Continental margin deformation analysis and reconstruction: Evolution of the East China Sea Basin and adjacent plate interaction.

摘要

The East China Sea Basin (ECSB), located on the eastern Asian continental margin, consists of the East China Sea Shelf Basin and the Okinawa Trough Basin separated by the Taiwan-Sinzi Folded Zone. The strata of the ECSB have been deformed and the structural framework modified by multiple stages of extension and contraction since late Mesozoic times. Because of this strong deformation, past depths and positions of basins are not easily determined. Such information though, is important both to constrain regional tectonics and to understand basin evolution mechanisms.; An algorithm developed for this study is used to restore the ECSB to its original depth and position through a series of extensions and contractions. The method uses a three dimensional decompaction, backstripping, and deformation restoration approach. Stretching analysis restores basin extension or contraction, and subsidence analysis restores basin depth. Sequence depth data and basin deformation history, based on seismic interpretation, and lithologic information are required for these analyses. Seismic interpretation which combines both seismic and structural analyses of synrift and postrift sequences is used to establish and map seismic sequences, to delineate the structural framework, and to extract deformation events. The ages of the seismic sequences are controlled by data from twelve wells. Seismic facies analysis calibrated with the well logs is used to determine lithological information. The application of the basin reconstruction method in the ECSB was used for 37 different ages. This reconstruction method is a practical tool to reconstruct basin evolutionary processes and can be used in other basins for geohistory study and basin-scale reconstructions.; Results from the extension and subsidence analyses are used in regional tectonic reconstructions to analyze the origins of the strata deformation events in the ECSB. Although the eastward extrusion of Asia, caused by the India-Eurasia collision, is still considered the primary causative mechanism for other sedimentary basins in East Asia, the basin evolutionary processes in the ECSB were primarily the result of plate interactions with the western Pacific. Basin inversion forces came mainly from collisions between the Philippine Sea Plate and East Asia in mid-Oligocene and Late Pliocene times.