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University of Waterloo (2021)

Assessment of saltwater origin in the Rub’ al-Khali basin and its relation to the formation of sabkha Matti

Saeed, Waleed

Titre : Assessment of saltwater origin in the Rub’ al-Khali basin and its relation to the formation of sabkha Matti

Auteur : Saeed, Waleed

Université de soutenance : University of Waterloo

Grade : Doctor of Philosophy 2021

Résumé partiel
The Rub’ al Khali sand sea is the largest uninterrupted sand desert on Earth that occupies an area of approximately 650,000 km2 of the Arabian Peninsula. Yet, the desert basin is underlying by one of the largest multi-level aquifer systems of the arid world that is the Rub’ al Khali (RAK) structural basin. In this study, water resources in the Cenozoic aquifer systems within the RAK basin were assesses using a combination of geological, hydraulic, hydrochemical, and isotopic approaches. The main goal of this research is to initiate the building of a conceptual model of the regional hydrogeology of the RAK basin in order to assess the constraints and opportunities of the available water resources for future developments. The study shows that the RAK basin is a potential source of fresh to brackish water, with total dissolved solids concentrations (TDS) less than 10,000 mg/l. However, groundwater with up to 200,000 mg/L TDS has been found in the vicinity of a potential discharge zone, known as sabkha Matti. An isotope and solute evaluation was applied to identify the origin and mechanisms of this salinization in three major Tertiary aquifers in the RAK basin. The studied geological succession comprises sedimentary rocks of the Lower Paleocene to Lower Miocene age, and the aquifers primarily consist of the Umm Er Radhuma, Dammam, and Hadrukh. It is demonstrated that the groundwater chemistry evolved from a low- (< 2,000 ppm) to high- (>120,000 ppm) salinity Na-Cl water type, regardless of the aquifer. The similarity in water types between the groundwater from the different formations suggests that the same origin and geochemical processes may be controlling the salinity and major ion chemistry in these aquifers. The suite of hydrogeological, hydrochemical (Cl vs. Br), and isotopic (Cl vs δ18O and Br vs δ81Br) data indicate that the source of solutes is associated with the entrapment of evaporated paleo-seawater (connate water) in nearshore and lagoonal environments during the time of deposition. Moreover, the results from the 87Sr/86Sr ratios show no evidence of significant vertical connectivity between the three Tertiary aquifers.

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Page publiée le 11 avril 2021