Carnian (Late Triassic) ostracods from the Sorgun Ophiolitic Mélange (Southern Turkey): Taxonomy, palaeoenvironment, and evidence of predation

Abstract

The Mersin Ophiolitic Complex is situated in southern Turkey and contains the relics of the Palaeotethys and Neotethys Oceans and of the Huglu-Pindos basin. The succession exposed at the Tavuscayiri Block has been intensely studied but ostracods are still poorly documented. This paper illustrates and discusses the ostracods extracted from a radiolarian-rich limestone of the lower Tuvalian Spongotortilispinus moixi radiolarian Zone (Carnian, Late Triassic) intercalated with thick green tuffs. The moderately abundant assemblage (40 specimens) is composed of 29 species, 16 genera of seven families, including one new species: Bairdiacypris sorgunensis Forel sp. nov. This assemblage points to a moderately shallow subtidal environment submitted to short-lived environmental instabilities. In regards to the slightly older ostracods recently reported from the Tavuscayiri Block, the present record illustrates an upwards shallowing trend for the Carnian succession. All the taxa found are of typical Mesozoic-Cenozoic affinity, in contrast to the slightly older assemblage from the Julian of the Tavuscayiri Block (Kilek section), which also include Palaeozoic taxa. This different pattern could relate either to the disappearance of Palaeozoic taxa during the intervening interval or to their survival only in relatively deeper waters. Finally, we also report the oldest known record of a boring trace on the surface of an ostracod valve, probably of predatory origin. It represents the first evidence of predation on micro-benthos in the Triassic and is in line with several recent studies attesting the establishment of boring predation in the Late Triassic.