In The Name Of God

In The Name Of God
Marine Sediments
Classification Of Marine Sediments
Based On Origin
Marine Sediments
Lithogenous
Biogenous
Hydrogenous
Cosmogenous
Lithogenous Sediment
• Lithogenous (lithos = stone, generare = to
produce) sediment is derived from
preexisting rock material. Since most
lithogenous sediment comes from the
landmasses, it is also called terrigenous
(terri = land, generare = to produce)
sediment. However, volcanic islands in
the open ocean are also important sources
of lithogenous sediment. Lithogenous
sediment in the ocean is ubiquitous: At
least a small percentage of lithogenous
sediment is found nearly everywhere on
the ocean floor .
• Origin
Lithogenous sediment originate from
continents & Islands. Rock material is
eroded by weathering & broken into
smaller pieces .Smaller pieces are
transported to :
- Bays , Lagoons , continental margins ,
shorelines , beaches by actions such as
wind , glaciers , streams
- Deep oceans by turbidity currents &
gravity .
Composition
Mainly composed of quartz , one of
the most abundant and Chemically
stable minerals.
Weathering
Often occurs along weaknesses
• Sediment texture
Grain size : indicate the energy of environment.
• Sorting :
Poorly sorted
sediment like those
carried by glacial.
Well sorted sediment like beach sand .
• Maturity : it depends on the distance of
transportation .
Increasing sediment maturity is indicated by:
(1) decreasing clay content,
(2) increased sorting,
(3) decrease of non-quartz minerals, and
(4) increased rounding of the grains
within the deposit.
• Mature sediment : well sorted beach sand
• Immature sediment : glacial sediment
Sediment Maturity
Lithogeneous Beach Sand
Biogenous Sediment
These sediment is derived from the remains of
hard parts of organisms. Under appropriate
environmental conditions that allow marine
organisms to live, biogenous material slowly
settles onto the ocean floor.
• Origin
Biogeneous sediments originate from the hard
remains of living organisms.
organisms- from minute algae and protozoan
to large animals
hard parts are constructed directly from the
dissolved materials in seawater or from the
material supplied by feeding.
Biogenous sediment classification
• Macroscopic biogenous sediment
Seen without the aid of a microscope and includes
shells, bones, and teeth of large organisms.
Founds in certain tropical beach localities, is
volumetrically rare in the marine environment
• Microscopic biogenous sediment
Contains particles so small that a microscope is
needed to see these hard remains.
Microscopic organisms produce tiny shells called
tests.
These microscopic tests can accumulate on the deepocean floor and form deposits called ooze.
Composition
• They are composed from two most
•
common chemical compounds, calcium
carbonate (CaCO3) and silica (SiO2).
Calcium Carbonate
Two
significant
contributor
are
microscopic algae called coccolithophores
(coccus = berry; lithos = stone;phorid =
carrying and the foraminifers (foramen =
an
opening),
close
relatives
of
radiolarians, are a source for calcium
carbonate biogenous ooze
Microscopic Calcareous Tests
Coccolithophores
Foraminifera
Calcareous
Ooze
• Silica
Contributing most of the silica in
biogenous ooze are microscopic algae
called diatoms (diatoma = cut in half)
and protozoans called radiolarians
(radio = a spoke or ray).
Diatom
Radiolarian
Siliceous Ooze
Hydrogenous Sediment
Hydrogenous sediment is derived from the dissolved material in
water.
• Origin
Seawater contains many dissolved materials. Chemical reactions
within seawater cause certain minerals to come out of solution or
precipitate.
• Composition
Hydrogenous sediments are volumetrically not very significant in
the ocean, they have many different compositions and
environments of deposition.
• Manganese Nodules:
Manganese nodules are rounded, hard lumps of manganese,
iron, and other metals up to 30 centimeters (12 inches) long.
• Phosphates:
Phosphorus-bearing compounds (phosphates) occur abundantly
as coatings on rocks and as nodules on the continental shelf and on
banks at depths shallower than 1000 meters (3300 feet).
• Carbonates:
The two most important carbonates (a mineral containing CO3 in
its chemical formula) in marine sediment are the minerals
aragonite and calcite.
• Metal Sulfides:
Associated with hydrothermal vents and black smokers along the
mid-ocean ridge are deposits of metal sulfides. The composition of
these metal sulfides includes iron, nickel, copper, zinc, silver and
other metals in varying proportions.
• Evaporites:
Evaporite minerals form where there is restricted open ocean
circulation and where evaporation rates are high.
Cosmogenous Sediment
Cosmogenous (cosmos = universe, generare = to produce)
sediment is derived from extraterrestrial sources. Volumetrically
insignificant on the ocean floor.
Cosmogenous Sediment
Microscopic Spherules
Macroscopic Meteor Debris
Cosmogenous sediment classification
• Spherules are microscopic globular masses composed of silicate
•
rock material, called tektites (tektos = molten), or composed
mostly of iron and nickel and form in the asteroid belt between the
orbits of Mars and Jupiter and are produced when asteroids
collide.
Meteor debris is rare on Earth and is associated with the more
than 110 meteor impact sites identified.
Mixtures
• Rarely do lithogenous and biogenous sediment occur as an
absolutely pure deposit that does not contain other types of
sediment
Classification Of Marine Sediments
Based On Depth Deposition
Marine Sediments
Neritic Deposits
Pelagic Deposits
Neritic deposits
• Lithogenous sediment dominates most. This is not
•
surprising, since lithogenous material is derived from
rocks on nearby landmasses. It consists of coarsegrained deposits and accumulates rapidly on the
continental shelf, slope, and rise.
Neritic deposits also contain biogenous, hydrogenous,
and cosmogenous particles, but these constitute only a
minor percentage of the total sediment mass.
Neritic Deposits
((Continental Margin Sediments ))
Neritic Deposits
Relict Sediments
Turbidite Deposits
Glacial Deposits
Carbonate Deposits
Relict Sediments
• At the end of the last Ice Age, around 18,000 years ago,
glaciers melted and sea level rose. As a result, many
rivers of the world today deposit their sediment in
drowned river mouths rather than carry it onto the
continental shelf as they did during the geologic past. In
many areas the sediments that cover the continental
shelf, called relict sediments, were deposited from 3000
to 7000 years ago and have not yet been covered by
deposits, which are more recent. Such sediments
presently cover about 70 percent of the world’s
continental shelves.
Turbidite Deposits
• Wave action and ocean current systems could carry
•
•
coarse material beyond the continental shelf into the
deep- ocean basin, there is evidence that much neritic
material has been deposited at the base of the
continental slope forming the continental rise. These
accumulations thin gradually toward the abyssal
plains.
Such deposits are called turbidite deposits and are
thought to have been deposited by turbidity currents
that periodically move down the continental slopes
through the submarine canyons, carrying loads of
neritic material that spreads out across the continental
rise.
Turbidite deposits are composed of characteristic
layering called graded bedding.
Glacial Deposits
• Poorly sorted deposits containing particles of all sizes,
•
•
from boulders to clays, may be found in the highlatitude portions of the continental shelf.
These glacial deposits were laid down by melting
glaciers that covered the continental shelf area during
the Ice Age, when glaciers were more widespread than
today and sea level was lower.
Glacial deposits are still forming around the continent
of Antarctica and around the island of Greenland by ice
rafting.
Carbonate Deposits
• During the geologic past, deposits of limestone (CaCO3)
in the marine environment appear to have been
widespread and indicate shallow, warm water
conditions.
Pelagic deposits
• Pelagic deposits are composed of fine-grained material
•
•
that accumulates at a slow rate on the deep-ocean floor.
Biogenous ooze is the most common type of pelagic
deposit. The reason is because there is so little
lithogenous sediment deposited at great distances from
the continents.
In areas deeper than about 4.5 kilometers (3 miles),
there is very little biogenous sediment, and fine-grained
lithogenous sediment dominates the deeper regions of
the ocean floor. In shallower pelagic areas, biogenous
and hydrogenous components are abundant.
Pelagic Deposits
((Deep-Ocean Sediments))
Pelagic Deposits
Biogenous Oozes
Siliceous Oozes
Abyssal Clay
Carbonate Oozes
Biogenous Oozes
• At somewhat shallower depths than those where abyssal clay
•
•
•
•
•
forms, biogenous ooze is a significant portion of the
sediment.
It consists of at least 30 percent biogenous material from the
hard tests of microscopic organisms.
The rate of accumulation of biogenous material on the ocean
floor depends on three fundamental processes-productivity,
destruction, and dilution.
Productivity is the amount of organisms present in the
surface water above the ocean floor.
Destruction of skeletal remains occurs by dissolving in
seawater at depth.
Dilution refers to the inability of oozes to form where other
sediments keep the amount of biogenous test material below
30 percent of the sediment.
Siliceous Ooze
• Siliceous ooze contains at least 30 percent of the hard
•
•
remains of silica-secreting organisms. If accumulations
consist mostly of diatoms, diatomaceous ooze is
produced.
The ocean is under-saturated with silica at all depths, so
seawater continually but slowly dissolves silica. One
way is to accumulate the siliceous tests faster than
seawater dissolves them.
siliceous ooze is commonly found in areas below surface
waters with high biologic productivity of silicasecreting organisms .
Calcareous ooze
• Calcareous ooze contains at least 30 percent of the hard
•
•
remains of calcareous-secreting organisms.
If accumulations consist mostly of coccolithophores,
coccolith ooze is formed.
If foraminifers abound, it is called a foraminifer ooze.
Calcium Carbonate In Modern Surface
Sediments Of The World’s Oceans
Abyssal Clay
• Abyssal clay is composed of at least 70 percent by
weight clay-sized particles derived from the continents
and carried by winds or ocean currents.
Distribution of
Neritic and Pelagic Deposits
• Coarse-grained neritic deposits dominate continental
•
•
•
margin areas .
Abyssal clays dominate the deep-ocean basins.
Calcareous oozes are abundant on the relatively
shallow deep-ocean areas along the mid- ocean ridge.
Siliceous oozes are found beneath areas of unusually
high biologic productivity such as the Antarctic and
equatorial Pacific Ocean .
Distribution Of
Plagic And Neritic Sediments
Ocean Sediments as a Resource
Ocean Sediments
Petroleum
Sand and Gravel
Evaporative Salts
Phosphorite
Manganese Nodules
Offshore Drilling Rig
Petroleum
• The remains of microscopic organisms, buried within
marine sediments before they could decompose, are the
source of our most valuable marine resource-petroleum
(oil and natural gas). Of the nonliving resources
extracted from the oceans, more than 95 percent of the
value is in petroleum products.
Sand and Gravel
• This resource, which includes rock fragments and shells
•
of marine organisms, is mined by offshore barges using
a suction dredge. The resource is used primarily for resupplying recreational beaches, filling in areas on
which to build, and for use as an aggregate in concrete.
Some gravel deposits are rich in valuable minerals. For
example, diamonds are recovered from gravel deposits
offshore of South Africa and Australia. Other sediments
rich in tin have been mined for years from Thailand to
Indonesia. Platinum and gold have been found in
deposits in gold mining areas throughout the world,
and some Florida beach sands are rich in titanium.
Evaporative Salts
• When seawater evaporates, water is removed and the
•
salts remain. Once the salts increase in concentration,
they can no longer be held in solution. Consequently, the
salts precipitate out of solution and form salt deposits.
The most economically notable salts are gypsum and
halite.
Evaporite Salt
Phosphorite (Phosphate Minerals)
• Phosphorite is a sedimentary rock made of various
•
phosphate minerals, which contain the element
phosphorus, an important plant nutrient.
Phosphorite Occurs at depths less than 300 meters
(1000 feet) on the continental shelf and slope.
Manganese Nodules and Crusts
• Manganese nodules contain significant concentrations
•
of manganese and iron and smaller concentrations of
copper, nickel, and cobalt.
Of the five metals, cobalt is the only metal deemed
"strategic" to the United States, which means that it is
essential to national security. It is required to produce
dense, strong alloys with other metals for use in highspeed cutting tools, powerful permanent magnets, and
jet engine parts.
Mining Manganese Nodules