Middle Carnian Arc-Type Basalts from the Lycian Nappes, Southwestern Anatolia: Early Late Triassic Subduction in the Northern Branch of Neotethys

The Turunç Unit, which represents one of the tectonic slices within the Lycian Nappes in southwestern Anatolia, preserves the remnants derived from the northern branch of Neotethys. The unit includes basalts intercalated with pelagic limestones of middle Carnian age (early Late Triassic) based on the characteristic radiolarian assemblage of the Tetraporobrachia haeckeli Zone. The Turunç lavas reflect trace element signatures resembling those from subduction zones, displaying selective enrichment of Th and light rare earth elements over high-field strength elements and heavy rare earth elements. Considering the overall geochemical characteristics of the Turunç basalts and given that they are found to be associated with no continent-derived detritus, the Turunç lavas appear to represent fragments of a Late Triassic island arc formed on the Neotethyan oceanic lithosphere. This result is of particular importance, since it reflects the oldest subduction age obtained from the entire Neotethyan realm to date. It may further indicate that the Neotethyan oceanic lithosphere had already been formed by the early Late Triassic, thus suggesting a pre–early Late Triassic oceanization of the northern branch of Neotethys. On the basis of this, we also suggest that the initial rifting leading to the opening of the northern branch of Neotethys should have taken place during the Middle Triassic or earlier.