GEOLOGY AND QUICKSILVER DEPOSITS. NEW ALMADEN DISTRICT. CALIFORNIA 



conchoidal fracture: but where it is shattered, it has 

 a splintery or shoe-peg fracture. White or pray ellip- 

 soidal limy concretions are scattered through the 

 shale, but are not common in the district. Most of 

 those observed were 1 or 2 inches thick and several 

 inches long, but some measure more than 1 foot in 

 length. Within the district no useful fossils were 

 found in the limy concretions, but on Mount Chuai, 1 

 mile south of the district, similar shale beds contain 

 septarian concretions in which we found fragments of 

 Inocerari 



Xo fossils were found in any of the other rocks of 

 this unit within the mapped areas, but in the upper 

 part of the southern branch of Almaden Canyon, at 

 an altitude of 2,300 feet, the graywacke yielded speci- 

 mens of a large Inoceranni* (fig. 49) and many pelecy- 

 pods similar to Buchia. Farther soutlr. along the 

 Loma Prieta road where it crosses the Santa Clara- 

 Santa Cruz County line, fossils are fairly abundant. 

 A few collected in this area by C. M. (illicit and by 

 us were examined by Dr. S. W. Muller. of Stanford 

 University. He found no forms well-enough preserved 

 to be determined specifically, but he recognized Tri- 

 gonia, (cf. T. evanxi). (Hycnm /-/X .~</></><i/y/<ix. Den- 

 tnl'ntm. and various small thin oysters -an a->emblage 

 that he regarded as indicating Late Cretaceous age. 



FIOURI 48. Interbedded graywacke and shale of Late Cretaceous age 

 In the Sierra Ami as exposed in readout south of Loma Prieta and 

 Just outside the New Almaden district. 



in figure 48 ; in other cuts the shale forms massive sec- 

 tions more than 100 feet thick with only a few inter- 

 bedded layers of graywacke a few inches thick. The 

 shale is olive drab, and in places is interlaminated 

 with lighter colored silt. It commonly breaks with a 



KKII-RE 49. CMU of Inoceramui up. from rocks of Late Cretaceous age In the upper part of the itouth branch of Almaden Canyon. 



