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102
"Prekambrij"PROTEROZOIK
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Proterozoik
• proterozoik– 2,5 mrd. do ~ 542
mil. god.
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Proterozoik
• donji (paleoproterozoik): 2,5 - 1,6 mrd. god.
• srednji (mezoproterozoik): 1,6 - 1,0 mrd. god.
• gornji (neoproterozoik): 1,0 - 542 mil. god.
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103
Proterozojska orogeneza
• formiranje velikih kratona
• orogeneza• orogen: svako
stijensko tijelo deformirano orogenezom
Wopmay orogen
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Proterozojska orogeneza
• debeli talozi kvarcnih pješčenjaka
• karbonatna platforma• prijelazne muljevite
stijene• taloženje fliša• turbiditi, a zatim
pukotine isušivanja i stromatoliti
• taloženje molase
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Proterozojska orogeneza
• karbonatnaplatforma– ciklično
taloženje indiciralo progradaciju plimskih ravnica preko lagune
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104
Proterozojski događaji
• široke glacijacije
• stromatoliti
• rani eukarioti
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Razvoj eukariota
• razvoj prokariotnih stanica: – mitohondrijski– kloroplast
• iz prokariota nastali protisti
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Alge
• višestaničniprotisti
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105
Alge
• prokariotneforme
• akritarki
• povećanje sadržaja kisika
a) fosilne prokariotne stanice Gunflint formacije
b) akritark Dicyotidiumc) akritark drugačije forme
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Proterozojski život
• fosilni trgovi– pojavili se prije
570 mil. god.
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Proterozojski život
• dokazi djelovanja organizama
• tendencija povećanja složenosti i varijacija
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Proterozojski život
• fosili bez skeleta– slični žarnjacima
• Ediacara fauna
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Proterozojski život
• mogući fosili člankonožaca
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Proterozojski život
• skeletalni fosili
• spikule spužvi
Cloudina
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107
Proterozojski kontinenti
• kontinentalna akrecija
– mikroploče prirasle kontinentu zbog subdukcije
– orogenska stabilizacija
– remobilizacija
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Proterozojski kontinentiOrogenska stabilizacijaa) akumulacija sedimenata,
subdukcijab) felsička kora kontinentac) subdukcija oceanske
kore pod kontinentalnu, stabilizacija sedimenata kontinentalnog ruba (metamorfizam), dodavanje magmatskih stijena kontinentalnom rubu
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Proterozojski kontinenti
• Baltički štit– transgresija na Jatulijsko kopno i
taloženje Jatulijskih naslaga– Švedska - metamorfozirani magmatiti i
sedimentne stijene (Leptit-formacija)– svekokarelidsko izdizanje 1,9-1,8 mrd.
god.
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108
Proterozojski kontinenti
• dezintegracija, diferencirano kretanje blokova, intruzije dijabaza, granita i vulkanizam - taloženje jotničkih naslaga
• konac proterozoika: izdizanje • čini cjelinu s Ukrajinskim štitom i Ruskom
pločom - Fenosarmacija
• Hebridi - Škotska• toridonski pješčenjak
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Proterozojski kontinenti
• Srpsko-makedonska masa i Rodopi:– donji dio: metamorfiti amfibolitnog
facijesa• gnajs, tinjčasti škriljavci, kvarciti, mramor
– gornji dio: metamorfiti facijesa zelenih škriljavaca
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Proterozojski kontinenti
Finska. Kompletni ofioliti 1,96 mrd. god. Dokaz konvergentnog ruba.
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Proterozojski kontinenti• Kanadski štit
• Laurencija se ubrzano širi
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Proterozojski kontinenti
• 1,95 - 1,85 mrd. god.– izgradnja
Laurencije od 5 mikrokontinenata
• 1,9 - 1,8 mrd. god.– odvajanje Superior
provincije • 1,8 - 1,6 mrd. god.
– prirast kontinenta prema JZ 800 km
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Proterozojski kontinenti
• abortirani rift 1,2 - 1,0 mrd. god.
• Grenville orogeneza 1,1mrd. god.– završni stadij
proterozojske kontinentalne akrecije Laurencije
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110
Proterozojski kontinenti
Srednjekontinentalni rift.
Konglomerati aluvijalne lepeze.
Vulkaniti.
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Proterozojski kontinenti
• Keweenawan bazalti– ruda bakra
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Proterozojski kontinenti
Srednje i gornjeproterozojska sedimentacija na zapadnoj obali Sj. Amerike.
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Proterozojski kontinenti
• Afrika– unutar kratona rovovi i bazeni– orogeneza 1,2-0,9 mrd. god.
• boranje naslaga Witwatersrand i Transvaal– panafrička (katanska) orogeneza 800-
550 mil. – stara kratonizacija + mlađe
intrakratonske orogeneze = formiranje prostrane "afričke" ploče
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Proterozojski kontinenti• u Sibiru - Angara• veliki kontinent: Indija, Arabija, veći dio Afrike i J.
Amerike, Australija, Antarktika - kasnije Gondvana
• prekambrijske orogeneze:• kenorijska (neoarhaik) - Kanadski štit• eburnijska (sr. paleoproteroziok) - Afrika• Wopmay (sr. paleoproterozoik) - Kanadski štit• hadsonijska (kasni paleoproterozoik) - Kanadski štit• Grenville (mezoproterozoik) - Kanadski štit• bajkalska (neoproterozoik) - Angara (Sibirija)• panafrička (neoproterozoik) - Afrika
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Proterozojski kontinenti
• Rodinija– superkontinent
izgrađen od kontinenata
– dezintegracija Rodinije prije 0,8 - 0,7 mrd. god.
a) Rodinija prije 1 mrd.. b) Drugi superkontinent?
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Proterozojski kontinenti
• Supergrupa pojasa - Kanada– 1,5 - 0,9 mrd. god.
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Formacije vrpčastog željeza
• završetak razvoja prije 1,9 mrd. god.– rožnjak
kontaminiran željezom - crvena ili smeđa boja
– proslojavanje s plavičastim slojevima bogatim željezom (magnetit)
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Crveni slojevi
• nisu nađeni u stijenama starijima od 2 mrd.
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Zemlja kao gruda snijega
• oledbe u gornjem proterozoiku – neoproterozojski
glacijalni sedimenti
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Zemlja kao gruda snijega
• Sturtian oledba - prije 700 mil. god.• Marinoan oledba - prije 600 mil. god.
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Zemlja kao gruda snijega
Tilit, dropstoni i karbonatne stijene.
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Zemlja kao gruda snijega
• dokaz za Marinoan ledeno doba u Maroku
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Proterozoik
• Mineralne sirovine• željezo: SAD, Kanada• nikal: Kanada• platina, krom: J. Afrika• nafta i plin: Sibir i Kina• pegmatitne žice: razni minerali
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Stromatolitiobilniji
Jednostavniakritarki
Višestaničnealge
Rodinijaprije 1 mrd.
Kad je prije 2 mrd.god. atmosfera doseg la umjerenu količinu kisika, formacije vrpčastog željeza završile razvoj.
Rast kontinenata
Maksimalni razvoj stromatolita
Prokario ti dominantni
Novi superkontinent(550 mil.) nakonloma Rodinije?Složen iji
akritarki
Eksplozivna radijacija životinja
Pri koncu protero-zoika rif tanje for-miralo glavne kon-tinente u paleozoiku
Brze k limatskepromjene -Zemljaprekrivena ledom.
Najstariji fo-sili životinja.
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