Adamantina-Formation
The Adamantina Formation is a lithostratigraphic unit ( formation ) of sedimentary rocks from the Upper Cretaceous of southern Brazil. It belongs to the Bauru Group, whose sediments in the Bauru Basin, a section of the Parana Basin, deposited. The name of the formation is derived from the city Adamantina in the Brazilian state of São Paulo.
Stratigraphic Classification
The Adamantina lineup overlaid conformably on an erosional unconformity of the basalts of the Serra Geral Formation and is of the Marília Formation or their southward equivalents (São José do Rio Preto lineup and Presidente Prudente Formation) covered. In the southwest it dovetails with the Santo Anastácio formation or superimposed on it, to the northeast it dovetails with the Uberaba Formation. It also contains the analcimführenden volcanic rocks of Taiúva lineup. The formation is divided into the following units:
- Vale do Rio do Peixe - formation and
- Araçatuba formation at the base in the central area of the depositional environment
Description
The sedimentary rocks of the Adamantina formation are disrupted in the Brazilian states of Goiás, Mato Grosso do Sul, Minas Gerais and in western São Paulo.
There is no absolute age dating of these rocks, they are usually placed in the Turonian to Santonian period, but also Campanian to Maastrichtian is contemplated.
The Adamantina Formation is a continental Rotfazies and consists mainly of sandstones and siltstones that were deposited under semi-arid conditions. With aeolian sandstones and associated intermediary Lößhorizonten ( together they form the Vale do Rio do Peixe - Formation) superimposed on it the Lower Cretaceous basalts of the Serra Geral Formation. In the basalts, a endorheisches drainage network ( wadis ) had emerged with a large wetland in its central part. In this swamp the generally fine-grained sediments of the Araçatuba lineup came to deposit - usually siltstone, but also gray-green sandstones with karbonathaltigem cement. The swamp was periodically dry - documented by dry cracks and pseudomorphs after gypsum and dolomite. Ultimately, the Paläosumpf was filled by the advancing sand dunes of the Vale do Rio do Peixe - formation.
Fossil content
The Adamantina lineup leads a moderate vertebrate fauna, including Dinosauriertaxa. Well known is the formation of Titanosauridae such as Adamantisaurus mezzalirai and Maxakalisaurus Topai. From dinosaurs also are osteoderms.
In general, the dinosaur discoveries are made up of remnants of typical representatives of the austral Gondwana ( Aeolosaurus and Abelisauridae ) and taxa of boreal Gondwana ( Carcharodontosauridae ).
Significant also are numerous findings of crocodile relatives ( Mesoeucrocodylia ), including the controversial taxon Brasileosaurus pachecoi and Notosuchidae ( navae Adamantinasuchus, Mariliasuchus amarali ) Goniopholidae ( Goniopholis paulistanus ) Baurusuchidae ( Baurusuchus pachecoi, Baurusuchus salgadoensis, Baurusuchus sp., Stratiotosuchus maxhechti ) and Peirosuchidae ( Montealtosuchus arrudacamposi ).
Also worth mentioning is the Schildkrötentaxa Podocnemis elegans and Roxoquelis wanderlii.
In addition to the remains of fish was also a representative of the Enantiornithes, a group dental bearing birds discovered.
Besides charophyte, photosynthetic eukaryotes, there are also invertebrates such as Muschelschalerkrebse, molluscs and ostracods.
See also: List of dinosaur leading rock formations