The lower and middle Pleistocene geological record of the San Lorenzo lacustrine succession in the Sant'Arcangelo Basin (Southern Apennines, Italy)

A facies analysis and preliminary palaeoclimate and biochronology investigation, are presented for the San Lorenzo lacustrine deposits, outcropping in the Pliocene to Pleistocene satellite Sant'Arcangelo Basin (Southern Apennines). Facies analysis shows that sedimentation developed in the inner zone of a terrigenous-dominated fresh water lake. The pollen record shows repeated alternations between two distinct vegetational assemblages, one dominated by steppe taxa, and the other one by forest taxa. The faunal assemblage is indicative of a late Biharian mammal age. The palaeomagnetic survey yielded three polarity intervals throughout the succession; the middle one is of reversed polarity (and is associated with a volcaniclastic layer radiometrically dated at approximately 1 Ma), and thus the two normal polarity intervals are identified as the Jaramillo subchron and the base of the Brunhes chron. The detailed geological and paleontological analyses as well as the preliminary results from the palynological and magnetostratigraphical investigation, indicates that these deposits may contain a continuous record of both climatic changes and tectonic activity within the Sant'Arcangelo Basin during the early and middle Pleistocene.