Answer :
Index fossils are typically used for relative dating of rock layers because they are distinctive, widespread, and existed for a relatively short period of time. Paradoxides, for example, is a trilobite genus that is often used as an index fossil due to its widespread distribution and short-lived existence during the Middle Cambrian period.
In the scenario you described, the scientist has discovered a new fossil next to some fossils of Paradoxides. However, due to geological activity in the area, she does not believe that she will be able to use Paradoxides as an index fossil. This could be because the geological activity has disrupted the rock layers containing the Paradoxides fossils, making it difficult to accurately determine their relative age.
In such a case, the scientist would need to use other methods for dating the rock layers, such as radiometric dating or stratigraphic correlation with other regions where the rock layers are more intact. While the absence of a reliable index fossil like Paradoxides may make dating more challenging, it is still possible to determine the relative ages of the rock layers using alternative methods.
