High-Resolution Study of Post-Glacial Transgressive Deposits in the Mid-Western Part of the Yellow Sea

Young Jae Shinn¹, S. K. Chough¹, Jusun Woo¹, and J. W. Kim^2
1 Seoul National University, Seoul, South Korea
² Daewoo International Co, Seoul, South Korea

An analysis of high-resolution seismic profiles (Chirp) and piston cores in the mid-western part of the Yellow Sea suggests that the seafloor is characterized by a distinctive surface of marine transgression and the associated transgressive deposits. A shelf-wide erosional surface is interpreted as a shoreface ravinement surface created by rapid retreat of shoreline. The ravinement surface gradually deepens seaward, forming a series of submarine terraces. Three distinctive transgressive deposits formed on the ravinement surface, which show abrupt landward shift across each terrace. On the most landward terrace (< 40 m in water depth), the surface is covered by a veneer of marine sand that originated from erosional retreat of shoreface, subsequently reworked by marine processes. Further offshore (< 60 m in water depth), lobe-shaped prograding mounds are isolated on the surface. They prograded obliquely to the present-day coastline, suggesting that along-shore currents played a significant role in sediment dispersal for the prograding mounds. Some mounds have a relatively flat top and fill local depression on the terrace, showing shore-normal progradation. These mounds are interpreted as regressive wedges, resulting from a combination of short-period stillstand in sea level and increase in sediment supply. On the most basinward terrace (< 80 m in water depth), a transgressive sediment sheet extensively overlies the ravinement surface. A series of submarine terraces formed by step-wised sea-level rise, where transgressive deposits reflect changes in sediment supply and oceanographic regimes.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005