Yo-yo tectonics in a wrench zone, Central Anatolian fault zone, Turkey

The Niǧde Massif, south-central Turkey, experienced two complete cycles of burial and exhumation during orogenesis and is, therefore, an excellent example of yo-yo tectonics. We propose that burial and exhumation of the metamorphic basement and, in the second cycle, the basement and its sedimentary cover rocks, were driven largely by transpression and transtension in an intracontinental strike-slip zone. The eastern margin of the massif, where it is adjacent and subparallel to the sinistral Central Anatolian fault zone, is comprised of Upper Cretaceous basement that was the source of, and is unconformably overlain by, early Tertiary sedimentary rocks. The contact between the Tertiary rocks and basement is an unconformity that is locally sheared and characterized by a low-angle oblique-normal shear system with cataclasite in the basement and brittle-ductile shear zones in the sedimentary rocks. These relationships, documented by geo/thermochronology to encompass 80 million years, define the timing and magnitude of the yo-yo process: burial and heating of Mesozoic sedimentary rocks during Late Cretaceous transpression to form the high- grade metamorphic basement (peak metamorphism at 85-91 Ma); Late Cretaceous (ca. 80-60 Ma) unroofing by transtension and erosion, with early Tertiary deposition of massif-derived clastic material at the edge of a marine basin along the Central Anatolian fault zone; reburial of basement and cover rocks involving folding, shearing, and greenschist facies metamorphism of the sedimentary cover in late Eocene through early Miocene time (ca. 50-20 Ma); and final exhumation in the middle Miocene (17-9 Ma) along strike-slip and normal faults. © 2007 The Geological Society of America. All rights reserved.