Pliocene morphological characteristics of the East Sea’s southwestern deep depression

Abstract

Pliocene morphological characteristics of the East Sea’s southwestern deep depression at the scale of 1:250,000 based on co-originated surfaces are presented in this paper. The study shows that the morphological characteristics of the study area in the Early, Middle and Late Pliocene reflect a clear structure of the Earth’s crust and consist of continental shelf, continental slope, deep sea floor and depression zone. The main morphological units in the Pliocene include the paleo-morphological continent and morphological sea floor. The morphological sea floor consists of horizontal surfaces, plane surfaces and slope surfaces. The morphological units in the Late Pliocene inherit features of the Early and Middle ones. Their inheritance is most visible on the guyots and the horst mountains existing throughout the Pliocene period. In the Early and Middle Pliocene, the paleo-continent mass distributed in a limited area in the north-west corner of the study area. In the Late Pliocene, the paleo-continental mass disappeared and the whole study area was dominated by the sea. Hence, the Early and Middle Pliocene were the period of transgression into the Vietnam continent. In the Late Pliocene, the study area was submerged in the deep sea.