末次盛冰期以来渤、黄、东海陆架底质分布演变过程模拟研究

Simulation Study on the Evolution Process of Distribution Pattern of Bottom Sediments on the Continental Shelves of the Bohai Sea, Yellow Sea and East China Sea Since the Last Glacial Maximum

渤、黄、东海陆架底质的形成分布与末次盛冰期之后的海侵密切相关。末次盛冰期结束、海侵开始以来 ,潮流是渤、黄、东海陆架上的永久性主导作用应力。为从长期沉积动力演变过程的角度 ,探讨渤、黄、东海陆架底质形成分布的有关成因问题 ,利用数值模拟手段 ,再现了末次盛冰期以来 6个时期渤、黄、东海陆架潮流作用下海底的冲淤格局及底质分布。结果表明 ,扬子浅滩南侧东海外陆架的砂质沉积基本上是自 - 80 m海面以来形成的。扬子浅滩形成于 -5 2 m海面之后 ,至 - 3 0 m海面时已有一定规模 ,全新世最大海侵之后 ,逐渐形成现在规模的扬子浅滩。南黄海中部泥自 - 5 2 m海面时就已开始形成 ,- 3 0 m海面时范围很大 ,侵入北黄海 ,全新世最大海侵以来 ,逐渐调整到现在的范围。渤海中央泥、北黄海西部泥、浙闽岸外泥、辽东半岛西侧与北侧的砂质沉积、西朝鲜湾与江华湾中的砂质沉积以及苏北浅滩是自全新世最大海侵以来逐渐形成的。海州湾中砂质沉积形成的盛期在公元 8世纪之后。济洲岛西南泥、南黄海东部泥很可能分别形成于 - 3 0 m海面、- 5 2 m海面以来。全新世渤、黄、东海陆架底质分布的演变过程大致分为 2个阶段 :全新世最大海侵之前为渤、黄、东海陆架底质分布宏观格局的形成阶段 ;全新世最大海侵至今为渤?

The formation and distribution of bottom sediments on the continental shelves of the Bohai Sea, Yellow Sea and East China Sea (BYECS) are closely related to the transgression after the Last Glacial Maximum (LGM). Tidal currents have become the permanant and dominant acting forces on the continental shelves of the BYECS since the transgression after the LGM. To study the formation cause of bottom sediment distributions on the continental shelves of the BYECS from the viewpoint of long-term sediment dynamic evolution process, the distribution patterns of seabed erosion/accretion and bottom sediment type on the continental shelves in six periods since the LGM under the actions of tidal current are simulated. It is shown from the simulated results that the sandy sediments on the outer shelf of the East China Sea south of the Yangtze Shoal have formed basically since the -80m sea level period. The Yangtze Shoal expanded to a fair size during the -30m sea level period, and has then adjusted gradually to the present size since the Holocene Transgression Maximum (HTM). The mud in the central southern Yellow Sea began to form during the -52m sea level period, extended to the northern Yellow Sea during the -30m sea level period, and has then adjusted gradually to the present size since the HTM. Many clayey and sandy sediments, such as the mud in the central Bohai Sea, the mud in the northwestern Yellow Sea, the sandy sediments west and north of the Liaodong Peninsula and the Subei Shoal, have gradually formed since the HTM. The evolution process of bottom sediment since the LGM is largely divided into two stages: (1) the first stage before the HTM is the formation stage of the general distribution pattern of bottom sediments; and (2) the second stage after the HTM is its local adjustement stage. In a special period, the distribution pattern of bottom sediments was mainly controlled by the tidal current field at that time, and the evolution of the distribution pattern of bottom sediment has been controlled mainly by the evolution of the tidal current field in the area since the LGM.