渤海海底埋藏黄土及沿岸出露黄土的成因

ORIGIN OF THE BURIED LOESS IN THE BOHAI SEA BOTTOM AND THE EXPOSED LOESS ALONG THE COASTAL ZONE

根据自60年代以来渤海海底的15个地质钻孔及最近的大量海上调查资料，在其他学者对渤海沿岸出露黄土各种特征详尽研究的基础上，分析了晚更新世末期以来渤海的陆架区环境特征。结果表明，晚更新世末期强劲的西北冬季风使出露的渤海海底部分发生沙漠化，在下风头形成黄土堆积。部分黄土被全新世海相层覆盖形成埋藏黄土，在辽东半岛、庙岛群岛及山东半岛沿岸则形成出露黄土。

The authors analyzed the LGM paleoenvironment based on study of cores drilled in the 1960's and recent Bohai Sea data, and found the buried loess under the Ho-locene marine stratum. It's the first time that we compared the buried loess with the exposed loess from the center of Bohai sea bottom, the buried loess became gra-dually thicker and thicker from northwest to southeast. Comparison of it with the exposed loess on Miaodao Islands and the southern coastal region showed obvious difference between the Bohai Sea loess and Luochuan loess.Study of the distribution, grain size, pollen, minerals, micro fossils and che-mical components of the loess showed it originated from the Bohai Sea bottom.When the Bohai Sea shelf was totally exposed in the LGM period, the winter mon-soon prevailed and aeolation were the major exogenetic force on the shelf region at that time. The exposed area was covered with loose sediment and was very easily eroded by the paleomonsoon. Desertization occurred in parts of the Bohai Sea shelf and deposited the loess in the lee direction of the N, NW, NE wind from Mongo-lia. Then the Holocene marine stratum covered part of the loess, and the other became the exposed loess along the coastal zone (Liaonan, Miaodao, Penglai and Weifang).