Agglutinated foraminifera and calcareous nannoplankton proxies for age determination and paleoenvironmental reconstruction of an Upper Cretaceous succession in the North Sudetic Cretaceous Basin (Germany)

The present study presents the findings of a comprehensive analysis of agglutinated foraminifera and calcareous nannoplankton from drill core Spremberg Cu Sp 101/6, situated within the North Sudetic Cretaceous Basin in Germany. These results provide refined biostratigraphic data and contribute to the paleoenvironmental reconstruction for both surface and bottom water conditions in the studied region. Several calcareous nannoplankton taxa facilitated the identification of specific biozones, including Eiffellithus eximius (UC8), Micula staurophora (UC10), and Lithastrinus grillii (UC11). Notably, M. staurophora and L. grillii display significantly earlier occurrences when correlated with inoceramid zonation, indicating a diachronous first appearance of these taxa. Using cluster analysis, principal component analysis, and taxonomical information, microfossil assemblages suggest that shallower, eutrophic conditions prevailed during the Cenomanian, whereas the Turonian was characterized by less diverse and poorly preserved assemblages. During the Coniacian, calcareous nannofossil assemblages indicate fluctuations between intervals of poor preservation and phases of increased assemblage diversity, probably associated with eutrophic conditions during the early Coniacian. This was followed by a transition to predominantly oligotrophic and deeper conditions during the middle to late Coniacian. Changes in the agglutinated foraminiferal assemblages likely reflect the grade of disturbance of bottom-water conditions mostly controlled by regional subsidence.