Crustal structure of the UAE-Oman mountain range and Arabian rifted
passive margin: new constraints from active and passive seismic methods
Abstract
The Semail ophiolite, a thick thrust sheet of Late Cretaceous oceanic
crust and upper mantle, was obducted onto the previously rifted Arabian
continental margin in the Late Cretaceous, and now forms part of the
United Arab Emirates (UAE)-Oman mountain belt. A deep foreland basin
along the west and SW margin of the mountains developed during the
obduction process, as a result of flexure due to loading of the
ophiolite and underlying thrust sheets. The nature of the crust beneath
the deep sedimentary basins that flank the mountain belt, and the extent
to which the Arabian continental crust has thickened due to the
obduction process are outstanding questions. We use a combination of
active- and passive-source seismic data to constrain the stratigraphy,
velocity structure and crustal thickness beneath the UAE-Oman mountains
and its bounding basins. Depth-migrated multichannel seismic-reflection
profile data are integrated in the modelling of traveltimes from long
offset reflections and refractions, which are used to resolve the
crustal thickness and velocity structure along two E-W onshore/offshore
transects in the UAE. Additionally, we apply the virtual deep seismic
sounding method to distant earthquake data recorded along the two
transects to image crustal thickness variations. Active seismic methods
define the Semail ophiolite as a high-velocity body dipping to the east
at 40-45˚. The new crustal thickness model presented in this work
provides evidence that a crustal root is present beneath the Semail
ophiolite, suggesting that folding and thrusting during the obduction
process may have thickened the crust by 16 km.