Chico Formation
The Chico Formation is a geologic formation of the Campanian Age during the Cretaceous Period, found in California and southern Oregon. Geology The MesozoicEra formation can regionally overlie the Vaqueros Formation, and can regionally underlie the Martinez Formation or Tejon Formation. The Chico Formation is exposed in the Southern California Coast Ranges, western San Joaquin Valley, north of Mount Diablo, and in the Chico area of the northeastern Sacramento Valley. Google Books: "The stratigraphic and faunal relations of the Martinez format ...
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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 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 ...
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