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Large bedrock slope failures in a British Columbia, Canada fjord: first documented submarine sackungen


Very large (>60×106 m3) sackungen or deep-seated gravitational slope deformations occur below sea level along a steep fjord wall in central Douglas Channel, British Columbia. The massive bedrock blocks were mobile between 13 and 11.5 thousand radiocarbon years BP (15,800 and 13,400 BP) immediately following deglaciation. Deformation of fjord sediments is apparent in sedimentary units overlying and adjacent to the blocks. Faults bound the edges of each block, cutting the glacial section but not the Holocene sediments. Retrogressive slides, small inset landslides as well as incipient and older slides are found on and around the large failure blocks. Lineations, fractures and faults parallel the coastline of Douglas Channel along the shoreline of the study area. Topographic data onshore indicate that faults and joints demarcate discrete rhomboid-shaped blocks which controlled the form, size and location of the sackungen. The described submarine sackungen share characteristic geomorphic features with many montane occurrences, such as uphill-facing scarps, foliated bedrock composition, largely vertical dislocation and a deglacial timing of development.

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Gwyn Lintern provided vital support as project leader, and at sea support by Greg Middleton and Peter Neelands is gratefully acknowledged. John Shaw provided insightful discussions. Thanks to Burg Fleming for a very helpful review that improved the paper.

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Correspondence to Kim W. Conway.

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Conway, K.W., Vaughn Barrie, J. Large bedrock slope failures in a British Columbia, Canada fjord: first documented submarine sackungen. Geo-Mar Lett 38, 195–209 (2018).

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