244 The American Geologist. "^p''^- ''-^'^^• 
Nearly all the contacts between important formations in the 
Klamath region, where observed, are faulted. Most of these 
faults are of small throw, not exceeding- several hundred feet, 
and are not worth considering. But there are evidences of 
several faults of great magnitude and probably more will be 
discovered in the future. 
In a former paper* I called attention to two in the Upper 
Coffee creek region which I denominated, respectively, the 
Lawrence and Keating faults. At that time I was laboring 
under the delusion that the serpentine involved by these sup- 
posed faults is an altered sedimentary, probably underlying the 
entire region except where gabbro rose from under it, and 
the recognition of the faults was partly based on this suppo- 
sition. But now that I have become aware of the true charac- 
ter of the serpentine as an altered intrusive, I see that the orig- 
inal argument was weak, but I none the less firmly believe in 
the existence of these faults. They trend north to south, paral- 
lel with each other and about one-half mile apart. They 
have been traced for ten miles. In the case of each, the up- 
throw is on the east and amounts to between looo and 2000 
feet. Mica and hornblende schists and serpentine are involved, 
and the latter has been displaced in such a way as to make it 
certain that the faulting occurred subsequent to the intrusion 
of peridotyte. Both are thrust faults and might be considered 
due to the same comprehensive strain as produced the folding 
of the region were it not for the evidence which places the 
peridotyte intrusion between the two. The Lawrence fault 
runs so close to a granite batholith without any displacement 
as to suggest that it is of later age. At the same time, acid 
dikes were intruded along the line of both faults so persistently 
as to make it evident that the faulting preceded them. The 
intrusion of these acid dikes followed closely upon the intrus- 
ion of the granite batholiths. Therefore, if my observations 
have been accurate, the faulting was due to a comprehensive 
strain exerted closely succeeding the intrusion of granite bath- 
oliths and long subsequent to the general folding of the region. 
In the paper mentioned above, I have also defined the 
"Trinity Center Fault." This is undoubtedly a fact as the 
actual fault plane between the ser pentine on the west and the 
• "Gold Bearing Lodes of the Sierra Costa Mountains in California," 
Amer. Geol., vol. XXV, February, 1900. 
