大川中地区须家河组层序-岩相古地理研究

四川盆地上三叠统须家河组油气勘探开始于20世纪40年代，其中须二段、须四段、须六段是主要勘探目的层段，也是盆地周边地区寻找新气源最有利层位之一。根据钻井岩心观察、野外剖面实测和室内镜下岩石薄片鉴定分析，并结合岩石学、测井及地震等沉积相标志研究，确定大川中地区须家河组主要发育扇三角洲、辫状河三角洲和湖泊等沉积相带，进一步划分出若干亚相和微相。利用高分辨率层序地层学理论和技术，在须家河组识别出2个超长期和5个长期基准面旋回层序。以沉积学理论为指导，选择各长期旋回层序为等时地层单元编制四川盆地层序—岩相古地理图。编图结果表明，须家河组5个长期岩相古地理沉降中心、迁移方向和沉积相带的展布严格受龙门山和米仓山—大巴山两造山带非同步的构造格局控制。

Study of Sequence and Lithofacies Paleogeography of the Xujiahe Formation in the Large Scale Central Sichuan

The oil and gas exploration began in the 1940s in the Xujiahe Formation,Upper Triassic, Sichuan Basin, of which the second, the fourth and the sixth members are not only main aim strata, but also one of the most favorable horizons in search for new gas sources. According to core of drilling observation, the actual measurement of field section, the identification and analysis of microscope thin sections, and combined the research of sedimentary facies marks with petrology, well logging and seismology, it is indicated that fan delta, braid river delta and lakes are developed in the Xujiahe Formation, large scale Central Sichuan,and further are divided into several subfacies and microfacies. Through the theory and technology of high resolution sequence stratigraphy, we identify two super long terms and five long terms of datum base level cycles sequences in the Xujiahe Formation. Using the sedimentary theory as a guidance, we choose the long term base level cycle sequences as isochronal stratigraphic units to map sequence lithofacies paleogeography of Sichuan basin. The result of maping diagram makes it clear that five long term lithofacies paleogeographic subsidence center, migration direction and the distribution rule of sedimentary facies are strictly controlled by the Longmen orogenic belt and Micang Mountains with the nonsynchronous tectonic framework.