Glacial geology and cosmogenic-nuclide exposure ages from the Tucker Glacier - Whitehall Glacier confluence, northern Victoria Land, Antarctica

Balco, Greg; Todd, Claire; Goehring, Brent M.; Moening-Swanson, Isaac; Nichols, Keir

doi:10.2475/04.2019.01

Cited by 12 publications

(21 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A SLE value of < 4.6 m places our estimate between those modelled by Bentley et al (2010) (1.4 to 2 m) and Bassett et al (2007) (13.1 to 14.1 m). Using the estimate based on all sites with the exception of the Lassiter Coast data, the minimum SLE estimate of < 1.5 m is consistent with the lower end of published SLEs for the sector.…”

Section: Sea Level Contributionsupporting

confidence: 53%

“…Whitehouse et al, 2017). Consequently, estimates based on ice models constrained by field evidence (Le Brocq et al, 2011) and by relative sea level records and earth viscosity models (Bassett et al, 2007) for the contribution of the sector to global sea level since deglaciation began vary by an order of magnitude, from 1.4 to 14.1 m, respectively. The lack of geological evidence for LGM thickening is also manifest in a misfit between presentday geodetic uplift rate measurements in southern Palmer Land and predicted uplift rates from a glacial isostatic adjustment (GIA) model (Wolstencroft et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

New Last Glacial Maximum ice thickness constraints for the Weddell Sea Embayment, Antarctica

et al. 2019

Self Cite

View full text Add to dashboard Cite

Abstract. We describe new Last Glacial Maximum (LGM) ice thickness constraints for three locations spanning the Weddell Sea Embayment (WSE) of Antarctica. Samples collected from the Shackleton Range, Pensacola Mountains, and the Lassiter Coast constrain the LGM thickness of the Slessor Glacier, Foundation Ice Stream, and grounded ice proximal to the modern Ronne Ice Shelf edge on the Antarctic Peninsula, respectively. Previous attempts to reconstruct LGM-to-present ice thickness changes around the WSE used measurements of long-lived cosmogenic nuclides, primarily 10Be. An absence of post-LGM apparent exposure ages at many sites led to LGM thickness reconstructions that were spatially highly variable and inconsistent with flow line modelling. Estimates for the contribution of the ice sheet occupying the WSE at the LGM to global sea level since deglaciation vary by an order of magnitude, from 1.4 to 14.1 m of sea level equivalent. Here we use a short-lived cosmogenic nuclide, in situ-produced 14C, which is less susceptible to inheritance problems than 10Be and other long-lived nuclides. We use in situ 14C to evaluate the possibility that sites with no post-LGM exposure ages are biased by cosmogenic nuclide inheritance due to surface preservation by cold-based ice and non-deposition of LGM-aged drift. Our measurements show that the Slessor Glacier was between 310 and up to 655 m thicker than present at the LGM. The Foundation Ice Stream was at least 800 m thicker, and ice on the Lassiter Coast was at least 385 m thicker than present at the LGM. With evidence for LGM thickening at all of our study sites, our in situ 14C measurements indicate that the long-lived nuclide measurements of previous studies were influenced by cosmogenic nuclide inheritance. Our inferred LGM configuration, which is primarily based on minimum ice thickness constraints and thus does not constrain an upper limit, indicates a relatively modest contribution to sea level rise since the LGM of < 4.6 m, and possibly as little as < 1.5 m.

show abstract

Section: Sea Level Contributionsupporting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

New Last Glacial Maximum ice thickness constraints for the Weddell Sea Embayment, Antarctica

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…The only way elevated in situ 14 C concentrations could be explained is with an unlikely geomorphic scenario in which the samples were exposed at much higher elevations for a significant period of time before being rapidly transported to their sampling location. This phenomenon was described by Balco et al (2016) and potentially observed by Balco et al (2019). Subsequent elevated in situ 14 C concentrations measured from bedrock samples led us to rule out this scenario as the sole source of the observed elevated in situ 14 C concentrations, and we began to explore other explanations.…”

Section: Initial Anomalous 14 C Measurementsmentioning

confidence: 80%

“…The additional measurements left two potential explanations for the elevated concentrations: unidentified systematic measurement issues or contamination of sample material. Repeat measurements of the quartz interlaboratory comparison material CRONUS-A (Jull et al, 2015;Goehring et al, 2019) and other samples allowed us to rule out systematic measurement issues and conclude that there must be an unidentified source of 14 C contamination. The measurements presented in Figs.…”

Section: Initial Anomalous 14 C Measurementsmentioning

confidence: 99%

“…We extracted carbon from the five quartz aliquots using the Tulane University Carbon Extraction and Graphitization System (TU-CEGS) following the method of Goehring et al (2019). Quartz is step-heated in the presence of a lithium metaborate (LiBO 2 ) flux and a high-purity O 2 atmosphere, first at 500 • C for 30 min, then at 1100 • C for 3 h. The former step is to remove any adsorbed atmospheric CO 2 and combust any carbon derived from sample handling.…”

Section: Systematic Investigationmentioning

confidence: 99%

See 1 more Smart Citation

Isolation of quartz for cosmogenic in situ <sup>14</sup>C analysis

Nichols

Goehring

2019

Geochronology

Self Cite

View full text Add to dashboard Cite

Abstract. Froth flotation is a commonly used procedure for separating feldspars and micas from quartz for the preparation of quartz mineral separates to carry out cosmogenic nuclide analysis. Whilst extracting carbon from quartz we observed in situ carbon-14 (14C) concentrations which were anomalously high and in excess of theoretical geological maximum concentrations. Further etching of sample material reduced carbon yields and 14C concentrations, yet the latter remained unrealistically high. When quartz from the original whole rock sample was isolated in our laboratory, we observed even lower carbon yields and geologically plausible in situ 14C concentrations. After ruling out unlikely geological scenarios and systematic measurement issues, we decided to investigate the quartz isolation procedure as a potential source of 14C contamination. We hypothesised that laurylamine (dodecylamine), an organic compound used as part of the froth flotation procedure, elevates 14C concentrations if residual laurylamine is present. We demonstrate that laurylamine has a 14C modern carbon source and thus has the potential to influence in situ 14C measurements if present in minute but measurable quantities. Furthermore, we show that insufficient sample etching results in contaminant 14C persisting through the step heating of quartz that is subsequently collected with the in situ component released at 1100 ∘C. We demonstrate that froth flotation contaminates in situ 14C measurements. We provide guidelines for the preparation of quartz based on methods developed in our laboratory and demonstrate that all froth-flotation-derived carbon and 14C is removed when applied. We recommend that the procedures presented be used at a minimum when using froth flotation to isolate quartz for in situ 14C measurements.

show abstract

Glacial history of Pyramid Trough, southern McMurdo Sound, Antarctica: Constraints on Koettlitz Glacier during the last glacial maximum and termination

Walther

Hall

Denton

et al. 2023

Quaternary Science Advances

View full text Add to dashboard Cite

Glacial geology and cosmogenic-nuclide exposure ages from the Tucker Glacier - Whitehall Glacier confluence, northern Victoria Land, Antarctica

Cited by 12 publications

References 42 publications

New Last Glacial Maximum ice thickness constraints for the Weddell Sea Embayment, Antarctica

New Last Glacial Maximum ice thickness constraints for the Weddell Sea Embayment, Antarctica

Isolation of quartz for cosmogenic in situ <sup>14</sup>C analysis

Glacial history of Pyramid Trough, southern McMurdo Sound, Antarctica: Constraints on Koettlitz Glacier during the last glacial maximum and termination

Contact Info

Product

Resources

About

Glacial geology and cosmogenic-nuclide exposure ages from the Tucker Glacier - Whitehall Glacier confluence, northern Victoria Land, Antarctica

Cited by 12 publications

References 42 publications

New Last Glacial Maximum ice thickness constraints for the Weddell Sea Embayment, Antarctica

New Last Glacial Maximum ice thickness constraints for the Weddell Sea Embayment, Antarctica

Isolation of quartz for cosmogenic in situ &lt;sup&gt;14&lt;/sup&gt;C analysis

Glacial history of Pyramid Trough, southern McMurdo Sound, Antarctica: Constraints on Koettlitz Glacier during the last glacial maximum and termination

Contact Info

Product

Resources

About

Isolation of quartz for cosmogenic in situ <sup>14</sup>C analysis