THERMAL HISTORY OF MULTIPLE CYCLES OF BURIAL AND EXHUMATION ALONG A SEGMENT OF THE CENTRAL ANATOLIAN FAULT ZONE

The Central Anatolian Fault Zone (CAFZ), Turkey, is a strike-slip fault zone that cuts through the interior of the Anatolian plate, from the Mediterranean Sea to the North Anatolian Fault. This lithosphere-scale sinistral fault has accommodated ~80 km of motion in the last ~60 million years and is seismically active. A portion of the southern segment of the CAFZ forms the eastern boarder of the Niğde Massif, an exhumed metamorphic core complex that experienced multiple cycles of exhumation and burial over the last 90+ million years, perhaps due to tectonic switches between transpression and transtension along the CAFZ. The Niğde Massif is key to resolving the magnitude, timing, and driving forces of vertical and lateral displacement along the CAFZ, which are important for understanding the Cenozoic evolution of exhumation, magmatism, and landscape development in central Anatolia.

In this study, we are examining the thermal and structural history of the eastern margin of the Niğde Massif and overlying basin deposits. Unlike the western portion of the massif, which is characterized by concordant ⁴⁰Ar/³⁹Ar age spectra and consistently oriented lineations, the second cycle of burial and exhumation caused locally intense deformation of Cenozoic basin deposits and disorganized mineral lineation patterns in basement rocks along the eastern margin. New ⁴⁰Ar/³⁹Ar ages from basement gneiss and detrital white mica in the structurally deepest basin deposits are Late Cretaceous in age (71.8±0.4 Ma to 78.2±0.3 Ma) and therefore record the first exhumation event. However, most age spectra suggest disturbance of the ⁴⁰Ar/³⁹Ar system, which we attribute to the second cycle of burial and exhumation. New and previously determined apatite fission-track ages from metamorphic rocks and detrital apatite from the structurally deepest basin levels show Miocene resetting during the second burial event. A particularly interesting new result is that although some regions of the basin seem to show less deformation than others (e.g., lack isoclinal folding), detrital apatite grains nevertheless show complete resetting, with final cooling at ~20 Ma. Work is ongoing to determine more completely the thermal and structural history of basement rocks and basins along this segment of the CAFZ.