12 C. D. WALCOTT ALGONKIAN FORMATIONS OF MONTANA 



Feet Feet 



irregular, bluish gray, limestone nodules, imbedded 

 in a siliceous matrix. Sometimes the siliceous matter, 

 and sometimes the calcareous, predominates, and occa- 

 sionally layers that are purely siliceous, or arenaceous 

 limestone, occur, and banded, cherty layers are of fre- 

 quent occurrence. Occasionally the nodules of lime- 

 stone are small, very irregular in size and form, and 

 almost make up the entire mass of the rock, the sili- 

 ceous matter simply holding them together 960 



(j. Light gray, cherty, siliceous, banded beds, 1 to 2 feet in 

 thickness, with partings of siliceous shale at irregular 

 intervals. Layers occur with numerous flattened bluish 

 gray, limestone nodules and stringers arranged parallel 

 to the bedding. Some of the shaly beds are 1 to 2 feet 

 in thickness and more or less argillaceous or calcareous. 

 On the weathered surface the calcareous beds weather 

 buff and dull gray. Seventy feet below the top there is 

 a band of arenaceous, gray shale 35 feet in thickness. . . 1,100 



The section was all carefully measured, with the ex- 

 ception of the lower 600 feet, which was estimated 

 from dip and occasional outcrops on the lower slopes of 

 the ridge. 



Total of Lower division 2,660 



Total thickness 4,988 



The Upper division contains more calcareous matter, and the Lower 

 division is more siliceous. The separation is somewhat arbitrary, and 

 probably would not hold good at any considerable distance from where 

 the section was measured. 



The general strike of the beds of the section is north 30 degrees west; 

 average dip, 35 degrees north. 



NOTES ON SECTION FROM BELTON, EAST 



Bad Rocks Canyon section. — During September, 1895, I made a rapid 

 trip along the line of the Great Northern Railroad track from Belton to 

 the vicinity of Essex, and thence north to the head of Nyack creek. 



In Bad Bocks canyon, Montana, on the line of the Great Northern 

 railroad, the section given below was measured. This portion of the 

 section appears to correspond with the Blackfoot limestone of the Mission 

 Eange section, 85 miles to the south, and to indicate that that horizon is 

 persistent on the line of the strike of the Mission and Swan ranges. The 

 section is as follows: 



