BISON, SNAILS, AND STABLE ISOTOPES: LATE GLACIAL PALEOECOLOGY AT THE FOLSOM TYPE SITE, NM David J. Meltzer, Department of Anthropology, CONCLUSIONS McHaffie Southern Methodist University, Dallas, Texas 75275 1. Multiple independent lines of evidence (Meltzer, in press), in addition to the Indian Creek Lake Ilo sites results shown here, testify to climatic conditions at the time of the Folsom 13 18 BISON AND LAND SNAILS AS PALEOECOLOGICAL INDICATORS RESULTS: SNAIL δ C and δ O ISOTOPE ANALYSES Paleoindian occupation that were relatively cooler and drier than at present. Wasden Hanson Bison basics: Bison are, of course, grazers, consuming primarily grasses and often particular species of grasses. CKM Results of the analysis of δ13C values in modern and fossil Vallonia gracilicosta are shown below. The results show: 2. Although precipitation was lower than at present, there is no evidence of Less prominent in the diet are sedges, forbs, and browse, though this varies by region. In general, the grasses they 13 15 RESULTS: BISON δ C and δ N ISOTOPE ANALYSES long term drought; there was sufficient precipitation to support tree Agate Basin (1) The δ13C values of modern V. gracilicosta, which range from -11.7‰ to -8.4‰, reflect the almost equal mix of C Hell Gap Hudson-Meng consume change seasonally, from C3 forms in the late fall through late spring, to C4 grasses the remainder of the The δ13C and δ15N values of the bison bone are shown below. Leaving aside the two outlying samples (δ13C < -17‰), 3 Rattlesnake Pass growth, and the growth of warm-season grasses. Krmpotich year. More specifically, the relative mix of C3:C4 grass in the diet is a function of several factors, including patch several observations can be made of these data: and C4 plants present in the Folsom region today. composition and diversity, competition, forage quality, etc. C and C grasses have distinct photosynthetic pathways 3. The pollen data (Meltzer, in press) indicates a landscape of open parkland, Lindenmeier 3 4 (2) The δ13C values of the fossil V. gracilicosta from the Folsom bonebed are more positive than the modern samples, that produce different degrees of isotopic fractionation (13C/12C ratios, or δ13C). Bison diet will be reflected in the (1) δ13C values extend over a wide range (~3.4‰), more than is common in a single herd, or a single site. covered with grasses and shrubs. The density of the woodland component Jones-Miller ranging from -8.0‰ to -4.1‰. Mean δ13C values by level and variation about the mean were relatively consistent in ABSTRACT 13 can be inferred from the snail fauna: the woodland-obligate snail δ C values of their bones, teeth, and tissue, with due allowance for the fractionation of the carbon isotopes within the (2) The values are within the isotopic range expected in animals with a diet of 60-80% of C4 plants (as per the equation, Mountaineer 12 Mile Creek 13 all excavation levels; note the bonebed was ~25 cm thick, and extended from Levels 146-150. The Late Glacial paleoecology of the Folsom site Zonitoides arboreus is absent from the Late Glacial age deposits, though Black Mtn San Luis animal (an upward shift of ~5‰ in δ C values). Percent C4 plants = (δ13Cobs + 21.5) / 0.14 [see Lovvorn et al. 2001]). (10,500 14C yr B.P.) has been reconstructed from Valley sites (3) The range of δ13C values in the Late Glacial-age V. gracilicosta at Folsom are comparable to δ13C values in the is present today in the Folsom region. Fewer trees were on this landscape. Analytical complications: 13 independent lines of evidence, including records FOLSOM Cooper/Waugh (3) Late Glacial age δ C values are comparable to those from Late Holocene bison from Folsom area and, save for a modern V. gracilicosta specimens from Black Mesa, Oklahoma, some 100 km east and ~800 m lower in elevation Lipscomb (1) Because of their body size and forage needs, bison can and often do range extensively over floristically diverse 4. The bison bone δ13C evidence indicates there was a substantial C4 grass of oxygen and carbon isotopes from fossil land snails, Rio Rancho/ slight negative offset, to the Historic period bison from Mustang Springs. Yet, Mustang Springs is more than 1300m than the Folsom site. Boca Negra Clovis Lake Theo settings in the course of a season, year, or lifetime. component to the diet of these animals. That C4 grass species were also and carbon and nitrogen isotopes from bison. Using Elida lower in elevation, and a treeless region of higher temperature, lower precipitation, dominantly (~85%) C4 grasses. Lubbock (2) Under certain circumstances bison are selective feeders (e.g. foraging on certain grass types in a mixed setting); present in the local vegetation is attested to by the δ13C evidence from data from bison and snails helps resolve the inevitable under other conditions, they are more akin to "lawn-mowers," consuming everything in their path. (4) The δ15N values are higher than expected, and could result from several factors, most especially a period of water 138 the Vallonia gracilicosta, which of course are not as mobile as bison. This does not preclude the possibility this herd question of whether the bison isotope signature reflects Winkler 1 Adair-Steadman Shifting Sands (3) Stable isotopes in bison bone (as opposed to seasonally- or annually-specific parts of teeth or horn), are "average" stress/aridity. However, diagentic processes can also strongly influence nitrogen isotope values. 139 of bison over its lifetime foraged elsewhere; it does mean that C4 grasses were available locally. local or distant conditions. Together, these data reveal Hot Tubb Midland values of long-term foraging. 140 a landscape cooler and drier and with a greater Chispa Creek Horn As for the two outliers, they could represent individuals from a separate kill or animals that died together but had 5. Using δ13C to C4 cover interpolations (Paruelo and Lauenroth 1996), and assuming bison diets are representative Bonfire Shelter Shelter The isotopic signature of bison bone at a specific site is therefore not a straightforward record of vegetation 141 dominance of C4 grasses than at present. The high different prior foraging histories, or be a result of differential diagenesis. At present, there is little evidence to support the of the local vegetation (as the snail evidence affirms), the C4 component made up 60% to 80% of the grass Kincaid at that locality, but a complicated composite of bison foraging history. 142 incidence of C4 grasses in Late Glacial times may Shelter first two possibilities; the last hypothesis is favored as the outliers were from the North Bank in a lower and different cover, thus occurring in greater proportion than it does at present (52%). result from several factors, including lower atmospheric , in contrast are not long lived, nor wide-ranging, nor highly mobile. They are active during relatively brief geological, hydrological, and taphonomic context than the other samples. 143 Folsom and select Land snails , 6. The vegetation of the Folsom area during the Late Glacial thus more closely resembled the modern biota of the CO2, and differences in seasonal precipitation patterns; periods of time within certain temperature ranges; their forage is generally related to the vegetation present in the 11 144 Paleoindian sites on the 13 Southern High Plains to the east, than it does the vegetation that presently surrounds the site. This extends the it also has broader implications for Late Glacial local area (Balakrishnan et al. 2005a). Thus, analysis of their stable isotopic composition provides a useful record of Folsom/Archuleta (Late Glacial) 145 V. gracilicosta δ C North American Great Plains 13 observations of Connin et al. (1998:187) and Koch et al. (2004), of a high incidence of C4 plants across much of the paleoecology. climate and ecology in a local area. The δ13C values in land snails are derived from the oxidation of ingested organic Range of δ C values in modern 10 Folsom region (Late Holocene) 146 values by excavation Late Glacial American southwest. matter; δ18O values are a function of temperature, relative humidity, ambient water vapor and ingested water. Both land snails in the Folsom area (2200 m asl) Mustang Springs (Historic) 147 level isotopes are recorded in shell aragonite (Balakrishnan et al. 2005b). 7. The underlying cause of that C4 dominance may be attributable in part to lowered atmospheric CO2 during Late 9 148

THE PRESENT ECOLOGY OF FOLSOM E x c a v t i o n l e Glacial times, which would have favored the growth of C4 over C3 plants, even at temperatures cooler than present Folsom is at an elevation of ~ 2100 m (~6900 ft) above sea level, and straddles Wild Horse Arroyo, a small tributrary 149 (Ehleringer et al. 1997). Lowered atmospheric CO2 is not likely the sole factor in play. As Paruelo & Lauenroth (1996) 950 960 970 980 990 1000 1010 1020 1030 1040 1050 8 of the Dry Cimarron River, which has its headwaters in this area of extensive basalt mesas and volcanic peaks. The 1080 1080 150 demonstrate, the amount of C4 grass cover is, within limits and under present atmospheric CO2 values, a function of area presently experiences a continental, semi-arid climate of cold winters and relatively warm summers. Summer B. antiquus and B. Bison 151 mean annual temperature (MAT), mean annual precipitation (MAP) and seasonality of precipitation (SEA). 7 δ13 δ15 Average δ13C value by level rainfall is dominant, but there is the potential for heavy winter snow. The area's topographic variability creates 1070 1070 C and N values, 152 8. As all independent evidence indicates that both MAT and MAP were lower in Late Glacial times than at present, SEA Measured δ13C value by level 13 considerable biotic diversity, from open grassland/meadow interspersed by oak and locust galleries in the vicinity of N ( ‰ ) P D B Range of δ C values in modern land snails Folsom and other sites 153 values must have been at least 12% higher than at present to produce the observed C4 values. This model does not 1 5 6 at Black Mesa, OK (1320 m asl) the site, to pine and spruce forest on the slopes and rolling grassland on the top of nearby Johnson Mesa. 1060 1060 δ 154 incorporate the effects of atmospheric CO2 values, so whether the higher C4 cover in Late Glacial times results from -12 -11 -10 -9 -8 -7 -6 -5 -4 a seasonal shift in precipitation, lowered atmospheric CO , or some combination thereof, remains to be resolved. The grasses include both cool (C3) and warm (C4) season forms; applying the function of Paruelo and Laurenroth 13 2 1050 1050 5 δ C (‰) PDB (1996), which derives the percentage of C4 plants from mean annual temperature (MAT), precipitation (MAP), and 9. A significant increase in precipitation occurred around 10,200 14C yr B.P., marked most clearly in a shift from an season of precipitation (SEA), returns an estimate of ~52% C4 species in the present setting.That function, however, The evidence for a greater percentage of C4 plants in the Folsom area in YDC times than at present is supported by δ18 1040 1040 4 aeolian depositional regime (f2) to an erosional (f3) regime, and in the O snail record, all of which is likely a result assumes modern atmospheric CO2 values; work by Ehleringer et al. (1997) has shown that lower atmospheric CO2 The Folsom site, showing historic and δ13C values in soil carbonate nodules from several units and levels across the bonebed, as seen (below) in Soil nodule M18 recent excavation areas of reorganization of atmospheric circulation at the end of the Younger Dryas. (which marked the Late Glacial) will also influence the relative amount of C :C plants. Datum D M17 group 1. The values in Soil nodule group 2 are significantly more negative, which may reflect near-surface oxidation 3 4 AMNH Pit C 1030 1030 3 of small amounts of biogenic methane, perhaps from the decay of bison carcasses (Balakrishnan et al. 2005b) There are few plants in this setting capable of sustaining long term occupations by hunter-gatherers. However, the Area of the 1926-1928 excavations -19 -18 -17 -16 -15 -14 -13 -12 -11 -10 -9 -8 -7 AMNH Pit D IMPLICATIONS FOR BISON AND HUMAN PALEOECOLOGY vegetation supports a rich fauna including elk, deer, and antelope, and in prehistoric times, bison. M15 In effect, it appears as though the local plant ecology at Folsom spanning the latter portion of the Late Glacial 1020 1020 δ13C (‰) PDB Folsom was good bison habitat during the summer months when C grasses covered the landscape. But there is no into the Early Holocene was not significantly different than the C dominated grassland present today on the 4 Excavation/test units, 1998-1999 4 evidence in the δ13C values of the Folsom bison of any significant contribution of cool-season C grasses to their diet, semi-arid Southern High Plains, as evidenced by both bison and land snail isotopic evidence. 3 1010 1010 Excavation/test units, 1997 IMPLICATIONS AND COMPLICATIONS which would be expected were herds over-wintering in this area. One possible hypothesis for why bison did not Late Glacial δ13C values from Folsom indicate a landscape with a greater component of C4 grasses than are inhabit the area year-round is that Late Glacial springtime temperatures may have kept snow on the ground longer, 1000 Datum C Datum AA 1000 3 here at present, this despite the fact that independent paleoclimatic indicators point to cooler temperatures which in turn would have delayed the emergence of early season C3 grasses on which bison depend. Under such 2 in Late Glacial times, which would suggest there should be a greater presence of C3 plants. circumstances, bison would likely have abandoned the area for lower, less snow-covered settings. If they did, their 990 990 1 movement may not be detectable in their isotopes, since they could have foraged on C4 grasses in those settings. This observation in turn raises two questions: mag N 0 980 980 Without a sufficient supply of winter game, and in the absence of other critical resources that might attract and support First, is the high percentage of C4 grasses more apparent than real, the result of either highly selective foraging in the -1 0 10 20 30 40 50 range of modern a residential group, It does not appear humans over-wintered in the Folsom area in Late Glacial times either. Nor is meters area, or perhaps an isotopic echo of foraging elsewhere, rather than a measure of local vegetation and climate? -2 13 18 970 970 δ C and δ O there is any evidence the Folsom hunters did: there is no hint of any winter features or activities, such as structures, 950 960 970 980 990 1000 1010 1020 1030 1040 1050 Second, if the apparent percentage of C4 grasses is real, and yet conditions were cooler and drier during the YDC -3 values in snails meat caches, intensive processing of skeletal elements for fat and bone grease, storage facilities, or of the exploitation as independent evidence suggests, what accounts for the high percentage of C4 grasses on the landscape? -4 V. gracilicosta and soil of additional food resources one might expect of long term encampment. The hunters killed these bison in the fall, and THE DATA 18 abandoned the site very soon thereafter. This does not falsify Amick's (1996) hypothesis Folsom groups wintered off 13 -5 CaCO nodule δ O The fossil bison bone (n = 8) and land snails (n = 81) in this analysis were recovered in the recent Folsom excavations. In regard to the first question, it can be observed (below) that the Folsom δ C values are comparable to those from 3 the Plains and in more protected settings such as this: it only means over-wintering did not occur in this particular area. -6 13 This insures precise provenience, and precludes any analytical complications from using bone from prior excavations other sites of Late Glacial age, all of which fall along a predictable latitudinal gradient. Additionally, a high C4 signal O ( ‰ ) P D B and δ C values

1 8 -7 that may have had chemical preservatives applied. All snails and most of the bison bone are from the South Bank of has been detected in other recent studies of Southern Plains bison (e.g. Connin et al. 1998; Koch et al. 2004). The δ Soil nodule group 2 REFERENCES CITED Wild Horse Arroyo, primarily in the M17 excavation block. The bonebed here is in primary context, and rests on and is high percentage C4 grasses appears to be real; the snail data shed light on whether such forage was locally available. -8 Amick, D. (1996) Regional patterns of Folsom mobility and land use in the American southwest. World Archaeology 27:411-426 blanketed by a fine-grained silt (f2), and overlain by a coarse shingle shale (f3) (Meltzer et al. 2002). -9 Balakrishnan, M., C. Yapp, J. Theler, B. Carter, and D. Wyckoff (2005a) Environmental significance of 13C/12C and 18O/16O ratios of 45 Soil nodule group 1 Bison bone is generally in excellent condition, and yielded good collagen on analysis. Extractions followed methods -10 modern land snail shells from the southern Great Plains of North America. Quaternary Research 63:15-30. The small herd of bison that Balakrishnan, M., C. Yapp, D. Meltzer, J. Theler (2005b) Paleoenvironment of the Folsom site ~10,500 14C years B.P. developed by Stafford (e.g. Stafford et al. 1988), and were done at Stafford Research Laboratory and the Alaska -11 Soil nodules presently lives just below 44 Carter Kerr-McGe as inferred from the stable isotope composition of fossil land snail shells. Quaternary Research 63:31-44. -12 Johnson Mesa. Quaternary Center (by P. Matheus). All specimens from the Folsom site are Bison antiquus and part of a cow-calf Snails Connin, S., J. Betancourt & J. Quade (1998) Late Pleistocene C4 plant dominance and summer rainfall in the southwestern United herd killed in late fall. For comparative purposes, additional specimens of Bison sp. of varying ages from the Folsom Agate Basin 43 -13 States from isotopic study of herbivore teeth. Quaternary Research 50:179-193. region (n = 4), and of Historic era Bison bison from Mustang Springs on the Southern High Plains (n = 7) are included. Hudson-Meng -18 -17 -16 -15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 Ehleringer, J., T. Cerling, and B. Helliker (1997) C4 photosynthesis, atmospheric CO2, and climate. Oecologia 112:285-299. δ13C (‰) PDB Koch, P., N. Diffenbaugh & K. Hoppe (2004) The effects of late Quaternary climate and pCO2 change on C4 plant abundance in the UNDERSTANDING THE PALEOECOLOGY OF THE FOLSOM SITE Vallonia gracilicosta 42 south-central United States. Palaeogeography, Palaeoclimatology, Palaeoecology 207:331-357. Little was known of the paleoecology of Folsom from the original work (1926-1928) at the site, and though there have (each square is 5 x 5 mm) Results of the analysis of δ18O values in modern and fossil Vallonia gracilicosta indicate: Lovvorn, M., G. Frison & L. Tieszen (2001) Paleoclimate and Amerindians: evidence from stable isotopes and atmospheric circulation. been a number of studies of Late Glacial climate and environment in the Great Plains and Rocky Mountains, most are 41 Proceedings of the National Academy of Sciences 98:2485-2490. at localities hundreds of kilometers distant and/or hundreds of meters higher or lower in elevation than Folsom. The (1) The δ18O values obtained from the fossil sample of V. gracilicosta are variable, even within specific levels, and Meltzer, D. (in press) Folsom: archaeological investigations at the Paleoindian type site. Berkeley, University of California Press. 13 matter is complicated by the fact that the Folsom Paleoindian occupation, now firmly dated to 10,500 14C yr B.P., falls Bison antiquus δ C range from a low of -6.9‰ to a high of 2.7‰ (a span of 9.6‰). In contrast, δ18O values of modern V. gracilicosta Meltzer, D., L. Todd and V. Holliday (2002) The Folsom (Paleoindian) type site: past investigations, current studies. American 40 Jones-Miller Antiquity 62:659-663. in the Younger Dryas Chronozone (YDC), a millenium-long (11,000 and 10,000 14C yr B.P.) return to near-glacial in the region range from -3.8‰ to -0.7‰ (Balakrishnan et al. 2005a). A portion of the Folsom values by latitude Metcalf, A. & R. Smartt (1997) Land snails of New Mexico: a systematic review. New Mexico Museum of Natural History and Science conditions. Recent research has shown that YDC climate was variable across space and through time. How it may bison bonebed, M17 block 39 (2) In contrast to the δ13C values, there is a slight but discernable stratigraphic trend in δ18O values; the most positive Bulletin 10:1-69. have played out in the Folsom region, and what effect it had on Paleoindian foragers or their prey, is unclear. trend line for the mean δ13Cvalues (+): Paruelo, J. & W. Lauenroth (1996) Relative abundance of plant functional types in grasslands and shrublands of North America. L a t i u d e ( g r s N o h ) values occur at the base of the bonebed, and become increasingly more negative up through the section (a 3.6‰ Land snails used in the analysis came from bulk sediment samples collected in 5 cm levels below, in, and above the y = -1.2886x + 20.447, r2 = .967 6:1212-1224. 38 Ecological Applications As part of a recent re-investigation of the Folsom site, various kinds of data were examined to help understand Late bonebed. The snails were recovered through fine screen-washing in the laboratory. The species Vallonia gracilicosta decrease overall). The most negative values are in snails from the overlying f3 shingle shale. Stafford, T., K. Brendel, and R. Duhamel (1988) Radiocarbon, 13C and 15N analysis of fossil bone: removal of humates with XAD-2 Glacial climate and ecology. These data included sediment, pollen, plant macrofossils, land snails and bison bone was used in the isotopic analysis. V. gracilicosta is today one of the most common land snails in northeastern New The most likely cause of this upward decrease in δ18O values is some combination of higher relative humidity, resin. Geochimica et Cosmochimica Acta 52:2257-2267. from the site, as well as pollen from a sediment core from nearby Bellisle Lake. Here I report principally on the stable 37 Theler, J., D. Wyckoff, and B. Carter (2004) The Southern Plains Gastropod Survey: the distribution of land snail populations in an Mexico, including the Folsom region (Metcalf and Smartt 1997; Theler et al. 2004). It was the most abundant species FOLSOM lower temperature, and lower δ18O of rain during periods when the snails are active. An increase in overall carbon isotope (δ13C) analysis of the land snails and bison bone, though I also refer to some of the other analyses. American grassland environment. American Malacological Bulletin 18:1-20. in the Late Glacial bonebed as well. Extraction and identifications were by J. Theler (UW LaCrosse); isotopic analysis Cooper precipitation is not required to explain this upward decrease, but such an increase would be consistent with A full discussion of the results and their implications for Folsom Paleoindian adaptations will appear in the volume, 36 was conducted by M. Balakrishnan (see Balakrishnan et al. 2005a, 2005b). Modern isotopic data was derived from the lower δ18O values in the snails derived from the f3 unit (Balakrishnan et al. 2005b) Folsom: archaeological investigations at the Paleoindian type site (University of California Press, forthcoming). V. gracilicosta specimens collected in the Southern Plains Gastropod Survey (Theler et al. 2004). -23 -22 -21 -20 -19 -18 -17 -16 -15 -14 -13 -12 -11 -10 -9 ACKNOWLEDGEMENTS Research at the Folsom site was supported by the Quest Archaeological Research Fund. I would like to thank M. Balakrishnan, δ13C (‰) PDB All isotope values are reported in ‰ relative to the PDB standard. P. Matheus, T. Stafford, L. Todd, J. Theler, and C. Yapp for discussions of these data and results.