Microfossils recovered from the Roseburg, Lookingglass, and Flournoy Formations (Umpqua Group) of southwest Oregon include 33 species and subspecies of planktonic foraminifers. Some of the faunas from these units include as many as 14 species per sample, and specimen preservation is moderate to good. The assemblages are similar to those from central and southern California but differ in that they are dominated by long-ranging, high-latitude species.

The Roseburg and Lookingglass Formations were deposited during early Eocene time and are assigned on the basis of planktonic foraminifers to Zone P7-8 of the standard tropical zonation. The planktonic foraminiferal faunas of these units are indistinguishable. The Flournoy Formation is assigned to lower middle Eocene Zone P10. Planktonic foraminifers and calcareous nannofossils indicate that the unconformity between the Lookingglass and Flournoy Formations represents an interval of approximately 1 to 2 m.y.

Despite reports of Paleocene microfossils occurring in the Roseburg and Lookingglass Formations, no microfossils definitely of that age were found during this study. Cretaceous microfossils were recovered from a small outlier currently included in the Roseburg Formation. Although the rocks containing these fossils closely resemble those of the Roseburg Formation, they probably belong to a separate unit.