Accommodation Mechanics of Terrigenous Sequence Development in Fault-depressed Lacustrine Basin——A Case Study: the Upper Member of Eh₃, Shuanghe-Zhaoao, Biyang Fault-depression

Key words: 
• tectonic descent /
• lacustrine level change /
• accommodation /
• Fischer diagram /
• terrigenous sequence /
• Palaeogene /
• Biyang fault-depression

Abstract: In Biyang fault-depressed lacustrine basin, the tectonic descent of basement presented antihinge-typed subsidence. Due to the joint effect of lacustrine level change and basement structural subsidence, accommodation change in the steep slope zone of Biyang fault-depressed lacustrine basin only have three possibilities: a. decreasing at southern and northern rim zone but increasing in central zone; b. beingin-variant at southern rim zone but increasing in central zone and at northern rim zone; c. all increasing at southern and northern rim zone and in central zone. In the light of the three cases, the sedimentation-re-sponsed charteristics to the accommodation variation law at different structural positions of the steep slope zone in fault-depressed lacustrine basin have been respectively analy sed at different recharge rate of sediment-source. In this paper, accommodation mechanics to select reference well has been discussed; and by using well B207 as reference well, the terrigenous sequences of the upper member of Eh₃ have been di-vided; and by using Fischer diagram, the realized accommodation change curve of the terrigenous se-quences is acquired.