Typical Soft–Sediment Deformation Structures Induced by Freeze/Thaw Cycles: A Case Study of Quaternary Alluvial Deposits in the Northern Qiangtang Basin, Tibetan Plateau

Abstract

With the objective of establishing a distinction between deformation structures caused by freeze/thaw cycles and those resulting from seismic activity, we studied three well–exposed alluvial deposits in a section at Dogai Coring, northern Qiangtang Basin, Tibetan Plateau. Deformation is present in the form of plastic structures (diapirs, folds and clastic dykes), brittle structures (micro–faults) and cryogenic wedges. These soft–sediment deformation features (except the micro–faults) are mainly characterized by meter–scale, non–interlayered, low–speed and low–pressure displacements within soft sediments, most commonly in the form of plastic deformation. Taking into account the geographic setting, lithology and deformation features, we interpret these soft–sediment deformation features as the products of freeze/thaw cycles, rather than of earthquake–induced shock waves, thus reflecting regional temperature changes and fluctuations of hydrothermal conditions in the uppermost sediments. The micro–faults (close to linear hot springs) are ascribed to regional fault activity; however, we were unable to identify the nature of the micro–faults, perhaps due to disturbance by subsequent freeze/thaw cycles. This study may serve as a guide to recognizing the differences between deformation structures attributed to freeze/thaw cycles and seismic processes.

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

“…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).…”

Accumulation of a Last Deglacial Gravel Layer at Diexi, Eastern Tibetan Plateau and its Possible Seismic Significance

“…Considering the local geological background with frequent earthquakes, the lacustrine sediments of the Diexi section are most vulnerable to earthquake due to lack of glaciation and storms. On the other hand, the wings of flame structures related to cryoturbation are usually symmetrical (Vandenberghe, 1992;Harris et al, 2000;Zhong et al, 2020a). But the flame structures in the Diexi section were formed when fine clays were squeezed into thicker sand layers, showed the characteristics of asymmetric billows deformation.…”