The Guichón Formation is a

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

geologic

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondary ...

of the Paysandú Group in

Uruguay Uruguay (; ), officially the Oriental Republic of Uruguay ( es, República Oriental del Uruguay), is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast; while bordering ...

Dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

remains are among the fossils that have been recovered from the formation.Weishampel et al., 2004, pp.517-607

Description

The Guichón Formation comprises mainly pink-greyish to reddish

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

s, which contain moderate to well-sorted, subrounded, fine to medium-sized grains in a pelitic matrix. These sandstones (which compositionally are

feldspathic Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldspa ...

wacke Greywacke or graywacke (German ''grauwacke'', signifying a grey, earthy rock) is a variety of sandstone generally characterized by its hardness, dark color, and poorly sorted angular grains of quartz, feldspar, and small rock fragments or lith ...

s) are either massive or may instead exhibit parallel lamination, cross-lamination and graded bedding. These lithologies were deposited in southwest-trending

alluvial Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Al ...

–

fluvial In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluv ...

systems comprising low-sinuosity channels traversing through sandy plains. Subordinate to the already mentioned sandstones are conglomeratic and pelitic lithologies, interpreted as channel-fill and

overbank An overbank is an alluvial geological deposit consisting of sediment that has been deposited on the floodplain of a river or stream by flood waters that have broken through or overtopped the banks. The sediment is carried in suspension, and becaus ...

deposits, respectively. It is inferred that the Guichón Formation was deposited in warm, semi-arid climatic conditions. The formation has been correlated to the

Puerto Yeruá Formation The Puerto Yeruá Formation is a Late Cretaceous geologic formation in the Paraná Basin, pertaining to Entre Ríos Province, Argentina. Dinosaur remains are among the fossils that have been recovered from the formation,Weishampel et al., 2004, pp ...

of northwestern Argentina.Soto et al., 2009, p.13 The formation reaches a thickness of more than in wells perforating the formation.Tofalo et al., 2011, p.616 It is overlain by the Mercedes Formation and overlies the Arapey Formation.Tofalo et al., 2011, p.617

Fossil content

The following fossils have been reported from the formation:Guichón
at

Fossilworks Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cre ...

.orgSoto et al., 2009, p.19 * '' Uruguaysuchus aznarezi''Mones, 1972 * Iguanodontia indet.Soto et al., 2011 * Saltasauridae indet.Soto et al., 2012 * Theropoda indet. ;Fossil eggs * '' Sphaerovum sp.''

References

Bibliography

* * * * * * * {{DEFAULTSORT:Guichon Formation Geologic formations of Uruguay Cretaceous System of South America Cretaceous Uruguay Albian Stage Aptian Stage Cenomanian Stage Santonian Stage Turonian Stage Sandstone formations Conglomerate formations Fluvial deposits Ooliferous formations Formations Fossiliferous stratigraphic units of South America Paleontology in Uruguay Formations

Description

Fossil content

See also

References

Bibliography