Evidence for magmatic carbon bias in 14C dating of the Taupo and other major eruptions

Abstract

Prehistoric timescales, volcanic hazard assessment, and understanding of volcanogenic climate events rely on accurate dating of prehistoric eruptions. Most late Quaternary eruptions are dated by 14C measurements on material from close to the volcano that may be contaminated by geologic-sourced infinite-age carbon. Here we show that 14C ages for the Taupo (New Zealand) First Millennium eruption are geographically arrayed, with oldest ages closer to the vent. The current eruption wiggle match date of 232 ± 5 years CE is amongst the oldest. We present evidence that the older, vent-proximal 14C ages were biased by magmatic CO2 degassed from groundwater, and that the Taupo eruption occurred decades to two centuries after 232 CE. Our reinterpretation implies that ages for other proximally-dated, unobserved, eruptions may also be too old. Plateauing or declining tree ring cellulose δ13C and Δ14C values near a volcano indicate magmatic influence and may allow forecasting of super-eruptions.

Reply to ‘Wiggle-match radiocarbon dating of the Taupo eruption’

“…As can be seen in our original Fig. 1 2 and Supplementary Table 1, the pattern of calibrated date distributions is apparent regardless of the original age standard errors and carbon source(s) and associated methodology and treatment. We used median ages in the analyses because there are equal likelihoods of the actual date being older or younger.…”

“…We appreciate the opportunity to respond to Hogg et al’s critique 1 of HDK18 2 . We present responses to the four arguments and additional data analysis presented by Hogg et al Hogg et al focus on the wiggle match and Kaipo Bog (KB) dates out of >40 data points.…”

Wiggle-match radiocarbon dating of the Taupo eruption

“…The Taupo eruption 1 deposit is an isochronous marker bed that spans much of New Zealand’s North Island and pre-dates human arrival 2 . Holdaway et al 3 (HDK18 hereafter) propose that the current Taupo eruption date is inaccurate, and that the eruption occurred decades to two centuries after the published wiggle-match estimate of 232 ± 10 CE (2 SD) 4 derived from a tanekaha ( Phyllocladus trichomanoides ) tree at the Pureora buried forest site 5,6 . HDK18 propose that trees growing at Pureora (and other near-source areas) that were killed and buried by the climactic ignimbrite event were affected by 14 C-depleted (magmatic) CO 2 .…”

Volcanism and climate change as drivers in Holocene depositional dynamic of Laguna del Maule (Andes of central Chile – 36° S)

“…Summers are dry due to the strong influence of the SPSH, and easterly storms are infrequent (Viale and Garreaud, 2013). On interannual to interdecadal timescales, rainfall in subtropical central Chile is sensitive to variations in the El Niño-Southern Oscillation (ENSO), the Southern Annular Mode (SAM) and the Pacific Decadal Oscillation (PDO) (Jacques-Coper and Garreaud, 2014;Montecinos and Aceituno, 2003;Pittock, 1980;Quintana and Aceituno, 2012). These climate modes have a strong influence on the patterns of variability of the snowpack and streamflow in central Chile along with the occurrence of extreme events, such as protracted drought or torrential rains (Masiokas et al, 2010(Masiokas et al, , 2012.…”