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Data Set ID:

Blue Ice Tephra II - Mt. DeWitt, Version 1

This data set is the result of a study of volcanic ash and rock fragment (tephra) layers in exposed blue ice areas on Mt. DeWitt, Antarctica (77.12 deg S, 159.51 deg 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.

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.

Geographic Coverage

  • Ice Core Records
  • Glaciers/Ice Sheets > Ice Sheets
  • Ice Core Records > Volcanic Deposits
Spatial Coverage:
  • N: -77.12, S: -77.12, E: -159.51, W: -159.51

Spatial Resolution: Not Specified
Temporal Coverage:
  • 1 January 1996 to 31 December 1997
Temporal Resolution: Not specified
Data Format(s):
  • Microsoft Excel
  • TIFF
  • ASCII Text
Version: V1
Data Contributor(s): Nelia Dunbar
Data Citation

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Dunbar, N. 2003. Blue Ice Tephra II - Mt. DeWitt, Version 1. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: [Date Accessed].

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Detailed Data Description

Format and File Sizes
  • bit*.tif: Backscattered electron images of blue ice tephra samples (TIF format, 771 KB each, 18 MB combined)
  • dewitt.xls: Includes worksheets for general field descriptions, GPS locations, and analyses for chemical composition, electron microprobe, neutron activation, and petrography of the tephra layers. (Excel 97 format, 140 KB). Columns include:
    • Sample number
    • Location (DeWitt)
    • Station number
    • Latitude (degrees South)
    • Longitude (degrees East)
    • Elevation (m)
  • Text files (derived from the Excel file):
    • chem.txt - Chemical composition of tephra layers
    • gps.txt - Differential GPS locations of tephra layers
    • elect_micro.txt - Electron microprobe analyses of individual tephra shards
    • petrography.txt - Petrography of the tephra samples
    • neutron.txt - Neutron activation analyses of tephra
    • general.txt - General field descriptions, plus strikes and dips of tephra layers
  • Reference_map.gif and GPS_tephra_map.gif: Maps of sampling locations (GIF format, 136 KB combined)
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Spatial Coverage

Blue ice tephra samples were collected from Mt. DeWitt, Antarctica (77.12°S, 159.51°E).

Study Area Location Map:

Mt. Dewitt

See Dunbar's Maps: Blue Ice Tephra II - GPS and Reference Maps sampling location maps.

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Temporal Coverage

Data were collected between 15 November 1996 and 15 January 1997.

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Software and Tools

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Data Acquisition and Processing

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:

  • INAA was performed on separated samples at New Mexico Institute of Mining and Technology after having undergone irradiation at the University of Missouri Research Reactor.
  • Irradiation took place for approximately 40 hours at a flux of 2.5x1013N cm-2 s-1.
  • Analytical errors, based on replicate analysis of samples, to 1 sigma, are as follows for major element: FeO ± 0.01 wt%; Na2O ± 0.04 wt%, and for trace elements (in ppm), Sc±0.04, Cr±12, Co±0.13, Ni±1, Zn±1, As±0.7, Br±0.07, Rb±0.8, Sr±0.7, Sb±0.1, Cs±1.4, Ba±10, La±1.8, Ce±1.4, Nd±0.7, Sm±0.07, Eu±0.14, Tb±0.02, Yb±0.07, Lu±0.01, Hf±0.12, Ta±0.04, Ta±0.04, W±0.05, U±0.02, Th±1.

Notes on the electron microprobe analysis:

  • Analyses are made using a Cameca SX-100 electron microprobe. Geochemical quantities are in weight %. Analyses are normalized to 100 wt.%, and Na2O is normalized to the value obtained by neutron activation analysis. Analytical precision, based on replicate analyses of standard reference materials of similar composition to the unknowns, are as follows (all in wt.%): SiO2±0.47, TiO2±0.03, FeO±0.06, MnO±0.06, MgO±0.07, CaO±0.02, Na2O±0.55, K2O±0.27, P2O5±0.02, Cl±0.07.
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References and Related Publications

Contacts and Acknowledgments

Nelia Dunbar
New Mexico Bureau of Mines & Mineral Resources
Earth and Environmental Science Department
New Mexico Institute of Mining and Technology
Socorro, NM, USA


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").

Document Information


October 2002

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