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From The Fauna’s Mouth: Assessing Seasonality using CO2-Laser Ablation on Prehistoric Tooth Enamel from Island Southeast Asia

Journal of Undergraduate Research from the Center for Undergraduate Research
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Title:
From The Fauna’s Mouth: Assessing Seasonality using CO2-Laser Ablation on Prehistoric Tooth Enamel from Island Southeast Asia
Series Title:
Journal of Undergraduate Research
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Serial
Language:
English
Creator:
Schaub, Amelia
Krigbaum, John
Curtis, Jason
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University of Florida
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Gainesville, Fla.
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Paleoanthropology
Paleoclimate
Paleoecology
Laser Ablation Continuous Flow Isotope Ratio Mass Spectrometry
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serial   ( sobekcm )

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Abstract:
Accurate Paleoclimate reconstruction in paleoanthropology and archaeology is integral in understanding past human subsistence and settlement. However, fine-grained details of paleoclimate and paleoecology in Southeast Asia tropical rain forest environments are hampered by the coarseness of the record and limitations in analytical equipment. Here, the use of Laser Ablation Continuous-Flow Isotope Ratio Mass Spectrometry (LA-CR-IRMS) has been utilized to sample incrementally 10 mammalian teeth recovered from Niah Cave, located in Northern Borneo, from late Pleistocene and Holocene. Due to the nature of enamel formation, 18O values produced from sequentially sampling each tooth along the enamel surface provide insight into seasonal climate patterns.

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University of Florida
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University of Florida
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All applicable rights reserved by the source institution and holding location.
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sobekcm - UF00091523_00602
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UF00091523:00673

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MISSING IMAGE

Material Information

Title:
From The Fauna’s Mouth: Assessing Seasonality using CO2-Laser Ablation on Prehistoric Tooth Enamel from Island Southeast Asia
Series Title:
Journal of Undergraduate Research
Physical Description:
Serial
Language:
English
Creator:
Schaub, Amelia
Krigbaum, John
Curtis, Jason
Publisher:
University of Florida
Place of Publication:
Gainesville, Fla.
Publication Date:

Subjects

Subjects / Keywords:
Paleoanthropology
Paleoclimate
Paleoecology
Laser Ablation Continuous Flow Isotope Ratio Mass Spectrometry
Genre:
serial   ( sobekcm )

Notes

Abstract:
Accurate Paleoclimate reconstruction in paleoanthropology and archaeology is integral in understanding past human subsistence and settlement. However, fine-grained details of paleoclimate and paleoecology in Southeast Asia tropical rain forest environments are hampered by the coarseness of the record and limitations in analytical equipment. Here, the use of Laser Ablation Continuous-Flow Isotope Ratio Mass Spectrometry (LA-CR-IRMS) has been utilized to sample incrementally 10 mammalian teeth recovered from Niah Cave, located in Northern Borneo, from late Pleistocene and Holocene. Due to the nature of enamel formation, 18O values produced from sequentially sampling each tooth along the enamel surface provide insight into seasonal climate patterns.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
sobekcm - UF00091523_00602
System ID:
UF00091523:00673


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University of Florida | Journal of Undergraduate Research | Volume 12 Issue 3 | Spring 2012 1 2 Laser Ablation on Prehistoric Tooth Enamel from Island Southeast Asia Amelia Schaub Dr. John Krigbaum and Dr. Jason Curtis College of Liberal A r ts and Sciences, University of Florida Accurate Paleoclimate reconstruction in paleoanthropology and archaeology is integral in understanding past human subsistence and settlement. Ho wever, fine grained details of paleoclimate and paleoecology in Sout he ast Asia tropical rain for est environments are hampered by the coarseness of the record and limitations in analytical equipment. Here, the use of Laser Ablation Continuous Flow Isotop e Ratio Mass Spectrometry (LA CR IRMS) has been utilized to sample incrementally 10 mammalian teeth recovered from Niah Cave, located in Northern Borneo, from late Pleistocene and Holocene. Due to the nature of enamel formation, 18 O values produced from sequentially sampling each tooth a long the enamel surface provide insight into seasonal climate patterns. INTRODUCTION The Site: Niah Cave T his study focuses on applying methods of LA CR IRMS to provide information about sub annual weather patterns during the late Pleistocene and Holocene. F indings will be considered with respect to prior knowledge and information gathered about the region, and it is thereby necessary to detail the site context. Niah Cave is located withi n the district of Miri in Sarawak, Malaysia on the island of Borneo. The environment of the region is tropical and lush with vegetation as approximately one fourth of is located in Indo Australia (Heaney, 1991 ). D uri ng the late Pleistocene, however, g lobal climatic changes influenced the landscape of the region, and induced increased seasonality and rainfall (Heaney, 1991). During the last glacial maxima in particular, changes in climate impacting sea levels, flora, and regional weather patterns would in turn have had significant impact on the human populations living in the area at the time (Krigbaum, 2001). The e ffects of the South East Asian Monsoon are also key in understanding dynamics of climate, s uch as heavy rains and drier seasons, as the se changes in weather would a ffect human activity, subsistence, and dispersal (Stephens et al. 2008 ). Mammalian Enamel In this study, 18 O and 13 C values were obtained from prehistoric mammalian tooth enamel collected from Niah Cave in order to add to the paleoecological record of the region. While the tooth enamel samples used in this study are from various species, mammalian enamel formation has several fundamental properties that allow for sub a nnual assessment from isotopic values of each tooth. There is a rhythm to enamel formation as it mineralizes and there are layers that correspond to the formation of each tooth. At the beginning of amelogenesis, enamel is laid out in succ essive dome like increments until the ameloblasts at the apex of the dome reach maturation. After this point, enamel formation switches to sleeve like increments, and proceed down the tooth to the cervical part of the crown (Hillson, 1986) as shown in Fi gure 1 The nature of this incremental growth allows for discrete sampling along the surface of the tooth enamel from crown apex down to the Cementoenamel Junction providing successive snap shots of enamel formation. Figure 1. Structure of Enamel Formation (Hillson, 1986 )

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AMELIA SCHAUB DR JOHN KRIGBAUM & DR JASON CURTIS University of Florida | Journal of Undergraduate Research | Volume 12 Issue 3 | Spring 2012 2 Previous Regional Paleoclimate Studies Alth ough the record on South East Asian Paleoclimate is limited several studies that utilize various methods have been published that provide useful data on this topic. In Northern Borneo, for example, isotope analysis of Stalagmites has yielded information about millennial climatic changes over the last 27,000 years (Partin et al. 2007). Although the scaling of this data cannot be refined enough to provide any insight into sub annual seasonality it is useful to view the data gathered from this research within the context of their findings to better understand sub annual weather pa tterns within the scope of larger scale climatic changes. At the site of Niah Cave, Stephens et al ( 2008 ) have been able to assess seasonality from the incremental isotope analysis of modern and early Holocene harvested bivalves. Sawtooth like pattern s in 18 O values of the modern bivalves were correlated to seasonal changes in rainfall. Isotope analysis of prehistoric bivalves revealed similar cyclic shifts in 18 O values which were inferred to reflect the changing seasonality of the monsoon rains ( Stephens et al 2008 ). While Stephens et al provided high resolution and intra a nnual data, a disconnect remains between the aquatic and terrestrial records. The goals of this study are to: 1. e v aluate the ability of LA CF IRMS to sample sequentially small sized tooth samples. 2. a nalyze 18 O values for possible signs of seasonality. 3. a dd to the terrestrial record by documenting Paleoclimate of South East Asia METHOD Samples Ten mammalian teeth from four different species were used in this study. The teeth date from the late Pleistocene to the early and mid Holocene, and were all recovered from Niah Cave. The enamel sampled was from various teeth including molars and incisors Several of the teeth used in this study were also incomplete fragments while the entire tooth was available for other. Table 1 shows the characteristics of the ten teeth used. Table 1 Sample Characteristics Sample Taxon Approximate Age (years old) Tooth NC 142 Sus barbatus 15,365 +/ 60 Incisor NC 138 Sus barbatus ~3,000 Incisor NC 120 Bos ~20,000 Molar Fragment NC 122 Bos 15,365 +/ 60 Molar Fragment NC 121 Bos ~3,000 Molar Fragment NC 175 Pongo ~15,000 Molar Fragment LM 2 Bos 15,365 +/ 60 Molar Fragment LM 1 Bos ~15,000 Molar Fragment BOS 34 Bos 34,180 +/ 230 Molar Fragment LM 4 Rhinoceros ~20,000 Molar Fragment *Radiocarbon dates given for NC 142, NC 122, LM 2, and BOS 34 D ates for rema ining samples are approximate. Sample Preparation Selected teeth were prepared for laser ablation using a consistent cleaning process. The enamel surface of each tooth was first cleaned using a diluted ethyl alcohol solution, and then rinsed with deionized water. Teeth were then pla ced in a beaker filled with distilled water and place d in a sonicator for ten minutes. Each beaker was then emptied and refilled with fresh deionized water, and sonicated again for a period of ten minutes. The beake r was then drained and the sample was air dried for approximately thirty minutes. Samples were then placed in an evaporating oven set at 60 C for fifteen minutes or until completely dry. In the cases when teeth were too large as a whole to fit into the l aser cell cham ber, a portion of enamel, from crown apex to the cervix was removed using a D remel drill. The dentine was then removed from the backside of these pieces using a stainless steel pick, leaving a sample of pure enamel. The same procedure was fo llowed when tooth samples were fragments rather then full teeth. Samples were then submitted to the same methods of preparation as previously stated.

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ASSESSING S EASONALITY USING CO 2 L ASER A BLATION ON PREHISTORIC TOOTH EN AMEL University of Florida | Journal of Undergraduate Research | Volume 12 Issue 3 | Spring 2012 3 Laser Ablation Continuous Flow Isotope Ratio Mass Spectrometry Teeth were sampled used Laser Ablation Continuous Flow Isotope Ratio Mass Spectrometry (LA CF IRMS). While isotope analysis of tooth enamel is no t new the use of laser ab lation to produce CO 2 gas for isotope analysis allows for finer grained sampling of the specimen, which in tu rn allows for analysis of changing seasonality during enamel formation for the samples used in this stud y (Spotl et al. 2006, Cerling et al. 1996, Passey et al 2006). Three major techniques for micro sampling specimen at high spatial resolution s curre ntly exist, and while the two other methods require a separate handling step, the technique employed in this study, laser ablation, does not. When using a microdrill or micromill, it is necessary to transfer the sample powder created to a carbonate prepara tion system linked to a mass spectrometer. Laser ablation allows for direct linkage to a mass spectrometer via continuous gas flow ( Spotl et al. 2006). Here we used continuous He flow to interface the CO 2 gas produced from laser ablation directly on to the sample with an isotope ratio mass spectrometer. CO 2 gas is produced from a designated spot on tooth enamel controlled by computerized laser software, and then carried to the mass spectrometer by the flowing He gas, producing carbon and oxygen isotope ratios. Figure 2 displays the LA CF IRMS set up used. Procedure After each tooth was cleaned and prepared for sampling, they were transported t o the Stable Isotope Lab in t he Department of Geological Sciences at the University of Florida. Each tooth/toot h fragment was sampled individually, starting at the apex of the sample and then proceeding downward towards the cementoenamel junction. Each incremental sample consisted of a designated line of laser shots along the horizontal axis of the tooth (same grow th axis). Because of the variance in sample availability, shape, and size, laser settings were determined specifically for each tooth in order to produce the most CO 2 gas possible from the enamel without polluting the isotopic values with gas from the den tin or other components of the tooth besides ename l. As many individual samplings as could fit moving down the growth axes of eac h tooth sample were taken, and each individual sample on a tooth was consistently 1 mm apart. Carbon and oxygen isotopic values were recorded from the CO 2 gas prod uced. Figure 2. LA CF IRMS Set up in the Stable Isotope Lab at the University of Florida, Department of Geology Table 2. Laser Variable Settings for Each Sample Sample Power Pulse Width Scan Speed Pit Size ( m) Length ( m) Pits/Line Lines (#) Dist. btw (mm) NC 142 25 180 150 160 2641.1 17 25 1 NC 138 20 120 150 160 2313.6 14 22 1 NC 120 30 140 150 160 1985.8 12 40 1 NC 122 30 140 150 160 1976.6 12 16 1 NC 121 30 140 150 160 1974.6 12 19 1 NC 175 30 140 150 160 1976.5 12 4 1 LM 2 30 140 150 160 1987.6 12 15 1 LM 1 25 120 150 160 1982.3 12 25 1 BOS 34 20 120 150 160 982.7 6 40 1 LM 4 25 140 150 160 1594.7 9 10 1

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AMELIA SCHAUB DR JOHN KRIGBAUM & DR JASON CURTIS University of Florida | Journal of Undergraduate Research | Volume 12 Issue 3 | Spring 2012 4 RESULTS 18 O and 13 C values were obtained for each incremental sample on all ten teeth. A simple correction formula was then applied to the recorded isotopic values, derived from sampling a substance with known carbon and oxygen isotop e ratios Carrara Marble, and finding the difference between the known and recorded values. The number of samples taken on each tooth ranged from 4 to 40. Due to differences between each sample, each tooth was analyzed in dividual ly Table 3 reports the 18 O value statistics obtained and Table 4 the 13 C value statistics obtained. Table 3. Statistical Data for 18 O Values O btained Table 4. Statistical Data for 13 C Values O btained Sample Mean Standard Deviation Range ( 0 / 00 ) NC 142 15.2 0.73 2.04 NC 138 15.4 2.34 2.42 NC 120 17.0 0.66 2.63 NC 122 18.9 0.55 1.59 NC 121 17.5 0.61 2.41 NC 175 16.1 0.71 1.59 LM 2 20.1 0.23 0.81 LM 1 19.2 0.48 1.46 BOS 34 18.8 1.08 7.59 LM 4 18.6 0.19 0.53 Seasonal Analysis To assess seasonality, the 18 O values fro m each sample were plotted against distance down the tooth enamel as shown in Figures 3 12 Balasse et al. (2011) have shown a sinusoidal pattern of 18 O variation to indicate changing seasonality over the span of a year, with the lowest 18 O values corresponding to dry, cold seasons and the highest 18 O values to wet, warm weather. Several of the samples show signs of possible seasonality with observable swings in 18 O graphs and large standard deviations from the intra tooth mean. Figure 3 Sample NC 142: Sus barbatus. 18 O values ranged from 23.69 to 14.40 with an average of 19.15. Figure 4. Sample NC 138: Sus barbatus 18 O values ranged from 32.93 to 26.15 with an average of 28.42 Figure 5. Sample NC 120 : Bos 18 O values ranged from 16.71 to 12.66 with an average of 14.10 -24.0 -22.0 -20.0 -18.0 -16.0 -14.0 0 10 20 30 18 O PDB Distance (mm) NC 142 -35.0 -33.0 -31.0 -29.0 -27.0 -25.0 0 10 20 30 d18OPDB Distance (mm) NC 138 -20.0 -18.0 -16.0 -14.0 -12.0 -10.0 0 10 20 30 40 50 18 O PDB Distance (mm) NC 120 Sample Mean Standard Deviation Range ( 0 / 00 ) NC 142 19.2 3.47 9.29 NC 138 28.4 2.34 6.78 NC 120 14.1 1.23 4.05 NC 122 17.2 0.63 2.17 NC 121 12.7 1.65 5.27 NC 175 22.2 4.83 10.3 LM 2 19.1 2.46 9.21 LM 1 15.0 3.10 9.62 BOS 34 12.6 0.64 2.19 LM 4 17.0 1.57 5.35

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ASSESSING S EASONALITY USING CO 2 L ASER A BLATION ON PREHISTORIC TOOTH EN AMEL University of Florida | Journal of Undergraduate Research | Volume 12 Issue 3 | Spring 2012 5 Figure 6. Sample NC 122: Bos. 18 O values ranged from 18.27 to 16.10 with an average of 17.23. Figure 7. Sample NC 121: Bos. 18 O values ranged from 14.66 to 9.39 with an average of 12.70. Figure 8. Sample NC 175: Bos. 18 O values ranged from 28.08 to 17.76 with an average of 22.21. Figure 9. Sample LM 2: Bos. 18 O values ranged from 24.85 to 15.64 with an average of 19.09. Figure 10. Sample LM 1: Bos. 18 O values ranged from 20.16 to 10.54 with an average of 14.97 Figure 11. Sample: Bos 34: Bos. 18 O values ranged from 13.92 to 11.24 with an average of 12.58. -25.0 -23.0 -21.0 -19.0 -17.0 -15.0 0 5 10 15 20 d18OPDB Distance (mm) NC 122 18.0 13.0 8.0 0 10 20 18 O PDB Distance (mm) NC 121 -28.5 -23.5 -18.5 0 1 2 3 4 5 18 O PDB Distance (mm) NC 175 -25.0 -23.0 -21.0 -19.0 -17.0 -15.0 0 5 10 15 18 O PDB Distance (mm) LM 2 -20.3 -18.3 -16.3 -14.3 -12.3 -10.3 0 5 10 15 20 25 18 O PDB Distance (mm) LM 1 -19 -17 -15 -13 -11 -9 0 20 40 60 d18OPDB Distance (mm) Bos 34

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AMELIA SCHAUB DR JOHN KRIGBAUM & DR JASON CURTIS University of Florida | Journal of Undergraduate Research | Volume 12 Issue 3 | Spring 2012 6 Figure 12. Sample LM 4: Rhinoceros. 18 O valu es ranged from 20.49 to 15.14 with an average of 17.70. DISCUSSION The results of this study confirm LA CF IRMS as a successful m ethod for incrementally and sub annually analyzing small mammalian tooth enamel for 18 O and 13 C values. The isotopic ratios obtained reflect sub annual data during enamel formation, regardless of consistency or variance. 18 O graphs that do display sinusoidal curves may be due to changes in weather patterns occurring in the while 18 O graphs displaying consistency may correlate to weather conditions that were unchanging throughout the year. However analyzing each sample within a larger time context becomes difficult due to the variance in and uncertainty of age While radiocarbon dates are available for some samples, estimates according to site stratification and the position of sample recovery are the best indication of age available. If more specific ages were available, the success of this in situ laser ablation meth od of micro sampling faunal tooth enamel could prove useful in adding to the terrestrial record at Niah Cave during the periods of global and regional climate changes following the last glacial maximum, and ultimately provide insight into human patterns an d behaviors during these times during which the record is incomplete. REFERENCES Balasse, M., Obein, G., Ughetto Monfrin, J., Main land, I. (2011). Investigating seasonality and season of birth in past herds: A reference set of sheep enamel stable oxygen isotope r atios. Archaeometry doi:10.1111/j.1475.2011.00624.x Cerling T.E., Sharp, Z.D. (1996). Stable Carbon and oxygen isotope analysis of fossil tooth enamel using laser ablation. Palaeogeography, Palaeoclimatology, Palaeoecology 126: 173 186. Heaney, L.R. (1991). A s yno psis of climatic and vegetational c hange in South east Asia. Climatic Change. 19: 53 61. Hillson, S. (1986). Teeth. Cambridge University Press. Passey, B .H., Cerling, T.E., Levin, N.E. (2007). Temperature dependence of oxygen isotope acid fractionation for modern and fossil tooth enamels. Rapid Communic ations in Mass Spectrometery 21: 2853 2859. Krigbaum, J.S. (2001) Human Paleodiet in Tropical Southeast Asia: Isotopic Evidence from Niah Cave and Gua Cha. Unpublished Ph.D. dissertation, New York University. Nelson, S.V. (2005). Paleoseasonality inferr ed from equid teeth and intra tooth isotopic variability. Palaeogeography, Paleoclimatology, Palaeoecology 222:122 144. Partin et al (2007). M illennial scale trends in west P acific warm pool hydrology since the Last Glacial Maximum. Nature 449: 452 455. Passey, B.H., Cerling, T.E. (2006). In situ stable isotope analysis of very small teeth using laser ablation GC/IRMS. Chemical Geology 235: 238 249. Spotl, C., David, M. (2006). Stable isotope microsampling of speleotherms for palaeoenvironmental st udies: A comparison of microdrill, micromill, and laser ablation techniques. Chemical Geology 235: 48 58 Stephens, M., Mattey, D., Gilbertson, D.D., Murray Wallace, C.V. (2008). Shell gathering from mangroves and the seasonality of the Southeast Asian Mons oon using high resolution stable isotopic analysis of the tropical estuarine bivalve ( Geloina erosa ) from th e Great Cave of Niah, Sarawak: M ethods and reconnaissance of molluscs of early Holocene and modern times Journal of Archaeological Science. 35: 26 86 2697. -24.0 -22.0 -20.0 -18.0 -16.0 -14.0 0 2 4 6 8 10 18 O PDB Distance (mm) LM 4