University of Pennsylvania Museum of Archaeology and Anthropology

Shades of the Soil: Searching for Archaeological Features


By: Tom Stanley

June 17, 2015

The Smith Creek Archaeological Project is a new Penn Museum research project, conducting its first season in the field during the late spring of 2015. The Penn Museum’s Social Media Coordinator, Tom Stanley, is blogging about the project.


Archaeology is all about using material remains to learn about people and cultures of the past. In our last post, we discussed some of the artifacts that our team at Smith Creek has discovered during this year’s field season—which have included clear indicators of human activity, such as pottery sherds, arrowheads, food remains, and more. But as I’ve discovered, there’s more to a site than its artifacts.

The archaeological features on a site can tell a great deal about the ways in which it was used, and more broadly, about some of the things that happened there. Typically, features are elements that are not easily removed from their context (as opposed to a potsherd or animal bone that can be dug out and picked up by hand). More specifically, they appear to us as differences in soil, identifiable largely due to their contrast with the color or texture of the soil surrounding them.

Meg’s shadow points to an archaeological feature in the south plaza. Photo by Tom Stanley.
Meg’s shadow points to an archaeological feature in the south plaza. Photo by Tom Stanley.

For a first example, let’s go to Mound A. The mounds themselves can be considered archaeological features, but more specifically, we want to look at the stratigraphy of Mound A, as viewed from inside our excavation unit there. Along the eastern slope of the mound, the team dug this unit almost 3 meters down, revealing a staggering array of soil color levels along the way.

Chandler digging in the excavations unit at Mound A. Photo by Tom Stanley.
Chandler digging in the excavations unit at Mound A. Photo by Tom Stanley.

These soil colors represent various moments in the lifetime of the mound. The wider bands of color show individual stages in the mound’s construction, which as you can see, was not performed all in one fell swoop. Instead, the mound was created one level at a time; the color of each level changes based on the source of the soil and the types of activities that took place on it. One layer was made with baskets of soil from one spot nearby, while the next was made with a different type of soil from another spot, and so on. Between these episodes are mound surfaces, the platforms where prehistoric activities took place. Knowing about the artifacts and features on these surfaces is very important to help us understand how the mounds were used. Very thin layers of soil on top of these mound surfaces are also visible; these are evidence of erosion, as a weather event like a storm caused a portion of the surface soil to erode and leave a trace behind, almost reminiscent of rings in a tree.

“Mounds are like onions. They have layers.” Photo by Tom Stanley.
“[Mounds] are like onions. They have layers.” Paraphrased from Shrek.  Photo by Tom Stanley.
Let’s head to Mound C for a good example of another type of feature, called a midden. A midden is essentially ancient accumulation of trash—a collection of discarded materials such as food waste, broken pottery vessels, and, in our case, really anything that might have been tossed off the side of a mound by a human standing on top of it. In the case of Mound C, we believe its base to be largely surrounded by midden hidden beneath the top layers of fill; to help prove that, our excavation unit is dug on the edge of the mound rather than in the center. In this excavation, we have found both midden zones sitting on mound surfaces, and the flank midden we were hoping to hit at the bottom. These midden deposits are different in terms of color and in texture as well.

A view from above of the midden at Mound C. Photo courtesy of the Smith Creek Archaeological Project.
A view from above of the midden at Mound C. Photo courtesy of the Smith Creek Archaeological Project.

At our third unit in the south plaza, where there is no mound, we were particularly interested in the various features we’d be able to find—knowing that some had been identified here during a small excavation by a local avocational archaeologist named Joe Collins some years back. Sure enough, our 2 meter x 4 meter unit yielded a whopping 31 features of various shapes, sizes, and origins.

David the proud supervisor with his bounty of features. Photo by Tom Stanley.
David the proud supervisor with his bounty of features. Photo by Tom Stanley.

The largest feature we identified in the south plaza unit was identified as a pit. This is essentially an ancient hole that was dug in the ground long ago, and refilled with trash and eventually, soil. Further study of the materials identified inside the pit will give us an indication of why it was created in the first place.

An excavated pit in the south plaza. Photo courtesy of the Smith Creek Archaeological Project.
An excavated pit in the south plaza. Photo courtesy of the Smith Creek Archaeological Project.

But more plentiful in this area was evidence of postholes. These appear as generally circular discolorations in the soil, and are indicative of standing posts that had once been inserted into the ground for one purpose or another. Often, the purpose was to serve as posts for standing structures—particularly if you find several postholes arranged in line with one another, as if to form a wall. But not all postholes represent evidence for structures; at Feltus, the nearby Coles Creek mound site at which Meg and David each worked for several years, some of the postholes were found to have been filled with unique materials, including (in one particular case) the bones of a young bear interred with the remains of human infants, pipe fragments, and a variety of other materials. This may suggest a religious or ceremonial role for the creation of the feature, and so our team is being very careful to excavate the postholes at Smith Creek in such a way that will allow for extensive analysis of the soil contained therein.

A close shot into our unit in the south plaza. Visible postholes have been circled to help them stand out in the photo. Photo courtesy of the Smith Creek Archaeological Project.
A close shot into our unit in the south plaza. Visible postholes have been circled to help them stand out in the photo. Photo courtesy of the Smith Creek Archaeological Project.

Our team is excavating these features by digging “windowboxes.” This is done by bisecting the posthole, and digging a rectangular box that extends from the center of the feature to beyond the end of the feature. This box is dug beneath the lowermost portion of the posthole, and creates a “window” of sorts that allows our diggers to see how wide and deep the feature extends, before removing the feature altogether to closely analyze its soil for any objects within.

Features 17 and 18 in the south plaza, as viewed through a windowbox. Photo courtesy of the Smith Creek Archaeological Project.
Features 17 and 18 in the south plaza, as viewed through a windowbox. Photo courtesy of the Smith Creek Archaeological Project.

Dig a little deeper into the archaeological features with David as explains further.

All of these discoveries will allow us to learn more about the chronology of the site’s creation, as well as help to determine which portions of it were being used for what. And ultimately, this information will help us to form a better understanding of the Coles Creek culture, and how it relates to later periods in Native American history in the Lower Mississippi Valley.


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