The most useful index fossils are from animals that existed for only short periods of time, and that are found over a wide area. Theyre useful because they give us a more exact date for a rock, and they can be used to date more rocks since theyre common. These fossils are found all over the place!
How are index fossils used in dating?
Index fossils are fossils that are known to only occur within a very specific age range. If the fossil you are trying to date occurs alongside one of these index fossils, then the fossil you are dating must fall into the age range of the index fossil. Sometimes multiple index fossils can be used.
Why are index fossils important to geologic dating?
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.
How can index fossils assist in dating rocks?
Certain fossils, called index fossils, can be used to help find the relative age of rock layers. To be an index fossil - The shorter time period a species lived, the better an index it is.Fossils that are found in many rock layers, therefore living long periods of time, do not qualify as index fossils.
What are four qualities of a good index fossil?
A good index fossil is one with four characteristics: it is distinctive, widespread, abundant, and limited in geologic time. Because most fossil-bearing rocks formed in the ocean, the major index fossils are marine organisms. That being said, certain land organisms are useful in young rocks and specific regions.
Which best describes the relationship between rock layers and index fossils?
Which best describes the relationship between rock layers and index fossils? Different rock layers can be determined to be the same relative age if they contain the same index fossils.
What four characteristics are best for an index fossil to have?
A good index fossil is one with four characteristics: it is distinctive, widespread, abundant, and limited in geologic time. Because most fossil-bearing rocks formed in the ocean, the major index fossils are marine organisms. That being said, certain land organisms are useful in young rocks and specific regions.
Which fossil would make the best index fossil?
Trilobites serve as good index fossils, letting geologists date the age of the rocks that they are in.
Which rock type is most likely to contain fossils?
sedimentary rock There are three main types of rock: igneous rock, metamorphic rock, and sedimentary rock. Almost all fossils are preserved in sedimentary rock. Organisms that live in topographically low places (such as lakes or ocean basins) have the best chance of being preserved.
Why are index fossils used as guides to determine the age of rocks?
Index fossils are of organisms that lived over a wide area. They lived for a fairly short period of time. An index fossil allows a scientist to determine the age of the rock it is in. Different species of trilobite fossils can be used to narrow the age even more.
What are 3 considerations for choosing a fossil to correlating rocks?
To be considered an index fossil, it must meet 3 criteria: The fossilized organism must be easily recognizable. It must be easy to ID and look unique. 2. The fossils have to be geographically widespread, or found over large areas so that we can use them to match layers separated by huge distances.