Ground Truthing: The Pinson Environment and Archaeology Regional Landscape (PEARL) Project begins testing geophysical results

30 Days of Tennessee Archaeology 2015, Day 3

Sarah C. Sherwood, Stephen B. Carmody
Environmental Studies, The University of the South

Alice P. Wright
Department of Anthropology, Appalachian State University

The ca. 1916 site map (first published by Kwas and Mainfort in 1986 in the Tennessee Anthropologist with permission from the National Archives) overlaying the local LiDAR. Note the correlation of the mounds with the early map. The white arrows indicate specific distances.

The ca. 1916 site map (first published by Kwas and Mainfort in 1986 in the Tennessee Anthropologist with permission from the National Archives) overlaying the local LiDAR. Note the correlation of the mounds with the early map. The white arrows indicate specific distances.

The Pinson Environment and Archaeology Regional Landscape (PEARL) Project is focused on a concentration of Middle Woodland period mound sites (ca. 200 BC – AD 500) located along the South Fork of the Forked Deer River in West Tennessee, including Pinson Mounds, the largest Middle Woodland mound site in the Southeast. The Middle Woodland is known as a time when American Indian communities across the region erected earthen mounds and monuments that become the focus of complex religious and social activities. Based on previous archaeological research conducted at the Pinson Mounds State Archaeological Park, this area is interpreted as an ancient pilgrimage center, where groups came together to perform rituals, exchange goods and raw materials, and socialize with other communities.

As we related in a previous blog, this project began with many intriguing questions: Why was this particular location selected for such an important mound complex? What led to Pinson becoming a major mound center? What were the daily lives like for the people who built the mounds and where did they live? How did these communities interact with and transform their natural environment? How did non-local groups become involved at Pinson? These questions and many more are the focus of PEARL.

We began the PEARL project at the Johnston Site, a state-owned and protected, multi-mound site two miles away from the main Pinson complex.  A preliminary study suggested that mound building episodes at Johnston may slightly pre-date those at Pinson, making it an ideal place to investigate the origins and earliest expressions of such activities. Over the past two summers, PEARL researchers have conducted mapping and geophysical survey of a portion of the Johnston site using gradiometry and ground penetrating radar. This year we added an expedient form of magnetic susceptibility survey.  Geophysical prospection methods allow us to detect subtle differences below the surface (called anomalies) without disturbing the ground, and using multiple techniques ensures that we capture a wide range of subsurface features. Already, our preliminary results are helping us to assess the presence and organization of archaeological remains near the mounds.

Currently, we have collected gradiometer data across approximately one third of the 30 hectare site. In order to determine what the variable types of anomalies represent, we “ground truth” them by placing an excavation unit there to see exactly what the magnetic signal is responding to. This allows us to target specific areas for detailed excavation while leaving the other anomalies suggesting similar activities undisturbed.

Clockwise: Feature 1 at the Johnston site is shown here as it appeared in the gradiometer data in a cluster of similar anomalies (our 1x1 m excavation unit is shown in yellow); the pit is revealed below the base of the plowzone; bisected, the profile shows a 45 cm deep early Middle Archaic pit.

Clockwise: Feature 1 at the Johnston site is shown here as it appeared in the gradiometer data in a cluster of similar anomalies (our 1×1 m excavation unit is shown in yellow); the pit is revealed below the base of the plowzone; bisected, the profile shows a 45 cm deep early Middle Archaic pit.

The image above shows one area of our gradiometer data where there are several similar circular anomalies. This year we tested five of these from different parts of the site. Excavations over each anomaly revealed some form of pit feature, although the nature of their sediment fills and contents varied.  Based on the preliminary data, these appear to be storage pits and likely represent occupations from both the Middle Woodland and other time periods.

Excavation and completion of a quarter of Feature 3. Note the concentrated charcoal and organic zone at the base covered in lens of burned clay fragments.

Excavation and completion of a quarter of Feature 3. Note the concentrated charcoal and organic zone at the base covered in lens of burned clay fragments.

Each of these pits was bisected (or in case of Feature 3 quartered) in the field to create a profile that revealed the overall structure of the pit. Then, while half to three-quarters of each pit was left undisturbed, the contents of their excavated portions were floated. Flotation is a technique used to collect all the artifacts while separating carbonized plant remains from the archaeological sediments. Thus far we have floated 1085 liters from 5 pits.

Preliminary analysis from one pit has produced evidence of stone tool manufacture and charred plant remains, including hickory and acorn nutshell and a single wild chenopodium seed.  Radiocarbon analysis on a hickory nutshell fragment produced a date of 5700 cal BC, which dates to the early part of the Middle Archaic.  We expect similar Archaic period dates from two of the remaining unanalyzed pits while two pits containing ceramics will likely date to the Middle Woodland.

en Colley and Lydia Carmody processing float samples with a revision of the SMAP tank. The light fraction (charred plants) is caught in the fine white fabric while the heavy fraction (everything >1/16 in) is collected in the window screen.

Ben Colley and Lydia Carmody processing float samples with a revision of the SMAP tank. The light fraction (charred plants) is caught in the fine white fabric while the heavy fraction (everything >1/16 in) is collected in the window screen.

These data demonstrate that the landform, an ancient terrace overlooking a stream with numerous springs in the vicinity, likely supported seasonal occupation well before and after the Middle Woodland period.  This discovery adds a new dimension to our research: sorting through the palimpsests of site occupation that likely represent different uses of this place over time, from a seasonal occupation where nuts were processed and stored to sacred ritualized space.

Ongoing and future PEARL research will involve expanding the geophysical coverage of the Johnston site, undertaking survey around the South Fork Forked Deer River drainage, and conducting laboratory analysis of flotation samples, including additional radiocarbon dating. We will continue to consider the context of the natural environment so that we may grasp what first attracted people to this place, and how their occupation of the area changed over time. The PEARL team is made up of faculty and students from: University of the South, Appalachian State University, Bryn Mawr College, Texas State University, University of Tennessee Knoxville and Washington University in St. Louis.

The June 2015 Field Crew. Missing from this particular photo are our excellent geophysical colleagues Edward Henry and Stephen Yerka.

The June 2015 Field Crew. Missing from this particular photo are our excellent geophysical colleagues Edward Henry and Stephen Yerka.

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