Climate, dust, and fire across the Eocene-Oligocene transition, Patagonia

The Eocene-Oligocene transition (EOT) is typically interpreted as a time of drastic global cooling and drying associated with massive growth of a glacial icecap in Antarctica and the shift to an "icehouse" climate. The effects of this transition on the terrestrial environments, floras, and...

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Bibliographic Details
Published in:Geology (Boulder) 2015-07, Vol.43 (7), p.567-570
Main Authors: Selkin, Peter A, Strömberg, Caroline A. E, Dunn, Regan, Kohn, Matthew J, Carlini, Alfredo A, Davies-Vollum, K. Siân, Madden, Richard H
Format: Article
Language:English
Subjects:
Argentina
Cenozoic
clastic sediments
Climate
climate change
dust
Eocene
fires
Forest & brush fires
Geological time
Geology
grain size
lower Oligocene
magnetite
Minerals
Oligocene
oxides
paleoclimatology
paleoenvironment
Paleogene
Patagonia
phytoliths
Plant ecology
Precipitation
Sarmiento Formation
sedimentary rocks
sediments
size distribution
South America
stratigraphic boundary
Stratigraphy
Tertiary
upper Eocene
Vera Member
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Summary:The Eocene-Oligocene transition (EOT) is typically interpreted as a time of drastic global cooling and drying associated with massive growth of a glacial icecap in Antarctica and the shift to an "icehouse" climate. The effects of this transition on the terrestrial environments, floras, and faunas of the Southern Hemisphere, however, have been unclear. Here we document simultaneous changes in fire regime and plant community in Patagonia, Argentina. Decreases in the concentration of magnetite in loessites from the Eocene-Oligocene Vera Member of the Sarmiento Formation correlate with decreases in the fraction of burnt palm phytoliths as well as more consistently palm-dominated phytolith assemblages. Association of magnetite and burnt palm phytoliths suggests intense wildfires, which appear to have been suppressed for ∼200 k.y. shortly after the EOT. The disappearance of fire-related characteristics near the EOT is possible if changes in regional wind patterns-consistent with observed changes in sediment particle sizes-caused changes in seasonal precipitation. These results imply a more important role for fire in structuring Eocene-Oligocene landscapes than previously thought.
ISSN:0091-7613
1943-2682
DOI:10.1130/G36664.1