FOSSILS OF THE MIDDLE PARK BEDS. 281 



Laramie Land. — At the present time, within the mountain area roughly 

 defined by the east flanks of the Colorado range on the east, by the Laramie 

 plains, the Park range, White river plateau, and Elk and San Juan mountains 

 on the west, and by the southern flanks of the San Juan and Sangre de Cristo 

 ranges on the south, no beds of the Laramie or coal-bearing formation 

 proper are known with certainty to exist, except in the South park. The 

 beds which form the dividing ridge between the North and Middle parks, 

 and which were colored on the Hayden maps by Marvine as of Laramie age, 

 were so determined solely on the evidence of fossil plants, in spite of their 

 unconformity with Cretaceous rocks below and their want of lithological cor- 

 respondence with the Laramie beds developed elsewhere in Colorado. In 

 North park Mr. Marvine discovered, in beds which he referred also to the 

 Laramie group, though without expressing any opinion as to their strati- 

 graphical equivalence with the Middle park beds, a few molluscs, of which 

 Dr. White, after an examination of all the evidence both in field and office, 

 says : " Of themselves they are not sufficient to determine the age of the strata 

 containing them or their equivalency or otherwise with those of the Laramie 

 group."* A recent examination of these Middle park beds made under my 

 direction by one of my assistants has satisfied me that they were deposited 

 after the post-Cretaceous movement, and that if Laramie beds proper were 

 ever deposited in the Middle park they have since been removed by erosion. 

 As in the adjoining South park Laramie beds still remain under very similar 

 physical conditions, there seems to be some reason for assuming that the 

 Laramie shore-line did not reach as far south in the Middle and North park 

 depression as did that of the earlier Cretaceous seas in which case the bay in 

 which the South park Laramie was deposited must have had its connection 

 with the open sea by way of Canon City. 



In Huerfano park, which forms the southern end of the Wet Mountain 

 valley depression, Laramie beds still underlie unconformably the Eocene 

 Tertiary deposits which Mr. R. C. Hills has recently discovered there, but 

 it is not probable that they ever extended much further north in this depres- 

 sion than the present divide. 



No Cretaceous deposits whatever have been found in the depression of the 

 San Luis valley, and if this depression, as I assume on confessedly rather 

 indefinite grounds, was formed, like the valley of the upper Arkansas, 

 by post-Cretaceous displacements and recent erosion, the Cretaceous seas 

 did not cover it at all, except possibly the extreme southwestern border now 

 buried beneath recent eruptive rocks. 



On the western edge of the mountains, on the other hand, the great area 

 of the Uncompahgre plateau and the valleys of the Gunnison and lower 

 Grand river, from which the upper Cretaceous beds are now almost entirely 



* Op. cit, p. 203. 



