Near-surface brecciation of chalk, isle of thanet, south-east England: a comparison with ice-rich brecciated bedrocks in Canada and Spitsbergen

Experimental design for a pilot study on bedrock weathering near the permafrost table

“…A sample of chalk was cut by handsaw into a block measuring 0Á33 m high and 0Á30 Â 0Á31 m wide ( Figure 1). This large size was necessary to provide: (1) sufficient depth to permit freezing and thawing of a thin artificial active layer above permafrost; and (2) sufficient volume for the formation of centimetre-size fragments±a size comparable to those observed in naturally brecciated chalk (Cailleux, 1943;Williams, 1987;Murton, 1996).…”

Pleistocene Periglacial Processes and Landforms, Mid-Atlantic Region, Eastern United States

“…Experiments that simulate natural freezing regimes and frost cracking in wet chalk (Murton et al 2006) produce bedrock fractures with depths and geometries that match those in modern permafrost environments (Mackay 1999, French 2017b). These experimental and modern coldregion fractures are similar to those in weathering profiles of bedrock in formerly periglacial regions: Numerous mostly horizontal to subhorizontal fractures occur in the upper 0.5 to several meters of bedrock, decreasing in frequency with depth (Murton 1996, Murton et al 2006.…”

“…At this site, depth to bedrock determined from 16 hammer seismograph lines and 19 soil pits ranged from 3.0 to 6.3 m and was interpreted to be the result of deep frost weathering. It is probably not a coincidence that many reports of depth to bedrock in the region are within this range (e.g., West et al 2019) and are similar to descriptions of depths of brecciated rock produced from ice segregation by Murton (1996) and Murton et al (2006).…”

Fluvial response to Late Pleistocene and Holocene environmental change in a Thames chalkland headwater: the Lambourn of southern England

“…Under a regime of highly-variable, seasonal 354 stream discharges this favoured the transport and deposition of gravel in bedload-dominated rivers12 which are radically different from the clear chalk streams of today. Freeze-thaw cycles were also 356 important in maintaining an abundant supply of sediment through the rapid near-surface brecciation 357 of chalk (Murton, 1996) and in promoting mass wasting on hillslopes (Ballantyne and Harris, 1994). It 358 is likely that most of the gravelly sediments in the Lambourn valley were deposited during the 359 relatively warm permafrost conditions of the Younger Dryas, when where was sufficient humidity to 360 generate precipitation (Murton and Belshaw, 2011).…”