1978 



Limestone in the Coast Ranges 



15 



the west, south, and southeast sides of the hill. The 

 deposits probably formed from spring water during 

 Quaternary time, although only a few small springs 

 were noted in the area. However, brecciated sand- 

 stone and conglomerate (Domengine and Chico For- 

 mations, Weaver, 1949) cemented \\ith travertine 

 suggest that fault-associated springs may have been 

 more prevalent in the past. Travertine is the principal 

 carbonate material remaining, although little can be 

 said of the nature of the material cjuarried. 



Much of the travertine in the quarry areas is me- 

 dium to coarse crystalline, fairly dense, distinctly 

 banded, and nearly white to yellowish brown. It ap- 

 pears to have formed mainly as near-surface fracture 

 fillings. Elsewhere, particularly in SEVi sec. 8, the 

 travertine is fine crystalline, usually amber to honey 

 brown, thinly banded, and .somewhat porous (vuggy). 

 This variety seems to form at the ground surface. As- 

 sociated with the travertine are other carbonate 

 materials, including the softer calcareous tufa and 

 caliche, which appear to be somewhat impure. Analy- 

 ses of the pure travertine (Eckel, 1913, p. 121) show- 

 that the material consists mainly of calcium carbonate. 

 Some is also associated with brecciated sandstone and 

 conglomerate. The deposit is a sort of stockwork, 

 grading downward from relatively pure travertine 

 into fractured country rocks having vein fillings of 

 calcium carbonate (Goodyear, 1890, p. 670). 



Reserves of carbonate rock are difficult to estimate 

 because deposits are scattered over sec. 8 and adjacent 

 parts of sec. 7 and SW'^SW'Vi sec. 5. The largest depos- 

 it probably \^ as the one located just south of N\V cor. 

 sec. 8, where it covers an area 1,700 by 700 feet. A 

 hillside quarrv 1,100 by 700 feet with a maximum face 

 of 200 feet has nearly exhausted the deposit. Judging 

 from the depth of the quarry (visited April 1962), it 

 is estimated that the deposit was at least 60 to 70 feet 

 in maximum thickness. In S'/, sec. 8 another extensive 

 deposit covers a triangular area half a mile long by a 

 maximum of 1,800 feet wide. Sandstone exposed in a 

 series of broad, shallow benchcuts indicates the traver- 

 tine to be no more than 1.^ to 20 feet thick. This area 

 was worked most recently, probably for construction 

 materials used at Travis Air Eorce Base. 



A number of smaller deposits, some undeveloped, 

 lie on the southeast, southwest, and west slopes of 

 Cement Hill. The most impressive of these is a thin, 

 narrow body several hundred feet long situated 1,200 

 feet east-southeast of center sec. 8. Thinly banded, 

 yellowish-brown, fine-grained, vuggy travertine of 

 rather pleasing appearance constitutes the deposit. 

 Such material may be useful as terrazzo and for other 

 ornamental purposes. Reserves may be in the order of 

 10,000 tons. Larger reserves exist elsewhere on Cle- 

 ment Hill, but the travertine does not appear to have 

 as much ornamental value. 



Other relerencei: Browne, 1868, p 243; Wolls, 1890, p. 669 and 1893, 

 p. 191; Aobury, 1906, p. 108, 185-189; Loiiure, 1927, p. 205-208, 210; 

 Logon, 1947, p 332; Weover, 1949, p. 88, pi. 5, 7. 



Deming's Point deposit. Location: Approx. sec. 

 16, T. 3 N., R. 3 VV., M.D., 2 miles cast of Xallejo; 

 Benicia 7'/2-minute quadrangle. Ownership: Not de- 

 termined. 



"A large outcrop of rock suitable for making ce- 

 ment" is reported by Oawford (1894, p. 381). 'There 

 has been no known development. The area is under- 

 lain by the Chico Formation of Late Cretaceous age 

 (Weaver, 1949, plate 1.'!). 



Inverness Park (Lockhart Tract, Point Reyes, 

 Tomales Bay, Trout Farm) deposits. Location: 

 Near SE'/ sec. 34, \. 3 N.. R. 9 W. (proj.), M.D., l'/^ 

 miles west of Point Reyes Station; Point Reyes 15- 

 minute quadrangle. Ownership: J. W. Lockhart, In- 

 verness Park (1962). 



Coarse-crystalline, white to brown-stained lime- 

 stone similar to the Sur Series limestone is exposed as 

 scattered outcrops on the Lockhart Ranch near 

 Drakes Summit Road, 3,000 feet west of Inverness 

 Park. Reportedly, the limestone can be traced by 

 means of detached outcrops and float for nearly half 

 a mile northwest to a point not more than 200 yards 

 southeast of Drakes Summit (Ver Planck, 195.'>, p. 

 2 59). The presence of granitic soil between the de- 

 tached outcrops strongly indicates that the deposit 

 consists of small discontinuous masses of limestone. 

 According to Alan J. Galloway (unpublished report), 

 the limestone covers an area of about 30 acres and the 

 largest exposure is about 40 feet long by 20 feet high. 

 Additional limestone is exposed in Haggerty (iulch 

 about a quarter mile to the east of the summit expo- 

 sures. Here, coarse-crystalline white limestone is in- 

 terbedded with schist and cut by dikes of pegmatite 

 and quartz diorite. 



A number of limestone samples have been collected 

 and analyzed over the years and these are listed in 

 table 2. Samples 1-6 probably indicate the best grade 

 of limestone available. Some of the limestone, howev- 

 er, is locally siliceous or iron stained (sample 7). 



The Inverness Park deposits were developed in a 

 limited way many years ago. A small quarry and sev- 

 eral test pits are situated just northwest of Drakes 

 Summit Road on the Lockhart property. Another 

 quarrv is reported at the "'Trout Farm" locality (Eck- 

 el, 19.33, p. 353) which is believed to be in the canyon 

 at the north end of the deposits. Apparently the lime- 

 stone was used mainly as a source of lime. I wo small 

 kilns are reported by \'er Planck (1955, p. 259) close 

 to Drakes Summit Road within 100 yards of Sir Fran- 

 cis Drake Highway. These kilns apparently were op- 

 erated at least as early as 1856 ((Jalloway, unpublished 

 report) and were last used around the turn of the 

 century (Eckel, 1933, p. 353). Production was small, 

 although no official records exist. Potential of the 

 limestone near Inverness Park seems quite limited, as 

 limestone reserves appear to be small and distributed 

 among a number of small, scattered bodies. 



Other relerencei: Anderson, 1899, p. 131; Logon, 1947, p. 251; Weo»er, 

 1949, p. 88, plate 9; Golloway, 1962, p. 396, plote 26. 



