Preprints
https://doi.org/10.5194/gchron-2021-18
https://doi.org/10.5194/gchron-2021-18

  16 Jun 2021

16 Jun 2021

Review status: this preprint is currently under review for the journal GChron.

Late Holocene cryptotephra from Cascade Lake, Alaska: supporting data for a 21,000-year multi-chronometer Bayesian age model

Lauren J. Davies1,2, Britta J. L. Jensen1, and Darrell S. Kaufman3 Lauren J. Davies et al.
  • 1Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada
  • 2Department of Geography, University of Cambridge, Cambridge, UK
  • 3School of Earth and Sustainability, Northern Arizona University, Flagstaff, Arizona, USA

Abstract. Multiple chronometers can be employed for dating Holocene palaeoenvironmental records, each with its own inherent strengths and weaknesses. Radiocarbon dating is one of the most widely used techniques for producing chronologies, but its application at high-latitude sites can be problematic. Here, cryptotephra identified in the Late Holocene portion of a core from Cascade Lake, Arctic Alaska, resolve a divergence identified between radiocarbon and paleomagnetic secular variation (PSV) data in the top 1.5 m of the sediment sequence. Identifiable geochemical populations of cryptotephra are shown to be present in detectable concentrations in sediment from the north flank of the Brooks Range for the first time. Major element glass geochemical correlations are demonstrated between ultra-distal cryptotephra and reference samples from the Late Holocene caldera forming eruption of Opala, Kamchatka, as well as three eruptions in North America: the White River Ash (northern lobe), Ruppert tephra and the Late Holocene caldera forming eruption of Aniakchak. The correlated ages of these cryptotephra support the PSV ages reported in Steen et al. (this volume) and provide evidence for an old-carbon effect in Cascade Lake. Chronological data from the Cascade Lake were then combined using a Bayesian approach to generate an age-depth model that extends back to 21,000 cal yr BP.

Lauren J. Davies et al.

Status: open (until 20 Aug 2021)

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Lauren J. Davies et al.

Lauren J. Davies et al.

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Short summary
Subarctic/Arctic lake sediments provide key data to understand natural climate variability and future climate change, but are difficult to date and of limited use without a robust chronology. A ~21,000 year climate record from Cascade Lake (Alaska) has divergent age models based on two dating methods. We resolve this using volcanic ash deposits; proving paleosecular variation is a viable dating technique in the region, reporting new ash isochrons, and providing a reconciled Bayesian age model.