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

Very large (>60×10 6 m 3 ) 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) immedia...

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Bibliographic Details
Published in:Geo-marine letters 2018-06, Vol.38 (3), p.195-209
Main Authors: Conway, Kim W., Vaughn Barrie, J.
Format: Article
Language:English
Subjects:
Bedrock
Coastal zone management
Composition
Deformation
Deglaciation
Dislocations
Earth and Environmental Science
Earth Sciences
Escarpments
Failures
Faults
Fjords
Fractures
Geology
Geomorphology
Gravitation
Holocene
Joints (timber)
Landslides
Meltwater
Original
Radiocarbon dating
Recent sediments
Sea level
Sediment
Sediments
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Description
Summary:Very large (>60×10 6 m 3 ) 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.
ISSN:0276-0460
1432-1157
DOI:10.1007/s00367-018-0533-y