The kinematics of central-southern Turkey and northwest Syria revisited

Abstract

Central-southern Turkey, NW Syria, and adjacent offshore areas in the NE Mediterranean region form the boundary zone between the Turkish, African and Arabian plates. A great deal of new information has emerged in recent years regarding senses and rates of active crustal deformation in this region, but this material has not hitherto been well integrated, so the interpretations of key localities by different teams remain contradictory. We have reviewed and synthesized this evidence, combining it with new investigations targeted at key areas of uncertainty. This work has led to the inference of previously unrecognized active faults and has clarified the roles of other structures within the framework of plate motions provided by GPS studies. Roughly one third of the relative motion between the Turkish and Arabian plates is accommodated on the Misis-Kyrenia Fault Zone, which links to the study region from the Kyrenia mountain range of northern Cyprus. Much of this motion passes NNE then eastward around the northern limit of the Amanos Mountains, as previously thought, but some of it splays northeastward to link into newly-recognised normal faulting within the Amanos Mountains. The remaining two thirds of the relative motion is accommodated along the Karasu Valley; some of this component steps leftward across the Amik Basin before passing southward onto the northern Dead Sea Fault Zone (DSFZ) but much of it continues southwestward, past the city of Antakya, then into offshore structures, ultimately linking Central-southern Turkey and northwest Syria; Page 2; 30/12/2013 to the subduction zone bounding the Turkish and African plates to the southwest of Cyprus.However, some of this offshore motion continues southward, west of the Syrian coast, before linking onshore into the southern DSFZ; this component of the relative motion is indeed the main reason why the slip rate on the northern DSFZ, measured geodetically, is so much lower than that on its southern counterpart. In some parts of this region, notably in the Karasu Valley, it is now clear how the expected relative plate motion has been accommodated on active faults during much of the Quaternary: rather than constant slip rates on individual faults, quite complex changes in the partitioning of this motion on timescales of hundreds of thousands of years are indicated. However, in other parts of the region it remains unclear whether additional major active faults remain unrecognised or whether significant relative motions are accommodated by distributed deformation or on the many smaller-scale structures present. Highlights

River terrace development in the NE Mediterranean region (Syria and Turkey): Patterns in relation to crustal type

“…Further upstream, the Ceyhan has cut a substantial gorge, up to ~2000 m deep, through the northern Amanos Mountains, the maximum age for the initiation of incision being the start of the fault movement, ~3.7 Ma (Westaway et al, 2006b), implying an average rate of down-cutting of ~0.54 mm a −1 , higher than the range calculated from the lower-level river terraces (see above). As Seyrek et al (2014) have established, this gorge reach of the Ceyhan is in the footwall (upthrown side) of an active normal fault, whereas the terraced reach further downstream is in its hanging (downthrown) wall, all of which is entirely consistent with the aforementioned differential uplift rates. Fig.…”

“…2) the crustal properties reflect the typical geology of the Mediterranean region, resulting from its Cenozoic deformation in response to the subduction of the Tethys Ocean and the convergence of the African and Eurasian plates. (e.g., Aktaş and Robertson, 1984;Allen and Armstrong, 2008;Seyrek et al, 2014). Such crust, seen already in those reaches of the Orontes that flow close to the DSFZ (see above, especially the Upper Orontes), is considerably more dynamic than that of the Arabian Platform.…”

“…7). North of this gorge it flows into Turkey and into the second subsiding pull-apart basin, the Amik Basin (for recent discussion, see Seyrek et al, 2014), the flat surface of which forms the Antakya (Antioch) Plain (Fig. 7).…”

“…2). There are many localities within these fault zones where rivers have been laterally offset by slip on such faults, the rate of this movement having been quantified from dating of the fluvial deposits or other evidence (e.g., Barka and Kadinsky-Cade, 1988;Westaway, 1994;Demir et al, 2004;Westaway et al, 2006b;Seyrek et al, 2014). …”

Quantitative dating of Pleistocene deposits of the Kyrenia Range, northern Cyprus: implications for timing, rates of uplift and driving mechanisms

“…7). The entire process occurred within a region of dominantly compressional tectonics (Le Pichon & Kreemer 2010; Seyrek et al 2014), which was locally exaggerated by the collision of the Eratosthenes Seamount with the Cyprus active margin. This would also explain why the Kyrenia Range reaches its maximum height at a similar longitude to both the Eratosthenes Seamount and the Troodos Massif, and also why the Kyrenia Range submerges both to the east and the west away from the inferred north-south collision zone.…”