Tracing the source of Late Neolithic Spondylus shell ornaments by stable isotope geochemistry and cathodoluminescence microscopy

Determination of the source of Spondylus objects is essential for the interpretation of Late Neolithic exchange systems and the social role of shell ornaments. We performed stable isotope analysis combined with cathodoluminescence microscopy study on ornaments (beads, bracelets) made of Spondylus shells excavated at the Aszód-Papi földek archaeological site in Hungary, to define their origin. For comparison Spondylus finds from Neolithic sites of Greece, modern Spondylus shells from the Aegean and the Adriatic, as well as fossil Spondylus and Ostrea shells from the Carpathian Basin were also examined. Oxygen isotope composition of Spondylus finds from Aszód ranges between ?1.9 and 2.1‰ and overlaps with the oxygen isotope range of shell objects from other Neolithic sites. Modern Spondylus shells from the Aegean and the Adriatic show overlapping δ¹⁸O values with one another and with the Neolithic objects; while recent shells of the Black Sea clearly are separate isotopically from the Mediterranean ones and most of archaeological artefacts. Spondylus shells from the Aszód site have Mediterranean origin; their source can be the Aegean or the Adriatic. Based on a former strontium isotope study the use of fossil Spondylus shells is excluded as raw material used for ornaments, however, in recent years the use of fossil shells was reintroduced. The shell ornaments from Aszód-Papi földek and the fossil oyster shells collected from the Carpathian Basin exhibit some overlapping oxygen isotope values; however, cathodoluminescence microscopy indicates that the Spondylus objects retained their original aragonite material. Diagenetic calcite, which occurs typically in the fossil shells, was not detected in the ornaments suggesting that the studied objects were made of recent shells. Calcitic parts observed in some Spondylus objects are not related to fossilisation.     

THE INTRAMETROPOLITAN DISTRIBUTION OF R&D ACTIVITIES: THEORY AND EMPIRICAL EVIDENCE*

ABSTRACT. The paper presents a first attempt to unveil the underlying determinants of the geography of R&D labs within contemporary metropolises. To this end, the study builds on the premise of contemporary intraurban location and pricing models, suggesting that intraurban variations in property rents must reflect the imputed location preferences of firms or their workforce, as well as the extent to which local institutional constraints hinder these preferences. Against this background, the study proceeds with the econometric analysis of R&D property rent differentials within Greater Los Angeles. The empirical results indicate that access to research and nonresearch universities, transportation access, access to a host of worker amenities, as well as zoning and other local regulations play a critical role in shaping the intraurban geography of R&D labs.