Ceremonial structures like the 5,000-year-old temples I have been investigating at Huaricanga are marvels to behold. Often such buildings are well-maintained and represent the dedicated effort of ancient individuals who invested considerable time and materials in their construction. Walls and doorways tend to have elaborate decorations as well. When discovered, temples and churches receive quite a bit of attention from public media. For the field archaeologist, however, ceremonial architecture can be a pain in the butt. By its very nature, religious structures tend to lack any evidence of the activities that took place within them. Consider, for example, a contemporary church. Indeed it would be quite unusual to see domestic trash inside the walls of a place of worship. Culturally specific norms of sacred purity tend to forbid the accumulation of “unclean” remains within holy spaces resulting in a lack of artifacts in ceremonial contexts. Unfortunately, archaeologists rely on trash to interpret the past. Therefore, archaeologists need unconventional methods to reconstruct ancient ritual activities.
Modern scientific techniques available at the Field Museum can remedy the situation. The Huaricanga Archaeological Research Project (HARP) is one of the first projects in the Andes to utilize X-Ray Fluorescence (XRF) to reconstruct ancient religious rituals. XRF involves the use of X-Rays to penetrate a substance and excite the electrons within it. This electron “excitement” can be measured in parts per million for individual elements. XRF is often used to source ceramics or volcanic glass as individual clay or obsidian sources will have their own particular elemental signatures. This technique of measuring signatures can also be applied to archaeological surfaces.
All human activities leave residues. Take, for example, a coffee stain. Although you may be able to wash out the chai latte from your shirt, that liquid still leaves a material trace, a change in the elemental composition of the shirt that cannot be erased. This trace, however, can be detected using XRF.
During my archaeological fieldwork last year, I sampled a variety of temple floors for XRF analysis. This involved systematically scrapping off the uppermost layers of each floor with a clean trowel every 50 cm. Samples were taken across a single surface and between surfaces in order to look at rituals synchronically and diachronically. The bits of floor were placed in small baggies, labeled, and exported to the U.S. for analysis (see picture below).
With the help of Elise Blindauer (an undergraduate at the University of Illinois-Urbana/Champaign), I was able to analyze over 200 samples using the XRF device at the Field Museum’s Elemental Analysis Facility. Raw results were statistically cleaned and then separated according to their sampling location on the floor (GPS coordinates were taken with a Total Station). Elemental enrichment levels were coupled with their locations and plotted using GIS to create maps per element.
While it is obvious that the elemental concentrations are not consistent across single surfaces or over time, what these maps ultimately mean is a bit tricky. Since this is a new technique, interpretation is difficult. In Aztec temples, for example, areas with a high concentration of iron suggest that animals were sacrificed there since iron is a major component of blood. Other archaeological projects have clearly associated phosphorous with the use of plant remains. At Huaricanga, such interpretations will take time, but such is the difficulty in using cutting edge technology. I have attached a few slides in PDF form so that you can see some preliminary results. Stay tuned for more!