Comparing vertical profiles of natural tracers in the Williston Basin to estimate the onset of deep aquifer activation. Issue 8 (13th August 2014)

• Record Type: Journal Article
• Authors: Hendry, M. Jim; Harrington, Glenn A.
• Is Part Of: Water resources research. Volume 50:Issue 8(2014:Aug.)
• Page Start: 6496
• Page End: 6506
• Publication Date: 2014-08-13
• Subjects: Hydrology -- Periodicals; 333.91
• DOI: 10.1002/2014WR015652
• Languages: English
• ISSNs: 0043-1397

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>Comparing high‐resolution depth profiles of different naturally occurring environmental tracers in aquitards should yield consistent and perhaps complementary information about solute transport mechanisms and the timing of major hydrogeological and climatological events. This study evaluated whether deep, continuous profiles of aquitard pore water chloride concentration could provide further insight into the paleohydrology of the Williston Basin, Canada, than possible using high‐resolution depth profiles of stable H/O isotopes of water (<italic>δ</italic><sup>18</sup>O, <italic>δ</italic><sup>2</sup>H). Pore water samples were obtained from extracts of cores taken over 392 m of the thick Cretaceous shale aquitard. Water samples were also collected from wells installed in the underlying regional sandy aquifer (Mannville Group; 93 m thick) and from seepage inflows into potash mine shafts (to 825 m below ground). Numerical modeling of the 1‐D vertical Cl<sup>−</sup> profile supported diffusion dominated solute transport in the shales. The modeling also showed a similar time frame for development of the Cl<sup>−</sup> profile prior to activation of the aquifer as determined from the <italic>δ</italic><sup>18</sup>O profile (20–25 Ma); however, it provided a significantly longer and potentially better‐constrained time frame for evolution of the profile during the activation phase of the aquifer (0.5–1 Ma). The dominant paleoevent reflected in present‐day profiles of both tracers is the introduction of glaciogenic meteoric water to the Mannville aquifer underlying the shale during the Pleistocene. The source area of this water remains to be determined.</p> </abstract>