PalaeontologyPalaeontologyFossilization & Types of FossilsFossilization & Types of Fossils

ByByZoha Zoha 479 479

FossilizationFossilization

• The formation of Fossils is known as Fossilization.

• It is the process which enables the remains of formerly living creatures to be preserved after their death.

• It depends upon two factors.• Composition & Structure of Animals.

• Environment where the live.

Nature of Animal

Hard partsBones, teeth, shells

Soft partsMeat & parts with

More water content

Hard partHard part Soft partSoft part

• Hard parts of the animals have better chances of Fossilization.

• Soft parts of the body after death are decomposed by bacteria quickly and have less chances of fossilization.

• But sometimes under remarkable conditions they may be fossilized.

• For fossilization;• Escape from immediate destruction

• Rapid BurialThey are also important.

EnvironmentEnvironment

• It is the surrounding where animals live & get buried.

• Animals live in different surroundings such as some are terrestrial, marine, Fresh water etc.

• Animals live, interact with the environment & other things present in the environment.

Marine

Caves & Underground

caverns

Bogs & SandDeposits

AmberVolcanic Ash

& DustDeserts

Ice & Frozen Soil

Land & Natural Petroleum seeps

Environment

Marine EnvironmentMarine Environment

• Marine animals are more likely to be fossilized as decay is checked by saltwater.

• There are number of invertebrates which take Calcium carbonate from water and build shells.

• Bony fishes after their death, shells & skeleton fall at the bottom buried by soft sediments.

• In sea soft sediments are formed by precipitation of chemicals.

ShellsShells Fish SkeletonFish Skeleton

Land EnvironmentLand Environment

• Deposition on land is not a continual process but restricted to small areas.

• Fossils of terrestrial animals are mostly found in• Lakes

• Swamps• Deserts

• Preservation may be through Desiccation & mummification.

• Flood also plays very important role in fossilization.

Fossil of SnakeFossil of Snake MummyMummy

AmberAmber

• Essentially, Amber is tree sap that has hardened after many millions of years. Occasionally, insects and small animals would manage to get themselves caught in the sap, and would be preserved in almost pristine condition.

• You may be familiar with this method of fossilization due to the movie Jurassic Park, where dinosaur DNA was extracted from parasitic insects trapped in Amber. In real life though, this is impossible, due to the fact that the half life of DNA is about 521 years.

Bug in AmberBug in Amber An insectAn insect

Bogs & Sand depositsBogs & Sand deposits

• Semi fluid substances of sand and Asphalt make natural death trap for animals which are quickly preserved and fossilized.

• Asphalt wells up in thick sticky pools.

Volcanic Ash & DustVolcanic Ash & Dust

• Volcanic ash & dust in these cases even lava may act as preserving material.

Ice & Frozen soilIce & Frozen soil

• It is the best medium for preservation.• Many complete carcasses are found

frozen in soil.• Such as woolly mammoths, woolly

rhinoceros and Bison.• First woolly mammoth was discovered in

frozen soil of Siberia & Alaska.

Bison FossilBison Fossil Mammoth FossilMammoth Fossil

Caves & Underground CavernsCaves & Underground Caverns

• Sources of fine fossils are caves & underground caverns which are generally used by carnivores.

• Their prey is taken to caves & hard parts are left there which are preserved due to environmental conditions.

Natural petroleum seepsNatural petroleum seeps

• Large animals are usually trapped by natural petroleum seeps.

• Animals are nicely preserved in this medium even soft parts also.

• Volatile parts of oil evaporate & leave behind semisolid pool of Asphalt.

Types of FossilsTypes of Fossils

• After millions of years, most organic matter is either destroyed or broken. While there are forms of fossilization that will provide unaltered organic material, most fossils found are changed from their original composition.

Fossils

Altered Fossils Unaltered Fossils

Petrified Fossils Moulds & Casts Trace Fossils Complete Incomplete

Per-mineralization

Mineralization

Carbonization

Psedumorph

True Morph

Tracks & Trails

Corpolites

Gastroliths

Eggs

Unaltered FossilsUnaltered Fossils

• In these fossils organic parts of the organisms remain unchanged.

• Mediums for unaltered fossils are Oil, Ice or may be sediment.

• Complete unaltered Fossils• Incomplete unaltered Fossils.

Complete unaltered FossilsComplete unaltered Fossils

• Complete carcasses of large mammals like;

• Woolly Mammoth• Wooly Rhinoceros

• BisonHave been found in frozen soil of Siberia &

Alaska.

Incomplete unaltered FossilsIncomplete unaltered Fossils

• These are fragmentary fossil remains like pieces of wood, bones of vertebrates and shells of invertebrates.

• They are mostly found well preserved with little or no change since cretaceous.

Altered FossilsAltered Fossils

• Fossils that are changed due to different factors are known as Altered Fossils.

• Permineralization• Mold

• Replacement or Mineralization• Recrystallization

• Carbonization• Desiccation

• Amber

PermineralizationPermineralization

• Permineralization occurs when organic material, such as bones or wood, absorb and hold minerals before decaying themselves. This results in a drastically different & more stable composition of Fossil than the original organic material.

• Most Dinosaurs bones are result of Permineralization.

• Petrified wood is another good example of perminerlization.

Mold & CastsMold & Casts

• A mold occurs when organic material is buried by sediment.

• Eventually, organic material decays leaving a trace outline of the original organisms. In this manner, no organic material remains.

• These also include Foot prints or of textures from things such as feathers or leaves.

Replacement/MineralizationReplacement/Mineralization

• It is similar to permineralization in that a foreign mineral assumes the shape of organic material.

• It is also similar to mold as organic matter is already deteriorated.

• The result is foreign mineral being molded into the shape of original organism.

• Such as Iron pyrite replacing the form of an invertebrate’s shell mold.

RecrystallizationRecrystallization

• It occurs when organic material is not chemically stable enough after deposition to maintain it’s composition.

• This is most often found among invertebrate shells, which will change from aragonite to calcite.

Carbonization/DistillationCarbonization/Distillation

• It occurs when enough pressure is placed upon organic material that Carbon is left behind in the rock.

• Examples are characteristically black & In the shape of animal that was deposited.

DesiccationDesiccation

• It occurs when an animal dies in extremely dry & arid locations such as deserts or some caves. These conditions create an aseptic environment where it is highly unlikely that it’ll be able to decay.

• These fossils are rare.• It is almost identical to mummification although it

is conducted by natural conditions and are typically from further back in time.

ImprintsImprints

• Moulds of thin organisms like leaves are commonly known as Imprints.

CoprolitesCoprolites

• Trace fossils are droppings of the animals, fossilized faecal material, ranging in size from very small to very large (from coprolites of snails to those of dinosaurs and man).

• It include undigested hard parts of plants & animals that were eaten.

TracksTracks

• Animals leave impressions of certain body parts on mud or sand during travel e.g;

• Foot prints• Trails

• Tracks• By these fossils we can tell whether the

animals are bipedal or quadruped & their style of locomotion.

TrailsTrails

• These are impressions of the body of animal during crawling on earth e.g.

• Earthworm

GastrolithsGastroliths

• These are small rounded smooth stones present in rib cages of Dinosaurs.

• These were used for crushing the food.

ReferencesReferences• http://mukwevholufuno.blogspot.com/2006/05/describe-process-of-f

ossilization-and.html• http://www.geo.arizona.edu/geo3xx/geo308/FoldersOnServer/

2003/1fossil&taph&ichno.htm• http://mygeologypage.ucdavis.edu/cowen/~gel107/preservation.html• Fossilization, [internet] [cited 2006 may 5]. Available from:

http://www.museum.vic.gov.au/dinosaurs/sci-form.html•

2. Fossilization, [internet] [cited 2006 may 5]. Available from: http://www.musei.unina.it/Paleontologia/eng/3.2.4.1.htm

• http://www.fossilmuseum.net/fossilrecord/fossilization/fossilization.htm