chapter 4: marine sediments fig. co-4 s. marine sediments eroded rock particles and fragments eroded...
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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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04_06t
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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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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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04_18 P
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