CHAPTER%204:%20Marine%20Sediments

1
CHAPTER 4 Marine Sediments
2
Marine sediments

• Eroded rock particles and fragments
• Transported to ocean
• Deposit by settling through water column
• Oceanographers decipher Earths history through
  studying sediments

http//serc.carleton.edu/images/microbelife/topics
/proxies/.gif
3
Classification of marine sediments

• Classified by origin
• Lithogenous (derived from land)
• Biogenous (derived from organisms)
• Hydrogenous (derived from water)
• Also known as Authigenic
• Cosmogenous (derived from outer space)

4
Lithogenous sediments

• Eroded rock fragments from land
• Reflect composition of rock from which derived
• Transported from land by
• Water (e.g., river-transported sediment)
• Wind
• Ice/glacier
• Gravity

5
Lithogenous sediments

• Most lithogenous sediments at continental margins
• Coarser sediments closer to shore
• Finer sediments farther from shore
• Mainly mineral quartz (SiO2)

6
Relationship of fine-grained quartz and
prevailing winds
Fig. 4.6b
7
Distribution of sediments

• Neritic
• Found on continental shelves and shallow water
• Generally course grained
• Pelagic
• Found in deep ocean basins
• Typically fine grained

8
Distribution of sediments

• Neritic
• Shallow water deposits
• Close to land
• Dominantly lithogenous
• Typically deposited quickly

http//disc.gsfc.nasa.gov/oceancolor/images/SeaWiF
S_Feb28_sediments_enhanced.jpg
9
Distribution of sediments

• Pelagic
• Deeper water deposits
• Finer-grained sediments
• Deposited slowly
• Sources of fine pelagic lithogenous sediments
• Volcanic ash (volcanic eruptions)
• Wind-blown dust
• Fine-grained material transported by deep ocean
  currents

10
Pelagic lithogenous sediments

• Abyssal clay (red clay)
• At least 70 of clay-sized grains from continents
  
• Transported by winds and currents
• Oxidized iron gives reddish color
• Abundant if other sediments absent

http//www.ncptt.nps.gov/images/ac/prospection-in-
depth-2006/album/Whittington/16NA24120G520Closeu
p20on20red20clay20bleeding20into20lighetr20
soil.jpg
11
Biogeneous marine sediments

• Hard remains of once-living organisms
• Shells, bones, teeth
• Macroscopic (large remains)
• Microscopic (small remains)
• Tiny shells or tests settle through water column
• Biogenic ooze (30 or more tests)
• Mainly algae and protozoans

http//inst.sfcc.edu/gmead/ocbasins/CALCCORL.gif
12
Biogeneous marine sediments

• Commonly either calcium carbonate (CaCO3) or
  silica (SiO2 or SiO2nH2O)
• Usually planktonic (free-floating)
• When the plankton die, they settle on the bottom

13
Silica in biogenic sediments

• Diatoms (algae)
• Photosynthetic
• Where they are abundant, thick deposits
  accumulate when they die
• Diatomaceous earth light white rock
• Radiolarians (protozoans)
• heterotrophic
• Produces siliceous ooze

14
Siliceous ooze

• Seawater undersaturated with silica so
  continually dissolves back into water
• Therefore, detectable siliceous ooze found in
  the sediments is commonly associated with high
  biologic productivity in surface ocean because
  once buried, they dont dissolve easily

15
Calcium carbonate in biogeneous sediments

• Coccolithophores (algae)
• Photosynthetic
• Coccoliths (nano-plankton)
• Accumulation of dead ones results in
• Rock chalk

16
Calcium carbonate in biogeneous sediments

• Foraminifera (protozoans)
• Heterotrophic
• Calcareous ooze

Fig. 4.8c
http//serc.carleton.edu/images/microbelife/topics
/proxies/foraminefera.jpg
17
Carbonate deposits (CO3)

• Limestone
• Lithified carbonate sediments
• White Cliffs of Dover, England is hardened
  coccolithophore ooze
• CaCO3

• Stromatolites
• Warm, shallow-ocean, high salinity
• Cyanobacteria

Fig. 4.10a
18
Hydrogenous marine sediments

• Minerals precipitate directly from seawater
• Manganese nodules
• Phosphates
• Carbonates
• Metal sulfides
• Small proportion of marine sediments
• Distributed in diverse environments

Deep sea ferromanganese nodules on the floor of
the South Pacific Ocean (individual nodules are
5-10 cm diameter).
http//www2.ocean.washington.edu/oc540/lec01-16/99
.540.1.2.jpg
19
Hydrogenous marine sediments

• Phosphates
• Phosphorus-bearing apatite sedimentary rock
• Occur beneath areas in surface ocean of very high
  biological productivity ? phosphates released
  into interstitial water by decomposition
• Economically useful fertilizer

A phosphate mine in Hardee County in central
Florida. Seventy-five percent of the phosphate
used in the United States comes from the region.
http//www.nytimes.com/2007/08/04/us/04phosphates.
html?_r1orefslogin
20
Hydrogenous marine sediments
Aragonite

• Carbonates (CaCO3)
• Aragonite and calcite
• Calcite found in limestones, marbles, chalks
• Used in antacids, toothpaste
• Aragonite (marine shells) is less stable and
  reverts to calcite crystalline form over time
• Used in cement, fertilizer
• Oolites
• Small, round calcite spheres found in shallow,
  tropical waters with high carbonate
  concentrations
• Small, used in aquariums

Calcite
Oolitic sand
http//www.advancedaquarist.com/2005/2/short_album
/GreatSaltLakeSand.jpg/variant/medium
http//www.outreach.canterbury.ac.nz/resources/geo
logy/glossary/calcite.jpg
21
Hydrogenous marine sediments

• Metal sulfides
• Contain iron, nickel, copper, zinc, silver, and
  other metals
• Associated with hydrothermal vents

http//scienceblogs.com/deepseanews/2008/03/deep_o
ceans_and_deep_space.php
22
Hydrogenous marine sediments

• Evaporites
• Minerals that form when seawater evaporates
• Restricted open ocean circulation
• High evaporation rates
• Halite (common table salt) and gypsum

http//www.pitt.edu/cejones/GeoImages/1Minerals/2
SedimentaryMineralz/Gypsum_Halite/GypsumSelenite.J
PG
23
Cosmogenous marine sediments

• Macroscopic meteor debris
• Microscopic iron-nickel and silicate spherules
• Tektites
• Space dust
• Overall, insignificant proportion of marine
  sediments

Space dust
http//upload.wikimedia.org/wikipedia/commons/thum
b/5/5c/Two_tektites.JPG/800px-Two_tektites.JPG
24
Mixtures of marine sediments

• Usually mixture of different sediment types
• For example, biogenic oozes can contain up to 70
  non-biogenic components
• Typically one sediment type dominates in
  different areas of sea floor

http//lh5.ggpht.com/_xdSF9NzTieY/SGE4kkTxFEI/AAAA
AAAACsk/FPHuZspT7SM/Zouzou'smud2.JPG
25
Marine sediments often represent ocean surface
conditions ? preserves record of past

• Temperature
• Nutrient supply
• Abundance of marine life
• Atmospheric winds
• Ocean current patterns
• Volcanic eruptions
• Major extinction events
• Changes in climate
• Movement of tectonic plates

26
Retrieving sediments

• Dredge
• Gravity corer
• Rotary drilling

• Deep Sea Drilling Program
• Ocean Drilling Program
• Integrated Ocean Drilling Program

http//www.usgcrp.gov/usgcrp/images/ocp2007/galler
y-large/thumbnails/OCP07_Fig-10.jpg
27
Resources from marine sediments

• Energy resources
• Petroleum
• Mainly from continental shelves
• Gas hydrates
• Sand and gravel (including tin, gold, and so on)
• Evaporative salts
• Phosphorite
• Manganese nodules and crusts

Ultra-Deep Oil Drilling, capable of drilling in
10,000 feet of water and penetrating 30,000 feet
through earths crust.
http//joejaworski.files.wordpress.com/2007/09/oil
_plat.jpg
28
Other reasons to study sediments

• Contaminants in water column will sometimes
  settle in the sediment
• Conditions that effect toxicity of sediments
• Sediment type
• Sediment texture (in fine sediment, there is more
  surface area for toxins to adhere, increasing
  toxicity)
• Dredging and other human activity
• Sediment Toxicity in Indian River Lagoon
• http//www.teamorca.org/cfiles/fast.cfm

29
Misconceptions what have we learned that make
these statements false?

• Carbon is only produced by trees.
• The bioshpere has never caused major changes in
  the other spheres that make up the Earth system,
  such as the rocks and air.
• Few products we use everyday have anything to do
  with taking rocks and minerals from the ground.
• We will never run out of natural resources such
  as coal, oil, and other minerals.

30
Ocean Literacy Principles

• 1g. - The ocean is connected to major lakes,
  watersheds and waterways because all major
  watersheds on Earth drain to the ocean. Rivers
  and streams transport nutrients, salts, sediments
  and pollutants from watersheds to estuaries and
  to the ocean.
• 1h. - Although the ocean is large, it is finite
  and resources are limited.