Petroglyphs in Petrified Forest National Park: Role of Rock Coating in as Agents of Sustainability and as Indicators of Antiquity

Rock coatings formed on petroglyphs at Petrified Forest National Park both preserve the art from erosional processes and provide tools to understand the art’s chronology. Erosional processes of rock fall from fissuresol wedging, splintering of sandstone, and flaking are somewhat offset by case hardening surfaces by addition of rock coatings. 20th century graffiti can be distinguished from truly ancient petroglyphs by lead-profile dating. Microlaminations dating reveals that park engravings range in age from at least the early Holocene prior to about 8000 yr B.P. to the late Holocene in the last 2000 years. The next step in the research process is to utilize a Rock Art Stability Index to identify those panels in the greatest danger from loss through erosion, and then use available methods to record and sample petroglyphs to preserve knowledge while we can.