Greater India Basin Hypothesis and A Two-Stage Cenozoic Collision Between India and Asia     

Douwe VAN HINSBERGEN  Lippert Peter  Dupont-Nivet Guillaume  McQuarrie Nadine  Doubrovine Pavel  Spakman Wim  Torsvik Trond 《《地质学报》英文版》2013,87(Z1):15-15

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Multiproxy diet analysis of the last meal of an early Holocene Yakutian bison          下载免费PDF全文

BAS VAN GEEL  ALBERT PROTOPOPOV  IAN BULL  ELZA DUIJM  FIONA GILL  YOURI LAMMERS  ALINE NIEMAN  NATALIA RUDAYA  SVETLANA TROFIMOVA  ALEXEI N. TIKHONOV  RUTGER VOS  SNEZHANA ZHILICH  BARBARA GRAVENDEEL 《第四纪科学杂志》2014,29(3):261-268

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Chemographic relationships of biotite and cordierite in the McGerrigle thermal aureole, Gaspé, Quebec     

J.Y. VAN BOSSE  A.E. WILLIAMS-JONES 《Journal of Metamorphic Geology》1988,6(1):65-75

Abstract Biotite and cordierite occur in a 1-km wide zone of pelitic hornfelses around the McGerrigle pluton. These phases display systematic changes in X _Fe that can be attributed to continuous reactions involving chlorite or andalusite in the system KFMASH. Through much of the zone biotite and cordierite were products of the 'breakdown'of chlorite. Close to the pluton this continuous reaction was terminated by a discontinuous reaction that introduced andalusite. Pelites which interdigitate with apophyses of the intrusive at the pluton margin contain assemblages that record a continuous reaction between biotite, cordierite, andalusite, muscovite, and quartz or, alternatively, the discontinuous breakdown of muscovite and quartz to K-feldspar and andalusite.
The mole fraction of Fe in biotite and cordierite increased significantly with the progress of the first continuous reaction and apparently decreased during the second continuous reaction. The K _D of Fe-Mg between the minerals decreased and apparently increased, respectively, during the two reactions.
Biotite-cordierite-chlorite assemblages are interpreted to have been stable at temperatures between 525° C and 615° C and biotite-cordierite-andalusite assemblages stable at temperatures between 615° C and 635° C. The confining pressure was estimated to have been < 2 kbar.
The results of this study suggest that the K _D of Fe-Mg between biotite and cordierite is a function of temperature, the Fe-Mg exchange characteristics of the controlling continuous reaction and non-ideal mixing of Fe and Mg.  相似文献   

Contrasting flooding histories of Mississippian carbonate platforms revealed by marine alteration effects in palaeosols   总被引：1，自引：0，他引：1  

V. PAUL WRIGHT‡  SIMON D. VANSTONE  JAMES D. MARSHALL† 《Sedimentology》1997,44(5):825-842

Palaeosols associated with exposure surfaces in Mississippian platform carbonate sequences in Britain invariably show evidence for later alteration by sea water. These alteration effects can be attributed to flooding of the emergent platforms during transgressions that terminated exposure surface development. A study of 230 palaeosol profiles representing 60 stratigraphic levels has revealed a two fold division of these marine hydromorphic effects. Palaeosols in ramp sequences (Chadian-Arundian stages) are capped by ferroan dolomite horizons with carbonized rootlets, pyrite and thin coals. The ferroan dolomites exhibit δ¹³C and δ¹⁸O values indicative of formation in brackish waters. These are interpreted as coastal marshes that developed landward of a transgressive shoreline. Younger Asbian-Brigantian palaeosols lack these dolomites but have been extensively pyritised. The pyrite also developed through marine hydromorphic alteration but flooding was relatively instantaneous over the flat topped platforms. These differences in flooding history reflect both different platform configuration and more rapid transgressions during the Asbian-Brigantian, likely a result of glacio-eustatic effects. Flooding characteristics of the Asbian-Brigantian platforms differ from those associated with late Cainozoic examples, apparently because complete platform rims were not developed. Similar mineralogical alteration effects are likely to be common in other platform sequences in the geological record, but have not been documented.  相似文献   

Sedimentology and architecture of the Douglas Creek terminal splay,Lake Eyre,central Australia     

JOHN A. FISHER  CARMEN B. E. KRAPF  SIMON C. LANG  GARY J. NICHOLS  TOBIAS H. D. PAYENBERG 《Sedimentology》2008,55(6):1915-1930

Douglas Creek terminal splay, sited on the western shoreline of Lake Eyre North, central Australia, covers a surface area of approximately 4 km² with a down‐system length of 2·5 km from the distributary channels terminus to the splay fringe. Two distributary channels feed two sediment lobes which have amalgamated to form the terminal splay. Three primary facies associations have been identified sub‐dividing the creek terminus into distributary channel, proximal and distal splay sections. Proximal splay sediments are characterized by erosionally based, relatively thick (> 100 mm), stacked sheets of coarse to medium sand which commonly display trough and planar cross‐bedding, whereas the distal splay is characterized by thin (generally < 50 mm) massive beds of very fine sand, silt and clay. The change in splay sedimentology is interpreted as reflecting the transition from bedload‐dominated deposition to suspended load‐dominated deposition from decelerating sheetfloods as they spread out from the channel onto the dry lake bed. A proximal to distal splay transition zone is also noted where deposits of both facies associations interfinger laterally and vertically. In scale, geometry and facies associations, the Douglas Creek terminal splay is very different to the often cited Neales terminal splay complex located 70 km to the north. It is suggested that these architectural differences reflect variations in discharge volume, input sediment distribution and the degree of vegetation cover. Understanding the variation in terminal splay architecture has very significant implications for the modelling of analogous subsurface petroleum systems, which at present relies on few modern‐day analogues.  相似文献   

Lateral migration of sand-bed rivers: examples from the Devonian Glashabeg Formation, SW Ireland and the Cambrian Alderney Sandstone Formation, Channel Islands   总被引：1，自引：0，他引：1  

SIMON P. TODD  DAVID J. WENT† 《Sedimentology》1991,38(6):997-1020

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NUMERICAL MODELLING OF STANDARD AND CONTINUOUS VERTICAL ELECTRICAL SOUNDINGS1     

C. E. MOLANO  M. SALAMANCA  R. A. VAN OVERMEEREN 《Geophysical Prospecting》1990,38(7):705-718

Analytical solutions of vertical electrical soundings (VES) have mostly been applied to groundwater exploration and monitoring groundwater quality on terrains of fairly simple geology and geomorphology on which the electrode arrays are symmetrical (e.g. Schlumberger or Wenner configurations). The sounding interpretation assumes flat topography and horizontally stratified layers. Any deviations from these simple situations may be impossible to interpret analytically. The recently developed GEA-58 geoelectrical instrument can make continuous soundings along a profile with any colinear electrode configuration. This paper describes the use of finite-difference and finite-element methods to model complex earth resistivity distributions in 2D, in order to calculate apparent resistivity responses to any colinear current electrode distribution in terrains in which the earth resistivities do not vary along the strike. The numerical model results for simple situations are compared with the analytical solutions. In addition, a pseudo-depth section of apparent resistivities measured in the field with the GEA-58 is compared with the numerical solution of a real complex resistivity distribution along a cross-section. The model results show excellent agreement with the corresponding analytical and experimental data.  相似文献   

Source and Differentiation of Deccan Trap Lavas: Implications of Geochemical and Mineral Chemical Variations   总被引：7，自引：5，他引：7  

LIGHTFOOT  P. C.; HAWKESWORTH  C. J.; DEVEY  C. W.; ROGERS  N. W.; CALSTEREN  P. W. C. VAN 《Journal of Petrology》1990,31(5):1165-1200

The basalt stratigraphy of the Deccan Trap between MahabaleshwarGhat and Belgaum over-steps the basement from north to south.Sr-isotope and Zr/Nb ratios, and Sr, Rb, and Ba concentrationscorrelate portions of the post-Poladpur stratigraphy over 250km along the Western Ghats, thereby confirming a southerly componentof dip of 0?06?. At the southwestern margin, the stratigraphyextends upwards from the compositionally uniform Ambenali Formation(Cox & Hawkesworth, 1984) into a sequence of grossly heterogeneousflow units which have been allocated to the Mahabaleshwar andPanhala Formations (Lightfoot & Hawkesworth, 1988). TheMahabaleshwar Formation is represented only by a sequence ofhighly fractionated flows (termed the Kolhapur unit) with similar⁸⁷Sr/⁸⁶Sr₀ to the Mahabaleshwar (0?7045), but with Sr<240ppm and TiO₂>2?25%. Succeeding the Kolhapur unit are a seriesof flows with high ⁸⁷Sr/⁸⁶Sr₀ (0?7045-0?705), Zr/Nb > 13,and low Sr (< 200 ppm), which have been allocated to thePanhala Formation, and a group of flows with high ⁸⁷Sr/⁸⁶Sr₀(0?707–0?708) and Sr (>230), but trace element concentrationssimilar to the Mahabaleshwar Formation; these have been allocatedto the Desur unit of the Panhala. Geochemical variations in flows overlying the Ambenali definetwo distinct trends: one is attributed to gabbro fractionation,and the other to variations in the compositions of the parentalmagmas, and arguably their source regions. There is little evidencefor significant crustal contamination in these flows, and thedegree of fractionation and the composition of the phase extractare shown to vary along strike within the Mahabaleshwar Formation.The high TiO₂ content of Kolhapur unit flows is shown to bethe result of shallow-level gabbro fractionation, rather thanthe presence of a primitive high-Ti magma. Mahabaleshwar Formationbasalts exhibit a broad negative correlation between the degreeof fractionation and Sr-isotopic composition. The endmemberwith lower ⁸⁷Sr/⁸⁶Sr₀ has different Zr/Y from the Ambenali basalts,and would appear to have been generated by lower degrees ofmelting of a similar source. The other endmember has more radiogenicSr, lower Zr/Nb, similar Zr/Y, but higher mg-number. The simplestinterpretation is that these magmas were more primitive andhence hotter and more able to interact with the lithosphereen route to the surface, and that they then mixed to producethe Mahabaleshwar array. The Panhala Formation basalts ploton the Sr-Nd array defined by the Mahabaleshwar Formation, andthe Desur unit basalts plot on an extension of this array; thissuggests that the source characteristics are also lithospheric.The absolute elemental abundances may then be a function ofmelting and fractionation. We are impressed by the apparentswitch from crustal lithospheric contributions to mantle lithosphericcontributions through the stratigraphy, and suggest that this,together with the more protracted fractionation of the magma,reflects a change in the availability of the lithospheric componentsaccompanying the southerly migration of the volcanic edifice. ^* Present address: Geoscience Laboratories, Ontario Geological Survey, 11th Floor, 77, Grenville Street, Toronto, Ontario, M7A 1W4, Canada  相似文献   

SOME EXPERIMENTS ON THE GENESIS OF TURBIDITY CURRENTS     

W. VAN DER  KNAAP R. EIJPE 《Sedimentology》1968,11(1-2):115-124

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Growth, Production, and a Partial Energy Budget for the Amphipod, Talorchestia capensis (Crustacea; Talitridae) in the Eastern Cape, South Africa     

P. VAN SENUS  A. MCLACHLAN 《Marine Ecology》1986,7(2):165-179

Abstract. .A population of Talorchestia capensis was sampled in dune slacks over the period of one year. Two hatching periods, one in March and one in September, were observed. Growth was rapid, the amphipods reaching a size of 8.4 mm standard length in 18 months. Maximum growth occurred in spring and minimum growth in winter. Annual mortality rates for summer- and winter-hatched individuals were low, 0.22-y“¹ and 0.16-y”¹. Average production for the summer classes was 7.2g-y?‘ (dry mass) and for the winter classes 2.9-y“¹, with a P/B ratio of 2.25-y”’. Production values peaked during autumn and summer. Abundance and biomass estimates showed maxima during summer and minima in early spring. Reproductive output was low, 0.1 kJ ? m^-2 y“¹, indicating that 7 % of the total production is used for reproduction and 93 % for somatic production. The assimilated energy flow through the population was estimated to be 16.3 kJ m?² y?‘ and consumption about 81.6 kJ m^-2 y^_’.  相似文献