Origin of inner-shelf mud deposit in the southeastern Yellow Sea: Huksan Mud Belt

Abstract

A variety of previous sedinentological results, together with newly obtained hydrodynamic data, are summarized and reinterpreted with respect to the most likely origin of the Huksan Mud Belt (HMB) in the southeastern Yellow Sea. The HMB consists of two mud units that have similar grain texture and clay mineralogy but can be differentiated on seismic profiles because the lower unit is generally harder than the watery upper unit. The hydrographic measurements together with satellite imagery clearly indicate that the suspended plume covering the HMB originates from the west coast of Korea. The suspended plume becomes enhanced by winter monsoon winds beginning in late fall. Most of the studies of clay mineralogy, geochemistry, and isotherm distribution also suggest that the HMB has been derived from the west coast of Korea, particularly from the Keum River. An approximate evaluation of the depositional time for the HMB, based on its dimensions and the discharge rate of the Keum River, suggests a time duration of the order of 14,000 years. Hydrodynamic measurements across two transects over the northernmost HMB reveal that suspended matter travels southwest toward the main body of the HMB in a well-constrained corridor ultimately connected with the Keum River. Time-series (12.5 h) hydrodynamic measurements at a site over the HMB suggest that the winter-season suspended plume carries concentrations of suspended matter one to two orders of magnitude higher than those of the summer. Silt grains of 5-6 phi well sorted through numerous resuspension events, settle out onto the HMB, forming distinctive silt laminae alternating with clay-rich laminae,