塔里木盆地西北缘巴楚-乌什露头区奥陶系沉积相特征

奥陶纪是塔里木盆地及其周缘地区受中加里东运动影响,构造和沉积演化发生强烈转化的时期,盆地西北缘的巴楚、柯坪和乌什露头区岩性、岩相和生物相开始分异,沉积环境变化显著,基本特征如下:①中下奥陶统鹰山组是在拉张背景下形成的具有远端变陡的缓坡型碳酸盐岩沉积体系,平面上由南向北可分为内缓坡、中缓坡和外缓坡(斜坡)相沉积,垂向上由下到上水体缓慢加深,至顶部快速变浅;②中上奥陶统一间房组-吐木休克组沉积期是沉积转换和构造转换的关键时期,阿满台槽(盆)形成,沉积格局由弱镶边缓坡沉积体系演化为匀斜缓坡沉积体系,巴楚-乌什地区整体表现为“南缓北陡”的沉积格局;③在阿满台槽(盆)中沉积的萨尔干组黑色页岩向阿瓦提凹陷延生,在这套良好生油岩的两侧,为油气勘探的有利区域.

Ordovician Sedimentary Facies Characteristic in Bachu-Wushi Outcrop Area of Northwest Tarim Basin

The Caledonian movement impacted Tarim Basin and its periphery in Ordovician, during which the structure and sedimentary evolution were intensively transformed. The lithology, facies and biofacies began to segregate in Bachu, Keping and Wushi outcrop area of northwest Tarim basin. The sedimentary environment was apparently changed. The essential characteristics were as follows. (1) The Yingshan Group glacis sedimentation during Lower-Middle Ordovician was developed under pull-apart background with remote precipitous characteristic. It was divided into inner, middle and outer gentle slope from south to north in plain. And aquifer deepened from bottom to top in vertical. (2) The Yijianfang and Tumuxiuke of Middle-Upper Ordovician were the key period of sedimentary and structure transformation. The Aman platform trough was formed. Sedimentary framework was evolved from weak edge gentle slope to uniform gentle slope. It overall exhabited South Slow North Steep. (3) The black shale of Saergan group which sedimented in Aman platform trough, probably extended some distance to Awati Depression. It belongs to good source rock and has potential oil and gas exploration area in early and later strata.