黄海晚更新世以来的硅藻组合及其沉积环境

黄海更新世晚期以来的硅藻化石,自下而上可划分为五个硅藻带。在Ⅰ带的上下层位,各含一个淡水藻类化石带,显示黄海在大理冰期时,由于气候变冷,海面下降,黄海陆架三次出露成陆。亚间冰期时,气候转暖,海面回升,复为海水淹没,海域中生长着Ⅰ带的各种海生硅藻。随着全新世气候转暖,沉积物中发现Ⅱ-Ⅴ带海生硅藻带,其中Ⅲ带硅藻外洋种比例较大,含亚热带暖海种多,表明此时水温较大,海域扩大,相当于大西洋期,其他各带与全新世各期相当。

DIATOM ASSEMBLAGES AND THEIR DEPOSITIONAL ENVIRONMENT IN THE YELLOW SEA SINCE THE LATE PLEISTOCENE EPOCH

The fossil diatom in the Yellow Sea since the Late Pleistocene can be divided into five diatom zones in ascendant order. 1. Cyclotella striata-Coscinodiscus-H yalodiscus subtilis diatom zones 2. Coscinodiscus radiatus-H yalodiscus subtilis-Cyclotella stytorum diatom zone;3. Coscinocdiscus radiatus-Coscinodiscus perforatus-Coscinodiscus argus diatom zones 4. Corcinodiscus-Cyclotella-Coscinodiscus argus diatom zone;5. Coscinodiscus diatom zone or Cyclotella stylorum-Hyalodiscus subtilis diatom zone. Most kinds of the fossil diatom from the above zones are marine species, indicating the marine environment. The two beds above and beneath Zone Ⅰ contain two fresh water algal zones, reflecting that, because sea level lowered owing to the cold climate during the Late Pleistocene Dali glaciation (Subglaciation Ⅰ, Ⅱ), the continental shelf of the Yellow Sea exposed twice and became a plain dotted with many lakes and swamps in which various species of fresh water algae lived. When the climate became warm and the sea level rose during the subinterglaciation;the continental shelf of the Yellow Sea was submerged by sea water. There lived various diatoms contained in Zone Ⅰ. Transgression happened because the climate became warm globally during the Ho-locene Epoch. In the Yellow Sea there lived many diatoms mentioned in Zones Ⅱ, Ⅰ, Ⅳ and Ⅴ. Zone Ⅰ contains the most abundant pelagic species and more subtropical species, reflecting the maxium temperature and expanded sea area. It should be considered the Atlantic period. Zones Ⅳ and Ⅴ are considered the Subbreal and Subatla-ntic period, and Zone Ⅱ the Boreal-Preboreal period. All this can be proved by 14C data.