Topic 7
Borrow Pits

Earth was a valuable resource to the Plains Village peoples living in the West Pasture. They modified clay sediment into a plaster for shoring up surfaces such as hearths, storage pits, and interior floors and lower walls within their pithouse earthlodges. They used clay sediments to fashion trivets, and they mixed it with grass to form a strong daub that was placed over building timbers. They covered the roof of each lodge with a thick layer of earth that provided thick insulation during cold winters and scorching summers. Much like people do today, the Plains Village people “mined” various deposits to gather specific types of sediments for specific uses. The holes they dug to extract sediment are called borrow pits, although in reality the sediment was removed with no intent of ever returning it.

Feature 1 at the Hank B site (a subarea at 41RB109) is believed to be a borrow pit dug into a clayey deposit to remove sediment for some specific use. The dense blocky alluvial sediment found in this location would meet the requirements for many types of structural applications. The dense clay removed from the Feature 1 pit might also have been used for making ceramics. The pit was approximately 2 meters (6.6 ft) in diameter, and it had shallow basin shaped, being only 25 cm (9.8 inches) deep in the center.

Much like the larger storage pits found in the West Pasture, the Hank B borrow pit was filled with discarded refuse. This is not surprising because it seems that any depression or hole in or near where people lived was filled in with household garbage.

View of the profile of the borrow pit feature at Hank B. The pit was dug into a dense alluvial clay deposit and then filled with trash.

A good example of prehistoric people extracting sediment from one location to use it for a specific purpose in another place was found in Structure 4 at the Indian Springs site (41RB81). This site has multiple components, spanning from Late Archaic through the Plains Village period and into the early Protohistoric period. The site setting is unique within the West Pasture, with Indian Springs occupations being on a high colluvial terrace tucked up against the Caprock Escarpment. From this prominent knoll there, there is a commanding view of the valley to the south and west. The main occupation area is also situated immediately above the Indian Springs, an active fresh-water spring in the upper part of the West Pasture valley.

Structure 4, the small circular pithouse at Indian Springs site. The scale is 1-m long with 10-cm increments.

Archeological excavations revealed that Structure 4 was a small basin-shaped, roughly circular pithouse measuring 2.3 meters (7.5 ft) in diameter by 40 cm (15.7 inches) deep. The 0.6-meter-wide entry extended west for 1.8 meters (2.0 x 5.9 ft), and it had a raised sill or threshold at the entrance to the structure. Three small ephemeral hearths filled with ash were found on the floor in the center and near the south and east walls of the small structure. But it was the earthen fill inside this depression that was intriguing. Without question, this small structure once had an earthen roof. The entire house pit was filled with dense, blocky gray clay that was foreign to the terrace where the structure was found. So we know that this clay had been dug out somewhere else and brought to this location  to be used to construct the roof of this hut. The origin of this clay is unknown, but without a doubt, it derived from a borrow pit located somewhere else in the West Pasture valley.  

Organic remains recovered from Structure 4 were dated using the radiocarbon method by Beta Analytic (a well-known dating laboratory). Two dates were obtained on charred wood pieces from the hearths. One produced a radiocarbon date of A.D.1280-1400 (corrected two sigma range; conventional radiocarbon age is A.D.1330 ± 40) from Beta Analytic. A second charcoal date produced a date of A.D. 1290-1410 (corrected two sigma range; conventional radiocarbon age is A.D. 1370 ± 40) from Beta Analytic. These dates place Structure 4 squarely in the Plains village period, and it is notable that charred corn fragments were also recovered inside the small structure.

The function of Structure 4 is not known, and it will probably always remain a mystery. However, some speculative interpretations may be offered based on the structure’s attributes. This structure is unique in the West Pasture for its small size and the presence of three somewhat ephemeral hearth areas on the floor. It is also unique because the fill inside the pit was a large mass of clay that was certainly derived from an earthen roof. Notably, Structure 4 was perched in an isolated position on a prominent nick-point on the edge of the high terrace overlooking the valley. In this location, the clay fill inside the pithouse could not have washed in; it could only have been derived from the melting of an earthen roof. We believe that Structure 4 was a special-purpose structure, perhaps some type of ceremonial structure. The West Pasture archeological team has speculated that it may have been a sweat lodge—a small domed structure where water and hot rocks created a steamy environment used in purification rituals.

Few artifacts were found in Structure 4, but one unique and interesting item was recovered. It is a decorated pottery sherd with an unusual “bullseye” design (concentric rings) that is foreign to the Southern High Plains. While decorated pottery is common in West Pasture, nothing resembling this “bullseye” motif has been documented. This small sherd only adds to the mysteries we have in the West Pasture. Where did it come from and how did it get into the West Pasture and wind up in a small ceremonial hut?

Bullseye design on a potsherd found in Structure 4 at the Indian Springs site. Photo courtesy of Christopher Lintz.