GEOLOGICAL EEPORT. 293 



not represented, except possibly by No. 3 (!). Sandstone formations prevail there 

 entirely, consisting of more or less compact sandstones, some of which are con- 

 glomeratic, and of arenaceous and argillaceous shales, with only a few strata of lime- 

 stones. Their thickness amounts to many hundreds, perhaps thousands, of feet, and 

 their color is alternately white and red. These strata represent different epochs, the 

 Tertiary, Cretaceous, Jurassic, and Triassic. Still, their lithological character is so 

 uniform throughout, their stratification so much disturbed, and organic remains were 

 obtained at so few points only, that I have not been able to draw distinct limits 

 between them. Those of the sandstones Avhich appear to belong to the Tertiary 

 formation, and are distinguished from the others by their unconformable stratification, 

 have been described above as No. 3 of the Fort Bridger series. 



Underlying these latter, and in close contact with the estuary beds near the 

 junction of Sulphur Creek with Bear Kiver, we find along Sulphur ('reek a consid- 

 erable succession of white sandstones, interstratihed with red ami gray slaty sand- 

 stones and arenaceous and argillaceous shales. Some of these contain conglomeratic 

 seams. They trend from northeast to southwest, and are strongly, some of them even 

 vertically, tilted. A short distance below the crossing of the creek, on the old road, 

 a heavy bed of reddish siliceous conglomerate forms a rugged outcrop over the crest 



southeast, I observed a yellow sandstone with lunrmntms similar to /. probh'm<it/<t<.s. 

 A few yards farther east, above the crossing, prominent strata of white, rather line- 

 grained, soft sandstone, also varying only a few degrees from the vertical to southeast, 

 contain large numbers of Ostrea yhihra, another species of Ostrea, and an Anomia, 

 which by their abundance, make the rock fetid. It is immediately succeeded by 

 coal, the nearest stratum of which is several feet thick, while at least one more follow* 

 within a few feet of the first, and is separated from it only by some gray argillaceous 

 shales, but covered over with detritus, and not well exposed. The shales beyond it 

 attain a considerable thickness. Another upheaval, northeast from there, then inter- 

 rupts the regular succession of the strata, which seem to swing round, and to re-appear 

 higher up the creek with reversed dip, trending from south-southwest to north-north- 

 east, and dipping to north-northwest. At least I observed there a similar sandstone 

 with numerous Ostrea, and although I did not see the coal, the supposed place of 

 which, above the sandstonS, is occupied by the bed of the creek, I found an indication 

 of it in a hepatic spring, the like of which issues near the first coal. They apparently 

 originate from pyrites in these coal-beds. A spring of petroleum also issues in the 

 continuation of these strata a mile southwest of the crossing oi Sulphur Creek, which 

 latter has derived its name from those springs of sulphureous water. 



The coal and the sandstone with the Ostrea are unquestionably members of the 

 same formation, and the doubt in regard to that implied in a passage of Mr. Meeks 

 report, would never have been expressed if the writer had examined that locality him- 

 self, and also the analogous one on White Clay Creek, which leaves no room for ques- 

 tioning the position of the coal in the middle of the sandstone series. 



The paleontological evidence seems to point to the Lower Cretaceous (or even Ju- 

 rassic) age of this formation, and by general considerations I am, likewise, led to con- 



