W. Cross — Post- Laramie Deposits of Colorado. 23 



On Ohio creek, but a few miles beyond the southern limit 

 of the Ruby beds, there are two small isolated patches of loose 

 friable sandstones, grits, and fine conglomerates, resting on the 

 coal-measures of the Laramie, and seemingly in small basins of 

 erosion. Owing to the disturbances caused by adjacent lacco- 

 lites it is impossible to see the relationship of the formations 

 clearly. The chert pebbles of these beds contain crinoid stems 

 and other apparently Carboniferous fossils, and are identical 

 in character with those already mentioned as frequently found 

 in the basal conglomerate of the Ruby beds near Irwin. These 

 facts suggest that the chert pebbles of the Ruby conglomerate 

 may be the residuum from the destruction of Ohio creek beds 

 formerly existing to the north of the Anthracite range. Mr. 

 Hills does not mention such pebbles in the section near Coal 

 ridge above described, but he does suggest a possible correla- 

 tion between the Ohio creek beds and the soft yellowish sand- 

 stones found at the north between the " firm gray sandstones 

 of the coal-measures " and the Ruby conglomerate. He also 

 thinks that the Carboniferous chert pebbles of the Ohio creek 

 beds indicate a post-Laramie erosion of the entire Cretaceous 

 section, exposing Carboniferous strata. Whether this hypoth- 

 esis be established or not it is true that such materials are not 

 seen in the Cretaceous beds above the Dakota conglomerate, 

 and it is not known to the writer that they have been found 

 at that horizon in this region, though not uncommon along 

 the Front range and in Middle Park. 



Mr. Hills has found that on Grand river the Ruby beds lie 

 between the Wasatch and the Laramie. The lithological and 

 stratigraphical evidence given there distinctly suggests that 

 the Ruby beds may be the equivalent of the Denver forma- 

 tion, and less decidedly that the Ohio creek beds may possibly 

 represent the Arapahoe formation. JSFo fossils excepting car- 

 bonized plant stems have been found in the two new forma- 

 tions. The writer does not place much weight on the mere 

 coincidence in eruptive character of the materials in the Ruby 

 and Denver beds, beyond the marked fact which seems to be 

 developing from experience that a number of formations of 

 apparently the same stratigraphical position are thus charac- 

 terized. It may finally come to be a criterion of considerable 

 value. 



Yarn/pa River.— hi northwestern Colorado on the Yampa 

 river Mr. Hills finds reason to believe that there is a distinct 

 formation between the Laramie proper and the Wasatch, but 

 is at present able to give no positive evidence for this view 

 except that the normal series of the Laramie has above it a 

 formation " of soft sandy strata with some shales and clays " 

 containing impure lignitic beds, and of general different 



