278 EXPLORATIONS ACROSS THE GREAT BASIN OF UTAH. 



with some of the higher strata, to a thickness of about 100 feet, and also caps some of 

 the mountains west of La Bonte Creek. Its age is probably the Jurassic. 



13. Purple slaty and shaly sandstone, with thin interstratincations of other colors, 

 green, blue, &c, 150 to 200 feet. 



14. Some gray sandstone, and much purple slaty sandstone and arenaceous shales, 

 with a thin interstratiiication of an impure siliceous limestone, and much gypsum; the 

 latter parti}' in strata, of which there are at least six at the principal butte, each of 

 them over 2 feet thick, partly disseminated throughout the arenaceous material in thin 

 scales and seams, 150 to 200 feet. 



15. Hard siliceous sand-rock of considerable thickness, which may belong to an 



The rocks Nos. 13 and 14 do not retain their diameter unchanged, as is common 

 with such formations. Near La Bonte Creek, the second locality where they are well 

 exposed, I noticed with them heavy beds of white and light-yellowish, fine-grained, 

 friable, quartzose sandstones, and the gypsum is there distributed somewhat differently. 

 The petrographical features of Nos. 13 and 14 are similar to those of No. D of Dr. Hay- 

 den's Black Hill section, which is by him there provisionally referred to the Carbonif- 



of the bed I). From its stratigraphical position, as well as lithological characters, it 

 might with almost as much propriety be referred to the Permian or Triassic systems as 

 to the Carboniferous." Underlying it he observed beds of bluish and reddish gray, 

 very hard, gritty limestone, 10 to 50 feet thick, No. E of his section, in which he found 

 a smooth, Spirifer-like shell, and Pleurotomaritt, JLtcrocItniht.s, mid L'rlfrfojtlion, the two 

 latter of which genera are unknown in the Old World in strata above the Carboniferous, 

 but have, in Eastern Kansas, been also found in the Permo-Carboniferous formations, 

 it appears, therefore, that all below No. D of the Black Hill section is Permian or Car- 

 boniferous, and, from the remark of Dr. Hay den, "that near the southeastern base of 

 the Black Hills some loose masses of a cherty rock were seen on more than one occa- 

 sion, under circumstances indicating that the stratum from which they were derived 

 holds a position between the beds C and D, and that several of the fossils which they 

 contain are identical with species occurring in a formation in Northeast Kansas, now 

 known to he of Permian age," it would seem that I) is also Carboniferous or Permian. 

 The close similarity which appears to exist between the strata D and Nos. 13 and 14 

 leads me to suppose that the latter observation may be erroneous, as I hesitate much 

 to refer Xos. 13 and 14 to the Permian age. It is, however, possible that they are 

 altogether distinct. 



In the Black Hills, according to that section, the Paleozoic formations appear to 

 be developed on a small scale only, much less than 1 have observed them near our 

 line of travel, and before further south, and again further west in the Wahsatch Mount- 

 would seem that this is due more to the nature of the upheavals, and nerhans powerful 



