248 The American Geologist. April, 1894 
Since the post-Jurassic disturbance, there then appears to have been 
no greal orographic movements in the Sierra Nevada* accompanied b\ 
crumpling and folding of the strata. The block of the earth's crusl 
thai has been practicalh rigid since thai time is a large one. embrac- 
ing about 20,000 square miles, and taking in practically the entire Sierra 
Nevada and all thai portion of the greal valle\ to the easl of the San 
Joaquin and Sacramento rivers. Ii has been shown i»\ Gilbert, Le 
Conic and o1 hers, as is well known, thai i he easl edge of this greal block 
is bounded by a zone of normal faults, which have produced an eastern 
escarpment which is most marked west of Mono and Owen's lakes: but, 
so far as known f' the writer, attention has not been called to the west 
border of this block, which is perhaps also bounded by a zone of frac- 
tures along which normal faults may have formed. The proposition is 
here advanced as* a working hypothesis thai a great fracture, or, rat her. 
series of fractures, exists a1 about the middle of the great valley, which 
line of fractures is approximately followed b\ the Sacramento and San 
Joaquin rivers. The southward continuation of this hypothetical line 
of fracturing may cut the Tehachapi range, for Prof. Whitney* writes: 
"As we skill the base of the Sierra, however, in the region where this 
chain turns to the west towards Fort Tejon, we pass at once from un- 
disturbed Tertiary to strata of the same age which are elevated at a 
high angle, and in so doing we leave the system of the Sierra, and pass 
over to that of the Coasl ranges. This change 1 takes place aboul mid- 
way between tie- Tejon pass and the Canada de las Uvas: but no break 
in the mountain ranges indicates this transition." 
While the Cretaceous and Tertiary beds to the west of the greal block 
above outlined have been crushed and Folded to an enormous extent. 
forming extensive ridges in the present ('oast ranges, the block itself 
has been practically rigid, as is evidenced by the nearly horizontal beds 
of Cretaceous and Tertian strata that occur along the foot hills, and by 
the Tertian lulls and river deposits, also nearh horizontal, thai cap 
man} of the ridges even near the crest of the range. 
How much faulting, if any. lias taken place along the series of frac- 
tures that are supposed to exist along the western edge of I his orographic 
block, is not known, but the existence of faults along the easl edge is 
beyond question, and these normal faults appear to have been formed 
at the close of the Tert iary, chiefly as a result of "graA itating settling" 
which followed the elevation of the ridges al that time. 
Recent elevations of the range. It is well known that much 
of fche coast id' California lias risen in recent times. This is 
shown by the finely preserved wave-cut terraces along the 
coast that now stand some hundreds of feet above sea level, 
and concerning which Prof. Lawsonj lias recently written a 
valuable paper. If the Pleistocene gulf or inland sea that 0C- 
*( ieol. ( California, vol. i. p. 167. 
Il'.ull. Depl. (ieol.. Univ. of California, vol. I. pp. 115-100. 
