Internal structure and composition of a rock glacier in the Andes (upper Choapa valley, Chile) using borehole information and ground-penetrating radar
Internal structure and composition of a rock glacier in the Andes (upper Choapa valley, Chile) using borehole information and ground-penetrating radar
复制标题
使用钻孔信息和探地雷达研究安第斯山脉（智利乔帕山谷上游）岩石冰川的内部结构和成分
DOI：
10.3189/2013aog64a107
复制
发表时间：
2013
影响因子：
2.9
通讯作者：
C. Kinnard
中科院分区：
文献类型：
--
作者：
S. Monnier;C. Kinnard
摘要本研究利用钻孔，地温监测和探地雷达（GPR），以了解内部结构和组成的岩石冰川在上乔帕山谷，北方智利。岩石冰川是一个小的山谷边的功能，200米长，范围在3710和3780 ma.s.l.之间。使用金刚石钻孔技术，分别钻了两个深度为20米和25米的钻孔。在钻孔中遇到冰岩混合物，平均冰含量为15- 30%。从共中点（CMP）和恒定偏移距（CO）GPR调查获得的数据，分别在钻孔附近和整个岩石冰川进行处理，突出内部地层和雷达波速度的变化。探地雷达剖面描绘了一个岩石冰川，它由堆叠的、大体上一致的层组成，其厚度从上部的10米到末端的30米不等。CMP分析突出了结构前20 m的雷达波速度为0.13-0.16 m ns-1。CO数据突出显示了较大的垂直和横向速度变化，反映了岩石冰川的异质成分和结构中可能存在未冻水。鉴于现场记录的平均气温（+0.5 ° C），一年多来钻孔记录的近熔点温度以及从地质雷达数据推断的当地高含水量的存在，人们认为岩石冰川中的永久冻土目前正在退化。
Abstract This study uses boreholes, ground temperature monitoring and ground-penetrating radar (GPR) in order to understand the internal structure and composition of a rock glacier in the upper Choapa valley, northern Chile. The rock glacier is a small valley-side feature, 200 m long and ranging between 3710 and 3780 ma.s.l. Two boreholes were drilled down to depths of 20 and 25 m, respectively, using the diamond drillhole technique. An ice-rock mixture was encountered in the boreholes, with heterogeneous ice content averaging 15-30%. Data from common-midpoint (CMP) and constant-offset (CO) GPR surveys acquired, respectively, near the boreholes and across the whole rock glacier were processed to highlight the internal stratigraphy and variations in the radar-wave velocity. The GPR profiles depict a rock glacier constituted of stacked and generally concordant layers, with a thickness ranging from 10 m in its upper part to ∼30m towards its terminus. The CMP analysis highlights radar-wave velocities of 0.13-0.16 m ns–1 in the first 20 m of the structure. Larger vertical and lateral velocity variations are highlighted from CO data, reflecting the heterogeneous composition of the rock glacier and the likely presence of unfrozen water in the structure. Given the average air temperature registered at the site (+0.5°C), the near-melting-point temperature registered in the boreholes over more than a year and the presence of locally high water content inferred from GPR data, it is thought that the permafrost in the rock glacier is currently degrading.