GEOLOGY OF BAJA CALIFORNIA. 183 



and form the rough ranges and peaks of the coast range al- 

 ready mentioned in the introduction. So, for instance, north 

 of Ensenada, where they reach quite down to the sea, and con- 

 tinue towards the high peaks eastward; the hills east of San 

 Carlos are also composed of eruptives; they become still more 

 conspicuous in the high and abrupt range, south of the 

 Maneadero, ending in Punta Banda and extending southward 

 to Santo Tomas. 



These eruptive rocks have, on the whole, a porphyritic 

 habit, and possess the appearance of considerable geologi- 

 cal age; they are usually dense and hard, without accom- 

 panying tufaceous masses, and contain a number of second- 

 ary minerals, especially epidote; it is further evident that 

 they have suffered considerable erosion. The petrographic 

 character is rather varying and will be described more 

 minutely in another paper. At Ensenada Point the rock 

 has a dense, almost flinty ground mass, with small feldspar 

 crj'stals; between Ensenada and Sausal gray or reddish 

 porphyrites prevail; red and black porphyrites occur in 

 the mountains N. N. E. of Ensenada. East of San Carlos 

 light yellowish-red quartziferous porphyries or porphyrites 

 prevail, while normal brownish quartz porphyries may be 

 found in the hills north of Sausal. 



The Punta Banda range is composed of at least two or 

 three different eruptives: diorites of granular structure, 

 hornblende porphyrites with large hornblende crystals, and 

 finally a dense reddish porphyrite. 



Flow structure on a large scale is often apparent in these 

 rocks; so, for instance, along the coast from Ensenada to 

 Sausal, where a gray porphyrite flow about one hundred feet 

 thick is seen to have covered a similar eruptive of a reddish 

 color. In the hills east of San Carlos beautiful examples 

 of this structure, on a large scale, may also be seen. 



The age of these massive rocks is quite satisfactorily 

 determined as pre-cretaceous from the above mentioned 



2d Ser. Vol. I. (13) Issued reptember 25, 1888. 



