6. Conclusions
Structural field investigations, map analyses, satellite imagery
analyses, syndepositional thrusting, GPlates reconstructions and
absolute U-Pb dating of synkinematic calcite reveal that eastern Oman
was affected by widely distributed NW-oriented sinistral motion within
and along the Hajar Shear Zone, which is associated with a wrench-fault
assemblage. Shearing affected an area of ~250 km by
~50 km, lasted from ~32.5 to 20 Ma
(Rupelian to Burdigalian) and amounted to a few to several tens of
kilometers displacement. Most shearing was absorbed along
~250 km long major fault zones from the Batinah Coastal
Plain (Jabal Nakhl area), via the Fanja Saddle (Frontal Range Fault and
Wadi Mansah Fault Zone), along the southwestern margin of the Saih Hatat
Dome (Wadi Mansah Fault Zone, Wadi Tayin Fault, Issmaiya Fault Zone,
Coastal Parallel Shear Zone, Ja’alan Fault) to the Batain area. It is
likely that below these shear zones reactivated pre-existing faults
exist, that may have formed during the Pangean Neo-Tethys rifting or
earlier events.
Collected data indicates that pre-existing basement structures were
likely reactivated during times of suitably oriented stress fields.
Thus, such deep-seated structures are responsible for deformation/uplift
at passive margins such as the one in eastern Oman.
The deformation pattern of the Hajar Shear Zone can be correlated with
~N/S-oriented compressional structures in the northern
Oman Mountains (Hagab Thrust, Jabal Hafit Anticline). Thus, these
structures formed during the ~E/W-directed
Arabia/India-convergence and are not related to
~NNE/SSW-directed Arabia-Eurasia shortening. Convergence
between Arabia and India is responsible for a minimum of
~100-130 km E/W-shortening in the Oman Mountains during
the Oligocene and early Miocene.
The Oman Mountains were affected by largely coeval Oligocene/early
Miocene convergence of Arabia-India (E/W) and Arabia-Eurasia (NNE/SSW).
Previously, most mid-Cenozoic structures were belived to have formed in
response to the Arabia/Eurasia-convergence. Our results document that
many of these structures have developed due to the Arabia/India
convergence. Thus, E/W-shorteing in the Oman Mountains and eastern
Arabia played a more important role then previously considered.
A further conclusion related to the ongoing
~WSW/ENE-convergence between Arabia and India is that
respective deformation may have occurred at or near the Arabia-India
plate boundary. Frequently reported earthquakes in the Sea of Oman and
active tectonics/uplift in the Sur/Quriyat area may be due to this
shortening.