what is the origin of the word sediments
sedimentum = settling, mainly of eroded particles, fragments of dust, dirt, debris
what is suspension settling
sediments settle out of water and accumulate on ocean floor
what do marine sediments provide?
a record of earth history, important resources, and they have origins from many sources.
what clues do marine sediments provide about earth’s history
organism distribution
ocean floor movements,
ocean circulation patterns
climate change
global extinction events
do mountains contain ocean sediments?
yes, tall mountains contain marine fossils because sediments lithify into sedimentary rock.
what are the types of sediments?
lithogenous, biogenous, cosmogenous, and hydrogenous
how is sediment collected
early exploration used dredges with bucket like devices.
modern exploration uses cores to get sediment columns, and rotary drilling which collects deep ocean sediment cores
what is the national science foundation
NSF formed Joint Oceanographic Institutions for Deep Earth Sampling (JOIDES) in 1963.
what institutions does JOIDES include
Scripps Institution of Oceanography
Rosenstiel School of Atmospheric and Oceanic Studies \n Lamont-Doherty Earth Observatory of Columbia \n University \n Woods Hole Oceanographic Institution
What is the deep sea drilling project
DSDP was initiated in 1966 on Glomar Challenger drilling ship. Core collection in deep water up to 6000 m (3.7 miles)
what did DSDP confirm
existence of sea floor sprading,
ocean floor age,
sediment thickness,
magnetic polarity reversals
when did the DSDP become the ocean drilling project
DSDP became ODP in 1985. JOIDES resolution replaced Glomar Challenger. Drilling rig to conduct rotary drilling up to 2100 m (6900 ft). drilled > 2000 holes.
What is the integrated ocean drilling program
IODP replaced ODP in 2003, can drill up to 7000 m (23k ft) into sea floor. Chikyu- new exploration vessel in 2007. Expedition to japan trench after 2011 earthquake.
paleoceanography
study of how ocean atm, and land interactions have produced changes in ocean chemistry, circulation, biology and climate.
what do marine sediments provide
marine sediments provide clues to past environmental conditions. cores of sediment collected from sea floor.
what can oceanographers learn about environmental conditions from sediment cores
timing of major extinctions
global climate change
plate movements
historical info about earth’s geology and biology
lithogenous sediments
composed of fragments of pre existing rock material, that originates on continents or islands from erosion, volcanic eruptions, or blown dust. also terrigenous sediments
biogenous sediments
composed of hard remains of dead marine organisms
hydrogenous sediments
composed of material that is dissolved in water and precipitates to form deposits.
cosmogenous sediments
composed of material of extra terrestrial origin
how do lithogenous sediments form
eroded rock fragments from land. reflect composition of rock from which it was derived. produced by weathering (water, temp changes, chemical effects).
how are small lithogenous particles transported
carried to ocean by streams, wind, glaciers, gravity. greatest quantity around continental margins. deposited in bays and lagoons. beach deposits along shoreline. can be carried beyond continental margin to deep ocean basin
lithogenous transport mechanisms
streams, wind, glaciers, gravity
where are coarser sediments?
closer to shore, finer are further.
what is the main mineral in sediments?
quartz, SiO2. it is one of the most abundant and chemically stable minerals in the Earth’s crust. it is resistant to abrasion, and as a result it can be transported large distances and deposited far from the source.
what is the wentworth scale of grain size for sediments
boulder, cobble, pebble, granule, sand, silt, clay
what does texture indicate about environmental energy
high energy (strong wave action) conditions predominate close to shore, large particles. Low energy conditions predominate in deep ocean basins = small particles.
neritic sediment
shallow water deposits, close to land, mainly lithogenous, deposited quickly, coarse grained.
pelagic sediment
deeper water deposits, finer grained sediments, deposited slowly
beach deposits
wave deposited quartz rich sands
continental shelf deposits
relict sediments
turbidite deposits
graded bedding
glacial deposits
high latitude continental shelf, forming by ice rafting around Antarctica and greenland.
what are pelagic deposits made of
volcanic ash, wind blown dust, fine material.
abyssal clay
70% of clay sized particles from continents. Red clay oxidized iron. abundant if other sediments absent
two types of biogenous sediment
macroscopic: visible, shells, bones, teeth , microscopic: tiny shells or tests, biogenous ooze, algae and protozoans
two most common chemicals in biogenous sediment
Calcium carbonate, silica.
diatoms
photosynthetic algae, silica, perforated for passage of substances.
radiolarians
single celled protozoans, long spikes. tests are shells of microscopic organisms.
diatomaceous earth
siliceous ooze lithifies into this.
foraminiferans and coccolithophores
nannoplanktons, photosynthetic algae.
rock chalk
formed in cretaceous period, lithified coccolith rich ooze. like white cliffs of S England (dover)
calcareous ooze
protozoans, coccoliths, and other calcareous secreting organisms
distribution of biogenous sediments
productivity: # of organisms in surface water above floor, destruction: skeletal remains (tests) dissolve in seawater at depth, dilution: deposition of other sediments decreases percentage of biogenous sediments
neritic deposits
lithogenous sediment, some biogenous. Carbonate deposits like limestone. fossil shells
stromalites
lobate structures consisting of fine layers of carbonate forming in warm shallow ocean with high salinity. cyanobacteria produce these deposits.
calcite compensation depth (CCD)
depth where CaCO3 dissolves easiest.
lysocline
depth at which a significant amount of CaCO3 begins to dissolve rapidly
where are high concentrations of calcareous ooze
along mid ocean ridge, little is found in deep ocean basins below CCD
environmental conditions for oozes
siliceous: cool, high latitudes. Calcareous: warm, low latitudes, dissolves below CCD.
hydrogenous sediments
precipitate out of a solution, formed when solids left behind after water evaporates.
precipitates
occur when salts or minerals precipitate directly from seawater, at mid ocean ridges . Examples: manganese nodules, phosphates, carbonates, metal sulfides
manganese nodules
slow accumulation rates, discovered in 1872 by HMS challenger, commercial uses. origin and formation is unresolved. unsure why they’re not buried by seafloor sediments. central object for nucleation (teeth, bone, rock, coral)
metal sulfides
Iron, nickel, copper, zinc, silver, associated with hydrothermal vents
evaporites
minerals that form when seawater evaporates. restricted open ocean circulation, high evaoporation rates. Mediterranean
cosmogenous sediments
microscopic spherules, macroscopic meteor debris.
tektites
molten space dust
are marine sediments mixed
yes, lithogenous and biogenous sediment rarely occur as absolutely pure deposits that do not contian other types of sediment
where is pelagic and neritic sediment distributed
neritic is near shore, covers 1/4 of sea floor. coarse grained deposits dominate continental margins (lithogenous)
pelagic is deep ocean basin: 3/4 of sea floor, biogenous
what is the most dominant sediment worldwide
calcareous ooze 45%,
abyssal clay 38%
siliceous ooze 8%
energy resources from sediments
petroleum: ancient remains of microscopic organisms. 95% of economic value of oceanic nonliving resources. >30% of world’s offshore resources.
gas hydrates
clathrates: high pressures squeeze chilled water and gas into ice like solid. methane hydrates most common