GEOLOGICAL SURVEY OF THE TERRITORIES. 



71 



syncliunl the beds are mucli crushed, so that 

 very obscure. Ou the opposite side we pass 

 edges of the same series, comuieuc- 

 iiig with the Coal strata, but with 

 a reversed dip. The complete series 

 has been tilted beyoud a vertical, so 

 that some of the high ridges of lime- 

 Stone incline 45°. (Figs. 20 and 2L) 

 Xea'r the upper portion of the 

 Jurassic group there is a bed of gray 

 limestone six feet thi^k, made u[) of 

 an aggregate of small Gasteropod- 

 ous shells. Tills bed is well exposed 

 in both divisions of the synclinal. 

 Patches of the lake-deposits are 

 thinly scattered over the surface, 

 filling up the irregularities, occasion- 

 ally showing a moderate thickness 

 either of marls or conglomerates. As 

 we pass up the Gallatin Valley from 

 its mouth we observe that the river 

 flows along a high-bluff wall on the 

 east side. There are several local 

 synclinals as well as anticliuals, but 

 none of the Carboniferous beds seem 

 to have been affected. In the low 

 hills east of the river, about five miles 

 above the mouth, is a sort of local 

 depression, in which are remnants 

 of the Jurassic gronp. As I have 

 so often repeated in this report and ^ 

 in my previous reports, the evidence 

 is continually shown that the forma- 

 tions all originally extended over the 

 country in a horizontal position at 

 one period ; that they have since 

 been removed to a great extent bv 

 erosion, but here and there we find 

 indications of tbeir former existence. 

 The section will show a most exten- 

 sive series of Carboniferous lime- 

 stones rising gradually as we ascend 

 the Gallatin. I described these beds 

 somewhat in detail in my report for 

 1871. The series of Carboniferous 

 limestones is remarkably well 

 shown for a distance of about five 

 miles above the mouth of the Gal- 

 latin. Just opposite the grist-mill 

 the very compact, brittle beds, which 

 are supposed to be of Silurian age, 

 come in, forming massive bluff-ex- 

 posures. Ju8t beneath these nmss- 

 ive beds of limestone is a series of 

 loose, bi'owu shales and clays with 

 thin layers of impure limestone. 



they 

 over 



are 

 the 



rendered 

 ujiturned 





to 

 O 



layers 



lime 



