Frozen surficial sediments that are otherwise unconsolidated contain structures and characteristics that are different from those of the same sediments when in an unfrozen state. These differences are usually related to either the nature of the ice contained within the frozen sediment or to weathering processes and chemical precipitates that are associated with freezing and thawing. This paper summarizes (a) the manner in which ground freezes when a landscape experiences the onset of cold-climate conditions and (b) what happens when newly transported sediments freeze following deposition in that environment. In the absence of obvious morphological evidence, the recognition of previously-frozen sediments is problematic. Less well-understood evidence includes secondary precipitates, neoformed clay minerals, seasonal frost cracks and fragipans.
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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.