The hunter-gatherers of Abra del Toro rock shelter, northwestern Argentina, suffered the effects of the large 4.2 ka Cerro Blanco eruption

There is a dearth of information regarding prehistoric foraging societies from the intermontane longitudinal valleys of the South-Central Andes. Due to the intense anthropization of the landscape or the scarce research efforts on prehistoric populations of hunter-gatherers in the intermontane valleys of the Andes, occupation sites have been found on very few occasions. However, new perspectives in the Abra del Toro rock shelter in the Yocavil Valley (Catamarca province, Argentina) have opened up from recent and ongoing excavations. This rock shelter is the first archaeological case in which it is possible to analyze the relationship between a large-scale natural catastrophe and the prehistoric populations living in the Andean intermontane valleys of the southern Central Andes. This rock shelter's stratigraphy and archaeological remains contain the record of interactions between human communities and volcanism. The stratigraphic record of the rock shelter shows a 1-m-thick volcanic ash deposit formed by aeolian transport from primary outer ashfall deposits. Geomorphological and sedimentological context, texture, glass and mineral content, whole-rock chemical composition, and radiocarbon dating prove that the tephra was derived from the 4.2 ka BP eruption of the Cerro Blanco Volcanic Complex in southern Puna (NW Argentina). This volcanic eruption is the largest documented in the world in the last five thousand years and covered the surroundings of the archaeological site with an ash layer of approximately 1 meter thick. The stratigraphic sequence of the Abra del Toro rock shelter allows us to hypothesize that there were three main occupational moments: two hunter-gatherer moments, separated by the record of the large volcanic eruption, and a subsequent agro-pottery period (Carbonelli et al. 2022. J. Archaeol. Sci. Rep. 45, 103629). The rock shelter after the eruption remained in the memory of the hunter-gatherer groups. Good visibility, accessibility, and proximity to water were attributes of this space that made it possible for it to be re-occupied after the eruptive event. Our next objective is to reconstruct, using proxy analysis, how the paleoenvironment was in the intermontane valleys before and after the eruption. The evidence of this Mid-Holocene catastrophic volcanic event in the Abra del Toro rock shelter opens the possibility of knowing its impact on the contemporary hunter-gatherer community and drawing conclusions for similar future volcanic crises.

This work was supported by the National Scientific and Technical Research Council (Grant PIP 112-201301-00178), the University of Buenos Aires (Grant UBACyt 20020170100318BA) (University of Buenos Aires), the National Agency for the Promotion of Research, Technological Development and Innovation (Grant 2019-01229) and the QUECA Project (MINECO, Grant CGL2011-23307).