古地理学报2011，Vol.13Issue(5)：551-562,12.
鄂西—湘西北地区二叠纪栖霞期岩相古地理
Lithofacies palaeogeography of the Qixia Age of Permian in western Hubei-northwestern Hunan Provinces
摘要
Abstract
Detailed stratigraphic and depositional facies analyses for the Qixia to the Lower Maokou Formations from several sections in western Hubei-northwestern Hunan Provinces indicate an intra-craton carbonate ramp environment, including inner, middle and outer ramps, and basinal facies. The inner ramp facies consists of thick-bedded to massive bioclastic limestone, characterized by bioclastic grains of green algae and benthic foraminifera and lack of high-energy bioclastic shoals. The middle ramp faciesconsists of medium- to thick-bedded limestone bearing bioclasts and thick-bedded lime mudstone. This fa-cies is characterized by skeletal grains of crinoids, bryozoans and small foraminiferas, but is lack of the hummocky cross-stratification. The outer ramp facies consists of marlstone interbedded with thin-bedded lime mudstone bearing bioclastic grains of thin-shelled brachiopods. Basinal facies is characterized by dark-grey marlstone intercalated with black calcareous shales. These features suggest a low energy protected carbonate ramp (or shelf) environment. Three third-order sequences (S1, S2 and S3) were identified in the Qixia and Lower Maokou Formations, each spanning about 2 Ma. These sequences are domi-nantly composed of the lower transgressive and upper highstand systems tracts. The basal sequence SI was deposited during the initial transgression of Qixia Age, during which the carbonate ramp was established, developing intrashelf basin in the western Hubei area. Then an overall mild shallow carbonate ramp ( or shelf) environment predominated over as the intrashelf basin was filled up during S2 deposition. Sequence S3 was deposited during the largest-scale transgression in the Late Paleozoic, resulting in an apparent deepening in water depth. The deep outer ramp was then established once again and expanded in a mushroom-shaped area in Sangzhi-Changyang-Jingzhou-Changde area.关键词
岩相古地理/层序地层/碳酸盐岩缓坡/栖霞期/鄂西—湘西北Key words
lithofacies palaeogeography/sequence stratigraphy/carbonate rock ramp/Qixia Age/western Hubei-northwestern Hunan分类
天文与地球科学引用本文复制引用
韦恒叶,陈代钊..鄂西—湘西北地区二叠纪栖霞期岩相古地理[J].古地理学报,2011,13(5):551-562,12.基金项目
国家自然科学基金项目(编号:40839907)资助 （编号:40839907）
