Physicochemical Study of Black Pigments in ... - ACS Publications

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Physicochemical Study of Black Pigments in Prehistoric Paints from Oxtotitlán Cave, Guerrero, Mexico Joseph McPeak,1 Mary D. Pohl,2 Christopher L. von Nagy,3 Heather Hurst,4 Marvin W. Rowe,5 Eliseo F. Padilla Gutiérrez,6 and Jon Russ*,1 1Department

of Chemistry, Rhodes College, Memphis, Tennessee 38112 of Anthropology, Florida State University, Tallahassee, Florida 32306 3Department of Anthropology, University of Nevada, Reno, Nevada 89547 4Department of Anthropology, Skidmore College, Saratoga Springs, New York 12866 5Department of Chemistry, Texas A&M University-Qatar, Doha, Qatar and Office of Archaeological Studies and Conservation: Laboratory, Museum of New Mexico, Santa Fe, New Mexica 87507 6Escuela Nacional de Antropología e Historia, Mexico City 14030, Mexico *E-mail: [email protected] 2Department

This paper investigates the potential for identifying and dating black pigments in the Formative-style (800-400 B.C.E.) murals at Oxtotitlán Cave, Guerrero, Mexico, with the goal of studying prehistoric paint technology and the socio-political context of early Mesoamerican art. These murals are among the earliest in Mexico, if not the earliest, and represent the beginning of the highly influential Mexican muralism tradition that continues to this day. We employed multiple analytical techniques including pXRF, ATR-FTIR, SEM-EDS and Py-GC-MS to analyze black paints used to construct several motifs, including the depiction of a costumed, dancing lord at Oxtotitlán (Mural C-1). The

© 2013 American Chemical Society In Archaeological Chemistry VIII; Armitage, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2013.

results indicate that the pigment present is a byproduct of pyrolyzed plant material, most likely a mixture of soot and charcoal. The black pigment appears to occur directly on the surface of the limestone substrate but is completely covered by a natural rock coating composed of calcium oxalate, carbonate and sulfate. The presence of charcoal and biogenic oxalate promises to allow crucial radiocarbon analysis of the rock art.


Introduction The murals of Oxtotitlán Cave in Guerrero, Mexico (Figure 1) first came to the attention of academia in the late 1960s (1–3). Iconographic similarities with Gulf Coast Olmec monuments from La Venta (4, 5) were immediately apparent. Nevertheless, lack of chronological dates on the cave paintings has hindered analysis of historical relationships. The Oxtotitlán rock paintings are part of a body of public and private art found in caves and on mountainsides that can be incorporated into emerging architectural traditions that define an era. This era, The Formative Period, saw the emergence of many of the cultural features that would come to define Mesoamerican life: A complex set of secular and religious calendars, impressive public art, writing, large scale government, and an increasingly dynamic international trade between what were, or would soon become, kingdoms. Oxtotitlán Cave comprises a compact chain of several large grottos and deep caves along a limestone cliff face overlooking and marking the eastern edge of a large Formative site, Cerro Quiotepec (6). The caves are decorated with numerous monochrome pictographs and polychrome murals that are presumed to range in date and style from the Archaic to the Postclassic periods (< 2000 BCE to 1519 CE). The pictographs tend to be small in size and appear in clusters, often on highly inaccessible areas meters above the c ave floor. The murals are located toward the front of the cave and are more public than many of the pictographs. The murals differ from the pictographs in that they are complex polychromatic paintings that arguably function architecturally within the context of the cave. The largest mural, a composite juxtaposition of the Mexican cara-cara raptor and a bird-costumed lord and probable ruler, was painted high on the cliff face above the cave and is easily visible from the ancient town below (Figure 2). Archaeological materials at the lip of the cave, including grinding stones, suggest that the cave site may have served as a living area or may be the result of feasting or offertory rituals commonly associated with caves in Mesoamerica. Many of the paintings are faint, eroded, and covered with a natural mineral accretion making them difficult to see. Sandra Cruz Flores of the Mexican National Institute of Anthropology and History finished selective cleaning of the Oxtotitlán paintings in 2009 as part of a conservation program, exposing new images that were previously concealed by the mineral accretion. Mural C-1 was cleaned at this time, revealing previously obscured parts of the mural that lay beneath the natural mineral coating. 124 In Archaeological Chemistry VIII; Armitage, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2013.


Figure 1. Map showing the location of the Oxtotitlán Cave.

125 In Archaeological Chemistry VIII; Armitage, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2013.


These developments have further highlighted similarities between the Gulf Coast Olmec monuments and Oxtotitlán Cave, and have renewed questions about the nature of their relationship. Accurate dating of pigments within these murals is essential for evaluating relationships developing throughout Mexico between 800-400 B.C.E. Breakthroughs in chemical analysis and radiocarbon dating have made this an opportune time to reevaluate the connections between caves in southwestern Mexico and early Olmec ceremonial centers on the Gulf Coast.

Figure 2. Digitally enhanced image of Mural C-1 at Oxtotitlán Cave. Samples of black paint were collected from this mural for this study. The mural is ~ 3 m x 3 m. (see color insert)


Experimental Methods and Results


Preliminary in Situ pXRF Analysis One of the primary objectives of the project was to establish the age of one or more of the iconographic pictographs and murals in the Oxtotitlán Cave. The first phase of this study was to identify paints that appear to be most favorable for radiocarbon dating, either directly by 14C assay of bioorganic matter in the paint, or indirectly via 14C dating of the rock coating that covers the natural rock surfaces and the rock art in the site. Our strategy for identifying artifacts for direct dating was based on the assumption that black pigments at that time would have been produced from either manganese oxides or burned plant material (charcoal), both of which are used in wall painting traditions throughout Mesoamerica (7). Since the latter can be more reliably radiocarbon dated, black paints lacking manganese would be candidates for sampling and further study. Charcoal has been identified as a component in numerous prehistoric rock paintings worldwide, and radiocarbon assays of the material have provided absolute ages of these artifacts (8). We analyzed the rock paints at the study site using a portable X-ray florescence (pXRF) spectrophotometer. This technique is non-invasive and provides semiquantitative data on a variety of metals in the paints and natural surfaces (9–12). We used an Innov-X Alpha Series pXRF system that consists of a silver (Ag) anode X-ray tube source and a SiPIN diode detector. The instrument was operated in “soil mode” using 40 kV excitation energy with 30-second analysis times. Each artifact was analyzed at multiple locations, with several background analyses performed on adjacent unpainted surfaces. The results from the pXRF analyses of black pigments (N = 43) showed that Mn was below the instrument detection limit in 35 (81%) of the measurements (Table I). For the eight analyses where Mn was detected the average concentration in the paints was 0.0139 ± 0.004 %. In the background analyses (N = 22) Mn was undetected in 18 measurements (82%); the average concentration of the four where Mn was detected was 0.0138 ± 0.003 %. As a comparison, the analysis of red paints in the site (N = 22) and the background (N = 27) resulted in an average Fe concentrations of 0.95 ± 0.83% and 0.17 ± 0.17%, respectively. The assumption that the red pigments were produced from iron based minerals, most likely iron oxides, was confirmed since the mean Fe concentration in the paints is significantly greater than the background (p = 7.3 x 10-5). In the case of Mn, however, the concentration of the metal in the paint is statistically indistinguishable to that in the background (p = 0.98). We conclude that all the black paints in the Oxtotitlán Cave that we analyzed were produced using pigments other than manganese, and thus most likely pyrolyzed carbon.


128


Table I. Semi-quantitative metal concentrations from the pXRF analysis of rock paints and background (∗ indicates below detection limits) black paints

Mn (wt %)

Fe (wt %)

Cu (wt %)

As (wt %)

Sr (ppm)

Pb (ppm)

Zn (wt %)

Panel D, PET 1

0.021

0.22

2.78

0.06

67

69

*

Panel D, PET 1

*

0.23

2.89

0.07

68

52

*

alcove

*

0.12

1.29

0.05

65

363

*

alcove

*

0.31

2.26

0.06

65

101

*

alcove

*

0.13

0.41

0.01

67

38

*

alcove

*

0.26

0.63

0.03

118

66

*

C-1

*

0.23

2.37

0.05

142

*

*

C-1

0.015

0.58

0.01

0.01

220

*

0.027

C-1

*

0.59

0.01

0.01

208

*

0.035

C-1

0.012

0.21

1.80

0.01

69

*

*

Panel D, PET 1

*

0.05

0.01

*

48

*

*

Panel D, PET 1

*

0.06

*

*

68

44

*

Panel D, PET 1

*

0.66

*

0.02

53

25

Handprints

*

0.10

0.01

*

29

*

0.010

Handprints

0.010

0.15

0.01

*

29

28

0.010

*

0.08

*

*

72

*

*

Panel C PET 3

In Archaeological Chemistry VIII; Armitage, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2013.

Mn (wt %)

Fe (wt %)

Cu (wt %)

As (wt %)

Sr (ppm)

Pb (ppm)

Zn (wt %)

Panel 3, PET 2

*

0.06

*

*

55

30

0.002

Panel 3, PET 2

*

0.04

*

*

57

*

*

Panel 3, PET 2

*

0.05

*

*

57

45

0.002

Panel 3, PET 2

*

0.05

*

*

61

15

*

Panel 3, PET 2

*

0.03

*

*

65

*

*

Panel 3, PET 2

*

0.08

*

*

76

25

0.002

Jaguar man

*

0.20

0.01

*

73

39

0.006

Jaguar man

*

0.05

*

*

83

*

*

Jaguar man

*

0.05

*

*

70

16

Jaguar man

*

0.05

*

*

73

24

0.003

Jaguar man

*

0.48

0.01

*

75

*

0.004

critters

*

0.06

*

*

49

34

0.003

critters

*

0.06

*

*

57

40

0.003

critters

0.011

0.07

*

*

62

*

0.002

Jaguar man

*

0.10

*

*

66

17

*

Jaguar man

*

0.04

*

*

76

27

0.005

C-1

*

0.30

0.06

0.02

68

*

0.003

129


black paints

Continued on next page.


130


Table I. (Continued). Semi-quantitative metal concentrations from the pXRF analysis of rock paints and background (∗ indicates below detection limits) Mn (wt %)

Fe (wt %)

Cu (wt %)

As (wt %)

Sr (ppm)

Pb (ppm)

Zn (wt %)

*

0.18

0.42

0.02

131

*

*

alcove

0.018

1.03

0.02

0.03

120

94

0.009

shield

*

0.32

*

*

84

*

0.002

shield

0.011

0.25

*

*

28

*

0.003

shield

0.011

0.24

*

*

78

*

*

shield

*

0.19

*

0.01

75

51

0.004

shield

*

0.13

*

*

63

*

0.002

shield

*

0.03

*

*

125

*

*

*

0.19

0.01

0.01

89

34

0.004

*

0.08

*

*

72

*

*

*

0.05

*

0.02

58

*

*

0.011

0.12

0.01

37

17

0.008

0.013

0.17

*

0.03

107

*

0.008

*

0.17

*

0.02

77

*

0.003

*

0.07

*

69

*

*

black paints C-1

Background Panel C PET 3

Monkey


Panel 3, Pet 2

jaguar man

panel C-2

shield

131


black paints

left of panel 1

Mn (wt %)

Fe (wt %)

Cu (wt %)

As (wt %)

Sr (ppm)

Pb (ppm)

Zn (wt %)

*

0.05

*

*

80

*

*

*

0.09

*

*

60

*

*

*

0.07

*

0.01

79

95

*

*

0.11

*

*

71

15

0.003

*

0.07

*

*

60

55

0.003

*

0.02

*

*

7

*

*

*

0.04

*

*

53

*

0.002

*

0.08

*

*

76

*

*

*

0.20

*

0.01

85

32

*

*

0.09

*

*

58

*

*

*

0.04

*

*

63

*

*

*

0.26

*

*

235

*

0.005

*

0.03

*

*

125

*

*

*

0.08

*

*

158

*

0.006

0.014

0.44

*

*

274

25

0.003

0.017

0.40

*

*

159

*

0.005



Based on the assumption that the black pigments were carbon based, we collected samples from three paintings including the C-1 mural (Figure 2) and an image that appears to be a warrior and shield (Figure 3). We also collected samples from unpainted surfaces adjacent to the artifacts to serve as background for the pigment analyses. Sample sizes were typically less than 1 cm2 surface area and were taken directly from the shelter wall and placed immediately into Al foil for transport back to the laboratory.

Figure 3. View of the bi-chrome (black and red) warrior and shield painting (Panel 4-05) at the mouth of the north cave at Oxtotitlán. The primary lines of the painting are black with red filling the centers of the tab-like projections of the shield. The scale is 1.0 m with 10.0 cm increments. Laboratory Analyses We analyzed paint and unpainted (background) samples using optical microscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, environmental scanning electron microscopy with energy dispersive X-ray spectrometry (ESEM-EDS), and pyrolysis-gas chromatography–mass spectrometry (Py-GC-MS). Optical microscopy revealed that the paints were covered by a natural rock coating; however, because of the limited amount of sample available we did not construct thin-sections to discern the coating/paint/substrate stratigraphy. Instead we broke two samples manually and observed each fragment microscopically in cross-section. These observations were consistent with the black paint occurring primarily on or near the limestone substrate. Nevertheless, a considerable amount of the black pigment was dispersed within the ~0.5mm thick rock coating. 132 In Archaeological Chemistry VIII; Armitage, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2013.


To determine the general molecular composition of the rock coating we analyzed sub-milligram aliquots of the material (scraped from the surface using a needle) using a Perkin-Elmer Spectrum 100 ATR-FTIR. The ATR crystal used was diamond/ZnSe and all spectra were background corrected. The instrument was set at 4 cm-1 resolution and four scans collected. We identified oxalate as the principle component of the coating based on the characteristic broad absorption band centered at 1630 cm-1 and the sharp peak at 1320 cm-1 (Figure 4). Sulfate was also present as indicated by the broad absorbance between 1080 and 1180 cm-1. There was evidence of carbonate based on the broad band at 1360 cm-1.

Figure 4. An ATR-FTIR spectrum of the rock coating that covers the black paint showing the presence of oxalate, sulfate and carbonate.

High magnification imaging and elemental analyses were performed using a Philips XL 30 ESEM operated at 30 keV in the “wet mode.” This technique allowed us to analyze samples without adding a conductive coating, thereby leaving the samples unaltered for further study. We analyzed bulk sample surfaces, cross-sectional views of bifurcated samples, and powdered aliquots scraped from the surfaces using a needle The ESEM/EDS analysis of the natural accretion revealed two distinctive microcrystalline forms comprising the rock coating (Figure 5). One consisted of relatively larger, platy crystals with high concentrations of Ca and S (Figure 5A). This is likely gypsum (CaSO4·2H2O), which is prevalent on rock and stone surfaces, usually as a result of efflorescence (13). The second component appeared microcrystalline and was chemically consistent with calcium oxalate, either whewellite (CaC2O4·H2O) or weddellite (CaC2O4·2H2O), based on the relative concentrations of Ca, C and O (Figure 5B). Oxalates are also common on rock surfaces inside dry rock shelters and under rock overhangs, i.e., surfaces not exposed to direct rain or runoff (14). 133 In Archaeological Chemistry VIII; Armitage, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2013.


Figure 5. ESEM photomicrograph showing the rock coating in cross-sectional view. Two distinctive types of structures are observed. The EDS spectra (A) suggests that the platy material is calcium sulfate (probably gypsum), while the microcrystalline substance appears to be calcium oxalate (B).

High magnification of the paint samples using the ESEM/EDS also revealed two physically different pigment morphologies, although both pigment forms were chemically similar. One form of the paint appeared amorphous and smooth under high magnification, with small fractures occurring on the surface (Figures 6 & 7). The elemental composition of these areas was predominantly carbon (~70% C) with O/C ratios of 0.3. A second form of pigment consisted of small, black, cylindrical shaped particles, ~15 µm in height with ~3µm radii, and carbon rich, containing 70% to 80% C with O/C ratios between 0.2 – 0.3 (Figures 8 & 9). Experiments using pyrolysis GC-MS were performed on scrapings from a black paint sample and a non-painted background sample using a CDS Pyroprobe 5200 coupled to a Varian PE Autosystem GC/MS system. The powdered samples (~10 mg) were placed in a boat that was inserted into the pyrolyzer and first heated to 250°C then to 600°C. Whereas there was no significant detection of compounds at 250°C, at 600°C there were a considerable number of organic compounds released from both the paint and background samples. Moreover, the chromatograms and mass spectra revealed essentially the same suite of compounds from both the paint and background sample, indicating that there were no unique materials released in the pyrolysis of the paint (Figure 10; Table 2). There were three groups of organic compounds released during the pyrolysis: aromatics, oxygenates and normal hydrocarbons. This result demonstrated that there is a considerable quantity of organic matter in the samples, but that these compounds were native to the oxalate-rich coating and not unique to the paint.



Figure 6. ESEM photomicrograph of a small fragment of the coating with exposed paint. The painted areas appear smooth and amorphous. 135 In Archaeological Chemistry VIII; Armitage, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2013.


Figure 7. A highly magnified region in the top of Figure 7 showing the smooth texture of the paint. The EDS analysis (at arrow) demonstrates the paint matieral is predominately carbon.



Figure 8. An ESEM photomicrograph of material scraped from the surface of a paint sample. The small particles labeled A and B are carbon rich, as shown in the EDS spectra A & B.



Figure 9. A high magnification ESEM photomicrograph showing what appears to be a charcoal fragment in the paint. 138 In Archaeological Chemistry VIII; Armitage, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2013.


Figure 10. Pyrograms of a black paint sample from the C-1 Mural (Top) and a sample of the natural rock coating.collected adjacent to the mural (Bottom).


Table 2. Compounds identified in the pyrograms of black paint and natural rock coating


Peak number

Compound

1

Benzene

2

Methylbenzene (toluene)

3

1-Octene

4

2-Cyclopenten-1-one

5

Ethylbenzene

6

Phenylethene (styrene)

7

2-Methyl-2-Cyclopenten-1-one

8

Benzaldehyde

9

2,2-dihydroxy-1-phenylethanone

●

n-Alkane/Alkene pair

c

Contamination

Conclusions One of the principal goals of this study was to investigate the feasibility of radiocarbon dating the rock art in the Oxtotitlán Cave. The results demonstrate that the pigments in samples of black paint from the site are most likely from pyrogenic carbon (PyC), specifically a combination of amorphous black carbon and charcoal. The incomplete combustion of plant material can produce a variety of PyC residues that have a continuum of physical and chemical properties (15). Depending on the extent of combustion based on factors such as temperature, chemical reformation (16), and oxygen availability, the combustion byproducts can take on a variety of characteristics. For example, partially charred plant materials that retain much of the original plant cellular structure are referred to as charred biomass (or simply char); when a more complete decomposition occurs but with particles > 0.2 µm2 remaining the substance is defined as charcoal; and finally, higher temperatures with limited available oxygen produces soot (15–17). The amount of oxygen remaining in the PyC relative to carbon also decreases continuously with these trends, with O/C ratios of ~0.6 for char, ~0.4 for charcoal, and ~0.2 for soot (15, 16). The characteristics of the black pigments, with observable carbon rich particles mixed with amorphous carbonaceous matter, both with O/C ratios between 0.2 – 0.3, suggest that the pigment material is a mixture of charcoal and soot. Because there is PyC in the paint it is therefore feasible to radiocarbon date the pigment, assuming that this material can be isolated from the oxalate-rich 140 In Archaeological Chemistry VIII; Armitage, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2013.


coating and limestone substrate for the 14C assay. Absolute dating of the paint will allow evaluation of socio-political relationships that are suggested by similarities in iconography between the sacred Oxtotitlán Cave and the capitals of early kingdoms, most especially the Olmec ceremonial center of La Venta, which was one of Mesoamerica’s first cities. A second strategy for establishing age constraints of the paintings is also feasible in the Oxtotitlán site. The samples of rock paint that we collected are covered by a Ca oxalate-rich rock coating. These coatings are the byproduct of either lichen or microbial activity (14, 18, 19) and as the oxalate is a biogenic byproduct it can be 14C dated. Since the coating is superimposed over the paint, the creation of the paintings occurred prior to the formation of the oxalate. Thus, 14C dating of the oxalate provides a minimum age. The strategy of using radiocarbon assays of oxalate coatings to constrain the age of rock art has been used worldwide, including Europe (20), Africa (21), Australia (22–24), South America (25, 26), North America (27, 28) and the Middle East (29).

Discussion Our goal is to investigate early Mesoamerican social networks and the symbols and public representational art that developed alongside and mediated political power in the region’s emerging kingdoms. The Formative period saw the emergence of multiple traditions of writing in Mesoamerica and rich iconographic systems that linked political power to history, core cultural myths, the landscape, and a tradition of performative political and religious theatre. This cave, as a portal to the world of night and death, and as a place of rebirth and transformation, is often represented as such within this cultural phenomenon. Accurate dating is essential for reconstructing how cave ritual evolved over millennia within the framework of the rise and fall of these prehistoric societies. A chronological framework allows evaluation of stylistic similarities, and underlying Formative period socio-economic relationships, between Oxtotitlán in southwestern Mexico and early ceremonial centers such as La Venta (ca. 800–400 B.C.E.) to the east on the Gulf Coast and Chalcatzingo to the northeast in Central Mexico. The technology of prehistoric painting has the potential to contribute to this study in addition to dating. In the future we would like to characterize the composition of colors such as black and compare paint formulas used in Oxtotitlán to those identified different geographical regions and time periods. Mesoamerica has a long tradition of muralism, and the use of paints extended to decorating paper, cloth and animal hide, and the creation of painted manuscripts. The practitioners of these traditions were often highly trained individuals, and data from a variety of regions shows the emergence of schools characterized by particular stylistic and technological approaches to art and writing (30–33). Thus, understanding the underlying compositional formulae of early Mesoamerican muraling paints will contribute to our understanding of the evolution of technical skill and stylistic schools among Mesoamerica’s artisans. The presence of murals such as C-1 from Oxtotitlán is a testament to the technical expertise of their anonymous authors. 141 In Archaeological Chemistry VIII; Armitage, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2013.

Acknowledgments Thanks to Paul Simone, Heather Fleming, Joe Furlong, Madison Fuller, Tom Wampler, David Jeter, and the Rhodes Fellowship Program. We appreciate the Qatar Foundation and Texas A&M University-Qatar for the use of the pXRF spectrophotometer.

References


1. 2. 3. 4. 5. 6. 7.

8. 9. 10. 11. 12.

13. 14. 15. 16.

17. 18. 19. 20. 21. 22.

Gay, C. Nat. Hist. 1967, 4, 28–35. Grove, D. Dumbarton Oaks, Studies in Precolumbian Art and Archaeology; No. 6; Harvard University Press: Washington, DC, 1970. The Middle Preclassic Paintings at Oxtotitlán, Guerrero. http:// www.famsi.org/research/grove/ (accessed July 13, 2013). Drucker, P.; Heizer, R. F.; Squier, J. Bureau of American Ethnology; Bulletin 170; Smithsonian Institution: Washington, DC, 1959. González Lauck, R. Olmec Art of Ancient Mexico; Benson, E., de la Fuente, B., Eds.; National Gallery of Art: Washington, DC, 1996; pp 73−81. Schmidt Shoenberg, P. Thule Riv. ital. di studi americanistici 2010, 22, 277–291. Magaloni, D. La pintura mural prehispánica en México: Área Maya; de la Fuente, B., Staines Cicero, L., Eds.; Universidad Nacional Autónoma de México, Instituto de Investigaciones Estéticas: México, 2001; pp 155−198. Rowe, M. W. Rock Art Res. 2012, 29, 118–131. Newman, B.; Loendorf, L. L. Plains Anthropol. 2005, 50, 277–283. Rowe, M. W.; Mark, R.; Berrier, M.; Billo, E.; Steelman, K. L.; Dillingham, E. Am. Indian Rock Art 2011, 37, 37–47. Huntley (née Ford), J. Austral. Archaeol. 2012, 75, 78–94. Beck, L.; Genty, D.; Lahlil, S.; Lebon, M.; Tereygeol, F.; Vignaud, C.; Reiche, I.; Lambert, E.; Valladas, H.; Kaltnecker, E.; Plassard, F.; Menu, M.; Paillet, P. Radiocarbon 2013, 55, in press. Charola, A. E.; Pühringer, J.; Steiger, M. Environ. Geol. 2007, 52, 339–352. Hofmann, B. A.; Bernasconi, S. M. Chem. Geol. 1998, 149, 127–146. Preston, C. M.; Schmidt, M. W. I. Biogeosciences 2006, 3, 397–420. Hedges, J. I.; Eglinton, G.; Hatcher, P. G.; Kirchman, D. L.; Arnosti, C.; Derenne, S.; Evershed, R. P.; Kögel-Knabner, I.; de Leeuw, J. W.; Littke, R.; Michaelis, W.; Rullkötter, J. Organic Geochem. 2000, 31, 945–958. Thevenon, F.; Williamson, D.; Bard, E.; Anselmetti, F. S.; Beaufort, L.; Cachier, H. Global Planet. Change 2010, 72, 381–389. Russ, J.; Palma, R. L.; Loyd, D. H.; Boutton, T. W. Quaternary Res. 1996, 46, 27–36. Hess, D.; Coker, D. J.; Loutsch, J. M.; Russ, J. Geoarchaeology 2008, 23, 3–11. Ruiz, J. F.; Hernanz, A.; Armitage, R. A.; Rowe, M. W.; Viñas, R.; GaviraVallejo, J. M.; Rubio, A. J. Archaeol. Sci. 2012, 39, 2655–2667. Mazel, A. D.; Watchman, A. L. South Afr. Humanit. 2003, 15, 59–73. Watchman, A.; O’Coonor, S.; Jones, R. J. Archaeol. Sci. 2005, 32, 369–374. 142 In Archaeological Chemistry VIII; Armitage, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2013.


23. Smith, M. A.; Watchman, A.; Ross, J. Geoarchaeology 2009, 24, 191–203. 24. Aubert, M. J. Archaeol. Sci. 2012, 39, 573–577. 25. Hedges, R. E. M.; Ramsey, C. B.; Van Klinken, G. J.; Pettitt, P. B.; Nielsen-Marsh, C.; Etchegoyen, A.; Fernandez Niello, J. O.; Boshcin, M. T.; Llamazeres, A. M. Radiocarbon 1998, 40, 35–44. 26. Steelman, K. L.; Rickman, R.; Rowe. M. W.; Boutton, T. W.; Russ, J.; Guidon, N.; Archaeological Chemistry; Jakes, K. A., Ed.; ACS Symposium Series 831; American Chemical Society: Washington, DC, 2002; pp 22−35. 27. Russ, J.; Kaluarachchi, W. D.; Drummond, L.; Edwards, H. G. M. Stud. Conserv. 1999, 44, 91–103. 28. Scott, S. A.; Davis, C. M.; Steelman, K. L.; Rowe, M. W.; Guilderson, T Plains Anthropol. 2005, 50, 57–71. 29. Hassiba, R.; Cieslinski, G. B.; Chance, B.; Al-Naimi, F. A.; Pilant, M.; Rowe, M. W. QScience Connect 2012, 4. DOI: http://www.qscience.com/doi/abs/ 10.5339/connect.2012.4 (accessed July 11, 2013). 30. Lacadena, A. PARI J. 2008, 8, 1–22. 31. Reents-Budet, D. Painting the Maya Universe: Royal Ceramics of the Classic Period; Duke University Press: Durham, NC, 1994. 32. Rice, P. M. J. Arch. Meth. Theory 2009, 16, 117–156. 33. O’Grady, C. R; Hurst, H. In ICOMM-CC 16th Triennial Preprints; Bridgland, J., Ed.; Lisbon, Portugal, 2011; pp 869−879.


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