Exploring climate and environmental changes in Sardinia around the end of the Nuragic Era

In Sardinia, precisely dated Holocene climate and environmental records are derisory. Indeed, availability of lacustrine sediments is scarce, because this Island has one natural relatively large lake only. Accordingly, the most comprehensive Holocene lake-based climate reconstruction, spanning the last 8000 years, has been published only recently (Pedrotta et al., 2021). However, the authors admit a low reliability of their age model to the top of the sequence, around the last ~2500 years. Considering the location of Sardinia at the center of the Western Mediterranean basin, this gap of knowledge is unfortunate, given the number of studies carried out in nearby continental/marine areas. Additionally, the lack of palaeoclimate/environmental information still hampers a thorough comprehension on the evolution of ancient populations, including the possibly most sophistically advanced Bronze and Late Iron Age culture in Europe: the Nuragic civilization (~1700-500 BC). An efficient way to retrieve palaeoclimate information in Sardinia is through speleothems, considering that: 1) the Island counts almost 4000 caves; and 2) for pre-Holocene times, we have already reported the reliability of Sardinian speleothems as powerful records of past climates (Columbu et al., 2017; 2019). This work presents the first speleothem-based Holocene environmental reconstruction from Sardinia, by reporting the preliminary 230Th dating, stable isotopes (δ18O, δ13C) and petrographic results from 5 stalagmites. Samples were recovered in Suttaterra de Sarpis cave (Urzulei), which is strategically located less than 1 Km from Or Murales Nuragic village. The surface was an ideal location for ancient anthropic activities, such as livestock, agriculture and/or deforesting. In general, the whole area was densely frequented during Nuragic times, as attested by other nearby important archaeological sites. After 230Th dating (n=20), the studied stalagmites comprehensively span the last ~7000 years. Peculiarly, they all show a net discontinuity: while the bottom appears brownish, the top is sensibly lighter in each of the 5 stalagmites. Such a marked change is also visible at micro scale, looking at the thin sections. Age modeling attested that this shift occurred, within uncertainties, toward the end of the “Nuragic” era, when Sardinia had first strict contacts with Phoenicians (a phase called “Orientalization”, ~700-600 BC), was then invaded by Punics (~500 BC) and later controlled by Romans (Depalmas & Melis, 2010). We here start to investigate the meaning of such a petrographical and geochemical discontinuity. Is it related to climate? Were different uses of the land above the cave, boosted by the arrival of new cultures, playing a role? Could climate and anthropic- cultural factors be interconnected? We will try to respond to these questions by comparing 230Th dating, stable isotopes and petrography within the archaeological framework of the studied area. Columbu A., Drysdale R., Capron E., Woodhead J., De Waele J., Sanna L., Hellstrom J. & Bajo P. (2017) - Early last glacial intra-interstadial climate variability recorded in a Sardinian speleothem. Quaternary Science Reviews, 169, 391-397. Columbu A., Spötl C., De Waele J., Yu TL., Shen CC. & Gázquez F. (2019) - A long record of MIS 7 and MIS 5 climate and environment from a western Mediterranean speleothem (SW Sardinia, Italy). Quaternary Science Reviews, 220, 230-243. Depalmas A. & Melis R. (2010) - The Nuragic people: their settlements, economic activities and use of the land, Sardinia, Italy. In: Landscapes and Societies, Springer, 167-186. Pedrotta T., Gobet E., Schwörer C., Beffa G., Butz C., Henne PD., Morales-Molino C., Pasta S., van Leeuwen JFN., Vogel H., Zwimpfer E., Anselmetti FS., Grosjean M. & Tinner W. (2021) - 8,000 years of climate, vegetation, fire and land-use dynamics in the thermo-mediterranean vegetation belt of northern Sardinia (Italy). Vegetation History and Archaeobotany, 1-25.