差异型碳酸盐岩缓坡特征及沉积格局——以川西地区中二叠统栖霞-茅口组为例

1.西南石油大学 地球科学与技术学院,成都 610500; 2.西南油气田分公司 川西北气矿,江油 621709

四川盆地; 中二叠统; 差异型碳酸盐岩缓坡; 沉积相模式

Depositional characters and framework of differential carbonate ramp in Qixia and Maokou formation,the middle Permian of western Sichuan Basin
LIU Xiao-hong1,LIU Chang1,LI Ning-xin1,FENG Ming-you1,WANG Xing-zhi1,ZHANG Ben-jian2,YIN Hong2

(1.School of Geoscience and Technology,Southwest Petroleum University,Chengdu 610500,China; 2.Northwest Sichuan Gas Field,Southwest Oil and Gasfield Company,PetroChina,Jiangyou 621709,China)

Sichuan basin; middle Permian; differential carbonate ramp; depositional facies

DOI: 10.13800/j.cnki.xakjdxxb.2017.0215

备注

复杂构造背景导致川西地区中二叠统碳酸盐岩沉积格局不清。为明确有利沉积相带展布规律,采用碳酸盐岩石学、古生物、地震资料结合的方法,对区内栖霞-茅口组沉积特征进行系统分析。研究表明川西地区中二叠统碳酸盐岩受龙门山-米仓山前带差异性构造沉降背景控制,原始沉积物类型复杂,多发育虫-藻组合,地震剖面显示为低缓沉积背景、典型台地特征不明显,总体属北东倾斜的差异型碳酸盐岩缓坡沉积。栖霞组二段及茅口组3段内缓坡砂屑滩及生屑滩于龙门山前缘呈狭长形分布,中缓坡生物滩在广元-旺苍一带呈宽弧状分布。古地貌差异控制了栖霞-茅口组滩体“八”字形分布的沉积格局。

The Middle Permian Qixia and Maokou succession of the western Sichuan Basin represents a differential carbonate ramp depositional system. Depositional characters and geometry of Qixia and Maokou Formation in study area are analyzed from lithology,palaeontology and seismic data.Carbonate rocks prominent made up of wackestone,packstone and siliceous shale.Palaeocoenosis that composed by assemble of foraminifer alga has high differentiation index.Moreover,seismic profile shows the gentle slope deposits.Bioclastic banks and psammitic banks of inner ramps in steep side of differential carbonate ramp are slim and parallel with longman mountains.Whereas bioclastic banks of middle ramp in gentle side main rolling parallel with Guangyuan-Wangcang ocean trough,bioclastic banks of high energy are partly developed.Depositional framework of banks which shows herringbone shaped are controlled by palaeogeomorphology in Qixia and Maokou periods.