A morphological and sedimentological analysis of rogen moraine on the Avalon Peninsula, Newfoundland

Marich, Andrea S. (2006) A morphological and sedimentological analysis of rogen moraine on the Avalon Peninsula, Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

This thesis re-examines the glacial landscape of the central Avalon Peninsula, Newfoundland, Canada. Specifically, it focuses on an area of moraine ridges, previous studies of which have generated conflicting interpretation of genesis and deglacial significance. For instance, it has been interpreted as a series of recessional moraines, and as a field of Rogen moraines. In light of new developments in our understanding of subglacial landscape processes, and in the available technology for mapping and analysis of digital topographic data, it is an appropriate time to re-analyse this landscape and evaluate past interpretations. -- Several methods of data acquisition were employed for this study; air photo interpretation of black and white photos at the 1:50 000 scale and colour photos at the 1:12 500 scale, field research including a review of the sedimentology of the moraine ridges, the construction of a Digital Elevation Model (OEM) for a portion of the study area, and the calculation of moraine ridge orientation within a GIS. -- The moraine ridges of the central Avalon Peninsula are considered to be classical examples of Rogen moraine. An examination of the moraine field using the 1:5000 scale digital elevation model (OEM) with an elevation resolution between 5 and 10m revealed a suite of glacial landforms, including Rogen moraine, hummocky moraine, flutes, meltwater channels and large streamlined bedrock ridges. Rogen and hummocky moraine were found in close association with each other and represent end members of a transitional landform assemblage, with neither landform overprinting the other. An examination of the intern al composition of both Rogen and hummocky moraine revealed similar sediments and structures that suggest deposition via melt-out and sediment gravity flows. The sediment within Rogen moraines and hummocky moraines was transported and deposited subglacially, and later melted out of stagnating ice. -- The timing of glacial events on the Avalon Peninsula are difficult to constrain, but the internal composition and morphology of the Rogen moraines suggest that they were formed during deglaciation. During this phase the ice centre shifted from over the central Avalon Peninsula to the head of St. Mary's Bay. Ice flow out of St. Mary's Bay was radial, with the dominant ice flow direction being in the northeastward direction, and a secondary ice flow northwards into Trinity Bay. The final deglaciation of the Avalon Peninsula is constrained by the C¹⁴ date of 10 100 +/- 250 y BP, from pollen in basal pond sediments. -- The predominant hypotheses of Rogen moraine formation found in the literature were examined in the context of the Avalon Rogen moraines, but currently it is difficult to use any of these previous developed ideas to explain the formation of Rogen moraine on the Avalon Peninsula.

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