New Find and Dating of Holocene Composite Glacial Deposits in Lanmaqiang,Mengshan,Shandong Province:Concurrently Discussing the Symmetry of Glacial Deposits and Its Causes
In recent years,the origin of the Lanmaqiang boulders ridges in Mengshan,Shandong Province has at-tracted the attention of academic circles,and two views of the cause of formation,glaciation and debris flow,have been formed.The research has integrated numerous research data of glacial deposits,it was found that these later-al moraines showed"symmetry"which was the most common feature of glaciation.This feature was determined by the unique deposition process of glaciers,as it was a fundamental difference in the topographic feature between it and the fan-shaped deposits formed by floods and debris flows.Therefore,a more extensive survey has been car-ried out on the boulders ridges in the study area based on this.It was found that the boulders ridges were not one-sided,as previously thought,but symmetrical moraines composed of left lateral moraines,middle moraines and right lateral moraines.These moraines were the products of two glaciers(composite glaciers)at the intersection of Fotagu Valley and Lanxi Valley.Additionally,the other three lateral moraines in Lanxi Valley upstream of Lan-maqiang boulder ridges also showed remarkable symmetry.The sedimentation time of several rows of moraines rid-ges in the valley was(5.36±0.25)ka,(9.93±0.38)ka and(12.9±0.38)ka obtained by Cosmogenic Nu-clide Dating,The deposition time of these lateral moraines correspond to the 5.3 ka cooling event(Qingrong Gla-cial Age),C2 cooling event and Younger Dryas event,and had good correspondence with the results of lichenom-etry dating.Specifically,the symmetrical lateral moraines in Lanxi Valley formed in the Early Holocene and Mid-dle Holocene cooling events,and the lateral moraines formed by the Younger Dryas cold event were first discov-ered.The research results reveal the existence of Holocene glacial remains in eastern China.
glacial remainsHolocenecosmogenic nuclide datinglichenometry dating
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