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TitleSandstone composition and diagenesis of the Paskapoo Formation and their significance for shallow groundwater aquifer in the Fox Creek area, west-central Alberta
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorLavoie, DORCID logo; Tremblay, V; Rivard, CORCID logo
SourceGeological Survey of Canada, Open File 8982, 2023, 92 pages, Open Access logo Open Access
PublisherNatural Resources Canada
Documentopen file
Mediadigital; on-line
File formatpdf
AreaFox Creek
Lat/Long WENS-118.0000 -116.0000 55.0000 54.0000
Subjectshydrogeology; stratigraphy; sandstones; diagenesis; groundwater; aquifers; hydrostratigraphic units; petrography; calcite; isotopes; oxygen isotopes; stable isotope studies; Paskapoo Formation; Haynes Member; Lacombe Member; Dalehurst Member
Illustrationslocation maps; stratigraphic columns; tables; lithologic logs; diagrams; plots
ProgramGroundwater Geoscience Fox Creek Regional Aquifer System
Released2023 06 06
AbstractThe shallow aquifer in the Fox Creek area is hosted by the Paleocene Paskapoo Formation. The formation consists of fluvial deposits with channel-filled high-energy sandstone cutting through fine-grained, low energy overbank sediments. Three internal members are recognized, these members define three hydrostratigraphic units (two aquifers versus one aquitard). In fall 2022, three boreholes were drilled and cored. The succession is slightly dominated by sandstone with subordinate fine-grained sediments and thin coal intervals. The calcareous to non-calcareous sandstone is either tight and well compacted or porous, friable to unconsolidated. The litharenite is composed of quartz, various types of rock fragments, chert, and feldspars. Detrital carbonates can be abundant. The post-sedimentation history of the sandstone recorded cementation and dissolution events from near surface, through shallow burial and late tectonic exhumation. The events include early clay coatings on grains, dissolution of metastable minerals, cementation from calcite, kaolinite and minor chlorite and late near surface fault-controlled freshwater circulation and dissolution. The late event resulted in friable to unconsolidated sandstone intervals.
Summary(Plain Language Summary, not published)
The fluvial deposits of the Paleocene Paskapoo Formation form the shallow aquifer in the Fox Creek area. The cores of three boreholes drilled in 2022 contain, at various depths, intervals of unconsolidated sands present between well compacted sandstones. These enigmatic intervals were rarely described previously and the cause for these was never addressed. Understanding the reason for these is important as they constitute preferential intervals for aquifer high transmissivity. The petrography of 20 sandstone samples has shown that they are dominated by quartz and rock fragments, the coarse-grained sandstone commonly displays high porosity. Particles are locally surrounded by thin clay rims and small volume of cements were precipitated in the pore space before the exhumation of the formation in Eocene. Evidence of dissolution of feldspars, carbonate and volcanic rock fragments are visible, all of which increased the total porosity of the sandstone. Late freshwater infiltration along faults and fractures was responsible for a final major dissolution event in some highly porous beds leading to the creation of the unconsolidated sandstone intervals.

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