Consideration of Al-Wajid graben tectono-stratigraphy by analysis of geophysical data, Saudi Arabia

Al-Wajid graben is one of the largest Precambrian fault-bound basins in Saudi Arabia. Seismic reflection data show a deep-seated dome structure in the middle of the graben, which can be interpreted as a salt dome, an inversion structure, or even an igneous pluton. This ambiguity makes it difficult to understand the tectono-stratigraphy of Al-Wajid graben. In this paper we sought to understand the tectono-stratigraphy of Al-Wajid graben by analysis of various remote sensing geophysical data including vertical seismic profile (VSP), gravity, magnetic and seismic reflection data. Determination of depth to basement from the magnetic data suggests that the dome structure is non-magnetic since the depth solutions were obtained at the bottom of the structure. Processing of the VSP data was useful in estimating some physical parameters for the structure in question such as acoustic impedance, velocity, and density. The estimated density is 2700 kg/m(3), which suggests that the structure is unlikely to be salt and most likely to be a dense mafic or metamorphic of non-magnetic rocks. This interpretation is consistent with extension and subsidence of the graben. The integrated interpretation of seismic, VSP, gravity, and magnetic data proposes that Al-Wajid graben is a deep trough intruded by dense magmatic rocks before opening the graben. The cooling of these igneous rocks has caused local densification and continuous subsidence that implied downward bending of the crust, creating the basin as a cratonic graben. Since Precambrian, the graben has been affected by several tectonic phases of extension and compression, ending with positive inversion. (C) 2020 Elsevier B.V. All rights reserved.