2007: Ice-flow history of Placentia Bay, Newfoundland: Multibeam seabed mapping

• Main Authors: D. Brushett, T. Bell, M. J. Batterson, J. Shaw
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Ice Sheet; Newfoundland
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.470.8843; http://www.nr.gov.nl.ca/nr/mines/geoscience/publications/currentresearch/2007/brushett.pdf

This paper reports recent progress made on ice-flow mapping in Placentia Bay, Newfoundland, using multibeam sonar imagery. Flow-parallel features identified on the imagery include drumlins, flutes, mega-lineations, and crag-and-tail land-forms. These features show a general trend of convergent ice flow, which is interpreted to represent fast-flowing ice (an ice stream) down the axis of Placentia Bay. Drumlins and fluted terrain onshore demonstrate that the convergent ice flow can be traced up-ice to regional dispersal centres. Flow-transverse features interpreted as deGeer moraines occur in water depths of 100 to 350 m, and were likely deposited during the deglaciation of the bay as tidewater margins became grounded in shal-low water. Ice-flow mapping of Placentia Bay also demonstrated that the largely depositional record preserved on the seabed is incomplete, with the apparent absence of a strong westward flow onto the Burin Peninsula. The mostly erosional ice-flow record on land also appears incomplete because there is no evidence, to date, for a southwestward ice flow that is recorded by a fluting field on the seabed of southwestern Placentia Bay. The integration of onshore and offshore glacial records in New-foundland represents an important development in mapping palaeo ice-flows and the understanding of ice-sheet behaviour during the transition from largely marine-based to land-based glacial conditions.