Map of the Paraná Riverdrainage basin with the river indicated. Most outcrops of the Ituzaingó Formation flank the middle course of the Paraná River.
The Ituzaingó Formation was first described by De Alba in 1953 and later by Herbst in 1971.[2] The up to 150 metres (490 ft), but in most areas between 10 and 20 metres (33 and 66 ft) thick formation is found in an area of 120,000 square kilometres (46,000 sq mi),[3] stretching from the Paraná River to 40 kilometres (25 mi) east of Tostado.[4] The Ituzaingó Formation crops out in the northeasternmost part of Argentina (Mesopotamia), in the provinces of Corrientes, Santa Fe and Entre Ríos, among other locations along the banks of the Paraná River.[5]
The formation contains a basal conglomeratic member "Conglomerado osífero" (bony conglomerate) with abundant vertebrate remains.[11] This conglomerate is overlain by almost unfossiliferous whitish to yellow brown sandstones and green mudstones. The Ituzaingó Formation (as Entre Ríos Formation) was correlated with the Puelches Formation of the subsurface of Buenos Aires Province. According to the mammals occurring in the conglomerate and the stratigraphic relationships, the age of the base of Ituzaingo Formation is almost exclusively Tortonian (Late Miocene) or Huayquerian in the SALMA classification.[12]
The formation, as the Paraná and Puelches Formations, has been deposited in a vast Miocene tidal flat environment.[13] Both the terrestrial and freshwater fauna of the Ituzaingó Formation indicates a climate warmer than present. The freshwater vertebrate record suggests important basin connections with Amazonian basins.[11]
Alternatively, the Conglomerado Osífero Member has been interpreted as tide-dominated fluvial channels, pertaining to the marine Paraná Formation.[14]
The Ituzaingó Formation has provided a large variety of fossils, of various groups, from mammals to birds and reptiles to fish and flora. The terrestrial fauna is predominant while a few marine genera are also present.[15] The presence of typical Amazonian freshwater fish and absence of austral fauna in both the underlying Paraná and the Ituzaingó Formation suggests a connection with northern areas of South America. The faunas has been correlated to the older Miocene faunas of the Honda Group at La Venta in Colombia, the Urumaco Formation at Urumaco in Venezuela and the Pebas Formation of the Amazon region of Colombia, Ecuador, Peru and Brazil.[16] Several ground sloth genera present in the Ituzaingó Formation are endemic from this unit, whereas other are also present in the Arroyo Chasicó Formation of Buenos Aires Province, the Andalhuala and Corral Quemado Formations of Catamarca Province, and the Toro Negro Formation of La Rioja Province.[17]
Cione, A.L.; M.M. Azpelicueta; M. Bond; A.A. Carlini; J.R. Casciotta; M.A. Cozzuol; M. Fuente; Z. Gasparini, and F.J. Goin, J. Noriega, G.J. Scillato Yané, L. Soibelzon, E.P. Tonni, D. Verzi, and M.G. Vucetich. 2000. Miocene vertebrates from Entre Rios province, eastern Argentina. Serie Correlación Geológica 14. 191–237. Accessed 2018-10-08.
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Argentina
Uruguay
Brazil
Peru
Bolivia
Venezuela
Huayquerian volcanoclastics
Huayquerian flora