Asked by: Bouchara Babeshkin
science geology

What are the characteristics of a useful index fossil?

Last Updated: 12th May, 2020

A useful index fossil must be distinctive oreasily recognizable, abundant, and have a wide geographicdistribution and a short range through time. Index fossilsare the basis for defining boundaries in the geologic time scaleand for the correlation of strata.

Click to see full answer.

Considering this, what are three characteristics of a good index fossil?

A good index fossil is one with fourcharacteristics: it is distinctive, widespread, abundant,and limited in geologic time. Because most fossil-bearingrocks formed in the ocean, the major index fossils aremarine organisms. That being said, certain land organisms areuseful in young rocks and specific regions.

One may also ask, how do you identify an index fossil? Identify Index Fossils

  1. They know it is about the same age as any other rock layersthat contain the same index fossil.
  2. * An index fossil must have lived for a relatively short periodof time an in many place.
  3. If geologists identify an index fossil in a rock layer, theycan be pretty sure of the age of the rock layer in which it wasfound.

Subsequently, one may also ask, what is an index fossil used for?

Index fossils (also known as guide fossilsor indicator fossils) are fossils used to define andidentify geologic periods (or faunal stages). Index fossilsmust have a short vertical range, wide geographic distribution andrapid evolutionary trends.

What is an index fossil example?

Index fossils are commonly found, widelydistributed fossils that are limited in time span.Examples of index fossils include: Ammonites werecommon during the Mesozoic Era (245 to 65 mya), They were not foundafter the Cretaceous period, as they went extinct during the K-Textinction (65 mya).

Related Question Answers

Francy Garlichs


What is an index fossil and why are they important?

Index fossils are important becausethey help to separate different periods of time in thegeological history of the planet. This short time of existenceprovides data for the rock strata in which they arefound.

Coralina Korzec


How do you find a good index fossil?

A good index fossil is found in a wide geologicalrange. Scientists look for fossils all across the world. Ifa new fossil is found in the same strata as an indexfossil, then the new fossil's age can be correlated totime period during which the index fossillived.

Soña Kovac


How do you describe a fossil?

fossil. The remains or imprint of an organismfrom a previous geologic time. A fossil can consist of thepreserved tissues of an organism, as when encased in amber, ice, orpitch, or more commonly of the hardened relic of such tissues, aswhen organic matter is replaced by dissolved minerals.

Limberg Doppelgatz


What are the four different types of fossils?

There are four main types of fossils, all formedin a different way, which are conducive to preservingdifferent types of organisms. These are mold fossils,cast fossils, trace fossils and true formfossils.

Wenwen Lazarrasa


What is the law of superposition and how is it used?

In its plainest form, it states that in undeformedstratigraphic sequences, the oldest strata will be at the bottom ofthe sequence. This is important to stratigraphic dating, whichassumes that the law of superposition holds true and that anobject cannot be older than the materials of which it iscomposed.

Sarka Chabin


Which unit of geologic time is the longest?

Geologic time is divided into eons, eras,periods, and epochs. As the first division, the eonrepresents the longest segment of geologic time. TheArchean Eon (ahr-KEE-uhn) is the oldest, beginning with theformation of Earth's crust almost 4 billion years ago. The earliestknown rocks formed during this eon.

Lesbia Mojio


Where did the index fossil ammonites live?

Ammonites are perhaps the most widely knownfossil, possessing the typically ribbed spiral-form shell aspictured above. These creatures lived in the seas between 240 - 65million years ago, when they became extinct along with thedinosaurs.

Talita Vingada


Why is an index fossil useful?

A useful index fossil must be distinctive oreasily recognizable, abundant, and have a wide geographicdistribution and a short range through time. Index fossilsare the basis for defining boundaries in the geologic time scaleand for the correlation of strata.

Felice Añale


What is meant by the absolute age of rock?

The age of a rock in years is called itsabsolute age. Geologists find absolute ages bymeasuring the amount of certain radioactive elements in therock. When rocks are formed, small amounts ofradioactive elements usually get included.

Esdras Nastase


Why are index fossils useful for dating rocks?

Index fossils are used to identify layersof rocks. In other words, a certain layer will containfossils that are unique to that layer. Geologists haveslowly, using different methods been able to determine the age ofthe rock layers. Once the age of the rock is knownthen the age of the fossil in that layer isknown.

Ermerinda Elmhirst


Are trilobites index fossils?

Trilobite fossils are found worldwide, with manythousands of known species. Because they evolved rapidly, andmoulted like other arthropods, trilobites serve as excellentindex fossils, enabling geologists to date the age of therocks in which they are found.

Marlies Batskaev


Why is the law of superposition important?

This Law of Superposition is fundamental to theinterpretation of Earth history, because at any one location itindicates the relative ages of rock layers and the fossils in them.Layered rocks form when particles settle from water orair.

Hermenegil Steffen


What is the largest time period in the history of Earth?

Explanation; -Phanerozoic Eon is the geologicaltime scale Eon is the longest period of time.-Phanerozoic Eon is the span of geologic time extendingabout 541 million years from the end of the Proterozoic Eon (whichbegan about 2.5 billion years ago) to the present.

Neoma Deulenko


What is an index fossil quizlet?

Index Fossil. a fossil known to have livedin a particular geologic age that can be used to date the rocklayer in which it is found. Order of Rock Layers. A way in whichscientists can find the relative age of a fossil and canonly be used when rock layers are preserved in their originalsequence. Trilobites.

Christele Nous


What is Zone fossil?

n. The fossil remains of an organism that livedin a particular geologic age, used to identify or date the rock orrock layer in which it is found.

Yaneris Rempel


How are fossils formed?

The Formation of Fossils. Fossilsare formed in a number of different ways, but most areformed when a plant or animal dies in a watery environmentand is buried in mud and silt. Soft tissues quickly decomposeleaving the hard bones or shells behind. Over time sediment buildsover the top and hardens into rock.

Igors Bagdasaryan


What is fossil assemblage?

In archaeology and paleontology a faunalassemblage is a group of associated animal fossilsfound together in a given stratum. The biostratigraphic unit beinga section of geological strata that is defined on the basis of itscharacteristic fossil taxa or faunalassemblage.

Jewel Benedetti


What type of fossil is a trilobite?

Trilobite, any member of a group of extinctfossil arthropods easily recognized by their distinctivethree-lobed, three-segmented form. Trilobites, exclusivelymarine animals, first appeared at the beginning of the CambrianPeriod, about 542 million years ago, when they dominated theseas.

Melaine Dontel


What is a fossil record?

The "fossil record" refers to the placement offossils throughout the surface layers of the Earth. Olderfossils are buried more deeply than younger ones. Scientistsuse the placement of fossils as a guide for determining whenlife forms existed, and how they evolved.