Anomalous geochemical provenance and weathering history of Plio-Pleistocene glaciomarine fjord strata, Bardin Bluffs Formation, East Antarctica

Sandra Passchier, Jason M. Whitehead

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Major and trace element chemical analyses of the Plio-Pleistocene Bardin Bluffs Formation, on the margin of a major ice-stream of the East Antarctic Ice Sheet, yield an anomalous chemically altered sediment composition. The Bardin Bluffs Formation of the Pagodroma Group is one of the key deposits on the Antarctic continent recording glaciomarine sedimentation under open marine fjord conditions as recently as the Plio-Pleistocene. In modern fjords occupied by outlet glaciers of ice sheets, the composition of fine-grained terrigenous sediments approaches that of unweathered rock types exposed upstream. In the Bardin Bluffs Formation, average abundances of stable elements (Ti, Al, Zr) approach average upper crustal compositions and the element ratios are consistent with sediments with a cratonic source, implying glacial dispersal from a large shield area through the Lambert Glacier drainage system. Interestingly, the chemical index of alteration (CIA) of these sediments has values similar to those of average shales formed under conditions of chemical weathering. The sediments are particularly depleted in silicate Ca, which has been observed elsewhere in glacial muds sourced from pre-glacial saprolites. The anomalous chemistry of the Bardin Bluffs Formation can be explained by a sequence of events, involving chemical weathering prior to glacial expansion and erosion. The presence of a remnant 1·5 m deep late Neogene weathering profile at the base of the Bardin Bluffs sequence corroborates this conclusion. Supply of large quantities of chemically weathered materials to Antarctic marginal basins requires at least partial deglaciation of the continent and was previously regarded as uncharacteristic for late Neogene Antarctica.

Original languageEnglish
Pages (from-to)929-942
Number of pages14
JournalSedimentology
Volume53
Issue number4
DOIs
StatePublished - 1 Aug 2006

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fjord
provenance
weathering
Pleistocene
history
sediment
chemical weathering
Neogene
ice sheet
glacier
weathering profile
marginal basin
ice stream
deglaciation
shield
mud
silicate
Antarctica
trace element
sedimentation

Keywords

  • Antarctica
  • Geochemistry
  • Glaciomarine environment
  • Pleistocene
  • Pliocene

Cite this

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title = "Anomalous geochemical provenance and weathering history of Plio-Pleistocene glaciomarine fjord strata, Bardin Bluffs Formation, East Antarctica",
abstract = "Major and trace element chemical analyses of the Plio-Pleistocene Bardin Bluffs Formation, on the margin of a major ice-stream of the East Antarctic Ice Sheet, yield an anomalous chemically altered sediment composition. The Bardin Bluffs Formation of the Pagodroma Group is one of the key deposits on the Antarctic continent recording glaciomarine sedimentation under open marine fjord conditions as recently as the Plio-Pleistocene. In modern fjords occupied by outlet glaciers of ice sheets, the composition of fine-grained terrigenous sediments approaches that of unweathered rock types exposed upstream. In the Bardin Bluffs Formation, average abundances of stable elements (Ti, Al, Zr) approach average upper crustal compositions and the element ratios are consistent with sediments with a cratonic source, implying glacial dispersal from a large shield area through the Lambert Glacier drainage system. Interestingly, the chemical index of alteration (CIA) of these sediments has values similar to those of average shales formed under conditions of chemical weathering. The sediments are particularly depleted in silicate Ca, which has been observed elsewhere in glacial muds sourced from pre-glacial saprolites. The anomalous chemistry of the Bardin Bluffs Formation can be explained by a sequence of events, involving chemical weathering prior to glacial expansion and erosion. The presence of a remnant 1·5 m deep late Neogene weathering profile at the base of the Bardin Bluffs sequence corroborates this conclusion. Supply of large quantities of chemically weathered materials to Antarctic marginal basins requires at least partial deglaciation of the continent and was previously regarded as uncharacteristic for late Neogene Antarctica.",
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Anomalous geochemical provenance and weathering history of Plio-Pleistocene glaciomarine fjord strata, Bardin Bluffs Formation, East Antarctica. / Passchier, Sandra; Whitehead, Jason M.

In: Sedimentology, Vol. 53, No. 4, 01.08.2006, p. 929-942.

Research output: Contribution to journalArticle

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