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GEOLOGIC GUIDEBOOK ALONG HIGHWAY 49 



[Bull. 141 



FIG. 37. Sierra Buttes, a group of volcanic remnants, as seen from the foot of Yuba 

 Pass, Sierra County, looking southwest. Photo by C. V. Averill. 



FIG. 39. The California Rock and Gravel Company limestone quarry on the south side 

 of the South Fork of the American River east of Auburn. Photo by Olaf P. Jenkins. 



FIG. 38. A group of "tombstone rocks," the eroded tilte<l edges of meta-volcanics 

 of the Logtown Ridge formation, exposed along the road near Campo Seco. Photo by 

 Olaf P. Jenkins. 



FIG. 40. Spheroidal weathering in massive granodioisite of Abbotts Pass road 

 west of Calaveras Big Trees. Spheroids such as this may be seen along Highway 49 in 

 Yuba Pass between Sierra C'ity and Sattley. Photo by Olaf P. Jenkint. 



