Tectonics of the Pliocene Homs basalts (Syria) and implications for the Dead Sea Fault Zone activity

Timing of activity along the Yammuneh segment (Lebanon-Syria) of the Dead Sea Fault Zone and its northward continuation is still a subject of controversy. Our field structural analysis and observations on radar, Landsat and digital elevation model imagery of the Horns region (Syria) are of concern for Plio-Quaternary tectonics of the whole northern part of the Dead Sea Fault Zone. We show in this paper that the northern Dead Sea Fault Zone has remained active since the onset of the Horns basalts at c. 6 Ma. Continuing movement in Recent times is indicated by the occurrence of Quaternary pull-apart structures and offset of active ravines along the fault. The Homs basalts are related to the distinct oval-shaped Shin volcanic edifice, of which the long axis trends NW. The volcano was fed through NW-striking tension fractures, which now form dykes and volcanic ridges. These patterns are consistent with a NE-SW extension that occurred c. 6 Ma ago. The northwestern end of the Shin volcano is left-laterally displaced c. 20 km, yielding a c. 3.3 mm a(-1) mean rate of relative movement between the Arabian and African plates. In the northern part of the Dead Sea Fault Zone, the overall trace of the main active Dead Sea Fault Zone is not a single transform but forms an irregular plate boundary composed of transform fault and collision belt segments. Fine-grained mylonite developed in the fault corridor may have favoured aseismic deformation in the Shin volcano area.