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1

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

NASA Astrophysics Data System (ADS)

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

2

Palynomorphs of Permian Gondwana coal from borehole GDH-38, Barapukuria Coal Basin, Bangladesh  

NASA Astrophysics Data System (ADS)

Thirty-two core samples of Permian Gondwana coal from three coal beds of borehole GDH-38, Barapukuria Coal Basin, Dinajpur, the north-northwestern part of Bangladesh, have been collected for palynological analysis. All samples except one yielded palynomorphs and some samples contain well-preserved and abundant palynomorphs of the gymnospermal and cryptogamic groups that are considered to be useful for future correlation studies. The lower coal bed (331.6-372.5 m) can easily be differentiated from the upper two coal beds by the presence of Alisporites, Cordaitina, Corisaccites, Hamiapollenites, Leuckisporites, Nuskoisporites, Tumoripollenites, Vestgisporites and Vittatina. It is difficult to palynologically differentiate the middle (198.1-208 m) and upper (162.3-172.9 m) coal beds as they contain a very limited number of specimens by which they can be identified. The middle bed is distinguished by the presence of Microbaculispora and Weylandites and the upper bed by the presence of a single taxon Acanthotriletes. Some of the vesiculate or saccate taxa extracted from these coal beds are typical of those occurring in Permian strata of Gondwana in India, South Africa, South America, Russia, Australia and Antarctica. They are thought to be derived from Glossopteris flora, which is characterised by an abundance of Pteridospermic plants of the gymnosperm group.

Akhtar, A.; Kosanke, R. M.

2000-07-01

3

Palynomorphs of Permian Gondwana coal from borehole GDH-38, Barapukuria Coal Basin, Bangladesh  

USGS Publications Warehouse

Thirty-two core samples of Permian Gondwana coal from three coal beds of borehole GDH-38, Barapukuria Coal Basin, Dinajpur, the north-northwestern part of Bangladesh, have been collected for palynological analysis. All samples except one yielded palynomorphs and some samples contain well-preserved and abundant palynomorphs of the gymnospermal and cryptogamic groups that are considered to be useful for future correlation studies. The lower coal bed (331.6-372.5 m) can easily be differentiated from the upper two coal beds by the presence of Alisporites, Cordaitina, Corisaccites, Hamiapollenites, Leuckisporites, Nuskoisporites, Tumoripollenites, Vestgisporites and Vittatina. It is difficult to palynologically differentiate the middle (198.1-208 m) and upper (162.3-172.9 m) coal beds as they contain a very limited number of specimens by which they can be identified. The middle bed is distinguished by the presence of Microbaculispora and Weylandites and the upper bed by the presence of a single taxon Acanthotriletes. Some of the vesiculate or saccate taxa extracted from these coal beds are typical of those occurring in Permian strata of Gondwana in India, South Africa, South America, Russia, Australia and Antarctica. They are thought to be derived from Glossopteris flora, which is characterised by an abundance of Pteridospermic plants of the gymnosperm group. ?? 2000 Elsevier Science Limited. All rights reserved.

Akhtar, A.; Kosanke, R. M.

2000-01-01

4

The breakup of East Gondwana: Assimilating constraints from Cretaceous ocean basins around India into a best-fit tectonic model  

NASA Astrophysics Data System (ADS)

models for the Cretaceous seafloor-spreading history of East Gondwana result in unlikely tectonic scenarios for at least one of the plate boundaries involved and/or violate particular constraints from at least one of the associated ocean basins. We link East Gondwana spreading corridors by integrating magnetic and gravity anomaly data from the Enderby Basin off East Antarctica within a regional plate kinematic framework to identify a conjugate series of east-west-trending magnetic anomalies, M4 to M0 (~126.7-120.4 Ma). The mid-ocean ridge that separated Greater India from Australia-Antarctica propagated from north to south, starting at ~136 Ma northwest of Australia, and reached the southern tip of India at ~126 Ma. Seafloor spreading in the Enderby Basin was abandoned at ~115 Ma, when a ridge jump transferred the Elan Bank and South Kerguelen Plateau to the Antarctic plate. Our revised plate kinematic model helps resolve the problem of successive two-way strike-slip motion between Madagascar and India seen in many previously published reconstructions and also suggests that seafloor spreading between them progressed from south to north from 94 to 84 Ma. This timing is essential for tectonic flow lines to match the curved fracture zones of the Wharton and Enderby basins, as Greater India gradually began to unzip from Madagascar from ~100 Ma. In our model, the 85-East Ridge and Kerguelen Fracture Zone formed as conjugate flanks of a "leaky" transform fault following the ~100 Ma spreading reorganization. Our model also identifies the Afanasy Nikitin Seamounts as products of the Conrad Rise hotspot.

Gibbons, Ana D.; Whittaker, Joanne M.; Müller, R. Dietmar

2013-03-01

5

Geochemistry and age of the Nouméa Basin lavas, New Caledonia: Evidence for Cretaceous subduction beneath the eastern Gondwana margin  

NASA Astrophysics Data System (ADS)

The Nouméa Basin in New Caledonia is perhaps the best preserved sequence of in-situ Late Cretaceous marine sediments and volcanic rocks in the western Pacific region. Previous tectonic interpretations suggest that the basin formed during a period of large-scale extension between New Caledonia and Antarctica during the break-up of the eastern Gondwana margin. However, new geochemical analyses have identified continental arc signatures in the lavas, suggesting a well-developed Late Cretaceous volcanic arc system active in the New Caledonia sector of the eastern Gondwana margin, possibly extending as far south as New Zealand. There are two distinct suites of lavas in the Nouméa Basin. The older lavas are predominately mafic, low to high-K, and have a calc-alkaline fractionation trend. Chondrite normalised trace element plots show patterns that are light rare earth element (LREE) enriched, and mid-ocean ridge basalt (MORB) normalised trace element plots show enrichment of most incompatible trace elements with discernable negative Nb, Ta and Ti anomalies. Trace element ratios identify a continental arc signature in these lavas which were generated from an N-MORB-like source. Overlying the mafic lavas is a sequence of younger voluminous siliceous, generally subalkaline lavas (+/-88 Ma). These lavas are LREE enriched with slight positive Nb-Ta anomalies and negative Eu and Ti anomalies. The geochemical data indicates these lavas have within plate characteristics with minor continental affinities and an enriched source. We propose that the older mafic lavas were generated during large scale subduction under the eastern Gondwana margin during the Late Cretaceous. Whereas the younger lavas may have been generated during extension; caused by slab roll-back of the subduction system along the Southwest Pacific plate boundary. The presence of fragments of a detached slab in this process would result in lavas chemically similar to those found in the Nouméa Basin, with minor continental characteristics, and generated from an enriched mantle source. What is of fundamental importance is the evidence that the arc system extended from New Caledonia southwards to New Zealand and was likely contemporaneous.

Nicholson, K. N.; Maurizot, P.; Black, P. M.; Picard, C.; Simonetti, A.; Stewart, A.; Alexander, A.

2011-07-01

6

An Interpretation of the Seafloor Spreading History of the West Enderby Basin between Initial Breakup of Gondwana and Anomaly C34  

Microsoft Academic Search

The seafloor spreading evolution in the Southern Indian Ocean is key to understanding the initial breakup of Gondwana. We summarize the structural lineaments deduced from the GEOSAT 10?Hz sampled raw altimetry data as well as satellite derived gravity anomaly map and the magnetic anomaly lineation trends from vector magnetic anomalies in the West Enderby Basin, the Southern Indian Ocean. The

Yoshifumi Nogi; Kumiko Nishi; Nobukazu Seama; Yoichi Fukuda

2004-01-01

7

Cyclic development of sedimentary basins at convergent plate margins — 1. Structural and tectono-thermal evolution of some gondwana basins of eastern Australia  

NASA Astrophysics Data System (ADS)

The Devono-Carboniferous Drummond Basin of eastern Australia formed by extensional tectonics, most probably in a back-arc setting, as an oceanic plate subducted westward under Gondwana's continental margin. Within this basin a syn-rift sequence and a relatively thick post-rift sequence are recognized, and the latter is separated from the overlying Galilee Basin by a mid-Carboniferous unconformity, which heralds a time of relatively mild compression, uplift and folding. The lower Galilee Basin formed as a foreland, secondary peripheral bulge, or mixed-style basin during the Late Carboniferous to Early Permian time interval. A mid-Permian unconformity separates it from the extensive Late Permian to Mid-Triassic upper Galilee Basin, here suggested to be a platform basin. Nest, the main, Mid- to Late Triassic compressional event led to reverse movement along previously normal faults, folding, uplift and erosion of up to 2 km of section from the Galilee and Bowen basins. During Jurassic and Cretaceous times, the Eromanga/Surat/Carpentaria Basin, a platform basin originally >1.7 million km 2 in extent, developed cratonward of the zone of continuing subduction. Subsequently, the culminating extensional event took place further east, where Lord Howe Rise rifted apart from the continental landmass and drifted eastward as oceanic seafloor spread in the Tasman Basin, and widespread uplift and erosion occurred over the eastern Australian coastal area. New data, re-interpretation of existing data and extensive literature support the interpretation of the Phanerozoic tectonic evolution of eastern Australia in a context of convergent plate margins. Within this context, overall eastward migration through time of the subduction zone and associated morphotectonic entities (e.g. the Warburton, Adavale, Drummond, Bowen and Tasman extensional basins) and vertical stacking of unconformity-bound extensional, foreland and platform basins (e.g. the Drummond, Galilee and Eromanga basins) occurred.

de Caritat, Patrice; Braun, Jean

1992-12-01

8

Fluvial architecture of Early Permian Barakar rocks of Korba Gondwana basin, eastern-central India  

NASA Astrophysics Data System (ADS)

The Early Permian Barakar Formation of the Korba basin represents repeated deposition of fining upward sequences of coarse to medium grained sandstone, fine grained sandstone-shale, shale and coal. The sandstones are channel, sheet like, multistory, and profusely cross-bedded. The shale beds are lens as well sheet like and laminated; coal facies is thin to moderately thick and shows splitting. Paleocurrent analysis suggests a northwesterly paleoslope during Barakar sedimentation. However, the deflection of paleoslope towards northeast in the eastern part of the basin supports the existence of a watershed in the depositional area. The Barakar paleochannel were 4.05 m deep and 176 m wide (single channel) with an average sinuosity of 1.27. The average flow velocity and sediment load during flood stage are in the order of 1.77 m/s and 4.15. These results indicate bed-load (braided) to mixed load nature of the Barakar streams of the Korba basin. The study suggests that the Early Permian braided Barakar streams deposited the coal measure sequence subsequent to deglaciation in a northwesterly slopping paleovalley. The basin floor was highly uneven marked by the presence of a basement high in the northwestern part that bifurcates the paleostreams into northwestern and northeastern branches.

Tewari, Ram Chandra; Hota, Rabindra Nath; Maejima, Wataru

2012-06-01

9

Gondwana breakup via double-saloon-door rifting and seafloor spreading in a backarc basin during subduction rollback  

NASA Astrophysics Data System (ADS)

A model has been developed where two arc-parallel rifts propagate in opposite directions from an initial central location during backarc seafloor spreading and subduction rollback. The resultant geometry causes pairs of terranes to simultaneously rotate clockwise and counterclockwise like the motion of double-saloon-doors about their hinges. As movement proceeds and the two terranes rotate, a gap begins to extend between them, where a third rift initiates and propagates in the opposite direction to subduction rollback. Observations from the Oligocene to Recent Western Mediterranean, the Miocene to Recent Carpathians, the Miocene to Recent Aegean and the Oligocene to Recent Caribbean point to a two-stage process. Initially, pairs of terranes comprising a pre-existing retro-arc fold thrust belt and magmatic arc rotate about poles and accrete to adjacent continents. Terrane docking reduces the width of the subduction zone, leading to a second phase during which subduction to strike-slip transitions initiate. The clockwise rotated terrane is caught up in a dextral strike-slip zone, whereas the counterclockwise rotated terrane is entrained in a sinistral strike-slip fault system. The likely driving force is a pair of rotational torques caused by slab sinking and rollback of a curved subduction hingeline. By analogy with the above model, a revised five-stage Early Jurassic to Early Cretaceous Gondwana dispersal model is proposed in which three plates always separate about a single triple rift or triple junction in the Weddell Sea area. Seven features are considered diagnostic of double-saloon-door rifting and seafloor spreading: earliest movement involves clockwise and counterclockwise rotations of the Falkland Islands Block and the Ellsworth Whitmore Terrane respectively; terranes comprise areas of a pre-existing retro-arc fold thrust belt (the Permo-Triassic Gondwanide Orogeny) attached to an accretionary wedge/magmatic arc; the Falklands Islands Block is initially attached to Southern Patagonia/West Antarctic Peninsula, while the Ellsworth Whitmore Terrane is combined with the Thurston Island Block; paleogeographies demonstrate rifting and extension in a backarc environment relative to a Pacific margin subduction zone/accretionary wedge where simultaneous crustal shortening occurs; a ridge jump towards the subduction zone from east of the Falkland Islands to the Rocas Verdes Basin evinces subduction rollback; this ridge jump combined with backarc extension isolated an area of thicker continental crust — The Falkland Islands Block; well-documented EW oriented seafloor spreading anomalies in the Weddell Sea are perpendicular to the subduction zone and propagate in the opposite direction to rollback; the dextral strike-slip Gastre and sub-parallel faults form one boundary of the Gondwana subduction rollback, whereas the other boundary may be formed by inferred sinistral strike-slip motion between a combined Thurston Island/Ellsworth Whitmore Terrane and Marie Byrd Land/East Antarctica.

Martin, A. K.

2007-12-01

10

Geochemistry of some banded iron-formations of the Archean supracrustals, Jharkhand-Orissa region, India  

Microsoft Academic Search

Banded iron-formations (BIF) form an important part of the Archean supracrustal belts of the Jharkhand-Orissa region, India.\\u000a Major, trace and REE chemistry of the banded iron-formation of the Gandhamardan, Deo Nala, Gorumahisani and Noamundi sections\\u000a of the Jharkhand-Orissa region are utilized to explore the source of metals and to address the thermal regime of the basin\\u000a floor and the redox

H. N. Bhattacharya; Indranil Chakraborty; Kaushik K. Ghosh

2007-01-01

11

R-mode factor analysis of lithologic variables from cyclically deposited Late Paleozoic Barakar sediments in Singrauli Gondwana sub-basin, Peninsular India  

NASA Astrophysics Data System (ADS)

The quantitative relationships between lithological variables from the Late Paleozoic coal bearing cycles have been investigated using factor analysis in an attempt to analyze net subsidence during the deposition of these cycles. The results suggest that there are only two non-zero eigenvalues in varimax matrix which indicate that the hyper ellipsoid enclosing the data points have seven axes of zero length and exists an ordinary two dimensional ellipsoid. The data points can be located with reference to two mutually perpendicular axes. Loading on thickness of sandstones, thickness of shale, number of sandstone beds and number of shale beds are extremely high on RF-I and low on the other factor. This would lead to the interpretation that a balance was maintained throughout the Barakar sedimentation between the rate of deposition and the rate of subsidence. On the other hand, loading on number of coal beds is high on ' suggesting that the development of peat swamps (coal beds) is not a normal feature during the Late Paleozoic Barakar sedimentation in this Gondwana sub-basin.

Khan, Z. A.; Tewari, R. C.

2011-01-01

12

A Late Jurassic fossil assemblage in Gondwana: Biostratigraphy and correlations of the Tacuarembó Formation, Parana Basin, Uruguay  

Microsoft Academic Search

The Tacuarembó Formation has yielded a fossil assemblage that includes the best known body fossils, consisting of isolated scales, teeth, spines, and molds of bones, recovered from thin and patchy bonebeds, from the Botucatu Desert, Parana Basin, South America. The remains are preserved in the sandstones widespread around the city of Tacuarembó. We propose a new formalized nomenclature for the

Daniel Perea; Matías Soto; Gerardo Veroslavsky; Sergio Martínez; Martín Ubilla

2009-01-01

13

Preliminary Environmental Analysis of Gondwana in Candiota Region, Rio Grande Do Sul.  

National Technical Information Service (NTIS)

The geological results obtained in the Candiota Region by NUCLEBRAS, during the evaluation of the uranium economic potential from basal Gondwana Sequence - Itarare Group and Rio Bonito Formation - at South-East of the Parana Sedimentary Basin, are studied...

L. C. da Silveira Fontes L. T. Cava

1980-01-01

14

Analysis of orientation of maximum horizontal tensional stress (? ? ? ?Hmax) of the Gondwana Barapukuria coal basin, NW Bangladesh: By means of finite element modeling  

Microsoft Academic Search

This paper uses two-dimensional Finite Element Method (FEM) numerical modeling to analyze the orientation of maximum horizontal tensional stress of the Barapukuria coal basin in Bangladesh. An elastic plane stress model incorporating elastic rock physical properties for the coal basin area was used consisting of 2916 elements with a network of 1540 nodes. The stress field at any point of

Rafiqul Islam

15

Heartbeat of a mountain: diagnosing the age of depositional events in the Karoo (Gondwana) Basin from the pulse of the Cape Orogen  

NASA Astrophysics Data System (ADS)

Careful consideration of the effects of the Cape orogeny on sedimentation in the Carboniferous-Jurassic Karoo Basin provides an indirect tool for accurately dating these rocks. Fossil and radiometric data, especially when combined with sedimentological and structural information, yield partly overlapping age brackets which can be used to correlate the successive tectonic pulses with specific depositional events. Application of these principles to associated basins in Gondwanaland can provide a firm foundation for more dependable stratigraphic correlation on a global scale. The exercise also suggests that a number of widely held opinions on the age of certain stratigraphic units in the Karoo Supergroup may be incorrect.

Le Roux, J. P.

1995-09-01

16

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

NASA Astrophysics Data System (ADS)

The occurrence of synkinematic and authigenic clay minerals is a common feature in fault gouges. Few attempts have been made to date fault gouges. We present the first age data in Australia for synkinematic illite-smectite growth in two fault zones of the northern Sydney Basin, NSW. The faults occur at Burwood Beach, NSW in the northern part of the Sydney Basin and are hosted by Early Permian siltstones, tuffs and coals of the Lambton Formation, Newcastle Coal Measures. The faults are 1.5 m apart, show normal displacement and trend N-S with steep easterly dips. Foliated gouge zones, comminution and dilational breccias are developed along both fault surfaces. K-Ar ages extracted from samples in the gouge and tuffs in the damage zones are 172 (6-10 ?m) to 119 Ma (<0.4 ?m), respectively. Older ages of 272-281 Ma for the coarse fractions (>2 ?m), 237-245 Ma for the <2 ?m fraction, 218 Ma for the <0.4 ?m fraction and 196 Ma for the <0.1 ?m fraction have been obtained from siltstones within and outside the damage zone. We believe the younger ages of 196-237 Ma indicate the time at which diagenetic illite-smectite formed and the 122-150 Ma dates from the <2 ?m fraction represent the maximum age of gouge formation. The younger ages are thought to reflect the last slip event occurring on the faults, which is related to the rifting and dispersal of the eastern margin of the Australian continent.

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

2004-12-01

17

Geochemistry of banded iron formation of Orissa, India  

Microsoft Academic Search

Major and trace element analyses of representative samples of various types of banded iron-formation and its various minerals, associated sediments, iron ores and volcanic tuff from different localities of Orissa, India, are presented in this paper. The Orissa banded iron-formation is classified as Precambrian banded iron formation and is similar to the oxide facies iron formation of Lake Superior type.

Tapan Majumder; K. L. Chakraborty; Auditeya Bhattacharyya

1982-01-01

18

Neodymium isotope constraints on the tectonic evolution of East Gondwana  

NASA Astrophysics Data System (ADS)

East Gondwana incorporates a collage of polymetamorphic terrains with long-lived tectonic histories from the Early Archaean to the Neoproterozoic. The oldest cratonic areas have been identified in South India (north of the Palghat-Cauvery shear zone) and East Antarctica (the Napier Complex). These terrains are remnants of an East Gondwana craton that underwent initial crustal growth during the Early Archaean and granulite-facies metamorphism at ˜2.5 Ga. Both were virtually unaffected by the Pan-African orogeny (1.1-0.5 Ga). In contrast, Proterozoic terrains were subject to high-grade metamorphism during the Pan-African event. On the basis of published Nd model ages, a direct correlation can be made between southern Madagascar (south of the Ranotsara shear zone), southern India (the Madurai Block and Kerala Khondalite Belt) and the Highland/Southwestern Complex of Sri Lanka, which comprise a Later Archaean-Palaeoproterozoic (3.2-2.0 Ga) mobile belt that may extend eastwards into East Antarctica. The youngest period of crustal growth in East Gondwana has been recognised at 1.5-0.8 Ga from isotopic studies of the Mozambique Belt of East Africa, the Vijayan Complex of Sri Lanka and the Yamato-Belgica Complex/Sør Rondane Mountains of East Antarctica. Small slivers of terrain of intermediate age (1.9-1.2 Ga) have been recognised in South India (Achankovil metasediments) and Sri Lanka (Wanni Complex) that may represent mixed-age contributions to clastic sedimentary basins.

Harris, N. B. W.; Bartlett, J. M.; Santosh, M.

19

Some observational aspects and modeling results of the Orissa super cyclone, October 1999  

NASA Astrophysics Data System (ADS)

The super cyclone that crossed the Orissa coast near Paradeep port (20.3 N, 86.7 E) around 0600 UTC on 29 October 1999, caused enormous damage - death of 10,000 people and 400,000 cattle, property damage worth Ind. Rs. 10,000 crores ( about USD 2 billion), salinization of about 1.8 million hectares of agricultural land, destruction of paddy crop paddy crop worth Ind. Rs.1,500 crores (USD 300 million), and severe damage to transmission lines, power supply, roads and buildings sustained severe damages. This cyclone was identified as a low pressure in the Gulf of Thailand on 24th October 1999. It moved westwards and gradually intensified reaching the intensity of a severe cyclonic storm on 27 October. The cyclone further intensified reaching very high intensity to be called as a super cyclone when it crossed the Orissa coast near Paradeep around 0600 UTC of 29 October. The observational installations on the Orissa coast were severely damaged and failed to record. However rough estimates have been made using the satellite and radar pictures. Average speed of the storm was about 20 km/hour and increased to 30 km/hour while intensifying, but reduced before and after crossing the coast. The central surface pressure is estimated as 912 hPa on 29 October with the T-number as T7; correspondingly the maximum wind speed is estimated as 260 km/hour with the radius of the eye at 15 km. Heavy rainfall was reported on 29, 30 and 31 October with maximum amounts of 955 mm in Bhadrak district of Orissa and 600-800 mm in Mahanadi river basin. A storm surge of 5 to 6m above the astronomical tide is reported at Paradeep on 29 October. All the above parameters, namely, strong winds with gale, torrential rains with heavy rainfall rate and high storm surge, caused the devastation. An attempt has been made to simulate the intensification and movement of the cyclone using a high resolution mesoscale model. The simulation study indicated that the models are capable of predicting the intensification of the storm as well as the movement. However the model errors range below 50 km with respect to the track.

Rao, N. J.; Rao, D. B.

2001-05-01

20

Development of the Mozambique and Ruvuma sedimentary basins, offshore Mozambique  

Microsoft Academic Search

Two major sedimentary basins have been identified on the continental margin of Mozambique—Mozambique Basin and Ruvuma Basin. The formation of the basins is related to the break-up of Gondwana and opening of the western part of the Indian Ocean. The basins are relatively young, having developed discordantly to the structural plan of Gondwana sedimentary basins.The history of the formation of

G. Salman; I. Abdula

1995-01-01

21

Characterization of the Sukinda and Nausahi ultramafic complexes, Orissa, India by platinum-group element geochemistry  

USGS Publications Warehouse

Samples of 20 chromitite, 14 ultramafic and mafic rock, and 9 laterite and soil samples from the Precambrian Sukinda and Nausahi ultramafic complexes, Orissa, India were analyzed for platinum-group elements (PGE). The maximum concentrations are: palladium, 13 parts per billion (ppb); platinum, 120 ppb; rhodium, 21 ppb; iridium, 210 ppb; and ruthenium, 630 ppb. Comparison of chondrite-normalized ratios of PGE for the chromitite samples of lower Proterozoic to Archean age with similar data from Paleozoic and Mesozoic ophiolite complexes strongly implies that these complexes represent Precambrian analogs of ophiolite complexes. This finding is consistent with the geology and petrology of the Indian complexes and suggests that plate-tectonic and ocean basin developement models probably apply to some parts of Precambrian shield areas. ?? 1985.

Page, N. J.; Banerji, P. K.; Haffty, J.

1985-01-01

22

Environmental health impact assessment of National Aluminum Company, Orissa  

PubMed Central

Environmental Health Impact Assessment of industries is an important tool help decision-makers make choices about alternatives and improvements to prevent disease/injury and to actively promote health around industrial sites. A rapid environmental health hazard and vulnerability assessment of National Aluminum Company was undertaken in the villages in the vicinity plant in Angul region of Orissa. Aluminum smelter plant was known to discharge hundreds of tones of fluoride in to the environment contaminating the ecosystem around the plant. The present Environmental health impact assessment was carried out in 2005-06 at the request of officials from Government of Orissa. The findings showed adverse effects on human, veterinary and ecological health. Human health effects manifestations included dental and skeletal fluorosis. Veternary health effects were manifested through skeletal fluorosis. Ecological adverse effects were manifested by damage to paddy fields and crop yield.

Patil, Rajan R.

2011-01-01

23

Social Exclusion and Land Administration in Orissa, India  

Microsoft Academic Search

May 1999Which factors prevent the rural poor and other socially excluded groups from having access to land in Orissa, India?The authors report on the first empirical study of its kind to examine--from the perspective of transaction costs--factors that constrain access to land for the rural poor and other socially excluded groups in India. They find that:-Land reform has reduced large

Robin Mearns; Saurabh Sinha

1999-01-01

24

Implications for Gondwana of new Ordovician paleomagnetic data from igneous rocks in southern Victoria Land, East Antarctica  

NASA Astrophysics Data System (ADS)

New paleomagnetic data presented here from the southern Victoria Land (SVL) region of East Antarctica further refine the Gondwana early Paleozoic apparent polar wander path. The results are based on paleomagnetic analyses of Early to Middle Ordovician granitoids and dike swarms from which a new SVL pole (23°E, 3.5°S, A95 = 5.9°) was calculated. The new SVL paleomagnetic pole agrees with less well-determined Ordovician poles from other parts of East Antarctica indicating little or no translation/rotation across the East Antarctic craton since the Middle Ordovician. A new Gondwana ˜475 Ma mean pole (11°E 36°N, A95 = 7°, N = 4 studies, in African coordinates) has been calculated from African, Australian, and Antarctic Early and early Middle Ordovician paleomagnetic poles. Age reassignment of the Antarctic Sør Rondane paleopole (Zijderveld, 1968) places it into the Cambrian period and when combined with other Gondwana Cambrian poles results in a new Gondwana ˜515 Ma pole (7°E, 22°N, A95 = 9.5°, N = 7 studies, in African coordinates). The new Gondwana ˜515 Ma and ˜475 Ma poles, when compared with poles of similar age from Laurentia, allow paleogeographic reconstructions to be made that are in keeping with models predicting that Iapetus Ocean basin opening and closure may have been related first to rifting and then collision of Laurentia with Gondwana. The paleomagnetic data also suggest that most of West Gondwana moved toward lower latitudes between the Middle/Late Cambrian and the late Early Ordovician which may be reflected in the fossil record.

Grunow, Anne M.

1995-07-01

25

Storm Protection by Mangroves in Orissa: An Analysis of the 1999 Super Cyclone  

Microsoft Academic Search

This study assesses the storm protection role afforded by mangroves. It uses data on human casualties, damages to houses and livestock losses suffered in the Kendrapada district of the State of Orissa during the super cyclone of October 1999. The cyclone (of T 7 category) devastated 12 of the 30 districts of Orissa causing 9,893 human casualties and 441,531 livestock

Saudamini Das

26

An assessment of the olive ridley turtle ( Lepidochelys olivacea) nesting population in Orissa, India  

Microsoft Academic Search

Olive ridley mass nesting events or ‘arribadas’ have been documented in Orissa, India since 1974. However, since standardised techniques have not been used to census turtles, actual population trends remain unknown. Herein, we summarise information on nesting populations in Orissa, using data from multiple sources to arrive at consensus estimates and to derive trends. We conducted a quantitative estimate of

Kartik Shanker; Bivash Pandav; B. C. Choudhury

2004-01-01

27

Geophysical evidence for a causative process for fragmentation in western Gondwana  

SciTech Connect

The existence and subsequent fragmentation of the Gondwana supercontinent are well established in the geological literature. Debate continues, however, on the exact prefragmentation geometry and the causative process of breakup. The easter Walvis Ridge and the Agulhas and the Mozambique plateaus, which surround southern Africa, exhibit geophysically anomalous oceanic crust and lithosphere. In the vicinity of these aseismic bathymetry highs, the crust is considerably thicker than normal, and the uppermost mantle has lower than normal densities and seismic velocities. Within a Gondwana framework, these anomalies coincide with a highly fragmented region at the triple junction of the three major plates (Africa, South America, and Antarctica). This anomalous oceanic crust and lithosphere, the ubiquitous and contemporaneous magmatism, and the basin and range-type tectonism of the region are consonant with a hot-mantle-upflow tectonic framework as the causative process for fragmentation.

Antoine, L.A.G.; Moyes, A.B. (Univ. of Witwatersrand, Johannesburg (South Africa))

1992-07-01

28

The Mesozoic Continental Magmatism in Brazil: its Role in the Western Gondwana Evolution from Integrated Paleomagnetic and Geochemical Data  

NASA Astrophysics Data System (ADS)

Most of the Paleozoic era in the South American platform represents a period of tectonic quiescence during which large sedimentary basins evolved. Subsequently an intense magmatic activity took place preceding the disclosure of the Gondwana from Pangea, and later the disruption of the western Gondwana blocks (South America and Africa separation). In Brazil Early Jurassic (~220-180 Ma) tholeiitic basalts erupted mostly in the northern area (Amazonas and Parnaíba basins), whereas the Early Cretaceous (~140-120 Ma) is best represented by the huge magmatism of the Serra Geral Formation (Paraná basin, southeastern Brazil). An intense associated intrusive activity in the form of dykes and sills of both ages is widespread all over the country but tends to concentrate towards the continental margins. The integration of paleomagnetic and geochemical data on the Brazilian Mesozoic magmatism put some constraints on the timing, duration and the mantle sources involved in the generation of the magma products related to the different magmatic events.

Ernesto, M.; Marques, L. S.

2011-12-01

29

Deep resistivity sounding studies for probing deep fresh aquifers in the coastal area of Orissa, India  

NASA Astrophysics Data System (ADS)

Exploration and exploitation of groundwater in sedimentary areas are reasonably simple. However, the problem of salinity in coastal areas makes the job very difficult, especially when the freshwater aquifers are not extensive and are entrapped between saline aquifers. States along the eastern coast of India, particularly Orissa with respect to the Mahanadi basin, have acute problems with groundwater salinity. It has been possible to locate horizons of fresh groundwater entrapped between deep saline aquifers in the southwestern part of Mahanadi delta, with the help of deep resistivity soundings along the Delang-Puri profile. This finding has been validated through boreholes and checked with electrical logs of this region. Three freshwater aquifers have been detected: one at shallow depth between 20 and 60 m, the second in the depth range of 90-160 m, and the third in the fractured/weathered basement. The second freshwater aquifer has the most potential; it has a thickness range of 20-80 m and it could be exploited to overcome problematic salinity issues. In general, the depth to basement is variable and it increases seaward.

Singh, S. B.; Veeraiah, B.; Dhar, R. L.; Prakash, B. A.; Tulasi Rani, M.

2011-03-01

30

Gondwana facies started when Gondwanaland merged in Pangea  

Microsoft Academic Search

The late Paleozoic and early Mesozoic Gondwana sequence of peninsular India and its equivalents in the present southern continents were deposited during the merging of the continents in Pangea and are a facies of the Pangean super-sequence distinguished by late Carboniferous and Early Permian glacial deposits and a provincial biota, in particular the Glossopteris flora. The Gondwana facies owes its

J. J. Veevers

1988-01-01

31

Gondwana and associated rocks of the Himalaya and their significance  

NASA Astrophysics Data System (ADS)

The two tectonostratigraphic domains in which Gondwana sediments are present are the Lesser Himalayan and the Tethyan Himalayan belts. The widespread occurrence of diamictite, Glossopteris flora, and Eurydesma fauna provide important correlative links between these two domains. Development of Gondwana rocks in the Lesser Himalaya has been noted only in the eastern Himalaya from central Nepal to Arunachal Pradesh. Coal deposits and flora of the Damuda Group of Peninsular India type are present here. Sedimentary rocks were deposited in a linear trough representing the northernmost rift system of Gondwana India, which is a taphrogenic lineament quite distinct from an orogenic trough. This represents continental rifting near the margin of the Gondwana supercontinent. A recent discovery of a Late Gondwana (Jurassic) flora in the Lesser Himalaya of central Nepal closely resembling the Rajmahal flora further supports the extension of the Peninsular Gondwana continent. Gondwana rocks of the Tethyan belt show an extensive development from Kashmir to Sikkim-Bhutan. These represent Permian and Jurassic-Lower Cretaceous sediments with a more extensive development of Paleozoic-Mesozoic rocks. The depositional environment may have been either a coast or an island developed within the Tethyan realm. These rocks contain a mixed flora of Gondwanian-Cathaysian elements with several endemic species. The reported isolated occurrences of Mesozoic (Jurassic-Lower Cretaceous) flora in several parts of the Tethyan Himalaya, particularly in Nepal and Bhutan, show affinity with the Upper Gondwana of Peninsular India. However, north of the Indus Suture in Ladakh, the Jurassic flora contains different elements resembling Laurasian northern elements. The classification of the Gondwana flora of the Himalaya into two distinct environments (botanic provinces), the Lesser Himalayan belt representing the continuation of the typical Gondwana flora and the Tethyan belt representing mixed flora continuing northward into Tibet, suggests that the paleo-Tethys may have been a narrow sea rather than a wide ocean.

Tripathi, C.; Singh, Gopal

32

Surge simulations for 1999 Orissa super cyclone using a finite element model  

Microsoft Academic Search

The Orissa super cyclone which crossed the Orissa coastal region near Paradip on October 29, 1999 proved to be disastrous.\\u000a The strong winds, torrential rains with heavy rainfall and high storm surge associated with the cyclone caused havoc that\\u000a resulted in the death of thousands of people, cattle and extensive damage to agricultural land, paddy crop, transmission lines,\\u000a power supply,

G. Latha; E. P. Rama Rao

2007-01-01

33

Rapid onset of late Paleozoic glaciation on Gondwana: Evidence from Upper Mississippian strata of the Midcontinent, United States  

NASA Astrophysics Data System (ADS)

Direct evidence of the late Paleozoic glaciation of Gondwana from glacial deposits suggests that geographically extensive continental glaciation began some time in the Namurian (Late Mississippian). However, the timing and characteristics of the onset of glaciation are poorly understood because of a lack of reliable paleontological control and reworking of initial glacial deposits by subsequent glacial advances. Indirect evidence of glaciation preserved in unconformity-bounded, low-latitude ramp sequences in the Illinois basin, United States, suggests that geographically extensive continental glaciation of Gondwana actually began in the late Visean. An abrupt change from carbonate-dominated sequences bounded by disconformities with little evidence of erosion to mixed carbonate-siliciclastic sequences bounded by unconformities with deep incised valleys was likely produced by a three-fold increase in the magnitude of eustatic sea-level fluctuations. The increase in the magnitude of sea-level fluctuations was likely driven by an equally abrupt increase in ice volume and marks the onset of the geographically extensive late Paleozoic glaciation of Gondwana. A possible explanation for the rapid onset of glaciation is the closing of the equatorial seaway between Laurussia and Gondwana. Closing of this seaway would have led to an abrupt change in oceanic and atmospheric circulation patterns that could have initiated major continental glaciation in the Southern Hemisphere.

Smith, Langhorne B., Jr.; Read, J. Fred

2000-03-01

34

Late Palaeozoic crustal block rotations within the Gondwana sector of Pangea  

Microsoft Academic Search

From the Late Carboniferous to the onset of the Triassic, Gondwana was transected by several major shear systems the location of which was controlled by weak zones joining the ancient cratons. These shear systems subdivided Gondwana into mega-blocks each of which experienced rotational motions at different angular speeds. Collisions between Gondwana and Laurussia in the north and between Gondwana and

Johan N. J. Visser; Hermann E. Praekelt

1998-01-01

35

Global changes during Carboniferous Permian glaciation of Gondwana: Linking polar and equatorial climate evolution by geochemical proxies  

NASA Astrophysics Data System (ADS)

The most prevalent Phanerozoic glaciation occurred during the Carboniferous Permian on the Southern Hemisphere Gondwana supercontinent. Sediments from the Pennsylvanian Dwyka Group deposited in the Karoo Basin of South Africa provide a complete record of glaciation and deglaciation phases. The direct correlation of glaciation events in southern Gondwana basins with the well-studied climate evolution of equatorial regions was previously hampered by lack of precise radiometric dating. As dating has now become available for the Karoo Basin, the Gondwana glaciation can be viewed in a global paleoclimatic framework with high temporal resolution. Element geochemical proxies (CIA [chemical index of alteration], Zr/Ti, Rb/K, V/Cr) record three confined shifts in climate and paleoenvironment of the Karoo Basin. These shifts were induced by changes in sea level, weathering rate, provenance, and redox conditions. Because of the low availability and diagenetic overprint of carbonates, ocean and atmosphere pCO2 variations had to be reconstructed from ?13Corg values of marine organic matter. The ?13Corg signatures are affected by variable proportions of marine versus terrestrially derived organic matter and its state of preservation. Organic geochemical investigations (TOC [total organic carbon], C/N, lipid biomarkers) indicate the organic matter in the central Karoo Basin was primarily of algal origin. In agreement with element proxies, the varying ?13Corg values mirror shifts in pCO2, rather than variations of organic-matter type. A covariation trend between carbon isotope signatures of equatorial carbonates and ?13Corg values from the Karoo Basin argues against local forcing factors and instead implies a global climate-control mechanism. The 5 7 m.y. duration of a complete glacial cycle is not in tune with any known orbital frequency. Processes such as changes in equator-pole temperature gradients or newly developing atmosphere-ocean circulation pathways can be regarded as controlling factors.

Scheffler, K.; Hoernes, S.; Schwark, L.

2003-07-01

36

Ordovician K-bentonites in the Argentine Precordillera: relations to Gondwana margin evolution  

USGS Publications Warehouse

This paper is included in the Special Publication entitled 'The proto- Andean margin of Gondwana', edited by R.J. Pankhurst and C.W. Rapela. Ordovician K-bentonites have now been recorded from >20 localities in the vicinity of the Argentine Precordillera. Most occur in the eastern thrust belts, in the San Juan Limestone and the overlying the Gualcamayo Formation, but a few ash beds are known also from the central thrust belts. The oldest occur in the middle Arenig I, victoriae lunatus graptolite (Oe. evae conodont) Zone, and the youngest in the middle Llanvirn P. elegans (P. suecicus) Zone. Mineralogical characteristics, typical of other Ordovician K-bentonites, include a matrix of illite/smectite mixed-layer clay and a typical felsic volcanic phenocryst assemblage: biotite, beta-form quartz, alkali and plagioclase feldspar, apatite, and zircon, with lesser amounts of hornblende, clinopyroxene, titanite and Fe-Ti oxides. The proportions of the mineral phases and variations in their crystal chemistry are commonly unique to individual (or small groups of) K-bentonite beds. Glass melt inclusions preserved in quartz are rhyolitic in composition. The sequence is unique in its abundance of K-bentonite beds, but a close association between the Precordillera and other Ordovician sedimentary basins cannot be established. The ash distribution is most consistent with palaeogeographical reconstructions in which early Ordovician drifting of the Precordillera occurred in proximity to one or more volcanic arcs, and with eventual collision along the Andean margin of Gondwana during the mid-Ordovician Ocloyic event of the Famatinian orogeny. The Puna-Famatina terrane northeast of the Precordillera might have served as the source of the K-bentonite ashes, possibly in concert with active arc magmatism on the Gondwana plate itself.

Huff, W. D.; Bergstrom, S. M.; Kolata, D. R.; Cingolani, C. A.; Astini, R. A.

1998-01-01

37

Gondwana (Africa) from top to base in space and time  

NASA Astrophysics Data System (ADS)

Gondwana with Africa at its core is reviewed from the unification of its several cratons in the Late Neoproterozoic, through its combination with Laurussia in the Carboniferous to form Pangea and up to its progressive fragmentation in the Mesozoic. For much of that time it was the largest continental unit on Earth and its remnants constitute 64% of all land areas today. New palaeogeographical reconstructions are presented, ranging from the Early Cambrian (540 Ma) through to just before the final Pangea breakup at 200 Ma. In Late Palaeozoic and Early Mesozoic times, Gondwana lay over the African large low shear-wave velocity province (LLSVP), one of two major thermochemical piles covering ca. 10% of the core-mantle boundary. The edges of the LLSVPs (Africa and its Pacific antipode) are the plume generation zones (PGZs) and the source regions of kimberlite intrusions and large igneous provinces (LIPs). Our palaeomagnetic reconstructions constrain the configuration of Gondwana and adjacent continents relative to the spin axis, but in order to relate deep mantle processes to surface processes in a palaeomagnetic reference frame, we have also rotated the PGZs to account for true polar wander. In this way, we visualize how the surface distribution of LIPs and kimberlites relate to Gondwana's passage over the PGZs. There are only two LIPs in the Palaeozoic (510 and 289 Ma) that directly affected Gondwanan continental crust, and kimberlites are rare (83 in total). This is because Gondwana was mostly located between the two LLSVPs. The majority of Palaeozoic kimberlites are Cambrian in age and most were derived from the African PGZ. Sixty-six Early Mesozoic kimberlites are also linked to the African LLSVP. All known LIPs (Kalkarindji, Panjal Traps, Central Atlantic Magmatic Province and Karoo) from 510 to 183 Ma (the lifetime of Gondwana) were derived from plumes associated with the African LLSVP, and three of them probably assisted the breakup of Gondwana and Pangea.

Torsvik, Trond H.; Cocks, L. Robin M.

2014-05-01

38

Parasitological aspects of malaria persistence in Koraput district Orissa, India.  

PubMed

A sample survey in 37 villages covering 10,733 people in 1986-87 in the Koraput district, Orissa showed that the malaria prevalence is of a much higher order than that reported by the National Malaria Eradication Programme (annual parasite incidence between 14.3 and 26.8 during 1981-86). Out of 833 positives detected 714 had Plasmodium falciparum, 86 had P. vivax, 12 had P. malariae and 21 had mixed infections. There were 650 asymptomatic parasite carriers and 127 gametocyte carriers. The infant parasite rate was 15.82 per cent and average enlarged spleen (AES) in 2 to 9 yr old children was 1.98. In a year round fever survey in 22 villages, 5520 blood smears were collected and 1364 were found positive for malaria, with 77.3 per cent P. falciparum. In a mass blood survey conducted in a labour camp at an irrigation project, 610 people were examined, and 181 were positive. Nearly 40 per cent of migrants and 22 per cent of locals were positive, P. falciparum being dominant. PMID:2345029

Rajagopalan, P K; Das, P K; Pani, S P; Jambulingam, P; Mohapatra, S S; Gunasekaran, K; Das, L K

1990-01-01

39

Accuracy of self reporting malaria in Orissa--a case study.  

PubMed

For rapid assessment of malaria in difficult forested areas in Orissa a study on the accuracy of self-reporting of malaria showed 72 per cent accuracy along with the sensitivity and specificity values of 46 per cent and 76 per cent respectively. The study clearly indicates its utility in the ongoing national malaria eradication programme and can be effectively used for rapid assessment of the disease prevalence. The information so gathered can be used for rapid assessment by the planners and programme managers in devising the strategies for the containment of malaria in the forested areas of Orissa. PMID:7759804

Kumar, A; Sharma, R C

1994-12-01

40

Paleomagnetic Constraints on the Neoproterozoic Evolution of West Gondwana  

NASA Astrophysics Data System (ADS)

In order to constrain the paleogeographic evolution of West Gondwana, an updated paleomagnetic database for Africa and South America is presented. The most striking feature that sorts out from the compilation is the contrasting evolution of most western Gondwana blocks with respect to Amazonia and the other Rodinian affiliates surrounding Laurentia. In our configuration they are separated from Laurentia and surrounding blocks by the Brasiliano Ocean which starts to close at around 940 Ma. The assembly of most of these blocks seems to have been accomplished by 630 Ma as indicated by the coincidence of their paleomagnetic poles, and the collisional ages recorded throughout the western Gondwana. On the other hand, paleomagnetic evidence is compatible with a Rodinian affiliation of Amazonia. In contrast to the other considered cratons, Amazonia seems to have joined the western Gondwana comparatively late, in the Early Cambrian, after rifting away from Laurentia at the end of Proterozoic times. In such scenario, the western Gondwana was formed through at least two distinct orogenic episodes comprising the assembly of central blocks around the Congo-Sao Francisco craton at ~630 Ma, which have collided later with Amazonia, Rio Apa, and Pampean blocks at ~520 Ma.

Trindade, R. I.

2005-05-01

41

Upper Permian fluviolacustrine deposits of southern Africa and the late Permian climate southern Gondwana  

SciTech Connect

Upper Permian-age fluviolacustrine deposits are widespread throughout southern Africa. In the southern part of the subcontinent, where deposition took place in foreland basin settings, the sequences are thicker and fluvial-dominated whereas, lacustrine-dominated deposits accumulated in settings of low relief, broad warping and mild faulting at the northern end. The geographic extent and lateral correlatability of these deposits suggest the existence of concurrent, perhaps interconnected, giant lakes within major fluvial frameworks throughout the subcontinent, thousands of miles inland from the sea. This period of major lake development within fluvial depositional settings suggests climatic conditions that sustained a uniquely wet continental environment, deep in the heart of the Gondwanan supercontinent. Simulations based on various general circulation and energy balance climate models predict extreme seasonal temperatures and aridity for Gondwana at the palaeolatitudes of southern Africa during the Late Permian. On the other hand, distribution of climate-sensitive rocks, palynologic and palaeobotanic data and vertebrate fossils, coroborate the temperature climate documented by sedimentologic studies. The erroneous modeling results may have arisen from the fact that the models do not employ palaeogeographies that accommodate the existence of the vast lakes and rivers of Gondwana. The Late Permian palaeogeography of series of giant lakes within major fluvial frameworks would have had considerable influences on the regional climate. This suggests that it is imperative that numerical modeling studies incorporate accurate palaeogeographies, constructed based on available geological data, in order to recreate past climates with acceptable degree of accuracy.

Yemane, K. (Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Geology Bryn Mawr Coll., PA (United States). Dept. of Geology)

1993-03-01

42

Locating South China in Rodinia and Gondwana: A fragment of Greater India Lithosphere? (Invited)  

NASA Astrophysics Data System (ADS)

From the formation of Rodinia at the end of the Mesoproterozoic through to the breakup of Pangea in the Mesozoic, the South China craton first formed and then occupied a position adjacent to Western Australia and northern India. Early Neoproterozoic supra-subduction zone magmatic arc-back arc assemblages in the craton range in age from ca. 1000 Ma to 820 Ma and display a sequential northwest decrease in age. These relations suggest formation and closure of arc systems through southeast-directed subduction and resulted in progressive northwestward accretion onto the periphery of an already assembled Rodinia. Siliciclastic units within an early Paleozoic succession that transgresses across the craton were derived from the southeast and include detritus from beyond the current limits of the craton. Detrital zircon age spectra require an East Gondwana source and are very similar to the Tethyan Himalaya and younger Paleozoic successions from Western Australia suggesting derivation from a common source and by inference accumulation in linked basins along the northern margin of Gondwana, a situation that continued until rifting and breakup of the craton in the late Paleozoic.

Cawood, P. A.; Zhao, G.; Wang, Y.; Xu, Y.

2013-12-01

43

The Basement of the Andes: the Gondwana-Laurentia Connections Revisited  

NASA Astrophysics Data System (ADS)

The research performed in the last decade in the basement of the Andes have shown that the Precambrian and Paleozoic rocks have recorded a series of igneous and metamorphic events through time. These episodes can be grouped in discrete orogenic events, which have different paleogeographic distribution and intensity. The first and most important orogenic event is widely distributed along the margin and correspond to the Sunsas-Grenville orogen. Evidence of metamorphism and associated magmatic rocks are found from Colombia to the southernmost Patagonia. This episode produced the amalgamation of Amazonia, Pampia and Patagonia, among other cratonic blocks, to form Rodinia. The Rodinia break-up leaved several cratonic blocks accreted in the Gondwana side, such as Marañón, Arequipa, and Antofalla, although the generalized extension of this period produced crustal attenuation, rifted basins, and limited oceanic realms during late Proterozoic times. The Brasiliano-Pampean orogeny reamalgamated these blocks against the Gondwana margin. A new episode of break-up produced the dispersal of several Gondwanian blocks, separation along some previous sutures, crustal attenuation and magmatism in Late Cambrian times, until the new amalgamation occurred in Middle Late Ordovician times. These processes led to the Famatinian orogeny when metamorphism and arc magmatism was widely spread along the continental margin, as seen in Chibcha, Marañón, Arequipa and Sierras Pampeanas. Besides the re-accretion of some parautochthonous terranes, new exotic blocks were derived from Laurentia, such as the Cuyania terrane, which finally collided against the Andean proto-margin at ~ 460 Ma to form the Argentine Precordillera and surrounding regions. Late accretion in Early to Middle Devonian times of Chilenia and related terranes formed most of the basement of Central Andes. Final collision between Laurentia and Gondwana in the Late Carboniferous - Early Permian times to form the Alleghanides, left behind some Laurentian pieces like Tahami, Tres Lagunas and Tahuin terranes of Colombia, Ecuador and Perú. This set of rifting episodes and subsequent collisions along the continental margin of western South America were the result of changes of the absolute motion of Gondwana related to global plate reorganizations during Proterozoic to Paleozoic times.

Ramos, V. A.

2009-05-01

44

Patterns of Gondwana plant colonisation anddiversification  

NASA Astrophysics Data System (ADS)

Charting the broad patterns of vascular plant evolution for Gondwana againstthe major global environmental shifts and events is attempted here for the first time. This is based on the analysis of the major vascular plant-bearing formations of the southern continents (plus India) correlated against the standard geological time-scale. Australia, followed closely by South America, are shown to yield by far the most complete sequences of productive strata. Ten seminal turnover pulses in the unfolding evolutionary picture are identified and seen to be linked to continental drift, climate change and mass global extinctions. The rise of vascular plants along the tropical belt, for instance, followed closely after the end-Ordovician warming and extinction. Equally remarkable is that the Late Devonian extinction may have caused both the terrestrialisation of the vertebrates and the origin of the true gymnosperms. The end-Permian extinction, closure of Iapetus, together with warming, appears to have set in motion an unparalleled, explosive, gymnosperm radiation; whilst the Late Triassic extinction dramatically curtailed it. It is suggested that the latitudinal diversity gradient clearly recognised today, where species richness increases towards the tropics, may have been partly reversed during phases of Hot House climate. Evidence hints at this being particularly so at the heyday of the gymnosperms in the Late Triassic super-Hot House world. As for the origin of terrestrial, vascular, plant life, the angiosperms seem closely linked to a phase of marked shift from Ice House to Hot House. Insect and tetrapod evolutionary patterns are discussed in the context of the plants providing the base of the ever-changing ecosystems. Intimate co-evolution is often evident. This isn't always the case, for example the non-linkage between the dominant, giant, long-necked, herbivorous sauropod dinosaurs and the dramatic radiation of the flowering plants in the Mid Cretaceous.

Anderson, J. M.; Anderson, H. M.; Archangelsky, S.; Bamford, M.; Chandra, S.; Dettmann, M.; Hill, R.; McLoughlin, S.; Rösler, O.

45

The Karoo basins of south-central Africa  

Microsoft Academic Search

The Karoo basins of south-central Africa evolved during the first-order cycle of supercontinent assembly and breakup of Pangea, under the influence of two distinct tectonic regimes sourced from the southern and northern margins of Gondwana. The southern tectonic regime was related to processes of subduction and orogenesis along the Panthalassan (palaeo-Pacific) margin of Gondwana, which resulted in the formation of

O. Catuneanu; H. Wopfner; P. G. Eriksson; B. Cairncross; B. S. Rubidge; R. M. H. Smith; P. J. Hancox

2005-01-01

46

Family Characteristics and Adolescent Competence in India: Investigation of Youth in Southern Orissa.  

ERIC Educational Resources Information Center

Examined the relationship between a host of family characteristics and indicators of adolescent competence in 107 eighth and ninth graders in Orissa state, India. Families of more socially competent students tended to be verbally and emotionally expressive, and democratic with respect to discipline, input, and decision making. (SLD)

Carson, David K.; Chowdhury, Aparajita; Perry, Cecyle K.; Pati, Chetana

1999-01-01

47

57Fe Mössbauer and EDXRF studies on three representative banded iron formations (BIFs) of Orissa, India  

Microsoft Academic Search

Three representative banded iron formation (BIF) samples from different mines of Orissa, India have been studied using Mössbauer spectroscopy and energy dispersive X-ray fluorescence (EDXRF) techniques. Mössbauer spectroscopy, which quantifies goethite in iron-bearing phases, has also been used to find out the degree of weathering. The EDXRF analysis quantifies 16 trace elements, which have been used in determining the origin

P. K. Nayak; D. Das; V. Vijayan; P. Singh; V. Chakravortty

2001-01-01

48

PERFORMANCE OF BUILT ENVIRONMENT IN THE OCT 1999 ORISSA SUPER CYCLONE  

Microsoft Academic Search

The October 1999, Super Cyclone ransacked and devastated vast portions of the Indian State of Orissa, leaving behind a huge trail of death and destruction. Rated as one of the worst cyclones to hit the Indian coast ever, the super cyclone surpassed the tragedy of the 1977 Chirala cyclone, killing nearly 15,000 people and causing extensive damage to property, crops

Simon Francis; Prasad V S K Gunturi; Munish Arora

49

Global deglaciation and the re-appearance of microbial matground-dominated ecosystems in the late Paleozoic of Gondwana.  

PubMed

The extensive matgrounds in Carboniferous-Permian open-marine deposits of western Argentina constitute an anachronistic facies, because with the onset of penetrative bioturbation during the early Paleozoic microbial mats essentially disappeared from these settings. Abundant microbially induced sedimentary structures in the Argentinean deposits are coincident with the disappearance of trace and body fossils in the succession and with a landward facies shift indicative of transgressive conditions. Deposits of the Late Carboniferous-Early Permian glacial event are well developed in adjacent basins in eastern Argentina, Brazil, South Africa and Antarctica, but do not occur in the western Andean basins of Argentina. However, the deglaciation phase is indirectly recorded in the studied region by a rapid rise in sea level referred to as the Stephanian-Asselian transgression. We suggest that an unusual release of meltwater during the final deglaciation episode of the Gondwana Ice Age may have dramatically freshened peri-Gondwanan seas, impacting negatively on coastal and shallow-marine benthic faunas. Suppression of bioturbation was therefore conducive to a brief re-appearance of matground-dominated ecosystems, reminiscent of those in the precambrian. Bioturbation is essential for ecosystem performance and plays a major role in ocean and sediment geochemistry. Accordingly, the decimation of the mixed layer during deglaciation in the Gondwana basins may have altered ecosystem functioning and geochemical cycling. PMID:23621394

Buatois, L A; Netto, R G; Gabriela Mángano, M; Carmona, N B

2013-07-01

50

Revealing the continental margin of Gondwana: the Ordovician arc of the Cordón de Lila (northern Chile)  

NASA Astrophysics Data System (ADS)

The tectonic evolution of the proto-Andean margin of western Gondwana has been commonly seen in terms of terrane accretion processes, requiring the existence of early Palaeozoic terrane boundaries and associated sutures. A new study of the Cordón de Lila Ordovician volcano-sedimentary successions in northern Chile reveals for the first time an arc assemblage deposited on thin crust within a continental arc system, having regional implications. Primitive basalts, rhyolites, volcanogenic wackes and siltstones are associated, bearing not only debris from mainly arc sources but also basement rocks; the latter is only accessory in the form of metamorphic lithoclasts and detrital zircons with ages around 1.0 Ga. Magmatic zircons in rhyolites reveal an eruptive age of ca. 478 Ma, concordant with Upper Arenigian to Lower Llanvirnian ages of brachiopods in overlying conglomerates. Bimodal volcanic associations, including low-K tholeiites, characterize the magmatic rocks, with evolved rhyolitic rocks showing pronounced arc-like geochemical signatures (negative anomalies in Ti, Nb and Ta). Some of the basaltic rocks are tholeiitic and display Ce/Y ratios below 1 and might point to a Moho depth of less than 10 km, hence a thin continental crust, coinciding with depletions in Zr and Hf concentrations. Associated volcaniclastic rocks display generally low Th/Sc (0.4-1), La/Sc (mostly <3.5), Zr/Sc (6-20) and high Ti/Zr (~10-60) ratios. The rock succession resembles the same geochemical and lithostratigraphical trends as retro-arc basin deposits further east in the Argentinean Puna of similar age. However, in the Cordón de Lila, the intercalated mafic rocks are less evolved, and the percentage of arc debris is higher, while the percentage of metamorphic lithoclasts and rounded quartz grains is much lower, indicating the existence of a thinned continental margin underpinning. We propose a transition in the Ordovician of the Central Andes from trench-ward fore-arc deposits to a dominantly intra-arc basin (Cordón de Lila), transitioning further eastwards towards a retro-arc basin (Puna) and foreland basin deposits of the Cordillera Oriental of northwestern Argentina. The Cordón de Lila intra-arc assemblage and associated fore-arc basin deposits therefore defined the western margin of Gondwana during the Ordovician. The absence of any terrane boundaries and sutures across strike is consistent with an evolving continental margin arc constructed on attenuated crust of the proto-Andean margin.

Zimmermann, Udo; Niemeyer, Hans; Meffre, Sebastien

2010-10-01

51

Piecing Together the Eastern Australian Margin in Gondwana: Origin of Metamorphic Rocks in the Woodlark Rift, SE Papua New Guinea  

NASA Astrophysics Data System (ADS)

Fragments of the former Australian continental margin in East Gondwana occur as submarine plateaus and rises in the southwestern Pacific. This study examined the isotopic composition and zircon age populations in the low and high grade metamorphic rocks along the southern margin of the active Woodlark Basin to evaluate whether these rocks were derived from continental crust, either as detritus or as a fragment since rifted off of northeastern Australia. In the Woodlark Basin of southeastern Papua New Guinea, metamorphic grade decreases eastward from HP/UHP in the D’Entrecasteaux Islands within the western part of the basin to subgreenschist facies in the Louisiade Archipelago, on the southern rifted margin. The ~45 islands comprising the Louisiade Archipelago are distributed over >160 km with some islands reaching 100’s of km 2 in size and elevations up to 850 m asl. The metapelitic Calvados Schist is the dominant rock unit in the Louisiade Archipelago, yet none of the islands are in proximity to a source of terrigeneous sediments that are the likely protoliths of the schist. The provenance and protoliths of the HP/UHP and amphibolite facies rocks in the western Woodlark Basin remain poorly constrained. There, the shear zone carapace of metamorphic core complexes in the D’Entrecasteaux Islands contain Late Mesozoic garnet amphibolites indicating prograde metamorphism was synchronous with previously documented arc-continent collision on mainland PNG. It is possible that these rocks were rifted away from Australia prior to being metamorphosed in the complex plate-boundary zone that developed in the southwest Pacific following the breakup of East Gondwana. We examined high and low grade metamorphic rocks with a wide range of bulk and trace element compositions. The samples have a range of isotopic compositions (?Hf -0.79 to +11.85 and ?Nd -3.39 to +6.24) but none of these are the highly unradiogenic values that would be expected of Precambrian continental crust. The Nd isotopic compositions of these rocks are similar to previously reported Nd values of Late Cretaceous aged magmatic rocks and volcaniclastic sediments comprising the Whitsunday Volcanic Province (WVP) in northeastern Australia. The WVP is a Late Cretaceous rift-related igneous province whose origin is likely related to the breakup of East Gondwana. Zircons from the metamorphic rocks in the Woodlark Basin also commonly have cores with Late Cretaceous U-Pb ages that coincide temporally with WVP volcanism. The similarities between the metamorphic rocks in the Woodlark Basin and the rocks in the WVP suggest that either: 1) the metamorphic rocks now exposed in the Woodlark Basin originated as part of the Late Cretaceous aged rift-related WVP, and were rifted away from Australia during the opening of the Coral Sea basin, or 2) that detritus from that province provided the protoliths for metamorphic rocks found in the Woodlark Basin or 3) volcanic activity associated with the breakup of east Gondwana extended into the region currently occupied by these islands, and that these rocks were never actually situated near present day Australia.

Zirakparvar, N. A.; Baldwin, S.; Fitzgerald, P. G.; Vervoort, J. D.

2010-12-01

52

The Cathaysian and Gondwana floras: their contribution to determining the boundary between eastern Gondwana and Laurasia  

NASA Astrophysics Data System (ADS)

Permian floras around the suggested boundary between eastern Gondwana and Laurasia are analysed to see if their distribution provides any supporting evidence for this placement. This boundary is supported by evidence based on recent palaeobotanical studies, especially new discoveries from W. New Guinea (Indonesia), W. Yunnan, the Qinghai-Xizang Plateau of China and Kashmir in the Himalayas, coupled with the rapid advances in geological researches in these areas. This boundary runs along the Bangongco-Dengqen suture of the Qinghai-Xizang plateau, turns abruptly southward near Qamdo in East Xizang across the Nujiang River to meet the Lancangjiang River, and then possibly extends through the Baoshan District of W. Yunnan to link up with the Pham Som and Bentong-Raub sutures of Thailand-Peninsular Malaysia from where it continues further southwards across East Sumatra to the Indian Ocean, then changes to the east-west direction, extending along the deep-sea trench south of Java and, subsequently, it turns northeastward running through the Banda Sea to link up with western New Guinea.

Xingxue, Li; Xiuyuan, Wu

53

Some observational aspects and modeling results of the Orissa super cyclone, October 1999  

Microsoft Academic Search

The super cyclone that crossed the Orissa coast near Paradeep port (20.3 N, 86.7 E) around 0600 UTC on 29 October 1999, caused enormous damage - death of 10,000 people and 400,000 cattle, property damage worth Ind. Rs. 10,000 crores ( about USD 2 billion), salinization of about 1.8 million hectares of agricultural land, destruction of paddy crop paddy crop

N. J. Rao; D. B. Rao

2001-01-01

54

A new Late Triasssic phytogeographical scenario in westernmost Gondwana.  

PubMed

Floral provincialism within the Southern Hemisphere during the Late Triassic (230?Ma) is characterized by the Ipswich and Onslow provinces, recognized originally in eastern Gondwana. However, new palynological assemblages from the Ischigualasto Formation, northwestern Argentina (231-225?Ma), change the phytogeographic interpretation for the Carnian-Norian in the westernmost Gondwana, which was previously considered part of the southern floral Ipswich province. Here we show the presence of diagnostic Euramerican species within assemblages dominated by Gondwanan taxa that allows us to refer the palynofloras to the Onslow province. Our new data extend the Onslow floral belt, previously recognized from the western edge of Tethys to Timor, to the western margin of South America. This has implications for palaeophytogeography, palaeoclimate reconstructions and the palaeoecology of a Triassic ecosystem, which has yielded significant vertebrate remains and is regarded important in the early evolution of groups such as the Dinosauria. PMID:23695683

Césari, Silvia N; Colombi, Carina E

2013-01-01

55

A new Late Triasssic phytogeographical scenario in westernmost Gondwana  

NASA Astrophysics Data System (ADS)

Floral provincialism within the Southern Hemisphere during the Late Triassic (230Ma) is characterized by the Ipswich and Onslow provinces, recognized originally in eastern Gondwana. However, new palynological assemblages from the Ischigualasto Formation, northwestern Argentina (231-225Ma), change the phytogeographic interpretation for the Carnian-Norian in the westernmost Gondwana, which was previously considered part of the southern floral Ipswich province. Here we show the presence of diagnostic Euramerican species within assemblages dominated by Gondwanan taxa that allows us to refer the palynofloras to the Onslow province. Our new data extend the Onslow floral belt, previously recognized from the western edge of Tethys to Timor, to the western margin of South America. This has implications for palaeophytogeography, palaeoclimate reconstructions and the palaeoecology of a Triassic ecosystem, which has yielded significant vertebrate remains and is regarded important in the early evolution of groups such as the Dinosauria.

Césari, Silvia N.; Colombi, Carina E.

2013-05-01

56

Taphonomic analysis in lacustrine environments: Two different contexts for Triassic lake paleofloras from Western Gondwana (Argentina)  

NASA Astrophysics Data System (ADS)

During the earliest Triassic several rift basins developed along the western margin of Gondwana associated with the pre-breakup of Pangea. They were filled by exclusively non-marine sediments including alluvial, fluvial, and lacustrine deposits. In the Ischigualasto-Villa Unión Basin, the lacustrine-deltaic succession is placed in the Los Rastros Formation and consists of several coarsening-upward cycles of black shale, siltstone, and sandstone. The paleontologic content of the succession includes abundant floral remains (related to the Dicroidium-type flora), invertebrates (conchostracans, insects), and vertebrates (fishes, a temnospondyl amphibian, ichnites). At the Cerro Puntudo area in the Cuyana Basin, the lacustrine succession forms the upper part of the Cerro Puntudo Formation and consists of limestone, stromatolitic limestone, mudstone, sandstone, and tuff. The paleontologic content includes scarce floral remains and rhizoliths; invertebrates are represented exclusively by traces (associated with ichnofacies of Skolithos and Scoyenia), and vertebrates by a fragment of the pelvic girdle of a basal arcosaur. The taphonomic analysis performed in the two Triassic lacustrine successions allows recognition of two different taphonomic histories for the plant remains. The Los Rastros lake preserved both autochthonous (originated in the littoral zone) and allochthonous (originated in the upstream fluvial system) elements. The offshore lacustrine area was dominated by autochthonous well-preserved elements and allochthonous plant debris and wood, which formed time-averaged accumulations. The delta deposits are characterized by allochthonous elements with varied preservational conditions, usually showing evidence of mechanical degradation and accumulation within a short time. Autochthonous and allochthonous material were preserved in the Los Rastros Lake by means of anoxic conditions in the offshore lacustrine area and high sedimentation rates in the delta. In contrast, the Cerro Puntudo Lake preserved only autochthonous elements (originated in the littoral zone), including rhizoliths and foliar material, which formed autochthonous and parautochthonous accumulations at the littoral zone in spite of aerobic conditions. This was the result of tuffaceous material that enhanced preservation. Thus, these very different lacustrine environmental contexts are showing different preservational modes. The fossil assemblages allowed the reconstruction of the original communities from this part of Gondwana. Thus, the Los Rastros lake margins were characterized by shrubs and small trees of Ginkgoales and Corystospermales, and herbaceous members of the Sphenophyta. The sphenophytes were also the dominant floral component along the river margins whereas the Corystospermales, Cycadales, Pteridophyta, and conifers formed the woodland upstream probably related to the floodplains of a trunk fluvial system. The littoral zone of the Cerro Puntudo Lake was dominated mainly by herbaceous sphenophytes and lycopsids. These fossil assemblages characterize the paleoflora associated with lacustrine systems. A fuller understanding of the processes that generate these assemblages is essential for comparisons with other continental paleobotanical records in the Middle Triassic of Gondwana (e.g., Australia, South Africa).

Mancuso, Adriana Cecilia

2009-12-01

57

Proterozoic Tectonic History of Borborema Province, NE Brazil: Implications For Assembly of West Gondwana  

NASA Astrophysics Data System (ADS)

The Borborema Province of NE Brazil comprises the west-central part of a wide Pan- African - Brasiliano continental collision belt that formed during ca. 600 Ma assembly of West Gondwana. Our studies over the past decade, in collaboration with many other workers, demonstrate a complex Proterozoic history that created or modified crustal domains at 2.1, 1.7, 1.0, 0.8, and 0.6 Ga. Although NE Brazil contains a few small Archean domains included within early Paleoproterozoic orogens, the first major event was formation of extensive continental crust about 2.35 to 2.1 Ga, before and during the so-called Transamazonian orogeny. We believe that this occurred in conjunction with formation of a larger Paleoproterozoic continent about 2.05 Ga that included present-day West African, Amazonian, Congo, and São Francisco cratons. Incipient extension within this continent occurred in Brazil about 1.8 to 1.7 Ga, resulting in intracratonic sedimentation and bimodal volcanism, but equivalent rocks are less well known in Africa. A successful breakup occurred before or about 1.1 Ga, resulting in separation of parts of this continent into two major stable masses containing (a) the Amazon-West African craton, and (b) the São Francisco-Congo (SF/C) craton. The break-up also created many smaller fragments between these two large masses, particularly in the east (present-day NE Brazil and Saharan Africa) and including the Ceará-Rio Grande do Norte (CE/RN) craton in NE Brazil. About 1.0 Ga a magmatic arc more than 700 km long (Cariris Velhos orogen) developed in NE Brazil, possibly as a result of convergence between the CE/RN and SF/C cratons; eastward extension of the 1.0 Ga Cariris Velhos orogen into West Africa is presently unknown. About 850 to 700 Ma several extensional basins developed in NE Brazil, with intraplate bimodal volcanism and clastic sedimentation; coeval basins may have formed in west-central Africa. From 700 to 600 Ma plate convergence among the CE/RN craton, SF/C craton, Amazon-West African craton, and several other microcontinents (e.g., Nigerian block) culminated in formation of West Gondwana. Accretion of pre-600 Ma juvenile oceanic arcs occurred elsewhere in Brazil and West Africa, but such terranes have not been found in NE Brazil. The continental collisions in NE Brazil began about 640 to 630 Ma, peaked about 610-590 Ma, and were followed by 580-570 Ma post-tectonic plutonism. Collisional tectonism, including transcurrent faulting associated with escape tectonics, continued through much of the Cambrian.

van Schmus, W. R.; Brito Neves, B. B.

58

Effect of the Mahanadi River on the Development of Storm Surge Along the Orissa Coast of India: A Numerical Study  

NASA Astrophysics Data System (ADS)

River-ocean coupled models are described for the evaluation of the interaction between river discharge and surge development along the Orissa coast of India. The models are used to study the effect of fresh water discharge from the Mahanadi River on the surge response along the Orissa coast due to the October 1999 super cyclone which led to severe flooding of the coastal and delta regions of Orissa. The so-called 1999 Paradip cyclone was one of the most severe cyclones; causing extensive damage to property and loss of lives. The present study emphasizes the impact of the Mahanadi River on overall surge development along the Orissa coast. Therefore, we have developed a location specific fine resolution model for the Orissa coast and coupled it with a one dimensional river model. The numerical experiments are carried out, both with and without inclusion of fresh water discharge from the river. The bathymetry for the model has been taken from the naval hydrographic charts extending from the south of Orissa to the south of west Bengal. A simple drying scheme has also been included in the model in order to avoid the exposure of land near the coast due to strong negative sea-surface elevations. The simulations with river-ocean coupled models show that the discharge of fresh water carried by the river may modify the surge height in the Bay, especially in the western Bay of Bengal where one of the largest river systems of the east coast of India, the Mahanadi River, joins with the Bay of Bengal. Another dynamic effect of this inlet is the potentially deep inland penetration of the surge originating in the Bay. The model results are in good agreement with the available observations/estimates.

Dube, S. K.; Sinha, P. C.; Rao, A. D.; Jain, Indu; Agnihotri, Neetu

2005-08-01

59

What stress in the lithosphere tells us about strength of Pennsylvanian dextral transcurrent fault systems within the Appalachian mountain chain during final closure of Laurentia and Gondwana  

NASA Astrophysics Data System (ADS)

In the Appalachian Basin, joints and coal cleat reflect a rectilinear stress field lasting in excess of 10 My with an along-strike dimension > 1500 km at approximately 300 Ma. This is an Appalachian-wide stress field (AWSF). Given the duration and dimension of the AWSF, it is reasonable to presume that this stress field within Laurentian crust arose from tractions at its Alleghanian boundary with Gondwana. The strength of this conjecture rests with trajectories of the AWSF pointing in the direction of the oblique convergence between African Gondwana and Laurentia. During this same 10 My, Laurentian fragments and peri-Gondwanan microcontinents were driven dextrally as much as 400 km (Valentino, et al., 1994; Bartholomew and Tollo, 2004). Consequently, several dextral transcurrent sutures within Avalonian and peri-Gondwanan terranes were caught within this Laurentian-Gondwana stress field with SH cross cutting the dextral fault systems at ~ 30°. If dextral transcurrent systems were strong, the friction angle on these faults would have been SH ~ 30°. Weaker faults would have caused SH trajectories to curve and cross cut the fault system at a higher angle, like the situation along the San Andreas (Hardebeck and Michal, 2004). It is noteworthy that no evidence of weak-fault curving of SH is seen along the 1500 km with the AWSF. Evidence, however circumstantial, suggests that transcurrent sutures at the edge of Laurentia were strong during assembly of Pangea.

Engelder, T.

2006-05-01

60

Title: Geophysical definition of PARANAPANEMA Proterozoic Block and its importance for the Rodinia to Gondwana evolutionary theories  

NASA Astrophysics Data System (ADS)

For the last decade, only three cratonic blocks (Amazonian, S. Francisco and Rio de LaPlata) were attributed to the South America portion for the Rodinia reconstitution. The probability of existing other blocks has been ignored. Taking into account a large gravity survey, the premise of a considerable Paleoproterozoic fragment as part of the Paraná basin basement is highly probable. After removing the gravity contribution of its sedimentary load, the gravity pattern of the basin basement framework discriminates the boundaries of a high density block (Paranapanema) from other structures, most of which outcrop beyond the limits of the basin itself. The gravity high, bounded by deep gradients is clearly isolated from the other structures, among which the buried segments of Goiás Arch, Ribeira and Brasilia Belts, and Rio de LaPlata Craton, are easily identified through their outcropping portion. The Goiás Arch gravity signature merges with the topographically defined Paraguay Arch. Important faults as Jacutinga and Lancinha-Cubatäo (NE) and Torres-Posadas lineament (NW) are clearly identified through the geophysical signature; these structures define contacts among blocks at East and South of Paranapanema. The geophysical analysis also shows that any liaison between this block and Rio de LaPlata (south), or Luis Alves / Curitiba (east) Proterozoic blocks is improbable. Deep borehole data provided the lithology, thickness and area distribution of each volcano and sedimentary layer, as well as a geochronology age determination for a number of basement samples. Through a back stripping geophysical analysis, based on borehole data, the maximum attenuation distribution was identified for the two main extensional tectonic events that formed the Paraná basin, for a time interval that lasted from the Silurian to the Triassic. Results, based on a thermo-mechanical model, indicate that for both events the maximum attenuation sites are sub-parallel to the Brasiliano faults (NE), while the lineaments Torres-Posadas and Tietê (NW), better denoted for the second event, are parallel to the Early Cretaceous Ponta Grossa Arch. From geological observations, the Apiaí Belt, a continental Atlantic margin to the East, the Goiás Arch, an active margin to the northwest, and the Socorro-Guaxupé Orogen, an active margin with arch formation to the northeast of Paranapanema, assign great importance to this block for describing the western Gondwana evolution and assembly. Therefore, Paranapanema should be taken into account among the lithosphere segments derived from Rodinia, and later from Western Gondwana, after undergoing a series of orogenic events. Samples from deep boreholes prove the existence of a Paleoproterozoic basement buried by volcano-sedimentary Paleo to Mesoproerozoic layers as also been observed for the Amazonian and the S. Francisco craton. Moreover, geological and geochronology studies of the Ribeira Belt infrastructure identify an increase of Mesoproterozoic rocks towards the border of Paranapanema. Shear faults of Late-Brasiliano age developed significant transitional depressions forming the precursor rifts filled with Silurian to Triassic sediments. As for Paranapanema, analogous blocks may exist under the Parnaiba basin and other structures that were activated during the Brasiliano Cycle to form Gondwana. In this light, we consider that a revision is required in order to amend the present theories on the evolutionary process from Rodinia to Gondwana.

Mantovani, M.; de Brito Neves, B.; Quintas, M.; Shukowsky, W.

2003-04-01

61

The break-up of Rodinia, birth of Gondwana, true polar wander and the snowball Earth  

Microsoft Academic Search

A major global plate reorganisation occurred between ?750 and ?550 Ma. Gondwana was assembled following the dispersal of Rodinia, a supercontinent centred on Laurentia in existence since ?1050 Ma. The reorganisation began when tectonic elements, later composing East Gondwana, rotated piecemeal away from the Pacific margin of Laurentia. These elements swept across the ancestral Pacific (Mozambique) Ocean that lay between

Paul F. Hoffman

1999-01-01

62

The Neoproterozoic assembly of Gondwana and its relationship to the Ediacaran–Cambrian radiation  

Microsoft Academic Search

The assembly of the Gondwana supercontinent during the waning stages of the Proterozoic provides a tectonic backdrop for the myriad biological, climatological, tectonic and geochemical changes leading up to, and including, the Cambrian radiation. A polyphase assembly of Gondwana during the East Africa, Brasiliano, Kuungan and Damaran orogenies resulted in an extensive mountain chain which delivered nutrients into a shifting

Joseph G. Meert; Bruce S. Lieberman

2008-01-01

63

Negotiating with Dharma Pinnu: towards a social history of smallpox in colonial Orissa.  

PubMed

This paper explores the social complexities associated with the history of smallpox in colonial Orissa in Eastern India. It focuses on tribal communities while taking into account their interactions with non-tribal communities and colonialism. This research grapples with the phenomenon of of the Hinduisation of tribes and the way this implies an acceptance as well as a rejection of the various aspects of non-tribal, Hindu society. Thus, I examine the specific elements of non-tribal groups inoculation, black magic, and subversive cults, demonstrating the close affinities some of these features have with tribal communities. PMID:12776728

Pati, Biswamoy

2002-01-01

64

Study of enzyme polymorphism and haemoglobin patterns amongst sixteen tribal populations of central India (Orissa, Madhya Pradesh, and Maharashtra)  

Microsoft Academic Search

Summary A survey was conducted to study the genetic differentiation among 16 tribal groups of Orissa, Madhya Pradesh, and Maharashtra belonging to different ethnic and linguistic affiliations. Sixteen hundred and fifteen blood samples from both sexes were tested for 5 red cell enzyme systems: ACP, ESD, PGD, GLO, LDH, and Hb pattern. Three hundred and nineteen male individuals were tested

Ketaki Das; Monami Roy; M. K. Das; P. N. Sahu; S. K. Bhattacharya; K. C. Malhotra; B. N. Mukherjee; H. Walter

1993-01-01

65

Influence of language and ancestry on genetic structure of contiguous populations: A microsatellite based study on populations of Orissa  

Microsoft Academic Search

BACKGROUND: We have examined genetic diversity at fifteen autosomal microsatellite loci in seven predominant populations of Orissa to decipher whether populations inhabiting the same geographic region can be differentiated on the basis of language or ancestry. The studied populations have diverse historical accounts of their origin, belong to two major ethnic groups and different linguistic families. Caucasoid caste populations are

Sanghamitra Sahoo; VK Kashyap

2005-01-01

66

Drop-Out in Schools in India: Minor Field Studies in Orissa 1990. Educational and Psychological Interactions. No. 112.  

ERIC Educational Resources Information Center

This document consists of a report on the Minor Field Studies (MFS) program of the Swedish International Development Authority (SIDA) and contains two MFS papers by teacher trainees at the Malmo School of Education in Sweden. The papers presented are "Drop-outs in Orissa," by Elisabeth Rosen, and "Education in India: A Study of Drop-Out Children…

Ekstrand, Gudrun, Ed.

67

Effect of mechanical activation on the kinetics of sulfuric acid leaching of beach sand ilmenite from Orissa, India  

Microsoft Academic Search

The effect of mechanical activation on the phase constitution, particle size and distribution, surface area, unit cell parameters, crystallite size and strain of a beach sand ilmenite concentrate from Chatrapur, Orissa, India and their effect on the kinetics of sulfuric acid leaching have been investigated. It was observed that mechanical activation significantly enhances the dissolution of both iron and titanium

C. Sasikumar; D. S. Rao; S. Srikanth; B. Ravikumar; N. K. Mukhopadhyay; S. P. Mehrotra

2004-01-01

68

An unusual diagenetic structure in the Precambrian banded iron formation (BIF) of Orissa, India, and its interpretation  

Microsoft Academic Search

An unusual type of late diagenetic tectonic and compaction structure simulating boudinage phenomena is described and documented from the Precambrian banded iron formation (BIF) of Orissa, India. The structure was seemingly initiated by the development of tension cracks in the hydroplastic stage followed by rotation and imbrication of the segments of the iron (magnetite) bands. The tension cracks were subsequently

K. L. Chakraborty; T. Majumder

1992-01-01

69

A Sickle Cell Disease Carrier Family with a Pair of Dizygotic Twins from Kalahandi District of Western Orissa, India  

Microsoft Academic Search

The sickle cell disease is a genetically inherited commonly encountered hematological disorder that causes high degree of morbidity, mortality and fetal wastage. The suspected cases of hemoglobinopathies suffering from anemia are routinely referred from different peripheral Primary Health Centres and Hospitals in the state of Orissa (India) to our Centre for detailed investigations and genetic\\/marriage counselling. Of these, a scheduled

R. S. Balgir

70

Delineation of fluoride contaminated groundwater around a hot spring in Nayagarh, Orissa, India using geochemical and resistivity studies  

Microsoft Academic Search

Geochemical and geoelectrical investigations were carried out around a hot spring near village Singhpur, Nayagarh District of Orissa to delineate the extent of fluoride contamination in groundwater. Fluoride concentration is observed to be very high in both hot spring and groundwater of Singhpur village compared with surrounding ones. Vertical electrical sounding (VES) studies in the area reveal the presence of

N. Kundu; M. Panigrahi; S. Sharma; S. Tripathy

2002-01-01

71

Genetic Structure and Wolbachia Genotyping in Naturally Occurring Populations of Aedes albopictus across Contiguous Landscapes of Orissa, India  

PubMed Central

Background Aedes albopictus has recently been implicated as a major vector in the emergence of dengue and chikungunya in several parts of India, like Orissa, which is gradually gaining endemicity for arboviral diseases. Ae. albopictus is further known to be naturally infected with Wolbachia (maternally inherited bacterium), which causes cytoplasmic incompatibility (CI) in mosquitoes leading to sperm-egg incompatibility inducing the death of embryo. Knowledge of genetic diversity of Ae. albopictus, along with revealing the type of Wolbachia infection in Ae. albopictus is important to explore the genetic and biological characteristics of Ae. albopictus, prior to exploring the uses of CI-based vector control strategies. In this study, we assessed the population genetic structure and the pattern of Wolbachia infection in Ae. albopictus mosquitoes of Orissa. Methods and Results Ae. albopictus mosquitoes were collected from 15 districts representing the four physiographical regions of Orissa from 2010–2012, analyzed for genetic variability at seven microsatellite loci and genotyped for Wolbachia strain detection using wsp gene primers. Most microsatellite markers were successfully amplified and were polymorphic, showing moderate genetic structure among all geographic populations (FST?=?0.088). Genetic diversity was high (FST?=?0.168) in Coastal Plains populations when compared with other populations, which was also evident from cluster analyses that showed most Coastal Plains populations consisted of a separate genetic cluster. Genotyping analyses revealed that Wolbachia-infected Ae. albopictus field populations of Orissa were mostly superinfected with wAlbA and wAlbB strains. Wolbachia superinfection was more pronounced in the Coastal Plain populations. Conclusion High genetic structure and Wolbachia superinfection, observed in the Coastal Plain populations of Orissa suggested it to be genetically and biologically more unique than other populations, and hence could influence their vectorial attributes. Such high genetic diversity observed among Coastal Plains populations could be attributed to multiple introductions of Ae. albopictus in this region.

Das, Biswadeep; Satapathy, Truptimayee; Kar, Santanu K.; Hazra, Rupenangshu K.

2014-01-01

72

Plate motions, Gondwana dinosaurs, Noah's arks, beached Viking funeral ships, ghost ships, and landspans.  

PubMed

Gondwana landmasses have served as large-scale biogeographic Noah's Arks and Beached Viking Funeral Ships, as defined by McKenna. The latitudinal trajectories of selected Gondwana dinosaur localities were traced through time in order to evaluate their movement through climate zones relative to those in which they originally formed. The dispersal of fauna during the breakup of Gondwana may have been facilitated by the presence of offshelf islands forming landspans (sensu Iturralde-Vinent and MacPhee) in the Equatorial Atlantic Gateway and elsewhere. PMID:21437374

Jacobs, Louis L; Strganac, Christopher; Scotese, Christopher

2011-03-01

73

Gondwana breakup and plate kinematics: Business as usual  

NASA Astrophysics Data System (ADS)

A tectonic model of the Weddell Sea is built by composing a simple circuit with optimized rotations describing the growth of the South Atlantic and SW Indian oceans. The model independently and accurately reproduces the consensus elements of the Weddell Sea's spreading record and continental margins, and offers solutions to remaining controversies there. At their present resolutions, plate kinematic data from the South Atlantic and SW Indian oceans and Weddell Sea rule against the proposed, but controversial, independent movements of small plates during Gondwana breakup that have been attributed to the presence or impact of a mantle plume. Hence, although supercontinent breakup here was accompanied by extraordinary excess volcanism, there is no indication from plate kinematics that the causes of that volcanism provided a unique driving mechanism for it.

Eagles, Graeme; Vaughan, Alan P. M.

2009-05-01

74

Bouguer anomaly of the Godavari basin, India and magnetic characteristics of rocks along its coastal margin and continental shelf  

Microsoft Academic Search

The Bouguer anomaly map of the Godavari basin has delineated several transverse and median ridges that have divided this basin into several sub-basins. Modelling of a gravity profile in the central part of the basin suggests 5.0km of Gondwana sediments and high density rocks along the shoulders which may represent upthrusted lower crustal rocks related to the Eastern Ghats orogeny.

D. Ch Venkata Raju; R. S Rajesh; D. C Mishra

2003-01-01

75

Bouguer anomaly of the Godavari basin, India and magnetic characteristics of rocks along its coastal margin and continental shelf  

Microsoft Academic Search

The Bouguer anomaly map of the Godavari basin has delineated several transverse and median ridges that have divided this basin into several sub-basins. Modelling of a gravity profile in the central part of the basin suggests 5.0km of Gondwana sediments and high density rocks along the shoulders which may represent upthrusted lower crustal rocks related to the Eastern Ghats orogeny.

D. Ch Venkata Raju; R. S Rajesh; D. C Mishra

2002-01-01

76

An Outbreak of Cholera Associated with an Unprotected Well in Parbatia, Orissa, Eastern India  

PubMed Central

In November 2003, an outbreak (41 cases; attack rate–4.3%; no deaths) of severe diarrhoea was reported from a village in Orissa, eastern India. Thirteen of these cases were hospitalized. A matched case-control study was conducted to identify the possible exposure variables. Since all wells were heavily chlorinated immediately after the outbreak, water samples were not tested. The cases were managed symptomatically. Descriptive epidemiology suggested clustering of cases around one public well. Vibrio cholerae El Tor O1, serotype Ogawa was isolated from four of six rectal swabs. The water from the public well was associated with the outbreak (matched odds ratio: 12; 95% confidence interval 1.2–44.1). On the basis of these conclusions, access to the well was barred immediately, and it was protected. This investigation highlighted the broader use of field epidemiology methods to implement public-health actions guided by epidemiologic data to control a cholera epidemic.

Das, Amitav; Hutin, Yvan; Pal, B.B.; Chhotray, G.P.; Kar, S.K.; Gupte, M.D.

2009-01-01

77

Mosquitoes of the mangrove forests of India: Part 1--Bhitarkanika, Orissa.  

PubMed

In this first paper of a series on mosquitoes of the mangrove forests of India, details of mosquito species recorded in Bhitarkanika, Orissa, are presented. Forty-three species of mosquitoes belonging to 21 subgenera and 13 genera, Aedes, Anopheles, Armigeres, Coquillettidia, Culex, Ficalbia, Heizmannia, Lutzia, Mansonia, Ochlerotatus, Toxorhynchites, Uranotaenia, and Verrallina, were recorded. Predominant larval habitat was the tree holes, from which 15 species were taken. Adults were mostly found resting in crab holes, tree holes, and hoof prints in the forest area and on walls in the guesthouse area. About 14 species were caught in light traps, while 19 species landed on humans for feeding. Ae. franciscoi and Oc. feegradei are 2 new country records for India. Ae. cancricomes and Cx. perplexus, known only from Andaman Islands of India, are new records for mainland India. PMID:16033113

Rajavel, A R; Natarajan, R; Vaidyanathan, K

2005-06-01

78

Improving maternal health through social accountability: a case study from Orissa, India.  

PubMed

As maternal health specialists accelerate efforts towards Millennium Development Goal Five, attention is focusing on how to best improve service accountability to target communities as a strategy for more effective policy implementation. We present a case study of efforts to improve accountability in Orissa, India, focusing on the role of local women, intermediary groups, health providers and elected politicians. We highlight three drivers of success: (1) the generation of demand for rights and better services, (2) the leverage of intermediaries to legitimise the demands of poor and marginalised women and (3) the sensitisation of leaders and health providers to women's needs. We use the concepts of critical consciousness, social capital and 'receptive social spaces' to outline a social-psychological account of the pathways between accountability and service effectiveness. PMID:23230827

Papp, Susan A; Gogoi, Aparajita; Campbell, Catherine

2013-01-01

79

Dust accumulation and leaf pigment content in vegetation near the national highway at Sambalpur, Orissa, India.  

PubMed

An investigation on the seasonal variation in dust accumulation on leaves and leaf pigment content of six plant species of mixed habits was carried out at the side of the National Highway (NH 6) at Sambalpur, Orissa, India. The plants selected for study were Pongamia pinnata, Tabernaemontana divaricata, Ipomea carnea, Ficus relogiosa, Ficus benghalensis, and Quisqualis indica. The observed trend of dust accumulation was in the order T. divaricata>I. carnea>P. pinnata>F. religiosa>F. benghalensis>Q. indica. One-way analysis of variance showed significant difference in dust accumulation among plant species (F1 = 4.674, P < 0.01) and between seasons (F2 = 9.240, P < 0.01). It was seen that dust load increases with increasing number of vehicles using the highway (major emission source). The result shows significant correlation (negative) between dust load and pigment content in summer and rainy season. PMID:15546639

Prusty, B A K; Mishra, P C; Azeez, P A

2005-02-01

80

Oculosporidiosis in a tertiary care hospital of western Orissa, India: a case series.  

PubMed

The authors present a case series of 54 subjects of Rhinosporidium. They were reported in two years at a tertiary care hospital of Western Orissa. The clinically diagnosed cases by ophthalmologists were confirmed by histopathological samples following surgery. In our series, we noted Rhinosporidium seeberi organisms as the main causative agent. Males were affected three times more than females. Children less than 10 years of age comprised more than 50% of our series. In 91% of cases, the conjunctiva was the site of this infection. Total excision of fungal mass was carried out in all cases and two cases had recurrence between 9 and 12 months following intervention. Although this is an endemic area for such infestation, unilateral manifestation observed in all cases is interesting to note. Low recurrence rate in limited follow-up period could be due to early detection and standard management. PMID:17595481

Chowdhury, Ravindra K; Behera, Sharmistha; Bhuyan, Debendranath; Das, Gunasagar

2007-01-01

81

'First we go to the small doctor': First contact for curative health care sought by rural communities in Andhra Pradesh & Orissa, India  

PubMed Central

Background & objectives: Against the backdrop of insufficient public supply of primary care and reports of informal providers, the present study sought to collect descriptive evidence on 1st contact curative health care seeking choices among rural communities in two States of India - Andhra Pradesh (AP) and Orissa. Methods: The cross-sectional study design combined a Household Survey (1,810 households in AP; 5,342 in Orissa), 48 Focus Group Discussions (19 in AP; 29 in Orissa), and 61 Key Informant Interviews with healthcare providers (22 in AP; 39 in Orissa). Results: In AP, 69.5 per cent of respondents accessed non-degree allopathic practitioners (NDAPs) practicing in or near their village; in Orissa, 40.2 per cent chose first curative contact with NDAPs and 36.2 per cent with traditional healers. In AP, all NDAPs were private practitioners, in Orissa some pharmacists and nurses employed in health facilities, also practiced privately. Respondents explained their choice by proximity and providers’ readiness to make house-calls when needed. Less than a quarter of respondents chose qualified doctors as their first point of call: mostly private practitioners in AP, and public practitioners in Orissa. Amongst those who chose a qualified practitioner, the most frequent reason was doctors’ quality rather than proximity. Interpretation & conclusions: The results of this study show that most rural persons seek first level of curative healthcare close to home, and pay for a composite convenient service of consulting-cum-dispensing of medicines. NDAPs fill a huge demand for primary curative care which the public system does not satisfy, and are the de facto first level access in most cases.

Gautham, Meenakshi; Binnendijk, Erika; Koren, Ruth; Dror, David M.

2011-01-01

82

An unusual diagenetic structure in the Precambrian banded iron formation (BIF) of Orissa, India, and its interpretation  

NASA Astrophysics Data System (ADS)

An unusual type of late diagenetic tectonic and compaction structure simulating boudinage phenomena is described and documented from the Precambrian banded iron formation (BIF) of Orissa, India. The structure was seemingly initiated by the development of tension cracks in the hydroplastic stage followed by rotation and imbrication of the segments of the iron (magnetite) bands. The tension cracks were subsequently filled up by finely crystalline diagenetic quartz veins.

Chakraborty, K. L.; Majumder, T.

1992-01-01

83

Socio-clinical profile of rabis cases in anti-rabies clinic, M. K. C. G. Medical College, Orissa.  

PubMed

A hospital based study was conducted in the anti-rabies clinic of a medical college of Orissa during April 1988 to May 2002. Of 24 clinically diagnosed and reported rabies cases during the four years study period, 62.5% were children below 15 years of age, 67% were males, 87.5% were victims of stray dogs, 79% had not taken any anti-rabies treatment though all had undergone treatment by traditional systems of medicine. PMID:16479908

Satapathy, D M; Sahu, T; Behera, T R; Patnaik, J K; Malini, D S

2005-01-01

84

Bio-concentration of chromium—an in situ phytoremediation study at South Kaliapani chromite mining area of Orissa, India  

Microsoft Academic Search

Mine waste water at South Kaliapani usually contains toxic levels of hexavalent Cr(VI). The present in situ study was conducted at South Kaliapani chromite mine area in Orissa state, India, to assess the phytoremediation ability\\u000a of three plants, namely, rice (Oryza sativa L.), paragrass (Brachiaria mutica), and an aquatic weed (Eichhornia crassipes), in attenuating Cr(VI) from mine waste water and

Monalisa Mohanty; Mausumi M. Pattnaik; Aruna K. Mishra; Hemanta K. Patra

85

Sergentomyia (Parrotomyia) jerighatiansis, a new species of sand fly (Diptera: Psychodidae: Phlebotominae) from Kandhamal district, Orissa, India.  

PubMed

Sergentomyia (Parrotomyia) jerighatiansis a new species of sand fly (Diptera: Psychodidae: Phlebotominae) from the villages of Kandhamal district, Orissa, located on the east coast of India is described. Descriptive morphology, character measurements, and illustrations of males and females are provided and its taxonomic position within the genus is also defined. Voucher specimens of the new species have been deposited at the museum, Vector Control Research Centre (Indian Council of Medical Research), Puducherry, India and Zoological Survey of India, India. PMID:24076324

Srinivasan, R; Jambulingam, P

2013-12-01

86

Cultivation of Gracilaria verrucosa (Huds) Papenfuss in Chilika Lake for livelihood generation in coastal areas of Orissa State  

Microsoft Academic Search

The agarophyte red alga Gracilaria verrucosa occurs widely in Chilika Lake, one of the RAMSAR wetland sites in India. The lake is situated in the extreme southeast corner\\u000a of Orissa between latitudes 19°28? and 19°54? N and longitudes 85°06? and 85°35? E. The natural biomass production is not\\u000a sufficient for the agar industry, and the only alternative is to maximize

Sailabala Padhi; Prasanna K. Swain; Sasmita K. Behura; Sivaram Baidya; Santosh K. Behera; Manas R. Panigrahy

2011-01-01

87

The petrogenesis of Mesozoic Gondwana low-Ti flood basalts  

NASA Astrophysics Data System (ADS)

New major, trace element and isotopic data for Jurassic basalts from SE Australia indicate that they are strikingly similar to the Jurassic tholeiitic rocks of Tasmania and the Transantarctic Mountains. These rocks are all characterised by low TiO 2, P 2O 5, Na 2O, Fe 2O 3, Ti/Zr, Ti/Y and ? Nd, and high SiO 2, Rb/Ba, Rb/Sr, 87Sr/ 86Sr and 207Pb/ 204Pb, relative to oceanic basalts. They therefore comprise a major province, termed the Ferrar magmatic province, which extended for 3000-4000 km across the Gondwana supercontinent. A review of the other Mesozoic low-Ti CFB's suggests that the Ferrar rocks are an extreme example of these magma types. It is striking that both the major and trace element compositions are different from oceanic basalts, which suggests that these features are linked, and it is argued that they were derived from distinctive source regions in the sub-continental mantle. Such source regions were variably depleted in major and minor elements, and then relatively enriched in highly incompatible elements and Sr and Pb isotopes, which is best explained by the introduction of a small amount of subducted sediment. The tectonic setting of the Ferrar magmatism is poorly constrained, but at present there is no clear geochemical evidence for the involvement of asthenospheric plume material in the petrogenesis of these low-Ti CFB's.

Hergt, J. M.; Peate, D. W.; Hawkesworth, C. J.

1991-07-01

88

Resultados Do Projeto Gondwana: Um Exemplo de Correlacao Geologica Intercontinental Utilizando Imagens Landsat (Results of the Gondwana Project: An Example of Intercontinental Geologic Correlation Utilizing Landsat Imagery).  

National Technical Information Service (NTIS)

The main results in INPE's GONDWANA Project are presented. The project focus was on a geological comparison between Northeast Brazil and West Africa using LANDSAT and RADAR imageries. It is shown that Northeast Brazil and West Africa in the Late Proterozo...

R. Pereiradacunha, P. R. Martini, E. Crepani

1989-01-01

89

Gondwana Tales: an inquiry approach to plate tectonics  

NASA Astrophysics Data System (ADS)

Plate tectonics and its effects on the constitution of seas and continents are key models in science education. Fossil evidences are usually taught in demostrative key when Wegener's discoverings about Pangea are introduced. In order to introduce inquiry-based science education (IBSE) approaches to this topic, we propose "Gondwana Tales", an activity where students are asked to use fossil data to reconstruct the geologic history of an imaginary planet. Grouped in independent teams, each team is furnished with stratigraphic columns from several sites containing faunistic successions of real organisms existing in the past in Earth. Students are told to reconstruct a model of the evolution of the continents, by making calculations of relative ages of the fossils, and relating each fossil to a geologic era. The different teams have incomplete and complementary information. After a first step where they have to propose a partial model based on incomplete data, each team receives a "visitor scientist" from another team, this implying an informal scientific communication event. This process is performed several times, engaging a discussion in each team and getting a final consensus model created by the whole class. Correct answer is not given to the students, even at the end of the activity, to keep the activity under the parameters of real scientific experience, where there is not a "correct answer" to compare. Instead of this, and following the IBSE standards, a reflection on the process is proposed to students. The lack of complete information and the need to collaborate are part of classroom dynamics focused to the understanding of the process of creation of the scientific knowledge. This activity is part of the C3 Project on Creation of Scientific Knowledge that is being applied in the school.

Domènech Casal, Jordi

2014-05-01

90

A fatal waterborne outbreak of pesticide poisoning caused by damaged pipelines, sindhikela, bolangir, orissa, India, 2008.  

PubMed

Introduction. We investigated a cluster of pesticide poisoning in Orissa. Methods. We searched the village for cases of vomiting and sweating on 2 February 2008. We described the outbreak by time, place, and person. We compared cases with controls. Results. We identified 65 cases (two deaths; attack rate: 12 per 1000; case fatality: 3%). The epidemic curve suggested a point source outbreak, and cases clustered close to a roadside eatery. Consumption of water from a specific source (odds ratio [OR]: 35, confidence interval [CI]: 13-93) and eating in the eatery (OR: 2.3, CI: 1.1-4.7) was associated with illness. On 31 January 2008, villagers had used pesticides to kill street dogs and had discarded leftovers in the drains. Damaged pipelines located beneath and supplying water may have aspirated the pesticide during the nocturnal negative pressure phase and rinsed it off the next morning in the water supply. Conclusions. Innapropriate use of pesticides contaminated the water supply and caused this outbreak. Education programs and regulations need to be combined to ensure a safer use of pesticides in India. PMID:20130775

Panda, Manjubala; Hutin, Yvan J; Ramachandran, Vidya; Murhekar, Manoj

2009-01-01

91

Preliminary indoor thoron measurements in high radiation background area of southeastern coastal Orissa, India.  

PubMed

This paper presents the preliminary results of radon and thoron measurements in the houses of Chhatrapur area of southeastern coast of Orissa, India. This area is one of the high radiation background radiation areas in India, which consists of monazite sand as the source of thoron. Both active and passive methods were employed for the measurements. Radon and thoron concentrations were measured in the houses of Chhatrapur area using twin cup radon dosemeters, RAD7 and radon-thoron discriminative detector (Raduet). Thoron progeny concentration was also measured in the houses using deposition rate measurements. Radon and thoron concentrations in the houses of study area were found to vary from 8 to 47 Bq m(-3) and the below detection level to 77 Bq m(-3), respectively. While thoron progeny concentration in these houses ranges between 0.17 and 4.24 Bq m(-3), preliminary investigation shows that the thoron concentration is higher than radon concentration in the houses of the study area. The thoron progeny concentration was found to be comparatively higher, which forms a base for further study in the area. The comparison between the results of various techniques is presented in this paper. PMID:20833682

Ramola, R C; Prasad, G; Gusain, G S; Rautela, B S; Choubey, V M; Sagar, D Vidya; Tokonami, S; Sorimachi, A; Sahoo, S K; Janik, M; Ishikawa, T

2010-10-01

92

Man in Biosphere Reserve: a Remote Sensing Study in Similipal, Orissa  

NASA Astrophysics Data System (ADS)

The Similipal is a densely forested hill-range in the heart of Mayurbhanj district,Orissa, lying close to the eastern-most end of the Easternghats. Similipal Biosphere Reserve is located in the Mahanadian Biogeographical Region and within the Biotic Province, Chhotanagpur Plateau.There are 4 villages in the core and 61 villages in the buffer area of the biosphere reserve .Agriculture is not well developed and employment opportunities are very poor , most of the people derive their income from collection of NTFP and sale of firewood and timber. A collaborative work is carried out by Regional Remote Sensing Centre(East) and Anthropological survey of India,Kolkata to study the impact of those four villages in the core area of SBR on the conservation of natural resources over the decades.Change in vegetation density as measured by NDVI over the decades is analysed to study the impact of these villages on the core area of Similipal Biosphere Reserve.

Biswal, A.; Mukherjee, S.; Jeyaram, A.; Krishna Murthy, Y. V. N.

2011-08-01

93

Petrographic composition, sedimentary structures and palaeocurrent analysis in Northern Gondwana: The Lower Permian Warchha Sandstone of the Salt Range, Pakistan  

NASA Astrophysics Data System (ADS)

The Warchha Sandstone is a Lower Permian fluvial succession present in both outcrop and subsurface throughout the Salt Range and the Potwar Basin of Pakistan that originally accumulated in a palaeogeographic setting adjacent to the northern margin of Gondwana. Sandstone beds are feldspatho-quartzose, including dominantly monocrystalline quartz, more K-feldspar than plagioclase, and mainly plutonic and low-grade metamorphic rock fragments. Twenty-eight fining-upward cycles, composed of conglomerate, sandstone, siltstone and claystone are identified. A varied range of sedimentary structures is recognised, including different forms of cross-bedding, ripple marks, flute casts, load casts, desiccation cracks, rain prints, cone-in-cone structures, and a variety of types of concretions and bioturbation. The occurrence and abundance of these structures varies in a systematic manner throughout the vertical thickness of the succession. Sedimentary structures, palaeocurrent data and lithofacies arrangement indicate deposition in a high-sinuosity meandering river system. Detailed palaeocurrent analysis reveals a broad unimodal palaeoflow within each cycle with dominant flow direction having been towards the north-northwest, but with significant changes in local bedform migration direction between each cycle. The northward flowing river transported sediments from the Aravalli and Malani Ranges that lay to the south to the Salt Range, northwards to the Tethyan proto-ocean in the north.

Ghazi, Shahid; Mountney, Nigel P.

2012-10-01

94

Refining Gondwana and Pangea palaeogeography: estimates of Phanerozoic non-dipole (octupole) fields  

Microsoft Academic Search

Reliable Phanerozoic paleopoles have been selected from the stable parts of the Gondwana continents and, upon appropriate reconstruction, have been combined in an apparent polar wander (APW) path, which can be compared with a previously compiled path for Laurussia. This comparison once again confirms that Pangea-A reconstructions for Late Palaeozoic and early Mesozoic times cannot be reconciled with the available

Trond H. Torsvik; Rob van der Voo

2002-01-01

95

Sedimentary history of the Tethyan basin in the Tibetan Himalayas  

Microsoft Academic Search

After an epicontinental phase, the sedimentary rocks in the Tibetan Himalayas document a complete Wilson cycle of the Neo-Tethyan (Tethys Ill) evolution between the Gondwana supercontinent and its northward drifting margin (Lhasa block) from the Late Permian to the Eocene.During the Triassic rift stage, the basin was filled with a huge, clastic-dominated sediment wedge with up to > 5 000

Guanghua Liu; G. Einsele

1994-01-01

96

Geochemistry of Papandayan and Cikuray volcanoes: mapping the extent of Gondwana continental fragment beneath Java, Indonesia  

NASA Astrophysics Data System (ADS)

In recent years, the presence of Gondwana continental fragment beneath southern Java has become a much debated topic. Several studies have indicated the presence of micro continents beneath southern West and East Java, uncertainty still remains as to whether the two fragments are linked forming part of a larger micro-continent. Since there is missing link between micro continent beneath West and East Java, detailed petrological and geochemical of contiguous Papandayan and Cikuray volcanoes were employed to elucidate the problem and give better understanding of tectonic development in Java. The eruptive product of Papandayan volcano comprises medium-K series of basaltic andesite (Early Stage), andesite (Middle Stage) and dacite (Late Stage) with high 87Sr/86Sr (0.705243-0.705907) and low 143Nd/144Nd (0.512504-0.512650) ratios. In contrast to the Papandayan volcano, the Cikuray volcanic rocks are low-K series, with low 87Sr/86Sr (0.704172-0.704257) and high 143Nd/144Nd (0.512823-0.512858) ratios. The high 87Sr/86Sr and low 143Nd/144Nd isotope ratios of Papandayan can be explained by a mixing model of low-K Cikuray type magma with Pre-Cambrian and Silurian to Devonian Australian granites as Gondwana continental fragment. Therefore, we interpret that the low-K Cikuray type magma rising through the upper crust comprising Gondwana continental fragment to produce the medium-K Papandayan magma. We suggested that this diversity coincided with the change in the basement type of West Java where the northern part is underlain by part of Sunda Land and southern part by a fragment of Gondwana continent fragment. Therefore, the suture zone should be laid between both volcanoes and Papandayan volcano probably is the only of Quaternary volcanoes which is underlain by Gondwana continental fragment. If that so, the extension of East Java continental fragment can be continued to the West Java.

Abdurrachman, M.; Masatsugu, Y.

2011-12-01

97

Incidence of bacterial enteropathogens among hospitalized diarrhea patients from Orissa, India.  

PubMed

Bacteriological analysis of 1,551 stool/rectal swabs from all age groups of diarrhea patients of different hospitals of Orissa from January 2004 to December 2006 was carried out using standard procedures. Among all enteropathogens isolated in 886 culture-positive samples, Escherichia coli constituted 75.5%, including 13.2% pathogenic E. coli; Vibrio cholerae O1 constituted 17.3%; V. cholerae O139, 1%; Shigella spp., 4.5% (Shigella flexneri type 6, 2.9%, S. dysenteriae type I, 0.7%, S. sonnei, 0.6%, and S. boydii, 0.3%); Salmonella spp., 0.7%; and Aeromonas spp., only 2.0%. The isolation of bacterial enteropathogens was highest during July, 2005, followed by September, 2006. The prevalence of shigellosis in this region was relatively low. Cholera cases were more frequent during the rainy seasons. The dominance of V. cholerae O1 Inaba over Ogawa serotypes was observed in 2005, whereas this trend was reversed in 2006. The resistance profile of V. cholerae O1 was co-trimoxazole (Co), furazolidone (Fr), and nalidixic acid (Na); for Aeromonas spp., it was ampicillin (A), Fr, ciprofloxacin (Cf), Na, norfloxacin (Nx), and Co. Pathogenic E. coli strains were resistant to A, Fr, Co, streptomycin (S), Cf, Na, Nx, and neomycin (N); Shigella spp. were resistant to Fr, Na, Co, and S; and Salmonella spp. were resistant to A and Fr. Active surveillance should be continued among diarrhea patients to look for different enteropathogens and to define the shifting antibiogram patterns in this region. PMID:18806340

Samal, Surya Kanta; Khuntia, Hemant Kumar; Nanda, Prafulla Kumar; Satapathy, Chandra Sekhar; Nayak, Sudeep Ranjan; Sarangi, Ashok Kumar; Sahoo, Nilamani; Pattnaik, Sanjay Kumar; Chhotray, Guru Prasad; Pal, Bhibhuti Bhusan

2008-09-01

98

Emissions Of Greenhouse Gas And Biochemical Properties Of Soil From Bhitarkanika Mangrove,Orissa  

NASA Astrophysics Data System (ADS)

Coastal areas have been recognized as one of the major contributors to the atmospheric flux of greenhouse gases at local, regional and global scales. Mangrove forests are constantly affected from the anthropogenic activities mainly intensive cultivation. In a study in the tropical mangrove areas of Bhitarkanika sancturary, NE Orissa and adjoining paddy fields, a comparative estimation of emission rates of two climatologically important greenhouse gases, viz. CH4 and N2O were measured for monsoon and post-monsoon seasons. Methane emission was higher in paddy fields and varied from 2.22 to 6.0 mg.m-2.h-1 as compared to flux rates of 0.08 to 3.23 mg.m-2.h-1 from mangrove areas for the monsoon season. For the post-monsoon season, CH4 flux was higher although it maintained almost similar trend for the two ecosystems. In contrast, N2O emission flux was higher for mangrove sediments than the rice fields. Readily mineralizable carbon (RMC) and microbial biomass-C (MBC) contents were higher in the paddy soils than the native mangrove sediments so also dehydrogenase and FDA hydrolase activities, suggesting higher microbial activity in the paddy soils. Overall CH4 and N2O yields varied depending upon both the magnitude and chemical nature of the sediment C and N sources and microbial activity that were in turn affected by the salinity. Results indicate that paddy fields (anthropogenic intrusion) are bigger emitters of greenhouse gases than the mangrove sediments and together constitute a significant contributor to the global GHG budget.

Chauhan, R.; Adhya, T. K.; Ramanathan, A.

2008-12-01

99

Petrology, geochemistry and geochronology of the Chilka Lake igneous complex, Orissa state, India  

NASA Astrophysics Data System (ADS)

The Chilka Lake igneous complex of Orissa, the largest known anortosite massif of the Indian Shield, occurs in a catazonal environment of high-grade metamorphics of the Eastern Ghats Precambrian Orogenic Province. The syntectonic massif consists of the anorthositic Balugaon dome, leuconoritic Rambha lobe and quartz-mangeritic Kallikota cover. A completely gradational suite comprising anorthosite-leuconorite-norite-minor jotunite (the anorthositic suite) constitutes most of the complex. The subordinate of suite of acid rocks spatially associated with this is of a broad quartz-mangeritic lithology with minor granitic rocks (the acidic suite). Geochemical evolution of the complex in the sequence anorthosite-leuconorite-norite-jotunite-acidic rocks shows moderate iron enrichment in the noritic-jotunitic stage and is marked by an overall decrease in Al 2O 3, CaO, MgO, Ni/Co, Sr/Ba, K/Rb and increase in SiO 2, K 2O, V/Ni, K/Ba and Rb/Sr. Such progressive variation in geochemical parameters appears (i) essentially gradual and frequently overlapping in rock members of the intergradational anorthositic suite and (ii) rather abrupt across transition zones between the anorthositic suite and the acidic suite due to near absence of intervening intermediate lithologies. Rb?Sr whole rock isochron studies indicate that the complex was emplaced ca. 1400 Ma ago. The initial 87Sr/ 68Sr (0.70661) implies limited hybridisation of the parent magma prior to emplacement. A critical appraisal of all the available evidence suggests that (i) the anorthositic suite of rocks form a perfectly consanguinous and comagmatic assemblage and (ii) the spatially associated acidic suite emerged through a convergence of magmatic and metasomatic processes (the latter brought about by contact anatexis of the host rocks). The complex as well as the host metamorphics are intruded by an atectonic suite of noritic dykes emplaced ca 850 Ma ago.

Sarkar, Amitabha; Bhanumathi, L.; Balasubrahmanyan, M. N.

1981-04-01

100

Chromium Bioaccumulation in Rice Grown in Contaminated Soil and Irrigated Mine Wastewater—A Case Study at South Kaliapani Chromite Mine Area, Orissa, India  

Microsoft Academic Search

The level of chromium (Cr) contamination in soils and irrigated mine wastewater at South Kaliapani chromite mine region of Orissa, (India) were investigated. Chromium bioaccumulation in rice plants (Oryza sativa L. cv. Khandagiri) irrigated with Cr contaminated mine wastewater was analyzed along with its attenuation from mine wastewater. The levels of Cr in irrigated mine wastewaters in successive rice grown

Monalisa Mohanty; Mousumi Madhusmita Pattnaik; Aruna Kumari Mishra; Hemanta Kumar Patra

2011-01-01

101

Short Report: Environmental Vibrio Cholerae O139 May Be the Progenitor of Outbreak of Cholera in Coastal Area of Orissa, Eastern India, 2000: Molecular Evidence  

Microsoft Academic Search

Cholera has been reported in the state of Orissa, India during the past decades. An outbreak of diarrheal disease occurred during November 1 to November 9, 2000 in Rusi- pada village near Puri, which was inhabited by a population of approximately 560. During the outbreak, Vibrio cholerae O139 strains were isolated from clinical specimens collected from patients with acute diarrhea

Hemant Kumar Khuntia; Bibhuti Bhusan Pal; Prem Kumar Meher; Guru Prasad Chhotray

2008-01-01

102

Non-Formal Education--A Worthwhile Alternative to the Formal Education in India? Case Studies from Ganjam, Orissa. Reprints and Miniprints, No. 757.  

ERIC Educational Resources Information Center

This report discusses the advantages and disadvantages of non-formal education (NFE) compared to the formal school system in Ganjam, a rural district on the east coast of Orissa, India. The aim of the research was to investigate whether or not NFE, would be a worthy target of aid from the Swedish aid organization SIDA (Swedish International…

Svensson, Anna

103

Characterization and evaluation of stress and heavy metal tolerance of some predominant Gram negative halotolerant bacteria from mangrove soils of Bhitarkanika, Orissa, India  

Microsoft Academic Search

In the present study both Gram positive and Gram negative bacteria were isolated using enrichment media from five different stations from mangroves soils of Bhitarkanika, Orissa, India. Among the bacterial populations studied, the Gram negative bacterial population was found to be more in all the stations. Out of several Gram negative bacterial isolates, six predominant and morphologically distinct isolates were

Rath B

104

Early Cambrian granitoids of North Gondwana margin in the transition from a convergent setting to intra-continental rifting (Ossa-Morena Zone, SW Iberia)  

NASA Astrophysics Data System (ADS)

Two distinct Cambrian magmatic pulses are recognized in the Ossa-Morena Zone (SW Iberia): an early rift-(ER) and a main rift-related event. This Cambrian magmatism is related to intra-continental rifting of North Gondwana that is thought to have culminated in the opening of the Rheic Ocean in Lower Ordovician times. New data of whole-rock geochemistry (19 samples), Sm-Nd-Sr isotopes (4 samples) and ID-TIMS U-Pb zircon geochronology (1 sample) of the Early Cambrian ER plutonic rocks of the Ossa-Morena Zone are presented in this contribution. The ER granitoids (Barreiros, Barquete, Calera, Salvatierra de los Barros and Tablada granitoid Massifs) are mostly peraluminous granites. The Sm-Nd isotopic data show moderate negative ?Ndt values ranging from -3.5 to +0.1 and TDM ages greatly in excess of emplacement ages. Most ER granitoids are crustal melts. However, a subset of samples shows a transitional anorogenic alkaline tendency, together with more primitive isotopic signatures, documenting the participation of lower crust or mantle-derived sources and suggesting a local transient advanced stage of rifting. The Barreiros granitoid is intrusive into the Ediacaran basement of the Ossa-Morena Zone (Série Negra succession) and has yielded a crystallization age of 524.7 ± 0.8 Ma consistent with other ages of ER magmatic pulse. This age: (1) constrains the age of the metamorphism developed in the Ediacaran back-arc basins before the intrusion of granites and (2) defines the time of the transition from the Ediacaran convergent setting to the Lower Cambrian intra-continental rifting in North Gondwana.

Sánchez-García, T.; Pereira, M. F.; Bellido, F.; Chichorro, M.; Silva, J. B.; Valverde-Vaquero, P.; Pin, Ch.; Solá, A. R.

2013-08-01

105

Neoproterozoic–Early Cambrian isotopic variation and chemostratigraphy of the Lesser Himalaya, India, Eastern Gondwana  

Microsoft Academic Search

The Rodinia supercontinent had fragmented by 750 Ma and East Gondwana (India, Australia and Antarctica) separated from West Laurentia. Baltica, Africa and South America occupied other side of the Rodinia. Neoproterozoic rifting, breakup of Rodinia low latitude glaciation and global warming events have been recorded from the Lesser Himalaya of India. Chemostratigraphy of the Blaini–Krol–Tal succession indicates Precambrian–Cambrian transition lies in

V. C. Tewari; A. N. Sial

2007-01-01

106

Paleomagnetism of Early Cambrian Itabaiana mafic dikes (NE Brazil) and the final assembly of Gondwana  

NASA Astrophysics Data System (ADS)

Paleomagnetic analysis on 15 early Cambrian mafic dikes from Itabaiana (Paraíba State) yielded a southern (northwestern) direction with steep upward (downward) inclination ( Dm = 167.5°, Im = - 63.7°, ?95 = 7.3°). AF and Thermal demagnetization, thermomagnetic curves, and hysteresis results suggest that this component is dominantly carried by fine-grained SD magnetite. The high stability of this component and positive baked contact tests on three dikes indicate it represents a primary thermoremanent magnetization. Ar-Ar analysis on whole-rock samples from two sites provides a strong constraint on the age of the Itabaiana paleomagnetic pole (134.6° E, 34.9° S; A95 = 7.3, K = 28) defined by plateau ages of 525 ± 5 and 526 ± 4 Ma. This pole completely satisfies six out of the seven quality criteria proposed by Van der Voo [R. Van der Voo, The reliability of paleomagnetic data, Tectonophysics 184 (1990) 1-9.] and permits a tight constraint on the Early Cambrian sector of the Gondwana apparent polar wander path. Paleogeographic reconstructions consistent with the available paleomagnetic and geological record show that Gondwana was sutured along three major orogenies, the Mozambique (Brasilano/Pan-African) Orogeny (800-650 Ma), the Kuunga Orogeny (570-530 Ma) and the Pampean-Araguaia Orogeny (540-520 Ma). We suggest that after rifting away from Laurentia at the end of the Neoproterozoic, opening the Iapetus ocean, the Amazonian craton and minor adjoining blocks, such as Rio Apa and Pampia, collided with the proto-Gondwana by Cambrian times at ca. 530-520 Ma. Unless for small adjustments, Gondwana was completely formed by 525 Ma whose paleogeography is defined by the Itabaiana pole.

Trindade, Ricardo I. F.; D'Agrella-Filho, Manoel S.; Epof, Igor; Brito Neves, Benjamim B.

2006-04-01

107

A Southern Hemisphere origin for campanulid angiosperms, with traces of the break-up of Gondwana  

PubMed Central

Background New powerful biogeographic methods have focused attention on long-standing hypotheses regarding the influence of the break-up of Gondwana on the biogeography of Southern Hemisphere plant groups. Studies to date have often concluded that these groups are too young to have been influenced by these ancient continental movements. Here we examine a much larger and older angiosperm clade, the Campanulidae, and infer its biogeographic history by combining Bayesian divergence time information with a likelihood-based biogeographic model focused on the Gondwanan landmasses. Results Our analyses imply that campanulids likely originated in the middle Albian (~105 Ma), and that a substantial portion of the early evolutionary history of campanulids took place in the Southern Hemisphere, despite their greater species richness in the Northern Hemisphere today. We also discovered several disjunctions that show biogeographic and temporal correspondence with the break-up of Gondwana. Conclusions While it is possible to discern traces of the break-up of Gondwana in clades that are old enough, it will generally be difficult to be confident in continental movement as the prime cause of geographic disjunctions. This follows from the need for the geographic disjunction, the inferred biogeographic scenario, and the dating of the lineage splitting events to be consistent with the causal hypothesis.

2013-01-01

108

New constraints on the structure and evolution of the eastern margin of Gondwana from ambient noise Rayleigh wave anisotropic tomography  

NASA Astrophysics Data System (ADS)

The Tasmanides of Australia represent the eastern third of the Australian continent that formed along the eastern margin of Gondwana through tectonic events that took place from early Palaeozoic to Cretaceous. In southeast Australia, where the Tasmanides are represented by the Delamerian and Lachlan orogens, most of the complex geological structure inherited from those events lies below Cenozoic basins and Quaternary volcanic deposits, and is therefore not accessible via direct observation. In this work, we exploit the ambient noise wavefield recorded by the largest transportable seismic array experiment in the southern hemisphere, which has operated in eastern Australia from 1998 to present and involves the deployment of over 700 temporary stations with an average interstation distance of about 50 km. We analyze Rayleigh wave phase dispersion curves obtained in a previous study on more than 8,200 cross-correlograms using data from 450 sites, and we perform an anisotropic tomography inversion for periods ranging from 1 to 20 s in order to account for the apparent dependence of Rayleigh wavespeed on azimuthal propagation direction. While the isotropic velocity maps are in good agreement with previous tomographic studies, the anisotropic component of the velocity field brings new constraints on the crustal structure and Phanerozoic evolution of the Tasmanides in southeast Australia. One of the most remarkable results of our study is to show a fast axis of anisotropy almost mimicking the magnetic lineations which appear to wrap around a region now referred to as the Hay-Booligal Zone. That region, recently identified on the basis of high resolution aeromagnetic maps, has been interpreted as a remnant fragment of Precambrian lithosphere embedded within the Lachlan Orogen, possibly originating from the break-up of Rodinia.

Arroucau, Pierre; Rawlinson, Nicholas; Young, Mallory; Salmon, Michelle

2014-05-01

109

Impact assessment of chromite mining on groundwater through simulation modeling study in Sukinda chromite mining area, Orissa, India.  

PubMed

The pre-Cambrian chromites ore deposits in Sukinda valley, Jajpur District, Orissa, India, are well known for chromite ore deposits. The exploitation of the ore is carried out through open cast mining method since the last few decades. In the process, the overburden and ore dumps are stored on ground surface, where leaching of chromite and other toxic element takes place particularly during monsoon seasons. This leachate may cause threat to groundwater in the vicinity. An integrated approach has been adopted to evaluate possibility of pollution due to mine seepage and leachate migration on groundwater regime. The approach involves geophysical, hydrogeological, hydro-chemical and aquifer modeling studies. The investigation has the significance as many habitats surround the mining area facing groundwater problems. PMID:18450374

Dhakate, Ratnakar; Singh, V S; Hodlur, G K

2008-12-30

110

Foraminiferal assemblages and geochemistry for interpreting the incidence of Early Toarcian environmental changes in North Gondwana palaeomargin (Traras Mountains, Algeria)  

NASA Astrophysics Data System (ADS)

The Early Toarcian was characterised by important environmental changes and a mass extinction event usually related to a global oceanic anoxic event. The analysis of ecostratigraphic fluctuations of foraminiferal morphogroups, elemental geochemical proxies and C and O stable isotopes of the Mellala section (Tlemcen Domain, North Algeria) makes it possible to determine the incidence of the anoxic event in this sector of the north Gondwana palaeomargin. The end of the Pliensbachian is characterised by a diverse foraminiferal assemblage with equilibrium species suggesting good oxygen and nutrient availability. The beginning of the Toarcian (Polymorphum Zone) evidences major changes in foraminifera with the disappearance of species, decreasing proportions of epifauna and shallow infauna, and fluctuations in diversity and dominance of Lenticulina toarcense and Lingulina tenera confirming a perturbation in the palaeoecological conditions in the sea-bottom. Redox proxies (Co/Al, Cr/Al and V/Al) with local maximum values suggest a decrease in oxygenation degree. A negative excursion of ?13C is recorded right at the Polymorphum/Levisoni Zone boundary, and the subsequent disappearance of epifauna, decreasing diversity and abundance of foraminifera (foram/100 g) would be related to the accentuation of stressing conditions. Also at the Polymorphum/Levisoni Zone boundary, suboxic waters at the sea-bottom indicate the maximum values of redox proxies (Co/Al, Cu/Al, Cr/Al and V/Al). The upper part of the Levisoni Zone is more calcareous, with increasing diversity of shallow infauna and a decrease in potentially deep infauna related to more favourable conditions. The incidence of the Toarcian Oceanic Anoxic Event in this context was very low in comparison with the Saharan Basin (Raknet El Kahla section, Saharan Atlas), where a benthic barren interval, higher total organic carbon and redox proxies are recorded. The low incidence of the biotic crisis and the rapid recovery of assemblages in the Tlemcen Domain is compared with the high incidence and delayed recovery in the Saharan Basin, where the palaeogeography determined restricted water circulation between the Saharan Craton and the Oran Massif.

Reolid, Matías; Marok, Abbas; Sèbane, Abbes

2014-07-01

111

Impact of 1999 Orissa Cyclone on Dynamics and Heat Budget of the Bay of Bengal  

NASA Astrophysics Data System (ADS)

The impacts of two consecutive strong tropical cyclones (TCs) - 04B and 05B in 1999 - on dynamics, thermodynamics and mixed-layer processes of the Bay of Bengal (BoB) are examined using Hybrid Coordinate Ocean Model (HYCOM). This research is composed of three unique features: a) testing the influence of strong stratification and salinity gradient of the BoB, b) examining the ocean response to a sequence of two TCs and season change, and c) examining the effect of individual TC-associated forcings by adopting Lanczos filtering method. HYCOM is driven by ERA-Interim reanalysis data, CCMP wind and TRMM 3B42 rain rate. A series of experiments are performed in order to isolate the effects of each cyclone and their individual forcings. Due to the slow translation velocity and rapid intensification as both the cyclones approach the seashore of Orissa, India, sea surface temperature (SST) decreases the most on the cyclone track, instead of to the right of the track. Mixed layer thickness is largely deepened along the TC tracks except near Ganges river mouth, where fresh river water discharge results in strong stratification. The land-sea contrast introduces evident temperature and humidity diurnal cycle to the BoB, and increases surface turbulent heat flux (sensible and latent flux) variations. On the other hand, intraseasonal variability and upcoming cold season after the TC events hamper the recovery of SST to its pre-storm values. The impact of the TCs on turbulent heat flux in the BoB accounts for substantial proportion of its monthly climatologic value. The results from the experiment run that adopts modified Rankine Vortex for the wind of 04B and 05B, which are significantly underestimated by ERA-Interim reanalysis data, exhibits much stronger SST response. TMI observations show that the SST decreases by more than 2.5 K in the eastern, northwestern and western BoB after 05B diminishes, and in the meantime increases slightly at the center. Our model SST resembles the lower SST area in the eastern and northwestern BoB. For the top 50 m, the BoB loses ~500x10^18 J, while below 50 m gains ~1600x10^18J. Surface turbulent heat flux is ~450x10^18 J upward (~92% of the total loss). Despite the enhanced downward turbulent heat flux, the model result suggests that 05B causes the sea surface to lose heat (~5.3x10^18 J) from late October to the end of 1999 when also considering radiative flux, which is ~21% of the OHC decrease for the BoB. The other ~79% is attributed to merdional OHC flux along 10°N southern boundary. Our simulations also suggest that two consecutive TCs result in 68% less surface energy loss of the top 50m than the sum of two stand-alone TCs. The comparisons between the simulations with TC-associated forcings and without TC-associated forcings show that surface shortwave radiative flux dominates the SST decrease over the eastern BoB water in the early stage of 05B, while wind stress-induced warm water advection mitigates it. Although TC-associated wind stress predominately reduce SST and enhance downward turbulent heat flux through mixing process over the northwestern BoB water in the later stage of 05B, the reduced downward solar radiation by the TC clouds significantly decreases the heat into the ocean. The overall effect of each forcing is not linearly additive.

Wang, J.; Han, W.

2011-12-01

112

An Assessment of Solitary and Arribada Nesting of Olive Ridley Sea Turtles (Lepidochelys olivacea) at the Rushikulya Rookery of Orissa, India  

Microsoft Academic Search

The solitary and arribada population of Olive Ridley Sea Turtles at the Rushikulya rookery of Orissa of India was monitored for two nesting seasons (2003-04 and 2004-05). Mass nesting population census of turtles was carried out using standard IUCN\\/SSC Marine Turtle Specialist Group recommended statistical technique (number of turtles counted: n = 11024). Curved carapace measurements of egg laying females

BASUDEV TRIPATHY

2008-01-01

113

The evolution of Gondwana: U-Pb, Sm-Nd, Pb-Pb and geochemical data from Neoproterozoic to Early Palaeozoic successions of the Kango Inlier (Saldania Belt, South Africa)  

NASA Astrophysics Data System (ADS)

The provenance of Neoproterozoic to Early Palaeozoic rocks at the southern margin of the Kalahari craton reveals a depositional setting and evolution with a significant position in the formation of Gondwana. The sedimentary record shows a progression from immature, moderately altered rocks in the Ediacaran Cango Caves Group; to mature, strongly altered rocks in the Early Palaeozoic Kansa Group and overlying formations; culminating below very immature quartzarenites of Ordovician age. Petrographic and geochemical observations suggest the evolution of a small restricted basin with little recycling space towards a larger continental margin where substantial turbidite deposition is observed. For the southern Kalahari craton, a tectonic evolution comparable to supracrustal rocks in southern South America, Patagonia and Antarctica is supported by similarities in U-Pb ages of detrital zircons (Mesoproterozoic, Ediacaran and Ordovician grain populations); Sm-Nd isotopes (TDM: 1.2-1.8 Ga); and Pb-Pb isotopes. The maximum depositional age of the Huis Rivier Formation (upper Cango Caves Group) is determined at 644 Ma, but a younger age is still possible due to the limited zircon yield. The Cango Caves Group developed in a retro-arc foreland basin syntectonically to the Terra Australis Orogeny, which fringed Gondwana. The Kansa Group and overlying Schoemanspoort Formation are related to an active continental margin developed after the Terra Australis Orogen, with Patagonia being the 'missing link' between the Central South American arc and Antarctica during the Ordovician. This explains the occurrence of Ordovician detritus in these rocks, as a source rock of this age has not been discovered in South Africa. The absence of arc characteristics defines a position distal to the active continental margin, in a retro-arc foreland basin. The similarity of isotope proxies to major tectonic provinces in Antarctica and Patagonia, with those on the margins of the Kalahari craton, also points to a common geological evolution during the Mesoproterozoic and highlights the global relevance of this study.

Naidoo, Thanusha; Zimmermann, Udo; Chemale, Farid

2013-08-01

114

Geological and geometrical constraints on reconstructions of Gondwana: implications for the derivation of Gondwanan fragments in Asia  

SciTech Connect

The relative positions of east (India, Madagascar, Antarctica, Australia, etc.) and west (Africa, S. America, Arabia) Gondwana remains controversial. The authors present a new reconstruction based on (1) tight fit of Madagascar within the Somalian embayment which satisfies both sea-floor spreading data, and Karoo and older geology: (2) a tight fit of India against a reconstructed Africa-Arabian margin, such that the east stepping margin south of Socotra is matched with the east stepping re-entrant of the Suliaman Range east of Quetta; (3) a two-phase motion history of east and west Gondwana characterized by initial NW-SE spreading, followed by essentially N-S motion parallel with the Davies Ridge. Although rifting occurred episodically within Gondwana from the Carboniferous onwards, sea floor spreading did not occur until early late Jurassic and was characterized by long right lateral transform-short ridge geometry. Break-up of E and W Gondwana succeeded early Middle Jurassic spreading along the northern margin of Gondwana from at least Oman to New Guinea. Spreading directions preserved off northwest Australia suggest that motions of the rifted fragments was directed toward the northwest into Tethys. This suggests that the Lhasa, central Pamir, Sistan, Lut (.), and Central Iranian Plateau blocks which collided with Asia after the Jurassic were derived from the southeast, as opposed to the SW as generally portrayed.

Rowley, D.B.; Ziegler, A.M.; Sahagian, D.; Nie, S.Y.; Lottes, A.L.; Jacobs, D.; Hulver, M.

1985-01-01

115

High prevalence of Wuchereria bancrofti infection as detected by immunochromatographic card testing in five districts of Orissa, India, previously considered to be non-endemic.  

PubMed

India accounts for over one-third of the world's burden of lymphatic filariasis (LF). Although most coastal districts of Orissa state (eastern India) are LF-endemic, the western districts of Orissa are considered non-endemic. During a large-scale insecticide-treated bed net/microfinance trial, we tested one randomly selected adult (age 15-60 years) for LF from a random sample of microfinance-member households in five districts of western Orissa, using immunochromatographic card testing (ICT). Overall, 354 (adjusted prevalence 21%, 95%CI 17-25%) of 1563 persons were ICT positive, with district-wide prevalence rates ranging from 15-32%. This finding was not explained by immigration, as only 3% of subjects had ever lived in previously known LF-endemic districts. These results therefore suggest ongoing autochthonous transmission in districts where LF control programs are not operational. Our results highlight the importance of broad, systematic surveillance for LF in India and call for the implementation of LF control programs in our study districts. PMID:21122883

Foo, Patricia K; Tarozzi, Alessandro; Mahajan, Aprajit; Yoong, Joanne; Krishnan, Lakshmi; Kopf, Daniel; Blackburn, Brian G

2011-02-01

116

Amalgamation and initial break-up of Gondwana along the East African - Antarctic Orogen  

NASA Astrophysics Data System (ADS)

East- and West-Gondwana, or parts thereof, amalgamated along the East African - Antarctic Orogen at c. 550 Ma. The initial Gondwana break-up roughly followed the length of the orogen and reactivated Pan-African suture and shear zones 350 Ma after amalgamation. In Antarctica, the collision of E- and W-Gondwana overprinted wide continental margins but the location of the principle suture zone(s) is a matter of ongoing debate. Both, the northern and southern part of the East African - Antarctic Orogen are characterised by tectonic escape. In the southern part of the orogen, escape tectonics was associated with large-scale shear zones, that were reactivated during the break-up, resulting in a number of microplates. In Antarctica, the western orogenic front of the orogen is well exposed as the Heimefront Shear Zone in western Dronning Maud Land. This shear zones was reactivated during Mesozoic rifting and separates strongly thinned crust to the W from little affected crust to the E. It also coincides with a deep graben that reaches 800 mbsl, totalling the present relief in Heimefrontjella to more than 3500 m. Apatite fission-track data from this area indicate that the main geomorphic evolution does not coincide with the initial break-up and the formation of a margin, but was contemporaneous with the opening of the South Atlantic. During initial rifting at c. 180 Ma, the area was affected by the Bouvet mantle plume, that caused reheating of the basement to T > 120°C, followed by erosional unroofing in the Cretaceous. In the central portion of the East African - Antarctic Orogen, the break-up followed structures in the eastern part of the orogen. In Madagascar, rifting and break-up followed again Pan-African shear zones, such as the Ejeda and Ranotsara shear zones. In contrast to western Dronning Maud Land, fission-track data from Madagascar indicate that some of the main geomorphic features formed early during the break-up history. For example, combined titanite and apatite fission-track analyses indicate that the Ranotsara valley is an old rift zone, that developed early in the Gondwana rift history and underwent only little geomorphic modification thereafter.

Jacobs, J.; Emmel, B.

2003-04-01

117

Silurian magmatism in eastern Senegal and its significance for the Paleozoic evolution of NW-Gondwana  

NASA Astrophysics Data System (ADS)

Submarine basalt and trachyte of the Nandoumba group occur in eastern Senegal within the Bassarides branch of the Mauritanides orogen. The unit forms part of the parautochthonous domain which is stacked between underlying Neoproterozoic to Paleozoic foreland and overlying Variscan nappes. The crystallisation age of the volcanic to subvolcanic rocks has been determined by U-Pb single zircon SHRIMP method at 428 ± 5.2 Ma whereas zircon xenocryst ages vary from 500 to 2200 Ma. The shape of the xenocryst grains document proximal Neo- and Paleoproterozoic and distal Mesoproterozoic provenance areas for assimilated sediments. This is compatible with the Paleoproterozoic Birimian basement and Neoproterozoic cover rocks nearby whereas an origin from the Amazonian craton could be assumed for distal Mesoproterozoic zircons. Geochemical and Sm-Nd isotope whole rock analysis show that basalts of the Nandoumba group are similar to modern transitional to alkaline volcanic lavas in intraplate settings. Those basalts have a deep mantle source with a great contribution of a recycled mantle component such as EM1 and/or EM2. The basalts resemble in their composition those from the Meguma terrane of Nova Scotia which are of similar age suggesting a common source and therefore connection of Meguma with Gondwana during this period. Review of circum-Atlantic Silurian magmatism indicates ongoing fragmentation of NW-Gondwana that started in Cambro/Ordovician times.

Fullgraf, Thomas; Ndiaye, Papa Moussa; Blein, Olivier; Buscail, François; Lahondère, Didier; Le Métour, Joël; Sergeev, Sergey; Tegyey, Monique

2013-02-01

118

Paleomagnetism of the Newcastle Range, northern Queensland: Eastern Gondwana in the Late Paleozoic  

NASA Astrophysics Data System (ADS)

The Newcastle Range is an extensive (2500 km2) and well-exposed caldera system erupted on the trailing edge of Eastern Gondwana between 325 and 295 Ma. Paleomagnetic samples were collected from ignimbrites and associated microgranitoid intrusions from the central, northern and southern calderas from which three components of magnetization are recognized. Component 1 is considered to be a viscous magnetization acquired during the Brunhes Chron. A presumed Permian component, C2, is found in seven paleomagnetic sites with a mean pole at 30.9°S, 139.7°E (K = 13.9, A95 = 16.8°, ASD = 21.7°), agreeing with previously reported Permian data from Australia. Carboniferous units have a well-defined characteristic component, C3, distinguished by dual polarity (predominantly reversed) and moderate to steep inclination directions. Paleomagnetic polarities in the Newcastle Range Volcanics are formation dependent and new constraints on the timing of Carboniferous volcanism (˜325-317 Ma) are consistent with recent reanalysis of the base of the Permo-Carboniferous Reversed Superchron (PCRS). A mean paleomagnetic pole, calculated from 15 VGPs, lies at 63.4°S, 125°E (K = 26.22, A95 = 7.6°, ASD = 15.8°), suggesting that Australia remained at midlatitudes into the Middle Carboniferous. This paleomagnetic pole is consistent with similarly aged poles from Western Gondwana, the conformity of which indicates contributions from nondipole components of the Earth's paleofield were probably not significant in the time immediately preceding the PCRS.

Anderson, Kari L.; Lackie, Mark A.; Clark, David A.; Schmidt, Phil W.

2003-06-01

119

Subgenotype D5, BCP and MHR mutations in hepatic complications among hepatitis B virus infected patients from Orissa, India.  

PubMed

The study was undertaken to investigate the clinical implications of hepatitis B virus (HBV) genotypes, basal core promoter (BCP), precore (PC) and surface gene mutations in HBV infected patients from Orissa, southeastern India. HBV infections were identified by serology testing and HBV DNA amplification by polymerase chain reaction among the 152 patients. After sequencing, surface gene mutation were studied by sequence analysis as well as by using BLOSUM scores and BCP mutations were studied only by sequence analysis. A high proportion of HBV/D5 (66.0%) was found among the study samples having significant relation with liver cirrhosis (LC) and hepatocellular carcinoma (HCC) patients (p<0.05). The BCP mutation, TA (81.4%) and C1753/TA (75.0%) was found in significant proportion (p<0.05) among HCC cases and in fact a gradual increase in these mutations were noted between inactive carriers (IC) to HCC group and also showed higher viral load. An increasing trend of major hydrophilic region (MHR) mutations in S gene was also observed from IC (56.0%) to chronic liver disease (CLD) (60.4%) to LC (72.4%) to HCC (95.0%) patients. In conclusion, our study suggests that the predominant HBV subgenotype HBV/D5 with high viral load and BCP mutations (double and triple) and high mutations in MHR region was significantly associated with advanced liver disease (LC and HCC) and might act as predictor of severe hepatic complications. PMID:22820088

Panigrahi, Rajesh; Biswas, Avik; Banerjee, Arup; Singh, Shivaram Prasad; Panigrahi, Manas K; Roque-Afonso, Anne Marie; Das, Haribhakti Seba; Mahapatra, Pradip K; Chakrabarti, Sekhar; Chakravarty, Runu

2012-12-01

120

Neoproterozoic to Palaeozoic assembly, dismemberment and assembly of Peri-Gondwana -recorded in (East Avalonian) Anglesey (Ynys Môn), NW Wales, UK  

NASA Astrophysics Data System (ADS)

Late Neoproterozoic accretion at the outboard margin of East Avalonian Gondwana is recorded on Anglesey in ca. 650 Ma metamorphism in the Coedana Complex and the ca. 615 Ma supra-subduction zone Coedana Granite. Iapetan extension fragmented that assembly, crustal thinning is recorded in Anglesey by ca. 560 Ma exhumation of the Penmynydd Zone blueschists. Anglesey's present architecture is however largely a product of accretionary collisions that commenced in the Early Ordovician when coaxial to intensely non-coaxial deformation assembled those Late Neoproterozoic rocks with the Middle Cambrian (to earliest? Ordovician) Monian Supergroup greenschist facies metasediments. In western Anglesey, the Monian Supergroup rocks record NW-facing coaxial D1 deformation sheared by SE-vergent, strongly non-coaxial, D2/D3 strain after an intervening episode of mafic magmatism. In northern Anglesey, Monian Supergroup rocks record only SE-facing deformation from the onset of collision. Deformed ocean floor and slices of garnetiferous basement gneiss are located between these structurally distinct regions and imply separation of these Monian tracts prior to earliest-Arenig? onset of Caledonian collision and accretion. This deformation is contemporaneous with Penobscottian accretion in the northern Appalachians and Newfoundland. The Monian rocks were at surface (and deeply weathered?) before sub-aerial eruption of the (mid-Arenig?) Church Bay Tuff Formation. These acid to intermediate tuffs are overlain unconformably by an Upper Arenig to Llandovery marine transtensional foreland basin succession. Renewed convergence resulted in a SSE-vergent (late-Salinic?) fold and thrust imbricate stack; locally, thrusts override molasse deposits derived from an advancing thrust sheet. Active over-riding of tectonic molasse is continued in Anglesey until the Early Devonian at least. The axially sourced fluvial Old Red Sandstone of central eastern Anglesey is arranged in south-vergent folds and thrusts during Acadian deformation. The geology of Ynys Môn showcases the geometrical complexity of the continental fragments that make up late-Neoproterozoic to Palaeozoic peri-Gondwana, and of the punctuated extensional and compressional deformations that affected the exterior of that continental assembly. This fragment of the UK Caledonides provides an important trans-Atlantic link to the Appalachian geology of North America.

Leslie, Graham; Schofield, David; Wilby, Phil

2014-05-01

121

Paleozoic paleogeographic and depositional developments on the central proto-Pacific margin of Gondwana: Their importance to hydrocarbon accumulation  

NASA Astrophysics Data System (ADS)

During the Paleozoic Era, the western portion of the Gondwana continent between the equator and latitude 27°S of present-day South America bordered the proto-Pacific Ocean as a predominantly convergent margin. Following the Middle Cambrian accretion of the Arequipa-Belen-Antofalla Terrane, an epicontinental sea with communication to the proto-Pacific Ocean established itself along the length of the western margin of Gondwana during Late Cambrian and Early Ordovician time. The emergence of a proto-Cordillera led to significant separation of the epicontinental sea from the proto-Pacific Ocean during Silurian and Devonian times. Gradual erosion of that proto-Cordillera during Carboniferous and Early Permian time once again facilitated widespread transgression of the proto-Pacific Ocean into the epicontinental domain. At the end of the Early Permian, the sea retreated from Gondwana and a proto-Cordillera was re-established. The proto-Cordillera and the craton of Gondwana controlled sediment type and distribution in the epicontinental sea. Deposition occurred in five tectono-sedimentary cycles, which were separated by orogenic pulses that resulted in regional erosion of the previously deposited section. Oil and gas have been produced from the Paleozoic epicontinental sediments of Argentina, Bolivia, Peru, and Brazil, in an area in which exploration efforts are ongoing. Sandstone reservoirs and argillaceous source rocks of commercial importance formed during the episodes of sedimentation, but carbonates do not contribute to commercial hydrocarbon generation and accumulation. Cap rocks are provided by shales or evaporites.

Gohrbandt, K. H. A.

1992-11-01

122

The role of the Variscan eastern Gondwana-Laurussia\\/Laurasia boundary in the evolution of the central Mediterranean area  

Microsoft Academic Search

The geodynamic evolution of the central Mediterranean area is linked to the interaction between Gondwana and Laurussia\\/Laurasia plates. The interaction between these plates led to the development of Variscan, Alpine and Apennine Orogenic belts. In spite of the different ages of the orogenic systems, it is possible to hypothesize that their geodynamic evolution was linked to the complex interactions between

M. Padovano; F. M. Elter; E. Pandeli

2010-01-01

123

First record of the family Dromaeosauridae (Dinosauria: Theropoda) in the Cretaceous of Gondwana (Wadi Milk Formation, northern Sudan)  

Microsoft Academic Search

\\u000a Kurzfassung  Die cenomane Wadi Milk Formation des Sudan lieferte eine reiche kontinentale Wirbeltierfauna. Neben Fragmenten von großen\\u000a Theropoden verweisen disartikulierte Fußphalangen-Elemente und ein Zahn auf die Existenz von dromaeosauriden Theropoden in\\u000a der Oberkreide des Sudan; damit ist diese Theropodenfamilie zum ersten Mal auf den Gondwana-Kontinenten nachgewiesen.

Oliver W. M. Rauhut; Christa Werner

1995-01-01

124

A Gigantic Sarcopterygian (Tetrapodomorph Lobe-Finned Fish) from the Upper Devonian of Gondwana (Eden, New South Wales, Australia)  

PubMed Central

Edenopteron keithcrooki gen. et sp. nov. is described from the Famennian Worange Point Formation; the holotype is amongst the largest tristichopterids and sarcopterygians documented by semi-articulated remains from the Devonian Period. The new taxon has dentary fangs and premaxillary tusks, features assumed to be derived for large Northern Hemisphere tristichopterids (Eusthenodon, Hyneria, Langlieria). It resembles Eusthenodon in ornament, but is distinguished by longer proportions of the parietal compared to the post-parietal shield, and numerous differences in shape and proportions of other bones. Several characters (accessory vomers in the palate, submandibulars overlapping ventral jaw margin, scales ornamented with widely-spaced deep grooves) are recorded only in tristichopterids from East Gondwana (Australia-Antarctica). On this evidence Edenopteron gen. nov. is placed in an endemic Gondwanan subfamily Mandageriinae within the Tristichopteridae; it differs from the nominal genotype Mandageria in its larger size, less pointed skull, shape of the orbits and other skull characters. The hypothesis that tristichopterids evolved in Laurussia and later dispersed into Gondwana, and a derived subgroup of large Late Devonian genera dispersed from Gondwana, is inconsistent with the evidence of the new taxon. Using oldest fossil and most primitive clade criteria the most recent phylogeny resolves South China and Gondwana as areas of origin for all tetrapodomorphs. The immediate outgroup to tristichopterids remains unresolved – either Spodichthys from Greenland as recently proposed, or Marsdenichthys from Gondwana, earlier suggested to be the sister group to all tristichopterids. Both taxa combine two characters that do not co-occur in other tetrapodomorphs (extratemporal bone in the skull; non-cosmoid round scales with an internal boss). Recently both ‘primitive’ and ‘derived’ tristichopterids have been discovered in the late Middle Devonian of both hemispheres, implying extensive ghost lineages within the group. Resolving their phylogeny and biogeography will depend on a comprehensive new phylogenetic analysis.

Young, Ben; Dunstone, Robert L.; Senden, Timothy J.; Young, Gavin C.

2013-01-01

125

A gigantic sarcopterygian (tetrapodomorph lobe-finned fish) from the upper Devonian of Gondwana (Eden, New South Wales, Australia).  

PubMed

Edenopteron keithcrooki gen. et sp. nov. is described from the Famennian Worange Point Formation; the holotype is amongst the largest tristichopterids and sarcopterygians documented by semi-articulated remains from the Devonian Period. The new taxon has dentary fangs and premaxillary tusks, features assumed to be derived for large Northern Hemisphere tristichopterids (Eusthenodon, Hyneria, Langlieria). It resembles Eusthenodon in ornament, but is distinguished by longer proportions of the parietal compared to the post-parietal shield, and numerous differences in shape and proportions of other bones. Several characters (accessory vomers in the palate, submandibulars overlapping ventral jaw margin, scales ornamented with widely-spaced deep grooves) are recorded only in tristichopterids from East Gondwana (Australia-Antarctica). On this evidence Edenopteron gen. nov. is placed in an endemic Gondwanan subfamily Mandageriinae within the Tristichopteridae; it differs from the nominal genotype Mandageria in its larger size, less pointed skull, shape of the orbits and other skull characters. The hypothesis that tristichopterids evolved in Laurussia and later dispersed into Gondwana, and a derived subgroup of large Late Devonian genera dispersed from Gondwana, is inconsistent with the evidence of the new taxon. Using oldest fossil and most primitive clade criteria the most recent phylogeny resolves South China and Gondwana as areas of origin for all tetrapodomorphs. The immediate outgroup to tristichopterids remains unresolved - either Spodichthys from Greenland as recently proposed, or Marsdenichthys from Gondwana, earlier suggested to be the sister group to all tristichopterids. Both taxa combine two characters that do not co-occur in other tetrapodomorphs (extratemporal bone in the skull; non-cosmoid round scales with an internal boss). Recently both 'primitive' and 'derived' tristichopterids have been discovered in the late Middle Devonian of both hemispheres, implying extensive ghost lineages within the group. Resolving their phylogeny and biogeography will depend on a comprehensive new phylogenetic analysis. PMID:23483884

Young, Ben; Dunstone, Robert L; Senden, Timothy J; Young, Gavin C

2013-01-01

126

Late Paleozoic paleolatitude and paleogeography of the Midland basin, Texas  

SciTech Connect

During the Late Pennsylvanian through Early Permian, the Midland basin was located in the low latitudes. In the Desmoinesian (Strawn), the basin was astride the equator; during the Missourian (Canyon), the center of the basin had migrated northward so it was located at 1-2N latitude. In the Virgilian (Cisco), the basin center was located around 2-4N latitude, and by the Wolfcampian, it was positioned at around 4-6N latitude. From the Desmoinesian (312 Ma) through the Missourian (306 Ma), the relative motion of the basin was 63NE. Later during the Virgilian (298 Ma) to Wolfcampian (280 Ma), the direction of motion was 24NE. This change in motion reflects a major tectonic event, occurring between the Missourian and Virgilian, that greatly modifed the movement of the Laurentian (North American) plate. At that time, Laurentia had collided with Gondwana and become part of the supercontinent Pangea. Throughout the late Paleozoic, Laurentia was rotated so the Midland basin was oriented 43{degree} northeast from its current setting. Late Paleozoic paleogeography and paleolatitude controlled the direction of prevailing winds and ocean currents, thereby influencing the distribution of carbonate facies in the Midland basin. Present prevailing winds and ocean currents have been shown to have a major impact on modern carbonate sedimentation and facies distribution in Belize, the Bahamas and Turks, and Caicos. A clearer understanding of how late Paleozoic latitude and geography affected sedimentation helps explain and predict the distribution of carbonates throughout the Midland basin.

Walker, D.A. (Mobil Exploration and Producing U.S., Midland, TX (United States)); Golonka, J. (Mobil Exploration and Producing Services Inc., Dallas, TX (United States)); Reid, A.M.; Reid, S.T. (Consulting Geologist, Midland, TX (United States))

1992-04-01

127

Plume-Lithosphere Interaction in the Ethiopian CFB Province: Breaking up Gondwana  

NASA Astrophysics Data System (ADS)

The Ethiopia-Yemen continental flood basalt (CFB) province formed 30 Ma and today covers some 600,000 sq. km with an approximate total volume of 350,000 sq. km of basalt and associated rhyolite. The majority of lavas were extruded over about 1 my (Baker et al. 1996; Pik et al. 1998) and have not been subject to tectonism, making this area ideal for study of processes associated with continental break-up, mantle plume impacts and CFB magmatism. The Ethiopian province is the youngest of the Mesozoic CFB occurrences associated with break-up of Gondwana, following the Karoo and Ferrar (180-175 Ma), Parana-Etendeka (134- 132 Ma) and Deccan (67-65 Ma) events. In Ethiopia, as with other Gondwana CFB provinces, basalts have been separated into high titanium (HT) and low titanium (LT) series (Pik et al. 1998). Stratigraphic studies indicate HT and LT units erupted contemporaneously so temporal control cannot explain the chemical variations; Pik et al (1998) drew a NE-SW trending line separating the region into HT and LT sub-provinces. Detailed investigation of new study sites along the SW margin of the flood basalt province (Tesfaye 2006) found interlayered LT and HT units indicating more complex spatial controls. Our investigation of Ethiopian CFBs evaluates source and process heterogeneities that could produce voluminous mafic magmatism in these two distinctive series. To first order the mildly alkalic HT lavas have higher incompatible trace element abundances than the tholeiitic LT basalts (Pik et al. 1998, 1999; Keiffer et al. 2004), suggesting derivation of the former by lower degrees of partial melting at greater pressures (Furman et al. 2006). Sr-Nd-Pb isotopic signatures of the LT and HT series largely overlap with one another and with the modern Afar plume; in detail the highest Ti-lavas (HT2 of Pik et al. 1998) are isotopically and geochemically distinct from LT and HT1 basalts, which form a broad continuum in all representations of data. HT2 basalts have mantle-like values of Ba/Rb, Rb/Sr, Ce/Pb, La/Nb whereas LT and HT1 basalts show contributions from enriched mantle or crustal sources. Comparison of Ethiopian CFBs to other Gondwana provinces reveals temporal, and possibly spatial, patterns of basalt genesis. Notably, Ethiopian basalts have lower Sr isotope values than those observed in the other CFB provinces. Ethiopian lavas include the greatest contribution from mantle plume source material relative to enriched mantle and crust, with high He isotopic values that are not observed in the other provinces. Crustal thicknesses in Ethiopia are not anomalously thin, suggesting that gradual lithospheric erosion took place during prolonged break-up of Gondwana over the South African Superplume (e.g., Hawkesworth et al. 1999). Baker et al. 1996, Geochim Cosmochim Acta, 60, 2559-2581; Furman et al 2006, J Geol Soc London, Sp. Pub. 269, 95-119; Hawkesworth et al. 1999, J Af Earth Sci, 28, 239-261; Kieffer et al. 2004, J Petrology, 45, 793-834; Pik et al. 1998, J Volcan Geotherm Res, 81, 91-111; Pik et al. 1999, Geochim Cosmochim Acta 63, 2263-2279; Tesfaye 2006, MS thesis: Addis Ababa University, 106 pp

Plummer, C. L.; Furman, T.

2006-12-01

128

Aeromagnetic legacy of early Paleozoic subduction along the Pacific margin of Gondwana  

USGS Publications Warehouse

Comparison of the aeromagnetic signatures and geology of southeastern Australia and northern Victoria Land, Antarctica, with similar data from ancient subduction zones in California and Japan, provides a framework for reinterpretation of the plate tectonic setting of the Pacific margin of early Paleozoic Gondwana. In our model, the plutons in the Glenelg (south-eastern Australia) and Wilson (northern Victoria Land) zones formed the roots of continental-margin magmatic arcs. Eastward shifting of arc magmatism resulted in the Stavely (south-eastern Australia) and Bowers (northern Victoria Land) volcanic eruptions onto oceanic forearc crust. The turbidites in the Stawell (southeastern Australia) and Robertson Bay (northern Victoria Land zones) shed from the Glenelg and Wilson zones, respectively, were deposited along the trench and onto the subducting oceanic plate. The margin was subsequently truncated by thrust faults and uplifted during the Delamerian and Ross orogenies, leading to the present-day aeromagnetic signatures.

Finn, C.; Moore, D.; Damaske, D.; Mackey, T.

1999-01-01

129

Avian evolution, Gondwana biogeography and the Cretaceous-Tertiary mass extinction event.  

PubMed

The fossil record has been used to support the origin and radiation of modern birds (Neornithes) in Laurasia after the Cretaceous-Tertiary mass extinction event, whereas molecular clocks have suggested a Cretaceous origin for most avian orders. These alternative views of neornithine evolution are examined using an independent set of evidence, namely phylogenetic relationships and historical biogeography. Pylogenetic relationships of basal lineages of neornithines, including ratite birds and their allies (Palaleocognathae), galliforms and anseriforms (Galloanserae), as well as lineages of the more advanced Neoves (Gruiformes, (Capimulgiformes, Passeriformes and others) demonstrate pervasive trans-Antarctic distribution patterns. The temporal history of the neornithines can be inferred from fossil taxa and the ages of vicariance events, and along with their biogeographical patterns, leads to the conclusion that neornithines arose in Gondwana prior to the Cretaceous Tertiary extinction event. PMID:11296857

Cracraft, J

2001-03-01

130

Avian evolution, Gondwana biogeography and the Cretaceous-Tertiary mass extinction event.  

PubMed Central

The fossil record has been used to support the origin and radiation of modern birds (Neornithes) in Laurasia after the Cretaceous-Tertiary mass extinction event, whereas molecular clocks have suggested a Cretaceous origin for most avian orders. These alternative views of neornithine evolution are examined using an independent set of evidence, namely phylogenetic relationships and historical biogeography. Pylogenetic relationships of basal lineages of neornithines, including ratite birds and their allies (Palaleocognathae), galliforms and anseriforms (Galloanserae), as well as lineages of the more advanced Neoves (Gruiformes, (Capimulgiformes, Passeriformes and others) demonstrate pervasive trans-Antarctic distribution patterns. The temporal history of the neornithines can be inferred from fossil taxa and the ages of vicariance events, and along with their biogeographical patterns, leads to the conclusion that neornithines arose in Gondwana prior to the Cretaceous Tertiary extinction event.

Cracraft, J.

2001-01-01

131

Evolution of the APWP for Gondwana: constraints based on the geology of eastern Australia  

NASA Astrophysics Data System (ADS)

The many iterations of the APWP for Gondwana over the past 40 years will be reviewed. They involve all the uncertainties that challenge the determination of the correct record: nature of NRM; age and correlation; geography and history of tectonic units etc. Most arguments about the Paleozoic section of this path depend upon the interpretation of results from the various terranes of eastern Australia. The two extreme views are either that none of the results from eastern Australia can be used for APWP definition or that all of them can be used. The terrane geology of eastern Australia is now reasonably well known and the paleomagnetic results can be placed in an appropriate terrane concept. This suggests that the Molong-Monaro terrane, where most results come from, was certainly accreted to the main craton by the Middle Devonian and probably by the Early Devonian. Early Devonian palaemagnetric results from the north and south of eastern Australia confirm this to be the case. However, the often used Late Carboniferous results from glacial horizons in eastern Australia are from the New England Fold Belt, where accretion to the main craton may not have been completed until the Middle Triassic. Results from this region now also confirm this to be the case. Both the geological setting and paleomagnetic results now confirm that the South Pole APWP makes a rapid transition from North Africa to south of South Africa between the Late Ordovician (455 Ma) and the Early Devonian (405 Ma). This places Bolivia and adjacent regions of South America near the south pole in Silurian times, a position supported by sedimentological evidence for glaciation in Bolivia at that time. The pole then loops back across southwest Gondwana to reach central Africa by the Early Carboniferous.

Briden, J. C.; McElhinny, M. W.

2004-12-01

132

The timing and duration of the Karoo igneous event, southern Gondwana  

NASA Astrophysics Data System (ADS)

A volcanic event of immense scale occurred within a relatively short period in early Jurassic time over large regions of the contiguous Gondwana supercontinent. In southern Africa, associated remnants of thick volcanic successions of lava flows and extensive dike and sill complexes of similar composition have been grouped together as the Karoo Igneous Province. Correlative volcanic and plutonic rocks occur in Antarctica and Australia as the Ferrar Province. Thirty-two new 40Ar-39Ar incremental heating experiments on feldspars and whole rocks from Namibia, South Africa and East Antarctica produce highly resolved ages with a vast majority at 183±1 Ma and a total range of 184 to 179 Ma. These are indistinguishable from recent, high-resolution 40Ar-39Ar and U-Pb age determinations reported from the Antarctic portion of the province. Initial Karoo volcanism (Lesotho-type compositions) occurred across the entire South African craton. The ubiquitous distribution of a plexus of generally nonoriented feeder dikes and sills intruding Precambrian crystalline rocks and Phanerozoic sediments indicates that these magmas penetrated the craton over a broad region. Lithosphere thinning of the continent followed the main pulse of igneous activity, with volcanism focused in the Lebombo-Nuanetsi region, near the eventual split between Africa and Antarctica. Seafloor spreading and dispersion of east and west Gondwana followed some 10-20 m.y. afterward. The volume of the combined Karoo-Ferrar province (˜2.5×106 km3) makes it one of the largest continental flood basalt events. The timing of this event correlates with a moderate mass extinction (Toarcian-Aalenian), affecting largely marine invertebrates. This extinction event was not as severe as those recorded at the Permian-Triassic or Cretaceous-Tertiary boundaries associated with the Siberian and Deccan flood basalts events, respectively. The difference may be due to the high southerly latitude and somewhat lower eruption rates of the Karoo event.

Duncan, R. A.; Hooper, P. R.; Rehacek, J.; Marsh, J. S.; Duncan, A. R.

1997-08-01

133

Geochronological data from the Faxinal coal succession, southern Paraná Basin, Brazil: A preliminary approach combining radiometric UPb dating and palynostratigraphy  

Microsoft Academic Search

A radiometric zircon age of 285.4±8.6Ma (IDTIMS U-Pb) is reported from a tonstein layer interbedded with coal seams in the Faxinal coalfield, Rio Grande do Sul, Brazil. Calibration of palynostratigraphic data with the absolute age shows that the coal depositional interval in the southern Paraná Basin is constrained to the Sakmarian. Consequently, the basal Gondwana sequence in the southern part

Margot Guerra-Sommer; Miriam Cazzulo-Klepzig; Rualdo Menegat; Milton Luiz Laquintinie Formoso; Miguel Ângelo Stipp Basei; Eduardo Guimarães Barboza; Margarete Wagner Simas

2008-01-01

134

Toarcian–Kimmeridgian depositional cycles of the south-western Morondava Basin along the rifted continental margin of Madagascar  

Microsoft Academic Search

After rifting and final breakup of Gondwana along the former East-African-Antarctic Orogen during the Toarcian–Aalenian, passive\\u000a margins formed around the Proto-Indian Ocean. Sedimentological and stratigraphic studies in the southern Morondava Basin contribute\\u000a to an improved reconstruction of palaeoenvironmental changes during the syn-rift and post-rift margin formation. Depositional\\u000a models based on outcrop and literature data in combination with subsurface data sets

Markus Geiger; Günter Schweigert

2006-01-01

135

Bio-concentration of chromium--an in situ phytoremediation study at South Kaliapani chromite mining area of Orissa, India.  

PubMed

Mine waste water at South Kaliapani usually contains toxic levels of hexavalent Cr(VI). The present in situ study was conducted at South Kaliapani chromite mine area in Orissa state, India, to assess the phytoremediation ability of three plants, namely, rice (Oryza sativa L.), paragrass (Brachiaria mutica), and an aquatic weed (Eichhornia crassipes), in attenuating Cr(VI) from mine waste water and to correlate the bio-concentration factors (BCF) of Cr. Water hyacinth (E. crassipes) showed 24% to 54% reduction whereas paragrass (B. mutica) was able to reduce 18% to 33% of Cr(VI) from mine water. This reduction was studied over a period of 100 days of plant growth. The reduction was observed through a passage of a sum total of 2,000 sq. ft. cultivated plots and ponds separately. Reduction in Cr(VI) content in mine water varies with plant age as well as with the distance of passage. Cr accumulation and BCF values increased with high soil Cr levels as well as the age of plants. High BCF and transportation index (Ti) values, i.e., 10,924 and 32.09, respectively, were noted for water hyacinth. The Ti values indicated that the root-to-shoot translocation of Cr was very high after 100 days of growth. The total accumulation rate was maximum (8.29 mg Cr kg dry biomass(-1) day (-1)) in paragrass. The BCF values for roots were noted to be higher than those of leaves, stems, and grains of the 125-day-old plants. Hence, paragrass and water hyacinth may be used as tools of phytoremediation to combat the problem of in situ Cr contamination. PMID:21487717

Mohanty, Monalisa; Pattnaik, Mausumi M; Mishra, Aruna K; Patra, Hemanta K

2012-01-01

136

Serological evidence of foot-and-mouth disease virus infection in randomly surveyed goat population of Orissa, India.  

PubMed

India is endemic for foot-and-mouth disease (FMD), and goats constitute the second largest susceptible population of domestic livestock. FMD surveillance and control strategies in the country largely ignore small ruminants, known to be critical in the epidemiology of the disease. Here, serological investigations were carried out to generate estimates of antibody prevalence in goats of Orissa state to both non-structural (NSP-Ab) and structural proteins (SP-Ab) of FMD. The apparent overall NSP-Ab and SP-Ab seroprevalences were 38% and 20.7%, respectively, which signifies a very high level of FMD virus circulation in the goat population despite the lack of clinical signs in this species. The apparent prevalence of NSP-Ab and SP-Ab was positively correlated in the sampling areas. Interestingly, the values found for NSP-Ab prevalence were almost consistently higher than those found for SP-Ab prevalence. This could have been attributable to either issues related to sensitivity and specificity of the test systems employed or differences in the post-infection kinetics of NSP- and SP-Ab. The pattern that emerged from SP-Ab analysis indicated goats being infected with all three prevalent serotypes (O, A and Asia 1) and reinforces the concept that non-vaccinated goats can be exploited as tracer animals for detecting serotypes involved in outbreaks. The results underscore the requirement to bring caprine species under comprehensive surveillance and vaccination campaigns to check silent amplification, excretion and transmission of the virus. PMID:20723161

Ranabijuli, S; Mohapatra, J K; Pandey, L K; Rout, M; Sanyal, A; Dash, B B; Sarangi, L N; Panda, H K; Pattnaik, B

2010-12-01

137

Two New Trematodes of Family Acanthocolpidae Luhe, 1906 From Marine Fish Leiognathus daura (Cuvier) from the Coast of Puri, Orissa, India  

PubMed Central

Background Genus Acanthocolpus (Trematoda: Acanthocolpiidae) is one of the most important zoonotic digenean with wide geographic distribution in the world. The purpose of the present study was to describe morphological and morphometrical characteristics of Acanthocolpus species, currently prevalent in marine fish fauna of Puri coast, Orissa, India. Methods Gastro-intestinal organs of Leiognathus daura (Cuvier) in Puri coast, Orissa, India, were examined for infectivity with digenean trematode species. For examination and measurements of helminthes, acetoalum carmine staining was performed, followed by camera Lucida drawings of morphological characters and measurements of morphometrical criteria with a calibrated microscope. Using valid trematode systematic keys, almost all the parasites were identified at the level of species. Results Overall, 36 marine fishes were found infected with at least one species of Acanthocolpus. Considering morphological characteristics of Acanthocolpus, two species were identified as new species including Acanthocolpus durghai sp.nov. and Acanthocolpus amrawatai sp.nov. Conclusion During the survey of helminth parasites, collected six different species of the genus Acanthocolpus, out of these two are new species, another is redescribed to show certain variation, the new parasite was obtain from the intestine of marine fish Leiognathus daura (Cuvier)

MISHRA, Sushma; CHANDRA, Satish; SAXENA, Anand Murari

2013-01-01

138

Lower Paleozoic relative motion of the Arequipa block and Gondwana; Paleomagnetic evidence from Sierra de Almeida of Northern Chile  

NASA Astrophysics Data System (ADS)

Paleomagnetic results have been obtained from a suite of Paleozoic samples from Sierra de Almeida within the high eastern portions of the Atacama desert. Characteristic directions are discussed for two sequences of pre-Silurian lavas of probable Cambro-Ordovician age, the Late Cambrian Choscas pluton, three Late Ordovician-Early Silurian plutons, the Devonian-Carboniferous Lila Formation and late Paleozoic volcanic units of the Pular and Cas Formations. The Choschas pluton and one lava series yield similar northerly and shallow directions which for the presence of reversals and their concordance are suggested to represent early Paleozoic Arequipa plate directions. Directions in the three Late Ordovician-Early Silurian plutons pass a tilt test using an overlying erosional unconformity, and these also include reversals. Together with directions from a second lava series (a roof pendant in an Early Silurian pluton) these define poles compatible with Silurian Gondwana results from Africa and Australia. In situ directions from the basal red beds of the Devonian Lila Formation are inconsistent with Devonian Gondwana or stable South American Poles, but (like the Devonian strata of the Appalachians) they are consistent with a tilt-corrected overprint of Kiaman Superchron age. These results, together with previous results from the late Paleozoic Cas and Pular Formations are discordant from the Gondwana path only for the latest Cambrian-earliest Ordovician. The discordance in paleomagnetic data, together with regional geologic constraints, can be explained by a model in which the Arequipa block, representing a paraautothonous finger of Gondwana (like Japan or the Iberian Peninsula) rotated about a nearby pole but was then resutured during the Silurian. Such a scenario resolves much of the discrepancies in the models which have emerged from Peru, Chile, and Argentina.

Forsythe, Randall D.; Davidson, John; Mpodozis, Constantino; Jesinkey, Christopher

1993-02-01

139

Metamorphic Evolution of the Main Collisional Suture Zone Between East and West Gondwana  

NASA Astrophysics Data System (ADS)

Petrological and metamorphic constraints from five metamorphic complexes which were exhumed during the collision between East- and West-Gondwana across the main collisional suture zone are presented. These include: (a) Meatiq complex in Eastern Desert of Egypt, (b) Feiran-Solaf complex in Sinai, Egypt (c) Sa'al-Zaghra complex in Sinai, Egypt, (d) Great Ruaha River area in the Mozambique Belt, and (e) Western Dronning Maud Land, East Antarctica. The metamorphic results from these complexes are compared and provide insight into the nature of Pan-African crust formation processes during Gondwana assembly. In this study we present differences and similarities between various field areas in the central collisional suture zone of Gondwana that sheds light on the crustal accretion and supercontinent assembly process from a metamorphic perspective. The Meatiq complex in the Eastern Desert of Egypt consists of a low-grade volcanic arc sequence that covers a higher-grade, biotite-garnet gneiss metamorphic core complex. A sinistral shear zone - the Najd Fault System - separates the high-grade rocks from the low-grade volcanic sequence. The combination between published data and new thermodynamic modeling shows that both the high-grade and the low-grade rocks record single clockwise P -T paths. The peak metamorphic conditions of the high-grade rocks are T = 650-700 oC and P = 7-7.5 kbar, whereas the low-grade rocks record conditions of T = 400-450 oC and P = 3-4 kbar. In Sinai, the Najd Fault System is not exposed due to the voluminous intrusion of ca. 540 Ma post-tectonic granites. However, both the garnet-biotite gneisses of the Feiran-Solaf complex (T = 700-750 oC and P = 7-8 kbar) and the low-grade rocks (T = 400-450 oC and P = 2-3 kbar) of Wadi El Kid record very similar metamorphic conditions and clockwise P -T paths to those in Eastern Desert, Egypt. Conversely, the Sa'al-Zaghra complex shows anticlockwise P-T path with peak conditions of 2.5 kbar and 42 oC. It worth mention that the peak metamorphic age of the Sa'al-Zaghra complex is much older than the Pan-African event (ca. 1100 Ma). In western Dronning Maud Land (Antarctica), a petrological and metamorphic comparison of Mesoproterozoic metabasic rocks on the eastern margin of the Archean Grunehogna Craton and the adjacent Maud Belt, revealed a difference in peak metamorphic conditions from T = 280 ± 30 oC to 710-750 oC and P = 2 ± 1.5 to 8.5-11 kbar over a distance of only 30 km across a major glacial valley. The high-grade PT-constraints derived for the western extreme of the Maud Belt, is very similar to that reported for the eastern Maud Belt dated at ca. 550 Ma. These PT-constraints do not support the presence of a westward decreasing metamorphic field gradient within the Maud Belt as previously proposed. The data presented here suggests that the inferred sub-glacial boundary between the Grunehogna Craton and the Maud Belt, might reflect a major Pan-African thrust, with the Maud Belt representing the continuation of the East African Mozambique Belt into East Antarctica.

Abu-Alam, Tamer; Grosch, Eugene

2013-04-01

140

The influence of inherited structures on dyke emplacement during Gondwana break-up in southwestern Africa  

NASA Astrophysics Data System (ADS)

A kinematic analysis of Cretaceous and pre-Cretaceous faulting and fracturing was carried out along the west coast of Southern Africa extending from the greater Cape Town area to the Orange River and beyond into southern Namibia. This study was augmented by the geometric analysis of mainly Cretaceous mafic dykes exposed from SW Angola to the southern tip of Africa. The kinematic analysis shows that the Cretaceous rifting event that led to the opening of the modern South Atlantic was largely controlled by NW-SE and NE-SW-striking structures. In the coastal areas of South Africa the Cretaceous deformation was dominated by NE-SW extension, whereas a general E-W-oriented extension prevailed further north. Analysis of reverse and strike-slip faulting in the Gariep and western Saldania Belts shows that the Pan-African constrictional deformation in South Africa was mainly controlled by ENE-WSW- to ESE-WNW-oriented shortening. Further north, the geometry of the Odgen Rock Mylonites in Namibia is controlled by N-S-striking strike-slip faults. The geometric analysis of the orientation of the mafic dykes also points to an E-W-oriented extension direction in the coastal areas extending from southern Angola to Meob and Conception Bay in west-central Namiba and changes to a generally NE-SW-oriented extension along the west coast of South Africa. Further inland in the Damara Belt sensu strictu, the geometric analysis of dykes belonging to the Hentjes Bay-Outjo Dyke Swarm also indicates NE-SW-oriented extension but, in addition, also a strong component of NW-SE-directed extension controlled dyke emplacement. The results of this study suggest that Pan-African (or older) structural discontinuities were re-utilised during the opening of the South Atlantic in the Early Cretaceous. The extension directions associated with Cretaceous Gondwana break-up structures are subparallel to the Pan-African shortening orientations. The inherited structural anisotropies are generally parallel to major lineaments and/or shear zones that, in turn, follow the trend of older mobile belts and/or are parallel to Archaean and/or Proterozoic craton boundaries. Consequently, the inherited Pan-African and/or older structures provided lithospheric anisotropies that controlled the Cretaceous rifting of SW Gondwana and the opening of the modern South Atlantic.

Will, Thomas; Frimmel, Hartwig

2013-04-01

141

Paired ?34S data from carbonate-associated sulfate and chromium-reducible sulfur across the traditional Lower-Middle Cambrian boundary of W-Gondwana  

NASA Astrophysics Data System (ADS)

In this study, we present the first high-resolution data from coupled ?34S analyses of carbonate-associated sulfate (CAS) and chromium-reducible sulfur (CRS) from three Lower-Middle Cambrian sections in western Gondwana. CAS and CRS were extracted and analyzed from marine dolostone, limestone, and nodular limestone from Spanish and French successions. In parallel, carbonate samples were also analyzed for ?13Ccarb, ?18Ocarb, and major/trace element concentrations (Ca, Fe, Mg, Mn, Sr). ?34SCAS values vary between 17.6‰ and 33.2‰, with a maximum CAS concentration of ca. 900 ppm. ?34SCRS data show a similar broad range between -5.1‰ and 29.7‰, with maximal CRS contents up to ca. 3700 ppm. Notably, there is little stratigraphic variation in the ?34SCAS data in each of the sections confounding inter-basinal chemostratigraphic correlations. Nonetheless, the absolute differences in ?34SCAS between sections as well as variations in CAS and CRS concentrations are attributed to paleoenvironmental differences between proximal and distal parts of the carbonate ramp, as well as effects of subaerial exposure and riverine input. Thus, the generated ?34SCAS data deliver not only valuable paleoecological and paleoenvironmental information, they also illustrate a heterogeneity in the seawater sulfate sulfur isotopic composition of the western Gondwanan ocean. Consequently, the lack of correlation between our Gondwanan ?34SCAS data and time equivalent sections of Laurentia and Siberia is probably not only caused by the absence of an internationally accepted biostratigraphic correlation, but rather supports the view that sulfate was non-conservative anion in seawater during the Cambrian Period.

Wotte, Thomas; Strauss, Harald; Fugmann, Artur; Garbe-Schönberg, Dieter

2012-05-01

142

Tectonic history of the Illinois basin  

SciTech Connect

The Illinois basin began as a failed rift that developed during breakup of a supercontinent approximately 550 Ma. A rift basin in the southernmost part of the present Illinois basin subsided rapidly and filled with about 3,000 m of probable Early and Middle Cambrian sediments. By the Late Cambrian, the rift-bounding faults became inactive and a broad relatively slowly subsiding embayment, extending well beyond the rift and open to the Iapetus Ocean, persisted through most of the Paleozoic Era. Widespread deformation swept through the proto-Illinois basin beginning in the latest Mississippian, continuing to the end of the Paleozoic Era. Uplift of basement fault blocks resulted in the formation of many major folds and faults. The timing of deformation and location of these structures in the forelands of the Ouachita and Alleghanian orogenic belts suggest that much of the deformation resulted from continental collision between North America and Gondwana. The associated compressional stress reactivated the ancient rift-bounding faults, upthrusting the northern edge of a crustal block approximately 1,000 m within the rift. Concurrently, dikes (radiometrically dated as Early Permian), sills, and explosion breccias formed in or adjacent to the reactivated rift. Subsequent extensional stress, probably associated with breakup of Pangea, caused the crustal block within the rift to sink back to near its original position. High-angle, northeast- to east-west-trending normal faults, with as much as 1,000 m of displacement, formed in the southern part of the basin. These faults displace some of the northwest trending Early Permian dikes. Structural closure of the southern end of the Illinois basin was caused by uplift of the Pascola arch sometime between the Late Pennsylvanian and Late Cretaceous.

Kolata, D.R.; Nelson, J.W. (Illinois Geological Survey, Champaign (USA))

1990-05-01

143

Geometry and kinematics of the late Proterozoic Angavo Shear Zone, Central Madagascar: Implications for Gondwana Assembly  

NASA Astrophysics Data System (ADS)

This paper documents the 20 to 60 km wide N-S trending Angavo Shear Zone (ASZ) in central Madagascar and its tectonic implications by examining its structural styles, kinematics and geometry. Our study indicates that the ASZ is characterized by at least two ductile Late Proterozoic deformation events (D1 and D2) followed by a brittle neotectonic deformation (D3). The early D1 event produced a regionally extensive S1 foliation, stretching/flattening mineral lineation L1 and symmetrical structural fabrics such as recumbent and isoclinal intra-folial folds (F1), implying a flattening deformation. D1 deformational fabrics are locally overprinted by D2 structures. D2 is characterized by a penetrative S2 foliation, shallow south plunging L2 lineation, asymmetric and sheath folds (F2) consistent with a right lateral sense of movement exhibited by delta- and sigma-type porphyroclast systems and asymmetric boudinage fabrics. D2 represents a non-coaxial flow regime formed in a dextral west over east shear zone during a partitioned transpression in response to east-west-directed compression during the assembly of Gondwana. A close resemblance with the Achankovil shear zone in India is noticed; however the continuation of the ASZ in Africa is uncertain.

Raharimahefa, Tsilavo; Kusky, Timothy M.; Toraman, Erkan; Rasoazanamparany, Christine; Rasaonina, Imboarina

2013-04-01

144

A late Devonian impact event and its association with a possible extinction event on Eastern Gondwana  

NASA Technical Reports Server (NTRS)

Evidence from South China and Western Australia for a 365-Ma impact event in the Lower crepida conodont zone of the Famennian stage of the Late Devonian (about 1.5 Ma after the Frasnian/Famennian extinction event) includes microtektitelike glassy microspherules, geochemical anomalies (including a weak Ir), a probable impact crater (greater than 70 k) at Taihu in South China, and an Ir anomaly in Western Australia. A brachiopod faunal turnover in South China, and the 'strangelove ocean'-like c-delta 13 excursions in both Chinese and Australian sections indicate that at least a regional-scale extinction might have occurred at the time of the impact. A paleoreconstruction shows that South China was very close to and facing Western Australia in the Late Devonian. The carbon isotopic excursions, which occur at the same stratigraphic level in both South China and Western Australia cannot be explained as being coincidental. The c-delta 13 excursions and the brachiopod faunal turnover in South China indicate that there might have been at least a regional (possibly global) extinction in the Lower crepida zone. The impact-derived microspherules and geochemical anomalies (especially the Ir) indicate a Lower crepida zone impact event on eastern Gondwana. The location, type of target rocks, and possibly age of the Taihu Lake crater qualify as the probable site of this Late Devonian impact.

Wang, K.; Geldsetzer, H. H. J.

1992-01-01

145

Review on the Precambrian geotectonics of the Brazilian Shield and its correlations within West Gondwana  

NASA Astrophysics Data System (ADS)

Within the Brazilian Shield, Paleoproterozoic and Mesoproterozoic rocks are widespread in the large Amazonian Craton, as well as in the São Francisco, São Luiz, Rio de La Plata and other smaller cratonic fragments. Archean nuclei are present as granite-greenstone terrains in the Carajás region and in Central Bahia, and as medium to high-grade crustal fragments within younger belts. The Neoproterozoic tectonic provinces of Borborema, Tocantins and Mantiqueira, that include several orogenic belts active between 950 and 520 Ma, are associated to the process of agglutination of West Gondwana. Their correlative tectonic units in West and South-West Africa are the Trans-Saharan, West Congo, Damara, Gariep and Saldania belts. Juvenile, mantle derived, intra-oceanic magmatic arcs are found within the Tocantins province and the Trans-Saharan belt. They are associated to the Transbrasiliano lineament in South America, and indicate the existence of a large oceanic domain separating Amazonia and West-Africa from the São Francisco-Congo craton in the Neoproterozoic. On the other hand, the crustal signature of granitoid rocks suggests that the Neoproterozoic Adamastor ocean may not have been very large, and that the Rio de La Plata and Kalahari cratons were always relatively close together and to the São Francisco-Congo.

Cordani, U. G.

2003-04-01

146

Geology and metallogeny of the Ar Rayn terrane, eastern Arabian shield: Evolution of a Neoproterozoic continental-margin arc during assembly of Gondwana within the East African orogen  

USGS Publications Warehouse

The Neoproterozoic Ar Rayn terrane is exposed along the eastern margin of the Arabian shield. The terrane is bounded on the west by the Ad Dawadimi terrane across the Al Amar fault zone (AAF), and is nonconformably overlain on the east by Phanerozoic sedimentary rocks. The terrane is composed of a magmatic arc complex and syn- to post-orogenic intrusions. The layered rocks of the arc, the Al Amar group (>689 Ma to ???625 Ma), consist of tholeiitic to calc-alkaline basaltic to rhyolitic volcanic and volcaniclastic rocks with subordinate tuffaceous sedimentary rocks and carbonates, and are divided into an eastern and western sequence. Plutonic rocks of the terrane form three distinct lithogeochemical groups: (1) low-Al trondhjemite-tonalite-granodiorite (TTG) of arc affinity (632-616 Ma) in the western part of the terrane, (2) high-Al TTG/adakite of arc affinity (689-617 Ma) in the central and eastern part of the terrane, and (3) syn- to post-orogenic alkali granite (607-583 Ma). West-dipping subduction along a trench east of the terrane is inferred from high-Al TTG/adakite emplaced east of low-Al TTG. The Ar Rayn terrane contains significant resources in epithermal Au-Ag-Zn-Cu-barite, enigmatic stratiform volcanic-hosted Khnaiguiyah-type Zn-Cu-Fe-Mn, and orogenic Au vein deposits, and the potential for significant resources in Fe-oxide Cu-Au (IOCG), and porphyry Cu deposits. Khnaiguiyah-type deposits formed before or during early deformation of the Al Amar group eastern sequence. Epithermal and porphyry deposits formed proximal to volcanic centers in Al Amar group western sequence. IOCG deposits are largely structurally controlled and hosted by group-1 intrusions and Al Amar group volcanic rocks in the western part of the terrane. Orogenic gold veins are largely associated with north-striking faults, particularly in and near the AAF, and are presumably related to amalgamation of the Ar Rayn and Ad Dawadimi terranes. Geologic, structural, and metallogenic characteristics of the Ar Rayn terrane are analogous to the Andean continental margin of Chile, with opposite subduction polarity. The Ar Rayn terrane represents a continental margin arc that lay above a west-dipping subduction zone along a continental block represented by the Afif composite terrane. The concentration of epithermal, porphyry Cu and IOCG mineral systems, of central arc affiliation, along the AAF suggests that the AAF is not an ophiolitic suture zone, but originated as a major intra-arc fault that localized magmatism and mineralization. West-directed oblique subduction and ultimate collision with a land mass from the east (East Gondwana?) resulted in major transcurrent displacement along the AAF, bringing the eastern part of the arc terrane to its present exposed position, juxtaposed across the AAF against a back-arc basin assemblage represented by the Abt schist of the Ad Dawadimi terrane. Our findings indicate that arc formation and accretionary processes in the Arabian shield were still ongoing into the latest Neoproterozoic (Ediacaran), to about 620-600 Ma, and lead us to conclude that evolution of the Ar Rayn terrane (arc formation, accretion, syn- to postorogenic plutonism) defines a final stage of assembly of the Gondwana supercontinent along the northeastern margin of the East African orogen. ?? 2007 Elsevier B.V. All rights reserved.

Doebrich, J. L.; Al-Jehani, A. M.; Siddiqui, A. A.; Hayes, T. S.; Wooden, J. L.; Johnson, P. R.

2007-01-01

147

Metamorphic Evolution of Selected Pan-African Terrains across central Gondwana  

NASA Astrophysics Data System (ADS)

New petrological and metamorphic constraints from three Pan-African mobile belts across the main collisional suture zone that separates East and West Gondwana are presented. These include: (a) the Wadi Kariem area in Eastern Desert of Egypt, (b) the Wadi Taba-El-Kid in Sinai, Egypt and (c) Western Dronning Maud Land, East Antarctica. The metamorphic results from these three terrains are compared and provide insight into the nature of Pan-African crust formation processes during Gondwana assembly. Thermodynamic modelling in THERMOCALC combined with conventional thermobarometry is used to derive metamorphic PT-estimates. However, we show that for low-grade rocks deriving PT-constraints is challenging and requires a multi-disciplinary thermodynamic modelling approach. In addition, a new thermodynamic solid-solution model is presented for the epidote mineral group, whereby the M2 site contains only Al3+ and Fe3+ and Mn3+ prefers to substitute Al3+ in the M3 site. Pseudosection modelling shows that the substitution process between Fe3+ and Al3+ in the M3 and the M1 sites is sensitive to pressure, which suggests using epidote mineral compositions in geobarometry. Wadi Kariem in the Eastern Desert of Egypt consists of a low-grade volcanic arc sequence that covers a higher-grade, biotite-garnet gneiss metamorphic core complex, namely the Meatiq Complex. A sinistral shear zone, the Najd Fault System, separates the high-grade rocks from the low-grade volcanic sequence. Using pseudosection modelling combined with epidote mineral isopleths, both the high-grade and the low-grade rocks show single clockwise P-T paths. The peak metamorphic conditions of the high-grade rocks are T = 700-750 oC and P = 6-7 kbar, whereas the low-grade rocks record conditions of T = 350-400 oC and P = 3-4 kbar. In Sinai, the Najd Fault System is not exposed due to the voluminous intrusion of ca. 540 Ma post-tectonic granites. However, both the garnet-biotite gneisses of the Taba area (T = 650-700 oC and P = 6 kbar) and the low-grade rocks (T = 400-450 oC and P = 2-3 kbar) of Wadi El Kid record very similar metamorphic conditions and clockwise P-T paths to those in Eastern Desert, Egypt. In western Dronning Maud Land (Antarctica), a petrological and metamorphic comparison of Mesoproterozoic metabasic rocks on the eastern margin of the Archean Grunehogna Craton and the adjacent Maud Belt, revealed a difference in peak metamorphic conditions from T = 280 ± 30 oC to 710-750 oC and P = 2 ± 1.5 to 8.5-11 kbar over a distance of only 30 km across a major glacial valley. The high-grade PT-constraints derived for the western extreme of the Maud Belt, is very similar to that reported for the eastern Maud Belt dated at ca. 550 Ma. These PT-constraints do not support the presence of a westward decreasing metamorphic field gradient within the Maud Belt as previously proposed. The data presented here suggests that the inferred sub-glacial boundary between the Grunehogna Craton and the Maud Belt, might reflect a major Pan-African thrust, with the Maud Belt representing the continuation of the East African Mozambique Belt into East Antarctica.

Abu-Alam, T. S.; Grosch, E. G.

2012-12-01

148

Early to mid Cretaceous vegetation of northern Gondwana - the onset of angiosperm radiation and climatic implications  

NASA Astrophysics Data System (ADS)

Early Cretaceous Northern Gondwana seems to be the cradle of many early flowering plants, especially mesangiosperms that include magnoliids and monocots and basal eudicots. So far our knowledge was based mostly on dispersed pollen and small flowering structures. New fossil finds from Brazil include more complete plants with attached roots, leaves and flowers. Taxonomic studies show that these fossils belonged to clades which are, based on macroscopic characters and molecular data, also considered to be rather basal, such as several members of Nymphaeales, Piperales, Laurales, Magnoliales, monocots (Araliaceae) and Ranunculales. Various parameters can be used in order to understand the physiology and habitat of these plants. Adaptations to climate and habitat are partly mirrored in their root anatomy (evidence of tap roots), leaf size and shape, leaf anatomy including presence of glands, and distribution of stomata. An important ecophysiolocical parameter is vein density as an indicator for the plants' cabability to pump water, and the stomatal pore index, representing the proportion of stomatal pore area on the leaf surface, which is related to the water vapor resistance of the leaf epidermis. During the mid-Cretaceous leaf vein density started to surpass that of gymnosperms, one factor that made angiosperms very successful in conquering many kinds of new environments. Using data on these parameters we deduce that during the late Early to mid Cretaceous angiosperms were already diverse, being represented as both herbs, with aquatic members, such as Nymphaeles, helophytes (e.g. some monocots) and plants that may have grown in shady locations. Other life forms included shrubs and perhaps already small trees (e.g. Magnoliales). These flowering plants occupied various habitats, ranging from xeric (e.g. some Magnoliales) to mesic and shady (e.g. Piperales) or aquatic (e.g. Araceae, Nymphaeales). Overall, it seems that several of these plants clearly exhibited some mechanisms to withstand drought, which in turn let us assume that the climate was characterized by dry and wet seasons.

Coiffard, Clément; Mohr, Barbara

2014-05-01

149

Changes in carbon dioxide during an oceanic anoxic event linked to intrusion into Gondwana coals.  

PubMed

The marine sedimentary record exhibits evidence for episodes of enhanced organic carbon burial known as 'oceanic anoxic events' (OAEs). They are characterized by carbon-isotope excursions in marine and terrestrial reservoirs and mass extinction of marine faunas. Causal mechanisms for the enhancement of organic carbon burial during OAEs are still debated, but it is thought that such events should draw down significant quantities of atmospheric carbon dioxide. In the case of the Toarcian OAE (approximately 183 million years ago), a short-lived negative carbon-isotope excursion in oceanic and terrestrial reservoirs has been interpreted to indicate raised atmospheric carbon dioxide caused by oxidation of methane catastrophically released from either marine gas hydrates or magma-intruded organic-rich rocks. Here we test these two leading hypotheses for a negative carbon isotopic excursion marking the initiation of the Toarcian OAE using a high-resolution atmospheric carbon dioxide record obtained from fossil leaf stomatal frequency. We find that coincident with the negative carbon-isotope excursion carbon dioxide is first drawn down by 350 +/- 100 p.p.m.v. and then abruptly elevated by 1,200 +/- 400 p.p.m.v, and infer a global cooling and greenhouse warming of 2.5 +/- 0.1 degrees C and 6.5 +/- 1 degrees C, respectively. The pattern and magnitude of carbon dioxide change are difficult to reconcile with catastrophic input of isotopically light methane from hydrates as the cause of the negative isotopic signal. Our carbon dioxide record better supports a magma-intrusion hypothesis, and suggests that injection of isotopically light carbon from the release of thermogenic methane occurred owing to the intrusion of Gondwana coals by Toarcian-aged Karoo-Ferrar dolerites. PMID:15917805

McElwain, Jennifer C; Wade-Murphy, Jessica; Hesselbo, Stephen P

2005-05-26

150

Provenance of north Gondwana Cambrian-Ordovician sandstone: U-Pb SHRIMP dating of detrital zircons from Israel and Jordan  

USGS Publications Warehouse

A vast sequence of quartz-rich sandstone was deposited over North Africa and Arabia during Early Palaeozoic times, in the aftermath of Neoproterozoic Pan-African orogeny and the amalgamation of Gondwana. This rock sequence forms a relatively thin sheet (1-3 km thick) that was transported over a very gentle slope and deposited over a huge area. The sense of transport indicates unroofing of Gondwana terranes but the exact provenance of the siliciclastic deposit remains unclear. Detrital zircons from Cambrian arkoses that immediately overlie the Neoproterozoic Arabian-Nubian Shield in Israel and Jordan yielded Neoproterozoic U-Pb ages (900-530 Ma), suggesting derivation from a proximal source such as the Arabian-Nubian Shield. A minor fraction of earliest Neoproterozoic and older age zircons was also detected. Upward in the section, the proportion of old zircons increases and reaches a maximum (40%) in the Ordovician strata of Jordan. The major earliest Neoproterozoic and older age groups detected are 0.95-1.1, 1.8-1.9 and 2.65-2.7 Ga, among which the 0.95-1.1 Ga group is ubiquitous and makes up as much as 27% in the Ordovician of Jordan, indicating it is a prominent component of the detrital zircon age spectra of northeast Gondwana. The pattern of zircon ages obtained in the present work reflects progressive blanketing of the northern Arabian-Nubian Shield by Cambrian-Ordovician sediments and an increasing contribution from a more distal source, possibly south of the Arabian-Nubian Shield. The significant changes in the zircon age signal reflect many hundreds of kilometres of southward migration of the provenance. ?? 2006 Cambridge University Press.

Kolodner, K.; Avigad, D.; McWilliams, M.; Wooden, J. L.; Weissbrod, T.; Feinstein, S.

2006-01-01

151

Nouvelles découvertes de vertébrés dévoniens en Amérique du Sud et leurs implications dans le contact entre le Gondwana et l'Euramérique.  

NASA Astrophysics Data System (ADS)

A new fossil fish fauna from western Venezuela provides the first South American Devonian record of antiarch and phyllolepid placoderms, and sarcopterygians including lungfishes, groups widely distributed on other continents. Endemic elements in the fish fauna indicate Gondwana affinities, and the age of the phyllolepid placoderm occurrence is consistent with a model of biotic dispersal between Gondwana and Euramerica near the Frasnian-Famennian boundary. A narrow marine barrier separating northern and southern landmasses is indicated, in contrast to the wide equatorial ocean for the Late Devonian postulated from palaeomagnetic data.

Young, Gavin C.; Moody, John M.; Casas, Jhonny E.

2000-12-01

152

The deep crust beneath island arcs: Inherited zircons reveal a Gondwana continental fragment beneath East Java, Indonesia  

NASA Astrophysics Data System (ADS)

Inherited zircons in Cenozoic sedimentary and igneous rocks of East Java range in age from Archean to Cenozoic. The distribution of zircons reveals two different basement types at depth. The igneous rocks of the Early Cenozoic arc, found along the southeast coast, contain only Archean to Cambrian zircons. In contrast, clastic rocks of north and west of East Java contain Cretaceous zircons, which are not found in the arc rocks to the south. The presence of Cretaceous zircons supports previous interpretations that much of East Java is underlain by arc and ophiolitic rocks, accreted to the Southeast Asian margin during Cretaceous subduction. However, such accreted material cannot account for the older zircons. The age populations of Archean to Cambrian zircons in the arc rocks are similar to Gondwana crust. We interpret the East Java Early Cenozoic arc to be underlain by a continental fragment of Gondwana origin and not Cretaceous material as previously suggested. Melts rising through the crust, feeding the Early Cenozoic arc, picked up the ancient zircons through assimilation or partial melting. We suggest a Western Australian origin for the fragment, which rifted from Australia during the Mesozoic and collided with Southeast Asia, resulting in the termination of Cretaceous subduction. Continental crust was therefore present at depth beneath the arc in south Java when Cenozoic subduction began in the Eocene.

Smyth, H. R.; Hamilton, P. J.; Hall, R.; Kinny, P. D.

2007-06-01

153

Structural anatomy of a dismembered ophiolite suite from Gondwana: The Manamedu complex, Cauvery suture zone, southern India  

NASA Astrophysics Data System (ADS)

Detailed geological and structural mapping of the Manamedu ophiolite complex (MOC), from the south-eastern part of the Cauvery suture zone (CSZ) within the Gondwana collisional suture in southern India reveals the anatomy of a dismembered ophiolite succession comprising pyroxenite actinolite-hornblendite, hornblendite, gabbro-norite, gabbro, anorthosite, amphibolite, plagiogranite, mafic dykes, and associated pelagic sediments such as chert-magnetite bands and carbonate horizons. The magmatic foliation trajectory map shows inward dipping foliations and a variety of fold structures. Structural cross-sections of the MOC reveal gentle inward dips with repetition and omission of different lithologies often marked by curvilinear hinge lines. The succession displays imbricate thrust sheets and slices of dismembered ophiolite suites distributed along several localities within the CSZ. The MOC can be interpreted as a deformed large duplex structure associated with south-verging back thrust system, consistent with crustal-scale 'flower structure'. The nature and distribution of ophiolitic rocks in the CSZ suggest supra-subduction zone setting associated with the lithospheric subduction of the Neoproterozoic Mozambique Ocean, followed by collision and obduction during the final stage of amalgamation of the Gondwana supercontinent in the end Precambrian.

Chetty, T. R. K.; Yellappa, T.; Nagesh, P.; Mohanty, D. P.; Venkatasivappa, V.; Santosh, M.; Tsunogae, T.

2011-08-01

154

Magma sources during Gondwana breakup: chemistry and chronology of Cretaceous magmatism in Westland, New Zealand  

NASA Astrophysics Data System (ADS)

Cretaceous-Paleogene rifting of the Eastern Gondwana margin thinned the continental crust of Zealandia and culminated in the opening of the Tasman Sea between Australia and New Zealand and the Southern Ocean, separating both from Antarctica. The Western Province of New Zealand consists of a succession of metasedimentary rocks intruded by Palaeozoic and Mesozoic granitoids that formed in an active margin setting through the Phanerozoic. Upon cessation of subduction, the earliest stages of extension (~110-100 Ma) were expressed in the formation of metamorphic core complexes, followed by emplacement of granitoid plutons, the deposition of terrestrial Pororari Group sediments in extensional half-grabens across on- and offshore Westland, and the intrusion of mafic dikes from ~90 Ma. These dikes are concentrated in the swarms of the Paparoa and Hohonu Ranges and were intruded prior to and simultaneous with volumetrically minor A-type plutonism at 82 Ma. The emplacement of mafic dikes and A-type plutonism at ~82 Ma is significant as it coincides with the age of the oldest seafloor in the Tasman Sea, therefore it represents magmatism coincident with the initiation of seafloor spreading which continued until ~53 Ma. New 40Ar-39Ar ages indicate that the intrusion of mafic dikes in basement lithologies both preceded and continued after the initial opening of the Tasman Sea, including an additional population of ages at ~70 Ma. This indicates either a prolonged period of extension-related magmatism that continued >10 Ma after initial breakup, or two discrete episodes of magmatism during Tasman Sea spreading. Volumetrically minor Cenozoic within-plate magmatism continued sporadically throughout the South Island and bears a characteristic HIMU (high time integrated U/Pb) signature. A detailed geochemistry and chronological study of Cretaceous mafic and felsic magmatism is currently in progress and aims to better understand the transition of magma sources from a long lived active continental margin through breakup to a passive setting, and to constrain the onset and evolution of the chemical characteristics of the magmas and their sources, including the origin of the distinctive HIMU signature.

van der Meer, Quinten H. A.; Waight, Tod E.; Scott, James M.

2013-04-01

155

The Río de la Plata craton and the assembly of SW Gondwana  

NASA Astrophysics Data System (ADS)

The extent and nature of the Archaean-Palaeoproterozoic craton of Río de la Plata of southern South America, a major but poorly understood crustal component in Neoproterozoic plate reconstructions, as well as the depositional, metamorphic and magmatic history of the surrounding orogenic belts, are reviewed and reassessed, in part through the analysis of material recovered from deep boreholes in western Argentina that penetrated Palaeozoic cover into basement. U-Pb SHRIMP zircon ages for these samples of 2162 ± 6 Ma (diorite), 2189 ± 14 Ma (amphibolitic schist) and 2088 ± 6 Ma (granite) encompass the range of ages determined for the major Palaeoproterozoic orogenic events in the exposed parts of the craton close to the Atlantic coasts of Uruguay and Argentina. Taken together with the geochemical and Nd-isotope characteristics of these samples and an olivine gabbro from a further borehole that failed to yield zircon, these results strongly suggest that the Río de la Plata craton is extremely uniform in its dominant chrono-tectonic and lithological make-up, and that it extends westwards as far as the 535-520 Ma Pampean orogenic belt, against which it probably has a fault contact. U-Pb SHRIMP zircon detrital age patterns are presented for representative metasedimentary samples from the craton cover in the Tandilia belt of eastern Argentina, and from the Pampean (Cambrian) and Famatinian (Ordovician) belts to the west of the craton. Whereas the oldest cover rocks in Tandilia clearly show material derived from the underlying craton, such detritus only appears in the younger (Ordovician) units to the west. Sedimentary protoliths in the Pampean belt were dominated by Neoproterozoic (broadly ˜ 600 Ma) and late Mesoproterozoic (broadly ˜ 1100 Ma) provenance, and derivation from the Río de la Plata craton is highly unlikely. Regional considerations, including previously published zircon data, palaeocurrent and structural data, suggest that these rocks must have had an origin within Gondwana-forming blocks, for which the closest identifiable sources are 'Brazilian' and 'African' (Namaqua-Natal). Consequently, the preferred model for the Pampean orogeny is that the Río de la Plata craton reached its present position by large-scale dextral strike-slip movement against fore-arc sedimentary sequences that had developed on the southern and western margins of the Kalahari craton during the Early Cambrian. In the final stage the displaced sedimentary sequences outboard of the RPC collided with the Mesoproterozoic Western Sierras Pampeanas terrane, which was at the time attached to the large Amazonia craton and other smaller continental blocks, such as Arequipa-Antofalla and Río Apa. Protracted relative displacement of the RPC after the Pampean Orogeny led to its final position.

Rapela, C. W.; Pankhurst, R. J.; Casquet, C.; Fanning, C. M.; Baldo, E. G.; González-Casado, J. M.; Galindo, C.; Dahlquist, J.

2007-07-01

156

Is the Palaeozoic of Istanbul a part of Gondwana-Land or Laurasia, or both?  

NASA Astrophysics Data System (ADS)

The Istanbul Zone, northwestern Turkey, located along the southwestern Black Sea coast, consists of a Neoproterozoic (almost entirely Ediacaran) middle to high-grade crystalline basement with relicts of oceanic lithosphere, volcanic arc and continental crust of unknown affinity and it is overlain by a continuous, well-developed transgressive sedimentary sequence extending from the late Ordovician to the Carboniferous. The Palaeozoic sequence was folded and thrust-faulted during the Carboniferous Hercynian orogeny, and is unconformably overlain by Lower Triassic and younger sedimentary strata. The Istanbul Zone is separated from the Sakarya Zone by the Intra- Pontide suture of early to medial Eocene and from the Strandja Massif by an inferred right-lateral strike-slip West Black Sea Fault. The Sakarya and Strandja fragments exhibit late Triassic and late Jurassic-Early Cretaceous metamorphism and deformation, respectively, which are not observed in the Istanbul Zone. The Palaeozoic sequences of Istanbul and Zonguldak have been compared and correlated with similar sequences in Europe, including the Moesian platform in Romania and Bulgaria, Moravo-Silesia (Brunovistulian) in the Czech Republic and the Rhenohercynian zone in Germany and Belgium, all deposited on the northern passive margin of the Rheic ocean. However, these correlations are based on insufficient knowledge of the correlated rock sequences. By contrast, the ?stanbul sequence resembles the Carnic Alps, the Montaigne Noir, the Bohemian (Saxo-Thuringian), the Morocco, the Pyrenean sequences and thus northern Gondwana-Land of the Palaeozoic times. Istanbul Zone thus combines the characteristics of both the north and south Hercynian margins! The Istanbul Zone shows characteristics of graben-facies deposits during the Ordovician-early Silurian followed by Atlantic-type continental margin sediments of late Silurian- late Devonian age. Since the arc is missing, the ocean facing ?stanbul must have been consumed in a now unknown direction, colliding with a now unidentified Devonian-Carboniferous magmatic arc. The Carboniferous flysch of the Trakya Formation marks the progress of this collision. That collision created a dominantly (now) west vergent marginal fold and thrust belt on the eastern side of the Bosphorous and what now seems an east vergent (but with many inconsistencies) on the western side as a retrocharriage. The region of ?stanbul shows essentially no metamorphism and only a weak cleavage development. What collided with ?stanbul is unknown. The structural style of folds and faults in ?stanbul requires a décollement underneath the whole city which thrusts the entire structure westward.

Lom, Nalan; Ülgen, Semih Can; Özgül, Necdet; Celal ?engör, A. M.

2014-05-01

157

Sub-horizontal channel flow: an exhumation mechanism during the Gondwana collision  

NASA Astrophysics Data System (ADS)

The Arabian-Nubian Shield is made up of juvenile crust which was formed due to arc-arc accretion during the East- and West-Gondwana collision (Pan-African event) and the closing of the Mozambique Ocean. Thus the shield is composed of ophiolitic and volcanic material with oceanic affinity. However rocks with continental affinity can be found as high grade metamorphic complexes that were exposed from underneath the arc-related rocks during the late stages of the Pan-African event. Two tectonic models explain the exhumation mechanism of these metamorphic complexes. The first model is exhumation as core complexes in extension setting. This model appears to pertain to the metamorphic complexes of the Eastern Desert of Egypt. The second model is exhumation in oblique transpressional regime as it was found - for example - for the Feiran-Solaf complex of Sinai Peninsula. These models are correct with regard to the structural elements in the outer zones of the metamorphic complexes, which formed during the final exhumation mechanism during the later stages of the deformation history (e.g. D3 of the Feiran complex). However the models cannot explain the sub-horizontal lineations that formed during the early deformation phases and are still recorded in the core of the metamorphic complexes (e.g. D1 of the Feiran-Solaf complex). Here we propose sub-horizontal channel flow as a mechanism to exhume the metamorphic complexes and a mechanism that can account for both types of structural elements as part of one exhumation history. We suggest that the rocks flowed horizontally at mid-crustal levels to the NW of the Arabian-Nubian Shield. The front of the channel flows was then exhumed to the Earth surface in a transpression regime. This middle crustal flow will produce extensional tectonic regime in the upper crust (i.e. ?3 is horizontal and oriented in the NW-SE direction). This extensional setting produces low-angle detachments which assisted the middle crustal rocks to be exhumed as tectonic windows of the Eastern Desert of Egypt. The complexes then can be exhumed completely to the Earth surface in either extensional or oblique transpressional regime depend on the orientation of the principle stresses. Examples from Saudi Arabia will be presented during the EGU2013 to demonstrate this new tectonic model.

Abu-Alam, Tamer; Stüwe, kurt

2013-04-01

158

The largest flying reptile from Gondwana: a new specimen of Tropeognathus cf. T. mesembrinus Wellnhofer, 1987 (Pterodactyloidea, Anhangueridae) and other large pterosaurs from the Romualdo Formation, Lower Cretaceous, Brazil.  

PubMed

A very large pterosaur (MN 6594-V) from the Romualdo Formation (Aptian/Albian), Santana Group, Araripe Basin, is described. The specimen is referred to Tropeognathus cf. T. mesembrinus mainly due to the presence of a low and blunt frontoparietal crest, the comparatively low number of teeth and the inclined dorsal part of the occipital region. Two distinct wingspan measurements for pterosaurs are introduced: the maximized wingspan (maxws), which essentially consists of doubling the addition of all wing elements and the length of the scapula or the coracoid (the smaller of the two), and the normal wingspan (nws), which applies a reducing factor (rfc) to the maximized wingspan to account for the natural flexures of the wing. The rfc suggested for pteranodontoids is 5%. In the case of MN 6594-V, the maxws and nws are 8.70 m and 8.26 m, respectively, making it the largest pterosaur recovered from Gondwana so far. The distal end of a larger humerus (MCT 1838-R) and a partial wing (MPSC R 1395) are also described showing that large to giant flying reptiles formed a significant part of the pterosaur fauna from the Romualdo Formation. Lastly, some comments on the nomenclatural stability of the Santana deposits are presented. PMID:23538956

Kellner, Alexander W A; Campos, Diogenes A; Sayão, Juliana M; Saraiva, Antônio A F; Rodrigues, Taissa; Oliveira, Gustavo; Cruz, Lilian A; Costa, Fabiana R; Silva, Helder P; Ferreira, Jennyfer S

2013-03-01

159

Deep seismic reflection profiling of sedimentary basins offshore Brazil: Geological objectives and preliminary results in the Sergipe Basin  

NASA Astrophysics Data System (ADS)

The first deep seismic reflection profiles offshore Brazil were acquired in Campos Basin and processed to 10 s TWT in 1984. Starting in 1989, Petrobrás acquired an extensive data set of deep seismic profiles using special acquisition equipment capable of effectively penetrating through the sedimentary layers and imaging the whole crustal architecture. These deep (18 s TWT) seismic reflection profiles extend across the Atlantic-type marginal basins, from the platform to the deepwater province, presently considered frontier regions for petroleum exploration. This work addresses the geological objectives of a deep seismic profile in the Sergipe Basin and discusses the results obtained by integrating regional seismic, gravity and magnetic data. When combined, these data provide evidence that deep seismic reflectors observed in the Sergipe Basin are related to intracrustal-upper mantle structures rather than sedimentary features. The deep seismic reflection profile in the Sergipe Basin also suggests that, rather than a non-volcanic passive margin, the deepwater extension of this basin is marked by several magmatic structures, including thick wedges of seaward-dipping reflectors and volcanic plugs. These magmatic features are associated with basinforming processes resulting from lithospheric extension during the breakup of Gondwana in the Early Cretaceous and subsequent emplacement of oceanic crust. These results are compared to the crustal scale structures observed in the Campos Basin, in the southeastern margin of Brazil. The interpretation of the deep structure of these basins indicates that final separation between the South American and African plates formed passive margins characterized by different patterns of crustal attenuation underlying the rift blocks.

Mohriak, Webster Ueipass; Lira Rabelo, JoséHenrique; De Matos, Renato Darros; De Barros, Mozart C.

1995-12-01

160

Punctuated Caledonian accretion on the fragmented (East Avalonian) Palaeozoic margin of Peri-Gondwana - a record from Anglesey (Ynys Môn), NW Wales, UK  

NASA Astrophysics Data System (ADS)

Late Neoproterozoic accretion at the outboard margin of East Avalonia is recorded on Anglesey in ca. 650 Ma metamorphism in the Coedana Complex, the ca. 615 Ma supra-subduction zone Coedana Granite, and ca. 560 Ma exhumation of the Penmynydd Zone blueschists. However, much of Anglesey's present architecture is a product of accretionary collisions that commenced in the Early Ordovician when coaxial to intensely non-coaxial deformation assembled the Late Neoproterozoic rocks with the Middle Cambrian (to earliest? Ordovician) Monian Supergroup greenschist facies metasediments. In western Anglesey, the Monian Supergroup rocks record initial (D1) NW-facing coaxial deformation but SE-vergent, strongly non-coaxial, D2/D3 strain reorients the earlier structures after an episode of mafic magmatism. In northern Anglesey, Monian Supergroup rocks record only SE-facing deformation from the onset of collision. Deformed mafic igneous rocks and slices of garnetiferous basement gneiss are located between these structurally distinct regions and suggest separation of the Monian tracts prior to the (earliest-Arenig?) onset of collision. This cycle is contemporaneous with Penobscottian accretion in the northern Appalachians and Newfoundland. The Monian rocks were at surface (and deeply weathered?) before sub-aerial eruption of the (mid-Arenig?) Church Bay Tuff Formation. The tuffs are overlain unconformably by a Upper Arenig to Llandovery marine transtensional foreland basin succession. Renewed convergence resulted in a SSE-vergent (late-Salinic?) fold and thrust imbricate stack. Locally, thrusts override molasse deposits derived from an advancing thrust sheet and the basal thrust must have been emergent at the foot of an active fault. This theme of active over-riding of tectonic molasse is continued in Anglesey until the Early Devonian at least. The axially sourced fluvial Old Red Sandstone of central eastern Anglesey is arranged in south-vergent folds and thrusts during Acadian deformation. This fragment of the UK Caledonides is an important trans-Atlantic link to the Appalachian geology of North America. The geology of Ynys Môn serves to remind us of the geometrical complexity of the continental fragments that make up Palaeozoic peri-Gondwana, and of the episodic collision that accompanied punctuated accretion of the orogenic wedge. There is no single key to a solution - only total geology.

Leslie, Graham; Schofield, David; Wilby, Philip

2013-04-01

161

The Choiyoi volcanic province at 34°S-36°S (San Rafael, Mendoza, Argentina): Implications for the Late Palaeozoic evolution of the southwestern margin of Gondwana  

NASA Astrophysics Data System (ADS)

The Choiyoi rhyolitic province of Chile and Argentina (23°S-42°S) was emplaced at the SW margin of Gondwana during the Permian. The San Rafael Massif (Mendoza, Argentina, 34°-36°S), is a key area to analyse the relative timing of Choyoi magmatism and related deformation as it bears one of the most complete and well exposed succession. Stratigraphic, structural and magmatic studies indicate that major changes of geodynamic conditions occurred during the Permian since arc-related sequences syntectonic with transpression (lower Choiyoi) were followed by transitional to intraplate, postorogenic suites coeval with transtension (upper Choiyoi). During the Early Permian, a major event of N-NNW dextral transpressional motions deformed the Carboniferous foreland basin in the San Rafael Massif. This event is attributed to the first episode of the San Rafael orogeny and can be related to oblique subduction (Az. 30°) of the Palaeo-Pacific plate. Ca. 280 Ma the inception of voluminous calc-alkaline volcanism (lower Choiyoi) syntectonic with WNW sinistral transpression of the second episode of the San Rafael orogeny, is associated with an eastward migration of the magmatic arc at this latitude. To the southeast of San Rafael, magmatism and transpression continued to migrate inland suggesting that a progressively younger, WNW, sinistral, thick skinned deformation belt broadens into the foreland and can be traced from San Rafael to Sierra de la Ventana, linking the San Rafael orogeny with the Gondwanide orogeny of the Cape Fold Belt in South Africa. This distribution of magmatism and deformation is interpreted as being the consequence of a progressive shallowing of the Palaeo-Pacific plate starting to the north of San Rafael, and culminating with a flat-slab region south of 36°S. Ca. 265 Ma the onset of predominantly felsic volcanism (upper Choiyoi) in San Rafael occurred in a Post-San Rafael extensional setting. Kinematic indicators and strain fabric analyses of San Rafael orogeny transpression and Post-San Rafael extension show a tectonic reversion. The Post-San Rafael event could be the result of the extensional collapse of the San Rafael orogen, triggered by continental-scale clockwise rotations. These rotations would account for subduction ceasing earlier in the north (31°S-36°S) than in the south, thus explaining the coexistence, after ˜ 265 Ma, of extension in San Rafael with compression in the Sierra de la Ventana-Cape Fold Belt area.

Kleiman, Laura E.; Japas, María S.

2009-08-01

162

Pangea Megasequences of Tethyan Gondwana-margin reflect global changes of climate and tectonism in Late Palaeozoic and Early Triassic times—A review  

Microsoft Academic Search

The maximum concentration of continental crust at the Pangea stage is characterized by a specific depositional sequence generally referred to as the Pangea Megasequence. Extending in time from the Late Carboniferous to the middle of the Triassic, the succession exhibits similar trends across the whole of Gondwana. Invariably, the sequence was initiated by Late Carboniferous to Early Permian glacial and

H. Wopfner; X. C. Jin

2009-01-01

163

Stratigraphy of Midland basin in regional and global context  

SciTech Connect

A new correlation of 85 well logs provides the data for a continuous set of structure and isopach maps covering one square degree of longitude and latitude from 101 to 102 west and 32 to 33 north. A corresponding set of maps showing paleogeography and tectonics relates each of the above maps to its surroundings in the southwest quarter of North America. A further set of maps of the globe then relates the paleogeographic settings to global plate tectonics. The logs were chosen for an even distribution throughout the study areas and they illustrate the stratigraphic development of the Midland basin from the Early Ordovician up to the middle of the Leonardian stage, i.e., up to the union of Gondwana.

Robinson, R.M. (Robinson Drilling of Texas, Big Spring, TX (United States)); Hayner, D. (Greenstar Exploration, Dallas TX (United States))

1994-03-01

164

New Rb-Sr mineral ages temporally link plume events with accretion at the margin of Gondwana  

USGS Publications Warehouse

Five of six Rb-Sr muscovite mineral isochron ages from the Scotia Metamorphic Complex of the South Orkney Islands, West Antarctica, average 190 ± 4 Ma. The muscovite ages are interpreted to date foliation-formation and thus also accretion and subduction at the Gondwana margin. Coincident picrite and ferropicrite magmatism, indicative of melts from deep-seated depleted mantle, permits a causative link between accretion and the arrival of the Karoo – Ferrar – Chon Aike mantle plume in the Early Jurassic. Three biotite Rb-Sr mineral isochron ages are consistently younger and average 176 ± 5 Ma. The biotite ages may record post-metamorphic cooling or more likely retrogressive metamorphic effects during uplift.

Flowerdew, M.J.; Daly, J.S.; Riley, T.R.

2007-01-01

165

Chromium bioaccumulation in rice grown in contaminated soil and irrigated mine wastewater--a case study at South Kaliapani chromite mine area, Orissa, India.  

PubMed

The level of chromium (Cr) contamination in soils and irrigated mine wastewater at South Kaliapani chromite mine region of Orissa, (India) were investigated. Chromium bioaccumulation in rice plants (Oryza sativa L. cv. Khandagiri) irrigated with Cr+6 contaminated mine wastewater was analyzed along with its attenuation from mine wastewater. The levels of Cr+6 in irrigated mine wastewaters in successive rice grown plots were analyzed on 75 days and 100 days after transplantation of seedlings. Total chromium content in different parts of rice plants and soil samples from different plots was analyzed during harvesting stage (125 days after transplantation). Cr accumulation was significantly high in surface soils (0-20 cm) with a mean value of 11,170 mg kg(-1), but it decreased significantly after the crop harvest. About 70% to 90% reduction of Cr+6 levels was observed in irrigated mine wastewater when passed through successive rice plots. High bio-concentration of Cr in leaves with values ranging from 125-498 mg kg(-1) as compared to stem (25-400 mg kg(-1)) and grain (5-23 mg kg(-1)) was noticed. The reduction of Cr+6 levels is related to plant age, high biomass and area of water passage and was attributed to rhizofiltration technique. PMID:21598771

Mohanty, Monalisa; Pattnaik, Mousumi Madhusmita; Mishra, Aruna Kumari; Patra, Hemanta Kumar

2011-01-01

166

Field trial of the effectiveness of indoor-spraying with pirimiphos-methyl emulsion for malaria control in a tribal area of Phulbani district, Orissa State, India.  

PubMed

A field trial of malaria vector control was conducted in Phulbani district, Orissa, during 1984 and 1985. Indoor-spraying of pirimiphos-methyl emulsion formulation was undertaken at an application rate of 2 g/m2 in two sections (population 14,692) of Nuagaon Primary Health Centre. Houses in two adjacent sections (population 21,450) were sprayed with DDT a water dispersible powder (wdp) formulation at 1 g/m2 for comparison purposes. Operational problems in this area come from the tendency of tribal people to re-plaster over wdp applications. Pre-spray malariological indices in the trial area were 38% slide positivity rate, 37% slide falciparum rate and 12.1% annual parasite incidence. Densities of Anopheles annularis Van der Wulp, An. culicifacies Giles, An. fluviatilis Theobald and other potential malaria vectors were reduced in the pirimiphos-methyl trial area 2-35-fold more than in the area sprayed with DDT. Malariological indices were reduced by 65-68% in the pirimiphos-methyl sprayed area compared with only 26-35% reduction in the DDT sprayed area. Spraymen and villagers experienced no adverse side-effects from residual house-spraying with pirimiphos-methyl emulsion and it is concluded that this organophosphate product has advantages for malaria vector control, especially in operationally difficult situations. PMID:2979544

Das, M; Srivastava, B N; Rao, C K; Thapar, B R; Sharma, G K

1987-07-01

167

Parana basin  

SciTech Connect

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

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

1987-05-01

168

A review of the stratigraphy and sedimentary environments of the Karoo-aged basins of Southern Africa  

NASA Astrophysics Data System (ADS)

The Karoo Basin of South Africa was one of several contemporaneous intracratonic basins in southwestern Gondwana that became active in the Permo-Carboniferous (280 Ma) and continued to accumulate sediments until the earliest Jurassic, 100 million years later. At their maximum areal extent, during the early Permian, these basins covered some 4.5 million km 2. The present outcrop area of Karoo rocks in southern Africa is about 300 000 km 2 with a maximum thickness of some 8000 m. The economic importance of these sediments lies in the vast reserves of coal within the Ecca Group rocks of northern and eastern Transvaal and Natal, South Africa. Large reserves of sandstone-hosted uranium and molybdenum have been proven within the Beaufort Group rocks of the southern Karoo trough, although they are not mineable in the present market conditions. Palaeoenvironmental analysis of the major stratigraphic units of the Karoo succession in South Africa demonstrates the changes in depositional style caused by regional and localized tectonism within the basin. These depocentres were influenced by a progressive aridification of climate which was primarily caused by the northward drift of southwestern Gondwana out of a polar climate and accentuated by the meteoric drying effect of the surrounding land masses. Changing palaeoenvironments clearly influenced the rate and direction of vertebrate evolution in southern Gondwana as evidenced by the numerous reptile fossils, including dinosaurs, which are found in the Karoo strata of South Africa, Lesotho, Namibia and Zimbabwe. During the Late Carboniferous the southern part of Gondwana migrated over the South Pole resulting in a major ice sheet over the early Karoo basin and surrounding highlands. Glacial sedimentation in upland valleys and on the lowland shelf resulted in the Dwyka Formation at the base of the Karoo Sequence. After glaciation, an extensive shallow sea covered the gently subsiding shelf, fed by large volumes of meltwater. Marine clays and muds accumulated under cool climatic conditions (Lower Ecca Group) including the distinctive Mesosaurus-bearing carbonaceous shales of the Whitehill Formation. Subduction of the palaeo-Pacific plate reslted in an extensive chain of mountains which deformed and later truncated the southern rim of the main Karoo Basin. Material derived from these "Gondwanide" mountains as well as from the granitic uplands to the north-east, accumulated in large deltas that prograded into the Ecca sea (Upper Ecca Group). The relatively cool and humid climate promoted thick accumulations of peat on the fluvial and delta plains which now constitute the major coal reserves of southern Africa. As the prograding deltas coalesced, fluvio-lacustrine sediments of the Beaufort Group were laid down on broad gently subsiding alluvial plains. The climate by this time (Late Permian) had warmed to become semi-arid with highly seasonal rainfall. Vegetation alongside the meander belts and semi-permanent lakes supported a diverse reptilian fauna dominated by therapsids or "mammal-like reptiles". Pulses of uplift in the southern source areas combined with possible orographic effects resulted in the progadation of two coarse-grained alluvial fans into the central parts of the basin (Katberg Sandstone Member and Molteno Formation). In the upper Karoo Sequence, progressive aridification and tectonic deformation of the basin through the late Triassic and early Jurassic led to the accumulation, in four separate depositories, of "redbeds" which are interpreted as fluvial and flood-fan, playa and dune complexes (Elliot Formation). This eventually gave way to westerly wind-dominated sedimentation that choked the remaining depositories with fine-grained dune sand. The interdune areas were damp and occasionally flooded and provided a habitat for small dinosaurs and the earliest mammals. During this time (Early Jurassic), basinwide volcanic activity began as a precursor to the break-up of Gondwana in the late Jurassic and continued until the early Cretaceous. This

Smith, R. M. H.; Eriksson, P. G.; Botha, W. J.

1993-02-01

169

Palynology of Sub-Saharan Karoo Basins: Key to Early Mesozoic palaeoclimate reconstruction  

NASA Astrophysics Data System (ADS)

Palynological data of Permian-Triassic formations of the Sub-Saharan Karoo basins play a crucial role in the study and for the understanding of Gondwana's climate history and biodiversity in this time of major global changes in terrestrial and marine ecosystems. The palynological record reflects changes in land plant communities and vegetational patterns related to climate change and thus provides significant data for high-resolution palaeoclimate reconstructions in deep time. Recent palynological investigations of Triassic successions of South Africa, Mozambique and Tanzania document major changes in palaeoclimate. The spore/pollen ratios are used as a proxy for humidity changes. Stratal variations in the composition of the pollen group indicate warming and cooling phases. Variations in the amount and in the type, size and shape of phytoclasts reflect short-term changes in transport and weathering. The detected palaeoclimate signals are used for high-resolution correlation on basin-wide, intercontinental and intra-Gondwanic scales.

Götz, Annette E.

2014-05-01

170

From northern Gondwana passive margin to arc dismantling: a geochemical discrimination of Ordovician volcanisms (Sardinia, Italy)  

NASA Astrophysics Data System (ADS)

In Sardinia, one of the southernmost remain of the European Variscan belt, a crustal section through northern Gondwanan paleodomains is largely preserved. It bears significant evidence of igneous activity, recently detailed in field relationships and radiometric dating (Oggiano et al., submitted). A Cambro - Ordovician (491.7 ± 3.5 Ma ÷ 479.9 ± 2.1 Ma, LA-ICP-MS U-Pb zircon age) bimodal volcanic suite occurs with continuity in external and inner Variscan nappes of Sardinia below the so-called Sardic unconformity. The igneous suite represents an intraplate volcanic activity developed through subsequent episodes: i) an intermediate explosive and effusive volcanism, i.e. pyroclastic fall deposits and lava flows, embedded into epicontinental clastic sediments, culminating in silicic ignimbrite eruptions, and ii) mafic effusives. Geochemical data document a transitional, within-plate signature, e.g. the average Th/Ta (4.5) and La/Nb (2.7) overlap the upper continental crust values. The volcanites are characterized by slight fractionation of LREEs, nearly flat HREE abundance. The negative Eu anomaly increases towards evolved compositions. Some prominent HREE depletion (GdCN/YbCN = 13.8), and the high Nb/Y suggest a garnet-bearing source. The high 87Sr radiogenic content (87Sr/86Sr 490 Ma = 0.71169) and the epsilon Nd 490 Ma value of -6.54 for one dacite sample, imply a time integrated LREE-enriched source with a high Rb/Sr, such as a metasedimentary source. The stratigraphy of the succession and the geochemical composition of igneous members suggest a volcanic passive margin along the northern Gondwana at the early Ordovician. The bimodal Mid-Ordovician arc volcanism (465.4 ± 1.4 Ma, U-Pb zircon age; Oggiano et al., submitted) is developed in the external nappes (e.g. in Sarrabus and Sarcidano) and in the foreland occurs as clasts at the base of the Hirnantian succession (Leone et al. 1991). The Mid Ordovician sub-alkalic volcanic suite has reliable stratigraphic and palaeontological constraints, as it post-dates the Sarrabese (i.e. Sardic) unconformity and pre-dates the Upper Ordovician transgression. It consists of basaltic - andesites and abundant andesites and rhyolites. The negative Ta-, Nb-, Sr-, P-, Yb- and Ti-anomalies in mantle-normalized spiderdiagrams and Th/Ta compare with volcanic rocks from active continental margins. Andesite and dacite samples reveal Sr and Nd isotopic compositions consistent with a less depleted mantle source than rhyolites (epsilon Nd 465 Ma = -3.03 to -5.75; 87Sr/86Sr 465 Ma = 0.70931-0.71071). The positive epsilon Nd 465 Ma values of rhyolites (+1.15 to +2.42) suggest that their precursors, with a crustal residence age of ~1 Ga (TDM), were derived from a long-term depleted mantle source. On the whole, the isotopic data for Mid Ordovician volcanites suggest partial melting of an isotopically heterogeneous mantle. The bimodal suite has been unanimously interpreted as a marker of the Rheic ocean subduction. An Upper Ordovician transitional to alkalic volcanic activity is documented both in the foreland, and in the external and internal nappes (Di Pisa et al. 1992). The Late Ordovician alkalic mafic suite (440 ± 1.7 Ma) i.e. the Ordovician-Silurian boundary, occurs as sills, epiclastites and lava flows within the post-Caradocian transgressive sequence. The volcanic rocks are characterized by fractionation of REEs (LaCN/YbCN ~ 4.4-13), variable LILE abundances and significant Ta, Nb and LREE enrichments. Th/Ta in the range 1-2 and La/Nb < 1 evidence an anorogenic intraplate setting. The epsilon Nd 440 Ma values are positive (+1.60 to +4.14), reflecting an origin in a depleted mantle source, while the 87Sr/86Sr vary from 0.70518 to 0.71321. Negative epsilon Nd 440 Ma values (-4.76 and -4.62) in trachy-andesites suggest a less depleted mantle source, while the 87Sr/86Sr 440 Ma (0.70511 to 0.70694) and the Sm/Nd up to 0.36 align along the mantle array. The Late Ordovician alkalic suite suggest a continental rift geodynamic setting, and likely represent an early phase of the major rifting e

Gaggero, L.; Oggiano, G.; Buzzi, L.; Funedda, A.

2009-04-01

171

Hydrocarbon potential of the Lamu basin of south-east Kenya  

SciTech Connect

The Lamu basin occupies the coastal onshore and offshore areas of south-east Kenya. This fault bounded basin formed as a result of the Paleozoic-early Mesozoic phase of rifting that developed at the onset of Gondwana dismemberment. The resultant graben was filled by Karroo (Permian-Early Jurassic) continental siliciclastic sediments. Carbonate deposits associated with the Tethyan sea invasion, dominate the Middle to Late Jurassic basin fill. Cessation of the relative motion between Madagascar and Africa in the Early Cretaceous, heralded passive margin development and deltaic sediment progradation until the Paleogene. Shallow seas transgressed the basin in the Miocene when another carbonate regime prevailed. The basin depositional history is characterized by pulses of transgressive and regressive cycles, bounded by tectonically enhanced unconformities dividing the total sedimentary succession into discrete megasequences. Source rock strata occur within Megasequence III (Paleogene) depositional cycle and were lowered into the oil window in Miocene time, when the coastal parts of the basin experienced the greatest amount of subsidence. The tectono-eustatic pulses of the Tertiary brought about source and reservoir strata into a spatial relationship in which hydrocarbons could be entrapped. A basement high on the continental shelf has potential for Karroo sandstone and Jurassic limestone reservoirs. Halokinesis of Middle Jurassic salt in Miocene time provides additional prospects in the offshore area. Paleogene deltaic sands occur in rotated listric fault blacks. A Miocene reef Play coincides with an Eocene source rock kitchen.

Nyagah, K.; Cloeter, J.J.; Maende, A. (National Oil Corp. of Kenya, Nairobi (Kenya))

1996-01-01

172

A Megaraptor-like theropod (Dinosauria: Tetanurae) in Australia: support for faunal exchange across eastern and western Gondwana in the Mid-Cretaceous.  

PubMed

The fossil record of Australian dinosaurs in general, and theropods in particular, is extremely sparse. Here we describe an ulna from the Early Cretaceous Eumeralla Formation of Australia that shares unique autapomorphies with the South American theropod Megaraptor. We also present evidence for the spinosauroid affinities of Megaraptor. This ulna represents the first Australian non-avian theropod with unquestionable affinities to taxa from other Gondwanan landmasses, suggesting faunal interchange between eastern and western Gondwana during the Mid-Cretaceous. This evidence counters claims of Laurasian affinities for Early Cretaceous Australian dinosaur faunas, and for the existence of a geographical or climatic barrier isolating Australia from the other Gondwanan continents during this time. The temporal and geographical distribution of Megaraptor and the Eumeralla ulna is also inconsistent with traditional palaeogeographic models for the fragmentation of Gondwana, but compatible with several alternative models positing connections between South America and Antarctica in the Mid-Cretaceous. PMID:18544511

Smith, Nathan D; Makovicky, Peter J; Agnolin, Federico L; Ezcurra, Martín D; Pais, Diego F; Salisbury, Steven W

2008-09-22

173

Imprints of post-glacial climates and palaeogeography in the detrital clay mineral assemblages of an Upper Permian fluviolacustrine Gondwana deposit from northern Malawi  

Microsoft Academic Search

Detailed quantitative clay mineral studies on an Upper Permian fluviolacustrine Gondwana deposit (?55°S) from northern Malawi (9°S, 32°E) in central-southern Africa show imprints of Late Permian climates on the clay mineral assemblages. The clay mineral assemblage in the bottom 75 m is characterised by abundant illite, chlorite, regular smectite-chlorite (corrensite), regular illite-smectite, and vermiculite (Zone I). Between 75–240 m, illite

Keddy Yemane; Gunther Kahr; Kerry Kelts

1996-01-01

174

The role of the Variscan eastern Gondwana-Laurussia/Laurasia boundary in the evolution of the central Mediterranean area  

NASA Astrophysics Data System (ADS)

The geodynamic evolution of the central Mediterranean area is linked to the interaction between Gondwana and Laurussia/Laurasia plates. The interaction between these plates led to the development of Variscan, Alpine and Apennine Orogenic belts. In spite of the different ages of the orogenic systems, it is possible to hypothesize that their geodynamic evolution was linked to the complex interactions between the eastern boundary of Gondwana and the western boundary of Laurussia/Laurasia. This irregular boundary could have played the role of a pre-existing tectonic barrier which started to develop during the Upper Carboniferous. The kinematic along the boundary was related to a transpressive regime which evolved through a shear zones system (“snake” strike-slip and oblique shear zones). The transpressive environment led to the formation of restraining/releasing bends along the boundary between the two plates. The exhumation of middle/deep crustal rocks by telescoping processes, coeval with the transcurrent movement, occurred in the core of this narrow shear zone. The first occurrences of restraining/releasing bends are related to the Early Visean-Bashkirian (Variscan orogeny). The Variscan eastern boundary between the two colliding plates is characterized by a long-narrow band of HT rocks (East Variscan Shear Zone, EVSZ). From South to North they are: Calabria-Peloritani Terrane (Calabria and Sicily), deep basement of northern Apennines, Sardinia, Corsica, Maures-Tanneron Massif and Alpine Massifs. The same boundary was later reworked by the opening of the Alpine Tethys, dated at the Middle-Upper Jurassic. The opening of the Alpine Tethys led to the separation of the Variscan crust which will represent the future Alpine Massifs (External and Internal Massifs). The closure of the Alpine Tethys and the beginning of the Alpine Orogeny (Late Cretaceous to Eocene) re-assembled the system. The roto-translation of the Sardinia-Corsica and Calabrian-Peloritan blocks during the Upper Eocene-Early Miocene partially shifted the EVSZ, as well as the southern sector of the Alpine Belt, to the East and led to the beginning of the Apenninic orogenic events. The shifted portion has been again reworked by the opening of the northern Tyrrhenian Sea in the Late Miocene simoultaneously to the migration toward SE of the Calabrian-Peloritan sector. The evolution of the northern Apennines orogenic sector developed through transpressive and transtensive structures such as restraining and releasing bends which were active during the Upper Oligocene-Pliocene time interval. The aim of this work, in spite of the well knowledge of the geodynamic frame of the central Mediterranean area, is to emphasize the role played by the eastern boundary between Gondwana and Laurussia/Laurasia plates (EVSZ) as a persistent tectonic barrier from the Late Carboniferous to Late Miocene.

Padovano, M.; Elter, F. M.; Pandeli, E.

2010-12-01

175

Disparities in child mortality trends: what is the evidence from disadvantaged states in India? the case of Orissa and Madhya Pradesh  

PubMed Central

Introduction The Millennium Development Goals prompted renewed international efforts to reduce under-five mortality and measure national progress. However, scant evidence exists about the distribution of child mortality at low sub-national levels, which in diverse and decentralized countries like India are required to inform policy-making. This study estimates changes in child mortality across a range of markers of inequalities in Orissa and Madhya Pradesh, two of India’s largest, poorest, and most disadvantaged states. Methods Estimates of under-five and neonatal mortality rates were computed using seven datasets from three available sources – sample registration system, summary birth histories in surveys, and complete birth histories. Inequalities were gauged by comparison of mortality rates within four sub-state populations defined by the following characteristics: rural–urban location, ethnicity, wealth, and district. Results Trend estimates suggest that progress has been made in mortality rates at the state levels. However, reduction rates have been modest, particularly for neonatal mortality. Different mortality rates are observed across all the equity markers, although there is a pattern of convergence between rural and urban areas, largely due to inadequate progress in urban settings. Inter-district disparities and differences between socioeconomic groups are also evident. Conclusions Although child mortality rates continue to decline at the national level, our evidence shows that considerable disparities persist. While progress in reducing under-five and neonatal mortality rates in urban areas appears to be levelling off, polices targeting rural populations and scheduled caste and tribe groups appear to have achieved some success in reducing mortality differentials. The results of this study thus add weight to recent government initiatives targeting these groups. Equitable progress, particularly for neonatal mortality, requires continuing efforts to strengthen health systems and overcome barriers to identify and reach vulnerable groups.

2013-01-01

176

The effect of improved rural sanitation on diarrhoea and helminth infection: design of a cluster-randomized trial in Orissa, India  

PubMed Central

Background Infectious diseases associated with poor sanitation such as diarrhoea, intestinal worms, trachoma and lymphatic filariasis continue to cause a large disease burden in low income settings and contribute substantially to child mortality and morbidity. Obtaining health impact data for rural sanitation campaigns poses a number of methodological challenges. Here we describe the design of a village-level cluster-randomised trial in the state of Orissa, India to evaluate the impact of an ongoing rural sanitation campaign conducted under the umbrella of India’s Total Sanitation Campaign (TSC).We randomised 50 villages to the intervention and 50 villages to control. In the intervention villages the implementing non-governmental organisations conducted community mobilisation and latrine construction with subsidies given to poor families. Control villages receive no intervention. Outcome measures include (1) diarrhoea in children under 5 and in all ages, (2) soil-transmitted helminth infections, (3) anthropometric measures, (4) water quality, (5) number of insect vectors (flies, mosquitoes), (6) exposure to faecal pathogens in the environment. In addition we are conducting process documentation (latrine construction and use, intervention reach), cost and cost-effectiveness analyses, spatial analyses and qualitative research on gender and water use for sanitation. Results Randomisation resulted in an acceptable balance between trial arms. The sample size requirements appear to be met for the main study outcomes. Delays in intervention roll-out caused logistical problems especially for the planning of health outcome follow-up surveys. Latrine coverage at the end of the construction period (55%) remained below the target of 70%, a result that may, however, be in line with many other TSC intervention areas in India. Conclusion We discuss a number of methodological problems encountered thus far in this study that may be typical for sanitation trials. Nevertheless, it is expected that the trial procedures will allow measuring the effectiveness of a typical rural sanitation campaign, with sufficient accuracy and validity.

2012-01-01

177

Evidence of pre-Gondwana tectono-thermal event from the Bhilwara Supracrustal units of Rajasthan, north-west India  

NASA Astrophysics Data System (ADS)

In the Indian subcontinent, two pre- Gondwana (pre- Pan African) orogenies are mostly recorded and well-studied from the Eastern Ghat Mobile Belt: (i) >1.1 Ga and (ii) ~950 Ma. During the ~950Ma orogeny, the pre-existing granulites have been re-melted under granulite facies conditions at ~8 kbar, 800-850ºC in the sillimanite stability field with formation of garnet-orthopyroxene in the restites. In this study we report garnet-sillimanite bearing and garnet-staurolite-kyanite bearing supracrustal rocks from the Bhilwara Supergroup in Rajasthan, N-W India. Peak assemblage in the garnet-sillimanite bearing metapelite is: garnet-sillimanite-biotite-plagioclase-quartz. Garnet porphyroblasts contain sillimanite-biotite bearing inclusion trails. Matrix foliations consist of biotite, sillimanite, quartz. Peak pressure-temperature calculated for garnet formation are ~7-8 kbar, 800ºC. Garnet is replaced along the margins by biotite during retrogression. Within garnet-staurolite-kyanite schist, peak assemblage is formed of garnet-staurolite-biotite-kyanite quartz, where garnet and staurolite occur as porphyroclasts and the matrix foliations are formed of kyanite-biotite-quartz. Mineral assemblages and compositions in the rock indicate peak pressure-temperature >8 kbar, 600ºC. The ages of the metamorphic events at sillimanite and kyanite facies are not well-constrained. However since the Bhilwara supracrustal units occur close to the Grenvillian orogenic belt at Sandmata Complex, the timing of the peak metamorphism can be constrained at ~1.0 Ga. Garnet-sillimanite-bearing assemblages noted in the Bhilwara Supracrustal Belt, has also been noted from the Grenvillian belts in the Eastern Ghat Mobile Belt. So the question that needs to be addressed is whether the Grenvillian orogenic belt recorded form the Sandmata Complex in Rajasthan and that of the Eastern Ghat Belt had been a continuous orogenic belt? Such possibilities can be addressed by establishing detailed structural analyses from the two domains. Such study can provide well-constrained facts about the position of Indian sub-continent in the reconstruction of Rodinia and Gondwana.

Saha, Lopamudra; Sarkar, Saheli; Rakshit, Nibedita; Nasipuri, Pritam

2014-05-01

178

Triassic arc-derived detritus in the Triassic Karakaya accretionary complex was not derived from either the S Eurasian margin (Istanbul terrane) or the N Gondwana margin (Taurides)  

NASA Astrophysics Data System (ADS)

We present new U-Pb zircon source age data for Upper Triassic sandstones of the Istanbul Terrane (S Eurasian margin) and also for Triassic sandstones of the Taurides (N Gondwana margin). The main aim is to detect and quantify the contribution of Triassic magmatism as detritus to either of these crustal blocks. This follows the recent discovery of a Triassic magmatic arc source for the Triassic sandstones of the Palaeotethyan Karakaya subduction-accretion complex (Ustaömer et al. 2013; this meeting). Carboniferous (Variscan) zircon grains also form a significant detrital population, plus several more minor populations. Six sandstone samples were studied, two from the ?stanbul Terrane (Bak?rl?k?ran Formation of the Kocaeli Triassic Basin) and four from the Tauride Autochthon (latest Triassic Üzümdere Formation and Mid-Triassic Kas?mlar Formations; Bey?ehir region). Detrital zircon grains were dated by the laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) U-Pb method at Goethe University, Frankfurt. Our results do not reveal Triassic detritus in the Üzümdere Formation. The U-Pb age of the analysed zircon grains ranges from 267 Ma to 3.2 Ga. A small fraction of Palaeozoic zircons are Permian (267 to 296 Ma), whereas the remainder are Early Palaeozoic. Ordovician grains (4%) form two age clusters, one at ca. 450 Ma and the other at ca. 474 Ma. Cambrian-aged grains dominate the zircon population, while the second largest population is Ediacaran (576 to 642 Ma). Smaller populations occur at 909-997 Ma, 827-839 Ma, 1.8-2.0 Ga and 2.4-2.6 Ga. The sandstones of the Kas?mlar Formation have similar zircon age cluster to those of the somewhat younger Üzümdere Formation, ranging from 239 Ma to 2.9 Ga. A few grains gave Anisian ages. Cambrian zircon grains are less pronounced than in the Kas?mlar Formation compared to the Üzümdere Formation. The detrital zircon record of Tauride sandstones, therefore, not indicates significant contribution of Triassic or Carboniferous (Variscan) arc sources, in marked contrast to those of the Triassic Karakaya subduction complex. In comparison, the ages of the analysed zircons in the Upper Triassic sandstones of the Istanbul Terrane range from 294 Ma to 3.1 Ga. Triassic zircons are again absent, while Variscan-aged zircons (294 to 339 Ma) dominate the zircon population. Additional zircon populations are dated at 554 to 655 Ma, 0.9 to 1.2 Ga, 1.5 Ga, 1.65 Ga, 2.0 to 2.15 and 2.5 to 2.8 Ga. The Precambrian zircon age spectra are compatible with derivation from an Avalonian/Amazonian/Baltic crustal provenance. In summary, there is no evidence in either the Triassic sandstones of the ?stanbul Terrane or of the Taurides of the Triassic magmatic arc source that dominates the Triassic Karakaya subduction-accretion complex. Where then was the source of the Karakaya arc detritus? A likely option is that the Karakaya subduction-accretion complex is an exotic terrane that was detached from a source magmatic arc and displaced to its present location, probably prior the initial deposition of the Early Jurassic cover sediments. This study was supported by TUBITAK, Project No: 111R015

Ustaömer, Timur; Ayda Ustaömer, Petek; Robertson, Alastair H. F.; Gerdes, Axel; Zulauf, Gernold

2014-05-01

179

Paleomagnetic study of Siluro-Devonian volcanic rocks from the central Lachlan Orogen: Implications for the apparent pole wander path of Gondwana  

NASA Astrophysics Data System (ADS)

The apparent pole wander (APW) path for Gondwana is still not clearly established, in particular, for Silurian-Devonian times. A controversial debate places authors who argue for an "X path," running directly through Africa on a reconstruction of Gondwana against those who advocate a large loop passing by southern South America, the "Y path." Most of the paleomagnetic data used to draw this loop come from the Lachlan Orogen (Australia). A paleomagnetic study was carried out in the well-dated Ambone and Ural volcanics in the central subprovince of Lachlan Orogen, New South Wales. Anisotropy of magnetic susceptibility measurements confirms detailed mapping of the region and shows that these massive dacitic sills and/or lava flows are flat lying. Among the different localities studied, only one yields interpretable paleomagnetic results. Two components of magnetization can be identified: a midtemperature direction yielding a corresponding pole in Australian coordinates ? = 67.9°S/? = 084.4°E (B = 5; n = 21; dp = 17.5°/dm = 23.1°) and a high-temperature direction with a corresponding VGP ? = 24.4°S/? = 060.6°E (B = 5; n = 25; dp = 1.4°/dm = 2.5°). The first is interpreted as corresponding to an Early Carboniferous pole position and can be regarded as an overprint probably related to the Early Carboniferous Kanimblan orogenic event. The second does not correspond to any expected Silurian-Devonian or younger pole position. This magnetization is thought to be primary in origin; however, secular variation has apparently not been averaged out in the single lava flow sampled. Therefore the earliest Devonian paleopole position probably lies in a 30° cone around the obtained VGP, and this position can only match the X-type APW path for Gondwana. It is in particular very different from coeval poles obtained in the eastern subprovince of the Lachlan Orogen, and it is mostly used as key poles supporting the Silurian-Devonian loop for the APW path of Gondwana. Therefore some poles from the Lachlan Orogen must be affected by rotation to explain these results. The Lachlan Orogen was hence not stable up to the mid-Paleozoic, and data from this region should not be used as representative for Gondwana.

VéRard, Christian; Tait, Jennifer; Glen, Richard

2005-06-01

180

Correlation between plate motions and tectonic subsidence of sedimentary basins in Africa  

SciTech Connect

From the early Mesozoic until the Holocene, the African continent was generally in a state of extension, based on plate tectonic reconstructions and sedimentary basin subsidence studies. Beginning with the breakup of Gondwana in the Permian-Triassic, this resulted in the formation of the present-day African continental margins and a series of intracontinental rift basins, located mainly on older (late Proterozoic) shear zones. Numerous wells from marginal, as well as intracontinental rift basins, have been backstripped to elucidate their Mesozoic and Tertiary tectonic histories. They show a generally consistent patterns of subsidence and uplift phases in all basins. During the evolution of these basins, the direction of African plate motion changed several times. This was related to the differential opening of the central and south Atlantic oceans, changes in spreading rates in both the Atlantic and Indian oceans, and the collision between Africa and Europe. Episodes of compressional deformation related to these plate tectonic changes are revealed in backstripped tectonic subsidence curves.

Janssen, M.E. (Vrije Universiteit, Amsterdam (Netherlands))

1993-09-01

181

Provenance study of Pliocene-Pleistocene sands based on ancient detrital zircons (Alvalade Basin, SW Iberian Atlantic coast)  

NASA Astrophysics Data System (ADS)

Pliocene-Pleistocene sand of the Alvalade basin was taken from the sea-cliffs of SW Iberia coast for a provenance study using radiometric dating. The U-Pb ages obtained revealed a wide interval ranging from Cretaceous to Archean, with predominance of Paleozoic, Neoproterozoic and Cretaceous zircon ages. Cretaceous ages interpreted to indicate a Sines Massif provenance are dominant in sands close to Cape Sines but are absent in sand sampled 12 km north. Carboniferous ages younger than ca. 315 Ma suggesting a possible contribution from the Central-Iberian Zone originally; however, these zircons may be multi-cyclic, having been reworked from Eocene-Miocene siliciclastic deposits related to transport from central Iberia (Lower Tagus basin drainage evolution). These signatures provide important constraints on the location and extent of the Pliocene-Pleistocene topography and drainage system that were probably controlled by: i) Miocene to Pleistocene landscape rejuvenation driven by Alpine movements along major faults; and ii) residual reliefs related to inherited Variscan structure. The U-Pb ages obtained also trace the pre-Cenozoic paleotectonic evolution of SW Iberia recorded in their sources: i) the North Gondwana accretion and breakup; ii) the Gondwana and Laurussia collision; and iii) the Pangea breakup and opening of the Atlantic Ocean.

Albardeiro, Luís; Pereira, Manuel Francisco; Gama, Cristina; Chichorro, Martim; Hofmann, Mandy; Linnemann, Ulf

2014-06-01

182

The Mississippian Pedroches Basin: A failed attempt to propagate a Palaeotethys Arm across Southern Iberia?  

NASA Astrophysics Data System (ADS)

The Pedroches basin, straddling the boundary between the Ossa Morena (OMZ) and the Central Iberian (CIZ) zones of the Iberian Massif, forms one of the largest exposures of Mississippian rocks in the Iberian Peninsula. With the only exception of transitional facies near the northern and southern margins, the basin fill mostly consists of volcanic and sedimentary rocks deposited in relatively shallow continental shelf environments, in which storm activity was the main process of sediment supply and dispersal. Significantly, the Pedroches basin is split into several compartments (structural units), among which three syn-sedimentary, sigmoidal shape igneous belts, produced the most severe facies, structural and palaeogeographic changes. Owing to its timing of formation during the period of Variscan convergence, its location within an area undergoing active Variscan deformation, and the fact that the basin fill was itself affected by the Variscan orogeny, the Pedroches basin was considered a typical example of a syn-orogenic, peripheral foreland basin. Recent stratigraphical, sedimentological and isotope geology work has allowed a reinterpretation of the basin fill, in which two different sequences may be distinguished, with distinct tectono-stratigraphic significance. Above a basal conglomerate, the several hectometres thick lower part of the basin fill succession shows the highest variability among the various structural units in terms of lithology, facies and thickness. Most volcanic rocks are located within this lower part, within and in between the igneous belts, suggesting the important role of lithosphere-through, extension-related faulting in the origin of the basin. Significant across-strike thickness changes attest for syn-sedimentary horst and graben formation at this stage. On the contrary, the upper part of the basin fill is very similar in all units and corresponds to flyschoid greywacke-mudstone alternations (Culm facies). The change between the lower and the upper parts of the basin fill is interpreted as evidence for a transition from an overall extensional (transtensional?) regime during basin generation to an overall transpressional one, during which the basin was transformed into a sort of peripheral foreland basin and inverted soon after. A possibility opened to further research, here outlined as a provocative hypothesis, is that during the Variscan collision between Laurussia and Gondwana the latter might have been pushed southeastwards and eventually collided with a Palaeotethys spreading ridge or, perhaps, a branch departing from it. In this context, the first part of the evolution of the Pedroches basin could in fact be the consequence of a combination of both transtension and the overriding of a slab window developed as a result of ridge-trench collision, itself inducing rifting in the upper (Iberian) plate. Final collision of the southern margin of the OMZ (south Iberian part of Gondwana) with Laurussia by the late Viséan, which culminated the closure of this part of the Rheic Ocean, imposed a change to more orthogonal strain conditions that may have caused the abortion of the propagating rift and also triggered subsequent basin inversion.

Armendáriz, Maider; Quesada, Cecilio; Rosales, Idoia

2013-04-01

183

Paleozoic evolution of active margin basins in the southern Central Andes (northwestern Argentina and northern Chile)  

NASA Astrophysics Data System (ADS)

The geodynamic evolution of the Paleozoic continental margin of Gondwana in the region of the southern Central Andes is characterized by the westward progression of orogenic basin formation through time. The Ordovician basin in the northwest Argentinian Cordillera Oriental and Puna originated as an Early Ordovician back-arc basin. The contemporaneous magmatic arc of an east-dipping subduction zone was presumably located in northern Chile. In the back-arc basin, a ca. 3500 meter, fining-up volcaniclastic apron connected to the arc formed during the Arenigian. Increased subsidence in the late Arenigian allowed for the accomodation of large volumes of volcaniclastic turbidites during the Middle Ordovician. Subsidence and sedimentation were caused by the onset of collision between the para-autochthonous Arequipa Massif Terrane (AMT) and the South American margin at the Arenigian-Llanvirnian transition. This led to eastward thrusting of the arc complex over its back-arc basin and, consequently, to its transformation into a marine foreland basin. As a result of thrusting in the west, a flexural bulge formed in the east, leading to uplift and emergence of the Cordillera Oriental shelf during the Guandacol Event at the Arenigian-Llanvirnian transition. The basin fill was folded during the terminal collision of the AMT during the Oclóyic Orogeny (Ashgillian). The folded strata were intruded post-tectonically by the presumably Silurian granitoids of the "Faja Eruptiva de la Puna Oriental." The orogeny led to the formation of the positive area of the Arco Puneño. West of the Arco Puneño, a further marine basin developed during the Early Devonian, the eastern shelf of which occupied the area of the Cordillera Occidental, Depresión Preandina, and Precordillera. The corresponding deep marine turbidite basin was located in the region of the Cordillera de la Costa. Deposition continued until the basin fill was folded in the early Late Carboniferous Toco Orogeny. The basin originated as an extensional structure at the continental margin of Gondwana. Independent lines of evidence imply that basin evolution was not connected to subduction. Thus, the basin could not have been in a fore-arc position as previously postulated. Above the folded Devonian-Early Carboniferous strata, a continental volcanic arc developed from the Late Carboniferous to the Middle Triassic. It represents the link between the Choiyoi Province in central Chile and Argentina, and the Mitu Group rift in southern Peru. The volcanic arc succession is characterized by the prevalence of silicic lavas and tuffs and volcaniclastic sedimentary rocks. During the latest Carboniferous, a thick ostracod-bearing lacustrine unit formed in an extended lake in the area of the Depresión Preandina. This lake basin originated in an intra-arc tensional setting. During the Early Permian, marine limestones were deposited on a marine platform west and east of the volcanic arc, connected to the depositional area of the Copacabana Formation in southern Peru.

Bahlburg, H.; Breitkreuz, C.

184

Model a Catchment Basin  

NSDL National Science Digital Library

The purpose of this resource is to introduce what a catchment basin is and how it works. Students will make a 3-dimensional model of a catchment basin to understand how water moves through the basin and explore how water is affected when there are changes in the basin.

The GLOBE Program, UCAR (University Corporation for Atmospheric Research)

2003-08-01

185

Magnetic fabric and microstructures of Late Paleozoic granitoids from the North Patagonian Massif: Evidence of a collision between Patagonia and Gondwana?  

NASA Astrophysics Data System (ADS)

Widespread Late Paleozoic magmatism in northern Patagonia is a target to test hypotheses on the long standing question over the origin of Patagonia. In recent years, a dispute over whether it is an accreted crustal block that collided with Gondwana in Paleozoic times or an autochthonous part of South America has taken place. As part of a multidisciplinary study, an integrated microstructural and magnetic fabric study was carried out on the Late Carboniferous Yaminué Complex and the Early Permian Navarrete Plutonic Complex, both exposed in the northeastern corner of the North Patagonian Massif (40.5°S, 67.0°W). Other investigated units are the Late Carboniferous Tardugno Granodiorite, the newly defined Cabeza de Vaca Granite and the Late Permian San Martin pluton. Over 300 oriented cores from 60 sites were collected for anisotropy of magnetic susceptibility (AMS) measurements. A systematic analysis of around 100 petrographic thin sections was performed to characterize the microstructures of the different magmatic units. Microstructures in the Yaminué Complex are indicative of a transition from magmatic to solid-state deformation. Microstructures of the orthogneiss of tonalitic composition suggest an early stage in the emplacement history of this complex. The Cabeza de Vaca Granite, intrusive in Yaminué Complex, is the most evolved unit and records less intense high-temperature solid-state deformation which suggests that the stress field that controlled the emplacement of the Yaminué Complex outlasted it. According to petrologic and structural considerations, the Navarrete Plutonic Complex has been subdivided into three facies, i.e. Robaina, Guanacos and Aranda, respectively. Microstructures of the Navarrete Plutonic Complex are mostly magmatic to submagmatic, versus the solid-state fabric that characterizes the Robaina facies at the contact with the Yaminué Complex. Combined analyses of AMS and microstructural data lead us to suggest that the Yaminué Complex, Cabeza de Vaca Granite and possibly Tardugno Granodiorite were intruded during a major compressional event associated with top-to-the-SSW thrusting. This event is most likely related to a frontal collision of the North Patagonian Massif and the southwestern Gondwana margin at around 300 Ma. The Navarrete Plutonic Complex and San Martin pluton were emplaced after that tectonic event, which must have ended by 281 Ma. Previous magmatic, geochronological and paleomagnetic data that suggest close connection of the North Patagonian Massif with the South American Gondwana blocks during the Paleozoic, can be reconciled with a Late Paleozoic collision by a model of a para-autochthonous North Patagonian Massif that rifted away from Gondwana after the Ordovician and collided again in the Late Carboniferous-Early Permian.

López de Luchi, Mónica G.; Rapalini, Augusto E.; Tomezzoli, Renata N.

2010-10-01

186

Stable carbon isotope chemostratigraphy and tectonic setting of the Pennsylvanian Ely-Bird Spring basin, Nevada and Utah: interpreting three-dimensional basin evolution using multiple stratigraphic techniques  

NASA Astrophysics Data System (ADS)

The Pennsylvanian was a tectonically active time throughout Laurasia. In western Laurasia, the Ely-Bird Spring basin (EBSB) formed during early to middle Pennsylvanian time as one of a series of tectonically-generated, stacked, late Paleozoic basins. Timing and extent of these basins is well constrained; but the tectonic framework that resulted in basin formation is poorly known. Farther east, Ancestral Rocky Mountain basins and uplifts formed synchronously with the EBSB, as a far-field response to collision between Laurasia and Gondwana. This dissertation was undertaken in order to develop a method that combines whole-rock carbon isotope chemostratigraphy with lithostratigraphy and biostratigraphy. These data were used to elucidate the three-dimensional evolution and tectonic setting of the EBSB. To do this, six nearly complete sections located throughout Nevada and western Utah were densely sampled for carbon isotope stratigraphy. The results of this work are presented in three chapters as outlined below. Chapter 1 tests the hypotheses that carbon isotope shifts mirror cyclothemic lithologic shifts and that these systematic isotopic shifts can be used as a correlation tool. Three sections from the north, central, and southern portions of the EBSB were densely sampled for carbon isotope stratigraphy. Generally, the isotopes tracked changes in rock type, with shifts to more positive carbon isotope values toward the tops of shallowing-upward lithologic cycles. Therefore, pattern matching of whole-rock isotope shifts, tied to lower resolution biostratigraphy, is a feasible method for high-resolution correlation within the basin. Chapter 2 presents new fine-scale carbon isotope stratigraphy from six sections around the basin, combined with existing biostratigraphy, to elucidate the three- dimensional evolution of the basin. Correlations between sections were investigated using Match-2.3 (Lisiecki and Lisiecki, 2002), a dynamic programming algorithm developed for stratigraphic signal correlation. Based on these correlations, the highest initial relative sediment accumulation rates occurred in the eastern part of the basin. However, for most of the life of the basin, the highest relative accumulation rates were in the northwestern part of the basin. High rates of sediment accumulation in the northwestern part of the basin may be a response to renewed tectonism to the west. This corroborates previous work which shows that tectonism culminated in angular unconformities and overturned folding that deformed the northern basin strata during middle Pennsylvanian time, but left southern basin strata relatively unaffected. Chapter 3 compares the three-dimensional evolution of the EBSB to broadly coeval Ancestral Rocky Mountains basins. The purpose was to test whether the Ancestral Rocky Mountains and EBS basins were related tectonically. Geohistory analyses for the EBSB and four Ancestral Rocky Mountains basins indicate that the basins were in different tectonic settings. Three-dimensional subsidence analysis of the EBSB suggests it is more compatible with a foreland basin subsidence model whereas most of the Ancestral Rocky Mountains basins are consistent with subsidence models for strike-slip basins.

Sturmer, Daniel M.

187

Sands of West Gondwana: An archive of secular magmatism and plate interactions — A case study from the Cambro-Ordovician section of the Tassili Ouan Ahaggar (Algerian Sahara) using U-Pb-LA-ICP-MS detrital zircon ages  

NASA Astrophysics Data System (ADS)

Enormous masses of highly mature quartz sands were deposited in Western Gondwana during the Cambrian-Ordovician time, and provide a wide range of information concerning magmatic events through time, provenance, paleoclimate, and basin history. We present a provenance study based on 630 U-Pb (LA-ICP-MS) ages of detrital zircon from the latest Cambrian to Ordovician siliciclastic rocks of the Tassili Ouan Ahaggar basin situated in the Algerian Sahara. Most authors suggest local sources only for the sandstones. Instead, we demonstrate that the detritus is derived from different cratons and terranes which contributed to the deposition of a Cambrian-Ordovician overstep sequence covering western and northern Africa. Most zircon ages (61.0%) fall in the range of ~ 540 to 740 Ma and are interpreted to have been derived from Pan-African orogenic belts such as the Trans-Saharan Belt of NW Africa and previously from the Brazila belt of South America. Other potential sources for this zircon population are terranes of Cadomian affinity situated marginal to West Africa. The second-largest zircon population (20.2%) is 2.0 to 2.2 Ga, and is attributed to sources in the West African craton, such as the Birimian basement and the Eburnean orogenic belt, with possible partial input from the Amazonian craton. A zircon population of 7.1% yields Mesoproterozoic and early Paleoproterozoic ages in the range of ~ 1.3 to ~ 1.8 Ga and was probably derived from source rocks outside of the West African basement, the Tuareg shield and other adjoining areas. The Amazonian craton is a potential source region. A population of 6.7% of all zircon ages scatter from ~ 750 Ma to ~ 980 Ma and may reflect input from latest stages of the formation of Rodinia and its subsequent dispersal. A smaller population (3.2%) of zircon ages lie between ~ 2.3 and 2.65 Ga, and may be derived from late Paleoproterozoic to early Archaean rocks from the West African craton and possibly from Amazonia. Less than 1% of all zircons are Meso- to Paleoarchaean ones and provide evidence for the input of very old cratonic basement, most likely from cratonic inliers of the West African craton (Leonian, Liberian). Because of the potential input of detrital zircon from the Amazonian craton, which is reflected in the Mesoproterozoic and late Paleoproterozoic grains, we speculate that some of the Paleoproterozoic to Neoarchean (2.0 Ga to 2.6 Ga) zircons were also derived from Amazonia. Due to the total lack of 1.0-1.2 Ga old zircon, our data set excludes all crustal domains situated in the Arabian-Nubian shield and the East African belt, as well as the Sunsás belt of Amazonia ("Sunsás-Grenvillian") as potential sediment sources. Sedimentation in the Tassili Ouan Ahaggar basin started in uppermost Cambrian to Ordovician time due to the opening of the Rheic Ocean. This event led to subsidence related to the rift and drift of Avalonia and related terranes from the northwestern Gondwanan margin. The basal Early Tassili quartzite has detrital zircon populations that suggest a local provenance either from West African or from a related terrane in the Tuareg shield. A dramatic change occurs in the deltaic to shallow marine strata of the Lower Ordovician Ajjers Formation and in the overlying marine sandstones of the Middle Ordovician d'In Azaoua Formation. Our data for both formations indicate the Pan-African orogen, and very likely Cadomian terranes as the main source for the detritus. During this time, the region was affected by rift tectonics due to the opening of the Rheic Ocean and therefore amenable to erosion at rift shoulders and escarpments. Our data also indicate that glacial erosion in Upper Ordovician (Hirnantian) time must have affected larger areas of old cratonic surfaces as the populations of Paleoproterozoic to Archaean zircons are significantly higher than in other age clusters. Large parts of highly mature sands of the Cambro-Ordovician section in the Tassili Ouan Ahaggar basin were derived from a peneplain in the interior of Gondwana, that formed during Cambrian time

Linnemann, Ulf; Ouzegane, Khadidja; Drareni, Amar; Hofmann, Mandy; Becker, Sindy; Gärtner, Andreas; Sagawe, Anja

2011-04-01

188

Late Cainozoic drainage evolution in the Zambezi basin: Geomorphological evidence from the Kalahari rim  

NASA Astrophysics Data System (ADS)

The development of the Zambezi drainage system is discussed within the framework of the post-Gondwana tectonic evolution of southern Africa. An internal drainage system, including teh proto-Upper Zambezi, has been progressively captured during the late Cainozoic by a more agressive coastwise system. Supporting geomorphic evidence is presented from the eastern Kalahari rim. Drainage alignments and gradients, and terrace sequences are discussed. Lacustrine features found on the present watershed between the Middle Zambezi and internal systems are described and explained as remnants of the former proto-Upper Zambezi tributary system. Their interaction with linear dune activity is also examined. Despite the problems of dating the drainage changes described, it is concluded that their elucidation is important in understanding sedimentation and landform development in the eastern part of the Kalahari basin.

Thomas, David S. G.; Shaw, Paul A.

189

Age and tectonic evolution of Neoproterozoic ductile shear zones in southwestern Madagascar, with implications for Gondwana studies  

NASA Astrophysics Data System (ADS)

Southern Madagascar comprises a complex Precambrian terrain of high-grade metamorphic rocks with a history of polyphase deformation and metamorphism. Two prominent N-S trending late Neoproterozoic ductile shear zones, the Ampanihy and Vorokafotra shears, each with projected strike length of > 450 km and between 10 and 20 km in width, crosscut the region. A third set of en echelon shears forms part of the early Paleozoic Ranotsara Shear Zone that cuts the basement in a NW-SE direction over a combined strike length of > 400 km. The host rocks of these shears comprise paragneisses (metasediments) with detrital zircons ranging in age between 720 and 1900 Ma. A felsic layer, interpreted as a metavolcanic rock, gives a date of 722±1 Ma. Remnants of late Archean orthogneisses in the central part of the study area may represent basement to the paragneisses. Four episodes of deformation and metamorphism have been recognized on the combined basis of field observations, petrogenesis, and U/Pb analyzes of zircons, monazites, sphenes, and rutiles. Two episodes of early simple shear deformation (D1 and D2) at midcrustal levels occurred between 627 and 647 Ma, during which northeast verging recumbent sheath folds and ductile thrusts were formed and peak prograde metamorphism reached 7-12 kbar at 750°-900°C. Early prolate mineral fabrics (L1/L2) are preserved in massif-type anorthosite bodies and their marginal country rocks. D1 occurred between 630 and 647 Ma, while D2 occurred at 627-628 Ma. This was followed by a 10-15 Myr period of static, annealing metamorphism until 609-614 Ma when bulk shortening (D3) took place. D2 and D3 are coaxial but are separated in time by leucocratic dykes that intruded between 610 and 620 Ma. D3 was focused zonally, forming the prominent N-S shear zones between 607 and 609 Ma; its oblate strain resulted in a strong composite D2/D3 fabric defined by subvertical S-tectonites and subhorizontal intersection lineations. A variety of post-D3 pegmatites accompanied ˜85 Myr of relatively static annealing and metasomatic/metamorphic mineral growth, during which numerous occurrences of phlogopite, uranium, and rare earth elements formed. A continuum of concordant monazite dates suggests that this thermal event is part of an extended period of low-pressure (3-5 kbar) charnockite-producing processes between 520 and 605 Ma. The continuum, however, appears to be punctuated at ˜580, 550, and 520 Ma. Deformation (D4) recorded within the Ranotsara Shear Zone overlaps with the youngest parts of the regional metamorphic conditions between 520 and 550 Ma. Prevailing low-pressure, high-temperature amphibolite-granulite facies rapidly gave way to greenschist facies conditions between 490 and 530 Ma, as is evident from overlapping ages of zircon, monazite, sphene, and rutile. We conclude that D1 to D3 represents a period of 40 Myr of compressional deformation that we interpret to be related to collisional events during the amalgamation of Gondwana. The first part of the thermal continuum between 550 and 605 Ma reflects ˜55 Myr of slow cooling and annealing at midcrustal levels, while the onset of the last episode, between 520 and 530 Ma, heralds accelerated exhumation accompanied by extensional tectonics between 490 and 520 Ma. We believe that this postcollisional time span represents a prolonged period of evolution of a Tibetan-style plateau into an Aegean-style extensional terrain. This ˜100 Myr event in southern Madagascar is similar to that recorded throughout large sectors of the East African Orogen between ca. 500 and 600 Ma. We believe that this type of postconvergent thermotectonism best represents the original definition of "Pan-African" [Kennedy, 1964], which in today's terminology equates with "postorogenic extensional collapse" [Dewey, 1988], or "destabilization of an orogen" [Lipps, 1998]. Kennedy's Pan-African was widespread throughout the interior a supercontinent, when Gondwana's periferal margins were subjected to far-field tensional forces. This suggests that neith

de Wit, Maarten J.; Bowring, Sam A.; Ashwal, Lew D.; Randrianasolo, Leon G.; Morel, Vincent P. I.; Rambeloson, Roger A.

2001-02-01

190

Forearc basin correlations from around the Texas Orocline, New England Orogen, east Australia  

NASA Astrophysics Data System (ADS)

The late Paleozoic to early Mesozoic New England Orogen occupies much of the eastern seaboard of Australia. The orogen formed by west-dipping subduction (present-day coordinates) of the paleo-Pacific plate beneath eastern Gondwana. The southern part of the orogen exhibits a series of tight bends (oroclines) that are evident in the curvature of a Devonian-Carboniferous subduction complex, in particular the forearc basin and accretionary complex. The Emu Creek Block is thought to be part of the forearc basin that is exposed in the eastern limb of the Texas Orocline, but until now the tectonostratigraphic origin of the Emu Creek Block has only been inferred from limited geological data. Here we present detrital zircon geochronology (U/Pb ICP-MS ages), a new geological map of the block, and a revised stratigraphic section. Lithological investigation of strata within the block and the age distribution of detrital zircons indicate that the sediments in the Emu Creek Block were derived from a Carboniferous magmatic arc and were most likely deposited in a forearc basin. Our new geochronological constraints indicate deposition during the late Carboniferous. We therefore propose that rocks in the Emu Creek Block are arc-distal correlatives of the forearc basin in the opposing (western) limb of the Texas Orocline, specifically the Willuri and Currabubula formations. Extensive orocline-parallel structures in the forearc basin indicate that the eastern limb of the Texas Orocline was rotated in the course of oroclinal bending by approximately 135 degrees relative to the western limb. The correlation of the forearc basin blocks on opposite limbs of the Texas Orocline provides an independent constraint on its geometry and further improves our understanding of New England Orogen tectonostratigraphy and the crustal structure of eastern Australia.

Hoy, Derek; Rosenbaum, Gideon; Shaanan, Uri; Wormald, Richard

2014-05-01

191

Depositional evolution of permo-triassic karoo basins in Tanzania with reference to their economic potential  

NASA Astrophysics Data System (ADS)

The Karoo basins of Tanzania contain in excess of 3000 m of sediments which were preserved in several NNE-NE striking half grabens or other structural basin conditions. They are all intracratonic basins, most of which filled with terrestrial sediments. In some basins situated nearer the coastal region short marine incursions occurred in the Late Permian. The Ruhuhu Rasin in SW Tanzania provides a typical depositional sequence of a Karoo basin in eastern Africa. Sedimentation commenced with glacigene deposits. These are of Late Carboniferous to Early Permian age and may be equated with other glacial successions in Africa and elsewhere in Gondwana. The glacigene beds are overlain by fluvial-deltaic coal-bearing deposits succeeded by arkoses and continental red beds. A transitionary formation of carbonaceous shales with impure coals gradually develops into thick lacustrine series which are topped by Late Permian bone bearing beds. The Triassic is characterized by a very thick fluvio-deltaic succession of siliciclastics resting with regional unconformity on the Permian. This Early Triassic sequence exhibits well-developed repetitive depositional cycles. Current azimuth measurements indicate fluctuating flow regimes in the Early Permian but relative stable source areas to the west of the basin later on. The depositional evolution of the Ruhuhu Basin is controlled by both tectonic and climatic factors. During basin evolution important energy resources were deposited such as considerable reserves of coal and source rocks of moderate potential for hydrocarbon generation. Uranium enrichment is observed in the Triassic arenaceous series where diagenetic alterations and subsequent cementation processes led to the formation of laumontite. Post Karoo dykes and plugs had only local effect on thermal evolution of potential source rocks. Enrichments of elements, i.e., Nb, Zr, Rb, Cr, and V present additional exploration targets. A comparison with the Karoo basins of the coastal region indicates possible lithological correlation by the application of sequence stratigraphy. No early Permian deposits are exposed in the coastal Karoo basins but their existence within the deeper parts of these basins cannot be ruled out. There, composition of organic matter analysed so far suggests subsidence and heat exposure exceeding post maturity stage.

Kreuser, T.; Wopfner, H.; Kaaya, C. Z.; Markwort, S.; Semkiwa, P. M.; Aslandis, P.

192

The Peary Plateau, fragment of Gondwana (barrier in the oceanic gates of the Western Antarctica in the Scotia Sea): A part of the earth’s bipolar climatic machine  

Microsoft Academic Search

Marine geological-geophysical research in 1998? 2005, processing of the materials gathered in 2004? 2005, and compilation of a new bathymetric chart led to the discovery of the Peary underwater plateau or bank (hereafter, Peary Plateau), a large fragment of Gondwana, in the Scotia Sea (Southern Ocean). This fragment played the role of a barrier in the oceanic gates of Western

G. B. Udintsev; G. V. Shenke; A. Beier; A. V. Kol’tsova; L. G. Domoratskaya; A. F. Beresnev; N. A. Kurentsova; D. E. Teterin; V. G. Udintsev

2006-01-01

193

New 40ar\\/39ar Radiometric, Geochemistry And Structural Data On The Giant Okavango Mafic Dike Swarm And Lava-flows From The Karoo Province In Botswana: Implications For Gondwana Break-up  

Microsoft Academic Search

The lower Jurassic Karoo magmatism represents one of the most important conti- nental flood basalt (CFB) provinces of the Phanerozoic. It is dominated by tholeiites occurring as traps and apparently radiating giant dike swarms and is associated with the disruption of Gondwana and the opening of the Indian Ocean. The Karoo volcanic province located at the South-East of the African

F. Jourdan; G. Tshoso; G. Féraud; H. Bertrand; B. Legall; J. J. Tiercelin; A. B. Kampunzu

2002-01-01

194

Long Hair Shampoo Basin.  

National Technical Information Service (NTIS)

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

K. Schulken

2005-01-01

195

Break-up of Gondwana and opening of the South Atlantic: Review of existing plate tectonic models  

USGS Publications Warehouse

each model. We also plot reconstructions at four selected epochs for all models using the same projection and scale to facilitate comparison. The diverse simplifying assumptions that need to be made in every case regarding plate fragmentation to account for the numerous syn-rift basins and periods of stretching are strong indicators that rigid plate tectonics is too simple a model for the present problem.

Ghidella, M.E.; Lawver, L.A.; Gahagan, L.M.

2007-01-01

196

Palynodating of subsurface sediments, Raniganj Coalfield, Damodar Basin, West Bengal  

NASA Astrophysics Data System (ADS)

The Gondwana sediments comprising fine-grained shales, carbonaceous shales, sandstones and the coal horizon in borecore RT-4 (approximately 547.00m thick) from Tamra block, Raniganj Coalfield, Damodar Basin, are analyzed palynologically. Based on the distribution pattern of marker palynotaxa, two assemblage zones are identified. In the Barren Measures Formation, dominance of enveloping monosaccate ( Densipollenites) along with striate bisaccate ( Striatopodocarpites, Faunipollenites) pollen taxa, and the FAD's of Kamthisaccites and Arcuatipollenites observed at 30.75, have equated this strata (30.75-227.80 m thick) with the Raniganj Formation of Late Permian in age. Downwards in the Barakar Formation, between 423.80-577.70 m depths, an abundance of non-striate ( Scheuringipollenites) and striate ( Faunipollenites and Striatopodocarpites) bisaccate pollen taxa is observed, that dates late Early Permian in age. Fair occurrences of hyaline, distorted and blackish-brown plant matter is observed within 231.00-408.40 m depths. Present study infers the existence of the Raniganj Formation in the lithologically delimited Barren Measures Formation in the study area, and the underlying unproductive strata (approx. 177.40m) might represent the part of the Barren Measures Formation.

Murthy, Srikanta; Chakraborti, B.; Roy, M. D.

2010-10-01

197

The Huqf Supergroup of Oman: Basin development and context for Neoproterozoic glaciation  

NASA Astrophysics Data System (ADS)

The Huqf Supergroup of the Sultanate of Oman provides important information on the geological evolution of the Arabian-Persian Gulf region during a protracted period of continental dispersal and reassembly on the periphery of the Gondwanan supercontinent during the Neoproterozoic, and also provides important constraints on the nature of extreme climate swings during this critical period in the evolution of Earth's biosphere. The Huqf Supergroup spans the period ca. 725-540 Ma, and is composed of three groups. The Abu Mahara Group ( ca. 725 to < 645 Ma) hosts two glacial successions separated by an interval of non-glacial, deep to shallow marine sedimentary rocks. The base of the overlying Nafun Group ( ca.< 645-547 Ma) is marked by a transgressive post-glacial carbonate, which initiates an overstepping of basement-cored structural highs and the deposition of an extensive blanket of carbonate and siliciclastic stratigraphy. The Ara Group ( ca. 547-540 Ma), which is known mostly from the subsurface, comprises carbonates, evaporites and organic-rich shales, with interbedded ashes, deposited in a large number of N-S trending troughs and platforms. The three groups of the Huqf Supergroup correspond to three phases of basin development. The Abu Mahara Group was deposited on an eroded crystalline and metasedimentary basement. An early stage of basin formation preserved < 1.5 km of marginal to deeper marine sedimentary rocks, including an older Cryogenian glacial succession infilling erosional palaeovalleys. Renewed tectonic subsidence associated with submarine volcanism allowed the preservation of a > 1 km-thick, cyclical, rift basin-fill of glacial and non-glacial sedimentary rocks representing a younger Cryogenian icehouse epoch. Progressively older source areas were exhumed during the interval ca. 725 to < 645 Ma, with unroofed 800+ Ma granitoid plutons providing the bulk of sediment, supplemented by syn-extension volcanics, and eventually by distant Meso- and Palaeoproterozoic sources. The wide extent of the Nafun Group, basin-wide correlation of major lithostratigraphic units, and its modest thickness (˜ 1 km) suggest a period of thermal contraction following Abu Mahara rifting. The Oman area was probably a region of slightly stretched continental lithosphere (which passed to the NE into a passive continental margin), occupied by a continental margin rim basin during deposition of the Nafun Group. The Nafun Group bears little resemblance to the coeval small basin-fills choked with calc-alkaline volcanic detritus in the Arabian Shield, but the correlation of the Nafun Group with the Jibalah Group indicates that the contiguous continental rim basin extended from Oman across the tectonically deformed eastern fringe of the Arabian-Nubian Shield. Inundation of the Arabian Shield area and incorporation within the Nafun basin was probably facilitated by extensional collapse and tectonic escape. Sources for 600-640 Ma zircons, found in the Nafun Group, can readily be identified in the Arabian-Nubian Shield. Renewed volcanism, compartmentalization of the basin by N-S trending structural highs and troughs, and an increase in sediment accumulation rates, typifies the Ara Group. The Ara Group deposits formed part of an extensive, latitudinal evaporite belt, with a depocentre translated outwards relative to the Nafun basin, suggesting continuing tectonic progradation of the eastern margin of the Arabian-Nubian Shield. Subduction of ocean floor along the former passive continental margin along the periphery of eastern Gondwana is the most likely cause of Ara volcanism and tectonism, in which case the Oman area can be viewed as occupying a retro-arc setting at this stage, between a subducting margin and the East African orogen. Coeval calc-alkaline plutons and rhyolitic to andesitic volcanics are found in the Central Iranian Terrane. Neoproterozoic glaciations are recorded in the rift and passive margin stratigraphy predating the final amalgamation of continental fragments into greater Gondwana. In Oman, glaciation w

Allen, Philip A.

2007-10-01

198

Major strike-slip faulting along the tectonic boundary between East and West Antarctica: implications for early Gondwana break-up and Jurassic granitic magma emplacement  

NASA Astrophysics Data System (ADS)

The fragmentation of the Gondwana supercontinent began with continental rifting between the Weddell Sea region of Antarctica and South Africa during the Jurassic. This initial Jurassic phase of continental rifting is critical for understanding the process that initiated supercontinent breakup and dispersal, including the role of mantle plumes and major intracrustal tectonic structures. However, due to the remote location and blanketing ice sheets, the tectonic and magmatic evolution of the Weddell Sea Sector of Antarctica has remained relatively poorly understood. Our recent aeromagnetic and airborne gravity investigations have revealed the inland extent of the Weddell Sea Rift system beneath the West Antarctic Ice Sheet, and indicate the presence of a major left-lateral strike slip fault system separating the Ellsworth Whitmore block (a possible exotic microcontinent derived from the Natal Embayment, or the Shackleton Range region of East Antarctica) from East Antarctica (Jordan et al., 2013 Tectonophysics). In this study we use GPlates plate-tectonic reconstruction software to start evaluating the influence of strike-slip faulting between East and West Antarctica on Gondwana breakup models. Specifically, we investigate the possibility of poly-phase motion along the fault system and explore scenarios involving more diffuse strike slip faulting extending into the interior of East Antarctica in the hinterland of the Transantarctic Mountains. Our preliminary models suggest that there may be a link between the prominent step in the flank of the later Cretaceous-Cenozoic West Antarctic Rift System (at the southern end of Ellsworth-Whitmore Block) and the earlier Jurassic Weddell Sea rift system. Additionally, we present preliminary joint 3D magnetic and gravity models to investigate the crustal architecture of the proposed strike-slip fault system and assess its influence on the emplacement of voluminous Jurassic granitic magmatism along the boundary of the Ellsworth-Whitmore block.

Jordan, T. A.; Ferraccioli, F.; Anderson, L.; Ross, N.; Corr, H.; Leat, P. T.; Bingham, R.; Rippin, D. M.; Le Brocq, A. M.; Siegert, M. J.

2013-12-01

199

Community mobilisation with women's groups facilitated by Accredited Social Health Activists (ASHAs) to improve maternal and newborn health in underserved areas of Jharkhand and Orissa: study protocol for a cluster-randomised controlled trial  

PubMed Central

Background Around a quarter of the world's neonatal and maternal deaths occur in India. Morbidity and mortality are highest in rural areas and among the poorest wealth quintiles. Few interventions to improve maternal and newborn health outcomes with government-mandated community health workers have been rigorously evaluated at scale in this setting. The study aims to assess the impact of a community mobilisation intervention with women's groups facilitated by ASHAs to improve maternal and newborn health outcomes among rural tribal communities of Jharkhand and Orissa. Methods/design The study is a cluster-randomised controlled trial and will be implemented in five districts, three in Jharkhand and two in Orissa. The unit of randomisation is a rural cluster of approximately 5000 population. We identified villages within rural, tribal areas of five districts, approached them for participation in the study and enrolled them into 30 clusters, with approximately 10 ASHAs per cluster. Within each district, 6 clusters were randomly allocated to receive the community intervention or to the control group, resulting in 15 intervention and 15 control clusters. Randomisation was carried out in the presence of local stakeholders who selected the cluster numbers and allocated them to intervention or control using a pre-generated random number sequence. The intervention is a participatory learning and action cycle where ASHAs support community women's groups through a four-phase process in which they identify and prioritise local maternal and newborn health problems, implement strategies to address these and evaluate the result. The cycle is designed to fit with the ASHAs' mandate to mobilise communities for health and to complement their other tasks, including increasing institutional delivery rates and providing home visits to mothers and newborns. The trial's primary endpoint is neonatal mortality during 24 months of intervention. Additional endpoints include home care practices and health care-seeking in the antenatal, delivery and postnatal period. The impact of the intervention will be measured through a prospective surveillance system implemented by the project team, through which mothers will be interviewed around six weeks after delivery. Cost data and qualitative data are collected for cost-effectiveness and process evaluations. Study registration ISRCTN: ISRCTN31567106

2011-01-01

200

The oldest sediments of Greece revealed by detrital zircon LA-ICP-MS U-Pb dating: Cambro-Ordovician sandstones from northern Gondwana in the External Hellenides - implications on the evolution of the eastern Mediterranean  

NASA Astrophysics Data System (ADS)

Detrital zircon U-Pb ages of a quartzite from the Feneos locality of Peloponnesus, S. Greece, were determined by LA-ICPMS. The rock classifies as a mature quartz arenite and belongs to an original shale-sandstone succession now metamorphosed into a phyllite-quartzite unit. The latter chiefly represents the External Blueschist Belt of the Hellenides widely known as the Arna or Phyllite - Quartzite (PQ) Unit. Zircon age clusters at 0.5-0.75, 0.85, 0.95-1.1, 1.75-2 and 2.4-3 Ga point at the Saharan Metacraton and the Transgondwanan Supermountain as contributing sources; the youngest concordant grain is 522 Ma old. Based on great similarities in lithology, zircon age-distribution patterns and depositional setting between the Feneos quartzite and intact Cambro-Ordovician sandstone-shale sequences of Libya (Murzuq and Kufrah basins) we propose that the protolith of the former was deposited in an epeiric sea north of Libya during the Cambro-Ordovician. Feneos, as part of the Cimmerian block, had become detached from the NE Gondwanan margin during Late Carboniferous - Early Permian times and drifted northward. In central Crete, similar-looking sequences (Galinos beds) were originally deposited in an accretionary/fore-arc complex outboard of the south Laurussian active margin (Pelagonia) between ~297-230 Ma. The southern Pelagonian margin eventually collided (mild docking) with the northward drifting Cimmerian block signaling the closure of Palaeotethys by early Late Triassic. The Gondwanan affinity of the Feneos quartzite strongly contrasts the European one of the Galinos beds; the suture of Palaeotethys can thus be traced in S. Greece within the pre-Triassic sedimentary sequences of Peloponnesus and Crete. In the eastern Mediterranean realm, rocks with similar age clusters crop out in Greece (Peloponnesus, this study; eastern Crete, Sfaka locality; north-central Macedonia, Vertiskos terrane), NW Turkey (central Sakarya terrane), Libya (Murzuq and Kufrah basins), Israel (Elat locality) and Jordan (El-Quweira locality). Their zircon age spectra plotted with respect to sediment depositional age indicate a collisional margin setting for all. Evaluating the depositional setting of the arguably similar sedimentary sequences above we demonstrate their common provenance from the Gondwana Super-fan System which draped the northern Gondwanan periphery from ~525 to 460 Ma (Lower Cambrian - Middle Ordovician). Using as anchoring points the non-metamorphosed Early Palaeozoic outcrops of Libya and the Middle East that remained intact at their original deposition sites we have traced, in space and time, the path of the remainder time- and facies-equivalent rocks presently cropping out in the Hellenic and Turkish mountain belts. The fate of the northern Gondwanan margin was multiple rifting and travelling of the fragments thereof throughout the Palaeozoic before their final incorporation into younger orogenic belts.

Kydonakis, Konstantinos; Kostopoulos, Dimitrios; Poujol, Marc; Brun, Jean-Pierre; Papanikolaou, Dimitrios; Paquette, Jean-Louis

2013-04-01

201

Magnetic Fabric of the Itararé Group, Paraná Basin Brazil: Preliminary Results  

NASA Astrophysics Data System (ADS)

The late Paleozoic Itararé Group and equivalent beds in the Paraná Basin of Brazil extend into Paraguay, Argentina, and Uruguay. The Itararé Group contains the most extensive lithological record of Gondwana glaciation in the world. The succession has a maximum subsurface thickness of around 1400 m and extends over a total area greater than 1 million km2. The lower boundary of the Itararé Group is nonconformable with Precambrian to early Paleozoic crystalline basement and with Devonian strata of the Furnas and Ponta Grossa Formations, which together constitute the base of the Gondwana supersequence of the Paraná Basin. This boundary encompasses a hiatus that is loosely estimated in 45 Ma. The upper contact with the overlying Rio Bonito Formation is described as conformable to partially erosional. We performed our study on 13 sites from sedimentary rocks (sandstones and siltites) from the Itararé beds in the Brazilian portion of the Paraná Basin (mainly in São Paulo State). Magnetic fabrics were determined on oriented cylindrical specimens (2.54 cm x 2.2 cm) using the anisotropy of low-field magnetic susceptibility (AMS). Rock-magnetic analyses reveal that magnetite is the main magnetic mineral. In one of the sampled site, however, the ferromagnetic minerals are both magnetite and hematite. Regarding the eingenvector orientations, the sites usually gave good results. The analysis at the individual-site scale defines three AMS fabric types. The first type (7 sites) shows Kmin perpendicular to the bedding plane while Kmax and Kint are scattered within the bedding plane itself. This fabric is usually interpreted as primary (sedimentary-compactional), typical of undeformed sediments. The second type (5 sites) shows good clustering of the AMS principal axes with Kmin still sub-perpendicular to the bedding plane. The third type, pertaining to an intensely folded site previously interpreted as slumped, is characterized in geographic coordinates by well-clustered Kmax in the bedding plane, while Kmin and Kint are distributed along a NE-SW girdle with a sub-vertical, yet elongate Kmin distribution. In stratigraphic coordinates Kmax maintains the same NNW-SSE clustering, yet Kmin and Kint become scattered within the girdle. The second fabric type would be interpreted as combination of sedimentary-compactional and tectonic contributions if some strain markers or evidence for tectonic deformation had been found in the studied area. On the other hand, the tight Kmax grouping in this fabric type could be explained by the action of currents since they cause Kmax to be aligned sub-parallel to the paleocurrent direction.

Raposo, M. B.; Bilardello, D.; Santos, P. R.

2012-12-01

202

Origin of cratonic basins  

NASA Astrophysics Data System (ADS)

Tectonic subsidence curves show that the Illinois, Michigan, and Williston basins formed by initial fault-controlled mechanical subsidence during rifting and by subsequent thermal subsidence. Thermal subsidence began around 525 Ma in the Illinois Basin, 520 460 Ma in the Michigan Basin, and 530 500 Ma in the Williston Basin. In the Illinois Basin, a second subsidence episode (middle Mississippian through Early Permian) was caused by flexural foreland subsidence in response to the Alleghanian-Hercynian orogeny. Resurgent Permian rifting in the Illinois Basin is inferred because of intrusion of well-dated Permian alnoites; such intrusive rocks are normally associated with rifting processes. The process of formation of these cratonic basins remains controversial. Past workers have suggested mantle phase changes at the base of the crust, mechanical subsidence in response to isostatically uncompensated excess mass following igneous intrusions, intrusion of mantle plumes into the crust, or regional thermal metamorphic events as causes of basin initiation. Cratonic basins of North America, Europe, Africa, and South America share common ages of formation (around 550 to 500 Ma), histories of sediment accumulation, temporal volume changes of sediment fills, and common dates of interregional unconformities. Their common date of formation suggests initiation of cratonic basins in response to breakup of a late Precambrian super-continent. This supercontinent acted as a heat lens that caused partial melting of the lower crust and upper mantle followed by emplacement of anorogenic granites during extensional tectonics in response to supercontinent breakup. Intrusion of anorogenic granites and other partially melted intrusive rocks weakened continental lithosphere, thus providing a zone of localized regional stretching and permitting formation of cratonic basins almost simultaneously over sites of intrusion of these anorogenic granites and other partially melted intrusive rocks.

Dev. Klein, George; Hsui, Albert T.

1987-12-01

203

Bouguer anomaly of the Godavari basin, India and magnetic characteristics of rocks along its coastal margin and continental shelf  

NASA Astrophysics Data System (ADS)

The Bouguer anomaly map of the Godavari basin has delineated several transverse and median ridges that have divided this basin into several sub-basins. Modelling of a gravity profile in the central part of the basin suggests 5.0 km of Gondwana sediments and high density rocks along the shoulders which may represent upthrusted lower crustal rocks related to the Eastern Ghats orogeny. The total intensity magnetic map of the coastal part of the Godavari basin shows a well-defined magnetic anomaly of approximately 200 nT along the coast which coincides with the Kaza basement ridge. The modelling of this magnetic anomaly indicates 2-2.5 km of sediments over the Kaza ridge and 5.5-6 km thick sediments in the depressions towards the west of this ridge which are constrained from the basement configuration based on seismic sections in the surrounding region. The Kaza ridge, with a susceptibility of 10 -4 SI units, appears to be composed of basic rocks which may be part of the exposed Eastern Ghats towards the west. This magnetic map also shows several high amplitude short wavelength anomalies which are caused by sub-surface basic rocks. These basic rocks are related to the Rajahmundry trap, equivalent to the Deccan traps of late Cretaceous age, and are exposed nearby by. Modelling of the magnetic anomaly across the continental shelf, off the coast of the Godavari basin, suggests an almost 45° inclined contact away from shore at a depth of 2.5 km and having a thickness of 3.5 km. However, this magnetic anomaly could be matched only with a remanent magnetization with declination 310° and inclination -67° which corresponds to the direction of magnetization reported for the Rajmahal traps.

Venkata Raju, D. Ch; Rajesh, R. S.; Mishra, D. C.

2002-12-01

204

Palaeoenvironmental and geochemical approach of Archaeocyath-rich facies from Lower Cambrian of Western Gondwana margin at Central Iberian Zone (Urda, Toledo Mountains, Spain)  

NASA Astrophysics Data System (ADS)

Archaeocyath-rich facies are located in a quarry close to Urda village, at Toledo Mountains, Spain. The outcrops belong to the Caliza de los Navalucillos Formation and they record a considerably high diverse archaeocyath assemblage in the Lower Cambrian successions from the Central Iberian Zone (Julivert et al. 1972 [1974]). In fact, it is first time recorded the presence of Agyrekocyathus, Dokidocyathus, and Plicocyathus in the Central Iberian Zone. Therefore Plicocyathus is no longer exclusive to biozone VI in Spain. The presence of Anthomorpha is characteristic for the early Botomian, presently early Stage 4 (ICS, 2009), and the assemblage corresponds to the biozone VII (late Ovetian, following the biozonation of Perejón & Moreno-Eiris, 2006). The fossiliferous part of the succession is formed by seven lithofacies, all of them tectonically folded and with a low grade metamorphic overprint. They are comprised by two main groups of facies: (a) mound-shaped to massive lithofacies (A1, A2, A3, A4) and (b) massive to bedded and nodular lithofacies (B1, B2, B3). Archaeocyaths occur in several facies: (A1) mound-shaped white marble with irregular to stromatactoid cavities; (A2) massive mottled white to grey limestone; (A3) massive grey limestone with slumps levels; (A4) massive archaeocyath-rich orange limestone; as well as in carbonate nodules embedded in siltstones and cherts (B1, B2 and B3). The best preserved assemblage comes from the nodule record, where fossils are partially pyritized. This type of preservation is exceptional and has never been described before. XRD and wavelength-dispersive electron microprobe analyses reveal the presence of pyrite and pyrrotine partially altered to iron oxides and hydroxides (hematite and goethite) surrounding the archaeocyath cups. In Central Iberian Zone, the development of mounds and nodular facies like those described here is unusual, although the Botomian marks the peak for Early Cambrian archaeocyathan-microbial mounds in Western Gondwana margin. Powdered microsamples have been analysed for their elemental and isotopic composition (?13C values range from + 0.41 to + 3.05). Sulphur minerals and silicates where analyzed with XRD and wavelength-dispersive electron microprobe. Major elements were measured with ICP-OES and minor and trace elements were analyzed with ICP-MS. These are the first palaeontological, sedimetological, geochemical and isotopical data provided to reconstruct the depositional environment of these Archaeocyath-rich facies at the Western Gondwana margin. References Julivert, M., Fontboté, J.M., Ribeiro, A., Nabais Conde L.E. 1972. Mapa tectónico de la Península Ibérica y Baleares, Escala 1: 1.000.000, Memoria Explicativa [1974], 113 pp. Instituto Geológico y Minero de España. Perejón, A., Moreno-Eiris, E. 2006. Biostratigraphy and palaeobiography of the archaeocyaths on the south-western margin of Gondwana. Zeitschrift der Deutschen Gesellschaft für Geowissenschaften 157 (4): 611-627.

Menéndez, Silvia; Rodríguez-Martínez, Marta; Moreno-Eris, Elena; Perejón, Antonio; Reitner, Joachim

2010-05-01

205

Geysers: Lower Geyser Basin  

NSDL National Science Digital Library

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.

206

WILLISTON BASIN PROVINCE (031)  

Microsoft Academic Search

Plains and extends northward into Canada. The basin region is a generally flat lying, moderately dissected plain with minimum topographic relief. The basin is bordered on the east and southeast by the Canadian Shield and the Sioux Uplift. The western and southwestern borders are defined by the Black Hills Uplift, Miles City Arch, Porcupine Dome, and Bowdoin Dome. The United

James A. Peterson; James W. Schmoker

207

ROANOKE RIVER BASIN DATA  

EPA Science Inventory

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

208

Tectonics and basin development of the offshore Tasmanian area incorporating results from deep ocean drilling  

NASA Astrophysics Data System (ADS)

Tasmania and adjoining continental blocks, the South Tasman Rise (STR) and East Tasman Plateau (ETP), are central components of a major fragmentation of east Gondwana that began in early Late Cretaceous. The tectonic development of the Tasmanian region is key to understanding (i) the kinematics and geological evolution of adjacent plates and former neighboring continents and microcontinents that have now dispersed, (ii) formation of the extensive sedimentary basins off Tasmania, and (iii) major changes in ocean circulation, climate and sedimentation patterns associated with the opening of a deep-water seaway between Tasmania and Antarctica at the end of the Eocene. From Late Cretaceous to early Miocene the western and southern parts of the region were part of a large sinistral transform system, which until the Paleocene trended NW (Tasmanian-Antarctic Shear Zone) then changed orientation to N-S (Tasman Fracture Zone). Wrench basins up to 6 km deep developed in the Sorell Basin off west Tasmania, and narrow transtensional rifts with up to 4 km of fill were created on the STR. During the Paleocene shift in plate kinematics the western STR terrane, including the Ninene Basin, transferred to the Australian plate. Before that, the Ninene Basin had been part of the NNE-trending Rennick Graben in northern Victoria Land. In the east of the region, Tasman Basin rifting began in early Late Cretaceous, with onset of seafloor spreading in early Campanian. Small rift grabens, now filled with up to 4 km of sediment, developed on the east Tasmanian margin, eastern STR, and ETP. The Australian and Antarctic continents separated at the SW tip of the STR at 33.5 Ma, opening a deep seaway that led to circum-Antarctic circulation as the continents continued to drift apart. Significant flow-through may have begun several million years earlier across passages in the southern Ninene Basin and South Tasman Saddle, due to basin extension and increased margin subsidence. Sedimentation changed from siliciclastics-dominated to biogenic (mainly pelagic) carbonate-dominated, with post-Eocene accumulations no thicker than about 1000 m anywhere in the region. Although there is no recorded activity since the late Miocene, volcanism was extensive earlier. It is attributed to breakup volcanism (Campanian-Paleocene) close to the continent-ocean boundary, and an Eocene episode of widespread and voluminous basaltic eruptions that produced large seamounts and fields of volcanic cones.

Hill, Peter J.; Exon, Neville F.

209

Anomalous electrical structure in the northwestern Paraná Basin, Brazil, observed with broadband magnetotellurics  

NASA Astrophysics Data System (ADS)

The deep structure of the northern part of the Paraná Basin has been investigated through the analysis of a SW-NE magnetotelluric (MT) profile composed of 24 broadband stations with periods from 0.001 to ˜1000 s that are regularly spaced ˜10 km apart. The SW portion of the profile crosses a negative Bouguer anomaly with amplitudes of ˜20 mGal. Our analyses show that there are two lithospheric domains with different gravity and electric conductivity properties. In the regularized two-dimensional MT inversion model the mid-to-lower crust in the SW part of the profile is almost two orders in magnitude more conductive compared to the NE portion. This difference in conductivity extends to the uppermost mantle depths, suggesting the existence of a major lithospheric discontinuity in the north-central Paraná Basin, locally coincident with the position of the Aporé River. We interpret this discontinuity as a juxtaposition of terranes with distinct natures and ages, possibly as result of tectonic accretion during the formation of Western Gondwana.

Bologna, Mauricio S.; Nunes, Higo O.; Padilha, Antonio L.; Vitorello, Ícaro; Pádua, Marcelo B.

2013-03-01

210

Drainage Basins Field Lab  

NSDL National Science Digital Library

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

Marshall, Jeff

211

Not all supercontinents are created equal: Nd and Hf depleted mantle model ages reveal fundamental differences in the assembly of Rodinia and Gondwana  

NASA Astrophysics Data System (ADS)

Hf isotopes in zircon show a strong relationship with the 87Sr/86Sr ratios of seawater through time in that periods of low zircon "Hf values also show more crustal 87Sr/86Sr ratios. This implies the mechanisms that drive these isotopic systems are linked in similar Earth processes. In turn, the Sr isotopic record in seawater and global zircon Hf averages have been proposed as proxies for the formation and destruction of supercontinents. During supercontinent assembly, when subaerial exposure of the continent and the degree of magmatic crustal reworking is maximized, the 87Sr/86Sr ratio of seawater and the evolved signature of Hf isotopes in zircon should increase and vice versa as supercontinents break apart (Condie, 2011; Roberts, in press). Although this relationship is found during the assembly of Gondwana from the Pan-African orogeny, it is not seen during the growth of Rodinia and the Grenville orogeny. One explanation for this is the ages of material involved in the assembly of supercontinents were different and so had different isotopic signatures. If an orogen reworked young material then the zircon Hf and 87Sr/86Sr would not show a strong excursion to more crustal values than if the orogen incorporated much older material with more extreme isotope ratios. To quantify the relative proportions of young versus old material in these orogenies, depleted mantle model ages of whole rock Nd in felsic rocks and zircon Hf derived from the Pan-African and Grenville orogenies are normalized to equate the ages of the contributing material to the beginning of each orogeny. Integration of probability density plots reveal the Grenville orogeny contains between 56% (zr Hf) and 60% (WR Nd) of pre-900 Ma depleted mantle ages. Conversely the Pan-African orogeny has between 61% (WR Nd) and 69% (zr Hf) of post-900 Ma material. The division of 900 Ma is chosen simply because there is a slight trough of depleted mantle ages from the beginning of each orogeny. These normalized percentages imply the Hf and Nd isotopic signatures of the assembly of Rodinia are not as prominent as that for the assembly of Gondwana simply because the age of the material involved in the reworking and collision were relatively younger for the Grenville orogeny and older for the Pan-African orogeny. This also implies the 87Sr/86Sr record cannot be used to identify periods of supercontinent formation. It is therefore apparent, that simple comparison of isotopic signatures cannot accurately identify periods of increased continental amalgamation.

Spencer, C.; Cawood, P.; Hawkesworth, C.; Dhuime, B.

2012-04-01

212

Palaeomagnetic confirmation of Palaeozoic clockwise rotation of the Famatina Ranges (NW Argentina): implications for the evolution of the SW margin of Gondwana  

NASA Astrophysics Data System (ADS)

Palaeomagnetic results from Palaeozoic volcanic and sedimentary units of the Famatina Ranges, in NW Argentina (28.7°S, 67.8°W) are reported. A late Early to late Middle Ordovician palaeomagnetic pole was obtained from a pre-tectonic remanence carried by magnetite and isolated in volcanics of the Molles Formation and the Cerro Morado Group (MCM1, 16.7°S, 357.2°E, A95 = 6.5°, K = 38.5, N = 14 sites). This pole position is rotated 39° clockwise respect to the coeval reference pole for Gondwana but it is consistent with previous Early Ordovician poles from the Famatina belt and the Faja Eruptiva Oriental in the Puna region of NW Argentina. The sedimentary layers of the Molles Formation, however, present a secondary magnetization carried by hematite, which is interpreted of Permian age and yields a pole position (MCM2) at 78.7°S, 330.8°E (A95 = 7.2°, K = 16.1, n = 27 samples). Two additional independent palaeomagnetic poles were obtained from the Permian De La Cuesta Formation, exposed at two different localities in the same area. While one consisted in a exclusively reverse polarity magnetization and a pole position (LC1, 76.9°S, 345.2°E, A95 = 6.0°, K = 21.1, n = 29 samples) compatible with the late Early to early Late Permian palaeomagnetic poles from South America, the other presented only normal polarities and a pole position (LC2, 74.5°N, 275.4°E, A95 = 2.0°, K = 258.3, n = 21 samples) suggestive of a Cretaceous remagnetization. These new palaeomagnetic results confirm on a much more robust database previous proposals that the Ordovician rocks of the Famatina belt have undergone a large clockwise rotation. They also constrain the rotation to pre-Permian times. Different tectonic models involving the Late Ordovician docking of a large para-authochthonous terrane or a pattern of systematic large-scale rotations in the Early Palaeozoic continental margin of Western Gondwana are discussed.

Spagnuolo, C. M.; Rapalini, A. E.; Astini, R. A.

2008-04-01

213

The stability and origin of sodicgedrite in ultrahigh-temperature Mg-Al granulites: a case study from the Gondwana suture in southern India  

NASA Astrophysics Data System (ADS)

Mg-Al-rich rocks from the Palghat-Cauvery Shear Zone System (PCSZ) within the Gondwana suture zone in southern India contain sodicgedrite as one of the prograde to peak phases, stable during T = 900-990°C ultrahigh-temperature metamorphism. Gedrite in these samples is Mg-rich (Mg/[Fe + Mg] = X Mg = 0.69-0.80) and shows wide variation in Na2O content (1.4-2.3 wt.%, NaA = 0.33-0.61 pfu). Gedrite adjacent to kyanite pseudomorph is in part mantled by garnet and cordierite. The gedrite proximal to garnet shows an increase in NaA and AlIV from the core (NaA = 0.40-0.51 pfu, AlIV = 1.6-1.9 pfu) to the rim (NaA = 0.49-0.61 pfu, AlIV = 2.0-2.2 pfu), suggesting the progress of the following dehydration reaction: Ged + Ky ? Na-Ged + Grt + Crd + H2O. This reaction suggests that, as the reactants broke down during the prograde stage, the remaining gedrite became enriched in Na to form sodicgedrite, which is regarded as a unique feature of high-grade rocks with Mg-Al-rich and K-Si-poor bulk chemistry. We carried out high- P-T experimental studies on natural sodicgedrite and the results indicate that gedrite and melt are stable phases at 12 kbar and 1,000°C. However, the product gedrite is Na-poor with only <0.13 wt.% Na2O (NaA = 0.015-0.034 pfu). In contrast, the matrix glass contains up to 8.5 wt.% Na2O, suggesting that, with the progressive melting of the starting material, Na was partitioned into the melt rather than gedrite. The results therefore imply that the occurrence of sodicgedrite in the UHT rocks of the PCSZ is probably due to the low H2O activity during peak P-T conditions that restricted extensive partial melting in these rocks, leaving Na partitioned into the solid phase (gedrite). The occurrence of abundant primary CO2-rich fluid inclusions in this rock, which possibly infiltrated along the collisional suture during the final amalgamation of the Gondwana supercontinent, strengthens the inference of low water activity.

Kanazawa, Tomohito; Tsunogae, Toshiaki; Sato, Kei; Santosh, M.

2009-01-01

214

Petrology and fluid inclusions of garnet-clinopyroxene rocks from the Gondwana suture zone in southern India: Implications for prograde high-pressure metamorphism  

NASA Astrophysics Data System (ADS)

The Palghat-Cauvery Suture Zone (PCSZ) in the southern granulite terrane, India, which separates Pan-African granulite blocks (e.g., Madurai and Trivandrum Blocks) to the south and Archean terrane (e.g., Salem Block and Dharwar Craton) to the north is regarded as a major suture zone in the Gondwana collisional orogeny. It probably continues westwards to the Betsimisaraka suture in Madagascar, and eastwards into Sri Lanka and possibly into Antarctica. The available geochronological data including U-Pb zircon and EPMA monazite ages indicate that the rocks along the PCSZ underwent an episode of high-grade metamorphism at ca. 530 Ma that broadly coincides with the time of final assembly of the Gondwana supercontinent. Recent investigations on high-grade metamorphic rocks in this region have identified several new occurrences of garnet-clinopyroxene rocks and associated meta-gabbros from Perundurai, Paramati, Aniyapuram, Vadugappatti, and Mahadevi areas in Namakkal region within the central domain of the PCSZ. They occur as elongated boudins of 1 m to 1 km in length within hornblende-biotite orthogneiss. The garnet-clinopyroxene mafic granulites contain coarse-grained (up to several cm) garnet (Alm30-50 Pyr30-40 Grs10-20) and clinopyroxene (XMg = 0.70-0.85) with minor pargasite, plagioclase (An30-40), orthopyroxene (hypersthene), and rutile. Garnet and clinopyroxene are both subidioblastic and contain few inclusions of clinopyroxene (in garnet) and plagioclase. Orthopyroxene occur only as Opx + Pl symplectite between garnet and clinopyroxene in almost all the localities, suggesting the progress of decompressional reaction: Grt + Cpx + Qtz => Opx + Pl, which is a dominant texture in the PCSZ. The prograde mineral assemblage of the rocks is therefore inferred to be Grt + Cpx + Qtz, although quartz was probably totally consumed by the progress of the reaction. The metamorphic P-T calculations using Grt-Cpx-Pl-Qtz geothermobarometers yield T = 850-900°C and P >13 kbar, which is consistent with the occurrence of high-pressure Mg-rich staurolite in Mg-Al-rich rocks from this region. Fluid inclusion study of some garnet-clinopyroxene rock samples identified CO2-rich fluid inclusions trapped as primary phases within garnet, suggesting that prograde high-pressure metamorphism was dominated by CO2-rich fluids. The results therefore confirmed that the PCSZ underwent regional dry high-pressure metamorphism followed by the peak ultrahigh-temperature event probably associated with the continent-continent collisional and suturing history along the PCSZ.

Tsunogae, T.

2012-04-01

215

The Namuskluft and Dreigratberg sections in southern Namibia (Kalahari Craton, Gariep Belt): a geological history of Neoproterozoic rifting and recycling of cratonic crust during the dispersal of Rodinia until the amalgamation of Gondwana  

NASA Astrophysics Data System (ADS)

This paper presents combined U/Pb, Th/U and Hf isotope analyses on detrital and magmatic zircon grains together with whole-rock geochemical analyses of two basement and eight sedimentary rock samples from the Namuskluft and the Dreigratberg in southern Namibia (Gariep Belt). The sedimentary sections evolved during the Cryogenian on the SW part of the Kalahari Craton and where therefore deposited in an active rift setting during the break-up of Rodinia. Due to insufficient palaeomagnetic data, the position of the Kalahari Craton within Rodinia is still under discussion. There are possibilities to locate Kalahari along the western side of Australia/Mawsonland (Pisarevski et al. in Proterozoic East Gondwana: supercontinent assembly and break-up, Geological Society, London, 2003; Evans in Ancient Orogens and modern analogues. Geological Society, London, 2009; and others) or together with the Congo-Sao Francisco and Rio de la Plata Cratons (Li et al. in Prec Res 45: 203-2014, 2008; Frimmel et al. in Int J Earth Sci (Geol Rundsch) 100: 323-354, 2011; and others). It is sill unclear which craton rifted away from the Kalahari Craton during the Cryogenian. Although Middle to Upper Cryogenian magmatic activity is known for the SE Kalahari Craton (our working area) (Richtersveld Suite, Rosh Pinah Fm), all the presented samples show no U/Pb zircon ages younger than ca. 1.0 Ga and non-older than 2.06 Ga. The obtained U/Pb ages fit very well to the exposed basement of the Kalahari Craton (1.0-1.4 Ga Namaqua Province, 1.7-2.0 Ga Vioolsdrif Granite Suite and Orange River Group) and allow no correlation with a foreign craton such as the Rio de la Plata or Australia/Mawsonland. Lu-Hf isotopic signatures of detrital zircon point to the recycling of mainly Palaeoproterozoic and to a smaller amount of Archean crust in the source areas. ?Hf(t) signatures range between -24 and +14.8, which relate to TDM model ages between 1.05 and 3.1 Ga. Only few detrital zircon grains derived from magmas generated from Mesoproterozoic crustal material show more juvenile ?Hf(t) signatures of +14, +8 to +4 with TDM model ages of 1.05-1.6 Ga. During Neoproterozoic deposition, only old cratonic crust with an inherited continental arc signature was available in the source area clearly demonstrated by Hf isotope composition of detrital zircon and geochemical bulk analysis of sedimentary rocks. The granodiorites of the Palaeoproterozoic basement underlying Namuskluft section are ca. 1.9 Ga old and show ?Hf(t) signatures of -3 to -5.5 with TDM model ages of 2.4-2.7 Ga. These basement rocks demonstrate the extreme uplift and deep erosion of the underlying Kalahari Craton at its western margin before general subsidence during Cryogenian and Ediacaran time. The sedimentary sequence of the two examined sections (Namuskluft and Dreigratberg) proposes the presence of a basin and an increasing subsidence at the SW part of the Kalahari Craton during the Cryogenian. Therefore, we propose the initial formation of an intra-cratonic sag basin during the Lower Cryogenian that evolved later to a rift basin at the cratonic margin due to increasing crustal tension and rifting together with the opening of the Adamastor Ocean. As the zircons of the sedimentary rocks filling this basin show neither rift-related U/Pb ages nor an exotic craton as a possible source area, the only plausible sedimentary transport direction providing the found U/Pb ages would be from the E or the SE, directly from the heart of the Kalahari Craton. Due to subsidence and ongoing sedimentation from E/SE directions, the rift-related magmatic rocks were simply covered by the input of old intra-cratonic material that explains the absence of Neoproterozoic zircon grains in our samples. The geochemical analyses show the erosion of a continental arc and related sedimentary rocks with an overall felsic provenance. The source area was a deeply eroded and incised magmatic arc that evolved on continental crust, without any evidence for a passive margin. All of this can be explained by the erosion of rocks related to

Hofmann, Mandy; Linnemann, Ulf; Hoffmann, Karl-Heinz; Gerdes, Axel; Eckelmann, Katja; Gärtner, Andreas

2013-08-01

216

Processing and interpretation of seismic reflection data from Ogaden basin, Ethiopia  

SciTech Connect

The Ogaden basin is believed to be an extensional basin created during the early rifting of Gondwana and the development of the western Indian Ocean. Preliminary studies conducted by various oil companies and national geoscientists suggest that the area is prospective for hydrocarbon accumulation. Prior to these studies, however, very little was known of the surface geology in this area and virtually nothing was known of the subsurface. The objectives of the study were to implement state-of-the-art seismic and gravity data processing and interpretation techniques in order to identify structural and/or stratigraphic trap sequences and indicate their significance in the hydrocarbon exploration of the basin. In this study, high resolution multi-channel reflection seismic data, acquired in 1993 from the Ogaden Basin, are used. The data were acquired for Hunt Oil Company using Vibroseis as an energy source. Various data enhancement techniques were applied to these data in order to produce an interpretable final seismic section for the identification of possible hydrocarbon habitats. These included discrimination and filtering of coherent noise from the signal, enhancing, focussing of the identified reflectors and static corrections. Statics solutions from shallow wells and automatic refraction statics were compared, with the best results obtained when automatic refraction solutions were applied. Our study has revealed various reflection horizons that can be potential stratigraphic traps at pinch outs and may be porous strata which are terminated by lateral transitions or interconnected lines of either elastic sediments or carbonates. We discuss these results in the light of gravity modelling designed to estimate maximum sediment thickness along the line.

Tadesse, K.; Ebinger, C.J.; Clark, R.A. (Univ. of Leeds (United Kingdom))

1996-01-01

217

UPPER SNAKE RIVER BASIN, PRELIMINARY BASIN EVALUATION  

EPA Science Inventory

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...

218

Amazon rift and Pisco-Juruá fault: Their relation to the separation of North America from Gondwana  

NASA Astrophysics Data System (ADS)

The Amazon fault passes eastward from south of Guayaquil on the Pacific to the Amazon mouth on the Atlantic coast. Along its eastern segment, a rift with pyroxenite intrusions opened up at the start of Paleozoic time; its Early Jurassic reactivation produced more than 100,000 km3 of diabase sills, intruded into the evaporitic upper Paleozoic simultaneously with North Atlantic rifting. Pliocene reactivation faulted the coastal Tertiary and sheared the subducted slab beneath the Pacific end of the fault. The northeast-trending Pisco-Juruá fault, first described here, cuts across the continent from Pisco on the Pacific to the Guyana-Surinam border on the Atlantic coast. In early Mesozoic time the fault formed the southwestern continuation of the North Atlantic Rift; its Guyanan end opened up as the North Atlantic Rift opened. The separation of North and South America caused northwestern South America to move southwest along the Pisco-Juruá fault, creating the Tacutu graben in the Guyanan Shield, the gently folded Juruá zone across the Amazon Basin, and the Pisco-Abancay deflection in the Andes. Pliocene reactivation at the Pacific end of the fault sheared the subducted slab of the Nazca plate and may have contributed to the formation of the Nazca Ridge.

Szatmari, Peter

1983-05-01

219

Major shear zones of southern Brazil and Uruguay: escape tectonics in the eastern border of Rio de La plata and Paranapanema cratons during the Western Gondwana amalgamation  

NASA Astrophysics Data System (ADS)

The Mantiqueira Province represents a series of supracrustal segments of the South-American counterpart formed during the Gondwana Supercontinent agglutination. In this crustal domain, the process of escape tectonics played a conspicuous role, generating important NE-N-S-trending lineaments. The oblique component of the motions of the colliding tectonic blocks defined the transpressional character of the main suture zones: Lancinha-Itariri, Cubatão-Arcádia-Areal, Serrinha-Rio Palmital in the Ribeira Belt and Sierra Ballena-Major Gercino in the Dom Feliciano Belt. The process as a whole lasted for ca. 60 Ma, since the initial collision phase until the lateral escape phase predominantly marked by dextral and subordinate sinistral transpressional shear zones. In the Dom Feliciano Belt, southern Brazil and Uruguay, transpressional event at 630-600 Ma is recognized and in the Ribeira Belt, despite less coevally, the transpressional event occurred between 590 and 560 Ma in its northern-central portion and between ca. 625 and 595 Ma in its central-southern portion. The kinematics of several shear zones with simultaneous movement in opposite directions at their terminations is explained by the sinuosity of these lineaments in relation to a predominantly continuous westward compression.

Passarelli, C. R.; Basei, M. A. S.; Wemmer, K.; Siga, O.; Oyhantçabal, P.

2011-04-01

220

Efficacy of permethrin treated long-lasting insecticidal nets on malaria transmission and observations on the perceived side effects, collateral benefits and human safety in a hyperendemic tribal area of Orissa, India.  

PubMed

Studies were conducted on the efficacy of Olyset nets-a long-lasting insecticidal net (LLIN) factory treated with 2% (w/w) permethrin on malaria transmission in an area under the influence of pyrethroid susceptible vector species Anopheles culicifacies and A. fluviatilis in Sundargarh District, Orissa, India. The study area comprised 22 villages that were randomized into three clusters and designated as Olyset net, untreated net, and no net area. Malaria incidence in the study population was measured through longitudinal active surveillance at fortnightly intervals. There was a reduction of 65-70% in malaria incidence in Olyset net area as compared to the control areas. The attack rate of Plasmodium falciparum or number of episodes per person per year in different age groups also showed significant reduction in Olyset net area as compared to untreated net and no net areas. Cross-sectional point prevalence surveys showed 45.7% reduction of malaria prevalence in Olyset net users, whereas there was an increase of 33.3% and 51% in untreated net and no net villages respectively. The compliance rate of Olyset net usage in the study population was 80-98% during different months, whereas it was between 70% and 90% for untreated nets. There were minimal complains of skin irritation (4%), itching (8%) and eye irritation (1.2%). However, these effects were only transitory in nature lasting for few hours of the first usage. Olyset nets also provided collateral benefits in terms of relief not only from mosquitoes and malaria but also from other household pests such as head lice, bed bugs, cockroaches, ants and houseflies. The Olyset nets were found to be safe to humans as no adverse event was recorded in the net users that can be attributed to the use of net. The study showed that Olyset nets are effective personal protection tool that can be used in a community based intervention programme. PMID:19647715

Sharma, Surya K; Tyagi, Prajesh K; Upadhyay, Ashok K; Haque, Mohammed A; Mohanty, Suman S; Raghavendra, Kamaraju; Dash, Aditya P

2009-11-01

221

Personal-protection measures against mosquitoes: a study of practices and costs in a district, in the Indian state of Orissa, where malaria and lymphatic filariasis are co-endemic.  

PubMed

In a study undertaken among rural and urban communities in a district of Orissa, India, the personal-protection measures used against mosquitoes, and the household costs of these measures, were investigated. Most people living in the study communities perceived mosquitoes as a problem, both as a biting nuisance and as vectors of human disease. Almost all (99%) of the urban households investigated and most (84%) of the rural each reported the use of at least one measure against mosquitoes. Most of the study households (92% of the urban and 64% of the rural) used a 'modern' chemical method (coils, vaporizing mats, liquid vaporizers or sprays), with mosquito coils used more frequently than any other personal-protection measure. Untreated bednets were also used by most of the households investigated (76% of the urban and 58% of the rural) and some households (about 10% of the urban and 8% of the rural) still used the more traditional method of burning dried dung or vegetation indoors, specifically to create smoke to drive away mosquitoes. Setting, house type, as indicated by the material used as roofing, and number of people in the household were each a significant predictor of the use of personal protection, with households in an urban setting, large households, and households occupying a concrete-roofed building relatively more likely to use some form of personal protection. Although 'modern', chemical-based methods were frequently employed, about one in every two interviewees (57% of the urban and 43% of the rural) considered the use of such methods to be harmful to their health. The mean monthly expenditures on personal-protection measures were 101 Indian rupees (U.S.$2.20)/urban household and 72 Indian rupees (U.S.$1.60)/rural household. Setting, family income, family size and number of sleeping rooms in the house each affected such expenditure significantly. As a proportion of household income, expenditure on controlling mosquitoes was surprisingly high. PMID:17877879

Babu, B V; Mishra, S; Mishra, S; Swain, B K

2007-10-01

222

3D Geophysical Modelling of the Beattie Magnetic Anomaly and Karoo Basin, South Africa  

NASA Astrophysics Data System (ADS)

The Karoo Basin, the broad arid plateau that covers much of the interior of South Africa, is supported by the stable Archean Kaapvaal Craton in the north and several surrounding Proterozoic basement blocks in the south, and formed within the continental interior of Gondwana during the Late Carboniferous (300 Ma) to Middle Jurassic (125 Ma). No clear tectonic model exists for the Karoo Basin, with several hypotheses regarding the nature of the subsidence resulting in basin formation. To the southern edge of the Karoo basin the enigmatic Beattie magnetic anomaly (BMA) is seen, which stretches east to west for ~1000 km across a large portion of South Africa, and for which a variety of explanations have been proposed. Here we present detailed 2D gravity and magnetic models across the southwestern Karoo along with a combined first-order regional 3D model. The models presented here are based on seismic and potential field data, along with geological and structural information that cover the entire basin. Information about the Moho structure was derived from teleseismic data. The models have been further constrained using deep boreholes, as well as on- and off-shore seismic lines, Magnetotelluric data, and magnetic depth-to-basement estimates. Density and susceptibility values are based on borehole and hand sample data, as well as on the conversion of p-wave seismic velocity to densities. In order to produce an accurate potential field model of the Karoo basin and to understand the evolution of the basin, a clear understanding is needed of the source of the Beattie. Seismic data over the western section of the Beattie magnetic anomaly place the source in the mid-crust (10-15 km). Earlier studies have attributed the anomaly to partially serpentinized oceanic lithosphere possibly linked to a suture zone, or to massive disseminate magnetite-sulphide bodies within the basement. However, our analysis lets us support the idea that the BMA is part of the tectono-metamorphic Namaqua-Natal Mobile Belt and associated shear zones.

Scheiber-Enslin, Stephanie; Ebbing, Jörg; Eberle, Detlef; Webb, Susan

2013-04-01

223

Tharsis Basin Aquifer System  

NSDL National Science Digital Library

This is a QuickTime movie animating an enormous ancient drainage basin and aquifer system in the Tharsis region of Mars. The movie shows the geological stages of the aquifer system, as reported in a University of Arizona study.

Arizona, University O.; Spaceref.com

224

Tectono-stratigraphic evolution and exhumation of the Haymana basin: Unravelling the subduction and collision history of Neotethys in Turkey  

NASA Astrophysics Data System (ADS)

The Haymana basin straddles the Izmir-Ankara-Erzincan Suture Zone (IAESZ) in the north and Intra-Tauride Suture Zone (ITSZ) in the south. The two suture zones developed in response to the subduction and demise of Neotethys Ocean in Turkey during the late Cretaceous to early Tertiary; the tectonic significance of the basin and its relationship with the ITSZ are still poorly constrained. In order to unravel subduction and subsequent collision history of the Neotethys in the region, we have carried out a detailed analysis of the stratigraphy and sedimentology of the Haymana basin infill and, using a combination of palaeomagnetic and thermochronometric data we have unravelled its structural evolution since its formation. The basin developed on the IAESZ and comprises fore-arc late Cretaceous to foreland Middle Eocene sedimentary sequences. The analysis of the sedimentogical facies and depositional environments indicate four Late Cretaceous to Paleogene key sequences in the basin. These sequences grade laterally and vertically into each other and are continuous from the late Cretaceous to Eocene whereas local progressive syn-sedimentary unconformities and frequent depocenter migrations are common. Late Cretaceous sequences fine upward whereas coarsening upwards sequences are common in the later units. These characteristics possibly reflect the response to local uplift and subsidence in front of south-verging thrust faults associated with the transition from fore-arc to foreland basin settings, following the terminal subduction of the Neotethys at the end of Cretaceous. About 4000 paleomagnetic and magnetostratigraphic data from the basin infill units and the Neogene cover indicate large clockwise vertical axes rotations in the NW and counter-clockwise rotations in the SE part of the basin. We suggest that these rotations are related to the northward movement and indentation of the Gondwana-derived continental blocks into Eurasia. A model of southward thrust propagation is also supported by apatite fission track (AFT) and (U+Th)/He thermochronometric data from 12 samples of basin infill, which show a consistent northward age increase. The major change in the rotation senses and structural trends within the basin are related to a large strike-slip fault which might be the westward extension into the Haymana Basin of the Savc?l? Thrust Zone, an important structural feature that separated the K?rsehir Block into two sectors.Fault kinematic analysis, based on 2000 fault slip data from 50 stations, indicates that the basin was subjected to NE-SW directed compression and coeval E-W extension during the late Cretaceous to Neogene. Constructed and balanced cross-sections for different time intervals indicate northward thickening, wedge-like geometry of the basin and large vertical axes rotations. We propose that the Haymana basin was a fore-arc basin developed at the southern margin of Eurasia along the northwards subducted Neotethys Ocean. From the Palaeogene, the basin evolved into a foreland basin in front of a south-vergent fold and thrust belt developed during continental collision. The northward move- ment of KB caused the basin to rotate along vertical axes, whereas the thrust propagation promoted its exhumation.

Gülyüz, Erhan; Özkaptan, Murat; Lefebvre, Côme; Kaymakci, Nuretdin; Persano, Cristina; Stuart, Finlay M.

2014-05-01

225

K Basin Hazard Analysis  

SciTech Connect

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

PECH, S.H.

2000-08-23

226

K Basins Hazard Analysis  

SciTech Connect

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

WEBB, R.H.

1999-12-29

227

Lake Superior Rift basins  

NASA Astrophysics Data System (ADS)

Sedimentary basins of late Precambrian age have been identified beneath Lake Superior using seismic reflection profiles leased by Argonne National Laboratory, Argonne, Ill., from Grant Norpac, Inc. [McGinnis et al., 1989]. These data, along with 650 km of Great Lakes International Multidisciplinary Program for Crustal Evolution (GLIMPCE) profiles [Behrendt et al., 1988], are being used to develop an understanding of failed rift processes, from initial plate separation, through basin evolution, to final quiescence.

McGinnis, L. D.

228

The tectonic evolution of Cenozoic extensional basins, northeast Brazil: Geochronological constraints from continental basalt 40Ar/39Ar ages  

NASA Astrophysics Data System (ADS)

The Boa Vista and Cubati Basins, Paraíba, Brazil, are NW-SE extension-related intracratonic basins that resulted from tectonic stresses after the opening of the South Atlantic. These basins contain lacustrine fossiliferous sediments, bentonite beds, and basalt flows that preserve Cenozoic continental records. 40Ar/39Ar ages for six whole-rocks from two distinct basaltic flows underlying the sediments in the Boa Vista basin are 27.3 ± 0.8 and 25.4 ± 1.3 Ma, while three grains from a basaltic flow overlying the sediments yield 22.0 ± 0.2 Ma. The sediments at the nearby Cubati Basin are overlain by a basalt flow with ages of ˜25.4 Ma. Three whole-rocks from an NE-SW-trending trachytic dyke cross cutting the sediments at the Boa Vista Basin yield 40Ar/39Ar ages of ˜12.45 ± 0.06, 12.59 ± 0.07, and 12.58 ± 0.07 Ma. Three whole-rocks from a nearby volcanic plug (Chupador) yield an age of 23.4 ± 0.1 Ma. The geochronological results combined with stratigraphic correlations between the two basins allow bracketing the age of the main sedimentary and bentonic units within the Boa Vista and Cubati Basins between 25.5 ± 1.3 and 24.9 ± 0.1 Ma. The ages, combined with field observations reveal that the formation of the Boa Vista and Cubati basins is associated with mantle-derived magmas channelled through reactivated Precambrian shear zones. Our geochronological results suggest that a temporal link with the Fernando de Noronha and Saint Helena hot spots can be excluded as possible sources of the Boa Vista and Cubati magmas. Rather, the extensional tectonics in the 30-20 Ma interval, long after Gondwana break-up, may be associated with the re-activation of continental-scale shear zones that channelled small batches of mantle-derived magmas.

de Souza, Zorano Sérgio; Vasconcelos, Paulo Marcos; Knesel, Kurt Michael; da Silveira Dias, Luiz Gustavo; Roesner, Eduardo Henrique; Cordeiro de Farias, Paulo Roberto; de Morais Neto, João Marinho

2013-12-01

229

Structure of the Millen Schist Belt (Antarctica): Clues for the tectonics of northern Victoria Land along the paleo-Pacific margin of Gondwana  

NASA Astrophysics Data System (ADS)

Victoria Land (Antarctica) belonged to the active proto-Pacific margin of Gondwana, which was the site of convergence during the Paleozoic. This study provides new insights into the structural architecture of northern Victoria Land, focusing on the boundary area between the Bowers and Robertson Bay terranes, i.e., in the Millen Schist Belt. It is a high-strain equivalent of the adjoining terranes, presently delimited by the Leap Year and the Handler faults. Our study reveals that these two faults overprint a preexisting transitional deformational boundary and are associated with a significant syntectonic circulation of fluids and mineralization. The Millen Schist Belt consists of two lithotectonic packages, juxtaposed along the Crosscut-Aorangi duplex thrust system, related to late Ross deformation. As there is increasing evidence of a post-Ross contractional event in northern Victoria Land, we suggest that the structural architecture of the Bowers-Robertson Bay terrane boundary results from a long-lasting SW-NE contractional regime, during the Ross-Delamerian Orogeny and still active afterward. This points to an extension of the Australian Lachlan Orogeny in Antarctica. The similarity of the structural architecture, the gold mineralization, the rock type, and the age supports the correlation of the Bowers and the Robertson Bay terranes with the Stawell Zone of the Lachlan Fold Belt. In our new tectonic scenario the Lanterman Fault (northern Victoria Land) plays the same role as the Moyston Fault (southeastern Australia), and the Leap Year and Handler faults correlate with the "intra-zone faults" of the Stawell Zone (e.g., the Ararat-Stawell Fault Zone).

Crispini, Laura; Federico, Laura; Capponi, Giovanni

2014-04-01

230

Geochemistry, zircon U-Pb geochronology and Hf isotopes of granites in the Baoshan Block, Western Yunnan: Implications for Early Paleozoic evolution along the Gondwana margin  

NASA Astrophysics Data System (ADS)

The leucogranites in the Baoshan Block of the Tethyan belt in Western Yunnan, are composed mainly of two-mica granite with subordinate muscovite granite. Here we present zircon U-Pb ages from four intrusions that show ages of 448-476 Ma suggesting that these rocks were emplaced during the Ordovician. The leucogranites are high-K calc-alkaline and strongly peraluminous, with K2O/Na2O > 1 and A/CNK = 1.12-1.54. These rocks are enriched in large-ion lithophile elements (LILEs) and light rare-earth elements (LREEs) [(La/Yb)N = 1.13-32.4] and Pb, and are depleted in high field-strength elements (HFSEs). They show similar chondrite-normalized REE patterns, with negative Eu anomalies (Eu/Eu* = 0.03-0.46). A wide range of zircon ?Hf(t) values (- 9.6 to - 2.6) and varying Hf-isotope crustal model ages (2.1-1.6 Ga) are also observed. The geochemical signatures indicate that the leucogranites are S-type granites derived mainly from the anatexis of ancient crustal materials. The ages, geochemistry and tectonics in the Baoshan Block and the Lhasa Terrane are closely comparable, suggesting that the Baoshan Block might represent part of an Early Paleozoic magmatic arc in the Gondwana continental margin facing the proto-Tethyan Ocean. The Pinghe granites of the early phase in the Baoshan Block which are coeval with the Cambrian magmatism (ca. 492 Ma) identified in the central and southern Lhasa subterranes can be interpreted as products of the slab break-off associated with the subduction of proto-Tethyan oceanic lithosphere. However, the late leucogranite stocks are analogous to the North Himalayan leucogranites, which formed in a short-lived extensional setting caused by the slab break-off associated with the subduction-collision system.

Dong, Meiling; Dong, Guochen; Mo, Xuanxue; Santosh, M.; Zhu, Dicheng; Yu, Junchuan; Nie, Fei; Hu, Zhaochu

2013-10-01

231

Moa's Ark or volant ghosts of Gondwana? Insights from nineteen years of ancient DNA research on the extinct moa (Aves: Dinornithiformes) of New Zealand.  

PubMed

The moa (Aves: Dinornithiformes) of New Zealand represent one of the extinct iconic taxa that define the field of ancient DNA (aDNA), and after almost two decades of genetic scrutiny of bones, feathers, coprolites, mummified tissue, eggshell, and sediments, our knowledge of these prehistoric giants has increased significantly. Thanks to molecular and morphological-based research, the insights that have been obtained into moa phylogenetics, phylogeography, and palaeobiology exceeds that of any other extinct taxon. This review documents the strengths of applying a multidisciplinary approach when studying extinct taxa but also shows that cross-disciplinary controversies still remain at the most fundamental levels, with highly conflicting interpretations derived from aDNA and morphology. Moa species diversity, for example, is still heavily debated, as well as their relationship with other ratites and the mode of radiation. In addition to increasing our knowledge on a lineage of extinct birds, further insights into these aspects can clarify some of the basal splits in avian evolution, and the evolutionary implications of the breakup of the prehistoric supercontinent Gondwana. Did a flightless moa ancestor drift away on proto New Zealand (Moa's Ark) or did a volant ancestor arrive by flight? Here we provide an overview of 19 years of aDNA research on moa, critically assess the attempts and controversies in placing the moa lineage among palaeognath birds, and discuss the factors that facilitated the extensive radiation of moa. Finally, we identify the most obvious gaps in the current knowledge to address the future potential research areas in moa genetics. PMID:21596537

Allentoft, Morten E; Rawlence, Nicolas J

2012-01-20

232

K Basin Hazard Analysis  

SciTech Connect

The K East (KE)/K West (KW) Basins in the 100 K Area of the Hanford Site have been used for storage of irradiated N Reactor and single-pass reactor fuel. Remaining spent fuel is continuing to be stored underwater in racks and canisters in the basins while fuel retrieval activities proceed to remove the fuel from the basins. The Spent Nuclear Fuel (SNF) Project is adding equipment to the facility in preparation for removing the fuel and sludge from the basins In preparing this hazard analysis, a variety of hazard analysis techniques were used by the K Basins hazard analysis team, including hazard and operability studies, preliminary hazard analyses, and ''what if'' analyses (WHC-SD-SNF-PHA-001, HNF-2032, HNF-2456, and HNF-SD-SNF-SAD-002). This document summarizes the hazard analyses performed as part of the safety evaluations for the various modification projects and combines them with the original hazard analyses to create a living hazard analysis document. As additional operational activities and modifications are developed, this document will be updated as needed to ensure it covers all the hazards at the K Basins in a summary form and to ensure the subsequent safety analysis is bounding. This hazard analysis also identifies the preliminary set of design features and controls that the facility could rely on to prevent or reduce the frequency or mitigate consequences of identified accident conditions based on their importance and significance to safety. The operational controls and institutional programs relied on for prevention or mitigation of an uncontrolled release are identified as potential technical safety requirements. All operational activities and energy sources at the K Basins are evaluated in this hazard analysis. Using a systematic approach, this document identifies hazards created by abnormal operating conditions and external events (e.g., earthquakes) that have the potential for causing undesirable consequences to the facility worker, the onsite individual, or the public. This report describes the methodology used in conducting the K Basins Hazard Analysis, which provides the foundation for the K Basins Final Safety Analysis Report. This hazard analysis was performed in accordance with guidance provided by DOE-STD-3009-94, Preparation Guide for U.S. Department of Energy Nonreactor Nuclear Facility Safety Analysis Reports and complies with the requirements of 10 CFR 830.

SEMMENS, L.S.

2001-04-20

233

SURVEY OF CROSS-BASIN BOAT TRAFFIC, ATCHAFALAYA BASIN, LOUISIANA  

EPA Science Inventory

For flood control and for the preservation and enhancement of environmental quality of overflow swamp habitats, introduction of sediment from the Atchafalaya Basin Main Channel into backwater areas of the Atchafalaya Basin Floodway should be minimized. This introduction occurs ma...

234

Nam Con Son Basin  

SciTech Connect

The Nam Con Son basin is the largest oil and gas bearing basin in Vietnam, and has a number of producing fields. The history of studies in the basin can be divided into four periods: Pre-1975, 1976-1980, 1981-1989, and 1990-present. A number of oil companies have carried out geological and geophysical studies and conducted drilling activities in the basin. These include ONGC, Enterprise Oil, BP, Shell, Petro-Canada, IPL, Lasmo, etc. Pre-Tertiary formations comprise quartz diorites, granodiorites, and metamorphic rocks of Mesozoic age. Cenozoic rocks include those of the Cau Formation (Oligocene and older), Dua Formation (lower Miocene), Thong-Mang Cau Formation (middle Miocene), Nam Con Son Formation (upper Miocene) and Bien Dong Formation (Pliocene-Quaternary). The basement is composed of pre-Cenozoic formations. Three fault systems are evident in the basin: north-south fault system, northeast-southwest fault system, and east-west fault system. Four tectonic zones can also be distinguished: western differentiated zone, northern differentiated zone, Dua-Natuna high zone, and eastern trough zone.

Tin, N.T.; Ty, N.D.; Hung, L.T.

1994-07-01

235

Illinois Basin ultradeep drillhole  

NASA Astrophysics Data System (ADS)

Throughout the Phanerozoic, the depocenter of the Illinois Basin has remained at or above the intersection of the Reelfoot Rift, the Rough Creek Graben, the Cottage Grove Fault System, and the Wabash Valley Fault System. A proposed Illinois Basin Ultradeep Drillhole (IBUD) (Figure 1) will explore the crustal processes that resulted in the deposition of 400,000 km3 of sediment in this mid-continent region of the North American plate.At a workshop held April 1-4, 1986, in Champaign, Ill., more than 120 geologists, geochemists, geophysicists, and drilling engineers addressed the scientific and economic significance of IBUD and prepared a draft science plan to be incorporated in a later formal proposal. The science plan includes the experiments, expected results, and scientific justifications for investigations of basement age, composition, and evolution; tectonics and structure; rock mechanics; basin analysis, hydrogeology, and brine geochemistry; geophysics and seismology; and hydrocarbon and ore deposit studies in IBUD.

Frost, Joyce K.; Eidel, J. James; Goodwin, Jonathan H.

236

Great Basin National Park  

NSDL National Science Digital Library

This National Park Service site describes the biology of Great Basin's plants and animals; geology and ecology of the Lehman Caves; air quality of the park; and past human activities in the Great Basin such as farming, ranching, and gold mining. There is a list of historical, geological, and archeological dates important to the park and an instructor guide containing activities such as creating a nature notebook and adopting a tree. There is also information on: planning a visit to the park and the Lehman Caves, park projects such as weeding out non-native plants and the reintroduction of Bonneville Cutthroat Trout, and a self-guided geology field trip.

237

Genetic diversity of hemoglobinopathies, G6PD deficiency, and ABO and Rhesus blood groups in two isolates of a primitive Kharia Tribe in Sundargarh District of Northwestern Orissa, India.  

PubMed

Tribal communities constitute about 8.2% of the total population of India. Their health needs are even larger than elsewhere in India; this study investigates the genetic diversity in relation to hemoglobinopathies, G6PD deficiency and, ABO and Rhesus (D) blood groups in two sects, i.e. Dudh (converted Christian) and Dhelki (Hinduised) Kharia, a primitive tribe in Sundargarh district of Orissa in Central-Eastern India. A randomized screening of 767 Kharia tribals (377 males and 390 females) belonging to all age groups and both sexes was done. Laboratory analysis was carried out following the standard methodology and techniques. Contrasting differences were observed in the frequency of hematological genetic disorders such as ?-thalassemia, sickle cell, hemoglobin E, G6PD deficiency, ABO and Rhesus (D) blood groups between the two subgroups. Dudh Kharia had no hemoglobin variant allele other than the high prevalence of ?-thalassemia trait (8.1%), whereas, their counterpart Dhelki Kharia had the high prevalence of sickle cell allele (12.4%), hemoglobin E allele (3.2%), and ?-thalassemia allele (4.0%). Frequency distribution of hemoglobin variants between Dudh and Dhelki Kharia tribe was statistically highly significant (p?

Balgir, R S

2010-09-01

238

Sediment entrainment in karst basins  

Microsoft Academic Search

:   In this paper, the suspension of sediments induced by groundwater jets in two basins of a karst lake (basin I and II of lake\\u000a Banyoles, Catalonia) is studied. Field experiments were carried out during the period 1989-1994 to investigate the sediment\\u000a dynamics within the basins. During this period, the sediment in basin I (B1) was found to be permanently

Jordi Colomer; John Alan Ross; Xavier Casamitjana

1998-01-01

239

Sedimentary cycles related to the late Palaeozoic cold-warm climate change, Talchir Formation, Talchir Basin, India  

NASA Astrophysics Data System (ADS)

Attributes of sedimentary facies within Permo-Carboniferous Talchir Formation (Gondwana Supergroup), Talchir Basin, India, attest to sedimentation under glaciomarine setting. Facies architecture reveals three sedimentary cycles of distinct orders. Cycle-1 sediments are 10s of m thick and are represented by repeated occurrences of glacigenic/reworked-glacigenic sediments followed by storm-reworked glacial outwash deposits. Juxtaposition of multiple Cycle-1 sequences indicate repeated ice-front advance-retreats related to climatic fluctuations, which led to accumulation of glacier-laden coarse-grained sediments, and subsequent flooding by marine storm surges. Cm-thin sandstone-mudstone interbeds of Cycle-2 belong within the Cycle-1 sequences and represent deposition from episodic storm surges. Mm-thin Cycle-3 sediments occur within the Cycle-2 sequences and attribute their genesis to semi-diurnal tidal fluctuations. Open marine storm surges have reworked these tidal sediments. In absence of major tectonic influences, the studied sedimentary cycles and associated palaeogeographic changes in the ice-marginal Talchir marine basin bear direct relation to late Palaeozoic cold-warm climatic transitions.

Bhattacharya, Biplab

2013-06-01

240

Crinoids columnals (Echinodermata) of the Ererê Formation (late Eifelian-early Givetian, Amazon Basin), State of Pará, Brazil  

NASA Astrophysics Data System (ADS)

The faunal composition of stalked echinoderms in the Brazilian Devonian is still largely unknown despite the great abundance of crinoids in the shallow epicontinental seas of the Paleozoic. The first Devonian crinoids of Brazil, recorded in the literature in 1875 and 1903, were from the sedimentary rocks of the Ererê Formation in the Amazon Basin. Since then, the echinoderms of this formation have not been studied. This study, based on isolated pluricolumnals and columnals, described and identified Botryocrinus meloi n. sp., the first record for this genus in Brazil. In addition to this species, two other morphological patterns were identified: Tjeecrinus sp. and Morphotype AM/Er-01. The form of occurrence of the crinoid material and the paleoautoecology of B. meloi allow preliminary characterization of the habitat as a moderately deep water with weak to moderate currents and soft substrate. The similarity between B. meloi and Botryocrinus montguyonensis and of Tjeecrinus? sp. and T. crassijugatus, from the Devonian of the Armorican and Rhenan Massif, represents new evidence for the existence of contact between the faunas of the Amazon Basin with those of northern Gondwana and Armorica during the Middle Devonian.

Scheffler, S. M.; Fernandes, A. C. S. F.; da Fonseca, V. M. M.

2014-01-01

241

Pacific basin energy  

SciTech Connect

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.

Not Available

1980-01-01

242

Weber Basin Project.  

National Technical Information Service (NTIS)

In 1969, the Bureau of Reclamation completed the Weber Basin Project in Utah; an endeavor that had been over twenty-five years in the making, constructed in response to the growing populations of cities such as Ogden, Bountiful, and Layton. Consisting of ...

C. J. McCune

2001-01-01

243

Sedimentary basins and crustal thickening  

NASA Astrophysics Data System (ADS)

We consider the development of sedimentary basins in a tectonic context dominated by horizontal shortening and vertical thickening of the crust. Well-known examples are foreland basins; others are ramp basins and buckle basins. We have reproduced various styles of compressional basins in experiments, properly scaled for gravity. A multilayered model lithosphere, with brittle and ductile layers, floats on a model asthenosphere. A computer-driven piston provides shortening and thickening, synchronous with erosion and sedimentation. After a first stage of lithospheric buckling, thrust faults appear, mainly at inflection points. Slip on an isolated reverse fault is accompanied by flexure. Footwall flexure results in a foreland basin and becomes accentuated by sedimentation. Hangingwall flexure is less marked, but may become accentuated by erosion. Motion on a fault leads to hangingwall collapse at the surface. Either footwall sedimentation or hangingwall erosion tends to prolong the active life of a reverse fault. Slip on any pair of closely spaced reverse faults of opposite vergence results in a ramp basin. Simultaneous slip produces a symmetric ramp basin, whereas alternating slip results in a butterfly-shaped basin, with superposed foredeeps. Some well-developed ramp basins become pushed down, until bounding faults meet at the surface and the basin disappears from view. At this stage, the basin depth is equivalent to 15 km or more. Slip on any pair of widely spaced reverse faults of opposite vergence results in a pronounced central anticline, between two distinct foredeeps. In Central Asia and in Western Europe, Cenozoic crustal thickening is due to continental collision. For Central Asia (Western China, Kyrgyzstan, Uzbekistan, Tajikistan), we have compiled a regional structure-contour map on the base of the Tertiary, as well as 4 regional sections. Foreland basins and ramp basins are numerous and associated with Cenozoic thrusts. Large basins (Tarim, Junggar, Fergana, Tajik) occur around and between mountain ranges, but smaller basins (Issyk-Kul, Naryn) occur within them. In Western Europe, the Alps and Pyrenees are surrounded by foreland basins, ramp basins or intermediate styles. In the Andes and its foreland, Neogene thrusts and compressional basins are due to subduction of oceanic lithosphere. In Colombia, they account for much of the Cordillera Oriental; in NW Argentina, for the Altiplano; in West-Central Argentina, for the Sierras Pampeanas. Compressional basins are also common in other areas of older crustal thickening.

Cobbold, P. R.; Davy, P.; Gapais, D.; Rossello, E. A.; Sadybakasov, E.; Thomas, J. C.; Tondji Biyo, J. J.; de Urreiztieta, M.

1993-07-01

244

Sapphirine + quartz corona around magnesian ( XMg ~ 0.58) staurolite from the Palghat-Cauvery Suture Zone, southern India: Evidence for high-pressure and ultrahigh-temperature metamorphism within the Gondwana suture  

NASA Astrophysics Data System (ADS)

We report the first finding of equilibrium sapphirine + quartz assemblage from the Palghat-Cauvery Suture Zone (PCSZ) in southern India providing unequivocal evidence for extreme crustal metamorphism at ultrahigh-temperature (UHT) conditions associated with the collisional assembly of the Gondwana supercontinent in the Late Neoproterozoic-Cambrian. The sapphirine and quartz occur as coronas around Mg-rich ( XMg ~ 0.58) staurolite within poikiloblastic garnet in an Mg-Al-rich rock, suggesting the progress of the prograde dehydration reaction: staurolite + garnet ? sapphirine + quartz + H 2O. Although the occurrence of Mg-rich staurolite was previously noted from some localities in the PCSZ, no sapphirine + quartz direct association has yet been reported. The available experimental studies on Mg-rich staurolite indicate that the mineral is stable at P > 15 kbar, and suggest that the complex texture that we report here might correspond to a peak high-pressure regime prior to the UHT event. The symplectic sapphirine + quartz around staurolite probably implies decompression from P > 15 kbar toward the stability of sapphirine + quartz at temperatures of c. 1000 °C along a clockwise P-T path. The prograde high-pressure metamorphism and following UHT event correlate with the subduction-collision tectonics associated with the final stage of amalgamation of Gondwana supercontinent.

Nishimiya, Yuki; Tsunogae, Toshiaki; Santosh, M.

2010-02-01

245

Cenozoic basin development in Hispaniola  

SciTech Connect

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

246

Aerogeophysical evidence for strike-slip faulting at the boundary between East and West Antarctica: implications for Jurassic magma emplacement and Gondwana breakup models  

NASA Astrophysics Data System (ADS)

Fragmentation of the Gondwana supercontinent began in the Jurassic and was the most significant reconfiguration of the continents of the southern hemisphere in the last 500 Ma. Jurassic continental rifting began adjacent to South Africa in the Weddell Sea region of Antarctica. This region is therefore critical for understanding the process that initiated supercontinent breakup, including the role of mantle plumes, magmatism, and major plate and microplate re-configurations. However, due to the remote location and blanketing ice sheets, the magmatic and tectonic evolution of the Weddell Sea sector of Antarctica has remained poorly understood and controversial. Our recent aeromagnetic and airborne gravity investigations reveal the inland extent of the Weddell Sea Rift system beneath the West Antarctic Ice Sheet, and indicate the presence of a major left-lateral strike slip fault system, separating the Ellsworth Whitmore block from East Antarctica (Jordan et al., 2013 Tectonophysics). In this study we use 3D inversion of magnetic data to investigate the geometry and emplacement mechanism of Jurassic granites both along the boundary and within the Ellsworth-Whitmore block. Our models demonstrate a high degree of structural control on Jurassic granite emplacement along the newly identified left-lateral Pagano Shear Zone that flanks the Ellsworth-Whitmore block. Other granitoids emplaced further west within the Ellsworth-Whtimore block itself do not appear to have the same structural control, suggesting that this possible microplate or block was relatively more rigid. Extensive and likely more rigid Precambrian basement of Grenvillian-age is clearly delineated from aeromagnetic signatures at the northern edge of the Ellsworth-Whitmore block, lending support to this interpretation. Most intriguing, it that the high amplitude anomalies over the northern margin of the Ellsworth-Whitmore block are remarkably similar to those previously mapped over the Shackleton Range in East Antarctica. In the Shackleton Range, the association between Grenvillian-age basement and aeromagnetic anomalies is less well-constrained but nevertheless possible. Here we test in Gplates our new geodynamic model that involves the Ellsworth Whitmore block being originally closer to the Shackleton Range region in East Antarctica and then translated to West Antarctica in Jurassic times via ca 300 km of crustal extension in the Weddell Sea rift. We compare and contrast our new model with the currently more widely accepted geodynamic model that predicts significantly more complex movements of the Ellsworth-Whitmore microplate, including 180 degree rotation, and ~1500 km of strike-slip displacement from the Natal Embayment adjacent to South Africa to its current position in West Antarctica.

Jordan, Tom; Ferraccioli, Fausto

2014-05-01

247

Exotic ingredients in the mélange at Port Macquarie, southern New England Orogen, reveal a spicy history of crustal kneading along eastern Gondwana  

NASA Astrophysics Data System (ADS)

An exotic assemblage of Paleozoic subduction complex rocks occurs within the serpentinite mélange at Port Macquarie in the southern New England Orogen, eastern Australia. New U-Pb zircon dating of key components within the mélange reveals surprising results that require a complete re-evaluation of the tectonic evolution of the New England Orogen. The Rocky Beach eclogite contains detrital igneous zircon populations of Carboniferous and Permo-Triassic age which contradict previous Ordovician K-Ar ages. The Tacking Point gabbro was thought to represent a Permian intrusive equivalent to the Clarence River suite but is Devonian (390×7 Ma). Volcaniclastic sandstones of the Watonga Formation yielded 452×10 Ma igneous zircons confirming previous Ordovician conodont ages. However, volaniclastic sandstones structurally below the serpentinite melange contain volcanic/detrital zircons as young as 335 Ma that were derived from a Carboniferous arc. Post-serpentinite mafic-felsic dykes were emplaced into the mélange at ~250 Ma. We suggest that the eastern margin of Gondwana underwent episodic, thin-skinned island-arc collisions paired with widespread deformation events (e.g. Macquarie Arc - Benambran Orogeny; Gamilaroi terrane - Kanimblan Orogeny; and Gympie terrane - Hunter Bowen Orogeny). These arc collisions are followed by subduction flips that lead to periods of continental margin 'Andean-type' magmatism and accretion marked by the voluminous intrusion of S- and I-type granites. Oroclinal bending has been proposed by some to explain the overall northward displacement of the Port Macquarie serpentinite relative to the Peel Fault to the west. We introduce a new hypothesis to explain apparent oroclines within the New England Orogen involving vertical rather than lateral displacements. We propose that the Hunter-Bowen compressional event is responsible for exhuming portions of the Gamilaroi + Djungati terranes from under their Carboniferous carapace. Thus, the northward (sinistral) displacement of the Port Macquarie and Hastings Blocks and the dextral displacement of the Coffs Harbour Block associated with the Texas orocline, is apparent only, and due more in part to vertical displacements of an extensive, thin-skinned oceanic terranes that underlie the Tablelands Complex, rather than extensive lateral movements. Thus, there is no need to invoke large-scale ';oroclinal' folding or significant sinistral faulting to explain the repetition of Hastings and Port Macquarie blocks in the southern New England.

Buckman, S.; Nutman, A.

2013-12-01

248

Petrology and mineral equilibrium modeling of incipient charnockite from the Trivandrum Granulite Block, southern India: implications for granulite formation in a Gondwana fragment  

NASA Astrophysics Data System (ADS)

The Southern Granulite Terrane (SGT) in India is known for its classic exposures of regionally metamorphosed granulite-facies rocks formed during the collisional orogeny related to the amalgamation of Gondwana supercontinent. The SGT is composed of a collage of Proterozoic crustal blocks dissected by large Late Neoproterozoic shear/suture zones. The Trivandrum Granulite Block (TGB) is comprises dominantly metasedimentary sequence with khondalites, leptynites and charnockites with subordinate quartzite, mafic granulite, calc-silicate rocks, and meta-ultramafic rocks. The TGB is known as one of the classic examples for the spectacular development of 'incipient charnockites' within orthopyroxene-free felsic gneisses as exposed in several quarry sections in the states of Kerala and Tamil Nadu. The charnockite-forming process in the TGB is considered to have been triggered by the infiltration of CO2-rich anhydrous fluids along structural pathways within upper amphibolite facies gneisses, resulting in the lowering of water activity and stabilization of orthopyroxene through the breakdown of biotite. However, no quantitative study on the stability of charnockitic mineral assemblage using mineral equilibrium modeling approach has been done so far. In this study, we report a new occurrence of incipient charnockite from Mavadi in the TGB and discuss the petrogenesis of granulite formation in an arrested stage on the basis of petrography, geothermobarometry, and mineral equilibrium modeling. In Mavadi, patches and lenses of charnockite (Kfs + Qtz + Pl + Bt + Grt + Opx + Ilm + Mag) of about 30 to 120 cm in length occur within Opx-free Grt-Bt gneiss (Kfs + Qtz + Pl + Bt + Grt + Ilm) host rocks. The application of mineral equilibrium modeling on charnockite assemblage in NCKFMASHTO system to constrain the conditions of charnockitization defines a P - T range of 800° C at 4.5 kbar to 850° C at 8.5 kbar, which is broadly consistent with the results from the conventional geothermobarometry (810-880° C at 7.7-8.0 kbar) on these rocks. The P - T conditions are lower than the inferred peak metamorphic conditions from the ultrahigh-temperature granulites of the study area (T >900° C), which might suggest heterogeneity in peak P - T conditions within this crustal block in relation to local buffering of metamorphic temperature by Opx-Bt-Kfs-Qtz assemblage. The result of T versus mole H2O (M(H2O)) modeling demonstrated that Opx-free assemblage in Grt-Bt gneiss is stable at M(H2O) = 0.3 to 1.5 mol.%, and orthopyroxene occurs as a stable mineral at M(H2O)

Endo, T.; Tsunogae, T.; Santosh, M.

2012-04-01

249

Mercury's Caloris Basin  

NASA Technical Reports Server (NTRS)

Mercury: Computer Photomosaic of the Caloris Basin

The largest basin on Mercury (1300 km or 800 miles across) was named Caloris (Greek for 'hot') because it is one of the two areas on the planet that face the Sun at perihelion.

The Image Processing Lab at NASA's Jet Propulsion Laboratory produced this photomosaic using computer software and techniques developed for use in processing planetary data. The Mariner 10 spacecraft imaged the region during its initial flyby of the planet.

The Mariner 10 spacecraft was launched in 1974. The spacecraft took images of Venus in February 1974 on the way to three encounters with Mercury in March and September 1974 and March 1975. The spacecraft took more than 7,000 images of Mercury, Venus, the Earth and the Moon during its mission.

The Mariner 10 Mission was managed by the Jet Propulsion Laboratory for NASA's Office of Space Science in Washington, D.C.

2001-01-01

250

Albuquerque Basin seismic network  

USGS Publications Warehouse

The U.S. Geological Survey has recently completed the installation of a seismic network around the Albuquerque Basin in New Mexico. The network consists of two seismometer arrays, a thirteen-station array monitoring an area of approximately 28,000 km 2 and an eight-element array monitoring the area immediately adjacent to the Albuquerque Seismological Laboratory. This report describes the instrumentation deployed in the network.

Jaksha, Lawrence H.; Locke, Jerry; Thompson, J. B.; Garcia, Alvin

1977-01-01

251

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

SciTech Connect

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

252

Drainage Basin Morphometry  

NSDL National Science Digital Library

The goal of this activity is for to students to observe and quantify the inherent organization within the channel network of a single drainage basin (a la Horton, 1945). The students will use the contour-crenulation method to flesh out the channel network within a selected drainage basin. They will then use the Strahler system to deterime the stream order of each channel segment. They then measure and average various attributes (slope, length, etc.) of the channel segments, by stream order. These data will then be plotted on semi-log graph paper to illustrate the matematical relationships between channel attributes and stream order. This activity gives students practice in delineating drainage divides and channel networks on topographic maps, using map scales to measure distances on topographic maps, and graphing data using a semi-log format. In addition, they are asked to compare their "real-world" results against the classic "laws" of basin morphometry presented in their textbook. This permits a discussion of sample size and measurement error versus theoretical relationships presented in a textbook. Designed for a geomorphology course

Ford, Rick

253

Instantaneous dynamics of the cratonic Congo basin  

Microsoft Academic Search

Understanding the formation mechanisms of cratonic basins provides an examination of the rheological, compositional and thermal properties of continental cratons. However, these mechanisms are poorly understood because there are few currently active cratonic basins. One cratonic basin thought to be active is the Congo basin located in equatorial Africa. The Congo basin is coincident with a large negative free-air gravity

Nathan J. Downey; Michael Gurnis

2009-01-01

254

Antarctica — Before and after Gondwana  

Microsoft Academic Search

The origin of the Antarctic continent can be traced to a relatively small late Archaean cratonic nucleus centred on the Terre Adélie regions of East Antarctica and the Gawler Craton region of South Australia. From the late Archaean to the present, the evolution of the proto-Antarctic continent was remarkably dynamic with quasi-continuous growth driven by accretionary or collisional events, episodically

Steven D. Boger

2011-01-01

255

Susquehanna River Basin Commission Annual Report, 2008.  

National Technical Information Service (NTIS)

This is the Susquehanna River Basin Commission's (SRBC's) 2008 Annual Report. The Susquehanna River Basin Commission is an agency with a mission - management of the water resources of the basin under comprehensive watershed management and planning princip...

2008-01-01

256

Crustal-scale heat-flow evolution and heterogeneity at a young convergent margin: Taranaki Basin, New Zealand  

NASA Astrophysics Data System (ADS)

The Taranaki Basin lies in the west of New Zealand's North Island, only 400 km away from the convergent Australian-Pacific plate margin. It is an exceptional example of a basin that documents the evolution from a passive to a convergent margin. In it's less than 100 million year history, the basin has developed from a rift margin to a hybrid intra-arc/back-arc basin/fold-thrust belt in response to propagation of Pacific plate subduction beneath the Australian plate in the region, starting 25 Myrs ago. Yet, the Taranaki Basin is surprisingly cold, given it's proximity to the subduction front: the surface heat-flow in Central North Island decreases from a staggering 800 mW/m2 at the volcanic arc to an average of 60 mW/m2 in the Taranaki Basin. These heat flow values are extreme if compared to established margins, which raises the question of how crustal temperature patterns evolve during the transition from a passive to an active margin. To answer this question, a 3D crustal scale forward model was developed, using the industry-standard basin-modelling software Petromod. The Taranaki Basin has been well studied during decades of petroleum exploration and therefore offers unique possibilities to investigate the thermal evolution of the crust and sedimentary cover in the proximity of an evolving subduction zone. The composition of mid and lower crustal rocks of the Taranaki Basin can be correlated with exhumed equivalents elsewhere in New Zealand. On average, 40% of the heat is generated within the crust, and so, the crustal composition is an important control, not only on thermal properties, but also on content of heat producing radioactive elements. In the case of the Taranaki Basin, the heat generation potential between granitic basement, related to the Mesozoic Gondwana margin in the west, and mafic and metasedimentary rocks in the east varies by a factor of up to three. The challenge of this study therefore was to differentiate between the effects of variability in heat generation due to crustal heterogeneity, and changes in heat advection and effects of tectono-sedimentary processes related to the formation of a subduction zone. The results of the model indicate that surface heat flow in the Taranaki Basin varies by as much as 20 mW/m2 due to the variability in crustal heat generation. Other individual factors such as change in mantle heat advection, tectonic subsidence, uplift and crustal thickening, and related sedimentary processes, only result in a variability of up to 10 mW/m2. The model further suggests that increased heating of the upper crust due to additional mantle heat advection related to the onset of subduction is still an ongoing process. Combined with low heat generation potential of parts of the crust and a cooling effect of crustal thickening, the lag in the additional heat transfer from the mantle explains why the surface heat-flow in the Taranaki Basin is 10-20 mW/m2 lower than in more typical back-arc areas around other Pacific plate margins.

Kroeger, Karsten F.; Bland, Kyle J.; Fohrmann, Miko; Funnell, Rob H.

2010-05-01

257

MASSACHUSETTS DRAINAGE SUB-BASINS  

EPA Science Inventory

MassGIS has produced a statewide digital datalayer of the approximately 2300 sub-basins as defined and used by the USGS Water Resources Division and the Mass Water Resources Commission and as modified by Executive Office of Environmental Affairs (EOEA) agencies. These sub-basins...

258

Pilcomayo River Basin Institutional Structure  

Microsoft Academic Search

Water resources of the Pilcomayo River Basin are shared between three countries: Argentina, Paraguay, and Bolivia. It is a transboundary basin. It has several and significant peculiarities from the physical viewpoints (hydrological, sedimentological and geomorphological), as well as from the point of view of its people, cultures, ethnicity, economy, productive activities, and political and institutional organizations. The governments of the

Claudio Laboranti

2011-01-01

259

Atlantic marginal basins of Africa  

SciTech Connect

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

260

Advanced Chemistry Basins Model  

SciTech Connect

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

261

Reserves in western basins  

SciTech Connect

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

262

RESERVES IN WESTERN BASINS PART IV: WIND RIVER BASIN  

SciTech Connect

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

263

K-Basins design guidelines  

SciTech Connect

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

264

Lower Palaeozoic unconformities in an intracratonic platform setting: glacial erosion versus tectonics in the eastern Murzuq Basin (southern Libya)  

NASA Astrophysics Data System (ADS)

The stratigraphic record of the eastern Murzuq Basin has been importantly influenced by deformation resulting in angular and/or deeply erosional unconformities, though the overall context is intracratonic. Major transgressive events and the Ordovician glaciation are nevertheless documented, allowing the delineation of tectonic-, eustasy- or climate-driven unconformities. Lower Palaeozoic key events and related unconformities that characterize the North Gondwana platform have therefore a signature in the eastern Murzuq Basin. The basement/cover unconformity, also known as the infra-Tassilian surface, truncates all the deformed and metamorphosed Lower Cambrian and older rocks. Above is a ?Middle Cambrian to Lower Ordovician megasequence (Murizidié and Hasawnah Fms.), which is in turn truncated by an intra-Ordovician, angular unconformity. This megasequence is unconformably overlain by a Middle Ordovician (Hawaz Fm.) to Silurian (Tanzzuft and Akakus Fms) megasequence, which includes the Upper Ordovician glaciogenic unit (Mamuniyat Fm.), bounded at the base by a polygenic glacial erosion surface showing corrugated glacial lineations, tillites, and glaciotectonic structures. The Middle Ordovician to Silurian megasequence is finally truncated by a base-Devonian, angular unconformity overlain by fluvial sandstones. Regarding the possibility that those fluvial deposits may be as younger as Late Devonian in the eastern Murzuq Basin based on palaeoflora, the so-called Caledonian unconformity might be here a much younger (mid-Eifelian?) surface, and the occurrence of the Lower Devonian "Tadrart Fm." is questioned. The Upper Ordovician glacial erosion surface, which is sometimes referred to as the Taconic unconformity, usually truncates Middle Ordovician strata in the Murzuq Basin but reaches significantly deeper stratigraphic levels in places that have been previously involved in the intra-Ordovician deformation event. In the Murizidié (southeastern Murzuq Basin), the infra-Tassilian surface, the intra-Ordovician unconformity, and the Upper Ordovician glacial erosion surface amalgamate together. Here, an estimate of the glacial erosion depth cannot be derived from the stratigraphic hiatus beneath the glacial incision, the main part of which relate to the intra-Ordovician tectonic event. The Upper Ordovician climate-related glacial erosion surface is not a valid unconformity for a sequence hierarchy framework of the Lower Palaeozoic, although it presents most of the physical attributes of tectonic-driven unconformities.

Ghienne, Jean-François; Moreau, Julien; Degermann, Lionel; Rubino, Jean-Loup

2013-03-01

265

Frontier basins of Bering Sea  

SciTech Connect

The Bering Sea contains three hydrocarbon provinces: shelf, slope, and abyssal basin. The shelf province, which is underlain by three exceptionally large sedimentary basins, has been extensively covered by geophysical surveys. Exploration in this province has not discovered economic hydrocarbon deposits. Frontier basins, with future economic prospects, lie beneath the mostly unexplored slope and abyssal provinces of the Aleutian and Bowers basins of the Bering Sea. These expansive deep-water basins cover an area nearly two-thirds the size of Alaska. Sedimentary rocks of late Mesozoic(.) and Tertiary age make up the 3 to 11-km thick section that covers the entire area. These pelagic and fine-grained terrigenous rocks overlie slowly subsiding oceanic crust, which was trapped in the Bering Sea after the Aleutian Ridge formed during the Eocene. Thick (6-11 km) sedimentary sections and high basement relief (0.5-1.0 km) underlie parts of the 1700-km long Beringian-Koryak slope and rise. At the base of the margin, nearly flat strata of the Aleutian basin drape and onlap faulted acoustic-basement rock. Sparse information from the Deep Sea Drilling Project and US Geological Survey dredging indicates that source and reservoir rocks may exist within the upper and, possibly, lower parts of the sedimentary section. Beneath the central part of the abyssal basin, the sedimentary sequence is only 2-4 km thick, and buried basement relief is greater than 1.0 km. Near-surface temperature gradients are high (average = 58/sup 0/C/km), and acoustic anomalies that may be indicative of hydrocarbons are present. The slope and abyssal basins of the Beringian-Koryak margin have received minimal exploratory attention because water depths that cover the area are typically 2000-3700 m. Advances in deep-water production technology will eventually make these frontier basins attractive for hydrocarbon exploration.

Cooper, A.K.; Marlow, M.S.; Scholl, D.W.

1986-07-01

266

South Pole-Aitken Basin Mission (SPAM)  

Microsoft Academic Search

Recent Clementine data of the farside of the moon has shown high resolution details of the South Pole-Aitken basin. The basin is over 2500 km in diameter, making it the largest impact basin thus far identified in our solar system. Estimates for the excavation depth from the basin suggest that the lower crust\\/upper mantle may have been reached. Clementine UVVIS

C. M. Weitz; R. A. Yingst; M. Minitti; J. W. Head III; L. Prockter; J. M. Dahl; C. D. Cooper; L. Crumpler; R. Gershman; R. Welch

1997-01-01

267

Drainage basin responses to climate change  

Microsoft Academic Search

Recent investigations have shown that the extent of the channel network in some drainage basins is controlled by a threshold for overland flow erosion. The sensitivity of such basins to climate change is analyzed using a physically based model of drainage basin evolution. The GOLEM model simulates basin evolution under the action of weathering processes, hillslope transport, and fluvial bedrock

Gregory E. Tucker; Rudy Slingerland

1997-01-01

268

Thermal state of the Arkoma Basin and the Anadarko Basin, Oklahoma  

Microsoft Academic Search

One of the most fundamental physical processes that affects virtually all geologic phenomena in sedimentary basins is the flow of heat from the Earth's interiors. The Arkoma Basin and the Anadarko Basin, Oklahoma, are a prolific producer of both oil and natural gas. Both basins also have important geologic phenomena. Understanding the thermal state of the these basins is crucial

Youngmin Lee

1999-01-01

269

Tectonic framework of Turkish sedimentary basins  

SciTech Connect

Turkey's exploration potential primarily exists in seven onshore (Southeast Turkey platform, Tauride platform, Pontide platform, East Anatolian platform, Interior, Trace, and Adana) basins and four offshore (Black Sea, Marmara Sea, Aegean Sea, and Mediterranean Sea) regional basins formed during the Mesozoic and Tertiary. The Mesozoic basins are the onshore basins: Southeast Turkey, Tauride, Pontide, East Anatolian, and Interior basins. Due to their common tectonic heritage, the southeast Turkey and Tauride basins have similar source rocks, structural growth, trap size, and structural styles. In the north, another Mesozoic basin, the Pontide platform, has a much more complex history and very little in common with the southerly basins. The Pontide has two distinct parts; the west has Paleozoic continental basement and the east is underlain by island-arc basement of Jurassic age. The plays are in the upper Mesozoic rocks in the west Pontide. The remaining Mesozoic basins of the onshore Interior and East Anatolian basins are poorly known and very complex. Their source, reservoir, and seal are not clearly defined. The basins formed during several orogenic phases in mesozoic and Tertiary. The Cenozoic basins are the onshore Thrace and Adana basins, and all offshore regional basins formed during Miocene extension. Further complicating the onshore basins evolution is the superposition of Cenozoic basins and Mesozoic basins. The Thrace basin in the northwest and Adana basin in the south both originate from Tertiary extension over Tethyan basement and result in a similar source, reservoir, and seal. Local strike-slip movement along the North Anatolian fault modifies the Thrace basin structures, influencing its hydrocarbon potential.

Yilmaz, P.O. (Exxon Production Research Co., Houston, TX (USA))

1988-08-01

270

Permian Basin Location Recommendation Report.  

National Technical Information Service (NTIS)

Candidate study areas are screened from the Palo Duro and Dalhart Basin areas using data obtained from studies to date and criteria and specifications that consider: rock geometry; rock characteristics; human intrusion potential; surface characteristics; ...

1983-01-01

271

Hydrocarbon discoveries in Paleozoic Solimoes basin, Upper Amazon region, Brazil  

Microsoft Academic Search

The Solimoes basin, previously known as Upper Amazon basin, is located in northern Brazil and has a prospectable area of more than 300,000 km². The Purus arch, a regional positive feature, separates this basin from the Amazonas basin. As far as the basin geology is concerned, the Solimoes basin is strikingly different from its neighboring basin due to certain structural

N. Apoluceno; A. Ferreira; K. Tsubone

1989-01-01

272

Facies and petrophysical signature of the Tournaisian/Viséan (Lower Carboniferous) sea-level cycle in carbonate ramp to basinal settings of the Wales-Brabant massif, British Isles  

NASA Astrophysics Data System (ADS)

We studied the relationships between stratigraphic distribution of outcrop spectral gamma-ray, magnetic susceptibility and carbonate facies stacking patterns across the regionally significant transgressive-regressive cycle at the Tournaisian/Viséan boundary (Tn/V, early Carboniferous) in southern Great Britain and Ireland (South Wales, North Staffordshire and Dublin Basin). The Tn/V boundary coincides with a prominent climatic pulse connected with the Late Paleozoic glaciation of Gondwana. The aim was to correlate the gamma-ray and magnetic susceptibility log patterns in carbonate ramp- and basin settings and discuss the global/regional nature and magnitude of this transgressive-regressive cycle. A robust ramp-to-basin correlation was produced based on the log patterns, facies stacking patterns and foraminifer biostratigraphy. The concentrations of K and Th, the "clay" gamma-ray values and, partly, magnetic susceptibility are dependent on facies and show systematic changes along the inferred bathymetric profile from inner ramp to outer ramp and basin. A model of carbonate productivity-driven dilution of fine-grained siliciclastics in CaCO3 as the major control on the petrophysical patterns is discussed. The cleaning-up and cleaning-down petrophysical trends are related to down-dip and up-dip shifts of the carbonate factory with changing relative sea level. In middle-to-outer ramp and basin settings, this generates petrophysical trends just opposite to Paleozoic carbonate shelves where peaks in magnetic susceptibility are known to be associated with peak regressions. A distinct, late Tournaisian to early Viséan regressive-to-transgressive cycle with a prominent sequence boundary located close to the Tn/V stage boundary can be seen in the sections. Glacioeustatic origin of the sequence boundary is inferred from its correlation with Tn/V boundary sections from Europe, carbon isotope data from South China and the glacial deposits in the southern hemisphere mentioned by previous authors.

Bábek, Ond?ej; Kalvoda, Ji?í; Cossey, Patrick; Šimí?ek, Daniel; Devuyst, François-Xavier; Hargreaves, Simon

2013-02-01

273

The Baltic Sea Basin: Introduction  

Microsoft Academic Search

\\u000a The Baltic Sea Basin serves as an example of a region where the use of natural resources and the need of environmental protection\\u000a require a comprehensive and holistic approach in terms of geosciences, environmental sciences, and socio-economics. In this\\u000a book, authors from countries around the Baltic Sea and overseas shed light on the Baltic Sea Basin with respect to (1)

Jan Harff; Svante Björck; Peer Hoth

274

GRACE gravity evidence for an impact basin in Wilkes Land, Antarctica  

NASA Astrophysics Data System (ADS)

New details on the east Antarctic gravity field from the Gravity Recovery and Climate Experiment (GRACE) mission reveal a prominent positive free-air gravity anomaly over a roughly 500-km diameter subglacial basin centered on (70°S, 120°E) in north central Wilkes Land. This regional inverse correlation between topography and gravity is quantitatively consistent with thinned crust from a giant meteorite impact underlain by an isostatically disturbed mantle plug. The inferred impact crater is nearly three times the size of the Chicxulub crater and presumably formed before the Cretaceous formation of the east Antarctic coast that cuts the projected ring faults. It extensively thinned and disrupted the Wilkes Land crust where the Kerguelen hot spot and Gondwana rifting developed but left the adjacent Australian block relatively undisturbed. The micrometeorite and fossil evidence suggests that the impact may have occurred at the beginning of the greatest extinction of life on Earth at ~260 Ma when the Siberian Traps were effectively antipodal to it. Antipodal volcanism is common to large impact craters of the Moon and Mars and may also account for the antipodal relationships of essentially half of the Earth's large igneous provinces and hot spots. Thus, the impact may have triggered the ``Great Dying'' at the end of the Permian and contributed to the development of the hot spot that produced the Siberian Traps and now may underlie Iceland. The glacial ice up to a few kilometers thick that has covered the crater for the past 30-40 Ma poses formidable difficulties to sampling the subglacial geology. Thus, the most expedient and viable test of the prospective crater is to survey it for relevant airborne gravity and magnetic anomalies.

von Frese, Ralph R. B.; Potts, Laramie V.; Wells, Stuart B.; Leftwich, Timothy E.; Kim, Hyung Rae; Kim, Jeong Woo; Golynsky, Alexander V.; Hernandez, Orlando; Gaya-Piqué, Luis R.

2009-02-01

275

Alpine tectonics of the Pannonian basin  

SciTech Connect

The Neogene evolution of the Pannonian basin is fairly well understood in terms of back-arc extension behind the Carpathian thrust-fold belt. This middle Miocene-Holocene basin, however, is superimposed on an earlier middle Eocene-early Miocene basin traditionally called the Paleogene basin of Hungary. Although the Paleogene stratigraphy of the basin is well known, its structural evolution is not clear; however, a transtensional origin is assumed analogous to the overlying Pannonian basin. The existing data set on the Paleogene basin can be integrated easily into a compressional basin model. Other intra-Carpathian Paleogene basins, such as the Transylvanian and Slovenian basins, are now considered to be flexural in origin. Systematic interpretation of reflection seismic data shows that these Tertiary basins are superimposed on a Cretaceous Alpine thrust-fold belt. The internal geometry of this belt in the basement of the Pannonian basin indicates a close relationship to the surrounding mountain belts (Alps, Carpathians, and Dinarides). Whereas the neogene Pannonian basin is in a mature stage of exploration, the underlying Paleogene flexural basins are much less explored. Furthermore, the Cretaceous thrust-fold belts should be regarded as frontier areas for future oil and gas exploration efforts.

Tari, G. (Rice Univ., Houston, TX (United States))

1993-09-01

276

Basin Overflow Floods on Mars  

NASA Astrophysics Data System (ADS)

On Earth, the most intense recognized historical and paleofloods have been ice dambursts or overflows of large basins, often initiated by abundant runoff or meltwater from the contributing watersheds. Many impact craters and other basins also overflowed in the Martian cratered highlands, and some of their incised outlet valleys similarly record evidence of erosive floods. Otherwise, the commonly small, enclosed watersheds on Mars contain poorly developed valley networks and relatively simple depositional landforms, which record little evidence of intense (by terrestrial standards) meteorological floods. For these reasons, basin overflows may have been disproportionately important mechanisms for incision of large valleys on Mars. Many of the Martian outflow channels head in topographic settings that favored ponding, including large canyons, impact or intercrater basins, chaotic terrain basins, and grabens. This topography may have accumulated somewhat slower groundwater discharges from the subsurface to support peak channel discharges of 106-108 m3/s. To yield a discharge of 106, 107, and 108 m3/s from a dam failure with a width/depth ratio of 5, the model predicts that a breach of ~100, 250, and 640 m, respectively, must form rapidly with respect to the decline of lake level. Terrestrial damburst floods have not exceeded ~106 m3/s for earthen dams and ~107 m3/s for ice dams, but brecciation of the Martian surface by impact cratering may have allowed larger damburst failures, whereas solid bedrock was exposed at shallower depths in the terrestrial examples. Moreover, many of the Martian basins were much larger than enclosed continental basins on Earth, so long-lived overflows may have facilitated entrenchment of deeper channels. Some large, mid-latitude basins overflowed to carve Ma'adim Vallis and the Uzboi-Ladon-Margaritifer Valles system, which are similar in scale to the terrestrial Grand Canyon but record much larger formative discharges. Models of damburst floods yield peak discharges that are similar to values derived from channel dimensions in several cases. Smaller basin overflows incised smaller outlet valleys at many locations on Mars.

Irwin, R. P.

2006-12-01

277

Fuel storage basin seismic analysis  

SciTech Connect

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.

Kanjilal, S.K.; Winkel, B.V.

1991-08-01

278

Rainbow Basin, CA mapping project  

NSDL National Science Digital Library

Rainbow Basin is just north of Barstow, CA, and is an excellent badlands-style exposure of the Barstow syncline in the Miocene Barstow Formation. In the first mapping class, their assignment is to map the basic geology of the basin, using a couple of distinctive marker beds within the Barstow Formation. Several faults postdate the fold, and three different ages of alluvial deposits occur within the basin. We camp in the nearby Owl Canyon campground, and spend three days in the field. More time could be spent with an introductory class, but three suffices to get most of the basin on the map. They are charged with writing up descriptions of the rock units they encounter. From the field map, students transfer information to an office copy, add a map explanation, and draw a cross-section through the map area. Mapping is done on a topographic map, specifically developed for the basin, with 10-foot contour intervals. This is a proprietary map, so permission is needed for its use.

Fryxell, Joan

279

Vertical Analysis of Martian Drainage Basins  

NASA Technical Reports Server (NTRS)

We have performed a vertical analysis of drainage basins on Mars that were computationally extracted from DEMs based on the MOLA data. Longitudinal profiles of main streams are calculated and the slope-area relation is established for 20 basins coming from assorted martian locations. An identical analysis is done for 19 terrestrial river basins. Our results show that, in comparison to terrestrial basins, martian basins have more linear longitudinal profiles, more frequent existence of knickpoints, predominance of asymmetric location of the main stream in the basin, and smaller values of concavity exponent. This suggests a limited role for surface runoff on the global scale. However, two basins extracted from the slopes of martian volcanoes show a strong similarity to terrestrial basins, indicating a possible local role for the process of surface runoff.

Stepinski, T. F.; OHara, W. J.

2003-01-01

280

Origin of the earth's ocean basins  

NASA Technical Reports Server (NTRS)

The earth's original ocean basins are proposed to be mare-type basins produced 4 billion y.a. by the flux of asteroid-sized objects responsible for the lunar mare basins. Scaling upward from the observed number of lunar basins for the greater capture cross-section and impact velocity of the earth indicates that at least 50% of an original global crust would have been converted to basin topography. These basins were flooded by basaltic liquids in times short compared to the isostatic adjustment time for the basin. The modern crustal dichotomy (60% oceanic, 40% continental crust) was established early in the history of the earth, making possible the later onset of plate tectonic processes. These later processes have subsequently reworked, in several cycles, principally the oceanic parts of the earth's crust, changing the configuration of the continents in the process. Ocean basins (and oceans themselves) may be rare occurrences on planets in other star systems.

Frey, H.

1977-01-01

281

Origin of the earth's ocean basins  

NASA Technical Reports Server (NTRS)

The earth's original ocean basins were mare-type basins produced 4 billion years ago by the flux of asteroid-sized objects responsible for the lunar mare basins. Scaling upwards from the observed number of lunar basins for the greater capture cross-section and impact velocity of the Earth indicates that at least 50 percent of an original global crust would have been converted to basin topography. These basins were flooded by basaltic liquids in times short compared to the isostatic adjustment time for the basin. The modern crustal dichotomy (60 percent oceanic, 40 percent continental crust) was established early in the history of the earth, making possible the later onset of plate tectonic processes. These later processes have subsequently reworked, in several cycles, principally the oceanic parts of the earth's crust, changing the configuration of the continents in the process. Ocean basins (and oceans themselves) may be rare occurrences on planets in other star systems.

Frex, H.

1977-01-01

282

Western Pacific Basin: A Climatological Study.  

National Technical Information Service (NTIS)

This technical note is a climatological study of the Western Pacific Basin. After describing the geography and major meteorological features of the entire region, the study discusses in detail the climatic controls of each of the Western Pacific Basin's '...

D. Carey J. Louer M. Higdon R. Lilianstrom V. Killman

2003-01-01

283

Discrete Dynamical Networks and Their Attractor Basins  

Microsoft Academic Search

A key notion in the study of network dynamics is that state-space is connected into basins of attraction. Convergence in attractor basins correlates with order-complexity-chaos measures on space-time patterns. A network's \\

Andrew Wuensche

1998-01-01

284

Contrasting deglacial sedimentary architecture along paleofjord systems due to distance to open-sea, and its importance for hydrocarbon generation; Late Carboniferous units of W-Gondwana, Argentina  

NASA Astrophysics Data System (ADS)

The sedimentary fill of several exhumed paleovalleys cropping out at the Precordillera of San Juan Province Argentina, is compared. All these paleovalley fills show the fairly fast passage from proglacial conditions, well defined by dropstones or by redeposited units contained striated clasts, and eventually by the presence of striated pavements, to non-glacial deep water conditions defined by the lack of proglacial indicators, but instead a much finer-grained sedimentary unit, indicating a quite rapid transgression due to the eustatic rise after deglaciation. On spite of a similar climate-eustatic evolution, the paloefjord fills are quite contrasting in their detailed sedimentary architecture and in their capacity to produce source rock lithologies. We have basically differentiated three main type-cases, and we studied a few examples of each. Each type-case correspond to a realm (internal, intermediate, and marginal) that seems to be related to the distance to the open sea, and hence the capacity to produce restricted conditions in that local segment of the flooded paleovalley. The internal realm is characterized by its closest position to the ice-cap and hence records a maximum degree of glacioisostatic load and minimum connection to open sea processes. As a result, during deglaciation, these basins become deeper and more isolated and thus, better suited for source rock production. The degree of reworking of the deposits is minimum, and preservation is maximum and it is often to record high-slope systems prograding directly onto a fjord deep basin floor. Two paloefjords were studied in detail to characterize this sedimentation mode: the Quebrada Grande and Quebrada de las Lajas paleopjords. The intermediate realm is characterized by a medial position from the ice cap and the continent margin, and it is likely to only have recorded outlet glaciers presence. The glaciostatic load was not so strong and the resulting deglacial sequences are not as thick not so muddy as well. There is not accumulation of source rocks, although some coal beds can be produced during the last stage of palefjord filling. Accumulation at this realm is quite varied, from typical estuarine conditions to slope-complexes generated at the front of braid- and fan-deltas, but there is a high degree of reworking of the deposits due to limited accommodation space and high sediment yield, and as a result sequences are in general much sandier, although their granulometric evolution is similar to that of the internal realm. Two paleofjords were studied in this realm: the Talacasto and Rí San Juan paloefjords. The external realm is characterized by its furthest position with respect to the ice load and as a result the deglacial interval is the thinnest, although due to its distal position, this place has the advantage of recording more previous glacial advances, that were overridden at intermediate and internal positions in the last major glacial advance. At this realm, the postglacial transgression is again quite muddy, as in the internal realm, but in this case, there are no signs of restriction and muds tend to be green, and depleted of organic matter in spite of the rich marine invertebrate fauna, that was not observed at the other sectors. The quantity of wave structures suggest that wave action was much more intense than in the other cases, and in general, there are much less sediments product of gravity flows. We inspected in detail the El Paso and Hoyada Verde paloefjords. This study shows thus, that there is a very important paleogeographic control of depositional processes that have some economic importance. Potential hydrocarbon source rocks would be favored at the inner belt of these palefjords, some doubtful conditions would exist at intermediate positions and basically no source rock would be generated at the outer belt, bear the exits of these paleofjords into the open sea.

Milana, J. P.; Kneller, B.; Dykstra, M.

2009-04-01

285

Viscoelastic evolution of lunar multiring basins  

Microsoft Academic Search

We investigate the evolution of multiring basins on the Moon. The orbital geophysical and geochemical data collected by Lunar Prospector allow three distinct groups of basins to be identified. Group 1 basins show well-preserved topography, a bull's-eye gravity signature, and little mare basalt fill. Group 2 basins contain large amounts of mare basalt and show mare-dominated gravity and topography signatures.

P. Surdas Mohit; Roger J. Phillips

2006-01-01

286

IMPROVEMENTS IN PUMP INTAKE BASIN DESIGN  

EPA Science Inventory

Pump intake basins (or wet wells or pump sumps) designed in accordance with accepted criteria often pose many operation and maintenance problems. The report summarizes field surveys of three trench-type pump intake basins representative of 29 such basins that have been in satisfa...

287

IMPROVEMENTS IN PUMP INTAKE BASIN DESIGN  

EPA Science Inventory

Pump intake basins (or wet wells or pump sumps) designed in accordance with accepted criteria often pose many operation and maintenance problems. he report summarizes field surveys of three trench-type pump intake basins representative of 29 such basins that ave been in satisfact...

288

Waters of the Makarov and Canada basins  

Microsoft Academic Search

Hydrographic measurements from the 1994 Arctic Ocean Section show how the Makarov and Canada basins of the Arctic Ocean are related, and demonstrate their oceanographic connections to the Eurasian Basin. The inflow into the Makarov Basin consists largely of well-ventilated water within a broad band of densities from a boundary flow over the Siberian end of the Lomonosov Ridge. The

J. H. Swift; E. P. Jones; K. Aagaard; E. C. Carmack; M. Hingston; R. W. MacDonald; F. A. McLaughlin; R. G. Perkin

1997-01-01

289

Basin width control of faulting in the Naryn Basin, south-central Kyrgyzstan  

NASA Astrophysics Data System (ADS)

In Central Asia's Tien Shan, deformation is distributed across the wide orogen, a characteristic of intracontinental mountain building. Active faults are commonly found within intramontane basins that separate its constituent ranges. In order to explore the controls on this intramontane basin deformation, we study the Naryn Basin of south-central Kyrgyzstan. A series of five balanced cross-sections reveals a transition in patterns of faulting from faults confined to basin margins to faults focused within the basin center. The 20-km-wide eastern Naryn Basin displays deformation attributed to low-angle splays of the northern, basin-bounding fault. In the 40-km-wide western Naryn Basin, the pattern of deformation linked to the northern range remains, but is accompanied by steeper faults that dip both south and north without being directly linked to the basin-bounding fault. We compare these cross-sections to synthetic aperture radar interferometry (InSAR) measurements of surface deformation. Profiles of InSAR-derived surface deformation rates across the Naryn Basin reveal that in the west, deformation is distributed across the broad basin interior, whereas in the east, rapid uplift is concentrated at the margin of the narrower basin. From the geodetic and structural data, we infer that in the western Naryn Basin, deformation has migrated away from the northern basin margin and into the interior. Deformation of the eastern basin interior, however, remains linked to the basin-bounding fault. A simple mechanical model demonstrates that basin width may control basin deformation whereby basin-interior faulting in the narrow, eastern Naryn Basin is inhibited by the overburden of adjacent ranges.

Goode, Joseph K.; Burbank, Douglas W.; Bookhagen, Bodo

2011-12-01

290

Paleothermometry of the Sydney Basin  

Microsoft Academic Search

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 °C or higher. As vitrinite reflectance, an index of coal rank or coalification, is postulated to vary

M. F. Middleton; P. W. Schmidt

1982-01-01

291

Polyphemidae of the Pontocaspian Basin  

Microsoft Academic Search

Polyphemidae constitute one of the most characteristic groups of the peculiar auchtochthonous fauna of the Caspian Sea. While in all open seas and freshwaters of the globe they are represented by 8 species only, in Caspian Sea 24 polyphemid species are found and about 15 intraspecific forms. Except one species, all of them are endemic for the Pontocaspian basin (and

Mordukhai-Boltovskoi

1965-01-01

292

Guidebook 1991: Caribbean Basin Initiative.  

National Technical Information Service (NTIS)

Since its enactment seven years ago, the Caribbean Basin Initiative (CBI) has provided a unique impetus to the development of trade and investment between the United States and the 23 CBI beneficiary nations. U.S. companies seeking new sources of producti...

J. Phillips

1990-01-01

293

Geology of Canadian Arctic basin  

Microsoft Academic Search

The Canadian Beaufort Sea is underlain by up to 12,000 m of Upper Cretaceous to Quaternary sediments. These sediments were deposited in a series of prograding depositional complexes containing fluviodeltaic, shelf, slope, and basinal clastics. At least 10 major regional unconformities within the Upper Cretaceous to Quaternary section are recognized. The 2 most pronounced unconformities developed in late Eocene and

1985-01-01

294

Lake Chad Basin Transport Survey.  

National Technical Information Service (NTIS)

The need for good all-weather roads is evident in the Chad Basin Region of Central Africa, where four countries--Cameroon, Chad, Niger, and Nigeria--have regions which appear to offer potential for expanded agricultural development, but lack an adequate t...

1970-01-01

295

Evolution of the Congo Basin  

NASA Astrophysics Data System (ADS)

The Congo Basin is one of the largest basins in the World with very little knowledge on the geological evolution as well as the oil and gas potential. In the past, oil seeps are recorded in the central part of the basin. Four sides in the Congo basin have been drilled so far. The cores of the two drill sides Dekese and Samba are located at the Musée royal de l'Afrique Centrale, Belgium. In a reconnaissance survey, we sampled both drill cores in a nearly even spacing of ~ 150 m covering the whole stratigraphy from Albian to Proterozoic. The red and green to grey sandstone samples were prepared by usual heavy minerals separation technique. Most of the samples revealed enough apatite and zircon grains for the two thermochronometric techniques fission track and (U-Th-Sm)/He. The time-temperature (t-T) evolution for the two drill locations were modelled by using the determined thermochronological data within the software code HeFTy. We tested various geological evolutionary constrains. Both techniques provide us information on the thermal and exhumation of the possible source area and on the drill location by themselves.

Glasmacher, U. A.; Bauer, F. U.; Kollenz, S.; Delvaux, D.

2012-04-01

296

Great Basin Aquatic Systems History.  

National Technical Information Service (NTIS)

The 14 papers collected herein treat diverse aspects of the aquatic history of the Great Basin of the western United States and collectively attempt to summarize and integrate portions of the vast body of new information on this subject that has been acqu...

D. B. Madsen D. R. Currey R. Hershler

2002-01-01

297

BASIN: Beowulf Analysis Symbolic INterface  

NASA Astrophysics Data System (ADS)

BASIN (Beowulf Analysis Symbolic INterface) is a flexible, integrated suite of tools for multiuser parallel data analysis and visualization that allows researchers to harness the power of Beowulf PC clusters and multi-processor machines without necessarily being experts in parallel programming. It also includes general tools for data distribution and parallel operations on distributed data for developing libraries for specific tasks.

Vesperini, Enrico; Goldberg, David M.; McMillan, Stephen L. W.; Dura, James; Jones, Douglas

2013-08-01

298

Sandstone composition changes and paleocurrent reversal in the Upper Paleozoic and Triassic deposits of the Huaco area, western Paganzo Basin, west-central Argentina  

NASA Astrophysics Data System (ADS)

Sandstone detrital modes and paleocurrents in the Upper Paleozoic and Triassic deposits exposed near Huaco on the western sector of the Paganzo basin, western Argentina, reveal two distinctive petrofacies. A quartzofeldspathic petrofacies represented in the lacustrine and fluvial deposits of Carboniferous and early Permian age (Guandacol, Tupe and lower Patquía Formations) is characterized by a high content of monocrystalline quartz, low lithic content and high K-feldspar to total feldspar ratios. The fluvial facies of the lower Patquía grade vertically into eolian sandstones (upper Patquía Formation) which show a significant content of volcanic lithic fragments along with high proportions of monocrystalline quartz. This eolian succession is overlain by a volcaniclastic (lithofeldspathic) petrofacies represented by alluvial-fan and fluvial deposits of the late Permian to Triassic age (Cerro Morado and Cauquenes Formations). These sandstones are characteristic by high proportions of volcanic lithic fragments, plagioclase grains, low content of monocrystalline quartz and low K-feldspar to total feldspar ratios. This change in sandstone composition is accompanied by a reversal in paleocurrent patterns. The quartzofeldspathic petrofacies present in the Carboniferous and Lower Permian deposits show a general paleocurrent pattern from east to west with inferred cratonic provenances of plutonic and metamorphic composition. The volcaniclastic deposits indicate paleocurrents from west to east suggesting source areas associated with the magmatic arc developed on the Paleo-Pacific Gondwana margin during Permian and Triassic times.

Lopez Gamundi, Oscar; Espejo, Irene S.; Alonso, María S.

1990-02-01

299

Automated basin delineation from digital terrain data  

NASA Technical Reports Server (NTRS)

While digital terrain grids are now in wide use, accurate delineation of drainage basins from these data is difficult to efficiently automate. A recursive order N solution to this problem is presented. The algorithm is fast because no point in the basin is checked more than once, and no points outside the basin are considered. Two applications for terrain analysis and one for remote sensing are given to illustrate the method, on a basin with high relief in the Sierra Nevada. This technique for automated basin delineation will enhance the utility of digital terrain analysis for hydrologic modeling and remote sensing.

Marks, D.; Dozier, J.; Frew, J.

1983-01-01

300

A Plume Head and Tail in the Bengal Basin and Bay of Bengal: Rajmahal and Sylhet Traps with Surrounding Alkalic Volcanism and the Ninetyeast Ridge  

NASA Astrophysics Data System (ADS)

Although the 116-113 Ma-old Rajmahal-Sylhet Traps of the Bengal basin, potentially covering an area > 2x105 km2, can be directly linked via Ninetyeast Ridge to the Kerguelen Plume, more than 5,000 kms away, it is generally believed that this flood basalt volcanism originated from a normal MORB-type mantle at the boundary of a mantle plume. This model, primarily based on geochemical analysis of a limited number of Rajmahal basalts, requires initiation of rifting of the eastern Indian margin by a smaller thermal flux than necessary for creating a large igneous province. Here we show that the extent of volcanism associated with the Rajmahal-Sylhet Traps is far greater than usually assumed, thus requiring a direct involvement of the Kerguelen Plume. In addition to the surface exposures of the flood basalts in Rajmahal-Sylhet, the basaltic rocks have been encountered in many parts of the Bengal Basin in bore holes reaching a maximum thickness of 600 m in the western margin of the Basin (Sengupta, Bull. AAPG, 1966) Most importantly, several suites of ultrapotassic and alkalic intrusive complexes, similar to those associated with the Deccan and Siberia Traps, occur over wide areas within and outside the Basin: i) southwest of the surface exposures of Rajmahal basalts, distance 200km, intrusive in Lower Gondwana coalbeds, Ar-Ar age 114 Ma (P.R. Renne, personal communication), ii) 400 km north of Rajmahal, exposed in Sikkim, intrusive into metamorphic crystalline nappes of the Himalayas; distance here is not real and must be a minimum as the nappes have been transported from the north, iii) northeast of Rajmahal in Meghalaya State, distance 550 km, intrusive into metamorphic Precambrian basement rocks. Nd-Sr isotopic ratios and trace element characteristics of these above ultrapotassic and alkaline rocks are consistent with their origin associated with the Kerguelen Plume. The wide range in Nd-Sr array for these rocks, including the Sylhet and Rajmahal basalts, shows initial \\epsilonNd(T) values of +4 to -8 and 87Sr/86Sr of 0.7045 to 0.7100, which are similar to Kerguelen transitional and alkaline basalts, Bunburry Gosselin lavas and Naturaliste plateau basalts. Therefore, the zone of influence of the plume head with Rajmahal at the center would be at least 700 km in diameter, and such a large area would require direct involvement of the Kerguelen Plume head for magma genesis in the Bengal basin. Recognition of associated volcanism in the northeast of Sylhet Traps allows Nintyeast Ridge to be the appropriate hotspot track in the Bay of Bengal.

Basu, A. R.; Weaver, K. L.; Sengupta, S.

2001-12-01

301

Mississippian facies relationships, eastern Anadarko basin, Oklahoma  

SciTech Connect

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 Caney Formation. As basin subsidence rates accelerated, the southern edge of the Chester carbonate shelf was progressively drowned, causing a backstepping of the Chester Formation calcareous shale and carbonate facies. Springer Group sands and black shales transgressed northward over the drowned Chester Formation shelf.

Peace, H.W. (Oryx Energy, Inc., Midland, TX (United States)); Forgotson, J.M. (Univ. of Oklahoma, Norman (United States))

1991-08-01

302

Deep inflow into the Mozambique Basin  

NASA Astrophysics Data System (ADS)

More than 200 conductivity-temperature-depth (CTD) stations were worked around the Southwest Indian Ridge and Del Caño Rise as part of the World Ocean Circulation Experiment. A selection of these data provides information about the inflow of bottom water into the Mozambique Basin. The basin is closed below 3000 m, yet the inflow is significantly large, of order 1 Sv (1 Sv = 106 m3 s-1). Estimates of the basin-scale upwelling at 4000 m suggest that the vertical velocity is also large, 10 × 10-5 cm s-1 or more, an order of magnitude greater than global ocean estimates. Examination of the characteristics of the bottom water in the Mozambique and Agulhas Basins and the Prince Edward Fracture Zone shows that bottom water enters the Mozambique Basin from the Agulhas Basin and also directly from the Enderby Basin. Most of the transport enters the Mozambique Basin via the Agulhas Basin, where two regions of northward flow below 4000 m are found. The major flow, on the eastern flank of the Mozambique Ridge, is through and above the deep, extending (5900 m) trench that connects the Agulhas and Mozambique Basins. The second, weaker flow enters the Transkei Basin along the deep eastern flank of the Agulhas Plateau, then turning east into the Mozambique Basin. The only source of bottom water to the Agulhas Basin is the Enderby Basin, but a more direct route between the Enderby and Mozambique Basins exists via the Prince Edward fracture, which extends deeper than 4000 m throughout its length and links the two basins directly across the Southwest Indian Ridge. Full depth CTD stations trace the changing characteristics of the deep and bottom water in the fracture, and moored current meter data show the strength and persistence of the throughflow. Strong mixing with the overlying deep water elevates the salt content of the bottom water by comparison with the other water in the Mozambique Basin. Thus two distinct bottom waters of the Mozambique Basin originate in the same place (the Enderby Basin), and their different characteristics are solely a function of the routes they have taken and the processes encountered along the different pathways.

Read, J. F.; Pollard, R. T.

1999-02-01

303

THE ADVANCED CHEMISTRY BASINS PROJECT  

SciTech Connect

In the next decades, oil exploration by majors and independents will increasingly be in remote, inaccessible areas, or in areas where there has been extensive shallow exploration but deeper exploration potential may remain; areas where the collection of data is expensive, difficult, or even impossible, and where the most efficient use of existing data can drive the economics of the target. The ability to read hydrocarbon chemistry in terms of subsurface migration processes by relating it to the evolution of the basin and fluid migration is perhaps the single technological capability that could most improve our ability to explore effectively because it would allow us to use a vast store of existing or easily collected chemical data to determine the major migration pathways in a basin and to determine if there is deep exploration potential. To this end a the DOE funded a joint effort between California Institute of Technology, Cornell University, and GeoGroup Inc. to assemble a representative set of maturity and maturation kinetic models and develop an advanced basin model able to predict the chemistry of hydrocarbons in a basin from this input data. The four year project is now completed and has produced set of public domain maturity indicator and maturation kinetic data set, an oil chemistry and flash calculation tool operable under Excel, and a user friendly, graphically intuitive basin model that uses this data and flash tool, operates on a PC, and simulates hydrocarbon generation and migration and the chemical changes that can occur during migration (such as phase separation and gas washing). The DOE Advanced Chemistry Basin Model includes a number of new methods that represent advances over current technology. The model is built around the concept of handling arbitrarily detailed chemical composition of fluids in a robust finite-element 2-D grid. There are three themes on which the model focuses: chemical kinetic and equilibrium reaction parameters, chemical phase equilibrium, and physical flow through porous media. The chemical kinetic scheme includes thermal indicators including vitrinite, sterane ratios, hopane ratios, and diamonoids; and a user-modifiable reaction network for primary and secondary maturation. Also provided is a database of type-specific kerogen maturation schemes. The phase equilibrium scheme includes modules for primary and secondary migration, multi-phase equilibrium (flash) calculations, and viscosity predictions.

William Goddard; Peter Meulbroek; Yongchun Tang; Lawrence Cathles III

2004-04-05

304

Formation of lunar basin rings  

USGS Publications Warehouse

The origin of the multiple concentric rings that characterize lunar impact basins, and the probable depth and diameter of the transient crater have been widely debated. As an alternative to prevailing "megaterrace" hypotheses, we propose that the outer scarps or mountain rings that delineate the topographic rims of basins-the Cordilleran at Orientale, the Apennine at Imbrium, and the Altai at Nectaris-define the transient cavities, enlarged relatively little by slumping, and thus are analogous to the rim crests of craters like Copernicus; inner rings are uplifted rims of craters nested within the transient cavity. The magnitude of slumping that occurs on all scarps is insufficient to produce major inner rings from the outer. These conclusions are based largely on the observed gradational sequence in lunar central uplifts:. from simple peaks through somewhat annular clusters of peaks, peak and ring combinations and double ring basins, culminating in multiring structures that may also include peaks. In contrast, belts of slump terraces are not gradational with inner rings. Terrestrial analogs suggest two possible mechanisms for producing rings. In some cases, peaks may expand into rings as material is ejected from their cores, as apparently occurred at Gosses Bluff, Australia. A second process, differential excavation of lithologically diverse layers, has produced nested experimental craters and is, we suspect, instrumental in the formation of terrestrial ringed impact craters. Peak expansion could produce double-ring structures in homogeneous materials, but differential excavation is probably required to produce multiring and peak-in-ring configurations in large lunar impact structures. Our interpretation of the representative lunar multiring basin Orientale is consistent with formation of three rings in three layers detected seismically in part of the Moon-the Cordillera (basin-bounding) ring in the upper crust, the composite Montes Rook ring in the underlying, more coherent "heald" crust, and an innermost, 320-km ring at the crust-mantle interface. Depth-diameter ratios of 1 10to 1 15 are consistent with this interpretation and suggest that volumes of transient cavities and hence of basin ejecta may be considerably greater than commonly assumed. ?? 1978.

Hodges, C. A.; Wilhelms, D. E.

1978-01-01

305

The Central European Permian Basins; Rheological and structural controls on basin history and on inter-basin connectivity  

NASA Astrophysics Data System (ADS)

We analyse the relative importance of the major crustal-scale fault zones and crustal architecture in controlling basin formation, deformation and the structural connections between basins. The North and South Permian Basins of Central Europe are usually defined by the extend of Rotliegend sedimentary and volcanic units and not by a common tectonic origin or development. Instead, the sub-basins that together form the Permian Basins are each controlled by different structural and/or rheological controls that are inherited from Early Paleozoïc and older geodynamic processes, they are even located in different crustal/lithospheric domains. The North Permian basin is located on Baltic crust that was thinned during Late Proterozoïc - Early Paleozoïc times. South of the Thor suture, the South Permian basin and its sub-basins are located on Avalonian crust (Southern North Sea and North German Basins) and on the transition of East European cratonic and Avalonian crust (Polish Through). The size of crustal domains and of the faults that govern basin formation requires a regional-scale to assess their impact on basins and sub-basins. In the case of the Permian Basins this encompasses East Avalonia and surroundings, roughly speaking the area north of the Variscan Rheïc suture, east of the Atlantic and southwest of the Teisseyre-Tornquist line. This approach sheds light on the effects of long lived differences in crustal fabric which are responsible for spatial heterogeneity in stress and strain magnitudes and zonations of fracturing, burial history and temperature history. The focus on understanding the geomechanical control of large crustal-scale fault structures will provide the constraints and geometrical and compositional input for local models of stress and strain. Considering their fundamentally different structural and rheological controls, the Permian (sub)basins have a remarkably common history of subsidence and inversion, suggesting a more or less continuous link between them. Post-Variscan, Late Carboniferous-Early Permian wrench tectonics is the oldest and main identified cause for regional basin formation in Central Europe. This relatively short-lived tectonic regime cannot explain the observed common history of subsidence of the Permian Basins during the 200 My that followed. Our analysis demonstrates that transfer faults that both follow and cross rheological transitions and inherited fault zones continued to be active after the early Permian. We therefore suggests that crustal-scale transfer faults may be the missing link that explains the common subsidence history of basins with a fundamentally different crustal architecture and structural history.

Smit, Jeroen; Van Wees, Jan-Diederik; Cloetingh, Sierd

2014-05-01

306

Large Double-ringed Basin  

NASA Technical Reports Server (NTRS)

Taken about 40 minutes before Mariner 10 made its close approach to Mercury on September 21, this picture (FDS 166684) shows a large (230 kilometers, 142 miles) double-ringed basin (center of picture) located in the planet's south polar region - 75 degrees S. Lat. 120 degrees W. Long. Mercury saw the basin from a different viewing angle on Mariner 10's first sweep last March. This picture was taken from about 55,000 kilometers (44,000 miles). North is toward upper left.

The Mariner 10 mission, managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, explored Venus in February 1974 on the way to three encounters with Mercury-in March and September 1974 and in March 1975. The spacecraft took more than 7,000 photos of Mercury, Venus, the Earth and the Moon.

Image Credit: NASA/JPL/Northwestern University

1974-01-01

307

Geology of the Campeche Basin  

SciTech Connect

Due to the discovery of 8 large oil and gas reservoirs in the Campeche Basin in the last 5 years, the Gulf of Mexico has become one of the most important offshore petroliferous regions in the world. Even though the geophysical work has included the north side of the Yucatan Peninsula, the most exploited area contains approximately 8000 sq km. The column of Cenozoic rocks has a thickness of 3600 m of which 1400 m is Mesozoic rocks. The oldest rocks being those of the Oxfordian Upper Jurassic. The depositional environments vary from deep seas to platform. The tectonic frame of this province is constituted by the Yucatan Platform and the Comalcales and Macuspane basins. The average depth of the reservoir varies between 1260 to 3600 m, the producing rocks being dolomites of the Upper Jurassic and Cretaceous.

De Gyves, J.M.

1980-06-01

308

Geology of interior cratonic sag basins  

SciTech Connect

Interior cratonic sag basins are thick accumulations of sediment, generally more or less oval in shape, located entirely in the interiors of continental masses. Some are single-cycle basins and others are characterized by repeated sag cycles or are complex polyhistory basins. Many appear to have developed over ancient rift systems. Interior cratonic sag basins are typified by a dominance of flexural over fault-controlled subsidence, and a low ratio of sediment volume to surface area of the basin. The Baltic, Carpentaria, Illinois, Michigan, Parana, Paris, and Williston basins are examples of interior cratonic sag basins. Tectonics played a dominant role in controlling the shapes and the geometries of the juxtaposed packets of sedimentary sequences. While the mechanics of tectonic control are not clear, evidence suggests that the movements are apparently related to convergence of lithospheric plates and collision and breakup of continents. Whatever the cause, tectonic movements controlled the freeboard of continents, altering base level and initiating new tectono-sedimentologic regimes. Sag basins situated in low latitudes during their development commonly were sites of thick carbonates (e.g., Illinois, Michigan, Williston, and Paris basins). In contrast, siliciclastic sedimentation characterized basins that formed in higher latitudes (e.g., Parana and Carpentaria basins). Highly productive sag basins are characterized by widespread, mature, organic-rich source rocks, large structures, and good seals. Nonproductive basins have one or more of the following characteristics: immature source rocks, leaky plumbing, freshwater flushing, and/or complex geology due to numerous intrusions that inhibit mapping of plays.

Leighton, M.W.; Eidel, J.J.; Kolata, D.R.; Oltz, D.F. (Illinois Geological Survey, Champaign (USA))

1990-05-01

309

Indians of the Great Basin  

NSDL National Science Digital Library

Tad Beckman, professor at Harvey Mudd College, has developed the Indians of the Great Basin site in conjunction with a course he taught on "Indigenous People of the Western United States" at Harvey Mudd College. The eleven "chapters" discuss the archaeology of the region; the material, social, and political cultures; spiritualism; and the arts. Illustrations (photos and maps) and related Internet resources accompany each discussion. Finally, a complete bibliography of all the cited works is available.

Beckman, Tad.

1996-01-01

310

Geology of Canadian Arctic basin  

SciTech Connect

The Canadian Beaufort Sea is underlain by up to 12,000 m of Upper Cretaceous to Quaternary sediments. These sediments were deposited in a series of prograding depositional complexes containing fluviodeltaic, shelf, slope, and basinal clastics. At least 10 major regional unconformities within the Upper Cretaceous to Quaternary section are recognized. The 2 most pronounced unconformities developed in late Eocene and late Miocene times. In the Beaufort-Mackenzie basin, the Upper Cretaceous to upper Miocene sediments were deformed primarily by gravity tectonics into large-scale diapiric anticlines and rotated listric fault-bounded blocks. Some reverse faulting, associated with mud diapirism, is evident in the western part of the basin. The late Miocene unconformity separates the deformed sediments below from the essentially undeformed, overlying Pliocene-Pleistocene strata. Beneath the eastern Beaufort Sea, seaward of Amundsen Gulf and Banks Island, the Upper Cretaceous and younger strata thicken abruptly basinward across a hinge line developed at the edge of the Arctic platform (mostly composed of pre-Mesozoic strata). The Upper Cretaceous to Quaternary sedimentary prism along this part of the continental margin is not disrupted by diapirism or listric faulting; in fact it is relatively undeformed, with only minor normal faulting in the older part of the prism.

Dixon, J.

1985-02-01

311

Great Basin geoscience data base  

USGS Publications Warehouse

This CD-ROM serves as the archive for 73 digital GIS data set for the Great Basin. The data sets cover Nevada, eastern California, southeastern Oregon, southern Idaho, and western Utah. Some of the data sets are incomplete for the total area. On the CD-ROM, the data are provided in three formats, a prototype Federal Data Exchange standard format, the ESRI PC ARCVIEW1 format for viewing the data, and the ESRI ARC/INFO export format. Extensive documentation is provided to describe the data, the sources, and data enhancements. The following data are provided. One group of coverages comes primarily from 1:2,000,000-scale National Atlas data and can be assembled for use as base maps. These various forms of topographic information. In addition, public land system data sets are provided from the 1:2,500,000-scale Geologic Map of the United States and 1:500,000-scale geologic maps of Nevada, Oregon, and Utah. Geochemical data from the National Uranium Resource Evaluation (NURE) program are provided for most of the Great Basin. Geophysical data are provided for most of the Great Basin, typically gridded data with a spacing of 1 km. The geophysical data sets include aeromagnetics, gravity, radiometric data, and several derivative products. The thematic data sets include geochronology, calderas, pluvial lakes, tectonic extension domains, distribution of pre-Cenozoic terranes, limonite anomalies, Landsat linear features, mineral sites, and Bureau of Land Management exploration and mining permits.

Raines, Gary L.; Sawatzky, Don L.; Connors, Katherine A.

1996-01-01

312

Biogeochemistry of a Suburban Basin  

NASA Astrophysics Data System (ADS)

A long-term research effort was recently established in the Lamprey River basin in southeastern New Hampshire. The watershed is largely forested, and has significant amounts of wetlands due to the relatively low topographic relief. Human population growth is rapid, resulting in conversion of forest and agricultural land to housing tracts. The primary focus of the project will be to examine the relationships between land use, land cover and water quality as the watershed continues to increase in population density. A secondary emphasis will be to examine the interactions between hydrologic flow paths, climatic variability, and biogeochemical processes that drive groundwater and surface water quality in the basin. Our initial work has quantified landscape attributes and related them to water quality. Results to date show that small tributary streams are relatively high in nitrogen relative to the main stem of the Lamprey; that human population density drives nitrate concentrations in the basin; and that DOC flux is predicted well by the model of Aitkenhead and McDowell that links DOC flux to watershed C:N ratio.

McDowell, W. H.; Daley, M. L.; Blumberg, J.

2002-12-01

313

Stratigraphic Analysis of Upper Cretaceous Rocks in the Mahajanga Basin, Northwestern Madagascar: Implications for Ancient and Modern Faunas.  

PubMed

Upper Cretaceous strata of the Mahajanga Basin, northwestern Madagascar, yield some of the most significant and exquisitely preserved vertebrate fossils known from Gondwana. The sedimentology of these strata and their stratigraphic relations have been the focus of renewed geological investigations during the course of five expeditions since 1993. We here designate stratotypes and formalize the terrestrial Maevarano Formation, with three new members (Masorobe, Anembalemba, Miadana), and the overlying marine Berivotra Formation. The Maevarano Formation accumulated on a broad, semiarid alluvial plain bounded to the southeast by crystalline highlands and to the northwest by the Mozambique Channel. The Berivotra Formation was deposited in an open marine setting that evolved from a clastic- to a carbonate-dominated shelf, resulting in deposition of the overlying Betsiboka limestone of Danian age. New stratigraphic data clearly indicate that the Maevarano Formation correlates, at least in part, with the Maastrichtian Berivotra Formation, and this in turn indicates that the most fossiliferous portions of the Maevarano Formation are Maastrichtian in age, rather than Campanian as previously reported. This revised age for the Maevarano vertebrate assemblage indicates that it is approximately contemporaneous with the vertebrate fauna recovered from the Deccan basalt volcano-sedimentary sequence of India. The comparable age of these two faunas is significant because the faunas appear to be more similar to one another than either is to those from any other major Gondwanan landmass. The revised age of the Maevarano Formation, when considered in the light of our recent fossil discoveries, further indicates that the ancestral stocks of Madagascar's overwhelmingly endemic modern vertebrate fauna arrived on the island in post-Mesozoic times. The basal stocks of the modern vertebrate fauna are conspicuously absent in the Maevarano Formation. Finally, the revised age of the Maevarano Formation serves to expand our global perspective on the K/T event by clarifying the age of a diverse, and arguably the best preserved, sample of Gondwanan vertebrates from the terminal Cretaceous. PMID:10769157

Rogers; Hartman; Krause

2000-05-01

314

Geology of the Douala basin, offshore Cameroon, West Africa  

Microsoft Academic Search

The Douala basin is predominantly an offshore basin extending from the Cameroon volcanic line in the north to the Corisco arch in the south near the Equatorial Guinea-Gabon border. The basin lies wholly within the territorial borders of Cameroon and Equatorial Guinea. The Douala basin is one of a series of divergent margin basins occurring along the southwest African coastline

R. J. Pauken; J. M. Thompson; J. R. Schumann; J. C. Cooke

1991-01-01

315

UPPER SNAKE RIVER PRIORITY BASIN ACCOMPLISHMENT PLAN, APRIL 1973  

EPA Science Inventory

The Upper Snake Accomplishment Basin (17040104, 170402, 170501) is defined as the Idaho and Oregon portions of 2 STORET Basins, the Upper Snake Basin and the Central Snake Basin. The Basin drains approximately 62,100 square miles in Southern Idaho and Southeastern Oregon. Four ...

316

Petroleum potential and stratigraphy of Holitna basin, Alaska  

Microsoft Academic Search

The Holitna basin, an interior Alaskan basin, is flanked by Cambrian to cretaceous sedimentary rocks that have been highly folded and faulted. Gravity mapping and modeling indicate up to 15,000 ft of sedimentary section is present within the basin. Cambrian rocks consist of trilobite-hash lime mudstone, red siltstone, and basinal chert. Ordovician through Devonian basinal facies rocks consist of platy

T. N. Smith; J. G. Clough; J. F. Meyer; R. B. Blodgett

1985-01-01

317

Namibe basin: geology and hydrocarbon potential, Angola  

SciTech Connect

Namibe basin is located in the south-central Atlantic off southern Angola. Its occurrence in Late Jurassic-Early Cretaceous continental rifting is coeval to the Santos of eastern Brazil. In this frontier-type, marginal sag basin, a 420-km sediment depocenter is estimated along a north-south elongation axis. Walvis Ridge bounds the basin's southern flank offshore, and desert sand covers the onshore strata. Regional unconformities are drawn from contiguous Kwanza and Congo basins. A potentially large reservoir is a 100-mi linear shelf-edge Albian carbonate inferred to be a buildup or bank. Other potential reservoirs are lacustrine sands/carbonates found near basement horst blocks and deep-basin Tertiary turbidites sourced from the shelf due to rapid sand deposition on a steep shelf-slope. The basin's excellent hydrocarbon potential is emphasized by marine and lacustrine source-rich shale deposition in optimal mature zones.

Abilio, S.; Inkollu, S.N.M.

1989-03-01

318

Biological science in the Great Basin  

USGS Publications Warehouse

The Great Basin is an expanse of desert and high moun-tains situated between the Rocky Mountains and the Sierra Nevada of the western United States. The most explicit description of the Great Basin is that area in the West where surface waters drain inland. In other words, the Great Basin is comprised of many separate drainage areas - each with no outlet. What at first glance may appear as only a barren landscape, the Great Basin upon closer inspection reveals island mountains, sagebrush seas, and intermittent aquatic habitats, all teeming with an incredible number and variety of plants and animals. Biologists at the USGS are studying many different species and ecosystems in the Great Basin in order to provide information about this landscape for policy and land-management decision-making. The following stories represent a few of the many projects the USGS is conducting in the Great Basin.

U.S. Geological Survey

2005-01-01

319

Gravity Anomalies of the Lunar Orientale Basin and the Mercurian Caloris Basin  

NASA Astrophysics Data System (ADS)

We model the formation and evolution of the lunar Orientale and mercurian Caloris basin gravity anomalies using a combination of hydrocode and finite-element methods, constrained by free-air and Bouguer gravity anomalies and basin topography.

Blair, D. M.; Johnson, B. C.; Freed, A. M.; Melosh, H. J.

2013-08-01

320

MidContinent basin: a reappraisal  

Microsoft Academic Search

One of the largest unevaluated basins in the Mid-Continent is the Salina basin in Kansas and its extension into eastern Nebraska. The purpose of this study is to update all older data, reconstruct new maps, and reappraise the potential for further exploration. The last comprehensive publications on the area were in 1948 and 1956. The Salina basin includes 12,700 mi²

1983-01-01

321

Ring spacing of Mercurian multi-ring basins and basin ring formation  

NASA Technical Reports Server (NTRS)

Recent systematic mapping of Mercury has revealed many ancient and previously unrecognized multiring basins. The population of these basins now stands at 20, possibly is as large as 25, and includes at least 76 measurable rings. From the new data base, we present some systematics of basin ring spacing on Mercury, compare them with similar data for the Moon, and draw some preliminary conclusions on conditions of ring formation for basins on the terrestrial planets.

Pike, R. J.; Spudis, P. D.

1984-01-01

322

Reserve estimates in western basins. Part 2: Piceance Basin  

SciTech Connect

This study characterizes an extremely large gas resource located in low permeability, sandstone reservoirs of the Mesaverde group in the Piceance Basin, Colorado. Total in place resource is estimated at 307.3 Tcf. Via application of geologic, engineering and economic criteria, the portion of this resource potentially recoverable as reserves is estimated. Those volumes estimated include probable, possible and potential categories and total 5.8 Tcf as a mean estimate of recoverable gas for all plays considered in the basin. About 82.6% of the total evaluated resource is contained within sandstones that have extremely poor reservoir properties with permeabilities considered too low for commerciality using current frac technology. Cost reductions and technology improvements will be required to unlock portions of this enormous resource. Approximately 2.7% of the total resource is contained within sandstone reservoirs which do not respond to massive hydraulic fracture treatments, probably due to their natural lenticular nature. Approximately 6.8% of the total resource is located in deeply buried settings below deepest established production. Approximately 7.9% of the total resource is considered to represent tight reservoirs that may be commercially exploited using today`s hydraulic fracturing technology. Recent technology advances in hydraulic fracturing practices in the Piceance Basin Mesaverde has resulted in a marked improvement in per well gas recovery which, where demonstrated, has been incorporated into the estimates provided in this report. This improvement is so significant in changing the risk-reward relationship that has historically characterized this play, that previously uneconomic areas and resources will graduate to the economically exploitable category. 48 refs., 96 figs., 18 tabs.

NONE

1995-10-01

323

Reserves in western basins: Part 1, Greater Green River basin  

SciTech Connect

This study characterizes an extremely large gas resource located in low permeability, overpressured sandstone reservoirs located below 8,000 feet drill depth in the Greater Green River basin, Wyoming. Total in place resource is estimated at 1,968 Tcf. Via application of geologic, engineering and economic criteria, the portion of this resource potentially recoverable as reserves is estimated. Those volumes estimated include probable, possible and potential categories and total 33 Tcf as a mean estimate of recoverable gas for all plays considered in the basin. Five plays (formations) were included in this study and each was separately analyzed in terms of its overpressured, tight gas resource, established productive characteristics and future reserves potential based on a constant $2/Mcf wellhead gas price scenario. A scheme has been developed to break the overall resource estimate down into components that can be considered as differing technical and economic challenges that must be overcome in order to exploit such resources: in other words, to convert those resources to economically recoverable reserves. Total recoverable reserves estimates of 33 Tcf do not include the existing production from overpressured tight reservoirs in the basin. These have estimated ultimate recovery of approximately 1.6 Tcf, or a per well average recovery of 2.3 Bcf. Due to the fact that considerable pay thicknesses can be present, wells can be economic despite limited drainage areas. It is typical for significant bypassed gas to be present at inter-well locations because drainage areas are commonly less than regulatory well spacing requirements.

Not Available

1993-10-01

324

Extensional Basins in a Convergent Margin: Oligocene-Early Miocene Salar de Atacama and Calama basins, Central Andes  

Microsoft Academic Search

The Salar de Atacama Basin (SdAB) is the largest and most persistent sedimentary basin of northern Chile, accumulating nonmarine sediment from Cretaceous to modern times. Its northwestern neighbor, the Calama, was a Cenozoic basin. Although SdAB was in the backarc zone early in the Andean orogeny, both are now forearc basins. Others demonstrated that the basins overlie anomalously cold, strong,

T. E. Jordan; C. Mpodozis; N. Blanco; P. Pananont; F. Dávila

2004-01-01

325

Propagating rift during the opening of a small oceanic basin: The Protector Basin (Scotia Arc, Antarctica)  

Microsoft Academic Search

The opening of oceanic basins constitutes one of the key features of Plate Tectonics because it determines the rifting and displacement of the continental crustal blocks. Although the mechanisms of development of large oceans are well known, the opening and evolution of small and middle size oceanic basins have not been studied in detail. The Protector Basin, located in the

Jesús Galindo-Zaldívar; Fernando Bohoyo; Andrés Maldonado; Anatoly Schreider; Emma Suriñach; Juan Tomas Vázquez

2006-01-01

326

Slope-apron deposition in an ordovician arc-related setting: The Vuelta de Las Tolas Member (Suri Formation), Famatina Basin, northwest Argentina  

USGS Publications Warehouse

The Ordovician Suri Formation is part of the infill of the Famatina Basin of northwest Argentina, which formed in an active setting along the western margin of early Paleozoic Gondwana. The lower part of this formation, the Vuelta de Las Tolas Member, records sedimentation on a slope apron formed in an intra-arc basin situated on a flooded continental arc platform. The coincidence of a thick Arenig-Llanvirn sedimentary succession and volcanic-plutonic arc rocks suggests an extensional or transtensional arc setting, and is consistent with evidence of an extensional regime within the volcanic arc in the northern Puna region. The studied stratigraphic sections consist of volcanic rocks and six sedimentary facies. The facies can be clustered into four facies associations. Association 1, composed of facies A (laminated siltstones and mudstones) and B (massive mudstones and siltstones), is interpreted to have accumulated from silty-muddy high-and low-density turbidity currents and highly fluid, silty debris flows, with subsequent reworking by bottom currents, and to a lesser extent, hemipelagic suspension in an open-slope setting. Facies association 2 is dominated by facies C (current-rippled siltstones) strata. These deposits are interpreted to record overbank sedimentation from fine-grained turbidity currents. Facies E (matrix-supported volcanic breccias) interbedded with andesitic lava units comprises facies association 3. Deposition was contemporaneous with subaqueous volcanic activity, and accumulated from cohesive debris flows in a coarse-grained wedge at the base of slope. Facies association 4 is typified by facies D (vitric fine-grained sandstones and siltstones) and F (channelized and graded volcanic conglomerates and breccias) deposits. These strata commonly display thinning-and fining-upward trends, indicating sedimentation from highly-concentrated volcaniclastic turbidity currents in a channelized system. The general characteristics of these deposits of fresh pyroclastic detritus suggest that their accumulation was contemporaneous with, or post-dated shallow-water or subaereal explosive volcanism. The Vuelta de Las Tolas Member tends to show an overall random facies patterns reflecting the strong influence of non-cyclical episodic processes related to arc volcanism and slope sedimentation. The scarcity of resident ichnofaunas and the presence of thick packages of uniform mudstones suggest deposition under oxygen-depleted conditions in a topographically confined, ponded sub-basin. Interbasinal correlations favor comparison with Middle Arenig slope-apron successions formed in the northern Puna Basin and suggest a southward prolongation of the Arenig volcanic arc.

Mangano, M. G.; Buatois, L. A.

1997-01-01

327

48 CFR 25.405 - Caribbean Basin Trade Initiative.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 2009-10-01 false Caribbean Basin Trade Initiative. 25.405 Section...ACQUISITION Trade Agreements 25.405 Caribbean Basin Trade Initiative. Under the Caribbean Basin Trade Initiative, the United...

2009-10-01

328

Enhancing Data Management for OKACOM (Okavango River Basin Water Commission).  

National Technical Information Service (NTIS)

As part of the USAID-funded Okavango River Basin Project, this assessment identifies data and information needs for the Permanent Okavango River Basin Water Commission (OKACOM) and other users of information on the Okavango River Basin. The primary result...

2005-01-01

329

18 CFR 725.7 - Regional or river basin planning.  

...2014-04-01 2014-04-01 false Regional or river basin planning. 725.7 Section 725...Responsibilities § 725.7 Regional or river basin planning. (a) In agreements between river basin commissions or other regional...

2014-04-01

330

Hydrogeology of Picacho Basin, South-Central Arizona.  

National Technical Information Service (NTIS)

The hydrogeology of Picacho Basin was studied to define the stratigraphy, basin structure, physical and hydraulic properties of the basin sediments, and predevelopment and postdevelopment conditions of ground-water flow as of 1985. The study area includes...

D. R. Pool R. L. Carruth W. D. Meehan

2001-01-01

331

75 FR 25877 - Colorado River Basin Salinity Control Advisory Council  

Federal Register 2010, 2011, 2012, 2013

...Bureau of Reclamation Colorado River Basin Salinity Control Advisory Council AGENCY: Bureau...SUMMARY: The Colorado River Basin Salinity Control Advisory Council (Council) was established by the Colorado River Basin Salinity Control [[Page 25878

2010-05-10

332

76 FR 24515 - Colorado River Basin Salinity Control Advisory Council  

Federal Register 2010, 2011, 2012, 2013

...Bureau of Reclamation Colorado River Basin Salinity Control Advisory Council AGENCY: Bureau...announces that the Colorado River Basin Salinity Control Advisory Council (Council...INFORMATION: The Colorado River Basin Salinity Control Advisory Council was...

2011-05-02

333

78 FR 70574 - Colorado River Basin Salinity Control Advisory Council  

Federal Register 2010, 2011, 2012, 2013

...REG0000, RR04084000] Colorado River Basin Salinity Control Advisory Council AGENCY: Bureau...SUMMARY: The Colorado River Basin Salinity Control Advisory Council (Council) was established by the Colorado River Basin Salinity Control Act of 1974 (Pub....

2013-11-26

334

78 FR 23784 - Colorado River Basin Salinity Control Advisory Council  

Federal Register 2010, 2011, 2012, 2013

...Bureau of Reclamation Colorado River Basin Salinity Control Advisory Council AGENCY: Bureau...SUMMARY: The Colorado River Basin Salinity Control Advisory Council (Council) was established by the Colorado River Basin Salinity Control Act of 1974 (Public Law...

2013-04-22

335

75 FR 27360 - Colorado River Basin Salinity Control Advisory Council  

Federal Register 2010, 2011, 2012, 2013

...Bureau of Reclamation Colorado River Basin Salinity Control Advisory Council AGENCY: Bureau...SUMMARY: The Colorado River Basin Salinity Control Advisory Council (Council) was established by the Colorado River Basin Salinity Control Act of 1974 (Pub. L....

2010-05-14

336

77 FR 61784 - Colorado River Basin Salinity Control Advisory Council  

Federal Register 2010, 2011, 2012, 2013

...Bureau of Reclamation Colorado River Basin Salinity Control Advisory Council AGENCY: Bureau...SUMMARY: The Colorado River Basin Salinity Control Advisory Council (Council) was established by the Colorado River Basin Salinity Control Act of 1974 (Pub. L....

2012-10-11

337

76 FR 61382 - Colorado River Basin Salinity Control Advisory Council  

Federal Register 2010, 2011, 2012, 2013

...Bureau of Reclamation Colorado River Basin Salinity Control Advisory Council AGENCY: Bureau...SUMMARY: The Colorado River Basin Salinity Control Advisory Council (Council) was established by the Colorado River Basin Salinity Control Act of 1974 (Pub. L....

2011-10-04

338

77 FR 23508 - Colorado River Basin Salinity Control Advisory Council  

Federal Register 2010, 2011, 2012, 2013

...Bureau of Reclamation Colorado River Basin Salinity Control Advisory Council AGENCY: Bureau...SUMMARY: The Colorado River Basin Salinity Control Advisory Council (Council) was established by the Colorado River Basin Salinity Control Act of 1974 (Pub. L....

2012-04-19

339

75 FR 66389 - Colorado River Basin Salinity Control Advisory Council  

Federal Register 2010, 2011, 2012, 2013

...Bureau of Reclamation Colorado River Basin Salinity Control Advisory Council AGENCY: Bureau...SUMMARY: The Colorado River Basin Salinity Control Advisory Council (Council) was established by the Colorado River Basin Salinity Control Act of 1974 (Pub. L....

2010-10-28

340

Geologic Storage at the Basin Scale: Region-Based Basin Modeling, Powder River Basin (PRB), NE Wyoming and SE Montana  

Microsoft Academic Search

Carbon capture and storage from the over 2000 power plants is estimated at 3-5 GT\\/yr, which requires large- scale geologic storage of greenhouse gasses in sedimentary basins. Unfortunately, determination of basin scale storage capacity is currently based on oversimplified geologic models that are difficult to validate. Simplification involves reducing the number of geologic parameters incorporated into the model, modeling with

J. J. Melick; M. H. Gardner

2008-01-01

341

Crustal structure of the Khartoum Basin, Sudan  

NASA Astrophysics Data System (ADS)

The crustal structure of the northern part of the Khartoum Basin has been investigated using data from 3 permanent seismic stations within 40 km of Khartoum and two modeling methods, H-k stacking of receiver functions and a joint inversion of receiver functions and Rayleigh wave group velocities. The Khartoum Basin is one of several Mesozoic rift basins in Sudan associated with the Central African Rift System. Results from the H-k-stacking indicate that crustal thickness beneath the Khartoum Basin ranges between 33 and 37 km, with an average of 35 km, and that the crustal Vp/Vs ratio ranges from 1.74 to 1.81, with an average of 1.78. From the joint inversion of receiver functions and Rayleigh wave group velocities, we obtained similar results for Moho depth, as well as an average shear wave velocity of 3.7 km/s for the crust. These results provide the first seismic estimates of Moho depth for a basin in Sudan. When compared to average crustal thickness for unrifted Proterozoic crust in eastern Africa, our results indicate that at most only a few km of crustal thinning may have occurred beneath the Khartoum Basin. This finding is consistent with estimates of effective elastic plate thickness, which indicate little modification of the Proterozoic lithosphere beneath the basin, and suggests that there may be insufficient topography on the lithosphere-asthenosphere boundary beneath the Sudanese basins to channel plume material westward from Ethiopia. We found the average crustal thickness beneath the Khartoum basin is 35 km. We found the average crustal Vp/Vs ratio is 1.78. We obtained the average shear wave velocities of 3.7 km/s for the crust. We found small amount of thinning beneath the Khartoum basin. Insufficient topography beneath the basin to channel plume material from Ethiopia.

El Tahir, Nada; Nyblade, Andrew; Julià, Jordi; Durrheim, Raymond

2013-05-01

342

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

NASA Astrophysics Data System (ADS)

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

Ghosh, Sampa; Sarkar, Soumen; Ghosh, Parthasarathi

2012-01-01

343

New 40ar/39ar Radiometric, Geochemistry And Structural Data On The Giant Okavango Mafic Dike Swarm And Lava-flows From The Karoo Province In Botswana: Implications For Gondwana Break-up.  

NASA Astrophysics Data System (ADS)

The lower Jurassic Karoo magmatism represents one of the most important conti- nental flood basalt (CFB) provinces of the Phanerozoic. It is dominated by tholeiites occurring as traps and apparently radiating giant dike swarms and is associated with the disruption of Gondwana and the opening of the Indian Ocean. The Karoo volcanic province located at the South-East of the African continent, covers a surface of about 3x106 km2. Whereas most of the geochronological and geochemical studies were per- formed in the Southern part of the province, very few data are available in the NW. This is particularly the case for lava flows and for the N110 oriented, 1500 km long and 100 km wide giant Okavango Dike Swarm (ODS) of Botswana. Lava-flows were sampled in a 800 m deep borehole located in the SE of Botswana and consist in low- Ti tholeiites. ODS dolerites are characterized mainly by augite and plagioclase with remnants of olivine and are high UTi tholeiites (TiO2> 2 wt%) enriched in LREE relative to HREE (La/Ybn = 3.5-9.7). 40Ar/39Ar plateau ages ranging from 177.3 s´ 2.1 (2 sigma) Ma (-58m deep) to 178.0 s´ 2.2 Ma (-719m deep), and from 178.3 s´ 1.1 Ma to 179.3 s´ 1.2 Ma have been obtained on pure plagioclase separates for the lava-flows and the ODS, respectively. No significant age variation could be identified along the 661m thick lava-flow section, but these lava-flows are slightly younger than both ODS dikes and high-Ti lava-flows from Zimbabwe (Jones et al., 2000, GC, v.2, p110). However, all these basaltic events (both low- and high- Ti) from the north- ern Karoo sub-province appear significantly younger than the southern low-Ti Karoo formations, particularly if we consider 40Ar/39Ar dates obtained only on plagioclase separates, yielding ages which range between 180.3 s´ 1.8 and 184.7 s´ 0.7 Ma (Duncan et al., 1997, Jour. Geoph. Res., v. 102, p18127). Therefore, a time-related northwards migration of the magmatism is suggested. Moreover, one dated ODS dike yields Pro- terozoïc age, suggesting that this ODS branch of the so-called triple junction structure, generally attributed to the Karoo mantle plume, may be at least partly due to injection and rejuvenation of inherited Proterozoïc basement structures.

Jourdan, F.; Tshoso, G.; Féraud, G.; Bertrand, H.; Legall, B.; Tiercelin, J. J.; Kampunzu, A. B.

344

Environmental control on concretion-forming processes: Examples from Paleozoic terrigenous sediments of the North Gondwana margin, Armorican Massif (Middle Ordovician and Middle Devonian) and SW Sardinia (Late Ordovician)  

NASA Astrophysics Data System (ADS)

Concretions of various compositions are common in the Paleozoic terrigenous successions of the north Gondwana margin. This study focuses on phosphatic (P) and siliceous (Si) concretions present in some successions of the Armorican Massif (NW France) and SW Sardinia (W Italy). It shows that they consist of mudstones, fine- to very fine-grained sandstones or shellbeds with a more or less abundant P-cement and form a continuum between a phosphatic end-member and a siliceous biogenic end-member. The P2O5 contents are ranging from 0.26% to 21.5% and are related to apatite. The SiO2 contents vary from 25% to 82% and are linked both to a terrigenous phase and to a biogenic silica phase. Concretions showing the lower P-contents (P2O5 < 1.5%) are often enriched in biogenic silica (SiO2/Al2O3 > 5). Comparison with the surrounding sediments shows that all the concretions are enriched in chlorite and in Middle Rare Earth Elements (Las/Gds: 0.12-0.72) and some of them in Y (up to 974 ppm), Rare Earth Elements (more than 300 ppm) and Sr (260-880 ppm). The concretions with highest biogenic silica concentrations are contained in the outer shelf sediments whereas the other concretions are present from the proximal part of the inner shelf to the outer shelf. A genetic model in two stages is proposed. During early diagenesis, the dissolution of shells and degradation of organic matter progressively enrich the pore water in dissolved Si, Ca and P. When the suboxic zone is reached, P-precipitation begins, leading to the formation of protoconcretions. In shallow environments, the relative permeability of sediments and the winnowing or reworking of the upper few centimetres by bottom currents allow for suboxic conditions to be maintained, leading to P-rich concretion formation. In deeper environments, the anoxic zone is reached more rapidly, thereby preventing extensive phosphogenesis. Nevertheless in the protoconcretions the early P-cement preserves pore spaces from compaction. In the presence of biogenic siliceous particles, the fluids are enriched in dissolved silica and diffuse towards the protoconcretions. Silica precipitation can thus occur later in the intergranular spaces.

Dabard, Marie-Pierre; Loi, Alfredo

2012-08-01

345

The Late Cambrian Takaka Terrane, NW Nelson, New Zealand: Accretionary-prism development and arc collision followed by extension and fan-delta deposition at the SE margin of Gondwana  

NASA Astrophysics Data System (ADS)

Re-evaluation of field and lab data indicates that the Cambrian portion of the Takaka Terrane in the Cobb Valley area of NW Nelson, New Zealand preserves the remnants of an accretionary prism complex, across which the Lockett Conglomerate fan-delta was deposited as a consequence of extension. Previous work has recognized that the structurally disrupted lower Takaka Terrane rocks present an amalgam of sedimentary and igneous rocks generated prior to convergence (Junction Formation) or during convergence (Devil River Volcanics Group, Haupiri Group), including arc-related and MORB components. Portions of the sequence have in the past been loosely described as an accretionary prism. Reevaluation of the detailed mapping, sedimentological and provenance studies shows that remnants of a stratigraphic sequence (Junction Formation, Devil River Volcanics Group, Haupiri Group) can be traced through 10 fault-bounded slices, which include a mélange-dominated slice (Balloon Mélange). These slices are the remnants of the accretionary prism; the stratigraphy within each slice generally youngs to the east, and the overall pattern of aging (based on relative age from provenance studies, sparse fossils, stratigraphic relations, and limited isotopic data) indicates that the older rocks generally dominate fault slices to the east, and younger rocks dominate fault slices to the west, delineating imbricate slices within an eastward-dipping subduction zone, in which the faults record a complex history of multi-phase reactivation. The Lockett Conglomerate is a ~500-m thick fan-delta conglomerate that is the preserved within one of the fault slices, where it is stratigraphically and structurally highest unit in the lower Takaka Terrane; it is also present as blocks within the Balloon Melange. The Lockett Conglomerate is marine at its base and transitions upwards to fluvial facies. The Lockett Conglomerate has previously been interpreted to result from erosion consequent on continued convergence, but is reinterpreted here as a ';true' fan-delta deposit, sedimentologically similar to deposits associated with extension. Textural and compositional data for the Lockett Conglomerate indicates rapid supply of new material (including quartzite, granite, gabbro, and amphibolitic metavolcanics). The Lockett Conglomerate is proposed here to record the initiation of extension, during which basement faults in the hinterland exposed previously buried source rocks. This new interpretation of the Lockett Conglomerate places that initiation of extension and subsequent passive margin sedimentation (Mt. Ellis and Mt. Arthur Groups) earlier (late Middle Cambrian) than previous work has suggested (Late Cambrian or Early Ordovician). These new interpretations provide input useful for correlations and interpretations of the complex mosaic that preserves a record of tectonic activity and processes at the Antarctic, Tasmanian and SE Australian portions of the Cambrian Gondwana margin.

Pound, K. S.

2013-12-01

346

Area Environmental Characterization Report of the Dalhart and Palo Duro Basins in the Texas Panhandle. Volume I. Dalhart Basin.  

National Technical Information Service (NTIS)

This area report describes the environmental characteristics of the Dalhart and Palo Duro basins of the Texas Panhandle portion of the Permian basin. Both basins are rather sparsely populated, and the overall population is decreasing. The economic base is...

1982-01-01

347

Potential for a basin-centered gas accumulation in the Albuquerque Basin, New Mexico  

USGS Publications Warehouse

The potential that a basin-centered or continuous-type gas accumulation is present in the Albuquerque Basin in central New Mexico was investigated. The Albuquerque Basin is one of the many rift basins that make up the Rio Grand rift system, an area of active extension from Oligocene to recent time. The basin is significantly different from other Rocky Mountain basins that contain basin-centered gas accumulations because it is actively subsiding and is at near maximum burial and heating conditions at the present time. Burial reconstructions suggest that Cretaceous-age source rocks began to generate gas in the deeper parts of the basin about 20 million years ago and are still generating large amounts of gas. The high mud weights typically used while drilling the Cretaceous interval in the deeper areas of the basin suggest some degree of over-pressuring. Gas shows are commonly reported while drilling through the Cretaceous interval; however, attempts to complete gas wells in the Cretaceous have resulted in subeconomic quantities of gas, primarily because of low permeabilities. Little water has been reported. All of these characteristics suggest that a basin-centered gas accumulation of some sort is present in the Albuquerque Basin.

Johnson, Ronald C.; Finn, Thomsa M.; Nuccio, Vito F.

2001-01-01

348

Tectonic History of the Shikoku Marginal Basin.  

National Technical Information Service (NTIS)

Studies of marine magnetic anomaly data from the Shikoku basin reveal magnetic lineations which strike northwest almost parallel to the trend of the Palau-Kyushu ridge. The lineation pattern is best developed in the western part of the basin and we can co...

A. B. Watts J. K. Weissel

1974-01-01

349

HYDROLOGIC MODELING OF THE RIO GRANDE BASIN  

Microsoft Academic Search

In this study we investigate the use of the NOAH model along with NLDAS2 forcing in building a hydrological model of the Rio Grande basin to study the effect of climate variability and change on water availability in the basin. The model was run retrospectively for the period 2002 to June 2009. This paper describes the steps taken in building

C. PRAKASH KHEDUN

350

K-Basin isolation barrier seal  

SciTech Connect

This report documents various aspects of the design, analysis, procurement, and fabrication of the hydraulic seal on the isolation barriers to be installed in the 100-K Area spent nuclear fuel basin. The isolation barrier is used to keep water in the basin in the event of an earthquake.

Ruff, E.S.

1994-10-01

351

Mackenzie - Liard Valley Hydrocarbon Basins, NWT  

Microsoft Academic Search

The Mackenzie - Liard area of the mainland Northwest Territories (NWT) is underlain by a series of superimposed sedimentary basins formed over the last billion years. Many of these basins have established hydrocarbon systems in which stacked reservoir rocks, trap seals and source rocks have been identified. The area includes the southern NWT where oil and gas pipelines are presently

James R. Taylor

352

Water Productivity from Integrated Basin Modeling  

Microsoft Academic Search

It is obvious that real water saving measures are only possible if the current water resources are clearly understood. For a basin in western Turkey, simulation modeling at three different scales, field, irrigation scheme and basin level was performed to obtain all terms of the water balance. These water balance numbers were used to calculate the Productivity of Water (PW)

Peter Droogers; Geoff Kite

1999-01-01

353

Organic acid metastability in sedimentary basins  

Microsoft Academic Search

Thermodynamic calculations indicate that COâ in sedimentary basins may be in stable redox equilibrium with organic acids found in basinal brines, but that CHâ is not. These calculations also show that the high concentrations of carboxylic acids are from equilibrium with decarboxylation reactions. A compilation of recent analyses of carboxylic acids from aqueous solutions associated with petroleum reservoirs shows that

Everett L. Shock

1988-01-01

354

Engineering assessment of 105 K basin monorails.  

National Technical Information Service (NTIS)

The engineering assessment of the 105 K Basins monorails was performed to provide the engineering analysis to justify the existing basin north-south monorail capacity. The existing monorails have a capacity of 2400 lbs posted on the north-south monorails....

W. A. Frier

1995-01-01

355

Geology Fieldnotes: Great Basin National Park, Nevada  

NSDL National Science Digital Library

This Great Basin National Park site contains park geology information, park maps, visitor information, and teacher features (educational resources and links for teaching geology using National Park examples). The park geology section discusses the region's biogeography, glacial history, and the Lehman Caves. A park map and a features/relief map of the Great Basin National Park are included.

356

Tensleep Reservoir, Oregon Basin Field, Wyoming  

Microsoft Academic Search

The Oregon Basin field in northwestern Wyoming is about 9 mi long and is composed of a north dome and south dome. Since its discovery in 1927, over 122 million bbl of oil have been produced from the Pennsylvanian Tensleep Sandstone at Oregon Basin. Geologists and engineers worked together to describe the reservoir and accumulate data that would aid in

J. T. Morgan; F. S. Cordiner; A. R. Livingston

1978-01-01

357

Devonian shale gas resource assessment, Illinois basin  

Microsoft Academic Search

In 1980 the National Petroleum Council published a resource appraisal for Devonian shales in the Appalachian, Michigan, and Illinois basins. Their Illinois basin estimate of 86 TCFG in-place has been widely cited but never verified nor revised. The NPC estimate was based on extremely limited canister off-gas data, used a highly simplified volumetric computation, and is not useful for targeting

R. M. Cluff; S. G. Cluff; C. M. Murphy

1996-01-01

358

K Basin sludge treatment process description  

Microsoft Academic Search

The K East (KE) and K West (KW) fuel storage basins at the 100 K Area of the Hanford Site contain sludge on the floor, in pits, and inside fuel storage canisters. The major sources of the sludge are corrosion of the fuel elements and steel structures in the basin, sand intrusion from outside the buildings, and degradation of the

Westra

1998-01-01

359

African sedimentary basins - Tectonic controls on prospectivity  

SciTech Connect

An important prerequisite for the evaluation of any sedimentary basin is the understanding of its regional tectonic setting. This is especially so in the underexplored regions of Africa. The majority of African sedimentary basins developed in an extensional setting although some have undergone subsequent compressional or transpressional deformation. The geometry and evolution of these basins is often influenced by basement structure. The extensional phase of basin development controls not only the distribution of syn-rift sediments but also the magnitude of post-rift regional subsidence and the preservation or removal of pre-rift sediments. This has important consequences for exploration models of syn-rift and pre-rift source rocks and reservoirs. Post-rift basin inversion and uplift provide crucial controls on the preservation of mature source rocks and quality of reservoirs. The distribution, nature, timing, and possible mechanisms of this uplift in Africa will be addressed. The hydrocarbon prospectivity of African basis appears to be highly variable although the limited exploration of some regions makes the exact extent of this variability unclear. Basins considered potentially prospective range from late Precambrian to Tertiary in age. The various tectonic controls outlined above, and criteria for the evaluation of underexplored areas, will be demonstrated by reference to basins studied by The Robertson Group. Examples described include basins from Bagon, Angola, Namibia, East Africa, Tertiary Rift and Karoo Rifts, and North Africa (Sudan, Egypt, Algeria, and Morocco).

Bunter, M.A.G.; Crossley, R.; Hammill, M.; Jones, P.W.; Morgan, R.K.; Needham, D.T.; Spaargaren, F.A. (Robertson Group plc, Gwynedd (England))

1991-03-01

360

Petroleum prospects of Southern Nigeria's Anambra Basin  

Microsoft Academic Search

Surrounded by the Benue trough, the Middle Niger River depression, the Niger River delta, and the Abakaliki anticlinorium, Nigeria's Anambra basin probably holds a thick, unexplored sequence with significant hydrocarbon potential. The basin's sediment could be 16,000 ft thick; a Bouguer gravity survey indicates two parallel northeast-southwest trending gravity lows (the Anambra low and the Awka depression) separated by the

A. A. Avbovbo; O. Ayoola

1981-01-01

361

Relation between Tethys sea and Tarim basin  

SciTech Connect

The Tarim basin is the largest continental basin in China. It is known as the heart of central Asia. Still it was related to the Mediterranean Sea in the geological past. Based on the investigations of paleontology, stratigraphy, tectonics, and remote sensing, it is suggested that Tethys and the Tarim basin should be connected from the Late Cretaceous to Miocene. The northern branch of the Tethys sea channel began to pass through the Alay gap and invade the Tarim basin at the beginning of the Late Cretaceous. Up to the Miocene, marine invasion and marine regression must have happened six times in the western Tarim basin. The Paleocene marine invasion encroached upon the widest area and lasted the longest of the six times, which extended to the region of the southern Hotan River. The occurrence of the Paleocene marine fossils in the Kuqa Seg indicates the influence of the marine invasion. At the end of the Miocene, seawater receded fully from the Tarim basin. A Miocene petroleum field has been found in the Yecheng Seg of the western Tarim basin. According to the relationship between Tethys and the Tarim basin, the potentialities of the Late Cretaceous-Miocene hydrocarbon source are considered to be great.

Wei Junchao (Lanzhou Institute of Geology, Lanzhou (China))

1988-08-01

362

The structure of Nansen and Amundsen Basin  

NASA Astrophysics Data System (ADS)

During the AMORE expedition in August/September 2001, a US-German joint project, the Gakkel Ridge and the adjoining basins were investigated. In this contribution we report on the results of the seismic investigations in the Nansen Basin as well as in the Amundsen Basin. We obtained two almost parallel profiles through the Nansen Basin from the northeastern continental margin of Svalbard (29°E and 32°E) to the Gakkel Ridge at 17°E and 21°E. To investigate the Amundsen Basin, we left Gakkel Ridge at about 70°E towards Lomonossov Ridge for another transect. In total 1360 km of seismic reflection data with very good data quality were recorded. Parallel to the seismic reflection transects up to 30 sonobuoys were deployed. The data from both basins shows striking differences in the basement topography. While in the Nansen Basin the oceanic crust is more or less continuously shallowing, this is not the case in the Amundsen Basin. This points to some asymmetric spreading history of the Gakkel Ridge in northern and southern directions. Some of the Sonobuoys recorded also weak arrivals from the Moho discontinuity. The analysis of the wide angle and gravity data shows, that there are areas with a significant thinning of the oceanic crust. Results of the reflection and refraktion seismic as well as the gravity interpretation will be presented.

Micksch, U.; Jokat, W.

2003-04-01

363

Construction of Sediment Budgets for Drainage Basins  

Microsoft Academic Search

A sediment budget for a drainage basin is a quantitative statement of the rates of production, transport, and discharge of detritus. To construct a sediment budget for a drainage basin, one must integrate the temporal and spatial variations of transport and storage processes. This requires: recognition and quantification of transport processes, recognition and quantification of storage elements, and identifi- cation

William E. Dietrich; Thomas Dunne; Neil F. Humphrey; Leslie M. Reid

364

Stratigraphy of Pennsylvanian detrital reservoirs, Permian basin  

Microsoft Academic Search

Significant oil reserves have been found to date in stratigraphic traps in Pennsylvanian detrital reservoirs on the Central Basin platform and Reagan uplift of the Permian basin. The 32 MMBOEG Arenoso field area, discovered in 1966, is the largest producing field. Along a 75 mi northwest-southeast trend, 23 other smaller fields will produce an average 850 MBOEG each, for a

Van Der Loop

1992-01-01

365

Exploration potential of offshore northern California basins  

Microsoft Academic Search

A series of exploratory wells was drilled in the northern California offshore basins in the 1960s following leasing of federal tracts off northern California, Oregon, and Washington. The drilling, although encountering numerous oil shows, was considered at the time to indicate low prospectivity in an area that extended as far south as the offshore Santa Maria basin. However, subsequent major

S. B. Bachman; J. K. Crouch

1988-01-01

366

Conservation in the Delaware River Basin  

Microsoft Academic Search

The Delaware River Basin Commission (DRBC) has embarked on an ambitious water conservation program to reduce the demand for water. Conservation has become an integral component of the commission's strategy to manage water supplies in the four-state Delaware River Basin. The program includes both regulatory and educational initiatives. DRBC has adopted five conservation regulations, which pertain to source metering, service

Jeffrey Featherstone

1996-01-01

367

THE RIVER BASIN APPROACH IN TOURISM PLANNING  

Microsoft Academic Search

The article describes advantages and disadvantages in tourism planning, using the river basins as background territory and borders. Tourism development planning is taking place according administrative territorial borders till nowadays in Latvia and in other tourism destinations in abroad. According tourist and visitor needs and environmental friendly approach it is more appropriate to use river basins in tourism planning. Tourists

Agita Slara

2005-01-01

368

INFORMATION INTEROPERABILITY FOR RIVER BASIN MANAGEMENT  

Microsoft Academic Search

Many countries are adopting water policies and legislative instruments for water management in conformance to the agenda 21. According to this agenda, the use and protection of surface water and groundwater are coordinated at a river basin level. The success of river basin management systems relies upon coordinated actions, including provision of and access to information as well as the

Jackson Roehrig

369

K Basin sludge dissolution engineering study  

Microsoft Academic Search

The purpose of this engineering study is to investigate the available technology related to dissolution of the K Basin sludge in nitric acid. The conclusion of this study along with laboratory and hot cell tests with actual sludge samples will provide the basis for beginning conceptual design of the sludge dissolver. The K Basin sludge contains uranium oxides, fragments of

Westra

1998-01-01

370

Global Warming and the Columbia River Basin  

Microsoft Academic Search

The Columbia River Basin was created out of the most powerful geologic and climatic processes on earth. The bedrock of the Basin rose up from the ocean floor and came from half a world away, enormous lava flows lay down basalt thousands of meters thick, wind blew in sediment over the course of millennia, and the main channel of Columbia

Martin Anderson

371

Central South Atlantic kinematics: a 3D ocean basin-scale model of the Walvis Ridge and Rio Grande Rise  

NASA Astrophysics Data System (ADS)

Prior to the breakup of western Gondwana, ca. 130 Ma, the Tristan da Cuhna mantle plume produced the eastern South American Parana, and western African Etendeka, flood basalts. As the South Atlantic basin opened, the ridge-centered plume produced seaward extending hotspot tracks: Rio Grande Rise on the South American Plate, and Walvis Ridge on the African Plate. Several ocean floor edifices on the hotspot trends appear to produce lower than expected amplitude free air gravity anomalies, suggesting that they are composed of lower density material. We have constructed a 3D gravity model of the South Atlantic basin to examine variations in crustal density associated with the hot spot trends. The model, which encompasses a region that extends from 46°S to 10 °S and from 20°E to 60°W, comprises the following layers: water, sediment, crust, and upper mantle. Variable density sediment and upper mantle layers are incorporated to estimate density changes related to sediment thickness and compaction, and upper mantle temperatures, respectively. The initial Moho horizon is estimated from isostatic equilibrium calculations; however the isostatic effect is scaled away from the seafloor spreading center to simulate the active spreading center. Three open-file grids were used to generate the model: satellite-derived free air gravity, global topography, and sediment thickness of the world. Inverting the model for crustal density reveals a distribution of low-density areas: along the coasts, the seafloor spreading axis, and along the Rio Grande Rise and Walvis Ridge hotspot trends. Coastal and spreading axis low density areas are thought to be related to continental crust and high temperature upper mantle. Hotspot track low density areas might be related to variable densities within the volcanic edifices, variations in their crustal thickness, or upper mantle densities beneath them. Detailed 2D models approximate reasonable density and geometry limits along select transects. Holding the African Plate fixed, we have rotated the South American Plate for 16 times corresponding to Chrons C5, C6, C13, C18, C21, C25, C31, C34, five interpolated times (ca. 89, 93, 100, 105, and 112 Ma), and Chrons M0, M2 and M4. Reconstructions, displaying inversion results illustrate the development of the hotspot tracks as the South Atlantic opened, suggest that Tristan da Cuhna was a ridge-centered plume until about 30 Ma.

Bird, D. E.; Hall, S. A.

2009-12-01

372

Seismic stratigraphic investigation of west Florida basin  

SciTech Connect

An Upper Jurassic (.)-Lower Cretaceous basin in the eastern deep Gulf of Mexico, referred to as the West Florida basin, has been described from University of Texas Institute for Geophysics multichannel seismic profiles, DSDP wells, and some gravity and magnetic data. The basin extends beyond the limits of Middle Jurassic salt deposition, and is possibly a westward extension of the Tampa embayment, implying a relatively continuous westward-dipping basement below the central portion of the Florida escarpment. The Lower Cretaceous sequence within the basin is though to be the Valanginian section missing from the Gulf Coast shelf stratigraphy. The early geologic history of the West Florida basin, inferred from this study, favors the evolutionary models for the Gulf of Mexico that rotate the Yucatan peninsula counter-clockwise from a close Gulf position to its present location.

Lord, J.P.

1987-09-01

373

Thermal state of the Arkoma Basin and the Anadarko Basin, Oklahoma  

NASA Astrophysics Data System (ADS)

One of the most fundamental physical processes that affects virtually all geologic phenomena in sedimentary basins is the flow of heat from the Earth's interiors. The Arkoma Basin and the Anadarko Basin, Oklahoma, are a prolific producer of both oil and natural gas. Both basins also have important geologic phenomena. Understanding the thermal state of the these basins is crucial to understanding the timing and extent of hydrocarbon generation, the genesis of Mississippi Valley-type ore deposits, and the origin of overpressures in the Anadarko Basin. In chapter one, heat flow and heat production in the Arkoma basin and Oklahoma Platform are discussed. Results of this study are not generally supportive of theories which invoke topographically driven regional groundwater flow from the Arkoma Basin in Late Pennsylvanian-Early Permian time (˜290 Ma) to explain the genesis of geologic phenomena. In chapter 2, different types of thermal conductivity temperature corrections that are commonly applied in terrestrial heat flow studies are evaluated. The invariance of the relative rankings with respect to rock porosity suggests the rankings may be valid with respect to in situ conditions. Chapter three addresses heat flow and thermal history of the Anadarko Basin and the western Oklahoma Platform. We found no evidence for heat flow to increase significantly from the Anadarko Basin in the south to the Oklahoma Platform to the north. In chapter four, overpressures in the Anadarko Basin, southwestern Oklahoma are discussed. Using scale analyses and a simple numerical model, we evaluated two endmember hypotheses (compaction disequilibrium and hydrocarbon generation) as possible causes of overpressuring. Geopressure models which invoke compaction disequilibrium do not appear to apply to the Anadarko Basin. The Anadarko Basin belongs to a group of cratonic basins which are tectonically quiescent and are characterized by the association of abnormal pressures with natural gas. (Abstract shortened by UMI.)

Lee, Youngmin

1999-12-01

374

BASINS  

EPA Science Inventory

Resource Purpose: The U.S EPA's water programs and their counterparts in states and pollution control agencies are increasingly emphasizing watershed- and water quality-based assessment and integrated analysis of point and nonpoint sources. Better Assessment Science Integra...

375

Crustal Structure of the Khartoum Basin, Sudan  

NASA Astrophysics Data System (ADS)

The Khartoum basin is one of several Mesozoic rift basins in Sudan associated with the Central Africa Rift System. Little is known about the deep crustal structure of this basin, and this limited knowledge hampers the development of a more detailed understanding of its origin and evolution. Constraints on crustal structure in Sudan are only available through regional gravity studies and continental-scale tomography models, but these studies have poor resolution in the Khartoum basin. Here, we investigate the crustal structure of the northern part of the Khartoum basin beneath 3 permanent seismic stations in Khartoum, Sudan through the H-k stacking of receiver functions and the joint inversion of receiver functions and Rayleigh-wave group velocities. Our H-k-stacking results indicate that crustal thickness beneath the Khartoum basin ranges between 33 and 37 km, with an average of 35 km and that crustal Vp/Vs ratio ranges from 1.74 to 1.81, with an average of 1.78. These results are consistent with 1D velocity models developed from the joint inversion of receiver functions and Rayleigh-wave group velocities, which display similar estimates for crustal thickness and an average shear-wave velocity of 3.7 km/s for the basin's crust. Our results provide the first seismic estimate of Moho depth for a basin in Sudan and, when compared to average crustal thickness for the unrifted Proterozoic crust in eastern Africa, reveal that at most a few kilometers of crustal thinning has occurred beneath the Khartoum basin. Keywords: Teleseismic P-waveforms; Moho depth; Shear wave velocity; Khartoum Basin.

El Tahir, Nada; Nyblade, Andrew; Julia, Jordi; Durrheim, Raymond

2013-04-01

376

Basin Width Control of Faulting and Structural Style  

NASA Astrophysics Data System (ADS)

A series of 5 balanced cross-sections across the Naryn Basin, Kyrgyzstan, reveals a transition in patterns of faulting. Each section is based on surface mapping of deformed basin-filling strata. Beginning in the 25-km-wide Eastern Naryn Basin, deformation within the basin is attributed to faults that are low-angle splays of the northern basin-bounding reverse fault. In 40-km-wide Western Naryn Basin, the pattern of deformation linked to the northern range front remains, but is accompanied by steeper faults that are both south and north dipping. These steeper faults in the west do not appear to be directly linked to the northern range-bounding fault, and likely penetrate the through the entire section of Cenozoic basin fill into the underlying Paleozoic limestone that forms the surrounding ranges. We compare these cross-sections to geodetic measurements of surface deformation. Synthetic aperture RADAR interferometry (InSAR) provides a measure of satellite line-of-sight range changes through time, a close approximation of vertical surface uplift rates. Profiles of deformation rates across the Naryn Basin reveal that in the west, surface deformation is distributed across the broad basin interior. In the east, uplift is concentrated at the northern basin margin of the narrower basin. From the geodetic and structural data, we infer that in the Western Naryn Basin, deformation has migrated away from the northern basin margin and into the interior. Deformation of the eastern basin interior, however, remains linked to the northern basin-bounding fault. These changes along the length of the basin are not accompanied by a consistent change in elevation of the basin-bounding range. Basin width may control basin deformation whereby formation of basin-interior faults in the narrow, eastern Naryn Basin is inhibited by the proximity of the basin-bounding ranges.

Goode, J. K.; Burbank, D. W.

2010-12-01

377

Bedrock geology and chemistry of rivers basins  

NASA Astrophysics Data System (ADS)

The lack of modern quantitative estimates of the Earth’s surface geology, one of the key parameters influencing river and ocean chemistry, is striking. While some attempts have been made to quantify the lithologic composition of bedrock in individual river basins (e.g., Reeder et al., 1972; Amiotte-Suchet et al., 2002), the geologic age distribution of bedrock in river basins has not been investigated. We have therefore initiated a project aimed at generating a worldwide dataset on the bedrock lithology and age distribution of river basins, using the latest digital geologic maps and modern geographic information system technology. To date we have completed analysis of the digital geologic maps North America. These data have been used in conjunction with digital river basin polygons (Revenga et al., 1998, World Resources Institute) to compute the lithologic composition and geologic age structure of major river basins in North America. The lithologic composition of 14 large river basins range from predominantly igneous rocks dominated (Frazer, Columbia), to those dominated by sedimentary rocks (Brazos, Susquehanna, Mississippi), to basins with an equal mix of igneous, metamorphic and sedimentary bedrock (Thelon). Subdividing sedimentary rocks into marine and continental rocks reveals that continental sediments account for no more than 25% of sedimentary rocks in these river basins (e.g., Nelson, Colorado, Mississippi). A further subdivision of igneous rocks into intrusive and volcanic rocks reveals the entire range of igneous composition, from basins dominated by intrusive rocks (Hudson, Mackenzie, Nelson) to those dominated by volcanic rocks (Susquehanna, Colorado, Frazer, Columbia). We are currently analyzing the age distribution of major lithologic units in each river basin. In cases where detailed hydrochemical data is available for major tributaries we will expand the analysis to sub-basins (e.g., Frazer, Mississippi). Basins smaller than about 40,000 km^2 will require analysis of higher-resolution digital geologic bedrock maps. In the next project phase we will combine bedrock data for major river basins with hydrochemical data to investigate the influence bedrock exerts on river chemistry, specifically radiogenic isotopes and macronutrients. Combining digital information on bedrock geology with digital maps of precipitation will allow us to use precipitation-weighted bedrock area rather than simple area-lithology relationships. Extending this analysis to pre-Quaternary periods is beyond the current focus of the project, but will be necessary to fully utilize reconstructions of ocean paleochemistry in models of global biogeochemical cycles (e.g., Bluth and Kump, 1991).

Peucker-Ehrenbrink, B.; Miller, M. W.

2003-04-01

378

Rocky Mountain Tertiary coal-basin models and their applicability to some world basins  

USGS Publications Warehouse

Tertiary intermontane basins in the Rocky Mountain region of the United States contain large amounts of coal resources. The first major type of Tertiary coal basin is closed and lake-dominated, either mud-rich (e.g., North Park Basin, Colorado) or mud plus carbonate (e.g., Medicine Lodge Basin, Montana), which are both infilled by deltas. The second major type of Tertiary coal basin is open and characterized by a preponderance of sediments that were deposited by flow-through fluvial systems (e.g., Raton Basin, Colorado and New Mexico, and Powder River Basin, Wyoming and Montana). The setting for the formation of these coals varies with the type of basin sedimentation, paleotectonism, and paleoclimate. The mud-rich lake-dominated closed basin (transpressional paleotectonism and warm, humid paleoclimate), where infilled by sandy "Gilbert-type" deltas, contains thick coals (low ash and low sulfur) formed in swamps of the prograding fluvial systems. The mud- and carbonate-rich lake-dominated closed basin is infilled by carbonate precipitates plus coarse-grained fan deltas and fine-grained deltas. Here, thin coals (high ash and high sulfur) formed in swamps of the fine-grained deltas. The coarse-clastic, open basins (compressional paleotectonism and warm, paratropical paleoclimate) associated with flow-through fluvial systems contain moderately to anomalously thick coals (high to low ash and low sulfur) formed in swamps developed in intermittently abandoned portions of the fluvial systems. These coal development patterns from the Tertiary Rocky Mountain basins, although occurring in completely different paleotectonic settings, are similar to that found in the Tertiary, Cretaceous, and Permian intermontane coal basins in China, New Zealand, and India. ?? 1989.

Flores, R. M.

1989-01-01

379

Bold enterprise in Amazon basin  

SciTech Connect

The aim of the Jari project in Brazil is to produce food and forest products for world markets by developing a 15,000 square km tract in the Amazon basin. A pumpmill and power plant came on stream in 1979 and since then have been meeting production targets of high quality bleached pulp. The key to the success of the project has been the introduction of a fast-growing hardwood native to S.E. Asia- Gmelina arborea which reaches a height of 30 m after 10 years, and is