舟山海区3178站柱状剖面孢粉组合带及其地质意义

The Pollen Assemblage Zones at the Site 3178 in East China Sea and Their Geological Significance

在长390cm的柱状岩芯中大致以10cm的间距采样,所取的34个孢粉样品经处理,几乎全含丰富的孢子花粉。在此基础上划分出3个孢粉组合带,自下而上为: 1.Chenopodiaceae-Artemisia带;2.Potamogeton,Sparganium,Typha-Gramineae带;3.trilete spores-Pinus带。 本文依据孢粉植物群所反映的沉积环境变迁探讨全新统与更新统的划分。 Chenopodiaceae-Artemisia带以滨岸盐生植物分子为主,反映为岸线附近的沉积环境;Potamogeton,Sparganium,Typha-Gramineae带主要分子的母体植物为静水水生与中生植物,反映湖沼沉积环境,说明当时当地离海岸线有一定的距离;trilete spores-Pinus带多见于我国东海海底现代表层沉积,指示了一种现代的海洋环境。 以上三种沉积环境反映了带1至带3期间海水的进退历史,即带2时期海退最大,带3时期海进最大,由于古气候的冷暖变化是第四纪海面升降的主要原因,因此推断带2时期气候最冷,而带3时期气候最暖,也即带2、带3间可能为更新统与全新统的界线。 根据孢粉分析所推断的全新统、更新统界线与岩芯特征、钙质超微化石以及^(14)C测年资料吻合。

34 pollen samples taken from site 3178 in Zhoushan sea region of East China Sea contain plenty of pollen and spores. The distance between two samples is nearly 10 cm. Three pollen assemblage zones from bottom to the top are as follows: Zone 1 Chenopodiaceae-Artemisia; Zone 2 Potamogeton, Sparganium, Typha-Gramineae; Zone 3 trilete spores-Pirus. Based on sedimental environment changes indicated by pollen flora, the boundary of Holocene and Pleistocene was determined. Chenopodiaceae-Artemisia zone, in which salty plants living in seaside prevail, reflects the environment near beach. Potamogeton, Sparganium, Typha-Gramineae zone indicates land environment and some distance from beach, because its main resource plants develope in lake or marsh. Trilete spores-Pinus zone indicates modern sea environment similar to zones often discovered in modern sediments of East China Sea. These three sedimentary environments reflect the history of sea water moving, that is the most regression occurred during zone 2 and the most transgression during zone 3. Because the variation of paleoclimate is the main cause of eustasy during Quaternary, it can be concluded that the climate during zone 2 is coldest and the climate during zone 3 is warmest. So the boundary of Holocene and Pleistocene may be exist between zone 2 and zone 3. The Holocene/Pleistocene boundary at this site from palynological analysis coincides with the data from petrology, calcareous nannofossils and 14C dating.