A Contextual Study of the `Fossilized' Prehispanic Canal Systems of the Tehuacan Valley, Puebla, Mexico
Neely, James A., Antiquity
Nearly three decades ago, Woodbury & Neely (1972) published the first analysis of the extensive and complex system of Prehispanic canals found in the northern portion of the Tehuacan Valley of Puebla, Mexico. These springfed canals, functioning to supply waters for irrigation and domestic uses, were uniquely preserved in near entirety by natural processes. The canals have been `fossilized' in place through a process of mineral deposition. They are clearly visible on the landscape for many kilometres and have aggraded in height, now standing 2 to 3 m high in several places. Tune, funding and the archaeological methodology of the mid 1960s limited Woodbury & Neely's fieldwork, and therefore the study did not fully investigate the system. Although a basic description and discussion of the technology and functioning of the system was accomplished, a detailed analysis of these aspects remained to be done. A schematic mapping of the system was accomplished, but an accurate mapping of the canals and associated habitation and administrative sites was lacking. The chronological placement of these canals was attempted by means of the cross-dating of ceramics on archaeological sites found bordering the channels, but an accurate chronological sequence of the system's development was not attainable. A general climatic reconstruction of the valley was generated, but since the emphasis placed by the Tehuacan Archaeological and Botanical Project was on the earlier periods of habitation that focused on the development of maize domestication, the climatic contexts into which the canals were later constructed was not known.
A recent fact-finding pilot project conducted by the author resulted in the discovery that organics had been trapped in the stratified canal layers. The presence of these organics revealed a potential to accurately and precisely date the canals through the use of radiocarbon assay. A cleansing process was then devised to remove the travertine, calcium carbonate and related minerals that would skew radiocarbon samples to date much earlier than the time of canal use. Cleansed test samples TX-7917, TX-8088, TX-8133, TX- 8255 and TX-8297 produced corrected and calibrated liquid scintillation dates of AD 441,408 BC, 300 BC, 33 BC and 777 Be, respectively. The dated organics were also found to contain large quantities of well-preserved pollen, phytoliths and diatoms. …