ABSTRACT

Nivation, the suite of weathering and transportation processes attributed to late-lying snowpatches, is linked to the formation of cryoplanation terraces (CTs). CTs resemble giant staircases arranged in repeating sequences of low-gradient treads and steep scarps that extend over hundreds of meters. The nivation hypothesis of CT development has been supported in recent literature examining weathering and erosion trends, but the mechanisms involved in transporting sediment across CT treads remain underinvestigated. Sorted stripes, a type of patterned ground encountered on CT treads, have been linked to efficient snow meltwater flow across low gradients, indicating that these features could be an important component of CT formation. In this study, we use short-term soil thermal and moisture records, particle-size analysis, and apparent thermal diffusivity calculations to examine periglacial processes operating on two incipient CTs. Initial results indicate that: (1) the coarse (boulder and cobble size) portions of sorted stripes function as subsurface channels for sediment transportation across gently sloping CT treads (generally < 12°) by flowing water; (2) hillslope hydrology is an important component of the erosion processes sculpting upland periglacial environments; and (3) late-lying snowbank environments are highly dynamic during warm weather, with large amounts of sediment transported over short periods.

摘要

Nivation 是归因于晚期积雪的一系列风化和运输过程，与冷冻平整梯田 (CT) 的形成有关。CT 类似于以重复序列排列的巨型楼梯，由低梯度踏板和延伸数百米的陡峭陡坡组成。CT 发展的起源假说在最近研究风化和侵蚀趋势的文献中得到了支持，但涉及通过 CT 踏板运输沉积物的机制仍未得到充分研究。分选条纹是 CT 踏板上遇到的一种带图案的地面，与穿过低梯度的有效融雪水流有关，表明这些特征可能是 CT 形成的重要组成部分。在这项研究中，我们使用短期土壤热和水分记录、粒度分析、和表观热扩散率计算，以检查在两个初期 CT 上运行的冰缘过程。初步结果表明：(1) 分选条带的粗糙（巨石和鹅卵石大小）部分用作沉积物通过流水穿过平缓倾斜的 CT 踏板（通常 < 12°）运输的地下通道；(2) 山坡水文是塑造高地冰缘环境侵蚀过程的重要组成部分；(3) 在温暖的天气里，晚伏雪堤环境是高度动态的，在短时间内输送了大量的沉积物。(1) 分选条带的粗（巨石和鹅卵石大小）部分用作沉积物通过流水穿过平缓倾斜的 CT 踏板（通常 < 12°）运输的地下通道；(2) 山坡水文是塑造高地冰缘环境侵蚀过程的重要组成部分；(3) 在温暖的天气里，晚伏雪堤环境是高度动态的，在短时间内输送了大量的沉积物。(1) 分选条带的粗（巨石和鹅卵石大小）部分用作沉积物通过流水穿过平缓倾斜的 CT 踏板（通常 < 12°）运输的地下通道；(2) 山坡水文是塑造高地冰缘环境侵蚀过程的重要组成部分；(3) 在温暖的天气里，晚伏雪堤环境是高度动态的，在短时间内输送了大量的沉积物。