A rare Mid-Würmian lithoid tuff in the Agro Pontino graben (Southern Lazio, Italy) and its identification as an Albano 5-7 related distal tephra deposit (41-36 kaBP): characteristics, provenance and palaeogeographical implications

Abstract

A lithoid tuff, found in 2011 (Ricci pit, Agro Pontino, Southern Lazio, Italy), was studied for its composition, origin and palaeogeographical implications. This tuff was the first occurrence of a Würmian-age tephra layer, encountered in the coastal basins of Southern Lazio. Based on its mineralogy and isotopic composition (Sr and Nd), its stratigraphic position and the pre- and post-depositional soil forma- tion and weathering, it was identified as a distal tephra deposit from the Colli Albani volcano, connected with the Albano 5-7 eruptive stage and dating from 40-36 ka BP. The lithoid tuff consists of tephra that were slightly reworked and subsequently lithified, when this central part of the Agro Pontino graben still consisted of a non-dissected, level lagoonal plain. The study confirms the earlier established importance of this tephra layer as stratigraphic marker for Central Italy, and shows that its distribution is wider than earlier assumed, notably to the SE of the Colli Albani volcano.