ABSTRACT Following the discovery of significant petroleum reserves in a part of the Santa Barbara Channel presently designated the Santa Ynez Unit, it became necessary to find a suitable location for an offshore platform from which development and production of these reserves could proceed. To obtain accurate and meaningful engineering data concerning the substrata at the proposed platform location, the uppermost 100 m of marine sediments were zoned by using changes in the coiling direction of the planktonic foraminifer Neogloboquadrina pachyderma (Ehrenberg). Biostratigraphic zones based on these coiling direction changes were traced throughout the area. When coupled with water depths interpreted from benthic foraminifera, depositional histories for each of the zones were obtained.