Diagnostic criteria for pronival ramparts: site, morphological and sedimentological characteristics

Abstract

ABSTRACT. Pronival ramparts are discrete debris accumulations found below steep rock faces at the foot of snowbeds or firn fields but they are often confused with moraines, protalus rock glaciers or rock-slope failure debris accumulations. This can be attributed to a poor understanding of the modes of rampart genesis, failure to recognise the significance of topography in their development and the use of inappropriate diagnostic criteria. Various characteristics have been suggested for identification of pronival ramparts but these are derived largely from relict features. Research on actively-accumulating ramparts has shown that some of the suggested criteria are no longer useful. This paper reviews existing criteria and shows that, for diagnostic purposes, more emphasis should be placed on the attributes of actively-accumulating features. A more robust set of criteria, derived from common characteristics of activelyaccumulating ramparts, are proposed that assists in discriminating relict and active pronival ramparts from other discrete bedrock cliff-foot debris accumulations.

Geomorphological processes and frozen ground conditions in Elephant Point (Livingston Island, South Shetland Islands, Antarctica)

“…Slope processes are widespread on the northern side of the moraine and less abundant in the southern exposed slope, where snow patches remain longer and have favoured the development of pronival ramparts. The structure of the pronival ramparts is similar to that described in other areas (Ballantyne, 1987;Shakesby, 1997;Hedding and Sumner, 2013), with arcuate ridges and basal talus at their foot. Frost mounds are distributed on the ice-rich permafrost terrain of the moraine; although not found in an ice-core moraine, frost mounds may include up to 80% of ice content as observed in other permafrost environments (Fortier et al, 2008).…”

Improved Schmidt-hammer exposure ages for active and relict pronival ramparts in southern Norway, and their palaeoenvironmental implications

“…Pronival (formerly protalus) ramparts are depositional landforms, usually ridges or ramps, produced by the accumulation of rock debris at the lower margins of perennial or semi-permanent snowbeds located typically beneath bedrock cliffs in periglacial environments (Shakesby, 1997(Shakesby, , 2014Hedding, 2011;Hedding and Sumner, 2013). Dating of ramparts is particularly problematic because usually they grow incrementally as sedimentary material is added episodically from a variety of sources.…”

Rock glaciers in the Western and High Tatra Mountains, Western Carpathians

“…Firstly, these landforms are usually very difficult to differentiate from talus rock glaciers not only from aerial imagery, but also in the field (e.g. Hedding, 2016;Hedding & Sumner, 2013). Secondly, these geomorphic features are largely genetically related to talus rock glaciers and Note: Parts of other rock glaciers and their contributing areas extending into the images are not highlighted.…”