page_title: Guabirotuba Formation
section_title: Lithologies
hierarchical_section_title: Guabirotuba Formation / Description / Lithologies
caption_attribution_description: English: This astronaut photograph shows a 29-kilometre stretch of the Paraná, downstream of the small city of Goya, Argentina (just off the top left of the image). The Paraná River ranges up to 3 kilometres wide along the reach illustrated in this image. The main channel is deep enough to allow smaller ocean-going ships to pass north to the capital city of Asunción, Paraguay, fully 1,200 kilometres inland and well out of the image. The river’s dark brown shading indicates a heavy load of muddy sediment; smaller side channels also carry this mud. Numerous lakes are typical on active floodplains, and appear here as irregular bodies of water. Some appear brown, indicating that they probably have been refilled during recent rises and floods of the active channels. The Paraná floodplain occupies the entire image; it is so wide—18 kilometres in this view—that its banks are not visible. Numerous curved, meandering channels are the most prominent characteristic of the floodplain, indicating prior positions of the river and its channels. As riverbeds move laterally by natural processes, they leave remnants of their channels, which appear as lakes and finally fill with mud. This is an excellent image for illustrating these meander forms. From a geological standpoint, it is interesting that almost all of the old channels are similar in curvature to today’s side channels. However, almost none of them seem to show prior positions of the main, wide Paraná channel.
context_page_description: The Guabirotuba Formation is a late Middle Eocene geologic formation of the Curitiba Basin in Paraná, Brazil. The formation crops out in and around the city of Curitiba and comprises mudstones and sandstones deposited in a fluvial floodplain environment.
  The 60 to 80 metres thick formation has provided several fossil mammals, and indeterminate side-neck turtle fossils, and indeterminate terror bird fossils. A newly described species of Cingulata; Proeocoleophorus carlinii was also found in the formation.
context_section_description: The 60 to 80 metres (200 to 260 ft) thick Guabirotuba Formation comprises a basal conglomerate, mudstones and sandstones, deposited in a fluvial floodplain environment.
  The sediments of the formation contain between 0.24 and 2.61% heavy minerals. Heavy mineral analysis on the very abundant zircons, abundant epidote, common tourmaline and kyanite and rare rutile has provided insight in the paleocurrents of the fluvial environment, with predominant flow directions towards the northwest and east-northeast.
caption: The depositional environment of the Guabirotuba Formation was a floodplain
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