Evolution of the southern Taiwan-Sinzi Folded Zone and opening of the southern Okinawa trough

Recent interpretation of seismic sections and free-air gravity anomalies in offshore northern Taiwan reveals that the southern Taiwan-Sinzi Folded Zon e began to form in late Middle Miocene, though it was mainly constructed in the Late Pliocene with strong reverse faulting and folding. Two westward p rogradational sequences were deposited in the shelf basin with sediments su pplied from the southern Taiwan-Sinzi Folded Zone and the southern Ryukyu A re. These two structures are displaced by several northwest-striking dextra l strike-slip faults that were active in the early Quaternary when the cloc kwise-rotated southern Ryukyu Are and the folded southern Taiwan-Sinzi Fold ed Zone were broken. It is believed that recent extension in the southern O kinawa Trough started in the early Quaternary because uplift on the souther n Taiwan-Sinzi Folded Zone continued to latest Pliocene-early Quaternary. P aleogene-Miocene sediments of the East China Sea Shelf in the western part of the southern Okinawa Trough Basin are interpreted to indicate that the E ast China Sea Shelf Basin extended to the east of the southern Taiwan-Sinzi Folded Zone. (C) 2000 Elsevier Science Ltd. All rights reserved.