When Did the Western Anatolian Grabens Begin to Develop?

TLDR

The timing and mechanism of the western Anatolian graben system’s formation have long been debated. This study sought to resolve that debate by gathering new mapping data from western Anatolia. The data show that north‑south trending grabens first formed under east‑west extension in the Early Miocene, followed by a north‑south extensional regime in the Late Miocene that produced a major breakaway fault, uplift, cross‑grabens, and alkaline basalt eruptions; subsequent erosion erased earlier topography, and later rejuvenated north‑south extension created east‑west trending grabens during the Plio‑Quaternary.

Abstract

Abstract To solve a long-lasting controversy on the timing and mechanism of generation of the western Anatolian graben system, new data have been collected from a mapping project in western Anatolia, which reveal that initially north-south trending graben basins were formed under an east-west extensional regime during Early Miocene times. The extensional openings associated with approximately north-south trending oblique slip faults provided access for calc-alkaline, hybrid magmas to reach the surface. A north-south extensional regime began during Late Miocene time. During this period a major breakaway fault was formed. Part of the lower plate was uplifted and cropped out later in the Bozdağ, Horst, and above the upper plate approximately north-south trending cross-grabens were developed. Along these fault systems, alkaline basalt lavas were extruded. The north-south extension was interrupted at the end of Late Miocene or Early Pliocene times, as evidenced by a regional horizontal erosional surface which developed across Neogene rocks, including Upper Miocene-Lower Pliocene strata. This erosion nearly obliterated the previously formed topographic irregularities, including the Bozdağ elevation. Later, the erosional surface was disrupted and the structures which controlled development of the Lower-Upper Miocene rocks were cut by approximately east-west trending normal faults formed by rejuvenated north-south extension. This has led to development of the present-day east-west trending grabens during Plio-Quaternary time.