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THE GEOPHYSICAL STUDY OF BURIED ARCHAEOLOGICAL REMAINS
AND THE PRESERVATION OF THE ARCHITECTURAL PATRIMONY
OF MEXICO CITY
L. Barba
Laboratorio de Prospección Arqueológica
Instituto de Investigaciones Antropológicas, UNAM
Ciudad Universitaria, México D.F. 04510
barba@servidor.unam.mx
KEY WORDS: Geophysics, Archaeology, Architectural Patrimony, Mexico City
ABSTRACT:
Five years ago, the Archaeological Research Laboratory established a pilot project to study the archaeological remains buried under
the present surface of the Coyoacan and Churubusco neighborhoods in southern Mexico City. The structures that once were part of
these important pre-Hispanic settlements were destroyed and their remains have been covered by sediments through the years.
Nowadays, the differential sinking of the floor of the Basin of Mexico is producing a topographic relief just in the places where a
previous compaction of the sediments has taken place. Our team has proved that the best approach to study archaeological remains
under modem urban developments is the application of geophysical techniques. Top date, results from the study carried out at
Coyoacan have demonstrated that magnetic gradient, electrostatic resistivity and earth penetrating radar are the best geophysical
techniques to locate and study buried archaeological structures avoiding any damage to the surface. Some studies have reached the
Churubusco neighborhood where some ceremonial and domestic structures were excavated. The same kinds of studies can be applied
to the whole of Mexico City. The long-term goal is to produce an inventory of the location of buried archaeological remains underneath
the city’s pavement to prevent any damage caused by the construction of modern private buildings or public urban structures. Besides
this evident function, we have observed that many problems affecting the stability of the structures included in the inventory of the
city’s heritage are closely related to the existence of archaeological remains underneath them. This is especially dangerous during the
seismic events the city frequently experiences. The main contribution of this project is to provide information to locate, evaluate and
preserve the buried archaeological remains and the patrimony that is part of the modern city.
1. INTRODUCTION
In some locations in Mexico City its surface appears rippled,
irregularities that are not evident in photos and drawings from
the turn of the century. This is associated to two origins: Location
of pre-Columbian settlements and the recent sinking of the city.
At the Anthropological Research Institute’s Archaeological
Prospection Laboratory a project is under way to systematically
study archaeological sites so to make an inventory to work in a
city where the predictive aspects are hard to consider. The
difference between geotechnical properties in pre-compacted soils
in relation to their environs has been remarked recently with the
intensification in the city’s rates of sinking. This differential
affectation can be seen in the re-accommodation and fractures
both on the surface as well as on the buildings. The speed with
which water is being extracted from the city’s subsoil ensures
that this process is unstoppable and the sinking will continue
thereby worsening the phenomenon. In this sense, studies will
enable us to locate most damaged areas and to explain the causes
that produce them.
In the present paper we resort to the geotechnical properties of
pre-compacted soil in respect of their environs, which are causing
differential sinking. The hypothesis under study is that if these
differences represent changes produced by human settlements,
then, archaeological sites covered by modern urban settlements
can be recognized and studied from the surface, using geophysical
techniques.
2. CARTOGRAPHIC BACKGROUND
To determine the approximate localization of sixteenth century
human settlements, we studied ancient maps of what used to be
the lake zone and its association with the present day city.
Furthermore the toponyms were analyzed for they indicate the
presence of ancient settlements. It’s surprising how many nahuatl
toponyms are still extant and can be seen in modern maps, in the
names of alleys, streets, neighborhoods and the like.
Sixteenth century maps show a recently rebuilt Mexico City with
some islets surrounding the center of the former Mexico-
Tenochtitlan. In the Cortez Map, chinampas are vaguely depicted
as concentric alignments surrounding the main settlement. The
Uppsala Map doesn’t pay much attention neither to the islet nor
to the chinampas, since it only identifies Iztacalco. Recently, the
map drawn by González Aparicio (1973) and published in a
modified fashion by thq Arqueología Mexicana magazine (1995),
shows the location of several islets built on the western part of
the Texcoco Lake. Sites of potential pre-Hispanic settlements
appear to be concentrated in a space spanning the western
lakeshore and the San Lázaro dyke, and between Tepeyac and
Culhuacán as well.
These maps show that the western part of the lake was the least
deep. This might have been the consequence of the buildup of
sediments coming from the Sierra de las Cruces range. Therefore,
this zone was the most likely to be settled, since its shallowness
