Field-based evidence of sedimentary and tectonic processes related to continental collision: the Early Cenozoic basins of Central Eastern Turkey
Booth, Matthew Graham
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Turkey is widely accepted to have formed from a collage of microcontinents that rifted from the northern margin of Gondwana and assembled from the Mesozoic to Mid Cenozoic in response to the closure, collision and suturing of numerous oceanic strands in the Eastern Mediterranean. Sedimentary-tectonic basins, which formed during ocean basin closure, can yield important information about the evolution, timing and processes related to the closure of these oceanic strands. The Darende Basin and the adjacent Hekimhan Basin are two sedimentary-tectonic basins which developed during the collision and suturing of the Neotethys Ocean in the Eastern Mediterranean. The Darende and Hekimhan Basins developed as part of the northern margin of the Tauride microcontinent during the collision and suturing of Neotethys. Both basins exhibit a Jurassic to Cretaceous regional carbonate platform 'basement' overlain by a dismembered ophiolite, which was emplaced southwards during the Late Cretaceous. The basins then developed in two main phases: In the Darende Basin the first phase is characterised by non-marine clastic sediments, overlain by transgressive shallow-marine rocks. In the Hekimhan Basin, hemi-pelagic facies are deposited synchronously with the eruption of within plate-type alkaline basaltic-trachytic lavas and associated volcaniclastic sediments (later intruded by a syenitic pluton) under an extensional tectonic regime. A Paleocene-aged unconformity followed. A second phase of basin evolution during the Eocene is characterised in both basins by the deposition of variable sedimentary facies including conglomerate, sandstone, marl, shallow-marine nummulitic limestone and evaporites (and localised basaltic eruptions). These record successive deepening, shallowing and finally emergence of both basins during the Late Eocene. The Oligocene is represented by continental fluvial deposits that are only exposed in the Hekimhan Basin. The deposition of faunally diverse, shallow-marine, Miocene limestones, Pliocene subaerial basalts and Pliocene-Recent continental deposits in both basins completes the sequence. The following tectonically and eustatically controlled stages of basin development are inferred: 1) Late Cretaceous extension initiated basin development (after ophiolite emplacement), possibly related to immediate isostatic compensation and on-going slabpull during northward subduction of the remaining Neotethyan oceanic crust. The eruption of within-plate lavas and the intrusion of alkaline syenite bodies in the Hekimhan Basin reflect this extensional setting; 2) Emergence of the Darende and Hekimhan Basins in the latest Cretaceous was possibly controlled by regional flexural uplift as the down-going plate approached the subduction zone to the north (and was possibly also influenced by eustatic sea-level change); 3) Early Eocene flexural subsidence related to ‘soft collision’ of the Tauride microcontinent with Eurasia, coupled with a significant eustatic sea level rise, allowed sedimentation to resume; 4) Mid-Late Eocene ‘hard collision’ resulted in regional uplift, progressive isolation and subaerial exposure of the basins; 5) Suture tightening and compression, during the Late Eocene- Miocene, resulted in reactivation of pre-existing extensional faults and terminated marine sedimentation. Both basins were affected by predominantly sinistral strike-slip faulting during the Plio-Quaternary westward tectonic escape of Anatolia.