贡嘎山玉龙西高寒钙华地貌对冰川活动的记录

Records of glacier activities by the alpine travertine landform in the Yulongxi area along Gongga mountain

文章选取贡嘎山西侧玉龙西断裂带附近的钙华及周边冰碛物为研究对象,在野外调查的基础上,通过卫星高光谱遥感数据进行钙华识别,对钙华进行航空摄影测量,并构建主要钙华体精细化DEM及三维模型,分析钙华分布规律及地貌特征。结果表明:研究区钙华集中分布于玉龙西区域南北向断裂带两侧,沟谷由高向低处延伸,部分残留钙华体长宽比及表面擦痕等形态特征符合鲸背石、羊背石的外观特点。根据XRD半定量测试结果,结合地形特征,推测覆盖于钙华体之上的堆积物可能是冰川活动的产物,冰川活动时期,上部杂谷脑组风化剥蚀的物质随着冰川作用搬运至钙华体之上,活跃的冰川活动导致早期钙华遭受强烈的冰川侵蚀作用,形成冰川侵蚀地貌。

As a carrier of geological historical records and climatic information,travertine has played a crucial role in the study of global climate change,and scholars have made significant progress in research on travertine over the past few decades.Travertine deposits are widely distributed on the Qinghai-Tibet Plateau,often referred to as the"Third Pole in the World".They are especially distributed in high mountains along the eastern edge of the plateau,forming a belt of travertine from northeast to southwest.These travertine formations in the high-altitude regions are predominantly found above the Quaternary ancient glaciers,closely associated with the development and distribution of these glaciers.Hence,the travertine geomorphology in these high-altitude areas may serve as evidence of the Quaternary glacial activities.Therefore,aiming to provide evidence for the Quaternary glacier activities,this study selects surface-exposed travertine in the Yulongxi area on the western side of Gongga mountain as the research subject to analyze records of glacial activities in high-altitude travertine.The specific research methods employed in this study are as follows:(1)conducting field geological work to survey glacial landforms surrounding travertine,such as glacial striations,sheep back stones,etc.,and collecting samples of moraines on and near the old travertine bodies;(2)utilizing GF-05 satellite hyperspectral remote sensing data to interpret the lithology of travertine developed in the fault zone of the Yulongxi area,thereby obtaining the distribution characteristics of travertine in the study area;(3)employing drones to perform low-altitude photogrammetric surveys on several typical travertine bodies in the study area,constructing refined DEMs and 3D models to analyze the distribution patterns and geomorphological characteristics of travertine,and combining terrain features to analyze the formation of sheep back stones and whalebacks;(4)using XRD testing technology to analyze the compositions of moraines and comparing the similarities and differences between the compositions of moraines deposited at different locations on the old travertine bodies;(5)integrating previous chronological data on travertine belts developed in the north-south direction on the eastern edge of the Qinghai-Tibet Plateau,and comprehensively discussing the potential records of glacial activities in travertine in the study area during the last Glacial Maximum.The research findings are summarized as follows.(1)Travertine in the study area is mainly distributed on both sides of the fault zone within the altitude range of 4,000 m to 4,500 m.Large travertine formations are more concentrated within a 200-meter elevation difference.Some residual travertine bodies are characterized morphologically by elongated shapes,surface striations,etc.,consistent with the appearance of whalebacks and sheep back stone.(2)Based on XRD test results and terrain features,it is inferred that the deposits covering the travertine bodies are likely the products from glacial activities.During glacial periods,material weathered and eroded from the upper part of the Zagunao Formation was transported onto the travertine bodies through glacial action.Simultaneously,with the Quaternary glacier activities,early travertine formations underwent intense glacial erosion,forming glacial erosional landforms.Combining previous research on travertine and moraines in the Gongga mountain area,this study draws the following conclusions regarding the potential records of glacial activities during the last Glacial Maximum in the study area.During interstadial periods of the last Glacial Maximum,warming climate led to glacier melting and retreat.The melting of ice and snow,coupled with rainfall,provided favorable material conditions for the formation of travertine deposits in the study area.Meltwater and rainfall infiltrated down to lower elevations along synclines of the Zagunao Formation,upwelled along the fault in the Yulongxi area,overflowed near the fault and downstream valleys,and finally formed extensive travertine deposits.During glacial periods,the entire region was covered by glaciers.Under the pressure of the upper glaciers,bedrock debris entrained at the glacier base eroded and abraded the bedrock(travertine).Early travertine formations were eroded,forming glacial erosional landforms,with travertine fragments and bedrock debris covering the travertine bodies in some areas.With global warming and rising temperature,travertine growth ceased in most areas,due to the rapid retreat of glaciers and the reduction of precipitation and meltwater.Early glacially eroded travertine landforms were subjected to erosion and weathering by water flow,and some moraines remained on the top of old travertine bodies.