An index fossil is a species that lived for a relatively short period of time but had a wide geographic distribution, making it useful for dating and correlating the age of rocks in different locations. Index fossils can be found in more than one type of rock because they lived in various environments and were able to adapt to different conditions. When a particular species was thriving and widespread, its remains could be preserved in a variety of sedimentary rocks formed in different environments, such as marine, freshwater, or terrestrial settings. Additionally, the process of fossilization can occur in different types of rocks if the necessary conditions, such as rapid burial and mineralization, are present. Therefore, an index fossil may be found in more than one type of rock due to its broad distribution and the variable conditions under which fossils can be preserved.
