Radiolarians as Paleoceanographic Indicators in the Miocene Monterey Formation, Upper Newport Bay, California

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Abstract
Radiolarians are useful paleoceanographic indicators in the Newport section of the Monterey Formation, Upper Newport Bay, California. The long-term stratigraphic changes (those lasting longer than 100,000 yr) in relative abundances of radiolarian taxa reflect a strong upwelling and temperature signal. Abundance fluctuations on shorter time scales (1000-100,000 yr) are also prominent in this section but more difficult to interpret. Taxa with modern equivalents living in cold, subsurface water increase in relative abundance during the late Miocene and dominate in the early Pliocene. These changes suggest that unwelling of cold, subsurface water increased during the deposition of the Monterey Formation. This paleoceanographic interpretation is consistent with isotopic data and lithologic studies, indicating an intensification of oceanic circulation and biological productivity around the north Pacific rim during the late Miocene.