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| Titel |
Pleistocene fluctuations of the Antarctic Ice Sheet in the Ross Embayment |
| VerfasserIn |
R. M. McKay, T. R. Naish, R. D. Powell |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250024790
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| Zusammenfassung |
| Past fluctuations of the marine-based Antarctic Ice Sheet in the Ross Embayment
are reconstructed for the Pleistocene by developing a model for the glacimarine
depositional sequences documented from the ANDRILL McMurdo Ice Shelf project drill
core AND-1B. This model reveals glacial to interglacial fluctuations of the AIS
in the Western Ross Embayment responding at orbital frequencies. Chronology
is constrained by an age model based on 40Ar/39Ar dating of volcanic ashes and
magnetostratigraphy. The glacimarine sequences in AND-1B appear to correlate one-to-one
with cycles in the benthic δ18O record for the past ~0.8 Myr (Marine Isotope Stages
20-2). Five sequences between ~1.7 and 1.0 Myr can also be matched with specific
intervals in the δ18O record, and indicate oscillations of the AIS grounding line
operating at a 40-kyr frequency. This record provides new insight into the response
of the AIS in the Ross Embayment across the Mid-Pleistocene Transition. Prior
to 1.0 Myr, glacimarine sequences have 40-kyr duration, whereas subsequently
100-kyr glacimarine cycles can be clearly recognised in the core. During this “100-kyr
world”, subglacial to grounding-zone sedimentation dominates at the AND-1B site,
with thin intervals of ice-shelf deposition during interglacials also preserved in
the AND-1B sedimentary record. An unconformity in AND-1B that spans most
(~200 kyr) of the Mid-Pleistocene Transition is inferred to represent large scale
expansion of AIS in the Ross Embayment at ~0.8 Myr. Prior to the Mid-Pleistocene
Transition, interglacial periods are characterised by open-water conditions with high
abundances of volcanoclastic deposits and occasional diatomaceous sediments,
indicating that the marine based ice sheet was more dynamic during this interval. |
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