276 EXPLOKATIONS ACROSS THE GREAT BASIN OF UTAH. 



reous, and changing into a gritty, impure limestone. It is fetid, from a large amount 

 of organic remains. This is the rock just referred to, in which I found the Jurassic 

 fossils. It contains one or two species of Belemnites, Pentarrhuis, Dnitalhiw, two Pecten, 

 two OstreOj a Gryphaa, some indistinct fragments of other Acephala, and also what 

 appears to be worm-tracks. 



11. More shales like 9. 



The relative superposition of these strata is not altogether plain, as I have stated 

 above, and from this enumeration of their geographical succession, together with my 

 other field-notes, two different geological sections may be formed. I am not positive 

 winch ot the two is the correct one. The main point upon which the question hinges is 

 whether Xos. 3 and 4 are Upper Cretaceous, corresponding to the Cretaceous sandstone 

 and Lignite formation higher up on Platte River, or if they are Lower Cretaceous, cor- 

 responding to Xo. 1 of the Cretaceous section of Nebraska, of Messrs. Meek and 

 Hayden. 



If the latter view is correct, then the strata appear to be enumerated in our sec- 

 tion above in the order in which they actually overlie each other, beginning with the 

 highest. The dip, although slight at that point, appears to be uniformly in the same 

 direction. 



Dr. Hayden, in the paper mentioned above (Proc. Acad, of Phil., March, 1858), 

 gives a section of the strata near the Black Hills, in which he assigns' this same posi- 

 tion to a series of rocks very much like our Nos. 3 and 4. He finds in them besides 

 indistinct vegetable remains, also seams and la vers of dark carbonaceous matter or 

 impure lignite, which I did not observe in Xos. ;>, and 4 below the Red Buttes, altlmu.-h 

 hgmte may perhaps, exist in those strata. 1 found seams of it a tew miles west frnm 

 there, which may possibly occupy this horizon. Farther west, in the Wahsuteh 

 Mountains, I have also observed a considerable sandstone formation containing some 

 beds of brown coal, overlying Jurassic strata (see section IV). The few' fossils" 

 found there point decidedly to the Lower Cretaceous, (or, possibly, even Jurassic) age 

 \ )[ that S ;:!' 1, ; S - !,11,j ;l,rh "^' h differently developed, according to local circumstances,"* 

 is must likely coeval with Xo. I of the Nebraska section. These observations show- 

 ing that the sandstones at the base of the Cretaceous formations of Kansas and Nebraska 

 extend with increasing thickness to the western limit of the secondarv formation, in 

 these latitudes, corroborate the opinion that Nos. 3 and 4, although no fossils have 

 hon n zon Und ^ them fr ° mWhich t0 determine their age, may represent that same 



w J^'- 5 1^ \f the . aW r 1 )™ eVklently bel ° n - t0 S ether; As ™ *"» ™nains 

 weie noticed in them, it must be left to further investigations to decide whether fchev 

 are Jurassic or Cretaceous. In their lithological character they resemble the follow- 

 ing Jurassic strata. J ow 



™ T ^* tm "°- 6 » ™ like an 7 «>™on rock or shale, and its present condition 

 seems to be due to chemical agencies. I would certainly consider it as quite local if 

 I had not seen exactly the same substance, in connection with similar shales and slates 

 on a previous expedition under Lieut. F. T. Bryan, Topographical Engineers some 

 80 miles south from there, near the Medicine Bow Buttes. In a piece of It, which had 



