贵州大方地区二桥组地层特征及沉积相分析

Stratigraphic features and sedimentary facies analysis of the Erqiao Formation in the Dafang area of Guizhou Province

为研究贵州大方地区晚三叠地层中二桥组岩石地层特征和沉积相,在研究区采集岩石样品进行分析。通过对区内岩石地层的岩性、沉积地球化学分析结果及沉积相的分析,描述了贵州大方地区二桥组地层剖面,并对二桥组的岩性组合特征、接触关系及横向变化进行对比,分析了该地层岩石特征和沉积相。研究区二桥组主要为一套陆相含植物化石的灰白、黄灰、褐灰色厚层夹薄层岩屑石英砂岩,由于二桥组与上覆及下伏地层均为平行不整合接触,地层厚度在各地差别较大。根据上述数据确定二桥组年代地层为上三叠统—下侏罗统,河流相辫状河-曲流河亚相沉积,地球化学特征显示其物源区的大地构造背景属于被动大陆边缘克拉通盆地。

This work analyzed the stratigraphic features and sedimentary facies of the Late Triassic Erqiao Formation in the Dafang area of Guizhou Province, and collected rock samples in this area, With analysis of lithology, sedimentary geochemical data and sedimentary facies, the paper described the stratigraphic profile of the Erqiao Formation, and compared and comprehensively studied the lithological combination, contact relationship and lateral variation. The Erqiao Formation in the study area is mainly continental gray, yellow gray and brown gray thick layer interbeded with thin lithic quartz sandstone containing plant fossils. For the unconformable contact between the Erqiao Formation and the overlying and underlying strata, the thickness of the formation varies greatly in the study area. All in all, the Erqiao Formation is chronostratigraphically Upper Triassic-Lower Jrassic, and belongs to fluvial braided river-meandering facies. Geochemical characteristics show that the tectonic setting of the provenance is a passive continental margin of craton basin.