Sedimentation of opaline skeletons (diatoms, radiolarians) is greatly reduced during the last glacial period in the Santa Barbara basin, compared with the Holocene. The overall pattern is similar to that of the accumulation of organic matter, but differs in detail. Apparently, both silicate and phosphate supply are reduced during glacial time within the basin, which derives its surface waters and thermocline waters from the California Current. The pattern of reduced glacial diatom productivity suggests a decrease in the estuarine aspects of the subarctic North Pacific, as a result of decrease in excess precipitation (which dominates the present situation). Variability is greater in silicate accumulation than in organic matter accumulation. We hypothesize that this difference is due to greater sensitivity of silicate to changes in nutrient enrichment and depletion in subsurface waters, as compared with phosphate.

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