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MezozoikKREDA

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Kreda

• podjela:– donja kreda (berijas, valendis, otriv,

barem, apt, alb): 145 - 100 mil. god.– gornja kreda (cenoman, turon, konijak,

santon, kampan, mastriht): 100 - 65,5 mil. god.

• ranije: cenoman, turon i senon– senon: konijak, santon, kampan, mastriht

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Kreda

• važniji biološki događaji– donja kreda - prvi placentalni sisavci,

prve cvijetne biljke (kritosjemenjače), prve diatomeje

– konac krede - potpuno izumiranje dinosaura, amonita, belemnita, inoceramusa, rudista, globotrunkana

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Kreda

• važniji paleogeografski događaji– donja kreda - širenje oceana između

Indije i Australsko-antarktičkog kopna– gornja kreda - početak dezintegracije

Australsko-antarktičkog kopna, širenje oceana između Australije i Antarktike, ubrzano kretanje Indije prema sjeveru

– Peter Skelton: The Cretaceous World. Cambridge University Press. 2003., ISBN 0 521 53843 2

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Život u kredi

• plankton– radijacija diatomeja– diverzifikacija

foraminifera– radijacija

vapnenačkog nanoplanktona

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Kreda

• planktonske foraminifere s velikim značajem u biostratigrafiji

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Život u kredi

• teleostei ribe– potpuno

okoštale– simetričan

rep– kratka čeljust

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Život u kredi

• morski gmazovi i dalje važni

• glavni morski mesojedi– mosasaur– hesperornis– morska kornjača

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Život u kredi

• bentos– foraminifere– briozoji enkrustiraju

morsko dno (danas i dno brodova) u prevlakama

– bivalve mekušci-bušaći– puževi– rakovi

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Život u kredi

• bivalve mekušci na dnu– savinute oštrige– rudisti formirali

velike tropske grebene

• grabežljivci (ribe, rakovi, puževi) reducirali broj brahiopoda i krinoida sa stapkom

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Život u kredi• cvijetne biljke

– pojava kritosjemenjača

– povećanje složenosti i forme sredinom krede

– golosjemenjače i dalje prevladavaju

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Život u kredi

Dijagramska rekonstrukcija tipične cenomanske šume na Aljasci.

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Život u kredi

• kralježnjaci– gornjokredni kralježnjaci

bolje poznati– dinosauri s "pačjim

kljunom"– umjesto nosoroga - rogati

dinosauri

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Život u kredi

Skrb za mladunčad.

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Život u kredi

• Tyrannosaurus rex• kopneni krokodili• leteći kralježnjaci

– gmazovi– ptice

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Život u kredi

• kopneni krokodili– 15 m

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Život u kredi

• razvoj sisavaca– mesojedi (insekte)– endotermički– velik mozak u

odnosu na tijelo: sluh i miris

– noćne životinje – penjali se na stablo

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Život u kredi

• razvoj u dva smjera– placentalni

sisavci– tobolčari

• Purgatorius– sisavac

sličan štakoru

– predak primata

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Klima

Donja kreda

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Klima

Gornja kreda

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Paleogeografija• kredne stijene pretrpjele manje metamorfizma i erozije

nego starije stijene • dokumentirani kopneni, plitkomorski i dubokomorski

sedimenti• u d. kredi Gondvana gotovo jedinstvena, u g. kredi J.

Amerika, Afrika i Indija samostalni kontinenti • u g. kredi većina kontinenata izolirana• d. kredno razmicanje kontinenata uzrokovalo širenje

mora

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Paleogeografija• Grenland se odvojio od Sj. Amerike• sredinom krede visoka razina mora

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Paleogeografija

• pojas vjetrova– taloženje

evaporita

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Paleogeografija

• razdoblje visoke razine mora– početak porasta u d. kredi– sredinom krede najviša razina u cijelom

fanerozoiku– dugo razdoblje bez reverznog magnetskog

pola

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PaleogeografijaTijekom središnjeg dijela krede velika produkcija kore s akumulacijama crnih šejlova i izostanak megnetskih reverzija.

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Paleogeografija

• stagnacija oceana– epikontinentalni

crni muljevi kada su mora prelila kopna - bogati organskom materijom

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Paleogeografija

• na visokim geografskim širinama toplo sredinom krede– biljke toplih krajeva na

sjevernoj Aljasci, Grenlandu i Antarktici

• gornjokredno polarno zahlađenje– snažnija cirkulacija

oceana - prijenos kisika u oceanske dubine

– neka izumiranja• rudisti

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Europa

Donja kreda(berijas - barem)

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Europa

Donja kreda(apt - alb)

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Europa

Gornja kreda(turon -kampan)

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Europa

• subdukcijske zone– Zapadne Alpe

• pelagička sedimentacija i fliš• urgonski facijes: rudistni vapnenac

– Sjeverne Alpe• klastična sedimentacija prevladava nad

karbonatnom (fliš)• gozavske naslage

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Europska pisaća kreda• gornja kreda

– preplavljivanje zapadne Europe, bez značajne tektonike

– velike akumulacije čistog CaCO3

– skeletalni frgmenti, 75% od vapnenačkog nanoplanktona

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Europska pisaća kreda

Paleogeografija sjeverozapadne Europe u vrijeme mastrihta.

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Europa

Uopćena povijest razvoja karbonatne platforme tijekom krede u tethysko-atlantskom prostoru.

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Europa

Shematski prikaz karbonatne platforme.

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Europa

Model koji objašnjava ubrzani rast karbonatne platforme.

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Europa

Slijed vanjske platforme, Središnji Pirineji.

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Hrvatska

JKP u najvišoj kredi.

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Hrvatska

• Jadranska karbonatna platforma– donja kreda

• plitkovodni vapnenci, emerzije (tektonika)• tragovi stopala i kosti dinosaura• d. apt: djelomično potapanje platforme• g. apt: regionalna emerzija

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Hrvatska

– gornja kreda• zrela platforma, početak dezintegracije• cenoman/turon - produbljavanje, ali SZ i SI

dijelovi u emerziji (boksiti)• dezintegracija• otisci stopala dinosaura sve do mastrihta

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Korelacija glavnih krednih facijesa JKP od Istre do Dubrovnika.

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Hrvatska• Sj. Hrvatska

– donja kreda• oceanska subdukcija (obdukcija)• dubokovodna sedimentacija• izdizanje

– gornja kreda• riječna, plitkovodna marinska, dubljevodna

sedimentacija (Scaglia)• magmatizam• konac krede: dubljevodni klastiti s prijelazom u

paleocen• izdizanje: laramijska faza alpske orogeneze

– Moslavačka gora• metamorfiti

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Tektonski događaji - zapadne SAD

• izgradnja Kordiljere• Sevier orogeneza

– cijela kreda

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Tektonski događaji - zapadne SAD

• pomak kuta subdukcije

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Tektonski događaji - zapadne SAD

• Mowry more– koncem d. krede arktičke

vode se proširile prema jugu i preplavile velike površine Sj. Amerike

– do gornje krede produžili se do Meksičkog zaljeva

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Tektonski događaji - zapadne SAD

• izgradnja planina potaknula taloženje

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Tektonski događaji - zapadne SAD

• gornjokredni tjesnac– specifična sedimentacija– transgresija praćena regresijom

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Tektonski događaji - istočne SAD

• formiranje kontinentalnog šelfa– sedimenti akumulirani u riftnim bazenima

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Tektonski događaji - istočne SAD

Profil kontinentalnog šelfa i dubokog mora.

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Sraz

• sraz = impakt• mikrosferule

Mikrosferule iz gline s anomalijom iridija.

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Sraz

• Chicxulub krater– gravitacijska

anomalija

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Sraz

• Fragmenti dolomita sa strijama izbačeni eksplozijom prilikom sraza.

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Sraz

• Što je sve mogao učiniti sraz Zemlje i asteroida promjera 10 km:– neprekidna noć

– globalno zahlađenje

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Sraz

– grijanje iz padajuće prašine

– zatopljenje iz zakašnjelog efekta staklenika iz aerosola

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Sraz

– naglo zagrijavanje zbog efekta staklenika uslijed oslobađanja CO2 iz vapnenačkih naslaga

– kisele kiše

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Sraz

– požari– snažan

zvuk– potresi– tsunami

SI Brazil: paleocenska breča na mastrihtskom plitkovodnom pješčenjaku.

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Kredno masovno izumiranje• vrlo naglo

– dinosauri– amoniti– mosasauri i drugi morski gmazovi– redukcija kritosjemenjača i golosjemenjača– 90% vapnenačkog nanoplanktona i foraminifera izumrlo– mnogobrojni mekušci (rudisti)

• sraz– anomalija iridija - visoka koncentracija iridija na granici

kreda/paleogen– međutim, ima pojava i postupnog izumiranja dinosaura– neki izumrli i prije impakta

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Kredno masovno izumiranje

• neki organizmi se odlično prilagodili

• nagli rast količine polena paprati neposredno iznad iridijske anomalije

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Mineralne sirovine

• fosforit: europska Rusija, Sj. Amerika• nafta: Kanada, Sj. Amerika, Meksiko,

Bliski Istok• ugljen: Mongolija, Kordiljera• dijamanti: J. Afrika• zlato: Sj. Amerika• Hrvatska: ukrasni i građevni kamen

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