94 H. W. FAIRBANKS — GEOLOGY OF THE COAST RANGES. 



becoming more apparent every day that the determinations of the age of 

 strata based merely on a scanty fauna are in many cases very uncertain. 



STRATIGRAPHIC AND LITHOLOGIC EVIDENCE. 



Although it is a general principle laid down in geology that correla- 

 tions based on stratigraphy and lithology in regions in which the strata 

 cannot be traced by continuous outcrop are to be accepted with caution, 

 yet the writer believes that in a study of the Coast ranges, where fossils 

 are rare in the older rocks, these determinations, properly used, are of the 

 highest importance. The fact that rocks of this series are marked every- 

 where by constant lithologic features and exhibit the same kind of meta- 

 morphism as the rocks of the Klamath mountains is sufficient to enable 

 us to separate them from the Cretaceous, The metamorphism, though 

 not always pronounced, is distinct enough, when taken in connection 

 with the lithologic features, to enable the lines to be drawn. The validity 

 of this demonstration of course rests upon the fact of the absence of 

 metamorphism, both dynamic and chemical, from all portions of the 

 known Cretaceous. The writer has examined portions of nearly all the 

 areas of Cretaceous in the central and southern Coast ranges, but has 

 never yet encountered any jasperoid rocks in that formation. 



The rocks of the pre-Cretaceous series generally show a character pe- 

 culiar to the Coast ranges, yet in places portions of the series resemble 

 the metamorphic rocks of the Sierra Nevada. In the northern counties 

 there are many outcrops of a finely cleavable slate. In Monterey county 

 a large area of slates extends southeast from Salmon creek for several 

 miles. The slates are black, cleave as finely as those along the Mother 

 lode in the gold belt and in manner of decay very closely resemble them. 

 The extraordinary development of sandstone and jasper are perhaps the 

 striking lithologic features. The abundance of sandstone would indicate 

 shallow waters not far removed from land areas. It seems' quite prob- 

 able that the basement complex of crystalline schists and granite stretch- 

 ing from point Reyes to the Peninsula range was in early Mesozoic times 

 far more elevated than at present. Toward the middle Mesozoic a sink- 

 ing began, continuing through the Jurassic, but insufficient to cover the 

 granite ridge on the flanks of which the pre-Cretaceous rocks were laid 

 down. This ancient granite range now appears, where not elevated by 

 recent movements, as a sunken range or one worn down to baselevel. 



The almost entire absence of limestone in the pre-Cretaceous series is 

 a remarkable fact. It is one of the evidences of shalloAV water near to 

 land areas. As we go north into the Klamath mountain region in 

 Trinity and Shasta counties the limestone becomes abundant. In that 

 region there is a less predominance of sandstone. These facts all point 



