Geological offsets and age constraints along the northern Dead Sea fault, Syria

North of the Lebanese restraining bend, the northern Dead Sea fault in Syria cuts Late MiocenePliocene intraplate alkali basalts that have [sup.40]Ar/[sup.39]Ar ages ranging between 6.4 [+ or -] 0.1 and 3.7 [+ or -] 0.1 Ma. Despite a wide (40 m) gouge zone in places, only between 5.3 and 16.8 km of Pliocene Recent left-lateral offset occurs along the segment south of Mesyef, where up to 1100 m of down-to-the-east throw has been measured using the base Neogene volcanic rocks as a datum horizon. Although theoretically possible, there is no geological evidence for pre-Pliocene movement along the fault in NW Syria. The fault splays into two transtensional faults bounding the Pliocene A1-Ghab depression and cuts basalts dated at 4.0-3.7 Ma. The minor lateral geological offsets and matching of Mesozoic and Tertiary stratigraphy across the fault show that the northern Dead Sea fault is not a plate boundary, but merely an intraplate fault. The kinematics of NW Syria can be related to a dynamically evolving stress field with time from Miocene NW--SE compression to Pliocene--Recent north--south strike-slip faulting, coupled with minor anti-clockwise rotation, initiation of the Dead Sea left-lateral transtensional strike-slip fault and the transtensional Al-Ghab basin. Supplementary material: Analytical procedures, data tables and concordia diagrams are available at http:// www.geolsoc.org.uk/SUP18423. doi: 10.1144/0016-76492010-009.