Depostional and Hydrocarbon-bearing Fealrues in The Jiangnan Platform and It's Two Slopes in Farly Triassic

This paper outlines the Jiangnan Carbonate platform of early Triassic (in brief, Which is called the plat-form fellow) by some cr:,parite beaches of high energy, and through the comparation of the longitudinal sec-tion with latitudinal action of the oosparite limestone, We have discovered the ooide beach migrated regular-1y in history and spaces. A large amount of various olistostrome structures and products of slumping such asslump breccia,nodular limestone are discovered in the deposits of both north and south sided of the Plat-for m,thus confirrn two .slope zone existed on the two sides of the platform. The slope zones are contiguousoutward to the zone cf wlf facies,b:,sin fades in turn. "rl:e slop zone in the onrth-west platform is bread,which distribute an extensive area in South Jiangsu and South Anhui according to the specialities of petrolo-gY .the sequences of sections :end palaeontology,we can distinguish two types of slopes:the frontier slop ofthe plafotm (the u):per slopel and the marginal slope of the shelf (the lower slope),it is verified by data thatthis two slopes have migrated in history and spaces. The slope zone in the south-east plaform is bounded bya contemporaneous normal fault,which adjacent to the Lianhua-Qiansan deep turbidite basin,it's lack of fa-cies variety- rnay relate to the later structural modificatiun. This cone is also a Loundary between the elasticrocks and carbonate rocks of early Triassic in South China. The early Triassic of Lower YanKtze region is of Significent source rocks regicnally, and facies distributefrom platform to basin in a good order,from south-east to north-west,they appear as:platform-themarginal oxide beach of the Platform-slop-shelf-basin in turn. The deep shelf and basins have yielded oil/gas,which have migiated and been trapped in the near :.lope zone and marginal ooic?e beach,forming a finematch of source rock and reservoir. The extensive marginal oxide beach in the north-west margin of theJiangnan plaform is fine oil/gas reservoir,besides,studiying dueply, -we have found extensive nocdulas lime-stone in slop/one that is a new reservoir type,and oil seepsges have been found already-. But,the structures of this region were modified strongly in the later,it is a decisive factor for oil/gas control. This area has ex-perienced two large scale sturctural activities after later Triassic: the compressional activity from later Trias-sic to early Cretaceous:the stretching and fault depressional activity after Cretaceous. These activities haveboth constructive and destructive contribution for accumulation of oil and gas.The conclusion is that the marginal ooide beach and slope zone in the north-east Jiangnan Platform arethe best favourable area for oil/gas exploration in this region. Because covered thickly by later Triassic-Jurassic,the source rocks of the shelf basin and a part of slope zone of lower Triassic have partly matured,it's products have migrated and been trapped by the slope zone. The data of the thermal history of regionallayers verified that,only in the fault basins that are covered by Cretaceous-Tertiary thicker than 1,500m,could the source rocks of lower Triassic completely enter into peak generation of hydrocarbone,they migrat-ed to the stractural traps existed before. So that,along Nanjing-Nantong,the region located at the centreposition of thrust faults and folds that have the features of base decapple and cover layer detachment in thenorth-east direction owing to the compressional activities of later Triassic-early Cretaceous,has been mod-ified weakerly and has been covered not only by deposits but also by nappies,the source rocks have maturedalready, and it's products have migrated laterally,so this region is prospective for oil/gas exploration.