Climate response to orbital forcing across the Oligocene-Miocene boundary

• Published in: Science
• Main Authors: Zachos, J.C., Shackleton, N.J., Revenaugh, J.S., Pälike, H., Flower, B.P.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2001
• Subjects: Antarctic; Antarc*; Ice Sheet
• Online Access: https://eprints.soton.ac.uk/13488/

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 Antarctic.