Abstract

ZURITA, Alfredo Eduardo et al. Paleontology of the Chaco Oriental: A new fossiliferous locality with Pleistocene fossil mammals in the Bermejo river (Formosa, Argentina). Rev. mex. cienc. geol [online]. 2009, vol.26, n.2, pp.277-288. ISSN 2007-2902.

The palustrian and loessic sediments of the late Pleistocene-early Holocene (ca. 130-8 ka) of Argentina contain and preserve one of the most important records of vertebrates (mainly mammals) of South America. However, except for the Pampean region of Argentina, largely studied from the middle of the 19th century, other areas, especially those located between 29°S and 21°S are, from a palaeontological point of view, very poorly known. In this contribution an association of Pleistocene mammals is reported, coming from the center area of the Chaco Oriental, which in addition constitutes the most complete record for the Formosa province, Argentina. This association was exhumed from the cliff of the Bermejo river, near the locality of Villa Escolar, and probably corresponds to the Fortín Tres Pozos Formation (Upper Pleistocene). This ensemble of fossil mammals is represented by the following taxa: Cingulata: Glyptodon sp., Neosclerocalyptus cf. N. paskoensis, Pampatherium typum; Phyllophaga: Megatherium sp.; Artiodactyla: cf. Morenelaphus, cf. Hemiauchenia paradoxa; Notoungulata: Toxodon sp. In this context, the presence of the Glyptodontidae Neosclerocalyptus cf. N. paskoensis suggests a Lujanian age (late Pleistocene-early Holocene), while recent optically stimulated luminescence (OSL) dating in the sediments of the Fortin Tres Pozos Formation indicate an approximate age of 58,160 years BP (± 4390). This set of mammals (plus those previously published for this region) are constituted by taxa adapted to cold and arid/semiarid environmental conditions, which is consistent with the inferred conditions of the deposition of sediments that forms the alluvial fan of the Bermejo river. Much of this fauna would be synchronous with the Isotope Stage 3 (59-28 ka) and probably relates to some of the cold and arid phases detected in this period.

Keywords : Quaternary; loess; megafauna; systematic; Fortín Tres Pozos Formation; Bermejo river; Argentina.

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