PALEOZOIC STRATIGRAPHY OF ROCKY MOUNTAINS 379 



This upper division of the Jefferson, as indicated by the correla- 

 tion diagrams, maintains a fairly constant development even where 

 the main body of the formation beneath it shows much variability. 



The beds doubtfully referred to Member 18 in the Goose Creek 

 Ridge and Rattlesnake Mountain sections are not typical of that 

 member, but resemble it in being massive and in underlying a 

 series of thin-bedded dolomites which possess all the essential 

 characters of Member 19. (See discussion of the Three Forks 

 formation, pp. 383-84.) It is perhaps more likely that the beds in 

 question really belong to the Richmond series. 



Misuse of the name "Jefferson" in Yellowstone Park and vicinity. 

 — The name " Jefferson" was first used by Peale 1 to describe the 

 dark limestones overlying the Gallatin formation in the Three 

 Forks quadrangle, Montana. The strata included by Peale under 

 that name are now believed to be entirely of Devonian age. 2 As 

 they comprise everything between the Gallatin formation below 

 and the Three Forks shale above in the type locality of the forma- 

 tion, it was natural for other geologists to apply the name "Jeffer- 

 son" to all the strata between those two formations in neighboring 

 areas. In the Livingston' quadrangle, 3 Montana, and in the Ab- 

 saroka 4 quadrangles, Wyoming, however, Hague confined the 

 name "Jefferson" to the strata which he regarded as Silurian, and 

 extended the name "Three Forks" to include all the limestones 

 carrying Devonian fossils. Iddings and Weed, in Yellowstone 

 Park, 5 employed the names in similar fashion, but not altogether 

 consistently in different parts of the Park. 



With the aid of his own field notes, and by as careful a correla- 

 tion of members as the published descriptions permit, the writer 



1 A. C. Peale, "The Paleozoic Section in the Vicinity of Three Forks, Montana," 

 U.S. Geol. Survey, Bull, no (1895). 



2 E. M. Kindle, letter of March 29, 1916; Edwin Kirk, letter of June 13, 1915. 



3 Arnold Hague, "Description of the Livingston Sheet," Geol. Atlas U.S., Folio 1 

 (1894). 



1 Arnold Hague, "Description of the Absaroka Quadrangle," Geol. Atlas U.S., 

 Folio 52 (1899). 



s J. P. Iddings and W. H. Weed, "Descriptive Geology of the Gallatin Moun- 

 tains," U.S. Geol. Survey, Monographs, XXXII, Part 2 (1899), chap, i; "Descriptive 

 Geology of the Northern End of the Teton Range," ibid., chap, iv; W. H. Weed, 

 "Geology of the Southern End of the Snowy Range," ibid., chap. vi. 



