24 



STRATIFIED ROCKS OF THE SAN BERNARDINO CHAIN, AND 

 PLAINS OF LOS ANGELES. 



The stratified rocks of tins chain consist of clay, clay-slate, sandstones, con 

 glomerate and bituminous shales ; these comprise 'those rocks only which have 

 been observed by outcrop along the coast-line and on the flanks of the hills to 

 the east. Commencing at Point Aguilla we find the coast-line presenting high 

 bluffs of a light brown sandstone, interlaminated with thin seams of clay and 

 slates, possessing the same color as the arenaceous rocks in which they are imbed 

 ded. As you recede from the sea, the land is found to become depressed to a 

 considerable degree until within a short distance of the base of the mountains, 

 when is is again observed to be more rapidly ascending. This fact will hold 

 good with regard to all the level lands fronting the coast from the above point 

 south and east of San Pedro in the county of Los Angeles.. 

 In traveling over this part of the coast another general and striking feature will 

 arrest the attention, and if the pedestrian has traveled in any of the great valleys 

 of this State, he will be struck with the remarkable coincidence which is manifest 

 along the entire range of that terraced structure found so general throughout the 

 whole extent of those valley sections. The superficial soil of the coast terraces 

 is composed of rich mould of a grayish brown color, this is mixed with a fine 

 sand, and a small quantity of mica witft a little clay. The sub-soil is composed of a 

 brown loam mingled with a blue clay and and white sand, the blue clay alone 

 forming a thick bed beneath the whole, and resting upon the rocky structure 

 forming the basis of these plains ; this may be considered the general structure 

 of those lands laying at the base of this chain, but will probably be found local 

 ly modified in portions lying adjacent to the hilly regions. 



The first suite of indurated rocks beneath this consists of a bed of loose sand 

 stone seven feet in thickness. Below this again is found a bed of light yellow and 

 brown infusorial clays interlaminated with thin seams of sandstone ; four feet 

 below this again are found sandstones of a brown color with thin seams of slate 

 containing much calcareous matter thirteen feet in thickness. A heavy bed of 

 bituminous shale succeeds the latter of about eighty feet in thickness, from which 

 issues in many places large quantities of fluid bitumen, and below this again is 

 found a bed of dark sandy clay above which I have frequently seen waters issue 

 in small quantities and under all the strata above named. The aggregate of 

 their thickness inclusive of the alluvial coverings amounts to 124 feet, and the 

 above description applies more particularly to the country stretching from the 

 coast-line towards the east or the interior. The following tabular arrangement 

 giving the line of dip will serve a better purpose of illustration of the position 

 of these strata : 



