Stratified slope deposits: periglacial and other processes involved
Stratified slope deposits occur on or at the base of slopes within a wide range of hilly or mountainous environments. Gelifraction, a lack of vegetation, and snowmelt-derived slopewash are thought to be important factors in their development. The relatively fine-grained grèzes litées found at many sites within the French Charente region are the prototype of this kind of deposit. The original, strictly limited and genetically intended definition has been enlarged by mainly non-French authors causing considerable confusion.
Other assemblages of cold-climate slope deposits are more heterogeneous, sometimes less clearly stratified, and show much larger variation in grain sizes and sedimentary structures than grèzes litées. The most important of these are stone-banked solifluction (sheets or lobes), rock fall, (dry) grain flow, frost-coated clast flow, debris flow, snow avalanching and, to a lesser degree, rain-generated overland flow and (niveo-) aeolian activity. Many of these processes are azonal and occur under a wide range of environmental conditions. A periglacial context may nevertheless influence process activity in these cases, for instance with regard to their magnitude and/or frequency.
Figures & Tables
Understanding the sediments deposited by glaciers or other cold-climate processes assumes enhanced significance in the context of current global warming and the predicted melt and retreat of glaciers and ice sheets.
This volume analyses glacial, proglacial and periglacial settings focusing, among others, on sedimentation at termini of tidewater glaciers, on hitherto not-well-understood high-mountain features, and on sediments such as slope and aeolian deposits whose clasts were sourced in glacial and periglacial regions, but have been transported and deposited by azonal processes. Difficulties are thus often encountered in inferring Pleistocene and pre-Pleistocene cold-climate conditions when the sedimentary record lacks many of the specific diagnostic indicators. The main objective of this volume is to establish the validity and limitations of the evidence that can be obtained from widely distributed clastic deposits, in order to achieve reliable palaeogeographic and palaeoclimatic reconstructions. At a more general level and on the much longer geological timescale, an understanding of ice-marginal and periglacial environments may better prepare us for the unavoidable reversal towards cooler and perhaps even glacial times in the future.