History of fossils; process of Fossilization

Sediment is transformed into sedimentary rocks

1. HISTORY OF FOSSILS
PROCESS OF FOSSILIZATION
19 DECEMBER 2020
PRINCIPLES OF PALEONTOLOGY (ZOL_651)
BY
KASHIF MANZOOR (PH.D SCHOLAR)
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2. HISTORY OF FOSSILS
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3. 3
HISTORY OF FOSSILS

4. 4
HISTORY OF FOSSILS

5. 5
HISTORY OF FOSSILS

6. Formation of fossils
Specific environmental conditions are necessary in order for
fossils to form.
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PROCESS OF FOSSILIZATION

7. HOW IS A FOSSIL FORMED?
1.Sediment
Ananimalisburiedby
sediment,suchasvolcanicash
orsilt,shortlyafteritdies.Its
bonesareprotectedfromrotting
bythelayerofsediment.
4. Erosion
Erosionfromrain,rivers,andwind
wearsawaytheremainingrocklayers.
Eventually,erosionorpeopledigging
forfossilswillexposethepreserved
remains.
2. Layers
Moresedimentlayersaccumulate
abovetheanimal’sremains,and
minerals,suchassilica(a
compound ofsiliconand
oxygen),slowlyreplacethe
calcium phosphate in
thebones.
3. Movement
Movement oftectonic
plates,orgiantrockslabs
thatmake upEarth’s
surface,liftsupthe
sedimentsandpushesthe
fossilclosertothesurface.
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8. Fossils can form in several ways.
•Permineralizationoccurswhenmineralscarriedbywater
aredepositedaroundahardstructure.
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9. •Anaturalcastformswhenflowingwaterremovesallof
theoriginaltissue,leavinganimpression.
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10. •Tracefossilsrecordtheactivityofanorganism.
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11. •Amber-preservedfossilsareorganismsthatbecome
trappedintreeresinthathardensafterthetreeisburied.
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12. •Preservedremainsformwhenanentireorganism
becomesencasedinmaterialsuchasice.
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13. •Specificconditionsareneededforfossilization.
•Onlyatinypercentageoflivingthingsbecamefossils.
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14. CONDITIONS FAVORING FOSSILIZATION
•Onlyatinyfractionoftheorganismsthatlivedduringthegeologicalpasthave
beenpreservedasfossils.Accordingtoanestimate,oneonlyoutofeach
thousandspeciesofprehistoricorganismshasbeenfossilized.Itisbecauseofthe
factthatnormallytheremainsofananimalorplantaretotallydestroyed.
•Threespecialconditionsappeartobenecessarysuchas;
a)Possessionofhardparts
b)Escapefromimmediatedestruction
c)Rapidburialinasuitablemedium
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15. a). POSSESSION OF HARD PARTS
•Animalsandplantshaveamuchbetterchanceofbeingpreservedas
partofthefossilsrecordiftheyhavehardparts.Thesehardparts
typicallyconsistofbones,teeth,shell,chitinofthewoodytissuesof
plants.
•Underexceptionallyfavorableconditions,however,eventhesoft
anddelicateorganismssuchasjellyfish,wormsandinsectsmaybe
preservedasimpressionsorcarbonresidues.
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16. b). ESCAPE FROM IMMEDIATE DESTRUCTION
•Usuallywhenanorganismdies,itssoftpartsarequicklyeatenby
scavengersordecomposedbybacteria.
•Again,theremainsoftheseorganismsaredestroyedbytheworkof
atmosphereandothermechanicalforces(suchasrain,heat,pressure,
waveaction,strongwindsandcrushing).Rapidburial,therefore,is
animportantconditionfavoringpreservation.
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17. c). RAPID BURIAL IN A SUITABLE MEDIUM
•Thetypeofprotectivematerialinwhichorganismisburied,usually
dependsupontheenvironmentinhabitedbytheorganismwhileit
wasliving.
•Marineanimalsaremorelikelytobepreserved.Decayischecked
bysaltwater,intheoceanslivemanyanimalswhichsecreteshells,
andtherearefisheswithbonyskeletons.Whentheseanimalsdie,
theirhardpartssettletothebottomandarecoveredbysoft
sedimentandthuspreventedfromoxidationandscavengers.Later
theyremainedburiedintherockthatformsfromthesedimentandare
thuspreservedasfossils.
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18. c). RAPID BURIAL IN A SUITABLE MEDIUM
•Organismslivingonlandarelesslikelytobefossilizedascompared
tothoseofmarinehabitats.Theremainsofterrestrialorganismsare
usuallyfoundinlakes,swamps,orwindblowndeposits.
•Animalslivingindesertmaybepreservedbydesiccation(i.e.,rapid
dryingupofbodyasaresultofwaterevaporation).Suchremainsare
called“naturalmummies”.Manyextinctinsectsandspidershave
beenfoundencasedinamber,thehardenedresinofancienttree.
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19. c). RAPID BURIAL IN A SUITABLE MEDIUM
•Largeranimalshavebeentrappedintarpitsandoilseeps.Oneofthe
mostfamouslocalitiesofthistypeisatRanchoLaBreainLos
Angeles,U.S.A.Hereanancientoilseep,throughlossofvolatile
substances,hasbeentransformedintoasemisolidpoolofasphalt.
Manyspecimensofprehistoricanimalshavebeenfoundtrappedin
thistarpit.
•Volcanicashordustandinrareinstanceslavamayalsoserveasa
protectivemediuminfossilization.Thebonesandteethofanyearly
rhinoceroshasbeenfoundinbasalt;andtheremainsofmanyplants
havebeenpreservedafterbeingburiedbylavaflowsandfallingash.
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20. c). RAPID BURIAL IN A SUITABLE MEDIUM
•Theprotectivematerialproducingthemostremarkablepreservationis
iceorfrozensoil.Animalslivinginperiodsofglacialcoldwere
frozenintoice.
•Theirremainsarefoundinsucharemarkablestateofpreservationthat
eventheflesh,hairandstomachcontentshavebeenperfectly
preserved.
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21. THE END
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