Structures and stratigraphy of Al Jaww Plain, southeastern Al Ain, United Arab Emirates: implications for aquifer systems and mantle thrust sheet

Abstract

The United Arab Emirates (UAE) is dependent on desalinated water and shallow aquifers to satisfy its freshwater requirements. Despite the paramount importance of understanding the depth and spatial extent of these aquifers, comprehensive investigations into the properties of these aquifers, as well as the underlying subsurface structures and stratigraphy, have been conspicuously lacking. This study presents the findings of integrated geophysical and borehole investigations conducted in the Al Jaww Plain, southeastern Al Ain, UAE, focusing on the properties of groundwater aquifers, the Semail ophiolite contact, and subsurface structures and stratigraphy. Through the analysis of groundwater borehole data, three interconnected types of groundwater aquifers have been identified, and characterized by their hydrogeological properties. The near-surface Quaternary unconfined aquifer, with an average thickness of 25 m, represents a fresh groundwater aquifer. The second aquifer, with an average thickness of 110 m, is connected to the upper Quaternary freshwater aquifer and is interpreted as part of the surficial aquifer system. The third aquifer has an average thickness of 200 m. By employing electrical resistivity tomography, the depth of the water table and groundwater potential in the shallow unconfined Quaternary aquifer near Jabal Mundassa have been estimated, aligning with the properties observed in the unconfined Quaternary aquifer across the entire Al Jaww Plain as depicted in the groundwater borehole cross section. In addition, this study provides insights into subsurface structures and stratigraphic features, revealing the westward extension of the Hawasina thrust sheet within the plain. Gravity and magnetic data analyses in the southeastern region of the Al Jaww Plain delineate the extent of the Semail ophiolite. Notably, magnetic data reveals the presence of an NW–SE-oriented magnetic anomaly detached from the main ophiolite thrust, which corresponds to the interpretation of the Semail ophiolite contact with sedimentary carbonate rocks on the Bouguer gravity map.