Tertiary Stratigraphy and Paleobotany of the Cook Inlet Region, Alaska
U.S. Geological Survey
Professional Paper 398-A
The nonmarine sedimentary rocks of Tertiary age in the Cook Inlet region, once thought to be entirely of Eocene age, are shown be paleobotanical evidence to be mostly of Paleocene, Miocene, and Pliocene age. Our study of Chickaloon Formation, as suggested by Barnes and Payne (1956). The Wishbone Formation has not yielded fossil plants, but its conformable and gradational relationship to the underlying Chickaloon Formation indicates that it is at least partly of Paleocene age, although some rocks of Eocene age may be included. Our study of Kenai floras, shown to be mostly of Miocene and probable Pliocene age, confirms the suggestion of Barnes and Payne that two different coal-bearing rock sequences of disparate age may be represented by the Chickaloon Formation of the Matanuska Valley and the Kenai Formation of the Cook Inlet-Susitna Lowlands. The Tsadaka Formation, which rests unconformably upon the Chickaloon and Wishbone Formations, represents a marginal conglomeratic facies of the Kenai Formation; the fossil floras indicate that the Tsadaka Formation was deposited during the first half of the Miocene Epoch.
Wolfe, J.A., Hopkins, D.M., Leopold, E.B. 1966. Tertiary stratigraphy and paleobotany of the Cook Inlet region, Alaska. U.S. Geological Survey Professional Paper 398-A:A1-A29.