A ~9myr cycle in Cenozoic ?13C record and long-term orbital eccentricity modulation: Is there a link?

Boulila, Slah, Galbrun, Bruno, Laskar, Jacques and Pälike, Heiko (2012) A ~9myr cycle in Cenozoic ?13C record and long-term orbital eccentricity modulation: Is there a link? Earth and Planetary Science Letters, 317-318, 273-281. (doi:10.1016/j.epsl.2011.11.017).

Abstract

The ~ 65-myr-long Cenozoic carbon isotope record (?13C) of Zachos et al. (2001, 2008) documents a strong long-term cycle with a mean pseudoperiodicity close to ~ 9 myr. This cyclicity modulates the ~ 2.4 myr eccentricity cycle amplitude, hinting at a possible link between long-term astronomical and geological variations. Some phase shifts between ~ 9-myr ?13C and astronomical cycles suggest that additional processes (e.g., tectonics) contribute to these long-term carbon-cycle variations.

The strong response of ?13C to long-term eccentricity periods (~ 9 myr, ~ 2.4 myr, ~ 400 kyr) supports the hypothesis that the long time-residence of carbon in the oceans amplifies lower frequency or dampens higher frequency orbital variations. Additionally, the strong expression of low-amplitude ~ 9 myr eccentricity cycle in the ?13C record could be explained by energy-transfer process from higher to lower frequency cycles, and all eccentricity components modulate the carrier climatic precession cycles.

Finally, the Paleocene–Eocene Thermal Maximum (PETM, 55.9 Ma) event, which corresponds to a pronounced ?13C negative excursion, is situated within a strong decrease in the most prominent ~ 9 myr ?13C cycle, hinting at a link between accelerated rates in ?13C variations and the PETM. This specific ~ 9 myr ?13C cycle seems to be amplified by non-orbital mechanisms in atmosphere–continent–ocean system, such as previously suggested methane release from gas hydrate and volcanism.

This record has no associated files available for download.

Contributors

Download statistics