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

Abstract

Identifying the driving mechanisms of soft-sediment deformation in the geological record is the subject of debate. Thawing of ice-rich clayey silt above permafrost was proved experimentally to be among the processes capable of triggering deformation. However, previous work has failed so far to reproduce similar structures in sand. This study investigates fluidization and intrusive ice formation from soil models in the laboratory. Experimental conditions reproduce the growth of ice-cored mounds caused by pore water pressure increase during freeze-back of sand in a permafrost context. Excess pore water pressure causes hydraulic fracturing and the development of water lenses beneath the freezing front. Later freezing of the water lenses generates intrusive ice. The main structures consist of sand dykes and sills formed when the increase in pore water pressure exceeds a critical threshold, and soft-sediment deformations induced by subsidence during ice melt. The combination of processes has resulted in diapir-like structures. The experimental structures are similar to those described in Pleistocene sites from France. These processes constitute a credible alternative to the seismic hypothesis evoked to explain soft-sediment deformation structures in other European regions subjected to Pleistocene cold climates.

Repetitive Late Pleistocene soft‐sediment deformation by seismicity‐induced liquefaction in north‐western Lithuania

“…Deciphering the trigger mechanism and the driving force of this type of deformation in different sedimentary environments is an important issue in Quaternary geology, sedimentology and tectonics, especially in formerly‐glaciated intraplate stable continental core regions of the Northern Hemisphere (e.g. Van Vliet‐Lanoë et al ., 2004; Brandes & Winsemann, 2013; van Loon et al ., 2016; Brandes et al ., 2018; Brooks, 2018; Pisarska‐Jamroży et al ., 2018a, 2019a; Bertran et al ., 2019; Grube, 2019; Brooks & Adams, 2020; van Loon et al ., 2020, and references therein). Recently, research focused on distinguishing between seismic and non‐seismic triggers based on SSDS and their position within the sedimentary record (e.g.…”

“…Recently, research focused on distinguishing between seismic and non‐seismic triggers based on SSDS and their position within the sedimentary record (e.g. Wheeler, 2002; Menzies & Taylor, 2003; Van Vliet‐Lanoë et al ., 2004; Horváth et al ., 2005; Owen & Moretti, 2008, 2011; Alsop & Marco, 2011; Loon & Maulik, 2011; Owen et al ., 2011; Brandes & Winsemann, 2013; Moretti & Loon, 2014; Pisarska‐Jamroży et al ., 2018a, 2019a; Bertran et al ., 2019; van Loon et al ., 2020; Zhong et al ., 2020).…”

Disaggregation bands as an indicator for slow creep activity on blind faults

“…Paleoseismological studies often rely on softsediment deformation structures, such as sand-volcanoes, to identify past seismic events, e.g., 2,3 . However, these structures can also form due to non-tectonic drivers, such as water discharge 4 or permafrost 5 . Consequently, soft-sediment deformation structures are ambiguous.…”

Geomorphic response to the Lateglacial–Holocene transition in high Alpine regions (Sanetsch Pass, Swiss Alps)

“…Frost and thaw processes have continually mobilized sediment patches from various depths (Bertran et al . 2019), causing light exposure of reworked sediments and the (partial) resetting of their luminescence signal. Similarly, stratigraphical inconsistency and large variability in luminescence ages have been observed for periglacial sediment deposits, and have been attributed to post‐depositional reworking due to active cryoturbation processes (Bateman 2008; Andrieux et al .…”