Print this pageStructure and Tectonic Evolution of the Xihu Trough and East China Sea
HICKMAN, ROBERT G., TIMOTHY P. SEELEY, KEVIN M. DOYLE, AND LARRY A. WILLIS
During the latest Mesozoic and Cenozoic, a series of extensional basins developed within the Chinese continental margin. These include the Bohal and Yellow Sea basins which developed in late Mesozoic times; the Xihu Trough which started to develop in Paleogene times and the Okinawa Trough that began to develop in Miocene times. Formation and deformation of these basins was closely related to the rate and direction of convergence between Pacific oceanic plates, the Philippine Sea plate and Eurasian plate. During periods of relatively slow convergence, extensional backarc basins developed; during periods of rapid convergence, arc magmatic activity increased and compressional deformation occurred in the backarc basins.
The Xihu Trough contains up to 10 kilometers of Cenozoic strata. It is bounded on the west by the Baoshu Shelf where a thin Cenozoic sequence overlies Precambrian crystalline rocks and younger continentally derived clastic and volcanoclastic sequences; it is bounded on the east by the Diaoyudao High which consists of block-faulted Oligocene and older strata that overlie deeply buried continental crust.
During initial rifting in the Eocene and early Oligocene, the northeast-trending Xihu Trough developed as a series of complex half grabens. In the late Oligocene, extensional faulting further defined the eastern margin of the basin and the Diaoyudao High. Basin subsidence during Oligocene to late Miocene resulted in the initial deposition of mixed estuarine and fluvial strata. Scattered arc-related plutons intruded the Diaoyudao High during the early-middle Miocene. Northwest-southeast shortening during the latest Miocene reactivated rift-related extensional faults as reverse faults and produced large inversion anticlines within some basin.