82 



California Division of Mines and Geology 



Bull. 197 



Several sinuous lenses of carbonate rock as long as 

 a mile are shown on Trask's geologic map (1926). 

 These lenses, plus some small nearby masses, form a 

 discontinuous belt 4'/2 miles long extending from the 

 sea coast just north of Hurricane Point southeast to 

 the western part of Dani Ridge. The limestone is part 

 of the Sur Series of metamorphic rocks which locally 

 have been thrust southwestward over Cretaceous (?) 

 sedimentary rocks along the Serra Hill fault (Trask, 

 1926, map and fig. 2). There has been no development 

 or even significant testing of the limestone, and little 

 is known about the commercial possibilities. The most 

 northwestern lens of limestone was observed briefly 

 where it is crossed by State Highway 1. Here it is 

 brecciated and somewhat impure, being associated 

 with schist and locally cut by granitic dikes. Two se- 

 lected samples of limestone, collected from the high- 

 way cut at the northwest end of the deposit belt, were 

 analyzed in 1955 and 1957 by Abbot A. Hanks, Inc. 



These samples are nearly white, fine- to coarse-crys- 

 talline material and represent the best limestone avail- 

 able near the highway. However, this part of the 

 deposit probably is not of commercial value due to 

 siliceous impurities and granitic intrusives which 

 were not sampled. Although the southeastern lime- 

 stone lenses also may be impure and less continuous 

 than indicated by Trask, their relative accessibility 

 warrants further examination and possible sampling 

 (Hart 1966b, p. 66). 



Tassajara deposit. Location: NE'^ sec. 29, T. 19 S., 

 R. 4 E., M.D., 17 miles west of Greenfield; Jamesburg 

 15-minute quadrangle. Ownership: Not determined. 



A small deposit of white crystalline limestone was 

 quarried many years ago as a source of lime for mortar 

 in construction of the hotel at Tassajara Hot Springs 

 (Fiedler, 1944, p. 203, 248, plate 9). The deposit is 

 situated on Tassajara Road less than 3 miles north of 

 the hot springs. Although easily accessible, the lime- 

 stone is remote and impure, being cut by pegmatite 

 dikes. 



PARKFIELD-COALINGA DISTRICT (C-4) 



Several deposits and prospects of carbonate rock 

 dispersed over parts of Monterey and Fresno Counties 

 are designated herein as the Parkfield-Coalinga dis- 

 trict. Except for a minor amount of "brown arago- 

 nite" (Montford deposit) used to make lime in the 

 1880s, none of the deposits is developed. 



Perhaps the most important deposits are the discon- 

 nected masses of crystalline limestone and dolo- 

 mite (?) (Little Cholame and Nelson Creek deposits) 

 which occur as fault slivers along the San Andreas 

 fault zone. Some fault slices of fine-grained limestone 

 similar to that of the Franciscan Formation also exist 



along the San Andreas fault zone. Because of their 

 remoteness from marketing areas, none of these 

 deposits has been prospected to any extent. The other 

 limestone and dolomite deposits reported appear to be 

 too small or impure to be of more than strictly local 

 interest. 



Little Cholame (Patriquin) deposits. Location: 

 SW'X sec. 31,T. 22S., R. 14 E., and SW'/ sec. 5 and sec. 

 6, T. 23 S., R. 14 E., M.D., 5 miles northwest of Park- 

 field and 15 miles southwest of Coalinga; San Miguel 

 and Parkfield 15-minute quadrangles. Ownership: 

 Not determined (1962). 



An "undeveloped deposit of white marble" in sec. 

 6 is mentioned by Waring and Bradley (1919, p. 607). 

 This undoubtedly is part of the sequence of three fault 

 blocks or slivers of Sur Series limestone shown by 

 Jennings ( 1958, based on unpublished mapping of N. 

 L. Taliferro). The limestone supposedly extends 2'/ 

 miles southeast along the San Andreas fault zone from 

 SW'X sec. 31 to E'X cor. sec. 8. Examination of the 

 southeast fault block in sec. 8 was made, but not a 

 single exposure of limestone was observed. However, 

 numerous fragments of white to gray, crystalline 

 limestone were noted in the ravines and in the late 

 Cenozoic gravel deposits exposed on the hills. To the 

 northwest in SE'/^ sec. 5, limited exposures of lime- 

 stone could be seen but were not visited. The deposit 

 indicated in sees. 5, 6, and 3 1 to the northwest is likely 

 to consist of small fault blocks and slivers of crushed 

 and sheared limestone interspersed with other rock 

 types, as is the case to the northwest along the San 

 Andreas fault zone (see Nelson Creek deposit). 

 However, this inference cannot be substantiated with- 

 out additional field work. 



Other references: Logon, 1947, p. 260; Hart, 1966b, p. 67, 69. 



Montford deposit. Location; Sec. 24, T. 21 S., R. 

 14 E., M.D., 4 to 5 miles southwest of Coalinga; Coa- 

 linga 15-minute quadrangle. Ownership: Not deter- 

 mined. 



Brown aragonite was reported in 40 acres of land 

 owned by Dr. G. T. Montford (Laizure, 1929, p. 317). 

 Logan (1947, p. 2 34) refers to this property as Mont- 

 ford marl — "a 'vein' of limestone" from which lime 

 was made in the 1880s. The limestone is reportedly 

 bituminous. 



Nelson Creek deposits. Location: Mainly sec. 22, 

 SWy, sec. 23, and N'/, sec. 26, T. 22 S., R. 13 E., M.D., 

 17 miles northeast of Bradley and 15 miles southwest 

 of Coalinga. Ownership: Possibly Hope Bagby, Hid- 

 den Valley Ranch, San Miguel (1960). 



Blocks and slivers of crystalline limestone and dolo- 

 mite (?) intermixed with Sur Series schist, granitic 

 rocks, Franciscan rocks, serpentine, and various 

 younger sedimentary rocks are found along the San 

 Andreas fault zone on the northeast side of Nelson 

 Creek. The carbonate rocks reportedly are exposed 

 over a distance of more than 2/2 miles from NW cor. 



