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在南沙岛礁区中西部实施海底岩石拖网，有3个站获得海底岩石样品。其中在巽它陆架东北缘水深200多米的NS99－17站见深灰色淤泥中有大量铁褐色含泥钙质结核，说明该区（可能在末次冰期时）处于滨海或海滩氧化环境形成结核，之后海平面上升了至少 150m。在南威岛西北方康泰滩的 NS99－57站 1360m水深的海底获强溶蚀的白垩状多孔灰岩，含底栖有孔虫化石，指示康泰滩是从早──中中新世或更早开始生长的生物礁。在永暑礁东北约55km处的NS99－52站新命名了“东生海山”，其西北坡获含第四纪钙质超微化石的礁灰岩，以及由抱球虫类等生物碎屑和胶磷矿组成的钙质磷块岩和含磷生物屑灰岩滚石，指示半深海环境，其中的钙质超微化石大部分时代为中始新世──渐新世，以始新世可能较大，小部分属第四纪。这次海底岩石拖网为研究南沙岛礁区中部地质构造演变和油气资源评价提供了重要的“硬证据”，尤其是发现早第三纪半深海相钙质磷块岩离南海西南次海盆很近，不但证实了南沙海域广布下第三系海相沉积的推断，而且为判断南海的张开时间提供了补充依据。
Seabed rock trawling was implemented in the central and western Nansha Islands, and three stations obtained seafloor rock samples. Among them, a large number of iron brown muddy calcareous nodules were observed in the NS99-17 station with a water depth of 200 meters at the northeastern margin of the Shelf shelf, indicating that the area was (possibly in the last Ice Age) a coastal or beach oxidative environment that formed tuberculosis. Sea level has risen at least 150m. Deeply corroded chalky porous limestone at the 1360m water depth at the NS99-57 station in the Conti Beach on the northwestern part of the island of Nanweis contains benthic foraminifera, indicating that the Conti Beach is from early Miocene or earlier Reefs that begin to grow. Newly named “Dongsheng seamount” at NS99-52, about 55km northeast of Yongshu reef, the reef limestone containing Quaternary calcareous nannofossils on the northwestern slope, Calcareous phosphate rock and phosphate rock containing bioclastic limestone, indicating the semi-deep sea environment, most of the calcareous nannofossils are Eocene-Oligocene, May be larger, a small part of the Quaternary. The seabed rock trawling provided important “hard evidence” for the study of the geological structural evolution and oil and gas resources evaluation in the central Nansha Islands. In particular, it was found that the early Tertiary and semi-deep marine calcareous phosphatic blocks are very close to the South China Sea sub-basin , Which not only confirmed the deduction of the marine sediments of the Tertiary in the Nansha sea area but also provided a supplementary basis for judging the opening time of the South China Sea.