黑龙江省富拉尔基晚新生代孢粉分析及其意义

PALYNOLOGICAL ANALYSIS OF THE LATE CENOZOIC AND ITS SIGNIFICANCE IN FULAERJI,HEILONGJIANG PROVINCE

本文根据富拉尔基 QH70孔(井深226.07m)73块孢粉样所取得的123科属埴物孢粉,依据其孢粉组合特征,从下至上划分出七个区域性孢粉带。第Ⅰ带属晚白垩世早期,植物群具热带-亚热带的面貌,反映当时的气候热而潮湿。第Ⅱ—Ⅲ带,地质时代为晚第三纪。组合中除葇荑花序植物为主外,同时又保存较多的亚热带落叶和常绿阔叶乔木树种,气候温暖潮湿。至第Ⅲ带晚期,草本植物和半灌木已占优势,表明气温下降,变干。第Ⅳ带由蒿、藜科、禾本科、蓼等中旱生的草本及半灌木组成温性草原,气候冷干。孢粉组合特征结合热释光和磁性地层,将该区上新世和更新世界限确定为距今240万年左右。第Ⅳ—Ⅶ带属更新世,各孢粉组合具明显的差异。在Ⅴ带的早期,植被尚属草原或冻原,气候寒冷干燥,但在其晚期,则属落叶阔叶林和草原,表明气候温暖半潮湿。在Ⅵ—Ⅶ带内,草本植物占优势,但在末次冰期时,由云杉、冷杉、落叶松和桦等组成的北方针叶林曾一度繁盛在低地和平原,气候寒冷潮湿。

The pollen analytical investigation of 226.07 m,deep QH70 core from Fulaerji district in the city of Qiqihar,Heilongjiang province have been carried out.Based on the characteristics of QH70 core sporo-pollen assemblages,seven pollen zones may be subdlvided in the order as follows:The first zone(Ⅰ)belongs to early period of the Late Cretaceous.When the flora was mainly composed of gymnosperm,the next was fern and a little original angisperm.Here the climate was hot and wet and the vegetation showed tropical-subtropical in aspects.In this core the author didn't find the Palaeogene flora.The Ⅱ-Ⅲ zones belonging to the Late Tertiary are characterized by predominance of arboreal pollens,mainly consisting of Amenti- ferae and some conifers.The flora of the Neogene was mainly composed of Pinus,Betula, Castanea,Ulmus,Corylus,Alnus,Juglans,Quercus,Carya,Fagus,Tsuga etc.some subtropical species of Hamamelis,Liquidambar,Castanopsis,Melia.Myrica and Taxodiaceae which still ex- isted.The climate was warm and humid with the annual temperature higher than that of the present.As to the last period of the third zone(Ⅲ)the assemblage of herbaceous plants and semi-shrub were predominant.The climate was changed into cool and less dry.The fouth pollen zone(Ⅳ)is represented by herbaceous plants such as Artemisia,Chenopodiaceae,Gram- ineae,Polygonaceae etc.indicating the Fulaerji was covered by cold-temperature grassland with a cold and dry climate.According to temperature decreasing at this zone,magnetostratigraphy and thermoluminescence dating we may take the start of the Ⅳ zone as the mark of the beginn- ing of Quaternary in this region.The age of the boundary between Pliocene and Pleistocene might be 2.4 million years or so.The geological age of pollen zones Ⅳ-Ⅶ,is assigned to Pleistocene.The characteritics of the sporo-pollen assemblage at these zones are quite different from one another.In the fifth pollen zone(Ⅴ),the vegetation was represented by a steppe or tundra with a cold and dry climate at its initial stage,but in the late stage the flora was characterized by a deciduous broadleaved forest and steppe,indicating the climate was warm and less humid.Pollen zones Ⅵ-Ⅶ,the herbaceous plants,such as Artemisia,Gramineae, Chenopodiaceae etc.were predominant.The climate was rather dry and cold.The plants of the boreal conifers as Picea,Abices,Larix,Pinus and the subpolor plants such as Betula were thriving in the low land and plain on the last glacial stage demonstrating that time the clim- ate was humid and cold. Judging from the pollen analyses of core QH70,the vegetational development and climatic changes in Fulaerji had been rapid since the Late Tertiary.It is more or less significance to use pollen analysis in hydrogeology and engineering geology.