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The Mammal Neogene zones or MN zones are system of biostratigraphic zones in the stratigraphic record used to correlate mammal-bearing fossil localities of the Neogene period of Europe.
In 1941, a committee chaired by Horace E. Wood II compiled a list of 19 "provincial ages" for North America, later called North American Land Mammal Ages (NMLAs). An example of an NMLA is the Rancholabrean, named after the Rancho La Brea fossil site. One of its characteristic fossils is the bison, which first appears in the Rancholabrean. [7]
By combining multiple geochronological (and biostratigraphic) indicators the precision of the recovered age can be improved. Geochronology is different in application from biostratigraphy, which is the science of assigning sedimentary rocks to a known geological period via describing, cataloging and comparing fossil floral and faunal assemblages.
Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them. [1] The primary objective of biostratigraphy is correlation , demonstrating that a particular horizon in one geological section represents the same period of time as another ...
Stages are primarily defined by a consistent set of fossils (biostratigraphy) or a consistent magnetic polarity (see paleomagnetism) in the rock. Usually one or more index fossils that are common, found worldwide, easily recognized, and limited to a single, or at most a few, stages are used to define the stage's bottom.
The North American land-mammal-age system was formalized in 1941 as a series of provincial land-mammal ages. [2] The system was the standard for correlations in the terrestrial Cenozoic record of North America and was the source for similar time scales dealing with other continents. The system was revised into a formal chronostratigraphic system.
In biostratigraphy, biostratigraphic units or biozones are intervals of geological strata that are defined on the basis of their characteristic fossil taxa, as opposed to a lithostratigraphic unit which is defined by the lithological properties of the surrounding rock. A biostratigraphic unit is defined by the zone fossils it contains. These ...
Chronostratigraphy is the branch of stratigraphy that studies the ages of rock strata in relation to time. The ultimate aim of chronostratigraphy is to arrange the sequence of deposition and the time of deposition of all rocks within a geological region, and eventually, the entire geologic record of the Earth .