1978 



Limestone in the Coast Ranges 



ss 



"Pure white, and blue-gray and white variegated, coorsely crys- 

 talline limestone is in a thin, lenticular, vertical-standing pendant 

 within granite and schist walls. It forms the crest of a ridge trending 

 N 65''-70'' W ond hos little or no overburden. The limestone is 

 exposed for a length of 1,800 feet and on average width of 120 

 feet. A maximum of 200 feet of depth is exposed above the level 

 of Bird Creek but the pendant continues downward for an undeter- 

 mined distance. Accessible reserves in the lens probably exceed 

 1,000,000 tons. A few small gronitic dikes penetrate the limestone 

 but are not believed to be o serious problem in quorrying. Most 

 of the limestone is white rather than colored. The following onol- 

 yses on samples collected by the outhors and analyzed by Abbot 

 A. Hanks, Incorporated, are believed to be representotive of the 

 variations found in the deposit."' 



Recent investigations by Oliver E. Bowen, Thomas 

 H. Rogers and Marshall E. Maddock (unpublished) 

 indicate that the deposit is considerably smaller and 

 contains substantially less limestone than the original 

 estimate (Bowen, 1968, personal communication). 



Considering the white color of most of the lime- 

 stone, the deposit may have use as a source of whiting 

 or for some other special purpose. 



Barbee Ranch deposits. Location: SE'X sec. 9, T. 

 13 S., R. 4 E., M.D., 2 miles south of San Juan Bautista; 

 San Juan Bautista l.vminute quadrangle. Ownership; 

 Ideal Cement Company, 420 Ideal Cement Building, 

 Denver, Colorado 80202 (1959). 



Large blocks and boulders of crystalline limestone 

 were quarried in a minor way many years ago in a few 

 places in the vicinity of SE'/ sec. 9 on the Barbee 

 Ranch. Limestone detritus of the Sur Series consti- 

 tutes a large percentage of reddish nonmarine breccias 

 and conglomerates that occur as thick lenses in the 

 X'aqueros Formation of early Miocene age. These 

 lenses are interbedded with fossiliferous sandstone 

 and constitute a unit as much as 1,000 feet thick. Con- 

 centrations of fragmental limestone e.\tend westward 

 for 5 miles between N W'X sec. 14, T. 1 3 S., R. 4 E., and 

 N'X sec. 12, T. 13 S., R. 3 E. (Allen, 1946, p. 28-30). 

 Three limestone samples collected and analyzed by 

 the owner gave the following results (Bowen and 

 Gray, 1959, p. 23): 



Simple CjO .UpO AI.O, Fe..O, h.-O "^'^.O SiO.. 



Although limestone reserves may be large, expected 

 variations in limestone composition and dilution with 

 noncarbonate detritus may make this deposit unat- 

 tractive as a future source of limestone. 



Hardin Ranch deposits. Location: SEVi sec. 33 and 

 SWy, sec. 34, T. 13 S., and NW'/, sec. 3, T. 14 S., R. 4 

 E., M.D.,9 miles northeast of Salinas; San Juan Bautis- 

 ta 1 5-minute quadrangle. Ownership: Bardin Ranch, 

 Salinas (19.S9). 



Three patches of potentially commercial limestone, 

 situated about a mile west of Fremont Peak, have been 

 mapped by Bowen and Gray (1959, p. 28 and plate 1). 

 These patches are parts of two larger carbonate masses 

 of mixed limestone and dolomite of the Sur Series. 

 Bowen and Gray briefly describe the patches: 



"Port of the rock in these deposits is medium-groined, blue-gray 

 material suitable for general use where color is not importont, ond 

 part is coarse-groined, pure-white material suitable for whiting and 

 white filler. None of the deposits has been developed or tested 

 except for a few samples token by the outhors but, judging from 

 surface exposures, more than o million tons of commercial material 

 might reasonably be developed in the three masses. They ore 

 currently accessible by Gabilon Creek Canyon via on unimproved 

 dirt road." 



Bird Canyon Ledge. Location: SE'/ sec. 31 

 (proj.), T. 13 S., R. 5 E., M.D., 7 miles southwest of 

 Hollister; Hollister 1 5-minute quadrangle. Owner- 

 ship: Ideal Cement Company, 420 Ideal Cement Build- 

 ing, Denver, Colorado 80202, holds the mineral rights 

 (19.59). 



Old Mission Portland Cement Company, predeces- 

 sor to the present owner, acquired and drilled the Bird 

 Canyon Ledge in 1925 in order to increase their re- 

 serves of cement raw materials. The deposit has been 

 mapped and described in some detail by Bowen and 

 Gray (1959, p. 31-32, plate 1): 



"The Bird Canyon Ledge occupies the south slope of o ridge 

 trending N. 65° E. The north border of the principal limestone moss 

 lies close to the ridge crest. The south border, which Is more regular, 

 lies close to the conyon bottom. In plan the deposit is about 600 

 feet long parallel to the ridge and 800 feet long perpendicular to 

 the ridge. From ridge crest to creek bottom, o depth of 560 feet 

 of limestone is exposed. The predominating surface trace of well- 

 developed joints in the limestone strikes N 55° -^0° E and the joint 

 surfaces dip very steeply southeast, but it is doubtful if this repre- 

 sents bedding. Bonofide bedding was not observed in the main 

 moss. The limestone is bounded on the north and south by quortz- 

 mico schist and granite; on the east by granite; ond on the west 

 by a mass of gray replacement silica. From exposures seen along 

 the creek the deposit bottoms in granite and silico and the chances 

 of it continuing down below the level of the creek bottom ore small. 

 Roughly 10,000,000 tons of corbonate rock ore present in the moin 

 mass but there is some question as to whether all of this is suitable 

 for monufocture of portlond cement.*" 



The analyses in table 11 indicate the deposit to be 

 too high in magnesia for use in Portland cement. The 

 deposit is undeveloped. 



Bluerock Mountain deposit. Location: SW'/^ sec. 

 25 and SE '/, sec. 26, T. 14 S., R. 4 E., M.D., 9 miles east 

 of Salinas and nearly 8 miles north and slightly east of 

 Chualar; Gonzales 1 5-minute quadrangle. Ownership: 

 Not determined. 



This deposit lies on the rugged west slopes of Blue- 

 rock Mountain. It is briefly described by Bowen and 

 Gray ( 1959, p. 37) as "an oval mass having a slight east 

 elongation and underlies most of the SW'/i sec. 25 ... . 



