Identifier: annualreportofun1711geol (find matches)
Title: Annual report of the United States Geological Survey to the Secretary of the Interior
Year: 1880 (1880s)
Authors: Geological Survey (U.S.)
Subjects: Geological Survey (U.S.) Geology Water-supply Forest reserves Mines and mineral resources
Publisher: Washington : G.P.O.
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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arge. Farther up the Xehalem, 1 mile beyond Yernonia.the same dark shales, weathering gray, occur as at Pittsburg. Thirtyfeet of them are exposed by the stream, and they are nearly horizontal.When wet and dried in the sun they fall to pieces, so that erosion israpid. Fossils are not uncommon. All those collected here w ere foundalso at Pittsburg excepting Pentacrinus and Periptoma. At Wilsons Bluff on the river, 3 miles above Yernonia. gray shalesappear, with concretions, some of which are 10 feet in diameter, parallelto the bedding and 2 feet perpendicular to it. Most of the concretionsare small, and. as already noted at many other places, contain the cara-pace or legs of crabs. The strata dip gently to the eastward, and it isevident that the shales above Yernonia are older than those at Pittsburg. Although the whole section seen on the Nehalem from WilsonsBluff to Pittsburg is at least 10 miles in length, it is not directly across ■Am.Naturalist, June, i8»o. Vol. xiv, p, 4:>T.
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OLIGOCENE. 467 the strike and does not expose more than a few hundred feet of shalesand overlying sandstone. The fossils found at Wilsons Bluff are Dolium petrosum Conr., Nuculatruncata Gabb, Yoldia impressa Conr., Pseudomusium peclchami Gabb,with Dentalium, Scaphander, Cylichna, Leda, and Tellina. The partydid not follow the Nehalem farther up than Wilsons Bluff, but thesection must be quite like that of Kock Creek, a short distance to thenorthwest, where the Oligocene shales are covered by Pliocene tuffsand are succeeded westward by Eocene shales and underlying volcanies.The southern part of Columbia County, taken in connection with theadjoining portion of Washington County, probably affords the bestground in the State for studying the relations of the Eocene, Oligo-cene, and Miocene. Extending south from Vernonia, the Oligocene soon passes under theMiocene, which forms the divide in that direction, aud was not seenagain along the eastern foot of the coast range until Polk County wa

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