STRUCTURE AND DEVELOPMENT OF THE JAPAN SEA BASEMENT

Abstract

In the Japan Sea region, there are three types of the Earth's crust: continental, subcontinental, and suboceanic. The first type is characteristic of the shelf, the second one of the submarine elevations, the third one of the deep-sea basins. The continental structures extend to the continental and island slopes. Metamorphic, sedimentary and magmatic rocks of Archean to Cenozoic age were dredged up on the submarine elevations. These rocks are similar to the formations of the surrounding land. The original continental crust of the Japan Sea region was formed in the late Proterozoic. Then, geosynclines successively developed. The Japan Sea depression started forming since the Cretaceous. Its formation can be explained by the intrusion of a mantle diapir into the lithosphere. The diapir stretched the Earth's crust. The stretching was accompanied by the compression of the crust in the periphery areas, resulting in the formation of folds and thrusts. By the end of the Paleocene, a continental slope was developed in general outlines. The submarine elevations became islands and peninsulas at that time. The subsidence of the submarine elevations began in the middle Miocene and coincided in time with the glacio-eustatic transgression.