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

• Published in: Acta geologica Sinica (Beijing) Vol. 94; no. 1; pp. 176 - 188
• Main Authors: ZHONG, Ning, LI, Haibing, JIANG, Hanchao, LU, Haijian, ZHENG, Yong, HAN, Shuai, YE, Jiachan
• Format: Journal Article
• Language: English
• Published: Richmond Wiley Subscription Services, Inc 01.02.2020; Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing, 100081, China%Key Laboratory of Deep-Earth Dynamics, Ministry of Natural Resources, Beijing 100037, China; Key Laboratory of Deep-Earth Dynamics, Ministry of Natural Resources, Beijing 100037, China; Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China; Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China%State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China
• Edition: English ed.
• Subjects: Alluvial basins; Alluvial deposits; Alluvium; Core sampling; Coring; Cycles; Deformation; Deformation mechanisms; Diapirs; Dogai Coring; Earthquakes; Fault detection; Fault lines; Faults; Freeze thaw cycles; Geological faults; Hot springs; Lithology; Plastic deformation; Qiangtang Basin; Quaternary; Rock intrusions; Sediment; Sediments; Seismic activity; Shock waves; soft–sediment deformation structures; Structures; Tibetan Plateau; freeze/thaw cycles; soft-sediment deformation structures; Dogai Coring; Qiangtang Basin
• ISSN: 1000-9515; 1755-6724
• DOI: 10.1111/1755-6724.14345

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.