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Hydrogeologic controls imposed by mechanical stratigraphy in layered rocks of the Cha??teauguay River Basin, a U.S.-Canada transborder aquifer

Journal of Geophysical Research B: Solid Earth

By:
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DOI: 10.1029/2006JB004485

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Abstract

The Cha??teauguay River Basin delineates a transborder watershed with roughly half of its surface area located in northern New York State and half in southern Que??bec 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. Copyright 2007 by the American Geophysical Union.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Hydrogeologic controls imposed by mechanical stratigraphy in layered rocks of the Cha??teauguay River Basin, a U.S.-Canada transborder aquifer
Series title:
Journal of Geophysical Research B: Solid Earth
DOI:
10.1029/2006JB004485
Volume
112
Issue:
4
Year Published:
2007
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Geophysical Research B: Solid Earth