台湾海峡西部海域晚更新世3次“海侵”依据的探讨

Discussion on the evidence of three Late-Pleistocene "transgressions" in the western Taiwan Strait waters

晚更新世是全球气候环境与海陆变迁频繁的重要地质时期.通过对上世纪80年代采集的活塞柱状样(长度<6.5 m)的分析研究,曾提出晚更新世台湾海峡存在"金门海侵"、"福州海侵"、"海峡海侵"3次海侵.为提高台湾海峡第四纪地质研究和认知水平,本文探讨了3次"海侵"的立论依据,认为现有柱状样沉积层是晚更新世—全新世的浅表层沉积.台湾海峡具有开放性沉积条件,该浅表层沉积层的14C年龄数据应用于地层年代可能偏老.此3次"海侵"地层划分依据不足,存在疑点,尤其是"海峡海侵".台湾海峡海底已发现数量及种类丰富的晚更新世各气候带陆生哺乳类动物遗骨,并有古人类遗骨化石,这些表明台湾海峡海底在玉木冰期鼎盛时期曾经出露成陆,并可能成为东亚大陆东缘冰期海退的海滨平原上,惟一有各种气候带古动物与古人类的生存地和避难地.

Late-Pleistocene was an important geological age witnessing frequent climatic environment and sea-land changes throughout the world. The events of Late-Pleistocene in Taiwan Strait, can be understood through the strata of that age. On the basis of the study of columnar samples （ 〈6.5 m） taken from the Taiwan Strait in the 1980s, three transgressions （＂ Jinmen＂, ＂Fuzhou＂, and ＂Strait＂ transgressions） in Late-Pleistocene were discovered. It was believed that the Taiwan Strait was a shallow sea environment with water depths of 30 -60 m, and did not out- crop 18 000 a ago during the height of Wurm glaciation. The current study analyzed the evidence of these three transgressions, especially the ＂Strait Transgression＂. Firstly, the sedimentary layer of columnar samples makes us believe that it belongs to the superficial-surface sedimentary layer of Q3 - Q4. Since the Taiwan Strait has an open sedimentary environment, ~4C-dating of this layer may appear older than its chronological age. Late-Pleistocene stratum of the west sea area in the Taiwan Strait had not been precisely delineated and the evidence for stratification of the three ＂transgressions＂ is doubtful. A large amount of Late-Pleistocene terrestrial mammals remain of various climatic zones and ancient human fossils on the seabed of the Taiwan Strait indicate that it had outcropped during the height of the Wurm glaciation.