WESTERN ARCHAIC PETROGLYPHS AND THE PERSISTENCE OF WATER SOURCES IN BEARS EARS NATIONAL MONUMENT, SOUTHEASTERN UTAH

On December 28, 2016, President Barak Obama created Bears Ears National Monument on 1.35 million acres in southeastern Utah, primarily to protect the archaeological heritage of the Basketmaker (0-700 AD) and Ancestral Pueblo (700-1300 AD) cultures. One of the primary archaeological questions in the Bears Ears area is the cause of the migration of the Ancestral Pueblo from southern Utah and the Four Corners region to the Rio Grande valley of New Mexico about 1300 AD. Climate change, especially long-term drought, is often invoked as a cause, but understanding migration involves combining the occurrence of climate change with the resilience of the ecosystem and social system. Other studies have focused on social inequality and the investment in non-productive infrastructure as elements of a non-resilient social system. The objective of this study has been to assess the resilience of the ecosystem in the Bears Ears area, specifically the persistence of groundwater sources in the event of a long-term drought. The objective has been addressed by collecting water samples from 36 springs and measuring stable isotope compositions and concentrations of the anthropogenic gas CFC in order to determine the sources and residence times of groundwater. Stable isotope compositions indicate that 46% of springs are recharged by fall rains, 36% are recharged by snowmelt or spring rains, and 17% are recharged by late summer monsoon rains. Analysis of CFC concentrations indicate that groundwater residence times range from 24-69 years, with 33% of springs having residence times exceeding 50 years. The above results suggest an exceptionally resilient ecosystem, in which numerous groundwater sources would persist even after a half-century of severe drought. Moreover, a pattern is emerging in which characteristic petroglyphs seem to be associated with more persistent (residence time > 50 years) springs. These petroglyphs belong to the Glen Canyon Linear Style that was created by the Western Archaic culture and may date as far back as 6000 BC. Characteristic elements of these petroglyphs include concentric circles or spirals, plant motifs, snakes, mountain sheep, deer, and rabbit-eared anthropomorphic figures. The significance of a persistent groundwater source as a venue for art-making will be discussed at the meeting.