SENSITIVE GRAIN SIZE OF THE MUD DEPOSITS OFFSHORE QINGDAO AND ITS IMPLICATIONS FOR SEDIMENTARY ENVIRONMENTS

Three cores (Z14, Z16 and QDZ03) retrieved from the Qingdao offshore mud area were analyzed for grain size distribution and AMS ¹⁴C dating in order to study the grain size distribution pattern and their sensitive components for revealing of the transporting mechanism and their environmental implications. The sediments in the three cores are mostly composed of silt and clayey silt. Observed are three sensitive grain sizes, i.e. the sensitive grain size 1, the sensitive grain size 2 and the sensitive grain size 3, respectively corresponding to the components of the fine end, medium-grained and coarse end in the particle size distribution. The sediment mainly consists of suspended load and saltation load, with a little bed load. It is mainly transported by the nearshore currents and the particle sizes are gradually getting smaller from northeast to southwest. It means that the hydrodynamics is gradually weakened from northeast to southwest. Among the three, the sensitive grain size 2 represents the record of the enhanced winter monsoon event. The sensitive grain size (15.63-210μm) in the upper part (0-3.94m) of the Core QDZ03 reveals that there are five enhanced events of East Asian Winter Monsoon (230-370a BP, 1050-1180a BP, 1400-1550a BP, 1850-1950a BP and 2250-2350a BP) over the past 3ka. The case proves that the sensitive grain size could be used as a good indicator of paleoclimate records.