COAST RANGES OF THE PACIFIC AND THE SAN ANDREAS FAULT SYSTEM 



471 



other side of the fault. This juxtaposition of unlike facies again demonstrates 

 substantial lateral movement. In this case the general trend of the western 

 margin of the continental facies in the Caliente Range is northward across the 

 Carrizo Plain toward the San Andreas, whereas possibly the same transition line 

 may be extrapolated southward from along the east side of the San Joaquin 

 Valley to the fault. Thus, by simple projections the right lateral offset on the 

 fault since the upper Miocene time would be about 65 miles, although the 

 probability of irregularities in trend of this facies contact precludes a strictly 

 quantitative solution of that cumulative shift. Note the comparable offset of 

 the upper Miocene "Pancho Rico"-"Santa Margarita" shale, shown in the same 

 figure. 



11. Going back only slightly farther in the geologic record, approximately 

 175 miles of right lateral offset may have accumulated on the San Andreas 

 fault since early Miocene time. This is suggested by the unique similarities of 

 rock types and sequences in the San Emigdio Mountains, as described by 

 Wagner and Schilling (1923), and the Gabilan Range as described by Kerr 

 and Schenck (1925), and Allen (1946). In each of these areas, a section of 

 lower Miocene volcanics, red beds, and marine lower Miocene and Oligocene 

 strata occurs [B-B' of Fig. 29.13]. 



12. A similar relationship is suggested by some lithologic and faunal simi- 

 larities between the Eocene formations of the Temblor-San Emigdio and the 

 Santa Cruz Mountains which indicate the possibility of an offset of approxi- 

 mately 225 miles since late Eocene time [C-C of Fig. 29.13]. 



13. Also the southern limit of Cretaceous strata in the Temblor Range may 

 match with the southern limit of Cretaceous beds near Fort Ross which would 

 indicate an offset of approximately 320 miles [D-D' of Fig. 29.13]. 



These evidences of progressive movement from the Cretaceous to the 

 present are consistent with each other and yield a rate of 0.2 to 0.3 inch 

 of movement per year. However, geodetic measurements of rates since 

 the turn of the century are about tenfold the ones based on offsets of 

 rock masses (Hill and Dibblee, 1953). 



Contrary to the substantial evidence of large horizontal movement 

 south of San Francisco, Higgins ( 1961 ) concludes that less than 15 miles 

 of right-lateral displacement has occurred along the San Andreas north 

 of San Francisco since mid-Pliocene time. During the same time the east 

 i side has been raised about 500 feet relative to the west side. 



Big Pine and Garlock faults 



Both the Big Pine and Garlock faults have left lateral movement in 

 contrast to the right lateral movement of the San Andreas. The one is 



Fig. 29.13. Maps showing postulated strike-slip movement along the San Andreas fault. Left 

 map shows position of Baja California and Coast Ranges of California (shaded area) in 

 Cretaceous time. Right map shows the present position. D and D' were juxtaposed in Cretaceous 

 time; C and C in Eocene; B and B' in Oligocene and early Miocene; D and D' offset of Big Pine 

 fault. Hill and Dibblee, 1953; Hill, 1954. 



