The Sediment Flux of the Longmen Shan Foreland Basin During the Late Triassic Epoch and the Uplift and Denudation of the Orogenic Belt
YAN Zhao-kun LI Yong DONG Shun-li HAN Bing CHEN Hao ( State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059)
Based on boreholes and stratigraphic sections,we draw maps about uniformly thick residual formation in the Longmen Shan Foreland Basin with Surfer 8. 0 software,work out the total amount of sediment of residual formation,and figure out the sediment flux in each phase:21. 4t/( m2·Ma) ,184. 2t/( m2·Ma) ,278. 0t/( m2·Ma) ,147. 6t/( m2·Ma) ,703. 5t/( m2·Ma) ,and 272. 0t/( m2·Ma). Then we denude back the sediment to the orogen-ic belt based on material balance method and carry out depressure correction. We can work out the aggregate thickness denuded is about 2 514 m on Longmen Shan during the late Triassic Epoch,and the speeds of denudation in each phase are:0. 009 mm/a,0. 114 mm/a,0. 133 mm/a,0. 094 mm/a,0. 423 mm/a and 0. 133 mm/a. At last,we reconstruct the history of uplifting during the late Triassic Epoch of the Longmen Shan orogenic belt:the crust in the Longmen Shan orogenic belt uplift about 4. 3 ～ 4. 6 km and the surface of the Longmen Shan orogenic belt uplift about 1. 8 ～ 2. 1 km in the time between 228. 0 Ma and 199. 6 Ma ago,and the process of uplift had the obvious stage features,which could be divided into the initial uplift stage( 228. 0 ～ 216. 5 Ma) ,the accelerated uplift stage( 216. 5 ～ 211. 0 Ma) ,the slow uplift stage ( 211. 0 ～ 203. 6 Ma) ,the steeprise uplift stage( 203. 6 ～ 202. 7 Ma) and the slow uplift stage( 202. 7 ～ 199. 6 Ma).