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我国西沙群岛的石岛上,更新世生物碎屑灰岩中所见小型背斜构造不是地壳构造运动的产物,而是沉积过程中形成的沉积背斜,它反映了海岸沙嘴、沙堤等堆积体固有的层理特征。在海岸带沉积中,这类现象较普遍;不仅在生物碎屑中存在,在陆源碎屑中也存在;在研究古老沉积岩的组构时也须引起充分重视。沉积组构是辩别沉积相的重要标志。在综合分析岩石各种组构的基础上,确定石岛更新世生物碎屑灰岩的沉积相属于广海浅水碳酸盐台礁上的灰沙岛砂沉积。它们在渗流带坏境内,经受早期成岩作用,由亮晶方解石胶结成岩。
The small anticlinal structures seen in the Pleistocene bioclastic limestone are not the product of the crustal tectonic movement but the sedimentary anticlines formed during deposition in the Shiqiao Islands of the Xisha Islands in the country. They reflect the accumulation of sediment and sand banks on the coast, Body inherent layered features. In coastal sediments, such phenomena are prevalent; not only in biological debris but also in terrestrial debris; attention should be paid to the study of the structure of ancient sedimentary rocks. Sedimentary structure is an important symbol of sedimentary facies. Based on a comprehensive analysis of various rock structures, the sedimentary facies of the Shidao Pleistocene bioclastic limestone is determined to be the sandstone of the Lisha sandstone on the carbonate reef in the Guanghai area. They are experiencing early diagenesis in the seepage zone and are digested by bright-calcite calcites.