WorldWideScience
 
 
1

Diagenesis and fracture development in the Bakken Formation, Williston Basin; implications for reservoir quality in the middle member  

Science.gov (United States)

The middle member of the Bakken Formation is an attractive petroleum exploration target in the deeper part of the Williston Basin because it is favorably positioned with respect to source and seal units. Progressive rates of burial and minor uplift and erosion of this member led to a stable thermal regime and, consequently, minor variations in diagenesis across much of the basin. The simple diagenetic history recorded in sandstones and siltstones in the middle member can, in part, be attributed to the closed, low-permeability nature of the Bakken petroleum system during most of its burial history. Most diagenesis ceased in the middle member when oil entered the sandstones and siltstones in the Late Cretaceous. Most oil in the Bakken Formation resides in open, horizontal fractures in the middle member. Core analysis reveals that sandstones and siltstones associated with thick mature shales typically have a greater density of fractures than sandstones and siltstones associated with thin mature shales. Fractures were caused by superlithostatic pressures that formed in response to increased fluid volumes in the source rocks during hydrocarbon generation

Pitman, Janet K.; Price, Leigh C.; LeFever, Julie A.

2001-01-01

2

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 determination 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) 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.

Carrell, L. A., Luff Exploration Co., Denver, CO

1997-12-01

3

Geology and natural gas occurrence, western Williston Basin  

Energy Technology Data Exchange (ETDEWEB)

The W. Williston Basin has produced gas since a 1913 discovery at Cedar Creek anticline, but during the past decade nearly all the gas found has been in solution in oil. In a sedimentary rock section averaging 10,000 ft in thickness, about one-third of the material, in approx. the lower half of the section, consists of carbonate and evaporites. The rest of the beds are principally sandstone and shale of shallow-marine deposition. All commercial gas in Paleozoic rocks is in solution in oil. Small gas reserves have been found in fractured siltstones of the Cretaceous Colorado shale at Hardin, and in the Shannon sandstone at Pumpkin Creek. Most of the gas in the W. Williston Basin is in nonassociated accumulations in and adjacent to the Cretaceous Judith River and Eagle formations. The trapping is related partly to folding, but also is at the extreme seaward limits of sandstone tongues. Porosity of less than 10% and low permeability values are characteristic of the reservoirs and fracturing is regarded as important in improving overall permeability of the reservoirs. At Cedar Creek anticline, 6 million cu ft a day of 90% nitrogen gas was treated in a Cambrian sandstone.

McCrae, R.O.; Swenson, R.E.

1968-01-01

4

Feasibility of air injection- based processes for Williston Basin reservoirs  

Energy Technology Data Exchange (ETDEWEB)

The paper describes the following aspects of in-situ combustion of a petroleum deposit: as an air injection process, types of air injection processes, spontaneous and nitrogen MMP, Williston Basin air injection projects, novel thermal recovery technology, and screening criteria for air injection-based enhanced oil recovery (EOR) processes. As an air injection process ISC has two phases: ignition and propagation of the in-situ combustion (ISC) front, both high temperature oxidation and low temperature oxidation, and the ISC process definition assumes that HTO is present. There are 4 types of air injection processes: immiscible air flooding with intensive oxidation, immiscible air flooding without intensive oxidation, and miscible air flooding with and without intensive oxidation. Aspects of spontaneous ignition referred to are: what it is, how it happens, and its advantages and disadvantages. Williston Basin air injection projects are discussed referring to: very low permeability rock, micro- vs. extended macro-fractures, gas processing plant to recover NGL, and successful application at 17$/bbl of oil for an application in patterns. The novel thermal recovery technology involves toe-to-heel air injection, and is illustrated. The screening criteria for air injection-based EOR processes include: oil viscosity, depth, reservoir temperature, nitrogen MMP, net pay thickness, oil saturation, and no fracturing, large gas cap or bottom water.

Turta, A.T.; Singhal, A.K. [Petroleum Recovery Inst., Calgary, AB (Canada)

1999-12-01

5

77 FR 12281 - Williston Basin Interstate Pipeline Company; Notice of Request Under Blanket Authorization  

Science.gov (United States)

...Commission's Regulations. The sales tap installation included a steel pipe riser with a shut-in valve and other pipe fittings at the location located in Williston Basin's existing pipeline right-of-way. The sales tap was necessary...

2012-02-29

6

Sulfur isotope ratios in petroleum research and exploration: Williston basin  

International Nuclear Information System (INIS)

The three major types of crude oil in the Williston basin - the type I oils of the Winnipeg-Red River system, the type II oils of the Bakken-Madison system, and the type III oils of the Tyler-Pennsylvanian system - can be distinguished by their sulfur isotope compositions. They have characteristic delta34S values of 5.8 +- 1.2 parts per thousand (ppt), 2.8 +- 0.8 ppt, and -4.0 +- 0.7 ppt respectively. Highly mature oils have less typical values. Type II oils which have migrated over a distance of some 150 km beyond the region of generation have maintained their characteristic delta34S values even though sulfur may have been lost. This indicates little or no interaction with reservoir sulfates under normal circumstances. On the periphery of the basin, type II oils altered by water washing and biodegradation have altered delta34S values which increase from +2.9 to +9.4 ppt with the increasing degree of crude oil degradation. The Bakken shales, source of the type II oils, have delta34S distribution patterns in the reduced sulfur typical of marine sediments. The delta34S values for the type II oils match most closely the delta34S value of organic sulfur in the black bituminous shales of the lower Bakken

7

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

8

Palaeo-hydrogeology of the Cretaceous Sediments of the Williston Basin using Stable Isotopes of Water  

Science.gov (United States)

Hydraulic and isotopic data collected from aquifers are typically used to characterize hydrogeological conditions within sedimentary basins. Similar data from confining units are generally not collected despite their ability to provide insights into important water/solute transport controls. In this study, we characterized palaeo-groundwater flow and solute transport mechanisms across 384 m of a Cretaceous shale aquitard in the Williston Basin, Canada, using high-resolution depth profiles of water isotopes (?18O and ?2H). Water samples were also collected from wells installed in the underlying regional aquifer (Mannville Fm; 93 m thick) and from seepage inflows into potash mine shafts (to 825 m below ground). 1-D numerical transport modeling of isotopic profiles yielded insight into large-scale/long-term solute transport in both Cretaceous sediments and the Basin. Molecular diffusion was determined to be the dominant solute transport mechanism through the aquitard. Transport model simulations suggest average vertical groundwater velocities of meteoric water to the aquifer underlying the aquitard, likely along an aquifer outcrop area east of the site or through local vertical conduits in the aquitard. Simulations suggest these recharge events occurred during one or more glacial periods. The isotopic profile over the upper 25 m of Pleistocene till and shale is consistent with glacial deposition and transport processes within these units during the Holocene (past 10 ka).

Hendry, Michael J.; Barbour, S. Lee; Novakowski, Kent; Wassenaar, Len I.

2013-04-01

9

Paleohydrogeology of the Cretaceous sediments of the Williston Basin using stable isotopes of water  

Science.gov (United States)

Hydraulic and isotopic data collected from aquifers are routinely used to characterize hydrogeological conditions within sedimentary basins, but similar data from confining units are generally not collected despite their ability to provide insights on important water/solute transport controls. We characterized paleogroundwater flow and solute transport mechanisms across 384 m of Cretaceous shale (aquitard) in the Williston Basin, Canada, using high-resolution depth profiles of water isotopes (?18O, ?2H). Water samples were also collected from wells installed in the underlying regional sandy aquifer (Mannville Fm; 93 m thick) and from seepage inflows into potash mine shafts (to 825 m below ground). The 1-D numerical transport modeling of ?18O profiles provided insight into large-scale/long-term solute transport in both Cretaceous sediments and the basin. Despite the potential for significant advective migration during glaciations, molecular diffusion appears to be the dominant solute transport mechanism through the aquitard. Simulations suggest average vertical groundwater velocities of meteoric water to the aquifer underlying the shale, likely along an aquifer outcrop area east of the site or through local vertical conduits. Simulations suggest these recharge events occurred during one or more glacial periods. The isotopic profile over the upper 25 m of Pleistocene till and shale is consistent with glacial deposition and transport processes within these units over the Holocene (past 10 ka).

Hendry, M. Jim; Barbour, S. L.; Novakowski, K.; Wassenaar, L. I.

2013-08-01

10

Regional-scale flow of formation waters in the Williston basin  

Energy Technology Data Exchange (ETDEWEB)

The Williston basin is a structurally simple intracratonic sedimentary basin that straddles the United States-Canada border east of the Rocky Mountains and that contains an almost continuous stratigraphic record since the Middle Cambrian. Based on the wealth of data generated by the oil industry, the regional-scale characteristics of the flow of formation waters were analyzed for the Canadian side of the basin, and integrated with previous studies performed on the American side. Several aquifers and aquifer systems identified in the basin were separated by intervening aquitards and aquicludes. The Basal, Devonian, and Mannville (Dakota) aquifers are open systems, being exposed at the land surface in both recharge and discharge areas. Recharge takes place in the west-southwest at relatively high altitude in the Bighorn and Big Snowy mountains and at the Black Hills and Central Montana uplifts, whereas discharge takes place in the east and northeast at outcrop along the Canadian Precambrian shield in Manitoba and the Dakotas. The Mississippian and Pennsylvanian aquifer systems are semi-open, cropping out only in the west-southwest where they recharge, but discharging in the northeast into adjacent aquifers through confining aquitards. On regional and geological scales, the entire system seems to be at steady-state, although locally transient flow is present in places due to water use and hydrocarbon exploitation, and to some erosional rebound in the uppermost confining shales. On the western flank of the basin, the interplay between the northeastward structural downdip direction and the northeastward flow of formation waters creates conditions favorable for hydrodynamic oil entrapment.

Bachu, S. [Alberta Department of Energy, Edmonton (Canada); Hitchon, B. [Hitchion Geochemical Services Ltd., Alberta (Canada)

1996-02-01

11

Stable isotope and organo-geochemical studies on Phanerozoic sediments of the Williston Basin, North America  

International Nuclear Information System (INIS)

Carbon isotope studies have been carried out on marine Phanerozoic sediments of the Williston Basin, North America. Special attention was given to the recognition of systematic variations with age. 13C abundance measurements show a 3 per mil. depletion from the Cambrian to the Mississippian and a 1-2 per mil. enrichment to the Jurassic. It is suggested that real variations in the rate of photosynthesis may have been the driving force for these changes with age. A significant 3 per mil. depletion was observed from the Devonian to the end of the Carboniferous. This depletion seems to occur on a worldwide scale. It is therefore proposed that a rise in the rate of photosynthesis as a consequence of the colonization of the continents by higher plants is the global cause of this displacement in the isotope record of the total organic carbon. The bitumen fraction does not show any systematic isotope variations with age. During the Ordovician-Mississippian time period no significant (>1 per mil.) differences in the isotope values of bitumen and organic matter can be observed. In contrast the bitumen fraction is depleted in 13C as compared to the total organic carbon in the Cambrian as well as in the Pennsylvanian-Cretaceous time interval. Several parameters support the theory that the rank of the organic matter may be responsible for the observed isotopic pattern. (Auth.)

12

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

13

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

Science.gov (United States)

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

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

2008-12-01

14

Bakken/Madison petroleum systems in the Canadian Williston Basin. Pt. 4: diphenylmethanes and benzylcyclohexanes as indicators for oils derived from the Madison petroleum system  

Energy Technology Data Exchange (ETDEWEB)

Alkyl derivatives of diphenylmethane and benzylcyclohexane were identified as significant components of the Family C oils, and related Mississippian source rocks, in the Canadian Williston Basin. The co-occurrence of these two structurally related compound classes in this specific source rock interval, and their relatively low abundance in other petroleum systems, indicates the great utility of these aromatic hydrocarbons as effective molecular markers for oil-oil and oil-source correlation, particularly for highly mature light oils. (Author)

Chunqing Jiang; Maowen Li [Geological Survey of Canada, Calgary (Canada)

2002-07-01

15

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

Science.gov (United States)

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

Hendry, M. Jim; Harrington, Glenn A.

2014-08-01

16

Geology of the Cannonball Formation (Paleocene) in the Williston basin, with reference to uranium potential. Report of investigation No. 57  

International Nuclear Information System (INIS)

The Paleocene Cannonball Formation is a marine, non-lignitic-bearing clastic sequence in the lower part of the Fort Union Group. It is overlain by the lignite-bearing Tongue River Formation in places and both overlain and underlain by the lignite-bearing Ludlow Formation in places. The Cannonball crops out primarily in southwest-central North Dakota and probably occurs throughout the western one-half of the state. It occurs also in northwestern South Dakota and may extend into parts of Saskatchewan and Manitoba. Poorly consolidated, very fine- to fine-grained, light to medium brownish yellow-weathering sandstone and light gray-weathering, sandy mudstone are the principal types of lithology. Mudstone generally predominates in North Dakota whereas sandstone seems to predominate in South Dakota. Although uranium in the Williston basin has been found almost entirely in lignite and nonmarine carbonaceous rocks, its occurrence in the marine Cannonball Formation is possible. If the Cannonball, Ludlow, Tongue River, and Sentinel Butte Formations are at least partly penecontemporaneous, a variety of depositional environments were in areal juxtaposition during the Paleocene. Streams originating or passing through coastal plain bogs could have carried uranium ions (derived from volcanic materials) to the Cannonball sea where they were deposited syngenetically. Epigenetic uranium may occur in Cannonball mudstones or sandstones that directly underlie the Ludlow Formation, which isly underlie the Ludlow Formation, which is known to contain volcanic materials

17

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

18

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

Science.gov (United States)

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

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

2005-01-01

19

Geology of the upper part of the Fort Union Group (Paleocene), Williston Basin, with reference to uranium  

International Nuclear Information System (INIS)

Tabular sandstone beds in the Sentinel Butte Formation are thicker (as much as 30 m thick), more laterally extensive (more than 2 km wide in many places), and more abundant than in the Tongue River Formation. This indicates that high-sinuosity streams were more abundant where the Sentinel Butte Formation was deposited, and the streams were deeper and occupied wider meander belts, as would be found on the landward part of the delta plain. Siltstone, claystone, lignite, and a small amount of limestone were deposited on natural levees, crevasse splays, and in flood basins. The vertical arrangement of the two formations indicates a progradation of a large deltaic complex into the sea in which the Cannonball Formation was deposited. Sandstone in the Tongue River Formation classifies mostly as carbonate litharenite, and the fine fraction of the formation consists mostly of mica-group minerals, some kaolinite-group minerals, and a little montmorillonite. Sandstone in the Sentinel Butte Formation classifies mostly as volcanic litharenite, and the fine fraction consists mostly of montmorillonite, some kaolinite-group minerals, and a little of the mica-group minerals. The highest-grade uranium deposits in North Dakota are in the Sentinel Butte Formation in the area of the Little Missouri River escarpment in eastern Billings and northwestern Stark Counties. Little uranium has been found in the Tongue River Formation. Uranium may be more abundant in the Sentinel Butte Formation babundant in the Sentinel Butte Formation because of the abundance of glassy volcanic matter, which has now been largely altered to montmorillonite, and the abundance of fragments of volcanic rock. Weathering of the upper part of the Sentinel Butte Formation during formation of the Eocene paleosol in the northern Great Plains may have mobilized uranium that was deposited in the formation below the paleosol before deposition of the overlying Oligocene and younger sediment

20

Manitoba Williston Basin activity update  

Energy Technology Data Exchange (ETDEWEB)

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

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

2003-07-01

 
 
 
 
21

75 FR 65224 - Amendment of Class E Airspace; Williston, ND  

Science.gov (United States)

...IFR) operations at the airport. DATES: Effective date: 0901 UTC, January 13, 2011...the Williston VORTAC 317[deg] radial extending from the 6.6-mile...the Williston VORTAC 135[deg] radial extending from the 6.6-...

2010-10-22

22

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

Science.gov (United States)

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

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

2014-07-01

23

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

International Nuclear Information System (INIS)

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

24

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.

Forsberg, René

2003-01-01

25

AEROBIC DENITRIFICATION: IMPLICATIONS FOR THE MOM RIVER BASIN  

Science.gov (United States)

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

26

Geochemical characterization of Parana Basin volcanic rocks: petrogenetic implications  

International Nuclear Information System (INIS)

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

27

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

International Nuclear Information System (INIS)

ocene and into the Pliocene. This work is to be extended to other well sections in the basin that intersect other inversion structures. The implications of this work for the hydrocarbon prospectivity of the basin is that it better defines the timing of the formation of the potential trapping structures in relation to the timing of maturation. Copyright (1999) Geological Society of Australia

28

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

Scientific Electronic Library Online (English)

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

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

29

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

30

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

31

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

32

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

Directory of Open Access Journals (Sweden)

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

C. A. Scott

2013-07-01

33

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

34

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

Science.gov (United States)

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

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

2013-06-01

35

Topography of Beethoven and Tolstoj Basins, Mercury: Implications for Lithospheric Flexure  

Science.gov (United States)

Interior structures of two mercurian basins, Beethoven and Tolstoj, are characterized using topography derived from Mariner 10 stereo images. The topography of the two mercurian basins is similar to that of lunar mare-filled basins, such as Serenitatis. In addition to topography, the tectonic features within Beethoven and Tolstoj basins are compared to those of lunar basins. Beethoven and Tolstoj basins exhibit little evidence of deformation compared to Caloris basin and their lunar counterparts. Well-developed basin-concentric wrinkle ridges and arcuate graben are characteristic of many lunar basins and are thought to result from lithospheric flexure in response to the superisostatic load from the mare basalts. The presence of wrinkle ridges in the floor of Caloris basin suggests that the basin interior has undergone compression, possibly the result of subsidence of the interior fill. Because both Beethoven and Tolstoj lack basin-concentric wrinkle ridges and arcuate graben, we suggest that either Mercury's elastic lithosphere was too strong for significant lithospheric flexure and subsidence to occur, or the basin fill material provides little density contrast and thus exerts little net load on the mercurian lithosphere. Compositional evidence from color-derived parameter images of Tolstoj basin indicates that the basin fill has an FeO abundance comparable to that of average mercurian crust. This suggests that the basin fill has a similar density to the surrounding crustal material and that the load may be insufficient to induce flexure.

Andre, S. L.; Watters, T. R.

2005-12-01

36

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

International Nuclear Information System (INIS)

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

37

Evolution of the intracratonic Officer Basin, central Australia: implications from subsidence analysis and gravity modelling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The intracratonic basins of central Australia are distinguished by their large negative Bouguer gravity anomalies, despite the absence of any significant topography. Over the Neoproterozoic to Palaeozoic Officer Basin, the anomalies attain a peak negative amplitude in excess of 150 mGal, amongst the largest of continental anomalies observed on Earth. Using well data from the Officer and Amadeus basins and a data grid of sedimentary thicknesses from the eastern Officer Basin, we have assessed ...

Haddad, D.; Watts, Ab; Lindsay, J.

2001-01-01

38

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Silva Gonza?lez, Patricio

2010-01-01

39

Late Vendian Early Palæozoic tectonic evolution of the Baltic Basin: regional tectonic implications from subsidence analysis  

Science.gov (United States)

Subsidence analysis was performed on 43 boreholes penetrating the Upper Vendian-Lower Palaeozoic sedimentary succession of the Baltic Basin. The results were related to lithofacial and structural data to elucidate subsidence mechanisms and the regional tectonic setting of basin development. Tectonic subsidence patterns are consistent throughout the basin for the time period studied. An extensional tectonic subsidence event, possibly of two phases, is indicated from the Late Vendian to the beginning of the Middle Cambrian. This event is seen in the southwestern part of the Baltic Basin (Peri-Tornquist zone) until the earliest Cambrian after which it is also observed in the SW-NE-trending Baltic Depression part of the basin. Basin development during this time is interpreted as recording the latest stages of break-up of the Precambrian super-continent Rodinia and ultimately the formation of the Tornquist Sea. The late Middle Cambrian to Middle Ordovician tectonic subsidence pattern of the Baltic Basin is characteristic of post-rift thermal subsidence of the newly formed passive continental margin of Baltica, developed along its southwestern edge. A gradual increase in subsidence rate is observed from the (Middle?) Late Ordovician and throughout the Silurian (particularly for Ludlow and Pridoli times) creating subsidence curves with convex shapes typical of foreland basin development. The rate of Late Silurian tectonic subsidence increases significantly towards the southwest margin of the Baltic basin, adjacent to the present location of the North German-Polish Caledonides. The Baltic Basin therefore appears to have developed primarily as a flexural foreland basin during Silurian oblique collision of Baltica and Eastern Avalonia. A foreland setting is supported by the influx of distal turbidites into the basin from southwest sources in the Late Silurian. Compressional deformation structures of Early Devonian (Lochkovian) age are seen in seismic sections in the central part of the Baltic Basin (Lithuania). These, together with a change in subsidence pattern, mark the end of the Caledonian stage of basin development of the Baltic Basin.

Poprawa, P.; Šliaupa, S.; Stephenson, R.; Lazauskien?, J.

1999-12-01

40

Basin and Crater Ejecta Contributions to the South Pole-Aitken Basin (SPA) Regolith; Positive Implications for Robotic Surface Samples  

Science.gov (United States)

The ability of impacts of all sizes to laterally transport ejected material across the lunar surface is well-documented both in lunar samples [1-4] and in remote sensing data [5-7]. The need to quantify the amount of lateral transport has lead to several models to estimate the scale of this effect. Such models have been used to assess the origin of components at the Apollo sites [8-10] or to predict what might be sampled by robotic landers [11-13]. Here we continue to examine the regolith inside the South Pole-Aitken Basin (SPA) and specifically assess the contribution to the SPA regolith by smaller craters within the basin. Specifically we asses the effects of four larger craters within SPA, Bose, Bhabha, Stoney, and Bellinsgauzen all located within the mafic enhancement in the center of SPA (Figure 1). The region around these craters is of interest as it is a possible landing and sample return site for the proposed Moon-Rise mission [14-17]. Additionally, understanding the provenance of components in the SPA regolith is important for interpreting remotely sensed data of the basin interior [18-20].

Petro, Noah E.; Jolliff, B. L.

2011-01-01

 
 
 
 
41

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

42

Field development with 3D seismic --a Williston basin case history  

Energy Technology Data Exchange (ETDEWEB)

The Medicine Lake field survey demonstrates that 3D seismic data, as a result of its enhanced subsurface imaging and areal sampling, can assist field development by providing: an improved structural picture; recognition of stratigraphic variations; and detection of possible porosity zones. For fields of a similar structural complexity and size, a ''mini-3D,'' costing less than a fifth of a dry hole, is a viable field development tool.

Robinson, G.C.; Baixas, F.; Hooyman, P.J.

1983-09-05

43

Three-dimensional seismic survey applied to field development in Williston basin  

Energy Technology Data Exchange (ETDEWEB)

The Medicine Lake field of Sheridan County, Montana, was discovered in March 1979 by the drilling of a seismic anomaly. Production is obtained from Paleozoic carbonate reservoirs ranging in age from Ordovician to Mississippian. Cumulative production from the field, as of March 1982, is 1.2 million bbl. A mini-3D seismic survey was acquired in October 1981 to facilitate development drilling. The survey covered 2.4 mi/sup 2/ (6.2 km/sup 2/), encompassing the field's seven producing wells and two dry holes. The purpose of this survey was to provide an accurate image of the subsurface structure and delineate the extent of the producing formations. The areal coverage and improved subsurface imaging of the 3D survey provided a detailed view of the Medicine Lake anomaly. The seismic data reveals that the structure results from a local basement (Precambrian) high. Mapping of the Ordovician Winnipeg Formation revealed a domal structure covering approximately 0.6 mi/sup 2/ (1.5 km/sup 2/) with closure in excess of 180 ft (55 m). Although all producing wells are located on the Medicine Lake structure, stratigraphic variations within the reservoirs may localized production within structural closure. Porosity in several producing formations is diagenetic; prediction of reservoir trends from well data alone is difficult. Inversion and interactive modeling were used to study these stratigraphic variations. A correlation between relative acoustic impedance and porosity was established for several formations. Vertical and horizontal relative acoustic impedance sections were then employed to locate zones of possible porosity. This information, combined with the improved structural data, should aid in further development of the Medicine lake field.

Robinson, G.C.; Baixas, F.; Hooyman, P.J.

1983-08-01

44

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

45

Strymon and Strymonikos Gulf basins (Northern Greece): Implications on their formation and evolution from faulting  

Science.gov (United States)

In Central and Eastern Macedonia of Northern Greece large NW-SE trending basins filled up mainly with terrestrial sediments developed during the Neogene over the Alpine basement rocks. Among them, the Strymon basin was established along the NNW-SSE trending Strouma/Strymon Lineament which formed over the tectonic boundary of the Serbomacedonian and Rhodope massifs, both representing the hinterland of the Hellenic orogen. The present study suggests that the Strymon basin was not formed as a syn-detachment basin over the Strymon Valley Detachment Fault, considered to have caused exhumation of the Rhodope massif metamorphic complex. Instead, transpressional s.l. tectonics dominated the region in the Late Oligocene-Early Miocene and it progressively changed into a wrench tectonics under which the Strymon basin has been initiated in the Middle Miocene. The basin continued to develop further under a short-lived NW-SE extension in the Middle-Late Miocene. The whole deformation is attributed to the late-stage collisional processes between the Apulia and Eurasia plates. The prevalent NE-SW extension has been constrained later on in the Late Miocene and Pliocene times activating both low-angle and high-angle NW-SE trending faults and causing the regional tilting towards the SW of the mountain fault blocks (i.e., mountain chains). From Quaternary onwards, the Strymon basin has been separated from the Strymonikos Gulf basin due to an N-S extension that mainly activates E-W striking normal faults.

Tranos, Markos D.

2011-04-01

46

Anatomy of a 2nd-order unconformity: stratigraphy and facies of the Bakken formation during basin realignment  

Energy Technology Data Exchange (ETDEWEB)

Because classic Laramide compressional structures are relatively rare, the Williston Basin is often considered as structurally simple, but because of the presence of numerous sub-basins, simplistic lithofacies generalization is impossible, and detailed facies mapping is necessary to unravel Middle Bakken paleogeography. The unconformity above the Devonian Three Forks is explained by the infilling and destruction of the Devonian Elk Point basin, prepares the Bakken system, and introduces a Mississippian Williston Basin with a very different configuration. Black shales are too often considered as deposits that can only be found in deep water, but to a very different conclusion must be drawn after a review of stratigraphic geometry and facies successions. The whole Bakken is a 2nd-order lowstand to transgressive systems tract lying below the basal Lodgepole, which represents an interval of maximal flooding. This lowstand to transgressive stratigraphic context explains why the sedimentary process and provenance shows high aerial variability.

Skinner, Orion; Canter, Lyn; Sonnenfeld, Mark; Williams, Mark [Whiting Oil and Gas Corp., Denver, CO (United States)

2011-07-01

47

Stratigraphy and structure of Liyue Basin and its implication for South China Sea break-up  

Science.gov (United States)

Locating in the north of Nansha block, Liyue Basin departed from South China in middle Cenozoic. Experienced four tectonic phases, it is a complicated superimposed basin. Through seismic reflection profile interpretation and drilling as well as dredge sample analysis, we conjectured that there developed Mesozoic and Cenozoic marine deposits. The sedimentary strata are divided into three structural layers by two regional unconformities, which are Late Cretaceous interface and Mid-Miocene interface respectively. The bottom layer is thick Mesozoic sediment, where tilting fault-block and broad fold structures developed. The middle layer is thin rift stage sediment from Palaeocene to mid-Miocene. Absent in uplift area, it displayed typical half graben sediment filling. The top layer is post-rifting marine sediments, continuous and steady. The northeast-trending faults developed in early Cenozoic and controlled the early Cenozoic sediment filling in half graben. These faults indicated that Liyue basin underwent strong tensional tectonic movement above the Mesozoic sedimentary formation. Undergoing the Mesozoic and Cenozoic tectonic evolution, Liyue Basin recorded the transformation process from active margin to passive margin. Through physical and numerical simulation and comparision with Chaoshan depression, we made two conclusions. First,based on previous study results, the Liyue Basin was neighboring Chaoshan depression in Mesozoic, both developed NE-trending wide fold. There are some differences between them too. Reverse faults were revealed in Mesozoic Chaoshan depression but not in Liyue basin. During early Cenozoic, Liyue Basin rifted strongly with many tilt normal faults, while we don’t find rift fault in Chaoshan depression. Considering that the compression in Mesozoic came from the westward subduction of Pacific toward Eurasia, we conjecture that Liyue Basin may locate to the west of Chaoshan depression in Mesozoic, thus the Chaoshan depression underwent stronger compression than Liyue Basin. Second, Liyue Basin located above thinned continental crust before South China Sea opening. The existence of the rigid Reed Bank north of Liyue Basin may be an important factor for basin tectonic evolution. The slightly thinned Reed Bank may cause its northern neighbor areas thinned greatly and caused the cliffy faults developed toward the sea basin. Liyue Basin experienced weak extension and subsidence in Cenozoic.

Sun, L.; Sun, Z.

2009-12-01

48

Brine-mineral reactions in evaporite basins: Implications for the composition of ancient oceans  

Science.gov (United States)

The chemical evolution of several European Mesozoic and Tertiary evaporite basins was reconstructed by using mineral associations, primary fluid-inclusion analyses, and numerical simulations of evaporation scenarios. The solute proportion recorded in the fluid inclusions can be explained by the evaporation of present-day seawater as a major recharge. The sulfate depletion in the brines is responsible for the type of potash deposit formed, potassium-magnessium sulfates or sylvite. This sulfate depletion can be due either to dolomitization or to the addition of a CaCl2-rich solution to the basin. The sulfate depletion occurred in varying intensity in basins of the same age, as well as throughout the evolution of the same basin. Therefore, changes in potash mineralogy and sulfate depletion in fluid inclusions are not conclusive arguments in favor of secular variations in the composition of the ocean, as recently proposed by several authors.

Ayora, C.; Cendón, D. I.; Taberner, C.; Pueyo, J. J.

2001-03-01

49

The Botrychiopsis genus and its biostratigraphic implications in Southern Paraná Basin  

Directory of Open Access Journals (Sweden)

Full Text Available Botrychiopsis has been considered an important floristic element of Westphalian/Artinskian associations of the Paraná Basin. The occurrence of Botrychiopsis in roof-shales of the Rio Bonito Formation in Southern Paraná Basin (Quitéria area, supported by the identification of Botrychiopsis valida, enlarges the genus biochron. Consequently, the stratigraphic hierarchy for Botrychiopsis plantiana and Botrychiopsis valida was defined for the Paraná Basin. Although it is climatically controlled and related to a deglaciation icehouse stage, stratigraphic distribution of the genus presents a substantial climate tolerance, from cold/cool to warm/temperate conditions. A new phytostratigraphic zonation is proposed for the southern portion of the basin that includes the Botrychiopsis Zone (Asselian/Kungurian, which is subdivided into the Botrychiopsis plantiana (Asselian/Artinskian and Botrychiopsis valida (Late Artinskian/Kungurian subzones.

Jasper André

2003-01-01

50

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

51

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

52

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

53

The foreland basin geometry along Longmen Range from high resolution Gravity data and its tectonic implication  

Science.gov (United States)

New gravity and new topographic survey from Sichuan Basin to the eastern Tibetan plateau across the Longmen Range was conducted at 231 stations along two transects to infill the original sparse measurements. The higher resolution gravity helps to constrain the geometry of the foreland basin along the eastern margin of the Tibetan plateau and promotes the further understanding of the dynamic interaction between Sichuan Basin and the eastern margin of the Tibetan plateau. The foredeep geometry and the upper crust structure are modeled by integrating the crustal flexure and basin density profile in order to interpret the observation Bouguer gravity data. The sediment thickness in the modeling is extrapolated 12km in the southern profile and ~10km in the northern profile in conjunction with the seismic constrained basement depth. In contrast with the geometry of the homogeneous thickness of the strata in the northern part of the foredeep basin from the seismic structural interpretation, the southern part shows clear thickening of Cretaceous and Paleogene. The thickening towards the foredeep indicates that the more active tectonics has been happening in the southwest part of the basin than in the northeast since Cretaceous. The reflection seismic data reveal multiple thrusts and fault-bend folds soled into detachments which are up-dipping basin-wards. The stacked thrust imbricates consist predominantly of Mesozoic strata that over-thrust the younger, undeformed Paleogene sediments to the east. The Cenozoic sediment package is about 2km thick, consistent with the recent regional survey of Sichuan Basin ~4km at southwestern basin. Even though the crustal flow model could explain the east-ward propagation of the high plateau, in order to make the theory work, the crust first needs to reach a critical thickness of about 60 km that is the middle-lower crustal thickness is close to 25 km. This zone of dominantly brittle deformation as we documented above tends to end at the western boundary of the Longmenshan Range, where the crustal thickness reaches 60-65 km to permit the decoupling between the stronger upper crust and the strong mantle lithosphere by a week, viscous, middle-lower crust. Flexure modeling and reflection seismic data analysis help us to exclude the necessity of the lower-crustal flow along the Longmenshan portion of the eastern margin of the Tibetan Plateau. Instead, the topographic relief was likely caused entirely by the brittle imbrication in the upper crust. Gravity flexural modeling and basin sediment correction for a transect across the Longmen Range.

Jiang, X.; Jin, Y.

2012-12-01

54

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

55

New Mesozoic paleomagnetic results from the northeastern Sichuan basin and their implication  

Science.gov (United States)

This paper presents the results of a paleomagnetic study undertaken on samples from Lower Triassic and Lower Cretaceous sediments within the northeastern Sichuan Basin, China, in an area close to the Daba Mountains. Stepwise thermal demagnetization was used to isolate the characteristic higher temperature component (HTC) for these samples. These HTC (T1: D = 53.7°, I = 21.6°, ?95 = 6.5°; K1: D = 28.9°, I = 25.7°, ?95 = 6.6°) passed both fold and reversal tests, and indicate that these sediments have undergone sequential clockwise rotations relative to the Sichuan basin. These detected tectonic rotations were probably caused by the obstruction of the Hannan massif during Mesozoic thrusting within the southern Daba Mountains. The northeastern Sichuan Basin and the central Yangtze Fold Belt formed part of a continuous belt of basins (the northern Yangtze Basin), and acted as a coherent tectonic domain during the Early-Middle Jurassic. The Daba Mountains and the central Yangtze Fold Belt subsequently underwent rapid uplift and cooling around the Late Jurassic and Early Cretaceous. This suggests that tectonic rotations within both the central Yangtze Fold Belt and the Daba Mountains were very probably caused by intra-continental deformation over a long period of time rather than a single tectonic event.

Wang, Bin; Zhang, Guowei; Yang, Zhenyu

2013-11-01

56

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

International Nuclear Information System (INIS)

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

57

Structure of the western Cumberland Basin : implications for coalbed-methane exploration  

Energy Technology Data Exchange (ETDEWEB)

The Athol Syncline is a prominent structure in the western Cumberland Basin of Nova Scotia. The basin contains a Carboniferous succession and is currently a target for exploration for coalbed methane. Subsidence and tectonism in the Cumberland Basin were partly controlled by differential flow of Windsor Group evaporites. The Joggins Formation in the Athol Syncline is famous for preserved upright fossil trees. New seismic profiles reveal that the Athol Syncline has potential traps for conventional hydrocarbons where thick fluvial sand units rest against salt walls at the margins of minibasins. The Cumberland Group is thin and lacks significant coals. A basinwide comparison showed that salt withdrawal at depth was responsible for much of the subsidence responsible for the preservation of the coal-bearing Joggins Formation. Contouring of reflections in the seismic profiles provided better definition of the subsurface geometries and potential extent of coal-bearing units in the Athol syncline. The subsurface geometries revealed some new exploration targets for this and similar depocentres in the Maritimes Basin. Coal distribution was found to be influenced by both tectonism and differential withdrawal of evaporites.

Waldron, J.W.F. [Alberta Univ., Edmonton, AB (Canada). Dept. of Earth and Atmospheric Sciences; Rygel, M.C. [Nebraska-Lincoln Univ., Lincoln, NE (United States). Dept. of Geosciences

2006-07-01

58

Crustal structure beneath Hudson Bay from ambient-noise tomography: implications for basin formation  

Science.gov (United States)

The Hudson Bay basin is the least studied of four major Phanerozoic intracratonic basins in North America and the mechanism by which it formed remains ambiguous. We investigate the crustal structure of Hudson Bay based on ambient-noise tomography, using 21 months of continuous recordings from 37 broad-band seismograph stations that encircle the Bay. Green's functions that emerge from the cross correlation of these ambient noise recordings are dominated by fundamental-mode Rayleigh waves. In the microseismic period band (5-20 s), these signals are most prominently expressed in certain preferred azimuths indicative of stationary coastal source regions in southern Alaska and Labrador. Seasonal variations are subtle but consistent with more energetic noise sources during winter months, when wave heights in the Pacific and north Atlantic are larger than in the summer. Noise emanating from Hudson Bay does not appear to contribute significantly to the cross correlograms. Group-velocity dispersion curves are obtained by time-frequency analysis of cross-correlation functions. We test and implement a signal-to-noise ratio (SNR) selection method for producing one-sided cross correlograms, which yields better-defined dispersion ridges than the standard two-sided averaging approach. Tomographic maps and cross sections obtained in the 5-40 s period range reveal significantly lower crustal velocities beneath Hudson Bay than in the bounding Archean Superior craton. The lowest mid-crustal velocities correspond to a previously determined region of maximum lithospheric stretching near the centre of the basin. Pseudosections extracted from the tomographic inversions along profiles across Hudson Bay provide the first compelling direct evidence for crustal thinning beneath the basin. Our results are consistent with a recent estimate of 3 km of crustal thinning, but not consistent with a proposed model for basin subsidence triggered by eclogitization of a remnant crustal root.

Pawlak, Agnieszka; Eaton, David W.; Bastow, Ian D.; Kendall, J. Michael; Helffrich, George; Wookey, James; Snyder, David

2011-01-01

59

Crayfish Group hydrocarbons: Implications for palaeoenvironment of Early Cretaceous rift fill in the western Otway Basin  

Energy Technology Data Exchange (ETDEWEB)

The Otway Basin is one of several extensional sedimentary basins of Mesozoic and Tertiary age which are located on the southern continental margin of Australia and formed in response to the rifting of Australia from Antarctica. A growing inventory of hydrocarbon discoveries, including gas and condensate in Haselgrove-1, Haselgrove-2, Katnook-2, Katnook-3, Ladybroke Grove-1 and Troas-1, gas, condensate and oil in Wynn-1, and oil in Sawpit-1, highlights the petroleum potential of the Crayfish Group. This paper documents the geochemistry of these hydrocarbons and uses biomarker signatures to characterize their inferred source rocks in terms of lithology and contributing biota. The ultimate aim is to build up a picture of the depositional environments that existed during the Late Jurassic-Early Cretaceous in the western Otway Basin and identify the source formations of these petroleum accumulations. To address these objectives, palynological studies were undertaken in parallel with organic geochemical analyses of source rocks from the Casterton Formation and Crayfish Group in the Robe and Penola Troughs, western Otway Basin. These strata have traditionally been regarded as fluvial and lacustrine deposits. The source rock characteristics inferred from the geochemistry of the Katnook Field condensate and the oils from Wynn-1 and Sawpit-1 are those of siliciclastic freshwater facies. However, the biomarker assemblage of the Troas-1 condensate implies that its source beds were deposited in a marginal marine setting. Even more unexpected are the biomarker compositions of reservoir bitumens from Crayfish-A1 and Zema-1 which provide evidence for the existence of saline to hypersaline playa lakes during the early rift phase of the Otway Basin. (author). 3 tabs., 10 figs., 6 photos., 35 refs.

Padley, D. [Adelaide Univ., SA (Australia). Department of Geology and Geophysics; McKirdy, D.M. [Adelaide Univ., SA (Australia). Department of Geology and Geophysics; Skinner, J.E. [SAGASCO Resource Ltd, Adelaide, SA (Australia); Summons, R.E. [Australian Geological Survey Organisation, Canberra, ACT (Australia); Morgan, R.P. [Morgan Palaeo Associates, Maitland, SA (Australia)

1995-12-31

60

Geodynamic models assist in determining the South Loyalty Basin's slab location and its implications for regional topography  

Science.gov (United States)

In the Western Pacific, two competing kinematic reconstructions exist: one with wholly westward subduction of the Pacific plate at what is now the Tonga-Kermadec trench and one combining a degree of eastward subduction under what has been termed the New Caledonia trench. New seismological observations indicate that eastward subduction could explain the existence of a fast anomaly, the hyothesised South Loyalty Basin slab, below the 660km transition zone distinct from the fast anomaly aligned with the Tonga-Kermadec slab. A plate reconstruction dated from the suggested initiation of New Caledonia subduction in the Eocene has been developed. This reconstruction is then used to predict the thermal history of the region and together provide kinematic and thermal boundary conditions for a regional mantle convection model. The model-predicted location of the South Loyalty Basin slab's location will be presented along with the location's dependence on the mantle rheological parameters and the hotspot reference frame. The implications for the topography of the region will also be discussed.

Clark, Stuart R.

2010-05-01

 
 
 
 
61

Subsurface images of the northern Newark basin, New York, USA and their implications for carbon sequestration  

Science.gov (United States)

The Triassic-Jurassic Newark rift, a large onshore sedimentary basin close to northeast US metropolitan areas, may have potential for safe geological storage of CO2 in a suitably deep formation overlain by appropriate confining units. Filled with continental synrift sedimentary rocks and CAMP (Central Atlantic Magmatic Province) basaltic intrusions and flows, the basin is bounded on the NW by the NE-striking, SE-dipping Ramapo fault. Funded by the Department of Energy's (DOE) National Energy Technology Laboratory's (NETL) Carbon Sequestration Program's portion of the American Recovery and Reinvestment Act of 2009 (ARRA) and NYSERDA, the TriCarb Consortium for Carbon Sequestration acquired two seismic-reflection profiles in Rockland County, NY that were processed to obtain depth-migrated images of the basin's subsurface geometry. The E-trending dip profile crosses most of the basin, while the shorter N-trending profile provides a strike-view. Five seismic facies are present: (1) shallow continuous, closely spaced, W-dipping reflections suggestive of lacustrine deposits; (2) short, non-coherent reflections suggestive of conglomeritic fluvial strata; (3) high-amplitude parallel reflections, locally exhibiting reverse separation, suggestive of prerift early Paleozoic strata Cambro-Ordovician carbonates; (4) a facies at the bottom of both lines and the western end of the ESE-trending line that lacks reflections, suggestive of prerift metamorphic rocks such as Precambrian gneiss, and/or highly deformed Taconic (Ordovician) phyllites; and (5) a seismically transparent band commonly bounded by high-amplitude reflections that cuts across the stratigraphy of facies 1-3, suggestive of a scoop-shaped intrusive diabase sheet that projects to the surface to outcrops of the CAMP-related Palisade sill. Basin geometry is well-imaged conforming to a deeply eroded half graben. Reflections of facies 3 are truncated by facies 2 marking the angular pre-rift unconformity. Distinct fanning in facies 1 suggests syndepositional faulting with reflections dipping and thickening toward the poorly imaged Ramapo fault to the NW. Because Jurassic CAMP lavas crop out at the NW edge of the basin, the full thickness of Triassic strata are imaged on the seismic data. Our favored interpretation has the Palisade sheet intruding the pre-rift unconformity in the axis of the basin, climbing up-section into Triassic strata to the NW, NE, and SE. The base of the intrusion and the contact with prerift strata appears to be at a depth of ~ 2 km (6600 ft) in the location of a planned basin-characterization core hole to be drilled in late summer/early fall of 2011. In this location, our favored interpretation has the intrusion underlying Triassic sandstones and conglomerates of the Stockton Formation (best reservoir candidate), in turn overlain by mudstones of the Lockatong Formation (best confining unit candidate), overlain by upwardly coarsening mudstones, sandstones, and conglomerates of the Passaic Formation. These hypotheses should be tested by "ground truth" from the borehole by the time of this presentation.

Olsen, P. E.; Withjack, M. O.; Schlische, R. W.; Goldberg, D.; Kent, D. V.; Tamulonis, K.; Couëslan, M.; Collins, D. J.

2011-12-01

62

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

Science.gov (United States)

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

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

1990-01-01

63

Paleomagnetism of the Neogene Jiuxi Basin, Hexi Corridor, China: implications for a non- rigid deformation mechanism?  

Science.gov (United States)

The uplift of the northeastern Tibetan Plateau has attracted wide attention recently. The ongoing sequence of uplift phases of the plateau has been suggested to be a young continuous outgrowth of the Tibetan Plateau. Hence, the research of the deformation and evolution of this part of the plateau will lead to the further understanding of the kinematics and mechanisms during the evolution of the entire Tibetan Plateau. However, so far the deformation history within the northeastern Tibetan Plateau is still not fully understood. Recent paleomagnetic data within the Qaidam-Altyn Tagh region are contradictory, in that they are being used as arguments for significant as well as insignificant rotations in the region. In addition, paleomagnetic studies in the Gonghe-Guide and Longzhong basins are marred by a lack of comprehensive understanding as to whether significant clockwise rotations of the region were diachronous or whether they all occurred before 29 Ma. We report here on a paleomagnetic study of two magnetostratigraphic sections sampled in the Jiuxi Basin in the western Hexi Corridor, a foreland basin of the northern Qilian Shan (Mts.) at the northern margin of the Tibetan Plateau, to help explain the deformation of the region. The two sections: Laojunmiao and Hongshuiba, yield magnetostratigraphic ages of about 13-0 Ma and 11-5.7 Ma, respectively. The declinations observed in the sedimentary strata of the Laojunmiao section show similar values with the mean of about 0.1 degrees, suggesting insignificant rotation; whereas those from the Hongshuiba section, with a mean declination of about 317.3 degrees, imply significant counterclockwise rotations of about 43 degrees. We attribute the difference in the mean declinations of the two sections in the Jiuxi Basin during the same period to local deformation. This and other apparently contradictory paleomagnetic data within the Altyn Tagh-Qaidam area may imply non-rigid deformation in the region.

Fang, X.; Yan, M.; van der Voo, R.; Li, J.; Zhao, X.; Zhao, Z.; Song, C.

2006-12-01

64

Implications of Transient Deformation in the Northern Basin and Range, Western United States  

Science.gov (United States)

Coherent transient events observed in Global Positioning System (GPS) data from the Basin and Range extensional province may help to illuminate qualitatively similar transient events observed in subduction zones and other tectonic environments. We examine GPS time series at twenty-two sites using a time series modeling approach that combines hyperbolic tangent function analysis (HTFA) with elastic load deformation estimated independently from climatological data sets. We identify two transient events, ~2000.4 and ~2004.4, with roughly similar timing and similar displacement to transients described previously by other research groups. The first few years of GPS observations, adopted as a reference state in earlier studies, are also found to be anomalous. Our results differ from previous studies in two respects. First, we find that a significant component of northward transient motion occurs during both the ~2000.4 and ~2004.4 events, despite a reversal of sign in east component motion. Second, both of these events affect sites coherently in the eastern as well as the western Basin and Range. Examination of independently-derived surface mass loading, the largest source of transient stress forcing in the region, reveals no evidence of a simple relationship. These observations suggest Basin and Range transients are similar to slow-slip events in subduction zones in that they require a mechanism involving state-dependent behavior, and they are sensitive to exceedingly small perturbations in ambient stress. Previous studies inferred slip on a single, province-wide 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 most widely accepted for subduction zone transient events provided that slip is occurring on discontiguous detachment surfaces at mid-crustal depths.

Chamoli, A.; Lowry, A. R.; Jeppson, T.

2013-12-01

65

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 oilhern area appears more prospective for oil with minor amounts of gas

66

Sedimentary Basin Analysis of Sachun Formation in Southwestern Iran: Implication for Sedimentary Environments and Tectonic Setting  

Directory of Open Access Journals (Sweden)

Full Text Available

The Sachun Formation (Paleocene- Lower Eocene, has been formed in Zagros basin, and has 1415 meters thickness in its type section. Sachun Formation sequence at the southern part of Kuh- E- Mianjangal, in Folded Zagros Zone in southwest of Iran, with a thickness of 580 meters was formed of two members. The Lower Member consists of about 280 meters thin to medium bedded of marl, marlstone and argillaceous, silty and sandy limestone with color of light gray to bluish gray, and associated with gypsum inter- layers, which are repeated continuously upward. In each of the alternations or cycles, the terrigenous grains size increase upward which is due to the depth decreasing in each cycle. The Upper Member consists of about 300 meters alternation of gypsum and marl, light gray to bluish gray associated with inter- layers of argillaceous and silty limestone. Microscopic studies of argillaceous limestone, in both members, have showed micrite and pelmicrite microfacies. No distinct fossils, either microscopic or macroscopic, are found in these members in the studied section. Sachun Formation facies have been deposited in a shallow depositional basin which has been controlled by a permanent sea level changes. Among the marine environments, peritdal environments show the most and the best correlation with the Sachun Formation facies. According to the sedimentary records, Sachun Formation has been deposited in a tectonically instable basin.

Mohammad Bahrami

2013-06-01

67

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

68

Basin-Scale Hydrologic Impacts of CO2 Storage: Regulatory and Capacity Implications  

Energy Technology Data Exchange (ETDEWEB)

Industrial-scale injection of CO{sub 2} into saline sedimentary basins will cause large-scale fluid pressurization and migration of native brines, which may affect valuable groundwater resources overlying the deep sequestration reservoirs. In this paper, we discuss how such basin-scale hydrologic impacts can (1) affect regulation of CO{sub 2} storage projects and (2) may reduce current storage capacity estimates. Our assessment arises from a hypothetical future carbon sequestration scenario in the Illinois Basin, which involves twenty individual CO{sub 2} storage projects in a core injection area suitable for long-term storage. Each project is assumed to inject five million tonnes of CO{sub 2} per year for 50 years. A regional-scale three-dimensional simulation model was developed for the Illinois Basin that captures both the local-scale CO{sub 2}-brine flow processes and the large-scale groundwater flow patterns in response to CO{sub 2} storage. The far-field pressure buildup predicted for this selected sequestration scenario suggests that (1) the area that needs to be characterized in a permitting process may comprise a very large region within the basin if reservoir pressurization is considered, and (2) permits cannot be granted on a single-site basis alone because the near- and far-field hydrologic response may be affected by interference between individual sites. Our results also support recent studies in that environmental concerns related to near-field and far-field pressure buildup may be a limiting factor on CO{sub 2} storage capacity. In other words, estimates of storage capacity, if solely based on the effective pore volume available for safe trapping of CO{sub 2}, may have to be revised based on assessments of pressure perturbations and their potential impact on caprock integrity and groundwater resources, respectively. We finally discuss some of the challenges in making reliable predictions of large-scale hydrologic impacts related to CO{sub 2} sequestration projects.

Birkholzer, J.T.; Zhou, Q.

2009-04-02

69

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

70

Stratigraphic analysis of Brejo Santo Formation, Araripe Basin, Northeast Brazil: paleogeographic implications  

Directory of Open Access Journals (Sweden)

Full Text Available The Araripe Basin has been the subject of several publications in the recent years, notably with respect to the rich paleontological collection of Brejo Santo, Crato and Romualdo Formations. However, papers detailing stratigraphic aspects of Brejo Santo Formation are scarce. The formation (Mesozoic era - Dom João Stage is represented by a predominantly pelithic succession (up to 450 m thick outcropping in eastern portion of the basin. The Brejo Santo Formation unconformably overlies the Cariri Formation, presumably of Paleozoic age, and makes gradational contact with the overlying Missão Velha Formation. It consists of pelithes, such as massive to laminated reddish-brown chalks and calciferous shales with decimetric intercalations of white to greenish-grey siltstones and centimetric layers of reddish mottled, speckled and striped shales, with calcareous nodules, and subordinately, muddy limestones and highly fossiliferous calciferous sandstones and fine sandstones with planar cross-stratifications. The measured paleocurrents have a consistent dispersion pattern for SE, SW and S, suggesting the installation of an open wide basin toward the south. The facies and facies associations described were interpreted as generated by (i lake systems in which periodically the level of the lakes and/or ponds suffered sudden variations, causing changes in coloration related to seasonal fluctuations in the level of the lake (periods of subaerial exposure and (ii ephemeral river systems which fed these lakes. The widespread occurrence of fossil organisms, such as non-marine ostracods and conchostracheans suggest that the sediments of Brejo Santo Formation were possibly deposited in lacustrine-fluviatile systems favorable to the formation of redbeds layers, under hot climatic conditions with well-defined dry seasons, corroborating the depositional system interpretation.

Gelson Luís Fambrini

2013-12-01

71

Hydrogeology of an ancient arid closed basin: Implications for tabular sandstone-hosted uranium deposits  

International Nuclear Information System (INIS)

Hydrogeologic modeling shows that tabular-type uranium deposits in the grants uranium region of the San Juan basin, New Mexico, formed in zones of ascending and discharging regional ground-water flow. The association of either lacustrine mudstone or actively subsiding structures and uranium deposits can best be explained by the occurrence of lakes at topographic depressions where ground water having different sources and compositions is likely to converge, mix, and discharge. Ascending and discharging flow also explains the association of uranium deposits with underlying evaporites and suggests a brine interface. The simulations contradict previous suggestions that ground water moved downward in the mudflat

72

Parental basaltic melts and fluids in eastern Manus backarc Basin: implications for hydrothermal mineralisation  

Science.gov (United States)

The eastern Manus Basin is an actively forming backarc extensional zone behind the New Britain Island arc, which hosts a number of submarine volcanic edifices and hydrothermal fields. Isotopic and trace element geochemical characteristics of the edifices are comparable with those of the adjacent subaerial New Britain arc, and differ significantly from those of MORB-like lavas on and near the Manus Spreading Ridge in the central part of the basin. Fractional crystallisation dominates magma evolution from primitive basalts to andesites, dacites and rhyodacites in the eastern Manus Basin, but several lineages with differing trace element enrichment have been delineated. Melt inclusions within olivine phenocrysts (Fo 82-92) of two representative east Manus basalts, respectively, with modest (0.2 wt%) and high (0.8 wt%) potassium contents, host ubiquitous CO 2-bearing vapour bubbles, denoting presence of an immiscible fluid phase at early stages of crystallisation. Bubbles often carry precipitate phases whose abundance is broadly proportional to the bubble size reaching a maximum in fluid bubbles with little or no melt. Among the precipitates, detected by laser Raman spectroscopy and EDS-scanning electron microscopy, carbonates are common and include magnesite, calcite, ankerite, rhodochrosite and nahcolite (NaHCO 3). Gypsum, anhydrite, barite, anglesite, pyrite, and chalcopyrite have also been found. Some amorphous precipitates recrystallise after bubbles are opened to Na-Ca carbonates, halite and Na-K-Ca alumino-silicates. Copper abundances decrease from basalt to dacite across the eastern Manus fractionation spectrum, whereas Pb behaves as an incompatible element, increasing to highest values in the dacites. Zinc abundance reaches maximum concentrations in andesite, and decreases during further fractionation. Loss of Cu especially from the fractionating magmas, in the absence of immiscible sulphide liquid, strongly implies metal partitioning into CO 2-H 2O fluid, which is degassed significantly during magma fractionation. Hydrothermal fluids in the PACMANUS system may carry a direct contribution of the magmatic metal-bearing fluid, exsolved from the crystallising arc-like magmas at this immature backarc basin, and are able to transport and concentrate major amounts of ore metals, particularly Cu.

Kamenetsky, V. S.; Binns, R. A.; Gemmell, J. B.; Crawford, A. J.; Mernagh, T. P.; Maas, R.; Steele, D.

2001-01-01

73

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

Energy Technology Data Exchange (ETDEWEB)

The Paleoproterozoic Thelon Basin, located on the border between Nunavut and the Northwest Territories of Canada, is a contemporaneous analog of the uranium-rich Paleoproterozoic Athabasca Basin in Canada. Early diagenesis resulted in precipitation of extensive hematite on the surfaces of detrital quartz grains throughout the Thelon Formation and minor hydroxy-phosphate in veins locally. Continued diagenesis then resulted in syntaxial quartz cementation of detrital quartz at 130 degrees C from fluids having ca. 17 wt.% equivalent NaCl, similar to the Athabasca Basin. Cementation of this type is most pronounced in fine-grained sequences in the Thelon Basin. A period of extensive desilicification during continued burial was followed by formation, at ca. 200 degrees C, of peak-diagenetic illite having Ar-Ar ages of ca. 1400-1690 Ma in the Thelon Formation. This illite was associated with fluids with {delta}{sup l8}O and {delta}D values of ca. 6%o and -50%o,respectively, similar to those during peak diagenesis of the Athabasca Basin. Although the timing, salinity, and isotopic composition of the peak-diagenetic fluids in the Thelon and Athabasca Basins are similar, the peak-diagenetic mineral assemblage in the Athabasca Formation is dickite and illite, with minor dravite and goyasite rather than simply illite. Consequently, the fluids at peak diagenesis, which in the Athabasca Basin are synchronous with formation of world-class unconformity-type uranium deposits, had different compositions in each basin. Post-peak diagenesis in the Thelon Basin was quite distinct from that in the Athabasca Basin in that illite was replaced in the central portion of the basin by K-feldspar and then sudoite, which crystallized from saline brines at ca. 1000 Ma and 100 degrees C. Evidence for later infiltration of these brines is absent in the Athabasca Basin, although uranium mobilization at ca. 900 Ma from fluids having the same characteristics as those at peak diagenesis was pronounced in the Athabasca Basin. Recent incursion of meteoric waters along reactivated structures into the Athabasca Basin has variably affected hydrous and uraniferous minerals, but evidence for this is lacking in the Thelon Basin. The Thelon Basin reflects less intensive fluid-rock interaction in its early history than that recorded in the basal units of the Athabasca Basin. (author)

Renac, C. [Univ. de St. Etienne, Dept. de Geologie, Saint Etienne (France); Kyser, T.K.; Durocher, K. [Queen' s Univ., Dept. of Geological Sciences and Geological Engineering, Kingston, Ontario (Canada); Dreaver, G.; O' Connor, T. [Cameco Corp., Saskatoon, SK (Canada)

2002-01-01

74

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

Science.gov (United States)

Large volumes of magma emplaced within sedimentary basins have been linked to multiple climate change events due to release of greenhouse gases such as CH4. Basin-scale estimates of thermogenic methane generation show that this process alone could generate enough greenhouse gases to trigger global incidents. However, the rates at which these gases are transported and released into the atmosphere are quantitatively unknown. We use a 2D, hybrid FEM/FVM model that solves for fully compressible fluid flow to quantify the thermogenic release and transport of methane and to evaluate flow patterns within these systems. Our results show that the methane generation potential in systems with fluid flow does not significantly differ from that estimated in diffusive systems. The values diverge when vigorous convection occurs with a maximum variation of about 50%. The fluid migration pattern around a cooling, impermeable sill alone generates hydrothermal plumes without the need for other processes such as boiling and/or explosive degassing. These fluid pathways are rooted at the edges of the outer sills consistent with seismic imaging. Methane venting at the surface occurs in three distinct stages and can last for hundreds of thousands of years. Our simulations suggest that although the quantity of methane potentially generated within the contact aureole can cause catastrophic climate change, the rate at which this methane is released into the atmosphere is too slow to trigger, by itself, some of the negative ?13C excursions observed in the fossil record over short time scales (<10,000 years).

Iyer, Karthik; Rüpke, Lars; Galerne, Christophe Y.

2013-12-01

75

Provenance and palaeogeographic implications of Eocene-Oligocene sedimentary rocks in the northwestern Basin and Range  

Science.gov (United States)

A thick sequence of uppermost Eocene to lower Oligocene volcaniclastic and sedimentary rocks is exposed at the base of the Warner Range in northeastern California. This isolated exposure provides insight into the palaeogeographic setting of the northwestern Basin and Range during this time period. Significant thinning of the unit over 35km of lateral exposure and predominantly volcanic clast compositions suggest that the sequence was deposited in an alluvial plain adjacent to a volcanic arc. Palaeocurrent indicators in the conglomerates define a NNE transport direction. Detrital zircon analysis on coarse sandstones and dating of individual granite cobbles show a range of ages consistent with a local, volcanic source area primarily from the SSW with some far-travelled input from northern Nevada; the far-travelled component increases in influence as the unit thins to the north. Comparison with other sedimentary sequences of Eocene age and integration with palaeofloral and geophysical data help to define drainage divides, and suggest that this sequence accumulated in a relatively isolated, intra-arc basin. This localized accumulation differs markedly from contemporaneous drainages to the south that transported material westwards from central Nevada to the palaeoshoreline, and suggests that ongoing volcanism had a strong influence on palaeogeography in this region during the Eocene and Oligocene.

Egger, A.E.; Colgan, J.P.; York, C.

2009-01-01

76

Different aerosol loading and their radiative implication over Indo-Gangetic Basin  

Science.gov (United States)

Abstract: The climate and environmental effects of atmospheric aerosols are presently the most critical issues in global science community because of their various emission sources and different impacts to earth’s radiation budget. Different types of atmospheric aerosols have different optical as well as radiative properties which are crucial to reduce possible uncertainties in climate forcing. Indo-Gangetic Basin (IGB)in northern part of India has been recognized for different types of aerosol loading due to various emission sources (natural and anthropogenic) of aerosols and unique topography of the region. In the present study, we have identified different aerosol types using Aerosol Robotic NETwork (AERONET) level 2 aerosol products during 2010-2011 at four different locations in the Indo-Gangetic Basin (IGB) viz. Karachi (24.870N, 67.03 E), Lahore (31.540 N, 74.320 E), Jaipur (26.900 N, 75.900E), and Kanpur (26.4? N, 80.4? E). Five different aerosol types were identified using fine-mode fraction, (FMF) and single scattering albedo (SSA) at the stations over IGB viz. PD (polluted dust), PC (polluted continental), MBC (mostly black carbon), MOC (mostly organic carbon) and NA (non-absorbing). Very interesting results are observed which are discussed in terms of different aerosol types associated with their different optical as well as radiative properties. Keywords: aerosol types, radiative properties, IGB.

Tiwari, Shani; Singh, Abhay Kumar; Srivastava, Atul Kumar

77

Age of the Payogastilla Group: Implications for foreland basin development, NW Argentina  

Science.gov (United States)

The Corte El Cañón Tuff from the lower part of the Angastaco Formation, Payogastilla Group, NW Argentina, was dated at 13.4±0.4 Ma by the 40Ar/ 39Ar method. The Payogastilla Group was deposited in an Andean foreland basin, includes strata associated with the development of the modern arc, and is now exposed in the southern Cordillera Oriental. To date, the Payogastilla Group has been correlated with the Saladillo Formation/Santa María Group sequence that is exposed immediately to the south in the northern SierrasPampeanas. The date of the Corte El Cañón Tuff shows that as much as the lower third of the Payogastilla Group strata is older than the oldest Saladillo Formation/Santa María Group strata. This suggests that the region of the northern Sierras Pampeanas was topographically higher than the region of the southern Cordillera Oriental when foreland basin deposition began. It may also suggest that the eastward progression of Andean deformation was more rapid at the latitude of the Cordillera Oriental than at the latitude of the northern Sierras Pampeanas.

Grier, M. E.; Dallmeyer, R. D.

78

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

Science.gov (United States)

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.

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

79

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

80

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

Directory of Open Access Journals (Sweden)

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

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

Jaffal, M.

2009-12-01

 
 
 
 
81

Implications of customary norms and laws for implementing IWRM: findings from Pangani and Rufiji basins, Tanzania  

Science.gov (United States)

This paper presents the preliminary findings of a WARFSA-funded study, whose objective is to facilitate the formulation of better policies and guidelines for implementing IWRM through a case study of local water conflicts. It is observed that, although the current water reforms in the country focus on the use of statutory legal systems to regulate the use of water resources, the country operates under a plural legal system. Apart from the statutory laws, diverse customary systems are relied upon in resolving water-related conflicts. Neglect of these norms and laws may have negative consequences for the majority of the villagers who rely on them. The paper presents some of the water-related conflicts in the study areas and the views of government authorities and river basin managers regarding customary norms and laws for water resource management. Also, the paper describes how different types of conflicts over water resources are handled through official legal channels.

Maganga, Faustin P.; Kiwasila, Hilda L.; Juma, Ibrahim H.; Butterworth, John A.

82

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.

2014-09-01

83

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

84

Late Yeadonian (Upper Sandstone Group) incised valley supply and depositional systems in the South Wales peripheral foreland basin: implications for the evolution of the Culm Basin and for the Silesian hydrocarbon plays of onshore and offshore UK  

Energy Technology Data Exchange (ETDEWEB)

The Upper Sandstone Group of South Wales has previously been interpreted as a simple NNW-SSE trending incised valley that was filled during the late Yeadonian (Namurian G1b). Data presented in this study indicate a far more complex scenario. The group is well developed in the Pembrokeshire sub-basin but it is absent from the main part of the South Wales Basin located to the east of the Penlan Axis. The principal source area for sediment flux was the forebulge of the basin located to the north in Lower Palaeozoic (foreland) strata. Variscan flexural uplift of this source area and an accompanying rapid, high magnitude fall in sea level produced a very high sediment budget. Thus, during the late Yeadonian lowstand of sea level, massive amounts of sediment were being generated and transported via an incised valley system across the western part of the South Wales peripheral foreland basin. The location and orientation of the incised supply system and its related interfluves were controlled by intrabasinal, synsedimentary Variscan structures, many of which were reactivated Caledonian extensional faults. During the succeeding sea-level rise the incised valley was filled, initially by fluvio-deltaic sands and later by estuarine argillaceous sediments. The implications of this combined tectonic-sedimentological-high resolution sequence stratigraphic model for the evolution of the late Namurian (Crackington Formation) turbidites of the Culm Basin are discussed. Examples of Silesian incised valley fill sandstone reservoirs developed in the East Midlands Oilfield and the Southern Gas Basin are briefly summarised and their spatial and temporal distributions are appraised. Data, generated from these case studies, are assessed in terms of their use for the modelling of incised valley fill sequences in foreland basins and other tectonic settings. (author)

George, G.T. [University of Greenwich, Chatham Maritime (United Kingdom). School of Earth and Environmental Science

2001-06-01

85

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

Science.gov (United States)

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

Pervez, Md Shahriar; Henebry, Geoffry M.

2014-01-01

86

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

87

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

88

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

Science.gov (United States)

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

Zakharova, N. V.; Goldberg, D.

2013-12-01

89

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

90

Isotopic composition of rainfall and runoff in a small arid basin with implications for deep percolation  

International Nuclear Information System (INIS)

The aim of this work was to characterize the isotopic composition of potential recharge in an arid rocky watershed. Unique field observations were obtained from an arid watershed in the Negev Highlands, Israel, through utilization of the dynamic variations in the isotopic composition of rainfall and runoff. The hydrological system's inputs are rainfall and its isotopic composition. Rainfall and runoff were sampled in eight storms. High variability in the isotopic composition of rainfall was observed during any single rainstorm. The isotopic distribution in the runoff at the outlet of the basin appeared often not to be correlated to the isotopic patterns of the associated rain storm. A new mathematical model was developed to describe these physical processes. The model called A Double-Component Kinematic Wave Flow and Transport Approach, was designated to assess the dynamic isotopic distribution in arid rain storms and runoff. This model simulates the transport of rainfall into overland flow and runoff in an arid rocky watershed with uniformly distributed shallow depression storage. A numerical solution for the problem was developed, to estimate the depression storage parameters. The model also reflects the isotopic memory effect due to the depression storage between sequential rain showers. A good agreement between the observed and computed hydrograph and the change of the ?18O values in runoff in time confirms the validity of the model. (author) 138 figs., 125 refs

91

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

92

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

Directory of Open Access Journals (Sweden)

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

93

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

Directory of Open Access Journals (Sweden)

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

94

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  

Directory of Open Access Journals (Sweden)

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

95

Arsenic in glacial drift aquifers and the implication for drinking water - Lower Illinois River Basin  

Science.gov (United States)

The lower Illinois River Basin (LIRB) covers 47,000 km2 of central and western Illinois. In the LIRB, 90% of the ground water supplies are from the deep and shallow glacial drift aquifers. The deep glacial drift aquifer (DGDA) is below 152 m altitude, a sand and gravel deposit that fills the Mahomet Buried Bedrock Valley, and overlain by more than 30.5 m of clayey till. The LIRB is part of the USGS National Water Quality Assessment program, which has an objective to describe the status and trends of surface and ground water quality. In the DGDA, 55 % of the wells used for public drinking-water supply and 43 % of the wells used for domestic drinking water supply have arsenic concentrations above 10 ??g/L (a new U.S. EPA drinking water standard). Arsenic concentrations greater than 25 ??g/L in ground water are mostly in the form of arsenite (AsIII). The proportion of arsenate (AsV) to arsenite does not change along the flowpath of the DGDA. Because of the limited number of arsenic species analyses, no clear relations between species and other trace elements, major ions, or physical parameters could be established. Arsenic and barium concentrations increase from east to west in the DGDA and are positively correlated. Chloride and arsenic are positively correlated and provide evidence that arsenic may be derived locally from underlying bedrock. Solid phase geochemical analysis of the till, sand and gravel, and bedrock show the highest presence of arsenic in the underlying organic-rich carbonate bedrock. The black shale or coal within the organic-rich carbonate bedrock is a potential source of arsenic. Most high arsenic concentrations found in the DGDA are west and downgradient of the bedrock structural features. Geologic structures in the bedrock are potential pathways for recharge to the DGDA from surrounding bedrock.

Warner, K.L.

2001-01-01

96

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

International Nuclear Information System (INIS)

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

97

Arsenic in glacial drift aquifers and the implication for drinking water--lower Illinois River Basin.  

Science.gov (United States)

The lower Illinois River Basin (LIRB) covers 47,000 km2 of central and western Illinois. In the LIRB, 90% of the ground water supplies are from the deep and shallow glacial drift aquifers. The deep glacial drift aquifer (DGDA) is below 152 m altitude, a sand and gravel deposit that fills the Mahomet Buried Bedrock Valley, and overlain by more than 30.5 m of clayey till. The LIRB is part of the USGS National Water Quality Assessment program, which has an objective to describe the status and trends of surface and ground water quality. In the DGDA, 55% of the wells used for public drinking-water supply and 43% of the wells used for domestic drinking water supply have arsenic concentrations above 10 micrograms/L (a new U.S. EPA drinking water standard). Arsenic concentrations greater than 25 micrograms/L in ground water are mostly in the form of arsenite (AsIII). The proportion of arsenate (AsV) to arsenite does not change along the flowpath of the DGDA. Because of the limited number of arsenic species analyses, no clear relations between species and other trace elements, major ions, or physical parameters could be established. Arsenic and barium concentrations increase from east to west in the DGDA and are positively correlated. Chloride and arsenic are positively correlated and provide evidence that arsenic may be derived locally from underlying bedrock. Solid phase geochemical analysis of the till, sand and gravel, and bedrock show the highest presence of arsenic in the underlying organic-rich carbonate bedrock. The black shale or coal within the organic-rich carbonate bedrock is a potential source of arsenic. Most high arsenic concentrations found in the DGDA are west and downgradient of the bedrock structural features. Geologic structures in the bedrock are potential pathways for recharge to the DGDA from surrounding bedrock. PMID:11341009

Warner, K L

2001-01-01

98

Arsenic in glacial drift aquifers and the implication for drinking water - Lower Illinois River Basin  

Energy Technology Data Exchange (ETDEWEB)

The lower Illinois River Basin (LIRB) covers 47,000 km{sub 2} of central and western Illinois. In the LIRE, 90% of the ground water supplies are from the deep and shallow glacial drift aquifers, The deep glacial drift aquifer (DGDA) is below 152 m altitude, a sand and gravel deposit that fills the Mahomet Buried Bedrock Valley, and overlain by more than 30.5 m of clayey till. The LIRE is part of the USGS National Water Quality Assessment program, which has an objective to describe the status and trends of surface and ground water quality. In the DGDA, 55% of the wells used for public drinking-water supply and 43% of the wells used for domestic drinking water supply have arsenic concentrations above 10 {mu}g/L (a new U.S. EPA drinking water standard). Arsenic concentrations greater than 25 {mu}g/L in ground water are mostly in the form of arsenite (AsIII). The Proportion of arsenate (AsV) to arsenite does not change along the flowpath of the DGDA. Because of the limited number of arsenic species analyses, no clear relations between species and other trace elements, major ions, or physical parameters could be established. Arsenic and barium concentrations increase from east to west in the DGDA and are positively correlated. Chloride and arsenic are positively correlated and provide evidence that arsenic may be derived locally from underlying bedrock. Solid phase geochemical analysis of the till, sand and gravel, and bedrock show the highest presence of arsenic in the underlying organic-rich carbonate bedrock. The black shale or coal within the organic-rich carbonate bedrock is a potential source of arsenic. Most high arsenic concentrations found in the DGDA are west and downgradient of the bedrock structural features. Geologic structures in the bedrock are potential pathways for recharge to the DGDA from surrounding bedrock.

Warner, K.L. [US Geological Survey, Urbana, IL (USA)

2001-07-01

99

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

Science.gov (United States)

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

Hurwitz, Debra M.; Kring, David A.

2014-06-01

100

Integrated Analysis on Gravity and Magnetic Fields of the Hailar Basin, NE China: Implications for Basement Structure and Deep Tectonics  

Science.gov (United States)

The Hailar Basin is one of the typical basins among the NE China Basin Groups, which is situated in the east of East Asia Orogene between the Siberia Plate and the North China Plate. Based on the detailed analysis of magnetic, gravity, petrophysical, geothermal and seismological data, we separate the Gravity and Magnetic Anomalies (GMA) into four orders using Wavelet Multi-scale Decomposition (WMD). The apparent depths of causative sources were then assessed by Power Spectrum Analysis (PSA) of each order. Low-order wavelet detail anomalies were used to study the basin's basement structure such as major faults, the basement lithology, uplifts and depressions. High-order ones were used for the inversion of Moho and Curie discontinuities using the Parker method. The results show that the Moho uplifting area of the Hailar Basin is located at the NE part of the basin, the Curie uplifting area is at the NW part, and neither of them is consistent with the basin's sedimentary center. This indicates that the Hailar Basin may differ in basin building pattern from other middle and eastern basins of the basin groups, and the Hailar Basin might be of a passive type. When the Pacific Plate was subducting to NE China, the frontier of the plate lying on the mantle transition zone didn't pass through the Great Khingan Mountains region, so there is not an obvious magma upwelling or lithospheric extension in the Hailar Basin area. Finally, based on the seismological data and results of WMD, a probable 2D crust model is derived from an across-basin profile using the 2D forward modeling of the Bouguer gravity anomaly. The results agree with those from seismic inversion, suggesting WMD is suitable for identifying major crustal density interfaces.

Sun, Bin; Wang, Liangshu; Dong, Ping; Wu, YongJing; Li, Changbo; Hu, Bo; Wang, Chong

2012-11-01

 
 
 
 
101

Is there a remnant Variscan subducted slab in the mantle beneath the Paris basin? Implications for the late Variscan lithospheric delamination process and the Paris basin formation  

Science.gov (United States)

The Paris basin (northern France) is a Late Paleozoic-Mesozoic intracratonic basin that settled upon the collapsed Variscan collisional belt. The lithospheric roots of the Variscan orogenic system, below the Paris basin, have been investigated using a European-scale P-wave velocity tomographic model. Tomography points out the existence of a significant high velocity anomaly in the upper mantle below the western part of the basin. At ~ 150-200 km depth, the anomaly extends with a NW-SE trend along the buried Northern France trace of the Northern Variscan Suture Zone i.e. the Bray segment of the Upper Carboniferous Lizard-Rhenohercynian (LRH) suture. Moreover, the high-velocity anomaly is spatially correlated with the prominent Paris Basin Magnetic Anomaly. Its downdip extent reaches depths greater than 200 km below the southern margin of the Paris basin. As suggested in previous tomographic studies below ancient suture zones, these data argue for such anomaly being the remnant of a Variscan subducted slab that escaped the extensive late orogenic delamination process affecting the lithospheric roots by Late Carboniferous-Early Permian times and that was preserved stable over 300 Ma at the base of the lithosphere. On a general geodynamical perspective, these results provide a new insight into the long-term evolution of subducted lithosphere into the mantle. In the case of the Western European Variscan orogenic belt, they suggest that the subduction of the LRH slab below the previously thickened Variscan crust, and its final detachment from the orogenic root, have played an important role in the collapse of the belt, inducing thermal erosion and extension of the overriding lithosphere. The spatial evolution of late orogenic extension across the belt and of subsequent thermal subsidence in the Paris basin is suggested to result from the heterogeneous delamination of the lithospheric roots along strike and from the resultant pattern of asthenospheric rise.

Averbuch, O.; Piromallo, C.

2012-08-01

102

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

103

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

Scientific Electronic Library Online (English)

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

Jonathan, Liria; Juan-Carlos, Navarro.

2009-12-01

104

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

Science.gov (United States)

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

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

2013-12-01

105

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2002-01-01

106

Geophysical Images of the North Anatolian Fault Zone in the Erzincan Basin, Eastern Turkey, and their Tectonic Implications  

Science.gov (United States)

The collision between the Arabian and Eurasian plates in eastern Turkey causes the Anatolian block to move westward. The North Anatolian Fault (NAF) is a major strike-slip fault that forms the northern boundary of the Anatolian block, and the Erzincan Basin is the largest sedimentary basin on the NAF. In the last century, two large earthquakes have ruptured the NAF within the Erzincan Basin and caused major damage ( M s = 8.0 in 1939 and M s = 6.8 in 1992). The seismic hazard in Erzincan from future earthquakes on the NAF is significant because the unconsolidated sedimentary basin can amplify the ground motion during an earthquake. The amount of amplification depends on the thickness and geometry of the basin. Geophysical constraints can be used to image basin depth and predict the amount of seismic amplification. In this study, the basin geometry and fault zone structure were investigated using broadband magnetotelluric (MT) data collected on two profiles crossing the Erzincan Basin. A total of 24 broadband MT stations were acquired with 1-2 km spacing in 2005. Inversion of the MT data with 1D, 2D and 3D algorithms showed that the maximum thickness of the unconsolidated sediments is ~3 km in the Erzincan Basin. The MT resistivity models show that the northern flanks of the basin have a steeper dip than the southern flanks, and the basin deepens towards the east where it has a depth of 3.5 km. The MT models also show that the structure of the NAF may vary from east to west along the Erzincan Basin.

Av?ar, Üm?t; Türko?lu, Er?an; Unsworth, Martyn; Ça?lar, ?lyas; Kaypak, Bülent

2013-03-01

107

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.)

108

Integrated Analysis on Gravity and Magnetic Fields of the Hailar Basin, NE China: Implications for Basement Structure and Deep Tectonics  

Science.gov (United States)

The Hailar Basin is one of the most representative basins among the Northeast China Basin Group, which is situated in the east of East Asia Orogene between the Siberia Plate and the North China Plate. Based on the detailed analysis of the Bouguer gravity anomaly, aeromagnetic anomaly as well as petrophysical data, we studied the features of gravity-magnetic fields in the basin and its neighboring areas. A combined approach of Wavelet Multi-scale Decomposition and Power Spectrum Analysis was adopted to quantitatively grade the gravity and magnetic anomalies into four levels. Accordingly, the apparent depths of the source fields can be assessed. The results reveal the crustal density and magnetic structures of the Hailar Basin. Low-order wavelet details of gravity-magnetic anomalies were carried out on studying basin basement structure. Seven major basement faults of the basin were identified, and the basement lithology was discussed and predicted. Three major uplifts and 14 depressions were delineated according to basement depth inversion by the Park method. High-order wavelet approximations of gravity-magnetic anomalies were carried out on studying deep tectonics of the basin. The average Moho depth of the study area is about 40 km, with a mantle uplift located in the northeast of the basin. The average depth of the Curie interface is about 19 km, while the uplift of the Curie interface is in the basin center and its east and west sides are depressions. Finally, inversion of Bouguer gravity anomalies was conducted on an across-basin GGT profile using the Wavelet Multi-scale Decomposition. The inversion results are consistent with those of GGT seismic inversion, suggesting that the Wavelet Multi-scale Decomposition can be applied to distinguish major crustal density interfaces.

Sun, B.; Wang, L.; Dong, P.; Scientific Team Of Applied Geophysics

2010-12-01

109

Anthropogenic driven modern recharge and solute flux to arid basin aquifers: Results and implications for sustainability based on field observations and computational modeling  

Science.gov (United States)

Development of natural grass and scrubland for agricultural use (grazing and irrigated agriculture) has changed recharge mechanisms and raised questions about the sustainability of groundwater resources in the Trans-Pecos region of Texas. When quantifying the availability of water in the region, previous research relied upon the ';classic' conceptual model; minimal modern recharge, no widespread recharge on basin floors, and no recharge from anthropogenic sources such as irrigation return flow. Increasing nitrate (NO3-) concentrations in basin groundwater from the 1950's to present (median increase of 3-4 mg/L (as NO3-) over approximately 40 years) belie the model of limited modern recharge and pose a risk to water quality throughout the basins. We posit that grazing practices and irrigated agriculture have affected hydrologic processes in the basins by altering 1) the vegetation regime on the basin floors and 2) the magnitude and spatial distribution of infiltrating water. These impacts have increased recharge and transported Cl- and mobile nitrogen (N) from the vadose zone to the underlying groundwater. Using a spatially distributed net infiltration model, we estimate that between 7-20% of recharge occurring in the basins results from widespread recharge on the basin floors and that between 1960 and 2000 an additional 8.5 x 10^3 to 1.2 x 10^6 cubic meters of irrigation water has potentially been returned through irrigation return flow. Vadose zone cores collected from beneath land used for agricultural purposes document changes in water content and pore water chemistry that imply an increase in downward flux of moisture and solute resulting from human alteration of the natural system; reservoirs of NO3- and Cl- typically observed beneath the rooting depth of un-impacted vegetation are either displaced downward or flushed beyond the core depth under land with historical or ongoing irrigated agriculture. There are significant implications for the sustainability of groundwater resources in this system based upon the trends in groundwater NO3- concentrations, vadose zone core data, and results of the net infiltration models: 1) there may be more recharge to the basins than previously estimated and 2) there is a potential long-term concern for water quality. Due to the thick unsaturated zone in much of the system, long travel times are expected between the base of the root zone and the water table. It is unclear if the flux of NO3- and Cl- to the groundwater has peaked or if effects from the alteration of the natural vegetation regime will continue for years to come.

Robertson, W. M.; Sharp, J. M.

2013-12-01

110

The Paleogeothermal Conditions of the Swiss Molasse Basin: Implications for Hydrocarbon Potential La paléogéothermie du bassin molassique suisse : implications pour le potentiel hydrocarbures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The paleogeothermal conditions in the Swiss Molasse basin (Tertiary foredeep sediments north of the Alps) have been investigated by means of coalification studies. These data suggest a generally low-temperature geothermal regime in the Molasse basin which apparently prevailed since the deposition of the sediments. In the light of these findings some general trends for the hydrocarbon potential can be specified; corresponding exploration targets are delineated. On a tenté de reconstrui...

Rybach L.

2006-01-01

111

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)

112

Diagenesis of the Purington Shale in the Illinois Basin and implications for the diagenetic state of sedimentary rocks of shallow Paleozoic basins  

Science.gov (United States)

The clay minerals, micas, and feldspars of the Pennsylvanian-age Purington Shale have been more diagenetically active than generally recognized. They have undergone diagenetic changes comparable to those of Cenozoic and Mesozoic sedimentary rocks buried three to four times as deeply and heated to approximately twice the temperature. The Purington Shale on the Western Shelf of the Illinois Basin has experienced maximum burial of ???1.0 km and was never heated to more than 60??C, except for a very brief time at about 80??C. The illite/smectite (I/S) of the Purington Shale has ???90% illite. The chemical compositions of the feldspar assemblage in the 0.09-0.063-mm fraction differ from most modern detrital suites of feldspars but are similar to diagenetic sequences described by others from much greater burial depths and are extensively, but not completely, albitized. The simplest interpretation of the apparently advanced stage of diagenesis is that the diagenetic processes have been operating at less pressure and lower temperature but for a longer time; an example of low-temperature, time-dependent diagenesis. By similar reasoning, the apparently anomalously advanced maturity of all of the sedimentary rocks in the relatively shallow Illinois Basin is explained. This generalization should be considered for all shallow Paleozoic basins and should influence (1) exploration for petroleum, (2) use of modal and chemical analyses for determining provenance, and (3) use of chemical composition of shales as proxy for crustal evolution.

Moore, D. M.

2000-01-01

113

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

114

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

115

Procedure for calculating estimated ultimate recoveries of Bakken and Three Forks Formations horizontal wells in the Williston Basin  

Science.gov (United States)

Estimated ultimate recoveries (EURs) are a key component in determining productivity of wells in continuous-type oil and gas reservoirs. EURs form the foundation of a well-performance-based assessment methodology initially developed by the U.S. Geological Survey (USGS; Schmoker, 1999). This methodology was formally reviewed by the American Association of Petroleum Geologists Committee on Resource Evaluation (Curtis and others, 2001). The EUR estimation methodology described in this paper was used in the 2013 USGS assessment of continuous oil resources in the Bakken and Three Forks Formations and incorporates uncertainties that would not normally be included in a basic decline-curve calculation. These uncertainties relate to (1) the mean time before failure of the entire well-production system (excluding economics), (2) the uncertainty of when (and if) a stable hyperbolic-decline profile is revealed in the production data, (3) the particular formation involved, (4) relations between initial production rates and a stable hyperbolic-decline profile, and (5) the final behavior of the decline extrapolation as production becomes more dependent on matrix storage.

Cook, Troy A.

2013-01-01

116

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

Science.gov (United States)

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

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

2012-12-01

117

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

Science.gov (United States)

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

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

2013-12-01

118

Provenance of Cretaceous-Oligocene Sedimentary Strata of the Floresta Basin, Eastern Cordillera, Colombia and Tectonic Implications  

Science.gov (United States)

We use integrated detrital zircon U-Pb geochronology, sandstone petrography, sedimentary facies analysis, and paleocurrent measurements from a Mesozoic-Cenozoic clastic succession preserved in the northern Andean fold-thrust belt to address foreland-basin disruption in the Paleogene. The Floresta basin is situated along the axis of the Eastern Cordillera of Colombia. Detrital zircon U-Pb ages and sandstone petrography indicate that the Floresta basin first received sediment from the eastern craton (Guyana shield) in the Cretaceous-early Paleocene and then from the western magmatic arc (Central Cordillera) starting in the mid-Paleocene. The upper-crustal magmatic arc was replaced by a metamorphic basement source, which we identify as Magdalena valley basement equivalent, in the middle Eocene. This, in turn, was replaced by an upper-crustal thrust-belt source in the late Eocene which persisted until Oligocene truncation of the Cenozoic section by the eastward advancing Soapaga thrust. This upper crustal source is interpreted to represent uplift of the western flank of the Eastern Cordillera. The combined provenance data indicates that sediments were derived from eastward-migrating sources. Throughout the Paleogene, paleocurrent and sediment provenance data point to a uniform western or southwestern sediment source with no evidence of the complex sourcing or sediment dispersal patterns emblematic of a broken foreland basin. Therefore, these data show that the Floresta basin existed as part of a laterally extensive, unbroken foreland basin connected with the western (Magdalena) basin from Cretaceous to late Eocene time, when it was isolated by uplift of the western flank of the Eastern Cordillera. The Floresta basin was also connected with the eastern (Llanos) basin from the Cretaceous until its late Oligocene truncation by the advancing thrust front.

Saylor, J.; Corredor, J.; Mora, A.; Horton, B. K.; Nie, J.

2010-12-01

119

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

120

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

 
 
 
 
121

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

122

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

123

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

Directory of Open Access Journals (Sweden)

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

124

Some postulates on the tecto magmatism, tectonostratigraphy and economic potential of kirana - malani basin: implications for occurrence of petroleum  

International Nuclear Information System (INIS)

The so called shield elements exposed to the west of the Aravalli Orogen and exposed in Kirana, Nagar Parkar, Jodhpur, Malani, Tosham, Mount Abu and Erinpura are nether a part of Aravalli Orogen nor do they belong to the Vindhyan Basin. These volcano plutonic and sedimentary rocks represent a distinct cratonic rift assemblage. They were deposited in extensional basin formed as a result of rising of the mantle plume around 1000 ma. This basin is named by us as Malani-Kirana Basin. The stratigraphy of Kirana area has been revised and correlated with the Indian counterpart areas west of the Aravalli range. The Hachi volcanics are correlated with Tosham volcanics. The later are a part of an extensive volcano plutonic igneous province with other centres in Rajasthan and Nagar Parkar. The overlying sedimentary package of Kirana area is designated by us as Machh Super Group and it includes Tuguwali formation, Asian wala quartzites. Hadda quartzites and Sharaban conglomerates. The Machh Super Group is correlated with the lower part of the Marwar Supergroup. The equivalents of the upper Marwar Super group must occur in Pakistan to the south and south west of Kirana adjoining Bikaner - Nagaur Basin of India. Metamorphism in the Machh Super Group sediments must decrease in this direction, therefore hydrocarbon prospects may occur in Pakistani region adjoining hydrocarbon bearing Bikaner - Nagaur Basin of India. Volcanic hosted massive oxide-sulfide deposits have recently been diide-sulfide deposits have recently been discovered in the subsurface in Hachi volcanics near Chiniot. Such deposits must exist throughout Kirana-Malani Basin west of the Aravalli Orogen. (author)

125

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

Science.gov (United States)

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

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

2014-10-01

126

Anomalous crustal and lithospheric mantle structure of southern part of the Vindhyan Basin and its geodynamic implications  

Science.gov (United States)

Tectonically active Vindhyan intracratonic basin situated in central India, forms one of the largest Proterozoic sedimentary basins of the world. Possibility of hydrocarbon occurrences in thick sediments of the southern part of this basin, has led to surge in geological and geophysical investigations by various agencies. An attempt to synthesize such multiparametric data in an integrated manner, has provided a new understanding to the prevailing crustal configuration, thermal regime and nature of its geodynamic evolution. Apparently, this region has been subjected to sustained uplift, erosion and magmatism followed by crustal extension, rifting and subsidence due to episodic thermal interaction of the crust with the hot underlying mantle. Almost 5-6 km thick sedimentation took place in the deep faulted Jabera Basin, either directly over the Bijawar/Mahakoshal group of mafic rocks or high velocity-high density exhumed middle part of the crust. Detailed gravity observations indicate further extension of the basin probably beyond NSL rift in the south. A high heat flow of about 78 mW/m2 has also been estimated for this basin, which is characterized by extremely high Moho temperatures (exceeding 1000 °C) and mantle heat flow (56 mW/m2) besides a very thin lithospheric lid of only about 50 km. Many areas of this terrain are thickly underplated by infused magmas and from some segments, granitic-gneissic upper crust has either been completely eroded or now only a thin veneer of such rocks exists due to sustained exhumation of deep seated rocks. A 5-8 km thick retrogressed metasomatized zone, with significantly reduced velocities, has also been identified around mid to lower crustal transition.

Pandey, O. P.; Srivastava, R. P.; Vedanti, N.; Dutta, S.; Dimri, V. P.

2014-09-01

127

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

128

Peleolakes and impact basins in southern Arabia Terra, including Meridiani Planum: Implications for the formation of hematite deposits on Mars  

Science.gov (United States)

The hematite deposit in Meridiani Planum was selected for a Mars Exploration Rover (MER) landing site because water could be involved in the formation of hematite, and water is a key ingredient in the search for life. Our discovery of a chain of paleolake basins and channels along the southern margin of the hematite deposits in Meridiani Planum with the presence of the strongest hematite signature adjacent to a paleolake basin, supports the possible role of water in the formation of the hematite and the deposition of other layered materials in the region. The hematite may have formed by direct precipitation from lake water, as coatings precipitated from groundwater, or by oxidation of preexisting iron oxide minerals. The paleolake basins were fed by an extensive channel system, originating from an area larger than Texas and located south of the Schiaparelli impact basin. On the basis of stratigraphic relationships, the formation of channels in the region occurred over much of Mars' history, from before the layered materials in Meridiani Planum were deposited until recently. The location of the paleolake basins and channels is connected with the impact cratering history of the region. The earliest structure identified in this study is an ancient circular multiringed basin (800-1600 km diameter) that underlies the entire Meridiani Planum region. The MER landing site is located on the buried northern rim of a later 150 km diameter crater. This crater is partially filled with layered deposits that contained a paleolake in its southern portion. Copyright 2003 by the American Geophysical Union.

Newsom, H. E.; Barber, C. A.; Hare, T. M.; Schelble, R. T.; Sutherland, V. A.; Feldman, W. C.

2003-01-01

129

Assessing differences in topographic form between arctic and temperate drainage basins: Possible implications for dominant erosion processes  

Science.gov (United States)

The extent and topology of channel networks are first-order controls on the timing and magnitude of flood events, as well as the rate of landscape drainage. The latter is particularly important in arctic environments, where the release of greenhouse gases from organic-rich permafrost is partially governed by the presence of water. Recent studies are in disagreement as to whether arctic channel networks will contract or expand due to a warming climate. A challenge in predicting arctic landscape adjustment is quantifying the uncertain role permafrost and ground ice play in erosional processes. An improved understanding of the dominant geomorphic processes in low-order arctic drainage basins is required to better inform predictions of the network response to warming. In both temperate and Arctic systems, researchers often use topographic analyses to suggest scaling breaks at which there are transitions between processes. This study utilizes 2-m resolution digital elevation models to investigate divergence in topographic form between temperate systems and Trail Valley Creek basin (TVC), a 63-km2 basin in Northwest Territories, Canada that is underlain by continuous permafrost and high amounts of ground ice. The valley bottoms of the low-order basins in TVC contain vegetated swales in place of incised channels. We constructed cumulative drainage area distributions and slope-area plots in order to assess any differences in scaling breaks and network topology. We also calculated estimates of fluvial basal shear stress along flow paths with drainage areas larger than an estimated threshold (~10,000 to 20,000 m2). Our analysis includes five sub-basins within TVC, three exhibiting relatively well-developed ridge and valley topography and two less dissected landscapes that are drained by small, closely-spaced swales. The cumulative drainage area distribution curves for these sub-basins do not reveal any scaling breaks that are different from those seen in temperate regions. The slopes of the fluvial portions of the curves suggest greater network branching in the more developed sub-basins than in the temperate basins, however, all network metrics are within the range of those measured in temperate environments. Slope-area plots suggest modest variability between TVC sub-basins in their transition from convex to concave topography, also within the range measured in temperate environments. Neither of these analyses suggests a significant divergence in landscape form between temperate basins and those analyzed in TVC. Furthermore, they do not suggest that the more developed networks exhibit features that can be considered more temperate. Preliminary results for our basal shear stress estimates reveal that shear stresses in arctic networks, and therefore potential for fluvial erosion, drops off much more quickly than in temperate networks as drainage area is reduced. This deviation may suggest that the fluvial erosion processes that dominate temperate networks may not be as significant in low-order arctic basins.

Prancevic, J. P.; Rowland, J. C.; Wilson, C. J.; Marsh, P.; Wilson, H.

2010-12-01

130

The Paleogeothermal Conditions of the Swiss Molasse Basin: Implications for Hydrocarbon Potential La paléogéothermie du bassin molassique suisse : implications pour le potentiel hydrocarbures  

Directory of Open Access Journals (Sweden)

Full Text Available The paleogeothermal conditions in the Swiss Molasse basin (Tertiary foredeep sediments north of the Alps have been investigated by means of coalification studies. These data suggest a generally low-temperature geothermal regime in the Molasse basin which apparently prevailed since the deposition of the sediments. In the light of these findings some general trends for the hydrocarbon potential can be specified; corresponding exploration targets are delineated. On a tenté de reconstruire la paléogéothermométrie du bassin molassique suisse (sédiments tertiaires d'avant-fosse des Alpes du Nord à partir de l'étude des phénomènes de houillification. Les résultats suggèrent qu'un régime géothermique de basse température a prédominé la plupart du temps depuis le dépôt des sédiments. On en déduit quelques tendances générales pour le potentiel en hydrocarbures ainsi qu'une délimitation des objectifs pour l'exploration pétrolière.

Rybach L.

2006-11-01

131

In situ stresses in the Southern Bonaparte Basin, Australia: Implications for first- and second-order controls on stress orientation  

Science.gov (United States)

Four-arm dipmeter logs from six wells and a Formation MicroScanner (FMS) image log from one well in the southern Bonaparte Basin were interpreted for in situ stress indicators. Results of the analysis reveal a consistent NE-SW in situ maximum horizontal stress (?Hmax) orientation (055°N). This orientation is parallel to the average ?Hmax determined in the northern Bonaparte Basin, the onshore Canning Basin, and in New Guinea. The data support the interpretation that the NE-SW ?Hmax orientation in the area reflects a first-order stress pattern controlled by plate boundary forces along the northeastern margin of the Indo-Australian Plate (IAP) and contradict the suggestion that NE-SW ?Hmax in the northern Bonaparte Basin is a second-order effect associated with boundary induced flexural stresses. Numerical modeling suggests that the divergence of ?Hmax from an orientation parallel to plate motion can be explained by the heterogeneous nature of the northeastern boundary of the IAP.

Mildren, Scott D.; Hillis, Richard R.

132

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

133

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

Science.gov (United States)

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

Espenshade, Thomas J.

134

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

Science.gov (United States)

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

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

2011-12-01

135

Senonian basin inversion and rejuvenation of rifting in Africa and Arabia: synthesis and implications to plate-scale tectonics  

Science.gov (United States)

The late Paleozoic to Tertiary stratigraphic record of much of the African plate reflects the effects of continental rifting and passive margin development. Several short-lived, but widespread and tectonically important, compressional or wrench-dominated events occurred, however, during the Permian to Recent evolution of Africa. We focus here on the best documented of these events, which occurred during the late Santonian. At that time, older sedimentary basins, mostly ENE-WSW trending, were folded and inverted, including some basins along the Tethyan margin from Morocco to the Syrian Arc and the intraplate Benue-southern Chad basins and the Lugh-Mandera basin. In Oman, ophiolites were obducted. Following the Santonian tectonism, an extensive phase of rifting occurred in Central and North Africa and northern Arabia, spanning from Campanian to Maastrichtian or Paleocene times. Rejuvenation or acceleration of subsidence occurred in several basins located along the Tethyan margin, along the Atlantic and Indian Ocean margins, as well as within the intraplate domain. Rifting was sometimes accompanied by magmatic activity, especially in offshore northern Libya and along the Indian Ocean margin. Compressional deformations rejuvenated or developed by latest Maastrichtian times along the Tethyan margin and locally within the intraplate domain. One of the most remarkable attributes of the Santonian tectonic event, which we consider representative of the major trans-African stress field changes, is the rapidity with which the change was reflected stratigraphically across North and Central Africa, and its short duration. The cause of the Santonian compressional event is directly linked to the change in poles of rotation for the opening of the Atlantic at ˜83-85 Ma, the end of the Cretaceous Normal Magnetic Quiet Zone. This was also synchronous with the obduction of ophiolites along the northeast margin of Arabia (Oman), the onset of separation between India and Madagascar with formation of the Mascarene oceanic basin, and the development of the European Alpine Chain. We interpret these phenomena as causally related aspects of a global tectonic event. The Santonian compressional event, as well as the Campanian-Maastrichtian rifting event and the end Cretaceous compressional event, illustrate the critical connection between intraplate tectonic histories and processes occurring at sometimes very distant plate boundaries.

Guiraud, René; Bosworth, William

1997-12-01

136

Sedimentary features and ages of fluvial terraces and their implications for geomorphic evolution of the Taomi River catchment: A case study in the Puli Basin, central Taiwan  

Science.gov (United States)

Fluvial terraces play an important role for research on previous geomorphic processes as their sediments can record various sedimentation stages. In the mountains of central Taiwan, however, the formation time of sediments in the Puli Basin is still unclear. In this study, we investigate the fluvial sediments of a fluvial terrace in the Taomi River catchment in the Puli Basin in terms of sedimentology and geochronology and consider their implications for geomorphic evolution in the Puli Basin. Optically stimulated luminescence (OSL) dating shows that fine-grained and homogeneous sediment in the studied fluvial terrace was deposited at 12.3 ± 1.7 ka and 12.0 ± 2.1 ka. These dating results are consistent with the age of 14.5 ± 0.4 ka cal B.P. from the radiocarbon dating of a charcoal fragment. A third OSL age of 8.7 ± 1.4 ka suggests that the overlying fluvial gravels started to form in the early Holocene. Based on the dating results and the sedimentological and geomorphic characteristics of the fluvial terrace under study, a preliminary model of the geomorphic evolution of the Taomi River catchment is proposed: I. The fine-grained sediment had been deposited at the end of the Late Pleistocene. II. In the early Holocene, fluvial gravel deposits were formed, probably caused by a climatic shift (from dry to wet). III. Huge-scaled incision of the Taomi River took place possibly associated with rapid Holocene river incision. IV. Incision stopped, and the studied fluvial terrace was formed. Later, young fluvial terraces, as derived from the analysis of a high resolution DTM, related to episodic incision of the river were formed. The modern river channel is 20 m below the studied outcrop.

Tseng, Chia-Han; Wenske, Dirk; Böse, Margot; Reimann, Tony; Lüthgens, Christopher; Frechen, Manfred

2013-01-01

137

Hellas Planitia, Mars - Site of net dust erosion and implications for the nature of basin floor deposits  

Science.gov (United States)

Hellas Planitia, located within an enclosed basin which includes the lowest topography on Mars, appears to be undergoing net erosion. Dust is removed from the basin. It probably contributes to global dust storms and should leave behind a coarse lag. The particle size distributions and particularly the rock or boulder populations in this lag might be useful for distinguishing between processes which formed the lithologic units that comprise Hellas Planitia. This report concludes that the abundance of rock particles larger than coarse sand is very low. Although this hypothesis awaits confirmation from forthcoming spacecraft data, the origins for Hellas floor deposits favored by this study are indurated volcanic airfall or ancient loess, lacustrine deposits, and some types of volcanic mud flows. The conclusions of this study tend to disfavor such geologic processes as blocky lava flows, glacial deposits (e,g., moraines), or boulder-laden catastrophic flood outwash.

Moore, Jeffrey M.; Edgett, Kenneth S.

1993-01-01

138

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

Directory of Open Access Journals (Sweden)

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

Chengze Zhang

2011-12-01

139

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 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

140

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Fischietto, Nicholas E.

2009-01-01

 
 
 
 
141

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

Science.gov (United States)

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

Ings, Steven; Albertz, Markus

2014-05-01

142

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

143

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

144

Neogene wrench reactivation of the Barcoo sub-basin, northwest Australia: implications for Neogene tectonics on the northern Australian margin  

Energy Technology Data Exchange (ETDEWEB)

The Barcoo Sub-basin forms the southern part of the Browse Basin of Australia's northwestern margin. Miocene reactivation of older Precambrian through Mesozoic-aged structures has resulted in a present-day complex right-lateral wrench zone. The fault system displays restraining and releasing bends separated by areas of almost pure strike-slip displacement, along its 180 km length. Reactivation and inversion varies along the system, with the southern end structurally highest, offsetting beds up to and including the seafloor. The location of restraining and releasing bends controls the occurrence of oil and gas shows in nine wells drilled in the sub-basin, with Neogene inversion causing trap leakage in a number of cases. Right-lateral motion on the Barcoo Fault system, in contrast to a proposed regional-scale left-lateral movement component on the northwestern margin as a whole, implies strong strain partitioning along the margin with regional tectonic control. We propose that the structural domain boundaries may be controlled in part by the location of the continental collision zone between the northernmost limit of Australian continental crust with the southernmost continental fragments of the Eurasian plate, in the vicinity of the island of Sumba. (Author)

Keep, M.; Bishop, A. [University of Western Australia, Nedlands, WA (Australia). Dept. of Geology and Geophysics; Longley, I. [Woodside Offshsore Petroleum, Perth (Australia)

2000-08-01

145

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

International Nuclear Information System (INIS)

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

146

Hydrodynamics and overpressuring in the Jeanne d'Arc Basin, offshore Newfoundland, Canada: Possible implications for hydrocarbon exploration; Discussion  

Energy Technology Data Exchange (ETDEWEB)

Rogers and Yassir (1993) presented a new interpretation of subsurface fluid flow in the Jeanne d'Arc Basin on the Grand Banks. They suggested that groundwater flow in the basin is largely vertical and fault-controlled, with vertically upward flow from geopressured zones and vertically downward flow through sediments overlying those zones. A discussion of this hypothesis is presented which highlights the uncertainties associated with establishing the regional hydrostatic gradient in the basin and the possibility of introducing systematic error into the determination of hydraulic heads. Important assumptions, such as linearity and homoscedasticity, in the linear regression analysis of pressure data appear to have been violated, producing a systematic misfit to pressure data and leading to the doubtful interpretation of apparent downward fluid flow. This calls into question the existence of significant downward fluid flow in the hydrostatic regime and removes the requirement for postulating a mechanism that would drive such a flow system. In the absence of supporting data such as temperature, hydraulic parameters, and diagenetic effects, the arguments favoring downward flow appear to be weak at best. 9 refs., 1 fig.

Issler, D.R. (Inst. of Sedimentary and Petroleum Geology, Calgary, AB (Canada))

1994-06-01

147

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

Science.gov (United States)

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

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

2004-12-01

148

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

149

Active tectonics of the Atacama Basin area, northern Chile: Implications for distribution of convergence across the central Andes  

Science.gov (United States)

The central Andes in South America is formed as the Nazca plate subducts northeastward beneath the South American plate along the Peru-Chile trench, parallel to the coastline. It has been shown that the convergence rate between the two plates is ~70-80 mm/yr, and about 10-15 mm/yr of the convergence is absorbed in the sub-Andean belt, east of the active volcanic arc. However, the convergence in the forearc region is still not well constrained. In order to understand how much convergence is absorbed in the forearc region, we analyzed the active tectonic characteristics of the Atacama Basin, just west of the active volcanic arc. With the help of various remote sensing datasets such as 30-m and 90-m resolution digital elevation models (DEM) produced from SRTM data, thermal infrared radiometer (TIR) ASTER images, Landsat, and Google Earth images, we identified many N-S trending compressional structures around the Atacama Basin. The active structures are found mainly in the northern and southern part of the basin. The structures in the north deformed many volcanic rocks at the surface, such as ignimbrites and several lava flows. Structures may extend southward to San Pedro de Atacama, the largest town in the Atacama Basin, and produced tectonic scarps inside the town. River terraces also formed in the hanging-wall block of the structures, north of San Pedro. From field surveys, we measured the offset amount of the structures and collected volcanic rocks in order to constrain the age of the deformation. These results enabled us to calculate the long-term deformation rate of the structures. Our results indicate that the long-term slip rate of the structures in the southern part of the basin is quite low, in the order of 10-1 mm/yr. Furthermore, we obtained detailed topographic profiles across the structures. In the south, the profiles were surveyed by using real-time kinematic (RTK) GPS. Together with the attitudes of bedding planes, we constructed the subsurface geometry of the structures based on the shear fault-bend fold model. Our results indicate that the shortening rate in this area is about 0.2 mm/yr, significantly lower than the shortening rates in the backarc region of the central Andes. Thus the forearc region of the central Andes may act as rigid block, and most of the plate convergence west of the volcanic arc is absorbed along the subduction interface.

Chuang, Yi-Rung; Lin, Yen-Sheng; Shyu, J. Bruce H.

2013-04-01

150

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

151

Late Cenozoic basalt and gabbro in the subsurface in the Phetchabun Basin, Thailand: Implications for the Southeast Asian Volcanic Province  

Science.gov (United States)

Fragments of basaltic and gabbroic rocks were obtained in cuttings from 15 exploration wells in the Na Sanun area of the Wichian Buri Sub-basin of the Phetchabun Basin in central Thailand. The samples represent flows and sills in lacustrine and fluvial sedimentary rocks of the Lower to mid-Miocene Wichian Buri Group. Mafic igneous units were identified in the sections based on their typically high-amplitude seismic reflections, confirmed by the examination of several hundred well cuttings and magnetic susceptibility measurements. Cross-sections of the sub-basin were constructed on the basis of previously published subsurface interpretations, seismic and well data, and petrological observations. Basaltic flows A, B, E, and F have ages of ca. 2 Ma, 16 Ma, 24 Ma and 18 Ma, based on inferred stratigraphic position. Gabbroic sill C and dioritic sill G are inferred to be correlative at ca. 11.6 Ma, and differ petrologically from ca. 12.8 Ma gabbroic sill D. Major minerals in both basaltic and gabbroic samples are plagioclase (ca. An50), anorthoclase, and augite, with pervasive alteration to Na- and Ca- zeolite minerals and analcime. Leucodioritic sill G also contains amphibole and high Ti-phlogopite. Overall, the rocks show within-plate tholeiitic to alkalic characteristics, and show similarities to basaltic surface outcrops of similar ages in the Wichian Buri-Lop Buri area. No evidence was seen in the subsurface for the andesitic to rhyolitic rocks of similar ages that occur at surface, but their presence cannot be precluded based on our limited data.

Barr, S. M.; Cooper, M. A.

2013-10-01

152

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

DEFF Research Database (Denmark)

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

Sandrin, Alessandro; Thybo, Hans

2008-01-01

153

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

154

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 ate 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

155

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

Science.gov (United States)

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

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

2014-01-01

156

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

157

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

158

Evidence of clastic evaporites in the canyons of the Levant basin (Israel): implications for the Messinian salinity crisis  

Science.gov (United States)

The recognition of widespread and thick evaporite deposits below the floor of the Mediterranean Sea has boosted a long standing controversy concerning their depositional setting (shallow versus deep) and their correlation with the onshore sequences. Until a new scientific campaign might be launched to cross those deposits, the discussion is still open to speculation. Many Messinian evaporitic deposits have been interpreted as primary precipitates in very shallow-water or coastal environments, thus favouring the idea of a desiccated Mediterranean basin (Hsu et al., 1973). Recent studies have questioned this interpretation (Hardie and Lowenstein, 2004) and widespread, thick, clastic evaporite facies have been identified in the Mediterranean (Manzi et al., 2005). These clastic deposits are not compatible with a desiccation model as they were clearly emplaced by fully subaqueous, deep-water processes, ranging from submarine slides, to high- and low-density gravity flows. One of the most relevant areas for the understanding of the salinity crisis is the Levant basin where the Messinian evaporites partially fill some of the erosional features (canyons) considered to have formed as a consequence of significant drawdown related to the desiccation of the Mediterranean Sea (up to - 850 m, Druckman et al., 1995). Our complete revisitation of the available cores from onshore Israel cutting through the sedimentary filling of the Messinian canyons (Afiq 1, Ashdod 2, Be'eri Sh1, Be'eri Sh4, Jaffa 1 and Talme-Yaffe 3) revealed exclusively clastic sulfate facies. This is the first direct evidence that the Lower Evaporite Unit offshore Israel may actually consist of deep-water resedimented evaporites that were originally deposited on the margin of the Levant Basin. References Druckman Y., Buchbinder B., Martinotti G.M., Tov R.S., Aharon P., 1995. The buried Afiq Canyon (eastern Mediterranean, Israel): a case study of a Tertiary submarine canyon exposed in Late Messinian times. Marine Geology, 123, 167-185. Hardie L.A. & Lowenstein T.K., 2004. Did the Mediterranean Sea dry out during the Miocene? A reassessment of the evaporite evidence from DSDP Legs 13 and 42A cores. JSR, 74, 453-461. Hsu, K.J., Cita, M.B., and Ryan, W.B.F, 1973. The origin of the Mediterranean evaporites, in Ryan, W.B.F., et al. eds., Initial Reports of the Deep Sea Drilling Project, v. 13, Washington, 1203-1231. Manzi V., Lugli S., Ricci Lucchi F., Roveri M., 2005. Deep-water clastic evaporites deposition in the Messinian Adriatic foredeep (northern Apennines, Italy): did the Mediterranean ever dry out? Sedimentology, 52, 875-902.

Lugli, Stefano; Schreiber, B. Charlotte; Gvirtzman, Zohar; Manzi, Vinicio; Roveri, Marco

2013-04-01

159

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

Science.gov (United States)

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

Biondi, F.; Strachan, S. D.

2011-12-01

160

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

Science.gov (United States)

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

Guzman Espinal, Jose Ignacio

1999-11-01

 
 
 
 
161

Hydrologic impacts of climate change on the Nile River basin: Implications of the 2006 IPCC climate scenarios  

Science.gov (United States)

The potential impact of climate change on the hydrology and flow regime of the Nile River basin is assessed by downscaling and bias correcting climate model output from 11 General Circulation Models (GCMs) under two global emissions scenarios to one-half degree latitude-longitude spatial resolution. The downscaled and bias corrected climate model output was then used to force the Variable Infiltration Capacity (VIC) land surface model over the Nile River basin for the 100-year period 2001-2100. The model was first calibrated and tested using historical data for the period 1950-99 at three stream gauging stations: the main stem Nile at Dongola, the main stem at High Aswan Dam (HAD), and the Blue Nile at El Diem. Although there are large variations among the different GCMs, over the entire Nile basin, the multi-model average for the study period 2001-2100 showed an initial increase in precipitation, and then decreases, with the initial increase, and subsequent decreases, larger in the multimodel average for emissions scenario A2 (more or less business as usual) as compared with B1 (global emissions levelling off by about 2100). Temperature consistently increased through the century, with larger changes for Scenario A2 as compared with B1. Averaged over all models and ensembles, annual streamflow at HAD for scenario A2 was predicted to increase to 111% of the 1950-99 mean during 2010-2039, but then to decrease to 92% and 79% of the 1950-99 mean during 2040-2069 and 2070-2099, respectively. For scenario B1, the corresponding numbers were 117% (increase) during 2010- 2039, and decreases to 96% and 83% of the 1950-99 mean from 2040-2069 and 2070-2099, respectively. The effects of these hydrologic changes are evaluated using a simple water management operations model of the system which considers historical irrigation, hydropower and domestic use of water as well as future scenarios for water demand in these three sectors.

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

2006-12-01

162

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

163

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

Science.gov (United States)

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

Iyer, K. H.; Rupke, L.

2013-12-01

164

The Thermo-Tectonic Evolution of Hoodoo Dome, Ellef Ringnes Island: Implications for Petroleum Exploration in the Sverdrup Basin  

Science.gov (United States)

Over one hundred evaporite diapirs, cored by Carboniferous Otto Fiord Fm., reside along the Sverdrup Basin's axis in the Canadian High Arctic. However, due to the remoteness of this region their tectonic evolution and hydrocarbon potential remain poorly understood. This study focuses on one of the better known diapirs, Hoodoo Dome, located on Ellef Ringnes Island. We use ground-based geological mapping as well as (U-Th)/He thermochronology to better understand the thermal evolution of the rocks around the dome and tectonic influences on salt migration. Our goal is to improve the understanding of thermal histories and hydrocarbon potential of the salt structures in the Sverdrup Basin. The Sverdrup Basin is a steep sided pericratonic trough estimated to contain approximately thirteen kilometers of Carboniferous to Tertiary strata. At Hoodoo Dome, sandstone samples from the Early Cretaceous Isachsen Fm. and Late Cretaceous Hassle Fm. were collected at Hoodoo Dome for apatite and zircon (U-Th)/He thermochronology, a fairly new low temperature thermochronometric technique that yields cooling ages marking a sample's passage through the ~ 70°C and ~175-193°C isothermal surfaces. Samples were collected along 2 transects (north-south and east-west) across Hoodoo Dome, where seven samples yielded sufficient apatite grains and ten samples yielded sufficient zircon grains. The apatite sample suite exhibits a large distribution of apatite helium (AHe) ages, both reset and non-rest. Only 2 samples, BG 14-35-2 and BG 14-34-4 are interpreted as completely reset. Sample BG 14-35-2, the stratigraphically oldest sample, yielded a mean AHe age of 59.2 ±3.9 Ma, whereas sample BG 14-34-4, approx. 150m up section from BG 14-35-2 yielded a mean AHe age of 69.4 ±4.2 Ma. These reset ages suggest that dome uplifting was active by ?70 Ma at the latest and continued until at least ?60 Ma, consistent with the timing the Eurekan Orogeny. The remaining AHe ages from samples collected farther from the dome core and up-section of BG 14-34-4 by ?500m-1300m exhibit both reset and non-reset AHe ages ranging from ?41.3 Ma-1670 Ma. These data suggest long-term residence in the Partial retention zone (PRZ) where grains have experienced partial He loss at shallow depths (seismic and well log back-stripping across Hoodoo Dome which were used to qualitatively answer questions regarding the rate, mechanism, and regional influence of diapirism during the Dome's development. Our results add new quantitative data regarding the ascent of the evaporite core as well as thermal histories for the rocks surrounding Hoodoo Dome. Finally, we hypothesize that salt cored structures elsewhere in the Sverdrup Basin will exhibit similar thermal history patterns, interpreted here as indicating compression induced salt extrusion in the Latest Cretaceous at the onset of the Eurekan Orogeny.

Springer, A. C.; Guest, B.

2011-12-01

165

Chemostratigraphic implications of spatial variation in the Paleocene-Eocene Thermal Maximum carbon isotope excursion, SE Bighorn Basin, Wyoming  

Science.gov (United States)

The Paleocene-Eocene Thermal Maximum (PETM) is marked by a prominent negative carbon isotope excursion (CIE) of 3-5‰ that has a characteristic rapid onset, stable body, and recovery to near pre-CIE isotopic composition. Although the CIE is the major criterion for global correlation of the Paleocene-Eocene boundary, spatial variations in the position and shape of the CIE have not been systematically evaluated. We measured carbon isotope ratios of bulk organic matter (?13Corg) and pedogenic carbonate (?13Ccarb) at six PETM sections across a 16 km transect in the SE Bighorn Basin, Wyoming. Bed tracing and high-resolution floral and faunal biostratigraphy allowed correlation of the sections independent of chemostratigraphy. The onset of the CIE in bulk organic matter at all six sections occurs within a single laterally extensive geosol. The magnitude of the CIE varies from 2.1 to 3.8‰. The absolute and relative stratigraphic thickness of the body of the CIE in bulk organic matter varies significantly across the field area and underrepresents the thickness of the PETM body by 30%-80%. The variations cannot be explained by basinal position and instead suggest that ?13Corg values were influenced by local factors such as reworking of older carbon. The stratigraphic thickness and shape of the CIE have been used to correlate sections, estimate timing of biotic and climatic changes relative to the presumed carbon isotope composition of the atmosphere, and calculate rates of environmental and biotic change. Localized controls on ?13Corg values place these inferences in question by influencing the apparent shape and duration of the CIE.

Baczynski, Allison A.; McInerney, Francesca A.; Wing, Scott L.; Kraus, Mary J.; Bloch, Jonathan I.; Boyer, Doug M.; Secord, Ross; Morse, Paul E.; Fricke, Henry C.

2013-10-01

166

Cenozoic foreland basin system in the central Andes of northwestern Argentina: Implications for Andean geodynamics and modes of deformation  

Science.gov (United States)

Cenozoic strata in the central Andes of northwestern Argentina record the development and migration of a regional foreland basin system analogous to the modern Chaco-Paraná alluvial plain. Paleocene-lower Eocene fluvial and lacustrine deposits are overlain by middle-upper Eocene hypermature paleosols or an erosional disconformity representing 10-15 Myr. This `supersol/disconformity' zone is traceable over a 200,000 km2 area in the Andean thrust belt, and is overlain by 2-6 km of upward coarsening, eastward thinning, upper Eocene through lower Miocene fluvial and eolian deposits. Middle Miocene-Pliocene fluvial, lacustrine, and alluvial fan deposits occupy local depocenters with contractional growth structures. Paleocurrent and petrographic data demonstrate westerly provenance of quartzolithic and feldspatholithic sediments. Detrital zircon ages from Cenozoic sandstones cluster at 470-491, 522-544, 555-994, and 1024-1096 Ma. Proterozoic-Mesozoic clastic and igneous rocks in the Puna and Cordillera Oriental yield similar age clusters, and served as sources of the zircons in the Cenozoic deposits. Arc-derived zircons become prominent in Oligo-Miocene deposits and provide new chronostratigraphic constraints. Sediment accumulation rate increased from ˜20 m/Myr during Paleocene-Eocene time to 200-600 m/Myr during the middle to late Miocene. The new data suggest that a flexural foreland basin formed during Paleocene time and migrated at least 600 km eastward at an unsteady pace dictated by periods of abrupt eastward propagation of the orogenic strain front. Despite differences in deformation style between Bolivia and northwestern Argentina, lithosphere in these two regions flexed similarly in response to eastward encroachment of a comparable orogenic load beginning during late Paleocene time.

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

2011-12-01

167

The implications of climate change scenario selection for future streamflow projection in the Upper Colorado River Basin  

Directory of Open Access Journals (Sweden)

Full Text Available The impact of projected 21st century climate conditions on streamflow in the Upper Colorado River Basin was estimated using a multi-model ensemble approach wherein the downscaled outputs of 112 future climate projections from 16 global climate models (GCMs were used to drive a macroscale hydrology model. By the middle of the century, the impacts on streamflow range, over the entire ensemble, from a decrease of approximately 30% to an increase of approximately the same magnitude. Although prior studies and associated media coverage have focused heavily on the likelihood of a drier future for the Colorado River Basin, approximately 25 to 35% of the ensemble of runs, by 2099 and 2039, respectively, result in no change or increases in streamflow. The broad range of projected impacts is primarily the result of uncertainty in projections of future precipitation, and a relatively small part of the variability of precipitation across the projections can be attributed to the effect of emissions pathways. The simulated evolution of future temperature is strongly influenced by emissions, but temperature has a smaller influence than precipitation on flow. Period change statistics (i.e., the change in flow from one 30-yr period to another vary as much within a model ensemble as between models and emissions pathways. Even by the end of the current century, the variability across the projections is much greater than changes in the ensemble mean. The relatively large ensemble analysis described herein provides perspective on earlier studies that have used fewer scenarios, and suggests that impact analyses relying on one or a few climate scenarios are unacceptably influenced by the choice of projections.

B. L. Harding

2012-11-01

168

The implications of climate change scenario selection for future streamflow projection in the Upper Colorado River Basin  

Directory of Open Access Journals (Sweden)

Full Text Available The impact of projected 21st century climate conditions on streamflow in the Upper Colorado River Basin was estimated using a multi-model ensemble approach wherein the downscaled outputs of 112 future climate scenarios from 16 global climate models (GCMs were used to drive a macroscale hydrology model. By the middle of the century, the impacts on streamflow range, over the entire ensemble, from a decrease of approximately 30% to an increase of approximately the same magnitude. Although prior studies and associated media coverage have focused heavily on the likelihood of a drier future for the Colorado River Basin, approximately one-third of the ensemble of runs result in little change or increases in streamflow. The broad range of projected impacts is primarily the result of uncertainty in projections of future precipitation, and a relatively small part of the variability of precipitation across the projections can be attributed to the effect of emissions scenarios. The simulated evolution of future temperature is strongly influenced by emissions, but temperature has a smaller influence than precipitation on flow. Period change statistics (i.e., the change in flow from one 30-yr period to another vary as much within a model ensemble as between models and emissions scenarios. Even over the course of the current century, the variability across the projections is much greater than the trend in the ensemble mean. The relatively large ensemble analysis described herein provides perspective on earlier studies that have used fewer scenarios, and suggests that impact analyses relying on one or a few scenarios, as is still common in dynamical downscaling assessments, are unacceptably influenced by choice of projections.

B. L. Harding

2012-01-01

169

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

170

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

171

Late Mesozoic bimodal volcanic rocks in the Jinniu basin, Middle-Lower Yangtze River Belt (YRB), East China: Age, petrogenesis and tectonic implications  

Science.gov (United States)

Late Mesozoic intrusive and volcanic rocks are widespread in the southeast Hubei Province, Middle-Lower Yangtze River Belt (YRB), East China. Detailed in situ zircon U-Pb and Hf isotope, elemental and Sr-Nd-Pb isotopic data are presented in this paper for Late Mesozoic volcanic rocks from the Jinniu Basin, YRB, aiming to constrain their age, petrogenesis, and tectonic implications. The Jinniu volcanic rocks show a bimodal distribution in composition, with dominant rhyolite and dacite, and subordinate basalt and basaltic andesite. New SHRIMP and LA-ICPMS zircon U-Pb ages indicate that the volcanic rocks of three Formations in the Jinniu basin were erupted at quite a short age range of about 5 Ma during the Early Cretaceous (130-125 Ma). The mafic rocks are moderately enriched in large-ion-lithophile-elements (LILE) (e.g., Ba, Th, U, and Pb) and light rare-earth-elements (LREE), and are characterized by negative Nb, Ta, and Ti anomalies, and relatively high TiO2 (0.72-2.06%) and Nb (9.20-26.5 ppm) contents. These analyses indicate that the geochemical characteristics of the mafic rocks in the Jinniu basin are similar to worldwide Phanerozoic Nb-enriched basalt and andesites (NEBA). New in situ zircon U-Pb ages and field geological relationships demonstrate that NEBA in the southeast Hubei Province are not spatially or temporally associated with high-silica adakitic rocks, but were most likely derived from an enriched lithospheric mantle with assimilation of minor crustal materials, and then fractional crystallization during the evolution of the magma. Overall, the felsic rocks in the Jinniu basin have geochemical characteristics, and Sr-Nd-Pb signatures, and in situ zircon Hf isotopic compositions similar to those of the mafic rocks. Compared with the mafic rocks, the felsic rocks are characterized by enriched and variable concentrations of LILE and REE (e.g., Ba = 33.3-1372 ppm, Y = 11.4-33.6 ppm, YbC = 5.07-18.7), and negative Eu anomalies (?Eu = 0.22-0.98), as well as a wide range of radiogenic Nd-Pb isotopic values with ?Nd (t) = - 10.2 to - 2.4, (206Pb/204Pb)i = 17.659-18.705, (207Pb/204Pb)i = 15.478-15.663, and (208Pb/204Pb)i = 37.654-38.935, and in situ zircon Hf compositions of ?Hf (t) = - 12.7 to - 1.8. These features indicate that the genesis of felsic magma in the Jinniu basin is consistent with extensive fractional crystallization and large amounts of crustal contamination from an evolved mafic magma (SiO2 = ~ 55%). The bimodal volcanic rocks in this study provide convincing evidence that Early Cretaceous volcanic rocks in the YRB developed in a back-arc extensional tectonic regime.

Xie, Guiqing; Mao, Jingwen; Xiongwei, Li; Duan, Chao; Yao, Lei

2011-11-01

172

Implications for Ecosystem Services of Watershed Processes that affect the Transport and Transformations of Mercury in an Adirondack Stream Basin  

Science.gov (United States)

Mercury (Hg) is a potent neurotoxin that can affect the health of humans and wildlife through the ingestion of methyl Hg. Mercury contamination of ecosystems originates from human activities such as mining, coal burning and other industrial emissions, and the use of Hg-containing products. Natural sources such as volcanic and geothermal emissions and the weathering of Hg-bearing minerals also contribute to Hg contamination, but are believed to be minor sources in most ecosystems. Various ecosystem disturbances including fires, forest harvesting, and the submergence of land by impoundment may also contribute to Hg ecosystem contamination by mobilizing stores that have previously originated from the sources described above. Mercury from a mix of regional and global emissions sources is transported in the atmosphere to remote landscapes that are distant from local emissions sources. The Adirondacks of New York State is a forested, mountainous region characterized by abundant lakes and streams, and is distant from local emissions sources. Recreational fishing, wildlife viewing, hiking, and hunting are valued ecosystem services in this region. Here, we report on the relevance to ecosystem services of findings based on five years of Hg data collection of stream water, groundwater, invertebrates, and fish in the upper Hudson River basin in the central part of the Adirondack region. The New York State Dept. of Health has issued fish consumption advisories for the entire Adirondacks based on elevated levels previously measured in lakes and rivers of this region. Our work seeks improved understanding and models of the landscape sources and watershed processes that control the transformation of Hg to its methyl form (MeHg), the transport of MeHg to streams, and bioaccumulation of MeHg in aquatic food webs. Mean annual atmospheric Hg deposition was 6.3 ?g/m2/yr during 2007-09, compared to mean annual filtered total Hg stream yields of 1.66 ?g/m2/yr and filtered MeHg stream yields of 0.095 ?g/m2/yr in a sub-basin of the upper Hudson during this same period. Our work shows that Hg in stream biota, which is largely in the methyl form, is strongly related to MeHg measured in the water column; food web factors that affect Hg bioaccumulation also play a role. In brook trout, the top aquatic predator in the food web of the upper Hudson, Hg concentrations average about 0.1 ?g/g, a level believed to affect fish behavior, and a few values were greater than 0.3 ?g/g, a level at which human fish consumption advisories are issued. Landscape-based regression models that account for about 80% of the variation in stream MeHg concentrations at 25 sites across the upper Hudson basin include metrics of riparian area and open water indicating the importance of these landscape types in affecting methylation rates, losses of MeHg (through demethylation and other processes), and the transport of MeHg to surface waters. These and other study results indicate that factors such as watershed geomorphology, seasonal variations in discharge and air temperature, and the location and connection of riparian wetlands to streams are the strongest factors that affect stream MeHg concentrations and therefore, the potential ecosystem services provided by fish and other wildlife in the Adirondack region.

Burns, D. A.; Riva-Murray, K.; Bradley, P. M.

2012-12-01

173

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

Science.gov (United States)

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

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

2008-04-01

174

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

Science.gov (United States)

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

Barker, C.E.; Dallegge, T.

2006-01-01

175

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

Directory of Open Access Journals (Sweden)

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

176

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

177

Structural studies near Pevek, Russia: implications for formation of the East Siberian Shelf and Makarov Basin of the Arctic Ocean  

Science.gov (United States)

The Pevek region of Arctic Russia provides excellent beach cliff exposure of sedimentary and igneous rocks that yield detailed information on the nature, progression and timing of structural events in this region. Regional folding and thrust faulting, with the development of a south-dipping axial plane cleavage/foliation developed during N-S to NE-SW directed shortening and formation of the Chukotka-Anyui fold belt. This deformation involves strata as young as Valanginian (136-140 Ma, Gradstein et al., 2004). Fold-related structures are cut by intermediate to silicic batholiths, plutons and dikes of Cretaceous age. Reported K-Ar whole rock and mineral ages on the granitoids range from 144 to 85 Ma, but to the south, more reliable U-Pb zircon ages on compositionally similar plutons yield a much narrower age range of ~120-105 Ma (Miller et al., this volume) and a pluton in Pevek yields a U-Pb age on zircon of 108.1±1.1 Ma with evidence for inheritance of slightly older 115 Ma zircons. Magmas were intruded during an episode of E-W to ENE-WSW directed regional extension based on the consistent N-S to NNW-SSE orientation of over 800 mapped dikes and quartz veins. Analysis of small-offset faults and slickensides yield results compatible with those inferred from the dikes. Younger tectonic activity across this region is minor and the locus of magmatic activity moved southward towards the Pacific margin as represented by the Arctic, forming the Makarov Basin north of the Siberian shelf at this longitude. A synthesis of available seismic reflection, gravity and magnetic data for the offshore Siberian Shelf reveals a widespread, seismically mappable basement-sedimentary cover contact that deepens northward towards the edge of the shelf with few other significant basins. Various ages have been assigned to the oldest strata above the unconformity, ranging from Cretaceous (Albian - 112-100 Ma) to Tertiary (Paleocene-Eocene - ~60-50 Ma). The period of uplift and erosion documented along the Arctic coast of Russia at this longitude could represent the landward equivalent of the (yet undrilled) offshore basement-sedimentary cover contact, thus overlying sedimentary sequences could be as old as early Late Cretaceous. Although quite speculative, these conclusions suggest that land-based geologic, structural, petrologic and geochronologic studies could provide useful constraints to help resolve the plate tectonic history of the Arctic Ocean.

Miller, E. L.; Verzhbitsky, V. E.

2009-09-01

178

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

International Nuclear Information System (INIS)

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

179

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

180

Biostratigraphic and palaeoenvironmental implications of an Early Cretaceous miospore assemblage from the Muling Formation, Jixi Basin, northeast China  

Energy Technology Data Exchange (ETDEWEB)

In the Jixi Basin, eastern Heilongjiang Province, China, the lower part of the Lower Cretaceous succession consists of coal-bearing strata including the Muling Formation, which, in addition to plant megafossils, yields abundant spores and pollen grains and a few dinoflagellate cysts. The spore-pollen assemblage consists of more than 42 species belonging to 34 genera. Most of these are derived from pteridophytes and gymnosperms. The association of Aequitriradites echinatus, Cicatricosisporites australiensis, C. imbricatus, C. mediostriatus, C. undosus, Contignisporites glebulentus, Crybelosporites punctatus, Foranminisporis asymmetricus, Gleicheniidites laetus, Impardecispora purverulenta, Kuylisporites lunaris, Pilosisporites trichopapillosus and Triporoletes singularis suggests that the formation is unlikely to be older than late Hauterivian and younger than Aptian, with emphasis placed on the Barremian-early Aptian. The composition of the dinoflagellate cyst and plant megafossil assemblages is consistent with this determination. Based on palynofloral content, a comparison between the miospores recovered and the spores and pollen produced by extant plant taxa, the associated plant megafossils, and the sedimentary facies that characterize the Muling Formation, it is concluded that the source vegetation was dominated by ferns and that the climate was wet subtropical but seasonally dry.

Yang, X.J.; Li, W.B.; Batten, D.J. [Chinese Academy of Sciences, Nanjing (China)

2007-04-15

 
 
 
 
181

Fluid inclusion analysis of twinned selenite gypsum beds from the Miocene of the Madrid basin (Spain). Implication on dolomite bioformation  

Science.gov (United States)

This research work is centred on continental lacustrine gypsum deposits of Miocene age cropping out in the easternmost part of the Madrid Basin. These gypsum deposits, accumulated in a continental saline lake, are characterized by a spectacular, distinctive Christmas-tree morphology and a peculiar dolomite replacement. A combination of microscopic (petrography and scanning electron microscopy) and analytical techniques (fluid inclusion microthermometry, X-ray energy dispersive spectroscopy and X-ray diffractometry) was used in order to study the crystallographic distribution and the composition of the fluid inclusions within the gypsum. The objectives were to characterize the continental brine from which the mineral precipitated, and to detect mineral and element traces that could indicate early diagenetic processes altering the gypsum deposits. Data from primary fluid inclusions indicated that gypsum precipitated from an aqueous fluid (lake water) of low to moderate total salinity (between 20 and 90 g/L NaCl). Secondary fluid inclusions represent interstitial lake brine in contact with gypsum, slightly enriched in total salt content as crystal formation proceeded. Textural, ultrastructural and microanalytical analysis indicate that the presence of dolomite precipitates inside the gypsum layers is related to the microbial colonization of the gypsum deposits and the biomineralization of the cell walls and extracellular polymeric substances around the cells. Our investigation emphasizes necessity of a multidisciplinary approach to assess geobiological processes.

Ayllón-Quevedo, F.; Souza-Egipsy, V.; Sanz-Montero, M. E.; Rodríguez-Aranda, J. P.

2007-09-01

182

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2012-01-01

183

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

International Nuclear Information System (INIS)

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

184

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

185

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

Directory of Open Access Journals (Sweden)

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

D. L. Ficklin

2014-06-01

186

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

187

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

188

Palinspastic reconstruction of Lower Mesozoic stratigraphic sequences near the latitude of Las Vegas: Implications for the entire Great Basin  

Energy Technology Data Exchange (ETDEWEB)

On the Colorado Plateau, lower Mesozoic stratigraphy is subdivided by regional unconformities into the Lower Triassic Moenkopi, Upper Triassic Chinle, Lower and Middle( ) Jurassic Glen Canyon, and Middle Jurassic lower San Rafael tectonosequences. Palinspastic reconstruction for Cenozoic extensional and mesozoic compressional deformations near the latitude of Las Vegas indicates the Moenkopi tectono-sequence constructed a passive-margin-like architecture of modest width overlapping folded. Thrust-faulted, and intruded Permian strata, with state boundaries fixed relative to the Colorado Plateau, comparison of the location of the Early Triassic shelf-slope break near latitude 36[degree] with the palinspastically restored location of the shelf-slope break in southeastern Idaho implies strata of the Moenkopi tectonosequence in the Mesozoic marine province of northwest NV lay in western utah in the Early Triassic. This reconstruction: suggests that the Galconda and Last Chance faults are part of the same thrust system; aligns late Carnian paleovalleys of the chinle tectonosequence on the Colorado Plateau with a coeval northwest-trending paleovalley cut across the Star Pea, and the Norian Cottonwood paleovalley with the coeval Grass Valley delta; defines a narrow, northward deepening back-arc basin in which the Glen Canyon tectonosequence was deposited; aligns east-facing half grabens along the back side of the arc from the Cowhole Mountains to the Clan Alpine Range; projects the volcan-arc/back-arc transition from northwest Arizona to the east side of the Idaho batholith; and predicts the abrupt facies change from silicic volcanics to marine strata of the lower San Rafael sequence lay in western Utah. The paleogeographic was altered in the late Bathonian to Callovian by back-arc extension north of a line extending from Cedar City, UT to Mina, NV. The palinspastic reconstruction implies the Paleozoic was tectonically stacked at the close of the Paleozoic.

Marzolf, J.E. (Southern Illinois Univ., Carbondale, IL (United States). Dept. of Geology)

1993-04-01

189

Implications of apatite fission track analysis for the thermal history of the Scotian Basin, offshore Nova Scotia, Canada  

International Nuclear Information System (INIS)

Forty apatite samples of sandstone from ten exploration wells in the Scotian Basin, offshore Nova Scotia, Canada, were used for fission track analysis and thermal history reconstruction. The sample depths range from 1000 to 5500 m. Fission tracks in all apatite samples are at least partially annealed. Apatite fission track ages for the the shallowest samples, from the Logan Canyon Formation, are older than their stratigraphic ages and therefore retain some record of cooling in the detrital source area. samples from deeper formations (Mississauga, Mic Mac and Verrill Canyon) have apatite fission track ages younger than their stratigraphic ages (some give zero ages), indicating partial to total annealing of fission tracks in apatite. The degree of annealing in most samples modelled is significantly higher than would be expected given their present-day temperatures. This indicates that these samples experienced a thermal overprint; they have been hotter in the past than at present. Inverse modelling by a Constrained Random Search (CRS) technique was carried out on the six best data sets. The results indicate that strata at depths of 1650-2600 m in the modelled wells were heated to paleotemperatures of about 80-110oC at some time during the interval 100-40 Ma. The magnitude of the thermal overprint predicted (estimated) by the modelling ranges from 1o to 55oC among the five wells modelled. Zircon fission track data from fifteen samples in ission track data from fifteen samples in four wells do not constrain burial temperatures. These data indicate a mixed provenance for the sediments. (author). 71 refs., 3 tabs., 7 figs

190

High but balanced sedimentation and subsidence rates (Moodies Group, Barberton Greenstone Belt), followed by basin collapse: Implication for Archaean tectonics  

Science.gov (United States)

Archaean tectonophysical models distinguish between thick, rigid and thin, mobile crust; from these the major mechanisms and rates for continental growth are derived. Archaean sedimentary rocks, preserved in metamorphosed and highly deformed greenstone belts, can contribute to constrain these models by estimating subsidence rates, derived from the combination of facies changes and precise age dates. Largely siliciclastic strata of the Moodies Group form the topmost unit of the Barberton Supergroup of the Barberton Greenstone Belt (BGB), South Africa, represent one of the world's oldest unmetamorphosed quartz-rich sedimentary sequences, and reach ca. 3500m thick (Lowe and Byerly, 2007). Large parts of the Moodies Group were deposited in apparent sedimentary continuity in alluvial, fluvial, shoreline and shallow-marine environments (e.g., Eriksson, 1979; Heubeck and Lowe, 1994). Distinctive sources and variations in facies indicate that Moodies deposition occurred at times in several basins. In several now tectonically separated regions, a regional basaltic lava (unit MdL of Anhaeusser, 1968) separates a lower unit (ca. 2000m thick and possibly representing an extensional setting) from an upper unit (ca. 1500m thick and characterized by progressive unconformities, rapidly changing facies, thicknesses, and sandstone petrographic composition). Single zircons separated from a felsic air-fall tuff of the middle Moodies Group and immediately overlying the basaltic lava in the Saddleback Syncline were dated on the Stanford-USGS SHRIMP RG. Out of 24 dated grains, two near-concordant groups have mean ages of 3230,6+-6,1Ma (2?; n=9) and 3519+-7 Ma (2?; n=9), respectively. We interpret the former age as representing the depositional age of the tuff, the latter as representing inherited zircons from underlying Onverwacht-age basement. The interpreted depositional age of the Moodies tuff is indistinguishable from numerous similar ages from felsic and dacitic volcanics at the top of the underlying Fig Tree Group (Schoongezicht Fm.; Byerly et al., 1996), implying that ca. 2000m of Moodies sandstones and subordinate siltstones and conglomerates were deposited in not more than a few (0-6) Ma. Their comparatively low degree of facies variation and lithological change implies a balance between rates of sediment supply and of subsidence, creating thick stacked units. Ferruginous shales and thin BIFs of the upper Moodies Group suggest that background 'Fig-Tree-style' sedimentation continued during Moodies time but was mostly overwhelmed by the apparently brief but massive influx of medium- to coarse-grained quartzose sediment. Because two progressive unconformities, marking Moodies basin uplift and onset of renewed overall BGB shortening, occur only 50 m above this dated unit, they are likely of a similar age and imply that dominant NW-SE-directed shortening in the BGB began shortly after 3230+-6 Ma. The combination of these new data with published information thus suggest that the Moodies Basin formed after 3225+-6 Ma (i.e., at the earliest at 3231) but was already largely filled and began to be deformed by 3231+-6 (i.e., at the latest by 3225). Moodies deposition thus happened geologically nearly instantaneously following the end of Fig Tree volcanism, took very little time and deposited large volumes of sediments on a rapidly subsiding basement just prior to large-scale BGB deformation. REFERENCES Byerly, G.R., Kroner, A., Lowe, D.R., Todt W., Walsh, M.M., 1996, Prolonged magmatism and time constraints for sediment deposition in the early Archean Barberton greenstone belt: Evidence from the Upper Onverwacht and Fig Tree groups: Precambrian Research, 78, p. 125-138. Eriksson, K.A., 1979, Marginal marine depositional processes from the Archaean Moodies Group, Barberton Mountain Land, South Africa: Evidence and significance: Precambrian Res., 8, p. 153-182. Heubeck, C. and Lowe, D.R., 1994, Depositional and tectonic setting of the Archaean Moodies Group, Barberton Greenstone Belt, South Africa: Precambrian Res., 68, p. 257-290. Lowe, D.R.,

Heubeck, Christoph; Lowe, Donald R.; Byerly, Gary R.

2010-05-01

191

Estimates of recharge in two arid basin aquifers: a model of spatially variable net infiltration and its implications (Red Light Draw and Eagle Flats, Texas, USA)  

Science.gov (United States)

Methods of estimating recharge in arid basin aquifers (such as the 1 % rule, Maxey-Eakin method, storm-runoff infiltration and others) overlook the potential contribution of direct recharge on the basin floors. In the Trans-Pecos region of west Texas, USA, this has resulted in potential recharge and solute flux to basin aquifers being ignored. Observed trends in groundwater nitrate (NO3 -) concentrations and the presence of young (Eagle Flats. The INFIL model provides insight into the mechanisms by which recharge and solute flux occurs in arid basin systems. This method demonstrated that recharge is widespread; it is not limited to the mountainous areas and mountain-front recharge mechanisms, and up to 15 % of total potential recharge in these basins occurs across widespread areas of the basin floors. Models such as this should improve scientific understanding and sustainable management of arid basin aquifers in Texas and elsewhere.

Robertson, Wendy Marie; Sharp, John M.

2013-12-01

192

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

Science.gov (United States)

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

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

2014-02-01

193

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.

194

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

Science.gov (United States)

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

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

2010-05-01

195

Paleosol architecture of a late Quaternary basin-margin sequence and its implications for high-resolution, non-marine sequence stratigraphy  

Science.gov (United States)

Paleosol stratigraphy, a technique commonly applied in basin-margin settings to depict cyclic alluvial architecture on time scales of 10-100 ky, can be consistent with regional accommodation trends at even higher temporal resolution (1-10 ky), having strong implications for the sequence stratigraphy of late Quaternary, non-marine deposits. Three closely-spaced late Pleistocene paleosols (P1-P3), dating back approximately to 42-39, 35-31, and 29-26 cal kyr BP, respectively, form prominent stratigraphic markers across a lithologically homogeneous interfluve succession in the subsurface of Bologna, close to the Apenninic foothills. These paleosols are weakly developed (Inceptisols) and can be tracked continuously for 6 km across the triangle-shaped interchannel zone between two gravel/sand-filled channel systems (Reno and Savena rivers). In particular, the thickest paleosol (P3) is a distinctive stiff horizon that can be traced into laterally extensive, erosional-based fluvial bodies. We infer the correlation between (P3) soil development (and channel downcutting) and the final stage of the stepwise Late Pleistocene sea-level fall that culminated at the marine isotope stage 3/2 transition around 29 cal kyr BP (low accommodation systems tract). A fourth laterally extensive Inceptisol, encompassing the Pleistocene-Holocene boundary (PH), represents the major phase of soil development since the Last Glacial Maximum and is inferred to be related to channel entrenchment at the onset of the Younger Dryas. With the exception of the Iron Age-Roman paleosol, which reflects a predominantly anthropogenic control, the Holocene paleosols are laterally discontinuous and invariably more immature (Entisols) than their Pleistocene counterparts. This trend of decreasing paleosol development (and correlatability) upsection is interpreted to reflect increasing (transgressive-equivalent) accommodation during sea-level rise, thus confirming the possible extension of models used to interpret the ancient rock record to short-term depositional cycles.

Amorosi, Alessandro; Bruno, Luigi; Rossi, Veronica; Severi, Paolo; Hajdas, Irka

2014-01-01

196

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

197

Geology of the Eel River basin and adjacent region: implications for late Cenozoic tectonics of the southern Cascadia subduction zone and Mendocino triple junction  

Science.gov (United States)

Two upper Cenozoic depositional sequences of principally marine strata about 4000m thick overlie accreted basement terranes of the Central and Coastal belts of the Franciscan Complex in the onshore-offshore Eel River basin of northwestern California. The older depositional sequence is early to middle Miocene in age and represents slope basin and slope-blanket deposition, whereas the younger sequence, late Miocene to middle Pleistocene in age, consists largely of forearc basin deposits. -from Author

Clarke, S.H., Jr.

1992-01-01

198

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

Science.gov (United States)

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

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

2014-09-01

199

Paleomagnetism of Eocene and Miocene sediments from the Qaidam basin: Implication for no integral rotation since the Eocene and a rigid Qaidam block  

Science.gov (United States)

Qaidam basin is the largest topographic depression inside the Tibetan Plateau and it is a key factor to understanding the Cenozoic evolution of the northern Tibetan Plateau. Paleomagnetic data was obtained from the middle to late Eocene Xiaganchaigou Formation and the early to middle Miocene Xiayoushashan Formation from seven localities. The paleomagnetic results indicate that the Qaidam basin has not undergone obvious basin-scale vertical axis rotation with respect to the Eurasia Plate since the Eocene. Local clockwise rotation took place only at a few special locations along the northern margin of the Qaidam basin. The uniform paleomagnetic results at different localities support that the Qaidam basin is a relatively rigid block. Regional paleomagnetic and geodetic observations also suggest that crust south of the Kunlun fault moves eastward faster than crust north of the Kunlun fault.

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

2014-06-01

200

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

Science.gov (United States)

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

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

2014-06-01

 
 
 
 
201

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

Science.gov (United States)

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

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

2006-01-01

202

Evolutionary characteristics of the sags to the east of Tan-Lu Fault Zone, Bohai Bay Basin (China): Implications for hydrocarbon exploration and regional tectonic evolution  

Science.gov (United States)

Some Cenozoic half-grabens (sags) have been found to the east of the Tan-Lu Fault Zone in the Bohai Bay Basin, east China. The evolutionary history of these sags is consistent with the entire Bohai Bay Basin; besides, some remarkable characteristics which had not been mentioned in previous studies of the Bohai Bay Basin are presented, and they are the keys to understand the regional tectonic evolution. Among them, two characteristics are emphasized: (1) the structural and evolutionary features of the sags were markedly changed at about 38 Ma; (2) the Paleogene basin underwent several times of uplifts and denudations during Paleogene. The first characteristic shows that the normal faulting was the dominant structural deformation before 38 Ma, and after then, the strike-slip movement might initiate to influence the basin. The second characteristic indicates remarkable reducing of the present-day residual basin relative to the original basin and, implies the episodic uplifting of the Jiaoliao massif. Besides, our estimation on the hydrocarbon exploration potential of these sags shows that part of them can sustain the formation of medium-large oilfield independently, while, part can contribute to the formation of large oilfield.

Huang, Lei; Liu, Chi-yang

2014-01-01

203

Diagenesis in Okavango fan and adjacent dune deposits with implications for the record of palaeo-environmental change in Makgadikgadi Okavango Zambezi basin, northern Botswana  

Science.gov (United States)

This work considers the spatial distribution and ages of western MOZ basin siliclastic sediments prior to providing insights into the diagenesis of degraded dune and alluvial fan sands. Previously published and new TL/OSL ages imply that extensive over-washing of dune sands took place at least 100 ka ago while ages on Okavango floodplains imply that the fan was formed ca. 40 ka and has since undergone periods of higher and lower flood regimes. Sediment analyses indicate that both dune and fan sands contain a diagenetic matrix of clay-enhanced amorphous silica (CEAS) which bonds weakly formed aggregates. The time of formation of diagenetic matrix products is inconclusive but may have been accelerated during or shortly after events dated using OSL/TL techniques. Hence earlier dune over-washing may have led to greater porewater of an acidic to near neutral nature which in turn promoted smectite formation and silicic acid precipitation > 100 000 years ago. The relatively abundant CEAS matrix in floodplain sands implies more recent semi-continuous flood events again of an acidic-near neutral nature leading to the formation of smectite. In this case the floodplain sediments are dated as having been deposited around 40 and 11 ka, when porewater content may have accelerated clay formation and silica dissolution. The dual nature of the CEAS in the islands reflects a changing environment from smectite-dominated flooding events to sepiolite-dominated desiccation events. Flooding may also correspond to TL/OSL ages over the past 40 000 years which contributed to accelerated CEAS formation. The sepiolite is associated with a Ca-rich matrix implying desiccation which may relate to drying events over the 40 000 year period or to riparian tree root pumping and selective salt accumulation. This work shows that sedimentation in incipient rifts is complex and rarely explained totally in terms of primary depositional events. The implications of different stages of sand diagenesis may be significant in enhancing palaeo-environmental interpretations in semi-arid fluvial environments.

Ringrose, Susan; Huntsman-Mapila, Philippa; Downey, William; Coetzee, Stephan; Fey, Martin; Vanderpost, Cornelis; Vink, Bernard; Kemosidile, Thebe; Kolokose, Dikitso

2008-11-01

204

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

205

HYDROGEOMORPHIC SETTING, CHARACTERISTICS, AND RESPONSE TO STREAM INCISION OF MONTANA RIPARIAN MEADOWS IN THE CENTRAL GREAT BASIN--IMPLICATIONS FOR RESTORATION  

Science.gov (United States)

Riparian wet meadow complexes in the mountains of the central Great Basin are scarce, ecologically important systems that are threatened by stream incision. An interdisciplinary group has investigated 1) the origin, characteristics, and controls on the evolution of these riparian...

206

Late Miocene to Plio-Pleistocene fluvio-lacustrine system in the Karacasu Basin (SW Anatolia, Turkey): Depositional, paleogeographic and paleoclimatic implications  

Science.gov (United States)

The sedimentary record of the late Cenozoic Karacasu Basin, a long-lived continental half-graben from southwestern Turkey, is characterized by siliciclastic and carbonate deposits. Sedimentation was controlled by an active NW-SE trending major normal fault along the basin's southern margin and by climatically-induced lake-level changes. Detailed facies analysis subdivides the entire Neogene-Quaternary basin-fill into three distinct litostratigraphic units representing paleogeographic changes and sedimentation patterns throughout the basin evolution. Sedimentation commenced in the late Miocene with the deposition of proximal-medial alluvial fan and fluvial facies (Damdere Formation; FA1). At this stage, alluvial fans developed in elevated areas to the south, prograding towards the basin center. At the beginning of the Pliocene, fresh to slightly alkaline, shallow lake deposits (FA2a) of the Karacaören Formation formed. The lake became open and meromictic conditions developed (FA2b). Pollen data from the FA2b facies show that climate was arid to humid. Climate probably changed cyclically through time producing alternation of Artemisia steppe (cold and dry periods) and more forested vegetation (warm and wet). The open lake facies passes upwards into lake margin facies (FA2c), but it was still dominated by alkaline to slightly saline lake conditions. Sedimentation was almost continuous from the late Miocene to Pleistocene. In the early Quaternary, the basin was dissected by the re-activation of basin bounding faults. The unconformable base of the overlying Quaternary deposits (Karacasu Formation; FA3) reflected the basin's transformation from a half-graben into a full-graben system. Oxygen isotope data from carbonates show an alternation of humid climatic periods, when freshwater settings predominated, and semiarid/arid periods in which the basin hosted alkaline and saline water lakes. Neotectonic activity has rejuvenated many of the basin-bounding faults, causing development of talus aprons and local alluvial fans. The basin was progressively incised by modern rivers that have largely smoothed out the topographic relief of the graben margins. id="ab0010" The study highlights to the paleo-geography/-climatology in the east Mediterranean.

Alçiçek, Hülya; Jiménez-Moreno, Gonzalo

2013-06-01

207

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

208

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

209

Progressive changes in sedimentary facies and stratal patterns along the strike-slip margin, northeastern Jinan Basin (Cretaceous), southwest Korea: implications for differential subsidence  

Science.gov (United States)

In strike-slip basins, proximal stratal patterns are a function of displacement on basin-bounding faults. In order to better understand factors that control changes in sedimentary facies and stratal patterns of the northeastern part of the Jinan Basin (Cretaceous), a strike-slip basin, we made a detailed analysis of sedimentary facies, depositional architecture and paleoflows. The sedimentary successions can be grouped into five facies associations representing five depositional environments: (1) facies association FA I (alluvial fan); (2) FA II (small-scale Gilbert-type delta); (3) FA III (large-scale, steep delta slope); (4) FA IV (base of large-scale, steep delta slope and prodelta); and (5) FA V (lacustrine plain). The successions are divided into two distinct sedimentary fills on the basis of facies associations, depositional architecture and paleocurrents: (1) marginal fill and (2) longitudinal fill. The marginal fill (ca. 3.2 km thick) is present along the strike-slip basin-bounding fault. The lower part of the marginal fill (ca. 1.3 km thick) consists of alluvial-fan deposits (FA I) along the bounding fault which are transitional northward to small-scale Gilbert-type delta (FA II) and lacustrine plain (FA V) deposits. The upper part of the marginal fill (ca. 1.9 km thick) contains large-scale, steep delta slope (FA III) and base of delta slope/prodelta (FA IV) deposits accompanied with a northward change in facies associations. In the marginal fill, the successive alluvial fan, small-scale Gilbert-type delta and large-scale, steep delta/prodelta deposits are overlapped (shingled) northeastward. The longitudinal fill (ca. 2 km thick) is characterized by eastward overlapped stacks of large-scale, steep delta slope (FA III) and base of delta slope/prodelta (FA IV) deposits with a westward progradation. The longitudinal fill was overstepped by the marginal fill. The northeastward shingled geometry of the marginal fill was most likely caused by sinistral strike-slip displacements on the basin-bounding fault. The slightly oblique (northward) progradation of the marginal fill was due to the northward basin-floor tilting. In the marginal fill, the progressive changes in facies and depositional architecture from the lower alluvial fan/small-scale Gilbert-type delta to the upper large-scale, steep delta/prodelta are suggestive of increase in basin subsidence along the strike-slip basin margin that was closely related to the variation in displacement on the basin-bounding fault. The sinistral strike-slip movements on the bounding fault also caused the eastward overlapping of the longitudinal fill.

Lee, S. H.; Chough, S. K.

1999-01-01

210

Lateral drilling and completion technologies for shallow-shelf carbonates of the Red River and Ratcliffe Formations, Williston Basin. Topical report, July 1997  

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 lateral 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 2,590 to 2,890 m in Richland County, MT; Bowman County, ND; and Harding County, SD. In theory, all of the horizontal drilling techniques explored in this project have merit for application fitting specific criteria. From a realistic point of view, the only relatively trouble-free, adequately-proven technology employed was the medium-radius steered motor/MWD technology. The slim-tool steered motor/MWD re-entry technology has been used extensively but appears to still be significantly in developmental stages. This technology will probably always be more troublesome than the technology used to drill new wells because the smaller diameter required for the tools contributes to both design and operational complexities. Although limited mechanical success has been achieved with some of the lateral jetting technologies and the Amoco tools, their predictability and reliability is unproven. Additionally, they appear to be limited to shallow depths and certain rock types. The Amoco technology probably has the most potential to be successfully developed for routinely reliable, field applications. A comparison of the various horizontal drilling technologies investigated is presented.

Carrell, L.A.; George, R.D.; Gibbons, D.

1998-07-01

211

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

Science.gov (United States)

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

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

2007-01-01

212

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

213

Sandstone distribution at the 14At1 level in the E-G area, south central Bredasdorp Basin: implications for a predictive depositional model  

International Nuclear Information System (INIS)

In the E-G sub-basin of the south central Bredasdorp Basin, an Albian age unconformity, termed the 14At1 surface, displays an erosional topography of submarine channels. Gamma ray log motifs, together with seismic, and petrographic evidence in the form of sidewall cores and drill cuttings, suggest that these sandstones were deposited in a submarine fan environment. It is proposed that these fans represent the first phase of sedimentation on the 14At1 surface, during sea-level lowstand conditions. 2 figs., 2 refs

214

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

DEFF Research Database (Denmark)

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

Ólavsdóttir, Jana; Andersen, Morten Sparre

2013-01-01

215

Sequence stratigraphy of the Bowthorn block in the northern Mount Isa basin, Australia: Implications for the base-metal mineralization process  

Science.gov (United States)

Precipitation of base metals, dolomitization, and paleothermal anomalies all occur near the top of organic-rich highstand system tracts within the Paleoproterozoic-Mesoproterozoic (1800 to 1500 Ma) northern Mount Isa basin, Australia. These highstand systems occur below major regional unconformities (and their correlative conformities) in the foreland sequence of the basin. The mineralization appears to be epigenetic, associated with migration through lowstand system tract aquifers. Deposits associated with maximum flooding surfaces at the tops of transgressive system tracts are different from epigenetic mineralization. Transgressive system tracts fine upward to maximum flooding surfaces where phosphate, manganese, and glauconite are commonly concentrated in condensed sequences. These syndepositional minerals are in contrast to epigenetic ores, such as zinc, lead, silver, and copper, that are precipitated from brines migrating through lowstand deposits and along sequence boundaries overlying fine-grained highstand systems tracts that act as basal seals. Both these mineral-rich systems are clearly identifiable in the Bowthorn block of the northern Mount Isa basin and it is possible to predict facies distribution from seismic interpretation, preferred migration pathways from regional basin analysis, and likely trap sites from structural analysis in conjunction with the above.

McConachie, Bruce A.; Dunster, John N.

1996-02-01

216

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

Science.gov (United States)

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

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

2013-08-01

217

A Cretaceous-Eocene depositional age for the Fenghuoshan Group, Hoh Xil Basin: Implications for the tectonic evolution of the northern Tibet Plateau  

Science.gov (United States)

Fenghuoshan Group marks the initiation of terrestrial deposition in the Hoh Xil Basin and preserves the first evidence of uplift above sea level of northern Tibet. The depositional age of the Fenghuoshan Group is debated as are the stratigraphic relationships between the Fenghuoshan Group and other terrestrial sedimentary units in the Hoh Xil Basin. We present new radiometric dates and a compilation of published biostratigraphic data which are used to reinterpret existing magnetostratigraphic data from the Fenghuoshan Group. From these data, we infer an 85-51 Ma depositional age range for the Fenghuoshan Group. U-Pb detrital zircon age spectra from this unit are compared to age spectra from Tibetan terranes and Mesozoic sedimentary sequences to determine a possible source terrane for Fenghuoshan Group strata. We propose that these strata were sourced from the Qiangtang Terrane and may share a common sediment source with Cretaceous sedimentary rocks in Nima Basin. Field relationships and compiled biostratigraphic data indicate that the Fenghuoshan and Tuotuohe Groups are temporally distinct units. We report late Oligocene ages for undeformed basalt flows that cap tilted Fenghuoshan Group strata. Together, our age constraints and field relationships imply exhumation of the central Qiangtang Terrane from the Late Cretaceous to earliest Eocene, followed by Eocene-Oligocene deformation, and shortening of the northern Qiangtang and southern Songpan-Ganzi terranes. Crustal shortening within the Hoh Xil Basin ceased by late Oligocene time as is evident from flat-lying basaltic rocks, which cap older, deformed strata.

Staisch, Lydia M.; Niemi, Nathan A.; Hong, Chang; Clark, Marin K.; Rowley, David B.; Currie, Brian

2014-03-01

218

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

Science.gov (United States)

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

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

2014-11-01

219

Implications of diapir-derived detritus and gypsic paleosols in Lower Triassic strata near the Castle Valley salt wall, Paradox Basin, Utah  

Science.gov (United States)

Gypsum-bearing growth strata and sedimentary facies of the Moenkopi Formation on the crest and NE flank of the Castle Valley salt wall in the Paradox Basin record salt rise, evaporite exposure, and salt-withdrawal subsidence during the Early Triassic. Detrital gypsum and dolomite clasts derived from the middle Pennsylvanian Paradox Formation were deposited in strata within a few kilometers of the salt wall and indicate that salt rise rates roughly balanced sediment accumulation, resulting in long-term exposure of mobile evaporite. Deposition took place primarily in flood-basin or inland sabkha settings that alternated between shallow subaqueous and subaerial conditions in a hyperarid climate. Matrix-supported and clast-supported conglomerates with gypsum fragments represent debris-flow deposits and reworked debris-flow deposits, respectively, interbedded with flood-basin sandstone and siltstone during development of diapiric topography. Mudstone-rich flood-basin deposits with numerous stage I to III gypsic paleosols capped by eolian gypsum sand sheets accumulated during waning salt-withdrawal subsidence. Association of detrital gypsum, eolian gypsum, and gypsic paleosols suggests that the salt wall provided a common source for gypsum in the surrounding strata. This study documents a previously unrecognized salt weld with associated growth strata containing diapir-derived detritus and gypsic palesols that can be used to interpret halokinesis.

Lawton, Timothy F.; Buck, Brenda J.

2006-10-01

220

Geochemistry of the sedimentary rocks from the Nanxiong Basin, South China and implications for provenance, paleoenvironment and paleoclimate at the K/T boundary  

Science.gov (United States)

Cretaceous and Tertiary clastic sedimentary rocks from the Nanxiong Basin, South China have been analyzed to constrain their provenance, depositional climate and environment. Evidence from discrimination diagrams for sedimentary provenance and tectonic setting show that the Nanxiong Basin sediments were derived from typical continental sources. Geochemical signatures (e.g. Eu/Eu *, Th/Ti, La/Ti, Ta/Ti, Yb/Ti and Y/Ti ratios of the claystone) are nearly constant, suggesting the provenance of the Nanxiong Basin remained similar throughout the Late Cretaceous to Early Paleocene (83-56 Ma). In contrast Rb/Ti, Cs/Ti ratios and TOC and CaCO 3 concentrations require an obvious change in climate across the Late Cretaceous and Early Paleocene boundary. Singularly higher CaCO 3 contents and lower TOC values and Rb/Ti, Cs/Ti ratios in the Late Cretaceous indicate that a long period extreme dry climate occurred at that time in South China. Rb/Ti, Cs/Ti ratios and TOC values escalated and CaCO 3 contents decreased in the Early Paleocene suggesting that the climate became relatively wet, which resulted in greater vegetation cover. The lasting extreme dry climate in the Late Cretaceous may provide a clue to the extinction of the dinosaurs in the Nanxiong Basin.

Yan, Yi; Xia, Bin; Lin, Ge; Cui, Xuejun; Hu, Xiaoqiong; Yan, Pin; Zhang, Faqiang

2007-04-01

 
 
 
 
221

Stratigraphic and provenancial evidence for recognition of an underfilled foreland basin in central Himalaya: implication for timing of India-Asia initial collision  

Science.gov (United States)

The Himalayan peripheral foreland basin developed when India and Asia collided. Previous studies in the Himalayan foreland were mostly concentrated on Neogene continental clastic sedimentation in sub-Himalaya or Paleogene shallow marine sedimentation along Pakistan, India, and Nepal in Lesser Himalaya. The lack of early stage of underfilled, deep-water facies in the Himalayan foreland basin is intriguing, because classic peripheral foreland basins involves generally a progression from “underfilled” (deep-water flysch facies), to “overfilled” (continental facies) stage. In this study, we present a new model of an early (underfilled) Himalayan foreland basin, through stratigraphic, sedimentologic and provenance analysis of Upper Cretaceous - Lower Paleogene deposits at the Zhepure Mountain, southern Tibet. Four main conclusions were achieved: 1) Detrital zircon U-Pb and Hf isotopic data indicated that sediments of both the Eocene Enba Formation and overlying Zhaguo Formation have mainly sourced from rocks of the Trans-Himalaya, with minor contribution from the Tethyan Himalaya. The first arrival of orogenic detritus occurred around 50.6 Ma (P8, Zhu et al., 2005), when the siliclastic sediments of Enba Formation were deposited. 2) The Paleocene-Early Eocene Zhepure Shan Formation represents establishment of a stable carbonate ramp, which began with deposition of oolitic bars at high-energy shoals, and progressively changed to a typical open marine ramp environment (Willems et al., 1996). This carbonate ramp is interpreted to develop on the northern flank of the peripheral forebulge of the underfilled Himalayan foreland basin, analogous to carbonate build-ups that occupy submarine forebulges in many other collisional foreland regions such as Alps, Papua New Guinea, Pyrenees, and Arabian Gulf. 3) The Zhepure Shanpo Formation (middle Maastrichtian - Lower Danian) and the overlying Jidula Formation (Upper Danian) show an overall shallowing-upward trend from the upper slope environment deposition to a terrigenous/ siliciclastic-dominated coastline deposition near the top. This shallowing-upward sequence was interpreted to be deposited close to the crest of the forebulge when it passed through the area of Tingri. 4) The change in sedimentation between the Zhepure Shanpo and Zhepure Shanbei formations could represent the transition from Indian passive margin to onset of Himalayan foreland basin deposition. Our data indicated that onset of Himalayan foreland basin and India-Asia initial collision in central Himalaya could be happed as early as at latest Campanian (~72 Ma). This study was financially supported by the Chinese NSFC Project (40772070) and MOST 973 Project (2006CB701402).

Hu, X.; Wang, J.; Jansa, L.; Wu, F.; Yu, J.

2009-12-01

222

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

223

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

224

Modeling the sulfur and oxygen isotopic composition of sulfates through a halite-potash sequence: Implications for the hydrological evolution of the Upper Eocene Southpyrenean Basin  

Science.gov (United States)

The isotopic composition of sulfates sampled throughout a complete evaporite sequence has contributed to the understanding of the evolution of the Southpyrenean Upper Eocene basin. The ? 34S and ? 18O values appear to be constant in thick segments of the sequence. This pattern is clearly different from the continuous decrease in ? values predicted by the evaporation processes in a closed system. The observed trend of the ? 34S and ? 18O values can be successfully modeled by an evaporation process in an open system, where steady state conditions are reached, separated by periods of significant changes in the hydrological regime of the basin. Moreover, in the segments of the sequence where they are constant, the ? 34S and ? 18O values help to constrain the hydrological parameters of the model. A first marine stage of the evolution of the basin corresponds to the formation of the Basal Anhydrite and Lower Halite Units. The mineral sequence corresponds to evaporation in a basin with a progressive degree of restriction and evaporation compensated by equal inflow of major marine origin. The sharp decrease in the ? 34S and particularly the ? 18O values, recorded at the end of the Basal Anhydrite Unit, illustrates a limited reservoir effect produced by the increase of restriction leading to the halite precipitation. The modeling of the constant isotopic values through the Lower Halite Unit confirms the isotopic composition of Eocene marine dissolved sulfate (? 34S = +20.0%0; ? 18O = +8.7%0) deduced from the average values of marginal gypsum. The second continental stage of basin evolution corresponds to the formation of the Potash Unit and the Upper Halite Unit. The mineral sequence and lateral extension indicate that the basin evolved with a decreasing brine volume after disconnection from the sea. The dilution of the residual brine stopped the precipitation of camallite, and the basin then evolved as a perennial endorreic lake with continental recharge replacing evaporation. The sharp decrease in the ? 34S and ? 18O values in the sylvite member is consistent with the massive precipitation of sulfate occurring during the decrease in the volume of water. The ? values of the sulfates intercalated in the camallite and the Upper Halite Unit indicate the influence of the recycling of both the already deposited Upper Eocene sulfates and the Upper Triassic sulfates carried by continental recharge. The constant ? 34S and ? 18O values from the uppermost half of the Upper Halite Unit is used to constrain the sulfate source as 80% recycled Upper Triassic and 20% recycled Eocene gypsum.

Ayora, Carlos; Taberner, Conxita; Pierre, Catherine; Pueyo, Juan-José

1995-05-01

225

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

226

Coupled Heat and Fluid Flow Modeling of the Earth's Largest Zinc Ore Deposit at Red Dog, Alaska: Implications for Structurally-Focused, Free Convection in Submarine Sedimentary Basins  

Science.gov (United States)

Crustal heat flow can provide a strong mechanism for driving groundwater flow, particularly in submarine basins where other mechanisms for driving pore fluid flow such as topography, compaction and crustal deformation are too weak or too slow to have a significant effect on disturbing conductive heat flow. Fault zones appear to play a crucial role in focusing fluid migration in basins, as inferred in ancient rocks by many examples of hydrothermal deposits of sediment-hosted ores worldwide. Many rift-hosted deposits of lead, zinc, and barite ore appear to have formed at or near the seafloor by focused venting of hot basinal fluids and modified seawater, although the geophysical nature of these systems is not so well known. For example, the upper Kuna Formation, a finely laminated, black, organic-rich siliceous mudstone and shale in the Western Brooks Range of northwest Alaska, is host to the largest resources of zinc yet discovered in the Earth's crust, containing ore reserves in excess of 175 Mt averaging about 16% Zn and 5% Pb. Although situated today in a highly-deformed series of structural allocthonous plates thrusted during the Jurassic to Cretaceous Brookian Orogeny, the stratiform ores are thought to have formed much earlier in the anoxic, mud-rich Carboniferous-age Kuna Basin when adjacent carbonate platforms were drowned by rifting and tectonic subsidence. Fluid inclusion studies of ore-stage sphalerite and gangue minerals indicate sub-seafloor mineralization temperatures less than 200oC and most likely between 120 to 150 oC, during a period of sediment diagenesis and extensional faulting. We have constructed fully-coupled numerical models of heat and fluid flow to test hydrologic theories for free convection, submarine venting and subsequent ore formation, as constrained by paleoheat flow and petrologic observations. A finite element grid was designed and adapted for a cross section of the Kuna Basin, geologically restored to latest Mississippian time. Hydrologically, the Kuna Basin was a 200-km wide, rifted asymmetric basin layered with calcareous turbidites, mudstones and carbonates overlying a thick conglomerate and sandstone aquifer, which likely was thickest and more faulted near Red Dog (Ikalukrok graben). Buoyancy-driven free convection cells drive fluid migration to km-depths in the submarine basin, at rates of about 5 m/yr within permeable normal faults, which are assumed to be conduits. Mostly lateral flow is predicted to occur in the deep clastic formations. The clastic aquifers appear to be the principal reservoir for metal-bearing brines that ultimately discharged near the seafloor within slightly permeable, highly porous and organic rich muds, where sulfate can be reduced to form massive zinc-lead sulfide ores. Basin-wide paleoheat flows of 150 to 160 mW/m2 and focused fluid discharge along normal faults are required to explain the hot thermal venting recorded within these ore fields. This mineralized hydrothermal system provides a remarkable geophysical model for the role of faults, free convection and extensional basin heat flow in ore genesis.

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

2002-12-01

227

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

228

The Middle Miocene lacustrine mollusc fauna of the Kupres Basin: palaeobiogeography, palaeoecology, and taxonomic implications (Dinaride Lake System, Bosnia and Herzegovina)  

Science.gov (United States)

During the Early and Middle Miocene the Dinaride Lake System displayed one of the largest freshwater systems in the Neogene of Europe, forming a palaeogeographic barrier between the Paratethys and the Mediterranean seas. It is widely known for its exceptional mollusc fauna, which experienced major radiations resulting in a high level of endemicity. Despite advanced investigations in that region our knowledge on the mollusc fauna is still fragmentary or out-dated. A major problem for taxonomic revisions is the complex geographic and geologic setting with numerous basins. Therefore, most authors were unable to assign already described taxa and localities in the literature to discrete basins and palaeo-lakes. The herein presented results give insight into the outstandingly preserved mollusc fauna of the Kupres Basin. Except for few descriptions, partly dating back to the early 20th century, and a preliminary list of species, a concise taxonomic frame is entirely missing. Consequently, the presented results provide the base for a systematic revision of several supraspecific taxa among the Hydrobiidae. Moreover, the faunal composition allows inferences on palaeobiogeography and hydrological connections within the Dinaride Lake System during the early Middle Miocene. About one third of the described taxa are restricted to the Kupres basin. The other taxa document faunistic relations to the coeval faunas of the Sinj, Drniš, and Džepi basins. Phases of hydrological isolation, indicated by carbonate dominated lithology, coincide with a high frequency of sculptured morphologies within the gastropods. Phases of increased aridity led to high evaporation, a lowered lake level and enhanced carbonate production which seem to have promoted strongly calcified shells. The stratigraphic ranges of the species imply a depositional age of 15.5 ± 0.2 Ma (earliest Middle Miocene; Langhian).

Neubauer, T. A.; Mandic, O.; Harzhauser, M.; Hrvatovi?, H.

2012-04-01

229

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

Science.gov (United States)

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

Minor, Scott A.; Hudson, Mark R.

2006-01-01

230

Buried paleo-sedimentary basins in the north-eastern Black Sea-Azov Sea area and tectonic implications (DOBRE-2)  

Science.gov (United States)

A number of independent but inter-related projects carried out under the auspices of various national and international programmes in Ukraine including DARIUS were aimed at imaging the upper lithosphere, crustal and sedimentary basin architecture in the north-eastern Black Sea, southern Crimea and Kerch peninsulas and the Azov Sea. This region marks the transition from relatively undisturbed Precambrian European cratonic crust and lithosphere north of the Azov Sea to areas of significant Phanerozoic tectonics and basin development, in both extensional as well as compressional environments, to the south, including the eastern Black Sea rift, which is the main sedimentary basin of the study area. The wide-angle reflection and refraction (WARR) profile DOBRE-2, a Ukrainian national project with international participation (see below), overlapping some 115 km of the southern end of the DOBREfraction'99 profile (that crosses the intracratonic Donbas Foldbelt) in the north and running to the eastern Black Sea basin in the south, utilised on- and offshore recording and energy sources. It maps crustal velocity structure across the craton margin and documents, among other things, that the Moho deepens from 40 km to ~47 km to the southwest below the Azov Sea and Crimean-Caucasus deformed zone. A regional CDP seismic profile coincident with DOBRE-2, crossing the Azov Sea, Kerch Peninsula and the north-eastern Black Sea southwest to the Ukraine-Turkey border, acquired by Ukrgeofisika (the Ukrainian national geophysical company) reveals in its inferred structural relationships the ages of Cretaceous and younger extensional and subsequent basin inversion tectonic events as well as the 2D geometry of basement displacement associated with post mid-Eocene inversion. A direct comparison of the results of the WARR velocity model and the near-vertical reflection structural image has been made by converting the former into the time domain. The results dramatically demonstrate that there are major, rift-like, sedimentary basins underlying the area of the Azov Sea and the inverted north-eastern margin of the Black Sea. It can be speculated that one of these basins may represent the previously unknown western prolongation of the Jurassic-aged Greater Caucasus back-arc basin and that the other may be the legacy of earlier - Late Palaeozoic-Triassic - extensional tectonics in this area. Individuals (in alphabetical order) from each institution involved scientifically in DOBRE-2 (listed alphabetically according to country) include: H. Thybo (Department of Geography and Geology, University of Copenhagen, Denmark); A. Dannowski and E. Flüh (IFM-GEOMAR, Kiel, Germany); W. Czuba, A. Guterch and P. ?roda (Institute of Geophysics, Polish Academy of Sciences, Warsaw, Poland); M. Grad (Institute of Geophysics, University of Warsaw, Warsaw, Poland); D. Gryn, K. Kolomiyets, O. Legostaeva, D. Lysynchuk, V. Omelchenko and O. Rusakov (Institute of Geophysics, National Academy of Sciences of Ukraine, Kyiv); M. Pobedash, N. Polyvach, G. Sydorenko and Z. Voitsytskyi (Ukrgeofisika, Kyiv, Ukraine); as well as the named co-authors of this presentation.

Starostenko, Vitaly; Stephenson, Randell; Janik, Tomasz; Tolkunov, Anatoly

2014-05-01

231

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-03-15

232

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

International Nuclear Information System (INIS)

Approximately 500 samples from the Archaean granitic basement of the southern Kaapvaal Craton have been analysed for U and Th. When viewed in conjunction with geological relationships, the radioelement distribution patterns in the Archaean basement provide contraints regarding the origin of uranium in the Witwatersrand Basin. Granites in the Barberton region are sub-divided into three magmatic cycles, the earliest cycle comprising tonalite-trondjemite gneisses, the intermediate cycle comprising laterally extensive K-rich batholiths and the final stage consisting of discrete intrusive granitic plutons. Uranium and thorium contents vary as a function of age and rock type, and increase progressively from the first cycle through to the third cycle. Certain of the late granite plutons may be S-type in origin, have relatively low Th/U ratios, high U contents, and are characterized by accessory minerals dominated by monazite-like phases. The late granite plutons with the highest radioelement contents appear to have formed circa 2,8 Ga ago, an age which coincides with granulite facies metamorphism and uranium-thorium depletion in the lower crust, as recorded in the Vredefort crustal profile. Uranium has been leached from portions of the regolith profile, but also concentrated into leucoxene-rich zones derived from the breakdown of pre-existing titanium-bearing phases. The widespread development of an uraniferous leucoxene protore in weathered source rocks of the Witwatersrand Basin has relevance to the genesis of authigenic U-Ti phases (brannerite) in the reefs themselves. The study of radioelement distribution in Archaean granites adjacent to the Witwatersrand Basin provides a framework within which considerations regarding the origin of the uranium deposits in the basin can be viewed. The secular evolution of the Archaean granitic basement, hydrothermal processes, and palaeoweathering all played a role in the formation of the Witwatersrand deposits. 22 figs., 5 tabs., 51 refs

233

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

International Nuclear Information System (INIS)

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

234

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

235

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

236

Stable carbon isotopes of alkane gases from the Xujiahe coal measures and implication for gas-source correlation in the Sichuan Basin, SW China  

Energy Technology Data Exchange (ETDEWEB)

The Upper Triassic Xujiahe Formation in the Sichuan Basin, SW China consists of a series of coal measures. The first, third and fifth members of this formation are dominated by gas prone dark mudstones and coals. The mudstones contain Type II and III kerogens with average organic carbon contents around 1.96%. These source rocks are mature in the central Sichuan and highly mature in the western Sichuan Basin, characterized by gas generation with subordinate amounts of light oil or condensate oils. The source rocks are intercalated with the sandstone dominated second, fourth and sixth members of the Xujiahe Formation, thus leading to three separate self contained petroleum systems in the region. The proven gas reserves in the Xujiahe Formation are only less than that of the Triassic Feixianguan Formation and the Xujiahe Formation has the second largest gas field (Guang'an gas field) in the basin. Gases derived from the Xujiahe Formation coals generally show a normal stable carbon isotopic trend for C{sub 1}-C{sub 4} n-alkanes, with the highest {delta}{sup 13}C{sub 2} values among the nine gas pay zones in the basin (-20.7% to -28.3%), and {delta}{sup 13}C{sub 1} values as low as -43.0%. in the central Sichuan. Gas accumulations with an oil leg have also been found in the eastern and southern Sichuan where the thickness of the Xujiahe Formation is significantly reduced. Gases in these accumulations tend to show low {delta}{sup 13}C{sub 2} values (-30.0 parts per thousand to -36.3 parts per thousand), characteristic of oil prone source rocks.

Dai, J.X.; Ni, Y.Y.; Zou, C.N.; Tao, S.Z.; Hu, G.Y.; Hu, A.P.; Yang, C.; Tao, X.W. [PetroChina, Beijing (China)

2009-05-15

237

Rock magnetic properties and paleoenvironmental implications of an 8-Ma Late Cenozoic terrigenous succession from the northern Tian Shan foreland basin, northwestern China  

Science.gov (United States)

In the northern Tian Shan foreland basin, northwestern China, the thick Cenozoic terrigenous succession is crucial for paleoclimate-environmental reconstruction of the Asian interior. Here we present a detailed rock magnetic investigation on 245 samples from the ~ 1200-m-thick Neogene Taxi He section with a magnetostratigraphic age span of ca. 8.0 to 2.0 Ma in the northern Tian Shan foreland basin. Our rock magnetic results indicate that the significant variations in composition, concentration and grain size of magnetic minerals occurred at ca. 6.0, 3.7 and 2.7 Ma. The comparable compositions of rare earth elements (REEs) throughout the Neogene Taxi He section suggest no significant modification of the source materials during the interval between ca. 8.0 and 2.0 Ma, and thus sediment provenance is not regarded as responsible for these observed variations in rock magnetic properties. Our further analyses show that the variations in magnetic properties of the Taxi He section are casually linked mainly with lithofacies transition due to range encroachment into foreland basin as well as climate aridification. Identified enhancement of aridification was chronologically constrained at ca. 6.0 and 2.7 Ma. Such climate events are important archives for reconstructing the Late Cenozoic paleoclimatic history of the Asian interior. Further comparison between different paleoclimate records clearly indicates that magnetic parameters such as S- 100mT are potentially effective proxy indices for paleoclimate-environmental reconstruction in the Tian Shan foreland basins and the nearby areas.

Lu, Honghua; Zhang, Weiguo; Li, Youli; Dong, Chenyin; Zhang, Tianqi; Zhou, Zuyi; Zheng, Xiangmin

2013-12-01

238

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Fournier, Marc; Agard, Philippe; Petit, Carole

2008-01-01

239

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 relativ...

Pe?rez Cruz, L.; Urrutia Fucugauchi, J.

2009-01-01

240

Water and nutrient fluxes from major Mediterranean and Black Sea rivers: Past and future trends and their implications for the basin-scale budgets  

Science.gov (United States)

The aim of this study is to produce future scenarios on the river inputs of water and nutrients (nitrate and phosphate) into the Mediterranean and Black Sea. They are based on the four contrasting scenarios that were developed by the Millenium Ecosystem Assessment (MEA) for the years 2030 and 2050 and implemented in a spatially explicit manner into the IMAGE model. We first identified the major drivers of the river fluxes by regression analyses, then tested the retained models against the past evolutions between 1970 and 2000, and finally applied the models to the MEA scenarios. For nutrients, the considered river data mainly refer to the large rivers for which long-term time series exist (Rhone, Po, Ebro, and Danube). Here, recent trends were principally driven by fertilizer spreads (NO3, PO4), together with urban wastewater releases (PO4). Future trends remain in the envelope of the observed variability during the last 40 years, both for the large rivers and, when extrapolated to the basin scales, also for the entire Mediterranean and Black Sea. At regional scales, however, the budgets considerably change. In the northern parts of the Mediterranean drainage basin, they uniformly tend to decrease, but they may strongly increase in the south and east. Water discharge is examined on a basis of 37 rivers, showing that this parameter is clearly linked to the evolution of climate. Because of the ongoing evolution toward dryer and warmer conditions, we predict a significant trend of decreasing freshwater fluxes for the future, which already started in the past. Regional hot spots for this decrease are the drainage basin of the Alboran Sea and, when also considering the inhabitant specific water fluxes, the basins of the Aegean and north Levantine seas.

Ludwig, W.; Bouwman, A. F.; Dumont, E.; Lespinas, F.

2010-12-01

 
 
 
 
241

STEM/AEM evidence for preservation of burial diagenetic fabrics in Devonian shales: Implications for fluid/rock interaction in cratonic basins (U.S.A.)  

Energy Technology Data Exchange (ETDEWEB)

Fabrics, microstructures, and compositions of authigenic illite-rich clays in Devonian intracratonic basin shales were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and scanning transmission electron/analytical electron microscopy (STEM/AEM) methods in order to relate the extent of clay diagenesis to the timing of mudstone-system closure and to reconcile conflicting radiogenic and paleomagnetic ages obtained from these shales and associated limestones and bentonites. Authigenic illite in these Devonian shales is similar to post-transition illite-rich mixed-layer illite/smectite (I/S) in Gulf Coast and other young basin mudstones that have formed through replacement of detrital smectite or smectite-rich I/S without subsequent diagenetic modification. Preservation of burial diagenetic, authigenic, mixed-layer I/S microstructures in these Devonian shales implies that they have remained effectively closed systems following the smectite-to-illite transformation. Later Alleghenian (ca. 300 Ma) tectonic or fluid-flow events recorded by authigenic minerals in bentonites and carbonate lithologies throughout the US. Midcontinent are apparently not recorded in these Devonian shales. Preservation of diagenetic fabrics indicates that radiogenic isotope dating of cratonic basin shales should yield syndepositional to early burial diagenetic ages corresponding to the timing of I/S authigenesis.

Hover, V.C.; Peacor, D.R.; Walter, L.M. [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Geological Sciences

1996-05-01

242

Provenance, volcanic record, and tectonic setting of the Paleozoic Ventania Fold Belt and the Claromecó Foreland Basin: Implications on sedimentation and volcanism along the southwestern Gondwana margin  

Science.gov (United States)

This study focuses on the provenance, volcanic record, and tectonic setting of the Paleozoic Ventania System, a geologic province which comprises the Cambro-Devonian Ventania Fold Belt and the adjoining Permo-Carboniferous Claromecó Foreland Basin, located inboard the deformation front. The Ventania Fold Belt is formed of the Curamalal and Ventana groups, which are composed mainly of mature quartzites that were unconformably deposited on igneous and metamorphic basement. The Pillahuincó Group is exposed as part of the Claromecó Basin and it has lithological and structural features totally distinct from the lowermost groups. This group is composed of immature arkoses and subarkoses with intercalated tuff horizons, unconformably overlaying the quartzites and associated with glacial-marine deposits of the lower Late Carboniferous to Early Permian section. The petrography, as well as major and trace elements (including rare earth elements) support that the Ventania quartzites were derived from cratonic sources and deposited in a passive margin environment. For the Pillahuincó Group, we suggest a transition between rocks derived from and deposited in a passive margin environment to those with geochemical and petrographical signatures indicative of an active continental margin provenance. LA-MC-ICP-MS analysis performed on euhedral and prismatic zircon grains of the tuffs revealed an age of 284 ± 15 Ma. The geochemical fingerprints and geochronological data of the tuffs found in the Claromecó Basin support the presence of an active and widespread Lower Permian pyroclastic activity in southwestern Gondwana, which is interpreted as part of the Choiyoi Volcanic Province in Argentina and Chile.

Alessandretti, Luciano; Philipp, Ruy Paulo; Chemale, Farid; Brückmann, Matheus Philipe; Zvirtes, Gustavo; Matté, Vinícius; Ramos, Victor A.

2013-11-01

243

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

244

Contrasting isotopic mantle sources for proterozoic lamproites and kimberlites from the Cuddapah basin and eastern Dharwar craton: implication for proterozoic mantle heterogeneity beneath southern India  

International Nuclear Information System (INIS)

Kimberlites intruding the Precambrian basement towards the western margin of the Cuddapah basin near Anantapur (1090 Ma) and Mahbubnagar (1360 Ma) in Andhra Pradesh have initial 87Sr/86Sr between 0.70205 to 0.70734 and ?Nd between +0.5 to +4.68. Mesoproterozoic lamproites (1380 Ma) from the Cuddapah basin (Chelima and Zangamarajupalle) and its NE margin (Ramannapeta) have initial 87Sr/86Sr between 0.70520 and 0.7390 and ?Nd from -6.43 to -8.29. Combined Sr- and Nd- isotopic ratios suggest that lamproites were derived from enriched sources which have time-averaged higher Rb/Sr and lower Sm/Nd ratios than the Bulk Earth whereas kimberlites were derived from depleted source with lower Rb/Sr and higher Sm/Nd ratios. Calculated TDM model ages suggest that the lamproite source enrichment (?2 Ga) preceded that of kimberlites (?1.37 Ga). Our work demonstrates the existence of isotopically contrasting upper mantle sources for southern Indian kimberlites and lamproites and provides evidence for a lateral, isotopically heterogeneous mantle beneath the Cuddapah basin and eastern Dharwar craton. The significance of our results in the context of diamond exploration is also highlighted. (author)

245

Data-driven modeling of radionuclide inventory at the Savannah River Site F-area seepage basins and implications for long-term behavior predictions  

Science.gov (United States)

The availability of data is a major constraint in the development of a conceptual model and predictions of physical and chemical processes impacting contaminant behavior in the subsurface. For example, a wealth of data has been collected over the past 60 years from a network of several hundred groundwater wells and surface water monitoring stations at the Department of Energy (DOE) Savannah River Site (SRS). The data were collected during and following the release of low-level liquid waste into seepage basins, as well as during the application of various groundwater remediation techniques. The result is a dataset of over 350,000 measurements. To analyze these data, we used a new data management system being developed as part of the DOE initiative on Advanced Simulation Capability for Environmental Management (ASCEM). This system was developed for easier access, management, visualization, and exploration of large amounts of heterogeneous data. Using this system, we developed a data-driven model for the evaluation of a mass balance and the inventory of the F-Area seepage basins and the groundwater plume. Process operations at the F-area led to the discharge of more than 4×109 L of low-level liquid radioactive waste containing tritium, uranium and fission products into the seepage basins. Between 1953 and 1989, 8.6×104 Ci (corrected for evaporation and decay to 1989) of tritium was released into the basins according to operational data. Starting in the 1960s, SRS monitored radioactivity in the Fourmile Branch (FMB) located downgradient of the basins. Through 1989 around 43% of the total release was detected in FMB, leaving an estimated inventory of 57% in the subsurface as of 1989. This model was used to assess t he sources of uncertainty in the mass balance calculations. The results of calculations of the tritium inventory in groundwater were compared with those from monitoring data prior to remediation, as well as were used to estimate the time needed to achieve the tritium MCL level under natural attenuation conditions.

Wiedmer, A.; Hunt, J. R.; Agarwal, D.; Faybishenko, B.

2012-12-01

246

Rare Earth Elements of the Permian-Triassic Conodonts from Shelf Basin to Shallow Platform: Implications for Oceanic Redox Conditions immediately After the End-Permian Mass Extinction  

Science.gov (United States)

Rare-earth elements (REEs) can provide information regarding the influence of weathering fluxes and hydrothermal inputs on seawater chemistry as well as processes that fractionate REEs between solid and aqueous phases. Of these, cerium (Ce) distributions may provide information about variations in dissolved oxygen in seawater, and thus assess the redox conditions. The short residence times of REEs in seawater (~300-1,000 yr) can result in unique REE signatures in local watermasses. REE patterns preserved in biogenic apatite such as conodonts are ideal proxies for revealing original seawater chemistry. Here, we measured the REE content of in-situ, single albid crowns using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) in combination with an ArF (?=193 nm) excimer laser (Lambda Physiks GeoLas 2005) and quadrupole ICP-MS (Agilent 7500a). LA-ICP-MS is ideally suited for analyzing conodonts due to its ability to measure compositional variation within single conodont elements. It has the capability to determine, with high spatial resolution, continuous compositional depth profiles through the concentric layered structure of component histologies. To evaluate paleoceanographic conditions immediately after the Permian-Triassic (P-Tr) mass extinction in various depositional settings, we sampled a nearly contemporaneous strata unit, the P-Tr boundary bed, just above the extinction horizon from six sections in South China. They represent various depositional settings from shelf basin (Chaohu and Daxiakou sections), lower part of ramp (Meishan section), normal shallow platform (Yangou section), and platform microbialite (Chongyang and Xiushui sections). The sampled unit is constrained by conodonts Hindeodus changxingensis, H. parvus, and H. staeschei Zones in Meishan. REE results obtained from conodont albid crowns show that the seawater in lower ramp and shelf basin settings contains much higher REE concentrations than that in shallow platform. Ce/Ce* ratios in shelf basin and lower ramp are similar to one another, ranging from 0.7-1.0. The same ratios, however, are much lower in shallow platform and microbialite settings, ranging from 0.17-0.22 and 0.2-0.45, respectively. Eu/Eu+ ratios also show similar patterns: 0.7-1.0 in shelf basin and lower ramp and 0.3-0.7 in shallow platform. If the Ce/Ce* was truly influenced by environmental redox conditions, then Ce/Ce* values of 0.7-1.0 in shelf basin and lower ramp settings are indicative of a suboxic to anoxic depositional system, while the same proxy of 0.17-0.45 in shallow platform and microbialite points to a well-oxygenated setting immediately after the P-Tr mass extinction.

Li, Y.; Zhao, L.; Chen, Z.; Chen, J.; Chen, Y.

2013-12-01

247

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

248

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

249

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

250

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-08-15

251

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 US 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 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. -from Authors

Drake, D.E.; Cacchione, D.A.; Gardner, J.V.; McCulloch, D.S.; Masson, D.

1989-01-01

252

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

253

Ar-40 to Ar-39 dating of pseudotachylites from the Witwatersrand basin, South Africa, with implications for the formation of the Vredefort Dome  

Science.gov (United States)

The formation of the Vredefort Dome, a structure in excess of 100 km in diameter and located in the approximate center of the Witwatersrand basin, is still the subject of lively geological controversy. It is widely accepted that its formation seems to have taken place in a single sudden event, herein referred to as the Vredefort event, accompanied by the release of gigantic amounts of energy. It is debated, however, whether this central event was an internal one, i.e., a cryptoexplosion triggered by volcanic or tectonic processes, or the impact of an extraterrestrial body. The results of this debate are presented.

Trieloff, M.; Kunz, J.; Jessberger, E. K.; Reimold, W. U.; Boer, R. H.; Jackson, M. C.

1992-01-01

254

Water balance of the Indus River Basin and moisture source in the Karakoram and western Himalayas: Implications from hydrogen and oxygen isotopes in river water  

Science.gov (United States)

Stable isotope measurements of hydrogen and oxygen for surface waters from the Indus River Basin (IRB), together with historical records for river discharge, annual precipitation, and groundwater levels, are used to assess water balance for the basin. The Indus River presently drains 53 km3 yr-1 or roughly one-eighth of the 398-km3 water that annually falls on the basin in the form of rain and snow, with the remainder returned to the atmosphere by evapotranspiration. Monthly samples for the Indus River close to its mouth, for the water year March 1994 to February 1995, show a tight correlation in ?D and ?18O space. The slope of the linear regression is 7.5, which is not significantly different from the slopes of the Local Meteoric Water Lines (LMWL; 7.3 and 7.1). This observation argues against significant loss of water by direct evaporation from river surfaces or from soils in hydrologic continuum with surface waters. An upper limit for evaporation from poorly drained soils is calculated to be ˜10 km3 yr-1 or only 2.5% of the annual precipitation flux. Groundwater storage in the entire Canal Command Area received a maximum of 23 km3 yr-1 or 5.8% of the annual precipitation during the early stages of irrigation, but modern recharge is probably balanced by discharge to rivers and well exploitation. Transpiration by natural vegetation and crops annually returns 83% of the precipitation flux and constitutes the largest pathway for the loss of water from the basin. Deuterium excess (d-excess) in the IRB ranges between 4‰ and 28‰, with values for 95% of the sample population exceeding 10‰. The Indus main channel close to its mouth varies in d-excess between 12‰ and 20‰ during low and high water stands, respectively, with a discharge weighted average of 18‰. These values are distinctly higher than the long-term average for the Indian monsoon (˜8‰) and reflect contributions from water vapor originating in the Mediterranean (22‰) or other inland seas. Using these end-member compositions and the discharge weighted average d-excess, isotope balance calculations require that up to 72% of the Indus discharge close to its mouth must be derived from the Mediterranean end-member and implies that bulk of the Indus discharge is the result of delayed runoff from the Karakoram and the Himalayas.

Karim, Ajaz; Veizer, Jan

2002-09-01

255

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

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 the socio-economy and the 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 the unsaturated vadose zone and groundwater reservoir is a critical link to understanding regional water table dynamics. This flux is substantially influenced by anthropogenic activities. In the Tarim River basin of western China, where agriculture consumes over 90% of available water resources, the exchange flux between the unsaturated vadose zone and groundwater reservoir is influenced strongly by irrigation. Recently, mulched drip irrigation, a sophisticated water-saving irrigation method, was 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 gaining a better understanding of regional groundwater dynamics. In this study, comprehensive observations of water balance components in an irrigated cropland were implemented in 2012 and 2013 in a typical oasis within the 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 at the groundwater table is mostly downward (310.5 mm year-1), especially during drip irrigation period and spring flush period, while the upward flux is trivial (16.1 mm year-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 the ecological system. This could lead to an increased 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) which face similar water shortages and human development problems.

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

2014-10-01

257

Results of recent drilling of specific lowstand systems tracts targets, the implications to future exploration, and the seismic-sequence stratigraphic model Pletmos basin, offshore South Africa  

Energy Technology Data Exchange (ETDEWEB)

The Pletmos basin is a complex series of subbasins off the south coast of South Africa. Depositional styles displayed in the postrift mid-Valanginian to recent sediments reflect the complex interplay of variations in subsidence, sediment supply, eustatic change, and climate. An extensive seismic sequence stratigraphic framework study carried out in 1988 served as the basis for further oil exploration and the evaluation of lowstand systems tracts. Wells were drilled to intersect shelf-margin wedges, basin-floor fans, slope-front fans, prograding lowstand wedges, and incised valley-fill successions depicted by detailed mapping of recent seismic data, integrated with well data. Sequences that apparently resulted from both major and minor downward shift in relative sea level were tested. Although there appears to be adequate sand accumulations on the relict shelf edge in the provenance area, there was little sand in the lowstand target. Seismically, the interpreted lowstand elements are located beyond and below the relict shelf and reflect geometries clearly indicative of component elements of a lowstand systems tract. However, there seems to be some contention about the processes that brought about their deposition. It is important to d toiibe sh between lowstand systems that have been derived by slumping and slope failure, and those that have developed as a result of sediment removal from the shelf and subareal regions during relative sea-level fall. Sand prediction and the relationships between source rock, migration pathways, and reservoir can, therefore, be ascertained with a higher degree of certainty.

Keenan, J.H.G. (Soekor Ltd., Parow (South Africa))

1991-03-01

258

Lesula: a new species of Cercopithecus monkey endemic to the Democratic Republic of Congo and implications for conservation of Congo's central basin.  

Science.gov (United States)

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 that C. lomamiensis is distinct from its nearest congener, C. hamlyni, from which it is separated geographically by both the Congo (Lualaba) and the Lomami Rivers. C. lomamiensis, like C. hamlyni, is semi-terrestrial with a diet containing terrestrial herbaceous vegetation. The discovery of C. lomamiensis highlights the biogeographic significance and importance for conservation of central Congo's interfluvial TL2 region, defined from the upper Tshuapa River through the Lomami Basin to the Congo (Lualaba) River. The TL2 region has been found to contain a high diversity of anthropoid primates including three forms, in addition to C. lomamiensis, that are endemic to the area. We recommend the common name, lesula, for this new species, as it is the vernacular name used over most of its known range. PMID:22984482

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

259

Ages of detrital zircon from siliciclastic sucessions of the Brasilia belt, southern border of Sao Francisco craton: Implications for the evolution of proterozoic basins  

International Nuclear Information System (INIS)

The determination of the age distribution of detrital zircon suites from greenschist and amphibolite facies metassedimentary rocks using 207Pb/206Pb laser-ablation inductively couple plasma mass spectometry (LA-ICPMS) was previously discussed by Machado and Gauthier (1996) and is an useful tool on determinating the ages interval of the source area. Although 207Pb/206Pb ages are, in principle, mimimum ages, Feng et al. (1993) and Machado and Gauthier (1996) showed that these ages are identical within error to U-Pb ages. The advantage of the method for sedimentary provenance studies is that the number of grains that can be analysed per day (ca. 50) on the same sample, providing a stastically meaningful age distribution. The most significant limitations of the method used in this work are the inability to yield reliable U-Pb values and the large analytical error of, at least, 1-10%. Neverthless, in provenance studies high precision are not required. In this work we report ages of detrital zircon from from lower greenschist metamorphic facies quartzites from the Proterozoic Sao Joao del Rei and Andrelandia basin successions. The data yield information about the ages of the source areas and provide an approach for constraining sedimentation ages in these basins (au)

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

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

Science.gov (United States)

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

Goguitchaichvili, A.; Martin-Del Pozzo, A. L.; Rocha-Fernandez, J. L.; Urrutia-Fucugauchi, J.; Soler-Arechalde, A. M.

2009-01-01

262

Unusual twinning features in large primary gypsum crystals formed in salt lake conditions, Middle Miocene, Madrid Basin, Spain—palaeoenvironmental implications  

Science.gov (United States)

A gypsum formation in the Middle Miocene saline lake deposits of the Madrid Basin is composed of large twinned crystals displaying an unusual habit characterised by the twin re-entrant angles systematically opening downward. Such a habit is an exception to the commonly accepted Mottura's rule for the growth of large twinned crystals which have been observed in marine-derived evaporitic settings. The crystals, twinned along (100), are composed of elongated sub-crystals formed by the intersection of the pinacoid {010} and the hemipyramid {111}. Field and petrographic evidence indicate a primary origin by subaqueous growth on the bottom, ruling out a secondary origin. Brine composition, dominated by Ca, Na, SO 4, Cl, can be one of the several factors potentially controlling the selective growth of this habit. Further observations could indicate that such inverted twinned crystals may be considered diagnostic of gypsum growth in continental settings as such a pattern has not been recognised in marine evaporite formations.

Rodríguez-Aranda, J. P.; Rouchy, J. M.; Calvo, J. P.; Ordóñez, S.; García del Cura, M. A.

1995-02-01

263

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)

264

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  

Science.gov (United States)

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

265

Tectonic setting of the Late Triassic volcaniclastic series of the Luang Prabang Basin, Laos, and geodynamic implications from the Triassic to Jurassic in SE Asia  

Science.gov (United States)

The Luang Prabang Basin, located on the eastern margin of the Indochina block, is mainly composed of volcaniclastic continental deposits. The interpretation of U-Pb zircon geochronological dates shows that volcanism is contemporaneous with the sedimentation during the Late Triassic (c.a. 225 to 215 Ma; Blanchard et al., 2013, J. Asian Earth Sci., 70-71; 8-26). At the same time, volcanism is also known along the Eastern margin of the Indochina block (present day Thailand). There are currently two main contrasting interpretations concerning the tectonic setting related to these volcanic events: are they arc-related (e.g. Barr et al., 2006, J. Geol. Soc. London, 163; 1037-1046) or post collisional (e.g. Srichan et al., 2009, Island Arc, 18; 32-51)? We have performed geochemical analysis on both sedimentary and volcanic rocks of the Luang Prabang Basin in order to evaluate the relationships between the volcanic events and to propose a geodynamic interpretation. The geochemical characteristics of the Luang Prabang Late Triassic volcaniclastic and volcanic rocks are compatible with a volcanic arc setting. The confrontation of these results with the stratigraphic evolution of the eastern margin of the Indochina block leads to reconsider the Late Triassic to Jurassic geodynamic evolution of this area. Arc-related volcanism seems to occur during nearly the whole Triassic, implying a subduction of the Paleotethys beneath the Indochina block. As the stratigraphic record of north-eastern Thailand and western Myanmar shows an important stratigraphic gap spanning from the Early to the Middle Jurassic, the collision between the Indochina and the Sibumasu blocks likely occurred at that period.

Rossignol, Camille; Bourquin, Sylvie; Dabard, Marie-Pierre; Hallot, Erwan; Poujol, Marc; Nalpas, Thierry

2014-05-01

266

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

International Nuclear Information System (INIS)

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

267

The variability of vertical structure of precipitation in Huaihe River Basin of China: Implications from long-term spaceborne observations with TRMM precipitation radar  

Science.gov (United States)

current study investigates the variability of vertical structure of precipitation in the Huaihe River Basin (HRB) of China. The precipitation characteristics have been revealed by the long-term observations of vertical profile of reflectivity (VPR) from the first spaceborne precipitation radar (PR) onboard the National Aeronautics and Space Administration (NASA)'s Tropical Rainfall Measuring Mission (TRMM) satellite. This study has statistically analyzed the latest TRMM 2A-23 and 2A-25 products (version 7, released in 2012) with ˜15 years time span (from 11 December 1997 to 19 August 2012). First, the spatial and seasonal variations of storm height and freezing level have been investigated. The results show a climatological relation connecting the storm height with the rainfall rate in HRB. Second, mean VPRs have been studied for the stratiform and convective precipitation. The VPR variability has been analyzed for different seasons and rain intensities. Third, the characteristics of rain intensification and weakening in the vertical direction have been examined by the statistical analysis of VPR slope below the melting layer. The results show that the rainfall tends to be reduced (or intensified) with the height changing downward in the light (or moderate and heavy) precipitating clouds, no matter stratiform or convection. Finally, the S-band climatological VPRs have been characterized by converting the VPR from Ku-band to S-band. Considering the wide application of national radar network for weather surveillance in China, the developed S-band climatological VPRs can be potentially applied in a VPR correction scheme to improve the ground radar-based quantitative precipitation estimation (QPE) in this river basin.

Cao, Qing; Qi, Youcun

2014-05-01

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

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

DEFF Research Database (Denmark)

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

Petersen, H. I.; Sherwood, N.

2008-01-01

270

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

271

Summer Watering Patterns of Mule Deer in the Great Basin Desert, USA: Implications of Differential Use by Individuals and the Sexes for Management of Water Resources  

Science.gov (United States)

Changes in the abundance and distribution of free water can negatively influence wildlife in arid regions. Free water is considered a limiting factor for mule deer (Odocoileus hemionus) in the Great Basin Desert. Consequently, a better understanding of differential use of water by individuals and the sexes could influence the conservation and management of mule deer and water resources in their habitats. We deployed remote cameras at all known water sources (13 wildlife water developments and 4 springs) on one mountain range in western Utah, USA, during summer from 2007 to 2011 to document frequency and timing of water use, number of water sources used by males and females, and to estimate population size from individually identified mule deer. Male and female mule deer used different water sources but visited that resource at similar frequencies. Individual mule deer used few water sources and exhibited high fidelity to that resource. Wildlife water developments were frequently used by both sexes. Our results highlight the differing use of water sources by sexes and individual mule deer. This information will help guide managers when siting and reprovisioning wildlife water developments meant to benefit mule deer and will contribute to the conservation and management of this species. PMID:23125557

Shields, Andrew V.; Larsen, Randy T.; Whiting, Jericho C.

2012-01-01

272

THE GULLY FORMATION PROCESSES OF THE BASINS AND THEIR IMPLICATIONS ON THE SLOPES STABILITY, A RELIEF EVOLUTION MODEL ON THE BRAZILIAN SAVANNA DOMAIN  

Directory of Open Access Journals (Sweden)

Full Text Available This article brings on the results of specific studies over erosion carried out for twenty years by a crew of researchers of Universidade Federal de Uberlândia. The researches at all took place in Uberlândia, Monte Carmelo, Iraí de Minas counties and others, prior focusing the basins of Douradinho at Uberlândia, Pantaninho and Divisa at Iraí de Minas and Boa Vista at Prata.This Triângulo Mineiro specific area has been through several geographical changes over the twentieth century implying alteration on its landscape structure. According to this, the need of knowing the processes dynamic as well as the diagnoses methods and also how toelaborate bating corrections and means to recover degraded areas has become extremely necessary. The main goal was the identification of either the mechanisms or the conditions stablishers responsible for erosion processes.“The tropical environment is characterized by a damaged landscape composed by potentially affected areas and others recently occupied which present initial effects. Both the areas need planning research. Whenever those environments get altered by human action, their fragilities show up” (Baccaro, 1994:19.

Claudete Ap. Dallevedove Baccaro

2005-05-01

273

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

Science.gov (United States)

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

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

2009-07-01

274

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

275

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

Science.gov (United States)

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

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

2012-04-01

276

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

277

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

Science.gov (United States)

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

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

2013-12-01

278

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

Scientific Electronic Library Online (English)

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

L, Pérez-Cruz; J, Urrutia-Fucugauchi.

2009-09-01

279

Biomarker characterization of the record of the OAE1a (early Aptian) in Betic and Cantabrian basins (Spain)-Sedimentary implications  

Science.gov (United States)

Molecular analyses of sedimentary organic matter are powerful tools in assessing the origin of organic matter and its thermal maturity as well as constraining ancient environmental conditions, such as as marine productivity, anoxia in bottom waters or the photic zone and sea surface temperatures. This communication presents the study of four sections recording the OAE1a (early Aptian) in Spain, which are located in two broad basins respectively located in the South and the North of Iberia: the Southern Iberian Palaeomargin (Carbonero - CAB, La Frontera - XF and Cau - CAU sections) and the Cantabrian Basin (Puente Nansa - PN section). These sections represent depositional settings ranging from platform (CAU, PN) to pelagic environments (CAB, XF). C-isotope profiles and biostratigraphic data are used to define the interval corresponding to the OAE 1a. Here we focus on the biomarker composition of the organic-rich facies, and the integration of these data with the sedimentology, stratigraphy and paleogeography. The study has been based mainly upon the analysis of samples with Gas Chromatography-Mass Spectrometry (GCMS). Four main groups of compounds are present in all sections: n-alkanes, isoprenoids, hopanes and steranes. n-Alkanes and isoprenoids (pristane and phytane) are dominant in most samples. To facilitate interpretation of these distributions, we have calculated the TAR (terrestrial aquatic ratio derived from the ratio of long to short chain compounds) and also the OEP (odd over even predominance of n-alkanes). The ratio of pristane to phytane and various isoprenoid/n-alkanes ratios have also been calculated. The hopanes are represented by a range of C27 to C35 components, with the specific isomers varying amongst the sections due to differences in thermal maturity. Steranes occur as a range of C27, C28 and C29 isomers, whereas diasteranes only occur in the most thermally mature section (CAB). Other compounds of interest include gammacerane and dinosterane. The analysis of the data shows interesting differences between the studied sections, of which thermal maturity appears to be a first order control. The n-alkane distribution (OEP) and sterane and hopane epimer ratios (20S/(20R+20S) steranes and 22S/(22R+22S) hopanes) all reveal that the CAB section is thermally mature, whereas the nearby XF section is very immature. CAU section shows a very low maturity, and PN shows intermediate values. The isoprenoids/n-alkanes ratios also present different values between the four sections. These differences help constrain the paleogeograhic and sedimentary interpretation of the studied sections. Organic matter is derived from a range of terrestrial, marine and bacterial sources. Maturity varies strongly, even between nearby sections (CAB and XF), probably in relation with tectonic and volcanic synsedimentary activity. The distribution of n-alkanes (TAR ratios), would indicate a trend from predominance of marine plants in the CAB samples, towards a higher proportion of continental input to XF, PN and CAU sections, consistent with the paleogeography, but observed differences in thermal maturity could also account for this trend. The dominance of the C29 isomers in steranes in all sections would indicate a contribution from higher plants. The presence of gammacerane as well as a high C29/C30 hopane ratios could indicate water column stratification and anoxia at the water/sediment interface, respectively, although these features are not always present and other proxies for anoxia (e.g. isorenieratene derivatives) have not been detected with the method used. The vertical trends observed reveal notable changes through time; therefore, a higher resolution study along the sections will provide new evidence for furthering our understanding of the causes and extent of OAE1a. This work is a contribution of the University of Jaén research project UJA-07-16-41, and Research Group of the Junta de Andalucía (Spain) RNM-200.

Quijano, María. Luisa; Castro, José Manuel; Pancost, Richard D.; de Gea, Ginés. A.; Najarro, María.; Aguado, Roque; Rosales, Idoia; Martín-Chivelet, Javier

2010-05-01

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, ihenomenon 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)

 
 
 
 
281

Present-day stress analysis of the St. Lawrence Lowlands sedimentary basin (Canada) and implications for caprock integrity during CO2 injection operations  

Science.gov (United States)

A geomechanical analysis of the St. Lawrence Lowlands sedimentary basin is important to reliably estimate the maximum sustainable fluid pressures for CO2 injection that will not reactivate pre-existing faults in the caprock thereby inducing a breeched CO2 reservoir. This requires the determination of prevailing stresses (orientations and magnitudes), fault and fractures geometries and rock strengths. The average maximum horizontal stress orientation (SHmax) is estimated N59°E ± 20° in the St. Lawrence Lowlands. The stress orientations were obtained from stress-induced wellbore breakouts inferred from four-arm dipmeter caliper data in 17 wells. These wellbore failure features are confined to Paleozoic lithological units of the St. Lawrence Platform succession and frontal thrusts of the Quebec Appalachians at depths from 250 m to 4 km. Our results are consistent with the regional NE-SW SHmax stress orientation trend that is generally observed in eastern Canada and the U.S. The stresses/pressure gradients estimated for the St. Lawrence Lowlands (depths high-angle NE-SW regional faults and fractures in the Paleozoic sedimentary succession and the Grenvillian basement are oblique to the SHmax stress orientations (10° to 36°) and could be reactivated (slip tendency 0.34 to 0.58) under the present-day stress field if fluid pressures exceeded the critical threshold. Further refinement of regional geomechanical model is required to estimate the maximum sustainable injection pressure necessary for shear reactivation along the regional faults. The regional pore pressure-stress coupling ratio under assumed parameters is about 0.5-0.65 and may contribute to reduce the risk of shear reactivation of faults and fractures. The maximum sustainable Pp that would not cause opening of vertical tensile fractures during CO2 operations is about 18.5-20 MPa for the depth of 1 km.

Konstantinovskaya, E.; Malo, M.; Castillo, D. A.

2012-01-01

282

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

Science.gov (United States)

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

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

2014-07-01

283

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

Science.gov (United States)

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

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

2014-07-01

284

Evaluation of triclosan and triclocarban at river basin scale using monitoring and modeling tools: implications for controlling of urban domestic sewage discharge.  

Science.gov (United States)

Triclosan (TCS) and triclocarban (TCC) are two commonly used personal care products. They may enter into aquatic environments after consumption and pose potential risks to aquatic organisms. We investigated the occurrence and fate of TCS and TCC in five large rivers (the Liao River, Hai River, Yellow River, Zhujiang River and Dongjiang River) in China, and compared the monitoring data with the predicted results from Level III fugacity modeling. TCS and TCC were detected in the five large rivers with the detection frequencies of 100% or close to 100% in surface water and sediments of almost every river. TCS and TCC were found at concentrations of up to 478 ng/L and 338 ng/L in surface water, and up to 1329 ng/g and 2723 ng/g in sediments. Cluster analysis indicated that the sites with higher concentrations were usually located in or near urban area. Meanwhile, principal component analysis also suggested that the mass inventories of TCS and TCC in water and sediment were significantly influenced by the factors such as the total or untreated urban domestic sewage discharge at river basin scale. The concentrations and mass inventories from the fugacity modeling were found at the same order of magnitude with the measured values, suggesting that the fugacity modeling can provide a useful tool for evaluating the fate of TCS and TCC in riverine environments. Both monitoring and modeling results indicated that the majority of mass inventories of TCS and TCC were stored into sediment, which could be a potential pollution source for river water. The wide presence of TCS and TCC in these large rivers of China implies that better controlling of urban domestic sewage discharge is needed. PMID:23127624

Zhao, Jian-Liang; Zhang, Qian-Qian; Chen, Feng; Wang, Li; Ying, Guang-Guo; Liu, You-Sheng; Yang, Bin; Zhou, Li-Jun; Liu, Shan; Su, Hao-Chang; Zhang, Rui-Quan

2013-01-01

285

Petrology, palynology and organic geochemistry of Eocene lignite of Matanomadh, Kutch Basin, western India: Implications to depositional environment and hydrocarbon source potential  

Energy Technology Data Exchange (ETDEWEB)

Petrological, palynological and organic-geochemical investigations were undertaken to determine the source vegetation, depositional conditions and hydrocarbon source potential of Eocene Matanomadh lignites from Kutch Basin, western India. The maceral study reveals that studied lignites are rich in huminite (av. 63%) with sub-ordinate amount of liptinite (av. 19%) and low inertinite (av. 3%), along with low to moderately high associated mineral matters (av. 15%). The overall petrographic composition points to a lagoonal condition for the formation of these lignites. The mean huminite reflectance values (R{sub r}: 0.28-0.34%, av. 0.31%) as well as low Rock-Eval T{sub max} (av. 417 C) values for the seams, suggest brown coal or lignitic stage/rank for the studied lignites. The palynological assemblages, dominated by tropical angiospermic pollen, suggest prevalence of warm humid tropical climate during the deposition of these lignites. The total organic carbon (TOC) content of lignites ranges between 26 and 58 wt.%, whereas the TOC content of the associated carbonaceous shales is around 4 wt.%. The Hydrogen Index (HI) ranging from 23 to 452 mg HC/g TOC indicates that the lignite sequence has the potential to produce mixed oil and gaseous hydrocarbons on maturation. The major pyrolysis products of lignites, derived from Curie point pyrolysis-GC-MS, are straight chain aliphatics, phenols and cadalene-based C{sub 15} bicyclic sesquiterpenoids. The exclusive occurrence of C{sub 15} bicyclic sesquiterpenoids suggests that these compounds are derived from dammar resin of angiosperm plants, belonging to family Dipterocarpaceae. (author)

Dutta, Suryendu; Mathews, Runcie P.; Saraswati, Pratul K.; Banerjee, Santanu [Department of Earth Sciences, Indian Institute of Technology Bombay (India); Singh, Bhagwan D.; Tripathi, Suryakant M.; Singh, Alpana [Birbal Sahni Institute of Palaeobotany, Lucknow (India); Mann, Ulrich [Forschungszentrum Juelich (Germany). Institut fuer chemie und Dynamik der Geosphaere

2011-01-01

286

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

International Nuclear Information System (INIS)

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

287

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. PMID:23213629

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

2012-01-01

288

Reactivity of organic-rich sediment in seawater at 350°c, 500 bars: experimental and theoretical constraints and implications for the guaymas basin hydrothermal system  

Science.gov (United States)

Hydrothermal alteration of organic-rich diatomaceous sediment by seawater was modelled experimentally at 350°C, 500 bars and seawater/sediment mass ratio of 3. The experiment was performed to assess the effect of organic matter reactivity on solution speciation and sediment alteration processes at an elevated temperature and pressure and provide requisite data to better understand the chemistry of hydrothermal fluids issuing from vents in the Guaymas Basin, Gulf of California. Seawater chemistry changed greatly during the experiment. In particular, Na, Mg and SO 4 decreased, while ? CO 2, ? NH 3, ? H 2S, SiO 2, Ca, K, H 2, CH 4 and heavy and base metals increased. Moreover, owing to the thermal alteration of sediment organic matter, organic acids, phenolic derivatives and phthlate were released to solution. Examination of solid alteration products revealed the effects of extensive dissolution and precipitation processes characterized by total elimination of diatoms and formation of cristobalite, quartz (?), pyrite, pyrrhotite, mixed layer chlorite/smectite and calcite. Plagioclase feldspar (An 40) recrystallized to a more albitic form owing to Na fixation and Ca cycling to calcite. A graphitic residue was also present in the products of the experiment. Mg and Na fixation reactions during the experiment generated significant H +, although the pH measured at 25°C was approximately 6.2. SO 4 reduction and thermal alteration and dissolution of organics, however, consume H + and are chiefly responsible for the near neutral pH for the overall reaction. Speciation calculations including ammine and acetate protonation reactions give a pH at experimental conditions of approximately 5.1, while mineral solubility relations involving virtually all alteration phases require a pH of 5.57 to 5.94. A near neutral pH at experimental conditions constrains the mobility of Fe, Mn, Zn, Cu and Ni, which existed in solution as chloro-complexes. Dissolved concentrations of Pb and Al, in contrast, covaried with dissolved organics, especially acetate, suggesting organo-metallic complex formation.

Thornton, Edward C.; Seyfried, W. E., Jr.

1987-07-01

289

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

290

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

291

Combined Sm-Nd and Lu-Hf dating of garnets from the Putomayo foreland basin in south-central Colombia and implications  

Science.gov (United States)

Garnet-whole rock (Grt-WR) ages of metapelites determined by the Lu-Hf decay system are almost always older than those determined by the Sm-Nd system. Unambiguous interpretation of the observed age differences has been hindered by a lack of adequate information about grain size, diffusion data for Hf in garnet, and in many cases about peak metamorphic conditions and cooling rates, all of which affect the closure temperatures of these decay systems. As part of a broader study on basement rocks from the Andean Putomayo foreland basin in south-central Colombia, we have determined the Lu-Hf and Sm-Nd Grt-WR ages of these rocks using painstakingly handpicked garnets of ~50 ?m radius, and obtained ages of 1070 × 5.6 and 1007 × 2.9 Ma, respectively. By modeling the retrograde Fe-Mg zoning in garnet adjacent to biotite according to an asymptotic cooling model (1/T = 1/To + ?t) with the diffusion data from [1], an initial cooling rate of ~2-5 °C/Ma is obtained independently of the geochronological data; peak P-T conditions of ~8 kb, 675 °C are imposed by garnet-orthopyroxene thermobarometry. Using the above data in conjunction with the Nd diffusion data from [2] and Hf diffusion data from our recent study, we obtain closure temperatures for the Lu-Hf and Sm-Nd decay systems in garnet of ~545-565 °C and 415-430 °C, respectively. Results from analytical solutions [3, 4] and a more flexible numerical method are found to be in good agreement with one another. The calculated difference of closure temperatures predicts a difference of ~105-40 Ma between the ages determined by the two decay systems, as compared to the observed age difference of 63 × 6 Ma. The predicted peak metamorphic age derived from the measured and calculated resetting ages of the two decay systems is between ~1030 and 1185 Ma, as compared to the Lu-Hf age of 1070 ×1.9 Ma; we are currently working to obtain U-Pb zircon ages to better constrain this peak metamorphic age. In calculating these results, we have made the simplifying assumptions that there was no retention of prograde radiogenic 176Hf in garnet and no rotation of the Lu-Hf Grt-WR isochron during cooling as a result of the somewhat lower closure temperature of Lu compared to that of Hf. Further work is in progress to refine the model taking these effects into account and explore the consequence of using diffusion data from other groups [5, 6]. A review of available experimental REE in garnet diffusion data suggests that low-REE garnets produce diffusion coefficients which are in agreement with [2], while higher-REE garnets produce diffusion coefficients which fall on the Arrhenius trend of [5] and [6]. Because there is no obvious reason why the experimental data presented in [2] or [6] should be erroneous, it is concluded that the variation in these datasets represents a change in diffusion mechanism as a consequence of garnet REE concentration. We hope that the results of this study will help to elucidate the circumstances under which each of these datasets is appropriate. [1] Chakraborty and Ganguly (1992) CMP 111, 74-86. [2] Tirone et al. (2005) Geochim. Cosmochim. Acta 69, 2385-2398. [3] Dodson (1973) CMP 40, 259-274. [4] Ganguly & Tirone, EPSL 170, 131-140. [5] Carlson (2012) Amer. Mineral. 97, 1598-1618. [6] Van Orman et al. (2002) Cont. Min. Petr. 142, 416-424.

Bloch, E. M.; Ibanez-mejia, M.; Ganguly, J.

2013-12-01

292

Residual basins  

International Nuclear Information System (INIS)

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

293

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

International Nuclear Information System (INIS)

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

294

Earlier River Basin Planning  

...North Western River Basin...Member State Law. Identify River Basin Districts, International River Basin Districts and competent authorities....River and Lake Small Water Body Identification (.PDF 284Kb)...

295

Metabolic principles of river basin organization.  

Science.gov (United States)

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

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

2011-07-19

296

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

297

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

298

High Resolution Audiomagnetotelluric Investigation of the Porosity at the Margin of the Hudson Bay Basin, Canada  

Science.gov (United States)

Seismic exploration from 1968 to 1985 within the intracratonic Hudson Bay basin in northern Canada resulted in five dry wells drilled on a structural high in the central part of the basin (Hamblin, 2008). Recent work (Bertrand and Malo, 2012) has indicated successions at margins of the basin are well within the oil and gas "window". To test this conjecture a magnetotelluric (MT) survey was carried out in the vicinity of Churchill, Manitoba, at the margin of the basin. The primary goal of the survey was to identify potential source or reservoir rocks in the Upper Ordovician section of the Palaeozoic strata. MT surveys have been utilized in the northeastern portion of the Williston basin and have successfully imaged lower Palaeozoic carbonate units (Gowan et al., 2009). The MT method provides information on the electrical conductivity of the subsurface though the measurement of the natural time-varying electric and magnetic fields at the surface. Due to the dependence of the depth of investigation of the fields on their frequency, an estimate of conductivity variation with depth can be attained. A total of 46 high frequency audio-magnetotelluric (AMT) sites were collected, 38 along one approximately N-S corridor perpendicular to the coastline and 8 in a more E-W direction closer to the town of Churchill. Simultaneous collection of broadband MT data (BBMT) at a limited number of sites was done in order to calculate a response function over a wider range of frequencies at each AMT site. The combined AMT and BBMT MT data have been edited and processed to produce response functions at all sites, and 1-D modelling has provided resistivity vs. depth curves in the top 200 m of the basin. The 1-D models have been stitched together to create a continuous, approximately N-S resistivity section. In addition, the data have been input to a 3D inversion program and preliminary 3D resistivity and conductivity volumes have been generated along with an estimate of 3-D porosity variations to a depth of approximately 200 m.

Craven, J. A.; Roberts, B.

2012-12-01

299

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

300

09 river basin planning  

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

 
 
 
 
301

Detrital zircon and apatite fission track data in the Liaoxi basins: Implication to Meso-Cenozoic thermo-tectonic evolution of the northern margin of the North China Craton  

Science.gov (United States)

Detrital zircon and apatite fission track (ZFT and AFT) data of the sandstones collected from the Liaoxi basins served as a significant probe to study the Meso-Cenozoic thermo-tectonic reactivation events in the northern margin of the North China Craton. All sandstones show wide ZFT and AFT age spectrum and most of ZFT and AFT ages are younger than depositional age of respective host rocks, which suggest widespread track resetting of the host rocks in the Liaoxi basins after deposition. This hot geothermal status in the Liaoxi basins deduced from ZFT and AFT data is temporal consistent with the lithospheric evolution of the North China Craton, which implies that the lithosphere under the northern margin of the North China Craton underwent similar thermo-tectonic destruction process as the intracratonic Bohai Sea. The young ZFT peak age, which ranges from ˜50 Ma to 20 Ma, to some extend, provides a temporal constraint on the time that lithosphere significantly thinned and following reverse of the Liaoxi basins and uplift of the eastern part of the Yan-Liao Orogenic Belt. Exhumation of 1.5-2 km can be estimated in the eastern part of the Yan-Liao Orogenic Belt since ˜30 Ma to 10 Ma.

Yan, Yi; Hu, Xiaoqiong; Lin, Ge; Liu, Weiliang; Song, Zhengjiang

2010-08-01

302

40Ar/ 39Ar ages of mafic dykes from the Mesoproterozoic Chhattisgarh basin, Bastar craton, Central India: Implication for the origin and spatial extent of the Deccan Large Igneous Province  

Science.gov (United States)

We present 40Ar/ 39Ar whole-rock ages of 63.7 ± 2.7 Ma (2?, 92% Ar release) and 66.6 ± 2.2 Ma (2?, 96% Ar release) for two samples of sub-surface mafic dykes intrusive into the sedimentary rocks of the Mesoproterozoic Chhattisgarh basin, Bastar craton, Central India. The obtained ages are synchronous with those of the Deccan Traps whose nearest exposures are at a distance of ~ 200 km to the west, and the recently dated diamondiferous orangeites (Group-II kimberlites) of the Mainpur area (located ~ 100 km SE within the Bastar craton). The chemical composition of the Chhattisgarh mafic dykes is indistinguishable from the chemostratigraphic horizons of the upper Deccan lavas of the Wai Subgroup (Ambenali and Poladpur Formations) and confirms them to be a part of the Deccan Large Igneous Province (LIP). The geological setting of the Deccan-age mafic dykes in the Chhattisgarh basin is analogous to that observed in other LIPs of the world such as (i) Pasco Basin of NW U.S.A, (ii) Ellisras sub-basin of southern Africa, (iii) Rift basins of New England in the NE U.S.A and (iv) the West Siberian Basin of Russia where LIP-related basalts and sills have been emplaced in distant domains from the main province. The Deccan-age of the Chhattisgarh dykes and the Mainpur orangeites permits a substantial increase of at least 8.5 × 10 4 km 2 in the spatial extent of the Deccan LIP. The temporal link at ~ 65 Ma between the Deccan Traps and (i) sub-surface mafic dykes within the Chhattisgarh basin and orangeites in the Bastar craton, (ii) Ambadongar carbonatite in western India, (iii) Salma mafic dyke in the Eastern Indian craton, (iv) Rajahmundry Traps off the eastern coast of southern India and (v) tholeiitic dykes and basalts from the Seychelles, suggests a common tectonomagmatic control, via a vast mantle plume-head of the order of 2000-2500 km. Our study has relevance to the (i) origin (plume vs non-plume) of the Deccan LIP, (ii) plumbing system for Deccan dykes and lavas in domains far away from the presently exposed Trap regions, (iii) palaeo-environmental issues at the K-T boundary and (iv) metallogeny (diamond, Ni-Cu-PGE) in the Bastar craton.

Rao, N. V. Chalapathi; Burgess, R.; Lehmann, B.; Mainkar, D.; Pande, S. K.; Hari, K. R.; Bodhankar, N.

2011-08-01

303

Tectonic and thermal history of the western Serrania del Interior foreland fold and thrust belt and Guarico Basin, north central Venezuela: Implications of new apatite fission track analysis and seismic interpretation  

Science.gov (United States)

Structural analysis, interpretation of seismic reflection lines, and apatite fission-track analysis in the Western Serrania del Interior fold and thrust belt and in the Guarico basin of north-central Venezuela indicate that the area underwent Mesozoic and Tertiary-to-Recent deformation. Mesozoic deformation, related to the breakup of Pangea, resulted in the formation of the Espino graben in the southernmost portion of the Guarico basin and in the formation of the Proto-Caribbean lithosphere between the diverging North and South American plates. The northern margin of Venezuela became a northward facing passive margin. Minor normal faults formed in the Guarico basin. The most intense deformation took place in the Neogene when the Leeward Antilles volcanic island arc collided obliquely with South America. The inception of the basal foredeep unconformity in the Late Eocene-Early Oligocene marks the formation of a perisutural basin on top of a buried graben system. It is coeval with minor extension and possible reactivation of Cretaceous normal faults in the Guarico basin. It marks the deepening of the foredeep. Cooling ages derived from apatite fission-tracks suggest that the obduction of the fold and thrust belt in the study area occurred in the Late Oligocene through the Middle Miocene. Field data and seismic interpretations suggest also that contractional deformation began during the Neogene, and specifically during the Miocene. The most surprising results of the detrital apatite fission-track study are the ages acquired in the sedimentary rocks of the easternmost part of the study area in the foreland fold and thrust belt. They indicate an Eocene thermal event. This event may be related to the Eocene NW-SE convergence of the North and South American plates that must have caused the Proto-Caribbean lithosphere to be shortened. This event is not related to the collision of the arc with South America, as the arc was far to the west during the Eocene.

Perez de Armas, Jaime Gonzalo

304

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

Scientific Electronic Library Online (English)

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

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

305

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

Scientific Electronic Library Online (English)

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

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

2002-12-01

306

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

307

Groundwater recharge environments and hydrogeochemical evolution in the Jiuquan Basin, Northwest China  

International Nuclear Information System (INIS)

dominated moving along the flow path from the Jiuquan-Jiayuguan Basin to the Jinta Basin, and the confined water was SO42-dominated. The results have important implications for groundwater management in the Basin, where a high proportion of the water being used is in effect being mined (i.e., extracted faster than its replacement rate); thus, significant changes are urgently needed in the regional water-use strategy.

308

BASINS 2.0  

Science.gov (United States)

The Environmental Protection Agency (EPA) first created BASINS (Better Assessment Science Integrating Point and Nonpoint Sources) in 1996 as an aid to water resource planners concerned with water quality and watershed analyses. The strength of BASINS is its integration of "a geographic information system (GIS), national watershed data, and state-of-the-art environmental assessment and modeling tools." The updated version of the program, BASINS 2, can be downloaded from this site.

1998-01-01