72 



California Division of Mines and Geology 



Bull. 197 



lion tons of limestone. A similar but smaller deposit 

 caps the knoll a few hundred feet to the southwest. 

 Other small limestone deposits are scattered through 

 the area but are locally dolomitic and siliceous and 

 commonly interleaved with granite and schist. 



The only dolomite body of note is an arcuate lens 

 situated just west of the center of sec. 4 (proj.). It 

 crosses a saddle in the main ridge and extends at least 

 1,000 feet to the north into NW'X sec. 4. The average 

 thickness may be SO to 100 feet. At one point, the body 

 consists of white coarse-crystalline dolomite, but it is 

 not known if dolomite is the predominant carbonate. 

 Reserves are undetermined and none of the above- 

 mentioned deposits is developed. 



Sugarloaf deposits. Location: NW'/ sec. 36 and 

 S'/z sec. 25, T. 13 S., R. 3 E. (proj.), M.D., 7 miles 

 northeast of Salinas; San Juan Bautista and Salinas 

 15-minute quadrangles. Ownership; Not determined. 



Bowen and Gray (19.S9, p. 28) have described the 

 deposit on Sugarloaf Peak: 



"A broad belt of carbonate rock 600 to 700 feet wide and over 

 a mile long crosses Sugarloaf Peak, in a northeasterly direction. 

 The southwest third of the moss is mainly dolomite but toward the 

 northeast this grades into mixed dolomite-calcite rock. Northeast 

 of the crest of the peak the moss is poorly exposed because of thick 

 brush and soil mantle. Thus for, there has been no commercial 

 utilization of the Sugarloaf Peak rocks. 



"The dolomite is grayish-white, mottled with small spots and 

 clots of red iron oxide. Veinlets of iron oxide and ferruginous silica 

 cut the moss in numerous places. Where the carbonate mass is 

 poorly exposed east of the peak, float consists of medium-grained 

 and coarse-grained, blue-gray to white dolomitic limestone and 

 finer-groined off-white dolomite. 



"Because of the impure nature of the dolomite on the southwest 

 slope of Sugorloaf Peak and because of the opporent mixture of 

 colcite and dolomite rock east of the peak, it is doubtful if satisfac- 

 tory commercial deposits con be developed in this vicinity." 



Another broad northeasterly-trending belt of car- 

 bonate rock is shown by Allen (1946, plate 1) in sec. 

 36, a short distance southeast of the Sugarloaf Peak 

 belt. Nothing is known about the quality of limestone 

 or dolomite in this large mass, but Allen (1946, p. 67, 

 72, and plate 2) states that limestone was obtained 

 from a quarry at the top of the hill half a mile south 

 of Sugarloaf Peak. This limestone was reportedly 

 burned in an old brick kiln located at the forks of 

 Gabilan Creek a mile northeast of Sugarloaf Peak. 

 Allen (1946, plate 1) shows several other large masses 

 of carbonate rock '/j to 2 miles southeast of Sugarloaf 

 Peak but docs not describe them or differentiate the 

 limestone and dolomite. On the basis of size alone, 

 these deposits would appear to warrant further exami- 

 nation and exploration to as.sess their economic value. 



Underwood deposits. Location: Near center sec. 

 13 (proj.), r. 13 S., R. 4 E., M.D., 4'/, miles southeast 

 of San Juan Bautista; Hollister l.S-minute quadrangle. 

 Ownership: Ideal Cement Company, 420 Ideal Ce- 

 ment Building, Denver, Colorado 80202 (1959). 



This deposit is described by Bowen and Gray ( 1959, 

 p. 25): 



"The Underwood deposits ore o series of small, discontinuous 

 masses of limestone located near the San Andreas fault zone close 

 to and on the northeast side of the Son Juan Canyon Road half 

 o mile north of the Peorce-Twohy deposit. The Underwood prop- 

 erty is port of the former Cienega del Gabilan land grant. It was 

 operated for many years as a source of cement rock by the San 

 Juan Portland Cement Company. The limestone reserves hove been 

 largely depleted and the quarries have been long idle. 



"The limestone masses are within a triangular area bordered on 

 the north and east by faults and on the west by Son Juan Valley 

 alluvium. The total reserves probably never exceeded a million 

 tons, and individual masses ranged from a few thousand tons to 

 several hundred thousand tons. The masses ore in granite and 

 quartz-mica schist wall rocks. The rock is similar in character to that 

 of the Bryan and Pearce-Twohy deposits." 



Other references: Bradley and Logon, 1919, p. 628; Logon, 1947, p. 276; 

 Taliaferro, 1948 (map). 



Upper Bird Creek deposit. Location: NE'/i sec. 6 

 (projected), T. 14 S., R. 5 E., M.D., 1% miles south- 

 west of Hollister; Hollister and Gonzales 15-minute 

 quadrangles. Ownership: Dr. Rollin Reeves, Salinas; 

 mineral rights probably held by Ideal Cement Com- 

 pany (1959). 



This limestone deposit is described by Bowen and 

 Gray (1959, p. 32): 



"In plan this deposit is shaped like a T-bone steak with the longest 

 axis trending northwest. It is about 1,600 feet long, 800 feet in 

 maximum width, ond hos been exposed to a depth of over 400 feet. 

 Most of the rock is medium-grained, blue-groy moterial suitable for 

 Portland cement, but o dolomite streak crosses the northwest end of 

 the mass ond the deposit would hove to be thoroughly tested by 

 drilling to establish whether the moss as a whole is sufficiently low 

 in magnesium. Five to 10 million tons of limestone could probably be 

 developed in the Upper Bird Creek deposit. The following analyses 

 done by L.A. Caetano, courtesy Ideal Cement, on type somples col- 

 lected by Gray are representative of most of the deposit:" 



There is no known development of the deposit. 



Westphal Ranch deposit. Location: Sees. 10 and 

 11, T. 15 S., R. 5 E., M.D., on the south slope of Mt. 

 Olds, 8 miles northeast of Chualar; Gonzales 15- 

 minute quadrangle. Ownership: Herald Ranch (a 

 trust estate), HerbG. Meyer, 145 Auburn Street, Sali- 

 nas (1959). 



The general distribution of carbonate rock of the 

 Westphal Ranch deposit is shown in plate 2. The 

 deposit is described by Bowen and Gray (1959, p. 

 38-39): 



"The beds are sinuous but hove a general east strike and a steep 

 south dip. The corbonate rocks are interbedded with quortz-mtca 

 schist and quartzite, and some skorn-rock hos developed along 

 granitic contacts. None of the lenses exceed 200 feet in width and 

 they ore scottered olong more than a mile of strike length. The rock 



