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Abstract: Calcareous pericarps of the tribe Lithospermeae (fam. Boraginaceae) are a common component of archaeobotanical macroremain assemblages in the Mediterranean region. In this study, the relationship between oxygen isotopic composition of fruit biogenic carbonate and climatic conditions was examined. δ 18O and δ 13C values of biogenic carbonate were measured in modern Lithospermeae fruits from seven Eurasian sites (Berlin, Kirchentellinsfurt, Göttingen, Athens, Ankara, Tbilisi, and Almaty) and in fossil fruits from three archaeological sites in the eastern Mediterranean (Troy, Kumtepe, and Hirbet ez-Zeraqon). Additionally, three 14C measurements were performed on ancient fruit carbonate from Hirbet ez-Zeraqon. The δ 18O and δ 13C values varied from −9 to 5‰ PDB and between −35 and −7‰ PDB respectively. In modern fruits, δ 18O of biogenic carbonate was correlated to local summer precipitation amounts (inversely proportional) and summer air temperatures (proportional). In fossil fruits, the δ 18O values of carbonate from Troy and Kumtepe were significantly lower than that from Hirbet ez-Zeraqon (ca. −5 vs. 2‰ PDB respectively). The vertical distribution of stable isotopic values and 14C dates in cultural layers of Hirbet ez-Zeraqon indicate that fruit biogenic carbonate can persist in sediment without appreciable diagenetic alteration. These findings suggest that biogenic carbonate of Lithospermeae fruits can be useful as a paleoclimate proxy at least in the Mediterranean. [Copyright &y& Elsevier]

Abstract: Lithospermum (Boraginaceae) belongs to a small group of plant taxa that accumulate biogenic carbonate in their fruits. In this genus, carbonate incrustations form in the cells of the epidermis and sclerenchyma of the pericarp. Fossil Lithospermum fruits (nutlets) with well-preserved calcified tissues commonly occur in Quaternary sediments and cultural layers. We tested the suitability of biogenic carbonate of Lithospermum fruits for radiocarbon dating using a total of 15 AMS measurement results from four modern and 11 fossil samples. The 14C data from modern samples suggest that Lithospermum utilises only atmospheric carbon to synthesise calcite in the nutlets. In general, the ages determined through 14C dating of fossil fruitscorresponded well with the absolute-age intervals for archaeological sites over the last 5000 yr. Biogenic carbonate of Lithospermum fruits, like that of Celtis, represents a new source of chronological information for late Quaternary studies. [Copyright &y& Elsevier]