Medicine Creek: Seventy Years of Archaeological Investigations

4. The La Sena and Shaffert Mammoth Sites: History of Investigations, 1987–1998

Two mammoth sites in the Medicine Creek valley, La Sena and Shaffert , contain highly fragmented limb bones in well-dated late Wisconsinan loess (Figure 4.1). This chapter introduces the reader to the sites and the history of investigations. It also summarizes the geological contexts, radiocarbon ages, and preliminary interpretations of the two sites. Our intent, however, is not to provide complete site reports or research reports because the site assemblages are still being analyzed. The broader controversy regarding the interpretation of highly fractured proboscidean bone is also discussed brie®y. A major study of green-fractured proboscidean bone and other ungulate faunal elements from the Old Crow Basin in the Yukon was undertaken in the 1970s and early 1980s by Robson Bonnichsen, Richard Morlan, and others (Bonnichsen 1978, 1979; Morlan 1979, 1986; Morlan and Cinq-Mars 1982). Their initial interpretation indicated that these green-fractured and ®aked limb bones, some dating to 40,000 years rcybp or older, were the result of human breakage. The faunal elements were in secondary contexts on gravel bars along the Old Crow River, and the authors were criticized for their interpretation that humans were responsible for the observed fracture patterns (Guthrie 1984). This criticism probably also stemmed from the mid-Wisconsinan age of many specimens. The Dutton and Selby sites also were discovered in the 1970s. They are in lacustrine and alluvial deposits in northeastern Colorado and yielded green-fractured and ®aked mammoth and other ungulate bone (Stanford 1979b; Stanford et al. 1981). A preliminary assessment attributed the fracture patterns to human action. Radiocarbon ages of these sites were reported to be older than the ages of Clovis sites 4 The La Sena and Shaffert Mammoth Sites History of Investigations, 1987–1998 Steven R. Holen and David W. May 4.1. Map of mammoth sites in the Medicine Creek valley. (11,500–10,900 rcybp). Interpretation of a pre-Clovis occupation at these sites based on fracture patterns on bones also was criticized. The controversies over pre-Clovis human breakage and ®aking of proboscidean limb bone from the Yukon and the Colorado sites were never resolved, and the interpretations were never widely accepted by the archaeological community. The two Nebraska mammoth sites discussed here represent in situ documentation of the same types of fracture patterns recorded in the Yukon and northeastern Colorado. The two Nebraska sites, however, are in ¤ne-grained, wind-deposited silts and consequently offer new geoarchaeological and taphonomic evidence with which to reevaluate the earlier interpretations. The La Sena Mammoth Site, 25FT177 Bureau of Reclamation archaeologists Bob Blasing and Brad Coutant discovered the La Sena mammoth site (25FT177) in 1987 while they were conducting a shoreline survey of Medicine Creek Reservoir. They actually were looking for the location of Woodland site 25FT71 when they found mammoth bone eroded out of place and lying in a slump block on the beach (Blasing 1987). Two pieces of chipped stone lying directly on the slump block indicated a potential human association. Additional mammoth bone was noted in the vertical loess bluff above the beach. Bob Blasing, archaeologist for Reclamation’s Nebraska/Kansas area of¤ce, contacted Steve Holen, who in turn contacted geomorphologist David May. Bob Blasing led a preliminary trip to the site in the summer of 1988. A more thorough examination of the site was recommended after this brief reconnaissance. 1988 Preliminary Investigation Detailed ¤eldwork conducted by Steve Holen and David May in October 1988 consisted of pro¤ling the bluff, mapping, and deep coring from the terrace surface. A detailed map of mammoth-bone fragments and a preliminary stratigraphy of the loess bluff were produced. Numerous bone fragments were found along 20 m of the bluff. Many fragments were heavily coated with concretions. The center of the bone bed was beneath 3.6 to 3.8 m of Peorian loess. The bone horizon was on a 1 percent slope to the south, so the bone bed dipped from north to south. A truck-mounted drill rig was used to core from the surface of the loess-mantled terrace down through the mammoth-bone level. Ten core holes, each measuring 5 cm in diameter, were drilled in each of 22 / Steven R. Holen and David W. May two east-west transects above the mammoth bone. The coring transects were perpendicular to the bluff and 12 m apart. The core holes in each transect were spaced 1 m apart. Core...