CGRG Bibliography of Canadian Geomorphology
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Author : Daigle, A.E.; and Broster, B.E.
Date : 2004.
Title : Three-dimensional glacial stratigraphy: a tool for aquifer characterization of glacial valley-fills.
Publication : Atlantic Geoscience Society. 2004 Colloquium & Annual General Meeting, January 30 & 31, 2004. Moncton, New Brunswick.
Issue :
Page(s) :
Abstract
Most of New Brunswick.s major river valleys are host to glacial valley-fills demonstrating the characteristic advance and retreat sequences associated with the Wisconsinan Glaciation across North America. Advance sequences are generally characterized by lacustrine, marine, or aeolian sediments of intermixed sands and silts deposited in a proglacial environment; overlain by, coarsening upward glaciofluvial sediments of well sorted stratified sand and gravel with rounded clasts; in turn overlain by, ice contact deposits of poorly-sorted sand and gravel with occasional lenses of till; under-laying over-consolidated basal till of mixed lithologies and grain sizes. The overlying retreat sequence is characterized as the inverse of the advance sequence and is overlain by glaciolacustrine or glaciomarine silts and clays in most of New Brunswick. Post-glacial sediments deposited during the Holocene in fluvial and aeolian environments are commonly found at surface. The false assumption of lateral continuity of valley-fill deposits can lead to over-simplifications of glacial stratigraphy and to the false conclusion that the aquifer is confined at depth. Often vertical pathways are recognized only after the aquifer has been contaminated from conflicting land-uses. However, the stratigraphic relationships and continuity of units can be better assessed spatially, through the use of computer-assisted three-dimensional stratigraphic mapping programs. Advances in computer technology now allow for the rapid processing of large multidisciplinary datasets necessary for the three-dimensional visualization of complex stratigraphic units. By entering existing well logs and borehole data into modeling programs such as RockWorks., geologists, engineers, government agencies and other environmental professionals can add a third dimension to the more common one and two-dimensional mapping techniques currently utilized. This visualization technique leads to a better understanding of complex glacial stratigraphy and the potential environmental concerns associated with land-use practices in glaciated regions, particularly as they pertain to water-supply aquifers associated with valley-fills. The threedimensional glacial stratigraphy of Fredericton, New Brunswick is presented here as an example of the relevance and applicability of this visualization technique for aquifer delineation and wellfield protection.
Bibliography of Canadian Geomorphology