Mesozoic fill-sequences in Hefei Basin: Implication for Dabie Orogenesis, central China

A research on the Mesozoic fill-sequences of Hefei basin, locatedat the north foot of Dabie Mountains, shows two-phase evolution. The first phase, early- to mid-/late-Jurassic, is characterized by terrestrial clastic deposits, with four times of reverse-grading units at least, and forms greatly thick molass reconstruction in the mid-/late-phase, which reflects gradually strong thrusting-orogenesis in the north Dabie and flexural depression in the north foreland of Dabie Mountains. The second phase, late-Jurassic to Cretaceous, includes two-episode rifting processes. The first episode (J3) shows calc-alkalic and alkali volcanic rocks interstratified pyroclastic rocks, which may reflect upwelling igneous magma from mantle-source due to the Yangtze continent slab breakoff induced by deep subduction process. A suite of lacustrine, fluvial and piemount facies, about 3000?/FONT>3500 m in thickness, develops in the second episode (J3 -K1), which reflects regional extensional setting and intense elevator diversity of mountain-basin in the study area. This research renews and deepens cognition for the Mesozoic Dabie orogenesis.

A research on the Mesozoic fill-sequences of Hefei basin, located at the north foot of Dabie Mountains, shows two-phase evolution. The first phase, early- to mid-/late-Jurassic, is characterized by terrestrial clastic deposits, with four times of reverse-grading units at least, and forms greatly thick molass reconstruction in the mid-/late-phase, which reflects gradually strong thrusting-orogenesis in the north Dabie and flexural depression in the north foreland of Dabie Mountains. The second phase, late-Jurassic to Cretaceous, includes two-episode rifting processes. The first episode (J3) shows calc-alkalic and alkali volcanic rocks interstratified pyroclastic rocks, which may reflect upwelling igneous magma from mantle-source due to the Yangtze continent slab breakoff induced by deep subduction process. A suite of lacustrine, fluvial and piemount facies, about 3000 –3500 m in thickness, develops in the second episode (J3-K1), which reflects regional extensional setting and intense elevator diversity of mountain-basin in the study area. This research renews and deepens cognition for the Mesozoic Dabie orogenesis