CGRG Bibliography of Canadian Geomorphology
Search Results
Author : Marquette, G.; Gray, J,T,.; Courchesne, F.; and Gosse, J.
Date : 2000.
Title : Studies on felsenmeer-covered surfaces in the Torngat Mountains, Northern Québec-Labrador.
Publication : 30th International Arctic Workshop, Program and Abstracts, 2000. Institute of Arctic and Alpine Research, University of Colorado at Boulder
Issue :
Page(s) : 121-123.
Abstract
Over the last century two fundamentally opposing views have been expressed concerning the felsenmeer covered summits of the Torngat Mountains. From observations along the Labrador coast, Daly (1902), Coleman (1921), Dahl (1946), Ives (1958, inter alia) and Clark (1991) have suggested that they represent, either 1) nunataks, not covered by the Laurentide ice sheet during the Last Glacial Maximum (LGM), or 2) summits protected from glacial erosion by cold-based ice. Odell (1933) and Tanner (1944) argued for the production of the felsenmeer by postglacial weathering, and suggested that the summits had been overridden by the continental ice sheet. Excavations by Gangloff (1983) into three of the felsenmeer surfaces revealed a matrix with grain size and shape characteristics and clay mineralogy totally indistinguishable from tills of the last glaciation at low altitudes. Recently the concept of a Torngat mountain ice dispersal centre during the LGM, with subsequent invasion of the valleys by the continental ice sheet from the west has been invoked for the Ungava Bay flank of the northern Torngat Mountains (Gray et al., 1996; Gray (in press)), and the existence of felsenmeer surfaces at relatively low elevations (ca 750 m) on isolated plateau surfaces appears to support this concept. Against this background, a research program aimed at studying the nature, the spatial and vertical distribution and the chronology of the felsenmeer covered surfaces of the Torngat Mountains was begun in the summer of 1999. Three overall objectives have been defined for this program: 1) computer and remote sensing assisted mapping of the spatial and vertical distribution of the felsenmeer surfaces; 2) examination of the relative weathering characteristics of the fine matrix for selected felsenmeer summits; and 3) exposure dating of stable rock surfaces using terrestrial cosmogenic nuclides. We are also compiling results of recent glacial studies by others in the region. The ultimate objective is to use the field observations, mapping, and exposure ages as boundary conditions for a refined ice sheet model of the Québec-Labradorean sector of the Laurentide Ice sheet. In this talk, our remarks will be restricted mainly to the initial results. Firstly, field observations made up to and including 1999 by us, and by previous researchers (Ives, 1957; Loken, 1962), for approximately 30 summit zones along an east-west transect through the northern Torngat Mountains, along with isolated observations obtained during a brief visit to a summit zone in the Kaumajet Mountains on the Labrador coast (Figure 1) will be used as training sites to classify the felsenmeer surfaces. Initially, for a local area mapping of the lower felsenmeer limit for low gradient surfaces used a combination of newly acquired Radarsat fine mode imagery with a resolution of 10 m and digitised air photographs draped over a DEM. The potential of such imagery for detecting the contrast between smooth glaciated bedrock or till covered surfaces and high rugosity felsenmeer surfaces will be discussed. Extension of such mapping to a regional scale will be attempted using a newly acquired Landsat enhanced thematic mapper, with a 15 m spatial resolution panchromatic channel, and 6 visible and short wave infra-red channels for defining the spectral and textural signatures of the felsenmeer surfaces. Secondly, we will present the result of some pedological analyses of samples from three soil pits dug beneath the angular surface rubble of three summits, two transitional zones and one summit overridden by an ice sheet (Figure 1). These analyses are designed to assess the degree of relative weathering of such surfaces and will complement the results of ongoing terrestrial cosmogenic nuclide exposure dating. Initially they have included the measurement of pH, percentage of organic carbon and clay mineralogy. Planned analyses also include the quantification of iron and aluminum oxides and SEM analyses of quartz grains.
Bibliography of Canadian Geomorphology