Typical Soft-Sediment Deformation Structures Induced by Freeze/Thaw Cycles: A Case Study of Quaternary Alluvial Deposits in the Northern Qiangtang Basin, Tibetan Plateau
Typical Soft-Sediment Deformation Structures Induced by Freeze/Thaw Cycles: A Case Study of Quaternary Alluvial Deposits in the Northern Qiangtang Basin, Tibetan Plateau
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冻融循环诱发的典型软沉积物变形结构——以青藏高原羌塘盆地北部第四纪冲积矿床为例
DOI：
10.1111/1755-6724.14345
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Ye Jiachan
中科院分区：
文献类型：
--
作者：
Zhong Ning;Li Haibing;Jiang Hanchao;Lu Haijian;Zheng Yong;Han Shuai;Ye Jiachan
变形以塑性构造（底辟、褶皱和碎屑岩）、脆性构造（微断层）和低温楔的形式存在。这些软沉积物变形特征（除微断层外）主要表现为软沉积物内部的米尺度、非层间、低速、低压位移，多以塑性变形形式出现。考虑到地理环境、岩性和变形特征，我们将这些软沉积物变形特征解释为冻融循环的产物，而不是地震引起的冲击波，从而反映了区域温度变化和上部沉积物热液条件的波动。微断层（接近线性温泉）归因于区域断裂活动；然而，我们无法确定微断层的性质，这可能是由于随后的冻结/解冻循环的干扰。该研究可作为认识冻融循环和地震过程引起的变形结构差异的指南。
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.