GRAIN SIZE DISTRIBUTION IN THE TIDAL ZONE AND SHALLOW SEA ON THE NORTH SIDE OF THE HUANGHUA HARBOR

1 core (132 cm long and 44 samples) and 50 bottom sediments samples were collected in the offshore area on the north side of the Huanghua Harbor, and grain size analysis was carried out with Mastersizer2000. Results indicate that there are three types of bottom sediments, namely sandy silt, silt and clayey silt, in the area. Sandy silt is distributed in the subtidal zone on the north side of the harbor, silt mainly in the offshore area -2m~-5m in water depth at Daxinpu and sampling site 13, and clayey silt in the other area. The Harbor has cut off the coastal current, and changed it to the direction along the dam of the Harbor, that caused the currents-carried sediments deposited on the tidal flat and the area near the dam. As an evidence of the abandoned deltaic coast, sandy silt near the Harbor suggests that the impact of the construction of the Harbor is limited to the tidal flat and its nearshore area. According to the vertical grain size distribution pattern of the sediments, the Hole HHG2 can be divided into four segments from bottom to top:(1) the segment with slight fluctuation of coarse-fine grains in 132~100.5 cm, (2) the segment slowly coarsening up in 100.5~56 cm, (3) the segment with rapidly coarse-fine fluctuation caused by episodic events in 56~16 cm, and (4) the segment rapidly coarsening up in 16~0 cm. Furthermore, the forth segment of 16~0 cm is well correlated to the period from 1917 up to present defined by ¹³⁷Cs tracing and dating. During the period, the fluvial process was weakened due to the shift of the Yellow River eastward, and the enhancement of marine process by sea level rise.