--> --> Abstract: Sequential Paleogeographic Models of the San Andreas Fault System ~70 to ~2 MA, by K. Burnham; #90088 (2009)
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Sequential Paleogeographic Models of the San Andreas Previous HitFaultNext Hit System ~70 to ~2 MA

K. Burnham
Independent research, Oakland, CA, [email protected]

Paleogeographic reconstructions at ~70-30 Ma, ~11 Ma, ~5 Ma, and ~2 Ma juxtapose more than 60 previously published pairs of correlative features.

Eight pairs of correlatives reported by Dibblee, 1966; Cummings, 1968; Wakabayashi and Hengesh, 1995; and McLaughlin et al., 1996 indicate only ~30 km lateral offset across the section of the San Andreas Previous HitfaultNext Hit between its intersections with the Calaveras and San Gregorio faults. The Cretaceous-Pleistocene ages of these correlatives indicate dextral offset of this section of the San Andreas Previous HitfaultNext Hit was not initiated until after 3-4 Ma (McLaughlin et al., 1996).

The 315 km offset of the San Andreas Previous HitfaultNext Hit from Pinnacles to Neenach volcanics is partitioned between ~30 km offset of the San Andreas Previous HitfaultNext Hit north of the Calaveras Previous HitfaultNext Hit intersection, and ~285 km offset of the San Andreas-Calaveras-Hayward-(Rodgers Creek?)-Maacama Previous HitfaultNext Hit. Offset distance of the Calaveras-Previous HitfaultNext Hit leg of this partition is verified by paleogeographic juxtaposition (~70-21.3 Ma) (Burnham, 2006, 2009) of Wakabayashi’s (1999) Skaggs Springs Schist near Healdsburg and Pacheco Pass. Dextral offset of the San Andreas-Calaveras-Hayward-(Rodgers Creek?)-Maacama Previous HitfaultNext Hit commenced after 21.3 Ma, and slipped at least 77 km before 11 Ma.

The ~205 km offset of the northernmost San Andreas Previous HitfaultNext Hit from the Delgada fan to the Wilson Grove Formation is partitioned between ~180 km offset of the San Gregorio-northern San Andreas Previous HitfaultNext Hit and ~30 km offset of the San Andreas Previous HitfaultNext Hit south of the San Gregorio Previous HitfaultNext Hit intersection. Dextral offset of the San Gregorio-northern San Andreas Previous HitfaultNext Hit began after ~19 Ma and had slipped at least 70 km before 5.3 Ma.

The Hosgri-San Gregorio-northern San Andreas Previous HitfaultNext Hit and the San Andreas-Calaveras-Hayward-Maacama Previous HitfaultNext Hit moved separately in parallel before they were connected by formation of the San Francisco peninsula section of the San Andreas Previous HitfaultNext Hit and the Previous HitfaultTop system began to resemble its modern configuration.

AAPG Search and Discovery Article #90088©2009 Pacific Section Meeting, Ventura, California, May 3-5, 2009