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This data set is the result of a study of volcanic ash and rock fragment (tephra) layers in exposed bare blue ice areas on Mt. DeWitt, Antarctica (77.12°S, 159.51° E). Tephra samples were collected between 15 November 1996 and 15 January 1997.
Data include the following information for each sample site: a general description, electron microprobe analysis, GPS location, neutron activation analysis, and a visual description of the petrography. Data are provided as an Excel 97 data file (this file is also divided into various text files) and TIF images. Data are available via ftp.
The Antarctic ice sheets preserve a record of the volcanic ash layers and chemical aerosol signatures of local and distant volcanic eruptions. Correlation of individual tephra layers, or sets of layers, in blue ice areas will allow a better understanding of the geometry of ice flow in these areas. Tephra layers in deep ice cores can also provide unique time-stratigraphic markers in cores that are difficult to date.
Please cite these data as follows:
Dunbar, N. 2002. Blue Ice Tephra II - Mt. DeWitt. Boulder, CO, USA: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5GQ6VPV.
|Parameter(s)||Backscattered electron images and GPS locations of blue ice tephra samples|
|Spatial coverage||Mt. Dewitt, Antarctica (77.12°S, 159.51°E)|
|Temporal coverage||Data were collected between 15 November 1996 and 15 January 1997.|
|Data format||Backscattered electron (BSE) images of blue ice tephra samples: TIF format
Differential GPS locations
Excel 97 (.xls)file
Text (.txt) files (contain same information as the Excel file)
|File sizes||Excel file: 140 KB
Text files: 51 KB
TIF files: 18 MB combined
|Procedures for obtaining data||Data are available via ftp.|
New Mexico Bureau of Mines & Mineral Resources
Earth and Environmental Science Department
New Mexico Institute of Mining and Technology
Socorro, NM, USA
NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA
phone: +1 303.492.6199
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This research was supported by NSF grant OPP-9527373 ("Collaborative Research: Volcanic Record in Antarctic Ice: Implications for Climatic and Eruptive History and Ice Sheet Dynamics of the South Polar Region").
Blue ice tephra samples were collected from Mt. DeWitt, Antarctica (77.12°S, 159.51°E).
See Dunbar's Maps: Blue Ice Tephra II - GPS and Reference Maps sampling location maps.
Data were collected between 15 November 1996 and 15 January 1997.
Data are available via ftp.
Because of their ease of access and sampling, blue ice areas offer an alternative to deep ice cores in the reconstruction of regional and possible global volcanic records. Dunbar sampled and mapped volcanic ash (tephra) layers in exposed bare blue ice areas on Mt. Dewitt, Antarctica. She processed backscatter electron images of tephra samples with a Cameca SX-100 microprobe.
Notes on the neutron activation analysis:
Notes on the electron microprobe analysis:
Dunbar, N., G. Zielinski, and D. Voisins, D. 2002. Tephra layers in the Siple and Taylor Dome Ice Cores, Antarctica: Sources and Correlations. Journal of Geophysical Research 108 (B8).
Dunbar, N., R. Esser, and W. McIntosh. 1998. Englacial tephra layers in West Antarctica: Implications for the history of the West Antarctic Ice Sheet. Antarctic Journal of the U.S. XXXIII.
Dunbar, N., R. Esser, W. McIntosh, P. Kyle, and G. Zielinski. 1997. Englacial tephra layers in the East and West Antarctic ice sheets: Indicators of glacial flow patterns on ice sheet margins. EOS 78: F250.
Dunbar, N., R. Esser, W. McIntosh, G. Zielinski, and P. Kyle. 1997. Englacial tephra layers in West Antarctica: Implications for the history of the West Antarctic Ice Sheet. 4th Annual West Antarctic Ice Sheet workshop.
Dunbar, N., W. McIntosh, R. Esser, T. Wilch, and G. Zielinski. 1998. Direct dating and geochemical correlations of englacial tephra layers at two sites in West Antarctica, in Proceedings of the West Antarctic Ice Sheet Meeting Chapman Conference, Sept. 13-18, 1998, Orono, Maine, p. 18-19.
Dunbar, N., W. McIntosh, R. Esser, T. Wilch, and G. Zielinski. 1999. Englacial tephrochronology in West Antarctica: Constraints on ice sheet history, and potential longer ice records, in 8th International Symposium on Antarctic Earth Science, Victoria University of Wellington, New Zealand, p. 95.
Esser, R., P. Kyle, and N. Dunbar. 1999. 40Ar/39Ar chronology of the Pleiades Volcanic Centre, Northern Victoria Land, Antarctica: A potential source of late-pleistocene englacial tephra layers, in 8th International Symposium on Antarctic Earth Science, Victoria University of Wellington, New Zealand, p. 100.
Licht, K., N. Dunbar, A. Jennings, and J. Andrews. 1999. Sedimentological evidence for the maximum extent of grounded ice in the western Ross Sea, Antarctica during the last glacial maximum. Geological Society of America Bulletin 111(1): 91-103.
Wilch, T. 1998. Volcanic record of the West Antarctic ice sheet in Marie Byrd Land [PhD thesis]: New Mexico Institute of Mining and Technology. 160 pp.
Wilch, T., W. McIntosh, and N. Dunbar. 1999. Late quaternary volcanic activity in Marie Byrd Land: Potential 40Ar/39Ar dated time horizons in West Antarctic ice and marine cores. Geological Society of America Bulletin 111: 1563-1580.
anorth - anorthite
BIT - blue ice tephra
BSE - backscattered electron (images)
bw - bubble wall
contam - contaminants
cpx - clinopyroxene
frag - fragments
ksp - potassium feldspar
low RI - low refractive index
mod - moderate
ol - olivine
pl - plagioclase feldspar
plag - plagioclase feldspar
pum - pumice
pyx - pyroxene
san - sanidine
Station - the name of the location data file for a GPS sample
vesic or ves - vesicular
xtals - crystals
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