UTAH ACADEMY OF SCIENCES 25 
operation commences anew. This is what Dutton named 
“Weathering by recession of cliffs” and is very character- 
istic of the whole formation. 
The upper, or Castlegate sandstone, is very different. 
It attains a thickness of over 500 feet, is very compact 
and is broken by joints and cross joints into large blocks. 
One set of these joints is parallel to the bedding plane and 
the other at right angles to it. Consequently the talus 
from this stratum is formed of large angular blocks, 
while the talus of the lower strata consists of rounded 
boulders. The Castlegate sandstone is also underlaid by 
a layer of shale and this preserves the recession of cliffs 
uniform throughout the formation. Its general resem- 
blance to cyclopean masonry makes it easy to identify. 
Apart from its fauna the Laramie has strong lines 
of demarcation. The abrupt change from argillaceous to 
arenaceous at the bottom, and the gradual transition 
from arenaceous to calcareous at the top presents an 
unfailing index to its delimiting lines. These character- 
istic lines of demarcation, so I find, are coextensive with 
the Laramie exposures in other portions of Utah. 
The Laramie is divisible into three natural zones, viz., 
Upper Zone—Heavy sandstones with a few beds 
of shale, and makes precipitous 
CULES ON a ae Rd eee 1500 feet 
Middle Zone—Thin beds of sandstone and shale, 
many seams of coal; makes 
talus-like slopes ............ 500 feet 
Lower Zone—Heavy bedded sandstones grading 
into thin argillaceous sandstones 
at the bottom, makes bluffs on 
top merging into talus-like 
Slopes at. base nike cel 1000 feet 
Having thus described the general features and succes- 
sion of the Laramie as it occurs near Castlegate and Sunny- 
side, I shall now give a general description of the Mesa 
Verde as it occurs at the type locality, where I have had 
two seasons of geological work. 
