Relations between Monterey Formation deposition and middle Miocene global cooling: Naples Beach section, California

An oxygen and carbon isotopic stratigraphy has been established for the Miocene Monterey Formation (∼18 to 8 Ma) at Naples Beach, Santa Barbara County, California. Correlation to the deep-sea climatic record provides a test of the Monterey hypothesis, which suggests that organic-carbon-rich deposition in the Monterey Formation fostered middle Miocene global cooling through drawdown of atmospheric partial CO₂. Oxygen isotopic correlation of the Naples Beach section to the deep-sea record suggests that increased organic-carbon-rich deposition coincided closely with deep-water cooling and major East Antarctic ice-sheet growth from 14.5 to 14.1 Ma and with a δ¹³C maximum in deep-sea records. These results support a corollary of the Monterey hypothesis, that episodic organic-carbon-rich deposition within the Monterey Formation contributed to deep-sea δ¹³C maxima and to synchronous global cooling.