摘要
本文用高能的亮晶鲕粒滩图定了江南碳酸盐台地(以下简称台地),发现了鲕滩在纵横向有规律的迁移,台地的南北两侧都存在台地边缘斜坡带,西北宽缓的台地边缘斜坡带是纵横向迁移造成的;东南陡峻的台地边缘斜坡带属碎屑岩型,该带亦是我国华南早三叠世碎屑岩与碳酸盐岩的分布界线,台地西北侧台缘高能鲕粒滩是下扬子区早三叠世找油气的有利远景区;苏南皖南广布的瘤状灰岩(斜坡带特有产物)是一个值得重视的新型储集层。
This paper outlines the Jiangnan Carbonate platform of early Triassic (in brief, Which is called the plat-form bellow) by some oosparite beaches of high energy, and through the comparation of the longitudinal section with latitudinal section of the oosparite limestone, We have discovered the ooide beach migrated regularly in history and spaces- A large amount of various olistostrome structures and products of slumping such as slump breccia, nodulas limestone are discovered in the deposits of both north and south sided of the Platform, thus confirm two slope zone existed on the two sides of the platform. The slope zones are contiguous outward to the zone of self facies, basin fades in turn. The slop zone in the onrth -west platform is broad, which distribute an extensive area in South Jiangsu and South Anhui, according to the specialities of petrology, the sequences of sections and palaeontology, we can distinguish two types of slopes; the frontier slop of the plaform (the upper slope) and the marginal slope of the shelf (the lower slope); it is verified by data that this two slopes have migrated in history and spaces. The slope zone in the south-east plaform is bounded by a contemporaneous normal fault, which adjacent 10 the Lianhua - Qiansan deep turbidite basin, it's lack of facies variety may relate to the later structural modification. This zone is also a boundary between the clastic rocks and carbonate rocks of early Triassic in South China.
The early Triassic of Lower Yangtze region is of Significent source rocks regionally, and facies distribute from platform to basin in a good order, from south -east to north-west, they appear as : platform -the marginal ooide beach of the Platform -slop -shelf- basin in turn. The deep shelf and basins have yielded oil/ gas, which have migrated and been trapped in the near slope zone and marginal ooide beach, forming a fine match of source rock and reservoir. The extensive marginal ooide beach in the north - west margin of the Jiangnan Plaform is a fine oil/gas reservoir, besides, studying deeply, we have found extensive nodulas limestone in slop zone that is a new reservoir type, and oil seepages 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 experienced two large scale sturctural activities after later Triassic: the compressional activity from later Triassic to early Cretaceous: the stretching and fault depressional activity after Cretaceous. These activities have both constructive and distructive contribution for accumulation of oil and gas.
The conclusion is that the marginal ooide beach and slope zone in the north-east Jiangnan Platform are the 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 regional layers 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 migrated to the stractural traps existed before. So that, along Nanjing -Nantong, the region located at the centre position of thrust faults and folds that have the features of base decapple and cover layer detachment in the north - east direction owing to the compressional activities of later Triassic -early Cretaceous , has been modified weakerly and has been covered not only by deposits but also by nappies, the source rocks have matured already, and it's products have migrated laterally, so this region is prospective for oil/gas exploration.
出处
《沉积学报》
CAS
CSCD
北大核心
1993年第4期47-55,共9页
Acta Sedimentologica Sinica
