1.What is the principle of original horizontality? Law of superposition? The pri

Question

1.What is the principle of original horizontality? Law of superposition? The principle of cross- cutting relationships? The principle of inclusions? The principle of faunal succession? Explain in detail each of these principles. Why are these principles significant for interpreting geologic history? 1.What is the principle of original horizontality? Law of superposition? The principle of cross- cutting relationships? The principle of inclusions? The principle of faunal succession? Explain in detail each of these principles. Why are these principles significant for interpreting geologic history? 1.What is the principle of original horizontality? Law of superposition? The principle of cross- cutting relationships? The principle of inclusions? The principle of faunal succession? Explain in detail each of these principles. Why are these principles significant for interpreting geologic history?

Explanation / Answer

ANSWER-

Principle of original horizontality-

The principle states that sedimentary strata are originally deposited in layers that are horizontal or nearly horizontal ,parallel and near parallel to the Earth's surface.Sediments which are deposited on steep slopes will be washed away efore it is being buried and lithified to become sedimentary rock,but sediments deposited in nearly horizontal layers can be buried and lithified.

Law of superposition-

Deposition of sediments on the earth surface occurs such that older layers are deposited first and successively followed by younger layers with ongoing deposition.Thus in a sequence of layers not overturned by any deformational event ,the oldest rock will be at the bottom and youngetst layer on top.

this principle is used to determine the relative age of rocks from the Earth's surface deposited in basins.

Principle of cross cutting relationships-

younger features truncate(cut across) older features on the Earth's surface .Like faults,dikes and erosion etc. must be younger than the material that is faulted ,intruded or eroded by them.

Principle of inclusions-

when a rock segment of different characteristics is found within another rock ,we say fragment is an inclusion .If the enclosing rock is an igneous rock ,the inclusions are called xenoliths.In either case,the inclusions had to be present before they are included in the younger rock ,therefore inclusions represents fragments of older rock.

this principle is also used to find the relative age of host rocks and the underlying rocks it intruded.

Principle of faunal succession-

Fossils are a very important tool for stratigraphy specially the index fossils which is present for fixed time span and large geographical extent. This principle states that there is a succession of fossils that relate to the age of the rock and gives information on the rocks within which it is present.

These principles are very important to determine the relative age of rocks,correlation among them ,stratigraphy of the area and using it to determine the geological history of the rocks formed.

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