浙江长兴中—晚更新世红土植硅体与分子化石记录及其环境意义

MID-LATE PLEISTOCENE PALAEOVEGETATION AND PALAEOCLIMATE CHANGE RECONSTRUCTED BY PHYTOLITH AND MOLECULAR FOSSIL RECORDS OF VERMICULAR RED EARTH IN CHANGXING,ZHEJIANG

在野外地貌、岩性和相关沉积环境调查分析基础上,对浙江长兴中—晚更新世红土进行了分析,发现其中含有较丰富的植硅体形态类型,主要来自草本、阔叶和裸子植物等,植硅体含量分布具有一定的组合特征。在温暖指数和草本覆盖指数计算基础上,获得了中—晚更新世以来的3个古植被、古气候演化组合带;运用植硅体和分子化石的相关指标(C21-/C22+、C23/C30)揭示了洪积扇红土沉积时期的植被与气候信息,即间冰期气候暖湿,风化作用强,降水较多,高等草本植物繁盛;而冰期时气候干凉,风化作用弱,降水减少和地下水位降低等则有利于洪积扇体上木本类植被发育。

On the basis of geomorphology, lithology, dating and sedimentary environment survey on Quaternary red earth in the field, pbytolitb analyses show that red earth contains abundant pbytolitb morpbotypes, mainly originating from grasses, broad-leaved and gymnosperm trees. Distribution patterns of pbytolitb percentage, warmth index and grass cover index demonstrate that there occur 3 assemblage zones in response to palaeo-vegetation and palaeo-climate changes in mid-late Pleistocene, respectively. Correlation of phytolith assemblages and relative indices （C21^- /C22^＋, C23/C30 ） of molecular fossils indicates that palaeo-vegetation and palaeo-climate are characterized by the alternation of glaciation （arid-cool, weak weathering） and interglaciation （warm-humid, strong weathering） during red earth deposition on an alluvial fan. Due to abundant rainfall and high level of underwater, grasses were common in the surface of alluvial fan during interglaciation.