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The geology of ice scour.

Lynas, Christopher M T.Woodworth- (1992) The geology of ice scour. PhD thesis, Prifysgol Bangor University.

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Abstract

Ice scour is the phenomenon that occurs when the keel of a floating mass of ice (iceberg, sea ice or freshwater ice) touches, penetrates and continues to move forward through unlithified seabed or lakebed sediments. The typically curvilinear excavation made by the scouring keel is called a scour mark. Scouring ice keels present logistical problems to the safe installation and operation of, for example, oil and gas production pipelines and power and telecommunication cables in several cold ocean regions. The typical surface morphologies of modern iceberg scour marks on the Labrador continental shelf are described, and mechanisms that operate at or near the sediment surface during the period of ice/seabed interaction are suggested. Scouring action also disturbs sediments beneath the seabed or lakebed. Sub-scour deformation is accommodated by compression and pore space-reduction beneath the scour mark, by corresponding volume increase adjacent to the trough and by folding and faulting. Deformation structures are described from beneath ancient large scale (30-40 m-wide) iceberg scour marks exposed in clays of the former glacial Lake Agassiz in southern Manitoba, and from small scale (< 5 m wide) contemporary scour marks that form on tidal flat sediments in Cobequid Bay, Nova Scotia, and the St. Lawrence estuary, Quebec. Structural data from the Lake Agassiz features are presented and discussed with respect to scour mark-forming mechanisms. Criteria for the recognition of ice scour marks and of ice keel turbates are developed. The criteria are discussed with respect to observations, frequently of striated bedding plane surfaces, contained in the published works of others. The analysis reveals that possible ice scour marks and ice keel turbates may occur in glacimarine and glacilacustrine sediments of Precambrian, Ordovician, Devonian, Carboniferous and Permian age at a number of localities worldwide.

Item Type: Thesis (PhD)
Uncontrolled Keywords: Geology Mineralogy Sedimentology Ships Offshore structures
Subjects: Degree Thesis
Departments: College of Natural Sciences > School of Ocean Sciences
Degree Thesis
Date Deposited: 14 May 2015 04:23
Last Modified: 19 Sep 2016 12:24
URI: http://e.bangor.ac.uk/id/eprint/4200
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