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Sample records for gondwana basin orissa

  1. Occurrence of Cordaitales from lower Gondwana sediments of Ib-River Coalfield, Orissa, India: An Indian scenario

    NASA Astrophysics Data System (ADS)

    Singh, Kamal Jeet; Goswami, Shreerup; Chandra, Shaila

    2007-03-01

    The Ib-River Coalfield in Orissa State is a part of Mahanadi Master Basin. Recent extensive investigations were conducted in this Coalfield to locate fossiliferous beds in the Lower Gondwana deposits and as a result a large cache of plant fossils were recovered from Lower Permian sediments (Barakar Formation) exposed in Jurabaga and Lajkura Collieries. The complete flora includes 23 genera representing nine orders viz., Lycopodiales, Equisetales, Sphenophyllales, Filicales, Cordaitales, Coniferales, Ginkgoales, Cycadales and Glossopteridales. Only the Cordaitales, represented by four genera i.e., Noeggerathiopsis, Cordaites, Euryphyllum and Kawizophyllum are discussed in this paper. Cordaitalean leaves are described for the first time from this coalfield; the remaining plant groups will be considered in a subsequent publication. Cordaitalean leaves attributable to Noeggerathiopsis hislopii, Noeggerathiopsis minor, Euryphyllum whittianum, Euryphyllum maithyi, Kawizophyllum dunpathriensis and Cordaites sp. constitute about 13.90% (111 specimens) of the total plant assemblage collected from this Coalfield. Of the cordaitaleans, N. hislopii is most abundant (47.75%; 53 specimens) followed by E. whittianum (40.54%; 45 specimens). A summary of the distribution of Cordaitales throughout the Indian Gondwana is also presented. Floristic composition varies stratigraphically at the two Barakar exposures (Lajkura and Jurabaga Collieries). Cordaitales are preserved only in the lowermost (4th) horizon (lower floral zone). Strata in these collieries have been assigned to the lower and upper Barakar Formation based on floristic content and an Early Permian (Artinskian) age is assigned.

  2. Pteridophytes from Lower Gondwana formations of the Ib River Coalfield, Orissa and their diversity and distribution in the Permian of India

    NASA Astrophysics Data System (ADS)

    Goswami, Shreerup; Jeet Singh, Kamal; Chandra, Shaila

    2006-12-01

    Recent extensive investigations carried out in the Ib River Coalfield, Mahanadi Master Basin, Orissa, identified numerous fossiliferous beds in the lower Gondwana deposits. Six exposures of the Barakar and lower Kamthi formations yielded diverse and abundant plant remains. The flora includes twenty-three genera representing nine groups viz., Lycopodiales, Equisetales, Sphenophyllales, Filicales, Cordaitales, Coniferales, Ginkgoales, Cycadales and Glossopteridales. Systematic descriptions of the pteridophyte taxa namely Cyclodendron (Lycopodiales), Schizoneura, Raniganjia, Bengalia, equisetaceous stems (Equisetales), Trizygia, Benlightfootia (Sphenophyllales), Neomariopteris, and Dichotomopteris (Filicales) are presented in this paper. Pteridophytic leaves comprising nine taxa viz., Cyclodendron leslii, Schizoneura gondwanensis, Raniganjia bengalensis, Bengalia raniganjensis, Trizygia speciosa, Benlightfootia indica, Neomariopteris hughesii, N. talchirensis, and Dichotomopteris sp. together with equisetaceous stems constitute about 7.88% (72 specimens) of the total plant assemblage collected from this coalfield. Among the pteridophytes, equisetaceous stems are most abundant (40.3%; 29 specimens) followed by Schizoneura gondwanensis (20.8%, 15 specimens) and Trizygia speciosa (13.9%, 10 specimens). A summary of the known diversity of pteridophytes in the Indian Permian as a whole is provided. Barakar Formation exposures have been assigned to a lower and upper series based on possession of different floristic assemblages. Pteridophytes do not occur in the lower series. On this basis the beds of Lajkura, Jurabaga collieries, Ratanpur Fireclay Quarry and the locality near Belpahar Railway Station with pteridophyte fossils are assigned to the upper Barakar Formation (late Artinskian). Based on assemblages containing different pteridophytes, beds exposed at Sitaram and Dungri Pahar are assigned to the lower Kamthi Formation (Lopingian). The floristic composition suggests a palaeoclimatic shift from temperate warm moist to warm dry conditions during the late Artinskian and warm and humid during Lopingian. The Permian pteridophytes grew in semi-aquatic conditions, i.e. in marshy places around small ponds, lakes and river-banks.

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

    USGS Publications Warehouse

    Akhtar, A.; Kosanke, R.M.

    2000-01-01

    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.

  4. Aparajita Orissa.

    PubMed

    Mukhopadhyay, Alok

    2007-01-01

    Following the 1999 cyclone, which devastated important areas in the state of Orissa, India, the Voluntary Health Association of India (VHAI) established Aparajita as the long-term aid and reconstruction programme. Aparajita aims at empowering the local community and building their capacity to recover from devastation and prepare for future natural disasters. The programme operates in three main areas of the state: Jagatsinghpur, Kendrapara and Puri. After an assessment study of the damage and the communities' socio-economic and health status, Aparajita focused its interventions on livelihood support, infrastructure development, capacity building, savings and credit, and health interventions. This programme has served to establish the basis of a disaster management process, which includes two main components, preparedness and relief. Given the number of natural adversities in India, there is a need to both empower the communities in the management process, as well as influence government to support and institutionalise initiatives like Aparajita. PMID:17665702

  5. Sedimentary record of a fluctuating ice margin from the Pennsylvanian of western Gondwana: Paraná Basin, southern Brazil

    NASA Astrophysics Data System (ADS)

    Vesely, Fernando F.; Trzaskos, Barbara; Kipper, Felipe; Assine, Mario Luis; Souza, Paulo A.

    2015-08-01

    The Paraná Basin is a key locality in the context of the Late Paleozoic Ice Age (LPIA) because of its location east of the Andean proto-margin of Gondwana and west of contiguous interior basins today found in western Africa. In this paper we document the sedimentary record associated with an ice margin that reached the eastern border of the Paraná Basin during the Pennsylvanian, with the aim of interpreting the depositional environments and discussing paleogeographic implications. The examined stratigraphic succession is divided in four stacked facies associations that record an upward transition from subglacial to glaciomarine environments. Deposition took place during deglaciation but was punctuated by minor readvances of the ice margin that deformed the sediment pile. Tillites, well-preserved landforms of subglacial erosion and glaciotectonic deformational structures indicate that the ice flowed to the north and northwest and that the ice margin did not advance far throughout the basin during the glacial maximum. Consequently, time-equivalent glacial deposits that crop out in other localities of eastern Paraná Basin are better explained by assuming multiple smaller ice lobes instead of one single large glacier. These ice lobes flowed from an ice cap covering uplifted lands now located in western Namibia, where glacial deposits are younger and occur confined within paleovalleys cut onto the Precambrian basement. This conclusion corroborates the idea of a topographically-controlled ice-spreading center in southwestern Africa and does not support the view of a large polar ice sheet controlling deposition in the Paraná Basin during the LPIA.

  6. The late Paleozoic palynological diversity in southernmost Paraná (Uruguay), Claromecó and Paganzo basins (Argentina), Western Gondwana

    NASA Astrophysics Data System (ADS)

    Beri, Ángeles; Gutiérrez, Pedro R.; Balarino, M. Lucía

    2015-12-01

    This study explores the changes in palynoflora diversity of the late Paleozoic in boreholes DI.NA.MI.GE. 254 (26 samples) and DI.NA.MI.GE. 221 (14 samples) of the Paraná Basin in Uruguay and in 18 surface samples of the La Deheza Formation (Paganzo Basin) and 10 samples of borehole UTAL.CMM1.La Estrella.x-1 (Claromecó Basin) in Argentina. Possible relationships among biostratigraphic zones, diversity levels, facies and climatic evolution patterns in Western Gondwana are studied. Diversity curves of boreholes 221 and 254 and the La Deheza Formation outcrop exhibit similar diversity evolution patterns, i.e., an increase in lower strata diversity and a decrease in upper strata diversity. The disappearance events are determined to be more prominent in biozones of the Cisuralian to the Guadalupian age and less prominent in biozones of the early Cisuralian age. The number of genera raises from the glaciomarine facies, through the deltaic and the marine facies, up to the shallow marine or lagoon facies, in which the disappearance rates become more prominent. . The diversity of the lower part of the La Estrella borehole is lesser than that of the other sequences These diversity, disappearance and appearance behaviors may reflect post-glacial climatic amelioration patterns and the beginning of an arid phase.

  7. Shallow lacustrine system of the Permian Pedra de Fogo Formation, Western Gondwana, Parnaíba Basin, Brazil

    NASA Astrophysics Data System (ADS)

    Araújo, Raphael Neto; Nogueira, Afonso César Rodrigues; Bandeira, José; Angélica, Rômulo Simões

    2016-04-01

    The Permian Period of the Parnaíba Basin, northern Brazil, represented here by deposits from the Pedra de Fogo Formation, records important events that occurred in Western Gondwana near its boundary with the Mesozoic Era. The analysis of outcrop based facies from the Permian Pedra de Fogo Formation, which is 100 m thick, carried out along the eastern and western borders of the Parnaiba Basin, allowed the identification of eleven sedimentary facies, which were grouped into three distinct facies associations (FA), representative of a shallow lacustrine system associated with mudflats and ephemeral rivers. Bioturbation, desiccation cracks, silcretes and various siliceous concretions characterize the Pedra de Fogo deposits. The FA1 mudflat deposits occur predominantly at the base of the Pedra de Fogo Formation and consist of laminated claystone/mudstone, mudcrack-bearing sandstones/mudstones and sandstones exhibiting cross-lamination, massive and megaripple bedding. Popcorn-like silicified nodules and casts indicate evaporite deposits. Other common features are silica concretions, silicified tepees and silcretes. FA2 represents nearshore deposits and consists of fine-grained sandstones with evenly parallel lamination, climbing ripple cross-lamination, massive and megaripple bedding and mudstone/siltstone showing evenly parallel lamination. FA3 refers to wadi/inundite deposits, generally organized as fining-upward cycles of metric size, composed of conglomerates and medium-grained pebbly sandstones showing massive bedding and cross-stratification, as well as claystone/siltstone showing evenly parallel to undulate lamination. Scour-and-fill features are isolated in predominantly tabular deposits composed of mudstones interbedded with fine to medium-grained sandstones showing planar to slightly undulate lamination. Silicified plant remains previously classified as belonging to the Psaronius genus found in the uppermost levels of the Pedra de Fogo Formation, near the contact with the Motuca Formation, are considered here as excellent biostratigraphic markers. Fish remains, ostracods, bryozoans and scolecodonts represent other fossils that are present in the succession. Mudflat deposits developed in an arid and hot climate probably in the Early Permian. Semi-arid conditions prevailed in the Middle Permian allowing the proliferation of fauna and flora in adjacent humid regions and onto the lake margin. The climate variation was responsible for the contraction and expansion phases of the lake, fed by sporadic sheet floods carrying plant remains. The reestablishment of the arid climate, at the end of Permian, marks the final sedimentation of the Pedra de Fogo Formation, linked to the consolidation of the Pangaea Supercontinent. This last event was concomitant with the deposition of the Motuca Formation red beds and the development of extensive ergs related to the Triassic Sambaíba Formation in Western Gondwana.

  8. Early Callovian ingression in southwestern Gondwana. Palaeoenvironmental evolution of the carbonate ramp (Calabozo Formation) in southwestern Mendoza, Neuquen basin, Argentina

    NASA Astrophysics Data System (ADS)

    Armella, Claudia; Cabaleri, Nora G.; Cagnoni, Mariana C.; Panarello, Héctor O.

    2013-08-01

    The carbonatic sequence of the Calabozo Formation (Lower Callovian) developed in southwestern Gondwana, within the northern area of the Neuquén basin, and is widespread in thin isolated outcrops in southwestern Mendoza province, Argentina. This paper describes the facies, microfacies and geochemical-isotopic analysis carried out in five studied localities, which allowed to define the paleoenvironmental conditions of a homoclinal shallow ramp model, highly influenced by sea level fluctuations, where outer, mid and inner ramp subenvironments were identified. The outer ramp subenvironment was only recognized in the south of the depocenter and is characterized by proximal outer ramp facies with shale levels and interbedded mudstone and packstone layers. The mid ramp subenvironment is formed by low energy facies (wackestone) affected by storms (packstones, grainstones and floatstones). The inner ramp subenvironment is the most predominant and is characterized by tidal flat facies (wackestones, packstones and grainstones) over which a complex of shoals (grainstones and packstones) dissected by tidal channels (packstone, grainstones and floatstones) developed. In the north area, protected environment facies were recorded (bioturbated wackestones and packstones). The vertical distribution of facies indicates that the paleoenvironmental evolution of the Calabozo Formation results from a highstand stage in the depocenter, culminating in a supratidal environment, with stromatolitic levels interbedded with anhydrite originated under restricted water circulation conditions due to a progressive isolation of the basin. δ13C and δ18O values of the carbonates of the Calabozo Formation suggest an isotopic signature influenced by local palaeoenvironmental parameters and diagenetic overprints. The δ13C and δ18O oscillations between the carbonates of the different studied sections are related with lateral facies variations within the carbonate ramp accompanied with dissimilar reactivities in relation to diagenetic fluids. The δ18O values of all sections exhibit a rather broad scatter which may be attributed to diagenesis and recrystallisation while the carbon isotopic composition has been less affected by those processes. Carbon isotope system has best retained the primary isotopic signal and δ13C values (0-3.9‰) are within the Callovian isotope range. The 87Sr/86Sr ratios of the bulk carbonates of El Plomo creek, La Vaina creek and Potimalal River sections are in agreement with the Callovian seawater Sr-isotope curve.

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

    NASA Astrophysics Data System (ADS)

    Martin, A. K.

    2007-12-01

    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.

  10. Three stages in the Late Paleozoic to Triassic magmatism of southwestern Gondwana, and the relationships with the volcanogenic events in coeval basins

    NASA Astrophysics Data System (ADS)

    Sato, Ana María; Llambías, Eduardo J.; Basei, Miguel A. S.; Castro, Carlos E.

    2015-11-01

    The intermediate to acid Choiyoi Magmatic Province is the most conspicuous feature along the Late Paleozic continental margin of southwestern Gondwana, and is generally regarded as the possible source for the widespread ash fall deposits interlayered with sedimentary sequences in the adjacent Gondwana basins. The Choiyoi magmatism is geologically constrained between the early Permian San Rafael orogenic phase and the Triassic extensional Huarpica phase in the region of Argentine Frontal Cordillera, Precordillera and San Rafael Block. In order to better assess the Choiyoi magmatism in Argentine Frontal Cordillera, we obtained 6 new LA-ICPMS U-Pb ages between 278.8 ± 3.4 Ma and 252.5 ± 1.9 Ma from plutonic rocks of the Colangüil Batholith and an associated volcanic rock. The global analysis of age data compiled from Chilean and Argentine Late Paleozoic to Triassic outcrops allows us to identify three stages of magmatism: (1) pre-Choiyoi orogenic magmatism, (2) Choiyoi magmatism (286-247 Ma), and (3) post-Choiyoi magmatism related to extensional tectonics. In the Choiyoi stage is there an eastward shift and expansion of the magmatism to the southeast, covering an extensive region that defines the Choiyoi magmatic province. On the basis of comparison with the ages from volcanogenic levels identified in the coeval Gondwana basins, we propose: (a) The pre-Choiyoi volcanism from the Paganzo basin (320-296 Ma) probably has a local source in addition to the Frontal Cordillera region. (b) The pre-Choiyoi and Choiyoi events identified in the Paraná basin (304-275 Ma) are likely to have their source in the Chilean Precordillera. (c) The early stage of the Choiyoi magmatism found in the Sauce Grande basin (284-281 Ma) may have come from the adjacent Las Matras to Chadileuvú blocks. (d) The pre-Choiyoi and Choiyoi events in the Karoo basins (302-253 Ma) include the longest Choiyoi interval, and as a whole bear the best resemblance to the age records along the Chilean and Argentine Frontal Cordillera.

  11. Sedimentary sequences and timing of a complex rift to stable passive margin transition during Gondwana Breakup - the Morondava Basin of western Madagascar

    NASA Astrophysics Data System (ADS)

    Geiger, M.; Clark, D. N.

    2003-04-01

    The tectono-sedimentary interpretation of seismic sections and detailed microfacies and mesofacies analyses of Bajocian to Kimmeridgian sediments from outcrops in the southern Morondava Basin, their basinwide correlation, and their integration into modern basin concepts led to a temporally more precise and conceptionally more perspicuous model of the Gondwana rifting and breakup history. The breakup of Gondwana along the East-African/Antarctic Orogen was preceded by a complex polyphase rift activity from the Late Carboniferous to the Early Jurassic, while Karoo aged sediments were being deposited. At the end of these Karoo Rifts, the final crustal separation of East- and West-Gondwana commenced after the westward migration of the rift axis during the Toarcian/Aalenian (Clark and Ramanampisoa, 2002). The sedimentary successions of this Gondwana Breakup Rift can be ascribed to three depositional stages: (1) The prerift stage comprises basement and Karoo aged strata; (2) deposits of the synrift stage related to the Andafia Fm. filled the half graben structures above tilted blocks; (3) during the postrift stage a carbonate platform developed from the Bajocian on the stable passive margin above the breakup unconformity, namely the Sakaraha/Bemaraha Fms. Compared to the sediment succession architecture of different rifts, the particular synrift strata of the Andafia Fm. in the Morondava Basin are mainly marine. Characterized by the wide absence of volcanics, the nonvolcanic Atlantic-type margin is built up by temporally and spatially varying carbonate and clastic sequences. The filling of the passive margin basin was mainly controlled by third order sealevel fluctuations (Hardenbol et al., 1998). The Bemaraha/Sakaraha Fms. carbonate platform environment represents the response to the global Bajocian to Lower Bathonian sealevel high, whereas the clastic pulse of the Ankazoabo/Sakananvaka Fms. during the Upper Bathonian to Lower Callovian was initiated by a eustatic sealevel fall. Comparable sedimentary response in the northern parts of the Morondava Basin is documented by the Besabora Fm. A basinwide transgression during the Callovian introduced an open marine environment (Duvalia Fm.), until clastic pulses of perideltaic sandstones recorded a regressional cycle during the Lower Oxfordian. At the end of the Lower Oxfordian a quick eustatic sealevel rise re-established open marine conditions with a comparably thin succession of condensed carbonate beds (maximum flooding) throughout the Oxfordian. These beds are succeeded by distal open marine shales of Lower Kimmeridgian Age, which are finally cut by the Aptian transgression. Clark, D.N. and Ramanampisoa, L. 2002. Review of the Occurrence and Distribution of Potential Source Rocks in Madagascar. In: Tracts, Plays and Fairways Along the Tethyan Margin - Abstracts and Programme. Kingston University, unpaged. Kingston. Hardenbol, J., Thierry, J., Farley, M.B., Jacquin, T., De Graciansky, P.-C. and Vail, P.R. 1998. Jurassic Sequence Chronostratigraphy. In: Mesozoic and Cenozoic Sequence Stratigraphy of European Basins (Eds P.-C. De Graciansky, J. Hardenbol, T. Jacquin and P.R. Vail), 60. SEPM Spec. Publ.

  12. Sedimentological characteristics and depositional environment of Upper Gondwana rocks in the Chintalapudi sub-basin of the Godavari valley, Andhra Pradesh, India

    NASA Astrophysics Data System (ADS)

    Ramamohanarao, T.; Sairam, K.; Venkateswararao, Y.; Nagamalleswararao, B.; Viswanath, K.

    2003-03-01

    The Kota (Early to Middle Jurassic) and Gangapur (Early Cretaceous) rocks of the Chintalapudi sub-basin of Gondwana are poorly to very poorly sorted, positively to very positively skewed, and leptokurtic to very leptokurtic. The Kota rocks show a single prominent truncation line at the inflection of saltation/suspension at 2.0 ? of the river mode of transportation. The Gangapur rocks show two truncation lines of saltation/suspension, one at 0.5-1.7 ? and the other at 2.4-4.0 ?. These are inferred to be due to a high turbulent phase of the river. On the multigroup multivariant discriminant functions V1- V2 diagram, the bulk of the samples from Kota and Gangapur fall in the field of turbidite deposition. This study supports the view that the discrimination of river from turbidite deposits on this diagram is poor since both deposits are identical in terms of settling velocity distribution. On the C- M diagram, the Kota and Gangapur rocks show segments of rolling, bottom suspension, and graded suspension during river transport of sediment. The Q-R segments of graded suspension for these rocks have a C/ M ratio of 2.5, which is close to the ratio of the turbidites. The Kota and Gangapur rocks have nearly the same assemblage of heavy minerals. The provenance is inferred to consist of basic igneous rocks, acid igneous rocks, high-grade metamorphic rocks and sedimentary rocks.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Perea, Daniel; Soto, Matas; Veroslavsky, Gerardo; Martnez, Sergio; Ubilla, Martn

    2009-08-01

    The Tacuaremb 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 Tacuaremb. We propose a new formalized nomenclature for the Tacuaremb Formation, naming its "Lower" and "Upper" members as the Batov (new name) and Rivera (new rank) members, respectively. An assemblage zone is defined for the Batov Member (fluviolacustrine and aeolian deposits). In this unit, the freshwater hybodontid shark Priohybodusarambourgi D'Erasmo is well represented. This species was previously recorded in Late Jurassic-Early Cretaceous units of the Sahara and the southern Arabian Peninsula. Globally considered, the fossil assemblage of this member ( P. arambourgi, dipnoan fishes, Ceratosaurus-like theropods, and conchostracans) is indicative of a Kimmeridgian-Tithonian age, which in combination with the stratigraphic relationships of the Tacuaremb Formation with the overlying basalts of the Arapey Formation (132 My average absolute age) implies that the latter was deposited during the Kimmeridgian-Hauterivian interval.

  15. The Chachil Limestone (Pliensbachian-earliest Toarcian) Neuquén Basin, Argentina: U-Pb age calibration and its significance on the Early Jurassic evolution of southwestern Gondwana

    NASA Astrophysics Data System (ADS)

    Leanza, H. A.; Mazzini, A.; Corfu, F.; Llambías, E. J.; Svensen, H.; Planke, S.; Galland, O.

    2013-03-01

    New radiometric U-Pb ages obtained on zircon crystals from Early Jurassic ash layers found within beds of the Chachil Limestone at its type locality in the Chachil depocentre (southern Neuquén Basin) confirm a Pliensbachian age (186.0 ± 0.4 Ma). Additionally, two ash layers found in limestone beds in Chacay Melehue at the Cordillera del Viento depocentre (central Neuquén Basin) gave Early Pliensbachian (185.7 ± 0.4 Ma) and earliest Toarcian (182.3 ± 0.4 Ma) U-Pb zircon ages. Based on these new datings and regional geological observations, we propose that the limestones cropping out at Chacay Melehue are correlatable with the Chachil Limestone. Recent data by other authors from limestones at Serrucho creek in the upper Puesto Araya Formation (Valenciana depocentre, southern Mendoza) reveal ages of 182.16 ± 0.6 Ma. Based on these new evidences, we consider the Chachil Limestone an important Early Jurassic stratigraphic marker, representing an almost instantaneous widespread flooding episode in western Gondwana. The unit marks the initiation in the Neuquén Basin of the Cuyo Group, followed by widespread black shale deposition. Accordingly, these limestones can be regarded as the natural seal of the Late Triassic -earliest Jurassic Precuyano Cycle, which represents the infill of halfgrabens and/or grabens related to a strong extensional regime. Paleontological evidence supports that during Pliensbachian-earliest Toarcian times these limestones were deposited in western Gondwana in marine warm water environments.

  16. Gondwana to Asia: Preface

    NASA Astrophysics Data System (ADS)

    Kwon, Sanghoon; Kim, Sung Won; Santosh, M.

    2014-12-01

    The Korean Peninsula, China, Japan, India, Sri Lanka, and Timor, among other regions, preserve important clues for the tectonic evolution of present-day Asia derived from the break-up of Mesozoic supercontinent Pangea. Evidence for the formation, evolution, and destruction of Earth's first coherent supercontinent Columbia during Paleoproterozoic, followed by the Neoproterozoic Rodinia and late Neoproterozoic-Cambrian Gondwana supercontinents are also recorded in many of these regions. The debates surrounding some of these aspects and the state-of-the-art knowledge from these terranes were the focal themes of discussion during the "2013 Annual Convention of the International Association for Gondwana Research (IAGR) and the 10th Gondwana to Asia International Conference" held at the Korea Institute of Geoscience and Mineral Resources (KIGAM), Korea during September 30th to October 2nd 2013. The conference was attended by more than 200 delegates representing 11 countries. The discussion continued at the "International conference on Continental Dynamics" held in Xian, China during April 2014. This special issue of Journal of Asian Earth Sciences, assembling 24 research papers is an outcome of the deliberations under various sessions of the above conferences. In assembling this special issue, we attempt to provide evidence-driven discussions on the construction and destruction of Precambrian and Paleozoic supercontinents preserved in present-day Asian continents. We also address a variety of themes including magmatic, metamorphic and metallogenic processes, as well as issues related to natural environment. We hope that the papers assembled in this special issue offer new insights into some of the key issues surrounding the geological, geophysical and geodynamic milieu in Asia, and a better understanding of analogous processes in other parts of the world.

  17. Gondwana sedimentation in the Pranhita Godavari Valley: a review

    NASA Astrophysics Data System (ADS)

    Sengupta, Supriya

    2003-03-01

    The post-Talchir Gondwana sequence in the central Godavari Valley consists of bands of arenaceous and argillaceous sediments of mainly fluvial origin. Limestones occur only rarely. Profusely cross-bedded, shoestring sand bodies represent point-bar deposits of the ancient Gondwana river. Thinly laminated, argillaceous, flood plain deposits interfinger with the point-bar sands. Possible dimensions of the Gondwana streams have been estimated from thicknesses of the cross-beddings. The flow velocities in the Gondwana River ranged between 0.4 and 0.7 m/s. Textural and geochemical evidence suggests marine influence during Kundaram (Permian) sedimentation, at least locally. Lacustrine sedimentation is inferred for the Early Jurassic Kota Limestone. In the coastal areas, marginal marine inundation occurred during Gollapilli (Cretaceous) sedimentation. The continental environment reappeared soon after. The petrology of the Gondwana sandstones indicates derivation from the low-grade Precambrian metamorphic rocks at the southern fringe of the Gondwana basin. This conclusion is supported by a consistently northerly palaeocurrent direction within the Gondwana rocks. A reversal of the palaeoslope during the Late Jurassic or Early Cretaceous is inferred. Sudden uplift of the source area together with quick burial of sediments is indicated by the presence of fresh feldspars in some formations. Periodic monsoonal conditions of deposition in an otherwise dry climate prevailed. Deposition was uninterrupted between Talchir and Gangapur sedimentation. Shifting river channels caused repetition of the channel and interchannel facies both in time and space. The six major 'groups' recognized by King [Geol. Surv. India Mem. 18 (1881) 151] within the Gondwana of the Godavari Valley have been reclassified by subsequent workers into a larger number of 'formations', following the criteria laid down in the Stratigraphic Code. Correlation between these formations has not always been easy. The technique of Sequence Stratigraphy, which recommends correlation by genetic criteria, might help resolve some of the confusion.

  18. 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)

    Le Roux, J. P.

    1995-09-01

    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.

  19. Linking the End of Glaciation in Gondwana to Aridity in the Tropics: Coupled Sr Chemostratigraphy and Cyclostratigraphy From the Permian Basin, Texas

    NASA Astrophysics Data System (ADS)

    Rasbury, E. T.; Hemming, N. G.; Saller, A. H.; Dickson, J.

    2007-05-01

    Crowell (1978) suggested the Earth was poised on the brink of glaciation throughout the Paleozoic and that closure of the low-latitude seaway between North America and Europe was responsible for diversion of moisture- laden currents to the south to feed the long-lived Carboniferous-Permian glaciers. This same diversion of currents also produced dramatic aridity in the tropics. This is seen in changes in paleosol types as well as in widespread loess and erg deposits. It also coincides with a dramatic decline in Sr isotopes across the Carboniferous-Permian boundary. Sr chemostratigraphy from cores taken across this boundary on the Central Basin Platform (CBP) of the Permian Basin in Texas show the same dramatic shift as seen in data from the type sections in the Urals across this boundary. This confirms that the fusulinid based stage boundaries for the Permian Basin are correct. On the CBP, high-frequency high-amplitude cycles end at a major stepback of the shelf margin at Abo/Clearfork time (Sakmarian). We suggest this transgression represents the end of major Gondwanan glaciation. If we assume the decline in 87Sr/86Sr is reflecting the aridity of the topics and calculate the reduction in continental Sr flux to the oceans, we can relate this to decreased silicate weathering and the consequent increase in atmospheric CO2. Assuming crustal values of [Sr] of 350 ppm, congruent weathering, that the total number of moles of Sr in the ocean is the same as today, and that all of the change is due to a change in flux of Sr from the continents, the change from a late Carboniferous 87Sr/86Sr high of 0.7082 to a value of 0.7078 (the end of cyclothems), equates to an increase in the ocean-atmosphere system of approximately 4 * 106 gigatons of carbon. Preindustrial carbon concentration in the atmosphere is estimated at 578 gigatons. Obviously there are feedbacks that will remove some of the carbon from the ocean-atmosphere system, perhaps to the biosphere, but this simple calculation shows that no special circumstances are needed to account for the increase in pCO2 shown by published proxy data. It also demonstrates why a model that only considers tectonic changes might fail to reproduce this part of the Sr curve. However, the 87Sr/86Sr continues to decrease to a late Permian low of 0.7069 without reversal while the proxy data show a decrease in pCO2 in the middle Permian to near Carboniferous values. Nevertheless, the change is coincident with a flattening in the most recently published Permian Sr curve.

  20. The Dispersal of East Gondwana from Continental Breakup to the Start of the Cretaceous Quiet Zone

    NASA Astrophysics Data System (ADS)

    Davis, J. K.; Lawver, L. A.; Norton, I. O.; Gahagan, L.

    2014-12-01

    Existing plate models for the breakup of Africa and East Gondwana (Australia, East Antarctica, India, Madagascar, the Seychelles, and Sri Lanka) are problematic and require revision. Specific problems include the utilization of dubious Gondwana configurations, improbable plate motion, and/or a failure to satisfy the holistic marine magnetic anomaly data. I present here a new model for the breakup of East Gondwana. This new model begins from a constrained, pre-breakup, Gondwana configuration. Out of this initial "tight-fit" configuration, East Gondwana rifts from West Gondwana (Africa & South America) as a cohesive unit. During this breakup and subsequent seafloor spreading, East Gondwana is devoid of any internal compression or anomalous plate motion. The overall motion of East Gondwana is constrained by seafloor spreading in the coeval Somali Basin and Mozambique/Riiser Larsen Basins. Seafloor spreading in these basins is modeled using existing marine magnetic anomaly interpretations and satellite-derived gravity data. Our model is uniquely able to satisfy the magnetic anomaly observations in both of the aforementioned basins without invoking improbable plate motion or configurations. Additionally, our plate model provides valuable insight into the breakup of India and East Antarctica. In this model, we fix India to Madagascar from breakup to 90 Ma, thus eventual separation between India and East Antarctica is an output, not an input of our model. We suggest that this separation occurred diachronously from ~140 Ma in the east to ~120 Ma in the west. This modeled motion between India and East Antarctica agrees well with geophysical observations from the margin of East Antarctica and our preliminary analysis of margin character and variability.

  1. The relations between Cadomian peri-Gondwana blocks and the interior of Gondwana

    NASA Astrophysics Data System (ADS)

    Garfunkel, Zvi

    2013-04-01

    The Variscan and Alpine orogenic edifices of Europe-Turkey contain many blocks that were located along the periphery of Gondwana in Late Neoproterozoic and Early Paleozoic times. In particular the Cadomian-type blocks were probably located next to the West and North Africa and Arabia (WNAA) part of Gondwana. Here the relations between them, and their implications for the plate tectonic setting and paleogeography, are examined. As the WNAA formed by assembly of many originally separate terranes 650-620 Ma ago or somewhat later, it was only then a continuous peripheral array of terranes could form along the margin of this part of Gondwana. In earlier periods these terranes were most likely not adjacent to the components of WNAA. To accrete to the WNAA, oceanic areas between them had to be eliminated. When positioned next to the WNAA, the peripheral terranes were delimited by a subduction zone, whereas the plate boundaries that separated the components of the WNAA were eliminated. In the Ediacaran WNAA was stabilized and considerably eroded in the aftermath of the Pan African orogeny, while in the peripheral domain igneous activity occurred in many places, and sedimentary basins formed. Then many areas were affected to various extents by the Cadomian orogenic phase. Since the Cambrian the WNAA became a stable platform, usually without any igneous activity, and was covered by an extensive veneer of mature silici-clastics. In contrast, in the Cambrian and Ordovician igneous activity occurred in the peripheral domain, while differential vertical motions and faulting created sedimentary basins and eroded highs. Most likely this activity was usually related to extension or transtension. During these periods the WNAA supplied abundant sediments to the peripheral domain. However, it appears that some sediments had sources located within the peripheral domain or along the junction of the two domains. Examination of the conditions that were required to allow the dispersal of the sediments provides important constrains on the paleogeography of the peripheral domain. Though the available information is still incomplete, an a wide zone along the junction between the WNAA and the peri-Gondwana domains is not exposed, examination of their relation can provided significant insights regarding the plate tectonic setting in which they developed. Moreover, the information regarding the nature and the dispersal of sediments over these domains provides important insights regarding their paleogeography and structure.

  2. Transmed Transect VIII: from Laurussia to Gondwana

    NASA Astrophysics Data System (ADS)

    Stephenson, R. A.; Mart, Y.; Okay, A.; Robertson, A.; Stovba, S.; Khriachtchevskaia, O.

    2003-04-01

    TransMed transect VIII crosses the easternmost Mediterranean Sea. Some 2600 km long, it runs from Laurussia in the north (Ukrainian Shield) to Gondwana in the south (Arabian Shield). The Late Palaeozoic aged intracratonic Dniepr-Donets rift basin lies near the northern end of the transect and the modern intracratonic Red Sea rift lies at the southern end. Intervening tectonic units, north to south, include the Scythian Platform and Crimean Orogen in Ukraine; the Black Sea; the Pontides, Kirsehir Massif, and Taurides in Turkey; Cyprus with the Troodos complex; the Levant Basin and distal parts of the Nile Delta in the eastern Mediterranean; and the Sinai in Egypt. Deep structure, including crustal thickness and affinity, is poorly known along much of the transect. Although all available crustal scale seismic data have been considered, much of the deeper parts of the transect are inferred from the exposed geology and how this can be modelled in terms of regional paleotectonics and are, accordingly, speculative. Palaeozoic and younger sediments of the Scythian Platform overlie basement that is surmised to be younger than the adjoining Archean Ukrainian Shield. The whole of the crust of the Crimean Orogen, underlying thrust nappes emplaced during the early Mesozoic, is speculated to comprise an accretionary complex of mainly Triassic age that is correlated with the Sakarya Zone of northern Turkey. The Black Sea is a back-arc rift basin that opened in Late Cretacous-Tertiary times but the margins of the Black Sea intersected by the transect are not conjugate. The Pontide margin of the Black Sea, in northern Turkey, is formed by the Istanbul Zone, with Proterozoic-aged basement correlative with Moesian crust found in southern Romania and Bulgaria. The Kirsehir Massif is made up of Cretaceous metamorphic and granitic rocks, and represents the deeper parts of a magmatic arc. The Taurides form a south-vergent thrust-stack involving Palaeozoic to Eocene sediments. The Troodos complex represents Late Cretaceous-aged marginal-basin-type oceanic crust, which has been uplifted by the ongoing subduction under Cyprus. The Eratosthenes "seamount", south of Cyprus, is part of an isolated small continental sliver that is in the process of subduction under Cyprus along with the Levant Basin. The Levant Basin comprises Mesozoic and Cenozoic sediments overlying Jurassic-aged oceanic crust of the eastern Mediterranean that adjoins the Precambrian crust of the Sinai across a rifted continental margin.

  3. AN INTRODUCTION TO ABHINAVA CHINTAMANI AN AYURVEDA TREATISE FROM ORISSA

    PubMed Central

    Kishore, Prem; Dash, S.; Nanda, M.C.

    1990-01-01

    A synopsis of the Sanskrit text, Abhinava Chintamani is presented in this paper. Attention is paid to highlight the novel features of this text composed in 18th Century A. D. by Mahamati Cakrapani Das of Orissa. PMID:22556512

  4. Diversity and biogeographic distribution of Jurassic nautiloids of Kutch, India, during the fragmentation of Gondwana

    NASA Astrophysics Data System (ADS)

    Halder, K.

    2000-07-01

    Biogeographic distribution patterns of nautiloid species found in the Jurassic rocks of Kutch, India, are considered in relation to the fragmentation of Gondwana. The pattern of early diversity and endemism during Late Bathonian-Early Callovian times, followed later by a dominance of cosmopolitan forms particularly during the Oxfordian, is interpreted as a consequence of the rifting of Gondwana. The creation of a shallow basin immediately followed by drifting of the Indian Plate triggered early speciation events. The later development of sea routes made free faunal exchanges across the Tethys possible and resulted in a marked increase of pandemism in faunal association. Possible barriers to the dispersal of nautiloids are also briefly reviewed.

  5. Principal stresses flipping during the East- West-Gondwana collision

    NASA Astrophysics Data System (ADS)

    Abu-Alam, T.; Stwe, K.

    2012-04-01

    During the Precambrian-Cambrian transition, the Arabian-Nubian Shield underwent final assembly and accretion to the Saharan Metacraton concurrent with the assembly of eastern and western Gondwana. The Arabian-Nubian Shield consisted of volcanic island-arc terranes, equivalent intrusions and the connecting oceanic crust. During the eastern and western Gondwana collision, the oceanic crust was thrust over the arc terranes and several shear zones were activated. Najd Fault System - the largest pre-Mesozoic shear zone on Earth - is one of these shear zones. Exhumation of mid-crustal level rocks (high-grade gneisses) as metamorphic complexes is closely connected to the activity of the Najd Fault System. In Eastern Desert of Egypt, high-grade rocks were exhumed in extension setting as classical metamorphic core complexes. In contrast, in Sinai, they were exhumed in an oblique transpression regime. In order to investigate reasons for this difference, a current project deals with the exhumation mechanism of the mid-crustal rocks in other parts of the Najd Fault System, namely in the Arabian part of the shield (Saudi Arabia). First results of fieldwork show that the geographic position of molasse basins, typically spatially associated with the gneiss domes, is different in the Eastern Desert than in Saudi Arabia. In Eastern Desert, these basins are located to the northwest and the southeast of the metamorphic complexes. In Saudi Arabia the basins are to the east and the west of the complexes. The geographic position of the molasse basins with respect to the metamorphic complexes and the overall geometry of the Najd Fault System may indicate that the principal stresses (?2 and ?3) of the system were flipped from the east to the west of the Arabian-Nubian Shield. Petrological and age dating work are currently in progress to check the field observations.

  6. New Permian fauna from tropical Gondwana.

    PubMed

    Cisneros, Juan C; Marsicano, Claudia; Angielczyk, Kenneth D; Smith, Roger M H; Richter, Martha; Fröbisch, Jörg; Kammerer, Christian F; Sadleir, Rudyard W

    2015-01-01

    Terrestrial vertebrates are first known to colonize high-latitude regions during the middle Permian (Guadalupian) about 270 million years ago, following the Pennsylvanian Gondwanan continental glaciation. However, despite over 150 years of study in these areas, the biogeographic origins of these rich communities of land-dwelling vertebrates remain obscure. Here we report on a new early Permian continental tetrapod fauna from South America in tropical Western Gondwana that sheds new light on patterns of tetrapod distribution. Northeastern Brazil hosted an extensive lacustrine system inhabited by a unique community of temnospondyl amphibians and reptiles that considerably expand the known temporal and geographic ranges of key subgroups. Our findings demonstrate that tetrapod groups common in later Permian and Triassic temperate communities were already present in tropical Gondwana by the early Permian (Cisuralian). This new fauna constitutes a new biogeographic province with North American affinities and clearly demonstrates that tetrapod dispersal into Gondwana was already underway at the beginning of the Permian. PMID:26537112

  7. New Permian fauna from tropical Gondwana

    PubMed Central

    Cisneros, Juan C.; Marsicano, Claudia; Angielczyk, Kenneth D.; Smith, Roger M. H.; Richter, Martha; Fröbisch, Jörg; Kammerer, Christian F.; Sadleir, Rudyard W.

    2015-01-01

    Terrestrial vertebrates are first known to colonize high-latitude regions during the middle Permian (Guadalupian) about 270 million years ago, following the Pennsylvanian Gondwanan continental glaciation. However, despite over 150 years of study in these areas, the biogeographic origins of these rich communities of land-dwelling vertebrates remain obscure. Here we report on a new early Permian continental tetrapod fauna from South America in tropical Western Gondwana that sheds new light on patterns of tetrapod distribution. Northeastern Brazil hosted an extensive lacustrine system inhabited by a unique community of temnospondyl amphibians and reptiles that considerably expand the known temporal and geographic ranges of key subgroups. Our findings demonstrate that tetrapod groups common in later Permian and Triassic temperate communities were already present in tropical Gondwana by the early Permian (Cisuralian). This new fauna constitutes a new biogeographic province with North American affinities and clearly demonstrates that tetrapod dispersal into Gondwana was already underway at the beginning of the Permian. PMID:26537112

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

    USGS Publications Warehouse

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

    1985-01-01

    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.

  9. Early Paleozoic paleogeography of the northern Gondwana margin: new evidence for Ordovician-Silurian glaciation

    NASA Astrophysics Data System (ADS)

    Semtner, A.-K.; Klitzsch, E.

    1994-12-01

    During the Early Paleozoic, transgressions and the distribution of sedimentary facies on the northern Gondwana margin were controlled by a regional NNW-SSE to almost north-south striking structural relief. In Early Silurian times, a eustatic highstand enabled the sea to reach its maximum southward extent. The counterclockwise rotation of Gondwana during the Cambrian and Early Ordovician caused the northern Gondwana margin to shift from intertropical to southern polar latitudes in Ordovician times. Glacial and periglacial deposits are reported from many localities in Morocco, Algeria, Niger, Libya, Chad, Sudan, Jordan and Saudi Arabia. The Late Ordovician glaciation phase was followed by a period of a major glacioeustatic sea-level rise in the Early Silurian due to the retreat of the ice-cap. As a consequence of the decreasing water circulation in the basin centers (Central Arabia, Murzuk- and Ghadames basins), highly bituminous euxinic shales were deposited. These shales are considered to be the main source rock of Paleozoic oil and gas deposits in parts of Saudi Arabia, Libya and Algeria. The following regression in the southern parts of the Early Silurian sea was probably caused by a second glacial advance, which was mainly restricted to areas in Chad, Sudan and Niger. Evidence for glacial activity and fluvioglacial sedimentation is available from rocks overlying the basal Silurian shale in north-east Chad and north-west Sudan. The Early Silurian ice advance is considered to be responsible for the termination of euxinic shale deposition in the basin centers.

  10. Late Ordovician volcanism in Korea constrains the timing for breakup of Sino-Korean Craton from Gondwana

    NASA Astrophysics Data System (ADS)

    Cho, Deung-Lyong; Lee, Seung Ryeol; Koh, Hee Jae; Park, Jun-Beom; Armstrong, Richard; Choi, Duck K.

    2014-12-01

    In the early Paleozoic the Sino-Korean Craton (SKC) and South China Craton (SCC) were situated along the margin of east Gondwana. The SKC was connected to core Gondwana by an epeiric sea which was the site for deposition of lower Paleozoic sequences of SKC. The SKC and SCC may have drifted away from core Gondwana sometime during the mid-Paleozoic and would have been outboard microcontinents in the late Paleozoic, until they collided to form the East Asian continent in the Triassic. The breakup of SCC from Gondwana was suggested to have taken place at ∼380 Ma, while no reliable suggestions have hitherto been made for breakup of SKC from Gondwana. This study presents a convincing evidence for breakup of SKC from Gondwana, based on the recognition of Late Ordovician volcanism in Korea. New SHRIMP U-Pb zircon ages, 445.0 ± 3.7 Ma and 452.5 ± 3.2 Ma, are obtained from trachytic rocks of the Ongnyeobong Formation of Taebaeksan Basin in Korea which occupied the marginal part of the SKC in the early Paleozoic. This Late Ordovician volcanism along with previous records of Ordovician volcanic activities along the western margin of the SKC is interpreted indicating the development of an incipient oceanic ridge. The oceanic ridge uplifted the SKC including the epeiric sea, which subsequently resulted in terminating the early Paleozoic sedimentation of the epeiric sea. The paucity of lower Paleozoic volcanic rocks across much of the SKC however suggests that the oceanic ridge did not extend into the epeiric sea. Instead, spreading of oceanic ridge entailed dextral movement of associated transform faults, which may have played a major role in breakup of SKC from mainland Gondwana by the end of Ordovician.

  11. A Mesozoic bird from Gondwana preserving feathers.

    PubMed

    Carvalho, Ismar de Souza; Novas, Fernando E; Agnolín, Federico L; Isasi, Marcelo P; Freitas, Francisco I; Andrade, José A

    2015-01-01

    The fossil record of birds in the Mesozoic of Gondwana is mostly based on isolated and often poorly preserved specimens, none of which has preserved details on feather anatomy. We provide the description of a fossil bird represented by a skeleton with feathers from the Early Cretaceous of Gondwana (NE Brazil). The specimen sheds light on the homology and 3D structure of the rachis-dominated feathers, previously known from two-dimensional slabs. The rectrices exhibit a row of rounded spots, probably corresponding to some original colour pattern. The specimen supports the identification of the feather scapus as the rachis, which is notably robust and elliptical in cross-section. In spite of its juvenile nature, the tail plumage resembles the feathering of adult individuals of modern birds. Documentation of rachis-dominated tail in South American enantiornithines broadens the paleobiogeographic distribution of basal birds with this tail feather morphotype, up to now only reported from China. PMID:26035285

  12. A Mesozoic bird from Gondwana preserving feathers

    PubMed Central

    de Souza Carvalho, Ismar; Novas, Fernando E.; Agnolín, Federico L.; Isasi, Marcelo P.; Freitas, Francisco I.; Andrade, José A.

    2015-01-01

    The fossil record of birds in the Mesozoic of Gondwana is mostly based on isolated and often poorly preserved specimens, none of which has preserved details on feather anatomy. We provide the description of a fossil bird represented by a skeleton with feathers from the Early Cretaceous of Gondwana (NE Brazil). The specimen sheds light on the homology and 3D structure of the rachis-dominated feathers, previously known from two-dimensional slabs. The rectrices exhibit a row of rounded spots, probably corresponding to some original colour pattern. The specimen supports the identification of the feather scapus as the rachis, which is notably robust and elliptical in cross-section. In spite of its juvenile nature, the tail plumage resembles the feathering of adult individuals of modern birds. Documentation of rachis-dominated tail in South American enantiornithines broadens the paleobiogeographic distribution of basal birds with this tail feather morphotype, up to now only reported from China. PMID:26035285

  13. Environmental health impact assessment of National Aluminum Company, Orissa.

    PubMed

    Patil, Rajan R

    2011-05-01

    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. PMID:22223954

  14. Gondwana dispersion and Asian accretion: Tectonic and palaeogeographic evolution of eastern Tethys

    NASA Astrophysics Data System (ADS)

    Metcalfe, I.

    2013-04-01

    Present-day Asia comprises a heterogeneous collage of continental blocks, derived from the Indian-west Australian margin of eastern Gondwana, and subduction related volcanic arcs assembled by the closure of multiple Tethyan and back-arc ocean basins now represented by suture zones containing ophiolites, accretionary complexes and remnants of ocean island arcs. The Phanerozoic evolution of the region is the result of more than 400 million years of continental dispersion from Gondwana and plate tectonic convergence, collision and accretion. This involved successive dispersion of continental blocks, the northwards translation of these, and their amalgamation and accretion to form present-day Asia. Separation and northwards migration of the various continental terranes/blocks from Gondwana occurred in three phases linked with the successive opening and closure of three intervening Tethyan oceans, the Palaeo-Tethys (Devonian-Triassic), Meso-Tethys (late Early Permian-Late Cretaceous) and Ceno-Tethys (Late Triassic-Late Cretaceous). The first group of continental blocks dispersed from Gondwana in the Devonian, opening the Palaeo-Tethys behind them, and included the North China, Tarim, South China and Indochina blocks (including West Sumatra and West Burma). Remnants of the main Palaeo-Tethys ocean are now preserved within the Longmu Co-Shuanghu, Changning-Menglian, Chiang Mai/Inthanon and Bentong-Raub Suture Zones. During northwards subduction of the Palaeo-Tethys, the Sukhothai Arc was constructed on the margin of South China-Indochina and separated from those terranes by a short-lived back-arc basin now represented by the Jinghong, Nan-Uttaradit and Sra Kaeo Sutures. Concurrently, a second continental sliver or collage of blocks (Cimmerian continent) rifted and separated from northern Gondwana and the Meso-Tethys opened in the late Early Permian between these separating blocks and Gondwana. The eastern Cimmerian continent, including the South Qiangtang block and Sibumasu Terrane (including the Baoshan and Tengchong blocks of Yunnan) collided with the Sukhothai Arc and South China/Indochina in the Triassic, closing the Palaeo-Tethys. A third collage of continental blocks, including the Lhasa block, South West Borneo and East Java-West Sulawesi (now identified as the missing "Banda" and "Argoland" blocks) separated from NW Australia in the Late Triassic-Late Jurassic by opening of the Ceno-Tethys and accreted to SE Sundaland by subduction of the Meso-Tethys in the Cretaceous.

  15. Geophysical evidence for a causative process for fragmentation in western Gondwana

    SciTech Connect

    Antoine, L.A.G.; Moyes, A.B. )

    1992-07-01

    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.

  16. Upper Kamthi: A riddle in the Gondwana stratigraphy of India

    NASA Astrophysics Data System (ADS)

    Dutta, Prodip K.

    The upper Kamthi, characterized by quartz arenite and interbedded with quartz conglomerate and highly indurated purple clays tone, forms a distinct lithological association in the Pranhita-Godavari basin, India. Stratigraphically, the unit was considered the upper section of the Kamthi Group (Upper Permian), occupying a conformable position between the underlying lower section of the Kamthi and presumably the overlying Maleri (Middle to Upper Triassic). Both the latter units have similar lithological attributes; they are characterized by feldspathic sandstone and interbedded mudstone and are distinctly different from the upper Kamthi unit. Between them, the upper Kamthi stands out "like a sore thumb." On the other hand, it shows remarkable lithological and petrographical similarities to the lower part of the Kota Group (Lower Jurassic) in the Pranhita-Godavari basin and Parsora Bed (Rhaetic Lower Jurassic) of the Rewa Gondwana basin in central India. In spite of a distinctly different lithological association, the upper Kamthi rocks have been merged with the lower section of Kamthi, solely on the basis of the rare occurrence of fragmentary fossils whose chronological significance is in doubt. Such a stratigraphic interpretation has led to many structural and stratigraphic anomalies involving only the upper Kamthi rocks. Lithofacies mapping demonstrates that the upper Kamthi overlies both the lower section of Kamthi and the Maleri. This stratigrahic relationship removes all the structural and stratigraphic anomalies and makes the upper Kamthi equivalent in time and stratigraphy to the Lower Jurassic Kota. Independent evidence based on the compositional maturity of upper Kamthi arenites and paleomagnetic poles obtained from the upper Kamthi also indicate an Early Jurassic age for the unit.

  17. Proterozoic East Gondwana: Supercontinent Assembly and Breakup, Special Publication 206

    NASA Astrophysics Data System (ADS)

    Meert, Joseph G.

    The Mozambique Belt, which runs the length of eastern Africa, was thought to have formed during the collision of a fully assembled east Gondwana with west Gondwana during the East Africa Orogen (EAO). Subsequent work demonstrated that the elements of the Gondwana super-continent were distributed along the margins of Laurentia in the antecedent super-continent of Rodinia. It was quickly recognized that west Gondwana was an amalgam of cratonic elements assembled in the latter part of the Neoproterozoic during the Brasiliano and “Pan-African” orogenic episodes (ca. 630-500 Ma). East Gondwana was traditionally depicted in Rodinia as a coherent landmass composed of Australia, the East Antarctic eraton, India, Madagascar, and Sri Lanka.

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

    NASA Astrophysics Data System (ADS)

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

    2003-07-01

    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.

  19. New data refine the travels of Gondwana

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2011-09-01

    The supercontinent Pangea, which existed roughly 300-200 million years ago as the only landmass on Earth, plays a special role in the history of geophysics. The geological, biological, and paleontological similarities between now distant shores—once connected in Pangea—gave the first evidence for the theory of continental drift. That Pangea came apart to form the modern world is well established, but exactly how, when, and where the individual plates moved are still up for debate. Drawing on new high-quality paleomagnetic data, Domeier et al. describe the movements of Gondwana that, until its separation from Laurasia 200 million years ago, formed the southern half of Pangea. The authors collected samples drawn from the Sierra Chica, a band of ancient volcanic rocks in central Argentina. Within the samples the magnetic minerals hematite and titanomagnetite were used to calculate the geographic location of the magnetic pole 263 million years ago. Because the Earth's magnetic poles drift only slightly over time and have well-known reversal episodes, deviations in the location of the calculated pole (paleopole) from the present location are an indication that the plate underlying the volcanic rock has moved since the lava solidified. Changes in the paleopole drawn from samples of different ages from the same plate give a map for the plate's movement. (Geochemistry, Geophysics, Geosystems, doi:10.1029/2011GC003616, 2011)

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  1. Patterns of Gondwana plant colonisation anddiversification

    NASA Astrophysics Data System (ADS)

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

    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.

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

    USGS Publications Warehouse

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

    1998-01-01

    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.

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

    SciTech Connect

    Yemane, K. . Dept. of Geology Bryn Mawr Coll., PA . Dept. of Geology)

    1993-03-01

    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.

  4. Kinematics of late Paleozoic continental collision between Laurentia and Gondwana

    USGS Publications Warehouse

    Sacks, P.E.; Secor, D.T., Jr.

    1990-01-01

    In the Appalachians, late Paleozoic Alleghanian orogenesis is widely regarded as resulting from dextral oblique collision between irregular margins of Gondwana and Laurentia. However, this relative plate motion cannot account for coeval convergence in the Ouachitas and Variscides and is incompatible with some tectonic transport indicators in the Appalachians. An alternative kinematic model is proposed in which early sinistral transpression in the Appalachians is followed by counterclockwise rotation of Gondwana and the development of a system of dextral strike-slip faults extending from southern Europe to Alabama.

  5. East Antarctic Rift Systems - key to understanding of Gondwana break-up

    NASA Astrophysics Data System (ADS)

    Golynsky, D. A.; Golynsky, A. V.

    2012-04-01

    The results of analysis of radio-echo sounding surveys, the RADARSAT satellite data, magnetic and gravity information give evidence that East Antarctica contains 13 riftogenic systems and/or large linear tectonic structures. Among known and suggested rifts of East Antarctica the Lambert rift has a pivotal position and it manifests oneself as symmetry axis. Six additional systems are revealed on both sides of it and any one of them possesses special features in geologic and geomorphologic aspects. In most cases they inherited the anisotropy of long-lived cratonic blocks. Riftogenic and/or large linear tectonic structures along the East Antarctica coastal regions are distributed with a steady regularity with average distance between them about 650 km. For six (7) structures from 13 (Lambert, Jutulstraumen-Penckskket, Vestfjella, Mellor-Slessor (Bailey), Wilkes Basin, Gaussberg (?) and Rennick) there is a distinct spatial coupling with trough complexes of the Beacon Supergroup and their subsequent reactivation in Late Jurassic - Permian time when the East Gondwana started break-up. Rift system of the Lambert-Amery Glaciers and Prydz Bay is related to Mesozoic extension events and it inherited structures of Paleozoic grabens. The total length of the rift system exceeds 4000 km of the same scale as largest the World rift belts. The length of the western branch of the Lambert rift that includes the Mellor rift and graben-like structures of the Bailey and Slessor glaciers exceeds 2300 km. Results of radio-echo sounding investigation of the subglacial Aurora Basin allow to suggest that this large basin of sub-meridian extension is underlain by an extensive (> 1000 km) riftogenic structure that is running towards the Transantarctic Mountains where it forms a triple junction with the eastern branch of the Lambert rift and structures of the Wilkes Basin. It is hereby proposed that Aurora-Scott rift is formed by complex system of sub-parallel depressions divided by fragmentary horsts. The spatial correlation of the Aurora-Scott rift system, Permian basins of the Western Australia margin and coal-bearing basins in Rajmahal Hills allows suggesting that this East Antarctic structure was also formed during Permian time and about the existence of triple junction rift systems (Aurora-Scott, Perth, Rajmahal) in the pre-breakup Gondwana.

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

    NASA Astrophysics Data System (ADS)

    Ernesto, M.; Marques, L. S.

    2011-12-01

    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.

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

    PubMed

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

    2013-07-01

    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

  8. Hardship financing of healthcare among rural poor in Orissa, India

    PubMed Central

    2012-01-01

    Background This study examines health-related "hardship financing" in order to get better insights on how poor households finance their out-of-pocket healthcare costs. We define hardship financing as having to borrow money with interest or to sell assets to pay out-of-pocket healthcare costs. Methods Using survey data of 5,383 low-income households in Orissa, one of the poorest states of India, we investigate factors influencing the risk of hardship financing with the use of a logistic regression. Results Overall, about 25% of the households (that had any healthcare cost) reported hardship financing during the year preceding the survey. Among households that experienced a hospitalization, this percentage was nearly 40%, but even among households with outpatient or maternity-related care around 25% experienced hardship financing. Hardship financing is explained not merely by the wealth of the household (measured by assets) or how much is spent out-of-pocket on healthcare costs, but also by when the payment occurs, its frequency and its duration (e.g. more severe in cases of chronic illnesses). The location where a household resides remains a major predictor of the likelihood to have hardship financing despite all other household features included in the model. Conclusions Rural poor households are subjected to considerable and protracted financial hardship due to the indirect and longer-term deleterious effects of how they cope with out-of-pocket healthcare costs. The social network that households can access influences exposure to hardship financing. Our findings point to the need to develop a policy solution that would limit that exposure both in quantum and in time. We therefore conclude that policy interventions aiming to ensure health-related financial protection would have to demonstrate that they have reduced the frequency and the volume of hardship financing. PMID:22284934

  9. Perceived Gender Role that Shape Youth Sexual Behaviour: Evidence from Rural Orissa, India

    ERIC Educational Resources Information Center

    Pradhan, Manas Ranjan; Ram, Usha

    2010-01-01

    The study attempts to understand the association of perceived gender role with youth sexual behavior using qualitative data such as focus group discussions (N = 8), in-depth interviews (N = 42), and free listing (N = 50) of rural married youths from Orissa, India. Data collection was conducted during July 2006-April 2007. Atlas. ti and ANTHROPAC

  10. Perceived Gender Role that Shape Youth Sexual Behaviour: Evidence from Rural Orissa, India

    ERIC Educational Resources Information Center

    Pradhan, Manas Ranjan; Ram, Usha

    2010-01-01

    The study attempts to understand the association of perceived gender role with youth sexual behavior using qualitative data such as focus group discussions (N = 8), in-depth interviews (N = 42), and free listing (N = 50) of rural married youths from Orissa, India. Data collection was conducted during July 2006-April 2007. Atlas. ti and ANTHROPAC…

  11. The basins on the Argentine continental margin

    SciTech Connect

    Urien, C.M.

    1996-08-01

    After the stabilization of the central Gondwana Craton, orogenic belts were accreted, as a result of convergence events and an extensive passive margin developed in southwestern Gondwana. Thermal subsidence in Parana, Karoo-Ventania basins and the Late Paleozoic-Early Mesozoic rifts, were modified by the Gondwana breakup and the South Atlantic opening. Early Paleozoic marine transgressions deposited the Table Mountain Group in Ventania. In southwestern Patagonia foreland clastics were deposited. Magmatic arcs and marine units indicate a tectonic trough was formed, alternating with continental sequences, over Late Paleozoic metamorphics and intrusives, resulting from plastered terrains along the Gondwana margin. In Patagonia, Permo-Carboniferous continental and glacio marine clastics infill the basins, while in Ventania, paralic sequences, grade from neritic to continental to the northeast, extending beneath the continental margin. The Triassic-Jurassic rift basins progressed onto regional widespread acid lavas and were infilled by lagoonal organic-rich sequences. Early drift phase built basins transverse to the margin, with fluvio-lacustrine sequences: Salado, Colorado, Valdes-Rawson, San Julian and North Malvinas intracratonic basins, which underwent transtensional faulting. Post-Oxfordian to Neocomian brackish sequences, onlapped the conjugate basins during the margin`s drift, with petroleum systems, as in Austral and Malvinas. In the Valanginian, basic extrusions commenced to form on the continental border, heralding the oceanic phase. Due to thermal subsidence, offlaping sediments prograded onto the remaining half-grabens. Several petroleum systems, proven and hypothetical, are identified in this region.

  12. The Cordon del Portillo Permian magmatism, Mendoza, Argentina, plutonic and volcanic sequences at the western margin of Gondwana

    NASA Astrophysics Data System (ADS)

    Gregori, Daniel; Benedini, Leonardo

    2013-03-01

    The Cerro Punta Blanca, Cerro Bayo and Cerro Punta Negra stocks, parts of the Cordillera Frontal Composite Batholith, cropping out in the Cordón del Portillo, records the Gondwana magmatic development of the Cordillera Frontal of Mendoza, in western Argentina. In this area, the San Rafael Orogenic phase, that represents the closure of the Late Carboniferous-Early Permian marine basins, begins at 284 Ma, and ceased before 276 Ma. The Cerro Punta Blanca, Cerro Bayo and Cerro Punta Negra stocks represent a post-orogenic magmatism and are equivalents to the Choiyoi Group. The Gondwana magmatic activity in the Cordón del Portillo area can be divided into two stages. The Cerro Punta Blanca stock (c.a. 276 Ma) represents an early post-orogenic, subduction-related magmatism similar to the basic-intermediate section of the Choiyoi Group (c.a. 277 Ma). The late post-orogenic second event was recorded by the Cerro Bayo (262 Ma) and Cerro Punta Negra stocks which represent a transition between subduction-related and intra-plate magmatism. This event represents the intrusive counterpart of the acidic facies of the upper section of the Choiyoi Group (c.a. 273 Ma). This extensional condition continued during the Triassic when the Cacheuta basin developed.

  13. Active or passive? Was it pushed or did it jump?: The breakup of Gondwana

    NASA Astrophysics Data System (ADS)

    Hunter, M. A.

    2003-04-01

    The breakup of the supercontinent Gondwana and subsequent "drift" of resultant continental blocks has been the focus of study for more than a decade. However, the mechanism behind the initial breakup has remained unresolved pending identification of a suitable test area. It is now fairly certain that mantle plumes were present during breakup, and that subduction has been active along the margin of the Supercontinent for hundreds of millions of years. But which force had the greatest effect on the ultimate demise of the Supercontinent? Evidence from silicic volcanics associated with breakup from the Antarctic Peninsula and Patagonian South America suggest subduction may not have been active during the early opening of the southern Atlantic Ocean at about 185 Ma. However, two subsequent pulses of volcanic activity at approximately 170 and 155 Ma show increasing subduction characteristics until magma was wholly subduction generated by 155 Ma. The sedimentary basins of the Antarctic Peninsula, South Africa and southern South America were being deposited throughout this period. The basin histories reflect what forces acted to create the basins and how they evolved with time. Sedimentary facies changes within the basins show a dramatic change in depositional setting. Sometime between the Middle and Late Jurassic low energy anoxic deposition, probably with restricted circulation, gives way to much higher energy facies in a larger, more widespread depositional basin. Extension directions within the basins indicate the underlying stress fields and show a change in orientation also between the Middle and Late Jurassic. Sediment chemistry and petrography show a shift in the dominant source area from continental to active arc. These observations suggest at least two independent phases of basin formation. When considered in conjunction with the volcanic evidence, the early the stages of breakup may have been driven by a different force than the subsequent and more dramatic rifting. It seems that early initial rifting was manifest as a series of small, restricted basins, tangential to the proposed area of plume related uplift. These were subsequently replaced by a more continuous, larger scale back-arc basin, with extension perpendicular to the palaeo-Pacific margin, and formed in response to subduction along the western margin of the Supercontinent.

  14. The evolution of the mobile zones of Gondwana and Laurasia in the Late Precambrian

    NASA Astrophysics Data System (ADS)

    Bozhko, N. A.

    1986-06-01

    The tectonic evolutions of Gondwana and Laurasia in the Late Precambrian show some differences, which become more striking after the Late Riphean (1000-700 m.y.), when Gondwana separated from Pangea. These differences include distributions of aulocogens and intrageosynclines as well as zones of non-geosyncline tectono-thermal reworking of basement. Geodynamics of interiors in Gondwana and Laurasia were quite different during the Vendian-Early Cambrian. The fragmentation of Laurasia and the opening of the Iapetus and the Paleo-Asian ocean coincide in time with the Pan-African orogeny and equivalent orogenies in Gondwana.

  15. Optical remote sensing a potential tool for forecasting malaria in Orissa, India

    NASA Astrophysics Data System (ADS)

    Nizamuddin, Mohammad; Akhand, Kawsar; Roytman, Leonid; Kogan, Felix; Goldberg, Mitch

    2013-05-01

    Information on current and anticipated moisture and thermal condition from satellite data represents a source of affordable yet careful information for malaria forecasters to implement and control of epidemic. During the last decades Orissa state in India suffered from highest level of malaria incidence. This situation requires frequent monitoring of environmental conditions and dynamics of malaria occurrence. During 1985 to 2004 the NOAA AVHRR global vegetation index (GVI) dataset and its vegetation health (VH) have been studied and used as proxy for malaria fluctuation. This paper discusses applications of VH for early detecting and monitoring malaria incidence in Orissa. A significant relationship between satellite data and annual malaria incidences is found at least three months before the major malaria transmission period.

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

    NASA Astrophysics Data System (ADS)

    Mancuso, Adriana Cecilia

    2009-12-01

    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).

  17. 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)

    Engelder, T.

    2006-05-01

    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.

  18. Origin and Evolution of Limestone Caves of Chhattisgarh and Orissa, India: Role of Geomorphic, Tectonic and Hydrological Processes

    NASA Astrophysics Data System (ADS)

    Gautam, P. K.; Allu, N. C.; Ramesh, R.; Yadava, M. G.; Panigrahi, C. P.

    2014-12-01

    Carbonate rocks undergo karstic process and karst morphology is a key to understand the nature and genesis of caves. The primary energy source for the formation of karst landforms is hydrological cycle. Geomorphic features along with hydrological characteristics provide important information not only on karst formation but also climate and environmental conditions. In this paper, we present the tectonic and geomorphic features that played a role in evolution of caves located in Chhattisgarh and Orissa States of India. The geomorphic and tectonic aspects of Kotumsar, Kailash, and Gupteshwar caves are discussed in relation to the origin and evolution of these caves. Caves are located near the water falls. The area is folded and faulted along the Eastern Ghat Mobile Belt (EGMB) due to tectonic reactivation. Shaly-limestone beds exhibit vertical dipping near Gupteshwar cave, and steeply inclined near Kotumsar and Kailash caves. Indrāvati and Sabari/Kolab tributaries of the Godavari River drain the area. The landscape evolution and the origin of caves in the region is a multistage process, where the lithology, orogeny, fluvial action, and monsoon are the main agents, which is similar to the four state model (Ford and Ewers, 1978). The river basin evolution and regional tectonism also caused the initiation of karstification in the region. The evolution of caves is believed to have taken place in Pre-Pliocene under more humid conditions that coincided with the initiation of monsoon in India. Further, during the Quaternary wet-dry/cold-warm phases altered physical and chemical weathering of limestone rocks. Contrasting relief features of Bastar plateau have also helped the extensive cave formation in the region. The dissolution along weak planes initiated the openings of caves, further enlarged by geomorphic agents. Both monsoon and tectonics have caused fluctuations in water levels along river courses, which acted as active agents in evolution of caves.

  19. Structural framework across the Bastar craton - the Eastern Ghats Granulite Belt interface: Implications for making of eastern Gondwana

    NASA Astrophysics Data System (ADS)

    Patole, Vishal; Nasipuri, Pritam

    2015-04-01

    The transformation of palaeo-continents involve breakup, dispersal and reassembly of cratonic blocks by collisional suturing that develop a network of orogenic (mobile) belts around the periphery of the stable cratons. During the collision, partial melting of the different crustal blocks produces migmatites at the craton-mobile belt interface. Thus, migmatites at the craton-mobile belt contact can provide valuable information regarding the pressure-temperature conditions of the melting of lower crust during supercontinent building processes. In this contribution, we document the structural framework across the Bastar craton- Eastern Ghats Granulite Belt (EGGB) interface that developed during the accretion of EGGB over Bastar craton. Near Bhawanipatna, Orissa, Eastern India, the granulites of the mobile belt are juxtaposed against the granitic rocks of the Bastar craton. Away from the contact domain, the cratonic granite is non-migmatitic and blasto-porphyritic in nature that gradually transforms to migmatitic variety towards the contact domain. In the non-migmatitic variety, the E-W trending stromatic leucozomes and biotite-hornblende rich fabric (S1) wraps around recrystallized K-feldspar augens. In the migmatitic variety towards the contact domain, NNE-SSW trending diatexite leucozomes (S2) are prominent and the intensity of melting and tightness of folding increases towards the contact domain. Structural measurements indicate that the S1 fabric is folded with the development of NNE-SSW axial plane with easterly plunging fold axis (50 -> 050N). To correlate the geological history of EGGB in the context of supercontinent reconstruction, the existence of a cratonic block consisting of India - Madagascar - Sri Lanka - Enderby Land-Kalahari ("IMSLEK") from 3000 Ma upto 750 Ma has been invoked by several authors. The apparent continuity of the Grenvillian metamorphic orogen along the East Antarctica-Australia-India margin has been taken as conclusive evidence for the existence of a single landmass since the time of Grenvillian orogeny (1000 Ma) and it is suggested that the same configuration was preserved up to the formation of East Gondwana. The EGGB orogenic belt is considered as intercontinental high grade domain with no evidence for the closing of Mesoproterozoic oceans and the younger Pan-African metamorphic events are the results of intercontinental reactivation of old crustal weakness during the Gondwana assembly in the late Neoproterozoic-Paleozoic. However, recent palaeomagnetic data from India and Australia indicate that India was at much higher palaeolatitude compared to the Australia-Antarctica block, and the accretion of Eastern Ghats Granulite Belt over Bastar craton should have occurred during the Pan-African orogeny. The presence of NNW-SSW trending melt bands and the increase in the intensity of melting and tightness of folding near the contact indicate that Eastern Ghats Granulite belt collided with the Bastar craton during the Paleozoic.

  20. The evolution of mammal-like crocodyliforms in the Cretaceous Period of Gondwana.

    PubMed

    O'Connor, Patrick M; Sertich, Joseph J W; Stevens, Nancy J; Roberts, Eric M; Gottfried, Michael D; Hieronymus, Tobin L; Jinnah, Zubair A; Ridgely, Ryan; Ngasala, Sifa E; Temba, Jesuit

    2010-08-01

    Fossil crocodyliforms discovered in recent years have revealed a level of morphological and ecological diversity not exhibited by extant members of the group. This diversity is particularly notable among taxa of the Cretaceous Period (144-65 million years ago) recovered from former Gondwanan landmasses. Here we report the discovery of a new species of Cretaceous notosuchian crocodyliform from the Rukwa Rift Basin of southwestern Tanzania. This small-bodied form deviates significantly from more typical crocodyliform craniodental morphologies, having a short, broad skull, robust lower jaw, and a dentition with relatively few teeth that nonetheless show marked heterodonty. The presence of morphologically complex, complementary upper and lower molariform teeth suggests a degree of crown-crown contact during jaw adduction that is unmatched among known crocodyliforms, paralleling the level of occlusal complexity seen in mammals and their extinct relatives. The presence of another small-bodied mammal-like crocodyliform in the Cretaceous of Gondwana indicates that notosuchians probably filled niches and inhabited ecomorphospace that were otherwise occupied by mammals on northern continents. PMID:20686573

  1. Paleogeography of Southwest Gondwana Boundary During the Upper Paleozoic

    NASA Astrophysics Data System (ADS)

    Tomezzoli, R. N.

    2005-05-01

    Current results are summarized from the southwest Gondwana boundary, from rocks from La Pampa province, Argentina. This area is the westward part of an orogenic belt, known as Sam Frau geosincline or Cordón de las Gondwánides and may represent the suture zone between the Gondwana and Patagonia terranes. This collision model is still uncertain and there are many controversies related to the age of the deformation of this belt. Paleomagnetism and the exploration of the magnetic fabric signatures (AMS) can be useful to evaluate the regional deformation and a better understanding of the assembly, deformation, and fragmentation of Gondwana / Pangea. A systematic paleomagnetic study was done in the Cerro Centinela: 36/deg S, 67/deg W, belong to the Choiyoi Group and consist of Lower Paleozoic volcanic rocks. In this paleomagnetic study is present results from 19 sites (84 specimens), sampled from the base to the top in different layers. Samples were demagnetized with thermal procedures. A high un¬blocking temperature component carried by hematite was defined between 580° C and 680° C, showing very good within site consistency (alpha 95<15° and k>20). Remanent magnetization ranges around 1500 mA m-1. In all samples it was possible to isolate one component with the same behavior and positive inclination. These stable remanent magnetization were group into two different Population: 1 and 2, clearly separated. Population 1 (from sites 1 to 12) in situ mean direction is: D=146°, I=63.5°, alpha 95=4°, k=104, N=12. Population 2 (from sites 13 to 19) in situ mean direction is: D=164°, I=42°, alpha 95=4°, k=197, N=7. Reversed characteristic remanence magnetization suggesting that the magnetization was acquired during the Kiaman interval, in accordance with their age. Two high quality paleomagnetic poles were computed for each population on the basis of the in situ remanence directions. The corresponding PP are for Population 1: 63° S, 353° E, Alpha 95=7 and K=44 and for Population 2: 71° S, 60° E, Alpha 95=5, K=169. These two poles are consistent with the age of the rocks and with others PP from the Gondwánides, and are reflecting a huge displacement of the continent during the Permian, before the final assembly of the Pangea.

  2. Bunbury Basalt: Gondwana breakup products or earliest vestiges of the Kerguelen mantle plume?

    NASA Astrophysics Data System (ADS)

    Olierook, Hugo K. H.; Jourdan, Fred; Merle, Renaud E.; Timms, Nicholas E.; Kusznir, Nick; Muhling, Janet R.

    2016-04-01

    In this contribution, we investigate the role of a mantle plume in the genesis of the Bunbury Basalt using high-precision 40Ar/39Ar geochronology and whole-rock geochemistry, and by using crustal basement thickness of the eastern Indian Ocean and the western Australian continent. The Bunbury Basalt is a series of lava flows and deep intrusive rocks in southwestern Australia thought to be the earliest igneous products from the proto-Kerguelen mantle plume. Nine new plateau ages indicate that the Bunbury Basalt erupted in three distinct phases, at 136.96 ± 0.43 Ma, 132.71 ± 0.43 Ma and 130.45 ± 0.82 Ma. All Bunbury Basalt samples are enriched tholeiitic basalts with varying contributions from the continental lithosphere that are similar to other Kerguelen plume-products. Based on plate reconstructions and the present geochronological constraints, the eruption of the oldest Bunbury Basalt preceded the emplacement of the Kerguelen large igneous province by at least 10-20 m.y. Such age differences between a precursor and the main magmatic event are not uncommon but do require additional explanation. Low crustal stretching factors beneath the Bunbury Basalt (β ≈ 1.4) indicate that decompression melting could not have been generated from asthenospheric mantle with a normal chemistry and geotherm. An elevated geotherm from the mantle plume coupled with the geochemical similarity between the Bunbury Basalt and other Kerguelen plume-products suggests a shared origin exists. However, new age constraints of the oldest Bunbury Basalt are synchronous with the breakup of eastern Gondwana and the initial opening of the Indian Ocean at ca. 137-136 Ma, which may mean an alternative explanation is possible. The enriched geochemistry can equally be explained by a patch of shallow mantle beneath the southern Perth Basin. The patch may have been enriched during Gondwana suturing at ca. 550-500 Ma, during early rifting events by magmatic underplating or by intruded melts into the subcontinental lithospheric mantle. This enriched geochemical signature would then be sufficient to trigger decompression melting from passive rifting between Greater India and Australia with no contribution from the Kerguelen hotspot. We conclude that although the proto-Kerguelen hotspot is certainly a possible explanation for the genesis of the Bunbury Basalt, decompression melting of an enriched patch of subcontinental lithospheric mantle is an alternative theory.

  3. Blindsnake evolutionary tree reveals long history on Gondwana

    PubMed Central

    Vidal, Nicolas; Marin, Julie; Morini, Marina; Donnellan, Steve; Branch, William R.; Thomas, Richard; Vences, Miguel; Wynn, Addison; Cruaud, Corinne; Hedges, S. Blair

    2010-01-01

    Worm-like snakes (scolecophidians) are small, burrowing species with reduced vision. Although largely neglected in vertebrate research, knowledge of their biogeographical history is crucial for evaluating hypotheses of snake origins. We constructed a molecular dataset for scolecophidians with detailed sampling within the largest family, Typhlopidae (blindsnakes). Our results demonstrate that scolecophidians have had a long Gondwanan history, and that their initial diversification followed a vicariant event: the separation of East and West Gondwana approximately 150 Ma. We find that the earliest blindsnake lineages, representing two new families described here, were distributed on the palaeolandmass of India+Madagascar named here as Indigascar. Their later evolution out of Indigascar involved vicariance and several oceanic dispersal events, including a westward transatlantic one, unexpected for burrowing animals. The exceptional diversification of scolecophidians in the Cenozoic was probably linked to a parallel radiation of prey (ants and termites) as well as increased isolation of populations facilitated by their fossorial habits. PMID:20356885

  4. Early breakup of Gondwana: constraints from global plate motion models

    NASA Astrophysics Data System (ADS)

    Seton, Maria; Zahirovic, Sabin; Williams, Simon; Whittaker, Joanne; Gibbons, Ana; Muller, Dietmar; Brune, Sascha; Heine, Christian

    2015-04-01

    Supercontinent break-up and amalgamation is a fundamental Earth cycle, contributing to long-term sea-level fluctuations, species diversity and extinction events, long-term greenhouse-icehouse cycles and changes in the long-wavelength density structure of the mantle. The most recent and best-constrained example involves the fragmentation of Gondwana, starting with rifting between Africa/Madagascar and Antarctica in the Early Jurassic and ending with the separation of the Lord Howe microcontinental blocks east of Australia in the Late Cretaceous. Although the first order configuration of Gondwana within modern reconstructions appears similar to that first proposed by Wegener a century ago, recent studies utilising a wealth of new geophysical and geological data provide a much more detailed picture of relative plate motions both during rifting and subsequent seafloor spreading. We present our latest global plate motion model that includes extensive, new regional analyses. These include: South Atlantic rifting, which started at 150 Ma and propagated into cratonic Africa by 145 Ma (Heine et al., 2013); rifting and early seafloor spreading between Australia, India and Antarctica, which reconciles the fit between Broken Ridge-Kergulean Plateau and the eastern Tasman region (Whittaker et al., 2013); rifting of continental material from northeastern Gondwana and its accretion onto Eurasia and SE Asia including a new model of microcontinent formation and early seafloor spreading in the eastern Indian Ocean (Gibbons et al., 2012; 2013; in review; Williams et al., 2013; Zahirovic et al., 2014); and a new model for the isolation of Zealandia east of Australia, with rifting initiating at 100 Ma until the start of seafloor spreading in the Tasman Sea at ~85 Ma (Williams et al., in prep). Using these reconstructions within the open-source GPlates software, accompanied by a set of evolving plates and plate boundaries, we can explore the factors that govern the behavior of plate motions during supercontinent break-up and subsequent dispersal. For example, a global analysis of absolute plate velocities over the past 200 million years shows that plates dominated by continental material and bounded by transforms and mid-ocean ridge segments, as is characteristic of plates involved in Gondwana break-up, have average speeds of ~2.6-2.8 cm/yr RMS. In contrast, oceanic plates surrounded by subduction have average speeds of ~8.5 cm/yr RMS. An exception, however, is the rapid motion of India (~18 cm/yr RMS) in the Paleocene preceding its collision with Eurasia, which suggests that plates with continental and cratonic keels can exhibit short-lived (~10 Myr) accelerations resulting from a combination of plume head arrival effects and other complementary plate boundary forces (i.e., slab pull and ridge push). In another example, our reconstructions illustrate that a spectrum of rifting styles from orthogonal to oblique is present during rifting, rather than dominantly orthogonal as often assumed. Although our approach has so far been limited to one supercontinent cycle, these types of models can be extended to cover the entire Phanerozoic, capturing continental rifting and plate behavior over several supercontinent cycles.

  5. Gondwana breakup and plate kinematics: Business as usual

    NASA Astrophysics Data System (ADS)

    Eagles, Graeme; Vaughan, Alan P. M.

    2009-05-01

    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.

  6. Permian-Triassic Magmatism Along the Southern Gondwana Margin: Correlating Proximal and Distal Volcanic Deposits

    NASA Astrophysics Data System (ADS)

    McKay, M. P.; Weislogel, A. L.; Fildani, A.

    2014-12-01

    Active margins are dominated by erosion, structural deformation, tectonic dissection, and igneous intrusions. These destructive processes lead to an incomplete record of past magmatism in active margins. Volcanic airfall tuffs that are transported and deposited in distal sedimentary basins may be more likely to be preserved in the rock record. Tuffs, however, may be affected by atmospheric fractionation during transport, postdepositional weathering, and diagenesis during burial, potentially altering ash texture, mineralogy, and geochemistry. We use outcrop observations, stratigraphic relationships, whole rock geochemistry, U-Pb zircon geochronology, and zircon rare-earth element geochemistry from Permian-Triassic strata of South Africa and South America to correlate distal volcanic ashes to proximal volcanic deposits and plutonic suites within southern Gondwana. U-Pb zircon signals of the tuffs are treated as "detrital"; the distinct zircon signals were then used to correlate distal airfall ashes to potential magmatic sources. This suggests that airfall fractionation of zircon populations is not a significant concern in tuff geochronology. Additionally, zircon inheritance may be a useful tool in matching far-traveled ashes with parental magmatic suites. Although previous studies have shown that the geochemistry of volcanic tuff deposits varies with distance from the volcanic vent, we employ whole rock and zircon REE compositions to differentiate distinct magmatic periods using distal ashes that were deposited >750 km from the volcanic source. The results of this study support a geochronologic interpretation that the Karoo strata of S. Africa are >10 Ma younger than previously thought based on biostratigraphy. Since the Karoo basin is heavily studied as a record of the end-Permian extinction and paleoclimate change, our results have major implication for this key time in Earth History.

  7. Micro-continents offshore Western Australia: implications for East Gondwana reconstructions

    NASA Astrophysics Data System (ADS)

    Whittaker, Joanne; Williams, Simon; Halpin, Jacqueline; Daczko, Nathan; Gardner, Robyn

    2014-05-01

    The southern part of the Western Australian margin formed at the nexus of rifting and breakup between the East Gondwanan continents India, Australia and Antarctica in the Early Cretaceous. However, understanding the basin evolution along this margin has been hampered by a lack of data from the offshore Perth Abyssal Plain, and from the conjugate Greater Indian margin, which was highly deformed during collision with Eurasia. The Batavia Knoll and Gulden Draak Knoll are two prominent, previously unsampled, bathymetric features located >1600 km offshore Australia that have typically been assumed to be igneous features. In late 2011, successful dredges on the western flanks of both knolls recovered continental basement rocks, revealing that both knolls are micro-continents. Felsic orthogneiss and granite from Gulden Draak and Batavia knolls yield 2.8 Ga, 1.3-1.2 Ga and 540-510 Ma U-Pb zircon ages. The affinity of these geological samples, coupled with existing geological sampling and geophysical data, allow us to test alternative reconstructions for East Gondwana breakup. A number of alternative models have been proposed for the pre-rift configuration of Australia and Antarctica. Competing models make very different predictions for the kinematics of Mesozoic rifting that produced the basins along the Southern Australian margin; the magnitude of extension during rifting; and how mapped Paleozoic and Proterozoic geological terranes and fault zones can be correlated between Australia and Antarctica. We will present reconstructions that reconcile our new samples from Indian Ocean micro-continents with observations from India, Antarctica, Australia, and the evolution of the Indian Ocean.

  8. A synopsis of events related to the assembly of eastern Gondwana

    NASA Astrophysics Data System (ADS)

    Meert, Joseph G.

    2003-02-01

    The assembly of the eastern part of Gondwana (eastern Africa, Arabian-Nubian shield (ANS), Seychelles, India, Madagascar, Sri Lanka, East Antarctica and Australia) resulted from a complex series of orogenic events spanning the interval from 750 to 530 Ma. Although the assembly of Gondwana is generally discussed in terms of the suturing of east and west Gondwana, such a view oversimplifies the true nature of this spectacular event. A detailed examination of the geochronologic database from key cratonic elements in eastern Gondwana suggests a multiphase assembly. The model outlined in this paper precludes the notion of a united east Gondwana and strongly suggests that its assembly paralleled the final assembly of greater Gondwana. It is possible to identify at least two main periods of orogenesis within eastern Gondwana. The older orogen resulted from the amalgamation of arc terranes in the Arabian-Nubian shield region and oblique continent-continent collision between eastern Africa (Kenya-Tanzania and points northward) with an, as of yet, ill-defined collage of continental blocks including parts of Madagascar, Sri Lanka, Seychelles, India and East Antarctica during the interval from 750 to 620 Ma. This is referred to as the East Africa Orogen (EAO) in keeping with both the terminology and the focus of the paper by Stern [Annu. Rev. Earth Planet. Sci. 22 (1994) 319]. The second major episode of orogenesis took place between 570 and 530 Ma and resulted from the oblique collision between Australia plus an unknown portion of East Antarctica with the elements previously assembled during the East African Orogen. This episode is referred to as the Kuunga Orogeny following the suggestion of Meert et al. [Precambrian Res. 74 (1995) 225]. Paleomagnetic data are currently too few to provide a rigorous test of this proposal, but the extant data do not conflict with the notion of a polyphase assembly of eastern Gondwana. The major conclusion of this paper is that east Gondwana did not exist until its Cambrian assembly.

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

    PubMed

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

    2011-03-01

    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

  10. Seasonal levels of radon and thoron in the dwellings along southern coastal Orissa, Eastern India.

    PubMed

    Sulekha Rao, N; Sengupta, D

    2010-01-01

    Inhalation of radon ((222)Rn) and thoron ((220)Rn) are a major source of natural radiation exposure. Indoor radon-thoron study has been carried out in some dwellings of Ganjam district, southern coastal Orissa, India using LR-115 type II plastic track detectors. Seasonal variation of indoor radon and thoron shows high values in winter and low values in both summer and rainy. The inhalation dose lies in the range of 0-0.06muSvh(-1) and is not high from those found elsewhere in India. PMID:19822438

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

    PubMed

    Pati, Biswamoy

    2002-01-01

    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

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

    ERIC Educational Resources Information Center

    Ekstrand, Gudrun, Ed.

    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…

  13. Palynological records of Gondwana's mid-Permian climate amelioration: New insights from black shale deposits (Collingham Formation, South Africa)

    NASA Astrophysics Data System (ADS)

    Gtz, Annette E.

    2015-04-01

    Permian black shale deposits of the southern Karoo Basin were studied with respect to palynostratigraphy, palaeoenvironment, and palaeoclimate signatures recorded in palynomorph assemblages. The 28 m thick black shales of the Collingham Formation, exposed along road cuttings of the Ecca Pass north of Grahamstown (Eastern Cape Province, South Africa), are rich in sedimentary organic matter with a high content of amorphous organic matter and prasinophytes, characteristic of a deep, stratified marine basin. Moderately preserved pollen grains of the lower part of the formation reveal a mid-Permian (Roadian) age, corresponding to the stratigraphic position of the Collingham Formation in the Namibian part of the Karoo with an absolute age of 270 Ma obtained from a tuff (Stollhofen et al., 2000). The samples from the lower Collingham Formation show a very similar composition as samples from coal seams of the upper Vryheid Formation in the northeastern part of the Karoo Basin. Additionally, a similar stratigraphic trend in changes of palynomorph assemblages was detected, showing a striking increase in taeniate bissacate pollen grains up section. This signature points to a warm-temperate bisaccate-producing plant community in the hinterland, replacing cool-temperate floras of the underlying Whitehill Formation (Ruckwied et al., 2014). The detected palaeoclimate signatures document Gondwana's mid-Permian climate amelioration and have proved to be a powerful tool for high-resolution basin-wide correlation of marine and non-marine successions. References Ruckwied, K., Gtz, A.E., Jones, P. 2014. Palynological records of the Permian Ecca Group (South Africa): Utilizing climatic icehouse-greenhouse signals for cross basin correlations. Palaeogeography, Palaeoclimatology, Palaeoecology 413, 167-172. Stollhofen, H., Stanistreet, I.G., Bangert, B., Grill, H. 2000. Tuffs, tectonism and glacially related sea-level changes, Carboniferous-Permian, southern Namibia. Palaeogeography, Palaeoclimatology, Palaeoecology 161, 127-150.

  14. Arabian Shield magmatic cycles and their relationship with Gondwana assembly: Insights from zircon U-Pb and Hf isotopes

    NASA Astrophysics Data System (ADS)

    Robinson, F. A.; Foden, J. D.; Collins, A. S.; Payne, J. L.

    2014-12-01

    The Arabian Shield preserves a protracted magmatic record of amalgamated juvenile terranes that host a diverse range of early Neoproterozoic to Cambrian granitoids intruding volcanosedimentary basin assemblages that have corollaries in other parts of the East African Orogen. New zircon U-Pb geochronology of 19 granitoids intruding eight Arabian Shield terranes, define four discrete magmatic events: island arc (?845 Ma), syncollisional (?710 Ma), post-tectonic (?620 Ma) and anorogenic (?525 Ma). Zircon Lu-Hf isotopic analyses indicate that all studied granitoids are juvenile with typical ?Hf values of >+5 to +10 and Stenian-Tonian (?1100-900 Ma) model ages, regardless of their precise intrusive ages or spatial relationship. Subtle changes in isotopic signatures between ?850 and 600 Ma, suggest the result from changes in granite source materials brought about by; basaltic underplating, limited crustal interaction with Palaeoproterozoic basement and a change to lithospheric delamination/subduction roll-back processes driving juvenile ANS crustal growth. The cycle of granite intrusion reflects accretionary cycles initiated during Mozambique Ocean closure and during Gondwana amalgamation and final assembly. Post-tectonic magmatism is divided into a ?636-600 Ma phase and post 600 Ma event that reflects first subduction and then within-plate related processes. The identification of magmatism at ?525 Ma is now the youngest granitoid identified so far in the Saudi Arabian Shield and may change the identified age of the regional, basal Palaeozoic unconformity. This late magmatism may be generated by the Najd Fault reactivation correlating with the Malagasy/Kunnga Orogeny that marked the final stages of Gondwana assembly.

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

    NASA Astrophysics Data System (ADS)

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

    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.

  16. Gondwana Tales: an inquiry approach to plate tectonics

    NASA Astrophysics Data System (ADS)

    Domènech Casal, Jordi

    2014-05-01

    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.

  17. A key Temporal and Spatial Constraint for India in the Neoproterozoic: Implications for Eastern Gondwana

    NASA Astrophysics Data System (ADS)

    Gregory, L. C.; Meert, J. G.; Bingen, B.; Pandit, M. K.; Torsvik, T. H.

    2008-05-01

    The late Neoproterozoic, c. 550 Ma, marks the estimated final assembly of the supercontinent Gondwana. Paleogeography of major cratons is relatively well established within Gondwana, but individual continental paleolocations prior to final Gondwana suturing are often poorly constrained. It is generally accepted that components of western Gondwana were not a coherent group prior to the late Neoproterozoic, and that the Neoproterozoic assembly of these cratons was complex and polyphase. The amalgamation of eastern Gondwana cratons is more elusive, and is commonly described as one of two contrasting models. Eastern Gondwana cratons either existed as a longstanding stable group throughout the mid to late Proterozoic, or were assembled in a more complex manner in the late Proterozoic with the suturing of Gondwana. Key temporal and spatial constraints on continent locations have crucial implications for testing models of both eastern and western Gondwana amalgamation. New paleomagnetic and geochronologic data from the Malani Igneous Suite (MIS), Rajasthan, Central India, improve the paleogeographic reconstruction of the Indian subcontinent (eastern Gondwana) between dispersal of the supercontinent Rodinia and Neoproterozoic assembly of Gondwana. The MIS comprises a voluminous initial phase of felsic and mafic volcanism followed by granitic plutonism. A zircon U-Pb age on a rhyolitic tuff constrains initial volcanism in the MIS to 771 ±5 Ma. Large (up to 5 m wide) mafic dikes mark the final phase of igneous activity. A virtual geomagnetic pole from 4 mafic dikes has a declination=358.8 and inclination=63.5 (with k=91.2 and α95=9.7). This normal polarity direction includes a fine-grained mafic dikelet that showed a reversed direction with declination=195.3 and inclination=-59.7 (k=234.8 and α95=8.1) and also records an overprint of normal polarity from the larger dikes. The VGP obtained from this study on mafic dikes is combined with previous studies of the Malani suite to obtain a mean paleomagnetic pole of 67.8N, 72.5E (A95=8.8). Supported by a tentative baked contact test, we argue that this pole is primary, and permits improved reconstruction of the Indian subcontinent at around 770 Ma. Data on the MIS, and equivalent data on Seychelles at 750 ±3 Ma, are compared with paleomagnetic data on the 755 ±3 Ma Mundine Well dikes in Australia, to indicate a latitudinal separation of nearly 45 between the reconstructed Indian plate and its location in a traditional Gondwana fit. This suggests that East Gondwana was not amalgamated at c. 750 Ma and therefore that these two cratons were assembled later into the Gondwana supercontinent, during the Pan-African c. 550 Ma Kuunga Orogeny.

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

    PubMed

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

    2013-01-01

    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

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

    PubMed Central

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

    2009-01-01

    In November 2003, an outbreak (41 cases; attack rate4.3%; 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 1.244.1). 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. PMID:19902800

  20. Amalgamating eastern Gondwana: The evolution of the Circum-Indian Orogens

    NASA Astrophysics Data System (ADS)

    Collins, Alan S.; Pisarevsky, Sergei A.

    2005-08-01

    The Neoproterozoic global reorganisation that saw the demise of Rodinia and the amalgamation of Gondwana took place during an incredibly dynamic period of Earth evolution. To better understand the palaeogeography of these times, and hence help quantify the interrelations between tectonics and other Earth systems, we here integrate Neoproterozoic palaeomagnetic solutions from the various blocks that made up eastern Gondwana, with the large amount of recent geological data available from the orogenic belts that formed as eastern Gondwana amalgamated. From this study, we have: (1) identified large regions of pre-Neoproterozoic crust within late Neoproterozoic/Cambrian orogenic belts that significantly modify the geometry and number of continental blocks present in the Neoproterozoic world; (2) suggested that one of these blocks, Azania, which consists of Archaean and Palaeoproterozoic crust within the East African Orogen of Madagascar, Somalia, Ethiopia and Arabia, collided with the Congo/Tanzania/Bangweulu Block at 650-630 Ma to form the East African Orogeny; (3) postulated that India did not amalgamate with any of the Gondwana blocks until the latest Neoproterozoic/Cambrian forming the Kuunga Orogeny between it and Australia/Mawson and coeval orogenesis between India and the previously amalgamated Congo/Tanzania/Bangweulu-Azania Block (we suggest the name 'Malagasy Orogeny' for this event); and, (4) produced a palaeomagnetically and geologically permissive model for Neoproterozoic palaeogeography between 750 and 530 Ma, from the detritus of Rodinia to an amalgamated Gondwana.

  1. Ferrar magmatic province rocks discovered in New Zealand: Implications for Mesozoic Gondwana geology

    NASA Astrophysics Data System (ADS)

    Mortimer, N.; Parkinson, D.; Raine, J. I.; Adams, C. J.; Graham, I. J.; Oliver, P. J.; Palmer, K.

    1995-02-01

    On the basis of similar ages, major and trace element concentrations, and Sr, Nd, and Pb isotopic ratios, we correlate the Kirwans Dolerite of western New Zealand with Jurassic low-Ti tholeiites of the well-known Ferrar magmatic province of Gondwana. Field relations and preliminary paleomagnetic data also support this correlation. Although the 1 km2 Kirwans Dolerite is the first, and so far only, Ferrar correlative to be reported from New Zealand, it considerably increases the known shape and areal extent of the Ferrar province to close to the paleo-Gondwana margin. The presence of Ferrar rocks in New Zealand can be used to test several models of Ferrar magma genesis and Gondwana regional tectonics.

  2. Potential geodynamic relationships between the development of peripheral orogens along the northern margin of Gondwana and the amalgamation of West Gondwana

    NASA Astrophysics Data System (ADS)

    Murphy, J. Brendan; Pisarevsky, Sergei; Nance, R. Damian

    2013-10-01

    The Neoproterozoic-Early Cambrian evolution of peri-Gondwanan terranes (e.g. Avalonia, Carolinia, Cadomia) along the northern (Amazonia, West Africa) margin of Gondwana provides insights into the amalgamation of West Gondwana. The main phase of tectonothermal activity occurred between ca. 640-540 Ma and produced voluminous arc-related igneous and sedimentary successions related to subduction beneath the northern Gondwana margin. Subduction was not terminated by continental collision so that these terranes continued to face an open ocean into the Cambrian. Prior to the main phase of tectonothermal activity, Sm-Nd isotopic studies suggest that the basement of Avalonia, Carolinia and part of Cadomia was juvenile lithosphere generated between 0.8 and 1.1 Ga within the peri-Rodinian (Mirovoi) ocean. Vestiges of primitive 760-670 Ma arcs developed upon this lithosphere are preserved. Juvenile lithosphere generated between 0.8 and 1.1 Ga also underlies arcs formed in the Brazilide Ocean between the converging Congo/So Francisco and West Africa/Amazonia cratons (e.g. the Tocantins province of Brazil). Together, these juvenile arc assemblages with similar isotopic characteristics may reflect subduction in the Mirovoi and Brazilide oceans as a compensation for the ongoing breakup of Rodinia and the generation of the Paleopacific. Unlike the peri-Gondwanan terranes, however, arc magmatism in the Brazilide Ocean was terminated by continent-continent collisions and the resulting orogens became located within the interior of an amalgamated West Gondwana. Accretion of juvenile peri-Gondwanan terranes to the northern Gondwanan margin occurred in a piecemeal fashion between 650 and 600 Ma, after which subduction stepped outboard to produce the relatively mature and voluminous main arc phase along the periphery of West Gondwana. This accretionary event may be a far-field response to the breakup of Rodinia. The geodynamic relationship between the closure of the Brazilide Ocean, the collision between the Congo/So Francisco and Amazonia/West Africa cratons, and the tectonic evolution of the peri-Gondwanan terranes may be broadly analogous to the Mesozoic-Cenozoic closure of the Tethys Ocean, the collision between India and Asia beginning at ca. 50 Ma, and the tectonic evolution of the western Pacific Ocean.

  3. A tectonic reconstruction of accreted terranes along the paleo-Pacific margin of Gondwana

    NASA Astrophysics Data System (ADS)

    Bammel, Brandon

    The southern oceanic margin of Gondwana was nearly 40,000 km long or 24,854.8 miles. The southern margin was the result of the Terra Australis orogen. Spanning 18,000 km or 11,184.7 miles and is proposed as one of the largest and longest lived orogens in Earth history. The paleo-Pacific margin of Gondwana consisted of segments of the Australian-Antarctic craton, southern South America (modern Argentina and Chile), southern South Africa, Marie Byrdland, New Zealand and its adjacent continental shelf, the Ellsworth Mountains, and the Transantarctic Mountains. The process of terrane accretion has played a substantial part in the assembly of the continents as they look today. The paleo-Pacific margin of Gondwana was an active region of terrane accretion from the Neoproterozoic to the Late Mesozoic. This research study examines the accretion of terranes across the paleo-Pacific Gondwana margin to provide a comprehensive reconstruction. A paleogeographic basemap was created using PALEOMAP Project maps and the geology data was provided by the School of Geoscience from the University of Witwatersrand of South Africa. Location and data analyzed for terranes were collected building a PDF library of journal articles across numerous geological publications.

  4. Neoproteozoic to Cambrian Tectonic Evolution of the Proto-Andean Margin of Gondwana: Implications for the Opening of Iapetus

    NASA Astrophysics Data System (ADS)

    van Staal, C. R.; Escayola, M.; Davis, B.

    2009-05-01

    We present a new tectonic model for the Pampean accretion of the Arequipa-Antofalla-Pampia (AAP) ribbon continent to the Proto-Andean margin of Gondwana represented by the Amazonia and Rio de La Plata cratons, based on our studies of the Puncoviscana Formation in northern and central Argentina. A compilation of existing detrital zircon ages of the Puncoviscana Formation and correlative units along strike in the Pampean orogenic belt to the south combined with our new U-Pb SHRIMP zircon ages of Puncoviscana Formation felsic tuffs and mafic volcaniclastic rocks (c. 531 Ma) suggests this unit mainly represents an Early Cambrian arc- trench gap to foreland basin succession formed during east-directed closure of a late Neoproterozoic marginal basin. The marginal basin, which probably remained relatively narrow, initially had opened behind an east- facing 650-570 Ma island arc (eastern Pampia arc), built upon the rifted, leading edge of the AAP. The 531 Ma felsic tuffs are interpreted to represent the products of a new, short-lived Early Cambrian magmatic arc built upon the now composite Proto-Andean margin, following Late Neoproterozoic, soft-accretion of the eastern Pampia arc and a subduction polarity reversal. Puncoviscana Formation conglomerates previously interpreted as early rift-related deposits are better interpreted as late-orogenic basin fills and/or were deposited after basin closure. Our new U-Pb zircon age of the post-collision Canani tonalite (c. 517 Ma), which intruded into Tilcarian deformed Puncoviscana Formation rocks in the north westernmost part of Argentina in the Puncoviscana type locality, combined with the existing 529-517 Ma zircon ages for post-collision peraluminous granites and tonalites in the Eastern Pampean Ranges to the south indicates that the synorogenic Puncoviscana Formation formed between 540 and 517 Ma, progressively cannibalizing its orogenic hinterland over time. In addition, the Tilcarian and Pampean orogenies represent the same event. We suggest that AAP rifted-off from Laurentia between 700 and 650 Ma, shortly after Amazonia's departure during Rodinia's break-up. We emphasize that it is the departure of AAP, not Amazonia that opened Iapetus in the Late Neoproterozoic. We also suggest that Ganderia in the northern Appalachians, originally formed an extension of the AAP.

  5. Luminescence dating of the barrier spit at Chilika Lake, Orissa, India.

    PubMed

    Murray, A S; Mohanti, M

    2006-01-01

    Optically stimulated luminescence dating has been used to investigate the chronological development of the outer barrier spit forming Chilika Lake (Orissa, India), the largest brackish-water lagoon in Asia. Sixteen samples were examined, and these yielded equivalent doses of between 153 +/- 3 mGy and 2.23 +/- 0.07 Gy, corresponding to ages from approximately 40 y at the top of the spit to approximately 300 y at the bottom. The youngest ages are consistent with the age of the overlying vegetation, and modern material taken from the sub-tidal beach gave a dose of 4 +/- 2 mGy (corresponding to an age of 0.7 +/- 0.4 y), confirming that any previous potential luminescence signal in the source sediment is completely set to zero before incorporation into the spit. A clearly defined period of >2.5 m of barrier construction approximately 40 y ago is identified; prior to that the deposition rate was relatively constant for approximately 300 y. PMID:16565209

  6. Politics of Co-Optation: Community Forest Management Versus Joint Forest Management in Orissa, India

    NASA Astrophysics Data System (ADS)

    Nayak, Prateep K.; Berkes, Fikret

    2008-05-01

    The article considers the impact of introducing government co-management policy in the form of Joint Forest Management (JFM) in an area with a five-decade-old self-organized community forest management system in Orissa, India. We ask a question that appears not to have been previously examined: What happens when JFM replaces an already existing community forest management arrangement? Our comparison of the JFM arrangement with the self-organized community forest management regime (pre- and post-2002 in a selected village) provides three conclusions: (1) The level of villager participation in forest management has declined, along with the erosion of the bundle of common rights held by them; (2) multiple institutional linkages between the village and outside agencies, and reciprocal relations with neighboring villages have been abandoned in favor of a close relationship with the Forestry Department; and (3) the administration of the forestry resource has become politicized. We conclude that the one-size-fits-all approach of the JFM, with its pre-packaged objectives and its narrow scope of forest management, is likely to limit experimentation, learning, and institutional innovation that characterizes community forest management.

  7. Disaster management for Nandira watershed district Angul (Orissa) India, using temporal Remote Sensing data and GIS.

    PubMed

    Gupta, P K; Singh, A P

    2005-05-01

    NALCO--the largest exporter of aluminium in India has a power plant of 720 MW capacity in Nandira watershed in Angul district of Orissa. The power plant utilises local coal to generate thermal power and disposes of large amount of ash which accumulates in slurry form at nearby two ash ponds. These ash ponds were breached on 31 December 2000, causing ash accumulation for entire regime of the Nandira river. An attempt has been made towards preparation of recovery and rehabilitation plan for NALCO using temporal Remote Sensing data and GIS. Indian remote sensing satellite data for pre-breach condition 12 December 2000, during breach event 31 December 2000 and post-breach condition 4 and 6 January 2001 has been digitally analysed for Nandira watershed. The satellite data of coarse spatial resolution provides the absence and presence of fresh sediment deposition along Nandira watershed and Brahmani river pertaining to pre-breach and post-breach conditions respectively on regional scales. The temporal comparison of fine resolution has clearly highlighted the aerial extent of damage caused by the disaster for entire watershed on local scales. The GIS has helped in demarcation of freshly accumulated ash at interval of 500 m along the river length as well as in delineation of maximum ash accumulation across the river width. The study has clearly demonstrated the use of temporal Remote Sensing data in conjunction with GIS for disaster management in terms of recovery and rehabilitation plan preparation of the Nandira watershed. PMID:15932001

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

    PubMed

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

    2009-01-01

    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

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

    PubMed

    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

    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

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

    NASA Astrophysics Data System (ADS)

    Hoffman, Paul F.

    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 Laurentia and the combined African cratons of Congo and Kalahari, which were loosely joined after 820 Ma. Simultaneously, the Adamastor (Brasilide) Ocean closed by subduction bordering the West Gondwana cratons, drawing virtually all of Gondwana together by 550 Ma. The final assembly of Gondwana occurred contemporaneously with the separation of Laurentia from West Gondwana. It has been postulated that the imprint of Rodinia's long-lived existence on lower mantleconvection produced a prolate ellipsoidal geoid figure. This could give rise to episodic inertial interchange true polar wander (IITPW), meaning that the entire silicate shell of the Earth (above the core-mantle boundary) rolled through 90 with respect to the diurnal spin axis in 15 Ma (equivalent to an apparent polar wander velocity of 66 cm a -1. Although empirical arguments for IITPW of Cambrian age appear to be flawed, evidence for an ultra-fast ( > 40 cm a -1) meridional component of apparent polar wander for Laurentia between 564 and 550 Ma suggests that IITPW might have occurred at that time. The break-up of Rodinia increased the continental margin area and preferential organic C burial globally, which is reflected by high ? 13C values in seawater proxies. The consequent drawdown of CO 2 is implicated in a succession of runaway ice-albedo catastrophes between 750 and 570 Ma, during each of which the oceans completely froze over. Each "snowball" Earth event must have lasted for millions of years because their terminations depended on extreme CO 2 levels, built up by subaerial volcanic outgassing in the absence of sinks for C. A succession of ice-albedo catastrophes, each terminated under ultra-greenhouse conditions, must have imposed an intense environmental filter on the evolution of life. They may have triggered the radiation of Ediacaran fauna in the aftermath of the final snowball event. It is increasingly recognised that the Late Neoproterozoic was one of the most remarkable periods in Earth history, and it appears to exemplify the interplay of tectonics, the environment and biology in deep time.

  11. A monozygotic twin pair with β-thalassemia carrier status in a Dudh Kharia tribal family of Orissa

    PubMed Central

    Balgir, R. S.

    2007-01-01

    BACKGROUND: The β-thalassemia syndrome is a genetically inherited commonly encountered hematological disorder in the state of Orissa. It causes high degree of morbidity, mortality and fetal wastage in the poor vulnerable people. AIMS AND OBJECTIVES: There is an equal probability (50% chance) in every singleton pregnancy that a carrier parent of β-thalassemia major would either bear normal or carrier offspring, but not two offspring with carrier of β-thalassemia major genotype together. For the first time, a carrier parent of β-thalassemia major gene has born progeny (three daughters and a twin male offspring) with a carrier status of β-thalassemia major in Dudh Kharia tribal family studied from Sundargarh district of Orissa. MATERIALS AND METHODS: We screened randomly selected population of Dudh Kharia tribe from Sundargarh district of Orissa for hemoglobinopathies to assess the extent of the problem, design possible interventions and provide genetic counseling to them. A family with twin children was identified during screening in Lata Gaon in Bargaon block of Sundargarh district of Orissa for the above-mentioned study. Background information for this family such as name, age, sex, tribe, native place, reproductive history, family pedigree and clinical signs and symptoms were also recorded. Standardized genetic and hematological procedures and techniques were followed for analysis. RESULTS: Laboratory investigations for alkaline electrophoresis of blood lysate on cellulose acetate membrane showed raised hemoglobin A2 level in mother (Hb A2 = 5.3%), in three daughters (Hb A2 =6.5, 5.9, 5.5% in chronological and birth order), in two twin sons (Hb A2 =5.9% and 6.0%) and normal (Hb A2 = 3.3%) for father. Hence, all the children i.e., three daughters and two twin sons, including the mother were β-thalassemia carriers. Since all the hematological parameters i.e., red cell indices, G-6-PD enzyme activity, ABO and Rhesus blood groups and identical β-thalassemia (trait) genotypes with identical clinical manifestations and hematological profile of the twin sons under similar environmental conditions, hence they were labeled as identical monozygotic twins. CONCLUSIONS: It is a rare occasion when a single pregnancy carries either one or two abnormal genotypes at a time in a womb in human beings. Monozygotic twins are genetically alike and provide appraisal of the expression of identical genotype under the different environmental conditions. PMID:21957337

  12. Bending and slicing of eastern Gondwana's continental margin: late Paleozoic to early Mesozoic reconstruction

    NASA Astrophysics Data System (ADS)

    Rosenbaum, G.; Li, P.; Babaahmadi, A.; Shaanan, U.; Mochales, T.

    2012-12-01

    The SW Pacific is a classic example of "ribbon tectonics" whereby continental fragments were either accreted to the continental margins by subduction processes or separated from it by backarc extension. While the more recent tectonic processes (e.g. the latest Mesozoic and Cenozoic opening of the Tasman Sea), are relatively well constrained, the earlier tectonic history of eastern Gondwana is poorly understood. Here we present results from onshore study in eastern Australia, showing that bending and fragmentation of eastern Gondwana's continental margin in a backarc extensional environment commenced at ~300 Ma, giving rise to large vertical-axis block rotations and oroclinal bending. The subduction zone has subsequently migrated eastward, in a series of episodes of trench rollback and backarc extension, alternating with episodes of contractional and transpressional tectonism. We attribute this behavior to switches between trench rollback and trench advance, controlled by the heterogeneous nature of the subducted oceanic lithosphere.

  13. Antibiotic use, resistance development and environmental factors: a qualitative study among healthcare professionals in Orissa, India

    PubMed Central

    2010-01-01

    Background Antibiotic resistance is a major public health problem affecting both current and future generations. The influence of environmental factors on antibiotic use and resistance development in bacteria is largely unknown. This study explored the perceptions of healthcare providers on antibiotic use and resistance development in relation to environmental factors i.e. physical, natural, social and behavioural factors. Methods A qualitative interview study was conducted using face-to-face, semi-structured interviews among registered allopathic doctors, veterinarians and drug dispensers in Orissa, India. The interview transcripts were analyzed using latent content analysis. Results The main findings of this study relate to two themes: 'Interrelationship between antibiotic use, resistance development and environment' and 'Antibiotic management contributing to the development and spread of resistance'. The interviewees viewed the following as possible contributors to antibiotic use/misuse and resistance development: changes in the natural and physical environment i.e. climate variability, pollution, physiography and population growth; the socioeconomic environment affecting health-seeking behaviour and noncompliance with medication; a lack of healthcare facilities and poor professional attitudes; and ineffective law enforcement regarding medicine dispensing and disposal. Conclusions Generally, the interviewees perceived that although behavioural and social environmental factors are major contributors to resistance development, changes in the physical and natural environment also influence development of antibiotic resistance. The respondents also perceived that there is a lack of information about, and poor awareness of, what constitutes prudent use of antibiotics. They suggested a need for information, education, dissemination and proper implementation and enforcement of legislation at all levels of the drug delivery and disposal system in order to improve antibiotic use and prevent pharmaceutical contamination of the environment. PMID:20964815

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

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

    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.

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

    PubMed Central

    2013-01-01

    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. PMID:23565668

  16. 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

    Svensson, Anna

    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…

  17. A Cambrian Arc Built on the Neoproterozoic Rifted Margin of Gondwana

    NASA Astrophysics Data System (ADS)

    Musgrave, R. J.

    2009-12-01

    Cambrian convergence along the northeastern side of the Curnamona Craton, the Gondwana margin in southeastern Australia, resulted in the development of the Delamerian Orogen. A Neoproterozoic rifted margin, marked by the alkalic Mount Arrowsmith Volcanics, forms the substrate on which is built a NE-facing Cambrian arc, complete with a clearly delineated inner imbricate accretionary prism (the Wonnaminta Zone) and outer thin-skinned wedge (the Kayrunnera Zone). Arc volcanism, represented by the calc-alkaline Mount Wright Volcanics, exhibits mixed arc-rift geochemistry. Interpretation and modelling of magnetic data reveals a chain of volcanic edifices of the Mount Wright Arc, now below 3 to 7 km of Devonian sandstones in the Bancannia Trough. Remarkably, a simple rotation around an Euler pole reconstructs the Wonnaminta Zone against the craton, and aligns structural elements on the two sides of the trough. Arc volcanism evidently occupied a rift in marginal continental crust, and the geometry, geochemistry and geophysical properties of the Mount Wright Arc are closely analogous to the Taupo Zone of New Zealand. Rifting of the arc divided Delamerian structures, indicating that at least part of the Delamerian deformation developed in a subduction accretion setting, rather than in some terminal collision. Below the Wonnaminta Zone a 3 to 5 km thick body can be traced as a large magnetic source along the length of the zone. Overridden by the thrust stack of the accretionary prism, this body is mostly planar and dips towards the east, although it is deformed into a broad antiform in the central part of the zone. Physical properties suggest that this body may be a thick rift-volcanic pile equivalent to the Mount Arrowsmith Volcanics. In the southern part of the belt a re-entrant in the Wonnaminta Zone faces a large magnetic anomaly sourced in the basement of the Kayrunnera Zone. The geometry of the re-entrant, and the development of Silurian and Devonian basins over the surrounds, suggests analogy with structures observed in modern accretionary margins associated with the subduction of seamounts. Bounding the Kayrunnera Zone to the northeast is the Thomson Orogen, a Neoproterozoic to early Palaeozoic structural zone largely covered by Mesozoic sediments. Deformation by the Late Ordovician to Silurian Benambran Orogeny affects both the Kayrunnera Zone and the Thomson Orogen. Seismic reflection indicates overprinted NE and SE facing thrusts below the Kayrunnera Zone, and deformation features project both towards and away from the Thomson Orogen. A plausible explanation interprets the Benambran Orogeny as an arc-arc collision between the Mount Wright Arc and a Thomson Arc. Propagation of the frontal thrust of the Thomson Arc resulted in capture of former Mount Wright fore-arc. This abstract is published with the permission of the Director, Geological Survey of NSW, Department of Industry & Investment.

  18. Late-Proterozoic to Paleozoic history of the peri-Gondwana Calabria-Peloritani Terrane inferred from a review of zircon chronology.

    PubMed

    Fornelli, Annamaria; Micheletti, Francesca; Piccarreta, Giuseppe

    2016-01-01

    U-Pb analyses of zircon from ten samples of augen gneisses, eight mafic and intermediate metaigneous rocks and six metasediments from some tectonic domains along the Calabria-Peloritani Terrane (Southern Italy) contribute to knowledge of peri-Gondwanan evolution from Late-Proterozoic to Paleozoic times. All samples were equilibrated under amphibolite to granulite facies metamorphism during the Variscan orogeny. The zircon grains of all considered samples preserve a Proterozoic memory suggestive of detrital, metamorphic and igneous origin. The available data fit a frame involving: (1) Neoproterozoic detrital input from cratonic areas of Gondwana; (2) Pan-African/Cadomian assemblage of blocks derived from East and West African Craton; (3) metamorphism and bimodal magmatism between 535 and 579 Ma, within an active margin setting; (4) rifting and opening of Ordovician basins fed by detrital input from the assembled Cadomian blocks. The Paleozoic basins evolved through sedimentation, metamorphism and magmatism during the Variscan orogeny involving Palaeozoic and pre-Paleozoic blocks. The Proterozoic zircon records decidedly decrease in the high grade metamorphic rocks affected by Variscan pervasive partial melting. PMID:27026906

  19. Measurement of Radon Exhalation Rate in Sand Samples from Gopalpur and Rushikulya Beach Orissa, Eastern India

    NASA Astrophysics Data System (ADS)

    Mahur, Ajay Kumar; Sharma, Anil; Sonkawade, R. G.; Sengupta, D.; Sharma, A. C.; Prasad, Rajendra

    Natural radioactivity is wide spread in the earth's environment and exists in various geological formations like soils, rocks, water and sand etc. The measurement of activities of naturally occurring radionuclides 226Ra, 232Th and 40K is important for the estimation of radiation risk and has been the subject of interest of research scientists all over the world. Building construction materials and soil beneath the house are the main sources of radon inside the dwellings. Radon exhalation rate from building materials like, cement, sand and concrete etc. is a major source of radiation to the habitants. In the present studies radon exhalation rates in sand samples collected from Gopalpur and Rushikulya beach placer deposit in Orissa are measured by using "Sealed Can technique" with LR-115 type II nuclear track detectors. In Samples from Rushikulya beach show radon activities varying from 389 24 to 997 38 Bq m-3 with an average value of 549 28 Bq m-3. Surface exhalation rates in these samples are found to vary from 140 9 to 359 14 mBq m-2 h-1with an average value of 197 10 mBq m-2 h-1, whereas, mass exhalation rates vary from 5 0.3 to 14 0.5 mBq kg-1 h-1 with an average value of 8 0.4 mBq kg-1 h-1. Samples from Gopalpur radon activities are found to vary from 371 23 to 800 34 Bq m-3 with an average value of 549 28 Bq m-3. Surface exhalation rates in these samples are found to vary from 133 8 to 288 12 mBq m-2h-1 with an average value of 197 10 mBq m-2 h-1, whereas, mass exhalation rates vary from 5 0.3 to 11 1 mBq kg-1 h-1 with an average value of 8 0.4 mBq kg-1 h-1.

  20. Processing and Analysis of Hyperspectral Fingerprints to Characterise Haematite of Singbhum Iron Ore Belt, Orissa, India

    NASA Astrophysics Data System (ADS)

    Magendran, T.; Sanjeevi, S.

    2014-12-01

    The demand for iron ore has been increasing in the recent years, thereby requiring the adoption of fast and accurate approaches to iron ore exploration and its grade-assessment. It is in this context that hyperspectral sensing is deemed as a potential tool. This paper examines the potential of hyperspectral fingerprints in the visible, NIR and SWIR regions of the EMR to assess the grades of haematite of the western Singhbhum iron ore belt of Orissa, eastern India, in a rapid manner. Certain spectro-radiometric measurements and geochemical analysis were carried out and the results have been presented. From the spectral measurements, it is seen that the strength of reflectance and absorption at definite wavelength regions is controlled by the chemical composit ion of the iron ores. It is observed that the primary spectral characteristics of these haematites lie in the 650-750 nm, 850 to 900 nm and 2130-2230 nm regions. The laboratory based hyperspectral fingerprints and multiple regression analysis of spectral parameters and geochemical parameters (Fe% and Al2O3%) predicted the concentration of iron and alumina content in the haematite. A very strong correlation (R2 = 0.96) between the spectral parameters and Fe% in the haematite with a minimum error of 0.1%, maximum error of 7.4% and average error of 2.6% is observed. Similarly, a very strong correlation (R2 = 0.94) between the spectral parameters and Al2O3% in the iron ores with a minimum error of 0.04%, maximum error of 7.49% and average error of 2.5% is observed. This error is perhaps due to the presence of other components (SiO2, TiO2, P2O etc.) in the samples which can alter the degree of reflectance and hence the spectral parameters. Neural network based multi-layer perception (MLP) analysis of various spectral parameters and geochemical parameters helped to understand the relative importance of the spectral parameters for predictive models. The strong correlations (Iron: R2 = 0.96; Alumina: R2 = 0.94) indicate that the laboratory hyperspectral signatures in the visible, NIR and SWIR regions can give a better estimate of the grades of haematite in a rapid manner.

  1. Acceptability, willing to purchase and use long lasting insecticide treated mosquito nets in Orissa State, India.

    PubMed

    Gunasekaran, K; Sahu, S S; Vijayakumar, K N; Jambulingam, P

    2009-11-01

    Long lasting insecticide treated nets (LLINs) that require no re-treatment have been advocated as an effective tool against malaria transmission. However, success of this community based intervention measure largely depends on its acceptability and proper usage by the target population, besides assuring access to bed nets. To determine the acceptability of LLIN, its usage and people's willingness to buy the net, a study was conducted in two tribal districts viz., Malkangiri (with ongoing ITN programme) and Koraput (no ITN programme) of Orissa State, India. Both qualitative and quantitative data collection methods were used to collect information regarding the objective of the study. A total of 2457 LLINs (Olyset Nets) were distributed in the selected villages of these districts at free of cost. In the study villages of Malkangiri, 58% of the households had either ITNs (73%) or other types of mosquito nets aside from the LLINs and in the villages of Koraput, only 8% had other nets, as majority (96%) informed that buying nets from market was not affordable to them. Physical verification of the nets during the house visits revealed that 75.4% and 83% (in ITNs and non-ITNs villages, respectively) of the LLINs and 76% of the other nets (including ITNs) were used by the respondents, the night before the survey as nets were in a hanging position at the time of the visit. Majority of the respondents (76-98%) felt that reduction of mosquito bites as the main perceived benefit of using the LLINs. About 55% and 67% of the respondents from non-ITNs and ITNs areas, respectively, expressed their willingness to buy the LLINs. Among them, 76.8% and 94.7% offered to pay INR<100 for a net and also ready to buy it by cash payment. Social marketing of LLINs at a subsidized price or free supply to the deserving sections of people (socially/economically poor and/or under-privileged) and ensuring the availability of nets during harvesting season could encourage people to buy and use LLINs. PMID:19631186

  2. 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)

    Reolid, Matas; Marok, Abbas; Sbane, Abbes

    2014-07-01

    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.

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

    SciTech Connect

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

    1985-01-01

    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.

  4. Laurentia and Salvador-Congo: Keystone cratons in Late Proterozoic break-up of Rodinia and assembly of Gondwana supercontinents

    SciTech Connect

    Unrug, R. . Dept. of Geological Sciences)

    1992-01-01

    The break-up of Rodinia, the supercontinent assembled in the Middle Proterozoic chelogenic cycle (1.65--1.0 Ga), and the simultaneous assembly of the Gondwana Supercontinent were the major tectonic events of the Neoproterozoic. Laurentia occupied a central keystone position in the configuration of Rodinia. Its break-up resulted in rearrangement of Rodinia fragments: some were incorporated in the accreting Gondwana, while Laurentia, Baltica and Siberia drifted independently. Reconstructions of the position of Laurentia in the Rodinia Supercontinent are based on two criteria. The first is the continuity of Middle Proterozoic mobile belts suturing the older cratons and the match of piercing points of the mobile belts at the post- Middle Proterozoic margins of the older cratons. The second is the similarity of sedimentary sequences along Late Proterozoic passive margins formed during break-up of Rodinia. The first criterion allows for several interpretations. The second may be invalid, as conjugate margins developing over an oblique detachment will accumulate dissimilar sedimentary sequences. In reconstructions of the Gondwana Supercontinent the recently redefined Salvador-Congo craton occupied the central keystone position, between the East Gondwana continent and a number of smaller cratons of West Gondwana. It is entirely surrounded by collisional mobile belts, all containing important transcurrent shear zone systems. The margins of the Salvador-Congo craton were facing three major Late Proterozoic oceans.

  5. A review of the Late Cambrian (Furongian) palaeogeography in the western Mediterranean region, NW Gondwana

    NASA Astrophysics Data System (ADS)

    lvaro, J. Javier; Ferretti, Annalisa; Gonzlez-Gmez, Cristina; Serpagli, Enrico; Tortello, M. Franco; Vecoli, Marco; Vizcano, Daniel

    2007-11-01

    The Cambrian-Ordovician transition of the western Mediterranean region (NW Gondwana) is characterized by the record of major erosive unconformities with gaps that range from a chronostratigraphic stage to a series. The hiatii are diachronous and involved progressively younger strata along the Gondwanan margin, from SW (Morocco) to NE (Montagne Noire). They can be related to development of a multi-stage rifting (further North), currently connected to the opening of the Rheic Ocean, and concomitant erosion on southern rift shoulders. The platforms of this margin of Gondwana occupied temperate-water, mid latitudes and were dominated by siliciclastic sedimentation, while carbonate factories were only episodically active in the Montagne-Noire platform. The Upper Cambrian is devoid of significant gaps in the southern Montagne Noire and the Iberian Chains. There, the sedimentation took place in a transgressive-dominated depositional system, with common offshore deposits and clayey substrates, and was bracketed by two major regressive trends. The Late Cambrian is also associated with the record of volcanic activity ( e.g., in the Cantabrian and Ossa-Morena zones, and the northern Montagne Noire), and widespread development of a tectonic instability that led to the episodic establishment of palaeotopographies and record of slope-related facies associations. Several immigration events are recognized throughout the latest Middle Cambrian, Late Cambrian and Tremadocian. The trilobites show a stepwise replacement of Acado-Baltic-type families ( e.g., the conocoryphid-paradoxidid-solenopleurid assemblage) characterized by: (i) a late Languedocian (latest Middle Cambrian) co-occurrence of Middle Cambrian trilobite families with the first anomocarid, dorypygid and proasaphiscid invaders; (ii) a Late Cambrian immigration replacing previous faunas, composed of trilobites (aphelaspidids, catillicephalids, ceratopygids, damesellids, eulomids, idahoiids, linchakephalids, lisariids, onchonotinids, and pagodiids), linguliformean brachiopods (acrotretids, obolids, scaphelasmatids, siphonotretids, and zhanatellids), echinoderms (mitrates, glyptocystitid cystoids, and stromatocystoids), and conodonts belonging to the lower Peltura Zone; and (iii) the subsequent input of new trilobites (asaphids, calymenids, catillicephalids, nileids and remopleurids), which marks the base of the Proteuloma geinitzi Zone, associated with pelmatozoan holdfasts ( Oryctoconus), and a distinct input of late Tremadocian conodonts ( Paltodus deltifer Zone). The biogeographic distribution of latest Middle and Late Cambrian trilobites supports brachiopod data indicating strong affinities between the western Mediterranean region, East Gondwana (North China/Korea, South China, Australia, and Antarctica) and Kazakhstania during the late Languedocian, which became significantly stronger during the Late Cambrian. This major shift may suggest modification in oceanic circulation patterns throughout Gondwana across the Middle-Late Cambrian transition.

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

    PubMed

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

    2008-12-30

    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

  7. Geological appraisal over the Singhbhum-Orissa Craton, India using GOCE, EIGEN6-C2 and in situ gravity data

    NASA Astrophysics Data System (ADS)

    Pal, S. K.; Majumdar, T. J.

    2015-03-01

    The gravity field and derivatives generated with the high resolution EIGEN-6C2 gravity model which includes satellite gravity data of GOCE (Gravity field and steady-state Ocean Circulation Explorer) has been utilized for geological appraisal of the Singhbhum-Orissa Craton, India. The GOCE only field gravity data and in situ gravity data of the same area have been utilized for comparative assessment to validate the results derived by EIGEN-6C2 gravity data. The GOCE and EIGEN-6C2 Bouguer gravity data have been generated from GOCE and EIGEN-6C2 Free-air gravity data, respectively, after removing topography effect. The result shows that correlation coefficient and covariance between the Bouguer gravity anomaly distribution of in situ and EIGEN-6C2 data of the entire study area are 0.68 and 93.9 mgal2, respectively. The GOCE field compares well to the terrestrial derivative fields in the long-wavelength part of the signal. Further, EIGEN-6C2 and in situ Bouguer gravity data have been analyzed using the 1st and 2nd Vertical Derivatives, Analytical Signal and Tilt Derivative mapping techniques. Published geological and structural maps of the area have been overlapped over different derivative maps and the analytical signal map to analyze the correlation with the subsurface geology and geological structures of the area. Major distinct geological signatures, on different derivative maps and analytical signal map, are correlated well with the existing geological map. The TDR derived from the EIGEN-6C2 Bouguer anomaly has been used to map geologic contacts. The source boundaries and depths are determined from the zero contours, and the half distance between ?/4 contours or the distance between zero and +?/4 or -?/4 contour of TDR, respectively. The gravity data generated from EIGEN-6C2 model provides sufficient resolution for understanding of the geological setting of the Singhbhum-Orissa Craton.

  8. Geochronological data from the Faxinal coal succession, southern Paran Basin, Brazil: A preliminary approach combining radiometric U-Pb dating and palynostratigraphy

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

    A radiometric zircon age of 285.4 8.6 Ma (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 Paran Basin is constrained to the Sakmarian. Consequently, the basal Gondwana sequence in the southern part of the basin should lie at the Carboniferous-Permian boundary, not within the Sakmarian as previously considered. The new results are significant for correlations between the Paran Basin and the Argentinian Paganzo Basin (302 6 Ma and 288 7 Ma) and with the Karoo Basin, specifically with the top of the Dwyka Tillite (302 3 Ma and 299.2 3.2 Ma) and the lowermost Ecca Group (288 3 Ma and 289.6 3.8 Ma). The evidence signifies widespread latest Carboniferous volcanic activity in western Gondwana.

  9. Frontier sedimentary basins of New Zealand region

    SciTech Connect

    Beggs, J.M. )

    1991-03-01

    Petroleum-prospective basins of New Zealand began to form by mid-Cretaceous rifting of crustal elements previously assembled at the Gondwana continental margin. During the latest Cretaceous-early Cenozoic New Zealand separated from Australia and Antarctica by sea-floor spreading. An overall transgression in widely recorded in this post-rift phase, with decreasing clastic sediment supply as land area and relief were reduced. Mid-Cenozoic initiation of the modern plate boundary has resulted in uplift of mountain ranges, subsidence and filling of troughs, progradation of the shelf, and common reactivation or eversion of older structures. Petroleum potential of less explored basins can be compared to the productive Taranki basin. Source rocks are coal-rich deposits of the rift phase, also developed in Great South, Canterbury/Chatham, Western Southland, West Coast, and Northland basins. A different source contributes to oil and gas seeps on the East Coast, a continental margin during Late Cretaceous. The main reservoirs of Taranaki are early Cenozoic coastal and fluvial sands, also present in Great South, Canterbury, and West Coast and possibly other basins. Other Taranaki reservoirs include mid-Cenozoic limestone and Miocene turbidites, which are widespread in most other basins. Pliocene limestones have excellent reservoir potential on the East Coast. Late Cenozoic tectonics, essential to trap development and significant for maturation in Taranaki, have created similar structures in basins near the plate boundary but are less significant in the development of Great South, eastern Canterbury/Chatham, and Northland basins.

  10. Ediacaran to Cambrian oceanic rocks of the Gondwana margin and their tectonic interpretation

    NASA Astrophysics Data System (ADS)

    von Raumer, Jrgen F.; Stampfli, Grard M.; Arenas, Ricardo; Snchez Martnez, Sonia

    2015-07-01

    In tectonic maps of Variscan Europe, allochthonous pieces of Cadomian basement clearly stand out with their predominant metabasic to ultrabasic elements, the so-called exotic terranes with ophiolites. Most of these domains are observed in basements of the Central Iberian Allochthone, the South Armorican domain, the nappe structures of the French Massif Central, the Saxothuringian Zone and the Bohemian Massif. Similar relics can be recognized in many Alpine basement areas, and correlations with supposedly more autochthonous basements, such as the Ossa Morena Zone and the Central Iberian basement, can be envisaged. All of these relics are thought to represent the interrupted trace of a former continuous or discontinuous structure, characterized by the presence of ocean-derived proto-Rheic rock suites. These can be interpreted as pieces of former magmatic arcs of Ediacaran to Cambrian age accreted to the Gondwana margin, which later were scattered as allochthonous units during the Variscan plate-tectonic processes. The presence of similar rock suites of Ordovician age in the Alpine realm is explained by the accretion of exotic China-derived basements and their collision with the Gondwana margin during the opening of the Rheic Ocean.

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    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.

  12. Evidence of Middle Jurassic magmatism within the Seychelles microcontinent: Implications for the breakup of Gondwana

    NASA Astrophysics Data System (ADS)

    Shellnutt, J. G.; Lee, T.-Y.; Chiu, H.-Y.; Lee, Y.-H.; Wong, J.

    2015-12-01

    The breakup of East and West Gondwana occurred during the Jurassic, but the exact timing is uncertain due to the limited exposure of rocks suitable for radioisotopic dating. Trachytic rocks from Silhouette Island, Seychelles, yielded a range of zircon ages from Paleoproterozoic to Cenozoic. The 206Pb/238U age of the trachyte is 64.9 ± 1.6 Ma (Danian) but the majority of zircons yielded an age of 163.8 ± 1.8 Ma (Callovian) with a small subset yielding an age of 147.7 ± 4.5 Ma (Tithonian). The Hf isotopes of the Callovian (ɛHf(t) = +4.1 to +13.4) and Danian (ɛHf(t) = +1.9 to +7.1) zircons indicate that they were derived from moderately depleted mantle sources whereas the Tithonian zircons (ɛHf(t) = -7.0 to -7.3) were derived from an enriched source. The identification of middle Jurassic zircons indicates that rifting and magmatism were likely contemporaneous during the initial separation of East and West Gondwana.

  13. Nilonema gymnarchi Khalil, 1960 and N. senticosum (Baylis, 1922) (Nematoda: Dracunculoidea): Gondwana relicts?

    PubMed

    Santos, Cludia Portes; Gibson, David I

    2007-07-01

    Data-base searches of records of the helminth parasites of South American and African freshwater fishes revealed only two pairs of species from genera endemic to the two regions. One pair, species of the primitive amphilinid cestode genus Nesolecithus Dnges & Harder, 1966, has already been designated as likely Gondwana relicts. The second pair are the philometrid nematodes Nilonema gymnarchi Khalil, 1960 from Gymnarchus niloticus Cuvier (Gymnarchidae) in Africa and N. senticosum (Baylis, 1922) from the South American fish Arapaima gigas (Cuvier) (Arapaimidae). Both species are partly redescribed on the basis of light and scanning electron microscopical observations of the type-specimens, and their relationships are discussed. In view of the fact that both hosts are basal teleosts of the order Osteoglossiformes and they are the same two fish which harbour the amphilinid cestodes already indicated as Gondwana relics, the nematode pair is also deemed to be relictual. However, these species are suggested as being of limited potential value for calibrating a molecular clock. PMID:17464484

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

    NASA Astrophysics Data System (ADS)

    Wang, J.; Han, W.

    2011-12-01

    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 10N 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.

  15. 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 Central

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

    2010-01-01

    Summary India accounts for over one-third of the worlds 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 1560 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 1725%) of 1563 persons were ICT positive, with district-wide prevalence rates ranging from 1532%. 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

  16. 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

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

    2011-02-01

    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

  17. Post-Gondwana geomorphic evolution of southwestern Africa: Implications for hte controls on landscape development from observations and numerical experiments

    NASA Astrophysics Data System (ADS)

    Gilchrist, Alan R.; Kooi, Henk; Beaumont, Christopher

    1994-06-01

    The relationship between morphology and surficial geology is used to quantify the denudation that has occurred across southwestern Africa sicne the fragmentation of Gondwana during the Early Mesozoic. Two main points emerge. Signficant denudation, of the order of kilometers, is widespread except in the Kalahari region of the continental interior. The denudation is systematically distributed so that the continental exterior catchment, draining directly to the Cape basin, is denuded to a greater depth than the interior catchment inland of the Great Escarpment. The analysis also implies tha the majority of the denudation occurred before the beginning of the Cenozoic for both teh exerior and interior catchments. Existing models of landscape development are reviewed, and implications of the denudation chronology are incorporated into a revised conceptual model. This revision implies tha thte primary effect of rifting on the subsequent landscape evolution is that it generates two distinct drainage regimes. A marginal upwarp, or rift flank uplift, separates rejuvenated rivers that drain into the subsiding rift from rivers in the continetal interior that are deflected but not rejuvenated. The two catchments evolve independently unless they are integrated by breaching of hte marginal upwarp. If this occurs, the exterior baselevel is communicated to the interior catchment that is denuded accordingly. Denudation rates generally decrease as the margin evolves, and this decrease is reinforced by the exposure of substrate that is resistant to denudation and/or a change to a more arid climate. The observations do not reveal a particular style of smaller-scale landscape evolution, sucha s escarpment retreat, that is responsible for the differential denudation across the region. It is proposed that numerical model experiments, which reflect the observational insights at the large scale, may identify the smaller-scale controls on escarpment development if the model and natural systems are analogous. Four numerical experiments are presented in which the roles of antecedent topography, resistant substrate, climte change, and lowering the baselevel of the interior catchment are investigated for an initially high elevation margin bordered by an escarpment. The model results suggest several styles of landscape evolution that are compatible with the observations. Escarpments may retreat in a regular manner, but they also degrade and are destroyed, only to reform at the drainage divide between exterior and interior catchments.

  18. Post-Gondwana geomorphic evolution of southwestern Africa: Implications for hte controls on landscape development from observations and numerical experiments

    NASA Technical Reports Server (NTRS)

    Gilchrist, Alan R.; Kooi, Henk; Beaumont, Christopher

    1994-01-01

    The relationship between morphology and surficial geology is used to quantify the denudation that has occurred across southwestern Africa sicne the fragmentation of Gondwana during the Early Mesozoic. Two main points emerge. Signficant denudation, of the order of kilometers, is widespread except in the Kalahari region of the continental interior. The denudation is systematically distributed so that the continental exterior catchment, draining directly to the Cape basin, is denuded to a greater depth than the interior catchment inland of the Great Escarpment. The analysis also implies tha the majority of the denudation occurred before the beginning of the Cenozoic for both teh exerior and interior catchments. Existing models of landscape development are reviewed, and implications of the denudation chronology are incorporated into a revised conceptual model. This revision implies tha thte primary effect of rifting on the subsequent landscape evolution is that it generates two distinct drainage regimes. A marginal upwarp, or rift flank uplift, separates rejuvenated rivers that drain into the subsiding rift from rivers in the continetal interior that are deflected but not rejuvenated. The two catchments evolve independently unless they are integrated by breaching of hte marginal upwarp. If this occurs, the exterior baselevel is communicated to the interior catchment that is denuded accordingly. Denudation rates generally decrease as the margin evolves, and this decrease is reinforced by the exposure of substrate that is resistant to denudation and/or a change to a more arid climate. The observations do not reveal a particular style of smaller-scale landscape evolution, sucha s escarpment retreat, that is responsible for the differential denudation across the region. It is proposed that numerical model experiments, which reflect the observational insights at the large scale, may identify the smaller-scale controls on escarpment development if the model and natural systems are analogous. Four numerical experiments are presented in which the roles of antecedent topography, resistant substrate, climte change, and lowering the baselevel of the interior catchment are investigated for an initially high elevation margin bordered by an escarpment. The model results suggest several styles of landscape evolution that are compatible with the observations. Escarpments may retreat in a regular manner, but they also degrade and are destroyed, only to reform at the drainage divide between exterior and interior catchments.

  19. Paleomagnetism of Jurassic and Cretaceous rocks in central Patagonia: a key to constrain the timing of rotations during the breakup of southwestern Gondwana?

    NASA Astrophysics Data System (ADS)

    Geuna, Silvana E.; Somoza, Rubn; Vizn, Haroldo; Figari, Eduardo G.; Rinaldi, Carlos A.

    2000-08-01

    A paleomagnetic study in Jurassic and Cretaceous rocks from the Caadn Asfalto basin, central Patagonia, indicates the occurrence of about 25-30 clockwise rotation in Upper Jurassic-lowermost Cretaceous rocks, whereas the overlying mid-Cretaceous rocks do not show evidence of rotation. This constrains the tectonic rotation to be related to a major regional unconformity in Patagonia, which in turn seems to be close in time with the early opening of the South Atlantic Ocean. The sense and probably the timing of this rotation are similar to those of other paleomagnetically detected rotations in different areas of southwestern Gondwana, suggesting a possible relationship between these and major tectonic processes related with fragmentation of the supercontinent. On the other hand, the mid-Cretaceous rocks in the region yield a paleopole located at Lat. 87 South, Long. 159 East, A95=3.8. This pole position is consistent with coeval high-quality paleopoles of other plates when transferred to South American coordinates, implying it is an accurate determination of the Aptian (circa 116 Ma) geomagnetic field in South America.

  20. An in situ shelly fauna from the lower Paleozoic Zapla diamictite of northwestern Argentina: Implications for the age of glacial events across Gondwana

    NASA Astrophysics Data System (ADS)

    Benedetto, Juan L.; Halpern, Karen; de la Puente, G. Susana; Monaldi, César R.

    2015-12-01

    A shelly fauna from the upper part of the Zapla glacial diamictite includes the lingulate brachiopod Orbiculoidea radiata Troedsson, the rhynchonelliforms Dalmanella cf. testudinaria (Dalman) and Paromalomena sp., the bivalve Modiolopsis? sp., and the trilobite Dalmanitina subandina Monaldi and Boso. Both taphonomic and paleoecologic data indicate a lack of transport reflecting the original community. The assemblage is closely comparable to the widespread latest Ordovician Hirnantia-Dalmanitina fauna. The Hirnantian age of the Zapla diamictite is further corroborated by the record of the northern Gondwana chitinozoans Spinachitina cf. oulebsiri Paris and Desmochitina minor typica Eisenack. The graptolites and chitinozoans from the overlying Lipeón Formation indicate that the postglacial transgression took place in the earliest Llandovery (Parakidograptus acuminatus Biozone). According to the tectonosedimentary evidence, the Early Silurian age of the Cancañiri and San Gabán diamictites of north-central Bolivia and south Peru based on their palynological record is more likely the age of posglacial gravity flows and not that of the glaciation. We support the hypothesis that the weakly lithified glacigenic deposits of Hirnantian age were reworked and redistributed by high-energy marine processes during the postglacial transgression and then transported to the adjacent deep-marine trough. Iron-rich horizons have been recognized in many basins of southern South America reflecting eustatic and paleoclimatic fluctuations. Most of them formed during the early stages of the postglacial transgression at the Ordovician/Silurian transition and are associated with low sedimentation rates and condensed intervals. The mild maritime postglacial climate, the increasing atmospheric CO2, and possibly the presence of incipient vegetated areas led to extensive weathering of glacigenic sediments supplying iron into the marine system to form ferruginous deposits. The sea level fall related to the peak of glaciation is recorded by both paleovalley incision and a sharp subaerial to subglacial unconformity. The transgressive systems tract starts with fluvio-estuarine deposits within incised valleys followed by widespread deposition of subtidal to open marine organic-rich shales onlapping regionally the basement rocks. The recognition of key stratigraphic markers (e.g. sequence boundary, flooding surface, ferruginous beds), alongside reliable micro and macropaleontological evidence allow a more accurate correlation between the Central Andean Basin of Peru, Bolivia and NW Argentina, the W Puna region, the Paraguayan and Brazilian sectors of the Paraná Basin, the Precordillera Basin of W Argentina, and the Cape Basin of South Africa.

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

    NASA Astrophysics Data System (ADS)

    Leslie, Graham; Schofield, David; Wilby, Phil

    2014-05-01

    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 Mn 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.

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

    PubMed

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

    2013-01-01

    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

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

    USGS Publications Warehouse

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

    1999-01-01

    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.

  4. A stem acrodontan lizard in the Cretaceous of Brazil revises early lizard evolution in Gondwana

    PubMed Central

    Simões, Tiago R.; Wilner, Everton; Caldwell, Michael W.; Weinschütz, Luiz C.; Kellner, Alexander W. A.

    2015-01-01

    Iguanians are one of the most diverse groups of extant lizards (>1,700 species) with acrodontan iguanians dominating in the Old World, and non-acrodontans in the New World. A new lizard species presented herein is the first acrodontan from South America, indicating acrodontans radiated throughout Gondwana much earlier than previously thought, and that some of the first South American lizards were more closely related to their counterparts in Africa and Asia than to the modern fauna of South America. This suggests both groups of iguanians achieved a worldwide distribution before the final breakup of Pangaea. At some point, non-acrodontans replaced acrodontans and became the only iguanians in the Americas, contrary to what happened on most of the Old World. This discovery also expands the diversity of Cretaceous lizards in South America, which with recent findings, suggests sphenodontians were not the dominant lepidosaurs in that continent as previously hypothesized. PMID:26306778

  5. A stem acrodontan lizard in the Cretaceous of Brazil revises early lizard evolution in Gondwana.

    PubMed

    Simões, Tiago R; Wilner, Everton; Caldwell, Michael W; Weinschütz, Luiz C; Kellner, Alexander W A

    2015-01-01

    Iguanians are one of the most diverse groups of extant lizards (>1,700 species) with acrodontan iguanians dominating in the Old World, and non-acrodontans in the New World. A new lizard species presented herein is the first acrodontan from South America, indicating acrodontans radiated throughout Gondwana much earlier than previously thought, and that some of the first South American lizards were more closely related to their counterparts in Africa and Asia than to the modern fauna of South America. This suggests both groups of iguanians achieved a worldwide distribution before the final breakup of Pangaea. At some point, non-acrodontans replaced acrodontans and became the only iguanians in the Americas, contrary to what happened on most of the Old World. This discovery also expands the diversity of Cretaceous lizards in South America, which with recent findings, suggests sphenodontians were not the dominant lepidosaurs in that continent as previously hypothesized. PMID:26306778

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

    NASA Astrophysics Data System (ADS)

    Plummer, C. L.; Furman, T.

    2006-12-01

    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

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

    PubMed Central

    Cracraft, J.

    2001-01-01

    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

  8. Extending the Cantabrian Orocline to two continents (from Gondwana to Laurussia). Paleomagnetism from South Ireland

    NASA Astrophysics Data System (ADS)

    Pastor-Galn, Daniel; Ursem, Bart; Meere, Patrick A.; Langereis, Cor

    2015-12-01

    Regional Variscan structure in southern Ireland follows a gentle arcuate trend of ca. 25 concave to the SE that apparently follows the geometry of the Cantabrian Orocline (NW Iberia) when Iberia is restored to its position prior to the opening of the Biscay Bay. We report paleomagnetic results from Devonian and Carboniferous rocks in southern Ireland: (i) a pervasive and consistent remagnetization during the Late Carboniferous and (ii) an average rotation of ?25 counterclockwise with respect to the Global Apparent Polar Wander Path and kinematically compatible with the Cantabrian Orocline. These results support the participation of Laurussia in the formation of the Cantabrian Orocline involving, at least, southern Ireland and the South Portuguese Zone (S Iberia). We conclude that a Greater Cantabrian Orocline extends beyond its current boundaries to include shear zones in the Variscan hinterland and the Rheic Ocean suture, thereby enlarging its size to plate-scale affecting as it does the Laurussia and Gondwana margins.

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

    NASA Astrophysics Data System (ADS)

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

    1997-08-01

    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 1831 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 (2.5106 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.

  10. Molecular variants and clinical importance of beta-thalassaemia traits found in the state of Orissa, India.

    PubMed

    Nishank, Sudhansu Sekhar; Ranjit, Manoranjan; Kar, Shantanu K; Chhotray, Guru Prasad

    2009-10-01

    Prevention of beta thalassaemia implies knowledge of the molecular spectrum occurring in the population at risk. This knowledge is necessary, especially when a prevention protocol is applied to a multiethnic population. For this purpose, we carried out molecular analysis of 431 beta thalassaemia subjects belonging to tribal (aboriginal) and non-tribal communities of Orissa, a part of peninsular India and found six types of mutation (four previously unreported and two reported). Molecular analysis of beta gene mutation showed that out of 431 beta thalassaemia cases (265 beta thalassaemia traits, 64 beta thalassaemia major, 47 haemoglobin E-beta thalassaemia, 55 haemoglobin S-beta thalassaemia cases), 71% of cases (n=306) showed the IVS I-5(G-->C) mutation, 12% of cases (n=52) showed FS 41/42(-CTTT), 7% of cases (n=30) showed CD 15(G-->A), 4.8% of cases (n=21) showed CD 30 (G-->C), 3% of cases (n=13) showed FS 8/9 (+G), and 2% of cases (n=9) showed IVSI-1(G-->T). The tribal populations possess only the IVS I-5(G-->C) mutation whereas the non-tribal groups possess the FS 41/42(-CTTT), FS 8/9 (+G), IVS I-1(G-->T), CD30(G-->C) and IVS I-5(G-->C) mutations. Among the non-tribal communities, Muslims did not have the IVS I-1 (G-->T) mutation. Clinically, anaemia was mild to moderate in beta thalassaemia trait and was found to be associated with the majority of abnormalities such as pyrexial episodes, fatigue, headache, lethargy and pallor. However, there were no differences in the incidence of clinical abnormalities between tribal and non-tribal populations and also among the different molecular variants of beta gene. This is the first report from Orissa on the prevalence of different molecular variants of beta thalassaemia. The clinical presentation of beta thalassaemia trait cases and their variation from other population have been discussed with reference to the different genetic variants. PMID:19843386

  11. Natural radioactivity and radiation exposure in the high background area at Chhatrapur beach placer deposit of Orissa, India.

    PubMed

    Mohanty, A K; Sengupta, D; Das, S K; Saha, S K; Van, K V

    2004-01-01

    A high natural background radiation area is reported for the Chhatrapur beach placer deposit of Orissa state, on the southeastern coast of India, due to the presence of radiogenic heavy minerals. The average activity concentrations of radioactive elements 232Th, 238U and 40K were measured by gamma-ray spectrometry using a HPGe detector, and found to be 2500 +/-1850, 230 +/- 140 and 120 +/- 35 Bq kg-1, respectively, for the bulk sand samples. The absorbed gamma dose rates in air due to the naturally occurring radionuclides varied from 375 to 5000 nGy h-1, with an average value of 1625 +/- 1200 nGy h-1. The external annual effective dose rate of the region ranged from 0.46 to 6.12 mSv y-1, with an average value of 1625 +/- 1200 mSv y-1. The absorbed gamma dose rate levels of Chhatrapur beach area were similar to the monazite sand-bearing high background radiation areas of southern and southwestern coastal tracts of India and other similar areas of the world. The major contributors to the enhanced level of radiation are monazite and zircon sands. PMID:15149759

  12. "We all knew that a cyclone was coming": disaster preparedness and the cyclone of 1999 in Orissa, India.

    PubMed

    Thomalla, Frank; Schmuck, Hanna

    2004-12-01

    Imagine that a cyclone is coming, but that those living in the affected areas do nothing or too little to protect themselves. This is precisely what happened in the coastal state of Orissa, India. Individuals and communities living in regions where natural hazards are a part of daily life develop strategies to cope with and adapt to the impacts of extreme events. In October 1999, a cyclone killed 10,000 people according to government statistics, however, the unofficial death toll is much higher. This article examines why such a large loss of life occurred and looks at measures taken since then to initiate comprehensive disaster-preparedness programmes and to construct more cyclone shelters. The role of both governmental organisations and NGOs in this is critically analysed. The good news is that, based on an assessment of disaster preparedness during a small cyclone in November 2002, it can be seen that at community-level awareness was high and that many of the lessons learnt in 1999 were put into practice. Less positive, however, is the finding that at the state level collaboration continues to be problematic. PMID:15569379

  13. Shared Sanitation Versus Individual Household Latrines in Urban Slums: A Cross-Sectional Study in Orissa, India.

    PubMed

    Heijnen, Marieke; Routray, Parimita; Torondel, Belen; Clasen, Thomas

    2015-08-01

    A large and growing proportion of the global population rely on shared sanitation facilities despite evidence of a potential increased risk of adverse health outcomes compared with individual household latrines (IHLs). We sought to explore differences between households relying on shared sanitation versus IHLs in terms of demographics, sanitation facilities, and fecal exposure. We surveyed 570 households from 30 slums in Orissa, India, to obtain data on demographics, water, sanitation, and hygiene. Latrine spot-checks were conducted to collect data on indicators of use, privacy, and cleanliness. We collected samples of drinking water and hand rinses to assess fecal contamination. Households relying on shared sanitation were poorer and less educated than those accessing IHLs. Individuals in sharing households were more likely to practice open defecation. Shared facilities were less likely to be functional, less clean, and more likely to have feces and flies. No differences in fecal contamination of drinking water or hand-rinse samples were found. Important differences exist among households accessing shared facilities versus IHLs that may partly explain the apparent adverse health outcomes associated with shared sanitation. As these factors may capture differences in risk and promote sanitary improvements, they should be considered in future policy. PMID:26123953

  14. Fish from the Upper Devonian of the Shan-Thai terrane indicate proximity to east Gondwana and south China terranes

    NASA Astrophysics Data System (ADS)

    Long, John; Burrett, Clive

    1989-09-01

    We report the first discovery of abundant Devonian vertebrates from Thailand. An unusual form of coronodontid shark tooth with six equal-sized cusps occurs only in the Upper Devonian of Thailand (Shan-Thai terrane) and south China, and a new species of Phoebodus is reported that occurs elsewhere only in south China and Australia (east Gondwana terrane). The occurrence of the chondrichthyan Harpagodens (Thrinacodus) ferox Turner 1982 in the Late Devonian of Thailand, Australia, and south China predates the appearance of this species in Euramerica (early Carboniferous). These data suggest Late Devonian proximity of the Shan-Thai, south China, and east Gondwana terranes, and is in accord with recent paleomagnetic data.

  15. Challenges and opportunities for policy decisions to address health equity in developing health systems: case study of the policy processes in the Indian state of Orissa

    PubMed Central

    2011-01-01

    Introduction Achieving health equity is a pertinent need of the developing health systems. Though policy process is crucial for planning and attaining health equity, the existing evidences on policy processes are scanty in this regard. This article explores the magnitude, determinants, challenges and prospects of 'health equity approach' in various health policy processes in the Indian State of Orissa - a setting comparable with many other developing health systems. Methods A case-study involving 'Walt-Gilson Policy Triangle' employed key-informant interviews and documentary reviews. Key informants (n = 34) were selected from the departments of Health and Family Welfare, Rural Development, and Women and Child Welfare, and civil societies. The documentary reviews involved various published and unpublished reports, policy pronouncements and articles on health equity in Orissa and similar settings. Results The 'health policy agenda' of Orissa was centered on 'health equity' envisaging affordable and equitable healthcare to all, integrated with public health interventions. However, the subsequent stages of policy process such as 'development, implementation and evaluation' experienced leakage in the equity approach. The impediment for a comprehensive approach towards health equity was the nexus among the national and state health priorities; role, agenda and capacity of actors involved; and existing constraints of the healthcare delivery system. Conclusion The health equity approach of policy processes was incomprehensive, often inadequately coordinated, and largely ignored the right blend of socio-medical determinants. A multi-sectoral, unified and integrated approach is required with technical, financial and managerial resources from different actors for a comprehensive 'health equity approach'. If carefully geared, the ongoing health sector reforms centered on sector-wide approaches, decentralization, communitization and involvement of non-state actors can substantially control existing inequalities through an optimally packaged equitable policy. The stakeholders involved in the policy processes need to be given orientation on the concept of health equity and its linkage with socio-economic development. PMID:22099141

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

    NASA Astrophysics Data System (ADS)

    Will, Thomas; Frimmel, Hartwig

    2013-04-01

    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.

  17. Evidence of post-Gondwana breakup in Southern Brazilian Shield: Insights from apatite and zircon fission track thermochronology

    NASA Astrophysics Data System (ADS)

    Oliveira, Christie Helouise Engelmann de; Jelinek, Andréa Ritter; Chemale, Farid; Bernet, Matthias

    2016-01-01

    Apatite and zircon fission track thermochronology studies are applied to basement and sedimentary rocks from the Sul-Rio-Grandense Shield to unravel the tectonic history of the onshore southernmost Brazilian margin. The Sul-Rio-Grandense Shield is a major geotectonic feature of southernmost Brazil that includes Paleoproterozoic basement areas and Neoproterozoic fold belts linked to the Brasiliano/Pan-African orogeny. Crustal reworking and juvenile accretion events related to this cycle were dated in the region between 900 and 500 Ma and were responsible for the assembly of southwestern Gondwana in southeastern South America. Apatite fission track (AFT) ages range from 340 ± 33 to 77 ± 6 Ma and zircon fission track (ZFT) ages range from ca. 386 to 210 Ma. Based on thermal history modeling, the most part of the samples record an early cooling event during the Carboniferous, which reflect the main tectonic activity of the final stages of the Gondwanides at the Pacific margin of West Gondwana. Subsequently, the Permo-Triassic cooling event is related to the last stages of the Gondwanides, with convergence along the southern border of Western Gondwana and consequent reactivation of N-S and NE-SW trending basement structures. The onset of initial breakup of southwestern Gondwana with opening of the South Atlantic Ocean is mostly recorded in the eastern terrain and ZFT ages show that the temperature during this period was high enough for total or at least partial resetting of fission tracks in zircon. The last cooling event of the Sul-Rio-Grandense Shield records the final breakup between South America and Africa, which began during the Late Cretaceous. However, the Cenozoic rapid cooling episode probably is a result of plate adjustment after breakup and neotectonic reactivation of faults associated with South Atlantic rift evolution.

  18. Tectonically controlled sedimentation in the Mesozoic basins of the Antarctic Peninsula

    SciTech Connect

    MacDonald, D.I.M.; Butterworth, P.J. )

    1990-05-01

    The Antarctica Peninsula (AP) lies on a medium-size block of continental crust and is one of a mosaic of west Antarctica coastal block that underwent a complex tectonic evolution during Gondwana breakup. The peninsula represents the eroded roots of a microcontinental volcanic arc; this arc lay above the easterly subducting proto-Pacific plate, and was active throughout the Mesozoic. The exposed Mesozoic basins display a complex stratigraphy, reflecting local tectonic and volcanic events. There are a few general trends. Almost all basins are post-late Oxfordian, their fill is entirely clastic, and is largely derived from the Antarctica peninsula volcanic arc. Most basins were affected by a period of arc expansion in the latest Jurassic or earliest Cretaceous, which manifests itself as inputs of lava or coarse volcaniclastic sediment overlying mudstones with an open marine fauna. Barriasian and older mudstones are generally finer grained and darker than mudstones from post-Berriasian strata. However, it must be emphasized that these are only general trends. Deformation is variable, commonly progressive. No lithostratigraphic units can be correlated between any two basins, nor are there any interregional unconformities. No matching is possible with basins of equivalent age in formerly contiguous areas of Gondwana. There is evidence that some global eustatic events are recorded in the sedimentary records of at least two of the AP Mesozoic basins, but these have effect only in periods of local tectonic quiescence. The dominant control on sedimentation in this large segment of the Pacific rim was arc tectonics.

  19. Deducing the ancestry of terranes: SHRIMP evidence for South America derived Gondwana fragments in central Europe

    NASA Astrophysics Data System (ADS)

    Friedl, Gertrude; Finger, Fritz; McNaughton, Neal J.; Fletcher, Ian R.

    2000-11-01

    We present here an example of how the sensitive high-resolution ion microprobe (SHRIMP) zircon dating method can provide a terrane-specific geochronological fingerprint for a rock and thus help to reveal major tectonic boundaries within orogens. This method, applied to inherited zircons in a ca. 580 Ma metagranitoid rock from the eastern Bohemian Massif, has provided, for the first time in the central European Variscan basement, unequivocal evidence for Mesoproterozoic and late Paleoproterozoic geologic events ca. 1.2 Ga, 1.5 Ga, and 1.65 1.8 Ga. The recognition of such zircon ages has important consequences because it implies that parts of the Precambrian section of Variscan central Europe were originally derived from a Grenvillian cratonic province, as opposed to the common assumption of an African connection. A comparison with previously published SHRIMP data suggests, however, that these Mesoproterozoic and late Paleoproterozoic zircon ages may be restricted to the Moravo-Silesian unit in the eastern Variscides, whereas the Saxothuringian and Moldanubian zones appear to contain a typical north African (i.e., Neoproterozoic plus Eburnian) inherited-zircon age spectrum. This finding supports new tectonic concepts, according to which Variscan Europe is composed of a number of completely unrelated terranes with extremely different paleogeographic origins. The Moravo-Silesian unit can be best interpreted as a peri-Gondwana terrane, which was situated in the realm of the Amazonian cratonic province by the late Precambrian, comparable to the Avalonian terranes of North America and the United Kingdom.

  20. Larval cases of caddisfly (Insecta: Trichoptera) affinity in Early Permian marine environments of Gondwana

    PubMed Central

    Mouro, Lucas D.; Zatoń, Michał; Fernandes, Antonio C.S.; Waichel, Breno L.

    2016-01-01

    Caddisflies (Trichoptera) are small, cosmopolitan insects closely related to the Lepidoptera (moths and butterflies). Most caddisflies construct protective cases during their larval development. Although the earliest recognisable caddisflies date back to the early Mesozoic (Early and Middle Triassic), being particularly numerous and diverse during the Late Jurassic and Early Cretaceous, the first records of their larval case constructions are known exclusively from much younger, Early to Middle Jurassic non-marine deposits in the northern hemisphere. Here we present fossils from the Early Permian (Asselian–Sakmarian) marine deposits of Brazil which have strong morphological and compositional similarity to larval cases of caddisflies. If they are, which is very probable, these finds not only push back the fossil record of true caddisflies, but also indicate that their larvae constructed cases at the very beginning of their evolution in marine environments. Since modern caddisflies that construct larval cases in marine environments are only known from eastern Australia and New Zealand, we suggest that this marine ecology may have first evolved in western Gondwana during the Early Permian and later spread across southern Pangea. PMID:26765261

  1. Larval cases of caddisfly (Insecta: Trichoptera) affinity in Early Permian marine environments of Gondwana.

    PubMed

    Mouro, Lucas D; Zatoń, Michał; Fernandes, Antonio C S; Waichel, Breno L

    2016-01-01

    Caddisflies (Trichoptera) are small, cosmopolitan insects closely related to the Lepidoptera (moths and butterflies). Most caddisflies construct protective cases during their larval development. Although the earliest recognisable caddisflies date back to the early Mesozoic (Early and Middle Triassic), being particularly numerous and diverse during the Late Jurassic and Early Cretaceous, the first records of their larval case constructions are known exclusively from much younger, Early to Middle Jurassic non-marine deposits in the northern hemisphere. Here we present fossils from the Early Permian (Asselian-Sakmarian) marine deposits of Brazil which have strong morphological and compositional similarity to larval cases of caddisflies. If they are, which is very probable, these finds not only push back the fossil record of true caddisflies, but also indicate that their larvae constructed cases at the very beginning of their evolution in marine environments. Since modern caddisflies that construct larval cases in marine environments are only known from eastern Australia and New Zealand, we suggest that this marine ecology may have first evolved in western Gondwana during the Early Permian and later spread across southern Pangea. PMID:26765261

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

    NASA Astrophysics Data System (ADS)

    Cordani, U. G.

    2003-04-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

  4. Ediacaran 2,500-km-long synchronous deep continental subduction in the West Gondwana Orogen

    NASA Astrophysics Data System (ADS)

    Ganade de Araujo, Carlos E.; Rubatto, Daniela; Hermann, Joerg; Cordani, Umberto G.; Caby, Renaud; Basei, Miguel A. S.

    2014-10-01

    The deeply eroded West Gondwana Orogen is a major continental collision zone that exposes numerous occurrences of deeply subducted rocks, such as eclogites. The position of these eclogites marks the suture zone between colliding cratons, and the age of metamorphism constrains the transition from subduction-dominated tectonics to continental collision and mountain building. Here we investigate the metamorphic conditions and age of high-pressure and ultrahigh-pressure eclogites from Mali, Togo and NE-Brazil and demonstrate that continental subduction occurred within 20 million years over at least a 2,500-km-long section of the orogen during the Ediacaran. We consider this to be the earliest evidence of large-scale deep-continental subduction and consequent appearance of Himalayan-scale mountains in the geological record. The rise and subsequent erosion of such mountains in the Late Ediacaran is perfectly timed to deliver sediments and nutrients that are thought to have been necessary for the subsequent evolution of sustainable life on Earth.

  5. >2500-km-Long Contemporaneous Deep Continental Subduction in the West Gondwana Orogen

    NASA Astrophysics Data System (ADS)

    Rubatto, D.; Ganade de Araujo, C. E.; Hermann, J.; Cordani, U. G.; Caby, R.; Basei, M. A. S.

    2014-12-01

    The 5000-km-long, deeply eroded West Gondwana Orogen (WGO) is a major continental collision zone that exposes numerous occurrences of deeply subducted rocks (i.e. eclogites) along its strike. The position of these eclogites marks the suture zone between colliding cratons and the age of metamorphism constrains the transition from subduction-dominated tectonics to continental collision and mountain building. We investigated the metamorphic conditions and age of high-pressure (HP) and ultrahigh-pressure (UHP) eclogites from Mali, Togo and NE-Brazil . P-T estimates confirm UHP to HP conditions for all these localities. The U-Pb age and trace element composition of metamorphic zircon domains demonstrate that continental subduction in the WGO occurred within 20 m.y. over at least 2500 km during the Ediacaran period (620-610 Ma). We consider this to be the first record of modern, large-scale deep-continental subduction and the consequent appearance of Himalayan-scale mountains in the geological record. The rise of such mountains in the Late Ediacaran is perfectly timed to deliver by erosion the sediments (nutrients) that have been deemed necessary for life sustainability in the following Earth evolution.

  6. Ediacaran 2,500-km-long synchronous deep continental subduction in the West Gondwana Orogen.

    PubMed

    Ganade de Araujo, Carlos E; Rubatto, Daniela; Hermann, Joerg; Cordani, Umberto G; Caby, Renaud; Basei, Miguel A S

    2014-01-01

    The deeply eroded West Gondwana Orogen is a major continental collision zone that exposes numerous occurrences of deeply subducted rocks, such as eclogites. The position of these eclogites marks the suture zone between colliding cratons, and the age of metamorphism constrains the transition from subduction-dominated tectonics to continental collision and mountain building. Here we investigate the metamorphic conditions and age of high-pressure and ultrahigh-pressure eclogites from Mali, Togo and NE-Brazil and demonstrate that continental subduction occurred within 20 million years over at least a 2,500-km-long section of the orogen during the Ediacaran. We consider this to be the earliest evidence of large-scale deep-continental subduction and consequent appearance of Himalayan-scale mountains in the geological record. The rise and subsequent erosion of such mountains in the Late Ediacaran is perfectly timed to deliver sediments and nutrients that are thought to have been necessary for the subsequent evolution of sustainable life on Earth. PMID:25319269

  7. EVOLUTION. A four-legged snake from the Early Cretaceous of Gondwana.

    PubMed

    Martill, David M; Tischlinger, Helmut; Longrich, Nicholas R

    2015-07-24

    Snakes are a remarkably diverse and successful group today, but their evolutionary origins are obscure. The discovery of snakes with two legs has shed light on the transition from lizards to snakes, but no snake has been described with four limbs, and the ecology of early snakes is poorly known. We describe a four-limbed snake from the Early Cretaceous (Aptian) Crato Formation of Brazil. The snake has a serpentiform body plan with an elongate trunk, short tail, and large ventral scales suggesting characteristic serpentine locomotion, yet retains small prehensile limbs. Skull and body proportions as well as reduced neural spines indicate fossorial adaptation, suggesting that snakes evolved from burrowing rather than marine ancestors. Hooked teeth, an intramandibular joint, a flexible spine capable of constricting prey, and the presence of vertebrate remains in the guts indicate that this species preyed on vertebrates and that snakes made the transition to carnivory early in their history. The structure of the limbs suggests that they were adapted for grasping, either to seize prey or as claspers during mating. Together with a diverse fauna of basal snakes from the Cretaceous of South America, Africa, and India, this snake suggests that crown Serpentes originated in Gondwana. PMID:26206932

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

  9. 150 m.y. of Tectonism along the Western Gondwana as Revealed by the Peruvian Cordillera Oriental Batholiths

    NASA Astrophysics Data System (ADS)

    Miskovic, A.; Schaltegger, U.

    2006-05-01

    A striking geochemical relationship exists between the three principal plutonic belts of the Eastern Cordillera of Peru: 1) Mississippian to Pennsylvanian, I-type, metaluminous, hornblende and magnetite dominated granitoids are restricted to the segment north of 11S, and display calc-alkaline evolutionary trends with elevated LILE/HFSE ratios characteristic of continental subduction zones; 2) Permian to Early Triassic, peraluminous, I to S-type, mica and ilmenite rich granitoids of the east-central Peru, are comagmatic with the bimodal tholeiitic lavas of the Mitu Group, and characterized by restricted bimodal compositional range, moderate Fe enrichments, low LILE/HFSE values, and higher Ga/Al ratios, all of which are associated with transitional, post-orogenic (within-plate) suites; 3) Late Triassic, initially A-type monzogranitoids of the southern Cordillera de Carabaya terminate as peralkaline, SiO2-undersaturated intrusives (Ne-syenites) of the Allincapac complex emplaced in the Mitu Gr. shoshonites. The latter exhibit mineralogy characteristic of a shallow and dry source (< 1 kbar H2O-saturated conditions), display extreme Fe enrichments, steep REE profiles, and overall low LILE/HFSE ratios. Combined Sr-Nd-Pb isotope systematics from all three intrusive provinces however, lack variation, and suggest uniformly large degrees of assimilation of the Proterozoic Amazonian basement. In addition to the systematic change in the plutonic chemistry, the U/Pb and 39Ar/40Ar chronometries reveal a general younging-southward trend. The 20 m.y. long magmatism associated with the Mississippian arc in the north-central Cordillera Oriental culminated between 336-325 Ma (Pataz batholith). It was followed by c.a. 40 m.y. hiatus briefly punctuated during a 314-312 Ma episode of orogenic Au-Ag mineralization associated with a period of tectonic uplift. Resumption of the Permo-Triassic magmatism (279- 230 Ma) saw deposition of the bimodal Mitu Group volcanics contemporaneously with the intrusion of the post- collisional plutons in the central Eastern Cordillera (Carrizal, San Ramon batholiths). Sporadic magmatic activity throughout Triassic was marked by eruption of progressively more alkalic Mitu lavas and initiation of the A-type plutonism, which peaked between 216-205 Ma in the southernmost Carabaya Batholith. The 188 Ma old alkaline magmas of the Allincapac complex in the SE Peru mark the latest and most enriched pulse of rift magmatism. Our preliminary geodynamic model envisions an originally orthogonal eastward subduction of the paleo-Pacific crust below the Western Gondwana during the Late Devonian which became strongly oblique towards southeast in the Late Carboniferous, thus imposing a sinistral strike-slip stress regime on the western Amazonian margin. Accretion of a buoyant segment of oceanic crust eventually plugged the subduction zone. This scenario explains both the "craton- free" basement underlying the present Western Cordillera of northern Peru and the sudden termination of arc-related magmatism along the northern Cordillera Oriental in Pennsylvanian. Subsequent uplift and eventual relaxation of the cratonic margin facilitated emplacement of the central S-type granitoids in mid-to-late Permian. The progressive strike-slip duplexing, development of trans- tensional basins capturing the Mitu Gr. molasses, and subsequent back-arc extension in Permian occurred along the inherited suture between the Gondwanan craton and the Arequipa-Antofalla terrane. This model however, precludes the existence of an Arequipa terrane north of its presently delineated isotopic and structural boundaries and its wholesale detachment in Triassic.

  10. European Sedimentary Basins: Deciphering Palaeozoic intra-Pangea Wrench Faulting

    NASA Astrophysics Data System (ADS)

    Aubele, K.; Bachtadse, V.; Muttoni, G.; Ronchi, A.; Durand, M.

    2012-04-01

    Thick sections of sedimentary deposits act as tape recorders of the geomagnetic field over time and allow high resolution paleogeographic reconstructions. Over the past years, we were able to put together a considerable paleomagnetic data set collected from Early Permian and Mesozoic deposits in numerous sedimentary basins throughout Southwest Europe. This data set monitors relative block rotations about vertical axis in this area and thus provides convincing evidence for intra-Pangean wrench faulting in the Early Permian (~ 285-265 Ma). Here, we present previously processed data from Permian sedimentary sections from Southwest France and Sardinia together with data from the Saar-Nahe basin in West Germany. New data from the Permian/Triassic boundary from Sardinian sedimentary basins and data from Permian dyke swarms add further information to draw a more complete picture of the paleogeographic evolution of the Gondwana/Laurasia plate boundary and help to describe controversial intra-Pangean mobility and wrench faulting in the Early Permian.

  11. Cambrian arc evolution along the SE Gondwana active margin: A synthesis from Tasmania-New Zealand-Australia-Antarctica correlations

    NASA Astrophysics Data System (ADS)

    Mnker, Carsten; Crawford, Anthony J.

    2000-06-01

    Belts of Cambrian rocks with arc affinities in eastern Australia, Tasmania, New Zealand, and Antarctica are part of a single convergent margin, active over 30-40 Ma from the latest Early Cambrian to the Late Cambrian. Two of the most complete sequences are exposed in western Tasmania and the northern South Island of New Zealand (Takaka Terrane). Throughout the Middle Cambrian, magmatism in these two regions, in the Lachlan Fold Belt (SE Australia) and the Bowers Terrane (Antarctica) is represented by intra-oceanic arc and back arc sequences. In the mid-Middle Cambrian, collision of these arc segments with the proto-Gondwana continent is recorded by obducted boninite-bearing ophiolites in Tasmania and SE Australia. Postcollisional magmatism of latest Middle to early Late Cambrian age (e.g., Mount Read Volcanics of Tasmania and Stavely Volcanic Complex of Victoria) terminates convergent tectonics in SE Australia and Tasmania. In contrast, no postcollisional volcanism is known from the Bowers Terrane in Antarctica and from New Zealand. In Antarctica, Cambrian igneous activity in the Wilson Terrane and Transantarctic Mountains formed in an active continental margin setting and lasted through the Middle and Late Cambrian. This suggests that the Wilson Terrane is the lateral continuation on continental basement of the Bowers and Takaka Terrane arcs. The differences between the Australian - Tasmanian and New Zealand - Antarctic arc segments may result from a change in subduction polarity along the arc chain, suggested by structural features, sedimentation patterns, and isotope systematics. In the SE Australian and Tasmanian arc segments the proto-Gondwana plate subducted beneath the Pacific plate whereas subduction in the Antarctic and New Zealand segments was of opposite polarity. Common to most Cambrian fragments in SE proto Gondwana is the tectonic overprint by the Ross-Delamerian orogeny from the Middle Cambrian to Early Ordovician, thus paleogeographically linking all the fragments by the end of the Cambrian. The presence of Early Cambrian intra-oceanic rocks at the SE proto-Gondwana margin suggests separation of Laurentia from Gondwana prior to the Early Cambrian.

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    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 event at the Northern Gondwana margin, that probably attained to the palaeo-Tethys expansion (von Raumer et al., 2003). Thus, Sardinia as other Palaeozoic terranes issued from the former northern Gondwana margin (as the French Massif Central and Iberia) experienced an evolution from continental break-up to volcanic arc dismantling and subsequent ensialic rifting (e.g. Sánchez-Garcia et al. 2003; Etxebarria et al. 2006; Chichorro et al. 2008; Pin & Lancelot 1982; Pin & Marini 1993). References Chichorro M., Pereira M.F., Díaz-Azpiroz M., Williams I.S., Fernández C., Pin C., Silva J.B. (2008) Cambrian ensialic rift-related magmatism in the Ossa-Morena Zone (Évora-Aracena metamorphic belt, SW Iberian Massif): Sm-Nd isotopes and SHRIMP zircon U-Th-Pb geochronology. Tectonophysics, 461, 91-113. Etxebarria M., Chalot-Prat F., Apraiz A., Ehuiluz L. (2006) Birth of a volcanic passive margin in Cambrian time: rift paleogeography of the Ossa - Morena Zone, SW Spain. Precambrian Research, 147, 366-386. Leone F., Hamman W., Laske R., Serpagli E., Villas E. (1991) Lithostratigraphic units and biostratigraphy of the post-sardic Ordovician sequence in south-west Sardinia. Bollettino della Società Paleontologica Italiana, 30, 201-235. Oggiano G., Gaggero L., Funedda A., Buzzi L., Different Early Palaeozoic volcanic events at the northern Gondwana margin: U-Pb age evidence from the Southern Variscan branch (Sardinia, Italy). Pin C., Lancelot J. (1982) U-Pb Dating of an Early Paleozoic Bimodal Magmatism in the French Massif Central and of Its Further Metamorphic Evolution. Contrib. Mineral. Petrol., 79, 1-12. Pin C., Marini F. (1993) Early Ordovician continental break-up in Variscan Europe: Nd-Sr isotope and trace element evidence from bimodal igneous associations of the Southern Massif Central, France. Lithos, 29, 177-196. Sánchez-García T., Bellido F., Quesada C. 2003. Geodynamic setting and geochemical signatures of Cambrian - Ordovician rift-related igneous rocks (Ossa-Morena Zone, SW Iberia). Tectonophysics, 365, 233-255. von Raumer J.F., Stampfli G.M., Bussy F. (2003) Gondwana-derived microcontinents — the constituents of the Variscan and Alpine collisional orogens. Tectonophysics, 365, 7-22.

  13. Proterozoic history of the Borborema province (NE Brazil): Correlations with neighboring cratons and Pan-African belts and implications for the evolution of western Gondwana

    NASA Astrophysics Data System (ADS)

    Neves, SRgio Pacheco

    2003-08-01

    Geological and geochronological correlations between Borborema province (NE Brazil) and neighboring cratons and Brasiliano/Pan-African belts indicate that the Amazonian, West African, and So Francisco/Congo cratons and the basement of the Araguaia, Borborema, Nigerian, and Cameroon provinces were part of the Atlantica supercontinent. This continent was established at the end of the Transamazonian/Eburnean cycle (2.0 Ga) and, apart from ubiquitous taphrogenesis in the 1.8-1.7 Ga interval, remained largely unaffected for the following 1 Ga. Around 1 Ga an important magmatic event in Borborema province correlates with rifting episodes and anorogenic magmatism in the So Francisco, Congo, and Amazonian cratons. These events are interpreted as failed attempts to break up Atlantica, which at this time may have been part of the larger Rodinia supercontinent. Renewed extensional conditions in Borborema province during the middle and late Neoproterozoic are attributed to far-field stresses transmitted to the interior of Atlantica by outwardly dipping subduction zones that encircled its northern (present day coordinates) portion. The rarity of petrotectonic assemblages typical of subduction zone environments indicates that extension did not evolve enough to form large oceans basins and thus that the Borborema province essentially includes reworked intracontinental domains. Regional deformation and metamorphism, starting at 650-640 Ma, and shear zone development, beginning at 590-595 Ma, were continuously developed through time and were synchronous throughout most of the Borborema, Araguaia, Cameroon, and Nigerian provinces. Postorogenic conditions were reached 540-530 Myr ago, while active deformation was still occurring in other belts that accreted around Atlantica to form western Gondwana.

  14. Paired δ34S data from carbonate-associated sulfate and chromium-reducible sulfur across the traditional Lower-Middle Cambrian boundary of W-Gondwana

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    In this study, we present the first high-resolution data from coupled δ34S 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 δ13Ccarb, δ18Ocarb, and major/trace element concentrations (Ca, Fe, Mg, Mn, Sr). δ34SCAS values vary between 17.6‰ and 33.2‰, with a maximum CAS concentration of ca. 900 ppm. δ34SCRS 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 δ34SCAS data in each of the sections confounding inter-basinal chemostratigraphic correlations. Nonetheless, the absolute differences in δ34SCAS 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 δ34SCAS 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 δ34SCAS 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.

  15. Late Paleozoic paleolatitude and paleogeography of the Midland basin, Texas

    SciTech Connect

    Walker, D.A. ); Golonka, J. ); Reid, A.M.; Reid, S.T. )

    1992-04-01

    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.

  16. Mass drug administration under the programme to eliminate lymphatic filariasis in Orissa, India: a mixed-methods study to identify factors associated with compliance and non-compliance.

    PubMed

    Babu, Bontha V; Mishra, Suchismita

    2008-12-01

    The present study aimed to identify the factors responsible for compliance and non-compliance of mass drug administration (MDA) under the programme to eliminate lymphatic filariasis (LF) from Orissa, India. It was based on both quantitative (through household MDA coverage survey) and qualitative data (through semi-structured interviews with heads of compliant and non-compliant households) collected during an MDA held in November 2005 in two districts of Orissa. In these districts, 83% of the eligible population received the drug (coverage) and only 49.5% people actually consumed the drug (compliance). Seventeen percent of the population did not even receive the drug. The predominant reason for not receiving the drug at household level was that the drug distributor did not visit the household, while the fear of adverse reactions is the predominant reason for not consuming it. The qualitative data revealed that the major contributor to taking the drug was the awareness that drug protects them from LF. Motivation by health workers was another reason for compliance. In many endemic areas, the issues related to non-compliance were taken casually during implementation. Hence, it is imperative to make the programme more efficient by addressing the issues linked to low compliance. PMID:18632125

  17. A new glucose-6-phosphate dehydrogenase variant, G6PD Orissa (44 Ala{yields}Gly), is the major polymorphic variant in tribal populations in India

    SciTech Connect

    Kaeda, J.S.; Bautista, J.M.; Stevens, D.

    1995-12-01

    Deficiency of glucose-6-phosphate dehydrogenase (G6PD) is usually found at high frequencies in areas of the world where malaria has been epidemic. The frequency and genetic basis of G6PD deficiency have been studied in Africa, around the Mediterranean, and in the Far East, but little such information is available about the situation in India. To determine the extent of heterogeneity of G6PD, we have studied several different Indian populations by screening for G6PD deficiency, followed by molecular analysis of deficient alleles. The frequency of G6PD deficiency varies between 3% and 15% in different tribal and urban groups. Remarkably, a previously unreported deficient variant, G6PD Orissa (44 Ala{yields}Gly), is responsible for most of the G6PD deficiency in tribal Indian populations but is not found in urban populations, where most of the G6PD deficiency is due to the G6PD Mediterranean (188 Ser{yields}Phe) variant. The K{sup NADP}{sub m} of G6PD Orissa is fivefold higher than that of the normal enzyme. This may be due to the fact that the alanine residue that is replaced by glycine is part of a putative coenzyme-binding site. 37 refs., 2 figs., 3 tabs.

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

    PubMed

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

    2005-05-26

    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

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

    NASA Astrophysics Data System (ADS)

    Coiffard, Clément; Mohr, Barbara

    2014-05-01

    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.

  20. Origin of northern Gondwana Cambrian sandstone revealed by detrital zircon SHRIMP dating

    NASA Astrophysics Data System (ADS)

    Avigad, D.; Kolodner, K.; McWilliams, M.; Persing, H.; Weissbrod, T.

    2003-03-01

    Voluminous Paleozoic sandstone sequences were deposited in northern Africa and Arabia following an extended Neoproterozoic orogenic cycle that culminated in the assembly of Gondwana. We measured sensitive high-resolution ion microprobe (SHRIMP) U-Pb ages of detrital zircons separated from several Cambrian units in the Elat area of southern Israel in order to unravel their provenance. This sandstone forms the base of the widespread siliciclastic section now exposed on the periphery of the Arabian-Nubian shield in northeastern Africa and Arabia. Most of the detrital zircons we analyzed yielded Neoproterozoic concordant ages with a marked concentration at 0.55 0.65 Ga. The most likely provenance of the Neoproterozoic detritus is the Arabian-Nubian shield; 0.55 0.65 Ga was a time of posttectonic igneous activity, rift-related volcanism, and strike-slip faulting there. Of the zircons, 30% yielded pre-Neoproterozoic ages grouped at 0.9 1.1 Ga (Kibaran), 1.65 1.85 Ga, and 2.45 2.7 Ga. The majority of the pre-Neoproterozoic zircons underwent Pb loss, possibly as a consequence of the Pan-African orogeny resetting their provenance. Rocks of the Saharan metacraton and the southern Afif terrane in Saudi Arabia (1000 km south of Elat) are plausible sources of these zircons. Kibaran basement rocks are currently exposed more than 3000 km south of Elat (flanking the Mozambique belt), but the shape of the detrital zircons of that age and the presence of feldspar in the host sandstone are not fully consistent with such a long-distance transport. Reworking of Neoproteorozoic glacial detritus may explain the presence of Kibaran detrital zircons in the Cambrian of Elat, but the possibility that the Arabian-Nubian shield contains Kibaran rocks (hitherto not recognized) should also be explored.

  1. Origin of northern Gondwana Cambrian sandstone revealed by detrital zircon SHRIMP dating

    USGS Publications Warehouse

    Avigad, D.; Kolodner, K.; McWilliams, M.; Persing, H.; Weissbrod, T.

    2003-01-01

    Voluminous Paleozoic sandstone sequences were deposited in northern Africa and Arabia following an extended Neoproterozoic orogenic cycle that culminated in the assembly of Gondwana. We measured sensitive high-resolution ion microprobe (SHRIMP) U-Pb ages of detrital zircons separated from several Cambrian units in the Elat area of southern Israel in order to unravel their provenance. This sandstone forms the base of the widespread siliciclastic section now exposed on the periphery of the Arabian-Nubian shield in northeastern Africa and Arabia. Most of the detrital zircons we analyzed yielded Neoproterozoic concordant ages with a marked concentration at 0.55–0.65 Ga. The most likely provenance of the Neoproterozoic detritus is the Arabian-Nubian shield; 0.55–0.65 Ga was a time of posttectonic igneous activity, rift-related volcanism, and strike-slip faulting there. Of the zircons, 30% yielded pre-Neoproterozoic ages grouped at 0.9–1.1 Ga (Kibaran), 1.65–1.85 Ga, and 2.45–2.7 Ga. The majority of the pre-Neoproterozoic zircons underwent Pb loss, possibly as a consequence of the Pan-African orogeny resetting their provenance. Rocks of the Saharan metacraton and the southern Afif terrane in Saudi Arabia (∼1000 km south of Elat) are plausible sources of these zircons. Kibaran basement rocks are currently exposed more than 3000 km south of Elat (flanking the Mozambique belt), but the shape of the detrital zircons of that age and the presence of feldspar in the host sandstone are not fully consistent with such a long-distance transport. Reworking of Neoproteorozoic glacial detritus may explain the presence of Kibaran detrital zircons in the Cambrian of Elat, but the possibility that the Arabian-Nubian shield contains Kibaran rocks (hitherto not recognized) should also be explored.

  2. Episodic growth of the Gondwana supercontinent from hafnium and oxygen isotopes in zircon.

    PubMed

    Kemp, A I S; Hawkesworth, C J; Paterson, B A; Kinny, P D

    2006-02-01

    It is thought that continental crust existed as early as 150 million years after planetary accretion, but assessing the rates and processes of subsequent crustal growth requires linking the apparently contradictory information from the igneous and sedimentary rock records. For example, the striking global peaks in juvenile igneous activity 2.7, 1.9 and 1.2 Gyr ago imply rapid crustal generation in response to the emplacement of mantle 'super-plumes', rather than by the continuous process of subduction. Yet uncertainties persist over whether these age peaks are artefacts of selective preservation, and over how to reconcile episodic crust formation with the smooth crustal evolution curves inferred from neodymium isotope variations of sedimentary rocks. Detrital zircons encapsulate a more representative record of igneous events than the exposed geology and their hafnium isotope ratios reflect the time since the source of the parental magmas separated from the mantle. These 'model' ages are only meaningful if the host magma lacked a mixed or sedimentary source component, but the latter can be diagnosed by oxygen isotopes, which are strongly fractionated by rock-hydrosphere interactions. Here we report the first study that integrates hafnium and oxygen isotopes, all measured in situ on the same, precisely dated detrital zircon grains. The data reveal that crust generation in part of Gondwana was limited to major pulses at 1.9 and 3.3 Gyr ago, and that the zircons crystallized during repeated reworking of crust formed at these times. The implication is that the mechanisms of crust formation differed from those of crustal differentiation in ancient orogenic belts. PMID:16452978

  3. Septarian carbonate concretions in the Permian Rio do Rasto Formation: Birth, growth and implications for the early diagenetic history of southwestern Gondwana succession

    NASA Astrophysics Data System (ADS)

    Alessandretti, Luciano; Warren, Lucas Veríssimo; Machado, Rômulo; Novello, Valdir Felipe; Sayeg, Isaac Jamil

    2015-08-01

    Between the Late Carboniferous and Early Triassic, the southwestern Gondwana supercontinent was characterized by the development of a huge intracratonic basin. A large confined epeiric sea and the accumulation of a transgressive-regressive sequence were formed by continuous subsidence related to tectonic effects caused by the Sanrafaelic Orogeny and the consequent generation of accommodation space. The Permian Rio do Rasto Formation documents the last progradational cycle related to the complete continentalization of this epeiric sea. The basal member of the Rio do Rasto Formation (Serrinha) is believed to have been deposited in a shallow epicontinental water body subjected to storms and influenced by episodic deltaic incursions. One of the most remarkable characteristics of the Serrinha Member is the presence of carbonate concretions hosted in mudstones and very fine sandstones. Here, we combine sedimentological and petrographic descriptions coupled with geochemical and stable carbon and oxygen isotopic data to elucidate the nature of these carbonate concretions. The non-deformed internal structure, decreasing proportion of carbonate cements relative to detrital grains toward the concretion edges, core-to-rim isotopic variations, and perhaps most importantly, the preservation of a well-developed cardhouse fabric support an early diagenetic origin for these structures at shallow burial depths of tens of meters. Stable isotope analyses of micritic calcite cements and calcites filling the septarian fractures reveal major negative excursions in both δ18O and δ13C values. Oxygen isotope ratios obtained for the micritic calcite cements vary between - 12.1 and - 2.6‰. The calcite filling septarian fractures also exhibit negative values of δ18O (- 14.2 to - 13.8‰), with an average of - 14‰. The δ13C values of micritic calcite cements range from - 5.0-0.2‰. The carbon isotopic data from the calcite-filling septarian fractures are also negative (- 4.4 to - 3.3‰). The δ18O signatures suggest that the early diagenetic carbonate concretions precipitated in a shallow freshwater environment rather than in a marine setting. The δ13C values suggest that the carbon isotopes were derived from a source with slightly depleted 13C, supporting at least a partial organogenic contribution with weak sulfate reduction rates typical of freshwater systems. Sedimentological analysis shows that the epicontinental water body in which the Serrinha Member was deposited was constantly supplied by rivers and meteoric waters, which suggests that an enormous freshwater basin with restricted marine connections to the Panthalassa Ocean once existed.

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

    USGS Publications Warehouse

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

    2006-01-01

    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.

  5. Origin of pegmatites and fluids at Ponta Negra (RJ, Brazil) during late- to post-collisional stages of the Gondwana Assembly

    NASA Astrophysics Data System (ADS)

    Bongiolo, Everton Marques; Renac, Christophe; Piza, Patricia d'Almeida de Toledo; Schmitt, Renata da Silva; Mexias, André Sampaio

    2016-01-01

    The Ponta Negra Pegmatites (PNP), part of a pegmatitic province in Rio de Janeiro State, Brazil, crop out along an intensely deformed, medium- to high-grade metamorphic area that is proximal to a crustal-scale thrust zone developed during the Brasiliano/Pan-African Orogeny. Fieldwork shows that the pegmatites formed in two distinct stages: (i) syn-collisional leucosome veins (Group I) conformable with the tectonic foliation of the gneissic host rocks and (ii) late- to post-collisional dykes (Group II) that cross-cut the same tectonic foliation at a high angle. In this paper, we use geochemistry of whole-rock and mineral separates (alkali-feldspar and biotite), fluid inclusion microthermometry and stable isotopic (δ18O, δD, δ13C) determinations on minerals (quartz, alkali-feldspar, biotite and magnetite) and fluid inclusions to provide insights into the composition of the pegmatite-forming melts, associated fluids, and their geotectonic significance. U-Pb SHRIMP dating of the Cajú syenogranite was performed to evaluate and compare the timing of magmatic events along the Cabo Frio Tectonic Domain as this is the closest post-collisional pluton to the studied pegmatites. The calculated temperature for the Group I syn-collisional veins (740 °C) is similar to previous estimates for the peak metamorphic conditions in the study area. Variations in the temperature of the Group II pegmatite dykes obtained from stable isotopes (380 to 720 °C), and microthermometric data from primary fluid inclusions with traces of N2 (Th = 280 to 360 °C), may reflect the thermodynamics of the pegmatite crystallization, exsolution textures and isotopic exchange. The composition of fluids in equilibrium within the pegmatite dykes consists of magmatic and metamorphic components. The minimum pressures calculated for the emplacement of the pegmatites are equivalent to a shallow crustal depth between 1.7 and 3.5 km, which corresponds to the exhumation of the orogen since the emplacement of the pegmatites. A linear trend of decreasing CO2 content and δ13CCO2 is consistent with mixtures between (i) carbon derived from organic matter or volatilization of skarns and (ii) inorganic carbon (carbonate). Based on the data obtained, we propose that the pegmatites of Ponta Negra are close to an LCT-type geochemical signature (highly peraluminous magmas with normative corundum), and originated by partial melting of the metasedimentary Palmital succession at depth, during the waning stages of the Búzios Orogeny. The primary melts of the PNP cross-cut both the Neoproterozoic supracrustals and the Paleoproterozoic orthogneissic basement during its ascent and emplacement at higher crustal levels. Variable melt sources explain the slight differences in geochemical compositions among the studied rocks within the metasedimentary succession, which probably include Mn-bearing exhalites, as well as differentiation processes. The 454 ± 5 Ma U-Pb (zircon) age of the Cajú syenogranite overlaps previous geochronological data of 440 ± 11 Ma obtained on a pegmatite dyke at Ponta Negra, bracketing and extending the time interval for the Gondwana assembly collapse magmatism in the region. The heat that triggered this magmatic event could still be a consequence of the collisional orogeny, increasing contents of heat-producing elements, or, a large intraplate extension that followed the Gondwana amalgamation and initiated the formation of Paleozoic basins.

  6. 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

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

    2007-01-01

    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.

  7. Paleozoic Orogens of Mexico and the Laurentia-Gondwana Connections: an Update

    NASA Astrophysics Data System (ADS)

    Ortega-Gutierrez, F.

    2009-05-01

    The present position of Mexico in North America and the fixist tectonic models that prevailed prior to the seventies of the past century, have considered the main Paleozoic tectonic systems of Mexico as natural extensions of the orogens that fringed the eastern and southern sides of the Laurentian craton. Well known examples of pre-Mesozoic orogens in Mexico are the Oaxacan, Acatlan, and Chiapas polymetamorphic terranes, which have been correlated respectively with the Grenville and Appalachian-Ouachitan orogens of eastern North America. Nonetheless, several studies conducted during the last decade in these Mexican orogenic belts, have questioned their Laurentian connections, regarding northwestern Gondwana instead as the most plausible place for their birth and further tectonic evolution. This work pretends to approach the problem by briefly integrating the massive amount of new geological information, commonly generated through powerful dating methods such as LA-ICPM-MS on detrital zircon of sedimentary and metasedimentary units in the Paleozoic crustal blocks, which are widely exposed in southern and southeastern Mexico. The Acatlan Complex bears the closest relationships to the Appalachian orogenic system because it shows thermotectonic evidence for opening and closure of the two main oceans involved in building the Appalachian mountains in eastern Laurentia, whereas two other Paleozoic terranes in NW and SE Mexico, until recently rather geologically unknown, may constitute fundamental links between the Americas for the last-stage suturing and consolidation of western Pangea. The buried basement of the Yucatan platform (400,000 squared km) on the other hand, remains as one of the most relevant problems of tectonostratigraphic correlations across the Americas, because basement clasts from the Chicxulub impact ejecta reveal absolute and Nd-model ages that suggest close Gondwanan affinities. Major changes in the comprehension of the Paleozoic orogens in Mexico include the swift of the Acatlan Complex from Iapetus to Rheic scenarios, and the apparent continuation of the Ouachita belt across northern Mexico into south central Sonora, rather than displaced eastwards along the legendary Mojave-Sonora megashear. And yet, poorly known suture-related lithotectonic associations of Paleozoic metamorphic rocks and arc granitoids that underlie the eastern margin of Mexico, have not been explained by existing models dealing with the Appalachian-Mexico-Gondwanan connections.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

  9. Isotopic characterisation of the sub-continental lithospheric mantle beneath Zealandia, a rifted fragment of Gondwana

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    The greater New Zealand region, known as Zealandia, represents an amalgamation of crustal fragments accreted to the paleo-Pacific Gondwana margin and which underwent significant thinning during the subsequent split from Australia and Antarctica in the mid-Cretaceous following opening of the Tasman Sea and the Southern Ocean. We present Sr, Nd and Pb isotopes and laser ablation trace element data for a comprehensive suite of clinopyroxene separates from spinel peridotite xenoliths (lherzolite to harzburgite) from the sub-continental lithospheric mantle across southern New Zealand. These xenoliths were transported to the surface in intra-plate alkaline volcanics that erupted across the region in the Eocene and Miocene (33-10 m.y.a.). Most of the volcanic suites have similar geochemical and isotopic properties that indicate melting of an OIB-like mantle source in the garnet stability zone and that contained a HIMU component. The volcanics have tapped two adjacent but chemically contrasting upper mantle domains: a fertile eastern domain and an extremely depleted western domain. Both domains underlie Mesozoic metasedimentary crust. Radiogenic isotope compositions of the clinopyroxene have 87Sr/86Sr between 0.7023 to 0.7035, 143Nd/144Nd between 0.5128 and 0.5132 (corresponding to ?Nd between +3 and +13) with a few samples extending to even more depleted compositions, 206Pb/204 Pb between ca. 19.5 to 21.5 and 208Pb/204 Pb between ca. 38.5 to 40.5. No correlations are observed between isotopic composition, age or geographical separation. These isotopic compositions indicate that the sub-continental lithospheric mantle under southern New Zealand has a regionally distinct and pervasive FOZO to HIMU - like signature. The isotopic signatures are also similar to those of the alkaline magmas that transported the xenoliths and suggest that most of the HIMU signature observed in the volcanics could be derived from a major source component in the sub-continental lithospheric mantle. Trace element abundances in clinopyroxene are highly heterogeneous and vary from LREE-enriched, relatively flat and MORB-like, strongly LREE-depleted, through to patterns displaying evidence for depletion and subsequent re-enrichment. These variations occur throughout the region and also between different xenoliths from a single eruption site. There are no clear correlations between REE characteristics and isotopic composition suggesting that much of the depletion and re-enrichment is relatively recent. A broad scatter of increasing 143Nd/144Nd with increasing Sm/Nd, plotting broadly between 150-350 Ma isochrons, may provide some constraints on these events.

  10. Petrography of Permian "Gondwana" coals from boreholes in northwestern Bangladesh, based on semiautomated reflectance scanning

    USGS Publications Warehouse

    Bostick, N.H.; Betterton, W.J.; Gluskoter, H.J.; Nazrul, Islam M.

    1991-01-01

    Drilling through Quaternary alluvium and Tertiary cover at low-gravity anomalies in northwestern Bangladesh showed the presence of Permian sedimentary rocks in depressions that may be as much as a thousand meters deep in the crystalline basement. These Permian strata include low-sulfur, high-volatile bituminous coals in beds as thick as 15 m. The maceral group composition of these coals was determined by semiautomated reflectance scanning with a motorized microscope stage, rather than by point counting. This method was chosen to give objectively recorded raw analytical data and to provide a graphical picture of each sample. The coals are mostly "Gondwana" type (poorly layered "plum pudding" with abundant minerals and inertinite in a vitrinite groundmass) that would be classed as semi-dull (inerto-gelitite) coals. However, six samples have more than 70% vitrinite. None of the samples would be classed as sapropelic (liptinitic). The upper, middle, and lower main seams in borehole GDH-45 were sampled in 10 benches (0.1-3 m thick) each. Inertinite ranges from 7 to 100 vol% (mineral free basis) in individual benches, but composite seam averages are 41, 54 and 67%. Inertinite increases toward the top of two main seams so the bottom would yield the most valuable first mine slices. Some benches with extremely high inertinite content, such as the top 7 m of the lower thick seam, might be mined specially for blending with foreign low-inert coals to increase coke strength. The free swelling index reaches 7.5 in several vitrinite-rich benches, which can indicate good coking coal. Much of the vitrinite is fluorescent, which indicates secondary bituminization characteristic of vitrinite in good coking coals. Ash yields range from 8 to 52%, with composite seam averages of 15, 14 and 24%. Rare visible pyrite is in veinlets or small nodules; framboids and dispersed pyrite are absent. In borehole GDH-40 near Barapukuria (200-500 m depth), the mean random reflectance of vitrinite "A" ranges from 0.60 to 0.80% Ro and vitrinite "B" ranges from 0.55 to 0.65%. In borehole GDH-45 near Khalaspir (287-442 m), the reflectance of vitrinite ranges from 0.79 to 0.94%. In individual cases, the vitrinite is difficult to define because of semivitrinite at higher reflectance (forming a separate peak on several reflectograms) and because of surface bitumen films or resinous (?) inclusions at lower reflectance. On the basis of vitrinite reflectance, the coals can be considered to have entered the "main phase of bitumen generation" of organic thermal maturation as understood in petroleum geochemistry. ?? 1991.

  11. Melt generation in the West Antarctic Rift System: the volatile legacy of Gondwana subduction?

    NASA Astrophysics Data System (ADS)

    Aviado, K.; Rilling-Hall, S.; Mukasa, S. B.; Bryce, J. G.; Cabato, J.

    2013-12-01

    The West Antarctic Rift System (WARS) represents one of the largest extensional alkali volcanic provinces on Earth, yet the mechanisms responsible for driving rift-related magmatism remain controversial. The failure of both passive and active models of decompression melting to explain adequately the observed volume of volcanism has prompted debate about the relative roles of thermal plume-related melting and ancient subduction-related flux melting. The latter is supported by roughly 500 Ma of subduction along the paleo-Pacific margin of Gondwana, although both processes are capable of producing the broad seismic anomaly imaged beneath most of the Southern Ocean. Olivine-hosted melt inclusions from basanitic lavas provide a means to evaluate the volatile budget of the mantle responsible for active rifting beneath the WARS. We present H2O, CO2, F, S and Cl concentrations determined by SIMS and major oxide compositions by EMPA for olivine-hosted melt inclusions from lavas erupted in Northern Victoria Land (NVL) and Marie Byrd Land (MBL). The melt inclusions are largely basanitic in composition (4.05 - 17.09 wt % MgO, 37.86 - 45.89 wt % SiO2, and 1.20 - 5.30 wt % Na2O), and exhibit water contents ranging from 0.5 up to 3 wt % that are positively correlated with Cl and F. Coupling between Cl and H2O indicates metasomatic enrichment by subduction-related fluids produced during dehydration reactions; coupling between H2O and F, which is more highly retained in subducting slabs, may be related to partial melting of slab remnants [1]. Application of source lithology filters [2] to whole rock major oxide data shows that primitive lavas (MgO wt % >7) from the Terror Rift, considered the locus of on-going tectonomagmatic activity, have transitioned from a pyroxenite source to a volatilized peridotite source over the past ~4 Ma. Integrating the volatile data with the modeled characteristics of source lithologies suggests that partial melting of lithosphere modified by subduction processes is the source of pyroxenite and volatiles in the mantle beneath the present-day rift. The earliest magmatic activity preferentially removed the most readily fusible components from the mantle, resulting in transition to a metasomatized peridotite source over time. [1] Straub & Layne, 2003, GCA; [2] Herzberg & Asimow, 2008, G3; [3] Rilling et al., 2009, JGR.

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

    NASA Astrophysics Data System (ADS)

    Lom, Nalan; lgen, Semih Can; zgl, Necdet; Celal ?engr, A. M.

    2014-05-01

    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 dcollement underneath the whole city which thrusts the entire structure westward.

  13. Tectonic history of the Illinois basin

    SciTech Connect

    Kolata, D.R.; Nelson, J.W. )

    1990-05-01

    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.

  14. Evidence of Gondwana early rifting process recorded by Resende-Ilha Grande Dike Swarm, southern Rio de Janeiro, Brazil

    NASA Astrophysics Data System (ADS)

    Guedes, Eliane; Heilbron, Monica; de Morisson Valeriano, Claudio; de Almeida, Julio César Horta; Szatmari, Peter

    2016-04-01

    Continental flood basalts and dike swarm have been related to continental breakup process through geological time. The Resende - Ilha Grande Dike swarm (RIGDS) located in the southeast Brazil, is related the Gondwana breakup and composed of dikes/sills intruded in Precambrian gneiss. The dikes have three distinguish orientations: NNW more inland; NS-NNE in the central segment and NE orientation in the coast line, consistent with Precambrian structural lineaments. The swarm comprises high-TiO2 tholeiitic basalts divided into three suites based on REE and Sr and Nd isotope data. The Resende and Volta Redonda suites present higher initial 87Sr/86Sr ratios between 0.7077 and 0.7065, while Angra dos Reis suite presents values of 0.7066 to 0.7057. Geochemical and isotopic data support the sub-continental lithospheric mantle (SCLM) as the main source for the high-TiO2 basalts. The suites heterogeneities are explained by different compositions of SCLM in accreted Precambrian terranes and/or different degree of partial melting and fractional. 40Ar/39Ar data indicate age interval between ca. 156 to 144 Ma for the swarm, older than the average for Gondwana breakup (ca. 130-120 Ma). The age interval places the RIGDS between the Karoo magmatism (181-178 Ma) and the Paraná-Etendeka magmatism (133-134 Ma) and indicates that extensional process affected the supercontinent prior the break-up.

  15. Evolutionary sequences and hydrocarbon potential of Kenya sedimentary basins

    SciTech Connect

    Cregg, A.K. )

    1991-03-01

    Kenya basins have evolved primarily through extension related to episodic continental rifting. In eastern Kenya, thick accumulations of sediments formed within grabens during the prerift phase (Precambrian to Carboniferous) of the Gondwana breakup. Synrift sedimentation (Late Carboniferous to Middle Jurassic) occurred within a north-south rift system, which included the Mandera basin, South Anza basin, and Lamu embayment. During the Early Jurassic, a marine transgression invaded the margins of the eastern Kenya rift basins, resulting in the deposition of platform carbonates and shales. A Callovian-aged salt basin formed in the offshore regions of the Lamu embayment. Intermittent tectonic activity and eustatic sea-level changes controlled sedimentation, which produced marine shales, carbonates or evaporites, and fluvio-deltaic to lacustrine sandstones. From the Early Cretaceous to recent, continental sediments were deposited within the North Anza and Turkana basins. These fluvial-lacustrine sediments are similar to the Lower Cretaceous sequences that have produced oil in the Mesozoic Sudanese Abu Gabra rift. Although exploration activities began in the early 1950s, significant occurrences of potential reservoir, source, and seal lithologies as well as trapping configurations remain in many areas. Favorable structures and sequences of reservoir sandstones and carbonates overlain by potentially sealing lacustrine or marine shales, evaporites, or volcanics have been noted. Potential source beds are believed to be present within shales of the lacustrine or marine depositional environments.

  16. Structural framework, stratigraphy, and evolution of Brazilian marginal basins

    SciTech Connect

    Ojeda, H.A.O.

    1982-06-01

    The structural framework of the Brazilian continental margin is basically composed of eight structural types: antithetic tilted step-fault blocks, synthetic untilted step-fault blocks, structural inversion axes, hinges with compensation grabens, homoclinal structures, growth faults with rollovers, diapirs, and igneous structures. The antithetic tilted and synthetic untilted step-fault blocks are considered as synchronous, complementary structural systems, separated by an inversion axis. Two evaporitic cycles (Paripueira and Ibura) were differentiated in the Sergipe-Alagoas type basin and tentatively correlated to the evaporitic section of other Brazilian marginal basis. Four phases are considered in the evolution of the Brazilian marginal basins: pre-rift, rift, transitional, and drift. During the pre-rift phase (Late Jurassic-Early Cretaceous), continental sediments were deposited in peripheral intracratonic basins. In the rift phase (Early Cretaceous), the breakup of the continental crust of the Gondwana continent gave rise to a central graben and rift valleys where lacustrine sediments were deposited. The transitional phase (Aptian) developed under relative tectonic stability, when evaporitic and clastic lacustrine sequences were being deposited. In the drift phase (Albian to Holocene), a regionl homoclinal structure developed, consisting of two distinct sedimentary sequences, a lower clastic-carbonate and an upper clastic. From the Albian to the Holocene Epoch, structures associated to plastic displacement of salt or shale developed in many Brazilian marginal basins. Two phases of major igneous activity occurred: one in the Early Cretaceous associated with the rift phase of the Gondwana continent, and the other in the Tertiary during the migration phase of the South American and African plates.

  17. 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

    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

    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

  18. Paleoclimate studies for controversial continental paleogeographies: The application of spherical geodesic grids and climate models to Gondwana's Devonian apparent polar wander path

    NASA Astrophysics Data System (ADS)

    Moore, Thomas Leonard, Jr.

    1999-11-01

    Paleomagnetic data acquired in the last 10 to 15 years have failed to clearly delineate the Devonian apparent polar wander (APW) path for Gondwana. Consequently, many paleogeographers and paleomagnetists have turned to paleoclimate data to assist in locating Gondwana. Paleoclimate data have been used to either support proposed paleomagnetic-based positions for Gondwana or to independently position the continent. Both of these approaches have problems, including how paleoclimate data are handled and the assumption of a zonal climate system. Several improvements of these approaches are proposed in this study. First, paleoclimate data were grouped into occurrences using a spherical geodesic grid system when statistical manipulations were to be performed. The use of occurrences reduces errors caused by variations in sampling resolution and post-depositional processes. Grid cells in the spherical geodesic grid systems are near-equal area and shape. A comparison between spherical geodesic grid systems with other grid systems showed that the spherical geodesic grids were the most stable grid system if used in combination with a technique called rotational minimization, which finds the fewest possible occurrences for a given data set. Second, two techniques commonly used in paleogeographic studies were modified and a third technique was introduced. The first two techniques, called the palepole zonality method and the modified pole-finder method, were designed to rate proposed pole positions for Gondwana using latitude-distribution models for paleoclimate data. The final method, the parametric climate-model method, uses a conceptual climate model to predict the climate of the continent, which was compared to regional climate inference models. The results of these techniques when applied to Gondwana suggested that the continent moved little during the Devonian: the pole moved from west-central Gondwana in the Early Devonian to the northwest or to the east by the Carboniferous. The results also show, however, that all of these techniques are limited in their ability to pick a single position for Gondwana. Consequently, the best path identified by these methods cannot be assumed to be correct and confirming paleomagnetic data are still required.

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

    USGS Publications Warehouse

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

    2007-01-01

    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.

  20. Early Paleozoic accretionary orogenesis along northern margin of Gondwana constrained by high-Mg metaigneous rocks, SW Yunnan

    NASA Astrophysics Data System (ADS)

    Xing, Xiaowan; Wang, Yuejun; Cawood, Peter A.; Zhang, Yuzhi

    2015-12-01

    SW Yunnan of China constituted part of the northern margin of Gondwana facing the proto-Tethys ocean in the early Paleozoic. However, the evolution of the region and its relationship with the accretionary orogenism have been poorly established. This paper reports a set of new zircon U-Pb age data and whole-rock major oxides, elemental and Sr-Nd isotopic data for early Paleozoic metavolcanic rocks from the previously defined Lancang Group and reveals the development of an Ordovician suprasubduction zone in SW Yunnan. Zircon U-Pb ages of 462 ± 6 and 454 ± 27 Ma for two representative samples indicate eruption of the volcanic rocks in the Late Ordovician. Geochemical data for the metavolcanic rocks together with other available data indicate a calc-alkaline affinity with high Al2O3 (13.04-18.77 wt%) and low TiO2 (0.64-1.00 wt%). They have Mg-numbers ranging from 62 to 50 with SiO2 of 53.57-69.10 wt%, compositionally corresponding to the high-Mg andesitic rocks. They display enrichments in LREEs and LILEs with significant Eu negative anomalies (δEu = 0.20-0.33), and depletions in HFSEs, similar to arc volcanic rocks. Their initial 87Sr/86Sr ratios range from 0.721356 to 0.722521 and ɛNd(t) values from -7.63 to -7.62 with Nd model ages of 2.06-2.10 Ga. Integration of ages and geochemical data with available geological observations, we propose the presence of Ordovician magmatism related to proto-Tethyan evolution in SW Yunnan and the metaigneous rocks formed in an island-arc setting. They were part of a regional accretionary orogen that extended along the northern margin of Gondwana during Neoproterozoic to early Paleozoic period.

  1. Cycles and stacking patterns in carboniferous rocks of the Black Warrior Foreland Basin

    SciTech Connect

    Pashin, J.C.

    1994-12-31

    Stratigraphic data from the Black Warrior Basin provide a robust basis for testing the influence of tectonics and climate on cyclicity in a foreland basin. The basin fill comprises carbonate-bearing Chester-type and coal-bearing Pottsville-type depositional cycles, and the composition, frequency, and stacking patterns of those cycles reflect dynamically interwoven tectonic and climate factors. Deformational loading evidently gave rise to flexural movements that determined cycle stacking patterns by controlling spatial and temporal variation of subsidence rate. Evolving tectonic highlands, moreover, provided shifting sources of terrigenous clastic sediment, thereby affecting stratal geometry. The transition from carbonate- to coal-bearing cycles reflects drift of southeastern North America into the humid equatorial belt. Change of average cycle duration from 1.1. to less than 0.5 m.y. corresponds to Gondwana glaciation, suggesting significant climatic forcing.

  2. Factors affecting treatment-seeking for febrile illness in a malaria endemic block in Boudh district, Orissa, India: policy implications for malaria control

    PubMed Central

    2010-01-01

    Background Orissa state in eastern India accounts for the highest malaria burden to the nation. However, evidences are limited on its treatment-seeking behaviour in the state. We assessed the treatment-seeking behaviour towards febrile illness in a malaria endemic district in Orissa. Methods A cross-sectional community-based survey was carried out during the high malaria transmission season of 2006 in Boudh district. Respondents (n = 300) who had fever with chills within two weeks prior to the day of data collection were selected through a multi-stage sampling and interviewed with a pre-tested and structured interview schedule. Malaria treatment providers (n = 23) were interviewed in the district to gather their insights on factors associated with prompt and effective treatment through a semi-structured and open-ended interview guideline. Results Majority of respondents (n = 281) sought some sort of treatment e.g. government health facility (35.7%), less qualified providers (31.3%), and community level health workers and volunteers (24.3%). The single most common reason (66.9%) for choosing a provider was proximity. Over a half (55.7%) sought treatment from appropriate providers within 48 hours of onset of symptoms. Respondents under five years (OR 2.00, 95% CI 0.84-4.80, P = 0.012), belonging to scheduled tribe community (OR 2.13, 95% CI 1.11-4.07, P = 0.022) and visiting a provider more than five kilometers (OR 2.04, 95% CI 1.09-3.83, P = 0.026) were more likely to have delayed or inappropriate treatment. Interviews with the providers indicated that patients' lack of trust in community volunteers providing treatment led to inappropriate treatment-seeking from the less qualified providers. The reasons for the lack of trust included drug side effects, suspicions about drug quality, stock-outs of drugs and inappropriate attitude of the provider. Conclusion Large-scale involvement of less qualified providers is suggested in the malaria control programme as volunteers after appropriate capacity development since the community has more trust in them. This should be supported by uninterrupted supply of drugs to the community volunteers, and involvement of the community-based organizations and volunteers in the planning, implementation, and monitoring of malaria control services. There is also a need for continuous and rigorous impact evaluations of the program to make necessary modifications, scale up and to prevent drug resistance. PMID:21192825

  3. Prepared to react? Assessing the functional capacity of the primary health care system in rural Orissa, India to respond to the devastating flood of September 2008

    PubMed Central

    Phalkey, Revati; Dash, Shisir R.; Mukhopadhyay, Alok; Runge-Ranzinger, Silvia; Marx, Michael

    2012-01-01

    Background Early detection of an impending flood and the availability of countermeasures to deal with it can significantly reduce its health impacts. In developing countries like India, public primary health care facilities are frontline organizations that deal with disasters particularly in rural settings. For developing robust counter reacting systems evaluating preparedness capacities within existing systems becomes necessary. Objective The objective of the study is to assess the functional capacity of the primary health care system in Jagatsinghpur district of rural Orissa in India to respond to the devastating flood of September 2008. Methods An onsite survey was conducted in all 29 primary and secondary facilities in five rural blocks (administrative units) of Jagatsinghpur district in Orissa state. A pre-tested structured questionnaire was administered face to face in the facilities. The data was entered, processed and analyzed using STATA 10. Results Data from our primary survey clearly shows that the healthcare facilities are ill prepared to handle the flood despite being faced by them annually. Basic utilities like electricity backup and essential medical supplies are lacking during floods. Lack of human resources along with missing standard operating procedures; pre-identified communication and incident command systems; effective leadership; and weak financial structures are the main hindering factors in mounting an adequate response to the floods. Conclusion The 2008 flood challenged the primary curative and preventive health care services in Jagatsinghpur. Simple steps like developing facility specific preparedness plans which detail out standard operating procedures during floods and identify clear lines of command will go a long way in strengthening the response to future floods. Performance critiques provided by the grass roots workers, like this one, should be used for institutional learning and effective preparedness planning. Additionally each facility should maintain contingency funds for emergency response along with local vendor agreements to ensure stock supplies during floods. The facilities should ensure that baseline public health standards for health care delivery identified by the Government are met in non-flood periods in order to improve the response during floods. Building strong public primary health care systems is a development challenge. The recovery phases of disasters should be seen as an opportunity to expand and improve services and facilities. PMID:22435044

  4. Anomalous values of gravity and magnetism in the western margin of Gondwana

    NASA Astrophysics Data System (ADS)

    Weidmann, Cecilia; Gimenez, Mario; Klinger, Federico Lince; Alvarez, Orlando

    2016-01-01

    This research is based on a joint geological and geophysical study performed in the South Central Andes region. We acquired and processed terrestrial and satellite gravity data, as well as terrestrial and aeromagnetic data. Balanced geological cross-sections were constrained by physical properties of rocks (densities and magnetic susceptibilities obtained from field samples and well log). This study was performed in order to interpret a complex region that is still under debate: the location of Famatinian magmatic arc and its boundary with the Cuyania terrain. By means of gravity anomaly we developed direct and inverse models constrained by field data. The existence of a major high-density geological structure was evidenced from these models, located below the Vinchina basin and to the east of Cerro Rajado respectively. The existence of such gravity high could be linked to the boundary between the Famatinian magmatic arc and the accreted Cuyania wedge.

  5. Tectonostratigraphic history of the Ediacaran-Silurian Nanhua foreland basin in South China

    NASA Astrophysics Data System (ADS)

    Yao, Wei-Hua; Li, Zheng-Xiang

    2016-04-01

    This paper presents the tectonostratigraphic evolution of the Ediacaran-Silurian Nanhua Basin in South China and explores the relationship between clastic sedimentation in the basin and evolution of the adjacent Wuyi-Yunkai orogen. Sedimentary facies in the basin comprises, in an ascending order, turbiditic marine, shallow marine, and fluvial-dominated deltaic facies, featuring a lateral migration from southeast to northwest. We interpret the Ediacaran-Silurian Nanhua Basin as a foreland basin with a three-stage evolution history. Stage 1: the Ediacaran-Cambrian stage, recording the start of tectonic subsidence with turbiditic marine siliciclastic deposition, fed by exotic orogens outboard South China; Stage 2: the Ordovician to earliest-Silurian stage, characterized by a migrating depocenter with dominant shallow marine and deltaic siliciclastic deposition, fed by the local and northwestward propagating Wuyi-Yunkai orogen; Stage 3: the Silurian stage, showing the arrival of depocenter in the Yangtze Block during the waning stage of the orogeny with deltaic deposition in the remanent foreland basin. The Wuyi-Yunkai orogen remained the dominant sedimentary source region during Stage 3. Stage 1 was likely related to the collision of the South China Block toward northern India during the assembly of Gondwana, whereas Stages 2 and 3 recorded sedimentation during the northwestward propagation and subsequent orogenic root delamination/collapse of the Wuyi-Yunkai orogen, respectively. The Wuyi-Yunkai orogeny in South China is interpreted to have resulted from the far-field stress of the collision between South China and Indian Gondwana.

  6. Cyclicity and stacking patterns in Carboniferous strata of the Black Warrior Foreland Basin

    SciTech Connect

    Pashin, J.C.

    1994-09-01

    Cyclicity in Carboniferous stratigraphic successions has long been attributed to tectonism and climate, but the ways these variables interact to determine the architecture of sedimentary basin fills remain a subject of intense debate. Geophysical well logs and cores from the Black Warrior basin were used to test the effects of tectonism and climate on cyclicity and stacking patterns in a foreland-basin setting. The Black Warrior basin formed in Carboniferous time by diachronous tectonic loading of the Alabama continental promontory along the Appalachian-Ouachita juncture. Climatic changes affecting the basin during this time include drift of southeastern North America from the arid southern tradewind belt toward the humid equatorial belt, as well as the onset of a major Gondwana glaciation just prior to the end of the Chesterian. The fill of the Black Warrior basin comprises carbonate and coal-bearing depositional cycles, and the composition, frequency, and stacking patterns of those cycles reflect dynamically interwoven tectonic and climatic factors. Tectonic loading evidently gave rise to flexural movements that determined cycle stacking patterns by controlling spatial and temporal variation of subsidence rate. Evolving tectonic highlands, moreover, fostered a shift from cratonic to orogenic sources of terrigenous elastic sediment, thereby affecting stratal geometry. Climate, by contrast, regulated the composition and frequency of the cycles. The transition from carbonate-bearing cycles with oxidized, calcic paleosols to coal-bearing cycles with reduced, histic paleosols reflects drift of southeastern North America into the humid equatorial belt. Change of average cycle duration from 1.3 m.y. to less than 0.4 m.y. corresponds with the onset of Gondwana glaciation, suggesting significant climatic forcing of sea level variation.

  7. 3D crustal-scale heat-flow regimes at a developing active margin (Taranaki Basin, New Zealand)

    NASA Astrophysics Data System (ADS)

    Kroeger, K. F.; Funnell, R. H.; Nicol, A.; Fohrmann, M.; Bland, K. J.; King, P. R.

    2013-04-01

    The Taranaki Basin in the west of New Zealand's North Island has evolved from a rifted Mesozoic Gondwana margin to a basin straddling the Neogene convergent Australian-Pacific plate margin. However, given its proximity to the modern subduction front, Taranaki Basin is surprisingly cold when compared to other convergent margins. To investigate the effects of active margin evolution on the thermal regime of the Taranaki Basin we developed a 3D crustal-scale forward model using the petroleum industry-standard basin-modelling software Petromod™. The crustal structure inherited from Mesozoic Gondwana margin breakup and processes related to modern Hikurangi convergent margin initiation are identified to be the main controls on the thermal regime of the Taranaki Basin. Present-day surface heat flow across Taranaki on average is 59 mW/m2, but varies by as much as 30 mW/m2 due to the difference in crustal heat generation between mafic and felsic basement terranes alone. In addition, changes in mantle heat advection, tectonic subsidence, crustal thickening and basin inversion, together with related sedimentary processes result in variability of up to 10 mW/m2. Modelling suggests that increased heating of the upper crust due to additional mantle heat advection following the onset of subduction is an ongoing process and heating has only recently begun to reach the surface, explaining the relatively low surface heat flow. We propose that the depth of the subducted slab and related mantle convection processes control the thermal and structural regimes in the Taranaki Basin. The thermal effects of the subduction initiation process are modified and overprinted by the thickness, structure and composition of the lithosphere.

  8. Geochronologic constraints of granulite terranes of South India and their implications for the Precambrian assembly of Gondwana

    NASA Astrophysics Data System (ADS)

    Yoshida, M.; Bindu, R. S.; Kagami, H.; Rajesham, T.; Santosh, M.; Shirahata, H.

    Recent geochronologic data allow us to propose a new characterization of Precambrian granulite terranes in Peninsular India. The Archean granulite terranes, including the Godavari Granulite Belt (GGB) along the Godavari Valley and the Nilgiri-Madras Granulite Belt (NMGB) along the southern fringe of the Dharwar Craton and north of the Palghat-Cauvery Shear Zone, are characterized by metamorphic events at ca. 2.8-3.0 Ga and intense granitic activity at ca. 2.5 Ga associated with middle- to high-grade metamorphism. The Proterozoic granulite terranes include the Eastern Ghats Granulite Belt (EGGB) along the Bengal Bay Coast of India, the Periyar-Madurai Granulite Belt (PMGB) south of the Palghat-Cauvery Shear Zone and north of the Achankovil Lineament, and the Trivandrum Granulite Belt (TGB) south of the Achankovil Lineament. The Proterozoic granulite belts are characterized by model Nd ages ( TDM) of mostly ca. 2.0-3.0 Ga with local 1.3-1.8 Ga. Intense deformation and regional high-grade metamorphism predates emplacement of A-type granitic plutons at ca. 550-740 Ma and the last granulite metamorphism took place at ca. 550 Ma. Both GGB and NMGB have similar geochronologic characteristics to the Napier Complex of East Antarctica in that they suffered ca. 2.8-3.0 Ga and ca. 2.5 Ga tectonothermal events. EGGB, PMGB and TGB have similar ranges in Nd TDM ages as the Rayner and the Ltzow-Holm complexes in East Antarctica. They are also similar to the Sri Lankan Precambrian, when the three Precambrian units in Sri Lanka are not differentiated and mixed altogether. In this assembled East Gondwana, late Archean granulite terranes form a continuous belt from NMGB to GGB through the Napier Complex, forming a horseshoe-shaped belt surrounding the Dharwar Craton. The Paleoproterozoic-Mesoproterozoic terranes form a broad belt continuing from EGGB to PMGB through the Rayner and the Ltzow-Holm complexes. This belt forms a major part of the Mesoproterozoic Circum East Antarctic Mobile Belt surrounding East Antarctica, which is important for the assembly of East Gondwana. Within the Proterozoic terrains, signatures in the distribution of TDM ages facilitate the differentiation of the Paleoproterozoic and Mesoproterozoic terranes which have distinct distributional characteristics.

  9. Neoproterozoic continental growth prior to Gondwana assembly: Constraints from zircon-titanite geochronology, geochemistry and petrography of ring complex granitoids, Sudan

    NASA Astrophysics Data System (ADS)

    Shang, C. K.; Morteani, G.; Satir, M.; Taubald, H.

    2010-07-01

    Neoproterozoic continental growth in the Saharan Metacraton in central North Sudan is marked by juvenile A-type magmatism (the Jebel Arusa and Jebel Sherif ring complexes). Chemical features are characteristic of within plate (A-type) magmatism marked by Y/Nb ratios > 1.2 typical of the A2 group. Zircon U-Pb analyses yield an age of 707 19 Ma for the Jebel Arusa complex and an age of 718 18 Ma for the Jebel Sherif complex. Titanite U-Pb dating gives closely similar concordant ages of 704 4 Ma and 706 4 Ma for the Jebel Arusa complex and the Jebel Sherif complex, respectively. This ca. 707-718 Ma A-type magmatism in Sudan was induced by the first collisional contact in the north between East and West Gondwana. The 600 Ma titanite recrystallization ages are attributed to tectonothermal effects of the culminating phase of the Pan-African orogeny by collision of East and West Gondwana in the south, forming the Mozambique belt and the final amalgamation of East and West Gondwana to Greater Gondwana. The much younger titanite age of ca. 460 Ma, marks later recrystallization due to localized shear reactivations. Low initial 87Sr/ 86Sr ratios (0.70000 to 0.70346) and high ?Ndi values (+ 5.4 to + 6.8) indicate the juvenile nature of the A-type magma source which is characteristic of a typical Neoproterozoic asthenospheric mantle. The tightly clustered Nd model ages, identical to, or closely similar to, or slightly older than the zircon crystallization ages, depending on the depleted mantle model used, further confirm the juvenile nature of the source. This post-collisional A-type magmatism is characteristic of delamination of a thickened asthenospheric mantle triggering mantle upwelling, high heat flow and partial remelting of the juvenile sources.

  10. Linking the Indochina block and Gondwana during the Early Paleozoic: Evidence from U-Pb ages and Hf isotopes of detrital zircons

    NASA Astrophysics Data System (ADS)

    Usuki, Tadashi; Lan, Ching-Ying; Wang, Kuo-Lung; Chiu, Han-Yi

    2013-02-01

    To constrain the paleoposition of Indochina within Gondwana during the Early Paleozoic, we performed in-situ U-Pb and Hf isotope analyses on detrital zircons from three river sediment samples in the Truong Son Belt of the Indochina block. The age distributions yield dominant Neoarchean (~ 2.5 Ga), Mesoproterozoic (1.7-1.4 Ga), Grenvillian (~ 0.95 Ga), and Pan-African (0.65-0.5 Ga) age groups and minor Paleo- to Meso-archean zircons. Hf isotope compositions of zircons for each age group exhibit large ranges of ?Hf(T), suggesting that the zircon host rocks have diverse sources. The oldest Hf model ages for zircons of Neoarchean, Grenvillian, and Pan-African age group yield ~ 3.7 Ga or older, while those of Mesoproterozoic age group show ~ 3.3 Ga. The remarkable similarity of age distribution and Hf isotope compositions among detrital zircons of Indochina and those of Tethyan Himalaya, western Cathaysia, and Qiangtang suggests that Indochina was located outboard of Qiangtang and south of South China in the Indian margin of Gondwana during the Early Paleozoic. Our results are consistent with the paleontological correlations of east Gondwana margin during the Early Paleozoic.

  11. Geodynamic basin classification

    SciTech Connect

    Klein, G.

    1987-05-01

    Four criteria (continental margin type, basin position within a plate, crustal type, geodynamic models and processes of basin formation) are used to classify sedimentary basins. Within plate interiors, cratonic margin basins and interior cratonic basins are distinguished by position on a tectonic plate. In passive margins, rift basins, aulacogens, and flexure basins are distinguished by orientation with respect to margins (rifts parallel and aulacogens normal to margins) and geodynamic process (rifts and aulacogens form by stretching, flexure basins by elastic or viscoelastic flexure). Basins associated with active continental margins are distinguished by position with respect to margin, crustal type, and stress regimen. Trench-slope basins involve compressional-extensional regimens, whereas trench basins, forearc basins and retroarc basins form in compressional regimes (retroarc basins on continental crust; forearc and trench basins occupy different positions on margin boundaries). Extensional intra-arc basins form on continental crust whereas backarc basins form by rifting oceanic crust and rapid thermal subsidence. Both pull-apart and transform basins form in transform margins by rifting and thermal subsidence with different translational stress regimens. In collision margins, foreland basins occur within continental plates, and superposed (or collage) basins occur along suture zones. Polyhistory basins include successor basins involving changing tectonic styles, and resurgent basins involving repeated tectonic styles. Many mapped basins show polyhistory. Thus the cratonic Illinois basin evolved through stages of a rift basin, followed by thermal subsidence akin to passive margins, followed by viscoelastic basin formation akin to a foreland basin.

  12. Stratigraphy of Midland basin in regional and global context

    SciTech Connect

    Robinson, R.M. ); Hayner, D. )

    1994-03-01

    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.

  13. Signatures of Late Neoproterozoic Gondwana assembly and Maronian glaciation in Lesser Himalaya: a palaeogeographical and stratigraphical approach

    NASA Astrophysics Data System (ADS)

    Umar, Muhammad; Betts, Peter; Saud Khan, Malik Muhammad; Amjad Sabir, Muhammad; Farooq, Muhammad; Zeb, Asif; Khan Jadoon, Umair; Ali, Shoaib

    2015-03-01

    Stratigraphical and sedimentological analyses of Late Neoproterozoic successions in Lesser Himalaya are combined herein with palaeogeographical considerations and comparisons with equivalent successions in India and South China. The succession starts with the Hazara Formation, which contains complete and incomplete Bouma sequences suggesting its deposition in deep marine turbidite settings. The overlying Tanawal Formation, rich in massive sandstone, shale and siltstone, was deposited in shallow marine conditions, as indicated by the presence of parallel lamination, large scale tabular, trough cross- and hummocky cross-stratifications. The Tanawal Formation facies shift laterally from proximal (south-southeast) to distal (north-northwest). The glaciogenic Tanaki Boulder Bed, overlying the Tanawal Formation, was deposited during the Maronian glaciation. It is equivalent to the Blaini Formation of India, and to the Sinian diamictites of South China. The Abbottabad Formation of Cambrian age overlies the Tanaki Boulder Bed, and is composed of dolomite, chert nodules and phosphate-rich packages; similar successions are documented in India and South China at the same stratigraphical interval. The similarities of the Neoproterozoic successions of Lesser Himalaya (both in Pakistan and India) and South China suggests their possible proximity during the break-up of Rodinia and the assembly of the Gondwana Supercontinent.

  14. 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)

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

    2014-05-01

    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 (Ustamer 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 zmdere 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 zmdere 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 zmdere 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 zmdere 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

  15. Parana basin

    SciTech Connect

    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

    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).

  16. Collision-related Early Paleozoic evolution of a crustal fragment from the northern Gondwana margin (Slavonian Mountains, Tisia Mega-Unit, Croatia): Reconstruction of the P-T path, timing and paleotectonic implications

    NASA Astrophysics Data System (ADS)

    Balen, D.; Massonne, H.-J.; Petrinec, Z.

    2015-09-01

    An orthogneiss from the oldest metamorphic complex at Mt. Papuk (Tisia Mega-Unit, Croatia) enables the quantification of the P-T evolution of Early Paleozoic rocks of the Panonian Basin basement in contrast to neighboring peri-Gondwanan terrains which are significantly overprinted by pre-Variscan, Variscan, and Alpine events. Two different groups of Ce-rich monazite within oval-shaped corona microstructures have been observed. Age dating of the corona cores yielded two populations with average ages of 528 7 (2?) Ma and 465 7 Ma, respectively. Furthermore, an Y-rich group, found inside garnet cores, was dated at 616 23 Ma. Th-rich monazite included in garnet rims yielded an age of 491 6 Ma. The youngest monazite group at 417 20 Ma is located inside mica. The orthogneiss precursor was a calc-alkaline to high-K calc-alkaline igneous peraluminous crustal rock (diorite) from an active continental marginal setting. The calculated P-T pseudosection in the MnNCKFMASHTO system in combination with assemblage characteristics and mineral chemistry data provides good constraints on the P-T evolution: for stage I peak P-T conditions of 13 kbar and 670 C were derived followed by stage II, which was characterized by moderate cooling accompanied by uplift to mid-crustal levels (5.2 kbar and 610 C). Subsequently, the system cooled to 480 C at ~ 4.4 kbar (stage III). Formation of titanite rims on ilmenite suggests further cooling to 4 kbar and 400 C (stage IV). The clockwise P-T path implies exhumation from a tectonically thickened crustal setting (ca. 45 km depth at a geothermal gradient of ~ 15 C/km) to mid-crustal levels (ca. 18 km) followed by cooling at depths < 14 km. Crustal thickening was due to the collision of a continental plate (Gondwana) with a smaller plate, which was underthrust.

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

    NASA Astrophysics Data System (ADS)

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

    1993-02-01

    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 extrusion of extensive flood basalts (Drakensberg Group) onto the Clarens landscape eventually brought Karoo sedimentation to a close.

  18. Permian Basin

    SciTech Connect

    Donaldson, D.A.

    1981-12-01

    A description of the geology of the Permian Basin of the West Texas And Southeastern New Mexico was presented. Also, a brief history of the petroleum and natural gas drilling in the region was given. It was concluded that the New Mexico portion of the Permian Basin has the greatest potential for future fuel production. During 1980, there were 646 oil well completions, and 168 dry holes were recorded in southeast New Mexico. The average total depths of new wells completed was 4,901 feet for oil wells, 8,987 feet for gas wells, and 6,250 feet for dry holes.

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

    PubMed Central

    2013-01-01

    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 Indias 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: ruralurban 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. PMID:23802752

  20. Post-traumatic stress disorder in children and adolescents one year after a super-cyclone in Orissa, India: exploring cross-cultural validity and vulnerability factors

    PubMed Central

    Kar, Nilamadhab; Mohapatra, Prasanta K; Nayak, Kailash C; Pattanaik, Pratiti; Swain, Sarada P; Kar, Harish C

    2007-01-01

    Background It has been asserted that psychological responses to disasters in children and adolescents vary widely across cultures, but this has rarely been investigated. The objectives of the study were to clinically evaluate the construct of traumatic stress symptoms and disorder in children and adolescents after a super-cyclone in Orissa, India; to find out the prevalence at one year; compare the effect in high and low exposure areas and study the factors associated with it. Methods Clinical examination of children and adolescents (n = 447) was done, supplemented by a symptoms checklist based on International Classification of Mental and Behavioural Disorders, Diagnostic Criteria for Research and a semi-structured questionnaire for disaster related experiences. Results A majority of children had post-traumatic symptoms. Post-traumatic stress disorder (PTSD) was present in 30.6% (95% confidence interval: 26.4 to 34.9), and an additional 13.6% had sub-syndromal PTSD. Parents or teachers reported mental health concerns in 7.2% subjects, who were a minor proportion (12.8%) of subjects with any syndromal diagnosis (n = 196). Significantly more (43.7%) children in high exposure areas had PTSD than that (11.2%) in low exposure areas (p < 0.001). Depression was significantly associated with PTSD. Binary logistic regression analysis indicated that high exposure, lower educational level and middle socioeconomic status significantly predicted the outcome of PTSD. Extreme fear and perceived threat to life during the disaster, death in family, damage to home, or staying in shelters were not significantly associated with PTSD. Conclusion Following natural disaster PTSD is a valid clinical construct in children and adolescents in Indian set up; and though highly prevalent it may be missed without clinical screening. Its manifestation and associated factors resembled those in other cultures. PMID:17300713

  1. Impact of Indian Total Sanitation Campaign on Latrine Coverage and Use: A Cross-Sectional Study in Orissa Three Years following Programme Implementation

    PubMed Central

    Barnard, Sharmani; Routray, Parimita; Majorin, Fiona; Peletz, Rachel; Boisson, Sophie; Sinha, Antara; Clasen, Thomas

    2013-01-01

    Background Faced with a massive shortfall in meeting sanitation targets, some governments have implemented campaigns that use subsidies focused on latrine construction to overcome income constraints and rapidly expand coverage. In settings like rural India where open defecation is common, this may result in sub-optimal compliance (use), thereby continuing to leave the population exposed to human excreta. Methods We conducted a cross-sectional study to investigate latrine coverage and use among 20 villages (447 households, 1933 individuals) in Orissa, India where the Government of Indias Total Sanitation Campaign had been implemented at least three years previously. We defined coverage as the proportion of households that had a latrine; for use we identified the proportion of households with at least one reported user and among those, the extent of reported use by each member of the household. Results Mean latrine coverage among the villages was 72% (compared to <10% in comparable villages in the same district where the Total Sanitation Campaign had not yet been implemented), though three of the villages had less than 50% coverage. Among these households with latrines, more than a third (39%) were not being used by any member of the household. Well over a third (37%) of the members of households with latrines reported never defecating in their latrines. Less than half (47%) of the members of such households reported using their latrines at all times for defecation. Combined with the 28% of households that did not have latrines, it appears that most defecation events in these communities are still practiced in the open. Conclusion A large-scale campaign to implement sanitation has achieved substantial gains in latrine coverage in this population. Nevertheless, gaps in coverage and widespread continuation of open defecation will result in continued exposure to human excreta, reducing the potential for health gains. PMID:23990955

  2. Marriage, Sex, and Hydrocele: An Ethnographic Study on the Effect of Filarial Hydrocele on Conjugal Life and Marriageability from Orissa, India

    PubMed Central

    Babu, Bontha V.; Mishra, Suchismita; Nayak, Abhaya N.

    2009-01-01

    Background Lymphatic filariasis (LF), a leading cause of permanent and long-term disability, affects 120 million people globally. Hydrocele, one of the chronic manifestations of LF among 27 million people worldwide, causes economic and psychological burdens on patients and their families. The present study explores and describes the impact of hydrocele on sexual and marital life as well as on marriageability of hydrocele patients from rural areas of Orissa, an eastern state of India. Methodology/Principal Findings This paper is based on ethnographic data collected through focus group discussions and in-depth interviews with hydrocele patients, wives of hydrocele patients, and other participants from the community. The most worrisome effect of hydrocele for patients and their wives was the inability to have a satisfactory sexual life. The majority of patients (94%) expressed their incapacity during sexual intercourse, and some (87%) reported pain in the scrotum during intercourse. A majority of hydrocele patients' wives (94%) reported dissatisfaction in their sexual life. As a result of sexual dissatisfaction and physical/economic burden, communication has deteriorated between the couples and they are not living happily. This study also highlights the impact on marriageability. The wives of hydrocele patients said that a hydrocele patient is the “last choice” and that girls show reluctance to marry hydrocele patients. In some cases, the patients were persuaded by their wives to remove hydrocele by surgery (hydrocelectomy). Conclusions/Significance The objective of the morbidity management arm of the Global Programme to Eliminate LF should be to increase access to hydrocelectomy, as hydrocelectomy is the recommended intervention. Though the study area is covered by the programme, like in other endemic areas, hydrocelectomy has not been emphasised by the national LF elimination programme. The policy makers and programme managers should be sensitised by utilising this type of research finding. PMID:19381283

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

    PubMed Central

    2012-01-01

    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 Indias 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. PMID:23148587

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

    NASA Astrophysics Data System (ADS)

    Gtz, Annette E.

    2014-05-01

    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.

  5. Petrogenesis of middle Ordovician peraluminous granites in the Baoshan block: Implications for the early Paleozoic tectonic evolution along East Gondwana

    NASA Astrophysics Data System (ADS)

    Li, Gong-Jian; Wang, Qing-Fei; Huang, Yu-Han; Gao, Lei; Yu, Li

    2016-02-01

    Peraluminous granitic magmatism in the Baoshan block is long-lasting roughly from 500 Ma to 450 Ma. The petrogenesis and geodynamics for this long-lived magmatism remain controversial. To address this controversy, this study reports the zircon U-Pb age and Hf-isotope, and bulk-rock major and trace element data of the granites from the Shuangmaidi and Mengmao areas in the Baoshan block. LA-ICPMS zircon U-Pb dating reveals that the granitic rocks from the two areas were emplaced between 470 and 459 Ma. These rocks are high silicic and strongly peraluminous, with SiO2 = 73.6-77.6 wt.%, A/CNK ratios of 1.0-1.6, and CIPW normative corundum contents of 0.7-5.3 wt.%. They are enriched in LREEs, LILEs (e.g., Rb, Th, U, and K) and Pb, and depleted in HFSEs (e.g., Nb, Ta, P, Zr, and Ti), Eu, Sr, and Ba. The εHf(t) values for co-magmatic zircons of the Shuangmaidi coarse- and fine-grained porphyritic granites show wide ranges from - 11.6 to + 5.2 and from - 8.1 to + 7.0, concentrating in - 7.1 to + 0.5 and - 8.1 to + 0.7, respectively; and those of the Mengmao granites concentrate between - 4.6 and - 0.5. The primary magmas of these granites can be mainly attributed to the partial melting of ancient metasedimentary rocks, while small amounts of mantle-derived components were introduced into the magma sources for the Shuangmaidi granites. The primary magma of the Shuangmaidi granites experienced biotite-dominant mineral fractionation, and that of the Mengmao granite mainly fractionated K-feldspar and plagioclase. Combining our data with the regional sedimentary unconformity, multi-type magmatism, and high-pressure metamorphism in the Baoshan and its periphery blocks, we propose that these ca. 470-460 Ma peraluminous granites were formed in the tectonic setting of the thickened lithospheric delamination following the final amalgamation of outboard Asian microcontinents onto the East Gondwana margin at ca. 490-475 Ma. Our study favors that the long-lasted (ca. 500-450 Ma) peraluminous granitic rocks in the Baoshan block constitute of the early Paleozoic magmatic belt along the East Gondwana marginal blocks like Himalaya, Lhasa, and Qiangtang. This magmatism was produced in successive stages, including proto-Tethyan slab rollback period to ca. 500 Ma, slab break-off at ca. 500-490 Ma, lithospheric thickening at ca. 490-475 Ma, and lithospheric delamination at ca. 475-460 Ma; and then it vanished at ca. 450 Ma signifying the end of proto-Tethyan accretionary orogenesis.

  6. Extensional and magmatic nature of the Campbell Plateau and Great South Basin from deep crustal studies

    NASA Astrophysics Data System (ADS)

    Grobys, J. W. G.; Gohl, K.; Uenzelmann-Neben, G.; Davy, B.; Barker, D.

    2009-07-01

    The Campbell Plateau is one of the largest submarine parts of the microcontinent of New Zealand. Although the opening of the Great South Basin played an important role in the late Gondwana break-up, the crustal structure of the basins and plateaus southeast of New Zealand are unknown to a large extent. Here we present results from a combined gravity, magnetic, multichannel seismic and seismic wide-angle reflection/refraction transect across the Great South Basin and parts of the Campbell Plateau and interpret this on the basis of velocity distribution and crustal thickness. The lower crust exhibits a zone of southeastward increasing P-wave velocities ( vp ≈ 7.1-7.4 km/s) beneath the central Campbell Plateau. In this area, crustal thickness averages to ˜ 27 km. We interpret this high-velocity zone as underplating beneath a previously extended crust. Our results hint that the extension of the Great South Basin was not accompanied by widespread magmatic activity, although signs of younger magmatism have been found across the Pukaki Rise and within the Great South Basin. Based on comparisons with nearby plateaus like the Lord Howe Rise and the Challenger Plateau, as well as probable paleo-positions of the magnetic anomaly systems of New Zealand and the Campbell Plateau, we suggest that an early phase of extension of the Campbell Plateau predated the opening of the Great South Basin.

  7. Hydrocarbon potential of the Lamu basin of south-east Kenya

    SciTech Connect

    Nyagah, K.; Cloeter, J.J.; Maende, A. )

    1996-01-01

    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.

  8. Hydrocarbon potential of the Lamu basin of south-east Kenya

    SciTech Connect

    Nyagah, K.; Cloeter, J.J.; Maende, A.

    1996-12-31

    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.

  9. Records of Late Permian surface temperatures in continental Gondwana in isotope geochemistry of upper Permian early diagenetic calcite concretions

    SciTech Connect

    Yeman, E. ); Kelts, K. )

    1996-01-01

    We present geochemical and isotopic evidence of paleotemperatures from freshwater continental deposits from 55[degrees]S in interior southern Gondwana. Lacustrine shales host spheroidal concretions with abundant septarian cracks. Cement carbonate varies from 65% at the centre to 15% at the edges. Cistraccide remains are preserved. Septarian calcite occurs in dull and bright bands, with three distinct generations of vein-fills. Early-formed cement both in concretions and septarian veins is magnesium-rich whereas, later-formed carbonates are pure calcite. Carbon- and oxygen-isotope ratios (PDB) are: host shales, [delta][sup 13]C= -4.36 to o.77[per thousand], [delta][sup 18]O= -12.73 to -17.12[per thousand]; concretion cements, [delta][sup 13]C=+0.26 to [delta][sup 18]O= -9.34[per thousand]; and vein-fills, [delta][sup 13]C= -7.05 to +1.09[per thousand], [delta][sup 18]O= -8.28 to -18.24[per thousand]. 13C and 18O ratios are depleted from the center of concretions to the periphery, as well as from the centre of veins to the tip. Near-surface cementation is suggested by textural evidence. [delta]18O in the range of -12.636[per thousand] to -8.989 SMOW is calculated for the meteoric palaeowaters, from which average annual surface temperatures of 5-8[degrees]C are inferred. [delta]18O of early-formed cements also yields a mean annual surface temperature of 2-6[degrees]C. Based on continentality and palaeolatitudes of northern Malawi during the Late Permian, we propose that mean annual surface palaeotemperatures may have been as high as 10[degrees]C, similar to those found in modern continental temperate climates.

  10. Records of Late Permian surface temperatures in continental Gondwana in isotope geochemistry of upper Permian early diagenetic calcite concretions

    SciTech Connect

    Yeman, E.; Kelts, K.

    1996-12-31

    We present geochemical and isotopic evidence of paleotemperatures from freshwater continental deposits from 55{degrees}S in interior southern Gondwana. Lacustrine shales host spheroidal concretions with abundant septarian cracks. Cement carbonate varies from 65% at the centre to 15% at the edges. Cistraccide remains are preserved. Septarian calcite occurs in dull and bright bands, with three distinct generations of vein-fills. Early-formed cement both in concretions and septarian veins is magnesium-rich whereas, later-formed carbonates are pure calcite. Carbon- and oxygen-isotope ratios (PDB) are: host shales, {delta}{sup 13}C= -4.36 to o.77{per_thousand}, {delta}{sup 18}O= -12.73 to -17.12{per_thousand}; concretion cements, {delta}{sup 13}C=+0.26 to {delta}{sup 18}O= -9.34{per_thousand}; and vein-fills, {delta}{sup 13}C= -7.05 to +1.09{per_thousand}, {delta}{sup 18}O= -8.28 to -18.24{per_thousand}. 13C and 18O ratios are depleted from the center of concretions to the periphery, as well as from the centre of veins to the tip. Near-surface cementation is suggested by textural evidence. {delta}18O in the range of -12.636{per_thousand} to -8.989 SMOW is calculated for the meteoric palaeowaters, from which average annual surface temperatures of 5-8{degrees}C are inferred. {delta}18O of early-formed cements also yields a mean annual surface temperature of 2-6{degrees}C. Based on continentality and palaeolatitudes of northern Malawi during the Late Permian, we propose that mean annual surface palaeotemperatures may have been as high as 10{degrees}C, similar to those found in modern continental temperate climates.

  11. The role of abiotic factors in the Cambrian Substrate Revolution: A review from the benthic community replacements of West Gondwana

    NASA Astrophysics Data System (ADS)

    Álvaro, J. Javier; Zamora, Samuel; Clausen, Sébastien; Vizcaïno, Daniel; Smith, Andrew B.

    2013-03-01

    The Cambrian Substrate Revolution refers to a substantial and "rapid" change to the nature of marine sedimentary substrates in the early Cambrian and is widely interpreted as a biologically-driven event, a direct response to evolutionary innovations in metazoan burrowing and the development of new shelly faunas. However, abiotic factors such as tectonic and climatic evolution also had the potential to restructure Cambrian substrates, and are here shown to be more plausible drivers of change in the benthic faunas of western Gondwana. The western Mediterranean region underwent a southward drift during Cambrian times, which drove a switch from subtropical carbonates to temperate siliciclastic substrates with short-term episodes of temperate carbonate productivity. As a result, microbial and shelly carbonates disappeared diachronously in a stepwise manner across the lower-middle Cambrian boundary interval. Archaeocyathan-microbial reefs were replaced by chancelloriid-eocrinoid-(spiculate) sponge meadows, in which the stepwise immigration of new echinoderm taxa was primarily controlled by extensional tectonic events, first recorded in rifting settings and later in passive-margin platforms. Availability of new kinds of substrate was thus the primary factor that controlled where and when evolutionary innovations in benthic strategies arose. Examples of this include the early Cambrian colonization of phosphatic hardgrounds and thrombolite crusts by chancelloriids, archaeocyathan and spiculate sponges, and the exploitation by benthos to the increasingly widespread availability of shelly grounds and carbonate firmgrounds by early-diagenetic cementation. A microbial mat/epifaunal antagonistic relationship is demonstrated for echinoderm pelmatozoans based on the non-overlapping palaeogeographic distributions of microbial reefs and mats versus mud-sticker pelmatozoans. Cambrian benthic communities thus evolved in parallel with substrates in response to abiotic factors rather than being the primary drivers of substrate change.

  12. Kinematic constraints on buckling a lithospheric-scale orocline along the northern margin of Gondwana: A geologic synthesis

    NASA Astrophysics Data System (ADS)

    Weil, A. Brandon; Gutiérrez-Alonso, G.; Johnston, S. T.; Pastor-Galán, D.

    2013-01-01

    The Paleozoic Variscan orogeny was a large-scale collisional event involving amalgamation of multiple continents and micro-continents. Existing data, suggests oroclinal buckling of an originally near-linear convergent margin during the last stages of Variscan deformation in the late Paleozoic. Closure of the Rheic Ocean resulted in E-W shortening (present-day coordinates) in the Carboniferous, producing a near linear N-S trending, east-verging belt. Subsequent N-S shortening near the Carb-Permian boundary resulted in oroclinal buckling. This late-stage orogenic event remains an enigmatic part of final Pangea amalgamation. The present-day arc curvature of the Variscan has inspired many tectonic models, with little agreement between them. While there is general consensus that two separate phases of deformation occurred, various models consider that curvature was caused by: dextral transpression around a Gondwana indentor; strike-slip wrench tectonics; or a change in tectonic transport direction due to changing stress fields. More recent models explain the curvature as an orocline, with potentially two opposite-facing bends, caused by secondary rotations. Deciphering the kinematic history of curved orogens is difficult, and requires establishment of two deformation phases: an initial compressive phase that forms a relatively linear belt, and a second phase that causes vertical-axis rotation of the orogenic limbs. Historically the most robust technique to accurately quantify vertical axis-rotation in curved orogens is paleomagnetic analysis, but recently other types of data, including fracture, geochemical, petrologic, paleo-current and calcite twin data, have been used to corroborate secondary buckling. A review of existing and new Variscan data from Iberia is presented that argues for secondary buckling of an originally linear orogenic system. Together, these data constrain oroclinal buckling of the Cantabrian Orocline to have occurred in about 10 Ma during the latest Carboniferous, which agrees well with recent geodynamical models and structural data that relate oroclinal buckling with lithospheric delamination in the Variscan.

  13. Control of deep lithospheric roots on crustal scale GOCE gravity and gradient fields evident in Gondwana reconstructions

    NASA Astrophysics Data System (ADS)

    Braitenberg, Carla; Mariani, Patrizia

    2015-04-01

    The GOCE gravity field is globally homogeneous at the resolution of about 80km or better allowing for the first time to analyze tectonic structures at continental scale. Geologic correlation studies based on age determination and mineral composition of rock samples propose to continue the tectonic lineaments across continents to the pre-breakup position. Tectonic events which induce density changes, as metamorphic events and magmatic events, should then show up in the gravity field. Therefore gravity can be used as a globally available supportive tool for interpolation of isolated samples. Applying geodynamic plate reconstructions to the GOCE gravity field places today's observed field at the pre-breakup position. In order to test the possible deep control of the crustal features, the same reconstruction is applied to the seismic velocity models, and a joint gravity-velocity analysis is performed. The geophysical fields allow to control the likeliness of the hypothesized continuation of lineations based on sparse surface outcrops. Total absence of a signal, makes the cross-continental continuation of the lineament improbable, as continental-wide lineaments are controlled by rheologic and compositional differences of lithospheric mantle. It is found that the deep lithospheric roots as those found below cratons control the position of the positive gravity values. The explanation is that the deep lithospheric roots focus asthenospheric upwelling outboard of the root protecting the overlying craton from magmatic intrusions. The study is carried out over the African and South American continents. The background for the study can be found in the following publications where the techniques which have been used are described: Braitenberg, C., Mariani, P. and De Min, A. (2013). The European Alps and nearby orogenic belts sensed by GOCE, Boll. Bollettino di Geofisica Teorica ed Applicata, 54(4), 321-334. doi:10.4430/bgta0105 Braitenberg, C. and Mariani, P. (2015). Geological implications from complete Gondwana GOCE-products reconstructions and link to lithospheric roots. Proceedings of 5th International GOCE User Workshop, 25 - 28 November 2014. Braitenberg, C. (2015). Exploration of tectonic structures with GOCE in Africa and across-continents. Int. J.Appl. Earth Observ. Geoinf. 35, 88-95. http://dx.doi.org/10.1016/j.jag.2014.01.013 Braitenberg, C. (2015). A grip on geological units with GOCE, IAG Symp. 141, in press.

  14. Cadomian (Ediacaran-Cambrian) arc magmatism in the Bitlis Massif, SE Turkey: Magmatism along the developing northern margin of Gondwana

    NASA Astrophysics Data System (ADS)

    Ustamer, P. Ayda; Ustamer, Timur; Collins, Alan S.; Robertson, Alastair H. F.

    2009-07-01

    Small granitic plutons and associated granitic dykes that intrude the pre-Devonian basement of the Bitlis Massif were previously inferred to have a broadly Late Palaeozoic crystallisation age related to the Hercynian orogeny; this was tested during this work. The brittle-ductile-deformed Mutki granite pluton and nearby granitic dykes comprise mainly quartz, alkali feldspar, plagioclase, subordinate biotite, muscovite and rare amphibole. Based on the results of whole-rock major-element and trace-element analysis, the Mutki pluton and associated dykes are inferred to have crystallised from metaluminous, to peraluminous subduction influenced I-type melts. Sm-Nd isotope systematics indicate melting of a mantle source (of notional 1.3 Ga age), with increasing amounts of crustal contamination through time. U/Pb zircon dating of the Mutki granite and a nearby granitic dyke by laser inductively coupled plasma mass spectrometry (LA-ICP-MS) yielded 238U/ 206Pb crystallisation ages of 545.5 6.1 Ma and 531.4 3.6 Ma, respectively (Ediacaran-Early Cambrian). This shows for the first time that the regionally extensive Bitlis Massif was affected by Cadomian arc-type magmatism. The Ediacaran-Early Cambrian granitic rocks of the Bitlis Massif can be compared with similar-aged metagranitic and metavolcanic rocks within basement units exposed in the Tauride-Anatolide Platform (Menderes-Taurus Block) in western Anatolia and also in NW Turkey. Similar-aged rocks are also exposed in the basement of Iran. All of these magmatic units and their host rocks are interpreted as fragments of a Cadomian active margin bordering the northern margin of Gondwana after its final amalgamation. Formation of the Bitlis Massif granites and contemporaneous granitic units elsewhere in Turkey as fragments of an Andean-type margin adjacent to the Arabian-Nubian Shield is favoured over an alternative explanation as exotic terranes transported > 2000 km eastwards from a Cadomian active margin near West Africa-Amazonia (now NW Africa).

  15. Promoting latrine construction and use in rural villages practicing open defecation: process evaluation in connection with a randomised controlled trial in Orissa, India

    PubMed Central

    2014-01-01

    Background Our group conducted a cluster-randomised trial in 100 villages of Orissa, India to measure the impact of a rural sanitation intervention implemented under the government of India's Total Sanitation Campaign, on diarrhoea and soil-transmitted helminth infections. This paper reports on a process evaluation conducted in the context of the trial. Methods Process evaluation data were collected through review of key documentation, quantitative surveys, direct observations, and semi-structured interviews with staff from implementing NGOs and community members. Between March 2011 and March 2012, trained enumerators recorded observations on latrine construction status every 6–8 weeks in the 50 intervention villages and noted activities reported to have taken place based on NGO staff interviews and review of NGO records. A survey among 10% of households in intervention and control villages was conducted to compare levels of awareness of key intervention components. In addition, 10% of village water and sanitation committee (VWSC) members were interviewed to measure their level of involvement in the intervention delivery. Results The percentage of households with a latrine (completed or under construction) increased from 8% at baseline to 66% one year after the start of the intervention in March 2012. Almost none of the intervention households recall any form of participatory community-level activities at the start of the programme, although intervention households were generally more aware of the Total Sanitation Campaign (91% versus 49%, p < 0.001), VWSCs (51% versus 9%, p < 0.001), adolescent girls groups (23% versus 8%, p < 0.01), wall paintings (44% versus 7%, p < 0.001) and were more likely to report a household visit on sanitation during the past three months (65% versus 3%, p < 0.001). We found no strong evidence of an association between levels of awareness of or participation in mobilisation activities and levels of latrine coverage in intervention villages. Conclusions The levels of coverage achieved and the levels of awareness of the mobilisation process in our intervention villages were lower than planned, but similar to those reported elsewhere in India under the TSC. Our process evaluation highlights important gaps between the TSC guidelines and their implementation on the ground. Trial registration Number on clinicaltrial.gov: NCT01214785 PMID:25084699

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

    SciTech Connect

    Janssen, M.E. )

    1993-09-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    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.

  18. Reassembling Gondwana: A new high quality constraint from vibroseis exploration of the sub-ice shelf geology of the East Antarctic continental margin

    NASA Astrophysics Data System (ADS)

    Kristoffersen, Yngve; Hofstede, Coen; Diez, Anja; Blenkner, Richard; Lambrecht, Astrid; Mayer, Christoph; Eisen, Olaf

    2014-12-01

    The breakup of Gondwana is manifested by coeval early Jurassic Karoo magmatism in South Africa and East Antarctica. In South Africa, the large volumes of volcanic rocks of the adjoining Lebombo and Mwenetzi-Save monoclines represent a volcanic rift margin, and in East Antarctica, a corresponding feature, the Explora Wedge is buried below sediments and floating ice shelves on the continental margin of Dronning Maud Land. We use the seismic vibrator source to explore the sub-ice geology in Antarctica, and the new seismic reflection and available regional aeromagnetic data enable us to outline a dogleg landward extent of the Explora Wedge in Dronning Maud Land. The congruent inboard wedge geometries on the two continents define a high quality constraint, which facilitate for the first time, a geologically consistent and tight reconstruction of Africa relative to East Antarctica within Gondwana. The uncertainties in correlations of major geological features (mobile belts) from one continent to the other may now be of the order of ten's of kilometers rather than hundreds of kilometers.

  19. Tracking the late Paleozoic to early Mesozoic margin of northern Gondwana in the Hellenides: paleotectonic constraints from U-Pb detrital zircon ages

    NASA Astrophysics Data System (ADS)

    Chatzaras, Vasileios; Drr, Wolfgang; Gerdes, Axel; Krahl, Jochen; Xypolias, Paraskevas; Zulauf, Gernold

    2016-01-01

    We report new detrital zircon U-Pb ages of nine quartzites sampled along the Phyllite-Quartzite unit sensu stricto (PQ unit s.s.), in the high-pressure belt of the southern Hellenides. The detrital zircon age spectra are dominated by two significant age peaks at ca. 600 and ca. 1000 Ma, which are typical for an east Gondwana provenance. The absence of zircons of Carboniferous-Triassic ages suggests that the depositional environment was isolated from Variscan and early Mesozoic sources. Our data are in support of paleogeographic configurations placing the protolith of the PQ unit s.s. south of the Paleotethys ocean and along the northern Gondwana margin. The zircon age spectra do not show significant variations with respect to the tectonostratigraphic position within the PQ unit s.s. and the position along the high-pressure belt. Combining the new (this study) with published detrital zircon ages, we suggest that the siliciclastic metasediments of the PQ unit s.s. on Crete, Kythera, and the Peloponnesus have a common paleogeographic origin.

  20. Fish faunas from the Late Jurassic (Tithonian) Vaca Muerta Formation of Argentina: One of the most important Jurassic marine ichthyofaunas of Gondwana

    NASA Astrophysics Data System (ADS)

    Gouiric-Cavalli, Soledad; Cione, Alberto Luis

    2015-11-01

    The marine deposits of the Vaca Muerta Formation (Tithonian-Berriasian) houses one of the most diverse Late Jurassic ichthyofaunas of Gondwana. However, most of the specimens remain undescribed. Jurassic fishes have been recovered from several localities at Neuquén Province (i.e., Picún Leufú, Plaza Huincul, Cerro Lotena, Portada Las Lajas, Los Catutos, and Arroyo Covunco) but also from Mendoza Province (i.e., La Valenciana, Los Molles, and Arroyo del Cajón Grande). Presently, the fish fauna of Los Catutos, near Zapala city (Neuquén Province), has yielded the highest number of specimens, which are taxonomically and morphologically diverse. At Los Catutos locality, the Vaca Muerta Formation is represented by the Los Catutos Member, which is considered the only lithographic limestones known in the Southern Hemisphere. Here, we review the Tithonian fish faunas from the Vaca Muerta Formation. During Late Jurassic times, the actual Argentinian territory could have been a morphological diversification center, at least for some actinopterygian groups. The apparently lower species diversity recorded in marine Jurassic ichthyofaunas of Argentina (and some Gondwanan countries) in comparison with Chilean and European fish faunas could be related to the fish paleontological research history in Gondwana and the low number of detailed studies of most of specimens recorded.

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

    NASA Astrophysics Data System (ADS)

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

    2001-02-01

    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 neither gravitational collapse of the Pan-African-Braziliano Orogens nor delamination were the sole or even the dominant driving forces for the postconvergent extension.

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

    NASA Astrophysics Data System (ADS)

    Armendáriz, Maider; Quesada, Cecilio; Rosales, Idoia

    2013-04-01

    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.

  3. Upper Devonian microvertebrates from the Canning Basin, Western Australia

    NASA Astrophysics Data System (ADS)

    Roelofs, Brett; Playton, Ted; Barham, Milo; Trinajstic, Kate

    2015-03-01

    A diverse microvertebrate fauna is described from the Virgin Hills and Napier formations, Bugle Gap Limestone Canning Basin, Western Australia. Measured sections at Horse Spring and Casey Falls (Virgin Hills Formation) and South Oscar Range (Napier Formation) comprise proximal to distal slope carbonates ranging in age from the Late Devonian Frasnian to middle Famennian. A total of 18 chondrichthyan taxa are identified based on teeth, including the first record of Thrinacodus tranquillus, Cladoides wildungensis, Protacrodus serra and Lissodus lusavorichi from the Canning Basin. A new species, Diademodus dominicus sp. nov. is also described and provides the first record of this genus outside of Laurussia. In addition, the upper range of Australolepis seddoni has been extended to Late Devonian conodont Zone 11, making it the youngest known occurrence for this species. The Virgin Hills and Napier formations microvertebrate faunas show close affinities to faunas recovered from other areas of Gondwana, including eastern Australia, Iran, Morocco and South China, which is consistent with known conodont and trilobite faunas of the same age.

  4. Controls on volatile content and distribution in the continental upper mantle of Southern Gondwana (Patagonia & W. Antarctica)

    NASA Astrophysics Data System (ADS)

    Rooks, Eve; Gibson, Sally; Petrone, Chiara; Leat, Phillip

    2015-04-01

    Water content is known to affect many physical and chemical properties of the upper mantle, including melting temperature and viscosity. Water is hosted by hydrous phases, such as amphibole and phlogopite, and also by more dominant, nominally-anhydrous mantle minerals (e.g. olivine and pyroxene). The latter have the potential to incorporate hundreds of ppm of water in point defects, and may explain geophysical observations such as seismic and conductivity anomalies in the upper mantle [1]. However, the significance of the reported concentrations of H2O in nominally anhydrous minerals in mantle xenoliths is still a subject of debate primarily due to the effects of post-entrainment loss [1,2]. Unlike H2O and Li, F is less susceptible to post entrainment loss and can potentially be used to constrain the source of volatiles. We present high-precision SIMS analyses of H2O, Li and F in mantle xenoliths hosted by recently-erupted (5-10 Ka) alkali basalts from south Patagonia and the Antarctic Peninsula. These two regions formed part of the southern margin of the Gondwana supercontinent, prior to break-up, and were located above long-lived subduction zones for at least 200 M.yr., making them highly-appropriate to investigating long term evolution of the sub-continental lithospheric mantle in this setting. The xenoliths are well characterised peridotites, sourced from the off-craton spinel- and spinel-garnet facies lithospheric mantle (40-80 km). Samples are relatively dry: H2O contents of olivine span 0-49 ppm, orthopyroxene 150-235 ppm and clinopyroxene 100-395 ppm. West Antarctic samples are more hydrated than Patagonian samples, on average. These H2O concentrations fall within the global measured range for off-craton mantle minerals [4]. We attribute low H2O concentrations in olivine to diffusive loss, either by exchange with the host magma, shallow level degassing or during cooling [2]. F shows less variability than H2O and is most highly concentrated in clinopyroxenes - with one Antarctic sample (a websterite)k having abundances of up to 200 ppm. In other samples, values rarely exceed 65 ppm. F/Nd ratios of MORB are around 20.5, with arc magmas displaying higher ratios [4] and while some clinopyroxenes have similar or lower values than MORB, others show F/Nd >> 20.5, implying potential interaction with subduction-related melts. Li concentrations follow similar patterns as F in all minerals. Slightly higher average H2O and generally higher F contents in the West Antarctic lithospheric mantle correlate with other indicators of subduction-related metasomatism, and most likely reflect the closer proximity of this region to the continental margin and also a younger, shallower slab than beneath south Patagonia. Here we explore in detail correlations between H, Li, F and other tracers of mantle processes in both localities, in order to determine the primary control on volatile content in the sub-continental lithospheric mantle. [1] Peslier et al. 2006. EPSL, 242, 392-319 [2] Plank, T. et al. 2014. AGU Fall V51E-04 [3] Koga, K.T. et al. 2014. AGU Fall V51E-05 [4] Bonadiman et al. 2009., Eur. J. Mineral. 21, 637-64

  5. A Study on Ground Water Resource Management in Gondwana Formations in Western Part of West Godavari District Andhra Pradesh India

    NASA Astrophysics Data System (ADS)

    Singara, S.

    2006-05-01

    Groundwater source forms nearly fifty percent of the total irrigation in the country. With green revolution, there has been an increasing demand for water for agricultural and this led to overexploitation of groundwater resources in many parts of the state and the study area is not an exception. With the success of groundwater exploration and development through deep tube wells in the study area, the farmers plunged into hectic activity of tapping groundwater. The present study was taken up to assess to groundwater recharge and draft in the area and to suggest remedial measures to redress overexploitation condition. The study area is underlain by a vide range of geological formations from Archean to Tertiary age. Crystallines consist of two-tier setting of aquifers with weathered and fracture zones. The Gondwana formations with Sandstone, shale and clay zones form unconfined to confined aquifer system. Deccan trap basalt occurs subsurface in some parts. Crystalline aquifers are exploited through borewells with a depth range of 29 to 101.5 m. Static water levels range in depth from 2.5 and 19.27 m bgl. Their yields range from 2.53 to 19.27 m3/hr. Sedimentary aquifers are exploited through tube wells with a depth range of 18 to 293 m and static water levels range from 2.1m agl to 48.0 m bgl. Yields of the wells vary form 1.3 to 67 m3 /hr. Groundwater is lifted by monoblock pumpsets of 5 HP in some places but mostly by submersible pumpsets with 5 to 12.5 HP. The tube wells are subjected to pumping from 5 to 18 hours per day depending on availability of electricity (power supply). They are operated form 90 days to throughout the year in different places. Groundwater development in the study area shows a steady increase since 1960 with number of tube wells uniformly increasing in each decade, from an initial figure of 592 wells in 1960 to 17,173 tube wells in 2002. Crop pattern was shifted from dry crops to paddy and sugar cane as major crops and irrigated dry crops like maize, tobacco, palm oil, garden crops in minor extent and coconut was planted in large extents. Piezometric surface shows uniform gradient over the entire area indicating hydraulic continuity between different geological formations. The water budgeting was computed by using norms recommended by GEC (Ground Water Estimation Committee) of CGWB 1997, Govt. of India. For the present study, June 2000 to May 2001 period is taken as groundwater year. Groundwater recharge is calculated (formation wise) by rainfall infiltration and water table fluctuation methods, and recharge from other sources reservoirs, tanks, canals, irrigation water returns etc. the total recharge comes to be 626 MCM. Groundwater draft for irrigation and domestic purposes is found to be 994.96 MCM. Groundwater balance shows overdraft by 364.15 MCM. Well density is increased from <1/Sq. km in 60s to >30/Sq.km in 2000. Piezometric surface profiles in N-S direction also show a drop from 1960 to 2000 year by 44m. Taking into consideration, the mined water during 1990-2000, the overdraft comes to 704 MCM i.e. 70.4 MCM/year. Groundwater draft in the study area is found to be 2.85 times more than the actual requirement (342 MCM) of the crops in the area due to highly permeable sandy soils. In view of the alarming imbalance in the groundwater recharge and draft, some management practices are suggested to restore the original groundwater condition which includes proper well spacing, artificial recharge, change of cropping pattern and irrigation methods to suit to the local conditions. Quality of groundwater is suitable for drinking and agricultural purposes.

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

    USGS Publications Warehouse

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

    2007-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Bahlburg, H.; Breitkreuz, C.

    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 Oclyic 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 Puneo. West of the Arco Puneo, a further marine basin developed during the Early Devonian, the eastern shelf of which occupied the area of the Cordillera Occidental, Depresin 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 Depresin 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.

  8. The Precambrian terranes of Yemen and their correlation with those of Saudi Arabia and Somalia: Implications for the accretion of Gondwana

    USGS Publications Warehouse

    Windley, B.F.; Whitehouse, M.J.; Stoeser, D.B.; Al-Khirbash, S.; Ba-Bttat, M. A. O.; Al-Ghotbah, A.

    2001-01-01

    Most of the basement of Yemen consists of early Precambrian continental high-grade terranes and Neoproterozoic low-grade island arcs that were accreted together to form an arc-continent collage during the Pan-African orogeny (Windley et al., 1996; Whitehouse et al., 1998; Whitehouse et al., in press). The suture zones between the arc and gneiss terranes are major crustal- scale tectonic boundaries. The terranes are situated east of the Nabitah suture and of the collage of low-grade, mainly island arc terranes of the Arabian Shield, but they have been reworked by a Neoproterozoic event associated with island arc accretion. Further east in Yemen are mostly unconformable, very weakly deformed and very low-gradeor unmetamorphosed sediments. Thus Yemen provides key information on the broad zone of Neoproterozoic reworking associated with the collisional boundary between western and eastern Gondwana.

  9. Linking south China to northern Australia and India on the margin of Gondwana: Constraints from detrital zircon U-Pb and Hf isotopes in Cambrian strata

    NASA Astrophysics Data System (ADS)

    Xu, Yajun; Cawood, Peter A.; Du, Yuansheng; Hu, Lisha; Yu, Wenchao; Zhu, Yanhui; Li, Wenchao

    2013-12-01

    sedimentary rocks in the southern part of the South China Craton were derived from a source that lay to the south or southeast, beyond the current limits of the craton and which is no longer preserved nearby. U-Pb ages and Hf isotope data on detrital zircons from the Cambrian sequence define two distinctive age peaks at 1120 Ma and 960 Ma, with ?Hf(t) values for each group identical to the coeval detrital zircons from Western Australia and the Tethyan Himalaya zone, respectively. The circa 1120 Ma detrital zircons were most likely derived from the Wilkes-Albany-Fraser belt between southwest Australia and Antarctica, whereas the circa 960 Ma detrital zircons could have been sourced from the Rayner-Eastern Ghats belt between India and Antarctica. Derivation of detritus from these sources suggests that south China was located at the nexus between India, Antarctica, and Australia, along the northern margin of East Gondwana during the Cambrian.

  10. Detrital zircon age patterns and provenance in late Paleozoic early Mesozoic New Zealand terranes and development of the paleo-Pacific Gondwana margin

    NASA Astrophysics Data System (ADS)

    Wysoczanski, R. J.; Gibson, G. M.; Ireland, T. R.

    1997-10-01

    Permian-Triassic strata from Parapara Peak in the Takaka terrane, western province, New Zealand, are dominated by detrital zircon peaks at ca. 240 Ma comparable to the Torlesse terrane of the eastern province. This contrasts with lower Paleozoic strata (Onekaka schist), which is comparable to other lower Paleozoic terranes (including adjacent Buller terrane) from the Gondwana margin that are characterized by detrital zircon patterns with characteristic peaks at ca. 500 650 Ma and ca. 1000 1150 Ma, a less distinct peak around 1400 1700 Ma, and scattered Archean ages. These data indicate the close proximity of the eastern and western provinces by Permian time and a probable source region of Parapara Peak strata and Torlesse terrane in the New England fold belt of southeast Australia.

  11. Petrogenesis of early Paleozoic peraluminous granite in the Sibumasu Block of SW Yunnan and diachronous accretionary orogenesis along the northern margin of Gondwana

    NASA Astrophysics Data System (ADS)

    Wang, Yuejun; Xing, Xiaowan; Cawood, Peter A.; Lai, Shaocong; Xia, Xiaoping; Fan, Weiming; Liu, Huichuan; Zhang, Feifei

    2013-12-01

    Zircon U-Pb and Hf isotopic data along with whole-rock elemental and Sr-Nd isotopic data for early Paleozoic granitoids from the Tengchong, Baoshan and Shan-Thai Blocks that originally formed along the northern margin of Gondwana and now lie in SW Yunnan constrain the character of early Paleozoic orogenesis along the margin. Twelve analyzed samples yield zircon U-Pb crystallization age of 492-460 Ma. These granitic rocks have CIPW-normative corundum and are strongly peraluminous with A/CNK of 1.10-1.39, similar to S-type granites. They are characterized by high SiO2, Rb/Sr and Rb/Ba but low Al2O3, MgO, TiO2, FeOt and CaO/Na2O ratios, and are enriched in LILE and depleted in Nb, Sr, P, Eu and Ti. Initial 87Sr/86Sr ratios range from 0.7084 to 0.7230 and ?Nd(t) values from - 5.3 to - 8.1 with Nd model ages of 1.7-2.8 Ga, consistent with those of the published synchronous granitic rocks in South Tibet. Zircons with early Paleozoic magmatic ages have ?Hf(t) values ranging from - 0.37 to - 14.1 and Hf model ages from 1.49 Ga to 2.35 Ga. Their petrogenesis can be interpreted as melting of an ancient metapelite-dominated crustal source with the residual mineral assemblage of plagioclase hornblende garnet zircon. The Ordovician granitoids in SW Yunnan represent the southward continuation of the early Paleozoic granitic belt that extended along the northern margin Gondwana. The granites along with associated deformation, metamorphism and exhumation and erosion, mark a pulse of progressive along strike orogenesis that ranges in age from end Neoproterozoic to Cambrian in Turkey to Ordovician in Shan-Thai.

  12. Cambrian rift-related magmatism in the Ossa-Morena Zone (Iberian Massif): Geochemical and geophysical evidence of Gondwana break-up

    NASA Astrophysics Data System (ADS)

    Sarrionandia, F.; Carracedo Sánchez, M.; Eguiluz, L.; Ábalos, B.; Rodríguez, J.; Pin, C.; Gil Ibarguchi, J. I.

    2012-10-01

    Volcanic rocks of Cambrian age from Zafra (Ossa-Morena Zone, Iberian Massif) are the result of rift processes that affected Cadomian arc units accreted to the NW edge of Gondwana during the Neoproterozoic-Early Cambrian transition. Tephrite to rhyolite volcanics define an alkaline transitional association (Coombs type). Basic-ultrabasic rocks exhibit typical alkaline REE-patterns, strongly enriched in LREE with respect to HREE. Two parental magmas are identified, one with a mantle signature, lack of Nb negative anomaly and εNd500Ma + 3.8 to + 4.2; another with crustal contribution, minor Nb negative anomaly and εNd500Ma + 0.8 to + 1.8. Intermediate-acid rocks show variable REE fractionation and share geochemical characteristics of both basic-ultrabasic groups with restricted εNd500Ma + 2.2 to 3.1 and general absence of Nb negative anomaly. Basic-ultrabasic melts resulted from different amounts of partial melting of a homogeneous source and segregation at the garnet-spinel transition zone. We argue that the "Hales transition" recently recognized in reflection seismic experiments of SW Iberia might image such a source region. Mantle-derived magmas ponded at the base of the crust and weakly interacted with crustal rocks/melts, whilst intermediate-acid rocks were generated by plagioclase ± clinopyroxene ± amphibole fractionation. Melt ascent took place through fractures, with limited crustal interaction. Based upon the new geochemical results and complementary cartographic and geophysical data, a model is presented for the Cambrian break-up of North Gondwana due to magma ascent from the mantle.

  13. Sedimentary basins on the connugate margins of South America and Africa

    SciTech Connect

    Moore, G.T. )

    1990-05-01

    An Early Cretaceous spreading system formed the South Atlantic by separating South America from Africa along two subparallel major transform fault systems. The distribution of major sedimentary depocenters is controlled by the complex interplay of two factors: the late Mesozoic-Cenozoic cycle of sea-floor spreading and the legacy of a Precambrian collage of ancient cores that comprised western Gondwana. Three spreading modes created this configuration: rift, transform, and subduction. Each produces a different geometry and tectonic framework for the accumulation of sediment. Rifted margins (60%) contain basins that are elongate, form with their depocenter axes inboard of the ocean-continent transition, and rest on a tectonically complex, foundered basement. Transform margins have abrupt ocean-continent transitions. Such margins (30%) may be sediment starved or contain a thick sedimentary section controlled by the volcanic ridges of transform faults. Off Tierra del Fuego, Burdwood Bank is bounded on the north by a fossil (aseismic) subduction zone. The associated basin is an elongate, deformed accretionary prism of sediments on a gently dipping, faulted oceanic plate. The South Atlantic margins are divisible into 68 basins or segments that collectively contain over 33 {times} 106 km{sup 3} of syn- and postbreakup sediments. The South American margin contains 22 {times} 10{sup 6} km{sup 3} in 46 basins, and the African margin, 11 {times} 10{sup 6} km{sup 3} in 22 basins. Over 65% of the basins have a sediment column greater than 5 km with some depocenters that locally exceed 10 km. The source rock quality and character vary along both margins. The top of the oil generation window averages about 3.3 km; however, due to differing thermal histories, individual basins can depart significantly from this average.

  14. Seismo and sequence stratigraphy of Cenozoic units of the Morondava Basin, offshore western Madagascar

    NASA Astrophysics Data System (ADS)

    Kaufmann, Dirk; Stollhofen, Harald; Klimke, Jennifer; Franke, Dieter

    2015-04-01

    The N-S trending Morondava Basin extends in width from western onshore Madagascar over about 350 km westwards to the offshore Davie Ridge in the Mozambique Channel. Although basin formation was initiated during Karoo times, the main basin evolution took place during Jurassic rifting and subsequent drifting until middle Cretaceous as a result of Gondwana breakup (Geiger et al., 2004). Contemporaneous to the separation of India and Madagascar widespread flood basalts were emplaced during the late Cretaceous (Storey et al., 1995). Present knowledge of the Morondava Basin is mainly based on outcrop studies, seismic surveys and borehole information (e.g. Geiger et al., 2004), gathered in western onshore Madagascar, although the fast majority of the basin, including its depocenter is located offshore in the Mozambique Channel, now at up to 3,500 m water depth. Almost all of the recent offshore studies of the Morondava Basin rely on industrial data but up to date publications of exploration results are generally rare and mostly anonymized. Our study aims to extend knowledge, particularly on the offshore seismic and sequence stratigraphy of the Morondava Basin. A key question is also to test the proposed tectonic stability of the Davie Ridge over the last 40 Ma. For this purpose 12 seismic profiles and bathymetric data, acquired in early 2014 by RV SONNE, are interpreted. Most of the profiles cover the distal deep marine areas of the northern Morondava Basin between the Davie Ridge and the shelf break of Madagascar. Top Cretaceous, Top Eocene, Top Oligocene, the Middle Miocene Unconformity and the Base Pliocene, are mapped as major seismic marker horizons. Especially shelf and slope sedimentary units are important resources to reconstruct the tectonostratigraphic basin evolution. At the continental slope diffuse to chaotic seismic pattern of Miocene and younger age are identified which are subdivided by laterally continuous, high frequency reflectors with a higher impedance contrast. Bounded by the Base Tertiary and the Base Pliocene these units can be used to develop and verify a sequence stratigraphic approach for the Cenozoic in the Morondava Basin. Prelimary results indicate that the major sedimentation at the continental slope moved after Early Pliocene significantly landwards. In general the thickness of post-Pliocene units increases to the east. Work in progress encompasses the application of seismo and sequence stratigraphic concept for Mesozoic sedimentary units and a correlation with other, potentially time-equivalent, basins in the area, such as the Mandawa Basin in northern Mozambique. References Geiger, M., Clark, D.N., und Mette, W., 2004, Reappraisal of the timing of the break-up of Gondwana based on sedimentological und seismic evidence from the Morondava Basin, SW Madagascar: Journal of African Earth Sciences, v. 38, p. 363-381. Storey, M., Mahoney, J. J., Saunders, A. D., Duncan, R. A., Kelley, S. P., und Coffin, M. F., 1995, Timing of Hot Spot--Related Volcanism und the Breakup of Madagascar und India: Science, v. 267, no. 5199, p. 852-855.

  15. Permian and Triassic microfloral assemblages from the Blue Nile Basin, central Ethiopia

    NASA Astrophysics Data System (ADS)

    Dawit, Enkurie L.

    2014-11-01

    Palynological investigation was carried out on surface samples from up to 400 m thick continental siliciclastic sediments, here referred to as “Fincha Sandstone”, in the Blue Nile Basin, central Ethiopia. One hundred sixty species were identified from 15 productive samples collected along a continuous road-cut exposure. Six informal palynological assemblage zones have been identified. These assemblage zones, in ascending order, are: “Central Ethiopian Permian Assemblage Zone - CEPAZ I”, earliest Permian (Asselian-Sakmarian); “CEPAZ II”, late Early Permian (Artinskian-Kungurian); CEPAZ III - Late Permian (Kazanian-Tatarian); “CETAZ IV”, Lower Triassic (Olenekian Induan); “CETAZ V”, Middle Triassic (Anisian Ladinian); “CETAZ VI”, Late Triassic (Carnian Norian). Tentative age ranges proposed herein are compared with faunally calibrated palynological zones in Gondwana. The overall composition and vertical distribution of miospores throughout the studied section reveals a wide variation both qualitatively and quantitatively. The high frequency of monosaccate pollen in CEPAZ I may reflect a Glossopterid-dominated upland flora in the earliest Permian. The succeeding zone is dominated by straite/taeniate disaccate pollen and polyplicates, suggesting a notable increase in diversity of glossopterids. The decline in the diversity of taeniate disaccate pollen and the concomitant rise in abundance of non-taeniate disaccates in CEPAZ III may suggest the decline in Glossopteris diversity, though no additional evidence is available to equate this change with End-Permian extinction. More diverse and dominant non-taeniate, disaccate, seed fern pollen assignable to FalcisporitesAlisporites in CETAZ IV may represent an earliest Triassic recovery flora. The introduction of new disaccate forms with thick, rigid sacci, such as Staurosaccites and Cuneatisporites, in CETAZ V and VI may indicate the emergence of new gymnospermous plants that might have favourably adapted to coastal plain wetland environments with the return of humid conditions in the Middle to early Late Triassic. The present data constitute the first paleontologically substantiated record for the existence of Permian strata in the Blue Nile Basin. The new results allow for the first time a reliable biostratigraphic subdivision of the central Ethiopia Karoo and its correlation with coeval strata of adjacent regions in Gondwana. From a phytogeographic point of view, the overall microfloral evidence is in support of the position of central Ethiopia occupying the northern part of the southern Gondwana palynofloral province. In view of palaeoecological and paleoclimatic conditions, the microfloral change from the base to the top of the studied section may indicate a response to shifting climatic belts from warm- and cool-temparate climate in the earliest Permian to progressively drier seasonal conditions at successively higher palaeolatitudes during the Late Permian to Middle Triassic.

  16. New Sakmarian ages for the Rio Bonito formation (Paraná Basin, southern Brazil) based on LA-ICP-MS U-Pb radiometric dating of zircons crystals

    NASA Astrophysics Data System (ADS)

    Cagliari, Joice; Lavina, Ernesto Luiz Correa; Philipp, Ruy Paulo; Tognoli, Francisco Manoel Wohnrath; Basei, Miguel Angelo Stipp; Faccini, Ubiratan Ferrucio

    2014-12-01

    Two ash fall beds (tonstein) sampled from the post-glacial Permian deposits of the Paraná Basin have provided new U-Pb radiometric age constraints for this stratigraphic interval. The zircon grains were recovered from tonstein layers interbedded with fine-grained and carbonaceous lithologies in the middle portion of the Rio Bonito Formation. In both samples, the dominant population is interpreted as generated by explosive volcanism, as having formed immediately before the eruption. Based on 238U/206Pb, the selected zircon grains from the dominant population have weighted mean ages of 290.6 ± 2.8 Ma and 281.7 ± 3.2 Ma, corresponding to the Sakmarian and Kungurian ages in the Cisuralian epoch, respectively. These ages constrain the time of the deposition of the tonstein horizons and have important stratigraphic implications for the Late Paleozoic evolution of both the Paraná Basin and the southwestern region of Gondwana. The results presented here and the radiometric data already published suggest that deposition of the post-glacial coal-bearing deposits of the Rio Bonito Formation was probably initiated before the Early Permian. Thus, we infer that the climate had already ameliorated by this period in order to allow for the formation and accumulation of peat in this region of Gondwana.

  17. Mineralogical and geochemical characteristics of the Noamundi-Koira basin iron ore deposits (India)

    NASA Astrophysics Data System (ADS)

    Mirza, Azimuddin; Alvi, Shabbar Habib; Ilbeyli, Nurdane

    2015-04-01

    India is one of the richest sources of iron ore deposits in the world; and one of them is located in the Noamundi-Koira basin, Singhbhum-Orissa craton. The geological comparative studies of banded iron formation (BIF) and associated iron ores of Noamundi-Koira iron ore deposits, belonging to the iron ore group in eastern India, focus on the study of mineralogy and major elemental compositions along with the geological evaluation of different iron ores. The basement of the Singhbhum-Orissa craton is metasedimentary rocks which can be traced in a broadly elliptical pattern of granitoids, surrounded by metasediments and metavolcanics of Greenstone Belt association. The Singhbhum granitoid is intrusive into these old rocks and to younger, mid Archaean metasediments, including iron formations, schists and metaquartzites and siliciclastics of the Precambrian Iron Ore Group (Saha et al., 1994; Sharma, 1994). The iron ore of Noamundi-Koira can be divided into seven categories (Van Schalkwyk and Beukes 1986). They are massive, hard laminated, soft laminated, martite-goethite, powdery blue dust and lateritic ore. Although it is more or less accepted that the parent rock of iron ore is banded hematite jasper (BHJ), the presence of disseminated martite in BHJ suggests that the magnetite of protore was converted to martite. In the study area, possible genesis of high-grade hematite ore could have occurred in two steps. In the first stage, shallow, meteoric fluids affect primary, unaltered BIF by simultaneously oxidizing magnetite to martite and replacing quartz with hydrous iron oxides. In the second stage of supergene processes, deep burial upgrades the hydrous iron oxides to microplaty hematite. Removal of silica from BIF and successive precipitation of iron resulted in the formation of martite- goethite ore. Soft laminated ores were formed where precipitation of iron was partial or absent. The leached out space remains with time and the interstitial space is generally filled with kaolinite and gibbsite, which make it low grade. Massive iron ores are devoid of any lamination and usually associated with BHJ and lower shale. The thickness of the massive ore layer varies with the location. The massive iron ore grades in to well-developed bedded BHJ in depth. Blue dust occurs in association with BHJ as pockets and layers. Although blue dust and friable ore are both powdery ores, and subjected to variable degree of deformation, leading to the formation of folding, faulting and joints of complex nature produce favourable channels. Percolating water play an important role in the formation of blue dust and the subterranean solution offers the necessary acidic environment for leaching of quartz from the BHJ. The dissolution of silica and other alkalis are responsible for the formation of blue dust. The friable and powdery ore on the other hand are formed by soft laminated ore. As it is formed from the soft laminated ore, its alumina content remains high similar to soft laminated ore compaired to blue dust. Mineralogy study suggests that magnetite was the principal iron oxide mineral, now a relict phase whose depositional history is preserved in BHJ, where it remains in the form of martite. The platy hematite is mainly the product of martite. The different types of iron ores are intricately related with the BHJ. Hard laminated ores, martite-goethite ore and soft laminated ore are resultant of desilicification process through the action of hydrothermal fluids. Geochemistry of banded iron-formations of the Noamundi-Koira iron ore deposits shows that they are detritus-free chemical precipitates. The mineralogical and geochemical data suggest that the hard laminated, massive, soft laminated ores and blue dust had a genetic lineage from BIF's aided with certain input from hydrothermal activity. The comparative study of major elemental composition of the basin samples and while plotting a binary diagram, it shows a relation between major oxides against iron oxides, in which iron oxides is taken as a reference oxide (Mirza, 2011). On the other hand, by plotting a binary diagram between chemical index of alteration (CIA) and other oxides while taking the samples of lower, middle and upper shales. It reflects an immobility and mobility of ions during partial and complete weathering processes (Mirza, 2011). Geochemical data indicate that BIF are in general detritus free chemical precipitates. Fe2O3 content of BHJ are varies in between 36.6% to 65.04%. In hard laminated ore, Fe2O3 content varies from 93.8% to 96.38%, Soft laminated ore varies from 83.64% to 89.5% and laterite ore varies from 53.5% to 79.11%. Fe2O3 content in Martite- Goethite ore varies from 86.38% to 89.42% and blue dust having 90.74% to 95.86% and all other oxides like SiO2, Al2O3, CaO, MgO, K2O, Na2O are decreases. Major part of the iron could have been added to the bottom sea water by hydrothermal solutions derived from hydrothermally active anoxic marine environments. The presence of intacalated tuffaceous shales pointing towards the genesis of iron, which could have leached from sea floor by volcanogenic process. Iron and silica of BIF were provided by the hydrothermal solutions emplaced at the vent sites situated at the Archean-Mid Oceanic Ridges. References: Mirza A (2011). Major element geochemistry of iron ore deposits in Noamundi-Koira basin of Singhbhum-Orissa craton (India). MSc thesis, Aligarh Muslim University, India. Saha AK (1994). Crustal evolution of Singhbhum, North Orissa, Eastern India; Geol. Soc. India Memoir 27 341. Sharma M, Basu AR and Ray SL (1994). Sm-Nd isotopic and geochemical study of the Archaean tonalite-amphibolite association from the eastern Indian craton. Contrib. Mineral Petrol. 117:45-55. Van Schalkwyk J and Beukes N J (1986). The Sishen iron ore deposit, Griqualand West; In: Mineral deposits of Southern Africa (eds) Annhaeusser C R and Maske S S, Geological Society of South Africa, Johannesburg, 931-956.

  18. Evolution of faulting and plate boundary deformation in the Southern Taranaki Basin, New Zealand

    NASA Astrophysics Data System (ADS)

    Reilly, Cathal; Nicol, Andrew; Walsh, John J.; Seebeck, Hannu

    2015-05-01

    Faulting and folding in the Southern Taranaki Basin constrain the evolution of the New Zealand plate boundary since ~ 80 Ma. Sedimentary rocks up to 8 km thick record multiple phases of deformation which have been examined using 2D and 3D seismic reflection data, resulting in fault displacement-time curves and basin-wide isopach maps with temporal resolutions of 5-10 Myr and 1-4 Myr pre- and post-~ 23 Ma respectively. Three main phases of tectonic activity have been recognised; Late Cretaceous and Palaeocene extension (~ 80-55 Ma), mainly Oligocene and younger contraction and Plio-Pleistocene (~ 3.7-0 Ma) extension. Most of the largest faults (e.g., Cape Egmont Fault) accrued displacement during the Late Cretaceous and were reactivated one or more times during subsequent episodes of deformation. The oldest phase of extension occurred during Gondwana break-up and was ubiquitous throughout the basin. Contraction along the eastern boundary of the basin, associated with the onset of Hikurangi Margin subduction, commenced as early as Late Eocene. The zone of contraction widened and migrated westward during the Miocene with reverse faults and folds in westernmost parts of the basin formed in the Late Miocene (~ 7-5 Ma). Initiation and episodic widening of this zone of contraction may have been partly triggered by changes in the rate of plate convergence. Contraction is now mainly confined to the northern South Island and has been succeeded to the north by Plio-Pleistocene extension. The present day transition zone between extension in the north and contraction in the south is defined by a WNW-trending line across the basin. The extension-contraction transition migrated southward during the Late Miocene and Pliocene consistent with steepening of the subducting plate and associated southward movement of the southern termination of the Hikurangi subduction system.

  19. Deformation of the Proterozoic successions in the Pranhita Godavari basin, south Indiaa regional perspective

    NASA Astrophysics Data System (ADS)

    Saha, Dilip; Chaudhuri, Asru K.

    2003-03-01

    A number of Proterozoic intracratonic basins, namely Cuddapah, Pranhita-Godavari (PG), Abujhmar, Indravati, Ampani, Chattisgarh and Khariar basins, occur to the immediate west of the Eastern Ghats granulite belt (EGGB) in India. Of these, the PG basin hosts an axial outcrop of late Paleozoic-Mesozoic Gondwana rocks flanked on either side by Proterozoic sedimentary successions. Among the latter, the Somanpalli Group in the eastern part and the Penganga and Yellandlapad Groups in the western part show contractional folds, imbricate thrusts and cleavage. These deformed rock groups and the Pakhal Group in the western belt include shallow to deep marine sedimentary successions. Stratigraphic relations indicate that the major episode of deformation in the PG basin occurred prior to deposition of the unconformably overlying Sullavai Group. The latter is a Neoproterozic, undeformed fluvial sequence with some aeolian intercalation. Deformed successions also occur in other Proterozoic basins of the south Indian craton, notably those in the Nallamalai fold belt (NFB) along the eastern part of the Cuddapah basin. The major fold-fault structures in the arcuate NFB vary in trend from NNW-SSE in the southern part to NE-SW in the northern part. At least one phase of folding and thrusting predates the 1000 Ma old event in the EGGB. Deformation associated with the Grenville and later Pan-African tectonic mobility has imprints on the Neoproterozic Kurnool Group in the Palnad sub-basin (northern NFB). The major structural trend in the PG basin is NW-SE, except for the Yellandlapad area in the southern part, where late superposed folds trend E-W. The deformation along the eastern margin of the Chattisgarh basin, its southern extension in Khariar, Ampani and Indravati basins may also be related with the main (Grenville) deformation in the EGGB. A regional, Mesoproterozic episode of basin closure and inversion is thus evident from the Proterozoic cratonic successions west of the Eastern Ghats. This occurred prior to a regional development of Neoproterozoic successions at these sites.

  20. Evaporite cycles and cycle boundaries in the upper part of the Paradox Member, Hermosa Formation of Pennsylvanian age in the Paradox basin, Utah and Colorado

    SciTech Connect

    Raup, O.B.; Hite, R.J. )

    1991-03-01

    The evaporites of the Paradox Member of the Hermosa Formation of Pennsylvanian age in southeastern Utah and southwestern Colorado are direct precipitates from marine brines and have been changed only slightly by subsequent events. Geophysical logs of deep wells indicate that the Paradox Member is composed of at least 30 evaporite cycles. Lithologies that make up the cycles, in order of increasing salinity, are organic carbon-rich carbonate shale (black shale), dolomite, anhydrite, and halite (with or without potash). Studies of core from two wells in the central part of the basin show that some of the cycles in the upper part of the Paradox Member are remarkably symmetrical, indicating regular changes in salinity. Detailed petrologic studies have revealed newly recognized lithologic textures and cycle boundaries in 11 evaporite cycles, indicating very regular cyclicity of subaqueous sedimentation in a basin in which salinity was probably controlled by Gondwana glaciation.

  1. 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

    2011-01-01

    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 PMID:21787392

  2. 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)

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

    2010-05-01

    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 (δ13C 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.

  3. Petrogenesis of the Early Cretaceous Laguila bimodal intrusive rocks from the Tethyan Himalaya: Implications for the break-up of Eastern Gondwana

    NASA Astrophysics Data System (ADS)

    Liu, Zheng; Zhou, Qing; Lai, Yang; Qing, Chengshi; Li, Yingxu; Wu, Jianyang; Xia, Xiangbiao

    2015-11-01

    The Kerguelen mantle plume triggered the rift of Eastern Gondwana to open the eastern Indian Ocean, with the formation of ~ 132 Ma Comei-Bunbury large igneous province (LIP). The Comei area is located in the eastern Tethyan Himalaya, paleogeographically belonging to Greater India. The Laguila bimodal intrusive rocks from the Comei area consist of mafic (gabbro-diabase) and felsic rocks (quartz monzonite-granodiorite). This paper presents detailed LA-ICP-MS zircon U-Pb chronology, major and trace elements, and Sr-Nd-Pb isotope geochemistry of the Laguila bimodal intrusive rocks, in order to constrain the early activity of the Kerguelen mantle plume. LA-ICP-MS zircon U-Pb dating shows that the Laguila intrusive rocks were emplaced in the Early Cretaceous (~ 134-130 Ma). The Laguila mafic rocks are enriched in LREE, LILE and HFSE, similar to those of oceanic island basalts (OIB). Their 87Sr/86Sri (0.7054 to 0.7066), 143Νd/144Nd (T) (0.512548 to 0.512619) and (206Pb/204Pb)t ratios (18.492 to 18.859) are comparable with those basalts derived by the Kerguelen hot spot. Elemental and isotopic data suggest that they were likely derived by partial melting of the Kerguelen plume source in the spinel-garnet transition zone (~ 60-80 km). The Laguila felsic rocks share most of the geochemical features of A-type granite and show different 87Sr/86Sri (0.7171 to 0.7204), 143Νd/144Nd (T) (0.511874 to 0.511956) and (206Pb/204Pb)t ratios (19.087 to 19.274) from those of the mafic rocks. They were likely derived by partial melting of crustal rocks at a shallow depth (< 30 km) triggered by underplating of the coeval basaltic magmas. The Laguila intrusive rocks were emplaced in a rift setting during the breakup of eastern Gondwana, associated with the Kerguelen plume activity. We calculated the magmatic volume of Comei-Bunbury basalts and the result is ~ 1.1 × 104 km3. The small volume is not reconciled with those typical models for the initial magmatic eruption of mantle plume. It was possible that the thick lithosphere (> 150 km) underneath Greater India prevented the Kerguelen plume from large-scale melting because of the high pressure when the latter impinged onto the former at ~ 132 Ma. The shallow source (~ 60-80 km) of the Laguila mafic rocks indicate that they originated likely from a series of "diapirs" or "fingers" rising from the head of the Kerguelen plume, which penetrated into the thick lithospheric mantle of Eastern Gondwana at enough shallow depth for melting.

  4. Tiarajudens eccentricus and Anomocephalus africanus, two bizarre anomodonts (Synapsida, Therapsida) with dental occlusion from the Permian of Gondwana

    PubMed Central

    Cisneros, Juan Carlos; Abdala, Fernando; Jashashvili, Tea; de Oliveira Bueno, Ana; Dentzien-Dias, Paula

    2015-01-01

    Anomodontia was a highly successful tetrapod clade during the Permian and the Triassic. New morphological information regarding two bizarre basal anomodonts is provided and their palaeoecological significance is explored. The osteology of the recently discovered Tiarajudens eccentricus Cisneros et al. 2011, from the Brazilian Permian, is described in detail. The taxon exhibits unusual postcranial features, including the presence of gastralia. Additional preparation and computed tomography scans of the holotype of Anomocephalus africanus Modesto et al. 1999 discovered in the Karoo Basin of South Africa allow a reappraisal of this genus. Anomocephalus is similar to Tiarajudens with regard to several traits, including a battery of large, transversally expanded, palatal teeth. Molariform teeth are present in the mandible of the African taxon, providing additional insight into the function of the earliest tooth-occlusion mechanism known in therapsids. At least two waves of tooth replacement can be recognized in the palate of Anomocephalus. The outsized, blade-like caniniforms of the herbivorous Tiarajudens allow several non-exclusive ecological interpretations, among which we favour intraspecific display or combat. This behaviour was an alternative to the head-butting practised by the contemporary dinocephalians. Combat specializations that are considered typical of Cenozoic herbivores likely evolved during the Middle Permian, at the time the first communities with diverse, abundant tetrapod herbivores were being assembled. PMID:26587266

  5. Tiarajudens eccentricus and Anomocephalus africanus, two bizarre anomodonts (Synapsida, Therapsida) with dental occlusion from the Permian of Gondwana.

    PubMed

    Cisneros, Juan Carlos; Abdala, Fernando; Jashashvili, Tea; de Oliveira Bueno, Ana; Dentzien-Dias, Paula

    2015-07-01

    Anomodontia was a highly successful tetrapod clade during the Permian and the Triassic. New morphological information regarding two bizarre basal anomodonts is provided and their palaeoecological significance is explored. The osteology of the recently discovered Tiarajudens eccentricus Cisneros et al. 2011, from the Brazilian Permian, is described in detail. The taxon exhibits unusual postcranial features, including the presence of gastralia. Additional preparation and computed tomography scans of the holotype of Anomocephalus africanus Modesto et al. 1999 discovered in the Karoo Basin of South Africa allow a reappraisal of this genus. Anomocephalus is similar to Tiarajudens with regard to several traits, including a battery of large, transversally expanded, palatal teeth. Molariform teeth are present in the mandible of the African taxon, providing additional insight into the function of the earliest tooth-occlusion mechanism known in therapsids. At least two waves of tooth replacement can be recognized in the palate of Anomocephalus. The outsized, blade-like caniniforms of the herbivorous Tiarajudens allow several non-exclusive ecological interpretations, among which we favour intraspecific display or combat. This behaviour was an alternative to the head-butting practised by the contemporary dinocephalians. Combat specializations that are considered typical of Cenozoic herbivores likely evolved during the Middle Permian, at the time the first communities with diverse, abundant tetrapod herbivores were being assembled. PMID:26587266

  6. The Fairway-Aotea Basin and the New Caledonia Trough, witnesses of the Pacific-Australian plate boundary evolution : from mid-Cretaceous cessation of subduction to Eocene subduction renewal

    NASA Astrophysics Data System (ADS)

    Collot, J.; Geli, L. B.; Lafoy, Y.; Sutherland, R.; Herzer, R. H.; Roest, W. R.

    2009-12-01

    The geodynamical history of the SW Pacific is controlled since the Mesozoic by the evolution of peri-Pacific subduction zones, in a trench retreat by slab roll-back process, which successively occurred along the Eastern Gondwana margin. In this context, most basins which formed after 45 Ma reached a stage of seafloor spreading, have recorded the inversions of the earth's magnetic field and present typical oceanic crust morphologies. By contrast, the New Caledonia and Fairway basins, which are narrower and present thick sedimentary covers have a less known and more controversial origin. Based on a regional geological synthesis and on interpretation of multichannel seismic reflection and refraction data, combined with drill hole data off New Zealand and a compilation of regional potential data, we distinguish 2 phases of the evolution of the Fairway-Aotea Basin (FAB) and the New Caledonia Trough (NCT), which reflect the evolution of the Gondwana-Pacific plate boundary: Phase 1: Mid Cretaceous formation of the FAB in a continental intra- or back- arc position of the Pacific-Gondwana subduction system. The formation of this shallow basin reflects the onset of continental breakup of the Eastern Gondwana margin during Cenomanian which was most probably caused by a dynamic change of the subduction zone through a verticalization of the slab. This event may be the result of the 99 Ma kinematic plate reorganization which probably led to subduction cessation along the Gondwana-Pacific plate boundary. A tectonic escape mechanism, in relation with the locking of the subduction zone by the Hikurangi Plateau, could also be responsible of the trench retreat leading to backarc extension. Phase 2: Regional Eocene-Oligocene uplift followed by rapid subsidence (3-4 km) of the system Lord Howe Rise - FAB - Norfolk Ridge . The structural style of this deformation leads us to suggest that detachment of the lower crust is the cause of subsidence. We therefore propose a model in which the system, initially shallow during Cretaceous (phase 1), would have greatly subsided during Eocene-Oligocene, giving birth to the NCT, as the renewal of the Australia-Pacific convergent plate boundary took place. This renewal of convergence at 45 Ma would have driven the lithosphere of the system to thicken (uplift), leading to a root instability and to its detachment in the mantle (subsidence). Superposed on these two main phases, some local effects, controlled by the geometry of the plate boundary, also appear. Particularly, latest late Eocene local deformation of the Northern NCB is documented, synchronously with the New Caledonian obduction. This asymmetrical deformation which lasted less than a few million years led to the uplift of the Fairway Ridge and the subsidence of the Eastern margin of the basin along NCs western coast (10 km vertical amplitude). We suggest that as the oceanic crust of the South Loyalty Basin was being obducted onto the Norfolk Ridge at 37 Ma, the NCB subsided under the effect of the overloading and underthrusted to accommodate the compressional deformation as a foreland flexural basin.

  7. 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)

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

    2014-07-01

    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 the Namaqua Belt, which represents one of the two major peaks of zircon U-Pb ages in all analysed samples. Therefore, the Namaqua Belt was well exposed during the Cryogenian, available to erosion and apart from the also well-exposed Palaeoproterozoic basement of the Kalahari Craton one potential source area for the sedimentary rocks in the investigated areas.

  8. Miocene transgression in the central and eastern parts of the Sivas Basin (Central Anatolia, Turkey) and the Cenozoic palaeogeographical evolution

    NASA Astrophysics Data System (ADS)

    Poisson, André; Vrielynck, Bruno; Wernli, Roland; Negri, Alessandra; Bassetti, Maria-Angela; Büyükmeriç, Yesim; Özer, Sacit; Guillou, Hervé; Kavak, Kaan S.; Temiz, Haluk; Orszag-Sperber, Fabienne

    2016-01-01

    We present here a reappraisal of the tectonic setting, stratigraphy and palaeogeography of the central part of the Sivas Basin from Palaeocene to late Miocene. The Sivas Basin is located in the collision zone between the Pontides (southern Eurasia) and Anatolia (a continental block rifted from Gondwana). The basin overlies ophiolites that were obducted onto Anatolia from Tethys to the north. The Central Anatolian Crystalline Complex (CACC) experienced similar ophiolite obduction during Campanian time, followed by exhumation and thrusting onto previously emplaced units during Maastrichtian time. To the east, crustal extension related to exhumation of the CACC created grabens during the early Tertiary, including the Sivas Basin. The Sivas Basin underwent several tectonic events during Paleogene-Neogene. The basin fill varies, with several sub-basins, each being characterised by a distinctive sequence, especially during Oligocene and Miocene. Evaporite deposition in the central part of the basin during early Oligocene was followed by mid-late Oligocene fluvio-lacustrine deposition. The weight of overlying fluvial sediments triggered salt tectonics and salt diapir formation. Lacustrine layers that are interbedded within the fluviatile sediments have locally yielded charophytes of late Oligocene age. Emergent areas including the pre-existing Sivas Basin and neighbouring areas were then flooded from the east by a shallow sea, giving rise to a range of open-marine sub-basins, coralgal reef barriers and subsiding, restricted-marine sub-basins. Utilising new data from foraminifera, molluscs, corals and nannoplankton, the age of the marine transgression is reassessed as Aquitanian. Specifically, age-diagnostic nannoplankton assemblages of classical type occur at the base of the transgressive sequence. However, classical stratigraphic markers have not been found within the planktic foraminiferal assemblages, even in the open-marine settings. In the restricted-marine sediments, there are rich planktic foraminiferal assemblages of classical type but these are of little use in stratigraphy. In contrast, the gastropod fauna indicate a Burdigalian age. Sediment reworking in the restricted-marine environments precludes stratigraphic determination. In such environments, micro- and nano-organisms experienced atypical developmental conditions. The small benthic foraminifera and associated ostracod assemblages are good indicators of salinity which varied considerably within the restricted-marine sub-basins. Some of the corals within the coralgal reefs barriers are also dated as Aquitanian. A combination of the salt tectonics and the late Miocene north-westward-verging thrusting created the present basin complexity.

  9. Miocene transgression in the central and eastern parts of the Sivas Basin (Central Anatolia, Turkey) and the Cenozoic palaeogeographical evolution

    NASA Astrophysics Data System (ADS)

    Poisson, Andr; Vrielynck, Bruno; Wernli, Roland; Negri, Alessandra; Bassetti, Maria-Angela; Bykmeri, Yesim; zer, Sacit; Guillou, Herv; Kavak, Kaan S.; Temiz, Haluk; Orszag-Sperber, Fabienne

    2015-11-01

    We present here a reappraisal of the tectonic setting, stratigraphy and palaeogeography of the central part of the Sivas Basin from Palaeocene to late Miocene. The Sivas Basin is located in the collision zone between the Pontides (southern Eurasia) and Anatolia (a continental block rifted from Gondwana). The basin overlies ophiolites that were obducted onto Anatolia from Tethys to the north. The Central Anatolian Crystalline Complex (CACC) experienced similar ophiolite obduction during Campanian time, followed by exhumation and thrusting onto previously emplaced units during Maastrichtian time. To the east, crustal extension related to exhumation of the CACC created grabens during the early Tertiary, including the Sivas Basin. The Sivas Basin underwent several tectonic events during Paleogene-Neogene. The basin fill varies, with several sub-basins, each being characterised by a distinctive sequence, especially during Oligocene and Miocene. Evaporite deposition in the central part of the basin during early Oligocene was followed by mid-late Oligocene fluvio-lacustrine deposition. The weight of overlying fluvial sediments triggered salt tectonics and salt diapir formation. Lacustrine layers that are interbedded within the fluviatile sediments have locally yielded charophytes of late Oligocene age. Emergent areas including the pre-existing Sivas Basin and neighbouring areas were then flooded from the east by a shallow sea, giving rise to a range of open-marine sub-basins, coralgal reef barriers and subsiding, restricted-marine sub-basins. Utilising new data from foraminifera, molluscs, corals and nannoplankton, the age of the marine transgression is reassessed as Aquitanian. Specifically, age-diagnostic nannoplankton assemblages of classical type occur at the base of the transgressive sequence. However, classical stratigraphic markers have not been found within the planktic foraminiferal assemblages, even in the open-marine settings. In the restricted-marine sediments, there are rich planktic foraminiferal assemblages of classical type but these are of little use in stratigraphy. In contrast, the gastropod fauna indicate a Burdigalian age. Sediment reworking in the restricted-marine environments precludes stratigraphic determination. In such environments, micro- and nano-organisms experienced atypical developmental conditions. The small benthic foraminifera and associated ostracod assemblages are good indicators of salinity which varied considerably within the restricted-marine sub-basins. Some of the corals within the coralgal reefs barriers are also dated as Aquitanian. A combination of the salt tectonics and the late Miocene north-westward-verging thrusting created the present basin complexity.

  10. Divergent/passive margin basins

    SciTech Connect

    Edwards, J.D. ); Santogrossi, P.A. )

    1989-01-01

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

  11. Ogaden Basin subsidence history: Another key to the Red Sea-Gulf of Aden tectonic puzzle

    SciTech Connect

    Pigott, J.D.; Neese, D.; Carsten, G.

    1995-08-01

    Previous work has attempted to understand the tectonic evolution of the Red Sea-Gulf of Aden region through a focus upon plate kinematics and reconstruction of plate interactions in a two dimensional sense. A significant complement to the three dimensional puzzle can be derived from a critical examination of the vertical component, tectonic subsidence analysis. By removing the isostatic contributions of sediment loading and unloading, and fluctuations in sea level, the remaining thermal-mechanical contribution to a basin`s subsidence can be determined. Such an analysis of several Ogaden Basin wells reveals multiple pulses of tectonic subsidence and uplift which correspond to far-field tectonic activities in the Red Sea and Gulf of Aden. One of the more dramatic is a Jurassic tectonic pulse circa 145-130 m.a., and a later extensional event which correlates to a major subsidence event ubiquitous through-out the Gulf of Aden, related to Gondwana Land breakup activities. Tectonic uplift during the Tertiary coincides with early Red Sea rifting episodes. Such activities suggest the Ogaden Basin has been a relatively stable East African cratonic basin, but with heating-extension events related to nearby plate interactions. In terms of hydrocarbon generation, the use of steady state present day geothermal gradients, coupled with subsidence analysis shows that potential Paleozoic and Mesozoic source rocks initiated generation as early as the Jurassic. The generating potential of Paleozoic source rocks would only be exacerbated by later heating events. Furthermore, cooling and tectonic uplift during the Tertiary would tend to arrest on-going hydrocarbon generation for Jurassic source rocks in the Ogaden area.

  12. Satellite magnetic anomalies of the Antarctic Wilkes Land impact basin inferred from regional gravity and terrain data

    NASA Astrophysics Data System (ADS)

    von Frese, R. R. B.; Kim, H. R.; Leftwich, T. E.; Kim, J. W.; Golynsky, A. V.

    2013-02-01

    The GRACE gravity and subglacial terrain data of Wilkes Land are consistent with the presence of a mascon produced by giant impact perhaps at the end of the Permian. In contrast to the relatively extensive ice probing radar coverage, aeromagnetic data coverage is limited across the basin. However, Magsat, rsted, and CHAMP satellite magnetic observations reveal the thinned crust of the impact site to be associated with the largest satellite altitude crustal magnetic anomaly of Antarctica. The underlying region of enhanced magnetization is consistent with the GRACE gravity and BEDMAP terrain data and extends into south-central Australia in a reconstructed Gondwana. The strongly magnetized crust can reflect the impact's thermal enhancement of lower crustal viscous remanent magnetization as well as the production of positively magnetized melt rocks within the fractured crust.

  13. The Heidelberg Basin Drilling Project basin analysis

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

  14. Devonian shelf basin, Michigan basin, Alpena region

    SciTech Connect

    Gutschick, R.C.

    1986-08-01

    This biostratigraphic study involves the Devonian paleogeography-paleoecology-paleobathymetry of the transition from carbonate platform shelf margin to basinal sedimentation for the northern part of the Michigan basin in the Alpena region. Shelf-basin analysis is based on lithofacies, rock colors, concretion, biostratigraphy, paleoecology of faunas - especially microfaunas and trace fossils - stratified water column, eustasy, and application of Walther's Law. Field observations were made on Partridge Point along Lake Huron, where type sections of the Middle Devonian Thunder Bay Limestone and Late Devonian Squaw Bay Limestone are exposed; and the Antrim black shale at Paxton quarry. The Thunder Bay Limestone evolved as a carbonate platform, subtidal shelf-margin aerobic environment dominated by sessile benthic coralline organisms and shelly fauna, but not reef framework. The Squaw Bay Limestone is transitional shelf to basin, with aspects of slope environment and deeper water off-platform, pelagic organic biostromal molluscan-conodont carbonate deposited during the onset of a stratified water column (dysaerobic benthos-polychaete. agglutinated tubes, sulfides) and pycnocline. The Antrim Shale, in an exceptional black shale exposure in the Paxton quarry, represents deep-water basinal deposition whose bottom waters lacked oxygen. Faunas (conodonts, styliolines, radiolarians) and floras (tasmanitids, calamitids, palynomorphs) are from the aerobic pelagic realm, as indicated from concretions and shale fossil evidence. A benthos is lacking, except for bioturbation from organisms introduced by entrained oxygenated distal turbidite dispersion into the barren bottom black muds. Basinal hydrocarbon source rocks are abundant and updip carbonate reservoirs rim the basin. The Antrim Shale sequence contains the interval of Frasnian-Famennian faunal extinction.

  15. Penobscot River Basin overview

    SciTech Connect

    Not Available

    1981-09-01

    The New England River Basins Commission has prepared summary reports on each of the region's major river basins. These reports concentrate on identifying problems in the existing network of planning and resource management programs. The most significant water resources issues identified in the Penobscot River basin are concerned with hydropower development, minerals development, forestry, and acid rain. Other water resource problems in the basin, principally related to the urban centers in the southern portion, include point source wastewater discharges, water supply needs, some flooding, and access to water-related recreation.

  16. Magnetic Fabric of the Itarar Group, Paran Basin Brazil: Preliminary Results

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    The late Paleozoic Itarar Group and equivalent beds in the Paran Basin of Brazil extend into Paraguay, Argentina, and Uruguay. The Itarar 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 Itarar 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 Paran 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 Itarar beds in the Brazilian portion of the Paran Basin (mainly in So 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.

  17. A new Late Triassic age for the Puesto Viejo Group (San Rafael depocenter, Argentina): SHRIMP U-Pb zircon dating and biostratigraphic correlations across southern Gondwana

    NASA Astrophysics Data System (ADS)

    Ottone, Eduardo G.; Monti, Mariana; Marsicano, Claudia A.; de la Fuente, Marcelo S.; Naipauer, Maximiliano; Armstrong, Richard; Mancuso, Adriana C.

    2014-12-01

    The Puesto Viejo Group crops out in the San Rafael Block, southwest Mendoza, at approximately 35° S and 68°20‧ W. It consists of the basal mainly grayish Quebrada de los Fósiles Formation (QF) overlying by the reddish Río Seco de la Quebrada Formation (RSQ). The basal unit includes both plant remains (pleuromeians and sphenopsids) and vertebrates (scattered fish scales, dicynodont synapsids and remains of an archosauriform). In contrast, the RSQ beds have yielded only tetrapods, although a more diverse fauna. The latter includes cynodonts as Cynognathus, Pascualognathus and Diademodon, and also dicynodonts (Vinceria and Kannemeyeria). Based on the assemblage of tetrapod taxa the bearing levels were correlated to the Cynognathus AZ of South Africa and thus referred to the Middle Triassic (Anisian). We obtained a SHRIMP 238U/206Pb age of 235.8 ± 2.0 Ma from a rhyolitic ignimbrite interdigitated between the QF and RSQ formations at the Quebrada de los Fósiles section. This new radiometric date for the Puesto Viejo Group suggests that the tetrapod fauna in the RSQ beds existed, instead, during the Late Triassic (early Carnian) some 10 Ma later than the currently accepted age. Two scenarios might explain our results: first, the Cynognathus AZ of South Africa is wrongly assigned to the lower Middle Triassic (Anisan) and should be considered younger in age, Late Triassic (Carnian); second, the relative age of the Cynognathus AZ of South Africa is correct but the inferred range of Cynognathus and Diademodon is incorrect as they were present during the Late Triassic (Carnian) at least in South America. In any case, this new date pose serious doubts about the validity of biostratigraphic correlations based solely on tetrapod taxa, a common practice for Triassic continental successions across Gondwana.

  18. The Oquirrh basin revisited

    SciTech Connect

    Erskine, M.C.

    1997-04-01

    The upper Paleozoic succession in the Oquirrh basin in unusually thick, up to 9300 m, and consists mainly of a Pennsylvanian-middle Permian miogeocline of northwestern Utah. Previous workers have suggested a tectonic origin for the Oquirrh basin that is incompatible with the basin location in both time and space. There is no evidence for Pennsylvanian and Lower Permian tectonism in the middle of the miogeocline. Thermal evidence from the Mississippian Mission Canyon shale does no support the implied deep burial of the crustal sag models of basin formation. Stratigraphic and facies evidence indicates a growth fault origin for the basin. Regional isopach maps and facies maps are powerful tools in interpreting depositional environments and in reconstructing fold-and-thrust belts. However, the location of measured sections relative to the location of the growth fault basin. The Charleston-Nebo thrust may have essentially reversed the movement on a growth fault. Thick Oquirrh basin sedimentary rocks may not be required to balance structural sections across this thrust fault. A thin-skinned, extensional growth fault origin for the Oquirrh basin implies that the Cordilleran miogeocline did not participate in the Pennsylvanian north-vergent uplifts of the Ancestral Rocky Mountains.

  19. K Basin safety analysis

    SciTech Connect

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

    1994-12-16

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

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

    NASA Astrophysics Data System (ADS)

    Ferreira-Oliveira, Luis Gustavo; Rohn, Rosemarie

    2010-03-01

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

  1. Refined stratigraphy of the Middle Permian Abrahamskraal Formation (Beaufort Group) in the southern Karoo Basin

    NASA Astrophysics Data System (ADS)

    Jirah, Sifelani; Rubidge, Bruce S.

    2014-12-01

    Fluvially deposited rocks of the Abrahamskraal Formation of the lower Beaufort Group in the South African Karoo record sediment deposition during the Middle Permian, the earliest terrestrial environment of Gondwana. A rich diversity of fossil tetrapods from this Formation provides a unique opportunity for understanding Middle Permian biodiversity changes in Gondwanan terrestrial ecosystems, but this is dependent on the existence of a robust stratigraphic framework that has been hampered by lack of lateral continuity of lithological markers combined with structural complexities relating to formation of the Cape Fold Belt. Because the Abrahamskraal Formation covers a large geographic area of the main Karoo Basin previous stratigraphic studies have been undertaken over large areas. This study combines geology and palaeontology to refine the stratigraphy of the Abrahamskraal Formation in a part of the southwestern Karoo Basin and revealed mappable lithological units with lateral continuity throughout the study area. The measured stratigraphic section manifests a total thickness of 2565 m for the Formation (the thickest occurrence of the Abrahamskraal Formation in the Beaufort Group). For the first time stratigraphic ranges of biostratigraphically important Middle Permian index taxa which have restricted stratigraphic ranges have been determined and, apart from dicynodonts, include the parareptile Eunotosaurus and the biarmosuchid therapsid Hipposaurus. The Abrahamskraal Formation comprises a 1104 m thick basal Eodicynodon Assemblage Zone, overlain by a 1441 m thick Tapinocephalus Assemblage Zone whose upper limit is 20 m below the Poortjie Member of the Teekloof Formation.

  2. Stratigraphy and reservoir potential of glacial deposits of the Itarare Group (Carboniferous-Permian), Parana basin, Brazil

    SciTech Connect

    Franca, A.B. ); Potter, P.E. )

    1991-01-01

    Drilling in the Parana basin of Brazil in the mid-1980s discovered gas and condensate in the Itarare Group, and showed that glacial deposits in Brazil can contain hydrocarbons. The reservoir potential of the Carboniferous-Permian Itarare Group of the basin is analyzed using new subsurface data from 20 deep wells drilled in the early to middle 1980s. Central to the analysis was the construction of over 3000 km of cross sections based on more than 100 wells, the description of more than 400 m of core, and study of 95 thin sections. Subsurface exploration and mapping of the Itarare are greatly aided by the recognition of three recently defined and described formations and four members, which are traceable for hundreds of kilometers. These units belong to three major glacial cycles in which the pebbly mudstones and shales are seals and glacially related sandstones are reservoirs. The best sandstone reservoirs in the deep subsurface belong to the Rio Segredo Member, the upper-most sandy unit of the Itarare. The Rio Segredo Member is the best petroleum target because it is overlain by thick seals and massive pebbly mudstones and shales, and because it is shallower and less compacted than underlying, more deeply buried sandstones. This member has little detrital matrix and much of its porosity is secondary, developed by carboxylic acid and CO{sub 2} generated when Jurassic-Cretaceous basalts, sills, and dikes were intruded into the Parana basin as Gondwana broke up.

  3. South American sedimentary basins

    SciTech Connect

    Urien, C.M.

    1984-04-01

    More than 64 sedimentary basins have been identified on the South American continent. According to their regional structural character and tectonic setting, they are classified in 4 super groups. About 20 interior or intracratonic basins occur on South American cratons (Guayanas, Brazilian, and Patagonian). In most cases, their sedimentary fill is Paleozoic or early Mesozoic. Rift or transverse grabens resulting from incipient sea floor spreading extend towards the continental margin. Seventeen basins are located along the Atlantic stable margin, and consist primarily of half grabens with downfaulted seaward blocks. These rifts (or pull-apart basins) were separated as results of the migration of the African and American continental blocks. Therefore the sedimentation is chiefly Cretaceous and Tertiary. On the western edge of South American cratons, almost 20 basins of downwarped blocks extend from Orinoco down to the Malvinas plateau in a relatively uninterrupted chain of retroarc basins, bordered by the Andean orogen. They lie on a flexured Precambrian and Paleozoic basement, and are highly deformed in the west (Subandean belt) due to the action of compressional forces caused by the tectonic influence of the Mesozoic Andean batholith. Westward, the Pacific margin is bordered by 27 foreland and forearc basins, which alternate from north to south on an unstable or quasistable margin, fringed by a trench and slope complex where the ocean crust is subducted beneath the continental plate.

  4. Tertiary Basins of Spain

    NASA Astrophysics Data System (ADS)

    Friend, Peter F.; Dabrio, Cristino J.

    1996-01-01

    During the Tertiary, Spain suffered compressional collision between France and Africa, and its Atlantic and Mediterranean coasts have been further modified by extensional rifting. Because it includes sectors of two separate foreland basins, and an intervening craton with basins that have been influenced by extensional and strikeSHslip deformation, Spain provides excellent material for the development and testing of theories on the study of sedimentary basin formation and filling. This book is one of the few studies available in English of the important Tertiary geology of Spain.

  5. Stratigraphic framework and evolution of the Cretaceous continental sequences of the Bauru, Sanfranciscana, and Parecis basins, Brazil

    NASA Astrophysics Data System (ADS)

    Batezelli, Alessandro; Ladeira, Francisco Sergio Bernardes

    2016-01-01

    With the breakup of the supercontinent Gondwana, the South American Plate has undergone an intense process of tectonic restructuring that led to the genesis of the interior basins that encompassed continental sedimentary sequences. The Brazilian Bauru, Sanfranciscana and Parecis basins during Late Cretaceous have had their evolution linked to this process of structuring and therefore have very similar sedimentary characteristics. The purpose of this study is to establish a detailed understanding of alluvial sedimentary processes and architecture within a stratigraphic sequence framework using the concept of the stratigraphic base level or the ratio between the accommodation space and sediment supply. The integration of the stratigraphic and facies data contributed to defining the stratigraphic architecture of the Bauru, Sanfranciscana and Parecis Basins, supporting a model for continental sequences that depicts qualitative changes in the sedimentation rate (S) and accommodation space (A) that occurred during the Cretaceous. This study discusses the origin of the unconformity surfaces (K-0, K-1 and K-1A) that separate Sequences 1, 2A and 2B and the sedimentary characteristics of the Bauru, Sanfranciscana and Parecis Basins from the Aptian to the Maastrichtian, comparing the results with other Cretaceous Brazilian basins. The lower Cretaceous Sequence 1 (Caiuá and Areado groups) is interpreted as a low-accommodation systems tract compound by fluvial and aeolian systems. The upper Cretaceous lacustrine, braided river-dominated alluvial fan and aeolian systems display characteristics of the evolution from high-to low-accommodation systems tracts (Sequences 2A and 2B). Unconformity K-0 is related to the origin of the Bauru Basin itself in the Early Cretaceous. In Sanfranciscana and Parecis basins, the unconformity K-0 marks the contact between aeolian deposits from Lower Cretaceous and Upper Cretaceous alluvial systems (Sequences 1 and 2). Unconformity K-1, which was generated in the Late Cretaceous, is related to an increase of the A/S ratio, whereas Unconformity K-1A is the result of the decrease in the A/S ratio. Unconformity K-1A bound Sequence 2A (lacustrine and fluvial systems) and Sequence 2B (alluvial deposits) in Bauru Basin whereas in the Sanfranciscana and Parecis basins this unconformity marks the transition from alluvial system to aeolian system (Sequences 2A and 2B). Changes in depositional style in both basins correspond to two distinct tectonic moments occurring within the South American plate. The first associated with post-volcanic thermal subsidence of the Early Cretaceous (Serra Geral and Tapirapuã volcanismos), and the second moment associated with the uplift occurred in the Late Cretaceous (Alto Paranaíba, Vilhena and Serra Formosa Arcs).

  6. Early evolution of the southern margin of the Neuquén Basin, Argentina: Tectono-stratigraphic implications for rift evolution and exploration of hydrocarbon plays

    NASA Astrophysics Data System (ADS)

    D'Elia, Leandro; Bilmes, Andrés; Franzese, Juan R.; Veiga, Gonzalo D.; Hernández, Mariano; Muravchik, Martín

    2015-12-01

    Long-lived rift basins are characterized by a complex structural and tectonic evolution. They present significant lateral and vertical stratigraphic variations that determine diverse basin-patterns at different timing, scale and location. These issues cause difficulties to establish facies models, correlations and stratal stacking patterns of the fault-related stratigraphy, specially when exploration of hydrocarbon plays proceeds on the subsurface of a basin. The present case study corresponds to the rift-successions of the Neuquén Basin. This basin formed in response to continental extension that took place at the western margin of Gondwana during the Late Triassic-Early Jurassic. A tectono-stratigraphic analysis of the initial successions of the southern part of the Neuquén Basin was carried out. Three syn-rift sequences were determined. These syn-rift sequences were located in different extensional depocentres during the rifting phases. The specific periods of rifting show distinctly different structural and stratigraphic styles: from non-volcanic to volcanic successions and/or from continental to marine sedimentation. The results were compared with surface and subsurface interpretations performed for other depocentres of the basin, devising an integrated rifting scheme for the whole basin. The more accepted tectono-stratigraphic scheme that assumes the deposits of the first marine transgression (Cuyo Cycle) as indicative of the onset of a post-rift phase is reconsidered. In the southern part of the basin, the marine deposits (lower Cuyo Cycle) were integrated into the syn-rift phase, implying the existence of different tectonic signatures for Cuyo Cycle along the basin. The rift climax becomes younger from north to south along the basin. The post-rift initiation followed the diachronic ending of the main syn-rift phase throughout the Neuquén Basin. Thus, initiation of the post-rift stage started in the north and proceeded towards the south, constituting a diachronous post-rift event. This arrangement implies that the lower part of Cuyo Cycle, traditionally related to regional thermal subsidence, may be deposited during either mechanical subsidence or thermal subsidence according to its position within the basin.

  7. The tectonostratigraphic evolution of the offshore Gippsland Basin, Victoria, Australia---results from 3D seismic interpretation and 2D section restoration

    NASA Astrophysics Data System (ADS)

    Weller, Mitchell

    The Gippsland Basin is located primarily offshore Victoria, Australia (between the Australian mainland and Tasmania) approximately 200 km east of Melbourne. The formation of the east-west trending Gippsland Basin is associated with the break-up of Gondwana during the late Jurassic/early Cretaceous and the basin has endured multiple rifting and inversion events. Strong tectonic control on the sedimentary development of the basin is reflected in the deposition of several major, basin scale sequences ranging in age from the early Cretaceous to Neogene, which are usually bounded by angular unconformities. Schlumberger's Petrel software package has been used to structurally and stratigraphically interpret a basin-wide 3D seismic data set provided by the Australian Government (Geoscience Australia) and four 2D kinematic reconstruction/restorations through the basin have been completed with Midland Valley's Move software to achieve a better understanding of the structural evolution of the Gippsland Basin. Rift phase extension calculated from the restorations (5.0--10.5%) appears anomalously low to accommodate the amount of sediment that has been deposited in the basin (>10km). Distributed extension on small faults and subsidence history from backstripping are employed to answer this anomaly. The 2D restorations completed illustrate structural time relationships across the basin and allow for a minimum estimate of erosion that has occurred along the inverted northern basin margin. Differences between previous work completed by Power et al. (2001) and this study as well as several extension models and associated implications are discussed as they relate to the interpretation carried out in this study. Extension calculated from section restorations ranged from approximately 5.0--10.5%. These measured extensional values appear too low to wholly accommodate the accumulated sediment thickness in the basin. Subsidence modelling and backstripping estimates approximately 50--90% extension. Several hundred meters of missing syn-rift sediments are estimated to have eroded as a result of partial inversion along the basin's northern margin. The structural interpretation in this study suggests that previous extensional models proposed by Wilcox et al. (1992) may be oversimplified.

  8. 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)

    Buckman, S.; Nutman, A.

    2013-12-01

    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.

  9. Petrology and mineral equilibrium modeling of incipient charnockite from the Ltzow-Holm Complex, East Antarctica: implications for granulite formation in a Gondwana fragment

    NASA Astrophysics Data System (ADS)

    Tsunogae, Toshiaki

    2015-04-01

    Charnockite (orthopyroxene-bearing granitoid) is regarded as one of the fundamental lithologies in many high-grade metamorphic terranes including Neoproterozoic collisional orogen formed during the amalgamation of Gondwana supercontinent. Although both magmatic (massive) and metamorphic charnockites have been reported, several classic examples for the spectacular development of 'incipient charnockites' within orthopyroxene-free felsic gneisses are exposed in several quarry sections in Neoproterozoic granulite terrenes in southern India (e.g., Trivandrum Block) and Sri Lanka. (e.g., Wanni Complex). The charnockite-forming process in these localities 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 detailed study of incipient charnockites in the Ltzow-Holm Complex of East Antarctica, which is regarded as an extension of Neoproterozoic to Cambrian orogeny in India and Sri Lanka, has been reported so far. This study thus reports new petrological data of incipient charnockite patches in orthopyroxene-free felsic gneiss from Skallevikshalsen in the granulite-facies region of the Ltzow-Holm Complex, East Antarctica, and discuss the timing and process of charnockite formation. Incipient charnockite (Opx + Qtz + Pl + Kfs + Grt) occurs as dark brownish patches of several cm in length within coarse-grained leucocratic gneiss (Qtz + Pl + Kfs + Grt) interlayered with various supracrustal lithologies such as mafic granulite, pelitic granulite, and marble. Orthopyroxene, which occurs only in garnet-bearing portion of the rock, probably formed by a FMAS continuous reaction: Grt + Qtz => Opx + Pl. Phase equilibrium modeling in the system NCKFMASH suggests a wide range of P-T stability (>780 C, >6 kbar), although the condition is broadly consistent with retrograde P-T conditions of the region. The texture and estimated P-T range suggest that the incipient charnockite formation in Skallevikshalsen is a post-peak event probably related to decompression after the peak event possibly without the effect of infiltration of low H2O activity fluids.

  10. The Palu Metamorphic Complex, NW Sulawesi, Indonesia: Origin and evolution of a young metamorphic terrane with links to Gondwana and Sundaland

    NASA Astrophysics Data System (ADS)

    van Leeuwen, Theo; Allen, Charlotte M.; Elburg, Marlina; Massonne, Hans-Joachim; Palin, J. Michael; Hennig, Juliane

    2016-01-01

    The Palu Metamorphic Complex (PMC) is exposed in a late Cenozoic orogenic belt in NW Sulawesi, Indonesia. It is a composite terrane comprising a gneiss unit of Gondwana origin, a schist unit composed of meta-sediments deposited along the SE Sundaland margin in the Late Cretaceous and Early Tertiary, and one or more slivers of amphibolite with oceanic crust characteristics. The gneiss unit forms part of the West Sulawesi block underlying the northern and central sections of the Western Sulawesi Province. The presence of Late Triassic granitoids and recycled Proterozoic zircons in this unit combined with its isotopic signature suggests that the West Sulawesi block has its origin in the New Guinea margin from which it rifted in the late Mesozoic. It docked with Sundaland sometime during the Late Cretaceous. U-Th-Pb dating results for monazite suggest that another continental fragment may have collided with the Sundaland margin in the earliest Miocene. High-pressure (HP) and ultrahigh-pressure (UHP) rocks (granulite, peridotite, eclogite) are found as tectonic slices within the PMC, mostly along the Palu-Koro Fault Zone, a major strike-slip fault that cuts the complex. Mineralogical and textural features suggest that some of these rocks resided at depths of 60-120 km during a part of their histories. Thermochronological data (U-Th-Pb zircon and 40Ar/39Ar) from the metamorphic rocks indicate a latest Miocene to mid-Pliocene metamorphic event, which was accompanied by widespread granitoid magmatism and took place in an extensional tectonic setting. It caused recrystallization of, and new overgrowths on, pre-existing zircon crystals, and produced andalusite-cordierite-sillimanite-staurolite assemblages in pelitic protoliths, indicating HT-LP (Buchan-type) metamorphism. The PMC was exhumed as a core complex at moderate rates (c. 0.7-1.0 mm/yr) accompanied by rapid cooling in the Plio-Pleistocene. Some of the UHP rocks were transported to the surface at significantly higher rates (⩾16 mm/yr). The results of our study do not support recent plate tectonic reconstructions that propose a NW Australia margin origin for the West Sulawesi block (e.g. Hall et al., 2009).

  11. Gondwana to Asia: Plate tectonics, paleogeography and the biological connectivity of the Indian sub-continent from the Middle Jurassic through latest Eocene (166 35 Ma)

    NASA Astrophysics Data System (ADS)

    Ali, Jason R.; Aitchison, Jonathan C.

    2008-06-01

    Using the most up-to-the-date information available, we present a considerably revised plate tectonic and paleogeographic model for the Indian Ocean bordering continents, from Gondwana's Middle Jurassic break-up through to India's collision with Asia in the middle Cenozoic. The landmass framework is then used to explore the sometimes complex and occasionally counter-intuitive patterns that have been observed in the fossil and extant biological records of India, Madagascar, Africa and eastern Eurasia, as well those of the more distal continents. Although the paleogeographic model confirms the traditional view that India became progressively more isolated from the major landmasses during the Cretaceous and Paleocene, it is likely that at various times minor physiographic features (principally ocean islands) provided causeways and/or stepping-stone trails along which land animals could have migrated to/from the sub-continent. Aside from a likely link (albeit broken by several marine gaps) to Africa for much of this time (it is notable, that the present-day/recent biota of Madagascar indicates that the ancestors of five land-mammal orders, plus bats, crossed the > 400-km-wide Mozambique Channel at different times in the Cenozoic), it is possible that the Kerguelen Plateau connected India and Australia-Antarctica in the mid-Cretaceous (approximately 115-90 Ma). Later, the Seychelles-Mascarene Plateau and nearby elevated sea-floor areas could have allowed faunas to pass between southern India and Madagascar in the Late Cretaceous, from around 85-65 Ma, with an early Cenozoic extension to this path forming as a result of the Reunion hot-spot trace islands growing on the ocean floor to the SSW of India. The modelling also suggests that India's northward passage towards Asia, with eventual collision at 35 Ma, involved the NE corner of the sub-continent making a glancing contact with Sumatra, followed by Burma from ~ 57 Ma (late Paleocene) onwards, a scenario which is compatible with the fossil record indicating that India-Asia faunal exchanges began occurring at about this time. Finally, we contend that a number of biologically-based direct terrestrial migration routes that have been proposed for last 15 m.y. of the Cretaceous (Asia to India; Antarctica to Madagascar and/or India) can probably be dismissed because the marine barriers, likely varying from > 1000 up to 2500 km, were simply too wide.

  12. Late Permian Palynology and depositional environment of Chintalapudi sub basin, Pranhita-Godavari basin, Andhra Pradesh, India

    NASA Astrophysics Data System (ADS)

    Jha, Neerja; Pauline Sabina, K.; Aggarwal, Neha; Mahesh, S.

    2014-01-01

    The present study deals with the palynological dating, correlation and depositional setting of the sediments from bore cores MGP-11 and MGP-4 from Gauridevipet area of Chintalapudi sub-basin of Godavari master basin, south India. On the basis of palynological studies, three palynoassemblages have been identified, one in bore core MGP-11 a Faunipollenites (=Protohaploxypinus) and Striasulcites assemblage and two in bore core MGP-4; one is characterized by the dominance of striate bisaccates and Densipollenites and the other by Striatopodocarpites and Cresentipollenites palynoassemblages. The other stratigraphically significant taxa include Guttulapollenites hannonicus, Lunatisporites noviaulensis, Lunatisporites pellucidus, Densoisporites contactus, Chordasporites australiensis, Goubinispora spp., Lundbladispora microconata, Lundbladispora raniganjensis and Klausipollenites schaubergeri. The recovered taxa suggest a Late Permian, Lopingian age for these rocks. This interpretation is based on the correlation of the assemblages with similar assemblages from previous Gondwana studies chiefly Densipollenites magnicorpus Zone of Damodar Basin, India and Late Permian palynoassemblages from Africa, Antarctica, Australia and South America. On the basis of palaeobotanical affinity of the identified microflora it has been inferred that the peat forming plant community was composed mainly of gymnosperm pollen attributable to glossopterids, that includes striate and non-striate bisaccates and paucity of cordaites which includes monosaccates. Spores are subordinate and are derived from lycopsids (Lundbladispora, Densoisporites), sphenopsids (Latosporites) and filicopsids (Horriditriletes, Lophotriletes, Verrucosisporites, Osmundacidites, Leiotriletes, Callumispora, Brevitriletes and Microbaculispora) occurring in variable proportions. The dominance of subarborescent/arborescent vegetation suggests a development in a forest swamp probably in a small distant marginal part of the mire or periods of standing water. This flooding environment favoured the growth of herbaceous lycopsids, filicopsids and sphenopsids in the palaeomire. More or less similar environments of deposition have been deduced for both the sedimentary sequences on the basis of palynofacies analysis. Anaerobic, reducing, water logged peat-forming conditions have been inferred based on the abundance of phytoclasts. The relative abundance of structured organic matter implies the existence of a fairly dense vegetation cover in the hinterland. The charcoal fragments recovered from the present study area reflects a possible wildfire in the accumulated swamps or a wildfire in the hinterland after which the sediments were flushed by fluvial systems into the swamps.

  13. K Basins Hazard Analysis

    SciTech Connect

    WEBB, R.H.

    1999-12-29

    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.

  14. K Basin Hazard Analysis

    SciTech Connect

    PECH, S.H.

    2000-08-23

    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.

  15. Phanerozoic tectono-stratigraphic evolution of the Trans-Pecos and Permian basin regions (Mexico, Texas, New Mexico) using Landsat imagery, subsurface and outcrop data

    SciTech Connect

    Markello, J.R.; Sarg, J.F.

    1996-08-01

    Integrating regional Landsat imagery, outcrop field studies, and subsurface data has resulted in a more comprehensive understanding and delineation of the tectono-stratigraphic evolution of the Trans-Pecos region. Landsat imagery were acquired and registered to the existing 1:25000 scale maps and mosaiced to create a regional view of the Trans-Pecos and Permian basin region. The imagery were used to extrapolate and map key stratigraphic and tectonic elements after calibration from documented outcrop and subsurface data. The interpretations aided in the extrapolation of scattered control information and were critical in the complete reconstruction of the geologic history of the area. The Trans-Pecos Phanerozoic history comprises five tectono-depositional phases, and these have controlled the shape of the modem landscape: (1) Late Proterozoic rifting (Gondwana from Laurentia), and development of the Early-Middle Paleozoic Tobosa basin; (2) Pennsylvanian collision (South and North Americas), and differentiation of the Tobosa basin into the Midland, Delaware, Orogrande, and Pedregosa basins separated by basement blocks: Central Basin Platform, Diablo Platform, Burro-Florida Platform; (3) Middle Mesozoic transtensional rifting (Mexico from North America), and Late Jurassic failed rifting of the Mexican Chihuahua and Coahuila Troughs west and south of the Diablo Platform; (4) Late Mesozoic Laramide collision (Mexico and Texas), and development of the Chihuahua fold/thrust belt limited by the western margin of the Diablo Platform; (5) Late Cenozoic North American basin and Range rifting, and development of Rio Grande grabens, block-faulted mountains, and volcanics. The Tobosa basin was a passive-margin interior sag; its continental margin was south of the Marathons.

  16. Permian basin gas production

    SciTech Connect

    Haeberle, F.R.

    1995-06-01

    Of the 242 major gas fields in the Permian basin, 67 are on the Central Basin Platform, 59 are in the Delaware basin, 44 are in the Midland basin, 28 are in the Val Verde basin, 24 are on the Eastern Shelf, 12 are in the Horshoe Atoll and eight are on the Northwest Shelf. Eleven fields have produced over one trillion cubic feet of gas, 61 have produced between 100 billion and one trillion cubic feet of gas and 170 have produced less than 100 billion cubic feet. Highlights of the study show 11% of the gas comes from reservoirs with temperatures over 300 degrees F. and 11% comes from depths between 19,000 and 20,000 feet. Twenty percent of the gas comes from reservoirs with pressures between 1000 and 2000 psi, 22% comes from reservoirs with 20-24% water saturation and 24% comes from reservoirs between 125 and 150 feet thick. Fifty-three reservoirs in the Ellenburger formation have produced 30% of the gas, 33% comes from 88 reservoirs in the Delaware basin and 33% comes from reservoirs with porosities of less than five percent. Forty percent is solution gas and 46% comes from combination traps. Over 50% of the production comes from reservoirs with five millidarcys or less permeability, and 60% of the gas comes from reservoirs in which dolomite is the dominant lithology. Over 50% of the gas production comes from fields discovered before 1957 although 50% of the producing fields were not discovered until 1958.

  17. Mechanics of forearc basins

    NASA Astrophysics Data System (ADS)

    Cassola, Teodoro; Willett, Sean D.; Kopp, Heidrun

    2010-05-01

    In this study, the mechanics of forearc basins will be the object of a numerical investigation to understand the relationships between wedge deformation and forearc basin formation. The aim of this work is to gain an insight into the dynamics of the formation of the forearc basin, in particular the mechanism of formation of accommodation space and the preservation of basin stratigraphy. Our tool is a two-dimensional numerical model that includes the rheological properties of the rock, including effective internal friction angle, effective basal friction angle and thermally-dependent viscosity. We also simulate different sedimentation rates in the basin, to study the influence of underfilled and overfilled basin conditions on wedge deformation. The stratigraphy of the basin will also be studied, because in underfilled conditions the sediments are more likely to undergo tectonic deformation due to inner wedge deformation. We compare the numerical model with basins along the Sunda-Java Trench. This margin shows a variety of structural-settings and basin types including underfilled and overfilled basins and different wedge geometries. We interpret and document these structural styles, using depth migrated seismic sections of the Sunda Trench, obtained in three surveys, GINCO (11/98 - 01/99), MERAMEX (16/09/04 - 7/10/04) and SINDBAD (9/10/06 - 9/11/06) and made available through the IFM-GEOMAR and the Bundesanstalt fr Geowissenschaften and Rohstoffe (BGR). One important aspect of these margins that we observe is the presence of a dynamic backstop, characterized by older accreted material, that, although deformed during and after accretion, later becomes a stable part of the upper plate. We argue that, following critical wedge theory, it entered into the stable field of a wedge either by steepening or weakening of the underlying detachment. As a stable wedge, this older segment of the wedge acts as a mechanical backstop for the frontal deforming wedge. This dynamic backstop moves seaward in time, in response to isostatic loading by the growing wedge, or due to seaward retreat of the slab with a consequent steepening of the base of the wedge.

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

    NASA Astrophysics Data System (ADS)

    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

    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.

  19. 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

    Balgir, R S

    2010-09-01

    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?

  20. Nam Con Son Basin

    SciTech Connect

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

    1994-07-01

    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.

  1. 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...

  2. Anadarko Basin conodont studies

    USGS Publications Warehouse

    Repetski, John E.

    1989-01-01

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

  3. River basin management

    SciTech Connect

    Newsome, D.H.; Edwards, A.M.C.

    1984-01-01

    The quality of water is of paramount importance in the management of water resources - including marine waters. A quantitative knowledge of water quality and the factors governing it is required to formulate and implement strategies requiring an inter-disciplinary approach. The overall purpose of this conference was to bring together the latest work on water quality aspects of river basin management. These proceedings are structured on the basis of five themes: problems in international river basins; the contribution of river systems to estuarial and marine pollution; the setting of standards; monitoring; and practical water quality management including use of mathematical models. They are followed by papers from the workshop on advances in the application of mathematical modelling to water quality management, which represent some of the current thinking on the problems and concepts of river basin management.

  4. Central basin pipeline completed

    SciTech Connect

    Watts, J.

    1986-01-01

    A colorless, odorless gas - carbon dioxide - is providing a way for oil producers to wring additional millions of barrels of crude oil out of formations that have held them tightly for millions and millions of years. A recently completed pipeline, Northern Natural Resource Co.'s central basin pipeline, will keep oil fields in the Permian Basin of west Texas and New Mexico productive many years after their expected economic life would have been over. The central basin line is one of the first of the second generation CO/sub 2/ lines, delivering the gas to enhanced oil recovery efforts throughout the southern Permian Basin from the main CO/sub 2/ transmission lines bringing the gas from natural deposits in the northern New Mexico and southern Colorado area. The line stretches from Denver City to McCamey. Carbon dioxide flooding is one of the fastest growing methods of enhanced oil recovery in the U.S. Huge, almost pure deposits of the gas has been found, totaling more than 15 tcf. The oil fields in the Permian Basin of west Texas and New Mexico are prime candidates for CO/sub 2/ flooding for a variety of technical reasons, including the gravity of the oil and the depth of the wells. A study by the National Petroleum Council says miscible CO/sub 2/ flooding in the Permian Basin could produce an additional 3.1 billion bbl. The NPC study says total U.S. miscible EOR production could reach 500,000 b/d by 2004 (assuming $30/bbl) and will exceed thermal EOR production at some time beyond 2005.

  5. Integrated Salt Basin Evaluation

    NASA Astrophysics Data System (ADS)

    Kukla, P. A.

    2012-04-01

    Salt tectonics plays a major role in the development of many sedimentary basins. Basins containing salt thus frequently display a complex geodynamic evolution characterized by several phases of halokinesis and associated sedimentation. One classic area of salt tectonics is the Central European Basin System (CEBS). Here, the mobile Permian Zechstein salt formed a large number of salt structures such as anticlines, diapirs, pillows, sheets, stocks, and walls during an extended period of salt tectonic activity in Mesozoic and Cenozoic times. Major changes in sedimentation patterns and structural regimes are associated and common in this setting. Increasingly complex subsurface evaluation therefore requires an approach to study salt basins including analogue and numerical models, field studies and laboratory studies which combine seismic, structural and sedimentary studies with analysis of rheological properties, and geomechanic modelling. This concept can be demonstrated using case studies from Permian Salt Basins in Europe and the Late Neoproterozoic to Early Cambrian South Oman Salt Basin. There salt-influenced sedimentary responses to renewed phases of tectonism can be clearly discerned from detailed sequence analysis based on seismic and log data combined with retrodeformation modelling studies. High quality 3-D seismic data integrated with structural modelling improves the definition of the internal dynamics of salt structures and associated sediment architecture in salt-controlled sequences. Paleo-caprocks inside the diapirs point to long phases of dissolution. Salt wedges formed by extrusion and lateral flow of salt glaciers during periods of diapir emergence and reduced sediment accumulation can be accurately modelled. Although salt is widely regarded as a perfect seal, it can become permeable for one- or two-phase fluids under certain conditions of fluid pressure, temperature and deviatoric stress. The fluid pathways can be either along zones of diffuse grain boundary dilatancy, or along open fractures, depending on the fluid overpressure and deviatoric stress.

  6. What role does crustal heterogeneity play on continental break-up; the interplay of a foldbelt, rift system and ocean basin in the South Atlantic

    NASA Astrophysics Data System (ADS)

    Paton, Douglas; Mortimer, Estelle; Hodgson, Neil

    2015-04-01

    Although extensively studied, two key questions remain unanswered regarding the evolution of the southern South Atlantic. Firstly, where is the Cape Foldbelt (CFB) in offshore South Africa? The CFB is part of the broader Gonwanian Orogeny that prior to South Atlantic rifting continued into the Ventana Foldbelt of Argentina but to date its location in the offshore part of South Africa remains enigmatic. Secondly, the conjugate rift basin to South Africa is the Colorado Basin in Argentina but why does it trend east-west despite its perpendicular orientation to the Atlantic spreading ridge? Current plate models and structural understands cannot explain these fundamental questions. We use newly acquired deep reflection seismic data in the Orange Basin, South Africa, to develop a new structural model for the southern South Atlantic. We characterise the geometry of the Cape Foldbelt onshore and for the first time correlate it into the offshore. We show that it has a north-south trend immediately to the north of the Cape Peninsula but then has a syntaxis (Garies syntaxis) that results in a change to an east-west orientation. This forms the missing jigsaw piece of the Atlantic reconstruction as this is directly beside the restored Colorado Basin. When considered within the pre-break up structural configuration our observations imply that prior to the main phase of Atlantic rifting in the Mezosoic there was significant variation in crustal geometry incorporating the Orange Basin of South Africa, the Colorado Basin and the Gariep Belt of Namibia. These faults were active during Gondwana rifting, but the Colorado rift failed resulting in the present day location of the South Atlantic. Not only do our results improve our understanding of the evolution of the South Atlantic ocean, they highlight the importance of differentiating between early rift evolution and strain localisation during the subsequent rift phase prior to seafloor spreading.

  7. UNCOMPAHGRE RIVER BASIN SELENIUM PHYTOREMEDIATION

    EPA Science Inventory

    The Uncompahgre River Basin Selenium Phytoremediation Project will evaluate the ability of selected agricultural crops and trees to accumulate and volatilize selenium from contaminated soils in the basin. Three different species of plants (two types will be campanion planted) an...

  8. Geochemical and isotopic composition of Pan-African metabasalts from southwestern Gondwana: Evidence of Cretaceous South Atlantic opening along a Neoproterozoic back-arc

    NASA Astrophysics Data System (ADS)

    Will, Thomas M.; Frimmel, Hartwig E.; Gaucher, Claudio; Bossi, Jorge

    2014-08-01

    A lithogeochemical and Sr-Nd-Pb isotope study of former oceanic crustal rocks from the Cuchilla Dionisio Terrane in the southern Dom Feliciano Belt, Uruguay (La Tuna amphibolites) and metabasites in the Chameis Subterrane of the Marmora Terrane in the Gariep Belt, Namibia/South Africa shows that these rocks are compositionally very similar and probably represent the same unit on opposite sides of the modern South Atlantic. The mafic rocks from both terranes are tholeiitic metabasalts and -andesites and have depleted rare earth element patterns, generally low TiO2 (< 1.5 wt.%), very low Th/Nb ratios and lack negative Nb-Ta anomalies, all features that are typical of normal' mid-ocean ridge basalts (N-MORB) and/or back-arc basin basalts (BABB). In addition, both rock suites have extremely depleted Nd isotope compositions (?Nd630 Ma = 6.7-9.4), superchondritic 147Sm/144Nd ratios, and low 206Pb/204Pb and 207Pb/204Pb initial ratios. The 87Sr/86Sr initial ratios of the La Tuna mafic rocks are low, whereas the Chameis metagabbro samples have higher, possibly alteration-related ratios. The geochemical and isotopic signatures are consistent with the formation of both rock suites in the same mature Neoproterozoic back-arc basin (Marmora Basin), supporting conclusions drawn from earlier provenance studies of metasedimentary units from these terranes. Other mafic rocks from the Marmora Terrane are interpreted as ocean island basalts that formed in a within-plate setting. A corollary of the conclusion that the mafic rocks in the Cuchilla Dionisio and Marmora Terranes formed in the same back-arc basin is (1) that the main Pan-African suture between the Ro de la Plata Craton and the Kalahari Craton lies to the west of the Dom Feliciano Belt in South America, and (2) that the opening of the modern South Atlantic did not occur along that suture but along the axis of the Neoproterozoic Marmora back-arc basin.

  9. Crinoids columnals (Echinodermata) of the Erer Formation (late Eifelian-early Givetian, Amazon Basin), State of Par, Brazil

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    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 Erer 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.

  10. Age and position of the sedimentary basin of the Ocoee Supergroup western Blue Ridge tectonic province, southern Appalachians

    SciTech Connect

    Unrug, R.; Unrug, S. . Dept. of Geological Sciences); Ausich, W.I. . Dept. of Geological Sciences); Cuffey, R.J. . Dept. of Geosciences); Mamet, B.L. . Dept. de Geologie); Palmes, S.L. . Dept. of Geology)

    1994-03-01

    The stratigraphic continuity of the Ocoee Supergroup established recently allows one to extrapolate the Paleozoic age of the Walden Creek Group determined on paleontological evidence to the entire Ocoee succession. The Walden Creek Group rocks contain a fossil assemblage of fenestrate bryozoan, algal, trilobite, ostracod, brachiopod and echinozoan fragments and agglutinated foraminifer tests that indicate Silurian or younger Paleozoic age. The fossils occur in carbonate clasts in polymict conglomerates, and debris-flow breccia beds, and in olistoliths of bedded carbonate and shale, and calcarenite turbidite beds. These carbonate lithologies form a minor, but characteristic constituent of the Walden Creek Group. Fossil have been found also in shale and mudstone siliciclastic lithologies of the Walden Creek Group. The fossils are fragmented and poorly preserved because of several cycles of cementation and solution in the carbonate rocks and a pervasive cleavage in the fine-grained siliciclastic rocks. Recently reported Mississippian plant fossils from the Talladega belt indicate widespread occurrence of Middle Paleozoic basins in the Western Blue Ridge. These pull-apart basins formed in the stress field generated by northward movement of Laurentia past the western margin of Gondwana after the Taconian-Famatinian collision in the Ordovician.

  11. Identifying glacial influences on sedimentation in tectonically-active, mass flow dominated arc basins with reference to the Neoproterozoic Gaskiers glaciation (c. 580 Ma) of the Avalonian-Cadomian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Carto, Shannon L.; Eyles, Nick

    2012-06-01

    Neoproterozoic 'Avalonian-Cadomian' volcanic arc basins once lay peripheral to Gondwana and are now found around the North Atlantic Ocean in New England, Atlantic Canada and northwestern Europe as 'peri-Gondwanan terranes.' Their thick (up to 9 km) marine fills are dominated by turbidites, debrites (diamictites and variably graded conglomerates), slumps and olistostromes recording the dominance of mass flow processes in arc basins oversupplied with volcaniclastic sediment. Several diamictite horizons in these basins were identified as glacial tillites more than one hundred years ago on the basis of poor textural sorting, and the lack of any understanding of mass flow processes. An association with thin-bedded turbidite facies, then interpreted as glaciolacustrine varvites, was seen as evidence for widespread glacial conditions which is still the basis today of a near global 'Gaskiers glaciation' at c. 580 Ma, despite classic sedimentological work which shows that the 'tillites' and 'varvites' of these basins are deep marine sediment gravity flow deposits. Only in two basins (Gaskiers Formation, Avalon Peninsula in Newfoundland, and the Konnarock Formation of Virginia) is a distal and regionally-restricted glacial influence on marine sedimentation identified from ice-rafted, striated dropstones in turbidites but terrestrial 'ice-contact' facies are absent. As revealed in this study, terrestrial glacial facies may not have survived frequent volcanic activity such as seen today on glaciated active plate margin volcanoes such as Mount Rainier in Washington USA, and Cotopaxi Volcano in Ecuador where primary glacial sediment is frequently reworked by lahars, pyroclastic flows, debris avalanches and outburst floods. The weight of evidence presented in this study indicates that ice covers during the Gaskiers glaciation were not widespread across the Avalonian-Cadomian back arc basins; the deep marine Grenada Basin (Caribbean Sea) filled with turbidites, debrites (lahars) and debris avalanches from the adjacent Lesser Antilles Arc is identified here as a modern analogue for these ancient basins.

  12. Sedimentology of the Neoproterozoic (c. 580 Ma) Squantum 'Tillite', Boston Basin, USA: Mass flow deposition in a deep-water arc basin lacking direct glacial influence

    NASA Astrophysics Data System (ADS)

    Carto, Shannon L.; Eyles, Nick

    2012-08-01

    The Squantum 'Tillite' (c. 593-570 Ma) consists of thick (up to 215 m) massive and crudely-stratified diamictites conformably interbedded with subaqueously-deposited conglomerates and sandstones within a thick (~ 7 km) Boston Basin fill which is dominated by argillite turbidites. The Squantum Tillite was first interpreted as being glacigenic in origin in 1914 because of the presence of diamictites; argillites were interpreted as glaciolacustrine 'varves' with rare ice-rafted debris, and conglomerates as glaciofluvial outwash. More recently these have been shown to be the product of deep marine mass flow processes with no glacial influence, yet because of its age equivalence with the deep marine, glacially-influenced Gaskiers Formation, the Squantum Tillite is still seen by some as supporting evidence for a widespread 'Snowball Earth' event at c. 580 Ma. New sedimentological work confirms that conglomerate and sandstone facies are deep marine sediment gravity flows genetically related to massive (homogeneous) and crudely-stratified (heterogeneous) diamictites produced subaqueously by downslope mixing of gravel and cobbles with muddy facies. Rare horizons of 'ice rafted debris' in thin-bedded and laminated turbidite facies interbedded with thick debrites show a weak but positive correlation of lamina thickness with grain size, suggesting these facies are non-glacial co-genetic 'debrite-turbidite' couplets. A significant volcanic influence on sedimentation is identified from reworked lapilli tuff beds and reworked ash in turbidites. The depositional setting of the Squantum 'Tillite' appears to be that of a submarine slope/fan setting in an open marine volcanic arc basin receiving large volumes of poorly-sorted sediment on the mid-latitude active margin of Gondwana. No direct glacial influence is apparent.

  13. Contrasting Permo - Carboniferous Evolution of Resita and Sirinia - Presacina Basins (South Carpathians, Romania); an overview.

    NASA Astrophysics Data System (ADS)

    Tatu, M.; Seghedi, I.; Nutu, L. M.; Nicolae, I.

    2009-04-01

    Two important Permo-Carboniferous molasses basins Resita and Sirinia - Presacina occur in Romanian Banat (south-western part of Carpathian chain), unconformable overlie the Getic and Danubian domains with different pre-Variscan and Variscan geodynamic history. They show differences in their lithology reflecting various geotectonic settings and evolutions. In the Resita domain the Upper Carboniferous deposits (Westphalian - Stephanian in age, according to the previous paleobotanic and palynological data) are important in volume and they contain terrigeneous siliciclastic rocks represented by sandy - conglomerate and argillaceous - sandy rocks variable in thickness with siltstone, carbonaceous shale and coal beds interlayering. There are not volcanic rocks present in Upper Carboniferous of Resita domain. In contrast with Resita in the Sirinia - Presacina basins the Upper Carboniferous deposits are volumetrically more restrictive. These deposits transgresively overlie pre-Sudetian formations and consist of continental - lacustrine terrigeneous formations, rarely associated with limnic carbonatic rocks. In this association the alternating conglomerate, siliceous sandstone, siltstone and clay with lens - like coal inter-layers prevails. In two small areas Dragosela - Tulinecea - Camenita (in the western part) and Baia Noua - Cucuiova (in the eastern part) the terrigeneous deposits are associated with basaltic andesite and andesite rocks with alkaline affinity. In both of these basins the Lower Permian deposits (according to the paleobotanic data) unconformably overlie the Upper Carboniferous formations and/or pre-Sudetian basements. The Lower Permian deposits in the Resita basin occur in two superposed formations (Nastaseanu, 1987): (1) Walchia Beds dominated by black argillaceous shales, slightly bituminous with rare sandy-conglomerate interlayers and (2) Red Beds composed by sandy-conglomerate deposits with some argillaceous intercalations, all red in color, with rarely lens-like fresh water limestone. During the Permian in the Resita basin the volcanic activity was absent. In the Sirinia - Presacina basin the Lower Permian deposits are characterized by huge volcanic and volcano - sedimentary assemblages inter-fingering with red beds detritic formations. The Permian volcanism in the Sirinia - Presacina basin is dominant rhyolitic and started in subaqueous conditions. Early subaqueous domes (as isolated or as clusters) and lava flows led to the generation at their margins of huge volume of hyaloclastic breccias that turn unstable forming marginally turbiditic hyaloclastite aprons. In the Sirinia zone, where the magmas get to the shallower waters and/or to subaerial, the volcanic activity turned progressively to be explosive, generating phreatomagmatic eruptions. The result of this activity is up to several hundred meters of various deposits represented by pyroclastic flow (dominantly non-welded and welded ignimbrites), pyroclastic surge and fall out, all rich in accretionary lapilli. At the distal, marginal part of the volcanic environs the epiclastic, mostly lahar deposits are dominating, sometimes including layers of fallout deposits with accretionary lapilli that suggest their contemporaneous deposition. In the eastern part of Sirinia - Presacina basin (Cucuiova Hill) the presence of basalts as sills in the Permian sandstone deposits may be a sign of bimodal magmatic activity. As in the some of the Central Europe Permian basins the volcanic activity from Sirinia - Presacina basin is related to intra-basinal active faults and in particular with the intersection of fault systems having a pull-apart features (e.g. Stollhofen et al., 1999). The most important factor which was controlled the Permo - Carboniferous complex evolution of the Western and Central Europe was tectonic. The continue convergence between Laurasia and Gondwana during the Upper Carboniferous - Lower Permian (Ziegler, 1990) was generated a conjugate dextral - sinistral shear fault system adjacent to the Tornquist - Teisseyre Line, which induced the fragment

  14. Late Mississippian (Chesterian) carbonate to carbonate-clastic cycles in the eastern Illinois Basin

    SciTech Connect

    Smith, L.B.; Read, J.F. )

    1994-03-01

    Late Mississippian (Chesterian) rocks of the eastern Illinois Basin in Kentucky and Indiana show depositional cycles (3--20 meters thick) composed of a range of facies deposited during the transition from carbonate-dominated deposition of the Middle Mississippian to the predominantly siliciclastic regime of the Pennsylvanian. Within the basal Ste. Genevieve Formation (30--70 meters thick) there are five predominantly carbonate cycles. Cycle bases vary from thin calcareous sandstone near the northern clastic source to ooid-quartz dolomitic pelletal grainstone and mudstone further south. Massive cross-bedded and channeled ooid-skeletal grainstones represent the cycle tops and are commonly capped by caliche and subaerial breccia, particularly where there was no subsequent siliciclastic deposition. The cycles are interpreted to be driven by fourth-order (400 k.y.) glacio-eustatic sea-level fluctuations based on coincidence of the calculated cycle period with the long-term eccentricity signal, the Late Mississippian onset of Gondwana glaciation and cycle correlation over more than 100 kilometers. The breccia and caliche formed during lowstands, the siliciclastics, eolianites and dolomitic pelletal grainstones are transgressive facies and the ooid-skeletal grainstones represent sea-level highstands.

  15. Bransfield Basin and Cordilleran Orogenesis

    NASA Astrophysics Data System (ADS)

    Dalziel, I. W.; Austin, J. A.; Barker, D. H.; Christensen, G. L.

    2003-12-01

    Tectonic uplift of the Andean Cordillera was initiated in the mid-Cretaceous with inversion of a composite marginal basin along 7500 km of the continental margin of South America, from Peru to Tierra del Fuego and the North Scotia Ridge. In the southernmost Andes, from 50-56 degrees S, the quasi-oceanic floor of this basin is preserved in the obducted ophiolitic rocks of the Rocas Verdes (Green Rocks) basin. We suggest that the basin beneath Bransfield Strait, 61-64 degrees S, separating the South Shetland Islands from the Antarctic Peninsula, constitutes a modern analog for the Rocas Verdes basin. Marine geophysical studies of Bransfield basin have been undertaken over the past 12 years by the Institute for Geophysics, University of Texas at Austin, under the auspices of the Ocean Sciences Division and United States Antarctic Program, National Science Foundation. These studies have elucidated the structure and evolution of Bransfield basin for comparison with the Rocas Verdes basin, with a view to eventual forward modeling of the evolution of a hypothetical cordilleran orogen by compression and inversion of the basin. These are the processes that can be observed in the tectonic transformation of the Rocas Verdes basin into the southernmost Andean cordillera, as South America moved rapidly westward in an Atlantic-Indian ocean hot-spot reference frame during the mid-Cretaceous. Multi-channel reflection seismic data from the Bransfield basin reveal an asymmetric structural architecture characterized by steeply-dipping normal faults flanking the South Shetlands island arc and gently dipping listric normal faults along the Antarctic Peninsula margin. Normal fault polarity reversals appear to be related to distributed loci of magmatic activity within the basin. This architecture is remarkably similar to that deduced from field structural studies of the Rocas Verdes basin. Notably, the oceanward-dipping, low angle normal faults along the Antarctic Peninsula margin constitute ideally oriented surfaces for reactivation as thrust faults, leading to obduction of the basin floor rocks during any ensuing compressional event. Seismic refraction studies of Bransfield basin using Institute for Geophysics ocean bottom seismographs indicate along-strike northeastward thinning of the crust associated with southwestward rift propagation, comparable to that indicated for the Rocas Verdes basin by the results of U-Pb zircon dating of the ophiolitic rocks. Cross-strike segmentation of Bransfield basin also mirrors the isolated ophiolitic complexes of the inverted Rocas Basin in South America and on South Georgia Island. The results of our geophysical studies of Bransfield basin reveal close similarities in structure and evolution with the Cretaceous Rocas Verdes basin, and therefore encourage the next step of forward modeling in an effort to help elucidate fundamental cordilleran orogenic processes.

  16. Cenozoic basin development in Hispaniola

    SciTech Connect

    Mann, P.; Burke, K.

    1984-04-01

    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.

  17. Frontier petroleum basins of Colombia

    SciTech Connect

    Keith, J.F. Jr.; Perez, V.E.

    1989-03-01

    The frontier basins of Colombia with hydrocarbon potential are numerous, have varying geological histories, and are in different stages of exploration development. In this paper, sedimentary or structural basins are classified as frontier petroleum basins if commercial discoveries of hydrocarbons are lacking, if the basin has not attained a high degree of exploration development, or if a new play concept has been perceived or developed for a portion of a mature exploration basin. Using these criteria for classification, the authors discuss the Cauca-Patia Choco-Pacifico, and Lower Magdalena basin complexes; the Cordillera Oriental foreland basin; and the Cesar-Rancheria, Sabana, and Amazonas basins. A comprehensive geological and structural setting of each of these frontier basins will be presented. The depositional and tectonic evolution of the basins will be highlighted, and the play concepts for each will be inventoried, catalogued, and categorized as to whether they are theoretical or established. The discussion of the available plays in each of these basins will include the main play concept elements of reservoirs traps, seals, source rocks, maturation, and timing. When detailed data permit, the reservoir and trap geometry will be presented.

  18. Buried-euxenic-basin model sets Tarim basin potential

    SciTech Connect

    Hsu, K.J. )

    1994-11-28

    The Tarim basin is the largest of the three large sedimentary basins of Northwest China. The North and Southwest depressions of Tarim are underlain by thick sediments and very thin crust. The maximum sediment thickness is more than 15 km. Of the several oil fields of Tarim, the three major fields were discovered during the last decade, on the north flank of the North depression and on the Central Tarim Uplift. The major targets of Tarim, according to the buried-euxenic-basin model, should be upper Paleozoic and lower Mesozoic reservoirs trapping oil and gas condensates from lower Paleozoic source beds. The paper describes the basin and gives a historical perspective of exploration activities and discoveries. It then explains how this basin can be interpreted by the buried-euxenic-basin model. The buried-euxenic-basin model postulates four stages of geologic evolution: (1) Sinian and early Paleozoic platform sedimentation on relic arcs and deep-marine sedimentation in back-arc basins in Xinjiang; (2) Late Paleozoic foreland-basin sedimentation in north Tarim; (3) Mesozoic and Paleogene continental deposition, subsidence under sedimentary load; and (4) Neogene pull-apart basin, wrench faulting and extension.

  19. Canada Basin revealed

    USGS Publications Warehouse

    Mosher, David C.; Shimeld, John; Hutchinson, Deborah R.; Chian, D; Lebedeva-Ivanova, Nina; Jackson, Ruth

    2012-01-01

    More than 15,000 line-km of new regional seismic reflection and refraction data in the western Arctic Ocean provide insights into the tectonic and sedimentologic history of Canada Basin, permitting development of new geologic understanding in one of Earth's last frontiers. These new data support a rotational opening model for southern Canada Basin. There is a central basement ridge possibly representing an extinct spreading center with oceanic crustal velocities and blocky basement morphology characteristic of spreading centre crust surrounding this ridge. Basement elevation is lower in the south, mostly due to sediment loading subsidence. The sedimentary succession is thickest in the southern Beaufort Sea region, reaching more than 15 km, and generally thins to the north and west. In the north, grabens and half-grabens are indicative of extension. Alpha-Mendeleev Ridge is a large igneous province in northern Amerasia Basin, presumably emplaced synchronously with basin formation. It overprints most of northern Canada Basin structure. The seafloor and sedimentary succession of Canada Basin is remarkably flat-lying in its central region, with little bathymetric change over most of its extent. Reflections that correlate over 100s of kms comprise most of the succession and on-lap bathymetric and basement highs. They are interpreted as representing deposits from unconfined turbidity current flows. Sediment distribution patterns reflect changing source directions during the basin’s history. Initially, probably late Cretaceous to Paleocene synrift sediments sourced from the Alaska and Mackenzie-Beaufort margins. This unit shows a progressive series of onlap unconformities with a younging trend towards Alpha and Northwind ridges, likely a response to contemporaneous subsidence. Sediment source direction appeared to shift to the Canadian Arctic Archipelago margin for the Eocene and Oligocene, likely due to uplift of Arctic islands during the Eurekan Orogeny. The final stage of sedimentation appears to be from the Mackenzie-Beaufort region for the Miocene and Pliocene when drainage patterns shifted in the Yukon and Alaska to the Mackenzie valley. Upturned reflections at onlap positions may indicate syn-depositional subsidence. There is little evidence, at least at a regional seismic data scale, of contemporaneous or post-depositional sediment reworking, suggesting little large-scale geostrophic or thermohaline-driven bottom current activity.

  20. A review of stratigraphy and sedimentary environments of the Karoo Basin of South Africa

    NASA Astrophysics Data System (ADS)

    Smith, R. M. H.

    The Karoo Supergroup covers almost two thirds of the present land surface of southern Africa. Its strata record an almost continuous sequence of continental sedimentation that began in the Permo-Carboniferous (280 Ma) and terminated in the early Jurassic 100 million years later. The glacio-marine to terrestrial sequence accumulated in a variety of tectonically controlled depositories under progressively more arid climatic conditions. Numerous vertebrate fossils are preserved in these rocks, including fish, amphibians, primitive aquatic reptiles, primitive land reptiles, more advanced mammal-like reptiles, dinosaurs and even the earliest mammals. Palaeoenvironmental analysis of the major stratigraphic units of the Karoo sequence demonstrates the effects of more localised tectonic basins in influencing depositional style. These are superimposed on a basinwide trend of progressive aridification attributed to the gradual northward migration of southwestern Gondwanaland out of polar climes and accentuated by the meteoric drying effect of the surrounding land masses. Combined with progressive climatic drying was a gradual shrinking of the basin brought about by the northward migration of the subducting palaeo-Pacific margin to the south. Following deposition of the Cape Supergroup in the pre-Karoo basin there was a period of uplift and erosion. At the same time 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 both upland valley and shelf depositories resulted in the basal Karoo Dwyka Formation. After glaciation, an extensive shallow sea remained over the gently subsiding shelf fed by large volumes of meltwater. Black clays and muds accumulated under relatively cool climatic conditions (Lower Ecca) with perhaps a warmer "interglacial" during which the distinctive Mesosaurus-bearing, carbonaceous shales of the Whitehill Formation were deposited. Deformation of the southern rim of the basin, caused by the subducting palaeo-Pacific plate, resulted in mountain ranges far to the south. Material derived from this source, as well as granitic uplands to the west and morth-east, was deposited on large deltas that built out into the Ecca sea (Upper Ecca). The relatively cool climate and lowland setting promoted thick accumulations of peat on the coastal and delta plains and which now constitute the major coal reserves of southern Africa. Later the prograding deltas coalesced to fill most of the basin after which fluvial sedimentation of the Beaufort Group dominated. The climate by this time (Late Permian) had warmed to become semi-arid with highly seasonal rainfall. The central parts of the basin were for the most part drained by fine-grained meanderbelts and semi-permanent lakes. Significant stratabound uranium reserves have been delimited in the channel sandstones of the Beaufort Group in the southwestern parts of the basin. Pulses of uplift in the southern source areas combined with a possible orogenic effect resulted in two coarser-grained alluvial fans prograding into the more central parts of the basin (Katberg Sandstone Member and Molteno Formation). In the upper Karoo sequence progressive aridification dominated depositional style with playa lake and wadi-type environments (Elliot Formation) that finally gave way to a dune sand dominated system (Clarens Formation). Basinwide volcanic activity of the early Jurassic Drakensberg Group brought deposition in the Karoo Basin to a close.

  1. Albuquerque Basin seismic network

    USGS Publications Warehouse

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

    1977-01-01

    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.

  2. Impact basin relaxation at Iapetus

    NASA Astrophysics Data System (ADS)

    Robuchon, Guillaume; Nimmo, Francis; Roberts, James; Kirchoff, Michelle

    2011-07-01

    We investigate impact basin relaxation on Iapetus by combining a 3D thermal evolution model (Robuchon, G., Choblet, G., Tobie, G., Cadek, O., Sotin, C., Grasset, O. [2010]. Icarus 207, 959-971) with a spherical axisymmetric viscoelastic relaxation code (Zhong, S., Paulson, A., Wahr, J. [2003]. Geophys. J. Int. 155, 679-695). Due to the progressive cooling of Iapetus, younger basins relax less than older basins. For an ice reference viscosity of 10 14 Pa s, an 800 km diameter basin relaxes by 30% if it formed in the first 50 Myr but by 10% if it formed at 1.2 Gyr. Bigger basins relax more rapidly than smaller ones, because the inferred thickness of the ice shell exceeds the diameter of all but the largest basins considered. Stereo topography shows that all basins 600 km in diameter or smaller are relaxed by 25% or less. Our model can match the relaxation of all the basins considered, within error, by assuming a single basin formation age (4.36 Ga for our nominal viscosity). This result is consistent with crater counts, which show no detectable age variation between the basins examined.

  3. Dimension of fractal basin boundaries

    SciTech Connect

    Park, B.S.

    1988-01-01

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

  4. Characteristics of foreland basin fill

    SciTech Connect

    Schwab, F.L.

    1985-01-01

    The sedimentary fill of foreland basins straddles the transitional zone separating mountain belts from cratons, exhibits a unique sedimentary tectonic evolution, and has a high economic potential. The mineral composition of foreland basin sandstones show that most detritus is derived from a recycled orogen provenance, except for an early stage in which debris is eroded from subjacent continental blocks. Magmatic arcs and subduction complexes are not important sources of foreland basin detritus, probably due to topographic effects. Evidence for systematic unroofing of foreland basin sources is tenuous at best. The bulk chemical composition of foreland basin assemblages (estimated using published analyses of average sedimentary rock types) most resembles the fill of ancient geosynclines in general, and eugeoclines (eugeosynclines) specifically. It is almost meaningless to compare foreland basin fill with modern continental margin and ocean basin sediments because of secular changes in the site of carbonate deposition. The rate at which sediment accumulates in foreland basins (.044 to .927 m/1000yrs; mean is .186 m/1000yrs) exceeds sediment accumulation rates for cratonic basins and the abyssal ocean floor by a factor of 5 to 30. Comparably high rates of sediment accumulation characterize ancient aulacogens and modern rift valleys, successor basins, and (surprisingly) some modern trenches.

  5. Great Basin Paleontological Bibliography

    USGS Publications Warehouse

    Blodgett, Robert B.; Zhang, Ning; Hofstra, Albert H.; Morrow, Jared R.

    2007-01-01

    Introduction This work was conceived as a derivative product for 'The Metallogeny of the Great Basin' project of the Mineral Resources Program of the U.S. Geological Survey. In the course of preparing a fossil database for the Great Basin that could be accessed from the Internet, it was determined that a comprehensive paleontological bibliography must first be compiled, something that had not previously been done. This bibliography includes published papers and abstracts as well as unpublished theses and dissertations on fossils and stratigraphy in Nevada and adjoining portions of California and Utah. This bibliography is broken into first-order headings by geologic age, secondary headings by taxonomic group, followed by ancillary topics of interest to both paleontologists and stratigraphers; paleoecology, stratigraphy, sedimentary petrology, paleogeography, tectonics, and petroleum potential. References were derived from usage of Georef, consultation with numerous paleontologists and geologists working in the Great Basin, and literature currently on hand with the authors. As this is a Web-accessible bibliography, we hope to periodically update it with new citations or older references that we have missed during this compilation. Hence, the authors would be grateful to receive notice of any new or old papers that the readers think should be added. As a final note, we gratefully acknowledge the helpful reviews provided by A. Elizabeth J. Crafford (Anchorage, Alaska) and William R. Page (USGS, Denver, Colorado).

  6. Crustal geoelectric structure of the Sikkim Himalaya and adjoining Gangetic foreland basin

    NASA Astrophysics Data System (ADS)

    Pavan Kumar, G.; Manglik, A.; Thiagarajan, S.

    2014-12-01

    We present the results of a broadband magnetotelluric survey along a 200-km-long profile across the Sikkim Himalaya. The data were acquired at average station spacing of 5-6 km and transfer functions of 31 sites in 0.01-1000 s period range have been used for 2-D joint inversion of TE and TM modes. The composite model incorporating the effect of transverse strike reveals several features that correlate with the available seismic and kinematic models of the region. A major result of the present study is that the Main Himalayan Thrust forms the base of several resistive blocks within the wedge and that a ramp structure is present south of the Main Central Thrust Zone (MCTZ). Another significant result is that the crust and mantle lithosphere beneath the MCTZ and the Higher Himalayan Crystallines (HHC) seem to be compositionally/geologically different from the lithosphere south of the MCTZ. A steep crustal-scale fault with the Moho offset of 14 km is inferred to be separating these two blocks. The deep crustal seismicity could be related to this fault whereas shallow seismicity can be linked to the deformation within the wedge. The results also reveal the presence of some more conductors. We relate the conductor within the HHC to the sedimentary rocks of the Tethyan sequence exposed in a window about 40 km west of the profile and north of the South Tibetan Detachment System (STDS). The conductor at 90 km profile location is linked to the Gondwana rocks exposed in the Rangit Window. A 4-6 km thick sedimentary layer overlies the basement in the Gangetic foreland basin. We also delineate a sub-crustal conductor at 50-60 km depth beneath the foreland basin at the southern end of the profile, the cause of which is not apparent and needs to be explored.

  7. Provenance and paleogeography of the Devonian Durazno Group, southern Parana Basin in Uruguay

    NASA Astrophysics Data System (ADS)

    Uriz, N. J.; Cingolani, C. A.; Basei, M. A. S.; Blanco, G.; Abre, P.; Portillo, N. S.; Siccardi, A.

    2016-03-01

    A succession of Devonian cover rocks occurs in outcrop and in the subsurface of central-northern Uruguay where they were deposited in an intracratonic basin. This Durazno Group comprises three distinct stratigraphic units, namely the Cerrezuelo, Cordobés and La Paloma formations. The Durazno Group does not exceed 300 m of average thickness and preserves a transgressive-regressive cycle within a shallow-marine siliciclastic shelf platform, and is characterized by an assemblage of invertebrate fossils of Malvinokaffric affinity especially within the Lower Devonian Cordobés shales. The sedimentary provenance of the Durazno Group was determined using petrography, geochemistry, and morphological studies of detrital zircons as well as their U-Pb ages. Sandstone petrography of Cerrezuelo and La Paloma sequences shows that they have a dominantly quartz-feldspathic composition with a minor contribution of other minerals. Whole-rock geochemical data indicate that alteration was strong in each of the three formations studied; chondritic-normalized REE patterns essentially parallel to PAAS, the presence of a negative Eu-anomaly, and Th/Sc and La/Hf ratios point to an average source composition similar to UCC or slightly more felsic. Within the Cerrezuelo Formation, recycling of older volcano-metasedimentary sources is interpreted from Zr/Sc ratios and high Hf, Zr, and REE concentrations. U-Pb detrital zircon age populations of the Cerrezuelo and La Paloma formations indicate that the principal source terranes are of Neoproterozoic age, but include also minor populations derived from Mesoproterozoic and Archean-Paleoproterozoic rocks. A provenance from the Cuchilla Dionisio-Dom Feliciano, Nico Pérez and Piedra Alta terranes of Uruguay and southern Brazil is likely. This study establishes an intracratonic extensional tectonic setting during Durazno time. Considering provenance age sources, regional paleocurrent distributions and the established orogenic history recorded in SW Gondwana, we suggest that the basin fill was derived from paleohighs located in what is currently SE Uruguay.

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

    SciTech Connect

    Kolarsky, R.A.; Mann, P. )

    1991-03-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Allen, Philip A.

    2007-10-01

    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 was contemporaneous with the development of an Andean-type orogen in the Arabian-Nubian Shield while passive margin basins continued to subside in northern Iran, India and South China. The elevated topography associated with the Andean-type orogen together with passive margin mega-escarpments may have promoted nucleation of ice caps that sourced marine-terminating valley glaciers and ice streams. However, the triggering of Cryogenian glaciation must ultimately be related to the biogeochemical cycles operating on a planet with a nascent land biota, lack of calcifying plankton and reduced solar luminosity.

  10. Rift architecture and evolution: The Sirt Basin, Libya: The influence of basement fabrics and oblique tectonics

    NASA Astrophysics Data System (ADS)

    Abdunaser, K. M.; McCaffrey, K. J. W.

    2014-12-01

    The Cretaceous-Tertiary northwest-trending Sirt Basin system, Libya, is a rift/sag basin formed on Pan-African to Paleozoic-aged basement of North Africa. In this study, we investigate the rift-basin architecture and tectonic framework of the western Sirt Basin. Using remote sensed data, supported by borehole data from about 300 deep wells and surface geologic maps, we constructed geological cross sections and surface geology maps. Indication of the relative timing of structures and movement along faults has been determined where possible. Direction statistics for all the interpreted linear features acquired in the study area were calculated and given as a total distribution and then the totals are broken down by the major basin elements of the area. Hundreds of lineaments were recognized. Their lengths, range between a hundred meters up to hundreds of kilometers and the longest of the dominant trends are between N35W-N55W and between N55E-N65E which coincides with Sirt Basin structures. The produced rose diagrams reveal that the majority of the surface linear features in the region have four preferred orientations: N40-50W in the Zallah Trough, N45-55W in the Dur al Abd Trough, N35-55W in the Az Zahrah-Al Hufrah Platform, and in contrast in the Waddan Uplift a N55-65E trend. We recognize six lithostratigraphic sequences (phases) in the area's stratigraphic framework. A Pre-graben (Pre-rift) initiation stage involved the Pre-Cretaceous sediments formed before the main Sirt Basin subsidence. Then followed a Cretaceous to Eocene graben-fill stage that can divided into four structurally-active and structurally-inactive periods, and finally a terminal continental siliciclastics-rich package representing the post-rift stage of the development in post-Eocene time. In general five major fault systems dissect and divide the study area into geomorphological elevated blocks and depressions. Most of the oil fields present in the study area are associated with structural hinge zones and adjoining highs. Late Eocene rocks exposed in the western part of the basin exhibit a complex network of branching segmented normal and strike-slip faults, generally with a NNW-SSE structural orientations. Many surface structural features have been interpreted from satellite images which confirm sinistral strike-slip kinematics. Relay ramp structures, numerous elongate asymmetric synclines associated with shallow west limbs and steeper dipping east limbs are developed in the hangingwalls adjacent to west downthrowing normal faults. These structural patterns reflect Cretaceous/Tertiary extensional tectonics with additional control by underlying pre-existing Pan-African basement fabrics and ENE-WSW trending Hercynian structures. We relate the Sirt Basin rift development as exemplified in our study area to the break-up of Gondwana represented by the structural evolution of the West-Central African rift system, and the South and Central Atlantic, the Tethys and the Indian Oceans.

  11. SOME ETHNOMEDICINAL PLANTS OF KORAPUT DISTRICT ORISSA

    PubMed Central

    Das, P.K.; Misra, M.K.

    1988-01-01

    The paper presents the ethnomedicinal use of 35 plants by the tribals of Koraput district to cure 25 diseases they suffer from. Apart from this, a note on the vegetation pattern, tribal population and geography of the district is given here. PMID:22557632

  12. The National Basin Delineation Project.

    NASA Astrophysics Data System (ADS)

    Arthur, Ami T.; Cox, Gina M.; Kuhnert, Nathan R.; Slayter, David L.; Howard, Kenneth W.

    2005-10-01

    The National Basin Delineation Project (NBDP) was undertaken by the National Severe Storms Laboratory to define flash-flood-scale basin boundaries for the country in support of the National Weather Service (NWS) Flash Flood Monitoring and Prediction (FFMP) system. FFMP-averaged basin rainfall calculations allow NWS forecasters to monitor precipitation in flash-flood-scale basins, improving their ability to make accurate and timely flash-flood-warning decisions. The NBDP was accomplished through a partnership with the U.S. Geological Survey Earth Resources Observation Systems (EROS) Data Center (EDC). The one-arc-second (approximately 30 m)-resolution digital terrain data in the EDC's National Elevation Dataset provided the basis for derivation of the following digital maps using a geographic information system: 1) a grid of hydrologically conditioned elevation values (all grid cells have a definned flow direction), 2) a grid of flow direction indicating which of eight directions water will travel based on slope, 3) a grid of flow accumulation containing a count of the number of upstream grid cells contributing flow to each grid cell, 4) synthetic streamlines derived from the flow accumulation grid, and 5) flash-flood-scale basin boundaries. Special techniques were applied in coastal areas and closed basins (basins with no outflow) to ensure the accuracy of derived basins and streams. Codifying each basin with a unique identifier and including hydrologic connectivity information produced a versatile, seamless dataset for use in FFMP and other national applications.

  13. Initial constraints on crustal structure across the Suwanee Suture and South Georgia Basin from the SUGAR seismic refraction experiment

    NASA Astrophysics Data System (ADS)

    Shillington, D. J.; Lizarralde, D.; Harder, S. H.

    2014-12-01

    Some of the most important unresolved questions in plate tectonics concern the formation and rupture of continents. How does the accretion of terranes contribute to the construction of continental lithosphere, and what processes enable continental lithosphere to rupture? The South Georgia Basin was at the center of the most recent sequence of continental collision and rifting events to shape eastern North America. It is the largest of the failed Mesozoic rift basins that formed during the breakup of Pangea. It straddles the Suwannee Suture, the only well-defined remnant of the Alleghenian suture that joined North America and Gondwana, forming Pangea. The South Georgia Basin also lies at the center of the Central Atlantic Magmatic Province (CAMP). Here we present initial results from the first phase of the SUwanee Suture and GA Rift basin (SUGAR) project, an active-source seismic refraction project to image the crustal structure across these features. During March 2014, we acquired data along a ~325-km-long, NW-SE oriented profile that crossed the Suwanne Suture and western part of South Georgia Basin, extending from north of Columbus, GA to northernmost Florida east of Jasper, FL. The profile was densely instrumented with single-channel RekTek 125A seismometers ("Texans") spaced at ~250 m and deployed along state and country roads, yielding a total of 1193 seismometers along the profile. Thirty-three students and young scientists were involved in the deployment and recovery. The sources were 100 to 1800 lb shots spaced at ~20-50 km. The data are of exceptionally high quality. On nearly all shots, we observe arrivals out to the largest shot-receiver offsets. Within the basin, refractions through the sedimentary section with apparent velocities of ~3-4 km/s are observed to maximum offsets of 7 km. Crustal refractions are observed at a wide-range of offsets with apparent velocities increasing from ~5.5 km/s to as high as ~7.25 km/s. At offsets greater than 150-180 km, first arrivals have apparent velocities > ~8 km/s, suggesting that they are turning waves through the uppermost mantle. Prominent reflections are also observed on most shotgathers. We will present initial velocity models of these data and discuss their implications for the tectonic configuration and history of this region.

  14. New insights into the tectono-stratigraphic evolution of the Malvinas Basin, offshore of the southernmost Argentinean continental margin

    NASA Astrophysics Data System (ADS)

    Baristeas, N.; Anka, Z.; di Primio, R.; Rodriguez, J. F.; Marchal, D.; Dominguez, F.

    2013-09-01

    A detailed tectono-stratigraphic analysis of the Malvinas Basin was achieved by the interpretation of around 65,000 km of 2D seismic reflection profiles. Five main seismo-stratigraphic units and their sub-units, informally named units U1 to U5 a/b, bound by major unconformities were identified and correlated with the Mesozoic to Cenozoic main tectonic phases of the basin. Unit U1 (Pre-168 Ma) represents the seismic basement. Unit U2 (168-150.5 Ma, syn rift phase) thickens and deepens southwards. Units U1 and U2 are affected by several syn-rift normal faults that exhibit a main NE-SW strike direction in the south of the basin and a NW-SE strike direction in the centre of the basin. This suggests that the Malvinas Basin may have developed initially as a rift basin with two different extensional directions: (1) a NW-SE directed extension probably linked with the opening of the Weddell Sea (Early Mid-Jurassic), and (2) a NE-SW directed extension most likely linked with the Jurassic back-arc extension of Gondwana and probably later with the onset of the opening of the South Atlantic during Late Jurassic to Early Cretaceous time. Unit U3 (150.5-68 Ma, sag phase) is mainly an aggradational wedge-shaped unit. Unit U4 (68-42.5 Ma, transtensional foredeep phase) overlies unconformable unit U3. It deepens in the south because of an N-S/NW-SE directed extensional regime. Accumulation rates decrease during units U2, U3, and U4 from 4.84, to 1.23 to 0.8 km3/Ma 103. Units U5a and U5b (42.5-5.5 and 5.5-0 Ma, transpressional foredeep phase) finally represent a change from aggradation to progradation sedimentary pattern and to a left-lateral transpressional regime in the south. The sediment supply was considerably higher than before and a thick sedimentary wedge has been deposited until today. Accumulations rates increased in units U5a and U5b from 2.28 to 8.91 km3/Ma 103.

  15. Hydrocarbon associations in evaporite basins

    SciTech Connect

    Warren, J.

    1988-01-01

    Evaporite deposition today is not representative of the diversity of scale of evaporites of the past. Ancient evaporites were deposited in two main settings: platform wide or basin wide. Platform evaporites were composed of relatively thin stratiform units (usually <5-10 m thick) deposited on either ramps or behind rimmed shelves. Basinal evaporites were deposited as thick bedded units 10s to 100s of m thick, and laid down in 4 main tectonic settings--rift, collision, transform, and intracratonic. Basins could be further subdivided into three main depositional settings: deep basin-shallow water, deep basin-deep water, and shallow basin-shallow water. Thick basinal salts were remobilized into salt structures in all tectonic settings except intracratonic. Salt flow was due to inherent instability and differential loading in tectonically active settings. Hydrocarbon accumulations associated with these various platforms and basins followed a predictable, but not mutually exclusive, pattern related to the classification of evaporite settings presented in this paper. Reservoirs in platform and ramp settings tended to be of two types--depositional and diagenetic--with most of the diagenesis following patterns predicted by the porosity and plumbing established at or soon after evaporite emplacement. Ramp reservoirs were almost always found in Zone Y, while shelf reservoirs were most common in the grainstone shoals associated with rim or island-crest facies, or their dolomitized equivalents. Reservoirs associated with basinal evaporites were also depositional or diagenetic. Depositional reservoirs were almost all related to topography present during deposition of the carbonates in the basin, often immediately preceding or just beginning evaporitic conditions in the basin.

  16. 40Ar/39Ar Thermochronometry of the Sisters Shear Zone, Stewart Island, New Zealand; Implications for Driving Mechanisms and Multi-Stage Breakup of the Pacific Margin of Gondwana

    NASA Astrophysics Data System (ADS)

    Kula, J. L.; Tulloch, A. J.; Spell, T. L.; Wells, M. L.

    2006-12-01

    New mapping, structural analysis, and thermochronometry of the Sisters Shear Zone (SSZ) indicate this detachment system played a role in continental extension leading to separation of New Zealand from West Antarctica. The SSZ extends 40 km along the southeast coast of Stewart Island, southernmost New Zealand with a footwall consisting of variably deformed 300-105 Ma granites and a hanging wall of coarse non-marine conglomerate and undeformed granite. The trace of the SSZ is subparallel to seafloor isochrons adjacent to the Campbell Plateau and stretching lineations throughout the shear zone are oriented 155/335 10; consistent with the spreading direction along the Pacific-Antarctic Ridge. Mica and K-feldspar 40Ar/39Ar thermochronometry of SSZ footwall rocks indicate moderately rapid cooling (20-30C/Ma) over the interval ~89-82 Ma followed by slow cooling. Interpretation of the moderately rapid cooling as due to tectonic denudation makes the SSZ the youngest structure yet identified in New Zealand related to Gondwana breakup. The decrease in cooling rate at 82 Ma coincides with the age of oldest seafloor adjacent to the Campbell Plateau (chron 33r), possibly reflecting the mechanical transition from continental extension to lithospheric rupture and Pacific-Antarctic ridge initiation. The orientation of the SSZ has implications for driving mechanisms of extension. Major arc/forearc terrains through South Island and Stewart Island trend northwest-southeast, and include paired plutonic belts of thick inboard arc terrain adjacent to a thin older, outboard arc belt. Crustal collapse due to the across-arc gradient in gravitational potential energy would have resulted in extension directed normal to the arc trend. The SSZ cuts the paired plutonic belts at a high angle indicating extension was not the result of gravitational collapse, but more likely driven by plate boundary forces such as microplate capture as the dynamics of subduction along the continental margin changed. Combined with published data from New Zealand and West Antarctica, a two-stage rift model for the Gondwana margin is proposed. Stage one was the northward unzipping of the Tasman ridge as recorded first in mylonite dredged from the Ross Sea and later by the Paparoa core complex in northern South Island. Stage two was extension along the SSZ and separation of the Campbell Plateau and West Antarctica with formation of the Pacific-Antarctic ridge.

  17. Ichnofabric and basin analysis

    SciTech Connect

    Bottjer, D.J. ); Droser, M.L. )

    1991-06-01

    Utilization of ichnofabric indices for measuring recorded extent of bioturbation allows comparative studies of ichnofabric between different facies. In vertical sequences, measurements of ichnofabric indices can be normalized to percent of the total thickness measured for each ichnofabric index. These data can be presented as histograms, or ichnograms, when measurements are from strata deposited in a single genetically-defined sedimentary environment. Ichnograms can be used in conjunction with ichnofacies analysis to present a more complete summary of bioturbation in a sedimentary unit. Using a knowledge of the factors which contribute towards producing ichnofabric in different sedimentary environments, the range of possible ichnograms for any environment can be modeled. In addition to ichnograms, an average ichnofabric index also can be calculated as a useful summary characterization of the extent of bioturbation recorded in a sedimentary unit. Through measurement of ichnofabric indices, construction of ichnograms, and calculation of average ichnofabric index, broad-scale summary data are produced that can allow a more complete understanding of the physical and biological dynamics of sedimentary basins, especially when employed in conjunction with other basin analysis approaches.

  18. Advanced Chemistry Basins Model

    SciTech Connect

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

    2003-02-13

    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.

  19. Foreland basins and fold belts

    SciTech Connect

    Macqueen, R.W.; Leckie, D.A. )

    1992-01-01

    The papers in this book describe six foreland basins and fold belts in terms of their regional setting, stratigraphy, tectonics, and structure, and their oil and gas systems. All of the basins show general similarities, but each differs significantly in detail from the others, posing something of a problem in terms of arriving at a 'typical' foreland basin and fold belt. Some are major hydrocarbon producers; others are not. The major characteristics of the six foreland basins and fold belts are summarized in Tables 1 through 5, which provide a convenient means of comparing and contrasting these basins and their hydrocarbon resources. The Western Canada foreland basin and fold belt serves as the type example for several reasons. These include: its setting and clear relationship to a major orogene of Mesozoic-Cenozoic age; the fact that it is uncomplicated by later overprinting, segmentation, or cover rocks unlike the Ouachita, Eastern Venezuela, and U.S. Rocky Mountain foreland basins and fold belts); the fact that there is a large volume of publicly available data on the basin and an active exploration and research community; and the fact that it has reasonable oil and gas reserves in a well-defined stratigraphic framework.

  20. 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...

  1. Atlantic marginal basins of Africa

    SciTech Connect

    Moore, G.T.

    1988-02-01

    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.

  2. Hydrocarbon associations in evaporite basins

    SciTech Connect

    Warren, J.

    1988-02-01

    Evaporite deposition today is not representative of the diversity or scale of evaporites of the past. Ancient evaporites were deposited in two main settings: platform wide or basin wide. Platform evaporites were composed of relatively thin stratiform units (usually <5-10 m thick) deposited on either ramps or behind rimmed shelves. Basinal evaporites were deposited as thick bedded units 10s to 100s of m thick, and laid down in 4 main tectonic settings - rift, collision, transform, and intracratonic. Basins could be further subdivided into three main depositional settings: deep basin-shallow water, deep basin-deep water, and shallow basin-shallow water. Thick basinal salts were remobilized into salt structures in all tectonic settings except intracratonic. Salt flow was due to inherent instability and differential loading in tectonically active settings. Hydrocarbon accumulations associated with these various platforms and basins followed a predictable, but not mutually exclusive, pattern related to the classification of evaporite settings presented in this paper. Reservoirs in platform and ramp settings tended to be of two types - depositional and diagenetic - with most of the diagenesis following patterns predicted by the porosity and plumbing established at or soon after evaporite emplacement.

  3. Out in the Atchafalaya Basin

    USGS Multimedia Gallery

    USGS Scientists Dan Kroes and Charlie Demas set out into the Atchafalaya Basin to inspect flooding conditions in the Basin. In late 2015/early 2016 unusually large rainfall in the Upper Mississippi River Valley led to significant flooding in Arkansas, Illinois, Louisiana, Mississippi, Missouri, and...

  4. Estancia Basin dynamic water budget.

    SciTech Connect

    Thomas, Richard P.

    2004-09-01

    The Estancia Basin lies about 30 miles to the east of Albuquerque, NM. It is a closed basin in terms of surface water and is somewhat isolated in terms of groundwater. Historically, the primary natural outlet for both surface water and groundwater has been evaporation from the salt lakes in the southeastern portion of the basin. There are no significant watercourses that flow into this basin and groundwater recharge is minimal. During the 20th Century, agriculture grew to become the major user of groundwater in the basin. Significant declines in groundwater levels have accompanied this agricultural use. Domestic and municipal use of the basin groundwater is increasing as Albuquerque population continues to spill eastward into the basin, but this use is projected to be less than 1% of agricultural use well into the 21st Century. This Water Budget model keeps track of the water balance within the basin. The model considers the amount of water entering the basin and leaving the basin. Since there is no significant surface water component within this basin, the balance of water in the groundwater aquifer constitutes the primary component of this balance. Inflow is based on assumptions for recharge made by earlier researchers. Outflow from the basin is the summation of the depletion from all basin water uses. The model user can control future water use within the basin via slider bars that set values for population growth, water system per-capita use, agricultural acreage, and the types of agricultural diversion. The user can also adjust recharge and natural discharge within the limits of uncertainty for those parameters. The model runs for 100 years beginning in 1940 and ending in 2040. During the first 55 years model results can be compared to historical data and estimates of groundwater use. The last 45 years are predictive. The model was calibrated to match to New Mexico Office of State Engineer (NMOSE) estimates of aquifer storage during the historical period by making adjustments to recharge and outflow that were within the parameters uncertainties. Although results of this calibrated model imply that there may be more water remaining in the aquifer than the Estancia Water Plan estimates, this answer is only another possible result in a range of answers that are based on large parameter uncertainties.

  5. Magmatic evolution in the N-Gondwana margin related to the opening of the Rheic Ocean—evidence from the Upper Parautochthon of the Galicia-Trás-os-Montes Zone and from the Central Iberian Zone (NW Iberian Massif)

    NASA Astrophysics Data System (ADS)

    Dias da Silva, Ícaro; Díez Fernández, Rubén; Díez-Montes, Alejandro; González Clavijo, Emilio; Foster, David A.

    2015-08-01

    LA-MC-ICP-MS U-Pb zircon ages and whole-rock geochemical data obtained from volcanic rocks erupted in the northern margin of Gondwana provide new insights on the polyphase magmatic evolution of the NW Iberian domain during the establishment of passive margin conditions in Lower Paleozoic times. The U-Pb data show crystallization ages of ca. 455 Ma for two calc-alkaline rhyolites sampled in the Upper Parautochthon of the eastern Galicia—Trás-os-Montes Zone (GTMZ) and for an intraplate basalt intruded into Middle Ordovician slates of the autochthonous series of the Central Iberian Zone (CIZ). Together with previous data, the ages obtained reveal a periodic magmatic activity across the northern Gondwana margin during the Lower Paleozoic, which is comparable to that observed in NE Iberia and in other massifs of the Mediterranean realm. Both geochronological and geochemical data reinforce paleontological and stratigraphic evidences for paleogeographic proximity between these domains and contribute to the recognition of extensional-related magmatism along the northern margin of Central Gondwana associated with the opening of the Rheic Ocean.

  6. Impact basin relaxation on Iapetus

    NASA Astrophysics Data System (ADS)

    Robuchon, Guillaume; nimmo, F.; roberts, J.

    2010-10-01

    The evolution of the icy satellites is complex and currently poorly understood. Here we combine thermal evolution models with basin relaxation calculations to place tighter constraints on the early history of these bodies. We have coupled the results of a model for the internal evolution of Iapetus (Robuchon et al, 2010) with a computation of the surface relaxation (Zhong et al, 2003). The evolution of Iapetus is calculated using a 3D model with a temperature-dependent viscosity, while the relaxation is computed with a Maxwell viscoelastic rheology. Our relaxation model was benchmarked against the analytical results given by Melosh (1989) . At each timestep we recompute the effective ice viscosity using the parameters of Goldsby and Kohlstedt (2001). We also investigate the effect of a cutoff in effective viscosity (cf. Dombard and McKinnon, 2006). Our baseline simulation assumes 72ppb of 26Al, consistent with the results of Robuchon et al. (2010). Bigger basin relax more rapidly than smaller ones, because the inferred thickness of the ice shell of Iapetus exceeds the diameter of even the largest basins considered. Due to the cooling of Iapetus, the younger basins relax less than the older. Our results show a maximum relaxation of less than 20% for the older and bigger basins and less than 5% for the smaller. These results are in good agreement with measurements of basin depth (Schenk and Moore, 2007) assuming that basin formation occurred about 900 Myr after the formation of the Solar System. By linking models of internal evolution and basin relaxation, we can place tighter constraints on the histories of the Saturnian icy satellites. For instance, our initial results are consistent with basin formation at the time of the Late Heavy Bombardment. A critical observational requirement is the ages of the largest impact basins on the icy satellites.

  7. RESERVES IN WESTERN BASINS PART IV: WIND RIVER BASIN

    SciTech Connect

    Robert Caldwell

    1998-04-01

    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.

  8. Permian-Carboniferous arc magmatism in southern Mexico: U-Pb dating, trace element and Hf isotopic evidence on zircons of earliest subduction beneath the western margin of Gondwana

    NASA Astrophysics Data System (ADS)

    Ortega-Obregn, C.; Solari, L.; Gmez-Tuena, A.; Elas-Herrera, M.; Ortega-Gutirrez, F.; Macas-Romo, C.

    2014-07-01

    Undeformed felsic to mafic igneous rocks, dated by U-Pb zircon geochronology between 311 and 255 Ma, intrude different units of the Oaxacan and Acatln metamorphic complexes in southwestern Mexico. Rare earth element concentrations on zircons from most of these magmatic rocks have a typical igneous character, with fractionated heavy rare earths and negative Eu anomalies. Only inherited Precambrian zircons are depleted in heavy rare earth elements, which suggest contemporaneous crystallization in equilibrium with metamorphic garnet during granulite facies metamorphism. Hf isotopic signatures are, however, different among these magmatic units. For example, zircons from two of these magmatic units (Cuanana pluton and Honduras batholith) have positive ?Hf values (+3.8-+8.5) and depleted mantle model ages (using a mean crustal value of 176Lu/177Hf = 0.015) ( T DMC) ranging between 756 and 1,057 Ma, whereas zircons from the rest of the magmatic units (Etla granite, Zaniza batholith, Carbonera stock and Sosola rhyolite) have negative ?Hf values (-1 to -14) and model ages between 1,330 and 2,160 Ma. This suggests either recycling of different crustal sources or, more likely, different extents of crustal contamination of arc-related mafic magmas in which the Oaxacan Complex acted as the main contaminant. These plutons thus represent the magmatic expression of the initial stages of eastward subduction of the Pacific plate beneath the western margin of Gondwana, and confirm the existence of a Late Carboniferous-Permian magmatic arc that extended from southern North America to Central America.

  9. Terminal suturing of Gondwana along the southern margin of South China Craton: Evidence from detrital zircon U-Pb ages and Hf isotopes in Cambrian and Ordovician strata, Hainan Island

    NASA Astrophysics Data System (ADS)

    Xu, Yajun; Cawood, Peter A.; Du, Yuansheng; Zhong, Zengqiu; Hughes, Nigel C.

    2014-12-01

    Hainan Island, located near the southern end of mainland South China, consists of the Qiongzhong Block to the north and the Sanya Block to the south. In the Cambrian, these blocks were separated by an intervening ocean. U-Pb ages and Hf isotope compositions of detrital zircons from the Cambrian succession in the Sanya Block suggest that the unit contains detritus derived from late Paleoproterozoic and Mesoproterozoic units along the western margin of the West Australia Craton (e.g., Northampton Complex) or the Albany-Fraser-Wilkes orogen, which separates the West Australia and Mawson cratons. Thus, in the Cambrian the Sanya Block was not part of the South China Craton but rather part of the West Australian Craton and its environs. In contrast, overlying Late Ordovician strata display evidence for input of detritus from the Qiongzhong Block, which constituted part of the southeastern convergent plate margin of the South China Craton in the early Paleozoic. The evolving provenance record of the Cambrian and Ordovician strata suggests that the juxtaposition of South China and West Australian cratons occurred during the early to mid-Ordovician. The event was linked with the northern continuation of Kuungan Orogeny, with South China providing a record of final assembly of Gondwana.

  10. Record of tide-wave influence on the coal-bearing Permian Barakar Formation, Raniganj Basin, India

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Biplab; Bandyopadhyay, Sandip; Mahapatra, Samiran; Banerjee, Sudipto

    2012-08-01

    The coal-bearing Barakar Formation (early Permian) of the Raniganj Gondwana basin was previously interpreted as continental fluvial sediments with little evidence for tide-wave influences. The present contribution details the sedimentary attributes of marginal marine tidal and wave activities preserved within an overall braided-meandering fluvial depositional setting from the Barakar Formation. Tide-dominated sedimentary features include (i) tidal-bundle sequences showing sandstone foresets with mud drapes, (ii) periodic variation in foreset thickness, (iii) lateral and vertical accretion of cross-strata bundles with a downcurrent change to sigmoidal cross-strata, (iv) mutually opposite cross-strata sets separated by sub-horizontal, plane laminated sandstone-mudstone, and (v) alternate sand- and mud-dominated rhythmites. Draping of the tidal stratifications by wavy laminated muddy-siltstone suggests immediate invasion by low energy, silt/mud depositing waves that helped preserve the tidal features during subsequent reworking. Open marine storm wave activities are evident from hummocky cross-stratification and various types of wave ripples, preserved separately within coarse- to fine-grained sandstone in the middle-upper part of the succession. Recognition of tide-storm influenced marine sedimentation significantly changes the existing paleogeographic model to a fluvial-estuarine depositional environment.

  11. Aleutian basin oceanic crust

    USGS Publications Warehouse

    Christeson, Gail L.; Barth, Ginger A.

    2015-01-01

    We present two-dimensional P-wave velocity structure along two wide-angle ocean bottom seismometer profiles from the Aleutian basin in the Bering Sea. The basement here is commonly considered to be trapped oceanic crust, yet there is a change in orientation of magnetic lineations and gravity features within the basin that might reflect later processes. Line 1 extends ∼225 km from southwest to northeast, while Line 2 extends ∼225 km from northwest to southeast and crosses the observed change in magnetic lineation orientation. Velocities of the sediment layer increase from 2.0 km/s at the seafloor to 3.0–3.4 km/s just above basement, crustal velocities increase from 5.1–5.6 km/s at the top of basement to 7.0–7.1 km/s at the base of the crust, and upper mantle velocities are 8.1–8.2 km/s. Average sediment thickness is 3.8–3.9 km for both profiles. Crustal thickness varies from 6.2 to 9.6 km, with average thickness of 7.2 km on Line 1 and 8.8 km on Line 2. There is no clear change in crustal structure associated with a change in orientation of magnetic lineations and gravity features. The velocity structure is consistent with that of normal or thickened oceanic crust. The observed increase in crustal thickness from west to east is interpreted as reflecting an increase in melt supply during crustal formation.

  12. K-Basins design guidelines

    SciTech Connect

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

    1995-06-01

    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.

  13. Rock physics template (RPT) analysis of well logs and seismic data for lithology and fluid classification in Cambay Basin

    NASA Astrophysics Data System (ADS)

    Datta Gupta, Saurabh; Chatterjee, Rima; Farooqui, M. Y.

    2012-07-01

    The Cambay Basin is 450-km-long north-south-trending graben with an average width of 50 km, having maximum depth of about 7 km. The origin of the Cambay and other Basins on the western margin of India are related to the break up of the Gondwana super-continent in the Late-Triassic to Early-Jurassic (215 ma). The structural disposition of the Pre-Cambrian basement—a complex of igneous and metamorphic rocks exposed in the vicinity of the Cambay Basin—controls its architecture. The principal lineaments in the Basin are aligned towards NE-SE, ENE-WSW and NNW-SSE, respectively. Rock physics templates (RPTs) are charts and graphs generated by using rock physics models, constrained by local geology, that serve as tools for lithology and fluid differentiation. RPT can act as a powerful tool in validating hydrocarbon anomalies in undrilled areas and assist in seismic interpretation and prospect evaluation. However, the success of RPT analysis depends on the availability of the local geological information and the use of the proper model. RPT analysis has been performed on well logs and seismic data of a particular study area in mid Cambay Basin. Rock physics diagnostic approach is adopted in the study area placed at mid Cambay Basin to estimate the volume in the reservoir sands from 6 wells (namely; A, B, C, D, E and F) where oil was already encountered in one well, D. In the study area, hydrocarbon prospective zone has been marked through compressional (P wave) and shear wave (S wave) impedance only. In the RPT analysis, we have plotted different kinds of graphical responses of Lame's parameters, which are the function of P-wave velocity, S-wave velocity and density. The discrete thin sand reservoirs have been delineated through the RPT analysis. The reservoir pay sand thickness map of the study area has also been derived from RPT analysis and fluid characterization. Through this fluid characterization, oil-bearing thin sand layers have been found in well E including well D. The sand distribution results prove that this methodology has able to perform reservoir characterization and seismic data interpretation more quantitatively and efficiently.

  14. The Amazon basin in transition.

    PubMed

    Davidson, Eric A; de Arajo, Alessandro C; Artaxo, Paulo; Balch, Jennifer K; Brown, I Foster; C Bustamante, Mercedes M; Coe, Michael T; DeFries, Ruth S; Keller, Michael; Longo, Marcos; Munger, J William; Schroeder, Wilfrid; Soares-Filho, Britaldo S; Souza, Carlos M; Wofsy, Steven C

    2012-01-19

    Agricultural expansion and climate variability have become important agents of disturbance in the Amazon basin. Recent studies have demonstrated considerable resilience of Amazonian forests to moderate annual drought, but they also show that interactions between deforestation, fire and drought potentially lead to losses of carbon storage and changes in regional precipitation patterns and river discharge. Although the basin-wide impacts of land use and drought may not yet surpass the magnitude of natural variability of hydrologic and biogeochemical cycles, there are some signs of a transition to a disturbance-dominated regime. These signs include changing energy and water cycles in the southern and eastern portions of the Amazon basin. PMID:22258611

  15. Basin development and petroleum potential of offshore Otway basin, Australia

    SciTech Connect

    Williamson, P.E.; O'Brien, G.W.; Swift, M.G.; Scherl, A.S.; Marlow, M.S.; Exon, N.F.; Falvey, D.A.; Lock, J.; Lockwood, K.

    1987-05-01

    The Bass Strait region in southeastern Australia contains three sedimentary basins, which are, from east to west, the Gippsland, Bass, and Otway basins. The offshore Gippsland basin is Australia's most prolific petroleum-producing province and supplies over 90% of the country's production. In contrast, exploration has been unsuccessful in the offshore portion of the Otway basin; 17 wells have been drilled, and although shows of oil and gas have been common, no commercial discoveries have been made. Many of these wells, drilled in the 1960s and 1970s, were sited using poor-quality seismic data and, as a consequence, were frequently off structure. Seismic data quality has, however, improved significantly in recent years. The present study by the Australian Bureau of Mineral Resources (BMR) involved the collection, in the offshore Otway basin, of 3700 km of high-quality, 48-channel seismic reflection data by the BMR research vessel R/V Rig Seismic. These data have been integrated with existing industry seismic data, well data, limited dredged material, and geohistory analyses in a framework study of basin development and hydrocarbon potential in this under-explored area. The offshore Otway basin extends 500 km along the southern coastline and is typically 50 km wide in water depths of less than 200 m. It contains up to 10 km of predominantly late Mesozoic to early Cenozoic sediments, which are overlain by a thin sequence of middle to late Tertiary shelf carbonates. It has been divided into three main structural elements: the Mussel Platform in the east, the central Voluta Trough, and the Crayfish Platform in the west. The basin was initiated at the end of the Jurassic as part of the Bassian rift. Up to 6 km of Lower Cretaceous sediments were deposited prior to breakup at the end of the Early Cretaceous and the onset of sea-floor spreading between Australia and Antarctica.

  16. Arc Boudinage, Basin Inversion and Obduction in an Evolving Subduction System of East Antarctica

    NASA Astrophysics Data System (ADS)

    Ferraccioli, F.; Balbi, P.; Armadillo, E.; Crispini, L.; Capponi, G.

    2014-12-01

    The paleo-Pacific margin of Gondwana experienced protracted subduction and accretionary tectonics starting in late Neoproterozic-early Cambrian times. Northern Victoria Land (NVL), in East Antarctica, preserves a cryptic record of these active margin processes. Most models indicate that NVL contains three main terranes, namely the Robertson Bay, Bowers and Wilson terranes. Significant debate centres, however, on whether these are far travelled terranes with respect to the East Antarctic Craton, and on the tectonic and magmatic processes that affected its active margin and were ultimately responsible for the formation of the Ross Orogen. Here we interpret new aeromagnetic, aerogravity and land-gravity compilations that enable us to trace the extent of major subglacial faults in the basement of NVL, examine crustal architecture, and propose a new evolutionary model for the active margin of the craton. Prominent aeromagnetic anomalies at the edge of the Wilkes Subglacial Basin delineate the extent of an early-stage magmatic arc (ca 530 Ma?). This arc may have accreted as an exotic element onto the former Neoproterozoic rifted margin of East Antarctica or (perhaps more likely) developed in situ upon a pre-existing suture. Remnants of magnetic arc basement are also identified ca 150 km further to the east within the Wilson Terrane (WT). We propose that these were originally adjacent arc segments and that transtension triggered significant arc boudinage separating these segments. Transtension may have created accommodation space for the development of thick Cambrian sedimentary basins, which are marked by regional magnetic lows with an en-echelon geometry. Basin inversion likely occurred in a later traspressional stage of the Ross-Delamerian Orogen (ca. 490-460 Ma) that triggered the development of a major pop-up structure within the WT. Several buried thrusts of the pop-up can be traced in the aeromagnetic images and a prominent residual gravity high delineates its high-grade metamorphic core. High amplitude magnetic and gravity anomalies also delineate buried oceanic basement of the northern Bowers Terrane. Oceanic basement was likely uplifted and obducted onto to the margin either because of oblique subduction or because of docking of a microcontinent inferred to underlie part of the Robertson Bay Terrane.

  17. Basin Electric Leland Olds Station

    USGS Multimedia Gallery

    Basin Electric Leland Olds Station located near Stanton, North Dakota. It is a coal-fired power plant that use the Missouri River water for cooling. Photo taken by USGS personnel on a Civil Air Patrol flight....

  18. Tectonic framework of Turkish sedimentary basins

    SciTech Connect

    Yilmaz, P.O. )

    1988-08-01

    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.

  19. Andean Altiplano, Amazon Basin burning

    NASA Technical Reports Server (NTRS)

    1991-01-01

    This view is centered over Lake Poopo, Bolivia, in the central Andean Altiplano, (20.0S, 65.0W) with a view looking northeast into the lower elevations of Bolivia and Brazil. Extensive dry seasonal burning in the Amazon Basin produces a thick haze which is trapped in the lower atmosphere by a stable air layer. The clarity difference in the scene is caused by the Andes Mountains extending above the haze into cleaner upper atmosphere air. Amazon Basin burning

  20. Provenance and basin evolution, Zhada basin, southwestern Tibet

    NASA Astrophysics Data System (ADS)

    Saylor, J.; Decelles, P.; Gehrels, G.; Kapp, P.

    2007-12-01

    The Zhada basin is a late Miocene - Pliocene intermontane basin situated at high elevations in the Himalayan hinterland. The fluvial and lacustrine sediments of the Zhada formation are undeformed and sit in angular unconformity above the deformed Tethyan Sedimentary Sequence (TSS). The basin sits just south of the Indus suture in a structural position occupied elsewhere in the Himalayan orogen by some of the highest mountains on earth, including Everest. The occurrence of a basin at this location demands explanation. Currently, the Sutlej River flows parallel to the structural grain of the Himalaya, westward through the basin, towards the Leo Pargil (Qusum) range. Near the range front it takes a sharp southward turn, cuts across the structural grain of the Himalaya and out into the Gangetic foreland. Palaeocurrent indicators in the lower part of the Zhada formation show that the basin originated as a northwest flowing axial river. Palaeocurrent indicators are consistently northwest oriented, even to within to within 10 km of the Leo Pargil range front in the north-western end of the basin. This implies that at the onset of sedimentation in Zhada basin the Leo Pargil range was not a barrier as it is today. In the upper part of the Zhada formation, palaeocurrent indicators are generally directed towards the centre of the basin. In the central and southern portions of the basin this indicates a transition from an axial, northwest flowing river to prograding fluvial and alluvial fans. However, in the north-western part of the basin the change between lower and upper Zhada formation involves a complete drainage reversal. This change in palaeocurrent orientation is also reflected in the detrital zircon signal from basin sediments. Low in the Zhada formation the detrital zircon signal is dominated by zircons from the Kailash (Gangdese) batholith (or associated extrusives, see below). However, higher in the sections, a local source, either from the TSS or the core of the Leo Pargil range dominates the detrital zircon signal. Finally, there is a shift in the sandstone composition from unmetamorphosed sedimentary lithic fragments and extrusive felsic volcanic fragments in the lower part of the Zhada formation to metasedimentary and metaigneous fragments in the upper part of the Zhada formation. This is likely linked either to unroofing of the source terrain or a change to another source terrain. Based on the palaeocurrent and detrital zircon data, a change to another source terrain is favoured. This combination of evidence suggests that the Zhada basin evolved from a through-going fluvial plain to a dammed lake primarily due to uplift of the Leo Pargil range. This uplift would have dammed and ponded the river, and exposed higher grade metamorphic rocks at the surface for incorporation into Zhada formation sandstones. It also would have introduced a new source for detrital zircons. Uplift of the Leo Pargil range along a low angle normal fault would also have evacuated portions of the mid-crust, providing a mechanism for subsidence in the Zhada region. Lacustrine sedimentation would have coincided with progradation of marginal alluvial fans and would have continued until the basin was filled in to the level of a new spill point. At this time incision and re- establishment of the Sutlej River would have occurred.

  1. 77 FR 45653 - Yakima River Basin Conservation Advisory Group; Yakima River Basin Water Enhancement Project...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-01

    ... Bureau of Reclamation Yakima River Basin Conservation Advisory Group; Yakima River Basin Water... on the structure, implementation, and oversight of the Yakima River Basin Water Conservation Program... of the Water Conservation Program, including the applicable water conservation guidelines of...

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

    NASA Astrophysics Data System (ADS)

    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-Piqu, Luis R.

    2009-02-01

    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 (70S, 120E) 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.

  3. Flexural analysis of two broken foreland basins; Late Cenozoic Bermejo basin and Early Cenozoic Green River basin

    SciTech Connect

    Flemings, P.B.; Jordan, T.E.; Reynolds, S.

    1986-05-01

    Lithospheric flexure that generates basin in a broke foreland setting (e.g., the Laramide foreland of Wyoming) is a three-dimensional system related to shortening along basin-bounding faults. The authors modeled the elastic flexure in three dimensions for two broken foreland basins: the early Cenozoic Green River basin and the analogous late Cenozoic Bermejo basin of Argentina. Each basin is located between a thrust belt and a reverse-fault-bounded basement uplift. Both basins are asymmetric toward the basement uplifts and have a central basement high: the Rock Springs uplift and the Pie de Palo uplift, respectively. The model applies loads generated by crustal thickening to an elastic lithosphere overlying a fluid mantle. Using the loading conditions of the Bermejo basin based on topography, limited drilling, and reflection and earthquake seismology, the model predicts the current Bermejo basin geometry. Similarly, flexure under the loading conditions in the Green River basin, which are constrained by stratigraphy, well logs, and seismic profiling and summed for Late Cretaceous (Lance Formation) through Eocene (Wasatch Formation), successfully models the observed geometry of the pre-Lance surface. Basin depocenters (> 4 km for the Green River basin; > 7 km for the Bermejo basin) and central uplifts are predicted to result from constructive interference of the nonparallel applied loads. Their Bermejo model implies that instantaneous basin geometry is successfully modeled by crustal loading, whereas the Green River basin analysis suggests that basin evolution can be modeled over large time steps (e.g., 20 Ma). This result links instantaneous basin geometry to overall basin evolution and is a first step in predicting stratigraphic development.

  4. Viscoelastic Relaxation of Lunar Basins

    NASA Astrophysics Data System (ADS)

    Mohit, P. S.; Phillips, R. J.

    2004-12-01

    The large lunar impact basins provide a unique glimpse into early lunar history. Here we investigate the possibility that the relief of the oldest lunar basins (with the exception of South-Pole Aitken) has decayed through viscous relaxation. We identify nine ancient multi-ring basins with very low relief and low-amplitude Bouguer and free-air gravity anomalies. The characteristics of these basins are consistent with either 1) relaxation of topographic relief by ductile flow (e.g. Solomon et al., 1982) or 2) obliteration of basin topography during crater collapse immediately following impact. Both scenarios require that the basins formed early in lunar history, when the Moon was hot. The latter possibility appears to be unlikely due to the great topographic relief of South Pole-Aitken basin (SPA), the largest and oldest impact basin on the Moon (with the possible exception of the putative Procellarum basin; Wilhelms, 1987). On the other hand, the thin crust beneath SPA may not have allowed ductile flow in its lower portions, even for a hot Moon, implying that a thicker crust is required beneath other ancient basins for the hypothesis of viscous relaxation to be tenable. Using a semi-analytic, self-gravitating viscoelastic model, we investigate the conditions necessary to produce viscous relaxation of lunar basins. We model topographic relaxation for a crustal thickness of 30 km, using a dry diabase flow law for the crust and dry olivine for the mantle. We find that the minimum temperature at the base of the crust (Tb) permitting nearly complete relaxation of topography by ductile flow on a timescale < 108 yrs is 1400 K, corresponding to a heat flow of 55mW/m2, into the crust. Ductile flow in the lower crust becomes increasingly difficult as the crustal thickness decreases. The crust beneath SPA, thinned by the impact, is only 15-20 km thick and would require Tb ? 1550 K for relaxation to occur. The fact that SPA has maintained high-amplitude relief suggests that Tb dropped below 1550 K no later than 100 Myr after the formation of SPA. When did these basins form? The formation of a stable lunar crust ( 4.4 Ga) is clearly an upper limit on their age. The precipitation of ilmenite from the magma ocean is predicted to occur at 1373 K, which suggests that the lunar magma ocean had not fully crystallized when the oldest basins formed. From thermal evolution models (e.g., Solomon and Longhi, 1977) and crystallization ages of Mg-suite rocks (mostly 4.2-4.4 Ga; Nyquist and Shih, 1992; Snyder et al., 1995) 4.2 Ga appears to be a lower bound on the freezing of the magma ocean (although some residual liquid may have remained in the Procellarum KREEP Terrane). Therefore, the basins that relaxed almost completely due to high crustal base temperatures probably formed between 4.2-4.4 Ga.

  5. Paleothermometry of the Sydney Basin

    SciTech Connect

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

    1982-07-10

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

  6. Stratigraphy of the southern Norfolk Ridge and the Reinga Basin: a record of initiation of Tonga-Kermadec-Northland subduction in the southwest Pacific

    NASA Astrophysics Data System (ADS)

    Bache, Francois; Sutherland, Rupert; Stagpoole, Vaughan; Herzer, Richard; Collot, Julien; Rouillard, Pierrick

    2013-04-01

    Seismic-stratigraphic interpretations of a large new 2D seismic-reflection dataset from the Reinga Basin region northwest of New Zealand constrain the history of Cretaceous fragmentation of Gondwana and Cenozoic initiation of Tonga-Kermadec-Northland subduction. The southern Norfolk Ridge system lay in a proximal location to plate boundaries that were active during both Cretaceous and Cenozoic events, and persistent marine conditions led to a relatively complete record of sedimentation. Cretaceous extension was followed by regional subsidence and transgression. Two Cenozoic contractional events are separated by substantial (>1 km) subsidence. Late Eocene contraction led to reverse faulting and folding between New Caledonia and the southern Norfolk Ridge system, and topographic highs created in the north-western sector were locally eroded by wave abrasion. Reinga Basin was located at the southern tip of this event, which had only limited impact in adjacent northern New Zealand. Regional Oligocene and Miocene subsidence was contemporaneous with Late Oligocene and Early Miocene emplacement of nappes in northern New Zealand, and the onset of arc volcanism. Early Miocene contraction in the Reinga Basin led to formation of the Wanganella Ridge. These events can be related to calculated plate motions, and are shown to be consistent with models of induced subduction nucleation that require c. 150 km of convergence. The first contraction is associated with regional inception of Tonga-Kermadec subduction, whereas Oligocene to Miocene events and the onset of Hikurangi-Northland subduction were in response to a local change in plate boundary displacement rate and consequent linkage between subduction north of New Zealand with Alpine Fault formation farther south.

  7. Analogue models of pull-apart basins

    NASA Astrophysics Data System (ADS)

    McClay, Ken; Dooley, Tim

    1995-08-01

    Sandbox analogue models of pull-apart basins that developed in sedimentary strata above releasing steps in underlying basement faults are characterized by rhombic basins that are flat-bottomed box grabens with a subhorizontal synkinematic basin infill. Steep to nearly vertical, sigmoidal oblique-slip and segmented oblique-extensional faults are the dominant bounding structures of the pull-apart basins. Cross-basin, short-cut faults link the offset principal displacement zones that are characterized by flower structure development. The structural architectures of the physical models compare directly in form and dimensions to natural examples of strike-slip pull-apart basins.

  8. Basin Overflow Floods on Mars

    NASA Astrophysics Data System (ADS)

    Irwin, R. P.

    2006-12-01

    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.

  9. Inversion of Extensional Sedimentary Basins

    NASA Astrophysics Data System (ADS)

    Buiter, Susanne J. H.; Pfiffner, O. Adrian

    The evolution of extensional sedimentary basins is governed by the surrounding stress field and can, therefore, be expected to be highly sensitive to variations in these stresses. Important changes in basin geometry are to be expected in the case of an even short-lived reversal from extension to compression. We investigate the evolu- tion of fold and thrust structures which form in compression after extension, when basin forming processes have come to a complete stop. To this purpose, we use a two- dimensional, viscoplastic model and start our experiments from a pre-existing exten- sional geometry. We illustrate the sensitivity of the evolving structures to inherited extensional geometry, sedimentary and erosional processes, and material properties. One series of our model experiments involves the upper- to middle crust only in order to achieve a high detail in the basin area. We find that our results agree with examples from nature and analogue studies in, among others, the uplift and rotation of syn-rift sediments, the propagation of shear zones into the post-rift sediments and, in specific cases, the development of back-thrusts or basement short-cut faults. We test the out- come of these models by performing a second series of model simulations in which basins on a continental margin are inverted through their progressive approach of a subduction zone. These latter models are on the scale of the whole upper mantle.

  10. Basin stability in delayed dynamics.

    PubMed

    Leng, Siyang; Lin, Wei; Kurths, Jrgen

    2016-01-01

    Basin stability (BS) is a universal concept for complex systems studies, which focuses on the volume of the basin of attraction instead of the traditional linearization-based approach. It has a lot of applications in real-world systems especially in dynamical systems with a phenomenon of multi-stability, which is even more ubiquitous in delayed dynamics such as the firing neurons, the climatological processes, and the power grids. Due to the infinite dimensional property of the space for the initial values, how to properly define the basin's volume for delayed dynamics remains a fundamental problem. We propose here a technique which projects the infinite dimensional initial state space to a finite-dimensional Euclidean space by expanding the initial function along with different orthogonal or nonorthogonal basis. A generalized concept of basin's volume in delayed dynamics and a highly practicable calculating algorithm with a cross-validation procedure are provided to numerically estimate the basin of attraction in delayed dynamics. We show potential applicabilities of this approach by applying it to study several representative systems of biological or/and physical significance, including the delayed Hopfield neuronal model with multistability and delayed complex networks with synchronization dynamics. PMID:26907568

  11. Water Accounting from Ungauged Basins

    NASA Astrophysics Data System (ADS)

    Bastiaanssen, W. G.; Savenije, H.

    2014-12-01

    Water scarcity is increasing globally. This requires a more accurate management of the water resources at river basin scale and understanding of withdrawals and return flows; both naturally and man-induced. Many basins and their tributaries are, however, ungauged or poorly gauged. This hampers sound planning and monitoring processes. While certain countries have developed clear guidelines and policies on data observatories and data sharing, other countries and their basin organization still have to start on developing data democracies. Water accounting quantifies flows, fluxes, stocks and consumptive use pertaining to every land use class in a river basin. The objective is to derive a knowledge base with certain minimum information that facilitates decision making. Water Accounting Plus (WA+) is a new method for water resources assessment reporting (www.wateraccounting.org). While the PUB framework has yielded several deterministic models for flow prediction, WA+ utilizes remote sensing data of rainfall, evaporation (including soil, water, vegetation and interception evaporation), soil moisture, water levels, land use and biomass production. Examples will be demonstrated that show how remote sensing and hydrological models can be smartly integrated for generating all the required input data into WA+. A standard water accounting system for all basins in the world - with a special emphasis on data scarce regions - is under development. First results of using remote sensing measurements and hydrological modeling as an alternative to expensive field data sets, will be presented and discussed.

  12. Stormwater detention basin sediment removal

    SciTech Connect

    Gross, W.E.

    1995-12-31

    In the past, stormwater runoff from landfills has been treated mainly by focusing on reducing the peak storm discharge rates so as not to hydraulically impact downstream subsheds. However, with the advent of stricter water quality regulations based on the Federal Clean Water Act, and the related NPDES and SPDES programs, landfill owners and operators are now legally responsible for the water quality of the runoff once it leaves the landfill site. At the Fresh Kills Landfill in New York City, the world`s largest covering over 2000 acres, landfilling activities have been underway since 1945. With the main objective at all older landfill sites having focused on maximizing the available landfill footprint in order to obtain the most possible airspace volume, consideration was not given for the future siting of stormwater basin structures. Therefore, when SCS Engineers began developing the first comprehensive stormwater management plan for the site, the primary task was to locate potential sites for all the stormwater basins in order to comply with state regulations for peak stormwater runoff control. The basins were mostly constructed where space allowed, and were sized to be as large as possible given siting and subshed area constraints. Seventeen stormwater basins have now been designed and are being constructed to control the peak stormwater runoff for the 25-year, 24-hour storm as required by New York State. As an additional factor of safety, the basins were also designed for controlled discharge of the 100-year, 24 hour storm.

  13. Exploration potential of offshore northern California basins

    SciTech Connect

    Bachman, S.B.; Crouch, J.K.

    1988-01-01

    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 discoveries in this decade in the offshore Santa Maria basin, such as the Point Arguello field, indicate that these offshore basins may be highly prospective exploration targets. Many of the key features of Monterey production in central and southern California are also present in the offshore basins of northern California. A new 5-year leasing plan has scheduled leasing in the northern California OCS starting in early 1989. The first basins on the schedule, the Point Arena and Eel River basins, differ in some respects. The Point Arena basin is more typical of a Monterey basin, with the potential for fractured chert reservoirs and organic-rich sections, deep burial of basinal sections to enhance the generation of higher gravity oils, and complex folding and faulting. The Eel River basin is more clastic-rich in its gas-producing, onshore extension. Key questions in the Eel River basin include whether the offshore, more distal stratigraphy will include Monterey-like biogenic sediments, and whether the basin has oil potential in addition to its proven gas potential. The Outer Santa Cruz basin shares a similar stratigraphy, structure, and hydrocarbon potential with the Point Arena basin. The Santa Cruz-Bodega basin, also with a similar stratigraphy, may have less exploration potential because erosion has thinned the Monterey section in parts of the basin.

  14. Dynamic reorganization of river basins.

    PubMed

    Willett, Sean D; McCoy, Scott W; Perron, J Taylor; Goren, Liran; Chen, Chia-Yu

    2014-03-01

    River networks evolve as migrating drainage divides reshape river basins and change network topology by capture of river channels. We demonstrate that a characteristic metric of river network geometry gauges the horizontal motion of drainage divides. Assessing this metric throughout a landscape maps the dynamic states of entire river networks, revealing diverse conditions: Drainage divides in the Loess Plateau of China appear stationary; the young topography of Taiwan has migrating divides driving adjustment of major basins; and rivers draining the ancient landscape of the southeastern United States are reorganizing in response to escarpment retreat and coastal advance. The ability to measure the dynamic reorganization of river basins presents opportunities to examine landscape-scale interactions among tectonics, erosion, and ecology. PMID:24604204

  15. Testing for Basins of Wada

    PubMed Central

    Daza, Alvar; Wagemakers, Alexandre; Sanjuán, Miguel A. F.; Yorke, James A.

    2015-01-01

    Nonlinear systems often give rise to fractal boundaries in phase space, hindering predictability. When a single boundary separates three or more different basins of attraction, we say that the set of basins has theWada property and initial conditions near that boundary are even more unpredictable. Many physical systems of interest with this topological property appear in the literature. However, so far the only approach to study Wada basins has been restricted to two-dimensional phase spaces. Here we report a simple algorithm whose purpose is to look for the Wada property in a given dynamical system. Another benefit of this procedure is the possibility to classify and study intermediate situations known as partially Wada boundaries. PMID:26553444

  16. Testing for Basins of Wada

    NASA Astrophysics Data System (ADS)

    Daza, Alvar; Wagemakers, Alexandre; Sanjuán, Miguel A. F.; Yorke, James A.

    2015-11-01

    Nonlinear systems often give rise to fractal boundaries in phase space, hindering predictability. When a single boundary separates three or more different basins of attraction, we say that the set of basins has theWada property and initial conditions near that boundary are even more unpredictable. Many physical systems of interest with this topological property appear in the literature. However, so far the only approach to study Wada basins has been restricted to two-dimensional phase spaces. Here we report a simple algorithm whose purpose is to look for the Wada property in a given dynamical system. Another benefit of this procedure is the possibility to classify and study intermediate situations known as partially Wada boundaries.

  17. Testing for Basins of Wada.

    PubMed

    Daza, Alvar; Wagemakers, Alexandre; Sanjun, Miguel A F; Yorke, James A

    2015-01-01

    Nonlinear systems often give rise to fractal boundaries in phase space, hindering predictability. When a single boundary separates three or more different basins of attraction, we say that the set of basins has theWada property and initial conditions near that boundary are even more unpredictable. Many physical systems of interest with this topological property appear in the literature. However, so far the only approach to study Wada basins has been restricted to two-dimensional phase spaces. Here we report a simple algorithm whose purpose is to look for the Wada property in a given dynamical system. Another benefit of this procedure is the possibility to classify and study intermediate situations known as partially Wada boundaries. PMID:26553444

  18. H-Area Seepage Basins

    SciTech Connect

    Stejskal, G.

    1990-12-01

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

  19. Origin of the earth's ocean basins

    NASA Technical Reports Server (NTRS)

    Frex, H.

    1977-01-01

    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.

  20. Caribbean basin framework, 4: Maracaibo basin, northwestern Venezuela

    SciTech Connect

    Lugo, J. )

    1991-03-01

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

  1. The Anadarko: Two basins, not one

    SciTech Connect

    Evans, J.L.

    1995-09-01

    Located at the core of the Sooner Trend on the northeast shelf of the Anadarko Basin is the Enid Embayment. Using regional mapping and production trends it is possible to expand the idea of an Enid Embayment to a concept of two basins, a northern shallow basin and the main basin to the south. From a terminology point of view, it would also be appropriate to map a single basin with a northwest trending arch cutting across the shelf of that basin. The evidence for this concept is most pronounced in the Pennsylvanian producing trends by can also be inferred as early as Siluro-Devonian Hunton time. There also clearly exists the presence of a through going linear on the Landsat interpreted data suggesting the existence of a deep seated, basement fault system underlying the arch which separates the two basin axes. Shoreline trends in the northern basin are very pronounced because the basin was very shallow, and the shelf edges were very low dip. Therefore, small changes in sea level caused large movements in shoreline locations. The mapping of shoreline locations through time in the shallow basin can produce a better understanding of shoreline deposits in the deep basin and assist in the understanding of producing fairways and their potential extensions. Although the concept is not new, the recognition and interpretation of two basin concept can be of assistance in exploring for, and finding, the more elusive fields that remain in this mature area.

  2. 33 CFR 401.48 - Turning basins.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    .... 1Opposite Brossard. (b) Turning Basin No. 2Between Lock 7 and the Guard Gate Cut for vessels up to... vessels up to 107 m in overall length. (b) Turning Basin No. 2Between Lock 7 and the Guard Gate Cut for...). (d) Turning Basin No. 4North of Lock No. 8 for vessels up to 170 m in overall length. (e)...

  3. 33 CFR 401.48 - Turning basins.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    .... 1Opposite Brossard. (b) Turning Basin No. 2Between Lock 7 and the Guard Gate Cut for vessels up to... vessels up to 107 m in overall length. (b) Turning Basin No. 2Between Lock 7 and the Guard Gate Cut for...). (d) Turning Basin No. 4North of Lock No. 8 for vessels up to 170 m in overall length. (e)...

  4. 33 CFR 401.48 - Turning basins.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    .... 1Opposite Brossard. (b) Turning Basin No. 2Between Lock 7 and the Guard Gate Cut for vessels up to... vessels up to 107 m in overall length. (b) Turning Basin No. 2Between Lock 7 and the Guard Gate Cut for...). (d) Turning Basin No. 4North of Lock No. 8 for vessels up to 170 m in overall length. (e)...

  5. 33 CFR 401.48 - Turning basins.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    .... 1Opposite Brossard. (b) Turning Basin No. 2Between Lock 7 and the Guard Gate Cut for vessels up to... vessels up to 107 m in overall length. (b) Turning Basin No. 2Between Lock 7 and the Guard Gate Cut for...). (d) Turning Basin No. 4North of Lock No. 8 for vessels up to 170 m in overall length. (e)...

  6. 33 CFR 401.48 - Turning basins.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    .... 1Opposite Brossard. (b) Turning Basin No. 2Between Lock 7 and the Guard Gate Cut for vessels up to... vessels up to 107 m in overall length. (b) Turning Basin No. 2Between Lock 7 and the Guard Gate Cut for...). (d) Turning Basin No. 4North of Lock No. 8 for vessels up to 170 m in overall length. (e)...

  7. Supplementary information on K-Basin sludges

    SciTech Connect

    MAKENAS, B.J.

    1999-03-15

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

  8. 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...

  9. 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...

  10. Hydrocarbon prospectivity and classification of extensional basins

    SciTech Connect

    Harris, C.; Goodman, E.D.

    1994-12-31

    Based on studies of 125 basins, the authors subdivide extensional basins into four classes: (1) core complex (e.g., Betic basin), (2) organic collapse (Newark basin), (3) narrow rift (Gulf of Suez), and (4) wide rift (Viking Graben). The hydrocarbon potential of core complex and orogenic collapse basins generally is poor, while that of narrow- and wide-rift basins can be fair to excellent. Narrow-rift and wide-rift basins are more hydrocarbon prone because multiphase extension and thermal subsidence improve source, reservoir, and trap potential and lead to favorable maturation-migration histories. A generalized pattern of evolution leads from basins formed on overthickened crust (>45 km, core complex and orogenic collapse basins) to those formed on normal thickness crust. Core complex and orogenic collapse basins that are generated by simple shear commonly owe their internal geometry and low-angle fault dips to structures formed during compression or duplication of continental crust. Extension on low-angle faults occurs within 50 m.y. of the last compressional event and is attributed to isostatic and gravitational instabilities. Either these early faults are reactivated, or new faults supersede and over-print existing structures. Narrow- and wide-rift basins develop on crust <40 km thick, with the average to elevated regional heat flow. Their formation postdates by >50 m.y. any previous crustal thickening. High-angle normal faults are prevalent in narrow- and wide-rift basins.

  11. K Basins Groundwater Monitoring Task, K Basins Closure Project: Report for July, August, and September 2006

    SciTech Connect

    Peterson, Robert E.

    2006-12-08

    This report provides information on groundwater monitoring at the K Basins during July, August, and September 2006. Conditions remain very similar to those reported in the previous quarterly report, with no evidence in monitoring results to suggest groundwater impact from current loss of basin water to the ground. The K Basins monitoring network will be modified in the coming quarters as a consequence of remedial action at KE Basin, i.e., removal of sludge and basin demolition.

  12. Evolution of the Congo Basin

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    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 Muse 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.

  13. BASIN: Beowulf Analysis Symbolic INterface

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    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.

  14. 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)

    Pound, K. S.

    2013-12-01

    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 mlange-dominated slice (Balloon Mlange). 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.

  15. 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)

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

    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- terozoc 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 Proterozoc basement structures.

  16. 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)

    Dabard, Marie-Pierre; Loi, Alfredo

    2012-08-01

    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.

  17. Tectonic development of Michigan basin

    SciTech Connect

    Prouty, C.E.

    1986-08-01

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

  18. A paleomagnetic study of Permian and Triassic rocks from the Toulon-Cuers Basin, SE France: Evidence for intra-Pangea block rotations in the Permian

    NASA Astrophysics Data System (ADS)

    Aubele, K.; Bachtadse, V.; Muttoni, G.; Ronchi, A.; Durand, M.

    2012-06-01

    The identification of a massive shear zone separating Gondwana from Laurasia during late Palaeozoic times is one of the prerequisites for the controversial Pangea B to A transition. Here we present new paleomagnetic data from Permian and Triassic sediments and volcanic rocks from the Toulon-Cuers basin, SE France, likely to be situated within this intra-Pangea shear zone. A total of 150 samples from 14 sites were collected in the field; 108 samples yielded reliable paleomagnetic component directions based on stepwise thermal demagnetization up to maximum temperatures of 690°C. After removal of an initial viscous magnetic component from room temperature up to 200°C, a second component of reverse polarity, oriented to the south-and-up, was identified in almost all samples of Permian age. The Triassic samples behave similarly, with the notable difference that here, two polarities of magnetization are present. Positive field tests suggest the primary character of this characteristic magnetization. The latitudes of the resulting Early to Mid Permian paleopoles agree well with the corresponding segment of the apparent polar wander path (APWP) for Europe, whereas the longitudes are strung out along a small circle segment, indicating relative rotations between the sampled regions and stable Europe. The Triassic poles, instead, plot close to the Triassic segment of the European APWP and provide an upper time limit for the observed rotations. These results suggest a wrench faulting event associated with intra-Pangea crustal instability and transformation during the Permian.

  19. Automated basin delineation from digital terrain data

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

    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.

  20. Hydrocarbon accumulations in the Tarim basin, China

    SciTech Connect

    Li Desheng; Liang Digang; Jia Chengzao; Wang Gang

    1996-10-01

    The Tarim basin is the largest and least explored inland basin in China. The areal extent of the basin reaches 560,000 km{sup 2}. The interior of the basin is mostly covered by the Takla Mekan Desert, which is about 330,000 km{sup 2} in areal extent. The basin has become the object of special attention since China set aside first- and third-round onshore bidding blocks in the Tarim basin for foreign oil firms to explore. The Tarim basin is a polyhistory superimposed basin that has experienced seven evolutionary stages: (1) Sinian-Cambrian-Ordovician aulacogen stage, (2) Silurian-Devonian intracratonic depression stage, (3) Carboniferous marginal sea stage, (4) Permian rift basin stage, (5) Triassic-Jurassic foreland basin stage, (6) Cretaceous-Paleogene NeoTethys bay stage, and (7) Neogene-Pleistocene foreland and inland basin stage. Both the basin`s Paleozoic marine platform sequences and the Mesozoic-Cenozoic terrestrial fills are believed to contain substantial volumes of hydrocarbons. After recent years of exploration, nine oil and gas fields have been proven and 23 discoveries have been made in the Tabei, Tazhong, and Southwest areas. Kekeya, Lunnan, Sangtamu, Jiefangqudong, Donghetang, and Tazhong 4 oil fields have been put into production. Output of crude oil was 2.6 million t (metric tons) (52,000 BOPD) in 1995. The production will increase to 5 million t (100,000 BOPD) in 1997. Giant oil and gas traps probably will be discovered in the Tarim basin. The prospect is promising.

  1. Permian geology of Gondwana countries: An overview

    SciTech Connect

    Dickins, J.M. )

    1992-10-01

    Earliest Permian sequences of Antarctica, southern and east-central Africa, the southern part of the Arabian Peninsula, Pakistan, peninsular and Himalayan India, Tibet, western and eastern Australia, New Zealand, and South America are all characterized by glacial deposits and cold-water marine faunas. In the course of the Permian, considerable faunal (and floral) and climatic divergence occurred. Although folding is not necessarily present, the effects of the strong compressive tectonic phase (Hunter-Bowen Orogenic Folding Phase of Dickins) beginning in the mid-Permian (traditional two-fold subdivision) and of acidic and intermediate volcano-magmatic activity are apparent in all these regions as in other parts of the world. The progressive continentality of the Upper Permian (worldwide regression) culminates at the Permian-Triassic (Changxingian-Griesbachian) boundary.

  2. THE ADVANCED CHEMISTRY BASINS PROJECT

    SciTech Connect

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

    2004-04-05

    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.

  3. Formation of lunar basin rings

    USGS Publications Warehouse

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

    1978-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  5. CLEAR LAKE BASIN 2000 PROJECT

    SciTech Connect

    LAKE COUNTY SANITATION DISTRICT

    2003-03-31

    The following is a final report for the Clear Lake Basin 2000 project. All of the major project construction work was complete and this phase generally included final details and testing. Most of the work was electrical. Erosion control activities were underway to prepare for the rainy season. System testing including pump stations, electrical and computer control systems was conducted. Most of the project focus from November onward was completing punch list items.

  6. Biogeochemistry of a Suburban Basin

    NASA Astrophysics Data System (ADS)

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

    2002-12-01

    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.

  7. Basin stability in delayed dynamics

    NASA Astrophysics Data System (ADS)

    Leng, Siyang; Lin, Wei; Kurths, Jürgen

    2016-02-01

    Basin stability (BS) is a universal concept for complex systems studies, which focuses on the volume of the basin of attraction instead of the traditional linearization-based approach. It has a lot of applications in real-world systems especially in dynamical systems with a phenomenon of multi-stability, which is even more ubiquitous in delayed dynamics such as the firing neurons, the climatological processes, and the power grids. Due to the infinite dimensional property of the space for the initial values, how to properly define the basin’s volume for delayed dynamics remains a fundamental problem. We propose here a technique which projects the infinite dimensional initial state space to a finite-dimensional Euclidean space by expanding the initial function along with different orthogonal or nonorthogonal basis. A generalized concept of basin’s volume in delayed dynamics and a highly practicable calculating algorithm with a cross-validation procedure are provided to numerically estimate the basin of attraction in delayed dynamics. We show potential applicabilities of this approach by applying it to study several representative systems of biological or/and physical significance, including the delayed Hopfield neuronal model with multistability and delayed complex networks with synchronization dynamics.

  8. Basin stability in delayed dynamics

    PubMed Central

    Leng, Siyang; Lin, Wei; Kurths, Jürgen

    2016-01-01

    Basin stability (BS) is a universal concept for complex systems studies, which focuses on the volume of the basin of attraction instead of the traditional linearization-based approach. It has a lot of applications in real-world systems especially in dynamical systems with a phenomenon of multi-stability, which is even more ubiquitous in delayed dynamics such as the firing neurons, the climatological processes, and the power grids. Due to the infinite dimensional property of the space for the initial values, how to properly define the basin’s volume for delayed dynamics remains a fundamental problem. We propose here a technique which projects the infinite dimensional initial state space to a finite-dimensional Euclidean space by expanding the initial function along with different orthogonal or nonorthogonal basis. A generalized concept of basin’s volume in delayed dynamics and a highly practicable calculating algorithm with a cross-validation procedure are provided to numerically estimate the basin of attraction in delayed dynamics. We show potential applicabilities of this approach by applying it to study several representative systems of biological or/and physical significance, including the delayed Hopfield neuronal model with multistability and delayed complex networks with synchronization dynamics. PMID:26907568

  9. Tectonic mechanisms for formation of the Central Basin platform and adjacent basinal areas, Permian basin, Texas and New Mexico

    SciTech Connect

    Yang, Kennming; Dorobek, S.L. )

    1992-04-01

    Formation of the Central Basin platform (CBP), with the Delaware basin to its west and the Midland basin to its east, has been attributed to the crustal deformation in the foreland area of the Marathon Orogen during the late Paleozoic. Because of complexities in the areal distribution and magnitudes of uplift along the length of the CBP, its formative mechanisms are still controversial. Previous interpretations about the mechanisms for uplift of the CBP are based on the characteristics of the boundary faults between the CBP and adjacent basinal areas. Here, an integrated tectonic model is proposed for formation of the uplift and adjacent basins based on studies of the structure of sedimentary layers overlying Precambrian basement rocks of the uplift and restoration of the lower Paleozoic strata in the Delaware basin.

  10. Magnetostratigraphic constraints on the age of the lower Beaufort Group, western Karoo basin, South Africa, and a critical analysis of existing U-Pb geochronological data

    NASA Astrophysics Data System (ADS)

    Tohver, E.; Lanci, L.; Wilson, A.; Hansma, J.; Flint, S.

    2015-10-01

    We studied three partially overlapping sections with a composite thickness of ˜600 m in the upper Permian fluvial siltstones and fine-grained sandstones of the Abrahamskraal Formation, the basal unit of the Beaufort Group, in the Karoo Basin of Western Cape Province, South Africa. Paleomagnetic analysis reveals three components of Natural Remanent Magnetization (NRM). Heating to ˜180°C removes a remanent magnetization parallel to the present-day field, which is interpreted as a viscous overprint. An intermediate unblocking temperature component is removed by heating to 450°C; this direction is always of normal polarity and is identical to a regional overprint imparted during the Early Jurassic emplacement of the Karoo Large Igneous Province. A high-temperature component isolated above 450°C is of dual polarity and is interpreted as primary on the basis of a positive reversals test. The virtual geomagnetic pole position for the Abrahamskraal Formation computed from the average high-temperature characteristic remanent magnetization direction is in agreement with the late Permian directions for stable Gondwana and with previous results from the lowermost Abrahamskraal Formation and Waterford Formation at the Ouberg Pass section. The predominantly normal polarity of this magnetization is in agreement with either a middle-late Lopingian age (ca. 254-256 Ma) or a late Guadalupian age (ca. 262 Ma) according to the global geomagnetic polarity time scale. We integrate these new results with existing magnetostratigraphic, biostratigraphic, and geochronological results from the Karoo Basin, with particular emphasis on the controversy over zircon age data reported from the underlying Ecca Group.

  11. Palaeobotanical evidence of wildfires in the Late Palaeozoic of South America - Early Permian, Rio Bonito Formation, Paraná Basin, Rio Grande do Sul, Brazil

    NASA Astrophysics Data System (ADS)

    Jasper, André; Uhl, Dieter; Guerra-Sommer, Margot; Mosbrugger, Volker

    2008-12-01

    Fossil charcoal, as direct evidence of palaeowildfires, has repeatedly been reported from several plant-bearing deposits from the Late Palaeozoic of the Northern Hemisphere. In contrast charcoal reports from the Late Palaeozoic deposits of the Southern Hemisphere are relatively rare in comparison to the Northern Hemisphere. Although the presence of pyrogenic coal macerals has repeatedly been reported from Late Palaeozoic coals from South America, no detailed anatomical investigations of such material have been published so far. Here is presented an anatomical analysis of charcoal originating from Early Permian sediments of the Quitéria Outcrop, Rio Bonito Formation, Paraná Basin, located in the central-eastern portion of Rio Grande do Sul, Brazil. This charcoal comes from two different coaly facies, and it was possible to scrutinize between three types, based on anatomical characters of the charcoal. Two of these charcoal types can be correlated to gymnosperm woods, and the other type corresponds to strongly permineralized bark with characteristic features of lycopsids. The presence of charcoal in different facies, ranging from parautochtonous to allochtonous origin, indicates that different vegetation types, i.e. plants which grew under wet conditions in the lowland as well as in the more dry hinterland, have experienced wildfires. Taking into account previous petrographic and lithological analyses from the facies in which the charcoal occurs and from the conditions of the wood and bark fragments, it was possible to speculate that the intensity of such wildfires most probably corresponds to forest-crown fires. Moreover, it is possible to state that wildfires have been a more or less common element in distinct Late Palaeozoic terrestrial ecosystems in the South American part of Gondwana. The data support previous assumptions on the occurrence of wildfires in the Early Permian of the Paraná Basin which were based solely on coal-petrographic data.

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

    PubMed

    Rogers; Hartman; Krause

    2000-05-01

    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

  13. Biological science in the Great Basin

    USGS Publications Warehouse

    U.S. Geological Survey

    2005-01-01

    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.

  14. Strange nonchaotic attractors with Wada basins

    NASA Astrophysics Data System (ADS)

    Zhang, Yongxiang

    2013-09-01

    We demonstrate strange nonchaotic attractors with Wada basins (SNAsWB), and verify the abundance of SNAsWB in a quasiperiodically forced Holmes map. We identify the routes to the creation of the SNAsWB in a two-parameter space. The SNAsWB are characterized by the maximal Lyapunov exponent, by the estimation of the phase sensitivity exponent, and by the singular-continuous spectra. We observe that the SNAs basins are totally Wada basins in a large range of parameters. The topological structures of the SNAs Wada basins are distinguished by the basin cell method. We investigate the underlying mechanism for the abundance of SNAsWB, which is responsible for different types of basin cell in the absence of forcing. This suggests that the SNAs cannot be predicted reliably for specific initial conditions. These SNAsWB can thus be expected to occur more commonly in dynamical systems.

  15. 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 ...

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

    SciTech Connect

    Not Available

    1993-10-01

    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.

  17. Reserve estimates in western basins. Part 2: Piceance Basin

    SciTech Connect

    1995-10-01

    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.

  18. Analysing diagenetic effects of flood basalts on sedimentary basins during Gondwanan break-up: case studies from NW Namibia.

    NASA Astrophysics Data System (ADS)

    Thompson, G. A.; Jerram, D. A.; Harris, C.; Pearson, D. G.

    2003-04-01

    ABSTRACT The eruption of large volumes of lava associated with the break-up and dispersal of the Gondwana Supercontinent is a phenomenon that has been well documented in literature. The Etendeka Flood Basalt Province of NW Namibia is correlated with the Paran Flood Basalt Province of South America and was extruded between 139Ma for the earliest flows and 130Ma for the most recent. The passive, inflated pahoehoe lava flows have preserved bedforms within sand dunes found in the Huab Basin without significant deformation. This allows the internal structures of the palaeo-dunes to be analysed with great accuracy; a phenomenon rarely seen within the geological record. The sediments directly beneath, and interbedded with, the Etendeka Flood Basalt are lithostratigraphically similar to those in the Kudu Gas Province, offshore Namibia, where gas-bearing aeolian sands are interspersed with lava flows. Research by the authors is focussed on the diagenetic effects, both direct and indirect, of the emplacement of the lava, and the associated sills and dykes, on the aeolian sands. Specific interests include: the compartmentalisation of the basin by sills/dykes/lava: how does this affect fluid flow paths? Diagenesis along hot contacts: is the dramatic reduction in porosity/permeability along such contacts the result of the igneous bodies alone or do they need ground water present? Can large igneous events trigger the movement of hot fluids through the basin and to what extent does this cause alteration to sediments? To address these issues we have identified a number of outcrop case studies within the Huab Basin in NW Namibia. Here, excellent 3 dimensional outcrop coupled with almost 100 percent exposure allows detailed sampling strategies to be employed on locations of interest. In some cases igneous dykes have acted as flow barriers to pore fluids and have therefore altered the type and degree of cementation either side of the dyke. Geochemical analysis of the cement can shed some light on the origin of the associated fluids and determine whether hot fluids have been triggered by the lava. The systematic burial of aeolian landforms by pahoehoe lava flows has preserved the original features in many of the dunes and has created ponds of lava in inter-dune areas. Suites of samples collected from the igneous contact have been analysed to assess the extent of diagenesis related, either directly or indirectly, to the lava eruption. The sandstone is shown to be well-cemented in an indurated zone (visually 1-2m wide) beside the contact but less well-cemented with distance from it. The degree of porosity change away from the contact has been measured using image analysis software on stained thin sections and the chemistry of pore-filling cement analysed using laser microsampling and spectroscopic analysis. Normalised del.18O values decrease steadily from values of 15.6 (+/- 0.2)percent at the contact to 14.4 (+/- 0.2)percent at a distance of 4m from it. The sediments from the Etendeka in NW Namibia provide examples of intrusion and lava contacts in an essentially dry basin setting. This allows the investigation of the direct effect of the igneous bodies on the sediments without massive overprinting due to further diagenesis caused by ground water. In the few areas where later groundwater fluids have entered the basin we are able to successfully compare the direct with indirect effects of the igneous rocks. ACKNOWLEDGEMENTS This research is part of a PhD thesis currently being undertaken by Graham Thompson under the supervision of Dr. Dougal Jerram and Dr. Graham Pearson. The research is funded by Enterprise Oil / Shell (UK). I acknowledge with gratitude Dr. Chris Harris and his colleagues at the University of Cape Town who provided oxygen isotope data for a number of samples.

  19. Late Paleozoic structural evolution of Permian basin

    SciTech Connect

    Ewing, T.E.

    1984-04-01

    The southern Permian basin is underlain by the NNW-trending Central Basin disturbed belt of Wolfcamp age (Lower Permian), the deep Delaware basin to its west, and the shallower Midland basin to its eat. The disturbed belt is highly segmented with zones of left-lateral offset. Major segments from south to north are: the Puckett-Grey Ranch zone; the Fort Stockton uplift; the Monahans transverse zone; the Andector ridges and the Eunice ridge; the Hobbs transverse zone; and the Tatum ridges, which abut the broad Roosevelt uplift to the north. The disturbed belt may have originated along rift zones of either Precambrian or Cambrian age. The extent of Lower and Middle Pennsylvanian deformation is unclear; much of the Val Verde basin-Ozona arch structure may have formed then. The main Wolfcamp deformation over thrust the West Texas crustal block against the Delaware block, with local denudation of the uplifted edge and eastward-directed backthrusting into the Midland basin. Latter in the Permian, the area was the center of a subcontinental bowl of subsidence - the Permian basin proper. The disturbed belt formed a pedestal for the carbonate accumulations which created the Central Basin platform. The major pre-Permian reservoirs of the Permian basin lie in large structural and unconformity-bounded traps on uplift ridges and domes. Further work on the regional structural style may help to predict fracture trends, to assess the timing of oil migration, and to evaluate intrareservoir variations in the overlying Permian giant oil fields.

  20. Regional geophysics and the basement of cratonic basins: a comparative study with the Michigan basin

    SciTech Connect

    Hinze, W.J.; Lidiak, E.G.

    1986-08-01

    The basement of the Michigan basin consists of four major provinces - the complex metasedimentary, metavolcanic, and igneous rocks of the Penokean orogenic assemblage in the north, the felsic anorogenic igneous rocks to the south, the highly metamorphosed schists, gneisses, and related igneous intrusions of the Grenville province in the east, and a middle Proterozoic rift zone, which transects the basin from the north to the southeast margin. Sparse basement drill holes and characteristic geophysical patterns support this interpretation. The direct geologic information on the basement of other cratonic basins is not as well known. However, regional geophysical surveys and sparse, poorly distributed basement drill holes provide information on the complex character and structural relationships of the basement of other basins. Like the Michigan basin, many cratonic basins (e.g., Illinois, Williston, and Paris basins) are underlain by dense and commonly more magnetic rocks than adjacent areas. As in the Michigan basin, these rocks are interpreted to have a profound effect on the origin and tectonic development of the basins. Geologic and geophysical evidence indicates that many of these dense basement rocks originated in rifts that formed hundreds of millions of years prior to basin development. A comparison of the basement in cratonic basins provides important constraints on the origin and tectonic development of the Michigan basin.

  1. Fault kinematics and depocenter evolution of oil-bearing, continental successions of the Mina del Carmen Formation (Albian) in the Golfo San Jorge basin, Argentina

    NASA Astrophysics Data System (ADS)

    Paredes, José Matildo; Plazibat, Silvana; Crovetto, Carolina; Stein, Julián; Cayo, Eric; Schiuma, Ariel

    2013-10-01

    Up to 10% of the liquid hydrocarbons of the Golfo San Jorge basin come from the Mina del Carmen Formation (Albian), an ash-dominated fluvial succession preserved in a variably integrated channel network that evolved coeval to an extensional tectonic event, poorly analyzed up to date. Fault orientation, throw distribution and kinematics of fault populations affecting the Mina del Carmen Formation were investigated using a 3D seismic dataset in the Cerro Dragón field (Eastern Sector of the Golfo San Jorge basin). Thickness maps of the seismic sub-units that integrate the Mina del Carmen Formation, named MEC-A-MEC-C in ascending order, and mapping of fluvial channels performed applying geophysical tools of visualization were integrated to the kinematical analysis of 20 main normal faults of the field. The study provides examples of changes in fault throw patterns with time, associated with faults of different orientations. The "main synrift phase" is characterized by NE-SW striking (mean Az = 49°), basement-involved normal faults that attains its maximum throw on top of the volcanic basement; this set of faults was active during deposition of the Las Heras Group and Pozo D-129 formation. A "second synrift phase" is recognized by E-W striking normal faults (mean Az = 91°) that nucleated and propagated from the Albian Mina del Carmen Formation. Fault activity was localized during deposition of the MEC-A sub-unit, but generalized during deposition of MEC-B sub-unit, producing centripetal and partially isolated depocenters. Upward decreasing in fault activity is inferred by more gradual thickness variation of MEC-C and the overlying Lower Member of Bajo Barreal Formation, evidencing passive infilling of relief associated to fault boundaries, and conformation of wider depocenters with well integrated networks of channels of larger dimensions but random orientation. Lately, the Mina del Carmen Formation was affected by the downward propagation of E-W to ESE-WNW striking normal faults (mean Az = 98°) formed during the "third rifting phase", which occurs coeval with the deposition of the Upper Member of the Bajo Barreal Formation. The fault characteristics indicate a counterclockwise rotation of the stress field during the deposition of the Chubut Group of the Golfo San Jorge basin, likely associated to the rotation of Southern South America during the fragmentation of the Gondwana paleocontinent. Understanding the evolution of fault-controlled topography in continental basins allow to infer location and orientation of coeval fluvial systems, providing a more reliable scenario for location of producing oil wells.

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

    USGS Publications Warehouse

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

    1997-01-01

    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.

  3. Delaware Basin Monitoring Annual Report

    SciTech Connect

    Washington Regulatory and Environmental Services; Washington TRU Solutions LLC

    2001-09-28

    The Delaware Basin Drilling Surveillance Program (DBDSP) is designed to monitor drilling activities in the vicinity of the Waste Isolation Pilot Plant (WIPP). This program is based on Environmental Protection Agency (EPA) requirements. EPA requires the Department of Energy (DOE) to demonstrate the expected performance of the disposal system using a probabilistic risk assessment or performance assessment (PA). This PA must show that the expected repository performance will not release radioactive material above limits set by the EPA's standard and must consider inadvertent drilling into the repository at some future time.

  4. Free energy basin-hopping

    NASA Astrophysics Data System (ADS)

    Sutherland-Cash, K. H.; Wales, D. J.; Chakrabarti, D.

    2015-04-01

    A global optimisation scheme is presented using basin-hopping with the acceptance criterion based on approximate free energy for the corresponding local minima of the potential energy. The method is illustrated for atomic and colloidal clusters and peptides to examine how the predicted global free energy minimum changes with temperature. Using estimates for the local free energies based on harmonic vibrational densities of states provides a computationally effective framework for predicting trends in structure at finite temperature. The resulting scheme represents a powerful tool for exploration of energy landscapes throughout molecular science.

  5. The Effects of Basin Formation on the Lunar Geochemical Terranes

    NASA Astrophysics Data System (ADS)

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

    2006-03-01

    Investigation of the basin history of lunar geochemical terranes reveals added differences between the near and farside.The FHT and SPAT cover areas that received little post-SPA basin modification, while the PKT was significantly modified by basins.

  6. Structure and Morphology of the Multiring Lunar Basins

    NASA Astrophysics Data System (ADS)

    Pugacheva, S. G.; Shevchenko, V. V.; Chikmachev, V. I.

    The morphological features of the multiring lunar basins are considered. The common characteristics of the multiring basins were researched. The South Pole-Aitken Basin (SPA) represents a compositionally and topographically unique lunar formation.

  7. Stratigraphic Signatures of Forearc Basin Formation Mechanisms

    NASA Astrophysics Data System (ADS)

    Mannu, U.; Ueda, K.; Gerya, T.; Willett, S.; Strasser, M.

    2014-12-01

    Forearc basins are loci of active sedimentation above the landward portion of accretionary prisms. Although these basins typically remain separated from the frontal prism by a forearc high, their evolution has a significant impact on the structure and deformation of the entire wedge. Formation of forearc basins has been proposed as a consequence of changes in wedge stability due to an increase of slab dip in subduction zones. Another hypothesis attributes this to higher hinterland sedimentation, which causes the rear of the wedge to stabilize and eventually develop a forearc basin. Basin stratigraphic architecture, revealed by high-resolution reflection seismic data and borehole data allows interpretation of structural development of the accretionary prism and associated basins with the goal of determining the underlying driving mechanism(s) of basin formation. In this study we supplement data interpretation with thermo-mechanical numerical models including high-resolution isochronal surface tracking to visualize the developing stratigraphy of basins that develop in subduction zone and wedge dynamic models. We use a dynamic 2D thermo mechanical model incorporating surface processes, strain weakening and sediment subduction. The model is a modification of I2VIS model, which is based on conservative, fully staggered finite differences and a non-diffusive marker- in-cell technique capable of modelling mantle convection. In the model different driving mechanisms for basin formation can be explored. Stratigraphic simulations obtained by isochronal surface tracking are compared to reflection pattern and stratigraphy of seismic and borehole data, respectively. Initial results from a model roughly representing the Nankai Trough Subduction Zone offshore Japan are compared to available seismic and Integrated Ocean Drilling (IODP) data. A calibrated model predicting forearc basin stratigraphy will be used to discern the underlying process of basins formation and wedge dynamics.

  8. Cenozoic evolution of San Joaquin basin, California

    SciTech Connect

    Bartow, J.A.

    1988-03-01

    The Neogene San Joaquin basin in the southern part of the 700-km long Great Valley of California is a successor to a late Mesozoic and earliest Tertiary forearc basin. The transition from forearc basin to the more restricted Neogene marine basin occurred principally during the Paleogene as the plate tectonic setting changed from oblique convergence to normal convergence, and finally to the initiation of tangential (transform) movement near the end of the Oligocene. Regional-scale tectonic events that affected the basin include: (1) clockwise rotation of the southernmost Sierra Nevada, and large-scale en echelon folding in the southern Diablo Range, both perhaps related to Late Cretaceous and early Tertiary right slip on the proto-San-Andreas fault; (2) regional uplift of southern California in the Oligocene that resulted from the subduction of the Pacific-Farallon spreading ridge: (3) extensional tectonism in the Basin and Range province, particularly in the Miocene; (4) wrench tectonism adjacent to the San Andreas fault in the Neogene; (5) northeastward emplacement of a wedge of the Franciscan complex at the west side of the Sierran block, with associated deep-seated thrusting in the late Cenozoic; and (6) the accelerated uplift of the Sierra Nevada beginning in the late Miocene. Neogene basin history was controlled principally by the tectonic effects of the northwestward migration of the Mendocino triple junction along the California continental margin and by the subsequent wrench tectonism associated with the San Andreas fault system. East-west compression in the basin, resulting from extension in the Basin and Range province was an important contributing factor to crustal shortening at the west side of the valley. Analysis of the sedimentary history of the basin, which was controlled to some extent by eustatic sea level change, enables reconstruction of the basin paleogeography through the Cenozoic.

  9. Basin-scale relations via conditioning

    USGS Publications Warehouse

    Troutman, B.M.; Karlinger, M.R.; Guertin, D.P.

    1989-01-01

    A rainfall-runoff model is used in conjunction with a probabilistic description of the input to this model to obtain simple regression-like relations for basin runoff in terms of basin and storm characteristics. These relations, similar to those sought in regionalization studies, are computed by evaluating the conditional distribution of model output given basin and storm characteristics. This method of conditioning provides a general way of examining model sensitivity to various components of model input. The resulting relations may be expected to resemble corresponding relations obtained by regionalization using actual runoff to the extent that the rainfall-runoff model and the model input specification are physically realistic. The probabilistic description of model input is an extension of so-called "random-model" of channel networks and involves postulating an ensemble of basins and associated probability distributions that mimic the variability of basin characteristics seen in nature. Application is made to small basins in the State of Wyoming. Parameters of the input variable distribution are estimated using data from Wyoming, and basin-scale relations are estimated both, parametrically and nonparametrically using model-generated runoff from simulated basins. Resulting basin-scale relations involving annual flood quantiles are in reasonable agreement with those presented in a previous regionalization study, but error estimates are smaller than those in the previous study, an artifact of the simplicity of the rainfall-runoff model used in this paper. We also obtain relations for peak of the instantaneous unit hydrograph which agree fairly well with theoretical relations given in the literature. Finally, we explore the issues of sensitivity of basin-scale, relations and error estimates to parameterization of the model input probability distribution and of how this sensitivity is related to making inferences about a particular ungaged basin. ?? 1989 Springer-Verlag.

  10. Morphometric Analysis of Martian Valley Network Basins

    NASA Astrophysics Data System (ADS)

    Luo, W.; Arvidson, R. E.; Howard, A. D.

    2005-05-01

    Whether the Martian valley networks were formed predominantly by groundwater sapping or surface fluvial runoff continues to be debated and has profoundly different implications for the climatic history of Mars and the possible evolution of life there. This paper attempts to evaluate the relative role of groundwater sapping vs. surface runoff in valley networks generation through quantitative morphometic analysis at watershed basin scale using the highest resolution MOLA DEM data. Treating the hypsometric curve of each basin as a cumulative probability distribution, its integral, skewness, kurtosis, density skewness, and density kurtosis (collectively called hypsometric attributes) can serve as quantitative measures of the basin's morphology. The hypsometric attributes are sensitive to variations in overall basin characteristics and thus are diagnostic of possible processes. These attributes of typical terrestrial sapping basins, typical terrestrial fluvial basins, and typical lunar impact cratering basins were used as endmembers to establish discriminant functions to classify Martian basins. The posteriori probability of each class membership for each Martian basin then serves as the measure of the relative role of sapping, fluvial or cratering process in forming that basin. Initial results in Margaritifer Sinus area show that groundwater sapping played a more dominant role than surface runoff, generally consistent with previous findings based on lower resolution data and supporting a precipitation-recharged groundwater sapping origin for valley networks. Using a circularity function (a ratio of area and perimeter as a function of elevation) as the measure for basin morphology in the discriminant analysis produced similar results. Other traditional morphometric parameters such as drainage density, width function, cumulative area distribution, and slope-area relationship will also be derived for Margaritifer and other areas. The overall spatial pattern of the distribution will be examined to shed more light on past climatic conditions for generating the Martian valley networks.

  11. The record of India-Asia collision preserved in Tethyan ocean basin sediments.

    NASA Astrophysics Data System (ADS)

    Najman, Yani; Jenks, Dan; Godin, Laurent; Boudagher-Fadel, Marcelle; Bown, Paul; Horstwood, Matt; Garzanti, Eduardo; Bracialli, Laura; Millar, Ian

    2015-04-01

    The timing of India-Asia collision is critical to the understanding of crustal deformation processes, since, for example, it impacts on calculations regarding the amount of convergence that needs to be accommodated by various mechanisms. In this research we use sediments originally deposited in the Tethyan ocean basin and now preserved in the Himalayan orogeny to constrain the timing of collision. In the NW Himalaya, a number of workers have proposed a ca 55-50 Ma age for collision along the Indus suture zone which separates India from the Kohistan-Ladakh Intraoceanic Island arc (KLA) to the north. This is based on a number of factors including the age of youngest marine sediments in the Indus suture (e.g. Green et al. 2008), age of eclogites indicative of onset of Indian continental subduction (e.g. de Sigoyer et al. 2000), and first evidence of detritus from north of the suture zone deposited on the Indian plate (e.g. Clift et al. 2002). Such evidence can be interpreted as documenting the age of India-Asia collision if one takes the KLA to have collided with the Asian plate prior to its collision with India (e.g. Petterson 2010 and refs therein). However, an increasing number of workers propose that the KLA collided with Asia subsequent to its earlier collision with India, dated variously at 85 Ma (Chatterjee et al. 2013), 61 Ma (Khan et al. 2009) and 50 Ma (Bouilhol et al. 2013). This, plus the questioning of earlier provenance work (Clift et al. 2002) regarding the validity of their data for constraining timing of earliest arrival of material north of the suture deposited on the Indian plate (Henderson et al. 2011) suggests that the time is right for a reappraisal of this topic. We use a provenance-based approach here, using combined U-Pb and Hf on detrital zircons from Tethyan ocean basin sediments, along with petrography and biostratigraphy, to identify first arrival of material from north of the Indian plate to arrive on the Indian continent, to constrain the time of collision. With the recent discovery that the Indus Group sediments in the suture zone cannot be used for this purpose as previously proposed (Henderson et al. 2011) we turn to the 54 Ma Kong and Chulung La Formation youngest Tethyan sediments on the Indian margin (Garzanti et al. 1987) to investigate whether we can identify such material, and whether it be Spong arc (Fuchs and Willems 1990), KLA or Trans-Himalayan derived, thus determining what collided with India and when. References Bouilhol P, Jagoutz O, Hanchar JM, Dudas FO. 2013. Dating the India-Eurasia collision through arc magmatic records. Earth and Planetary Science Letters 366, 163-175. Chatterjee S, Goswami A, Scotese CR. 2013. The longest voyage: Tectonic, magmatic, and paleoclimatic evolution of the Indian plate during its northward flight from Gondwana to Asia. Gondwana Research 23, 238-267. Clift P, Carter A, Krol M, Kirby E. 2002. Constraints on India-Eurasia collision in the Arabian sea region taken from the Indus Group, Ladakh Himalaya, India. The tectonic and climatic evolution of the Arabian Sea region Geological Society of London Special Publication 195, 97-116. de Sigoyer J, Chavagnac V, Blichert-Toft J, Villa IM, Luais B, Guillot S, Cosca M, Mascle G. 2000. Dating the Indian continental subduction and collisional thickening in the northwest Himalaya: Multichronology of the Tso Morari eclogites. Geology 28, 487-490. Fuchs G, Willems H. 1990. The final stages of sedimentation in the Tethyan zone of Zanskar and their geodynamic significance (Ladakh - Himalaya). Jahrbuche Geologische Bundenstalt 133: 259-273. Garzanti E, Baud A, Mascle G. 1987. Sedimentary Record of the Northward Flight of India and Its Collision with Eurasia (Ladakh Himalaya, India). Geodinamica Acta 1, 297-312. Green OR, Searle MP, Corfield RI, Corfield RM. 2008. Cretaceous-tertiary carbonate platform evolution and the age of the India-Asia collision along the Ladakh Himalaya (northwest India). J Geol 116: 331-353. Henderson AL, Najman Y, Parrish R, Mark D, Foster GL. 2011. Constraints to the timing of India-Eurasia collision; a re-evaluation of evidence from the Indus Basin sedimentary rocks of the Indus-Tsangpo Suture Zone, Ladakh, India. Earth Science Reviews 106, 265-292. Khan SD, Walker DJ, Hall SA, Burke KC, Shah MT, Stockli L. 2009. Did the Kohistan-Ladakh island arc collide first with India? Geological Society of America Bulletin 121, 366-384. Petterson MG. 2010. A review of the geology and tectonics of the Kohistan island arc, north Pakistan. in The Evolving Continents: Understanding Processes of Continental Growth (eds. TM Kusky, M-G Zhai, W Xiao), pp. 287-327. Journal of the Geological society of London Special publication.

  12. 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...

  13. Paradox Basin: a model pull-apart basin of Pennsylvania age

    SciTech Connect

    Stevenson, G.M., Baars, D.L.

    1984-07-01

    The Paradox basin of the east-central Colorado Plateau province is an elongate, roughly rhombic salt basin of Middle Pennsylvanian age. It is bounded on the northeast by the Uncompahgre-San Luis segments of the Ancestral Rockies. J.C. Crowell's classic model of a pull-apart basin along anastomosing transform fault zones is directly applicable to the Paradox basin, with the one exception that the Paradox is an intracratonic basin developed on continental crust. As the Paradox basin episodically deepened during the Middle Pennsylvanian by rejuvenation of basement faults, it was being filled contemporaneously with salt, which may have reached a thickness of 6000-8000 ft (1800-2400 m), and arkoses of 15,000-20,000 ft (4600-6100 m) thickness along the Uncompahgre front. A pull-apart of only about 5% of extension would account for a basin of this magnitude. By about mid Desmoinesian time, the wrenching pull-apart was nearly completed. Folding caused by minor wrench movements formed shoaling conditions along the southwest shallow shelf of the basin where algal bioherms developed. Meanwhile, pull-apart stretching of the basin floor may have triggered salt flowage and diapirism in the eastern, deepest part of the basin. From the late Desmoinesian through Permian, the basin filled with marine and nonmarine sediments as the wrench tectonism subsided.

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

    USGS Publications Warehouse

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

    2001-01-01

    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.

  15. Scientific review of great basin wildfire issues

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The University Nevada Reno, College of Agriculture and Resource Concepts Inc., co-sponsored a Great Basin Wildfire Forum in September 2007 to address a “Scientific Review of the Ecological and Management History of Great Basin Natural Resources and Recommendations to Achieve Ecosystem Restoration”. ...

  16. Relation between Tethys sea and Tarim basin

    SciTech Connect

    Wei Junchao )

    1988-08-01

    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.