山旺中新世植被演替及古气候定量研究

PALAEOVEGETATION SUCCESSION AND QUANTITATIVE PALAEOCLIMATE RECONSTRUCTION OF THE MIOCENE SHANWANG ASSEMBLAGE

本文详细研究了山旺中新世 2 2 .95m厚的硅藻土沉积剖面上以 10～ 30cm为间距所采集的 130块孢粉样品 ,鉴定出 111个孢粉类型。古植被演替的研究结果表明由老至新经历了 5个阶段 :“湿润环境下的混交中生林”、“干旱环境下的混交中生林”、“湿润湖岸环境下的混交中生林”、“山地、湿润及碱性等环境下的混交中生林”和“碱性环境下的混交中生林”。同时 ,首次成功地运用共存分析法定量地恢复了山旺中新世古气候 ,得出古气候参数定量值 :年平均温度 15 .6～ 17.2℃ ,最热月份平均温度 2 4 .7～ 2 7.8℃ ,最冷月份平均温度 5 .0～ 6 .6℃ ,温度年较差 2 0 .5～ 2 5℃ ;平均相对湿度 72 %～ 75 % ,年平均降雨量 116 2～ 130 8mm ,最湿月份平均降雨量 148～ 180mm ,最干月份平均降雨量 16～ 5 9mm ,最干及最湿月份降雨量的差值 81～ 15 3mm ,最热月份的平均降雨量 10 8～ 111mm。山旺中新世时期的气候波动范围为 :年平均温度波动约 3℃左右 ,最冷月份平均温度波动约 4℃左右 ,最热月份平均温度波动约 1℃左右 ,年平均降雨量波动约 10 0mm左右。总体反映出山旺中新世气候温暖潮湿 ,冬季凉爽 。

pollen samples collected in a space of 10～30 cm from Shanwang sedimentary profile with a thickness of 22.95 m are studied in detail in this paper. 111 pollen and spore taxa, as well as their nearest living relatives have been recognized. The reconstruction of palaeovegetation indicates that the Shanwang Miocene flora was a mixed mesophytic forest. The studied section shows that this mixed mesophytic forest experienced 5 stages of 'mixed mesophytic forest from wet habitats','mixed mesophytic forest from dry habitats','mixed mesophytic forest from wet riparian habitats','mixed mesophytic forest from upland, riparian and alkaline soils habitats','mixed misophytic forest from alkaline habitats'. Quantitative palaeoclimatic data have been obtained using the coexistence approach. The results indicate that the mean annual temperature (MAT) might be 15.6～17.2℃,the mean temperature of the coldest month (TCM) be 5.0～6.6℃, and the mean temperature of the warmest month (TWM) be 24.7～27.8℃. Mean annual precipitation (MAP) might be in the range of 1162～1308 mm, with the precipitation of the warmest month (PwarmM) being 108～111 mm, precipitation in the driest month (PDM) being 16～59 mm and precipitation of 148～180 mm occurring in the wettest month (PwetM). Relative humidity (RH) has been calculated as 72%～75%. This also indicates that there were climatic fluctuations between the high resolution pollen samples. It was up to 3℃ of mean annual temperature, up to 4℃ in the coldest month, up to 1℃ in the warmest month, up to 100 mm of mean annual precipitation.