西秦岭白依沟群沉积环境分析

ANALYSIS OF SEDIMENTAL ENVIRONMENT OF BAIYIGOU GROUP IN WEST QINLING

白依沟群是西秦岭地区迄今发现的最古老地层,厘定为震旦系下统,是一套浅变质水携火山碎屑岩—陆源碎屑岩建造。依据其沉积环境的差异和岩石组合,划分为上、中、下三段。通过笔者研究,认为是大陆山间河流出口处近源冲积扇体中形成的辫状河体系,为主河道—河道心滩—洪泛平原与湖泊等环境的沉积产物。

The Baiyigou Group is the oldest epimetamorphic stratigraphic unit in west Qinling and is defined as lower Sinian. The sedimentary environments were of a series of volcanic basins. In ancient continental margin volcanic eruptions and water current processes piled up a set of clastic sedimentary and volcanic-clastic rocks. On the basis of sedimentary facies and lithologic assemblages the Baiyigou Group is divided into 3 parts. The lower part records the point bars deposited in braided rivers developed on fluvial fans of inter-monts. In the middle portion, braided channel system were deposited on alluvial fans. The upper part represents floodplain, river channel and poit bar environments. They show typical river model with upward fining sequences and current structures. Besides the lake facies are also can be seen.