Missão Velha Formation
The Missão Velha Formation is a Jurassic, late Jurassic geologic geologic formation, formation in northeastern Brazil's Araripe Basin where the states of Pernambuco, Piauí and Ceará come together. The formation is the middle stratigraphic unit of the Vale do Carirí Group, overlying the Brejo Santo Formation and overlain by the Abaiara Formation. The formation comprises whitish fine-to-medium quartzose arenites, with subrounded to rounded grains, deposited in an alluvial fan depositional environment, environment during the syn-rift phase of the Araripe Basin. The Missão Velha Formation has provided macrofossils of various genera of fish and reptiles as snakes, crocodylomorphs and turtles. Ichnofossils of dinosaurs were also discovered in the formation, as well as a tooth from an abelisaurid theropod. Geology Fossil content The following fossils were reported from the formation:
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Geological Formation
A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exposed in a geographical region (the stratigraphic column). It is the fundamental unit of lithostratigraphy, the study of strata or rock layers. A formation must be large enough that it can be mapped at the surface or traced in the subsurface. Formations are otherwise not defined by the thickness (geology), thickness of their rock strata, which can vary widely. They are usually, but not universally, tabular in form. They may consist of a single lithology (rock type), or of alternating beds of two or more lithologies, or even a heterogeneous mixture of lithologies, so long as this distinguishes them from adjacent bodies of rock. The concept of a geologic formation goes back to the beginnings of modern scientific geology. The term was used by ...
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