Download Paleo-oceanography

Marine Sediments
(“dirt of the sea”)
Four major classes of sediments based on their origin
1a) Terrigenous – Riverine
Mississippi River Delta into
the Gulf of Mexico
1b) Sahara Desert
dust blows west
over the Atlantic.
1c) Glaciers are
responsible for
carrying large
boulders and
cobble from
their moraine
via ice flows
and bergs
2a) Biogenous -Carbonate
Sediments
• Biological source of shell-like carbonate
parts:
– Foraminifera protozoa;
– Coccolithophore algae.
• Requires high surface productivity
(growth).
• Accumulate in shallower waters.
• Carbonates dissolve at great depth, called
the “Calcium Carbonate Compensation
Depth”.
2b) Biogenous - Siliceous
Sediments
• Biological source of shell-like silica parts:
– Radiolarian protozoa (Equatorial)
– Diatom algae (higher latitudes)
• Requires high surface productivity (growth).
• However, they don’t dissolve with depth to the
extent of carbonates, so found deeper than
biogenous carbonate sediments.
• Fecal pellets package microorganisms into
heavier faster sinking particles, facilitating
sedimentation
Zooplankton turd = fecal pellet
3) Hydrogenous: formed by microbe mediated chemical
precipitation of dissolved seawater minerals, like Mn.
Manganese
(Mn) nodule
cross-section.
They form
near the
sediment or
basalt /water
interface.
Bacteria are
involved in
the adding
layers of
precipitate.
4) Cosmogenic:
micro-meteorites
Microtektites (tiny
melted crust
particles created by
meteor impact)
Global Sediment Distribution
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Vertical transport
Biological production
Aeolian contributions
Horizontal transport
Depth
Authigenic production
Sediments are sampled with grabs or cores.
Here is a clamshell-sampler. Next is a piston-corer.
Paleo-oceanography =
studying past ocean
conditions from
sediment core samples.
JOIDES
Resolution
<<click>>
Joint Oceanographic Institutions for Deep Earth Sampling.