Post‐Depositional Elemental Alterations in Pottery: Neutron Activation Analyses of Surface and Core Samples*

From 38 sherds with ‘corroded’ surfaces, two samples per sherd were examined using Neutron Activation Analysis, one from the surface and one from the core of each sherd, in order to analyse post‐depositional alterations of minor and trace elements. The most striking effect was that a leaching of Ca could be found at the surface. Another group of elements that is severely affected are the alkali metals, with Cs and Rb showing the strongest changes. A third conspicuous group of elements are the Rare Earth Elements. Finally, the effect of such alterations on a statistical data evaluation to classify pottery according to provenance is investigated.     

THOUGHTS ON THE UTILITY OF A BIVARIATE‐SPLITTING APPROACH TO OLMEC CERAMIC DATA INTERPRETATION*

A recently resolved debate centred on the interpretation of a major set of INAA data that was based on Olmec ceramics from Mexico. In an attempt to answer questions arising from the debate, this paper discusses the effect of numbers of samples chosen for data interpretation. It also presents interpretations of the ceramic data set based on a bivariate data‐splitting approach and compares the results of this with the multivariate analysis approaches employed by the initial publishers of the data.     

Model‐based Cluster Analysis of Artefact Compositional Data

Cluster analysis is the most widely used multivariate technique in archaeometry, with the majority of applications being exploratory in nature. Model‐based methods of clustering have their advocates, but have seen little application to archaeometric data. The paper investigates two such methods. They have potential advantages over exploratory techniques, if successful. Mixture maximum‐likelihood worked well using low‐dimensional lead isotope data, but had problems coping with higher‐dimensional ceramic compositional data. For our most challenging example, classification maximum‐likelihood performed comparably with more standard methods, but we find no evidence to suggest that it should supplant these.     

MAGNETIC SUSCEPTIBILITY VARIATIONS AT MONS CLAUDIANUS AND IN ROMAN COLUMNS: A METHOD OF PROVENANCING TO WITHIN A SINGLE QUARRY

Mons Claudianus in the Eastern Desert of Egypt was an important source of granodiorite for Roman columns. Computer contouring of 1119 magnetic susceptibility measurements at the quarry shows systematic variations, with low readings in the west of the quarry area and higher readings in the east. One hundred and seventy measurements on 62 columns of Mons Claudianus type in Rome and its environs were compared with the quarry readings, using a t-test based procedure. Some columns with distinctively low or high magnetic susceptibility could be provenanced very precisely to areas of about 700 × 700m within the 9km² of Mons Claudianus. Columns with susceptibility in the middle of the Mons Claudianus range could not be provenanced precisely. Results indicate early (first century AD) use of both west and east parts of Mons Claudianus, and contemporaneous use of several parts of the quarry, rather than systematic or sequential opening of the area. Columns found in third-century AD monuments, provenanced to the same parts of Mons Claudianus as earlier material, may indicate reuse of columns in some monuments. Magnetic susceptibility constitutes a portable and non-destructive method capable of provenancing not only to a quarry, but to specific areas within a single quarry.     

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.     

A REVIEW OF SUPERVISED AND UNSUPERVISED PATTERN RECOGNITION IN ARCHAEOMETRY*

Principal component, cluster and discriminant analysis are multivariate statistical methods that are widely used in archaeometry. They are examples of what are known in some literatures as unsupervised and supervised learning methods. Over the past 20 years or so, a wide variety of other learning methods have been developed that take advantage of modern computing power and, in some cases, have been designed to handle data sets more complex than those often used in archaeometric data analysis. To date, these methods have had little impact on archaeometry. This paper reviews, in a largely non‐technical manner, the ideas behind these newer methods; illustrates their use on a variety of data sets; and attempts to assess their potential for future archaeometric use.     

PHYSICOCHEMICAL COMPOSITIONAL ANALYSIS OF CERAMICS: A CASE STUDY IN KENTING,TAIWAN*

The composition of ceramics does not just reflect the component of some specific, unprocessed, geological, raw material source, but also certain forms of human behaviour involved in its manufacture. The purpose of this research project is to apply the acid‐extraction chemical method, complemented by a thin‐section petrographic study, to the compositional analyses of certain local ceramic collections (mainly from several sites in the southern Taiwan area). The results present the raw materials that the ceramic manufacturers of the two cultural traditions (O‐laun‐pi Phase II and Phase III–IV), which overlapped temporally, used. These materials came from the same sources, but the ceramics were manufactured in different ways. Particularly, the people of O‐laun‐pi Phase III–IV also procured certain materials from either local sources or from somewhere in eastern Taiwan to make their pots. The results also indicate that there might have been a variation in terms of their manufacture among sites of the same cultural tradition.     

STATISTICAL ANALYSIS OF CHEMICAL COMPOSITIONAL DATA AND THE COMPARISON OF ANALYSES

Recent statistical work on approaches to analysing compositional data - where variables sum to a constant for each row of a data matrix - may encounter difficulties when applied to data of the kind typically arising in scientific archaeology. The reason is that results obtained may be unsatisfactory from a substantive viewpoint for identifiable technical reasons. This paper explores and illustrates some possible resolutions of the problem. A feature of the approach used is to analyse subsets of the variables on separate scales. A synthesis of the results obtained from separate analyses is essential and the use of multiple correspondence analysis for this purpose is illustrated.     

STEATITE SOURCE CHARACTERIZATION IN EASTERN NORTH AMERICA: NEW RESULTS USING INSTRUMENTAL NEUTRON ACTIVATION ANALYSIS*

Doubts have recently been cast on the ability to characterize steatite sources using rare earth elements (REEs). By increasing the number of samples and elements examined using instrumental neutron activation analysis (INAA) and multivariate statistics, this study shows that, with unhomogenized samples, transition metals, not REEs, make the greatest contribution in characterizing steatite sources in the Middle Atlantic region of eastern North America. Preliminary results suggest that INAA has the potential to assign provenance to steatite artefacts, at least at a regional level.