no CRUISE OF THE BARRERA 



opposite. The softer sandstone resting upon the 

 sides of the folded limestone below, yielding more 

 rapidly to denudation and gradually receding from 

 the sierras, finally left them exposed and to weather 

 down in their own peculiar fashion of fantastic 

 castellated peaks and vertical walls. The sand- 

 stones, on the other hand, have been eroded more 

 evenly into smooth rounded hills without particu- 

 lar alignment or system. Subsequent subsidence 

 and elevation would account for the occasional Ter- 

 tiary deposits and the Pleistocene coral rock fringes. 



The absolute correctness of this explanation can 

 only be confirmed by the determination of several 

 facts — as yet unknown. One would be the finding 

 of limestone of the sierra series below by borings 

 through the sandstone, or by the discovery of a 

 point of actual contact of the two series, or, finally, 

 by discovery of fossil remains in the sandstone to 

 determine its age. 



As a contribution to the theory of overlying 

 sandstones, Mr. Morse cited the lack of calcite 

 about the ore beds lying within the sandstone. 

 As these ore beds are intrusions from below forced 

 up in acid solution through the fault channels, 

 the presence of calcites scattered about the shales 



