Gross photo shows reassembled bone, charred and partly calcified, showing a complex spiral fracture and a central wedge flake. There are 2 inverted cone hammerstone type impacts, one of which is shown (at right) in a lateral CAT scan, with a rebound flake from an anvil below it. Another blow, 45 degrees apart rotationally, was required to complete the break (E. Johnson, 1985, Advances in Archaeological Method and Theory, vol. 8, 157-235).

Below right, is a similar lateral view following an experimental stone hammer blow to a modem fresh bovine humerus, showing inward conical flaking and an opposite rebound flake.

Below, the curved edge of the Pendejo bison humerus fracture demonstrates 2 of 5 hammerstone percussion notches made after the bone had been charred. Under this, for comparison, are two typical humanly made notches made with a pointed hammerstone on modern fresh bison bones of similar size (S. Capaido, 1994, American Antiquities 59(4), 724-748).

Radiocarbon Dating Pendejo Cave

Collection Procedures
A total of 171 samples consisting of wood charcoal, wood, bone, leaves, seeds, fibers, feces and nuts were collected from 19 of the 22 major stratigraphic zones for radiocarbon analysis. The samples were collected with tweezers and the majority was placed into sterile mason jars and sealed prior to analysis. 72 of these samples have been radiocarbon assayed. AFAR personnel collected 52 of these samples during the 1990-1992 excavation seasons and Fort Bliss personnel subsequently collected an additional 15 specimens in 1996. The radiocarbon dates indicate the cave sediment ranges from approximately 350 to in excess of 55,000 radiocarbon years BP.

Sample Provenience
Twenty of the radiocarbon samples were directly associated with features within the cave. 13 of these features' samples were collected directly from the fill matrix of apparent hearths in layers D1, H, J and M. Two of the samples were areas directly adjacent to apparent hearths in layers L and N. Two hair samples, forensically identified as human, were collected from a living surface and fireplace in zone C2. The hair has been directly date by accelerator mass spectrometry (AMS). The remaining feature samples consist of a sandal fragment from an archaic age (zone C) pit "bedding" feature, sticks associated with Clovis age "bedding material" and wood associated with a modified bison humerus from zone M. The remaining 52 samples were principally composite samples of the above mentioned materials collected from individual layers within individual 1 x 1 meter units.

Laboratories
The radiocarbon samples were submitted for both conventional radiocarbon decay counting and AMS procedures. The conventional decay counting laboratories included University of California, Riverside (39 samples); Beta Analytic Inc. (10 samples); University of California, Los Angeles (1 sample); and the Quaternary Research Laboratory at the University of Washington (3 samples). The Lawrence Livermore National Laboratory measured 19 AMS samples. The University of California, Riverside pretreated these AMS samples. ¹³C values were determined only on the UCR radiocarbon samples and any normalization required has been incorporated into the final age expression. Radiocarbon samples processed at the remaining laboratories assume ¹³C values of -25 per ml. None of the radiocarbon dates have been calibrated to adjust for known fluctuations between radiocarbon and solar time but are reported as convention radiocarbon ages.

Results
17 of the 72 radiocarbon dates are infinite, meaning that the count rate of the sample was indistinguishable at the two-sigma level from the background count rate. The respective laboratories have given these samples a minimum age value. These minimum age values range in age from >32,830 (zone H) to >55,000 (zone N). 13 of the 72 radiocarbon dates are stratigraphically anomalous. Nine of these dates appear to represent organics transported downward in the site and four appear in layers that are younger. The accompanying table excludes these anomalous values and represents an estimation of ¹⁴C year spans for the associated zones of stratigraphy based on the reported age range of the finite dates and the minimum infinite age values of the infinite specimens.

Characterization of ¹⁴C Values in Relationship to Stratigraphy

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