海南岛早二叠世冰海相沉积的确定及其板块构造意义

THE DETERMINATION OF THE EARLY PERMIAN GLACIOMARINE DEPOSIT IN HAINAN ISLAND AND ITS TECTONIC SIGNIFICANCE

海南岛西南部东方县境内,分布着一套石炭、二叠纪地层,其中含有特殊沉积——杂砾岩(diamictite)。笔者从地层的剖面组合,沉积组构、砾石特征和岩石薄片等方面对杂砾岩进行了研究。研究表明,这是一种属于冰海相的沉积建造,它在剖面组合、岩性特征和地质时代等方面与西藏北部、云南西部以及东南亚地区分布的冰海相沉积相同或相似,与冈瓦纳大陆冰碛岩亦属同时代产物。本区冰海沉积的存在表明,海南岛在古生代后期与冈瓦纳大陆有密切联系,属于冈瓦纳大陆北缘构造区,是冈瓦纳大陆分裂出来的一个地体。

An important discovery of the Carboniforous—Posmian diamictite is reported which is distributed in southwestern Hainas Island on studies of the stratigraphic sequence, sedimentary structureaand texture,gravel feature and thinsections. The diamictite can be interpreted as a glacio-marine deposit which is quite similar or even identical to those eqivalents seen in North Tibet,West Yunnan and Southeast Asia iu sedimentary sequonce, lithological feature and goochron, and also comtemporaneeus with the tillite of Gondwana. It is assumed that there was a close link in both tectonics and sedimentology with Gondwana during the late Paleozoie time. Hence,the Hainan Island is a frament riftod away from Gondwana after or at the end of the Paleozoic Era. Now. the Island become a terrane.