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Canyon Sketches Vol 26 - March 2013

Archaic Roasting Pit Excavated Near Three-Mile Resthouse on Bright Angel Trail
Allyson Mathis
 
Swithcbacks on Bright Angel Trail

Bright Angel Trail switchbacks

Grand Canyon Archaeology Day is Sat. March 23, 2013

Today's Bright Angel Trail is the most heavily traveled trail for people hiking in and out of the canyon. The trail follows the Bright Angel Fault, which produces natural breaks in the canyon's generally sheer cliffs.

The modern Bright Angel Trail was constructed following an aboriginal trail leading to Indian Garden and the Tonto Plateau.

The longer human history of the Bright Angel Trail, extending back at least 4000 years before present, is evidenced by archeological sites, including a rock art panel near the first tunnel and an archeological site excavated near Three-Mile Resthouse.
 
overview of the excavation site.

Overview of the excavation site.

In March 2008, archeologists from the Museum of Northern Arizona (MNA) and Grand Canyon National Park excavated a prehistoric roasting pit near Three-Mile Resthouse where new composting toilets were to be constructed.

This archeological site had already been heavily impacted during historic use of the trail and, in fact, more than half of the roasting feature had already been destroyed. After consultation with Traditionally Associated Tribes, park and MNA archeologists completed a plan for excavation of the remaining portions of the site in hopes of collecting information to add to our understanding of the prehistoric human use of the area.
 
Thermal oven technology illustration

Thermal oven technology

NPS illustration by Ian Hough

The Three-Mile Resthouse archeological site was known to be a large "donut-shaped" roasting pit. Such roasting features were used to cook a variety of both plant and animal foods. Foodstuffs were placed on rocks that had been heated by fire in a pit at the center of the roaster, then covered by grasses or other vegetative matter. Everything would have been then buried under soil to retain moisture while the food cooked. Afterwards, the burnt rock and soil covering the roaster were raked out into a ring resulting in the typical donut shape. This roaster, like many large roasting pits in Grand Canyon, is at the edge of a slope which allowed the pit to be repeatedly raked out without debris mounding up at the perimeter of the earthen oven.
 
trench dug through roasting pit

One of the trenches cutting across the roasting pit.

The excavation of the roaster near the Three-Mile Resthouse was led by MNA archeologist Ted Neff. After mapping and collecting artifacts on the surface, the crew excavated two meter-wide trenches at right angles across the remaining sides of the roasting feature and donut ring. Neff explained, "We decided to excavate two trenches across the feature because of logistical and time constraints, and because the center of the roaster, where the food itself would have been cooked, had already been destroyed by historic use near the Three-Mile Resthouse. Trenching allowed us to determine the internal structure of the roaster and the vertical and lateral extent of it."
 
Excavated roasting pit

Smaller basin-shaped feature

While they were excavating the large donut-shaped roaster, they uncovered another smaller basin-shaped feature within it that had an oxidized soil base and contained larger charcoal fragments than the rest of the roaster. Neff said, "In archeology, remains of the human use of fire are called thermal features. Thermal features include large roasting pits, slab-lined hearths, subfloor pits, scatters of rocks that have been cracked by fire, and charcoal stains in the soil. This smaller thermal feature initially appeared to be older than the large roaster, but the age relationships were somewhat muddled because part of it had been disturbed by the historic use in the area."

 
view of excavation with screens

Screens were used to recover artifacts.

During excavation, the crew screened the removed material to recover artifacts. A variety of stone artifacts were recovered, mostly made from chert found in the Kaibab Limestone on the canyon's rim. The crew also collected soil samples for analysis of the lightweight plant material contained in it.

MNA archeologist Jim Collette said, "We often collect soil samples for analyses when we excavate thermal features because they can help us discern what the feature was being used for, such as the cooking of food. Additionally, we hoped to recover plant material for carbon-14 dating. As it turned out, the plant remains led to some of our most significant, and unanticipated, insights into the past human use of this site."
 
In addition to wood charcoal, almost 2,800 charred plant fragments were recovered with all but two fragments being fibrous leaf fragments from agave plants. Collette said, "One of the interesting findings of this excavation is that although other large donut-shaped roasters are known in Grand Canyon, there is little evidence that they were used to roast agave. This one clearly was."

Three small carbonized plant fragments were dated using carbon-14 analysis. Two samples from the large donut-shaped roaster and one from the small thermal feature were analyzed. The dates obtained from the large roaster were 1460 - 1410 B.C and 800 - 780 B.C.; while the small thermal feature was used between A.D. 980 and 1030. Neff said, "The older dates are near the end of the Late Archaic time period, when small game hunters and plant gatherers utilized the canyon. The smaller thermal feature appears to have been used during the ancestral Puebloan, or Formative, time period, when people who practiced agriculture lived in this region, and which was about 1500 years after the last use of the large roaster."
 
detail of agave plant

Detail of agave


Neff continued, "A couple of our findings at this site were particularly significant. One, we recovered the oldest dated evidence for agave roasting in the park. And, two, it appears that something about the Three-Mile Resthouse site made it uniquely suitable for agave roasting in Grand Canyon.

Three-Mile Resthouse is located on both the Bright Angel travel route and a bench on top of the Redwall Limestone that allowed lateral travel, so this site provided access to a variety of wild foods both above and below, and east and west of this site. And the Redwall Limestone itself may also be significant since limestone retains heat longer than other local rocks."

 
Rock art along Bright Angel Trail

Rock art along Bright Angel Trail.

Jan Balsom, Deputy Chief of Science and Resource Management at Grand Canyon National Park said, "We are continually learning more about the prehistory of Grand Canyon. I think one of the lessons of this site is that, while we already knew that people have used the Bright Angel Trail route for thousands of years, every archeological site in the park-even ones that had been previously impacted by historic use like the Three-Mile Resthouse roaster-can add important pieces of information that improves our understanding of the past.

It is remarkable that the data show that this roasting pit was used by different peoples at different times over a course of 2,500 years. We keeping seeing that only certain places within the canyon landscape were and are good for people to live and travel. We certainly see this in these thermal features and in Three-Mile Resthouse itself."

This article was originally published in Canyon Views, Volume XVI, number 1, Spring 2010. Canyon Views is a publication of
Grand Canyon Association.

 

Did You Know?

SUMMER HEAT MAY RESTRICT TRAIL ACCESS

During the summer months temperatures within the Grand Canyon are extremely high. Plan your day so you are not hiking between the hours of 10am and 4pm. Take a break near shade and water to avoid the worst heat of day. Enjoy a predawn start and a late afternoon finish. More...