Structural controls on groundwater flow in a fractured bedrock aquifer underlying an agricultural region of northwestern New Brunswick, Canada

DesRoches, Aaron; Danielescu, Serban; Butler, Karl

Structural controls on groundwater flow in a fractured bedrock aquifer underlying an agricultural region of northwestern New Brunswick, Canada | Contrôles structuraux sur les écoulements souterrains d’un aquifère de roche fracturée au droit d’une région agricole au nord-ouest de New Brunswick au Canada Controles estructurales sobre el flujo de agua subterránea en un acuífero de basamento fracturado subyacente a una región agrícola en el noroeste de New Brunswick, Canadá 加拿大新布伦瑞克省西北部农业区断裂基岩含水层中地下水的结构控制因素 Controlos estruturais sobre o fluxo de águas subterrâneas num aquífero de rocha fraturada subjacente a uma região agrícola no noroeste de New Brunswick, Canadá

2014

DesRoches, Aaron | Danielescu, Serban | Butler, Karl

A hydrogeological study was conducted in northwestern New Brunswick, Canada, to improve the predictability of fracture-dominated groundwater flow within folded bedrock composed of fine-grained turbidites. Borehole televiewer logging and outcrop mapping, integrated with hydraulic packer tests revealed enhanced hydraulic conductivity associated with northeasterly striking bedding-plane fractures formed during folding and flexural slip. These fractures impart azimuthal anisotropy to the aquifer because of moderately dipping fold limbs. High-angle fractures form a well-developed non-stratabound network, comprising two open fracture sets striking NNE parallel to the current direction of principal stress, and WNW parallel to the direction of principal stress that dominated during the Acadian orogeny. The subset of fractures showing significant oxidation, deemed most important to the groundwater flow system, is dominated by bedding-plane and high-angle fractures striking near-parallel to the maximum principal stress direction, resulting in extensional opening and enhanced hydraulic conductivities. An equivalent porous media model, incorporating anisotropy and varying hydraulic conductivity with depth, indicates that horizontal flow dominates the aquifer with relatively minor exchange between different model layers. These findings have implications for understanding flow directions in the Black Brook Watershed and elsewhere in the Matapédia Basin where fractures formed under similar stress conditions.

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