34 
THE GRAND CASON DISTlilOT. 
Grand Canon district. The Kaiparowits wall, broken for a moment at the 
mouth of the Glen Canon, resumes its course south of the river on the sum- 
mit of the Echo Cliffs and reaches 80 miles beyond the Colorado. Its 
meaning here is the same as that of the terminal edges of the Cretaceous 
in the terraces of the High Plateaus. In the terraces we find the edges of 
the Mesozoic system forming the northern margin of the Grand Canon dis- 
trict. In the Kaiparowits front and in its continuation along the line of the 
Echo Cliffs we find the edges of the same strata forming the eastern margin 
of the district. Thus, upon two sides of the Grand Cation platform, the 
Cretaceous, pi’eserved in full force, presents the abruptly terminated edges 
of its strata towards that platform and overlooks it. The littoral belt of 
southwestern Utah and southern Nevada may be looked upon as part of a 
third side of the district, disclosing a fringe of Cretaceous remnants. Alto- 
gethei’, the eroded edges of this formation are found upon about two-thirds 
of the periphery of the Grand Canon district. Of the remaining third of 
the circuit our knowledge is very imperfect, for it has not been geologically 
explored with thoroughness. 
THE JURA. 
To the student whose mind is engaged chiefly with problems of strati- 
graphy the Jura- Trias system of the plateaus, (and the Permian may be 
considered as indissolubly linked with it), is a most alluring field of study. 
True, it yields him more questions than answers, but the questions are fiill 
of suggestion, opening many avenues of thought which he is fain to follow. 
All things considered, this series is probably the most conspicuous and typi- 
cal one in the Plateau Country, and it there displays a development grander 
and more extensive than in any other region of the world. 
The division of the Jurassic from the Trias is often difficult to make. 
The primary reason is the want of fossils. The uppermost members of the 
Jurassic contain an abundant marine fauna ; but thence downwards we find 
no organic forms sufficient for purposes of discrimination until we reach the 
lower members of the Permian. A few plants, an abundance of silicified 
wood, a few unrecognizable dermal scutes of fishes, are all that the great 
