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The thickness of annual sediment laminations in the Santa Barbara Basin is compared to southern California drought-resistant tree growth and to regional indices of rainfall and temperature. The rate of sedimentation was found to be independent of temperature, but it is highly correlated with rainfall and tree growth. We suggest that sedimentation, like tree growth, is a function of the amount of rainfall in the prior seasons as well as the current season. The natural filter displayed by the sedimentation and tree-growth records can be described by a simple mathematical model which, in the case of sedimentation, can be related to upstream aggradation or to distributional processes on the shelf. The pair of laminae that constitute a single year9s sediment accumulation are directly related. This suggests that the process of detrital sediment delay and redistribution operates primarily in the marine environment. The density difference that distinguishes “winter” laminae and “summer” laminae is ascribed to the interaction of the seasonal rate of deposition and the growth of a mat-forming organism endemic to the surface sediment of the Santa Barbara Basin.

The sill depth (480 m) in the Santa Barbara Basin, California, separates two strikingly different planktonic sediment assemblages. The anaerobic part of the basin below the sill depth contains abundant aragomtic shells (pteropods and pelecy-pods) and relatively high concentrations of calcitic shells (planktonic foraminifera). In the oxygenated region above sill depth there are no aragonitic shells and concentrations of planktonic foraminifera are much reduced. Percentages of species, size classes, and morphological variants of planktonic foraminifera differ between samples from above and below the sill depth. In contrast, concentrations and faunal composition of siliceous shells (radiolarians and diatoms) apparently are essentially the same above and below the sill. The most important mechanism responsible for the differences between oxygenated and anaerobic calcareous assemblages probably is selective dissolution. Bottom transport may also be important, especially for slowly settling shells that may frequently be returned to suspension by benthomc activity in the aerobic region and consequently settle preferentially in the undisturbed anaerobic region. The accumulation rate of large planktonic fora-minifera in the anaerobic sediment provides an excellent measure of shell output. Comparison with the standing stock of planktonic foraminifera in the productive surface waters yields minimum turnover times of 2 to 3 weeks for the living planktonic foraminifera in the Santa Barbara Basin.