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冰川冻土 ›› 2022, Vol. 44 ›› Issue (4): 1150-1164.doi: 10.7522/j.issn.1000-0240.2022.0107

• 第二次青藏高原综合科学考察研究 • 上一篇    下一篇

山地冰川冰消后(paraglacial)沉积的粒度与石英颗粒表面特征——以贡嘎山东坡为例

王杰1,2(), 雷满红1, 郑利敏1,3   

  1. 1.兰州大学 资源环境学院 西部环境教育部重点实验室,甘肃 兰州 730000
    2.甘肃省石羊河流域野外科学观测研究站,甘肃 兰州 730000
    3.中国药科大学 中药学院,江苏 南京 210009
  • 收稿日期:2022-06-24 修回日期:2022-08-05 出版日期:2022-08-25 发布日期:2022-09-14
  • 作者简介:王杰,教授,主要从事冰川地貌与环境变化研究. E-mail: wangjie@lzu.edu.cn
  • 基金资助:
    国家自然科学基金项目(41971003);第二次青藏高原综合科学考察研究项目(2019QZKK0205)

Grain size and quartz grain SEM microtextures of glacial tills and paraglacial deposits: a case study on the eastern slope of Mt. Gongga

Jie WANG1,2(), Manhong LEI1, Limin ZHENG1,3   

  1. 1.Key laboratory of Western China’s Environmental Systems,Ministry of Education,College of Earth and Environmental Sciences,Lanzhou University,Lanzhou 730000,China
    2.Shiyang River Basin Scientific Observing Station of Gansu Province,Lanzhou 73000,China
    3.School of the Traditional Pharmacy,China Pharmaceutical University,Nanjing 211198,China
  • Received:2022-06-24 Revised:2022-08-05 Online:2022-08-25 Published:2022-09-14

摘要:

冰期向间冰期转换或现代全球气候变暖等背景下,冰川一旦退缩就会引发基岩和冰碛边坡失稳,甚至冰川泥石流等冰消后(paraglacial)地表过程;因此,该过程成为驱动原冰川作用区及其下游谷地地貌演化的重要因子。然而,冰消后过程时空变化特征及其驱动因子等相关研究,目前仍面临两方面问题:其一,各种冰消后沉积、冰碛等混杂堆积间判别的手段缺乏;其二,冰消后过程对下游谷地演化影响的关注不足。为此,本文以典型海洋型冰川作用区——贡嘎山东坡的冰碛和冰消后沉积为研究对象,并结合两处大陆型冰川冰碛,探讨了粒度和石英颗粒表面形态特征两个指标区分上述混杂堆积的有效性。结果表明,各种冰消后沉积物继承了源区冰碛的很多特征,但也呈现出一定独特性,指示出这两个指标综合对比的方法能实现各类冰消后沉积、冰碛的有效判别;同时,鉴于冰川性质、冰川作用期次和岩性等因素都可能影响源区冰碛的粒度和石英颗粒表面形态,以这两个指标判别时应限于同区域,避免选用沉积物的共性特征。基于贡嘎山东坡冰碛、各种冰消后沉积物与磨西台地不同层位粒度与石英颗粒表面形态的对比和聚类分析,确认台地底部和中部可能分别为MIS3冰碛与MIS3以来的泥石流沉积,上部则可能为河流沉积或河流改造过的冰川泥石流沉积。磨西谷地冰消后过程堆积和暴露时代,指示出强烈冰消后过程使得磨西河谷地末次冰期向全新世转换时一直在堆积,甚至持续到约6~7 ka前后才停止,之后转为侵蚀下切。

关键词: 冰消后(paraglacial)沉积, 贡嘎山, 粒度, 石英颗粒表面特征, 磨西台地

Abstract:

Under the background of the transition from Quaternary glaciation to interglacial period or modern global warming, glacier retreat will cause instability of bedrock and till slopes, and even glacier debris flow and other paraglacial surface processes. Therefore, these processes have become important factors driving the geomorphic evolution in paraglacial area and its downstream valley. However, there are still two problems in the study of the temporal and spatial variation characteristics and driving factors of paraglacial processes. Firstly, there is a lack of discriminating methods between various paraglacial deposits, till and other diamictons. Secondly, insufficient attention has been paid to the effects of paraglacial processes on downstream valley evolution. Therefore, we studied the till and paraglacial deposits on the eastern slope of Mt. Gongga, a typical temperate glacial area, and compared the grain size and quartz grain microtextures with two continental glacial tills. The results show that all kinds of paraglacial deposits have formed certain uniqueness when inheriting various characteristics of the till in the source area, indicating that the comprehensive comparison method of these two indicators can realize the effective discrimination of various paraglacial deposits and till. At the same time, due to the type of glacier, action period and lithology could affect the grain size of till and quartz grain microtextures in the source area, the discrimination based on these two indicators should be limited to the same area, and the common characteristics of deposits should be avoided. Based on the comparison and cluster analysis of till on the eastern slope of Mt. Gongga, various paraglacial deposits and grain size and quartz grain microtextures in different layers on the Moxi Platform, it is confirmed that the bottom of the platform is MIS3 till, the middle is debris flow deposits since MIS3, and the upper may be fluvial deposits or glacial debris flow deposits transformed by rivers. The accumulation and exposure age of paraglacial process in the Moxi Valley indicate that the intense paraglacial process caused the Moxi Valley to continue accumulating during the transition from the last glaciation to the Holocene, even until about 6~7 ka, and then turning into incision.

Key words: paraglacial deposit, Mt. Gongga, grain size, quartz grain microtextures, Moxi Platform

中图分类号: 

  • P512.4+2