GEOLOGIC MAPS AND NOTES ALONG HIGHWAY 49 BOWEN AND CRIPPEN 



73 



A mile and a half north of Cool, a group of limestone quarries can 

 be seen on the north side of the highway. Limestone was first quarried and 

 burned there some 40 or 50 years ago by the Cave Valley Lime Company. 

 One of the old kilns can be seen close to Highway 49 near the abandoned 

 quarry, a quarter of a mile south of the road turnoff to the main workings. 

 The kiln walls were made of limestone lined with greenstone. Local wood 

 was used to fire the kilns. The present operators of the quarry, the Cali- 

 fornia Rock and Gravel Company, quarry and crush the limestone for 

 conversion into lump lime but do not produce either lime or cement 

 themselves. 



A mile beyond the limestone quarries, Highway 49 winds down to 

 the bottom of the canyon of the North Fork of the American River. Both 

 branches of the North Fork are deeply incised and transverse profiles 

 appear youthful. However, an aerial view of the course of the river shows 

 a scries of broad intrenched meanders indicating that the pattern has 

 been superimposed from an ancestral land surface and that the V-shaped 

 transverse profile is produced 'by rejuvenation. Half a mile from the 

 bridge, the junction of the North and Middle Forks of the American may 

 be seen. 



The American River bridge is at the El Dorado-Placer County line. 

 The river is both wide and deep at this point and the effect of deep green 

 water against green rocks is striking. The massive greenstones strike 

 diagonally across the river and have been planed off and polished below 

 high water mark. The railroad bridge and roadbed of the Pacific Portland 

 Cement Company Railroad can be seen close to the highway bridge. 

 This railroad formerly connected the limestone quarries along the Ameri- 

 can River with the Southern Pacific tracks at Auburn. The rails were 

 removed during the last war. Beyond the bridge, the highway begins the 

 ascent up the opposite canyon wall and continues on into Auburn. A new 

 all-steel-and-concrete bridge has been recently completed to replace the 

 old wood-and-steel structure. 



Auburn, county seat of Placer County, was founded in 1848 as a 

 rich placer mining camp. Present day Auburn consists of Old Auburn, 

 with its "roaring '50 V look and numerous historical spots, and New 

 Auburn, a modern up-to-date town. Auburn is one of few towns which 

 have acted as county seat of two counties. Before Placer County was 

 created from a portion of Sutter County in 1851, Auburn acted as county 

 seat of Sutter County. Auburn has always been a transportation center 

 and large lumber and cattle interests have long been connected with it. 

 The De Witt army hospital is located north of town. Highway 40, which 

 connects with Reno and other transcontinental points passes through. 

 Auburn and it is served by the Southern Pacific Railroad. 



Three miles west of Auburn near Highway 40 is the Ophir mining 

 district. Ophir, first known as Spanish Corral, was one of the main placer 

 camps of Auburn ravine and has since been the main gold-quartz mining 



center of Placer County. Although little is left of the town, the orchard 

 and vineyard landscape is attractive. 



Six miles northeast of Auburn at Hotaling, near Clipper Gap, one 

 of the earliest iron mining operations in California was located. Clipper 

 Gap and Hotaling can be reached via Highway 20 east from Auburn. 

 The Hotaling iron mine was located in 1857 but no ore was shipped until 

 1869. The deposit was in the form of lenses at the contact of granodiorite 

 and a metamorphic series of probable Paleozoic age. The ore minerals 

 were magnetite and hematite containing from 40 percent to 65 percent 

 iron. A blast furnace was operated on the property between 1880 and 

 1885 using charcoal made locally and limestone mined near by. It pro- 

 duced thirty to thirty-five tons of pig iron daily. Although red and 

 yellow ocher were shipped from the vicinity in the late 1920 's for mineral 

 paint, no attempt to exploit the lower grade ores for their iron content 

 has been made since the turn of the century. 



AUBURN TO NORTH SAN JUAN MAP 8 



Between Auburn and the Bear River, Highway 49 traverses rolling 

 open grassland broken here and there by patches of brush and scrub 

 trees. The somewhat monotonous landscape to the north of Auburn gives 

 no inkling of the splendid scenery soon to be in evidence from Grass Val- 

 ley to the end of Highway 49. The bedrock between Auburn and Grass 

 Valley is mainly green meta-volcanics of doubtful age which have been 

 intruded by irregular bodies of serpentine and by basic dikes of several 

 types. Between the forks of Dry Creek a narrow belt of Calaveras meta- 

 sediments begins which rather closely parallels Highway 49, on its west 

 side, as far north as Rattlesnake Creek. The Calaveras rocks are mainly 

 mica schist, chert, and limestone. There are large granodiorite intrusions 

 near Grass Valley and the bedrock from Nevada City to North San Juan 

 is principally of plutonic igneous rock approaching granodiorite in aver- 

 age composition. All the Quaternary stream and bench gravels have been 

 worked for gold. Tertiary deposits are absent between Auburn and Grass 

 Valley along the route of Highway 49. There are no mines of any conse- 

 quence south of the Grass Valley district of which the Bullion claim of 

 the Idaho-Maryland Mines Company, Ltd., is the southernmost member. 



Highway 49 crosses the Bear River and the Placer-Nevada County 

 line 8.7 miles north of Auburn. The vicinity of the Bear River bridge is 

 of considerable geologic interest and is an attractive spot for fishing 

 enthusiasts and pleasure seekers. A major thrust fault diagonally crosses 

 the Highway in a NW-SE direction and the crumpled rocks along its 

 trace are an interesting study. West of the bridge along the eastern bank 

 of the river, the sheared and crumpled meta-volcanics are, in places, a 

 lattice-work of silica-carbonate veinlets. Discontinuous, irregular bodies 



