DOI: 10.5066/p1edrz6l
title: Radiocarbon dating of silicified wood from around Artemisia Geyser in the Upper Geyser Basin, Yellowstone National Park

description: Samples of silicified wood remnants from 8 trees were collected under research permit YELL-SCI-8030 on June 17, 2023, and on September 19, 2023 adjacent to Artemisia Geyser in the Upper Geyser Basin of Yellowstone National Park. Samples were collected for radiocarbon (14C) dating of the wood to determine when the trees grew. Trees do not grow on active geyser mounds (Hurwitz and others, 2020, 2024) and therefore, trees grew around Artemisia Geyser during a protracted period of eruption quiescence. The study of silicified trees at Artemisia Geyser follows similar studies at Old Faithful Geyser in the Upper Geyser Basin (Hurwitz and others, 2020) and at Steamboat Geyser in Norris Geyser Basin (Hurwitz and others, 2023). Around Old Faithful Geyser trees grew during periods of sustained drought between 1233 and 1362 CE. Around Steamboat Geyser, trees grew during three episodes that are temporally correlated with periods of severe or sustained drought in the Yellowstone region during the 15th–17th centuries CE.

Five samples AG101, AG102, AG103, AG104, and AG106 were split into subsamples for 14C analysis. For tree sample AG107, samples were collected at three locations within the trunk: AG107A (innermost portion of tree), AG107B (central portion of tree), AG107C (outermost portion of tree). AG107B was found to have 13 well-defined mineralized annual rings and was subdivided into three annual ring samples. The innermost annual ring sample of AG107B was designated as ring 0, the central annual ring sample (ring +5) is five years later than ring 0, the outermost annual ring sample (ring +12) is 12 years later than ring 0.

Radiocarbon (14C) dating of the mineralized wood and stable carbon isotope analyses (δ13C) were performed at the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility at the Woods Hole Oceanographic Institution. Measurement and calculation methods are described in the laboratory’s web page.

The Bayesian software package Bchron (Haslett and Parnell, 2008) was used with the measured radiocarbon ages and the IntCal20 calibration curve (Reimer et al., 2020) to calculate age probability density functions for the most probable ages of tree growth.

For tree samples AG105 and AG108, only a single sample was dated, and the calibrated 14C dates for these samples yielded younger dates than for other samples. For sample AG105, calibrated ages range between 1806 and 1926 CE (with a probability of 58.1%) or between 1685 and 1731 CE (probability of 36.9%). For sample AG108, calibrated ages range between 1721 and 1780 CE (probability of 34.2%), between 1669 and 1700 CE (probability of 23.3%), or between 1833 and 1890 (probability of 20.8%).

References Cited
Haslett, J. and Parnell, A., 2008. A simple monotone process with application to radiocarbon-dated depth chronologies. Journal of the Royal Statistical Society: Series C, 57, 399-418. https://doi.org/10.1111/j.1467-9876.2008.00623.x

Hurwitz, S., King, J.C., Pederson, G.T., Martin, J.T., Damby, D.E., Manga, M., Hungerford, J.D. and Peek, S., 2020. Yellowstone's Old Faithful Geyser shut down by a severe thirteenth century drought. Geophysical Research Letters, 47(20), p.e2020GL089871. https://doi.org/10.1029/2020GL089871

Hurwitz, S., King, J.C., Pederson, G.T., Reed, M.H., Harrison, L.N., Hungerford, J.D., Vaughan, R.G. and Manga, M., 2023. The relation between decadal droughts and eruptions of Steamboat Geyser in Yellowstone National Park, USA. Geochemistry, Geophysics, Geosystems, 24(7), p.e2023GC010988. https://doi.org/10.1029/2023GC010988

Reimer, P.J., Austin, W.E., Bard, E., Bayliss, A., Blackwell, P.G., Ramsey, C.B., Butzin, M., Cheng, H., Edwards, R.L., Friedrich, M. and Grootes, P.M., 2020. The IntCal20 Northern Hemisphere radiocarbon age calibration curve (0–55 cal kBP). Radiocarbon, 62, 725-757. https://doi.org/10.1017/RDC.2020.41