塔里木盆地阿瓦提凹陷三叠系层序特征与沉积古地理演化

为阐明塔里木盆地阿瓦提凹陷三叠系的沉积特征、层序格架及沉积古地理,根据陆相层序地层学和湖盆沉积学研究思路,利用钻井、岩心、地震等基础资料,提出了井震结合层序划分、物源与沉积特征、沉积古地理分布与演化等研究新认识。将阿瓦提凹陷三叠系俄霍布拉克组和克拉玛依组划分了7个三级层序,俄霍布拉克组分为5个层序(SQ1—SQ5),克拉玛依组分为2个层序(SQ6—SQ7)。各层序自下而上由低位体系域(LST)、湖侵体系域(TST)和高位体系域(HST)组成。研究认为阿瓦提凹陷三叠系发育多物源控制下的扇三角洲相、辫状河三角洲相和滨浅湖亚相等沉积。凹陷周边存在4大物源,主要来自西南部巴楚隆起和西部柯坪断隆,其次是北部塔北隆起和东南部塔中隆起。辫状河三角洲平原亚相主要分布在凹陷的南部—西南部边缘,以辫状分流河道微相的粗粒砂岩和砂砾岩体为主。湖盆主体位于凹陷东部地区,向凹陷内为辫状河三角洲前缘亚相和湖泊相,以水下分流河道、滩坝砂体为主。三叠纪湖盆经历了从初始形成、发育鼎盛、到充填消亡的过程。早三叠世早期(SQ1—SQ2),即俄霍布拉克组下段时期,是三叠纪阿瓦提湖盆的初始形成期。物源主要来自南部的巴楚隆起和西部的柯坪断隆地区,沉积相带从南向北呈不对称带状分布,发育辫状河三角洲平原—辫状河三角洲前缘—滨浅湖亚相等,湖盆呈南浅北深、西浅东深。早三叠世中—晚期(SQ3—SQ5),即俄霍布拉克组上段时期,是湖盆扩张发育鼎盛期。伴随着西南部和西部物源不断向盆地进积,形成扇三角洲相沉积。同时,湖盆向北部和北东部扩展,形成自南向北不断进积的辫状河三角洲平原和前缘亚相,北东部为滨浅湖—半深湖亚相。中三叠世早—中期(SQ6—SQ7),即克拉玛依组沉积时期,是湖盆充填消亡期。沉降中心向北东方向迁移,物源不断进积造成湖盆迅速萎缩,直至消亡。

贵州省晚二叠系龙潭组地层厚度分布特征

通过对贵州省晚二叠系龙潭组古地理及古地理沉积演化特征分析,结合晚二叠系龙潭组地层含煤分布情况,对贵州省晚二叠系龙潭组地层厚度变化作出评价,归纳出贵州省晚二叠系龙潭组地层厚度的变化规律,并对晚二叠系龙潭组地层可采煤层及含煤性影响进行了分析。

Characteristics and evolution of lacustrine turbidite of Chang-7 Member of Yanchang Formation in northern Shaanxi

Lacustrine turbidite of Chang-7 Member in the studied area consists of sihstone and fine sandstone with respect to grain size, which is feldspathic lithie sandstone, syrosem arkose and arkose with respect to mineral constitution affected by provenance. There are such apparent signatures as lithology, sedimentary structure, sedimentary sequence and well logs, to recognize turbidite. During the paleogeographic evolution of Chang-7 Member, lake basin and deep lake are both at their maximum extent during Chang-73 stage, resulting in the deposition of Zhangjiatan shale with widespread extent and of turbidite with fragmental-like. Deep lake line is gradually moving toward lake center and turbidite sand bodies are gradually turning better with better lateral continuity, connectivity and more thickness, from stages of Chang-73, Chang-72 and Chang-7t, which can be favorable reservoir in deep-water.