66

SEDIMENTI I SEDIMENTNE STIJENE

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Procesi sedimentnog ciklusa

• trošenje• erozija• transport• taloženje (sedimentacija)• zatrpavanje• dijageneza

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Stupnjevi taloženja u stijenskom ciklusu

1. trošenje i erozija

2. transport i taloženje

3. zatrpavanje i dijageneza

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67

Sedimentne stijene

• detritične ili klastične

• kemijske

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Sedimentne stijene

• 5% volumena gornje kore• 75% kontinentalnih prostora

• često jedina zabilješka geoloških događaja

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Transport i taloženje klastičnih

sedimenata

• prijenos sedimenta vjetrom, ledom i vodom

• način transporta proizvodi različite taloge

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Način djelovanja transporta na sediment

Sortiranost– varijacije u rasponu veličine zrna u

klastičnoj stijeni ili sedimentu

• dobra sortiranost

• loša sortiranost

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Sortiranost

dobra sortiranost loša sortiranost

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Način djelovanja transporta na sediment

Zaobljenost

Sferičnost

• sortiranost, zaobljenost i sferičnost se povećavaju s duljinom transporta

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69

Zaobljenost i sferičnost

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Vrste klastičnih stijenaTemeljene na veličini zrna koja

mogu biti izgrađena od različitog materijala.

• konglomerat• breča• pješčenjak• siltit• glina (šejl)• lapor

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Sedimentne teksture

• pojedinačne teksture nam mogu dati informacije o taložnom okolišu

• teksture nam pokazuju je li sloj u normalnom položaju

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70

Sedimentne teksture

stratifikacija = uslojenost

• proizvedena uslijed različite:1. veličine zrna2. vrste zrna

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Gradacijska slojevitost

mjerilo može biti od mm do m

d

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Turbulentne struje

• suspenzija vode, pijeska i mulja • brzina turbulentnih struja prvi put

saznana 1920.

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Ostali pokazatelji taloženja

• kosa slojevitost• riplovi• pukotine isušivanja• otisci kišnih kapi• fosili

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Činjenice za interpretaciju taložnog

okoliša

• sedimentne teksture• sortiranost, zaobljenost,

sferičnost• slijed slojeva

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Vrste kemijskih taložnih stijena

• vapnenac• rožnjak• sol• gips• ugljen

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72

Kemijski okoliši: karbonati

• bistra voda

• topla voda

• organski

• anorganski

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Kemijski okoliši: evaporiti

ograničeni okoliši

• minerali se precipitiraju u skladu s njihovom topivošću

gips halit50% 90%

CaSO4•2H2O NaCl

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Model postanka evaporita

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Od sedimenta do sedimentne

stijene (litifikacija)

• kompakcija

• cementacija

• rekristalizacija

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Diskordancija

• zatrpana površina erozije

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Glavni taložni okoliši

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Postanak kose slojevitosti

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mulj, glina šejl

pijesak pješčenjak

šljunak konglomerat

vapnoviti mulj vapnenac i dolomit

Produkti litifikacije

sediment sedimentna stijena(nevezan) (vezana)

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Kompakcija (prvenstveno mulja)

Precipitacija novih minerala ili prirast na stare minerale

gubitak vode

cementacija

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Otapanje lakše topivih minerala

Rekristalizacija nestabilnih minerala

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Relativna zastupljenost sedimentnih stijena.

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Četiri glavne skupine

pješčenjaka

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Kvarcni arenit: čisti kvarc

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Arkoza: bogata feldspatima

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Litični pješčenjak: bogat fragmentima stijena

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Grauvaka: bogata matriksom

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