SHELLY RIDGE ACCUMULATION AND SEA-LAND INTERACTION ON THE WEST COAST OF THE BOHAI BAY
渤海湾西岸贝壳堤堆积与海陆相互作用*

On the muddy west coast of the Bohai Bay, two kinds of sandy bodies have been discovered. The first is the offshore bar formed in underwater area initially, which afterward under marine dynamic effect gradually accumulated on the inter-tidal zone and on the land with shoreline progradation. The other is the widespread shelly ridge (chenier). The initial shelly ridge is formed when the coast enters into its weak erosion phase. The present paper reports that when the shoreline progressing and sea-land interaction are stable, under the effect of wind- and wave-landward, the sandy body of the initial shelly ridge could be formed near the shoreline. Shelly accumulation on the coast in the studied area includes three types: The shelly ridge on the front margin of the abandoned delta lobe; the storm shelly accumulation on the head of tidal river gulf and/or the outer side of tidal channel (the shell could accumulate from the underwater area of channel to the low land continuously); irregular shelly accumulation on the low delta plain under the setting of spring tide or storm weathers. The shelly ridge includes the instantaneous/episodic high energy accumulation and that under the comprehensive activity of spring and wind-landward. The shelly ridge could not be used to interprete sea-level change because the shell dating and the system of beds in shelly ridge have shown that the formation process of shelly ridge is a complex re-accumulation. In the highly disturbed progressing process of the delta, the irregular shoreline could be formed. The effect of wind- and wave-landward for different topographic shoreline parts could thus cause the formation of shelly ridge which is unparallel to modern shoreline. Terminology of shelly ridge has been used at random, causing the study of shoreline change a simplified one. To use rigorous concept of shelly ridge, the deltaic lobe change could be precisely subdivided when event deposits have been excluded. When the study of shelly ridge is combined with the dating of delta top peat, the formation process of muddy coast could be precisely reconstructed.