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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er north of Mohawk post-office, as may be seen in Plate XXIV, which represents both the Ter-tiary beds and theoverlying Pleistocene gravels. The illustration alsoshows that the older beds have been eroded before the deposition of thelate coarse gravelly material. Embedded in the Pleistocene gravel andsand are angular blocks of the Tertiary shale. The same Tertiary bedsmaybe seen at numerous pointsin Mohawk Valley. What are probablyportions of the beds of the same Tertiary lake are exposed along theFeather River east of the valley on the farm of Abel .Jackson.1 Fossilleaves were obtained here at two points, and a list of some of these maybe found in the previous report.2 Other material was obtained later,which has not yet been studied. Oak leaves are abundant. Professor It is likely, however, that tlie leaf Weds nt .Taeksona are later than the whiteheil.x eon tninin £ lajCM of carbonaceous shale.. Fourteenth Ann. Kept. U. S. Gool. Survey,Part 11,1884. p.488,and Mohawk lakebeds,p.tfil.
Text Appearing After Image:
TTBKEB.) TERTIARY LAKE BEDS. 599 Knowlton considers tbe deposit to be of Tertiary age. The beds atlocality 115 are covered by andesitic breccia, and tbe upper layers ofshale were so intercalated with andesitic material as to indicate thatthe andesite eruptions had begun at the time the leaf beds were form-ing. The beds at locality 111 (about 1,000 feet up stream from 115) aremade up of sandy material with layers of Carbonaceous shale, restingon pre-Cretaceous stratified tuffs. Only one species was recognizedhere—Platcmus dtssecfa? Lx. The beds dip westerly at a gentle angle.There appears to have been erosion before the beds were buried underthe andesitic breccia, as they are distinctly cut off to the south by theuustratified breccia, which reaches down to the level of the water.About one-fourth mile upstream, around a sharp bend of the river, aresome beds of granite detritus, also covered by the andesite breccia.This detritus is probably another exposure of the beds seen at locality

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