Age and driving mechanisms of the Eocene–Oligocene transition from astronomical tuning of a lacustrine record (Rennes Basin, France)
<p>The Eocene–Oligocene Transition (EOT) marks the onset of the Antarctic glaciation and the switch from greenhouse to icehouse climates. However, the driving mechanisms and the precise timing of the EOT remain controversial mostly due to the lack of well-dated stratigraphic records, especiall...
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| Autores principales: | , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
Copernicus Publications
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/14ac1be47d144f7096009dbf3312b097 |
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| Sumario: | <p>The Eocene–Oligocene Transition (EOT) marks the onset of
the Antarctic glaciation and the switch from greenhouse to icehouse
climates. However, the driving mechanisms and the precise timing of the EOT
remain controversial mostly due to the lack of well-dated stratigraphic
records, especially in continental environments. Here we present a
cyclo-magnetostratigraphic and sedimentological study of a <span class="inline-formula">∼</span> 7.6 Myr long lacustrine record spanning the late Eocene to the earliest
Oligocene, from a drill core in the Rennes Basin (France).
Cyclostratigraphic analysis of natural gamma radiation (NGR) log data yields
duration estimates of Chrons C12r through C16n.1n, providing additional
constraints on the Eocene timescale. Correlations between the orbital
eccentricity curve and the 405 kyr tuned NGR time series indicate that 33.71 and 34.10 Ma are the most likely proposed ages of the EO boundary.
Additionally, the 405 kyr tuning calibrates the most pronounced NGR
cyclicity to a period of <span class="inline-formula">∼</span>1 Myr, matching the g1–g5 eccentricity term,
supporting its significant expression in continental depositional
environments, and hypothesizing that the paleolake level may have behaved as
a low-pass filter for orbital forcing. Two prominent changes in the
sedimentary facies were detected across the EOT, which are temporally
equivalent to the two main climatic steps, EOT-1 and Oi-1. We suggest that
these two facies changes reflect the two major Antarctic cooling/glacial
phases via the hydrological cycle, as significant shifts to drier and cooler
climate conditions. Finally, the interval spanning the EOT precursor glacial
event through EOT-1 is remarkably dominated by obliquity. This suggests
preconditioning of the major Antarctic glaciation, either from obliquity
directly affecting the formation/(in)stability of the incipient Antarctic Ice
Sheet (AIS), or through obliquity modulation of the North Atlantic Deep
Water production.</p> |
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