﻿87 Outcrops 



interpolated in the darker beds. A band of dark red shale about 

 40 feet thick occurs about 120 feet below the top of the formation 

 north of Logan. 



Fossils are rare in the formation about Logan. The collection 

 made here is limited to a small coral of undetermined species, 

 Schuchertella chemungensis cf. arctostriatus, and fragments of fish 

 teeth. 



The Threeforks shales appear to have a much more limited dis- 

 tribution than the Jefferson limestone. They are present, how- 

 ever, in the Melrose section, on Camp Creek, some 30 miles west 

 of Threeforks. The following section is seen along Camp Creek: 



Section on Camp Creek, Montana 



K. Gray nonmagnesian limestone (Madison limestone) 300 + 



J. Bluish gray argillaceous shale, huffish shale in lower part, 



with limestone bands near middle (Threeforks shale) 200 ± 



I. Black magnesian limestone, with minor beds of gray lime- 

 stone distributed through the series (Jefferson limestone) . . 500=*= 

 H. Buff-gray, hard magnesian limestone, with some shaly bands . 30 

 G. Buffish gray nonmagnesian limestone in i-inch to 3-inch 



laminae, separated by thin bands of shale 35 



F. Dark-red sandy shales 20 



E. Light-gray magnesian limestone, with some dark bands in 



lower half 500='= 



D. Shale 100 



C. Shale and thin-bedded brownish sandstone 50 



B. Gray shale 40 



A Quartzite weathering brownish buff 65 



The Jefferson limestone seems to reach its maximum thickness 

 in the western part of the State. In the Philipsburg nearly 1,000 

 feet of the Paleozoic section is represented by the dark limestones 

 of the Jefferson formation. The following section indicates the 

 relationship of these beds in this region, as seen along Boulder 

 Creek, west of Princeton. 



