Chapter 29, Problem 13TE

Suppose you see a sequence of sedimentary rock layers covered by a basalt flow. A fault cuts through the sedimentary rock layers but does not cut into the basalt. Relate the fault to the ages of the two rock types in the formation.

To determine

The relation between the fault to the ages of the two rock types in the formation.

Answer to Problem 13TE

The fault is younger than the sedimentary rock layers and older than the basalt.

Explanation of Solution

The fault that cuts through rock is younger than the rock through which it faulted or cut. It is the relative dating postulate of cross-cutting. Here, the fault cuts through the sedimentary rock layers. Hence, using the cross-cutting principle, the fault is younger than the sedimentary rock layers. The sedimentary rock layers were formed before the cutting took place.

Since the fault does not cut the basalt, the basalt is younger than the fault. The basalt was formed after the fault made the cut.

Conclusion:

Therefore, the fault is younger than the sedimentary rock layers and older than the basalt.