THE GENERAL PLAINS STRUCTURE. 147 



Quaternary deposits of the Platte Valley. Probably, however, the western 



sin] f the Laramie hill continues to sink, while the Arapahoe and Denver 



meet around its spur, the latter covering the former in the same irregular 

 manner as it does in resting elsewhere upon the formations beneath. 



The depth of the Laramie beneath the area under discussion probably 

 varies, but to what extent and in what direction is indefinite. It is believed, 

 however, from artesian Hows in the valley of the Platte and from a g< neral 

 examination for dips over the entire region, that there is a basiuing ip of 

 the strata east of the river by which the depth that would otherwise be 

 attained by the formation is considerably lessened. Without ii 

 Laramie would, in the vicinity of Section Y, reach a development of 

 2,400 feet — a thickness perfectly possible, indeed, and even adi ! ble, 

 but nevertheless abnormally great in comparison with its known th 

 in every other part of the Denver field and in much of the couhtn • mud. 

 The thickness assigned the Laramie at the eastern end of Section V is 

 1,500 feet. 



Along the line of Section III, the Laramie strata have been taken as 

 horizontal, the base of the formation at the eastern end of the section being 

 thus placed at a depth of 1,450 feet. This maybe regarded as the extreme 

 limit at which the coal series may here be found, and it is quite possible 

 that unrecognized upward flexures may make it less. The depth of the 

 Arapahoe on the western slope of the Laramie rise in Section III is deter- 

 mined chiefly by its depth beneath the Platte River, the wells along here 

 indicating for it a thickness of between 300 and 100 feet, ami the line of 

 division being drawn accordingly. Northeast of the Laramie the deposit 

 of Arapahoe sediment is but slight, the underlying formation apparently 

 sloping off very gradually. 



At the eastern end of Section IV. without flexure in the strata, the 

 base of the Laramie probably lies about 1,584 feet beneath the surface 

 This oives it approximately the same level as at Denver. A slight i iward 

 flexure might, however, be allowed the strata by way of connecting 

 Sections III and V, along the latter of which an upward flexure is highly 

 probable. The artesian wells on the line of Section IV afford no data in 

 regard to the question, unless it be in favor of a horizontal position or of 

 a flexure affording a very slight rise to the east, in which case the depth 



