46 SEDIMENTARY GROUPS OF THE PLATEAU PROVINCE. 



Creek and Black Buttes Stations. A fine section- can be obtained by com- 

 mencing at Pine Bluffs at the foot of the limestone beds and passing in a 

 direction a little north of west until the massive gray sandstone of the next 

 group is reached. Across this stretch of country the beds dip to the east, 

 and their outcropping edges stand in a succession of ledges and can be well 

 studied. It is better to follow the line which I have indicated than to make 

 a section along Bitter Creek, as there is a fault passing between old Hall- 

 ville and Black Buttes Station, and it is difficult along that line to determine 

 the amount of the fault, and hence there is a liability of duplicating or omit- 

 ting some of the lower members of this section. This fault will be explained 

 hereafter. 



The junction of the Bitter Creek Group with the Lower Green River 

 can be very well seen in the escarpment at Pine Bluffs; one hand can be 

 placed upon a limestone of the upper group and the other on a massive bad- 

 land sandstone of the lower. In like manner the junction between this 

 group and the next lower can be well seen in an escarpment east of and 

 facing Black Butte. There is an escarpment on the northeast side of Bitter 

 Creek, facing that stream and extending from Hallville Section House to 

 Point of Rocks, where the upper sandstones of the Point of Rocks Group 

 stand in an almost vertical cliff, and the lower members of the Bitter Creek 

 series can be seen to rest upon this sandstone unconformably. These beds 

 are exceedingly friable, ferruginous sandstones and shales, and in many 

 places a shelf or terrace is seen between the foot of the Bitter Creek shales 

 and the brink of the cliffs formed of the Point of Rocks sandstone. 



This group can be studied along the Union Pacific Railroad west of Rock 

 Springs. Three-fourths of a mile east of Lawrence Section House the railroad 

 passes with an abrupt curve around a ledge of rocks, where the junction of 

 the Bitter Creek series and the Lower Green River can be plainly seen. 

 Here you may place your forefinger on a limestone of the Lower Green 

 River and your thumb on a bad-land sandstone of the Bitter Creek Group. 

 In the escarped hills on either side, the line between the limestones and 

 buff and pink sandstones can be plainly seen. These rocks dip to the west 

 at an angle of about four degrees, and as you go eastward this dip gradually 

 increases, and bed after bed of the Bitter Creek Group can be seen well ex- 



