Integrative Structural Evolution of the Eastern Arabian Platform: Decoupling Salt-induced Halokinesis and Zagros-related Compression in the Fractured Neogene and Paleogene Successions

The structural architecture of the Eastern Province of Saudi Arabia is defined by a complex interplay between localized halokinesis and regional compressional stresses. This study provides a comprehensive geological investigation into the mechanical and tectonic linkages between the heavily fractured Late Miocene-Pliocene Hofuf Formation and the Eocene Rus Formation situated at the apex of the Dammam Dome. Historically, these two units have been studied as distinct stratigraphic entities; however, this analysis integrates field observations from Jabal Al-Shuʿba with regional geophysical data to demonstrate a shared deformation history. The Dammam Dome, an oval-shaped structure covering approximately 500 km, is cored by the Infracambrian Hormuz Salt. Its diapiric rise, occurring at rates of up to 7.5 m/Ma during the Neogene, induced a systematic fracture network in the Rus Formation characterized by radial and concentric Mode I tension joints. Concurrently, the Arabian Plate's collision with Eurasia, the Zagros Orogeny, transmitted far-field intraplate stresses that reactivated these older structural grains. Field data from the Hofuf Formation at Jabal Al-Shuʿba reveal a high-intensity, multidirectional fracture system within alternating sandstone and mudstone beds. Unlike the uniform patterns observed at the Dammam Dome apex, the Hofuf fractures exhibit bimodal and conjugate orientations (NNE-NE and NW-SE) with apertures reaching 15 cm. This disparity is attributed to mechanical stratigraphy; the bed-bounded nature of fracturing in the clastic Hofuf Formation prevents the stress relief found in the massive Eocene carbonates, leading to increased fracture density. Furthermore, the identification of a soft-sediment detachment within the Rus Formation suggests that the Dammam Dome served as a sensitive stress sensor for the initial stages of the Zagros collision. By establishing a structural bridge between the Eocene and the Neogene, this study explains how salt-induced uplift and plate-scale compression have combined to create the heavily fractured landscape of Al-Ahsa. These findings offer critical insights for reservoir characterization, groundwater flow modeling, and urban geomechanical stability in the region.