北黄海西部与南黄海中部泥质区岩芯敏感粒级及其环境意义

用激光粒度仪对南黄海中部(YSZD01孔)与北黄海西部(B45孔)泥质区沉积物短柱样进行高分辨选样(0.5 cm)的粒度测试与分析,并对柱样进行210Pb测年分析.B45孔柱样沉积时间为1913~2010年,沉积物以粉砂为主,粒度参数垂向波动较大.YSZD01孔柱样沉积时间为1909~2012年,沉积物为泥与砂质泥,粒度参数垂向变化较小.两孔在1958年、1971年、1980年左右砂含量突增,很可能归因于强度大的寒潮,其增强了黄海两泥质区的水动力环境,导致两孔在这些年份左右的粗颗粒沉积物含量突增.用粒级-标准偏差法得到B45孔沉积物敏感粒级组分为15.6~71.8 μm,YSZD01孔沉积物敏感粒级组分为23.7~500.0 μm,用其作为东亚季风变化的指标,显示自1910年代以来东亚冬季风强度增强,两孔在1925~1935年、1955~1964年、1974~1977年、1982~1986年这四个时期敏感粒级含量出现增加趋势,对应冬季风强度增强较为明显.从岩芯粒度来看,季风强度的变化体现为敏感粒级组分含量变化,季风频率的变化体现为敏感粒级含量波动的程度.

Sensitive Grain Size and its Environmental Significance of Modern Mud Patches in Southern and Northern Parts of the Yellow Sea

High resolution (0.5 cm) grain size analysis by laser particle size analyzer and 210Pb dating of two short cores collected from the mud patches of central part of the southern Yellow Sea (Core YSZD01) and western part of the northern Yellow Sea (Core B45) were performed. Our results show that Core B45, which was deposited from 1913 to 2010, is mainly composed of silt, and its grain size parameters fluctuate vertically. The main sediment of Core YSZD01, which was developed from 1909 to 2012, is mud and sandy mud, and its grain size parameters change little along the core length. Sand fractions in the two cores around 1958, 1971 and 1980 are abruptly increased. We argue that strong cold-air outbreaks probably occurred in the study area, which enhanced ocean hydrodynamics and thereby resulted in abrupt increase in coarse fraction. By the grain size-standard deviation method, we got the environmental sensitive grain size components of Cores B45 and YSZD01, 15.6~71.8 μm and 23.7~500.0 μm, respectively, which are used to indicate variations of the East Asian Monsoon since 1910. The increased percentages of sensitive components during four periods of 1925~1935, 1955~1964, 1974~1977, and 1982~1986, are consistent with significant increase of the East Asian winter monsoon. It seems that the changes in content and fluctuation of sensitive grain size component in the mud patches of the Yellow Sea can be used to indicate variations in intensity and frequency of the East Asian Winter Monsoon.