ABSTRACT: Évaluation quantitative de l'affouillement glaciel de la plate-forme intertidale à Neuville, Québec

CGRG Bibliography of Canadian Geomorphology
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Abstract

At Neuville, the intertidal shore platform cut into Ordovician Utica shales is largely disturbed by shore ice scouring and plucking. Field measurements have been made in order to determine the importance of ice scouring in rock plafform development. Scoured depressions and associated debris mounds in a selected area were surveyed. The number of depressions and mounds was determined and their sizes were measured; in addition the size of large shale slabs removed by scouring was also measured to evaluate the pressure exerted on the rock substrate by ice floes. In a plot 100 x 100 m subdivised into 16 sub-plots 25 x 25 m, 780 scoured depressions and mounds were observed. The number of features in individual plots range from 25 to 65 with a median of 50. Thirty-six scoured depressions and debris mounds were measured in an enlarged area 200 x 500 m. The volume of rock debris removed amounts to 21 558 400 cm^3 for depressions and 32 472 000 cm^3 for mounds which correspond to an approximate weight of 50 tons. The difference in volume between depressions and mounds is related to empty spaces between the rock fragments removed and irregularities in the shape of mounds. In addition 52 single slabs among the largest in individual mounds were measured. The two largest were 184 x 140 x 18 cm and 213 x 111 x 17 cm for an approximate weight 811 and 781 kg respectively. The weight of main slabs measured in the 100-m side plot amounts to 7.6 metric tons. Measurements made in the 100-m side plot indicate that about 1085 tons of rock debris were removed by shore ice recently. Consequently this erosion process is really important for the Neuville intertidal platform development

Bibliography of Canadian Geomorphology