What is the age of the hypothetical rock layer that these fossils were collected from? based on the age determined, do you think that this group of fossils could be considered index fossils? why or why not? suppose that the particular trilobite listed in line 7 of the data table is limited to rocks of lower devonian age and that these trilobite fossils are widespread throughout north america. can this fossils be considered an index fossil? why or why not? the fossils in this group were collected from limestone and shale rocks. based on what you have learned about the formation of these rock types, what type of environment did these organisms live in? shale often contains fossils of leaves. if the gastropods listed in line 3 and line 6 were collected from shale containing leaf fossils, could you use radiocarbon dating to assign a numerical date to this rock unit? explain