Sagnotti, Leonardo, Florindo, Fabio, Verosub, Kenneth L., Wilson, Gary S. and Roberts, Andrew P.
Environmental magnetic record of Antarctic palaeoclimate from Eocene/Oligocene glaciomarine sediments, Victoria Land Basin
Geophysical Journal International, 134, (3), .
Full text not available from this repository.
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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