On establishing ceramic chemical groups: exploring the influence of data analysis methods and the role of the elements chosen in analysis (original) (raw)
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On establishing ceramic chemical groups
Open Journal of Archaeometry
"Since the 1970s, archaeologists have increasingly depended on archaeometric rather than strictly stylistic data to explore questions of ceramic provenance and technology, and, by extension, trade, exchange, social networks and even identity. It is accepted as obvious by some archaeometrists and statisticians that the results of the analyses of compositional data may be dependent on the format of the data used, on the data exploration method employed and, in the case of multivariate analyses, even on the number of elements considered. However, this is rarely articulated clearly in publications, making it less obvious to archaeologists. In this short paper, we reexamine compositional data from a collection of bricks, tiles and ceramics from Hill Hall, near Epping in Essex, England, as a case study to show how the method of data exploration used and the number of elements considered in multivariate analyses of compositional data can affect the sorting of ceramic samples into chemical groups. We compare bivariate data splitting (BDS) with principal component analysis (PCA) and centered log ratio-principal component analysis (CLR-PCA) of different unstandardized data formats [original concentration data and logarithmically transformed (i.e. log10 data)], using different numbers of elements. We confirm that PCA, in its various forms, is quite sensitive to the numbers and types of elements used in data analysis."
2018
Oxford Archaeology East undertook a program of archaeological evaluation and excavation work at the site of the former RAF Brampton, Cambridgeshire. Significantly, the excavators encountered a cluster of previously unknown early Roman pottery kilns. Small-scale potting industries, like this one, offer a unique opportunity to investigate British ceramic traditions. The presence of variation provides an opportunity to use Roux’s methods for ceramic analysis, to independently investigate what technological choices were made and then explore the main themes raised in original report: who were these potters and how did they organise themselves? Two phases of study, using three techniques, were employed. Technical and stylistic groups were sought by examining the material in hand-specimen. Thin-section petrography determined the fabric groups present and portable X-Ray Fluorescence helped to establish the geochemical composition of the sample. Comparison of the degree of heterogeneity at each stage, helped to unpick the chaîne opératoire and reconstruct the organisation of production. At each investigative phases of this study, it was possible to glimpse at the effects of technological choice. It was possible to conclude that this site was the meeting point of several (perhaps returning) potters; some of whom left clearer indications of their technological choices than others.
Journal of Archaeological Science: Reports, 2017
The so-called ‘chemical fingerprints’ of production sites that are determined in provenance studies of archaeological ceramics comprise not only an estimate of the intrinsic chemical compositions but also an estimate of their variability. The compositional variability of ceramics from a specific production site is affected by the natural variability of the raw materials used, variation in the ceramic production process and potential post-depositional alteration. In order to characterise the production site as whole, average concentrations and their variations are estimated on the basis of a necessarily limited number of samples selected for analysis. The sampling strategy therefore has a significant impact on the results. The compositional variability is interfered from uncertainties introduced during the analysis subject to the analytical method chosen. This paper provides an overview of the sources of variability that influence such analyses. Case studies challenging the classical unbiased provenancing approach are presented using examples from the eastern Mediterranean region.
Theory, Sampling, and Analytical Techniques in the Archaeological Study of Prehistoric Ceramics
American Antiquity, 1993
How archaeologists analyze pottery is determined by archaeological theory, sampling considerations, and available analytical techniques. The most damaging impediment to methodological advance is lack of a theory of how patterns of ceramic variation are generated. It is argued herein that Darwinian evolutionary theory (or selectionism) provides a body of concepts capable of explaining patterned variation and specifies measurements to make in testing specific explanatory statements. Most existing analytical procedures (e.g., the "Type-Variety" system) are regarded as aspects of sampling, the role of which is to help reduce some of the bewildering heterogeneity in ceramic collections before attempting to measure evolutionarily significant variation. Technical analysis, often considered the domain of nonarchaeological specialists, actually produces the measurements needed to test explanatory statements made about pottery observed in the archaeological record.
American Antiquity, 1996
We criticize the acid-extraction approach to chemical characterization of ceramics previously advocated in this journal by Burton and Simon (1993). The instrumental technique used by Burton and Simon (inductively coupled plasma emission spectroscopy [ICP]) is a highly precise chemical characterization technique, but noise introduced by characterizing acid extracts from sherds nullifies the usefulness of the resulting elemental concentration data for archaeological sourcing.
Journal of Archaeological Science, 2009
Cooking pots and bowls from two production locations ca. 200 m from each other at the rural settlement of Kefar Hananya in Roman Galilee were compared employing chemical element composition and vessel-shape analyses. Splits of each pulverized sample, all of which were taken from ceramic wasters, were analyzed by both instrumental neutron activation and high-precision X-ray fluorescence analyses, and computerized vessel-shape analysis was employed for morphological analysis of the same vessel forms from each location. Several statistical techniques (bivariate plots, principal component analysis and discriminant analysis) were used for analyzing the resultant data. It was found that both the cooking pots and bowls made at each location could be distinguished by employing either chemical composition or morphological analysis. The implications of this work, with regard to investigating both production and consumption sites, and for pottery provenance studies, are discussed. The findings suggest that these analytical techniques can be useful as an aid for chronological differentiations of archaeological pottery.
Provenance Study of Archaeological Ceramic
Journal of Trace and Microprobe Techniques, 2003
One hundred sixty three ceramic fragment samples from three archaeological sites were analyzed using instrumental neutron activation analysis (INAA) to determine the concentration of 24 chemical elements: As, and Zn. Bivariate plots and a multivariate statistical method, discriminant analysis, were performed on the data set. Discriminant analysis identified three compositional grouping and derived two discriminant functions that account for 100% of the variance between groups. The results show, at a confidence level of 98%, that ceramics of each separate site are statistically similar among them and it can be said that a common source of raw material was used independently in each of these sites.