The Powers-Yonkee Bison Trap

Abstract

Site 24 PR5 lies on the Fred Yonkee ranch in Powder River County, Montana, and was reported by Mrs, Margaret Powers, president of Sheridan Chapter of the Wyoming Archaeological Society. This site has a history of being pot-hunted by artifact collectors for at least 35 years. The Sheridan Chapter, with the kind per mission of the ranch owners, decided to conduct an investigation of this site while there was yet undisturbed soil. The bulk of the site had already been destroyed and hundreds of projectile points taken away. In July and August of 1961 a concrete datum post was placed; a survey made of the immediate and surrounding area; an examination made by two competent geolo gists (Dr. Frank Koucky, Professor of Geology at the University of Cincinnati, and Dr. Wilton Melhorn, Professor of Geology at Purdue University); and a camp set up at the site. Fourteen members worked a total of 39 man-days in exca vating 3 different locations on the site, and approximately 25 cubic yards of material was moved, all by hand labor and a wheelbarrow. Geologically, the site lies on a high terrace (elevation about 3600 feet above sea level) of pleistocene origin and con sisting of residual ridges and cones sup ported by sandstone or clinker beds, (Fig. 1). The present change rate is slow. The last period of heavy precipi tation (Little Ice Age) was probably about 3500 years ago, with heavy gully cutting. Since then there had been increasing dry ness and stabilization of gullies. The terrain consists of Fort Union or Wasatch beds, 40 to 60 million years old, with a contmuing sequence sandstone to shale to coal to limey-bed with fossils, follow ed by a repetition of this same sequence . The present surface is predominately heavy gumbo soil with outcroppings of red shale. Prairie grasses and sagebrush are the predominant vegetation, with Ponderosa pine and Colorado juniper scattered along ridges and arroyos . Mule deer and antelope are plentiful in the area, with considerable numbers of sage grouse, jackrabbits, cottontails, badgers, porcupines, and some raccoons. The country is quite arid, and the tem perature was extremely hot with the sun beating down mercilessly during the ex cavation period. The cultural area lies mostly along the north bank of a small arroyo which drains from east to west, emptying into a larger arroyo which drains to the north into a broad, rather flat valley. It appears that ancient man probably drove the bison from the broad valley or collecting basin into the large, north-south arroyo; then, with the aid of a barricade, shunted them into the smaller, east-west arroyo, which at that time probably had more or less verti cal walls. In the east or upper end of this arroyo, the bison were helplessly trapped, and it was an easy matter for the hunters to slay them at practically point-blank range with their stone-tipped projectiles. The rib cage was apparently the favorite target area on the bison, because the majority of the points were found in asso ciation with rib bones. It was decided to excavate at three differ ent locations on the site where surface evidence gave assurance of the presence of a cultural zone with undisturbed soil. The first location, which is called Site #1, was a small, loaf-shaped ridge lying at the head of the arroyo with a steep gully on either side. Some pot-hunting had been done here and much bone was evident in the disturbed dirt. A vertical profile was cut at right angles through the end of the ridge and in undisturbed soil, (Fig. 2). This revealed a cultural layer averaging