La Amarga Formation
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La Amarga Formation
The La Amarga Formation is a geologic formation with outcrops in the Argentina, Argentine provinces of Rio Negro Province, Río Negro, Neuquen Province, Neuquén, and Mendoza Province, Mendoza. It is the oldest Cretaceous terrestrial formation in the Neuquén Basin. The type locality is La Amarga Arroyo and China Muerta Hill.Musacchio, 1970 The La Amarga Formation unconformity, unconformably overlies the marine (ocean), marine Agrio Formation of the Mendoza Group. It is in turn overlain by the Lohan Cura Formation, separated by another unconformity. Composition There are three Geologic unit, members within the La Amarga Formation. # The oldest is the Puesto Antigual Member, which is approximately thick and consists mainly of sandstone deposited in the channels of a braided river system. Paleosols, or soil deposits, are well-developed. # The Bañados de Caichigüe Member is the next highest, approximately thick. Alternating limestones, shales, and siltstones make up this member, ...
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Geological Formation
A geological formation, or formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguish 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 Abraham Go ...
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