1978 



Limestone in the Coast Ranges 



93 



calcareous and tuffaceous, pebbly, fossiliferous sand- 

 stone (Dibblee, 1950, p. 81, plate 4). 



The deposit is developed by a quarry at its east end 

 and was worked intermittently from 1928 to 1941. 'I"he 

 limestone was crushed to various sizes and used for 

 road construction (surfacing?) by Santa Barbara 

 County. No analyses are available, and the deposit 

 may be dolomitic. 



Bee Rock deposit. Location: SW'/i sec. 3 1, T. 6 N., 

 R. 29 \V., S.B., 7'/, miles north of Naples and 18 miles 

 northwest of Santa Barbara; San Rafael Mountain 15- 

 minute quadrangle. Ownership: Not determined. 



Dense, massive, light-gray limestone, containing 

 several layers of chert, is exposed prominently at Bee 

 Rock 2 miles south of Cachuma Dam. 1 he deposit dips 

 gently to the south and is truncated down dip by a 

 north branch of the Santa Ynez fault. The limestone 

 is a basal unit of the Monterey Formation (Miocene) 

 which locally rests on .Matilija Sandstone(?). A thin 

 overburden of siliceous shale overlies the limestone in 

 places. 1 he maximum thickness of the limestone se- 

 quence is 200 feet (Dibblee, 1966a, p. 47, 89-90, plate 

 3; T.W. Dibblee, Jr., 1963, personal communication). 



The deposit extends over a strike length of half a 

 mile, a maximum width of 900 feet, and a relief of 

 more than 500 feet. Based on topography, limestone 

 reserves above the base (1,800 feet elevation) of the 

 sheer cliff defining the south side of Bee Rock are 

 estimated to be about 6 million tons. Total reserves of 

 the deposit cannot be estimated, as the average thick- 

 ness is unknown. Although reserves are relatively 

 large, it is not known if sufficient limestone is avail- 

 able for cement manufacture. Further, the chemical 

 quality of the limestone is not known and needs to be 

 determined — particularly because carbonate rock of 

 the Monterey Formation is generally dolomitic and 

 siliceous. 



The limestone was used in construction of the Ca- 

 chuma earth and rock fill dam, completed in 1953. 

 Apparently a large amount of limestone was used as 

 a rock blanket or riprap. The limestone came from a 

 quarry on the south side of Bee Rock, 2 miles south of 

 the dam. 



El Jaro deposits (including Dibblee quarry). Lo- 

 cation: Sees. 19, 20, 28, 29, 30, and 33 (pro).), T. 6 N., 

 R. 33 W., SB., 6 to 8 miles southeast of Lompoc; Lom- 

 poc 1 5-minute quadrangle. Ownership: W. C. H. Dib- 

 blee (Rancho San Julian) (1950). 



Gently folded carbonate beds at the base of the 

 Monterey Formation are exposed extensively on both 

 sides of El Jaro Creek, as shown by Dibblee (1950, 

 plate 3). According to Dibblee (p. 79), the carbonate 

 unit is a maximum of 1 50 feet thick and consists of 70 

 feet of "pure limestone" which grades downward into 

 "calcareous tuffaceous sandstone with local occur- 

 rences of conglomerate at the base". The carbonate 

 unit grades by interbedding into the overlying .Monte- 

 rey shale. Actually, the rocks exposed along State 



Highway 1 are largely dolomite as shown by the anal- 

 yses in table 20. Where sampled, the dolomite is gener- 

 ally brown to grayish brown and bituminous, 

 weathering to a light buff color. It is also hard, dense 

 to slightly vuggy, locally brecciated, and commonly 

 contains concentrations of replacement chert. The 

 beds are faintly laminated to massive, commonly be- 

 ing broken and contorted. The main deposits lie in S'/j 

 sees. 19, 20, and 28, and W/, sec. 29. Dolomite reserves 

 may be large; more sampling, and perhaps drilling, 

 needs to be done to evaluate the quality and sizes of the 

 various deposits. It is possible that some of the dolo- 

 mite, if selectively quarried, may be of value as a re- 

 fractory material. 



Toble 20. Chemical analyses of carbonate rock (Monterey 

 Formation) from the El Jaro deposit, Santa Barbara County. 



Simp/e Si(P FejO, A/,0, CiO Jf^) Ko, 



LJ-1 6.48% 0.66% 0.8J% 29,98% 17,89% 0.11% 



LJ-2 6.03 0.5S 0.94 28,84 19,07 0.05 



LJ-3 1.86 0.62 1.71 30.02 19,88 0.14 



LJ-4 1.89 0.29 0.58 30.59 20.18 0.22 



LJ-5 3.53 0.62 0.51 30.49 19 46 0.12 



LJ-6 3.70 0,18 1.96 29,65 19,51 0,28 



LJ-7* 2.33 0.70 1.12 53.14 0,22 O.OS 



Samples collecied by Oliver E, Bowen at intervals from south to north in road 

 cuts east of El jaro Creek in E'/, of SE'/. sec 19(proj,).T 6N.R H W, 

 Samples LJ-1 to LJ-4 are from lower l>eds; LJ-5 and LJ-6 are from middle 

 t)eds. and LJ-7 is from upper bed. Most samples are bituminous, and some 

 contain small patches of chert. Sample LJ-1 is brecciated. Analyzed by 

 Abbot A Hanks. Inc . 1956 



• Analysis questionable, as hand specimen retained is dolomite. 



One of the carbonate deposits east of El Jaro Creek 



was worked intermittently from 1928 to 1944 through 

 a large quarry located in SW'X sec. 20. According to 

 Dibblee (1950, p. 80), "the limestone here is about 40 

 feet thick, grading upward into brittle chertv shales. 

 About 1 5 feet of conglomerate occurs at the base of the 

 limestone". The beds dip north into the hill. Produc- 

 tion has been limited to crushed rock utilized for road 

 construction (surfacing) in the Lompoc area. 



La Salle-Sloan Canyon deposits. Location: Ap- 

 prox. sees. 11 and 12 (proj.), T. 6 N., R. 35 VV., S.B., 

 3/2 to 5 miles west-southwest of Lompoc; Point Ar- 

 guello 1 5-minute quadrangle. Ownership: U.S. Naval 

 Missile Facility (west half only). 



Dibblee (1950, p. 79-80, plate 3) shows four elon- 

 gate exposures of limestone, each half a mile long or 

 less, that form a west-trending arcuate belt 2 miles 

 long uithin the Monterey Formation. The deposits 

 are crossed by La Salle Canyon on the west and Sloan 

 (San Pascual ?) Canyon on the east. The limestone 

 beds have a maximum thickness of 100 feet and dip 

 steeply north. The Tranquillon \'olcanics (agglomer- 

 ate) underlies the limestone unit, and shale of the 

 Monterey Formation overlies the unit. "The lime- 

 stone is similar to that of El Jaro Canyon, consisting 

 of pure limestone grading downward into calcareous 

 sandstone" (Dibblee, 1950, p. 80). As at the El Jaro 

 deposits, the carbonate rock at La Salle and Sloan Can- 



