Santa Cruz County History - Making a Living

Mineral Survey of Santa Cruz County - Petroleum and Potash
by C. McK. Laizure

Prepared by C. McK. Laizure,
Mining Engineer of the California State Mining Bureau

There has been no commercial production of petroleum in Santa Cruz County, although small seepages of crude oil have been found and a number of wells drilled. According to J. C. Branner, J. F. Newson and Ralph Arnold, ("Geology of the Santa Cruz Quadrangle", U. S. Geological Survey Folio No. 163, 1910), who reported only upon that portion of the county within the Santa Cruz quadrangle,

"apparently the most promising locality for, prospecting for oil is that along the coast west and southwest from the outcropping bituminous rock beds, since those beds pass down under overlying shale in that region. Wells drilled here, however, failed to find oil, and it is supposed that the oil which must formerly have existed in the sandstones of the region has been drained off through large fractures which extended from the surface of the shale down to the underlying sandstone. Many sandstone dykes, some of them of large size, occur along the coast in this region. These were formed from the underlying oil-bearing sandstones and the larger ones probably represent the channels through which the oil from the underlying strata escaped."

The geology and oil possibilities of the county are further discussed by Vanderleck, (Vanderleck, Lawrence. "Petroleum Resources of California", State Mining Bureau Bulletin. No. 89, 1921.) who says,

"In the area around Ben Lomond Mountain, running from Little Basin to the town of Santa Cruz, the formations consist of granitic rocks, together with areas of ancient crystalline schists. In the region to the north of this crystalline area there are outcrops of the San Lorenzo formations, the Vaqueros sandstone and the diatomaceous shale of the Monterey. These have been all sharply folded and faulted. The Monterey contains numerous seepages, but there is an almost total lack of an overlying formation which could act as a reservoir. This, together with the unfavorable structural conditions, make the possibility of obtaining oil in paying quantities in this area remote. In some cases, by reason of faulting, the oil has migrated from the Monterey into the underlying beds of the Vaqueros and San Lorenzo. It is possible that wells drilled in this area in either the Monterey, or the underlying Tertiary beds will encounter small showings of oil, but not of sufficient size to be of commercial importance.

"In the area between Ben Lomond Mountain and the coast, the Vaqueros and Monterey lie in a monocline, dipping about 25' to the southwest. The Monterey is heavily bituminized and has been extensively quarried for asphaltum.

"The remainder of the county, which embraces the district lying between Santa Cruz and Watsonville and southwest of the Santa Cruz Mountains, may be likened to a coastal plain. In the country north of Aptos this likeness is not generally apparent, as the hills frequently rise to a height of 1500 to 1800 feet. Between Aptos and Watsonville, however, the county is characterized by low rolling hills, varying in elevation from 100 to 500 feet. The northeast boundary is marked by the steep escarpment of the west side of the Santa Cruz Mountains, formed by the San Andreas fault. The greater portion of the district is covered by loose incoherent sands and clay, varying in color from yellow to brown and having no distinctive strike or dip. The age is not definitely known, but very probably they belong to the Merced formation (upper Pliocene). With the exception of an area about three miles northeast of Watsonville (which will be discussed below) no distinctive structure could be made out in these beds.

"Near the town of Santa Cruz, the Monterey shale apparently dips under the Merced beds and very probably it underlies this entire area. Between the San Andreas fault and the Santa Clara County line is an area of Monterey shale, referred to in the article on Santa Clara County. The shale apparently lies in a synclinal trough; the eastern limb resting on the Franciscan; the axis of the syncline approximately coinciding with the county line and the west limb is faulted against the Merced beds by the San Andreas fault.

"On the Mount Madonna road, about four miles north of Watsonville and about one-half mile south of the Casserly school, is the axis of a small anticline in the Merced beds, the west limb of which is sharply compressed against the Monterey shales by the San Andreas fault. It is in this area that the indications of oil occur. On the Webb Ranch, it is reported that two shallow wells were drilled and obtained gas. In the canyon just back of the ranch house there is apparently a dry seepage of black oil. On the Hughes Ranch, one well was drilled up the canyon just back of the house. A depth of 700 feet was reached and considerable gas was encountered. At the present time (1921) the Cymric Oil Company is drilling a well at this location. This area may be considered as worthy of being tested. As regards the remainder of the area under discussion it is worthy of being thoroughly investigated for structure before being condemned. It is apparently underlaid by bituminous shales of the Monterey and should detailed mapping reveal any favorable structure in the Merced beds, the locality would be worth testing."

The following data regarding prospect wells drilled within the county from 1914 to 1924, inclusive, are from records compiled by the State Oil and Gas Supervisor. (Bush, R.D. "Result of Wildcat Drilling in California, 1914-1924, Summary of Operations," California Oil Fields, Vol. 11, No. 1, July 1925.)

Company Well Location Date
Sec. T. R.
Cymric Oil Co. 1 14 11S 2E 1921 1500
Danish Oil & Development Co. 1 22 11S 2W 1922 1200
Danish Oil & Development Co. 2 22 11S 2W 1923 2400
Rhoads and Schmitt 1 17 9S 1W 1918 1000
Santa Cruz Laveaga Trust Oil Co. 1 5 11S 1W 1924 800
United Royalties Co. 1 Hughes Tract 1924

Sec. 23, T. 11 S., R. 2 W., was reported ready to drill subsequent to the above compilation.


There is a small annual production of sulphate of potash, which is recovered from the flue dust and gasses from the kilns at the plant of the Santa Cruz Portand Cement Company at Davenport. During the war period there was also reported to have been some potash produced from a deposit of decomposed sandstone containing soda and potash feldspar located at Olive Springs (see under Mineral Water).

>>Continue with:

Bituminous Rock   Gold Mineral Water
Black Sand Granite Moulding Sand & Peat
Cement Iron Petroleum & Potash
Clay Lime Stone Industry
Coal Limestone   

The Mineral Survey of Santa Cruz County was printed in the Santa Cruz Chamber of Commerce Annual Report, 1926. Reproduced by permission of the Santa Cruz Area Chamber of Commerce.

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geology, mining


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