Question

Scientists find trilobites during a routine dig. Trilobites were common in the Paleozoic Era (540 to 245 million years ago) and went extinct during the late Permian period (248 million years ago). On another site, the scientists find ammonites. Ammonites lived during the Mesozoic Era (245 to 65 million years ago) and are not found after that period. What can be concluded about the rock layers? Choose all that apply.

The rock layers must have formed at the same time because they both contain biozones.


The rock layers must have formed at different times because they contain two different biozones.


The rock layer containing the trilobites must have formed before the one containing the ammonites.


The rock layer containing the trilobites must have formed after the one containing the ammonites.

Answer 1

The rock layers must have formed at the same time because they both contain bio-zones.

Step-by-step explanation:

• Trilobites are the extinct marine arthropods form an earlier know group of fossils and they have flourished through the lower Paleozoic era and during the Devonian periods, all of these trilobites were dried out. And ammonites are a molluscan animal that appeared in shell shapes in the Devonian periods and got extinct in Paleogene extinction.

• The fossil records of the trilobites show that they originated in present-day Siberia, and the ammonites lived in the open seas and thus were found in the rocks that were found in the bottom-dwelling conditions.

Answer 2

The answer is; The rock layers must have formed at different times because they contain two different biozones

The rock layer with amniotes formed later after the rock layer with trilobites. This is beaus the former layer is younger in age than the latter layer. The ages of rocks is determined by absolute dating.