J. Jacob Parnell and Dr. Richard E. Terry

In the 1930’s, O. Arrhenius was contracted by a Swedish sugar beet company to test soil fertility levels for fertilizer applications. While testing a specific area, he realized a peculiar occurrence associated with phosphorus levels and an area of ancient habitation. Since that time, other studies have been completed on the relationship between the chemical signatures left in the soil and their relationship to activities of ancient inhabitants. The procedure of determining phosphate concentrations has been used to help delineate site boundaries, indicate agricultural areas, and interpret activity areas.

The logic of the association of phosphate and these areas lies in the phosphorus cycle. Small amounts of phosphates are naturally found in the soil. Plants extract the soluble forms of phosphate. When the plants are harvested and transported, the phosphates become relocated with them. As the plants in the form of organic garbage (sewage waste or food remains) decompose, the phosphates become readily sorbed on the surface of the soil particles where they remain for centuries. Thus leaving the area from which the plant was harvested depleted in phosphates with relation to the normal background level while the phosphate concentration of the area where of compost is increased. Areas such as backdoor gardens, latrines, and middens would show increased concentrations and areas of intensive agriculture that did not benefit from the enrichment of decomposing plants or remains would have lower concentrations. These differences in the chemical concentration can then be read, mapped, and interpreted according to results of ethnographic studies.

Piedras Negras is a Classic Maya city located on the eastern bank of the Usumacinta River in the northwestern concession of the Petén rainforest of Guatemala. Piedras Negras is very important because it is well documented in Mesoamerican archaeology for its architecture as well as epigraphy. Late in the history of Piedras Negras, the city was slowly abandoned leaving a succession of squatters inhabiting the once glorious city. The gradual abandonment of Piedras Negras brought about a displacement of artifacts from their original location, thus making the interpretation of activity areas more complex.

In 1997, Dr. Stephan Houston of Brigham Young University and Hector Escobedo of the Universidad del Valle began a planned five-year study of this Classic Maya city. Our archaeological investigations have included expansive excavations in more modest, non-elite structures at the site. Some, such as the N/O sector, are hypothesized to have served as service areas for the royal palace of Piedras Negras (Houston et al. 1999). The project has focused its sampling efforts on numerous residential areas within the city. To date, excavations in these locations have produced data on household size and composition through the excavation of human burials, production activities revealed by artifact distribution, and residential growth documented by the construction stages of domestic buildings.

In 1997, Dr. Richard Terry developed an analytical method (Terry et al., n.d) for measuring the extractable phosphate concentrations in the soils of Piedras Negras. As an ORCA project, we collected approximately 2000 soil samples throughout the Piedras Negras valley and used this method to determine the phosphate concentrations.

In April of 1999, I flew to Villahermosa, Mexico, where Mark Child, the project camp director was waiting. We got in a taxi that same night and drove about three hours to the small city of Tenosique. Early the next morning, we took another taxi to the pueblo of Corregidora Ortiz, on the Mexican-Guatemalan border. After about four hours and twelve miles of hiking on the trail through the rainforest, we reached Piedras Negras, my home for the next five weeks.

After setting up the soils lab in a large tent, I began taking soil samples. Samples were taken on a grid using a tape measure and a compass. We found this to be most effective because of the low visibility due to the undergrowth. The first area I sampled was the patio around an ancient sweatbath. The archaeologists wanted to know what kind of activities had been taking place there. Once they had cleared the inside rooms of the sweatbath, I sampled the floors (0-6 cm). The results from these samples were very good, so we decided to do the same thing with two other sweatbaths. We are currently working with the archaeologist (from Yale University) on writing a publication on the results that we are finding.

Another archaeologist was working on a small platform that was about a twenty minute hike to the north of the city center. This site was riddled with crypts and proved to be interesting to the archaeologists. Just to the south of this platform was a group of mounds. We decided to test the soil chemical analysis as a means of prospecting in this area. We took samples on a grid and analyzed them in the lab there in the camp. Once we had the results, we dug several test pits in several different locations. Two test pits were dug in each of three different levels of phosphates; high, medium, and low. Preliminary results of this study have been very positive. There was a positive correlation between the phosphate concentration and the density of ceramic sherds. With these positive results, we decided to use the P analysis as a prospection tool. One of the advantages to prospection is the time that is saved in excavating. At Piedras Negras there is a relatively short field season due to the heavy rain in the wet season. Prospecting gives the archaeologist an idea of the activities that took place in a certain site. Using the patterns of activity, they can orient their excavations for higher efficiency. We took prospection samples of five other sites that we will analyze and use to help next season’s excavations. I am now starting a master’s program in the department of Agronomy and my focus will probably be in this area. I will probably do a statistical analysis of the chemical patterns and their association with artifact density.

We recently finished an article that will appear sometime this year in Journal of Archaeological Science. The focus of this article was the chemical patterns of areas that were already excavated. As I mentioned above, the activities of the ancient inhabitants leave behind chemical patterns. In this case, those patterns help us to determine what was being done in each room. We took samples of a house group and analyzed them for phosphorus and heavy metals. We discovered where the ancient Maya were dumping their garbage, where they were doing craft, and we were also able to see the signs of possible paintings on the walls (Wells et al. n.d.). In all, over one thousand soil samples (Houston et al. n.d.) were collected and analyzed with the help of Fabian Fernandez, Anahi Fernandez and Ben Crozier.

Next year I will be giving a presentation at the XIII symposium of archaeology in the national museum of anthropology in Guatemala City, Guatemala, on the results we have been finding. This summer, Dr. Richard Terry was awarded a substantial grant from the National Science Foundation to continue research of the chemical analysis of these soils used anciently. I would like to thank the ORCA scholarship program for the help they have given for us to start this research that has moved on to a new sphere.

REFERENCES

• Houston, S., H. Escobedo, P. Hardin, R. Terry, D. Webster, M. Child, C. Golden, and D. Stuart. 1999. Between mountains and sea: Investigations at Piedras Negras, Guatemala, 1998. Mexicon.
• Houston, S. D., H. Escobedo, R.E. Terry, D. Webster, G. Veni, and Kitty S. Emery. 2000. Among the river kings: Archaeological research at Piedras Negras, Guatemala. Mexicon (submitted).
• Terry, R.E., P.J. Hardin, S.D. Houston, S.D. Nelson, M.W. Jackson, J. Carr, and J.J Parnell. 1999. Quantitative phosphorus measurement: A field test procedure for archaeological site analysis at Piedras Negras, Guatemala. Geoarchaeology (submitted).
• Wells, E.C., R.E. Terry, P.J. Hardin, J.J. Parnell, and S.D. Houston. 1999. Chemical analyses of ancient antrhosols at Piedras Negras, Guatemala. J. Archaeological Science (in press).