A Paleogene calcareous microfossil Konservat-Lagerstatte from the Kilwa Group of coastal Tanzania

Microfossil assemblages and their shell geochemistry are widely used in paleoceanography, but they can be significantly altered by subtle variations in preservation state. Clay-rich, hemipelagic sediments of the Paleogene Kilwa Group of coastal Tanzania host calcareous microfossils that are exceptionally preserved, as evidenced by morphological, taxonomic, and geochemical data. The planktonic foraminifera are preserved as glassy, translucent tests with original microgranular wall textures that resemble well-preserved modern specimens, and they arguably yield geochemical values that are relatively unaffected by recrystallization. The calcareous nannofossils are extraordinarily diverse and represented by unique assemblage compositions that include dissolution-susceptible taxa, especially holococcoliths and rhabdoliths, and fragile and very small ( Keywords: calcareous nannofossils, foraminifera, preservation, Lagerstatte, Paleogene, diversity.