CHAPTER 4: Marine CHAPTER 4: Marine SedimentsSediments

Fig. CO-4

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Marine sedimentsMarine sediments

Eroded rock particles and fragmentsEroded rock particles and fragments Transported to or produced in the Transported to or produced in the

oceanocean Deposit by settling through water Deposit by settling through water

columncolumn Oceanographers decipher Earth Oceanographers decipher Earth

history through studying sedimentshistory through studying sediments

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Classification of marine Classification of marine sedimentssediments Classified by originClassified by origin Lithogenous Lithogenous (derived from (derived from landland)) BiogenousBiogenous (derived from (derived from

organismsorganisms)) HydrogenousHydrogenous (derived from (derived from waterwater)) CosmogenousCosmogenous (derived from (derived from outer outer

spacespace))

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Lithogenous sedimentsLithogenous sediments

Eroded rock fragments from land Eroded rock fragments from land ((originorigin))

TransportedTransported from land from land byby Water (e.g., Water (e.g., riverriver transported sediment) transported sediment) WindWind (e.g., windblown dust) (e.g., windblown dust) IceIce (e.g., ice-rafted rocks) (e.g., ice-rafted rocks) Gravity (e.g., Gravity (e.g., turbidity currentsturbidity currents))

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BY PERCENTTransport Mechanism

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Lithogenous sedimentsLithogenous sediments

Fig. 4.5

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Lithogenous sedimentsLithogenous sediments

Most lithogenous sediments at Most lithogenous sediments at continental marginscontinental margins

Coarser sediments closer to shoreCoarser sediments closer to shore Finer sediments farther from shore Finer sediments farther from shore

WHY?WHY? Mainly mineral quartz (SiOMainly mineral quartz (SiO22))

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distance = rate x time

d = rt

t = d/r = 4km/ 2.5cm/sec

= 4,000m/ 2.5cm/sec

=4,000m(100cm.m)/ 2.5cm/sec

=400,000cm / 2.5cm/sec

=160,000sec/ 24hr/day x 3600sec/hr

=160,000sec/ 86,400sec/day

=1.85 days

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Clay sinks 10,000 times slower than sank, so

1.8 days x 10,000 (or 104) = 18,000 days

18,000 days = 49.3 years365 days/year

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Smaller particles have a larger SA/Vol. ratio,increasing the frictional drag (sinking rates) and

making small particles sink more slowly than large particles

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Relationship of fine-grained Relationship of fine-grained quartz and prevailing windsquartz and prevailing winds

Fig. 4.6b

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Brazos River Meets the Brazos River Meets the Gulf of MexicoGulf of Mexico

FLOCCULATIONFLOCCULATION - THE JOINING - THE JOINING TOGETHER OF ELECTRICALLY TOGETHER OF ELECTRICALLY CHARGED CLAY PARTICLES CHARGED CLAY PARTICLES

WHICH SETTLE MORE RAPIDLY WHICH SETTLE MORE RAPIDLY THAN INDIVIDUAL ONESTHAN INDIVIDUAL ONES

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Brazos River

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Distribution of sedimentsDistribution of sediments NeriticNeritic

Shallow water depositsShallow water deposits Close to landClose to land Dominantly lithogenousDominantly lithogenous Typically deposited quicklyTypically deposited quickly

PelagicPelagic Deeper water depositsDeeper water deposits Finer-grained sedimentsFiner-grained sediments Deposited slowlyDeposited slowly

UNDERSTANDING THE PROCESSES WOULD UNDERSTANDING THE PROCESSES WOULD ALLOW YOU TO GENERATE THIS TABLE ALLOW YOU TO GENERATE THIS TABLE YOURSELVESYOURSELVES

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Neritic lithogenous Neritic lithogenous sedimentssediments Beach depositsBeach deposits

Mainly wave-deposited quartz-rich Mainly wave-deposited quartz-rich sandssands

Continental shelf depositsContinental shelf deposits Relict sedimentsRelict sediments

Turbidite depositsTurbidite deposits Glacial depositsGlacial deposits

High latitude continental shelfHigh latitude continental shelf

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Pelagic lithogenous Pelagic lithogenous sedimentssediments Sources of fine material:Sources of fine material:

Volcanic ashVolcanic ash (volcanic eruptions) (volcanic eruptions) Wind-blown dustWind-blown dust Fine grained material transported Fine grained material transported

by deep ocean currentsby deep ocean currents Abyssal clay (red clay)Abyssal clay (red clay)

Oxidized ironOxidized iron Abundant if other sediments Abundant if other sediments

absentabsent

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BiogenousBiogenous marine marine sedimentssediments Hard remains of once-living Hard remains of once-living

organismsorganisms Shells, bones, teethShells, bones, teeth Macroscopic (large remains)Macroscopic (large remains) Microscopic (small remains)Microscopic (small remains)

Tiny shells or testsTiny shells or tests settle through settle through water columnwater column

Biogenic ooze (30% or more tests)Biogenic ooze (30% or more tests)Mainly algae and protozoansMainly algae and protozoans

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Biogenous marine Biogenous marine sedimentssediments

Commonly either Commonly either calcium calcium carbonatecarbonate (CaCO(CaCO33)) oror silicasilica (SiO(SiO22 or SiOor SiO22.nH.nH22O)O)

Usually Usually planktonicplanktonic (free-floating) (free-floating)

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SilicaSilica in biogenic sediments in biogenic sediments DiatomsDiatoms

(algae)(algae) PhotosyntheticPhotosynthetic Diatomaceous Diatomaceous

earthearth

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Siliceous oozeSiliceous ooze Seawater undersaturated with silicaSeawater undersaturated with silica Siliceous ooze commonly associated Siliceous ooze commonly associated

with high biologic productivity in with high biologic productivity in surface oceansurface ocean

Fig. 4.12

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Calcium carbonateCalcium carbonate in in biogenous sedimentsbiogenous sediments

CoccolithoCoccolithophoresphores (algae)(algae) Photo-Photo-

syntheticsynthetic CoccolithsCoccoliths

(nanno-(nanno-plankton)plankton)

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SWhite Cliffs of Dover

Calcium carbonateCalcium carbonate in in biogenous sedimentsbiogenous sediments ForaminiferaForaminifera

(protozoans)(protozoans) Use external Use external

foodfood Calcareous Calcareous

oozeooze

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Living ForaminiferaS

Distribution of biogenous Distribution of biogenous sedimentssediments Most common as pelagic Most common as pelagic

depositsdeposits Factors controlling distributionFactors controlling distribution

ProductivityProductivity Destruction (dissolution)Destruction (dissolution)

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Calcareous ooze and the Calcareous ooze and the CCDCCD Warm, shallow ocean saturated Warm, shallow ocean saturated

with calcium carbonatewith calcium carbonate Cool, deep ocean undersaturated Cool, deep ocean undersaturated

with calcium carbonatewith calcium carbonate LysoclineLysocline--depth at which CaCO--depth at which CaCO33

begins to dissolve rapidlybegins to dissolve rapidly Calcite compensation depthCalcite compensation depth CCD-- CCD--

depth where CaCOdepth where CaCO33 readily readily dissolvesdissolves

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Calcareous ooze and the Calcareous ooze and the CCDCCD

Scarce calcareous ooze below 5000 m in Scarce calcareous ooze below 5000 m in modern oceanmodern ocean

Ancient calcareous oozes at greater Ancient calcareous oozes at greater depths if moved by sea floor spreadingdepths if moved by sea floor spreading

Fig. 4.13

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Distribution of calcareous oozes in Distribution of calcareous oozes in surface sediments of modern surface sediments of modern seafloorseafloor

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Why in these places?

Hydrogenous marine Hydrogenous marine sedimentssediments Minerals precipitate directly from Minerals precipitate directly from

seawaterseawater Manganese nodulesManganese nodules PhosphatesPhosphates CarbonatesCarbonates Metal sulfidesMetal sulfides

Small proportion of marine Small proportion of marine sedimentssediments

Distributed in diverse environmentsDistributed in diverse environments

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Iron-Manganese nodulesIron-Manganese nodules Fist-sized lumps of manganese, iron, Fist-sized lumps of manganese, iron,

and other metalsand other metals Very slow accumulation ratesVery slow accumulation rates

Fig. 4.15a

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Manganese Manganese nodulesnodules

Fig. 4.26

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Cosmogenous marine Cosmogenous marine sedimentssediments

Macroscopic meteor debrisMacroscopic meteor debris MicroscopicMicroscopic iron-nickel and iron-nickel and

silicate spherulessilicate spherules TektitesTektites Space dustSpace dust

Overall, insignificant proportion Overall, insignificant proportion of marine sedimentsof marine sediments

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Microtektites - extraterrestrial

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04_E

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Mixtures of marine Mixtures of marine sedimentssediments Usually mixture of different Usually mixture of different

sediment typessediment types For example, biogenic oozes can For example, biogenic oozes can

contain up to 70% non-biogenic contain up to 70% non-biogenic componentscomponents

Typically one sediment type Typically one sediment type dominates in different areas of dominates in different areas of the sea floorthe sea floor

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Distribution of neritic and pelagic marine Distribution of neritic and pelagic marine sedimentssediments

Fig. 4.19

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04_T04

1 m

.01 m

.001 m

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