PALL 2008

(3D-Render of Area)

After a season of materials analyses in 2007, fieldwork resumed at La Laguna in 2008.  This season marked the initiation of a multidisciplinary collaboration with researchers from UNAM.  Our primary goals for the season were to use remote-sensing techniques in the site center in order to register buried structures and cultural deposits.  We believe this was a responsible first step prior to excavations, since it gave us a familiarity of what to expect beneath the surface before putting a shovel in the ground.  Yet the methods also were extremely successful in quickly outlining the form of structures underneath the surface over a large area that would have required many months to learn through excavations only.  Remote-sensing techniques included aerial photography, magnetometry, ground-penetrating radar, and soil resistivity.  They were combined with limited excavations aimed at verifying the results of these methods and at recovering datable materials.  More information is provided by Barba et al. (2009).

Agustín, Jorge, and Mónica with ground-penetrating radar.

Aerial photos were taken over approximately 4.5 hectares of the site center using a captive, helium-filled balloon with an attached camera that could be operated remotely.  The site posed particular challenges to our efforts: especially trees that entangled the fishing line the balloon was tethered to; a breeze that picked up by late morning; and pointy maguey plants and horned cattle which threatened to pop the balloon if it got too low.  Nevertheless, the photos that we were able to capture provide a much higher resolution rendering of the terrain in the site center than is available through existing plane and satellite photos, in some cases highlighting mounds where buried structures are probable.

Luis taking aerial photos over a temple structure with remote-controlled camera on balloon.

Remote sensing by magnetic gradient was the most successful ground-based method, since the volcanic stone the inhabitants of La Laguna built with is easily detectable with a fluxgate magnetometer.  The method helped to define the I-shaped ball court to the east of the plaza, the limits and sunken nature of the rectangular plaza, and structures behind the large temple west of the plaza that are not immediately visible from the surface.  Ground-penetrating radar and electrical resistivity verified the architectural features detected by the magnetometer, but also provided data on the depth of walls, floors, and deposits.  These were very useful for planning excavations in 2009 as we knew how deep we needed to excavate in order to encounter cultural deposits.

Composite aerial photos draped over topographic map of site.  The central plaza is visible in the center, and the highest mound is at the top.  Missing areas are filled in using an image from Google Earth.

Limited excavations were also undertaken in 2008, focused on the system of retaining walls west of the ball court, in the center of the plaza (both as Area G), and on the smaller mound to the east of the plaza group (Area I).  The excavation of the retaining walls demonstrated that the site center was also artificially flattened for construction of the plaza and ball court, while the two units on top of the small mound showed that this public structure was also burned prior to the abandonment of the community.  A deposit of notched obsidian blades, greenstone, and shell was encountered on the floor of this structure, underneath the collapse of the superstructure.

Excavation of burnt deposits on floor of temple to the west of the site.

Greenstone, shell, and obsidian blades found on floor of temple to the west of the site.

Map of subsurface architecture and features in central plaza, made using magnetic gradient.