Miocene geochronology and stratigraphy of western Anatolia: Insights from new Ar/Ar dataset

Abstract

Understanding the dynamic evolution of orogenic belts and intra-continental basins depend on field-based (tectono-) stratigraphic observations paired with geochronologic data such as 40Ar/39Ar analyses. Independent dating of tectono-stratigraphic units is a crucial tool to place them in a broader framework. In this study, we focus on the geodynamic development of western Anatolia, with an emphasis on the timing and progression of volcanism along the İzmir-Balıkesir Transfer Zone (İBTZ). We present 36 new 40Ar/39Ar ages of both volcanic complexes/domes and volcanic rocks coevally emplaced within Miocene sediments from western Anatolian extensional basins. In combination with existing ages from the literature and paleontological records from Miocene basin in-fills, we build an improved and integrated stratigraphic framework for the region. Our results show a remarkable break in volcanism from this area during the Langhian (15.97–13.82 Ma), encompassing a major unconformity in the İBTZ, and a pulse in the exhumation of metamorphic core complexes in western Anatolia. Hence we attribute this magmatic pause to the tectonic reorganization and change in the partitioning of extensional deformation between Cycladic and Menderes core complexes, facilitated by the acceleration of roll-back of African oceanic lithosphere below western Anatolia.