CGRG Bibliography of Canadian Geomorphology
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Author : Ayers, K.L.; and Brennand, T.A.
Date : 2005.
Title : Undulating terrain, a new subglacial bedform on the southeastern Plains, Canada.
Publication : Water, Ice, Land, And Life: The Quaternary Interface. Canadian Quaternary Association 2005 Conference June 5-8, 2005, University of Manitoba, Winnipeg, Manitoba.
Issue : Abstract Volume:
Page(s) : A1.
Abstract
Digital Elevation Models and Landsat images of the Southeastern Plains reveal at least five fields of undulating terrain. This landscape consists of fields of subparallel ridges separated by depressions, ranging in relief from 2 to 30 m, and with intracrest spacing typically greater than 1 km. Each undulating terrain field is located on a regional slope or at a topographic step within broad subglacial landsystem tracts. Although a conspicuous feature on DEMs and Landsat images, undulating terrain of this scale has not been identified in previous research on the Southeastern Canadian Plains. This paper describes the composition of undulating terrain spanning the Qu'Appelle and Pembina valleys and abutting the Assiniboine valley. Formative processes are inferred from morpho-sedimentary relationships and landform associations. Exposures reveal highly variable ridge compositions including massive diamicton, deformed sand and gravel, stacked and folded shale and diamicton, and fractured horizontally-bedded shale. Substrate deformation is consistent with a glaciotectonic origin for the sediments within some ridges; however, structural measurements indicate that the deforming force acted at an oblique angle to the ridge axes. Therefore, glaciotectonism was not the sole formative agent of the undulating terrain observed today. A glaciotectonic origin is also inconsistent with ridge formation in truncated, horizontally-bedded and fractured shale. A subglacial origin is inferred from the facts that (i) undulating terrain is superimposed on megascale lineations, and (ii) smaller flutings, eskers and subglacial channels are superimposed on undulating terrain. An erosional origin is inferred from the facts that (i) some ridges are composed entirely of horizontally-bedded shale (truncated at the land surface) and (ii) ridge composition differs between and within tracts of undulating terrain. Erosion by broadly channelized subglacial meltwater flows is consistent with the morpho-sedimentary characteristics of undulating terrain and the landform associations observed. The nascent glaciotectonic or bedrock structures may have provided favourable preconditions for the development of undulating terrain at each locality.
Bibliography of Canadian Geomorphology