Describe absolute dating and relative dating
Failing that, the repetition of a certain layered sequence (e.g., a black shale sandwiched between a red sandstone and a white limestone) lends confidence to physical correlation.
Finally, the measurement of a host of rock properties may well be the ultimate key to correlation of separated outcrops.
Correlating two separated outcrops means establishing that they share certain characteristics indicative of contemporary formation.
The most useful indication of time equivalence is similar fossil content, provided of course that such remains are present.
Following Smith’s pioneering work, generations of geologists have confirmed that similar and even more extensive fossil sequences exist elsewhere.
To this day, fossils are useful as correlation tools to geologists specializing in stratigraphy.
The basis for assuming that like fossils indicate contemporary formation is faunal succession.
From an examination of such outcrops with special focus on the sequence of animal forms comes the empirical generalization that the faunas of the past have followed a specific order of succession, and so the relative age of a fossiliferous rock is indicated by the types of fossils it contains.fossil assemblages.
Furthermore, useful fossils are either rare or totally absent in rocks from Precambrian time, which constitutes more than 87 percent of Earth history.
Precambrian rocks must therefore be correlated by means of precise isotopic dating.faunal succession is a secondary principle.
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.