Lecture%202%20Marine%20Sediments%20And%20Florida%20Sediments

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Lecture 2Marine SedimentsAnd Florida Sediments
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Marine sediments

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

http//serc.carleton.edu/images/microbelife/topics
/proxies/.gif
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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)

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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
• Gravity

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Distribution of sediments

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

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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
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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
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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

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Siliceous ooze

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

Fig. 4.11
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Calcareous Ooze

• Destruction of calcium carbonate varies with
  depth
• At warmer surface, seawater is saturated with
  calcium carbonate so calcite doesnt dissolve
• However, as decomposed material sinks further, it
  reaches cold ocean water
• Colder water holds more dissolved CO2
• CO2 forms carbonic acid and causes calcareous
  material to dissolve
• High pressure also helps with this
• This is where the CCD is reached (Calcite
  Compensation Depth) below this little calcium
  carbonate survives

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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
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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
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Cosmogenous marine sediments

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

Tektites
Space dust
http//upload.wikimedia.org/wikipedia/commons/thum
b/5/5c/Two_tektites.JPG/800px-Two_tektites.JPG
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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

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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
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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
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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

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Florida Sediments

• 3 characteristics distinguish Florida from
  regions to the north
• Marine sediments, limestone and calcium magnesium
  carbonate, lie in thick layers at or below
  surface
• Whole southeastern US coastal plain is deeply
  layered with clay, silt, sand, and gravel
• Layer of organic soil lies on or is mixed into
  surface sediments
• Can be very thick under wetlands

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• Clay hills of north Florida
• Carried from Appalachian mountains

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• Sand hills
• Ancient barrier islands and dunes

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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.

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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.