扬子及周缘地区晚古生代总体沉积格局与含油气领域的探讨

THE LATE PALEOZOIC SEDIMENTARY FRAMEWORK AND THE OIL/GAS POTENTIAL OF THE YANGTZE BLOCK AND ITS BORDERING AREAS

晚古生代华南陆块（扬子及南华加里东褶皱带）是古特提斯洋中的一个陆板块，周缘为由早期的陆内断陷，至晚期演变为拉张离散的被动大陆边缘（北缘南秦岭海槽属于陆内拗拉槽）。陆块内部则由海西早期的湘洼海盆逐步海侵达到中下扬子，至石炭纪末期的云南运动，迎来了华南区二、三叠纪广覆性海侵，形成周缘为岛链环绕、内部台、盆分异的受限陆表海，类似于今日之南海海盆和加勒比海海盆的地理格局，且规模相当，而南海海盆和加勒比海海盆今日之丰富的油气资源，说明华南，尤其是扬子区二、三叠系受限陆表海盆有寻找大油气田的前提条件。

The S. China Continental Block (i.e equivalent to the Yangtze together with the southern China Cakdonian Foldbelt) is an ancient continent in the Paleo-Tethyan Ocean,whose bordering areas had been intracontinental faultdowns during the early evolutionarystage, which transformed into a devergent and passive continental margin ( the oceanictrough of the S. Qinling belt along the N. margin should be attributed to an intraconti-nental aulocogen) in the late stage. At the sametime, the enlargement of the Xiang-Guisea basin by transgression reached the middle and lower Yangtze areas during early Hercy- nian period, followed by a more extensive transgression during the Permian-Triassic timedue to the Yunnan movement initiated at the end of the Carboniferous, Therefore, thecontinental plate was surrounded by island chain system on the bordering areas while theepicontinental sea occurred within the plate dominated by the differentiation of the plat-form and the basin regime, in a pattern similar to that of the present South China Sea andthe Caribbean Sea basins. Since the two sea basins are rich in oil/ gas resources, in turn, itis suggested that large oil/gas fields should be discovered in the S. China, especially inPermian-Triassic systems dominated by epicontinental sea basin environment.