藏东南冻错曲塘布段冰碛物电阻率特征

Resistivity of moraine deposits in the Tangbu section,Dongcuoqu,southeastern Tibet

藏东南怒江流域冻错曲塘布段周边区域普遍发育有冰斗、刀脊、角峰、高山湖泊等冰川地貌,表明该区历史上曾发生强烈的冰川活动,但实地调查发现该段第四系地表主要分布崩坡积物、冲洪积物。对该区域音频大地电磁测深和高密度测量成果开展综合分析时发现,该段第四系电性特征与冰碛堆积结构具有高度一致性,结合周边普遍发育的冰川地貌,推断该段第四系主要是以冰碛堆积为主、在冰碛堆积上覆盖有一层崩坡积物和冲洪积物。从物探成果电性结构特征看,音频大地电磁测深电阻率成果可有效反映冰碛堆积厚度、基岩面冰蚀凹谷、冰碛透镜体等结构特征;高密度测量电阻率成果可较好反映冰碛混杂堆积、冰碛透镜体、大体积块石长轴方向等特征。

Glacial landforms,such as cirques,razorback ridges,horn peaks,and alpine lakes,are commonly developed in the surrounding areas of the Tangbu section of Dongcuoqu in the Nujiang River Basin in southeastern Tibet,indicating that intensive glacial activities once occurred in this area.However,field surveys show that proluvium and alluvial-diluvial deposits are mainly distributed in the Quaternary surface of this section.The comprehensive analysis of the audio-frequency magnetotellurics and high-density measurement results of this area show that the electrical characteristics of the Quaternary in this section are highly consistent with the moraine deposit structure.Combined with the commonly developed glacial landforms in the surrounding area,it can be inferred that the Quaternary stratum in this section is mainly dominated by moraine deposits,which are covered with a layer of proluvium and alluvial-diluvial deposits.From the perspective of the electrical structure characteristics of the geophysical exploration results,the resistivity results of the audio-frequency magnetotellurics can effectively reflect the structural characteristics including the thickness of the moraine deposits,glacial valleys on the bedrock surface,and moraine lenses,and the resistivity results from high-density measurement can well reflect the characteristics of moraine melange,moraine lenses,and the long axis direction of large boulders.