If a sandstone lies on top of a shale,
A) the shale must be older,according to the principle of superposition.
B) the sandstone must be older,according to the principle of superposition.
C) the shale must be older,according to the principle of original horizontality.
D) their relative ages cannot be determined from the information given.

Question

Quizplus · Accepted Answer

The principle of superposition states that in an undisturbed sequence of sedimentary rocks, the oldest layers are at the bottom and the youngest layers are at the top. Therefore, if sandstone is on top of shale, the shale must be older.

If a Sandstone Lies on Top of a Shale