1978 



Limestone in the Coast Ranges 



77 



Coast Ridge deposits (includes Marble Peak). 



Location: T. 19 and 20 S.. R. 2 E., I". 20 S., R. 3 E., and 

 T. 21 S., R. 3 and 4 E., M.D., 24 to 42 miles southeast 

 of Monterey; Lucia 15-niituite quadrangle. ()v\ner- 

 ship: Not determined, but partly Los Padres National 

 Forest (1960). 



A large number of small to medium-sized bodies of 

 Sur Series carbonate rock occur discontinuousiy along 

 an 18-milc northwest-trending belt (figure 5). These 

 lie between the (^oast Ridge fault and the McWay fault 

 and are described in a general way by Reiche (1937, 

 p. 123-126, 193, map). The deposits of the northwest 

 half of this belt, which are exposed intermittently 

 along the Coast Ridge road, were examined briefly in 

 1960 and found to be too small and impure to be of 

 economic interest (Hart, 1966b, p. 130-131). Most of 

 these carbonate bodies showed significant amounts of 

 silicate minerals due to contact metamorphism. The 

 deposits examined include some of the small un- 

 developed deposits reported in the vicinity of Marble 

 Peak (SW/, sec. 22, T. 20 S., R. 3 E.) by Logan (1947, 

 p. 259). 



The deposits southeast of Marble Peak were not 

 visited. 



Horse Canyon deposit. Location: S'/i sec. 35, T. 19 

 S., R. 5 E., and N'/; sec. 2 and NE'/, sec. 3, T. 20 S., R. 

 5 E., M.D., 11 miles southwest of Greenfield; Junipero 

 Serra 15-minute quadrangle. Ownership: mainly Los 

 Padres National Forest (1968). 



According to D. L. Durham (1968, personal com- 

 munication), pre- lertiary crystalline limestone is 

 well exposed along Horse Canyon in sees. 35 and 3 and 

 on the high ridge to the east in sec. 2. The limestone 

 is associated with other metamorphic rocks of the Sur 

 Series that form a northwest-trending fault block 

 bounded by Miocene sandstone and calcareous shales 

 on the northeast and Eocene sandstone resting on pre- 

 Tertiary crystalline rocks (undifferentiated) on the 

 southwest. The limestone apparently crops out in an 

 elliptical area roughly a mile long by a third of a mile 

 wide and has a relief of about 1,200 feet on the ridge 

 east of Horse Canyon. 



Just how much of the deposit area is underlain by 

 limestone, and the relationship of the limestone to 

 associated Sur Series rocks, remain to be determined. 

 Much of the limestone is reported to be white. A small 

 sample provided by Durham consists almost entirely 

 of coarse-crystalline calcite with scattered flakes of 

 graphite and small grains of iron ore (limonite?). It is 

 not known if the sample is representative of the depos- 

 it. 



Preliminary data justify a closer look at this deposit 

 to determine its size, distribution, relationship to 

 other Sur Series rocks and possible granitic intrusivcs, 

 and chemical variations. Should a large limestone 

 deposit — or even modest reserves of high-quality lime- 

 stone — prove to exist, its economic value uould be 

 enhanced by its relative accessibility to major trans- 



portation lines and favorable topographic relief. Oliv- 

 er E. Bowen (personal communication, 1970) 

 estimates reserves of carbonate rock to be roughly 10 

 to 1 5 million tons. 



Jolon deposit. Location: Not determined. Owner- 

 ship: Not determined. 



A "shell deposit" a few miles south of Jolon, Monte- 

 rey (-ountw reportedly supplied material for a lime 

 kiln operated prior to 1893. 



References: Preston, 1893, p. 260; Logan, 1947, p. 259. 



Junipero Serra deposits. Location: Sec. 6, T. 21 S., 

 R. 5 E., and sees. 1 3, 24, and 36, T. 20 S., R. 4 E.. M.D., 

 19 to 20 miles west of King C^ity; Junipero Serra 15- 

 minute quadrangle. Ownership: U.S. Government; 

 claimed by Sparks, Pearson, and Talcott in sec. 6 and 

 by Frank Watkins in SW'/, sec. 36 (1958-1959). 



A number of Sur Series carbonate bodies of unde- 

 termined size lie 3 to 5 miles from Junipero Serra Peak 

 within half a mile of Indians Road. They are situated 

 in rugged terrain that is accessible over many miles of 

 improved dirt and paved roads from King City and 

 Greenfield. The deposits are undeveloped except for 

 claim location work and minor sampling. 



Perhaps the largest deposit lies in the SE'X sec. 6 on 

 the Sparks, Pearson, and Talcott claims. Exposures of 

 limestone just north of Roosevelt Creek show the 

 deposit to be 150 to 200 feet thick and to dip steeply 

 into the hill. Exposures of carbonate rock can be 

 traced visually to the northwest along a common 

 trend, but it is not known if they represent a contigu- 

 ous deposit or multiple lenses. At the southeast end of 

 the trend, the deposit largely consists of very coarse- 

 crystalline, nearly white limestone containing local 

 concentrations of crystalline graphite and possibly 

 some silica (Hart, 1966b, p. 66). An analysis of SP-1, 

 a typical example, is given in table 16. Samples SP-2 

 and 3 are siliceous dolomite of the Miocene Monterey 

 Formation exposed southwest of the limestone in sec. 

 6. 



A mile or more northwest of the above claims and 

 along the same deposit trend are the claims of Frank 

 Watkins in SW/, sec. 36. Here, the carbonate rock is 

 impure and not well exposed. Chemical analysis of 

 two samples (Jun-1 and 2 in table 16) indicate the 

 material to be siliceous and strongly dolomitic. Five 

 other samples (Indians 1-5), taken from bodies 50 feet 

 thick or less, shou that relatively pure limestone and 

 dolomite are present along Indians Road. Other car- 

 bonate bodies are indicated a short distance west of the 

 road by Reiche (1937, map), but have not been exam- 

 ined. 



The carbonate deposits examined appear to be of 

 limited economic interest at the present time because 

 of their small size, variable quality, and remote loca- 

 tions with respect to markets. However, more work 

 needs to be done to evaluate the Junipero Serra depos- 

 its. The nearest rail facilities are 30 to 35 miles away 

 by road. 



