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| Titel |
Subglacial sediment provenance and transport in West Antarctica from micropaleontologic analysis of Subglacial Lake Whillans and the upstream sectors of the Whillans and Kamb ice streams |
| VerfasserIn |
Reed Scherer, Jason Coenen, Sophie Warny |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250093766
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| Publikation (Nr.) |
 EGU/EGU2014-8817.pdf |
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| Zusammenfassung |
| The WISSARD (Whillans Ice Stream Subglacial Access Research Drilling) project recovered
sediment cores from Subglacial Lake Whillans (SLW) in West Antarctica. We report
preliminary micropaleontological analyses of SLW sediments, augmented by analysis of
sediments previously recovered from beneath the upstream camps of the Whillans Ice Stream
(WIS) and Kamb Ice Stream (KIS). Microfossils in these sediments (notably diatoms, sponge
spicules, and organic-walled palynomorphs), include information regarding sediment
transport, subglacial physical processes and ice sheet history. Absolute abundance (particles
per gram dry sediment) of identifiable diatoms and diatom fragments in different
size classes were calculated to compare and contrast each environment. Sponge
spicules are being analyzed for taphonomic effects from subglacial transport and
shearing. Palynomorphs are analyzed for abundance, diversity, and source rock
ages.
In SLW the upper 30 cm is softer and more water-rich than the underlying sediments.
However, no statistically significant variation in microfossil and fragment abundance or
taphonomy is noted in these diamictons, which is in agreement with the stratigraphic
homogeneity evident from geochemical and geological analyses performed to date. SLW
contains 1.52x106 to 1.13x107 diatom fragments per gram, compared with 6.43x106 to
4.63x108 at upstream WIS and 6.13 107 to 1.58x108 at KIS. Whole diatoms are
orders of magnitude lower in concentration. Low abundance and poor preservation
of diatoms and spicules at SLW suggests relatively long distance transport from
their marine sediment source, with evidence of high shear strain, following the
subglacial shearing index of Scherer et al. (2004). Upper Miocene diatoms dominate all
samples analyzed, though older and younger diatoms are noted as well. The WIS
samples exhibit the highest diversity of diatoms, including Paleogene freshwater
diatoms. KIS sediments have the highest abundance of whole diatoms, but they
are characterized by low diversity, indicating local erosion of an Upper Miocene
deposit. Palynomorphs in all of the samples demonstrate a sizable contribution of
Eocene terrigenous material. The quantitative analysis of microfossils preserved in
these sediments is revealing a complex set of subglacial processes. Constraining the
heterogeneity of subglacial sedimentary environments and sediment transport is
providing important data for understanding and modeling current and past WAIS
behavior. |
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