Final answer:
Ichnofossils above the fair weather wave base are part of an ichnofacies reflecting deeper water conditions. Exercises may compare grain sizes and trace fossils to infer environmental details. Fern spore abundance shifts across the Cretaceous-Paleogene boundary convey ecological changes.
Step-by-step explanation:
The types of ichnofossils found above the fair weather wave base can be indicative of the environmental conditions prevalent at the time the organisms were active. These trace fossils are part of an ichnofacies, which is an assemblage of trace fossils that reflect a certain paleoenvironment.
When examining ichnofossils, one of the exercises might involve comparing the grain size of the surrounding rock to the trace fossil itself, which could provide information on the type of sediment the organisms inhabited. As an example, a coarse-grained sandstone with trace fossils might indicate a higher energy environment compared to fine-grained shale.