Abstract
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 (~53°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 230Th/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 (A1). 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.
Highlights
IntroductionIn southernmost Patagonia, the ages of widespread Holocene tephra layers from Plinian eruptions from volcanoes of the Patagonian Andes[6] in the southern segment of the Southern (41.5–46°S) and the Austral (49–55°S) Volcanic Zones were mainly deduced from 14C-dated materials of terrestrial outcrops, peat and marine/lacustrine sediment cores[3,5,7,8]
Volcanic ash layers are important markers for the chronostratigraphy of paleoclimate and paleoenvironmental archives at the southern tip of South America
Particular conspicuous spikes of S, P, U, Sr, and partly of Si and Zr, occur at 4.216, 2.978, 2.291, and 0.853 kyrs BP. These conspicuous spikes are followed by (i) a series of mostly smaller, but discrete, short-term peaks for the same elements decreasing in height or by (ii) more extended periods characterized by consistently elevated concentrations from ~4.20 to 4.14 kyrs BP, respectively
Summary
In southernmost Patagonia, the ages of widespread Holocene tephra layers from Plinian eruptions from volcanoes of the Patagonian Andes[6] in the southern segment of the Southern (41.5–46°S) and the Austral (49–55°S) Volcanic Zones were mainly deduced from 14C-dated materials of terrestrial outcrops, peat and marine/lacustrine sediment cores[3,5,7,8]. This tephrochronological framework constitutes the principal reference for the stratigraphy of most geological records used in paleoclimate/. Large errors in age determination of volcanic ash layers occur from the interpolation of bracketing 14C dates[4] and/or age constraints based on estimated sedimentation/peat accumulation rates[12,13]
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