CHAPTER 4: Marine CHAPTER 4: Marine SedimentsSediments

Fig. CO-4

Marine sedimentsMarine sediments

Eroded rock particles and fragmentsEroded rock particles and fragments Transported to oceanTransported to ocean Deposit by settling through water Deposit by settling through water

columncolumn Oceanographers decipher Earth Oceanographers decipher Earth

history through studying sedimentshistory through studying sediments

Classification of marine Classification of marine sedimentssediments

Classified by originClassified by origin LithogenousLithogenous (derived from land) (derived from land) BiogenousBiogenous (derived from organisms) (derived from organisms) HydrogenousHydrogenous (derived from water) (derived from water)

Also known as Also known as AuthigenicAuthigenic CosmogenousCosmogenous (derived from outer (derived from outer

space)space)

Lithogenous sedimentsLithogenous sediments

Eroded rock fragments from landEroded rock fragments from land Reflect composition of rock from Reflect composition of rock from

which derivedwhich derived Transported from land byTransported from land by

Water (e.g., river-transported sediment)Water (e.g., river-transported sediment) Wind (e.g., windblown dust) - Wind (e.g., windblown dust) - aolian aolian

transporttransport Ice (e.g., ice-rafted rocks)Ice (e.g., ice-rafted rocks) Gravity (e.g., turbidity currents)Gravity (e.g., turbidity currents)

Lithogenous sedimentsLithogenous sediments

Fig. 4.5

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 shoreFiner sediments farther from shore Mainly mineral quartz (SiOMainly mineral quartz (SiO22))

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

Fig. 4.6b

Sediment textureSediment texture Grain sizeGrain size

Proportional to energy of Proportional to energy of transportation and depositiontransportation and deposition

Table 4.2

Sediment textureSediment texture Grain size sortingGrain size sorting

Indication of selectivity of Indication of selectivity of transportation and deposition transportation and deposition processesprocesses

Textural maturityTextural maturity Increasing maturity ifIncreasing maturity if

Clay content decreasesClay content decreasesSorting increasesSorting increasesNon-quartz minerals decreaseNon-quartz minerals decreaseGrains are more rounded (abraded)Grains are more rounded (abraded)

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

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

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

Volcanic ash (volcanic eruptions)Volcanic ash (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

Biogenous marine Biogenous 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 tests settle through Tiny shells or tests settle through water columnwater column

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

Biogenous marine Biogenous marine sedimentssediments

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

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

Silica in biogenic sedimentsSilica in biogenic sediments DiatomsDiatoms

(algae)(algae) PhotosyntheticPhotosynthetic Diatomaceous Diatomaceous

earthearth RadiolariansRadiolarians

(protozoans)(protozoans) Use external Use external

foodfood Siliceous oozeSiliceous ooze

Fig. 4.7a

Fig. 4.7b

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. 4.11

Calcium carbonate in Calcium carbonate in biogenous sedimentsbiogenous sediments

CoccolithophorCoccolithophores (algae)es (algae) PhotosynthetiPhotosyntheti

cc CoccolithsCoccoliths

(nano-(nano-plankton)plankton)

Rock chalkRock chalk

Fig. 4.8a

Calcium carbonate in Calcium carbonate in biogenous sedimentsbiogenous sediments ForaminiferaForaminifera

(protozoans)(protozoans) Use external Use external

foodfood Calcareous Calcareous

oozeooze

Fig. 4.8c

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) DilutionDilution

Carbonate depositsCarbonate deposits

StromatolitesStromatolites Warm, Warm,

shallow-ocean, shallow-ocean, high salinityhigh salinity

CyanobacteriaCyanobacteria

LimestoneLimestone (lithified carbonate (lithified carbonate sediments)sediments)

Fig. 4.10a

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

calcium carbonatecalcium carbonate Cool, deep ocean undersaturated Cool, deep ocean undersaturated

with calcium carbonatewith calcium carbonate LysoclineLysocline--depth at which --depth at which a significant a significant

amount ofamount of CaCO CaCO33 begins to dissolve begins to dissolve rapidlyrapidly

Calcite compensation depthCalcite compensation depth CCD--depth CCD--depth where CaCOwhere CaCO33 readily dissolves readily dissolves

Rate of supply = rate at which the shells Rate of supply = rate at which the shells dissolvedissolve

Calcareous ooze and the Calcareous ooze and the CCDCCD

Scarce calcareous ooze below 5000 m Scarce calcareous ooze below 5000 m in modern oceanin modern 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

Distribution of calcareous oozes in Distribution of calcareous oozes in surface sediments of modern sea surface sediments of modern sea floorfloor

Fig. 4.14

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

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 Why are they on surface sea floor?Why are they on surface sea floor?

Fig. 4.15a

Hydrogenous marine Hydrogenous marine sedimentssediments PhosphatesPhosphates

Phosphorus-bearingPhosphorus-bearing Occur beneath areas in surface Occur beneath areas in surface

ocean of very high biological ocean of very high biological productivityproductivity

Economically useful: fertilizerEconomically useful: fertilizer CarbonatesCarbonates

Aragonite and calciteAragonite and calcite OolitesOolites

Hydrogenous marine Hydrogenous marine sedimentssediments

Metal sulfidesMetal sulfides Contain iron, nickel, copper, zinc, Contain iron, nickel, copper, zinc,

silver, and other metalssilver, and other metals Associated with hydrothermal ventsAssociated with hydrothermal vents

EvaporitesEvaporites Minerals that form when seawater Minerals that form when seawater

evaporatesevaporates Restricted open ocean circulationRestricted open ocean circulation High evaporation ratesHigh evaporation rates Halite (common table salt) and Halite (common table salt) and

gypsumgypsum

Cosmogenous marine Cosmogenous marine sedimentssediments

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

silicate spherulessilicate spherules TektitesTektites Space dustSpace dust

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

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

Distribution of neritic and pelagic Distribution of neritic and pelagic marine sedimentsmarine sediments

Neritic sediments cover about ¼ of Neritic sediments cover about ¼ of sea floorsea floor

Pelagic sediments cover about ¾Pelagic sediments cover about ¾ Distribution controlled byDistribution controlled by

Proximity to sources of lithogenous Proximity to sources of lithogenous sedimentssediments

Productivity of microscopic marine Productivity of microscopic marine organismsorganisms

Depth of waterDepth of water Sea floor featuresSea floor features

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

Fig. 4.19

How sea floor sediments How sea floor sediments represent surface ocean represent surface ocean conditionsconditions Microscopic tests sink slowly from Microscopic tests sink slowly from

surface ocean to sea floor (10-50 surface ocean to sea floor (10-50 years)years)

Tests could be moved horizontallyTests could be moved horizontally Most biogenous tests clump Most biogenous tests clump

together in fecal pelletstogether in fecal pellets Fecal pellets large enough to sink Fecal pellets large enough to sink

quickly (10-15 days)quickly (10-15 days)

Marine sediments often represent Marine sediments often represent ocean surface conditionsocean surface conditions

TemperatureTemperature Nutrient supplyNutrient supply Abundance of marine lifeAbundance of marine life Atmospheric windsAtmospheric winds Ocean current patternsOcean current patterns Volcanic eruptionsVolcanic eruptions Major extinction eventsMajor extinction events Changes in climateChanges in climate Movement of tectonic platesMovement of tectonic plates

Retrieving sedimentsRetrieving sediments

DredgeDredge Gravity corerGravity corer Rotary drillingRotary drilling

Deep Sea Drilling Deep Sea Drilling ProgramProgram

Ocean Drilling Ocean Drilling ProgramProgram

Integrated Ocean Integrated Ocean Drilling ProgramDrilling Program

Studies reveal support for plate Studies reveal support for plate tectonics, drying of the tectonics, drying of the Mediterranean Sea, global climate Mediterranean Sea, global climate changechange

Resources from marine Resources from marine sedimentssediments Energy resourcesEnergy resources

PetroleumPetroleum Mainly from continental shelvesMainly from continental shelves

Gas hydratesGas hydrates Sand and gravel (including tin, gold, Sand and gravel (including tin, gold,

and so on)and so on) Evaporative saltsEvaporative salts PhosphoritePhosphorite Manganese nodules and crustsManganese nodules and crusts

Salt depositsSalt deposits

Fig. 4.26

Manganese Manganese nodulesnodules

Fig. 4.27

End of End of CHAPTER CHAPTER 44Marine Marine SedimentSedimentss

Fig. 4E