The Kermanshah Crush Zone (Zagros, Iran) comprises elements from the
Tethys Ocean and the former ocean-continent transition. Serpentinites
and gabbros exposed in this area were formerly interpreted as originated
from Tethys ocean and other residual Tethys oceanic domains all situated
northeast of the Bisotoun platform. However, the structural
relationships between these ultramafic units remained unclear. New field
work in the Kermanshah-Harsin area led to the description of detachment
faults over serpentinised mantle. ``Mid-Cretaceous'' carbonate
``extensional allochthons'' (pre-rift) and pelagic sediments (syn- to
post-rift) dated from the Liassic are exposed above these detachments.
Such an age mismatch can be explained by a polyphased mantle exhumation
in a narrow basin along the Arabian margin with the assumption that no
radiolarite nappe has been thrusted over the Bisotoun. Another
detachment has been identified further to the NE on Eocene gabbro. So
far, this one is considered as an intra-oceanic detachment from the
residual Tethys. A first evolution model is proposed from early Jurassic
to late Cretaceous obduction along with how this interpretation may be
improved by future field work.