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The sedimentary characteristics and formation mechanism of shell ridges along the southwest coast of Bohai Bay
Authors:Liu?Zhijie  Email author" target="_blank">Zhuang?Zhenye?Email author  Han?Deliang  Qi?Xingfen
Institution:1. Marine Geo-science College, Ocean University of China, Qingdao 266003, P.R. China2 Department of Geology, University of Regina, Regina, Sk., S4S OA2, Canada
2. Department of Geology, University of Regina, Regina, Sk., S4S OA2, Canada
Abstract:The present paper studies the sedimentary characteristics and mechanism of the shell ridges on the southwestern coast of Bohai Bay, which are the largest and have the highest shell (or shell fragment) content in the world. These shell ridges are composed of two sedimentary subfacies: the ridge subfacies and the ridge infill subfacies with different inner textures and sedimentary structures. The ridge subfacies primarily consists of fresh shells and/or shell fragments with parallel beddings and high-angle oblique beddings. The ridge infill subfacies consists of finer shell fragments and silty sand with parallel beddings oblique to land. The evolution of the shell ridge is controlled by the accumulation of substantial shell material, the relative slow erosion of shoreline, storm waves, winds and the shift of river routes. Wind tunnel tests indicate that the critical movement velocity of shell is lower than that of quartz sand of the same grain size. Deltaic progradation alternates with shell ridge growth. While the Yellow River empties into the sea through this area, accompanied by deltaic progradat-ing, the shell material is scarce, which is unfavorable to the growth of the shell ridge. Conversely, erosion occurs along an abandoned delta coast where a shell ridge may develop, e.g. the shell ridge on the southwest of Bohai Bay.
Keywords:Bohai Bay  shell ridge  sedimentary facies  formation mechanism
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