AbstractsEarth & Environmental Science

Integrating thermal, geological and hydrogeologic methods to study fractured carbonate rock hydrogeology

by Erin Mundy

Institution: McGill University
Year: 2016
Keywords: Civil Engineering & Applied Mechanics
Posted: 02/05/2017
Record ID: 2064206
Full text PDF: http://digitool.library.mcgill.ca/thesisfile139178.pdf


Proper management of carbonate rock aquifers requires an understanding of the aquifers hydraulic properties and flow dynamics. Faulted carbonate rock aquifers have complex permeability patterns, as faults can act as hydraulic conduits, barriers or combined conduit-barrier systems. Integrated, multi-disciplinary methods are needed in order to gain a more comprehensive understanding of fractured carbonate rock hydrogeology. The objective of this thesis is to use thermal, geological and hydrogeologic methods to better understand fractured rock hydrogeology of carbonate rocks. This was completed using two study areas: 1) an unused quarry in St. Dominique, Quebec, Canada, and 2) an outcrop of the Champlain Thrust fault at Lone Rock Point, Burlington, Vermont, USA. Thermal imagery of groundwater seeps at the quarry was collected over a 22-month period to determine the efficacy of using thermal imagery to quantify groundwater discharge. Thermal imagery is effective at locating and qualitatively characterizing the flux of groundwater seeps. However, the application of thermal imagery is limited by diverse factors including technical issues of image acquisition, diurnal changes in radiation and temperature, and rock face heterogeneity. Groundwater discharge rates could not be directly quantified from thermal imagery in either winter or summer because of these limitations. At the outcrop of the Champlain Thrust fault, structural geology observations were integrated with surficial and subsurface hydrogeological observations. Here, the fault core thickness thickens on the meter-scale, splays out into multiple strands and is offset by a minor normal fault. Groundwater seeps are prevalent in the heavily fractured footwall but limited in the fault core and hanging wall, suggesting at the cliff face the water table is generally near the fault core and groundwater flow in the hanging wall is limited. At the well field, the Champlain Thrust fault is offset significantly by a high-angle structure, the water table is near the surface and aquifer pumping tests reveal a complex hydrogeologic system, with karst and steep fractures as strong hydraulic conduits in the hanging wall and fault core. The most salient features of the fault zone hydrogeology in the surface and subsurface data are different but can be integrated into a preliminary conceptual model. Together the surface and subsurface methods underscore and emphasize the complexity and heterogeneity of the hydrogeology of this low angle sedimentary fault. Une bonne gestion des aquifères des roches carbonatées nécessite une compréhension des aquifères propriétés hydrauliques et dynamique de l'écoulement. Faillées aquifères des roches carbonatées ont des motifs de perméabilité complexes, comme des défauts peuvent agir comme des conducteurs hydrauliques, des barrières ou des systèmes combinés conduit-barrière. Méthodes intégrées, multi-disciplinaires sont nécessaires afin d'obtenir une compréhension plus complète de la fracture hydrogéologie carbonate de roche. L'objectif de cette… Advisors/Committee Members: Susan J Gaskin (Internal/Cosupervisor2), Thomas Gleeson (Internal/Supervisor).