Based on the geological principles shown in the image, here is the step-by-step reasoning to determine the answer:
1.
Analyze the Goal: The question asks to identify which fossil is the
oldest.
2.
Apply the Law of Superposition: In geology, rock layers are formed by sediment settling over time.
* Newer layers settle on top of older layers.
* Therefore, the
bottom layers are the oldest, and the
top layers are the youngest.
3.
Examine the Rock Layers: Look at the stack of rock layers in the diagram.
*
Top Layer: Contains Corals. (Youngest)
*
Second Layer: Contains Ammonites.
*
Third Layer: Contains Gastropods.
*
Fourth Layer: Contains Ferns.
*
Bottom Layer: This is the lowest visible layer of sediment.
4.
Identify the Fossil in the Bottom Layer: Look at the very bottom of the central rock formation. There is a single fossil embedded in the lowest rock layer shown.
* Comparing this fossil to the legend in the top-left corner, the round, segmented bug-like fossil is a
Trilobite.
5.
Conclusion: Since the Trilobite is found in the lowest rock layer, it was deposited first. Therefore, it is the oldest fossil among the choices shown.
Final Answer: Trilobite
Parent Tip: Review the logic above to help your child master the concept of index fossils worksheet.
