重庆彭水地区震旦系灯影组沉积地质新认识

重庆彭水太原乡老厂坪背斜核部的灯影组白云岩自下而上可划分为两段,下段"富藻",上段"富硅";沉积环境为浅水台地背景下的潮坪-局限台地,可据沉积物差异、沉积构造特征划分出潟湖、潮下、潮间及潮上四个微相类型。通过区域对比,建立了上扬子地区震旦系灯影组的沉积模式。纵向上,沉积相序表明其沉积时期海平面经历了两次升降变化,海侵十分短暂,海退为主体,海平面总体呈下降趋势;横向上,由北西至南东,水体逐渐加深,沉积环境经历了由潮坪-潟湖到局限台地-开阔台地,再到台地边缘以及陆棚的过渡。

Sedimentary characteristics of the Sinian Dengying Formation in Pengshui,Chongqing

The petrographic and sedimentological characteristics of the dolostones from the Sinian Dengying Formation in Pengshui, Chongqing are explored on the basis of the Dengying Formation section in the coral part of the Laochangping anticline. These dolostones may be divided, from the base upwards, into two parts： ＂algae-rich＂ and ＂silica-rich＂ intervals. The sedimentary environments consist of the tidal-fiat to restricted platform subfacies, including the lagoon, subtidal, intertidal and supratidal microfacies. The sedimentary model has been constructed for the Sinian Dengying Formation in the upper Yangtze area. Vertically, the Dengying Formation once went through two phases of sea-level changes dominated by regression and displays the shallowing-upward depositional sequences. Horizontally, the sedimentary environments passed, from NW to SE, into the tidal fiat-lagoon through restricted platform to the open platform, and finally to the platform margin and continental shelf.