High-resolution stalagmite stratigraphy supports the Late Holocene tephrochronology of southernmost Patagonia

Volcanic ash layers are important markers for the chronostratigraphy of paleoclimate and paleoenvironmental archives at the southern tip of South America. However, this requires that tephras are well-dated. We report geochemical data from stalagmite MA1 formed in a non-karst cave near Mt. Burney volcano in southernmost Patagonia (similar to 53 degrees S). High-resolution LA-ICP-MS analyses, SEM imagery, EPMA data, and NanoSIMS enable to identify volcanogenic signals during the last 4.5 kyrs from sub-annual trace element variations and tephra particles in distinct laminae. Our new Th-230/U-chronology of MA1 provides precise dating of tephra from Mt. Burney (MB) and, probably, Aguilera (A) at 4,216 (+93)/(-193) yrs BP (MB2), 2,291 +/- 33 yrs BP (MB3), 853 (+41)/(-60) yrs BP (MB4) and 2,978 (+91)/(-104) yrs BP (A(1)). This unique high-resolution record holds potential to date further eruptions from Southern Andean volcanoes for the tephrochronology in this critical region, and potentially also large-volume explosive volcanism off South America.

Automated summary

Volcanic ash layers in southernmost South America serve as important indicators for studying paleoclimate and paleoenvironment, but accurate dating of these ash layers is crucial. This study presents a new high-resolution chronology of tephra deposits from Mt. Burney and possibly Aguilera, based on geochemical analyses of stalagmites. The findings provide valuable information for tephrochronology in the region, as well as potential insights into large-volume explosive volcanism off South America.