Early-middle Carnian radiolarian cherts within the Eymir Unit, Central Turkey: Constraints for the age of the Palaeotethyan Karakaya Complex

Abstract

A chert-pelagic carbonate formation within the mass flow deposits of the Palaeotethyan Karakaya Complex (mélange) in Ankara has yielded poorly preserved radiolaria. The critical fauna: Paronaella claviformis (Kozur and Mostler), Canoptum cucurbita (Sugiyama), Canoptum inornatum Tekin and Canoptum levis Tekin is the late Early Carnian to the early Middle Carnian in age, corresponding to “unnamed radiolarian Zone” and “ Tetraporobrachia haeckeli Zone” and partly to Capnuchosphera Lowest-Occurrence Zone. This is so far the first finding of deep marine sediments from the Karakaya Complex in primary association with the olistostromes including the olistoliths of high pressure/low temperature (HP/LT) metabasic rocks and Paleozoic carbonates in the Ankara area. Considering the available data, we suggest that during the Late Triassic the mélange-forming processes in the South Palaeotethyan margin, which is of both tectonic and sedimentary character, included subduction of Mid-Triassic oceanic islands, HP/LT metamorphism, exhumation and transportation into the foreland basins on the Sakarya continental crust.