Evidence from seismites for glacio-isostatically induced crustal faulting in front of an advancing land-ice mass (Rügen Island, SW Baltic Sea)
Evidence from seismites for glacio-isostatically induced crustal faulting in front of an advancing land-ice mass (Rügen Island, SW Baltic Sea)
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DOI：
10.1016/j.tecto.2018.08.004
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发表时间：
2018-10
期刊：
影响因子：
2.9
通讯作者：
M. Pisarska‐Jamroży;Szymon Belzyt;A. Börner;G. Hoffmann;H. Hüneke;M. Kenzler;K. Obst;H. Rother;A. V. van Loon
中科院分区：
文献类型：
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作者：
M. Pisarska‐Jamroży;Szymon Belzyt;A. Börner;G. Hoffmann;H. Hüneke;M. Kenzler;K. Obst;H. Rother;A. V. van Loon
迄今为止，人们普遍认为，由厚陆冰块的波动范围引起的压力的地质快速变化所引发的地震只在冰退缩期间发生。我们对波罗的海西南部r<s:1>根岛沿岸悬崖上未变形的冰川湖和冰川河流演替中的变形沉积层的研究，挑战了这种普遍的观点。根据其构造和变形特征，研究层被解释为地震液化形成的震积岩。光学激发发光（OSL）测年辅助的地层背景表明，记录的震积岩一定是在末次盛冰期更新世斯堪的纳维亚冰盖前缘到达研究区之前不久形成的，因此处于冰进阶段。这意味着，在冰推进过程中，由于冰荷载的影响，地壳的弯曲均衡反应可能伴随着地震，这可能是由于先前存在的断层的局部重新激活。因此，地壳对冰负荷增加的反应并不像以前有关冰川相关构造的研究所表明的那样缓慢。
It is hitherto commonly thought that earthquakes triggered by geologically rapid changes in the pressure caused by the fluctuating extent of thick land-ice masses occur exclusively during ice retreat. Our study of deformed sediment layers within an undeformed glaciolacustrine and glaciofluvial succession exposed in a coastal cliff on Rügen Island, south-western Baltic Sea, challenges this widespread idea. Based on their structural and deformational features, the layers under investigation are interpreted as seismites which formed as a result of seismically-induced liquefaction. The stratigraphic context aided by optically stimulated luminescence (OSL) dating indicate that the documented seismites must have formed shortly before the front of the Pleistocene Scandinavian Ice Sheet reached the study area during the Last Glacial Maximum, thus during a stage of ice advance. This implies that the flexural isostatic response of the Earth's crust as a consequence of the ice load during ice advance was accompanied by earthquakes probably due to local re-activation of pre-existing faults. The crustal response to an increasing ice load was consequently less gradual than previous studies about glaciation-related tectonics suggest.