T148 Basin Analysis, Strike-Slip Faults, and Tectonics I: Honoring the Contributions of Paul Umhoefer

Tuesday, 11 October 2022
8:00 AM - 12:00 PM
607

DEVELOPMENT OF THE ANATOLIAN PLATE AND TECTONIC ESCAPE SYSTEM

Paper number: T148-3
Program: Technical Sessions
Time: 8:30 AM – 8:45 AM

Authors

Abstract

Strike-slip dominated movement of lithospheric fragments from zones of horizontal shortening (escape tectonics) has characterized convergent settings from the onset of plate tectonics to the present and is a mechanism for the formation of new plates. The Anatolian plate was created in the late Cenozoic and represents a near-ideal case of tectonic escape, and yet the modern escape system required ~20 million years to become fully operational: formation of the escape system was complete when the East Anatolian Fault Zone (EAFZ) became a throughgoing strike-slip fault that connected the North Anatolian Fault Zone to the Dead Sea Fault at ~5 Ma. We used low-temperature (T) thermochronology to investigate the timing of cooling of mid-crustal rocks in the EAFZ and integrated results with seismic data for modern lithosphere structure to evaluate the evolution of the fault zone during the development of an escape tectonics system.

Cooling ages for mid-crustal rocks exhumed in the EAFZ are significantly younger than those in other strike-slip fault zones in the region; apatite fission-track: 22-12 Ma (EAFZ), cf. 53-29 Ma; apatite U-Th/He: 11-4 Ma (EAFZ), cf. 27-13 Ma. The youngest ages (~5 Ma) are similar to ages of volcanic rocks in the Anatolia-Arabia-Africa triple junction. The restriction of younger ages to the EAFZ marks a change to rapid exhumation focused along the EAFZ at the inception of significant strike-slip displacement, consistent with modern earthquake focal mechanisms.

Results of the CD-CAT seismic experiment for the western segment of the EAFZ – specifically, S-wave velocities and receiver function analysis – indicates that strong but thin (30 km) lithospheric mantle, inferred to be Arabian plate mantle, underlies Anatolian crust today and extends 50-150 km N of the suture. At 5 Ma, the northern edge of this domain was further south and may have formed a rheological boundary along the Arabian-Eurasian suture that facilitated formation of the EAFZ, similar to the mechanism by which the older (~15-11 Ma) North Anatolian Fault Zone formed. Prior to inception of the escape system, SE Anatolia experienced 20 m.y. of widespread distributed deformation in a transitional (proto-escape) phase between Arabia-Eurasia collision and the development of the full escape system that demarcates the Anatolian plate today.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-380195

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