Study Guide available! Web site (dusk2.geo.orst.edu/oceans) Go to the syllabus page and click on the Study Guide for Test#1.

Study Guide available!Study Guide available!Web site Web site

(dusk2.geo.orst.edu/ocean(dusk2.geo.orst.edu/oceans)s)

Go to the syllabus page Go to the syllabus page and click on the Study and click on the Study

Guide for Test#1Guide for Test#1

Lecture 9: Marine Lecture 9: Marine SedimentsSediments

What’s all that muck at What’s all that muck at the bottom of the ocean, the bottom of the ocean, and what’s it good for?and what’s it good for?

Marine Sediments are:Marine Sediments are:

Particles of various sizes derived Particles of various sizes derived from a variety of sources that are from a variety of sources that are deposited on the ocean floordeposited on the ocean floor

A vast “library” recording A vast “library” recording geologic, oceanographic and geologic, oceanographic and climatic conditionsclimatic conditions

Remarkably complete compared to Remarkably complete compared to landland

Where do these come Where do these come from?from?

Inputs are:Inputs are:-- rivers-- rivers-- atmosphere-- atmosphere-- surface waters-- surface waters-- volcanoes (both on land and -- volcanoes (both on land and submarine) -- deep ocean watersubmarine) -- deep ocean water-- outer space-- outer space

ClassificationsClassifications

By SizeBy SizeClay -- Silt -- Sand -- Pebble -- Cobble Clay -- Silt -- Sand -- Pebble -- Cobble

0.001 mm 1 mm 100 mm0.001 mm 1 mm 100 mm Effects of water velocity on transport: Effects of water velocity on transport: rivers and near-shore vs open oceanrivers and near-shore vs open ocean

Sediment TransportSediment Transport

Fluid velocityFluid velocitydetermines thedetermines thesize of thesize of theparticles thatparticles thatcan be movedcan be moved

Size SortingSize Sorting

ClassificationsClassifications

By OriginBy Origin

BiogenousBiogenousTerrigenousTerrigenousHydrogenousHydrogenousCosmogenousCosmogenous

Terrigenous sediments Terrigenous sediments (from land)(from land)

RiversRivers Winds (eolian)Winds (eolian) Glaciers (ice-rafted debris, Glaciers (ice-rafted debris, IRD)IRD)

TurbiditesTurbidites Sea level changesSea level changes

River sediment loads (10River sediment loads (1066 tons/yr)tons/yr)

Glacial (Ice-rafted Glacial (Ice-rafted debris)debris)

TurbiditesTurbidites

Rapidly-accumulated terrestrial Rapidly-accumulated terrestrial sedimentssediments

Earthquake-triggered submarine Earthquake-triggered submarine avalanchesavalanches

High velocity (~50 mph!), erosive High velocity (~50 mph!), erosive eventsevents

Good examples preserved on Mary’s Good examples preserved on Mary’s PeakPeak

Turbidites Turbidites (avalanches)(avalanches)

Sea Level ChangesSea Level Changes

Biogenous sedimentsBiogenous sediments (from (from living things)living things)

Calcareous (CaCOCalcareous (CaCO33))Foraminifera -- animalsForaminifera -- animalsCoccolithophores -- plantsCoccolithophores -- plants

Siliceous (SiOSiliceous (SiO22))Radiolaria -- animalsRadiolaria -- animalsDiatoms -- plantsDiatoms -- plants

m = micron = millionth of a meter!

m = micron = millionth of a meter!

m = micron = millionth of a meter!

m = micron = millionth of a meter!

Productivity = Productivity = skeletons and soft skeletons and soft tissuetissue

Accumulation depends on Accumulation depends on production and preservationproduction and preservation

SiOSiO22 is preserved everywhere is preserved everywhere CaCOCaCO33 is variable, depending is variable, depending on P, T, pHon P, T, pH

Carbonate Compensation Carbonate Compensation DepthDepth

CCarbonate arbonate CCompensation ompensation DDepthepth

The depth at which carbonate input The depth at which carbonate input from the surface waters is from the surface waters is balanced by dissolution in balanced by dissolution in corrosive deep waterscorrosive deep waters

In today’s ocean this depth (CCD) In today’s ocean this depth (CCD) varies between 3 km (polar) and 5 varies between 3 km (polar) and 5 km (tropical)km (tropical)

Thus, accumulation rates vary a Thus, accumulation rates vary a lot!lot!

Accumulation Rates for Accumulation Rates for OozesOozes

ProductivityProductivity–reproduction of planktonic reproduction of planktonic organismsorganisms

PreservationPreservation–silica dissolves only very slowlysilica dissolves only very slowly–calcium carbonate varies with calcium carbonate varies with depthdepth

RatesRates are variable: <1 to 15mm/1000 are variable: <1 to 15mm/1000 yryr

Coastal waters are often highly Coastal waters are often highly productive, with abundant planktonic productive, with abundant planktonic

organisms thriving in the surface waters. organisms thriving in the surface waters. Why then are biogenous oozes rarely found Why then are biogenous oozes rarely found

nearshore??nearshore??

Do biogenous sediments dissolve Do biogenous sediments dissolve readily at shallow depths on the readily at shallow depths on the continental shelf? NOcontinental shelf? NO

Do plankton species in coastal Do plankton species in coastal waters lack skeletons? NOwaters lack skeletons? NO

Are planktonic organisms consumed Are planktonic organisms consumed by large organisms, preventing by large organisms, preventing deposition of skeletons? NOdeposition of skeletons? NO

the large input of the large input of terrigenous sediment to the terrigenous sediment to the continental margin overwhelms continental margin overwhelms the biogenous component in the biogenous component in the sediment. YESthe sediment. YES

Hydrogenous (from sea Hydrogenous (from sea water)water)

Metalliferous sediments at Metalliferous sediments at spreading ridgesspreading ridges

Manganese nodulesManganese nodules Evaporites -- Salt depositsEvaporites -- Salt deposits

baseball to bowling ball size!

Cosmogenous (from outer Cosmogenous (from outer space)space)

Meteorites and cometsMeteorites and comets

Sediment AccumulationSediment Accumulation

Sediment successionSediment succession

Distribution of Marine Distribution of Marine SedimentsSediments