Caracterización espacial de un paisaje de extracción prehispánico: el yacimiento de dacita de Las Minas, Zacapu, Michoacán
Résumé
Dacite, a volcanic rock with high silica composition, was a strategic resource for the ancient inhabitants living in the lacustrine basin of Zacapu (Michoacan), between 100 b.c. and a.d. 1450. It was used to make a diverse range of artifacts for subsistence, craft, and ritual activities. Our research started in 2011 at the Cerro Vicente deposit and unexpectedly revealed that dacite had been intensively exploited through well-organized quarry-workshops as complex as those developed for obsidian (Darras et al. 2017). In 2015, another important mining complex was identified, thanks to a LiDAR survey, on the dacite lava flow known as Las Minas. This article aims to demonstrate how the use of LiDAR data, combined with other information sources (field survey and mapping, quarry and workshops areas characterization, and stratigraphic excavations), provides a powerful tool to investigate dacite exploitation strategies. The application of LiDAR technology in such a context makes it possible to acquire a complete and integrated assessment of a mining complex and thus to discuss the quarry landscape concept defined by Bloxam and Heldal (Bloxam et al. 2007; Heldal and Bloxam 2008; Stöllner 2003, 2008, 2014). The site of Las Minas (Mich. 428) is located on a lava flow northwest of the Zacapu basin, which is integrated into the Middle Pleistocene Las Flores volcanic dome complex (Reyes-Guzmán et al. 2018; Siebe et al. 2014). To understand the mechanisms of anthropic dacite exploitation, different scales of spatial analysis were carried out to characterize the evidence linked to mining and workshop activities. Four complementary steps were followed. First, topographic anomalies potentially related to mining activities were methodically identified on the LiDAR image; these were then verified in the field through a systematic survey covering the entire site. A thorough surface study was then conducted in order to classify the different production modules of the Las Minas site and to understand their spatial organization and interconnection. Finally, three extraction units were chosen for further surface analysis and excavation. The mapping and inventory of the archaeological evidence revealed an extension of 40 ha organized in six areas, which were regrouped in three functional entities: (a) exploitation zones dedicated to mining and workshop activities: 71 extraction units registered; (b) the areas with agricultural terraces; and (c) those with an architectural complex. Results highlight that open-pit mining was the principal extraction method, as evidenced by depressions, trenches, and extraction fronts that were implemented to take advantage of the surficial and/or shallow deposits. However, the need for high-quality raw material also resulted in the digging of subterranean mines, in the form of horizontal galleries. Fieldwork suggests that these mining activities were mainly developed during the Epiclassic period—that is, a.d. 600–900. The combination of these different approaches allowed us to glimpse the spatial organization of the activities at different scales carried out at the site of Las Minas. To achieve our objectives, the high-resolution digital elevation model obtained from the LiDAR data was a fundamental. However, the information provided by the LiDAR image was fragmentary and needed thorough ground-trothing fieldwork to be completed. For example, surface extraction and workshops areas were identified only through surveys and excavations. These complementary methods helped to visualize the site of Las Minas as a pre-Hispanic quarry landscape. The coexistence of well-structured exploitation areas with architectural complexes and agricultural terraces reveals that dacite was part of a composite socioeconomic system and was clearly integrated into a broader regional network.
En la cuenca lacustre de Zacapu a lo largo de su ocupación prehispánica (100 a.C. a 1450 d.C.), la dacita, una roca de origen volcánico, fue un recurso estratégico dentro de la economía regional, con el cual los antiguos habitantes de la zona elaboraron una serie de artefactos líticos ligados tanto a actividades de subsistencia y artesanales como rituales. Las investigaciones iniciadas en 2011 en dos minas-taller del yacimiento de dacita del Cerro Vicente expusieron una explotación extensa y organizada en torno a este recurso. En 2015, a partir de la cobertura LiDAR, se identificó un tercer complejo minero con evidencias de una explotación a cielo abierto y subterránea, esta vez en el yacimiento de Las Minas. Con el fin de comprender los mecanismos de explotación de la dacita, se ha llevado a cabo un análisis espacial de este sitio con distintas escalas de aproximación, para caracterizar las evidencias materiales vinculadas con la actividad extractiva. La combinación en nuestra investigación de la información que aporta el LiDAR y la proveniente de la prospección en el campo, nos ofrece un panorama completo del yacimiento, su organización espacial y funcional en un contexto más amplio como un paisaje prehispánico de extracción.
Domaines
Sciences de l'Homme et Société
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