江汉盆地始新世中、晚期气候变化周期性的孢粉学证据

采用时间序列分析方法对江汉盆地明钾1孔的孢粉数据进行了处理，发现在中、晚始新世时期孢粉植物群的波动存在各种周期成分。长周期有1.2Ma、2.0Ma及5.0Ma，中周期有0.2Ma、0.4Ma、0.6Ma、0.8Ma，其中1.2Ma及0.2Ma、0.4Ma、0.6Ma的周期成分在第四纪孢粉植物群的演化中也存在，且与8.0Ma B.P.以来的构造气候旋回，亚旋回的准1.2Ma及0.4Ma周期相一致。这表明地球运动轨道变化对气候的制约作用由来已久。该孔孢粉时间序列的趋成分显示最少有4个水平，反映了孢粉植物群演化的4个阶段。曲线还揭示36Ma B.P.前后的波动周期及振幅都有明显的变异，可能预示了一次大的环境变革。这一变化在很大程度上与喜马拉雅一期运动和地球南半球一次大的海洋和气候变冷事件相吻合。

Palynological Evidence of Middle-Late Eocene Climatic Cycles in Jianghan Basin

The time sequence of sporo-pollen record from Core Mingjia 1, Jianghan Basin, was analysed to exhibit its climatic significance. Evidence shows that some cycling elements occurred in the Middle-Late Eocene palynoflora, with 1.2 Ma,2.0 Ma and 5.0 Ma as the long-term cycles, and 0.2 Ma, 0.4 Ma, 0.6 Ma and 0.8 Ma as the intermediate-term cycles. Among them, the cycling elements with terms of 1.2 Ma and 0.2 Ma, 0.4 Ma, 0.6 Ma are also recognized in the evolution of the Quaternary pollen floras. They coincide with the 0.4 Ma and 1.2 Ma tectonic-climatic sub-cycle since 8.0 Ma B.P., implying that the astronomical influence on climate could date back to Eocene. The index pollen elements in the time sequences of the core indicate at least four development levels, reflecting four evolutional stages in the palynoflora. A distinct change in the palynoflora is recognized around 36 Ma BP, exhibiting a major environmental transition. It is mostly consistent with the first stage of the Himalayan Movement as well as a major oceanographic and climatic cooling event in the Southern Hemisphere.