General Structural History 



93 



Figure 80. Profiles of probable 

 small fold in Santa Barbara 

 Basin as compared with one of 

 Dominguez Hills, part of the 

 Newport-Inglewood structure 

 in the Los Angeles Basin. 



DISTANCE IN YARDS 



2000 [000 1000 2000 3000 



as the Franciscan. The folding and thick- 

 ening resulted in isostatic uplift which con- 

 verted the former sea floor into a land area. 

 However, the uplift is incomplete even now, 

 as shown by an existing coastal belt of neg- 

 ative isostatic anomalies, and it has not been 

 great enough to expose the base of the 

 metamorphic series. 



Traces of a nearly filled marginal trench 

 exist at the base of the present continental 

 slope off" southern California, and well- 

 developed trenches are present farther south 

 off" Central and South America, where still 

 smaller supplies of sediment are available. 

 Perhaps these trenches are modern relatives 

 of the geosyncline in which sediments ac- 

 cumulated and were downfolded and altered 

 to become the metamorphic basement rocks 

 of coastal California; however, they may 

 differ from the earlier geosyncline in that 

 the latter is believed to have received much 



sediment from a bordering highland to the 

 west (Taliaferro, 1943, p. 187). The fact 

 that the modern trenches are parallel to and 

 seaward of the Mesozoic geosyncline indi- 

 cates a seaward migration of the zone of 

 downfolding, perhaps similar to the progres- 

 sive seaward shifting of belts of geosynclinal 

 folding in Australia, Japan, and elsewhere 

 in the world. 



Late Cretaceous Chico strata, chiefly 

 sandstones, have been found only in a nar- 

 row coastal belt in southern California. 

 The meager distribution of Paleocene rocks 

 is similar. However, Eocene sedimentary 

 rocks, mostly sandstones, are more widely 

 distributed in the continental borderland, 

 being found also on San Nicolas and some 

 of the northern islands. Next, Oligocene 

 marine sedimentary rocks are known only 

 from the northern islands and the mainland 

 near Point Conception. Nonmarine coarse 



