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根据D_1A段单道地震剖面反射特征发现了南海东北部晚第四纪地层不整合,并被第四系浅钻ZK3孔岩心的岩性、古生物和测年所证实。上部不整合造成中更新统顶部至上更新统上部间的缺失。该不整合主要是由于末次冰期盛冰期海平面下降形成,其次是受末次冰期前局部构造变动的影响。据测年推算,15.6 ka B.P.海平面相对现代海平面下降了146 m,当时的古海岸线位于距今海岸约170 km处。这就为南海东北部末次冰期盛冰期海平面下降幅度提供了实际证据。
Based on the reflection characteristics of the single channel seismic profile in section D_1A, the Late Quaternary stratigraphic unconformity was found in the northeastern South China Sea and was confirmed by the lithology, paleontology and dating of Quaternary shallow ZK3. The unconformity in the upper part resulted in the absence of the Upper Pleistocene upper part of the Pleistocene. This unconformity was mainly due to the sea level decline during the last glacial ice age, and secondly to the local structural change before the last glacial period. According to the dating, the 15.6 ka B.P. sea level is 146 m lower than the modern sea level, with the ancient coastline located about 170 km away from the present coast. This provides practical evidence for the declining sea level over the ice age in the northeastern South China Sea.