Haynes: Fauna of the Upper Devonian in Montana. 19 



The following sections of the Three Forks Formation were measured 

 by the writer south of Jefferson River between Willow and Antelope 

 Creeks. 



Section K, measured one and one-half miles west of Willow Creek. 

 Here the strata are vertical and have an east-west strike. 



Base of gray Madison limestone. 



I and 2. Yellow sandstone and shales 70 feet. 



3. Black coaly shale 5 



4 and 5. Green shale calcareous at the top, with white and 



yellowish shales at the base 87 



6. Massive gray limestone 41 



7. Yellow nodular limestone 53 



Total 256 feet. 



Top of brown Jefferson limestone. 



Section L, farther west in Three Forks ravine. Strike of strata N. 

 80° W. dip 70° N. 



Base of gray Madison limestone. 



I. Yellow sandstone and talus obscuring 2, 3, 4, s 108 feet. 



6. Gray massive limestone 15 



7. Yellowish red thinly bedded limestone 25 



7a. Nodular red limestone, nodules 2 to 3 inches in diameter . . 73 



Total 221 feet. 



Section M was measured just east of Sand Creek. The strata 

 strike N. 60° E. and dip 40° N. 



Base of gray Madison limestone. 



1. Yellow sandstone in cliff 10 feet- 



2. 3, 4, and 5. Contacts obscured and therefore not measured 



separately 135 



Sa. Thinly bedded white and yellowish limestone 18 " 



Sb. Pale pink shaly limestone 12 "" 



Top of grayish yellow limestone No. 6. 



Section N, measured about a half miles west of Sand Creekr- 



Base of gray Madison limestone. 



I and 2. Yellow arenaceous limestone and nodular yellowish gray 



limestone 76 feet. 



3. Black coaly shale 5 "" 



4. Gray nodular limestone. 

 Remainder of section obscured. 



Section O, the westernmost section, was measured about a quarter of 

 a mile east of Antelope Creek. Strike E.-W., dip 30° N. 



