258 
GREAT BASIN OVERTHRUSTS 
scarp. Influenced evidently by the Gilbertian hypothesis of Basin 
Range structure, Longwell,^ who recently spent considerable time 
in this region, so figures the structure, notwithstanding the fact 
that his accompanying sketch-map, crude as it is, and without in¬ 
terpretation, is the strongest possible evidence directly to the 
contrary. 
The Longwell tectonics of this region are particularly defective 
and incomplete. There are faults marked where there are none; 
and there are many others where none are recognized. Then, 
too, neglect to group his faults as orogenic resultants, and accord¬ 
ing to their time periods, prevents simplification of the tectonic 
framework of the scheme or making intelligible thisi phase of the 
theme. As it is there is too much impossible physics presented as 
fact, when often it is not even plausible. It is difficult to under¬ 
stand how a major normal fault could coincide with a great over¬ 
thrust so that the two would have a common scarp forming one 
face of the range. Or, if the west face of the mountain be a 
normal fault scarp in accordance with orthodox Basin Range 
theory why should a great thrust-plane emerge on the same line 
near the plains level? It is beyond kin how this writer could be 
so obesed by the Basin Range claim that he is unable properly 
to interpret the facts which he actually records on his map. These 
features, however, need not be especially, considered at this time. 
In a still more recent reference to the Muddy Mountain struc¬ 
ture Longwell ^ does not locate the time movement, except in a 
most general way associating it with distant Sierra Nevada oro¬ 
genies of Jurassic date. This is, of course, mere surmise. It is, 
however, the important and essential feature of the whole theme 
and its explanation is left out. 
There are other systems of faults and other stratigraphic evi¬ 
dences which seem to fix within narrow limits the movement 
time of the thrust. In the interior borate basin are numerous 
horizontal faults which appear to trend parallel to the direction 
of the thrust movement. They are not only horizontal slips but 
they cut the boraciferous beds. They may not have any direct 
connection with the major thrust but they probably do. If they 
are actually a necessary and ordinary expression of the thrusting, 
then the latter movement must be assigned a Miocene date, or at 
2 American Jour. Sci., (5), Vol. I, p. 41, 1921. 
3 Journal of Geology, Vol. XXX, p. 63, 1922. 
