Nature, Genesis, and Significance of the Gazikoy and Kesan Formations (Thrace Basin, Turkey): Eocene Turbidites and Olistostromes Formed on an Active Tethyan Margin

Abstract

Sediments of the Gazikoy and Kesan Formations (Middle-Upper Eocene) exposed in the southwestern sector of the Thrace Basin of northwestern Turkey yield evidence of activity of two main depositional systems: a slope apron and a submarine fan. The deposits attributed to an upper slope setting are characterized by mudstone intervals and interbeds of mudstones with nongraded sandstones, while the lower slope apron is characterized by fine-grained turbidites, allochthonous blocks, and debris-flow and slump deposits. By contrast, the submarine fan deposits are composed of pebbly sandstones interbedded with graded sandstones and mudstones and are interpreted as high-density turbidites formed in lobe and interlobe environments. Overall, these Early Cenozoic successions and their tectonic location show ample evidence of deposition on the margin of a tectonically active retroforeland basin where sedimentation was ultimately controlled by thrust tectonics. The fan development was probably linked to regional tectonic uplift, thrusting, and rejuvenation of the source region. Facies analysis and tectonic assessments in this study suggest that allochthonous blocks of exotic lithologies outcrop in association with the geologically recent extension of effects of the North Anatolian Fault in the lower slope apron deposits.