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Cintura Formation
The Cintura Formation is a geologic formation in the northeastern Sonora of Arizona and Mexico. It preserves fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ... dating back to the Cretaceous period. Description The Cintura Formation is divided into 3 stratigraphic members which represent deltaic depositional elements: the basal Marquechi Member, medial San Marcos Member and the uppermost San Juan Member. The delta is thought to have prograded southward and have an immediate source to its north based on paleocurrents and provenance data. Fossil content See also * List of fossiliferous stratigraphic units in Arizona * Paleontology in Arizona References * Cretaceous Arizona {{Cretaceous-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 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 Abraham Gottlob Wer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cheirolepidiaceae
Cheirolepidiaceae is an extinct family of conifers. They first appeared in the Triassic, and were widespread during most of the Mesozoic era. They are united by the possession of a distinctive pollen type assigned to the form genus '' Classopollis''. The name Frenelopsidaceae (as a separate family) or "frenelopsids" has been used for a group of Cheirolepidiaceae with jointed stems, thick internode cuticles, sheathing leaf bases and reduced free leaf tips. The leaf morphology has been noted as being similar to that of halophyte ''Salicornia.'' Several members of the family appear to have been adapted for semi-arid and coastal settings, with a high tolerance of saline conditions. Cheirolepidiaceae disappeared from most regions of the world during the Cenomanian-Turonian stages of the Late Cretaceous, but reappeared in South America during the Maastrichtian, the final stage of the Cretaceous, increasing in abundance after the K-Pg extinction and being a prominent part of the regional ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schizaeaceae
Schizaeaceae is a family of ferns in the order Schizaeales. In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), it includes only two genera. Alternatively, two families kept separate in PPG I, Lygodiaceae and Anemiaceae, may be included in Schizaeaceae (as the subfamilies Lygodioideae and Anemioideae) so that the family has four genera. In this approach, the Schizaeaceae of PPG I is treated as the subfamily Schizaeoideae. Species are mainly distributed in the tropics, but several are found in temperate regions in North America, South Africa, Australasia and Northeast Asia. The sporangia are borne on specialised pinnae, distinct from ordinary vegetative pinnae. The pinnae form small comb-like, pinnate structures on which the sporangia are formed. Genera In the narrow circumscription of the family, there are two genera: *'' Actinostachys'' Wall *'' Schizaea'' Sm. Two further genera are included in the broader circumscription: *''Anemia'' Sm. – otherwise placed i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
