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Isotopic interrogation of a suspected late Eocene glaciation

Isotopic interrogation of a suspected late Eocene glaciation
Isotopic interrogation of a suspected late Eocene glaciation
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, although 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 ?18O record at Ocean Drilling Program (ODP) Site 738 (Kerguelen Plateau; Southern Ocean). This event, named the Priabonian oxygen isotope maximum (PrOM) Event, lasted ~140?kyr and is tentatively placed within magnetochron C17n.1n (~37.3?Ma) based on the 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 <63?µm fraction of decarbonated and reductively leached sediment samples. Changes in the mixture of bottom waters, based on fossil fish tooth ?Nd, were less pronounced and slower relative to the benthic ?18O and terrigenous ?Nd changes. Terrigenous sediment ?Nd 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 ?Nd reached a minimum value during the PrOM Event, although the shift begins much earlier than the terrigenous ?Nd 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.
late Eocene, glaciation, Antarctica, Kerguelen Plateau, neodymium isotopes, sediment provenance
0883-8305
628-644
Scher, Howie D.
e8ccbb0d-3b13-449f-be6a-b3bdc0f19e08
Bohaty, Steven M.
af9dbe78-8b9f-44f2-ba1d-20795837d2d1
Smith, Brian W.
49fb04df-5a81-4f01-b103-1783594c942a
Munn, Gabrielle H.
568b8788-f4c5-438b-a311-eeeb4fdda4e9
Scher, Howie D.
e8ccbb0d-3b13-449f-be6a-b3bdc0f19e08
Bohaty, Steven M.
af9dbe78-8b9f-44f2-ba1d-20795837d2d1
Smith, Brian W.
49fb04df-5a81-4f01-b103-1783594c942a
Munn, Gabrielle H.
568b8788-f4c5-438b-a311-eeeb4fdda4e9

Scher, Howie D., Bohaty, Steven M., Smith, Brian W. and Munn, Gabrielle H. (2014) Isotopic interrogation of a suspected late Eocene glaciation. Paleoceanography, 29 (6), 628-644. (doi:10.1002/2014PA002648).

Record type: Article

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, although 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 ?18O record at Ocean Drilling Program (ODP) Site 738 (Kerguelen Plateau; Southern Ocean). This event, named the Priabonian oxygen isotope maximum (PrOM) Event, lasted ~140?kyr and is tentatively placed within magnetochron C17n.1n (~37.3?Ma) based on the 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 <63?µm fraction of decarbonated and reductively leached sediment samples. Changes in the mixture of bottom waters, based on fossil fish tooth ?Nd, were less pronounced and slower relative to the benthic ?18O and terrigenous ?Nd changes. Terrigenous sediment ?Nd 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 ?Nd reached a minimum value during the PrOM Event, although the shift begins much earlier than the terrigenous ?Nd 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.

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More information

Accepted/In Press date: June 2014
Published date: June 2014
Keywords: late Eocene, glaciation, Antarctica, Kerguelen Plateau, neodymium isotopes, sediment provenance
Organisations: Paleooceanography & Palaeoclimate

Identifiers

Local EPrints ID: 366467
URI: http://eprints.soton.ac.uk/id/eprint/366467
ISSN: 0883-8305
PURE UUID: 69fa3fca-5d7d-4eb7-b109-97fdf670b875
ORCID for Steven M. Bohaty: ORCID iD orcid.org/0000-0002-1193-7398

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Date deposited: 30 Jun 2014 10:44
Last modified: 15 Mar 2024 03:27

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Contributors

Author: Howie D. Scher
Author: Brian W. Smith
Author: Gabrielle H. Munn

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