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Furthermore, biostratigraphic units are divided into six principal kinds of biozones: Taxon range biozone, [6] Concurrent range biozone, [6] Interval biozone, Lineage biozone, Assemblage biozone, and Abundance biozone. The Taxon range biozone represents the known stratigraphic and geographic range of occurrence of a single taxon. Concurrent ...
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 ...
A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features that characterize it. Units must be mappable and distinct from one another, but the contact need not be particularly distinct ...
The basic concept in stratigraphy, called the law of superposition, states: in an undeformed stratigraphic sequence, the oldest strata occur at the base of the sequence. Chemostratigraphy studies the changes in the relative proportions of trace elements and isotopes within and between lithologic units.
[1]: 230 A rock unit has a characteristic assemblage of fossils, independent of its lithology. [ 1 ] : 229 Thus, the fossils can be used to compare the ages of different rock units. The basic unit of biochronology is the biostratigraphic zone, or biozone , a collection of fossils found together in a rock unit.
The International Commission on Stratigraphy defines a Taxon-range zone as follows: "The body of strata representing the known range of stratigraphic and geographic occurrence of specimens of a particular taxon. It is the sum of the documented occurrences in all individual sections and localities from which the particular taxon has been ...
Also called Indianite. A mineral from the lime-rich end of the plagioclase group of minerals. Anorthites are usually silicates of calcium and aluminium occurring in some basic igneous rocks, typically those produced by the contact metamorphism of impure calcareous sediments. anticline An arched fold in which the layers usually dip away from the fold axis. Contrast syncline. aphanic Having the ...
Type locality, also called type area, is the locality where a particular rock type, stratigraphic unit or mineral species is first identified. [1] If the stratigraphic unit in a locality is layered, it is called a stratotype, whereas the standard of reference for unlayered rocks is the type locality. [2] The concept is similar to type site in ...