CHAPTER 5 ~ OCEAN Sediments

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HOMEWORK 1 DUE(Long Marine lab Field Trip)

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The Oceans Memory Foundations of Paleoceanography

Classification of Marine SedimentsSedimentary ProcessesGlobal Distribution of Sediments

OUTLINE

• The Oceans Memory–Paleoceanography?

• Study of Oceans sedimentary record– Analyze Sediment Cores

Challenge Question

What is the Principle of Superposition?

In a deposit of undisturbed sedimentary rocks,oldest rocks at the bottom,youngest at the top

Sediments tell a story

The Oceans Memory Foundations of Paleoceanography

Classification of Marine SedimentsSedimentary ProcessesGlobal Distribution of Sediments

OUTLINE

Foundations of Paleoceanography

• Cesare Emiliani (1922-1995)– Godfather of Paleoceanography– Measure ratio oxygen (18O) vs normal oxygen (16O)

• in shells of Fomanifera (plankton)

• Varies w/ temp.– Good Indicator of seaH2O temp/time

» Cold H2O (high [18O] vs 16O» Warm H2O (low [18O] vs 16O» aka - delta O-18» Look at O-18 in sediment cores

Foundations of Paleoceanography

• Emergence of Kullenberg piston corer– Cores of 10-20m into ocean basins. . .

• Representing 1-2 million years of sediments

• DEEP Sea Drilling Projects (Sediment Cores)• NSF (1971-1982) – Changes in Climate ~ 700,000 years

Climate: Long Range Investigation, Mapping and Prediction

aka (CLIMAP)

– Demonstrated Ice Ages result from Mileneum-Scale deviations

From Earth’s Orbit around Sun

-aka Milankovitch cycle

Foundations of Paleoceanography

                                                                                                         

                                                                                                         

Milankovitch cycles (1-3)

I

2

3What do the Milankovitch cycles vary the amount of?

Challenge Question?

~ 10*C temp changes Ice Ages

Solar radiation that reaches the earth

What can this lead to / result in?

From Sediment Cores

Heinrich Events discovered – What are they?

Abrupt climate change/ rapid cooling within decades/ centuries

Scientists concerned modern lifestyle leading to another. . .e.g. Global Warming Mini ice age . . .

6 in last 75,000 years. . .

http://www.youtube.com/watch?v=Cs56_GqTyIQ&feature=related

1

2

3

4

56

• Confirming your Knowledge

– Using plankton (fomanifera) shells what elemental • ratio is used to gauge cold/warmer sea water temp/time?

– delta O18 vs O16

– What are Heinrich events/ how many occurred in last 75000 years?

• Rapid change in seawater temp/decades, 6

The Oceans Memory Foundations of Paleoceanography

Classification of Marine SedimentsSedimentary ProcessesGlobal Distribution of Sediments

OUTLINE

Classification of Marine Sedimentsmany source types:-based on grain size & organism type

Old Ocean Sediments:Mostly PhytoplanktonFormanifera (carbonate) ooze - 50%Diatom (silica) ooze - 15%

Phytoplankton

Ocean Sediment CORE

The Oceans Memory Foundations of Paleoceanography

Classification of Marine SedimentsSedimentary ProcessesGlobal Distribution of Sediments

OUTLINE

Sedimentary ProcessesWhat are they? = production, transport, deposition of

sediments

Sedimentary ProcessesHow and where do sediments move about on the

planet?

1. Starts w/ theHydrologic Cycle

-Exchange of H2Ob/w various reservoirs

Sedimentary Processes2. Continental Weathering

– what is it?

• Challenge Question• What are the 3 types weathering processes?

• 1. Physical – breaking apart of rocks via– Rock slides, earthquakes, debris flow

• 2. Chemical – dissolving of rocks via– Natural acidic rain, rivers etc.

• 3. Biological – activities of organisms via– fracture, dissolve, chemically alter rocks etc.

Dissolving, fracturing/ chemical alteration of rocks – -important role in cycling of elements (Iron, Calcium etc. ) and salinity in Sea Water

Sedimentary Processes• Sediment Sinking

• Grain size effects sinking

– Sediment traps measure carbon flux • Estimates Global carbon cycle

• Important For study of Climate change

–

plankton

Sedimentary Processes• Biological sedimentation

– The biological pump – complex– phytoplankton

• aka algae

=

PhytoPlankton ~ = Trees

Take in CO2 (from Atmosphere)

give off Oxygen

Lots of Stored Carbon (CO2) in sediments

Which Produces more O2 (Air) for earth and by how much?

Challenge Q

Algae, 70-80%!

Where does CO2 come from?

Sedimentary Processes• Calcium-Carbonate (calcite) Compensation Depth (CCD)

– Below certain depth, calcite shells dissolve

– aka “the lysocline”

– Challenge Q• What factors influence the solubility (dissolution) of calcite shells?

– Lower temp., Higher pressure

Sedimentary Processes• Calcium-Carbonate (calcite) Compensation Depth (CCD)

– The CCD - What is it? • Depth/Region where: solid Calcite shells = dissolving Calcite shells

– No net change (1:1)

• Area of high plankton growth – shallow CCD (Artic, Antartic)

• Area of low plankton growth – deep CCD (Hawaii)– Based on solubility of Calcite in Water (think of Sugar in Water)

» If have LOTS, area is saturated (need more Liq. space to dissolve it)

HAWAII-clear H2O

AntarticGreen/dark H2OLots of algae

ArticGreen/dark H2OLots of algae

ALGAE

ALGAE

Shells dissolve Shells dissolve

Shells dissolve

The Oceans Memory Foundations of Paleoceanography

Classification of Marine SedimentsSedimentary ProcessesGlobal Distribution of Sediments

OUTLINE

Global Distribution of Sediments

• Calcite (Carbonate) sediments occupy – ~68% Atlantic ~36% Pacific

• Lower microorganism (algae growth) responsible? Final Challenge QWhy does the N. Pacific NOT

have the same Calcite deposition

as the N. Atlantic?

–Red clay occupies deepest regions

(calcite)

Think Geology(bathymetry)

No Mid ocean ridge In N. Pacific for shells to land on

They dissolve before then Can settle on something

Global Distribution of Sediments

The Oceans Memory Foundations of Paleoceanography

Classification of Marine SedimentsSedimentary ProcessesGlobal Distribution of Sediments

OUTLINE

BREAK

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Fig. 5.9

Fig. 5.18

Fig. 5.2

Fig. 5.5

Fig. 5.7

Fig. 5.8

Fig. 5.8.a

Fig. 5.8.b

Fig. 5.8.c

Fig. 5.12

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TABLES

Tab. 5.1