General Structural History 



89 



history. Knowledge of the origin of the 

 basement complex of metasediments and 

 metaigneous rocks is little more complete 

 than when Reed and Hollister (1936, p. 7) 

 and Taliaferro (1943) wrote of it as probably 

 made up of deposits in a Mesozoic geosync- 

 Une. The Franciscan series and its prob- 

 able Catalina equivalent have such a great 

 thickness and a distribution in a belt with a 

 length of about 1200 miles (Cedros Island, 



Mexico, to Oregon) and a width of less than 

 100 miles as to be suggestive of eugeo- 

 synclinal or perhaps paraliageosynclinal 

 geometry. Accumulation of thick sediments 

 in deep trenches marginal to continents or 

 continental-type areas is common around the 

 Pacific Ocean. With intense compression 

 and downfolding during Middle Cretaceous 

 time these materials were converted into the 

 metasediment and metaigneous series known 



' Ay^At). ' 



Figure 76. Folds in shallow water shown by kelp living atop beveled edges of alternating hard and soft Miocene 

 strata at Rincon Point. Photograph by Fairchild Aerial Surveys, Inc. 



