Flexural Development in the Foreland Basin Adjacent to Northern Oman-UAE Mountain Belt: Effect of Lithospheric Weakening

Abstract

Inception of obduction is a rare phenomenon in the Wilson cycle and requires specific prerequisites to transfer relatively high-density oceanic lithosphere over the less-dense continental lithosphere. The world's famous Semail ophiolite belt developed during the Late Cretaceous, when Neo-Tethyan oceanic lithosphere obducted onto the rifted Arabian continental margin, forming a foreland basin west of the Oman-United Arab Emirates (UAE) mountain belt. Thus, for a complete understanding of the ophiolite emplacement and formation of the foreland basin, the determination of continental basement rheology is essential. This study assesses lateral variations in the flexural rigidity of the continental lithosphere beneath the eastern Arabian Peninsula and its role in shaping the Late Cretaceous foreland basin. We employ 2D flexural backstripping analysis along two crustal-scale cross-sections, coupled with exploration well data, to reconstruct paleogeographic conditions and determine the effective elastic thickness (Te) of the lithosphere. Te exhibits contrasting values, with higher values (40 km) in the western UAE and lower values (20–25 km) beneath the foreland basin and Semail ophiolite belt. Elevated Te in the western basin indicates a minor influence of Late Permian and Late Jurassic extensional phases on flexural rigidity, with the decreasing trend toward the orogenic belt attributed to the obduction process. Furthermore, we carried out forward flexural modeling to simulate a ∼6.0 km deep and 60 km wide Late Cretaceous foreland basin. The model incorporates lateral variations in flexural rigidity (Te range from 20 to 45 km), sediment loading (up to 6 km), and lithospheric plate shortening. It predicts enduring deep-water conditions and a flexed Arabian continental margin since the Late Cretaceous, aligning with geological findings from subsurface and structural data. The shortening due to plate convergence allows in situ vertical movement of the forebulge and narrowing of the foreland basin. Our modeling underscores the sensitivity of foreland basin architecture and bulge migration to variations in flexural rigidity and paleo-topographic loading during thrust belt accretion.