DOMINANCE FACTORS OF THE TERRIGENOUS SEDIMENT GRANULOMETRIC DISTRIBUTION IN THE LOWER SUNDA SLOPE

High resolution grain size analysis was performed on sediments of Core 18268-2, drilled during the "SONNE-115" cruise. Detailed granulometric distribution record of lower Sunda slope sediments for the last 25 ka was obtained. The analysis revealed that sediments in this core were fine grained, predominated by 2~10 μm grains and short of grains larger than 63 μm. Statistical parameters such as mean and median values of the grain size were highly correlative with the relative percentage of the 10~63 μm fraction, implying that short-term change of the sediment grain size distribution was controlled by the paleocurrent speed. All statistical parameters and the relative percentage of the fractions underwent a notable transformation at about 15 ka, attributed to the rapid rising of the sea level during the MWP-1a (Melt Water Pulse 1a, 14.6~14.3 ka). Simultaneous with the rapid flooding of the Sunda shelf, the coastline retreated for several hundred kilometers, which changed the sediment supply of the region dramatically. We can conclude that the relative long-term variation of the siliclastic sediment granulometric distribution was controlled by the sediment supply.