Relative dating quizzes
In dating the past, the primary value of fossils lies within the principle of faunal succession: each interval of geologic history had a unique fauna that associates a given fossiliferous rock with that particular interval.
The basic conceptual tool for correlation by fossils is the index, or guide, fossil.
Correlation is, as mentioned earlier, the technique of piecing together the informational content of separated outcrops.
When information derived from two outcrops is integrated, the time interval they represent is probably greater than that of each alone.
In addition, its fossilized population should be sufficiently abundant for discovery to be highly probable.
Such an array of attributes represents an ideal, and much stratigraphic geology is rendered difficult because of departure of the natural fossil assemblage from this ideal.
Only a partial listing of physical characteristics is necessary to indicate the breadth of approach in this area.
Furthermore, useful fossils are either rare or totally absent in rocks from Precambrian time, which constitutes more than 87 percent of Earth history.