THE ITUZAINGÓ FORMATION (PLIOCENE-PLEISTOCENE), PARANÁ RIVER BASIN, ARGENTINA: PALEOBOTANICAL RECORDS

FRANCO, M. J.; BREA, M.

Iquitos

Simposio; Annual Symposium ICGP 582-Tropical Rivers; 2012

IGCP

The Ituzaingó Formation is an important fluvial deposit of the Paleoparaná river and its outcrops are widely distributed in the western riverside cliff of the Paraná River (from the north of Corrientes province to the south to near Paraná city in Entre Ríos province), Argentina. This unit is composed of sands and consolidated and unconsolidated sandstones. Dark gray and greenish clay lens intercalations are common among the sands. The more frequents sedimentary structure are tangential cross-bedding, troughs and planar bedding. Also, low-angle ripple cross-laminations of fluvial origin are recognized. The paleobotanical records of the Ituzaingó Formation are based on studies of sporomorph, fossil leaves, cuticles, fossils woods, palm trunks and culms, found in various fossiliferous locality in Entre Ríos and Corrientes provinces, Argentina. These records revealed a rich and diverse flora. The objective of the present work is show the first detailed fossil wood study for the Ituzaingó Formation (Pliocene-Pleistocene), in Entre Rios and Corrientes (Argentina). This study provided data by the anatomical, morphological and systematic analysis of the woody species and allowed a better understanding of the Plio-Pleistocene paleoflora which in turn allowed the advance in the development of paleoclimatic, paleoecological and paleobiogeographical inferences for this formation. Eleven fossiliferous locality (Toma Vieja, Planta Potabilizadora de Agua, Villa Urquiza, La Celina, Curtiembre, Pueblo Brugo, Hernandarias, Arroyo Feliciano, Puente Carmona, El Espinillo and Bella Vista ) were recognized and 7 sedimentological profiles were developed in detail. Thirty one different taxa, belonging to the families: Podocarpaceae, Lauraceae, Polygonaceae, Moraceae, Fabaceae, Myrtaceae, Proteaceae, Celastraceae, Anacardiaceae, Rutaceae and Arecaceae, were described. Seven new morphospecies and eleven new morphogeneros were described. The presence of coniferous fossil wood was confirmed for the first time in the Mesopotamia. The first fossil wood with Polygonaceae affinity and the first Celastraceae and Moraceae Argentinian records were described. Anatomical wood characteristics were analyzed in terms of paleoecological requeriments, and there was a tendency for taxa to exhibit xerophytic and seasonality characters indicators. The Vulnerability Index (V) and Mesomorphy ratios (M) were calculated, and indicated a dry climate with some species adapted to wet environments. Quantitative estimation of temperature and precipitation were obtained, among other climatic parameters. The comparison with the nearest living relatives suggests that the Ituzaingó Formation flora have elements linked with Chaco, riparian and components of Seasonally Dry Tropical Forest (SDTF). Ituzaingó Formation flora responds to a tropical-subtropical climate.