New fossils record from Uruguay basin related to EI Palmar Formation floristic composition

BREA, M Y A. F. ZUCOL

Corrientes

Otro; Reunión Anual de Comunicaciones de la Asociación Paleontológica Argentina; 2007

CECOAL-CONICET y UNNE

EI Palmar Formation is a fluvial unit deposited during the Middle Pleistocene that the probably belongs to the Last Interglacial (IS 5), an interval considered the most humid and warm of the Middle Pleistocene. These deposits (TL dated 80,670± 13,420 years BP) are found in outcrops along the western margin of the Uruguay River, between the Mocoreta River and Concepcion del Uruguay city. The profile is mainly composed of medium, reddish and yellowish sand. Lenses of gravel and pebbles, dozens of meters long up to 2 m thick, are interspersed in quartzose sand mass. The coarse fractions are composed of chalcedony. In sectors lateral to these conglomerate lenses, the presence of medium to thick sandstone with planar stratification rich in fossil woods remains is frequent. The phytolith assemblages were presented throughout the profile. In this contribution four new morpho taxa are proposed on the basis of new material from these sediments. These fossils were assigned to the Anacardiaceae and Fabaceae. The floristic compositon of the EI Palmar Formation is integrated by Anacardiaceae, Fabaceae, Arecaceae, Lauraceae, Combretaceae, Myrtaceae, Poaceae, Cyperaceae and Podostomaceae. The reconstruction of the vegetation based on paleobotanical records and sedimentary deposits indicated a warm-temperate and humid to subhumid climate. The palaeovegetation would have comformed subtropical dry forests dominated by Anacardiaceae and Fabaceae, subtropical humid mixed forests and palm savanna. 80,670± 13,420 years BP) are found in outcrops along the western margin of the Uruguay River, between the Mocoreta River and Concepcion del Uruguay city. The profile is mainly composed of medium, reddish and yellowish sand. Lenses of gravel and pebbles, dozens of meters long up to 2 m thick, are interspersed in quartzose sand mass. The coarse fractions are composed of chalcedony. In sectors lateral to these conglomerate lenses, the presence of medium to thick sandstone with planar stratification rich in fossil woods remains is frequent. The phytolith assemblages were presented throughout the profile. In this contribution four new morpho taxa are proposed on the basis of new material from these sediments. These fossils were assigned to the Anacardiaceae and Fabaceae. The floristic compositon of the EI Palmar Formation is integrated by Anacardiaceae, Fabaceae, Arecaceae, Lauraceae, Combretaceae, Myrtaceae, Poaceae, Cyperaceae and Podostomaceae. The reconstruction of the vegetation based on paleobotanical records and sedimentary deposits indicated a warm-temperate and humid to subhumid climate. The palaeovegetation would have comformed subtropical dry forests dominated by Anacardiaceae and Fabaceae, subtropical humid mixed forests and palm savanna.