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Subglacial squeeze-up moraines adjacent to the Vaalajärvi-Ristonmännikkö glacially-induced fault system, Finnish Lapland
Geomorphology ( IF 3.9 ) Pub Date : 2021-03-23 , DOI: 10.1016/j.geomorph.2021.107716
Raimo Sutinen , Aleksi Sutinen , Maarit Middleton

The Vaalajärvi-Ristonmännikkö glacially induced fault (GIF) system in central Finnish Lapland is attributed to multiple slip events (Mw ≈ 6.7–7.0 earthquakes), likely contributing to subglacial and postglacial sediment deformations. We applied light detection and ranging digital elevation models (LiDAR DEMs), electrical-sedimentary anisotropy (orientation) measurements and trenching to study the related geomorphology, particularly subglacial moraines on the hanging wall of the Ristonmännikkö GIF segment striking SW-NE direction. Transverse-to-ice-flow-oriented moraines and the Pulju moraines were found to cover the distal tails of the Early Weichselian rock-drumlins and they are interpreted as seismically induced crevasse infill landforms. The electrical-sedimentary anisotropy suggests squeeze-up origin rather than active ice oscillation end moraine formation processes. Based on our recent OSL-data, the squeeze-up moraines are also superimposed on a till-covered esker system yielding an age of 87 ka. Erosional V-shaped features with apices pointing up-ice were found on convex surfaces of the distal rock-drumlin tails and were attributed to subglacial mass-flows rather than glaciofluvial erosion or frozen bed fracturing mechanisms. The area lacks glaciofluvial/hummocky corridors, but a substantial outburst system on the streak of Ristonmännikkö GIF suggests an earthquake-triggered outburst of the former subglacial Lake Unari. Our recent 14C ages of paleolandslides suggest that the Vaalajärvi-Ristonmännikkö GIF terrain was ice-free already 11.3 cal kyr BP, but was subjected to lithospheric water discharge and landslide events at 2.9 and 10.6 cal kyr BP. The squeeze-up moraines most likely formed during the later phase of the Younger Dryas, between ca. 12.0–11.5 cal kyr BP. We propose that subglacial seismicity within a glacial isostatic adjustment (GIA) environment was a notable trigger for the squeeze-up and mass-flow features beneath the retreating Fennoscandian Ice Sheet (FIS) during the later phase of the Younger Dryas.



中文翻译:

Vaalajärvi-Ristonmännikkö冰川诱发的断层系统,芬兰拉普兰附近的冰川下挤压冰rain

芬兰拉普兰中部的Vaalajärvi-Ristonmännikkö冰川诱发断层(GIF)系统归因于多次滑动事件(M w ≈6.7-7.0级地震),可能会导致冰川下和冰川后沉积物变形。我们应用了光探测和测距数字高程模型(LiDAR DEM),电沉积各向异性(定向)测量和挖沟来研究相关的地貌,特别是沿SW-NE方向的RistonmännikköGIF分段悬挂壁上的冰下mo。发现横向流向的冰rain和Pulju冰to覆盖了早期魏克塞勒岩-鼓膜的末端,被解释为地震引起的裂隙充填地貌。电沉积各向异性表明挤压起源,而不是活跃的冰振荡末端冰m形成过程。根据我们最近的OSL数据,紧缩的谷粒也被叠加在覆盖了盖的埃斯克系统上,产生了87 ka的年龄。在远侧岩石-鼓膜尾巴的凸表面上发现了带有尖顶冰的侵蚀性V形特征,其归因于冰川下的物质流动,而不是冰川流冲蚀或冰冻床破裂机制。该地区没有冰川河道/丘陵走廊,但是RistonmännikköGIF条纹上的大量爆发系统表明,地震触发了前冰河以下Unari湖的爆发。我们最近 但是RistonmännikköGIF条纹上的实质性爆发系统表明,地震触发了前冰河以下Unari湖的爆发。我们最近 但是RistonmännikköGIF条纹上的实质性爆发系统表明,地震触发了前冰河以下Unari湖的爆发。我们最近14 C年龄的古滑坡表明Vaalajärvi-RistonmännikköGIF地形已经是11.3千卡BP的无冰层,但在2.9和10.6千卡的BP发生了岩石圈水排放和滑坡事件。挤压的花rain很可能在年轻的树妖的后期,大约在大约之间形成。12.0-11.5千卡BP。我们认为,在冰期等静态调整(GIA)环境下的冰下地震活动是在年轻的树蛙的后期阶段撤退的Fennoscandian冰原(FIS)下方挤压和质量流特征的显着触发因素。

更新日期:2021-04-05
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