ABSTRACT: Crustal Structures of East China Sea

Xu Weiling, Le Qunyin

East China Sea was formed from the interaction of Pacific, Eurasia, and Indian Plates. Seven layers have been recognized, i.e., water, Cenozoic sediments, Upper Jurassic to Lower Cretaceous volcanites and sediments, Paleozoic low grade metamorphics, Precambrian medium to high grade metarocks, lower crust, and upper mantle. Rhykyu Trench is a divide; west of it is continental or transitional crust, while east of it is oceanic in nature. Diaoyudao uplifted zone is another divide that separates the continental part into western shelf basin and east arc-island and trench system. Structural discontinuities, stratigraphic unconformities, and jumps in seismic velocities have been delineated.

Four convergent zones can be revealed. From west to east, (1) Early Cretaceous subduction zone evolved from a transform fault and changed to strike-slip fault in the north; (2) Late Cretaceous subduction zone that located in the Central Range of Taiwan to Diaoyudao, some of which existed on the west of the shelf basin by the splitting of Okinawa Trench; (3) Late Cretaceous to early Tertiary subduction zone connected with the Shiwanshi zone of southwest Japan; and (4) Miocene to Quaternary subduction zone along the Rhykyu Trench.

Old continental nuclei amulgated with accreted terrane and growth to be a continent before Mesozoic; after that the subduction, back-arc spreading caused the disintegration of the continent and generated the present framework.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990