Abstract:
This dataset consists of measurements of cosmogenic Be-10 and Al-26 in quartz for a set of cobbles collected from a moraine proximal to Mount Murphy, a nunatak located between Pope and Thwaites glaciers, West Antarctica. The cobbles were collected during the 2015-2016 Antarctic field season. The dataset includes cosmogenic nuclide (Be-10 and Al-26) surface exposure ages and all field (location, elevation, shielding, thickness) and analytical laboratory (quartz, beryllium and aluminium carrier masses, Be-10/Be-9 and Al-26/Al-27 ratios) data for field samples and procedural blanks required to calculate the ages.
Funding source: Natural Environment Research Council (NERC: Grants NE/S006710/1 (JSJ), NE/K012088/1 (JSJ), NE/S006753/1 (DHR), NE/K011278/1 (DHR)). Australian Nuclear Science and Technology Organisation (ANSTO) Centre for Accelerator Science award AP12872 (DHR) through the National Collaborative Research Infrastructure Strategy (NCRIS).
Keywords:
Antarctica, Glacial geology, Holocene, Pope Glacier, Surface exposure ages, Thwaites Glacier, West Antarctic Ice Sheet
Nichols, K., Roberts, S., Rood, D., Johnson, J., Wilcken, K., & Brown, K. (2024). Cosmogenic Be-10 and Al-26 data and calculated surface exposure ages for cobbles collected from a moraine adjacent to Mount Murphy, West Antarctica (Version 1.0) [Data set]. NERC EDS UK Polar Data Centre. https://doi.org/10.5285/1efc0048-5f0f-4ae7-a3a6-7728fe2ccf48
| Access Constraints: | No restrictions apply. |
|---|---|
| Use Constraints: | This data is governed by the NERC data policy http://www.nerc.ac.uk/research/sites/data/policy/ and supplied under Open Government Licence v.3 http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/. |
| Creation Date: | 2024-04-25 |
|---|---|
| Dataset Progress: | Complete |
| Dataset Language: | English |
| ISO Topic Categories: |
|
| Parameters: |
|
| Personnel: | |
| Name | UK PDC |
| Role(s) | Metadata Author |
| Organisation | British Antarctic Survey |
| Name | Keir A Nichols |
| Role(s) | Investigator, Technical Contact |
| Organisation | Imperial College London |
| Name | Dr Stephen J Roberts |
| Role(s) | Investigator |
| Organisation | British Antarctic Survey |
| Name | Dylan H Rood |
| Role(s) | Investigator |
| Organisation | Imperial College London |
| Name | Joanne S Johnson |
| Role(s) | Investigator |
| Organisation | British Antarctic Survey |
| Name | Klaus Wilcken |
| Role(s) | Investigator |
| Organisation | Australian Nuclear Science and Technology Organisation |
| Name | Katie Brown |
| Role(s) | Investigator |
| Organisation | University College London |
| Parent Dataset: | N/A |
| Reference: | Associated paper: Nichols, K.A., Adams, J., Brown, K., Creel, R., McKenzie, M., Venturelli, R.A., Johnson, J.S., Rood, D.H., Wilcken, K., Woodward, J., Roberts, S. (2024). Direct geologic constraints on the timing of Late Holocene ice thickening in the Amundsen Sea Embayment, Antarctica. Geophysical Research Letters, 51, https://doi.org/10.1029/2024GL110350 Methodology/Lineage references: Balco, G., Stone, J.O., Lifton, N.A., and Dunai, T.J., 2008, A complete and easily accessible means of calculating surface exposure ages or erosion rates from 10Be and 26Al measurements: Quaternary Geochronology, v. 3, p. 174-195, doi:10.1016/j.quageo.2007.12.001. Corbett, L.B., Bierman, P.R., Rood, D.H., 2016. Constraining multi-stage exposure- burial scenarios for boulders preserved beneath cold-based glacial ice in Thule, northwest Greenland. Earth Planet Sci. Lett. 440, 147-157. Kohl, C.P., Nizhiizumi, K., 1992. Chemical isolation of quartz for measurement of in-situ -produced cosmogenic nuclides. Geochim Cosmochim Acta 56, 3583-3587. Nishiizumi, K., 2004. Preparation of 26Al AMS standards. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 223, pp.388-392. Nishiizumi, K., Imamura, M., Caffee, M.W., Southon, J.R., Finkel, R.C., McAninch, J., 2007. Absolute calibration of 10Be AMS standards. Nucl. Instrum. Methods B 258, 403-413. Wilcken, K.M., Fink, D., Hotchkis, M., Garton, D., Button, D., Mann, M., Kitchen, R., Hauser, T., O'Connor, A., 2017. Accelerator mass spectrometry on SIRIUS: new 6MV spectrometer at ANSTO. Nucl. Instrum. Methods B 406, 278-282. |
|
|---|---|---|
| Quality: | Quartz purity was tested using inductively coupled plasma optical emission spectrometry (ICP-OES). For isotope dilution chemistry, one procedural blank (beryllium and aluminium carrier processed with no quartz) was processed with each batch of 11 samples. Because the five samples in this dataset were processed across two batches of samples (along with other Antarctic surface samples), there are two procedural blanks in this dataset that are used to correct Be-10 and Al-26 concentrations. Be-10 concentrations were corrected using the mean and standard deviation (SD) of two blanks (Be-9/Be-10 ratios: mean 2.71 x 10-15, SD 3.61 x 10-16, or Be-10 atoms: mean 47410 ± SD 6255). Al-26 concentrations were corrected using the weighted average and standard error of the measured ratios of two blanks as well as two carrier blanks (Al-26/Al-27 ratios: weighted average 7.79 x 10-16, SE 1.54 x 10-16). This weighted average Al-26/Al-27 ratio is used with the mass of carrier used with each quartz sample to calculate the background correction (in number of Al-26 atoms) for each Al-26 concentration. In other words, the blank correction for the Al-26 concentrations scales with the amount of aluminium carrier used. These values range from 34,573 to 43,757 Al-26 atoms and are found in '26Al blank (atoms/sample)' and '26Al blank (atoms/sample) ±' columns of Al_analytical_data_and_ages.csv. Carrier blanks are ~2.5 mg of aluminium carrier precipitated with the two process blanks above, but with no prior steps (quartz dissolution, isotope dilution chemistry). We also processed one aliquot of the laboratory intercomparison material CRONUS A (sample ID STDA050922 in the data tables). | |
| Lineage: | Samples (cobbles located on the surface of a moraine adjacent to Mount Murphy, West Antarctica) were collected by Dr Stephen J. Roberts (British Antarctic Survey) during the 2015-2016 austral summer. Laboratory chemistry was conducted in the CosmIC Laboratory at Imperial College London. Quartz purification followed the methods of Kohl and Nishiizumi (1992). Isotope dilution chemistry and beryllium and aluminium purification followed the methods of Corbett et al. (2016). Be-10/Be-9 and Al-26/Al-27 ratios were measured by accelerator mass spectrometry at ANSTO using the methods of Wilcken et al. (2017) and normalised to the standard values of Nishiizumi et al. (2007) and Nishiizumi (2004), respectively. Laboratory data were then converted to Be-10 or Al-26 concentrations and, finally, exposure ages using an online exposure age calculator (Balco et al., 2008). Exposure ages were calculated using the default global production rate and two different cosmogenic nuclide scaling methods (known as St (or Stone) and LSDn). The ages were also calculated assuming no erosion, using the Antarctic-specific (ant) elevation/pressure relationship, and the topographic shielding and sample thickness values in sample_information.csv. Samples were collected in the field on 2016-01-07. Be ratios were measured on 2022-10-19 and Al ratios were measured on 2023-6-5. |
|
| Temporal Coverage: | |
|---|---|
| Start Date | 2023-06-05 |
| End Date | N/A |
| Start Date | 2016-01-07 |
| End Date | N/A |
| Start Date | 2022-10-19 |
| End Date | N/A |
| Spatial Coverage: | |
| Latitude | |
| Southernmost | -75.22002 |
| Northernmost | -75.21829 |
| Longitude | |
| Westernmost | -111.0247 |
| Easternmost | -111.0137 |
| Altitude | |
| Min Altitude | 204 |
| Max Altitude | 236 |
| Depth | |
| Min Depth | N/A |
| Max Depth | N/A |
| Location: | |
| Location | Antarctica |
| Detailed Location | West Antarctica |
| Location | Antarctica |
| Detailed Location | Mount Murphy |
| Location | Antarctica |
| Detailed Location | Thwaites Glacier |
| Location | Antarctica |
| Detailed Location | Pope Glacier |
| Location | Antarctica |
| Detailed Location | Amundsen Sea Embayment |
| Data Collection: | Exposure ages were calculated using version 3 of the online exposure age calculators available at http://hess.ess.washington.edu. |
|---|
| Data Storage: | Five .xcsv files 1. sample_information.csv 2. Be_analytical_data_and_ages.csv 3. Be_process_blanks.csv 4. Al_analytical_data_and_ages.csv 5. Al_process_blanks.csv |
|---|