DISCREPANT UPLIFTING PROCESSES OF THE QINLING-DABIE AND JIANGNAN OROGENS: EVIDENCE FROM MESO-CENOZOIC SEDIMENTARY RECORDS IN THE JIANGHAN SUPERIMPOSED BASIN
Xu Zhengyu1, Lu Wenzhong1, Lin Ge2, Liu Chiyang3, Wang Yuejun2, Guo Feng2
1. Hangzhou Institute of Petroleum Geology, China National Petroleum Corp., Hangzhou 310023;
2. Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510650;
3. Department of Geology, Northwest Universty, Xi’an 710069
The Jianghan basin in the Middle Yangtze area, sandwiched in between the Qinling-Dabie and Jiangnan orogens, was a typical superimposed basin. It developed on the Middle Triassic shallow marine platform and transited from alternating marine-continent facies to continent basin, with the deposits of Triassic to Neogene thickened than 10000 m. The developing process of the basin, coupled with orogenic processes of the Qinling-Dabie and Jiangnan orogens, could be divided into four phases, namely, the initial orogenic, the main orogenic, the post orogenic and extensional (non-orogenic) periods. The stratigraphical sequences of the fillings in the basin were marked by four supper-sequences (or four basin generations), namely, the continental shelf margin, foreland, rift and depression basins. By analyse distribution of the sedimentary detritals in the basin, it was discovered that the Jiangnan orogen entered a strong activation stage during Middle Triassic, and a quiet stage of post-orogenic collapse in the end of Cretaceous; and the main orogeny occurred, in the Qinling-Dabie orogenic area, during Late Triassic and early Early Jurassic, with a relatively quiet stage during Paleogene. The basin developing showed a tendency that the orogeny and uplifting were earlier in the east part, correspondingly, the uplifting and erosion continued a longer time so the metamorphic basement rocks outcropped in Late Triassic; while in the west part of the basin, the orogeny and uplifting were relatively later, and the metamorphic rocks outcropped in Early Jurassic. The mountain chains to the nonrth and the south of the Jianghan superimposed basin had undergone obviously discrepant uplifting processes.
Xu Zhengyu,Lu Wenzhong,Lin Ge et al. DISCREPANT UPLIFTING PROCESSES OF THE QINLING-DABIE AND JIANGNAN OROGENS: EVIDENCE FROM MESO-CENOZOIC SEDIMENTARY RECORDS IN THE JIANGHAN SUPERIMPOSED BASIN[J]. Chinese Journal of Geology, 2005, (2): 179-197.