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The Washakie, a volcanic ash formation. Bulletin of the AMNH ; v. 26, article 4.

Show simple item record Sinclair, William John, 1877-1935. en_US Granger, Walter, 1872-1941. en_US 2005-10-06T15:44:08Z 2005-10-06T15:44:08Z 1909 en_US
dc.description p. 25-27 ; 24 cm. en_US
dc.description Includes bibliographical references. en_US
dc.description.abstract "The difference in petrographic character between the Bridger and Washakie has an important bearing on the problem of correlation in time. The Bridger rocks are rhyolite tuffs containing glassy sanidine while the Washakie rocks are andesitic with soda-lime feldspar. From the absence of agglomerates and the fine-grained character of much of the ash it seems probable that it was transported mainly by the wind, and as the prevailing winds are at present from the west and had probably the same direction in Tertiary time, the centers of eruption should be located somewhere in the west or southwest. The absence of agglomerates does not favor the idea of local contemporaneous vents discharging rhyolitic and andesitic ash respectively and the great thickness and uniform petrographic character of each formation is opposed to the conception of rapid variation in the chemical composition of the ash at a single center of eruption. Assuming contemporaneous deposition from two centers of eruption it seems probable, in view of the comparatively short distance separating the areas occupied by the two formations (about 50 miles)¹ that some intermixture of the two types of ash should be found, but the conspicuous absence of plagioclase feldspar from all the Bridger tuffs and its presence in all those of the Washakie shows that this has not occurred. The lithologic evidence, therefore, does not favor the idea of contemporaneity for any part of the Bridger or Washakie. The faunistic evidence of contemporaneity of the lower Washakie and Upper Bridger is therefore in contradiction to the lithological evidence. ¹Estimate based on map of Fourth Parallel Survey"--P. 26-27. en_US
dc.format.extent 256219 bytes
dc.format.mimetype application/pdf
dc.language eng en_US
dc.language.iso en_US
dc.publisher New York : Published by order of the Trustees, American Museum of Natural History en_US
dc.relation.ispartofseries Bulletin of the American Museum of Natural History ; v. 26, article 4. en_US
dc.subject.lcc QH1 .A4 vol.26, art.4, 1909 en_US
dc.subject.lcsh Volcanic ash, tuff, etc. -- Wyoming. en_US
dc.subject.lcsh Geology, Stratigraphic -- Eocene -- Wyoming. en_US
dc.subject.lcsh Geology -- Wyoming. en_US
dc.subject.lcsh Stratigraphic correlation -- Wyoming. en_US
dc.title The Washakie, a volcanic ash formation. Bulletin of the AMNH ; v. 26, article 4. en_US
dc.type text en_US

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  • Bulletin of the American Museum of Natural History
    The Bulletin, published continuously since 1881, consists of longer monographic volumes in the field of natural sciences relating to zoology, paleontology, and geology. Current numbers are published at irregular intervals. The Bulletin was originally a place to publish short papers, while longer works appeared in the Memoirs. However, in the 1920s, the Memoirs ceased and the Bulletin series began publishing longer papers. A new series, the Novitates , published short papers describing new forms.

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