DEPOSITIONAL FEATURES OF HIGH-FREQUENCY CYCLES IN THE DUOBA FORMATION,LOWER CRETACEOUS IN GERZE-BAINGOIN AREA, XIZANG
Wang Guanmin1, Zhong Jianhua2, Wang Jianping3, Chen Qinghua2
1. Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640; 2. College of Earth Resources and Information, University of Petroleum, Dongying, Shandong 257061; 3. Henan Institute of Geological Survery, Zhengzhou 450007
The three vertical depositional sequences, which were developed in the Duoba formation of Lower Cretaceous in the Gerze-Baingoin area, Tibet, were: (Ⅰ) clastic sequence deposited of tidal facies; (Ⅱ) combined depositional sequence of clastic and carbonate; and (Ⅲ) carbonate sequence of shallow-sea facies. Among which, the Ⅰ-1 and Ⅲ were depositional sequences characterized by shallowing water depth. However, the sequence Ⅱ was of typical terrigenous debris deposition with features of first progradation and then retrogradation, and therefore might be further divided into three sub-types: Ⅱ-1, Ⅱ-2 and Ⅱ-3. Laterally, the sequence changes might be from Ⅰ to Ⅱ-1 to Ⅱ-2 and Ⅲ from the south resource area to the north. Based on the basin tectonic background and depositional features, it was suggested in this paper that the form of high-frequency Duoba Formation might correspond with the upthrusting caused by upthrown fault block in the south of retroarc basin. During the upthrusting, the basin was deposited with abundant coarse debris sediments from the source area, and might surpass the basin subsidence, so as to shallowing the water body. In contrast, in the intermittent period of upthrusting, the water body was deeper due to the decreased input of the sediments which could not compensate the subsidence of the basin.
Wang Guanmin,Zhong Jianhua,Wang Jianping et al. DEPOSITIONAL FEATURES OF HIGH-FREQUENCY CYCLES IN THE DUOBA FORMATION,LOWER CRETACEOUS IN GERZE-BAINGOIN AREA, XIZANG[J]. Chinese Journal of Geology, 2004, (3): 346-355.