新疆库车坳陷古近系膏泥岩层分层特征及沉积演化分析

库车坳陷古近系库姆格列木群下部的膏泥岩段存在明显的分层特征,根据岩性序列变化将其划分为5个亚段,自上而下依次为第1亚段(上泥岩段)、第2亚段(上化学岩段)、第3亚段(中泥岩段)、第4亚段(下化学岩段)、第5亚段(下泥岩段)。该岩性序列在克拉苏构造带不同部位发育程度不同,东部的克深-克拉地区发育第1~3亚段,仅西部DB303井附近发育完整的5个亚段。通过解剖各亚段内部岩性特征,明确其分布规律,并对库姆格列木群沉积初期的古地貌和沉积环境进行初步探讨,确立各亚段原始沉积演化序列和沉积模式。研究认为:(1)库姆格列木群沉积时期古地貌为东高西低,地貌幅度小;(2)膏泥岩段沉积序列呈碎屑岩-化学岩交替发育特征,受古地貌影响,不同地区发育的岩性序列旋回个数不同,但岩性序列变化规律相同。

Division and sedimentary models for the Palaeogene gypsum mudstones in the Kuqa depression, Xinjiang

In terms of lithologic sequences, the gypsum mudstones in the lower part of the Palaeogene Kumugeliemu Group in the Kuqa depression, Xinjiang are divided, from top to bottom, into five lithologic submembers:(1) No. 1 submember,i. e. the upper mudstone submember dominated by brown mudstone;(2) No. 2 submember, i. e. the upper chemical rock submember dominated by gypsolith and salt rocks;(3) No. 3 submember, i. e. the middle mudstone submember;(4) No. 4 submember,i. e. the lower chemical rock submember dominated by gyposlith and salt rocks intercalated with dolostone, and limestone, and (5) No. 5 submember, i. e. the lower mudstone submember dominated by mudstones. The approaches to the palaeogeomorphological features and sedimentary evolution of the Kumugeliemu Group in this study lead to the proposition of the sedimentary models for individual submembers of the gypsum mudstones in the lower part of the Palaeogene Kumugeliemu Group, and restoration of the palaeogeomorphological and sedimentary features during the early stages of the deposition of the Kumugeliemu Group.