chapter 4: marine sediments
DESCRIPTION
CHAPTER 4: Marine Sediments. Fig. CO-4. Marine sediments. Eroded rock particles and fragments Transported to ocean Deposit by settling through water column Oceanographers decipher Earth history through studying sediments. Classification of marine sediments. Classified by origin - PowerPoint PPT PresentationTRANSCRIPT
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