Sporopollen Assemblages And Palaeoenvironmental Evolution Since 20ka BP In Taiyuan Basin

In recent years,paleoclimatology has become a heated topic in contemporary geological science due to its unique research reference value on modern climate change.The pollen has become an important indicator of the paleovegetation and palaeoclimate reconstruction as it record the information form the environment changes,and preserved well in the stratum.By studying the climate proxies of lacustrine sediments,it has important research value to study the climate change of Taiyuan basin.Therefore,in this paper,by extracting the sporopollen and granularity,substitute indexes of Taiyuan basin lacustrine sediments and based on the framework of OSL chronology,combining with 71 surface pollen data,we are able to reconstruct climate in Yinchuan plain using the weighted average method of least squares(WAPLS)model.1.The 71 surface sediments and moss samples from the Taiyuan basin indicated that the sporopollen corresponded to the vegetation zone very well.Sporopollen in Taiyuan basin was mainly from different types of vegetation lived in and around the bisect,and sporopollen originated from the long distance transportation was rare.Vegetation evolution stage since 20 ka BP in the north district of Taiyuan basin: shingle steppe-grass meadow grassland in the main form of artemito and graminadeciduous broad-deciduous shrub grass-he grass of artemiseis gramineae;Vegetation evolution period since 20 ka BP in the south district of Taiyuan basin: the grassland of the main steppe-broadleaf deciduous shrub-wormwood-the savanna-savannas and chenopodiaceae.2.Combined with research in meteorological site data to establish a reliable sporopollen-climate models,fitting out of NZ profile and BYC section 20 ka BP since the mean temperature(Tann),the annual precipitation(Pann)sequence.The results reflect that since the Holocene,the reconstructed T and P curves have been decreasing.3.Through the analysis of each alternative indicators,20 ka BP to Taiyuan basin characteristics of the ancient climate change can be divided into the following several stages: at the end of the terminal(20.1-17.1ka BP)during the last glacial stage dry cleaning,the last deglaciation(17.1-13.7ka BP)dry periods and phase(13.7-11.5ka BP)person,the Holocene(11.5-0.4ka BP)frequent fluctuations in climate change process,Earlier(11.5-11.5ka BP),temperature rise and the previous stage,the annual average temperature rise 3?,gradually warmer,whole slant warm dry climate,at around 8.2ka,sporopollen percentage map and grading curve indicating cold climate,but the change is not big,speculated that a change that correspond to 8.2ka events;In the medium term(8.0-5.3ka BP),it entered the holocene warm period and the climate was warm and humid.5.3-2.4ka BP climate to drought trend development,average annual rainfall of 48mm;By the end of the period(2.4-0.4ka BP),the climate was moderately dry and tended to be dry,and the average annual rainfall curve of the reconstructed 20 ka was also indicative of this result.