Middle-Late Triassic radiolarian cherts from the Arkotdağ mélange in northern Turkey: implications for the life span of the northern Neotethyan branch

摘要

Moderately to well-preserved, relatively diverse Middle and Late Triassic radiolarian assemblages have been obtained from the chert slide-blocks within the Late Cretaceous mélange of the IntraPontide Suture Zone at the Pelitören village to the NE of Kastamonu- Araç in northern Central Anatolia. In this locality, chert slide-blocks are tectonically overlain by metamorphic sole of the serpentinized peridotites belonging to the IntraPontide ophiolites. The oldest radiolarian assemblages, with the middle Late Anisian and late Early Ladinian ages, were found in green cherts in a pebbly mudstone. They are underlain by a larger slide-block composed of an alternation of radiolarian cherts and mudstones with late Early and early Late Carnian radiolarians. Another slide-block with cherts and mudstones between the sub-ophiolitic amphibolite and the Carnian cherts includes the late Early to early Middle Norian radiolarian assemblages. These new data reveal that the IntraPontide basin was already open during the Middle to Late Triassic time and deep enough for radiolarian cherts to deposit. Moreover, it suggests that the IntraPontide Ocean is contemporaneous with a number of inferred Paleo- and Neotethyan oceanic basins in SE Europe and NW Anatolia, which were proposed in copious tectonic models.