7. base your answer on the cross sections bel...
7. base your answer on the cross sections below, which represent two kilometers apart. the rock layers have been numbered for identification index fossil remains shown. evidence best indicates that rock layers 4 and 8 were deposited during the period because both layers a. contain the same index fossil b. are composed of glacial sediments c. contain index fossils of the same age d. are found in the same area
Answer
# Explanation:
## Step1: Recall index - fossil concept
Index fossils are used to date rock layers. If two rock layers contain index fossils of the same age, the rock layers were likely deposited during the same period.
## Step2: Analyze each option
- Option A: Just having the same index - fossil is not as accurate as having index fossils of the same age. Different populations of the same species could have existed at different times.
- Option B: There is no indication in the problem that the layers are composed of glacial sediments.
- Option C: This is the correct principle. If rock layers 4 and 8 contain index fossils of the same age, they were likely deposited during the same period.
- Option D: Being in the same area does not necessarily mean they were deposited at the same time.
# Answer:
C. contain index fossils of the same age