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1

Saskatchewan Williston Basin horizontal well update  

Energy Technology Data Exchange (ETDEWEB)

Drilling statistics for Saskatchewan`s Williston Basin were presented. The statistics included the number of vertical wells and horizontal wells drilled from 1989 to 1996. Average well productivity for Mission Canyon horizontal wells and monthly crude oil production (from horizontal and vertical wells) for southeast Saskatchewan were summarized. Remaining recoverable oil reserves for south-east Saskatchewan were also discussed. 8 figs.

Wimmer, C. [Saskatchewan Dept. of Energy and Mines, Regina, SK (Canada)

1997-04-01

2

Williston in the family of cratonic basins  

Energy Technology Data Exchange (ETDEWEB)

The Williston basin is one of a clan of subcircular to elliptical elements in the interiors of all cratons; such basins are distinguished by characteristics common to all. In each, the basement consists of continental crust and each basin is surrounded by areas of continental crust. Subsidence rates are typically low, so that conditions near depositional base level prevailed during much of the history of sediment accumulation. Episodic subsidence occurred over time spans of 10/sup 7/-10/sup 8/ years; major episodes of subsidence are broadly concurrent on all cratons. Tectonic tempo and mode of subsidence evolved synchronously on all cratons; therefore, similar isopach and facies patterns (and similar oil or gas maturation, migration, and trap potentials) occur on all cratons. All members of the clan exhibit a range of individual variations imposed by latitude and climate. Intraplate tectonism and volcanism, approach to or distance from source areas, and distribution paths of detrital sediment. Nevertheless, facts and concepts developed by intensive study of basins with high-density documentation (outcrop and subsurface) are commonly applicable to basins such as the Williston, which is in a less mature stage of exploration.

Sloss, L.L.

1985-05-01

3

Mississippian Lodgepole Play, Williston Basin: A review  

Energy Technology Data Exchange (ETDEWEB)

Waulsortian-type carbonate mud mounds in the lower Mississippian Lodgepole formation (Bottineau interval, Madison Group) comprise an important new oil play in the Williston basin with strong regional potential. The play is typified by wells capable of producing 1000-2500 bbl of oil per day and by reserves that have as much as 0.5-3.0 million bbl of oil per well. Currently centered in Stark County, North Dakota, along the southern flank of the basin, the play includes 38 wells, with 21 producers and 6 new fields. Initial discovery was made at a Silurian test in Dickinson field, traditionally productive from Pennsylvanian sands. The largest pool discovered to date is Eland field, which has 15 producers and estimated total reserves of 12-15 million bbl. This report summarizes geologic, well-log, seismic, and production data for this play, which promises to expand considerably in the years to come.

Montgomery, S.L. [Petroleum Consultant, Seattle, WA (United States)

1996-06-01

4

Regional aquifers and petroleum in Williston Basin region of US  

Energy Technology Data Exchange (ETDEWEB)

At least five major aquifers underlie the northern Great Plains of the US, which includes parts of the Williston basin in Montana and North Dakota. These aquifers form a hydrologic system that extends more than 960 km from recharge areas in the Rocky Mountains to discharge areas in eastern North Dakota and the Canadian Provinces of Manitoba and Saskatchewan. The regional flow system in the aquifers has had a major effect on the chemical composition of ground water within the Williston basin. Hydrodynamic forces may contribute to the accumulation of petroleum within the basin.

Downey, J.S.; Busby, J.F.; Dinwiddie, G.A.

1985-05-01

5

Regional scale groundwater geochemistry of the Lower Paleozoic Formations in the Williston Basin, Canada-USA: preliminary results  

Energy Technology Data Exchange (ETDEWEB)

Many of the economic resources within the Williston Basin are influenced by hydrogeology. Understanding the regional hydrology of the Basin is necessary to optimize the use of energy-related resources such as potash and even the brines themselves. Water in the basin is subject to evaporite dissolution and other water/rock chemical interactions which can result in density contrasts between recharging waters and deep basin brines. A digital geochemical database for the Paleozoic formations of the Williston Basin has been compiled. The data is being used to describe the geochemistry of the formation waters in the Basin. It was noted that fresh water recharging at the southwest of the Basin increased in salinity rather quickly as it flowed down-dip towards the northeast. These results illustrate the complexity of the hydrogeology of the Williston Basin, and have strong implications for petroleum, mineral and water exploration. 11 refs.

Benn, A.A.; Rostron, B.J. [Saskatchewan Univ., Saskatoon, SK (Canada)

1997-04-01

6

Economic appraisal of oil potential of Williston basin  

Energy Technology Data Exchange (ETDEWEB)

An economic appraisal was made of the potential of more than 80 producing fields in the Williston basin of Montana, North Dakota, and South Dakota. The major oil producing formations investigated were in the Mississippian, Devonian, Silurian and Ordovician. Data for the study came from field production and drilling statistics. An extrapolated oil production decline curve for a theoretical average producing well first was made for each field. The value of the total extrapolated amount of producible oil for the average well was then calculated, discounted for royalty, taxes, etc., and divided by the estimated cost for a completed producing well. This gave an estimate of the return per dollar invested. No considerations were given for exploration and land acquisition costs. The estimated return per dollar values, after posting on Williston basin geologic maps, show relative economic comparisons of producing formations and where within the basin the best economic returns can be expected.

Jennings, A.H.

1983-08-01

7

Paleotopography and hydrocarbon accumulation: Williston, Powder River, and Denver basins  

Energy Technology Data Exchange (ETDEWEB)

Recent geomorphic analyses of 1:24,000 scale topographic maps in the three major basins of the northern Great Plains have disclosed a persistent system of basement paleotopographic features that trend north-northeast throughout the region. Superimposed across this system and subtly influenced by it, are the northwesterly trending Laramide structural features. Paleozoic depositional patterns have been strongly influenced by the paleoridge and trough system formed by the north-northeast features. Mesozoic deposition has also been affected by the ancient subsurface system but in a more subtle manner. Many of the Paleozoic and Mezoxoic hydrocarbon locations in the three basins appear to be the results of paleotopographic control on hydrocarbon accumulation sites. This affect ranges from Paleozoic reef sites in the Williston basin through paleotrough localization of Pennsylvanian Minnelusa production in the Powder River basin to fractured Cretaceous Niobrara production at the Silo field in the Denver basin. Basement paleotopography is the underlying factor in all deposition and subsequent hydrocarbon migration in any basin. As such, it should be considered a major factor in the exploration for oil and gas.

Thomas, G.E. (Thomas and Associates, Denver, CO (United States))

1991-06-01

8

Paleotectonic controls on carbonate reservoir development in central Williston basin  

Energy Technology Data Exchange (ETDEWEB)

The Williston basin has been portrayed as the archetype intracratonic basin, wherein tectonics have played only a minor role in geologic history. This may be demonstrated in the subtle manner in which tectonics have controlled the locus and development of most of the producing reservoirs in the Paleozoic sedimentary sequence. The pattern of the initial sedimentary sequence covering the crystalline basement is that of a westerly to southwesterly thickening wedge. Limited penetration of the Deadwood sequence has restrictted full understanding of its hydrocarbon potential. Major unconformities mark tectonic episodes at the close of the Silurian and near the close of the Devonian. Mississippian seas flooded across the late Devonian unconformity and deposited thick sequences of carbonates and evaporites again in a predominantly basin-centered pattern. Rapid subsidence and rapid sedimentation caused a filling of the basin, and a strong regressive pattern of facies developed. Peritidal sedimentary facies dominate in development of reservoir and seal. Traps are thus influenced by very subtle tectonic topographic variations throughout the basin. Late Paleozoic to early Mesozoic uplift, tilting, and erosion, followed by deposition of early Mesozoic seals has had a profound effect on the distribution of hydrocarbons in the previously developed traps. A more complete understanding of this final episode and its relation to source rock maturation and migration holds the key to much of the future development of the basin.

Kerr, S.D.

1983-08-01

9

Impact origin of the Newporte structure, Williston basin, North Dakota  

Energy Technology Data Exchange (ETDEWEB)

The Newporte field is located just south of the United States-Canada border in Renville County, North Dakota, in the north-central portion of the Williston basin. Integration of seismic, well-log, and core data supports the interpretation of an impact origin for the Newporte structure. The structure involves both Precambrian basement and lower Paleozoic sedimentary units. Oil and gas production began in 1977 from brecciated basement rocks along the rim of the 3.2-km-diameter circular structure. Both well logs and seismic data were used to determine thickness changes of sedimentary units overlying the structure. Resulting isopach maps reveal a circular, bowl-shaped feature with a recognizable rim. Microscopic shock metamorphic features in quartz and feldspar are visible in basement clasts that form a mixed breccia with Cambrian Deadwood sandstone within the western rim of the structure. A Late Cambrian-Early Ordovician age is suggested for the structure because of the presence of flatlying Deadwood sandstone overlying mixed basement/sandstone breccia along portions of the rim. Identification of the Newporte structure as an impact crater adds to the growing base of evidence revealing the relevance of impact craters to petroleum exploration.

Forsman, N.F.; Gerlach, T.R. [Univ. of North Dakota, Grand Forks, ND (United States); Anderson, N.L. [Univ. of Missouri, Rolla, MO (United States)

1996-05-01

10

Interpretation of regional seismic sections from Williston Basin - a `Slossian` approach  

Energy Technology Data Exchange (ETDEWEB)

A seismic survey of the Williston Basin has produced three east-west and two north-south regional seismic cross sections totaling 3,800 km. The dataset was synthesized to establish an advanced regional sequence stratigraphic correlation of the basin fill and to provide a view of the basin evolution. The general shape of the basin was described with the Sloss-type bivariate normal distribution for the time interval of megasequences and the entire sedimentary column.

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

1997-09-01

11

Geologic setting and natural gas potential of Niobrara formation, Williston Basin  

Energy Technology Data Exchange (ETDEWEB)

Chalk units in the Niobrara Formation (Upper Cretaceous) have potential for generation and accumulation of shallow, biogenic gas in the central and eastern Williston basin. Similar to area of Niobrara gas production in the eastern Denver basin, Niobrara chalks in South and North Dakota were deposited on carbonate ramps sloping westward off the stable eastern platform of the Western Interior seaway. Within the Williston basin, the Niobrara of the western Dakotas, eastern North Dakota, and central South Dakota has different stratigraphic relationships. These three areas can be further subdivided and ranked into six areas that have different exploration potential. The south margin of the Williston basin in central South Dakota is the most attractive exploration area. Niobrara chalk reservoirs, source rocks, and structural traps in the southern Williston basin are similar to those in the eastern Denver basin. Chalk porosities are probably adequate for gas production, although porosity is controlled by burial depth. Organic carbon content of the chalk is high and shows of biogenic gas are reported. Large, low-relief structural features, which could serve as traps, are present.

Shurr, G.W.; Rice, D.D.

1985-05-01

12

Integrated study of Mississippian Lodgepole Waulsortian Mounds, Williston Basin, USA  

Energy Technology Data Exchange (ETDEWEB)

Waulsortian-type carbonate buildups in the Mississippian Lodgepole Formation, Williston Basin, constitute prolific oil reservoirs. Since the initial discovery in 1993, five fields have been discovered: Dickinson Field (Lodgepole pool); Eland Field; Duck Creek Field, Versippi Field; and Hiline Field. Cumulative production (October, 1995) is 2.32 million barrels of oil and 1.34 BCF gas, with only 69,000 barrels of water. Oil gravity ranges from 41.4 to 45.3 API. Both subsurface cores from these fields as well as outcrop (Bridget Range, Big Snowy and Little Belt Mountains, Montana) are composed of facies representing deposition in mound, reworked mound, distal reworked mound, proximal flank, distal flank, and intermound settings. Porosity values within the mound and reworked mound facies are up to 15%; permeability values (in places fracture-enhanced) are up to tens of Darcies. Geometries of the mounds are variable. Mound thicknesses in the subsurface range from approximately 130-325 feet (40-100 meters); in outcrop thicknesses range from less than 30 ft (9 m) to over 250 ft (76 m). Subsurface areal dimensions range from approximately 0.5 x 1.0 mi (0.8 x 1.6 km) to 3.5 x 5.5 mi (5.6 x 8.8 km). Integration of seismic data with core and well-log models sheds light on the exploration for Lodgepole mounds. Seismic modeling of productive mounds in the Dickinson and Eland fields identifies characteristics useful for exploration, such as local thickening of the Lodgepole to Three Forks interval. These observations are confirmed in reprocessed seismic data across Eland field and on regional seismic data. Importantly, amplitude versus offset modeling identifies problems with directly detecting and identifying porosity within these features with amplitude analyses. In contrast, multicomponent seismic data has great potential for imaging these features and quantifying porous zones within them.

Kupecz, J.A.; Arestad, J.F.; Blott, J. E. [Kupecz and Associates, Ltd., Denver, CO (United States)

1996-06-01

13

Williston Basin subsidence and sea level history: Chronological and lithofacies constraints  

Energy Technology Data Exchange (ETDEWEB)

The intent is to use lithofacies information to identify the top-driven components of sediment accumulation-depositional environments, sediments supply, compaction, sediment and water load. Physical carbonate stratigraphy is used to determine sediment accumulation corrections. Physical stratigraphic geometric patterns are used to estimate the original thicknesses of dissolved salts and to determine absolute water depth. Seawater strontium chronostratigraphy constrains the ages and paleo-oceanographic setting of Devonian-Mississippian strata. The measured strontium stratigraphy can be used for correlation, age assignment and diagentic study. Removing sediment compaction, sediment/water load effects and using the newly derived Devonian-Mississippian chronostratigraphy to examine the behavior of the Williston Basin reveals a number of facts. (1) Temporal and spatial variation in the surficial components of sediment accumulation is significant and, unless removed, obscures tectonic subsidence and sea-level change patterns. (2) Both the corrected tectonic subsidence/sea level record and lithofacies patterns of the Devonian Williston Basin show flexural or in-plane stress interference reflecting plate boundary reorganization along the near edge of the Paleozoic North American craton, culminating the Antler orogeny. (3) The tectonic subsidence and sea level change record of the Williston Basin which has been corrected for sediment compaction, water and sediment load, has extremely linear subsidence through time. This is interrupted by changes in global sea level of 100-140 m over 25-35 my and apparent sea level change of 35-60 m over 2-4 my.

Lee Roark, C.K.

1989-01-01

14

Notes from a meeting to examine southern Saskatchewan Geoscience needs: results of a government/industry geoscience workshop on Williston Basin  

Energy Technology Data Exchange (ETDEWEB)

Current and future geoscience activities in Saskatchewan`s Williston Basin were discussed at a joint workshop sponsored by the Geological Survey of Canada, Saskatchewan Energy and Mines, and the University of Saskatchewan. The workshop was proof positive of the essential ties and mutual dependence between government, industry and academia. The goal of the workshop was to: (1) improve communications among Williston Basin researchers, (2) explore future cooperative and collaborative geoscience projects in the Williston Basin, and (3) discuss deep rights reversion in Saskatchewan. The workshop consisted of a thematic review of current and proposed geoscience activities in the Williston Basin, a geographical appraisal of current activities and an evaluation of remaining geoscience needs. A geoscience action plan for the Williston Basin was formulated. Several important funding issues were also discussed.

Gilboy, C. [Saskatchewan Dept. of Energy and Mines, Regina, SK (Canada)

1997-04-01

15

Progradational sequences in lower Ordovician portion of Deadwood Formation, Williston basin  

Energy Technology Data Exchange (ETDEWEB)

In the Williston basin, the Cambrian and Ordovician Deadwood Formation can be divided into six informal members based on gamma-ray log characteristics. Members C through F are Early Ordovician (Tremadocian to Arenigian) and consist of three progradational sequences. In ascending order, the sequences consist of (1) a mixed sandstone-limestone lithotype, (2) limestone lithotypes ranging from mudstone to grainstone, (3) bioturbated, peloidal, calcareous, siliciclastic mudstone and siltstone, (4) bioturbated to planar-laminated, peloidal, calcareous siltstone and sandstone, (5) Skolithos-bored, cross-bedded to planar-laminated quartzarenite, (6) bioturbated dolomite and anhydrite-cemented fossiliferous quartz wacke, and (7) silty laminated dolomudstone. The asymmetrical sequences represent progradation of a siliciclastic shoreline, back-barrier lagoon, and intertidal algal flat over a siliciclastic shelf and a distal carbonate shoal. The present distribution of the sequences and individual lithotypes in the Williston basin is a function of the limited eastward advance of the carbonate shoal during transgression, the limited westward advance of the shoreline during progradation, deep shoreface erosion of the previous sequence during rapid transgression, and Middle Ordovician erosion.

Anderson, D.

1988-07-01

16

Madison Group (Mississippian) reservoir facies of Williston Basin, North Dakota  

Energy Technology Data Exchange (ETDEWEB)

Twenty-seven oil fields producing from the Mission Canyon Limestone and Charles Formation (Madison Group) were studied: 1) along the eastern basin margin (Bluell, Sherwood, Mohall, Glenburn, Haas, and Chola fields), 2) northeast of Nesson anticline (Foothills, North Black Slough, South Black Slough, Rival, Lignite, and Flaxton), 3) along Nesson anticline (North Tioga, Tioga, Beaver Lodge, Capa, Hoffland, Charlson, Hawkeye, Blue Buttes, Antelope, and Clear Creek), and 4) south of the basin center (Lone Butte, Little Knife, Big Stick, Fryburg, and Medora). Mission Canyon reservoirs along the eastern margin are in several shoaling-upward carbonate to anhydrite cycles of pisolitic packstone or grainstone buildups. South of the basin center, only a single shoaling-upward sequence is present, with dolomitized, mostly restructed-marine skeletal wackstone to pelletal wackstone or packstone reservoir facies. Nesson anticline, between these 2 areas, contains a single shoaling-upward sequence without an anhydrite cap. In northern Nesson anticline, Mission Canyon reservoir facies are oolitic-pisolitic, intraclastic wackestone or grainstone buildups or open-marine skeletal packstone or grainstone. Both limestones and dolostones are productive in southern Nesson anticline. Limestone reservoir facies are transitional, open to restricted-marine slightly intraclastic, skeletal wackestone or packstone facies. Dolostone reservoir facies are restricted-marine mudstone to skeletal mudstone and pelletal wackestone or packstone. Northeast of the Nesson anticline, production is from oolitic to pisolitic packstone or grainstone buildups in the Rival subinterval and from restricted-marine, dolomitized spiculitic mudstone in the Midale subinterval (base of Charles Formation). In the northern Nesson anticline, Rival reservoir facies are offshore open to restricted-marine, skeletal, intraclastic, pelletal wackestone and/or packstones.

Lindsay, R.F.

1985-02-01

17

Koch`s experience with deep in situ combustion in Williston basin  

Energy Technology Data Exchange (ETDEWEB)

Koch Exploration Company has been active with the combustion process in the Williston basin of North and South Dakota since 1979. Koch has three ongoing combustion projects in the basin. The Medicine Pole Hills Unit (MPHU) and the Capa Madison Unit (CMU) are located in the North Dakota, while the Buffalo Unit is situated in South Dakota. Because of low primary recovery from these deep carbonate reservoirs, studies were conducted to determine how the large volume of remaining oil could be recovered, and decisions were made to initiate an in situ combustion by air injection, pressure maintenance project in these reservoirs. The principal objective of this talk is to review the past performance of these combustion projects and discuss some of the operating problems we encountered. The other objectives are to outline the economics of the projects and to speculate on the future of in situ combustion technology as Koch sees it.

Miller, R.J. [Koch Exploration Co., Wichita, KS (United States)

1995-02-01

18

Improved recovery demonstration for Williston Basin carbonates. Quarterly report, January 1, 1996--March 31, 1996  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this project is to demonstrate targeted infill and extension drilling opportunities, better determinations of oil-in- place, methods for improved completion efficiency and the suitability of waterflooding in certain shallow-shelf carbonate reservoirs in the Williston Basin, Montana, North Dakota and South Dakota. Improved reservoir characterization utilizing 3-dimensional and multi-component seismic area 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 extended- reach jetting lance and other ultra-short radius lateral technologies. Improved completion efficiency, additional wells at closer spacings better estimates of oil-in-place will result in additional oil production by primary and enhanced recovery processes. Technical progress is described for field demonstrations at the Ratcliffe and Buffalo fields and geophysical evaluations at Ratcliffe and Red River.

NONE

1996-07-01

19

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-09-01

20

Definition and characterization of petroleum compositional families in Williston Basin, North America using principal component analysis  

Energy Technology Data Exchange (ETDEWEB)

Petroleum hydrocarbons in the gasoline range (GRH) and saturate (SFH- >210{sup o}C boiling point) fractions carry information that is often obscured by compositional diversity and multiple processes working simultaneously. Multivariate statistical methods can enhance the analysis and interpretation of compositional data from these fractions, especially in conjunction with independent geological information. In the present study, Principal Component Analysis (PCA) was applied to the GRH and SFH data for 171 oil samples from the Williston Basin. These oils were previously classified using polycyclic terpane and sterane biomarker traits. Our results indicate that only Family A oils can be uniquely classified using PCA. Families B, C and D oils show GRH and SFH characteristic compositions consistent with biomarker-defined families, but these characteristics are insufficient for independent classification. However, the PCA analyses of the GRH and SFH compositional traits proves to be a useful technique in recognizing the effect of mixing of oils derived from different sources. (author)

Pasadakis, N. [Technical University of Crete (Greece). Mineral Resources Engineering Dept.; Obermajer, M.; Osadetz, K.G. [Geological Survey of Canada, Calgary (Canada)

2004-04-01

 
 
 
 
21

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1995-09-01

22

Apatite fission-track dating of two crater structures in the Canadian Williston Basin  

International Nuclear Information System (INIS)

The High Rock Lake and Lake St. Martin structures, on the northeastern flank of the Williston Basin in Manitoba, are circular craters commonly thought to be astroblemes. Apatite fission-track (FT) ages from basement rocks in the two structures are markedly younger than those previously derived in the region. Constraints from regional geohistory combined with forward modelling of apatite FT data indicate the following: 1. At High Rock Lake, apatites in a weakly foliated granite and a brecciated and metasomatised granite from the uplifted southwestern crater rim, were totally, or nearly totally, annealed in the range of ?435 ± 10 Ma. This range is interpreted as dating the time of cratering and is in excellent agreement with stratigraphic evidence which constrains the event as Late Ordovician to Mid-Silurian; 2. At Lake St. Martin, apatite from the central basement uplift was totally annealed in Late Triassic-Early Jurassic time in the range ?208 ± 14 Ma. This range is concordant with a previous Rb/Sr isotope estimate of 219 ± 32 Ma for the impact event. The crater rim at Lake St. Martin records an older apatite FT age which is attributed to the partial annealing effect (temperatures of ?125-130 deg C) from the same impact event; and 3. The resetting of apatite FT clocks within the basement rocks by two discrete Phanerozoic cratering events provides a unique opportunity to study the post cratering thermal history of the region. At High Rock Lake and Lake St. Martin samples achieved maximum paleotemperatures (?60-70 deg C) during the Eocene. This temperature range is in good agreement with data independently attained from organic maturity indicators elsewhere in the northeastern Williston Basin area. (author). 44 refs., 2 tabs., 6 figs.

1995-01-01

23

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

Energy Technology Data Exchange (ETDEWEB)

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

Hendricks, M.L.

1988-07-01

24

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1983-08-01

25

Fingerprinting formation waters using stable isotopes : applications to petroleum exploration and production in the Williston Basin  

Energy Technology Data Exchange (ETDEWEB)

A variety of water chemical techniques have historically been used to determine if the fluid recovered during well-testing is pure formation water or contaminated with drilling fluid. However, standard chemical fingerprinting techniques can be problematic or ambiguous, and therefore, a new fingerprinting technique using stable isotopes of hydrogen, oxygen and strontium and the trace element bromine in formation waters has been developed that overcomes many of the problems associated with previous methods. This presentation discussed this new fingerprinting technique. The presentation provided an introduction to stable isotopes; a discussion of measurement and nomenclature of isotopes; and, information on industry applications and fingerprinting methodology. Water fingerprinting examples from the Williston Basin were also presented along with case studies of the Lignite Field in North Dakota and the Pinto Field in Saskatchewan. The presentation also addressed some of the most common sampling and analytical problems and pitfalls. It was concluded that stable isotopes are reliable natural tracers, without requiring injection and without danger of radioactive contamination. tabs., figs.

Arkadakskiy, S.V.; Rostron, B.J. [Isobrine Solutions Inc., Edmonton, AB (Canada); Jensen, G.K. [Alberta Univ., Edmonton, AB (Canada)

2007-07-01

26

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

Energy Technology Data Exchange (ETDEWEB)

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

Carrell, L.A.; Nautiyal, C.

1995-05-01

27

Stratigraphy and depositional environments of Fox Hills Formation in Williston basin  

Energy Technology Data Exchange (ETDEWEB)

The Fox Hills Formation (Maestrichtian), representing part of a regressive wedge deposited during the withdrawal of the sea from the Western Interior at the close of the Cretaceous, consists of marginal marine strata transitional between the offshore deposits of the underlying Pierre Shale and the terrestrial deltaic and coastal deposits of the overlying Hell Creek Formation. An investigation of outcrops of the Fox Hills Formation along the western and southern flanks of the Williston basin and study of over 300 oil and gas well logs from the central part of the basin indicate that the formation can be divided both stratigraphically and areally. Stratigraphically, the Fox Hills can be divided into lower and upper sequences; the lower includes the Trail City and Timber Lake Members, and the upper sequence includes the Colgate Member in the west and the Iron Lightning and Linton Members in the east. Areally, the formation can be divided into a northeastern and western part, where the strata are 30-45 m thick and are dominated by the lower sequence, and into a southeastern area where both the lower and upper sequences are well developed in a section 80-130 m thick. Typically, the lower Fox Hills consists of upward-coarsening shoreface or delta-front sequences containing hummocky bedding and a limited suite of trace fossils, most notably Ophiomorpha. In the southeast, however, these strata are dominated by bar complexes, oriented northeast-southwest, composed of cross-bedded medium to very fine-grained sand with abundant trace and body fossils. The upper Fox Hills represents a variety of shoreface, deltaic, and channel environments. The strata of the Fox Hills Formation exhibit facies similar to those reported for Upper Cretaceous gas reservoirs in the northern Great Plains.

Daly, D.J.

1988-07-01

28

Stratigraphy and depositional environments of Fox Hills Formation (Late Cretaceous), Williston basin  

Energy Technology Data Exchange (ETDEWEB)

The Fox Hills Formation (Late Cretaceous, Maestrichtian) was investigated where it crops out along the southern flank of the Williston basin and in the subsurface over the central portion of the basin, using 300 well logs. The formation is conformable and gradational with the underlying Pierre formation and can be either conformable or unconformable with the overlying Hell Creek Formation. The Fox Hills Formation is younger, thicker, and stratigraphically more complex to the east and is comprised of marginal marine sediments deposited during the final Cretaceous regression. To the west, the Fox Hills Formation is an upward-coarsening unit generally 30 to 45 m thick and usually contains three members: from the base, Trail City, Timber Lake, and Colgate. The lower Fox Hills (Trail City, Timber Lake) is generally dominated by hummocky bedding and contains a variety of trace fossils, most notably Ophiomorpha. The upper Fox Hills (Colgate), where present, is characterized by cross-bedding. To the east, including the type area, the section is generally 80 to 100 m thick and contains four members: from the base, Trail City, Timber Lake, Iron Lightning (Colgate and Bullhead lithofacies), and Linton. In contrast to the section in the west, this section is as much as three times thicker, contains abundant body fossils, generally lacks hummocky bedding, and contains the Bullhead and Linton strata. In the west, the strata represent lower shoreface deposits, predominantly of storm origin (lower Fox Hills), overlain by upper shoreface and fluvial deposits (upper Fox Hills). In the east, the lower Fox Hills contains deposits of the lower shoreface (Trail City) and a barrier bar complex (Timber Lake), overlain by the deltaic deposits of the upper Fox Hills (Iron Lightning, Linton).

Daly, D.J.

1986-08-01

29

Dickinson field lodgepole reservoir: Significance of this Waulsortian-type mound to exploration in the Williston Basin  

Energy Technology Data Exchange (ETDEWEB)

Conoco`s No. 74 Dickinson State well, a deep test in Dickinson Field, Stark County, North Dakota, was completed in early 1993 capable of producing over 2,000 BOPD. It represents the first commercial oil production from the Lower Mississippian Lodgepole Formation in the U.S. portion of the Williston Basin. Three additional oil producers have now been completed and this Lodgepole discovery is fully developed. The producing reservoir, at depths of 9,700 to 10,000 ft, is a Waulsortian-type mound approximately 300 ft thick with a characteristic faunal assemblage of bryozoans and crinoids. The mound has an areal extent of slightly more than 1 square mile. Similar Waulsortian-type mounds have been recognized in rocks of Paleozoic age around the world, but have only been reported in the Williston Basin during the past decade. Such mounds are shallow to deep water deposits, tend to develop over structurally or topographically-positive areas, and may form by algal or by current action in conjunction with baffling action caused by bryozoans. The prolific nature of the Conoco discovery, plus several more-recent excellent mound discoveries in this same area, have caused renewed drilling and leasing activity. These events have also encouraged a review of existing seismic data, the shooting of new 3-D seismic programs and re-analysis of wells previously drilled through the Lodgepole Formation for evidence of similar mounds elsewhere in the basin.

Johnson, M.S. [Rocky Mountain Association of Geologists, Denver, CO (United States)

1995-07-01

30

Assessment of undiscovered resources in petroleum plays: U.S. portion of Williston Basin and north-central Montana  

Energy Technology Data Exchange (ETDEWEB)

This assessment of conventional and unconventional petroleum resources is based on analysis of confirmed and hypothetical plays, using field-size distributions, discovery process models, and statistical estimation procedures that yield probabilistic estimates for undiscovered accumulations. For the U.S. portion of the Williston Basin, more than 400 accumulations greater than 6 BCF or 1 MMBO ultimate recoverable production has been discovered as of 1993. The National Petroleum Assessment listed six confirmed or hypothetical conventional plays, and four continuous-type unconventional plays. This portion contains an estimated mean value of 650 MMBO and 1.69 TCFG from undiscovered resources in conventional plays. For the North-Central Montana portion of the Basin, more than 50 accumulations greater than 6 BCF or 1 MMBO ultimate recoverable production have been discovered as of 1993. It contains an estimated mean value of 270 MMBO and 840 BCFG from undiscovered resources in conventional plays. The whole Williston Basin contains an estimated mean value of 167.4 MMBO and 43.4 TCFG from unconventional oil and gas plays. 63 refs., 8 figs., 2 tabs.

Dyman, T.S.; Peterson, J.A.; Schmoker, J.W.; Spencer, C.W.; Rice, D.D.; Porter, K.W.; Lopez, D.A.; Heck, T.J.; Beeman, W.R.

1995-12-31

31

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1998-07-01

32

Early and later diagenetic alteration of Ordovician Red River carbonates, Tioga Deep field, Williston basin, North Dakota  

Energy Technology Data Exchange (ETDEWEB)

The Ordovician Red River Formation in the Williston basin is generally subdivided into three restrictive-upward cycles referred to as 'A,' 'B,' and 'C' zones in descending order. Most Red River production in western North Dakota and eastern Montana comes from dolomitized burrowed and laminated members of the C-cycle. Four cores taken by Amerada Hess Corporation within the Tioga Deep field, Williams and Montrail Counties, North Dakota, were studied in detail to establish depositional and diagenetic controls on porosity distribution within the Red River. Dolomitized portions of the Red River C member are genetically related to downward-descending Mg-rich brines derived from hypersaline basin waters depleted of their sulfate content throught attendant precipitation of gypsum. Calcite associated with this early dolomitization phase occupied intercrystalline positions between dolomite rhombs. Following burial, limestones tended to chemically compact through pressure solution, whereas late stage fractures were localized in the more brittle dolomitic portions of the Red River. These fractures served as conduits for late stage leaching fluids, possibly associated with hydrocarbon generation, that enhanced porosity in the dolomites through the removal of associated calcite. Late-stage leaching is reflected in 'overly porous' dolomite haloes around cemented burrow centers and highly porous dolomite seams along stylolitic contacts. Previous models proposed to explain porosity distribution within Red River reservoirs should be modified to include the overprint of deep diagenetic effects.

Perkins, R.D. (Duke Univ., Durham, NC (United States))

1991-03-01

33

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1995-12-31

34

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1998-07-01

35

Williston hunt goes on despite slowdown  

Energy Technology Data Exchange (ETDEWEB)

Despite a decline of nearly 24% in reported well completions in the Williston basin last year, exploratory interest is still very much alive, expecially on the far west side of the international region. Petroleum Information reports that completions in the basin dropped from 1,127 to 860 last year. There were several important discoveries made in the basin during the year, and the current slate calls for some more very soon. Basin exploration interest centers on the province's west side, mostly in Daniels and Valley counties, Mont. But there continues to be development work in North Dakota, hugging the Missouri River near Williston where McKenzie County, at the basin's center, ranked eighth in the region with 155 reported well completions last year, according to the Denver publication.

McCaslin, J.C.

1986-04-07

36

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1993-12-01

37

Input-form data for the U.S. Geological Survey assessment of the Devonian and Mississippian Bakken and Devonian Three Forks Formations of the U.S. Williston Basin Province, 2013  

Science.gov (United States)

In 2013, the U.S. Geological Survey assessed the technically recoverable oil and gas resources of the Bakken and Three Forks Formations of the U.S. portion of the Williston Basin. The Bakken and Three Forks Formations were assessed as continuous and hypothetical conventional oil accumulations using a methodology similar to that used in the assessment of other continuous- and conventional-type assessment units throughout the United States. The purpose of this report is to provide supplemental documentation and information used in the Bakken-Three Forks assessment.

U.S. Geological Survey Bakken-Three Forks Assessment Team; Gaswirth, Stephanie B.; Marra, Kristen R.; Cook, Troy A.; Charpentier, Ronald R.; Gautier, Donald L.; Higley, Debra K.; Klett, Timothy R.; Lewan, Michael D.; Lillis, Paul G.; Schenk, Christopher J.; Tennyson, Marilyn E.; Whidden, Katherine J.

2013-01-01

38

Magnetostratigraphy and Magnetic Mineralogy of the Ludlow Member of the Fort Union Formation (Lower Paleocene) of the Williston Basin in North Dakota  

Science.gov (United States)

A continuous succession of Cretaceous through lowermost Eocene terrestrial sediments contains a nearly complete Paleocene record, in the Little Missouri River Valley of North Dakota, USA. We aim to calibrate the rates of post-Cretaceous ecological recovery from mass extinction, by determining a detailed chronostratigraphy of plant and mammal fossils in the basin. Using the Cretaceous-Paleogene (K-T) boundary as the basal datum, we have constructed a ca.300 meter composite section of the Upper Cretaceous Hell Creek Formation and the Lower Paleocene Ludlow Member of the Fort Union Formation. We analyzed paleomagnetic samples from 12 stratigraphic sections using a combined low-AF and thermal demagnetization strategy. Instability of magnetization above 200 °C has been reported in previous studies, which we reproduced when heating in air; however, when the samples were heated in nitrogen the stability field extended to well above 300 °C. The analyzed samples demonstrate a series of geomagnetic reversals that can be correlated from C29n through C27r of the Geomagnetic Polarity Time Scale (GPTS). Bulk susceptibility vs. temperature studies on sandstone, siltstone, and carbonaceous shale indicate predominately irreversible curves suggesting titanomaghemite as the magnetic carrier in the Ludlow Member sediments. IRM acquisition in our samples consistently shows non-saturation above 100 mT indicating an additional anti-ferromagnetic component, most likely goethite. The dominant iron oxide in these samples, titanomaghemite, was generated either during weathering of the source terrain during Laramide uplift, or weathered in-situ prior to diagenesis, or during alteration after burial. We infer that the magnetization of the samples is primary because the polarity direction is consistent with that of the Paleocene of North America and the reversal stratigraphy from this section corresponds to the GPTS with reasonable sedimentation rates. Our results imply a temporal restriction of the Puercan North American land mammal age subzones Pu1 and Pu2 in the Williston Basin from ~1 Myr, as previously considered, to ~250 kyr, which suggests that post-extinction mammal speciation occurred more rapidly then previously supposed.

Peppe, D. J.; Evans, D. A.

2006-12-01

39

Lessons to be learned from the Williston Wildcatters Oil Corporation (`Williston`) case; CD-ROM ed.  

Energy Technology Data Exchange (ETDEWEB)

The chronology and the final outcome of the Herc Oil Corporation deal was described. A creditor (Herc) applied for permission to pursue a creditor-driven plan of arrangement and extend the stay of proceedings of an insolvent oil and gas company (Williston Wildcatters Oil Corp). The plan put forth by Herc was a proposal to acquire all of the assets from the Trustee in return for assuming all of the secured liabilities and paying the amount necessary to satisfy the preferred claims. Unsecured creditors, who would otherwise receive nothing, will receive 49 per cent of the shares of the acquiring company in satisfaction of their claims.

Nelson, R.R. [Deloitte and Touche, Guelph, ON (Canada)

1996-04-01

40

Lessons to be learned from the Williston Wildcatters Oil Corporation ('Williston') case  

International Nuclear Information System (INIS)

The chronology and the final outcome of the Herc Oil Corporation deal was described. A creditor (Herc) applied for permission to pursue a creditor-driven plan of arrangement and extend the stay of proceedings of an insolvent oil and gas company (Williston Wildcatters Oil Corp). The plan put forth by Herc was a proposal to acquire all of the assets from the Trustee in return for assuming all of the secured liabilities and paying the amount necessary to satisfy the preferred claims. Unsecured creditors, who would otherwise receive nothing, will receive 49 per cent of the shares of the acquiring company in satisfaction of their claims

1996-01-01

 
 
 
 
41

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

International Nuclear Information System (INIS)

[en] 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 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)

2004-01-01

42

Tritium concentrations in the Yukon River Basin and their implications  

International Nuclear Information System (INIS)

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

43

Implications of Paralia sulcata abundance in Scottish isolation basins  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Diatom assemblages from eight basins of northwest Scotland, isolated from the sea during the Late Devensian and Holocene, show Paralia sulcata abundant towards the ingression and isolation contacts of the sedimentary sequences. Across the contacts, Paralia sulcata is commonly replaced by, or associa...

Zong, Y

44

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).

1988-01-01

45

Basinwide fold evolution and geometric development of cratonic - foreland basin interaction  

Energy Technology Data Exchange (ETDEWEB)

Latest results of the Williston Basin Project incorporate a north-south regional seismic line, which is crossing the deepest part of the Williston Basin from Saskatchewan to South Dakota. The integration of this new profile to the two, existing east-west regional seismic sections, gives a quasi-3D image of the basin. The combined seismic data illustrate alternating extensive and compressive phases during basin development, marked by basinwide circular and radial folds. This alternating pattern of basin subsidence is the very nature of crotonic basin evolution. The structural necessity for compressive phases during crotonic basin subsidence, is shown in a regional scale interpretation that has undergone an Earth-curvature correction. The geometrical evolution of the neighboring foreland basin is also interpreted from data that has been corrected with the Earth-curvature function. It shows that basinwide folds sub-parallel and perpendicular to the longitudinal axis of the basin are analogous to the circular and radial folds of the crotonic basins. These folds, in the foreland belt, are less pronounced because larger scale structural elements can overprint them. Where the crotonic and foreland basins overlap, a complex, deformed zone is present, and contains late stage volcanism, in this area. The geometry of the Williston Basin can be modeled by the Sloss-type [open quote]inverted Gaussian function[close quote] that is modified by the periodic westward tilting of the basin and the Earth-curvature function.

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

1996-01-01

46

Basinwide fold evolution and geometric development of cratonic - foreland basin interaction  

Energy Technology Data Exchange (ETDEWEB)

Latest results of the Williston Basin Project incorporate a north-south regional seismic line, which is crossing the deepest part of the Williston Basin from Saskatchewan to South Dakota. The integration of this new profile to the two, existing east-west regional seismic sections, gives a quasi-3D image of the basin. The combined seismic data illustrate alternating extensive and compressive phases during basin development, marked by basinwide circular and radial folds. This alternating pattern of basin subsidence is the very nature of crotonic basin evolution. The structural necessity for compressive phases during crotonic basin subsidence, is shown in a regional scale interpretation that has undergone an Earth-curvature correction. The geometrical evolution of the neighboring foreland basin is also interpreted from data that has been corrected with the Earth-curvature function. It shows that basinwide folds sub-parallel and perpendicular to the longitudinal axis of the basin are analogous to the circular and radial folds of the crotonic basins. These folds, in the foreland belt, are less pronounced because larger scale structural elements can overprint them. Where the crotonic and foreland basins overlap, a complex, deformed zone is present, and contains late stage volcanism, in this area. The geometry of the Williston Basin can be modeled by the Sloss-type {open_quote}inverted Gaussian function{close_quote} that is modified by the periodic westward tilting of the basin and the Earth-curvature function.

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

1996-12-31

47

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

Directory of Open Access Journals (Sweden)

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

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

2012-01-01

48

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

Scientific Electronic Library Online (English)

Full Text Available 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 setting reflecting glacial marine through deltaic to fluvial and aeolian desert conditions. The contact between the Ecca and Beaufort Groups (at the top of the Waterford Formation (more) 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.

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

2012-01-01

49

Williston Reservoir: Site preparation and post-flood cleanup  

International Nuclear Information System (INIS)

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

1990-01-01

50

Dust control option for Williston Reservoir: preliminary recommendations  

Energy Technology Data Exchange (ETDEWEB)

The physical conditions which contribute to the dust problem at British Columbia`s largest reservoir, were studied. The Williston Reservoir covers 180,000 hectares along the Rocky Mountain trench. Dust storms have occurred from wind erosion of large areas, causing a hazard for air navigation and problems for the aboriginal village of Tsay Keh. Potential dust source areas were identified, and an inventory was taken of the native plants in the drawdown zone. The use of vegetation as a possible reclamation method to control wind erosion was investigated. 24 soil samples were collected and analyzed for pH, total N, C, P, and K. The results of particle size analysis showed that the establishment of 30 per cent vegetation cover could reduce soil erosion by 80 per cent. Increasing the cover to 60 per cent would decrease the soil loss by 95 percent. 11 refs., 6 tabs., 1 fig.

Arocena, J.M.; Young, J.P.; Baker, D. [University of Northern British Columbia, Prince George, BC (Canada)

1996-06-01

51

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

Science.gov (United States)

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

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

2013-07-01

52

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

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

2013-01-01

53

Definition of basin phases in the Petrel Sub-basin (Australia): Implications for the development of Palaeozoic petroleum systems  

Energy Technology Data Exchange (ETDEWEB)

An study of the Petrel Sub-basin (Bonaparte Basin) on Australia`s northwest margin has identified seven main phases of basin development spanning the Early Cambrian to Tertiary. Each phase was initiated and terminated by distinct, primarily tectonic events that have controlled the structural and stratigraphic evolution of the basin and the development of petroleum systems. These phases include periods of major extension (Early Cambrian, Middle Devonian to early Carboniferous) and compression (Early Devonian, mid-Triassic), as well as rapid and slow subsidence phases in the Early to Late Carboniferous and Late Carboniferous to Triassic, respectively. Basin inversion in the mid-Triassic has been critical in controlling the development of broad anticlinal features that presently reservoir the large, but as yet undeveloped gas/condensate fields Petrel and Tern. An earlier period of minor compression during the late Carboniferous initiated limited movement of Paleozoic salt within the deeper basin, forming salt-cored, low amplitude anticlines in the predominantly carbonate Tanmurra Formation, a play which remains untested. In the southern Petrel Sub-basin, early phases of hydrocarbon generation and fluid migration associated with salt movement are poorly understood. Preliminary results of geochemical studies indicate that there are at least two oil families in Devonian and Carboniferous reservoirs. This suggests multiple source intervals within the deeper flanks of the basin, thus the understanding of sedimentation during early basin phases may be critical in evaluating petroleum systems.

Blevin, J.E.; Colwell, J.B.; Kennard, J.M. [Australian Geological Survey Organisation (AGSO), Canberra (Australia)

1996-12-31

54

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

55

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1995-08-01

56

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-04-01

57

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

International Nuclear Information System (INIS)

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

1999-01-01

58

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1990-05-01

59

Mesozoic stratigraphy of Canadian Arctic archipelago and implications for opening of Amerasian basin  

Energy Technology Data Exchange (ETDEWEB)

Mesozoic strata in the Canadian Arctic archipelago occur mainly in the Sverdrup basin where the succession is up to 9 km thick. The strata consist of alternating sandstone-dominant units and argillaceous intervals and record 25 regional transgressions and regressions. These resulted from the interplay of sedimentation, tectonics, and eustatic sea level changes. Subaerial unconformities occur on the basin margins and disappear basinward. Most of these unconformities are interpreted to be the product of eustatic sea level fall on the basis of correlation with global sea level charts. However, unconformities of latest Aalenian, late Callovian, Hauterivian, and Coniacian ages are interpreted to be related to tectonic activity and the formation of the Amerasian basin. Normal faulting and basic dike and sill intrusion occurred in the Sverdrup basin from Middle Jurassic to early Late Cretaceous. The latest Aalenian and late Callovian unconformities probably reflect early rifting events. Hauterivian uplift was widespread and coincides with the final phase of rifting and initiation of sea-floor spreading in the Amerasian basin. Marine onlap across the breakup unconformity began in Barremian time and by Albian much of the Arctic archipelago had been transgressed. Basalt flows are intercalated with Barremian to Turonian strata in the northeastern Sverdrup basin and represent the cratonward extension of the Alpha-Mendeleyev volcanic ridge, which was active during the opening of the Amerasian basin. Coniacian uplift coincided with the cessation of volcanism in the Sverdrup basin and of sea-floor spreading in the ocean basin to the north.

Embry, A.F.

1985-02-01

60

Corrosion and pyrophoricity of ZPPR fuel plates: Implications for basin storage  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the results of recent experimentation and analysis of the pyrophoric behavior of corroded Zero Power Physics Reactor (ZPPR) HEU fuel plates and the implications of these results for the handling, drying, and passivation of uranium metal fuels stored in water basins. The ZPPR plates were originally clad in 1980; crevice corrosion of the uranium metal in a dry storage environment has occurred due to the use of porous cladding end plugs. The extensive corrosion has resulted in bulging and, in some cases, breaching of the cladding over a 15 year storage period. Processing of the plates has been initiated to recover the highly enriched uranium metal and remove the storage vulnerability identified with the corroded plates, which have been shown to contain significant quantities of the pyrophoric compound uranium hydride (UH{sub 3}). Experiments were undertaken to determine effective passivation techniques for the corrosion product; analysis and modeling was performed to determine whether heat generated by rapid hydride re-oxidation could ignite the underlying metal plates. The results of the initial passivation experiment showed that simple exposure of the hydride-containing corrosion product to an Ar-3 vol.% O{sub 2} environment was insufficient to fully passivate the hydride--flare-up of the product occurred during subsequent vigorous handling in air. A second experiment demonstrated that corrosion product was fully stable following grinding of the product to a fine powder in the Ar-3 vol.% O{sub 2} atmosphere. Numerical modeling of a corroded plate indicated that ignition of the plate due to the heat from hydride re-oxidation was likely if hydride fractions in the corrosion product exceeded 30%.

Totemeier, T.C.; Hayes, S.L.; Pahl, R.G.; Crawford, D.C.

1997-04-01

 
 
 
 
61

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

Science.gov (United States)

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

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

2009-12-01

62

Tectonic evaluation of Big Horn basin using Landsat imagery - implications of structural style and hydrocarbon exploration  

Energy Technology Data Exchange (ETDEWEB)

Landsat imagery reveals that the Big Horn basin can be divided into three regions. This aids understanding the kinematic history and defining exploration fairways and leads. Linear northwest-trending folds southwest of the Bighorn Mountains characterize the northeast portion of the basin. South of the Tensleep fault, the basis is characterized by west-northwest-trending curves folds that become more curved to the west. West of Elk Basin thrust, north-northwest-trending curves folds characterize the basin. North of the Pat O'Hara thrust, these folds bend west into the Nye-Bowler structure. To the south they bend east and merge with the southern portion of the basin. These differences probably reflect reorientation of principal horizontal stress from east-northeast during the early phase to northeast during the late phase of the Laramide orogeny. The linearity of structures comprising the northeast portion of the basin suggests they were subjected to predominantly direct compression throughout the orogeny. The strong curvature of structures elsewhere suggests that late Laramide compression overprinted early Laramide deformation. West-northwest-trending structures in the south were initially left-slip faults and subsequently became thrusts. North-northwest-trending structures in the west were originally thrusts and subsequently became right-slip compressional faults. In the western and southern portions of the basin there are several features, previously unrecognized as overprinted structures, consisting of curved folds riding on thrusts that crosscut one another, revealing the sequence of overprinting.

Merin, I.S.; Everett, J.R.

1987-05-01

63

Morphology of the Yucatan Basin: implications as to its origin and age  

Energy Technology Data Exchange (ETDEWEB)

Basement morphology and sediment distribution with the Yucatan Basin, Caribbean Sea, suggest that it formed as a rift basin. The age of rifting, as determined from heat flow and subsidence measurements is Early Tertiary. Analyses of multichannel and single channel seismic profiles crossing the basin show that it is underlain by a SW-NE trending, rectangular deep which extends the length of the basin and which is flanked to the NW and SE by topographic rises cut by SW-NE trending grabens. Seismic refraction and reflection and gravity profiles all suggest that the deep is floored with oceanic crust. Both deep and rise are transected by several NW-SE trending lineaments interpreted to be traces of transform faults. The rises are covered with acoustically layered sediments deposited during graben formation and overlain with thin, acoustically transparent sediments which postdate faulting. The deep is filled with flat lying, undeformed acoustically layered sediments which onlap all basement structure. Lack of a precise rifting age precludes establishing the exact relationship of basin opening to he Antilles-Cuban collision. The nature of the basin, its approximate age, and the tectonics of the region all suggest, however, the basin formed after the Cuban collision as Caribbean plate motion readjusted from northward to eastward.

Rosencrantz, E.

1985-01-01

64

Biotic response to late Quaternary rapid climate switches in Santa Barbara Basin: Ecological and evolutionary implications  

International Nuclear Information System (INIS)

Benthic foraminiferal assemblages from Santa Barbara Basin exhibit major faunal and ecological switches associated with late Quaternary millennial- to decadal-scale global climate oscillations. Repeated turnovers of entire faunas occurred rapidly (

1999-01-01

65

Soil gas 222Rn in sedimentary basins in Central Italy: its implications in radiation protection zoning  

International Nuclear Information System (INIS)

Soil gas investigations for tectonic prospecting in clayey basins highlighted, over tectonic discontinuities, the occurrence of high Rn concentrations induced by a vertical and rapid migration of deep seated gases through faulted rocks. (author).

1993-07-02

66

Tectonic implications of Paleocene-Eocene Foreland Basin, Lake Maracaibo, Venezuela  

Energy Technology Data Exchange (ETDEWEB)

A compilation of industry geological and geophysical data indicates that Paleocene-Eocene clastic sedimentation in the Maracaibo basin records the first manifestation of Cenozoic foreland basin tectonics in northern South America. Isopach maps based on industry seismic data and well logs suggest that the Maracaibo foreland basin formed a 100 to 200 km wide elongate trough along the northeastern edge of the present-day Lake Maracaibo. The basin is asymmetric with a deep (7 km) northeastern margin adjacent to an exposed southwest-verging thrust belt mapped by previous workers. Isopach mapping of seven seismic units within the Eocene suggest a nor-northwest to southeast migration of the depocenter from Paleocene to Middle Eocene time at a rate of 0.6 cm/year. A similar style of foreland basin has been previously identified over a distance of 1000 Km from western central Venezuela to Trinidad. Eocene to Pliocene ages of foreland basin sedimentation in these areas suggest time transgressive, oblique collision of the Caribbean plate along the northern margin of South America. Comparison of the age of deformation along both the northern and southern edges of the pro-Caribbean plate yield reasonable estimates for the rate of relative motion of this small plate relative to the larger America plates.

Lugo, J. (Lagoven S.A., Caracas (Venezuela)); Mann, P. (Univ. of Texas, Austin (United States))

1993-02-01

67

Assessing regional hydrology and water quality implications of large-scale biofuel feedstock production in the Upper Mississippi River Basin.  

UK PubMed Central (United Kingdom)

A recent U.S. Department of Energy study estimated that more than one billion tons of biofuel feedstock could be produced by 2030 in the United States from increased corn yield, and changes in agricultural and forest residue management and land uses. To understand the implications of such increased production on water resources and stream quality at regional and local scales, we have applied a watershed model for the Upper Mississippi River Basin, where most of the current and future crop/residue-based biofuel production is expected. The model simulates changes in water quality (soil erosion, nitrogen and phosphorus loadings in streams) and resources (soil-water content, evapotranspiration, and runoff) under projected biofuel production versus the 2006 baseline year and a business-as-usual scenario. The basin average results suggest that the projected feedstock production could change the rate of evapotranspiration in the UMRB by approximately +2%, soil-water content by about -2%, and discharge to streams by -5% from the baseline scenario. However, unlike the impacts on regional water availability, the projected feedstock production has a mixed effect on water quality, resulting in 12% and 45% increases in annual suspended sediment and total phosphorus loadings, respectively, but a 3% decrease in total nitrogen loading. These differences in water quantity and quality are statistically significant (p < 0.05). The basin responses are further analyzed at monthly time steps and finer spatial scales to evaluate underlying physical processes, which would be essential for future optimization of environmentally sustainable biofuel productions.

Demissie Y; Yan E; Wu M

2012-08-01

68

Association of the Purana basins and the middle Proterozoic mobile belts in peninsular India: implications on targeting uranium deposits  

International Nuclear Information System (INIS)

[en] The disparate Archaean Cratonic Nuclei of the Indian peninsular shield coalesced together through late Archaean - Palaeoproterozoic accretionary tectonic events. The subsequent Mesoproterozoic and Neoproterozoic sequences are preserved either in the Purana basins or in the middle Proterozoic mobile belts (MPMB). The latter contain deformed and metamorphosed supracrustal sequences; and can be ascribed to compressive tectonic regimes. The Purana basins on the other hand represent shallow marine, epicratonic, passive-margin sequences deposited in an extensional tectonic regime. Major deformational events and metamorphism of the MPMB are known to have taken place around 1600 ±200 Ma and 900 ± 100 Ma. These two periods coincide with the ages of initiation and major intrabasinal breaks in the growth of the Purana basins. The contemporary juxtapositioning of these two dissimilar tectonic regimes in peninsular India, is examined within the framework of the available data on them and the current models of Proterozoic tectonics. Its implications on uranium mineralization and possible regions for targeting exploration activities are discussed on this basis. (author). 112 refs., 4 figs

1995-01-01

69

Occurrence of pore-filling halite in carbonate rocks, Nesson Anticline, Williston basin, North Dakota  

Energy Technology Data Exchange (ETDEWEB)

Clear, colorless pore-filling halite of late diagenetic origin occurs locally in the Devonian Dawson Bay, Winnipegosis, and Ashern Formations, the Silurian Interlake Formation, and the Ordovician Red River Formation. The halite occludes a variety of pore types and individual pores are filled with single crystals or aggregates of only a few crystals. This halite is present in quantities ranging from a trace to approximately 12%. Cores from McGregor field, Williams County, show the Winnipegosis Formation consists of mixed-skeletal lime wackestones and mudstones. These contain vugs up to 4 in. (10 cm) in size, intraparticle pores, and shelter porosity within pelecypod shells, up to 4 in. (10 cm) in size, which are occluded with halite. Halite also fills common small discontinuous vertical fractures. The upper 200 ft (61 m) of the Interlake Formation locally exhibits the most striking occurrences of pore-filling halite. These dolostones consist predominantly of intraclast-peloid mudstones, wackestones, packstones, occasional grainstones, algal boundstones, and solution-collapse breccias containing vug, fenestral, interparticle, shelter, intercrystalline, moldic, channel, breccia, and fracture porosity types. All porosity types, except intercrystalline, can be halite filled. A rare occurrence of pore-filling halite exists in Red River cores from Blue Buttes field, McKenzie County, where a dolomitic, mixed-skeletal, lime mudstone and wackestone lithofacies contains vugs, discontinuous vertical fractures, and intraparticle porosity types occluded with halite. In most occurrences, the pore systems were noneffective prior to halite infilling and had no potential as hydrocarbon reservoirs. However, it has been demonstrated that halite plugging in the Interlake Formation has locally formed updip seals to hydrocarbon migration.

Bucher, E.J.

1988-07-01

70

Wabek and Plaza fields: Carbonate shoreline traps in the Williston basin of North Dakota  

Energy Technology Data Exchange (ETDEWEB)

Wabek and Plaza fields in Mountrail and Ware counties, North Dakota, will ultimately produce 8 million and 3 million bbl of oil, respectively, from reservoirs in the Sherwood and Bluell intervals of the Mississippian Mission Canyon Formation. Both fields produce from porous, oolitic, and pisolitic lime packstones and grainstones deposited as shoals along a low-energy shoreline. A facies change to impermeable dolomitic and salina/sabkha environments to the east provides the updip trap. The Sherwood at Wabek has more than 100 ft of oil column driven by solution gas and water influx. Effective porosity consists of interparticle, vuggy, and minor dolomitic intercrystalline porosity. Log porosities range from 6 to 26%, averaging about 10%, and net pay averages about 26 ft. One mile west of Wabek, Plaza field produces from the Bluell, stratigraphically overlying the Sherwood. Log porosities range from 6 to 16%, averaging about 9%. Net pay averages about 6 ft. An oil-water contact is not yet defined, but at least 120 ft of oil column are present. Regional depositional slope and local depositional topography were major controls on Mission Canyon shoreline trends and the development of reservoir facies. In the Wabek-Plaza complex, the position and trend of the Sherwood and Bluell shorelines can be related to structural trends indentified in the crystalline basement from aeromagnetic data. Locally, thickness variations in the underlying Mohall interval amplified relief on the Wabek-Plaza structure and influenced the deposition of shoreline reservoirs.

Sperr, T. (Presidio Oil Co., Denver, CO (United States)); Hendricks, M.L. (Hendricks and Associates, Inc., Denver, CO (United States)); Stancel, S.G.

1991-06-01

71

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

Energy Technology Data Exchange (ETDEWEB)

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

Pound, W.

1988-07-01

72

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

International Nuclear Information System (INIS)

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

2009-01-01

73

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

International Nuclear Information System (INIS)

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

1985-01-01

74

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

Directory of Open Access Journals (Sweden)

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

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

2011-01-01

75

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

Scientific Electronic Library Online (English)

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

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

2011-06-01

76

Distribution of oceanic versus transitional crust in deep Gulf of Mexico Basin - implications for early history  

Energy Technology Data Exchange (ETDEWEB)

Regional studies of seismic reflection and refraction data in the deep Gulf of Mexico basin outline in considerable detail the distribution of oceanic vs. transitional crust. Oceanic crust forms a narrow east-west belt up to 300 km wide across the deep Gulf. Most current models for early Gulf evolution suggest the belt was emplaced in the Late Jurassic following widespread deposition of salt on rifted and attenuated continental crust (transitional crust). The southern boundary is defined by a zone of prominent salt structures along the northern margin of the Sigsbee salt basin. The northern boundary is obscured below the Texas-Louisiana slope, but is inferred from the distribution of large vertical salt structures. The eastern boundary is clearly marked by onlap and pinch-out of thick Jurassic sedimentary sequences. This distribution is corroborated by regional magnetic and gravity data and total tectonic subsidence analysis, and provides constraints for early Gulf basin reconstructions. An appropriate reconstruction must account for plate motion accommodated by ocean crust formation and extension of continental crust. The data seem most consistent with a model in which the Yucatan block moved generally south and rotated somewhat counterclockwise. This reconstruction implies very little lateral displacement along transform faults between Yucatan and Florida during early basin history. This is supported by seismic stratigraphic studies and DSDP drilling in the southeastern Gulf.

Buffler, R.T.; Sawyer, D.S.

1985-02-01

77

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Most of the flow in the River Indus from its upper mountain basin is derived from melting snow and glaciers. Climatic variability and change of both precipitation and energy inputs will therefore affect rural livelihoods at both a local and a regional scale through effects on summer runoff in the Ri...

Dr Hayley Jane Fowler; D Archer

78

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Most of the flow in the River Indus from its upper mountain basin is derived from melting snow and glaciers. Climatic variability and change of both precipitation and energy inputs will, therefore, affect rural livelihoods at both a local and a regional scale through effects on summer runoff in the ...

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

79

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.

1990-01-01

80

Laramide tectonic evolution of San Juan sag, Colorado: Implications of Animas and Blanco basin formations  

Energy Technology Data Exchange (ETDEWEB)

The lower member of the Animas Formation (McDermott Member) is a volcaniclastic sequence derived from a north-northwest source (San Juan-La Plata area). It consists of purple andesitic debris flows, green fan-delta sandstones and mud rocks, and dark gray conglomerates with clast compositions indicating that the Precambrian core of the source uplift was exposed. The upper member is a sand-dominated alluvial plain sequence deposited by southwest-flowing braided streams. It includes green-gray-brown carbonaceous mudstones and pebbly sandstones containing clasts of mudstone, andesite, and detritus from Precambrian and Mesozoic sources in the Brazos-San Luis uplift to the east and northeast. by the end of Animas deposition, the San Juan sag (then a northeastern extension of the San Juan basin) was a broad, southwest-plunging synclinal downwarp bounded by hogback monoclines to the north and east. An erosional period followed Animas deposition; the greatest thickness of Animas was preserved along the axis of this synclinal feature. Bright-red sandy mudstones and yellow-gray pebbly sandstones and cobble conglomerates comprise the proximal alluvial-fan deposits of the Blanco Basin Formation. They unconformably overlie Precambrian through Paleocene rocks and clast compositions reflect these sources. Renewed uplift and segmentation of the Brazos-San Luis uplift resulted in the shedding of detritus southwestward into the San Juan sag and eastward into a narrow, asymmetrical, north-trending wrench basin within the uplift. Following Blanco Basin deposition, the last Laramide event is represented by the separation of the San Juan sag from the San Juan basin by uplift of the Archuleta anticlinorium.

Brister, B.S. (New Mexico Institute of Mining and Technology, Socorro (USA))

1989-09-01

 
 
 
 
81

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

82

The Botrychiopsis genus and its biostratigraphic implications in Southern Paraná Basin  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese O gênero Botrychiopsis tem sido considerado um elemento florístico importante das associações do intervalo Westphaliano/Artinskiano da Bacia do Paraná. O registro de formas relacionadas ao gênero Botrychiopsis, especificamente Botrychiopsis valida, em roof-shales na área de Quitéria, Formação Rio Bonito, no sul da Bacia do Paraná amplia o biocron do gênero, definindo uma hierarquia estratigráfica para as espécies Botrychiopsis plantiana e Botrychiopsis valid (more) a para esta bacia. A distribuição estratigráfica do gênero está condicionada a controle climático relacionado a um ciclo de deglaciação em estágio icehouse, com espectro de tolerância climática abrangente, desde condições climáticas do tipo frio até temperado/ quente. É proposto um novo zoneamento fitoestratigráfico para essa porção da bacia, incluindo uma Zona Botrychiopsis (Asseliano/Kunguriano) com duas sub-zonas Botrychiopsis plantiana (Asseliano/Artinskiano) e Botrychiopsis valida (topo do Artinskiano/Kunguriano). Abstract in english 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 (more) 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; Guerra-Sommer, Margot; Cazzulo-Klepzig, Miriam; Menegat, Rualdo

2003-12-01

83

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1995-12-31

84

Agricultural implications of reduced water supplies in the Green and Upper Yellowstone River Basins  

Energy Technology Data Exchange (ETDEWEB)

The growth of the energy sector in the energy-rich but water-restricted Western US has presented a potential conflict for water now used by the irrigated agricultural sector. This study measures the direct impacts on farm income and employment resulting from the transfer of water from agriculture to energy in two specific geographical areas - the Green and Upper Yellowstone River Basins. We used a linear programming model to evaluate the impacts of reduced water supplies. Through the use of regional multipliers, we expanded our analysis to include regional impacts. In the Green River Basin, we found that Duchesne and Uintah Counties, Utah, would experience the greatest economic impacts when agricultural water supplies were reduced by 50%. In the Upper Yellowstone River Basin, Treasure and Rosebud Counties, Montana, would experience the greatest total income and employment reductions when water supplies were reduced less than or equal to 40%. When these supplies were reduced by more than 40%, Stillwater, Carbon, Yellowstone, and Big Horn Counties, Montana, would experience the greatest reductions.

Lansford, R.R.; Roach, F.; Gollehon, N.R.; Creel, B.J.

1981-07-01

85

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; Solmaz Arzaghi; Mohammad Sahraeyan

2013-01-01

86

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; H.J. Fowler

2004-01-01

87

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

International Nuclear Information System (INIS)

[en] The Paleoproterozoic Thelon Basin, located on the border between Nunavut and the Northwest Territories of Canada, is a contemporaneous analog of the uranium-rich Paleoproterozoic Athabasca Basin in Canada. Early diagenesis resulted in precipitation of extensive hematite on the surfaces of detrital quartz grains throughout the Thelon Formation and minor hydroxy-phosphate in veins locally. Continued diagenesis then resulted in syntaxial quartz cementation of detrital quartz at 130 degrees C from fluids having ca. 17 wt.% equivalent NaCl, similar to the Athabasca Basin. Cementation of this type is most pronounced in fine-grained sequences in the Thelon Basin. A period of extensive desilicification during continued burial was followed by formation, at ca. 200 degrees C, of peak-diagenetic illite having Ar-Ar ages of ca. 1400-1690 Ma in the Thelon Formation. This illite was associated with fluids with ?l8O and ?D values of ca. 6%o and -50%o,respectively, similar to those during peak diagenesis of the Athabasca Basin. Although the timing, salinity, and isotopic composition of the peak-diagenetic fluids in the Thelon and Athabasca Basins are similar, the peak-diagenetic mineral assemblage in the Athabasca Formation is dickite and illite, with minor dravite and goyasite rather than simply illite. Consequently, the fluids at peak diagenesis, which in the Athabasca Basin are synchronous with formation of world-class unconformity-type uranium deposits, had 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)

2002-01-01

88

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1991-12-01

89

Agricultural implications of reduced water supplies in the Green and Upper Yellowstone River Basins  

Energy Technology Data Exchange (ETDEWEB)

The growth of the energy sector in the energy-rich but water-restricted Western US has presented a potential conflict with the irrigated agricultural sector. This study measures the direct impacts on farm income and employment resulting from the transfer of water from agriculture to energy in two specific geographical areas - the Green and Upper Yellowstone River Basins. We used a linear programming model to evaluate the impacts of reduced water supplies. Through the use of regional multipliers, we expanded our analysis to include regional impacts. Volume I provides the major analysis of these impacts. Volume II provides further technical data.

Lansford, R. R.; Roach, F.; Gollehon, N. R.; Creel, B. J.

1982-02-01

90

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

International Nuclear Information System (INIS)

[en] 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

1990-01-01

91

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

92

Geochemical characteristics of oil seepages from Dam Thi Nai, central Vietnam: implications for hydrocarbon exploration in the offshore Phu Khanh Basin  

Energy Technology Data Exchange (ETDEWEB)

Dam Thi Nai is a semi-enclosed embayment on the coast of central Vietnam, adjacent to the northern part of the offshore and largely unexplored Phu Khanh Basin. Seepages of oil have been known in Dam Thi Nai since the early part of the twentieth century. This paper presents organic geochemical data on a number of samples of seepage oil collected from Dam Thi Nai and discusses their implications for the prospectivity of the Phu Khanh Basin. The results indicate that the petroleum was generated from a Tertiary marine marl source rock. Seepage oils are found in varying degrees of biodegradation and modes of occurrence at different locations in the embayment. Thus, oil was observed to fill fractures in freshly quarried outcrops of Cretaceous granite, and also occurs in shallow pits dug in the beach sand and in shallow basins used for shrimp farming. The oils indicate active seepage from kitchen areas or leaking accumulations in the Phu Khanh Basin. Seismic data suggest the existence of both source rocks and kitchens, and indicate a possible migration route from the deep basin to the surface at the bay. A few samples show anomalous compositions, indicating the presence of two other oil types which have different sources. These occurrences cannot at present be explained. However, the results obtained are encouraging for future exploration in the Phu Khanh Basin. (Author)

Bojesen Koefoed, J.A.; Nielsen, L.H.; Nytoft, H.P.; Petersen, H.I. [Geological Survey of Denmark and Greenland, Copenhagen (Denmark); Dau, N.T.; Van Hien, L.; Duc, N.A.; Quy, N.H. [Vietnam Petroluem Inst., Hanoi (Vietnam)

2005-01-01

93

Implications of Mesozoic-Recent basin development in the western Inner Moray Firth, UK  

Energy Technology Data Exchange (ETDEWEB)

A new interpretation of a comprehensive seismic database, consisting of over 5000 km of seismic lines, contradicts the notion that strike-slip motion on the Great Glen Fault (GGF) was the dominant control on Mesozoic basin development in the Inner Moray Firth, UK. It is suggested that the GGF, which may have been active during Palaeozoic times, lay dormant during the Mesozoic and that normal fault systems, formed during two extensional events, were the dominant controls on Mesozoic basin evolution. The present expression of the GGF as a discrete, sub-vertical through-going fault attests to its subsequent activity as a divergent wrench structure as part of limited oblique-slip motion after the Early Cretaceous. It seems most likely that such movements occurred in the Tertiary and may have been contemporaneous with regional uplift of the Scottish Highlands during Palaeocene-Eocene (Thulean) events, in response to north-east Atlantic rifting or subsequent Oligo-Miocene (Alpine) tectonism. (author)

Underhill, J.R. (Edinburgh Univ. (United Kingdom). Grant Inst.)

1991-08-01

94

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.

95

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

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

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

2011-01-01

96

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

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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.

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

2009-01-01

97

Geochemical indicators of hydrogeologically isolated structures in the Danube Basin; implications for potential gas storage objects  

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Full Text Available One of the key conditions for underground gas storage (UGS) objects establishment is the presence of hydrogeologically isolated structures. These are mainly exhausted hydrocarbon deposits and aquifers in the Cenozoic fill and the basement of the Danube Basin. The geochemical indicators used to determine the aquifer isolation level of potential underground gas storage objects are based on the ratio of stagnant and dynamic water components. The most widely used indicator is the rHCO3/rCl molar ratio, assuming that the HCO3 - concentration represents the dynamic origin of dissolved rock material by meteoric water and that the Cl- concentration is the stagnant marine component. To distinguish these two components of the water in the aquifers the rHCO3/rCl indicator was combined with other parameters, such as rCl/rSO4 and rCl/rBr molar ratios. As for more aquifers of the Danube Basin contain higher amounts of carbon-dioxide we attempted to quantify the influence of the carbon dioxide on the water chemistry. The numerical model simulating rock-marine water interactions under different PCO2 temperature and ion-exchange conditions proved the rHCO3/rCl molar ratio increase caused higher carbon dioxide partial pressure for this purpose. Consequently under the conditions of higher partial carbon dioxide pressure the rHCO3/rCl ratio is indicating a lower isolation level of the structure. Taking in account signs of the higher carbon dioxide pressure based on the numerical model combined with the abovementioned geochemical indicators the most convenient aquifers for UGS establishment were identified within the Slovak part of the Danube Basin. These are located within Badenian sediments in the Trakovice and Sere? areas, due to the presence of hydrogeologically isolated structures buried at depth intervals of 800 to 1150 m below ground level. Other potential convertible aquifers are present in the Lower and Middle Badenian sediments in the Komjatice and Želiezovce Depressions, especially in the following localities: Modrany at 1145 to 1670 m below the surface, Vráble approximately up to 2110 m and Zlaté Moravce at 1364 to 1374 m below surface.

Tomáš Lánczos; Ján Mili?ka; Miroslav Pereszlényi

2011-01-01

98

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

Science.gov (United States)

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

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

2005-01-01

99

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

100

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

Science.gov (United States)

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

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

2012-11-01

 
 
 
 
101

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

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

Stojanovi? Ksenija; Životi? Dragana; Šajnovi? Aleksandra; Cvetkovi? Olga; Nytoft Peter Hans; Scheeder Georg

2012-01-01

102

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

Science.gov (United States)

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

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

1990-07-01

103

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1990-07-01

104

Sedimentologic and biostratigraphic implications for early Eocene lacustrine systems, eastern Great Basin, Nevada  

Energy Technology Data Exchange (ETDEWEB)

A multidisciplinary study integrating sedimentology, molluscan paleontology and paleoecology, structural and geologic mapping, and [sup 40]Ar/[sup 39]Ar dating of volcanic flows indicates the White Sage Formation north of the Deep Creek Range on the NV-UT border was deposited during the early Eocene in marginal-lacustrine, lacustrine, freshwater-marsh, and minor terrestrial settings. Sedimentary facies include wave-reworked, locally derived Paleozoic carbonate-clast basal conglomerates in contact with bedrock; carbonate tufa mounds; organic-rich mudstones; and laminated to medium-bedded carbonates. The wave-reworked conglomerate implies a broad lake with considerable fetch to generate large waves, but one with only small drainage basins with sharp relief to supply the locally-derived clasts. There is a striking lack of any fluvial, deltaic, or alluvial-fan deposits that would indicate development of substantial drainage areas. The large tufa mounds indicate a high-wave-energy shoaling environment with stable substrate and topography. The profusion of lacustrine carbonates indicates dominantly chemical- or biochemical-induced deposition in a carbonate-saturated lake. The aquatic molluscan fauna indicates shallow, quiet lacustrine conditions with emergent vegetation. The limpets inhabited areas of rooted aquatic vegetation, and the terrestrial gastropods indicate marshes adjacent to the lacustrine system. The molluscan assemblage constrains the age of the White Sage as early Eocene, indicating a lacustrine system equivalent to the Sheep Pass Formation and to outcrops near Illipah, NV that have similar facies and molluscan faunas and that also lack significant fluvial, deltaic, or alluvial fan deposits. The data are consistent with a model wherein the White Sage, Sheep Pass, and Illipah carbonates were deposited in a large lake superimposed on preexisting topography with low relief and little or no syndepositional extension.

Dubiel, R.F.; Potter, C.J.; Snee, L.W. (Geological Survey, Denver, CO (United States)); Good, S.C. (State Univ. Coll., Cortland, NY (United States))

1993-04-01

105

Cenozoic magmatism in the South China Basin: Decompression melting and implications of an enriched mantle source  

Energy Technology Data Exchange (ETDEWEB)

A widespread eposide of interplate volcanism followed the cessation of seafloor spreading in the South China Basin (SCB), affecting the South China Sea, and fringing areas of southern China and Indochina. Geochemical data for basalts from South China Sea islands and seamounts, Hainan Island, and Taiwan define an enriched (Dupal-like) mantle domain yielding oceanic island basalt (OIB) suites with {Delta}7/4Pb = 2-13, {Delta}8/4Pb = 45-73, {sup 87}Sr/{sup 86}Sr > {approximately}0.70325, Th/Ta > 2, and Th/Ba > 0.02. Opening of the SCB resulted from disaggregation of the South China block in response to the Indo-Eurasian collision, a process involving at least one seafloor spreading episode, terminated by collision of microcontinents with the Philippines and Borneo. The lack of precursive flood basalt suggests that active mantle upwelling was not involved and that melting was a passive effect of lithosphere stretching. However, while mantle decompression at ambient stretching factors ({approximately}1.7-2.5) appears to permit melting on the observed scale, the enriched source may preclude such a simple mantle dynamic. Three alternatives are considered: (1) passive melting of a mature metasomatised boundary layer, (2) active melting of thermally eroded subcontinental lithosphere (deep enrichment) or metasomatised boundary layer (shallow enrichment), and (3) relict diapirs of pre-SCB and/or Java trench subduction slabs (intermediate/deep enrichment). These models are evaluated in terms of chemical and isotopic mass balances associated with the generation and movement of small melt fractions in depleted, nondepleted, and enriched mantle.

Flower, M.F.J.; Kan Tu; Ming Zhang (Univ. of Illinois, Chicago (USA)); Guanghong Xie (Institute of Geochemistry, Guangzhou (China))

1990-06-01

106

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

107

Pre-monsoon aerosol characteristics over the Indo-Gangetic Basin: implications to climatic impact  

Energy Technology Data Exchange (ETDEWEB)

Sun/sky radiometer observations over the Indo- Gangetic Basin (IGB) region during pre-monsoon (from April-June 2009) have been processed to analyze various aerosol characteristics in the central and eastern IGB region, represented by Kanpur and Gandhi College, respectively, and their impacts on climate in terms of radiative forcing. Monthly mean aerosol optical depth (AOD at 500 nm) and corresponding Angstrom Exponent (AE at 440-870 nm, given within the brackets) was observed to be about 0.50 (0.49) and 0.51 (0.65) in April, 0.65 (0.74) and 0.67 (0.91) in May and 0.69 (0.45) and 0.77 (0.71) in June at Kanpur and Gandhi College, respectively. Results show a positive gradient in AOD and AE from central to eastern IGB region with the advancement of the pre-monsoon, which may be caused due to diverse geographical location of the stations having different meteorological conditions and emission sources. Relatively lower SSA was observed at the eastern IGB (0.89) than the central IGB (0.92) region during the period, which suggests relative dominance of absorbing aerosols at the eastern IGB as compared to central IGB region. The absorbing aerosol optical properties over the station suggest that the atmospheric absorption over central IGB region is mainly due to dominance of coarse-mode dust particles; however, absorption over eastern IGB region is mainly due to dominance of fine-particle pollution. The derived properties from sun/sky radiometer during pre-monsoon period are used in a radiative-transfer model to estimate aerosol radiative forcing at the top-of-the atmosphere (TOA) and at the surface over the IGB region. Relatively large TOA and surface cooling was observed at the eastern IGB as compared to the central IGB region. This translates into large heating of the atmosphere ranging from 0.45 to 0.55Kday{sup -1} at Kanpur and from 0.45 to 0.59Kday{sup -1} at Gandhi College. (orig.)

Srivastava, A.K.; Tiwari, S.; Bisht, D.S. [Indian Institute of Tropical Meteorology, New Delhi (India); Devara, P.C.S. [Indian Institute of Tropical Meteorology, Pune (India); Srivastava, Manoj K. [Banaras Hindu Univ., Varanasi (India). Dept. of Geophysics; Tripathi, S.N. [Indian Institute of Technology, Kanpur (India). Dept. of Civil Engineering; Goloub, P. [Lille Univ./CNRS, Villeneuve d' Ascq (France). Lab. d' Optique Atmospherique; Holben, B.N. [NASA Goddard Space Flight Center, Greenbelt, MD (United States)

2011-07-01

108

Pre-monsoon aerosol characteristics over the Indo-Gangetic Basin: implications to climatic impact  

Directory of Open Access Journals (Sweden)

Full Text Available Sun/sky radiometer observations over the Indo-Gangetic Basin (IGB) region during pre-monsoon (from April–June 2009) have been processed to analyze various aerosol characteristics in the central and eastern IGB region, represented by Kanpur and Gandhi College, respectively, and their impacts on climate in terms of radiative forcing. Monthly mean aerosol optical depth (AOD at 500 nm) and corresponding Angstrom Exponent (AE at 440–870 nm, given within the brackets) was observed to be about 0.50 (0.49) and 0.51 (0.65) in April, 0.65 (0.74) and 0.67 (0.91) in May and 0.69 (0.45) and 0.77 (0.71) in June at Kanpur and Gandhi College, respectively. Results show a positive gradient in AOD and AE from central to eastern IGB region with the advancement of the pre-monsoon, which may be caused due to diverse geographical location of the stations having different meteorological conditions and emission sources. Relatively lower SSA was observed at the eastern IGB (0.89) than the central IGB (0.92) region during the period, which suggests relative dominance of absorbing aerosols at the eastern IGB as compared to central IGB region. The absorbing aerosol optical properties over the station suggest that the atmospheric absorption over central IGB region is mainly due to dominance of coarse-mode dust particles; however, absorption over eastern IGB region is mainly due to dominance of fine-particle pollution. The derived properties from sun/sky radiometer during pre-monsoon period are used in a radiative-transfer model to estimate aerosol radiative forcing at the top-of-the atmosphere (TOA) and at the surface over the IGB region. Relatively large TOA and surface cooling was observed at the eastern IGB as compared to the central IGB region. This translates into large heating of the atmosphere ranging from 0.45 to 0.55 K day?1 at Kanpur and from 0.45 to 0.59 K day?1 at Gandhi College.

A. K. Srivastava; S. Tiwari; P. C. S. Devara; D. S. Bisht; Manoj K. Srivastava; S. N. Tripathi; P. Goloub; B. N. Holben

2011-01-01

109

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

110

Structural evolution of the Laurentian margin revisited (southern Quebec Appalachians): Implications for the Salinian orogeny and successor basins  

Science.gov (United States)

The Laurentian margin of the Appalachians is divided into external and internal zones on the basis of metamorphic and structural contrasts. In the southern Quebec internal zone, Silurian to Early Devonian southeast-verging structures are superimposed on northwest-verging structures, whereas most of the external zone lacks such overprints. Regional backthrust faults define a major upper plate lower plate boundary; the external-zone rocks are in the hanging wall, and internal-zone rocks are in the footwall. Metamorphic rocks with Silurian Early Devonian 40Ar/39Ar ages (430 410 Ma) characterize the lower plate. To the east, the Saint-Joseph fault and the Baie Verte Brompton line are southeast- dipping normal faults that crosscut the upper plate lower plate boundary. Metamorphic rocks with Middle Ordovician 40Ar/39Ar ages (469 461 Ma) and rocks of the external zone both occur in the downthrown side of the Saint-Joseph fault and the Baie Verte Brompton line. U-Pb and 40Ar/39Ar ages suggest that the northwest-verging structures are related to ophiolite obduction and crustal thickening during the Taconian orogeny (ca. 480 445 Ma), whereas the southeast-verging structures formed during Silurian Early Devonian backthrusting and normal faulting. The revised structural interpretation has implications for the Salinian orogeny and involves (1) southeast-directed transport of the Taconian crustal wedge of the upper plate, followed by normal faulting and juxtaposition with the lower plate along the Saint-Joseph fault and the Baie Verte Brompton line, and (2) the formation of fault-bounded sedimentary basins, such as the Connecticut Valley Gaspé trough.

Tremblay, Alain; Castonguay, Sébastien

2002-01-01

111

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1993-09-01

112

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

International Nuclear Information System (INIS)

The composition of basalts erupted at the earliest stages in the evolution of back-arc basin permit unique insights into the composition and structure of the sub-arc mantle. We report major and trace element chemical data and O-, Sr-, Nd-, and Pb-isotopic analyses for basalts recovered from four dredge hauls and one ALVIN dive in the northern Mariana Trough near 22deg N. The petrography and major element chemistry of these basalts (MTB-22) are similar to tholeiites from the widest part of the Trough, near 18deg N (MTB-18), except that MTB-22 have slightly more K2O and slightly less TiO2. The trace element data exhibit a very strong arc signature in MTB-22, including elevated K, Rb, Sr, Ba, and LREE contents; relatively low K/Ba and high Ba/La and Sr/Nd. The Sr- and Nd-isotopic data plot in a field displaced from that of MTB-18 towards Mariana arc lavas, and the Pb-isotopic composition of MTB-22 is indistinguishable from Mariana arc lavas and much more homogeneous than MTB-18. Mixing of 50-90% Mariana arc component with a MORB component is hypothesized. We cannot determine whether this resulted from physical mixing of arc mantle and MORB mantle, or whether the arc component is introduced by metasomatism of MORB-like mantle by fluids released from the subducted lithosphere. The strong arc signature in back-arc melts from the Mariana Trough at 22deg N, where the back-arc basin is narrow, supports general models for back-arc basin evolution whereby early back-arc basin basalts have a strong arc component which diminishes in importante relative to MORB as the back-arc basin widens. (orig.)

1990-01-01

113

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

Energy Technology Data Exchange (ETDEWEB)

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

Stanley, R.G.

1987-05-01

114

Genetic relationships of tui chub populations in the northwestern Great Basin and conservation implications for the Cow Head Tui Chub  

UK PubMed Central (United Kingdom)

The Cow Head Tui Chub, Siphateles thalassinus vaccaceps, is restricted to the small Cow Head basin in far northeastern California and northwestern Nevada. Using microsatellite DNA loci, we found extensive genetic variation among tui chub populations in the Cow Head and surrounding basins of the northwestern Great Basin. Our data support the systematic conclusions of earlier authors, while showing distinct intraspecific differences between populations in most subbasins within the pluvial basins examined. The Cow Head Tui Chub forms a distinctive population within S. thalassinus with greatest affinity to the tui chub in the Warner Valley into which the Cow Head Lake drains. Tui chubs from the Goose Lake and Pit River basins are genetically very similar. Warner, Abert, Summer Lake, Catlow and Guano basin tui chubs appear distinct, both from each other and from tui chubs in the other basins. However, genetic proximity and some overlap between populations in presumably isolated hydrologic basins (i.e. Summer-Goose-Warner) suggest the possibility of unrecognized hydrologic connections or anthropogenic transport across barriers. Current genetic diversity in the Cow Head Tui Chub population is similar to that of stream-associated populations. We suggest that the Cow Head Tui Chub should remain a species of conservation concern due to its highly restricted distribution in an arid environment. Successful conservation of this unique fish will depend on stewardship of its limited habitat and maintenance of connectivity between subpopulations in a manner that ensures its long-term viability.

Chen Yongjiu; Reid Stewart; May Bernie

2009-02-01

115

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)

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

1997-01-01

116

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

Directory of Open Access Journals (Sweden)

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

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

2013-01-01

117

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2005-06-01

118

Spectral and photogeologic mapping of Schrödinger Basin and implications for post-South Pole-Aitken impact deep subsurface stratigraphy  

Science.gov (United States)

Schrödinger Basin provides a window into the stratigraphy of the lunar crust adjacent to the South Pole-Aitken Basin region that we have probed with Lunar Reconnaissance Orbiter, Moon Mineralogy Mapper (M3), and crater-scaling relationships. The composition of materials that make up the basin wall, impact melt, and peak ring provide a cross-section of the lunar crust, which reveals products of the lunar magma ocean, subsequent magmatism, and reworking of those components into a megaregolith. Large hectometer- to kilometer-size areas of anorthite-rich material (anorthosite), low-Ca pyroxene material (a noritic unit), and olivine-rich material (troctolite or dunite) are exposed, with a few areas of intermediate composition. The Schrödinger impact excavated ˜20 km into an orthopyroxene + plagioclase (noritic) lunar crust, which is exposed in the basin walls, rim, and proximal ejecta, and dominates the composition of materials that make up the basin floor. Substantially later in lunar history, two spatially and chronologically isolated volcanic eruptions occurred on the basin floor. Two large craters east of Schrödinger excavated a compositionally gabbroic subsurface unit that was not tapped by Schrödinger. This indicates a compositional crustal facies change, which may be from SPA ejecta, but could reflect heterogeneity in the original lunar crust.

Kramer, Georgiana Y.; Kring, David A.; Nahm, Amanda L.; Pieters, Carlé M.

2013-03-01

119

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

Science.gov (United States)

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

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

2013-05-01

120

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-07-01

 
 
 
 
121

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

Science.gov (United States)

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

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

2010-08-01

122

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 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 recon (more) ocidas 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 arboreal 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, (more) is a new record for this country. We show here an update of the taxonomic status and the geographical distribution of the genus in Venezuela and the first photographical key using simple terms for non-expert personnel.

Liria, Jonathan; Navarro, Juan-Carlos

2009-12-01

123

Thermo-tectonic evolution of the Purros Shear Zone and its implications in Walvis Basin, NW Namibia  

Energy Technology Data Exchange (ETDEWEB)

The Namibian marginal basins record a long history of tectonic activity since the Proterozoic. The collision between the Congo and Rio de La Plata craton generated NNW-trend crustal weakness zones in the Kaoko mobile belt which became the preferential site to the Phanerozoic tectonic activity. The pre-existing structures reactivated in mobile belts are intimately related with the evolution of adjacent marginal basins. The Pre-Cambrian Purros Shear Zone is an important crustal discontinuity located in Kaoko mobile belt that put side by side basement rocks with basaltic lavas related to the South Atlantic opening. Apatite fission track thermo chronology could provide a better understanding about reactivation phases, denudation rates and paleotemperature data. Through all these information will be possible to make the correlation with the main unconformities in the stratigraphic record of the Walvis marginal basin. (author)

Fernandes, Fernanda M. [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil)]|[Agencia Nacional do Petroleo, Rio de Janeiro, RJ (Brazil). Programa de Recursos Humanos]. E-mail: fernanda.fernandes@ufrgs.br; Chemale Junior, Farid; Lelarge, Maria Lidia M.V. [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Lab. de Geologia Isotopica e Tracos de Fissao]. E-mail: farid.chemale@ufrgs.br; Luft Junior, Joao Luiz [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Programa de Pos-graduacao em Geociencias]. E-mail: joao.luft@ufrgs.br

2003-07-01

124

Seismic reflection and refraction profiling in central Australia: Implications for understanding the evolution of the Amadeus Basin  

Science.gov (United States)

Seismic reflection sections for the Arunta Block generally show abundant, steep, north-dipping events that are interpreted as reflections from dipping faults, many of which are evident in surface geological mapping. The Redbank Thrust Zone, a major thrust feature, has been imaged to depths of at least 30 km. South of the Redbank Thrust Zone, steep, north-dipping reflections are generally absent; subhorizontal basement reflections predominate below the Southern Arunta Province and Amadeus Basin. Beneath the Southern Arunta Province, a zone of strong reflections dipping gently to the north occurs at depths between 21 and 30 km. A similar zone of south-dipping reflections is observed between depths of 18 and 30 km over a distance of about 40 km in the southern platform region of the Amadeus Basin. A south-dipping thrust fault has also been imaged to depths of 18 km near the southern limit of the reflection profile. These results suggest that the basement south of the Redbank Thrust Zone to the southern margin of the Amadeus Basin forms a single tectonic province. The seismic reflection data also provide support for a 'thick-skinned' style of tectonic deformation in the Arunta Block, and probably in the Musgrave Block too. The seismic refraction profiles indicate that the crust is on average more than 50 km thick below both the border region between the Central and Southern Arunta Provinces and the northern part of the Amadeus Basin, providing further evidence of the predominance of compressional tectonics in the evolution of the region. Expanding reflection spreads and a three-dimensional refraction survey have added fine details to the results in regions of special geological interest. An expanding reflection spread recorded in the northern part of the Amadeus Basin has enabled the resolution of complicated variations in seismic velocity throughout the 10 km thick sedimentary section, thus assisting lithological interpretation of the deeper formations, and enabling more accurate estimates of basin and formation thickness.

Wright, C.; Goleby, B. R.; Shaw, Russell D.; Collins, C. D. N.; Korsch, Russell J.; Barton, T.; Greenhalgh, S. A.; Sugiharto, S.

125

C4 Plants Decline in the Himalayan Basin Since the LGM: Implications for the Evolution of the Monsoon  

Science.gov (United States)

The Bengal Fan turbiditic system, supplied by the Ganga-Brahmaputra (G-B) river system, provides an integrated record of Himalayan erosional system. Recently, we showed that riverine organic carbon delivered by G-B is very efficiently buried in Bengal Fan sediments (Galy et al. 2007, Nature v450 p407). Thus, thanks to minor inputs of marine organic matter, organic matter buried in Bengal Fan sediments is a proxy of Himalayan basin paleo-vegetation. The active channel levee system of the middle fan documents the last 19 ka and allows the reconstruction of vegetation change in the Himalayan basin since the Last Glacial Maximum (LGM). We measured ?13C of organic carbon (OC) in order to track changes in the proportions of C3 and C4 plants in the Himalayan basin (Galy et al. 2008, QSR v27 p1396). From LGM to mid-Holocene, ?13C of bulk OC shifts of 3 to 4‰ towards more negative values. Relative abundance of individual n-alkanes reveals that terrestrial higher plant inputs represent a dominant fraction of OC buried in Bengal Fan sediments. ?13C of higher plants biomarkers mimic that of bulk OC showing that the later can be used as continental paleo-vegetation proxy. ?13C negative shift from LGM to mid- Holocene, mostly indicates the transition from a dominant input of C4 plants to a dominant input of C3 plants and therefore reveals that C4 plants were more abundant in the basin under glacial conditions. Vegetation repartition in the basin simulated using the CARAIB dynamic vegetation model is consistent with OC data. The model indicates a dominance of C4 plants in the Gangetic plain during the LGM while eastern part of the basin remains dominated by C3 plants. The comparison between our basin scale record and proxies of regional paleo-climate suggests that the large decline of C4 plants after the LGM was due to combined increase of atmospheric CO2 and humidity levels. Integrated record of Himalayan basin paleo-vegetation suggests more arid conditions during the LGM than during the mid-Holocene and agrees with reconstructions of the monsoon indicating stronger SW monsoon during interglacial and stronger NE monsoon during glacial periods.

France-Lanord, C.; Galy, V.; François, L.

2008-12-01

126

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

Science.gov (United States)

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

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

2006-01-01

127

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

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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 t...

Diego-Orozco, Arturo; Chen, Yan; Henry, Bernard; Becq-Giraudon, Jean-François

128

The application of iodine and magnetic susceptibility surface geochemical surveys in the Lodgepole Play, Eastern Williston Basin, North Dakota  

Energy Technology Data Exchange (ETDEWEB)

The use of surface geochemistry as a first pass exploration tool is becoming more prevalent in petroleum exploration. This is especially true due to the high cost of 2-D and 3-D surveys in defining small targets such as the Waulsortian mounds of the Lodgepole Formation. Surface geochemical surveys are very effective in pinpointing specific target areas for seismic surveying and thus reducing costs. Presented are examples of surface geochemical surveys utilizing magnetic susceptibility and iodine methods in delineating reservoirs in the Lodgepole, Mission Canyon and Red River formations. The types of surveys presented vary from reconnaissance to detail and examples of how to define a grid will be discussed. Surface geochemical surveys can be very effective when the areal extent of the target(s) and the purpose of the survey are clearly defined prior to implementation. By determining which areas have microseepage and which areas do not, surface geochemistry can be a very effective tool in focusing exploration efforts and maximizing exploration dollars.

Tedesco, S.A. [Atoka Geochemical Services Corp., Englewood, CO (United States)

1996-06-01

129

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.

2006-01-01

130

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

Science.gov (United States)

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

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

131

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

UK PubMed Central (United Kingdom)

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

Swatdipong A; Vasemägi A; Niva T; Koljonen ML; Primmer CR

2013-09-01

132

Modified gulf of California model for South Georgia, north Scotia Ridge, and implications for the Rocas Verdes back-arc basin, southern Andes  

Energy Technology Data Exchange (ETDEWEB)

New field mapping and an integrated trace element and Nd isotopic study have been undertaken on the Jurassic-Cretaceous Larsen Harbour Complex on the island of South Georgia, recognized as a displaced part of the southern Andes ensialic, autochthonous Rocas Verdes marginal basin. Five basalt groups (Groups I-V) are identified from trace element data; initial Nd isotopic compositions suggest that they are derived from only two sources. Magmas produced during early stages of continental lithospheric attenuation (Groups I-III) were derived by varying degrees of partial melting and fractional crystallization from a large ion lithophile element (LILE)-enriched, low-{epsilon}{sub Nd} mantle source relative to normal (N)-type mid-ocean ridge basalt (MORB). Magmas produced during later stages of rifting (Groups IV and V) were, however, derived from a high-{epsilon}{sub Nd} asthenospheric mantle source similar to N-type MORB, unaffected by earlier LILE enrichment. Our data do not occur with previous suggestions that the Larsen Harbour Complex and, by implication, the Rocas Verdes formed in a supra-subduction-zone setting. On the basis of geologic and geochemical evidence, we favor basin formation along an oblique-slip margin akin to that of the Gulf of California.

Alabaster, T.; Storey, B.C. (Natural Environment Research Council, Cambridge (England))

1990-06-01

133

Paleontology and sedimentology of upper clastic member of Wanakah Formation, Chama basin, New Mexico: Lacustrine paleoenvironmental implications  

Energy Technology Data Exchange (ETDEWEB)

Lacustrine strata of the upper part of the Jurassic Wanakah Formation were restricted to the Chama basin of north-central New Mexico by mid-Jurassic tectonic activity in the Brazos and Nacimiento uplifts and along the Gallina-Archuleta anticlinorium. Lateral and vertical facies of the upper Wanakah exposed around the southern margin of the Chama basin indicate that the deeper part of the lake was north of the outcrop belt. The upper 3-5 m of the Wanakah consists of thin-bedded rippled sandstone, interbedded mudstone, and limestone containing trace fossils and freshwater mollusks characteristic of marginal lacustrine facies. Taphonomic studies of mollusks in the Wanakah Formation have been combined with application of ecophenotypic variation documented in extant unionid bivalves to produce paleoenvironmental interpretations of these lacustrine rocks.

Good, S.J.; Ridgley, J.L. (Univ. of Colorado, Boulder (USA))

1989-09-01

134

Late orogenic magmatism and sedimentation within Late Carboniferous to Early Permian basins in the Balkan terrane (Bulgaria): geodynamic implications  

Science.gov (United States)

The orogenic Balkanid belt, which developed between the Moesian Plate and the Moravian-Rhodopi-Thracian Massifs, was affected by the Late Carboniferous and Early Permian opening of W-E oriented graben structures. The progressive tectonic rejuvenation of the basins is demonstrated by the deposition of repeated regional sedimentary cycles, associated with volcanism that was mostly localised along the tectonic boundaries, in an intramontane setting.

Cortesogno, Luciano; Gaggero, Laura; Ronchi, Ausonio; Yanev, Slavcho

2004-09-01

135

Burial and thermal history modelling of the Gafsa-Matlaoui intracontinental basin (Southern Tunisia): implications for petroleum exploration  

Energy Technology Data Exchange (ETDEWEB)

This paper is a contribution to the evaluation of the petroleum potential of southern Tunisia. Its purpose is to report on the burial and thermal histories of the Gafsa-Metlaoui Basin and the surrounding area in the time interval between the triassic and the Quaternary. We have used a one-dimensional deterministic model, which enabled us to integrate the burial and thermal influences on potential source rocks with kinetic parameters, in order to define the timing of hydrocarbon generation and expulsion in relation to the main structural episodes in the study area. The Mesozoic burial history of this basin is characterized by two principal phases of rifting, each of which was followed by a brief episode of thermal (post-rift) subsidence. The first phase occurred during the Triassic and Jurassic, and was related to the break-up of Gondwana; the second phase occurred during the Cretaceous and Early Tertiary, and was related to the opening of the neo-Tethyan Mediterranean Sea. Geothermal studies of this basin have allowed us to determine an average surface heat flow of 60mW/sq m and an average geothermal gradient of about 25.5{sup o}C/km. Middle Jurassic source rocks expelled oil from the Cenomanian (about 100 million years ago) to the Quaternary. (author)

Hlaiem, A. [Laboratoire de Geologie Appliquee, Universite PMC-Paris VI, (France); Biju-Duval, B.; Vially, R. [Institut Francais du Petrole, Rueil-Malmaison (France); Laatar, E. [Institut Superieur d`Etudes Technologiques de Gafsa (Tunisia); M`Rabet, A. [ETAP (Tunisia)

1997-10-01

136

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1986-04-01

137

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1995-12-31

138

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

International Nuclear Information System (INIS)

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

1995-01-01

139

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

140

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

 
 
 
 
141

Evaluating NOx emissions in the LA basin and their implications for O3 and NOx during CalNex-2010  

Science.gov (United States)

We evaluate NOx emissions in the Los Angeles Basin during the CalNex-2010 field campaign by analyzing O3 and NOy observations using WRF/Chem. Model simulations are conducted at 4-km spatial resolution over the basin and the results are compared against ARB surface measurements as well as CalNex surface and aircraft observations. We adjust the 2005 National Emissions Inventory (NEI'05) for the CalNex simulations with a 24% reduction in NOx and 28% reduction in CO according to the emission statistics from California ARB. WRF/Chem O3 reproduces the observed diurnal cycle and day-to-day variations in surface O3 (r2 = 0.92, n = 114, p = 0.01) across the basin. Model results underestimate daytime O3 at the CalNex-LA supersite (Caltech) by 20-40 ppbv during May 29-30 when O3 levels approached 80-100 ppbv. The underestimate is in large part because of the deeper than observed PBL heights in the model and the model's inability to simulate observed strong stratospheric intrusion that penetrated deep into the basin on May 29th (Langford et al., 2011). Titration due to excessively high NOx emissions at downtown L.A. sites leads to near-zero nighttime O3. The vertical profiles of CO below 3 km show good agreement with the observation (r2=0.64, n=576, p=0.01), but with ~90 ppb overestimation for the altitude below 400 m altitude. Model NO2 and NOy concentrations along the June 2-3 NOAA P-3 flights over the basin are biased high by 106% and 48%, respectively. Model results capture the overall variability in the LP-DOAS observed NO2 and O3 but overestimate NO2 below 500 m altitude. A 45% reduction of NOx emissions from 2005 to 2010, as implied by OMI NO2 columns (Russell et al., 2010), significantly improves model comparisons of NO2, NOy and O3 during CalNex.

Chen, D.; Li, Q.; Stutz, J.; Pikelnaya, O.; Tsai, C.; Haman, C. L.; Lefer, B. L.; Flynn, J. H.; Roberts, J. M.; De Gouw, J. A.; Holloway, J. S.; Pollack, I. B.; Ryerson, T. B.

2011-12-01

142

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

DEFF Research Database (Denmark)

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

Sandrin, Alessandro; Thybo, Hans

2008-01-01

143

Evidence for Focused Accumulations of Methane Hydrate with Possible Resource Implications for the Deep Water Bering Sea Basins  

Science.gov (United States)

Velocity-amplitude anomalies (VAMPs), comprising coincident seismic travel time anomalies and gas bright spots, are features widely identified in seismic reflection images from the deep-water Aleutian and Bowers Basins in the Bering Sea. The structures are interpreted as acoustic images of large deposits of natural methane hydrate directly overlying columns of ascending fluids that deliver methane gas to the hydrate stability zone. Because these chimneys extend downward to depths where thermocatalytic processes are underway, methane involved in Bering Sea VAMP structures is presumed to be petroleum generated. Interval travel time anomalies have been used to objectively detect these features and to quantify implied resource content in several example cases. Relative travel time variation in the sedimentary intervals above and below a gas hydrate bottom simulating reflection (BSR) are a selected diagnostic for VAMP detection, measuring velocity pull-up in the hydrate stability zone and push-down in the underlying gas zone. The largest VAMP anomalies studied, including all of those associated with hydrate indicators, are located above prominent basement highs. This association suggests that long-lived fluid migration patterns in these undeformed deep- water basins were originally established in response to sedimentation and compaction over the oceanic basement topography, perhaps augmented by hydrothermal circulation involving the crust itself. Thousands of VAMP anomalies occur in the Bering Sea. Individual large VAMP structures appear to involve a volume of methane (0.6-0.9 TCF) equivalent to that of a large gas field. If the hydrate interpretation is correct, then a genuinely vast number of targets for concentrated accumulations of methane (either as gas or hydrate) occur in the Bering Sea Basin.

Barth, G. A.; Scholl, D. W.; Childs, J. R.

2007-05-01

144

Silcrete in the uppermost Cambrian and Lower Ordovician of the Wisconsin arch and Michigan basin - Implications for subaerial exposure  

Energy Technology Data Exchange (ETDEWEB)

Silcrete within uppermost Cambrian strata and the Lower Ordovician Prairie du Chien Group delineates the basinward extent of subaerial exposure during three relative sea-level lowstands that exposed portions of the Wisconsin arch and Michigan basin before, during, and after Prairie du Chien deposition. Shallow-water Prairie du Chien carbonates and Cambrian sandstones were deposited in tropical, epeiric seas during relative sea-level highstands. Fabrics identical to Cenozoic silcretes consist of cryptocrystalline microquartz (chert), microquartz ({lt}0.02 mm), megaquartz ({lt}0.02 mm), and length-slow and length-fast chalcedony. Silicified crusts of oolitic grainstones and/or anhydrite nodule typically coat uppermost Cambrian and Prairie du Chien unconformities. Silicification associated with intra- and post-Prairie du Chien unconformities is generally restricted to within 5 m of the overlying unconformity. Highly permeable lithologies, such as oolitic grainstones, boundstones, and paleokarst breccias, were preferentially silicified during intra- and post-Prairie du Chien exposure. Reworked silcrete clasts typically overlie unconformities. Silcrete is a practical exposure indicator as it is easily identified in outcrop and well cuttings. Silcrete within uppermost Cambrian strata is generally restricted to the Wisconsin arch axis, but occurs as far east as western Michigan. Silcrete below the intra-Prairie du Chien unconformity indicates subaerial exposure of the entire arch and basin. In contrast, silcrete below the post-Prairie du Chien, pre-St. Peter unconformity indicates that exposure was restricted to the Wisconsin arch and western margin of the Michigan basin in eastern Wisconsin.

Smith, G.L. (Univ. of Wisconsin, Madison (United States))

1991-03-01

145

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

Energy Technology Data Exchange (ETDEWEB)

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 fission track ages significantly older than the stratigraphic age. By contrast, apatites from contemporaneous volcanogenic detritus record a characteristic spread of chlorine content (0-2.5 wt% Cl, many > 0.5 wt%) and syndepositional fission track ages. Where post-depositional thermal annealing ( > 70 degree C) has significantly reduced the fission track age, provenance information is preserved in the apatite Cl composition alone. In the Otway Supergroup, evidence for contemporaneous volcanism was found in both the Eumeralla Formation (Albian-Aptian), and Crayfish Group (Aptian-Berriasian) in samples located towards the central rift, where less sandy facies dominate. Results suggest that Crayfish Group sediments deposited along the northern margin of the basin were predominantly derived from eroding basement material, while the section located towards the central rift contains a greater proportion of volcanogenic detritus. Evidence from this study suggests that volcanogenic detritus was a distal sediment source throughout the entire early rift phase, prior to the main influx of arc-related volcanogenic material during deposition of the Eumeralla Formation. As diagenesis of volcanogenic sediments significantly reduces porosity and permeability of the sandstones, reservoir quality and petroleum potential may be significantly reduced in the Crayfish Group in deeper parts of the basin where a greater proportion of volcanogenic detritus is suggested. The results presented here provide important information regarding Lower Cretaceous Otway Basin stratigraphy and clearly indicate that this methodology may have wider application. (authors). 32 refs., 1 tab., 6 figs.

Mitchell, M.M. [La Trobe Univ., Bundoora, VIC (Australia). School of Earth Sciences

1997-12-01

146

Evidence of syn tectonic tephrites with nepheline in the Sidi Said Maachou Cambrian basin (coastal Meseta, Morocco); geo dynamic implications  

International Nuclear Information System (INIS)

Based on a combined structural, petrographic, and geochemical analysis, a new interpretation of the basic magmatism of Sidi Said Maachou (coastal Meseta) in two stages of emplacement is proposed. The first stage is characterized by transitional pyroclastic flows that have accompanied the opening of the West-Mesetian basin, during the Cambrian; the second stage is made of dykes of basalts, dolerites, and tephrites bearing nepheline. The emplacement of this undersaturated alkaline magma is associated to a sinistral sub meridian shear zone which has been activated at the end of the Caledonian orogenesis, by a mantellic advection. (Author) 32 refs.

2009-01-01

147

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

Energy Technology Data Exchange (ETDEWEB)

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 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. [US Geological Survey, Lakewood, CO (United States)

2006-09-15

148

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

Directory of Open Access Journals (Sweden)

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

R. P. M. Topper; J. Trabucho Alexandre; E. Tuenter; P. Th. Meijer

2011-01-01

149

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

Directory of Open Access Journals (Sweden)

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

R. P. M. Topper; J. Trabucho Alexandre; E. Tuenter; P. Th. Meijer

2010-01-01

150

Fluvial and glacial implications of tephra localities in the western Wind River basin, Wyoming, U. S. A  

Energy Technology Data Exchange (ETDEWEB)

Examination of Quaternary fluvial and glacial deposits in the western Wind River Basin allows a new understanding of the Quaternary Wind River fluvial system. Interbedded fluvial sediments and volcanic ashes provide important temporal information for correlation of Quaternary deposits. In the western Wind River Basin, six mid-Pleistocene localities of tephra, the Muddy Creek, Red Creek, Lander, Kinnear, Morton and Yellow Calf ashes are known. Geochronologic studies confirm the Muddy Creek, Red Creek, Kinnear and Lander ashes as the 620--650ka Lava Creek tephra from the Yellowstone region in northwestern Wyoming. The stratigraphic position and index of refraction of volcanic glass from the Morton and Yellow Calf ashes are consistent with identification as Lava Creek tephra. Approximately 350 feet (106 meters) above the Wind River and 13 miles downstream from Bull Lake, interbedded Wind River fluvial gravels, volcanic glass and pumice at the Morton locality correlate to late (upper) Sacajawea Ridge gravels mapped by Richmond and Murphy. Associated with the oxygen isotope 16--15 boundary, the ash-bearing terrace deposits reveal the nature of the Wind River fluvial system during late glacial-early interglacial times. The Lander and Yellow Calf ashes, are found in terrace deposits along tributaries of the Wind River. Differences in timing and rates of incision between the Wind River and its tributary, the Little Wind River, results in complex terrace development near their junction.

Jaworowski, C. (Univ. of Wyoming, Laramie, WY (United States). Dept. of Geology)

1993-04-01

151

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

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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).  

Pamela J. Schofield; Lauren J. Chapman

2011-01-01

152

Provenance of sediments from Mesozoic basins in western Shandong: Implications for the evolution of the eastern North China Block  

Science.gov (United States)

This paper reports LA-ICP-MS U-Pb dates and in situ Hf isotope analyses of detrital zircons from the Mesozoic basins in western Shandong, China, with the aim to constrain the depositional ages and provenances of the Mesozoic strata as well as the Mesozoic tectonic evolution of the eastern North China Block (NCB). The Mesozoic strata in western Shandong, from bottom to top, include the Fenghuangshan, Fangzi, Santai and Wennan formations. Most of the analyzed zircon grains exhibit oscillatory growth zoning and have relatively high Th/U ratios (generally 0.2-3.4), suggesting a magmatic origin. Zircons from the Fenghuangshan Formation in the Zhoucun Basin yield six main age populations (2489, 1854, 331, 305, 282, and 247 Ma). Zircons from the Fangzi Formation in the Zhoucun and Mengyin basins yield eight main age populations (2494, 1844, 927, 465, 323, 273, 223, and 159 Ma) and ten main age populations (2498, 1847, 932, 808, 540, 431, 315, 282, 227, and 175 Ma), respectively, whereas zircons from the Santai Formation in the Zhoucun and Mengyin basins yield nine main age populations (2519, 1845, 433, 325, 271, 237, 192, 161, and 146 Ma) and six main age populations (2464, 1845, 853, 277, 191, and 150 Ma), respectively. Five main age populations (2558, 1330, 609, 181, and 136 Ma) are detected for zircons from the Wennan Formation in the Pingyi Basin. Based on the youngest age, together with the contact relationships among formations, we propose that the Fenghuangshan Formation formed in the Early-Middle Triassic, the Fangzi Formation in the Middle-Late Jurassic, the Santai Formation after the Late Jurassic, and the Wennan Formation after the Early Cretaceous. These results, together with previously published data, indicate that: (1) the sediments of the Fenghuangshan Formation were sourced from the Precambrian basement and from late Paleozoic to early Mesozoic igneous rocks in the northern part of the NCB; (2) the sediments of the Fangzi and Santai formations were sourced from the Precambrian basement, late Paleozoic to early Mesozoic igneous rocks in the northern part of the NCB, and the Sulu terrane, as well as from Middle-Late Jurassic igneous rocks in the southeastern part of the NCB; and (3) the Wennan Formation was sourced from the Tongshi intrusive complex, the Sulu terrane, and minor Precambrian basement and Early Cretaceous igneous rocks. The evolution of detrital provenance indicates that in the Early-Middle Triassic, the northern part of the NCB was higher than its interior; during the Late Triassic to Early Jurassic, the eastern NCB was uplifted, resulting in a period of non-deposition; and an important transition from a compressional to an extensional tectonic regime occurred during the Middle-Late Jurassic. The presence of Neoproterozoic and Triassic detrital zircons in the Fangzi Formation sourced from the Sulu terrane suggests that large-scale sinistral strike-slip movement along the Tan-Lu Fault Zone did not occur after the Middle Jurassic (ca. 175 Ma).

Yang, De-Bin; Xu, Wen-Liang; Xu, Yi-Gang; Pei, Fu-Ping; Wang, Feng

2013-10-01

153

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

154

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

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

Guzman Espinal, Jose Ignacio

1999-11-01

155

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

International Nuclear Information System (INIS)

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

1987-01-01

156

Dissolved organic matter composition of winter flow in the Yukon River basin: Implications of permafrost thaw and increased groundwater discharge  

Science.gov (United States)

Groundwater discharge to rivers has increased in recent decades across the circumpolar region and has been attributed to thawing permafrost in arctic and subarctic watersheds. Permafrost-driven changes in groundwater discharge will alter the flux of dissolved organic carbon (DOC) in rivers, yet little is known about the chemical composition and reactivity of dissolved organic matter (DOM) of groundwater in permafrost settings. Here, we characterize DOM composition of winter flow in 60 rivers and streams of the Yukon River basin to evaluate the biogeochemical consequences of enhanced groundwater discharge associated with permafrost thaw. DOC concentration of winter flow averaged 3.9 ± 0.5 mg C L-1, yet was highly variable across basins (ranging from 20 mg C L-1). In comparison to the summer-autumn period, DOM composition of winter flow had lower aromaticity (as indicated by specific ultraviolet absorbance at 254 nm, or SUVA254), lower hydrophobic acid content, and a higher proportion of hydrophilic compounds (HPI). Fluorescence spectroscopy and parallel factor analysis indicated enrichment of protein-like fluorophores in some, but not all, winter flow samples. The ratio of DOC to dissolved organic nitrogen, an indicator of DOM biodegradability, was positively correlated with SUVA254 and negatively correlated with the percentage of protein-like compounds. Using a simple two-pool mixing model, we evaluate possible changes in DOM during the summer-autumn period across a range of conditions reflecting possible increases in groundwater discharge. Across three watersheds, we consistently observed decreases in DOC concentration and SUVA254 and increases in HPI with increasing groundwater discharge. Spatial patterns in DOM composition of winter flow appear to reflect differences in the relative contributions of groundwater from suprapermafrost and subpermafrost aquifers across watersheds. Our findings call for more explicit consideration of DOC loss and stabilization pathways associated with changing subsurface hydrology in watersheds underlain by thawing permafrost.

O'Donnell, Jonathan A.; Aiken, George R.; Walvoord, Michelle A.; Butler, Kenna D.

2012-12-01

157

Implications of calcite twin style in midcontinent carbonate rocks of the LaSalle anticlinal belt, Illinois Basin  

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Standard strain gage'' analysis of twinning in calcite was completed on oriented samples from localities in the northernmost extension of the LaSalle anticlinal belt in the Illinois Basin. Units examined included Ordovician and Pennsylvanian bioclastic dolomitic calcarenites and limestones. These strata have been affected by outcrop-scale low-amplitude folding and reverse faulting. Preliminary results indicate that penetrative strain magnitudes associated with the twinning are low. The majority of twins observed in the Ordovician units are thick twins, and within the ordovician units the number of twins is low. Locally, thick twins pinch out toward the edge of a grain and/or taper to thin twins midway along the width of the grain. Within a very small percentage of the grains, the trace of the twin planes is continuously curved into an open arc. The majority of twins in the Pennsylvanian units are noticeably thinner than those of Ordovician units, suggesting a possible change in twin characteristics with stratagraphic level. Observed features of twinning in the Ordovician strata are comparable to borderline high temperature features of twinned calcite reported by Ferrill (1991), suggesting that twinning strain in the LaSalle anticlinal belt developed at temperatures of approximately 150-200 C. Such temperatures are higher than would be expected for shallow platform carbonate strata on the margin of an intracratonic basin, and are compatible with models in which formation of the twins was synchronous with regional hot-brine migrations linked to the Alleghanian orogeny. Heat transferred to shallow strata by these brine migrations may have effectively weakened midcontinent carbonate rocks, thereby permitting twinning to develop even though differential tectonic stresses were low.

Qi, S.L.; Marshak, S. (Univ. of Illinois, Urbana, IL (United States). Dept. of Geology)

1992-01-01

158

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

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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; A. W. Wood; J. R. Prairie

2012-01-01

159

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

160

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

International Nuclear Information System (INIS)

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

1990-01-01

 
 
 
 
161

Predicting the probability of elevated nitrate concentrations in the Puget Sound Basin: Implications for aquifer susceptibility and vulnerability  

Energy Technology Data Exchange (ETDEWEB)

The occurrence and distribution of elevated nitrate concentrations in ground water in the Puget Sound Basin, Washington, were determined by examining existing data from more than 3,000 wells. Models that estimate the probability that a well has an elevated nitrate concentration were constructed by relating the occurrence of elevated nitrate concentrations to both natural and anthropogenic variables using logistic regression. The variables that best explain the occurrence of elevated nitrate concentrations were well depth, surficial geology, and the percentage of urban and agricultural land within a radius of 3.2 kilometers of the well. From these relations, logistic regression models were developed to assess aquifer susceptibility and ground-water vulnerability. Both models performed well at predicting the probability of elevated nitrate concentrations in an independent data set. This approach to assessing aquifer susceptibility and ground-water vulnerability has the advantages of having both model variables and coefficient values determined on the basis of existing water quality information and does not depend on the assignment of variables and weighting factors based on qualitative criteria.

Tesoriero, A.J.; Voss, F.D. [Geological Survey, Tacoma, WA (United States). Water Resources Div.

1997-11-01

162

Evidence of syntectonic tephrites with nepheline in the Sidi Saïd Maâchou Cambrian basin (coastal Meseta, Morocco); geodynamic implications  

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Full Text Available Based on a combined structural, petrographic, and geochemical analysis, a new interpretation of the basic magmatism of Sidi Saïd Maâchou (coastal Meseta) in two stages of emplacement is proposed. The first stage is characterized by transitional pyroclastic flows that have accompanied the opening of the West-Mesetian basin, during the Cambrian; the second stage is made of dykes of basalts, dolerites, and tephrites bearing nepheline. The emplacement of this undersaturated alkaline magma is associated to a sinistral submeridian shear zone which has been activated at the end of the Caledonian orogenesis, by a mantellic advection.Basée sur des critères structuraux, pétrographiques et géochimiques, une réinterprétation du magmatisme basique de Sidi Saîd Maâchou (meseta côtière) en deux stades de mise en place est proposée. Le premier stade est caractérisé par des coulées pyroclastiques transitionnelles accompagnant l’ouverture du bassin ouest mésétien au Cambrien. Le second stade, de nature fissural, comprend des basaltes, dolérites et téphrites à néphéline spécifiques d’un magmatisme alcalin sous-saturé. La mise en place de ce dernier est associée à un couloir de cisaillement senestre subméridien activé à la fin de l’orogenèse calédonienne, engendrant un flux géothermique élevé.

Remmal, T.; Mohsine, A.; El Hatimi, N.

2009-01-01

163

Implications for the water level change triggered moderate (M ? 4.0) earthquakes in Lake Van basin, Eastern Turkey  

Science.gov (United States)

The water level in Lake Van has shown alternating rises and decreases in history, causing economical, environmental and social problems over the littoral area. The water level changes were obtained to be in the order of 100 m between 18000 and 1000 B.C., in the order of 10 m between 1000 B.C. and 500 A.D. and relatively stable and fluctuating in the order of a few metres during the past 1500 years. The most recent change of the water level took place between 1987 and 1996, during which the water level increased episodically about 2 m and its altitude changed from approximately 1648.3 m to about 1650.2 m. All these changes were mainly related to climate changes. In this study, the water level changes in the lake after 1860 are compared with the seismic activity of faults lying close to the basin. Temporal correlations of seismicity with the water level changes are very persuasive and dramatic, indicating hydrogeological triggering of the earthquakes. This study shows that 14 M ? 5.0 earthquakes and increasing number of 4.0 ? M < 5.0 earthquakes accompanied or followed the dramatic (about 1 m or larger) changes of the annual mean of the water level in the lake and that there was a tendency of M ? 4 earthquakes to occur between November and February, during which the lake level is low within a year.

Utkucu, Murat

2006-01-01

164

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

165

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)

[en] 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

1990-01-01

166

Flexure of Anadarko basin  

Energy Technology Data Exchange (ETDEWEB)

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

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

1983-03-01

167

A Reconstruction of Paleo-Positions of Basin and Range Volcanic Rocks, and Implications for Tectonic Controls on Volcanism  

Science.gov (United States)

A key problem in understanding the tectonic triggers of Basin-and-Range magmatism relates to the fact that many volcanic rocks have been translated from the latitudes and longitudes at which they were erupted. We present a reconstruction of the paleo-latitudes and paleo-longitudes of volcanic rocks using the work of Snow and Wernicke (2000). These reconstructed volcanic rock positions are used to 1) test whether the formation and northward migration of the Mendocino Triple Junction (MTJ) may have initiated volcanism and 2) whether the demise of subduction processes may have affected volcanic compositions. We utilize Figure 13 from Snow and Wernicke (2000) in the reconstruction, which illustrates a deformation grid that covers the most extended parts of the Basin and Range in CA, NV and AZ. We apply deformation a vector to each grid point and assigned an age of initiation of deformation, which we allow to migrate from south to north based on field evidence for the initiation of extensional faulting in the map area (Anderson et al., 1988; Beratan and Nielsen, 1996; Fridrich et al., 1998; Faulds et al., 2002; Jacobsen et al., 2002; Busby and Putirka, 2009). Our model, derived from the field data, yields an initiation age (for extension) as a function of latitude: Age of initiation of deformation [Ma]=130.6 - 3.14[Latitude]. This reconstruction provides a consistency test for the extension model of Snow and Wernicke (2000) because our reconstruction yields strain rates for each grid point; we obtain a mean strain rate of 13 mm/year, which is consistent with strain rates obtained from field data. Interestingly, the latitudinal changes for volcanic rocks are mostly minimal; even though in the Walker Lane belt crustal components have experienced significant latitudinal displacement, most volcanic rocks erupted in the Walker Lane are too young to be greatly translated. However, many volcanic rocks are sufficiently old so that longitudinal positions are significantly different. MTJ migration is mostly a latitudinal change, which we calibrate as a function of time using Atwater and Stock (1998). We then employ volcanic age dates from NAVDAT and our reconstructed latitudes to determine whether the MTJ was north or south of the location of volcanism at the time of eruption. By comparing time of eruption relative to time of MTJ arrival at a given latitude, we find a pronounced peak of volcanism at 3.4 Ma post MTJ arrival. Volcanism tends to die off at 4 Ma post-MTJ, but then is rejuvenated at 10-20 Ma after the MTJ has past. Since passage of the MTJ should also affect the input of subduction related fluids, we compare indices of subduction-inputs, such as La/Nb and Ba/Nb (both increase with increases in fluid inputs into the mantle wedge) with time of MTJ arrival. The results of this analysis reveal very high La/Nb and Ba/Nb ratios up until 8 Ma post-MTJ arrival. Clearly, such high indices of fluid inputs for so long after the demise of subduction cannot be related to active fluid inputs into the mantle wedge. However, the Cordilleran mantle also has very high La/Nb and Ba/Nb ratios, and so the decreases in La/Nb and Ba/Nb may reflect either the dehydration of Cordilleran mantle, or perhaps even its physical demise.

Platt, B. W.; Putirka, K. D.

2011-12-01

168

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

International Nuclear Information System (INIS)

[en] 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 four wells do not constrain burial temperatures. These data indicate a mixed provenance for the sediments. (author). 71 refs., 3 tabs., 7 figs

1995-01-01

169

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

Science.gov (United States)

Arsenic concentrations in shallow groundwaters from the Hetao Basin of Inner Mongolia range between 0.6 and 572 microg/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, HCO(3)(-), P and S(2-), and low concentrations of NO(3)(-) and SO(4)(2-). Low SO(4)(2-) coupled with high S(2-) suggests that SO(4)(2-) 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 microg/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 low concentrations. The competition between As and other anions (such as HPO(4)(2-)) 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. PMID:18234287

Guo, Huaming; Yang, Suzhen; Tang, Xiaohui; Li, Yuan; Shen, Zhaoli

2008-01-30

170

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

Energy Technology Data Exchange (ETDEWEB)

Arsenic concentrations in shallow groundwaters from the Hetao Basin of Inner Mongolia range between 0.6 and 572 {mu}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, HCO{sub 3}{sup -}, P and S{sup 2-}, and low concentrations of NO{sub 3}{sup -} and SO{sub 4}{sup 2-}. Low SO{sub 4}{sup 2-} coupled with high S{sup 2-} suggests that SO{sub 4}{sup 2-} 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 {mu}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 low concentrations. The competition between As and other anions (such as HPO{sub 4}{sup 2-}) 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.

Guo Huaming [School of Water Resources and Environment, China University of Geosciences, Beijing 100083 (China)], E-mail: hmguo@cugb.edu.cn; Yang Suzhen; Tang Xiaohui; Li Yuan; Shen Zhaoli [School of Water Resources and Environment, China University of Geosciences, Beijing 100083 (China)

2008-04-01

171

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 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.

1000-01-00

172

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

173

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

Science.gov (United States)

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

Shane, Phil; Hoverd, Joy

2002-04-01

174

Sedimentology and paleogeographic evolution of the intermontane Kathmandu basin, Nepal, during the Pliocene and Quaternary. Implications for formation of deposits of economic interest  

Energy Technology Data Exchange (ETDEWEB)

The Kathmandu Valley is an intermontane basin in the center of a large syncline of the Lesser Himalayas. The sedimentary basin fill comprises three units of Plio-Pleistocene to Holocene age. The study aimed at modeling the paleogeographic evolution of the basin, with emphasis on sedimentary series of fossil fuels and non-metallic deposits. The lithological setting of the basin and the tectonic framework were instrumental to basin subsidence. The results of this basin analysis may be used predictively in the exploration for coal, natural gas, diatomaceous earths and quarrying for sand or clay. The gas potential is at its maximum in the lacustrine facies, sand and clay for construction purposes may be quarried economically from various fluvial and deltaic deposits. Diatomaceous earths predominantly accumulated in marginal parts of the lake and some landslide-dammed ponds. Lignitic brown coal can be mined together with combustible shales from poorly drained swamps.

Dill, H.G.; Kharel, B.D.; Singh, V.K.; Piya, B.; Busch, K.; Geyh, M. [Federal Institute of Geoscience & Natural Resources, Hannover (Germany)

2001-07-01

175

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

International Nuclear Information System (INIS)

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

1985-01-01

176

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

Energy Technology Data Exchange (ETDEWEB)

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.

Means, J.L.; Hubbard, N.J.

1985-05-01

177

Sedimentary record and climatic implications of recurrent deformation in the Tian Shan: Evidence from Mesozoic strata of the north Tarim, south Junggar, and Turpan basins, northwest China  

Energy Technology Data Exchange (ETDEWEB)

Detailed stratigraphic, sedimentologic, paleocurrent, and subsidence analyses were conducted on Mesozoic nonmarine sedimentary sections of the south Junggar, north Tarim, and Turpan basins, Xinjang Uygur Autonomous Region, northwest China. These three basins have been foreland basins throughout the Mesozoic and Cenozoic eras, as demonstrated by asymmetrically distributed basinwide sediment accumulations, foreland-style subsidence profiles, and a variety of outcrop and subsurface facies data. Mesozoic paleocurrent indicators measured in the south Junggar and north Tarim basins, as well as Mesozoic sandstone compositions from both basins, indicate that the intervening Tian Shan has existed as a positive physiographic feature partitioning the two basins throughout Mesozoic and Cenozoic time. Paleocurrent, facies, and subsurface isopach data suggest that the Turpan basin was established as a discrete feature by the Early Jurassic period. The timing and style of depositional systems within the north Tarim Mesozoic depocenter, the south Junggar Mesozoic depocenter, and the central Turpan basin are remarkably similar. Upper Triassic strata of each basin consist of alluvial conglomerate and associated braided-fluvial sandstone and siltstone which fine upward into lower through Middle Jurassic, locally organic-rich, meandering-fluvial, and lacustrine strata. Upper Jurassic braided-fluvial red beds in each basin are overlain by a distinct pulse of uppermost Jurassic alluvial conglomerate. Lower Cretaceous exposures consist of fine-grained red beds in north Tarim and Turpan and interbedded red and gray shale with local silty carbonates in south Junggar. Upper Cretaceous strata of the north Tarim and south Junggar basins are composed of alluvial conglomerate with associated braided-fluvial sandstone and siltstone. 94 refs., 17 figs.

Hendrix, M.S.; Graham, S.A.; Sobel, E.R. [Stanford Univ., CA (United States)] [and others

1992-01-01

178

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

The gravity method may be used in the exploration of deep sedimentary basins. It allows the structuring and the lateral and vertical extent of sedimentary fill to be determined. This study has concerned a qualitative and quantitative gravity analysis of Sidi Bouzid Basin in Central Tunisia. Bouguer ...

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

179

Oil and gas potential of Amazon Paleozoic basins  

Energy Technology Data Exchange (ETDEWEB)

The Paleozoic basins, covering an area of about 800,000 km/sup 2/ (309,000 mi/sup 2/) in the Amazon region, are elongate symmetrical intracratonic synclines filled with as much as 4000 m (13,000 ft) of sediments, separated by basement uplifts or major arches and located in continental interior areas (as are the United State Illinois, Michigan, and Williston basins). Tectonics affected differentially these basins during the Triassic Jurassic and Early Cretaceous, associated with widespread basic volcanism. Adjacent to those faults and extending for over 500 km (310 mi), large natural gas accumulations occur in several domal features. Sandstones of the Permian Monte Alegre Formation, sealed by evaporite strata, are the main reservoir rock. Geologic estimates of natural gas resources are presently rated at 120 billion m/sup 3/ (4.237 tcf) and exploration follows the productive trend toward the west-southwest. Potential reservoir rocks in Middle and Lower Amazon basis are Permian Monte Alegre and Devonian Oriximina sandstones. Major source rocks in all three basins are Devonian Barreirinha black, shales. Forecasts for the major exploratory trends in the Upper Amazon indicate a good possibility of extending the already discovered natural gas province. In the Lower Amazon basin, further exploration will consist in drilling well-defined structural features identified for the first time by seismic methods, with a possibility of discovering another gas province. Prospects in the Middle Amazon basin are for both oil and gas, but the main problem is identification of adequate structures, as well as stratigraphic traps.

Mosmann, R.; Falkenhein, F.U.H.; Goncalves, A.; Nepomuceno, F.

1984-09-01

180

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1985-05-01

 
 
 
 
181

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...

182

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

2011-01-01

183

Assessment of undiscovered conventional oil and gas resources of the Western Canada Sedimentary Basin, Canada, 2012  

Science.gov (United States)

The U.S. Geological Survey recently completed a geoscience-based assessment of undiscovered oil and gas resources of provinces within the Western Canada Sedimentary Basin. The Western Canada Sedimentary Basin primarily comprises the (1) Alberta Basin Province of Alberta, eastern British Columbia, and the southwestern Northwest Territories; (2) the Williston Basin Province of Saskatchewan, southeastern Alberta, and southern Manitoba; and (3) the Rocky Mountain Deformed Belt Province of western Alberta and eastern British Columbia. This report is part of the U.S. Geological Survey World Petroleum Resources Project assessment of priority geologic provinces of the world. The assessment was based on geoscience elements that define a total petroleum system (TPS) and associated assessment unit(s). These elements include petroleum source rocks (geochemical properties and petroleum generation, migration, and accumulation), reservoir description (reservoir presence, type, and quality), and petroleum traps (trap and seal types, and timing of trap and seal formation relative to petroleum migration). Using this framework, the Elk Point-Woodbend Composite TPS, Exshaw-Fernie-Mannville Composite TPS, and Middle through Upper Cretaceous Composite TPS were defined, and four conventional assessment units within the total petroleum systems were quantitatively assessed for undiscovered resources in the Western Canada Sedimentary Basin.

Higley, Debra

2013-01-01

184

Chronology of the late Turolian deposits of the Fortuna basin (SE Spain): implications for the Messinian evolution of the eastern Betics  

Science.gov (United States)

The magnetostratigraphy of the mammal-bearing alluvial fan-fan delta sequences of the Fortuna basin (SE Spain) has yielded an accurate chronology for the late Turolian (Messinian) basin infill. From early to late Messinian (at least between 6.8 and 5.7 Ma), the Fortuna basin records the sedimentation of alluvial-palustrine deposits over a confined shallow basin. Changing environmental conditions in the latest Messinian are illustrated by the retreat of palustrine facies. A rapid progradation of the marginal clastic wedges and the initiation of an efficient basin drainage at ~5.8 Ma (lower part of chron C3r) most likely represents the onshore response to the drastic drop of base level taking place during the Messinian salinity crisis. This study further provides improved age estimates for the late Turolian land mammal events in southern Spain. The oldest MN 13 locality in the studied sections is correlated to chron C3Ar at an age of 6.8 Ma. The entry of camels and the murid Paraethomys in southern Spain occurs in chron C3An.1n at 6.1 Ma, and gives further support for land mammal exchange between Africa and the Iberian peninsula prior to the salinity crisis, in good agreement with results from northern Africa [M. Benammi, M. Calvo, M. Prévot, J.J. Jaeger, Magnetostratigraphy and paleontology of Aït Kandoula basin (High Atlas, Morocco) and the African-European late Miocene terrestrial fauna exchanges, Earth Planet. Sci. Lett. 145 (1996) 15-29]. The age of the studied sequences provides important constraints on the understanding of the sedimentary evolution of the eastern Betic margin, and shows that previous interpretations of the evaporitic-diatomitic sequences of the Fortuna basin, as being coeval to the late Messinian salinity crisis in the Mediterranean, are not correct. The confinement leading to the emergence of the Fortuna basin occurred in the late Tortonian to earliest Messinian, similar to other intramontane basins in the Betics. Therefore, the inclusion of the Fortuna basin in a hypothetical marine Betic Corridor during the late Messinian is no longer tenable.

Garcés, M.; Krijgsman, W.; Agustí, J.

1998-11-01

185

Provenance analysis of the Permo-Carboniferous fluvial sandstones of the southern part of the Boskovice Basin and the Zöbing Area (Czech Republic, Austria): implications for paleogeographical reconstructions of the post-Variscan collapse basins  

Science.gov (United States)

The provenance analyses of Permo-Carboniferous fluvial sandstones of the southern part of the Boskovice Basin and the Zöbing area are based on a wide spectrum of analytical techniques (petrography, heavy mineral assemblages, chemistry of garnet, rutile and spinel, zircon study, major and trace elements). The studied sandstones are poorly sorted and reveal a relatively immature composition implying short distance transport, rapid deposition, a high-relief source area, mainly physical weathering and the minor role of chemical weathering. Different source areas for the Boskovice Basin and the Zöbing area were proved. The Zöbing material was predominantly derived from crystalline units, mainly formed by metamorphic complexes, although the portions of magmatic and volcanic material were significant. The source area is supposed to be located in the Moldanubian Unit. The Boskovice Basin deposits, on the other hand, seem to be mainly derived from metamorphic complexes, corresponding especially to the Moravian Unit, with a relatively wider spectrum of metamorphites, together with the derivation of the detritus from pre-existing sedimentary rocks (especially from Moravo- Silesian Paleozoic deposits/Drahany Culm unit). The transport direction in the basin was more complex, both from the west and east. These results did not confirm the possibility of communication between the Boskovice Basin and the Zöbing area during the Late Paleozoic. The existence of “colinear” marginally offset half grabens with predominant transversal sources is here hypothesized. The general heavy mineral evolution in time does not indicate the successive exhumation of a simple structured orogen but may be interpreted as differences in the extent of the source areas.

Nehyba, Slavomír; Roetzel, Reinhard; Maštera, Lubomír

2012-11-01

186

Miocene tectono-stratigraphic history of La Mision basin, northwestern Baja California: implications for early tectonic development of southern California continental borderland  

Energy Technology Data Exchange (ETDEWEB)

The middle Miocene La Mision basin in northwestern Baja California, Mexico, provides a rare opportunity to study an onshore portion of the southern California continental borderland. Stratigraphy, geometry of dispersal, and a variety of lithotypes within the volcanic and volcaniclastic sediments of the Rosarito Beach Formation provide clues to the nature of early tectonic evolution of this area during the Miocene. The elongated, trough-shaped La Mision basin formed in response to peninsular basement uplifts and the formation of volcanic highlands west of the present coastline. Lithologies and depositional environments represented within the basin sediments include: subaerial basalt flows and airfall tuffs, submarine muddy- and sandy-matrix mudflow breccias, lapilli tuffs, crystal tuffs, tuffaceous sandstones,d diatomites, and conglomerates. The environments of deposition range from fluvatile to intertidal to shallow marine. Early basin infilling is characterized by sediments and basalts, with a western source terrane, that were deposited against the faulted seacliffs. progressive infilling against the seacliff resulted in the formation of an extensive eastward-sloping basaltic platform extending eastward to the foothill coastal belt of the Peninsular Ranges. Marine transgression and subsequent regression are recorded by diverse marine volcaniclastic lithologies. Abundant fossils, K-Ar dates, and paleomagnetic data obtained from the La Mision basin allow precise correlation with other areas in the continental borderland and provide conclusive evidence that this block of the borderland was formed and in its present position by 16-14 Ma.

Ashby, J.R.; Minch, J.

1988-03-01

187

Apparent overconsolidation of mudstones in the Kumano Basin of southwest Japan: Implications for fluid pressure and fluid flow within a forearc setting  

Science.gov (United States)

The Kumano Basin is located in the Nankai Trough subduction zone of southwest Japan. During the past 1.6 million years, approximately 800 meters of sandy turbidites and hemipelagic mud were deposited near the distal edge of the forearc basin, at Site C0002 of the Integrated Ocean Drilling Program. Constant-rate-of-strain consolidation tests yield estimates of in situ permeability that range from 2.6 × 10-17 m2 to 2.5 × 10-18 m2; overconsolidation ratios range from 1.7 to 2.6, and values of the compression index range from 0.39 to 0.78. Several processes contributed to the apparent overconsolidation. Strata dip toward land, and pore fluids probably migrate up-dip and vent along a bathymetric notch near the seaward edge of the basin. Efficient lateral drainage through sandy turbidites has kept pore pressures within interbeds of mudstone at (or close to) hydrostatic. In addition, alteration of dispersed volcanic glass, precipitation of authigenic clay minerals, and collapse of random grain fabric has probably strengthened the bonding among grains. Cementation is particularly likely within the lower basin (unit III), where values of porosity remain anomalously high. If fluid overpressures (and underconsolidation) exist anywhere within the basin, the most likely loci are where sandy turbidites terminate against impermeable mudstones along landward-dipping on-lap surfaces. Those types of on-lap geometries, in addition to structural closures, might provide promising targets for oil/gas accumulation in other forearc basins, particularly where petroleum source rocks have been buried to the optimal depths of catagenesis.

Guo, Junhua; Underwood, Michael B.; Likos, William J.; Saffer, Demian M.

2013-04-01

188

Hydrological implications of 234U/238U disequilibria observed along pressure dissolution structures within deep mesozoic limestone formations of the Eastern Paris basin  

International Nuclear Information System (INIS)

This study is part of geological investigations conducted by ANDRA (French agency for nuclear waste management) around the Underground Research Laboratory excavated in a clay layer of the Eastern part of the sedimentary Paris Basin, France. The safety of such nuclear waste disposal relies on a multi-barrier approach that must prevent radionuclide migration from the disposal site to the biosphere. Fluid circulations constitute a critical parameter for the confining capacities of the system, since they are the most effective and fastest mechanism by which radionuclides can reach the biosphere. Consequently, knowledge of the past and present hydrological and geochemical regimes within the geological system is fundamental to making predictions of the behavior of radionuclides when they are released from the 'near field'. In a previous study, we reported systematic (234U/238U) disequilibria only in the vicinity of pressure dissolution structures -stylolites- localized in the Bathonian and Oxfordian limestones that under- and overly the target argilite unit. This finding provides in situ indications of the confining capacities of these deep formations and highlights a mobility of uranium within the carbonated units. This is a major and surprising result since these deep, low-permeability, compact formations are generally supposed to behave as a chemically stable system. More precisely, these results highlight an active re-localization of uranium in the last 1-2 Ma within the stylolitized zones of the Bathonian and Oxfordian formations. The question arises now of the driving phenomena responsible for the 'recent' re-localization of uranium and of their hydrological implications. Uranium fractionation and re-localization can be, indirectly or directly, related to the phenomenon of stylolitization. The stylolitic discontinuities present high chemical and mineralogical heterogeneities due to the accumulation of non-soluble minerals. The (234U/238U) disequilibria observed in these zones may highlight geochemical transfers due to the high gradient of uranium concentration between the detrital material within the seams and the embedding carbonate matrix. Other possible explanation is an active stylolitization or reactivation of this phenomenon in the recent time (in the last 1-2 Ma). Pressure dissolution process, particularly in horizontal plane, may result from overburden. One cannot therefore exclude that the current gravitational loading causes stylolitization within the most stressed domains of the limestones. Pressure dissolution goes with mass transfer through an aqueous phase, either by diffusion or bulk flow, of the material dissolved within stylolitic seams. Therefore, uranium associated with the dissolved carbonate material was redistributed in the surrounding carbonate matrix together with other dissolution products (major or trace elements). This may lead to precipitation of secondary carbonate cement within pore spaces of less stressed zones. If this case arises, this would have important hydrological consequences since stylolitization goes with reprecipitation of secondary carbonate phases within pore spaces of the host matrix, thereby reducing the porosity and permeability of the limestone formations. In both cases discussed above, the (234U/238U) disequilibria observed within stylolitic zones would characterize late epi-diagenetic phenomena that do not involve massive transport of uranium into or out of the system and open-system behavior at large scale. Water/rock interactions induced by the physical and chemical perturbation associated with flowing fluids are often put forward to explain U-series disequilibria observed on rocks in the upper lithosphere. In the present case, although this assumption cannot be totally ruled out, there is no other clear geochemical evidence for such a phenomenon. Moreover, from an hydrologic point of view, these limestones have also very low porosities and permeabilities. In this second hypothesis, pressure dissolution surfaces could act as preferential conduits for flowing fluids. Flu

2004-01-01

189

An interprovincial structural database for the Western Canada Sedimentary Basin  

Energy Technology Data Exchange (ETDEWEB)

The Geological Surveys of Alberta, Saskatchewan and Manitoba have designed a prototype database of regional geological structures in order to improve exploration for economic deposits in the Western Canada Sedimentary Basin (WCSB). The structural compilation in digital format is the first undertaking of a tectono-stratigraphic framework for hydrocarbons, metallic mineral and diamond exploration in the WCSB that encompasses the Cordilleran foreland, Elk Point and Williston basins. It allows government and industry to assess and better target possible occurrences of energy and non-energy minerals in the WCSB. Thousands of lineaments from literature and survey work inferred on isopach and structural maps for various stratigraphic intervals are being compiled into GIS shapefiles and linked to a Microsoft Access database for distribution via web pages and on CD-ROM. The digital format is meant to be flexible and allow for continuous updates and refinements. The structural database can also serve as a reconnaissance level mapping tool that delineates zones of interest for further exploration, but not as immediate drilling targets. The compilation of this structural information is intended to encourage further study of the relationship between tectonics, sedimentation, diagenesis and mineral occurrences, particularly since oil migration and trapping is often related to local areas of uplift and subsidence, the distribution of lithofacies and erosional trends that are associated with structural elements. 6 refs., 3 figs.

Pana, D.; Waters, J. [Alberta Geological Survey, Edmonton, AB (Canada)]|[Alberta Energy and Utilities Board, Edmonton, AB (Canada); Bamburak, J.; Lenton, P.; Pacey, M. [Manitoba Geological Survey, Winnipeg, MB (Canada)]|[Manitoba Industry, Economic Development and Mines, Winnipeg, MB (Canada); Nimegeers, A.; Marsh, A.; Opseth, M.; Whittaker, S. [Saskatchewan Industry and Resources, Regina, SK (Canada). Petroleum Geology Branch

2006-07-01

190

Origin of minerals in joint and cleat systems of the Pottsville Formation, Black Warrior basin, Alabama: Implications for coalbed methane generation and production  

Energy Technology Data Exchange (ETDEWEB)

Coalbed methane is produced from naturally fractured strata in the lower Pennsylvanian Pottsville Formation in the eastern part of the Black Warrior basin, Alabama. Major fracture systems include orthogonal fractures, which consist of systematic joints in siliciclastic strata and face cleats in coal that strike northeast throughout the basin. Calcite and minor amounts of pyrite commonly fill joints in sandstone and shale and, less commonly, cleats in coal. Stable-isotope data reveal large variations in the carbon isotope composition of joint- and cleat-fill calcite but only a relatively narrow range in the oxygen isotope composition of this calcite. Negative carbon values can be attributed to {sup 13}C-depleted CO{sub 2} derived from the oxidation of organic matter, and moderately to highly positive carbon values can be attributed to bacterial methanogenesis. Assuming crystallization temperatures of 20-50{sup o}C, most joint- and cleat-fill calcite precipitated from fluids with {delta}-{sup 18}O ratios ranging from about -11 to + 2 parts per thousand standard mean ocean water (SMOW). Uplift and unroofing since the Mesozoic led to meteoric recharge of Pottsville strata and development of freshwater plumes that were fed by meteoric recharge along the structurally upturned, southeastern margin of the basin. Influxes of fresh water into the basin via faults and coalbeds facilitated late-stage bacterial methanogenesis, which accounts for the high gas content in coal and the carbonate cementation of joints and cleats.

Pitman, J.K.; Pashin, J.C.; Hatch, J.R.; Goldhaber, M.B. [US Geological Survey, Denver, CO (USA)

2003-05-01

191

Hydrochemistry of formation water with implication to diagenetic reactions in Sanzhao depression and Qijia-gulong depression of Songliao Basin, China  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Sanzhao depression and Qijia-gulong depression are two of the most important hydrocarbon-bearing sub-depressions in the Songliao basin, dominated by Cretaceous fluvial and lacustrine strata with volcanic and volcaniclastic rocks. In this paper, the pressure distributions and hydrochemistry varia...

Cheng, J; McIntosh, JC; Xie, X; Jiao, JJ

192

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

193

Occurrence of hydrogen sulfide in Solimoes Basin: geological model and implications; Ocorrencia de gas sulfidrico na Bacia do Solimoes: modelo geologico e implicacoes  

Energy Technology Data Exchange (ETDEWEB)

Occurrence of hydrogen sulfide associated with hydrocarbons in the Solimoes Basin, its geological explanation, considerations about the reservoir rocks and temperature variations into the rifts, which could be caused this problem are discussed. Safety criteria establishment and financial concerns, based on the geological studies are also reported. 10 figs., 4 tabs., 18 refs.

Oliveira Castro, L.O.C. de [PETROBRAS, Natal (Brazil). Distrito de Exploracao da Bacia Potiguar; Silva, O.B. da [PETROBRAS, Macae, RJ (Brazil). Distrito de Exploracao do Sudeste

1990-07-01

194

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

195

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 nodul...

Tripathi, S.K.M.

196

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

197

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

198

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

International Nuclear Information System (INIS)

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

1994-01-01

199

Geochemistry of the Mesozoic bedded cherts of Central Baja California (Vizcaino-Cedros-San Benito): implications for paleogeographic reconstruction of an old oceanic basin  

Science.gov (United States)

In central Baja California (Vizcaino Peninsula, and Cedros and San Benito Islands) two distinct radiolarian bedded chert sequences of late Triassic and late Jurassic/lowermost Cretaceous age, can be differentiated on lithostratigraphic and geochemical criteria. These bedded chert sequences are part of the conformable sedimentary cover of more or less dismembered ophiolites, which are overthrusted by the San Andrès-Cedros volcanic arc system of middle late Jurassic age. Major and trace elements permit paleogeographic zonation of the late Jurassic/lowermost Cretaceous radiolarites lying conformably upon ophiolites considered as fragments of an oceanic basin floor which developed westward of the San Andrès volcanic arc. Progressive accretion of this oceanic basin floor, along the continental margin is supported by the fact that the more distal radiolarian chert sequences belong to the lowermost structural units of this area. Also Groupe des Sciences de la Terre, Laboratoire Pierre Sue, Saclay.

Rangin, Claude; Steinberg, Michel; Bonnot-Courtois, Chantal

1981-07-01

200

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

 
 
 
 
201

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)

[en] 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

1990-01-01

202

Implications of paleobotany of Pennsylvanian-age coal of the central Appalachian basin for climate and coal-bed development. [USA - Appalachia  

Energy Technology Data Exchange (ETDEWEB)

Lycopod abundance in coal is used to estimate climatic 'wetness' during the Pennsylvanian period in the central Appalachian basin. Plants were identified from their anatomy using etched, polished coal rather than using permineralized peat, compressions/impressions, or palynology. The data indicate that two drier intervals occurred: one in the Westphalian B (middle of the Kanawha Formation), the other in the early Stephanian (Conemaugh Formation). Both drier intervals have been previously recognized in the Illinois basin, but only the second has been previously recognized in the Appalachian basin. In 9 of 18 localities, lycopod abundance decreases upward within coal beds, whereas at the other nine localities, no statistically significant trends in lycopod abundance were observed. An upward decrease in lycopod abundance is suggestive of coal that formed in the central region of a domed peat swamp, but peat-dome formation is not demonstrated. Within coalbeds, pteridosperms are most abundant in samples which are split or contain abundant mineral matter. 2 figs., 2 tabs.

Winston, R.B. (Geological Survey of Alabama, Tuscaloosa, AL (USA))

1990-12-01

203

Finite-element models on spatiotemporal variations in intraplate seismicity caused by postglacial unloading and rebound: Implications for active normal faults in the Basin and Range Province  

Science.gov (United States)

The actively extending Basin and Range Province was covered by numerous pluvial lakes and glaciers on several of the higher ranges during the Last Glacial Maximum (Osburn and Bevis, QSR, 2001). The largest lakes were Lake Bonneville and Lake Lahontan, located in the eastern and western parts of the Basin and Range Province, respectively. Regression of these lakes at the end of last glacial period caused significant isostatic rebound of the lithosphere (Bills et al., JGR, 1994; Bills et al., JGR, 2007). The rebound associated with the regression of Lake Bonneville has been shown, using two-dimensional numerical models, to affect the stress field of the lithosphere and to cause a slip rate increase on the Wasatch normal fault (Hetzel and Hampel, Nature 2005). Here we use three-dimensional finite-element models of normal fault arrays to investigate spatiotemporal variations in the regional stress field and in the rate of normal faulting caused by glacial-interglacial variations of the surface load. Our models indicate that regression of Lake Lahontan but also of smaller lakes and glaciers alter the regional stress field and hence may ultimately affect the intraplate seismicity. Paleoseismological data from faults in the east-central and northern Basin and Range Province seem to support the idea of an increase in seismicity after the Last Glacial Maximum (Friedrich el al., JGR, 2003; Stickney and Bartholomew, BSSA, 1987; Wesnousky et al., JGR, 2005).

Karow, T.; Hampel, A.

2007-12-01

204

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

205

Correlation of Paleocene Harmon and Hansen lignite beds, Adams, Billings, Bowman, Golden Valley, Hettinger, and Slope Counties, Williston Basin, North Dakota  

Energy Technology Data Exchange (ETDEWEB)

In southwestern North Dakota, minable lignite beds in the Paleocene Fort Union Formation include the Harmon and Hansen beds in the Bowman-Gascoyne area. Data from more than 700 drill holes penetrating these beds was used to construct stratigraphic cross sections. The Harmon and Hansen beds are the thickest and most laterally persistent lignites found under < 150 ft of overburden. The Harmon coal bed is as much as 34 ft thick, and is often split by claystone interbeds of variable thickness. The Hansen coal bed typically occurs 10--100 ft below the Harmon coal bed; it rarely attains a thickness of 15 ft, and averages 4 ft in thickness.

Keighin, C.W.; Flores, R.M.; Ochs, A. [Geological Survey, Denver, CO (United States)

1998-12-31

206

Subalkaline andesite from Valu Fa Ridge, a back-arc spreading center in southern Lau Basin: petrogenesis, comparative chemistry, and tectonic implications  

Science.gov (United States)

Tholeiitic andesite was dredged from two sites on Valu Fa Ridge (VFR), a back-arc spreading center in Lau Basin. Valu Fa Ridge, at least 200 km long, is located 40-50 km west of the active Tofua Volcanic Arc (TVA) axis and lies about 150 km above the subducted oceanic plate. One or more magma chambers, traced discontinuously for about 100 km along the ridge axis, lie 3-4 km beneath the ridge. The mostly aphyric and glassy lavas had high volatile contents, as shown by the abundance and large sizes of vesicles. An extensive fractionation history is inferred from the high SiO2 contents and FeO* MgO ratios. Chemical data show that the VFR lavas have both volcanic arc and back-arc basin affinities. The volcanic arc characteristics are: (1) relatively high abundances of most alkali and alkaline earth elements; (2) low abundances of high field strength elements Nb and Ta; (3) high U/Th ratios; (4) similar radiogenic isotope ratios in VFR and TVA lavas, in particular the enrichment of 87Sr 86Sr relative to 206Pb 204Pb; (5) high 238U 230Th, 230Th 232Th, and 226Ra 230Th activity ratios; and (6) high ratios of Rb/Cs, Ba/Nb, and Ba/La. Other chemical characteristics suggest that the VFR lavas are related to MORB-type back-arc basin lavas. For example, VFR lavas have (1) lower 87Sr 86Sr ratios and higher 143Nd 144Nd ratios than most lavas from the TVA, except samples from Ata Island, and are similar to many Lau Basin lavas; (2) lower Sr/REE, Rb/Zr, and Ba/Zr ratios than in arc lavas; and (3) higher Ti, Fe, and V, and higher Ti/V ratios than arc lavas generally and TVA lavas specifically. Most characteristics of VFR lavas can be explained by mixing depleted mantle with either small amounts of sediment and fluids from the subducting slab and/or an older fragment of volcanic arc lithosphere. The eruption of subalkaline andesite with some arc affinities along a back-arc spreading ridge is not unique. Collision of the Louisville and Tonga ridges probably activated back-arc extension that ultimately led to the creation and growth of Valu Fa Ridge. Some ophiolitic fragments in circum-Pacific and circum-Tethyan allochthonous terranes, presently interpreted to have originated in volcanic arcs, may instead be fragments of lithosphere that formed during early stages of seafloor spreading in a back-arc basin. ?? 1991.

Vallier, T. L.; Jenner, G. A.; Frey, F. A.; Gill, J. B.; Davis, A. S.; Volpe, A. M.; Hawkins, J. W.; Morris, J. D.; Cawood, P. A.; Morton, J. L.; Scholl, D. W.; Rautenschlein, M.; White, W. M.; Williams, R. W.; Stevenson, A. J.; White, L. D.

1991-01-01

207

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

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

L. Pérez Cruz; J. Urrutia Fucugauchi

2009-01-01

208

Statistical aspects of major (Intense) Hurricanes in the Atlantic Basin during the past 49 hurricane seasons (1950-1998): Implications for the current season  

Science.gov (United States)

Statistical aspects of major (intense) hurricanes, those of category 3 or higher on the Saffir-Simpson scale (e.g., having a maximum sustained wind speed of ?50 m s-1), in the Atlantic basin during the interval of 1950-1998 are investigated in relation to the El Niño-Southern Oscillation cycle and to the postulated “more” versus “less” activity modes for intense hurricane activity. Based on Poisson statistics, when the hurricane season is simply classified as “non-El Niño-related” (NENR), the probability of having three or more intense hurricanes is ? 53%, while it is only ? 14% when it is classified as “El Niño-related” (ENR). Including the activity levels (“more” versus “less”), the probability of having three or more intense hurricanes is computed to be ? 71% for the “more-NENR” season, 30% for the “less-NENR” season, 17% for the “more-ENR” season, and 12% for the “less-ENR” season. Because the 1999 hurricane season is believed to be a “more-NENR” season, the number of intense hurricanes forming in the Atlantic basin should be above average in number, probably about 4±1 or higher.

Wilson, Robert M.

209

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

UK PubMed Central (United Kingdom)

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.

Hart JA; Detwiler KM; Gilbert CC; Burrell AS; Fuller JL; Emetshu M; Hart TB; Vosper A; Sargis EJ; Tosi AJ

2012-01-01

210

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)

2001-01-01

211

Out-of-sequence thrusting in experimental Coulomb wedges: Implications for the structural development of mega-splay faults and forearc basins  

Science.gov (United States)

We have investigated how an arc-ward increase in bulk mechanical strength in an experimental accretionary prism influences the development, timing, and duration of slip on out-of-sequence thrusts. We have monitored the structural development and kinematics, in side-view, during the development of a frontally accreting Coulomb wedge growing out in front of a critically tapered and mechanically stronger inner wedge. The inner-wedge initially behaved as classic backstop to deformation with the most actively slipping thrust occurring near the deformation front on the forward most thrust structures. With continued growth, however, significant out-of-sequence slip on reactivated fore-thrusts occurred in conjunction with slip on newly formed back-thrusts in the inner-wedge. This out-of-sequence deformation resulted in punctuated, rapid uplift of the model forearc basin and a noticeable break in topographic slope in the outer pro-wedge. Cyclical out-of-sequence fore- and back-thrusting, driven by ongoing frontal thrust imbrication, continued with periodic recovery of taper and was followed by additional out-of-sequence faulting and associated basin uplift.

Haq, Saad S. B.

2012-10-01

212

Major and trace element and Sr-Nd isotope signatures of the northern Lau Basin lavas: Implications for the composition and dynamics of the back-arc basin mantle  

Science.gov (United States)

We present new major element, trace element and Sr-Nd isotope analyses of volcanic glasses from Mangatolu Triple Junction (MTJ), Peggy Ridge (PR), Rochambeau Bank (RB), and Niuafo'ou Island (NF) within the northern Lau Basin (NLB). Lavas from MTJ range from tholeiitic basalts to basaltic andesites and andesites: such a lava series can be ascribed to fractional crystallization. Lavas from NF, RB and PR are mainly tholeiitic basalts save for two transitional basalts from RB. The lavas came from a compositionally heterogeneous mantle that exhibits compositional features similar to those of the mantle source of Indian mid-ocean basalt and bears the influence of both subduction and ocean island basalt (OIB) components. The subduction components consist mainly of fluid dehydrated from subducted oceanic crust and a minor amount of sediment melt. The geochemically enriched signature of enriched RB, PR and NF lavas comes from two OIB end-member components, most likely derived from enriched Samoan mantle plume materials leaking into NLB. The Rochambeau Rifts (RR)-RB corridor receives the greatest, although still variable, influence from the mantle source of Samoan shield magmatism whereas the outlying PR and NF regions experience a Samoan plume post-erosional type of magmatism. The relatively recent mixing of Samoan plume materials with the subduction-metasomatized Indian-type mantle may be responsible for some of the observed complex relationships between noble gases and other geochemical tracers in some NLB lavas.

Tian, Liyan; Castillo, Paterno R.; Hilton, David R.; Hawkins, James W.; Hanan, Barry B.; Pietruszka, Aaron J.

2011-11-01

213

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

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

Ganesh Raj Joshi; Daigoro Hayashi

2010-01-01

214

Styles of deposition and diagenesis in the Monahans Clear Fork reservoir: Implications for improved characterization of Leonard reservoirs on the Central basin platform  

Energy Technology Data Exchange (ETDEWEB)

The Leonard Series (Lower Permian) of west Texas contains a substantial hydrocarbon resource; the original oil in place in these predominantly carbonate rocks totaled about 14.5 billion bbl. Recovery of this resource has proven difficult, however. Current recovery efficiencies average about 20%, far below the 35% average for other Permian basin carbonate reservoirs. Detailed characterization of the Leonard in the Monahans field (Ward and Winkler counties, Texas) illustrates that poor reservoir performance in these reservoirs is the result of extreme lithologic heterogeniety resulting from cyclic rise and fall of relative sea level. Patterns of both depositional and diagenetic facies are a function of this cyclicity. Three orders of cyclicity are apparent in the Leonard: high-frequency, fifth-order cycles averaging 1-2 m in thickness, fourth-order cycles averaging 15-20 m in thickness, and third-order cycles averaging 200 m in thickness. Diagenetic patterns reflect control by fourth-order and third-order cyclicity. Both depositional and diagenetic trends are modified by local topography. Porosity and permeability also manifest cycle-related trends. Porosity and permeability exhibit opposite relationships to paleotopography. Porosity, which is encountered in tidal-flat and subtidal facies, is greatest on paleotopographic highs, whereas permeability, which is most commonly developed in subtidal facies, is most common on paleotopographic lows. Preliminary investigation of Leonard carbonate sequences elsewhere in the Permian basin reveals analogous styles and patterns of facies development. The concepts and models developed in the Monahans field should help improve characterization of these sequences as well.

Ruppel, S.C. (Univ. of Texas, Austin (United States))

1992-04-01

215

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)

[en] 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)

1990-01-01

216

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

International Nuclear Information System (INIS)

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

1000-01-00

217

Synchrotron X-ray fluorescence (SXRF) analysis of palaeofluid chemistry from the McArthur River uranium deposit, Athabasca Basin, Canada: Results and implications  

International Nuclear Information System (INIS)

Unconformity-type uranium deposits of the Athabasca Basin in northern Saskatchewan and northeastern Alberta, Canada, represent the world's highest-grade and large-tonnage uranium resources. However, despite the wealth of research on these deposits, almost no information is available regarding the trace element content of the ore forming fluids and especially about their metal contents. We present here, for the first time, information on the trace element geochemistry of the o reforming fluids that resulted in the formation of the world-class McArthur River uranium deposit using the SXRF technique. Measurements were performed at the Hamburger Synchrotronstrahlungslabor (HASYLAB), part of the Deutsches Elektronen-Synchrotron (DESY), using the micro-fluorescence beamline (beamline L). The fluid inclusions investigated by SXRF are ca. 20 to 50 microns in size, and are either two (L+V) or three (L+V+S) phase inclusions. Solid phases include halite, phyllosilicates and haematite, and, possibly, dravite. The results indicate that all the fluid inclusions contain Fe, Br and Sr. In addition, there are a number of other elements present: Ca, K, Ce, Cu, Pb, U, Zn and Zr. The presence of these metals varies between inclusions and samples. On the basis of element associations, the data suggest that two different fluids may be present 1) Br-Sr-Fe +- U-Pb-Ce and 2) Br-Sr-Fe-Ca +-Zr-Zn-Ce. Preliminary analysis suggest that U is present in both the NaCl- and CaCl2-dominant fluids. With the exception of Fe, transition metals are rarely detected in the analyses. However, Zn was detected in the majority of inclusions in samples AJM2 and MAC8, however U was not detected in these samples. In contrast, those samples that did contain uranium were devoid of Zn. This may indicate that Zn and U were transported in mutually exclusive fluids. The general absence of transition metals such as Ni, Cu and Co is not unexpected. McArthur River is poor in these metals, compared to other deposits/occurrences in the Athabasca Basin, such as Key Lake and Moore Lakes. Future work will examine fluid inclusions from these and other areas in order to 1) further characterize the ore fluid in terms of trace element chemistry, 2) determine if the uranium and base metals were transported in a single or multiple fluid(s), and 3) quantify the results

2005-01-01

218

New magnetic Polarity Stratigraphy of the Mae Moh Basin in northern Thailand, and Implications for the Age of the First Miocene Hominoids  

Science.gov (United States)

This magnetostratigraphic study has been conducted on the Miocene Mae Moh basin, in the Lampang province, Northern Thailand. 194 paleomagnetic samples were collected from 65 stratigraphics levels from Na Khaem and Huai Luang formations. The studied sections are mainly composed of clay, sandstone and lignite. Rock magnetic experiments revealed that titanomagnetite, magnetite and hematite are the mains carriers of magnetisation. Samples subjected to progressive thermal or alternating field demagnetization procedures exhibit a low stability and a high stability component, with either normal and reversed polarities. The reversal test is positive and indicates that the characteristic remnant magnetization directions correspond to the primary magnetization directions (McFadden and Mc Elhinny, 1990). The mean direction calculated for section 1 are: incl : 23.24 and decl. : 5.01 and incl. : 31.22 et decl. : 7.01 for section 2. These results don't document any rotation with respect to previous study (Benammi et al., 2002). In total, nine polarity zones (four normal and five reverse), that can be reliably be correlated the geomagnetic polarity time scale developed by Gradstein et al, 2004, are recognized from the studied sections. Based on the biochronological constraints, the magnetostartigraphic column of the Mae Moh formations correlates best with chron C5ACr-C5r.3r, between 14.1and 12 Ma. This correlaton revealed a mean sedimentation rate of approximately 21 cm/ky, and a age of 12.7 et 13.2 for for the fossilferous levels (J5, K1, K2) where the mammals remains were found. The analysis of the elements traces spectrum of two ash levels coming from the basins of Mae Moh and Chiang Muan made it possible to establish a new correlation of the Chiang Muan sequence with the GPTS. This correlation prove that the age of the Chiang Muan sequence would be between 13.1 and 12 Ma, and the fossiliferous levels with hominoid (Khoratpithecus Chiangmuanensis) would be dated between 12.2 and 12.4 Ma for the upper lignite and between 13 and 12.8 My for the lower lignite.

Benammi, M.; Coster, P.; Jaeger, J.; Chaimanee, Y.

2007-05-01

219

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

220

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

Science.gov (United States)

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

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

1990-10-01

 
 
 
 
221

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

Energy Technology Data Exchange (ETDEWEB)

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

Lorenz, J.C.

1997-05-01

222

Hydraulic Communication Between Coalbeds and Overlying Sands in the Powder River Basin, Wyoming and Montana: Implications for Re-injection of Coalbed Methane Water  

Science.gov (United States)

Coalbed methane (CBM) production in the Powder River Basin (PRB) is associated with the production of large volumes of CBM water. CBM water from the PRB has high saline and sodium contents, making it unsuitable for agriculture and environmentally damaging. One option for the disposal of CBM water is re-injection into aquifers, but for injection to be feasible the porosity and permeability of the sands needs to be high, the pore pressure needs to be low, and the aquifer cannot be in hydraulic communication with the coalbeds. In order to determine if pore pressures in the aquifers are low enough to allow for significant CBM water re-injection and to determine whether the coals and sands are in hydraulic communication with each other we have calculated pore pressures in 220 wells that monitor water levels in coalbeds and adjacent sands within the PRB. All 220 wells have pore pressures below hydrostatic pressure, implying that re-injection of CBM water should be feasible. However, by analyzing pore pressure changes with time for both the coals and their overlying sands, we find that sands less than 100 ft from coal appear to be in communication with the coalbed. Therefore, re- injection of CBM water should be carried out in sands further than 100 ft from adjacent coalbeds. It also follows that CO2 sequestration in PRB coalbeds should not be carried out in areas where sands and coals are hydraulically connected, as potential leakage pathways for CO2 maybe present.

Ross, H. E.; Zoback, M. D.

2006-12-01

223

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

224

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

Science.gov (United States)

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

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

2011-12-01

225

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

Science.gov (United States)

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

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

2010-05-01

226

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 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 estratigráfico 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 magné (more) tica 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 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 (more) 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.

Pérez-Cruz, L; Urrutia-Fucugauchi, J

2009-09-01

227

Recognition, correlation, and hierarchical stacking patterns of cycles in the Ferry Lake - Uppe Glen Rose, East Texas Basin: Implications for grainstone reservoir distribution  

Energy Technology Data Exchange (ETDEWEB)

Core descriptions and regional log correlation/interpretation of Ferry Lake-Upper Glen Rose strata in the East Texas Basin exhibit the uniformity of cyclicity in these shelf units. The cyclicity is defined by an upward decrease in shale content within each cycle accompanied by an upward increase in anhydrite (Ferry Lake) or carbonate (Upper Glen Rose). Core-to-log calibration of facies indicates that formation resistivity is inversely proportional to shale content and thus is a potential proxy for facies identification beyond core control. Cycles (delineated by resistivity log patterns) were correlated for 90 mi across the shelf; they show little change in log signature despite significant updip thinning due to the regional subsidence gradient. The Ferry-Lake-Upper Glen Rose intervals is interpreted as a composite sequence composed of 13 high-frequency sequences (4 in the Ferry Lake and 9 in the Upper Glen Rose). High-frequency sequences contain approximately 20 ({+-}5) cycles; in the Upper Glen Rose, successive cycles exhibit decreasing proportions of shale and increasing proportions of grain-rich carbonate. High-frequency sequences were terminated by terrigenous inundation, possibly preceded by subaerial exposure. Cycle and high-frequency sequence composition is interpreted to reflect composite, periodic(?) fluctuations is terrigeneous dilution from nearby source areas. Grainstones typically occur (stratigraphically) within the upper cycles of high-frequency sequences, where terrigeneous dilution and turbidity were least and potential for carbonate production and shoaling was greatest. Published mid-Cretaceous geographic reconstructions and climate models suggest that precipitation and runoff in the area were controlled by the seasonal amplitude in solar insolation. In this model, orbital variations, combined with subsidence, hydrography, and bathymetry, were in primary controls on Ferry Lake-Upper Glen Rose facies architecture and stratigraphic development.

Fitchen, W.M.; Bebout, D.G.; Hoffman, C.L. [Univ. of Texas, Austin, TX (United States)

1994-12-31

228

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

UK PubMed Central (United Kingdom)

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.

Zhao JL; Zhang QQ; Chen F; Wang L; Ying GG; Liu YS; Yang B; Zhou LJ; Liu S; Su HC; Zhang RQ

2013-01-01

229

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-02-01

230

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

Science.gov (United States)

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

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

2012-01-01

231

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

UK PubMed Central (United Kingdom)

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

Munyeme M; Munang'andu HM; Nambota A; Muma JB; Phiri AM; Nalubamba KS

2012-01-01

232

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

International Nuclear Information System (INIS)

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

2005-01-01

233

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.

Nielsen, Ole B.; Seidenkrantz, Marit-Solveig; Abrahamsen, Niels; Schmidt, Birthe J.; Koppelhus, Eva B.; Ravn-Sørensen, Helle; Korsbech, Uffe; Nielsen, K Gynther

2003-01-01

234

Temperature-pressure conditions in coalbed methane reservoirs of the Black Warrior basin: Implications for carbon sequestration and enhanced coalbed methane recovery  

Science.gov (United States)

Sorption of gas onto coal is sensitive to pressure and temperature, and carbon dioxide can be a potentially volatile supercritical fluid in coalbed methane reservoirs. More than 5000 wells have been drilled in the coalbed methane fields of the Black Warrior basin in west-central Alabama, and the hydrologic and geothermic information from geophysical well logs provides a robust database that can be used to assess the potential for carbon sequestration in coal-bearing strata.Reservoir temperature within the coalbed methane target zone generally ranges from 80 to 125 ??F (27-52 ??C), and geothermal gradient ranges from 6.0 to 19.9 ??F/1000 ft (10.9-36.2 ??C/km). Geothermal gradient data have a strong central tendency about a mean of 9.0 ??F/1000 ft (16.4 ??C/km). Hydrostatic pressure gradients in the coalbed methane fields range from normal (0.43 psi/ft) to extremely underpressured (coalbed methane fields are high enough that reservoirs never cross the gas-liquid condensation line for carbon dioxide. However, reservoirs have potential for supercritical fluid conditions beyond a depth of 2480 ft (756 m) under normally pressured conditions. All target coal beds are subcritically pressured in the northeastern half of the coalbed methane exploration fairway, whereas those same beds were in the supercritical phase window prior to gas production in the southwestern half of the fairway. Although mature reservoirs are dewatered and thus are in the carbon dioxide gas window, supercritical conditions may develop as reservoirs equilibrate toward a normal hydrostatic pressure gradient after abandonment. Coal can hold large quantities of carbon dioxide under supercritical conditions, and supercritical isotherms indicate non-Langmiur conditions under which some carbon dioxide may remain mobile in coal or may react with formation fluids or minerals. Hence, carbon sequestration and enhanced coalbed methane recovery show great promise in subcritical reservoirs, and additional research is required to assess the behavior of carbon dioxide in coal under supercritical conditions where additional sequestration capacity may exist. ?? 2003 Elsevier Science B.V. All rights reserved.

Pashin, J. C.; McIntyre, M. R.

2003-01-01

235

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)

[en] 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

2005-01-01

236

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

Science.gov (United States)

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

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

2010-12-01

237

Regional sedimentology, conodont biostratigraphy and correlation of Middle Cambrian - Lower Ordovician (?) strata of the {sup F}innegan` and Deadwood Formations, Alberta subsurface, Western Canada Sedimentary Basin  

Energy Technology Data Exchange (ETDEWEB)

Detailed sedimentological and paleontological analysis of 187 cores from the Alberta subsurface were carried out to gain a better understanding of depositional settings and preserved stratigraphy of Middle Cambrian to possibly Lower Ordovician strata within the Western Canada Sedimentary Basin. Analysis indicates that the Cambrian successions were emplaced and reworked as mixed clastic and carbonate ramps or marine shoals within a broad, shallow marine intracontinental basin south of the Peace River Arch, in an area known as the Lloydminster Embayment. Results of detailed sampling and core-logging programs show that the preserved stratigraphy of the Alberta subsurface differs markedly from outcrop sections preserved in the Canadian Rocky Mountain Main Ranges. Indeed, the preserved Cambro-Ordovician stratigraphy of the Western Canadian Sedimentary Basin relates more to the preserved successions to the east and to the south, in the present Williston Basin of Saskatchewan, northern Montana, and North Dakota. Since distinctions of the {sup F}innegan` and Deadwood Formations are very difficult to establish in the Alberta Plains subsurface, it was suggested that the term `Finnegan` be abandoned, and units formerly considered as `Finnegan` be considered part of the Deadwood Formation. Similarly, stratigraphic nomenclature of Cambrian formations should be changed to accommodate similarities in lithology, sedimentary structures and conodont zonation. 66 refs., 3 tabs., 8 figs.

Hein, F. J. [Alberta Geological Survey, Calgary, AB (Canada); Nowlan, G. S. [Geological Survey of Canada, Calgary, AB (Canada)

1998-06-01

238

Debris flows of the mountain massif of Hjorthfjellet and Adventtoppen, Svalbard: Implications for gullies on mountains in the Argyre basin, Mars  

Science.gov (United States)

Martian gullies resemble terrestrial features formed by mass-wasting processes of a flowing mixture of clastic debris and water (debris flows). Their existence on Mars is interpreted to indicate liquid water in the recent past because of their pristine appearance, their stratigraphic relationships to young surface features, their lack of superimposed impact craters, and their distinct albedo relative to the surroundings, indicating limited dust cover [1]. The global distribution of gullies is limited to midand high-latitudes poleward of 30° in both hemispheres, with the highest frequency in the 30°- 50° latitude bands [1, 2]. Gullies occur preferentially on poleward-facing slopes [1, 2, 3, 4]. The most likely and physically most plausible medium to explain the gully morphology is liquid water [e.g., 1, 5]. Two main theories exist for the water source. One holds that water was released from the subsurface [1]. The other proposes that water is deposited as nearsurface ice or snow from the atmosphere and is subsequently melted by insolation [6, 7]. Debris flows found in Arctic climates on Earth could be an equitable analog for the Martian gullies. A comparative analysis might help to understand their formation mechanisms and the latitude-dependent, but clustered distribution as well as their specific orientations. The comparative analysis in the Arctic environment of Svalbard will be carried out in July/August of 2008. First results of the analog study of gullies will be presented at the conference. Debris flows on Svalbard Svalbard is located at 76°-81°N and 10°-35°E (Fig. 1), in the discontinuous zone of permafrost. Because the landscape of Svalbard is under the influence of the polar desert climate, it is a good analog for comparative Martian studies. These were performed in the last two years in the valley of Longyearbyen and on costal slopes of Isfjorden [8]. This study is complementary to the one described by Carlsson et al., 2008, this issue). Here we will focus on the regional distribution of gullies on the Hjorthfjellet and Adventtoppen mountain massif (Fig. 1, inset and Fig. 2), and detailed local studies of individual gullies on the same mountain massif are carried out as described by [8] and [9]. The Hjorthfjellet and Adventtoppen mountain massif consists of four stratigraphic units of sandstone and shales from the Tertiary and Mesozoic [10]. Several studies concerning talus slopes and debris flows on Svalbard have been performed in the last decades [e.g., 11, 12, 13, 14]. Regional studies of [14] using airborne imagery revealed that there are differences in the frequency and activity of debris flows on Svalbard between east- and west-facing slopes. Åkerman [14] suggested that differences in the solar radiation, the depth of the active layer and the amount of precipitation cause variances in the morphology and morphometry of the debris slopes as well as variances in the frequency and age of debris flows between east- and west-facing slopes. Studies and direct observations imply that debris flows on Svalbard are triggered by high intensity rainfall [e.g., 14, 15]. Gullies on mountains in Argyre basin, Mars For a comparative study on Mars we chose the Argyre region. Several isolated mountain massifs occur in the Nereidum and Charitum Montes (Fig. 3) with similar morphologies as the studied massif in Svalbard. A first data analysis with High Resolution Stereo Camera (HRSC) data revealed that gullies occur on the mountain slopes only at specific orientations. Fig. 4 shows an example of an isolated mountain, on which gullies only occur on west-facing slopes. Project Description The formation of gullies on Earth depends on several parameters, including rainfall and/or melting of snow, the presence of steep slopes, and sufficient amounts of fines/debris [e.g., 16]. As on Earth, the differences of slope angles and variabilities in bedrock and grain sizes influence the regional occurrence of gullies [17]. The main goals in both study regions on Earth and Mars are to classify different gully morphologies, map thei

Reiss, D.; Hiesinger, H.; Zanetti, M.; Hauber, E.; Johnsson, A.; Carlsson, E.; Raack, J.; Olvmo, M.; Johansson, H. A. B.; Johansson, L.; Fredriksson, S.; Schmidt, H. T.; McDaniel, S.; Heldmann, J. L.; McKay, C. P.

2008-09-01

239

Petroliferous basins of India  

Energy Technology Data Exchange (ETDEWEB)

This special volume on petroliferous basins of India presents a summary of exploratory efforts in different basins, giving a cohesive picture incorporating historical perspective, review, and analysis of each basin in terms of its hydrocarbon potential. Arranged in order of defined categories of basins, the 15 papers cover extensively explored, partially explored, moderately explored, and essentially unexplored basins; a few papers overlapping these categories are structured to accommodate an overall assessment of the respective areas.

1983-11-01

240

1-D/3-D geologic model of the Western Canada Sedimentary Basin  

Science.gov (United States)

The 3-D geologic model of the Western Canada Sedimentary Basin comprises 18 stacked intervals from the base of the Devonian Woodbend Group and age equivalent formations to ground surface; it includes an estimated thickness of eroded sediments based on 1-D burial history reconstructions for 33 wells across the study area. Each interval for the construction of the 3-D model was chosen on the basis of whether it is primarily composed of petroleum system elements of reservoir, hydrocarbon source, seal, overburden, or underburden strata, as well as the quality and areal distribution of well and other data. Preliminary results of the modeling support the following interpretations. Long-distance migration of hydrocarbons east of the Rocky Mountains is indicated by oil and gas accumulations in areas within which source rocks are thermally immature for oil and (or) gas. Petroleum systems in the basin are segmented by the northeast-trending Sweetgrass Arch; hydrocarbons west of the arch were from source rocks lying near or beneath the Rocky Mountains, whereas oil and gas east of the arch were sourced from the Williston Basin. Hydrocarbon generation and migration are primarily due to increased burial associated with the Laramide Orogeny. Hydrocarbon sources and migration were also influenced by the Lower Cretaceous sub-Mannville unconformity. In the Peace River Arch area of northern Alberta, Jurassic and older formations exhibit high-angle truncations against the unconformity. Potential Paleozoic though Mesozoic hydrocarbon source rocks are in contact with overlying Mannville Group reservoir facies. In contrast, in Saskatchewan and southern Alberta the contacts are parallel to sub-parallel, with the result that hydrocarbon source rocks are separated from the Mannville Group by seal-forming strata within the Jurassic. Vertical and lateral movement of hydrocarbons along the faults in the Rocky Mountains deformed belt probably also resulted in mixing of oil and gas from numerous source rocks in Alberta.

Higley, D. K.; Henry, M.; Roberts, L. N. R.; Steinshouer, D. W.

2005-01-01

 
 
 
 
241

The thermal environment of Cascadia Basin  

Science.gov (United States)

Located adjacent to the NE Pacific convergent boundary, Cascadia Basin has a global impact well beyond its small geographic size. Composed of young oceanic crust formed at the Juan de Fuca Ridge, igneous rocks underlying the basin are partially insulated from cooling of their initial heat of formation by a thick layer of pelagic and turbidite sediments derived from the adjacent North American margin. The igneous seafloor is eventually consumed at the Cascadia subduction zone, where interactions between the approaching oceanic crust and the North American continental margin are partially controlled by the thermal environment. Within Cascadia Basin, basement topographic relief varies dramatically, and sediments have a wide range of thickness and physical properties. This variation produces regional differences in heat flow and basement temperatures for seafloor even of similar age. Previous studies proposed a north-south thermal gradient within Cascadia Basin, with high geothermal flux and crustal temperatures measured in the heavily sedimented northern portion near Vancouver Island and lower than average heat flux and basement temperatures predicted for the central and southern portions of the basin. If confirmed, this prediction has implications for processes associated with the Cascadia subduction zone, including the location of the "locked zone" of the megathrust fault. Although existing archival geophysical data in the central and southern basin are sparse, nonuniformly distributed, and derived from a wide range of historical sources, a substantial N-S geothermal gradient appears to be confirmed by our present compilation of combined water column and heat flow measurements.

Johnson, H. Paul; Hautala, Susan L.; Bjorklund, Tor A.

2012-07-01

242

Classification of sedimentary basins  

Energy Technology Data Exchange (ETDEWEB)

Classification of sedimentary basins is akin to the purpose of investigation. Therefore, it varies a lot. Our chief interest is laid mainly upon the kind of sedimentary deposits that are relevant to the genetic history of sedimentary basins. To meet this end, we have first differentiated the temporal sequence relationship between sedimentation and basin-forming, and second have given due consideration to the genetic processes of sedimentary basins.

Ye, L.; Sun, S.

1980-07-01

243

Basin workshop Aarhus 1989  

Energy Technology Data Exchange (ETDEWEB)

Papers presented at the Basin Workshop held at the University of Aarhus on April 20-22, 1989 under the auspices of the Department of Earth Sciences (Geologisk Institut). The main subject was sedimentary basins and a wide range of geological topics was covered. These included regional and deep geology, stratigraphy, source rock and reservoir analysis and basin and hydrocarbon modelling. (AB).

Balling, N.; Bjoerslev Nielsen, O.; Korstgaard, J.A.; Nielsen, S.B. (eds.)

1990-01-01

244

Regional focus: Victorian basins  

Energy Technology Data Exchange (ETDEWEB)

Victoria is the largest oil producing state in Australia. Exploration activity in 1994/95 has resulted in a number of exploration wells drilled in the Gippsland Basin, and the Otway Basin. This feature contains several articles on the geology and hydrocarbon potential of these basins together with the Murray Basin, the Portland Trough and Torquay Sub-basin. Production licenses for petroleum and exploration permits are listed, showing the tenement number, tenement holder, the area covered by the license and the date of expiration. Tables. figs.

Anon.

1995-10-01

245

Divergent/passive margin basins  

Energy Technology Data Exchange (ETDEWEB)

This book discusses the detailed geology of the four divergent margin basins and establishes a set of analog scenarios which can be used for future petroleum exploration. The divergent margin basins are the Campos basin of Brazil, the Gabon basin, the Niger delta, and the basins of the northwest shelf of Australia. These four petroleum basins present a wide range of stratigraphic sequences and structural styles that represent the diverse evolution of this large and important class of world petroleum basins.

Edwards, J.D. (Shell Oil Company (US)); Santogrossi, P.A. (Shell Offshore Inc. (US))

1989-01-01

246

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 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 (more) 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 system 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 t (more) ransitional matrices, Indicated a small tendency towards improvement in the basin s hydrological conditions at a regional level However, as a consequence of the increase in urban land-use. The basin's plains piedmonts showed a rise in runoff. In addition, the basins' lower areas exhibited a high demand for water resources due to an increased urban land-use in both years, along with the Cuitzeo lake degradation, particularly in terms of pollution and reduction of surface water inflow. The integrated approach used herein constitutes a viable alternative for understanding changes in the amount and spatial distribution of water available in poorly gauged water basins as a consequence of LCLUC.

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

2002-12-01

247

The Heidelberg Basin Drilling Project — basin analysis  

Science.gov (United States)

Within the context of the Heidelberg Basin Project (Gabriel et al. 2008), we present the first results of three-dimensional structural modelling of the basin, based on interpretation of reflection seismics and decompaction using porosity data measured from core material. Firstly, we interpreted six horizons (Base Quaternary, Internal and Base Pliocene, Base Upper Miocene, Internal and Base Mid Miocene Hydrobien beds) from all available industrial (ca. 100 km) and our own reflection seismic sections (ca. 15 km), which lie within a 8 km radius around the Heidelberg UniNord 1/2 boreholes. This data was used to construct a three-dimensional geometrical model of the Heidelberg Basin. Using 300 core samples, we determined the porosity of the Quaternary sediments and constructed an exponential porosity/depth relationship for these rocks, which were then attributed to the model. Lower strata were given values from the literature. The model shows that the Heidelberg basin has a N-S and E-W areal extent of only 10 × 6 km, directly abutting the eastern fault boundary of the Upper Rhine Graben. The strongest synsedimentary tectonic subsidence occurred during the Upper Miocene, Upper Pliocene, and Quarternary. Faults are not seen within the basin at this level, but a NW-SE striking strike-slip structure is recorded to the west of the basin. Furthermore, the sedimentary depocentre shifted 2 km northwards over time to the present location, directly below the city of Heidelberg. We determined that Quaternary sediments have porosities of over 60% at the surface, but at the Base Quaternary porosity is less than 35%. This strong decrease means that 740 m of sediments were compacted to produce the present ca. 500 m thickness of Quaternary strata. Gabriel, G., Ellwanger, D., Hoselmann, C. & Weidenfeller, M. (2008): The Heidelberg Basin Drilling Project. -- Quaternary Science Journal, 57, 3-4, 253-260.

Tanner, David C.; Martini, Nicole; Buness, Hermann; Gabriel, Gerald; Krawczyk, Charlotte M.

2010-05-01

248

Depositional environment of the Upper Jorsalfar - lower Vaale Formation (across the K-T boundary), at the eastern margin of the Moere Basin; implications for reservoir development of the Ormen Lange Field  

Energy Technology Data Exchange (ETDEWEB)

The Ormen Lange Dome of the Moere Basin is one of a series of Cenozoic domal structures in the Norwegian Sea.Significant compression occurred during Oligocene-Miocene, and probably continues up to the present. The reservoir interval of the Ormen Lange Field comprises sandstones both of Maastrichtian and early Palaeocene age. The presentation discusses the structural setting, the stratigraphic setting, the sedimentology of the Maastrichtian-Danian reservoir interval of the Ormen Lange Field, and the tectono stratigraphic development.

Gjelberg, J.; Enoksen, T.; Mangerud, G.; Martinsen, O.J.; Roe, E.

1999-07-01

249

Diagenesis of the Carmopolis member within Siririzinho field, Sergipe-Alagoas basin: implications to fresh-water sensitivity; Diagenese do Membro Carmopolis no Campo de Siririzinho, Bacia de Sergipe-Alagoas: implicacoes quanto a susceptibilidade ao fluxo de agua doce  

Energy Technology Data Exchange (ETDEWEB)

Problems caused in formations sensible to the fresh water influx, deficiency of electric charges, cations or water adsorptions on the rocks surface, changing its porosity properties are discussed. The case of water infiltration on Siririzinho field in Sergipe-Alagoas basin, problems caused in rocks porosity when in presence of Corrensite (a swelling mixed-layer clay mineral), and tests made in wells drilling on the field to verify its water susceptibility are presented. 8 figs., 2 tabs., 15 refs

Sombra, Cristiano L. [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas

1988-01-01

250

Changing Trends of Natural Resources Degradation in Kagera Basin: Case Study of Kagera Sub-Basin, Uganda  

Directory of Open Access Journals (Sweden)

Full Text Available In many respects, river basins are extremely convenient natural resources management units and hence calls for an integrated approach in case of transboundary nature. Environmental resources in Kagera basin are under great threat due to demographic factors leading to wide spread environmental degradation. Land degradation and biodiversity loss are central issues in the basin, but the extent and severity of the degradation pressures are not yet clearly illustrated and their implications largely unknown. To date, natural resource mapping in Kagera basin has been based on isolated case studies for specific purposes and not much has been done in mapping resources and classification of resources degradation by remote sensing applications considering the whole basin. In this study, basin-wide mapping approach was adopted and hot spot areas associated with natural resources use in the basin identified and trends over time established. However, this paper presents results from Kagera River sub-basin, Uganda. Mapping exercise was done by using landsat images and aerial photos of Kagera basin covering the years 1984-2002. Overall, bushland in Kagera sub-basin, Uganda increased by 78% and woodland cover showed mere 6% gain; but a 53% decrease in open woodland sub-type and 29% decrease in closed woodland. Significant shift occurred in cultivation with herbaceous crops (mainly banana) from year 1984-2002 moving from east to west of Kagera sub-basin, Uganda representing 167% increase. Area occupied by permanent swamp decreased 31%. Over the same period, land cover change detection matrix indicates main land cover changes include conversion to bushland (59.34%) followed by conversion to grassland (7.29%) and cultivated land (7.16%), with only 24.19% of the land cover remaining unchanged. It is concluded that the observed changes are, a result of human-induced factors and show unsustainable utilization of natural resources as most of the changes make the land susceptible to degradation.

Casim Umba Tolo; Enock Amos Majule; Joseph Perfect

2012-01-01

251

Geysers: Lower Geyser Basin  

Science.gov (United States)

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

Park, Yellowstone N.

252

Perturbed Basins of Attraction  

CERN Multimedia

Let F be an automorphism of C^k which has a fixed point. It is well known that the basin of attraction is biholomorphically equivalent to C^k. We will show that the basin of attraction of a sequence of automorphisms is also biholomorphic to C^k if all the automorphisms are small perturbations of the original map F.

Peters, H

2004-01-01

253

K Basin safety analysis  

International Nuclear Information System (INIS)

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

1994-01-01

254

K Basin safety analysis  

Energy Technology Data Exchange (ETDEWEB)

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

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

1994-12-16

255

The Ogaden Basin, Ethiopia: an underexplored sedimentary basin  

Energy Technology Data Exchange (ETDEWEB)

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

Teitz, H.H.

1991-01-01

256

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

International Nuclear Information System (INIS)

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

1999-01-01

257

UPPER SNAKE RIVER BASIN, PRELIMINARY BASIN EVALUATION  

Science.gov (United States)

The purpose of this paper was to provide a process and a plan by which the Environmental Protection Agency can insure that water quality goals established in the Water Pollution Control Act Amendments of 1972 are met in the waters of the Upper Snake Basin (17040201, 17040206, 170...

258

Reserves in western basins  

Energy Technology Data Exchange (ETDEWEB)

The objective of this project is to investigate the reserves potential of tight gas reservoirs in three Rocky Mountain basins: the Greater Green River (GGRB), Uinta and Piceance basins. The basins contain vast gas resources that have been estimated in the thousands of Tcf hosted in low permeability clastic reservoirs. This study documents the productive characteristics of these tight reservoirs, requantifies gas in place resources, and characterizes the reserves potential of each basin. The purpose of this work is to promote understanding of the resource and to encourage its exploitation by private industry. At this point in time, the GGRB work has been completed and a final report published. Work is well underway in the Uinta and Piceance basins which are being handled concurrently, with reports on these basins being scheduled for the middle of this year. Since the GGRB portion of the project has been completed, this presentation win focus upon that basin. A key conclusion of this study was the subdivision of the resource, based upon economic and technological considerations, into groupings that have distinct properties with regard to potential for future producibility, economics and risk profile.

Caldwell, R.H.; Cotton, B.W. [Scotia Group, Dallas, TX (United States)

1995-04-01

259

South Pacific Sedimentary Basins  

Energy Technology Data Exchange (ETDEWEB)

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

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

1993-01-01

260

Wandel Sea Basin: Basin analysis. Vol. 1  

Energy Technology Data Exchange (ETDEWEB)

The Wandel Sea Basin project (EFP-91 0012) summarizes a prolonged contribution towards the understanding of the geology of the Wandel Sea Basin in North Greenland. This work commenced when the Geological Survey of Greenland (GGU) launched its first North Greenland mapping campaign in 1978. Since then work around the sediments of this basin have continued - including several expeditions - with financial and practical support from GGU, the Carlsberg Foundation and the Danish Natural Science Research Council. This report consists of a summary, 22 single reports contained in 3 volumes and a full reference list covering this work, included here as Appendix A. Within the EFP-91 project period field work has included expeditions in 1991 and 1993, with additional support granted from the Danish Natural Science Research Council and the Carlsberg foundation. The second expedition was originally planned for 1992, but logistic realities forced it to be postponed one year. This extension allowed further fieldwork to be carried out in the summer of 1994, in Northern Peary Land together with the CASE II expedition from the Bundesamt fuer Geowissenschaften und Rohstoffe, Hannover. A major purpose of the EFP-supported Wandel Sea Basin project was to provide detailed sedimentological and biostratigraphical data for an improved evaluation of the hydrocarbon potential onshore eastern North Greenland, and to provide data for evaluation of the offshore areas in the northern part of the East Greenland Shelf. Similarly an evaluation of the structural evolution was a target, in order to understand the distribution of the now fairly scattered sedimentary successions constituting the Wandel Sea Basin. (EG)

Haakansson, E. (ed.); Heinberg, C.; Madsen, L.; Moelgaard, S.; Schack Pedersen, S.A.; Piasecki, S.; Audun Rasmussen, J.; Stemmerik, L.; Zinck-Joergensen, K.

1994-11-01

 
 
 
 
261

Wandel Sea Basin: Basin analysis. Vol. 2  

Energy Technology Data Exchange (ETDEWEB)

The Wandel Sea Basin project (EFP-91 0012) summarizes a prolonged contribution towards the understanding of the geology of the Wandel Sea Basin in North Greenland. This work commenced when the Geological Survey of Greenland (GGU) launched its first North Greenland mapping campaign in 1978. Since then work around the sediments of this basin have continued - including several expeditions - with financial and practical support from GGU, the Carlsberg Foundation and the Danish Natural Science Research Council. This report consists of a summary, 22 single reports contained in 3 volumes and a full reference list covering this work, included here as Appendix A. Within the EFP-91 project period field work has included expeditions in 1991 and 1993, with additional support granted from the Danish Natural Science Research Council and the Carlsberg foundation. The second expedition was originally planned for 1992, but logistic realities forced it to be postponed one year. This extension allowed further fieldwork to be carried out in the summer of 1994, in Northern Peary Land together with the CASE II expedition from the Bundesamt fuer Geowissenschaften und Rohstoffe, Hannover. A major purpose of the EFP-supported Wandel Sea Basin project was to provide detailed sedimentological and biostratigraphical data for an improved evaluation of the hydrocarbon potential onshore eastern North Greenland, and to provide data for evaluation of the offshore areas in the northern part of the East Greenland Shelf. Similarly an evaluation of the structural evolution was a target, in order to understand the distribution of the now fairly scattered sedimentary successions constituting the Wandel Sea Basin. (EG)

Haakansson, E. (ed.); Heinberg, C.; Madsen, L.; Moelgaard, S.; Schack Pedersen, S.A.; Piasecki, S.; Audun Rasmussen, J.; Stemmerik, L.; Zinck-Joergensen, K.

1994-11-01

262

Wandel Sea Basin: Basin analysis. Vol. 3  

Energy Technology Data Exchange (ETDEWEB)

The Wandel Sea Basin project (EFP-91 0012) summarizes a prolonged contribution towards the understanding of the geology of the Wandel Sea Basin in North Greenland. This work commenced when the Geological Survey of Greenland (GGU) launched its first North Greenland mapping campaign in 1978. Since then work around the sediments of this basin have continued - including several expeditions - with financial and practical support from GGU, the Carlsberg Foundation and the Danish Natural Science Research Council. This report consists of a summary, 22 single reports contained in 3 volumes and a full reference list covering this work, included here as Appendix A. Within the EFP-91 project period field work has included expeditions in 1991 and 1993, with additional support granted from the Danish Natural Science Research Council and the Carlsberg foundation. The second expedition was originally planned for 1992, but logistic realities forced it to be postponed one year. This extension allowed further fieldwork to be carried out in the summer of 1994, in Northern Peary Land together with the CASE II expedition from the Bundesamt fuer Geowissenschaften und Rohstoffe, Hannover. A major purpose of the EFP-supported Wandel Sea Basin project was to provide detailed sedimentological and biostratigraphical data for an improved evaluation of the hydrocarbon potential onshore eastern North Greenland, and to provide data for evaluation of the offshore areas in the northern part of the East Greenland Shelf. Similarly an evaluation of the structural evolution was a target, in order to understand the distribution of the now fairly scattered sedimentary successions constituting the Wandel Sea Basin. (EG)

Haakansson, E. (ed.); Heinberg, C.; Madsen, L.; Moelgaard, S.; Schack Pedersen, S.A.; Piasecki, S.; Audun Rasmussen, J.; Stemmerik, L.; Zinck-Joergensen, K.

1994-11-01

263

Potential basin-centered gas accumulation: Raton Basin, Colorado  

Energy Technology Data Exchange (ETDEWEB)

The Raton basin of south-central Colorado is a small basin of Laramide age that is analogous structurally to other Rocky Mountain basins that contain commercial basin-centered gas deposits in tight Cretaceous sandstones. Moreover, the mineralogy, depositional setting, and stratigraphic succession of Cretaceous rocks in the Raton basin generally are comparable to gas-productive basins in the Rocky Mountain region where similar thick, gas-prone, thermally mature source rocks are present. Oil, condensate, and abundant natural gas shows occur in Cretaceous and Tertiary beds throughout the Raton basin, but substantial petroleum production has not yet been established. Certain geologic features may have influenced gas accumulation, such as ground-water movement, fracturing, igneous intrusions, CO/sub 2/ generation, mildly elevated heat flow, sandstone mineralogy, and diagenesis. Drilling density is low, particularly in the deeper parts of the basin. Prospects of developing a basin-centered gas deposit here appear favorable.

Rose, P.R.; Everett, J.R.; Merin, I.S.

1984-04-01

264

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

International Nuclear Information System (INIS)

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

1997-01-01

265

Identification of long-chain 1,2-di- n -alkylbenzenes in Amposta crude oil from the Tarragona Basin, Spanish Mediterranean: Implications for the origin and fate of alkylbenzenes  

Science.gov (United States)

Homologous series of C 15 -C 40 1,2-di- n -alkylbenzenes (with alkyl side chains containing 2 or more carbon atoms) were identified in the Amposta crude oil (Tarragona Basin, Spain). Structural assignments were confirmed by synthesis of the C 18 members of this series. These 1,2-dialkylbenzenes in combination with monoalkylbenzenes and 2-alkyltoluenes dominate the alkylbenzene distribution in this "immature" oil. This phenomenon lends support to the hypothesis that alkylbenzenes are formed in the subsurface by cyclisation and aromatisation reactions of linear, functionalised precursors. In other, more mature, oils other alkyltoluenes isomers are present as well and 1,2-dialkylbenzenes have not been reported. Isomerisation reactions of initially formed 2-alkyltoluenes during catagenesis may lead to the formation of thermodynamically more stable isomers (i.e., ortho and para alkyltoluenes) encountered in these more mature crude oils.

Sinninghe Damsté, Jaap S.; Kock-van Dalen, A. C.; Albrecht, Pierre A.; de Leeuw, Jan W.

1991-12-01

266

Identification of long-chain 1,2-di-n-alkylbenzenes in Amposta crude oil from the Tarragona Basin, Spanish Mediterranean: Implications for the origin and fate of alkylbenzenes  

Energy Technology Data Exchange (ETDEWEB)

Homologous series of C{sub 15}-C{sub 40} 1,2-di-n-alkylbenzenes (with alkyl side chains containing 2 or more carbon atoms) were identified in the Amposta crude oil (Tarragona Basin, Spain). Structural assignments were confirmed by synthesis of the C{sub 18} members of this series. These 1,2-dialkylbenzenes in combination with monoalkylbenzenes and 2-alkyltoluenes dominate the alkylbenzene distribution in this immature' oil. This phenomenon lends support to the hypothesis that alkylbenzenes are formed in the subsurface by cyclization and aromatization reactions of linear, functionalized precursors. In other, more mature, oils other alkyltoluenes isomers are present as well and 1,2-dialkylbenzenes have not been reported. Isomerization reactions of initially formed 2-alkyltoluenes during catagenesis may lead to the formation of thermodynamically more stable isomers (i.e., ortho and para alkyltoluenes) encountered in these more mature crude oils.

Sinninghe Damste, J.S.; Kock-Van Dalen, A.C.; Leeuw, J.W. De (Delft Univ. of Technology (Netherlands)); Albrecht, P.A. (Univ. Louis Pasteur, Strasbourg (France))

1991-12-01

267

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

Science.gov (United States)

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

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

2013-08-16

268

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

UK PubMed Central (United Kingdom)

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

Zell C; Kim JH; Abril G; Sobrinho RL; Dorhout D; Moreira-Turcq P; Sinninghe Damsté JS

2013-01-01

269

Clastic sabkhas and diachroneity at the top of the Sherwood Sandstone Group: East Irish Sea Basin  

Energy Technology Data Exchange (ETDEWEB)

The identification of early evaporite sulphate cements with a marine isotopic signature within the Ormskirk Sandstone Formation supports previous models of diachroneity at the contact of the Sherwood Sandstone Group and the Mercia Mudstone Group in the East Irish Sea Basin. Basin-wide correlations suggest that, at the onset of transgression, a range of sandflat and aeolian dune environments co-existed on the margins of the basin with marginal marine environments toward the basin centre. One of the major implications of this model is that the high quality aeolian sandstone reservoirs encountered near the top of the Ormskirk Sandstone in the southern parts of the East Irish Sea Basin have no reservoir correlatives in large areas of the basin but can be predicted on the margins. (author)

Thompson, Jillian; Meadows, Neil S. [Geochem Group Ltd., Chester (United Kingdom)

1997-12-31

270

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

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

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

2006-01-01

271

Geochemistry and characteristics of nitrogen transport at a confined animal feeding operation in a coastal plain agricultural watershed, and implications for nutrient loading in the Neuse River basin, North Carolina, 1999-2002  

Science.gov (United States)

Chemical, geologic, hydrologic, and age-dating information collected between 1999 and 2002 were used to examine the transport of contaminants, primarily nitrogen, in ground water and the pathways to surface water in a coastal plain setting in North Carolina. Data were collected from more than 35 wells and 4 surface-water sampling sites located in a 0.59 square-mile basin to examine detailed hydrogeology and geochemical processes affecting nutrient fate and transport. Two additional surface-water sampling sites were located downstream from the primary study site to evaluate basin-scale effects. Chemical and flow data also were collected at an additional 10 sites in the Coastal Plain portion of the Neuse River basin located between Kinston and New Bern, North Carolina, to evaluate loads transported in the Neuse River and primary tributary basins. At the Lizzie Research Station study site in North Carolina, horizontal flow is induced by the presence of a confining unit at shallow depth. Age-dating, chemical, and piezometric data indicate that horizontal flow from the surficial aquifer is the dominant source of ground water to streamflow. Nitrogen applied on cultivated fields at the Lizzie Research Station is substantially reduced as it moves from recharge to discharge areas. Denitrification in deeper parts of the aquifer and in riparian zones is indicated by a characterization of redox conditions in the aquifer and by the presence of excess nitrogen gas. Direct ground-water discharge of nitrate to surface water during base-flow conditions is unlikely to be significant because of strongly reducing conditions that occur in the riparian zones of these streams. Nitrate loads from a drainage tile at the study site may account for much of the nitrate load in the receiving stream, indicating that a major source of nutrients from ground water to this stream is artificial drainage. During base-flow conditions when the streams are not flowing, it is hypothesized that the mineralization of organic matter on the streambed is the source of nitrate and(or) ammonium in the stream. Base flow is a small contributor to nitrogen loads, because both flows and inorganic nitrogen concentrations are low during summer months. Effects of a confined hog operation on ground-water quality also were evaluated. The use of sprayed swine wastes to fertilize crops at the Lizzie Research Station study site since 1995 resulted in increased concentrations of nitrate and other chemical constituents in ground water beneath spray fields when compared to ground water beneath fields treated with commercial fertilizer. The nitrate concentration in ground water from the spray field well increased by a factor of 3.5 after 4 years of spray applications. Nitrate concentrations ranged from 10 to 35 milligrams per liter, and one concentration as high as 56 milligrams per liter was observed in water from this well in spring 2002. This finding is in agreement with findings of other studies conducted in the Coastal Plain of North Carolina that nitrate concentrations were significantly higher in ground water from cultivated fields sprayed with swine wastes than from fields treated with commercial fertilizer. Loads and yields of nitrogen and phosphorus in 14 streams in the Neuse River basin were evaluated for calendar years 2000 and 2001. Data indicate that anthropogenic effects on nitrogen yields were greatest in the first-order stream studied (yields were greater than 2 tons per square mile [ton/mi2] and 1 ton/mi2 or less in second- and higher-order streams) in the Little Contentnea Creek subbasin. Nitrogen yields in streams in the Contentnea Creek subbasin ranged from 0.59 to 2 ton/mi2 with typical yields of approximately 1 ton/mi2. Contentnea Creek near Evansdale had the highest yield (2 ton/mi2), indicating that a major source of nitrogen is upstream from this station. Nitrogen yields were lower at Contentnea Creek at Hookerton in 2000 and 2001 compared to previous yi

Spruill, T. B.; Tesoriero, A. J.; Mew, H. E., Jr.; Farrell, K. M.; Harden, S. L.; Colosimo, A. B.; Kraemer, S. R.

2005-01-01

272

Impact craters: their importance in geologic record and implications for natural resource development  

Energy Technology Data Exchange (ETDEWEB)

Impacting bodies of sufficient size traveling at hypervelocities carry tremendous potential energy. This relatively infrequent process results in the instantaneous formation of unique structures that are characterized by extensive fracturing and brecciation of the target material. Impacts onto continental shield areas can create rich ore deposits, such as the Sudbury mining district in Canada. Impacts into the sedimentary column can instantaneously create hydrocarbon reservoirs out of initially nonporous rocks, such as at Red Wing Creek and Viewfield in the Williston basin. Associated reservoirs are usually limited to a highly deformed central uplift in larger craters, or to the fractured rim facies in smaller craters. The presence of reservoirs and trapping mechanisms is largely dependent, however, upon the preservation state of the crater in the subsurface. A catastrophic extraterrestrial event (a large asteroid impact) has also been suggested as the cause for the extinction of the dinosaurs, but the latest theory proposes a companion star with a 26 m.y. periodicity as the cause for numerous lifeform extinctions over a similar time interval. Regardless of their magnitude and distribution over the earth, it is clear that catastrophic extraterrestrial events have been responsible for altering the geologic column locally, regionally, and quite possibly on a global scale.

Levie, D. Jr.

1986-05-01

273

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

Science.gov (United States)

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

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

2001-11-01

274

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

Directory of Open Access Journals (Sweden)

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

Juan Miguel Iwaszkiw; Francisco Firpo Lacoste

2011-01-01

275

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

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

Antonio Rangel; Roberto Hernández

2007-01-01

276

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

Scientific Electronic Library Online (English)

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

Iwaszkiw, Juan Miguel; Firpo Lacoste, Francisco

2011-06-01

277

Anadarko Basin conodont studies  

Science.gov (United States)

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

Repetski, John E.

1989-01-01

278

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

International Nuclear Information System (INIS)

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

2012-01-01

279

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

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

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

2007-01-01

280

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

Scientific Electronic Library Online (English)

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

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

2007-03-01

 
 
 
 
281

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

International Nuclear Information System (INIS)

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

1983-01-01

282

Pacific basin energy  

Energy Technology Data Exchange (ETDEWEB)

Testimony is presented concerning pending legislation which provides for the assessment and development of the potential for renewable energy sources in the U.S. insular areas, including the trust territories. Options for self-sufficiency throughout the Pacific basin are considered in light of rapidly escalating fuel costs.

1980-01-01

283

Cenozoic basin development in Hispaniola  

Energy Technology Data Exchange (ETDEWEB)

Four distinct generations of Cenozoic basins have developed in Hispaniola (Haiti and Dominican Republic) as a result of collisional or strike-slip interactions between the North America and Caribbean plates. First generation basins formed when the north-facing Hispaniola arc collided with the Bahama platform in the middle Eocene; because of large post-Eocene vertical movements, these basins are preserved locally in widely separated areas but contain several kilometers of arc and ophiolite-derived clastic marine sediments, probably deposited in thrust-loaded, flexure-type basins. Second generation basins, of which only one is exposed at the surface, formed during west-northwesterly strike-slip displacement of southern Cuba and northern Hispaniola relative to central Hispaniola during the middle to late Oligocene; deposition occurred along a 5-km (3-mi) wide fault-angle depression and consisted of about 2 km (1 mi) of submarine fan deposits. Third generation basins developed during post-Oligocene convergent strike-slip displacement across a restraining bend formed in central Hispaniola; the southern 2 basins are fairly symmetrical, thrust-bounded ramp valleys, and the third is an asymmetrical fault-angle basin. Fourth generation basins are pull-aparts formed during post-Miocene divergent strike-slip motion along a fault zone across southern Hispaniola. As in other Caribbean areas, good source rocks are present in all generations of basins, but suitable reservoir rocks are scarce. Proven reservoirs are late Neogene shallow marine and fluvial sandstones in third generation basins.

Mann, P.; Burke, K.

1984-04-01

284

Comparison of Driving Conditions and the Frequency of Rich Open Loop Operation for the South Coast Air Basin and the Federal Test Procedure with a 1991 Ffv Ford Taurus: Implications for Mobile Source Emissions Models.  

Science.gov (United States)

To aid in resolving critical questions about the accuracy of mobile source emissions models (e.g. EMFAC and MOBILE), this study provided a direct evaluation of real-time, on-road vehicle and engine operating parameters, and investigated their relationship to rich open loop emissions and driving pattern characteristics. More than 200,000 seconds of data were collected using a 1991 Ford Taurus under varying conditions in the South Coast Air Basin over a matrix of routes. Dynamometer emissions tests were conducted with the vehicle and the emissions data were used to model on-road emissions. The average on-road speed was 31.2 mph compared to 20.7 mph for the FTP and the maximum acceleration rate on-road was 10.0 mph s^{-1} compared to 3.3 mph s^{-1} for the FTP. Rich open loop operation occurred an average of 0.40% of the time on-road but was not observed during FTP and HFET tests. Factors which increased the frequency of rich open loop operation included aggressive driving, up-hill grades, merging and free flowing traffic conditions. Rich open loop emission rates were ~100, ~1700 and ~ 80 times higher than closed loop for HC, CO and NO_{rm x} (0.038 g s^{-1}, 3.17 g s ^{-1}, and 0.106 g s^ {-1} respectively during open loop operation). Modeling emissions as a function of load and speed was more accurate than with an acceleration-and speed-based model. The average modeled on-road emission rates were lower than the current emissions certification standards, but they were all greater than the emission rates measured for the FTP (33%, 190%, and 120% for HC, CO and NO _{rm x} respectively). Rich open loop operation accounted for ~ 70% of the increase in CO and ~ 40% of the increase in HC and NO, with the remainder attributed to differences between the FTP and on-road driving patterns. The results of the modeling studies suggest emissions from rich open loop operation, because they are not included in the FTP, may account for a portion of the under-estimation of current mobile source emissions models. Much more needs to be known about the frequency of rich open loop operation on-road and the emission rates during this operation for a variety of vehicles.

St. Denis, Michael Joseph

285

Nature of the Crust in the Laxmi Basin, Western Continental Margin of India  

Science.gov (United States)

The nature of the crust in the Laxmi Basin, western margin of India is an uncertain issue; more importantly this has implications on paleo-geographic reconstructions of the western Indian Ocean. We have analysed three geophysical datasets and modelled gravity and magnetic anomalies for determining nature of the crust. Basement of the Laxmi Basin includes numerous highs, which make the basement uneven and shallower compared to the Western Basin. The Laxmi Basin is characterised by a broad gravity high and a narrower prominent gravity low within it, while within the basin the broad anomaly gradually increases towards north. The Panikkar Ridge is associated with the gravity low, which is comparable, at least in sign, to known negative gravity anomaly of Laxmi Ridge. Intrusive structures mapped in the Laxmi Basin coincide with significant magnetic anomalies, which were earlier interpreted as seafloor-spreading anomalies. Model studies reveal that the Laxmi Basin consists of ~14 km thick stretched continental crust, in which magmatic bodies have been emplaced, whereas Panikkar Ridge remains less altered stretched continental crust. The crust of the Laxmi Basin is mostly thinner than crust under Laxmi Ridge and continental margin. In addition to the rift-drift related stretching of the continental margin the Laxmi Basin possibly has undergone extra stretching in E-W direction during the pre-Tertiary period. At ~68 Ma Deccan volcanism on western India may have disrupted the initial conditions that were leading to onset of spreading in the basin. Subsequently the Réunion hotspot had emplaced the volcanic material within the stretched thinned continental crust. We interpret the Laxmi Basin as a failed rift, undergone stretching following intraplate kinematics prior to Deccan volcanism. Key words: Laxmi Basin, Laxmi Ridge, Panikkar Ridge, stretched continental crust, Deccan volcanism, northwest continental margin of India

Krishna, K. S.; Gopala Rao, D.; Sar, D.

2006-05-01

286

Dimension of fractal basin boundaries  

Energy Technology Data Exchange (ETDEWEB)

In many dynamical systems, multiple attractors coexist for certain parameter ranges. The set of initial conditions that asymptotically approach each attractor is its basin of attraction. These basins can be intertwined on arbitrary small scales. Basin boundary can be either smooth or fractal. Dynamical systems that have fractal basin boundary show final state sensitivity of the initial conditions. A measure of this sensitivity (uncertainty exponent {alpha}) is related to the dimension of the basin boundary d = D - {alpha}, where D is the dimension of the phase space and d is the dimension of the basin boundary. At metamorphosis values of the parameter, there might happen a conversion from smooth to fractal basin boundary (smooth-fractal metamorphosis) or a conversion from fractal to another fractal basin boundary characteristically different from the previous fractal one (fractal-fractal metamorphosis). The dimension changes continuously with the parameter except at the metamorphosis values where the dimension of the basin boundary jumps discontinuously. We chose the Henon map and the forced damped pendulum to investigate this. Scaling of the basin volumes near the metamorphosis values of the parameter is also being studied for the Henon map. Observations are explained analytically by using low dimensional model map.

Park, B.S.

1988-01-01

287

Western Canadian Sedimentary Basin  

International Nuclear Information System (INIS)

Ziff Energy Group is a large energy consulting and research organization with offices in Calgary and Houston. Ziff Energy offers wellhead to burner expertise. Their products and services include natural gas consulting, regulatory services, estimating producer finding and development costs, reducing field operating costs and heavy oil operating cost benchmarking. Canadian and U.S. domestic demands for natural gas were compared and an overview of natural gas pipeline projects and growth in exports was presented. The resource potential of the Western Canadian Sedimentary Basin (WCSB) was reviewed and was found to have grown steadily. It was suggested that significant opportunities still exist in the Basin for future resource development. The total number of wells completed in the WCSB for 1994 to 1997 has grown from 11,706 to 16,173. Finding and development costs for the increase in supply were estimated. tabs., figs.

1998-01-01

288

U-Pb and Pb-Pb study of the Murchison Greenstone Belt and of the Evander gold-bearing basin, South Africa. Implications for the evolution of the Kaapvaal craton; Etude U-Pb et Pb-Pb de la Murchison Greenstone Belt et du bassin aurifere d'Evander, Afrique du Sud. Implications pour l'evolution du Kaapvaal craton  

Energy Technology Data Exchange (ETDEWEB)

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

Poujol, M

1997-12-01

289

Basin fillings and sequences development in Xinlicheng basin of the eastern of Songliao  

Energy Technology Data Exchange (ETDEWEB)

The basin fillings of Shahezi Formation (J{sub 3}sh) in Xinlicheng basin of the east margin of the Songliao demonstrates a transgressive-regressive process during which the different sequences including lake basin sequence and alluvial sequence (river basin sequence) developed at different stages. The lake basin sequence occurred in lake basin belonging to early stage of Xinlicheng basin`s development and the alluvial sequence occurred in river basin belonging to a later stage of that. The developments of those two types of sequences are the sedimentary and stratal response to the basin dynamics of the Songliao basin at rifting time. 12 refs., 2 figs.

Cheng Rihui; Liu Zhaojun; Xu Yong [Changchun University of Earth Sciences (China)

1996-12-31

290

Caribbean basin framework, 3: Southern Central America and Colombian basin  

Energy Technology Data Exchange (ETDEWEB)

The authors recognize three basin-forming periods in southern Central America (Panama, Costa Rica, southern Nicaragua) that they attempt to correlate with events in the Colombian basin (Bowland, 1984): (1) Early-Late Cretaceous island arc formation and growth of the Central American island arc and Late Cretaceous formation of the Colombian basin oceanic plateau. During latest Cretaceous time, pelagic carbonate sediments blanketed the Central American island arc in Panama and Costa Rica and elevated blocks on the Colombian basin oceanic plateau; (2) middle Eocene-middle Miocene island arc uplift and erosion. During this interval, influx of distal terrigenous turbidites in most areas of Panama, Costa Rica, and the Colombian basin marks the uplift and erosion of the Central American island arc. In the Colombian basin, turbidites fill in basement relief and accumulate to thicknesses up to 2 km in the deepest part of the basin. In Costa Rica, sedimentation was concentrated in fore-arc (Terraba) and back-arc (El Limon) basins; (3) late Miocene-Recent accelerated uplift and erosion of segments of the Central American arc. Influx of proximal terrigenous turbidites and alluvial fans in most areas of Panama, Costa Rica, and the Colombian basin marks collision of the Panama arc with the South American continent (late Miocene early Pliocene) and collision of the Cocos Ridge with the Costa Rican arc (late Pleistocene). The Cocos Ridge collision inverted the Terraba and El Limon basins. The Panama arc collision produced northeast-striking left-lateral strike-slip faults and fault-related basins throughout Panama as Panama moved northwest over the Colombian basin.

Kolarsky, R.A.; Mann, P. (Univ. of Texas, Austin (United States))

1991-03-01

291

Movement of water infiltrated from a recharge basin to wells.  

UK PubMed Central (United Kingdom)

Local surface water and stormflow were infiltrated intermittently from a 40-ha basin between September 2003 and September 2007 to determine the feasibility of recharging alluvial aquifers pumped for public supply, near Stockton, California. Infiltration of water produced a pressure response that propagated through unconsolidated alluvial-fan deposits to 125 m below land surface (bls) in 5 d and through deeper, more consolidated alluvial deposits to 194 m bls in 25 d, resulting in increased water levels in nearby monitoring wells. The top of the saturated zone near the basin fluctuates seasonally from depths of about 15 to 20 m. Since the start of recharge, water infiltrated from the basin has reached depths as great as 165 m bls. On the basis of sulfur hexafluoride tracer test data, basin water moved downward through the saturated alluvial deposits until reaching more permeable zones about 110 m bls. Once reaching these permeable zones, water moved rapidly to nearby pumping wells at rates as high as 13 m/d. Flow to wells through highly permeable material was confirmed on the basis of flowmeter logging, and simulated numerically using a two-dimensional radial groundwater flow model. Arsenic concentrations increased slightly as a result of recharge from 2 to 6 µg/L immediately below the basin. Although few water-quality issues were identified during sample collection, high groundwater velocities and short travel times to nearby wells may have implications for groundwater management at this and at other sites in heterogeneous alluvial aquifers.

O'Leary DR; Izbicki JA; Moran JE; Meeth T; Nakagawa B; Metzger L; Bonds C; Singleton MJ

2012-03-01

292

ADVANCED CHEMISTRY BASINS MODEL  

Energy Technology Data Exchange (ETDEWEB)

The advanced Chemistry Basin Model project has been operative for 48 months. During this period, about half the project tasks are on projected schedule. On average the project is somewhat behind schedule (90%). Unanticipated issues are causing model integration to take longer then scheduled, delaying final debugging and manual development. It is anticipated that a short extension will be required to fulfill all contract obligations.

William Goddard III; Lawrence Cathles III; Mario Blanco; Paul Manhardt; Peter Meulbroek; Yongchun Tang

2004-05-01

293

Advanced Chemistry Basins Model  

Energy Technology Data Exchange (ETDEWEB)

The DOE-funded Advanced Chemistry Basin model project is intended to develop a public domain, user-friendly basin modeling software under PC or low end workstation environment that predicts hydrocarbon generation, expulsion, migration and chemistry. The main features of the software are that it will: (1) afford users the most flexible way to choose or enter kinetic parameters for different maturity indicators; (2) afford users the most flexible way to choose or enter compositional kinetic parameters to predict hydrocarbon composition (e.g., gas/oil ratio (GOR), wax content, API gravity, etc.) at different kerogen maturities; (3) calculate the chemistry, fluxes and physical properties of all hydrocarbon phases (gas, liquid and solid) along the primary and secondary migration pathways of the basin and predict the location and intensity of phase fractionation, mixing, gas washing, etc.; and (4) predict the location and intensity of de-asphaltene processes. The project has be operative for 36 months, and is on schedule for a successful completion at the end of FY 2003.

William Goddard; Mario Blanco; Lawrence Cathles; Paul Manhardt; Peter Meulbroek; Yongchun Tang

2002-11-10

294

The Kuznetsk coal basin  

Energy Technology Data Exchange (ETDEWEB)

Reports on a visit of Polish coal mine designers from the Central Office of Study and Mine Design to the Kuznetsk coal basin. General information on the basin, where proved reserves amount to 725,000 Mt, is presented. The deposit includes 260 seams with average seam thickness of 4 m and coal quality among the best in the world. Annual coal production is 150 Mt (20% of the total USSR coal production) and expected to rise to 200 Mt/a in the year 2000. Polish longwall equipment sets are widely used in the basin despite their price being 2-3 times higher than the price of similar Soviet-made sets. Information on unique mining industry projects is given. Such Soviet organizations as the Coal Institute of the Soviet Academy of Sciences (Siberian Branch) and Mine Design Office Kuzgiproshakht are characterized. The Butovskaya mine (20 km from Kemerovo) is described. Cooperation possibilities between Polish and Soviet mine design offices are outlined.

Mazurek, A.

1989-06-01

295

Geology of the Bornholm Basin  

Energy Technology Data Exchange (ETDEWEB)

The present volume is collection of papers dealing with various aspects of the geology of the Bornholm Basin. Although most of the papers del with results from a joint Russian, German and Danish expedition to the Bornholm Basin in 1989, also results from previous Russian expeditions to the basin are included. Here we present an introduction to the study area and the locality names used in the papers as well as a general description of the volume content. (au) 329 refs.

Emelyanov, E.; Christiansen, C.; Michelsen, O. [eds.

1995-12-31

296

Positive implicative ordered filters of implicative semigroups  

Directory of Open Access Journals (Sweden)

Full Text Available We introduce the notion of positive implicative ordered filters in implicative semigroups. We show that every positive implicative ordered filter is both an ordered filter and an implicative ordered filter. We give examples that an ordered filter (an implicative ordered filter) may not be a positive implicative ordered filter. We also give equivalent conditions of positive implicative ordered filters. Finally we establish the extension property for positive implicative ordered filters.

Young Bae Jun; Kyung Ho Kim

2000-01-01

297

Solimoes Basin; Bacia do Solimoes  

Energy Technology Data Exchange (ETDEWEB)

Stratigraphic maps of the sedimentary Solimoes Basin, its formation, geographic localization, geological age, rocks characterization on its several layers are presented. Based on PETROBRAS internal works, the stratigraphic maps shows the facies distribution, depositional sequences, lithology, and geological structure of the basin. 24 figs., 22 refs.

Eiras, J.F.; Becker, C.R.; Gonzaga, F.G.; Silva, J.G. da; Matsuda, N.S. [PETROBRAS, Belem, PA (Brazil). Distrito de Exploracao do Norte; Souza, E.M.; Daniel, L.M.F. [PETROBRAS, Salvador, BA (Brazil). Distrito de Exploracao da Bahia; Feijo, F.J. [PETROBRAS, Rio de Janeiro, RJ (Brazil)

1994-01-01

298

Atlantic marginal basins of Africa  

Energy Technology Data Exchange (ETDEWEB)

The over 10,000-km long Atlantic margin of Africa is divisible into thirty basins or segments of the margin that collectively contain over 18.6 x 10/sup 6/ km/sup 3/ of syn-breakup and post-breakup sediments. Twenty of these basins contain a sufficiently thick volume of sediments to be considered prospects. These basins lie, at least partially, within the 200 m isobath. The distribution of source rocks is broad enough to give potential to each of these basins. The sedimentation patterns, tectonics, and timing of events differ from basin to basin and are related directly to the margin's complex history. Two spreading modes exist: rift and transform. Rifting dates from Late Triassic-Early Jurassic in the northwest to Early Cretaceous south of the Niger Delta. A complex transform fault system separated these two margins. Deep-water communication between the two basins became established in the middle Cretaceous. This Mesozoic-Cenozoic cycle of rifting and seafloor spreading has segmented the margin and where observable, basins tend to be bounded by these segments.

Moore, G.T.

1988-02-01

299

Basin modeling and hydrocarbon exploration  

Energy Technology Data Exchange (ETDEWEB)

The generation, migration and accumulation of oil and gas are a series of dynamic processes linked to the evolution of sedimentary basins. A sedimentary basin is formed by very complex interrelated processes, which form a multiparameter dynamic system. Therefore, evaluation and prediction of the hydrocarbon potential of a basin requires an accurate and quantified reconstruction of the relevant processes. Computer-aided, integrated basin modeling on the basis of numerical simulation enables such a reconstruction. Processes which should be either simulated or considered in a forward modeling approach, aiming to predict the location and type of hydrocarbon accumulations are discussed. Additionally, parameters which are required for a reliable simulation of different processes, such as sediment accumulation, compaction, fluid flow and pressure development, transfer of heat, basin deformation, oil and gas generation, oil expulsion and secondary migration are evaluated. Furthermore, with the help of simulated case histories the close interrelations between different parameters are demonstrated. 14 figs., 1 tab., 74 refs.

Yalcin, M.N. (TUEBITAK, Marmara Research Center, Gebze-Kocaeli (Turkey))

1991-06-01

300

Reserves in western basins  

Energy Technology Data Exchange (ETDEWEB)

Work is continuing on the Greater Green River Basin area. Of the five plays identified by the USGS, we chose to firstly address the Lewis. Lewis Technical work on the Lewis is now completed, including relevant geological work, rock property determination and rationalization of test and performance data. This has resulted in the generation of a recovery factor model for the Lewis and initial results have been summarized and were presented at a DOE/GRI workshop in Denver during November, 1992. Following completion of the Lewis technical work, we have chosen to move on to the Mesaverde which represents the largest play in terms of potential volume, number of wells, thickness and complexity. As of this date, work on the Mesaverde is well underway with initial dataset and base map construction completed and work commenced on calculation of thickness and rock property information, concentrating firstly on the eastern side of the Greater Green River Basin. The following items highlight accomplishments to date: (1) Log Analysis: We have been working with EG G Morgantown to obtain digitized well logs to avoid having to go through the process of digitizing material unnecessarily. (2) Test Data and Effectiveness of Frac Treatment: Through the work on the Lewis, an investigation was completed on attempting to correlate well performance with frac treatment. (3) Mapping and Analysis: The Mesaverde base maps have been constructed and the relevant well information identified.

Caldwell, R.H.

1993-01-08

 
 
 
 
301

Atlantic Basin refining profitability  

International Nuclear Information System (INIS)

A review of the profitability margins of oil refining in the Atlantic Basin was presented. Petroleum refiners face the continuous challenge of balancing supply with demand. It would appear that the profitability margins in the Atlantic Basin will increase significantly in the near future because of shrinking supply surpluses. Refinery capacity utilization has reached higher levels than ever before. The American Petroleum Institute reported that in August 1997, U.S. refineries used 99 per cent of their capacity for several weeks in a row. U.S. gasoline inventories have also declined as the industry has focused on reducing capital costs. This is further evidence that supply and demand are tightly balanced. Some of the reasons for tightening supplies were reviewed. It was predicted that U.S. gasoline demand will continue to grow in the near future. Gasoline demand has not declined as expected because new vehicles are not any more fuel efficient today than they were a decade ago. Although federally-mandated fuel efficiency standards were designed to lower gasoline consumption, they may actually have prevented consumption from falling. Atlantic margins were predicted to continue moving up because of the supply and demand evidence: high capacity utilization rates, low operating inventories, limited capacity addition resulting from lower capital spending, continued U.S. gasoline demand growth, and steady total oil demand growth. 11 figs

1998-01-01

302

Advanced Chemistry Basins Model  

Energy Technology Data Exchange (ETDEWEB)

The objective of this project is to: (1) Develop a database of additional and better maturity indicators for paleo-heat flow calibration; (2) Develop maturation models capable of predicting the chemical composition of hydrocarbons produced by a specific kerogen as a function of maturity, heating rate, etc.; assemble a compositional kinetic database of representative kerogens; (3) Develop a 4 phase equation of state-flash model that can define the physical properties (viscosity, density, etc.) of the products of kerogen maturation, and phase transitions that occur along secondary migration pathways; (4) Build a conventional basin model and incorporate new maturity indicators and data bases in a user-friendly way; (5) Develop an algorithm which combines the volume change and viscosities of the compositional maturation model to predict the chemistry of the hydrocarbons that will be expelled from the kerogen to the secondary migration pathways; (6) Develop an algorithm that predicts the flow of hydrocarbons along secondary migration pathways, accounts for mixing of miscible hydrocarbon components along the pathway, and calculates the phase fractionation that will occur as the hydrocarbons move upward down the geothermal and fluid pressure gradients in the basin; and (7) Integrate the above components into a functional model implemented on a PC or low cost workstation.

Blanco, Mario; Cathles, Lawrence; Manhardt, Paul; Meulbroek, Peter; Tang, Yongchun

2003-02-13

303

Organic geochemistry of the Callovo-Oxfordian argillo-carbonated sedimentary series of the East of the Paris basin and of England. Variabilities and paleo-environmental implications; Geochimie organique des series argilo-carbonatees du Callovo-Oxfordien de l'Est du bassin de Paris et d'Angleterre: Variabilites et implications paleoenvironnementales  

Energy Technology Data Exchange (ETDEWEB)

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

Hautevelle, Y

2005-12-15

304

Carboniferous Ostracodes in the Rhadamès Basin of Western Libya: Paleoecological Implications and Comparison with North America, Europe and the Ussr Les Ostracodes d'âge Carbonifère du bassin de Rhadamès de Libye occidentale : implications paléoécologiques et comparaison avec l'Amérique du Nord, l'Europe et l'URSS  

Directory of Open Access Journals (Sweden)

Full Text Available Carboniferous ostracode assemblages from two boreholes in the Rhadamès Basin of western Libya are compared with ostracode assemblages of the same age in North America, Western Europe and the USSR. The assemblages of the M'rar and Assedjefar Formations are characteristic of intertidal environments. These are compared with intertidal ostracode faunas from the late Devonian to early Dinantian of Belgium, and with near-shore faunas from the Upper Carboniferous of Spain and northwestern Europe. The assemblage of the Dembaba Formation is characteristic of a substital environment. Similar ostracode faunas have been described from subtidal or offshore deposits in the Devonian and Carboniferous of North America, Western Europe and the USSR. One genus (Rhadamesella) and nine species (Mammoides bouckaerti, Monoceratina kockeli, Marginohealdia africana, Marginohealdia paprothae, Paracavellina fernetae, Cribroconcha streeli, Graphiadactyllis beckeri; Rhadamesella rhadamesensis and Rhadamesella bourdoni) are new. Des associations d'Ostracodes d'âge Carbonifère sont étudiées et comparées avec des associations similaires d'Amérique du Nord, d'Europe occidentale et d'URSS. Le matériel étudié provient de deux sondages pétroliers implantés dans le bassin de Rhadamès en Libye occidentale. Les associations présentes dans les Formations M'rar et Assedjefar sont caractéristiques d'environnements intertidaux. Elles peuvent être comparées avec des faunes d'Ostracodes intertidaux connues du Dévonien supérieur au Dinantien inférieur de Belgique et avec des faunes côtières connues dans le Carbonifère supérieur d'Espagne et d'Europe nord-occidentale. L'association d'Ostracodes de la Formation Dembaba est caractéristique d'un environnement subtidal. De semblables faunes d'Ostracodes ont été décrites qui provenaient de dépôts subtidaux ou marins du Dévonien et du Carbonifère d'Amérique du Nord, d'Europe occidentale et d'URSS. Un genre, (Rhadamesella) et neuf espèces (Mammoides bouckaerti, Monoceratina kockeli, Marginoheaidia africana, Marginoheaidia paprothae, Paracavellina fernetae, Cribroconcha streeti, Graphiadactyllis beckeri, Rhadamesella rhadamesensis et Rhadamesella bourdoni) sont nouvelles.

Bless M. J. M.; Massa D.

2006-01-01

305

K-Basins design guidelines  

Energy Technology Data Exchange (ETDEWEB)

The purpose of the design guidelines is to enable SNF and K Basin personnel to complete fuel and sludge removal, and basin water mitigation by providing engineering guidance for equipment design for the fuel basin, facility modifications (upgrades), remote tools, and new processes. It is not intended to be a purchase order reference for vendors. The document identifies materials, methods, and components that work at K Basins; it also Provides design input and a technical review process to facilitate project interfaces with operations in K Basins. This document is intended to compliment other engineering documentation used at K Basins and throughout the Spent Nuclear Fuel Project. Significant provisions, which are incorporated, include portions of the following: General Design Criteria (DOE 1989), Standard Engineering Practices (WHC-CM-6-1), Engineering Practices Guidelines (WHC 1994b), Hanford Plant Standards (DOE-RL 1989), Safety Analysis Manual (WHC-CM-4-46), and Radiological Design Guide (WHC 1994f). Documents (requirements) essential to the engineering design projects at K Basins are referenced in the guidelines.

Roe, N.R.; Mills, W.C.

1995-06-01

306

K-Basins design guidelines  

International Nuclear Information System (INIS)

[en] The purpose of the design guidelines is to enable SNF and K Basin personnel to complete fuel and sludge removal, and basin water mitigation by providing engineering guidance for equipment design for the fuel basin, facility modifications (upgrades), remote tools, and new processes. It is not intended to be a purchase order reference for vendors. The document identifies materials, methods, and components that work at K Basins; it also Provides design input and a technical review process to facilitate project interfaces with operations in K Basins. This document is intended to compliment other engineering documentation used at K Basins and throughout the Spent Nuclear Fuel Project. Significant provisions, which are incorporated, include portions of the following: General Design Criteria (DOE 1989), Standard Engineering Practices (WHC-CM-6-1), Engineering Practices Guidelines (WHC 1994b), Hanford Plant Standards (DOE-RL 1989), Safety Analysis Manual (WHC-CM-4-46), and Radiological Design Guide (WHC 1994f). Documents (requirements) essential to the engineering design projects at K Basins are referenced in the guidelines

1995-01-01

307

KE Basin Sludge Flocculant Testing  

International Nuclear Information System (INIS)

[en] In the revised path forward and schedule for the K Basins Sludge Retrieval and Disposal Project, the sludge in K East (KE) Basin will be moved from the floor and pits and transferred to large, free-standing containers located in the pits (so as to isolate the sludge from the basin). When the sludge is pumped into the containers, it must settle fast enough and clarify sufficiently that the overflow water returned to the basin pool will not cloud the water or significantly increase the radiological dose rate to the operations staff as a result of increased suspended radioactive material. The approach being evaluated to enhance sludge settling and speed the rate of clarification is to add a flocculant to the sludge while it is being transferred to the containers. In February 2004, seven commercial flocculants were tested with a specific K Basin sludge simulant to identify those agents that demonstrated good performance over a broad range of slurry solids concentrations. From this testing, a cationic polymer flocculant, Nalco Optimer 7194 Plus (7194+), was shown to exhibit superior performance. Related prior testing with K Basin sludge and simulant in 1994/1996 had also identified this agent as promising. In March 2004, four series of jar tests were conducted with 7194+ and actual KE Basin sludge (prepared by combining selected archived KE sludge samples). The results from these jar tests show that 7194+ greatly improves settling of the sludge slurries and clarification of the supernatant

2004-01-01

308

Marketing San Juan Basin gas  

International Nuclear Information System (INIS)

Marketing natural gas produced in the San Juan Basin of New Mexico and Colorado principally involves four gas pipeline companies with significant facilities in the basin. The system capacity, transportation rates, regulatory status, and market access of each of these companies is evaluated. Because of excess gas supplies available to these pipeline companies, producers can expect improved take levels and prices by selling gas directly to end users and utilities as opposed to selling gas to the pipelines for system supply. The complexities of transporting gas today suggest that the services of an independent gas marketing company may be beneficial to smaller producers with gas supplies in the San Juan Basin

1988-01-01

309

The Amazon basin in transition.  

UK PubMed Central (United Kingdom)

Agricultural expansion and climate variability have become important agents of disturbance in the Amazon basin. Recent studies have demonstrated considerable resilience of Amazonian forests to moderate annual drought, but they also show that interactions between deforestation, fire and drought potentially lead to losses of carbon storage and changes in regional precipitation patterns and river discharge. Although the basin-wide impacts of land use and drought may not yet surpass the magnitude of natural variability of hydrologic and biogeochemical cycles, there are some signs of a transition to a disturbance-dominated regime. These signs include changing energy and water cycles in the southern and eastern portions of the Amazon basin.

Davidson EA; de Araújo AC; Artaxo P; Balch JK; Brown IF; C Bustamante MM; Coe MT; DeFries RS; Keller M; Longo M; Munger JW; Schroeder W; Soares-Filho BS; Souza CM Jr; Wofsy SC

2012-01-01

310

Ground-water quality in the Red River of the North Basin, Minnesota and North Dakota, 1991--1995  

Energy Technology Data Exchange (ETDEWEB)

The report presents the results of the Red River Basin NAWQA study-unit survey. The specific purposes of the report are: (1) to describe the water quality in surficial aquifers (in three physiographic areas) and in shallow buried aquifers; (2) to contrast and explain the water-quality differences among surficial aquifers (in each physiographic area) and between surficial and shallow buried aquifers; and (3) to describe the implications of ground-water quality on drinking water in the Red River Basin.

Cowdery, T.K.

1998-12-31

311

The isolation of the Pannonian basin (Central Paratethys): New constraints from magnetostratigraphy and biostratigraphy  

Science.gov (United States)

In this paper we establish when and how the Pannonian basin and associated Central Paratethys basins were isolated from the remainder of the Paratethys, a system of back-arc basins and inland seas that once extended over a large part of Europe. The isolation, which occurred at the beginning of the Late Miocene, is marked by a paleoenvironmental change from marine to fresh water conditions that caused the regional Sarmatian-Pannonian Extinction Event. It also had significant paleogeographical implications for the basin fill and for sedimentary transport across the Carpathian Mountains. The exact age of and cause for the isolation are still subject to debate. Here, we use magnetostratigraphic dating coupled to ostracod and mollusc biostratigraphy to establish the isolation age of the Pannonian basin. We dated the isolation of the Pannonian basin at 11.63 ± 0.04 Ma in a section on the northern flank of the Fruška Gora inselberg (northern Serbia). This age is in line with recent results from the Vienna basin but predates the isolation of the Transylvanian by 0.33 Myr, suggesting that isolation took place in two steps. We conclude that the uplift of the Carpathian Mountains caused the isolation but that eustatic sea level fluctuations may have had a minor influence as well.

ter Borgh, Marten; Vasiliev, Iuliana; Stoica, Marius; Kneževi?, Slobodan; Matenco, Liviu; Krijgsman, Wout; Rundi?, Ljupko; Cloetingh, Sierd

2013-04-01

312

Environmental implications  

Energy Technology Data Exchange (ETDEWEB)

The authors examine the environmental implications and applications of current information and communication technologies. The book also reviews emerging trends in information technology and some of the attendant issues for policy makers, particularly those relating to economic growth in developing countries.

Elkington, J.; Shopley, J.

1988-01-01

313

U.S. Geological Survey and Bureau of Land Management Cooperative Coalbed Methane Project in the Powder River Basin, Wyoming  

Science.gov (United States)

Introduction: Evidence that earthquakes threaten the Mississippi, Ohio, and Wabash River valleys of the Central United States abounds. In fact, several of the largest historical earthquakes to strike the continental United States occurred in the winter of 1811-1812 along the New Madrid seismic zone, which stretches from just west of Memphis, Tenn., into southern Illinois (fig. 1). Several times in the past century, moderate earthquakes have been widely felt in the Wabash Valley seismic zone along the southern border of Illinois and Indiana (fig. 1). Throughout the region, between 150 and 200 earthquakes are recorded annually by a network of monitoring instruments, although most are too small to be felt by people. Geologic evidence for prehistoric earthquakes throughout the region has been mounting since the late 1970s. But how significant is the threat? How likely are large earthquakes and, more importantly, what is the chance that the shaking they cause will be damaging?The Bureau of Land Management (BLM) Wyoming Reservoir Management Group and the U.S. Geological Survey (USGS) began a cooperative project in 1999 to collect technical and analytical data on coalbed methane (CBM) resources and quality of the water produced from coalbeds in the Wyoming part of the Powder River Basin. The agencies have complementary but divergent goals and these kinds of data are essential to accomplish their respective resource evaluation and management tasks. The project also addresses the general public need for information pertaining to Powder River Basin CBM resources and development. BLM needs, which relate primarily to the management of CBM resources, include improved gas content and gas in-place estimates for reservoir characterization and resource/reserve assessment, evaluation, and utilization. USGS goals include a basinwide assessment of CBM resources, an improved understanding of the nature and origin of coalbed gases and formation waters, and the development of predictive models for the assessment of CBM resources that can be used for such purposes in other basins in the United States (for example, the Bighorn, Greater Green River, and Williston Basins) and in other countries throughout the world (for example, Indonesia, New Zealand, and the Philippines). Samples of coal, produced water, and gas from coalbed methane drill holes throughout the Powder River Basin, many of which are adjacent to several active mine areas (figs. 1, 2), have been collected by personnel in the USGS, BLM Reservoir Management Group, and Casper and Buffalo BLM Field Offices. Sampling was done under confidentiality agreements with 29 participating CBM companies and operators. Analyses run on the samples include coal permeability, coal quality and chemistry, coal petrography and petrology, methane desorption and adsorption, produced-water chemistry, and gas composition and isotopes. The USGS has supplied results to the BLM Reservoir Management Group for their resource management needs, and data are released when the terms of the confidentiality agreements are completed and consent is obtained.

Geological Survey (U.S.)

2006-01-01

314

RESERVES IN WESTERN BASINS PART IV: WIND RIVER BASIN  

Energy Technology Data Exchange (ETDEWEB)

Vast quantities of natural gas are entrapped within various tight formations in the Rocky Mountain area. This report seeks to quantify what proportion of that resource can be considered recoverable under today's technological and economic conditions and discusses factors controlling recovery. The ultimate goal of this project is to encourage development of tight gas reserves by industry through reducing the technical and economic risks of locating, drilling and completing commercial tight gas wells. This report is the fourth in a series and focuses on the Wind River Basin located in west central Wyoming. The first three reports presented analyses of the tight gas reserves and resources in the Greater Green River Basin (Scotia, 1993), Piceance Basin (Scotia, 1995) and the Uinta Basin (Scotia, 1995). Since each report is a stand-alone document, duplication of language will exist where common aspects are discussed. This study, and the previous three, describe basin-centered gas deposits (Masters, 1979) which contain vast quantities of natural gas entrapped in low permeability (tight), overpressured sandstones occupying a central basin location. Such deposits are generally continuous and are not conventionally trapped by a structural or stratigraphic seal. Rather, the tight character of the reservoirs prevents rapid migration of the gas, and where rates of gas generation exceed rates of escape, an overpressured basin-centered gas deposit results (Spencer, 1987). Since the temperature is a primary controlling factor for the onset and rate of gas generation, these deposits exist in the deeper, central parts of a basin where temperatures generally exceed 200 F and drill depths exceed 8,000 feet. The abbreviation OPT (overpressured tight) is used when referring to sandstone reservoirs that comprise the basin-centered gas deposit. Because the gas resources trapped in this setting are so large, they represent an important source of future gas supply, prompting studies to understand and quantify the resource itself and to develop technologies that will permit commercial exploitation. This study is a contribution to that process.

Robert Caldwell

1998-04-01

315

Helminth parasites of freshwater fishes, Nazas River basin, northern Mexico  

Directory of Open Access Journals (Sweden)

Full Text Available This paper represents the first study of the helminth parasites of freshwater fishes from the Nazas River basinin northern Mexico. Between July 2005 and December 2008, 906 individual fish were collected and examined for helminthparasites in 23 localities along the river basin. Twenty-three species of fish were examined as a part of this inventory work.In total, 41 helminth species were identified: 19 monogeneans, 10 digeneans, seven cestodes, one acanthocephalan, andfour nematodes. The biogeographical implications of our findings are briefly discussed.

León, G. Pérez-Ponce; Rosas-Valdez, R.; Aguilar-Aguilar, R.; Mendoza-Garfias, B.; Mendoza-Palmero, C.; García-Prieto, L.; Rojas-Sánchez, A.; Briosio-Aguilar, R.; Pérez-Rodríguez, R.; Domínguez-Domínguez, O.

2010-01-01

316

Paleothermometry of the Sydney Basin  

Energy Technology Data Exchange (ETDEWEB)

Evidence from overprinting of magnetizations of Late Permian and Mesozoic rocks and from the rank of Permian coals and Mesozoic phytoclasts (coal particles) suggests that surface rocks in the Sydney Basin, eastern Australia, have been raised to temperatures of the order of 200 /sup 0/C or higher. As vitrinite reflectance, an index of coal rank or coalification, is postulated to vary predictably with temperature and time, estimates of the paleotemperatures in the Sydney Basin based on observed vitrinite reflectance measurements can be made in conjunction with reasonable assumptions about the tectonic and thermal histories of the basin. These estimates give maximum paleotemperatures of present day surface rocks in the range 60--249 /sup 0/C, depending on factors such as location in the basin, the thickness of the sediment eroded, and the maximum paleogeothermal gradient. Higher coal rank and, consequently, larger eroded thicknesses and paleogeothermal gradients occur along the eastern edge of the basin and may be related to seafloor spreading in the Tasman Sea on the basin's eastern margin. A theory of thermal activation of magnetization entailing the dependence of magnetic viscosity on the size distribution of the magnetic grains is used to obtain an independent estimate of the maximum paleotemperatures in the Sydney Basin. This estimate places the maximum paleotemperature in the range 250--300 /sup 0/C along the coastal region. Both coalification and thermal activation of magnetization models provide strong evidence of elevated paleotemperatures, which in places exceed 200 /sup 0/C, and the loss of sediment thicknesses in excess of 1 km due to erosion.

Middleton, M.F.; Schmidt, P.W.

1982-07-10

317

Fuel storage basin seismic analysis  

International Nuclear Information System (INIS)

The 105-KE and 105-KW Fuel Storage Basins were constructed more than 35 years ago as repositories for irradiated fuel from the K East and K West Reactors. Currently, the basins contain irradiated fuel from the N Reactor. To continue to use the basins as desired, seismic adequacy in accordance with current US Department of Energy facility requirements must be demonstrated. The 105-KE and 105-KW Basins are reinforced concrete, belowground reservoirs with a 16-ft water depth. The entire water retention boundary, which currently includes a portion of the adjacent reactor buildings, must be qualified for the Hanford Site design basis earthquake. The reactor building interface joints are sealed against leakage with rubber water stops. Demonstration of the seismic adequacy of these interface joints was initially identified as a key issue in the seismic qualification effort. The issue of water leakage through seismicly induced cracks was also investigated. This issue, coupled with the relatively complex geometry of the basins, dictated a need for three-dimensional modeling. A three-dimensional soil/structure interaction model was developed with the SASSI computer code. The development of three-dimensional models of the interfacing structures using the ANSYS code was also found to be necessary. 8 refs., 7 figs., 1 tab

1991-01-01

318

Geology, exploration status of Uruguay's sedimentary basins  

Energy Technology Data Exchange (ETDEWEB)

This article attempts to present the geological characteristics and tectonic and sedimentary evolution of Uruguayan basins and the extent to which they have been explored. Uruguay is on the Atlantic coast of South America. The country covers about 318,000 sq km, including offshore and onshore territories corresponding to more than 65% of the various sedimentary basins. Four basins underlie the country: the Norte basin, the Santa Lucia basin, the offshore Punta del Este basin, and the offshore-onshore Pelotas-Merin basin. The Norte basin is a Paleozoic basin while the others are Mesozoic basins. Each basin has been explored to a different extent, as this paper explains.

Goso, C.; Santa Ana, H. de (Administracion Nacional de Combustibles, Alcohol y Portland (Uruguay))

1994-02-07

319

Nature of the crust in the Laxmi Basin (14°-20°N), western continental margin of India  

Science.gov (United States)

The nature of the crust in the Laxmi Basin, western margin of India, is an uncertain issue; more importantly, this has implications on paleogeographic reconstructions of the western Indian Ocean. We have analyzed three geophysical data sets and modeled gravity and magnetic anomalies for determining nature of the crust. Basement of the Laxmi Basin includes numerous highs, which make the basement uneven and shallower compared to the Western Basin. The Laxmi Basin is characterized by a broad gravity high and a narrower prominent gravity low within it, while within the basin the broad anomaly gradually increases toward north. The Panikkar Ridge is associated with the gravity low, which is comparable, at least in sign, to known negative gravity anomaly of the Laxmi Ridge. Intrusive structures mapped in the Laxmi Basin coincide with significant magnetic anomalies, which were earlier interpreted as seafloor-spreading anomalies. Model studies reveal that the Laxmi Basin consists of ˜14 km thick stretched continental crust, in which magmatic bodies have been emplaced, whereas the Panikkar Ridge remains less altered stretched continental crust. The crust of the Laxmi Basin is mostly thinner than crust under the Laxmi Ridge and continental margin. In addition to the rift-drift-related stretching of the continental margin, the Laxmi Basin possibly has undergone extra stretching in E-W direction during the pre-Tertiary period. At ˜68 Ma Deccan volcanism on western India may have disrupted the initial conditions that were leading to onset of spreading in the basin. Subsequently the Réunion hot spot had emplaced the volcanic material within the stretched thinned continental crust. We interpret the Laxmi Basin as a failed rift, undergone stretching following intraplate kinematics prior to Deccan volcanism.

Krishna, K. S.; Gopala Rao, D.; Sar, D.

2006-02-01

320

Muskingum River Basin Comprehensive Coordinated Joint Plan.  

Science.gov (United States)

The plan includes recommended studies, projects, and non-structural programs which the Ohio River Basin Commission has agreed are required to meet the economic, environmental and social needs of the sub-basin, the Muskingum River.

1976-01-01

 
 
 
 
321

Oil in the Malvinas Basin  

Energy Technology Data Exchange (ETDEWEB)

The Malvinas Basin is petroliferous. The main source rocks are Late Jurassic and Early Cretaceous outer shelf to basinal shales known as the Pampa Rincon and Lower Inoceramus formations. Main reservoirs are fluvial and shallow-marine sandstones of the coeval Springhill Formation. On the western flank of the basin, 17 wells drilled the Cenozoic and Mesozoic column. Three of these wells discovered hydrocarbons within the Springhill Formation, and one discovered oil in Early Paleogene sandstones. Additionally, some wells recorded shows at different levels within the stratigraphic succession. A detailed overview of the drilled portion of the basin permitted the construction of a sequence stratigraphic framework, and yielded clues on a complex history of deformation. Interpretation of facies and stratal stacking and termination patterns determined that the main reservoir and source rocks were deposited in a ramp-style depositional setting. They represent the lower transgressive phase of a Late Jurassic to Early Cretaceous megasequence deposited during the early sag stage of the basin. Alternative reservoirs to the Springhill sandstones include early Paleogene glauconitic sandstones and carbonates, and Miocene deep-water turbidites. Structural trap styles include normal fault features of Jurassic to Early Cretaceous age, and compressional and inverted positive structures due to Neogene compression. Possible combination and stratigraphic traps include: little tested onlap pinchout of Late Jurassic to Early Cretaceous and Paleogene sandstones and untested erosionally truncated Paleogene sandstones; Early Paleogene carbonate buildups and Miocene deep-water turbidite mounds. The understanding of the geology of the western Malvinas Basin is the key to success of exploration in the huge frontier surrounding areas.

Galeazzi, J.S. [Astra, Anzoategui (Venezuela)

1996-08-01

322

H-Area Seepage Basins  

Energy Technology Data Exchange (ETDEWEB)

During the third quarter of 1990 the wells which make up the H-Area Seepage Basins (H-HWMF) monitoring network were sampled. Laboratory analyses were performed to measure levels of hazardous constituents, indicator parameters, tritium, nonvolatile beta, and gross alpha. A Gas Chromatograph Mass Spectrometer (GCMS) scan was performed on all wells sampled to determine any hazardous organic constituents present in the groundwater. The primary contaminants observed at wells monitoring the H-Area Seepage Basins are tritium, nitrate, mercury, gross alpha, nonvolatile beta, trichloroethylene (TCE), tetrachloroethylene, lead, cadmium, arsenic, and total radium.

Stejskal, G.

1990-12-01

323

Triple basin active solar still  

Energy Technology Data Exchange (ETDEWEB)

The Runge-Kutta method has been used to solve three coupled differential equations to determine the performance of an active triple basin solar distillation system. Hourly variation of various temperatures and yield have been evaluated along with overall thermal efficiency. Optimisation of various parameters namely collector and basin area, and water depth with respect to daily yield has been carried out. Numerical computations have been performed for a typical day of Delhi climate. On the basis of numerical results, it has been observed that optimisation of the collector area reduces with number of effects. (Author)

Kumar, Sanjeev [M.M.H. Coll., Physics Dept., Ghaziabad (India); Tiwari, G.N. [Indian Inst. of Technology, Centre for Energy Studies, New Delhi (India)

1999-07-01

324

A Review of Bovine Tuberculosis in the Kafue Basin Ecosystem  

Science.gov (United States)

The Kafue basin ecosystem is the only remaining natural habitat for the endangered Kafue lechwe antelope (Kobus leche Kafuensis). However, hydroelectricity power production, large-scale sugar plantations, commercial fishing and increasing livestock production are threatening its natural existence and sustainability. Further, increasing human settlements within and around the Kafue basin have resulted in decreased grazing grounds for the Kafue lechwe antelopes despite a corresponding increase in cattle population sharing the same pasture. Baseline epidemiological data have persistently reported findings of bovine tuberculosis (BTB) in both wild and domestic animals, although these have been deficient in terms of describing direct evidence in the role of either lechwe antelopes or cattle in the reported observations. Despite the current literature being deficient in establishing the casual role and transmission patterns of BTB, a bimodal route of infection at the livestock/wildlife interface has been postulated. Likewise, it is not known how much of (BTB) has the potential of causing disease in humans. This paper, seeks to underline those aspects that need further research and update available data on BTB in the Kafue basin with regards to the prevalence, distribution, risk factors, threats on wildlife conservation, livestock production, public health implications, and possible mitigatory measures.

Munyeme, Musso; Munang'andu, Hetron Mweemba

2011-01-01

325

A review of bovine tuberculosis in the kafue basin ecosystem.  

UK PubMed Central (United Kingdom)

The Kafue basin ecosystem is the only remaining natural habitat for the endangered Kafue lechwe antelope (Kobus leche Kafuensis). However, hydroelectricity power production, large-scale sugar plantations, commercial fishing and increasing livestock production are threatening its natural existence and sustainability. Further, increasing human settlements within and around the Kafue basin have resulted in decreased grazing grounds for the Kafue lechwe antelopes despite a corresponding increase in cattle population sharing the same pasture. Baseline epidemiological data have persistently reported findings of bovine tuberculosis (BTB) in both wild and domestic animals, although these have been deficient in terms of describing direct evidence in the role of either lechwe antelopes or cattle in the reported observations. Despite the current literature being deficient in establishing the casual role and transmission patterns of BTB, a bimodal route of infection at the livestock/wildlife interface has been postulated. Likewise, it is not known how much of (BTB) has the potential of causing disease in humans. This paper, seeks to underline those aspects that need further research and update available data on BTB in the Kafue basin with regards to the prevalence, distribution, risk factors, threats on wildlife conservation, livestock production, public health implications, and possible mitigatory measures.

Munyeme M; Munang'andu HM

2011-01-01

326

Caribbean basin framework, 4: Maracaibo basin, northwestern Venezuela  

Energy Technology Data Exchange (ETDEWEB)

The Maracaibo basin is presently located in a topographic depression on the Maracaibo block, a triangular, fault-bounded block within the Caribbean-South America plate boundary of northwestern Venezuela. Intense oil exploration over the last 50 years has produced a large amount of seismic and well data that can be used to constrain four Jurassic to Recent tectonic and depositional events that affected the region: (1). Late Jurassic rift phase and subsidence along normal faults striking north-northeast across the floor of the basin; (2) Cretaceous to early Eocene subsidence recorded by shallow to deep marine carbonate and clastic rocks that thicken from south to north and completely cover Permian rocks of the Merida arch; (3) Eocene folding, thrusting, and initial reactivation of Jurassic normal faults as convergent strike-slip and reverse faults. Eocene clastic sediments are thickest in a narrow northwest-trending foredeep on the northeastern margin of the basin; (4) Late Miocene to Recent northwest-southeast convergence is marked by continued reactivation of Jurassic normal faults as reverse and left-lateral strike-slip faults, uplift of mountain ranges bordering the basin, and deposition of up to 10 km of clastic sediment.

Lugo, J. (Univ. of Texas, Austin (United States))

1991-03-01

327

Supplementary information on K-Basin sludges  

International Nuclear Information System (INIS)

Three previous documents in this series have been published covering the analysis of: K East Basin Floor and Pit Sludge, K East Basin Canister Sludge, and K West Basin Canister Sludge. Since their publication, additional data have been acquired and analyses performed. It is the purpose of this volume to summarize the additional insights gained in the interim time period.

1999-01-01

328

Supplementary information on K-Basin sludges  

Energy Technology Data Exchange (ETDEWEB)

Three previous documents in this series have been published covering the analysis of: K East Basin Floor and Pit Sludge, K East Basin Canister Sludge, and K West Basin Canister Sludge. Since their publication, additional data have been acquired and analyses performed. It is the purpose of this volume to summarize the additional insights gained in the interim time period.

MAKENAS, B.J.

1999-03-15

329

Hydrologic evolution of drainage basins disturbed by surface mining, central Pennsylvania  

Energy Technology Data Exchange (ETDEWEB)

The hydrologic evolution of drainage basins disturbed by surface mining in central Pennsylvania is regulated by infiltration capacity of minesoils and its control on hillslope runoff processes. Steady-state infiltration capacity of newly reclaimed minesoils is uniformly low, less than 1 cm/hr, and it generally increases up to 6 cm/hr with time, the magnitude of increase being dependent on soil characteristics and vegetation. In drainage basins where steady-state infiltration capacity recovers to less than 3 cm/hr, the dominant runoff process is infiltration-excess overland flow. Increased peak runoff rates associated with infiltration-excess overland flow are sufficient to initiate drainage network evolution in these basins, with phases of expansion and abstraction. Storm hydrographs are characterized by (1) increasing peak and total runoff and decreasing time to peak runoff during periods of network extension and (2) decreasing peak and total runoff and increasing time to peak runoff during network abstraction. Trends in hydrograph evolution are due to the relative efficiency of channeled-versus overland-flow processes for removing excess rainfall from the basin. In contrast, in drainage basins where steady-state infiltration capacity recovers to greater than 3 cm/hr, runoff is initially dominated by infiltration-excess overland flow, but saturation overland flow is increasingly dominant with time. Drainage network evolution is limited to skeletal network initiation and elongation, which occur while the basin is dominated by infiltration-excess overland flow. The hydrologic response of drainage basins to changes in the dominant runoff process has important implications for models of long-term drainage-basin evolution, particularly those used to evaluate climate change and associated changes in vegetation and soil chemical and physical properties, each of which may affect infiltration capacity. 50 refs., 12 figs., 4 tabs.

Ritter, J.B.; Gardner, T.W. (Pennsylvania State Univ., Univeristy Park (United States))

1993-01-01

330

Great Basin paleoenvironmental studies project  

International Nuclear Information System (INIS)

Project goals, project tasks, progress on tasks, and problems encountered are described and discussed for each of the studies that make up the Great Basin Paleoenvironmental Studies Project for Yucca Mountain. These studies are: Paleobotany, Paleofauna, Geomorphology, and Transportation. Budget summaries are also given for each of the studies and for the overall project.

1993-01-01

331

Intermingled basins in coupled Lorenz systems.  

UK PubMed Central (United Kingdom)

We consider a system of two identical linearly coupled Lorenz oscillators presenting synchronization of chaotic motion for a specified range of the coupling strength. We verify the existence of global synchronization and antisynchronization attractors with intermingled basins of attraction such that the basin of one attractor is riddled with holes belonging to the basin of the other attractor and vice versa. We investigated this phenomenon by verifying the fulfillment of the mathematical requirements for intermingled basins and obtained scaling laws that characterize quantitatively the riddling of both basins in this system.

Camargo S; Viana RL; Anteneodo C

2012-03-01

332

Petrography and Provenance of Early Triassic Pachmarhi Formation Sandstones, Satpura Gondwana Basin, Madhya Pradesh, Central India  

Directory of Open Access Journals (Sweden)

Full Text Available The Pachmarhi, Denwa and Bagra Formations comprise of terrigenous sediments predominantly constitute the Mesozoic Gondwana sequence in Satpura basin of Madhya Pradesh, central India. The Pachmarhi Formation sandstones were studied with a view to understand the nature of the Satpura basin in relation to provenance and tectonic setting. Twenty representative samples of sandstone from Pachmarhi were examined for detrital mineralogy, petrofacies and tectonic implications. These sandstones are medium to coarse grained, moderately to moderately well sorted, subangular to subrounded and of moderate sphericity and composed of several varieties of quartz, feldspar, rock fragments, mica and a suite of heavy minerals. Petrographically, the Pachmarhi sandstones are quartzarenite and subarkose. The petrofacies studies reflect derivation of the sediments from continental block provenance and stable cratonic to fault-bounded basement uplift tectonic setting. The study suggests that the Precambrian granitoids occurring in the southern margin of the Satpura basin contributed sediments during Pachmarhi sedimentation.

Abdullah Khan; Anis   Shahnawaz  

2013-01-01

333

Real and relict direct hydrocarbon indicators in the East Irish Sea Basin  

Energy Technology Data Exchange (ETDEWEB)

Seismic amplitude anomalies associated with the presence of hydrocarbon gas now play an important role in the exploration of the East Irish Sea Basin. Tilted flat spots were first observed on data acquired by JEBCO Seismic Ltd. in 1986 within the productive Triassic reservoir of the Sherwood Sandstone Group located in Quadrant 110 (offshore North Wales). With hindsight Direct Hydrocarbon Indicators (DHIs) can now be identified on seismic data acquired in earlier phases of the exploration of the East Irish Sea Basin, although many anomalies were not always identified as such at that time. This study determines the geophysical parameters by which amplitude anomalies associated with diagenetic variations could be separated from anomalies associated with the presence of gas in the reservoir. The predicted model results are compared with the seismic response of proven fields, discoveries and relict or palaeo-DHIs around the basin. Practical implications for effective exploration, development and production methods in the Sherwood Sandstone are suggested. (author)

Francis, A.; Hargrave, M. Millwood; Mulholland, P.; Williams, D. [IKODA Ltd., Twickenham (United Kingdom)

1997-12-31

334

XXI Century Climatology of Snow Cover for the Western River Basins of the Indus River System  

CERN Multimedia

Under changing climate, freshwater resources of Hindu Kush-Karakoram-Himalaya (HKH) region can be affected by changes in temperature and in amount, type and distribution of precipitation. This can have serious implications for the water supply and in turn threaten the food security and economic wellbeing of Indus basin. Using MODIS daily snow products (Terra & Aqua), this study focuses on the assessment of the 2000-2010 snow cover dynamics on seasonal/annual basis against geophysical parameters (aspect, elevation and slope) for the so called western river basins of Indus River System (IRS), namely Indus, Kabul, Jhelum, Astore, Gilgit, Hunza, Swat, Shigar and Shyok basins. Results show that inputs from MODIS instrument provide unprecedented better opportunity to study by using GIS techniques the snow cover dynamics in the remote areas like HKH region at such hyper-temporal and finer planar resolution. Adapted non-spectral cloud filtering techniques have significantly reduced cloud coverage and improved sno...

Hasson, Shabeh ul; Lucarini, Valerio

2012-01-01

335

K Basin spent fuel sludge treatment alternatives study. Volume 2, Technical options  

International Nuclear Information System (INIS)

[en] Approximately 2100 metric tons of irradiated N Reactor fuel are stored in the KE and KW Basins at the Hanford Site, Richland, Washington. Corrosion of the fuel has led to the formation of sludges, both within the storage canisters and on the basin floors. Concern about the degraded condition of the fuel and the potential for leakage from the basins in proximity to the Columbia River has resulted in DOE's commitment in the Tri-Party Agreement (TPA) to Milestone M-34-00-T08 to remove the fuel and sludges by a December 2002 target date. To support the planning for this expedited removal action, the implications of sludge management under various scenarios are examined. This report, Volume 2 of two volumes, describes the technical options for managing the sludges, including schedule and cost impacts, and assesses strategies for establishing a preferred path

1995-01-01

336

Tectonic development of Michigan basin  

Energy Technology Data Exchange (ETDEWEB)

The general form of the Michigan basin and surrounding frame structures - the Findlay, Kankakee, and Wisconsin arches - was inherited from the Precambrian. An ongoing study has provided new information on present basin configuration and the evolution of intrabasinal structures during the Paleozoic. This study involves: (1) isopach, structure contour, depocenter, and lithofacies map preparation; (2) diagenetic and epigenetic dolomitization processes and patterns; (3) Landsat imagery and lineament interpretation; (4) recognition of shearing mechanics and the resulting shear faulting and folding; and (5) the recognition of radial faults in contrast to shear faults. Monitoring of the above throughout the Paleozoic indicates that tectonic events within the basin were episodic in nature. Stresses are recognized as external and, through Fourier analysis of lineaments (shear faults), may be demonstrated as from the southeast, probably the Appalachian mobile belt. Shear faults are seated in Precambrian rocks, although they are probably not of that age. The faults occur with accompanying shear folds in rocks possibly as early as the Late Ordovician or Middle Silurian, but definitely by the Middle Devonian with the principal faulting and folding during the post-Osage Mississippian. Local shifting of the depocenter within the general Saginaw Bay area occurred during the early Paleozoic with a major shift westward to the present central basin position accompanied by the development of the present north-northwest ellipticity of the basin during the post-Osage, pre-Meramecian Mississippian. Barrier separation of the West Michigan Lagoon occurred in the Middle Ordovician and Middle and Late Devonian. Radial structures can be demonstrated in at least the Upper Silurian and Upper Devonian.

Prouty, C.E.

1986-08-01

337

Mississippian facies relationships, eastern Anadarko basin, Oklahoma  

Energy Technology Data Exchange (ETDEWEB)

Mississippian strata in the eastern Anadarko basin record a gradual deepening of the basin. Late and post-Mississippian tectonism (Wichita and Arbuckle orogenies) fragmented the single large basin into the series of paired basins and uplifts recognized in the southern half of Oklahoma today. Lower Mississippian isopach and facies trends (Sycamore and Caney Formations) indicate that basinal strike in the study area (southeastern Anadarko basin) was predominantly east-west. Depositional environment interpretations made for Lower Mississippian strata suggest that the basin was partially sediment starved and exhibited a low shelf-to-basin gradient. Upper Mississippian isopach and facies trends suggest that basinal strike within the study area shifted from dominantly east-west to dominantly northwest-southeast due to Late Mississippian and Early Pennsylvanian uplift along the Nemaha ridge. Within the study area, the Chester Formation, composed of gray to dove-gray shales with interbedded limestones deposited on a carbonate shelf, thins depositionally into the basin and is thinnest at its facies boundary with the Springer Group and the upper portion of the