Structure and Hydrocarbon Potential of Sedimentary Basins of the Far East Marginal Seas: ABSTRACT

Abstract

Crustal structural of the Bering, Okhotsk Japan, East China, and South China marginal seas consists of continental plates and deep sea basins that are the elements of the lowermost order in the structure of transition zone from the Asia continent to the Pacific Ocean. Two stages are recognized in the crustal evolution of the northwest Pacific transition zone: (1) geosyncline development that began in the pre-Paleozoic and continues to the present within island arcs; and (2) quasiplatform stage that began in the late Cretaceous and continues to the Holocene within shelf plates. The continental margins of the Far East seas consist of Cenozoic terrigenous cover and pre-Cenozoic basement composed of geosyncline rock association. Normal faults control graben features in the basement and develop rift systems. Paleogene subcontinental formations make up the lowermost section of the cover. A major Oligocene-Holocene sequence (marine formations) overlies and smooths rough topography of the basement and creates giant sedimentary basins. Sediment thickness of the basins attains 10 km. Tectonic evolution of the marginal seas implies the shelf plates to be young platforms and deep-sea basins are believed to be parts of the Pacific thalassocraton fenced by island arcs. The tectonic criterion enables us to differmore » and grade the provinces according to a hydrocarbon potential. Nearly 100 promising sedimentary basins are presently known in the Bering, Okhotst Japan, East China, and South China seas. About ten basins have been identified as hydrocarbon resources. Deep-sea basins also look promising for hydrocarbons. All the economically significant hydrocarbon accumulations in the Far East marginal seas are attributed to the Cenozoic sediment cover. Major resources are concentrated in the Miocene and Pliocene terrigenous sequences composed of progradation facies within the shelf plates.« less