While debates have raged over the relationship between trance and rock art, unambiguous evidence of the consumption of hallucinogens has not been reported from any rock art site in the world. A painting possibly representing the flowers of Datura on the ceiling of a Californian rock art site called Pinwheel Cave was discovered alongside fibrous quids in the same ceiling. Even though Native Californians are historically documented to have used Datura to enter trance states, little evidence exists to associate it with rock art. A multianalytical approach to the rock art, the quids, and the archaeological context of this site was undertaken. Liquid chromatography−mass spectrometry (LC-MS) results found hallucinogenic alkaloids scopolamine and atropine in the quids, while scanning electron microscope analysis confirms most to be Datura wrightii. Three-dimensional (3D) analyses of the quids indicate the quids were likely masticated and thus consumed in the cave under the paintings. Archaeological evidence and chronological dating shows the site was well utilized as a temporary residence for a range of activities from Late Prehistory through Colonial Periods. This indicates that Datura was ingested in the cave and that the rock painting represents the plant itself, serving to codify communal rituals involving this powerful entheogen. These results confirm the use of hallucinogens at a rock art site while calling into question previous assumptions concerning trance and rock art imagery.

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Abstract:How can the utilization of newly developed advanced portable technologies give us greater understandings of the most complex of prehistoric rock art? This is the questions driving The Gordian Knot project analysing the polychrome Californian site known as Pleito. New small transportable devices allow detailed on-site analyses of rock art. These non-destructive portable technologies can use X-ray and Raman technology to determine the chemical elements used to make the pigment that makes the painting; they can use imaging techniques such as Highlight Reflective Transformation Imaging and dStretch© to enhance their visibility; they can use digital imagery to disentangle complex superimposed paintings; and they can use portable laser instruments to analyse the micro-topography of the rock surface and integrate these technologies into a 3-D environment. This paper outlines a robust methodology and preliminary results to show how an integration of different portable technologies can serve rock art research and management.

This paper deals with the documentation, and virtual visual analysis of pictographs using interactive relighting, digital image enhancement techniques and diagrammatic representations. It discusses areas of interest for the analysis of low surface detail, large and geometrically complex superimposed pictographs. The synergy of reflectance transformation imaging (RTI) and decorrelation stretch (DS) aimed to improve the study of superimposition via the enhanced visualization of the surface morphology, dominant features, paint characteristics and layering. Additionally, diagrammatic representations of the results of the image-based analysis provided a valuable tool for interpretation and integration of the diverse dataset from the ongoing research in the Pleito Cave in California. This method allows revisiting unresolved hypotheses concerning the site by unpacking chemical and visual data in superimposed sequences.

Abstract:The Native inhabitants of South Central California produced rock art containing red, orange, black, white, green and blue colours using a range of mineral and organic materials. Many of these same colours were used on material culture and body painting. This paper focuses on a sub-group of the Chumash, called the Emigdiano, who produced an enigmatic blue colour used in the creation of rock art. Here, we focus on the blue pigment at the rock shelter site of Three Springs in the Wind Wolves Preserve in South Central California. The composition of blue pigments has previously been the focus of discussion with suggestions that they were produced either using European pigments taken from Spanish missions, or that azurite from a local quarry was the source. Previous experimental work had demonstrated that it was possible for the blue to be produced from locally available azurite. Here we present the in situ analyses of these enigmatic blue pigments using handheld X-ray Fluorescence (pXRF). Results from pXRF analysis of rock art, quarried azurite samples and experimental rock art reconstructions showed that the Emigdiano Blue at Three Springs were not azurite based and was composed of optical blue (a mixture of black and white or grey materials which mimic the appearance of blue). This paper discusses the surprising implications of the use, given the availability of a 'true' blue pigment, and the wider ontological importance of combining multiple colours to produce the effect of blue in a rock art panel.