Jurassic Formations in 8. E. Idaho, etc. 61 



the red bed member has increased in thickness from 

 about 200 feet in the Freedom quadrangle to 1,000 feet 

 or more in Home Canyon. Here the apparent increase 

 is in part due to folding. These red beds and the over- 

 lying limestone which belong in the Thaynes as traced 

 southward were included in the Ankareh shale as traced 

 northward in the earlier mapping. 



The "Ankareh sandstone" of the Fort Hall Indian 

 Reservation as traced soutkward decreases in tkickness 

 and in tke Home Canyon section east of Montpelier is 

 only about 100 feet thick, tkougk farther south it appears 

 to be somewhat thicker. This sandstone was perhaps 

 originally included by Gale and Richards with tke over- 

 lying conglomeratic bed in tke Nugget and not considered 

 a part of tke Ankarek skale. In tkeir description of tke 

 Ankarek skale 14 tkey state tkat a massive limestone 

 marks tke top of tke formation, but in tkeir description 

 of tke Nugget tkey refer to tke conglomeratic bed as 

 "near tke base." This sandstone was, however, consid- 

 ered a part of the Ankareh in a section measured in 

 1912 by Mr. Richards and the present writer in a branch 

 of Indian Creek east of Bear Lake. 



The four subdivisions of the Nugget as previously 

 described are present in the Home Canyon section but 

 the conglomeratic member is represented by a dense 

 purplish quartzite and the shaly tendency of the lower 

 part of the limestone member above mentioned has 

 there developed so that the limestone appears in the 

 midst of shale rather than below the shale member. 



Present classification. — The foregoing account of at- 

 tempts to carry the Triassic terminology of Boutwell and 

 Veatch into southeastern Idaho shows the necessity for a 

 revision or redefinition of Triassic formation names. 

 The terms Woodside, Thaynes, and Nugget are well 

 established in the literature of the general region and 

 apply to rocks that are characteristically developed and 

 readily recognized, though showing considerable varia- 

 tion from their character at their type localities. These 

 names are, therefore, retained respectively as the Wood- 

 side shale, the Thaynes group, and the Nugget sandstone. 



The conglomeratic, calcareous, and shaly members in 

 the lower part of the Nugget as described in the Fort 

 Hall Indian Reservation are designated formations with 



14 Gale, H. S., and Bichards, E. W., op. eit., p. 420. 



