Marian Hyman

Direct Radiocarbon Dating of Rock Art

In 14C dating of pictographs, we use a low-temperature oxygen plasma coupled with high-vacuum techniques to selectively remove carbon-containing material in the paint without contamination from the rock substrate, even if limestone (CaCO3). In addition to one previously published measurement, we analyzed two more pictograph samples, which are in accord with archaeological inference. A sample of known age charcoal, also processed by our method, matched the control. This technique produces little mass fractionation, the maximum 813C being 0.16%o from the untreated sample. Limestone decomposition does not occur during our procedure. Although the technique development is in its infancy, these new results demonstrate that our non-destructive technique has great potential for producing accurate 14C ages.

Ams radiocarbon dates for charcoal from three Missouri pictographs and their associated iconography

This report presents four radiocarbon dates of charcoal pigments from Picture Cave, a site located in a remote wooded area in east-central Missouri. Carbon from charcoal pigments was extracted from three rock drawings on the wall of this cave. The four pigment samples contained sufficient carbon for accelerator mass spectrometric radiocarbon analysis. These black pigment samples (red and white paints are also present in the cave) yielded dates that place their affiliated motifs in a time-frame associated with Cahokia ca. 950 years ago. The dates are somewhat earlier than expected. We discuss the dates in connection with the iconography of the three motif panels tested.

14C dating of ancient rock art: A new application of plasma chemistry

We have developed a new statically operated oxygen plasma method that allows direct14C dates to be obtained from ancient rock paintings. The method is applicable even to paintings on limestone (CaCO3) walls. A sample of a pictograph which had naturally spalled offa shelter wall in the Lower Pecos region of Texas was subjected to a low temperature (∼ 150°C) oxygen plasma to selectively remove the organic carbon-containing material used in the paint as CO2, without contamination from the limestone substrate. The Zürich EHT accelerator mass spectrometer was then used to determine the radiocarbon age of this prehistoric rock painting. It was successfully dated at 3865 ± 100 years BP, in good accord with the archaeological context which has set the onset of this Pecos River style of pictograph between 4100 and 3200 years BP. The method appears feasible and is applicable to rock art in which organic materials were used in the paint.

Rock-art image in Fern Cave, Lava Beds National Monument, California: not the AD 1054 (Crab Nebula) supernova

The visual manifestation of the recent Hale-Bopp comet reminds us how telling are those rare objects which suddenly flare in the sky. One can suppose ancient people living by natural light were more compellingly struck by the sight of comets and supernovae, and understandably researchers seek images of them in the shapes of rock-art motifs. An absolute dating contradicts that supposition in respect of a presumed image of the visible supernova of AD 1054.

Dating a Pictograph in the Pryor Mountains, Montana

We have dated a sample of red paint taken near an anthropomorphic pictograph in Elk Creek Cave in the Pryor Mountains, Montana. The radiocarbon date obtained, 840?50 years BP, is in agreement with expectations based on archaeological inference.

DATED ROCK PAINTINGS AT RED CLIFFS, ARIZONA

ABSTRACT This article presents radiocarbon dates for painted motifs at Red Cliffs, west of Sedona in the northeastern corner of Yavapai County, Arizona. All rock painting shields at the Red Cliffs sites have usually been attributed to the Sinagua. Black pigment from one shield motif and an overlying white dot on another motif yielded uncalibrated radiocarbon dates of 1080 and 550 years B.P., respectively. The black pigment sample dates to a time when the region was extensively used. Assuming that the two shields were painted contemporaneously, the age of the white dot sample suggests that a later cultural group altered Sinagua paintings at Red Cliffs after the Sinagua abandoned the region.