OROGEN-PARALLEL VARIATIONS IN STRUCTURAL STYLE AND TECTONIC EXHUMATION DURING THE MIOCENE COLLISION-ESCAPE TRANSITION IN ANATOLIA

The Anatolian Orogen is a world-class example of tectonic escape embedded within the Afro/Arabia-Eurasia collision zone. The Eurasian margin exhibits significant variations in deformation magnitude and style along strike, including major strike-slip and transtensional fault systems oriented both parallel and oblique to the orogen. Much of this variability is related to the contrasting influences of the Arabian indenter and the Hellenic-Cyprean subduction zone in eastern and western Anatolia, respectively. Despite our understanding of modern escape tectonics here, the spatiotemporal evolution of strain during the transition from collision to escape are poorly understood.

New geologic mapping, structural analysis, and low-temperature thermochronology reveal distinct differences in deformation style east and west of the active sinistral Central Anatolian fault zone (CAFZ), an inherited structure between the Kırşehir Massif and Tauride micro-continents known as the Inner Tauride Suture. East of the CAFZ, apatite fission track (AFT) data from Paleocene-Eocene detrital and crystalline samples indicate rapid cooling at ~38–31 Ma related to foreland fold-thrust belt development in the eastern Taurides and adjacent Sivas Basin. Folding and thrusting of middle Miocene rocks and an unconformity with undeformed latest Miocene-Pliocene strata indicate that contraction ended there in the late Miocene. West of the CAFZ, AFT and apatite (U-Th)/He data from Eocene and older crystalline rocks reveal similar ~40–31 Ma exhumation related to the same regional contraction event recorded in the east, but in a transpressional zone. Rocks west of the CAFZ also record a later cooling event in the Miocene (~22–15 Ma) associated with both erosion and exhumation along major extensional and transtensional structures in the Kırşehir and Niğde Massifs.

We interpret that these orogen-parallel variations in structural style are related to the irregular collisional margin and the dominant role of the Arabian indenter in the east, which caused predominantly contractional strain since the late Eocene that waned by the late Miocene switch to escape tectonics. Farther west and outside of the direct influence of the Arabian indenter, a switch to extensional exhumation at ~20 Ma was related to rollback of the Hellenic-Cyprean slabs.