Oceanography Chapter 11

fecal pellets

undigested food particles are packaged together in animal guts to form fecal material that is excreted, larger so they sink faster

Heinrich Layer

unusual sediments that were deposited during episodes of exceptionally low- surface temperatures

distributaries

water flows in a series of branching channels, these periodically flood and spread nutrient-rich sediment over the surface of the delta

A turbidite forms _____.

when a tubidity current flows down a submarine canyonalong the ocean floorwhere grain size progressively decreases upward

Red clays found in the deep ocean are deposited by _____.

wind

eolian transport

wind carries sediement to the ocean, desert region of North Africa, china, mongolia

pteropods and foraminifera

zooplankton that use calcium carbonate for their skeletal material

delta

A landform made of sediment that is deposited where a river flows into an ocean or lake

Maganese nodules

Dark brown, rounded lumps of rock. deep ocean floor, grow slowly (1-10 mm per million years) 30% manganese dioxide, 20% iron dioxide, up to 1% or 2% or copper, nickel, and cobalt, form around a lg sediment particle, then build layers

sorted

a well-sorted sediment deposit has a narrow range of grain sizes whereas a poorly sorted deposit has a broad range of grain sizes, deep ocean floor more sorted, continental margin coarser and less sorted

Ocean Sediments

accumulation of particles that collect on the ocean floor are known, the rate at which they accumulate depends on their source, composition, and size

hydrothermal minerals

are formed at hydrothermal vents, which are primarily located on or near oceanic ridges or undersea volcanos, rich in metals, iron, magnesium, copper, cobalt, lead, nickel, silver, and zinc

rivers that discharge onto active continental margins at subduction zones

are generally short and drain limited land areas between the coastline and the ridges of the coastal mountain ranges created by the subduction process, pacific coasts of North and South America, small loads or rock particles

hydrogenous sediment

are mineral particles that are chemically precipitated, often as a coating on other sediment particles, ocean water is altered to produce such sediment, other conditions are evaportes, carbonates (including oolites), hydrothermal minerals, manganese nodules, and phosphorite nodules and crust

ocean sediments

are mixed with varying proportions of lithogenous, biogenous, hydrogenous, and cosmogenous

turbidity currents

are similar to land avalanches, sediment accumulated on the continental shelf edge and slope until they become unstable, break loose, and flow down the continental slope, triggered by earthquakes, or large discharges of sediment by rivers, 70 km

Diatoms

are the dominant group of photoplankton that produces their shells out of silica

radiolaria

are zooplankton that produce silica skeletons, dominant source of biogenous sediment in highly productivity tropical areas

ocean acidification

as climate changes the ocean becomes more acidic, has shifted the CCD an estimated 50 to 200m shallower since the beginning of the industrial revolution

isotopes

atoms of any element may occur in several different forms

coarsest sediments transported by rivers toward the ocean are trapped and deposited in

bays, wetlands, estuaries, beaches, or deltas, 5% is on continental shelf or slope and very little sediment is transported beyond the continental margin, Mississippi, Ganges, Yangtze

bioturbation

bottom dwelling organisms rework, mix the upper= few centimeters of tens of centimeters of sediment as they consume organic matter or build burrows,their churring of the sediment is called bioturbation

skeletal and shell material of marine organism is either

calcareous (calcium carbonate) or siliceous (silica)

As water flows through the deep ocean and the CCD shallows, it becomes more acidic to _____.

calcareous shells

turbidity current

can travel long distances on the abyssal plain before finally depositing their entire terrigenous sediment load, 70 km, sediment avalanches in water

hydrothermal mineral deposits as the dominant sediment type

central basin of the Red Sea

classifications of Ocean Sediment

clay, silt, or sand and lithogenous (rock), biogenous(organisms or their remains) , hydrogenous(ocean water), and cosmogenous(outer space)

phosphorite nodules

composed of up to 30% phosphorite, form in limited areas of the continental shelf and continental slope and on some seamounts, low dissolved oxygen concentrations in bottom of waters and an abundant supply of phosphorus, upwelling high, falling detritus depletes oxygen and supplies large quantities of phosphorus slowly grow 1 to 10mm per year

siliceous ooze

composed primarily of the skeletal and shell material of diatoms and radiolaria, commonly found under regions of high surface productivity

pelagic deposits

consist of fine grained sediments that gradually accumulate particle by partical on the deep ocean floor

Calcareous oozes _____.

consist of the hard parts of coccolithophores, pteropods, and foraminifera are the most abundant of the pelagic oozes occur where the deep ocean is shallower than the carbonate compensation depth

Hydrogenous sediemnt

consists of particles that are chemically precipitated from ocean water

carnonate compensation depth (CCD)

depth of the ocean below which calcium carbonate skeletal and shell materials dissolve and do not accumulate, depends on pressure and temperature and concentration of dissolved carbon dioxide

hydrothermal vents

discovered in the late 1970s, surrounded by mineral rich sediment and they support a unique communities of organisms, many found nowhere else on earth

coccolithophores

dominant group of calcareous phytoplankton, spherical shells made of numerous individual calcium carbonate plates called coccoliths

biogeneous sediments

encompassing the excretions, secretions, and skeletal and shell remains of organisms, is composed of calcium carbonate or silica

deltas may form because

estuaries trap sediment deposited by rivers, common of the Atlantic coast of North America

tektites

formed from silicate rocks that are thought to be material blasted off other planets or the moon by meteorite impacts, 2.5 to 5 cm resemble lithogenous, tear drop and black

five natural transport mechanisms bring lithogenous sediment to the ocean

freshwater runoff, glaciers, waves, winds, and landslides

turbidite layers

graded beds of sediments on the abyssal ocean floor within which the largest grains are at the bottom and grain size progressively decreases upward

cosmogeneous sediment

grains consist of tiny particles that bombard earth from outer space

thickest sediment on earth is

high lithogenous sediment input including the Gulf of Mexico, Arabian Sea, Bay of Bengal, along the western coast of the African continent, can reach up to 20km thick

Biogenous sediment

high proportions of the grains are composed of the skeletal or shell material of marine organism, primarily plankton, detritus- non living particles from the surface layers

ratio of oxygen-18 to oxygen-16

in the shells or skeletal material of calcareous organisms in sediments is used to reconstruct past ocean temperatures

calcareous ooze

is make up of the hard parts of coccolithophores, pteropods, and foraminifera, confined to ocean water shallower than the carbonate compensation depth

stratigraphy

is the study of earth's history through investigation of the sediment layers beneath the ocean floor and on land where sediments have been compressed and converted into sedimentary rock

stratigraphy

is the study of earths history through investigation of the sediment layers beneath the ocean floor and on land.

90% of all what reach the ocean through rivers, and 80% is derived from

lithogenous sediment, derived from Asia, glaciers and ice sheets transport large amounts of this sediment

a majority of marine sediments are

lithogenous, derived from weathering and erosion of rock and usually composed of silicate minerals

ooze

made of pelagic deposit that is more than 30% biogenous by weight

sediments are dated using

magnetic, fossil, and radioisotope analyses

terrigenous

material eroded from land

ice rafts

materials is transported by icebergs that break off the glaciers

neritic deposits

mostly lithogenous sediments that dominate the shallow ocean along the continental margin

thinnest sediment

new crust of oceanic ridge and in deep ocean basins remote from land where surface layer productivity is low and the water column is deep enough that calcareous organisms are completely dissolved before reaching the ocean floor

lithogeneous sediment

particles are the product of weathering and erosion of terrestrial rocks by water and wind, running water or waves, freezing or thawing ice, plants or animals can cause chips of rock

ooids

ph rises, and as result calcium carbonate precipitates around suspended sediment in many area, collect in shallow water areas, sand sized grain with fish egg appearance

ocean sediments can provide a history of the

plate tectonics and climate changes extending back about 170 million years

radiolarian shells

prolific in tropical waters, and the rate to the sediment is much higher here than in other deep ocean mud areas, buried before being fully dissolved

sediment size, sorting, and composition

provide info on past environmental conditions

red clays

reddish or brownish sediments that consist predominantly of very fine-grained lithogeneous material, due to the oxidation of iron, pelagic particles that make it to deep ocean take a long time to get there oxidized the iron and turn color

most lithogenous sediment are transported to ocean by

rivers

evaporties

salinity progressively increases until the ocean water becomes saturated with salts, examples are the dead sea, the red sea, and persian sea

Which particle will sink the fastest in calm water?

sand grain

aggregates

settling rate can be enhanced when sediment grains stick together to form larger particles, heavier and larger so the settle faster

diatoms dominate

siliceous phytoplankton in upwelling areas except in the tropical upwelling zone where radiolaria dominate

suspended sediment

sink to the ocean floor when currents are slow or absent in response to gravity, they do not all sink at the same rate less dense they sink slower than denser particles

A diatomaceous ooze is commonly found in the _____.

southern ocean near antartica

A siliceous ooze is more common in the Pacific Ocean than a calcareous ooze because _____.

the CCD is shallower in the Pacific Oceanthe ocean is less corrosive to silica in the Pacific Ocean