CHAPTER 5 ~ OCEAN Sediments

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CHAPTER 5 ~ OCEAN Sediments

See Syllabus
-
revised Webpage


HOMEWORK 1 DUE

(Long Marine lab Field Trip)




Turn in after class


HOMEWORK

problem sets 2


Late Policy
:

Lab assignments are due the week after posting. ~ mondays



We ask that you complete your work on time, and will deduct 10% of the
credit per day for any late assignments. NO EXCEPTIONS. If you have
questions about or need help on the assignments, we invite you to come
to the TAs' office hours.



If you can't make office hours, we encourage you to make an
appointment to meet with the TAs.



TA


Sami


alesix78@gmail.com







The Oceans Memory


Foundations of Paleoceanography


Classification of Marine Sediments


Sedimentary Processes


Global 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 Sediments


Sedimentary Processes


Global Distribution of Sediments



OUTLINE

Foundations of Paleoceanography



Cesare Emiliani (1922
-
1995)


Godfather of Paleoceanography


Measure ratio oxygen (
18
O) vs normal oxygen (
16
O)


in shells of Fomanifera (plankton)


Varies w/ temp.


Good Indicator of seaH
2
O temp/time

»
Cold H
2
O (high [
18
O] vs
16
O

»
Warm H
2
O (low [
18
O] vs
16
O

»
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

3

What 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

5

6


Confirming your Knowledge






Using plankton (fomanifera) shells what elemental


ratio is used to gauge cold/warmer sea water temp/time?


delta O
18

vs O
16



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 Sediments


Sedimentary Processes


Global Distribution of Sediments



OUTLINE

Classification of Marine Sediments

many source types:

-
based on grain size

& organism type



Old Ocean Sediments:

Mostly Phytoplankton

Formanifera (carbonate) ooze
-

50%

Diatom (silica) ooze
-

15%


Phytoplankton

Ocean Sediment


CORE







The Oceans Memory


Foundations of Paleoceanography


Classification of Marine Sediments


Sedimentary Processes


Global Distribution of Sediments



OUTLINE

Sedimentary Processes



What are they?

= production, transport, deposition of sediments




Sedimentary Processes



How and where do sediments move about on the planet?




1. Starts w/ the

Hydrologic Cycle


-
Exchange of H2O

b/w various reservoirs

Sedimentary Processes



2.
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. C
hemical



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 CO
2
(from Atmosphere)



give off Oxygen

Lots of Stored
Carbon

(CO
2
) in sediments

Which Produces more O
2

(Air) for earth


and by how much?

Challenge Q

Algae, 70
-
80%!

Where does CO
2

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 H
2
O

Antartic

Green/dark


H
2
O

Lots of algae


Artic

Green/dark


H
2
O

Lots of algae

ALGAE

ALGAE

Shells dissolve


Shells dissolve


Shells dissolve








The Oceans Memory


Foundations of Paleoceanography


Classification of Marine Sediments


Sedimentary Processes


Global Distribution of Sediments



OUTLINE

Global Distribution of Sediments


Calcite (Carbonate) sediments occupy



~68% Atlantic


~36% Pacific




Lower microorganism (algae growth) responsible?





Final Challenge Q

Why 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 Sediments


Sedimentary Processes


Global Distribution of Sediments



OUTLINE

BREAK

Page 73

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

Page 81

Page 84

TABLES

Tab. 5.1