PRINCIPLE OF BIO-STRATIGRAPHY

 

     Biostratigraphy is a branch/element of stratigraphy which deals with the distribution of fossils in the stratigraphic units to determine the age of the strata.

Unlike lithostratigraphy, it only deals with the biological contents that are preserved in the rock sequence during the time of formation of the strata.

According to this, with respect to the relative age of the biological content or simply fossil content present in the rock, the age of the rock sequence can be determined by knowing the age of the fossil content.

During the formation of the rock sequence, parts of dead plants and animals are preserved in the form of trace as trace fossil, when whole body is preserved it is called body fossil and sometime the characteristic dominant fossil of one geological age called index fossil  and  many others are preserved in the rocks.

The different sequence of the bed contains different type of fossils and it is very important to know that different plant and animals possess different lifespan in different geological ages. And when they as preserved as fossils in any particular sequence then they represent the relative age of that particular geological history.

That’s why biostratigraphy plays a vital role to describe the geological history of the earth.

 

Biostratigraphic correlation:

It is a scientific study of determining the geological age of the rocks or simply strata by comparing the fossil content present in different sequence or geological profile.

 

Principle of Biostratigraphy:

1)    Principle of floral and faunal succession:

 The “Principle of Floral and Faunal succession” states that plants and animals evolves into new species with respect to geological time and the sedimentary rocks of different ages will contain fossils of different species which represents that particular geological age. By knowing the age of the fossil the relative as well as absolute age of the rock sequence can be determined. Index fossils, often called as a characteristic fossil of one certain geological age exists for very short time and are especially valuable to determine the age of the rock sequence. And it suggest that two rock sequence of different locations containing the same index fossil most be of same geological age.