中扬子北部上震旦统陡山沱组沉积特征及演化

中扬子区上震旦统陡山沱组中下部为一大套灰黑色、黑灰色泥页岩，且大部分地区深埋地腹，具有较好的页 岩气勘探潜力。基于钻井岩芯及野外剖面测量观察，开展了系统的基础地质研究，建立了陡山沱组区域地层格架，进 行了层序和沉积相分析。上震旦统陡山沱组岩性具有四分特征，钻井岩芯和实测剖面各分段的岩性特征和沉积厚度 有所不同，地层厚度在90～250 m，总体上呈东西走向展布，即自北西向东、南逐渐增厚的趋势。将陡山沱组划分为一 个二级层序（SS1），其中包含4 个三级层序（SQ1、SQ2、SQ3、SQ4）。沉积相包括滨岸潮坪相和台地相，台地相划分为 开阔台地、局限台地和台内盆地3 类亚相。陡山沱期，研究区整体上为台地相沉积，区内东南部为开阔台地沉积，西北 部为局限台地，西南部花鸡坡-X1 井-九里垭一带为相对深水的台内盆地相沉积。

Sedimentary Characteristics and Evolution of the Upper Sinian#br# Doushantuo Formation in the North of Middle Yangtze Area

A large set of dark grey to black colored mudstone and shale deposited in the middle to lower part of the upper Sinian Doushantuo Formation in the middle Yangtze Platform，most of which are deeply buried in the Basin and with a good shale gas resource potential. Based on drilling cores and outcrop section investigation，a systematical study on fundamental geology was carried out. We also analyzed the sequence stratigraphy and sedimentary facies of the Doushantuo Formation，and established regional stratigraphic framework. The lithology of the upper Sinian Doushantuo Formation is characteristic of four different lithofacies，and the thickness of which is different in drilling cores and outcrop sections with variation ranges from 90 to 250 m. In general，the stratum is thickening along the direction of northwest to southeast. Doushantuo Formation was divided into a second-order sequence（SS1），which contains four third-order sequences（SQ1、SQ2、SQ3、SQ4）. Sedimentary facies of Doushantuo Formation were subdivided into tidal-flat and platform with three subfacies as open platform，shallow water shelf and intra-platform basin respectively. In Doushantuo period，the sedimentary environments of Doushantuo Formation varied from southeast to northwest as open platform and restricted platform in the study area，intra-platform basin face in the area of Huajipo，Well X1 and Jiuliya.