PRINCIPLE OF LITHOSTRATIGRAPHY

 “LITHOSTRATIGRAPHY” is considered as a branch of stratigraphy which deals with the layered rock sequence (rock strata) with respect to their time of formation.

Lithological change occurs with respect to time so which it deals with that change in the sequential arrangement of the layered rocks. As the term “Litho” means the rock and “stratigraphy” means the study of strata (layer of rocks) deals only with the formation and lithological change of strata with time excluding all the biological content like fossils.

 

There are certain principles which bounds the theory of lithostratigraphy . All of these principles are based on the sequential arrangement of the layered rock and the change that occurs within these beds with respect to the time. These principles are:

1)             Principle of original horizontality:

This is the basic and the most important principle of lithostratigraphy. According to this, the sediments that form the sedimentary rocks are first deposited in horizontal basin. So the basin where the sediments deposits first are essentially horizontal. But the bed we observe today are uplifted, eroded etc are the result of different geological action.

 

2)             Principle of superposition:

This is one of the important principles of lithostratigraphy which suggest that younger strata lie on the top of older strata. During the time of deposition, the sediments are deposited on horizontal basin first and the new sediments keep on adding above the old sediments. From this we conclude that in any geologically un-deformed sequence of bed, the sequence settling at the bottom are deposited first than its overlying beds.

 

3)             Principle of cross cutting relations:

The beds deposited in horizontal basin are acted by different geological activities resulting in deformed structures. So the “principle of cross cutting relation” states that when a certain layer of a bed is cut by a fault or may be intruded by igneous intrusion then the cut layer of bed is supposed to be older than the causing events.

 

4)             Principle of lateral continuity:

When the beds are deposited in a basin and later with respect to time they gradually expose on the surface by the means of geological activities. So these beds exposes on the large scale area on the surface. Then “principle of lateral continuity” explains that when the bed is exposed in large scale area and is cut off by action of erosion turning it into valley in between separating a laterally continuous sequence of bed. So the same sequence of the bed is divided into two or more sequences.

 

Hence these are the principles that explains lithostratigraphy.