UO 2561 - McMahn Branch [Eugene Fm] (Eocene of the United States)

Also known as #44 (Hickman)

Where: Polk County, Oregon (45.0° N, 123.2° W: paleocoordinates 45.3° N, 110.9° W)

• coordinate based on nearby landmark

• outcrop-level geographic resolution

When: Eugene Formation, Priabonian (38.0 - 33.9 Ma)

• Eugene Formation can be subdivided faunally: a lower unit correlating to the Keasey Fm, a middle unit correlating to the Gries Ranch Beds of WA, and a upper unit correlated with the Pittsburg Bluff Fm. Thickness of formation may be up to 15,000 feet, but probably around 5,000 feet. Most of the outcrops are scattered so it is difficult to estimate their relative stratigraphic placement

• bed-level stratigraphic resolution

Environment/lithology: coastal; lithified, tuffaceous, brown, gray, blue sandstone and tuffaceous, brown, gray, blue siltstone

• Tuffaceous and highly feldspathic sandstone or siltstone which is bluish-gray to olive when fresh and weathers to a buff or orange-brown color. Gray sandstone and siltstone beds may range from several to 50 feet in thickness and are interbedded with minor amounts of sandy sahel and clay shale, occasional beds of conglomerate, and thin lenses of gray or buff-colored volcanic ash

Size class: macrofossils

Preservation: mold/impression, trace

Reposited in the CAS

Collection methods: quarrying,

• Collections held at University of Oregon, University of California, Californian Academy of Sciences (CAS), United States Geological Survey (USGS), and Stanford University (NP).

Primary reference: C. J. S. Hickman. 1969. The Oligocene marine molluscan fauna of the Eugene Formation in Oregon. University of Oregon Museum of Natural History Bulletin 16:1-112 [A. Miller/A. Hendy/P. Wagner]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 39031: authorized by Austin Hendy, entered by Austin Hendy on 18.05.2004

Creative Commons license: CC BY (attribution)

Taxonomic list

• Exhaustive for mollusca
Bivalvia
 Cardiida - Mactridae
"Spisula pittsburgensis" = Mactromeris pittsburgensis
"Spisula pittsburgensis" = Mactromeris pittsburgensis Clark 1925 clam
 Cardiida - Tellinidae
 Hiatellida - Hiatellidae
"Panopea (Panopea) ramonensis" = Panopea ramonensis
"Panopea (Panopea) ramonensis" = Panopea ramonensis Clark 1925 clam
 Solenida - Solenidae
 Nuculida - Nuculidae
Acila (Truncacila) shumardi Dall 1909 divaricate nutclam
 Protobranchia - Nuculanidae
"Nuculana washingtonensis" = Litorhadia washingtonensis
"Nuculana washingtonensis" = Litorhadia washingtonensis Weaver 1916 pointed nut clam
Cephalopoda
 Nautilida - Aturiidae
Aturia angustata Conrad 1849 nautiloid