HIGH-RESOLUTION PALEOENVIRONMENTAL RECORD OF THE MUD SEDIMENTS OF THE EAST CHINA SEA INNER SHELF

Based on a high-resolution grain-size analysis and AMS ¹⁴C dating of core MD06-3040, located in the mud area off the Fujian-Zhejiang coast on the inner-shelf of the East China Sea, we attempt to recover the Holocene paleoenvironment evolution of the East China Sea inner-shelf. The core was divided into 3 sections according to its changes in lithology, color and sedimentary structure. The sedimentary environments belong to nearshore, transitional stage and shallow sea, respectively. From 10 kaBP, the studied area was influenced by Zhejiang-Fujian Coastal Current (ZFCC). River-derived materials were transported southward. Since 7 kaBP, the sedimentary environment was dominated by the ZFCC and mud sedimentation began to form. Linear sedimentation rates of the core show clear steps through time:~0.4 cm/a since 1.5 Ka, 0.11 cm/a between 1.5 and 4 ka,and 0.2~0.3 cm/a between 4 and 8 ka. When compared with changes of growth rates of a stalagmite (D4) from Dongge Cave in South China, which is a measure of summer monsoon intensity, they show very strong correlation. This indicates that the supply of sediments to the inner shelf is strongly affected by summer monsoon intensity. The increase of sedimentation rate at 1.5 ka may indicate increasing land use due to human activity. Previous studies claimed that there existed a good correlation between the mean grain-size of fine shelf sediments and the mean annual temperature of mainland China. It was also claimed that the mean annual temperature correlated well with winter monsoon intensity, which in turn controlled the strength of the coastal currents which transported the sediments. Therefore, mean grain-size of the fine population was used as a proxy of winter monsoon intensity. However, our results of end-member modeling and standard deviation of grain-size analysis do not seem to support the above-mentioned correlation. The present study suggests that the supply, transportation and deposition of the sediments in the inner shelf are controlled by very complex processes.