Tephrochronology of recent events in the Andean Range (northern Patagonia): spatial distribution and provenance of lacustrine ash layers in the Nahuel Huapi National Park

Abstract

Tephrochronology is a powerful tool for dating sedimentary sequences, especially in Patagonia, where a large number of active volcanoes have produced frequent historical eruptions. Short lacustrine sedimentary sequences were extracted from the lakes Moreno Oeste and Ton cek (Nahuel Huapi National Park). Seventeen volcanic ash layers were identified in both cores, 210 Pb and 137 Cs were used for dating techniques, and historical volcanic records were employed for correlation. White pumice and glass shards from the tephras were characterised by measuring major and trace element contents by instrumental neutron activation analysis. Two volcanic sources -the Cordó n Caulle and the Calbuco volcanoes -were recognised as the prevailing systems that impacted the area in the past 800-1000 a. The Calbuco volcano was mainly responsible for the nine tephras identified in the Lake Ton cek sequence. Four of these nine tephras also contained material from the Cordó n Caulle complex, and could be interpreted as composite tephras or possible reworked ones. The Calbuco volcano showed predominant influences in the Lake Moreno Oeste sequence. Six of the eight tephras identified in such a sequence were from the Calbuco volcano, and three of these six contained material from the Cordó n Caulle complex. The other two were from the Cordó n Caulle complex, with contributions from the Calbuco volcano in one of them. These findings show that the high frequency of volcanic events in the study region demands an accurate characterisation of the products generated by each source, as well as an evaluation of their spatial distribution, to obtain a consistent framework for dating recent environmental changes.

Stratigraphy, age and correlation of Lepué Tephra: a widespread c. 11 000 cal a BP marker horizon sourced from the Chaitén Sector of southern Chile

“…Tephra layers have been routinely recorded in lakes (i.e. Haberle and Lumley, 1998;Daga et al, 2010;Moreno et al, 2015a) but in many studies the occurrence of tephra has been a subordinate focus in dominantly paleoecologically and paleoclimatically directed investigations (i.e. Abarz ua et al, 2004;Bertrand et al, 2008;Iglesias et al, 2012;Moreno and Videla, 2016).…”

Palaeolimnology of Lake Hess (Patagonia, Argentina): multi-proxy analyses of short sediment cores

“…from Nahuel Huapi National Park shows that both natural and anthropogenic events (long-range atmospheric transport of pollutants) occurred in the region during the last 900 years (Rizzo et al, 2007;Daga et al, 2008b;Ribeiro Guevara et al, 2009). The study of sub-fossil chironomid assemblages showed the predominance of Pseudosmittia and cold-stenothermic Podonominae from eleventh to seventeenth centuries, which decrease in the upper layers (eighteenth century to present) being replaced by the warmadapted Tanypodinae.…”

Reconstructing recent environmental changes using non-biting midges (Diptera: Chironomidae) in two high mountain lakes from northern Patagonia, Argentina

“…Environmental changes at Lake Toncek Lake Toncek recorded three volcanic events along the sediment sequence, 1893-1895, 1919-1922, and 1960-1961 PCC/C volcanic eruptions, chronologies from Daga et al (2010). The most important chironomid changes driven by these ash falls are recorded following the 1960-1961 eruption (Zone 3), with the increase of Parapsectrocladius and Cricotopus, the decrease of Apsectrotanypus and Pseudosmittia, and the disappearance of Parakiefferiella, Paralimnophyes, and Eukiefferiella.…”