Define biostratigraphic dating
The boundaries of an interval of maximal abundance are not easily established and can be recognized only through a quantitative survey of the fossils assemblage.
Abundance zones may be of limited, local utility because abundances of taxa in the geologic record are largely controlled by paleoecology, taphonomy, and diagenesis.
Partial range biozone is a body of rock located between the last appearance of a taxon and the first appearance of another taxon.
Range zones are especially useful in areas where the stratigraphical sequence is poorly understood, as they can be identified by the presence of the index taxon or taxa in isolated assemblages.
In 1796 William Smith, a British civil engineer, addressed this, adding the principle of In 1815, Smith published the first geologic map of England.
An interval biozone is a body of rock between two specified biostratigraphic biohorizons (surfaces).
There are two types of interval biozones: – The boundaries based on first appearance; – The boundaries based on last appearance.
Where the full succession of strata in an area is better documented, however, greater biostratigraphical precision is normally possible using the interval zone.
These are defined purely by their upper and lower boundaries, witch are placed in the stratigraphical sequence at defined levels called biohorizons, where there is a significant change in the fossil record , such as the lowest or highest occurrence of a taxon or taxa.
Through biostratigraphy, and the correlation of geological formations that it promoted, the modern geological timescale was developed.