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中沙、西沙群岛海区表层沉积物中微型腹足类、双壳类主要由热带、亚热带种类和广温性种类组成，并以典型的热带珊瑚礁型种类为主，见有腹足类176种，双壳类48种。可划分出3个沉积组合类型。温度、水深、底质、海底地貌是控制本区腹足类、双壳类分布的主要环境因素。腹足类、双壳类遗壳埋藏群由原地埋藏类型和异地埋藏类型组成。在珊瑚礁深水处这两种类型呈明显混合分布。在水深22，90，115m处属原地埋藏的潮间带或浅水类型含量丰富，优势属种明显，这表明自晚更新世末次冰期以来，南海海平面上升过程出现3次间歇性停顿。随水深增大，异地埋藏类型增多，反映了群岛区陡峻的地势与海流在礁壁处形成的垂直分流对生物埋藏群分布的影响。
In the sediments of the Middle and Lower Xisha Islands, the microcroplids and bivalves are mainly composed of tropical and subtropical species and broad-temperature species, with typical types of tropical coral reefs, with 176 species of gastropods, 48 kinds of bivalves. Can be divided into three sedimentary combinations. Temperature, water depth, sediment quality and seabed topography are the main environmental factors that control the distribution of gastropods and bivalves in this area. Gastropods, bivalve hull burial group consists of in-situ burial types and off-site burial types. In coral reef deep water these two types showed obvious mixed distribution. The abundance of intertidal or shallow water types buried in situ at the depths of 22,90 and 115 m, with obvious dominant species, indicates that there have been three intermittent pause in sea level rise in the South China Sea since the last Pleistocene. With the increase of water depth, the types of buried land increased, reflecting the influence of the steep terrain of the islands and the vertical diversion formed by the sea currents at the reef walls on the distribution of the biological burial groups.