In several places in the Salinas Valley, California, the very siliceous, extensive Monterey Shale contains zones of pelletal phosphate. In two measured sections through the Monterey, one in the west-central and one in the southeast part of the valley, Foraminifera were examined to determine the age and paleoenvironment of the rocks. The early and early middle Miocene rocks contain faunas indicating bathyal (4,000± ft) water depth. Above this, in the late middle Miocene rocks that include the pelletal phosphorites, the faunas indicate shallow water (150± ft). The very siliceous rocks, thought to be formed by alteration of thick diatomite deposits, indicate deposition in conditions of upwelling nutrient-rich waters.