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 components.
D)their relative ages cannot be determined without additional information.

Question

Quizplus · Accepted Answer

According to the principle of superposition, in an undisturbed sequence of sedimentary rocks, the oldest layers are at the bottom and the youngest are at the top. Therefore, if a sandstone lies on top of a shale, the shale must be older.

If a Sandstone Lies on Top of a Shale