The current understanding of contaminant migration in fractured sedimentary rock aquifers is inadequate due to the difficulty in describing the geologic and hydrogeologic controls on contaminant fate and transport with appropriate detail. To address contamination at fractured rock sites, multiple methods focusing on different aspects of the hydrologic system are required, and particular emphasis needs to be placed on the rock matrix. This thesis shows the further development and utility of the decade-old rock core VOC method (i.e. CORETM), a rock matrix method, when used in conjunction with multiple high resolution datasets as it applies to a 100 m thick highly productive dolostone aquifer in Guelph, Ontario. The research site and surrounding area, located in the northwestern quadrant of the municipality of Guelph, was a productive zone for water supply until the early 1990s when the two closest municipal supply wells (Sacco, Smallfield) were shut down (1991, 1993 respectively) due to volatile organic compounds (VOCs) in the groundwater. Trichloroethene (TCE), a VOC, was used as a degreaser at the Guelph site and likely entered the groundwater more than 20 years ago. The thin overburden, shallow water table, relatively constant dolostone mineralogy, proximity to the UW analytical laboratory, relatively simple plume composition showing minimal degradation, and local importance make this an excellent study site for TCE fate and migration in fractured sedimentary rocks. This thesis is composed of four chapters. Chapter 1 provides a brief background to the rock core VOC method and gives the conceptual framework for the investigation. Chapter 2 focuses on the further development of the rock core VOC method by providing the field validation of a recently adapted extraction method for VOCs in rock core using microwave assisted extraction (MAE), demonstrating the importance of rapid field preservation of samples, and comparing to the industry standard purge and trap method for VOCs on solid matrices. Results indicate that the microwave assisted extraction (MAE) method typically provides equivalent or higher concentrations when compared with the shake-flask and purge and trap extraction methods, indicating more complete extraction or less loss during transfer and/or storage. The purge and trap method provided false negatives (i.e. non-detects) due to inadequate preservation, incomplete extraction, and the elevated detection limit for TCE. The necessity for field preservation was examined by comparing crushed rock samples preserved in methanol in the field to samples unpreserved in the field with a laboratory addition of methanol less than 12 hours later. Chapter 3 creates high resolution porosity and bulk density logs by using selected geophysical logging tools in combination with core derived physical properties for the purpose of calculating porewater concentrations from total contaminant mass concentrations obtained from the rock core VOC method and sample specific rock properties relevant to the conversion. This is beneficial because total mass estimates obtained from the rock core VOC method are not necessarily indicative of the groundwater concentrations given the presence of solid organic carbon controlled sorption. Chapter 4 is a demonstration of the discrete fracture network approach (Parker 2007) applied to the Guelph field site with emphasis on the insights gained through high resolution contaminant profiles generated from cored holes in or near the source area and along a transect. Together, these four chapters present a framework for investigating VOC contamination in fractured sedimentary rocks and with emphasis on evaluating recent advances in the rock core VOC methodology in a field site context.

The current understanding of contaminant migration in fractured sedimentary rock aquifers is inadequate due to the difficulty in describing the geologic and hydrogeologic controls on contaminant fate and transport with appropriate detail. To address contamination at fractured rock sites, multiple methods focusing on different aspects of the hydrologic system are required, and particular emphasis needs to be placed on the rock matrix. This thesis shows the further development and utility of the decade-old rock core VOC method (i.e. CORETM), a rock matrix method, when used in conjunction with multiple high resolution datasets as it applies to a 100 m thick highly productive dolostone aquifer in Guelph, Ontario. The research site and surrounding area, located in the northwestern quadrant of the municipality of Guelph, was a productive zone for water supply until the early 1990s when the two closest municipal supply wells (Sacco, Smallfield) were shut down (1991, 1993 respectively) due to volatile organic compounds (VOCs) in the groundwater. Trichloroethene (TCE), a VOC, was used as a degreaser at the Guelph site and likely entered the groundwater more than 20 years ago. The thin overburden, shallow water table, relatively constant dolostone mineralogy, proximity to the UW analytical laboratory, relatively simple plume composition showing minimal degradation, and local importance make this an excellent study site for TCE fate and migration in fractured sedimentary rocks. This thesis is composed of four chapters. Chapter 1 provides a brief background to the rock core VOC method and gives the conceptual framework for the investigation. Chapter 2 focuses on the further development of the rock core VOC method by providing the field validation of a recently adapted extraction method for VOCs in rock core using microwave assisted extraction (MAE), demonstrating the importance of rapid field preservation of samples, and comparing to the industry standard purge and trap method for VOCs on solid matrices. Results indicate that the microwave assisted extraction (MAE) method typically provides equivalent or higher concentrations when compared with the shake-flask and purge and trap extraction methods, indicating more complete extraction or less loss during transfer and/or storage. The purge and trap method provided false negatives (i.e. non-detects) due to inadequate preservation, incomplete extraction, and the elevated detection limit for TCE. The necessity for field preservation was examined by comparing crushed rock samples preserved in methanol in the field to samples unpreserved in the field with a laboratory addition of methanol less than 12 hours later. Chapter 3 creates high resolution porosity and bulk density logs by using selected geophysical logging tools in combination with core derived physical properties for the purpose of calculating porewater concentrations from total contaminant mass concentrations obtained from the rock core VOC method and sample specific rock properties relevant to the conversion. This is beneficial because total mass estimates obtained from the rock core VOC method are not necessarily indicative of the groundwater concentrations given the presence of solid organic carbon controlled sorption. Chapter 4 is a demonstration of the discrete fracture network approach (Parker 2007) applied to the Guelph field site with emphasis on the insights gained through high resolution contaminant profiles generated from cored holes in or near the source area and along a transect. Together, these four chapters present a framework for investigating VOC contamination in fractured sedimentary rocks and with emphasis on evaluating recent advances in the rock core VOC methodology in a field site context.

Late Ordovician Red River strata of southeastern Saskatchewan were deposited in a broad epicontinental sea. In the lower part, the Yeoman and Herald formations comprise two cycles of carbonateevaporite sequences. Although these units possess an overall layer-cake aspect, thickness variations especially in the Herald Formation show that accumulation was affected by syndepositional flexure, differential subsidence and displacement of fault-bounded blocks. The mainly laminated dolomudstones and anhydrites of the Lake Alma and Coronach members of the Herald Formation were deposited under relatively tranquil conditions. These units host different kinds of synsedimentary deformation features, interpreted to have been induced by earthquakes generated because of movements along basement faults thought to have been oriented orthogonally NE−SW and NW−SE. The low-energy environmental setting was conducive to preserving these features, referred to as seismites.<p> The variety of seismites in the Herald Formation is related to the varying rheology of the carbonate or evaporite sediment, as well as shaking intensity. Brittle and quasi-brittle failure is represented by faults, microfaults, shear-vein arrays and pseudo-intraclastic breccias, mostly in dolomudstones which must have been stiff at the time of deformation. Plastic behaviour is recorded by soft-sediment deformation, comprising a family of features that includes loop bedding, folded laminae and convolute bedding. Indeed, these structures in enterolithic anhydrite are more reasonably interpreted as due to deformation than crystal growth, volume expansion and displacement, the more usual explanations. Sediment shrinkage and concomitant fluidization are recorded by dikelets containing injected carbonate mud or granular gypsum, the latter now preserved as anhydrite. Evidence for wholesale liquefaction, however, was not observed. These rheological differences were caused by the primary nature of the sediment plus modifications due to early diagenesis and burial confinement. Shaking intensity is difficult to gauge, but it is presumed that a minimum of VI on the modified Mercalli scale was required to produce these features. Consequently, shaking of lesser magnitude was probably not recorded.<p> The geographic distribution of seismites should reflect the location of basement faults presumed to have been active during deposition, and indeed there is a concentration adjacent to the known location of syndepositonal fault lineaments. In addition, the stratigraphic distribution of seismites records higher frequencies of activity of these same faults. These distributions show that earthquake-induced ground motion was common during deposition of the Lake Alma Member in southeastern Saskatchewan but less so during deposition of the Coronach Member.<p> Seismites serve as proxies for the activity of relatively nearby syndepositional faults making up the tectonic fabric of sedimentary basins. They also point to basement features that, if re-activated, can induce fracture porosity or influence subsurface fluid flow. Syndepositional tectonism undoubtedly had a much more profound influence on many successions than is presently accepted, and its effects are more widespread than currently appreciated.