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



partly from the excessive developnient of the Tertiary, thus hiding the 

 contacts, and partly from the almost universal tendency to the erosion 

 of canyons along this line. The best region with which the writer is 

 acquainted for observing the contact is on the coast of Monterey county, 

 where the crystalline axis of the Santa Lucia leaves the shoreline at a small 

 angle, and is gradually replaced southward by the pre-Cretaceous series 

 without any break in the topography. Numerous deep canyons descend 

 to the ocean, cutting across both the crystalline schists and the younger 

 series, giving fairly good exposures. South of point Sur, for a distance 

 of 25 miles along the coast, the belt of noncrystalline rocks, consisting 

 of slate, sandstone and jasper, is quite narrow. In the vicinity of 

 Slates Springs this series terminates downward by a coarse conglomerate 

 nearly 1,000 feet thick and traceable for several miles. Slate forms the 

 coastline at the springs. The strike is parallel to the coast ; dip about 

 vertical. It is followed by sandstone toward the mountains, and that 

 by the thoroughly cemented conglomerate. The latter is formed of 

 smoothly rounded granitic boAvlders of all sizes, embedded in a sand of 

 the same composition. The matrix is so hardened and metamorphosed 

 as to closely simulate a crystalline mass. Most of the bowlders resemble 

 the chlorite-granite which occurs along the w^estern slope of the range. 

 On the mountains north of Mill creek, and also on Vicente creek, the 

 slightly metamorphosed sandstones of the pre-Cretaceous series were 

 observed resting on the crystalline complex, with no intervening con- 

 glomerate. 



The reason for the assertion that this noncrystalline series is older 

 than the Cretaceous will be given later. 



PRE-CRE TA CEO US SERIES. 



Character, Extent and Relations. — One of the most prominent features of 

 the Coast Range geology is a series of rocks of rather peculiar lithologic 

 character, concerning the exact age of which little is definitely known. 

 It has undergone intense crushing over large areas, and exhibits more or 

 less distinctly a silicious metamorphism, which as a rule makes its separa- 

 tion from the more recent formations easy. The series has been variously 

 classed by different geologists as Tertiary, Cretaceous and metamorphic 

 Cretaceous. The comparative uniformity of the rocks of this series from 

 its most southern exposure to the Oregon line is a most remarkable feature. 



The northern limit of the series along the coast never has been deter- 

 mined. The writer has been informed by Mr Watts, of the State Mining 

 Bureau, that jasper and sandstone similar to that in the vicinity of San 

 Francisco have been observed by him in Del Norte county along the 



