Articles | Volume 1, issue 1
https://doi.org/10.5194/gchron-1-43-2019
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/gchron-1-43-2019
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
09 Oct 2019
Research article |
| 09 Oct 2019
| 09 Oct 2019
Isolation of quartz for cosmogenic in situ 14C analysis
Department of Earth and Environmental Sciences, Tulane University, New
Orleans, LA 70118, USA
Brent M. Goehring
Department of Earth and Environmental Sciences, Tulane University, New
Orleans, LA 70118, USA
Related authors
Joanne S. Johnson, John Woodward, Ian Nesbitt, Kate Winter, Seth Campbell, Keir A. Nichols, Ryan A. Venturelli, Scott Braddock, Brent M. Goehring, Brenda Hall, Dylan H. Rood, and Greg Balco
EGUsphere, https://doi.org/10.5194/egusphere-2024-1452, https://doi.org/10.5194/egusphere-2024-1452, 2024
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Determining where and when the Antarctic ice sheet was smaller than present requires recovery and exposure dating of subglacial bedrock. Here we use ice sheet model outputs and field data (geological and glaciological observations, bedrock samples and ground-penetrating radar from subglacial ridges) to assess the suitability for drilling of sites in the Hudson Mountains, West Antarctica. We find that no sites are perfect, but two are feasible, with the most suitable being Winkie Nunatak.
Greg Balco, Nathan Brown, Keir Nichols, Ryan A. Venturelli, Jonathan Adams, Scott Braddock, Seth Campbell, Brent Goehring, Joanne S. Johnson, Dylan H. Rood, Klaus Wilcken, Brenda Hall, and John Woodward
The Cryosphere, 17, 1787–1801, https://doi.org/10.5194/tc-17-1787-2023, https://doi.org/10.5194/tc-17-1787-2023, 2023
Short summary
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Samples of bedrock recovered from below the West Antarctic Ice Sheet show that part of the ice sheet was thinner several thousand years ago than it is now and subsequently thickened. This is important because of concern that present ice thinning in this region may lead to rapid, irreversible sea level rise. The past episode of thinning at this site that took place in a similar, although not identical, climate was not irreversible; however, reversal required at least 3000 years to complete.
Jonathan R. Adams, Joanne S. Johnson, Stephen J. Roberts, Philippa J. Mason, Keir A. Nichols, Ryan A. Venturelli, Klaus Wilcken, Greg Balco, Brent Goehring, Brenda Hall, John Woodward, and Dylan H. Rood
The Cryosphere, 16, 4887–4905, https://doi.org/10.5194/tc-16-4887-2022, https://doi.org/10.5194/tc-16-4887-2022, 2022
Short summary
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Glaciers in West Antarctica are experiencing significant ice loss. Geological data provide historical context for ongoing ice loss in West Antarctica, including constraints on likely future ice sheet behaviour in response to climatic warming. We present evidence from rare isotopes measured in rocks collected from an outcrop next to Pope Glacier. These data suggest that Pope Glacier thinned faster and sooner after the last ice age than previously thought.
Joanne S. Johnson, Ryan A. Venturelli, Greg Balco, Claire S. Allen, Scott Braddock, Seth Campbell, Brent M. Goehring, Brenda L. Hall, Peter D. Neff, Keir A. Nichols, Dylan H. Rood, Elizabeth R. Thomas, and John Woodward
The Cryosphere, 16, 1543–1562, https://doi.org/10.5194/tc-16-1543-2022, https://doi.org/10.5194/tc-16-1543-2022, 2022
Short summary
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Recent studies have suggested that some portions of the Antarctic Ice Sheet were less extensive than present in the last few thousand years. We discuss how past ice loss and regrowth during this time would leave its mark on geological and glaciological records and suggest ways in which future studies could detect such changes. Determining timing of ice loss and gain around Antarctica and conditions under which they occurred is critical for preparing for future climate-warming-induced changes.
Trevor R. Hillebrand, John O. Stone, Michelle Koutnik, Courtney King, Howard Conway, Brenda Hall, Keir Nichols, Brent Goehring, and Mette K. Gillespie
The Cryosphere, 15, 3329–3354, https://doi.org/10.5194/tc-15-3329-2021, https://doi.org/10.5194/tc-15-3329-2021, 2021
Short summary
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We present chronologies from Darwin and Hatherton glaciers to better constrain ice sheet retreat during the last deglaciation in the Ross Sector of Antarctica. We use a glacier flowband model and an ensemble of 3D ice sheet model simulations to show that (i) the whole glacier system likely thinned steadily from about 9–3 ka, and (ii) the grounding line likely reached the Darwin–Hatherton Glacier System at about 3 ka, which is ≥3.8 kyr later than was suggested by previous reconstructions.
Keir A. Nichols, Brent M. Goehring, Greg Balco, Joanne S. Johnson, Andrew S. Hein, and Claire Todd
The Cryosphere, 13, 2935–2951, https://doi.org/10.5194/tc-13-2935-2019, https://doi.org/10.5194/tc-13-2935-2019, 2019
Short summary
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We studied the history of ice masses at three locations in the Weddell Sea Embayment, Antarctica. We measured rare isotopes in material sourced from mountains overlooking the Slessor Glacier, Foundation Ice Stream, and smaller glaciers on the Lassiter Coast. We show that ice masses were between 385 and 800 m thicker during the last glacial cycle than they are at present. The ice masses were both hundreds of metres thicker and remained thicker closer to the present than was previously thought.
Joanne S. Johnson, John Woodward, Ian Nesbitt, Kate Winter, Seth Campbell, Keir A. Nichols, Ryan A. Venturelli, Scott Braddock, Brent M. Goehring, Brenda Hall, Dylan H. Rood, and Greg Balco
EGUsphere, https://doi.org/10.5194/egusphere-2024-1452, https://doi.org/10.5194/egusphere-2024-1452, 2024
Short summary
Short summary
Determining where and when the Antarctic ice sheet was smaller than present requires recovery and exposure dating of subglacial bedrock. Here we use ice sheet model outputs and field data (geological and glaciological observations, bedrock samples and ground-penetrating radar from subglacial ridges) to assess the suitability for drilling of sites in the Hudson Mountains, West Antarctica. We find that no sites are perfect, but two are feasible, with the most suitable being Winkie Nunatak.
Greg Balco, Nathan Brown, Keir Nichols, Ryan A. Venturelli, Jonathan Adams, Scott Braddock, Seth Campbell, Brent Goehring, Joanne S. Johnson, Dylan H. Rood, Klaus Wilcken, Brenda Hall, and John Woodward
The Cryosphere, 17, 1787–1801, https://doi.org/10.5194/tc-17-1787-2023, https://doi.org/10.5194/tc-17-1787-2023, 2023
Short summary
Short summary
Samples of bedrock recovered from below the West Antarctic Ice Sheet show that part of the ice sheet was thinner several thousand years ago than it is now and subsequently thickened. This is important because of concern that present ice thinning in this region may lead to rapid, irreversible sea level rise. The past episode of thinning at this site that took place in a similar, although not identical, climate was not irreversible; however, reversal required at least 3000 years to complete.
Jonathan R. Adams, Joanne S. Johnson, Stephen J. Roberts, Philippa J. Mason, Keir A. Nichols, Ryan A. Venturelli, Klaus Wilcken, Greg Balco, Brent Goehring, Brenda Hall, John Woodward, and Dylan H. Rood
The Cryosphere, 16, 4887–4905, https://doi.org/10.5194/tc-16-4887-2022, https://doi.org/10.5194/tc-16-4887-2022, 2022
Short summary
Short summary
Glaciers in West Antarctica are experiencing significant ice loss. Geological data provide historical context for ongoing ice loss in West Antarctica, including constraints on likely future ice sheet behaviour in response to climatic warming. We present evidence from rare isotopes measured in rocks collected from an outcrop next to Pope Glacier. These data suggest that Pope Glacier thinned faster and sooner after the last ice age than previously thought.
Brent M. Goehring, Brian Menounos, Gerald Osborn, Adam Hawkins, and Brent Ward
Geochronology, 4, 311–322, https://doi.org/10.5194/gchron-4-311-2022, https://doi.org/10.5194/gchron-4-311-2022, 2022
Short summary
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We explored surface exposure dating with two nuclides to date two sets of moraines from the Yukon Territory and explain the reasoning for the observed ages. Results suggest multiple processes, including preservation of nuclides from a prior exposure period, and later erosion of the moraines is required to explain the data. Our results only allow for the older moraines to date to Marine Isotope Stage 3 or 4 and the younger moraines to date to the very earliest Holocene.
Joanne S. Johnson, Ryan A. Venturelli, Greg Balco, Claire S. Allen, Scott Braddock, Seth Campbell, Brent M. Goehring, Brenda L. Hall, Peter D. Neff, Keir A. Nichols, Dylan H. Rood, Elizabeth R. Thomas, and John Woodward
The Cryosphere, 16, 1543–1562, https://doi.org/10.5194/tc-16-1543-2022, https://doi.org/10.5194/tc-16-1543-2022, 2022
Short summary
Short summary
Recent studies have suggested that some portions of the Antarctic Ice Sheet were less extensive than present in the last few thousand years. We discuss how past ice loss and regrowth during this time would leave its mark on geological and glaciological records and suggest ways in which future studies could detect such changes. Determining timing of ice loss and gain around Antarctica and conditions under which they occurred is critical for preparing for future climate-warming-induced changes.
Trevor R. Hillebrand, John O. Stone, Michelle Koutnik, Courtney King, Howard Conway, Brenda Hall, Keir Nichols, Brent Goehring, and Mette K. Gillespie
The Cryosphere, 15, 3329–3354, https://doi.org/10.5194/tc-15-3329-2021, https://doi.org/10.5194/tc-15-3329-2021, 2021
Short summary
Short summary
We present chronologies from Darwin and Hatherton glaciers to better constrain ice sheet retreat during the last deglaciation in the Ross Sector of Antarctica. We use a glacier flowband model and an ensemble of 3D ice sheet model simulations to show that (i) the whole glacier system likely thinned steadily from about 9–3 ka, and (ii) the grounding line likely reached the Darwin–Hatherton Glacier System at about 3 ka, which is ≥3.8 kyr later than was suggested by previous reconstructions.
Perry Spector, John Stone, and Brent Goehring
The Cryosphere, 13, 3061–3075, https://doi.org/10.5194/tc-13-3061-2019, https://doi.org/10.5194/tc-13-3061-2019, 2019
Short summary
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We describe constraints on the thickness of the interior of the West Antarctic Ice Sheet (WAIS) through the last deglaciation. Our data imply that the ice-sheet divide between the Ross and Weddell sea sectors of the WAIS was thicker than present for a period less than ~ 8 kyr within the past ~ 15 kyr. These results are consistent with the hypothesis that the divide initially thickened due to the deglacial rise in snowfall and subsequently thinned in response to retreat of the ice-sheet margin.
Keir A. Nichols, Brent M. Goehring, Greg Balco, Joanne S. Johnson, Andrew S. Hein, and Claire Todd
The Cryosphere, 13, 2935–2951, https://doi.org/10.5194/tc-13-2935-2019, https://doi.org/10.5194/tc-13-2935-2019, 2019
Short summary
Short summary
We studied the history of ice masses at three locations in the Weddell Sea Embayment, Antarctica. We measured rare isotopes in material sourced from mountains overlooking the Slessor Glacier, Foundation Ice Stream, and smaller glaciers on the Lassiter Coast. We show that ice masses were between 385 and 800 m thicker during the last glacial cycle than they are at present. The ice masses were both hundreds of metres thicker and remained thicker closer to the present than was previously thought.
Related subject area
Cosmogenic nuclide dating
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Cosmogenic 3He chronology of postglacial lava flows at Mt Ruapehu, Aotearoa / New Zealand
Last ice sheet recession and landscape emergence above sea level in east-central Sweden, evaluated using in situ cosmogenic 14C from quartz
Cosmogenic 21Ne exposure ages on late Pleistocene moraines in Lassen Volcanic National Park, California, USA
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Cosmogenic nuclide geochronology requires accurately scaling production rates with altitude. The energy spectrum of cosmic radiation changes with altitude, and reactions that are sensitive to different energies may have different scaling behavior. Here, we model the altitude scaling of 36Cl production from Fe and evaluate this model against calibration data. The data are broadly consistent with the prediction of larger-altitude scaling factors for 36Cl from Fe than for other reactions.
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Cosmogenic nuclides, such as 10Be, are rare isotopes produced in rocks when exposed at Earth's surface and are valuable for understanding surface processes and landscape evolution. However, 10Be is usually measured in quartz minerals. Here we present advances in efficiently extracting and measuring 10Be in the pyroxene mineral. These measurements expand the use of 10Be as a dating tool for new rock types and provide opportunities to understand landscape processes in areas that lack quartz.
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We present an improved workflow for extracting and measuring chlorine isotopes in rocks and minerals. Experiments on seven geologic samples demonstrate that our workflow provides reliable results while offering several distinct advantages over traditional methods. Most notably, our workflow reduces the amount of isotopically enriched chlorine spike used per rock sample by up to 95 %, which will allow researchers to analyze more samples using their existing laboratory supplies.
Pedro Doll, Shaun Robert Eaves, Ben Matthew Kennedy, Pierre-Henri Blard, Alexander Robert Lee Nichols, Graham Sloan Leonard, Dougal Bruce Townsend, Jim William Cole, Chris Edward Conway, Sacha Baldwin, Gabriel Fénisse, Laurent Zimmermann, and Bouchaïb Tibari
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Bradley W. Goodfellow, Arjen P. Stroeven, Nathaniel A. Lifton, Jakob Heyman, Alexander Lewerentz, Kristina Hippe, Jens-Ove Näslund, and Marc W. Caffee
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Geochronology Discuss., https://doi.org/10.5194/gchron-2024-18, https://doi.org/10.5194/gchron-2024-18, 2024
Revised manuscript accepted for GChron
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Cosmogenic nuclide exposure dating is an exceptional tool for reconstructing glacier histories, but reconstructions based on common target nuclides (e.g., 10Be) can be costly and time consuming to generate. Here, we present a low-cost proof-of-concept 21Ne exposure age chronology from Lassen Volcanic National Park, CA, USA that broadly agrees with nearby 10Be chronologies but at lower precision.
Felix Martin Hofmann, Claire Rambeau, Lukas Gegg, Melanie Schulz, Martin Steiner, Alexander Fülling, Laëtitia Léanni, Frank Preusser, and ASTER Team
Geochronology, 6, 147–174, https://doi.org/10.5194/gchron-6-147-2024, https://doi.org/10.5194/gchron-6-147-2024, 2024
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We determined 10Be concentrations in moraine boulder surfaces in the southern Black Forest, SW Germany. We applied three independent dating methods to younger lake sediments. With the aid of independent age datasets, we calculated the growth of 10Be concentrations in moraine boulder surfaces.
Greg Balco, Alan J. Hidy, William T. Struble, and Joshua J. Roering
Geochronology, 6, 71–76, https://doi.org/10.5194/gchron-6-71-2024, https://doi.org/10.5194/gchron-6-71-2024, 2024
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We describe a new method of reconstructing the long-term, pre-observational frequency and/or intensity of wildfires in forested landscapes using trace concentrations of the noble gases helium and neon that are formed in soil mineral grains by cosmic-ray bombardment of the Earth's surface.
Eric W. Portenga, David J. Ullman, Lee B. Corbett, Paul R. Bierman, and Marc W. Caffee
Geochronology, 5, 413–431, https://doi.org/10.5194/gchron-5-413-2023, https://doi.org/10.5194/gchron-5-413-2023, 2023
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New exposure ages of glacial erratics on moraines on Isle Royale – the largest island in North America's Lake Superior – show that the Laurentide Ice Sheet did not retreat from the island nor the south shores of Lake Superior until the early Holocene, which is later than previously thought. These new ages unify regional ice retreat histories from the mainland, the Lake Superior lake-bottom stratigraphy, underwater moraines, and meltwater drainage pathways through the Laurentian Great Lakes.
Nathaniel Lifton, Jim Wilson, and Allie Koester
Geochronology, 5, 361–375, https://doi.org/10.5194/gchron-5-361-2023, https://doi.org/10.5194/gchron-5-361-2023, 2023
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We describe a new, fully automated extraction system for in situ 14C at PRIME Lab that incorporates more reliable components and designs than our original systems. We use a LiBO2 flux to dissolve a quartz sample in oxygen after removing contaminant 14C with a lower-temperature combustion step. Experiments with new Pt/Rh sample boats demonstrated reduced procedural blanks, and analyses of well-characterized intercomparison materials tested the effects of process variables on 14C yields.
Allie Balter-Kennedy, Joerg M. Schaefer, Roseanne Schwartz, Jennifer L. Lamp, Laura Penrose, Jennifer Middleton, Jean Hanley, Bouchaïb Tibari, Pierre-Henri Blard, Gisela Winckler, Alan J. Hidy, and Greg Balco
Geochronology, 5, 301–321, https://doi.org/10.5194/gchron-5-301-2023, https://doi.org/10.5194/gchron-5-301-2023, 2023
Short summary
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Cosmogenic nuclides like 10Be are rare isotopes created in rocks exposed at the Earth’s surface and can be used to understand glacier histories and landscape evolution. 10Be is usually measured in the mineral quartz. Here, we show that 10Be can be reliably measured in the mineral pyroxene. We use the measurements to determine exposure ages and understand landscape processes in rocks from Antarctica that do not have quartz, expanding the use of this method to new rock types.
Alexandria J. Koester and Nathaniel A. Lifton
Geochronology, 5, 21–33, https://doi.org/10.5194/gchron-5-21-2023, https://doi.org/10.5194/gchron-5-21-2023, 2023
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In situ 14C’s short half-life (5.7 kyr) is unique among cosmogenic nuclides, making it sensitive to complex exposure and burial histories since 25 ka. Current extraction methods focus on quartz, but the ability to extract it from other minerals would expand applications. We developed MATLAB® scripts to calculate in situ 14C production rates from a broad range of mineral compositions. Results confirm O, Si, Al, and Mg as key targets but also find significant production from Na for the first time.
Aaron M. Barth, Elizabeth G. Ceperley, Claire Vavrus, Shaun A. Marcott, Jeremy D. Shakun, and Marc W. Caffee
Geochronology, 4, 731–743, https://doi.org/10.5194/gchron-4-731-2022, https://doi.org/10.5194/gchron-4-731-2022, 2022
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Deposits left behind by past glacial activity provide insight into the previous size and behavior of glaciers and act as another line of evidence for past climate. Here we present new age control for glacial deposits in the mountains of Montana and Wyoming, United States. While some deposits indicate glacial activity within the last 2000 years, others are shown to be older than previously thought, thus redefining the extent of regional Holocene glaciation.
Nathan Vandermaelen, Koen Beerten, François Clapuyt, Marcus Christl, and Veerle Vanacker
Geochronology, 4, 713–730, https://doi.org/10.5194/gchron-4-713-2022, https://doi.org/10.5194/gchron-4-713-2022, 2022
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We constrained deposition phases of fluvial sediments (NE Belgium) over the last 1 Myr with analysis and modelling of rare isotopes accumulation within sediments, occurring as a function of time and inverse function of depth. They allowed the determination of three superposed deposition phases and intercalated non-deposition periods of ~ 40 kyr each. These phases correspond to 20 % of the sediment age, which highlights the importance of considering deposition phase when dating fluvial sediments.
Felix Martin Hofmann
Geochronology, 4, 691–712, https://doi.org/10.5194/gchron-4-691-2022, https://doi.org/10.5194/gchron-4-691-2022, 2022
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If topographical obstructions are present in the surroundings of sampling sites, exposure ages of rock surfaces need to be corrected. A toolbox for the ESRI ArcGIS software allows for quantifying topographic shielding with a digital elevation model, but it has only been validated with few field data. In this study, the output of the toolbox is evaluated with a more extensive dataset. If suitable elevation data are chosen, the toolbox provides a sound approach to determine topographic shielding.
Yiran Wang and Michael E. Oskin
Geochronology, 4, 533–549, https://doi.org/10.5194/gchron-4-533-2022, https://doi.org/10.5194/gchron-4-533-2022, 2022
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When first introduced together with the depth profile technique to determine the surface exposure age, the linear inversion approach has suffered with the drawbacks of not incorporating erosion and muons into calculation. In this paper, we increase the accuracy and applicability of the linear inversion approach by fully considering surface erosion, muogenic production, and radioactive decay, while maintaining its advantage of being straightforward to determine an exposure age.
Richard F. Ott, Sean F. Gallen, and Darryl E. Granger
Geochronology, 4, 455–470, https://doi.org/10.5194/gchron-4-455-2022, https://doi.org/10.5194/gchron-4-455-2022, 2022
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Cosmogenic nuclides are a tool to quantify denudation – the total removal of mass from near the Earth's surface. Chemical weathering can introduce biases to cosmogenic-nuclide-based denudation rates measurements. Here, we investigate the effects of weathering on cosmogenic nuclides and develop tools to correct for this influence. Our results highlight which additional measurements are required to determine accurate denudation rates in regions where weathering is not negligible.
Mae Kate Campbell, Paul R. Bierman, Amanda H. Schmidt, Rita Sibello Hernández, Alejandro García-Moya, Lee B. Corbett, Alan J. Hidy, Héctor Cartas Águila, Aniel Guillén Arruebarrena, Greg Balco, David Dethier, and Marc Caffee
Geochronology, 4, 435–453, https://doi.org/10.5194/gchron-4-435-2022, https://doi.org/10.5194/gchron-4-435-2022, 2022
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We used cosmogenic radionuclides in detrital river sediment to measure erosion rates of watersheds in central Cuba; erosion rates are lower than rock dissolution rates in lowland watersheds. Data from two different cosmogenic nuclides suggest that some basins may have a mixed layer deeper than is typically modeled and could have experienced significant burial after or during exposure. We conclude that significant mass loss may occur at depth through chemical weathering processes.
Klaus M. Wilcken, Alexandru T. Codilean, Réka-H. Fülöp, Steven Kotevski, Anna H. Rood, Dylan H. Rood, Alexander J. Seal, and Krista Simon
Geochronology, 4, 339–352, https://doi.org/10.5194/gchron-4-339-2022, https://doi.org/10.5194/gchron-4-339-2022, 2022
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Cosmogenic nuclides are now widely applied in the Earth sciences; however, more recent applications often push the analytical limits of the technique. Our study presents a comprehensive method for analysis of cosmogenic 10Be and 26Al samples down to isotope concentrations of a few thousand atoms per gram of sample, which opens the door to new and more varied applications of cosmogenic nuclide analysis.
Brent M. Goehring, Brian Menounos, Gerald Osborn, Adam Hawkins, and Brent Ward
Geochronology, 4, 311–322, https://doi.org/10.5194/gchron-4-311-2022, https://doi.org/10.5194/gchron-4-311-2022, 2022
Short summary
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We explored surface exposure dating with two nuclides to date two sets of moraines from the Yukon Territory and explain the reasoning for the observed ages. Results suggest multiple processes, including preservation of nuclides from a prior exposure period, and later erosion of the moraines is required to explain the data. Our results only allow for the older moraines to date to Marine Isotope Stage 3 or 4 and the younger moraines to date to the very earliest Holocene.
Caleb K. Walcott, Jason P. Briner, James F. Baichtal, Alia J. Lesnek, and Joseph M. Licciardi
Geochronology, 4, 191–211, https://doi.org/10.5194/gchron-4-191-2022, https://doi.org/10.5194/gchron-4-191-2022, 2022
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We present a record of ice retreat from the northern Alexander Archipelago, Alaska. During the last ice age (~ 26 000–19 000 years ago), these islands were covered by the Cordilleran Ice Sheet. We tested whether islands were ice-free during the last ice age for human migrants moving from Asia to the Americas. We found that these islands became ice-free between ~ 15 100 years ago and ~ 16 000 years ago, and thus these islands were not suitable for human habitation during the last ice age.
Tibor János Dunai, Steven Andrew Binnie, and Axel Gerdes
Geochronology, 4, 65–85, https://doi.org/10.5194/gchron-4-65-2022, https://doi.org/10.5194/gchron-4-65-2022, 2022
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We develop in situ-produced terrestrial cosmogenic krypton as a new tool to date and quantify Earth surface processes, the motivation being the availability of six stable isotopes and one radioactive isotope (81Kr, half-life 229 kyr) and of an extremely weathering-resistant target mineral (zircon). We provide proof of principle that terrestrial Krit can be quantified and used to unravel Earth surface processes.
Andrew J. Christ, Paul R. Bierman, Jennifer L. Lamp, Joerg M. Schaefer, and Gisela Winckler
Geochronology, 3, 505–523, https://doi.org/10.5194/gchron-3-505-2021, https://doi.org/10.5194/gchron-3-505-2021, 2021
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Cosmogenic nuclide surface exposure dating is commonly used to constrain the timing of past glacier extents. However, Antarctic exposure age datasets are often scattered and difficult to interpret. We compile new and existing exposure ages of a glacial deposit with independently known age constraints and identify surface processes that increase or reduce the likelihood of exposure age scatter. Then we present new data for a previously unmapped and undated older deposit from the same region.
Benedikt Ritter, Andreas Vogt, and Tibor J. Dunai
Geochronology, 3, 421–431, https://doi.org/10.5194/gchron-3-421-2021, https://doi.org/10.5194/gchron-3-421-2021, 2021
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We describe the design and performance of a new noble gas mass laboratory dedicated to the development of and application to cosmogenic nuclides at the University of Cologne (Germany). At the core of the laboratory are a state-of-the-art high-mass-resolution multicollector Helix MCPlus (Thermo-Fisher) noble gas mass spectrometer and a novel custom-designed automated extraction line, including a laser-powered extraction furnace. Performance was tested with intercomparison (CREU-1) material.
Florian Hofmann, Emily H. G. Cooperdock, A. Joshua West, Dominic Hildebrandt, Kathrin Strößner, and Kenneth A. Farley
Geochronology, 3, 395–414, https://doi.org/10.5194/gchron-3-395-2021, https://doi.org/10.5194/gchron-3-395-2021, 2021
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We use microCT scanning to improve the quality of 3He exposure ages measured in detrital magnetite. We show that the presence of inclusions can significantly increase the measured amount of 3He and thereby the exposure age. By prescreening magnetite with microCT and analyzing only inclusion-free grains, this problem can be avoided. We also calibrate the cosmogenic 3He production rate in magnetite relative to 10Be in quartz, which can be used for similar studies in the future.
Travis Clow, Jane K. Willenbring, Mirjam Schaller, Joel D. Blum, Marcus Christl, Peter W. Kubik, and Friedhelm von Blanckenburg
Geochronology, 2, 411–423, https://doi.org/10.5194/gchron-2-411-2020, https://doi.org/10.5194/gchron-2-411-2020, 2020
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Meteoric beryllium-10 concentrations in soil profiles have great capacity to quantify Earth surface processes, such as erosion rates and landform ages. However, determining these requires an accurate estimate of the delivery rate of this isotope to local sites. Here, we present a new method to constrain the long-term delivery rate to an eroding western US site, compare it against existing delivery rate estimates (revealing considerable disagreement between methods), and suggest best practices.
Joseph P. Tulenko, William Caffee, Avriel D. Schweinsberg, Jason P. Briner, and Eric M. Leonard
Geochronology, 2, 245–255, https://doi.org/10.5194/gchron-2-245-2020, https://doi.org/10.5194/gchron-2-245-2020, 2020
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We investigate the timing and rate of retreat for three alpine glaciers in the southern Rocky Mountains to test whether they followed the pattern of global climate change or were majorly influenced by regional forcing mechanisms. We find that the latter is most likely for these glaciers. Our conclusions are based on a new 10Be chronology of alpine glacier retreat. We quantify retreat rates for each valley using the BACON program in R, which may be of interest for the audience of Geochronology.
Greg Balco
Geochronology, 2, 169–175, https://doi.org/10.5194/gchron-2-169-2020, https://doi.org/10.5194/gchron-2-169-2020, 2020
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Geologic dating methods generally do not directly measure ages. Instead, interpreting a geochemical measurement as an age requires a middle layer of calculations and supporting data, and the fact that this layer continually improves is an obstacle to synoptic analysis of geochronological data. This paper describes a prototype data management and analysis system that addresses this obstacle by making the middle-layer calculations transparent and dynamic to the user.
Greg Balco, Kimberly Blisniuk, and Alan Hidy
Geochronology, 1, 1–16, https://doi.org/10.5194/gchron-1-1-2019, https://doi.org/10.5194/gchron-1-1-2019, 2019
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This article applies a new geochemical dating method to determine the age of sedimentary deposits useful in reconstructing slip rates on a major fault system.
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Short summary
We describe observations of anomalously high measurements of C-14 made from geologic material. We undertake a systematic investigation to identify the source of contamination, which we hypothesise is sourced from a commonly used method that is used prior to sample analysis. We find that the method does introduce modern carbon to samples and elevates C-14 measurements. We describe a standard procedure that effectively removes contamination from the aforementioned method.
We describe observations of anomalously high measurements of C-14 made from geologic material....
