Define biostratigraphic dating

04-May-2019 22:40 by 2 Comments

Define biostratigraphic dating - accuracy carbon dating fossils

Index fossils are fossils used to define and identify geologic periods (or faunal stages).

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Although the concept is generally straightforward, in practice biostratigraphic studies tend to be complex.

The concept of stage expresses a major subdivision of strata, each systematically following the other each bearing a unique assemblage of fossils called index fossils.

Therefore, stages can be defined as a group of strata containing the same major fossil assemblages.

A range biozone is a body of rock representing the known stratigraphic and geographic range of occurrence of any selected element or elements in the rock record.

There are three types of range biozones: – Taxon range biozone; – Concurrent range biozone; – Partial-range biozone.

A taxon-range biozone is a body of rock representing the known stratigraphic and geographic range of a chosen taxon.

A concurrent – range biozone is a body of rock including the concurrent, coincident, or overlapping part of the ranges of two specified taxa.Principal microfossil groups studied extensively over the last 30 years include palynomorphs (spores, pollen, dinoflagellates), foraminifera (planktonic and benthic), nannoplankton, radiolaria, marine diatoms and ostracods.Ammonites, graptolites, archeocyathids, and trilobites are index fossils that are widely used in biostratigraphy.Through biostratigraphy, and the correlation of geological formations that it promoted, the modern geological timescale was developed.Each of the geological periods in the modern geological timescale was originally defined as groups of formations that could be correlated from place to place known as the geological systems.The lineage zone, which is sometimes called zone of consecutive existence, satisfies entirely the criterion of exclusion but not that of coexistence since, by definition, the recognized evolutionary stages do not overlap in time.