The Role of Bedding Fractures in the Hydrogeology of Sedimentary Bedrock—Evidence from the Newark Basin, New Jersey

Abstract

Bedding‐plane partings, particularly those enlarged by stress relief, tend to provide principal ground‐water flow pathways which are often overlooked. In order to identify them, the use of a proper conceptual model of the bedrock aquifer system and appropriate methods of hydrogeologic characterization are necessary. Several pervasive bedding partings were identified at a study site located within a dipping sequence of mudstone and shales, typical of the Passaic Formation in the Newark Basin of New Jersey. These bedding fractures constitute the discrete aquifer units of a multiunit, leaky bedrock aquifer system. One such unit of exceptional transmissivity (the “Raritan unit”) was identified and selected for a detailed characterization. Results of three short‐duration pumping tests verified the continuity and relatively uniform transmissivity of the Raritan unit over distances exceeding 1,500 feet. Significant hydrochemical differences between the various aquifer units at this 100‐acre site were found to be consistent with the multiunit structure of the bedrock aquifer system. A similar pattern can be observed in regional hydrochemical data recently published by others. The principal finding, that a few bedding fractures dominate ground‐water flow at many sites in the region, has a major implication on hydrogeologic characterization requirements for the water supply, well‐head protection, and aquifer remediation projects in the Newark Basin and similar areas of sedimentary bedrock.

Fractured‐Aquifer Hydrogeology from Geophysical Logs: Brunswick Group and Lockatong Formation, Pennsylvania

“…Flowmeter measurements indicate that productivity is predominantly confined to the upper 80 m of this aquifer and, correspondingly, most ground water flow is channelled through the shallow-dipping features. Michalski and Britton (1997) conducted field investigations in other parts of the Newark Basin and similarly found the principal fluid pathways to be shallow bedding planes.…”

Comportement hydraulique des milieux faillés /

“…Un tel schéma demeure très approximatif, et l'allure des courbes est spéculative. Néanmoins, les tendances illustrées ici synthétisent les résultats publiés dans la littérature (e.g., Evan et al, 1997 ; Michalski et Britton, 1996 ;. En outre, la détermination des propriétés d'un objet particulier tel qu'une faille nécessite sa prise en compte explicite dans le modèle conceptuel.…”

“…L'approche la plus commune consiste à rechercher des informations sur la nature des écoulements en subsurface par des méthodes subsidiaires : géophysique (résistivité, diagraphies...), géochimie des eaux (e.g., Michalski et Britton, 1996), tests de traçage (e.g., Gierczak et al, 2005), tests d'interférences avec obturateurs (e.g., Lemieux et al, 2002 .…”

“…La ségrégation extrême induite par la présence d'une faille s'accompagne de modifications considérables des comportements hydrauliques permanent et transitoire à l'échelle du réservoir, comme le rapportent un grand nombre d'études de cas dans la littérature hydrogéologique et pétrolière (e.g., Michalski et Britton, 1996 ;Labaume et al, 2000 ;Van Tonder et al, 2001 ;Van Tonder et al, 2002 ;Babiker et Gudmunsson, 2004 ;Seaton et al, 2005 ;Gierczak et al, 2006). Ces modifications sont telles que, dans une majorité de cas, les comportements transmis par les milieux failles (et discontinus en général) ne peuvent être reproduits de manière satisfaisante par les modèles interprétatifs conventionnels.…”

Effects of crustal stresses on fluid transport in fractured rock: case studies from northeastern and southwestern USA

“…These deposits consist of gradational sequences of mudstone, siltstone, and sandstone, and encompass important regional aquifers such as the Brunswick Group and the Passaic Formation (Froelich and Robinson 1988). Primary porosity is typically low (3-5%) in these lithified rocks and fractures form the dominant pathways for groundwater flow (Michalski and Britton 1997).…”