Permian Basin and its Gondwanan Sediments in Central Xizang (Tibet) and Himalayas

Liu Guanghua

pp. 123-146, 3 plates, in English

Abstract:

Permian sedimentary rocks in the both central Tibet (Lhasa Block) and Northern Himalayas (northern margin of the Indian Plate) bear a Gondwanana flora and fauna and display similar sedimentary features. These indicate that there was no large biogeographic barrier or sea-way separating the Lhasa Block from the Himalayas and both of them were integral parts of the Gondwanan supercontinent during the Permian period. Permian deposits in the study area formed in an epi-continental of cratonic basin, which was open to the Paleo-Tethys in the north. In the Tibetan Himalayas, the Permian deposits are dominated by siliciclastics in the south and skeletal limestones in the north, representing barrier-lagoon systems and carbonate platforms with reefs respectively. A mega-cycle of transgression-regression has been recognized and interpreted to be a result of eustasy. In the Lhasa Block, the Permian is characterized by alternating chert-banded and skeletal carbonates, representing repeated progradation of carbonate platforms from offshore lower energy to shoal and reef higher energy settings. A thick coarse clastic wedge (up to 4000 m thick) occurs in the Lower Permian of Pomi, northern margin of the Lhasa block. It may represent an intracontinental rift, which probably marks the separation of the Qiangtang Block from the Gondwanaland. A sedimentary gap between Permian and Triassic in most areas and a paleo-karst surface filled with Triassic shale in the uppermost Permian at Kangmar indicate that the latest Permian was an uplifting period. It may represent a pre-rifting stage of the following Triassic rifting, in which Neo-Tethys began to open.

Keywords: Permian, Gondwana, Tibet, Himalayas