Question

What are index fossiles and how can they be used to correlate rock layers found large distances apart?
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Answer 1

Answer:

Ammonites, trilobites, and graptolites are often used as index fossils. Microfossils, which are fossils of microscopic organisms, are also useful index fossils.

Explanation:

Answer 2

The first person that answered is correct that would be the right answer I believe