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Metadata Files

Data Publication

Cosmogenic in situ 14C data and calculated surface exposure ages for 9 erratic cobbles collected from Mount Murphy, West Antarctica

Adams, Jonathan | Venturelli, Ryan | Goehring, Brent | Johnson, Joanne | Roberts, Stephen | Rood, Dylan

NERC EDS UK Polar Data Centre

(2024)

Descriptions

This dataset consists of measurements of cosmogenic 14C in quartz for cobbles collected from a series of nunataks (Turtle Rock, Notebook Cliffs, scoria cone) proximal to Mount Murphy, a volcanic edifice located between Pope and Thwaites glaciers, West Antarctica. The cobbles were collected during the 2015-2016 Antarctic field season. The dataset includes 13 cosmogenic nuclide surface exposure ages and all field (location, elevation, shielding, thickness) and analytical laboratory data required to calculate in situ 14C exposure ages. Analytical data includes quartz sample mass, total CO2 liberated from the sample, delta-13C, 14C/12C AMS ratios and 14C/12C AMS ratios of procedural blanks. Funding source: Natural Environment Research Council (NERC): Grants NE/S006710/1, NE/S006753/1 and NE/K012088/1 and National Science Foundation (NSF): Grant: OPP-1738989. The dataset is a component of the "Geological History Constraints" project of the NERC-NSF funded International Thwaites Glacier Collaboration (ITGC).
Quartz bearing erratic cobbles, which showed evidence of transport by ice, were collected in 2015-16 from rock outcrops adjacent to Pope Glacier in the Amundsen Sea Embayment of West Antarctica by Joanne S Johnson and Stephen J Roberts (British Antarctic Survey), following procedures outlined in Johnson et al., (2020). The top 2.0-5.5 cm of a suite of 9 cobbles were cut at British Antarctic Survey. Quartz mineral separation and purification was performed in the CosmIC Laboratory at Imperial College London largely based upon standard procedures. Samples were initially crushed and sieved to isolate the 250 - 500 micrometre grain size fraction. Further sample processing was based on standard procedures (Kohl and Nishiizumi, 1992; Corbett et al., 2016). Froth flotation was not used to minimise the introduction of contaminant carbon sources (Nichols and Goehring, 2019). Following determination of quartz purity using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) quartz mineral separates (~ 10 g) were shipped to Tulane University, New Orleans, USA for in situ 14C extraction. Extraction of in-situ 14C was performed by Ryan Venturelli using the fully automated Carbon Extraction and Graphitisation System (CEGS) at Tulane University. The first in situ 14C extraction (n = 9) followed the methods of Goehring et al., (2019). The quartz sample was fused with lithium metaborate (LiBO2) flux to ensure total sample melt <1300 degrees C and complete liberation of in-situ 14C (Lifton et al., 2001). First quartz was step heated at 500 degrees C for 1 hour to remove atmospheric 14C before being combusted at 1100 degrees C for 3 hours to liberate in situ 14C (in the form of CO2). Liberated CO2 was cryogenically purified before being collected in a measurement chamber, quantified monometrically and diluted with 14C-free CO2 to ensure a measurable sample size (Goehring et al., 2019). CO2 was graphitized using standard H2 reduction methods over an Fe catalyst (Slota et al., 1987). The configuration of the Tulane extraction line was changed prior to in situ 14C replicate measurements (n = 4). Alterations to the line included a new coil trap, which changes how gas is extracted and trapped following combustion (Lifton et al., 2023) and the introduction of a new mullite tube for 14C extraction due to failure of the previous tube. Mullite tubes often undergo a "break in" period, during which initial 14C blanks are higher but often fall with continued use (Goehring et al., 2014, 2019; Pigati et al., 2010). 14C/12C isotope ratios were measured by accelerator mass spectrometry at the National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS) (Woods Hole, USA) using the methods described in Longworth et al. (2015). Stable isotope (delta-13C) analysis was undertaken at the University of California, Davis Stable Isotope Facility. Data reduction (to convert 14C/12C ratios to 14C/C_total) followed methods outlined in Hippe and Lifton (2014) which account for the specific differences of 14C production within a mineral lattice compared to 14C incorporation into organic material. Exposure ages were calculated from in situ 14C concentrations using version 3 of the online calculators: https://hess.ess.washington.edu/math/v3/v3_age_in.html (Balco et al., 2008) with the "LSDn" production rate scaling method for neutrons, protons, and muons following Lifton et al., (2014) and the primary production rate calibration data set of Borchers et al., (2016).
Quartz purity was tested using inductively coupled plasma optical emission spectrometry (ICP-OES). Nine in situ 14C measurements, and four in situ 14C replicate measurements were made. In table AMS_14C.csv aliquot A indicates initial in situ 14C concentrations measured in each sample and aliquot B indicates repeat in situ 14C measurements on the same sample. A long-term average 14C blank used to correct the initial measurements of in situ 14C (n = 9) is 4.53 +/- 0.24 x 10^4 atoms g-1. For replicate measurements (n = 4), a higher short-term average 14C blank of 7.14 +/- 0.30 x 10^4 14C atoms g-1 was used. A 6 % (1 sigma) uncertainty was assigned to each in 14C measurement concentration reported by AMS before calculating exposure ages. The 6 % uncertainty exceeds the reported analytical uncertainty for all in situ 14C measurements made for this study and reflects the repeatability of measurements of CRONUS-A extracted at Tulane. The in situ 14C concentration of CRONUS-A extracted at Tulane is reported with a long-term value of 6.12 +/- 0.32 x 10^5 (n = 10) (Goehring et al., 2019). The distribution of the long-term 14C measurement background of samples from the Tulane University extraction facility is long-tailed and non-time dependent (Balco et al., 2022). Blank correction using a long tailed distribution is, therefore, appropriate for low concentration samples such as subglacial bedrock cores (Balco et al., 2023) where blank variability constitutes the dominant source of uncertainty in the in situ 14C measurements (Balco et al., 2022). Blank correction procedures for low concentration samples are discussed at length in Balco et al., (2022) and can be viewed directly via the following link: https://doi.org/10.5194/tc-2022-172-AC2
Agilent 5100 SVDV ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometer) Tulane University Carbon Extraction and Graphitisation System (TU-CEGS) NOSAMS 3MV Tandetron AMS (Accelerator Mass Spectrometer) system Version 3 of online calculator at hess.ess.washington.edu (formerly known as CRONUS Online calculator)

Keywords


Originally assigned keywords
"EARTH SCIENCE","CRYOSPHERE","GLACIERS/ICE SHEETS","GLACIERS"
"EARTH SCIENCE","CRYOSPHERE","GLACIERS/ICE SHEETS","ICE SHEETS"
"EARTH SCIENCE","SOLID EARTH","GEOCHEMISTRY","GEOCHEMICAL PROPERTIES","ISOTOPES"
Accelerator Mass Spectrometry
Amundsen Sea Embayment
Carbon-14
Pope Glacier
Surface exposure ages
erratic cobbles

MSL enriched keywords
analysis
geochronology
carbon-14 dating
measured property
age of sample
carbon-14 age
igneous rock - extrusive
pyroclastic rock
scoria
minerals
silicate minerals
tectosilicates
quartz
unconsolidated sediment
tephra
scoria
equipment
mass spectrometer
accelerator mass spectrometer
chemical elements
carbon
oxide mineral
ice
sample preparation for geochemical analysis
mineral separation
atomic emission spectrometer
lithium
Analyzed feature
grain size and configuration
grain size

MSL enriched sub domains i

geochemistry
microscopy and tomography

Source

https://data.bas.ac.uk/full-record.php?id=GB/NERC/BAS/PDC/01925

Source publisher

NERC EDS UK Polar Data Centre


DOI

10.5285/dbb30962-bbf3-434a-9f27-6de2f61a86e2


Creators

Adams, Jonathan

British Antarctic Survey

ORCID:

https://orcid.org/0000-0002-8511-8766

Venturelli, Ryan

Colorado School of Mines

ORCID:

https://orcid.org/0000-0001-9548-0382

Goehring, Brent

Los Alamos National Laboratory

ORCID:

https://orcid.org/0000-0001-6405-5156

Johnson, Joanne

British Antarctic Survey

ORCID:

https://orcid.org/0000-0003-4537-4447

Roberts, Stephen

British Antarctic Survey

ORCID:

https://orcid.org/0000-0003-3407-9127

Rood, Dylan

Imperial College London

ORCID:

https://orcid.org/0000-0002-4425-4702


Contributors

Adams, Jonathan

ContactPerson

British Antarctic Survey

ORCID:

https://orcid.org/0000-0002-8511-8766

Adams, Jonathan

Researcher

British Antarctic Survey

ORCID:

https://orcid.org/0000-0002-8511-8766

Venturelli, Ryan

ProjectManager

Colorado School of Mines

ORCID:

https://orcid.org/0000-0001-9548-0382

Goehring, Brent

Researcher

Los Alamos National Laboratory

ORCID:

https://orcid.org/0000-0001-6405-5156

Johnson, Joanne

ProjectManager

British Antarctic Survey

ORCID:

https://orcid.org/0000-0003-4537-4447

Roberts, Stephen

Researcher

British Antarctic Survey

ORCID:

https://orcid.org/0000-0003-3407-9127

Rood, Dylan

Researcher

Imperial College London

ORCID:

https://orcid.org/0000-0002-4425-4702

UK Polar Data Centre

DataManager

Natural Environment Research Council

UK Polar Data Centre

Distributor

Natural Environment Research Council

UK Polar Data Centre

HostingInstitution

Natural Environment Research Council


References

https://thwaitesglacier.org/

https://www.bas.ac.uk/project/reconstructing-millennial-scale-ice-sheet-change/

10.1016/j.quageo.2007.12.001

10.5194/tc-2022-172-ac2

10.5194/tc-17-1787-2023

10.1016/j.quageo.2015.01.009

10.1016/j.quageo.2016.02.001

10.1016/j.quageo.2013.01.004

10.1016/j.nimb.2019.02.006

10.2458/56.17917

10.1016/j.epsl.2020.116501

10.1016/0016-7037(92)90401-4

10.1016/j.epsl.2013.10.052

10.5194/gchron-5-361-2023

10.1016/s0016-7037(01)00566-x

10.5194/gchron-2019-7

10.1017/s0033822200046324

10.1017/s0033822200056988


Citation

Adams, J., Venturelli, R., Goehring, B., Johnson, J., Roberts, S., & Rood, D. (2024). Cosmogenic in situ 14C data and calculated surface exposure ages for 9 erratic cobbles collected from Mount Murphy, West Antarctica (Version 1.0) [Data set]. NERC EDS UK Polar Data Centre. https://doi.org/10.5285/DBB30962-BBF3-434A-9F27-6DE2F61A86E2


Dates

Collected:

2015-12-10/2016-01-31

Accepted:

2024-10-25

Created:

2024-10-25

Submitted:

2024-10-25

Issued:

2024-11-20


Language

en


Funding References

Funder name: Natural Environment Research Council

Funder identifier: https://ror.org/02b5d8509

Funder identifier type: ROR

Award number: NE/S006710/1

Award uri: https://gtr.ukri.org/projects?ref=NE/S006710/1

Award title: NSFPLR-NERC: Geological history constraints on the magnitude of grounding line retreat in the Thwaites Glacier system

Funder name: Natural Environment Research Council

Funder identifier: https://ror.org/02b5d8509

Funder identifier type: ROR

Award number: NE/S006753/1

Award uri: https://gtr.ukri.org/projects?ref=NE/S006753/1

Award title: NSFPLR-NERC: Geological history constraints on the magnitude of grounding line retreat in the Thwaites Glacier system

Funder name: Natural Environment Research Council

Funder identifier: https://ror.org/02b5d8509

Funder identifier type: ROR

Award number: NE/K012088/1

Award uri: https://gtr.ukri.org/projects?ref=NE/K012088/1

Award title: Reconstructing millennial-scale ice sheet change in the western Amundsen Sea Embayment, Antarctica, using high-precision exposure dating.

Funder name: National Science Foundation

Funder identifier: https://ror.org/021nxhr62

Funder identifier type: ROR

Award number: 1738989

Award uri: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1738989

Award title: NSF-NERC: Geological History Constraints on the Magnitude of Grounding Line Retreat in the Thwaites Glacier System.


Rights

Open Government Licence V3.0


Datacite version

1.0


Geo location(s)

Amundsen Sea Embayment Antarctica

Mount Murphy Antarctica

Pope Glacier Antarctica

Kay Peak Antarctica

Turtle Rock Antarctica


Spatial coordinates