Chapter 29, Problem 2RQ

A granitic dike is found across a sandstone layer. What can be said about the relative ages of the dike and the sandstone? What principle applies here?

To determine

The relative ages of dike and sandstone layer and the principle applicable here.

Answer to Problem 2RQ

The granitic dike is relatively newer than the sandstone, since a dike cutting into a rock body is newer or younger then the rock. The principle, which explains this concept is known as cross-cutting principle.

Explanation of Solution

When a dike cuts another dike and comes appears over to it, then this kind of formation explains that this dike is younger than the dike, which lies below.

Similarly, if a sandstone layer lies below any other dike layer, then it can be said that the sandstone layer is older than the dike.

Since granitic dike is found across a sandstone layer, therefore, it can be said that the granitic dike is formed after the formation of sandstone layer.

The principle that explains this concept is known as the principle of cross-cutting. Hence, the granitic dike is relatively newer as compared to the sandstone layer.

Conclusion:

Therefore, the granitic dike is relatively newer than the sandstone, since a dike cutting into a rock body is newer or younger then the rock. The principle, which explains this concept is known as cross-cutting principle.