What makes a fossil an index fossil?

Answer 1

a fossil found in rocks one time period

Index fossils are commonly found, widely distributed fossils that are limited in time span. They help in dating other fossils found in the same sedimentary layer. For example, if you find a fossil from an unknown era near a fossil from a known time, you can assume that the two species were from about the same time.

Answer 2

fossils are preserved animals or plants. but index fossils are fossils have wide distribution,many of them,evolves rapidly, and very easy to recognize.

Ammonites are index fossils.

The fossils were made only in a certain short time period.

Answer 3

fossils that are common and are found in rare places on earth

Answer 4

the fossil found in rocks from one time period

Answer 5

Index fossils (also known as guide fossils, indicator fossils or zone fossils) are fossils used to define and identify geologic periods (or faunal stages). They work on the premise that, although different sediments may look different depending on the conditions under which they were laid down, they may include the remains of the same species of fossil. If the species concerned were short-lived (in geological terms, lasting a few hundred thousand years), then it is certain that the sediments in question were deposited within that narrow time period. The shorter the lifespan of a species, the more precisely different sediments can be correlated, and so rapidly evolving types of fossils are particularly valuable. The best index fossils are common, easy-to-identify at species level, and have a broad distribution-otherwise the likelihood of finding and recognizing one in the two sediments is minor.

Ammonites fit these demands well, and are the best-known fossils that have been widely used for this. Other important groups that provide index fossils are the corals, graptolites, brachiopods, trilobites, and echinoids (sea urchins).Conodonts may be identified by experts using light microscopy such that they can be used to index a given sample with good resolution.{cn}}Fossilized teeth of mammals have also been used.

Geologists use both large fossils (called macrofossils) and microscopic fossils (called microfossils) for this process, known asbiostratigraphy. Macrofossils have the advantage of being easy to see in the field, but they are rarer, and microfossils are very commonly used by oil prospectors and other industries interested in mineral resources when accurate knowledge of the age of the rocks being looked at is needed.

Answer 6

The fossil has to be found in many parts of the world for it to be an index fossil

Answer 7

any fossil of wide geographical distribution and a short range in time

Answer 8

A fossil found in rocks from one time period - Apex