164 TJic America n Gco/oi^ist. M;ircli,i898 
OSCILLATIONS OF LEVELOFTHE PACIFIC COAST 
OF THE UNITED STATES. 
By William P. Ulake, 'I'ucsoii, Arizona. 
The oscillations of level of the California coast have of 
late years been ably discussed by Lawson,* Ransome,t David- 
son, Le Conte and others, and recently in this journal by 
Fairbanks.^ 
In these discussions the significance of the Ocoya Creek 
formation does not appear to have received the recognition 
it merits. 
Lying- at the western base of the Sierra Nevada in undis- 
turbed horizontal strata of marine origin of wide extent and 
at an altitude of from 700 to 1,500 feet above the sea, this 
formation records an epirogenic movement in strong contrast 
with the orogenic uplifts to which the initial topography of 
the Coast ranges is due. The beds consist, generally, of sandy 
sediments accumulated during a period of subsidence, and 
in comparatively shallow water. But they contain evidences 
of considerable volcanic activity, such as beds of pumice and 
even fragments of charcoal showing the prevalence of forest 
fires, due, probably, to incursion of lava in the ancient forests 
of the Sierra. 
The mar«ine remains consist of numerous genera and 
species of MuUusca piled together in a littoral accumulation at 
the base of the hills, and now some 700 feet above tide-water, 
while from the tops of the hills which rise som.e hundreds of 
feet higher the teeth of sharks and bones of cetaceans are 
strewn upon the mesa as upon the ocean floor. The evidence 
of recent epirogenic uplift appears to be conclusive. 
The exact altitudes of the ancient shell beds and of the tops 
of the hills need to be more carefully determined than was 
possible at the date of the reconnoissance in 1853, but it would 
appear from those observations that the upper beds are now at 
least 1,500 feet above tide. It is also desirable to have a re- 
*The Post-Pliocene Diastrophism of the Coast of Southern CaH- 
fornia, by Andrew C. Lawson, Univ. of Gal. Bull, of the Dept. of 
Geology, 1, No. 4, Dec, 1893. Also The Geomorphogeny of the Coast 
of Southern California, Ibid, No. 8, Nov. 1894. 
fThe Great Valley of California — A Criticism of the Theory of 
Isostasy, by F. Leslie Ransome, Ibid, No. 14, May, 1896. 
^Oscillation of the Coast of California during the Pliocene and Pleis- 
tocene, by Harold W. Fairbanks, Oct. 1897, No. 4, p. 213. 
