First record of fossil wood and phytolith assemblages of the Late Pleistocene in El Palmar National Park (Argentina) A.F. Zucol a, * , M. Brea a , A. Scopel b a Laboratorio de Paleobota ´nica, Centro de Investigaciones Cientı ´ficas, Diamante, CICYTTP-Diamante, CONICET, Materi y Espan ˜a SN, Diamante (3105) Entre Rı ´os, Argentina b IFEVA, CONICET and Facultad de Agronomı ´a, Universidad de Buenos Aires, Av. San Martı ´n 4453 (C1417 DSE) Buenos Aires, Argentina Received 1 April 2003; accepted 2 July 2005 Abstract Two paleoxylologic assemblages and two phytolith assemblages were recovered from Late Pleistocene sediments of El Palmar Formation. These deposits are found in outcrops along the western margin of the Uruguay River. The spectra of taxa obtained in both sets by different methods is complementary. The fossil remains are characterized in terms of floristic composition and paleoclimate. Seven families are recognized: Podostemaceae, Myrtaceae, Anacardiaceae, Mimosoideae, Arecaceae, Poaceace, and Cyperaceae. Sponge siliceous spicules also have been found in these assemblages. The state of preservation of the phytoliths and their weathering degree is analyzed. These studies can be used as a potential paleoecological tool for alluvial sediments. The comparison of fossil assemblages with modern analogs clarifies the paleoecological requirements and composition of two paleocommunities, one dominated by woody forests and the other by palms. The climatic conditions inferred from the reconstructed vegetation and sedimentary deposits indicate a temperate-warm, humid climate. The results constitute the first evidence of the floral diversity of the vegetation in El Palmar National Park during the Late Pleistocene. q 2005 Elsevier Ltd. All rights reserved. Keywords: Argentina; Fossil wood assemblages; Late Pleistocene; Paleovegetation; Phytolith assemblages 1. Introduction El Palmar National Park (31855 0 S; 58816 0 W, 8500 ha) protects the largest remnant population of Butia yatay (Mart.) Becc. and its associated temperate savanna ecosystem. B. yatay is an endemic species of the temperate-humid savannas of southern South America, and populations at El Palmar National Park represent the southernmost expression of this community. From a phytogeographic standpoint, the park belongs to the Uruguayense district of the Pampean province (Cabrera, 1976) and, in addition to the savannas dominated by B. yatay, includes a diverse array of vegetation, such as gallery forests and marshes, psammophytic steppes, and shrublands (Ciccero and Balabusic, 1994). The climatic conditions appear to have been mainly responsible for the geologic evolution in Entre Rı ´os province sediments during the Quaternary. Several geologi- cal formations have been defined for this region from the Lower Pleistocene to the Upper Holocene (Iriondo, 1980). The area corresponding to El Palmar National Park was drastically shaped by the Uruguay River during the Quaternary. El Palmar Formation, assigned to the Late Pleistocene (Iriondo, 1980), constitutes the upper terrace on the western bank of the Uruguay River and is conspicuously represented in the park. Thus far, no systematic studies of the paleoflora of this region have occurred, except for studies of the macro- floristic remains of fossil woods (Lauraceae, Anacardiaceae, Mimosoideae, Combretaceae, and Myrtaceae) of El Palmar Formation (Brea, 1998, 1999; Brea and Zucol, 2000, 2001; Brea et al., 2000, 2001; Zucol et al., 2004). This lack of information is a major impediment to the reconstruction of the history of vegetation and climate in these savannas and to the interpretation of possible changes that may be key to the conservation of the remnant population of B. yatay and its associated ecosystem. Journal of South American Earth Sciences 20 (2005) 33–43 www.elsevier.com/locate/jsames 0895-9811/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jsames.2005.07.007 * Corresponding author. Tel.: C54 343 498 3086; fax: C54 343 498 3087. E-mail addresses: cidzucol@infoaire.com.ar (A.F. Zucol), cidmbrea@ infoaire.com.ar (M. Brea), scopel@ifeva.edu.ar (A. Scopel).