Active crustal shortening in NE Syria revealed by deformed terraces of the River Euphrates

The Africa-Arabia plate boundary comprises the Red Sea oceanic spreading centre and the left-lateral Dead Sea Fault Zone (DSFZ); however, previous work has indicated kinematic inconsistency between its continental and oceanic parts. The Palmyra Fold Belt (PFB) splays ENE from the DSFZ in SW Syria and persists for similar to 400 km to the River Euphrates, but its significance within the regional pattern of active crustal deformation has hitherto been unclear. We report deformation of Euphrates terraces consistent with Quaternary right-lateral transpression within the PFB, indicating anticlockwise rotation (estimated as 0.3 degrees Ma-1 about 36.0 degrees N 39.8 degrees E) of the block between the PFB and the northern DSFZ relative to the Arabian Plate interior. The northern DSFZ is shown to be kinematically consistent with the combination of Euler vectors for the PFB and the Red Sea spreading, resolving the inconsistency previously evident. The SW PFB causes a significant earthquake hazard, previously unrecognized, to the city of Damascus.