苏南无锡地区二叠纪长兴期生物礁初探

THE PRELIMINARY STUDY OF THE CHANGXINGIAN(LATE PERMIAN)ORGANIC REEFS IN THE WUXI DISTRICT,SOUTHERN JIANGSU

苏南(包括浙北一部分)在晚二叠世长兴期,发育了一套碳酸盐岩沉积。因其颜色有深有浅,故俗称“黑白长兴灰岩”。笔者于1987年测量了位于无锡市以东约25公里的嵩山长兴剖面。通过野外和宝内研究确定它是一生物礁沉积,这在下扬子地区长兴期地层中还是第一次发现。本文意在抛砖引玉、希望能引起同行们的注意。一、古地理背景众所周知,在长兴期沉积以前。

Two types of limestones of different shades, locally named the 'black and white Changxingian limestones', were developed in southern Jiangsu (including part of northern Zhejiang) during the Changxingian of the Late Permian. The 'white Changxingian limestones' are composed dominantly of shallow-water carbonate rocks which are characterized by high carbonate content and comprise bioclastic and intraclastic limestones, whereas the 'black Changxingian limestones' consist of deepwater carbonate rocks which are noted for organic matter and comprise micritic limestones interbedded with chert bands. Two facies belts have been distinguished in southern Jiangsu: Changzhou—Suzhou—Huzhou carbonate platform facies and Shazhou—Wuxi—Guangde foreslope facies. The comparison of palaeogeographic settings, reef-building organisms, and stratigraphic sequences in the Gaoshan section, Wuxi with those in the Upper Yangzi area has revealed the development of the periplatform organic reefs at the boundary between deep-and shallow-water carbonate rocks (i. e. the 'black and white Changxingian limestones') in southern Jiangsu. Thus this has opened up good prospects for the hidden reef communities in the transitional zone between deep-and shallow-water carbonate rocks along the Middle and Lower Yangzi areas as well as in the southern Yellow Sea. Finally, hydrocarbon potentials of the 'black and white Changxingian limestones' are briefly discussed in this paper.