Evidence of a Late Eocene Paleogene Glaciations in Antarctica

Isotopic interrogation of a suspected late Eocene glaciation

Authors:

Scher et al

Abstract:

Ephemeral polar glaciations during the middle-to-late Eocene (48–34 Ma) have been proposed based on far-field ice volume proxy records and near-field glacigenic sediments, though the scale, timing, and duration of these events are poorly constrained. Here we confirm the existence of a transient cool event within a new high-resolution benthic foraminiferal δ18O record at Ocean Drilling Program (ODP) Site 738 (Kerguelen Plateau; Southern Ocean). This event, named the PrOM - Priabonian Oxygen isotope Maximum Event, lasted ~140-kyr and is tentatively placed within magnetochron C17n.1n (~37.3 Ma) based on correlation to ODP Site 689 (Maud Rise, Southern Ocean). A contemporaneous change in the provenance of sediments delivered to the Kerguelen Plateau occurs at the study site, determined from the less than 63 µm fraction of decarbonated and reductively leached sediment samples. Changes in the mixture of bottom waters, based on fossil fish tooth ϵNd, were less pronounced and slower relative to the benthic δ18O and terrigenous ϵNd changes. Terrigenous sediment ϵNd values rapidly shifted to less radiogenic signatures at the onset of the PrOM Event, indicating an abrupt change in provenance favoring ancient sources such as the Paleoproterozoic East Antarctic craton. Bottom water ϵNd reached a minimum value during the PrOM Event, though the shift begins much earlier than the terrigenous ϵNd excursion. The origin of the abrupt change in terrigenous sediment provenance is compatible with a change in Antarctic terrigenous sediment flux and/or source as opposed to a reorganization of ocean currents. A change in terrigenous flux and/or source of Antarctic sediments during the oxygen isotope maximum suggests a combination of cooling and ice growth in East Antarctica during the early late Eocene.