Marine Sediments

Presented by: Derek Lumary Rudy Marmolejo

Jazmin Quijada

What is a Marine Sediment? Why are they important?

Marine Sediments are particles of organic or inorganic origins that accumulate, and are found within the ocean.

They reveal much about Earth’s history, such as providing clues to past geographic distributions of Marine Organisms, movements of the ocean floor, ocean circulation patterns, climate changes on Earth, and even global extinction events.

Sedimentary Rock The formation of sediments

When sediments become lithofied they form sedimentary rock.

Most rocks found on the continents are sedimentary rocks, which are uplifted onto land by the plate tectonic process.

Clues to sediment origin are found in its mineral composition and its texture, which is the size and the shape of its particles.

Collecting Marine SedimentsDredging

One way to collect Marine Sediments is through dredging, which is a process that involves using a bucket-like device to scoop up sediments.

Example: The techniques inefficient.

Collecting Marine Sediments Cont…Rotary Drilling

The other common method used is rotary drilling, which uses a hollow steel tube with a heavy weight on top that’s drilled into the sea floors in order to collect cores.

Lithogenous SedimentsDEFINITION: CHARACTERISTICS:

Lithos = Stone Generare = To produce Sometimes referred to as

Terrigenous Sediment.

It derives from pre-existing rock material that originates on the continents or islands from erosion, volcanic eruptions, or blown dust.

Origin They begin as rocks on continents or islands. Over time weathering agents such as water,

temperature extremes and chemical effects brake rocks into smaller pieces.

When rocks are in smaller pieces, they can be picked and transported.

This eroded material is the basic component of which all Lithogenous Sediment are composed.

•

Origin Cont…

This newly eroded material from the continents is carried to the oceans by streams, wind, glaciers, and gravity.

The greatest quantity of Lithogenous material is found around margins of the continents, where it is constantly moved by high-energy currents along the shoreline and in deeper turbidity currents.

Composition of Lithogenous Sediment

The composition of Marine Sediments reflects the material from which it was derived.

The majority of Lithogenous deposits such as beach sands are composed primarily of quartz.

Quartz is a major component of most rocks, it is resistant to abrasion, it can be transported long distances and deposited far from its source area.

Sediment Texture

Distribution of Lithogenous Sediment

Neritic Deposits

Found on continental shelfs and in shallow waters near islands.

Pelagic Deposits

Found in the deep ocean basins and are typically fine-grained.

Neritic Deposits Beach Deposits Made of whatever material is locally

available. They are composed mostly of quartz and transported by waves that crash into the shoreline.

Continental Shelf Deposits We relict (left behind) sediments from 3k-7k years ago that hasn’t been covered yet. These sediments presently cover about 70% of the world’s continental shelfs.

Neritic Deposits Cont… Turbidite Deposits These deposits are spread out as deep sea

fans due to turbidity currents. They are called Turbidite Deposits and are composed of characteristic layering called graded bedding.

Glacial Deposits Rock particles trapped in glacial ice are carried out to sea by icebergs that break away from costal glaciers. As the icebergs melt Lithogenous particles of many sizes are released and settle onto the ocean floor, this process is called ice rafting.

Pelagic Deposits Abyssal Clay Also referred to as red

clay due to oxidized iron. It’s composed of at least 70 % fine clay sized particles from the continents. It transports itself by ocean winds and ends up deep down in the ocean floor.

Biogenous SedimentsDEFINITION: CHARACTERISTICS:

Bio = Life Generare = to produce

It is derived from the remains of hard parts of once-living organisms.

The organisms that contribute to biogenous sediment are mainly algae (seaweed) and protozoans (primitive sea organisms).

Origin They begin as the hard parts of living

organisms (i.e. shells, bones, and teeth) ranging from small protozoan's to fish and marine mammals.

When organisms such as these die, their remains settle onto the ocean floor and can become biogenous sediments.

2 Classifications1) MACROSCOPIC BIOGENOUS SEDIMENT

2) MICROSCOPIC BIOGENOUS SEDIMENT

Sediments that are large enough to be seen without the aid of a microscope, such as shells, bones, and teeth of large organisms.

Sediments that contains particles so small they can only be seen through a microscope.

They produce tiny shells called “tests” that begin to sink after the organisms die and continually rain down on the ocean floor, which can accumulate on the deep ocean floor and form deposits called “ooze”.

Ooze is typically a fine-grained lithogenous clay that is deposited in the deep ocean.

2 Main Compositions of Biogenous Sediment

[1] Silica Most of the silica in biogenous ooze comes from microscopic algae called “diatoms” and protozoans called “radiolarians”.

Diatoms are mostly free-floating or planktons. When there is an abundance of diatoms on the ocean surface, thick deposits of diatom-rich ooze can accumulate on the floor.

Radiolarians are microscopic single-celled protozoans, most of which are also planktonic.

The accumulation of siliceous tests of diatoms, radiolarians, and other silica-secreting organisms produces siliceous ooze.

DIATOM

RADIOLARIAN

2 Main Components Cont…

{1} Foraminifers are single-celled protozoans, many of which are planktonic, ranging in size from microscopic to macroscopic. Ex: shells that can be found at the beach.

{2} Coccolithophores (aka nannoplankton) are single-celled algae, which are mainly planktonic. When this organism dies, the individual plates disaggregate and can accumulate on the ocean floor as coccolith-rich ooze. Eventually, as this ooze lithofies over time, it forms a white deposit called chalk, which is used for purposes such as chalk sticks for writing on chalk boards.

[2] Calcium Carbonate The two sources of calcium carbonate biogenous ooze are the foraminifers and microscopic algae called coccolithophores.

Deposits comprised primarily of tests of foraminifers, coccoliths, and other calcareous-secreting organisms are called calcareous ooze.

COCCOLITHOPHORES

FORAMINIFERS

The White Cliffs of Southern England

Distribution of Biogenous Sediments

The distribution of biogenous sediment on the ocean floor depends on three fundamental processes.

[1] Productivity, which is the number of organisms present in the surface water above the ocean floor.

[2] Destruction, which occurs when skeletal remains (tests) dissolve in seawater at depth.

[3] Dilution, which occurs when the deposition of other sediments decreases the percentage of the biogenous sediment found in marine deposits.

Distribution of Biogenous Sediments Cont…

Neritic Deposits

Although Neritic Deposits are mainly composed of lithogenous sediment, microscopic and macroscopic biogenous material can be found within lithogenous sediment in these deposits.

Pelagic Deposits

Microscopic biogenous sediment (ooze) common on the deep ocean floor because there is so little lithogenous sediment deposited at great distances from the continents that could dilute the biogenous material.

Neritic Deposits Carbonate Deposits Rocks from the marine environment

composed primarily of calcium carbonate are called limestones. Most limestones contain fossil marine shells, suggesting a biogenous origin. Ancient marine carbonate deposits constitute 2% of Earth’s crust and 25% of all sedimentary rocks on Earth

Stromatolites Are roundish structures consisting of fine layers of carbonate that form in specific warm, shallow-water environments such as the high salinity tidal pools in Western Australia. As layer upon layer of these algae colonize the surface, a bulbous structure is formed.

Pelagic Deposits Siliceous Ooze Siliceous Ooze

contains at least 30% of the hard remains of silica-secreting organisms. One way to accumulate siliceous ooze on the ocean floor is to collect the siliceous tests faster than seawater can dissolve them. This process and ooze is commonly found in areas below surface waters with high biologic productivity of silica-secreting organisms.

*HOW IT ACCUMULATES*

Pelagic Deposits Cont… Calcareous Ooze and the CCD Calcerous ooze contains at roughly about 30% of

hard remains of calcerous-secreting organisms. The destruction of calcium carbonate varies with depth. The depth in the ocean at which the pressure is high enough and the amount of carbon dioxide is great enough to begin dissolving calcium carbonate is called the lysocline. Below this, calcium carbonate dissolves at an increasing rate with increasing depth until the calcite compensation depth (CCD)

is reached. Currently there has been an increase in ocean acidity due to higher levels of

atmospheric carbon dioxide caused by human-caused emissions. Aside from this, sea floor spreading causes the newly created sea floor and the

calcerous sediment on top of it to move into deeper water away from the ridge, eventually being transported below the CCD.

SEA FLOOR SPREADING AND SEDIMENT ACCUMULATION

Hydrogenous Sediments Hydrogenous Sediments are derived

from dissolved material in the water or are formed by the interaction of substances dissolved in water.

Manganese Nodules Rounded lumps of manganese, iron,

and other metals. When cut in half they reveal a

layered structure around a central object.

Phosphates Occur as coating on rocks and as

nodules. Typically found on the continental shelf and on banks at depths shallower than 1000 meters.

Carbonates Hydrogenous carbonate deposits can

precipitate directly from sea water in tropical climates.

Metal Sulfides Metal sulfides come from hydrothermal

vents and black smokers along the mid ocean ridge.

Deposits of metal sulfides contain nickel, iron, copper, zinc, and silver.

These deposits can be found throughout the ocean floor due to sea floor spreading.

Evaporites Evaporites minerals form where ever

there is a dry climate and restricted open ocean circulation.

Cosmogenous Sediments Cosmogenous comes from the root words

• Comso: universe • Generare: to produce o Sediments is derived from extraterrestrial source Consists of two main types:Microscopic spherules Macroscopic meteor debris

Microscopic spherules

• Small globular masses • Composed of silicate rock material

Cosmogenous sediments are extraterrestrial in nature and are generally like miniature meteorites. These sediments are the remains of impacts of large bodies of space material (such as comets and asteroids). They are comprised of silicates and mixtures of different metals.

Other spherules are composed from iron and nickel which are formed in the asteroids belt between the orbits of mars and Jupiter and are produced when these asteroids collide.

These tektites which are molten rain down on earth and can form tektite fields.

When this material rains down on earth they form a general component of space dust or micrometeorites that float harmlessly throughout the atmosphere of earth.

About 90% of these micrometeorites are destroyed by frictional heating as they enter the atmosphere.

Estimates show as much of 300,000 metric tons of space dust reach earth surface each year, and about 22 pounds over second of everyday.

The space dust that lands on the ocean is dissolved by the seawater once it is touched.

Glassy tektites do not easily dissolve and sometimes they comprise minute portions of

various marine sediments.

The debris from the meteors is called meteorite material which settles around the impact site and is either composed of silicate rock material which is called chondrites or iron and nickel.

This happens when meteoroids collide on earth at a fast speed and much larger meteoroids release energy equivalent to the explosion of multiple nuclear bombs.

Comsogenous sediments are different from any other types of sediments.

Cosmogenous particles from outer space typically contain more nickel than those that originate in other ways.

Most of the nickel in the earth crust sank below the surface during density stratification early in earths history.

What Marine Sediments Do For Us1. Petroleum2. Sand & Gravel3. Evaporative salts4. Rare-earth Elements