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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

    NASA Astrophysics Data System (ADS)

    Akhtar, A.; Kosanke, R. M.

    2000-07-01

    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.

  4. 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.

  5. 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.

  6. 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.

  7. Lower Cretaceous anoxic conditions IN the Austral basin, south-western Gondwana, Patagonia Argentina

    NASA Astrophysics Data System (ADS)

    Richiano, Sebastián

    2014-10-01

    The reconstruction of palaeo-oxygenation levels in marine deposits from the Cretaceous has obtained a huge interest all around the world in recent years. This fascinating topic is here pointed out for the first time in the Austral Basin using the information provided by the black shales of the Río Mayer Formation, Patagonia, Argentina. The combination of sedimentology, ichnology and geochemistry (TOC, Ce anomaly and MnO content) allow the identification of three major intervals respecting the oxygen content. During the Berriasian and early Valanginian anoxic conditions prevail in the outer shelf. After that, between the late Valanginian and Hauterivian dysoxic palaeoenvironments were developed. Finally, a more oxygenated palaeoenvironment occurred since Aptian associated with a progradation of a proximal deltaic system. The identification of anoxic conditions is of much interest for the hydrocarbon research in this stratigraphical unit, which represents the most significant source rock of the Austral Basin.

  8. Upper Paleozoic strata of the Chaco-Paraná basin, Argentina, and the great Gondwana glaciation

    NASA Astrophysics Data System (ADS)

    Winn, R. D.; Steinmetz, J. C.

    1998-03-01

    Late Paleozoic glaciation in the southern Chaco-Paranábasin, Argentina, is recorded in cores from the Ordoñez Formation. The upper Ordoñez Formation consists of diamictite with lesser amounts of sandstone and shale, and is up to 1600 m thick. The diamictite-bearing interval was deposited during the Potonieisporites- Lundbladispora to Cristatisporites palynozones, probably in the latest Carboniferous-Early Permian. Diamictites are red to gray, thickly bedded, very poorly sorted mixtures of clay, silt, and sand with floating pebbles up to 5 cm long. These beds are structureless or show soft-sediment shear banding. An origin of diamictites related to glaciation is interpreted because of the following: the presence of dropstone pebbly mudshale; the angularity of sand grains and pebbles; the mixture of clast types in diamictite; and the freshness of most sand grains and pebbles. Subaqueous mudflow deposition is suggested for some diamictites because of interbedding with dropstone-bearing strata. Medium-scale, moderate to high-angle cross bedding is interbedded with other diamictite. That diamictite is interpreted as having been deposited as subglacial till or from subaerial ice-related mudflows. Pebble and sandstone composition in the Ordoñez Formation indicate a provenance terrane consisting of limestone, granite, gneiss, shale, sandstone, and volcanic units that existed to the west. Ordoñez Formation diamictite also becomes redder in wells in the Chaco-Paranábasin toward the western provenance area. The upper Ordoñez Formation is inferred to be partly contemporaneous with Paleozoic glacial deposits of the Paranábasin of Brazil, but was associated with a different ice lobe. Overlying the Ordoñez Formation is the Permian Victoriano Rodrı´guez Formation, which consists of shale and sandstone that was deposited in fluvial, floodbasin, and shallow to possibly deep-aqueous environments when the basin apparently was free of ice.

  9. 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.

  10. 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.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-01-01

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

  13. 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.

  14. 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.

  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. Improved Moscovian part of the Gondwana APWP for paleocontinental reconstructions, obtained from a first paleomagnetic pole, age-constrained by a fold test, from In Ezzane area in the Murzuq basin (Algeria, stable Africa)

    NASA Astrophysics Data System (ADS)

    Amenna, M.; Derder, M. E. M.; Henry, B.; Bayou, B.; Maouche, S.; Bouabdallah, H.; Ouabadi, A.; Ayache, M.; Beddiaf, M.

    2014-11-01

    To improve paleocontinental reconstructions, paleomagnetic reference curves (Apparent Polar Wander Path: APWP) feature for large continents have to be continuously refined by adding up new high-quality data. For stable Africa, the Moscovian period was favorable for such aim, with well-dated and widespread geological formations. A new study has been conducted in the Upper “Dembaba” geological formation of Lower Moscovian age outcropping in the western part of the “Murzuq” basin (Saharan platform). Well-defined ChRMs, combined with remagnetization circles data, both constrained in age by a positive fold test, yield a new significant paleomagnetic pole (λ = 25.2°S, ϕ = 59.9°E, K = 55, A95 = 5.4°). When joined with previous African data of the same age, it gives an improved reference pole for Africa (λ = 28.9°S, ϕ = 54.5°E, K = 106, A95 = 3.6°). The Mean Moscovian paleomagnetic pole determined from an updated Gondwana Paleozoic APWP (λ = 29.4°S, ϕ = 51.5°E, K = 11, A95 = 1.8°), associated with the corresponding Laurussia pole (Domeier et al., 2012), yields a more constrained paleocontinental reconstruction for 310 Ma.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2001-05-01

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

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. 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

  10. 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

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

    PubMed Central

    Patil, Rajan R.

    2011-01-01

    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

  12. 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.

  13. 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.

  14. 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.

  15. Gondwana Six: Structure, Tectonics, and Geophysics

    NASA Astrophysics Data System (ADS)

    McKenzie, Garry D.

    This volume contains many of the papers presented at the Sixth International Gondwana Symposium, held at the Institute of Polar Studies, The Ohio State University, Columbus, Ohio, August 19-23, 1985. The symposium was the first held outside the Gondwanaland continents; other symposia were held in Buenos Aires, Argentina, 1967; Cape Town and Johannesburg, South Africa, 1970; Canberra, Australia, 1973; Calcutta, India, 1977; and Wellington, New Zealand, 1980. The Columbus symposium attracted 150 scientist from 19 countries to five days of technical sessions, six field trips, commission and working group meetings, and workshops. Topics covered in the technical sessions were generally similar to those of earlier meetings and included reconstruction of Gondwanaland, vertebrate and invertebrate paleontology, biogeography, glacial geology, Gondwana stratigraphy, economic geology, and tectonics and sedimentation at plate margins. A notable difference was in geographic coverage. As might be expected at a meeting co-hosted by the Institute of Polar Studies and the Department of Geology and Minerology at The Ohio State University, the focus of the meeting was on Antarctica, with 45% of the 102 papers covering the Ross Sea sector, West Antarctica, and northern Victoria Land.

  16. 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.

  17. 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)

  18. 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.

  19. 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.

  20. Paleomagnetic Constraints on the Neoproterozoic Evolution of West Gondwana

    NASA Astrophysics Data System (ADS)

    Trindade, R. I.

    2005-05-01

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

  1. Gondwana events and pal˦ogeography:A pal˦omagnetic review

    NASA Astrophysics Data System (ADS)

    Grunow, Anne M.

    Several important tectonic episodes stand out in Gondwana's major and microplatemotions: (1) Gondwana assembly; (2) the general movement of Gondwana towards higher latitudes in the Pal˦ozoic; (3) the influence of terranes on Gondwana Mesozoic break-up motions; and (4) Mesozoic-Cenozoic terrane motion along Gondwana's convergent margins. Current palaeomagnetic data indicate that the various fragments of Gondwana were assembled between ˜900 and ˜500 Ma. After assembly, the East Gondwana portion of Gondwana moved from more equatorial latitudes in the Early Pal˦ozoic into much higher latitudes by the Late Pal˦ozoic, whereas that of West Gondwana was the opposite. This overall motion and concomitant climatic change had a profound influence on the pal˦oevolution of different Gondwana faunas and floras in the Pal˦ozoic. During the Palaeozoic and Mesozoic, convergence along the Gondwana margin resulted in accretion of various microplates. By the Early to Mid-Jurassic, pal˦omagnetic data suggest that terrane motion along the pal˦o-Pacific margin of Gondwana was related to the initial break-up of the supercontinent. This motion, especially in West Antarctica and New Zealand, caused the intermittent occurrence of palaeoseaways and landbridges between East and West Gondwana. In the Tertiary, collision of India and Africa with Eurasia caused significant local rotations associated with regional deformation.

  2. 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.

  3. Upper carboniferous palæogmagnetic pole from the stable Saharan Craton and Gondwana reconstructions

    NASA Astrophysics Data System (ADS)

    Derder, M. E. M.; Henry, B.; Merabet, N.; Amenna, M.; Bourouis, S.

    2001-04-01

    A palæomagnetic study was conducted at different stratigraphical positions in rocks of Upper Carboniferous age (Bashkirian) in the Illizi Basin (Algeria). Three distinct remanence directions were isolated in these rocks. The first direction is associated with a Cenozoic magnetic overprint. The second direction yields a palæomagnetic pole (40.3°S, 64.3°E) that is similar to previously published African Permian poles and is interpreted as a Permian remagnetisation. The third direction gives a new Late Carboniferous (Bashkirian) African palæomagnetic pole (28.2°S, 55.5°E, K = 207, A 95 = 3.4°). This pole is in a good agreement with previously published Saharan poles for the neighbouring periods. The combination of the new given datum with the previous Carboniferous poles of Gondwana shows that the reconstruction of Gondwana should be based on the parameters of Ricou. (1990) rather than on those of the classical du Toit (1937) model.

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

    NASA Astrophysics Data System (ADS)

    Ramos, V. A.

    2009-05-01

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

  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-Pencksökket, 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. 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

  8. 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…

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

    ERIC Educational Resources Information Center

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

    1999-01-01

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

  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. Is the Indian Shield hotter than other Gondwana shields?

    NASA Astrophysics Data System (ADS)

    Gupta, Mohan L.

    1993-03-01

    Geothermal data on various Precambrian terrains from the African, Australian, Indian and South American (Brazil only) Gondwana landmasses have been compiled, synthesized and statistically analyzed. The results do not support the prevailing notion that the Indian Shield is hotter than other shields. The study clearly shows that the mean surface heat flow values from the various Precambrian cratons and mobile belts of the Indian landmass for which the data have become available are either equal to, or even lower in some cases, than that in similar terrains from other Gondwana continents. Further, on the basis of available data, it is found that the Moho and the reduced heat flow values and Moho temperatures in the South Indian, South African, Western Australian and Brazilian shields fall within a narrow range, thus indicating, within the error limits of the estimation, the similarity of these shields in terms of these characteristics. In conclusion it is shown that the Indian landmass is not hotter than the other Gondwana landmasses, including even the presently immobile African continent, and that the 'super-mobility' of the Indian landmass does not appear to be associated with its thermal characteristics. The cause of the latter lies elsewhere.

  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. Neoproterozoic geodynamic evolution of SW-Gondwana: a southern African perspective

    NASA Astrophysics Data System (ADS)

    Frimmel, H. E.; Basei, M. S.; Gaucher, C.

    2011-04-01

    Our current understanding of the tectonic history of the principal Pan-African orogenic belts in southwestern Africa, reaching from the West Congo Belt in the north to the Lufilian/Zambezi, Kaoko, Damara, Gariep and finally the Saldania Belt in the south, is briefly summarized. On that basis, possible links with tectono-stratigraphic units and major structures on the eastern side of the Río de la Plata Craton are suggested, and a revised geodynamic model for the amalgamation of SW-Gondwana is proposed. The Río de la Plata and Kalahari Cratons are considered to have become juxtaposed already by the end of the Mesoproterozoic. Early Neoproterozoic rifting led to the fragmentation of the northwestern (in today's coordinates) Kalahari Craton and the splitting off of several small cratonic blocks. The largest of these ex-Kalahari cratonic fragments is probably the Angola Block. Smaller fragments include the Luis Alves and Curitiba microplates in eastern Brazil, several basement inliers within the Damara Belt, and an elongate fragment off the western margin, named Arachania. The main suture between the Kalahari and the Congo-São Francisco Cratons is suspected to be hidden beneath younger cover between the West Congo Belt and the Lufilian/Zambezi Belts and probably continues westwards via the Cabo Frío Terrane into the Goiás magmatic arc along the Brasilia Belt. Many of the rift grabens that separated the various former Kalahari cratonic fragments did not evolve into oceanic basins, such as the Northern Nosib Rift in the Damara Belt and the Gariep rift basin. Following latest Cryogenian/early Ediacaran closure of the Brazilides Ocean between the Río de la Plata Craton and the westernmost fragment of the Kalahari Craton, the latter, Arachania, became the locus of a more than 1,000-km-long continental magmatic arc, the Cuchilla Dionisio-Pelotas Arc. A correspondingly long back-arc basin (Marmora Basin) on the eastern flank of that arc is recognized, remnants of which are found in the Marmora Terrane—the largest accumulation of oceanic crustal material known from any of the Pan-African orogenic belts in the region. Corresponding foredeep deposits that emerged from the late Ediacaran closure of this back-arc basin are well preserved in the southern areas, i.e. the Punta del Este Terrane, the Marmora Terrane and the Tygerberg Terrane. Further to the north, present erosion levels correspond with much deeper crustal sections and comparable deposits are not preserved anymore. Closure of the Brazilides Ocean, and in consequence of the Marmora back-arc basin, resulted from a change in the Río de la Plata plate motion when the Iapetus Ocean opened between the latter and Laurentia towards the end of the Ediacaran. Later break-up of Gondwana and opening of the modern South Atlantic would have followed largely along the axis of the Marmora back-arc basin and not along major continental sutures.

  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. The Marion and Bouvet Rises: Remelting Gondwana's Mantle

    NASA Astrophysics Data System (ADS)

    Dick, H. J.; Zhou, H.; Standish, J. J.

    2014-12-01

    Major, trace element and isotopic data along the SW Indian Ridge identify two major geochemical provinces centered on the Marion and Bouvet Hotspots with prominent correlations between the isotopic and major element composition of basalts, ridge depth, and mineralogy of spatially associated mantle peridotites. Both consist of axial rises with elevated ridge topography. Both the Bouvet and Marion Hotspots have small volcanic fluxes, while the associated axial-rises contrast sharply in size and geochemistry. The Bouvet Rise is small, proportional to the size of the hotspot, while the Marion, with Iceland, is one of the two largest oceanic rises. A mantle plume associated with the Marion Hotspot is incapable of supporting the rise; rather it appears to be supported by a large region of anomalously depleted mantle1. The Bouvet Plume, which likely originates above the mantle transition zone, appears to have had a direct control on the geometry of the western SWIR through time and thus likely does support the short Bouvet Rise. The bathymetric contrast between these two rises corresponds to notable differences in isotopic geochemistry: while the Marion Rise basalts exhibit a complex pattern of variability - it is a region where the classic 'Dupal' anomaly is well expressed, consistent with a major Archean mantle source that likely represents delaminated metasomatized sub-continental lithosphere entrained in the shallow mantle beneath the Ridge during formation of the central and SW Indian Ridges with the breakup of Gondwana. This is supported by a similar isotopic anomaly along the Rodriguez Rise on the Central Indian Ridge that also appears related to Gondwana breakup. By contrast, the mantle beneath the Bouvet Rise appears to represent largely post-Archean asthenosphere pulled from beneath the Gondwana lithosphere, interacting with a local small plume reflecting a local heterogeneity in the upper mantle. 1. Zhou, H.-y., Dick, H.J.B., 2013. Thin crust as evidence for depleted mantle supporting the MarionRise. Nature 494, 195-200.

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

    NASA Astrophysics Data System (ADS)

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

    2003-04-01

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

  19. 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.

  20. 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.

  1. Rotation and offset of the Gondwana convergent margin in the New Zealand region following Cretaceous jamming of Hikurangi Plateau large igneous province subduction

    NASA Astrophysics Data System (ADS)

    Davy, Bryan

    2014-08-01

    Jamming of the Hikurangi Plateau (large igneous province) subduction, within the Chatham Rise convergent margin of Gondwana at circa 105 Ma, led to offset and rotation of the convergent margin before subduction ceased in the New Zealand region at circa 100 Ma. The southern limit of the plateau, following leading slab break off, is highlighted by a lineament of prominent horst blocks in the southern Bounty Trough. Subduction jamming of the Gondwana margin, and accompanying compression of the onshore margin and/or extension of the offshore margin, has led to two 60 km left-lateral SSE offsets of the Chatham Rise convergent margin at the coast and in inland Canterbury. Recognition of the onshore Chatham Rise using the gravity data also highlights the correlation of the inland Chatham Rise and central South Island seismicity. In a similar manner to the rotation of Cretaceous spreading-ridge and transform-fault fabric adjacent to the Osbourn Trough spreading ridge, the convergence direction at the Gondwana margin was rotated anticlockwise to N-S between 105 and 100 Ma. Most of this rotation has been accommodated by offshore extension and margin offset. The divergence between the anticlockwise rotation of offshore crustal structure and the jammed onshore margin led to the development of the Great South Basin at 105-100 Ma. Further offshore in the Bounty Trough, extensional zones, formed between crustal blocks rotated to adjust to a changed Cretaceous direction of subduction, are evident in gravity and seismic profiles.

  2. 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.

  3. Tectonic insight based on anisotropy of magnetic susceptibility and compaction studies in the Sierras Australes thrust and fold belt (southwest Gondwana boundary, Argentina)

    NASA Astrophysics Data System (ADS)

    Arzadún, Guadalupe; Tomezzoli, Renata N.; Cesaretti, Nora N.

    2016-04-01

    The Sierras Australes fold and thrust belt (Buenos Aires Province, Argentina) was in the southwestern Gondwanaland margin during the Paleozoic. The Tunas Formation (Permian) is exposed along the eastern part of it and continues eastward beneath the Claromecó Basin. Anisotropy of magnetic susceptibility (AMS) and compaction studies are described and compared with previous paleomagnetic studies with the aim of determining direction and magnitude of the main stresses acting during the sedimentation of the Tunas Formation. The anisotropy ellipsoids are triaxial with oblate or prolate shapes, reflecting different stages of layer parallel shortening during the evolution of the basin. Kmax axes trend NW-SE, parallel to the fold axes, while Kmin move from a horizontal (base) to a vertical orientation at the top of the succession, showing a change from a tectonic to almost a sedimentary fabric. The magnitude of anisotropy and compaction degree decreases toward the top of the succession. The AMS results are consistent with the outcrop structural observations and the compaction and paleomagnetic data. Regional pattern indicates a compression from the SW along this part of Gondwana, with a migration of the orogenic front and attenuation toward the NE in the foreland basin during the Upper Paleozoic. This deformation, locally assigned to the San Rafael noncollisional orogenic phase, is the result of the latitudinal movements toward the Equator of Gondwana (southern plates) and Laurentia (northern plates) during the Permian. This movement is the result of a rearrangement of the microplates that collided with Gondwana during the Late Devonian, to configure Pangea during the Triassic.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Controls on post-Gondwana alkaline volcanism in Southern Africa

    NASA Astrophysics Data System (ADS)

    Moore, Andy; Blenkinsop, Thomas; Cotterill, Fenton (Woody)

    2008-04-01

    A comprehensive database of high precision (± 5 Ma) radiometric ages has been assembled for kimberlites and other alkaline volcanic pipes erupted in southern Africa during the period immediately preceding and following the disruption of Gondwana. These ages show that alkaline volcanic activity in southern Africa has been episodic since Gondwana break-up, and was broadly coeval with episodes of alkaline volcanism elsewhere in Africa. In southern Africa, offshore sedimentation patterns were also episodic, with periods of essentially continuous sedimentation broken by series of major unconformities, linked to plate spreading regimes. The volcanic episodes followed major changes in plate spreading histories and the associated unconformities in the offshore sedimentary record with a lag of 5-13 Ma. On a regional scale, there is an overall younging of volcanic activity from the interior to the margins of southern Africa. Some of the volcanic pipe clusters define a major igneous lineament, with a general age progression younging to the southwest. Parts of this alkaline lineament coincide with major rift zones, but the volcanism predated the surface expression of rifting by as much as 90 Ma. These relationships point to tectonic triggers for alkaline volcanic activity, rather than plumes initiated near the core-mantle boundary. There is also a systematic geographic variation in alkaline magma type across southern Africa, with Mg-rich, less evolved kimberlites emplaced into the Archean craton of the central portions of the sub-continent, and more evolved compositions emplaced into the marginal younger fold belts. These chemical trends are interpreted in terms of decreasing depth of intersection between the CO 2-H 2O peridotite solidus and the geotherm with increasing geothermal gradient from the Archean craton to the younger marginal fold belts.

  10. 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

  11. Paleogeography of the Congo and Kalahari Cratons During the Rodinia-Gondwana Supercontinent Cycle, Evidence from U-Pb Ages and Lu-Hf Isotopic Compositions of Detrital Zircons

    NASA Astrophysics Data System (ADS)

    Gregory, L. C.; Foster, D. A.; Stroud, M. M.; Newstead, B.; Kamenov, G. D.

    2008-12-01

    Constraining the paleogeography of the Rodinia-Gondwana supercontinent cycle is an enigmatic problem that is largely complicated by the difficulties in discerning sutures that represent intercratonic basin closure versus ocean closure. The timing and tectonic style of the Gondwana supercontinent assembly can be tested by comparing detrital zircon geochronology and geochemistry across PanGondwanan sutures. The relative spatial relationship of the Congo and Kalahari cratons throughout the Rodinia-Gondwana cycle is poorly constrained. Contrasting hypotheses propose that these cratons had proximal locations within Rodinia in the same configuration as they are found in today's southern Africa, or alternatively that one (or both) of the cratons did not participate in the Rodinia supercontinent at all. If the Congo and Kalahari were juxtaposed within Rodinia, it is also uncertain whether they remained adjacent until final Gondwana assembly or that the cratons took unique paths to Gondwana and were separated by a large ocean basin. The Damara-Lufilian- Zambezi orogenic system is the 550-530 Ma suture between the Congo and Kalahari cratons that records the Precambrian relationship of the two cratons and the nature of the basin between them. The belt comprises rift-to-drift sedimentary sequences intermingled with arc volcanics metamorphosed in the closure of either a small, Red-Sea type intercratonic basin or continent-continent collision with subduction and consumption of significant oceanic crust. Syn-rift, turbodite, and volcanic metasediments and select cratonic basement samples were collected from the Damara belt to compare the detrital zircon input from Congo and Kalahari. Detrial zircon populations from either continent have geochronologic and geochemical signatures that can be used to determine which craton contributed detritus into the intervening basin. Samples of metamorphosed accreted arc terranes have crystallization age peaks at 750-800 Ma and metamorphic peaks around 550 Ma, consistent with Pan-African uplift. Samples from syn-rift sediments on the southern Congo margin have a wide age distribution with notable peaks at ~750, 1100, 1800, 2400, 2600 and 3100 Ma. These U-Pb ages and Lu-Hf isotopics of detrital zircons along with Nd isotope data from Damara belt metasediments are consistent with known components within the Congo craton and no sample studied thus far requires a source from Kalahari. This is contingent on the population of zircon grains sourced from Kalahari actually reaching the Kalahari rift-to-drift sedimentary sequences. Further work will expand the U-Pb age and Lu-Hf signature databases for both Congo and Kalahari to provide a robust comparison for basin sediments on both cratonic margins.

  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. The delivery of veterinary services to poorer communities: the case of rural Orissa, India.

    PubMed

    Ahuja, V; Morrenhof, J; Sen, A

    2003-12-01

    This paper presents the results of a field survey on use patterns and demand for clinical veterinary services in one of the poorest states of India, namely, Orissa. A demand function was estimated using Poisson regression and demand elasticities were obtained for various income groups. The survey shows that large numbers of households, including the poor, pay prices that are significantly higher than those prescribed. There is no targeting of cheaper services towards the poor. The analysis also suggests that for a given service and place of service, the poor actually paid more on a per veterinary visit basis. As a result, the rate of service utilisation was significantly lower for poor households. Demand analysis confirmed that the demand for veterinary services is not determined by subsidised service delivery, but by access to output markets and general awareness levels. In the light of these findings, the paper makes a number of recommendations for redefining the role of the Government in veterinary service delivery in Orissa. PMID:15005551

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

    NASA Astrophysics Data System (ADS)

    Götz, 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., Götz, 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.

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

    PubMed Central

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

    2014-01-01

    Background Aedes albopictus has recently been implicated as a major vector in the emergence of dengue and chikungunya in several parts of India, like Orissa, which is gradually gaining endemicity for arboviral diseases. Ae. albopictus is further known to be naturally infected with Wolbachia (maternally inherited bacterium), which causes cytoplasmic incompatibility (CI) in mosquitoes leading to sperm-egg incompatibility inducing the death of embryo. Knowledge of genetic diversity of Ae. albopictus, along with revealing the type of Wolbachia infection in Ae. albopictus is important to explore the genetic and biological characteristics of Ae. albopictus, prior to exploring the uses of CI-based vector control strategies. In this study, we assessed the population genetic structure and the pattern of Wolbachia infection in Ae. albopictus mosquitoes of Orissa. Methods and Results Ae. albopictus mosquitoes were collected from 15 districts representing the four physiographical regions of Orissa from 2010–2012, analyzed for genetic variability at seven microsatellite loci and genotyped for Wolbachia strain detection using wsp gene primers. Most microsatellite markers were successfully amplified and were polymorphic, showing moderate genetic structure among all geographic populations (FST = 0.088). Genetic diversity was high (FST = 0.168) in Coastal Plains populations when compared with other populations, which was also evident from cluster analyses that showed most Coastal Plains populations consisted of a separate genetic cluster. Genotyping analyses revealed that Wolbachia-infected Ae. albopictus field populations of Orissa were mostly superinfected with wAlbA and wAlbB strains. Wolbachia superinfection was more pronounced in the Coastal Plain populations. Conclusion High genetic structure and Wolbachia superinfection, observed in the Coastal Plain populations of Orissa suggested it to be genetically and biologically more unique than other populations, and hence could influence their vectorial attributes. Such high genetic diversity observed among Coastal Plains populations could be attributed to multiple introductions of Ae. albopictus in this region. PMID:24714653

  16. The geodynamic setting of the Phanerozoic basins of Africa

    NASA Astrophysics Data System (ADS)

    Bumby, A. J.; Guiraud, R.

    2005-10-01

    The Pan-African event assembled the supercontinent of Gondwana during the Late Proterozoic, and is manifest within the African plate by an anastomosing pattern of tectonic sutures and mobile belts. The development of African basins during the Phanerozoic can be thought of as relating to the polyphase break-up of Gondwana, which was accomplished, in general, by reactivation along the Pan-African sutures. The present African plate occupied a relatively central position in Gondwana, with only the north-westernmost (Rif-Tell/Atlas) and southernmost (Cape Fold Belt) tips of the plate (present-day orientation) exposed directly to convergent plate margin activity. Although the African plate can be generally considered to have undergone extension throughout the Phanerozoic, compressive tectonism associated with the closure of the Paleotethys (Hercynian Rif-Tell) and the Neotethys Oceans (Alpine Atlas) and subduction of the Paleopacific plate (Hercynian Cape Fold Belt) are exceptions. Rifting associated with the break-up of Gondwana was dominant from the Late Carboniferous onwards, and basins developed as a result of this extension both at the margins and within the continental African plate. Rifting began in earnest during the Early-Middle Jurassic, when East and West Gondwana separated, and the central Atlantic Ocean began to open. From the Late Jurassic to Early Cretaceous, the South Atlantic opened progressively northwards, and intraplate extension led to the development of the West, Central and East African rift basins. The final episode of rifting took place between the Late Eocene and Early Miocene, and opened the Dead Sea-Red Sea-Gulf of Aden basins, with rifting in the East African Rift continuing to the present day. During the Phanerozoic, Africa (and Gondwana) migrated across the South Pole northwards to its present latitude, and the fill of preserved basins reflects a concomitant change in paleoclimate. Rises in sea level, in part related to the demise of Gondwanan glaciers during the Paleozoic, locally flooded the African plate. The rich fossil record of life on the African plate during the Mesozoic and Cenozoic can also be coupled with a more benevolent climate at lower latitudes as Gondwana passed away from south polar regions. The presence of plumes beneath the African plate during the Mesozoic and Cenozoic (the Karoo and Afar plumes, respectively), coupled with an absence of slab pull at the margins of the young post-Gondwana oceanic crust, has rendered Africa in a relatively stationary position since the Mesozoic, with only a slow rotation of the plate as the Central and South Atlantic, Indian Ocean and Red Sea have opened.

  17. 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.

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

    PubMed

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

    2005-02-01

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

  19. Perceived gender role that shape youth sexual behaviour: Evidence from rural Orissa, India.

    PubMed

    Pradhan, Manas Ranjan; Ram, Usha

    2010-08-01

    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 packages have been used for the analysis. Youths in general are expected to adhere to the roles ascribed for them based on their biological construct and any deviation is not warranted for, more so for young women. Moreover, for many young men perceived gender role coupled with poor self risk perception result into unsafe sexual activities, putting them as well as their partners at the risk of STI/HIV and unintended parenthood. PMID:19944457

  20. 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.

  1. 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.

  2. Models for evolution of Weddell basin

    SciTech Connect

    Labrecque, J.L.

    1987-05-01

    The evolution of the Weddell basin constitutes the keystone for Gondwana reconstructions. During the last decade major exploration efforts including marine and aerogeophysical surveys and OPD drilling have been directed toward the evolution of the Weddell sector. As a result of these efforts, they can now show that the Weddell basin formed as the result of the relative motion between East and West Antarctica, South America, and Africa. Both paleomagnetic and marine geophysical data support a reconstruction in which West Antarctica has undergone nearly 90/sup 0/ of clockwise rotation. Magnetic anomalies reveal both sea-floor spreading and fracture zone lineations which can be used to constrain this motion since Gondwana breakup in the Jurassic. The basement of the Weddell was formed at the southern flank of the America-Antarctica spreading system since the Jurassic. The northern flank of the spreading system was subducted beneath the Scotia Sea and the southern Andes since the Late Cretaceous. The eastern and western boundaries of the basin were developed as transcurrent faults, while the southern margin appears to have been an extensional margin. The Weddell basin is heavily sedimented with well over 3 km of sediment along the southern margin. While little to no seismic data have been gathered for the southern and western portions of the basin, profiles along the eastern margins show extensive erosion. Sedimentation within the basin appears to have been dominated by turbiditic deposition since formation.

  3. Triassic vegetation and geography of the New Zealand portion of the Gondwana supercontinent

    NASA Astrophysics Data System (ADS)

    Retallack, G. J.

    Middle Triassic (Ladinian) coal measures of the Torlesse Supergroup cropping out in three separate areas of the South Island (Tank Gully, Long Gully, and Benmore Dam) have yielded a variety of impressions of fossil leaves, fructifications, logs, and root traces. Natural associations of these plant fossils are thought to represent several kinds of coastal vegetation: Pachydermophylletum (mangrove), Linguifolietum (swamp woodland), and Dicroidietum odontopteroidium (mesophytic woodland). Judging from associated sedimentary rocks, these narrow coastal plains were dissected by powerful braided streams and hedged in by a fold mountain range of alpine proportions, largely composed of quartzofeldspathic sandstones. The low diversity of the fossil flora and the presence of possible ice-disrupted paleosols and of ferruginized fossil logs with growth rings are indications of a humid, cool temperate paleoclimate. Plant fossils are very rare in Triassic shallow marine rocks of the Murihiku Supergroup, but a considerable amount of material from numerous localities has accumulated in museum collections over the past century. These fossils include plant chaff incorporated in prodeltaic, graded beds of sandstone and siltstone. Large leaves and fructifications from shaly beds rich in marine invertebrates may have settled from flotsam. Fossil plants found are mainly representative of coastal plant associations better known in Triassic rocks elsewhere in New Zealand and Australia. In Early to Middle Triassic (Scythian and Anisian) rocks these include the Dicroidietum zuberi (floodplain forest and coastal heath) and Taeniopteretum lentriculiformis (river and delta levee scrub); and in Middle and Late Triassic (Ladinian to "Rhaetian") rocks, the Pachydermophylletum (mangrove) and Linguifolietum (swamp woodland). Considering the composition of these sedimentary rocks, the coast from which the plants were derived was geologically complex and included active andesitic volcanoes. The fossil plants are very similar to those of the Sydney Basin, New South Wales, and the Torlesse Supergroup, New Zealand, and like these, probably lived in a humid, cool temperate paleoclimate. The close similarity between Triassic fossil plants of New Zealand and other parts of the Gondwana supercontinent is evidence that both the Torlesse and Murihiku supergroups formed in different parts of the southeastern Gondwanian coast. Juxtaposition of the Torlesse and Murihiku supergroups is more likely a result of transcurrent shuffling of continental terranes than of collision of microcontinents or island arcs.

  4. 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.

  5. 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.

  6. Antarctic Peninsula Late Cretaceous-Early Cenozoic pal˦oenvironments and Gondwana pal˦ogeographies

    NASA Astrophysics Data System (ADS)

    Dingle, R. V.; Lavelle, M.

    2000-07-01

    A review is made of stratigraphical, geochemical and pal˦ogeographical data from the northern Antarctic Peninsula and the Southern Ocean for Late Mesozoic-Early Cenozoic times. Clay mineral and S/total organic C ratios are used to re-assess earlier scenarios, and it is suggested that eight climatic episodes affected the northern Antarctic Peninsula between Late Aptian and Pal˦ogene times. Evolving pal˦ogeographies in southern Gondwana allowed the connection of the inter-continental western Weddell Basin to the proto-Indian Ocean during Albian to Cenomanian times, and it is suggested that this caused an initial cooling of ambient temperatures in the northern Antarctic Peninsula area. This situation altered when the South Atlantic seaway was opened to equatorial regions, producing a Campanian warm episode. Throughout this period, the climate was humid and non-seasonal (ever-wet) and the adjacent seas were dominated by mineralwalled phytoplankton. A Maastrichtian to Mid-Pal˦ocene cool period is postulated following the establishment of more-polar ocean circulation routes along the southern edge of the Pacific Basin, and the climate became seasonally humid with phytoplankton production switching to organicwalled dominant. The global Pal˦ogene climatic optimum was a warm, ever-wet episode but as it waned from Mid-Eocene times, a further, relatively short, period of marked seasonality is recognised. Later, Eocene climates were again ever-wet and became progressively cooler. The Late Eocene-Early Oligocene opening of the Tasman Sea and Drake Passage seaways caused cold conditions on Seymour Island, followed rapidly by the earliest glacial sediments on King George Island and the establishment of mineral-walled phytoplankton dominance in the seas.

  7. Important Ayurvĕda literatures from the manuscripts available from Orissa (Cikitsărnava).

    PubMed

    Padhi, M M; Das, B; Audichya, K C; Rao, M M

    2005-01-01

    In the treasure of Ayurvĕdic literature, many texts are missing or partially available. Only references or few verses from many such texts are mentioned in later texts. Unfortunately, a large number of Ayurvĕdic texts are unexplored till today are likely to exist in palm-leaf manuscripts, which are decaying or undergoing permanent annihilation. As such many unique and valuable information contained in these texts are being lost. Though several Institutions have taken up work on literary Research, only few texts have been published during past decades. The present paper highlights the salient features of the text 'Cikitsărnava' authored by Viśvanăth Sena of 16th century of Orissa. Though his text on Pathyăpathya has already been published, which has got a place in the pages of history of Ayurvĕda, a very little is known about this important text on therapeutics. Various aspects of this text and its author have been discussed to bring it in to the knowledge of fraternity of Ayurvedic physicians and Sanskrit scholars. PMID:17333660

  8. Malaria outbreak in a non endemic tribal block of Balasore district, Orissa, India during summer season.

    PubMed

    Mahapatra, N; Marai, N; Dhal, K; Nayak, R N; Panigrahi, B K; Mallick, G; Ranjit, M; Kar, S K; Kerketta, A S

    2012-06-01

    A focal outbreak of malaria at Sialimal sub-centre of Balasore district of Orissa was reported during the month of March, 2010. Three villages of the above block were affected. Regional Medical Research Centre, Bhubaneswar has conducted an entomological survey and a central clinic simultaneously, with door to door household survey to identify the fever cases. Within a span of 18 days around 172 fever cases were reported with Slide Positivity Rate (SPR) of 24.4% and Pf % of 81%. The malaria epidemiological data of the sub-centre area for last three years indicates that the area is non endemic for malaria (API was 0.81). Entomological survey revealed the presence of three known vectors of malaria i.e. Anopheles culicifacies, Anopheles annularis and Anopheles subpictus (local vector). Per Man Hour Density (PMHD) of these three species were 4.2, 2.8 and 10.8 respectively. Plasmodium falciparum sporozoites were detected in two An. culicifacies, in one An. annularis and in one An. subpictus. Larval density of Anopheline mosquitoes per dip ranged between 12 to 20. The vectors were found to be resistant to DDT but susceptible to synthetic pyrethroid. With this finding necessary remedial measures were taken by the government to curtail the transmission. PMID:22735850

  9. Mental Health Consequences of the Trauma of Super-Cyclone 1999 in Orissa

    PubMed Central

    Kar, Nilamadhab; Jagadisha; Sharma, PSVN; Murali, N.; Mehrotra, Seema

    2004-01-01

    A super-cyclone hit 12 coastal districts of Orissa in October 1999 and caused over 20,000 deaths and a considerable damage to property. The psychiatric sequelae of the super-cyclone was studied using a semi-structured proforma for disaster experience, Self Reporting Questionnaire, Impact of Event Scale, Post Traumatic Symptoms Scale, Hopelessness Scale, Suicidality Screening Questionnaire, Hospital Anxiety and Depression Scale and Presumptive Stressful Life Event Scale. The coping style of the victims was also studied. It was observed that 80.4% of the subjects had probable psychiatric disorder. Posttraumatic stress disorder was found in 44.3%; anxiety disorder in 57.5% and depression in 52.7%. A considerable proportion (63.4%) of cases had comorbidity. Children and adolescents, elderly persons, lower socioeconomic status, lower educational levels, unemployment, physical injury, degree of exposure, need for evacuation, death in the family, fear of imminent death during the event, hopelessness, increased stress before disaster and past psychiatric history were associated with adverse psychological sequelae. Increase in suicidality was observed. Implications of these findings are discussed. PMID:21224904

  10. 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

  11. 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.

  12. 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

  13. Ordovician collision of the Argentine Precordillera with Gondwana, independent of Laurentian Taconic orogeny

    NASA Astrophysics Data System (ADS)

    Thomas, Willliam A.; Astini, Ricardo A.; Bayona, Germán

    2002-02-01

    The Argentine Precordillera, a rifted fragment of Laurentian crust and sedimentary cover, collided with Gondwana in Middle Ordovician time; the time of collision (Ocloyic orogeny) is similar to that of the Taconic orogeny of eastern Laurentia. Three hypotheses have been proposed to explain Ordovician docking of the Precordillera with western Gondwana: (A) the Precordillera microcontinent was rifted from Laurentia in Cambrian time and, following solitary drift, collided with Gondwana, independent of the Laurentian Taconic orogeny; (B) a continent-continent collision of Laurentia with Gondwana, producing a continuous Taconic-Ocloyic orogenic belt, was followed by rifting that left the Precordillera attached to Gondwana; and (C) the Precordillera at the tip of a distal plateau on greatly stretched Laurentian crust collided with Gondwana and subsequently separated from Laurentia. Contrasts in several aspects of Taconic and Ocloyic orogenic history provide for discrimination between the microcontinent and continent-continent-collision hypotheses. Stratigraphic gradients and lithologic assemblages within the synorogenic clastic wedges are incompatible with a single continuous orogenic belt, which, in palinspastic location, places the thin, fine-grained southern fringe of the Taconic clastic wedge adjacent to the thickest and coarsest part of the Ocloyic clastic wedge. Separate temporal and spatial distribution patterns of volcanic ash (bentonite) beds in Laurentia and the Precordillera indicate originally separate dispersal systems. Late Ordovician Hirnantian Gondwanan glacial deposits in the Precordillera indicate substantial latitudinal separation from Laurentia. Post-collision faults with large vertical separation in the Precordillera have no coeval counterparts on the Laurentian foreland. These contrasts indicate originally separate (not initially continuous, and subsequently dismembered) orogenic belts, favoring the microcontinent hypothesis and eliminating the continent-continent-collision hypothesis. Initial Taconic tectonic loading near the southern corner of the Alabama promontory of Laurentia and the lack of post-Taconic extension there are inconsistent with the tectonic history required by the plateau hypothesis, but are consistent with the tectonic history required by the microcontinent hypothesis. Paleobiogeography, distribution of bentonite beds, and the Hirnantian glacial deposits, all indicate wide separation (Iapetus Ocean) between the Precordillera and southern Laurentia at the time of the Ocloyic and Taconic orogenies, further favoring the microcontinent hypothesis.

  14. Child Feces Disposal Practices in Rural Orissa: A Cross Sectional Study

    PubMed Central

    Majorin, Fiona; Freeman, Matthew C.; Barnard, Sharmani; Routray, Parimita; Boisson, Sophie; Clasen, Thomas

    2014-01-01

    Background An estimated 2.5 billion people worldwide lack access to improved sanitation facilities. While large-scale programs in some countries have increased latrine coverage, they sometimes fail to ensure optimal latrine use, including the safe disposal of child feces, a significant source of exposure to fecal pathogens. We undertook a cross-sectional study to explore fecal disposal practices among children in rural Orissa, India in villages where the Government of India's Total Sanitation Campaign had been implemented at least three years prior to the study. Methods and Findings We conducted surveys with heads of 136 households with 145 children under 5 years of age in 20 villages. We describe defecation and feces disposal practices and explore associations between safe disposal and risk factors. Respondents reported that children commonly defecated on the ground, either inside the household (57.5%) for pre-ambulatory children or around the compound (55.2%) for ambulatory children. Twenty percent of pre-ambulatory children used potties and nappies; the same percentage of ambulatory children defecated in a latrine. While 78.6% of study children came from 106 households with a latrine, less than a quarter (22.8%) reported using them for disposal of child feces. Most child feces were deposited with other household waste, both for pre-ambulatory (67.5%) and ambulatory (58.1%) children. After restricting the analysis to households owning a latrine, the use of a nappy or potty was associated with safe disposal of feces (OR 6.72, 95%CI 1.02–44.38) though due to small sample size the regression could not adjust for confounders. Conclusions In the area surveyed, the Total Sanitation Campaign has not led to high levels of safe disposal of child feces. Further research is needed to identify the actual scope of this potential gap in programming, the health risk presented and interventions to minimize any adverse effect. PMID:24586864

  15. 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

  16. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2006-04-01

    Paleomagnetic analysis on 15 early Cambrian mafic dikes from Itabaiana (Paraíba State) yielded a southern (northwestern) direction with steep upward (downward) inclination ( Dm = 167.5°, Im = - 63.7°, α95 = 7.3°). AF and Thermal demagnetization, thermomagnetic curves, and hysteresis results suggest that this component is dominantly carried by fine-grained SD magnetite. The high stability of this component and positive baked contact tests on three dikes indicate it represents a primary thermoremanent magnetization. Ar-Ar analysis on whole-rock samples from two sites provides a strong constraint on the age of the Itabaiana paleomagnetic pole (134.6° E, 34.9° S; A95 = 7.3, K = 28) defined by plateau ages of 525 ± 5 and 526 ± 4 Ma. This pole completely satisfies six out of the seven quality criteria proposed by Van der Voo [R. Van der Voo, The reliability of paleomagnetic data, Tectonophysics 184 (1990) 1-9.] and permits a tight constraint on the Early Cambrian sector of the Gondwana apparent polar wander path. Paleogeographic reconstructions consistent with the available paleomagnetic and geological record show that Gondwana was sutured along three major orogenies, the Mozambique (Brasilano/Pan-African) Orogeny (800-650 Ma), the Kuunga Orogeny (570-530 Ma) and the Pampean-Araguaia Orogeny (540-520 Ma). We suggest that after rifting away from Laurentia at the end of the Neoproterozoic, opening the Iapetus ocean, the Amazonian craton and minor adjoining blocks, such as Rio Apa and Pampia, collided with the proto-Gondwana by Cambrian times at ca. 530-520 Ma. Unless for small adjustments, Gondwana was completely formed by 525 Ma whose paleogeography is defined by the Itabaiana pole.

  18. 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…

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. 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, Matías; Marok, Abbas; Sèbane, 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 δ13C 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.

  4. 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.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

    Álvaro, J. Javier; Ferretti, Annalisa; González-Gómez, Cristina; Serpagli, Enrico; Tortello, M. Franco; Vecoli, Marco; Vizcaïno, 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.

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

    NASA Astrophysics Data System (ADS)

    Naidoo, Thanusha; Zimmermann, Udo; Chemale, Farid

    2013-08-01

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

  9. 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 10°N southern boundary. Our simulations also suggest that two consecutive TCs result in 68% less surface energy loss of the top 50m than the sum of two stand-alone TCs. The comparisons between the simulations with TC-associated forcings and without TC-associated forcings show that surface shortwave radiative flux dominates the SST decrease over the eastern BoB water in the early stage of 05B, while wind stress-induced warm water advection mitigates it. Although TC-associated wind stress predominately reduce SST and enhance downward turbulent heat flux through mixing process over the northwestern BoB water in the later stage of 05B, the reduced downward solar radiation by the TC clouds significantly decreases the heat into the ocean. The overall effect of each forcing is not linearly additive.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Late Ordovician Early Silurian continental collisional orogeny in southern Mexico and its bearing on Gondwana-Laurentia connections

    NASA Astrophysics Data System (ADS)

    Ortega-Gutiérrez, Fernando; Elías-Herrera, Mariano; Reyes-Salas, Margarita; Macías-Romo, Consuelo; López, Robert

    1999-08-01

    New zircon and monazite U-Pb data, tectonic mapping, and petrologic studies in key units of the Acatlán Complex show a previously undocumented phase of continental collision orogeny of Late Ordovician Early Silurian age in southern Mexico. The event involved the partial eclogitization of oceanic lithosphere and continental crust, which traveled westward more than 200 km over siliciclastic metasedimentary rocks of the trench-forearc of an opposing continental margin. The overriding eastern margin was the Oaxaquia microplate attached to Gondwana, and the western overridden margin is considered to have been the eastern margin of Laurentia. This event, which we name the Acatecan orogeny, was roughly synchronous with the possible closure of Iapetus along the Appalachian margin, which involved, according to current models, either the docking of peri-Gondwanan terranes such as Avalonia and Carolina or the direct collision between Gondwana and Laurentia. The permanence of Oaxaquia in northwestern Gondwana until the end of the Silurian, as suggested by Tremadocian to Silurian marine faunas in the cover of Oaxaquia, is more consistent with the direct collision of Gondwana and Laurentia at the end of the Ordovician, forming the Acatlán Complex between.

  17. 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

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

    PubMed Central

    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

  19. 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

  20. 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.

  1. 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

  2. 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

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

    NASA Astrophysics Data System (ADS)

    Pastor-Galán, 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.

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. A new theropod dinosaur from India with remarks on the Gondwana-Laurasia connection in the Late Triassic

    NASA Astrophysics Data System (ADS)

    Chatterjee, S.

    Walkeria maleriensis (n. g., n. sp.) from the Late Triassic Maleri Formation of the Godavari Valley of India is the earliest known dinosaur from Asia. It is a small podokesaurid theropod, very similar to Procompsognathus of Germany, Coelophysis of North America, and Syntarsus from Zimbabwe and North America. The podokesaurs are of particular interest to students of organic evolution because they are the earliest known theropods from which Archaeopteryx, the oldest known fossil bird, was probably evolved. Traditionally, India has been regarded as a part of Gondwana. It is generally believed that Gondwana remained an integral geographic unit throughout the Triassic. If this is so, a strong faunal correlation between India and other Gondwana continents should be expected in Late Triassic time. Contrary to this, the Maleri fauna is overwhelmingly "northern". Walkeria occurs in association with metoposaurs, parasuchids, protorosaurs, aetosaurs, rhynchosaurs, and traversodonts. Most of these taxa have been identified in the Dockum fauna of North America, indicating a close paleontologic link between India and Laurasia. Possibly the route of faunal migration between India and North America during the Late Triassic was via northern Africa.

  13. 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.

  14. Epidemiology of episodic adenolymphangitis: a longitudinal prospective surveillance among a rural community endemic for bancroftian filariasis in coastal Orissa, India

    PubMed Central

    Babu, Bontha V; Nayak, Abhay N; Dhal, Kalpataru

    2005-01-01

    Background The epidemiological knowledge on acute condition of lymphatic filariasis is essential to understand the burden and issues on management of the disease. Methods A one year long longitudinal prospective surveillance of acute adenolymphangitis (ADL) was carried out in rural population of Orissa, India. Results The annual incidence of ADL per 1000 individuals is 85.0, and is slightly higher (P > 0.05) in male (92.0) than in female (77.6). A steady rise in the incidence of ADL episodes along with the age is recorded. The distribution indicates that persons with chronic disease are more prone to ADL attacks. The average number of episodes per year is 1.57 (1.15 SD) per affected person, and is gender dependent. Duration of the episode varies from 1 to 11 days with mean duration of 3.93 (1.94 SD) days. The chronic disease is the significant predictor for the duration of the episode. The data show that fever and swelling at inguinal regions are most common symptoms. Conclusion The incidence, frequency and duration of ADL episodes in this community are similar to that of other endemic areas. As the loss due to these ADL episodes is substantial, it should be considered while further estimating the burden due to lymphatic filariasis. The disability and loss caused by chronic forms of filariasis is higher, and the additional incapacity caused by the ADL episode, majority of which occur among chronic filariasis patients, further poses the burden on individuals and their families. Hence, morbidity management measures to prevent ADL episodes among endemic communities are to be implemented. PMID:15904537

  15. 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.

  16. 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

  17. 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

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. Sedimentological and sequence stratigraphic analysis of Carboniferous deposits in western Libya: Recording the sedimentary response of the northern Gondwana margin to climate and sea-level changes

    NASA Astrophysics Data System (ADS)

    Fröhlich, Sebastian; Petitpierre, Laurent; Redfern, Jonathan; Grech, Paul; Bodin, Stéphane; Lang, Simon

    2010-06-01

    Detailed sedimentological and sequence stratigraphic analysis of Carboniferous (Tournaisian to Moscovian) strata exposed in the north-western Murzuq Basin and southern Ghadames Basin, western Libya, provides new insights into the sedimentary response of the northern Gondwana margin to climate and sea-level change. The Lower Carboniferous Marar and Assedjefar Formations can be divided into five depositional sequences of 3rd order. In total 27 facies types are defined, grouped into four facies associations: offshore shales, shallow marine clastics, fluvial sandstones and marine carbonates. The bulk of the Lower Carboniferous interval is dominated by an alternation of offshore shales and shallow marine clastics, which were deposited during the transgressive and highstand systems tracts. The clastic deposits mostly consist of laterally persistent coarsening and thickening upward cycles with a common succession from basal hummocky cross-stratified sandstones to ripple-laminated sandstones, capped by multidirectional cross-stratified sandstones. Within the lowstand systems tracts, lenticular sandbodies have been identified, which vary in thickness from 1.5 m (ca. 40 m wide) to 50 m (ca. 1.5 km wide). These are interpreted to be fluvial channel complexes based on their geometry, erosive base, and presence of thick stacked sandstones with unidirectional planar and trough cross-bedding, the absence of bioturbation and occurrence of land plant fragments. These channel complexes mostly cut down into offshore shales, and are interpreted to be bound at the base by sequence boundaries. Palaeogeographic maps generated for each lowstand system show the location and palaeoflow direction of these fluvial channel complexes. They are interpreted to represent large incised valleys filled with thick fluvial sandstones. Their identification and distribution indicates repeated exposure of large areas of western Libya, most-likely controlled by major eustatic sea-level changes. The Assedjefar Formation exibits a gradual decrease in coarse clastic sediment supply throughout the Serpukhovian and by the Bashkirian and Moscovian during the deposition of the Dembaba Formation a carbonate depositional system was established. Limestones are dominantly made up of a heterozoan fauna (brachiopods, crinoids, bryozoans, gastropods) and are mostly preserved as shallow marine storm and coastal deposits. It is hypothesised that a local increase in aridity and/or the gradual erosion and decreasing topography of the hinterland mountains, with the resulting reduction in discharge, controlled this shift from clastic to carbonate deposition. Available data indicate that the Murzuq Basin was interconnected with the Ghadames Basin at this time and is a postdepositional basin with respect to the Carboniferous interval. The sedimentological and sequence stratigraphic data from the present study offer new insights into the depositional setting and facies distribution in the Carboniferous, and the recognition of major incised fluvial systems has significant implications in the search for potential Carboniferous hydrocarbon reservoirs in the Murzuq, Ghadames, and Illizi Basins.

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. Health status of the elderly population among four primitive tribes of Orissa, India: a clinico-epidemiological study.

    PubMed

    Kerketta, A S; Bulliyya, G; Babu, B V; Mohapatra, S S S; Nayak, R N

    2009-02-01

    Primitive tribal groups (PTGs) are the most marginalised and vulnerable communities in India. Clinico-epidemiological studies on morbidity patterns among the elderly primitive tribe members are essential to recommend special intervention programmes to improve the health of the elderly in these communities. A community-based cross-sectional study was carried out among the elderly populations of four different PTGs, namely Langia Saora (LS), Paudi Bhuiyan (PB), Kutia Kondh (KK) and Dongria Kondh (DK) living in the forests of Orissa, India. Clinical and anthropometric data were collected using standard methods and haemoglobin was estimated by the cyanomethaemoglobin method. The average number of illnesses per person was 3.0. Common disabilities like vision and hearing impairment and mobility-related problems were found in considerable numbers. Gastrointestinal problems like acid peptic disease were found among 2.6% to 20% of cases. Non-specific fever was marked in 10.2% to 24.2% of individuals. The iodine deficiency disorder, namely goitre, was found among 4.2% to 6.0% of individuals. Diseases of the respiratory tract, like upper and lower respiratory tract infection, asthma, tuberculosis and leprosy, were found in small numbers. The prevalence of hypertension among males and females was 31.8% and 42.2%, respectively. The LS had the highest prevalence of hypertension (63% among men and 68% among women). With regard to anaemia status, severe anaemia was marked in 70% of males and 76.7% of females in the LS, while in other groups the prevalence of severe anaemia ranged from 15% to 33%. Although the prevalence of severe anaemia in other tribal communities is lower than in the LS, mild to moderate anaemia was found to range from 60% to 80%. The present study revealed a high prevalence of physical disabilities with both non-communicable as well as communicable diseases among the elderly primitive tribal members. This warrants the implementation of a special health care strategy to reduce suffering at this crucial age and improve quality of life. PMID:18398631

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Aeromagnetic and gravity features of Gondwana and theirrelation to continental break-up: More pieces, less puzzle

    NASA Astrophysics Data System (ADS)

    Reeves, Colin V.

    Regional geophysical mapping techniques were initiated for economic exploration about 50 years ago and have now developed a completeness of coverage that can be exploited for geological research over large areas. The main strength of gravity and magnetic anomaly surveys lies in their ability to map 'basement' geology below cover. Suitably assembled and imaged at the continental-scale, the data give new insight into the mosaic of terranes that makes up the Precambrian continental crust, and into the margins of Precambrian continental fragments that have often been complicated by prolonged rifting before the onset of the drifting apart of continental fragments. Intrusions such as dykes, dyke swarms and plugs of small areal extent, that are often associated with continental disruption, can also be mapped with new totality. Examples using mainly aeromagnetic mapping are given to support a tight reassembly of the Precambrian crustal fragments of central Gondwana. In this, the outer margins of Precambrian blocks, known or interpreted from geophysical anomaly maps of the presently dispersed continents, are reassembled parallel and at a separation of only 50-80 km, typical of the width of present-day rift valleys. In the future, the wider availability of geophysical mapping data from both continents and oceans, with computer systems to process and interpret them, should contribute to a more fruitful co-operation of geologists and geophysicists in Gondwana research using more complete data coverage.

  7. 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

  8. Extreme freshwater release during the late Paleozoic Gondwana deglaciation and its impact on coastal ecosystems

    NASA Astrophysics Data System (ADS)

    Buatois, Luis A.; Netto, Renata G.; Mángano, M. Gabriela; Balistieri, Patricia R. M. N.

    2006-12-01

    Strata in the Paganzo, Tarija, and Paraná Basins of Argentina and Brazil provide evidence for reconstructing the effects of late Paleozoic glacial retreat. The depositional environment of the transgressive and early highstand fine-grained deposits has been controversial, with interpretations ranging from normal-marine shelves to estuaries to lakes. Whereas their counterparts from shallow-marine settings not influenced by glaciation host diverse, fully marine ichnofaunas, these fine-grained postglacial deposits are dominated by nonspecialized grazing trails, simple feeding traces, arthropod trackways, and fish trails. They are typical of freshwater environments and represent examples of the Mermia and Scoyenia ichnofacies. However, the local presence of acritarchs indicates sporadic marine influence. These observations suggest a new interpretation, that freshwater conditions in fjordlike settings across South America were widespread because Gondwanan basins were overwhelmed by strong meltwater discharge issuing from melting of the continental ice masses.

  9. Preliminary assessment of hydrocarbon potential of Larsen basin, Antarctica

    SciTech Connect

    MacDonald, D.I.M.; Barker, P.F.; Garrett, S.W.; Ineson, J.R.; Kinghorn, R.R.F.; Pirrie, D.; Storey, B.C.; Whitham, A.G.

    1987-05-01

    The Larsen basin, on the northwest margin of the Weddell Sea, formed as a Mesozoic ensialic basin during Gondwana breakup. At the northern end of this basin, 5-6 km of sedimentary rock crop out on James Ross Island, exposing elements of a large hydrocarbon system. Aeromagnetic and outcrop data suggest that the basin history inferred from James Ross Island persists to 70/sup 0/S. Deposition was in half-grabens on the extending Weddell Sea margin or in restricted back-arc basins. Upper Jurassic anoxic marine strata, deposited prior to rifting, form a rich potential source (TOC up to 2.5%) with both marine and terrestrial kerogens. Arc-derived volcaniclastic sediments of Barremian-Oligocene age form a regressive megasequence. Basal strata represent slope apron and rudaceous submarine fan deposits proximal to the margin; fan conglomerates form lenticular bodies hundreds of meters thick and tens of kilometers across, enveloped in slope-apron mudstones. Late Cretaceous fault reactivation and uplift led to dramatic shallowing of the basin, with deposition of shelf facies. Although there are many attractive reservoir targets, there may be problems of pore occlusion due to the abundant labile volcanic grains. However, there is evidence of more quartzose sandstone toward the top of the section and toward the basin center. In the northern Weddell basin, there is moderate potential for oil generated from Upper Jurassic source rocks and reservoired in Cretaceous and Tertiary sandstones and conglomerates, in large stratigraphic or structural traps caused by partial basin inversion during deposition.

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

    NASA Astrophysics Data System (ADS)

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

    2007-07-01

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

  11. 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.

  12. 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.

  13. 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.

  14. Late Paleozoic depositional controls in the Paradox basin, Colorado and Utah

    SciTech Connect

    Huffman, A.C. Jr. )

    1992-01-01

    The Paradox evaporite basin formed during the Desmoinesian to Wolfcampian intracratonic Ancestral Rocky Mountain orogeny in response to the Laurentia-Gondwana collision. Basin subsidence resulted from the southwestward thrusting and probably lateral movement on the Uncompahgre Fault along it's northeastern margin. This created a strongly asymmetrical basin that was similar in geometry to a foreland basin, with the Definace-Zuni and Piute platforms occupying the position of a foreland bulge. The evaporite basin was separated from its southeastern extension, the San Juan Trough, by the northeast-trending Hogback fault zone. An orthogonal pattern of northeast- and northwest-trending basement faults extends from the San Juan Basin into the Paradox Basin and can be shown to have exerted significant control on depositional patterns throughout the Phanerozoic. Paleogeographic and plate reconstructions indicate that the north-south-trending Uncompahgre and Front Range highlands lay at right angles to the prevailing easterly winds--thus removed most of the moisture and produced arid to semiarid conditions throughout the Paradox Basin and San Juan Trough. As many as 35 halite-bearing cycles have been identified in the Desmoinesian Paradox Formation. Each cycle is composed of a transgressive freshening phase and a regressive evaporitic phase with either halite or potash as the final product. All of the evaporite cycles are bounded by unconformities and can be divided into higher order sequences, particularly in the correlative carbonate shelf environments to the southwest.

  15. 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.

  16. 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.

  17. 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

  18. 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

  19. 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.

  20. 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.

  1. Coricladus quiteriensis gen. et sp. nov., a new conifer in Southern-Brazil Gondwana.

    PubMed

    Jasper, André; Ricardi-Branco, Fresia; Guerra-Sommer, Margot

    2005-03-01

    A new taxon of conifers (Coricladus quiteriensis) is described based on megafloristic remains from the roofshale level at the Quiteria Outcrop (Rio Bonito Formation-Lower Permian-Southern Parana Basin-Rio Grande do Sul-Brazil). This megafloristic community is included in the Botrychiopsis Zone--Botrychiopsis valida Sub-Zone (Kungurian/Roadian). The assemblage, preserved as impressions, do not present remains of epidermic characters, and is composed mainly of isolated vegetative branches with spirally disposed acicular leaves, presenting a conspicuous central vein and also isolated fertile branches with sparse and irregular leaves and terminal cones. Leafless principal branches, organically connected with sterile and fertile branches, are rare. Reproductive feminine scales, disposed in a plane, are organized in lax terminal cones on branches, composed by 4 (four) distal ovuliferous scales, and 8 (eight) elliptical-elongated anatropous seeds. Paleoecological data pointed out to a mesophylous to higrophylous habitat in swampy environments. PMID:15692685

  2. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

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

    PubMed Central

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

    2008-01-01

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

  5. 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).

  6. 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 ɛHf(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.

  7. 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.

  8. 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.

  9. Tectonic and paleoenvironmental evolution of Mesozoic sedimentary basins along the Andean foothills of Argentina (32°-54°S)

    NASA Astrophysics Data System (ADS)

    Franzese, Juan; Spalletti, Luis; Pérez, Irene Gómez; Macdonald, David

    2003-05-01

    Chronoenvironmental and tectonic charts are presented for Mesozoic basins located along the Andean foothills of the South American plate. On the basis of the main tectonic events, pre-Andean basins, break-up-related basins, extensional back-arc basins, and Andean foreland basins are recognized. The pre-Andean basins were formed by continental extension and strike-slip movement before the development of the Mesozoic-Cenozoic Andean magmatic arc. Upper Permian to Middle Triassic extension along Palaeozoic terrane sutures resulted in rifting, bimodal magmatism (Choiyoi group), and continental deposition (Cuyo basin). From the Late Triassic to the Early Jurassic, continental extension related to the collapse of the Gondwana orogen initiated a series of long, narrow half-grabens that filled with continental volcaniclastic deposits. These depocenters were later integrated into the Neuquén basin. Coeval development of the shallow marine Pampa de Agnia basin (42-44°S) is related to short-lived extension, probably driven by dextral displacement along major strike-slip faults (e.g. the Gastre fault system). Widespread extension related to the Gondwana breakup (180-165 Ma) and the opening of the Weddell Sea reached the western margin of the South American plate. As a result, wide areas of Patagonia were affected by intraplate volcanism (Chon Aike province), and early rifting occurred in the Magallanes basin. The Andean magmatic arc was almost fully developed by Late Jurassic times. A transgressive stage with starvation and anoxia characterized the Neuquén basin. In western Patagonia, back-arc and intra-arc extension produced the opening of several grabens associated with explosive volcanism and lava flows (e.g. Rı´o Mayo, El Quemado). To the south, a deep marginal basin floored by oceanic crust (Rocas Verdes) developed along the back-arc axis. In mid-to late Cretaceous times, Andean compressional tectonics related to South Atlantic spreading caused the inversion of previous extensional structures and the beginning of a retro-arc foreland phase in the Neuquén and Austral basins.

  10. 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.

  11. Evolution of the late Paleozoic accretionary complex and overlying forearc-magmatic arc, south central Chile (38°-41°S): Constraints for the tectonic setting along the southwestern margin of Gondwana

    NASA Astrophysics Data System (ADS)

    Martin, Mark W.; Kato, Terence T.; Rodriguez, Carolina; Godoy, Estanislao; Duhart, Paul; McDonough, Michael; Campos, Alberto

    1999-08-01

    Stratigraphic, structural, metamorphic, and geochronologic studies of basement rocks in the Andean foothills and Coast Ranges of south central Chile (39°-41°S) suggest a protracted late Paleozoic to middle Mesozoic deformational and metamorphic history that imposes important constraints on the tectonic development of the southwestern Gondwana margin. In the study area the late Paleozoic paired metamorphic belt, coeval magmatic arc, and overlying Triassic sedimentary units preserve a record of Late Carboniferous to Early Permian subduction and arc magmatism, subsequent deep exhumation of the Western Series subduction complex, and diminished uplift and erosion of the Eastern Series arc-forearc region by the Late Triassic. Late Paleozoic structural elements and metamorphic assemblages formed during early subduction and arc magmatism, collectively referred to as Dl, are largely erased in the Western Series by the dominant D2 schistosity and lower greenschist grade metamorphism. D1 structural features, as well as original sedimentary textures, are relatively well preserved in the less penetratively deformed Eastern Series. The regional distribution of late Paleozoic arc magmatism suggests that the late Paleozoic convergent margin deviated from a N-S trend north of this area to a NW-SE trend near this latitude and faced an open marine environment to the southwest. A transition from F2 isoclinal folding to more open, larger-scale F3 folds, interpreted as change in ductility during differential uplift of the Western Series, is not apparent in the Eastern Series. Despite a lesser degree of uplift during the main exhumational D2 event, delineation of unconformities and U-Pb dating of detrital zircons and intrusions into the Eastern Series allow tighter constraints to be placed on timing of uplift and denudation of the Eastern Series than on that in the Western Series. A regional unconformity exposed in the Lake District that separates more highly deformed Eastern Series lithologies from Late Triassic shallow marine to continental deposits suggests that substantial uplift also affected the inner forearc and magmatic arc region during the D2 event. We propose that dextral-oblique convergence, initiated during the middle Permian along this segment of the Gondwana margin, resulted in the transpressional uplift and juxtaposition of high pressure/temperature (P/T) Western Series against low P/T Eastern Series lithologies and culminated with deposition of Late Triassic, continental to shallow marine, coarse clastic sedimentary rocks in fault-bounded strike-slip basins adjacent to the exhumed Western Series. Large-scale dextral transpression and northward displacement of the accretionary complex during Late Permian to Late Triassic time along the Chilean margin of Gondwana are synchronous and kinematically compatible with widespread regional transpression, extension, and silicic magmatism inboard of the southern Gondwana margin at this time. We thank C. Mpodozis, M. Gardeweg, and J. Muñoz of the Servicio de Geología y Minería de Chile (SERNAGEOMIN) for their support of this work. Fruitful discussions with N. Blanco, F. Hervé, H. Moreno, C. Mpodozis, and F. Munizaga have aided in our understanding of the geology of the region. The hard work by the staff of SERNAGEOMIN's Puerto Varas office is graciously appreciated. We thank J.D. Walker and W.R. Van Schmus at the University of Kansas for allowing MWM use of their U-Pb and mass spectrometer facilities and J. Vargas and the staff of SERNAGEOMIN's geochemistry laboratory for their assistance in this project. F. Munizaga allowed us to cite an unpublished 40Ar-39Ar date. We thank G. Ya˜nez for access to aeromagnetic data. T. Kato wishes to thank W. G. Ernst. Comments by I. Dalziel, S. Kay, and V. Ramos helped clarify ideas presented in this paper and are greatly appreciated. This work is dedicated to our friend and colleague Alberto Campos C., who died in a climbing accident on Calbuco Volcano, 1996.

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

    NASA Astrophysics Data System (ADS)

    Götz, 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. Field evaluation of Olyset nets: a long-lasting insecticidal net against malaria vectors Anopheles culicifacies and Anopheles fluviatilis in a hyperendemic tribal area of Orissa, India.

    PubMed

    Sharma, S K; Upadhyay, A K; Haque, M A; Tyagi, P K; Mohanty, S S; Raghavendra, K; Dash, A P

    2009-03-01

    A village-scale trial was conducted on the efficacy of Olyset nets: a long-lasting insecticidal net (LLIN) factory treated with 2% wt:wt permethrin against malaria vectors Anopheles culicifacies Giles and Anopheles fluviatilis James, in Sundargarh District, Orissa, India. The study area comprised 22 villages that were randomized into three clusters and designated as Olyset net, untreated net, and no net clusters. Baseline studies showed that both vector species were 100% susceptible to permethrin. Results of wash resistance and bioefficacy of Olyset nets showed 100% mortality in An. culicifacies up to 11 washings, whereas 100% mortality was observed in An. fluviatilis even after 20 washings. The median knock-down time for these species ranged between 4.55-6.00 and 4.45-5.45 min, respectively, during 1 yr of intervention. In the Olyset net study area, there was a significant reduction of 80.6, 94.1, and 76.7% in the entry rate of An. culicifacies, An. fluviatilis, and other anopheline species, respectively, with an overall reduction of 63.5% in total mosquitoes. Floor sheet collections in houses with Olyset nets indicated 39% immediate mortality in total mosquitoes. The overall feeding success rate of mosquitoes in the trial village was only 18.0% in comparison to 44.2 and 79.1% in villages with untreated nets and no nets, respectively. A significant reduction was also recorded in parity rate and human blood index of vector species in the Olyset net area. This study showed that Olyset nets are an effective personal protection tool that can be used in a community-based intervention program. PMID:19351086

  18. 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

  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. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Rugose corals at the Tournaisian-Viséan transition in the Central Taurides (S Turkey) - Palaeobiogeography and palaeoceanography of the Asian Gondwana margin

    NASA Astrophysics Data System (ADS)

    Denayer, Julien

    2015-02-01

    This paper gives the first taxonomic description of the Upper Tournaisian-Lower Viséan rugose coral fauna of the Yaricak Formation (Aladag Unit, Central Taurides, South Turkey). Fifteen species belonging to twelve genera were identified, one species is newly described: Eokoninckocarinia gemmina. The corals are stratigraphically distributed in four assemblages. The two typical assemblages of the Upper Tournaisian are composed of widely distributed taxa (Uralinia, Caninia, Proheterelasma, Zaphrentites). The assemblage crossing the Tournaisian-Viséan boundary is characterized by Eurasian and cosmopolitan and widely distributed taxa (Calmiussiphyllum, Siphonophyllia, Bifossularia Amygdalophyllum, Caninophyllum, Keyserlingophyllum) and Asian taxa (Kueichouphyllum). The youngest assemblage, dominated by Eokoninckocarinia gemmina sp. nov., has yielded foraminifers Moliniacian (Lower Viséan) in age. These assemblages form a low diversity level-bottom community which is typical of the South Palaeotethys 'Kueichouphyllum Zone' extending along the Asian margin of Gondwana (Cimmerian Terrane) during Lower Carboniferous times. As in the other Cimmerian blocks, all the corals are solitary and colonial taxa are virtually absent. This absence is tentatively explained by the high palaeolatitude (c. 50°S) position of the Cimmerian Terrane in the southern part of the Palaeotethys Ocean for this time slice. A cold-water palaeo-current running eastward along the Gondwana margin might also be considered as it possibly could explain the wide distribution of the Kueichouphyllum fauna, restricted east of Africa in the southern coast of the Palaeotethys. Palaeoceanography, palaeoclimate and facies issues are discussed as possible causes of the diversity gradient observed between the eastern (Australia, Malaya) and the western (North Africa) margin of the Gondwana.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

    Albardeiro, Luís; 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.

  8. 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

  9. Was the easternmost segment of the Central Asian Orogenic Belt derived from Gondwana or Siberia: An intriguing dilemma?

    NASA Astrophysics Data System (ADS)

    Zhou, Jian-Bo; Wilde, Simon A.; Zhao, Guo-Chun; Zhang, Xing-Zhou; Wang, Hu; Zeng, Wei-Shun

    2010-09-01

    The Khanka Massif forms the easternmost segment of the Central Asian Orogenic Belt (CAOB) in NE China and its tectonic setting is highly controversial. Metasedimentary rocks from the Hulin Complex and the Mt. Huoshi sequence were selected to address this issue. For the Hulin Complex, SHRIMP detrital zircon U-Pb dating of a two-mica schist (sample HL-011) reveals a unimodal population with a weighted mean 206Pb/ 238U age of 257 ± 3 Ma, suggesting local derivation from nearby Permian granitoids. In contrast, a quartz schist (sample 04H-138) contains five zircon populations with ages of 233-270 Ma, 350-400 Ma, 473-570 Ma, 720-760 Ma and 930-970 Ma, and peaks at 252, 350, 520, 758 and 970 Ma, indicating a much more diverse provenance. Two samples of fine-grained gneiss were selected from Mt Houshi, with sample 06H-15 containing four zircon populations, with groupings at 260-340 Ma, 470-560 Ma, 710-940 Ma and a single grain at 2090 Ma, whereas zircons in sample 06H-16 define two populations with ages of 727-854 Ma, with a peak at 776 Ma, and a single grain with an age of 404 ± 13 Ma. The youngest detrital zircon was obtained from sample 04H-138 and has a 206Pb/ 238U age of 233 ± 9 Ma, limiting deposition of the Hulin Complex to after ˜233 Ma. The late Pan-African and Paleoproterozoic to Neoproterozoic ages, together with the ˜500 Ma age for granulite facies metamorphism previously determined for the Hutou Complex in the Khanka Massif, indicate that the Khanka and Jiamusi massifs (together with the Bureya Massif in Russia) formed a contiguous crustal unit. Detrital zircon data suggest that this combined block was not part of either the North China or the South China cratons. Instead, it was either derived from a peri-Gondwana position, a rifted portion of the Songliao Massif in the CAOB, an exotic block of unknown affinity, or from the Siberia Craton. We evaluate the possibility that the Khanka/Jiamusi/Bureya block may have originated in Siberia and once formed part of the Sayan-Baikal orogen at ˜500 Ma. Whatever its origin, the block drifted westward to collide with the Songliao Massif of NE China in the latest Triassic-Early Jurassic as a result of the onset of Pacific-plate subduction. It thus forms part of the evolving supercontinent of Eurasia.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  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 (2σ) 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. 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 Oclóyic Orogeny (Ashgillian). The folded strata were intruded post-tectonically by the presumably Silurian granitoids of the "Faja Eruptiva de la Puna Oriental." The orogeny led to the formation of the positive area of the Arco Puneño. West of the Arco Puneño, a further marine basin developed during the Early Devonian, the eastern shelf of which occupied the area of the Cordillera Occidental, Depresión Preandina, and Precordillera. The corresponding deep marine turbidite basin was located in the region of the Cordillera de la Costa. Deposition continued until the basin fill was folded in the early Late Carboniferous Toco Orogeny. The basin originated as an extensional structure at the continental margin of Gondwana. Independent lines of evidence imply that basin evolution was not connected to subduction. Thus, the basin could not have been in a fore-arc position as previously postulated. Above the folded Devonian-Early Carboniferous strata, a continental volcanic arc developed from the Late Carboniferous to the Middle Triassic. It represents the link between the Choiyoi Province in central Chile and Argentina, and the Mitu Group rift in southern Peru. The volcanic arc succession is characterized by the prevalence of silicic lavas and tuffs and volcaniclastic sedimentary rocks. During the latest Carboniferous, a thick ostracod-bearing lacustrine unit formed in an extended lake in the area of the Depresión Preandina. This lake basin originated in an intra-arc tensional setting. During the Early Permian, marine limestones were deposited on a marine platform west and east of the volcanic arc, connected to the depositional area of the Copacabana Formation in southern Peru.

  18. 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.

  19. 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

  20. 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.

  1. Effect of Household-Based Drinking Water Chlorination on Diarrhoea among Children under Five in Orissa, India: A Double-Blind Randomised Placebo-Controlled Trial

    PubMed Central

    Boisson, Sophie; Stevenson, Matthew; Shapiro, Lily; Kumar, Vinod; Singh, Lakhwinder P.; Ward, Dana; Clasen, Thomas

    2013-01-01

    Background Boiling, disinfecting, and filtering water within the home can improve the microbiological quality of drinking water among the hundreds of millions of people who rely on unsafe water supplies. However, the impact of these interventions on diarrhoea is unclear. Most studies using open trial designs have reported a protective effect on diarrhoea while blinded studies of household water treatment in low-income settings have found no such effect. However, none of those studies were powered to detect an impact among children under five and participants were followed-up over short periods of time. The aim of this study was to measure the effect of in-home water disinfection on diarrhoea among children under five. Methods and Findings We conducted a double-blind randomised controlled trial between November 2010 and December 2011. The study included 2,163 households and 2,986 children under five in rural and urban communities of Orissa, India. The intervention consisted of an intensive promotion campaign and free distribution of sodium dichloroisocyanurate (NaDCC) tablets during bi-monthly households visits. An independent evaluation team visited households monthly for one year to collect health data and water samples. The primary outcome was the longitudinal prevalence of diarrhoea (3-day point prevalence) among children aged under five. Weight-for-age was also measured at each visit to assess its potential as a proxy marker for diarrhoea. Adherence was monitored each month through caregiver's reports and the presence of residual free chlorine in the child's drinking water at the time of visit. On 20% of the total household visits, children's drinking water was assayed for thermotolerant coliforms (TTC), an indicator of faecal contamination. The primary analysis was on an intention-to-treat basis. Binomial regression with a log link function and robust standard errors was used to compare prevalence of diarrhoea between arms. We used generalised estimating equations to account for clustering at the household level. The impact of the intervention on weight-for-age z scores (WAZ) was analysed using random effect linear regression. Over the follow-up period, 84,391 child-days of observations were recorded, representing 88% of total possible child-days of observation. The longitudinal prevalence of diarrhoea among intervention children was 1.69% compared to 1.74% among controls. After adjusting for clustering within household, the prevalence ratio of the intervention to control was 0.95 (95% CI 0.79–1.13). The mean WAZ was similar among children of the intervention and control groups (−1.586 versus −1.589, respectively). Among intervention households, 51% reported their child's drinking water to be treated with the tablets at the time of visit, though only 32% of water samples tested positive for residual chlorine. Faecal contamination of drinking water was lower among intervention households than controls (geometric mean TTC count of 50 [95% CI 44–57] per 100 ml compared to 122 [95% CI 107–139] per 100 ml among controls [p<0.001] [n = 4,546]). Conclusions Our study was designed to overcome the shortcomings of previous double-blinded trials of household water treatment in low-income settings. The sample size was larger, the follow-up period longer, both urban and rural populations were included, and adherence and water quality were monitored extensively over time. These results provide no evidence that the intervention was protective against diarrhoea. Low compliance and modest reduction in water contamination may have contributed to the lack of effect. However, our findings are consistent with other blinded studies of similar interventions and raise additional questions about the actual health impact of household water treatment under these conditions. Trial Registration ClinicalTrials.gov NCT01202383 Please see later in the article for the Editors' Summary PMID:23976883

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

    NASA Astrophysics Data System (ADS)

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

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

  3. 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.

  4. 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-grade or unmetamorphosed sediments. Thus Yemen provides key information on the broad zone of Neoproterozoic reworking associated with the collisional boundary between western and eastern Gondwana

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. New African Lower Carboniferous paleomagnetic pole from intrusive rocks of the Tin Serririne basin (Southern border of the Hoggar, Algeria)

    NASA Astrophysics Data System (ADS)

    Derder, M. E. M.; Henry, B.; Bayou, B.; Ouabadi, A.; Bellon, H.; Djellit, H.; Khaldi, A.; Amenna, M.; Baziz, K.; Hemmi, A.; Guemache, M. A.

    2006-06-01

    A paleomagnetic study has been conducted on intrusive doleritic rocks cropping out within Devonian horizontal tabular formations of the Saharan craton (Tin Serririne basin, South of Hoggar shield). The 40K/ 40Ar dating of the dolerites gave an age of 347.6 ± 8.1 Ma, i.e. Tournaisian. The paleomagnetic data present three different directions. The first has a paleomagnetic pole close to the previous African poles of Permian age. This direction is therefore interpreted as a Permian remagnetization. The second direction, which is defined by both linear regression and remagnetization circles analysis, is considered as the primary magnetization. It yields a new African Tournaisian paleomagnetic pole ( λ = 18.8° S, ϕ = 31.2° E, K = 29, A95 = 7.5°) very close to the Ben Zireg Tounaisian pole [Aifa, T., Feinberg, H., Pozzi, J.P., 1990. Devonian/Carboniferous paleopoles for Africa. Consequences for Hercynian geodynamics. Tectonophysics, 179, 288-304]. The third direction has intermediate orientation between those of the first or second directions and that of the Upper Cenozoic field. It is interpreted as related to a composite magnetization. This new Tin Serririne pole improves the APWP of Gondwana, for this key period of the evolution of the Pangea. This APWP confirms the previous paleogeographic reconstruction which shows that the pre-Hercynian ocean between Gondwana and Laurussia is still not close during the beginning of the Carboniferous.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

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

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

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. Sequence stratigraphy of continental Triassic strata of Southernmost Brazil: a contribution to Southwestern Gondwana palaeogeography and palaeoclimate

    NASA Astrophysics Data System (ADS)

    Zerfass, Henrique; Lavina, Ernesto Luiz; Schultz, Cesar Leandro; Garcia, Antônio Jorge Vasconcellos; Faccini, Ubiratan Ferrucio; Chemale, Farid

    2003-09-01

    The continental Triassic succession of southernmost Brazil comprises two second-order depositional sequences—the Sanga do Cabral (Early Triassic) and the Santa Maria (Middle to Late Triassic) supersequences. The first one includes ephemeral, low-sinuosity fluvial deposits developed on a low gradient plain. Based on fossil tetrapods, especially procolophonids, an Upper Induan age is estimated for this sequence. Facies association of the Santa Maria Supersequence indicates low-sinuosity fluvial rivers, deltas and lakes. This supersequence can be further subdivided into three third-order sequences (age provided by palaeovertebrate biostratigraphic data) as follows: Santa Maria 1 (Ladinian), Santa Maria 2 (Carnian to Early Norian) and Santa Maria 3 (probably Raethian or Early Jurassic) sequences. The Gondwanides paroxysms I and II in the Sierra de la Ventana-Cape Fold Belt are directly related to the development of both supersequences. The source area of the Sanga do Cabral Supersequence was located to the south. It consisted of an uplifted peripheral bulge situated landward of the retro-foreland system, from where older sedimentary rocks were eroded. The source area of the Santa Maria Supersequence was also positioned southwards and related to the uplifted Sul-Rio-Grandense and Uruguayan shields. The Santa Maria Supersequence stratigraphic architecture is comparable to the Triassic rift basins of Western Argentina. Diagenesis, facies and palaeontology of the studied succession suggest a dominantly semiarid climate during the Triassic.

  2. 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

  3. 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.

  4. Upper Cisuralian palynology and palaeoclimate of Manuguru area Godavari basin, India and their global correlation

    NASA Astrophysics Data System (ADS)

    K, Pauline Sabina; Jha, Neerja

    2014-10-01

    The Permian system of the Palaeozoic Erathem is divided into three series, the Early Permian Cisuralian Series, the Middle Permian Guadalupian Series, and the Late Permian Lopingian Series. The Cisuralian Series encompasses the Asselian to Kungurian stages which constitute the basal part of the Gondwana supersequence I. In India, they are represented lithostratigraphically by the Talchir, Karharbari, and Barakar formations. This paper presents the palynological results from the Barakar Formation of the Upper Cisuralian Series from Manuguru which lies in the southeastern part of the Godavari basin. The succession studied comprises 35 subsurface samples from bore hole 1007 represented by clay, shale, sandstone, and coal. The palynofloras in this sequence have a homogenous composition demonstrating that not many significant floral changes took place through the considered stratigraphic range. The entire sequence is characterized by the dominance of nonstriate bisaccate genus Scheuringipollenites and sub-dominance of striate bisaccate genus Faunipollenites(= Protohaploxypinus). The other pollen genera among the nonstriate bisaccates are Rhizomaspora, Primuspollenites, Ibisporites, and Platysaccus. The striate bisaccates include Striatites, Striatopodocarpites, and Stroterosporites. The taeniate taxa are represented by Lueckisporites and Lunatisporites. The common monosaccate genera include Caheniasaccites, Potoniesporites, and Barakarites. Spores are less common and include Latosporites, Brevitriletes, Horriditriletes, Microbaculispora, and Callumispora. They characterize the palynofloral composition of the Lower Barakar Formation. The correlation of this assemblage with some of the biostratigraphic palynozones proposed previously for the Cisuralian sequences of the Paraná Basin of South America, Kalahari Karoo Basin of South Africa, Ruhuhu Basin of Tanzania, East Africa as well as palynoassemblages from South Victoria Land and Dronning Maud Land, Antarctica and Collie Basin of west Australia point out to their Early Permian (Late Sakmarian-Early Artinskian) age. Palynomorphs such as Botryococcus sp., Tetraporinia sp., Balmeela sp. and Leiosphaeridia sp. are also recorded which suggest that these sediments were deposited during post-glacial near shore, cool and humid environment.

  5. 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; Gärtner, 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. ɛHf( 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 ɛHf( 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 ɛHf( 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.

  6. 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.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

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

    SciTech Connect

    Tadesse, K.; Ebinger, C.J.; Clark, R.A.

    1996-12-31

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

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

    SciTech Connect

    Tadesse, K.; Ebinger, C.J.; Clark, R.A. )

    1996-01-01

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

  15. 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.

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

    PubMed

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

    2007-10-01

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

  17. 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.

  18. 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).

  19. 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.

  20. 3D Geophysical Modelling of the Beattie Magnetic Anomaly and Karoo Basin, South Africa

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  1. 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.

  2. 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.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  5. 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.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  8. 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).

  9. Petrology and mineral equilibrium modeling of incipient charnockite from the Lützow-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 Lützow-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 Lützow-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 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.

  11. Tectono-sedimentary evolution of the Gondwanan Satpura Basin of central India: evidence of pre-Trap doming, rifting and pal˦oslope reversal

    NASA Astrophysics Data System (ADS)

    Casshyap, S. M.; Khan, A.

    2000-07-01

    The Mesozoic Gondwanan Satpura Basin of central India, comprising an approximately 1300 m thick sequence of the Pachmarhi, Denwa and Bagra Formations, was subjected to at least three major tectonic events. These events are manifested by tectonic dislocation, marginal uplifts, basin subsidence and deformation, as well as by stratigraphical disposition, lithofacies assemblage, and palaeoslope and pal˦ocurrent patterns. The first tectonic event is manifested by the onset of Early Triassic Pachmarhi sedimentation, which is marked in the basal part by a sudden increase of conglomeratic, pebbly, gritty to coarsegrained cross-bedded sandstone. This contrasts with the underlying fine elastics of the Late Permian Bijori Formation. The stratigraphical relationship and lithofacies, together with pal˦ocurrent and petrographic data, reflect tectonic uplift in the source area to the southeast of the Satpura Basin during or prior to the deposition of Pachmarhi Formation. The pebbly coarse sandy facies of the Pachmarhi Formation represents a braided river assemblage, overlain by a meandering river facies of the Denwa Formation, with river systems flowing dominantly from southeast to northwest. The progressive change in lithofacies and grain size upward from Pachmarhi to Denwa implies that the source area became peneplained and that the basin stabilised. During the prolonged gap of non-deposition, following the Mid-Triassic break in sedimentation after deposition of the Denwa Formation, a second tectonic event resulted in the widespread faulting and uplift of Permo-Triassic Gondwana sediments and basement rocks, respectively, to the south and north of the Narmada-Son Lineament Zone of Peninsular India. A third tectonic event is manifested by Late Jurassic-Early Cretaceous Bagra conglomerate and sandstone-shale facies in the northern part of the Satpura Basin. This formation, which unconformably overlies the Precambrian, and Permian and Triassic Gondwana formations or abuts against faulted contacts, represents proximal and distal facies of an alluvial fan deposit in a rifted (pull-apart?) basin with uplifted highlands to the north. This tectonism, representing the termination of continental Gondwana sedimentation, preceded the widespread eruption of the Deccan Traps (65 Ma) after the break-up of India from Antarctica. As a consequence, a northward sloping, peninsular craton was tilted southward and small rift basins developed along peripheral parts to the north, west and along the east coast of Peninsular India. To the north of the study area, the doming before the Deccan volcanism and tectonic movement along the Narmada-Son Lineament caused uplift of the Palaeoproterozoic Mahakoshal/Bijawar terrane. This uplift was accompanied by a reversal of palaeoslope. Consequently, north to south pal˦currents followed the deposition of the Pachmarhi and Denwa Formations, as borne out by the alluvial fan-braided complex of the Bagra Formation.

  12. 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.

  13. 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...

  14. Putting the "Basin" Back in Southeastern Arizona's Basin and Range

    NASA Astrophysics Data System (ADS)

    Jungers, M. C.; Heimsath, A. M.

    2011-12-01

    The pace and pattern of southeastern Arizona's transition from a series of internally drained sedimentary basins to the modern, integrated Gila River system are poorly constrained. Steep normal faulting associated with the Basin and Range disturbance ~12-5 Ma created structural basins that filled with sediment throughout the Late Miocene and Early Pliocene. Early rates of basin deposition were rapid due to high upland erosion rates driven by continuous base level fall within the extensional basins. Subsequently, as tectonic forcing waned, sedimentation rates slowed until a combination of basin spillover events and headward capture integrated individual basins into a through-flowing drainage network. Newly integrated streams with suddenly lower base levels rapidly incised, perching the uppermost surfaces of basin fill and eroding large volumes of sediment throughout the Quaternary. Relatively thin (10-100 m), coarse-grained alluvial fan remnants on erosional surfaces of basin fill or bedrock pediments are commonly the highest elevation, undeformed deposits in basins of southeastern Arizona. Although they often overlie basin-bounding faults, it is rare that they are cut by these faults. This suggests quiescent tectonics both during and after the deposition of these alluvial fans. Early work on two complexes of these alluvial fan remnants (Menges and McFadden, 1981) used the degree of soil development of relict soils on the fan surfaces to estimate an age of at least 1 Ma for these basin high stands. Further, the degree of soil oxidation and the depth of weathering suggest a wetter climate when these relict soils were forming. This age estimate and inference of a different climate begin to inform a model for climatically driven deposition of these coarse-grained fan deposits at the Pliocene-Pleistocene shift, but absolute dates are lacking. Here we report spatial and temporal patterns of regional drainage integration focusing on the timing of abandonment for uppermost surfaces of basin fill (10Be derived surface exposure dates are pending) and we present basin surface reconstructions. Previous research has suggested that uppermost basin fill surfaces are roughly correlative. We use our data to 1) test the hypothesis of broadly synchronous timing for a regional shift from internal drainage to external drainage for southeastern Arizona's basins, and 2) infer incision rates through the Quaternary. We have identified basin high stand remnants throughout several basins of interest in southeastern Arizona, and use spline interpolations to reconstruct basin fill surfaces. By subtracting the modern day topography from reconstructed basin surfaces, we quantify first order estimates of incision rates through basin fill since drainage integration. Our surface exposure dates will allow accurate quantification of incision rates for each basin, and resolve regional patterns of drainage integration.

  15. 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.

  16. 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.

  17. Taunton River basin

    USGS Publications Warehouse

    Williams, John R.; Willey, Richard E.

    1970-01-01

    This report presents in tabular form selected records of wells, test wells, and borings collected during a study of the basin from 1966 to 1968 in cooperation with the Massachusetts Water Resources Commission, and during earlier studies. This report is released in order to make available to the public and to local, state, and federal agencies basic ground-water information that may aid in planning water-resources development. Basic records contained in this report will complement an interpretative report on the Taunton River basin to be released at a later date.

  18. 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.

  19. Geophysical evidence of pre-sag rifting and post-rifting fault reactivation in the Parnaíba basin, Brazil

    NASA Astrophysics Data System (ADS)

    Lopes de Castro, David; Hilário Bezerra, Francisco; Adolfo Fuck, Reinhardt; Vidotti, Roberta Mary

    2016-04-01

    This study investigated the rifting mechanism that preceded the prolonged subsidence of the Paleozoic Parnaíba basin in Brazil and shed light on the tectonic evolution of this large cratonic basin in the South American platform. From the analysis of aeromagnetic, aerogravity, seismic reflection and borehole data, we concluded the following: (1) large pseudo-gravity and gravity lows mimic graben structures but are associated with linear supracrustal strips in the basement. (2) Seismic data indicate that 120-200 km wide and up to 300 km long rift zones occur in other parts of the basins. These rift zones mark the early stage of the 3.5 km thick sag basin. (3) The rifting phase occurred in the early Paleozoic and had a subsidence rate of 47 m Myr-1. (4) This rifting phase was followed by a long period of sag basin subsidence at a rate of 9.5 m Myr-1 between the Silurian and the late Cretaceous, during which rift faults propagated and influenced deposition. These data interpretations support the following succession of events: (1) after the Brasiliano orogeny (740-580 Ma), brittle reactivation of ductile basement shear zones led to normal and dextral oblique-slip faulting concentrated along the Transbrasiliano Lineament, a continental-scale shear zone that marks the boundary between basement crustal blocks. (2) The post-orogenic tectonic brittle reactivation of the ductile basement shear zones led to normal faulting associated with dextral oblique-slip crustal extension. In the west, pure-shear extension induced the formation of rift zones that crosscut metamorphic foliations and shear zones within the Parnaíba block. (3) The rift faults experienced multiple reactivation phases. (4) Similar processes may have occurred in coeval basins in the Laurentia and Central African blocks of Gondwana.

  20. 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.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Biplab

    2013-06-01

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

  3. 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.

  4. 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 fragmentation of Variscan fold belt. With this process was associated the formation of many transtensional pull-apart continental - lacustrian sedimentary basins and intra-continental rifts in which or in adjacent areas the intrusive - extrusive magmatism was widespread and where the deep crustal fractures were active. From climatic point of view the main consequence of continue convergence between Laurasia and Gondwana is the transition from relatively wet regime during Stephanian to arid during the Permian induced by the elevation of the equatorial highlands Variscan fold belt was acted as a precipitation barrier for the whole territory located to the north. Tacking into account of all these aspects, the Resita domain presents the similarities in the lithological composition with Autun Basin and the Sirinia - Presacina zone displays many common features with Saar - Nahe and Thuringian Forest Basins and North German/Polish Depression. This work started during PALEOCLIM project (grant ANCS - PN2, 31-063/2007), which is gratefully acknowledged. References Nastaseanu S. 1987. In: Flügel E., Sassi F. & Grecula P. (eds): Pre-Variscan and Variscan events in the Alpine-Mediterranean mountain belts. - Mineralia Slovaca. Alfa Bratislava, 371-378. Stollhofen H., Frommherz B., Stanistreet I. G. 1999. J. Geol. Soc. London 156, 801-808. Ziegler P. A. 1990. Shell Int. Petrol. Mij. Dist. Geol. Soc. Publ. House, Bath, 1-239.

  5. 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 (εNd630 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 Río 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.

  6. 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.

  7. 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.

  8. Natural frequency of regular basins

    NASA Astrophysics Data System (ADS)

    Tjandra, Sugih S.; Pudjaprasetya, S. R.

    2014-03-01

    Similar to the vibration of a guitar string or an elastic membrane, water waves in an enclosed basin undergo standing oscillatory waves, also known as seiches. The resonant (eigen) periods of seiches are determined by water depth and geometry of the basin. For regular basins, explicit formulas are available. Resonance occurs when the dominant frequency of external force matches the eigen frequency of the basin. In this paper, we implement the conservative finite volume scheme to 2D shallow water equation to simulate resonance in closed basins. Further, we would like to use this scheme and utilizing energy spectra of the recorded signal to extract resonant periods of arbitrary basins. But here we first test the procedure for getting resonant periods of a square closed basin. The numerical resonant periods that we obtain are comparable with those from analytical formulas.

  9. 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.

  10. 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.

  11. Aeromagnetic signatures reveal a back-arc basin imposed upon the inherited rifted margin of the East Antarctic craton

    NASA Astrophysics Data System (ADS)

    Armadillo, E.; Ferraccioli, F.; Jordan, T. A.; Bozzo, E.

    2009-12-01

    The Wilkes Subglacial Basin (WSB) represents a largely unexplored, approximately 1400 km-long and up to 600 km-wide subglacial depression, buried beneath the over 3 km-thick East Antarctic Ice Sheet. During the 2005-06 austral summer an extensive aerogeophysical survey was flown to investigate the WSB adjacent to northern Victoria Land (NVL), and included the acquisition of new airborne radar, aeromagnetic and aerogravity data. Several contrasting models for the origin of the basin have been previously proposed, and are based primarily on relatively sparse gravity data. These range from Cenozoic flexure, to distributed crustal extension of unknown age (possibly Mesozoic to Cenozoic), and even compression along the margin of craton. Our recent aeromagnetic data reveal that the basin is structurally controlled and has a tectonic origin, at least adjacent to NVL. The eastern margin of the basin is imposed upon an Early Paleozoic thrust fault belt, which can be traced under the ice using aeromagnetic signatures from exposures in Oates Land and the Ross Sea coast. Aeromagnetic patterns reveal that the western margin of the basin is imposed upon a Proterozoic-age shear zone mapped in the Mertz Glacier, and that is interpreted from geological studies to represent the continuation of a coeval shear zone in Australia. The broad aeromagnetic and satellite magnetic low over the WSB contrasts with the high over the un-reworked Proterozoic craton to the west of the basin, and is interpreted to reflect Neoproterozoic-age sediments deposited along the rifted margin of the craton. Magnetic intrusions within the WSB are interpreted as back-arc plutons that formed later in response to Cambrian-Ordovician age subduction along the paleo-Pacific margin of Gondwana. The aeromagnetic interpretation for a former broad back-arc basin in the WSB is supported by the occurrence of low-grade metasedimentary rocks of back-arc affinity in Oates Land, and also by the similarity in long-wavelength magnetic anomaly signatures of the WSB and the back-arc mobile belt of the North American Cordillera.

  12. 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.

  13. Mercury's Caloris Basin

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Mercury: Computer Photomosaic of the Caloris Basin

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

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

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

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

  14. 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.

  15. ADVANCED CHEMISTRY BASINS MODEL

    SciTech Connect

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

    2004-05-01

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

  16. 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.

  17. 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).

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Geology of the Mesozoic-Tertiary sedimentary basins in southwestern Somalia

    NASA Astrophysics Data System (ADS)

    Kassim M, Ali; Carmignani, L.; Conti, P.; Fantozzi, P. L.

    2002-02-01

    Two main sedimentary basins can be recognized in southern Somalia, the NE-SW trending Mesozoic-Tertiary Somali coastal basin, and the NNE-SSW Mesozoic Luuq-Mandera basin. The two basins are separated by the Bur region where the Proterozoic-Early Paleozoic Metamorphic basement of southern Somalia outcrops. The investigated area covers part of the Metamorphic basement of southern Somalia and of the Luuq-Mandera basin, although this basement is not described in details in this paper. In the Bur region the basement outcrops discontinuously near inselbergs and monadnocks, which stand out of a blanket of recent sediments. Because of this patchy distribution and the limited areal extent of the outcrops, the structure of the metamorphic basement is difficult to reconstruct. A NW-SE trend of structures prevails and two metamorphic complexes (the Olontole and Diinsor complexes) can be recognized. The Luuq-Mandera basin is a wide NNE-SSW synclinorium, delimited to the SE by the basement high of the Bur region, and to the west by the crystalline basement high of NE Kenya (Northern Frontier district). The extreme thickness of Triassic sediments in the axial part of the basin, and the thinner and younger succession on both sides of the basin suggest that the Luuq-Mandera basin was a subsiding elongated area that was invaded by the sea in the early Mesozoic, during the dismembering of Gondwana. The Jurassic-Cretaceous succession that followed comprises two main cycles of transgression and regression; the carbonate sediments that lie at the bottom pass up section into shales, evaporites and sandstone deposits. Since late Cretaceous, continental contition prevaled, with a long phase of peneplanation, and then a general uplift, which brought about the creation of lake depressions and the capture of the Dawa river, with formation of the present Jubba valley. The main tectonic events in the study area, and throughout SW Somalia, are represented by strike-slip movements along vertical faults in the Sengif and Garbahaarrey belt. Deformation is localized within a narrow belt that extends for more than a 100 km in a NE-SW direction. The near parallelism between the fold axes and the regional orientation of faults indicates a right-lateral movements along faults. The structure of the Garbahaarrey belt consists of an anastomosing fault system that delimits elongated folded blocks, arranged in anticline-syncline structures, with subvertical axial surfaces and fold axes parallel to the main wrench faults. The orientation of folds and the typical "positive flower structure" profile of the anticlines indicate that shortening was perpendicular to the strike of the wrench, i.e. in a SE-NW direction. In the Garbahaarrey belt, strike-slip and shortening, therefore, occurred contemporaneously and led to a relative transpression between the NW and SE blocks. The observed parallelism between fold and fault orientation cannot be explained with a simple rotation of pre-existing fold axes during transpression, but can be regarded as an example of folding and strike-slip movements that occurred simultaneously but independently along frictionless faults. The faults delimiting the anticlines accommodated the strike-slip component of transpression only, whereas the compressive component led to the generation of fold axes parallel to the wrench zone. Results of the field work are summarized in two geological maps of the Gedo, Bakool, and Bay regions (1:250,000) which accompany this report (maps are attached with this issue).

  3. 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.

  4. Apollo Basin, Moon: Estimation of Impact Conditions

    NASA Astrophysics Data System (ADS)

    Echaurren, J. C.

    2015-07-01

    The Apollo Basin is a, pre-Nectarian, multi-ring basin located within the large South Pole-Aitken Basin (SPA). Multispectral data from both Galileo and Clementine showed that the composition of materials in Apollo is distinct…

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Moon: two new mascon basins.

    PubMed

    Campbell, M J; O'leary, B T; Sagan, C

    1969-06-13

    Lunar gravity data and orbital photography indicate that there is a mascon basin approximately 1000 kilometers in diameter on the farside of the moon and that Mare Marginis is the flooded fraction of a mascon basin approximately 900 kilometers in diameter. PMID:17772565

  10. Out in the Atchafalaya Basin

    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...

  11. 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.

  12. 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...

  13. 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.

  14. 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.

  15. Crinoids columnals (Echinodermata) of the Ererê Formation (late Eifelian-early Givetian, Amazon Basin), State of Pará, 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 Ererê Formation in the Amazon Basin. Since then, the echinoderms of this formation have not been studied. This study, based on isolated pluricolumnals and columnals, described and identified Botryocrinus meloi n. sp., the first record for this genus in Brazil. In addition to this species, two other morphological patterns were identified: Tjeecrinus sp. and Morphotype AM/Er-01. The form of occurrence of the crinoid material and the paleoautoecology of B. meloi allow preliminary characterization of the habitat as a moderately deep water with weak to moderate currents and soft substrate. The similarity between B. meloi and Botryocrinus montguyonensis and of Tjeecrinus? sp. and T. crassijugatus, from the Devonian of the Armorican and Rhenan Massif, represents new evidence for the existence of contact between the faunas of the Amazon Basin with those of northern Gondwana and Armorica during the Middle Devonian.

  16. Thermal evolution of the Sisters shear zone, southern New Zealand; Formation of the Great South Basin and onset of Pacific-Antarctic spreading

    NASA Astrophysics Data System (ADS)

    Kula, Joseph; Tulloch, Andy J.; Spell, Terry L.; Wells, Michael L.; Zanetti, Kathleen A.

    2009-10-01

    The separation of Zealandia from West Antarctica was the final stage in the Cretaceous breakup of the Gondwana Pacific margin. Continental extension resulting in formation of the Great South Basin and thinning of the Campbell Plateau leading to development of the Pacific-Antarctic spreading ridge was partially accommodated along the Sisters shear zone. This east-northeast striking brittle-ductile structure exposed along the southeast coast of Stewart Island, New Zealand, is a greenschist facies extensional shear zone that separates a hanging wall of chloritic, brecciated granites, and undeformed conglomerate from a footwall of mylonitic Carboniferous and Early Cretaceous granites. This complex structure exhibits bivergent kinematics and can be subdivided into a northern and southern segment. The 40Ar/39Ar thermochronology indicates that cooling of the shear zone footwall began at ˜94 Ma with accelerated cooling over the interval ˜89-82 Ma. Structural and thermochronological data indicate a spatial and temporal link between the Sisters shear zone, initial sedimentation within the offshore Great South Basin, extension of the Campbell Plateau, and initiation of the Pacific-Antarctic spreading ridge.

  17. 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.

  18. 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.

  19. 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.

  20. KE Basin Sludge Flocculant Testing

    SciTech Connect

    Schmidt, Andrew J.; Hallen, Richard T.; Muzatko, Danielle S.; Gano, Sue

    2004-06-23

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

  1. 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.

  2. 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.

  3. The Amazon basin in transition.

    PubMed

    Davidson, Eric A; de Araújo, 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

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  5. 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.

  6. 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.

  7. 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.

  8. Zircon U-Pb geochronology of granitic rocks of the Cordón de Lila and Sierra de Almeida ranges, northern Chile: 30 m.y. of Ordovician plutonism on the western border of Gondwana

    NASA Astrophysics Data System (ADS)

    Niemeyer, Hans; Meffre, Sebastien; Guerrero, Ricardo

    2014-12-01

    In this paper we determined the chronology of Lower Paleozoic arc-related granitic rocks in the Cordón de Lila and Sierra de Almeida ranges, northern Chile, based on new U-Pb ages obtained by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) on single zircons. Plutonism lasted ˜30 m.y., spanning from 490 to 460 Ma (Lower to Mid Ordovician). The obtained ages correspond to the plutonic units' crystallization ages and fit well with the observed contact relationships with their country rocks and mutual intrusion relationships, and also with biostratigraphical data from the sedimentary country rocks. Our geochronological results on the granitic rocks of Cordón de Lila and Sierra de Almeida ranges broadly agree with the known ages of the plutonic rocks in the Argentinian Puna, strengthening the idea that they formed part of the same magmatic arc in the western border of west Gondwana during the Early to Middle Ordovician.

  9. Martian lake basins and lacustrine plains

    NASA Astrophysics Data System (ADS)

    de Hon, R. A.

    1992-02-01

    A classification of Martian lake basins based on the location of the basin in respect to water sources is proposed. The classes are type 1: valley-head basins; type 2: intravalley basins; type 3: valley-terminal basins; and type 4: isolated basins. Martian lakes are ephemeral features. Many craters and irregular depressions impounded water only until the basins filled and overflowed. Water escaping by spillover rapidly cut crevasses in the downstream side of basins and drained the ponds. Clastic lacustrine sediments collected in the lakes as flowing water lost velocity and turbulence. Evaporitic deposits may be significant in those basins that were not rapidly drained. Sediments deposited in lake basins form smooth, featureless plains. Lacustrine plains are potentially candidate sites for Mars landings and for the search for evidence of ancient life.

  10. Basin Electric Leland Olds Station

    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....

  11. 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.

  12. 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

  13. 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.

  14. 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...

  15. 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.

  16. Basin geodynamics and sequence stratigraphy of Upper Triassic to Lower Jurassic deposits of Southern Tunisia

    NASA Astrophysics Data System (ADS)

    Carpentier, Cédric; Hadouth, Suhail; Bouaziz, Samir; Lathuilière, Bernard; Rubino, Jean-Loup

    2016-05-01

    Aims of this paper are to propose a geodynamic and sequential framework for the late Triassic and early Jurassic of and south Tunisia and to evidence the impact of local tectonics on the stratigraphic architecture. Facies of the Upper Triassic to Lower Jurassic of Southern Tunisia have been interpreted in terms of depositional environments. A sequential framework and correlation schemes are proposed for outcrops and subsurface transects. Nineteen middle frequency sequences inserted in three and a half low frequency transgression/regression cycles were evidenced. Despite some datation uncertainties and the unknown durations of Lower Jurassic cycles, middle frequency sequences appear to be controlled by eustasy. In contrast the tectonics acted as an important control on low frequency cycles. The Carnian flooding was certainly favored by the last stages of a rifting episode which started during the Permian. The regression accompanied by the formation of stacked angular unconformities and the deposition of lowstand deposits during the late Carnian and Norian occured during the uplift and tilting of the northern basin margins. The transpressional activity of the Jeffara fault system generated the uplift of the Tebaga of Medenine high from the late Carnian and led to the Rhaetian regional angular Sidi Stout Unconformity. Facies analysis and well-log correlations permitted to evidence that Rhaetian to Lower Jurassic Messaoudi dolomites correspond to brecciated dolomites present on the Sidi Stout unconformity in the North Dahar area. The Early-cimmerian compressional event is a possible origin for the global uplift of the northern African margin and Western Europe during the late Carnian and the Norian. During the Rhaetian and the early Jurassic a new episode of normal faulting occured during the third low frequency flooding. This tectonosedimentary evolution ranges within the general geodynamic framework of the north Gondwana margin controlled by the opening of both Neotethys and Atlantic oceans.

  17. 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.

  18. Alpine tectonics of the Pannonian basin

    SciTech Connect

    Tari, G. )

    1993-09-01

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

  19. 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.

  20. Structural framework for the emplacement of Proterozoic anorthosite massif in the Eastern Ghats Granulite Belts, India: implications for post Rodinia - pre Gondwana tectonics

    NASA Astrophysics Data System (ADS)

    Nasipuri, P.; Bhadra, S.

    2012-04-01

    This article deals with the origin of massif type anorthosite (950-1000 Ma) at the vicinity of Eastern Ghat Province (EGP), east coast of India - proto-Indian craton contact. The EGP comprises multiply deformed ortho and para gneiss and foliated igneous rocks intrusive into the otho- and para-gneiss. The earliest deformation is defined by prominent mineral segregation layering (D1) in the host gneiss around Bolangir, EGP, India. The mineral layering is isoclinally folded (D2) with development of pervasive foliation (S2). Asymmetric folds (F3) having short E-W trending and strongly attenuated NNE/NE-trending limbs in the host gneiss characterize D3deformation (950-1000 Ma). D4 deformation is manifested by a set of N/NNE-trending west-vergent folds and coeval shear zones (550 Ma). The gratitoid is characterized by an asymmetrically mono-phase fabric defined by stretched out K-feldspar + biotite + quartz that gradually disappear into a disjunctive foliation away from the pluton margin. The anorthosite pluton is characterized by outward dipping margin parallel foliation that dies out towards the pluton interior. In the southern part of the massif, N-S trending mm- 50 m wide Fe-Ti-Zr rich melt bands are emplaced transverse to the recrystallized igneous features in anorthosite and granitoids. Deflection of S2 foliation of the host gneiss around the pluton indicates that pluton was emplaced after D2 deformation. Evidence of a) diffusion creep in plagioclase within anorthosite, b) asymmetrically folded gneissic fabric in the granotoids, c) the similar πtpole distribution of margin parallel foliation in anorthosite and πtpole of S2 foliation in the host gneiss indicate that the pluton and granitoid rocks were emplaced during the D3deformation. The orientation of the shear and shear related fractures in anorthosite (N-S) overlaps with the S4 fabric of the host gneiss. Mean attitude of magnetic foliation (AMS) from the southern and western margin of the pluton confirms that D4 as the last deformation in the complex. In the central part of the pluton, NNE-SSW trending magnetic foliation is similar with the D3-deformation induced mesoscopic fabric. Sub-horizontal deflection of foliation-parallel lineation with increasing magnetic anisotropy (P/) and oblate shape parameter (T>0) in the complex indicate that AMS fabric was developed during transpressional orogeny. The anorthosite and the granitoids were emplaced post D2, syn D3 and pre D4 deformation. The observed mesoscopic and AMS data indicate a switch in the stress field from NNE-SSW (D3, 950-1000 Ma) to E-W (D4, around 550 Ma). The switch is significant in the context of tectonic architecture of Bolangir massif. Breakup of Columbia opened a new ocean between India and Antarctica where the sedimentary sequence of EGP was deposited in the Mesoproterozoic. Inversion of the rift basin tectonics occurred around 1000 Ma, that lead to the collision of eastern India-EGP-Antarctica as a part of Rodinia assembly. However recent studies indicate that EGP did not collide with the proto-Indian craton until the Paleozoic (around 550 Ma) after the final break up stage of Rodinia. This study indicate that anorthosite emplacement in EGP needs to be re-evaluated with recent paleo-geographic models coupled with structural studies.

  1. 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.

  2. Hydrogeologic framework of sedimentary deposits in six structural basins, Yakima River basin, Washington

    USGS Publications Warehouse

    Jones, M.A.; Vaccaro, J.J.; Watkins, A.M.

    2006-01-01

    The hydrogeologic framework was delineated for the ground-water flow system of the sedimentary deposits in six structural basins in the Yakima River Basin, Washington. The six basins delineated, from north to south are: Roslyn, Kittitas, Selah, Yakima, Toppenish, and Benton. Extent and thicknesses of the hydrogeologic units and total basin sediment thickness were mapped for each basin. Interpretations were based on information from about 4,700 well records using geochemical, geophysical, geologist's or driller's logs, and from the surficial geology and previously constructed maps and well interpretations. The sedimentary deposits were thickest in the Kittitas Basin reaching a depth of greater than 2,000 ft, followed by successively thinner sedimentary deposits in the Selah basin with about 1,900 ft, Yakima Basin with about 1,800 ft, Toppenish Basin with about 1,200 ft, Benton basin with about 870 ft and Roslyn Basin with about 700 ft.

  3. 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.

  4. 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.

  5. Basin stability in delayed dynamics.

    PubMed

    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

  6. 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.

  7. Flexural modeling of sedimentary basins

    SciTech Connect

    Cogan, J.C.; Lerche, I.

    1988-01-01

    Basement response to loading is of primary importance in the evolution of sedimentary basins, strongly influencing both the thermal and burial histories of the sediments. The presence of regional free-air gravity anomalies over large-scale features suggests that surface loads are not completely compensated by isostatic forces. Therefore, one must consider the role of nonisostatic lithospheric flexure in dynamic basin modeling. The basic assumption of the model is that the lithosphere behaves like an elastic thin plate of finite length, anchored at one end in cantilever fashion. In the forward mode, the loading history and plate parameters (flexural rigidity, initial length, initial dip angle, initial bending moment) are specified and the resultant basin geometry is calculated. However, this approach gives only a rough estimate of the plate parameters for a particular basin. Therefore, the model is inverted, employing a tomographic scheme to determine the parameters that best fit the data. This model yields tighter constraints on the plate parameters, hence a better knowledge of basement motion through time. The model can be used to determine the relative importance of flexure vs. isostatic subsidence in an individual basin as well as the sensitivity of basement motion to the various flexural parameters.

  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-Obregón, C.; Solari, L.; Gómez-Tuena, A.; Elías-Herrera, M.; Ortega-Gutiérrez, F.; Macías-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 Acatlán 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 ɛHf 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 ɛHf 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. Hellas Basin Dunes

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released 15 April 2004

    The Odyssey spacecraft has completed a full Mars year of observations of the red planet. For the next several weeks the Image of the Day will look back over this first mars year. It will focus on four themes: 1) the poles - with the seasonal changes seen in the retreat and expansion of the caps; 2) craters - with a variety of morphologies relating to impact materials and later alteration, both infilling and exhumation; 3) channels - the clues to liquid surface flow; and 4) volcanic flow features. While some images have helped answer questions about the history of Mars, many have raised new questions that are still being investigated as Odyssey continues collecting data as it orbits Mars.

    This daytime VIS image was collected on December 14, 2003 during the southern summer season on the Hellas Basin Rim.

    Image information: VIS instrument. Latitude -41.3, Longitude 46.4 East (313.6 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  10. 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.

  11. 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

  12. 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

  13. Oil in the Malvinas Basin

    SciTech Connect

    Galeazzi, J.S.

    1996-08-01

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

  14. 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.

  15. 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.

  16. Martian double ring basins - New observations

    NASA Technical Reports Server (NTRS)

    Wood, C. A.

    1980-01-01

    A description is presented of 18 Martian basins which were newly discovered on Viking photographs. A study of the basins reveals that diameter dependent differences in the morphology of Martian basins are more complex than previously realized. Basins have been classified according to ring morphology, and a diameter dependent sequence apparently exists. The obtained morphology sequence does not conform to the progression observed on the moon, Mercury, and earth. The small Martian basins are 50 to 100 km smaller than any basin on Mercury and the moon, supporting the view that they are unique to Mars. On earth there are significant terrain influences on crater and basin morphology that encourage the speculation that localized unique characteristics of the Martian crust led to basin formation at diameters where craters would normally be formed.

  17. 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.

  18. 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.

  19. 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 Musée royal de l'Afrique Centrale, Belgium. In a reconnaissance survey, we sampled both drill cores in a nearly even spacing of ~ 150 m covering the whole stratigraphy from Albian to Proterozoic. The red and green to grey sandstone samples were prepared by usual heavy minerals separation technique. Most of the samples revealed enough apatite and zircon grains for the two thermochronometric techniques fission track and (U-Th-Sm)/He. The time-temperature (t-T) evolution for the two drill locations were modelled by using the determined thermochronological data within the software code HeFTy. We tested various geological evolutionary constrains. Both techniques provide us information on the thermal and exhumation of the possible source area and on the drill location by themselves.

  20. 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.

  1. The Macleod evaporite basin, Western Australia

    SciTech Connect

    Not Available

    1988-01-01

    MacLeod is one of the few Quaternary basins that resembles the evaporite basins of earlier epochs in that a large-scale evaporite system, sustained by sea water inflow, continues to operate there today. New insights from MacLeod research relate to the definitive role of seepage in sustaining a large basin system and in controlling systems status. This book analyzes MacLeod as a desiccation basin and provides an actualistic basis for the desiccation-basin concept. It reviews contemporary environments and reconstructs paleoenvironments as dynamic, open systems defined in terms of interrelated water and salt budgets.

  2. 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.

  3. 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.

  4. 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 mélange-dominated slice (Balloon Mélange). These slices are the remnants of the accretionary prism; the stratigraphy within each slice generally youngs to the east, and the overall pattern of aging (based on relative age from provenance studies, sparse fossils, stratigraphic relations, and limited isotopic data) indicates that the older rocks generally dominate fault slices to the east, and younger rocks dominate fault slices to the west, delineating imbricate slices within an eastward-dipping subduction zone, in which the faults record a complex history of multi-phase reactivation. The Lockett Conglomerate is a ~500-m thick fan-delta conglomerate that is the preserved within one of the fault slices, where it is stratigraphically and structurally highest unit in the lower Takaka Terrane; it is also present as blocks within the Balloon Melange. The Lockett Conglomerate is marine at its base and transitions upwards to fluvial facies. The Lockett Conglomerate has previously been interpreted to result from erosion consequent on continued convergence, but is reinterpreted here as a ';true' fan-delta deposit, sedimentologically similar to deposits associated with extension. Textural and compositional data for the Lockett Conglomerate indicates rapid supply of new material (including quartzite, granite, gabbro, and amphibolitic metavolcanics). The Lockett Conglomerate is proposed here to record the initiation of extension, during which basement faults in the hinterland exposed previously buried source rocks. This new interpretation of the Lockett Conglomerate places that initiation of extension and subsequent passive margin sedimentation (Mt. Ellis and Mt. Arthur Groups) earlier (late Middle Cambrian) than previous work has suggested (Late Cambrian or Early Ordovician). These new interpretations provide input useful for correlations and interpretations of the complex mosaic that preserves a record of tectonic activity and processes at the Antarctic, Tasmanian and SE Australian portions of the Cambrian Gondwana margin.

  5. 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.

  6. Experimental Drainage Basins in Israel

    NASA Astrophysics Data System (ADS)

    Laronne, J. B.; Lekach, J.; Cohen, H.; Gray, J.

    2002-12-01

    Within the hyper-arid to semiarid areas of Israel are three experimental drainage basins. They are the Nahal (stream in Hebrew) Yael, subdivided into five sub-basins, Rahaf-Qanna'im (main and tributary, respectively) and Eshtemoa. These basins vary in drainage area and climate, and in monitoring duration and type. All are drained by gravel-bed channels. As the size of monitored drainage area is limited, 3-4 additional representative basins covering areas of 300, 1000, 2000 and 8000 square kilometers will likely be implemented in the next decade. The basins have precipitation, runoff, sediment and fluviomorphological records. Each was conceived for differing purposes, but all share the common two objectives for the continuous monitoring: 1. Many hydrological issues may be approached if, and only if, there are prototype databases on a wide spectrum of hydrological processes; and 2. There is a need for long-term records to assess large floods and subsequent hydrologic and geomorphic recovery. Lessons derived from a large number of research projects on these experimental basins focus on characteristics of runoff in arid climates. For example, the effect of the spatial distribution of rainfall on runoff generation becomes increasingly important with aridity. Rainfall angle on hillslopes and storm intensity and direction derived from rainfall recorders and radar backscatter are crucial for explanation of runoff response. Runoff hydrographs tend to have more bores, shorter-duration peaks, briefer recessions, longer dry periods, and are more variable in terms of flood volume and peaks with increased aridity. Suspended-sediment fluxes, yields and concentrations are relatively large in the semiarid realm, reaching maxima at the beginning of a flood season and after long dry spells. Bedload fluxes are exceptionally high from dryland basins in which hillslopes are minimally vegetated and where bedload transport takes place in channels lacking an armor layer. Bedload/suspended-sediment load ratios increase with aridity. Bedload yield may represent up to 70% of the total load. Hillslope to channel connectivity is high in drylands. In the hyperarid region suspended-sediment sources are hillslopes and the coarser, sandy fraction of the channel bedmaterial. The depth of channel bed activity is indicated by a fluvio-pedogenic unit beneath the channel surface. National and regional hydrological research needs will dictate future global monitoring in experimental basins. International collaboration may bring about considerable cost reduction by exclusion of monitoring aspects that can be evaluated based on the monitoring in other, similar conditions. Advanced international collaboration on validation and calibration of and consistency in monitoring means, as well as syntheses of lessons derived from international collaboration, such as from an International Watershed Research Network, are required for maximizing our understanding of water and sediment responses in varied global regions.

  7. Evaluation of Infiltration Basin Performance in Florida

    NASA Astrophysics Data System (ADS)

    Bean, E.

    2012-12-01

    Infiltration basins are commonly utilized to reduce or eliminate urban runoff in Florida. For permitting purposes, basins are required to recover their design volume, runoff from a one inch rainfall event, within 72 hours to satisfy the design criteria and are not required to account for groundwater mounding if volume recovery can be accomplished by filling of soil porosity by vertical infiltration below the basin surface. Forty infiltration basins were included in a field study to determine whether basin hydraulic performance was significantly different from their designed performance. Basins ranged in age from less than one year to over twenty years and land uses were equally divided between Florida Department of Transportation (FDOT) and residential developments. Six test sites within each basin were typically selected to measure infiltration rates using a double ring infiltrometer (DRI), a common method for infiltration basin sizing. Measured rates were statistically compared to designed infiltration rates, taking into account factors of safety. In addition, a surface soil boring was collected from each of the test sites for a series of analyses, including soil texture, bulk density, and organic matter content. Eleven of the 40 evaluated basins were monitored between March 2008 and January 2012 to evaluate whether basins recovered their volumes from one inch events within 72 hours and to evaluate the effectiveness of using DRI rates to evaluate basin performance. Based on DRI rates, 16 (40%) basins had rates less than their designed rates, 10 (25%) had rates equal to their designed rates, and 14 (35%) basins had rates greater than their designed rates. Additionally, basins with coarser soils were also more likely to have DRI rates greater than designs and FDOT basins were more likely than residential basins to have infiltration rates at or above their designed rates. Five of the eleven monitored basins were expected to function as designed by recovering their design volume within 72 h. Only one basin was expected not to function as designed and was confirmed by monitoring data. The remaining five basins expected to not function as designed, however, met their design criteria based on monitoring data. When groundwater mounding occurred above the surface of the ten functioning basins, drawdown rates were at least an order of magnitude below the design infiltration rates and affected recovery times for subsequent events, although this only resulted from individual events or successive events exceeding the design storm for functioning basins. Results of this study indicate that basins with coarser soils and FDOT basins were more likely to exceed their design performance based on DRI evaluations. However, using the DRI underestimated basin performance leading to an incorrect result for five basins and was overly conservative. Extended ponding resulting from extreme or successive events suggests that basin designs may benefit from using continuous simulation modeling, rather than single event simulations, for sizing.

  8. 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.

  9. 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.

  10. Late Cenozoic Basins of northern California

    NASA Astrophysics Data System (ADS)

    Nilsen, Tor H.; Clarke, Samuel H.

    1989-12-01

    The late Cenozoic basins of northern California developed in response to both convergent tectonics associated with subduction of the Farallon plate (and its modern representatives, the Juan de Fuca and Gorda plates) and transform tectonics associated with northward migration of the Mendocino triple junction and formation of the San Andreas fault system. The modern Eel River basin north of the Mendocino triple junction is an active forearc basin located between the Cascade magmatic arc to the east and the trench at the foot of the continental slope of northern California and Oregon to the west. Five different types of late Cenozoic basins or fragments of basins are preserved in onshore northern California south of the Mendocino triple junction: (1) remnants of a formerly more extensive Neogene forearc basin preserved locally in downdropped blocks within the San Andreas fault system; (2) remnants of slightly older trench-slope basins that generally developed west of but which may locally structurally underlie the younger forearc basin; (3) younger strike-slip-related structural basins that have developed along active right-lateral faults of the San Andreas fault system; (4) broad shallow embayments, perhaps similar to the modern San Francisco Bay, that were connected to the deeper Pacific Ocean to the west; and (5) structurally emplaced remnants of oceanic crust and its overlying sedimentary cover (the King Range terrane). Our preliminary stratigraphic and sedimentologic studies suggest that much of northern California was covered during the Neogene by a forearc basin that may have extended as far south as the San Francisco Bay region and into the southern San Joaquin Valley. As the Mendocino triple junction migrated northward during the late Cenozoic, the southern margin of the forearc basin was uplifted, basin deposits were stripped off by erosion, and the locus of forearc sedimentation shifted progressively northward through time. Preserved but isolated fragments of the forearc basin provide a partial record of the original paleogeography and tectonic framework of northern California during the late Cenozoic.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. Facies and depositional architecture according to a jet efflux model of a late Paleozoic tidewater grounding-line system from the Itararé Group (Paraná Basin), southern Brazil

    NASA Astrophysics Data System (ADS)

    Aquino, Carolina Danielski; Buso, Victoria Valdez; Faccini, Ubiratan Ferrucio; Milana, Juan Pablo; Paim, Paulo Sergio Gomes

    2016-04-01

    During the Late Paleozoic, the Gondwana supercontinent was affected by multiple glacial and deglacial episodes known as "The Late Paleozoic Ice Age" (LPIA). In Brazil, the evidence of this episode is recorded mainly by widespread glacial deposits preserved in the Paraná Basin that contain the most extensive record of glaciation (Itararé Group) in Gondwana. The Pennsylvanian to early Permian glaciogenic deposits of the Itararé Group (Paraná Basin) are widely known and cover an extensive area in southern Brazil. In the Doutor Pedrinho area (Santa Catarina state, southern Brazil), three glacial cycles of glacier advance and retreat were described. The focus of this article is to detail the base of the second glacial episodes or Sequence II. The entire sequence records a deglacial system tract that is represented by a proximal glacial grounding-line system covered by marine mudstones and shales associated with a rapid flooding of the proglacial area. This study deals with the ice proximal grounding-line systems herein interpreted according to lab model named plane-wall jet with jump. Detailed facies analysis allowed the identification of several facies ranging from boulder-rich conglomerates to fine-grained sandstones. No fine-grained deposits such as siltstone or shale were recorded. According to this model, the deposits are a product of a supercritical plane-wall outflow jet that changes to a subcritical jet downflow from a hydraulic jump. The hydraulic jump forms an important energy boundary that is indicated by an abrupt change in grain size and cut-and-fill structures that occur at the middle-fan. The sedimentary facies and facies associations show a downflow trend that can be subdivided into three distinct stages of flow development: (1) a zone of flow establishment (ZFE), (2) a zone of transition (ZFT), and (3) an established zone (ZEF). The proximal discharge is characterized by hyperconcentrated-to-concentrated flow due to the high energy and sediment-laden nature of the flows. At the transitional zone, a hydraulic jump produces a rapid shift of conglomeratic to sandy facies with associated scour features. Towards the distal zones, the jet detaches to originate a vertical turbulent jet characterized by more diluted flows. Discussion of fan facies and architecture within a framework of jet-efflux dynamics provides an improved understanding of grounding-line fans systems that produce coarse-grained strata commonly enclosed by fine-grained rocks. The results have clear implication in terms of prediction of facies tract and geometry of oil and gas reservoirs deposited under similar conditions. And also can be useful to identifying the position of a glacial terminus through time.

  18. The geologic history of Margaritifer basin, Mars

    NASA Astrophysics Data System (ADS)

    Salvatore, M. R.; Kraft, M. D.; Edwards, C. S.; Christensen, P. R.

    2016-03-01

    In this study, we investigate the fluvial, sedimentary, and volcanic history of Margaritifer basin and the Uzboi-Ladon-Morava outflow channel system. This network of valleys and basins spans more than 8000 km in length, linking the fluvially dissected southern highlands and Argyre basin with the northern lowlands via Ares Vallis. Compositionally, thermophysically, and morphologically distinct geologic units are identified and are used to place critical relative stratigraphic constraints on the timing of geologic processes in Margaritifer basin. Our analyses show that fluvial activity was separated in time by significant episodes of geologic activity, including the widespread volcanic resurfacing of Margaritifer basin and the formation of chaos terrain. The most recent fluvial activity within Margaritifer basin appears to terminate at a region of chaos terrain, suggesting possible communication between surface and subsurface water reservoirs. We conclude with a discussion of the implications of these observations on our current knowledge of Martian hydrologic evolution in this important region.

  19. Geology and deposits of the Serenitatis basin

    NASA Technical Reports Server (NTRS)

    Spudis, Paul D.; Hawke, B. Ray; Lucey, Paul G.

    1993-01-01

    The Serenitatis basin is prominent on the near side of the Moon, just east of Mare Imbrium. Originally thought to be one of the oldest lunar basins, re-interpretation of both geological relations and Apollo 17 isotopic data suggest instead that Serenitatis is one of the youngest basins, having formed in the Nectarian Period about 3.87 Ga ago. As part of our continuing effort to understand the geology of multi-ring basins on the Moon and to use basins as probes of the deep lunar crust, we here report results for the Serenitatis basin. Our examination of Serenitatis was stimulated in part by a new effort to re-examine the geology of the Apollo 17 landing site.

  20. 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.

  1. 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 ...

  2. Inter-basin dynamics on multidimensional potential surfaces. I. Escape rates on complex basin surfaces

    NASA Astrophysics Data System (ADS)

    Despa, Florin; Berry, R. Stephen

    2001-11-01

    In this report, we present a general prescription for computing the escape rate of the system from a basin with full consideration of the topographical fingerprint of that basin. The method is based on a solution of the reduced Fokker-Planck equation and built up to allow the separation of the inter-basin dynamics from that of the intra-basin motion. The main result is that when local well populations thermalize within a basin, local minima, especially those of higher energy, enhance the escape rate from the basin. Also, numerical analyses lead to the inference that kinetic traps of "wrong" structures are distinctive topographical patterns which may produce kinetic properties similar to those of the primary basin, i.e., that containing the global minimum, but lie in other basins.

  3. 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.

  4. 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.

  5. Sandakan basin prospects rise following modern reappraisal

    SciTech Connect

    Walker, T. )

    1993-05-10

    Borneo is fringed by six large Neogene deltaic basins, all but one producing substantial hydrocarbons. The Sandakan basin off Northeast Borneo is the exception, but the latest exploration results suggest that it will not remain so. The paper describes its complex history; its exploration history; exploration results; stratigraphy; and geologic structures and traps. The Sandakan basin is conservatively estimated to contain 1 billion bbl of oil and 3tcf of gas.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Central Nebraska river basins Nebraska

    USGS Publications Warehouse

    Huntzinger, Thomas L.; Ellis, Michael J.

    1993-01-01

    The Central Nebraska Basins (NAWQA) study unit includes the Platte River and two major tributaries, the Loup and Elkhorn Rivers. Platte River flows are variable of diversions, but the Loup and Elkhorn Rivers originate in an area of dune sand covered by grassland that generates consistent base flows. Ground water has no regional confining units and the system is a water table aquifer throughout. Macroinvertebrate and fish taxa were related to stream flow. One of the four wetland complexes includes habitat for threatened and endangered bird species. A water quality assessments will be based on the differences in environmental setting in each of four subunits within the study unit.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

    Ghosh, Sampa; Sarkar, Soumen; Ghosh, Parthasarathi

    2012-01-01

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

  17. 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.

  18. 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...

  19. 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.

  20. 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.

  1. 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”. ...

  2. Sedimentary basins in Ross Sea, Antarctica

    SciTech Connect

    Cooper, A.K.; Davey, F.J.

    1986-07-01

    The Ross Sea lies in the Pacific sector of the Antarctic continental margin. Three major sedimentary basins (from east to west, the Eastern, Central, and Victoria Land basins) lie beneath the broad, deep continental shelf of the Ross Sea. These north-south-trending