VERTICAL YO-YO TECTONICS ALONG THE CENTRAL ANATOLIAN FAULT ZONE, TURKEY

The Central Anatolian fault zone (CAFZ) is a > 700-km-long sinistral strike-slip fault that extends from the North Anatolian Fault to the Mediterranean Sea, and forms the eastern boundary of the metamorphic complexes in central Turkey, including the Nigde Massif. The massif is comprised of Late Cretaceous basement rocks that were the source of, and unconformably overlain by, early Tertiary sedimentary rocks. The cover rocks and basement were buried, deformed, and metamorphosed to greenschist facies before final unroofing. The contact between the Tertiary metasedimentary rocks and the basement is a sheared unconformity characterized by a low-angle, oblique-normal shear system with cataclasite in the basement and ductile shear zones in the metasedimentary rocks. The Nigde massif experienced two complete cycles of burial and exhumation during protracted orogenesis and is an excellent example of vertical yo-yo tectonics (cycles of burial/exhumation) along a major strike-slip fault. These relationships, documented by U-Pb, Ar-Ar, and fission track to encompass 70 million years, define the timing and magnitude of the yo-yo: Late Cretaceous subsidence and burial of Mesozoic sedimentary rocks to form the basement gneiss; Late Cretaceous to middle Eocene unroofing of the basement by transtension and erosion to produce locally derived conglomerate deposited at the edge of a marine basin along the CAFZ; re-burial of the basement and cover sediments, resulting in folding, shearing, and metamorphism of the sedimentary cover in late Eocene through Oligocene time; and final exhumation in the middle Miocene (9-12 Ma) along strike-slip and normal faults. Yo-yo tectonics may be common along major strike-slip zones, but the preservation potential of the basement-cover relationships necessary to interpret multiple cycles of burial and exhumation is low. Basement and cover may be separated by later faulting; basins may continue to subside and bury strata from the yo-yo episode; volcanism may dominate over deposition of sediments that would record the yo-yo; and jumps in strike-slip faults may produce the yo-yo process in different locations. Nevertheless, integrated basement-basin studies may recognize more examples of yo-yo tectonics and provide additional data on mechanisms and rates along strike-slip faults.