334 REPOET UNITED STATES GEOLOGICAL SURVEY. 



26. Drab shales, witli indurated layers. 



27. Eusty buff areno-argillaceous indurated layers. Dip 40° to 45Q, 



w. 150 S. 



28. Eusty-gray, chocolate-brown weathered, even-bedded limestone. 

 Dip 430, W. 20° S. Contains Aviculopecten f, a smaU PseudomonoUs f , 

 Cam^tonectes f , and a form resembling Mytilus; aU common forms in 

 Jurassic horizons in this region. There are several layers, at least five, 

 of this limestone alternating with softer deposits, making up a heavy 

 deposit 300 to 500 feet in ttdckness. 



29. Unexposed space, 500 to 800 yards. 



30. Light-gray limestone, similar to bed 28, showing several layers, dip- 

 ping 5° to 20°, E. to E. S. E. The upper layer is charged with a small 

 Fseudomonotis f and Aviculopecten. These layers bear a general resem- 

 blance in their lithology to those mentioned under No. 28, but their iden- 

 tity was not conclusively determined, although it seems very probable. 

 From this point, descending to the valley of Lincoln Creek j the strata 

 dip very gently easterly, forming the west slope of the synclmal trough, 

 the axis of which approximates that of the divide. 



31. Shaly limestone, like the last preceding, two or more layers. Like 

 the preceding limestone layers, the present layers dip gently south of 

 east at an angle of 5° to 10°, but soon increasing to 20°, with in- 

 dications of local disturbance in masses of strata dipping at a steeper 

 angle north of east. 



32. Eusty-gray, chocolate-brown weathered, thin-bedded limestone, 

 recalling the crest-ledges mentioned under ISTo. 28, also 'No. 25. 



33. Eeddish-buffj thin-bedded sandstone, and variegated, chocolate- 

 colored, partially mdurated shales, interbedded with drab-gray, frag- 

 mentary limestone. Its equivalent in the opposite side of the synclinal 

 was not recognized, although it probably holds a position below bed 

 No. 25. 



34. Drab-gray, fragmentary limestone, alternating with partially indu- 

 rated chocolate-variegated shales, imperfectly exposed over a wide space, 

 terminating in ridge overlooking Lyncoln Yalley, toward its head. 



35. Ledges of pink or pale-reddish, heavy-bedded sandstone, extend- 

 ing 150 to 300 feet below summit of above limestone-capped ridge. 



36. Heavy-bedded, gray, gritty limestone, 3 feet exposed,, dipping 

 gently southeasterly. 



37. Grassy slope, showing no exposure of rocks, thence to Lincoln 

 Creek. 



At the head of the little stream which joins the Lyncobi at Fort Hall, 

 a distance of 5 miles east of the post, the ridge rises into a prominence 

 on which Station IV was made, 2,200 feet above the plain in the de- 

 bouchure of Lincoln Yalley. The first rock encountered ascending this 

 little stream crowns a low hiU on the north side at an elevation of about 

 500 feet above the post, and one and a quarter miles distant. This con- 

 sists of reddish, yellow-mottled, coarse sandstone, dipping 20° to the 

 southward ; bed a. About a mile farther east a heavy deposit of deep red 

 sandstone forms the summit of a higher elevation, the beds dipping 25° 

 to 30°, W. 15° to 25° K ; bed &. One-half or three-quarters of a mile 

 east-southeast of the last exposure, in the north bluff of a gorge through 

 which a branch of the stream flows at this point, a heavy ledge of drab- 

 gray limestone appears, in the upper layers of which a few obscure fos- 

 sUs were found j a Fseudomonotis and a small Ostea-like shell, which in- 

 dicate the Jurassic age of the beds in which they occur. The limestone 

 shows a variable dip and strike at the several exposures examined, rang- 

 ing from 20° to 50°, W. 30° to 80° N. 5 bed c. These limestones are ap- 



