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Sedimentological distinction in glacigenic sediments between load casts induced by periglacial processes from those induced by seismic shocks
Geological Quarterly ( IF 0.9 ) Pub Date : 2020-09-07 , DOI: 10.7306/gq.1546
A.J. (Tom) VAN LOON , Małgorzata PISARSKA-JAMROŻY , Barbara WORONKO

Loading processes and the resulting load structures induced by processes related to periglacial conditions are compared to those induced by seismic shocks. The load structures themselves are relatively easily recognizable but the responsible trigger mechanism is, though depending on the geological context, commonly difficult to establish. Load structures like load casts, pseudonodules, ball-and-pillow structures and flame structures are commonly ascribed to instable density gradients within sediments and to differential loading, but their formation always requires liquefaction. In glacigenic sediments, deformation structures have most commonly been ascribed to periglacial processes (as a type of cryoturbations), but it becomes ever more clear that glacigenic sediments can, particularly during ice-front fluctuations, be affected by faulting-related earthquakes (due to glacio-isostatic adjustment), and the thus triggered seismic shocks may result in deformations, including – most commonly – load structures. We inventory the evidence that may help to distinguish, on the basis of textural and structural features, load structures with a seismic origin from those that result from periglacial processes, taking into account that truly diagnostic criteria do not exist.

中文翻译:

冰缘过程引起的载荷模型与地震冲击引起的载荷模型之间冰川沉积物的沉积学区别

将与冰缘条件相关的过程引起的载荷过程和由此产生的载荷结构与地震冲击引起的载荷结构进行比较。负载结构本身相对容易识别,但负责的触发机制虽然取决于地质环境,但通常难以确定。负载结构,如负载铸件、假结节、球枕结构和火焰结构,通常归因于沉积物中不稳定的密度梯度和不同的负载,但它们的形成总是需要液化。在冰川沉积物中,变形结构最常被归因于冰缘过程(作为一种低温扰动),但越来越清楚的是,冰川沉积物可以,特别是在冰前波动期间,受断层相关地震的影响(由于冰川均衡调整),因此触发的地震冲击可能导致变形,包括——最常见的——荷载结构。考虑到真正的诊断标准并不存在,我们列出了可能有助于根据纹理和结构特征区分具有地震起源的荷载结构与由冰缘过程产生的荷载结构的证据。
更新日期:2020-09-07
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