Joint work between experts from the National Institute of Anthropology and History (INAH) and the National Archaeomagnetic Service (SAN) of the UNAM revealed two lime kilns in Monte Albán, Oaxaca, which were key to its construction and represents a fundamental piece to complete the building map of the archaeological site.
Avto Goguitcghaichvili, head of the SAN, and Nelly M. Robles García, from the INAH Center in the state, emphasized that although these artifacts have been widely documented in the Maya area (Merida and surrounding areas), this is the first time they have been found in the Zapotec region, which means the use and appropriation of an essential technology to build a city.
"The finding of lime kilns in Monte Albán is important since they had not been registered in previous investigations and they are linked to the technology of construction in Mesoamerica, defining the materials used by the Zapotecs who inhabited the site," commented Goguitcghaichvili.
The first was dated between 1076 and 1321 A.D., while the second was between 713 and 883 A.D., coinciding with the last period of construction and the abandonment of Monte Albán.
In Mesoamerica, the production of lime is evidence of a complex technique, as well as controlled methods to burn limestone rock, which refers to artisans who had the necessary knowledge to manage and control the fire, the amount of fuel to be used, and the time to expose these materials.
Lime is known to have been manufactured since the Neolithic period and in Mesoamerica. The Archaeomagnetic Service has reviewed for five years buildings that produced it in the Mayan area but, until now, no kilns had been found that evidenced its manufacture in the South Pacific area of the country.
Monte Alban, considered Cultural Patrimony of Humanity since 1987, has been studied since the 1930s by experts such as Alfonso Caso, and in the great rock buildings we see today it is known that the interior was erected with rocks, earth, and lime, but until now the origin of this last material was unknown.
"With the presence of these ovens today we know that the lime was burned right there, from the limestone stones in the hill of Monte Albán and that is a great discovery because it allows us to almost see the construction process worked with a lot of labor and primarily local materials, which is a very interesting advance to understand the processes of massive construction," explained Robles García.
The discovery was made by INAH as part of the conservation project of the buildings damaged by the 2017 earthquakes in Monte Albán and Atzompa, which offered the opportunity to free and restore a possible sidewalk in building P of the site, where moisture was harmful to the site had been detected.
It is a Zapotec temple that, in a way, summarizes the architecture of the site, since its construction began in the Early Classic period and faced several stages of renovation until the abandonment of the space, approximately 800 or 900 AD. During the maintenance processes carried out in these buildings, limestone rocks were found arranged forming a circle of 2.05 centimeters (cm) in diameter at a depth of 35 cm, architectural evidence.
The studies carried out by the Archaeomagnetic Service showed that these structures withstood high temperatures in the past, which refers to a standardized and specialized process of lime production in the Zapotec state. Archaeomagnetism is a dating technique based on the existence of certain components of archaeological materials (especially ferromagnetic) capable of registering the variation (in time and space) of the earth's magnetic field, so the result is the last burn.
In the case of Monte Albán, it is not known when the technique arrived, but it can be affirmed that the first furnace was still in use between 1076 and 1321 A.D., that is, the last period of construction and abandonment of the site. Of the two structures, the second is smaller, but the evidence indicates that its use may be related, especially, to the priestly class that managed and controlled the construction works, as well as the use of urban and living spaces.
Due to the dates in which they ceased to be used, specialists suggest that the production of lime was marked by the productive dynamics and changes in the political-economic controls in Oaxaca, after its splendor. The Archaeomagnetic Service continues its collaboration with Robles Garcia's team in the Atzompa area, where burnt materials are being reviewed and particular mineralogy was found and is being analyzed, as well as ceramics and traces of burns in the area.