Kinematics of the Amanos Fault, southern Turkey, from Ar/Ar dating of offset Pleistocene basalt flows: Transpression between the African and Arabian plates

We report four new Ar/Ar dates and 18 new geochemical analyses of Pleistocene basalts from the Karasu Valley of southern Turkey. These rocks have become offset left-laterally by slip on the N20°E-striking Amanos Fault. The geochemical analyses help to correlate some of the less-obvious offset fragments of basalt flows, and thus to measure amounts of slip; the dates enable slip rates to be calculated. On the basis of four individual slip-rate determinations, obtained in this manner, we estimate a weighted mean slip rate for this fault of 2.89 ± 0.05 mm/a (± 2?). We have also obtained a slip rate of 2.68 ± 0.54mm/ a (±2?) for the subparallel East Hatay Fault farther east. Summing these values gives 5.57 ± 0.54mm/a (±2?) as the overall left-lateral slip rate across the Dead Sea fault zone (DSFZ) in the Karasu Valley. These slip-rate estimates and other evidence from farther south on the DSFZ are consistent with a preferred Euler vector for the relative rotation of the Arabian and African plates of 0.434 ± 0.012° Ma -1 about 31.1°N, 26.7°E. The Amanos Fault is misaligned to the tangential direction to this pole by 52° in the transpressive sense. Its geometry thus requires significant fault-normal distributed crustal shortening, taken up by crustal thickening and folding, in the adjacent Amanos Mountains. The vertical component of slip on the Amanos Fault is estimated as c. 0.15 mm/a. This minor component contributes to the uplift of the Amanos Mountains, which reaches rates of c. 0.2-0.4mm/a. These slip rate estimates are considered representative of time since. 3.73 ± 0.05Ma, when the modern geometry of strike-slip faulting developed in this region; an estimated 11 km of slip on the Amanos Fault and c. 10km of slip on the East Hatay Fault have occurred since then. It is inferred that both these faults came into being, and the associated deformation in the Amanos Mountains began, at that time. Prior to that, the northern part of the Africa-Arabia plate boundary was located further east. © The Geological Society of London 2007