W. Cross — Post-Laramie Deposits of Colorado. 31 



writer. Fossil plants are quite numerous in all parts of the 

 series. Of those collected by the members of the Hayden 

 survey a large majority came from Mt. Bross, and a few from 

 distant localities on "Willow and Troublesome Creeks, from 

 strata referred to the same general horizon by Marvine. This 

 material has been described by Lesquereux* bat there has been 

 such a serious confusion of localities in also assigning a num- 

 ber of other fossil plants to Middle Park, that little use can at 

 present be made of these identifications. Collections of fossil 

 plants made by Mr. Cannon and the writer in various horizons 

 of this series have been provisionally identified by L. F. Ward 

 and F. H. Knowlton. From these data it can be said that out 

 of about 35 well defined species more than 20 are known in 

 the Denver beds of Table Mountain, at Golden, a closer cor- 

 respondence of floras than is shown with any other horizon. 

 Until the investigation of the Laramie flora now in progress 

 has been completed it is useless to enter into more definite 

 comparisons. 



The so-called Laramie beds of Middle Park seem from the 

 foregoing facts to be the equivalent of the Denver beds. No 

 strata corresponding to either the Arapahoe or Laramie proper 

 are known in Middle Park, and the invertebrates collected by 

 Mr, Cannon indicate that the upper part of the Montana is 

 also wanting in the vicinity of Hot Sulphur Springs. Present 

 information gives little ground for an estimate of the extent 

 to which the missing formations were once developed in this 

 region. 



Age of the Lake-bed Deposits. 



The facts of stratigraphy and lithology which have been 

 recited show that in Colorado the great conformable series of 

 Cretaceous formations ended with the coal-bearing Laramie 

 strata. Deposition plainly ceased in this area because conti- 

 nental elevation, which had long been in progress, finally 

 caused the retreat of the Laramie seas. The magnitude of 

 this elevation, the time interval involved, and the question as 

 to the identity of this j>articular movement with the great 

 movement generally supposed to mark the ending of Mesozoic 

 time in the Tiocky Mountain area, are clearly problems of 

 great importance. Confining discussion at present to the in- 

 disputable evidence of the deposits described, it is clear that 

 when sedimentation began again in the region concerned it 

 was in comparatively small seas or lakes. In the pebbles of 

 the Arapahoe, Canon City, and Ohio Creek beds, is found 

 proof that adjacent landmasses consisted in part of upturned 

 sedimentary rocks, and in the first named is the record of the 



* Monographs of the Hayden Survey, vol. vi, Tertiary Flora. 



