Fluid pressure implications of erosional unloading,basin hydrodynamics and glaciation in the Alberta Basin, Western Canada

• Published in: Journal of geochemical exploration 2003-05, Vol.78, p.143-147
• Main Authors: Bekele, Elise B., Rostron, Benjamin J., Person, Mark A.
• Format: Article
• Language: English
• Subjects: Alberta Basin; Earth sciences; Earth, ocean, space; Exact sciences and technology; Paleohydrology; Tectonics. Structural geology. Plate tectonics; Underpressure
• ISSN: 0375-6742; 1879-1689
• DOI: 10.1016/S0375-6742(03)00148-1

Subhydrostatic fluid pressures in the Alberta Basin produce groundwater flow directions that directly oppose regional topography-driven flow, but the processes that contributed to the formation of large underpressures remain equivocal. Previous studies have largely neglected the influence of glacial unloading and focused primarily on erosion; however, the amount of underpressuring simulated by basin models that incorporate long-term erosion is insufficient. Moreover, conflicting rates and timing of erosion have been postulated for the study area. To address these problems, numerical simulations of regional groundwater flow were conducted along a 700-km-wide transect to test competing hypotheses of subnormal fluid pressure generation in the Alberta Basin. Results based on modeling erosion since the Early Eocene and unloading of the Late Wisconsin ice sheet correlate betterwith fluid pressure data from Cretaceous strata than results based on rapid erosion since the Late Pliocene. The effects of glacial unloading should be considered in paleohydrologic studies where recent glaciations have occurred. Subnormal fluid pressures have significance for the timing of major groundwater flow reversals and possible implications for hydrocarbon migration and entrapment.