TECTONIC EVOLUTION OF CENTRAL ANATOLIA FROM COLLISION TO ESCAPE – HONORING PAUL UMHOEFER’S INTEGRATED APPROACH TO GEOSCIENCE THROUGH STRUCTURE, STRATIGRAPHY, MAGMATISM AND PLATE RECONSTRUCTIONS (Invited Presentation)

The evolution of long-lived convergent plate margins is often complicated by the lateral translation and redistribution of crustal fragments along strike. Unraveling tectonic chronologies, the drivers of orogenesis, and their variations along strike requires a multidisciplinary perspective that spans all scales observation. Paul Umhoefer left a legacy of approaching these types of problems through detailed field studies, data integration and synthesis, big-picture thinking, and maintaining an open mind throughout. Paul and his students applied these principles in their study of the tectonic evolution of the Anatolia Orogen – a mosaic of accreted continental fragments at the west end of the Arabia-Eurasia collision zone (AECZ) that represents the type-example of an active tectonic escape system. Fortunately, rich stratigraphic, structural, and magmatic archives in Cenozoic basins across central Anatolia provide opportunities to resolve fundamental questions about the timing of Arabia collision, the transition to escape tectonics, and their relation to one another.

Structural, stratigraphic, and low-temperature thermochronologic data indicate rapid cooling and basin inversion in the Sivas and Ulukışla basins from 45–25 Ma associated with N-vergent shortening and transpression, respectively. Widespread erosional exhumation coincided with an extensive magmatic lull across Anatolia from 40–20 Ma. Plate kinematic reconstructions of the entire AECZ substantiate the results from basin- and regional-scale studies and indicate that Arabia collision initiated by ~42 Ma in eastern Anatolia and was diachronous toward the west and SE. Transtensional reactivation of the Ecemiş fault zone signaled a major change to a “proto-escape” stage west of central Anatolia by 25–15 Ma, coeval with the switch from soft to hard collision of thick Arabia crust and rapid slab rollback and extension in the Aegean Domain, followed by full tectonic escape at ~5 Ma. The long delay between collision onset and escape suggests that escape may develop by a “push, then pull” process, in which collision leads to crustal thickening ahead of the indenter, and rapid plate deceleration, slab rollback, trench retreat, and upper-plate extension adjacent to it permits the gravitational collapse and lateral extrusion of the orogen in its wake.