Gold 3 1 5 



primary veins. The Tertiary gravels were rich in secondary 

 gold. Here is another chapter in the story. 



The old rocks of the Calaveras and Mariposa formations, 

 long after the stresses of the earth by which they were so vio- 

 lently squeezed, folded, upheaved, and shattered, were weath- 

 ered by wind and storms and eroded by streams, then later were 

 submerged and covered by the sea. An entirely new series of 

 sediments was deposited over the broken edges of the tilted and 

 folded rocks. These formations constitute what is called the 

 Superjacent series as distinguished from the bed-rock series of 

 the older formations. An upheaval in Cretaceous time made 

 these later sea sediments dry land. Then streams began the 

 work of eroding and carrying away the thousands of feet of 

 sediments which had been deposited and solidified into stratified 

 rock formations. During Tertiary time (which followed Cre- 

 taceous) streams carried down the slopes from the Cretaceous 

 mountains vast loads of gravel. In these gravels was deposited 

 gold from veins which had been formed in the rocks which had 

 been upheaved in the great disturbance, and this secondary gold 

 was what first made California famous. 



Placer Gold Buried by Lavas 



But it was not all so simple. Volcanoes broke into action 

 along the crest of the Sierra range. Vast floods of liquid mol- 

 ten lava were poured out and flowed down the valleys. The 

 lavas cooled in time and became hard rock. The lavas which 

 had flowed down the valleys buried the gravels. Thus the 

 gravels with their secondary gold were entombed. The period 

 of maximum intensity of volcanic activity appears to be con- 

 temporaneous with or a little later than the close of the Jurassic 

 period. 



But time is long and things in nature never stay still or sta- 

 tionary. The outpourings of lava ceased. Rains continued to 

 fall, and erosion of streams kept incessantly on. Rivers formed 

 channels in the beds of lava. In some places gravels that had 



