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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 112,
B04403,
doi:10.1029/2006JB004485,
2007
Hydrogeologic controls imposed by mechanical stratigraphy in layered rocks of the Châteauguay River Basin, a U.S.-Canada transborder
aquifer
Roger Morin
U.S. Geological Survey, Denver, Colorado, USA
Réjean Godin
Centre d'Études sur les Ressources Minérales, Université du Québec à Chicoutimi, Chicoutimi, Québec, Canada
Miroslav Nastev
Geological Survey of Canada, Québec, Québec, Canada
Alain Rouleau
Centre d'Études sur les Ressources Minérales, Université du Québec à Chicoutimi, Chicoutimi, Québec, Canada
Abstract
The Châteauguay River Basin delineates a transborder watershed with roughly half of its surface area located in northern New
York State and half in southern Québec Province, Canada. As part of a multidisciplinary study designed to characterize the
hydrogeologic properties of this basin, geophysical logs were obtained in 12 wells strategically located to penetrate the
four major sedimentary rock formations that constitute the regional aquifers. The layered rocks were classified according
to their elastic properties into three primary units: soft sandstone, hard sandstone, and dolostone. Downhole measurements
were analyzed to identify fracture patterns associated with each unit and to evaluate their role in controlling groundwater
flow. Fracture networks are composed of orthogonal sets of laterally extensive, subhorizontal bedding plane partings and bed-delimited,
subvertical joints with spacings that are consistent with rock mechanics principles and stress models. The vertical distribution
of transmissive zones is confined to a few select bedding plane fractures, with soft sandstone having the fewest (one per
70-m depth) and hard sandstone the most (five per 70-m depth). Bed-normal permeability is examined using a probabilistic model
that considers the lengths of flow paths winding along joints and bedding plane fractures. Soft sandstone has the smallest
bed-normal permeability primarily because of its wide, geomechanically undersaturated joint spacing. Results indicate that
the three formations have similar values of bulk transmissivity, within roughly an order of magnitude, but that each rock
unit has its own unique system of groundwater flow paths that constitute that transmissivity.
Received 4
May
2006;
accepted 20
November
2006;
published 6
April
2007.
Keywords: hydrogeophysics;
fractured-rock hydrology;
elastic properties.
Index Terms: 1822 Hydrology: Geomechanics; 1829 Hydrology: Groundwater hydrology; 5104 Physical Properties of Rocks: Fracture and flow; 1835 Hydrology: Hydrogeophysics; 1895 Hydrology: Instruments and techniques: monitoring.
Read Full Article (file size: 676353 bytes) Cited by
Citation: Morin, R., R. Godin, M. Nastev, and A. Rouleau
(2007),
Hydrogeologic controls imposed by mechanical stratigraphy in layered rocks of the Châteauguay River Basin, a U.S.-Canada transborder
aquifer,
J. Geophys. Res.,
112,
B04403,
doi:10.1029/2006JB004485.
Copyright 2007 by the American Geophysical Union.
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