GEOLOGY

Detailed explanation-1: -Special fossils called “index fossils” indicate to geologists the boundaries in geological time. This is another tool to determine the age of rocks.

Detailed explanation-2: -Keyed to the relative time scale are examples of 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.

Detailed explanation-3: -A useful index fossil must be distinctive or easily recognizable, abundant, and have a wide geographic distribution and a short range through time. Index fossils are the basis for defining boundaries in the geologic time scale and for the correlation of strata.

Detailed explanation-4: -Index fossils are fossils of organisms that lived during only one short period of time. A layer rock with an index fossil in it is close in age to another layer of rock with the same type of index fossil in it. Even though rock layers are of different regions, index fossils indicates that the layers are close in age.

Detailed explanation-5: -Fossils of any kind are useful in “reading the rock record, ” meaning they help us decipher the history of the earth. They can help us determine the geologic age and environment (the paleoenvironment) in which they were deposited.