* Kuwait Institute for Scientific Research, P.O. Box 24885, 13109 Safat, Kuwait.
** Kuwait University, Department of Earth and Environmental Sciences, P.O. Box 5969, Safat, 13060, Kuwait.
ABSTRACT
The paper summarizes the lithology, structure and the geometry of the main aquifer systems in Kuwait (the Dammam Formation and the Kuwait Group) along with the hydrochemical characteristics of the aquifers.
Kuwait lies between the Arabian Shield and Zagros fold belt at the periphery of the Arabian platform. Structures associated with the Kuwait Arch noticeably control the subsurface configuration of the Dammam Formations and, hence regulate the distribution of the overlying Kuwait Group sediments. For the broad setting, the paleogeography of the Eocene has been constructed.
The main lithologies of concern, both in the surface and subsurface, are the recent and subrecent sediments. The Kuwait Group includes the Dibdibba Formation, and the undifferentiated Ghar and Fars Formations, as well as the Hasa Group comprising the Dammam, Rus and Umm Er-Radhuma Formations.
Subsurface geological cross-sections were constructed for the Dammam Formation, showing its structures, configuration, unconformity, and zones of uplift. Potential sites of karst formation in the Dammam limestone have been identified in the cross-sections. The structural study enables the reconstruction of the paleomorphostructural sections of the Dammam Formation. The chemical investigation indicates that the Kuwait Group aquifer is occupied by Na2SO4 and NaCl water types. In addition, the Kuwait Group aquifer is supersaturated with respect to calcite and is undersaturated with respect to halite, gypsum, anhydrite and dolomite. The Dammam Formation aquifer has Na2SO4, CaSO4 and NaC1 water types. Moreover, the Dammam Formation is supersaturated with calcite and dolomite and is undersaturated with respect to halite, gypsum, and anhydrite. The calculated mean values of the PCO2 of the Kuwait Group and the Dammam Formation aquifers are 3.8 x 10-3 atm. and 2.99 x 10-3 atm. respectively, which are significantly above the PCO2 of the Earth’s atmosphere. This may suggest a deep closed environment.
Keywords: Dibdibba basin; Pre-Neogene unconformity; Dammam Formation; Kuwait Group; Water types.