A Discussion on Paleogene Jiyang Depression Characteritics and Its Forming Mechanism.

According to the structural and sedimentary evolution,Jiyang depression is a compound and superim-posed basin with complex evolutionary history that there existed different basins of primary types and different sedimen-tary assemblages.It is confirmed that Jiyang depression of Paleogene occurred in trans-extensional behavior in the light of Moho uplifting,lithosphere thinning,development of basic and ultra basic igneous rocks in mantle source rocks,high geothermal gradient,halfgraben-like depression basin groups,extensional amount of more than50km and sedimentary velocity up to0.1mm/a,well-developed tensional fractures,lithosphere appearing sandwich-like rheological structure,seismic source mainly taking place in the middle crust and release of mantle source gases as well as property of Tanlu fault.The mechanism of trans-extensional basin is discussed.