THE FOSSIL RECORD

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THE FOSSIL RECORD Movement of Ocean
Water Surface currents Coriolis Effect
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THE FOSSIL RECORD Movement of Ocean
Water Surface currents Currents are also
affected by the Earth's rotation through the
Coriolis Effect. Currents in the northern
hemisphere tend to be deflected toward the
right (or clockwise), and currents in the
southern hemisphere tend to be deflected to the
left (or counter clockwise) as a result of the
Coriolis Effect.
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THE FOSSIL RECORD Movement of Ocean
Water Thermohaline currents Thermohaline
currents are initiated at the ocean surface by
temperature and salinity conditions. Gravity
acts to pull colder (or more saline) denser
water downward, displacing less dense water
upward.
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THE FOSSIL RECORD Movement of Ocean
Water Thermohaline currents
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THE FOSSIL RECORD Movement of Ocean Water Tides
Tides are generated by the effect of the Moon's
gravity (and to a lesser extent, the Sun's
gravity) on the oceans.
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THE FOSSIL RECORD Movement of Ocean Water Tides
Areas that are alternately submerged and exposed
by rising and falling tides are called tidal
flats.
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THE FOSSIL RECORD Water Temperature and Depth
Water temperature varies with latitude
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THE FOSSIL RECORD Water Temperature and Depth
Water temperature also varies with depth
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THE FOSSIL RECORD Water Temperature and Depth
A zone of rapid temperature decrease with depth
in a water mass is called the thermocline.At
great ocean depths, temperatures may be just
above freezing.
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THE FOSSIL RECORD Light
The well-illuminated water near the surface of
the ocean is called the photic zone.
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THE FOSSIL RECORD Light
Light is used by certain organisms in the water
for photosynthesis. Photosynthetic organisms
are restricted to the near-surface waters.
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THE FOSSIL RECORD Light
Light penetration into the sea depends on Sun
angle
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THE FOSSIL RECORD Light
Light penetration into the sea depends on
Atmospheric conditions
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THE FOSSIL RECORD Light
Light penetration into the sea depends on
Conditions at the water surface
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THE FOSSIL RECORD Light
Light penetration into the sea depends on
Clarity of the water (or conversely, the amount
of suspended sediment in the water)
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THE FOSSIL RECORD Light
In some areas, light may penetrate as deep as 200
m or more, but generally there is light
adequate to support photosynthesis only in the
upper tens of meters of the sea (to perhaps 100
m).
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THE FOSSIL RECORD Seafloor Sediments Terrigenous
Sediments Material weathered from the
continents Mostly silt and clay
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THE FOSSIL RECORD Seafloor Sediments Biogenic or
Organic Sediments Sediment of biologic origin
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THE FOSSIL RECORD Seafloor Sediments Biogenic or
Organic Sediments Calcareous oozes Form in
depths lt4000 m Foraminifera, coccolithophores,
and pteropods
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THE FOSSIL RECORD Ocean Chemistry Carbonate
Compensation Depth
The Carbonate Compensation Depth or CCD is a
particular depth in the oceans (varying from
place to place), which effects where
calcareous oozes may or may not accumulate.
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THE FOSSIL RECORD Ocean Chemistry Carbonate
Compensation Depth
Above the CCD, water is warmer, and
precipitation of CaCO3 is greater than
dissolution. Calcareous plankton can be found
in the water column, and on the bottom.
Bottom sediments can consist of calcareous
sediments forming chalk or limestone.
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THE FOSSIL RECORD Ocean Chemistry Carbonate
Compensation Depth
Below the CCD, water is colder, and CaCO3 tends
to dissolve (dissolution is greater than
precipitation) Tiny shells of CaCO3 dissolve,
and do not accumulate on the bottom if water
is deeper than the CCD Below the CCD, the bottom
sediments consist of clay and siliceous ooze
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THE FOSSIL RECORD Seafloor Sediments Biogenic or
Organic Sediments Calcareous oozes
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THE FOSSIL RECORD Seafloor Sediments Biogenic or
Organic Sediments Siliceous oozes Form in cold,
deep water Radiolarians and diatoms
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THE FOSSIL RECORD Seafloor Sediments Biogenic or
Organic Sediments Phosphatic sediments Fish
bones and teeth
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THE FOSSIL RECORD Seafloor Sediments Hydrogenous
Sediments Manganese nodules (Authigenic or
diagenetic minerals)
Minerals that precipitate from sea water by
chemical reactions.
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THE FOSSIL RECORD Reconstructing Ancient
Geography
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THE FOSSIL RECORD Ancient Climatic Conditions
Fossils can be used to interpret paleoclimates or
ancient climates Fossil spore and pollen grains
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THE FOSSIL RECORD Ancient Climatic Conditions
Presence of corals indicates tropical climates
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THE FOSSIL RECORD Ancient Climatic Conditions
Plant fossils showing aerial roots, drip tips
on leaves lack of yearly rings, large wood
cell structure Indicate tropical climates
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THE FOSSIL RECORD Ancient Climatic Conditions
Marine molluscs (clams, snails, etc.) with spines
and thick shells inhabit warm seas
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THE FOSSIL RECORD Ancient Climatic Conditions
Planktonic organisms vary in size and coiling
direction according to temperature foraminifer
Globorotalia
Right coiled warm Left coiled cold
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THE FOSSIL RECORD Ancient Climatic Conditions
Oxygen isotope ratios in shells. 16O evaporates
easier than oxygen-18 because it is lighter. 16O
falls as precipitation and gets locked up in
glaciers, leaving sea water enriched in 18O
during glaciations. Shells that are enriched in
18O indicate times of glaciation.
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THE FOSSIL RECORD Ancient Climatic Conditions
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THE FOSSIL RECORD Extinctions
The history of life has been marked by
extinctions. The five largest extinction events
are termed mass extinctions. These mass
extinctions were sudden, global in extent, and
very devastating. Mass extinctions occurred
at the ends of the following periods Ordovician
Devonian (roughly 70 of the ocean's
invertebrates disappeared) Permian (the greatest
extinction. More than 90 of all marine species
at that time disappeared or nearly went extinct)
Triassic Cretaceous (affecting the dinosaurs
ano other animals on land as well as organisms
in the sea, about one fourth of all known
families of animals became extinct)
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THE FOSSIL RECORD Extinctions