344 The American Geoloyist. June, 1895 
mas. In the Franciscan series we have, in addition to the 
detrital rocl^s, foraminiferal limestones and great formations 
of very peculiarly bedded radiolarian cherts. The conditions 
governing the deposition of these rocks are not clear, but 
there are strong suggestions that they are essentially chemi- 
cal deposits, although containing organic forms. In the same 
series certain rocks held by some earlier writers to be meta- 
morphic sediments are shown to be true igneous rocks, chiefly 
contemporaneous volcanic extravasations. The serpentines, 
which have also been held to be metamorphic sediments, are 
shown to be altered conditions of peridotites or pyroxenites, 
in harmony with the results already announced by Palache* 
and Ransome.f They are intrusive in the Franciscan series 
in the form of dikes and laccolitic lenses. There are certain 
highly crystalline schists which form part of the series. These 
are shown to be altered forms of the normal sedimentary and 
volcanic rocks of the series. They are associated with the 
serpentines and other basic intrusives, and the hypothesis is 
advanced that they represent contact zones of local metamor- 
phism on the borders of these intrusives, which hypothesis 
has been greatl}^ strengthened by the excellent work of Ran- 
some on the geology of Angel island, the results of which 
have already been published.;*; Reconnaissance observations 
have suggested the extension of this hypothesis to the effect 
that none of the crystalline schists of the Coast ranges are 
products of regional metamorphism as that term is commonly 
understood, but that they are contact zones of irruptive 
masses. 
Apart from the diastrophic disturbances, foldings and up- 
lifts which mark time intervals between the different terranes^ 
the field, from an orogenic point of view, resolves itself into 
two great fault blocks, each tilted to the northeast, with a 
structural valley between. The sculpture of these blocks dur- 
ing the remarkable oscillations of the coast in post-Pliocene 
time, together with the development of certain minor con- 
structional forms, yields us the geomorphy of the present time. 
The history of the diastrophic movements which have af- 
*Biill. Dt'pl. Geol. Univ. Cal., vol. i, no. 5. 
fibid., vol. I. no. 7. 
JLoc. cit. 
