Deposition of the 2011-2012 Cordón Caulle tephra (Chile, 40°S) in lake sediments: Implications for tephrochronology and volcanology

Abstract

Tephras preserved in lake sediments are commonly used to synchronize sedimentary archives of climate and environmental change and to correlate them with terrestrial environments. They also provide opportunities to reconstruct volcanic explosive activity, e.g., eruption frequency and tephra dispersal. Although sedimentary processes may affect the record of tephras in lakes, lake sediments are generally considered as one of the best archives of tephra stratigraphy. The 2011-2012 eruption of Cordón Caulle volcano (Chile, 40°S) offered an ideal opportunity to study the processes affecting tephra deposition in lakes. Although the prevailing westerlies transported the erupted pyroclastic material away from nearby Puyehue Lake, the tephra was identified within this relatively large lake with a thickness ranging from 1 to >10 cm. This is in contrast with smaller lakes, where tephra thickness was in agreement with ashfall distribution maps. Geomorphological observations and sedimentological analyses provide evidence that the tephra deposited in Puyehue Lake entirely consists of material reworked from the upper watershed, transported by rivers, and distributed by lake currents according to particle size and density. Our results have important implications for tephrochronology and volcanology. They suggest that (1) lakes do not act as passive tephra traps; (2) lakes with large watersheds record more eruptions than smaller lakes, which only register direct ashfalls, affecting conclusions regarding the recurrence of volcanic eruptions; and (3) using lakes with large watersheds for isopach mapping systematically leads to an overestimation of erupted tephra volumes. Smaller lakes with limited drainage basins are generally better suited for volcanological studies.

Water vapour variability in the high-latitude upper troposphere – Part 2: Impact of volcanic eruptions

“…The latter factor is assumed to be 6 % for both Cordón Caulle and Eyjafjallajökull, which is within 1 standard deviation (1.6 %) of the Eyjafjallajökull mean value of 4.6 % ( Table 6 of Woodhouse et al, 2013, assuming 80 % water vapour based on Pinto et al, 1989) and within the typical range of 4-6 % (Grove et al, 2009). The total erupted mass for Cordón Caulle is determined by multiplying a total erupted volume of 1.9 km 3 (Dr. Elizabeth Cottrelle, Global Volcanism Program, Smithsonian Institution, personal communication, 2015) by an ash density of 2300 kg m −3 appropriate for glass, since most of the erupted mass was glass (Bertrand et al, 2014). Bonadonna et al (2015) estimated the total erupted volume to be 1.1 ± 0.2 km 3 , while Bertrand et al (2014) imply > 3 km 3 .…”

“…The total erupted mass for Cordón Caulle is determined by multiplying a total erupted volume of 1.9 km 3 (Dr. Elizabeth Cottrelle, Global Volcanism Program, Smithsonian Institution, personal communication, 2015) by an ash density of 2300 kg m −3 appropriate for glass, since most of the erupted mass was glass (Bertrand et al, 2014). Bonadonna et al (2015) estimated the total erupted volume to be 1.1 ± 0.2 km 3 , while Bertrand et al (2014) imply > 3 km 3 . The total erupted mass for Eyjafjallajökull is 480 ± 120 Mt .…”

Tools and techniques for developing tephra stratigraphies in lake cores: A case study from the basaltic Auckland Volcanic Field, New Zealand

“…Bertrand et al, 2014;Shapley and Finney, 2015). The AVF maar craters are mostly closed systems; the surrounding tuff rings are outward dipping and composed of indurated, poorly sorted tuff, the surrounding topographic relief is very low, and the stream catchments that they intersect tend to be very small, resulting in minimal currents within the lakes (Striewski et al, 2013).…”

“…Alloway et al, 1994;Dirksen et al, 2011;Engwell et al, 2014); (2) reworked (e.g. Payne and Gehrels, 2010;Bertrand et al, 2014;Sorrentino et al, 2014); or (3) where geochemical signatures are ambiguous, preventing unique characterisation of a deposit (e.g. Pearce et al, 2004;Brendryen et al, 2010;Bourne et al, 2013;Davies et al, 2014).…”

Distal tephrochronology in volcanic regions: Challenges and insights from Kamchatkan lake sediments

“…Similar "patchiness" of tephras within lake systems has been observed also in 528 cryptotephra studies (Mangerud et al, 1984;Davies et al, 2001). Pyne-O'Donnell (2011) determined 529 that tephra concentrations in lakes were strongly influenced by lake catchment size and the 530 presence of inlet streams, and this has been borne out by the recent study of tephra distributions in 531 lakes following the 2011-2012 eruption of Cordón Caulle, Chile (Bertrand et al, 2014). Inflowing 532 streams are therefore likely to explain the greater thicknesses of tephras in Pechora Lake when 533 compared to Lifebuoy Lake, but it is interesting to note the similarities between the two 534 tephrostratigraphies that suggests that the lakes captured and recorded the main ashfall events in 535 this part of northern Kamchatka.…”