Abstract

Planktonic foraminifera occur sporadically throughout 395 feet of the Cannonball Formation at Garrison Dam, N. Dak. The assemblage (7 species, none new) is characteristic of the Globigerina edita Zone of Hillebrandt, 1965 (=Globorotalia pseudobulloides Zone of Bolli, 1966) and is considered diagnostic of the lower parts of the Danian stage (below the Globorotalia trinidadensis Zone). This precise correlation of the Cannonball indicates a similar age for equivalent nonmarine formations in Montana, Wyoming, and the Dakotas (Ludlow, Tullock). The Ludlow in North and South Dakota has been dated as Paleocene on plant, spore, and pollen evidence. The Tullock in Wyoming contains Paleocene plants. Recently the Tullock in eastern Montana has yielded Paleocene mammals of the Puercan stage.

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