Climate response to orbital forcing across the oligocene-miocene boundary

J. C. Zachos, N. J. Shackleton, J. S. Revenaugh, H. Pälike, B. P. Flower

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Spectral analyses of an uninterrupted 5.5-million-year (My)-long chronology of late Oligocene-early Miocene climate and ocean carbon chemistry from two deep-sea cores recovered in the western equatorial Atlantic reveal variance concentrated at all Milankovitch frequencies. Exceptional spectral power in climate is recorded at the 406-thousand-year (ky) period eccentricity band over a 3.4-million-year period [20 to 23.4 My ago (Ma)] as well as in the 125- and 95-ky bands over a 1.3-million-year period (21.7 to 23.0 Ma) of suspected low greenhouse gas levels. Moreover, a major transient glaciation at the epoch boundary (∼23 Ma), Mi-1, corresponds with a rare orbital congruence involving obliquity and eccentricity. The anomaly, which consists of low-amplitude variance in obliquity (a node) and a minimum in eccentricity, results in an extended period (∼200 ky) of low seasonality orbits favorable to ice-sheet expansion on Antarctica.

Original languageEnglish (US)
Pages (from-to)274-278
Number of pages5
Issue number5515
StatePublished - Apr 13 2001


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