BIOSTRATIGRAPHY

BIOSTRATIGRAPHY:-

A biostratigraphic unit is defined solely on the basis of the fossil continents irrespective of the rock types in which they occur.

Hierarchical order : (1)Biostratigraphic Zone

∙Component of a fossil assemblage that occur in any rock unit may have three different derivations-

(1) Biocoenose: Community of interrelated group of organisms inhabiting an area.

• Biotope: The area inhabited by the community adapted to its environment.

(2) Thenatocoenose: Fossil assemblage may have been derived from neighbouring or distant relatives.

(3) Fossils, which are derived from an older sequence by the usual sedimentary process.

     These derived fossils can be easily identified and separated from indigenous material.

Biostratigraphic zones is defined in primarily in two ways :

(1) RANGE ZONE: The first and last appearance of a species in a sequence of sedimentary rocks determine the lower and upper boundaries of biostratigraphic zone.

(2) ASSEMBLAGE ZONE: Considering the entire mineral assemblage.

∙BARREN ZONE: Toxic condition may completely destroy all traces of life in a part of sedimentary basin giving rise to the deposition of strata completely devoid of fossil record.

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