四川盆地寒武纪岩相古地理特征

Characteristics of Lithofacies Paleogeography of Cambrian in Sichuan Basin

通过露头、岩心、钻测井资料分析建立典型沉积相序列,结合单因素分析综合作图,编制了四川盆地寒武纪各个时期的岩相古地理图件。盆地整体西高东低、西部发育陆源碎屑沉积,中东部以碳酸盐岩沉积为主。寒武纪包含两个半海侵—海退旋回:首次海侵发生在早寒武世筇竹寺期,形成巨厚的浅海陆棚相泥质烃源岩;首次海退发生在早寒武世沧浪铺期,陆源碎屑供给充足,发育三角洲和碎屑滨岸相沉积;第二次和第三次海侵发生在早寒武世龙王庙期与中晚寒武世洗象池期,为碳酸盐岩滩相储层发育的主要时期,在局限台地的地形较高部位发育砂砾屑滩和鲕粒滩,砂砾屑滩主要发育在盆地的中西部,鲕粒滩主要发育在盆地的中东部,在盆地西南部发育具有继承性的泻湖相沉积。

Typical sedimentary facies are identified through integrated studies of outcrops,cores,well logging data,and combined with single factor analysis and comprehensive mapping,lithofacies paleogeography of each period of Cambrian in Sichuan Basin is determined. Depositional topography is higher in the west of the basin than in the east. Land source clastic rocks are mainly deposited in west basin and carbonate sediments are developed in the central-east of the basin. There exist two and a half transgression-regression circles in the Cambrian in Sichuan Basin. The first transgression took place in Qiongzhusi period of the early Cambrian,hydrocarbon source rocks are deposited in shallow continental shelf. The first regression took place in Changlangpu period of the early Cambrian,land source clastic supply is sufficient and delta,clastic shoreland sedimentary facies are developed. Bank facies carbonate reservoirs are mainly deposited in Longwangmiao period of the early Cambrian （ the second transgression） and Xixiangchi period of the middle-late Cambrian （ the third transgression） ,in the higher topography of the restricted platform psammitic bank and oolitic beach carbonates are deposited,with the psammitic bank mainly developed in the central-west basin and oolitic beach mainly developed in central-east basin,and in the west-south of the basin there exist inherited lagoon sediments.