The Geochemical Signature of Antarctic Glaciation
Abstract
Previous work on southern Kerguelen Plateau revealed that the neodymium (Nd) isotope signal of glacial weathering during the Eocene Oligocene Transition is preserved in fossil fish teeth as a large excursion toward negative ɛNd values (i.e., nonradiogenic; typical of ancient continental crust). The source of nonradiogenic Nd to southern Kerguelen Plateau is ancient Antarctic sediment sources. Transport vectors from Antarctica to bottom waters on Kerguelen Plateau include 1) the interplay of mechanical and chemical weathering during glacial advance and 2) incorporation of nonradiogenic shelf waters into the deep western boundary current that runs along Kerguelen Plateau. We present benthic foraminiferal δ18O and fossil fish tooth neodymium (Nd) isotope records from seven circum-Antarctic sediment cores that span the Eocene Oligocene Transition (EOT; ca. 34 Ma). The temporal resolution of these records range from 7 to 20 kyr and are correlated at high resolution using prominent inflections in δ18O and δ13O values. Among the high latitude sediment cores in the Atlantic, Indian, and Pacific fossil fish tooth ɛNd records illustrate stepwise ɛNd shifts that coincide with δ18O steps across the EOT. A remarkable aspect of the spatial pattern of these records is the magnitude of the excursion scales with the mantle extraction age of the most proximal sediment sources on Antarctica. This result strongly indicates that the main advance of Antarctic ice sheet occurred simultaneously in Dronning Maud Land, Prydz Bay, and Ross Sea sectors. Another significant finding is that the Nd isotope excursion becomes strongly attenuated in sediment cores moving northward into the South Atlantic, reflecting mixing with water masses from outside of the circum-Antarctic.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMPP23A1732M
- Keywords:
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- 4901 PALEOCEANOGRAPHY / Abrupt/rapid climate change;
- 4924 PALEOCEANOGRAPHY / Geochemical tracers