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INDEX FOSSIL. Fossil that defines and identifies geologic periods; often in only one layer of rock Easily recognizable Exists over a short geologic time range (found only in a few layers of rock) Wide distribution (geographic range is world-wide). Ex/ INDEX FOSSIL: AMMONITE.
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INDEX FOSSIL Fossil that defines and identifies geologic periods; often in only one layer of rock • Easily recognizable • Exists over a short geologic time range(found only in a few layers of rock) • Wide distribution(geographic rangeis world-wide)
Ex/ INDEX FOSSIL: AMMONITE Ammonite fossils • are found worldwide, • existed for only a very specific period of time This means ammonites are found in very specific layers of rock; Once we know the ammonites, then we can determine the age of any fossil found next an ammonite fossil.