Comprehensive studies of radiolarian faunal assemblages recovered from outcrop sections at Centerville Beach, Newport Back Bay, Palos Verdes Hills, and Chalk Hills in California and at Bahia Tortugas and Maria Madre Island, Baja California, provide the data base for regional paleo-oceanographic and stratigraphic analyses of Monterey and associated siliceous sediments of middle Miocene to early pliocene age within Neogene California marginal basins.

The sequential succession and development of characteristic radiolarian assemblages and the temporal and spatial variance in environmentally sensitive species in Luisian, lower and lupper Mohnian, and "Delmontian" sediments provide significant insight to regional paleo-oceanographic evolution. Documentation is provided by interpretation of paleoclimatic trends, variation in sediment accumulations rates, changes in water-mass interaction and distribution, and upwelling and productivity events.

Stratigraphically important species of radiolarian genera such as Theocorys, Lamprocyrtis, Stichocorys, Diartus, Eucyrtidium, Cyrtocapsella, and Botryocyrtis are used to differentiate potential biohorizons which are useful for inter- and intra-basinal and broad regional correlations. Within key intervals, radiolarians provide accurate identification of the low latitude Dorcadospyris alata and Diartus petterssoni Zones in lower Monterey formation sediments.

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