CHAPTER XVII, 



01' THE aUATERNAM TEKIOI) IN CALIFORNIA. 



Observations on the condition of califohnia, fkom the time of the defosition of the blue clat downwards. — Removal of 

 THE upper local drift of the pacific slope, its persistence in the basin and region east of the sierra NEVADA. — Ancient 

 terraces. — Height of the waters of that period. — Detailed notice of the terraces on the salinas and san bonito. — Santa 



MARGARITA. — ^TeRRACES OF SANTA MARIA VALLEY, PANZA VALLEY, AND CARRIZO. — ^TeRRACE LEVELS OF SANTA INEZ VALLEY. 



Terrace along santa Barbara shore. — Terraces op los angeles valley.— Synopsis of localities of terraces, with 



THEIR ALTITUDES. — UPRAISED BEACHES OF SAN LUIS OBISPO. — At SAN PEDRO. SECTION OF CLIFF ALONG SHORE. — RECENT 



shells in. 



An interesting portion of the physical history of California is that which relates to the period 

 immediately preceding the existing state of things ; a period subsequent to the deposition of 

 the blue clays, the sands and gravels, with the coarser local drift, (the chief portion of which 

 latter has since been removed,) and anterior to the present physical configuration of the coast 

 line. This period, when the present surface of California was an ocean, studded over with ellip- 

 tical shaped islands, which ran in linear meridional directions, with currents flowing between 

 them and the main land, was one of elevation with perhaps occasional depression, and is one 

 the history of which there are not materials sufficient to transcribe. 



In the geological history of this coast, depression of the land does not appear to have entered 

 largely as an element. There are no records of a continued slow depression, as evidenced else- 

 where, by the carboniferous limestone of the Rocky mountains or of the Jurassic beds further 

 east ; at tliose epochs it does not ajipear that this portion of the continent even skirted the main 

 land — far away out to the westward it formed the depressed bottom of an ocean whose shores 

 were no nearer than latitude 110°, if, indeed, at that epoch, there were any summits of the 

 continent from latitude 30° to 37° north, above the surface of the sea. So far out at sea was it 

 that it does not appear that the granitic bottom received much current deposits until the com- 

 mencement of the tertiary era, when, by the elevation of the land, basins, estuaries, and rivers 

 of greater magnitude aided in the formation of those sand and clay beds which have accu- 

 mulated to so remarkable a thickness. 



At the close of the tertiary period commenced the deposition of the thick blue clays with 

 broken shells ; then the yellow clays and gravel, and, lastly, a bed of conglomerate drift, of 

 mixed material, granitic and volcanic materials, which upon one valley plain at least has been 

 wholly removed. This drift is derived wholly from the degradation of the neighboring sierras, 

 and contains no masses of rock which cannot be traced to the hills in proximity. The removal 

 of this upper bed from the vallies of California has materially increased its fertility by dimin- 

 ishing the depth of the porous unconsolidated strata. East of the Sierra Nevada, in the 

 Mojave valley, the same unconsolidated strata are met with ; also of granitic and volcanic con- 

 glomerate in the upper bed ; but there it has not been removed, and, like the Sonoranian desert, 

 it is a barren plain which appears to have undergone but little physical alteration since its final 

 upheaval . 



With the deposition of these Quaternary beds, especially of the upper ones, and with the 



