The Cabin Branch and Cabin Creek (Cappy Avenue) outcrops are located along two small creeks in Prince George’s County, Maryland. The Cabin Branch outcrop contains exposures of silty sands of the Upper Cretaceous Severn Formation, and both outcrops contain Paleocene silty quartz and glauconitic sands of the Danian Brightseat Formation and highly fossiliferous glauconitic quartz sands of the Selandian Aquia Formation. Data from these two locations were generated in order to designate a Principal Reference Section for the Danian age Brightseat Formation. The Cabin Branch outcrop consists of disjunct exposures along an approximately 0.4-mile section of the creek. At the nearby Cabin Creek (Cappy Avenue) outcrop a more complete Brightseat/Aquia contact is exposed. Data generated from these two outcrops include a complete suite of sand/silt/clay percent abundances from each sample of each formation. Additionally, data for the sand-size fraction from each formation were further broken down into percent abundance of very fine, fine, medium, and coarse components. Petrographic data for the indurated beds at the Cabin Branch outcrop are also included. Calcareous nannofossil data from the two outcrops are presented in three occurrence charts: one for the Late Cretaceous and one for the Paleocene at Cabin Branch, and one for the Brightseat-Aquia contact interval at Cabin Creek (Cappy Avenue). Calcareous nannofossil data were used to determine the ages and zonation of each formation, and species richness, a measure used to detail community stability, is also provided. In addition to calcareous nannofossil biostratigraphy, samples were processed for other calcareous microfossils: planktic and benthic foraminifera and ostracods. A table for each outcrop presents the number of planktic and benthic foraminifera per 300 specimens, along with the total number of ostracods present per sample. An occurrence chart of ostracod species is provided for both outcrops.