Pleistocene Involutions and Patterned Ground in France: Examples and Analysis Using a GIS Database

Abstract

A georeferenced database is used to analyse the distribution of Quaternary soft‐sediment deformation structures across France. They include features visible in aerial photographs (soil stripes and cells) and features described in cross‐section (involutions). Overall, there is no clear relation between the distribution of features and the locations of known faults and earthquakes in available databases. In contrast, the distribution agrees with that of Pleistocene periglacial structures. Most of the soil stripes and cells are located north of 47.5°N, i.e. in the zone of ice‐wedge pseudomorphs, and can be interpreted as deformation structures of an active layer in permafrost terrain. The height of the involutions is influenced by the nature of the filling, the substrate and latitude. Deformation structures are larger in coarse material, reflecting the role of drainage and thermal conductivity. Their height increases northward to ca. 2 m at 48°N. This is thought to reflect the increase in thickness of the layer subjected to freeze–thaw cycles. Bowl‐shaped structures separated by coarse pillars, which correspond to soil stripes seen in section, have formed on slopes in settings unfavourable to the generation of high pore‐water pressure. Their genesis is probably related to differential frost heave. Ball‐and‐pillow structures and diapirs are common in flat and poorly drained terrain, and formed by liquefaction and sometimes fluidisation in a periglacial setting. Copyright © 2017 John Wiley & Sons, Ltd.

Features caused by ground ice growth and decay in Late Pleistocene fluvial deposits, Paris Basin, France

“…The sand injection was interpreted by Van Vliet-Lanoë et al (2016) as slow soft-sediment deformation following ice melting. Such a hypothesis seems equally unlikely, as it does not account for the isolated nature of the structure, which contrasts with classical load cast observed in periglacial contexts (Vandenberghe, 1992(Vandenberghe, , 2013Bertran et al, 2017), and for the lack of evidence for slow deformation of watersaturated material such as bedding deformed parallel to the structure outlines. In contrast, the sand body shows a lack of bedding, compatible with sand fluidization, an upward fining that testifies to settling of the particles from a suspension, and protrusions, which indicate hydraulic fracturing of the host sediment.…”

“…Over the past decade, the creation of a database of relict periglacial features in France allowed documentation of the maximum Pleistocene extent of permafrost and made it possible to delineate permafrost types at the scale of the whole territory (Bertran et al, 2014(Bertran et al, , 2017Andrieux et al, 2016aAndrieux et al, , 2016b. Ice wedge pseudomorphs, which indicate at least widespread discontinuous permafrost, were only observed north of latitude 47.5°N in lowlands (Fig.…”

Assèchement et dégradation des sols durant le Subatlantique : vers un niveau repère antique dans le Nord-Est de la France (Lorraine, Alsace) ?

“…7b) L'agencement polygonal est généralement lié à l'ouverture de fentes lors de la contraction thermique des sols par le gel en contexte périglaciaire. Des polygones sont alors de taille plurimétrique et souvent visibles en photo aériennes (Bertran et al, 2017 ;Andrieux et al, 2016) Langohr, 1981 ;Langohr, 2010). D'autres traits typiques sont observés comme une structure lamellaire du sédiment, la position verticale des cailloux, des cheminées d'involutions (Van Vliet-Lanoë et al, 1984, Bertran et al, 2017.…”

Experimental soft‐sediment deformation caused by fluidization and intrusive ice melt in sand

“…This clearly indicates that the increase in pore water pressure was sufficient at depth to cause the sand to fluidize. Such a process could cause the many deformations described in soft sandy sediments that has been subjected to Pleistocene periglacial climates (Bertran et al ., ). It has not yet been reproduced in the laboratory and, therefore, its effectiveness remains hypothetical.…”