In the spring and fall of 2010, Dr. Chester Walker of Archaeo-Geophysical Associates, LLC, accomplished the largest-scale magnetometer of a Mississippian site to date. He covered almost 60% of the Moundville site, including the entire plaza and almost all of the mound summits, in only ten days by towing the magnetometer array by ATV. Hundreds of magnetic anomalies representing ancient hearths, house walls, and other archaeological features manifested in shades of gray throughout the survey area, including the under-investigated and poorly understood plaza. Some anomalies appear to represent circular and rectangular buildings far larger than anything previously known at Moundville.
We cannot know for sure what the magnetometer detected until a sample of the anomalies has been excavated. This is called “ground-truthing.” For example, if we suspect that fuzzy, dark gray dots in the magnetometer survey map represent the locations ancient hearths, we must excavate at the locations of several “dots” to confirm. Since May 2011, I have been supervising University of Alabama field school students and volunteers in the ground-truthing of suspected hearth and building wall anomalies. I am pleased to report that with the help of the magnetometer map, we have been able to pinpoint specific kinds of ancient remains with an accuracy that is unprecedented in the history of archaeological investigations at Moundville.
In the process, we have learned a bit about the pre-plaza surface. The evidence suggests that it was a ridge-and-swale landscape that was frequently if not always flooded in places. We can tell this by comparing the soils layers encountered in each of the excavation units. Some of our units struck culturally sterile subsoil, a reddish clay, immediately under the 10-20 centimeter thick plowzone layer. This soil is typically encountered at deeper depths and below other natural soil horizons. Subsoil at such a shallow depth and without any overlying natural soil layers is evidence that the Early Moundville people stripped off the high points of the natural landscape in their construction of the plaza. Excavation units elsewhere in the plaza encountered up to a meter of redeposited soil overlying natural strata. At one location, we found this fill layer overlying clays that only form in anaerobic, swampy conditions.
Building remains, sherds (pieces of pottery), and other ceramic objects hint at local cultural continuity in addition to connections with populations to the north and east. We documented three different architectural forms on the pre-plaza surface: single-set post wall, wall-trench, and pit house. Single-set post construction was practiced in the Black Warrior Valley for centuries before the founding of Moundville. Wall-trench and pit house styles are introductions from elsewhere in the Southeast. The contemporaneity of these forms during the Early Moundville period suggests a culturally diverse community practicing local and nonlocal traditions.
Most of the sherds appear to come from locally made pots in recognizable Moundville shapes and styles. As with the architectural forms, some ceramics evidence interaction with more distant populations.
Not all of the preplaza contexts we encountered can be considered strictly domestic. For instance, some evidence for ritual activity and perhaps ritual crafting comes from a complex midden (trash heap) filling an earlier pit-house. The upper portion of this midden yielded an interesting array of apparent special purpose objects including a fragment of a hooded bottle, fragments of a burnished bowl that clearly contained red pigment and sheet mica, and multiple effigy pieces including two ceramic owl effigies. One of the owl effigies came from a small pocket in the soil that included several bird bones and a knapped quartz pebble. Aside from the artifacts, the midden included multiple fist-sized lumps of white, red, and purple clays. Painted pottery and some fine pottery coils suggest that at least some of the residues in this unit evidence pottery production nearby, and the thick charcoal layer may have resulted from firing pots. Beneath this layer, artifacts declined sharply in abundance, except for a scatter of large sherds lying flat against the house floor, some of which were stacked like decks of cards.
In sum, the magnetometer survey offers an unprecedented opportunity in Moundville archaeology to understand the plaza in both broad and fine strokes. The first phase of ground-truthing is not yet complete, and yet has already provided a stronger basis for classifying many untested anomalies. The great majority of artifacts and features derive from pre-plaza contexts. They evidence early and intensive use of the plaza area as both a ritual and domestic space in which old and new traditions were enacted, negotiated, and redefined. The plaza buried this fractional and contested landscape.
The magnetometer map offers many more opportunities and we will soon take advantage of some of them. Fieldwork begins again next Monday, May 21st.