What is the correlation between absolute and relative age dating
Ideally, an index fossil should be such as to guarantee that its presence in two separated rocks indicates their synchroneity.This requires that the lifespan of the fossil species be but a moment of time relative to the immensity of geologic history.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.Presumably if all the world’s outcrops were integrated, sediments representing all of geologic time would be available for examination.
Smith’s geologic map was extremely crude, but in its effect on Earth study it was a milestone.
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.
Unlike the principles of superposition and crosscutting, faunal succession is a secondary principle.
That is to say, it depends on other sequence-determining principles for establishing its validity.
Correlation is, as mentioned earlier, the technique of piecing together the informational content of separated outcrops.