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

The Sant’Arcangelo Basin is located in the southern part of the Apennine chain (Basilicata). It is filled by a siliciclastic sequence 3500m thick, dated to the Late Pliocene–Middle Pleistocene time interval. In this basin an Early Middle Pleistocene fluvio-lacustrine sequence, known as San Lorenzo Cycle, has been recognised. In the upper part of the sequence, in Rifreddo, a fairly diversified small vertebrate assemblage has been recovered. The occurrence of Mimomys savini allows to the fauna to be considered as Biharian. The presence of some faunal elements such as Microtus (Terricola) arvalidens, Microtus (Iberomys) ex gr. huescarensis-brecciensis, and Macroneomys cf. brachygnathus restricts the age of the Rifreddo assemblage to the latest part of this Mammal Age. In several European localities, sediments containing such late Biharian faunas are correlated with the lower part of Brunhes magnetochrone (e.g. the normally magnetised sections at West Runton in the United Kingdom, Voigtstedt in Germany and Prˇezletice in the Czech Republic) or just below this boundary (e.g. the negatively magnetised part of the Atapuerca section—levels TD4-6 in Spain). Taking into account the faunal composition and the positive magnetisation of the sediments outcropping at the Rifreddo locality, the chronological referral of the mammal assemblage can be restricted to the early Brunhes and therefore to the early middle part of Middle Pleistocene.