山东蒙山九龙潭冰川堆积“垄槽序列”的特征及演化过程研究--兼论冰川、泥石流堆积序列的差异性

中国东部中低山区是否存在第四纪冰川已经争议了一个世纪,作为东部地区冰川堆积重要依据的“泥砾”(冰碛),一直被持非冰川观点者称作是泥石流沉积物。但是,由于冰川与泥石流的堆积过程之间存在本质差别,这必然在堆积体的特征上表现出专属性差异。因此建立冰川与泥石流在堆积特征与堆积过程上的专属性差异,在冰碛物的成因分析、冰碛堆积过程恢复上就有着重要意义。文章在对比分析了冰川堆积与泥石流堆积的过程差异的基础上,发现两类堆积体在平面与剖面上都存在明确的专属性差别。冰川冰碛在平面上形成专属性的垄槽序列,剖面上显示为无层理、混杂堆积状态。泥石流形成堆积扇,扇面上呈放射状垄岗堆积,剖面上表现为韵律序列。这是区别冰川与泥石流堆积体的本质所在。在此基础上,对蒙山九龙潭一带混杂堆积体进行调查与恢复,发现其具有典型的冰川成因垄槽序列特征,结合其剖面上表现为无层理、混杂堆积特征,从沉积序列与沉积过程的角度,佐证了蒙山九龙潭混杂堆积为第四纪冰川作用的事实。垄槽序列既是堆积物是否为冰川作用属性判断的专属性特征,也是恢复冰碛堆积体基本地貌特征与堆积过程的理论基础。

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

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.