新疆阿克库勒地区三叠系中油组层序地层学研究

SEQUENCE STRATIGRAPHY OF THE TRIASSIC MIDDLE OIL-MEMBER IN THE AKEKULE AREA,XINJIANG

三叠纪中油组沉积期阿克库勒地区位于库车前陆盆地前隆及前隆南部斜坡带,呈北高南低的构造格局,物源位于东北和西北两个方向。这种构造格局决定了层序的格局和模式。中油组主要沉积中砂岩和含砾中砂岩,粒度整体较粗,分选性较好,磨圆度以次棱角状为主,岩石类型为长石岩屑砂岩。通过粒度分析和岩心观察,认为中油组主要沉积体系包括侵蚀沟谷充填沉积体系、湖泊沉积体系、湖底扇沉积体系、三角洲沉积体系,其中低位侵蚀沟谷主要分布在研究区北部,主要发育在低位体系域晚期,湖底扇主要分布在研究区南部阿克亚苏地区,主要为低位体系域早期沉积。湖侵体系域位于初始湖泛面与最大湖泛面之间,主要为湖泊沉积体系半深湖—深湖和滨浅湖沉积。最大湖泛面之上为高位体系域,其沉积体系包括三角洲和湖泊沉积体系的滨浅湖以及半深湖—深湖沉积。

The Akekule area lies in the front uplift and southern slope of the Triassic Kuche Foreland Basin. During deposition of the Triassic middle oil-member, the study area was higher in the northern part and lower in southern part, and the source area lied to the northeast and northwest. This structure framework controls sequence framework and model. The middle oil-member is characterized by medium-sized sandstone and pebbled sandstone, with fair sorting and subangular sphaericity. Rock types mainly were feldspar debris sandstone. Based on grain size analysis and core observation, main deposition systems have been recognized, including incised valley infilling system, lacustrine system, sublacustrine fan system and delta system. Among them, valley infilling system occurs in later lowstand system tract distributed in northern area, and sublacustrine fan system lies in southern area in early lowstand system tract. Trangressive system tract lies between initial flooding surface and maximum flooding surface, and the deposition system includes half deep lacustrine to deep lacustrine and etang lacustrine. High system tract is on the maximum flooding surface, and the deposition system includes delta and etang lacustrine and half deep lacustrine to deep lacustrine.