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Environmental magnetic record of Antarctic palaeoclimate from Eocene/Oligocene glaciomarine sediments, Victoria Land Basin

Environmental magnetic record of Antarctic palaeoclimate from Eocene/Oligocene glaciomarine sediments, Victoria Land Basin
Environmental magnetic record of Antarctic palaeoclimate from Eocene/Oligocene glaciomarine sediments, Victoria Land Basin
The onset of continent-wide glaciation in Antarctica is still poorly understood, despite being one of the most important palaeoclimatic events in the Cenozoic. The Eocene/ Oligocene boundary interval has recently been recognized as a critical time for Antarctic climatic evolution, and it may mark the preglacial-glacial transition. Magnetic susceptibility, intensity of natural and artificial remanences, hysteresis parameters and magnetic anisotropy of the lower half ( late Eocene/early Oligocene) of the CIROS-1 core (from McMurdo Sound, Antarctica) reveal alternating intervals of high and low magnetic mineral concentrations that do not correspond to lithostratigraphic units in the core. Pseudo-single-domain magnetite is the main magnetic mineral throughout the sequence, and sharp changes in magnetite concentration match changes in clay mineralogy beneath and at the Eocene/Oligocene boundary. The detrital magnetite originated from weathering of the Ferrar Group (which comprises basic extrusive and intrusive igneous rocks). Weathering processes and input of magnetite to the Victoria Land Basin were intense during periods when the Antarctic climate was warmer than today, but during intervals when the climate was relatively cool, chemical weathering of the Ferrar Group was suppressed and input of detrital magnetite to the Victoria Land Basin decreased. Our results also indicate that a cold and dry climate was not established in Antarctica until the Eocene/Oligocene boundary, with major ice sheet growth occurring at the early/late Oligocene boundary. Some earlier cold intervals are identified, which indicate that climate had begun to deteriorate by the middle/late Eocene boundary.
Cenozoic, palaeoclimate, palaeomagnetism, rock magnetism, sediments
0956-540X
652-662
Sagnotti, Leonardo
7c810d6f-8a83-4e71-9b56-194a54a59513
Florindo, Fabio
5953170b-79f7-431e-9e08-824a47e0fbd5
Verosub, Kenneth L.
396d0f22-35c1-42b9-8581-96fbb6df597d
Wilson, Gary S.
6dad8d23-23a6-4b25-bc69-1ea7ad428b3b
Roberts, Andrew P.
4f062491-5408-4edb-8dd1-140c6a42e93f
Sagnotti, Leonardo
7c810d6f-8a83-4e71-9b56-194a54a59513
Florindo, Fabio
5953170b-79f7-431e-9e08-824a47e0fbd5
Verosub, Kenneth L.
396d0f22-35c1-42b9-8581-96fbb6df597d
Wilson, Gary S.
6dad8d23-23a6-4b25-bc69-1ea7ad428b3b
Roberts, Andrew P.
4f062491-5408-4edb-8dd1-140c6a42e93f

Sagnotti, Leonardo, Florindo, Fabio, Verosub, Kenneth L., Wilson, Gary S. and Roberts, Andrew P. (1998) Environmental magnetic record of Antarctic palaeoclimate from Eocene/Oligocene glaciomarine sediments, Victoria Land Basin. Geophysical Journal International, 134 (3), 652-662.

Record type: Article

Abstract

The onset of continent-wide glaciation in Antarctica is still poorly understood, despite being one of the most important palaeoclimatic events in the Cenozoic. The Eocene/ Oligocene boundary interval has recently been recognized as a critical time for Antarctic climatic evolution, and it may mark the preglacial-glacial transition. Magnetic susceptibility, intensity of natural and artificial remanences, hysteresis parameters and magnetic anisotropy of the lower half ( late Eocene/early Oligocene) of the CIROS-1 core (from McMurdo Sound, Antarctica) reveal alternating intervals of high and low magnetic mineral concentrations that do not correspond to lithostratigraphic units in the core. Pseudo-single-domain magnetite is the main magnetic mineral throughout the sequence, and sharp changes in magnetite concentration match changes in clay mineralogy beneath and at the Eocene/Oligocene boundary. The detrital magnetite originated from weathering of the Ferrar Group (which comprises basic extrusive and intrusive igneous rocks). Weathering processes and input of magnetite to the Victoria Land Basin were intense during periods when the Antarctic climate was warmer than today, but during intervals when the climate was relatively cool, chemical weathering of the Ferrar Group was suppressed and input of detrital magnetite to the Victoria Land Basin decreased. Our results also indicate that a cold and dry climate was not established in Antarctica until the Eocene/Oligocene boundary, with major ice sheet growth occurring at the early/late Oligocene boundary. Some earlier cold intervals are identified, which indicate that climate had begun to deteriorate by the middle/late Eocene boundary.

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More information

Published date: 1998
Keywords: Cenozoic, palaeoclimate, palaeomagnetism, rock magnetism, sediments

Identifiers

Local EPrints ID: 66111
URI: http://eprints.soton.ac.uk/id/eprint/66111
ISSN: 0956-540X
PURE UUID: 120ffbb9-98f9-4aef-92ac-13c9c18ff2ee

Catalogue record

Date deposited: 30 Apr 2009
Last modified: 08 Nov 2021 16:33

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Contributors

Author: Leonardo Sagnotti
Author: Fabio Florindo
Author: Kenneth L. Verosub
Author: Gary S. Wilson
Author: Andrew P. Roberts

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