326 LTE JOURNAL IOLRANGBROEOGN. 
toward a baselevel before the close of the known upper limit of 
the Chuar terrane. 
The lithologic characters of the Unkar terrane are rather 
uniform in the upper portion, the strata consisting of reddish- 
brown and greenish sandy shales, and of layers of a medium- 
grained sandstone, varying from 2 inches to 3 feet in thickness. 
In the more thickly bedded portion there is a tendency to form 
cliffs that resemble the Triassic sandstones of the Vermilion 
Cliffs of southern Utah, and the shaly portions are much like 
those of the Trias. As a whole the prevailing color is‘a reddish- 
brown, much like that of the Carboniferous Lower Aubrey sand- 
stone cliffs in the canyon wall, 2000 feet above. Traces of life 
are as yet unknown; ripple-marks, fine and coarse mud-cracks, 
and all the markings of quiet, shallow water and a low shore-line 
that was frequently exposed to the action of both water and air, 
are abundant. 
The sandstones of the Unkar group are exposed directly in 
the Grand Canyon, below the mouth of Chuar Valley; and the 
rocks of the Chuar terrane occur in nearly all of the canyon val- 
leys between the eastern side of the Kiabab plateau and the six 
great buttes that form the west side of the lower portion of Mar- 
ble Canyon. 
As indicated by the section, the Chuar terrane was formed 
and calcareous muds, uniformly spread over a relatively level sea- 
by the deposition of a great series of argillaceous, arenaceous, 
bed. The strata now succeed one another as fine sandstones, 
shales and limestones, the lithologic characters resembling those 
of the Cretaceous, as seen in the cliffs a few miles to the north. 
In places the limestones and shales may be compared with the 
Trenton limestone and the Utica shale of the Lower Paleozoic 
of the East. The parti-colored shales, in one belt 700 feet in 
thickness, recall the friable Permian clays. In fact, there is no 
more evidence of metamorphism throughout the 12,000 feet of 
the Grand Canyon series than there is in the evenly bedded strata 
of the Permian, Triassic, and Cretaceous groups of the Plateau 
Province of northern Utah. 
