The schematic shows a geological cross-section of a faulted region of sedimentary rocks (beds P to U). Assuming continuous sedimentation, select the beds that record the earliest activation and the latest reactivation of the fault.
Show Hint
The earliest fault activation is recorded by the first bed displaced, and the latest reactivation is recorded by the youngest displaced bed in the sequence.
Step 1: Understanding the cross-section and faulting.
The fault is depicted in the schematic, and the beds (P to U) are affected by faulting, with the oldest beds at the bottom and the youngest at the top. Continuous sedimentation suggests that the beds record the progression of fault activity and reactivation over time.
Step 2: Analyzing the earliest activation of the fault.
The earliest activation of the fault would correspond to the first displacement, which occurred before the deposition of the overlying beds.
The first bed that shows displacement and corresponds to the earliest fault activation is Q. The next bed that records this early faulting is R, as it is displaced by the fault but is younger than bed Q.
Step 3: Analyzing the latest reactivation of the fault.
The latest reactivation of the fault corresponds to the most recent displacement, affecting the youngest beds. In the schematic, bed T is displaced, indicating the latest reactivation of the fault.
Step 4: Conclusion.
The beds that record the earliest activation and the latest reactivation of the fault are Q and R, respectively. Therefore, the correct answer is (C).
\[
\boxed{\text{Q, R}}
\]
