The Pınarbaşı metamorphic sole (Turkey) as a geological archive of subduction initiation in the Cretaceous Neotethys Ocean.

Metamorphic soles consist of metamorphosed oceanic crustal and pelagic sedimentary rocks that structurally underlie the mantle section of supra-subduction zone (SSZ) ophiolites. Both are considered geological records of subduction initiation: soles record the juvenile history of a subduction plate interface and the overlying SSZ ophiolites record the onset of upper plate extension, offering important clues for the dynamics of the subduction initiation process. Despite their importance and widespread occurrence, only few soles have been studied in detail, notably the Cretaceous Oman sole. Here, we describe the particularly well-preserved Cretaceous Pınarbaşı metamorphic sole that formed at the same Neotethyan subduction zone as the Oman sole, but farther west, in Central Anatolia. We report detailed field mapping and show that the 240 m thick sole has a 10 m thick hightemperature top that reached P-T conditions of 1.2-1.4 GPa and 775-825°C and includes felsic melt pockets, and a 240 m thick low-temperature amphibolite and greenschist-facies base. We show 40 Ar/ 39 Ar hornblende ages that reveal HT and LT sole cooling below ~500°C by 93-95 Ma, alike, or even a few million years older than ophiolitic crust ages constrained for ophiolites in the vicinity. The Pınarbaşı section contains a high-temperature slice interleaved in the low-temperature base that reveals regional sole imbrication by subduction erosion during sole growth. The Pınarbaşı metamorphic sole may serve as a lateral equivalent as the Oman sole, but with a few Myr younger cooling and ophiolite spreading ages. Comparing these soles offers ways to study the regional geodynamic drivers and plate kinematic context of subduction initiation.