2007-02-14 10:29:23 · 3 answers · asked by T 2 in Science & Mathematics ➔ Earth Sciences & Geology
An index fossil is a fossil that is very distinct and very abundant (globally) but only lived for a short time, and this allows the presence of it to be correlated to a specific date or age range. That way, when you see that fossil, it links to one time. The more easily identified and the more widely spread the species, the more applicable the index fossil.
An OK example would be a T-rex, which only lived from 68-66 million years ago. If you find it, your rocks are that old. Better examples are trilobites, especially in the Cambrian, conodonts in the Paleozoic, pollen for Mesozoic and Cenozoic samples, and microfossils and for almost all Phanerozoic time periods.
2007-02-14 11:00:03 · answer #1 · answered by QFL 24-7 6 · 2⤊ 0⤋
Index fossils, by definition, are of species with a wide geographic range and distribution that lived for only a short time period and are easy to identify. You can use them to correlate rocks--to tell if units in different locations are the same age, and what age they are.
2007-02-14 10:52:57 · answer #2 · answered by kiddo 4 · 0⤊ 0⤋
Index fossils, the forms of life which existed during limited periods of geologic time and thus are used as guides to the age of the rocks in which they are preserved. They are utilized for dating the strata that they are found in.
2007-02-14 11:10:48 · answer #3 · answered by Anonymous · 0⤊ 0⤋