The 2013 UWM Archaeological Field School at Aztalan

The 2013 field school was planned to obtain additional information on site chronology, focusing on the construction of the northeast mound, initially excavated by the Wisconsin Historical Society during the 1960s. UWM’s work was aided by Thomas Zych’s (2013) reporting and analysis of the 1960s WHS.




Excavating backfill and plastic sheeting to expose WHS profile walls in the Northeast Mound

Section in the Northeast Mound


Test Units 14 and 17 overlapped the WHS 1968 large excavation block. Initial excavations in this area exposed decomposing plastic sheeting placed to protect the WHS excavation walls. Removal of approximately 7.7 cubic meters of backfill exposed 4.5 meters of standing profile. Below the plowzone, the north and west walls of this unit exhibit a complex fill sequence of approximately 1.6 meters of alternating light and dark sediments. Below this, a prepared clay floor 10-12 centimeters thick was constructed over the sandy clay subsoil. Two shallow basins containing fired sediments were exposed in the prepared floor. Feature 15 was AMS dated to cal A.D. 1040-1220. Feature 18, contained burned animal bone that was dated between cal A.D. 1040-1220.

The 2013 season also revisited the copper working locale (Feature 8) exposed in 2011.


Crossection of bastion postmolds

Barrett’s map georeferenced to the UWM excavations

Excavation of the remainder of Feature 8, identified in 2011, produced additional examples of sheet copper and a variety of pottery. In addition, a series of circular soil stains were identified as postmolds. Barrett partially excavated and mapped these features in 1919, identifying them as part of a bastion attached to the riverbank palisade wall. Wood charcoal from a burned bastion post (Feature 13) was radiocarbon dated to cal 1220-1290 and may date the abandonment of the site.

The 2013 UWM field season at Aztalan produced radiocarbon and stratigraphic evidence to support the argument that the Northeast mound was constructed soon after the appearance of Middle Mississippian traits at the site. Investigations in a palisade bastion indicate that palisade construction occurred sometime after the introduction of Mississippian pottery. Charred posts within the bastion may date the abandonment of the site late in the 13th century A.D.