Abstract: Holothurian Microfossils and Eocene Stratigraphy of Southwest Oregon

W. N. Orr, G. A. Miles

Holothurian sclerites are reported for the first time from the Pacific Northwest. Scattered assemblages of these microfossils are present in the Roseburg, Looking-glass, and Flournoy formations of the Umpqua group in southwestern Oregon.

Radiolarian and foraminiferal faunas recovered from sclerite-bearing intervals indicate a late early Eocene to early middle Eocene age (zones P 7/8,P-10) correlative with the European Ypresian to early Lutetian Stages. The faunas reflect a temperate, cool climate probably in the path of an early version of the California current.

Umpqua group holothurian sclerite occurrences are dominated by species of the genus Priscopedatus. Occurring with that genus are Calcligula, Rhabdotites, and Calcancora.

Stratigraphic distributions presented may be misleading owing to the limited number of sclerite-bearing samples. Living holothurians have been shown elsewhere to yield as many as 20 million sclerites per individual. The very low frequency of holothurian microfossils in the Umpqua group is undoubtedly an expression of the high rates of sedimentation characteristic of southwest Oregon during the Eocene.

AAPG Search and Discovery Article #90963©1978 AAPG/SEG/SEPM Pacific Section Meeting, Sacramento, California