EGU21-16327
https://doi.org/10.5194/egusphere-egu21-16327
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Timing and distribution of the Los Chocoyos supereruption from Atitlán caldera (Guatemala) by zircon 238U-230Th and (U-Th)/He double-dating

Alejandro Cisneros de Leon1, Julie Christin Schindlbeck-Belo1,2, Steffen Kutterolf2, Martin Danišík3, Axel Karl Schmitt1, Armin Freundt2, Wendy Pérez2, Janet Harvey1, Kuo-Lung Wang4,5, and Hao-Yang Lee4
Alejandro Cisneros de Leon et al.
  • 1Institut für Geowissenschaften, Universität Heidelberg, Im Neuenheimer Feld 234-236, Deutschland.
  • 2GEOMAR Helmholtz Centre for Ocean Research Kiel SFB574, Wischhofstrasse 1-3, 24148 Kiel, Germany
  • 3GeoHistory Facility, John de Laeter Centre, TIGeR, Curtin University, Perth, WA 6845, Australia
  • 4Institute of Earth Sciences, Academia Sinica, Taipei 11529, Taiwan
  • 5Department of Geosciences, National Taiwan University, Taipei, Taiwan

The climactic Los Chocoyos (LCY) rhyolitic eruption from Atitlán caldera (Guatemala) is a key chronostratigraphic marker for the Late Quaternary period that has been widely used for relative dating of paleoenvironmental, paleoclimate, and volcanic events throughout Central America and adjacent marine basins in the Pacific Ocean, the Caribbean Sea, and the Gulf of Mexico. Despite LCY tephra being an important marker horizon, a radioisotopic age for this eruption has remained elusive. LCY tephra has been dated at ca. 84 ka BP based on its occurrence in marine sediments with model δ18O ages, but this inferred age has not been independently confirmed through radioisotopic methods. This is due to the inherent limitations of radiocarbon dating (which is practically limited to ˂50 ka) and a lack of suitable materials for 40Ar/39Ar analysis in LCY tephra. To overcome this limitation, we applied 238U-230Th and (U-Th)/He zircon double-dating (ZDD). Due to zircon being alteration-resistant this method establishes absolute chronologies for and correlations between silicic tephra deposits, which are unaffected by glass alteration or complex compositional signatures within a single eruption. 238U-230Th zircon crystallization rim ages were obtained from LCY proximal tephras (~17 km from Atitlán caldera) including sub-units that may bear distinct glass compositions (e.g., fallout, ignimbrite, surge) as well as ultra-distal fallout tephra samples (~300 km from source) collected from drill cores at Petén Itzá Lake (ICDP) and the Pacific Ocean (IODP). All samples yielded zircon with statistically indistinguishable 238U-230Th zircon rim age spectra. These reveal continuous zircon crystallization from ca. 160 ka to ca. 74 ka, with peaks in zircon crystallization between 90-100 ka. ZDD eruption ages from two LCY fallout and one ignimbrite deposit are indistinguishable with error-weighted averages of 75.1 ± 3.2 ka (1σ; n = 16; MSWD = 4.1), 76.0 ± 2.5 ka (n = 16; MSWD = 2.5), and 72.8 ± 3.5 ka (n = 16; MSWD = 3.7). Considering all individual zircon results as a single population, a weighted average ZDD age of 74.8 ± 1.7 (1σ; n = 48; MSWD = 3.3) is obtained and considered as the best estimate for LCY eruption age. GIS-based reassessment of LCY eruptive volume uses thickness information from new 113 outcrops including 6–10 m thick pyroclastic density currents in Chiapas, Mexico (>130 km from the source) and suggests a minimum estimate volume of ~1200 km3, confirming the LCY eruption as the first‐ever recognized supereruption in Central America. The new ZDD age of 74.8 ± 1.7 ka for the LCY eruption is significantly younger than the commonly cited O-isotope stratigraphic age of 84 ± 5 ka. This age is close to the voluminous (2,800-5,600 km3) Young Toba Tuff (YTT) supereruption at ca. 73.8 ± 0.3 ka from Toba Caldera, Indonesia. Both YTT and LCY eruptions have been previously linked to prominent Quaternary climate excursions. Based on the new LCY eruption age, climate-forcing effects that are usually attributed to YTT may in fact be exacerbated by another supereruption occurring within a short time window of the YTT event.

How to cite: Cisneros de Leon, A., Schindlbeck-Belo, J. C., Kutterolf, S., Danišík, M., Schmitt, A. K., Freundt, A., Pérez, W., Harvey, J., Wang, K.-L., and Lee, H.-Y.: Timing and distribution of the Los Chocoyos supereruption from Atitlán caldera (Guatemala) by zircon 238U-230Th and (U-Th)/He double-dating, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16327, https://doi.org/10.5194/egusphere-egu21-16327, 2021.

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