pealeJ DESCRIPTIVE GEOLOGY — GREEN RIVER BASIN. 537 



In the canon limestones probably outcrop, and if the qnartzites (No. 1 

 of the section) are Triassic, as I believe, the limestones would be of Car- 

 boniferous age. Professor Cope visited the canon and recognized Car- 

 boniferous rocks.* "In one of the Carboniferous strata," he says, "I 

 found a well-marked horizon of Carbonaceous shales extending as far as I 

 explored them." The erosion that has excavated the valley at the west 

 side of the ridge has therefore cut into a portion at least of the Carbon- 

 iferous. The ridge is therefore an anticlinal with the sharpest portion of 

 the fold on the western side. This is the portion eroded away. Erosion 

 has considerably obscured the beds, and at one time I thought it proba- 

 ble a fault extended along the ridge, especially as a fault was noticed 

 west of the fold at the canon of Ham's Fork. The latter fold is the 

 southern continuation of the Meridian Eidge. The valley between Me- 

 ridian Eidge and Absaroka Eidge is occupied by the Fontenelle Hog- 

 backs. The view from the former ridge is thus described by Professor 

 Cope in the report for 1872 : "From the summit we have had a beauti- 

 ful and interesting view of geological structure. The valley, of three or 

 four miles in width, is bounded on the west side by a range of low mount- 

 ains (Absaroka Ridges), whose summits are well timbered. The valley 

 is excavated at an acute angle to the strike of the strata, so that as far 

 as the eye can reach to north and south successive hogbacks issue en 

 echelon from the western side and run diagonally, striking the eastern 

 side many miles to the southward." 



The hogbacks, south, are not as numerous, because the fold of Meridian 

 Eidge is not so elevated, and the greater part of the beds curve over and 

 are found on both sides preserving the anticlinal. At the head of Slate 

 Creek I could find no evidence of any fault. The Wahsatch beds extend 

 farther to the westward below Slate Creek, so that the Jurassic beds do 

 not appear and the character of the ridge is completely lost. 



FONTENELLE HOGBACKS. 



These hogbacks have been partially described under the preceding 

 head, as they are formed by the western members of the Meridian Eidge 

 fold. They extend northward from Ham's Hill into the valley of Labarge 

 Creek. They are most marked on the Fontenelle, and hence their name. 

 A section carried across the valley or depression in which they outcrod 

 is in general as follows : 



Section No. 8. 

 Base. 



1. Shales and limestones, with bands of sandstone. The lower beds dip 



5° to the westward, and the upper beds 8° or 9°. The thickness, as 

 estimated, is about 500 feet. 



2. Above the layer No. 1 follow sandstones, with pink and gray shales 



above, which are yellow sandstones. The dip in these beds is 10° to 



west 900 feet. 



3. Yellow siliceous sandstones, forming well-marked hogbacks, dip 10°. .. 500 feet. 



4. Space probably tilled with sandstones and limestones, dipping 5° to 18° 



to west. In these is a bed full of Ostrea soleniscus. Thickness. . 1,000 to 1,500 feet. 



Some of the shales in larger IsTo. 1 resemble those of the Colorado Cre- 

 taceous ; but I could find no fossils, and failed also to recognize the Da- 

 kota Group. My time, however, was limited, and Professor Cope informs 

 me that he obtained Cretaceous fossils from some of the shales at a point 

 somewhere in this neighborhood. It is probable, therefore, that the 

 whole Cretaceous series is present. The beds, with the Ostrea, are un- 



* Report U. S. Geol. Survey, 1873, 1874, p. 440. 



