30 
THE GRAND OA^TON DISTRICT. 
the lake disappeared near the southern base of the Uinta Mountains. Nor 
does this inference rest wholly upon the facts thus I’ecited. Wherever the 
physical geology and evolution of the Grand Canon district touches the 
question of time, the same conclusion presents itself, sometimes dimly, some- 
times forcibly. Doubtless it will appear repeatedly and from many points 
of view as the discussion of the region progresses. 
Inasmuch as the most prominent theme of this work will be the recital 
of the evidences which this district presents of an enormous denudation 
during Tertiary time, we may with advantage proceed to the examination of 
the other remnants of Eocene strata which that denudation has spared; for 
by the study and comparison of residual masses some valuable indications 
may be found showing the original condition and distribution of the primi- 
tive masses. The principal body of the Eocene strata terminates south- 
wardly at the brinks of the High Plateaus. But there are other bodies of 
the same formation occurring in a fragmentary way far to the southwest. 
At the northeastern base of the Pine Valley Mountains some large rem- 
nants are seen, and upon the opposite side of the same range still others 
are found. A general idea of their distribution may be gained by advert- 
ing to the early Tertiary geography of the region lying west and south- 
west of the Markdgunt. The Eocene strata in these parts derived their 
materials from land which at that age occupied the site of the present Great 
Basin. The shore-line of that land extended from the southern end of the 
Wasatch southwardly, gradually swinging its trend more and more towards 
the west, until it had a direction very nearly southwest. It crossed the 
Nevada-Utah boundary very obliquely, and reached far to the southwest 
in the former State. In the littoral belt in the neighborhood of this ancient 
shore are many remnants of lower Eocene strata. They recur at intervals 
as we move southwestwardly from the Markdgunt through a distance 
of more than 70 miles, and possibly much further. West of the Marka- 
gunt and of the Grand Canon district the Eocene lake appears to have 
extended as a great gulf or bight, covering much of the southern portion 
of Nevada, and reaching well towards southern California. But as our 
knowledge of the geology of those regions is very imperfect at present, it 
is impossible to assert anything confidently concerning the course of the 
