Chemical characterization of the organic material in rock paintings is an important new direction in directly determining the age of such artifacts. Using plasma-chemical oxidation and accelerator ...mass spectrometry, radiocarbon dates (6250–5550
cal
b.c. and 1500–900
cal
b.c.) were obtained for two red-pigmented pictographs from La Casa de Las Golondrinas, the largest recorded rock art site in the Guatemalan Highlands. While the dates fell within or near the 6000-year span of human activity at the site, plasma-chemical oxidation yielded significant amounts of carbon from the unpainted tuff samples that were collected for comparison with the paint. The presence of organic material not related to the paint will render a radiocarbon date irrelevant at best. Qualitative analyses using thermally assisted hydrolysis/methylation (THM)-GC–MS were undertaken to clarify the nature of the organic matter in these paint samples from Guatemala and to determine if any binder could be identified in the paint samples. Results of the analyses show only small differences in composition between the paint samples and unpainted substrate. The older date is not related to a binder, but more likely to humic acids derived from soil organic matter that were not removed by the standard chemical pretreatments; that date, then, should not be considered anthropologically relevant to placing the painting activity in time. The results demonstrate the importance of collecting both appropriate substrate and paint samples for any attempt to date rock art. The THM-GC–MS method we describe has demonstrated excellent potential as a rapid screening method for the comparison of substrate and paint samples to determine which ones have the best chance of yielding a reliable direct radiocarbon date.
A conserved painting removed from a Neolithic collective grave in Marne, France, provided an opportunity for radiocarbon dating to place Les Ronces Hypogeum 21 (Villevenard) into the chronology of ...that region. Chemical analysis with direct analysis in real time (DART) mass spectrometry, Fourier transform infrared (FTIR) spectroscopy and gas chromatography-mass spectrometry (GC-MS) of samples from the painting revealed the presence of two kinds of wax (beeswax and paraffin or microcrystalline wax) that likely were added during the conservation, a drying oil like linseed oil, as well as markers of pine resin that may arise from turpentine or colophony. A new pretreatment protocol of chloroform followed by pH 8 phosphate buffer was developed, which yielded sufficient material for plasma-chemical oxidation and AMS radiocarbon dating. The radiocarbon dates place the image from Hypogeum 21 at the more recent end of the chronology that spans from the sixth to the third millennia cal BC for the Neolithic in France.
Abstract
Examination of fibers from a colored fabric fragment from Seip Mound Group, Ohio, demonstrates the utility of sequencing analytical techniques: (1) minimally destructive pretreatment to ...remove humic acids followed by plasma-chemical oxidation, in preparation for accelerator mass spectrometric determination of radiocarbon age and (2) direct analysis in real time mass spectrometry (DART-MS) of the pretreatment solution, for the determination of red colorants. Pretreatment followed by plasma-chemical oxidation provided the opportunity to date 3 mg of fiber using just 200 mcg of carbon. Examination of the pretreatment solution by DART-MS confirmed the composition of anthraquinones consistent with those from bedstraw root (Galium sp.). The date determined (1,805 ± 35 B.P.) places the textile in the midrange of radiocarbon dates previously obtained for the Seip earthworks; identification of the dye plant shows that the Hopewell possessed a sophisticated knowledge of plants and their uses.
Cueva la Conga, recorded in June 2006, is the first limestone cave in Nicaragua reported to contain prehistoric rock paintings, culturally modified natural formations called speleothems, and ...artifacts. Located in northcentral Nicaragua in the Department of Jinotega, Cueva la Conga is the farthest south on the Mesoamerican periphery that a cave of this type has been reported, and it extends our knowledge of ritual cave use, including cave painting and speleothem modification, to include Nicaragua. Radiocarbon analysis of charcoal in five samples of the paint, the first such dating of Nicaraguan rock art, yielded calibrated dates from cal A.D. 680—905 to cal A.D. 1403—1640. The baseline data provided by Cueva la Conga are of great importance for regional rock art analysis and for our growing understanding of regional and Nicaraguan prehistory. More archaeological survey and excavations in the area will be key in establishing a firm cultural context for the rock art and ritual cave use found at Cueva la Conga.
A black, shiny coating overlies rock paintings in Little Lost River Cave No. 1, located in southeastern Idaho. If this coating is the result of human activity within the cave – a condensate from ...cooking fires, for example – then a radiocarbon date on the coating would provide a minimum age for the underlying paintings. The work reported here was undertaken to test the assumption that the coating has an anthropogenic origin. Using pyrolysis-gas chromatography–mass spectrometry (py-GC–MS) and thermally assisted hydrolysis-methylation-GC–MS, we have compared samples of the black coating from Idaho to humic acid, an experimental cooking residue, and amberat from packrats. The results show that the coating is not amberat, but bears the most similarity to humic acid, which would indicate a geologic origin for the coating. The age of the coating, then, is not likely related to the age of the paintings.
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