- 1Institut des Géosciences de l’Environnement (IGE), University Grenoble-Alpes (UGA), France
- 2DISAT-Dept. Earth Environmental Sciences-Ed. U1 (DISAT), University Milano-Bicocca, Italy
- 3Institut des Sciences de la Terre (ISTerre), University Grenoble-Alpes (UGA), Grenoble France
Powerful volcanic eruptions inject into the stratosphere sulphur and tephra that may be spread globally and affect the Earth’s climate. Over the last 2500 years, Sigl et al. (2015) made a synthesis of the polar ice core atmospheric sulphur record and climate anomalies from dendrochronological records. Aside from a few historical events, most large eruptions with a bipolar imprint and a significant climate anomaly are from the tropical latitudes, but their sources are unknown.
We analysed the micron-size crytotephra composition accompanying the (stratospheric) sulphate of the 1458 CE and 426 BCE volcanic events recorded in three Antarctic ice cores. The 1458 CE event occurred within a cool climate and was initially attributed to the Kuwae (Vanuatu) eruption. This link is however questioned by Hartman et al. (2019) from their study of a South Pole ice core. The 426 BCE event appears concomitant with a significant global climate cooling, but its source is unknown.
Within the sulphate peak, the particle size distribution, when available, helps documenting the dynamics of the arrival of the stratospheric plume. Cryptotephra are collected by filtration and after carbon-coating, analysed by an EPMA microprobe. We applied the analytical procedure of Narcisi et al. (2019) (who identified the 1257 CE Samalas eruption), adapted to the micron-size of the crytotephra.
For the 1458 CE event, a medium-K dacite to rhyolite composition is consistently observed from Vostok and Dome C ice core samples (218 values). The dacite patch (SiO2~68%) fits well the composition of proximal Kuwae deposits as well as that of an ash layer (~140 values) on Efate Island (Standberg et al, 2023). The rhyolite composition patch (SiO2~72%) is unlikely from a South American source, but appears discretely represented in proximal Kuwae deposits as well as in sediments in the nearby Epi Submarine zone. We suggest that rhyolite is a daughter product from dacite by evolving in the upper layers of the magmatic chamber, and it was spread out first and far away by the eruption.
For the 426 BCE event, the cryptotephra composition (220 values) is consistently found within the three ice cores (Vostok, Dome C, Talos Dome) and belongs to high-K rhyodacite. Coincidentally such composition is very close to Kuwae’s (except for higher K) suggesting it was issued from a very similar magmatic chamber. The 10 km wide Ambrym caldera located 50 km north of Kuwae, collapsed ~2000 years ago appears the best candidate.
References
Hartman et al. (2019). Nature Sci. Rep. 9. https://doi.org/10.1038/s41598-019-50939-x.
Narcisi, B. et al., 2019. Quat. Sci. Rev. 210, 164-174 https://doi.org/10.1016/j.quascirev.2019.03.005.
Sigl, M., et al. Nature 523, 543–549 (2015). https://doi.org/10.1038/nature14565
Strandberg NA et al., (2023). Front. Ecol. Evol. 11: 1087577.doi: 10.3389/fevo.2023.1087577
How to cite: Petit, J.-R., Savarino, J., Delmonte, B., Gautier, E., Ginot, P., and Batanova, V.: Cryptotephra fingerprinting of 1458 CE and 426 BCE volcanic events in East Antarctic ice cores, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2329, https://doi.org/10.5194/egusphere-egu25-2329, 2025.
