PEALE.] GEOLOGY LIGNITIC GROUP. 155 



sometimes the Liguitic group rests on No. 4 or No. 3 Cretaceous.* I 

 have already (page 14:5) referred to the equivalence of the Judith Eiver 

 beds and some strata at the eastern base of the Eocky Mountains, west 

 of Greeley and Evans, Colo. The fossils upon which Professor Meek 

 predicated this equivalence " came from the very upper beds of well- 

 defiued marine Cretaceous, and below the horizon of all the coal-bearing 

 strata of the Colorado region." t 



In the report of United States Geological Survey for 1872, p. 459, Pro- 

 fessor Meek speaks of the resemblance of some of the fossils from the Black 

 Butte and Point of Eocks localities, to some species found in the brack- 

 ish-water beds at the mouth of the Judith Eiver. They would seem, 

 therefore, to be equivalent to those seen east of the mountains west of 

 Greeley. He says they are distinct from any found at Coalville or Bear 

 Eiver. In speakiug of Black Butte it must be remembered that there 

 is also a Black Butte station at which the beds are probably not of the 

 same horizon. Point of Eocks, Hallville, and Eock Spring are not all 

 of the same horizon. In goiug from Table Eock to Salt Wells (see re- 

 port of H. M. Bannister, U. S. Geological Survey, 1 872, p. 524), we go down 

 through a fresh-water series to brackish-water beds and fiually to ma- 

 rine Cretaceous at Salt Wells, which is in an anticlinal. Speaking of 

 the coal horizon of Point of Eocks, Bannister says:| "It seems almost 

 too low in geological position to be referred to the horizon of the Hall- 

 ville beds, although it may occupy the same." Meek, in the report 

 for 1872, p. 458, refers them to the same horizon, although in the re- 

 port for 1871 he refers Point of Eocks to the Cretaceous and Hallville 

 to the Eocene, from the affinities of the fossils. 



Until the stratigraphy of the region is thoroughly investigated there 

 must remain some little doubt. Professor Meek, in his table of fossils 

 of the Bitter Creek series, § evidently considers the Point of Eocks 

 locality at the lower part of the series. Professor Meek || has identified 

 some fossils from two hundred miles east of Greeley, Colo., as the same 

 that are found over one of the coal-beds at Hallville, Wyo., and at 

 Black Butte Station, Utah. He says: "That the formation from which 

 these fossils came, however, is the same as the Bitter Creek series of 

 Wyoming, including the Black Butte beds, the Hallville coal-mines, 

 Point of Eocks, and Eock Spring coal-mines, &c., I have scarcely a 

 shadow of doubt." 



It remains now to state the following conclusions : 



1. The lignite-bearing beds east of the mountains in Colorado are 

 the equivalent of the Fort Union group of the Upper Missouri, and are 

 Eocene-Tertiary ; also, that the lower part of the group, at least at the 

 locality two hundred miles east of the mountains, is the equivalent of 

 a part of the lignitic strata of Wyoming. 



2. The Judith Eiver beds have their equivalent along the eastern 

 edge of the mountains below the Lignite or Fort Union group, and 

 also in Wyoming, and are Cretaceous, although of a higher horizon than 

 the coal-bearing strata of Coalville and Bear Eiver, Utah. They form 

 either the upper part of the Fox Hills group (No. 5) or a group to be 

 called No. 6. 



3. That the upper part of the Fox Hills group is wanting in many 

 parts of Eastern Colorado, and when present seems to be thin and des- 

 titute of coal. 



* Hayden Bulletin No. .5, 2d series, U. S. Geological Survey of the Territories, p. 404. 



t Bulletin Xo. 1, 2d series, U. S. Geological Survey, p. 40. 



i Report U. S. Geological Survey, p. 532. 



$ U. S. Geological Survey, p. 477. 



II Bulletin No. 1, 2d series, p. 42. ; 



