Dizhi lixue xuebao (Feb 2021)
Characteristics and evolution process of the ridge-groove sequence of the Jiulongtan glacial accumulation in Mengshan, Shandong: with the discussion on the difference of accumulation sequence of glacier and debris flow
Abstract
The existence of Quaternary glaciers in the medium-low mountainous areas in the east of China has been disputed for a century. As an important evidence for glacial accumulation in the east, "mud-gravel" (moraine) has long been referred to as debris flow sediments by those who hold a non-glacial view. However, due to the essential difference of the accumulation process between glacier and debris flow, it would inevitably show specific differences in the characteristics of the accumulation body. Therefore, in the cause analysis of moraine and restoration of moraine accumulation process, it is of great significance to identifying and summarizing the specific differences between glacier and debris flow in accumulation characteristics and accumulation process. Based on the comparative analysis, it reveals that, the glacial moraine forms a specific ridge-groove sequence on the plane, and on the section it shows a state of unstratified and mixed accumulation; Debris flow forms an accumulation fan. The fan surface presents a radial ridge accumulation, and the section shows a prosodic sequence. This is what distinguishes glacier from debris flow deposit. On this basis, the diamictons in the Jiulongtan area were investigated and reconstructed. It is found that they have the typical ridge-groove sequence of glacial origin, and meanwhile they present a state of unstratified and mixed accumulation on the section, which proves they are the results of Quaternary glaciation. The ridge-groove sequence is not only the specific feature to judge whether the diamictons are the results of glaciation, but also the theoretical basis to restore the basic geomorphological features and accumulation process of moraine deposits.
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