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Two-stepping into the icehouse: East Antarctic weathering during progressive ice-sheet expansion at the Eocene-Oligocene transition

Two-stepping into the icehouse: East Antarctic weathering during progressive ice-sheet expansion at the Eocene-Oligocene transition
Two-stepping into the icehouse: East Antarctic weathering during progressive ice-sheet expansion at the Eocene-Oligocene transition
In conjunction with increasing benthic foraminiferal ?18O values at the Eocene–Oligocene transition (EOT; ca. 34 Ma), coarse-grained ice-rafted debris (IRD; >425 ?m) appears abruptly alongside fossil fish teeth with continentally derived neodymium (Nd) isotope ratios (?Nd) in Kerguelen Plateau (Southern Ocean) sediments. Increased Antarctic weathering flux, as inferred from two steps to less radiogenic ?Nd values, coincides with two steps in benthic foraminiferal ?18O values. These results indicate that two distinct surges of weathering were generated by East Antarctic ice growth during the EOT. Weathering by ice sheets during a precursor glaciation at 33.9 Ma did not produce significant IRD accumulation during the first ?Nd shift. Glacial weathering was sustained during a terrace interval between the two steps, probably by small high-elevation ice sheets. A large increase in weathering signals the rapid coalescence of small ice sheets into an ice sheet of continental proportions ca. 33.7 Ma. Rapid ice sheet expansion resulted in a suppression of weathering due to less exposed area and colder conditions. Parallel changes in Antarctic weathering flux and deep-sea carbonate accumulation suggest that ice-sheet expansion during the EOT had a direct impact on the global carbon cycle; possible mechanisms include associated changes in silicate weathering on the East Antarctic craton and enhanced fertilization of Southern Ocean waters, both of which warrant further investigation.
0091-7613
383-386
Scher, H.D.
12b5b557-cbbc-4b1d-9c34-6302e86718c7
Bohaty, S.M.
af9dbe78-8b9f-44f2-ba1d-20795837d2d1
Zachos, J.C.
2b8451ab-989c-4519-ad8f-208df1fba6eb
Delaney, M.L.
b340a7e7-7bcb-4fd8-b298-d1a73fb6bf78
Scher, H.D.
12b5b557-cbbc-4b1d-9c34-6302e86718c7
Bohaty, S.M.
af9dbe78-8b9f-44f2-ba1d-20795837d2d1
Zachos, J.C.
2b8451ab-989c-4519-ad8f-208df1fba6eb
Delaney, M.L.
b340a7e7-7bcb-4fd8-b298-d1a73fb6bf78

Scher, H.D., Bohaty, S.M., Zachos, J.C. and Delaney, M.L. (2011) Two-stepping into the icehouse: East Antarctic weathering during progressive ice-sheet expansion at the Eocene-Oligocene transition. Geology, 39 (4), 383-386. (doi:10.1130/G31726.1).

Record type: Article

Abstract

In conjunction with increasing benthic foraminiferal ?18O values at the Eocene–Oligocene transition (EOT; ca. 34 Ma), coarse-grained ice-rafted debris (IRD; >425 ?m) appears abruptly alongside fossil fish teeth with continentally derived neodymium (Nd) isotope ratios (?Nd) in Kerguelen Plateau (Southern Ocean) sediments. Increased Antarctic weathering flux, as inferred from two steps to less radiogenic ?Nd values, coincides with two steps in benthic foraminiferal ?18O values. These results indicate that two distinct surges of weathering were generated by East Antarctic ice growth during the EOT. Weathering by ice sheets during a precursor glaciation at 33.9 Ma did not produce significant IRD accumulation during the first ?Nd shift. Glacial weathering was sustained during a terrace interval between the two steps, probably by small high-elevation ice sheets. A large increase in weathering signals the rapid coalescence of small ice sheets into an ice sheet of continental proportions ca. 33.7 Ma. Rapid ice sheet expansion resulted in a suppression of weathering due to less exposed area and colder conditions. Parallel changes in Antarctic weathering flux and deep-sea carbonate accumulation suggest that ice-sheet expansion during the EOT had a direct impact on the global carbon cycle; possible mechanisms include associated changes in silicate weathering on the East Antarctic craton and enhanced fertilization of Southern Ocean waters, both of which warrant further investigation.

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Published date: April 2011

Identifiers

Local EPrints ID: 183125
URI: http://eprints.soton.ac.uk/id/eprint/183125
ISSN: 0091-7613
PURE UUID: 1e6f7910-3204-49a4-9317-76479d29238b
ORCID for S.M. Bohaty: ORCID iD orcid.org/0000-0002-1193-7398

Catalogue record

Date deposited: 26 Apr 2011 14:45
Last modified: 19 Nov 2019 01:44

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