Eocene Diatom Assemblages from the Kellogg and "Sidney" Shales, Mt. Diablo Area, California

This paper describes diatom species of two Eocene shales (Kellogg and "Sidney") in the Mt. Diablo area, California, and establishes a local diatom sequence of the "Kreyenhagen shale" and its equivalents in California. The shales crop out north and east of Mt. Diablo. The "Sidney" shale is a the middle member of the Markley formation, and the Kellogg shale is below the Markley. Nine samples from the Kellogg and nine from the "Sidney", all collected rom the same sections from which Clark and Campbell (1942) described radiolarian faunas, are selected to represent 90 feet of the Kellogg shale, and 85 feet of the diatomaceous part of the "Sidney" shale. Thirty-nine species, including a new one, are described from the samples. Frequencies of occurrences, and relative abundances of the species, taken by single counts of 200 specimens at each horizon, are shown in the distribution chart (Chart II). The assemblages of the Kellogg and "Sidney" shales are a common floral type