Distal cryptotephra records in the Falkland Islands refine South American tephrochronology

Abstract

Cryptotephra (non-visible volcanic ash) deposits in the Falkland Islands (Islas Malvinas) provide a distal record of South American volcanism and ash dispersal into the South Atlantic Ocean. Here, we present three new cryptotephra records from peatlands in the archipelago and use these data to refine the age estimates of key regional tephra isochrons. Major-minor-trace element glass geochemistry and high-resolution radiocarbon chronologies were used to correlate cryptotephra deposits with known explosive eruptions at Reclus volcano (R1), Monte Burney and Hudson volcano (H2). We also identify cryptotephra deposits likely originating from Chaitén volcano, the Antillanca volcanic complex and two Mid Holocene eruptions of Aguilera volcano. Careful examination of major-minor element data from tephras linked with Monte Burney MB1 demonstrates discrepancies between medial and distal deposits preserved in Patagonia, Laguna Potrok Aike and the Falkland Islands. These suggest that two Early Holocene tephra deposits from Monte Burney may be widely distributed. Our integrated Bayesian age-depth model refines the median ages of Hudson H2 (4230–3775 calibrated years before present; cal yr BP), deposits from Monte Burney (as viewed from the Falkland Islands, 9540-9455 cal yr BP) and Reclus volcano R1 (14,800-14,060 cal yr BP). We also propose that the age of Aguilera A1 is older than previously suggested and dates to 4390-4150 cal yr BP. Our expanded geochemical dataset of volcanic glasses and new age constraints for these isochrons aid distal and near source tephra correlations and complement the current tephrochronological framework of the region.