SUMMARY. 461 



Late in the Cretaceous a great part of the Coast Ranges was again 

 under water and the sea once more reached the flanks of the Sierra Ne- 

 vada. The sediments kiid down at that time, and now known as the Cliico 

 series, were of course deposited unconformably upon the metamorphosed 

 and eroded Neocomian rocks. There was no disturbance at the close of 

 the Cretaceous, and sedimentation and the gradual development of the ma- 

 rine fauna went on undisturbed througli the Eocene, which, in California, 

 is represented by the Trjon series. The non-conformity between the Chico 

 and the underlying rocks and the continuity of the Chico and Tejon were 

 first estabhshed in this investigation. 



Between the Eocene and Miocene there is a sharp faunal distinction, 

 but there is no general corresponding non- conformity. At tlie ch)SO of the 

 Miocene an important upheaval took place, though one which was much less 

 violent than the earlier uplift. Professor Whitney first studied this Post- 

 Miocene disturbance. Only a small amount of Pliocene territory exists in 

 this region, and part of i^; consists of lake deposits. It is of course uncon- 

 formable with the Miocene. 



After the close of the Jurassic no eruptions seem to have taken place 

 in the Coast Ptanges until the close of the Miocene, or possibly a little 

 hiter. Andesites were then ejected and outbursts of these rocks recurred 

 at intervals to the close of the Pliocene. The asperites of Clear Lake and 

 of Mt. Shasta date from the end of the Phocene. Only one dike of rhy- 

 olite is known to exist in the Coast Ranges. It is close to tlie New Alma- 

 den mine. It is probably later than the andesites, but its date is not cer- 

 tain. During the Quaternary and down to very recent times there have 

 been many basalt eruptions. 



The formation of cinnabar deposits was confined to the period of vol- 

 canic eruptions with which they are most intimately connected. Almost 

 all the massive and sedimentary rocks of the region inclose bodies of cin- 

 nabar, and the age and the chemical character of the rocks are witliout ap- 

 parent influence on the ore. 



Clear Lake district.— The Tcgiou of Clear Lake is a picturesque one, lying at 

 the northwestern extermity of a belt of lavas which extend southward as tar 

 as the Bay of San Francisco. Extinct volcanic cones, borax lakes, hot 



