The Stratigraphic Age Of The Loess And The Environmental Evolution Since 150,000 Years In Jinchuan County,Western Sichuan Plateau

The aeolian loess-paleosoil sequence in the western Sichuan Plateau records the evolution of the southwest monsoon and the plateau monsoon,and is of great significance for exploring the relationship between plateau uplift and atmospheric circulation.150,000 years ago is the beginning of the third phase of the Republican movement of the Qinghai-Tibet Plateau uplift.This movement has an important impact not only on the interior of the plateau but also on the environmental evolution of the surrounding plateau.It is of great significance for studying the environmental effects of the Qinghai-Tibet Plateau uplift.In this paper,the Jiaomuniu section of the western Sichuan Plateau is the focus of research,and based on paleomagnetic geochronology,the stratigraphic framework of the Jiaomuniu section is established by comparing with the loess layer of the Loess Plateau and the Machang profile of Jinchuan.On this basis,the environmental indicators such as the magnetic susceptibility,chromaticity and particle size of the Jinchuan profile were analyzed and compared with the deep sea oxygen isotope curve to discuss the environmental evolution of the Jinchuan area since 150,000 years.The results obtained are as follows:1.Based on paleomagnetic poles,marker layer,magnetic susceptibility and chromaticity index,by comparing with the Machang section and the typical loess layer on the Loess Plateau,the age of the loess layer in the Jiamuniu section of Jinchuan,western Sichuan was determined.2.Using susceptibility,chromaticity and particle size as environmental substitute indicators,the climate of Jinchuan Loess since 150,000 years is divided into three stages:?1?150 ka B.P.-100 ka B.P.?late L₂-mid S₁?.Cold and dry rapidly develop towards warm and wet;?2?100 ka B.P.-43 ka B.P.?mid-S₁-early L₁?,the climate develops slowly from warm and wet to cold and dry;?3?43 ka B.P.-0?early L₁-present?The climate rapidly changed from cold and dry to warm and humid,and then slowly developed to cold and dry.3.A regional comparison of the western Sichuan climate change curve with the Loess Plateau and Alaska,the deep sea oxygen isotope curve,the South China Sea oxygen isotope curve and the southern China stalagmite oxygen isotope.