Region 19, Northeastern Appalachians

Randall, Allan D.; Francis, Rory M.; Frimpter, Michael H.; Emery, James M.

doi:10.1130/dnag-gna-o2.177

Cited by 15 publications

(9 citation statements)

References 2 publications

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“…The permeability distribution is therefore highly variable. The most dominant feature for groundwater flow is the fractures and faults that formed along with the mountains (e.g., Randall et al [1988] for the Appalachians) as well as the deformed lithology (e.g., Foxworthy et al [1988] for the Cordillera). Water flows mainly through the fractures under gravity drainage from the high elevations to the lower valleys.…”

Section: Bedrock Hydrogeologymentioning

confidence: 99%

“…[11] The hydraulic properties of the shallow rocks of the Appalachians were compiled by Randall et al [1988]. Hydraulic conductivity values for porous and nonporous bedrock varies between 1.1 Â 10 À6 m/s (%35 m/a) to 1.65 Â 10 À5 m/s (%520 m/a).…”

Section: Bedrock Hydrogeologymentioning

confidence: 99%

“…Information is scarce regarding the groundwater chemistry of the orogenic belts. For the Appalachians, most of the bedrock is low soluble and the concentration of dissolved solids, even for deep wells, is low and rarely exceed 1000 mg/L [Randall et al, 1988].…”

Section: Groundwater Geochemistrymentioning

confidence: 99%

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Simulating the impact of glaciations on continental groundwater flow systems: 2. Model application to the Wisconsinian glaciation over the Canadian landscape

et al. 2008

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[1] A 3-D groundwater flow and brine transport numerical model of the entire Canadian landscape up to a depth of 10 km is constructed in order to capture the impacts of the Wisconsinian glaciation on the continental groundwater flow system. The numerical development of the model is presented in the companion paper of Lemieux et al. (2008b). Although the scale of the model prevents the use of a detailed geological model, commonly occurring geological materials that exhibit relatively consistent hydrogeological properties over the continent justify the simplifications while still allowing the capture of large-scale flow system trends. The model includes key processes pertaining to coupled groundwater flow and glaciation modeling, such a densitydependent (i.e., brine) flow, hydromechanical loading, subglacial infiltration, isostasy, and permafrost development. The surface boundary conditions are specified with the results of a glacial system model. The significant impact of the ice sheet on groundwater flow is evident by increases in the hydraulic head values below the ice sheet by as much as 3000 m down to a depth of 1.5 km into the subsurface. Results also indicate that the groundwater flow system after glaciation did not fully revert to its initial condition and that it is still recovering from the glaciation perturbation. This suggests that the current groundwater flow system cannot be interpreted solely on the basis of present-day boundary conditions and it is likely that several thousands of years of additional equilibration time will be necessary for the system to reach a new quasi-steady state. Finally, we find permafrost to have a large impact on the rate of dissipation of high hydraulic heads that build at depth and capturing its accurate distribution is important to explain the current hydraulic head distribution across the Canadian landscape.

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Section: Bedrock Hydrogeologymentioning

confidence: 99%

Section: Bedrock Hydrogeologymentioning

confidence: 99%

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Simulating the impact of glaciations on continental groundwater flow systems: 2. Model application to the Wisconsinian glaciation over the Canadian landscape

et al. 2008

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“…Yields are generally lower where till, as op posed to stratified drift, overlies bedrock, a condition that characterises both study areas (Randall et al, 1988). The Lawrencetown Till is the dom inant overburden cover and in general has a low conductivity (Fenton, 1998).…”

Section: G E O L O G Ymentioning

confidence: 99%

Influence of regional geology and hydrogeology on river habitat quality: examples from Mill Brook and Elderkin Brook, Kings County, Nova Scotia

Spooner

Fenton

Myers

1998

atgeol

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Elderkin Brook and M ill Brook are tributaries of the Cornwallis River and were investigated with the intent of understanding the geological conditions that could influence both habitat quality and river restoration efforts. The Cornwallis River and its tributaries have been the focus of restoration efforts in an attempt to re-establish brook trout (Salvelinus fontinalis) and Atlantic salmon (Salmo salar) populations. Both tributaries are relatively short, highgradient headwater streams that are ungraded along much of their length.Data from Elderkin Brook indicate that pyrite-rich slate of the Kentville and Halifax formations that dominate the watershed geology do not govern the pH of the river discharge. The carbonaceous New Canaan Formation buffers regional groundwater and has resulted in elevated pH levels (7.5-8.0). Springs in the ungraded portion of Elderkin Brook introduce slightly acidic iron-rich groundwater into the system and, upon contact with the alkaline discharge, have produced sporadic masses of flocculated ferric hydroxide (Fe(OH) 3). Along the upper reaches o f M ill Brook, iron-rich acidic groundwater (pH 5.0-5.5) originating from the Kentville Formation influences the chemistry of the river discharge during low-flow conditions. However, groundwater input from the porous, calcareous-cemented Wolfville Formation that underlies the lower portion of Mill Brook has resulted in locally elevated pH levels (6.0-6.5) and the precipitation of extensive Fe(OH)3 deposits.In both Elderkin Brook and M ill Brook, the precipitation, deposition and preservation of ferric hydroxide is controlled by regional and local, geological and hydrogeological conditions. During the winter and spring, increased discharge and dilution of the groundwater chemistry by precipitation keep iron in either solution or suspension. During low-flow periods (primarily in the fall) flocculated ferric hydroxide accumulations develop coincident with the spawning of both fish species. These conditions result in both temporally and spatially constrained habitat degradation that may be difficult to recognise using the habitat evaluation techniques that are presently being employed by river management groups.

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“…Randall et al (1988) noted that for the Northeastern Appalachian groundwater region, flow is generally most rapid in the uppermost 15 to 35 m below the bedrock surface, with fractures much less abundant below 75 m depth, but with localized productive zones at depths of 100 to 650 m. Diggins (2014) investigated fracturing in granite, schist, and amphibolite in the Appalachian belt in Massachusetts, noting minimal flow below 170 m and the majority of flow constrained to the upper 100 m. Dummer et al (2015) recorded that most of Nova Scotia's 117 000 domestic wells in bedrock aquifers are less than 155 m deep. Baechler and Boehner (2014) suggested that active karst solution of saline evaporite rocks on Cape Breton Island can occur locally at depths exceeding 400 m. Farvolden et al (1988) in an assessment of crystalline rocks in the Canadian Precambrian Shield stated that while a case can be made for a log-linear decrease in hydraulic conductivity with depth in the upper 100 to 400 m, fracture zones associated with steep fault zones have been encountered down to at least 1000 m.…”

Section: Present-day Hydrological Settingmentioning

confidence: 99%

Geology and Hydrogeology of Faults on Cape Breton Island, Nova Scotia, Canada: an overview

Baechler¹

2015

atgeol

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Cape Breton Island provides a hydrogeological view into the roots of an ancient mountain range, now exhumed, glaciated, and tectonically inactive. It exhibits deep crustal faults and magma chambers associated with formation of the Appalachian mountain belt and the Maritimes Basin during the Paleozoic, as well as Mesozoic rifting relating to the opening of the Atlantic Ocean. Cenozoic exhumation brought these features near surface and into the active groundwater flow field where they were impacted by glaciation and fluctuating sea level. The faults have been important from a societal viewpoint in development of municipal groundwater supplies, controlling inflows to excavations, hydrocarbon exploration, quarry development, and geotechnical investigations. Conceptual models presented here outline fault control on groundwater flow based on seven case studies. Future research should focus on basin-bounding faults in support of managing their role in aquifer development and protection, mountain-front recharge, controlling large-magnitude springs, groundwater-stream interaction, and channel morphology. The hydrogeological importance of these faults has historically been underappreciated. rÉSUMÉ L'île du Cap Breton procure un aperçu hydrogéologique des racines d'une ancienne chaîne de montagnes, maintenant exhumée, érodée par la glaciation et tectoniquement inactive. Elle présente des chambres magmatiques et des failles crustales profondes associées à la formation de la ceinture montagneuse des Appalaches et du bassin des Maritimes au cours du Paléozoïque, ainsi qu'au rifting du Mésozoïque lié à l' ouverture de l' océan Atlantique. L' exhumation survenue durant le Cénozoïque a rapproché ces particularités de la surface à l'intérieur du champ d' écoulement des eaux souterraines actif, où elles ont été touchées par la glaciation et les fluctuations du niveau de la mer. Les failles se sont avérées importantes sur le plan sociétal pour l' établissement de réserves municipales d'approvisionnement en eau souterraine, le contrôle des infiltrations d' eau dans les excavations, la prospection des gisements d'hydrocarbures, l'aménagement des carrières et les études géotechniques. Les modèles conceptuels présentés illustrent le contrôle par les failles de l' écoulement des eaux souterraines d'après sept études de cas. Les recherches futures devraient porter sur les failles délimitant des bassins aux fins de la gestion de leur rôle dans le développement et la protection des aquifères, l'alimentation du front des secteurs montagneux, le contrôle des sources de forte magnitude, l'interaction entre les eaux souterraines et les cours d' eau et la morphologie des canaux. L'importance hydrogéologique de ces failles a été sousestimée par le passé. [Traduit par la redaction]

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Region 19, Northeastern Appalachians

Cited by 15 publications

References 2 publications

Simulating the impact of glaciations on continental groundwater flow systems: 2. Model application to the Wisconsinian glaciation over the Canadian landscape

Simulating the impact of glaciations on continental groundwater flow systems: 2. Model application to the Wisconsinian glaciation over the Canadian landscape

Influence of regional geology and hydrogeology on river habitat quality: examples from Mill Brook and Elderkin Brook, Kings County, Nova Scotia

Geology and Hydrogeology of Faults on Cape Breton Island, Nova Scotia, Canada: an overview

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