1978 



Limestone in the Coast Ranges 



83 



sec. 22 southeast to W'/ cor. sec. 25 (N. L. Taliaferro 

 /n Jennings, \9>H, and /n Jennings and Strand, 1958). 

 Where examined in SEVi sec. 22 and SW'/ sec. 23, the 

 only carbonate rock exposed is limestone in small 

 blocks and slivers not more than U) to 40 feet wide and 

 interspersed with other rock types. The limestone is 

 principally blue gray, medium to coarse crystalline, 

 sheared, and brecciated. Samples of typical rock were 

 analyzed by Lydia Lofgren of the Division of Mines 

 and Geology on February 15, 196.?, as follows: 



Sjmple CiO MgO SiO,. AI.O, Fe.-O, P,0, 



Ign. 

 loss 



1 49.70% J.08% 4.+4% 0.10% 0.20% 0.04% 42.39% 



2 54.50 0.17 1.03 0.11 0.23 0.04 43.27 



In addition to the above type of limestone, off-white 

 to gray crystalline limestone and dolomite are found 

 as float in Nelson Creek and its tributaries. Presuma- 

 bly, this float was derived from small broken masses 

 (to the southeast, in sec. 26 ?) similar to those faulted 

 masses examined in sees. 22 and li. Although total 

 limestone reserves may be large in the Nelson Creek 

 area, the deposits appear to be too intermixed with 

 other rocks and too remotely situated to be of econom- 

 ic interest. The deposits are about a mile from the 

 Nelson Creek road which is about 24 miles (by road) 

 from San Miguel. 



Other references: Oowford. 1894, p. 392; Crowford, 1896, p. 629; Logan, 

 1947, p. 259; Hart, 1966b, p. 67, 69. 



Stone Corral deposits. Location: Sees. 25 and 36 

 (proj.), T. 24 S., R. 15 E., and sec. 31, T. 24 S., R. 16 

 E., M.D.,9to 11 miles southeast of Parkfield; Parkfield 

 15-minute quadrangle. Ownership: Probably Cho- 

 lame Ranch (1966). 



Several masses of limestone are shown northeast of 

 Cholame Valley by VV. R. Dickinson (1966, plate 2). 

 These are portrayed as lens- and wedge-shaped fault 

 slices that are distributed along a fault /.one for 2 miles 

 northwest of Stone Corral Canyon. The largest lime- 

 stone mass has maximum dimensions of 4,500 feet by 

 1,200 feet. The limestone is gray green and reddish 

 gray, fine grained, and commonly sheared. It contains 

 dark gray chert bands and nodules and resembles 

 limestone of the Franciscan Formation (Dickinson, 

 1966, p. 718). 



The above deposits have not been examined by this 

 writer. 



Webb and .Mingus calcite deposit. Location: Sec. 

 12, T. 20 S., R. 13 E., M.D., 10 miles northwest of 

 Coalinga; Priest \'alley 15-minute quadrangle. Own- 

 ership: Not determined. 



A calcite deposit is reported on "Sherman Peak" 

 (Laizure, 1929, p. 317; Logan, 1947, p. 235). Recent 

 maps show Sherman Peak to be in sec. 10 to the west. 

 There is no known development of the deposit. Sec. 1 2 

 is underlain by sedimentary rocks of Late Cretaceous 

 age. 



Webb and Mingus dolomite deposit. Location: 

 Sec. 28(?), r. 24 S., R. 16 F., .VI. D., 12 miles southeast 

 of Parkfield. Ownership; Not determined. 



Laizure (1925, p. 36) mentions an undeveloped 

 deposit of dolomite in sec. 28 on the 160-acre property 

 of E. A. Webb and S. M. Mingus in southeast Monte- 

 rey County. Sec. 28 is shown to be underlain by com- 

 plexly faulted and folded clastic sedimentary rocks 

 (Upper Oetaceous and Tertiary) and by brecciated 

 serpentine by Dickinson (1966, plate 2), who makes 

 no mention of dolomite in his description of these rock 

 units. However, Dickinson does show several masses 

 of limestone V/i to 2 miles to the west (see Stone 

 Corral deposits). 



SOUTHERN SANTA LUCIA RANGE DISTRICT (C-5) 



The southern Santa Lucia Range district includes 

 the southeast half of the Santa Lucia Range, La Panza 

 Range, and uppermost Salinas River in San Luis 

 Obispo County (plate IC). Although not quite as 

 rugged as the northern Santa Lucia Range, the south- 

 ern Santa Lucia and La Panza Ranges are nonetheless 

 mountainous — rising to maximum elevations of 3,594 

 feet and 4,054 feet, respectively. Most of the district is 

 fairly accessible by roads and the Southern Pacific 

 Railroad traverses the region from north to south, 

 connecting all major communities. Limited port facili- 

 ties (oil, fishing) exist at San Luis Obispo and Estero 

 Bays. The district is about half way between the major 

 marketing centers at Los Angeles and San Francisco, 

 the two cities being 400 miles apart. 



Limestone and dolomite of the southern Santa 

 Lucia Range district occur primarily as pre-Creta- 

 ceous metamorphic rocks and Miocene sedimentary 

 rocks. The metamorphic rocks are similar to the crys- 

 talline carbonate rocks of the Sur Series farther north. 

 In this district, crystalline limestone is found at the 

 Navajo deposit (see below) and also is reported in 

 SW'/ sec. 24, T. 30 S., R. 17 E., both localities being in 

 the La Pan/a Range. Localized in the northwest part 

 of the district is bioclastic limestone of the \'aqueros 

 Formation (lower Miocene). The two main occur- 

 rences are the Lime Mountain and Dubost deposits. 

 Other Miocene shell deposits are reported near the 

 Oceanic and Buena \'ista mercury mines, 4 to 5 miles 

 inland on San Simeon Creek and at various places in 

 the Huasna and Salinas \'alleys (Irelan, 1888, p. 532; 

 Fairbanks, 1904, p. 4; Logan, 1947, p. 303, 306). These 

 shell beds belong to the \*aqueros and Santa Margarita 

 formations of early and late Miocene ages, respective- 

 ly. Some of the shell beds, or reefs, are composed al- 

 most totally of shells and shell debris, one reportedly 

 being 30 feet thick or more (Fairbanks, 19(H, p. 4). 

 Although some shell beds have been used locally as 

 sources of lime, few if any are large enough or pure 

 enough to be of economic interest. 



In addition, impure carbonate rock constitutes the 

 bulk of a thick sequence in the lower part of the Mon- 



