Biostratigraphy of the CeAYmeler and Elmal iota Dere formations: First records of upper Cretaceous planktonic foraminifera and radiolarians from the Eastern Pontides (Ma double dagger ka, Trabzon, Turkey)

摘要

Upper Cretaceous pelagic deposits outcropping in the Ma double dagger ka (Trabzon) region include radiolarians and pelagic foraminifera. The Catak Group represented by the volcano-sedimentary successions consists of three formations having different properties. Two sections, CTK1 and CTK2, are selected from the Ce meler and Elmal iota Dere formations, respectively, establishing the biostratigraphy of outcropping sedimentary units. A total of 17 species of Whiteinella, Helvetoglobotruncana, Marginotruncana, Dicarinella, Praeglobotruncana, Archaeoglobigerina and Hedbergella demonstrating the early Turonian-Coniacian are established in the CTK1 stratigraphic section. The early Turonian radiolarian fauna consisting of Halesium sexangulum Pessagno, 1971, Crucella cachensis Pessagno, 1971, Stichomitra communis Squinabol, 1903 is also defined in the same section. A total of 30 species of Crucella, Halesium, Pessagnobrachia, Patulibracchium, Alievium, Archaeospongoprunum, Dicyomitra, Stichomitra, Diacanthocapsa, Dactiyliodiscus, Amphipydax, Pseudoaulophocus, Acaeniotyle, Archaeodictyomitra, Actinomma, Xitus, Neosciadocapsidae characterizing the early and late Turonian, as well as the Coniacian-early Santonian are recognized from red-coloured pelagic limestones of the CTK2 section. Also, planktonic foraminifera species of Marginotruncana, Hedbergella, Heterohelix, Globotruncana, Globotruncanita, Archaeoglobigerina, Dicarinella characterizing the Coniacian-Santonian are described in the thin sections of the same samples. The age of red-coloured limestones is identified as the Coniacian-Santonian benefit from radiolarians and pelagic foraminifera. Consequently, radiolarians and pelagic foraminifera within sedimentary successions of the investigation area are distributed in two intervals that coincide with the early Turonian-Coniacian and Coniacian-Santonian intervals.