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Arvicoline chronometry:
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Abstract

Introduction

Study Materials

Identification Methods

Results

Discussion

Conclusions

Acknowledgements

References

Appendix 1

Appendix 2

 

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STUDY MATERIALS

I examined 296 lower first molars (m1) from arvicoline rodents collected from Smith Creek Cave. My sample was restricted to the m1s because they are often identifiable to genus or species whereas other isolated molars tend to be taxonomically less informative (Bell and Repenning 1999; Semken and Wallace 2002). With one exception (noted below), all specimens discussed here are curated at the Nevada State Museum in Carson City. Prior to this report none of the SCC arvicoline specimens housed at the Nevada State Museum were uniquely numbered or curated independently from one another, or from the other faunal remains. Therefore, I was not able to provide re-evaluations of the specific specimens or abundance data listed in previous reports (Miller 1979; Mead et al. 1982). Individual specimens presented here were assigned permanent, unique numbers preceded by the prefix "SCCAR" (= Smith Creek Cave Arvicoline Rodent). Appendix 1 summarizes specimens examined for this study.

There was some inconsistency in the labeling of bags containing faunal remains from SCC. With the aid of original field notes housed at the Nevada State Museum and published stratigraphic data (Bryan 1979), I was able to clarify the provenience of most specimens examined for this study. All but 12 of the examined specimens were associated with a single sedimentary stratum identified from test pits near the rear of the cave (TP 2 and TP 3 of Figure 1; Appendix 2).

The color of this primary bone-bearing stratum was described in a variety of manners (reddish-brown, reddish-pink, red, and pink) on both bone bag labels and in the literature (Bryan 1979; Miller 1979). Within the framework of this paper, I refer to this stratum as the 'reddish-pink silt'. Although lacking a detailed discussion of sedimentological characteristics, Bryan's original report (1979) clearly separates the reddish-pink silt from overlying and underlying sediments on the characteristics of sediment itself and bone color. Cemented white sediments and bones exhibiting a coating of calcium carbonate occur below the reddish-pink silt (Bryan 1979). Sediments from the immediately overlying stratum are characterized by the presence of human artifacts, whereas evidence to suggest human activity during the time of deposition of the reddish-pink silt is equivocal (Bryan 1979). Bones collected from strata above the reddish-pink silt that I was able to observe in the collection of the Nevada State Museum are whitish and lack the characteristic red stain of bone from the reddish-pink silt. Bone preserved in rodent burrows that intruded into the reddish-pink silt exhibited different levels of staining, if any (Bryan 1979). There is no indication in the literature to suggest that bone was limited in distribution within the reddish-pink silt level. The relationship between sedimentary levels at the front and back of the cave remains unclear. The reddish-pink silt from the rear of the cave may stratigraphically correlate with a deposit of rubble and pink silt from near the cave mouth (Bryan 1979), although this equivalence was neither demonstrated in previous reports nor is it clearly evident from exposed trenches in the cave. However, bone was reported as being absent from lower sedimentary levels near the mouth of the cave (Miller 1979).

Given the sedimentary information presented above, it is reasonable to assume that Bryan's original interpretation of the reddish-pink silt as a discrete sedimentary level was appropriate. For my evaluation of the arvicoline rodents from SCC, I considered bags of curated bones ascribed to a red silt, reddish-pink silt, reddish-brown silt, or pink layer to be stratigraphically equivalent, as long as they could be tied to the test pits from the rear of the cave.

All arvicoline teeth presented here that were sorted from these bags retain a reddish stain and conform to Bryan's (1979) description of bone from the reddish-pink silt. The remaining specimens reported here either come from a layer of rodent dung and brown silt situated stratigraphically above the reddish-pink silt (five specimens), or were of unknown stratigraphic provenience due to limitations in associated data (seven specimens).

For strata that underlie unequivocal archaeological levels (e.g., reddish-pink silt) two radiocarbon dates are known (Bryan 1979). The first, based on bristlecone pine needles occurring in a layer near the mouth of SCC, resulted in an age of 12,600 170 14C yr BP (A-1565). The second resulted in a radiocarbon age of 28,650 760 14C yr BP (Tx-1639) and was based on a sample of bone collagen extracted from an unidentifiable bone fragment collected in the reddish-pink silt near the rear of the cave (Bryan 1979). I used the publicly accessible, online radiocarbon calibration program at http://www.radiocarbon.LDEO.columbia.edu/ to calibrate calendar ages for these radiocarbon dates (Fairbanks et al. 2005). Calibrated ages for the radiocarbon dates of 28,650 760 14C and 12,600 170 14C yr BP were 34,039 799 cal yr BP and 14,627 277 cal yr BP, respectively. Given the nature of the radiocarbon sample (collagen) from the reddish-pink silt and confusion surrounding the provenience of the sample, the date of 28,650 760 14C yr BP provides only a rough estimate of the age of the reddish-pink silt zone (Mead et al. 1982). All other radiocarbon dates from the site are younger and most are associated with archaeological materials (Bryan 1979; Thompson 1985).

 

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Arvicoline Chronometry
Plain-Language & Multilingual  Abstracts | Abstract | Introduction | Study Materials | Identification Methods
Results | Discussion | Conclusions | Acknowledgments | References
Appendix 1 | Appendix 2
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