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1

Improved Recovery Demonstration for Williston Basin Carbonates  

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. Improved reservoir characterization utilizing three-dimensional is 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 short-lateral and horizontal drilling technologies. Improved completion efficiency, additional wells at closer spacing and better estimates of oil-in-place will result in additional oil production by primary and enhanced recovery processes.

Larry A. Carrell

1997-12-31

2

Cedar Creek: a significant paleotectonic feature of Williston basin  

Energy Technology Data Exchange (ETDEWEB)

Cedar Creek is the major anticlinal structure demarcating the southwest flank of the Williston basin. This pronounced fold developed through a geologic history of recurrent tectonic movements along a northwest-southeast striking fault zone. The four major periods of tectonism documentable in the Cedar Creek area from early Paleozoic through mid-Tertiary affected the local and regional distribution, erosion, and/or preservation, and, though moderately, the depositional facies of sedimentary strata since Ordovician time.

Clement, J.H.

1983-08-01

3

Williston basin oil exploration: Past, present, and future  

Energy Technology Data Exchange (ETDEWEB)

Past: In 1951, modern oil exploration came to the Williston basin with the discovery of Paleozoic oil on the large Nesson anticline. This was quickly followed by similar discoveries on Cedar Creek and Poplar anticlines. To the north, the Canadians, lacking large structures, concentrated on Paleozoic stratigraphic traps and were highly successful. US explorationists quickly followed, finding similar traps on the basin's northeastern flank and center. The 1960s saw multiple Devonian salt dissolution structures produce on the western flank. To the northwest, shallow Mississippian and deeper Ordovician pays were found on small structural closures. These later were combined with pays in the Devonian and Silurian to give multiple pay potential. In the basin center large buried structures, visible only to seismic, were located. The 1970s revealed an Ordovician subcrop trap on the southeast flank. Centrally, a Jurassic astrobleme with Mississippian oil caused a flurry of leasing and deep drilling. The 1982 collapse of oil prices essentially halted exploration. 1987 saw a revival when horizontal drilling for the Mississippian Bakken fractured shale promised viable economics. Present: Today, emphasis is on Bakken horizontal drilling in the deeper portion of the basin. Next in importance is shallow drilling such as on the northeastern flank. Future: An estimated on billion barrels of new oil awaits discovery in the Williston basin. Additional exploration in already established production trends will find some of this oil. Most of this oil, however, will almost certainly be found by following up the numerous geological leads hinted at by past drilling.

Jennings, A.H.

1991-06-01

4

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)

2005-04-24

5

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

6

A preliminary comparison of Waulsortian mound facies in the Williston and Illinois basins  

Energy Technology Data Exchange (ETDEWEB)

The location of the Waulsortian-like mounds in the Williston Basin is associated with fault zones believed to have been active at various times during the Phanerozoic. However, a similar tectonic control for the development of these mounds in the Illinois Basin has not been established. Mounds in Illinois apparently developed on a ramp setting, but the only known petroleum productive mound in the Williston is interpreted to be on the basin floor at the toe of the shelf slope, or ramp. The mounds in both basins are lithologically similar, with crinoids and bryozoans as the dominant skeletal components. Oil production in the Williston Basin comes from the mound core facies. In contrast, oil production in the Illinois Basin comes from bryozoan-dominated bioherms and grainstone shoals overlying the mound complexes. Basinal mounds in the Williston have average estimated primary reserves of 2.5 MMBO per well, whereas mid-ramp buildups in Illinois have average estimated reserves of 90,000 BO per well. These differences indicate potential new play opportunities for each basin: in the Williston, shallow shelf-slope or ramp buildups are probable, and, in the Illinois, deep basin or lower ramp mounds are likely. 46 refs., 7 figs.

Burke, R.B. [North Dakota Geological Survey, Grand Forks, ND (United States); Lasemi, Z. [Illinois State Geological Survey, Champaign, IL (United States)

1995-12-31

7

Hydrocarbon resources of the North Dakota Williston Basin  

Energy Technology Data Exchange (ETDEWEB)

In this study, the undiscovered resources of the approximately 52,000 sq km in which oil is produced in the North Dakota part of the Williston Basin were estimated. The sample from which the characteristics of the total population of pools were estimated included 509 producing oil and gas pools, and 307 abandoned pools. Three stratigraphic intervals, the Madison, Devonian, and Ordovician, produce hydrocarbons from enough fields to allow statistical comparison. Estimated resources remaining to be discovered for the three zones for class 8 or larger pools are 157, 547, and 123 MMBOE for the Madison, Devonian, and Ordovician, respectively, which gives a total of 827 MMBOE. A volumetric estimate of undiscovered resources, which was done for comparison with the statistical estimates, yielded a total remaining reserve of about 842 MMBOE. The reservoirs most likely to contain these reserves are in Devonian and older strata. Most new pool discoveries will probably be in class 12 pools and smaller, but the discovery of larger pools cannot be ruled out. 28 refs., 12 figs., 4 tabs.

LeFever, R.D. [North Dakota Univ., Grand Forks, ND (United States). Dept. of Geology; Heck, T.J. [North Dakota Geological Survey, Bismarck, ND (United States)

1995-12-31

8

Three emerging horizontal plays in the Williston Basin, North Dakota  

Energy Technology Data Exchange (ETDEWEB)

This paper presented information on the Devonian Birdbear Formation, the Madison Charles Formation and the Madison Mission Canyon Formation. All three formations are emerging plays in the Williston Basin. Initial production tests in all plays showed some wells with rates over 660 barrels of oil per day. A dolomite reservoir in the upper portion of the Devonian Birdbear Formation has been a target for horizontal drilling development in Golden Valley and Billings Counties, North Dakota. The upper Birdbear Formation consists of 3 upward-shallowing carbonate cycles. It was noted that horizontal wells in this zone have initial rates that exceed 750 barrels of oil per day and may produce more than 300 thousand barrels of oil per well. However, vertical wells in this area have low initial production rates and small initial reserves. In addition, 2 Madison plays are under development in northwestern Dakota. Details of sub-intervals and reservoir depths were presented. The porosity in the Alexander subinterval measured over 19 per cent, with lithologies of the pay zone from calcitic dolostone to dolomitic limestone. Porosity was complex and ranged from dolomite replacement of limestone to dissolution of grains. Initial production rates averaged 309 barrels of oil per day with the highest rates at 689 barrels per day. Details of the Frobisher-Alida interval were also presented, including porosity, reservoir depths and dissolution features. Initial production tests of 4 wells in this play averaged 254 barrels of oil per day with the highest rate at 725 barrels per day. It was concluded that the success of these reservoirs is attributable to the advantages of horizontal drilling in heterogenous low permeability and low porosity zones that are not economic in vertical wells because of limited drainage efficiency.

Burke, R.B. [North Dakota Geological Survey (United States)

2005-07-01

9

Improved recovery demonstration for Williston Basin carbonates. Final report  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this project was to demonstrate targeted infill and extension drilling opportunities, better determinations of oil-in-place, and methods for improved completion efficiency. The investigations and demonstrations were focussed on Red River and Ratcliffe reservoirs in the Williston Basin within portions of Montana, North Dakota and South Dakota. Both of these formations have been successfully explored with conventional 2-dimensional (2D) seismic. Improved reservoir characterization utilizing 3-dimensional (3D) seismic was investigated for identification of structural and stratigraphic reservoir compartments. These seismic characterizations were integrated with geological and engineering studies. The project tested lateral completion techniques, including high-pressure jetting lance technology and short-radius lateral drilling to enhance completion efficiency. Lateral completions should improve economics for both primary and secondary oil where low permeability is a problem and higher-density drilling of vertical infill wells is limited by drilling cost. New vertical wells were drilled to test bypassed oil in ares that were identified by 3D seismic. These new wells are expected to recover as much or greater oil than was produced by nearby old wells. The project tested water injection through vertical and horizontal wells in reservoirs where application of waterflooding has been limited. A horizontal well was drilled for testing water injection. Injection rates were tested at three times that of a vertical well. This demonstration well shows that water injection with horizontal completions can improve injection rates for economic waterflooding. This report is divided into two sections, part 1 covers the Red River and part 2 covers the Ratcliffe. Each part summarizes integrated reservoir characterizations and outlines methods for targeting by-passed oil reserves in the respective formation and locality.

Sippel, M.A.

1998-07-01

10

Tectono-stratigraphic evolution of the Williston Basin - A regional seismic stratigraphic study  

Energy Technology Data Exchange (ETDEWEB)

The importance of considering the curvature of the earth in regional studies of basins was highlighted. A methodology based on regional seismic sections which required a display taking the curvature of the earth into account, were used for the Williston Basin. Regional seismic interpretation across the Basin illustrates how regional profiles allow better analysis of tectonic and stratigraphic characteristics than borehole information alone. The study showed that the Williston Basin did not subside continuously but with intermittent compressive stages that led to basin scale folding. The folding was greatest in the middle of the basin and decreased toward the flanks. The structural and stratigraphical patterns were influenced primarily by shortening of the basement/sediment contact during subsidence and, to some extent, by tectonism at the plate margins. 27 refs., 11 figs., 1 tab.

Redly, P.; Hajnal, Z. [Saskatchewan Univ., Saskatoon, SK (Canada)

1995-12-31

11

Basement tectonics and hydrocarbon production in the Williston Basin: An interpretive overview  

Energy Technology Data Exchange (ETDEWEB)

Basement tectonic features of the Williston Basin were presented and the advantages of gravity and magnetics were emphasized. In fact, the Williston Basin is a virtual casebook of basement tectonic features repeatedly affecting sedimentation and hydrocarbon accumulation. Basement features in this area are clearly expressed in gravity and magnetic data. Since the reactivation of the lithologic contacts are demonstrable, some predictions can be made about possible structural development in other less obvious areas. The Cedar Creek anticline is a prime example that shows repeated rejuvenation of an Archean lithologic contact. Analogs to the Cedar Creek basement feature can be identified in several locations in the basin, and Ordovician Red River facies trends may be affected by basement features similar to those at Cedar Creek. The Nesson anticline also follows old basement lithologic boundaries. Subtle disruptions in the gravity and magnetic data correlate with lines of small fields and may be related to facies such as oolite shoals in the Mississippian carbonates. Basement tectonics, inferred from gravity and magnetics, can therefore be used as a guide to exploration in multiple plays in the Williston Basin. 12 refs., 10 figs.

Gibson, R.I. [Gibson Consulting, Golden, CO (United States)

1995-12-31

12

Evaluation of injection well risk management potential in the Williston Basin  

Energy Technology Data Exchange (ETDEWEB)

The UIC regulations promulgated by the EPA under the Safe Drinking Water Act (SDWA) provide the EPA, or an EPA approved state agency, with authority to regulate subsurface injection of fluids to protect USDWs. Oil and gas producing industry interests are concerned primarily with Class 2 wells whose uses as defined by UIC regulations are: disposal of fluids brought to the surface and liquids generated in connection with oil and gas production (SWD); injection of fluids for enhanced oil recovery (EOR); and storage of liquid hydrocarbons. The Williston Basin was chosen for the pilot study of the feasibility of using the risk approach in managing Class 2 injection operations for the following reasons: it is one of the nine geologic basins which was classified as having a significant potential for external casing corrosion, which permitted an evaluation of the effectiveness of the injection well corrosion control measures used by industry; there are 731 active, 22 shut in and 203 temporarily abandoned SWD and water injection wells in the basin; and the basin covers three states. The broad objective of the Williston Basin study is to define requirements and to investigate the feasibility of incorporating risk management into administration of the UIC program. The study does not address the reporting aspects of UIC regulatory and compliance activities but the data base does contain essentially all the information required to develop the reports needed to monitor those activities. 16 refs., 10 figs., 11 tabs.

none,

1989-09-01

13

Relationship of salt patterns to hydrocarbon accumulations, North Dakota Williston Basin  

Energy Technology Data Exchange (ETDEWEB)

Salts, which are widespread throughout the Williston Basin, have had a profound effect on hydrocarbon accumulation (hydrocarbons have often been trapped due to dissolution and related collapse of underlying salts). Their mapping is therefore essential. Thicknesses of 24 major and minor salts were obtained from about 4300 wireline logs in North Dakota, and isopach maps of all salts were constructed. Areas of salt dissolution were identified by linking thinning on the salt isopach maps with thicker compensating sections in the overlying strata. The most significant salt in the basin occurs within the Prairie Formation; trapping of hydrocarbons and significant production related to dissolution of the Prairie Salt has been documented in several cases. However, examination of other salts within the North Dakota part of the basin suggests that such trapping can be documented for several other salts. In many cases, such dissolution appears to have occurred as a multi-stage process. 32 refs., 14 figs.

LeFever, J.A. [North Dakota Geological Survey, Grand Forks, ND (United States); LeFever, R.D. [North Dakota Univ., Grand Forks, ND (United States). Dept. of Geology

1995-12-31

14

Geochemistry and familial association of crude oils from the Birdbear Formation in southeastern Saskatchewan, Williston Basin  

Energy Technology Data Exchange (ETDEWEB)

An investigation was carried out to determine the geochemical composition of 9 crude oils from a subset of Upper Devonian Birdbear reservoirs in the Canadian Williston Basin. The geochemical signatures of these oils are compared with those of family D2 oils produced from the Middle Devonian Winnipegosis Formation. Also included in the sample set are 1 Birdbear- and 1 Winnipegosis-reservoired oil samples from the American Williston Basin. While considering a larger set of samples than that originally analyzed in the literature, emphasis is placed on the variations of gasoline range and saturated hydrocarbons. Following oil-oil correlation, a possible relationship between Birdbear-reservoired oils and Devonian source rocks is briefly introduced. Crude oils in the Upper Devonian Birdbear Formation have a distinctive geochemical composition and appear to belong to a separate compositional oil family. An oil-oil correlation with Winnipegosis-reservoired oils shows that not only is their stratigraphic occurrence different, but also that they have variable gasoline range characteristics, and different saturate biomarket compositions. Both stratigraphically restricted groups of oils have different Paraffin Indices and `Mango` parameters, different C13-C30 normal alkane profiles, different relative concentrations of acyclic isoprenoids and resulting Pr/Ph, Pr/nC17 and Ph/nC18 ratios. Although the distributions of terpane biomarkers show some similarities, Birdbear-reservoired oils have less pronounced C34 hopane predominance and Ts/Tm ratios typically less than 1.0. The sterane biomarker signatures are quite different with high concentrations of diasteranes and prominent C21 regular steranes in the Birdbear oil samples, and a very different relative abundance of C27, C28, and C29 regular steranes. There is no evidence for a maturity effect. These compositional differences may be genetic in nature showing a different source rock for oils found in the Birdbear Formation and possibly a previously unrecognized petroleum system in the Saskatchewan Group across the Canadian Williston Basin. 26 refs., 15 figs., 3 tabs.

Obermajer, M.; Osadetz, K.G.; Fowler, M.G.; Snowdon, L.R. [Geological Survey of Canada, Calgary, AB (Canada)

1999-09-01

15

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

16

Improved recovery demonstration for Williston Basin carbonates. Quarterly report, July 1 - September 30, 1996  

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. Improved reservoir characterization utilizing 3-dimensional (3D) and multi-component seismic are being investigated for identification of structural and stratigraphic reservoir compartments. Field demonstrations are in progress to collect data for evaluation of horizontal completions in both the Red River and Ratcliffe. A vertical well in the Red River will test attribute analysis of 3D seismic data for prediction of porosity development. Additional seismic acquisitions and interpretation are in progress for both the Ratcliffe and Red River. A water-injectivity test in a new horizontal completion in the Red Rive B zone at Buffalo Field is scheduled for next quarter.

Carrell, L.A.

1996-12-31

17

Improved recovery demonstration for Williston Basin carbonates. Annual report, June 10, 1995--June 9, 1996  

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.

Carrell, L.A.; Sippel, M.A.

1996-09-01

18

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

19

Fracture-enhanced porosity and permeability trends in the Bakken Formation, Williston Basin, western North Dakota  

Energy Technology Data Exchange (ETDEWEB)

The Bakken Formation in the Williston Basin is a known hydrocarbon source rock and a petroleum reservoir, but lacks rock matrix porosity and permeability common to most petroleum reservoirs. Core analysis showed that the effective porosity and permeability development within this formation is primarily related to fracturing. This fracturing is thought to have occurred along reactivated basement-block boundaries in response to varying tectonic stresses and crustal flexure throughout the Phanerozoic. Landsat-derived lineament maps were examined in an attempt to identify large-scale fracture trends. The association of Landsat-derived lineaments and fracture density in the subsurface is demonstrated by a statistically significant relation between proximity of wells to lineament traces and the percentage of drill stem test shut-in pressures indicating fracturing. A statistically significant relation is also identified between Bakken thickness and fracture density. 38 refs., 11 figs., 1 tab.

Freisatz, W.B. [Sunburst Consulting, Billings, MT (United States)

1995-12-31

20

Compressional and shear wave seismic studies in the Williston Basin of central Saskatchewan  

Energy Technology Data Exchange (ETDEWEB)

High resolution multicomponent seismic data were collected in the Williston Basin near Saskatoon, Saskatchewan. The study was conducted to determine parameters necessary to improve horizontal and vertical resolution in traditional seismic data, and to investigate shear wave behaviour. The study targeted evaporites and surrounding lithologies, where potash is mined. A specially designed survey procedure which increases propagation signal frequencies beyond 100 Hz at depths below 1000 m was used. The study demonstrated that shear waves can be induced and propagated to significant depths despite 100 m of near-surface glacial cover. Synthetic seismograms calculated from an S-wave sonic log further confirmed the strong contrast between the transverse wave velocity properties of the different subsurface strata of the area. By combining the P- and S-wave information, a more detailed seismo-lithologic model could be derived. 10 refs., 12 figs.

Carr, B.J.; Hajnal, Z. [Saskatchewan Univ., Dept. of Geological Sciences, Saskatoon, SK (Canada)

1995-12-31

 
 
 
 
21

Development and distribution of Rival reservoirs in central Williston basin, western North Dakota  

Energy Technology Data Exchange (ETDEWEB)

The Mississippian Rival (Nesson) beds in the central Williston basin, North Dakota, are a limestone to evaporite regressive sequence. Progradation of the depositional system produced several distinct shallowing-upward genetic units. Cyclicity in Rival beds was produced by periodic fluctuations in sea level. Rival oil reservoirs are porous and permeable packstones and grainstones. The dominant allochems in these reservoir rocks are peloids and skeletal and algal fragments. These sediments were deposited along carbonate shorelines and within algal banks that developed basinward of shorelines. The trapping mechanism along shorelines is a lithofacies change from limestone to anhydride. Algal banks are locally productive along paleostructural trends where bathymetric shallowing produced shoals dominated by the Codiacean alga Ortonella. Algal banks are flanked by impermeable carbonate mudstones and wackestones deposited in interbank and protected shelf environments. Two distinct Rival bank trends occur in the central basin: a northwest-southeast trend in McKenzie and Williams Counties, North Dakota, parallel with the Cedar Creek anticline, and a northeast-southwest trend along the Nesson anticline and the northeast flank of the basin, parallel with the Weldon-Brockton fault trend.

Hendricks, M.L.

1988-07-01

22

Origin and geometry of Red River Dolomite Reservoirs, Western Williston Basin  

Energy Technology Data Exchange (ETDEWEB)

Remarkably uniform distribution of limestone, laminated dolomite, and anhydrite as determined from compensated neutron-density logs suggests that the entire Ordovician Red River Formation of the central Williston Basin was deposited in subtidal ''brining-upward'' sequences. Study of cores and thin sections verifies this locally dolomitized fossiliferous wackestones and packstones, laminated to evenly bedded unfossiliferous mudstones (dolomitized in many wells), and bedded anhydrite. No evidence of subaerial exposure was observed in these rock units. Dolomitization in the Red River ''C'' zone is highly localized. An empirical study of dolomite distribution using data from well logs reveals the presence of dozens of pods of dolomite immediately beneath the ''C'' anhydrite. The pods are up to 200 ft (60 m) thick and 1 mi (1.6 km) in diameter and consist of concentered lenses of (1) tight (locally anhydritic) cryptocrystalline dolomite up to 40 ft (12.2 m) thick and 3,300 ft (1,000 m) in diameter, (2) fine to medium-grained porous dolomite that forms the reservoirs, and (3), still farther from the cryptocrystalline dolomite, relatively tight partly dolomitized limestones. could have been found through application of this model and others could be more efficiently developed.

Longman, M.W.; Fertal, T.G.; Glennie, J.S.

1983-05-01

23

Development of structure and porosity at Medicine Lake field, northeastern Montana, Williston Basin  

Energy Technology Data Exchange (ETDEWEB)

Medicine Lake field produces oil from the Mississippian Charles, Devonian Winnipegosis, Silurian Interlake, and Ordovician Stony Mountain and Red River Formations. Drill-stem tests also show a potential for production from the Devonian Birdbear and Duperow Formations. Noncommercial quantities of oil were recovered from the Mississippian Mission Canyon Limestone and Ordovician Winnipeg Formation. Different combinations of bioclastic bank development, dolomitization, solution, and fracturing have contributed to the porosity of each of the producing formations. Porosity development in the Winnipegosis and Red River Formations may have been influenced by the Medicine Lake paleostructure. The Medicine Lake structure is slightly elliptical, 1 mi (1.6 km) in diameter, and has 125 ft (38 m) of structural closure at the top of the Red River Formation. Growth of the structure was essentially complete by the end of Devonian time. On another structure at nearby Outlook field, structural movement can be shown to have continued into the Cenozoic. The configuration of Cambrian and Precambrian rocks at Medicine Lake suggests that the structure there formed by the compaction of Cambrian sediments deposited around a hill on the Precambrian land surface. Regional-scale southeast-plunging anticlines in the eastern Montana Williston basin may also have formed by compaction of Cambrian sediments on a differentially eroded Precambrian land surface.

Indorf, C.P.; Norwood, E.E.

1985-05-01

24

Macrofossils of Bakken Formation (Devonian and Mississippian), Williston Basin, North Dakota  

Energy Technology Data Exchange (ETDEWEB)

Results of this study of the macrofossils of the Bakken Formation in North Dakota have reinforced the suggestion, based on previous paleontological work in Saskatchewan, that the Bakken is of both Devonian and Mississippian age, rather than being entirely of Lower Mississippian age as originally considered. Increased drilling and coring activity in the North Dakota part of the Williston Basin has provided the opportunity for acquiring a larger fauna that was previously available. Based on lithologic character, the Bakken has been divided into three informal members. These consist of a calcareous siltstone unit between two lithologically similar units of carbonaceous shale. These black shales contain similar faunas distinct from that of the middle member. The black shales contain inarticulate brachiopods, conchostracans, and rare cephalopods and fish remains as well as more abundant conodonts, ostracods, and palynomorphs. The middle siltstone unit contains a more abundant and diverse fauna consisting of inarticulate and articulate brachiopods together with corals, gastropods, cephalopods, ostracods, echinoderm remains, and trace fossils. This is the first report of cephalopods, conchostracans, ostracods, corals, trace fossils, and some of the brachiopods in the Bakken, although all, except the gastropods, have been reported from stratigraphic equivalents (Exshaw Formation of south-central Montana, the Leatham Formation of northeastern Utah, and the middle member of the Pilot Shale in western Utah and eastern Nevada).

Thrasher, L.; Holland, F.D. Jr.

1983-08-01

25

Depositional environments and history of the Winnipeg Group (Ordovician), Williston Basin, North Dakota  

Energy Technology Data Exchange (ETDEWEB)

The Winnipeg Group represents the initial deposits in the Williston Basin of the Middle Ordovician transgression. It unconformably overlies the Deadwood Formation in most of North Dakota, and is conformably overlain by the Red River Formation. The Winnipeg Group consists of three formations, the Black Island, the Icebox, and the Roughlock. The Black Island Formation consists of sandstone and lesser amounts of shale, and is interpreted as deltaic and shallow marine deposits. The Icebox Formation is a fossiliferous bioturbated shale with minor sandstone, and is an offshore deposit. The Roughlock Formation is a fossiliferous, calcareous shale deposited in a deeper marine environment than the Icebox. At the end of the Early Ordovician there was a major sea level drop, causing erosion of much of the Deadwood Formation. Sea level rose again during the Early Ordovician, and the basal Black Island was deposited unconformably on the Deadwood. As sea level continued to rise, more Black Island was deposited, followed by offshore marine Icebox shales, more distal Roughlock calcareous shales, and finally Red River limestones. 14 refs., 12 figs., 1 appendix

Ellingson, J.B.; LeFever, R.D. [North Dakota Univ., Grand Forks, ND (United States). Dept. of Geology

1995-12-31

26

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

27

Reservoir characterization of the Mississippian Ratcliffe, Richland County, Montana, Williston Basin. Topical report, September 1997  

Energy Technology Data Exchange (ETDEWEB)

This topical report is a compilation of characterizations by different disciplines of the Mississippian Ratcliffe in portions of Richland County, MT. Goals of the report are to increase understanding of the reservoir rocks, oil-in-place, heterogeneity and methods for improved recovery. The report covers investigations of geology, petrography, reservoir engineering and seismic. The Ratcliffe is a low permeability oil reservoir which appears to be developed across much of the study area and occurs across much of the Williston Basin. The reservoir has not been a primary drilling target in the study area because average reserves have been insufficient to payout the cost of drilling and completion despite the application of hydraulic fracture stimulation. Oil trapping does not appear to be structurally controlled. For the Ratcliffe to be a viable drilling objective, methods need to be developed for (1) targeting better reservoir development and (2) better completions. A geological model is presented for targeting areas with greater potential for commercial reserves in the Ratcliffe. This model can be best utilized with the aid of 3D seismic. A 3D seismic survey was acquired and is used to demonstrate a methodology for targeting the Ratcliffe. Other data obtained during the project include oriented core, special formation-imaging log, pressure transient measurements and oil PVT. Although re-entry horizontal drilling was unsuccessfully tested, this completion technology should improve the economic viability of the Ratcliffe. Reservoir simulation of horizontal completions with productivity of three times that of a vertical well suggested two or three horizontal wells in a 258-ha (640-acre) area could recover sufficient reserves for profitable drilling.

Sippel, M.; Luff, K.D.; Hendricks, M.L.

1998-07-01

28

Conodonts of Bakken Formation (Devonian and Mississippian), Williston basin, North Dakota  

Energy Technology Data Exchange (ETDEWEB)

The Bakken Formation is a thin (maximum 145 ft, 45 m), clastic unit in the subsurface of Williston basin in the United States and Canada. The Bakken is similar in lithologic character and stratigraphic position to other black shale units deposited on the North American craton during the Late Devonian and Early Mississippian. The Bakken was initially considered entirely Mississippian in age. Paleontologic study of regional physical equivalents and analysis of the macrofauna in Saskatchewan has suggested that the Bakken is actually both Devonian and Mississippian. Conodonts were obtained from cores of the Bakken in an effort to determine the age of the formation in North Dakota and to assess the oil generation potential. Nearly 700 conodonts have been recovered, but are unevenly distributed within the Bakken Formation. A majority was obtained from thin (approximately 0.5 cm), fossil-rich beds within the upper shale. Conodonts from the top of the upper shale reveal a Mississippian (Kinderhookian) age and are here assigned to the Lower Siphonodella crenulata Zone. Only rare, fragmentary conodonts have been found in the middle member. Conodont evidence from the middle of the lower shale suggests a late Devonian (Famennian) age (Upper Polygnathus styriacus Zone) for this member. Conodont color has been established as a geothermometer in carbonate rocks. Color alteration indices of conodonts from the Bakken range from 1.5 to approximately 2.5 and indicate a pattern of increasing temperature with depth. These results suggest possible hydrocarbon generation from shallower depths than has been reported previously for the Bakken. The lack of agreement in interpreted hydrocarbon generation depths may be due to, among other things, the clastic nature of the Bakken Formation.

Hayes, M.D.; Holland, F.D. Jr.

1983-08-01

29

Magnesium and calcium isotope study of limestone and dolomite in Middle and Upper Ordivician strata of the Williston Basin  

Science.gov (United States)

Using Magnesium (Mg) and Calcium (Ca) isotopes, we investigate a complex, discontinuous, pattern of subsurface dolomitization including intervening beds of limestone through the Upper Yeoman and Lower Herald Formations within the Williston Basin, cored near the town of Midale in southeastern Saskatchewan. The character of the stratigraphic sequence suggests paleoaquifers as an explanation of the partially dolomitized units. Previous work has demonstrated a large range of fractionation with ? 44/40Ca between the precursor limestone value (inferred from mixing calculations) and the dolomite value within the Yeoman Formation, suggesting that Ca isotope values could be used to identify sources of dolomitizing fluids. ? 26Mg in conjunction with ? 44/40Ca may be used to better constrain the source of these Mg-rich fluids. Preliminary data reveal a range in limestone ? 26Mg values from -2.77±0.05 to -2.86±0.07permil with a mean value of -2.81permil. Dolomite ? 26Mg values range from -1.31±0.07 to -1.64±0.06permil with a mean value of -1.48permil. Measured dolomite Mg isotope values are consistent with reported dolomite values from a Mississippian aged carbonate aquifer [Jacobson et al., 2010]. Measured limestone Mg isotope values are analogous to modern day values reported in the literature [Wombacher et al., 2011], although modern limestones exhibit a much wider array of fractionation than dolomites. Further analyses of dolomite samples from younger stratigraphic levels within the Williston Basin sequence are being conducted in order to determine the extent of Mg isotope variability. Jacobson, A.D., Zhang, Z., Lundstrom, C., Huang, F. (2010) Behavior of Mg isotopes during dedolomitization in the Madison Aquifer, South Dakota, EPSL 297, 446-452. Wombacher, F., Eisenhauer, A., Boehm, F., Gussone, N., Regenberg, M., Dullo, W. -Chr., Rueggeberg, A. (in press) Magnesium stable isotope fractionation in marine biogenic calcite and aragonite. Geochim. Cosmochim. Acta., doi: 10.1016/j.gca.2011.07.017

Worsham, S. R.; Holmden, C. E.

2011-12-01

30

Preliminary study of geochemistry and fluid flow in Mississippian aquifers of the Williston Basin, Canada-U.S.A.  

Energy Technology Data Exchange (ETDEWEB)

The Williston Basin contains an active groundwater flow system. In order to trace fluid flow across the basin, this study obtained the hydrochemical and stable-isotope distributions for individual aquifers within the Mississippian strata, the main oil-producing zone in the basin. Oil and gas has been produced from these source rocks since 1951, with cumulative production totalling 1,500 MMBO. Previous regional-scale analyses of this zone have been restricted due to difficulties associated with correlation of aquifers across the international boundary and the large number of producing wells. In this study, water samples were collected from more than 200 producing oil wells from the Midale, Ratcliffe and Frobisher Beds across Saskatchewan, North Dakota and Montana. The Mississippian strata was divided into individual aquifers and detailed routine hydrochemical data was obtained in accordance with the hydrostratigraphic framework developed for the International Energy Agency's Greenhouse Gas Weyburn CO{sub 2} Monitoring and Storage Project. Stable isotopic compositions of the formation waters in the individual aquifers were then acquired. Mapped results indicate large variations in geochemical and isotopic compositions across the basins, reflecting a history of widely variable flow rates in the aquifers over time. The formation waters were found to have unique chemical fingerprints that can be used in various petroleum exploration and production activities. It was concluded that the highly variable Mississippian flow system has influenced petroleum migration and emplacement in this significant hydrocarbon-producing zone. 14 refs., 6 figs.

Jensen, G.; Rostron, B. [Alberta Univ., Edmonton, AB (Canada). Dept. of Earth and Atmospheric Sciences

2006-07-01

31

The primary sealing units for the Weyburn Midale reservoir, Williston Basin, (southeastern Saskatchewan, Canada) : sedimentology, petrography, and geochemistry  

Energy Technology Data Exchange (ETDEWEB)

The Weyburn Midale reservoir, located in southeastern Saskatchewan in the northern portion of the Williston Basin, is a Mississippian oil depleted reservoir that is currently under study for carbon dioxide (CO{sub 2}) sequestration. This paper demonstrated the spatial relationship of the three primary seals to the Weyburn Midale reservoir. These included the overlying Midale Evaporite; the underlying Frobisher Evaporite; and, the up-dip diagenetic cap-rock subjacent to the sub- Mesozoic unconformity surface. Together, the sedimentological, petrographic, and geochemical natures of these three sealing units help contain both the oil in the reservoir and the injected CO{sub 2}. It is important to characterize the sealing units for this reservoir because they represent the primary barriers to CO{sub 2} migration. It was concluded that the three main sealing units form the primary barriers to fluid flow in the Weyburn Midale pool. The Midale Evaporite is an effective vertical seal overlying the Midale reservoir rocks throughout the entire area of CO{sub 2} injection. Early-stage fractures in the Midale Evaporite have been sealed by later phases of diagenetic anhydrite. The Frobisher Evaporite forms an effective bottom seal for the Weyburn Midale pool. The altered zone is a zone of anhydritization and micritization related to the sub-Mesozoic unconformity. The broad range of diagenetic products have completely occluded porosity in the up-dip portion of the Midale Beds reservoir, forming another effective seal. 4 refs., 5 figs.

Nickel, E.H. [Saskatchewan Industry and Resources, Regina, SK (Canada); Qing, H. [Regina Univ., SK (Canada)

2005-07-01

32

Three-dimensional depth imaging of seismic data to help delineate petroleum reservoirs in the Williston Basin  

Energy Technology Data Exchange (ETDEWEB)

Seismic reflection data can be imaged in depth (3-D depth imaging) to form an accurate picture of the true geology of the earth in complex areas where the velocity changes abruptly, both vertically and laterally, such as some areas of the Williston Basin. A dome model with dipping layers above and below the dome were used to illustrate some advantages of 3-D depth imaging. This dome is a complex hydrocarbon trap in North Dakota characterized by large lateral and vertical velocity contrasts. Since the use of stacking velocities to derive interval velocities led to incorrect, contradictory geology, a well was drilled and the sonic data helped produce an improved depth model for the depth imaging process. A 2-D depth imaged section left some events unexplained; a 3-D depth imaging proved necessary to provide an accurate image and allow for an interpretation very close to reality. This recent technology helped to properly assess subsurface conditions and to make good drilling and production decisions. 10 refs., 10 figs.

Benson, A.K. [Brigham Young Univ., Provo, UT (United States)

1995-12-31

33

Effect of cross-basinal hydrodynamic flow on oil accumulations and oil migration history of the Bakken-Madison petroleum system; Williston Basin, North America  

Energy Technology Data Exchange (ETDEWEB)

The pervasive effect of cross-basinal hydrodynamic flow on the Bakken-Madison petroleum system in the Williston Basin was demonstrated. Madison fields around the basin show tilted oil-water contacts which closely match in magnitude and direction the tilts predicted from the regional hydraulic gradient. Madison fields of the Nesson anticline are hydrodynamically modified, and hydrodynamic flow appears to be the main trapping mechanism for the oil. Evolution of the Bakken-Madison petroleum system occurred in two phases: a late Cretaceous through Paleocene hydrostatic phase; and an Eocene to recent hydrodynamic phase. The system was hydrostatic when the Bakken began oil generation in the late Cretaceous, and became hydrodynamic when the Rocky Mountains were uplifted in the Laramide, synchronous with peak Bakken oil generation in the Eocene. Hydrodynamic flow profoundly modified both primary and secondary oil migration pathways during the early and middle Tertiary. Cross-basinal flow, and therefore Rocky Mountain topography, have persisted throughout the Tertiary. 58 refs., 11 figs.

DeMis, W.D. [Marathon Oil Company, Midland, TX (United States)

1995-12-31

34

Reservoir characterization of the Ordovician Red River Formation in southwest Williston Basin Bowman County, ND and Harding County, SD  

Energy Technology Data Exchange (ETDEWEB)

This topical report is a compilation of characterizations by different disciplines of the Red River Formation in the southwest portion of the Williston Basin and the oil reservoirs which it contains in an area which straddles the state line between North Dakota and South Dakota. Goals of the report are to increase understanding of the reservoir rocks, oil-in-place, heterogeneity, and methods for improved recovery. The report is divided by discipline into five major sections: (1) geology, (2) petrography-petrophysical, (3) engineering, (4) case studies and (5) geophysical. Interwoven in these sections are results from demonstration wells which were drilled or selected for special testing to evaluate important concepts for field development and enhanced recovery. The Red River study area has been successfully explored with two-dimensional (2D) seismic. Improved reservoir characterization utilizing 3-dimensional (3D) and has been investigated for identification of structural and stratigraphic reservoir compartments. These seismic characterization tools are integrated with geological and engineering studies. Targeted drilling from predictions using 3D seismic for porosity development were successful in developing significant reserves at close distances to old wells. Short-lateral and horizontal drilling technologies were tested for improved completion efficiency. Lateral completions should improve economics for both primary and secondary recovery where low permeability is a problem and higher density drilling is limited by drilling cost. Low water injectivity and widely spaced wells have restricted the application of waterflooding in the past. Water injection tests were performed in both a vertical and a horizontal well. Data from these tests were used to predict long-term injection and oil recovery.

Sippel, M.A.; Luff, K.D.; Hendricks, M.L.; Eby, D.E.

1998-07-01

35

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

1976-01-01

36

Algal bloom episodes and the formation of bituminite and micrinite in hydrocarbon source rocks: evidence from the Devonian and Mississippian, northern Williston Basin, Canada  

Energy Technology Data Exchange (ETDEWEB)

Organic petrology (incident light microscopy) of Middle Devonian inter-reef laminites and Devonian-Mississippian epicontinental black shales, Williston Basin, Canada, indicates that algal bloom episodes and consequential bacterial activity played a significant role in the accumulation of amorphous, bituminite III-rich organic microfacies. Corpohuminite-like algal akinete cells produced by filamentous algae during algal bloom periods are persistent maceral inclusions within the potential hydrocarbon source rock intervals. These cells (%R[sub o means] range 0.24-0.90) are regarded as positive indicators of stressful paleoenvironmental conditions. Unicellular Tasmanites and Leiosphaeridia marine alginite and variably degraded alginite remnants (ghosts) within the amorphous kerogen may be products of cell lysis, photo-oxidation and microbial alteration; these processes are characteristic of algal bloom periods. Minute (ca. 1[mu]m) spheroidal and coccoidal bacteria-like macerals are dispersed throughout the bituminite III network, attesting to the importance of microbial activity within the water column and sediment during and after organic matter accumulation. Dispersed granules, laminations and replacement textures of micrinite-like macerals within bituminite III are interpreted as remnants of microbial alteration rather than a residual product of thermal maturation and hydrocarbon generation. 34 refs., 8 figs.

Stasiuk, L.D. (University of Regina, Regina, SK (Canada). Dept. of Geology - Energy Research Unit)

1993-12-01

37

Multiple Magnetization Events Revealed in a Single Core in Upper Ordovician to Upper Devonian Carbonates of the Williston Basin, Manitoba (Canada)  

Science.gov (United States)

A paleomagnetic and rock magnetic study was conducted in well 16-33-5-24W1 from the southwestern corner of Manitoba, in the Williston Basin. The samples were taken from the Upper Ordovician to Upper Devonian carbonates of the Birdbear, Souris River, Winnepegosis, Interlake, and Red River formations. The strongest magnetization was found in the lower samples of the Red River carbonates, whereas Upper Birdbear, Winnepegosis and Interlake have significantly lower natural remanent magnetization (NRM) values. As revealed by the partial anhysteretic remanent magnetization (pARM) spectra, saturation isothermal remanent magnetization (SIRM) crossover plots, S-ratios, and unblocking temperatures, the magnetization is carried by hematite in the uppermost samples of the Birdbear Formation, whereas magnetite carries the magnetization in Souris River and Red River samples. In all other samples the magnetic signal is lost after 330C, therefore the magnetic carrier could be either magnetite or pyrrhotite. The pARM spectra and SIRM crossover plots and points reveal magnetite in the pseudosingle and single domain ranges. The Souris River and Red River samples show the smaller magnetite grain size through their higher S100 ratios, ARM/SIRM values, and SIRM cross over points. Two of the formations, the Souris River and Red River, carry similar paleomagnetic components, with reversed directions and inclination-only means of I = -49.1 +/- 4.5 degrees (n = 10 specimens/ 6 plugs, k = 104.6) and I = -48.1 +/- 2.4 (n = 21 specimens/ 11 plugs, k = 194.7) respectively. In addition, three specimens (2 plugs) from the Birdbear show a similar or slightly steeper reversed magnetization, with inclinations of -45.0 to -68.4. The similarity in some of their magnetic parameters (same inclination values and higher ARM/SIRM, S100 and SIRM crossover point values) leads to the conclusion that their magnetization is probably due to the same fluid- flow event. Since the Birdbear and Souris River carbonates were deposited during the Devonian, the timing of this fluid-flow event is placed between Lower and Middle Jurassic. Some of the magnetic properties found in the Red River carbonates (higher NRM and Hcr, lower S100) might indicate that the magnetizing fluid originated in the subbasement rocks of the Williston Basin. The remainder of the Birdbear, Winnepegosis and Interlake formations have poor paleomagnetic results. Three hematite-bearing specimens from the top of the Birdbear have very weak NRMs, and shallower positive inclinations (-0.1 to 44.1). The Winnepegosis has 5 specimens (3 plugs) giving an inclination mean of I = -35.5 +/- 10.6 (k = 37.2) that points to a primary or post-depositional magnetization. Interlake paleomagnetic directions were obtained from 3 specimens that show positive inclinations (12.5- 47.4).

Szabo, E.; Cioppa, M. T.

2009-05-01

38

Depositional history of the Newcastle Formation (Lower Cretaceous), Williston Basin, North Dakota, South Dakota and eastern Montana  

Energy Technology Data Exchange (ETDEWEB)

The Newcastle Formation was studied in light of additional drilling since the 1960s and using modern concepts of depositional models and sequences. Results of the study showed that this unit was formed as a result of the following sequence of events: (1) the sea level fell and a large area was exposed to erosion, (2) a major drainage system was incised in the previous formation and drained into the marine basin in central Montana, (3) the incised valleys were filled by fluvial sediments, (4) the sea level rose and a large volume of sand was redistributed across the study area, (5) when offshore marine conditions prevailed, the thick marginal marine Newcastle successions in eastern Dakota were deposited, (6) the sea level rose again and shales were deposited over the entire area 21 refs., 8 figs.

LeFever, R.D. [North Dakota Univ., Grand Forks, ND (United States). Dept. of Geology

1995-12-31

39

Cedar Creek - significant paleotectonic feature of Williston basin  

Energy Technology Data Exchange (ETDEWEB)

More than 327 million bbl of oil have been produced from Paleozoic carbonate reservoirs in 15 fields along the Cedar Creek anticline. Four major periods of tectonism from early Paleozoic through mid-Tertiary are documentable in the Cedar Creek area. Post-Silurian to pre-Middle Devonian: uplift and fault movement accompanied north and east tilting of the main Cedar Creek block. Several hundreds of feet of Silurian strata were eroded and a karst plain developed on the Silurian surface. Middle and Upper Devonian sediments onlapped and infilled the uplifted, northwest-plunging element. Late Devonian to pre-Mississippian: during latest late devonian and possibly earliest Mississippian, the Cedar Creek block was uplifted and tilted north and east. Extensive erosion resulted in the near peneplanation of the structure and significant truncation of Upper Devonian strata. Late Mississippian (Chester) through Triassic: during the Late Mississippian (Chester) and Early Pennsylvanian, the central and northern portion of the Cedar Creek area underwent gentle downwarping and periods of subsidence occurred with relative down-to-the-east fault movement along most of the ancestral master and subsidiary faults. Similar fault movement(s) and subsidence continued during the Permian and Triassic Periods. Relative tectonic stability was attained by the Middle Jurassic and essentially maintained until post-Paleocene time. Post-Paleocene: the Cedar Creek block underwent its greatest magnitude of uplift during post-Paleocene tectonism resulting in an extensive, linear belt of symmetric drape-folding generally aligned with the ancestral fault zones, and deep fault adjustment. During epeirogenic phases of the mid-Tertiary in the northern Rocky Mountain region, 1500 ft (475 m) of Paleocene and Upper Cretaceous strata were eroded along the axis of the present structure.

Clement, J.H.

1985-05-01

40

Chicxulub impact basin: Gravity characteristics and implications for basin morphology and deep structure  

Science.gov (United States)

The K-T-aged Chicxulub Impact Structure is buried beneath the Tertiary carbonate rocks of the Northern Yucatan Platform. Consequently its morphology and structure are poorly understood. Reprocessed Bouguer (onshore) and Free Air (offshore) gravity data over Northern Yucatan reveal that Chicxulub may be a 200-km-diameter multi-ring impact basin with at least three concentric basin rings. The positions of these rings follow the square root of 2 spacing rule derived empirically from analysis of multi-ring basins on other planets indicating that these rings probably correspond to now-buried topographic basin rings. A forward model of the gravity data along a radial transect from the southwest margin of the structure indicates that the Chicxulub gravity signature is compatible with this interpretation. We estimate the basin rim diameter to be 204 +/- 16 km and the central peak ring diameter (D) is 104 +/- 6 km.

Sharpton, Virgil L.; Burke, Kevin; Hall, Stuart A.; Lee, Scott; Marin, Luis E.; Suarez, Gerardo; Quezada-Muneton, Juan Manuel; Urrutia-Fucugauchi, Jaime

1993-01-01

 
 
 
 
41

Basin modeling of the Parang (Socotra) Basin, northern East China Sea shelf: Implications for hydrocarbon potential  

Science.gov (United States)

The hydrocarbon potential of the Parang (Socotra) Basin in the northern East China Sea shelf has remained poorly understood. We performed one-dimensional basin modeling for a dummy well located in the depocenter of the northern part of the Parang Basin to investigate the timings of hydrocarbon generation and expulsion. First, a depth-converted seismic profile crossing the dummy well was restored by backstripping and decompaction for eight regional and subregional unconformities, including the top of the acoustic basement, to reconstruct the subsidence history and to determine the timing of trap formation. The basin modeling, assuming rifting heat-flow model and source rocks with type III kerogen, suggests that the main phase of hydrocarbon (mostly gas) expulsion peaked in the Late Eocene, predating the inversion that created traps in the early Middle to latest Middle Eocene. Thus, the potential for large hydrocarbon accumulations in the northern Parang Basin is probably limited.

Kim, H.; Moon, S.; Lee, G.; Yoon, Y.; Kim, H.

2013-12-01

42

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

43

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 TiO_2 basalts appears to be a possibility to originate the Palmas and Chapeco acid melts, respectively. The study of ''uncontaminated'' or poorly contaminated low TiO_2 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 TiO_2 basalts and Chapeco volcanics. Differences in incompatible element ratios between low and high TiO_2 ''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)

1988-01-01

44

Pressure seals - Implications for deep gas exploration in Anadarko basin  

Energy Technology Data Exchange (ETDEWEB)

Pressure seals are economically significant geological phenomena because they play an important role in deep natural gas entrapment. Pressure seals identified in basins worldwide may offer a new frontier for exploring natural gas reservoirs below {minus} 10,000 ft. Pressure seals are low-permeability envelopes that enclose abnormally pressured internal reservoirs. There are three different types of seals: basal, lateral, and top planar. Basal seals define the bottom of abnormal pressure compartments and usually follow a stratigraphic horizon. Lateral seals are usually associated with fault patterns. Top planar seals may cut across time-stratigraphic boundaries, different lithologies, and structures, and are by far the most significant type. The southeastern portion of the Anadarko basin in the Mill Creek graben area displays a layered sequence of abnormally pressured fluid compartments between {minus} 3,000 and {minus} minus 16,000 ft. These compartments are separated from each other as well as from overlying and underlying normal pressure zones by pressure seals. In McClain County, a top planar pressure seal separating two abnormal pressured compartments is located between {minus} 11,000 and {minus} 12,000 ft within the Simpson Group. Diagenetic signatures identified in the seal zone are characterized by carbonate and/or silica cemented intervals alternating with more porous and permeable units generating distinctive banded and/or laminated structures, coined zebra structures. The resulting compositional and textural heterogeneity of the Simpson sandstones may be related to diagenetic modification that occurred during the seal evolution.

Tigert, V.A.; Al-Shaieb, Z. (Oklahoma State Univ., Stillwater (USA))

1989-08-01

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

1990-01-01

46

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 setting 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.

Richard Mason

2012-03-01

47

Petroleum geology of the Makran region: implications for hydrocarbon occurrence in cool basins  

Energy Technology Data Exchange (ETDEWEB)

Six basinal elements have been recognized in the Baluchistan Basin on the basis of plate-tectonic considerations. The Makran forms part of the sourthernmost coastal ''accretionary fore-arc basin'', where a more than six-kms thick, relatively undeformed succession of neritic sediment overlies the turbidites. A reported oil seepage in the north, several gas seepages along the coast, abundant ''bright spots'' in the seismic profiles offshore, and the occurrence of hydrocarbons in similar geologic settings elsewhere, all support the recently-emerging impression amongst the petroleum geologists involved in the area that the Makran region may provide a uniquely instructive setting in which to study petroleum occurrence in cool basin environments. Results of recent stratigraphic, sedimentological, tectonic and organic-geochemical studies in the Makran area are presented in this paper, in order better to understand the petroleum geology of the region and its implications for hydrocarbon accumulations. (author).

Khan, M.A. (Hawaii Univ., Honolulu, HI (US). Hawaii Inst. of Geophysics); Raza, H.A.; Alam, Shaji (Hydrocarbon Development Inst. of Pakistan, Islamabad (PK))

1991-01-01

48

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

49

Topography and morphology of the Argyre Basin, Mars: implications for its geologic and hydrologic history  

Science.gov (United States)

Argyre, located in the southern highlands southeast of Tharsis, is one of the largest impact basins on Mars and formed in Early Noachian time. We use Mars Global Surveyor (MGS) data to characterize the basin and its geologic features and units. It has been proposed that meltback of a south polar ice cap during the Noachian completely filled the basin with water, that the outflow channel in the north drained the basin, and that the water eventually entered the northern lowlands (Parker T.J., 1994.) If true, this would be the longest drainage system on either Mars or the Earth and would have immense implications for the hydrologic cycle and the evolution of the atmosphere on Mars. In order to address this question, we used topographic data from the Mars Orbiter Laser Altimeter (MOLA) and imaging data from the Mars Observer Camera (MOC). We also tested several alternative models proposed by previous workers (i.e., eolian, volcanic, mudflows, glaciers, fluvial/lacustrine) for the evolution of the Argyre basin. Based on our investigation we conclude that the Argyre basin went through a complex geologic history with several geologic processes contributing to its current appearance. Glacial and fluvial/lacustrine processes in conjunction with eolian modification were probably most important in the evolution of the interior of the Argyre basin. The Hesperian wrinkle ridged unit Hr was previously interpreted as volcanic in origin due to the occurrence of ridges. Based on our observations we conclude that ridges in Argyre Planitia are dissimilar to wrinkle ridges in other occurrences of unit Hr. The new data suggest that these are eskers and based on the occurrence of these esker-like features, we propose a model in which the floor of Argyre was covered by ice. There is evidence for areally significant amounts of water having ponded in the Argyre basin in its past history, but a complete fill to depths of ˜4 km and overflow remains questionable. On the basis of our findings it is unlikely that Uzboi Vallis drained the basin to the north, because the basin would have to be completely filled with at least 2.1×10 6 km3 of water and this is not consistent with current hydrologic models. Instead, new MOLA data show evidence for drainage into the basin from the north, south of crater Hale and Uzboi Vallis. We performed estimates of the available water and found that the amount of water that can be produced by meltback of a Hesperian ice cap appears insufficient to completely fill the Argyre basin. We propose that water that ponded in the Argyre basin would have sublimed, evaporated or migrated into the substrate rather than flowing through the northern outflow channel. In summary, a significant input of sediments and a partial fill of Argyre basin with water during the Hesperian is suggested by several channels emptying into the Argyre basin from the south and north, signs of fluvial erosion on the southern basin floor, the formation of small deltas at the mouths of Surius Vallis and the valley at the north rim, the amount of available water, and the smoothness of unit Hr. The formation of esker-like features indicates that this body of water very likely froze over. Finally MOC images reveal evidence that eolian activity, that is deflation of floor material and accumulation of dunes, modified the basin floor. On the basis of the MOLA and MOC data and our observations we outline a scenario for the evolution of the Argyre basin. In our model, water, produced by a Hesperian meltback of the south polar ice sheet, entered the Argyre basin, partly filling the floor of the basin to form a temporary ice covered lake. A downward freezing front propagated faster than the ice could sublime, resulting in an increasing ice thickness with time. As influx of water continued, in shallower regions of the lake (i.e., close to the incoming channels), the ice was grounded and incoming water formed subglacial channels in which esker-like ridges were deposited. After the influx ceased, continued sublimation and migration of water into the substrate reduced

Hiesinger, Harald; Head, James W., III

2002-08-01

50

How paleosols influence groundwater flow and arsenic pollution: A model from the Bengal Basin and its worldwide implication  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the Bengal Basin, the land surface exposed during the last lowstand of sea level around 20 ka, and now buried by Holocene sediment, is capped by an effectively impermeable clay paleosol that we term the Last Glacial Maximum paleosol (LGMP). The paleosol strongly affects groundwater flow and controls the location of arsenic pollution in the shallow aquifers of our study site in southern West Bengal and, by implication, in shallow aquifers across the Bengal Basin and As-polluted deltaic aqui...

Mcarthur, J. M.; Ravenscroft, P.; Banerjee, D. M.; Milsom, J.; Hudson-edwards, K. A.; Sengupta, S.; Bristow, C.; Sarkar, A.; Tonkin, S.; Purohit, R.

2008-01-01

51

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- 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.

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

2013-07-01

52

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

53

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

54

Archaeological implications of the geology and chronology of the Soa basin, Flores, Indonesia  

Science.gov (United States)

The timing of arrival of early hominids in Southeast Asia has major implications for models of hominid evolution. The majority of evidence for the earliest appearance of hominids in the region has previously come from Java in western Indonesia. Much of this evidence remains controversial owing to a poor understanding of the stratigraphic and chronologic relationships of the depositional units from which the material was derived. Before artifacts may be placed into their proper archaeological context, the geologic history of archaeological sites must be thoroughly understood, and deposits containing artifacts must be properly dated. An extensive investigation has been undertaken on the island of Flores, in eastern Indonesia, to determine the depositional and chronological history of stratigraphic units within the Soa basin; many of the units are associated with stone artifacts attributed to Homo erectus. Zircon fission-track dates of tuffaceous deposits within this lacustrine basin now provide the most reliable data concerning the true time of arrival of Homo erectus into Southeast Asia and indicate that these early hominids must have successfully begun colonizing eastern Indonesia by ca. 840 ka.

O'Sullivan, Paul B.; Morwood, Mike; Hobbs, Douglas; Aziz Suminto, Fachroel; Situmorang, Mangatas; Raza, Asaf; Maas, Roland

2001-07-01

55

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

Science.gov (United States)

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.

Weinreich, Daniel M.; Sindi, Suzanne; Watson, Richard A.

2013-01-01

56

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 a...

Ifabiyi Ifatokun Paul; Eniolorunda Nathaniel Bayode

2012-01-01

57

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 Caledoni...

Collot, Julien; Herzer, R.; Lafoy, Y.; Geli, Louis

2009-01-01

58

Quantification of exhumation in the Eromanga Basin and its implications for hydrocarbon exploration  

Energy Technology Data Exchange (ETDEWEB)

Exhumation in the Eromanga Basin of South Australia and Queensland has been quantified using compaction methodology. All methods of estimating exhumation utilize rock properties that are affected by, and retain a memory of, burial in excess of that presently observed. The tool used for estimating the exhumation in this study is analysis of the degree of overcompaction of rock units. Since porosity describes compaction state, the sonic log, controlled strongly by the amount of porosity, is an appropriate indicator of compaction and, hence, is used for quantifying exhumation from compaction. The standard method of estimating exhumation based on the degree of overcompaction of a single shale unit has been modified, and seven units, predominantly shales ranging in age from the Cretaceous to the Jurassic, have been analysed. All units yield similar results. Burial at depth greater than currently observed is the most likely cause of overcompaction since it is unlikely that sedimentological and/or diagenetic processes are responsible for similar amounts of overcompaction in different lithologies. The results of the compaction analysis reveal that Late Cretaceous-Tertiary exhumation increases eastwards from the Patchawarra Trough, through the Gidgealpa-Merrimelia-Innamincka Trend and Nappamerri Trough into the Queensland sector of the basins. This study has major implications for hydrocarbon exploration. Predicted maturation of source rocks will be greater for any given geothermal history if exhumation is incorporated in maturation modelling. The exhumation study helps to quantify velocity anomalies associated with overcompaction. Exhumation values can also be used to improve porosity predictions of reservoir units in undrilled targets. (author)

Mavromatidis, A.; Hillis, R.

2005-07-01

59

Reconstruction of pre-rift Pyrenean relief in the Oligo-Quitanian Camargue Basin (Gulf of Lion passive margin, SE France): Implications on thermal history of basins  

Energy Technology Data Exchange (ETDEWEB)

Fault reconstruction techniques commonly assume horizontal pre-rift level datum to calculate fault geometry from hanging-wall geometry or viceversa. Example from Camargue basin shows that neglecting pre-rift relief may lead to important errors in calculating the fault and hanging-wall geometries, and the total extension. These errors have direct implications on reconstruction of the thermal history of basins. The Camargue basin results front NW-SE extension and rifting of the Gulf of Lion passive margin. More than 4000m of Oligo-Aquitanian syn-rift series unconformably overlie a crust previously thickened during Pyrenean orogeny. The half-graben basin is controlled by the SE-dipping listric Nimes basement fault which generated a typical roll-over. As both fault and hanging-wall geometries are constrained, the pre-rift surface topography can be restored, using three reconstruction techniques. Either the constant-bed-length and constant-heave techniques produce a depression in the axis of the basin and a relief (1500m and 12(X)m respectively) atop the roll-over. The simple-shear (a=60{degrees}) technique generates a 1500m topography atop the roll-over, more coherent with regional data. Testing the hypothesis of a pre-rift horizontal datum leads to a roll-over 1400m too deep. Pre-rift surface elevation corresponds to the residual topography herited from the Pyrenean orogeny. Consequently, there has been some 1000m subsidence more than predicted by the syn-rift sedimentary record.

Benedicto, A.; Labaume, P.; Seranne, M. [Univ. Montpellier II (France)] [and others

1995-08-01

60

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

 
 
 
 
61

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

62

Changes of atmospheric water vapor budget in the Pearl River basin and possible implications for hydrological cycle  

Science.gov (United States)

In this study, we thoroughly analyzed abrupt behaviors, trends, and periodicity properties of water vapor flux and moisture budget entering and exiting the four edges of the Pearl River basin based on the NCAR/NCEP reanalysis dataset by using the continuous wavelet transform and the simple two-phase linear regression technique. Possible implications for hydrological cycle and water resource management of these changes are also discussed. The results indicate that: (1) the water vapor propagating through the four edges of the Pearl River basin is decreasing, and it is particularly true for the changes of the water vapor flux exiting from the north edge of the study river basin. The transition point from increase to decrease occurs in the early 1960s; (2) The wavelet transform spectra indicate that the monthly water vapor flux through the north edge decreases and this decrease is mainly reflected by intermittent distribution of the wavelet power spectra after early 1980s. The periodicity properties of the water vapor flux through the north edge imply that the northward propagation of water vapor flux decreases after the 1980s; (3) close relations between water vapor flux, precipitation and streamflow implies that the altered hydrological cycle in the Pearl River basin is mainly manifested by seasonal shifts of water vapor flux after early 1960s. One of the direct consequences of these changes of water vapor flux is the seasonal transition of wet and dry conditions across the Pearl River basin. Regional responses of hydrological cycle to climate variation/change could be different from one river basin to another. Hydrological responses of the Pearl River basin to the global warming are mainly demonstrated by seasonal shifts of precipitation changes: winter comes to be wetter and summer tends to be dryer. The finding of the seasonal transition of precipitation in the Pearl River basin is of great scientific and practical merits in basin scale water resource management in the Pearl River basin under the changing climate and global warming in particular.

Zhang, Qiang; Xu, Chong-Yu; Zhang, Zengxin; Chen, Yongqin David

2010-10-01

63

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 tabs

1993-01-01

64

Hydrological Cycle in the Heihe River Basin and Its Implication for Water Resource Management in Inland River Basins (Invited)  

Science.gov (United States)

Inland river basins take about 11.4% of the land area of the world and most of them are distributed over arid regions. Understanding the hydrological cycle of inland river basin is important for water resource management in water scarcity regions. This paper illustrated hydrological cycle of a typical inland river basin in China, the Heihe River Basin (HRB). First, water balance in upper, middle and lower reaches of the HRB was conceptualized by analyzing dominant hydrological processes in different parts of the river basin. Then, we used a modeling approach to study the water cycle in the HRB. In the upper reaches, we used the GBHM-SHAW, a distributed hydrological model with a new frozen soil parameterization. In the middle and lower reaches, we used the GWSiB, a three-dimensionally coupled land surface-groundwater model. Modeling results were compared with water balance observations in different landscapes and cross-validated with other results to ensure the reliability. The results show that the hydrological cycle in HRB has some distinctive characteristics. Mountainous area generates almost all of the runoff for the whole river basin. High-elevation zones have much larger runoff/precipitation ratio. Cryospheric hydrology plays an important role. Although snow melting and glacier runoff take less than 25% of total runoff, these processes regulate inter-annual variation of runoff and thus provide stable water resource for oases downstream. Forest area contributes almost no runoff but it smoothes runoff and reduces floods by storing water in soil and releasing it out slowly. In the middle reaches, artificial hydrological cycle is much more dominated than natural one. River water and groundwater, recharged by runoff from mountainous area, is the water resource to support the agriculture and nurture the riparian ecosystem. Precipitation, approximately 150 mm in average, is only a supplement to agriculture use but sufficient to sustain desert vegetation. Water resources are redistributed by very developed and extensive irrigation system. Irrigation water balance is complex because of strong interactions among surface, ground, river and irrigation water. Lower reaches is an extremely arid environment. Water availability in lower reaches has a great impact on the evolution of natural ecosystem and vice versa the landscape change reshapes the hydrological cycle. After the water resource reallocation project implemented in 2000, the water delivered to lower reaches has increased by 36%. Of all the available water resource, about 10% is used to sustain a terminal lake and other water bodies, 20% is used for irrigation to support very rapidly increased farmlands, 40-50% is used to nurture the natural oasis, and other water is lost due to evaporation. The features of hydrological cycle in the HRB is very typical for inland river basins in China's arid region. In this region, air temperature is rising and precipitation is most likely to increase. Accelerating glacier retreat will also produce more water. However, water demand increases more rapidly due to quickly developing economy and growing population. Therefore, how to turn our understanding of hydrological cycle in this environmental fragile region into more rational water resource management is a grand challenge.

Li, X.; Cheng, G.; Tian, W.; Zhang, Y.; Zhou, J.; Pan, X.; Ge, Y.; Hu, X.

2013-12-01

65

Paleomagnetism of Eocene Tuffs from Laramide Foreland Basins:Implications for the Geomagnetic Polarity Time Scale  

Science.gov (United States)

Paleomagnetic polarity determination of twenty-nine tuffs from Laramide foreland basins were used in conjunction with the published 40Ar/39Ar ages from the same tuffs to evaluate eight competing calibration models for the early to middle Eocene part of the Geomagnetic Polarity Time Scale (GPTS). Reliable paleomagnetic signals were recovered from a total of twenty-three sites, of which seventeen showed normal and six showed reversed polarity. We used the two independent chronostratigraphic constraints (paleomagnetic polarity and 40Ar/39Ar age) to evaluate eight calibration models based on the degree of agreement between predicted and measured polarity achieved in each model. Our original New Willwood model is tentatively favored and recommended as the best alternative yet available to the current GPTS calibration as it provides a framework into which known chronostratigraphic data from relevant sections are correlated most coherently. Three important implications are apparent in the new calibration scheme. First, under this new model the early Eocene (Ypresian) is shortened by 0.6 my whereas the middle Eocene (Lutesian) is lengthened by 0.48 my compared to GPTS 2004. Secondly, the Early Eocene Climatic Optimum is implied to have lasted from 50.42 to 52.08 Ma, a much shorter duration than is presently accepted, but overlaps in timing with the Wasatchian/Bridgerian faunal transition. Finally, the new calibration model implies that the seafloor spreading was more variable on short time scales than was modeled in the non-astronomical segment of the GPTS. In general, astronomically derived age models are not compatible with these data. This study demonstrates the potential of using closely spaced tuffs from a continental sedimentary sequence to provide both radiometric and paleomagnetic constraints with which to fine-tune calibration of the GPTS and reconstruct seafloor spreading rates at a higher resolution than has been done previously.

Tsukui, K.; Clyde, W. C.

2009-12-01

66

(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 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

2000-07-03

67

Basin development north of Great Salt Lake and implications for Neogene structural history of northern Utah  

Energy Technology Data Exchange (ETDEWEB)

Cenozoic deposits within and near the North Promontory Mountains comprise a tilted Miocene basin (Sand Hollow basin), Pliocene overlap deposits, and varied Quaternary deposits. The Sand Hollow basin contains the Salt Lake Formation, a complex tuffaceous unit deposited in lacustrine, fluvial, alluvial, eolian, and volcanic environments. Isotopic ages of tuffs indicate deposition spanning the middle Miocene. Initial deposition within sub-basins accounts for about 600 m of locally-derived conglomerate, sedimentary breccia, and finer grained tuffaceous materials. Moderate down-to-the-east tilting led to an eastward-deepening basin with deposits over 2.5 km thick. Subsequent tilting and erosional beveling of the tuffs took place before loess and alluvium, which contain little volcanic material, were deposited at [approximately]5 Ma. The Pliocene strata in turn were faulted to produce the basic physiographic and structural framework of the northern Great Salt Lake. Isotopic ages, correlations of tephra chemistry, and lithologic correspondence establish that several basins across northern Utah contain the Salt Lake Formation and are temporally equivalent. In several piedmont exposures, the formation was tilted and eroded much like the deposits in Sand Hollow basin. On the basis of this regional correlation, the authors suggest that Basin and Range magmatism and basin development began at about 18 Ma. Basins received thick deposits of tuffaceous sediment until about 9 Ma. Between [approximately]8 and 5 Ma, strata in some locations were uplifted, tilted, and eroded, presumably as adjacent basins deepened. Lower Pliocene overlap strata were faulted during the late Pliocene to form depocenters that coincide with present basins, suggesting that current topography is Pliocene and younger.

Miller, D.M.; Pringle, M.S.; Nakata, J.K.; Sarna-Wojcicki, A.; Meyer, C.E. (Geological Survey, Menlo Park, CA (United States))

1993-04-01

68

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

69

Silviculture of eucaliptus plantations in the Paraiba do Sul basin, Brazil, and its potential implication on the basin ecohydrology.  

Science.gov (United States)

Silviculture of eucaliptus plantations is an important driver of the Mata Atlântica biome conversion into another land use in the Paraíba do Sul basin, in the southeastern of Brazil. This region is located in one of the most developed areas in Brazil, between Rio de Janeiro and São Paulo, the most important cities in Brazil, linked by Presidente Dutra highway. Between both cities there are another cities that produce a variety of goods - from meat to planes, cars and mobile phones. This area is, at the same time, one the most important hot spot for the Mata Atlântica biome. Here we have a large Mata Atlântica fragment protected by law and others fragments being conversed to pasture, agriculture, silviculture and urban areas. Paraiba do Sul river drains the region and runs into Rio de Janeiro State. The basin is highly anthropized, with multiple approaches of its waters resources. Its waters also serve Rio de Janeiro metropolitan area. Because land use and land cover changes impact the water yield in a basin, the study of its dynamic its of great importance for water resources management. We study the land use and land cover change in the region between 1986 and 2010, focusing in the development of silviculture of eucaliptus plantations. We used the HAND (Height Above Nearest Drainage) approach that uses the height above the nearest water body, acquired from SRTM Data and transformed into a Terrain Numeric Mode, to classify the landscape into three different ecohydrological environments: floodplain, mountain top and hillslope. This classes were intersected with 1986 and 2010 land use and cover change classification obtained from Landsat imagery. Results show that silviculture has increased in the region from 1986 to 2010. In both years, silviculture areas are mainly located at the hillslope (47%), while floodplain and mountain top share 28 % and 23 % respectively. Available census data from the Brazilian Institute of Geography and Statistics, IBGE, for 1995 and 2006 years, show an increment in the number of small farmers, from 27 to 196, that are planting eucalyptus sp in the region and also an increase in the whole silvicuture production. Silviculture of eucaliptus plantations is recognized to be a great water consuming and a driver of water pollution by pesticides and fertilizers. The study carried out combines a landscape descriptor with land use and land cover changes mapping to provide an important database for ecohydrological studies, regarding the water resources management.

Carriello, Felix; Andres Rodriguez, Daniel; Marques Neves, Otto; Vicens, Raul

2014-05-01

70

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

71

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

72

Propped fracture stimulations : a technical overview with a regional perspective in the Williston Basin  

Energy Technology Data Exchange (ETDEWEB)

Various propped fracture stimulations were reviewed. Fracture treatments are applied to pump viscous proppant-laden fluids at various rates and pressures in order to create an open fracture from the wellbore. The fracture then closes on the proppant when pressure is released, providing a high-conductivity pathway for reservoir fluids to flow along. A chart of fracture geometry was provided as well as details of the first fracture treatment in Grant County, Kansas. Details of various fracturing fluids were presented, as well as details of proppants. Issues concerning fracture treatment design were discussed. Completion effectiveness was reviewed, as well as fracture flow impairment and fracturing, and various issues concerning water production control. A case study of Wascada Field in southern Manitoba was presented, along with an example of a pre-fracture analysis procedure. Horizontal well fracturing was also discussed, including the ineffectiveness of artificial fracture initiation techniques. Longitudinal and multiple parallel fractures were also examined, as well as transverse fractures. Challenges faced in open-hole fracturing include: propagation of the fracture; direction of the fracture; fracture prediction geometry; and the isolation of fracture treatments. The benefits of pumped fracture treatments include: a potential increase in economically recoverable reserves; the development of uneconomical reserves; improved productivity; and the potential to bypass wellbore damage. It was concluded that new technologies and analysis techniques are available to predict propped fracture growth but are still inexact. All available data must be utilized to make the best possible fracturing decisions. 10 figs.

Hlidek, B.T. [BJ Services Company, Calgary, AB (Canada)

2005-07-01

73

The upper Birdbear Formation (Nisku) of western North Dakota : another emerging Williston Basin horizontal play  

Energy Technology Data Exchange (ETDEWEB)

The Birdbear Formation is a carbonate-evaporite unit deposited during Late Devonian time in a shallow sea that extends from North Dakota into Alberta where the Birdbear is known as the Nisku Formation. Oilfield geologists have subdivided the Birdbear Formation into zones A and B. The upper zone A consists of 3 cycles, with the pay zone occurring in the second cycle. The thickness of the pay zone is about 2 feet with log porosities of about 10 to 15 per cent. This payzone has become a reservoir target for horizontal drilling in Golden Valley and Billings counties in North Dakota. Horizontal drilling operations drain 2 sections with 2 laterals drilled from a single vertical well. However, the reservoir is thinner than the typical resolution achieved by most geophysical tools. As such, the thin bed presents a challenge in accurately mapping the reservoir and accounting for the large volumes of oil produced from this zones. Oil is trapped by anhydrite occlusion of porosity updip near the subcrop edge of the reservoir. The potential area of this stratigraphic trap may be up to 250 square miles and could yield 25 to 35 million barrels of Birdbear oil. The reservoir is wet downdip from the oil column except on some rare structural closures. Initial production rates from horizontal wells have exceeded 500 barrels of oil per day and may eventually produce more than 300,000 barrels of oil per well. The A zone of the Birdbear Formation has not been a target for vertical wells because of its low initial production rates and limited ultimate reserves. 3 refs., 12 figs.

Sperr, J. [Barrett Corp., Denver, CO (United States); Burke, R. [Burke Consulting, Mandan, ND (United States)

2006-07-01

74

Calcimicrobes and microbialites in lagoonal sediments from Mississippian Midale Beds, Williston Basin, southeastern Saskatchewan, Canada  

Science.gov (United States)

Carbonates of Mississippian age (Viséan) in the Midale Beds, Charles Formation of southeastern Saskatchewan, Canada, produce significant amounts of hydrocarbons. The Midale Beds represent deposition in a shallow-water, periodically restricted, epeiric setting. The sedimentation is characterized by a variety of shallow-water carbonate lithologies ranging from wackestone, packstone, grainstone, to microbial boundstone. Algae, calcimicrobes, and related microbial fabrics are common features in these limestones. Cores and thin sections through the Midale Beds in the Glen Ewen and Midale pools of southeastern Saskatchewan were examined in order to study the contribution of calcimicrobes and microbial fabrics to the sedimentation of Mississippian carbonate rocks in southeastern Saskatchewan. Calcimicrobes and microbial fabrics are the important components in the grainstones and microbial boundstone. The calcimicrobes are commonly found as porostromate forms, including Garwoodia sp. and Ortonella sp., and other forms such as Archaeolithoporella-like, Girvanella-like, Wetheredella-like, and problematic microbes also occur but are not common. Microbial fabrics are characterized by microstromatolites, microbial laminations, thrombolite, clotted peloids, and fenestrate forms. Calcimicrobes stabilized grains and modified and created sediments, and the related syndepositional microbial fabrics affected the development of porosity/permeability of Midale carbonates. Calcimicrobes and microbial fabrics in Midale Beds highlighted a significant account of microbial facies associated with the Mississippian carbonates worldwide.

Shen, Jian-Wei; Yang, Hai-Jun; Qing, Hairuo; Zhang, Li-Juan; Yang, Hong-Qiang

2012-01-01

75

Geology and hydrocarbon potential of Dawson Bay Formation carbonate unit (Middle Devonian), Williston basin, North Dakota  

Energy Technology Data Exchange (ETDEWEB)

The Middle Devonian Dawson Bay Formation carbonate unit is present in the subsurface of North Dakota except where truncated by postdepositional erosion. The carbonate unit thickens from the erosional limit to a maximum thickness of 47.5 m (156 ft) in Renville County and reaches a maximum depth of 3798 m (12,460 ft) below the surface in McKenzie County. In North Dakota, a submarine hardground separates the carbonate unit from the underlying second red bed member of the Dawson Bay Formation. The upper contact with the Souris River Formation is conformable except in those areas where the Dawson Bay Formation was exposed to subaerial erosion prior to deposition of the Souris River sediments. The Dawson Bay carbonate unit is predominantly dolomitic and fossiliferous limestone or fossiliferous dolostone. The carbonate unit can be subdivided into five lithofacies on the basis of characteristic fossil fauna, flora, and other lithologic features. Lithofacies analysis of the Dawson Bay carbonates suggests a shallowing-upward succession of depositional environments and associated energy zones as follows: shallow epeiric sea (very low energy), stromatoporoid biostrome/bioherm (low energy), very shallow epeiric sea (very low energy), restricted shallow epeiric sea (extremely low energy), and shallow epeiric sea shoreline (variable energy). Eogenetic diagenesis includes color-mottling, dolomitization of micrite to microcrystalline dolomite with penecontemporaneous anhydrite replacement of cryptalgal mudstones and boundstones, cementation by sparry calcite, and vuggy porosity development. Mesogenetic diagenesis includes formation of mosaic dolomites, cementation by blocky equant calcite, neomorphism, pressure-solution, fracturing, halite cementation, and hydrocarbon emplacement.

Pound, W.

1988-07-01

76

Analyzing the drainage system anomaly of Zagros basins: Implications for active tectonics  

Science.gov (United States)

Morphometric analysis of hierarchical arrangement of drainage networks allows to evaluate the effects of external controls especially tectonics on basin development. In this study, a quantitative method for calculation of stream's hierarchical anomaly number is introduced. Morphometric parameters such as hierarchal anomaly index (?a), percent of asymmetry factor (PAF), basin Shape (Bs), basin length to mean width ratio (Bl/Bmw), stream's bifurcation ratio (Rb), bifurcation index (R), drainage density (Dd), drainage frequency (Df) and anticline's hinge spacing (Hs) of 15 basins in Zagros Mountains were examined. Results show that the strong correlations exist between pairs ?a-PAF (r = 0.844), ?a-Bs (r = 0.732), ?a-Bl/Bmw (r = 0.775), ?a-R (r = 0.517), PAF-Bl/Bmw (r = 0.519), Bs-R (r = 0.659), Bl/Bmw-R (r = 0.703), Hs-?a (r = - 0.708), Hs-PAF (r = - 0.529) and Hs-Bs (r = - 0.516). The variations in trend of anticlines control the shape of basins so that where anticlines hinges become closer to each other in the downstream direction, basin become narrower downward and hence the ?a increases. The more uplifted northeastern anticlines cause the trunk river of the basins to migrate toward the younger anticlines in southwest and hence ?a increases because the trunk river receives a lot of first order streams. Data reveal that the rate of ?a is higher in elongated synclinal basins. Due to the decrease in the intensity of deformation from northeast toward southwest of Zagros, the hinge spacing of anticlines increases southwestwards. Data reveal that the variation in hinge spacing of anticlines strongly controls the basin's shape and tilting as well as the hierarchical anomaly of drainage system. Since the elongation and tilting of basins are associated with the variations in rates of folding, uplift and hinge spacing of anticlines, it can be concluded that the hierarchical anomaly of drainages in studied basins is controlled by the intensity of Zagros tectonic activities.

Bahrami, Shahram

2013-11-01

77

Cenozoic tectonic jumping and implications for hydrocarbon accumulation in basins in the East Asia Continental Margin  

Science.gov (United States)

Tectonic migration is a common geological process of basin formation and evolution. However, little is known about tectonic migration in the western Pacific margins. This paper focuses on the representative Cenozoic basins of East China and its surrounding seas in the western Pacific domain to discuss the phenomenon of tectonic jumping in Cenozoic basins, based on structural data from the Bohai Bay Basin, the South Yellow Sea Basin, the East China Sea Shelf Basin, and the South China Sea Continental Shelf Basin. The western Pacific active continental margin is the eastern margin of a global convergent system involving the Eurasian Plate, the Pacific Plate, and the Indian Plate. Under the combined effects of the India-Eurasia collision and retrogressive or roll-back subduction of the Pacific Plate, the western Pacific active continental margin had a wide basin-arc-trench system which migrated or ‘jumped’ eastward and further oceanward. This migration and jumping is characterized by progressive eastward younging of faulting, sedimentation, and subsidence within the basins. Owing to the tectonic migration, the geological conditions associated with hydrocarbon and gashydrate accumulation in the Cenozoic basins of East China and its adjacent seas also become progressively younger from west to east, showing eastward younging in the generation time of reservoirs, seals, traps, accumulations and preservation of hydrocarbon and gashydrate. Such a spatio-temporal distribution of Cenozoic hydrocarbon and gashydrate is significant for the oil, gas and gashydrate exploration in the East Asian Continental Margin. Finally, this study discusses the mechanism of Cenozoic intrabasinal and interbasinal tectonic migration in terms of interplate, intraplate and underplating processes. The migration or jumping regimes of three separate or interrelated events: (1) tectonism-magmatism, (2) basin formation, and (3) hydrocarbon-gashydrate accumulation are the combined effects of the Late Mesozoic extrusion tectonics, the Cenozoic NW-directed crustal extension, and the regional far-field eastward flow of the western asthenosphere due to the India-Eurasia plate collision, accompanied by eastward jumping and roll-back of subduction zones of the Pacific Plate.

Suo, Yanhui; Li, Sanzhong; Yu, Shan; Somerville, Ian D.; Liu, Xin; Zhao, Shujuan; Dai, Liming

2014-07-01

78

Carboniferous coals of the Zonguldak basin (northwest Turkey): Implications for coalbed methane potential  

Energy Technology Data Exchange (ETDEWEB)

Carboniferous coals in the Zonguldak basin (northwest Turkey) were studied using petrographical and geochemical analyses, gas adsorption and gas content measurements, artificial maturation experiments on selected coals, and one-dimensional modeling of the basin evolution and hydrocarbon generation. The main emphasis was set on the definition of coalbed methane (CBM) generation capability and adsorption capacity of the coals. Considering these properties of coals and the amount and composition of gas within the coal seams, the CBM potential of the basin was evaluated. Three areas in the basin, Armutcuk, Zonguldak, and Amasra, were investigated. From the standpoint of petroleum (oil and/or gas) generation, the coals in the Armutcuk and Amasra areas are located within the oil generation window and those of the Zonguldak are located within the oil and gas generation window. Computer-aided basin modeling, suggests that significant quantities of gas have been generated only in the Zonguldak area. Modeling results indicate that major gas generation from the base, of the Westphalian A Kozlu Formation in the Zonguldak area occurred between 80 and 42 Ma (during the Late Cretaceous-early Eocene), prior to basin inversion that started at 42 Ma and continues at present. The predicted amount of generated coalbed gas from coal seams in the gas generation zone is several times higher than the adsorption capacity of the respective seams. A certain amount of this gas, is stored within the coal seams. Part of the expelled gas is accumulated in coal seams located above the gas generation zone. Coal seams within and above the gas generation zone are undersaturated Because the basin has not been explored for conventional gas reservoirs, a conclusive mass balance cannot yet be performed. Despite basin inversion and remigration of gas, some coal seams still contain gas amounts of up to 10 cm{sup 3}/g of coal, indicating a CBM potential.

Yalcin, M.N.; Inan, S.; Gurdal, G.; Mann, U.; Schaefer, R.G. [Istanbul University, Avcilar (Turkey). Dept. of Geological Engineerings

2002-07-01

79

Heavy oil in the central Jeanne d'Arc Basin and implications for exploration risk  

Energy Technology Data Exchange (ETDEWEB)

The Jeanne d'Arc Basin has the greatest economic potential for oil production from Newfoundland's Grand Banks. It is the deepest of many intracratonic Mesozoic to Cenozoic basins underlying the continental margin. Although most of the oils discovered in the basin are of medium density, 19 per cent of the exploration and delineation wells have shown that some heavy oils with API gravities of less than 25 exist, mostly at depths shallower than 2500 m below the seafloor. Since heavy oils in offshore settings are generally considered to be sub-economic, Late Cretaceous and younger targets in the basin have remained largely untested. Biodegradation is the most prevalent known cause of heavy oil in the basin. Early generation from sulphur-rich source rocks is a secondary cause. Many factors control whether biodegradation can occur. However, in this study area, it was possible to account for all the occurrences of biodegraded heavy oil with an assessment of paleotemperatures alone. Evidence of a 3-phase subsidence history and 2 main periods of hydrocarbon in the Terra Nova, Hebron, and Ben Nevis oilfields have been revealed through the integration of forward basin models, inverse models of apatite fission track lengths, petrography, fluid inclusion studies and geochemistry. The known occurrences of biodegraded heavy oil in the study area has been determined by evaluating paleotemperatures within the subsidence model. The information can be used to accurately predict the possibility of discovering heavy oil elsewhere. 58 refs., 2 tabs., 11 figs.

Shimeld, J.W.; Moir, P.N. [Natural Resources Canada, Dartmouth, NS (Canada). Geological Survey of Canada; MacRae, R.A.; Fowler, M.G.; Stasiuk, L.D. [Natural Resources Canada, Calgary, AB (Canada). Geological Survey of Canada

2005-07-01

80

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

Scientific Electronic Library Online (English)

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.

 
 
 
 
81

Stress magnitude and orientation in the Potiguar Basin, Brazil: Implications on faulting style and reactivation  

Science.gov (United States)

analyzed borehole breakout data and drilling-induced tensile fractures derived from resistivity image logs run at 10 oil wells to derive the orientation of the maximum horizontal stress SHmax from the Potiguar Basin in the continental margin of Brazil. Stress magnitudes are derived from density logs for the vertical stress, mini-frac tests for the minimum horizontal stress Shmin, and rock strength laboratory analysis to estimate the SHmax magnitudes. We compared these results with the stress regime and SHmax orientation derived from nine earthquake series located in the crystalline basement, where seismicity is concentrated, and previous breakout data from the basin. In the basin, the SHmax gradient is 20.0 MPa/km, and the SHmax/Shmin ratio is 1.154, indicating a normal tectonic stress regime from 0.5 to 2.0 km, whereas the SHmax gradient of 24.5 MPa/km and SHmax/Shmin ratio of 1.396 indicate a transition from a normal to strike-slip stress regime at 2.5 to 4.0 km. The deeper stress regime in the basin is similar to that in the basement at 1-12 km depth. This transition of the tectonic stress regime is consistent with an incipient tectonic inversion in the basin. We note that the SHmax orientation rotates from NW-SE in the western part of the Potiguar Basin to E-W in its central and eastern parts, roughly following the shoreline geometry, indicating that local features such as flexural stresses influence the local (scale < 100 km) stress pattern. We also conclude that the basement is critically stressed, but not the basin.

Reis, Álvaro F. C.; Bezerra, Francisco H. R.; Ferreira, Joaquim M.; Nascimento, Aderson F.; Lima, Cláudio C.

2013-10-01

82

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

Science.gov (United States)

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 sites within the basin and discusses the implications for risk assessment. At contaminated areas, the range of mercury concentrations are as follows: mill tailings, 3-1610 micrograms/g; unfiltered reservoir water, 53-591 ng/l; atmospheric vapor, 2-294 ng/m3. These values are three to five orders of magnitude greater than natural background. In all media at contaminated sites, concentrations are spatially variable, and air and water mercury concentrations vary temporally. The study are in situated in a natural mercuriferous belt, and regional background mercury concentrations in all environmental media are higher than values typically cited for natural background. As a mercury-contaminated site in North America, the Carson River Drainage Basin is unusual for a number of reasons, including its location in a natural mercuriferous belt, high and sustained levels of anthropogenic mercury inputs, long exposure time, aridity of the climate, and the riparian setting in an arid landscape, where biological activity is concentrated in the same areas that contain high levels of mercury in multiple media. PMID:9657709

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

1994-09-01

83

High levels of mercury contamination in multiple media of the Carson River Drainage Basin of Nevada: Implications for risk assessment  

Energy Technology Data Exchange (ETDEWEB)

Approximately 5.5 x 10[sup 9] g (4.0 x 10[sup 5] l) 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 km[sup 2] of the basin, and concentrations are some of the highest reported values in North America. This article documents the concentration of mercury in the air, water, and substrate at both contaminated and noncontaminated sites within the basin and discusses the implications for risk assessment. At contaminated areas, the range of mercury concentrations are as follows: mill tailings, 3-1610 [mu]g/g; unfiltered reservoir water, 53-591 ng/l; atmospheric vapor, 2-294 ng/m[sup 3]. These values are three to five orders of magnitude greater than natural background. In all media at contaminated sites, concentrations are spatially variable, and air and water mercury concentrations vary temporally. The study area is situated in a natural mercuriferous belt, and regional background mercury concentrations in all environmental media are higher than values typically cited for natural background. As a mercury-contaminated site in North America, the Carson River Drainage Basin is unusual for a number of reasons, including its location in a natural mercuriferous belt, high and sustained levels of anthropogenic mercury inputs, long exposure time, aridity of the climate, and the riparian setting in an arid landscape, where biological activity is concentrated in the same areas that contain high levels of mercury in multiple media. 37 refs., 4 figs., 3 tabs.

Gustin, M.S.; Taylor, G.E. Jr.; Leonard, T.L. (Univ. of Nevada, Reno, NV (United States) Desert Research Institute, Reno, NV (United States))

1994-09-01

84

Prevalence of Melioidosis in the Er-Ren River Basin, Taiwan: Implications for Transmission?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An increase in melioidosis cases compared to other areas in Taiwan was observed in the Er-Ren River Basin, southwestern Taiwan, from November 2001 to August 2006. The objective of this study was to determine the association between the level of exposure to Burkholderia pseudomallei and the incidence rate of melioidosis and to survey the transmission modes of B. pseudomallei in the Er-Ren River Basin. The serosurveillance of melioidosis gave seropositivity rates of 36.6%, 21.6%, and 10.9%, res...

Su, Hsun-pi; Yang, Hsiao-wei; Chen, Ya-lei; Ferng, Tien-lin; Chou, Yu-ling; Chung, Tung-ching; Chen, Chang-hsun; Chiang, Chuen-sheue; Kuan, Mei-mei; Lin, Hsi-hsun; Chen, Yao-shen

2007-01-01

85

Isotopic geochemistry in acidic volcanic rocks of the Parana Basin, and associated genetic implications  

International Nuclear Information System (INIS)

Three samples representatives of the acidic volcanism of the Parana Basin, collected in the States of PR, SC and RS, were dated by Rb-Sr and K-Ar methods. Chemical analyis classify the three occurrences as belonging to the group enriched in phosphorus, titanium and LIL elemets (HPT), compared to the other (LPT) defined for the Parana Basin. Mineral isochrons show the cogeneticity of the components, and the resultant Rb-Sr age is sytematically higher than the value obtained by K-Ar method in the plagioclase phenocrysts. Sr initial ratio indicates a common source for the three occurrences. (Author)

1985-01-01

86

Tectonic implications deduced from drill cores in the Qaidam basin, NE Tibetan Plateau (Invited)  

Science.gov (United States)

The Qaidam Basin is the largest intermontane basin of the NE Tibetan Plateau and an ideal place to study the paleoenvironmental evolution and erosion history related to tectonic activity and climate change. We studied two cores of lacustrine sediments drilled in the western basin within a distance of about 25 km, the 940 m deep SG-1 core in the Chahansilatu sub-depression and the 723 m deep SG-1b core in the Jianshan anticline. These cores comprise fine-grained lacustrine sediments and according to our magnetostratigraphic results span the ages of ~2.8-1.1 Ma (SG-1) and ~7.3-1.6 Ma (SG-1b). The proxy record reveals a long-term drying trend, and several proxy parameters can be matched with the marine oxygen isotope curve indicating a tie to global climate change. However, overlying trends and stepwise changes of average sediment accumulation rates (SAR) point towards an influence of tectonic processes. The results of average SARs of core SG-1b show three intervals with relatively higher values from the bottom (>7.3 Ma) to 6.0 Ma, between 5.2 and 4.2 Ma and between 3.6 and 2.6 Ma. These phases are in temporal agreement with the deposition of thick coarse-grained deposits in other parts of the Qaidam basin, the development of the en-echelon s-shaped structure of the basin, the separation of the western basin into shallow subbasins and the formation of a large synclinal trough in the eastern basin, and tectonic activities at the north-eastern plateau and other plateau regions. Growth strata are crucial to interpret the fold-and-thrust geometry, and the kinematics modeled by variations of the sedimentation rate and the uplift rate in the folding region. Several features indicate that the geometry of growth strata at our study site has developed by limb rotation with clear changes of growth strata dip and thicknesses on the forelimb, rather than by kink-band migration. Comparison of the SARs from SG-1 and SG-1b demonstrates that the development of the limb rotation was controlled by overlap before ~1.6 Ma. Rapid uplift is indicated after ~1.6 Ma caused the occurrence of offlap and the termination of deposition at the Jianshan anticline region. This all can be probably related to pulse tectonic uplift of the NE Tibetan Plateau and fault-propagation-folding in the Qaidam Basin.

Appel, E.; Zhang, W.; Fang, X.; Song, C.; Setzer, F.; Herb, C.

2013-12-01

87

Peace/Williston fish and wildlife compensation program: 1991-1992 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. A summary is presented of the activities undertaken by the public consultation program in 1991/92 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. 1 fig., 12 tabs

1992-01-01

88

Reinterpreting the Pinedale Anticline in the Green River Basin: Implications for future hydrocarbon exploration  

Energy Technology Data Exchange (ETDEWEB)

The Green River Basin is a northwest-southeast elongate structural feature located in southwestern Wyoming. Bounded by three basement uplifts, this complex mountain front basin possesses tremendous gas reserves. Production has been limited to a few structures, such as the Pinedale Anticline, because of the great depth of the basin. The Pinedale Anticline is an elongate structure that parallels the front of the Wind River Thrust. Earlier research has suggested that the anticline is not related to basement, but rather is associated with a foreland detachment structure. A new, high-resolution aeromagnetic survey has been modelled in detail and the results indicate that the Pinedale Anticline may actually be a basement related structure. Profile modelling normal to the anticline from the LaBarge Platform to the Wind River Mountains suggests that not only is Pinedale Field situated on a possible basement structure, but also that additional, heretofore unknown analogous features are also present in the basin. Additionally, an east-northeast structural grain is prevalent throughout the aeromagnetic dataset. This trend has been correlated with structures exposed in the Wind River Mountains and has also been shown to be important to locating hydrocarbon production. Thus, Cretaceous and Paleocene reactivation of Proterozoic age faults may have significantly affected location of structures, local stratigraphy and, subsequently, emplacement of hydrocarbons.

Fagan, J.P. Jr. [Pearson, deRidder and Johnson, Inc., Lakewood, CO (United States)

1996-06-01

89

New seismo-stratigraphic data of the Volturno Basin (northern Campania, Tyrrhenian margin, southern Italy): implications for tectono-stratigraphy of the Campania and Latium sedimentary basins  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A geological section of the Volturno Basin (northern Campania, continental margin, Italy) has been constructed based on new multi-channel seismic data, to show the stratigraphic relationships between the filling in the Quaternary basin and the Meso-Cenozoic acoustic basement. The new seismic sections presented here outline the underlying structures of the basin and their relationships to the filling in the Quaternary basin. Deep exploration wells in Campania and Latium on the Tyrrhenian margi...

Gemma Aiello; Anna Giuseppa Cicchella; Vincenzo Di Fiore; Ennio Marsella

2011-01-01

90

Spatial modeling of small stream hydrology in a North American river basin and implications under a warmer, drier future climate  

Science.gov (United States)

Stream flows are predicted to decrease in many arid regions worldwide as a result of climate change. In arid and semiarid southwestern US streamflow timing has shifted to earlier in the spring and mean annual streamflow is projected to decrease under climate change including late summer and fall discharge. It is likely that minimum flows will decrease and some perennial streams will shift to intermittent streamflow under climate-driven changes in timing and magnitude of precipitation and runoff, and increases in temperature. Streams shifting from perennial to intermittent flow could have significant effects on aquatic and riparian ecosystems as well as important implications for human water use. We studied small streams in the Upper Colorado River Basin, one of the most intensively managed river systems in the world and a vital water resource in the western US. Our objectives were to spatially model streamflow metrics using environmental variables and to project low flow metrics on ungaged streams across the study basin. We used random forest models to predict mean and minimum flow metrics at gaged streams based on environmental variables such as climate, geology, soils and land cover. We found winter and spring monthly precipitation, forest land cover, and PET were the most important variables for predicting mean flow. For low flow metrics, precipitation, PET, and drainage area were most important. For predicting zero flow days and months, percent snow, and soil rainfall and runoff factor index were also important. We then used our random forest models to project mean flow, low flow, and low flow variability to all small streams in the basin and generated maps suggesting where streams are at risk of shifting hydrologic regimes. Our resulting maps can be linked with biologic information to understand how stream-dependent communities may be affected in the future.

Reynolds, L. V.; Shafroth, P. B.; Poff, N.

2013-12-01

91

Morphology of large impact craters and basins on Venus: Implications for ring formation  

Science.gov (United States)

A nearly complete examination of the Magellan radar data for the Venusian surface reveals 72 unequivocal peak-ring craters and 4 larger structures that we interpret to be multiringed. This report updates our earlier studies and that of the Magellan team. The general morphology of peak-ring craters, decreasing ring diameter ratio trends with increasing crater diameter, and the general size-morphology progression from complex central-peak crater to peak-ring crater on Venus and the terrestrial planets suggest similar processes of peak-ring formation. Observations are consistent with a model of dynamic collapse, downward and outward, of an unstable central peak to form a ring. We interpret the four larger ringed structures (Klenova, Lise Meitner, Mead, and Isabella) to be morphologically similar to the Orientale Basin on the Moon, and thus, true multiringed basins.

Alexopoulos, Jim S.; McKinnon, William B.

1993-03-01

92

Timing of Late Quaternary productivity pulses in the Panama Basin and implications for atmospheric CO2  

Science.gov (United States)

High-resolution percent Corg and ?18Oforam records obtained from Panama Basin core Atlantis II 54-25PC and additional data from nearby core P7 show that enhanced burial of organic carbon has characterized every major glacial period for the last 500 kyr in that area. Both Corg concentration and mass accumulation rate profiles exhibit a sawtooth pattern with maxima occurring typically in the later stages of glacial periods. Comparison with dust records suggests that the carbon accumulation rate profile reflects both the upwelling history and a variable rate of iron input during the late Quaternary. The sawtooth character may derive from increased wind velocities and rates of upwelling during glacials which are indirectly related to ice volume (Sarnthein et al., 1988). The rapid decline in export production at the end of glacials in the equatorial Pacific may be attributed to the retreat of ice sheets (thus reduced wind velocities and upwelling) coupled with a coincident decline in atmospheric dust load and/or delivery rate. The Corg accumulation rate profiles do not correlate well with atmospheric CO2 records. For example, atmospheric CO2 was already at a minimum 40 kyr ago when production in the Panama Basin began increasing dramatically, commensurate with an increase in global dust levels. Using the relationship between the degree of photosynthetic fractionation and the concentration of free CO2 in the surface ocean postulated by Popp et al. (1989), ?13Corg measurements made on core P7 show that Panama Basin surface waters have been supplying CO2 to the atmosphere continually for at least the last 50 kyr. There is no evidence for a flux of CO2 into the surface ocean in this area at any time during this period despite the higher production. If the Panama Basin cores are representative of the eastern and central equatorial Pacific, then these observations weaken the influence on CO2 drawdown postulated for increased glacial productivity at low latitudes.

Pedersen, T. F.; Nielsen, B.; Pickering, M.

1991-12-01

93

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

94

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 precipitat...

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

2004-01-01

95

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 ...

2004-01-01

96

Thermal maturity history and implications for hydrocarbon exploration in the Catatumbo basin, Colombia  

International Nuclear Information System (INIS)

A thermal model integrated with oil and gas geochemical study has been constructed for the Catatumbo basin, Colombia for provides 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 of 1 0 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 youngest 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 for 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

2007-12-01

97

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

98

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

99

A curious case of downstream coarsening in a large mountain basin: Implications for landscape evolution models  

Science.gov (United States)

Field data from the Middle Fork of the Salmon River, Idaho, show a consistent downstream increase in reach-average median grain-size, D50, for drainage areas up to 1,200 km2. This unexpected observation differs from previous studies of mountain basins, where a transition to downstream fining occurs at drainage areas of about 10 km2. An inflection in the grain-size relation with drainage area is thought to mark a shift in dominant channel shaping processes -- previous studies demonstrate that debris-flow dominated channels show a downstream increase in bed surface grain size, whereas fluvially dominated channels show a general decrease in grain size with drainage area. However, area-slope relations derived from 30 m DEMs for the basin do not show an obvious scaling break that is typically attributed to the transition between debris-flow and fluvially dominated processes shaping the channel. Rather, DEM analysis suggests that this entire drainage basin is within the debris-flow and transitional domains, as indicated by a positive relation between unit stream power (?) and drainage area up to 7,500 km2. Additionally, we observe that D50 is positively related to ?, which would explain the downstream coarsening trend. But, how can such a large basin, with active fluvial processes, be within the debris-flow domain (an area typically associated with headwaters)? We hypothesize that the steep terrain, grussy soils, and frequent wildfires in the study area allow debris flows to play an important role in shaping channel morphology even at large drainage areas. DEM analysis indicates that channel slopes are steep enough to convey debris flows to the mainstem river throughout the drainage basin, as evidenced by the common occurrence of debris fans at most tributary junctions. Grussy soils and high-intensity thunderstorms following wildfire also promote bulking debris flows with long runout paths that extend to the mainstem river. These results challenge conventional assumptions regarding drainage area thresholds for the transition from debris-flow to fluvial process dominance in landscape evolution models.

Goode, J. 9; Buffington, J. M.

2013-12-01

100

Ecosystem performance assessment for grasslands in the Greater Platte River Basin: implications for cellulosic biofuel development  

Science.gov (United States)

This study identifies lands suitable for cellulosic biofuel (e.g., switchgrass) development across the Northern Great Plains, with an initial emphasis on the Greater Platte River Basin (GPRB), using satellite observations, climate data, and ecosystem models. Our approach is based on previous successful ecosystem performance (EP) studies in the Yukon River Basin and the Upper Colorado River Basin. We hypothesize that areas with fairly consistent high grassland productivity (i.e., high site potential) in fair to good range condition (persistent ecosystem overperformance or normal performance with few ecological disturbances) are potentially suitable for cellulosic biofuel (switchgrass) development. Ecosystem site potential was calculated using a 9-year (2000-2008) average of annually integrated growing season Normalized Difference Vegetation Index (GSN), geophysical and biophysical data, climate data, and a rule-based piecewise regression tree model. The GSN derived from eMODIS (expedited Moderate Resolution Imaging Spectroradiometer) observations was used as a proxy for the actual ecosystem performance. The weather-based expected EP (EEP) was computed using site potential, yearly seasonal climate variables, and piecewise regression tree models. The ecosystem performance anomaly (EPA) for a specific year was estimated based on the difference between the actual EP and the EEP during that year. The final EPA maps were categorized as normal performance, underperformance, and overperformance at the 90% confidence levels. Pixels that either overperformed or normally performed for three of four years from 2005 to 2008 and that have moderate or high site potential within the GPRB are identified as probable areas for future cellulosic biofuel development. Results from this study will help land managers and decision makers make optimal land use decisions for cellulosic biofuel development and sustainability within the grassland regions of the GPRB.

Gu, Y.; Boyte, S. P.; Wylie, B. K.; Tieszen, L. L.

2010-12-01

 
 
 
 
101

Postbreeding movements of American Avocets and implications for wetland connectivity in the western Great Basin  

Science.gov (United States)

Wetlands in the western Great Basin of the United States are patchily distributed and undergo extensive seasonal and annual variation in water levels. The American Avocet (Recurvirostra americana) is one of many shorebird species that use these wetlands as breeding and migratory stopover sites and must adjust to variable conditions. We used radio telemetry to determine postbreeding, premigratory movement patterns of avocets throughout the region. In 1996 and 1997, 185 breeding adults were captured and fitted with radio transmitters at five breeding areas in Oregon, California, and Nevada. Regular aerial and ground surveys were conducted at the five main study areas from June through September, or until all avocets had left a site. Other wetlands in the western Great Basin also were surveyed by aircraft for the presence of radio-marked birds. Fifty-six percent of radio-marked avocets were still detected in the region at least eight weeks after capture. Each of these individuals was detected at an average of 2.1 lakes (range 0 to 6), with 74% found at more than one lake system. Forty radio-marked individuals moved at least 200 km between wetlands prior to migration, most of which dispersed northward. Male and female patterns did not differ significantly. Overall, movements may be associated with a prebasic molt, exploitation of a superabundant food source in northern lakes, and reconnaissance for future breeding efforts or staging sites. These results also demonstrate wide-ranging patterns of dispersal in this species and suggest a need for the consideration of large-scale habitat connectivity issues in establishing conservation strategies for shorebirds in the western Great Basin.

Plissner, Jonathan H.; Haig, Susan M.; Oring, L. W.

2000-01-01

102

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ma...

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

2009-01-01

103

ENVIRONMENTAL AUDITING: An Integrated Approach to Reservoir Management: The Williston Reservoir Case Study.  

Science.gov (United States)

/ The management of industrial reservoirs for hydroelectric energy can cause severe impacts to surrounding communities. This study examines the generation of dust along the northern foreshore zones of Williston Reservoir in northern British Columbia. The dust is generated in the spring when the reservoir levels are low and impacts a relocated First Nations' village (Tsay Keh) at the north end of the reservoir. Data were gathered to provide an overview of the physical conditions that contribute to the dust problem, including a social survey, soil analysis, and vegetation inventory. The study provides a scoping method to assess a large-scale and complex problem with respect to dust management along a large reservoir. Methods for dust control include short- and long-term solutions that integrate the use of native vegetation along the foreshore zones of the reservoir. PMID:10742482

Baker; Young; Arocena

2000-05-01

104

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

105

Bajocian ammonoids from Pumani River area (Ayacucho, Peru): Palaeobiogeographical and palaeoenvironmental implications for the Arequipa Basin  

Science.gov (United States)

Deposits of the Socosani Formation in the Pucayacu and Pumani sections (Ayacucho Department, Peru), along several kilometres, have yielded Upper Bajocian ammonoid fossil-assemblages characterized by the occurrence of juvenile individuals belonging to endemic or pandemic genera, such as Megasphaeroceras and Spiroceras respectively. In addition, certain Bajocian genera relatively common in the Mediterranean-Caucasian Subrealm, but very scarce in the Eastern Pacific Subrealm, such as the strigoceratid Cadomoceras and the phylloceratid Adabofoloceras, occur in this area. According to the taphonomic, palaeoecological and palaeobiogeographical evidence from the Pumani River area, the maximum deepening, relative sea-level rise and oceanic accessibility of a Bajocian-Bathonian, second-order, transgressive/regressive facies cycle in the marine Arequipa Basin were reached during the Late Bajocian Niortense Biochron. However, synsedimentary regional tectonics in the Pumani River area disturbed this general deepening/shallowing cycle of the Arequipa Basin, particularly during the Late Bajocian post-Niortense time-interval of the Garantiana and Parkinsoni biochrons.

Fernandez-Lopez, Sixto; Carlotto, Victor; Giraldo, Edwin; Chacaltana, Cesar

2014-01-01

106

Gas-and water-saturated conditions in the Piceance Basin, Western Colorado: Implications for fractured reservoir detection in a gas-centered coal basin  

Energy Technology Data Exchange (ETDEWEB)

Mesaverde Group reservoirs in the Piceance Basin, Western Colorado contain a large reservoir base. Attempts to exploit this resource base are stymied by low permeability reservoir conditions. The presence of abundant natural fracture systems throughout this basin, however, does permit economic production. Substantial production is associated with fractured reservoirs in Divide Creek, Piceance Creek, Wolf Creek, White River Dome, Plateau, Shire Gulch, Grand Valley, Parachute and Rulison fields. Successful Piceance Basin gas production requires detailed information about fracture networks and subsurface gas and water distribution in an overall gas-centered basin geometry. Assessment of these three parameters requires an integrated basin analysis incorporating conventional subsurface geology, seismic data, remote sensing imagery analysis, and an analysis of regional tectonics. To delineate the gas-centered basin geometry in the Piceance Basin, a regional cross-section spanning the basin was constructed using hydrocarbon and gamma radiation logs. The resultant hybrid logs were used for stratigraphic correlations in addition to outlining the trans-basin gas-saturated conditions. The magnitude of both pressure gradients (paludal and marine intervals) is greater than can be generated by a hydrodynamic model. To investigate the relationships between structure and production, detailed mapping of the basin (top of the Iles Formation) was used to define subtle subsurface structures that control fractured reservoir development. The most productive fields in the basin possess fractured reservoirs. Detailed studies in the Grand Valley-Parachute-Rulison and Shire Gulch-Plateau fields indicate that zones of maximum structural flexure on kilometer-scale structural features are directly related to areas of enhanced production.

Hoak, T.E.; Decker, A.D.

1995-10-01

107

Implications of Paleogene Foreland Basin Evolution in NW Argentina for Timing of Andean Orogenesis  

Science.gov (United States)

The timing and paleogeography of early Andean mountain building are topics of ongoing debate. We track development of the early central Andes in Bolivia and NW Argentina by studying widespread Tertiary deposits in the Altiplano-Puna and Eastern Cordillera. These deposits accumulated on top of Late Cretaceous post-rift marginal marine facies and Precambrian-Paleozoic basement. Over a north-south distance of 1000 km, the Paleocene-Oligocene succession consists of three stratigraphic assemblages: (1) Paleocene-Eocene fluvial- lacustrine siltstone and marl, up to ~200 m thick; (2) a 10-100 m thick zone of stacked Eocene paleosols, including stage III-IV Calcisols, Vertisols, and strongly reduced Gleysols; and (3) an upward coarsening, several km-thick sequence of fluvial to alluvial fan deposits. Locally, upper Eocene-Miocene rocks consist of thick (>2 km), proximal alluvial fan deposits containing growth structures. Modal petrographic data indicate derivation from metasedimentary and plutonic source terranes, and paleocurrent data show eastward sediment transport. Detrital zircon U-Pb ages indicate derivation from Paleozoic low-grade metasedimentary and igneous source rocks. Eocene detrital AFT ages from apatite grains that yield early Paleozoic U-Pb crystallization ages require rapid exhumation (0.4 mm/yr to >1mm/yr) of western source areas in neighboring regions such as the Eastern Cordillera and indicate a constructional orogen. Combined with previous structural studies, our data are consistent with a Late Cretaceous-Eocene thrust belt in the Cordillera de Domeyko in northern Chile, flanked to the east by a several hundred km wide foreland basin system. Flexural subsidence dominated the proximal region, and back-bulge and post-rift thermal subsidence may have operated in the distal eastern part of the basin. Approximately 500 km of eastward migration of the foreland basin system produced the vertical succession preserved in the Paleogene of the Puna and Eastern Cordillera. Shortening estimates for NW Argentina combined with simple flexural modeling raise the issue of the possible whereabouts of a roughly 300 km long slab of underthrust South American lower crust and lithosphere.

Decelles, P. G.; Carrapa, B.; Horton, B. K.; Starck, D.; Gehrels, G. E.

2007-12-01

108

Electrical Conductance Map for the Kachchh Rift Basin: Constraint on Tectonic Evolution and Seismotectonic Implications  

Science.gov (United States)

Geomagnetic field variations recorded by an array of magnetometers spread across the Kachchh Rift basin are reduced to a set of induction arrows as a diagnostic of lateral electrical conductivity variations. A non-uniform thin-sheet electrical conductance model is developed to account for the salient induction patterns. It indicates that the imaged conductivity anomalies can be related to the sediment-filled structural lows in between the fault bounded uplifts. It is suggested that sagging structural lows preserved the marine sediments deposited during the Mesozoic sea transgression and later developed into first order embayment basins for the deposition of sediments in association with Late Eocene transgression. Depth integrated electrical conductance helped in mapping two depo-centres: along the ENE-WSW trending Banni half-Graben bounded by the Kachchh Main fault on the south and, second, along the Vinjan depression formed in response to the subsidence between the Vigodi fault and westward extension of the Katrol Hill fault together with the westward bending of the Median High. Presence of metamorphosed graphite schist clasts in shale dominated Mesozoic sequence and/or thin films of carbon resulting from the thermal influence of Deccan activity on Carbonate-rich formations can account for the high electrical conductivity anomalies seen in the depo-centres of thick Mesozoic and Tertiary sediments. Additionally two high conductivity zones are imaged encompassing a block defined by the 2001 Bhuj earthquake and its aftershocks. In agreement with gravity, magnetic and seismic velocity signatures, aqueous fluids released by recrystallizing magmatic bodies intruded in association with Deccan trap activity account for mapped high conductivity zones. High fluid pressure in such a fractured domain, surrounding the intruded magmatic plugs, perturb the regional stress concentrations to produce frequent and low magnitude aftershocks in the shallow section of the epicentral track of the 2001 Bhuj earthquake.

Subba Rao, P. B. V.; Arora, B. R.; Singh, A. K.

2014-05-01

109

Flow regime alterations under changing climate in two river basins: Implications for freshwater ecosystems  

Science.gov (United States)

We examined impacts of future climate scenarios on flow regimes and how predicted changes might affect river ecosystems. We examined two case studies: Cle Elum River, Washington, and Chattahoochee-Apalachicola River Basin, Georgia and Florida. These rivers had available downscaled global circulation model (GCM) data and allowed us to analyse the effects of future climate scenarios on rivers with (1) different hydrographs, (2) high future water demands, and (3) a river-floodplain system. We compared observed flow regimes to those predicted under future climate scenarios to describe the extent and type of changes predicted to occur. Daily stream flow under future climate scenarios was created by either statistically downscaling GCMs (Cle Elum) or creating a regression model between climatological parameters predicted from GCMs and stream flow (Chattahoochee-Apalachicola). Flow regimes were examined for changes from current conditions with respect to ecologically relevant features including the magnitude and timing of minimum and maximum flows. The Cle Elum's hydrograph under future climate scenarios showed a dramatic shift in the timing of peak flows and lower low flow of a longer duration. These changes could mean higher summer water temperatures, lower summer dissolved oxygen, and reduced survival of larval fishes. The Chattahoochee-Apalachicola basin is heavily impacted by dams and water withdrawals for human consumption; therefore, we made comparisons between pre-large dam conditions, current conditions, current conditions with future demand, and future climate scenarios with future demand to separate climate change effects and other anthropogenic impacts. Dam construction, future climate, and future demand decreased the flow variability of the river. In addition, minimum flows were lower under future climate scenarios. These changes could decrease the connectivity of the channel and the floodplain, decrease habitat availability, and potentially lower the ability of the river to assimilate wastewater treatment plant effluent. Our study illustrates the types of changes that river ecosystems might experience under future climates. Copyright ?? 2005 John Wiley & Sons, Ltd.

Gibson, C. A.; Meyer, J. L.; Poff, N. L.; Hay, L. E.; Georgakakos, A.

2005-01-01

110

Organic microfacies and basinal tectonic control on source rock accumulation: a microscopic approach with examples from an intracratonic and extensional basin  

Energy Technology Data Exchange (ETDEWEB)

Relationships among organic petrographic maceral assemblages and hydrocarbon source rock depositional environments distinguish broad marine, terrestrial and mixed kerogen accumulation settings. Organic microfacies from Paleozoic and Mesozoic source rock intervals in the intracratonic Williston Basin and the extensional Sverdrup Basin have been studied using incident white and fluorescent light microscopy. Distinct anoxic organic microfacies are defined in Upper Ordovician Bighorn Group subtidal, platformal kukersites and Middle Devonian upper Elk Point Group carbonate lithologies that preserve a progression of depositional environments from platformal to starved basinal. Paleozoic carbonate platform microfacies are characterized by well preserved cyanophyceae alginite stromatolitic mats displaying upper surface textural features such as pustules, pinnacles, endolithic algal borings and interlaminated vertical and horizontal alginite resulting from phototactic growth. Potential source intervals in Middle and Upper Triassic shelf shales from the Sverdrup Basin and Middle Devonian carbonate platform marginal mudstones in the Williston Basin are both characterized by high concentrations of sapropelic, bituminite kerogen hosting unicellular marine alginite. Similar bituminite-rich organic microfacies occur in Middle Devonian basinal settings associated with larger, more abundant alginite and significant amounts of dasycladacean calcareous algae. The main controls on source rock accumulation are water depth and chemistry as controlled by depositional setting and basin restriction. 49 refs., 5 figs., 2 tabs., 17 photos.

Stasiuk, L.D.; Osadetz, K.G.; Goodarzi, F.; Gentzis, T. (University of Regina, SK (Canada). Energy Research Unit, Dept. of Geology)

1991-12-01

111

Neogene evolution of the North New Guinea basin, Papua New Guinea: New constraints from seismic and subsidence analysis and implications for hydrocarbon exploration  

Energy Technology Data Exchange (ETDEWEB)

The present-day North New Guinea basin is a Plio-Pleistocene successor basin that formed subsequent to accretion of the Finisterre volcanic arc to the Australian Plate. The Ramu, Sepik, and Piore infrabasins formed in a forearc setting relative to the continental Maramuni magmatic arc. The evolution of these infrabasins was strongly influenced by accretion of the composite Torricelli-Prince Alexander terrane to the Australian Plate. Regional reflection seismic data and tectonic subsidence-subsidence rate calculations for seven wells drilled in the North New Guinea basin reveal a complex history. The timing and magnitude of subsidence and changes in subsidence rates differ between each of the Miocene infrabasins. A diachronous middle to late Miocene unconformity generally truncates infrabasin sequences. The Nopan No. 1 in the Sepik basin, however, has a complete middle Miocene to Pleistocene sedimentary record. This well records late Miocene negative subsidence rates documenting that the Nopan anticline grew as erosion occurred elsewhere in the region. This circumstance suggests that the major, sequence-bounding unconformity results from regional uplift and deformation, rather than changes in global sea level. The Plio-Pleistocene evolution of the North New Guinea basin has two profound implications regarding hydrocarbon exploration. First, the late Pliocene structural inversion of parts of the basin hinders stratigraphic and facies correlation inferred from the present setting. The recognition of basin inversion is particularly important in the Piore basin for predicting the distribution of potential reservoir facies in the Miocene carbonates. Second, the subsidence data suggest that although potential source rocks may be thermally within the oil window, these rocks may not have had sufficient time to mature owing to their recent burial.

Cullen, A.B.; Pigott, J.D. (Univ. of Oklahoma, Norman (USA))

1990-06-01

112

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  

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Full Text Available 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.

M. S. Pervez

2014-02-01

113

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

114

Textural and geochemical characteristics of the Ajali Sandstone, Anambra Basin, SE Nigeria: Implication for its provenance  

Science.gov (United States)

This study presents the mineralogical, textural and geochemical characteristics of the regional Maastrichtian Ajali Sandstone in Anambra Basin, SE Nigeria. The intent is to highlight possible constraints on the chemical weathering conditions of the source materials on one hand, and to infer the provenance on the other hand. The investigation approach involved field studies and collection of samples from 12 different outcrop locations, followed by laboratory studies involving grain-size analysis (GSA), major and trace elements analyses using the X-ray fluorescence (XRF) method as well as thin section petrography. Field studies show that the sandstones are friable at all locations and range in color from white in freshly cut stone, to reddish brown on weathering. In addition, the sandstone units are cross-bedded and show graded bedding exemplified by fining upward sequence. Textural examination indicates that the sandstones range from fine to medium sands, constituting about 76 to 99% sand fraction, with graphic mean grain size of 0.23 to 0.53 mm. Standard deviation (sorting) ranges from 0.56 to 1.24 Ø and implies moderately well sorted sediments. Inferred from the textural indices, the depo-environmental discrimination of the Ajali Sandstone revealed a fluvial/river system-dominated sedimentary process. The sandstones are quartz arenite with quartz greater than 90% and less than 5% K-feldspar which indicate a predominant basement source as also revealed by the heavy mineral assemblages. In addition, major elemental oxides shows SiO 2 content greater than 96% for the fresh Ajali Sandstone samples with extreme depletion of mobile oxides such as Na 2O, CaO and the ferromagnesian minerals through weathering and sedimentary processes. Provenance and tectonic setting discrimination using geochemical data and compositional maturity revealed typical felsic igneous-dominated cratonic environment while inter-elemental ratios (such as Zr/Cr, Y/Ni, Th/Sc, La/Sc and La/Co) and ternary plots (e.g. Th-Sc-Zr; La-Th-Sc and Th-Co-Zr) reflect passive continental margin setting for the Ajali Sandstone. Consequently, the source area is constrained to the Precambrian basement rock units of Adamawa-Oban massif areas to the east of the Anambra Basin and the adjacent Abakaliki Anticlinorium.

Tijani, Moshood Niyi; Nton, Matthew Essien; Kitagawa, Ryuji

115

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

116

Reconstruction of the Mesozoic subduction in the South China Sea and its implications on the opening of the South China Sea basins  

Science.gov (United States)

Reconstruction of the Mesozoic subduction system in the South China Sea (SCS) can improve our understanding of the tectonic evolution in the region and holds important implications on the opening of the SCS basins. Here we report the locations of the Mesozoic volcanic arc and trench in the SCS based on satellite-derived magnetic and gravimetric data, as well as drilling data from the China National Offshore Oil Corporation. The magnetic data allows us to identify the volcanic arc, which is characterized as high positive magnetic anomaly (HPMA) due to serpentinization. Furthermore, the volcanic arc is verified by distributions of intermediate rocks that are determined from the drilling data. The gravimetric data is used to determine the locations of the Mesozoic trench. Our preliminary results show two distinct HPMA belts along the two sides of the SCS basins. The first one locates northwest to the ridge axis of the SCS basins and extends from Taiwan in the northeast to the Xisha Island in the southwest. The second one locates on the Nansha-Dangerous Ground, southeast to the opening axis of the southwest sub-basin of the SCS, and is nearly parallel to the orientation of the first one. In addition, the distribution of intermediate rocks within the two HPMA belts indicates that the two belts represent the present locations of the Mesozoic volcanic arc. Furthermore, we recognize the corresponding Mesozoic trench by peak gross horizontal gradient of bouguer gravity anomaly in the northeastern SCS. It is located northwest to the ridge axis of the SCS basins and southeast to the Mesozoic arc. Moreover, drilling sample MZ-1-1 from the area between the Mesozoic arc and trench has shown clear signatures of forearc basin sediments, providing additional support to our arc and trench locations. Based on the opening direction of the SCS basins, we interpret that the two HPMA belts belong to the same Mesozoic volcanic arc that is located on the Eurasia continental crust. The arc was formed by the northwestward subduction of the Izanagi and Pacific plates beneath the Eurasia plate. The current locations of the Mesozoic arc indicate that it was separated by the opening of the SCS basins. In addition, the opening of the SCS basins may obliquely cut the proto-SCS oceanic crust in the northeast and the Eurasia continental crust in the southwest. Thus, the southwest segment of the Mesozoic arc is carried to the Nansha-Dangerous Ground, southeast to the ridge axis of the southwest sub-basin of the SCS. In comparison, the northeast portion of the Mesozoic subduction system is located northwest to the ridge axis of the SCS basins.

Li, F.; Sun, Z.; Yang, H.

2013-12-01

117

Globalization and the Spatial Economy: Implications for the Amazon Basin in the 21st Century  

Science.gov (United States)

Global demand for food and energy will increase in the next decades as world population grows, incomes in developing countries rise, and new energy sources from biofuels are sought. Despite gains in productivity, much of the future demand for those agricultural products will be met by bringing new lands into production. Tropical forests, and in particular the Brazilian Amazon, the focus of our article, are already facing pressures from expanding production of soy, beef, cotton, and biofuels as deforestation advances the agricultural frontier. This article begins by reviewing the recent literature and provides evidences of indirect land cover change in the Amazon driven by the tandem soy - cattle, whereby mechanized agriculture encroaches on existing pastures, displacing them to the Amazonian frontier. We then consider conditions in the spatial economy that potentially inhibit ongoing forest loss. In particular, we address the prospect of forest transition in the Amazon basin. This necessitates a review of the so-called Borlaug hypothesis, and the circumstances under which land sparing occurs. Land sparing, a sufficient if not necessary condition for forest transition, represents a potential solution to environmental problems associated with land change, one that promotes sustainability by furthering rural development with improved technologies. The paper concludes by contrasting the current Brazilian agricultural and environmental policies with the conditions set in the previous section.

Arima, E.; Walker, R.; Richards, P.

2011-12-01

118

Delineation of Piceance Basin basement structures using multiple source data: Implications for fractured reservoir exploration  

Energy Technology Data Exchange (ETDEWEB)

Fractured production trends in Piceance Basin Cretaceous-age Mesaverde Group gas reservoirs are controlled by subsurface structures. Because many of the subsurface structures are controlled by basement fault trends, a new interpretation of basement structure was performed using an integrated interpretation of Landsat Thematic Mapper (TM), side-looking airborne radar (SLAR), high altitude, false color aerial photography, gas and water production data, high-resolution aeromagnetic data, subsurface geologic information, and surficial fracture maps. This new interpretation demonstrates the importance of basement structures on the nucleation and development of overlying structures and associated natural fractures in the hydrocarbon-bearing section. Grand Valley, Parachute, Rulison, Plateau, Shire Gulch, White River Dome, Divide Creek and Wolf Creek fields all produce gas from fractured tight gas sand and coal reservoirs within the Mesaverde Group. Tectonic fracturing involving basement structures is responsible for development of permeability allowing economic production from the reservoirs. In this context, the significance of detecting natural fractures using the intergrated fracture detection technique is critical to developing tight gas resources. Integration of data from widely-available, relatively inexpensive sources such as high-resolution aeromagnetics, remote sensing imagery analysis and regional geologic syntheses provide diagnostic data sets to incorporate into an overall methodology for targeting fractured reservoirs. The ultimate application of this methodology is the development and calibration of a potent exploration tool to predict subsurface fractured reservoirs, and target areas for exploration drilling, and infill and step-out development programs.

Hoak, T.E.; Klawitter, A.L.

1995-10-01

119

Tectonic implications of a high-resolution aeromagnetic survey of the Portland basin, Oregon and Washington  

Energy Technology Data Exchange (ETDEWEB)

A high-resolution aeromagnetic survey of the Portland-Vancouver metropolitan area was conducted by the US Geological Survey during September, 1992, to determine the location and extent of faults in the area, especially where concealed by vegetation, water, and urban development. Magnetic anomalies in this area are caused principally by three volcanic units: Eocene basaltic basement, presumably representing an accreted oceanic terrane; folded and faulted flows of the Miocene Columbia River Basalt Group; and locally erupted basalt of Plio-Pleistocene age. Linear magnetic anomalies correlate with several known faults in these rocks, while other anomalies may reflect previously unrecognized faults beneath covered areas. The northwest-striking Portland-Hills fault, which lies beneath downtown Portland and which appears to be seismically active at the M [<=] 3 level, is clearly represented in the magnetic data as an anomaly extending southeast to the Clackamas River drainage, a total distance in excess of 50 km. This fault is thought to be the southwestern boundary of a complex pull-apart zone that formed the Portland Basin. The northeastern boundary of the pull-apart zone, the frontal fault northeast of downtown Vancouver, is less apparent in the magnetic data. The overall length of the magnetic anomaly associated with the Portland Hills fault indicates that the fault is at least 50 km in length. If the Portland Hills fault is seismically active along this entire length, seismic risk to the Portland-Vancouver metropolitan area may be greater than previously suspected.

Blakeley, R.J.; Wells, R.E. (Geological Survey, Menlo Park, CA (United States)); Beeson, M.H. (Portland State Univ., OR (United States). Geology Dept.); Madin, I.P. (Dept. of Geology and Mineral Industries, Portland, OR (United States)); Popowski, T. (GeoEngineers, Redmond, WA (United States)); Yelin, T.S. (Univ. of Washington, Seattle, WA (United States). Geological Survey)

1993-04-01

120

Drmno lignite field (Kostolac basin, Serbia: Origin and palaeoenvironmental implications from petrological and organic geochemical studies  

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Full Text Available The objective of the study was to determine the origin and to reconstruct the geological evolution of lignites from the Drmno field (Kostolac Basin, Serbia. For this purpose petrological and organic geochemical analyses were used. Coal from the Drmno field is typical humic coal. Peat-forming vegetation dominated by decay of resistant gymnosperm (coniferous plants, followed by prokaryotic organisms and angiosperms. Coal forming plants belonged to the gymnosperm families Taxodiaceae, Podocarpaceae, Cupressaceae, Araucariaceae, Phyllocladaceae and Pinaceae. Peatification was performed in neutral to slightly acidic, fresh water environment. Considering that organic matter of Drmno lignites was deposited at the same time, in the relatively constant climate, it could be supposed that climate probably had only small impact on peatification. Therefore, variations in compositions of macerals and biomarkers indicate changes in the water level, due to seasonal drying of the mire, which caused vegetation differences in the palaeoplant communities and changes of redox conditions (from anoxic to slightly oxic during peatification. Diagenetic transformations of the organic matter were mainly governed by microbial activity, rather than thermal alteration.

Stojanovi? Ksenija

2012-01-01

 
 
 
 
121

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

122

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

123

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

124

New seismo-stratigraphic data of the Volturno Basin (northern Campania, Tyrrhenian margin, southern Italy: implications for tectono-stratigraphy of the Campania and Latium sedimentary basins  

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Full Text Available A geological section of the Volturno Basin (northern Campania, continental margin, Italy has been constructed based on new multi-channel seismic data, to show the stratigraphic relationships between the filling in the Quaternary basin and the Meso-Cenozoic acoustic basement. The new seismic sections presented here outline the underlying structures of the basin and their relationships to the filling in the Quaternary basin. Deep exploration wells in Campania and Latium on the Tyrrhenian margin have gathered litho-stratigraphic and commercial multi-channel seismic data that can be used for better integration of the geological data for the area under study. The trending of the seismic units is controlled by the Massico Structural High, which forms the boundary of the Volturno Basin towards the north-west. This produces a geometry that is characteristic of a fan complex, with NE-SW trending. This qualitative calibration of the seismic sequences that fill the sedimentary basin was carried out through the litho-stratigraphic data of the «Castelvolturno 2» well, which highlights the pyroclastic layers and conglomeratic strata of the lagoon and delta environments as they evolve upwards towards marine sediments. Seismo-stratigraphic analysis shows the complex depositional geometries of the filling in the Volturno Basin, which overlie the Meso-Cenozoic carbonatic basement and the related flysch deposits. Coupled with regional geological evidence, the data interpretation here suggests that the Volturno Basin represents a half-graben structure that is characterized by down-thrown blocks along normal faults.

Ennio Marsella

2011-07-01

125

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

126

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

Energy Technology Data Exchange (ETDEWEB)

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, D.A.; Goydas, M.J.; Smith, G.N.; Chitwood, J.P. (Kansas State Univ., Manhattan (USA))

1990-07-01

127

Earthquake geology of Kashmir Basin and its implications for future large earthquakes  

Science.gov (United States)

Two major traces of active thrust faults were identified in the Kashmir Basin (KB) using satellite images and by mapping active geomorphic features. The ~N130°E strike of the mapped thrust faults is consistent with the regional ~NE-SW convergence along the Indian-Eurasian collision zone. The ~NE dipping thrust faults have uplifted the young alluvial fan surfaces at the SW side of the KB. This created a major tectono-geomorphic boundary along the entire strike length of the KB that is characterised by (1) a low relief with sediment-filled sluggish streams to the SE and (2) an uplifted region, with actively flowing streams to the SW. The overall tectono-geomorphic expression suggests that recent activity along these faults has tilted the entire Kashmir valley towards NE. Further, the Mw 7.6 earthquake, which struck Northern Pakistan and Kashmir on 8 October 2005, also suggests a similar strike and NE dipping fault plane, which could indicate that the KB fault is continuous over a distance of ~210 km and connects on the west with the Balakot Bagh fault. However, the geomorphic and the structural evidences of such a structure are not very apparent on the north-west, which thus suggest that it is not a contiguous structure with the Balakot Bagh fault. Therefore, it is more likely that the KB fault is an independent thrust, a possible ramp on the Main Himalayan Thrust, which has uplifting the SW portion of the KB and drowning everything to the NE (e.g. Madden et al. 2011). Furthermore, it seems very likely that the KB fault could be a right stepping segment of the Balakot Bagh fault, similar to Riasi Thrust, as proposed by Thakur et al. (2010). The earthquake magnitude is measured by estimating the fault rupture parameters (e.g. Wells and Coppersmith in Bull Seismol Soc Am 84:974-1002, 1994). Therefore, the total strike length of the mapped KB fault is ~120 km and by assuming a dip of 29° (Avouac et al. in Earth Planet Sci Lett 249:514-528, 2006) and a down-dip limit of 20 km, a Mw of 7.6 is possible on this fault.

Shah, A. A.

2013-02-01

128

The Fate of Failed Bank Material and Implications for Lateral Retreat: Lake Tahoe Basin  

Science.gov (United States)

The ability to deterministically predict the critical conditions for streambank failure in alluvial materials has improved markedly in recent years. Analytic tools such as the Bank-Stability and Toe-Erosion Model (BSTEM) account for a broad range of controlling processes and factors including hydraulic erosion of the bank toe, positive and negative pore-water pressures, layers of varying geotechnical resistance and root reinforcement. When failure is predicted, the failed mass is assumed to be transported away from the section by the flow, either as a single mass or as dispersed aggregates. Field observations indicate, however, that in cases where cohesive strength is high, either due to the effective cohesion of the soil skeleton or due to dense mats of fine roots, the failed block comes to rest in the vicinity of the bank toe. In this case, the resistance of the bank-toe region to hydraulic scour may be increased markedly and resistance to geotechnical failure may also be increased by buttressing. Conversely, deposition of blocks at bank toes may cause flow acceleration and scour landward of the block, resulting in further undercutting of the bank mass. Failure to account for these processes can lead to errors in predicting of rates of failure frequency, lateral retreat and streambank loadings.Once deposited at the bank toe, failed blocks can be eroded by hydraulic forces either as a mass and/or by erosion of aggregates comprising the block. Field research on the nature of hydraulic resistance and block erosion has been conducted along selected reaches of the Upper Truckee River (UTR) and Trout Creek, Lake Tahoe Basin, California. Block materials are generally characterized by lower apparent cohesive strength than their in situ counterparts due to the lower values of matric suction owing to their proximity to the water surface. Still, submerged jet-test device conducted in root-permeated blocks show critical shear stresses one to two orders of magnitude greater (10 - 30 Pa) than the non root-permeated materials (0.3 - 1.7 Pa). This effect is particularly enhanced along the top surface of the block where the highest critical shear stresses obtained. This is also the location where the above-ground biomass impacts flow resistance, causing a reduction in the shear stress applied to the block. Entrainment of entire blocks does occur, requiring shear stresses from 50 to 120 Pa, using a modified Shields criteria. Based on measurements of block dimensions taken in the summers of 2008 and 2009 along the UTR study reach, although the number of blocks doubled from 13 to 26, hydraulic erosion resulted in a 32% reduction in median block size and a 20% reduction in total block volume. The field experiments conducted here illustrate root-permeated blocks provide for greater hydraulic resistance than in situ bank-toe materials. With bank-toe erosion playing a vital role in streambank stability, these blocks tend to reduce lateral retreat of the bank. Further field tests are being conducted in other regions along with flume studies of the impact of blocks on flow acceleration and shear-stress generation landward of the failed block.

Simon, A.; Thomas, R. E.

2009-12-01

129

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

130

The nonmarine Lower Cretaceous of the North American Western Interior foreland basin: New biostratigraphic results from ostracod correlations and early mammals, and their implications for paleontology and geology of the basin—An overview  

Science.gov (United States)

The timespan represented by the hiatus between nonmarine Upper Jurassic (Early Berriasian?) and unconformably overlying Lower Cretaceous deposits throughout the North American Western Interior foreland basin has been under discussion for the entire 20th century and remains controversial to date. Ongoing research in revision of Early Cretaceous nonmarine ostracods of some respective North American formations leads to a breakthrough concerning the verification of their biostratigraphic utility as well as their subsequent application. These ostracods are not as endemic as hitherto believed and can be used for supraregional and regional correlation, as well as improvement of the age determination of North American units. New results strongly suggest a maximum age of Late Berriasian to Valanginian (˜ 142-138 Ma) for the lower part of the Lakota (Black Hills area, South Dakota) and Cedar Mountain (Utah) formations. A pre-Aptian maximum age for the Lakota Formation is supported by early mammals. These biostratigraphic results affect the correlatable formations as well, and therefore have broad implications on basin-related geologic and paleontologic topics that are overviewed and discussed herein. The central issue hampering an integrated synthesis of the foreland basin is its yet imprecise chronostratigraphic framework and documentation. Temporal relationships between the gologic processes of the basin and their control factors are still insufficiently calibrated or controversial. Detailed ongoing revision of North American Early Cretaceous nonmarine ostracods demonstrates their applicability, utility, and further potential as tool for improvement of the chronostratigraphy of the Western Interior foreland basin at both small and large scales. These ostracods also foster understanding of animal (e.g. early mammals and dinosaurs) and plant (angiosperms) evolution on the North American continent and show promise of providing age determinations for single-sample horizons in the near future.

Sames, Benjamin; Cifelli, Richard L.; Schudack, Michael E.

2010-08-01

131

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

International Nuclear Information System (INIS)

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 K2O and slightly less TiO2. 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.)

1990-01-01

132

Paleobathymetric maps of tertiary La Honda Basin and implications for offset along San Andreas fault in central California  

Energy Technology Data Exchange (ETDEWEB)

Paleobathymetric maps of the La Honda basin of central California were constructed for ten intervals of geologic time from late Paleocene (Nezian) to middle Miocene (Luisian). The maps are based on analyses of benthic foraminiferal biofacies in more than 800 faunal lists compiled from the literature and from subsurface data provided by oil companies. The sequence of paleobathymetric maps shows the paleogeographic evolution of the La Honda basin. From the late Paleocene (Ynezian) to the early Oligocene (early Zemorrian), deep-sea sands and muds accumulated at water depths of 2000 m and more on a surface that sloped gently to the north and northeast. Striking changes in the configuration of the La Honda basin occurred during the late Oligocene and early Miocene (late Zemorrian). Much of the basin floor remained at water depths of 2000 m and greater, but submarine volcanic rocks locally built up to form seamounts, and movement along the Zayante-Vergeles fault led to shoaling and development of a narrow shelf and very steep slope along the southwestern margin of the basin. During the early and middle Miocene (Relizian and Luisian), the entire basin shoaled to depths of less than 1500 m. Comparison of paleobathymetric maps of the La Honda and San Joaquin basins lends support to the notion that the two basins were once contiguous but have been separated by about 320 to 330 km of right-lateral displacement along the San Andreas fault since the earliest Miocene (late Zemorrian and Saucesian).

Stanley, R.G.

1987-05-01

133

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

134

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)

1997-01-01

135

Satellite Remote Sensing and Hydrological Modeling for Flood Inundation Mapping in Lake Victoria Basin: Implications for Hydrologic Prediction in Ungauged Basins  

Science.gov (United States)

Floods are among the most catastrophic natural disasters around the globe impacting human lives and infrastructure. Implementation of a flood prediction system can potentially reduce these losses. Typically, the set up and calibration of a hydrologic model requires in situ observations (e.g. rain gauges and stream gauges). Satellite remote sensing data have emerged as viable alternatives or supplements to in situ observations due to their coverage over ungauged regions. The focus of this study is to utilize the best available satellite products and integrate them in a state-of-the-art hydrologic model to characterize the spatial extent of flooding and associated hazards over sparsely-gauged or ungauged basins. This study presents a methodology based entirely on satellite remote sensing data to calibrate a hydrologic model, simulate the spatial extent of flooding, and evaluate the probability of detecting inundated areas. A raster-based distributed hydrologic model, CREST, was implemented for the Nzoia basin, a sub-basin of Lake Victoria (Africa). MODIS- and ASTER-based flood inundation maps were retrieved over the region and used to benchmark the distributed hydrologic model simulations of streamflow and inundation areas. The analysis showed the applicability of integrating satellite data products as input for a distributed hydrological model as well as direct estimation of flood extent maps. The quantification of flooding spatial extent through orbital sensors can help to evaluate hydrologic models and hence potentially improve hydrologic prediction and flood management strategies in ungauged catchments.

Khan, S. I.; Hong, Y.; Wang, J.; Yilmaz, K. K.; Gourley, J. J.; Adler, R. F.; Brakenridge, G. R.; Policelli, F.; Habib, S.; Irwin, D.

2009-12-01

136

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 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

1994-03-01

137

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.

Liria, Jonathan; Navarro, Juan-Carlos.

138

Late Oligocene Recent stress evolution in rift basins of northern and central Thailand: implications for escape tectonics  

Science.gov (United States)

The Tertiary rift basins of Thailand are known through sub-surface seismic and borehole data collected for hydrocarbon and coal exploration, outcrops in open-cast coal mines, and a few natural outcrops. These data provide mixed perspectives on how the basins evolved, some providing data on ages and structural geometries, others palaeostress data. In general, the region evolved under approximately E-W extension, although the extension direction probably changed periodically within basins. Extension was episodically interrupted by inversion events associated with sub-horizontal NW-SE to NE-SW ? 1 direction. There is no evidence to suggest that the string of rift basins running from N. Thailand and Laos into the Gulf of Thailand evolved in a similar way. On the contrary, the evolution of each basin seems different, although certain regional trends along the rift system are apparent as follows: (1) Oligocene-Lower Miocene extension is widespread in the region. (2) In central and northern Thailand Middle Miocene extension is also important, and extension persisted into the Upper Miocene-Pliocene. (3) In the extreme south of the area (W. Natuna basin, Penyu basin, Malay basin) extension ceased in the earliest Miocene. (4) In the northern Gulf of Thailand extension ceased in the Middle Miocene. (5) Thermal subsidence is greatest (up to 4 km) in the south (Malay, Pattani, W. Natuna and Penyu basins) and least in northern Thailand (a few tens to hundreds of metres). (6) Inversion in the southern Gulf of Thailand was intense and occurred during the Lower and Middle Miocene. In the northern Gulf of Thailand inversion is very mild and occurred during the Lower and Middle Miocene. Onshore inversion is patchy during the Miocene, but is strongest in the northwestern rift basins (particularly the Li basin). The most widespread inversion event that affects the north occurred during the Plio-Pleistocene. It might be associated with the change from left to right lateral motion on the Red River Fault. The relationship between strike-slip faults and rift basins in terms of timing of extensional and inversion events, and palaeostress orientation and evolution is more complex than can be explained by simple escape tectonic models.

Morley, C. K.; Woganan, N.; Sankumarn, N.; Hoon, T. B.; Alief, A.; Simmons, M.

2001-05-01

139

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

Science.gov (United States)

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.

Kwon, Sun-Ki; Choi, Sung Hi; Lee, Der-Chuen

2013-09-01

140

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

Science.gov (United States)

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

 
 
 
 
141

U-Pb zircon ages from the southwestern Karoo Basin, South Africa - Implications for the Permian-Triassic boundary  

Science.gov (United States)

U-Pb ages determined using sensitive high-resolution ion microprobe-reverse geometry on 205 single-grain zircons from 16 ash beds within submarine fan deposits of the Ecca Group provide the first evidence of a marine Permian-Triassic (P-T) boundary in the Karoo Basin of South Africa. These U-Pb ages provide an objective basis for correlating the deep-marine sediments of the southwest Karoo Basin with fluvial-deltaic deposits in the central and eastern parts of the basin where the P-T boundary is recorded in a diverse macrofauna. Furthermore, these new zircon ages and their correlation imply asymmetric subsidence and variable sedimentation rates across the basin. ?? 2009 Geological Society of America.

Fildani, A.; Weislogel, A.; Drinkwater, N. J.; McHargue, T.; Tankard, A.; Wooden, J.; Hodgson, D.; Flint, S.

2009-01-01

142

Physical Scales of Runoff Production in the Upper Colorado River Basin: Implications for Response to Climate Change (Invited)  

Science.gov (United States)

Roughly 15 million acre feet (maf) discharges annually from the Upper Colorado River Basin (UCRB). Yet, this is a mere drop in the bucket compared to the moisture dousing the basin--- weather systems deliver annual precipitation that is five-fold greater than the basin’s runoff. A fundamental question is the cause for the UCRB’s low runoff production efficiency (~20%), and whether knowledge of the region’s climatological surface water balance can offer clues on how the river will respond to global warming. Our study particularly explores the physics essential for runoff production in the Upper Colorado River Basin. We inquire how runoff production varies with elevation and spatial scale across the basin. To address these issues quantitatively, we use a simple two-layer water balance model to simulate annual runoff within the UCRB. Calculations are performed at 4km spatial resolution using monthly temperature and precipitation data derived from PRISM for 1895-2006. Our analysis reveals that the physical processes of UCRB runoff production and its climate sensitivity depends critically on representing the fine spatial scales of the water balance. In this regard, the empirical studies of how Colorado River flow would respond to climate change based on gross area-averaged water balance considerations should be interpreted with great caution. Likewise, the scales resolved in existing global climate models are likely too coarse to resolve critical land surface processes within the UCRB, and the sensitivity of the such IPCC projected runoff to climate change need to be viewed with great caution. Downscaling procedures are clearly crucial in modeling the basin’s runoff and its potential sensitivity to climate change realistically. Downscaling modeling approaches are not without their own limitations, and there is currently a wide spread among projections of UCRB runoff response to climate change among high resolution land surface models that requires explanation.

Hoerling, M.; Eischeid, J.

2009-12-01

143

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

Science.gov (United States)

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

144

Population genetic analysis of Arapaima gigas, one of the largest freshwater fishes of the Amazon basin : implications for its conservation  

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The present study reports the first population genetic analysis of Arapaima gigas, an important but critically over-exploited fish species of the Amazon basin. We sequenced two discontinuous mitochondrial DNA regions of 1204 base-pairs (bp) (NADH1 segment) and 1143 bp (ATPase segment) from 139 individuals of A. gigas representing eight localities spanning the Amazon basin from Iquitos, Peru to Macap´a, Brazil. We discovered 34 haplotypes separated by 44 segregating sites. The two most common...

Hrbek, Tomas; Farias, Izeni P.; Crossa, Marcelo; Sampaio, Iracilda; Porto, Jorge I. R.; Meyer, Axel

2005-01-01

145

Re-Os geochronology of a Mesoproterozoic sedimentary succession, Taoudeni basin, Mauritania: Implications for basin-wide correlations and Re-Os organic-rich sediments systematics  

Science.gov (United States)

The exceptionally well-preserved sedimentary rocks of the Taoudeni basin, NW Africa represent one of the world's most widespread (> 1 M km 2) Proterozoic successions. Hitherto, the sedimentary rocks were considered to be Mid Tonian based on Rb-Sr illite and glauconite geochronology of the Atar Group. However, new Re-Os organic-rich sediment (ORS) geochronology from two drill cores indicates that the Proterozoic Atar Group is ˜ 200 Ma older (1107 ± 12 Ma, 1109 ± 22 Ma and 1105 ± 37 Ma). The Re-Os geochronology suggests that the Rb-Sr geochronology records the age of diagenetic events possibly associated with the Pan African collision. The new Re-Os geochronology data provide absolute age constraints for recent carbon isotope chemostratigraphy which suggests that the Atar Group is Mesoproterozoic and not Neoproterozoic. The new Re-Os ORS geochronology supports previous studies that suggest that rapid hydrocarbon generation (flash pyrolysis) from contact metamorphism of a dolerite sill does not significantly disturb the Re-Os ORS systematics. Modelled contact conditions suggest that the Re-Os ORS systematics remain undisturbed at ˜ 650 °C at the sill/shale contact and ? 280 °C 20 m from the sill/shale contact. Moreover, the Re-Os geochronology indicates that the West African craton has a depositional history that predates 1100 Ma and that ORS can be correlated on a basin-wide scale. In addition, the Re-Os depositional ages for the ORS of the Taoudeni basin are comparable to those of ORS from the São Francisco craton, suggesting that these cratons are correlatable. This postulate is further supported by identical Os i values for the Atar Group and the Vazante Group of the São Francisco craton.

Rooney, Alan D.; Selby, David; Houzay, Jean-Pierre; Renne, Paul R.

2010-01-01

146

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

Energy Technology Data Exchange (ETDEWEB)

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

147

Structural interpretation of the Ifal Basin in north-western Saudi Arabia from aeromagnetic data: hydrogeological and environmental implications  

Science.gov (United States)

The Ifal (Midyan) Basin is one of the well defined basins along the Red Sea coast, north-western Saudi Arabia. Location, geometry, thick sedimentary cover and structural framework qualify this basin for groundwater, oil and mineral occurrences. In spite of being studied by two airborne magnetic surveys during 1962 and 1983, structural interpretation of the area from a magnetic perspective, and its uses for hydrogeological and environmental investigations, has not been attempted. This work thus presents interpretation of the aeromagnetic data for basement depth estimation and tectonic framework delineation, which both have a role in controlling groundwater flow and accumulation in the Ifal Basin. A maximum depth of 3.5km is estimated for the basement surface by this study. In addition, several faulted and tilted blocks, perpendicularly dissected by NE-trending faults, are delineated within the structural framework of the study area. It is also observed that the studied basin is bounded by NW- and NE-trending faults. All these multi-directional faults/fracture systems in the Ifal Basin could be considered as conduits for groundwater accumulation, but with a possibility of environmental contamination from the surrounding soils and rock bodies.

Elawadi, Eslam 124Zaman, Haider 3Batayneh, Awni 1Mogren, Saad 1Laboun, Abdalaziz 1Ghrefat, Habes 1Zumlot, Taisser

2013-09-01

148

Complex basin evolution in the Gökova Gulf region: implications on the Late Cenozoic tectonics of southwest Turkey  

Science.gov (United States)

Southwestern Turkey experienced a transition from crustal shortening to extension during Late Cenozoic, and evidence of this was recorded in four distinct basin types in the Mu?la-Gökova Gulf region. During the Oligocene-Early Miocene, the upper slices of the southerly moving Lycian Nappes turned into north-dipping normal faults due to the acceleration of gravity. The Kale-Tavas Basin developed as a piggyback basin along the fault plane on hanging wall blocks of these normal faults. During Middle Miocene, a shift had occurred from local extension to N-S compression/transpression, during which sediments in the Eskihisar-T?naz Basins were deposited in pull-apart regions of the Menderes Massif cover units, where nappe slices were already eroded. During the Late Miocene-Pliocene, a hiatus occurred from previous compressional/transpressional tectonism along intermountain basins and Yata?an Basin fills were deposited on Menderes Massif, Lycian Nappes, and on top of Oligo-Miocene sediments. Plio-Quaternary marked the activation of N-S extension and the development of the E-W-trending Mu?la-Gökova Grabens, co-genetic equivalents of which are common throughout western Anatolia. Thus, the tectonic evolution of the western Anotolia during late Cenozoic was shifting from compressional to extensional with a relaxation period, suggesting a non-uniform evolution.

Gürer, Ömer Feyzi; San?u, Ercan; Özburan, Muzaffer; Gürbüz, Alper; Sarica-Filoreau, Nuran

2013-11-01

149

Provenance of Miocene submarine fans in the Shikoku Basin: Results from NanTroSEIZE and implications for stratigraphic correlation of subduction inputs  

Science.gov (United States)

Seismo-stratigraphy, coring and LWD during IODP Expeditions 319, 322, and 333 (Sites C0011 / C0012) show three Miocene submarine fans in the NE Shikoku Basin, with broadly coeval deposits at ODP Site 1177 and DSDP Site 297, NW Shikoku Basin. Pickering et al. (2013) have shown that the sediment dispersal patterns for these fans have major implications for paleogeographies at that time. The oldest, Middle Miocene Kyushu Fan is the finest grained, has a sheet-like geometry, and was fed by quartz-rich sediment gravity-flows derived mostly from an ancestral landmass in the East China Sea. This likely sediment provenance is further supported by U-Pb zircon and fission track analysis of both zircons and apatites from sediments taken from the forearc and trench of the Nankai Trough, together with rivers from southwest Japan, that point to the influence of the Yangtze River in supplying into the Shikoku Basin prior to rifting of the Okinawa Trough at 10 to 6 Ma (Clift et al. 2013). During prolonged hemipelagic mud deposition at C0011-C0012 (12.2 to 9.1 Ma), sand supply continued at Sites 1177 and 297. Sand delivery to much of the Shikoku Basin, however, probably halted during a phase of sinistral strike-slip and oblique plate motion, after which the Daiichi Zenisu Fan (9.1 to 8.0 Ma) was fed by submarine channels. The youngest fan (Daini Zenisu; 8.0 to 7.6 Ma) has sheet-like geometry with thick-bedded, coarse-grained pumiceous sandstones. The pumice fragments were fed from a mixed provenance that included the collision zone of the Izu-Bonin and Honshu arcs. The shift from channelized to sheet-like flows was probably favored by renewal of relatively rapid northward subduction, which accentuated the trench as a bathymetric depression. Understanding the stratigraphic position and 3-D geometry of the sandbodies has important implications for stratigraphic correlation throughout the northern Shikoku Basin, together with subduction-related processes, including the potential for focused fluid flow and fluid overpressures above and below the plate-boundary fault. References Pickering, K.T., Underwood, M.B., Saito, S., Naruse, H., Kutterolf, S., Scudder, R., Park, J.-O., Moore, G.F. & Slagle, A. 2013. Geochemistry, Geophysics, Geosystems, 14, doi:10.1002/ggge.20107 Clift, P.D., Carter, A., Nicholson, U. & Masago, H. 2013. Tectonics, doi: 10.1002/tect.20033

Pickering, K. T.; Underwood, M.; Moore, G. F.

2013-12-01

150

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

151

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

152

Lateral Drilling and Completion Technologies for Shallow-Shelf Carbonates of the Red River and Ratcliffe Formations, Williston Basin  

Energy Technology Data Exchange (ETDEWEB)

Luff Exploration Company (LEC) focused on involvement in technologies being developed utilizing horizontal drilling concepts to enhance oil- well productivity starting in 1992. Initial efforts were directed toward high-pressure lateral jetting techniques to be applied in existing vertical wells. After involvement in several failed field attempts with jetting technologies, emphasis shifted to application of emerging technologies for drilling short-radius laterals in existing wellbores and medium-radius technologies in new wells. These lateral drilling technologies were applied in the Mississippi Ratcliffe and Ordovician Red River formations at depths of 2590 to 2890 m (8500 to 9500 ft) in Richland Co., MT; Bowman Co., ND; and Harding Co., SD.

David Gibbons; Larry A. Carrell; Richard D. George

1997-07-31

153

Cenozoic stratigraphic development in the north Chilean forearc: Implications for basin development and uplift history of the Central Andean margin  

Science.gov (United States)

Analysis of the Cenozoic stratigraphic development of the forearc of northern Chile between 18°S and 23°30'S, allows constraints to be placed on the timing and nature of basin formation and the uplift history of the Central Andes. Chronostratigraphic charts have been constructed from 20 lithostratigraphic sections distributed throughout the forearc. Sections were taken from the Longitudinal Valley, Central Depression, Calama Basin, Salar de Atacama, Precordillera and the western flank of the Western Cordillera. Correlation and timing of events is largely based on the presence of dated volcanic horizons in all the studied sections. Three chronostratigraphic units are defined based upon the presence of regional unconformities. Deposition of the Late Eocene to Early Miocene chronostratigraphic unit (38-19 Ma) commenced across an irregular unconformity surface between ˜ 38 and 30 Ma with alluvial fan and fluvial sediments derived from the east interbedded with rhyolitic ignimbrites. Aggradation after 25 Ma resulted in development of a large broad basin over much of northern Chile that expanded eastwards through onlap onto basement. Deposition terminated around 19 Ma with the development of an angular unconformity over much, but not all of the study area. During deposition of the Early to Late Miocene chronostratigraphic unit (18-10 Ma) emergent volcanic source areas to the east provided catchments for large fluvial systems that drained westwards into endorheic ephemeral lacustrine basins. Fold growth affected sedimentation restricting accommodation space to small intra-thrust basins in the Precordillera and localised disruption and unconformity development in the Longitudinal Valley. The Late Miocene to present day chronostratigraphic unit (10-0 Ma) followed the development of a regional angular unconformity at 10 Ma. Sedimentation was restricted to a series of thrust-bounded endorheic basins in both the Central Depression and the Precordillera sourced from the east with volcanic activity limited to the periodic eruption of extensive ignimbrite sheets. Alluvial fan, fluvial and lacustrine sedimentation dominated within the endorheic basins from ˜ 8 to 3 Ma. After development of a regional unconformity at 3 Ma a change to isolated evaporite sub-basins took place in the Central Depression with small lacustrine basins developed along the flank of the Western Cordillera. The scale and grain size recorded in the sedimentary systems indicates that a substantial source area was located in the present day area of the Western Cordillera by 30 Ma and that this has persisted to the present day. This area also shed material eastwards into the Altiplano. The presence of such a topographic feature by 30 Ma suggests that a significant proportion of Andean uplift had occurred prior to the Late Miocene. This important uplift phase should be incorporated into any model of Andean uplift. The evidence from the basin-fill succession suggests that sediments accumulated in a basin developed in front of a broad monocline between 38 and 19 Ma and that a transition to a thrust-bounded foreland style basin took place after the development of the unconformity at 19 Ma.

Hartley, Adrian J.; Evenstar, Laura

2010-11-01

154

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

155

The evolution of fluid pressures in the Alberta Basin: implications for secondary migration of petroleum through the Viking Formation  

Energy Technology Data Exchange (ETDEWEB)

A study was conducted in which the significance of different factors that controlled the distribution of petroleum in the Viking Formation of the Alberta Basin were assessed. A cross-sectional numerical model was used to reconstruct the petroleum generation, primary sourcing directions and the fluid pressures for an East-West transect across the Basin during active deposition and subsequent uplift. Heterogeneities within the Viking sandstone played a major role in the development of simulated oil migration pathways. High permeability sands in the Viking Formation permitted long-range migration, while low permeability zones trapped oil close to the mature source region.

Bekele, E.B.; Person, M. [Minnesota Univ., Duluth, MN (United States). Dept. of Geology; Rostron, B.J. [Saskatchewan Univ., Saskatoon, SK (Canada)

1997-09-01

156

Comparison of the Geologic Setting of the South Pole-Aitken Basin Interior with Apollo 16: Implications for Regolith Components  

Science.gov (United States)

The interior of the South Pole-Aitken Basin (SPA) contains ancient cratered terrain that is possibly remnant of the original interior of the basin. This terrain has been modified by the addition of and mixing with foreign material introduced by later basins and craters of all sizes (lateral and vertical mixing). Since much of our thinking about ancient regolith is based on detailed analysis of samples from one nearside ancient heavily cratered highland site, Apollo 16 (Ap16), it is instructive to compare the interior of SPA with the Ap16 landing site. For this comparison we use a central location within SPA (SPA-1 at 60 deg. S, 160 deg. W). Two models have recently been presented that allow estimation of the amount of original SPA interior material likely to remain in the regolith of SPA. Although the details of each model are different, results consistently range from 50-82% original material in the regolith. The models also allow the contribution from individual basins to be predicted.

Petro, N. E.; Pieters, C. M.

2004-01-01

157

Middle-Miocene counterclockwise rotation of rocks from west-central Nevada; implications for Basin and Range extension  

Energy Technology Data Exchange (ETDEWEB)

Drilling and geophysical data from Dixie Valley and Fallon Basin of west-central Nevada have shown that dip-slip normal faults accommodated post-Miocene Basin and Range extension in this area, but the presence of an earlier, less-understood phase of Basin and Range deformation is suggested in the adjacent West Humboldt, Stillwater, and Clan Alpine Ranges where the late-Miocene basalts lie in angular unconformity on Oligocene to early-Miocene ash-flow tuffs. Paleomagnetic components obtained from the tuffs and underlying gabbroic and basaltic rocks of the Jurassic Humboldt Lopolith have declinations that are statistically different and counterclockwise from the expected Oligo-Miocene and Jurassic directions for the area. Paleomagnetic components from the late-Miocene basalts statistically overlap their expected direction. These data imply that the rocks were rotated counterclockwise during middle-Miocene. The common association of such rotations with strike-slip faulting suggests that this earlier phase of Basin and Range extension was largely a strike-slip faulting deformation. If so, the total amount of extension in the area may be significantly larger than estimates based solely on the moderate tilts (<30/sup 0/) of the ranges.

Hudson, M.R.; Geissman, J.W.

1985-01-01

158

Heat flow in Railroad Valley, Nevada and implications for geothermal resources in the south-central Great Basin  

Science.gov (United States)

The Great Basin is a province of high average heat flow (approximately 90 mW m-2), with higher values characteristic of some areas and relatively low heat flow (heat sink associated with interbasin water flow in the Paleozoic carbonate aquifers. Evaluating this hypothesis and investigating the thermal state of the Eureka Low at depth is a high priority for the US Geological Survey as it prepares a new national geothermal resource assessment. Part of this investigation is focused on Railroad Valley, the site of the largest petroleum reservoirs in Nevada and one of the few locations within the Eureka Low with a known geothermal system. Temperature and thermal conductivity data have been acquired from wells in Railroad Valley in order to determine heat flow in the basin. The results reveal a complex interaction of cooling due to shallow ground-water flow, relatively low (49 to 76 mW m-2) conductive heat flow at depth in most of the basin, and high (up to 234 mW m-2) heat flow associated with the 125??C geothermal system that encompasses the Bacon Flat and Grant Canyon oil fields. The presence of the Railroad Valley geothermal resource within the Eureka Low may be reflect the absence of deep ground-water flow sweeping heat out of the basin. If true, this suggests that other areas in the carbonate aquifer province may contain deep geothermal resources that are masked by ground-water flow.

Williams, C. F.; Sass, J. H.

2006-01-01

159

Ground-Water Modeling of Pumping Effects near Regional Ground-Water Divides and River/Aquifer Systems in the Great Lakes Basin: Results and Implications of Numerical Experiments.  

Science.gov (United States)

This report presents the results and implications of scenario numerical modeling of ground-water flow near the boundaries of the Great Lakes Basin. Two primary regional aquifer systems were modeled to determine the effects of ground-water withdrawals on t...

R. A. Sheets D. H. Dumouchelle D. T. Feinstein

2005-01-01

160

The Sills of Guaymas Basin, Gulf of California: Implications for Crustal Melt Distribution and Thermogenic Carbon Flux  

Science.gov (United States)

Multi-channel (MCS) and wide-angle seismic data acquired in 2002 reveal the distribution of igneous sills emplaced into sediments and their relationship to the deeper crustal structure of Guaymas Basin, a young (Guaymas Basin is new igneous crust that is essentially oceanic. However, as a consequence of high sedimentation rates (1-2 km/m.y.), it does not have a typical oceanic Layer 2, but instead has an upper layer of intercalated sediments and igneous intrusions. The MCS data reveal shallow (i.e. recent) sills up to 50 km away from the ~200-m-deep seafloor grabens that delineate the two spreading segments of Guaymas Basin, with no systematic relationship between sill depth and distance from the grabens. For example, sills 42 km away from the graben (1.75 m.y. spreading age) lie beneath only 50 m (or 50 k.y.) of undisturbed sediments. Thus, ongoing sill emplacement is distributed over tens of km relative to the kinematic plate boundary, and the grabens do not mark the locus of focused shallow magmatic emplacement. This implies that the distribution of deeper melt is correspondingly broad, consistent with the deeper velocity structure. Magmatic emplacement in this and perhaps other young, sedimented rift system is thus substantially different from that of unsedimented mid-ocean ridges, where hydrothermal circulation tends to focus magmatic accretion to within <10 km of the ridge axis. The MCS data also reveal 50- to 150-m-thick regions of intense sediment disruption above intruded sills. These regions probably indicate induration from alteration processes accompanying sill intrusion, including the release of thermogenic methane and carbon dioxide. New sills appear to be emplaced at the boundary between high porosity uppermost sediments and the more dense indurated sediments. Active sill intrusion over a much broader region than previously thought greatly increases the predicted carbon flux into the ocean and atmosphere from this and similarly sedimented rift basins.

Lizarralde, D.; Soule, S. A.; Seewald, J. S.; Kent, G. M.; Harding, A. J.; Holbrook, W. S.; Umhoefer, P. J.; Axen, G. J.; Fletcher, J. M.; F, A. G.

2007-12-01

 
 
 
 
161

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

162

Eocene fluvial drainage patterns and their implications for uranium and hydrocarbon exploration in the Wind River Basin, Wyoming  

International Nuclear Information System (INIS)

Paleocurrent maps of the fluvial lower Eocene Wind River Formation in the Wind River Basin of central Wyoming define promising uranium- and hydrocarbon-exploration target areas. The Wind River Formation is thought to have the greatest potential for uranium mineralization in areas where it includes arkosic channel sandstones derived from the granitic core of the Granite Mountains, as in the channel-sandstone bodies deposited in Eocene time by a 40-kilometer segment of the eastward-flowing paleo-Wind River that exended westward from near the town of Powder River on the east edge of the basin. Channel-sandstone bodies with a Granite Mountains source occur south of this segment of the paleo-Wind River and north of the Granite Mountains. The southwestern part of this area includes the Gas Hills uranium district, but the channel-sandstone bodies between the Gas Hills district and the 40-kilometer segment of the paleo-Wind River may also be mineralized. This area includes the southeasternmost part of the Wind River Basin southeast of Powder River and contains northeasterly trending channel-sandstone bodies derived from the Granite Mountains. Limited paleocurrent information from the margins of the Wind River Basin suggests that the paleo-Wind River in Paleocene time flowed eastward and had approximately the same location as the eastward-flowing paleo-Wind River of Eocene time. The channel-sandstone bodies of the paleo-Wind Rivers are potential hydrocarbon reservoirs, particularly where they are underlain or overlain by the organic-rich shale and siltstone of the Waltman Shale Member of the Fort Union Formation. If leaks of sulfur-containing gas have created a reducing environment in the Eocene paleo-Wind River channel-sandstone bodies, then I speculate that the areas of overlap of the channel-sandstone bodies and natural-gas fields in the underlying rocks may be particularly favorable areas in which to search for uranium deposits

1978-01-01

163

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 is developed. A first order check of the results is performed by comparison with the results of a recent global Cenomanian CCSM3 run from which boundary and initial condi...

2010-01-01

164

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

2011-01-01

165

Eocene fluvial drainage patterns and their implications for uranium and hydrocarbon exploration in the Wind River Basin, Wyoming  

International Nuclear Information System (INIS)

Paleocurrent maps of the fluvial early Eocene Wind River Formation in the Wind River Basin of central Wyoming define promising uranium and hydrocarbon exploration target areas. The Wind River Formation is thought to have the greatest potential for uranium mineralization in areas where it includes arkosic channel sandstones derived from the granitic core of the Granite Mountains as in the channel sandstones deposited by the 25-mile segment of the Eocene Wind River extending westward from near the town of Powder River on the east edge of the basin. Channel sandstones with a Granite Mountain source occur south of this segment of the Eocene Wind River and north of the Granite Mountains. The southwestern part of this area includes the Gas Hills uranium district but channel sandstones between the Gas Hills district and the 25-mile segment of the Eocene Wind River are potentially mineralized. This area includes the entire southeasternmost part of the Wind River Basin southeast of Powder River and contains northeasterly trending channel sandstones derived from the Granite Mountains. Limited paleocurrent information from the margins of the Wind River Basin suggests that the Paleocene Wind River flowed eastward and had approximately the same location as the eastward-flowing Eocene Wind River. If leaks of sulfur-containing gas have created a reducing environment in the Eocene Wind River channel sandstones, then I speculate that the areas of overlap of the channel sandstones and natural gas fields in the underlying rocks may be particularly favorable areas in which to search for uranium deposits. The channel sandstones of the Paleocene and Eocene Wind Rivers are potential hydrocarbon reservoirs, particularly where underlain or overlain by the organic-rich shale and siltstone of the Waltman Shale Member of the Fort Union Formation

1975-01-01

166

Geologic implications of large-scale trends in well-log response, northern Green River Basin, Wyoming  

International Nuclear Information System (INIS)

Well-log response in lower Tertiary and Upper Cretaceous rocks in the northern Green River basin, Wyoming, is examined. Digitally recorded well-log data for selected wells located throughout the basin were processed by computer and displayed as highly compressed depth-scale plots for examining large-scale geologic trends. Stratigraphic units, formed under similar depositional conditions, are distinguishable by differing patterns on these plots. In particular, a strong lithologic contrast between Tertiary and underlying Upper Cretaceous non-marine clastic rocks is revealed and correlated through the study area. Laboratory analysis combined with gamma-ray spectrometry log data show that potassium feldspars in the arkosic Tertiary sandstones cause the contrast. The nature and extent of overpressuring has been examined. Data shift on shale conductivity and shale acoustic transit-time plots, previously ascribed to changes in pore pressure, correspond to stratigraphic changes and not necessarily with changes in pore pressure as indicated by drilling-mud weights. Gulf Coast well-log techniques for detecting overpressuring are unreliable and ineffectual in this basin, which has experienced significantly different geologic depositional and tectonic conditions

1986-01-01

167

Evidence of lacustrine sedimentation in the Upper Permian Bijori Formation, Satpura Gondwana basin: Palaeogeographic and tectonic implications  

Energy Technology Data Exchange (ETDEWEB)

The Upper Permian Bijori Formation of the Satpura Gondwana basin comprising fine- to coarse-grained sandstone, carbonaceous shale/mudstone and thin coal bands was previously interpreted as the deposits of meandering rivers. The present study documents abundance of wave ripples, hummocky and swaley cross-stratification and combined flow bedforms in the Bijori Formation, suggesting that a significant part of the formation was deposited in a wave-agitated environment. Evidence of near-emergent depositional conditions provided by repeated occurrence of rootlet beds and hydromorphic paleosols, local flooding surfaces denoting rapid fluctuation of water level, occurrences of temnospondyl vertebrate fossils, and absence of tidal signatures and marine fossils suggest a lacustrine rather than marine depositional regime. The lack of documented contemporaneous lacustrine or marine sediments in the Satpura Gondwana basin posed a major problem of basin-scale palaeogeographic reconstruction. The existence of Bijori lake solves the problem and the lake is inferred to have acted as repository for the contemporaneous alluvial drainage. Development of the large Bijori lake body implies generation of accommodation space exceeding the rate of sediment supplied and thus represents locus of high tectonic subsidence. Transition of fluvial sediments with red mudstone and calcareous soil profile in the lower part of the succession to carbonaceous shale and coal-bearing lacustrine sediments in the upper part, denote a change from a warm semi-arid climate with seasonal rainfall to a more humid one.

Chakraborty, T.; Sarkar, S. [Indian State Institute, Calcutta (India). Geological Studies Unit

2005-06-01

168

Magnetostratigraphy of drill-core SG-1b in the western Qaidam Basin (NE Tibetan Plateau) and tectonic implications  

Science.gov (United States)

The Qaidam Basin is an ideal archive to study long-term climate and erosion histories at the NE Tibetan Plateau. We present a magnetostratigraphic study of the 723 m deep drill-core SG-1b of lacustrine sediments at the Jianshan anticline in the western Qaidam Basin. The polarity sequence shows 18 normal and 19 reverse polarity zones which can be readily correlated with chrons C1n-C3Br of the Geomagnetic Polarity Time Scale 2004 (GPTS 2004), dating the core at about 7.3-1.6 Ma. The resulting mean sediment accumulation rate (SAR) between polarity boundaries ranges from 6.5 to 30.4 cm ka-1. High SARs occur within the intervals of >7.3-6.0, 5.2-4.2 and 3.6-2.6 Ma indicating three episodic phases of higher erosion. From the derived variation of SARs and previous results, we conclude that growth strata at the Jianshan anticline started to develop at ˜1.6 Ma by limb rotation. All this we relate to pulse tectonic uplift of the NE Tibetan Plateau and fault-propagation-folding in the Qaidam Basin.

Zhang, Weilin; Appel, Erwin; Fang, Xiaomin; Song, Chunhui; Setzer, Fabian; Herb, Christian; Yan, Maodu

2014-04-01

169

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

1995-10-01

170

Hydrocarbon-related diagenetic zones (HRDZs) in the Vulcan Sub-basin, Timor Sea: Recognition and exploration implications  

Energy Technology Data Exchange (ETDEWEB)

The Vulcan Sub-basin is located in the Timor Sea north west of the coast of Western Australia. In some areas of the Basin the shallow marine sandstones of the Eocene Grebe Formation are very strongly cemented with carbonate. Some studies from the US Gulf Coast and the North Sea show that surficial and near surface carbonate cementation is commonly associated with the oxidation of migrating hydrocarbons. Similar cementation observed in the Vulcan Sub-basin was thought to also be due to hydrocarbon oxidation. This paper outlines an investigation of the cemented zones within the Grebe Formation using isotopic, geochemical, mineralogical and petrologic techniques. The results have been integrated with regional geochemical `sniffer` and seismic data, and the origin and significance of the zones determined. The study established a causal relationship between the presence of these Hydrocarbon-Related Diagenetic Zones (or HRDZs) in the Eocene sandstones and Tertiary-Quaternary hydrocarbon seepage. It may be possible to determine, from the integration of seismic structural mapping and the characterisation of the seismic expression of the HRDZs, not only whether an individual structure is ever likely to have had a hydrocarbon column, but whether that column is likely to be preserved. 4 tabs., 18 figs., 63 refs.

O`Brien, G.W. [Australian Geological Survey Organisation, Canberra, ACT (Australia); Woods, E.P. [Norcen International Ltd., North Sydney, NSW (Australia); Juodvalkis, A.; Donaldson, I. (BHP Petroleum, Melbourne, VIC (Australia)); Woodhouse, G. (BHP Petroleum, Melbourne, VIC (Australia)); MIM Holdings Limited, Brisbane, Qld (Australia); SAGASCO Resource Ltd., Adelaide, SA (Australia); Heady, R. (Australian National Univ., Canberra, ACT (Australia). Research School of Biological Sciences)

1995-12-31

171

Paleoceanographic and paleoclimatic controls on ooid mineralogy of the Smackover Formation, Mississippi salt basin: Implications for Late Jurassic seawater composition  

Energy Technology Data Exchange (ETDEWEB)

The Late Jurassic Smackover Formation in the Mississippi salt basin consists of two 150 m thick shoaling-upward cycles, each capped by ooid grainstones. During deposition of the lower cycle, originally calcite ooids formed on the seaward side of the basin and former aragonite ooids were precipitated on the landward side. In the upper cycle, originally calcite ooids were precipitated on both the seaward and the landward sides of the basin. Because kinetic variables are incapable of totally preventing aragonite formation the authors suggest that Smackover calcite ooids were precipitated from seawater with low carbonate saturation state (possibly undersaturated relative to aragonite). The shift from seaward calcite to landward aragonite ooids in the lower cycle was controlled by a shoreward increase in seawater salinity. The net effect of the salinity gradient was a landward increase in seawater salinity. The net effect of the salinity gradient was a landward increase in the carbonate saturation state in response to decreasing dissolved CO[sub 2] and increasing CO[sub 3][sup 2[minus

Heydari, E.; Moore, C.H. (Louisiana State Univ., Baton Rouge, LA (United States))

1994-01-01

172

Southeastern extension of the Lake Basin fault zone in south-central Montana: implications for coal and hydrocarbon exploration  

Energy Technology Data Exchange (ETDEWEB)

The Lake Basin fault zone, which is the eastern extension of the Lewis and Clark line, is a structural lineament extending west-northwest across central Montana and consists mainly of en echelon northeast-striking normal faults that have been interpreted to be surface expressions of left-lateral movement along a basement wrench fault. Information gathered from recent field mapping of coal beds and from shallow, closely-spaced drill holes resulted in detailed coal bed correlations, which revealed another linear zone of en echelon faulting directly on the extended trend of the Lake Basin fault zone. This faulted area, referred to as the Sarpy Creek area, is located 30 mi east of Hardin, Montana. It is about 10 mi long, 8 mi wide, and contains 21 en echelon normal faults that have an average strike of N 63/sup 0/ E. The authors therefore extend the Lake Basin fault zone 20 mi farther southeast than previously mapped to include the Sarpy Creek area. The Ash Creek oil field, Wyoming, 60 mi due south of the Sarpy Creek area, produces from faulted anticlinal structures that have been interpreted to be genetically related to the primary wrench-fault system known as the Nye-Bowler fault zone. The structural similarities between the Sarpy Creek area and the Ash Creek area indicate that the Sarpy Creek area is a possible site for hydrocarbon accumulation.

Robinson, L.N.; Barnum, B.E.

1986-04-01

173

Southeastern extension of the Lake Basin fault zone in south- central Montana: implications for coal and hydrocarbon exploration ( USA).  

Science.gov (United States)

The Lake Basin fault zone consists mainly of en echelon NE-striking normal faults that have been interpreted to be surface expressions of left-lateral movement along a basement wrench fault. Information gathered from recent field mapping of coal beds and from shallow, closely-spaced drill holes resulted in detailed coal bed correlations, which revealed another linear zone of en echelon faulting directly on the extended trend of the Lake Basin fault zone. This faulted area, referred to as the Sarpy Creek area, is located 48 km E of Hardin, Montana. It is about 16 km long, 13 km wide, and contains 21 en echelon normal faults that have an average strike of N 63oE. We therefore extend the Lake Basin fault zone 32 km farther SE than previously mapped to include the Sarpy Creek area. The Ash Creek oil field, Wyoming, 97 km due S of the Sarpy Creek area, produces from faulted anticlinal structues that have been interpreted to be genetically related to the primary wrench-fault system known as the Nye-Bowler fault zone. The structural similarities between the Sarpy Creek area and the Ash Creek area indicate that the Sarpy Creek area is a possible site for hydrocarbon accumulation.-from Authors

Robinson, L. N.; Barnum, B. E.

1986-01-01

174

Geochemical and isotopic characterization of the Bodélé Depression dust source and implications for transatlantic dust transport to the Amazon Basin  

Science.gov (United States)

The Bodélé Depression (Chad) in the central Sahara/Sahel region of Northern Africa is the most important source of mineral dust to the atmosphere globally. The Bodélé Depression is purportedly the largest source of Saharan dust reaching the Amazon Basin by transatlantic transport. Here, we have undertaken a comprehensive study of surface sediments from the Bodélé Depression and dust deposits (Chad, Niger) in order to characterize geochemically and isotopically (Sr, Nd and Pb isotopes) this dust source, and evaluate its importance in present and past African dust records. We similarly analyzed sedimentary deposits from the Amazonian lowlands in order to assess postulated accumulation of African mineral dust in the Amazon Basin, as well as its possible impact in fertilizing the Amazon rainforest. Our results identify distinct sources of different ages and provenance in the Bodélé Depression versus the Amazon Basin, effectively ruling out an origin for the Amazonian deposits, such as the Belterra Clay Layer, by long-term deposition of Bodélé Depression material. Similarly, no evidence for contributions from other potential source areas is provided by existing isotope data (Sr, Nd) on Saharan dusts. Instead, the composition of these Amazonian deposits is entirely consistent with derivation from in-situ weathering and erosion of the Precambrian Amazonian craton, with little, if any, Andean contribution. In the Amazon Basin, the mass accumulation rate of eolian dust is only around one-third of the vertical erosion rate in shield areas, suggesting that Saharan dust is "consumed" by tropical weathering, contributing nutrients and stimulating plant growth, but never accumulates as such in the Amazon Basin. The chemical and isotope compositions found in the Bodélé Depression are varied at the local scale, and have contrasting signatures in the "silica-rich" dry lake-bed sediments and in the "calcium-rich" mixed diatomites and surrounding sand material. This unexpected finding implies that the Bodélé Depression material is not "pre-mixed" at the source to provide a homogeneous source of dust. Rather, different isotope signatures can be emitted depending on subtle vagaries of dust-producing events. Our characterization of the Bodélé Depression components indicate that the Bodélé "calcium-rich" component, identified here, is most likely released via eolian processes of sand grain saltation and abrasion and may be significant in the overall global budget of dusts carried out by the Harmattan low-level jet during the winter.

Abouchami, Wafa; Näthe, Kerstin; Kumar, Ashwini; Galer, Stephen J. G.; Jochum, Klaus Peter; Williams, Earle; Horbe, Adriana M. C.; Rosa, João W. C.; Balsam, William; Adams, David; Mezger, Klaus; Andreae, Meinrat O.

2013-10-01

175

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

176

Horizontal degasification and characterization of coals in the Sabinas Sub-basin, Mexico: implications for CBM production  

Energy Technology Data Exchange (ETDEWEB)

The Sabinas sub-basin in northern Mexico contains gassy coals in the Upper Cretaceous Los Olmos Formation, based on both historical evidence and current desorption testing. The 'Double Seam' coal is present at shallow depth (< 500 m), has high vitrinite content (> 86 vol%), is well-cleated, shows high diffusivity (average tau) value is 56 hours) and has high natural fracture permeability (> 30 mD) in the minesites. The coal averages 2.2 m in thickness but has a high ash content (32 wt%). A tonstein band is present in the middle of the Double Seam, consisting of vitrinite and inertinite embedded in a matrix of fine clays and quartz. Average desorbed gas content of this medium-volatile bituminous coal (Ro{sub max} = 1.30%) is highest in Mine V (Esmeralda Mine at > 9.0 cm{sup 3}/g). Maximum methane adsorption at an equivalent depth of 300 m is 15 cm{sup 3}/g (as-received basisarb). Coal bed methane is mainly methane (98%) with heating value of 38.21 MJ/m{sup 3} (1026 Btu/ft{sup 3}). The coal is under-pressured and reported to be dry, with possibly free gas in the cleat/fracture system and absence of discrete mineralization. In-seam horizontal drilling prior to longwall mining has resulted in the significant reduction of in-situ gas contents and in an increase of mined coal production per shift. The Sabinas sub-basin coals are suitable for a full-scale coal bed methane (CBM) development using in-seam single horizontal and multi-lateral horizontal drilling. Similarities, but also differences, exist between the Sabinas coals in Mexico and the same coals in the Maverick Basin, Texas.

Gentzis, T.; Murray, K.; Klinger, R.; Santillan, M. [CDX Canada Co., Calgary, AB (Canada)

2006-09-15

177

Impact of Heterogeneity on Flow in Fluvial-Deltaic Reservoirs: Implications for the Giant ACG field, south Caspian Basin  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract The Azeri, Chirag and Gunashli (ACG) oilfield is located in the offshore Azerbaijan sector of the south Caspian Basin~ This dissertation focuses on the Azeri Field which has over 8 billion barrels of oil in place. The major reservoir interval is the Pliocene Pereriv Suite, which is characterized by laterally continuous layers of variable net-to-gross (NTG) deposited in a fluvial-deltaic environment. The Azeri Field is being developed by both down-dip water injection and up-dip gas in...

Choi, Kevin

2011-01-01

178

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

Science.gov (United States)

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

179

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

Directory of Open Access Journals (Sweden)

Full Text Available 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.  

Lauren J. Chapman

2011-10-01

180

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

 
 
 
 
181

In situ stress analysis in the northern Newark Basin: Implications for induced seismicity from CO2 injection  

Science.gov (United States)

present detailed stress analysis in a deep well drilled in the northern Newark Rift Basin and evaluate the risk of induced seismicity for underground fluid injection at the locality. In situ stress orientation and magnitudes were estimated using quantitative analysis and modeling of borehole breakouts identified in high-resolution wellbore images. The distribution of breakouts and natural fractures in the well suggests significant variability in orientation of the principal horizontal stresses in the depth range of 450-1450 m. Evidence from surface seismic reflection imaging indicates potential presence of faults at about 800 m and 1200 m that bound zones of distinctly different stress orientation at this locality. Stability of natural fractures and faults under injection conditions was evaluated for a range of potential stress magnitudes and the observed stress variability with depth. Shallow crust above ~800 m appears to be critically stressed under ambient conditions, and further pore pressure increase would put it at risk of frictional failure on favorably oriented fractures and faults. Deeper reservoirs, however, may allow over 10 MPa increase in pore pressure without fault reactivation due to a more relaxed state of stress. Additional in situ test data are needed to more accurately constrain the magnitude of the minimum horizontal stress in the basin and to enable a more complete assessment of the induced seismic risk from potential CO2 injection in the region.

Zakharova, Natalia V.; Goldberg, David S.

2014-03-01

182

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

Directory of Open Access Journals (Sweden)

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

183

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

Directory of Open Access Journals (Sweden)

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 is developed. A first order check of the results is 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 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 be 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 can have enhanced primary production during OAE2. A low sea level in the pre-OAE scenario can inhibit large scale black shale formation, as can the opening of the Equatorial Atlantic Seaway in the post-OAE scenario.

R. P. M. Topper

2010-10-01

184

Chronostatigraphic basin framework for Palaeoproterozoic rocks (1730-1575 Ma) in northern Australia and implications of base-metal mineralisation  

International Nuclear Information System (INIS)

The new chronostratigraphic subdivision for Palaeoproterozoic rocks of northern Australia provides an improved framework for future resource exploration. The nine supersequence boundaries identified in the ca 1730-1575Ma Calvert and Isa Superbasins enable the timing of major tectonic events and their stratigraphic response to be better understood. Third- and 4th-order sequence boundaries facilitate the determination of stratigraphic architecture, ultimately providing the necessary information for constraining the flow of fluids in these basins. SHRIMP zircon ages are essential for determining the magnitude of depositional hiatuses at supersequence and some sequence boundaries, and together with palaeomagnetic data provide independent age constraints for the sequence interpretations. Pb/Pb model ages for the world class Broken Hill, Mt Isa, McArthur River and Century Zn Pb Ag deposits coincide with tectonic events recorded at the Gun, Loretta, River Supersequence boundaries and the superbasin boundary formed during closure of the Isa Superbasin during D2 at Mt Isa. The coincidence of a Pb/Pb model age for Broken Hill with an apparent polar wander path inflection at the Gun Supersequence boundary indicates that the regional chronostratigraphic basin framework developed for northern Australia is applicable to rocks of similar age elsewhere in Australia. Furthermore, if the ultimate cause of these inflections is interplate stress, the basin framework should be globally applicable. Hand-held spectrometers provide an efficient and cost-effective method for collecting gamma-ray data from outcrops. The resulting gamma-ray curves permit more accurate correlation with subsurface stratigraphies and together with facies information facilitate the identification of stratigraphic sequences and their bounding stratal surfaces, the essential building blocks of regional chronostratigraphic correlations. Contrary to general belief most of the sections measured in this study preserve their original gamma-ray signal and are not significantly altered by K-metasomatism, fluid-flow events. The absence of these overprints from the regional datasets suggests a local distribution for the fluids responsible for K-metasomatism. Copyright (2000) Geological Society of Australia

2000-06-01

185

Assessing Potential Implications of Climate Change for Long-Term Water Resources Planning in the Colorado River Basin, Texas  

Science.gov (United States)

While much of the focus on climate change impacts to water resources in the western United States has been related to snow-dominated watersheds, lower elevation basins such as the Colorado River Basin in Texas are dependent on rainfall as the predominant form of precipitation and source of supply. Water management in these basins has evolved to adapt to extreme climatic and hydrologic variability, but the impact of climate change is potentially more acute due to rapid runoff response and subsequent greater soil moisture depletion during the dry seasons. The Lower Colorado River Authority (LCRA) - San Antonio Water System (SAWS) Water Project is being studied to conserve water, develop conjunctive groundwater supplies, and capture excess and unused river flows to meet future water needs for two neighboring regions in Texas. Agricultural and other rural water needs would be met on a more reliable basis in the lower Colorado River Basin through water conservation, surface water development and limited groundwater production. Surface water would be transferred to the San Antonio area to meet municipal needs in quantities still being evaluated. Detailed studies are addressing environmental, agricultural, socioeconomic, and engineering aspects of the project. Key planning activities include evaluating instream flow criteria, water quality, bay freshwater inflow criteria, surface water availability and operating approaches, agricultural conservation measures, groundwater availability, and economics. Models used to estimate future water availability and environmental flow requirements have been developed largely based on historical observed hydrologic data. This is a common approach used by water planners as well as by many regulatory agencies for permit review. In view of the project's 80-yr planning horizon, contractual obligations, comments from the Science Review Panel, and increased public and regulatory awareness of climate change issues, the project team is exploring climate change projections and methods to assess potential impacts over the project's expected life. Following an initial qualitative risk assessment, quantitative climate scenarios were developed based on multiple coupled atmosphere-ocean general circulation model (AOGCM) simulations under a range of global emission scenarios. Projected temperature and precipitation changes were evaluated from 112 downscaled AOGCM projections. A Four scenarios were selected for detailed hydrologic evaluations using the Variable Infiltration Capacity (VIC) macroscale model. A quantile mapping procedure was applied to map future climatological period change statistics onto the long-term natural climate variability in the observed record. Simulated changes in runoff, river flow, evaporation, and evapotranspiration are used to generate adjustments to historical hydrology for assessment of potential changes to surface water availability, river water quality, riverine habitat, and Bay health. Projected temperature, precipitation, and atmospheric CO2 concentrations are used to estimate changes in agricultural demand. Sea level rise scenarios that include trends in Gulf Coast shelf subsidence are combined with changes in inflows to evaluate increased coastal erosion, upland migration of the estuary, and changes to the salinity regime. Results of the scenario-based analyses are being considered in the development of adaptive management strategies for future operations of the system and the proposed project.

Munevar, A.; Butler, S.; Anderson, R.; Rippole, J.

2008-12-01

186

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 (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

187

Re-Os Isotopic age Constraints on Deposition in the Neoproterozoic Amadeus Basin: Implications for the "Snowball Earth"  

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Re-Os isotopes have been measured on organic-rich sediments from the Neoproterozoic Aralka Formation in the Amadeus Basin, central Australia. These sediments closely predate the Marinoan glaciation, a correlative of the global "Snowball II" event. The Aralka formation sediments preserve an isochronous relationship defining an age of 592 +/- 14 Ma, which is interpreted to represent the age of deposition. This age is substantially younger than that inferred from global correlation studies. It indicates that the onset, duration and cessation of the glacial event, and subsequent deposition of >2km of sediment prior to radiation of the earliest metazoan life assemblages is confined to ca. 40 Myr. Our findings imply that the Terminal Proterozoic glaciations were of rapid onset and short duration.

Schaefer, B. F.; Burgess, J. M.

2001-12-01

188

The Lower Cretaceous in sedimentary basins of the Brazil south-eastern border: isotopic analysis and their paleoecological implications  

International Nuclear Information System (INIS)

Carbon isotope data of bitumen, and carbon and oxygen isotope data of limestone provided additional knowledge to the sedimentation environment of the Lower Cretaceous sedimentary sequences of Campos and Espirito Santo basins. In the Buracica stage the carbon isotope data of bitumen suggest a deposition in fresh water lake. The isotope data of bitumen and limestone from lower and middle section of Jiquia stage could indicate a sedimentation in fresh water lake but gradually more saline on the top. More positive ? 13C values of limestone in the upper portion of the Jiquia stage and in the Alagoas stage suggest a restrict marine environment or deposition in hippersaline lakes. During the Albian, the carbonate sedimentation could have occurred still in a marine environment and above normal salinity. According to ? 18O data, the surface waters were warm, with a tendency to become gradually cooler towards the top of Albian. (author)

1987-01-01

189

Multiscale variability of sediment load and streamflow of the lower Yangtze River basin: Possible causes and implications  

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SummaryLong monthly streamflow and sediment load series observed at the Datong station located in the lower Yangtze River basin were analyzed using the scanning t-test, F-test and coherency analysis techniques. The results indicated that: (1) different changing properties of the first and the second moments of the hydrological series on different time scales were observed, reflecting different driving factors influencing the hydrological processes of the lower Yangtze River basin; (2) a generally decreasing trend can be identified after the mid-1980s. Significant abrupt changes in sediment load were analyzed in the sediment load series. However, more complicated changing patterns can be observed in the changes in streamflow. Generally decreasing sediment load and increasing streamflow gave rise to anti-phase relations between sediment load and the streamflow on longer time scales. In-phase relations between sediment load and streamflow on shorter time scales may imply a considerable influence of the hydrological dynamics on sediment transport; and (3) human activities, particularly the construction of water storage reservoirs, exerted a massive influence on sediment load variations. Construction of a large amount of water reservoirs on the tributaries of the Yangtze River and the Gezhouba Dam on the mainstem of the Yangtze River seem to be the main factors responsible for abrupt changes in the sediment load. Construction of the Three Gorges Dam causes a sharp decrease and unstable variability in sediment load variations, which may pose new challenges for the ecological environment conservation and the deltaic management of the Yangtze Delta region.

Zhang, Qiang; Xu, Chong-Yu; Singh, V. P.; Yang, Tao

2009-04-01

190

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

191

Paleomagnetic and paleoenvironmental implications of magnetofossil occurrences in late Miocene marine sediments from the Guadalquivir Basin, SW Spain.  

Science.gov (United States)

Although recent studies have revealed more widespread occurrences of magnetofossils in pre-Quaternary sediments than have been previously reported, their significance for paleomagnetic and paleoenvironmental studies is not fully understood. We present a paleo- and rock-magnetic study of late Miocene marine sediments recovered from the Guadalquivir Basin (SW Spain). Well-defined paleomagnetic directions provide a robust magnetostratigraphic chronology for the two studied sediment cores. Rock magnetic results indicate the dominance of intact magnetosome chains throughout the studied sediments. These results provide a link between the highest-quality paleomagnetic directions and higher magnetofossil abundances. We interpret that bacterial magnetite formed in the surface sediment mixed layer and that these magnetic particles gave rise to a paleomagnetic signal in the same way as detrital grains. They, therefore, carry a magnetization that is essentially identical to a post-depositional remanent magnetization, which we term a bio-depositional remanent magnetization. Some studied polarity reversals record paleomagnetic directions with an apparent 60-70 kyr recording delay. Magnetofossils in these cases are interpreted to carry a biogeochemical remanent magnetization that is locked in at greater depth in the sediment column. A sharp decrease in magnetofossil abundance toward the middle of the studied boreholes coincides broadly with a major rise in sediment accumulation rates near the onset of the Messinian salinity crisis (MSC), an event caused by interruption of the connection between the Mediterranean Sea and the Atlantic Ocean. This correlation appears to have resulted from dilution of magnetofossils by enhanced terrigenous inputs that were driven, in turn, by sedimentary changes triggered in the basin at the onset of the MSC. Our results highlight the importance of magnetofossils as carriers of high-quality paleomagnetic and paleoenvironmental signals even in dominantly terrigenous sediments. PMID:24624124

Larrasoaña, Juan C; Liu, Qingsong; Hu, Pengxiang; Roberts, Andrew P; Mata, Pilar; Civis, Jorge; Sierro, Francisco J; Pérez-Asensio, José N

2014-01-01

192

Paleomagnetic and paleoenvironmental implications of magnetofossil occurrences in late Miocene marine sediments from the Guadalquivir Basin, SW Spain  

Directory of Open Access Journals (Sweden)

Full Text Available Although recent studies have revealed more widespread occurrences of magnetofossils in pre-Quaternary sediments than has been previously reported, their significance for paleomagetic and paleoenvironmental studies is not fully understood. We present a paleo- and rock-magnetic study of late Miocene marine sediments recovered from the Guadalquivir Basin (SW Spain. Well-defined paleomagnetic directions provide a robust magnetostratigraphic chronology for the two studied sediment cores. Rock magnetic results indicate the dominance of intact magnetosome chains throughout the studied sediments. These results provide a link between the highest-quality paleomagnetic directions and higher magnetofossil abundances. We interpret that bacterial magnetite formed in the surface sediment mixed layer and that these magnetic particles gave rise to a paleomagnetic signal in the same way as detrital grains. They, therefore, carry a magnetization that is essentially identical to a post-depositional remanent magnetization and that we term a bio-depositional remanent magnetization (BDRM. Some studied polarity reversals record paleomagnetic directions that appear to be delayed by 60-70 kyr. Magnetofossils in these cases are interpreted to carry a biogeochemical remanent magnetization (BGRM that is locked in at greater depth in the sediment column. A sharp decrease in magnetofossil abundance toward the middle of the studied boreholes broadly coincides with a major rise in sediment accumulation rates near the onset of the Messinian salinity crisis (MSC, an event caused by interruption of the connection between the Mediterranean Sea and the Atlantic Ocean. This correlation appears to have resulted from dilution of magnetofossils by enhanced terrigenous inputs that were driven, in turn, by sedimentary changes triggered in the basin at the onset of the MSC. Our study highlights the importance of magnetofossils as carriers of high-quality paleomagnetic and paleoenvironmental signals.

JuanCruzLarrasoaña

2014-03-01

193

Paleomagnetic and paleoenvironmental implications of magnetofossil occurrences in late Miocene marine sediments from the Guadalquivir Basin, SW Spain  

Science.gov (United States)

Although recent studies have revealed more widespread occurrences of magnetofossils in pre-Quaternary sediments than have been previously reported, their significance for paleomagnetic and paleoenvironmental studies is not fully understood. We present a paleo- and rock-magnetic study of late Miocene marine sediments recovered from the Guadalquivir Basin (SW Spain). Well-defined paleomagnetic directions provide a robust magnetostratigraphic chronology for the two studied sediment cores. Rock magnetic results indicate the dominance of intact magnetosome chains throughout the studied sediments. These results provide a link between the highest-quality paleomagnetic directions and higher magnetofossil abundances. We interpret that bacterial magnetite formed in the surface sediment mixed layer and that these magnetic particles gave rise to a paleomagnetic signal in the same way as detrital grains. They, therefore, carry a magnetization that is essentially identical to a post-depositional remanent magnetization, which we term a bio-depositional remanent magnetization. Some studied polarity reversals record paleomagnetic directions with an apparent 60–70 kyr recording delay. Magnetofossils in these cases are interpreted to carry a biogeochemical remanent magnetization that is locked in at greater depth in the sediment column. A sharp decrease in magnetofossil abundance toward the middle of the studied boreholes coincides broadly with a major rise in sediment accumulation rates near the onset of the Messinian salinity crisis (MSC), an event caused by interruption of the connection between the Mediterranean Sea and the Atlantic Ocean. This correlation appears to have resulted from dilution of magnetofossils by enhanced terrigenous inputs that were driven, in turn, by sedimentary changes triggered in the basin at the onset of the MSC. Our results highlight the importance of magnetofossils as carriers of high-quality paleomagnetic and paleoenvironmental signals even in dominantly terrigenous sediments.

Larrasoana, Juan C.; Liu, Qingsong; Hu, Pengxiang; Roberts, Andrew P.; Mata, Pilar; Civis, Jorge; Sierro, Francisco J.; Perez-Asensio, Jose N.

2014-01-01

194

The economics of irrigated paddy in Usangu Basin in Tanzania: water utilization, productivity, income and livelihood implications  

Science.gov (United States)

Globally, there is a general lack of consensus on how the available water resources can be allocated efficiently and equitably among its competing uses. In irrigated agriculture, this decodes to the central question of how this sector can be balanced in the manner that it produces more ‘crops per drop’ using less water and releasing adequate water for use by other sectors while concurrently enhancing rural income and livelihoods. This requires that the values and costs of irrigated agriculture, at all levels, are well understood and appropriate interventions made. Based on this ground, this paper presents an economic analysis of the value of irrigated paddy in Usangu basin. It attempts to answer the question of what will be the effects if farmers in Usangu stop producing irrigated paddy. The analysis shows that: (a) about 576 mm 3 of water--currently consumed in paddy irrigation, or 345.6 mm 3--traded inter-regionally as “virtual water” would be utilized in alternative ways, either as evaporation from seasonal swamps within the basin or made available for other intersectoral uses, (b) there will be a shrinkage in the annual paddy supply (both at the local and national levels) of about 105,000 t of paddy (66,000 t of rice)-equivalent to 14.4% of the total annual paddy production in Tanzania, (c) an opportunity cost of about US15.9 million will be incurred annually (equivalent to US530.95 per annum per household practicing irrigated paddy in Usangu), and d) the country’s current account of the balance of payments will be affected by an average of US$15.9 million per annum. The effect will either be in form of annual decline in rice exports or increase in imports depending on the country’s supply and demand for rice.

Kadigi, Reuben M. J.; Kashaigili, Japhet J.; Mdoe, Ntengua S.

195

Modern plant-derived terpenoids in an upper Michigan river basin and implications for interpreting the geologic record  

Science.gov (United States)

Di- and triterpenoids are taxonomically specific plant biomarkers, which are produced by conifers and angiosperms, respectively. Because of this source specificity, terpenoids are often used for paleovegetation reconstruction. However, few studies have evaluated weather terpenoid ratios in modern river systems reflect the surrounding plant community. It is likely that various processes that bias terpenoid ratios as they are transported from plants to sediments. To learn more about these important geologic biomarkers, we used a modern fluvial system as an ancient river analog to provide information on the utility of terpenoids as quantitative paleovegetation proxies. Di- and triterpenoid concentrations were quantified in plants, sediments, and particulate and dissolved organic matter in a small river in the Upper Peninsula of Michigan to (1) determine if the contribution of terpenoids from source vegetation is reflected in forested soil and river sediments, and (2) constrain the dispersal of these compounds in fluvial systems. In Miners River drainage basin, evergreen needleleaf conifers are six times less abundant than deciduous broadleaf angiosperms, yet contribute five times more terpenoids to the sediments, when scaled for leaf litter production and present vegetation cover. Thus, using sediment terpenoid ratios alone (ie. no corrections for production differences between major taxonomic groups) to reconstruct vegetation will drastically over represent evergreen conifer populations. Sediment di-/triterpenoid ratios are considerably lower than the expected terpenoid flux from vegetation, suggesting these compounds are preferentially lost between source and sink. In Miners River, terpenoids are transported in the particulate and dissolved organic matter (POM and DOM) fractions of river water. Fluvial transport of terpenoids does not appear to influence river sediment terpenoid concentrations in fresh water systems, like Miners River, however, transport by POM and DOM may affect terpenoid concentrations in estuarine and marine sediments. Despite the challenges of using terpenoids as paleovegetation proxies, when corrected for plant production, basin-wide terpenoid concentrations are useful in predicting the present plant community composition (based on plant census data) within 10-15%. This study suggests that the sedimentary record of terpenoids can broadly reconstruct paleovegetation, when corrected for differential terpenoid production and transport.

Giri, S.; Diefendorf, A. F.; Lowell, T. V.

2013-12-01

196

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

197

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

198

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

199

Preserved extensional structures in an inverted Cretaceous rift basin, northwestern Argentina: Outcrop examples and implications for fault reactivation  

Science.gov (United States)

During the Cretaceous-Eocene interval a system of intracontinental rift basins, the Salta group rift, evolved in northwestern Argentina. Individual segments of the rift later suffered different degrees of inversion during Cenozoic shortening. The Tres Cruces subbasin, on the west side of the Eastern Cordillera, was strongly deformed, being now part of a thick-skinned thrust belt with a predominantly N-S structural trend. On its eastern border, tilting due to folding and thrusting and subsequent erosion have produced exceptional outcrops of preserved east-trending extensional structures including half grabens, rollover anticlines, and extensional fault-propagation folds. Farther west, the synrift succession is only intermittently exposed, although the interference of north- and east-trending structures as well as peculiar, dome-shaped anticlines with spur-like extensions suggest that north- and east-trending Cretaceous faults were reactivated, particularly near their intersections. Compilation of published data and analysis of our new data focused on the Salta rift indicates three main factors favoring the contractional reactivation of normal faults: dip angles lower than approximately 60°, especially for faults striking roughly normal to contraction; strikes no closer to the contraction direction than approximately 30°; and low downdip fault curvatures. Occasional dip-slip reactivation of east-trending faults does not match the present and long-term Andean stress regimes and presents an unresolved problem.

Monaldi, CéSar R.; Salfity, José A.; Kley, Jonas

2008-02-01

200

Sediment filled fractures in the Permo-Triassic sandstones of the Cheshire Basin: observations and implications for pollutant transport  

Science.gov (United States)

Fracture mapping in a tunnel system and at nearby outcrop on the Runcorn Peninsula, UK, suggests the need for a review of the potential pathways for pollutant transport in Permo-Triassic sandstone aquifers. Sediment infilling is pervasive in the largest sub-vertical multi-layer fractures in the study area, both at the surface and to a depth of about 40 m below ground level. Sediment infill is inferred to have formed in situ. The conventional models of pollutant transport in fracture networks assume that they comprise open fractures, with pollutant mobility depending on fracture connectivity (a function of density, length, orientation and intersection) and aperture. The presence of extensive sediment fills in fractures will materially change their permeability, thereby reducing pollutant flux, and be of significance in the assessment of risks arising from chemical spillages. There has been little or no substantive evidence for such fills in Permo-Triassic sandstones in the UK, apart from observations at outcrop and anecdotes of sand being pumped from boreholes. Here, we report surface and rare, but complementary, subsurface observations of extensive fills in the Cheshire basin, and argue that they will only act as preferential pathways where they crosscut low-permeability horizons such as mudstones.

Wealthall, Gary P.; Steele, Adrian; Bloomfield, John P.; Moss, Richard H.; Lerner, David N.

2001-07-01

 
 
 
 
201

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 palaeoenvironment. 10 figs., 29 refs

1990-01-01

202

2D Seismic Interpretation of the Tumaco on-and offshore basin, SW Colombia. Implications for tectono-stratigraphic evolution and hydrocarbon exploration  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Tumaco on and offshore basin is located in the Pacific region of NW corner of South America, southwestern Colombia. It is classified as a forearc basin and it is considered a frontier exploration basin. The basin was formed during Paleogene-Recent convergence of oceanic derived terranes against South America. The stratigraphy consists of a volcano-clastic basement overlie by an Eocene to Recent clastic sedimentary cover. The last exploratory well, drilled in the 80’s, showed non-commerc...

Campin?o Restrepo, Luisa Fernanda

2013-01-01

203

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 current test environment. One wave energy converter (WEC was fully instrumented with mooring line load cells, optical motion tracker and accelerometers and tested in regular waves, short- and long-crested irregular waves and current. The wave and current test regimes were measured by six wave probes and a current meter. Arrays of three and five similar WECs, with identical mooring systems, were tested under similar environmental loading with partial monitoring of mooring forces and motions. The majority of loads on the mooring lines appeared to be broadly consistent with both logistic and normal distribution; whilst the right tail appeared to conform to the extreme value distribution. Comparison of the loads at different configurations of WEC arrays suggests that the results are broadly consistent with the hypothesis that the mooring loads should differ. In particular; the results from the tests in short crested seas conditions give an indication that peak loads in a multi WEC array may be considerably higher than in 1-WEC configuration. The test campaign has contributed essential data to the development of Simulink™ and Orcaflex™ models of devices, which include mooring system interactions, and data have also been obtained for inter-tank comparisons, studies of scale effects and validation of mooring system numerical models. It is hoped that this paper will help to draw the attention of a wider scientific community to the dataset freely available from the Marintek website.

Vladimir Krivtsov

2014-04-01

204

Middle Proterozoic mafic magmatism, east central Idaho: Implications for age of deposition of Belt Supergroup and basin subsidence models  

Energy Technology Data Exchange (ETDEWEB)

In the Salmon River Arch, a ca. 1,365 Ma rapikivi granite intrudes the Proterozoic Yellow Jacket Formation, which is commonly correlated with the basal Belt-Purcell Supergroup. The contact aureole of the granite contains andalusite and overprints greenschist-facies burial metamorphism in the undeformed sedimentary strata. To the north, the granite intrudes amphibolite-facies, migmatitic paragneiss and a mafic igneous complex. Textures within the migmatites attest to deformation during partial melting. Preliminary U-Pb zircon data from a quartz diorite that intrudes the Yellowjacket sediments yield an age of ca. 1,445 Ma. This is consistent with zircon ages from the Crossport C and Moyie sills in northern Idaho and southern BC that constrain the basal Belt Supergroup to be older than 1,440 Ma. U-Pb zircon data from an amphibolitized mafic dike within the mafic igneous complex along the Salmon River are nearly concordant and yield Pb/Pb ages of ca. 1,377 Ma. The zircons exhibit skeletal, magmatic morphologies and the age is interpreted to be the time of primary crystallization. This age is slightly older than the age of the rapikivi granite and overlaps with the U-Pb zircon age of leucosomes in the migmatites. Thus, bimodal magmatism and partial melting occurred ca. 1,370 Ma. Deformation accompanied these events, but was concentrated in the deeper level, high-grade rocks. These processes are syn-depositional, based on age constraints from the intrusive quartz diorite. The authors envision that burial metamorphism, deformation, partial melting mafic magmatism and granite emplacement occurred during extensional deformation in the base of the Yellowjacket basin.

Chamberlain, K.R. (Univ. of Wyoming, Laramie, WY (United States). Dept. of Geology and Geophysics); Doughty, P.T. (Queen' s Univ., Kingston, Ontario (Canada). Geological Sciences)

1993-04-01

205

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

206

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

207

A new species of Corydoras Lacépède (Siluriformes: Callichthyidae) from the Rio Tapajós basin and its phylogenetic implications  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Uma nova espécie de Corydoras é descrita dos tributários dos rios Arinos, Teles Pires e Preto, bacia do rio Tapajós. A nova espécie é membro de um grupo com pontilhados no corpo que inclui 36 espécies. Dentro desse grupo, a nova espécie pode ser facilmente distinguida pelo espinho dorsal menor que o [...] s três primeiros raios ramificados da nadadeira dorsal; nadadeiras peitorais, pélvicas e anal hialinas; membranas inter-radiais da nadadeira dorsal hialina; presença de pontilhados redondos no tronco restritas as placas dorsolaterais do corpo e porções dorsais das placas ventrolaterais não alcançando a base das nadadeiras pélvicas e anal. A nova espécie pode ser distinguida de Corydoras xinguensis por pontilhados com margens difusas e das demais espécies de Corydoras com pontilhado, exceto em C.multimaculatus, pela ausência de pequenas placas ventrais. Uma análise filogenética recuperou a nova espécie mais Corydoras metae e C.araguaiensis em um agrupamento compartilhando a presença de um processo pontiagudo para inserção do músculo retractor tentaculi no maxilar. A porção anterior do mesetmóide alongada e o processo uncinado do epibranquial 3 triangular indicam uma relação mais próxima com Corydoras metae. Abstract in english A new species of Corydoras is described from tributaries of the rio Arinos, rio Teles Pires and rio Preto, all in the rio Tapajós basin. The new species is a member of a group that includes 36 species with spots on the body. Within this group, the new species can be readily distinguished by having a [...] smaller dorsal-fin spine than the first three subsequent soft dorsal-fin rays; pectoral, pelvic and anal fins hyaline; dorsal-fin interradial membrane hyaline; rounded spots on trunk restricted to dorsolateral body plates and dorsal portion of ventrolateral body plates, not reaching the base of pelvic and anal fins. The new species can be further distinguished from Corydoras xinguensis by having spots with diffuse edges, and from all other species of spotted Corydoras except C.multimaculatus, by the absence of ventral platelets. A phylogenetic analysis recovered the new species plus Corydoras metae and C.araguaiensis in a clade sharing the presence of a pointed process on the maxilla for insertion of the retractor tentaculi muscle. In addition, the presence in the new species of an elongated anterior portion of the mesethmoid and a triangular uncinate process of the epibranchial 3 suggests a close relationship with Corydoras metae.

Vinicius C., Espíndola; Marcelo R.S., Spencer; Leandro R., Rocha; Marcelo R., Britto.

208

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

209

Flexure of Anadarko basin  

Energy Technology Data Exchange (ETDEWEB)

The Anadarko basin in Oklahoma has long been a major oil and gas producing region and contains the deepest wells drilled in North America. The region has had a long sedimentary-tectonic history reaching back to the Proterozoic and was the site of an early Paleozoic basin. The present shape of the Anadarko basin, however, was developed in late Paleozoic times as a result of the uplift of the Wichita Mountains. COCORP seismic reflection profiles show at least 8 to 9 km (5 to 5.6 mi) of overthrusting northward, and the Anadarko basin was developed as a result of flexural bending of the lithosphere due to this shortening. Down-warping of the basin can be observed to extend for over 300 km (185 mi) northward, indicating a high flexural rigidity (Te > 40 km (25 mi)). However, nearer the Wichita front, the basin steepens rapidly as the post-Mississippian sediments thicken to over 20,000 ft (6100 m). The shape of the bending is such that it cannot be explained by the use of a constant rigidity elastic plate model. We have modeled the post-Mississippian development of the Anadarko basin as the result of flexure of an elastic-plastic plate due to vertical and horizontal loading caused by the Wichita Mountains. Implications of these results for the development of the Anadarko basin and the mechanical properties of continental lithosphere will be discussed.

Steckler, M.S.; Brewer, J.A.

1983-03-01

210

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

1985-01-01

211

Evolution of the Gölba?? basin and its implications for the long-term offset on the East Anatolian Fault Zone, Turkey  

Science.gov (United States)

The left lateral East Anatolian Fault Zone (EAFZ) is one of the most active major neotectonic structures of the Eastern Mediterranean region. The fault zone runs for a distance of about 550 km between Karl?ova in northeast and Mediterranean Sea in southwest. Several fault-parallel basins (such as Hazar and Gölba?? basins) have been forming along the fault zone. The Gölba?? basin is the largest basin along the EAFZ and it is located near the junction of the Çelikhan-Erkenek and Gölba??-Türko?lu segments of the EAFZ. Different interpretations including pull-apart, fault wedge and fault ramp basin were made about the evolution of the basin in previous studies. Detailed mapping shows that the Çelikhan-Erkenek and Gölba??-Türko?lu segments are connected by a releasing bend around Gölba?? Lake. Our study also suggests that Gölba?? basin was a wide river valley in which the Aksu River flowed and occupied by a large lake. The valley was blocked by a large landslide at least 31,600 ± 500 years ago in the northeastern corner of the basin and as a result, the Aksu River was captured to the SW corner of the basin. Our scenario implies that the Aksu River valley is left laterally offset by the EAFZ about 16.5 ± 0.5 km, which is the largest documented morphological offset on the EAFZ.

Yönlü, Önder; Altunel, Erhan; Karabacak, Volkan; Akyüz, H. Serdar

2013-04-01

212

Large-Diameter Visible and Buried Impact Basins on Mars: Implications for age of the Highlands and (Buried) Lowlands and Turn-off of the Global Magnetic Field  

Science.gov (United States)

The global populations of visible and buried impact basins less than 200 km diameter revealed by high resolution gridded MOLA indicate: (a) a small (approx. 10) number of very large basins (D=1300-3000km), most of which have remained visible over martian history; (b) a much larger population of smaller basins (D=200-800 km) with many more buried than visible (on images); (c) a depletion of visible basins at intermediate diameters which may be a signature of some global-scale event (formation of the lowlands? origin of Tharsis?); and (d) a crater retention age for the buried lowlands greater than that of the visible highlands but less than that of the total (visible + buried) highlands. Crustal magnetic anomalies are generally not present in the interiors of the largest basins with two exceptions: these two (which appear to be the oldest) may predate the demise of the global magnetic field.

Frey, Herbert V.

2003-01-01

213

Coal geology, chemical and petrographical characteristics, and implications for coalbed methane development of subbituminous coals from the Sorgun and Suluova Eocene basins, Turkey  

Energy Technology Data Exchange (ETDEWEB)

The Sorgun and Suluova basins contain a thick and extensive Lower Eocene coal seam. The stratigraphy of both basins comprises basement rocks, the Yozgat Granitoid of Pre-Eocene age in the Sorgun basin and Jurassic-Cretaceous limestones in the Suluova basin, overlain unconformably by the coal-bearing Lower Eocene Celtek Formation and by transgressive units of Middle-Upper Eocene age. In the Sorgun basin the Artova Ophiolitic Complex tectonically overlies the transgressive units. Neogene and Quaternary deposits cover all the older units unconformably in both basins. The single coal seam is located at the base of the Celtek Formation and reaches a thickness of 6 m in the open-cast mine at Sorgun and 8 m in boreholes in the Suluova basin. A total of 75 coal samples from both basins were analysed chemically and petrographically. The coals are characterized by a relatively low moisture content, variable ash yields, and huminite contents. Measurements of the mean random reflectance of ulminite vary between 0.46 and 0.60%. These reflectance values and the chemical analyses show that the rank is subbituminous A or transitional to high-volatile bituminous C coal according to the ASTM classification. The coalbed methane potential of both basins is at present unknown. No borehole has been drilled to explore for this resource and no gas capacity value has been obtained for the coal seam and bituminous shales. The methane explosions which have occurred during coal production in the underground mines imply that both basins may have been an important potential for coalbed methane. 24 refs., 8 figs., 3 tabs.

Karayigit, A.I.; Eris, E.; Cicioglu, E. [Hacettepe University, Ankara (Turkey). Dept. of Geological Engineering

1996-08-01

214

Evidence for extension of Lake Basin Fault Zone from coal bed correlations in south-central Montana and implications for hydrocarbon exploration  

Energy Technology Data Exchange (ETDEWEB)

The Lake Basin fault zone is a structural lineament that extends west-northwest across central Montana. The lineament consists mainly of en echelon northeast-striking normal faults that are surface expressions of left-lateral movement along a basement wrench fault. Information gathered from the recent field mapping of coal beds and from shallow, closely spaced drill holes in the northwest part of the Powder River basin, Montana, permit detailed coal bed correlations, which revealed another linear zone of en echelon faulting directly on the extended trend of the Lake Basin fault zone. The faulted area, herein named the Sarpy Creek area, is located 48 km (30 mi) east of Hardin, Montana. It is about 13 km (8 mi) long and 10 km (6 mi) wide and contains 20 en echelon normal faults that have an average strike of N65/sup 0/E. The Lake Basin fault zone is therefore extended 32 km (20 mi) farther southeast than previously mapped to include the Sarpy Creek area. The Lake Basin oil field, Montana, and the Ash Creek oil field, Montana and Wyoming, produce from faulted anticlinal structures that have been interpreted to be genetically related to primary wrench-fault systems-the Lake Basin fault zone and Nye-Bowler fault zone, respectively. Therefore, the faulted area of Sarpy Creek (as yet unexplored), and areas southeastward from there along the trend of the Lake Basin fault zone are possible sites for hydrocarbon accumulation.

Robinson, L.N.; Barnum, B.E.

1985-05-01

215

Groundwater recharge and evolution in the Dunhuang Basin, northwestern China  

International Nuclear Information System (INIS)

ka, indicates that this groundwater was recharged during a humid climatic phases of the late Pleistocence or early Holocene. The results have important implications for inter-basin water allocation programmes and groundwater management in the Dunhuang Basin.

2013-01-01

216

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

217

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

218

Magnetic fabrics in the Jurassic-Cretaceous continental basins of the northern part of the Central High Atlas (Morocco): Geodynamic implications  

Science.gov (United States)

The aim of this work is to study the Anisotropy of the Magnetic Susceptibility (AMS) in two Jurassic-Cretaceous synclines located in the northern border of the Central High Atlas (Morocco): the Aït Attab and Ouaouizaght basins. AMS is used in order to obtain the magnetic fabric and its relationship with the kinematic evolution of both basins. The tectonic evolution of the basins, still under discussion, is mostly considered as the result of inversion during Tertiary and perhaps since Bathonian, of extensional and/or strike-slip Jurassic basins. Both basins are filled with Upper Jurassic to Lower Cretaceous silts and sandstones, with less frequent marine marly limestones. The bulk magnetic susceptibility (km) generally shows higher values in the red facies (163.2 E-6 in AT and 168.6 E-6 in WZ) than in the yellowish marly limestones (97.88 E-6 in AT and 132 E-6 in WZ). Most sites show an oblate magnetic fabric. The rock magnetic analyses indicate that the main carrier of the magnetic susceptibility for the red facies is hematite, whereas in the yellowish facies there is a dominance of paramagnetic minerals. In both basins, the magnetic lineation (long axis of the ellipsoid, kmax axes) shows a predominant E-W direction. The overlapping of the stress fields during the Atlasic basins evolution, in both compressional and extensional regimes and hinder the straightforward interpretation of the magnetic fabrics. However, a coeval N-S compression during the times of sedimentation with an E-W transtension can explain the magnetic lineation found in many of the sites analyzed in the present work. There are also other less frequent directions of kmax axes (NE-SW and NW-SE) are interpreted as the result of local change of the stress field during the early extensional stage of basin formation.

Moussaid, B.; El Ouardi, H.; Casas-Sainz, A.; Villalaín, J. J.; Román-Berdiel, T.; Oliva-Urcia, B.; Soto, R.; Torres-López, S.

2013-11-01

219

Spatial heterogeneity of stream environmental conditions and macroinvertebrates community in an agriculture dominated watershed and management implications for a large river (the Liao River, China) basin.  

Science.gov (United States)

Understanding the effects of watershed land uses (e.g., agriculture, urban industry) on stream ecological conditions is important for the management of large river basins. A total of 41 and 56 stream sites (from first to fourth order) that were under a gradient of watershed land uses were monitored in 2009 and 2010, respectively, in the Liao River Basin, Northeast China. The monitoring results showed that a total of 192 taxa belonging to four phyla, seven classes, 21 orders and 91 families were identified. The composition of macroinvertebrate community in the Liao River Basin was dominated by aquatic insect taxa (Ephemeroptera and Diptera), Oligochaeta and Molluscs. The functional feeding group GC (Gatherer/Collector) was dominant in the whole basin. Statistical results showed that sites with less watershed impacts (lower order sites) were characterized by higher current velocity and habitat score, more sensitive taxa (e.g., Ephemeroptera), and the substrate was dominated by high percentage of cobble and pebble. The sites with more impacts from agriculture and urban industry (higher order sites) were characterized by higher biochemical (BOD5) and chemical oxygen demand (COD), more tolerant taxa (e.g., Chironominae), and the substrate was dominated by silt and sand. Agriculture and urban-industry activities have reduced habitat condition, increased organic pollutants, reduced macroinvertebrate abundance, diversity, and sensitive taxa in streams of the lower Liao River Basin. Restoration of degraded habitat condition and control of watershed organic pollutants could be potential management priorities for the Basin. PMID:24292872

Gao, Xin; Niu, Cuijuan; Chen, Yushun; Yin, Xuwang

2014-04-01

220

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

 
 
 
 
221

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

222

Seismic imaging of deep low-velocity zone beneath the Dead Sea basin and transform fault: Implications for strain localization and crustal rigidity  

Science.gov (United States)

New seismic observations from the Dead Sea basin (DSB), a large pull-apart basin along the Dead Sea transform (DST) plate boundary, show a low velocity zone extending to a depth of 18 km under the basin. The lower crust and Moho are not perturbed. These observations are incompatible with the current view of mid-crustal strength at low temperatures and with support of the basin's negative load by a rigid elastic plate. Strain softening in the middle crust is invoked to explain the isostatic compensation and the rapid subsidence of the basin during the Pleistocene. Whether the deformation is influenced by the presence of fluids and by a long history of seismic activity on the DST, and what the exact softening mechanism is, remain open questions. The uplift surrounding the DST also appears to be an upper crustal phenomenon but its relationship to a mid-crustal strength minimum is less clear. The shear deformation associated with the transform plate boundary motion appears, on the other hand, to cut throughout the entire crust.

ten Brink, Uri S.; Al-Zoubi, Abdallah S.; Flores, Claudia H.; Rotstein, Yair; Qabbani, Isam; Harder, Steve H.; Keller, G. Randy

2006-12-01

223

Seismic imaging of deep low-velocity zone beneath the Dead Sea basin and transform fault: Implications for strain localization and crustal rigidity  

Science.gov (United States)

New seismic observations from the Dead Sea basin (DSB), a large pull-apart basin along the Dead Sea transform (DST) plate boundary, show a low velocity zone extending to a depth of 18 km under the basin. The lower crust and Moho are not perturbed. These observations are incompatible with the current view of mid-crustal strength at low temperatures and with support of the basin's negative load by a rigid elastic plate. Strain softening in the middle crust is invoked to explain the isostatic compensation and the rapid subsidence of the basin during the Pleistocene. Whether the deformation is influenced by the presence of fluids and by a long history of seismic activity on the DST, and what the exact softening mechanism is, remain open questions. The uplift surrounding the DST also appears to be an upper crustal phenomenon but its relationship to a mid-crustal strength minimum is less clear. The shear deformation associated with the transform plate boundary motion appears, on the other hand, to cut throughout the entire crust. Copyright 2006 by the American Geophysical Union.

ten, Brink, U. S.; Al-Zoubi, A. S.; Flores, C. H.; Rotstein, Y.; Qabbani, I.; Harder, S. H.; Keller, G. R.

2006-01-01

224

Coseismic Slip Beneath Forearc Basins in Great Subduction Zone Earthquakes: Implications for the Size and Mode of Rupture on the Cascadia Subduction Zone  

Science.gov (United States)

We have examined the relationship between coseismic slip and forearc structure for 29 of the largest circum-Pacific megathrust earthquakes. Coseismic slip distributions were compiled from published seismic, geodetic, and tsunami waveform inversions, and we interpreted forearc structure from satellite gravity and bathymetry and marine geology. Seismogenic slip is generally focused beneath forearc deep sea terraces and basins, which are underlain by relatively high velocity arc or continental crust. Along the non-accretionary margins of NE Japan, Kuriles, and Kamchatka, the high slip areas roughly correlate with the width of the deep sea terrace, and the landward edge of the terrace approximately coincides with the landward limit of interplate thrust focal mechanisms. Along accretionary margins, coseismic slip is commonly focused beneath the offshore forearc basins. In the 1923, 1944, 1946, and 1968 earthquakes along the Nankai and Sagamai Trough of SW Japan, slip was focused beneath five forearc basins, and the presently locked Tokai source region is centered on a sixth. The steep gravity gradient marking the landward edge of the basins coincides with the landward decrease in coseismic slip and the 350°C isotherm on the plate boundary, approximately marking the down-dip limit to stick-slip behavior. Similar coseismic slip beneath basins is also observed along the Aleutian, Mexico, Peru, and S. Chile subduction zones. Transverse forearc gravity highs which separate the basins commonly overlie areas of lower coseismic slip, as at Cape Erimo separating the 1952 and 1968 Tokachi-oki earthquakes off Hokkaido, the Shumagin gap separating the 1938 and 1946 earthquakes in S. Alaska, and the Portlock anticline separating the Kodiak and Prince William Sound asperities in 1964. If the long-term slip budget is balanced along the margin, then the intervening gravity highs may be future sources of great slip not observed historically, or more likely are regions of smaller interseismic strain accumulation, as is observed in the Shumagin gap. The empirical relationship between high coseismic slip and forearc basins suggests that forearc basins may be useful indicators of long-term seismic moment release in some subduction zones. The inferred source zone of the 1700 AD Mw~9 Cascadia earthquake contains five very large basin-centered gravity lows, the largest of which is 350 km long off the mouth of the Columbia River. These lows, corresponding to the Eel, Coos Bay, Newport-Willapa, and Olympic basins, lie within the locked and transition zones inferred from geodetic data and may indicate at depth. The steep gravity gradient marking the inboard edge of the basins and presumably the downdip limit to large coseismic slip lies beneath Grays Harbor and the western Olympic Peninsula in Washington and just offshore Oregon, between the 350°C and 450° C isotherms on the megathrust. Transverse gravity highs between the basins suggest the margin is seismically segmented and may produce a variety of large earthquakes.

Wells, R. E.; Blakely, R.; Sugiyama, Y.; Scholl, D.

2002-12-01

225

Oligocene and miocene continental sedimentation, tectonics, and S-type magmatism in the southeastern Andes of Peru (Crucero Basin): geodynamic implications  

Science.gov (United States)

The Crucero Basin, located north of Lake Titicaca (70°W, 14°20's), was probably connected with the Altiplano endoreic basin since Oligocene time. During the Oligocenne and Miocene, this basin was filled by nearly 1000 meters of fanglomerate and lacustrine sediments —e.g., the Cayconi Formation, which unconformably overlies upper Paleozoic and Cretaceous rocks and is unconformably overlain by fanglomerates and palustrine sediments of Pliocene age. Basic and silicic volcanic rocks are interbedded and associated with the Cayconi Formation. Major element analyses indicate intracrustal melting for the silicic volcanic rocks, whereas the basic volcanic seem to be mantle derived. K-Ar dating of these volcanic rocks yielded ages ranging from 25.9 Ma to 15.5 Ma. Thus, in the Cordillera Oriental, magmatism is at least as old as late Oligocene.

Laubacher, G.; Sebrier, M.; Fornari, M.; Carlier, G.

226

High 3He/4He ratios in the Manus backarc basin: Implications for mantle mixing and the origin of plumes in the western Pacific Ocean  

Science.gov (United States)

Helium isotope ratios in oceanic glasses provide a high-integrity tracer of contributions from mantle plumes. Despite a diverse array of petrogenetic affinities, glasses from the central part of the Manus Basin—a backarc basin in the western Pacific—have typical plume (or hotspot) 3He/4He ratios that cluster around 12.2RA (±1.0RA n =18, where RA =3He/4He of air), a value significantly higher than the range found in most mid-ocean-ridge basalts (MORB) ([8 ± 1]A). Lavas in other parts of the basin have MORB-like or lower 3He/4He values. A wide range of He concentrations characterizes the Manus Basin glasses: This is considered to reflect the high water content of some lavas, which promotes He loss through volatile degassing. For the most part, it is the degassed lavas that do not show the plume He isotope signature. Results of the present study, together with 3He/4He data for lavas and gases from islands to the south and east of the Bismark Sea, indicate that the focus of mantle plume upwelling is either the center of the Manus Basin or possibly the region to the northwest beneath the volcanic islands of the St. Andrew Strait. This region of plume or hotspot 3He/4He ratios coincides with a domain of anomalously low seismic velocities at the underlying core-mantle boundary, and indicates that the provenance of high-3He/4He magmas in the Manus Basin (and possibly elsewhere) is linked to this boundary layer—either by plume entrainment of lower mantle or, more speculatively, through addition of material from the core-mantle boundary.

MacPherson, Colin G.; Hilton, David R.; Sinton, John M.; Poreda, Robert J.; Craig, Harmon

1998-11-01

227

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

228

Seismic stratigraphic analysis of the Cenozoic sediments in the NW Faroe Shetland Basin â?? Implications 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 Oligoceneâ??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 â??normalâ? thermal subsidence and for predicting the prospectivity in the post-basalt succession in the Faroe-Shetland Basin.

�lavsdóttir, Jana; Andersen, Morten Sparre

2013-01-01

229

The discovery of ferrous bottom water conditions in the sealed mid-Proterozoic marine basin, northern part of North China Block: implications to evolution of ocean chemistry  

Science.gov (United States)

How the ferrous deep water keep as long as one billion years and why sulfidic water wedge come out near the terrestrial sources supplementary zone are the focus of the evolution of ocean chemistry in mid-Proterozoic. The study of the sealed mid-Proterozoic marine basin found that the low level of pyrite in the black shale of Kuancheng where is far from the terrestrial sources supplementary zone, nevertheless, the level of black shale of Jixian where is far near the terrestrial sources supplementary zone is higher. This may reflect that the shallow-to-deep sulfate concentration gradient the sealed marine basin. The ferrous and deficit of sulfidic bottom water conditions in the sealed marine basin is the great advances in the study. It was proved that the existence of Supercontinent Nuna made the aerobic weathering and the importation of sulfate dropping to the critical point though the bottom water is ferrous in the case of sufficient terrestrial sources supplementary. Due to the long-term stabilization of Supercontinent Nuna, it is possible that the ferrous bottom water conditions in the open ocean in mid-Proterozoic. It is referential for how the global tectonics control the evolution of ocean. The focus for the study of the evolution of ocean chemistry in mid-Proterozoic is how the ferruginous deep water can maintain as long as one billion years, and why sulfidic water wedge would come out near the terrestrial sources region. The present work on the sealed mid-Proterozoic marine basin found the trace level of pyrite exists in the black shale of Kuancheng far away from the terrestrial source region. Nevertheless pyrite is more abundant in the black shale of Jixian nearer from the terrestrial source. This may reflect that the shallow-to-deep sulfate concentration gradient in the sealed marine basin. However the most significant discovery in present work is that the prevailing ferrous bottom water conditions in the sealed marine basin deficit of any sulfidic indicators. Based on comprehensive evidences, we conclude that it was the occurrence of Supercontinent Nuna that decrease the aerobic weathering and sulfate input to a certain critical point that make ferrous bottom water condition in the sealed marine basin possible. The existence of Supercontinent Nuna would be also one of the reason for the wide-spread ferrous condition in the open ocean during that time. The discovery of this work would be of value for exploring the effects of global tectonic development on the evolution of chemistry of paleo-oceans.

Wang, S.; Huang, Y.; Zhang, S.; Shi, X.

2013-12-01

230

Coarse-grained sediment delivery and distribution in the Holocene Santa Monica Basin, California: Implications for evaluating source-to-sink flux at millennial time scales  

Science.gov (United States)

Utilizing accumulations of coarse-grained terrigenous sediment from deep-marine basins to evaluate the relative contributions of and history of controls on sediment flux through a source-to-sink system has been difficult as a result of limited knowledge of event timing. In this study, six new radiocarbon (14C) dates are integrated with five previously published dates that have been recalibrated from a 12.5-m-thick turbidite section from Ocean Drilling Program (ODP) Site 1015 in Santa Monica Basin, offshore California. This borehole is tied to high-resolution seismic-reflection profiles that cover an 1100 km2 area of the middle and lower Hueneme submarine fan and most of the basin plain. The resulting stratigraphic framework provides the highest temporal resolution for a thick-bedded Holocene turbidite succession to date, permitting an evaluation of source-to-sink controls at millennial (1000 yr) scales. The depositional history from 7 ka to present indicates that the recurrence interval for large turbidity-current events is relatively constant (300-360 yr), but the volume of sediment deposited on the fan and in the basin plain has increased by a factor of 2 over this period. Moreover, the amount of sand per event on the basin plain during the same interval has increased by a factor of 7. Maps of sediment distribution derived from correlation of seismic-reflection profiles indicate that this trend cannot be attributed exclusively to autogenic processes (e.g., progradation of depocenters). The observed variability in sediment accumulation rates is thus largely controlled by allogenic factors, including: (1) increased discharge of Santa Clara River as a result of increased magnitude and frequency of El Ni??o-Southern Oscillation (ENSO) events from ca. 2 ka to present, (2) an apparent change in routing of coarse-grained sediment within the staging area at ca. 3 ka (i.e., from direct river input to indirect, littoral cell input into Hueneme submarine canyon), and (3) decreasing rates of sea-level rise (i.e., rate of rise slowed considerably by ca. 3 ka). The Holocene history of the Santa Clara River-Santa Monica Basin source-to-sink system demonstrates the ways in which varying sediment flux and changes in dispersal pathways affect the basinal stratigraphic record. ?? 2009 Geological Society of America.

Romans, B. W.; Normark, W. R.; McGann, M. M.; Covault, J. A.; Graham, S. A.

2009-01-01

231

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

232

From source to sink in the sediment cascade of the Hei-River Basin: Implications for late Quaternary landscape dynamics in the Gobi Desert, NW China  

Science.gov (United States)

The Hei River Basin with a catchment size of ~130,000 km² is host to one of the largest continental alluvial fans in the world. The basin comprises: (1) its high-elevated river sources in the glacier and the permafrost zone of the Qilian Mountains, (2) the semi-arid foreland of the Hexi Corridor in the middle reaches and (3) the endorheic Ejina Basin (Gaxun Nur Basin) as its recent sink. The river basin is characterized by small subcatchments of hyper-arid mountain ranges of the Gobi-Tienshan and Beishan as well as of smooth and fuzzy water divides of the Hexi-Corridor and the Badain Jaran Sand Sea. Up to 300 m of Quaternary sediments establish the large Ejina Basin, with a size of 28,000 km², as an excellent archive for environmental reconstructions located at the recent intersection of westerly and monsoonal air masses. Three sediment cores (up to 230 m long) provide evidence of sedimentation dynamics over the last 250,000 years, and cover at least two terminations since OIS 6. The sediments have to be regarded as a result of the interplay between tectonic activity and climate dynamics, accompanied by a related eolian and hydrological response of the catchment. Thus, it is crucial to understand and reconstruct the sedimentary processes along the huge sediment cascades, and to identify the most important sediment sources. Here we present a provenance analysis from mineralogical fingerprints of modern sediments that have been deposited along recent pathways from the sources to the Ejina Basin. The methodical approach combines the analysis of clay minerals, bulk mineralogy, and bulk geochemistry. Furthermore, we use heavy mineral data obtained from automated particle-analysis via a computer-controlled scanning electron microscope (CCSEM) and XRD measurements. We analyzed ~200 surface samples from the whole catchment as reference material, as well as the upper 19 m of cored sediments, to gain insight into temporal changes of depositional processes and provenance. Geostatistical analyses of the compositional data reveal a clear discrimination between sediments from the Qilian Shan in the south and from local basin sediments in the north. Moreover the mineralogical fingerprints allow the differentiation of sources from intrusive rocks that are dominant in the Bei Shan mountain sub-catchment, and from greenschist-bearing metamorphic rocks, that are widespread in the Qilian Mountain catchment. Finally, we draw conclusions about the main transport processes and pathways from assumed source regions to the sink (Ejina Basin). The provenance analysis of the sediment core reveals strong changes from local (Bei Shan) to long-distant (Qilian Shan) sources. The Late Pleistocene record reveals frequently changing sediment supply between periodic high mountain runoff and local episodic runoff. We assume that these variations are related to basin internal processes (e.g. fan dynamics, tectonics) and changing environmental conditions that are linked with variations in meltwater runoff and precipitation in the upper reaches of the southern catchment. These conclusions are supported by grain size characteristics that indicate phases of predominant alluvial activity and limnic deposition around the Late Glacial to Holocene transition and enhanced pre-Holocene eolian activity.

Schimpf, Stefan; Nottebaum, Veit; Diekmann, Bernhard; Hartmann, Kai; Lehmkuhl, Frank; Wünnemann, Bernd; Zhang, Chi

2014-05-01

233

Sedimentology and stratigraphy of the middle Eocene Guara carbonate platform near Arguis, South-West Pyrenean foreland: Implications for basin physiography  

Science.gov (United States)

The Pyrenees results from the collision between Spain and Europe and developed between the upper Cretaceous (Santonian) and the Miocene. Its foreland basins are characterised by a thick fill of detrital and carbonate sediments. The diversity of Eocene deposits in the southern Pyrenean foreland basin is of particular use in facies sedimentology due to their exceptional outcropping quality and well established stratigraphic framework and has been taken as type examples of many different sedimentary environments. Most studies have concerned facies sedimentology of detrital series in turbiditic environments, meandering and braided rivers, alluvial fans, and deltas. In contrast, the Eocene carbonate series have attracted less attention. The marine Guara limestones are a formation of lower to middle Eocene age deposited on the southern border of the western Pyrenean foreland basin (Jaca basin). They were deposited as a retrogradational carbonate platform dominated by large benthic foraminifers near or at the flexural forebulge of the foreland basin as the Pyrenean orogen developed. This formation represents the last episode of carbonate platform in the Pyrenees and remains poorly studied. In the present work our aim is to provide a detailed facies analysis and physiographic reconstructions of the Guara carbonate platform. This is crucial to unravel the respective influences of tectonics, climate and rheology of the lithosphere on the foreland basin tectonic and stratigraphic development, and it brings new constraints on the paleoenvironments and paleogeography during the Lutetian, i.e. at the beginning of the major phase of activity of the Pyrenean orogenesis. Two outcrops were studied in the Sierras Marginales at the localities of Arguis and Lusera. The Lusera section once restored in its initial position is located to the North of the Arguis section in a basinward direction such that comparing time-equivalent facies between these two sections helps us reconstructing the paleobathymetric gradient on this side of the foreland basin. The sedimentological and paleontological content show that the Guara formation was deposited in shallow water environments (less than 80 m) and can be classified as a carbonate ramp. The evolution of paleobathymetries with time on these two sections allows us to identify three complete progradational - retrogradational cycles. Those cycles do not match global eustatic variations, perhaps indicating the dominating influence of tectonics in this area. The precise study of foraminifera allowed us to date our sections with respect to the SBZ time scale of Serra-Kiel et al. (1). The bottom of the Guara formation, in the Arguis section is dated from the lower Lutetian (SBZ 13) and the top corresponds to the upper Lutetian (SBZ 16). An important hiatus is recorded between the base of the carbonates and the lower Paleocene subjacent continental deposits. Moreover, the base of the formation is older at Lusera i.e. to the centre of the basin. This hiatus could thus represent the foreland flexural forebulge unconformity (2). By restoring the relative position of the two sections during the Lutetian, we have calculated the possible slope of the Guara ramp during this period for each MFS, with values always lower than 0.5°. Extrapolating this slope to the centre of the basin allows us to estimate the paleodepth of the coeval Eocene turbidites and address the important issue of the depth of deposition of submarine fan systems in foreland settings. Within the limits of our approach we propose that these clastic fan systems have been deposited under water depths of 400 to 200 metres. This is partly in agreement with the upper bound of other estimations based on foraminiferal assemblages and trace fossils, and thus favours a relatively "shallow" view of the Middle Eocene Ainsa-Jaca deep marine basin. 1. J. Serra-Kiel et al., Bulletin De La Societe Geologique De France 169, 281 (March 1, 1998, 1998). 2. S. L. Crampton, P. A. Allen, Aapg Bulletin 79, 1495 (October 1, 1995, 1995).

Huyghe, D.; Castelltort, S.; Serra-Kiel, J.; Filleaudeau, P.-Y.; Emmanuel, L.; Mouthereau, F.; Renard, M.

2009-04-01

234

Isotope evolution of strontium in carbonate cements from the Stevens Sandstone: Implications for calcium mass transfer in the San Joaquin basin, California  

Energy Technology Data Exchange (ETDEWEB)

Strontium isotopes have been used as geochemical tracers of calcium mass transfer and pore water evolution in the south-central San Joaquin basin, California. Carbonate cements in the Miocene Stevens sandstone record a systematic decrease in the {sup 87}Sr/{sup 86}Sr ratios of the pore water with time (temperature) since deposition in response to plagioclase alteration, and indicate three phases in the evolution of central basin pore waters: (1) Early dolomite cements (< 35C) have Sr ratios consistent with their formation from entrapped seawater. (2) Early calcites (35 to 75C) record decreasing Sr ratios with increasing temperature. {sup 87}Sr/{sup 86}Sr values of the earliest calcites vary significantly by geographic location, progressing from lower, more evolved water ratios in the deeper central parts of the basin 0.7080 at 40C, Coles Levee field, to higher, less evolved values toward the flanks (0.7087 at 40C near Fruitvale). This eastward progression toward higher ratio pore waters may be recording a flux of more evolved water from the center of the basin upward and outward toward the flanks. At Coles Levee, the input of low ratio Sr implies large-scale mass transfer, as at least 1 km of additional depth is required to reach temperatures at which plagioclase alteration occurs. (3) At > 80C, all calcite cements have ratios in the 0.7072-0.7075 range, and appear strongly influenced by plagioclase alteration. At Coles Levee, this low-ratio Sr can be accounted for by local plagioclase dissolution, and implies a significant decrease in regional mass transfer in the later stages of the basin's history.

Schultz, J.L.; Boles, J.R.; Tilton, G.R. (Univ. of California, Santa Barbara (United States))

1991-02-01

235

Enhanced sediment delivery in a changing climate in semi-arid mountain basins: Implications for water resource management and aquatic habitat in the northern Rocky Mountains  

Science.gov (United States)

The delivery and transport of sediment through mountain rivers affects aquatic habitat and water resource infrastructure. While climate change is widely expected to produce significant changes in hydrology and stream temperature, the effects of climate change on sediment yield have received less attention. In the northern Rocky Mountains, we expect climate change to increase sediment yield primarily through changes in temperature and hydrology that promote vegetation disturbances (i.e., wildfire, insect/pathogen outbreak, drought-related die off). Here, we synthesize existing data from central Idaho to explore (1) how sediment yields are likely to respond to climate change in semi-arid basins influenced by wildfire, (2) the potential consequences for aquatic habitat and water resource infrastructure, and (3) prospects for mitigating sediment yields in forest basins. Recent climate-driven increases in the severity and extent of wildfire suggest that basin-scale sediment yields within the next few years to decades could be greater than the long-term average rate of 146 T km - 2 year - 1 observed for central Idaho. These elevated sediment yields will likely impact downstream reservoirs, which were designed under conditions of historically lower sediment yield. Episodic erosional events (massive debris flows) that dominate post-fire sediment yields are impractical to mitigate, leaving road restoration as the most viable management opportunity for offsetting climate-related increases in sediment yield. However, short-term sediment yields from experimental basins with roads are three orders of magnitude smaller than those from individual fire-related events (on the order of 10 1 T km - 2 year - 1 compared to 10 4 T km - 2 year - 1 , respectively, for similar contributing areas), suggesting that road restoration would provide a relatively minor reduction in sediment loads at the basin-scale. Nevertheless, the ecologically damaging effects of fine sediment (material < 6 mm) chronically produced from roads will require continued management efforts.

Goode, Jaime R.; Luce, Charles H.; Buffington, John M.

2012-02-01

236

Petrology and source of lavas from seamounts in the Adare Basin, Western Ross Sea: Implications for the origin of Cenozoic magmatism in Antarctica  

Science.gov (United States)

Hundreds of volcanic seamounts are randomly distributed in the Adare Basin, northern Ross Sea, and on the adjacent continental shelf of north Victoria Land. The cluster of volcanic seamounts directly east of Cape Adare, which we designate as southern Adare Basin Seamounts (ABS), were intruded through a thick (~2000 m) pile of sediments that have been accumulating in the Adare Basin since its opening ~43 Ma and have youthful morphology suggesting that they were formed contemporaneously with the other Cenozoic volcanoes in West Antarctica. Lavas dredged from the southern ABS on the continental shelf (~600 to 400 mbsl) and within the ocean basin (~2000 to 1400 mbsl) range from basanite and phonotephrite to trachyte and rhyolite (MgO >10 to 300 to 1 to 600 to 0.51295) ratios. Lavas are fine-grained to glassy, porphyritic and vesicular with phenocrysts of olivine, pyroxene, feldspars, magnetite and rare amphibole. The incompatible trace element ratios of the most differentiated ABS lava are similar to those of more mafic ABS lavas, but have higher 87Sr/86Sr (0.7077). This is reminiscent of the compositional signature of the differentiated alkaline lavas produced by melting of previously erupted mafic lavas in a few oceanic islands. Overall, results show that volcanism within the Adare Basin is coeval and petrogenetically akin to continental volcanism in West Antarctica and thus expand the known extent of Cenozoic alkaline magmatism associated with the West Antarctic rift. The similarities between ABS and West Antarctic volcanism, as well as with other continental intraplate lavas from the southwest Pacific offer compelling support for an inherent connection between their mantle sources. Furthermore, the coupled extensional history of the oceanic and continental sectors in the northern Ross Sea, along with the broadly coincident age of the volcanic activity, strongly suggests that both continental and oceanic volcanism were triggered by the same mechanism.

Panter, K. S.; Castillo, P.

2008-12-01

237

Paleomagnetism of the Carboniferous-Permian Patquia Formation, Paganzo basin, Argentina: implications for the apparent polar wander path for South America and Gondwana during the Late Palaeozoic  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The magnetic properties of the Carboniferous-Permian red beds of the Patquía Formation at Punta del Viento, Sierra de Umango and some previously reported localities, all in the Paganzo Basin (Argentina), have been studied. Whereas all sites are characterized by hematite as the main magnetic carrier and a reversed-polarity magnetic remanence, we found a pattern of variation in magnetic properties along the integrated column for Patquía Formation. The Lower Member (Late Carboniferous) showed ...

Geuna, S. E.

2010-01-01

238

Lesula: A New Species of Cercopithecus Monkey Endemic to the Democratic Republic of Congo and Implications for Conservation of Congo’s Central Basin  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In June 2007, a previously undescribed monkey known locally as “lesula” was found in the forests of the middle Lomami Basin in central Democratic Republic of Congo (DRC). We describe this new species as Cercopithecus lomamiensis sp. nov., and provide data on its distribution, morphology, genetics, ecology and behavior. C. lomamiensis is restricted to the lowland rain forests of central DRC between the middle Lomami and the upper Tshuapa Rivers. Morphological and molecular data confirm tha...

Hart, John A.; Detwiler, Kate M.; Gilbert, Christopher C.; Burrell, Andrew S.; Fuller, James L.; Emetshu, Maurice; Hart, Terese B.; Vosper, Ashley; Sargis, Eric J.; Tosi, Anthony J.

2012-01-01

239

Sedimentary and provenance record of the Cianzo basin, Eastern Cordillera, NW Argentina: Implications for transition from postrift subsidence to Cenozoic Andean shortening  

Science.gov (United States)

The onset of Andean shortening in NW Argentina is poorly understood, with estimates ranging from late Cretaceous to late Miocene. The Cenozoic Cianzo basin (~7 km thick) represents a fault-bounded intermontane depocenter in the Eastern Cordillera at 23°S, with Cambrian metasedimentary rock to the west and Cretaceous strata to the east. New characterizations of sedimentation and provenance for this shortening-induced basin are used to constrain the transition from Late Cretaceous postrift thermal subsidence system to an Andean flexural basin. Measured stratigraphic sections and lithofacies of Miocene clastic sedimentary rocks show a change from a paleosol-rich, distal fluvial system (400m thick Paleogene Santa Barbara Group) to braided fluvial system represented by cross-stratified sandstones and interbedded mudstones with upward-fining cycles (1500m thick Miocene Casa Grande and 3100m thick Rio Grande formations) to an alluvial fan system with massive polymictic conglomerates interbedded with discontinuous sandstone lenses (2000m thick upper Miocene Pisungo Formation). Sandstone petrographic results and conglomerate clast compositions help distinguish sediment sources potentially related to the western magmatic arc (Western Cordillera) from the evolving fold-thrust belt (Puna plateau and Eastern Cordillera). Ongoing U-Pb geochronological analyses of detrital zircon populations provide further constraints on probable sediment sources, potentially enabling discrimination of deformation related to thrust displacement along the east-directed Cianzo thrust from oblique thrust reactivation of the NE-striking Hornocal fault. Field mapping throughout the Cianzo basin reveals an overall structure of a doubly plunging syncline within the Miocene clastic succession in the shared footwall of the Cianzo and Hornocal faults. New 40Ar/39Ar geochronological results on interbedded volcanic tuffs further constrain deposition of braided fluvial deposits of the Rio Grande Formation occurred from a minimum of ~17 to ~9 Ma, consistent with an early to middle Miocene activation of thrusting in the Eastern Cordillera.

Siks, B. C.; Horton, B. K.

2010-12-01

240

The floating astronomical time scale for the terrestrial Late Cretaceous Qingshankou Formation from the Songliao Basin of Northeast China and its stratigraphic and paleoclimate implications  

Science.gov (United States)

The Upper Cretaceous Qingshankou Formation (K 2qn) in the Songliao Basin (SLB) of Northeast China consists of up to 550 m thick, lacustrine mudstone and shale that constitute one of the most important source rocks of the Daqing oil field. A high-resolution cyclostratigraphic analysis of the natural gamma-ray logging from 10 wells of the Qingshankou Formation (K 2qn) reveals orbital cycles of precession (20 ka), obliquity (40 ka) and eccentricity (100 ka and 405 ka), providing strong evidence for astronomically driven climate changes in the Late Cretaceous terrestrial environments. Floating astronomical time scales (ATS) are established for all sections, which demonstrate variable durations of K 2qn across the basin (1.09 Ma-5.20 Ma) and strong diachroneity of the lacustrine strata. Four periods of high depositional rates can be identified in the central parts of the basin, possibly recording deposition during times of sustained wet climate and high chemical weathering. An ATS established from well M206 in the central depression zone of the basin, where the most complete and stable Milankovitch cycles are present, suggests that the maximum duration of the K 2qn is 5.20 Ma (from 94.27 Ma to 89.07 Ma; Late Cenomanian to Early Coniacian). The lacustrine anoxic event 1 (LAE1) at the Cenomanian-Turonian boundary lasted ~ 210-310 ka, during which the most prolific petroleum source rocks in SLB were deposited. The onset (~ 94.21-94.18 Ma) and duration (~ 210-310 Ka) of LAE1 in SLB are comparable to those of the oceanic anoxic event 2 (OAE2; onset at 94.21 Ma and duration of ~ 320-900 ka), suggesting that the same trigger mechanism, such as increased atmospheric CO 2 from large-scale igneous activity, may have initiated high primary productivity and organic carbon burial in both marine and terrestrial systems.

Wu, Huaichun; Zhang, Shihong; Jiang, Ganqing; Huang, Qinghua

2009-02-01

 
 
 
 
241

Unusual concentration of Early Albian arthropod-bearing amber in the Basque-Cantabrian Basin (El Soplao, Cantabria, Spain): Palaeoenvironmental and paleobiological implications.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The El Soplao site is a recently-discovered Early Albian locality of the Basque-Cantabrian Basin (northern Spain) that has yielded a number of amber pieces with abundant bioinclusions. The amber-bearing deposit occurs in a non-marine to transitional marine siliciclastic unit (Las Peñosas Formation) that is interleaved within a regressive-transgressive, carbonate-dominated Lower Aptian-Upper Albian marine sequence. The Las Peñosas Formation corresponds to the regressive stage of this sequenc...

Najarro, M.; Pen?alver, E.; Rosales, I.; Pe?rez La Fuente, Ricardo; Daviero-gomez, V.; Gomez, B.; Delclo?s Marti?nez, Xavier

2009-01-01

242

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Tripathi, S. K. M.

2009-01-01

243

Hydropolitics and Hydro-Hegemony in the Eastern Nile Basin - The Political Implications of the Grand Renaissance Dam to the Nile Cooperation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This piece of research scrutinizes the relationship between the Grand Renaissance Dam project and the struggling Nile cooperation. It incorporates the themes of transboundary river disputes and power asymmetries within regional cooperation into a qualitative case study in order to achieve a better understanding of the hydro-political situation at the Nile Basin. It approaches the issue through qualitative content analysis of 35 interviews and uses the framework of hydro-hegemony as a theoreti...

Rautiainen, Oona

2013-01-01

244

Assemblage characteristics of clay minerals and its implications to evolution of eolian dust input to the Parece Vela Basin since 1.95 Ma  

Science.gov (United States)

To understand the provenance and evolution of eolian input in the last 1.95 Ma in the Parece Vela Basin in the eastern Philippine Sea, the clay mineral assemblage of a gravity core PV090510 from the basin was investigated using paleogeomagnetic dating and X-ray diffraction. The assemblage of the core mainly consisted of smectite (˜46%) and illite (˜40%), with some chlorite (˜10%) and kaolinite (˜4%). Analysis of the provenance of these minerals suggested that smectite was mainly derived from volcanic rocks of the Mariana Arc, while illite, chlorite, and kaolinite were mainly transported as eolian dust by the East Asian monsoon from central Asia. We used the ratio of (illite+chlorite+kaolinite)/smectite as a proxy for Asian eolian input to the Parece Vela Basin since 1.95 Ma. This ratio followed glacial and interglacial cycles and was consistent with the intensity of the East Asian monsoon and aridity of central Asia since 1.95 Ma. The changes of the ratio reflected three different stages of the East Asian monsoon and provenance climate.

Ming, Jie; Li, Anchun; Huang, Jie; Wan, Shiming; Meng, Qingyong; Jiang, Fuqing; Yan, Wenwen

2014-01-01

245

Crustal thickness and affinity in the southern Beaufort Sea from old deep seismic reflection profiles and gravity modelling and implications for Canada Basin evolution  

Science.gov (United States)

The rifting and break-up of continental crust to form oceanic basins is a fundamental process in geodynamics that generates passive continental margins. While rifting itself is fairly extensively studied, the transition from continental extension through break-up into seafloor spreading is more poorly understood. In this study we focus on the southern Beaufort Sea where a propagating seafloor spreading centre ceased activity probably sometime in the Cretaceous. We have reinterpreteda series of deep seismic reflection profiles and modelled gravity data to elucidate the variations in crustal and mantle geometry in the marginal parts of the southern Beaufort Sea adjacent to that part of the Canada Basin considered to have formed as a result of seafloor spreading. We find that the sub-sedimentary crustal layer is very thin in parts of the Beaufort Sea margin and interpret this as representing hyperextended continental crust (overlying hyperextended continental lithosphere) rather than oceanic crust as has been proposed previously. We use this result in an extensional strain distribution analysis, which indicatesthat total crustal extension is evidently much higher than upper crustal extension alone.The subsidence analysis suggests that the lithospheric hyperextension occurred in front of the seafloor spreading domain at the same time that seafloor spreading was occurring and that the continental margin crust continued to extend even after the end of the seafloor spreading in the adjacent ocean basin, consistent with amodel of very weak lithosphere in the area of the southern Beaufort Sea shelf.

Li, L.; Stephenson, R.

2013-12-01

246

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

247

Earlier River Basin Planning  

...North Eastern River Basin...into Member State Law. Identify River Basin Districts, International River Basin Districts and competent authorities....Complete initial characterisation of River Basin Districts and International River Basin Districts. Establish registers of Protected...

248

Noble gases in crude oils from the Paris Basin, France: Implications for the origin of fluids and constraints on oil-water-gas interactions  

Science.gov (United States)

In order to investigate the potential of noble gases to trace the dynamics of oil reservoirs, we have analysed the abundance and isotopic composition of all noble gases (He, Ne, Ar, Kr, and Xe) in crude oils from the Paris Basin, France, using a new extraction and purification procedure. The main oil reservoirs are presently located in the Jurassic (Dogger) limestone and in the Triassic (Keuper) sandstone, but hydrocarbons originated from a common source rock formation located in the interbedded Liassic sequence. Despite this common origin, the abundance and isotopic ratios of the noble gases differ between the Dogger and the Keuper. The isotopic compositions of Kr and Xe are indistinguishable from that of air. 3He/ 4He ratios, higher than those predicted from radiogenic production in the sediments or in the crust, are attributed to the occurrence of mantle-derived 3He in the basin. Each sedimentary sequence is characterised by well defined and homogeneous 21Ne/ 22Ne and 40Ar/ 36Ar ratios, which average 0.0306 ± 0.0008 and 312 ± 10 for the Dogger and 0.0367 ± 0.0012 and 664 ± 30 for the Keuper, respectively. The main source of radiogenic noble gases appears to be the continental crust underlying the basin, with possible regional contributions of noble gas isotopes produced in the sediments. The helium and argon isotopic ratios of the Dogger oils are very similar to those observed in geothermal waters flowing in the Dogger aquifer throughout the basin, demonstrating that noble gases in oils derive from associated groundwaters. Oil reservoirs in the Paris Basin therefore accumulate noble gases from wide regions of the continental crust through cross-formational flow of groundwaters and subsequent partitioning into oil. This observation implies that noble gases cannot be directly used to date oils, but can provide time constraints if (1) water/oil interactions are quantified and (2) the residence time as well as the noble gas characteristics of associated groundwaters are known. Oil-water-gas partitioning processes are well recorded in the fractionation of noble gas elemental abundance. Two distinct processes have been identified: (1) accumulation of atmosphere-derived (ANG) and radiogenic noble gases both initially dissolved in groundwaters, resulting in a positive correlation between absolute amount of ANG and the extent of heavy noble gas fractionation and (2) subsequent fractional degassing, resulting in a negative correlation between ANG abundance and heavy noble gas fractionation. Degassing is particularly evident for the Keuper oils and might have occurred in the reservoirs following hydrodynamic gas stripping. The ANG abundance in the Dogger reservoirs requires that about one order of magnitude more water than presently observed has interacted with the oil. Given current estimates of the residence time for groundwaters in the Dogger aquifer, the duration of oil-water interaction is in qualitative agreement with a Palaeocene-Oligocene age for the major episode of secondary oil migration in the Paris Basin. High xenon contents in Keuper reservoirs suggest that they have experienced hydrodynamic interactions between flowing waters and oils for long time, and that the Trias might have reached hydrostatic condition only recently.

Pinti, Daniele L.; Marty, Bernard

1995-08-01

249

Morphology and growth history of delgada fan: Implications for the Neogene evolution of Point Arena Basin and the Mendocino Triple Junction  

Science.gov (United States)

Long-range side scan (GLORIA) sonographs and seismic reflection data acquired during a survey of the western U.S. Exclusive Economic Zone in 1984, coupled with information from Deep Sea Drilling Project sites, provide new insights into the growth and evolution of the Delgada Fan. Construction of the fan commenced in the latest Miocene (˜6 Ma) following the filling of the Neogene Point Arena Basin. The fan presently covers more than 50×103 km2 of the Pacific plate and contains approximately 15×103 km3 of predominantly terrigenous detritus. The large size of the fan is incompatible with the small present-day supply of sediment to the canyon system. The GLORIA data show the Delgada Fan to be a hybrid-type fan, exhibiting characteristics of both elongate and radial fans. The morphology and volume of the fan, along with evidence for a decline in accumulation rates on the lower fan during the Quaternary period, suggest that the fan experienced an early growth phase (latest Miocene and Pliocene) characterized by relatively rapid progradation of elongate fan lobes followed by a period (Quaternary) of slower growth that has featured a shift of depocenters to sites closer to the canyons and a transition to distributary channels bordered by less prominent levees and overbank deposits. We examine the growth of Delgada Fan in relation to the Neogene evolution of the North American-Pacific plate boundary using a series of paleogeographic reconstructions based on recently published time displacement histories of the Mendocino triple junction (MTJ), the San Andreas fault (SAF), and the Pacific plate, upon which the fan rests. The time displacement curves for the SAF and the MTJ suggest that the MTJ and Mendocino Fracture Zone overtook and passed Point Arena Basin at about 10 Ma when the basin lay immediately southwest of the present San Francisco Bay area. We suggest that the MTJ joined the SAF at approximately that time and location, thus making the SAF the master fault in the transform system. This interpretation is compatible with evidence from seismic reflection profiles over the fan, which demonstrate that the fan and the canyon system and therefore Point Arena Basin have moved as a unit since the inception of fan growth (˜6-7 Ma). Point Arena Basin lay southwest of the San Francisco area at 10-12 Ma, and the passage of the MTJ caused the disruption of the forearc shelf and slope and the development of local uplifted and subsiding blocks. In particular, uplift of the "bay block" immediately east of the SAF may have provided the source area for the late Miocene sediments that filled Point Arena Basin and set the stage for the growth of Delgada Canyon and Fan system. The growth rate of the fan has decreased, and the style of deposition has changed as the system was tectonically transported to its present location adjacent to the small youthful drainages of the King Range.

Drake, David E.; Cacchione, David A.; Gardner, James V.; McCulloch, David S.; Masson, Douglas

1989-03-01

250

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

251

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

International Nuclear Information System (INIS)

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.

2010-08-01

252

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

Science.gov (United States)

Studying the evolution and biogeographic distribution of dinosaurs during the latest Cretaceous is critical for better understanding the end-Cretaceous extinction event that killed off all non-avian dinosaurs. Western North America contains among the best records of Late Cretaceous terrestrial vertebrates in the world, but is biased against small-bodied dinosaurs. Isolated teeth are the primary evidence for understanding the diversity and evolution of small-bodied theropod dinosaurs during the Late Cretaceous, but few such specimens have been well documented from outside of the northern Rockies, making it difficult to assess Late Cretaceous dinosaur diversity and biogeographic patterns. We describe small theropod teeth from the San Juan Basin of northwestern New Mexico. These specimens were collected from strata spanning Santonian - Maastrichtian. We grouped isolated theropod teeth into several morphotypes, which we assigned to higher-level theropod clades based on possession of phylogenetic synapomorphies. We then used principal components analysis and discriminant function analyses to gauge whether the San Juan Basin teeth overlap with, or are quantitatively distinct from, similar tooth morphotypes from other geographic areas. The San Juan Basin contains a diverse record of small theropods. Late Campanian assemblages differ from approximately coeval assemblages of the northern Rockies in being less diverse with only rare representatives of troodontids and a Dromaeosaurus-like taxon. We also provide evidence that erect and recurved morphs of a Richardoestesia-like taxon represent a single heterodont species. A late Maastrichtian assemblage is dominated by a distinct troodontid. The differences between northern and southern faunas based on isolated theropod teeth provide evidence for provinciality in the late Campanian and the late Maastrichtian of North America. However, there is no indication that major components of small-bodied theropod diversity were lost during the Maastrichtian in New Mexico. The same pattern seen in northern faunas, which may provide evidence for an abrupt dinosaur extinction. PMID:24709990

Williamson, Thomas E; Brusatte, Stephen L

2014-01-01

253

Identification and numerical modelling of hydrocarbon leakage in the Lower Congo Basin: Implications on the genesis of km-wide seafloor mounded structures  

Science.gov (United States)

We present a combined approach of interpretation of 2D seismic-reflection data and numerical modelling of hydrocarbon generation and migration across the southern slope of the Lower Congo Basin, in order to investigate the factors controlling timing and distribution of hydrocarbon leakage in this area. We identified three main families of past and present-day leakage features: (1) Mid-Upper Miocene seismic chimneys concentrated basinwards and ending up on buried pockmarks, (2) Plio-Pleistocene chimneys, rather clustered to the east of the study area and ending up in seafloor pockmarks, and (3) fewer scattered chimneys identified within the Miocene sequences ending up in shallow enhanced reflectors ("Flat spots"). Stratigraphic and structural elements seem to control the distribution of these features. At least two major events of leakage occurred during the Middle-Late Miocene and intermittently during the Pliocene-Present. External factors as sediment supply are associated to the Miocene leakage event, whilst internal structural elements probably triggered the Pliocene to present-day leakage. A major seabed morphological feature, represented by a margin-paralleled belt of more than 1-km-wide mounds, was identified above growth faults to the east of the study area. Data-constrained 2D HC generation and migration modelling suggests a genetic link between these structures and vertical migration/leakage of thermogenic methane sourced from either currently mature Oligo-Miocene source rocks or secondary cracking and further expulsion from over-mature Upper-Cretaceous source rocks. Hence, the mounds are likely to represent a lineation of methane-derived carbonate build-ups. Despite the natural limitations of a 2D migration model, when combined and calibrated with observations from seismic data, it can be used as a valid tool to assess petroleum migration routes in sedimentary basins. To the best of our knowledge, this is the first integrated approach combining both seismic observations and numerical modelling carried out in the Angola basin.

Anka, Zahie; Ondrak, Robert; Kowitz, Astrid; Schødt, Niels

2013-09-01

254

Small Theropod Teeth from the Late Cretaceous of the San Juan Basin, Northwestern New Mexico and Their Implications for Understanding Latest Cretaceous Dinosaur Evolution  

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

Williamson, Thomas E.; Brusatte, Stephen L.

2014-01-01

255

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

256

Groundwater Dynamics under Water Saving Irrigation and Implications for Sustainable Water Management in an Oasis: Tarim River Basin of Western China  

Science.gov (United States)

Water is essential for life. Specifically in the oases of inland arid basins, water is a critically limited resource, essential for the development of socio-economy and sustainability of eco-environmental systems. Due to the unique hydrological regime present in arid oases, a moderate groundwater table is the goal of sustainable water management. A shallow water table induces serious secondary salinization and collapse of agriculture, while a deep water table causes deterioration of natural vegetation. From the hydrological perspective, the exchange flux between unsaturated vadose zone and groundwater reservoir is a critical link to understand regional water table dynamics. This flux is substantially influenced by anthropogenic activities. In Tarim River Basin of western China, where agriculture consumes over 90% of available water resources, the exchange flux is influenced strongly by irrigation. Recently, mulched drip irrigation, a very advanced water-saving irrigation method, has been widely applied in the Tarim River Basin, which greatly impacted the exchange flux and thus the regional groundwater dynamics. Capitalizing on recent progress in evaporation measurement techniques, we can now close the water balance and directly quantify the exchange flux at the field scale, thus gain a better understanding of regional groundwater dynamics. In this study, comprehensive observations of water balance components in an irrigated cropland were implemented in 2011 and 2012 in a typical oasis within Tarim River Basin. The water balance analysis showed that the exchange flux and groundwater dynamics were significantly altered by the application of water-saving irrigation. The exchange flux is mostly downward (310.5 mm yr-1), especially during drip irrigation period and spring flush period, while the upward flux is trivial (-16.1 mm yr-1) due to the moderate groundwater table depth (annual average depth 2.9 m). Traditional secondary salinization caused by intense phreatic evaporation (fed by upward exchange flux) is alleviated. However, a new form of secondary salinization may be introduced unwittingly if there is lack of water for periodic flushing, especially when brackish water is used in the irrigation. Furthermore, the water saved via drip irrigation has been used in further growth of irrigated lands instead of supporting ecological system. This would lead to increasing risk of eco-environmental degradation and calls for improved governance schemes. The insights gained from this study can be potentially applied to other arid inland areas (e.g., central Asia, sub-Saharan Africa) which face similar water shortages and human development problems.

Zhang, Z.; Hu, H.; Tian, F.; Yao, X.; Sivapalan, M.

2014-02-01

257

Magnetostratigraphy and Susceptibility of Deep Drilling Core SG-1 in the Western Qaidam Basin (ne Tibetan Plateau) and Their Tectonic and Climatic Implications  

Science.gov (United States)

The Qaidam Basin is the largest intermontane basin of the northeastern Tibetan Plateau and contains a continuous Cenozoic sequence of lacustrine sediments. A nearly 1000 m deep drilling (SG-1) with an average core recovery of ~95% was carried out in the depocenter of the western Qaidam Basin, aimed to obtain a high-resolution record of the paleoenvironmental evolution and the erosion history. The core consists of dark grayish mudstone and grayish siltstone, intercalated with salts and fine sandstones in the upper part. Stepwise alternating field and thermal demagnetization, together with rock magnetic results, revealed a stable remanent magnetization for most samples, carried by magnetite. The polarity sequence consists of sixteen normal and fifteen reverse zones which can be correlated with chrons 1n to 2An of the global geomagnetic polarity time scale. Magnetostratigraphic results date the entire core SG-1 at ~2.77 Ma to ~0.1 Ma and yield sediment accumulation rate (SAR) ranging from 26.1 cm/ka to 51.5 cm/ka. Maximum SARs occur within the intervals of ~2.6-2.2 Ma and after ~0.8 Ma indicating two episodic erosional periods. Detailed magnetic susceptibility and rock magnetic properties were analyzed for revealing the significance of ferro(i)magnetic concentration for past changes of climate and erosion. Mass-specific susceptibility (?) shows a striking cyclic and long-term variation. Samples with high ? values are dominated by magnetite and maghemite with pseudo-single-domain properties. In contrast, samples with low ? values contain maghemite from single-domain to multi-domain, and additionally a significant fraction of hematite. Combining with high resolution pollen-spore and geochemical records for representative time intervals, the driving mechanism of ? variation can be explained by low-temperature oxidation in the lake sediments (dry climate). Trends of match with sedimentation rates and are roughly synchronous with the deep-sea ?18O record on a glacial-interglacial timescale. Therefore, magnetic concentration in the western Qaidam Basin sediments is seemingly controlled by both tectonic influence and paleoenvironmental changes, but can be best interpreted by alternations and trends of dry-cold and more humid periods due to Asian drying and global cooling.

Fang, X.; Zhang, W.; Appel, E.; Song, C.

2013-05-01

258

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

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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

259

Geochemistry of Cenozoic basalts from the Bohai Bay Basin: Implications for a heterogeneous mantle source and lithospheric evolution beneath the eastern North China Craton  

Science.gov (United States)

Eocene and Miocene alkali basalts were collected from boreholes in the Jiyang Sag of the Bohai Bay Basin with the aim of investigating lithospheric evolution beneath the eastern North China Craton (NCC). These alkali basalts have oceanic island basalt (OIB)-like trace element characteristics and overall depleted Nd–Hf isotopes (?Nd(t) = 2.4–6.3; ?Hf(t) = 7.0–10.1), consistent with derivation from slightly enriched asthenosphere. The Miocene (< 23 Ma) Guantao basalts, like the Miocene basalts in Shandong, have relatively higher concentrations of incompatible trace elements and are more depleted in heavy rare earth elements (HREEs) than the Eocene Shahejie basalts (47–45 Ma), indicating a larger proportion of melts derived from the garnet peridotite/pyroxenite. We interpret this difference as resulting from lithospheric thickening. Lithospheric thickness, estimated from the basalt geochemistry, is ~ 65–85 km at ~ 45 Ma and ~ 85–95 km after about 23 Ma. This inferred lithospheric thickening beneath the eastern NCC after the end of the Oligocene is consistent with decreasing paleo-heat flow in the Bohai Bay Basin from ~ 23 Ma to the present. The geochemical variations of the Cenozoic basalts in the Jiyang Sag reveal that the lithospheric thinning beneath the eastern NCC was on-going at ~ 45 Ma, but ceased after the end of the Oligocene.

Li, Hong-Yan; Huang, Xiao-Long; Guo, Hua

2014-05-01

260

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

 
 
 
 
261

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

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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

262

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

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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 {epsilon}{sub Nd}(O) parameter than the other volcanic suite, and a third metasedimentary source with {epsilon}{sub 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 of two components, an Andean magmatic arc and the Brazilian shield-derived metasediments. The model is strongly supported by a plot of {epsilon}{sub Nd}(O) versus {epsilon}{sub 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).

Basu, A.R.; Sharma, M.; DeCelles, P.G. (Dept. of Geological Sciences, Rochester Univ., NY (USA))

1990-10-01

263

Rare-earth elements in Oligo-Miocenic pelitic sediments from Lagonegro Basin, southern Apennines, Italy: implications for provenance and source area weathering  

Science.gov (United States)

The Lagonegro Units are a part of the southern Apennines orogenic wedge. The age of the Lagonegro successions ranges from lower middle Triassic to Oligo-Miocene. During late Cretaceous and Oligocene the deposition of calcareous-clastic sediments occurred interbedded with shales (Flysch Rosso Fm). During Oligocene and early Miocene, in the Mediterranean area, an important variation of the tectonic regime occurred, and siliciclastic sediments of the Numidian Basin unconformably lay on the Meso-Cenozoic units of the Lagonegro Basin. In the Lucanian Apennine, the Aquitanian Langhian Numidian Flysch Fm overlies the Flysch rosso Fm. The shales of the Flysch rosso Fm have a peculiar geochemical fingerprint relative to typical shales of post-Archean age. The abundance of Ni and Cr is significantly higher and the HREE chondrite-normalized patterns are steep with a (Gd/Yb)ch>2. A supply of material from the African Archean terranes could be the cause. The palaeo-weathering indices record changes at the source, reflecting variations in the tectonic regime. The oldest samples are derived from an environment in which steady-state weathering conditions prevailed, whereas the youngest samples are related to non-steady-state weathering conditions. This difference could record deformational events that affected the Mediterranean area during the Oligocene and early Miocene. The sample at the top of the studied log has very high silica content and an abundant coarse grain-sized fraction. This suggests that this sample belongs to the Numidian Flysch Fm. The geochemical proxies of this sample are different from those associated with samples from the Flysch rosso Fm, indicating that the source-area of the Numidian Flysch Fm did not include the Archean terranes.

Mongelli, Giovanni

2004-09-01

264

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)

2009-01-01

265

Magnetostratigraphic and rock magnetic study of the Neogene upper Yaha section, Kuche Depression (Tarim Basin): Implications to formation of the Xiyu conglomerate formation, NW China  

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Magnetostratigraphic study of 251 horizons through the younger Yaha succession in the Kuche Depression of the Tarim Basin, NW China, lying beneath a massive regionally extensive (Xiyu) conglomerate formation identifies nine reversed and eight normal polarity chrons correlating with the Geomagnetic Polarity Time Scale to show that deposition spanned the interval ˜5.3 to ˜1.7 Ma. Sedimentation rates fell episodically from ˜49 to ˜24 cm/kyr as neotectonic deformation in the southern Tian Shan thrust belt became focused on two major anticlines with the northern (Qiulitage) anticline being initiated at ˜5.5 Ma and developing a northern hinged limb that embraces the basal part of the studied section. Rock magnetic parameters show multiple signatures of lithologic change, deformation, burial diagenesis, and climate with the latter identifying an early Pliocene warm/humid interval followed by cooling and desertification after ˜2.6 Ma. Diachronous commencement of Xiyu conglomerate deposition ranged from mid-Miocene in the north of the southern flank of the Tian Shan to Pleistocene in the south advancing as a clastic wedge derived from the uplifted range front to the north. This southward progradation was not climatically controlled although climatic effects may have modulated deposition during the Pleistocene. Uplift in the Tian Shan at ˜16-15 Ma correlates with rapid increase in sedimentation rate and episodic increases occurred subsequently until the initiation of the Qiulitage anticline. Reduced rates since ˜5.0 Ma contrast with increases more commonly recorded in foreland basins and have been controlled by accelerated growth of this regional structure counterbalancing uplift of the mountain front to the north.

Huang, Baochun; Piper, John D. A.; Qiao, Qingqing; Wang, Hailong; Zhang, Chunxia

2010-01-01

266

Irrigation Planning with Environmental Considerations: A Case Study of Pakistan's Indus Basin.  

Science.gov (United States)

The report is a case study for the Indus Basin irrigation system, which analyzes causes of waterlogging and salinity and suggests possible remedies. It begins with an overview of the Indus Basin Model Revised (IBMR); examines the environmental implication...

M. Ahmad G. P. Kutcher

1992-01-01

267

New U/Pb ages from Nanpanjiang Basin (South China): implications for the age and definition of the Early-Middle Triassic boundary  

Science.gov (United States)

Understanding the patterns and rates of the biotic recovery following the end-Permian extinction requires detailed calibration of both biotic and environmental fluctuations by precise and accurate U-Pb age determinations on zircon from volcanic ash beds within biostratigraphically well dated marine sedimentary sections. Recent analytical developments in U-Pb dating include chemical abrasion pre-treatment of zircon as well as the use of the well calibrated 202Pb-205Pb-233U-235U EARTHTIME tracer solution, leading to <0.1% analytical uncertainties and external reproducibilities. Utilizing these analytical techniques we report new data from the Jinya area in the Nanpanjiang Basin (South China) and compare them to radioisotopic and biochronologic data from Guandao in the same basin (Lehrmann et al. 2006, 2007) The so-called "green-bean rock" (GBR) is an interval rich in volcanic ash beds which is customarily used as a mapping unit to separate Lower from Middle Triassic marine rocks in the Nanpanjiang Basin (Lehrmann et al. 2006). In Guandao, the first occurrence (FO) of the conodont Chiosella timorensis is used to define the base of the middle Triassic. The position of this FO in Guandao is somewhat unstable and underwent a downward shift of 2.6 m between the two consecutive reports of Lehrmann et al. (2006, 2007). The new position of the FO, still bracketed by the same ash layers PGD2 and PGD3 led to a minor readjustment of its linearly interpolated age to 247.24 Ma (Lehrmann et al. 2007). In the basinal Luolou Fm., the GBR amounts to a ca. 3m thick series of composite, laterally transported ashes as indicated by internal sedimentary structures. Ammonoids bracketing the GBR in the Luolou Fm. invariably indicate a late Early Triassic age (Haugi Zone of the Spathian substage). A 13 m thick section straddling the transition between the Luolou Fm. and the overlying Baifeng Fm. was sampled along a new road cut at Monggan (3 km NNW of Jinya). In this section, the 3 m thick GBR occurs 3.4 m below the top of the Luolou Fm. (Galfetti et al. 2008). This stratigraphic position is consistent throughout the entire depositional area of the Luolou Fm. In Monggan, thin ash layers without any signs of lateral transport immediately below and above the GBR where sampled in addition to a sequence of samples taken from the base to the top of the GBR. Sample CHIN47 from a thin ash layer occurring 0.8 m below the base of the GBR yielded an age of 248.05 Ma, thus providing an estimate for the lower part of the Haugi Zone. CHIN45, another thin ash layer occurring 0.3 m above the top of the GBR yielded an age of 246.88 Ma, thus providing an estimate for the upper part of the Haugi Zone. A sequence of four samples within the 3 m thick GBR yielded an intermediate and well ordered series of ages ranging from 247.78 Ma at the base (CHIN46) to 247.02 Ma at the top (CHIN50). Taking the uncertainties into account, the minimal duration of the GBR is of 0.4 My (base with a minimal age of 247.6 Ma and top with a maximal age of 247.2). Comparisons of these new U/Pb ages from Monggan with the interpolated age of the FO of C. timorensis in Guandao indicate that this FO falls between the minimal basal and the maximal top U/Pb ages of the GBR, the latter being in turn included within the late Early Triassic Haugi Zone. Hence, the FO of C. timorensis in Guandao is most probably within the time interval of the late Early Triassic Haugi Zone. Independent support for this correlation also comes from North America, where this conodont species occurs within the late Early Triassic ammonoid Haugi Zone (Goudemand et al. in prep.). The new data from Monggan therefore indicate that the GBR cannot be used as a marker for the Lower-Middle Triassic boundary in the Nanpanjiang Basin (in contradiction to Lehrmann et al., 2006 and 2007). Galfetti et al. 2008 Sedimentary Geology 204: 36-60 Lehrmann et al. 2006 Geology 34:1053-1056 Lehrmann et al 2007 Forum GSA doi: 10.1130/G23941Y.1

Ovtcharova, Maria; Bucher, Hugo; Goudemand, Nicolas; Schaltegger, Urs; Brayard, Armand; Galfetti, Thomas

2010-05-01

268

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

269

Where does the South Anju suture go to in the New Siberian Islands and Laptev Sea?: implication to the rotational hypothesis of the Amerasian Basin opening.  

Science.gov (United States)

The South-Anuj suture is a trace of Late Palaeozoic-Jurassic ocean. The suture is believed to trend from the upper Big Anuj river (Chukotka) to Bigger Lyakhov Isl. (New Siberian Islands). It is commonly acknowledged that closing of the South Anuj Ocean at the end of Jurassic - beginning of Neocomian was synchronous with opening of the Amerasian oceanic basin. Most popular is the hypothesis of rotational opening of this basin. In accord with this hypothesis, the South Anuj suture must at some point meet the strike-slip global-scale transform trending along the eastern foot of the Lomonosov Ridge. The geometric contradictions arising from rotational hypothesis have been discussed by [Rowley and Lottes, 1988; Lane, 1997]. To avoid them, [Rowley and Lottes, 1988] suggest that the South Anuj suture does not reach Bigger Lykhov Is. but ends up in the vicinity of the Kolyma river mouth and meets the transform there. In fact, the suture's westward tracing is based only on geophysical data. The earlier published data on the rocks exposed on the Bigger Lyakhov island have permitted to assume that these rocks had nothing in comman with those in the South Anuj region. Our 2000 fieldwork on the Bigger Lyakhov Isl. was aimed to verify this assumption. The results have shown that all rock complexes exposed on the island are analogous to those in the South Anuj area - tectonotype of the suture. This confirmed the first assumption of the suture's trend. However, the question was still unsettled where the suture further goes to from the island and were it joins the transform. It is generally accepted that the suture turns northwards from the B.Lyakhov Is. to Zemlya Bunge or Kotel'ny Ils [Spector et al., 1981; Parfenov et al., 1999; Fujita et al., 1997]. We can not agree with this idea since the Jurassic rocks on these islands are undeformed and even unlithified. So, if the suture has a NW continuation, it must lie W-SW of Belkovsky Island and meet the transform nearby. This was the reason to explore if such large-scale tectonic features as the transform and suture were somehow manifested in the structure of Belkovsky Island. The prelilminary results of the 2002 fieldwork are as follows: 1) The Devonian-Carboniferous deposits of the Bel'kovsky Is. were folded due to SW-NE compression and were stronger deformed in Neocomian as compared to those on Kotel'ny Is. This suggests the suture to lie SW of the Bel'kovsky Is. 2) A large-scale meridional dextral strike-slip fault was mapped on the Bel'kovsky Isl., which could be interpreted as a satellite of a global transform. These observations may be treated as a confirmation of rotational model of the Amerasian basin opening. But instead of reducing geometric inconsistencies arising from the plain rotational model, our results increased them. We intend to suggest another way to solve this problem in our next report at ICAM IV in Canada.

Kuzmichev, A.; Bogdanov, N.

2003-04-01

270

Parana basin  

Energy Technology Data Exchange (ETDEWEB)

The Parana basin is a large intracratonic basin in South America, developed entirely on continental crust and filled with sedimentary and volcanic rocks ranging in age from Silurian to Cretaceous. It occupies the southern portion of Brazil (1,100,000 km/sup 2/ or 425,000 mi/sup 2/) and the eastern half of Paraguay (100,000 km/sup 2/ or 39,000 mi/sup 2/); its extension into Argentina and Uruguay is known as the Chaco-Parana basin. Five major depositional sequences (Silurian, Devonian, Permo-Carboniferous, Triassic, Juro-Cretaceous) constitute the stratigraphic framework of the basin. The first four are predominantly siliciclastic in nature, and the fifth contains the most voluminous basaltic lava flows of the planet. Maximum thicknesses are in the order of 6000 m (19,646 ft). The sequences are separated by basin wide unconformities related in the Paleozoic to Andean orogenic events and in the Mesozoic to the continental breakup and sea floor spreading between South America and Africa. The structural framework of the Parana basin consists of a remarkable pattern of criss-crossing linear features (faults, fault zones, arches) clustered into three major groups (N45/sup 0/-65/sup 0/W, N50/sup 0/-70/sup 0/E, E-W). The northwest- and northeast-trending faults are long-lived tectonic elements inherited from the Precambrian basement whose recurrent activity throughout the Phanerozoic strongly influenced sedimentation, facies distribution, and development of structures in the basin. Thermomechanical analyses indicate three main phases of subsidence (Silurian-Devonian, late Carboniferous-Permian, Late Jurassic-Early Cretaceous) and low geothermal gradients until the beginning of the Late Jurassic Permian oil-prone source rocks attained maturation due to extra heat originated from Juro-Cretaceous igneous intrusions. The third phase of subsidence also coincided with strong tectonic reactivation and creation of a third structural trend (east-west).

Zalan, P.V.; Wolff, S.; Conceicao, J.C.J.; Vieira, I.S.; Astolfi, M.A.; Appi, V.T.; Zanotto, O.; Neto, E.V.S.; Cerqueira, J.R.

1987-05-01

271

Magnetic fabric data from regionally extensive Miocene ignimbrites in the western Great Basin; Implications for Neogene tectonism and ignimbrite emplacement mechanisms  

Science.gov (United States)

Magnetic fabric data from regionally extensive ignimbrites in the western Great Basin, some of which are part of the southwest Nevada volcanic field (SWNVF), are overall consistent with those from many ignimbrites, in that a well-developed imbrication fabric allows for approximating source calderas and transport direction, as well as characterizing the petrofabric of the ignimbrite. The three ignimbrites studied are the Tuff of Stonewall Flat, tuffs of the Timber Mountain Group, and Tuff of Mount Dunfee (dated with high precision 40Ar/39Ar on sanidine crystals at 7.62 × 0.01 Ma, 11.55 × 0.012 Ma, and 16.31 × 0.009 Ma, respectively) and were sampled at 277 different sites between near Beatty and Goldfield, NV, yielding 6,237 individual specimens for anisotropy analyses. The cumulative anisotropy of magnetic susceptibility (AMS) data set from all sites reveals source calderas to the east and southeast. Although each ignimbrite has been subjected to varying degrees of vertical axis rotation, representative AMS data (Tuff of Stonewall Flat, site GP233) yields a K3 trend of 315.2° and plunge of 54.7° (confidence angles (CA) = 3.8/3.5) and a source direction (K1 trend) of 183.9° and plunge of 25.0° (CA = 15.8/3.5, based on n=27 specimens). The degree of anisotropy for these ignimbrites ranges from 1.01 to 1.05, with low-field bulk susceptibilities averaging 4.25E-03 SI Volume. Typical of ignimbrites, the magnetic foliation dominates the magnetic lineation, with a well developed oblate fabric in 96% of the sites; the remaining generally exhibit a triaxial fabric. Anisotropy of remanence (anhysteretic remanent magnetization (AARM) and isothermal remanent magnetization (AIRM)) analyses help elucidate controls on specific AMS data sets, as bulk AMS data integrate contributions from paramagnetic and ferro/ferri magnetic sources, including single domain magnetite. Petrographic examination and study of the bulk susceptibility vs. temperature show that the principal magnetic phase in these deposits is magnetite. These magnetic fabric studies bear on the tectonic history of the SWNVF as the area was deformed during the initiation and evolution of a major displacement transfer system in the western Great Basin.

Fitter, T.; Geissman, J. W.; Oldow, J. S.; Jackson, J.

2013-12-01

272

Seismic reflection surveys of the Kr\\vsko basin structure: implications for earthquake hazard at the Kr\\vsko nuclear power plant, southeast Slovenia  

Science.gov (United States)

To improve the geologic model and test the approach, high-resolution seismic reflection methods were used in a re-evaluation study of earthquake hazard assessment at the Kr\\vsko nuclear power plant (NPP) site. In a 13-km long profile recorded across the eastern part of the Kr\\vsko basin (20-km long and 10-km wide), which is filled with up to 2 km of Neogene to Quaternary molasse sediments, the most prominent reflection was obtained from the top of the Badenian limestone, whereas the Mesozoic basement was less reflective. A syncline-anticline was interpreted that indicates a compressional tectonic style contrary to the prevailing hypothesis of a graben structure with normal border faults. In addition, very high-resolution shallow reflection profiling was performed at two locations close to the NPP for the detection of near-surface faults. Portable engineering seismic equipment was used for data acquisition to reduce costs and enable measurements in areas with difficult access. Geophone arrays were necessary for the suppression of strong ground roll and guided waves generated in the thick layer of dry gravel. Serious spatial aliasing of ground-coupled air-waves precludes f-k filtering, necessitating the application of an internal mute. Two new subvertical normal faults with displacements of 50 and 80 m at the middle/upper Miocene interface were interpreted in the central part of the basin, while other faults, suggested by surface geological observations, were not confirmed. The further north of the two faults was traced in Pliocene-Quaternary deposits to a depth of 250 m. Reinterpretation of old analogue oil-exploration seismic profiles and gravity modelling has allowed the extension of results to a wider area. In the very high-resolution profile, recorded 0.5-km east of the NPP site, some discontinuities in reflections were established that were interpreted as faults. The possible vertical displacement at the sand (Pl, Q)/marl (Pl) interface is 7 m. The new structural-tectonic data obtained in the vicinity of the NPP requires essential changes to the model for earthquake hazard assessment.

Gosar, Andrej

1998-07-01

273

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 â??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 â??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

274

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

275

Predominance of even carbon-numbered n-alkanes from lacustrine sediments in Linxia Basin, NE Tibetan Plateau: Implications for climate change  

International Nuclear Information System (INIS)

Research highlights: ? This study reports the first observation of predominant even carbon-numbered n-alkanes of sediments in the continuous lacustrine-sedimentary section (Maogou) from the Late Miocene to the Early Pliocene (13-4.4 Ma) in the Linxia Basin, NE Tibetan Plateau. ? Certain types of special autochthonous bacteria are a possible source for the special distribution of even carbon-numbered n-alkanes in lacustrine sediments. ? These bacteria may have a high production rate in weak oxic-anoxic and arid depositional environments, in which a variety of geochemical parameters have recorded palaeoclimate change. ? A close correspondence among the low ratio of n-C27/n-C31, the heavy ?13C values of TOC and a strong even carbon-number predominance (low OEP16-20 values) from approximately 6.5 to 4.4 Ma and at approximately 8 Ma in the studied section suggests that n-alkanes with a high predominance of even carbon-numbers may be treated as geochemical proxies for arid climate. - Abstract: This study reports the first observation of predominant even C-numbered n-alkanes from sediments in the continuous lacustrine-sedimentary section (Maogou) from the Late Miocene to the Early Pliocene (13-4.4 Ma) in the Linxia Basin, NE Tibetan Plateau. The n-alkanes showed a bimodal distribution that is characterised by a centre at n-C16-n-C20 with maximum values at n-C18 and n-C27-n-C31 as well as at n-C29. The first mode shows a strong even C-number predominance (OEP16-20 0.34-0.66). In contrast, the second mode has a strong odd C-number predominance (OEP27-31 1.20-2.45). Certain types of special autochthonous bacteria are a possible source for this distribution of even C-numbered n-alkanes in lacustrine sediments. These bacteria may have a high production rate in weak oxic-anoxic and arid depositional environments, in which a variety of geochemical parameters have recorded palaeoclimate change.

2010-10-01

276

Tephra layers from Holocene lake sediments of the Sulmona Basin, central Italy: implications for volcanic activity in Peninsular Italy and tephrostratigraphy in the central Mediterranean area  

Science.gov (United States)

We present a new tephrostratigraphic record from the Holocene lake sediments of the Sulmona basin, central Italy. The Holocene succession is represented by whitish calcareous mud that is divided into two units, SUL2 (ca 32 m thick) and SUL1 (ca 8 m thick), for a total thickness of ca 40 m. These units correspond to the youngest two out of six sedimentary cycles recognised in the Sulmona basin that are related to the lake sedimentation since the Middle Pleistocene. Height concordant U series age determinations and additional chronological data constrain the whole Holocene succession to between ca 8000 and 1000 yrs BP. This includes a sedimentary hiatus that separates the SUL2 and SUL1 units, which is roughly dated between 1000; from 3600 to 3100; and from 7600 to 4700 yrs BP. The first, youngest cluster, comprises six layers and correlates with the intense explosive activity of Mt. Somma-Vesuvius that occurred after the prominent AD 79 Pompeii eruption, but only the near-Plinian event of AD 472 has been tentatively recognised. The intermediate cluster (3600-3100 yrs BP) starts with tephra that chemically and chronologically matches the products from the "Pomici di Avellino" eruption (ca 3800 ± 200 yrs BP). This is followed by eight further layers, where the glasses exhibit chemical features that are similar in composition to the products from the so-called "Protohistoric" or AP eruptions; however, only the distal equivalents of three AP events (AP3, AP4 and AP6) are tentatively designated. Finally, the early cluster (7600-4700 yrs BP) comprises 12 layers that contain evidence of a surprising, previously unrecognised, activity of the Mt. Somma-Vesuvius volcano during its supposed period of quiescence, between the major Plinian "Pomici di Mercato" (ca 9000 yrs BP) and "Pomici di Avellino" eruptions. Alternatively, since at present there is no evidence of a similar significant activity in the proximal area of this well-known volcano, a hitherto unknown origin of these tephras cannot be role out. The results of the present study provide new data that enrich our previous knowledge of the Holocene tephrostratigraphy and tephrochronology in central Italy, and a new model for the recent explosive activity of the Peninsular Italy volcanoes and the dispersal of the related pyroclastic deposits.

Giaccio, B.; Messina, P.; Sposato, A.; Voltaggio, M.; Zanchetta, G.; Galadini, F.; Gori, S.; Santacroce, R.

2009-12-01

277

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

278

Seismic reflection imaging of a paleo-strike-slip zone: Permain-Jurassic structures and implications for the evolution of the NW Junggar Basin, NW China  

Science.gov (United States)

The recognition of inactive paleo-strike-slip faults can be difficult, especially when their fault-related structures have been buried by several kilometers of sediments. However, the subsurface seismic data are able to identify the characteristics of the structures in these areas. In this study, we focus on the geometry and evolution of the strike-slip fault zones in the Northwest Junggar Basin, by using both 2-D and 3-D seismic reflection data. Based on the results of our analysis, we characterized the Dalabute and Hong-Che Domains, whose structures are both fitting for the Riedel shear model. In the Dalabute domain, the observed structures are mainly composed of en echelon folds and main P and R faults with other secondary reverse faults, while the Principal Deformation Zone (PDZ) is oriented to Northeast-Southwest. However, the structures in Hong-Che domain are characterized by main strike-slip faults with a narrow deformation zone along the straight fault traces, and compressional faults and folds within their restraining bends. As well, the orientation of the PDZ changes to North-South. Meanwhile, the extensional structures observed in both Dalabute and Hong-Che domains suggest the regional extension in the Early to Middle Permian. The growth strata associated with en echelon folds indicates the onset of strike-slip fault in Dalabute domain is Late Permian, whereas a few data show the onset of strike-slip fault in Hong-Che region is no later than Middle Triassic. The deformation in Northwest Junggar baisn lasted untill Late Jurassic. The Dalabute domain reactived and inversed to sinitral strike-slip during the Cenzoic time, whereas the Hong-Che domain was almost inactive then. We proposed that the observed Dalabute and Hong-che dextral strike-slip system might be a part of sinistral shear system in the Altaid orogenic collage in central Asia during the Late Permian to Jurassic time, which also helps to better understand the evolution of the NW Junggar Basin, NW China.

Yu, Y.; Wang, X.; Wang, R.

2013-12-01

279

Kinematic development and paleostress analysis of the Denizli Basin (Western Turkey): implications of spatial variation of relative paleostress magnitudes and orientations  

Science.gov (United States)

Paleostress orientations and relative paleostress magnitudes (stress ratios), determined by using the reduced stress concept, are used to improve the understanding of the kinematic characteristics of the Denizli Basin. Two different dominant extension directions were determined using fault-slip data and travertine fissure orientations. In addition to their stratigraphically coeval occurrence, the almost exact fit of the ?2 and ?3 orientations for the NE-SW and NW-SE extension directions in the Late Miocene to Recent units indicate that these two extension directions are a manifestation of stress permutations in the region and are contemporaneous. This relationship is also demonstrated by the presence of actively developing NE-SW and NW-SE elongated grabens developed as the result of NE-SW and NW-SE directed extension in the region. Moreover, stress ratios plots indicate the presence of a zone of major stress ratio changes that are attributed to the interference of graben systems in the region. It is concluded that the plotting of stress orientations and distribution of stress ratios is a useful tool for detecting major differences in stress magnitudes over an area, the boundaries of which may indicate important subsurface structures that cannot be observed on the surface.

Kaymakci, Nuretdin

2006-07-01

280

Contact metamorphic effects of the basic intrusive rocks on the Proterozoic uraniferous dolostone in Cuddapah basin, Andhra Pradesh: implications on uranium mobilisation  

International Nuclear Information System (INIS)

Mafic intrusive rocks in the Vempalle formation of the mid-Proterozoic Cuddapah basin occur as sills and dykes. These include minor bodies of gabbro, olivine gabbro, olivine norite, basalt and mainly dolerite with basaltic andesite. The metamorphic effects of these intrusive rocks on the uraniferous phosphatic siliceous dolostone are mainly mineralogical (thermal) with subordinate changes in chemistry. These are manifested by (a) formation of plagioclase-hornblende hornfels, (b) notable mineralogical changes in the dolostone leading to enrichment of magnetite, epidote, anatase and de-dolomitised calcite, (c) decrease in specific gravity of dolostone from 3.0 to 2.8 due to volatilisation reaction products of epidote and smectite, and (d) formation of wollastonite, chalcedony, and secondary uranium minerals (autunite and uranophane) at places, in the contact aureole that led to notable changes in the chemistry of the intrusive body and the host rock. Intrusive rocks at the contact show enrichment in Fe2+, Mg, Cu, Cr, Pb, Zn, Ni, and depletion in Ca and Fe3+, whereas the dolostone shows enrichment in Ti, Ca, and depletion in Si, Al, alkalies and P. Depletion of uranium in the affected parts (0.003% U3O8) of mineralised dolostone (0.062% U3O8) adjacent to the basic intrusive rocks suggests its mobilisation, due to increase in temperature, resulting in baking. This phenomenon is also manifested, at places, in the formation of secondary uranium minerals - result of remobilisation of uranium from primary phases and its subsequent precipitation. (author)

1997-10-01

 
 
 
 
281

Sand-flat/playa mud-flat-lacustrine cycles in Fundy rift basin (Triassic-Jurassic), Nova Scotia: implications for climatic and tectonic controls  

Energy Technology Data Exchange (ETDEWEB)

Blomidon Formation red beds comprise over 200 m-scale cycles of (1) sand-flat sandstone (distal alluvial-fan deposits) and (2) playa sandy mudstone and/or lacustrine claystones. Rift basin subsidence and local sagging along the Glooscap fault system generated sand-flat/playa mud-flat cycles by shifting loci of active fan sedimentation toward and away from the playa surface as fan lobes migrated toward topographic lows. Episodes of intense aridity are recorded in the sand-flat and playa mud-flat deposits where amalgamated sheetflood packages are characterized by pervasive evaporite mineralization (principally gypsum) controlled by subsurface evolution of a Ca-SO/sub 4/-Na-Cl brine. Aridity is further evidenced by significant disruption of sedimentary fabrics beneath evaporite crusts, deep mud cracks, eolian sandstone layers and patches, and precipitation of authigenic calcium and magnesium-rich illite/smectite and analcime. Carbon isotopic data from early formed, low-magnesium calcite cements (pre-gypsum) reflect slightly to moderately elevated subsurface salinities that accompanied initial brine evolution. During relatively wetter periods, lacustrine platy claystones accumulated in shallow, oxidizing lakes that lapped onto the sand flats. Claystone units lack evaporite minerals and textures, and many units are partially burrowed. Carbon isotopic data from calcite cements are consistently lighter than sand-flat/playa mud-flat calcites and were in equilibrium with relatively fresh subsurface pore waters.

Mertz, K.A. Jr.; Hubert, J.F.

1989-03-01

282

First record of petrified Permian pecopterids from the Paraná Basin, Brazil (Corumbataí Formation, Passa Dois Group, northeastern State of São Paulo): Morphology, anatomy and paleoecological implications  

Science.gov (United States)

Petrified pecopterids are described for the first time in the Paraná Basin. They were collected at an outcrop of the Corumbataí Formation (Passa Dois Group, Middle Permian) in the Municipality of Piracicaba (State of São Paulo, Brazil). The assemblage is composed of Pecopteris taguaiensis Rohn and Rösler, 1986, Pecopteris sp. 1, Pecopteris sp. 2 and Pecopteris sp. 3. An emendation to the diagnosis of P. taguaiensis is proposed on the basis of the characteristics shown by the preserved three-dimensional external leaf morphology and partially by the epidermis (not available in the previously described impressions). The small size of the pinnules, the thick, downward-rolled leaf lamina, the thick veins, the straight walls of the epidermal cells, and the trichomes of the four pecopterid taxa may be interpreted as xeromorphic features developed in response to relatively dry climatic conditions and/or direct incidence of the sunlight. The leaves were impregnated with silica before the final burial, considering that they are fragmented, not deformed and associated with angular breccia clasts.

Tavares, Tatiane M. V.; Rohn, Rosemarie

2009-02-01

283

Regional importance of post-6 M.Y. old vocanism in the southern Great Basin: Implications for risk assessment of volcanism at the proposed Nuclear Waste Repository at Yucca Mountain, Nevada  

International Nuclear Information System (INIS)

This report summarizes our activities during the period July 1, 1987 to June 30, 1988. Our goal was to develop an understanding of late-Miocene and Pliocene volcanism in the Great Basin by studying late-Tertiary volcanic rocks to the north and south of the Nevada Test Site (Figure 1). We especially concentrated on detailed stratigraphic studies and geochemistry to determine the nature of chemical changes during the lifetime of a volcanic field, and on structural studies to determine the nature of the structures that control vent location. Also, K-Ar age dating provided important new information on the duration of activity at a single volcanic center. Geologic studies were concentrated in the Fortification basalt field in southern Nevada and in the Reveille Range in central Nevada. Our studies provide three important conclusions that have implications for volcanism about the proposed Nuclear Waste Repository at Yucca Mountain. There are no easily recognized geochemical characteristics that signify the termination of volcanism. The location of vent areas of basaltic volcanoes are not necessarily controlled by pre-existing structures. Volcanism at an individual basaltic center may last as long as 500,000 years. 32 refs., 34 figs., 6 tabs

1988-01-01

284

37 - Roe Basin  

...Hills35 - Magilligan Lowlands36 - Binevenagh37 - Roe BasinRoe Basin LandscapeRoe Basin Geodiversity...Digital DatasetsStrategic Environmental Assessment (SEA)37 - Roe BasinLast updated: 9 February 2007This...

285

09 river basin planning  

...coordinated planning system based within river basins. iMPort AncE oF riVEr BASin PLAnninG River basin planning is an ongoing...the sea at a single river mouth, estuary or delta. r iver Basin d istrict...iver Basin d istrict: A river basin or several small river basins combined with larger river basins or joined with neighbouring...

286

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; Basaltes de bassin arriere-arc de l`Eocene-Miocene et tholeiites d`arc insulaire associees du nord Sulawesi (Indonesie): implications pour l`evolution geodynamique du bassin des Celebes  

Energy Technology Data Exchange (ETDEWEB)

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) 37 refs.

Rangin, C. [Centre National de la Recherche Scientifique (CNRS), 75 - Paris (France); Maury, R.C.; Bellon, H.; Cotten, J. [Universite de Bretagne Occidentale, 29 - Brest (France); Polve, M. [Universite Paul Sabatier, 31 - Toulouse (France); Priadi, B.; Soeria-Atmadja, R. [Department of Geology, ITB, Bandung (Indonesia); Joron, J.L. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. de Recherche sur l`Etat Condense, les Atomes et les Molecules

1997-12-31

287

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 (<2.5%) shifts from the meteoric water line (MWL). Many fossil ore-forming systems were also dominated by meteoric water, but usually exhibit ??18O fluid-rock interactions with larger shifts of 5???-20??? from the MWL. Here we present a suite of two-dimensional regional (100 km) and local (40-50 km) scale hydrologic models that we have used to study the plumbing of modern and Tertiary hydrothermal systems of the Great Basin. Geologically and geophysically consistent cross sections were used to generate somewhat idealized hydrogeologic models for these systems that include the most important faults, aquifers, and confining units in their approximate configurations. Multiple constraints were used, including enthalpy, ??18O, silica compositions of fluids and/or rocks, groundwater residence times, fluid inclusion homogenization temperatures, and apatite fission track anomalies. Our results suggest that these hydrothermal systems were driven by natural thermal convection along anisotropic, subvertical faults connected in many cases at depth by permeable aquifers within favorable lithostratigraphic horizons. Those with minimal fluid ?? 18O shifts are restricted to high-permeability fault zones and relatively small-scale (???5 km), single-pass flow systems (e.g., Beowawe). Those with intermediate to large isotopic shifts (e.g., epithermal and Carlin-type 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

288

The detrital mineral record of Cenozoic deposits of the Central Myanmar Basin, Burma: implications for the evolution of the eastern Himalayan syntaxis  

Science.gov (United States)

The eastern syntaxis region of the Himalayas is a complex geological collision zone where exhumation, deformation and river capture have all influenced landscape evolution during the Cenozoic. Detrital minerals in the Eocene, Oligocene, and Miocene sandstones of the Central Myanmar Basin (Burma) provide a record of the evolution of the syntaxis, as well as an opportunity to explore how surface processes couple to exhumation and deformation over the past ~55 Ma. We have analysed detrital zircons (U/Pb and ?Hf, and fission track), muscovites (40Ar/39Ar), and garnets (EPMA) in order to build a database of provenance and exhumation rates, and have combined this with published datasets on bedrock crystallization and cooling ages in the region. The U/Pb ages and ?Hf values of detrital zircons demonstrate that as far back as 43 Ma, the Central Myanmar Basin sediments contain zircons that originated from the Gangdese batholith in Tibet. The detrital garnet geochemistry also shows a significant contribution from a granitic source, similar to garnets in the modern Tsangpo River sediments. We interpret these data as evidence that the Tsangpo was originally connected to the proto-Irrawaddy River through the eastern syntaxis region during the Eocene. Based on changes in the detrital zircon ?Hf values, the minimum age of Gangdese-derived detrital zircons, and the garnet geochemistry of the Miocene deposits, we constrain the timing of Tsangpo-Irrawaddy disconnection to about 18 Ma. In the "post-disconnection" Miocene deposits in Burma, the detrital garnets lose the granitic source and the ?Hf values of detrital zircons suggest that batholiths in the eastern syntaxis (Bomi-Chayu) and Burma (Dianxi-Burma) were the main provenance areas. The syntaxis batholiths are situated on the Jiali Fault and between the Bangong-Nujiang and Yarlung-Tsangpo suture zones. Based on present-day topography, the Jiali Fault is the most obvious position for the former Tsangpo-Irrawaddy river. We hypothesise that increased exhumation and focused deformation in the syntaxis contributed to the disconnection of the Tsangpo-Irrawaddy river, and the birth of the Tsangpo-Brahmaputra system. New 40Ar/39Ar detrital mica and ZFT data allow us to test this, and refine the age of disconnection. One significant aspect of the Tsangpo-Irrawaddy disconnection is that deformation appears to have been focused towards the interior of the syntaxis in the early Miocene, and the coupling of tectonics and erosion breaks down for this palaeo-river. In contrast, steep spatial gradients in rates of exhumation and deformation between the Jiali Fault and the Bangong-Nujiang and Jinacha sutures appear to influence the Salween and Mekong rivers' ability to keep pace with exhumation over the duration of the Himalayan collision.

Brezina, C. A.; Robinson, R. A.; Parrish, R. R.; Horstwood, M. S.; Barfod, D. N.; Carter, A.

2011-12-01

289

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)

2005-01-01

290

The Nexus between Bovine Tuberculosis and Fasciolosis Infections in Cattle of the Kafue Basin Ecosystem in Zambia: Implications on Abattoir Surveillance  

Science.gov (United States)

Bovine tuberculosis (bTB) and fasciolosis are important but neglected diseases that result in chronic infections in cattle. However, in Zambia, these diseases are mainly diagnosed at abattoirs during routine meat inspection. Albeit the coinfection status, these diseases have been reported as nothing more than normal separate findings without an explanatory phenomena. Forthwith, we formulated this study to assess the possible association of the two diseases in a known high prevalence area on the Kafue basin ecosystem. Of the 1,680 animals screened, 600 (35.7%; 95% CI 33.4%–38%) and 124 (7.4%; 95% CI 6.1%–8.6%) had fasciolosis and tuberculous lesions; respectively, whilst 72 had both fasciola and tuberculous lesions representing 12% (95% CI 9.4%–14.6%) and 58.1% (95% CI; 49.3%–66.7%) of the total positives for fasciola and tuberculosis, respectively. Jaundice was seen in 304 animals, 18.1% (95% CI; 16.3%–19.9%) and was significantly correlated to fasciolosis (r = 0.59, P < 0.0001). A significant association (?2 = 76.2, df = 1, and P < 0.0001) was found between fasciolosis and tuberculous lesions. Simple logistic regression intimated fasciolosis as a strong predictor for tuberculous lesions with animals that had fasciola being five times more likely to have tuberculous lesions (odds ratio = 4.8, 95% CI: 3.3–7.0). This study indicates that transmission and spatial risk factors of communicable and noncommunicable diseases such as bTB and fasciolosis can be correlated in an ecosystem such as the Kafue flats.

Munyeme, Musso; Munang'andu, Hetron Mweemba; Nambota, Andrew; Muma, John Bwalya; Phiri, Andrew Malata; Nalubamba, King Shimumbo

2012-01-01

291

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

Energy Technology Data Exchange (ETDEWEB)

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 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.

Maynard, J.B.; Ritger, S.D. (Univ. of Cincinnati, OH (USA)); Sutton, S.J. (Univ. of Texas, Austin (USA))

1991-03-01

292

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

293

High fluoride water in Bondo-Rarieda area of Siaya County, Kenya: a hydro-geological implication on public health in the Lake Victoria Basin  

Science.gov (United States)

Background Only a few studies to evaluate groundwater fluoride in Eastern Africa have been undertaken outside the volcanic belt of the Great Eastern Africa Rift Valley. The extent and impact of water fluoride outside these regions therefore remain unclear. The current study evaluated fluoride levels in household water sources in Bondo-Rarieda Area in the Kenyan part of the Lake Victoria Basin (LVB) and highlighted the risk posed by water fluoride to the resident communities. The results, it was anticipated, will contribute to in-depth understanding of the fluoride problem in the region. Methods A total of 128 water samples were collected from different water sources from the entire study area and analyzed for fluoride content using ion-selective electrodes. Results Lake Victoria was the main water source in the area but dams and open pans (39.5%), boreholes and shallow wells (23.5%), and streams (18.5%) were the principal water sources outside walking distances from the lake. The overall mean fluoride content of the water exceeded recommended limits for drinking water. The mean water fluoride was highest in Uyoma (1.39±0.84 ppm), Nyang’oma (1.00±0.59 ppm) and Asembo (0.92±0.46 ppm) and lowest in Maranda Division (0.69±0.42 ppm). Ponds (1.41±0.82 ppm), springs (1.25±0.43 ppm), dams and open pans (0.96±0.79 ppm), and streams (0.95±0.41 ppm) had highest fluoride levels but lake and river water did not have elevated fluoride levels. Groundwater fluoride decreased with increasing distance from the lake indicating that water fluoride may have hydro-geologically been translocated into the region from geochemical sources outside the area. Conclusions Lake Victoria was the main water source for the residents of Bondo-Rarieda Area. Majority of in-land residents however used water from dams, open pans, boreholes, shallow wells, ponds and streams, which was generally saline and fluoridated. It was estimated that 36% of children living in this area, who consume water from ground sources from the area could be at the risk of dental fluorosis.

2014-01-01

294

Response of River Discharge to Changing Climate Over the Past Millennium in the Upper Mackenzie Basin: Implications for Water Resource Management  

Science.gov (United States)

Runoff generated from high elevations is the primary source of freshwater for western North America, yet this critical resource is managed on the basis of short instrumental records that encompass an insufficient range of climatic conditions. Like other streams that drain this part of the continent and flow across the northern Great Plains, where seasonal and extended intervals of water deficit are a natural element of the landscape, the Peace and Athabasca rivers provide water that is crucial for societal needs. Climate variability and rapidly increasing industrial development are, however, raising concerns over the future availability of water resources for continued economic growth in these watersheds and to maintain the integrity of aquatic ecosystems, including the Peace-Athabasca Delta (PAD). This is particularly acute for the Athabasca River because the Alberta oil sands industry remains dependent on its water for bitumen extraction. Here we report the effects of climate change over the past 1000 years on river discharge in the upper Mackenzie River system based on paleoenvironmental information from the PAD and Lake Athabasca. The delta landscape responds to hydroclimatic changes with marked variability, capturing systematic changes in ice-jam flood frequency and perched basin water balance. Lake Athabasca level appears to directly monitor overall water availability with the highest levels occurring in concert with maximum glacier extent during the Little Ice Age, and the lowest during the 11th century prior to medieval glacier expansion. Recent climate-driven hydrological change appears to be on a trajectory to even lower levels as high-elevation snow and glacier meltwater contributions both continue to decline. The temporal perspective offered by these paleohydrological reconstructions indicates that climatic changes over the past millennium have led to characteristic responses in the quantity and seasonality of streamflow generated from the hydrographic apex of North America. For water resource managers, a key feature that emerges from these results is that the hydrograph of the 21st century may be evolving towards conditions unprecedented over the past 1000 years, extending beyond the 11th century when reduced glacier meltwater contributions were partly compensated by abundant snowmelt runoff. Continuing reduction in both peak and total discharge clearly underscores the need for stringent allocation of freshwater resources in these watersheds.

Wolfe, B. B.; Hall, R. I.; Edwards, T. W.; Jarvis, S. R.; Sinnatamby, R. N.; Yi, Y.; Johnston, J. W.

2009-05-01

295

The Jurassic of Denmark and Greenland: The Lower–Middle Jurassic of the Anholt borehole: implications for the geological evolution of the eastern margin of the Danish Basin  

Directory of Open Access Journals (Sweden)

Full Text Available This study of Upper Pliensbachian – Bajocian/Bathonian deposits in a borehole drilled on the island of Anholt, Denmark incorporates sedimentology, biostratigraphy (palynomorphs and foraminifera,palaeomagnetism and coal petrology. The studied succession records a gradual change from marine inner shelf storm-influenced clays to mainly terrestrial sands, clays, and lignite containing a flora ofmainly freshwater algae and pollen. The regression was initiated at the Pliensbachian–Toarcian boundary and marine influence ceased during Bajocian–Bathonian times; the regression thus took place earlier at Anholt than in the centre of the Danish Basin. The sediments in the Anholt borehole are referred to the Fjerritslev and Haldager Sand Formations. Although the Lower–Middle Jurassicboundary is commonly placed at the boundary between the two formations, our data indicate that at Anholt the upper Fjerritslev Formation (member F-IV is of Aalenian age. The Lower–Middle Jurassicboundary occurs close to the boundary between members F-III and F-IV of the Fjerritslev Formation.In contrast to other Lower–Middle Jurassic successions in the North Sea region, smectites of inferred volcanic origin are preserved in the Anholt section, suggesting limited burial and hence less intense diagenetic illitisation or chloritisation of smectites. A down-hole increase in diagenetic influence is reflected by the increase down-section both in the thermal stability of kaolinite and in the vitrinite reflectance. Kaolinite of inferred authigenic origin forms a white powder in the quartz-dominated sands of the Haldager Sand Formation; this kaolinite is thermally very unstable and is interpreted to be of late diagenetic, post-uplift origin. The vitrinite reflectance data indicate that the Jurassic formations have been exposed to thermal maturation corresponding to burial to a depth of 1000–1200 m below their present depth. Post-maturation uplift of the order of 1 km probably occurred partly during Late Cretaceous – Paleocene inversion in the Kattegat area and partly during Oligocene–Recent regional uplift, the latter being the most important of the two uplift phases. Palaeomagnetic data indicate that the main carrier of magnetic remanence is fine-grained magnetite. The stable remanence shows a pronounced inclination shallowing, which is attributed to post-depositional compaction.

Korsbech, Uffe

2003-10-01

296

Taphonomy of a Baurusuchus (Crocodyliformes, Baurusuchidae) from the Adamantina Formation (Upper Cretaceous, Bauru Basin), Brazil: Implications for preservational modes, time resolution and paleoecology  

Science.gov (United States)

Upper Cretaceous vertebrate accumulations from the Adamantina Formation are known due to their high taxonomic diversity. On the other hand, taphonomic analyses still are rare, limiting the understanding of processes related to the biostratinomic and fossildiagenetic histories of this lithostratigraphic unit. In 2005, fossils were collected from an outcrop located at Jales municipality, state of São Paulo, southeastern Brazil. From this outcrop, a well-preserved Baurusuchus was recovered, which displays a peculiar set of taphonomic signatures. This paper identifies and interprets taphonomic features of a specimen of Baurusuchus (Crocodyliformes, Baurusuchidae; UFRJ DG 418-R) from the Adamantina Formation (Upper Cretaceous of the Bauru Basin), in Jales municipality, state of São Paulo. Brief taphonomic comparisons with other specimens previously studied (crocodiles and dinosaurs) and a lithofaciological analysis of the outcrop were undertaken in order to enhance the knowledge of the stratigraphy and paleoenvironment and improve the time resolution for the Adamantina Formation in the region of Jales. Furthermore, paleoecological data were interpreted based on the taphonomic analysis. The fossil is composed of an articulated segment of vertebral column, ribs, part of the pelvic girdle and gastralia. There is no hydraulic equivalence between both the specimen of Baurusuchus and the size of quartz grain predominant in the fossiliferous layer, suggesting death in situ or short transport as a "water carcass". Teeth marks identified on the pubes were assigned to a small/juvenile baurusuchid crocodyliform or a theropod dinosaur. The repositioning of some elements (ribs and dorsal osteoderms) is suggestive of mummification. Desiccation marks were observed and attributed to the stage 1 of weathering. These features suggest subaerial exposure of the carcass prior to burial, however, probably after the mummification. On the other hand, the subaerial exposure was short, because the individual was not fully disarticulated. Furthermore, the degrees of articulation and preservation of the specimen nullify the hypothesis of reworking. Lithofaciological and taphonomic analyses suggest a well-drained floodplain as the burial environment and an arid or semi-arid climate in the region of Jales outcrop. In addition, the taphonomic signatures seem to indicate a time resolution about 100-104 years for the layer where the crocodyliforms were collected, but it seems to have, within this time limit, temporal-mixing among terrestrial crocodiles and dinosaurs collected from the same layer, suggesting time-averaging in this outcrop.

Araújo Júnior, Hermínio Ismael de; Silva Marinho, Thiago da

2013-11-01

297

Gravity anomaly across the Yap Trench, Sorol Trough, and southernmost Parece Vela Basin and its implications for the flexural deformation of the lithosphere and regional isostasy  

Science.gov (United States)

In June 2005, R/V Hakuho-maru (KH05-01-Leg 3) conducted a geological and geophysical survey of the southern tip of the Parece Vela Basin (PVB). The survey also profiled the Yap trench, the Yap arc and back-arc region, and Sorol Trough and collected multibeam bathymetry, gravity and magnetic data. In addition, one multichannel seismic reflection profiling across the Yap trench and two dredge rock samplings in the southwestern PVB were carried out. The shipboard free-air gravity field was measured by ZLS Dynamic Gravity Meter D-004 with calibration ties performed at Ocean Research Institute, University of Tokyo and at Apra Harbor in Guam. The shipboard gravity anomaly data show clear match with those derived from satellite altimetry. Also included in our analysis is the shipboard gravity data previously collected by R/V Onnuri. The Yap trench is unique in that it has a short trench-arc distance (approx. 50 km). This proximity has long been interpreted as feature resulting from a collision of over-thickened Caroline Ridge with the trench. In recent years, however, a new hypothesis has been put forward that such feature can be explained by initiation or rejuvenation of subduction, and that the style of subduction changes between north and south of the Sorol Trough. Our survey also revealed peculiar hook-shaped structures in the southernmost PVB and other evidences for large-scale, complex rotational deformation on the seafloor, whose origin remains unclear at this stage. To better understand the nature of these structures and features across Yap trench, Sorol Trough and in southernmost PVB, we examine the regional isostasy using the recently collected bathymetric and gravity data. The density information is deduced from studies conducted at other subduction systems, including Izu-Bonin Mariana trench, and from our own seismic experiment. Preliminary analysis shows that much of the features may be maintained by the flexural rigidity of the lithosphere, especially near and along the trench. To assess the significance of flexural strength of the crust, we apply various flexural models and see if they can explain the observed bathymetry and gravity. The results of this study may provide new clues that will help us to understand the overall tectonic framework of the region at the boundary between two plates, the Philippine Sea and Caroline plates, and their past interaction.

Kim, Y.; Lee, S.; Okino, K.; Koizumi, K.

2005-12-01

298

Deep seismic expression of a foreland basin: Taranaki basin, New Zealand  

Science.gov (United States)

A deep seismic-reflection profile shot across the South Taranaki basin, New Zealand, indicates up to 10 km of crustal thickening beneath the Taranaki boundary fault at the eastern margin of the basin. The seismic data also show a broad flexure of the entire crust, the locus of the flexure-producing load appearing to be in the vicinity of the Taranaki boundary fault. Such crustal thickening and flexure suggest a compressional, foreland-basin style of late Cenozoic development rather than the rift-graben origin previously assumed. This change in interpretation for the South Taranaki basin has implications for evaluating the thermal history of the basin and its possibilities for hydrocarbon prospects. The study therefore demonstrates the value of deep seismic exploration of a hydrocarbon-bearing basin in its early stage of exploration.

Stern, T. A.; Davey, F. J.

1990-10-01

299

Regional geologic characteristics relevant to horizontal drilling, Woodford Shale, Anadarko basin, Oklahoma  

Energy Technology Data Exchange (ETDEWEB)

Horizontal drilling in the Late Devonian-Early Mississippian Bakken Formation of the Williston basin has spurred new interest in other black shales as primary hydrocarbon reservoirs. The Late Devonian-Early Mississippian Woodford Shale, which is similar in some respects to the Bakken Formation, is a major source of oil and gas in the Anadarko basin of Oklahoma and could prove to be a significant reservoir rock as well. The three regional geologic characteristics of the Woodford discussed here are of likely importance to horizontal drilling programs, although direct relations to drilling strategy cannot be developed until empirical data from horizontal tests become available. First, the Woodford Shale is composed of three distinct depositional units (the upper, middle, and lower informal members) with different physical and geochemical properties. Second, a paleotopographic high that was rising before and during Woodford deposition divided the Woodford Shale into northeast and southwest depocenters. Third, Woodford depositional patterns are overprinted by thermal-maturity trends shaped primarily by differential burial of the Woodford during Pennsylvanian and Permian time. The Woodford Shale northeast of the forebulge is generally immature to marginally mature, whereas its thermal maturity southwest of the forebulge ranges from mature to postmature with respect to oil generation. A formation resistivity of about 35 ohm-m approximates the updip limit of oil-saturated Woodford Shale from which free oil might be produced from fracture systems.

Hester, T.C.; Schmoker, J.W. (Geological Survey, Denver, CO (United States))

1991-06-01

300

Neogene deformation and its implications for the structural framework of the oil fields in the Icapui-Ponta Grossa (CE) region, onshore Potiguar Basin, Brazil; Deformacao neogena e suas implicacoes na estruturacao dos campos de petroleo na regiao de Icapui-Ponta Grossa (CE), Bacia Potiguar emersa  

Energy Technology Data Exchange (ETDEWEB)

In coastal cliffs at the western portion of the Potiguar Basin (so-called Aracati Platform), the Barreiras Formation, of miocene age, displays structures pointing to high strain deformation. Detailed mapping of faults and folds geometry in the Barreiras Formation leads to recognition of extensional structures (at Ponta Grossa village) and contractional oblique structures (Vila Nova, next to Icapui town), both of them related to a trans current system bearing NE (at these locations) and NW trends (Afonso Bezerra Fault, in the central portion of the basin). These data point to a neo gene stress field which generated faults, folds and hydro plastics structures, including SL fabrics and shear zones, as well as reactivated older structures in the underlying neocretaceous sedimentary section. Reinterpretation of seismic sections from this region and other geological data at several places in the Potiguar Basin outline structures which are correlated (in style and kinematic regime) throughout the siliciclastic rocks of the Acu Formation, limestones of the Jandaira Formation and younger basalts of the Macau Formation, whose age straddles the Oligocene-Miocene boundary. This structural framework recognized at the surface has to be compatible with subsurface deformation as observed in seismic sections, which includes pulses/events of older, Neocretaceous to Paleocene age. This model has important implications as regards the structure (geometry, kinematics, age of traps) of oil reservoirs (especially the sandstones of the Acu Formation, in the Fazenda Belem Oil Field) and the processes of migration and hydrocarbon entrapment at this region of the Potiguar Basin. (author)

Sousa, Debora do Carmo [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Programa de Pos-Graduacao em Geodinamica e Geofisica]. E-mail: debora@geologia.ufrn.br; Sa, Emanuel Ferraz Jardim de; Antunes, Alex Francisco [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Dept. de Geologia

2008-06-15

 
 
 
 
301

North Western River Basin  

...2015North Eastern River BasinNorth Western River BasinRivers and LakesCoastal and...Visits WMUDevelopment ManagementStormwater ManagementNorth Western River BasinManaging our Shared Waters (.PDF 1...

302

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

1992-05-12

303

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

304

Distribution, Statistics, and Resurfacing of Large Impact Basins on Mercury  

Science.gov (United States)

The distribution and geological history of large impact basins (diameter D greater than or equal to 300 km) on Mercury is important to understanding the planet's stratigraphy and surface evolution. It is also informative to compare the density of impact basins on Mercury with that of the Moon to understand similarities and differences in their impact crater and basin populations [1, 2]. A variety of impact basins were proposed on the basis of geological mapping with Mariner 10 data [e.g. 3]. This basin population can now be re-assessed and extended to the full planet, using data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. Note that small-to- medium-sized peak-ring basins on Mercury are being examined separately [4, 5]; only the three largest peak-ring basins on Mercury overlap with the size range we consider here. In this study, we (1) re-examine the large basins suggested on the basis of Mariner 10 data, (2) suggest additional basins from MESSENGER's global coverage of Mercury, (3) assess the size-frequency distribution of mercurian basins on the basis of these global observations and compare it to the Moon, and (4) analyze the implications of these observations for the modification history of basins on Mercury.

Fassett, Caleb I.; Head, James W.; Baker, David M. H.; Chapman, Clark R.; Murchie, Scott L.; Neumann, Gregory A.; Oberst, Juergen; Prockter, Louise M.; Smith, David E.; Solomon, Sean C.; Strom, Robert G.; Xiao, Zhiyong; Zuber, Maria T.

2012-01-01

305

Unexpected renaissance : emerging smaller oil plays are energizing the Western Canadian Sedimentary Basin  

Energy Technology Data Exchange (ETDEWEB)

The article summarized the recent activities of companies using horizontal technology to tap reservoirs throughout Western Canada that were uneconomic with vertical wells. Some of these plays do not even require fracturing. The Pekisko play in southeastern Alberta, the Birdbear play in west central Saskatchewan, the Mannville Group in west central Alberta, and the 50-year-old Steelman field in the Williston Basin of southeastern Saskatchewan are all seeing renewed activities as a result of horizontal technology. Relying on the prospects inherent to horizontal technology, parcels in Sawn Lake, Otter, Slave, and Red Earth in northern Alberta have been aggressively acquired for potential new and emerging plays, and tight oil is being pursued at Swan Hills, Deer Mountain, House Mountain, and Judy Creek. In northeastern British Columbia, two companies have partnered in two wells just west of the Maxhamish gas field. The Montney, usually considered a gas play, is now being drilled for oil using horizontal technology. This surge in activity may reverse the long-term slide in Western Canada's light oil output. Emerging oil plays are providing prospects for small companies not large enough to pursue costly shale gas plays. The advent of horizontal technology has greatly increased the resource potential. In new plays where light oil can be tapped horizontally without the expense of fracs, operators are able to achieve payout more quickly. 4 figs.

Roche, P.

2010-11-15

306

Mechanisms and biogeochemical implications of Cenomanian/Turonian black shale formation in North Africa:An integrated geochemical, millennial-scale study from theTarfaya-LaAyoune Basin in SW Morocco  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Cenomanian/Turonian (C/T; ~94 Ma ago) black shale successions from various N African basins, in particular from the Tarfaya-LaAyoune Basin (SW Morocco), have been studied in great detail using data from the field (including gamma-ray resistivity logging), sedimentology and advanced geochemical trace metal, biomarker and stable isotope methods. Deposition of these black shale units in most of the region was restricted to a short time envelope termed the C/T oceanic anoxic event (OAE2). During ...

Kolonic Sadat

2003-01-01

307

Reserves in Western Basins  

Energy Technology Data Exchange (ETDEWEB)

The objective of this project is to investigate the reserves potential of overpressured tight (OPT) gas reservoirs in three Rocky Mountain basins. These are the Greater Green River Basin (GGRB), Uinta Basin and Piceance Basin. By documenting productive characteristics in these basins and characterizing the nature of the vast gas resources in place, the reserves potential may be understood and quantified. Through this understanding, it is hoped that the oil and gas industry will be encouraged to pursue exploitation of this resource. At this point in time, the GGRB work has been completed and the final report submitted for publication. Work on the Uinta basin has just commenced and work on the Piceance basin will commence next year. Since the GGRB portion of this project has been completed, further discussion centers upon this Basin.

Caldwell, R.H.; Cotton, B.W.

1993-12-31

308

Penobscot River Basin Overview.  

Science.gov (United States)

The New England River Basins Commission has prepared summary reports on each of the region's major river basins. These reports concentrate on identifying problems in the existing network of planning and resource management programs. The most significant w...

1981-01-01

309

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.

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

310

Identifying River Basin Districts  

Identifying River Basin Districts The Water Framework Directive requires us to identify River Basin Districts. These Districts are used in the WFD to manage water environments. In England and Wales we have identified 11 River Basin Districts: * Six entirely in England (Anglian, Humber, North West, South…

311

Long Hair Shampoo Basin.  

Science.gov (United States)

The present invention relates to a long hair shampoo basin for use at barber shops and beauty salons. More specifically, the present invention is directed to shampoo basins which are adapted for shampooing longer hair than is accommodated by present basin...

K. Schulken

2005-01-01

312

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  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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), ...

Gaulier J. M.; Chamot-Rooke N.; Jestin F.

2006-01-01

313

Uncertainty in soil physical data at river basin scale  

Digital Repository Infrastructure Vision for European Research (DRIVER)

For hydrological modelling studies at the river basin scale, decision makers need guidance in assessing the implications of uncertain data used by modellers as an input to modelling tools. Simulated solute transport through the unsaturated zone is associated with uncertainty due to spatial variability of soil hydraulic properties and derived hydraulic model parameters. In general for modelling studies at the river basin scale spatially available data at various scales must be aggregated to an...

2006-01-01

314

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  

Science.gov (United States)

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 rudimentary compared to the cyclostratigraphically constrained Mediterranean stages. This lack of chronostratigraphic control restricts the insight in the timing of geodynamic, climatic, and paleobiogeographic events and thereby hinders the identification of their causes and effects. In this paper, we here derive better age constraints on the Badenian, Sarmatian and Pannonian Central Paratethys regional stages through integrated 40Ar/39Ar, magnetostratigraphic, and biostratigraphic research in the Transylvanian Basin. The obtained results help to clarify the regions Middle Miocene geodynamic and paleobiogeographic evolution. Six new 40Ar/39Ar ages were determined for tuffs intercalating with the generally deep marine basin infill. Together with data from previous studies, there is now a total of 9 radio-isotopically dated horizons in the basin. These were traced along seismic lines into a synthetic seismic stratigraphic column in the basin center and serve as first order tie-points to the astronomically tuned Neogene timescale (ATNTS). Paleomagnetically investigated sections were treated similarly and their polarity in general corroborates the 40Ar/39Ar results. The integrated radio-isotopic and magnetostratigraphic results provide an improved high-resolution time-frame for the sedimentary infill of the Transylvanian Basin. Early Badenian deep water sedimentation is characterized by accumulation of the Dej Tuff Complex in response to a period of intensive volcanism, the onset of which is constrained between the first occurrence (FO) of Orbulina suturalis at 14.56 Ma and 14.38 ± 0.06 Ma. During the subsequent Badenian Salinity Crisis (BSC) up to 300 m of salt accumulate in the basin center. The faunal turnover that marks the Badenian-Sarmatian Boundary is dated at 12.80 ± 0.05 Ma. A second phase of intense volcanism occurs at 12.4 Ma and leads to deposition of the middle Sarmatian tuff complex (Ghiri?, H?d?reni, Turda and Câmpia Turzii tuffs). Rates of sediment accumulation strongly diminish in the basin center at the onset of the Pannonian stage coincident with an approximately 20° CW tectonic rotation of the Tisza-Dacia plate. Concurrent enhanced uplift in the Eastern a'nd Southern Carpathians leads to the isolation of the Central Paratethys and triggers the transition from marine to freshwater conditions. An additional Pannonian to post-Pannonian 6° of CW rotation is related to the creation of antiform geometries in the Eastern Carpathians which are notably larger in the north than in the south. An 8.4 Ma age is determined for the uppermost Pannonian sediments preserved in the central part of the Transylvanian Basin. Two sections belonging to middle Pannonian Zone D, and the lower part of Zone E (Subzone E1) are found to cover the 10.6-9.9 Ma time-interval.

de Leeuw, Arjan; Filipescu, Sorin; Ma?enco, Liviu; Krijgsman, Wout; Kuiper, Klaudia; Stoica, Marius

2013-04-01

315

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

316

Reserves in western basins  

Energy Technology Data Exchange (ETDEWEB)

This project requires generation of producible tight gas sand reserve estimates for three western basins. The requirement is to perform such reserve estimates using industry accepted practices so that results will have high credibility and acceptance by the oil and gas industry. The ultimate goal of the project is to encourage development of the tight gas formation by industry through reduction of the technical and economic risks of locating, drilling and completing commercial gas wells. The three geological basins selected for study are the Greater Green River Basin, Uinta Basin and Piceance Basin, located in the Colorado, Utah and Wyoming Rocky Mountain region.

Caldwell, R.H.; Cotton, B.W.

1992-06-01

317

Reserves in western basins  

Energy Technology Data Exchange (ETDEWEB)

This project requires generation of producible tight gas sand reserve estimates for three western basins. The requirement is to perform such reserve estimates using industry accepted practices so that results will have high credibility and acceptance by the oil and gas industry. The ultimate goal of the project is to encourage development of the tight gas formation by industry through reduction of the technical and economic risks of locating, drilling and completing commercial gas wells. The three geological basins selected for study are the Greater Green River Basin, Uinta Basin and Piceance Basin, located in the Colorado, Utah and Wyoming Rocky Mountain region.

Caldwell, R.H.; Cotton, B.W.

1992-01-01

318

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 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

1995-03-20

319

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, ...

2009-01-01

320

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  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 hyd...

Antonio Rangel; Roberto Hernández

2007-01-01