260 
GREAT BASIN OVERTHRUSTS 
Louderback produces not an actual fault-line framing a moun¬ 
tain block but merely adduces evidences which in his opinion ap¬ 
pear satisfying enough to warrant the inference of the presence 
of a fault. In reality this does not even touch the critical point 
involved in the issue. The fault-plane of Mount Rosa (p. 305) 
over wTich this author makes so much ado reaches sky two-thirds 
of the way up the side of the range. Surely the mountain must 
have stood forth fully formed long before the faulting took place. 
Such fault could not possibly have determined the mountain. The 
results of my own visit to the Humboldt, in response to Louder- 
back’s printed invitation (p. 345), were not only disappointing 
and far from satisfactory, but they were not at all convincing. 
Nothing critical concerning the issues had been added that was not 
already well known in scores of other desert ranges. No one 
whom I can recall, of those especially interested in Great Basin 
orogeny, ever called into question the possible presence in the 
region of normal faults. The point of askance was their pres¬ 
ence as essential factors in present mountain building. 
Bearing directly upon the validity of the Gilbertian hypothesis 
of Basin Range structure the tectonic phenomena claimed for the 
Humboldt region have other curious relations. All features which 
are so stressed have at least two other explanations, either of which 
is even more plausible than the one set forth. One in particular 
has endless counterpart throughout the arid regions, and casts 
grave doubt upon the very presence of the faulting as inferred. 
Nor are physiographic criteria for Basin Range faulting any 
more conclusive or illuminating.^ The inductive reasoning ends 
in utter chaos. Davis’ well-known, albeit strictly academic argu¬ 
ments, fit to minutest detail the Muddy Mountains. Yet the latter 
bring forth, not a normal fault-block but a thrust block! Is not 
that, too, older than the present mountains ? 
According to the hypothesis of differential deflation for the 
origin of the Desert Ranges the date of folding, faulting, or thrust¬ 
ing in the substructure has no essential bearing upon the problem 
of genesis of the present orogenic relief, and thus this entire 
difficulty in Basin Range discussion is happily obviated. 
Basin Range Structure hypothesis has thus at last arrived at 
the point where it is confronted by fact and feature, and not longer 
by brilliant plausibility alone. 
5 Science, N. S., Vol. XIV, p. 458, 1901. 
