UTILIZING FORAMINIFERA TO IDENTIFY LOWER -UPPER CRETACEOUS MARINE BEDS IN KENYON#1 CORE KANSAS

Marine foraminifera from the core collected by the Kansas Geological Survey are used to constrain the age of Cretaceous marine strata in north-central Kansas. The KGS Kenyon #1 core samples siliciclastic and carbonate lithologies of the Kiowa Formation, Graneros Shale, and lower members of the Greenhorn Limestone which represent deposition during the development of the Western Interior Seaway.

This analysis reveals a significant difference in foraminiferal diversity and abundance between the Lower and Upper Cretaceous strata. The Upper Cretaceous strata exhibit high diversity and abundance of planktonic foraminifera, while the Lower Cretaceous strata are characterized by low diversity. Samples from the Kiowa Formation (125.27 meters - 153.62 meters) contain a low diversity of foraminifera, represented by a single species, Microhedbergella miniglobularis, indicative of the Aptian/Albian stage. In contrast, thirteen samples from the Upper Cretaceous strata (4.87 meters - 26.36 meters) yielded abundant and diverse foraminifera, including Anaticinella multiloculata, Laviella bentonensis, Muricohedbergella planispira, Rotalipora cushmani evoluta, Planoheterohelix postmoremani, Praeglobotruncana delrionesis, and Whiteinella archaeocretacea. These findings suggest a Cenomanian age for the Graneros Shale and the lower members of the Greenhorn Limestone. The high diversity and abundance of planktonic foraminifera in these strata reflect fluctuations in water depth.