Abstract
The Karoo Basin in South Africa is a water-stressed region but little is known about the deep groundwater in the region. Sub-thermal groundwaters, defined for the Karoo as >25°C, emanate from springs or boreholes but there is no direct access to deep (>1500m) Karoo groundwater. Sub-thermal groundwaters are therefore taken to represent deeper groundwater since there is no heat source in the Karoo other than that generated by burial. Analysis of sub-thermal groundwaters, as a precursor to possible shale-gas development in the Karoo, has produced a complete set of 14C, 3H, 36Cl, 4He isotope data for a range of different groundwater types and allows comparison of their effectiveness for evaluating the residence time of Karoo groundwater. 14C activities range from > 94 pmC to as low as 20 pmC, implying a range of apparent ages from modern to >20,000 years. 3He/4He ratios indicate a similar range of ages and in both cases the shallow groundwater is younger whilst the sub-thermal spring waters are generally older. 36Cl/Cl ratios showed comparable differences between shallow and deep groundwater. Variations in 3H activities are less clear but shallow groundwaters generally have higher 3H activities. Deviations from this pattern suggest a range of mixing processes for the different groundwater types. In general, the sub-thermal groundwater showed much longer residence times than shallow groundwater, implying that sub-thermal groundwaters are a reasonable proxy for deep groundwater in the Karoo.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.