MESOZOIC FORMATIONS. 
3 
position, and a mud-brown sandstone appears on the summit of the walls. 
Six or seven miles beyond the mouth of the canon, the gypsum bed is at 
the level of its bottom, forming low, rounded hills at the base of the sand¬ 
stone cliffs, which rise to a height of 700 feet. From this point, the bottom 
of the canon slowly rises between the sandstone walls, wliich, continuing 
their northwest dip, add perhaps 150 feet of thickness before the road 
reaches their summit-level. The “road issues from the canon on to an 
elevated country, which is covered with more grass than the regions pre¬ 
viously traversed, with large patches of sage-brush. A short distance from 
this point, a line of low hills runs, parallel to the direction of travel, with a 
northwest and southeast strike. They support groves of pifiones, and 
examination showed that they form the outcrop of the bed of Cretaceous 
No. 2, and doubtless rest immediately on the sandstone below. They con¬ 
sist of lead-colored shales, which whiten on exposure, and contain Inocera- 
mus and Ostrea in abundance. 
Having determined this horizon, I recur to those previously described 
with the view of identifying them with a known standard of comparison 
viz: Doctor Hayden’s section at Colorado Springs. The resemblance is at 
once seen to amount to an identity. The sandstone of the northern half 
of the Canon Cangilon is the Cretaceous No. 1; thickness, 800 feet. Below 
it, the gypsum is that usually referred to the Jurassic, 50 feet, and doubtless 
inseparable from the brilliantly-colored beds below (400 feet), which 
are stated by Play den to be Jurassic beds. The hard sandstone underlying 
these is the upper member of the beds that correspond to the Trias of the 
Colorado section. Their thickness on the Chama was not determined. The 
feature of this section is the increased thickne* of the beds of the Jurassic 
and Cretaceous No. 1. 
Continuing the route, we reach a second line of low hills of yellowish, 
soft sandstone with Ostrea^ probably Cretaceous No. 3, and then descend 
into the shallow valley of Nutria Creek. ‘ From this point, the level of the 
country rises to Tierra Amarilla, which was determined by the topographers 
to stand 7,480 feet above the sea. To the south and east of this town, high 
hills of yellowish sandstone present escarpments to the north, which are 
apparently Cretaceous No. 3, and contain numerous Inocerami. The Rio 
