538 REPORT UNITED STATES GEOLOGICAL SURVEY. 



doubtedly tlie Fox Hills Group, and the sandstones in layer l^o. 3 may 

 represent tlie Fort Pierre Group (Cretaceous No. 4). 



The Fontenelle comes from the north on the west side of the principal 

 hogbacks until joined by a stream rising in the Absaroka ridges, where 

 it turns towards the east and cuts across the hogbacks, flowing in a zigzag 

 course, now across and now with the strike, until it reaches the head of 

 the caiion. Following southward through the trough-like depression 

 between the hogbacks and the Absaroka Eidge, we come to Crow Creek, 

 a branch of Ham's Fork. This stream flows southward west of the prin- 

 cipal sandstone hogback. Just outside of this sandstone ridge, where 

 the road from Slate Creek comes to the stream, I found an outcrop in 

 which the following fossils occurred in a bed of soft sandstone : 



Ostrea soleniscus. 



Ostrea ? 



Trapezium ? 



. Inoceramus f 



This layer I am inclined to think lower than the one from which Ostrea 

 soleniscus was obtained on the Fontenelle, although I cannot be certain. 

 The hogbacks at this point are much lower and the inchnation less 

 than on the Fontenelle. The hogbacks farther south, however, assume 

 greater proportions in the ridge of Ham's HiQ, and a small ridge in 

 which there is a coal-bed shows to the west of the latter. Farther 

 north I saw no evidences of this coal-bed, but the outcrops were so in- 

 distinct that it might easily be concealed by the debris, and I did not 

 have time to make a close detailed section at either of the points where 

 the hogbacks were crossed. The Fox Hills beds are seen abutting 

 against the Carboniferous limestone. Either there is a fault on the 

 west or the hill in which these limestones outcrop was a shore line 

 during Cretaceous times. This subj ect, however, will have to be deferred 

 to a future chapter. 



Looking north from the Fontenelle, the hogbacks are seen filling the 

 valley of Labarge Creek. Some of the branches of the latter stream 

 rise 7 or 8 miles south of the point where the Fontenelle emerges from 

 the Absaroka ridges, and have their valleys parallel to that of the latter, 

 although they flow in the opposite direction. On Labarge Creek the 

 trend of the hogbacks turns toward the west, and they become much 

 less prominent as viewed from Thompson Plateau, the nearest point 

 from which they were observed. 



THOMPSON PLATEAU. 



"Viewed from the Green Eiver Basin, the edge of this plateau presents 

 a very regular outline. It is about 10 miles in length and from 2 to 3 

 miles in width. Only one station (No. 47) was made on it, and that was 

 on the northern end. It is comj^osed of massive limestones dipping to 

 the west. Fragments of Zaphrentis were the only fossils. North from 

 the plateau there is an anticlinal fold that is on the direct line of the 

 fold of Meridian Eidge. It is probably the same fold, and I have called 

 it Meridian fold. At Station 47 the fold appears to be a monoclinal, 

 and the limestones appear to be connected with those on the west side 

 of Meridional Valley. Station 46 was on the axis of the anticlinal, but 

 the beds were concealed. The fold, however, could be distinctly seen 

 on the north side of the cafion of Piney Creek, and the section in an 

 accompanying plate gives the relations of the beds as noted. I am in 

 doubt about the gray beds in the centre, as no fossils were obtained. 



