Isabella Passariello

ZINC REDUCTION AS AN ALTERNATIVE METHOD FOR AMS RADIOCARBON DATING: PROCESS OPTIMIZATION AT CIRCE

The pretreatment of samples for radiocarbon measurements, transforming a variety of materials into graphite solid targets, represents a critical point in the accelerator mass spectrometry (AMS) procedure. We describe the new, state-of- the-art CIRCE AMS preparation laboratory, particularly the setup and optimization of an alternative method, the zinc reduc- tion method, for graphite target production, compared to the more common hydrogen reduction method. Measured 14C values on standard and blank samples reduced via zinc reaction revealed mean background levels, accuracy, and sensitivity compa- rable to those obtained by our conventional hydrogen reaction lines. Zinc line reduction at the CIRCE laboratory represents an effective and powerful alternative to the conventional hydrogen reduction, ensuring higher sample throughput with lower costs at a comparable performance level.

RADIOCARBON SAMPLE PREPARATION AT THE CIRCE AMS LABORATORY IN CASERTA, ITALY

A system with several lines for the preparation of graphite targets for radiocarbon analysis has been built at the new accelerator mass spectrometry (AMS) facility in Caserta, Italy. Special attention has been paid in the design to the reduc- tion of background contamination during sample preparation. Here, we describe the main characteristics of these preparation lines. Results of tests performed to measure 14C background levels and isotope fractionation in several blank samples with the Caserta AMS system are presented and discussed.

14C Chronology of Avellino Pumices Eruption and Timing of Human Reoccupation of the Devastated Region

The Avellino Pumices eruption was one of the most catastrophic volcanic events of Somma-Vesuvius, which hit prehistoric communities during the Early Bronze Age. In the last 30 yr, several authors reported assessments about its chronology, including radiocarbon datings, but with poor internal agreement and frequently with large experimental errors. A new and more accurate 14C dating of this eruption (1935-1880 BC, 1 σ) was obtained at the CIRCE laboratory in Caserta (Italy) by 3 AMS measurements on a bone sample of a goat buried by the eruption, collected in an Early Bronze Age village at Croce del Papa (Nola, Naples). These results were verified by other measurements on several samples chronologically related to the eruption. Our data show that human resettlement after the eruption occurred rather quickly but lasted only for a short time in areas affected by the volcanic products, like Masseria Rossa and San Paolo Belsito (Nola, Naples), according to 14C dating of archaeological samples collected below and above the eruption deposits. The state-of-the-art chronology of this eruption, emerging from the results obtained in this work as well as from data in the literature, is discussed.

RECONSTRUCTION OF PAST CO2 CONCENTRATION AT A NATURAL CO2 VENT SITE USING RADIOCARBON DATING OF TREE RINGS

Total CO2 exposure levels in a naturally enriched site (Lajatico, Italy) were reconstructed using radiocarbon analysis by accelerator mass spectrometry combined with dendrochronological analysis on wood cores extracted from trees grown in the fossil CO2 source proximity. Over 3 decades (1964-1998), the data show a mean CO2 concentration in the atmo- sphere of 650 ppm, about twice the current concentration in atmosphere, with a maximum around 1980.

Radiocarbon Chronology and Paleodiet Studies on the Medieval Rural Site of Zaballa (Spain): Preliminary Insights into the Social Archaeology of the Site

The archaeological site of Zaballa is a Medieval rural site located in the province of Álava (Basque Country, northern Iberia). The site has been excavated during a rescue archaeology project, over an area of about 4.5 ha, where human occupation has been documented ranging from the 6th to 15th century. The archaeological operations have shown the transformation of the village, in diachronic terms, by unearthing the structure of production areas (agricultural lands, storage areas, and craft activities), the shape of domestic spaces, and the Saint Tirso monastery, with its adjacent cemetery. Much of the evidence and features related to a peasant community are small and disturbed by recent agricultural activities, and are therefore difficult to be interpreted in social terms. Studying dietary patterns has helped to fill this gap by providing a protein-rich diet of the elitist population and by highlighting the existence of hierarchies separating the inhabitants of Zaballa. In this paper, we discuss the reconstruction of the chronological sequence of the site inhabitation, with a multidisciplinary approach. The archaeological evidences and the critical use of radiocarbon dating have been integrated with stable isotope analysis on human remains found in the cemetery of the church of San Tirso, resulting in a first attempt to find evidence of the social structure of the rural community of Zaballa.

Contribution of Radiocarbon Dating to the Chronology of Eneolithic in Campania (Italy)

Contribution of Radiocarbon Dating to the Chronology of Eneolithic in Campania (Italy) The paper presents new and important 14C data from eight Eneolithic sites in Campania measured at the Centre for Isotopic Research of Cultural and Environmental Heritage (CIRCE) AMS laboratory in Caserta (Italy). Twenty-four 14C determinations on bone and charcoal are used here for chronological reconstruction of human habitation and dating of some volcanic eruptions affecting the settlement activity. Our research has shed new light on absolute chronology of the whole Campanian Eneolithic, a period of profound cultural transformations triggered by introduction and use of metals, in particular copper.

Paleodiet characterisation of an Etrurian population of Pontecagnano (Italy) by Isotope Ratio Mass Spectrometry (IRMS) and Atomic Absorption Spectrometry (AAS)

Human bones recovered from the archaeological site of Pontecagnano (Salerno, Italy) have been studied to reconstruct the diet of an Etrurian population. Two different areas were investigated, named Library and Sant’ Antonio, with a total of 44 tombs containing human skeletal remains, ranging in age from the 8th to the 3rd century B.C. This time span was confirmed by 14C dating obtained using Accelerator Mass Spectrometry (AMS) on one bone sample from each site. Atomic Absorption Spectrometry (AAS) was used to extract information about the concentration of Sr, Zn, Ca elements in the bone inorganic fraction, whilst stable isotope ratio measurements (IRMS) were carried out on bone collagen to obtain the δ13C and δ15N. A reliable technique has been used to extract and separate the inorganic and organic fractions of the bone remains. Both IRMS and AAS results suggest a mixed diet including C3 plant food and herbivore animals, consistent with archaeological indications. #Revised version of a paper presented at the 1st Joint European Stable Isotope Users Group Meeting (JESIUM), August, 30 to September, 3, 2004, Vienna, Austria

Mortar Dating Methodology: Assessing Recurrent Issues and Needs for Further Research

Absolute dating of mortars is crucial when trying to pin down construction phases of archaeological sites and historic stone buildings to a certain point in time or to confirm, but possibly also challenge, existing chronologies. To evaluate various sample preparation methods for radiocarbon (14C) dating of mortars as well as to compare different dating methods, i.e. 14C and optically stimulated luminescence (OSL), a mortar dating intercomparison study (MODIS) was set up, exploring existing limits and needs for further research. Four mortar samples were selected and distributed among the participating laboratories: one of which was expected not to present any problem related to the sample preparation methodologies for anthropogenic lime extraction, whereas all others addressed specific known sample preparation issues. Data obtained from the various mortar dating approaches are evaluated relative to the historical framework of the mortar samples and any deviation observed is contextualized to the composition and specific mineralogy of the sampled material.

Radiocarbon Dating of Mortars with a Pozzolana Aggregate Using the Cryo2Sonic Protocol to Isolate the Binder

To date, finding a technique able to effectively isolate the carbon signal from the binder of a mortar is still an open challenge. In this paper, the radiocarbon (14C) dating of one of the most challenging and diffuse types of mortar, the one with pozzolana aggregate, is investigated. Eight mortar samples from three archaeological sites near Rome (Italy) underwent a selection process called Cryo2SoniC. The selected fractions were analyzed by the accelerator mass spectrometry (AMS) 14C technique and compared to known historical references. Additional scanning electron microscopy analysis and petrographic investigations were done, respectively, to check the grain size of the fractions selected by Cryo2SoniC, and further, to characterize the original mortar samples. The masses of carbon yielded from the dated fractions were almost half of those released from some aerial mortars. The 14C dating results were accurate for pozzolana mortars, from buried and unburied structures, with calcination relics and small contamination of secondary calcite. A limitation in the purification protocol was observed on samples with a massive contamination of secondary calcite deposition of ground water origin, occluding porosity and substituting up to the 80% of the original binder matrix

Preparation and Dating of Mortar Samples-Mortar Dating Inter-Comparison Study (MODIS)

Seven radiocarbon laboratories: Abo/Aarhus, CIRCE, CIRCe, ETHZ, Poznan, RICH, and Milano-Bicocca performed separation of carbonaceous fractions suitable for 14C dating of four mortar samples selected for the MOrtar Dating Inter-comparison Study (MODIS). In addition, optically stimulated luminescence (OSL) analyses were completed by Milano-Bicocca and IRAMAT-CRP2A Bordeaux. Each laboratory performed separation according to laboratory protocol. Results of this first intercomparison show that even though consistent 14C ages were obtained by different laboratories, two mortars yielded ages different than expected from the archaeological context.