Calcareous nannofossil and planktonic foraminiferal Biostratigraphy of Santonian to Danian in Göynük Basin, Bolu, Turkey

Abstract

Biostratigraphy of Santonian-Danian calcareous nannofossils and planktonic foraminifera was studied in Göynük village and close surroundings located in northwest Turkey. Calcareous nannofossil and planktonic foraminifera assemblages from this time interval were investigated in detail in seven stratigraphic sections measured in the Değirmenözü Member, Yenipazar Formation and Seben Formation. The UC12 zone in the Santonian, UC13 zone, UC14a-bTP and UC15a-b-c-dTP subzones in the Campanian and UC20a-b-c-dTP subzones in the Maastrichtian were defined with nannofossil species assemblages.Planktonic foraminifera assemblages determined included Dicarinella asymetrica Total Range Zone (TRZ) from the Santonian, Globotruncanita elevata Partial-range Zone and Globotruncana ventricosa Partial-range Zone from the Campanian and Racemiguembelina fructicosa Partial-range Zone and Pseudoguembelina hariaensis Partial-range Zone from the Maastrichtian. There was a significant reduction in nannofossil species at the Cretaceous-Paleogene (K-Pg) boundary with dominance of Braarudosphaera bigelowii, Thoracosphaera sp. and Markalius inversus species and increased abundance of biserial planktonic foraminifera species. Just above this boundary in the Danian NP1 and NP2 nannofossil zones and Parvularugoglobigerina eugubina Taxon-range Zone, Parasubbotina pseudobulloides Partial-range Subzone (P1a), S. triloculinoides Lowest Occurrence Subzone (P1b), and G. compressa/Praemurica uncinata Lowest Occurrence Subzone (P1c) were identified from planktonic foraminifera.