182 CALIFORNIA ACADEMY OF SCIENCES. 



sandstones more carefully on the eastern than on the west- 

 ern coast, and states expressly, regarding the former, that 

 they continue to skirt the coast for a long distance north of 

 the end of the second or middle division, where they occupy 

 the whole peninsula. His description of the appearance 

 of the sandstone corresponds very well indeed with the 

 Todos Santos occurrence. It must be remembered that 

 Gabb did not determine the age of the mesa sandstones, 

 but only conjectured, based on a very slight clew, that they 

 were Miocene. At the same time he describes the quite 

 extensive metamorphism which has affected the strata in 

 certain regions. This fact can not well be brought into ac- 

 cord with such a comparatively recent age as that to which 

 he assigns the rocks. At least nothing has been observed 

 in Upper California, indicating that any extensive meta- 

 morphism has occurred so recently."^ 



Definite palseontological evidence, establishing the age 

 of the mesa sandstones, would be very desirable, and help 

 to clear many doubtful points in the geology of the penin- 

 sula. 



Pre -CRETACEOUS Eruptives. — Gabb has already remarked 

 that eruptive masses occupy much room in the northern part 

 of the territory, and that they overlie tlie granite, but from 

 his description it is not always apparent whether these 

 eruptives are recent or older. From the southern end of 

 Todos Santos Bay to the boundary, they occupy large areas, 

 but are — at least in the section from Ensenada eastward — 

 confined to the first coast range, not extending more 

 than twenty miles west of the shore. 



On the sketch map massive eruptives occupy a large area, 



*The character of the miocene series recently found in the southern part 

 of the peninsula at Boleo (see ante p. 180, foot-note), appears to be very dif- 

 ferent from the mesa sandstones and from the Todos Santos occurrence; it 

 also encloses volcanic materials of andesitic and basaltic character. It is 

 probable that the shells referred to above (ostraea) came from a series equiv- 

 alent to this and not from the mesa sandstone. 



