Abstract: Late Miocene Paleobathymetry of California Continental Borderland North of 32°

Robert E. Arnal, John G. Vedder

Dart and gravity cores taken along the crests and flanks of present ridge systems in water depths of 1,000 m or less on the California continental borderland have provided a paleontologic basis for determining depth zonation in late Miocene strata. Using foraminifers as water-depth and time indicators, in combination with other criteria established during previous studies, seven biofacies are recognized that equate to seven paleobathymetric zones from the strandline to an excess of 2,500 m of water depth.

Bathyal depths generally prevail throughout late Miocene time. Early Mohnian foraminiferal assemblages indicate water depths ranging mostly from sublittoral to middle bathyal zones but late Mohnian Stage assemblages suggest lower bathyal environments of deposition. Thus a deepening trend is inferred for the present ridge and flank area during late Miocene time.

AAPG Search and Discovery Article #90976©1976 AAPG-SEPM-SEG Pacific Section Meeting, San Francisco, California