Fold-and-Thrust Belt and Foreland Basin of the UAE-Oman Mountains: Sedimentary Structures, Basement Morphology, Tectonostratigraphic Evolution, and Petroleum System

Abstract

The subsurface geological configuration encompassing structural elements, stratigraphic arrangements, and the petroleum system within the fold-and-thrust belt and foreland basin of the United Arab Emirates remains a subject with limited elucidation. The intricate interrelations between the deep-seated basement structures and sedimentary architecture remain unresolved. Employing seismic, borehole data, and surface geological information, this study entails the interpretation and cartographic representation of twelve stratigraphic horizons spanning from the Miocene to the Lower Jurassic, alongside the Sumeini and Hawasina nappes. Verification of these interpretations is attained through the generation of derivative gravity and magnetic maps. The backstripped analyses delineate a pronounced tectonic event of passive margin rifting, culminating during the early Aalenian period and extending through the Oxfordian epoch. Subsequent to the loading event associated with the Semail ophiolite at ca. 95 Ma, an episode of uplift followed by rapid subsidence is identified at 83 Ma. Enhanced subsidence phenomena are attributed to the late Oligocene-Miocene, correspondingly linked to the initial convergence of the Central Iran and Arabian plates. Employing outcomes from 3D gravity inversion, it is discerned that basement depths fluctuate from 11.5 km along elevated sectors of the FTB to 18.8 km within the foredeep domain. A conspicuous correlation emerges between the elevations of basement structures and adjacent shallower anticlinal configurations, thereby indicative of manifestation of thick-skinned tectonics. Henceforth, it is conjectured that the basement structures underwent reactivation events during the Late Cretaceous obduction phase, along with the late Oligocene to early Miocene collision. Drawing insights from geochemical diagrams and 1D/2D models, predominant source rock formations encompassing the Silurian, Upper Cretaceous, Paleocene-Eocene, and Oligocene strata are identified within the designated area. Maturation levels of Late Cretaceous and Cenozoic source rocks exhibit divergent gradients contingent upon their spatial alignment relative to the FTB and foredeep realms, characterized by a northward maturation gradient. Initiation of hydrocarbon expulsion from Silurian shale units is posited to have transpired during the Middle to Late Jurassic interval, followed by migratory pathways through overlying reservoir formations, primarily influenced by westward migration prompted by lithospheric flexural mechanisms, albeit with sporadic exceptions. Consequently, the hydrocarbons sourced from the Lower Fiqa Formation are inferred to have migrated upwards to the overlying Juwaiza Formation, constrained by the sealing capacity of the Upper Fiqa Formation.

Date of Award	20 Dec 2023
Original language	American English
Supervisor	Mohammed Ali (Supervisor)