Ransome.] 



The Great Valley. 



383 



and its continuation in the Tulare Valley, forming a vast amphi- 

 theatre, unbroken on all sides except to the north, but lowest to 

 the west at Paso Robles. The mountains south and east are espe- 

 cially high, rising to from 6,500 to 8,000 feet. From the base of these 

 a dry, gravelly or sandy slope stretches away with a very gentle 

 inclination into the plain; this is composed of coarser materials, and 

 has a steep angle near the mountains, gradually becoming more 

 nearly horizontal as it recedes from them. This detrital deposit 

 covers the base of the mountains to the height of 1,000 feet above 

 the plain, and is made up of the materials brought down the slopes 

 of the mountains by the wear of the elements. Near the mouths 

 of the cartons which issue from the hills there are accumulations of 

 boulders, which are also scattered over the plain to some extent, 

 around and near the base of the hills." 



According to the same writer, the line of division between the 

 Sierra Nevada and the Coast Ranges occurs somewhere between 

 Tejon Canon on the east, and the Canada de las Uvas on the west, 

 the Tertiary strata at the former place having the nearly horizontal 

 position characteristic of the Sierra, while at the latter the rocks of 

 the same age are highly tilted, as is commonly the case in the 

 Coast Ranges.* Mr. H. W. Turner f has suggested that the line 

 between the disturbed and undisturbed strata is really a fault, whose 

 northern prolongation determines the course of the San Joaquin and 

 Sacramento Rivers. There is nothing in the drainage, however, to 

 support the suggestion, for a river which meanders over a flood- 

 plain, in a broad valley, deeply filled with alluvium, can hardly be 

 supposed to have any necessary connection with an underlying 

 fault. An idea of the depth of the Pleistocene deposits in Tulare 

 Valley is given by a well-boring near Tulare Lake which passed 

 through sands and clays to a depth of 1,058 feet. Fresh-water 

 shells belonging to living species are reported from this depth. % 



THE HISTORY OF THE GREAT VALLEY. 



In any attempt to trace the geological evolution of the Great 

 * Loc. cit., p. ii)2. 



tAm. Geologist, Vol. XIII, p. 248; also Journal of Geology, Vol. Ill, p. 386. 

 t Watts, Gas and Petroleum Yielding Formations, Bull. 3, Calif. State 

 Mining Bureau, p. 20. 



