292 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. 



away. Even within the small area embraced in the map the diversity of 

 aspect is striking. The sonthwestern portion of the area surveyed is com- 

 posed of highly metamorphosed rocks, crumpled and dislocated out of all 

 semblance of regularity and weathered into more or less fantastic forms. 

 Except where the surface is occupied by pure serpentine, this area supports 

 fairly developed trees. To the northeast long and high sandstone bluffs 

 succeed one another in endless succession and, being in large i)art utterly 

 bare of vegetation, show to the most casual glance that they are composed 

 of strata striking in a direction par;illel to the trend of the range away from 

 which they dip at large angles. 



Questions presented. — Ncw IdHa luis bceu a large producer of quicksilver, 

 and was of course selected for study on that account. The geological inter- 

 est, however, is not coniined to the occurrence of ore, for the district happens 

 to be admirably suited to the elucidation of two most important problems 

 in the geology of the Pacific Coast These are the stratigraphical relations 

 between the Lower and Upper Cretaceous and the true character of the 

 fiunous Tejon beds. The last tpiestion has been a subject of controversy 

 for a quarter of a century. 



The metamorphic series. — Tlic mctamorphic Ijclt, a part of which is included 

 in the map of New Idria, is almost if not quite continuous from Mt. Diablo 

 southward. The lithological and physical character of the metamorphic 

 rocks at New Idria is identical with that of the altered strata at Mt. Diablo, 

 at Knoxville, at San Luis Obispo and, in short, at all the points where 

 members of this series have been found to contain characteri.stic fossils. 

 Wherever determinable fossils have been found in the metamorphic se- 

 ries — and localities are known in nine counties — the age is the same, viz, 

 the earliest portion of the Cretaceous period. No beds older than this 

 are known to exist in the Coast Ranges. At New Idria organic remains 

 are not altogether wanting in the rocks of this series, for plant remains are 

 found in the New Idria mine, but the specimens are f;ir too imperfect to 

 admit of identification. Nevertheless the fac'-s adduced above, together 

 with other general considerations enlarged upon in Chapter V, make it al- 

 most certain that these rocks are members of the Knoxville series. There 

 is a bare possibilit}-, which no observed facts support, that they may be 



