Large-scale Glacitectonism as a Result of Active Retreat of the Fennoscandian Ice Sheet Across Dogger Bank During the Last Glacial Maximum
Abstract
Detailed analysis of high resolution seismic data from the Dogger Bank area in the southern North Sea has revealed that the Dogger Bank Formation records a complex history of sedimentation and penecontemporaneous, large-scale, ice-marginal to proglacial glacitectonism. These processes led to the development of a large, thrust-block moraine complex, in the order of 10 to 15 km across and over 30 km in length, which is buried beneath a relatively thin sequence of Holocene to recent sediments. This buried glacial landsystem comprises a series of elongate, arcuate ridges separated by low-lying linear basins and/or meltwater channels, which preserve the shape of the former ice sheet margin. Individual thrust moraines range from only 200 m across, up to more complex systems over 10 km in width. The lower boundary of the deformed sequence (up to 40-50 m thick) is marked by a laterally extensive décollement which also forms the base of the Dogger Bank Formation. Internally the moraines show evidence of locally intense SE-verging folding and thrusting, with the overall geometry of these glacitectonic structures being consistent with their formation in response to south- to southeast-directed ice-push. The internal architecture of the moraines has been divided into a number of structural domains which have aided in the interpretation of the constructional deformation history recorded by these glaciotectonic landforms. In the more ice-distal parts of the thrust-block moraine proglacial deformation led to open, upright to asymmetrical folding and thrusting consistent with the formation of a "forward" propagating imbricate thrust stack. Whereas in the more ice-proximal parts of the landsystem, the more complex folding and thrusting is thought to record the accretion of thrust slices of highly deformed sediment to the rear of the evolving moraine system as the ice repeatedly reoccupied this ice marginal position. Consequently, the internal architecture of the Dogger Bank thrust block moraine complex can be directly related to ice sheet dynamics, recording the former positions of an oscillating Fennoscandian Ice Sheet ice margin as it retreated northwards at the end of the Last Glacial Maximum. Acknowledgements: The authors thank the Forewind consortium for providing the seismic data
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.C53C0751C
- Keywords:
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- 0726 Ice sheets;
- CRYOSPHEREDE: 0730 Ice streams;
- CRYOSPHEREDE: 0774 Dynamics;
- CRYOSPHEREDE: 1621 Cryospheric change;
- GLOBAL CHANGE