On the history of tectonic evolution and karstification in Wuhan

In order to reveal the karst development characteristics more comprehensively, the history of the tectonic evolution and the karst development in Wuhan is studied by means of history comparison method. During the Paleozoic and the early Mesozoic, the crustal movement in Wuhan and the surrounding area are characteristic of integral lifting, and strata in every periods is parallel unconformity contacted with each other. Two sets of the Carboniferous-Permian and Lower Triassic carbonate are formed by the late Paleozoic and early Mesozoic marine transgression-regression. It provides materials for karst development in Wuhan. The powerful compression stress of NNE to SSW in direction generated by the Indosinian movement at the end of the middle Triassic creates the linear folds with the trends of NWW to SEE, and controls the plane distribution of carbonate in Wuhan. During the late Triassic to Jurassic, the crust in west and north Wuhan uplifts as well as the Liangzihu in the east and southeast Wuhan began to depress gradually under the influence of Xiangfan-Guangji fault. The surface water and groundwater discharge overall to the Liangzihu depression, which controls the development of the karst groundwater system at the first phase in Wuhan. During the Cretaceous and Paleocene Periods, the crustal activity in Wuhan and the surround area is characteristic of differentiation subsidence, and the karstification stops. During the Neocene-early Pleistocene, the crust depresses continuously in Qianjiang, while uplifts overall in Wuhan. The paleo-topography in the period is high to the east and low to the west, surface water and groundwater flow from east to west, and the second phase of the karst groundwater system develop from east to west. During the middle and late Pleistocene, Wuhan and surrounding areas overall sinking, the old clay with the thickness of 10～30 m forms widely, and the karst groundwater systems of the former two periods are covered. Karstification basically stops due to the relatively impermeable layer barrier. In the Holocene period, the erosion of surface water has destroyed the continuity of the old clay layer. The carbonate is below 10～20 m of the Yangtze River water and the base level of erosion is much higher than that of carbonate, so the groundwater acts very weakly resulting only weak or no karstification.