Periglacial discontinuities in Eocene clays near Denham, Buckinghamshire

Abstract

In the investigation for part of the M25 motorway near Denham, Buckinghamshire, several types of sheared and unsheared discontinuities were found within the Eocene London Clay and Reading Beds clays which are considered to have formed under Pleistocene periglacial conditions. These consisted of two types of low angle, near-surface solifluction shears with associated discontinuous, random accommodation shears. These overlay and truncated high angle shears believed to have formed by collapse on thawing of the top of the permafrost. Deeper, low angle shears of two types, one continuous, subhorizontal and planar, the other discontinuous, random and undulose, are tentatively attributed to shearing at the base of a permafrost layer at a thawing front. Subvertical, unsheared discontinuities are considered to be contraction cracks.

Engineering geology of Quaternary soils: I. Processes and properties

“…Skempton et al (1991) have carried out an extensive study of the Carsington (Derbyshire) dam failure and movement along a shear zone has also been recognized by Spink (1991) but at a greater depth.…”

“…Some of these features have been attributed to the shearing of the at University of Iowa on May 24, 2015 http://egsp.lyellcollection.org/ Downloaded from Both Skempton et al (1991) and Spink (1991), rely upon the development of residual shear strength as opposed to peak strength as the controlling factor in the sliding failure mechanism of slopes. This is a realistic view as many investigations have shown.…”

After the ice: Lateglacial and Holocene landforms and landscape evolution in Scotland

“…Periglacial evidence from elsewhere in the British Isles and Western Europe nevertheless indicates that permafrost probably developed down to sea level in Scotland both in the wake of the retreating ice sheet and again during the YDS (Isarin 1997;Ballantyne 2017). There is evidence for YDS ice-wedge formation as far south as Lincolnshire (Worsley 2014), and in southern England active-layer detachment deposits overlie organic deposits of Lateglacial Interstadial age, implying at least discontinuous permafrost during the YDS (Chandler et al 1976;Spink 1991;Hutchinson 2010).…”

Engineering geology of the Quaternary

“…The 25th Annual Conference of the Engineering Group of the Geological Society at Heriot-Watt University in Edinburgh in September 1989 resulted in the 1991 Engineering Geology Special Publication on Quaternary Engineering Geology . This work is a significant collection of papers on all aspects of the engineering geology of the Quaternary Period addressing key Quaternary background themes (for example Fookes 1991;Culshaw et al 1991;Bell 1991a), Quaternary processes (for example Hutchinson 1991;Gostelow et al 1991;Parks 1991;Spink 1991;Blight 1991), the geotechnics of Quaternary soils (for example Bell 1991b; Bell & Coultard 1991;Bell & Forster 1991;Paul & Jobson 1991;Gregory & Bell 1991;Marsland & Powell), engineering implications (for example Cruden & Tsui 1991;Harris 1991;Hossain & McKinlay 1991;Matheson & Oliphant 1991;Skempton et al 1991) together with applied mapping of Quaternary terrains (for example Browne & McMillan 1991;Cornwell & McCann 1991). Both cold and temperate Quaternary conditions were discussed with summary papers reporting on the significant points presented (Fannin 1991;Little 1991;Muir-Wood 1991;Nash 1991;Petley 1991;Privett 1991).…”