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Upper Oligocene and Lower Miocene Stratigraphy of the San Joaquin Basin, California

Scott T. Hector1 and Karen E. Blake2
1Hobby Energy, 2500 Airport Drive, Rio Vista, CA 94571
2Plains Exploration and Production Company, 1200 Discovery Drive #500, Bakersfield, CA 93309

The upper Oligocene and lower Miocene stratigraphy of the San Joaquin Basin was dominated by nonmarine deposition in the northern portion, shallow-marine deposition in the central portion of the basin, and primarily by deeper marine deposition in the southern part of the basin, except for shallow marine and nonmarine deposits that rim the southern and southeastern margins of the basin. The time span of 16.2 - 30 Ma represented by these rock units is roughly equivalent to the Zemorrian and Saucesian foraminiferal stages. Recent detailed studies of the chronostratigraphy and lithostratigraphy have greatly expanded our knowledge of the rocks laid down during this portion of the Tertiary, but leave many questions unanswered and have not clarified the nomenclature problems that have plagued geologists working the basin for generations. The stratigraphy of this time reflects the dramatic changes in the basin caused by the collision of the East Pacific Rise with the North American continent and subsequent development of the San Andreas transform system.


AAPG Search and Discovery Article #90076©2008 AAPG Pacific Section, Bakersfield, California