Sedimentary facies of the uppermost Jurassic and Lower Cretaceous in
Gucuo area, southern Tibet
Hu Xiumian Wang Chengshan Li Xianghui Chen Lei
1 Department of Earth Sciences, Nanjing University, Nanjing 210093，Jiangsu
2 Geological Centre of the Qinghai-Tibetan Plateau, China University of Geosciences（beijing）,
Beijing 100083
3 School of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059,Sichuan
Based on the detailed field observation and sedimentological studies, the strata of the Late Jurassic - Early Cretaceous in the Gucuo area, southern Tibet was described and amended. Six types of lithofacies were recognized including rufous (weathered color) quartzose conglomerates, gray –greenish pyroclastic conglomerates, gray-whitish sandstones, gray-greenish pyroclastic sandstones, gray- greenish lithic arenite, gray and dark gray black shales. Many sedimentary structures were discovered including normal grading beds, parallel lamination, planar cross-bedding, low-angle cross bedding, hummocky cross-bedding, ripples, flute cast, load casts, sandstone dikes, erosion surface, imbrications, hard grounds, as well as lots of concretions and bioturbations. Two types of sedimentary facies were recognized in the Gucuo area,i.e.delta (including delta front and prodelta) and shelf (including storm-influenced shelf and open deep shelf). The delta front facies can be further divided into subaqueous distributary channels, mouth bar, and far bar. The vertical facies association of the Gucuo section was established, which allows us to discuss the evolution of the sedimentary environments.
