1978 



Limestone in the Coast Ranges 



47 



dense vegetation and soil overburden. The deposit 

 was worked through an open-faced quarry 300 feet by 

 150 feet u ith a maximum face of 70 feet. Heavy over- 

 growth indicates the quarry has not been worked for 

 at least .^0 to 40 years. Production is estimated to have 

 been on the order of 100,000 tons. The remains of old 

 stone kilns can be seen along the dirt road just south 

 of the deposit. 



Deposit F. Includes the extensive limestone expo- 

 sures along the Wilder Creek-Cave Gulch drainage in 

 SW'X sec. 3, E'/, sec. 9, and VV"/, sec. 10. As mapped by 

 G. W. Leo (1967 and unpublished Stanford thesis), 

 the limestone crops out over an irregular, sinuous area 

 a mile long and 600 feet to l,.'i00 feet wide. The lime- 

 stone is poorly exposed but appears to be interbedded 

 with schist and quartzite to some extent and cut local- 

 ly bv granitic dikes. \'ariable bedding attitudes sug- 

 gest that the limestone exists as several discontinuous 

 sequences or masses. The best quality limestone ap- 

 pears to be centered along Cave Gulch at the 

 northeastern end of the deposit. Much of this lime- 

 stone is high calcium, coarse crystalline, and off white 

 to light gray uith faint gray streaks or bands. Only a 

 few small dikes of granitic rock penetrate the lime- 

 stone in that area. Chemical analyses of samples ((>G-1 

 and 2, table 9) show the variations in the better quality 

 limestone found in the Cave Gulch area along Empire 

 Grade. In the western part of the deposit (near the 

 quarries in sec. 9), the limestone is more variable, 

 being off white to gray, fine to very coarse crystalline, 

 and locally siliceous. Some schist interbeds were not- 

 ed, and granitic dikes and quartz veins exist locally. 



Table 9. Chemical analyses of typical limestone samples 



from the Cowell Home Ranch, Holmes, and IXL cJeposits, Sonra 



Cruz district. 



ND — noi done. 



CH and CG samples collected by Earl W. Hart and analyzed by Maui Tavela 



and Lydia Lofgrcn of California Division of Mines and Geology. 1963. 

 S.\CR-1 lo 7 collected by Oliver E Bowcn of California Division of Mines 



and Geology and analyzed by Abbot \. Hanks, Inc. 1955. 

 CH-I and 2 from quarry near W'/. cor. 1I-IIS-2W, Cowell Home Ranch 



deposit A. 

 CH-) and 4 and SACR-I to 3 from quarry in SE'/. J-1IS-2W, Cowell Home 



Ranch deposit B. 

 CG-I and 2 from Cowell Home Ranch deposit F where crossed by Empire 



Grade— NWV, I0-1IS-2W and SW'/, M1S-2W, respectively 

 SACR-4 is float from quarry at Holmes deposit. NE'/, 20-IOS-2W 

 SACR-5 to 7 from quari7 at IXL deposit. SE'/, 17-IOS-2W. 



The Wilder Creek-Cave Gulch deposit has been de- 

 veloped only in sec. 9, where Henry Cowell Lime and 

 Cement C'ompany produced limestone for lime from 

 about 1880 until the turn of the century. Limestone 

 was worked in three quarries, the largest and most 

 easterly being 300 feet in diameter and having a max- 

 imum face of nearly 100 feet. Two smaller quarries are 

 situated to the west. Several hundred thousand tons of 

 limestone were produced and burned at the nearby 

 kilns, remnants of which still stand. The kilns were 

 oil-fired and when it became uneconomic to haul oil 

 to the kilns the operation was shut down. 



Reserves. Limestone reserves of the Cowell Home 

 Ranch deposits are difficult to estiinate accurately be- 

 cause of poor exposures (soil cover, dense vegetation). 

 However, based on an areal extent of about 2.50 acres 

 of limestone outcrop (figure 4), combined limestone 

 reserves may be estimated at 850,000 tons per foot of 

 depth. This figure is too large in that it disregards 

 limestone quality and includes noncarbonate rocks as- 

 sociated with the limestone. On the other hand, some 

 of the limestone deposits may extend under soil over- 

 burden beyond the deposit limits mapped. It is clear 

 that further exploration is necessary to assess the re- 

 serves of the various deposits. From an economic 

 viewpoint, some of the advantages of the Cowell 

 Home Ranch deposits are: 1) large reserves, 2) good 

 accessibility, and 3) proximity to markets and major 

 transportation lines. The main disadvantage is that 

 much of the limestone lies on the campus of the L'ni- 

 versity of California at Santa Cruz, construction of 

 which began about 1964, and may not be available for 

 future development. Beyond the campus boundary 

 (figure 4), only the Wilder Oeek-C^ave Gulch deposit 

 (F) appears to be of sufficient size to support large- 

 scale development, but very little is known about spe- 

 cific reserves and limestone quality of that deposit. 

 Deposits C, D, and E also lie partly outside the campus 

 site and may be of future interest. 



Other references: Browne, 1868, p. 244; Irelon, 1888, p. 554; Crowford, 

 1896, p. 631; Aubury, 1906, p. 83; Laizure, 1926, p. 84; Hubbard, 1943, p. 

 43; Leo, 1967, p. 31, 41. 



Holmes deposits. Location: NE% sec. 20, F. 10 S., 

 R. 2 W., M.D., I'/j miles west of Felton; Ben Lomond 

 15-minute quadrangle. Ownership: Citizens Utilities 

 Company of California, Boulder Creek, leased by 

 Limestone Products, Incorporated (1963). 



W. F. Holmes Lime Company produced large 

 amounts of limestone for lime from these deposits for 

 more than 52 years prior to 1936. when their opera- 

 tions ceased (Logan, 1947, p. 319). Production during 

 the early years amounted to 50,000 to 100.000 barrels 

 of lime per year (equal to about 10,000 to 20,000 tons 

 of limestone per year) but was less later on. The lime- 

 stone was burned in a series of pot and continuous 

 kilns located between the deposits and Felton. Since 

 early 1955, tailings at the main quarry have been 



