Explosive volcanism during the Holocene in the Upper Limay River Basin: The effects of ashfalls on human societies, Northern Patagonia, Argentina

摘要

In order to understand human response to Holocene ashfall events, tephra layers found in archaeological sites along the upper Limay River basin, Northern Patagonia, Argentina were bracketed with radiocarbon dates and correlated with tephra from a lacustrine sediment core and from outcrops and the archaeological evidence was analyzed. A dark tephra associated with seismic activity was identified in the El Trebol rockshelter filling interstices between fallen blocks together with remains of human activity and bones of extinct fauna, marking a seismo-volcanic event occurring between 11 758 and 12 866 cal yr BP. This same seismic event affected the Cuyin Manzano site, where the roof collapse made the site uninhabitable for a time. A white tephra, present in Epullan Grande, Epullan Chica and Traful I caves is correlated with Nahuel Huapi tephra (NHT), equivalent to Laya's Rio Blanco and Rio Pereyra members, (Rio Pireco Formation). NHT is considered to have been derived from the same eruptive event, with dates ranging between ca. 1950-2500 cal yr BP. A dark tephra from Ortega's cave and several tephra from Puerto Tranquilo I rockshelter ranging between 521 and 2069 cal yr BP show how the mobile hunters-gatherers of Northern Patagonia were able to cope with the changing circumstances.