Volcanic, tectonic and climate controls on lacustrine sedimentary supplies over the last millenia in NE Chilean Patagonia (Lake Esponja, Aysen, 45°S)

• Published in: Holocene (Sevenoaks) Vol. 33; no. 5; pp. 518 - 535
• Main Authors: Fagel, Nathalie, Pedreros, Pablo, Alvarez, Denisse, Israde Alcantara, Isabel, Vega Alay, Ignacio, Namur, Olivier, Araneda, Alberto, Schmidt, Sabine, Lepoint, Gilles, Urrutia, Roberto
• Format: Journal Article Web Resource
• Language: English
• Published: London, England SAGE Publications 01.05.2023; Sage Publications Ltd; London: Sage; SAGE Publications Ltd
• Subjects: Aluminum; Archeology; Archeology (arts and humanities); Benthos; Caesium 137; Cesium 137; Cesium isotopes; Cesium radioisotopes; Chile; Cores; Deposition; diatom assemblages; Diatoms; Earth sciences & physical geography; Earth-Surface Processes; Earthquakes; Ecology; Environmental Sciences; Fjords; Geochemistry; Global and Planetary Change; Grain size; Lacustrine sediment; Lake sediments; Lakes; Landslides; Late-Holocene; Lead isotopes; Magnetic permeability; Magnetic susceptibility; Marine microorganisms; Mass transport; Mineralogy; Organic matter; Paleontology; Physical, chemical, mathematical & earth Sciences; Physique, chimie, mathématiques & sciences de la terre; Plankton; Rainfall; Sciences de la terre & géographie physique; Sediment; sedimentary geochemistry; Sediments; Seismic activity; Seismic response; Seismic stability; Silica; Silicon dioxide; Tectonics; Tephra; Uplift; Volcanic activity; Volcanic eruptions; Volcanoes; Water levels; X-ray diffraction; diatom assemblages; Lacustrine sediment; Chile; Late-Holocene; tephra; sedimentary geochemistry
• ISSN: 0959-6836; 1477-0911; 1477-0911
• DOI: 10.1177/09596836231151828

The environmental variability of Northern Chilean Patagonia during the last millennia is evaluated using a multi-proxy analysis of sediment cores from Lake Esponja (45°S 72°W) to decipher if the sediment deposition is controlled by volcanic eruptions, landslides induced by earthquake or heavy rainfall. The lake is located in a glacio-tectonic valley in Patagonia. The organic-rich clayey silt sediment with low biogenic silica content was analysed for grain size, magnetic susceptibility, organic matter, biogenic silica content and diatom assemblages, mineralogy (X-ray diffraction), organic (IRMS C and N analyses) and inorganic (XRF core-scanner) geochemistry and glass shard major composition (Microprobe, SEM). The combination of 210Pb, 137Cs, 14C and tephrochronology indicates an averaged accumulation rate of 0.4 mm/year, leading to a record of ~3.5 kyr within 154 cm. The sedimentary geochemistry records changes in volcanic supplies, diatom productivity and detrital inputs. The sediments were interrupted by millimetric to centimetric layers corresponding to tephra deposition related to explosive eruptions of nearby volcanoes Macá, Melimoyu and Hudson. Concerning the diatoms, the dominant planktonic species (80–150 cm) are replaced by benthic species in a transition interval (55–80 cm) and then by Surirella spp. in the upper core. This last genus indicates a closure of the basin ~2 ka ago, probably related to an uplift linked to a rejuvenation of the Mañihuales fault. This local change could reflect regional tectonic instability. Indeed, a partial earthquake rupture occurred around ~AD100 along the southern part of the Valdivia segment, recorded as a mass transport deposit in Aysén fjord sedimentation. The fine detrital input varies over time with more variable Si/Al values in the lower part of the LEs14 core than in the upper 80 cm. The higher values may reflect wetter conditions, leading to an higher lake level and more turbid conditions in agreement with changes in diatom assemblages.