1978 



Limestone in the Coast Ranges 



35 



SANTA CLARA DISTRICT (B-4) 



This district covers the limestone deposits in Santa 

 Clara County and in southernmost San Mateo 

 County. Roughly 40 million tons of limestone have 

 been produced in the district since 1864, when Ciuada- 

 lupe l-ime C'ompanv commenced operations. Howev- 

 er, only small amounts were produced prior to 

 1939 — mainly for lime and for beet-sugar refining. 

 Since 1939, all of the limestone produced in the dis- 

 trict has come from the Permanente deposit. Most of 

 this was used in manufacturing cement; but a substan- 

 tial quantity of the more siliceous stone has been sold 

 as crushed rock and some high-quality limestone has 

 been sold for beet-sugar refining. 



Nearly all of the limestone deposits in the Santa 

 Clara district are part of the Franciscan Formation 

 and are Cretaceous in age. These deposits are situated 

 on the northeast flank of the Santa Ouz Mountains. 

 The Franciscan limestone occurs as numerous discon- 

 tinuous lenses and masses that form three distinct and 

 separate belts lying west of San Jose, southeast of Los 

 Gatos, and south of Gilroy. Distribution of these lime- 

 stone bodies is shown bv Allen ( 1946, plate 1), Walker 

 (1950b, plate 1), Bailey and Everhart (1964, plate 1), 

 and Dibblee (1966b). Because numerous chert in- 

 terbeds occur with the limetone, few deposits have 

 been worked commercially. However, by selective 

 quarrying and hand sorting, some high-grade lime- 

 stone has been obtained at the Permanente, Los Gatos 

 Lime Company, Guadalupe Creek, and other deposits 

 for use in sugar refining and lime manufacture. With 

 the exception of the Permanente deposit, none of the 

 Franciscan limestone deposits appears to be sufficient- 

 ly large or pure for industrial use. Many, however, 

 may be useful as local sources of crushed rock. 



Cummings et al. (1962, p. 192) describe lenses of 

 limestone up to 1,000 feet long and 100 feet thick in the 

 Mindego Formation (Oligo-Miocene) in southern 

 San Mateo (bounty, but there has been no commercial 

 production from any of them. 



Brecciated Eocene limestone, associated with Qua- 

 ternary caliche or calcareous tufa, also was used in 

 limited amounts (see Bernal deposit); but such occur- 

 rences no longer appear to be of economic interest. 

 Also, some Holocene shells may have been dredged 

 from the southern tip of San Francisco Bay (see San 

 Francisco Bay Shell deposits under San Francisco Bay 

 district). 



The only active limestone quarry in the Santa Clara 

 district is at the Permanente deposit, operated by Kai- 

 ser Cement and Ciypsum Corporation. This and other 

 deposits and operations are described alphabetically 

 below. 



Baldy Ryan deposits. Location: Sec. 13 (proj.), T. 

 9 S., R. 1 E. and sec. 18, T. 9 S., R. 2 E., M. D., 5'/j to 

 6 miles southwest of Coyote; Los Gatos IS-minute 

 quadrangle. Ownership: Not determined. 



Several small to moderate-sized bodies of limestone 

 of the Franciscan Formation form a group extending 

 1'/, miles westward from Baldy Ryan (Longwall) 

 Canyon to Fern Peak (Bailey and Everhart, 1964, plate 

 1). The largest and most accessible deposits lie at the 

 extremities of the group. The large deposit to the west 

 at Fern Peak is 1,000 feet long by a maximum of 75 to 

 100 feet wide. To the east in Baldy Ryan Canyon is a 

 similarly narrow deposit 1,700 feet long. This deposit 

 contains an unusual oolitic limestone that is exposed 

 conspicuously. Bailey and Everhart (1964, p. 23) de- 

 scribe the oolitic limestone as "dull battleship gray, 

 and the purest consists almost entireh' of oolites about 

 2 mm in diameter, embedded in a matrix of smaller 

 oolites averaging about 0.1 mm in diameter." Less 

 pure varieties, which grade into tuffs and shales, are 

 reported to be more common. A chemical analysis by 

 A. C. \'lisidis (Bailey and Everhart, 1964, p. 24) of the 

 oolitic limestone indicated 0.91% SiO,, 0.61% AliO,, 

 0.30% Fe^O,, 0.77% MgO, 55.11% CaO, 0.10% TiO^, 

 0.31% PjO,, 0.01% MnO and 42.24% CO^. 



Bailey and Everhart ( 1964, p. 24) consider the oolit- 

 ic limestone to offer "good commercial possibilities" 

 because of the virtual absence of chert lenses. Howev- 

 er, all of the limestone bodies of the Baldv Rvan drain- 

 age lie within a broad shear zone and are apt to be less 

 continuous than indicated on Bailey and Everhart's 

 map (plate 1). 



Other reference: Bailey, Irwin, ond Jones, 1964, p. 72-73. 



Bernal deposit. Location: SE'/^ sec. 19 (proj.), T. 

 8 S., R. 2 E., M. D., 1 mile northwest of Coyote Peak 

 and 3 miles west of Coyote; Los Gatos 15-minute quad- 

 rangle. Ownership: Mr. Gomez, Hollister(?) (1962). 



Fragmental limestone and associated caliche or cal- 

 careous tufa ("marl") were utilized intermittently 

 from 1915 to 1938 for beet-sugar refining and agricul- 

 tural purposes. Fhe deposit apparently was opened by 

 Spreckels Sugar Company, which shipped a few thou- 

 sand tons of limestone around 1915 to one of their 

 refineries (Huguenin and Costello, 1920, p. 186). L'n- 

 der the ownership of Pedro A. Bernal, the C.ilifornia 

 Lime Marl Fertilizer C'ompany produced roughly 10 

 to 20 thousand tons of soft "marl" for agricultural use. 



At the quarry, a coarse breccia of fragmental Eocene 

 limestone is imbedded in varying amounts in a soft 

 matrix of caliche or impure calcareous tufa. The 

 deposit, which ranges from 5 to 15 feet thick or more 

 overlies sheared sandstone at the south side of the 

 quarry. Sandstone fragments and other impurities 

 also are present in the carbonate matrix. It seems like- 

 ly that the deposit is the result of landsliding or fault- 

 ing in association with the surficial deposition of 

 calcium carbonate. The Eocene age of the hard lime- 

 stone is based on its abundant fossil debris (Bailey and 

 Everhart, 1964, p. 69-71). It is gray to yellowish tan, 

 dense to slightly vuggy, fine grained to medium crys- 

 talline, and locally is either sandy or argillaceous(?). 

 A typical sample of the hard limestone, analyzed by 



