Environmental analysis of Middle Pleistocene argillified sediments containing Acheulean stone tools filling up a karstic depression at Monte Cònero (Marche, central Italy)

Alessandro Montanari¹, Gaia Pignocchi², Timme Donders³, Markus Fiebig⁴, Gabriele Giuli², Christopher Lüthgens⁴, Maurizio Mainiero⁵ & Sabrina Nazzareni^6
1Osservatorio Geologico di Coldigioco, Cda. Coldigioco 4, 62021 Apiro (MC), Italy.
²Scuola di Scienze e Tecnologie, Sezione di Geologia, Università di Camerino, Via Gentile III da Varano, 62032 Camerino, Italy.
³Department of Physical Geography, Utrecht University, Winthontlaan 30C, 3526 KV Utrecht, The Netherlands.
⁴Institute of Applied Geology, BOKU University, Peter Jordan Strasse 82, A-1190 Vienna, Austria.
⁵Studio Geologico, Via XXIX Settembre 2/O, 60122 Ancona (AN), Italy.
⁶Department of Chemistry, Life Sciences, and Environmental Sustainability, University of Parma, Italy.
Corresponding author e-mail: sandro.coldigioco@gmail.com

We report herein the results of sedimentological and palynological analyses of a continuous core drilled through a ~4-m-thick clayey deposit here interpreted as an argillified loess, which filled up a karstic depression near the top of Monte Cònero, a 572-m-high calcareous promontory protruding on the Adriatic Sea just south of the port city of Ancona (Marche region of central Italy). This Middle to Upper Pleistocene loess deposit represents a unique occurrence in this north-eastern Apennine region, likely because it was preserved in a circumscribed karstic depression near the top of a mountain, which later became a swamp or a pond collecting just meteoric water, and thus it was prevented from post-depositional fluvial or aeolian erosion, or the accretion of siliciclastic material transported over there by the runoff or alluvial flooding. The source of this presumed aeolian sediment was the fine sand and silt that was deflated from the dry floor of the Adriatic basin during glacial maxima (i.e., the Penultimate Glacial Maximum and the Last Glacial Maximum) when, in fact, the global sea level was some 120-140 m lower than present. Another uniqueness of this deposit in the Palaeolithic context of the Umbria-Marche Apennines is that in the early 1960’s, 16 well-preserved bifaces knapped in situ from a distinctive local chert, were found in primary position at about 3-m-depth in this deposit during two well-documented archaeological excavation campaigns. These artefacts were originally attributed to a generic Acheulean lithic industry. In fact, our integrated sedimentological and palyno-stratigraphical analysis of this deposit suggests that this particular area of Monte Cònero was frequented by Acheulean hunters during some stages of the MIS 6 glacial period (i.e., 190-130 ka), and subsequently by Mousterian hunters through the Late Pleistocene cold period from MIS 5d to MIS 4.

North-eastern Apennines, Quaternary Loess Sedimentology, Quaternary Palynology, Acheulean lithic industry.