ransome.] The Great Valley. 379 



As a consequence of this, the town of Marysville, at an elevation of 

 66 feet above the sea, and formerly high and dry above the river, is 

 now considerably below it at high water.* 



The general drainage plan of the Sacramento Valley is compar- 

 atively simple. The Sacramento River follows a somewhat mean- 

 dering course along the axis of the valley and is joined by numerous 

 tributaries from the east and west. Those coming from the Sierra 

 Nevada have generally a strong southerly deflection, flowing almost 

 southwest, while those from the Coast Ranges flow in a general 

 easterly direction. The broad western slope of the Sierra furnishes 

 by far the larger part of the drainage and all of the important trib- 

 utaries. The smaller streams flowing from the Coast Ranges on 

 the west seldom reach the Sacramento River directly, but become 

 lost in the intricate plexus of sloughs which meander through the 

 tule-lands bordering the main river. The same is also true of the 

 smaller streams on the east — only the larger tributaries reaching the 

 Sacramento by a definite channel, and that often becoming an ex- 

 ceedingly tortuous one. 



It is unfortunate that so few records of deep borings in the late 

 sediments of the Sacramento Valley are known to the writer. Their 

 depth is accordingly largely a matter of conjecture, except at such 

 places on the edges of the valley as reveal the bottom in natural 

 sections or by borings. Two wells are reportedf to have been sunk, 

 about 20 years ago, nine miles northeast of Sacramento, to depths 

 of 2,250 and 1,600 feet, but there is apparently no record of the 

 materials passed through. In the town of Sacramento, a well is de- 

 scribed;); which pierced unconsolidated clays, sands, and gravels to a 

 depth of 965 feet. Lindgren and Turner, § defining the alluvium as 

 "the fluviate deposits of clays, sands, and gravels formed by the 

 steady erosion of the older formations by the shifting streams since 

 the Great Valley became dry land," give it a probable maximum 

 thickness of 100 feet. As we shall see, however, in the description of 

 the San Joaquin Valley, there is strong evidence that fluviatile 

 deposits reach a vastly greater thickness than this in the middle por- 



* Marysville Folio, U. S. Geol. Survey. 



t Bull. 3 of the State Mining Bureau of California, p. 10. 



% Ibid. 

 A Loc. cit. 



