontane basins dominated by continental deposits are exposed to the north. In this paper, we study the stratigraphy and structure of the continental Alt?napa Basin, and provide 40Ar/39Ar geochronology for volcanic deposits in the stratigraphy. The stratigraphy can be subdivided into a Lower Group, di...

Koc?, A.; Kaymakci, N.; Hinsbergen, D. J. J.; Kuiper, K. F.; Vissers, R. L. M.

2012-01-01

162

Geochemical and isotopic anomalies preceding K/T boundary in the Cauvery basin, South India : implications for end Cretaceous events  

International Nuclear Information System (INIS)

The Upper Cretaceous-Lower Tertiary deposits of the Cauvery basin show prominent geochemical and isotopic anomalies preceding the K/T boundary. Analysis of stratigraphic variations of whole-rock elemental concentrations and stable isotopic compositions in the light of sedimentation history, petrography and mineralogy of the rocks reveal that these anomalies may be due to increased detrital influx caused by sea-level and climatic changes, Deccan volcanism and release of volatile gases from buried hydrocarbons, presumably gas hydrates. Comparison of these interpretations with that of K/T sites located in Guatemala, New Mexico and Israel revealed that these interpretations are in conformity with records on gradually increasing environmental stress during Upper Cretaceous that culminated with two major catastrophic events such as bolide impact and Deccan Trap volcanism. Thus this communication provides additional support to the growing acknowledgement of the theory that higher faunal turnover across the K/T boundary the world over might have been the result of gradual environmental deterioration rather than a sudden impact in the global scale. (author)

163

Relationship between sea ice freeboard and draft in the Arctic Basin, and implications for ice thickness monitoring  

Science.gov (United States)

This study confirms the finding of Comiso et al. (1991) that the probability density function (pdf) of the ice freeboard in the Arctic Ocean can be converted to a pdf of ice draft by applying a simple coordinate factor. The coordinate factor, R, which is the ratio of mean draft to mean freeboard pdf is related to the mean material (ice plus snow) density, rho(m), and the near-surface water density rho(w) by the relationship R = rho(m)/(rho(w) - rho(m)). The measured value of R was applied to each of six 50-km sections north of Greenland of a joint airborne laser and submarine sonar profile obtained along nearly coincident tracks from the Arctic Basin north of Greenland and was found to be consistent over all sections tested, despite differences in the ice regime. This indicates that a single value of R might be used for measurements done in this season of the year. The mean value R from all six sections was found to be 7.89.

Wadhams, P.; Tucker, W. B., III; Krabill, W. B.; Swift, R. N.; Comiso, J. C.; Davis, N. R.

1992-01-01

164

On modeling the paleohydrologic response of closed-basin lakes to fluctuations in climate: Methods, applications, and implications  

Science.gov (United States)

reconstructions using tree rings and lake sediments have contributed significantly to the understanding of Holocene climates. Approaches focused specifically on reconstructing the temporal water-level response of lakes, however, are much less developed. This paper describes a statistical correlation approach based on time series with Palmer Drought Severity Index (PDSI) values derived from instrumental records or tree rings as a basis for reconstructing stage hydrographs for closed-basin lakes. We use a distributed lag correlation model to calculate a variable, ?t that represents the water level of a lake at any time t as a result of integrated climatic forcing from preceding years. The method was validated using both synthetic and measured lake-stage data and the study found that a lake's "memory" of climate fades as time passes, following an exponential-decay function at rates determined by the correlation time lag. Calculated trends in ?t for Moon Lake, Rice Lake, and Lake Mina from A.D. 1401 to 1860 compared well with the established chronologies (salinity, moisture, and Mg/Ca ratios) reconstructed from sediments. This method provides an independent approach for developing high-resolution information on lake behaviors in preinstrumental times and has been able to identify problems of climate signal deterioration in sediment-based climate reconstructions in lakes with a long time lag.

Liu, Ganming; Schwartz, Franklin W.

2014-04-01

165

Significant mineral variations in the Lower Karoo deposits of the Mid-Zambezi Basin, Zimbabwe, and their palaeoenvironmental implications  

International Nuclear Information System (INIS)

Mineralogical composition of Lower Karoo deposits from the Mid-Zimbabwe Basin, Zimbabwe, have been established by means of X-ray diffractometry to evaluate mineralogical variables as possible palaeoenvironment indicators. Mineral variations are stratigraphically controlled. Dwyka tillites are composed of quartz, K-feldspar and plagioclase. Varvites contain additional calcite. The clay fraction is dominated by kaolinite in the northwestern part of the study area while in the southwest only subordinate proportions of kaolinite occur associated with approximately equal amounts of mica, chlorite, smectite, and interstratifications. The overlying Ecca sediments are characterized by a high kaolinite content, traces of K-feldspar, mica and occasional pyrite. In mudstones of the uppermost Ecca, the kaolonite proportion decreases in favour of mica and chlorite. The mineral composition of Beaufort mudstones differs significantly with considerable amounts of plagioclase and a more than sporadic presence of analcime which is restricted to this stratigraphic unit. The clay fraction is dominated by either kaolinite, mica, or smectite. Within the geotectonical setting discussed by this paper the kaolinite dominance in Ecca sediments corresponds well with freshwater depositional conditions deduced from sedimentological and palaeontological evidence. However, the abundance of 2:1 phyllosilicates and especially analcime prevalence in the Beaufort section indicates an alkaline palaeoenvrt section indicates an alkaline palaeoenvironment. 10 figs., 29 refs

166

Organic geochemistry of the Lower Suban coal seam, South Sumatra Basin, Indonesia: Palaeoecological and thermal metamorphism implications  

Energy Technology Data Exchange (ETDEWEB)

Hydrocarbons extracted from the Tertiary age coals from the Lower Suban seam, South Sumatra Basin, Indonesia have been investigated using gas chromatography (GC) and combined gas chromatography/mass spectrometry (GC/MS). Low rank (vitrinite-huminite reflectance about to 0.41-0.45%) coals from the Tambang Air Laya mine represent different maceral assemblages of an ideal succession of ombrogenous palaeo-peat development in a vertical section. High rank coals (vitrinite reflectance about to 1.42-5.18%) from the Suban mine have been thermally metamorphosed by an andesitic intrusion. Variations in the distributions of n-alkanes, isoprenoids and saturated and aromatic biomarkers in the low rank coals reflect variations in local source input and palaeomire conditions. Terpenoid biomarkers, such as cadinane- and eudesmane-type sesquiterpenoids and oleanane- and ursane-type triterpenoids, indicate the predominance of angiosperm plants in the palaeomire, particularly Dipterocarpaceae. The distribution of hopanoids is affected by the organic facies of the coal and their maturity, and correlates with the palaeomire evolution as derived from petrological studies. Close to the igneous intrusion, rapid thermal stress has destroyed most of the biomarkers, but variations in n-alkane distributions, attributable to palaeomire conditions, remain. Reversals in the trends for molecular parameters based on aliphatic hydrocarbons (n-alkane distribution and pristane/phytane ratio) and aromatic hydrocarbons (methyl phenanthrenes) with coal rank are observed.

Amijaya, H.; Schwarzbauer, J.; Littke, R. [University of Aachen, Aachen (Germany)

2006-07-01

167

Ichnofabrics of the Capdevila Formation (early Eocene) in the Los Palacios Basin (western Cuba): Paleoenvironmental and paleoecological implications  

Science.gov (United States)

The ichnofabrics present in the early Eocene siliciclastic deposits of the Capdevila Formation exposed in the Pinar del Rio area (Los Palacios Basin, western Cuba) are analyzed in this paper and their paleoecological and paleoenvironmental significance are discussed. Nine ichnofabrics were recognized in the dominantly sandy sedimentary succession: Ophiomorpha, Asterosoma, Thalassinoides, Palaeophycus, Scolicia, Bichordites-Thalassinoides, Rhizocorallium, Scolicia-Thalassinoides and rhizobioturbation. Diversity of ichnofauna is low and burrows made by detritus-feeding organisms in well oxygenated and stenohaline waters predominate. Suites of the Cruziana and Skolithos Ichnofacies lacking their archetypical characteristics were recognized, being impoverished in diversity and presenting dominance of echinoderm and decapods crustacean burrows as a response to the environmental stress caused by the high frequency of deposition. The ichnofabric distribution in the studied succession, its recurrence in the sandstone beds and the presence of a Glossifungites Ichnofacies suite with rhizobioturbation associated reflect a shoaling-upward event with subaerial exposure of the substrate. The integrated analysis of the ichnology and the sedimentary facies suggests deposition in a shallow slope frequently impacted by gravitational flows and high-energy events. The evidence of substrate exposure indicates the occurrence of a forced regression and suggests the existence of a sequence boundary at the top of the Capdevila Formation.

Villegas-Martín, Jorge; Netto, Renata Guimarães; Lavina, Ernesto Luis Correa; Rojas-Consuegra, Reinaldo

2014-12-01

168

High precision radiometric ages from the northern Sydney Basin and their implication for the Permian time interval and sedimentation rates  

International Nuclear Information System (INIS)

Three pyroclastic samples that bracket the coal-bearing Permian System of the northern Sydney Basin have been dated using the zircon U/Pb and hornblende K/Ar methods. The Matthews Gap Dacitic Tuff Member, situated 170 m below the base of the Permian System, gives a best estimate of 309 ± 3 Ma. Its age correlates well with the Paterson Volcanics which suggests that the immediately overlying clastic sediments are equivalent to the Seaham Formation. The Awaba Tuff, which is located 50 m below the top of the Permian System, gives a best estimate of 256 ± 4 Ma. An intervening horizon, the Thornton Claystone of the Tomago Coal Measures, gives a best estimate of 266 ± 0.4 Ma. The ages indicate an earlier beginning ? 299 Ma BP), an earlier termination (? 255 Ma BP) and slightly longer duration (44±13 Ma) of the Permian System in the Hunter Valley than previously suggested. Sedimentation rates of ± 65m/Ma, calculated from proximal sequence thicknesses, are only half the rate calculated from the closest maximum thicknesses. Both are considerably lower than previously quoted rates. The estimated time interval of 10 Ma between the Thornton Claystone and the Awaba Tuff is more than twice the length of time previously attributed to accumulation of the combined Tomago and Newcastle Coal Measures. 38 refs., 5 tabs., 2 figs

169

Model of the development of the Rif/Prerif basin and implications for the hydrocarbon prospectivity of northern Morocco  

Energy Technology Data Exchange (ETDEWEB)

The geology of northern Morocco is dominated by the mountainous areas of the Rif and the Prerif. These mountains form the southern half of the Rif-Betic arc. The surface geology of the Prerif area is characterized by the allochthonous mass of the Prerif nappe, which is variously described as a tectonic melange, an olistostrome, or a combination of the two. It is structurally extremely complex and this fact has, in the past, deterred international companies from exploring for oil in the area. Recently acquired seismic data shed some light on the structure within the Prerif nappe; it tends to support a tectonic origin rather than one based on gravity drive. In this framework, a model is proposed for the tectonic development of the Rif/Prerif in particular and the Rif/Betic arc in general, based upon the interaction of the Iberian, Moroccan, and Alboran plates from the Triassic to the Neogene. The seismic data also show, however, that a sizeable Mesozoic trough exists beneath the mass of the Prerif nappe. In addition, several piggyback basins are developed above the nappe. Therefore, considerable potential for oil and gas discoveries exists both above and below the nappe.

Munro, S.E. (Williams Brothers Engineering Co., Haddington (Scotland))

1988-08-01

170

Climate change and stream temperature projections in the Columbia River Basin: biological implications of spatial variation in hydrologic drivers  

Directory of Open Access Journals (Sweden)

Full Text Available Water temperature is a primary physical factor regulating the persistence and distribution of aquatic taxa. Considering projected increases in temperature and changes in precipitation in the coming century, accurate assessment of suitable thermal habitat in freshwater systems is critical for predicting aquatic species responses to changes in climate and for guiding adaptation strategies. We use a hydrologic model coupled with a stream temperature model and downscaled General Circulation Model outputs to explore the spatially and temporally varying changes in stream temperature at the subbasin and ecological province scale for the Columbia River Basin. On average, stream temperatures are projected to increase 3.5 °C for the spring, 5.2 °C for the summer, 2.7 °C for the fall, and 1.6 °C for the winter. While results indicate changes in stream temperature are correlated with changes in air temperature, our results also capture the important, and often ignored, influence of hydrological processes on changes in stream temperature. Decreases in future snowcover will result in increased thermal sensitivity within regions that were previously buffered by the cooling effect of flow originating as snowmelt. Other hydrological components, such as precipitation, surface runoff, lateral soil flow, and groundwater, are negatively correlated to increases in stream temperature depending on the season and ecological province. At the ecological province scale, the largest increase in annual stream temperature was within the Mountain Snake ecological province, which is characterized by non-migratory coldwater fish species. Stream temperature changes varied seasonally with the largest projected stream temperature increases occurring during the spring and summer for all ecological provinces. Our results indicate that stream temperatures are driven by local processes and ultimately require a physically-explicit modeling approach to accurately characterize the habitat regulating the distribution and diversity of aquatic taxa.

D. L. Ficklin

2014-06-01

171

Paleoclimatic implications of fossil shoreline deposits in the southern basin and range province during the Pleistocene-Holocene transition  

Science.gov (United States)

Paleolake shoreline deposits throughout the southern Basin and Range (SBAR) signify past intervals of steady-state climatic conditions occuring during the late Pleistocene slightly before, as well as after the Last Glacial Maximum (LGM; ~23-19 Ka). Unfortunately, a lack of knowledge about the age of fossil shoreline deposits—due to C-14 related uncertainties and incomplete dating of shorelines—has resulted in a large gap in our knowledge about past climatic and surface hydrologic conditions in the SBAR. Several studies collectively reveal multiple lake level oscillations during the LGM and last part of the Pleistocene, with reasonably well dated shoreline deposits existing for only four paleolakes: one in central New Mexico (Estancia), two in southwestern New Mexico (Playas and Cloverdale), and one in southeastern Arizona (Cochise). In summary, there is evidence for a pre-LGM high-stand at Cochise (>26 Ka), LGM high-stands at Estancia and Cloverdale (>20-16 Ka), deglacial age high-stands at Playas and Cochise (16-13 Ka), and latest Pleistocene-early Holocene still stands of as yet undetermined elevation at Playas and Estancia (13-9K). Further, the absence of high-stands from 11-10 Ka suggests that the Younger Dryas climatic reversal—which is detected in the stable O isotopic composition of speleothems from Cave-of-the-Bells in southeastern Arizona—was marked there by a decrease in mean annual air temperature without a significant increase in precipitation. Alternatively, if a return to glacial precipitation levels did occur, then it was for an interval so short that sedimentological evidence was not preserved. This presentation will cover the afore mentioned chronologies, along with discussion about associated atmospheric circulation patterns in the SBAR and across western North America.

Kowler, A. L.

2010-12-01

172

Climate change and stream temperature projections in the Columbia River Basin: biological implications of spatial variation in hydrologic drivers  

Science.gov (United States)

Water temperature is a primary physical factor regulating the persistence and distribution of aquatic taxa. Considering projected increases in temperature and changes in precipitation in the coming century, accurate assessment of suitable thermal habitat in freshwater systems is critical for predicting aquatic species responses to changes in climate and for guiding adaptation strategies. We use a hydrologic model coupled with a stream temperature model and downscaled General Circulation Model outputs to explore the spatially and temporally varying changes in stream temperature at the subbasin and ecological province scale for the Columbia River Basin. On average, stream temperatures are projected to increase 3.5 °C for the spring, 5.2 °C for the summer, 2.7 °C for the fall, and 1.6 °C for the winter. While results indicate changes in stream temperature are correlated with changes in air temperature, our results also capture the important, and often ignored, influence of hydrological processes on changes in stream temperature. Decreases in future snowcover will result in increased thermal sensitivity within regions that were previously buffered by the cooling effect of flow originating as snowmelt. Other hydrological components, such as precipitation, surface runoff, lateral soil flow, and groundwater, are negatively correlated to increases in stream temperature depending on the season and ecological province. At the ecological province scale, the largest increase in annual stream temperature was within the Mountain Snake ecological province, which is characterized by non-migratory coldwater fish species. Stream temperature changes varied seasonally with the largest projected stream temperature increases occurring during the spring and summer for all ecological provinces. Our results indicate that stream temperatures are driven by local processes and ultimately require a physically-explicit modeling approach to accurately characterize the habitat regulating the distribution and diversity of aquatic taxa.

Ficklin, D. L.; Barnhart, B. L.; Knouft, J. H.; Stewart, I. T.; Maurer, E. P.; Letsinger, S. L.; Whittaker, G. W.

2014-06-01

173

Climate change and stream temperature projections in the Columbia River basin: habitat implications of spatial variation in hydrologic drivers  

Science.gov (United States)

Water temperature is a primary physical factor regulating the persistence and distribution of aquatic taxa. Considering projected increases in air temperature and changes in precipitation in the coming century, accurate assessment of suitable thermal habitats in freshwater systems is critical for predicting aquatic species' responses to changes in climate and for guiding adaptation strategies. We use a hydrologic model coupled with a stream temperature model and downscaled general circulation model outputs to explore the spatially and temporally varying changes in stream temperature for the late 21st century at the subbasin and ecological province scale for the Columbia River basin (CRB). On average, stream temperatures are projected to increase 3.5 °C for the spring, 5.2 °C for the summer, 2.7 °C for the fall, and 1.6 °C for the winter. While results indicate changes in stream temperature are correlated with changes in air temperature, our results also capture the important, and often ignored, influence of hydrological processes on changes in stream temperature. Decreases in future snowcover will result in increased thermal sensitivity within regions that were previously buffered by the cooling effect of flow originating as snowmelt. Other hydrological components, such as precipitation, surface runoff, lateral soil water flow, and groundwater inflow, are negatively correlated to increases in stream temperature depending on the ecological province and season. At the ecological province scale, the largest increase in annual stream temperature was within the Mountain Snake ecological province, which is characterized by migratory coldwater fish species. Stream temperature changes varied seasonally with the largest projected stream temperature increases occurring during the spring and summer for all ecological provinces. Our results indicate that stream temperatures are driven by local processes and ultimately require a physically explicit modeling approach to accurately characterize the habitat regulating the distribution and diversity of aquatic taxa.

Ficklin, D. L.; Barnhart, B. L.; Knouft, J. H.; Stewart, I. T.; Maurer, E. P.; Letsinger, S. L.; Whittaker, G. W.

2014-12-01

174

Controls on large landslide distribution and implications for the geomorphic evolution of the southern interior Columbia River basin  

Science.gov (United States)

Large landslides (>0.1 km2) are important agents of geomorphic change. While most common in rugged mountain ranges, large landslides can also be widespread in relatively low-relief (several 100 m) terrain, where their distribution has been relatively little studied. A fuller understanding of the role of large landslides in landscape evolution requires addressing this gap, since the distribution of large landslides may affect broad regions through interactions with channel processes, and since the dominant controls on landslide distribution might be expected to vary with tectonic setting. We documented >400 landslides between 0.1 and ~40 km2 across ~140,000 km2 of eastern Oregon, in the semiarid, southern interior Columbia River basin. The mapped landslides cluster in a NW-SE-trending band that is 50-100 km wide. Landslides predominantly occur where even modest local relief (~100 m) exists near key contacts between weak sedimentary or volcaniclastic rock and coherent cap rock. Fault density exerts no control on landslide distribution, while ~10% of mapped landslides cluster within 3-10 km of mapped fold axes. Landslide occurrence is curtailed to the NE by thick packages of coherent basalt and to the SW by limited local relief. Our results suggest that future mass movements will localize in areas stratigraphically preconditioned for landsliding by a geologic history of fluviolacustrine and volcaniclastic sedimentation and episodic capping by coherent lava flows. In such areas, episodic landsliding may persist for hundreds of thousands of years or more, producing valley wall slopes of ~7??-13?? and impacting local channels with an evolving array of mass movement styles. ?? 2011 Geological Society of America.

Safran, E.B.; Anderson, S.W.; Mills-Novoa, M.; House, P.K.; Ely, L.

2011-01-01

175

Groundwater geochemistry and its implications for arsenic mobilization in shallow aquifers of the Hetao Basin, Inner Mongolia  

International Nuclear Information System (INIS)

Arsenic concentrations in shallow groundwaters from the Hetao Basin of Inner Mongolia range between 0.6 and 572 ?g/L. High As groundwaters generally occur in the shallow alluvial-lacustrine aquifers, which are mainly composed of black (or dark grey) fine sands in a reducing environment. They are characterized by high concentrations of dissolved Fe, Mn, HCO3-, P and S2-, and low concentrations of NO3- and SO42-. Low SO42- coupled with high S2- suggests that SO42- reduction has been an active process. In the reducing groundwaters, inorganic As(III) accounts for around 75% of total dissolved As. Total As contents in the sediments from three representative boreholes are observed to be 7.3-73.3 mg/kg (average of 18.9 mg/kg). The total As is mildly-strongly correlated with total Fe and total Mn, while a quite weak correlation exists between total As and total S, suggesting that the As is associated with Fe-Mn oxides, rather than sulfides in the sediments. It is found in the sequential extraction that chemically active As is mainly bound to Fe-Mn oxides, up to 3500 ?g/kg. The mobilization of As under reducing conditions is believed to include reductive dissolution of Fe-Mn oxides and reduction of adsorbed As. Although exchangeable As is labile and very vulnerable to hydrogeochemical condition, the contribution is relatively limited due to the bution is relatively limited due to the low concentrations. The competition between As and other anions (such as HPO42-) for binding sites on Fe-Mn oxides may also give rise to the release of As into groundwater. Slow groundwater movement helps accumulation of the released As in the groundwaters

176

Distal record of multi-sourced tephra in Onepoto Basin, Auckland, New Zealand: implications for volcanic chronology, frequency and hazards  

Science.gov (United States)

We have documented 80 tephra beds dating from ca. 9.5 to >50 ka, contained within continuously deposited palaeolake sediments from Onepoto Basin, a volcanic explosion crater in Auckland, New Zealand. The known sources for distal (>190 km from vent) tephra include the rhyolitic Taupo Volcanic Centre (4) and Okataina Volcanic Centre (14), and the andesitic Taranaki volcano (40) and Tongariro Volcanic Centre (3). The record provides evidence for four new events between ca. 50 and 28 ka (Mangaone Subgroup) suggesting Okataina was more active than previously known. The tephra record also greatly extends the known northern dispersal of other Mangaone Subgroup tephra. Ten rhyolitic tephra pre-date the Rotoehu eruption (>ca. 50 ka), and some are chemically dissimilar to post-50 ka rhyolites. Some of these older tephra were produced by large-magnitude events; however, their source remains uncertain. Eight tephra from the local basaltic Auckland Volcanic Field (AVF) are also identified. Interpolation of sedimentation rates allow us to estimate the timing of 12 major explosive eruptions from Taranaki volcano in the 27.5-9.5-ka period. In addition, 28 older events are recognised. The tephra are trachytic to rhyolitic in composition. All have high K2O contents (>3 wt%), and there are no temporal trends. This contrasts with the proximal lava record that shows a trend of increasing K2O with time. By combining the Onepoto tephra record with that of the previously documented Pukaki crater, 15 AVF basaltic fall events are constrained at: 34.6, 30.9, 29.6, 29.6, 25.7, 25.2, 24.2, 23.8, 19.4, 19.4, 15.8 and 14.5 ka, and three pre-50 ka events. This provides some of the best age constraints for the AVF, and the only reliable data for hazard recurrence calculations. The minimum event frequency of both distal and local fall events can be estimated, and demonstrates the Auckland City region is frequently impacted by ash fall from many volcanoes.

Shane, Phil; Hoverd, Joy

2002-04-01

177

Late Triassic tuff intervals in the Ordos basin, Central China: Their depositional, petrographic, geochemical characteristics and regional implications  

Science.gov (United States)

Tuff intervals of Upper Triassic Yanchang Formation are laterally widespread in the Ordos basin, Central China. This paper focuses on magmatic origins and potential source regions of these tuff intervals through detail depositional, petrographic and geochemical analyses. Most of the tuff intervals are well-documented at the bottom of the Chang7 oil reservoir unit and can be correlated laterally, and certain tuff beds are reworked by turbidity current or seismic activity. Petrographic studies of the Chang7 tuffs indicate that they are composed of crystal shards, lithic shards and altered glass shards, and the crystal shards include plagioclase, quartz and biotite. Alteration of the Chang7 tuffs is ubiquitous, thus, most of these tuffs transformed into illite/smectite (I/S) mixed-layers which are identified by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Less common minerals are also detected in the Chang7 tuffs such as zircon, hematite, siderite, anatase. Major elements are determined by the X-ray fluorescence (XRF) analysis, the results indicate that the Chang7 tuffs are enriched in K2O (average 4.21%), the ratio of SiO2/Al2O3 ranges from 1.73 to 2.85 (average 2.17), and the ratio of TiO2/Al2O3 varies between 0.006 and 0.032 (average 0.017), which imply that the Chang7 tuffs originated from a felsic parental magma. Trace elements are determined by inductively coupled plasma mass spectrometry (ICP-MS), indicating the total rare earth element (?REE) concentrations are variable, and range from 117.46 to 466.83 ppm (average 251.88 ppm). REE distribution pattern of the Chang7 tuffs presents a LREE rightward incline with flat HREE curve. The value of ?Eu ranges from 0.151 to 0.837 (average 0.492), suggesting a strong to weak negative Eu anomaly. The Chang7 tuffs show positive anomalies in Rb, Th and U and negative anomalies in Nb, Sr and Eu on a primitive mantle normalized spidergram. A preliminary analysis of the geochemical composition of the Chang7 tuffs suggests a parental magma origin of rhyodacite/dacite, which came from volcanic arc-related setting along an active continental margin. Combined with the chronology and geochemical studies of the synchronous Tianshui rhyolite in the West Qinling Mountains, we propose that the west Qinling Mountains is one of the potential source regions of these tuffs, and the Middle-Late Triassic terminal closure of eastern Tethys provided the arc-related magma.

Qiu, Xinwei; Liu, Chiyang; Mao, Guangzhou; Deng, Yu; Wang, Feifei; Wang, Jianqiang

2014-02-01

178

Failure modes and normal faulting in Miocene carbonate rocks, Granada Basin, Spain: implications for fluid flow units  

Science.gov (United States)

Along the southeastern termination of the Padul normal fault zone, southern Spain, a potentially active tectonic structure as long ~15 km with throw of ~800 m, there are several small normal faults with lengths up to ~2km and throws up to ~100m. These small faults are vertically segmented, and crosscut lithologically heterogeneous Miocene carbonates of the Lecrin Basin. Within the carbonate multilayer, we recognized three fundamental structural elements: joints, pressure solutions and deformation bands., Joints are present preferentially within calcarenitic beds (Uniaxial Compressive Strength, UCS= ~70 N/mm2; 2D porosity, ?= ~5%), whereas pressure solution seams localized in marl-rich microconglomeratic beds (UCS= ~21 N/mm2 ; ?= ~7%). On the contrary, in a clay-rich conglomeratic unit (UCS= ~40 N/mm2; ?= ~10%) underneath the carbonate multilayer, deformation banding was predominant. According to their abutting relationship, first generation structures consist of two orthogonal sets of bed-perpendicular joints and one set of bed parallel solution seams, both probably formed in response to overburden loading. One additional generation of high-angle to bedding joints developed thanks to shearing across the pre-existing bed-perpendicular joints sets. Similarly, low-angle to bedding pressure solution seams formed at the extensional quadrants of normally sheared, pre-existing bed parallel pressure solution seams due bed tilting and contemporaneous uplift an exhumation. Within the individual carbonate beds, normal faulting initiated by shearing across all the aforementioned generations of joints and pressure solution seams, with formation of new sets of high-angle joints and low-angle pressure solution seams along the sheared parental discontinuities. Continued slip caused the linkage among structures present in neighboring beds, forming and discontinuous slip surfaces surrounded by pods of fragmented rocks. With further deformation, the isolated slip surfaces coalesced together forming through-going, segmented slip surfaces along which brecciation and cataclasis took place. In the conglomerate unit, normal faulting initiated by mean of two conjugate sets of compressive shear bands, which formed due to clast rotation and translation within the clay-rich matrix. Ongoing deformation was accompanied by smearing of the clay-rich matrix within the proto-faults (offsets up to several cm), jointing and dilational of the pre-existing discontinuities present within the individual clasts. Discontinuous slip surfaces formed along the sheared fractures and, often, on the hanging wall side of the deformation bands. Further deformation was solved by linkage of adjacent slips surfaces, diffuse jointing, and cataclastic deformation which localized along the evolving slips surfaces. The original fluid flow properties of the individual carbonate beds were alterated by the different structural elements: joints, sheared joints and sheared pressure solution seams enhanced the fluid flow in a direction parallel to these structures, whereas pressure solution seams and deformation bands inhibited the fluid flow in a direction orthogonal to them. Within the fault-bounded blocks, the fluid flow properties varied according to the structural elements they contained. Along the major faults, the fluid flow was compartimentalized along the through-going slip surfaces and fault breccia of the core, and in the fault damage zones. Conversely, the matrix-supported cataclasites formed seals for cross-fault fluid flow. The results of this work point out to the importance of a detailed structural analysis in the assessment of underground fluid pathways within carbonate rocks.

Agosta, Fabrizio; Tondi, Emanuele; Ruano, Patricia; Galindo-Zaldivar, Jesus

2010-05-01

179

Surface geology of Williston 7.5-minute quadrangle, Aiken and Barnwell Counties, South Carolina  

International Nuclear Information System (INIS)

Detailed geologic mapping has shown the distribution and lithologic character of stratigraphic units and sedimentary deposits in Williston quadrangle. A middle Eocene stratigraphic unit correlative with the restricted McBean Formation is the oldest unit at the surface. The McBean-equivalent unit occurs at low elevations along drainages in the north of the quadrangle but does not crop out. These beds are typically very fine- to fine-grained quartz sand, locally with abundant black organic matter and less commonly with calcium carbonate. The uppermost middle Eocene Orangeburg District bed, commonly composed of loose, clay-poor, very fine- to fine-grained quartz sand, occurs at the surface in the north and southwest of the quadrangle with sparse exposure. The upper Eocene Dry Branch Formation occurs on valley slopes throughout the quadrangle. The Dry Branch is composed of medium- to very coarse-grained quartz sand with varying amounts on interstitial clay and lesser bedded clay. The upper Eocene Tobacco road Sand occurs on upper valley slopes and some interfluves and consists of very fine-grained quartz sand to quartz granules. The upper Middle Miocene to lower Upper Miocene upland unit caps the interfluves and is dominantly coarse-grained quartz sand to quartz granules, with included granule-size particles of white clay that are weathered feldspars. Loose, incohesive quartzose sands of the eolian Pinehurst Formation, Upper Miocene to Lower Pliocene, occur on the easternne to Lower Pliocene, occur on the eastern slopes of some interfluves in the north of the quadrangle. Quartz sand with varying included humic matter occurs in Carolina bays, and loose deposits of windblown sand occur on the rims of several Carolina bays. Quaternary alluvium fills the valley floors

180

Clave fotográfica para hembras de Haemagogus Williston 1896 (Diptera: Culicidae) de Venezuela, con nuevo registro para el país / Pictorial key for females of Haemagogus Williston 1896 (Diptera: Culicidae) from Venezuela, with a new record for the country  

Scientific Electronic Library Online (English)

Full Text Available SciELO Venezuela | Language: Spanish Abstract in spanish El género neotropical Haemagogus Williston, está representado por mosquitos de actividad diurna, cuyas fases inmaduras se crían en fitotelmatas (huecos de árboles e internodos cortados de bambú). Especies de este género se han señalado involucradas en la transmisión de la Fiebre Amarilla selvática, [...] virus que circula en áreas boscosas de América Latina entre primates no humanos y marsupiales arborícolas por la picada de estos mosquitos. De las 28 especies reconocidas en el continente, 9 se encuentran en Venezuela. Una de ellas, Heamagogus (Conopostegus) clarki constituye un nuevo registro para el país. Se presenta una actualización de la taxonomía y de la distribución geográfica del género en Venezuela, así como la primera clave fotográfica con términos sencillos para el uso de personal no experimentado. Abstract in english The neotropical genus Heamagogus Williston includes mosquitoes with diurnal activity and immature breeding on Phytotelmata (tree-holes and cut bamboo internodes). Haemagogus species have been involved in sylvatic yellow fever transmission, a virus circulating in forest areas in Latin America among a [...] rboreal primates and marsupials by means of mosquito bite. The genus comprises 28 species, nine of them occurring in Venezuela. One of these, Haemagogus (Comopostegus) clarki, is a new record for this country. We show here an update of the taxonomic status and the geographical distribution of the genus in Venezuela and the first photographical key using simple terms for non-expert personnel.

Jonathan, Liria; Juan-Carlos, Navarro.

2009-12-01

 
 
 
 
181

Organic geochemistry of deep ground waters from the Palo Duro Basin, Texas: implications for radionuclide complexation, ground-water origin, and petroleum exploration  

International Nuclear Information System (INIS)

This report describes the organic geochemistry of 11 ground-water samples from the Palo Duro Basin, Texas and discusses the implications of their organic geochemical compositions in terms of radionuclide complexation, ground-water origin, and the petroleum potential of two candidate repository sites in Deaf Smith and Swisher Counties. Short-chain aliphatic acid anions are the principal organic constituents present. Stability constant data and simple chemical equilibria calculations suggest that short-chain aliphatic acids are relatively weak complexing agents. The extent of complexation of a typical actinide by selected inorganic ligands present in these brines is expected to far outweigh actinide complexation by the aliphatic acid anions. Various lines of evidence suggest that some portion of the bromide concentrations in the brines is derived from the same source as the short-chain aliphatic acid anions. When the postulated organic components are subtracted from total bromide concentrations, the origins of the Palo Duro brines, based on chloride versus bromide relationships, appear largely consistent with origins based on isotopic evidence. The short-chain aliphatic acid anion content of the Palo Duro brines is postulated to have been much greater in the geologic past. Aliphatic acid anions are but one of numerous petroleum proximity indicators, which consistently suggest a greater petroleum exploration potential for the area surrounding the Swisher County site than the region encompassing the candidate site in Deaf Smith County. Short-chain aliphatic acid anions appear to provide a useful petroleum exploration tool as long as the complex reactions that may dimish their concentrations in ground water are recognized. 71 refs., 10 figs., 10 tabs

182

Lineaments Extraction from Gravity Data by Automatic Lineament Tracing Method in Sidi Bouzid Basin (Central Tunisia): Structural Framework Inference andHydrogeological Implication  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The gravity method may be used in the exploration of deep sedimentary basins. It allows the structuring and the lateral and vertical extent of sedimentary fill to be determined. This study has concerned a qualitative and quantitative gravity analysis of Sidi Bouzid Basin in Central Tunisia. Bouguer anomaly analysis and Gravity data filtering allows us to emphasize the structures affecting the basin. The Automatic Lineament Tracing method helps to quantify the different gravity responses of fa...

Hajer Azaiez; Hakim Gabtni; Imen Bouyahya; Dorra Tanfous; Mourad Bedir

2011-01-01

183

230Th and 231Pa in the Arctic Ocean: implications for particle fluxes and basin-scale Th/Pa fractionation  

Science.gov (United States)

We report concentrations of 231Pa, 230Th, and 232Th measured in unfiltered seawater samples from three stations occupied during the 1994 Arctic Ocean Section; at the western edge of the Canada Basin, in the Makarov Basin, and in the Amundsen Basin at the North Pole. The North Pole data agree well with previously published profiles from the Amundsen Basin. 230Th and 231Pa concentrations in the Canada and Makarov Basins are intermediate between those reported previously for the Beaufort Sea and the Alpha Ridge, reinforcing the observation that scavenging rates are variable in the western and central Arctic and can be as rapid as in the Eurasian Basin and other oceans. Thorium-232 data indicate that relatively high rates of scavenging under the permanent ice cover are driven at least in part by offshore transport of detrital particulate material. A comparison of water column 230Th 231Pa ratios throughout the Arctic suggests that there may be little basin-scale fractionation of these two isotopes in this ocean, contrary to expectations based on the relatively large area of the continental shelves and their contrasts with the deep basins. Models of shelf-basin exchange and 230Th/ 231Pa scavenging, incorporating available constraints, support this suggestion and point to the need for more data from the Arctic shelves, where the imprint of Th/Pa fractionation, if any, is expected be most pronounced.

Edmonds, Henrietta N.; Moran, S. Bradley; Cheng, Hai; Edwards, R. Lawrence

2004-10-01

184

Detrital zircon U-Pb ages of Late Triassic-Late Jurassic deposits in the western and northern Sichuan Basin margin: constraints on the foreland basin provenance and tectonic implications  

Science.gov (United States)

Upper Triassic to Upper Jurassic strata in the western and northern Sichuan Basin were deposited in a synorogenic foreland basin. Ion-microprobe U-Pb analysis of 364 detrital zircon grains from five Late Triassic to Late Jurassic sandstone samples in the northern Sichuan Basin and several published Middle Triassic to Middle Jurassic samples in the eastern Songpan-Ganzi Complex and western and inner Sichuan Basin provide an initial framework for understanding the Late Triassic to Late Jurassic provenance of western and northern Sichuan Basin. For further understanding, the paleogeographic setting of these areas and neighboring hinterlands was constructed. Combined with analysis of depocenter migration, thermochronology and detrital zircon provenance, the western and northern Sichuan Basin is displayed as a transferred foreland basin from Late Triassic to Late Jurassic. The Upper Triassic Xujiahe depocenter was located at the front of the Longmen Shan belt, and sediments in the western Sichuan Basin shared the same provenances with the Middle-Upper Triassic in the Songpan-Ganzi Complex, whereas the South Qinling fed the northern Sichuan Basin. The synorogenic depocenter transferred to the front of Micang Shan during the early Middle Jurassic and at the front of the Daba Shan during the middle-late Middle Jurassic. Zircons of the Middle Jurassic were sourced from the North Qinling, South Qinling and northern Yangtze Craton. The depocenter returned to the front of the Micang Shan again during the Late Jurassic, and the South Qinling and northern Yangtze Craton was the main provenance. The detrital zircon U-Pb ages imply that the South and North China collision was probably not finished at the Late Jurassic.

Luo, Liang; Qi, Jia-Fu; Zhang, Ming-Zheng; Wang, Kai; Han, Yu-Zhen

2014-09-01

185

Anisotropy of magnetic susceptibility of Eocene and Miocene sediments in the Qaidam Basin, Northwest China: Implication for Cenozoic tectonic transition and depocenter migration  

Science.gov (United States)

Cenozoic evolution of the Qaidam basin, especially its paleostress field, can provide a better understanding of the dynamistic process of the northern Tibetan Plateau. Under certain conditions, Anisotropy of Magnetic Susceptibility (AMS) holds great potential for investigating early tectonic events, even where macroscopic and microscopic evidence of deformation is invisible. A basin-scale AMS study of the middle to late Eocene Xiaganchaigou Formation and the early to middle Miocene Xiayoushashan Formation from seven locations was conducted, covering most outcrops of these two formations within the Qaidam basin. In the western Qaidam basin, principal stress directions inferred from AMS ellipsoids consist with those inferred from fold axial traces, while at Eboliang and in the northern Qaidam basin, most principal stress directions reflected by AMS ellipsoids are different from those reflected by fold axial traces. Two epochs of compressive strain have been identified: an early N-S strain no later than Oligocene and a late NE-SW strain since Miocene. The early N-S compression is more intense in the northern Qaidam basin than that in the western Qaidam basin, while the late NE-SW compression, which dominates the modern NW-SE trending fold axial traces, is more intense in the western Qaidam basin than that in the northern Qaidam basin. The stress transfer provides a reasonable explanation for the southeastward migration of the deposition center in the Qaidam basin during Cenozoic. Moreover, the appearance of E-component compression may be in close relationship with the beginning of the left-lateral strike-slip Kunlun Fault or the eastward channel flow to the south of the Kunlun Fault.

Yu, Xiangjiang; Huang, Baochun; Guan, Shuwei; Fu, Suotang; Cheng, Feng; Cheng, Xiang; Zhang, Tuo; Guo, Zhaojie

2014-06-01

186

Basin Structure Beneath the Santa Rosa Plain, Northern California: Implications for Damage Caused by the 1969 Santa Rosa and 1906 San Francisco Earthquakes  

Science.gov (United States)

Regional gravity data in the northern San Francisco Bay region reflect a complex basin configuration beneath the Santa Rosa plain that likely contributed to the significant damage to the city of Santa Rosa caused by the 1969 M 5.6, 5.7 Santa Rosa earthquakes and the 1906 M 7.9 San Francisco earthquake. Inversion of these data indicates that the Santa Rosa plain is underlain by two sedimentary basins about 2 km deep separated by the Trenton Ridge, a shallow west-northwest-striking bedrock ridge west of Santa Rosa. The city of Santa Rosa is situated above the 2 km-wide protruding northeast corner of the southern basin where damage from both the 1969 and 1906 earthquakes was concentrated. Using the gravity-defined basin geometry, ground motion simulations of the 1969 and 1906 earthquakes, two events with opposing azimuths, show enhanced ground motions along the northeastern edge of this corner suggesting that basin-edge effects contributed to the concentration of shaking damage in these events. This indicates that basin edge effects will likely contribute to strong shaking in this area during future earthquakes. Characterization of low-velocity basins and their detailed three-dimensional subsurface geometry is an essential component for characterizing the seismic hazard in the northern San Francisco Bay region and elsewhere.

McPhee, D. K.; Langenheim, V. E.; Hartzell, S.; McLaughlin, R. J.; Aagaard, B. T.; Jachens, R. C.; McCabe, C. A.

2007-12-01

187

High resolution carbon isotope stratigraphy and glendonite occurrences of the Christopher Formation, Sverdrup Basin (Axel Heiberg Island, Canada): implications for mid Cretaceous high latitude climate change  

Science.gov (United States)

Understanding the evolution of Canada's Arctic region, as a crucial component of Earth's climate system, is fundamental to assess short and long-term climate, environmental, and paleogeographic change. However, the stratigraphy and paleoenvironmental evolution of the Cretaceous Arctic is poorly constrained and a detailed bio- and chemostratigraphic correlation of major mid-Cretaceous paleoceanographic turning points such as Oceanic Anoxic Events, cold snaps, and biotic turnovers with key locations of the high- and low latitudes is missing. Here we present for the first time a high resolution bio- and carbon isotope stratigraphy of the Arctic Albian Christopher Formation of the Sverdrup Basin at Glacier Fiord in the southern part of Axel Heiberg Island, Canadian High Arctic. By using these techniques we developed a high temporal framework to record major environmental changes as it is indicated by the occurrence of glendonites and sandstone intervals of our studied Albian succession. The Albian Christopher Formation is a shale dominated marine unit with a thickness of approximately 1200 m. Several transgressive/ regressive cycles can be recognized by prograding shoreface units that break up mudrock deposition. In addition, glendonites are mainly found in the lower part of the Christopher Formation. Glendonites are pseudomorphs of calcite, after the metastable mineral ikaite, and have been often described from high latitude Permian, Jurassic and Cretaceous marine environments from the Canadian Arctic, Spitsbergen and Australia. The formation of glendonites takes place in the uppermost layer of the sediment and requires near-freezing temperatures, high salinity, and orthophosphate-rich bottom water. Although the presence of glendonites implies a range of paleoenvironmental conditions there is a consensus in the scientific literature that they reflect cooler paleoenvironmental conditions. Preliminary bio- and carbon isotope stratigraphic results suggest that the glendonites are concentrated in regular beds during the late Aptian to early Albian of the Christopher Formation supporting the idea of a cold snap (Kemper, 1987; Herrle & Mutterlose 2003; Mutterlose et al. 2009) within the mid-Cretaceous greenhouse period. References Herrle, J.O., Mutterlose, J., 2003. Calcareous nannofossils from the Aptian - early Albian of SE France: Paleoecological and biostratigraphic implications. Cretaceous Research 24, 1-22. Kemper, E., 1987. Das Klima der Kreide-Zeit. Geologisches Jahrbuch 96, 185 pp. Mutterlose, J., Bornemann, A., Herrle, J.O., 2009. The Aptian - Albian cold snap: Evidence for "mid" Cretaceous icehouse interludes. Neues Jahrbuch für Geologie und Palaeontologie, Abhandlungen 252, 217-225.

Herrle, Jens O.; Schröder-Adams, Claudia J.; Galloway, Jennifer M.; Pugh, Adam T.

2013-04-01

188

Recent Advances in Modeling Phosphorus and Nitrogen Delivery to the Gulf of Mexico and Implications for Managing Nutrients n the Mississippi River Basin  

Science.gov (United States)

Although the increased availability of reactive nutrients in past decades has benefited society via food and energy production, the corresponding rise in nutrient loadings to aquatic ecosystems is of particular concern, especially in many estuaries globally where increased nutrient loads have contributed to eutrophic conditions. In the United States, elevated riverine nutrients have contributed to stressed trophic conditions in a majority of estuaries, including the shallow coastal waters of the Louisiana shelf in the northern Gulf of Mexico, where both nitrogen and phosphorus loadings are recognized as contributing to seasonal hypoxic conditions. Advances in geospatial modeling of nitrogen and phosphorus sources and transport in the Mississippi and Atchafalaya River Basins (MARB), as reported in a recent U.S. Geological Survey (USGS) study, provide important information to support improved assessments and management of nutrient loadings to the northern Gulf of Mexico. We summarize the findings of this study and discuss the implications for managing nutrient sources in the MARB. The study reveals important differences in the sources and aquatic transport of nitrogen and phosphorus that affect delivery to the Gulf. Although agricultural sources contribute a majority of the delivered nutrients to the Gulf, corn and soybean cultivation is the largest contributor of nitrogen whereas phosphorus originates primarily from animal manure on pasture and rangelands. Atmospheric deposition is the second leading source of nitrogen, with urban sources contributing relatively small quantities of both nutrients. Furthermore, we find that both nitrogen and phosphorus delivery to the Gulf is controlled by hydrological and biogeochemical processes (e.g., water travel time, denitrification, storage) that scale with stream size, although phosphorus also displays large local- and regional-scale differences in delivery caused by reservoir trapping. The importance of these processes underscores the need to account for the nonlinear interactions of aquatic transport processes with watershed nutrient sources in developing efficient nutrient reduction strategies for the MARB. Such strategies will need to consider a diversity of nutrient sources, including the different effects of agricultural production systems on nitrogen and phosphorus runoff to streams, the contributions of atmospheric nitrogen, and improved management of phosphorus sources downstream from reservoirs.

Alexander, R. B.; Smith, R. A.; Schwarz, G. E.; Boyer, E. W.; Nolan, J. V.; Brakebill, J. W.

2008-12-01

189

Hydrogeologic Characteristics of the St. Croix River Basin, Minnesota and Wisconsin: Implications for the Susceptibility of Ground Water to Potential Contamination  

Science.gov (United States)

Population growth in the St. Croix River Basin in Minnesota and Wisconsin has intensified concerns of county resource managers and the National Park Service, which is charged with protecting the St. Croix National Scenic Riverway, about the potential for ground-water contamination in the basin. This report describes a previously developed method that was adapted to illustrate potential ground-water-contamination susceptibility in the St. Croix River Basin. The report also gives an estimate of ground-water-residence time and surface-water/ground-water interaction as related to natural attenuation and movement of contaminants in five tributary basins. A ground-water-contamination-susceptibility map was adapted from a state-wide map of Wisconsin to the St. Croix River Basin by use of well-driller construction records and regional maps of aquifer properties in Minnesota and Wisconsin. Measures of various subsurface properties were combined to generate a spatial index of susceptibility. The subjective index method developed for the State of Wisconsin by Schmidt (1987) was not derived from analyses of water-quality data or physical processes. Nonetheless, it was adapted for this report to furnish a seamless map across state boundaries that would be familiar to many resource managers. Following this method, areas most susceptible to contamination appear to have coarse-grained sediments (sands or gravels) and shallow water tables or are underlain by carbonate-bedrock aquifers. The least susceptible areas appear to have fine-grained sediments and deep water tables. If an aquifer becomes contaminated, the ground-water-residence time can affect potential natural attenuation along the ground-water-flow path. Mean basin ground-water-residence times were computed for the Apple, Kettle, Kinnickinnic, Snake and Sunrise River Basins, which are tributary basins to the St. Croix Basin, by use of average aquifer properties of saturated thickness, porosity, and recharge rates. The Apple River Basin had the shortest mean ground-water-residence times (20-120 years), owing largely to the moderate saturated thickness and high recharge rate in the basin. The Kinnickinnic and Sunrise River Basins had the longest mean residence times (60-350 and 70-390 years, respectively) chiefly because of the relatively large saturated thickness of the basins. Owing to limitations of the residence-time calculations, actual ground-water-residence times will vary around the mean values within each basin and may range from days or weeks in karst carbonate aquifers to millennia in deep confined sandstone aquifers. Areas of relatively short residence time (less than the median residence time in each basin) were identified by use of ground-water-flow models for each of the five tributary basins. Results of simulations show that these areas, in which contaminants may have relatively less time for natural attenuation along the short flow paths, generally occur near streams and rivers where ground water discharges to the surface. Finally, the ground-water-flow models were used to simulate ground-water/surface-water interaction in the five tributary basins. Results of simulations show that some lakes and reservoirs leak surface water into the ground-water-flow system on their downgradient side, where the surface-water outflow has been restricted by a dam or a naturally constricted outlet. These locations are noteworthy because contaminated surface waters could potentially enter the ground-water-flow system at these locations.

Juckem, Paul F.

2007-01-01

190

Lineaments Extraction from Gravity Data by Automatic Lineament Tracing Method in Sidi Bouzid Basin (Central Tunisia: Structural Framework Inference andHydrogeological Implication  

Directory of Open Access Journals (Sweden)

Full Text Available The gravity method may be used in the exploration of deep sedimentary basins. It allows the structuring and the lateral and vertical extent of sedimentary fill to be determined. This study has concerned a qualitative and quantitative gravity analysis of Sidi Bouzid Basin in Central Tunisia. Bouguer anomaly analysis and Gravity data filtering allows us to emphasize the structures affecting the basin. The Automatic Lineament Tracing method helps to quantify the different gravity responses of faults located in the shallow and deep sedimentary sections and in the basement. The elaborated structural map of the study area constitutes a useful document for rationalizing the future groundwater exploration in the arid area of central Tunisia since it shows faults dipping and deep hydrogeologic sub-basin delineation.

Hajer Azaiez

2011-08-01

191

Geochemical Evolution of Groundwater in the Medicine Lodge Creek Drainage Basin with Implications for the Eastern Snake River Plain Aquifer, Eastern Idaho  

Science.gov (United States)

The eastern Snake River Plain aquifer (ESRPA) is an unconfined, continuous aquifer located in a northeast-trending structural basin filled with basaltic lava flows and sedimentary interbeds in eastern Idaho. The ESPRA is not an inert transport system, as it acts as both a sink and source for solutes found in the water. More than 90% of the water recharged naturally to the ESRPA is from the surrounding mountain drainage basins. Consequently, in order to understand the natural geochemistry of water within the ESRPA, the chemistry of the groundwater from the mountain drainage basins must be characterized and the processes that control the chemistry need to be understood. The U.S. Geological Survey, in cooperation with the U.S. Department of Energy and Idaho State University, has been studying these mountain drainage basins to help understand the movement of waste solutes in the ESRPA at the Idaho National Laboratory (INL) in eastern Idaho. This study focuses on the Medicine Lodge Creek drainage basin, which originates in the Beaverhead Mountains, extends onto the eastern Snake River Plain, and contributes recharge to the ESRPA beneath the INL as underflow along the northeastern INL boundary. Water and rock samples taken from the Medicine Lodge Creek drainage basin were analyzed to better understand water/rock interactions occurring in this system and to define the groundwater geochemistry of this drainage basin. Water samples were collected at 10 locations in the drainage basin during June 2012: 6 groundwater wells used for agricultural irrigation or domestic use and 4 springs. These water samples were analyzed for major ions, nutrients, trace metals, isotopes, and dissolved gasses. Samples of rock representative of the basalt, rhyolite, and sediments that occur within the drainage basin also were collected. These samples were analyzed using x-ray diffraction and petrographic study to determine the mineralogical constituents of the rock and the presence and composition of alteration products. The lithologic variability in this area leads to differing water-rock interactions occurring in different parts of the drainage basin. Anthropogenic influences also affect the water; at the far downgradient end of the drainage basin, increased levels of chloride and sulfate in the groundwater suggest an increased influence of irrigation recharge. Results from both water and rock analyses are combined in geochemical modeling software to determine plausible reactions that occur in groundwater collected at the sampling sites.

Ginsbach, M. L.; Rattray, G. W.; McCurry, M. O.; Welhan, J. A.

2012-12-01

192

Sedimentation record in the Konkan-Kerala Basin: implications for the evolution of the Western Ghats and the Western Indian passive margin  

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The Konkan and Kerala Basins constitute a major depocentre for sediment from the onshore hinterland of Western India and as such provide a valuable record of the timing and magnitude of Cenozoic denudation along the continental margin. This paper presents an analysis of sedimentation in the Konkan-Kerala Basin, coupledwith a mass balance study, and numerical modelling of flexural responses to onshore denudational unloading and o¡shore sediment loading in order to test competing conceptual mo...

Campanile, D.; Nambiar, C. G.; Bishop, P.; Widdowson, M.; Brown, R.

2007-01-01

193

Spatial and seasonal responses of precipitation in the Ganges and Brahmaputra river basins to ENSO and Indian Ocean dipole modes: implications for flooding and drought  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We evaluated the spatial and temporal responses of precipitation in the basins as modulated by the El Niño Southern Oscillation (ENSO) and Indian Ocean (IO) dipole modes using observed precipitation records at 43 stations across the Ganges and Brahmaputra basins from 1982 to 2010. Daily observed precipitation records were extracted from Global Surface Summary of the Day dataset and spatial and monthly anomalies were computed. The anomalies were averaged for...

Pervez, M. S.; Henebry, G. M.

2014-01-01

194

Formation of South Pole-Aitken Basin as the Result of an Oblique Impact: Implications for Melt Volume and Source of Exposed Materials  

Science.gov (United States)

The South Pole-Aitken Basin (SPA) is the largest, deepest, and oldest identified basin on the Moon and contains surfaces that are unique due to their age, composition, and depth of origin in the lunar crust [1-3] (Figure 1). SPA has been a target of interest as an area for robotic sample return in order to determine the age of the basin and the composition and origin of its interior [3-6]. As part of the investigation into the origin of SPA materials there have been several efforts to estimate the likely provenance of regolith material in central SPA [5, 6]. These model estimates suggest that, despite the formation of basins and craters following SPA, the regolith within SPA is dominated by locally derived material. An assumption inherent in these models has been that the locally derived material is primarily SPA impact-melt as opposed to local basement material (e.g. unmelted lower crust). However, the definitive identification of SPA derived impact melt on the basin floor, either by remote sensing [2, 7] or via photogeology [8] is extremely difficult due to the number of subsequent impacts and volcanic activity [3, 4]. In order to identify where SPA produced impact melt may be located, it is important to constrain both how much melt would have been produced in a basin forming impact and the likely source of such melted material. Models of crater and basin formation [9, 10] present clear rationale for estimating the possible volumes and sources of impact melt produced during SPA formation. However, if SPA formed as the result of an oblique impact [11, 12], the volume and depth of origin of melted material could be distinct from similar material in a vertical impact [13].

Petro, N. E.

2012-01-01

195

Coupled heat and fluid flow modeling of the Carboniferous Kuna Basin, Alaska: Implications for the genesis of the Red Dog Pb-Zn-Ag-Ba ore district  

Science.gov (United States)

The Red Dog deposit is a giant 175 Mton (16% Zn, 5% Pb), shale-hosted Pb-Zn-Ag-Ba ore district situated in the Carboniferous Kuna Basin, Western Brooks Range, Alaska. These SEDEX-type ores are thought to have formed in calcareous turbidites and black mudstone at elevated sub-seafloor temperatures (120-150??C) within a hydrogeologic framework of submarine convection that was structurally organized by large normal faults. The theory for modeling brine migration and heat transport in the Kuna Basin is discussed with application to evaluating flow patterns and heat transport in faulted rift basins and the effects of buoyancy-driven free convection on reactive flow and ore genesis. Finite element simulations show that hydrothermal fluid was discharged into the Red Dog subbasin during a period of basin-wide crustal heat flow of 150-160 mW/m2. Basinal brines circulated to depths as great as 1-3 km along multiple normal faults flowed laterally through thick clastic aquifers acquiring metals and heat, and then rapidly ascended a single discharge fault zone at rates ??? 5 m/year to mix with seafloor sulfur and precipitate massive sulfide ores. ?? 2003 Elsevier Science B.V. All rights reserved.

Garven, G.; Raffensperger, J.P.; Dumoulin, J.A.; Bradley, D.A.; Young, L.E.; Kelley, K.D.; Leach, D.L.

2003-01-01

196

Basin structure beneath the Santa Rosa Plain, Northern California: Implications for damage caused by the 1969 Santa Rosa and 1906 San Francisco earthquakes  

Science.gov (United States)

Regional gravity data in the northern San Francisco Bay region reflect a complex basin configuration beneath the Santa Rosa plain that likely contributed to the significant damage to the city of Santa Rosa caused by the 1969 M 5.6, 5.7 Santa Rosa earthquakes and the 1906 M 7.9 San Francisco earthquake. Inversion of these data indicates that the Santa Rosa plain is underlain by two sedimentary basins about 2 km deep separated by the Trenton Ridge, a shallow west-northwest-striking bedrock ridge west of Santa Rosa. The city of Santa Rosa is situated above the 2-km-wide protruding northeast corner of the southern basin where damage from both the 1969 and 1906 earthquakes was concentrated. Ground-motion simulations of the 1969 and 1906 earthquakes, two events with opposing azimuths, using the gravity-defined basin surface, show enhanced ground motions along the northeastern edge of this corner, suggesting that basin-edge effects contributed to the concentration of shaking damage in this area in the past and may also contribute to strong shaking during future earthquakes.

McPhee, D.K.; Langenheim, V.E.; Hartzell, S.; McLaughlin, R.J.; Aagaard, B.T.; Jachens, R.C.; McCabe, C.

2007-01-01

197

Evolution of the late Quaternary San Gregorio Magno tectono-karstic basin (southern Italy) inferred from geomorphological, tephrostratigraphical and palaeoecological analyses: tectonic implications  

Science.gov (United States)

The Pantano di San Gregorio Magno is a 4.7 km2 large tectono-karstic basin located in the axial belt of the Southern Apennines, an area affected by intense seismicity. The basin was formed in the Middle Pleistocene and is presently undissected. It is filled by lacustrine sediments (clays, silts and pyroclastic sands) passing laterally into alluvial fan deposits. Geomorphological investigations were integrated with tephrostratigraphical, palynological and palaeoecological analyses of a 61 m thick core (not reaching the bedrock). The multiproxy analysis of the S. Gregorio Magno record shows that, over the last 200k yr, the basin hosted a freshwater lake with an oscillating level. Age constraints provided by the tephrostratigraphic record allowed estimation of the sedimentation rate, which varied strongly through time. Evolution of the basin resulted from the complex combination of tectonic subsidence, karst processes and changing amounts of sedimentary inputs. The latter was influenced by allogenic contributions related both to primary and reworked volcanoclastic inputs and was climate-driven. The overall evidence, which indicates that in the long-term the accumulation rate substantially counterbalanced the accommodation space created by faulting, suggests that the basin evolution was also modulated by changing subsidence rates. Copyright

Aiello, G.; Ascione, A.; Barra, D.; Munno, R.; Petrosino, P.; Russo Ermolli, E.; Villani, F.

2007-03-01

198

Shale Tectonics in the Continental Slope and Rise Regions of Krishna-Godavari Basin, Bay of Bengal: Implication in Gas-Hydrate Exploration  

Science.gov (United States)

Increased oil and gas exploration activity has led to a detailed investigation of the deep offshore and adjacent slope regions of Mahanadi, Krishna-Godavari (KG) and Cauvery basins, which are categorized as promising petroliferous basins along the eastern continental margin of India. The high sedimentation rate, thick sedimentary prism, and deeply buried mobile shale strata favor shale tectonics in KG basin which is manifested in the form of large extensional growth faults in the shelf and upper slope regions, and mud diapirs and toe-thrusts in the deep offshore regions of KG basin. Multichannel seismic reflection data depict the acoustic signatures akin to imbricate thrust faults, escarpment, mud diapirs, and intraslope basins in the KG deep offshore. The multibeam swath bathymetry mosaic and the sub-bottom profiler (SBP) datasets confirm their surface and subsurface manifestations. Some of the structural elements are buried under large scale mass transport deposits. The shallow deposits associated with the shale tectonics structures like sliding/slumping deposits, debrites, sediment creep deposits, turbidites, pelagites/hemipelagites, and interlayered debrites and turbidites are inferred from SBP echo facies analysis and microtopography. Shallow structures associated with shale tectonics, and their spatial distribution is a precursor in understanding the subsurface occurrence of gas hydrate deposits. We believe that the shale tectonics structures are largely responsible for the distribution of gas hydrate deposits in KG-offshore basin, and the inferred toe-thrust and mud diapiric zones are favorable locales for gas hydrate accumulation. The results of recent drilling/coring in the KG-offshore (May-Aug, 2006) show the presence of thick accumulation of gas hydrate in the vicinity of the region associated with mud diapiric and toe-thrust fault zones. Further, the study of geophysical data and analysis of long sediment cores collected onboard Marion Dufresne (May, 2007) in the mud diapiric and toe-thrust regions suggest paleo-expulsion of methane and sulfidic fluid from the seafloor. However, the cores collected in the intraslope basin do not show any indications of methane venting. We prepared a regional tectonics map that illustrates the distribution of shale structures and shallow depositional environments. This map may serve as a better constraint in understanding the genesis and occurrence of gas hydrate deposits in KG-basin.

Dewangan, P.; Ramprasad, T.; Ramana, M. V.; Mazumdar, A.; Desa, M.; Badasab, F.

2008-12-01

199

Late Mesozoic to Paleogene stratigraphy of the Salar de Atacama Basin, Antofagasta, Northern Chile: Implications for the tectonic evolution of the Central Andes  

Science.gov (United States)

The Salar de Atacama basin, the largest "pre-Andean" basin in Northern Chile, was formed in the early Late Cretaceous as a consequence of the tectonic closure and inversion of the Jurassic-Early Cretaceous Tarapacá back arc basin. Inversion led to uplift of the Cordillera de Domeyko (CD), a thick-skinned basement range bounded by a system of reverse faults and blind thrusts with alternating vergence along strike. The almost 6000-m-thick, upper Cretaceous to lower Paleocene sequences (Purilactis Group) infilling the Salar de Atacama basin reflects rapid local subsidence to the east of the CD. Its oldest outcropping unit (Tonel Formation) comprises more than 1000 m of continental red sandstones and evaporites, which began to accumulate as syntectonic growth strata during the initial stages of CD uplift. Tonel strata are capped by almost 3000 m of sandstones and conglomerates of western provenance, representing the sedimentary response to renewed pulses of tectonic shortening, which were deposited in alluvial fan, fluvial and eolian settings together with minor lacustrine mudstone (Purilactis Formation). These are covered by 500 m of coarse, proximal alluvial fan conglomerates (Barros Arana Formation). The top of the Purilactis Group consists of Maastrichtian-Danian alkaline lava and minor welded tuffs and red beds (Cerro Totola Formation: 70-64 Ma K/Ar) deposited during an interval of tectonic quiescence when the El Molino-Yacoraite Late Cretaceous sea covered large tracts of the nearby Altiplano-Puna domain. Limestones interbedded with the Totola volcanics indicate that this marine incursion advanced westwards to reach the eastern CD slope. CD shortening in the Late Cretaceous was accompanied by volcanism and continental sedimentation in fault bounded basins associated to strike slip along the north Chilean magmatic arc to the west of the CD domain, indicating that oblique plate convergence prevailed during the Late Cretaceous. Oblique convergence seems to have been resolved into a highly partitioned strain system where margin-parallel displacements along the thermally weakened arc coexisted with margin-orthogonal shortening associated with syntectonic sedimentation in the Salar de Atacama basin. A regionally important Early Paleocene compressional event is echoed, in the Salar de Atacama basin by a, distinctive, angular unconformity which separates Paleocene continental sediments from Purilactis Group strata. The basin also records the Eocene-Early Oligocene Incaic transpressional episode, which produced, renewed uplift in the Cordillera de Domeyko and triggered the accumulation of a thick blanket of syntectonic gravels (Loma Amarilla Formation).

Mpodozis, Constantino; Arriagada, César; Basso, Matilde; Roperch, Pierrick; Cobbold, Peter; Reich, Martin

2005-04-01

200

Coeval Lower Miocene subsidence of the Eisenstadt Basin and relative updoming of its Austroalpine frame: implications from high-resolution geophysics at the Oslip section (Northern Burgenland, Austria)  

Science.gov (United States)

A fault system southeast of Eisenstadt was investigated with high-resolution geophysics using electric resistivity tomography, seismics and gravimetry. The St. Margarethen Fault separates the Neogene succession of the Eisenstadt Basin from the north south-trending Rust Range, which belongs to the Austroalpine frame. The interpretation of profiles down to a depth of 350 m derived from reflection and refraction seismics combined with the density model along the Oslip road section clearly reveals a listric fault, which dips westward towards the Eisenstadt Basin. Bed thickness of growth-strata regularly increases from west to east, and normal fault drags visible in the seismic profile west of the St. Margarethen Fault allow for interpreting this structure as a hanging-wall syncline. Thickness distribution of Neogene deposits reveals that the Eisenstadt Basin can be interpreted as a half-graben bounded by the listric St. Margarethen normal fault, which developed at the western flank of Rust Range. The subsidence of the Eisenstadt Basin during Lower to Middle Sarmatian times was accompanied by concurrent updoming of the Rust Range of at least 70 m. For the mechanism of the updoming of the Rust Range footwall uplift during hanging wall subsidence is inferred.

Häusler, Hermann; Scheibz, Jürgen; Chwatal, Werner; Kohlbeck, Franz

2014-11-01

 
 
 
 
201

U-Pb geochronology of the Raglan gabbro belt, Central Metasedimentary Belt, Ontario: implications for an ensialic marginal basin in the Grenville Orogen  

International Nuclear Information System (INIS)

The Raglan gabbro belt of the Ontario Grenville Orogen is coincident with the top of the Central Metasedimentary Belt boundary thrust zone, a major mid-crustal shear zone separating the Central Gneiss Belt in the footwall from the Central Metasedimentary Belt in the hanging wall. It has been suggested that the gabbros making up the belt are coeval, that they formed in a marginal basin within the Central metasedimentary Belt, and that they formed a horizon of rheologically stiff material that controlled the localization of the top of the boundary thrust zone during its initiation as the marginal basin closed at ca. 1190 Ma. U-Pb zircon dating of plutons within the Raglan gabbro belt was undertaken to test the coeval nature of intrusions in the belt. Magmatic crystallization ages for three of the gabbros fall in the range 1246-1227 Ma, and a fourth yields a minimum age of ca. 1175 Ma. The results are permissive of a common origin for the gabbros and allow that the Raglan gabbro belt may have been related to the marginal basin, at least with respect to the later stages of its evolution. Inherited 1440-1301 Ma zircons in the gabbros suggest interaction with underlying Central Gneiss Belt crust during magmatism and support an ensialic marginal-basin model, as opposed to an island-arc model, for the evolution of the northwestern part of the Central Metasedimentary Belt. (author). 57 refs., 1 tab., 5 figs

202

Seismic stratigraphic analysis of the Cenozoic sediments in the NW Faroe Shetland BasinImplications for inherited structural control of sediment distribution  

DEFF Research Database (Denmark)

The post-basalt strata in the Faroese area have been investigated based on interpretation of 2D and 3D reflection seismic data. The post-basalt package is divided into 5 units which have led to the constructions of 6 structural maps and 5 thickness maps. Within the 5 units 12 prograding sediment bodies have been identified. Based on the interpretation it is possible to obtain an overview during time of the location of depocentres and direction of prograding units. Within Eocene time the depocentre was placed in the central part of the basin and the sediment influx was mostly from south and southwest. During Oligocene–Pliocene time the sediment influx was from north and northwest and the depocentre had moved in a westward direction closer to the Faroe Platform area. Emplacement of the Cenozoic sediments in the Faroese sector of the Faroe-Shetland Basin is controlled by thermal subsidence of the basin, and local uplift of sediment source areas. Reactivation of older, Paleozoic and Mesozoic, structural elementsseem to control the sediment path way and restrict the depositional areas. Various structural elements being re-activated at different times caused considerable structural complexity. Understanding the older, structural elements and their control on sedimentation is a potential tool for understanding deviations from “normal” thermal subsidence and for predicting the prospectivity in the post-basalt succession in the Faroe-Shetland Basin.

Ólavsdóttir, Jana; Andersen, Morten Sparre

2013-01-01

203

Abrupt change in the rate of hemipelagic sedimentation at the Late Miocene (~11 Ma) in the Shikoku Basin: implications for the tectonic history of the southwestern Japan  

Science.gov (United States)

An abrupt change in the rate of hemipelagic sedimentation occurred at the Late Miocene (11 Ma) in the Shikoku Basin of the western Pacific region, which is evident from both biostratigraphic and paleomagnetic age constraints. Hemipelagic mudstones are deposits produced mainly by terrestrial weathering, transported into oceans by river flows, and left continental shelves by various diffusion processes such as stirring by waves and ocean currents. Generally, they form even-thickness drapes of the deep-sea basins with nearly constant rate of sediment accumulation. However, we discovered that there is a substantial decrease in the accumulation rate of hemipelagic mud at the Late Miocene (11 Ma) in the Shikoku Basin. The change of sedimentation rate can be observed in the entire region of the Shikoku Basin. IODP Sites C0011 and C0012, ODP Sites 808, 1173 and 1174, and DSDP Sites 442 and 444 were examined, and it was revealed that this change of rate of hemipelagic sedimentation also occurred in the Amatsu Formation of the Miura Group that is a fore-arc basin deposit exposed in the Boso Peninsula, Japan, suggesting that the rate of clay mineral production decreased in the widespread regions in the SW Japan Arc. This significant decrease of the rate of sediment production for the hemipelagites suggests the possibility of some fundamental paleoenvironmental change in the Shikoku Basin and/or a significant tectonic event that occurred in the SW Japan Arc such as a change from anomalous near-trench volcanism to forearc cooling. A numerical model of hemipelagic mud transport using a diffusion equation suggests that the observed decrease of rate of hemipelagic sedimentation can be explained by a drop of the rate of fine-sediment production on the SW Japan Arc to one-half at 11 Ma. Previous studies on a fission-track thermochronology have suggested that the accretionary complex of the SW Japan was rapidly uplifted during the late Miocene (15-10 Ma), and this uplift probably caused rapid denudation of the accretionary complex and metamorphic rocks. Thus, the drop of the rate of hemipelagic sedimentation at the Shikoku Basin may corresponds to the cessation of this tectonic event.

Naruse, H.; Pickering, K. T.; Scudder, R. P.; Kutterolf, S.; Labanieh, S.; Wu, H.; Oda, H.; Zhao, X.; Chiyonobu, S.; Govil, P.; Nakajima, T.; Underwood, M.; Saito, S.; Kubo, Y.; Kameo, K.; Shipboard Scientific Party, I.

2010-12-01

204

Mesozoic inversion in southeastern parts of the Neuquén Basin, west-central Argentina: Implications for tectonic deformation and stratigraphic development across the Andean foreland of Argentina  

Science.gov (United States)

The Neuquén Basin of west-central Argentina is a segment of the Andean foreland that has significant structural complexity due to protracted intraforeland deformation between Late Triassic to Recent time. Some structural features in the Neuquén Basin predate the main phases of the Andean orogeny although these structures were reactivated later and influenced basin configuration during the foreland-basin stage. The most conspicuous of these structures is the Huincul Arch, a 200-km-long right-lateral shear zone that was most active during Jurassic to Cretaceous time. Inversion structures along the Huincul Arch are associated with a restraining bend along the main east-west trending shear zone that cuts across the Argentine foreland. An extensive seismic and borehole data set was analyzed to evaluate the styles and intensity of Mesozoic foreland deformation in an approximately 10,000 sq km area north of the Huincul Arch. Transpressional and transtensional deformation is broadly distributed across the study area and other parts of the Neuquén foreland, although a series of inversion structures (e.g., Sierra Barrosa and Aguada Toledo anticlines) reflect more intense, localized deformation. These structures are the result of inversion of Late Triassic half-grabens and produced fault-propagation folds that affected the post-rift fill up to the Upper Jurassic (Tithonian). The most significant reactivation along the Huincul Arch south of our study area occurred during Kimmeridgian (Late Jurassic) time along the main displacement zone. To the north, however, significant inversion was slightly younger and occurred during and after deposition of the Tithonian to Berriasian (latest Jurassic-earliest Cretaceous) Vaca Muerta and Quintuco formations. Thus, early phases of tectonic inversion across the Argentine foreland were diachronous and likely reflect an accumulation of strain along the Huincul Arch was necessary before additional strain could propagate northward into our study area. Seismic-stratigraphic analyses also show that the growing inversion structures created bathymetric perturbations that affected sediment dispersal and stratigraphic development north of the Huincul Arch during deposition of the Vaca Muerta-Quintuco interval. This study contributes to the understanding of Pre-Andean deformation in the Neuquén Basin. 3D seismic data across the study area also provides a unique opportunity to investigate the geometries and kinematic history of inversion across the Andean foreland, as well as to evaluate tectonic controls on Mesozoic stratigraphic development in the poorly understood Northern Sub-basin of the Neuquén Basin.

Grimaldi, G. O.; Dorobek, S. L.

2004-12-01

205

Gas desorption and adsorption isotherm studies of coals in the Powder River basin, Wyoming and adjacent basins in Wyoming and North Dakota  

Science.gov (United States)

The U.S. Geological Survey (USGS), in cooperation with the State Office, Reservoir Management Group (RMG), of the Bureau of Land Management (BLM) in Casper (Wyoming), investigated the coalbed methane resources (CBM) in the Powder River Basin, Wyoming and Montana, from 1999 to the present. Beginning in late 1999, the study also included the Williston Basin in Montana and North and South Dakota and Green River Basin and Big Horn Basin in Wyoming. The rapid development of CBM (referred to as coalbed natural gas by the BLM) during the early 1990s, and the lack of sufficient data for the BLM to fully assess and manage the resource in the Powder River Basin, in particular, gave impetus to the cooperative program. An integral part of the joint USGS-BLM project was the participation of 25 gas operators that entered individually into confidential agreements with the USGS, and whose cooperation was essential to the study. The arrangements were for the gas operators to drill and core coal-bed reservoirs at their cost, and for the USGS and BLM personnel to then desorb, analyze, and interpret the coal data with joint funding by the two agencies. Upon completion of analyses by the USGS, the data were to be shared with both the BLM and the gas operator that supplied the core, and then to be released or published 1 yr after the report was submitted to the operator.

Stricker, Gary D.; Flores, Romeo M.; McGarry, Dwain E.; Stillwell, Dean P.; Hoppe, Daniel J.; Stillwell, Cathy R.; Ochs, Alan M.; Ellis, Margaret S.; Osvald, Karl S.; Taylor, Sharon L.; Thorvaldson, Marjorie C.; Trippi, Michael H.; Grose, Sherry D.; Crockett, Fred J.; Shariff, Asghar J.

2006-01-01

206

Regional Survey of Structural Properties and Cementation Patterns of Fault Zones in the Northern Part of the Albuquerque Basin, New Mexico - Implications for Ground-Water Flow  

Science.gov (United States)

Motivated by the need to document and evaluate the types and variability of fault zone properties that potentially affect aquifer systems in basins of the middle Rio Grande rift, we systematically characterized structural and cementation properties of exposed fault zones at 176 sites in the northern Albuquerque Basin. A statistical analysis of measurements and observations evaluated four aspects of the fault zones: (1) attitude and displacement, (2) cement, (3) lithology of the host rock or sediment, and (4) character and width of distinctive structural architectural components at the outcrop scale. Three structural architectural components of the fault zones were observed: (1) outer damage zones related to fault growth; these zones typically contain deformation bands, shear fractures, and open extensional fractures, which strike subparallel to the fault and may promote ground-water flow along the fault zone; (2) inner mixed zones composed of variably entrained, disrupted, and dismembered blocks of host sediment; and (3) central fault cores that accommodate most shear strain and in which persistent low- permeability clay-rich rocks likely impede the flow of water across the fault. The lithology of the host rock or sediment influences the structure of the fault zone and the width of its components. Different grain-size distributions and degrees of induration of the host materials produce differences in material strength that lead to variations in width, degree, and style of fracturing and other fault-related deformation. In addition, lithology of the host sediment appears to strongly control the distribution of cement in fault zones. Most faults strike north to north-northeast and dip 55? - 77? east or west, toward the basin center. Most faults exhibit normal slip, and many of these faults have been reactivated by normal-oblique and strike slip. Although measured fault displacements have a broad range, from 0.9 to 4,000 m, most are <100 m, and fault zones appear to have formed mainly at depths less than 1,000 m. Fault zone widths do not exceed 40 m (median width = 15.5 m). The mean width of fault cores (0.1 m) is nearly one order of magnitude less than that of mixed zones (0.75 m) and two orders of magnitude less than that of damage zones (9.7 m). Cements, a proxy for localized flow of ancient ground water, are common along fault zones in the basin. Silica cements are limited to faults that are near and strike north to northwest toward the Jemez volcanic field north of the basin, whereas carbonate fault cements are widely distributed. Coarse sediments (gravel and sand) host the greatest concentrations of cement within fault zones. Cements fill some extension fractures and, to a lesser degree, are concentrated along shear fractures and deformation bands within inner damage zones. Cements are commonly concentrated in mixed zones and inner damage zones on one side of a fault and thus are asymmetrically distributed within a fault zone, but cement does not consistently lie on the basinward side of faults. From observed spatial patterns of asymmetrically distributed fault zone cements, we infer that ancient ground-water flow was commonly localized along, and bounded by, faults in the basin. It is apparent from our study that the Albuquerque Basin contains a high concentration of faults. The geometry of, internal structure of, and cement and clay distribution in fault zones have created and will continue to create considerable heterogeneity of permeability within the basin aquifers. The characteristics and statistical range of fault zone features appear to be predictable and consistent throughout the basin; this predictability can be used in ground-water flow simulations that consider the influence of faults.

Minor, Scott A.; Hudson, Mark R.

2006-01-01

207

Palynology of Lower Palaeogene (Thanetian-Ypresian) coastal deposits from the Barmer Basin (Akli Formation, Western Rajasthan, India): palaeoenvironmental and palaeoclimatic implications  

Energy Technology Data Exchange (ETDEWEB)

The 32-m thick sedimentary succession of the Paleocene-Eocene Akli Formation (Barmer basin, Rajasthan, India), which is exposed in an open-cast lignite mine, interbed several lignite seams that alternate with fossiliferous carbonaceous clays, green clays and widespread siderite bands and chert nodules. The palynofloral assemblages consist of spore, pollen and marine dinoflagellate cysts that indicate a Thanetian to Ypresian age. The assemblage is dominated by angiospermic pollen and specimens showing affinity with the mangrove Palm Nypa are also very abundant. The Nypa-like pollen specimens exhibit a wide range of morphological variation, some of the recorded morphotypes being restricted to this Indian basin. Preponderance of these pollen taxa indicates that the sediments were deposited in a coastal swamp surrounded by thick, Nypa-dominated mangrove vegetation. The dispersed organic matter separated from macerated residues indicates the dominance of anoxic conditions throughout the succession, although a gradual transition to oxic conditions is recorded in the upper part.

Tripathi, S.K.M.; Kumar, M.; Srivastava, D. [Birbal Sahni Instititue of Paleobotany, Lucknow (India)

2009-03-15

208

Sedimentology and petrography of mass-emplaced limestone (Orahiri Limestone) on a late Oligocene shelf, western North Island, and tectonic implications for eastern margin development of Taranaki Basin  

International Nuclear Information System (INIS)

The Te Kuiti Group in North Wanganui Basin, North Island, New Zealand, of Oligocene - earliest Miocene (Whaingaroan-Waitakian) age, is dominated by calcareous siltstone, calcareous sandstone, and skeletal limestone. Exposures in the southwestern corner of the basin at Awakino Tunnel are distinctive because, compared with elsewhere, the group is generally thicker (>300 m), has strong dips (25-45 degrees E), exhibits an up-section decrease in the amount of dip, and the capping Orahiri Limestone includes several thick (up to 3 m) mass-emplaced units containing a variety of 1-10 cm sized calcareous lithoclasts of older Te Kuiti Group rocks. Petrographic and ?18O and ?13C data suggest that the source deposits of these lithoclasts were cemented at relatively shallow subsurface burial depths (100-500 m) before their uplift and erosion. The lithoclasts so produced were rounded by abrasion in shoal water, often bored profusely by pholad bivalves, and sometimes encrusted by coralline algae, before being periodically mass-emplaced from west to east onto a shelf accumulating coeval Orahiri Limestone lithofacies now in the vicinity of Awakino Tunnel. Pressure-dissolution during subsequent burial provided the main source of calcite cement in the host Orahiri Limestone, mainly at moderate burial depths of 500-1000 m, according to ?18O data. The source region for the lithoclasts probably lay west of Awakino Tunnel and corresponds to the southern pannel and corresponds to the southern part of the basement Herangi High, which otherwise separates North Wanganui Basin from Taranaki Basin, but must have been submarine and accumulating Te Kuiti Group-equivalent calcareous facies during the early Oligocene (Early Whaingaroan, 36-32 Ma). Uplift of this depocentre was accompanied by synsedimentary eastward tilting of the Te Kuiti Group strata already deposited immediately east of Herangi High, contributing to the dips now measured at Awakino Tunnel. Inversion and tilting of the high began in the Late Whaingaroan, after 32 Ma ago, concomitant with the onset of rapid subsidence along eastern Taranaki Basin margin directly west of Herangi High. Uplift continued throughout the Duntroonian (28-24 Ma), when erosion and mass-emplacement supplied the abundant calcareous lithoclasts in the Orahiri Limestone, and into the Waitakian (24-22 Ma), when erosion possibly expanded onto parts of the shelf, stripping out sections of the overlying Otorohanga Limestone, the topmost formation in the group. The uplift and partial emergence of Herangi High is viewed as a topographic response to the initiation of basement over thrusting from the east along the Taranaki Fault Zone. The resultant loading evolved a carbonate foredeep in eastern Taranaki Basin during the Duntroonian-Waitakian. This late Oligocene phase of deformation developed in a mildly compressive regime, which corresponds to a time of proto-plate boundary development through New Zealand that preceded propagation of the continuous and more localised present plate boundary through the country at 22-23 Ma. The latter was marked in both North Wanganui Basin and Taranaki Basin by rejuvenated, more active basement overthrusting, the influx of copious amounts of terrigenous sediment, and the termination everywhere of extensive limestone and Te Kuiti Group deposition. (author). 38 refs., 11 figs., 4 tabs

209

Micro-tectonic constraints on the evolution of the Barles half-window (Digne Nappe, southern Alps). Implications for the timing of folding in the Valensole foreland basin  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The "Vélodrome" overturned syncline, at the northern margin of the Cenozoic foreland basin of Valensole in SE France, was formed during the Late Cenozoic at the front of the Digne nappe. Microstructural analyses reveal that mesoscale faulting in the molassic series, from the Oligocene "Molasse Rouge" at the base to the middle to late Miocene "Valensole Conglomerates" at the top, partly occurred before the folding, as layer-parallel shortening: the NNE-SSW-directed compression is recorded by ...

Fournier, Marc; Agard, Philippe; Petit, Carole

2008-01-01

210

The distribution of radioelements in archaean granites of the Kaapvaal Craton, with implications for the source of uranium in the Witwatersrand Basin  

International Nuclear Information System (INIS)

Approximately 500 samples from the Archaean granitic basement of the southern Kaapvaal Craton have been analysed, for U and Th. When viewed in conjunction with geological relationships, the radioelement distribution patterns in the Archaean basement provide contraints regarding the origin of uranium in the Witwatersrand Basin. Granites in the Baberton region are sub-divided into three magnetic cycles, the earliest cycle comprising tonalite-trondhjemite gneisses, the intermediate cycle comprising literally extensive K-rich batholiths and the final stage consisting of discrete intrusive granitic plutons. Uranium and thorium contents vary as a function of age and rock type, an increase progressively from the first cycle through to the third cycle. Certain of the late granite plutons may have been S-type in origin, have relatively low Th/U ratios, high U contents, and are characterized by accessory minerals dominated by monazite-like phases. The late granite plutons with highest radioelement contents appear to have formed circa 2,8 Ga, an age which coincides with granulite facies metamorphism and uranium-thorium depletion in the lower crust, as recrorded in the Vredeford crustal profile. Uranium has been leached from portions of the regolith profile, but also concentrated into leucoxene-rich zones derived from the breakdown of pre-existing titanium-bearing phases. The widespread development of an uraniferous leucoxene protore in weathered source rocks of the Witwatersrandeathered source rocks of the Witwatersrand Basin has relevance to the genesis of authigenic U-Ti phases (brannerite) in the reefs themselves. The study of radioelement distribution in Archaean granites adjacent to the Witwatersrand Basin provides a framework within which considerations regarding the origin of the uranium deposits in the basin can be viewed. The secular evolution of the Archaean granitic basement, hydrothermal processes, and palaeoweathering all played a role in the formation of the Witwatersrand deposits

211

Late Pleistocene and Early Holocene lake-level fluctuations in the Lahontan Basin, Nevada: Implications for the distribution of archaeological sites  

Science.gov (United States)

The Great Basin of the western U.S. contains a rich record of late Pleistocene and Holocene lake-level fluctuations as well as an extensive record of human occupation during the same time frame. We compare spatial-temporal relationships between these records in the Lahontan basin to consider whether lake-level fluctuations across the Pleistocene-Holocene transition controlled distribution of archaeological sites. We use the reasonably well-dated archaeological record from caves and rockshelters as well as results from new pedestrian surveys to investigate this problem. Although lake levels probably reached maximum elevations of about 1230-1235 m in the different subbasins of Lahontan during the Younger Dryas (YD) period, the duration that the lakes occupied the highest levels was brief Paleoindian and early Archaic archaeological sites are concentrated on somewhat lower and slightly younger shorelines (???1220-1225 in) that also date from the Younger Dryas period. This study suggests that Paleoindians often concentrated their activities adjacent to large lakes and wetland resources soon after they first entered the Great Basin. ?? 2008 Wiley Periodicals, Inc.

Adams, K.D.; Goebel, T.; Graf, K.; Smith, G.M.; Camp, A.J.; Briggs, R.W.; Rhode, D.

2008-01-01

212

Structural styles and depositional architecture in the Triassic of the Ninian and Alwyn North fields: Implications for basin development and prospectivity in the Northern North Sea  

Energy Technology Data Exchange (ETDEWEB)

Interpretation of well-calibrated three-dimensional seismic volumes, sedimentological analysis and electrical well-log correlations from the Ninian and Alwyn North fields challenge the long-held view that Mid-Late Jurassic extensional faults in the East Shetland Basin represent a simple reactivation of older (Triassic) fault systems. Restoration for the effects of the younger, predominantly eastward-dipping, Mid-Late Jurassic structures clearly demonstrates that Triassic precursors had a steep, westerly dip. In contrast to the eastern flank of the Viking Graben (e.g. Troll and Oseberg areas), where the west-dipping Triassic structures are reutilised in the Mid-Late Jurassic, those of the East Shetland Basin have largely been dissected and rotated during the later event. Those west-dipping faults that did see later movement appear to have simply acted as minor antithetic structures to the throughgoing east-dipping ones. The Triassic normal fault patterns actively controlled sediment thicknesses and facies distribution within the Lunde and Teist Formations in the basin. Use of seismic stratigraphic surfaces, calibrated by biostratigraphy and chemostratigraphic markers, provides strong evidence that the Triassic depocentres are spatially offset from their Mid-Late Jurassic counterparts. The combination of structural, stratigraphic and sedimentary effects reveal the existence of an emergent deeper Triassic play opportunity in footwall locations to the Mid-Late Jurassic normal faults, which has the potential to extend the life of what is otherwise mature acreage. (author)

Tomasso, Mark [School of Geosciences, Grant Institute of Earth Science, The University of Edinburgh, The King' s Buildings, West Mains Road, Edinburgh EH9 3JW, Scotland (United Kingdom); Enhanced Oil Recovery Institute, University of Wyoming, 1000 E. University Avenue, Dept. 4068, Laramie, WY 82071 (United States); Underhill, John R. [School of Geosciences, Grant Institute of Earth Science, The University of Edinburgh, The King' s Buildings, West Mains Road, Edinburgh EH9 3JW, Scotland (United Kingdom); Hodgkinson, Richard A. [School of Geosciences, Grant Institute of Earth Science, The University of Edinburgh, The King' s Buildings, West Mains Road, Edinburgh EH9 3JW, Scotland (United Kingdom); Bowleven PLC, 1 North St. Andrew Lane, Edinburgh EH2 1HX, Scotland (United Kingdom); Young, Mike J. [School of Geosciences, Grant Institute of Earth Science, The University of Edinburgh, The King' s Buildings, West Mains Road, Edinburgh EH9 3JW, Scotland (United Kingdom); StatoilHydro, NO-4035 Stavanger (Norway)

2008-08-15

213

The earliest well-dated archeological site in the hyper-arid Tarim Basin and its implications for prehistoric human migration and climatic change  

Science.gov (United States)

The routes and timing of human occupation of the Tibetan Plateau (TP) are crucial for understanding the evolution of Tibetan populations and associated paleoclimatic conditions. Many archeological sites have been found in/around the Tarim Basin, on the northern margin of the Tibetan Plateau. Unfortunately, most of these sites are surface sites and cannot be directly dated. Their ages can only be estimated based on imprecise artifact comparisons. We recently found and dated an archeological site on a terrace along the Keriya River. Our ages indicate that the site was occupied at ~ 7.0-7.6 ka, making it the earliest well-dated archeological site yet identified in the Tarim Basin. This suggests that early human foragers migrated into this region prior to ~ 7.0-7.6 ka during the early to mid-Holocene climatic optimum, which may have provided the impetus for populating the region. We hypothesize that the Keriya River, together with the other rivers originating from the TP, may have served as access routes onto the TP for early human foragers. These rivers may also have served as stepping stones for migration further west into the now hyper-arid regions of the Tarim Basin, leading ultimately to the development of the Silk Road.

Han, WenXia; Yu, LuPeng; Lai, ZhongPing; Madsen, David; Yang, Shengli

2014-07-01

214

Stable isotopes in fossil mammals, fish and shells from Kunlun Pass Basin, Tibetan Plateau: Paleo-climatic and paleo-elevation implications  

Science.gov (United States)

We report the results of a stable isotope study of a late Pliocene fauna recently discovered in the Kunlun Mountain Pass area (˜ 4700 m above sea level) on the northern Tibetan Plateau. The ?13C values of enamel samples from modern herbivores from the Kunlun Pass Basin range from - 14.8 to - 10.6‰, with a mean of - 12.0 ± 0.7‰, indicating pure C3 diets consistent with the current dominance of C3 vegetation in the area. In contrast, enamel samples from fossil herbivores yielded ?13C values of - 5.4‰ to - 10.2‰ (with a mean of - 7.9 ± 1.3‰), significantly higher than those of modern herbivores in the area. The higher ?13C values indicate that these ancient herbivores, unlike their modern counterparts, had a variety of diets ranging from pure C3 to mixed C3/C4 vegetation. The local ecosystems in the Kunlun Pass area in the late Pliocene likely included grasslands that had small amounts of C4 grasses. The ?18O values of enamel from large herbivores shifted to higher values after the late Pliocene, indicating a significant change in the ?18O of local meteoric water. We estimate that there has been approximately 3.2‰ increase in annual ?18O values of meteoric water since ˜ 2-3 Ma, most likely driven by changes in the regional hydrological cycle possibly as a result of tectonic and climate change. The ?18O values of fossil fish teeth/bones and gastropod shells, along with abundance of aquatic plants and other invertebrate fossils, clearly indicate that the Kunlun Pass Basin once had plenty of water and was occupied by a freshwater lake in the late Pliocene. Our isotope data from both terrestrial and aquatic fossils suggest that the Kunlun Pass Basin was a hospitable place with a much warmer and wetter climate in the late Pliocene, very different from today's rock desert and cold steppe environments. The mean annual temperature in the late Pliocene estimated from the ?18O of fossil bone carbonate and paleo-water was about 10 ± 8 °C, much higher than the present-day mean annual temperature in the basin. If valid, the estimated temperature change would imply that the elevation of the basin has increased by ˜ 2700 ±1600 m since ˜ 2-3 Ma.

Wang, Yang; Wang, Xiaoming; Xu, Yingfeng; Zhang, Chunfu; Li, Qiang; Tseng, Zhijie Jack; Takeuchi, Gary; Deng, Tao

2008-06-01

215

B.C. Hydro Williston to Kelly Lake 500 kV transmission line public consultation report  

International Nuclear Information System (INIS)

A public consultation program was developed and implemented for a proposed third 500-kV transmission line from Williston Substation, east of Prince George in British Columbia, to Kelly Lake Substation near Clinton, British Columbia. The implemented program took place from July 1989 to January 1990 and involved discussions with about 14 local and regional governments and community associations, and 30 special interest groups. Eight public meetings were held as well as three meetings with native groups. A total of 73 public information requests were logged. The public consultation program was sufficiently comprehensive and objective to identify the public's concerns with respect to the proposed line. The overall goal of the program was to improve the project by incorporating public ideas and concerns into the planning process. It is believed that some important examples of how this has occurred on this project include a closer working relationship between British Columbia Hydro and property owners along the transmission line corridor, improved right-of-way clearing and maintenance standards, identification of ways to improve the economic benefits of the project to local contractors, improved public awareness about electric and magnetic fields, and an enhanced awareness of the utility's commitment to public consultation. 2 figs

216

Probabilistic Seismic Hazard Maps of Seattle, Washington, Including 3D Sedimentary Basin Effects and Rupture Directivity: Implications of 3D Random Velocity Variations (Invited)  

Science.gov (United States)

We have produced probabilistic seismic hazard maps of Seattle for 1 Hz spectral acceleration, using over five hundred 3D finite-difference simulations of earthquakes on the Seattle fault, Southern Whidbey Island fault, and Cascadia subduction zone, as well as for random deep and shallow earthquakes at various locations. The 3D velocity model was validated by modeling the observed waveforms for the 2001 M6.8 Nisqually earthquake and several smaller events in the region. At these longer periods (? 1 sec) that are especially important to the response of buildings of ten stories or higher, seismic waves are strongly influenced by sedimentary basins and rupture directivity. We are investigating how random spatial variations in the 3D velocity model affect the simulated ground motions for M6.7 earthquakes on the Seattle fault. A fractal random variation of shear-wave velocity with a Von Karman correlation function produces spatial variations of peak ground velocity with multiple scale lengths. We find that a 3D velocity model with a 10% standard deviation in shear-wave velocity in the top 1.5 km and 5% standard deviation from 1.5-10 km depth produces variations in peak ground velocities of as much as a factor of two, relative to the case with no random variations. The model with random variations generally reduces the peak ground velocity of the forward rupture directivity pulse for sites near the fault where basin-edge focusing of S-waves occurs. It also tends to reduce the peak velocity of localized areas where basin surface waves are focused. However, the medium with random variations also causes small-scale amplification of ground motions over distances of a few kilometers. We are also evaluating alternative methods of characterizing the aleatory uncertainty in the probabilistic hazard calculations.

Frankel, A. D.; Stephenson, W. J.; Carver, D.; Odum, J.; Williams, R. A.; Rhea, S.

2010-12-01

217

Petrographic and geochemical characteristics of the Paleogene sedimentary rocks from the North Jiangsu Basin, Eastern China: implications for provenance and tectonic setting  

Science.gov (United States)

The petrography and geochemistry (major, trace, and rare earth elements) of clastic sedimentary rocks from the Paleogene Dainan Formation (E2 d) in the North Jiangsu Basin, eastern China, are investigated to trace their provenance and to constrain their tectonic setting. The studied samples are characterized by LREE enrichment, flat HREE, and negative Eu anomaly similar to the upper continental crust composed chiefly of felsic components in the source area. Petrographic observation indicates that the sandstones contain predominant metamorphic and sedimentary clasts that were derived from peripheral recycled orogen and intrabasinal materials. The trace element ratios (Co/Th, La/Sc, La/Th, and Th/U) and the La-Th-Sc ternary plot further confirm that the sandstones are derived from granitic gneiss sources from recycled orogen and the intrabasinal mixed sedimentary provenance. The granitic gneiss source rocks may have derived from the Proterozoic granitic gneiss denuded in the eastern Dabie-Sulu orogen; and the intrabasinal provenance may come from the underlying strata during the Late Paleocene Wubao movement. The chemical index of alteration (CIA) and A-CN-K plot show that these source rocks may have experienced weak to medium chemical weathering. Analysis on tectonic setting of the source area suggests an active continental margin, which is intimate with tectonic feature of the Dabie-sulu orogen and the Yangtze block. In summary, we suggest that the North Jiangsu Basin is an ideal site for the study of the coupling between the uplift of the orogen and the subsidence of the foreland basin.

Zhang, Ni; Lin, Chun-Ming; Zhang, Xia

2014-08-01

218

A Conceptual Model of Water Quantity Impacts from Insect-Induced Tree Mortality in Coniferous Forests: Implications for Colorado River Basin Water Management  

Science.gov (United States)

In regions with snowpack-dominated hydrology, such as the upper Colorado River Basin, forested watersheds are the source of most (>70%) of the annual runoff. Widespread tree mortality significantly alters many ecohydrologic processes including transpiration, canopy transmission and interception, subcanopy wind regimes, soil infiltration, and snow surface albedo. Since 1996, an outbreak of the mountain pine beetle (MPB; Dendroctonous ponderosae) has killed most mature trees across 14,600 km2 of forests dominated by lodgepole pine (Pinus contorta) in Colorado, with the highest levels of mortality occurring around the headwaters of the Colorado River. Water managers are concerned about potential changes in water yield and timing of runoff resulting from the MPB infestation, but few empirical studies have documented the effects of such infestations on hydrologic processes. We synthesize these studies and other research on forest ecology, hydrology, and timber harvesting to create a conceptual model of the hydrologic effects of MPB-induced tree death during different stages of mortality. We separate out the primary hydrologic processes for living forest stands, stands in multiple stages of mortality, and long-dead stands undergoing regeneration. Our model outlines the direction of change in individual hydrologic processes, but continuing uncertainty over relative magnitude makes it difficult to understand the overall net effect of widespread tree mortality on runoff volume. Overall, the complexity of basin-specific factors that modulate hydrologic processes and differences between phases of stand mortality should caution water managers in the Colorado River Basin against assuming there will be significant changes in yield or timing due to MPB-induced tree mortality.

Gordon, E.; Pugh, E. T.

2010-12-01

219

Cyclostratigraphy of an orbitally-driven Tithonian-Valanginian carbonate ramp succession, Southern Mendoza, Argentina: Implications for the Jurassic-Cretaceous boundary in the Neuquén Basin  

Science.gov (United States)

Detailed sedimentological, sequence stratigraphical and cyclostratigraphical analyses have been made from four lower Tithonian-lower Valanginian sections of the Vaca Muerta Formation, exposed in the southern Mendoza area of the Neuquén Basin, Argentina. The Vaca Muerta Formation is characterized by decimetre-scale rhythmic alternations of marls, shales and limestones, and consists of five facies associations, which reflect different paleoenvironmental conditions: basin to restricted outer ramp, outer ramp, and middle ramp. Vertical organization within the Vaca Muerta Formation shows a well-ordered hierarchy of cycles, where elementary cycles, bundles and superbundles with frequencies within the Milankovitch band have been recognized. According to biostratigraphic data, elementary cycles have a periodicity of ~ 20 ky, which correlates with the precession cycle of Earth's axis. Spectral analysis based on series of cycle thickness allows us to identify frequencies of about 400 ky and 90-120 ky, which we interpret as the modulation of the precessional cycle by the Earth's orbital eccentricity. Cycles are probably driven by variations in carbonate exportation, as fluctuations in shallow-water carbonate production involve modifications in carbonate basinward exportation. Cyclostratigraphic data allowed us to build a floating orbital scale for the Tithonian-lower Valanginian interval in the Neuquén Basin. Correlation between studied sections allowed us to recognize a discontinuity between the Substeueroceras koeneni and Argentiniceras noduliferum ammonite zones in the Malargüe Anticline area. Orbital calibration of these sections is consistent with Riccardi's biostratigraphic scheme, wich place the Jurassic-Cretaceous boundary within the Substeueroceras koeneni ammonite Zone. On the other hand, the base of the Vaca Muerta Formation (Virgatosphinctes mendozanus ammonite Zone) would be probably placed in the base of the middle Tithonian rather than the lower Tithonian, which is also consistent with our preliminary palaeomagnetic data.

Kietzmann, Diego A.; Palma, Ricardo M.; Iglesia Llanos, Maria Paula

2015-01-01

220

Trace-element systematics of sediments in the Murray-Darling Basin, Australia: Sediment provenance and palaeoclimate implications of fine scale chemical heterogeneity  

Energy Technology Data Exchange (ETDEWEB)

A high-resolution dataset of trace element concentrations is presented for the Murray-Darling Basin, Australia, Australia's most important river system. The data were obtained by solution quadrupole ICP-MS resulting in concentrations for 44 elements. Of these, 21 were determined with a long-term external precision of better than 1% and a further 13 at a precision better than 2%. Trace element maps for the surface sediments constructed from such high precision data reveal small but coherent variations in the four major sub-catchments of the basin, even in ratios of elements with very similar geochemical behaviour, such as Y/Ho, Nb/Ta and Zr/Hf. The origin of these chemical fingerprints of drainage systems are discussed in terms of the geochemical character of the upper continental crust. The potential of trace element maps for palaeo-environmental and climatic reconstruction is then illustrated. First, a sample of dust collected in a trap located in the far southeastern corner of the study area is used to pinpoint the location of the dust source. Next the fine-scale change in down-stream alluvial sediment chemistry is analysed to estimate the importance of sediment contribution from tributaries with a view to reconstructing river flow dynamics. Finally, the chemistry of dune sediments is compared with surrounding floodplain alluvium to estimate relative age of deposition. These examples demonstrate that in low-elevation river systems, such as the Murray-Darling Basin, extended trace element maps of sediment offer substantially more applications than radiogenic isotope data alone.

Marx, Samuel K., E-mail: s.marx@uq.edu.au [Climate Research Group, School of Geography, Planning and Environmental Management, University of Queensland, St. Lucia, Brisbane, Qld 4072 (Australia); Kamber, Balz S. [Department of Earth Sciences, Laurentian University, Sudbury, Ontario, Canada P3E2C6 (Canada)

2010-08-15

 
 
 
 
221

Formation and preservation of greigite (Fe3S4) in sediments from the Santa Barbara Basin: Implications for paleoenvironmental changes during the past 35 ka  

Science.gov (United States)

Diagenetic processes are known to modify sedimentary records, but they can also reveal important paleoenvironmental changes. Here we investigate variations in sedimentary iron diagenesis and depositional environments for the last 35 ka by analyzing the rock magnetic and geochemical properties of two sediment cores collected in the Santa Barbara Basin (California). In organic-rich sediments, early diagenesis often leads to partial dissolution of detrital iron oxides and stepwise formation of authigenic pyrite (FeS2). The pyritization process takes place following several geochemical pathways, sometimes involving intermediate iron sulfide species such as greigite (Fe3S4). Sedimentary conditions in the basin appear to have recurrently favored preservation of greigite (identified by its magnetic properties) and inhibited its complete transformation into pyrite. The Holocene interval contains a series of centimeter-thick greigite-bearing layers that are associated with large flood deposits, which are known in the basin as "gray layers." We propose that greigite preservation was enabled in these sediments by their relative enrichment in reactive iron over organic matter and/or hydrogen sulfide (because of their high ratio of terrigenous over organic material), which limited pyritization reactions. Within the glacial deposits, formation and preservation of meter-thick greigite layers occurred in terrigenous-rich and organic-poor sedimentary layers and is proposed to result from a similar diagenetic process to that in the Holocene greigite-bearing layers (dominance of reactive iron over organic matter and/or HS-). The terrigenous enrichments in the glacial greigite-bearing layers are probably related to climatic or sea level changes because they occur at times of massive iceberg releases in the North Atlantic, the so-called Heinrich events.

Blanchet, C. L.; Thouveny, N.; Vidal, L.

2009-06-01

222

The upper crust laid on its side: tectonic implications of steeply tilted crustal slabs for extension in the basin and range  

Science.gov (United States)

Tilted slabs expose as much as the top 8–15 km of the upper crust in many parts of the Basin and Range province. Exposures of now-recumbent crustal sections in these slabs allow analysis of pre-tilt depth variations in dike swarms, plutons, and thermal history. Before tilting the slabs were panels between moderately dipping, active Tertiary normal faults. The slabs and their bounding normal faults were tilted to piggyback positions on deeper footwalls that warped up isostatically beneath them during tectonic unloading. Stratal dips within the slabs are commonly tilted to vertical or even slightly overturned, especially in the southern Basin and Range where the thin stratified cover overlies similarly tilted basement granite and gneiss. Some homoclinal recumbent slabs of basement rock display faults that splay upward into forced folds in overlying cover sequences, which thereby exhibit shallower dips. The 15-km maximum exposed paleodepth for the slabs represents the base of the brittle upper crust, as it coincides with the depth of the modern base of the seismogenic zone and the maximum focal depths of large normal-fault earthquakes in the Basin and Range. Many upended slabs accompany metamorphic core complexes, but not all core complexes have corresponding thick recumbent hanging-wall slabs. The Ruby Mountains core complex, for example, preserves only scraps of upper-plate rocks as domed-up extensional klippen, and most of the thick crustal section that originally overlay the uplifted metamorphic core now must reside below little-tilted hanging-wall blocks in the Elko-Carlin area to the west. The Whipple and Catalina Mountains core complexes in contrast are footwall to large recumbent hanging-wall slabs of basement rock exposing 8-15 km paleodepths that originally roofed the metamorphic cores; the exposed paleodepths require that a footwall rolled up beneath the slabs.

Howard, Keith A.

2005-01-01

223

Basin geometry and cumulative offsets in the Eastern Transverse Ranges, southern California: Implications for transrotational deformation along the San Andreas fault system  

Science.gov (United States)

The Eastern Transverse Ranges, adjacent to and southeast of the big left bend of the San Andreas fault, southern California, form a crustal block that has rotated clockwise in response to dextral shear within the San Andreas system. Previous studies have indicated a discrepancy between the measured magnitudes of left slip on through-going east-striking fault zones of the Eastern Transverse Ranges and those predicted by simple geometric models using paleomagnetically determined clockwise rotations of basalts distributed along the faults. To assess the magnitude and source of this discrepancy, we apply new gravity and magnetic data in combination with geologic data to better constrain cumulative fault offsets and to define basin structure for the block between the Pinto Mountain and Chiriaco fault zones. Estimates of offset from using the length of pull-apart basins developed within left-stepping strands of the sinistral faults are consistent with those derived by matching offset magnetic anomalies and bedrock patterns, indicating a cumulative offset of at most ???40 km. The upper limit of displacements constrained by the geophysical and geologic data overlaps with the lower limit of those predicted at the 95% confidence level by models of conservative slip located on margins of rigid rotating blocks and the clockwise rotation of the paleomagnetic vectors. Any discrepancy is likely resolved by internal deformation within the blocks, such as intense deformation adjacent to the San Andreas fault (that can account for the absence of basins there as predicted by rigid-block models) and linkage via subsidiary faults between the main faults. ?? 2009 Geological Society of America.

Langenheim, V.E.; Powell, R.E.

2009-01-01

224

Upper mantle diapers, lower crustal magmatic underplating, and lithospheric dismemberment of the Great Basin and Colorado Plateau regions, Nevada and Utah; implications from deep MT resistivity surveying  

Science.gov (United States)

In the rifted Basin and Range province of the southwestern U.S., a common faulting model for extensional basins based e.g. on reflection seismology data shows dominant displacement along master faults roughly coincident with the main topographic scarp. On the other hand, complementary data such as drilling, earthquake focal mechanisms, volcanic occurrences, and trace indicators such as helium isotopes suggest that there are alternative geometries of crustal scale faulting and material transport from the deep crust and upper mantle in this province. Recent magnetotelluric (MT) profiling results reveal families of structures commonly dominated by high-angle conductors interpreted to reflect crustal scale fault zones. Based mainly on cross cutting relationships, these faults appear to be late Cenozoic in age and are of low resistivity due to fluids or alteration (including possible graphitization). In the Ruby Mtns area of north-central Nevada, high angle faults along the margins of the core complex connect from near surface to a regional lower crustal conductor interpreted to contain high-temperature fluids and perhaps melts. Such faults may exemplify the high angle normal faults upon which the major earthquakes of the Great Basin appear to nucleate. A larger-scale transect centered on Dixie Valley shows major conductive crustal-scale structures connecting to conductive lower crust below Dixie Valley, the Black Rock desert in NW Nevada, and in east-central Nevada in the Monitor-Diamond Valley area. In the Great Basin-Colorado Plateau transition of Utah, the main structures revealed are a series of nested low-angle detachment structures underlying the incipient development of several rift grabens. All these major fault zones appear to overlie regions of particularly conductive lower crust interpreted to be caused by recent basaltic underplating. In the GB-CP transition, long period data show two, low-resistivity upper mantle diapirs underlying the concentrated conductive lower crust and nested faults, and these are advanced as melt source regions for the underplating. MT, with its wide frequency bandwidth, allows views of nearly a complete melting and emplacement process, from mantle source region, through lower crustal intrusion, to brittle regime deformational response.

Wannamaker, P. E.; Doerner, W. M.; Hasterok, D. P.

2005-12-01

225

Health risks from large-scale water pollution: Current trends and implications for improving drinking water quality in the lower Amu Darya drainage basin, Uzbekistan  

Science.gov (United States)

Safe drinking water is a primary prerequisite to human health, well being and development. Yet, there are roughly one billion people around the world that lack access to safe drinking water supply. Health risk assessments are effective for evaluating the suitability of using various water sources as drinking water supply. Additionally, knowledge of pollutant transport processes on relatively large scales is needed to identify effective management strategies for improving water resources of poor quality. The lower Amu Darya drainage basin close to the Aral Sea in Uzbekistan suffers from physical water scarcity and poor water quality. This is mainly due to the intensive agriculture production in the region, which requires extensive freshwater withdrawals and use of fertilizers and pesticides. In addition, recurrent droughts in the region affect the surface water availability. On average 20% of the population in rural areas in Uzbekistan lack access to improved drinking water sources, and the situation is even more severe in the lower Amu Darya basin. In this study, we consider health risks related to water-borne contaminants by dividing measured substance concentrations with health-risk based guideline values from the World Health Organisation (WHO). In particular, we analyse novel results of water quality measurements performed in 2007 and 2008 in the Mejdurechye Reservoir (located in the downstream part of the Amu Darya river basin). We furthermore identify large-scale trends by comparing the Mejdurechye results to reported water quality results from a considerable stretch of the Amu Darya river basin, including drainage water, river water and groundwater. The results show that concentrations of cadmium and nitrite exceed the WHO health-risk based guideline values in Mejdurechye Reservoir. Furthermore, concentrations of the since long ago banned and highly toxic pesticides dichlorodiphenyltrichloroethane (DDT) and ?-hexachlorocyclohexane (?-HCH) were detected in the reservoir water for the first time in a decade. However, a relatively pronounced temporal variability in concentrations was observed for many of the substances, implying that the reservoir could contain low-risk waters temporarily. Health risk factors related to lead and chromium concentrations in groundwater were up to 200 times higher than for river water. The identified major divergence in health risk between groundwater and surface water illuminates the risk of using groundwater for drinking water supply during recurrent surface water deficits in the study area. However, the severe water scarcity and lack of financial resources in the region makes the choices of alternative water supply sources limited. Due to the presence of multiple contaminants, it appears reasonable that the aggregated toxicity of contaminant mixtures should be in focus in surface and groundwater water monitoring and management in the region. Key words: Aral Sea, Drinking water, Groundwater, Health Risk, Surface Water

Törnqvist, Rebecka; Jarsjö, Jerker

2010-05-01

226

Numerical model simulations of small closed basin lake sediment core ?18O records from the upper Columbia River basin over the last millennium and implications for a mid-Holocene ‘megadrought’  

Science.gov (United States)

A suite of simulations conducted using a coupled lake-catchment hydrologic and isotope mass-balance model indicate that small, closed-basin lakes in the upper Columbia River basin are isotopically sensitive to changes in precipitation, and to a lesser extent, relative humidity and temperature. In an initial set of experiments, ~100 years of continuous monthly temperature and precipitation data were used as model inputs to simulate the intra- and interannual hydrologic and isotopic responses of Scanlon and Castor Lakes, located in the rainshadow of the Cascade Mountains within north-central Washington. At both sites, model-derived lake water ?18O data compare favorably to high-resolution lake sediment core ?18O records spanning the 20th century, as well as to instrumental records of drought variability and precipitation-evaporation balance (specifically, the Palmer Drought Severity Index, PDSI). Measured, decadally-averaged sediment core ?18O values from the last millennium were then simulated within the model by varying precipitation, relative humidity and temperature input data in an effort to provide quantitative estimates of both short-term hydroclimatic variability and mean climate state changes at the study sites. Comparison of these simulation results with regional tree-ring based PDSI reconstructions reveals a strong spatial and temporal coherence, suggesting that practicable quantitative paleohydroclimatic data can be derived from lake isotope mass-balance modeling methods. To provide a basis of comparison for evaluating mean state hydroclimate over the last ~1000 years, a final set of experiments were used to estimate mean state climate during the mid-Holocene (~7500 to 6500 cal. BP) ‘megadrought’. During this arid period, Castor Lake sediment ?18O values increased by over 2‰. The Scanlon Lake sediment record, however, shows no appreciable increase in ?18O at this time, but does exhibit clear sedimentological evidence for a two meter decrease in lake level. Model simulations of the ‘megadrought’ period suggest that the discrepancies in the Castor and Scanlon sediment core ?18O records are the result of differing lake outseepage rates. Specifically, at Scanlon Lake, with minimal outseepage, isotopic change is induced only by short-term hydroclimate variability and not by changes in mean climate state. In contrast, at Castor Lake, with appreciable outseepage, both short-term hydroclimate variability and variations in the mean climate state will induce isotopic changes. Comparison of model results with tree ring based PDSI reconstructions and with sediment record ?18O values spanning both the past one thousand years and the ‘megadrought’ period demonstrates that an alternate mean hydroclimatic state existed for the upper Columbia basin during the mid-Holocene and that such large-scale mean state shifts did not occur over the last millennium.

Steinman, B. A.; Rosenmeier, M. F.; Abbott, M.

2009-12-01

227

Magnetic mineral study of Holocene marine sediments from the Alfonso Basin, Gulf of California - implications for depositional environment and sediment sources  

Directory of Open Access Journals (Sweden)

Full Text Available Results of a rock magnetic study of marine sediments from the Alfonso Basin, Bay of La Paz are used to investigate sediment sources and depositional environment in the southern Gulf of California during the Holocene. Radiocarbon dating provides stratigraphic control, with age for the core bottom sediments of 7597-7831 cal. yr B.P. Magnetic signal is dominated by fine-grained titanomagnetites, derived from the silicic volcanic units surrounding the Bay of La Paz. Magnetic mineralogy is relatively homogenous as seen in bulk magnetic properties of low-field susceptibility, remanent intensity and coercivity. Magnetic hysteresis loops show strong variable paramagnetic components; after paramagnetic correction loops show saturation at low fields and high saturation magnetization values. Plots of hysteresis parameter ratios for domain state show that samples group in the pseudo-single domain field, with mixtures of single and multi-domain particles. Magnetic susceptibility log shows relatively high frequency dependence factors, particularly for the Middle Holocene, suggesting contribution of fine-grained superparamagnetic minerals related to eolian deposition. The well-preserved laminated sequence indicates predominant anoxic conditions in the basin floor. Depositional environment had a dominant supply of pluvial detrital sediments and eolian fimaterial with less abundant biogenic input.

L. Pérez Cruz

2009-07-01

228

K-Ar dating of fault gouge in the northern Sydney Basin, NSW, Australia—implications for the breakup of Gondwana  

Science.gov (United States)

The occurrence of synkinematic and authigenic clay minerals is a common feature in fault gouges. Few attempts have been made to date fault gouges. We present the first age data in Australia for synkinematic illite-smectite growth in two fault zones of the northern Sydney Basin, NSW. The faults occur at Burwood Beach, NSW in the northern part of the Sydney Basin and are hosted by Early Permian siltstones, tuffs and coals of the Lambton Formation, Newcastle Coal Measures. The faults are 1.5 m apart, show normal displacement and trend N-S with steep easterly dips. Foliated gouge zones, comminution and dilational breccias are developed along both fault surfaces. K-Ar ages extracted from samples in the gouge and tuffs in the damage zones are 172 (6-10 ?m) to 119 Ma (2 ?m), 237-245 Ma for the <2 ?m fraction, 218 Ma for the <0.4 ?m fraction and 196 Ma for the <0.1 ?m fraction have been obtained from siltstones within and outside the damage zone. We believe the younger ages of 196-237 Ma indicate the time at which diagenetic illite-smectite formed and the 122-150 Ma dates from the <2 ?m fraction represent the maximum age of gouge formation. The younger ages are thought to reflect the last slip event occurring on the faults, which is related to the rifting and dispersal of the eastern margin of the Australian continent.

Zwingmann, H.; Offler, R.; Wilson, T.; Cox, S. F.

2004-12-01

229

The strong diachronous Muschelkalk/Keuper facies shift in the Central European Basin: implications from the type-section of the Erfurt Formation (Lower Keuper, Triassic) and basin-wide correlations  

Science.gov (United States)

The transition from the shallow marine Upper Muschelkalk Sea to the Lower Keuper fluvial plain represents the most diachronous facies shift of the entire Germanic Triassic. The type-section of the fluvial Lower Keuper (Erfurt Formation) is described in detail for the first time including biostratigraphic dating of the Muschelkalk/Keuper boundary. The type-section is integrated into a NNE-SSW cross section through the Central European Basin, and the Muschelkalk/Keuper facies shift is constrained by high-resolution conodont and ceratite biostratigraphy. Thus, the fundamental changes in palaeogeography, shifts of facies belts and stratal pattern architecture are visualised. Forced by a rapid transgression from Tethyan waters, the shallow marine Upper Muschelkalk Sea attained its maximum flooding in the lower conodont zone 2 ( sequens/pulcher to philippi/robustus zones). Subsequent slow continuous regression to the South was accompanied by step-by-step progradation of coastal to fluvial plain environments of the Lower Keuper, culminating in a fluvial plain extending to South Germany. Based on stratal patterns, an improved sequence-stratigraphic interpretation for the Upper Muschelkalk/Lower Keuper interval is suggested. In combination with biostratigraphic arguments, the new sequence-stratigraphy points to a revised correlation of this interval within the Tethyan Triassic, incorporating the positions of the Anisian/Ladinian and Fassanian/Longobardian boundaries.

Franz, Matthias; Henniger, Matthias; Barnasch, Jens

2013-04-01

230

Middle to late Cenozoic basin evolution in the western Alborz Mountains: Implications for the onset of collisional deformation in northern Iran  

Science.gov (United States)

Oligocene-Miocene strata preserved in synclinal outcrop belts of the western Alborz Mountains record the onset of Arabia-Eurasia collision-related deformation in northern Iran. Two stratigraphic intervals, informally named the Gand Ab and Narijan units, represent a former basin system that existed in the Alborz. The Gand Ab unit is composed of marine lagoonal mudstones, fluvial and alluvial-fan clastic rocks, fossiliferous Rupelian to Burdigalian marine carbonates, and basalt flows yielding 40Ar/39Ar ages of 32.7 ± 0.3 and 32.9 ± 0.2 Ma. The Gand Ab unit is correlated with the Oligocene-lower Miocene Qom Formation of central Iran and is considered a product of thermal subsidence following Eocene extension. The Narijan unit unconformably overlies the Gand Ab unit and is composed of fluvial-lacustrine and alluvial fan sediments exhibiting contractional growth strata. We correlate the Narijan unit with the middle to upper Miocene Upper Red Formation of central Iran on the basis of lithofacies similarities, stratigraphic position, and an 8.74 ± 0.15 Ma microdiorite dike (40Ar/39Ar) that intruded the basal strata. Deformation timing is constrained by crosscutting relationships and independent thermochronological data. The Parachan thrust system along the eastern edge of the ancestral Taleghan-Alamut basin is cut by dikes dated at 8.74 ± 0.15 Ma to 6.68 ± 0.07 Ma (40Ar/39Ar). Subhorizontal gravels that unconformably overlie tightly folded and faulted Narijan strata are capped by 2.86 ± 0.83 Ma (40Ar/39Ar) andesitic lava flows. These relationships suggest that Alborz deformation had migrated southward into the Taleghan-Alamut basin by late Miocene time and shifted to its present location along the active range front by late Pliocene time. Data presented here demonstrate that shortening in the western Alborz Mountains had started by late middle Miocene time. This estimate is consistent with recent thermochronological results that place the onset of rapid exhumation in the western Alborz at ˜12 Ma. Moreover, nearly synchronous Miocene contraction in the Alborz, Zagros Mountains, Turkish-Iranian plateau, and Anatolia suggests that the Arabia-Eurasia collision affected a large region simultaneously, without a systematic outward progression of mountain building away from the collision zone.

Guest, Bernard; Horton, Brian K.; Axen, Gary J.; Hassanzadeh, Jamshid; McIntosh, William C.

2007-12-01

231

Petrology and K/Ar ages of volcanics dredged from the Eolian seamounts: implications for geodynamic evolution of the southern Tyrrhenian basin  

Science.gov (United States)

Systematic marine investigations carried out in the last decade indicate that the Eolian island orogenic volcanism extends to the seamounts located on the western (Sisifo, Enarete, Eolo Seamounts) and the northeastern (Alcione, Lametini Seamounts) sides of the emerged Eolian Island arc, as well as on the upper part of Palinuro and Marsili Seamounts, constituting on the whole a ring-like structure. Basaltic to rhyolitic lava samples dredged from these localities mostly belong to calc-alkaline and shoshonitic associations and are strictly comparable, both in petrographical and geochemical characteristics, to subaerial products outcropping on the Eolian islands. Moreover a few tholeiitic basalts, with island arc affinity, have been recovered for the first time from north Lametini and lowermost Eolian slope. The calc-alkaline magmatic activity appears to date as far back as1.3-0.9 ± 0.2m.y. to the west (Sisifo Seamount) and probably postdates (or is synchronous with) the tholeiitic episodes, whereas the oldest shoshonitic volcanism so far found at Eolo and Enarete Seamounts has an age of 0.85-0.64 ± 0.06m.y. The geochronological data indicate a general trend of within-serial rejuvenation of the volcanism moving counterclockwise from the Sisifo area, as well as a chronological zonation of magmatic products characterized by a rapid transition, within the time span of about 0.1 m.y., to more abundant shoshonitic and leucite-tephritic lavas in limited portions of the structure (Lipari, Vulcano and Stromboli). Model calculations based on a large spectrum of incompatible elements indicate that the parental melts of the various magma series could be derived by different partial melting degrees of spinel- to garnet-peridotite mantle sources heterogeneously enriched through the influx of distinct metasomatizing fluids driven off the subduction zone. Subduction reactivation and the related Eolian volcanism appear to be diachronous with respect to the oceanic spreading in the Tyrrhenian marginal basin and characteristically analogous, in timing, to the tectonic and magmatic evolution of the western Pacific island arc and back arc basin systems, where an earlier opening of the marginal basin was followed by an arc volcanism on the rifted-off migrating plate. The chronological zonation inside limited sectors of the structure coupled with the widespread age of volcanism of different serial affinity along the whole structure and the counterclockwise rejuvenation of the within-serial magmatic activity, could be related to deformation (via torsion, segmentation and lateral stretching) and progressive steepening of the subducted slab resulting in the present concavity of the Benioff zone which corresponds to a maximal oroclinal distortion of the Apenninic-Maghrebian chain.

Beccaluva, L.; Gabbianelli, G.; Lucchini, F.; Rossi, P. L.; Savelli, C.

1985-07-01

232

High-resolution sequence stratigraphy of an alluvial fan fan delta environment: stratigraphic and geodynamic implications An example from the Keuper Chaunoy Sandstones, Paris Basin  

Science.gov (United States)

Facies analysis of the Chaunoy Formation, conducted as the first stage of this study, reveals that the corresponding fluvial system essentially involved bedload deposition, 2-D and 3-D megaripple migration, and debris-flow deposition. Such processes are characteristic of alluvial fan depositional environments. These alluvial fan deposits pass laterally eastward into a shallow lacustrine environment. In stage 2 of the study, electrofacies are defined by well-log analysis and then matched with sedimentary facies defined by core analysis. Electrofacies associations and depositional environments are then inferred directly from well-logs on this basis. Six electrofacies characterizing the main sedimentary facies associations and depositional environments within the Chaunoy Formation are defined (channel, lag deposits, channel infilling, lake or flood-plain, overflow deposits and paleosols). Stage 3 involves establishing correlations based on high-resolution sequence stratigraphy. Within these continental deposits, the procedure consists in analysing high-frequency fluctuations in baselevel defined from sedimentological studies and calibrated on well-log signatures. The correlations show that the top of the Chaunoy Formation is diachronous. The formation is subdivided here into three stratigraphic units from base to top: Chaunoy I, II and III. This study shows that the degree of preservation of continental deposits varies with stratigraphic cycle: genetic sequences and genetic sequence sets are asymmetrical, with the baselevel rise being better preserved than the baselevel fall, while, for minor cycle, deposits may be similarly preserved during baselevel rise and fall. The sequence stratigraphy pattern of the genetic sequences and the genetic sequence sets can result from climatic and/or tectonic factors but their effects are difficult to distinguish. At the scale of the minor Chaunoy I cycle or the Chaunoy II cycle, preservation is similar during the baselevel rise and fall, that implies that the Chaunoy minor cycles were influenced by load discharge resulting in greater accommodation space which could result from climatic or tectonic fluctuations. The Chaunoy Formation was deposited as part of a major baselevel rise during the Carnian-Liassic cycle. During this cycle, the Paris basin was generally tilted to the northwest producing the intra-`Marnes irisées supérieures' truncation which seems to have been induced by large-scale wavelength tectonic deformation. Detailed isopach maps of minor baselevel cycles in Chaunoy I with inferred depositional environments are used to define the extent of depositional environments and fault activity during baselevel rise and fall. During emplacement of the braided alluvial fan and lacustrine deposits of the Chaunoy Formation, fault activity, which was confined to the western part of the basin, controlled the preservation potential, i.e. the thickness of the deposits, and depositional environment profiles. Within the Chaunoy I and II cycles, the increased thickness of the sandstone deposits to the northeast and the onlap at the top of Chaunoy I can be explained by local fault activity and by the general tilting of the basin. The Chaunoy III sandstones are confined to the western part of the basin and seem to have been controlled by local factors only.

Bourquin, Sylvie; Rigollet, Christophe; Bourges, Philippe

1998-11-01

233

Paleomagnetic and rock-magnetic study on volcanic units of the Valsequillo Basin: implications for early human occupation in central Mexico  

Science.gov (United States)

Alleged human and animal footprints were found within the upper bedding surfaces of the Xalnene volcanic ash layer that outcrops in the Valsequillo Basin, south of Puebla, Mexico (Gonzalez et al, 2005). The ash has been dated at 40 ka by optically stimulated luminescence analysis, thereby providing new evidence that America was colonized earlier than the Clovis culture (about 13.5 Ma). We carried out paleomagnetic and rock magnetic analysis on 18 Xalnene ash block and core samples collected at two distinct localities and 19 standard paleomagnetic cores belonging to nearby monogenetic volcanoes. Our data provide evidence that both the volcanic lava flow and Xalnene ash were emplaced during the Laschamp geomagnetic event spanning from about 45 to 39 ka.

Goguitchaichvili, Avto; Pozzo, Ana Lillian Martin-Del; Rocha-Fernandez, Jose Luis; Urrutia-Fucugauchi, Jaime; Soler-Arechalde, Ana Maria

2009-01-01

234

Finite element modelling of the pull-apart formation: implication for tectonics of Bengo Co pull-apart basin, southern Tibet  

Directory of Open Access Journals (Sweden)

Full Text Available The tectonic deformation and state of stress are significant parameters to understand the active structure, seismic phenomenon and overall ongoing geodynamic condition of any region. In this paper, we have examined the state of stress and crustal deformation during the formation of the Beng Co pull-apart basins produced by an enéchelon strike-slip fault systems using 2D Finite Element Modelling (FEM under plane stress condition. The numerical modelling technique used for the experiments is based on FEM which enables us to analyze the static behavior of a real and continues structures. We have used three sets of models to explore how the geometry of model (fault overlap and pre-existing weak shear zone and applied boundary conditions (pure strike-slip, transpressional and transtensional influence the development of state of stress and deformation during the formation of pull-apart basins. Modelling results presented here are based on five parameters: 1 distribution, orienttation, and magnitude of maximum (?H max and minimum (?H max horizontal compressive stress 2 magnitude and orientation of displacement vectors 3 distribution and concentration of strain 4 distribution of fault type and 5 distribution and concentration of maximum shear stress (?H max contours. The modelling results demonstrate that the deformation pattern of the en-échelon strike-slip pull-apart formation is mainly dependent on the applied boundary conditions and amount of overlap between two master strike-slip faults. When the amount of overlap of the two master strike-slip faults increases, the surface deformation gets wider and longer but when the overlap between two master strike-slip faults is zero, block rotation observed significantly, and only narrow and small surface deform ation obtained. These results imply that overlap between two master strike-slip faults is a significant factor in controlling the shape, size and morphology of the pull-apart basin formation. Results of numerical modelling further show that the pattern of the distribution of maximum shear stress (?max contours are prominently depend on the amount of overlap between two master strike-slip faults and applied boundary conditions. In case of more overlap between two masters strike-slip faults, ? max mainly concentrated at two corners of the master faults and that reduces and finally reaches zero at the centre of the pull-apart basin, whereas in case of no overlap, ?max largely concentrated at two corners and tips of the master strike-slip faults. These results imply that the distribution and concentration of the maximum shear stress is mainly governed by amount of overlap between the master strike-slip faults in the en-échelon pull-apart formation. Numerical results further highlight that the distribution patterns of the displacement vectors are mostly dependent on the amount of overlap and applied boundary conditions in the en-échelon pull-apart formation.

Ganesh Raj Joshi

2010-06-01

235

The upper limit of maturity of natural gas generation and its implication for the Yacheng formation in the Qiongdongnan Basin, China  

Science.gov (United States)

Vitrinite reflectance (VR, Ro%) measurements from residual kerogen of pyrolysis experiments were performed on immature Maoming Oil Shale substituted the samples for the gas-prone source rocks of Yacheng formation of the Qiongdongnan Basin in the South China Sea. The work was focused on determination an upper limit of maturity for gas generation (ULMGG) or "the deadline of natural gas generation". Ro values at given temperatures increase with increasing temperature and prolonged heating time, but ?Ro-value, given a definition of the difference of all values for VR related to higher temperature and adjacent lower temperature in open-system non-isothermal experiment at the heating rate of 20 °C/min, is better than VR. And representative examples are presented in this paper. It indicates that the range of natural gas generation for Ro in the main gas generation period is from 0.96% to 2.74%, in which ?Ro is in concordance with the stage for the onset and end of the main gas generation period corresponding to 0.02% up to 0.30% and from 0.30% up to 0.80%, respectively. After the main gas generation period of 0.96-2.74%, the evolution of VR approach to the ULMGG of the whole rock for type II kerogen. It is equal to 4.38% of VR, where the gas generation rates change little with the increase of maturation, ?Ro is the maximum of 0.83% corresponding to VR of 4.38%Ro, and the source rock does not nearly occur in the end process of hydrocarbon gas generation while Ro is over 4.38%. It shows that it is the same the ULMGG from the whole rock for type II kerogen as the method with both comparison and kinetics. By comparing to both the conclusions of pyrolysis experiments and the data of VR from the source rock of Yacheng formation on a series of selected eight wells in the shallow-water continental shelf area, it indicate that the most hydrocarbon source rock is still far from reaching ULMGG from the whole rock for type II kerogen. The source rock of Yacheng formation in the local areas of the deepwater continental slope basin have still preferable natural gas generative potential, especially in the local along the central depression belt (namely the Ledong, Lingshui, Songnan and Baodao sags from southwest to northeast) from the depocenter to both the margin and its adjacent areas. It help to evaluate the resource potential for oil and gas of the hydrocarbon source rock in the deepwater continental slope of the Qiongdongnan Basin or other basins with lower exploration in the northern of the South China Sea and to reduce the risk in exploration.

Su, Long; Zheng, Jianjing; Chen, Guojun; Zhang, Gongcheng; Guo, Jianming; Xu, Yongchang

2012-08-01

236

Natural CO2 migrations in the South-Eastern Basin of France: implications for the CO2 storage in sedimentary formations  

International Nuclear Information System (INIS)

Study of natural CO2 analogues brings key informations on the factors governing the long term stability/instability of future anthropogenic CO2 storages. The main objective of this work, through the study of cores from V.Mo.2 well crosscutting the Montmiral natural reservoir (Valence Basin, France), is to trace the deep CO2 migrations in fractures. Petrographic, geochemical and micro-thermometric studies of the V.Mo.2 cores were thus performed in order: 1) to describe the reservoir filling conditions and 2) to detect possible CO2-leakage through the sediments overlying the reservoir. Fluid inclusions from the Paleozoic crystalline basement record the progressive unmixing of a hot homogeneous aquo-carbonic fluid. The Montmiral reservoir was therefore probably fed by a CO2-enriched gas component at the Late Cretaceous-Paleogene. The study of the sedimentary column in V.Mo.2 well, demonstrates that the CO2 did not migrate towards the surface through the thick marly unit (Domerian-Middle Oxfordian). These marls have acted as an impermeable barrier that prevented the upward migration of fluids. Two main stages of fluid circulation have been recognized: 1) an ante- Callovian one related to the Tethysian extension 2) a tertiary stage during which the upper units underwent a karstification, with CO2 leakage related but which remained confined into the deeper parts of the Valence Basin. Since the Paleogene, the Montmiral reservoir has apparently remained stable, despite the Pyrenean and alpine orogeneses. This is mainly due to the efficient seal formed by the thick marly levels and also to the local structuration in faulted blocks which apparently acted as efficient lateral barriers. (author)

237

Nd, Sr-isotopic provenance and trace element geochemistry of Amazonian foreland basin fluvial sands, Bolivia and Peru: Implications for ensialic Andean orogeny  

International Nuclear Information System (INIS)

Nd and Sr isotopes and the trace element contents, including the rare earths, were determined for fluvial sands of lithic arenite composition from the Madre de Dios foreland basin of Bolivia and Peru. On standard petrologic ternary diagrams, the sands fall in the recycled orogen provenance field and thus are similar to typical ancient foreland basin composition. The average rare earth elemental pattern of the sands is identical to the upper continental crustal average, as estimated from post-Archean composite shales of different continents. Ratio of Th/U, Co/Th, La/Sc and Th/Sc of the fluvial sands are intermediate between an average magmatic arc and an upper crustal average compositions. The dispersion of some trace elemental patterns in the sands can be attributed to fractionation of dense minerals, including zircon, during the sedimentation process. The variations of Nd isotopes in conjunction with the petrographic parameters of lithic metamorphic (Lm) and volcanic (Lv) fragments allow a two-fold classification of the sands. These two sand types can be interpreted in terms of mixing among three different provenances: one volcanic rock-suit with less negative ?Nd(O) parameter than the other volcanic suite, and a third metasedimentary source with ?Nd(O) value of around -12, which is considered to be similar to the average western Brazilian shield composition. Thus the overall compositions of the sands has been modeled as mechanical mixtures ofs been modeled as mechanical mixtures of two components, an Andean magmatic arc and the Brazilian shield-derived metasediments. The model is strongly supported by a plot of ?Nd(O) versus ?Sr(O) of the sands. In this plot, the Type 1 and 2 sands define two coherent hyperbolic trends contiguous with two different portions of the Andean magmatic trend. (orig./WB)

238

Petrography and major element geochemistry of the Permo-Triassic sandstones, central India: Implications for provenance in an intracratonic pull-apart basin  

Science.gov (United States)

Detrital mode, composition of feldspars and heavy minerals, and major element chemistry of sandstones from the Permo-Triassic succession in the intracratonic Satpura Gondwana basin, central India have been used to investigate provenance. The Talchir Formation, the lowermost unit of the succession, comprises glacio-marine and glacio-fluvial deposits. The rest of the succession (base to top) comprising the Barakar, Motur, Bijori, Pachmarhi and Denwa formations, largely represent variety of fluvial depositional systems with minor fluvio-deltaic and fluvio-lacustrine sedimentation under a variety of climatic conditions including cold, warm, arid, sub-humid and semi-arid. QFL compositions of the sandstones indicate a predominantly continental block provenance and stable cratonic to fault-bounded basement uplift tectonic setting. Compositional maturity of sandstones gradually increases upwards from the Early Permian Talchir to the Middle Triassic Denwa but is punctuated by a sharp peak of increased maturity in the Barakar sandstones. This temporal change in maturity was primarily controlled by temporal variation in fault-induced basement uplift in the craton and was also influenced by climatic factors. Plots of different quartz types suggest plutonic source rocks for the Talchir sandstones and medium-to high-rank metamorphic plus plutonic source rocks for the younger sandstones. Composition of alkali feldspars in the Permo-Triassic sandstones and in different Precambrian rocks suggests sediment derivation from felsic igneous and metasedimentary rocks. Compositions of plagioclase in the Talchir and Bijori sandstones are comparable with those of granite, acid volcanic and metasedimentary rocks of the Precambrian basement suggesting the latter as possible source. Rare presence of high-K plagioclase in the Talchir sandstones, however, indicates minor contribution from volcanic source rock. Exclusively plagioclase-bearing metasedimentary rock, tonalite gneiss and mafic rocks are the probable sources of plagioclase in the Upper Denwa sandstones. Quartz-rich nature of the sandstones, predominance of K-feldspar over plagioclase and albite rich character of plagioclase in the sandstones is consistent with deposition in an intracratonic, pull-apart basin like the Satpura Gondwana basin. Composition of garnet and its comparison with that from the Precambrian basement rocks suggests mica-schist and amphibolite as possible sources. Predominance of dravite variety of tourmaline in the Permian sandstones suggests sediment supply from metasedimentary rocks. Presence of both dravite and schorl variety of tourmaline in subequal amount in the Triassic sandstones indicates sediment derivation from granitic and metasedimentary rocks. However, schorl-bearing rocks are absent in the basement complex of the study area. A-CN-K plot suggests granites, acid volcanic rock and meta-sediments of the basement as possible sources of the Talchir sandstones and metasedimentary rocks for the Barakar to Pachmarhi sandstones. The Denwa sandstones were possibly derived from K-feldspar-free, plagioclase-bearing metasediments, mafic rocks and tonalite gneiss. Chemical Index of Alteration (CIA) values suggest low intensity source rock weathering for the Talchir sandstones and higher intensity source rock weathering for the others. Various bivariate plots of major oxides composition of the sandstones suggest passive to active continental margin setting and even arc tectonic setting for a few samples.

Ghosh, Sampa; Sarkar, Soumen; Ghosh, Parthasarathi

2012-01-01

239

U-Pb geochronology of the Kap Washington Volcanic Province, North Greenland: Constraints on the timing of continental rifting and implications for the development of the Arctic Basin  

Science.gov (United States)

The Kap Washington volcanic sequence at the north coast of Greenland is bimodal with alkaline basalts, trachytic to rhyolitic lavas, tuffs and ignimbrites predominating. In terms of geochemistry and distribution of rock types, the sequence bears resemblance to presently active continental rift systems, e.g. the Main Ethiopian Rift. Associated with the volcanics is a swarm of coast-normal alkaline basaltic dykes which intensifies towards the outer coast. The volcanics are believed to be linked to rifting in the Arctic Basin and have featured prominently in geotectonic reconstructions of the Arctic region (e.g. Batten et al. 1981). Here we report the first U-Pb zircon ages from silicic lavas and intrusions of the Kap Washington sequence. A total of ten samples have been dated and the duration of magmatism is constrained at present to ca. 10 million years - from 71 to 61 Ma (based on 206Pb/238U ages of concordant analyses). Three age ‘groups’ have been identified: 71-69 Ma (n = 6); 68-65 Ma (n = 2); and 64-61 Ma (n = 2). The oldest group comprises trachytic and rhyolitic lava flows from Kap Kane and a rhyolitic sill from the Kap Washington peninsula. These ages agree well with new 40Ar/39Ar ages obtained on amphiboles from benmoreitic tuffs exposed on Kap Kane (Holm et al., this session) and suggest that most of the ~1.5 km thick Kap Kane sequence was extruded within a period of 1-2 million years. The two younger groups comprise silicic lavas exposed on Lockwood Island. The exposed sequence on Lockwood Island is estimated to be 3-4 km thick and was previously thought to be the oldest part of the succession (Brown et al. 1987). The large scatter in ages on Lockwood Island indicates that magmatism was episodic rather than continuous. The new age data from the Kap Washington volcanics together with 40Ar/39Ar ages for the associated dyke swarm (Kontak et al. 2001) suggest that continental extension and magmatism occurred in the area between ca. 82 and 61 Ma. This age bracket seems to preclude any relation to initial spreading on the Nansen-Gakkel Ridge (52 Ma-present) and an association with spreading in the Labrador Sea-Baffin Bay-Makarov Basin system seems the most probable. We propose that the Kap Washington magmatism ceased with the onset of seafloor spreading in the Northeast Atlantic-Eurasia Basin system, which shifted the tectonic regime in North Greenland from extensional to compressional, culminating with the Eurekan deformation in early Eocene (Holm et al., this session). References: Batten et al. (1981): Nature 294: 150-152. Brown et al. (1987): J Geol. Soc. Lond. 144: 707-715. Kontak et al. (2001): Can. Mineral. 39: 997-1020

Thorarinsson, S. B.; Holm, P. M.; Tappe, S.; Heaman, L.; Tegner, C.

2009-12-01

240

Genetic origins of marine gases in the Tazhong area of the Tarim basin, NW China: Implications from the pyrolysis of marine kerogens and crude oil  

Energy Technology Data Exchange (ETDEWEB)

Although abundant natural gases have been discovered in Carboniferous and Ordovician reservoirs in the Tazhong area, central Tarim basin, their genetic origins is still an open question because of significant variations in chemical and carbon isotopic compositions. In the present study, three samples representing the possible gas sources were pyrolyzed using sealed gold tubes to investigate their gas potentials, and chemical and carbon isotopic signatures. The samples were a crude oil, a low maturity kerogen and a high maturity kerogen. The results show that the chemical and isotopic compositions of gaseous pyrolysates from the three samples are quite different. Generally, the gases from oil cracking are compositionally wetter and isotopically lighter than those from kerogen cracking at similar thermal levels. The large quantities of methane experimentally observed in oil cracking gases are mainly associated with the re-cracking of wet gases at very high maturity levels. Methane in gases derived from kerogen, especially high maturity kerogen, in contrary, is mainly generated by the demethylation reaction. The diagrams of {delta}{sup 13}C{sub 1} vs. {delta}{sup 13}C{sub 2}-{delta}{sup 13}C{sub 3} and C{sub 2}/C{sub 3} vs. {delta}{sup 13}C{sub 2}-{delta}{sup 13}C{sub 3}, along with natural gas plots, have proven to be a very effective tool in the genetic interpretation of natural gases from kerogen and oil cracking in the Tarim basin. Their combined application shows that two types of gas source can be identified in the Tazhong area. The first type is oil cracking gas, mainly discovered in Carboniferous reservoirs of the central fault horst area, but also partly in Ordovician reservoirs, such as in the wells TZ45, TZ44b and TZ 16. The other is kerogen cracking gas occurring largely in Ordovician reservoirs, especially in the North Slope area. The two types of gases, however, are mixed in many reservoirs as their generation is overlapped in time and/or space. This mixing process is especially obvious for methane. (author)

Tian, Hui; Xiao, Xianming; Guo, Liguo; Yang, Liguo [State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Wilkins, Ronald W.T. [CSIRO Petroleum, P. O. Box 136, North Ryde, NSW (Australia); Gan, Huajun [Department of Coal and Coalbed Methane Engineering, Faculty of Earth Resources, China University of Geosciences, Wuhan 430074 (China)

2010-05-01

 
 
 
 
241

Vegetation and geomorphic significance of the riparian greenline in the Sprague River basin, southern Oregon: implications for biogeomorphic monitoring of riparian corridors in semi-arid mountain valleys  

Science.gov (United States)

Like many regions in the western U.S., valley-floor environments of the semi-arid Sprague River basin of southern Oregon are heavily irrigated and widely grazed by cattle. To better understand the impacts of grazing and other land uses on river quality, the Klamath Tribes have begun a long-term, basin-wide program aimed at: (1) establishing baseline geomorphic and vegetative conditions along the Sprague River and its tributaries, and (2) monitoring changes in these conditions over time. Because of its widespread use and ease of application, determining the composition of the lowest line of perennial vegetation above baseflow, or the “greenline,” has been included. The goal of this paper is to summarize results of 38 greenline surveys conducted at 19 sites in 2008-9 and to explore geomorphic hypotheses that may explain vegetation patterns evident in the surveys. Spikerush (Eleocharis ssp.) and reed-canary grass (Phalaris arudinacea) were the most commonly occurring vegetation in the greenline across all sites. Because these species are aggressive colonizers, they indicate high availability of fresh alluvium, which may be associated with sustained channel-bank disturbance. Sedges dominated some portions of the greenline at most of the sites, but occurred in less abundance. The late successional or early-to-late transitional state of these sedges, combined with their relatively low frequency, further supports the hypothesis that channel-bank systems remain chronically disturbed and dynamic. Grazing is common, but variable in intensity, at nearly all of the study sites, likely contributing to the persistence of channel-bank disturbance. Among meandering channels, the richness of dominant species (i.e., “community diversity”) was higher on the outer bends than on the inner bends of meanders at 10 of 12 sites. The variability of geomorphic surfaces (old floodplain, new floodplain, failed bank, accreted toe, etc.) incorporated in the greenline by the spatially discontinuous processes of channel-bank erosion and failure on the outer meander bends appears to increase the types of habitats surveyed and their combined biodiversity. In contrast, the spatial continuity of bar accretion on the inner meander bends appears to result in a more uniform geomorphic setting with fewer dominant species in the greenline. Despite widespread recognition that geomorphic processes influence riparian vegetation, factors such as the type and severity of bank erosion, the location of the survey with respect to meander geometry, and the type of geomorphic surface underlying greenline observations are not explicitly included in published guidance for biogeomorphic monitoring of the riparian greenline. Inclusion of such factors would improve communication, study design, and application of research by fluvial geomorphologists, riparian ecologists, and resource managers utilizing the greenline methodology.

Hughes, M. L.; Leeseberg, C.

2009-12-01

242

Implications of clumped-isotope thermometry for the deposition and alteration of evaporite-carbonate sabkha cycles in the Jurassic Weald Basin, U.K  

Science.gov (United States)

Marginal marine Jurassic evaporite-carbonate cycles in the Weald Basin, United Kingdom, are examined using clumped isotope thermometry to reconstruct the temperature of a sabkha system and determine their paleoenvironment and diagenetic histories. The objective is to provide insight into the depositional parameter and burial history of the sabkha deposits, and thus to constrain whether they have undergone secondary alteration. Previous studies of evaporite temperature distribution trends have utilized fluid inclusion micro-thermometry to derive the temperatures of precipitation for evaporites. However, we aim to couple ?18O and clumped isotope analyses to investigate meter-scale spatial variations in the temperature at which calcitic marls inter-bedded with evaporite sequences were precipitated. Furthermore, this approach will allow for the isotopic composition of the diagenetic fluid to be reconstructed. Discrete laterally-extensive marly horizons occur in anhydrite of the Lower Purbeck and our focus is placed on marly algal limestone outcropping ~300 m below surface in Brightling Mine. Preliminary data from one sample yields a datum with ?48 and ?48 values of 242.6‰ and 256.2‰, respectively, and a ?48 offset from the heated gas line larger than 2‰. The ?47 and ?47 values are 0.038×0.01‰ and 7.25×0.02‰, respectively. These results point out possible contamination (e.g., by sulfur) because a sample should not yield a signal at mass ?48 due to the low abundance of isotopologues of this mass. XRD analysis shows a high intensity calcite peak at 29.4 °2? (CuK? radiation), gypsum at 11.6 °2?, and a peak of anhydrite at 22.7 °2?. Subsequent to cleaning the sample twice utilizing a mixture of dilute 3% H2O2-Calgon-Nh3 solution, a second XRD analysis was conducted and only showed a high intensity calcite peak at 29.4 °2?. This indicates that the cleaning procedure dissolved evaporitic material and it will be repeated for future clumped isotope analyses. The reconstructed clumped isotope temperatures are independent from the ?18O composition of the fluid, and thus, the associated carbonates within evaporites can provide a more profound understanding of the temperature histories of carbonate depositional facies. Future work will also include reconstructing the temperature of precipitation and fluid composition involved in the precipitation of potential carbonate phases within another sabkha system, in the Upper Permian Zechstein Group in the Southern Permian Basin, which will allow for a comparison of precipitation temperatures within sulfate deposits.

Abbott, S.; John, C. M.; Fraser, A.

2013-12-01

243

Application of integrated vitrinite reflectance and FAMM analyses for thermal maturity assessment of the northeastern Malay Basin, offshore Vietnam: Implications for petroleum prospectivity evaluation  

DEFF Research Database (Denmark)

Several exploration wells have intersected a Cenozoic coal-bearing, fluvial-deltaic mudstone and sandstone succession in the northeastern Vietnamese part of the Malay Basin, and have successfully tested seismically identified direct hydrocarbon indicators (DHIs). The oil and gas/condensate discovery ell 46-CN-1x encountered a _55m thick section of lacustrine mudstones having considerable potential as an oil source. Vitrinite reflectance (VR) measurements from these alginite-bearing rocks introduce several problems in thermal maturity evaluation, including associated VR suppression and delineation of cavings and bitumens. Reliable thermal maturity gradients, however, may be established using a combination of conventional VR measurements and ‘equivalent VR' (EqVR) values derived from the fluorescence alteration of multiple macerals (FAMM) technique. These measurements, performed on dispersed organic matter (DOM) in cuttings from 46-CN-1x, allow separation of low-reflecting bitumens and vitrinite in cavings fromindigenous vitrinite and the FAMM results indicate VR suppression of 0.14% in an alginite-bearing mudstone with a high Hydrogen Index value. On the basis of available ‘raw' VR data, a highly irregular maturity trend is determined, with the deepest sample (2675-2680m) having a VR of _0.4%Ro. The EqVR value, however, for the deepest sample is 0.70%. The maturity trend determined from the FAMM data (and VR data, omitting samples having suppressed VR) indicates that the top of the oil window (VR of 0.75%Ro) is located at about 2800m depth. Modelling the geothermal gradient using the EASY%Ro algorithm yields _40 1C/km for both of the two maturity profiles; his is in the low end of the range for the Malay Basin. Modelled temperature histories indicate onset of hydrocarbon generation for the uppermost Oligocene source rocks between 2Ma and present-day, which post-dates trap formation. Seismic facies patterns suggest that lacustrine oil-prone units are in he oil window in the same graben complex a few km NW of the investigated well, and these rocks are likely to be the source of the hydrocarbons found in the well. A more widespread occurrenceof hydrocarbons sourced from this kitchen is indicated by other discoveries and mapping of DHIs in the area.

Petersen, H. I.; Sherwood, N.

2008-01-01

244

Clay mineral assemblages of terrestrial records (Xining Basin, China) during the Eocene-Oligocene climate Transition (EOT) and its environmental implications  

Science.gov (United States)

The Eocene-Oligocene Transition (EOT) between ~34.0 and 33.5 million years ago, where global climate cooled from 'greenhouse' to 'icehouse' at ~33.5 Ma ago, is one of the great events during Cenozoic climate deterioration. In contrast to the marine records of the EOT, significantly less research has focused on the continental climate change during this time, particularly in inner Asia. We present a comprehensive study of the upper Eocene to lower Oligocene succession with regular alternations of laterally continuous gypsum/gypsiferous layers and red mudstone beds in Tashan section of Xining Basin, which is located at the northeastern margin of the Tibetan Plateau. Clay minerals, which were extracted from this succession, were analyzed qualitatively and semi-quantitatively by using X-ray differaction (XRD). Base on detailed magnetostratigraphic time control, clay mineral compositions of this succession (33.1-35.5 Ma) are compared with open ocean marine records and Northern Hemisphere continental records to understand the process and characteristics of Asian climate change before, during and after EOT. Our results indicate that illite is the dominant clay mineral with less chlorite and variable smectite. Multi-parameter evidence suggests that the source areas of detrital inputs in Tashan have not changed and climate is the main control for the composition of the clay fraction. The characteristics of clay mineral concentrations suggest warm and humid fluctuations with cold and dry conditions and intense of seasonality during ~35.5-34.0 Ma in inner Asian. This changed to cold and dry condition at ~34 Ma and remained so from ~34-33.1 Ma. The comparisons between continental and marine records indicate that the climate changes experienced in the Xining basin region are more consistent with Northern Hemisphere rather than open oceans records. This indicates that paleoclimate changes for inner Asian before, during and after EOT was not controlled by Antarctic ice growth, but may be due to atmospheric cooling linked to the existence and expansion of Northern Hemisphere glaciation.

Zhang, C.; Guo, Z.

2013-12-01

245

New glacial evidences at the Talacasto paleofjord (Paganzo basin, W-Argentina) and its implications for the paleogeography of the Gondwana margin  

Science.gov (United States)

The Talacasto paleovalley is situated in the Central Precordillera of San Juan, Argentina, where upper Carboniferous-Permian rocks (Paganzo Group) rest on Devonian sandstones of the Punta Negra Formation. This outcrop is an excellent example of a glacial valley-fill sequence that records at least two high-frequency cycles of the advance and retreat of a glacier into the valley. The paleocurrent analysis shows transport predominantly to the south, indicating that at this site the ice flow differs from the other nearby paleovalleys. Evidence of the glacial origin of this valley can be seen in the glacial striae on the valley's sides, as well as the U-shape of the valley, indicated by very steep locally overhanging valley walls. Deglaciation is indicated by a set of retransported conglomerates deposited in a shallow-water environment followed by a transgressive succession, which suggests eustatic rise due to meltwater input to the paleofjord. The complete sedimentary succession records distinct stages in the evolution of the valley-fill, represented by seven stratigraphical units. These units are identified based on facies associations and their interpreted depositional setting. Units 1 to 5 show one cycle of deglaciation and unit 6 marks the beginning of a new cycle of glacier advance which is characterized by different types of glacial deposits. All units show evidence of glacial influence such as dropstones and striated clasts, which indicates that the glaciers were always present in the valley or in adjacent areas during sedimentation. The Talacasto paleofjord provides good evidence of the Late Paleozoic Gondwana glaciation in western Argentina and examples of sedimentary successions which have been interpreted as being deposited by a confined wet-based glacier in advance and retreat cycles, with eventual release of icebergs into the basin. The outcrop is also a key for reconstructing the local glacial paleogeography, and it suggests a new interpretation that is not in agreement with previous studies. Finally, the importance of the Talacasto paleovalley for the Paganzo basin lies in its orientation, because it allows the reconstruction of the ice paleoflow and indication, for the first time, that marine ingressions into this area were not taking place along the Jachal trough, as expected, but along a different connection to the sea, which for this work we will call the San Juan Paleotrough.

Aquino, Carolina Danielski; Milana, Juan Pablo; Faccini, Ubiratan Ferrucio

2014-12-01

246

Conjugate fracture pairs in the Molina Member of the Wasatch Formation, Piceance basin, Colorado: Implications for fracture origins and hydrocarbon production/exploration  

Energy Technology Data Exchange (ETDEWEB)

The sandstones of the Molina Member of the Wasatch Formation in the Piceance basin of northwestern Colorado contain a suite of fractures that have a conjugate-pair geometry. The fractures are vertical and intersect at an acute angle of between 20 and 40 degrees. Although direct evidence of shear is rare, the fracture surfaces commonly display small steps. The fracture geometries suggest that the maximum compressive stress during fracturing was in the plane of the acute angle of the conjugate fractures: the steps are interpreted as broken-face manifestations of very low angle en echelon fractures, formed within exceptionally narrow zones of incipient shear. In contrast to the highly anisotropic permeability enhancement created by subparallel vertical extension fractures in the underlying Mesaverde Formation, the conjugate pairs in the Molina sandstones should create a well connected and relatively isotropic mesh of fracture conductivity. Increases in stress magnitudes and anisotropy during production drawdown of reservoir pressures should cause shear offsets along the fractures, initially enhancing permeability.

Lorenz, J.C.

1997-05-01

247

Gangdese arc detritus within the eastern Himalayan Neogene foreland basin: Implications for the Neogene evolution of the Yalu-Brahmaputra River system  

Science.gov (United States)

In order to assess the spatial and temporal extent of sediment transport from the Gangdese batholith of Tibet to the eastern Himalayan Neogene foreland basin, we performed U-Pb and Lu-Hf analyses on eleven sandstone samples from three locations within the Arunachal and Sikkim Himalaya. We also analyzed detrital zircons from eight modern river sand samples of the Yalu-Brahmaputra River system and its major tributaries in the eastern Himalaya. Results from the river sands are used to contrast the provenance characteristics of the Gangdese arc in southern Tibet with nominally equivalent arc rocks east of the Himalaya in the northernmost Indo-Burma Ranges. Our results indicate that the deposition of Gangdese batholith-derived sediment within the eastern Himalayan foreland: (1) occurred throughout Late Miocene and Pliocene time (~ 10-3 Ma), (2) was limited to the Arunachal Himalaya, and (3) was sourced north of the Himalaya. This detritus may have been deposited by a transverse Himalayan river, such as the Subansiri River, as suggested by high percentages of the Gangdese-derived zircons within the Neogene samples (15-31%) and S- to SW-oriented paleocurrent directions from two of the Neogene sample localities. At this time, our preferred model to explain the data invokes capture of an originally westward-flowing Yalu River by the Subansiri River at ~ 10 Ma, followed by capture of the Yalu River by the Siang River at ~ 3-4 Ma.

Cina, Sara E.; Yin, An; Grove, Marty; Dubey, Chandra S.; Shukla, Dericks P.; Lovera, Oscar M.; Kelty, Thomas K.; Gehrels, George E.; Foster, David A.

2009-07-01

248

The distribution and characteristics of the igneous complexes in the northern East China Sea shelf basin and their implications for hydrocarbon potential  

Science.gov (United States)

This study presents results of two-dimensional seismic mapping of the northern East China Sea Shelf Basin. Various igneous features such as sills, volcanic edifices and stocks were identified by the geophysical exploration. The sills are most common, and are observed at more than 90 locations. Most mapped sills in the study area are characterized by high-amplitude continuous reflections with distinct terminations. Saucer- and cup-shaped sills are observed locally. The stocks are discordant (nearly vertical) igneous bodies and they are characterized by seismic transparency, with upturned host rocks and uplifted overburden. The volcanic edifices and/or necks consist of irregular mounds and peaks and are characterized by strong positive top reflections with chaotic internal facies. The oldest igneous activity in the northern ECSSB is late Cretaceous (123.3±3.7). This igneous activity coincides with those observed in eastern China which has been related mainly to the subduction of the Pacific Plate beneath Eurasia Plate. The Miocene igneous activity is well constrained based on seismic stratigraphic relationships within the folded stratigraphy, age dating, and the occurrence of igneous sills. The timing of this intrusion is coincident with the intensive igneous activity as previously suggested for the eastern China. Igneous rocks can produce hydrocarbon traps, reservoirs and they can act as a seal, and therefore are of great importance in petroleum study.

Cukur, D.; Horozal, S.; Lee, G. H.; Kim, D. C.; Han, H. C.

2012-04-01

249

Magnetic mineral study of Holocene marine sediments from the Alfonso Basin, Gulf of California: implications for depositional environment and sediment sources  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: English Abstract in spanish Se presentan los resultados del estudio de propiedades magnéticas en sedimentos marinos colectados en la Cuenca Alfonso en la Bahía de la Paz, los cuales se analizan en términos de las fuentes de aporte y el ambiente de depósito en el sur del Golfo de California durante el Holoceno. El control estra [...] tigráfico se basa en fechamientos de radiocarbono, que indican una edad para los sedimentos de fondo del núcleo de alrededor de 7597-7831 años cal. B.P. La señal magnética está dominada por minerales de grano fino de titanomagnetitas, los cuales provienen de las secuencias de tobas silícicas expuestas en la Bahía de la Paz. La mineralogía magnética es relativamente homogénea como lo indican las mediciones de propiedades de susceptibilidad magnética, magnetización remanente y coercitividad. Los ciclos de histéresis magnética indican la ocurrencia de componente paramagnéticas y los ciclos correspondientes después de la corrección paramagnética muestran ciclos que saturan en campos bajos y altos valores de magnetización de saturación. Las gráficas de discriminación de estado de dominio magnético empleando cocientes de los parámetros de histéresis muestran que las muestras se agrupan en el campo de dominio pseudos-sencillo, sugiriendo mezclas de dominios sencillo y múltiple. Los registros de susceptibilidad magnética revelan valores altos de factores de dependencia de frecuencia, en particular en el segmento del Holoceno Medio, lo que sugiere contribuciones de minerales superparamagnéticos de grano fino y posible transporte eólico. La presencia de laminaciones finas, características de la secuencia de Alfonso indica condiciones anóxicas en el fondo de la cuenca. El ambiente de depósito durante el Holoceno parece ser dominado por sedimentos detríticos pluviales y sedimentos de grano muy fino y transporte eólico, con menor contribución de sedimentos biogénicos. Abstract in english Results of a rock magnetic study of marine sediments from the Alfonso Basin, Bay of La Paz are used to investigate sediment sources and depositional environment in the southern Gulf of California during the Holocene. Radiocarbon dating provides stratigraphic control, with age for the core bottom sed [...] iments of 7597-7831 cal. yr B.P. Magnetic signal is dominated by fine-grained titanomagnetites, derived from the silicic volcanic units surrounding the Bay of La Paz. Magnetic mineralogy is relatively homogenous as seen in bulk magnetic properties of low-field susceptibility, remanent intensity and coercivity. Magnetic hysteresis loops show strong variable paramagnetic components; after paramagnetic correction loops show saturation at low fields and high saturation magnetization values. Plots of hysteresis parameter ratios for domain state show that samples group in the pseudo-single domain field, with mixtures of single and multi-domain particles. Magnetic susceptibility log shows relatively high frequency dependence factors, particularly for the Middle Holocene, suggesting contribution of fine-grained superparamagnetic minerals related to eolian deposition. The well-preserved laminated sequence indicates predominant anoxic conditions in the basin floor. Depositional environment had a dominant supply of pluvial detrital sediments and eolian fine-grained dust composed of siliciclastic volcanically-derived material with less abundant biogenic input.

L, Pérez-Cruz; J, Urrutia-Fucugauchi.

2009-09-01

250

Complementing data-driven and physically-based approaches for predictive morphologic modeling: Results and implication from the Red River Basin, Vietnam  

Science.gov (United States)

During the last 30 years, the delta of the Red River (Song Hong) in northern Vietnam experienced grave morphologic degradation processes which severely impact economic activities and endanger region-wide livelihoods. Rapidly progressing river bed incision, for example, threatens the irrigation of the delta's paddy rice crops which constitute 20% of Vietnam's annual rice production. Morphologic alteration is related to a drastically changed sediment balance due to major upstream impoundments, sediment mining and land use changes, further aggravated by changing hydro-meteorological conditions. Despite the severe impacts, river morphology was so far not included into the current efforts to optimize basin wide water resource planning for a lack of suitable, not overly resource demanding modeling strategies. This paper assesses the suitability of data-driven models to provide insights into complex hydromorphologic processes and to complement and enrich physically-based modeling strategies. Hence, to identify key drivers of morphological change while evaluating impacts of future socio-economic, management and climate scenarios on river morphology and the resulting effects on key social needs (e.g. water supply, energy production and flood mitigation). Most relevant drivers and time-scales for the considered processes (e.g. incision) - from days to decades - were identified from hydrologic and sedimentologic time-series using a feature ranking algorithm based on random trees. The feature ranking pointed out bimodal response characteristics, with important contributions of long-to-medium (5 - 15 yrs.) and rather short (10d - 6 months) timescales. An artificial neural network (ANN), built from identified variables, subsequently quantified in detail how these temporal components control long term trends, inter-seasonal fluctuations and day to day variations in morphologic processes. Whereas the general trajectory of incision relates, for example, to the overall regional sediment balance over an extended time-horizon (>15 yrs.), upstream impoundments induce a much more rapid adaptation (1-5 yrs.). The applicability of the ANN as predictive model was evaluated by comparing its results with a traditional, 1D bed evolution model. The next decade's morphologic evolution under an ensemble of scenarios, considering uncertainties in climatic change, socio-economic development and upstream reservoir release policies was derived from both models. The ANN greatly outperforms the 1D model in computational requirements and presents a powerful tool for effective assessment of scenario ensembles and quantification of uncertainties in river hydro-morphology. In contrast, the processes-based model provides detailed, spatio-temporally distributed outputs and validation of the ANN's results for selected scenarios. We conclude that the application of both approaches constitutes a mutually enriching strategy for modern, quantitative catchment management. We argue that physically based modeling can have specific spatial and temporal constrains (e.g. in terms of identifying key drivers and associated temporal and spatial domains) and that linking physically-based with data-driven approaches largely increases the potential for including hydro-morphology into basin-scale water resource management.

Schmitt, R. J.; Bernardi, D.; Bizzi, S.; Castelletti, A.; Soncini-Sessa, R.

2013-12-01

251

Coal petrology of coal seams from the Leao-Butia Coalfield, Lower Permian of the Parana Basin, Brazil - Implications for coal facies interpretations  

Energy Technology Data Exchange (ETDEWEB)

In the Leao-Butia Coalfield, Rio Grande do Sul the coal seams occur in the Rio Bonito Formation, Guata Group, Tubarao Supergroup of the Parana Basin, Brazil and are of Permian (Artinskian-Kungurian) age. This study is the first detailed investigation on the coal petrographic characterization of the coal-bearing sequence in relation to the depositional settings of the precursor mires, both in terms of whole seam characterization and in-seam variations. The study is based on the analyses of nine coal seams (I2, CI, L4, L3, L2, L1, S3, S2, S1), which were selected from core of borehole D-193, Leao-Butia and represent the entire coal-bearing sequence. The interpretation of coal facies and depositional environment is based on lithotype, maceral and microlithotype analyses using different facies-critical petrographic indices, which were displayed in coal facies diagrams. The seams are characterized by the predominance of dull lithotypes (dull, banded dull). The dullness of the coal is attributed to relatively high mineral matter, inertinite and liptinite contents. The petrographic composition is dominated by vitrinite (28-70 vol.% mmf) and inertinite (> 30 vol.% mmf) groups. Liptinite contents range from 7 to 30 vol.% (mmf) and mineral matter from 4-30 vol.%. Microlithotypes associations are dominated by vitrite, duroclarite, carbominerite and inertite. It is suggested that the observed vertical variations in petrographic characteristics (lithotypes, microlithotypes, macerals, vitrinite reflectance) were controlled by groundwater level fluctuations in the ancient mires due to different accommodation/peat accumulation rates. Correlation of the borehole strata with the general sequence-stratigraphical setting suggests that the alluvial fan system and the coal-bearing mudstone succession are linked to a late transgressive systems tract of sequence 2. Based on average compositional values obtained from coal facies diagrams, a deposition in a limno-telmatic to limnic coal facies is suggested. (author)

Silva, M.B. [Laboratorio de Oceanografia Geologica, Departamento de Geociencias, Fundacao Universidade Federal do Rio Grande, FURG, Av. Italia km 08, Campus Carreiros, 96201-900, Rio Grande, RS (Brazil); Kalkreuth, W.; Holz, M. [Instituto de Geociencias, UFRGS, Av. Bento Goncalves, 9500 91501-970 Porto Alegre, RS (Brazil)

2008-02-01

252

In situ geochemistry of Lower Paleozoic dolomites in the northwestern Tarim basin: Implications for the nature, origin, and evolution of diagenetic fluids  

Science.gov (United States)

Paleozoic sedimentary rocks in the northwestern Tarim basin were strongly altered by complicated geofluids, which resulted in the occurrence of various diagenetic minerals (e.g., dolomite). Here, in situ major, trace, and rare earth element geochemistry of Lower Ordovician diagenetic dolomite grains as well as petrography were performed to unravel the geochemical features, the nature, and origin of the diagenetic fluids. The results indicate that different geochemical information can be detected within a single sample, even within a single dolomite grain. Five generations of diagenetic dolomite have been identified based on geochemical signatures, resulting from four distinct types of diagenetic fluids: (1) HREE enrichment (PAAS-normalized), low ?REE, no Eu anomaly, low Mn, Ba, moderate Fe, and high Sr contents are probably due to early burial dolomitizing fluids; (2) MREE enrichment, high ?REE, high Mn, Fe, and low Sr content are likely to be associated with Devonian deep-circulating crustal hydrothermal fluids; (3) flat or LREE enrichment pattern with obviously positive Eu anomaly is inferred to be linked to Permian magmatic hydrothermal fluids; and (4) flat REE pattern, moderate ?REE, no Eu anomaly, low Mn, Ba, moderate Fe, and high Sr contents are probably due to late burial dolomitizing fluids. The significances of in situ method demonstrated in this study, compared with the whole rock analysis, include not only contamination-free analysis but also unraveling the internal geochemical variation within a single sample or a mineral grain. Thus, for the geochemical study of complicated diagenetic process, in situ method should be preferentially considered.

Zhang, Wei; Guan, Ping; Jian, Xing; Feng, Fan; Zou, Caineng

2014-07-01

253

Hydrothermal activity and its paleoecological implications in the latest Miocene to Middle Pleistocene lacustrine environments of the Baza Basin (Betic Cordillera, SE Spain)  

Science.gov (United States)

The continental sedimentary record of the Baza Basin (Guadix-Baza Depression, Betic Cordillera, SE Spain) shows six sedimentary units of lacustrine origin deposited from the latest Miocene to the Middle Pleistocene. Depending on the interval considered, the lacustrine deposits are mainly composed of marls, carbonates or gypsiferous evaporites, showing lithological, mineralogical and geochemical features (i.e., magnesium, strontium and sulfur contents, celestine deposits and travertine growths) that are evidence of intense, tectonically-induced hydrothermal activity. According to the high concentrations of strontium and sulfur as well as the abundance of travertines and magnesium clays, the supply of hot waters was greater during the Zanclean, the Gelasian and the Calabrian, as a result of tectonic activity. Hydrothermal activity has continued until the present time and is responsible of the hot springs that are nowadays active in the Guadix-Baza Depression. The paleoenvironmental consequences of these sublacustrine hot springs were that during some intervals the lakes maintained a relatively permanent water table, not subject to periodic desiccations in the dry season, and warmer temperatures throughout the year. This resulted in a high level of organic productivity, especially for the Calabrian, which allowed the development of a rich and well diversified mammalian community, similar to those of modern African savannas with tree patches. In this mild environment, the permanent water sheet favored the presence of drought intolerant megaherbivores such as the giant extinct hippo Hippopotamus antiquus. The high standing crop biomass of ungulates resulted in the availability of abundant carcasses for scavengers such as hyenas and hominins, which explains the very high densities of skeletal remains preserved in the sediments distributed along the lake surroundings.

García-Aguilar, José Manuel; Guerra-Merchán, Antonio; Serrano, Francisco; Palmqvist, Paul; Flores-Moya, Antonio; Martínez-Navarro, Bienvenido

2014-07-01

254

Organic geochemistry of the Callovo-Oxfordian argillo-carbonated sedimentary series of the East of the Paris basin and of England. Variabilities and paleo-environmental implications  

International Nuclear Information System (INIS)

The Callovo-Oxfordian clay-stones from the East of the Paris basin are studied by ANDRA in order to test the feasibility of a possible storage of radioactive waste. The molecular analysis of their organic matter indicates that they can be considered as homogenous from their organic content point of view because they are characterized by only one molecular facies. However, the transition to the surrounding limestones is underlined by a major evolution of the molecular facies indicating a change and an increase of the variability of the deposition and diagenesis conditions. The evolution of the distribution of the plant bio-markers indicates, at the end of the Lower Oxfordian, a paleo-floristic change characterized by the increase of the proportion of Pinaceae (a conifer family) or their forerunners on the London-Brabant massif. This paleo-floristic evolution reflects a paleo-climatic change characterized by the increase of aridity at the global scale. Other complementary results get on other sedimentary series of similar ages highlight the occurrence of a period of water anoxia during the Middle Callovian which certainly happened on the major part of the Western Europe. This event could be at the origin of the crisis of the carbonate production at the Dogger/Malm transition. On the other hand, an experimental technique based on artificial maturation of extant plants has been developed and will allow the acquisition of new palaeo-chemo-taxonomic data. These data will contribute to a better interpretation of plant bio-marker assemblages in terms of palaeo-floristic composition. (author)

255

Quantifying water requirements of riparian river red gum (Eucalyptus camaldulensis) in the Murray-Darling Basin, Australia: implications for the management of environmental flows  

Science.gov (United States)

Water resource development and drought have altered river flow regimes, increasing average flood return intervals across floodplains in the Murray-Darling Basin, Australia, causing health declines in riparian river red gum (Eucalyptus camaldulensis) forests and woodlands. Environmental flow allocations helped to alleviate water stress during the recent Millennium Drought (1997–2010), however, quantification of the flood frequency required to support healthy E. camaldulensis communities is still needed. We quantified water requirements of E. camaldulensis for two years across a flood gradient (trees inundated at frequencies of 1:2, 1:5 and 1:10 years) at Yanga National Park, New South Wales to help inform management decision-making and design of environmental flows. Sap flow, evaporative losses and soil moisture measurements were used to determine transpiration, evapotranspiration and plant-available soil water before and after flooding. A formula was developed using plant-available soil water post-flooding and average annual rainfall, to estimate maintenance time of soil water reserves in each flood frequency zone. Results indicated that soil water reserves could sustain 1:2 and 1:5 trees for 15 months and six years, respectively. Trees regulated their transpiration rates, allowing them to persist within their flood frequency zone, and showed reduction in active sapwood area and transpiration rates when flood frequencies exceeded 1:2 years. A leaf area index of 0.5 was identified as a potential threshold indicator of severe drought stress. Our results suggest environmental water managers may have greater flexibility to adaptively manage floodplains in order to sustain E. camaldulensis forests and woodlands than has been appreciated hitherto.

Doody, Tanya M.; Colloff, Matthew J.; Davies, Micah; Koul, Vijay; Benyon, Richard G.; Nagler, Pamela L.

2015-01-01

256

Chemistry of sands from the modern Indus River and the Archean Witwatersrand basin: Implications for the composition of the Archean atmosphere  

International Nuclear Information System (INIS)

Both the Indus River and the Witwatersrand basin contain sand with grains of detrital uraninite. Because this mineral is easily oxidized, its presence in Archean strata as a detrital particle has been used as evidence for a low-oxygen atmosphere before 2.5 Ga. However, its presence in modern sand from the Indus River system has been used to argue that detrital uraninite does not provide information about the oxygen concentration of Earth's early atmosphere. Petrographic and chemical study of sand from these two sources reveals differences that suggest the modern Indus sand cannot be used as an analog for the Archean Witwatersrand occurrences. The Witwatersrand quartzites are depleted in Ca, Mg, and Na, indicating that the original sand from which they formed had been subjected to intense weathering. The chemical index of alteration (CIA), a commonly used indicator of degree of weathering, yields an average value of about 0.80 for Witwatersrand quartzites, comparable to modern tropical streams such as the Orinoco that drain deeply weathered terrains under tropical conditions (CIA=0.75). In contrast, the CIA for Indus sand is 0.45, indicating virtually no chemical weathering. The significance of Archean quartz-pebble conglomerates is not just that they contain unstable detrital phases like uraninite and pyrite, but that these particles are associated with rocks whose compositions suggest intense weathering. These conglomerates must have been subjected to intense weatherust have been subjected to intense weathering under tropical conditions, either in their source area or at the site of deposition, and the preservation of minerals like uraninite such conditions is indeed strong evidence for a low-oxygen atmosphere

257

Hydrogeochemical contrasts between low and high arsenic groundwater and its implications for arsenic mobilization in shallow aquifers of the northern Yinchuan Basin, P.R. China  

Science.gov (United States)

Little is known about hydrogeochemical contrasts between low and high As groundwaters and their connection to As mobilization in the Yinchuan Basin. Investigations were carried out to evaluate As distribution and geochemical processes for As mobilization in three regions, including piedmont proluvial fans (PA), dry farmland (DF) and paddy farmland (PF). Ninety-two groundwater samples, 4 surface water samples, and 66 sediments samples were collected and analyzed for chemical and isotopic components. Results show that low As groundwater is generally found in PA. However, high As concentrations (up to 105 ?g L-1) are mainly observed in groundwaters from DF and PF, which are associated with reducing conditions. High As groundwater is characterized by high concentrations of NH4+, dissolved Mn, dissolved Fe and Fe(II), and low concentrations of NO3- and SO42-. The intensive irrigation in PF recharges the aquifers by vertical infiltration of the diverted Yellow River water, and leads to the higher redox potentials and the lower dissolved As in comparison with those in DF. Environmental isotopes (?18O and ?D) show that evaporation due to the intensive irrigation plays a minor role in As enrichment. The positive correlation between As and dissolved Fe suggests that groundwater As would result from the reductive dissolution of Fe oxides. Besides, dissolved P may be involved in competing with As for binding sites on Fe oxide minerals. Sediment As ranges between 3.94 and 75.2 mg kg-1. HCl-leached As accounts for 60% of total As in the sediments, while H3PO4-leached As accounts for 5%. Depth-matched samples show a good correlation between dissolved As and H3PO4-leached As in sediments. Arsenic distribution coefficient (Kd), calculated from H3PO4-leached As and dissolved As, ranges between 5.08 and 17.3 cm3 g-1, which generally depends on groundwater redox potentials. In reducing conditions, low values are found with As being preferentially partitioned into groundwater.

Guo, Qi; Guo, Huaming; Yang, Yuance; Han, Shuangbao; Zhang, Fucun

2014-10-01

258

Hydrologic models of modern and fossil geothermal systems in the Great Basin: Genetic implications for epithermal Au-Ag and Carlin-type gold deposits  

Science.gov (United States)

The Great Basin region in the western United States contains active geothermal systems, large epithermal Au-Ag deposits, and world-class Carlin-type gold deposits. Temperature profiles, fluid inclusion studies, and isotopic evidence suggest that modern and fossil hydrothermal systems associated with gold mineralization share many common features, including the absence of a clear magmatic fluid source, discharge areas restricted to fault zones, and remarkably high temperatures (>200 ??C) at shallow depths (200-1500 m). While the plumbing of these systems varies, geochemical and isotopic data collected at the Dixie Valley and Beowawe geothermal systems suggest that fluid circulation along fault zones was relatively deep (>5 km) and comprised of relatively unexchanged Pleistocene meteoric water with small (Au) had larger-scale (???15 km) loop convection cells with a greater component of flow through marine sedimentary rocks at lower water/rock ratios and greater endowments of gold. Enthalpy calculations constrain the duration of Carlin-type gold systems to probably <200 k.y. Shallow heat flow gradients and fluid silica concentrations suggest that the duration of the modern Beowawe system is <5 k.y. However, fluid flow at Beowawe during the Quaternary must have been episodic with a net duration of ???200 k.y. to account for the amount of silica in the sinter deposits. In the Carlin trend, fluid circulation extended down into Paleozoic siliciclastic rocks, which afforded more mixing with isotopically enriched higher enthalpy fluids. Computed fission track ages along the Carlin trend included the convective effects, and ranged between 91.6 and 35.3 Ma. Older fission track ages occurred in zones of groundwater recharge, and the younger ages occurred in discharge areas. This is largely consistent with fission track ages reported in recent studies. We found that either an amagmatic system with more permeable faults (10-11 m2) or a magmatic system with less permeable faults (10-13 m2) could account for the published isotopic and thermal data along the Carlin trend systems. Localized high heat flow beneath the Muleshoe fault was needed to match fl uid inclusion temperatures at Mule Canyon. However, both magmatic and amagmatic scenarios require the existence of deep, permeable faults to bring hot fluids to the near surface. ?? 2008 Geological Society of America.

Person, M.; Banerjee, A.; Hofstra, A.; Sweetkind, D.; Gao, Y.

2008-01-01

259

Small-scale sedimentary structures and their implications in recognizing large-scale ancient tidal bedforms. Example from Dur At Talah outcrop, Late Eocene, Sirt Basin, Libya  

Science.gov (United States)

The Dur At Talah escarpment (150 m thick and 150 km long) is exposed at the southern side of the Sirt Basin, central Libya. This outcrop exposes an Upper Eocene succession, composed by highly bioturbated fine grained sandstones to claystones at the base (New Idam Unit; 80-100 m thick), overlain by medium grained to microconglomeratic sandstones at the top (Sarir Unit; 60 m thick). The latter is split into two subunits of nearly equal thickness: the lower Sarir subunit, composed of medium to coarse cross-bedded sandstones; and the upper Sarir subunit, composed of very coarse to microconglomeratic sandstones. The whole succession evolves from shallow marine estuarine (the New Idam Unit) to fluvial deposits (the upper Sarir subunit). The sandstone of the lower Sarir subunit, which is the focus of this article, is previously misinterpreted as being deposited in a purely fluvial environment. However, close observations revealed that the depositional environment is largely tide-influenced. It is notably marked by conspicuous subaqueous dune cross-stratifications that bear a variety of discrete, multi-scale, sedimentary structures evidencing their deposition in tidal rather than fluvial setting. Mud drapes, tidal bundles, and perpendicularly draining and oppositely climbing ripples are largely developed. Among these structures, the most diagnostic are of millimetric to centimetric scale. As a prime aim of this article, all these sedimentary structures are described, interpreted, and discussed for the first time from this outcrop. Their style of association and the quality of their preservation provide an outstanding ancient example of tide-dominated siliciclastic systems. Such structures are rarely found together in one outcrop as they are in Dur At Talah, and they provide a significant indicators in identifying ancient bedforms of tidal origin. Evidences of subtidal and intertidal depositional environments are afforded by these structures. Criteria indicative of semidiurnal regime of the tide are also presented. These criteria are especially well-preserved in the bundled foresets of the spring tides, the neap tide record is also distinguishable but it provides no discernible structures. Moreover, sedimentary features that can be used to infer a macrotidal range during the depositional time are also afforded by a combination of these structures. Above all, this study also concludes that one of the most reliable sedimentary structures for recognizing the tidal bedforms are the ripple-scale (centimetric) sedimentary structures. These are preserved inside and at the base of the cross-sets.

Abouessa, Ashour; Duringer, Philippe; Schuster, Mathieu; Pelletier, Jonathan; Rubino, Jean-Loup

2014-12-01

260

Variations in Composition and Preservation of Peat Deposited Since 27 ka in the Baoxiu Basin, Southwestern China: Implications for Environmental and Climatic Changes  

Science.gov (United States)

Multi-proxy organic geochemical paleoclimate records have been obtained from a 200-cm peat core extending back to about 27 ka cal from the Baoxiu Lake Basin, Yunnan Province of southwestern China. Relatively low del 13C values (-26.3 to -24.3 per mil) of total organic carbon (TOC) and of n-fatty acids (-30.4 to -33.0 per mil), high TOC/TN ratios (17 to 64), and the presence of p-hydroxyphenyl, guaiacyl, and syringyl phenylpropanyl lignin units in pyrolysates show that the source of organic matter is dominated by terrestrial C3 grasses (herbaceous angiosperms) throughout this peat profile. Decomposition of peat is indicated by shortening of alkyl side-chains of methoxyphenols, an increase of oxidation products, and demethylation of methoxy groups of the lignin/polyphenol fraction. Lower amounts of these decomposition proxies below 100 cm indicate good preservation of peat from 26.8 to 22.6 ka and imply good reliability of climatic information derived from this time range in the peat profile. From 26.8 to 23.3 ka , lower inputs of terrestrial plants and lower aquatic productivity are suggested by relatively low concentrations of TOC and phosphorus, mirroring decreased precipitation. Relatively heavier carbon isotopic compositions of plant wax n-fatty acids (C24 - C30) indicate larger contributions of C4 plants, providing a further hint of dry climate. Intermediate del 13C values of TOC and of mid-chain n-fatty acids (C20 - C22) result from an overprint of organic matter from aquatic algae. From 23.3 to 22.6 ka, a rapid increase of precipitation and a resultant C3 land-plant expansion is documented by maxima in concentrations of TOC and phosphorus, a minimum in TOC del 13C, and relatively negative del 13C values of plant-wax n-fatty acids. Since 22.6 ka, climate reconstruction is not reliable because of disturbance of the peat layers. The disturbance is most likely caused by human activities, a conclusion that is supported by a rapid increase in peat decomposition as indicated by more phenol proxies and higher concentrations of phosphorus.

Lu, Y.; Sun, Y.; Meyers, P. A.; Weng, H.

2004-12-01

 
 
 
 
261

New high precision U-Pb ages for the Vinchina Formation: Implications for the stratigraphy of the Bermejo Andean foreland basin (La Rioja province, western Argentina)  

Science.gov (United States)

The Vinchina Formation is one of the thickest Cenozoic units related to the Andean orogeny in Argentina totaling more than 5100 m in thickness. Different ages, from Eocene to latest Miocene, have been postulated for this red-bed succession based on fission track, magnetostratigraphy and whole rock isotopic analyses. Two new high precision U-Pb zircon ages are reported herein for this unit. A maximum U-Pb age of 15.6 ± 0.4 Ma was obtained from detritic zircons collected from a thick tuffaceous interval of the Lower Member of the Vinchina Formation at La Cueva (Precordillera), while a depositional U-Pb age of 9.24 ± 0.034 Ma was derived from volcanic zircons collected from a thin tuff bed in the Upper Member at Quebrada de Los Pozuelos (Northwestern Sierras Pampeanas). At La Cueva, the Vinchina Formation unconformably overlies eolian sandstones of the Vallecito Formation and was divided into four units representing 1) deposits of high-sinuosity ephemeral rivers associated with 2) a playa-lake passing upwards to 3) low-sinuosity sandy ephemeral rivers and finally, 4) a gravelly-sandy braided plain. The tuffaceous level corresponding to unit 1 is located 280 m above the base of the formation. At Quebrada de Los Pozuelos, the Vinchina Formation unconformably overlies the Vallecito Formation and is covered by a deeply incised surface at the base of the Toro Negro Formation. We divided the Vinchina Formation into four units. Unit 1 represents sedimentation in shallow fluvial channels with sandy to muddy floodplains. Units 2 and 3 record sedimentation in braided, meandering and anastomosing rivers. Finally unit 4 represents deposition in braided and wandering fluvial systems. The sampled tuff is located within unit 4 at ?3470 m above the base of the formation. The new ages indicate that the bulk of the Vinchina Formation is Miocene in age but they do not preclude a longer time span for the sedimentation of the whole unit. Ages of the sampled volcanic zircons match an important episode of volcanism recorded in the Cerro Las Tórtolas Formation, located ?90 km to the west in the Andean Cordillera, but also the upper tuff could be related to the late Miocene Puna volcanism. Comparison of the new ages with previous chronological data suggests coetaneous sedimentation along different depocenters of the Bermejo basin (e.g., Vinchina and Talampaya depocenters in Western Sierras Pampeanas and La Troya depocenter and Huaco-Mogna sections in Precordillera) and strenghten the need for correlation among them. In addition the age of 15.6 ± 0.4 Ma constrains the end of the severe arid conditions recorded in the Sierras Pampeanas and Precordillera region.

Ciccioli, P. L.; Limarino, C. O.; Friedman, R.; Marenssi, S. A.

2014-12-01

262

Structural and Hydrologic Implications of Joint Orientations in the Warner Creek and Stony Clove Drainage Basins, Catskill Mountains, Eastern New York  

Science.gov (United States)

To investigate joint control on hydrology as well as tectonic implications, we conducted a study of joint orientations near the Stony Clove and Warner Creek drainages of the Catskill Mountains, Eastern New York. Specific goals of this research were to determine joint control on stream orientations and groundwater flow, to compare results with previous studies in the area, and to investigate their tectonic significance. Trails, streams, and road cuts were traversed to locate bedrock outcrops whose positions were determined using topographic maps and a handheld GPS unit. Additional outcrops were located using aerial photographs and GIS data. Joint orientations were measured using a standard Brunton pocket transit. The data was analyzed using Orient (Vollmer, 2010), an orientation analysis program, to plot joint and stream orientations on rose diagrams. ArcGIS was used to produce topographic, hill-shade, and stream drainage maps. Over 500 joint orientations at over 100 outcrop stations were collected. The data were plotted on a rose diagrams, and two major joint sets were found, one with a mean strike of 021° and one with a mean strike of 096°. Stream orientations were also plotted on a rose diagram showing an axial mean of 022°, and indicate that the joint set with mean strike of 021 may have a significant control on stream orientations. The hill-shade maps also demonstrate clearly the strong control of jointing on the topography. The data collected in this research expands on previous joint orientation studies of Engelder and Geiser (1980) in the southwestern and central Catskills, and is similar to joint orientations found by Isachsen et al. (1977) in their study of the Panther Mountain circular structure, a possible impact-related feature. The origin of this jointing is thought to be related to Alleghanian (Permian) and possibly Acadian (Devonian) orogenic events.

Haskins, M. N.; Vollmer, F. W.; Rayburn, J. A.; Gurdak, J. J.

2010-12-01

263

Laboratory investigation of coupled deformation and fluid flow in mudrock: implications for slope stability in the Ursa Basin, Gulf of Mexico  

Science.gov (United States)

Integrated Ocean Drilling Program (IODP) Expedition 308 was dedicated to the study of fluid flow, overpressure, and slope stability in the Ursa Basin, on the continental slope of the Gulf of Mexico. In this location, turbidite channel levees deposited a wedge-shaped body: the deposition rate in the thick part of the wedge exceeded 12 mm/yr. This rapid deposition of fine grained sediments generated excess pore pressure observed near the seafloor. IODP drilling focused on three Sites: U1322, U1323, and U1324, along the steepest slope (2°) on the eastern section of the Ursa Canyon levee deposits. In this study, we conducted a suite of deformation experiments on samples from Site 1324, to understand the stress-strain behavior and stress history of the recovered core material. Our samples were taken from depths of 30-160 meters below seafloor, and are composed of ~40% silt and ~60% clay, with porosities ranging from ~42-55%. We first conducted uniaxial consolidation tests to determine pre-consolidation stresses and define deformation behavior due to simulated vertical loading. In a subset of tests, we subjected the samples to undrained shearing following consolidation, to define the friction angle and define relationships between stress state and deformation. We find that the lateral effective stress during uniaxial compression is 56-64% of the vertical effective stress (avg. K0=0.6). Pre-consolidation stresses suggest that pore pressure is hydrostatic to 50 mbsf (meters below seafloor), and is overpressured below this, with excess pressures up to 70% of the hydrostatic effective vertical stress (?*=0.7) at 160 mbsf. The time coefficient of consolidation (cv) in these experiments is ~2.2x10-8 m2/s. Undrained shear tests define a failure envelope with a residual friction angle (?) of 23° and zero cohesion. In our shearing tests, we observed no pore pressure change during initial (primarily elastic) shear deformation, but note a monotonic increase in pore pressure during the later plastic shear deformation, possibly due to re-organization of sediment grains. Our consolidated undrained tests suggest that the slope in the study area should remain stable during sedimentation, despite the high overpressure (?*=0.7). However, this stress condition could be affected by gravitational and seepage forces that cause horizontal extension along the slope. In this case, a reduction in horizontal confining stress would render the slope sediments unstable (drive them to active failure) as defined by the Coulomb criterion. If shear strain during slope failure leads to plastic deformation of the sediments, this would also induce a pore pressure increase, further decreasing the factor of safety (FS) for landslides. For the landslides of the slope (i.e., FS=1.0), the overpressure rate ?* should reach 0.92 for the given slope (2°). However, active normal faulting takes place at lower values of ?* (0.2-0.8). Our analysis suggests that the instability of the slope may arise more likely from normal faults dipping stiff (45°+?/2) than from landslides slipping on a plane parallel to such a gentle slope of seafloor.

Flemings, P. B.; Song, I.; Saffer, D. M.

2012-04-01

264

Source and reservoir potential of the lower Lodgepole formation within the Bakken petroleum system in the Billings Nose area, Williston Basin  

Energy Technology Data Exchange (ETDEWEB)

The Billings Nose region of North Dakota includes the Bakken petroleum system which includes source beds in the upper Bakken shale and lower Lodgepole ('False Bakken'), as well as reservoirs in the upper Three Forks, middle Bakken, upper Bakken shale, and lower Lodgepole (Scallion) limestone. According to source rock analyses, the False Bakken is thermally mature and organic-rich. Several indications show that the system includes many reservoirs, each of which has low porosity and permeability and is enhanced by natural fractures. Development of the area began in the 1970s. When horizontal drilling began in the upper Bakken shale in 1987, the adjacent carbonates were also considered pay. The False Bakken source bed may be the cause of fractures found in the lower Lodgepole limestone. Because of the dynamic stratigraphy of the area, cause the fractures may extend beyond the Bakken edge. Therefore, the Scallion may hold additional reserves beyond the depositional edge of the upper Bakken shale.

Stroud, John W; Sonnenberg, Stephen A [Colorado School of Mines, Golden, CO, (United States)], email: Jstroud318@gmail.com

2011-07-01

265

Residual basins  

International Nuclear Information System (INIS)

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)

266

Mineralogy, geochemistry and diagenetic evolution of continental clastic proterozoic basins. The example of the Jotnian in the Baltic shield. Implications on the genesis of unconformity related U-deposits  

International Nuclear Information System (INIS)

The Satakunta and Muhos basins in Finland are Mesoproterozoic (Jotnian in Fennoscandia, Riphean in Russia) clastic basins unconformably overlying Paleoproterozoic metamorphic basements. These basins share similarities with the Athabasca (Canada) and Kombolgie (Australia) basins, which are associated with large unconformity-related uranium deposits. The aim of the study is to characterize their mineralogy and geochemistry and to compare them to the mineralized basins. The samples for this study have been taken from existing drill cores stored at the Loppi drill core depot of the Geological Survey of Finland. Geological setting, characteristics of the basement and the sediments, sandstone geochemical characteristics are reported. Degree of the sediments' maturity, pH and redox conditions, P-T conditions of the thermal events and evidence of hydrothermal alteration are discussed. It is concluded that extreme immaturity of Satakunta and Muhos basin sediments, strong silicification and weak diagenetic fluid circulation are unfavourable for significant U-deposit associated to them

267

Sedimentary Basin Inversion Without Lithospheric Compression  

Science.gov (United States)

The inversion of sedimentary basins, because of its implications for petroleum generation and trapping, has received attention in recent years. Because of the common use of lithospheric extension models of basin formation (e.g. Mckenzie, 1978 etc), it is not surprising that models of inversion mechanics have concentrated on the inverse of lithospheric extension, namely compression. Such models of inversion have no direct mechanism of localizing uplift (and thus inversion) at the site of the original basin. It is necessary to postulate mechanisms by which the presence of the basin weakens the lithosphere locally (e.g. by elevated geotherms cuased by the thermal blanketing of the basin). However, such mechanisms are variable in their effectiveness (Sandiford 1999). In this paper, we examine a different context for basin formation and inversion, in which the inversion is automatically localized at the original basin. Specifically, we examine the case where basin formation is driven by intra-crustal anomalous density loads induced subsidence of the elastic upper crust in response to elastic thickness reduction driven by sublithospheric heating. In such a case, if elastic thinning is sufficient, the density load can detach from the elastic upper crust and sink, by ductile flow, rapidly (Glazner, 1994) into the deep crust. The resultant relief permits the elastic upper crust to rebound upwards over the site of the prvious basin. Strikingly, such rebounds can be as much as 7 km (locally erasing a huge part of the detrital record). We demonstrate this by both semi-analytic modelling using an extended version of Kaufman and Royden's (1994) elastic-beam over ductile channel model, and with a full thermal and viscoelastic finite element model. Finite element modelling shows that in this type of inversion, surface horizontal stresses in the basin are compressive during basin formation, and become more tensional during inversion, in direct contrast to the lithospheric extension-compression models.

Pearse, J.; Bailey, R. C.

2004-12-01

268

The Mackenzie Basin impacts study  

International Nuclear Information System (INIS)

In 1989, a commitment was made to begin development of a framework for an integrated regional impact assessment of global warming scenarios in the Mackenzie Basin, the most populated region of Canada's north. The project, called Mackenzie Basin Impact Study (MBIS), is led by a multidisciplinary working group from government and non-governmental organizations with interests in the Basin. Objectives of MBIS include defining the direction and magnitude of regional-scale impacts of global warming scenarios on the physical, biological, and human systems of the Basin. MBIS will also identify regional sensitivities to climate, inter-system linkages, uncertainties, policy implications, and research needs. MBIS research activities as of March 1992 are outlined and policy concerns related to global warming are listed. Two new methodologies are being developed by MBIS to address particular economic and policy concerns: a socio-economic resource accounting framework and an integrated land assessment framework. Throughout MBIS, opportunities will be presented for western science and traditional native knowledge to be integrated

269

Metabolic principles of river basin organization.  

Science.gov (United States)

The metabolism of a river basin is defined as the set of processes through which the basin maintains its structure and responds to its environment. Green (or biotic) metabolism is measured via transpiration and blue (or abiotic) metabolism through runoff. A principle of equal metabolic rate per unit area throughout the basin structure is developed and tested in a river basin characterized by large heterogeneities in precipitation, vegetation, soil, and geomorphology. This principle is suggested to have profound implications for the spatial organization of river basin hydrologic dynamics, including the minimization of energy expenditure known to control the scale-invariant characteristics of river networks over several orders of magnitude. Empirically derived, remarkably constant rates of average transpiration per unit area through the basin structure lead to a power law for the probability distribution of transpiration from a randomly chosen subbasin. The average runoff per unit area, evaluated for subbasins of a wide range of topological magnitudes, is also shown to be remarkably constant independently of size. A similar result is found for the rainfall after accounting for canopy interception. Allometric scaling of metabolic rates with size, variously addressed in the biological literature and network theory under the label of Kleiber's law, is similarly derived. The empirical evidence suggests that river basin metabolic activity is linked with the spatial organization that takes place around the drainage network and therefore with the mechanisms responsible for the fractal geometry of the network, suggesting a new coevolutionary framework for biological, geomorphological, and hydrologic dynamics. PMID:21670259

Rodriguez-Iturbe, Ignacio; Caylor, Kelly K; Rinaldo, Andrea

2011-07-19

270

Facies and environmental setting of the Miocene coral reefs in the late-orogenic fill of the Antalya Basin, western Taurides, Turkey: implications for tectonic control and sea-level changes  

Science.gov (United States)

Facies and environmental setting of the Miocene coral reefs in the Late Cenozoic Antalya Basin are studied to contribute towards a better understanding of the time and space relationships of the reef development and the associated basin fill evolution in a tectonically active basin. The Antalya Basin is an extention-compression-related late post-orogenic basin that developed unconformably on a basement comprising a Mesozoic para-authocthonous carbonate platform overthrust by the Antalya Nappes and Alanya Massif metamorphics within the Isparta angle. The Late Cenozoic basin fill consists of thick Miocene to Recent clastic-dominated terrestrial and marine deposits with subordinate marine carbonates and extensive travertines. Late Miocene compressional deformation has resulted into three parts, referred as Aksu, Köprüçay and Manavgat sub-basins, bounded by north-south extending dextral K?rkkavak fault and the westward-verging Aksu thrust. Coralgal reefs are common within the Miocene sequences and are represented by coral assemblages closely similar to that of the circum-Mediterranean fauna. They occur as massive, small, isolated, patch reefs that developed in two contrasting depositional systems (progradational coastal alluvial fan and/or fan-delta conglomerates and transgressive shelf carbonates) during Early-Middle Miocene and Late Miocene. The Early-Middle Miocene reefs are represented by rich and high-diversity hermatypic corals, mainly comprising Tarbellastraea, Heliastraea, Favites, Favia, Acanthastraea, Porites, Caulastraea and Stylophora with occasional presence of solitary (ahermatypic) corals, Lithophyllia, Mussismilia and Leptomusso, locally reflecting relative changes in the bathymetry. Densely packed, massive, domal and hemispherical growth forms bounded by coralline algae and encrusting foraminifera Acervulina construct the reef framework. They occur in the fan-deltas and the transgressive open marine shelf carbonates of the Manavgat and the Köprüçay sub-basins. The Late Miocene reefs occur only in the Aksu sub-basin and are characterized by low-diversity hermatypic corals exclusively dominated by Porites and Tarbelastraea with minor Siderastraea, Favites and Platygyra. They developed on alluvial fan/fan-delta complexes and shallow marine shelf carbonates. The Miocene coral reef growth and development in the Antalya Basin are characterized by large- to small-scale, transgressive-regressive reefal cycles which are closely related to the complex interaction of sporadic influxes of coarse terrigeneous clastics derived from the tectonically active basin margins and the related sea-level fluctuations.

Karab?y?ko?lu, M.; Tuzcu, S.; Çiner, A.; Deynoux, M.; Örçen, S.; Hakyemez, A.

2005-01-01

271

Tectonostratigraphy and depositional history of the Neoproterozoic volcano-sedimentary sequences in Kid area, southeastern Sinai, Egypt: Implications for intra-arc to foreland basin in the northern Arabian-Nubian Shield  

Science.gov (United States)

This paper presents a stratigraphic and sedimentary study of Neoproterozoic successions of the South Sinai, at the northernmost segment of the Arabian-Nubian Shield (ANS), including the Kid complex. This complex is composed predominantly of thick volcano-sedimentary successions representing different depositional and tectonic environments, followed by four deformational phases including folding and brittle faults (D1-D4). The whole Kid area is divisible from north to south into the lower, middle, and upper rock sequences. The higher metamorphic grade and extensive deformational styles of the lower sequence distinguishes them from the middle and upper sequences. Principal lithofacies in the lower sequence include thrust-imbricated tectonic slice of metasediments and metavolcanics, whereas the middle and upper sequences are made up of clastic sediments, intermediate-felsic lavas, volcaniclastics, and dike swarms. Two distinct Paleo- depositional environments are observed: deep-marine and alluvial fan regime. The former occurred mainly during the lower sequence, whereas the latter developed during the other two sequences. These alternations of depositional conditions in the volcano-sedimentary deposits suggest that the Kid area may have formed under a transitional climate regime fluctuating gradually from warm and dry to warm and humid conditions. Geochemical and petrographical data, in conjunction with field relationships, suggest that the investigated volcano-sedimentary rocks were built from detritus derived from a wide range of sources, ranging from Paleoproterozoic to Neoproterozoic continental crust. Deposition within the ancient Kid basin reflects a complete basin cycle from rifting and passive margin development, to intra-arc and foreland basin development and, finally, basin closure. The early phase of basin evolution is similar to various basins in the Taupo volcanics, whereas the later phases are similar to the Cordilleran-type foreland basin. The progressive change in lithofacies from marine intra-arc basin to continental molasses foreland basin and from compression to extension setting respectively, imply that the source area became peneplained, where the Kid basin became stabilized as sedimentation progressed following uplift. The scenario proposed of the study area supports the role of volcanic and tectonic events in architecting the facies and stratigraphic development.

Khalaf, E. A.; Obeid, M. A.

2013-09-01

272

09 river basin planning  

...prescribed timescales. r iver Basin Management: the river basin planning process is followed by the implementation...by the implementation of the management measures. The planning process together with the implementation of...objectives Public Participation RIVER BASIN MANAGEMENT PLANNING PROCESS...

273

Implicaciones hidrológicas del cambio de la cobertura vegetal y uso del suelo: una propuesta de análisis espacial a nivel regional en la cuenca cerrada del lago de Cuitzeo, Michoacán / Hydrological implications of land-cover and land-use change: a proposal for spatial analysis at a regional level in the closed Cuitzeo-lake basin, Michoacán  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish Este estudio intenta contribuir en la comprensión de las implicaciones del cambio de la cobertura vegetal y uso del suelo (CCVUS) a nivel regional en el balance hídrico espacialmente distribuido (BHED) en una cuenca poco aforada para 1975 y 2000. Los resultados de esta investigación son producto de [...] la integración de herramientas de percepción remota y sistemas de información geográfica con un modelo de balance de agua; además, se utilizaron técnicas de análisis de dinámica de cambio. El análisis del cambio de los componentes del BHED a nivel de formas de relieve y por matrices de transición determinó que durante el periodo de estudio las condiciones hidrológicas regionales de la cuenca no se modificaron sustancialmente Sin embargo, las planicies y los piedemontes mostraron un incremento en los valores de escorrentia, como resultado de un incremento de la superficie ocupada por asentamientos humanos En ambos años, las formas de relieve de las zonas bajas de la cuenca mostraron fuerte presión sobre el recurso hídrico, lo cual repercute en el deterioro del lago de Cuitzeo, principalmente por contaminación y reducción del suministro de agua superficial al vaso. El enfoque integral utilizado puede representar una alternativa viable para entender el cambio en la distribución y cantidad del agua disponible en cuencas poco aforadas como resultado de un CCVUS. Abstract in english This study was undertaken to understand the implications of regional land-cover and land-use change ILCLUC) in a spatially distributed water balance (SDWB) within a poorly gauged basin in 1975 and 2000. Results from this work were derived by integrating remote sensing and geographic information syst [...] em tools with a water-balance model, along with the application of a transitional matrix analysis. The analysis of changes in water-balance components, based on landforms and transitional matrices, Indicated a small tendency towards improvement in the basin s hydrological conditions at a regional level However, as a consequence of the increase in urban land-use. The basin's plains piedmonts showed a rise in runoff. In addition, the basins' lower areas exhibited a high demand for water resources due to an increased urban land-use in both years, along with the Cuitzeo lake degradation, particularly in terms of pollution and reduction of surface water inflow. The integrated approach used herein constitutes a viable alternative for understanding changes in the amount and spatial distribution of water available in poorly gauged water basins as a consequence of LCLUC.

Manuel, Mendoza; Gerardo, Bocco; Erna, López Granados; Miguel, Bravo.

2002-12-01

274

Permo-Triassic changes in bulk crustal shortening direction during deformation and metamorphism of the Taebaeksan Basin, South Korea using foliation intersection/inflection axes: Implications for tectonic movement at the eastern margin of Eurasia during the Songrim (Indosinian) orogeny  

Science.gov (United States)

The Permo-Triassic Songrim (Indosinian) orogeny in South Korea was a major tectonic event involving complicated continental collisions at the eastern margin of Eurasia. Previous studies have examined the structural and metamorphic features of the Songrim orogeny in each of the Paleozoic terranes of the orogenic belt (i.e., the Taebaeksan Basin, the Okcheon Basin, and the Imjingang Belt), but correlations of these features among the terranes remain uncertain. The aim of this paper is to reveal deformation history including bulk crustal shortening directions in the Taebaeksan Basin, and to correlate the tectono-metamorphic evolution of the Taebaeksan Basin with other Phanerozoic mobile belts in eastern Asia based on a combined analysis of foliation intersection/inflection axes (FIA) trends and metamorphic P-T and T-t (time) paths. The orientations and relative timing of FIA preserved as inclusion trails within porphyroblasts of andalusite, chloritoid, garnet, and staurolite reveal two age groups of inclusion trails in the Pyeongan Supergroup at the northeastern margin of the Taebaeksan Basin. These microstructures indicate the development of early NNW-NNE-trending structures and fabrics, followed by later E-W-trending ones. These observations suggest a change in the orientation of bulk crustal shortening from E-W to N-S during the Songrim orogeny. Based on the similar microstructures and temperature-time paths of the three Paleozoic terranes, we interpret that the E-W bulk crustal shortening influenced the eastern part of the Korean Peninsula during the early stages of the Songrim orogeny, presumably related to amalgamation between the proto-Japan terrane and the eastern margin of Eurasia, whereas the N-S bulk crustal shortening was stronger in the western part of the peninsula during the later stages of the orogeny, related to collision between the South and North China blocks.

Kim, Hyeong Soo; Ree, Jin-Han

2013-03-01

275

Nouvelles données biostratigraphiques et sédimentologiques des formations carbonifères de la région de Bouqachmir (Maroc central). Implications sur la paléogéographie des bassins carbonifères nord-mésétiensNew biostratigraphic and sedimentological data of the Carboniferous formations in the Bouqachmir area (central Morocco). Implications on the palaeogeography of the north Mesetian Carboniferous basins  

Science.gov (United States)

New Visean formations and biozones of foraminifera were defined on the Bouqachmir map. The new biozonation concerns the Moroccan biozone, Cfm1, which is subdivided into two subzones, Cfm1a and Cfm1b. This map exhibited, from north-west to south-east, the Tilouine, Bouqachmir-Tougouroulmès and Fourhal turbiditic basins. The first one, from Tournaisian to Late Visean, was the equivalent of the Sidi Bettache basin, located westwards. The second extended the Tilouine basin eastwards during the Visean. The third was a basin from Visean to Westphalian. They were separated by the Zaer-Oulmes and El Hammam horsts, else emerged or immersed, bordered by faults and with materials feeding chaotic deposits.

Izart, Alain; Tahiri, Abdelfatah; El Boursoumi, Abdou; Vachard, Daniel; Saidi, Mariam; Chèvremont, Philippe; Berkhli, Mostafa

2001-02-01

276

Paleotopographic Reconstruction of the Tharsis Magmatic Complex Reveals Potential Ancient Drainage Basin/Aquifer System  

Science.gov (United States)

Paleotopographic reconstructions reveal the potential existence of an enormous Noachian drainage basin in the eastern part of the Tharsis region of significant geologic and paleohydrologic implications. Additional information is contained in the original extended abstract.

Dohm, J. M.; Ferris, J.; Anderson, R. C.; Baker, V.; Hare, T.; Barlow, N. G.; Strom, R. G.; Tanaka, K. L.; Scott, D. H.

2001-01-01

277

Interpretation of the trace element and ND, SR isotopic compositional evolutions along the distinct diagenetic facies of the pyroclastic Kopenetz formation within the Emet Basin (Turkey): implications for mass transport and fluid-rock interaction  

International Nuclear Information System (INIS)

A geochemical study comprising trace element and isotopic analysis (87Sr/86Sr, 143Nd/144Nd) has been carried out for each mineral zone of the low to mid-Miocene Kopenetz formation of the Emet basin (Turkey). This formation is composed of rhyolitic volcanic material with distinct diagenetic facies from NW to SE. The trace element and isotopic compositional evolutions are interpreted as due to continuous fluid-rock interactions along a NW-SE fluid path. (J.S.)

278

Paleomagnetic and chronostratigraphic constraints on the Middle to Late Miocene evolution of the Transylvanian Basin (Romania): Implications for Central Paratethys stratigraphy and emplacement of the Tisza-Dacia plate  

Digital Repository Infrastructure Vision for European Research (DRIVER)

From the Oligocene onwards, the complex tectonic evolution of the Africa–Eurasia collision zone led to paleogeographic and biogeographic differentiation of the Mediterranean and Paratethys, two almost land-locked seas, in the area formerly occupied by the western Tethys Ocean. Episodic isolation of the basins triggered strong faunal endemism leading to the introduction of regional stratigraphic stages for the Paratethys. Chronostratigraphic control on the Paratethys stages remains rudimenta...

Leeuw, A.; Filipescu, S.; Matenco, L. C.; Krijgsman, W.; Kuiper, K.; Stoica, M.

2012-01-01

279

Establishment of Chinook salmon (Oncorhynchus tshawytscha) in Pacific basins of southern South America and its potential ecosystem implications Establecimiento del salmón Chinook (Oncorhynchus tshawytscha) en cuencas del Pacífico sur de Sudamérica y sus potenciales implicancias ecosistémicas  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Salmon and trout species are not native to the southern hemisphere, however rainbow and brown trout have been established a century in southern South America. Yet most attempts to introduce anadromous salmon failed until the onset of aquaculture by 1980. Escapes of Oncorhynchus tshawytscha (Chinook salmon) from aquaculture after 1990 have apparently produced increasingly important reproductive returns "naturalized", to upper basins in Chile and Argentina south of 39º S. In this paper we show...

DORIS SOTO; IVÁN ARISMENDI; CECILIA DI PRINZIO; FERNANDO JARA

2007-01-01

280

Impact of seasonal hydrological variation on the distributions of tetraether lipids along the Amazon River in the central Amazon basin: Implications for the MBT/CBT paleothermometer and the BIT index  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Suspended particulate matter (SPM) was collected along the Amazonian rivers in the central Amazon basin and in three tributaries during the rising water (RW), high water (HW), falling water (FW) and low water (LW) season. Changes in the concentration and the distribution of brGDGTs, i.e. the methylation index of branched tetraethers (MBT) and the cyclization of brGDGTs (CBT), were seen in the main stem Amazon. The highest concentration of core lipid branched glycerol dialkyl glycerol tetraeth...

ClaudiaZell; GwenaëlAbril; RodrigoSobrinho; PatriciaMoreira-Turcq

2013-01-01

 
 
 
 
281

Impact of seasonal hydrological variation on the distributions of tetraether lipids along the Amazon River in the central Amazon basin: implications for the MBT/CBT paleothermometer and the BIT index  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Suspended particulate matter (SPM) was collected along the Amazon River in the central Amazon basin and in three tributaries during the rising water (RW), high water (HW), falling water (FW) and low water (LW) season. Changes in the concentration and the distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs), i.e., the methylation index of branched tetraethers (MBT) and the cyclization of brGDGTs (CBT), were seen in the Amazon main stem. The highest concentration of core lip...

ClaudiaZell; GwenaëlAbril; RodrigoSobrinho; PatriciaMoreira-Turcq

2013-01-01

282

Platform-induced clay-mineral fractionation along a northern Tethyan basin-platform transect: implications for the interpretation of Early Cretaceous climate change (Late Hauterivian-Early Aptian)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

High-resolution clay-mineral analyses were performed on upper Hauterivian to lower Aptian sediments along a platform-to-basin transect through the northern Tethyan margin from the Neuchâtel area (Switzerland), to the Vocontian Trough (France) in order to investigate links between climate change, carbonate platform evolution, and fractionation patterns in clay minerals during their transport. During the Hauterivian, the northern Tethyan carbonate platform developed in a heterozoan mode, ...

Godet, Alexis; Bodin, Ste?phane; Adatte, Thierry; Fo?llmi, Karl B.

2009-01-01

283

A comparison of groundwater ages based on 14C data and three dimensional advective transport modelling of the lower Chao Phraya Basin. Palaeohydrology and implications for water resources development in Thailand  

International Nuclear Information System (INIS)

A study has been undertaken to simulate the groundwater flow system of the Lower Chao Phraya Basin, Thailand. The study was performed using a three dimensional computer model of groundwater flow and advective transport. Results from these simulations include travel time analyses obtained through backward pathline tracking. The simulated ages were compared with observed 14C ages at over fifty discrete locations within the aquifer system. The comparisons reveal a major difference between 14C ages and ages predicted by steady state groundwater flow. Carbon-14 analyses generally indicate that the groundwater in the Bangkok area is 10,000 to 30,000 years old. Steady state flow and transport simulations imply that groundwater in this region should be 50,000 to 100,000 years old. One potential reason for the discrepancy between 14C and computer simulated ages is the assumption of steady state flow. Groundwater in the basin that is > 10,000 years old would have been affected by flow conditions that existed during the last glacial maximum. We hypothesize that groundwater velocities in the region during that time would have been greater because of both the absence of the Bangkok Clay and the more distal position of the coastline. These palaeoflow conditions were incorporated into a second set of simulations that assume current steady state flow conditions existed for the last 10,000 years, but were preceded by steady state conditions representatded by steady state conditions representative of flow during the last glacial maximum. This transient simulation yielded mean groundwater ages that were in much closer agreement with mean observed 14C ages. Carbon-14 ages from the basin have suggested slow natural groundwater replenishment rates to the Bangkok area, where groundwater extraction rates are currently high. Simulation results from this study imply that replenishment of groundwater to the basin may be even slower than previously thought. (author). 8 refs, 5 figs, 1 tab

284

Regional Drought Severity Assessment at a Basin Scale in the Limpopo Drainage System  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A spatial analysis of drought characteristics in the Limpopo basin is undertaken to evaluate its regional implications to water management challenges. In this study, drought duration, frequency and severity are investigated. In addition drought Severity-Area-Frequency (SAF) curves were constructed. The entire Limpopo River Basin is subdivided into four homogeneous regions based on topographic and climate var...

Alemaw, Berhanu F.; Kileshye-onema, J. M.; Love, D.

2013-01-01

285

K-Ar and 40Ar/ 39Ar ages of dikes emplaced in the onshore basement of the Santos Basin, Resende area, SE Brazil: implications for the south Atlantic opening and Tertiary reactivation  

Science.gov (United States)

New K-Ar and 40Ar/ 39Ar data of tholeiitic and alkaline dike swarms from the onshore basement of the Santos Basin (SE Brazil) reveal Mesozoic and Tertiary magmatic pulses. The tholeiitic rocks (basalt, dolerite, and microgabbro) display high TiO 2 contents (average 3.65 wt%) and comprise two magmatic groups. The NW-oriented samples of Group A have (La/Yb) N ratios between 15 and 32.3 and range in age from 192.9±2.2 to 160.9±1.9 Ma. The NNW-NNE Group B samples, with (La/Yb) N ratios between 7 and 16, range from 148.3±3 to 133.9±0.5 Ma. The alkaline rocks (syenite, trachyte, phonolite, alkaline basalts, and lamprophyre) display intermediate-K contents and comprise dikes, plugs, and stocks. Ages of approximately 82 Ma were obtained for the lamprophyre dikes, 70 Ma for the syenite plutons, and 64-59 Ma for felsic dikes. Because Jurassic-Early Cretaceous basic dikes have not been reported in SE Brazil, we might speculate that, during the emplacement of Group A dikes, extensional stresses were active in the region before the opening of the south Atlantic Ocean and coeval with the Karoo magmatism described in South Africa. Group B dikes yield ages compatible with those obtained for Serra Geral and Ponta Grossa magmatism in the Paraná Basin and are directly related to the breakup of western Gondwana. Alkaline magmatism is associated with several tectonic episodes that postdate the opening of the Atlantic Ocean and related to the upwelling of the Trindade plume and the generation of Tertiary basins southeast of Brazil. In the studied region, alkaline magmatism can be subdivided in two episodes: the first one represented by lamprophyre dykes of approximately 82 Ma and the second comprised of felsic alkaline stocks of approximately 70 Ma and associated dikes ranging from 64 to 59 Ma.

Guedes, Eliane; Heilbron, Monica; Vasconcelos, Paulo M.; de Morisson Valeriano, Cláudio; César Horta de Almeida, Júlio; Teixeira, Wilson; Thomaz Filho, Antonio

2005-03-01

286

Stable-isotope (H, O, and Si) evidence for seasonal variations in hydrology and Si cycling from modern waters in the Nile Basin: implications for interpreting the Quaternary record  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Seasonal variations in hydrology and Si cycling in the Nile Basin were investigated using stable-isotope (H, O, and Si) compositions and dissolved Si (DSi) concentrations of surface waters, as a basis for interpreting lacustrine diatom sequences. ?18O ranged from ?4.7 to +8.0‰ in the wet season and +0.6 to +8.8‰ in the dry season (through 2009–2011). Higher ?18O values during the dry season reflected increased evapotranspiration and open water evaporation under conditions of lower h...

Cockerton, H. E.; Street-perrott, F. A.; Leng, M. J.; Barker, P. A.; Horstwood, M. S. A.; Pashley, V.

2013-01-01

287

A record of Eocene (Stronsay Group) sedimentation in BGS borehole 99/3, offshore NW Britain: implications for early post-break-up development of the Faroe-Shetland Basin  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A punctuated Eocene succession has been recovered in British Geological Survey borehole 99/3 from the Faroe-Shetland Basin. The borehole was drilled close to the crest of the Judd Anticline and penetrated 110.5 m into the post-breakup Stronsay Group. The borehole proved 23.8 m of Ypresian–earliest Lutetian paralic to shallow-marine deposits, unconformably overlain by 43.85 m of mid-Lutetian lower shoreface to shallow-marine shelf deposits, in turn unconformably overlain by 42.85 m of late B...

Stoker, Martyn; Leslie, Alick; Smith, Kevin

2013-01-01

288

The Ipojuca Magmatic Suite: tectonic-stratigraphic relationships and implications on the Pernambuco sub-basin; A Suite Magmatica Ipojuca: relacoes e implicacoes tectono-estratigraficas na Sub-bacia de Pernambuco  

Energy Technology Data Exchange (ETDEWEB)

The rift section of the Pernambuco Sub-basin comprises siliciclastic rocks (the Cabo Formation) interlayered with basic and acid, alkaline volcanic and epizonal rocks, named as the Ipojuca Magmatic Suite. The presence of lavas and pyroclastic layers (even at the base of the section), together with intrusive bodies, implies that magmatism was contemporaneous and succeeded sediment deposition. Their expressive occurrence along faulted borders of the basin, as well as a number of examples of structural control at several scales (emplacement at extensional joints, pull-apart sites, faults and other dilatational structures), indicates that magmatism also was contemporaneous with rifting extensional tectonics. Examples of structures displaying partial ductility (shear zones, S-C fabrics) suggest between deformation and the emplacement of swarms of igneous bodies. Finally, some bodies of deeper structural level (especially the Cabo Granite), overlain by post-rift sediments (Estiva and Algodoais formations), mark a sharp unconformity at the base of those units, with exhumation and erosion of the upper portion of the heat generation, tectonism and erosion, which will be influent upon maturation of source rocks, evolution of reservoirs and the occurrence of hydrocarbons. (author)

Almeida, Camilla Bezerra de; Frutuoso Junior, Luiz Jorge [Rio Grande do Norte Univ., Natal, RN (Brazil). Curso de Geologia]. E-mail: camillaalmeida@aol.com; Sa, Emamuel Ferraz Jardim de; Silva, Fernando Cesar Alves da; Souza, Zorano Sergio de [Rio Grande do Norte Univ., Natal, RN (Brazil). Dept. de Geologia. Programa de Pos-graduacao em Geodinamica e Geofisica; Cruz, Liliane Rabelo; Nascimento, Marcos Antonio Leite do; Antunes, Alex Francisco; Guedes, Ingred Maria Guimaraes; Lima Filho, Mario Ferreira [Rio Grande do Norte Univ., Natal, RN (Brazil). Dept. de Geologia. Programa de Pos-graduacao em Geociencias

2003-07-01

289

ROANOKE RIVER BASIN DATA  

Science.gov (United States)

Data files for the Roanoke River Basin provided for use with the Roanoke River Basin Reservoir Model. Includes data on daily pan evaporation, monthly water usage and daily inflow. (see http://www.dwr.ehnr.state.nc.us/roanoke/index.htm)...

290

Melo carboniferous basin  

International Nuclear Information System (INIS)

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.

291

Geysers: Lower Geyser Basin  

Science.gov (United States)

This Yellowstone National Park web site is dedicated to Lower Geyser Basin. It includes images and descriptions of Queen's Laundry and Sentinel Meadows, Sentinel Cone, Ojo Caliente, Pocket Basin Mud Pots, Imperial Geyser, Spray Geyser, Octopus Spring, Great Fountain Geyser, White Dome Geyser, Pink Cone Geyser, Bead Geyser, Narcissus Geyser, Steady Geyser, Silex Spring, Fountain Paint Pot, Fountain Geyser, Clepsydra Geyser, and Jelly Geyser.

Yellowstone National Park

292

Drainage Basins Field Lab  

Science.gov (United States)

This exercise begins with a field trip to the San Gabriel Mountain foothills near our campus. Students are given a set of topographic maps and asked to follow our progress as we hike into a small drainage basin in the Claremont Wilderness Park. Through interactive discussion, we explore regional landscape and the geomorphic form, function, and processes of a drainage basin system. Students are expected to complete their assignment on drainage basin analysis during the following week, working from the maps provided. Students are asked to identify the basic landscape units in the San Gabriel Mountain foothill region, delineate a set of drainage basins, and analyze the geomorphic characteristics of these basins using longitudinal profiles and morphometric indices. From this information, they are expected to draw basic conclusions about the geomorphic processes affecting this landscape system, and its relative state of equilibrium. Designed for a geomorphology course

Jeff Marshall

293

K Basin safety analysis  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this accident safety analysis is to document in detail, analyses whose results were reported in summary form in the K Basins Safety Analysis Report WHC-SD-SNF-SAR-001. The safety analysis addressed the potential for release of radioactive and non-radioactive hazardous material located in the K Basins and their supporting facilities. The safety analysis covers the hazards associated with normal K Basin fuel storage and handling operations, fuel encapsulation, sludge encapsulation, and canister clean-up and disposal. After a review of the Criticality Safety Evaluation of the K Basin activities, the following postulated events were evaluated: Crane failure and casks dropped into loadout pit; Design basis earthquake; Hypothetical loss of basin water accident analysis; Combustion of uranium fuel following dryout; Crane failure and cask dropped onto floor of transfer area; Spent ion exchange shipment for burial; Hydrogen deflagration in ion exchange modules and filters; Release of Chlorine; Power availability and reliability; and Ashfall.

Porten, D.R.; Crowe, R.D.

1994-12-16

294

K Basin safety analysis  

International Nuclear Information System (INIS)

The purpose of this accident safety analysis is to document in detail, analyses whose results were reported in summary form in the K Basins Safety Analysis Report WHC-SD-SNF-SAR-001. The safety analysis addressed the potential for release of radioactive and non-radioactive hazardous material located in the K Basins and their supporting facilities. The safety analysis covers the hazards associated with normal K Basin fuel storage and handling operations, fuel encapsulation, sludge encapsulation, and canister clean-up and disposal. After a review of the Criticality Safety Evaluation of the K Basin activities, the following postulated events were evaluated: Crane failure and casks dropped into loadout pit; Design basis earthquake; Hypothetical loss of basin water accident analysis; Combustion of uranium fuel following dryout; Crane failure and cask dropped onto floor of transfer area; Spent ion exchange shipment for burial; Hydrogen deflagration in ion exchange modules and filters; Release of Chlorine; Power availability and reliability; and Ashfall

295

U-Pbdating on detrital zircon and Nd and Hf isotopes related to the provenance of siliciclastic rocks of the Amazon Basin: Implications for the origin of Proto-Amazonas River  

Science.gov (United States)

Previous provenance studies along the Amazonas river have demonstrated that the Amazon drainage basin has been reorganized since the Late Cretaceous with the uplift of the Andes and the establishment of the transcontinental Amazon fluvial system from Late Miocene to Late Pleistocene (Hoorn et al., 1995; Potter, 1997, Wesselingh et al., 2002; Figueiredo et al. 2009, Campbell et al., 2006, Nogueira et al. 2013).There is a lack of data from Eastern and Central Amazonia and only limited core data from the Continental Platform near to current Amazonas river mouth. Central Amazonia is strategic to unveil the origin of Amazonas River because it represents the region where the connection of the Solimões and Amazonas basin can be studied through time (Nogueira et al. 2013). Also, there is a shortage of information on the old Precambrian and Paleozoic sediment sources relative to Cretaceous and Miocene siliciclastic deposits of the Solimões and Amazonas basins. We collected stratigraphic data, detrital zircon U-Pb ages and Nd and Hf isotopes from Precambrian, Paleozoic, Cretaceous and Miocene siliciclastic deposits of the Northwestern border of Amazonas Basin. They are exposed in the Presidente Figueiredo region and in the scarps of Amazon River, and occur to the east of the Purus Arch. This Northwest-Southeast trending structural feature that divides the Solimões and Amazonas basin was active at various times since the Paleozoic. Detrital zircon ages for the Neoproterozoic Prosperança Formation yielded a complex signature, with different populations of Neoproterozoic (550, 630 and 800 Ma) and Paleoproterozoic to Archean sources (1.6, 2.1 and 2.6 Ga). Also Nd and Hf isotopes show two groups of TDM model ages between 1.4 to 1.53 Ga and 2.2 and 3.1 Ga. Sediments typical of Paleozoic sedimentary rocks of the Nhamundá and Manacapuru Formations revealed NdTDM model ages of 1.7, 2.2 and 2.7 Ga, but Hf isotopes and U-Pb zircon ages are more varied. They characterize a provenance dominated by Mesoproterozoic sources (1.0, 1.2 Ga) and subordinate Neoproterozoic(550-800 Ma) and Archean derivation (2.67 Ga). On the other hand, detrital zircon and Hf and NdTDM model ages for the Cretaceous Alter do Chão Formation yielded a unique Paleoproterozoicages between 2.0 and 2.3 Ga that can be correlated to sources derived from Maroni-Itacaiúnas and Central Amazonian basement provinces. The contribution of Precambrian and Paleozoic rocks exposed during the installationof the Amazonas drainage were probably significant .Such a large contribution from Neoproterozoic and Mesoproterozoic sources are not common in the proximal Amazon Craton basement .This new proposal open new perspectives to understand better the initial history of Amazon River with indication of the probable source areas during Late Cenozoic. Campbell Jr.; Frailey,C.D.; Romero-Pittman, G. 2006. The Pan-Amazonian UcayliPeneplain, late Neogenesedimentacion in Amazonia, and the Birth on the Modern Amazon River system.Palaeogeography,Palaeoclimatology, Palaeoecology. 239 (2006) 166-219 Figueiredo, J.,Hoorn, C., Van der Vem, P., Soares, E. 2009. Late Miocene onset of the Amazon River and the Amazon deep-sea fan: Evidence from the Fozdo Amazonas Basin. Geology, 37(7):619-622. Hoorn,C.; Guerrero, J.; Sarmiento, G. 1995. Andean tectonics as a cause for changing drainage patterns in Miocene Northern South America. Geology, v.23, p-237-240. Nogueira, A.C.R.; Silveira, R.R.; Guimarães, J.T.F. 2013. Neogene-Quaternary sedimentary and paleovegetation history of the eastern Solimões Basin, central Amazon region.Journal of South American Earth Sciences , v. 46, p. 89-99, 2013. Potter, P.E. 1997. The Mesozoic and Cenozoic paleodrainage of South America: a natural history. Journal of South American Earth Science.v.10. p.331-344 Wesselingh, F. P., et al., 2002. Lake-Pebas: a palaeocological reconstruction of a Miocene long-lived lake comples in Western Amazônia. Cainozoic Research 1 (1-2), 35-81.

Dantas, Elton Luiz; Silva Souza, Valmir; Nogueira, Afonso C. R.; Ventura Santos, Roberto; Poitrasson, Franck; Vieira Cruz, Lucieth; Mendes Conceição, Anderson

2014-05-01

296

The Rhodope Zone as a primary sediment source of the southern Thrace basin (NE Greece and NW Turkey): evidence from detrital heavy minerals and implications for central-eastern Mediterranean palaeogeography  

Science.gov (United States)

Detrital heavy mineral analysis coupled with a regional geological review provide key elements to re-evaluate the distribution of the Rhodope metamorphic zone (SE Europe) in the region and its role in determining the evolution of the Thrace basin. We focus on the Eocene-Oligocene sedimentary successions exposed in the southern Thrace basin margin to determine the dispersal pathways of eroded crustal elements, of both oceanic and continental origins, as well as their different contributions through time. Lithological aspects and tectonic data coupled with geochemistry and geochronology of metamorphic terranes exposed in the area point to a common origin of tectonic units exposed in NW Turkey (Biga Peninsula) with those of NE Greece and SE Bulgaria (Rhodope region). The entire region displays (1) common extensional signatures, consisting of comparable granitoid intrusion ages, and a NE-SW sense of shear (2) matching zircon age populations between the metapelitic and metamafic rocks of the Circum-Rhodope Belt (NE Greece) and those of the Çamlica-Kemer complex and Çetmi mélange exposed in NW Turkey. Detrital heavy mineral abundances from Eocene-Oligocene sandstones of the southern Thrace basin demonstrate the influence of two main sediment sources mostly of ultramafic/ophiolitic and low- to medium-grade metamorphic lithologies, plus a third, volcanic source limited to the late Eocene-Oligocene. Detrital Cr-spinel chemistry is used to understand the origin of the ultramafic material and to discriminate the numerous ultramafic sources exposed in the region. Compositional and stratigraphic data indicate a major influence of the metapelitic source in the eastern part (Gallipoli Peninsula) during the initial stages of sedimentation with increasing contributions from metamafic sources through time. On the other hand, the western and more external part of the southern Thrace margin (Gökçeada, Samothraki and Limnos) displays compositional signatures according to a mixed provenance from the metapelitic and metamafic sources of the Circum-Rhodope Belt (Çaml?ca-Kemer complex and Çetmi mélange). Tectonic restoration and compositional signatures provide constraints on the Palaeogene palaeogeography of this sector of the central-eastern Mediterranean region.

Caracciolo, L.; Critelli, S.; Cavazza, W.; Meinhold, G.; von Eynatten, H.; Manetti, P.

2014-12-01

297

The Ogaden Basin, Ethiopia: an underexplored sedimentary basin  

Energy Technology Data Exchange (ETDEWEB)

A brief article examines the Ogaden Basin in Ethiopia in terms of basin origin, basin fill and the hydrocarbon exploration history and results. The natural gas find in pre-Jurassic sandstones, which appears to contain substantial reserves, justifies continuing investigations in this largely underexplored basin. (UK).

Teitz, H.H.

1991-01-01

298

U-Pb and Pb-Pb study of the Murchison Greenstone Belt and of the Evander gold-bearing basin, South Africa. Implications for the evolution of the Kaapvaal craton  

International Nuclear Information System (INIS)

This study presents new U-Pb and Pb-Pb isotopic data for both the Central Rand Group from the Evander Goldfield and the Murchison Greenstone Belt (Republic of South Africa). The Evander Goldfield, where no previous isotopic data have been derived, is located in the eastern side of the Witwatersrand basin. The oldest age measured is ca. 3180 Ma, while the majority of detritus falls in the range 3050-2850 Ma. New growth of zircon (or isotopic resetting of older detritus) appears to have been associated with deposition of the Ventersdorp lavas at ca. 2.7 Ga. A small proportion of the pyrite, mainly extracted from unaltered sediments in the Kimberley Reef footwall, yields ages that are in excess of the minimum depositional age of the Witwatersrand Basin. Authigenic pyrite, as well as detrital grains from highly altered portions of the Kimberley Reef, define two main events. The Pb signature of the 2370 Ma event is probably associated with burial of the basin by the upper portion of the Transvaal sequence, and suggests circulation of highly radiogenic fluids. Isotopic signatures for the 2020 Ma event are probably related to Bushveld intrusion and/or Vredefort catastrophism, and appear to be associate with a fluid that was less radiogenic. The present study shows a number of new results which support a complex, multi-stage evolution and genesis of the Au-U deposits within the Witwatersrand Basin. The Murchison Greenstone Belt constitutes one of the world's largest antimony tutes one of the world's largest antimony producing areas and also hosts gold, as well as volcanogenic massive sulfide Cu-Zn mineralization and emeralds. The goal of this study is to determine the age of the belt as well as the timing of mineralization and, also, to assess the potential role of granitoids in the ore-forming processes. The data identify an episode of greenstone formation between 3.09 Ga and 2.97 Ga. Three main magmatic events are identified at ca. 2.97, 2.82 and 2.68 Ga. Pyrites associated with both Sb-Au and Cu-Zn mineralization define a secondary isochron with an age of 2.97 Ga suggesting that they are spatially and genetically associated with the 2.97 Ga Maranda Batholith and the volcanic Rubbervale Formation. Thus, VMS style Cu-Zn mineralization is syn-genetic with respect to the Rubbervale Formation, whereas Sb-Au lode mineralization along the Antimony Line appears to be related to magmatic fluid egress from the Maranda batholith. Pb-Pb signatures of pyrite associated with emerald along the southern flank of the reflect mixing between Pb derived from the older 3.23 Ga basement and the 2.97 Ga magmatic event. The 2.97 Ga Maranda batholith and Rubbervale Formation, therefore, represents a highly prospective metallotect that is relevant, not only to exploration in the Murchison region itself, but to the important question of the source of Witwatersrand gold. (authors)

299

Impact of seasonal hydrological variation on the distributions of tetraether lipids along the Amazon River in the central Amazon basin: implications for the MBT/CBT paleothermometer and the BIT index.  

Science.gov (United States)

Suspended particulate matter (SPM) was collected along the Amazon River in the central Amazon basin and in three tributaries during the rising water (RW), high water (HW), falling water (FW) and low water (LW) season. Changes in the concentration and the distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs), i.e., the methylation index of branched tetraethers (MBT) and the cyclization of brGDGTs (CBT), were seen in the Amazon main stem. The highest concentration of core lipid (CL) brGDGTs normalized to particulate organic carbon (POC) was found during the HW season. During the HW season the MBT and CBT in the Amazon main stem was also most similar to that of lowland Amazon (terra firme) soils, indicating that the highest input of soil-derived brGDGTs occurred due to increased water runoff. During the other seasons the MBT and CBT indicated an increased influence of in situ production of brGDGTs even though soils remained the main source of brGDGTs. Our results reveal that the influence of seasonal variation is relatively small, but can be clearly detected. Crenarchaeol was mostly produced in the river. Its concentration was lower during the HW season compared to that of the other seasons. Hence, our study shows the complexity of processes that influence the GDGT distribution during the transport from land to ocean. It emphasizes the importance of a detailed study of a river basin to interpret the MBT/CBT and BIT records for paleo reconstructions in adjacent marine setting. PMID:23966986

Zell, Claudia; Kim, Jung-Hyun; Abril, Gwenaël; Sobrinho, Rodrigo Lima; Dorhout, Denise; Moreira-Turcq, Patricia; Sinninghe Damsté, Jaap S

2013-01-01

300

Impact of seasonal hydrological variation on the distributions of tetraether lipids along the Amazon River in the central Amazon basin: Implications for the MBT/CBT paleothermometer and the BIT index  

Directory of Open Access Journals (Sweden)

Full Text Available Suspended particulate matter (SPM was collected along the Amazonian rivers in the central Amazon basin and in three tributaries during the rising water (RW, high water (HW, falling water (FW and low water (LW season. Changes in the concentration and the distribution of brGDGTs, i.e. the methylation index of branched tetraethers (MBT and the cyclization of brGDGTs (CBT, were seen in the main stem Amazon. The highest concentration of core lipid branched glycerol dialkyl glycerol tetraethers (brGDGTs normalized to particulate organic carbon was found during the HW season. During the HW season the MBT and CBT in the Amazon main stem was also most similar to that of lowland Amazon (terra firme soils, indicating that the highest input of soil-derived brGDGTs occurs due to increased water runoff. During the other seasons the MBT and CBT indicated an increased influence of in situ production of brGDGTs even though soils remained the main source of brGDGTs. Our results reveal that the influence of seasonal variation is relatively small, but can be clearly detected. Crenarchaeol is mostly produced in the river. Its concentration was lower during the HW season compared to that of the other seasons. Hence, our study shows the complexity of processes that influence the GDGT distribution during the transport from land to ocean. It emphasizes the importance of a detailed study of a river basin to interpret the MBT/CBT and BIT records for paleo reconstructions in adjacent marine setting.

ClaudiaZell

2013-08-01

 
 
 
 
301

Genetic relationship between quaternary NE Japan arc magmas and miocene Japan Sea back-arc basin basalts. Implications for a dynamic model of hot fingers in the mantle wedge  

International Nuclear Information System (INIS)

Mantle melting and production of magmas in NE Japan may be controlled by locally developed hot regions within the mantle wedge that form inclined, 50 km-wide fingers. In this case, are these hot fingers chemically and/or isotopically different from the host mantle wedge? Forty-four Quaternary volcanoes in NE Japan have been reviewed to evaluate two-dimensional strontium isotopic variations, and to infer 87Sr/86Sr contours of the source mantle. The isotopic composition of magma source materials at depth is found to have little relationship with slab depth, suggesting that mantle heterogeneity was established before the flux of fluid released from the subducting slab reached the magma source regions. On the other hand, Miocene Japan Sea back-arc Yamato basin basalts have the same isotopic variation as the Quaternary volcanic arc. Cousens et al. (1994)suggested the possibility that partial melts of sediments, forming at a depth of >200 km may mix with mantle wedge material (87Sr/86Sr ?0.703), resulting in a magma source component with enriched 87Sr/86Sr of ?0.705. I suggest that after the cessation of Yamato basin rifting, a MORB-like mantle source (87Sr/86Sr ?0.703) in the mantle wedge below the Quaternary NE Japan arc was replenished by a fertile mantle material (87Sr/86Sr ?0.705) through convection induced by the subducting lithosphere. On its way to tcting lithosphere. On its way to the shallower mantle wedge (87Sr/86Sr of ?0.705, extend from ?150 km below the back-arc region towards the shallower mantle (?50 km) beneath the volcanic front. A conveyor-like return flow is interpreted to carry the remnants of these fingers to depth, resulting in greater amounts of fertile material being incorporated in diapirs beneath the volcanic front, and smaller amounts incorporated in areas behind the front. (author)

302

Detours around basin stability in power networks  

Science.gov (United States)

To analyse the relationship between stability against large perturbations and topological properties of a power transmission grid, we employ a statistical analysis of a large ensemble of synthetic power grids, looking for significant statistical relationships between the single-node basin stability measure and classical as well as tailormade weighted network characteristics. This method enables us to predict poor values of single-node basin stability for a large extent of the nodes, offering a node-wise stability estimation at low computational cost. Further, we analyse the particular function of certain network motifs to promote or degrade the stability of the system. Here we uncover the impact of so-called detour motifs on the appearance of nodes with a poor stability score and discuss the implications for power grid design.

Schultz, Paul; Heitzig, Jobst; Kurths, Jürgen

2014-12-01

303

South Pacific Sedimentary Basins  

Energy Technology Data Exchange (ETDEWEB)

The geological development of the South Pacific can be viewed through four quite discrete time windows. The first is the main assembly of Gondwana in the Precambrian and Palaeozoic, we are still far from getting a coherent basin story, so no attempt was made to include Palaeozoic basins. The second window, early Permian through early Cretaceous, provides the great bulk of the rock that underpins mainland New Zealand, the Chatham Rise and the Norfolk Ridge. Apparently, non-stop subduction saw the creation and eventual amalgamation of at least five discrete subduction-related terranes and one abduction-related terrane. The original configurations, locations and relationships of these terranes have yet to be established, but by the early Cretaceous they were all assembled and docked with Gondwana. Subduction lingered but by the middle Cretaceous the region had entered the third window, the era of great extension and spreading of marginal basins. Gondwana had been breaking apart for a long time, but the New Zealand-Australia-Antarctica segment had remained intact. The local break-up was heralded by rifting followed by thermal relaxation and widespread passive margin subsidence. All the major marginal basins of the southwest Pacific formed then. Convergent margins were far away and the great bulk of New Zealand's coal, limestone and hydrocarbon source rocks were deposited. At the end of the Oligocene period the Pacific Ring of Fire propagated rapidly southward from Tonga into the North Island, and the region reverted to convergent margin status. Regression coal basins occurred. The fourth section of the book describes some basins with a dual history, initial deposition during the great extensional phase, followed by deposition relating to Neogene convergence. These include the region's major hydrocarbon basin, Taranaki Basin the Chatham Rise, the Challenger Plateau and the Great South Basin.

Ballance, P.F. (ed.) (University of Auckland, Auckland (New Zealand). Geology Department)

1993-01-01

304

Constraints on Moho Depth and Crustal Thickness in the Liguro-Provençal Basin from a 3d Gravity Inversion : Geodynamic Implications Contraintes sur la profondeur du moho et l'épaisseur crustale dans le bassin liguro-provençal à partir de l'inversion 3D de données gravimétriques : implications géodynamiques  

Directory of Open Access Journals (Sweden)

Full Text Available 3D gravity modelling is combined with seismic refraction and reflection data to constrain a new Moho depth map in the Liguro-Provençal Basin (Western Mediterranean Sea. At seismically controlled points, the misfit between the gravimetric solution and the seismic data is about 2 km for a range of Moho depth between 12 km (deep basin and 30 km (mainlands. The oceanic crust thickness in the deep basin (5 km is smaller than the average oceanic crust thickness reported in open oceans (7 km, pointing to a potential mantle temperature 30°C to 50°C below normal and/or very slow oceanic spreading rate. Oceanic crust thickness is decreasing towards the Ligurian Sea and towards the continent-ocean boundary to values as small as 2 km. Poor magma supply is a result of low potential mantle temperature at depth, lateral thermal conduction towards unextended continental margin, and decrease of the oceanic spreading rate close to the pole of opening in the Ligurian Sea. Re-examination of magnetic data (paleomagnetic data and magnetic lineations indicates that opening of the Liguro-Provençal Basin may have ceased as late as Late Burdigalian (16. 5 Ma or even later. The absence of significant time gap between cessation of opening in the Liguro-Provençal Basin and rifting of the Tyrrhenian domain favours a continuous extension mechanism since Upper Oligocene driven by the African trench retreat. Ce rapport présente un travail commun avec le Laboratoire de géodynamique de l'École normale supérieure (ENS. Ce travail doit être resitué dans son contexte : l'étude régionale du golfe du Lion a été possible dans le cadre du projet européen Integrated Basin Studies. Le développement du code d'inversion 3D avait fait l'objet de conventions avec l'ENS pendant les années précédentes. La mise en Suvre d'une telle inversion est désormais possible à l'IFP. Il n'y a pas d'interface pour ce calculateur. L'aide des collègues de l'ENS est souhaitable pour la mise en forme des données. Il a paru opportun, compte tenu des délais imprévus de publication du volume du BSGL pour lequel cet article a été accepté, de montrer l'existence et les potentialités de cette méthode. Il est vraisemblable qu'elle pourra être un apport significatif à l'étude des marges passives et plus particulièrement dans le cas des études concernant l'offshore profond. Elle a déjà retenu l'attention de plusieurs collègues de l'industrie pétrolière.

Gaulier J. M.

2006-12-01

305

Connecting Lunar Meteorite Dhofar 961 to the South Pole-Aitken Basin Through Lunar Prospector Gamma-Ray Data  

Science.gov (United States)

Lunar meteorite Dhofar 961, which contains mafic impact-melt components, is matched to locations within South Pole-Aitken Basin through the 5-degree Lunar Prospector gamma-ray data. Implications for a lower crustal provenance are discussed.

Jolliff, B. L.; Korotev, R. L.; Zeigler, R. A.; Prettyman, T. H.

2009-03-01

306

L'évolution paléoenvironnementale des faunes de poissons du Crétacé supérieur du bassin du Tafilalt et des régions avoisinantes (Sud-Est du Maroc) : implications paléobiogéographiquesPalaeoenvironmental evolution of the fish assemblages from the Late Cretaceous of the Tafilalt basin and surrounding areas, southeastern Morocco: palaeogeographical implications  

Science.gov (United States)

A critical revision of published data along with new field data allow to draw up the succession of the fish faunas from the Lower Cenomanian to the Lower Turonian in the Tafilalt basin and surrounding areas (southeast Morocco). The analysis of these faunas shows changes from freshwater to marine palaeoenvironments. The palaeogeographic distribution of some taxa is discussed. It shows that the crossing of strictly freshwater organisms between Africa and South America was likely impossible at the time of the formation of the deposits resting around the Tafilalt basin and named 'Kem Kem beds'. The Cenomano-Turonian transgression reached the Erfoud-Errachidia carbonate platform from the Central Tethys, and then connected the central Atlantic.

Cavin, Lionel; Boudad, Larbi; Duffaud, Sylvain; Kabiri, Lahcen; Le Lœuff, Jean; Rouget, Isabelle; Tong, Haiyan

2001-11-01

307

THERMAL MATURITY HISTORY AND IMPLICATIONS FOR HYDROCARBON EXPLORATION IN THE CATATUMBO BASIN, COLOMBIA / Historia de la madurez térmica e implicaciones para la exploración de hidrocarburos en la cuenca del Catatumbo, Colombia  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: English Abstract in spanish Un modelamiento integrado con un estudio geoquímico de gas y aceite ha sido realizado en la cuenca del Catatumbo, Colombia con el fin de proveer información para la exploración de hidrocarburos. El ajuste del modelo térmico con los datos de madurez fue posible a partir de un esquema de flujo de calo [...] r cambiante, que incluyó un incremento térmico hacia finales del Jurásico y otro en el Eoceno Temprano, asociados a eventos distensivos. Regionalmente, en los ejes de los sinclinales se identificaron pods de roca fuente activa en el presente. Los tiempos de expulsión de hidrocarburos para las rocas fuente Cretáceas (Formación Capacho y la Luna), inician en el Paleoceno-Eoceno Superior mientras que para la Formación Los Cuervos la generación y expulsión inicia hace 10 ma. Las acumulaciones de hidrocarburos se infiere que son el resultado principalmente de generación y migración dentro de la cuenca. La fracción de petróleo expulsado durante el Paleoceno-Mioceno posiblemente fue acumulada en estructuras que crecieron desde finales del Cretácico, mientras que las estructuras más jovenes resultantes de la orogenia andina se infiere que se han cargado con los productos de la remigración desde las estructuras más antiguas y adicionalmente con las últimas fracciones de hidrocarburos generadas. Los gases de la cuenca Catatumbo son del tipo termogénico húmedos con diferente grado de madurez termal que varía desde alrededor de 1,0 hasta 2,5 de Ro equivalente. De acuerdo con el grado de evolución termal, la geoquímica y el modelamiento térmico, se infiere que la región sur es prospectiva para gas húmedo y condensado, mientras que el sector central y norte es prospectivo para aceite y cantidades menores de gas asociado. Abstract in english A thermal model integrated with an oil and gas geochemical study has been constructed for the Catatumbo Basin, Colombia to provide petroleum system data for hydrocarbon exploration. The calibration of the thermal model with maturity data took into account a changing heat flow scheme which included a [...] thermal increase towards the end of the Jurassic and another one in the Early Eocene, associated with rifting events. Locally, active/generating source rocks are within the synclines axes. The hydrocarbon expulsion time for Cretaceous source rocks (Capacho and La Luna formations) started in the Upper Paleocene-Eocene, while for the Los Cuervos Formation the generation and expulsion started at 10 my. The petroleum expelled during the Paleocene-Miocene, were likely accumulated in structures formed since the end of the Cretaceous, while the younger structures that resulted from the Andean orogen were charged by remigration from the older structures and additionally with the yougest lately generated hydrocarbons. The accumulations of hydrocarbons are mainly the result of generation and migration locally within the basin. The Catatumbo basin contains thermogenic wet gases with different degrees of thermal maturity which varies from around 1,0 to 2,5 equivalent Ro. The highest degree of thermal evolution according to maturity indicators and thermal modeling is in the southern area, which is prospective for wet gas. The central and northern area appears more prospective for oil with minor amounts of gas.

Antonio, Rangel; Roberto, Hernández.

2007-12-01

308

La pesca artesanal en la Cuenca del Plata (Argentina) y sus implicancias en la conservación de la biodiversidad / Artisanal fish at del Plata basin (Argentina) and its implications for the biodiversity conservation  

Scientific Electronic Library Online (English)

Full Text Available SciELO Argentina | Language: Spanish Abstract in spanish El objetivo del presente trabajo es considerar distintos aspectos que surgen del análisis de las exportaciones pesqueras provenientes de la pesca comercial artesanal de la Cuenca del Plata, Argentina. Se trata de identificar aquellos impactos vinculados a las prácticas pesqueras sobre las poblacione [...] s naturales involucradas y los compromisos relacionados con la conservación de la biodiversidad de la ictiofauna de la cuenca. Se analizan 17 años de datos de las pesquerías comerciales artesanales correspondientes al tramo argentino del río Paraná sobre registros oficiales de los productos pesqueros exportados para distintas especies durante el período 1994-2010. Los registros de los productos exportados expresados en toneladas en peso (ton) se refieren particularmente a especies autóctonas de gran tamaño e interés comercial como el sábalo (Prochilodus lineatus), la boga (Leporinus obtusidens), la tararira (Hoplias malabaricus), el surubí (Pseudoplatystoma spp.), el dorado (Salminus brasiliensis) y el patí (Luciopimelodus pati), además de varias especies acompañantes en las capturas como bagres, armados y pejerreyes (Odontesthes bonariensis). Las exportaciones pesqueras muestran un incremento sumamente importante con un total de 331.517 ton para el período 1994-2010. La especie blanco de la pesquería es el sábalo con 88,77 % de las exportaciones totales y le siguen en orden de importancia la tararira con el 4,16 %, la boga con el 3,70 %, el patí con un 1,35 % y otras especies de menor captura. Los países de destino de los productos pesqueros son Brasil, Colombia, Bolivia y Nigeria, entre otros. Sin embargo, desde el 2003, Colombia compra en promedio el 50 % del total de las exportaciones pesqueras de la Argentina. El análisis de los datos históricos de las exportaciones pesqueras (1994-2010) evidencia la necesidad de implementar medidas mas claras sobre el control y manejo de los recursos pesqueros y las posibles implicancias derivadas de la pesquería sobre conservación de la biodiversidad de peces de la cuenca. Abstract in english The aim of this contribution is to consider different issues derived from fish captures from artisanal-commercial fisheries in the Paraná Basin in Argentina. We identify certain impacts related to fishing practices on the involved natural populations and its compromises in ichtiofaunal biodiversity [...] conservation. We consider 17 years of information based on data of fisheries exports for different inland species between 1994-2010. These data includes valuable commercial big sized native fishes like sábalo (Prochilodus lineatus), boga (Leporinus obtusidens), tararira (Hoplias malabaricus), surubí (Pseudoplatystoma spp.), dorado (Salminus brasiliensis) and patí (Luciopimelodus pati), together with several catfish species and minor species as silversides. Freshwater fish exports show a major rise resulting in 331517 ton for these years. The target species is sábalo (88.77 %), other accompanying species are tararira (4.16 %), boga (3.7 %) and Patí (1.35 %) whereas the remainig catches belong to other species. There is a strong rise in the catches of these other species in certain years while there is not a clear legislation for these fish species that allow implementing a proper fishery management along the basin. The importing countries are Brazil, Colombia, Bolivia and Nigeria among others. Since 2003 Colombia buy an average of 50% of inland fisheries exports from Argentina. The analysis historical data (1994-2010) reveals the need to implement measures to control and management of fisheries and its effects on fish biodiversity conservation in the basin.

Juan Miguel, Iwaszkiw; Francisco, Firpo Lacoste.

2011-06-01

309

La pesca artesanal en la Cuenca del Plata (Argentina y sus implicancias en la conservación de la biodiversidad Artisanal fish at del Plata basin (Argentina and its implications for the biodiversity conservation  

Directory of Open Access Journals (Sweden)

Full Text Available El objetivo del presente trabajo es considerar distintos aspectos que surgen del análisis de las exportaciones pesqueras provenientes de la pesca comercial artesanal de la Cuenca del Plata, Argentina. Se trata de identificar aquellos impactos vinculados a las prácticas pesqueras sobre las poblaciones naturales involucradas y los compromisos relacionados con la conservación de la biodiversidad de la ictiofauna de la cuenca. Se analizan 17 años de datos de las pesquerías comerciales artesanales correspondientes al tramo argentino del río Paraná sobre registros oficiales de los productos pesqueros exportados para distintas especies durante el período 1994-2010. Los registros de los productos exportados expresados en toneladas en peso (ton se refieren particularmente a especies autóctonas de gran tamaño e interés comercial como el sábalo (Prochilodus lineatus, la boga (Leporinus obtusidens, la tararira (Hoplias malabaricus, el surubí (Pseudoplatystoma spp., el dorado (Salminus brasiliensis y el patí (Luciopimelodus pati, además de varias especies acompañantes en las capturas como bagres, armados y pejerreyes (Odontesthes bonariensis. Las exportaciones pesqueras muestran un incremento sumamente importante con un total de 331.517 ton para el período 1994-2010. La especie blanco de la pesquería es el sábalo con 88,77 % de las exportaciones totales y le siguen en orden de importancia la tararira con el 4,16 %, la boga con el 3,70 %, el patí con un 1,35 % y otras especies de menor captura. Los países de destino de los productos pesqueros son Brasil, Colombia, Bolivia y Nigeria, entre otros. Sin embargo, desde el 2003, Colombia compra en promedio el 50 % del total de las exportaciones pesqueras de la Argentina. El análisis de los datos históricos de las exportaciones pesqueras (1994-2010 evidencia la necesidad de implementar medidas mas claras sobre el control y manejo de los recursos pesqueros y las posibles implicancias derivadas de la pesquería sobre conservación de la biodiversidad de peces de la cuenca.The aim of this contribution is to consider different issues derived from fish captures from artisanal-commercial fisheries in the Paraná Basin in Argentina. We identify certain impacts related to fishing practices on the involved natural populations and its compromises in ichtiofaunal biodiversity conservation. We consider 17 years of information based on data of fisheries exports for different inland species between 1994-2010. These data includes valuable commercial big sized native fishes like sábalo (Prochilodus lineatus, boga (Leporinus obtusidens, tararira (Hoplias malabaricus, surubí (Pseudoplatystoma spp., dorado (Salminus brasiliensis and patí (Luciopimelodus pati, together with several catfish species and minor species as silversides. Freshwater fish exports show a major rise resulting in 331517 ton for these years. The target species is sábalo (88.77 %, other accompanying species are tararira (4.16 %, boga (3.7 % and Patí (1.35 % whereas the remainig catches belong to other species. There is a strong rise in the catches of these other species in certain years while there is not a clear legislation for these fish species that allow implementing a proper fishery management along the basin. The importing countries are Brazil, Colombia, Bolivia and Nigeria among others. Since 2003 Colombia buy an average of 50% of inland fisheries exports from Argentina. The analysis historical data (1994-2010 reveals the need to implement measures to control and management of fisheries and its effects on fish biodiversity conservation in the basin.

Juan Miguel Iwaszkiw

2011-06-01

310

THERMAL MATURITY HISTORY AND IMPLICATIONS FOR HYDROCARBON EXPLORATION IN THE CATATUMBO BASIN, COLOMBIA Historia de la madurez térmica e implicaciones para la exploración de hidrocarburos en la cuenca del Catatumbo, Colombia  

Directory of Open Access Journals (Sweden)

Full Text Available A thermal model integrated with an oil and gas geochemical study has been constructed for the Catatumbo Basin, Colombia to provide petroleum system data for hydrocarbon exploration. The calibration of the thermal model with maturity data took into account a changing heat flow scheme which included a thermal increase towards the end of the Jurassic and another one in the Early Eocene, associated with rifting events. Locally, active/generating source rocks are within the synclines axes. The hydrocarbon expulsion time for Cretaceous source rocks (Capacho and La Luna formations started in the Upper Paleocene-Eocene, while for the Los Cuervos Formation the generation and expulsion started at 10 my. The petroleum expelled during the Paleocene-Miocene, were likely accumulated in structures formed since the end of the Cretaceous, while the younger structures that resulted from the Andean orogen were charged by remigration from the older structures and additionally with the yougest lately generated hydrocarbons. The accumulations of hydrocarbons are mainly the result of generation and migration locally within the basin. The Catatumbo basin contains thermogenic wet gases with different degrees of thermal maturity which varies from around 1,0 to 2,5 equivalent Ro. The highest degree of thermal evolution according to maturity indicators and thermal modeling is in the southern area, which is prospective for wet gas. The central and northern area appears more prospective for oil with minor amounts of gas.Un modelamiento integrado con un estudio geoquímico de gas y aceite ha sido realizado en la cuenca del Catatumbo, Colombia con el fin de proveer información para la exploración de hidrocarburos. El ajuste del modelo térmico con los datos de madurez fue posible a partir de un esquema de flujo de calor cambiante, que incluyó un incremento térmico hacia finales del Jurásico y otro en el Eoceno Temprano, asociados a eventos distensivos. Regionalmente, en los ejes de los sinclinales se identificaron pods de roca fuente activa en el presente. Los tiempos de expulsión de hidrocarburos para las rocas fuente Cretáceas (Formación Capacho y la Luna, inician en el Paleoceno-Eoceno Superior mientras que para la Formación Los Cuervos la generación y expulsión inicia hace 10 ma. Las acumulaciones de hidrocarburos se infiere que son el resultado principalmente de generación y migración dentro de la cuenca. La fracción de petróleo expulsado durante el Paleoceno-Mioceno posiblemente fue acumulada en estructuras que crecieron desde finales del Cretácico, mientras que las estructuras más jovenes resultantes de la orogenia andina se infiere que se han cargado con los productos de la remigración desde las estructuras más antiguas y adicionalmente con las últimas fracciones de hidrocarburos generadas. Los gases de la cuenca Catatumbo son del tipo termogénico húmedos con diferente grado de madurez termal que varía desde alrededor de 1,0 hasta 2,5 de Ro equivalente. De acuerdo con el grado de evolución termal, la geoquímica y el modelamiento térmico, se infiere que la región sur es prospectiva para gas húmedo y condensado, mientras que el sector central y norte es prospectivo para aceite y cantidades menores de gas asociado.

Antonio Rangel

2007-12-01

311

Nile Basin Climates  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The climate of the Nile Basin is characterised by a strong latitudinal wetness gradient. Whereas the areas north of 18°N remain dry most of the year, to the south there is a gradual increase of monsoon precipitation amounts. Rainfall regimes can be divided into 9 types, among which summer peak regimes dominate. In the southern half of the basin, mesoscale circulation features and associated contrasts in local precipitation patterns develop as a result of a complex interplay involving topogra...

Camberlin, Pierre

2009-01-01

312

K Basin Hazard Analysis  

Energy Technology Data Exchange (ETDEWEB)

This report describes the methodology used in conducting the K Basins Hazard Analysis, which provides the foundation for the K Basins Final Safety Analysis Report. This hazard analysis was performed in accordance with guidance provided by DOE-STD-3009-94, Preparation Guide for U. S. Department of Energy Nonreactor Nuclear Facility Safety Analysis Reports and implements the requirements of DOE Order 5480.23, Nuclear Safety Analysis Report.

PECH, S.H.

2000-08-23

313

K Basins Hazard Analysis  

International Nuclear Information System (INIS)

This report describes the methodology used in conducting the K Basins Hazard Analysis, which provides the foundation for the K Basins Safety Analysis Report (HNF-SD-WM-SAR-062/Rev.4). This hazard analysis was performed in accordance with guidance provided by DOE-STD-3009-94, Preparation Guide for U. S. Department of Energy Nonreactor Nuclear Facility Safety Analysis Reports and implements the requirements of DOE Order 5480.23, Nuclear Safety Analysis Report

314

K Basins Hazard Analysis  

Energy Technology Data Exchange (ETDEWEB)

This report describes the methodology used in conducting the K Basins Hazard Analysis, which provides the foundation for the K Basins Safety Analysis Report (HNF-SD-WM-SAR-062, Rev.4). This hazard analysis was performed in accordance with guidance provided by DOE-STD-3009-94, Preparation Guide for U. S. Department of Energy Nonreactor Nuclear Facility Safety Analysis Reports and implements the requirements of DOE Order 5480.23, Nuclear Safety Analysis Report.

WEBB, R.H.

1999-12-29

315

The Cretaceous Gyeongsang Basin  

Energy Technology Data Exchange (ETDEWEB)

Since 1992 sedimentary basin analysis to assess petroleum potential of the Cretaceous and Tertiary strata in the Korean onshore and continental shelf have been carried out. The Cretaceous non-marine strata mainly occupy the Gyeongsang Basin in southeastern part of the Korean Peninsula and small basins such as Haenam and Gyeokpo depressions in western coastal areas. The Tertiary strata are mostly distributed in Domi, Cheju, Socotra subbasins, and Okinawa Trough in the South Continental Shelf, and Kunsan and Heuksan basins in the West. The basin evolution and petroleum potential for each basins are characterized as follow. The Cretaceous Gyeongsang sediments were deposited in three subbasins including Milyang, Euisung and Yongyang subbasins. Based on the volcaniclastic sediment distribution, the Gyeongsang Supergroup can be subdivided into Sindong, Hayang and Yucheon Groups. The Sindong Group was deposited in alluvial fan, flood plain and lacustrine margin environments: the Hayang Group was formed in flood plain, alluvial fan, braided stream and shallow lacustrine environments. The black shales in Nakdong and Jinju formations are interpreted to contain abundant organic matter during the deposition, thermal maturity reaching up to the zone of dry gas formation. Because porosity and permeability are too low, the sandstones can act as a tight gas reservoir rather than conventional oil and gas reservoir. (author). 6 tabs., 9 figs.

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

1999-12-01

316

Generation of Continental Rifts, Basins and Swells by Lithosphere Instabilities  

Science.gov (United States)

Domal uplifts, volcanism, basin formation and rifting have often struck the same continent in different areas at the same time. Their characteristics and orientations are difficult to reconcile with mantle convection or tectonic forces and suggest a driving mechanism that is intrinsic to the continent. The rifts seem to develop preferentially at high angles to the edge of the continent whereas swells and basins seem confined to the interior. Another intriguing geometrical feature is that the rifts often branch out in complicated patterns at their landward end. In Western Africa, for example, magmatic activity currently occurs in a number of uplifted areas including the peculiar Cameroon Volcanic Line that stretches away from the continental margin over about 1000 km. Magmatic and volcanic activity has been sustained along this line for 70 My with no age progression. The mantle upwelling that feeds the volcanoes is not affected by absolute plate motions and hence is attached to the continent. The Cameroon Volcanic Line extends to the Biu swell to the North and the Jos plateau to the West defining a striking Y-shaped pattern. This structure segues into several volcanic domes including the Air, the Hoggar, the Darfur, the Tibesti and the Haruj domes towards the Mediterranean coast. Another example is provided by North America, where the late Proterozoic-early Ordovician saw the formation of four major basins, the Michigan, Illinois, Williston and Hudson Bay, as well as of major rifts in southern Oklahoma and the Mississipi Valley within a short time interval. At the same time, a series of uplifts developed, such as the Ozark and Nashville domes. Motivated by these observations, we have sought an explanation in the continental lithosphere itself. 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 and describe the peculiar horizontal planform that developed. Dynamical behaviour 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 inner region. In the outer annulus, upwellings and downwellings take the form of radial rolls spaced regularly. In the interior region, the planform adopts the more familiar form of polygonal cells. Translated to 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. The laboratory data lead to simple scaling laws for the dimensions and spacings of the convective structures. For the sub-continental lithospheric mantle, these dimensions and distances 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.

Milelli, L.; Fourel, L.; Jaupart, C. P.

2012-12-01

317

The organic petrology and thermal maturity of Lower Carboniferous and Upper Devonian source rocks in the Liard Basin, at Jackfish Gap-Yohin Ridge and North Beaver River, northern Canada: Implications for hydrocarbon exploration  

Energy Technology Data Exchange (ETDEWEB)

Basinal shales of the Besa River Fm. have TOC values ranging from 1 to 4% and contain abundant type II, dominantly amorphous, kerogen of marine origin. Shales in the Yohin, Clausen, Prophet, and Golata Formations are of mixed maring and terrestrial origins and yield TOC values of 1 to 3%. Kerogen in the Golata and Yohin Formations are dominated by terrestrial components, while the Clausen and Flett kerogen comprises marine liptinites and bitumens. Kerogen from the deltaic Mattson shales at Jackfish Gap are types II and III, having mixed marine and terrestrial origins consistent with shallow, nearshore, subtidal environments. The coals are sapropelic and probably lacustrine in origin. Algal laminites associated with coals in the Upper Mattson have >10% TOC values, while non-laminite shales contain between 2 and 5% TOC. Comparable measured and calculated vitrinite reflectance data indicate that kerogen in the Lower Carboniferous at Jackfish Gap is mature. Kerogen in correlative formations in the subsurface at North Beaver River is more marine. Vitrinites are rate and oxidized, but four populations of bitumens are distinguished on the basis of relative reflectivity and morphological or petrophysical associations. Types A and B bitumens are primary and by-products of hydrocarbon generation from type II (algal and amorphous) kerogens. Correlations between depth and reflectance of bitumens A and B are very good. Vitrinite reflectance data calculated from bitumen reflectance measurements for the Besa River, Prophet, and Golata indicate that they are potential sources of catagenic gas. The Mattson kerogen is mature, oil and gas-prone.

Potter, J. (Univ. of Newcastle-upon-Tyne (United Kingdom)); Richards, B.C.; Goodarzi, G. (Geological Survey, Calgary, Alberta (Canada))

318

Summary and conclusions from the SIWI Seminar for Young Water Professionals Drainage basin security--implications of virtual water trade and agricultural subsidies at regional, national and local levels.  

Science.gov (United States)

This is a summary of the Young Water Professionals Seminar involving more than 50 young people from all over the world working with water. The presentations and following discussion were very lively and were about how subsidies and trade barriers imposed by the developed countries are influencing the income-generating capacity of millions of people in the developing world. Even though this is a very complex issue not easily resolved during the seminar it was also clear that there are some fundamental problems that need to be addressed. The importance of looking for solutions at different levels (i.e. local, regional, national) was highlighted as well as the policy of double standards, preaching free trade but only for the benefit of overdeveloped countries themselves. Further it was discussed how to achieve basin security through food security, and managing water for food security. The conclusion was that win-win solutions would be made if agricultural subsidies were to be completely removed. PMID:15195442

Johannessen, A

2004-01-01

319

Establishment of Chinook salmon (Oncorhynchus tshawytscha) in Pacific basins of southern South America and its potential ecosystem implications / Establecimiento del salmón Chinook (Oncorhynchus tshawytscha) en cuencas del Pacífico sur de Sudamérica y sus potenciales implicancias ecosistémicas  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in spanish Los salmonídeos no son nativos del hemisferio sur, y es así que las truchas (arcoiris y café) se establecieron en el sur de Sudamérica hace un siglo. La mayoría de los intentos por introducir salmones anádromos falló hasta el establecimiento de la acuicultura en los años ochenta. A partir de 1990, a [...] parentemente debido a escapes de Oncorhynchus tshawytscha (salmón Chinook) de cultivo, se están produciendo retornos reproductivos de esta especie en cuencas chilenas y argentinas al sur de los 39º S. En este trabajo se muestra la ocurrencia histórica y espacial de salmón chinook en cuatro cuencas de vertiente Pacífica durante la última década. Nuestro objetivo es establecer el progreso de su establecimiento al tiempo que se proyectan algunos impactos así como alternativas de manejo. En Chile, el muestreo se realizó entre 1995 y 2005 incluyendo los ríos Petrohué, Poicas, Río Negro-Hornopirén, y el Lago Puyehue, en la X Región. En Argentina los ríos muestreados incluyen al Futaleufú, Carrenleufú y Pico. En las cuencas chilenas y argentinas los Chinook reproductivos alcanzaban 73 a 130 cm de largo total encontrándose los más pequeños en el Lago Puyehue donde la población estaría encerrada. En el Río Petrohué, los retornos variaron de año en año alcanzando máximos en 1996 y en el 2004 de hasta 500 kg de pescado en una extensión de 100 m de río. La distribución temporal de juveniles sugiere que principalmente se trata del tipo chinook oceánico ya que migrarían al mar durante el primer año de vida. Como se observa en Petrohué, poblaciones reproductivas de la especie aportarían cantidades relevantes de nutrientes de origen marino tal como ocurre en sus hábitats naturales, produciendo así una importante perturbación a los balances y ciclos naturales en estos sitios. El establecimiento de poblaciones de Chinook en el sur de Sudamérica, genera nuevos desafíos a pescadores y autoridades ya que se podría desarrollar una pesquería de la especie en el océano Pacífico con consecuencias sobre otros recursos pesqueros. Adicionalmente también se transforman en un recuso para la pesca deportiva. Por ello se hace necesario desarrollar herramientas de manejo y control sobre la población para evitar perturbaciones ecológicas y ecosistémicas irreversibles Abstract in english Salmon and trout species are not native to the southern hemisphere, however rainbow and brown trout have been established a century in southern South America. Yet most attempts to introduce anadromous salmon failed until the onset of aquaculture by 1980. Escapes of Oncorhynchus tshawytscha (Chinook [...] salmon) from aquaculture after 1990 have apparently produced increasingly important reproductive returns "naturalized", to upper basins in Chile and Argentina south of 39º S. In this paper we show data on the historic and spatial occurrence of chinook salmon in four Pacific basins during the past decade. Our objective is to establish the progress of the settlement forecasting some ecosystem disruptions in order to project and manage potential impacts. In Chile, sampling took place from 1995 to 2005 including rivers Petrohué, Poicas, and Río Negro-Hornopiren, and Lake Puyehue, in the X Region. In Argentina sampled rivers were Futaleufú, Carrenleufú and Pico. In Chile and Argentina reproductive Chinooks ranged in size between 73 and 130 cm total length, being the smallest sizes those of Lake Puyehue where the population is apparently landlocked. In Río Petrohué, the size of the runs varied from year to year reaching in the peak season of 1996 and 2004 up to 500 kg of fish along 100 m of riverbank. Temporal distribution of juvenile Chinooks suggested mainly a typical ocean type as they are gone to sea within the first year of age. As seen in Petrohue, reproductive populations could import significant quantities of marine derived nutrients as they do in their original habitats thus disturbing natural cycles and balances. Chinook establishme

DORIS, SOTO; IVÁN, ARISMENDI; CECILIA DI, PRINZIO; FERNANDO, JARA.

2007-03-01

320

Establishment of Chinook salmon (Oncorhynchus tshawytscha in Pacific basins of southern South America and its potential ecosystem implications Establecimiento del salmón Chinook (Oncorhynchus tshawytscha en cuencas del Pacífico sur de Sudamérica y sus potenciales implicancias ecosistémicas  

Directory of Open Access Journals (Sweden)

Full Text Available Salmon and trout species are not native to the southern hemisphere, however rainbow and brown trout have been established a century in southern South America. Yet most attempts to introduce anadromous salmon failed until the onset of aquaculture by 1980. Escapes of Oncorhynchus tshawytscha (Chinook salmon from aquaculture after 1990 have apparently produced increasingly important reproductive returns "naturalized", to upper basins in Chile and Argentina south of 39º S. In this paper we show data on the historic and spatial occurrence of chinook salmon in four Pacific basins during the past decade. Our objective is to establish the progress of the settlement forecasting some ecosystem disruptions in order to project and manage potential impacts. In Chile, sampling took place from 1995 to 2005 including rivers Petrohué, Poicas, and Río Negro-Hornopiren, and Lake Puyehue, in the X Region. In Argentina sampled rivers were Futaleufú, Carrenleufú and Pico. In Chile and Argentina reproductive Chinooks ranged in size between 73 and 130 cm total length, being the smallest sizes those of Lake Puyehue where the population is apparently landlocked. In Río Petrohué, the size of the runs varied from year to year reaching in the peak season of 1996 and 2004 up to 500 kg of fish along 100 m of riverbank. Temporal distribution of juvenile Chinooks suggested mainly a typical ocean type as they are gone to sea within the first year of age. As seen in Petrohue, reproductive populations could import significant quantities of marine derived nutrients as they do in their original habitats thus disturbing natural cycles and balances. Chinook establishment in these pristine watersheds in southern South America poses new challenges for decision makers and fishermen since they may develop a fishery in the Pacific Ocean with consequences to other fishery resources. Additionally they also become a resource for sport fishing. Therefore there is the need of developing management tools and approaches to control the populations avoiding irreversible ecosystem disruptions and social conflictsLos salmonídeos no son nativos del hemisferio sur, y es así que las truchas (arcoiris y café se establecieron en el sur de Sudamérica hace un siglo. La mayoría de los intentos por introducir salmones anádromos falló hasta el establecimiento de la acuicultura en los años ochenta. A partir de 1990, aparentemente debido a escapes de Oncorhynchus tshawytscha (salmón Chinook de cultivo, se están produciendo retornos reproductivos de esta especie en cuencas chilenas y argentinas al sur de los 39º S. En este trabajo se muestra la ocurrencia histórica y espacial de salmón chinook en cuatro cuencas de vertiente Pacífica durante la última década. Nuestro objetivo es establecer el progreso de su establecimiento al tiempo que se proyectan algunos impactos así como alternativas de manejo. En Chile, el muestreo se realizó entre 1995 y 2005 incluyendo los ríos Petrohué, Poicas, Río Negro-Hornopirén, y el Lago Puyehue, en la X Región. En Argentina los ríos muestreados incluyen al Futaleufú, Carrenleufú y Pico. En las cuencas chilenas y argentinas los Chinook reproductivos alcanzaban 73 a 130 cm de largo total encontrándose los más pequeños en el Lago Puyehue donde la población estaría encerrada. En el Río Petrohué, los retornos variaron de año en año alcanzando máximos en 1996 y en el 2004 de hasta 500 kg de pescado en una extensión de 100 m de río. La distribución temporal de juveniles sugiere que principalmente se trata del tipo chinook oceánico ya que migrarían al mar durante el primer año de vida. Como se observa en Petrohué, poblaciones reproductivas de la especie aportarían cantidades relevantes de nutrientes de origen marino tal como ocurre en sus hábitats naturales, produciendo así una importante perturbación a los balances y ciclos naturales en estos sitios. El establecimiento de poblaciones de Chinook en el sur de Sudamérica, genera nuevos desafíos a pescadores y autoridades ya que se podría desar

DORIS SOTO

2007-03-01

 
 
 
 
321

Geochronological (Rb-Sr and Sm-Nd) studies on intrusive gabbro and dolerite dykes from parts of Northern and Central Indian cratons: implications for the age of onset of sedimentation in Bijawar and Chattisgarh basins and uranium mineralisation  

International Nuclear Information System (INIS)

The Dargawan gabbros intrusive into the Moli Subgroup of Bijawar Group, yielded Rb-Sr whole rock isochron age of 1967 ± 140 Ma. Based on the oldest age from overlying Lower Vindhyan (1.6 Ga) and the underlying youngest basement ages (2.2 Ga), the time range of Bijawar sedimentation may be assigned as 2.1-1.6 Ga (Paleoproterozoic). Sm-Nd Model ages (TDM), obtained, for Dargawan gabbros, is c. 2876-3145 Ma. High initial 87Sr/86Sr ratio of 0.70451 (higher than the contemporary mantle) and negative ?Ndi (at 1.9 Ga) value of -1.5 to - 4.5, indicate assimilation of Archaean lower crustal component by the enriched mantle source magma at the time of gabbroic intrusion. The dolerite, from Damdama area, which is intrusive into the basement and overlying sediments of Chandrapur Group in the central Indian craton, yielded Rb-Sr internal isochron age of 1641 ± 120 Ma. The high initial 87Sr/86Sr ratio of 0.7098 and ?Ndi value of -3.5 to -3.7 (at 1.6 Ga) is due to contamination of the mantle source magma with the overlying sediments. These dolerites have younger Sm-Nd Model ages (TDM) than Dargawan gabbros as c. 2462-2675 Ma, which is similar to the age of the Sambalpur granite, from which probably sediments to this part of Chattisgarh basin are derived. Hence mixing of sediments with the Damdama dyke during its emplacement, gives rise to high initial 87Sr/86Sr and low ip>87Sr/86Sr and low initial 143Nd/144 ratios for these dykes. The c. 1600 Ma age indicates minimum age of onset of the sedimentation in the Chandrapur Group of Chattisgarh basin. Both the above mafic intrusions might have taken place in an intracratonic rift related (anorogenic) tectonic setting. This study is the first reliable age report on the onset of sedimentation in the Chandrapur Group. The total minimum time span of Chandrapur and Raipur Group may be 1.6 Ga to 1.0 Ga (Mesoproterozoic). The unconformably underlying Shingora Group of rocks of Chattisgarh Supergroup thus indicates Paleoproterozoic age (older than 1.6 Ga). Most part of the recently classified Chattisgarh Supergroup and Bijawar-Vindhyan sequence are of Mesoproterozoic-Paleoproterozoic age and not of Neoproterozoic-Mesoproterozoic age as considered earlier. Petrographic study of basic dykes from Damdama area (eastern margin of Chattisgarh Supergroup) indicated presence of primary uranium mineral brannerite associated with goethite. This is the evidence of mafic intrusive providing geotherm and helping in scavenging the uranium from the surrounding and later alterations causing remobilisation and reconcentration of pre-existing uranium in host rocks as well as in mafic dyke itself otherwise mafic rocks are poor source of uranium and can not have primary uranium minerals initially. It can be concluded that mafic dykes have role in uranium mineralisation although indirectly. (author)

322

Origin of Mesozoic and Tertiary granite in the Western United States and implications for Pre-Mesozoic crustal structure 1. Nd and Sr isotopic studies in the geocline of the Northern Great Basin  

International Nuclear Information System (INIS)

Mesozoic and Tertiary granite rocks in and adjacent to the northern Great Basin (NGB) in Nevada and Utah display a wide range of initial 143Nd/144Nd (epsilon/sub Nd/) and 87Sr/86Sr (epsilon/sub Sr/) values which vary regularly with geographic position. From the Klamath Mountains inland 500 km to central Nevada, granite epsilon/sub Nd/ values decrease regularly from +8 to -6 and correlate with epsilon/sub Sr/ values that increase from -20 to +60. In east-central Nevada, near the trace of the Roberts Mountains Thrust (RMT), the epsilon/sub Nd/ values decrease from -6 to an average of -18, while epsilon/sub Sr/ becomes highly variable with values generally greater than +100. These isotopic discontinuities correspond to the west-to-east facies transition from pelagic clastic sedimentary rocks to shelf carbonates and to the shift in the dominant granite bulk composition from metaluminous to peraluminous. In the eastermost NGB a second discontinuity in epsilon/sub Sr/ occurs with values dropping to approx.+60; average epsilon/sub Nd/ remains at -18. Combined with known aspects of NGB geology the isotopic data suggest that west of the RMT, granites formed via interaction of magma derived from a LREE-depleted pelagic sedimentary rock. Variations in 87Rb/86Sr with Sr, and 147Sm/144Nd with epsilon/sub Nd/, indicate that crystal fractionation accompanied assimilation, but that plagioclase wasied assimilation, but that plagioclase was not an important fractioning phase. East of the RMT, granites appear to be primarily derived fom precambrian continental basement with little mantle input. The isotopic discontinuities near the RMT mark the western edge of precambrian basement and occur 100-200 km east of the 87Sr/86Sr ( = 0.7060) line of Kistleer and Peterman [1973

323

Determination of groundwater recharge regime and flowpath in the Lower Heihe River basin in an arid area of Northwest China by using environmental tracers: Implications for vegetation degradation in the Ejina Oasis  

International Nuclear Information System (INIS)

Environmental tracers (CFCs, stable isotopes 18O, 2H, and 3H) and major ions were employed to study river infiltration and groundwater recharge in the aquifer system in the basin of the Lower Heihe River, Northwest China. Three groups of waters have been recognized: (1) young groundwater, connected to the river, with large variation of CFC apparent ages ranging from 18O and ?2H values which are similar to the river water; (2) regional background water, unaffected by the river, having CFC apparent ages >40 a, and being depleted in 18O and 2H compared with the river water; and (3) groundwater in Gurinai, a grassland located about 100 km from the river, in which the predominant discharge is from the Badain Jaran desert, with CFC apparent ages ranging from 25 to >50 a and being enriched in 18O and 2H compared to the river water. The groundwater along the river contains CFCs and 3H down to depths of about 120 m, and the shallow groundwater exhibits CFC apparent ages in a wide range which are not dependent on the well depth. Groundwaters along the river show a similar trend of enrichment in 18O and 2H as the river water whereas groundwaters in depression cones are depleted in heavier isotopes, and have low CFC and 3H concentrations. The CFC apparent age of the groundwater increases with increasing distance downsincreases with increasing distance downstream, indicating that the dominant part of the groundwater is from infiltration of river water in the upper reaches. Modifications of groundwater recharge are reflected in variations of stable isotope compositions, as well as CFC and 3H concentrations in the groundwater that was recharged from the river over the last decades. Despite recharging from river water, groundwater abstraction has induced a water balance deficit. The riparian ecosystem in the Ejina Oasis is constrained by both decreased river flow and increased groundwater abstraction. The vegetation degradation in the Ejina Oasis is controlled not only by natural aridification but also worsened by heavy groundwater abstraction and decreased river flow.

324

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)

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 latitude of the SLB began to open by about 28 Ma, some 1.5 Ma earlier than previously thought and coeval with late-stage volcanism in the San Juan region.

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

2009-12-01

325

Anadarko Basin conodont studies  

Science.gov (United States)

Preliminary analysis of early Paleozoic conodonts from the subsurface within and adjacent to the Anadarko basin demonstrates their utility in stratigraphic and thermal evolution studies in the basin. More than 100 samples from 30 drill holes produced conodonts that can be correlated with faunas known from rock sequences exposed along the southern flanks of the basin. For the Middle Ordovician to Devonian, extant biozonations and/or recent published literature based on Oklahoma surface sections allow good biostratigraphic correlation into the subsurface and often allow testing of physical correlations. In contrast, conodonts from the Arbuckle Group (Lower to Middle Ordovician) are less well known. Faunas from the upper half of the group are documented only in unpublished theses, and published faunas are in need of restudy and revision. However, this limited information, along with work in progress in Oklahoma and data from carbonate platform facies elsewhere in North America, still permit correlations into the subsurface with the promise of increasingly improved resolution.

Repetski, John E.

1989-01-01

326

Sampling South Pole-Aitken Basin: The Moonrise Approach  

Science.gov (United States)

The South Pole-Aitken basin (SPA) is the largest of the giant impact basins in the inner Solar System, and its location on Earth s Moon makes it the most accessible. Exploration of SPA through direct collection and analysis of representative materials addresses issues as fundamental as the characteristics of the chemical reservoir from which the Moon originated, early differentiation and production of crust and development of global asymmetry, relationships between magmatic activity and internal thermal evolution, and effects of giant impact events on the terrestrial planets. Owing to its great size and superposition relationships with other lunar impact basins, SPA is the oldest and as such anchors the lunar chronology. Moreover, numerous large impact craters and basins are contained within it such that materials (rocks) of the SPA basin contain a record of the early impact chronology, one less likely to have been affected by the large, late nearside basins (e.g., Imbrium). Understanding the early basin chronology is key to deciphering the sequence and effects of early giant impact bombardment of the inner Solar System. That record exists on the Moon, and materials of the SPA basin will allow us to read that record. Knowledge of the early bombardment history will test - and may reshape - a key paradigm relating to early Solar System evolution. Did the planets form with the alignment of today, or was there a major reorientation of the giant planets that led to destabilization of asteroid orbits, and a cataclysmic bombardment of the inner Solar System hundreds of millions of years after accretion of the planets? Implications include understanding environments for early life-supporting habitats on Earth and Mars, and relationships to new observations of extra-solar planetary systems.

Jolliff, B. L.; Sh