VARIATIONS IN SALINITY STRUCTURE IN SASKATCHEWAN’S DEVONIAN CARBONATES
Date
2019-03-12
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0003-3267-044X
Type
Thesis
Degree Level
Masters
Abstract
Industry provided and public domain geochemical and isotopic data from 1950 to present day were collected for the purpose of this research. The intent of this study is to better understand the groundwater flow patterns and hydrochemistry in Devonian carbonates within the Saskatchewan and Williston basins. The Birdbear, Duperow, Souris River, and Dawson Bay formations are of interest owing to their proximity to the mining units of the Prairie Evaporite Formation. Due to the undesirable outcomes of groundwater interacting with the soluble minerals of the mining unit, the understanding of the nature of the water contained in the overlying units is of great importance. The creation of a comprehensive database has allowed for graphical as well as spatial analysis of water chemistry data within the basin. In addition, it is now possible to assess for patterns of variation and to attempt to track chemical evolution at a regional scale through the manipulation of this data.
By combining data on water chemistry, interpreting the salinity characteristics and expressing the results in a spatial context, information on mineral precipitation, dissolution, and fluid migration were obtained. Patterns found were then utilized to assess regional scale hydrogeology, recharge and discharge. Through a graphical and regional assessment of the stratigraphic hydrochemistry it has been shown that the four units differ. The Birdbear, Duperow, Souris River, and Dawson Bay formations were shown to comprise of an end member type system ranging from meteoric water dominated to original syndepositional evaporated sea water dominated chemistries.
Ratios of Na to Cl and Br to Cl, TDS concentrations, as well as δD and δ18O isotope values of water samples have demonstrated Birdbear and Duperow formations have seen the greatest influence from meteoric water input and halite dissolution while the Dawson Bay Formation shows a signature indicative of syndepositional evaporated sea water. The Souris River Formation consists of a mixture of these two end-member hydrochemistries. At a regional scale, the four formations follow known trends in hydrogeology, with recharge indicated in in the south and south west sides of the basins, and discharge in the north and north east along the Manitoba escarpment. Concentrations of TDS also support the location of previously mapped large-scale evaporite dissolution features. It has been shown using TDS, Na/Cl, and δH2/δO18 that the signature of a water sample from a stratigraphic unit in the center of the basin can look identical to that of the signature of a different stratigraphy at the basin edge. Resultant variation in salinities, indicating the different sources of ground water as well as the evolution through various degrees of water rock interaction, has raised questions on the validity of attempting to use chemistry to stratigraphically fingerprint water samples. It has been shown groundwater salinity characteristics have a great degree of variability depending on the location in the basin. Therefore when attempting to use chemistry to determine which stratigraphic horizon a water sample comes from it is essential that both a thorough regional and local scale hydrochemical analysis are done.
Description
Keywords
Hydrogeology, Devonian, Fluid Flow, Groundwater, Mixing, Saskatchewan, Elk Point Basin, Williston Basin, Potash
Citation
Degree
Master of Science (M.Sc.)
Department
Civil and Geological Engineering
Program
Civil Engineering