Post on 24-Jul-2020
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Marine Sediments and Sedimentary Rocks
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Interest in Marine Sediment
• Sediments reveal– Past climates– Ocean floor movements– Circulation patterns– Nutrient supplies– Ocean chemical history
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Rock Cycle
1. Sediments deposited2. Lithification3. Burial, compression4. Deformation, melt5. Re-crystallization6. Tectonic uplift7. Weathering and further deposition
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Sedimentary Rock
• Deposited in horizontal layers
Strata (s. Stratum) –horizontal layers deposited on top of one another
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Law of Superposition
Sedimentary layers are deposited in a time sequence, with the oldest on the bottom and the youngest on the top.
Nicholas Steno
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Retrieval of Ancient Marine Sediment
• Drilling ships needed to access oldest marine sediments under sea – R/V JOIDES Resolution
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Retrieval of Ancient Marine Sediment
• Drilling ships now can theoretically drill to mantle – R/V Chikyu is a riser drilling platform
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Drill Ship Operations• Core through sediment layer
– Continuously pull core sections to the surface for analysis
• Find hole with sonar beacon– Ship uses thrusters for this purpose –
dynamic positioning• Rotary drill or Riser drill into
compacted, lithified layers below the sediment– Continuously bring core sections to
surface for analysis
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Sediment Coring
• http://www.iodp.org/coring-procedure/
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Marine Sedimentation
• Lithogenous Sediment– Generated from pre-existing rock material
• Biogenous Sediment– Originating from living organisms
• Hydrogenous Sediment– Precipitated from dissolved material in water
• Cosmogenous Sediment– Sourced extraterrestrially
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Sedimentation
• Energy dependent• Smallest grains in basins• Coarse grains nearer
coasts
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
From Sediment to Rock
• Lithification– Sediment compaction– Cementation
Figure: Dr. Bruce Railsback, UGA
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Sampling Lithified Marine Sediment
• http://www.iodp.org/deep-sea-drilling/2/• http://www.iodp.org/rotary-drilling/2/
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Core Analysis
• Retrieve core• Non-destructive analysis• Split• Measure and analyze
– Sample (one half)– Archive (the other half)
• http://www.iodp.org/core-analyzing-process/2/
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Sediment History
• What changes in sediment type ratios are there? (lithogenous vs. biogenous)
• How does biogenous sediment change through time? (biogenous)
• What evidence of impact sediments is apparent? (cosmogenous)
• How has ocean chemistry changed in the past? (hydrogenous and biogenous)
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Lithogenous Sediment
• Generated from pre-existing rock• Weathering, erosion, transport to ocean basin
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Lithogenous Sediment Deposition• Neritic deposits – continental margins and
islands, dominated by lithogenoussediment
• Pelagic deposits – deep ocean basins
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Lithogenous Sediment Sources
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Lithogenous Sediment Composition
• SiO2
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Lithogenous Sediment Transport• Water
– Terrigenous sediment transported in rivers
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Lithogenous Sediment Transport• Water
– Deposited in basins
photo: Lonnie Leithold
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Lithogenous Sediment Transport
• Air– Loess
• Wind blown dust• Finer material
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Quartz Distributions – Wind Transport
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Lithogenous Sediment Transport
• Ice– Calving ice sheets and
glaciers– Large, coarse fragments– Carried long distances by
icebergs
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Lithogenous Sediment Transport
• Ice-rafted debris
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Lithogenous Sediment Transport
• Ice-rafted debris– High rates of glaciation
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Lithogenous Sediment Transport
• Sea level change– Direct erosion of
vulnerable coastline– Transport out to sea and
deposition in basin
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Lithogenous Sediment Transport
• Volcanoes
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Lithogenous Sediment Transport
• Tephra layers
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Lithogenous Sediment Maturation
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Lithogenous Sediment Maturity
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Turbidites – From Neritic to Pelagic
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Turbidites – From Neritic to Pelagic
• Gravity transport – density current– underwater landslide
• Unique depositional record
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Turbidites – From Neritic to Pelagic
• Gravity transport – density current– underwater landslide
• Unique depositional record• High rate of speed
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Lithogenous Sediment
• Which ocean has the highest proportion of lithogenous sediments?
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Lithogenous Sediment
• Which ocean has the highest proportion of lithogenous sediments?
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Biogenous Sediment
• Sediment originating from living organisms– Foraminifera– Coccolithophorids– Radiolarians– Diatoms
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Calcareous Biogenic Sediment
• Ca2+ + CO32- CaCO3 (s)
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Calcareous Biogenous Sediment
• Calcareous Organisms– Foraminifera– Coccolithophorids– Pteropods
White cliffs of Dover (England) are made of chalk deposited in the Cretaceous Period. These cliffs are almost entirely made of coccoliths from ancient coccolithophorids.
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Coccoliths and Coccolithophorids
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Coccoliths and CoccolithophoridsCoccoliths
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Coccolithophorids
• Floating algae• Build coccoliths for protection and perhaps
light manipulation• Responsible for 25%CO2 sequestration by oceans every year
http://www.jochemnet.de/fiu/bot4404/BOT4404_16.html
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Coccolithophorids
• Dominant during Cretaceous Period– “creta” Latin for chalk
• Abundant in shallow inland seas• Warm and tropical
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Pteropods
Swimming sea snails, some form tine snail-type calcareous shells. These form a small part of calcareous sediment.
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Foraminifera
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
ForaminiferaForaminifera are floating and benthic protists (first ones –Greek for early life forms) . They form complex calcareous shells (tests) and use a cellular “net” to trap food. Those living in the surface of the oceans are normally symbiotic with photosynthetic algae.
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Foramifera
• Planktonic forams– Surface dwellers– Need and use light– Symbiosis– Tests fall to bottom
upon deathO.R. Anderson
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Foramifera
• Benthic Forams– Dwell bottom
sediments– Leave shells mixed
with planktic species upon death
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Foraminifera Records
• Many species are geologically short-lived, making them useful for paleontologist to date rocks
• Also useful for paleoceanography– Assemblages tell of climate change and
extinctions– Test (or shell) chemistry tells of global climate
change
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Foraminifera and Paleoceanography
• Cesare Emiliani –Father of Paleoceanography
• Sir Nicholas Shackleton – Emiliani’scounterweight
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Foraminifera and Paleoceanography
• Cesare Emiliani – isotopic change of oceans, recorded in foram tests, is related to temperature
• Sir Nicholas Shackleton – isotopic change of oceans is related to isotopic composition of oceans
• Answer – Both.
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Foraminifera and Paleoceanography
Whereas temperature probably played a large role in the isotope composition of planktic foraminifera, Shackletonmeasured benthic species which also showed change. We know that the deep oceans are fairly resistant to temperature change. Deep benthic foraminifera showing isotope variations meant that the isotope composition of the water had changed in concert with the temperature. More ice meant heavier values in the oceans. Cold temperatures meant heavier values in the oceans. Benthics vs. planktics offered a solution to this argument.
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Siliceous Biogenic Sediment
• Diatoms– Planktonic– Photosynthetic
• Radiolarians– Planktonic– Heterotrophic
• Siliceous Ooze
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
DiatomsPhotosynthic plankton with two halves (frustules). Like radiolarians, these collect in areas of high productivity.
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
RadiolariansNoted for their beauty, are best preserved in areas of high productivity where they rain at a higher rate than dissolution.
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Siliceous vs. Calcareous Ooze• Siliceous
deposits form in tropics and Antarctica –high productivity
• Calcareous deposits form where ocean chemistry allows preservation of delicate carbonate tests
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Carbonate Compensation Depth
• Lysocline– Stability of CaCO3 is related to temperature and pH– Lower temperatures dissolve more CO2, making
water more acidic– CaCO3 tends to dissolve when temperatures are low
(i.e. deep water)• CCD
– Where dissolution of CaCO3 balances production and CaCO3 can no longer accumulate
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Siliceous vs. Calcareous Ooze
• Pacific is largely below present day CCD.
• Abyssal clay is undiluted here
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Productivity and Preservation
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Productivity and Preservation
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
CCD and Lysocline
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
CCD and Lysocline
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Sedimentation on the Ocean Floor
• Sediment grows thicker away from mid-ocean ridge (spreading center)
• Oldest (thickest) sediment found toward continental margins
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Biogenous Sediments in Neritic Zone
• Coral reefs– Calcium carbonate
skeletons– Fragments
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Biogenous Sediments in Neritic Zone
• Mollusks– Calcium carbonate
skeletons– Shell hash
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Hydrogenous Sediments
• Forming from within the water column– Precipitation from dissolved constituents of
seawater
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Whitings – Calcium Carbonate• Oceans can be supersaturated with
regards to calcium carbonate (surface)• Whitings
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Why so blue?• Reflection of light through shallow waters
and white carbonate sands.– Biogenous– Hydrogenous
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Manganese Nodules
• Manganese, iron, and other metals– 5 cm in diameter, layered– Nucleates around a pre-existing grain
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Ooids – Calcium Carbonate
• Round grains of layered calcium carbonate
• Formed by repeated agitation in shallow, supersaturated water
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Ooids – Calcium Carbonate
• Make wonderful beach sand because of uniform spherical shape
• Lithified to oolite
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Metal Sulfides – Black Smokers
• Precipitation of reduced chemicals in hydrothermal vent fluids
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Cosmogenous Sediments
• Derived from extraterrestrial sources– Spherules– Meteorite debris
• Tektites
• 300,000 tons of space debris reach Earth’s surface every year
• Macroscopic debris is more rare
Microscopic debris
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Impact Debris
• Large impacts have been responsible for dramatically altering Earth’s conditions– Extinctions evidenced by impact
debris
Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Impact Debris
• Would the Permian extinction impact event (if there was one) be observable in ocean sediments?
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Prof. Rosenheim EENS/EBIO 223
Introductory Oceanography
Key Concepts
• Sediment types and genesis• Transport and deposition• Preservation• Uses of sediment records• Sampling techniques