Depositional Architecture of Paleogene System Tectonic Sequences and Evolvement of Sedimentary System in Jizhong Depression

Key words: 
• Jizhong Depression /
• structural evolvement /
• response to filling /
• structural subsidence

Abstract: Sedimentary sequence which belongs to the second grade sequence locates among the parallel, microangular or angular unconformities, and which is divided into 3 second order sequences, 13 third order sequences and numeral fourth or fifth order sequences. There are three series of sedimentary cycles for transgression to regression, and identifying alluvial fanfluvial facies, lakedelta and fluvial facies and so on. Structure, climate, sedimentary supply and variation in lake level and so on control the depositional architecture of the Paleogene System tectonic sequences and their response to tectonism in Jizhong depression. The analysis shows that the depression suffers for two sets of evolvement gyrations attributing to variation in deposition rate. Phase 1, slowness accelerating subsidence at Paleocene in Paleogene Period, earlymediumterm speediness subsidence at Eocene Epoch and terminal slowness subsidence at Eocene Epoch. Phase 2, telophase lowness accelerating subsidence at Eocene Epoch, earlyterm speediness subsidence at Oligocene and mediumterminal slowness subsidence accelerating subsidence at Oligocene. Settlement rate partly is 100～110 m·Ma1, 205～220 m·Ma1, 40～50 m·Ma1,30～40 m·Ma1, 135～142 m·Ma1 and 10～20 m·Ma1. Wring action in Paleogene Period shows sinistral movement makes enechelon structure as causes NNE or NE orient distribution at terminal of Sha4 and Dongying member, and dextral movement is reverse. At last the depression unfolds the structure of two sunkens champing one convex.