A Study On The Glacier Evolution History In Sangqu Valley

The Tibetan Plateau is the region with the most developed glaciers except for North and South Pole.The history of glaciers on the Tibetan Plateau and surrounding mountains has been the focus of quaternary scientific research for decades.A large number of studies have investigated the scope,time and climate impact of glaciers in the past.Studying the Quaternary glaciers on the Tibetan Plateau not only has the scientific significance to recognize the recent geological history,but also provides background coordinates for predicting future climate and environmental changes.There are few reports of cosmic nuclide exposure dating from the last glacial period in Gangrigabu Mountain in southeast Tibetan Plateau.This is the first time that this paper has carried out a dating study on the exposure of paleoglaciers in the Sangqu Valley of Gangrigabu,which is an important supplement to the ice age sequence and evolution history in southeastern Tibetan Plateau.In this paper,¹⁰Be and ²⁶Al were used to sample4 moraine ridges at the mouth of the Yudongqu Glacier in the Sangqu River Valley,and the nuclide concentration was determined.The data was screened using ²⁶Al/¹⁰Be-¹⁰Be concentration diageam and the year was determined.Finally,the paleoglacial advancement patterns and environmental characteristics since the Last Glacial Maximum in southeast Tibetan Plateau were summarized.The conclusions are:1)The exposure ages were:M1's ¹⁰Be age was 17.31±0.64ka BP,M2 was 18.20±0.50ka BP,M3 is 18.02±0.40ka BP;M1 ²⁶Al age is 15.42±0.27ka BP,M2 is 16.80±0.15ka BP,M3 is 17.22±0.21ka BP.M4 was not given an age.2)According to the statistics of the age distribution of the five paleoglaciers in the midstream and downstream of Yarlung Zangbo in southeastern Tibetan Plateau,it can be concluded that the ice age model in southeastern Tibetan Plateau since the last ice age can be roughly divided into 6 periods,namely Last Glacial Maximum(LGM),Late Glacial(LG)or Heirich event 1(H1),Younger Dryas(YD),Early Middle Holocene,Neoglaciation(NG)and Little Ice Age(LIA).Different combinations of several ice ages occurred in six ice ages under different locations and topographic conditions.The Yudongqu paleoglacier corresponds to the ice advance of the LG or H1 cold event.3)Based on the?ELA obtained by the Maximum Elevation of Lateral Moraines(MELM)method and previous estimates,the ELA in the Sangqu River valley decreased by?600-1000m during the Lateglacial period.The comparison shows that the sensitivity of glaciers to precipitation decreases from south to north in southeast Tibetan Plateau.4)Paleoclimate records show that the southeast Tibetan Plareau is generally in a cold and dry climate during the LG.The Indian summer monsoon has weakened and precipitation has decreased.The solar radiation is in a gradual rise period.Glacial meltwater has increased.Short-term sudden temperature drops or ice-melting heat absorption may be the main reason for glaciers expansion.Moreover,the lower temperatures experienced during LGM-LG or H1probably offset the effect of reduced precipitation by reducing ablation,resulting in a positive increase in glacier mass balance and glacier expansion,resulting in a large amount of ice in this stage,resulting in many moraine ridge.After entering the B(?)lling-Aller(?)d(BA)warm period,the Indian summer monsoon has greatly strengthened.Although it has experienced the YD cold period,the glacier has not reached the LG scale.