The case of the Holocene ?Lagostomus maximus biozone? at low latitudes outside the traditional bonaerian region Pampa Norte

VEZZOSI, R. I.

Mendoza

Congreso; 4th International Palaeontological Congress; 2014

The chronological scale and continental biostratigraphy of the South American late Cenozoic and mainly the Quaternary of Argentina are based on mammals. Especially, the reliability of the local biostratigraphical units lies on the authenticity of the stratigraphic position of the fossil mammals collected from the traditional Pampean region at the Buenos Aires Province, and the precision of its taxonomic studies. Consequently, the Lagostomus maximus biozone is the biostratigraphical unit representative of the local Platan Stage/Age which corresponds to the chronological Holocene Series sensu lato. Until the present, paleontological contributions had been scarce, principally consisting of reports of isolated discoveries and preliminary groupings of mammals without a good stratigraphical context. However, the substantial number of geological and stratigraphical studies conducted in the last twenty years, outside of the Bonarian region, has provided a useful basis for new biostratigraphic studies of the Pleistocene in Argentina. The aim of this work is to discuss the biostratigraphical/chronological hypothesis which sets the species L. maximus as the fossil guide taxon for the chronological Holocene Series (Platan Stage/Age) in lowlands. However, L. maximus is herein reported since the Middle Pleistocene (≈178 ±20 ka AP, LVD 2826 OSL dating) to Late Pleistocene-early Holocene (Tezanos Pinto Formation) from Santa Fe Province and surrounding area. In this sense, this new record in a suitable stratigraphical context, and recovered outside of the traditional Bonarian geomorphological province called Pampa Norte, clearly suggests an early ocurrence at low latitudes than that of the Pampean region at Buenos Aires. These new Pleistocene records allow establishing that L. maximus is not an accurate regional biostratigraphical indicator to the chronological age Holocene. Therefore, the Platan Stage/Age should be interpreted as a local sequence for the Buenos Aires Province and should not be extrapolated to a regional framework to define and compare lithostratigraphical sequences of Holocene age.