Filling Evolution Analysis Of Composite Basin With Shallow Basin And Multi-sag

Jiangling depression is the largest secondary tectonic unit in Jianghan basin, which developed fault sag sedimentary depression of cretaceous-tertiary on the bottom of precretaceous with near ten thousand meters continental clastic rock in channel-delta-lacustrine sedimentary systems. This paper use core, well logging, mud logging and seismic data, under the theory guidance of sequence stratigraphy, sedimentary and reservoir geology with the way of composition of geology and seismic, whole and regional searching, mainly rely on tectonic study and sequence analysis to learn tectonic and filling evolution character of Jiangling depression systematically with analyzing tectonic control function to sedimentary filling. Achievement comprise following:The base tectonic in Jiangling depression affected by Qingling and Xuefeng composite tectonic system, which developed northeast,northwest and near east-west three direction structures controlling evolution of basin forming and bringing complex landform northeast fault sag, near east-west sag and northwest. On the whole, Jiangling depression belong to sag. This depression went through fault-sag-drape three tectonic cycles and seven tectonic evolution parts in cretaceous, when faults developed and faults throw is shallow, through there are a lot of faults controlling sag but the fault parallel to long axis of depression is none,so composite tectonic pattern "shallow basin and multi-sag" formed in all.The sedimentary model, system types and characters of Jiangling depression are recognized. Channel, delta and lacustrine sedimentary system are main developed in searching area. On the whole, in the time of Yuyang group deposition, under the climate conditions of torridity,drought and windness, aeolian dune, alluvial plain and salt lake developed in area, while in time of Shashi group deposition, climate is still torridity, channels, delta and satl lake with few water recharge developed in searching area, and regional surface runoff water recharge area is easy to form freshwater river delta sediment.From the view of sedimentary evolution analysis in different time units of Shashi group, distribution of channel-delta sand has significant increase tendency and the main provenance(north of area) is recognized in Shashi deposition time. But it is not clear that salt lake and time have correlation which distributed cross pre-depression, different time has different distribution range.4.Jiangling depression comprises four sags, three processes and north-south slopes, all sags and processes have same attribute except that south part of Anjiacha sag belong to extrusion syncline. That is to say pre-tectonic pattern has multi-processes and multi-sags in fault sag times in Jiangling depression, every fault sag groove was not formed relatively independent lacustrine system but pre-lacutrine of Zhikou-Meihuaiqiao-Zifusi sag area, where is the depositional center in every time.