الملخص الإنجليزي
The unique tectonic setting of the Oman Mountains and the Semail Ophiolite, together
with ongoing hydrocarbon exploration, have focused geological research on the
sedimentary and ophiolite stratigraphy of Oman. However, there have been few
investigations of the crustal-scale structure of the eastern Arabian continental margin. In
order to rectify this omission, we made a 255-km-long, southwesterly oriented crustal
transect of the Oman Mountains from the Coastal Zone to the interior Foreland via the
3,000-m-high Jebel Akhdar. The model for the upper 8 km of the crust was constrained
using 152 km of 2-D seismic reflection profiles, 15 exploratory wells, and 1:100,000- to
1:250,000-scale geological maps. Receiver-function analysis of teleseismic earthquake
waveform data from three temporary digital seismic stations gave the first reliable
estimates of depth-to-Moho. Bouguer gravity modeling provided further evidence of
depths to the Moho and metamorphic basement.
Four principal results were obtained from the transect. (1) An interpreted mountain root
beneath Jebel Akhdar has a lateral extent of about 60 km along the transect. The depthto-Moho of 41 to 44 km about 25 km southwest of Jebel Akhdar increased to 48 to 51 km
on its northeastern side but decreased to 39 to 42 km beneath the coastal plain farther to
the northeast. (2) The average depth to the metamorphic basement was inferred from
Bouguer gravity modeling to be 9 km in the core of Jebel Akhdar and immediately to the
southwest. A relatively shallow depth-to-basement of 7 to 8 km coincided with the Jebel
Qusaybah anticline south of the Hamrat Ad Duru Range. (3) Based on surface, subsurface,
and gravity modeling, the Nakhl Ophiolite block extends seaward for approximately
80 km from its most southerly outcrop. It has an average thickness of about 5 km, whereas
ophiolite south of Jebel Akhdar is only 1 km thick. The underlying Hawasina Sediments
are between 2 and 3 km thick in the Hamrat Ad Duru Zone, and 2 km thick in the Coastal
Zone. (4) Southwest of Jebel Akhdar, reactivated NW-oriented strike-slip basement faults
that deformed Miocene to Pliocene sediments were inferred from the interpretation of
seismic reflection profiles.
