Basin Formation And Evolution During Complex Continental Collision: The Darende And Hekimhan Basins, Central Eastern Turkey

The Darende Basin and the adjacent Hekimhan Basin in the Malatya Region of central eastern Turkey developed as part of the northern margin of the Tauride microcontinent during collision and suturing of the Mesozoic Tethys Ocean. The Darende and Hekimhan Basins both exhibit a Jurassic-Upper Cretaceous carbonate platform basement overlain by a dismembered ophiolite that was thrust southwards onto part of the Mesozoic Tauride carbonate platform. Sedimentation on the emplaced ophiolites in both basins began in the latest Cretaceous (Maastrichtian), triggered by basin-wide transgression, coupled with tectonic subsidence. Ophiolite-derived clastics accumulated in basin depocentres, followed by Maastrichtian-aged, rudist-rich patch reefs and microbial carbonates on the basin margins and on palaeotopographic highs. An angular unconformity developed in the Darende Basin after the Maastrichtian. Basaltic to andesitic lavas were locally erupted above this. Sedimentation resumed in the Early Eocene in response to flexural subsidence, creating accommodation space. This then filled with various facies that successively record deepening, shallowing and finally emergence during the Late Eocene. In the Hekimhan Basin, Maastrichtian facies are overlain by ~1000 metres of subaqueous basaltic, to trachytic lavas and associated volcaniclastic material. Numerous intrusions cut the lavas including basaltic, to gabbroic dyke swarms, plagiogranite and a syenite body displaying orbicular structures, contact metamorphism, hydrothermal alteration and mineralisation. These lithologies are overlain by latest Cretaceous shallow marine-limestones and dolomites. Sedimentation was then continuous from the Late Cretaceous, with a localised pulse of volcanic activity during the Late Eocene, until the Middle Miocene when the basin became emergent.

The following tectonically controlled stages of basin development are inferred: 1) Late Cretaceous extension initiated basin development, possibly related to northward subduction of remaining Tethyan oceanic crust. The lavas and intrusive magma bodies in the Hekimhan Basin also reflect an extensional setting; 2) The Darende Basin became emergent in the Latest Cretaceous, possibly controlled by flexural uplift or sea-level change, while sedimentation continued in the Hekimhan Basin; 3) Early Eocene flexural subsidence, probably caused by crustal loading that accompanied initial collision of the Tauride microcontinent with Eurasia (“soft collision”), forcing the Darende Basin to subside and sedimentation to resume; 4) Late Eocene “hard collision” possibly caused regional uplift and progressive restriction of the Darende Basin, culminating in subaerial exposure. No further marine sedimentation occurred in the Darende Basin after the Late Eocene. In contrast, sedimentation continued in the Hekimhan Basin until it became emergent in the Middle Miocene.

Both basins remain well preserved, although they were affected by post Mid-Eocene, post-collisional suture tightening, followed by predominantly sinistral strike-slip Neotectonic deformation. The excellent preservation of the basins is attributed to their location within a strain “shadow” zone to the east of a large microcontinent, the Nid?e-K?r?ehir Massif, which acted as a regional-scale indenter between Eurasia to the north and the Taurides to the south.