Kinematic consistency between the Dead Sea Fault Zone and the Neogene and Quaternary left-lateral faulting in SE Turkey

Abstract

A revised quantitative kinematic model has been determined for the Dead Sea Fault Zone (DSFZ) and the left-lateral fault zones in SE Turkey. The relative motions of the African and Arabian plates across the DSFZ are represented by relative rotation about 31.1°N 26.7°E at 0.40±0.02° Ma −1. The northern DSFZ, in Syria and southern Turkey, is interpreted for the first time as a series of transpressional stepovers, along which the left-lateral slip rate is substantially less than the rate of relative plate motion, because this slip is oblique to the plate motion. The slip rate on the East Anatolian Fault Zone (EAFZ) is estimated as ∼8 mm a −1. Restoring its observed slip thus requires its age to be ∼4 Ma. The previous phase of deformation, which involved slip on the Malatya–Ovacık Fault Zone (MOFZ) before the EAFZ came into being, is thus dated to ∼7–4 Ma, suggesting initiation of the North Anatolian Fault Zone (NAFZ) at ∼7 Ma, not ∼5 Ma as previously thought. The total left-lateral slip on the northern DSFZ in southernmost Turkey is estimated as at least ∼65 km, partitioned with ∼45 km on the Amanos Fault, ∼10 km on the East Hatay Fault, and a further ∼10 km on the Kırkpınar Fault farther east. Much of this slip is inferred to have occurred during the Miocene, before the modern geometry of this plate boundary zone developed. When it first formed, the AF–AR plate boundary was relatively complex—it initially reactivated preexisting structures in the Palmyra foldbelt in Syria and in the Gaziantep region of southern Turkey, which were significantly misaligned relative to the plate motion, requiring major components of shortening as well as left-lateral slip. The transition, from this initial rather diffuse geometry to the present localised geometry of the DSFZ across western Syria, occurred within the Miocene. The predicted rate of relative motion between the stable interiors of the Turkish and African plates in the vicinity of their common boundary onshore of İskenderun Gulf in southern Turkey is estimated as westward at ∼9 mm a −1. However, this “promontory” of the African plate is itself moving westward relative to the stable interior of this plate at ∼7–8 mm a −1. The rate of localised left-lateral slip on the onshore part of this boundary, the NE-trending Yakapınar–Göksun Fault, is thus estimated as only ∼2 mm a −1. This locality can also be regarded as within the distributed boundary zone between the Turkish and Arabian plates. The estimated relative motion between these plates is at ∼8.7 mm a −1 towards the SSW, partitioned between localised left-lateral slip at ∼2 mm a −1 on the Yakapınar–Göksun Fault, and at least ∼1 mm a −1 on the Amanos Fault, and ∼2.5 mm a −1 on East Hatay Fault, with at most distributed left-lateral simple shear at ∼3.2 mm a −1 across the Amanos Mountains in between. However, the combined slip on left-lateral faults east of the Amanos Mountains may be as high as ∼6 mm a −1, with slip at ∼1.7 mm a −1 on the Amanos Fault and at ∼4.3 mm a −1 on the East Hatay Fault and any active faults farther east. This requires no more than ∼0.7 mm a −1 of distributed simple shear across the Amanos Mountains, raising the possibility that this component of deformation may in fact be zero, this small nonzero estimate possibly indicating a closure error arising from minor errors in predicted values of other relative motion vectors. It is proposed that this boundary between the Turkish and African plates first developed at the same time as the MOFZ and NAFZ, but its original geometry involving left-lateral slip on the Karataş–Osmaniye Fault has since become locked by the presence of relatively strong ophiolitic crust within this fault zone. This quantitative kinematic model demonstrates, for the first time, how it is possible for the left-lateral faulting accommodating the NNW–SSE relative motion between the Arabian and African plates in NW Syria to “dovetail” into the left-lateral faulting accommodating the WSW–ENE relative motion between the Turkish and Arabian plates in SE Turkey.