川西安宁河Ⅰ～Ⅲ级阶地孢粉记录反映晚更新世以来古气候变化

Pollen Records Reflecting Paleoclimate Change since Late-pleistocene in the Terraces Ⅰ～Ⅲ of Anning River in Western Sichuan Province

摘要:

植物孢子和花粉是理想的恢复环境变化的有机指标,对于第四纪地层划分和区域古气候的对比具有重要意义。本文在川西冕宁泸沽镇附近选取安宁河Ⅰ～Ⅲ级阶地剖面进行年代学测量和孢粉采样分析。结果表明:安宁河Ⅰ级阶形成时期为全新世,气候温和较湿或轻湿;Ⅱ级阶地沉积时期在晚更新世晚期或全新世早期,温度及湿度均比Ⅰ级阶地时低,在该时期无论植被和气候曾出现过两次以上比较明显的变化及波动;Ⅲ级阶地沉积时期为晚更新世中期,气候温和较湿或轻湿,堆积时期之温度及湿度均比Ⅱ级阶地时高,但又均比Ⅰ级阶地时低。同时探讨了安宁河阶地形成时期构造、气候的变化规律。根据河流的下切速率可以间接的推断晚更新世构造隆升速率大于晚更新世末期-全新世。

Abstract:

The plant spores and pollen are more desirable indicators to the recovery of environmental change.It had great significance using palynological indicators for the Quaternary stratigraphic subdivision and regional paleoclimate contrast.In this paper,theⅠ～Ⅲ terraces profiles of Anning river at Lugu township,Mianning county in western Sichuan province are selected to do chronology measurement and analysis of pollen samples.The results show that the terrace I formed during the Holocene（Q4）,climate was wet or light wet.The terrace Ⅱ deposited during the end of Late-pleistocene（Q33）or the early Holocene（Q14）,both temperature and humidity were lower than that of terrace Ⅰ,and vegetation and climate had more than two obvious changes and fluctuations.The terrace Ⅲ deposited during the middle Late-pleistocene（Q32）,climate was wet or light wet,the temperature and humidity were higher than terrace Ⅱ,lower than terrace Ⅰ.The tectonic and climate change during the formation of Anning river terraces are discussed.According to the speed of river downcutting,it is indicated that the uplift rate of epipleistocene to be bigger than the end of epipleistocene-Holocene.