This photograph shows an upper unit with fragments and a lower unit with tilted layers.Which of the following statements is true?
A)the upper unit is younger because it is on top
B)the upper unit is younger because it contains pieces of the underlying unit
C)the lower unit is older because it was tilted and eroded before deposition of the upper unit
D)all of these

Question

This photograph shows an upper unit with fragments and a lower unit with tilted layers.Which of the following statements is true? 
A)the upper unit is younger because it is on top 
B)the upper unit is younger because it contains pieces of the underlying unit 
C)the lower unit is older because it was tilted and eroded before deposition of the upper unit 
D)all of these

Quizplus · Accepted Answer

A) The principle of superposition states that in a sequence of undisturbed sedimentary rocks, the oldest rocks will be at the bottom while the youngest layers will be on top. Therefore, the upper unit is younger because it is on top.
B) The fragments in the upper unit are most likely derived from the lower unit through erosion and transport. Therefore, the upper unit is younger because it contains pieces of the underlying unit.
C) The lower unit must have been tilted and eroded prior to the deposition of the upper unit. Therefore, the lower unit is older because it was formed and then modified before the formation of the upper unit. 
Thus, all of the statements are true.

This Photograph Shows an Upper Unit with Fragments and a Lower