GEOLOGY OF BAJA CALIFORNIA. 181 



that the exposures are not very extensive; they are, in 

 fact, limited to a patch about three miles long east and west, 

 and one mile north and south, on the northern side of Punta 

 Banda. This promontory consists mainly of old porplwritic 

 rocks, against which the cretaceous strata have been de- 

 posited (See profile 2, Plate V) ; they form a perpendicular 

 sea cliff about fifty feet high, and extending for about two 

 and a half miles along the shore; in most places post-plio- 

 cene gravel and sand cover the top of the cliff, but cretace- 

 ous exposures may be found a little higher up, protruding 

 from the later, covering beds. 



The strata consist of a series of yellow, coarse sand- 

 stones, interstratified with heavy conglomerates of well rolled 

 pebbles up to a foot in diameter, evidently petrographically 

 identical with the massive rocks forming the peninsula and 

 derived from them. The beds being very heavy, exact dips 

 and strikes are difficult to obtain; they incline someAvhat 

 northward, dips from 10° to 20° being observed. 



In these heavy sandstones, generally void of fossils, there 

 are at intervals strata two to four feet thick composed en- 

 tirely of the calcareous shells of Coralliochama, accompanied 

 by a small specimen of Oerithium. The fauna is decidedly 

 monotonous, and but a few new forms were found. 



There are strong reasons for believing that this isolated 

 cretaceous mass is but the first of a series of similar strata 

 farther south, and I only regret that I could not extend my 

 trip in that direction. On Todos Santos Island, about 

 twelve miles from the coast, there appears to be an exposure 

 of sandstone similar to that of Punta Banda. At the har- 

 bor of Santo Tomas , 40 miles south of Ensenada, a steep sand- 

 stone cliff, containing many and large pebbles, is said to form 

 the coast. Similar sandstones occur at Cape Colnett, about 

 70 miles south of Ensenada. From here it is not very far to 

 where the mesa sandstones begin, and it appears to me 

 quite probable that these also will eventually be found to 

 belong to the cretaceous period. Gabb has followed the 



