DETAILED RECORDS. 191 
Feet. 
Clay 190r-234 
Gravel - 234-244 
Clay - - 244-250 
Gravel; water-bearing 250-280 
Clay - - - - 280-306 
Gravel; water-bearing 308-327 
Clay - 327-377 
Rig used, cable. Diameter of well, 12 inches. Main supply of water from 250 to 280 
feet. Completed well pumps 200 gallons per minute, lowering water 60 feet from its level of 
106 feet below surface. 
107. Well in San Luis Obispo County. 
[Well begun April, 1904; completed in 1904. Authority, Fred G. Plummer. No samples.] 
This well is situated in Carriso Plain, an arid upland west of the main easternmost ridge 
of the Coast Range. The rocks penetrated are of upper Miocene age. 
Record of well in sec. 4, T. 32, R. 19. 
Feet. 
Yellow clay 0-50 
Hard sandy shale ; water-bearing 50- 55 
Light clay 5.5-70 
Fossil shells; water 70- 80 
Yellow clay 80-90 
Hard blue sandstone 90-155 
White sandstone 15.5-183 
Blue shale 183-191 
Blue clay 191-211 
Blue sandy shale 211-291 
Hard white sandstone 291-386 
N Soft sandstone . 386-401 
Hard sandy shale 401-476 
Hard blue sandstone 476-481 
Blue shale 481-51 1 
Sandstone . . 511-531 
Blue shale 531-541 
Sandstone; water-bearing 541-561 
Blue shale 561-635 
Gray sandstone 63,5-640 
White sandstone ; water-bearing 640-700 
Coarse gravel ; large flow of water . 700-720 
Blue sandy shale 720-765 
Elevation of well about 2,500 feet. 
166. Well near Sunnyvale, Santa Clara County. 
[Well begun January 17, 1905; completed February 14, 1905. Authority, George A. Free, contractor and 
driller. Samples preserved.] 
The beds of sand, clay, and gravel penetrated by this well represent material brought 
down from the mountains to the south by streams flowing into San Francisco Bay and laid 
down in alluvial fans or in deltas. Individual beds vary considerably in thickness within 
short distances and are not persistent, so that logs of neighboring wells often show notable 
differences. Two water-bearing zones are recognized, however, the upper yielding water 
by pumping and the lower giving flows. The water from the lower zone is often notably 
pure. 
