All well and good for a given formation

All well and good for a given formation - different...

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All well and good for a given formation, but one would like to be able to make general statements about larger regions. This can be done by correlation of strata from different formations separated by some distance. Stratum "X" may lie near the top of one formation and many miles away, X may be found near the bottom of a new formation, at the top of which is a different layer "Y". Several miles further on, "Y" may lie at the bottom of a third formation, and in this way one can link or correlate the different strata. This may work for a large region but one would like to do this for the entire earth. It turns out that there are diagnostic fossils found in
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Unformatted text preview: different formations around the world. These Index fossils help correlate different formations on each of the major land masses. This was recognized by William Smith (see lecture 2). The phenomenon is more pronounced than an occasional fossil here and there: entire biotas go through successive changes in sequential strata, illustrating the principle of faunal (biotic) succession . We thus have the "age of trilobites" seen early in the fossil record. Later the age of fishes, age of reptiles, age of mammals are clear in formations around the world indicating the comparable ages of formations separated on different continents....
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