Pronival ramparts

Abstract

Pronival ramparts are debris ridges formed at the downslope margins of perennial or semi-permanent snowbeds beneath bedrock cliffs. These landforms, also previously known as protalus ramparts, are located in periglacial environments, but the apparent simplicity of rampart formation made these landforms far less interesting than other modified forms of talus in cold environments. As a result, limited research, use of supposed relict examples and assumed formative mechanisms led to the misidentification of ramparts, circular arguments regarding genesis and inappropriate palaeo-environmental inferences. Several advances have, however, been made in the past few decades, particularly where actively-forming ramparts have been studied. Thus, this paper provides a review of research on pronival ramparts. In particular, focus is placed on the advances made in our understanding of rampart genesis, identification (diagnostic criteria) and palaeo-environmental significance. Notable advances include the development of a retrogressive model of rampart genesis to supplement the conventional downslope model of development, revised diagnostic criteria for field identification and the use of calibration equations during Schmidt-hammer exposure dating of pronival rampart. The use of pronival ramparts as palaeo-environmental indicators is also examined to determine what relict examples of these landforms may reveal about past climates.