ABSTRACT: Quantitative methods in the evaluation of the Quaternary geology of the Sand River (73 L) map sheet, Alberta, Canada

CGRG Bibliography of Canadian Geomorphology
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Abstract

The Sand river map sheet, located in east-central Alberta, possesses several bedrock channels buried beneath Quaternary glacial deposits and known only from drill hole information. A total of 995 samples from 78 drill holes were analyzed for 22 compositional properties in an attempt to delineate the stratigraphy of the till units present. The measurements included granulometry, grain lithology, calcium carbonate equivalent and bulk (major and minor element) chemistry. A reliable, rapid, constant-volume carbonate analysis apparatus was developed for the project. Bulk chemistry was performed by fusing till samples into glasses and analyzing them using energy- dispersive electron microprobe techniques. The correction procedures required for quantitative energy-dispersive analysis are described in some detail, along with EDATA, a computer program for applying them. Corrections are applied for atomic number, absorption and fluorescence effects, instrumental calibration corrections, background (X-ray continuum) shaping and fitting as well as peak overlaps. Problems are often encountered in contour mapping of irregularly spaced data points by computer, and new techniques have been devised and implemented in the TRIMAP package, based on subdividing the map area into triangles. Features include the use of triangular element data structures, a local homogeneous coordinate system, the automatic generation of a triangular network, the selection of a suitable triangle optimization criterion and the choice of a suitable smooth interpolant over individual triangular domains. Four distinct till units were distinguished in the study area on the basis of their compositions. A high carbonate middle till separates an upper and a two member lower till.The compositional parameters of these tills were categorized as textural, erratic or local. In the fine fraction of a till unit, vertical compositional variation was low by comparison with lateral variation, which appeared to be related to sub-ice topography. The glacial history proposed relates the four suggested ice advances to the varying regional drainage as indicatedby the major bedrock channels. The regional topography at each stage was estimated. Compositional analysis of tills, as well as the topographic reconstruction of stratigraphic boundaries, is important in studies of glacial history

Bibliography of Canadian Geomorphology