Vol. 6] Jones: The Geology of the Sargent Oil Field. 



75 



ensued the greater part of the Merced sediments over the Pajaro 

 Valley were removed. The diorite offered more resistance to 

 erosion. 



Prior to a very recent uplift the Pajaro River meandered in 

 sweeping curves over the Chittenden Valley and the old river 

 gravels and sands can he followed among the low hills of that 

 basin. Chittenden Lake, which previous to the earthquake of 

 April, 1906, usually dried up during the dry season, occupies a 

 slight depression in this old river course. 



This recent slight uplift was the last event in the history of 

 the region. The Pajaro River abandoned its meandering course 

 and intrenched itself close to the steep south slope of the valley. 

 This uplift may have been due to an upward movement on the 

 northeast side of the San Andreas rift, for southwest of the 

 fault in the lower reaches of the Pajaro Valley the river is not 

 intrenched but meanders over the plain in broad curves. At the 

 same time the tributary streams of the Pajaro River all intrench 

 themselves to a depth of about twenty-five feet in their own 

 gravel and alluvial deposits. The San Benito River to the south 

 maintains its meandering course but flows in a trench twenty-five 

 feet below the level valley floor. 



ECONOMIC FEATURES. 



The economic resources of the region are, in the order of 

 their importance, oil, cement materials, stone, and sand. 



Oil. — Indications of oil in profitable quantities are good. The 

 oil-bearing rocks, the Lower Miocene, cover a wide area and the 

 general series of anticlines and synelines which these rocks and 

 the overlying Monterey shales occupy are good indications from 

 a structural point of view. Oil seepages are numerous and 

 occur over wide areas and wherever seen may be taken as an 

 indication of Lower Miocene rocks lying below the surface what- 

 ever the suface rock at that particular point may be. 



At present there are only two companies in the field, but the 

 output has not, up to the present, been large enough to place 

 the district among the productive oil regions of the state. The 

 Watsonville Oil Company has drilled a number of wells on the 

 La Brea anticline (see pi. 16, fig. 2) and the Sargent 's Ranch Oil 

 Company is prospecting at the eastern end of La Brea Canon. 



