Late Holocene droughts and cave ice harvesting by Ancestral Puebloans

Bogdan P Onac,Dylan S Parmenter,Eric Weaver,Steven M Baumann,Tiberiu B Sava

doi:10.1038/s41598-020-76988-1

Abstract

Water availability for Native Americans in the southwestern United States during periods of prolonged droughts is poorly understood as regional hydroclimate records are scant or contradicting. Here, we show that radiocarbon-dated charcoal recovered from an ice deposit accumulated in Cave 29, western New Mexico, provide unambiguous evidence for five drought events that impacted the Ancestral Puebloan society between ~ AD 150 and 950. The presence of abundant charred material in this cave indicates that they periodically obtained drinking water by using fire to melt cave ice, and sheds light on one of many human–environment interactions in the Southwest in a context when climate change forced growing Ancestral Puebloan populations to exploit water resources in unexpected locations. The melting of cave ice under current climate conditions is both uncovering and threatening a fragile source of paleoenvironmental and archaeological evidence of human adaptations to a seemingly marginal environment.

Highlights

The southwest United States has some of the best known and most conspicuous archeological sites in North America (Refs.[1,2] and Supplementary Information S1)
ELMA is located on the southeast edge of the Colorado Plateau (Fig. 1a) and is dominated by basalt flows originating from the Zuni-Bandera volcanic field (Supplementary Fig. S1)
We suggest that prior to Pueblo I people who left behind recognizable artifacts within ELMA, small groups of Basketmaker II and III utilized the cave seasonally for melt water for domestic purposes, while hunting or exploiting other resources but lived in communities in low land valleys of the Zuni area

Summary

Introduction

The southwest United States (hereafter the Southwest) has some of the best known and most conspicuous archeological sites in North America (Refs.[1,2] and Supplementary Information S1). Of the climate proxy records used to assess past precipitation and temperature in the southern Colorado Plateau, tree rings are among the most important[15,16]. They provide some of the most detailed studies on severe droughts and link Puebloan site occupation with periods of higher m oisture[13,14]. The use of fire by pre-contact populations to melt ice in the lava tubes was earlier suggested in ELMA17–19, to our knowledge, this is the earliest directly dated proof for in-cave burning practices to secure water in the Southwest. While this study focuses on a single lava tube, it illustrates a general methodological approach that links water resource availability with aspects of social variability caused by repetitive depopulation-repopulation of some settlement locations due to migrations across the landscape

Methods

Results

Discussion

Conclusion