Abstract: Considering the fact that only a few exploratory wells in southern East China Sea Basin were drilled,we resorted to sufficient seismic data here to restore the critical unconformity erosion thickness and study the basin infilling and tectonic evolution by employing approaches including stratigraphic trends contrast,acoustic travel time,and sedimentary fluctuation analyses.The results show that the denudation of the basin was the most intensive during the Late Paleocene and Early Eocene,leading to the formation of the T₄⁰ unconformity with the largest erosion thickness of 800-1 000 m in the slope and uplift zones of Jiaojiang-Lishui Sag,and the least erosion thickness of 200-400 m in Fuzhou Sag as well as the medium erosion thickness of 200~600 m in Diaobei Sag.During the Late Oligocene and Early Miocene when the denudation was less intensive,the unconformity T₂⁰ was formed with mostly 500 to 600 m erosion thickness in the western slope of Diaobei Sag,the northern part of Fuzhou Sag,Yandang Low Bulge,and southern segment of the western slope of Jiaojiang-Lishui Sag.In the Paleocene,rifting and faulting activities initiated in the western depression,forming a dustpan-shaped “eastern faulted and western overlapping” structure;then shifted to east depression (leaving the west part to enter the stage of depression-inversion in the Eocene),forming a “bidirectional faulted” structure in Diaobei Sag.The Oligocene saw the east part also entered the depression-inversion stage but less intensive with the depression gradually turning into the westward overlapping dustpan structure.After the Miocene,the East China Sea Shelf Basin slowly entered the regional subsiding stage from west to east.

Key words: acoustic travel time, sedimentary fluctuation, erosion thickness, tectonic evolution, East China Sea Shelf Basin