广东雷州半岛晚渐新世—早更新世孢粉共存因子分析及古气候变化重建

Palynological study of the Late Oligocene-Early Pleistocene in Leizhou Pen insula,Guangdong,China:Coexistence analysis and paleoclimate reconstruction

广东省雷州半岛新生代钻孔ZKA01揭露的地层序列自下向上为渐新统涠洲组、中新统下洋组、角尾组、灯楼角组、上新统望楼港组、下更新统湛江组和中更新统北海组,涠洲组—望楼港组为滨浅海沉积,湛江组和北海组为陆相河湖相沉积。本文在ZKA01钻孔地层中自下向上88个层位中获取的29311粒孢粉化石的81个属中,选取了常见的种子植物花粉种属42个,通过共存因子分析法,定量重建了研究区晚渐新世—早更新世的古气候参数,划分出晚渐新世—早中新世(25~17 Ma)、中中新世(17~13.5 Ma)、晚中新世—上新世初期(13.5~4 Ma)和上新世—早更新世(4~1.5 Ma)4个气候演化阶段。孢粉共存因子定量法重建的研究区晚渐新世—早更新世4个阶段的古气候变化过程能较好地与全球气候变化的趋势相匹配,晚渐新世—早中新世温度降低的时间拐点大致可与Mi1a气候变冷事件相吻合。中中新世可以与中中新世气候适宜期(MMCO)相对应,表现为炎热潮湿的气候特征。中中新世晚期的气温是下降的,在一定程度上响应了Mi3中中新世气候变冷事件。

The drill core ZKA01 from Leizhou Peninsula,Guangdong Province,revealed a Cenozoic stratigraphic sequence consisting of,upward from the bottom,the Oligocene Weizhou Formation,the Miocene Xiayang,Jiaowei,and Dengloujiao Formations,the Pliocene Wanglougang Formation,the Lower-Pleistocene Zhanjiang Formation,and the Middle Pleistocene Beihai Formation,where the Weizhou-Wanglougang Formations consist of littoral-neritic deposits,and the Zhanjiang Beihai Formations consist of continental fluvial and lacustrine deposits.In this paper,42 common seed plants,from 81 species identified from 29311 pollen fossil grains obtained from 88 layers in core ZKA01,were selected to reconstruct the paleoclimate parameters by the coexistence approach.It was found the Late Oligocene Early Pleistocene paleoclimate sequence can be divided into four stages:the Late Oligocene Early Miocene(25-17 Ma),Middle Miocene(17-13.5 Ma),Late Miocene-Pliocene(13.5-4 Ma),and Pliocene Early Pleistocene(4-1.5 Ma)stages.The study area’s paleoclimate change pattern through the four stages can match the trend of global climate change rather well.The period of decreasing temperature in the Late Oligocene-Early Miocene roughly coincides with the Mi1a climate cooling event,whilst the climate change in the Middle Miocene corresponds to the Middle Miocene Climatic Optimum(MMCO),which is characterized by a hot,humid climate;in the late Middle Miocene temperature drops in response to the Mi3 cooling event to certain extent.