CJEOLOCilC IIISIOKV 207 



close of the Paleozoic; the Rocky Mountains at the 

 close of the Mesozoic ; the Great Basin faulting during: 

 and at the close of the Eocene ; the Sierra Nevada and 

 Coast Ranges at the close of the Miocene ; and several 

 movements during the Pleistocene or Ice Age which are 

 reflected in the various glacial and interglacial epochs 

 and expressed by the various directional fault systems 

 of Southern California. 



The climaxes of epochs of earth movement in South- 

 ern California took place at the close of the Fernando 

 (late Pliocene) ; during Middle Miocene (Puente) ; at 

 the close of the Tejon and Martinez epochs of the Ter- 

 tiary; and at the close of the Cretaceous and Triassic 

 Periods.^ 



From the studies of the belted groups of faulted 

 structures herein given it seems that there might have 

 also been alternating epochs of earth movements in 

 Southern California since the great revolution during 

 the close of the Pliocene and in the Pleistocene, char- 

 acterized by times of intense fault-making stresses 

 intermittent with times when the stresses were less in- 

 tensive, and that the fault movements of each interval 

 of activity followed characteristic lines of direction, dif- 

 ferent from those of the others ; saj^ north-south in one 

 epoch, northeasterly in another, east-westerly in still 

 another and northwesterly at one or more times. 



Do the small present-day movements in California 

 mark the beginnings or close of one of the vast cycles ? 

 That is a most important question, because of its bear- 

 ings on seismology. 



'Well summarized by English in Bulletin 768 cf the U. S. Geological 

 Survey, Washington, l'J?6 



