No Quiz This Week Exam tomorrow night; here, 7 PMExam tomorrow night; here, 7 PM Bring a pen/pencil you can write a short essay withBring a pen/pencil you can write a short essay with Extra credit (up to 5% extra)- redo the exam with discussion in small groups (8:00)Extra credit (up to 5% extra)- redo the exam with discussion in small groups (8:00)

So Far, We’ve Covered... Basic Earth Properties and MapsBasic Earth Properties and Maps Ocean Basin FeaturesOcean Basin Features Plate TectonicsPlate Tectonics

What’s Next? SedimentsSediments Ocean Water: Physical PropertiesOcean Water: Physical Properties –Density, Evaporation Ocean Water: Chemical PropertiesOcean Water: Chemical Properties –Dissolved matter –Salinity –Nutrients

Class #11 OCEAN SEDIMENTS Introduction Marine sedimentary provinces Importance of particle size Terrigenous sediments Turbidity currents

"The sediments are a sort of epic poem of the Earth." -Rachel Carson

Ocean sediments are our best record of Earth history!

Ocean sediments are somewhat like a book of earth history- every detail says something about events on the earth. Many sedimentary rocks can be found on land today.

Layering -- oldest at bottom, youngest at topLayering -- oldest at bottom, youngest at top How thick are they?How thick are they? –very little on mid-ocean ridges –up to 10,000 m beneath continental rises –average = 500 m Sediments collect slowlySediments collect slowly –Deep ocean (avg.): cm/1000 yr –Continental margins: cm/1000 yr –River mouths may be higher Sedimentation Patterns

Where does all this stuff come from?Where does all this stuff come from? Continents (weathering and erosion)Continents (weathering and erosion) Biogenic particlesBiogenic particles Volcanic ashVolcanic ash Chemical precipitatesChemical precipitates Micro-meteoritesMicro-meteorites Why do we care?Why do we care? Oil, gas, and other resourcesOil, gas, and other resources Record of past conditions and processesRecord of past conditions and processes

Pelagic Neritic

Marine Sediment Provinces

Sediment Types (Table 4.1)

Coarse Finer Finest

(1) Larger --> sink faster (2) Faster-moving water holds coarser sediment and more of it. (3) Rapid currents transport coarse + fine seds. (4) Slow currents transport only fine sediments. So…. Coarsest Particles: beaches, near-shore, inner shelf -- "fast" currentsCoarsest Particles: beaches, near-shore, inner shelf -- "fast" currents Finest: quieter placesFinest: quieter places Particles Sizes in Sediment- Interpretation

Sediment Types (Table 4-1)

(1) Terrigenous sediment – ~75% of all marine sediment (by mass) – Mostly settles on continental margins So they DO NOT cover a very large areaSo they DO NOT cover a very large area – Atlantic: Large “fans” spread out on the deep-sea floor – Pacific Ocean: Trapped by trenches; little transported to deep-sea floor LITHOGENOUS SEDIMENTS

Erosion removes material from land: Where does it go?

Turbidity Currents: Move sediment down the continental margins

Turbidity Currents Dense, muddy water (turbid water) cloud or slurry that flows down the continental slope onto the continental rise- HUGE

Turbidity current: dense slurry (“avalanche”) of poorly sorted, suspended sedimentTurbidity current: dense slurry (“avalanche”) of poorly sorted, suspended sediment Sediment deposited as current slowsSediment deposited as current slows Largest particles settle first (poorly sorted)Largest particles settle first (poorly sorted) Finer particles settle nextFiner particles settle next Finest particles (mud) settle lastFinest particles (mud) settle last

Turbidity Currents

(2) "Red Clay" -- terrigenous dust + volcanic ash –Transported to open ocean by winds + water currents –Settles eventually –Dominant only in deep areas where other types absent. LITHOGENOUS SEDIMENT- Pelagic