Abstract: Tectonic evolution and its origin of the upper Paleozoic in the Dingyuan Sag are essential for the evaluation of coal resources and exploration targets of unconventional natural gas. Based on the latest geophysical and drilling data, combined with results from previous studies, we discussed the tectonic evolution and its origin in detail via structural analysis and regional comparison. Results show that the upper Paleozoic coal-bearing strata are comparable to the middle segment of the Huainan coalfield, which show an anticline pattern. The Dingyuan Sag has been affected by the strike-slip activities of the Tan-Lu Fault Zone and uplift of the Dabie Orogenic Belt from the Mesozoic to Cenozoic. The tectonic evolution in the Dingyuan Sag can be divided into six main stages, including foreland deformation in the Indosinian (T3), relative uplift in the early-middle Jurassic (J1+2), reformation by strike-slip activities of the Tan-Lu fault zone from the late Jurassic (J3) to early Cretaceous, reformation by extension activity from the early Cretaceous (K1) to Paleogene (E), inversion by compression activity in the late Paleogene, and depression with uniform deposition from the Neogene to Quaternary (N-Q).

Key words: Dingyuan Sag, Huainan coalfield, Tan-Lu fault zone, coal-bearing strata, tectonic implicaiton, regional tectonic
setting, evolution process