Mammals from the Pleistocene of the Tarija Valley (Bolivia). Correlation with the Pampean chronological Standard

TONNI, E. P.; SOIBELZON, E.; CIONE, A. L.; CARLINI, A. A.; SCILLATO-YANÉ, G. J.; ZURITA, A. E.; PAREDES RÍOS, F.

QUATERNARY INTERNATIONAL

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2009 vol. 210 p. 57 - 65

1040-6182

Most of the mammal collections of the Pleistocene from the Tarija valley (Bolivia) lack precise stratigraphicdata. Some fossil collections were made under stratigraphic control but have not been described.However, mammals were used for correlation and comparison with the pattern established for thePampean region of Argentina. The bearing units have been referred either to the Ensenadan andBonaerian stages, the ??Belgranan??, the Ensenadan, or the Lujanian in a broad sense, corresponding to themiddle-upper Pleistocene or the upper Pleistocene. Studies during the last twenty five years accomplishedby American authors and based on magnetostratigraphy and absolute dating suggest that theTarija sequence corresponds to the Ensenadan (early-middle Pleistocene) of the Pampean standard.Recently, Italian scientists, based on radiometric dating, discarded this age and considered that the wholesequence belongs to the late Pleistocene. New biostratigraphic and systematic studies allowed therecognition of Glyptodon munizi, Arctotherium angustidens, and Hippidion devillei, exclusive taxa of theMesotherium cristatum Biozone, the biostratigraphic base for the Ensenadan of the Pampean region.However, collections include mostly putative endemic species or those characteristic of the Equus(Amerhippus) neogaeus Biozone, the biostratigraphic base for the Lujanian of the Pampean area. In sum,from a biostratigraphic point of view, the Tarija sequence has taxa from the lower to middle Pleistocene(Ensenadan) and the upper Pleistocene-lower Holocene (Lujanian) of the Pampean area. From a paleofaunisticstandpoint, the association recovered from the Tarija valley shows significant differences withthe typical Pampean association. The high frequency of remains of Gomphotheriidae and Equidae and, inlower proportion, of Hydrochoeriidae and Tapiridae, are noteworthy. Members of these two latterfamilies are restricted today to warm and wet climates. Most Glyptodontidae records belong to Glyptodon,and in the Pampean region this family is much more diversified.