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Eyles, C.H., 1986

Sedimentation on glacially-influenced continental shelves

Bibliographic Reference

Eyles, C.H., 1986, Sedimentation on glacially-influenced continental shelves: Toronto, Ontario, Canada, University of Toronto, Ph.D. dissertation, 473 p. (5 Microfiches).


This thesis examines the detailed sedimentology of three glacially influenced continental shelf sequences ranging in age from Late Precambrian to Late Pleistocene and representing both ice proximal and distal settings. Glacial influence on sedimentation in distal environments is largely restricted to glacial sediment input and isostatic and eustatic controls on relative sea level; in ice proximal environments glacial influence involves direct deposition and deformation by grounded glacier ice. 1.3 km of vertical sequence through distal glaciomarine deposits of the Plio-Pleistocene Yakataga Formation are described from Middleton Island in the Gulf of Alaska. The succession is dominated by thick, tabular units of massive and stratified diamict formed by settling of suspended sediment and ice-rafting. Diamict lithofacies are interbedded with muds and muddy sands and contain extensive, planar erosion surfaces represented by striated boulder pavements and coquinas (shell-rich beds); boulder pavements formed as marine lag surfaces were overridden and striated by a grounding ice shelf. Channelized and variably graded gravels and sands at the base of the succession are interpreted as sediment gravity flow facies infilling a broad submarine channel cutting the Alaskan continental shelf edge. Late Precambrian diamictite lithofacies of the Port Askaig Formation, Scotland are similar to those of the Yakataga Formation on Middleton Island and form thick, tabular units with upper planar erosion surfaces represented by extensive boulder lags and horizons of soft sediment deformation. However, the Port Askaig diamictites differ from the Yakataga diamicts as they are associated with thick beds of clean, cross-bedded sandstones interpreted as tidal shelf sands. A model combining elements of glacially and tidally-influenced continental shelf sedimentation is developed. Finally, late Quaternary sedimentary sequences of the Isle of Man in the Irish Sea basin illustrate features of ice proximal glacially influenced continental shelf sedimentation. Coarse-grained diamicts, sands, and gravels form irregular drapes on a highly glacitectonized basement and are interpreted as the deposits of broad subaqueous outwash fans formed adjacent to a retreating tidewater ice margin.

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