Question

The diagram below represents a series of rock layers from a single location. Each different type of shape shown in the layers represents a fossil of a different species.



Suppose the blue star represents a certain fish species. When did this species go extinct at this location?
A.
during the Permian
B.
at the end of the Cretaceous
C.
at the end of the Triassic
D.
at the end of the Jurassic

Answer 1

I can't see the diagram you mean — could you either upload the image or describe which labeled rock layers contain the blue star?

How to tell (so you can check quickly): find the youngest (topmost) rock layer that contains the blue-star fossil. The species went extinct at that location when the next younger rock layer (the boundary above that topmost occurrence) was deposited. So:

- if the star only appears in rocks up through the Permian layer → it went extinct during the Permian (A).
- if the star last appears in rocks of the Cretaceous → it went extinct at the end of the Cretaceous (B).
- if it last appears in Triassic rocks → it went extinct at the end of the Triassic (C).
- if it last appears in Jurassic rocks → it went extinct at the end of the Jurassic (D).

Send the diagram or say which period is the highest layer that contains the blue star and I'll pick the correct letter.