Oceanography Ch. 4 Marine Sediments

what are the marine energy resources associated with marine sediments?

*Petrolium: draw backs-oil spills *gas hydrates: also called clathrates -most common methane hydrates -occur beneath the arctic permafrost

what are the two main organisms that contribute to biogenies sediment?

COLD SURFACE WATER *algae(primarily aquatic,eukaryotic, photosynthetic ranging in size from micro-macro) *protozoans (any of the large groups of single-celled eukaryotic, not photosynthetic, microscopic)

what is one of the most common types of foraminifer ooze?

Globigerina ooze named for a foraminifer that is very common in the atlantic

what do most marine substances occur as?

MIXTURES

what are the two different classifications of biogenies sediment?

Microscopic (tiny shells called test-begin to sink after the organism dies, continuously rain down in great numbers) macroscopic(shells bones teeth)

what are two significant sources of calcium carbonate biogenies?

WARM SURFACE WATER foraminifers(close to radiolarians) coccolithophores(microscopic algea)

oolites

small calcite spheres 2mm or less in diameter, have layers like onions and form in some shallow tropic waters

How do these sediments help tell about past environments?

surface temperature nutrient supply abundance of marine life atmospheric winds ocean currents volcanic eruptions extinction events changes in earths climate

North Atlantic Ocean

the most climatically sensitive regions on earth, region experienced abrupt changes due to fluctuations of freshwater melting glaciers

Paleoceanography

the study of how the ocean atmosphere and land have interacted to produce changes in ocean chemistry, circulation, biology, and climate

where is sediment thickest? thinest?

thickest in older sea floor thinnest in the newest sea floor by the mid-ocean ridge

what is upwelling?

when deep-ocean water comes to the surface and supplies nutrients that stimulate high rates of biological productivity

carbonite

widley used in the construction industry and medically as calcium supplements

How are Marine sedimentary deposits categorized?

*Neritic Deposits( course grain, found on continental shelfs) -Beach Deposits:whats locally available, waves crash into shoreline and transport sediment -continental shelf deposits: sediment called relict sediments deposited 3000-7000 years ago have not been covered by new sediment: cover 70% of the worlds continental shelves -turbidite deposits:spreads down to deep sea fans comprises the continental rise -Glacial deposit:poorly sorted deposits containing particles ranging from boulders to clays-ice rafting: rock particles trapped in the glaciers carried out to sea by icebergs, melt then large unsorted rocks released *Pelagic Deposits (deep-ocean basin, fine grained) -volcanic eruptions, windblown dust, and fine materials that are carried to the deep ocean -abyssal clay: composed of at least 70% fine,clay sized particles from the continents -commonly red-brown because they contain oxidized-iron

Phosphates

*abundant as coatings on rocks and as nodules on the continental shelf in depths less than 1000m *valuable to fertilizer

Lithogenous sediment

*derived from pre-existing rock material that originates on the continents or island from erosion, volcanic eruptions, or blown dust also sometimes called (terrigenous sediment) *break large rocks apart due to weathering agents -water -temperature extrmemes -chemical effects (when rocks are in smaller pieces they can eroded and transported more easily) *greatest amount found around the continents where it is constantly moved by high-energy currents along the shoreline *low energy currents distribute finer components that settle out onto the deep-ocean basin. *tend to be finer greater distances from shore

biogenous sediment

*derived from the remains of hard parts of once-living organisms *begins as the hard parts of living organisms when they die get sent to the bottom of the ocean floor *one of the most common types of pelagic deposits

Sediments

*eroded particals and fragmented dirt, dust, and other debris *over time sediments can be lithified(turned into rock) sedimentary rocks *texture:the size and shape of its particles

diatoms

*free floating (planktonic) *builds a gas green house out of silica as a protective covering and lives inside

what are examples of places where calcium carbonate is currently forming?

*great barrier reef, Persian gulf, Bahama banks

what are some uses of of diatomaceous earth? and what are some characteristics it has?

*light weight, resistant to high temperatures, has excellent filtering properties *uses -filters -mild abrasives -absorbents -chemical carriers

what rock is composed primarily of calcium carbonate? and what does it contain usually?

*limestone * fossil marine shells

stromatolites

*lobate structures consisting pf fine layers of carbonate that form a specific warm, shallow-water environments ex) high salinity tidal pools in shark bay, australia *structure produce by cyanobacteria by trading fine sediments in mucous mats

Radiolarians

*often have spikes of rays protruding from their siliceous shells * not photosynthetic *typically have well developed symmetry called "snowflakes of the sea"

manganese nodules

*rounded hard lumps of manganese, iron, and other metals typically 5cm in diameter max to 20cm *found in deep ocean floor concentrations *when cut in half they ofter have layers formed by precipitation around a central object *not sure how they form *but formation requires extremely low levels of lithogenous and biogenies sediment *major component manganese dioxide and iron oxide

Foraminifers

*single-celled *do not photosynthesis *tests are hard and have a segmented test and have prominent openings in one end *resembles large shells you find at the beach

Coccolithophores

*single-celled algae, most of which are planktonic *produce thin shields made of calcium carbonate *photosynthesize *nanoplankton *when it dies it forms coccolith-rich ooze creating chalk! *chalk found in the white cliffs of southern england

cosmogenous sediments 2 main types?

*spherules-small globular masses: show evidence of being formed by extraterrestrial impact events ejecting small molten pieces of crust into space called Tektites.(made of silicate) other rocks made of iron and nickel form between mars and jupiter produced when astroids collide *macroscopic meteor debris- rare on earth. debris called meteorite material composed of silicate rocks called chondrites or iron and nickel called irons.

What creates ooze?

*the microscopic test accumulating on the deep-ocean floor 30% biogenies test material by weight and 70% lithogenous clay *More micro than macro ooze on the ocean floor by volume

Processes for collecting marine sediments

*used dredge early on but ineffective because it disturbed many sediments, couldn't go very deep, often didn't work *Next used gravity corer: hollow steel tube with a heavy weight on top- thrust into the sea floor to collect the first cores * Rotary drilling used today collects cores from the deep parts of the ocean

what is lysocline? CCD?

*when depth in the ocean where the pressure is high enough and the amount of carbon dioxide in deep-ocean waters is great enough to begin dissolving calcium carbonate. AVG depth 4000m *CCD(calcite compensation depth) the point below the lysocline calcium carbonate disspolves at an increasing rate with an increasing depth until this point is met.

when does precipitate occur?

*when there is a change in conditions *such as a change in temperature or pressure or the addition of chemically active fluids

what are the 3 fundamental processes that determine the distribution of biogenous sediment?

1) productivity (how many organisms are present in the water above the ocean floor) 2)destruction(occurs when skeletal remains dissolve in seawater at depth 3)dilution(occurs when deposition of other sediment decreases the percentage of biogenies sediment or the ooze)

what do these cores help us do?

1) the age of the ocean floor increased progressively with the distance from the mi-ocean ridge 2) sediment thickness increased progressively with distance from the mid-ocean ridge 3) Earths magnetic field polarity reversals were recorded in the ocean floor rocks

How is sediments transported?

1)wind 2)stream 3)glacier 4) Gravity

how much of the ocean floor is covered in neurotic deposits? Pelagic? Calcareous ooze? abyssal clay?

1/4(continential) 3/4(biogenous calcereous oozes) 48% of the worlds deep-ocean floor 38%

Classification of marine sediments

TABLE 4.1 1)Lithogenous *rock fragments, quartz sand,volcanic ash *rivers coastal erosion, glaciers, turbidity currents, windblown dust, rivers, volcanic eruptions *found in continental shelf, Abyssal plains 2)Biogenous *Calcium Carbonate -calcareous ooze (microscopic) -shells and coral fragments(microscopic) -warm surface water -coral reefs -Low latitude regions *Silica -Siliceous ooze -cold surface waters -diatoms(algea) -radiolarians (protozoans) -High latitude regions 3)Hydrogenous *metal sulfides, Phosphorite -precipitations of dissolved materials directly from seawater due to chemical reactions -abyssal plain, continental shelf, shallow shelf 4)Cosmogenous *Iron nickel *space dust meteors *localized near meteor impact sights, mixed with all types of sediment

what are the two most important carbonite minerals in marine sediment?

arogonite calcite

metal sulfides

associated with hydrothermal vents and black smokers along the mid-ocean ridge

Grain size

boulders cobbles pebbles granules sand silt clay (tend to stick together by cohesive force when deposited) *sediment size proportional to the energy needed to lay down a deposit *sorting-selectivity of the transportation process

what are the two most common chemical components in biogenies sediment?

calcium carbonate (CaCO3) silica: compounded with water to produce a hydrated form also called opal

Calcareous ooze

composed of foraminifers, coccoliths, and other calcareous-secreting organisms * when it consists of mostly coccolithophore called coccolith ooze *when it consist of mostly foraminifers it is called foraminifer ooze

hydrogenous sediment

derived from the dissolved material in water

evaporites

form where there are high evaporation rates accompanied by restricted open ocean circulation ex) mediterranean sea thick layers on the ocean floor indicate that the sea completely dried up in geologic past

what has caused the oceans to be more acidic?

higher concentrations of carbon dioxide in the atmosphere have led to increased amounts of dissolved CO2 in the ocean

where is biogenies sediment most common?

in the deep-ocean floor because it is far away from the continents so there is a less likely chance of it being diluted by lithogenous sediment

what happens when the ooze from diatoms lithifies?

it becomes diatomaceous earth, a lightweight white rock composed of diatom test and clay

Where does most of the silica in biogenies ooze come from?

microscopic algea:diatoms (need strong sunlight) Protozoans: radiolarians

what are all rocks composed of?

minerals

what is one of the most abundant and chemically stable minerals?

quartz *major component of most rocks *resistant to abrasion, can be transported long distances *most sediment transported by winds

what do sudden released of methane hydrates cause?

seismic sea waves, tsunami

what is siliceous ooze composed of?

siliceous test of diatoms and radiolarians organisms *when it is mostly diatoms called diatomaceous ooze *when it is mostly radiolarians it is called radiolarian ooze *when it consists on mostly silicoflagellate called silicoflagellate ooze