A COMPARISON OF INDUCTIVELY-COUPLED PLASMA EMISSION SPECTROMETRY AND ATOMIC ABSORPTION SPECTROMETRY ANALYSIS ON STANDARD REFERENCE SILICATE MATERIALS AND CERAMICS

Analyses by inductively coupled plasma atomic emission spectrometry and atomic absorption spectrometry of 22 ceramic standards and sherds are compared. Further data from analyses of one of the ceramic standards analysed by both methods are also discussed. The results show that for most major elements, the methods are comparable, but that use of common standards would be advisable if data from the two methods are to be compared.     

MIDDLE HOLOCENE PERIODICITIES IN RAINFALL INFERRED FROM OXYGEN AND CARBON ISOTOPIC FLUCTUATIONS IN PREHISTORIC TROPICAL ESTUARINE MOLLUSC SHELLS

Stable oxygen and carbon isotopic ratios in modern and archaeological estuarine mollusc shells, Polymesoda radiata, change in accordance with seasonal salinity fluctuations in the Acapetahua estuary located on the Pacific coast of southern Mexico. This region receives ?3000 mm of precipitation annually, most during a wet season between April and October. The changing flux of fresh water and organic detritus into the estuary causes large changes in the oxygen and carbon isotopic composition of the estuarine waters and in the carbonate precipitated by P. radiata. Oxygen isotopic ratios in the shells of molluscs collected by late Archaic period populations (5000–4000 BP) in this region indicate that patterns of rainfall were similar to today. Modern shells, however, exhibit much more negative carbon isotopic values than observed in prehistoric shells. This change may be associated with the input of modern fertilizers into the estuary.     

THE CHEMICAL ANALYSIS OF ORIENTAL CERAMIC BODY COMPOSITIONS: PART 1: WARES FROM NORTH CHINA*

This paper presents the body analyses of 70 sherds of ceramics made in north China during the Late Tang and Northern Song dynasties (c. AD 80–1200). The major types represented are Ding, Xing and Cizhou-type wares. The analyses were obtained by atomic absorption spectrometry, giving information on nine major and minor constituents. These have been used to differentiate chemically between the major kiln sites in the north, with the aid of multivariate computer analysis. This has demonstrated that there are differing chemical characteristics associated with these kilns, but the study is hampered by the lack of authentic material from controlled excavations of the kiln sites.     

DIGITAL CEMENTUM LUMINANCE ANALYSIS AND THE HAUA FTEAH HOMININS: HOW SEASONALITY AND SEASON OF USE CHANGED THROUGH TIME*

The importance of environmental seasonality and the seasonal cycling of resources to human populations make studies of human responses to seasonality useful to test hypotheses about short‐ and long‐term changes in human behaviour. This paper utilizes digital dental cementum luminance analysis in order to better understand patterns of the seasons of death of Ammotragus lervia at Haua Fteah, Cyrenaica, and to test whether long‐term climatic changes can be detected in dental cement. The overall pattern of the season of death of A. lervia at Haua Fteah is that of year‐round utilization, with a slight increase over time in A. lervia use during the growth period/summer time. The use of digital cementum luminance analysis (DCLA) to detect changes in the seasonal differences between temperatures indicates a trend for increased seasonality in temperature over the past 40 000 years at Haua Fteah. Furthermore, DCLA patterns in the more recent assemblages indicate a shift to a warmer climate from Marine Oxygen Isotope Stage (MIS) 3 to MIS 1.     

ON THE INFLUENCE OF DRYING AND FIRING OF CLAY ON THE FORMATION OF TRACE ELEMENT CONCENTRATION PROFILES WITHIN POTTERY*

On experimentally fired briquettes made of five chemically and mineralogically different clays, trace element concentration profiles from the centre to the surface of the briquettes have been measured by Neutron Activation in order to examine if drying and firing of the clays lead to a mobilization and subsequent migration of single components within a sherd. Mineralogical changes during firing have been determined by X‐ray diffraction. Generally, no such migration could be found. For two clays, arsenic was lost from the briquette during firing, forming non‐constant concentration profiles. If NaCl is present in the clay paste, sodium migrates towards the surface. Additionally, in the special case in which the presence of NaCl coincides with that of calcite, the heavier alkali elements evaporate, forming significant concentration profiles within the sherd.     

MICRO‐RAMAN SPECTROSCOPY CHARACTERIZATION OF DELLA ROBBIA GLAZES*

Micro‐Raman spectroscopy and the laser‐induced transformation technique were used for systematic study of five coloured glazes on Saint John the Baptist (29 inch tondo), a majolica terracotta relief attributed to Luca Della Robbia and on permanent exhibit in The John and Mable Ringling Museum of Art. We suggest that ions in a lead silicate matrix, called ‘lead ultramarine’, could contribute to the famous Della Robbia blue colour, in addition to the effect of Co atoms as suggested previously by Pappalardo et al. (2004 ). The original yellow glaze contains lead(II) antimonate. The green is a mixture of the yellow and blue pigments, the brown contains hematite, and the white glaze contains tin dioxide as an opacifier. The use of lead oxide as a main fluxing agent is confirmed by laser‐induced micro‐crystallization.     

ARCHAEOMETRY AT TEXAS A&M UNIVERSITY: CHARACTERIZATION OF SAMOAN BASALTS

The Elemental Analysis Laboratory provides research support for campus users and service analyses for the University, other state and governmental agencies and private industry. The laboratory's primary concern is the application of unique methodology to a wide range of analytical problems that arise in the course of efforts by University researchers. For the past decade or so, compositional analysis by neutron activation analysis of archaeological artefacts for the purpose of studying provenance, trade or cultural patterns of prehistoric populations has become an area of focus. The present communication will discuss the laboratory in general and the scope and significance of the archaeology work done within the organization. A brief example of a current project involving the study of geologic samples from prehistoric stone tool quarries from American Samoa is presented as an illustration.     

THE ANALYSIS OF SEA TURTLE AND BOVID KERATIN ARTEFACTS USING DRIFT SPECTROSCOPY AND DISCRIMINANT ANALYSIS*

We investigated the utility of diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) for the analysis and identification of sea turtle (Family Cheloniidae) and bovid (Family Bovidae) keratins, commonly used to manufacture historic artefacts. Spectral libraries are helpful in determining the class of the material (i.e., keratin versus plastics), but do not allow for inferences about the species source of keratin. Mathematical post‐processing of the spectra employing discriminant analysis provided a useful statistical tool to differentiate tortoiseshell from bovid horn keratin. All keratin standards used in this study (n = 35 Bovidae; n = 24 Cheloniidae) were correctly classified with the discriminant analysis. A resulting performance index of 95.7% shows that DRIFTS, combined with discriminant analysis, is a powerful quantitative technique for distinguishing sea turtle and bovid keratins commonly encountered in museum collections and the modern wildlife trade.     

PROVENANCE STUDIES OF KOREAN CELADONS OF THE KORYǑ PERIOD BY NEUTRON ACTIVATION ANALYSIS*

Neutron activation analyses of the body fabric of celadons from the main production sites of the Koryǒ period have shown differences in composition between kilns. Comparison of over 50 celadon objects in the collections of the British Museum with this data base from the production sites has permitted the assignment of over 40 of the pieces to their kiln of origin The majority show the trace element pattern of the Sadangri kilns, a smaller proportion are assigned to Yuchǒnri, while others are assigned to the kilns at Chinsanri (underglaze iron) and Kyǒngsǒ-dong (unglazed). A representative group of Chinese Yue wares arc clearly different from Koryǒ celadons in trace element composition.     

DETECTION OF NEAR-SURFACE SILVER ENRICHMENT ON ROMAN IMPERIAL SILVER COINS BY X-RAY SPECTRAL ANALYSIS*

A collection of 218 Roman imperial silver coins, covering three centuries, was analysed non-destructively by two variants of X-ray spectral analysis. Electron beam excitation and energy-dispersive spectrometry was used for the analysis of the uppermost thin layer (3 μm) of each coin, while X-ray tube excitation and wavelength-dispersive spectrometry was applied for the analysis of thicker layers (30 μm), Ag and Cu as major constituents and 18 minor elements were determined quantitatively. Comparing the silver content of the obverse and the reverse of a coin, inhomogeneities could be identified. By comparison of the silver content of the upper thin and the thick surface layers, near-surface silver enrichment could be detected. Inhomogeneities and enrichments increase in the second and more so in the third century. A large scatter of the silver content and silver enrichment for coins of the same emperor was attributed to varying abrasion of Ag-enriched layers of the individual coins during decades of circulation.