Archaeological Chemistry

As part of the Topical Collection on the archaeometric study of ceramics, this paper focuses on terra sigillata ware. The main aims are to provide a review on the state of the art of the studies and to provide a guide to the most suitable analytical techniques. The text is divided into four main parts: (1) a brief archaeological introduction on the ancient production of terra sigillata; (2) a summary of the archaeometric studies carried out to date; (3) a reasoned list of the most suitable techniques for the investigation of the ceramic body and (4) an in-depth discussion on the most effective techniques for the study of the coating. The application of both destructive and non-destructive techniques is critically evaluated as well as the advantages and disadvantages provided by the different instrumentation, in terms of sample preparations and expected results.

Aragonite is one of the metastable polymorphs of calcium carbonate and is commonly found at archaeological sites in the form of mollusk shells and speleothems. Other occurrences include corals, fish otoliths, seed endocarps, wood ash and lime plaster. These materials contain microscopic embedded information of fundamental importance for the assessment of the state of preservation of the archaeological record, the reconstruction of paleoenvironments, the identification of pyrotechnological processes and the establishment of absolute chronologies. However, this information can be used only if the aragonite found at archaeological sites preserves its pristine structure and chemistry. Aragonite is metastable at ambient conditions and tends to dissolve and recrystallize into secondary aragonite or calcite, a process that entails the loss of its original elemental and isotopic signature. Therefore, well-grounded archaeological interpretations depend on the correct identification of aragonite and the careful characterization of its basic properties. This article aims at reviewing the dissolution processes of different types of aragonite, the methods used for their identification, and the archaeological information that can be extracted. Particular emphasis is given to the discussion of key issues regarding absolute dating and post-depositional processes of archaeological sediments, and to a detailed overview of the recently observed pyrogenic aragonite.

Over the last decade, the chemical analysis of archaeological bone has emerged a s a new method to address the dietary composition of past human populations. Paleodietary studies provide one means to obtain invaluable information regarding prehistoric intra-and inter-group behavioral differentiation. Unlike other prehistoric archaeological data, materials recovered from the mortuary context provide access to individual behavior. The total elemental and isotopic composition of bone record quantitative signatures of long-term individual dietary intake. These dietary signatures provide one means to make inferences about differential access to resources in prehistoric societies. Archaeological bone chemistry data can be used to establish prehistoric access to subsistence resources from different marine and terrestrial ecosystems by various individuals and territorial groups. The most reliable quantitative dietary information is derived from stable carbon and nitrogen isotope ratios in bone colla-gen. In contrast, in viuo elemental dietary signatures in bone mineral are obscured by postmortem chemical changes in the burial environment. Hence, accurate dietary inferences from inorganic bone apatite will depend on controls for these postmortem alterations. Schiffer's recent treatise, Formation Processes of the Archaeological Record (1987), provides a n explicit theoretical framework in which to address postmortem chemical changes in buried bone. Previous attempts to elucidate the nature of chemical interactions between buried bone and associated soils have been limited by their use of l) simple diffusion models , and 2) total elemental soil composition or acid soluble extracts rather than the soluble and exchangeable ions available to solution under field conditions. Models addressing the fossilization process in bone m u s t consider both ionic substitution and mineralization mechanisms of diagenesis. Current solubility profile techniques for the differentiation of biogenic and diagenetic chemical phases in fossil bone neglect ionic substitution. Ionic soil solution data from a n arid-land South Australian archaeologcal site are presented to demonstrate the importance of such information to the development and testing of these pre-dictive models.

Over the last decade, the chemical analysis of archaeological bone has emerged as a new method to address the dietary composition of past human populations. Paleodietary studies provide one means to obtain invaluable information regarding prehistoric intra- and inter-group behavioral differentiation.
Unlike other prehistoric archaeological data, materials recovered from the mortuary context provide access to individual behavior. The total elemental and isotopic composition of bone record quantitative signatures of long-term individual dietary intake. These dietary signatures provide one means to make inferences about differential access to resources in prehistoric societies. Archaeological bone chemistry data can be used to establish prehistoric access to subsistence resources from different marine and terrestrial ecosystems
by various individuals and territorial groups. The most reliable quantitative dietary information is derived from stable carbon and nitrogen isotope ratios in bone collagen. In contrast, in vivo elemental dietary signatures in bone mineral are obscured by postmortem chemical changes in the burial environment. Hence, accurate dietary inferences from inorganic bone apatite will depend on controls for these postmortem alterations.
Schiffer's recent treatise, Formation Processes of the Archaeological Record (1987), provides an explicit theoretical framework in which to address postmortem chemical changes in buried bone. Previous attempts to elucidate the nature of chemical interactions between
buried bone and associated soils have been limited by their use of l) simple diffusion models, and 2) total elemental soil composition or acid soluble extracts rather than the soluble and exchangeable ions available to solution under field conditions. Models addressing the fossilization process in bone must consider both ionic substitution and mineralization mechanisms of diagenesis. Current solubility profile techniques for the differentiation of biogenic and diagenetic chemical phases in fossil bone neglect ionic substitution. Ionic soil solution data from an arid-land South Australian archaeological site are presented to demonstrate the importance of such information to the development and testing of these predictive models.
The Roonka Flat Dune provides an excellent natural laboratory to address postmortem diagenesis in buried bone. The chemically homogenous sand dune was used as an Aboriginal burial ground during a major portion of the last 10,000 years. The ionically depleted soil solutions in this siliceous dune should limit both secondary mineralization and ionic substitution mechanisms of diagenesis. Thus, if bone mineral is ever expected to escape the ravages of postmortem chemical reactions this is one burial environment in which to test the null hypothesis. In order to address the various diagenetic mechanisms,
elemental ratios in the dune soil solutions were compared with those in rib bone from archaeological human skeletons and modern terrestrial mammal controls.
Even though significant diagenetic changes were not expected, the Roonka archaeological bone was enriched with Si, AI, Mn, Ba, Fe, S, Sr, K, and Ti and depleted in Mg relative to the modern controls. A variety of processes including physical contamination with quartz and secondary carbonates and ionic substitution from the soil solution are responsible
for these postmortem chemical alterations. The concentrations of the soluble alkaline earth metals Mg, Sr, and Ba increase relative to Ca with duration of burial, whereas the alkali metal K and the less soluble Ti, Si, Fe, AI, and Mn show no significant changes with time. The mobile Mg, Sr, and Ba occur in secondary minerals and substitute for Ca in the
hydroxyapatite lattice. In contrast, there is a rapid equilibration between the less soluble soil elements and the buried rib bone. It appears that the bone has been physically contaminated by sediments containing Ti, Si, Fe, Al, and Mn. Thus, diagenetic mechanisms involving secondary mineralization and ionic substitution from the soil solution are not likely
for these elements. These postmortem chemical changes will provide major obstacles to paleodietary inferences from the elemental composition of archaeological bone mineral. In the absence of
extensive archaeologically associated faunal controls with known diets, dietary inferences from elements in the inorganic apatite component of interred human bone will remain problematic.
Thesis on file at:
1) Australian Institute of Aboriginal Studies
2) Department of Prehistory, RSPacS, Australian National University
3) Department of Anthropology, University of Sydney
4) Division of Archaeology, South Australian Museum
5) Centre for Prehistory, University of Western Australia

Bone collagen stable carbon isotope values for the inland riverine Roonka Flat archaeological population of southeastern South Australia indicate that prehistoric Aboriginal diets were based on local C3-derived terrestrial foods throughout the Late Holocene. Whereas 91% of the sample had values indicative of a predominantly C3-based
terrestrial diet (mean d13C= - 20.0%, N=41), the remaining 9% had values indicating a mixed diet of C3- and C4-derived terrestrial foods and marine foods (mean d13C = - 16.1%,  N=4). There were no significant differences between mean d13C values for adult males, adult females, and subadults. These bone collagen d13C values suggest that there was limited hunter-gatherer mobility between the inland riverine site and adjacent coastal and arid interior habitats during the Late
Holocene. Bone collagen stable carbon isotope comparisons with the Early Holocene Roonka Flat population could not be made due to extensive collagen degradation in these older interments.

The soluble and exchangeable ions for a soil profile from the Roonka archaeological site. Lower Murray Basin. South Australia. arc compared with the total elemental content of the soils. Since the chemical composition of postmortem ionic substitution phases and secondary minerals in archaeological bone will depend on the availability of
ions to the soil solution under field conditions, it is suggested that models addressing diagenesis in bone employ soluble and exchangeable ions rather than total elemental soil data.

The Grosseto plain has undergone extensive morphological changes. The shoreline progression has been taking place during the last millennium and has deeply affected settlement, infrastructural, and socioeconomic dynamics. Consequently, this study aims to (a) localize the raw materials exploited during the Roman period for building materials production, (b) reconstruct the production technology, and (c) provide a meaningful reconstruction of the commercial dynamics between local “municipal” productions and “urban” imports. The chemical, mineralogical, and petrographic investigations performed on 34 stamped bricks from the Roman territories of Vetulonia, Rusellae, Heba (Aia Nova), and Saturnia supported the following major achievements: (a) Most of the Rusellan producers used the continental deposits outcropping along the Ombrone River while a few of them exploited the coastal or marine deposits. Aia Nova and Saturnia producers used the Zanclean marine deposits. (b) Brick‐making technology involved very little or no preparation of the paste and firing temperatures ranging between ~650°C and 900°C. Calcite temper was found in Rusellan bricks while decantation was hypothesized for Saturnia bricks only. (c) Commercial dynamics changed abruptly after the mid 1st century AD when local productions, run by local aristocracies, started declining in favour of urban imports, until being completely supplanted during the Trajan age.

We would like to invite you to participate in the 57° International Congress of Americanists Thematic Group entitled:
"Agropastoral practices in the Andean macro-region: assessing its heterogeneity through recent methodological advances and interpretative frames"

Dental modifications, especially dental inlays, were one of the most characteristic biocultural traditions in Ancient Mesoamerica. The main objective of this brief report is to identify the raw material used to elaborate dental inlays in the archaeological site of Reynosa, located in the Southern Pacific Coast of Guatemala. The recent discovery of a massive burial, dated roughly in the Middle-Late Preclassic Period (500 BC-200 BC), put the site in the spotlight. There were found some of the earliest carriers of dental incrustations in Mesoamerica, which represent part of the beginning of the inlay tradition. The analytical method used to determine the raw material was scanning electron microscopy (SEM) with X-ray spectroscopy. The identified raw materials were pyrite and hematite. These findings have opened new concerns about the obtaining and the usage of those materials in this millennial tradition.

Gregoricka, L.A. (2020). Negotiating contact in the periphery: Commingled mortuary practices and identity construction in Bronze Age Arabia. In: K.J. Knudson & C. M. Stojanowski (Eds.), Bioarchaeology and identity revisited (pp. 85-106). Gainesville: University Press of Florida.