The structure and stratigraphy of the southeastern San Joaquin basin were reviewed for evidence that would document the impact on the basin of Miocene rotation of the adjacent Tehachapi and San Emigdio Mountains. Outcrops of basement rocks and volcanic intervals at the southeast margin of the basin contain paleomagnetic data indicating up to 59 degrees of clockwise rotation. The study used cross sections and maps of oil fields published by the California Division of Oil, Gas and Geothermal Resources. Information extracted included fault age and orientation, and stratigraphic data including gross unit thickness and net sand thickness.

The geologic studies of the oil fields contain an abundance of evidence indicating Miocene extension. South of the Kern River, several fields contain numerous faults of early to middle Miocene age that generally fall on NW-SE or NE-SW trends. Fault offsets indicate a large amount of extension and correspond to the down-dropping of the floor of the Tejon embayment and break-up and collapse of the Edison high. Faults of similar age, present in fields north of the Kern River, have a slightly different NNW-SSE strike. Offsets on this latter set of faults are relatively minor and contributed in forming a wide shelf region.

Sediments deposited during the middle and late Miocene reflect different styles of structural extension. South of the Kern River, the depositional gradient was very steep, and sand bodies representing deltaic, shallow-marine and deep marine environments are very localized in extent. North of the Kern River, sands deposited on the wide shelf are laterally extensive and represent deltaic and shallow-marine environments deposited at the terminus of a river system.

The structural and depositional styles are similar between the Edison high and Tejon embayment area, indicating that the same structural events were responsible. The structural evidence is consistent with the rotation model of Goodman and Malin (1992). However, if the Edison high block has rotated, then additional faults may be necessary to accommodate slippage against the adjacent Maricopa sub-basin block. The faulting style north of the Kern River is not consistent with rotation; thus rotation is likely limited to south of the Bakersfield arch.