HR: 1340h
AN: PP23A-1074    [Abstracts]
TI: Tooth Enamel δ¹³C and δ¹⁸O Variations in Modern and Archaeological Horses From Northern Kazakhstan as Indicators of Regional Climate
AU: * Sikora, M T
EM: mts11@pitt.edu
AF: University of Pittsburgh, Department of Geology and Planetary Science, 4107 O'Hara Street, Pittsburgh, PA 15260, United States
AU: Rosenmeier, M F
EM: mrosenme@pitt.edu
AF: University of Pittsburgh, Department of Geology and Planetary Science, 4107 O'Hara Street, Pittsburgh, PA 15260, United States
AU: Stacy, E M
EM: ems37@pitt.edu
AF: University of Pittsburgh, Department of Geology and Planetary Science, 4107 O'Hara Street, Pittsburgh, PA 15260, United States
AU: Olsen, S L
EM: OlsenS@CarnegieMNH.Org
AF: Carnegie Museum of Natural History, Section of Anthropology, 5800 Baum Boulevard, Pittsburgh, PA 15206, United States
AB: In this study, the oxygen and carbon isotope values of tooth enamel were measured in forty-one modern and twenty-three Copper Age (3600 – 3100 B.C.) horse specimens from the grassland steppe region of northern Kazakhstan. Modern tooth enamel δ¹³C and δ¹⁸O values were compared with the carbon isotopic compositions of local vegetation and the δ¹⁸O values of meteoric waters. Tooth enamel isotope values within the Copper Age specimens (attributed to the so-called Botai culture) were, in turn, compared with modern samples. Average carbon isotopic values within modern bulk tooth enamel samples ranged between -13.7 and -12.0‰ (VPDB). This suggests that the diet of modern northern Kazakhstani horses is comprised almost entirely of C₃ plants (considering enamel-diet fractionation factors) consistent with documented grassland compositions within the region. The observed amplitude of δ¹³C variations within individual teeth (typically less than ~2‰) suggests only minimal seasonal variation in the δ¹³C of grasses attributed to heat and water stress. Alternatively, the minimal seasonal changes observed within intra-tooth δ¹³C values may be the direct result of fodder provisioning. Ingested water δ¹⁸O values derived from oxygen isotope ratios within bulk tooth enamel samples appear statistically indistinguishable from estimates of regional precipitation, suggesting that Kazakhstani horse tooth enamel δ¹⁸O measurements may be used as a direct estimate of the oxygen isotopic composition of meteoric waters. Intra-tooth oxygen isotopic variations therefore reflect the pronounced seasonal variability in precipitation δ¹⁸O values tied to temperature changes and amount effects observed annually within Kazakhstan. However, these intra-tooth isotopic variations exhibit slightly reduced amplitudes relative to meteoric water values, suggesting that horses likely consume water from buffered sources such as lakes and wells. Average bulk tooth enamel δ¹³C values within archaeological samples (-12.1 ±0.4 ‰) were nearly identical to values measured within modern horse specimens (-11.6±0.3 ‰) suggesting that dietary patterns and feeding regimes between the Copper Age and present were relatively similar. Average ingested water δ¹⁸O values derived from oxygen isotope ratios within Copper Age bulk tooth enamel samples were, however, significantly different (reduced by nearly 3‰) from modern samples. Intra-tooth δ¹⁸O values within archaeological samples also exhibit attenuated variations, ranging only ~4‰. In contrast, intra-tooth δ¹⁸O values within modern horse specimens varied by nearly 9‰. Observed differences between average bulk tooth enamel delta¹⁸O values may reflect reduced mean annual temperatures, greater rainfall, and/or changing source water δ¹⁸O values during the Copper Age. Alternatively, waters ingested by Copper Age horses may have been less affected by evapotranspiration. The relatively low delta¹⁸O suggests that meteoric waters ingested by Copper Age horses were either less affected by evapotranspiration or the region experienced more rainfall than at present. Furthermore, the reduced amplitude of intra-tooth variations within archaeological samples suggests that seasonality was likely less pronounced during the Copper Age.
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1650 Solar variability (7537)
DE: 4914 Continental climate records
DE: 9320 Asia
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting