Exercises: Geological cross-sections

State the principle of original horizontality and explain what must have happened if today we find tilted or folded strata.

Four undisturbed horizontal strata appear in a cross-section: sandstone, mudstone, limestone, and conglomerate, from bottom to top. Apply the principle of superposition to state which is the oldest and which is the youngest, and justify your answer.

In the geological cross-section shown in the diagram, five strata (A, B, C, D and E), an erosion surface (W) and a fault (X) are indicated. Order these events from oldest to youngest: formation of the five strata, erosion that caused W, and movement of fault X. State which principle you apply at each step.

A fault cuts through a series of strata and, in turn, is cut by an igneous dike. Apply the principle of cross-cutting relationships to order these three events: formation of the strata, movement of the fault, and intrusion of the dike.