Geological Notes on the Sierra Nevada. — Turner. 235 
beds are of the same age (Neocomian), at the same time recognizing the 
close resemblance of some of the ammonites i<> Jurassic forms of 
Europe Outside of the paleontologic evidence, there are certain facts 
in the physical geology of the Knoxville and .Mariposa beds which lead 
the writer to believe the latter to be the older. 
The Knoxville beds consist of sandstones and shales, which are never 
greatly altered: at least this is true of all those portions of the beds of 
which the age is certainly known by the presence of fossils. The strata 
have been nowhere greatly compressed, so that no slaty structure has 
been developed. The Aucellse and other fossils found in the Knoxville 
beds have seldom been compressed or otherwise distorted. They not 
only present their proper form, but the original shells of the fossils are 
generally present. The strata have nowhere, so far as known, been in- 
truded by granite* or diabase, although serpentine dikes occur in them. 
The Mariposa beds on the other hand have been greatly compressed, 
in places forming a good roofing slate: the fossils in them are also com- 
pressed, and the original shells of the fossils have in all cases disap- 
peared. The strata are. moreover, intruded by diabase and granite,. 
The fact of the Mariposa beds, as well as the other auriferous slates. 
having been cut off and metamorphosed by granite to the south of 
Mariposa was first noticed in print in this journal, vol. 7, 1891, p. 'ill. 
by Mr. Fairbanks. Although not stated by the author, the Mariposa 
beds form a part of the twenty miles of slates "that are greatly broken 
and metamorphosed." In December, 1893, the writer examined the re- 
gion about Mariposa and corroborated Fairbanks* general results, al- 
though he is mistaken in stating thai the "granite extends down from 
the high Sierras, cuts across all the other formations and terminates 
five miles west of the town of Mariposa." The granite of the high Si- 
erras is separated from the granite area south of Mariposa by a tongue 
of mica-schist and greenstone schists, which extends southeast from 
Sevastopol across the Chowchilla to the mining camp of Grub Gulch, 
and doubtless still further south, possibly to the Kaweah river sedi- 
mentary series, as schists are known to occur at several intermediate 
points. 
There is no possible doubt, however, of tin' .Mariposa slates being met- 
amorphosed by the granite area that extends from Mormon Bar, south of 
Mariposa, to the San Joaquin river. This large granite mass ma\ In' of 
the same age as the hornblendic granite to the east of the narrow schist 
bell just described; at must points, however, it contains little or no 
hornblende, but black mica is abundant. The Mariposa slates west of 
Mariposa, where thej terminate abutting againsl the granite, ha-\ e been 
*The following note is added as bearing indirectly on the subject, for i he 
metamorphic Coasl range series is either as held b\ Whittles mid others 
of the same age as the Knoxville beds, or older. The note is as follows: 
Mr. Fairbanks stated to me that he has discovered a basal conglomer- 
ate in the ('oast range metamorphic rocks in Monterej county, contain- 
ing granite pebbles, so that he no longer regards the granite of tie- Gav- 
ilan range as intrusive in the Const range metamorphic series, ;i^ stated 
in the American Geologist, vol. xi, p. 71. 
