Sediments Flashcards
what are marine sediments formed from
from weathered rock which gets transported to ocean by air/water
is erosion/deposition equal
no because of plate tectonics, sediments squeezed at subduction zones mountains eroded into sea
how to classify sediments
grain size
what is mud
silt and clay, fine
what are most common sediments in sea
mud/sand
what does grain size/sorting show
how it was transported/deposited
textural maturity
particles round overtime, sorting increases
factors controlling deposition
energy of transport, material, size
slow eroded rock
small/fine grain, well sorted, mature, mud/clay separated
fast eroded rock
high energy, large grains, not well sorted, gravel/sand mixed
high energy conditions
fine grains suspended, large grains roll, large grains deposited
low energy conditions
large grains too heavy to suspend, fine grain deposited
the larger the particle…
the larger the velocity needed to move it
why does clay need more energy then sand
clay sticks together so needs more energy to break apart
terrigenous/lithogenic
produced from weathered rocks, reflects composition of rocks where it was eroded, then gets transported by air/wind/ice
biogenous
produced from hard shells of organisms, macroscopic (bones), microscopic (shells, small)
hydrogenous
precipitated from water near seafloor, manganese nodules
volcanogenic
ejected from volcanoes
cosmogenic
from space
where is most terrigenous/lithogenic sediment found
continental margins
what does biogenic sediments do
settle on ocean and rains down ocean
biogenic ooze
when biogenic sediment clumps together and forms ooze (organisms dissolve), 30% is ooze, rest is mud
what happens after an organism dies
it sinks to floor and forms fecal pellat
calcareous ooze
CaCO3, foraminifer, coccolithophores
silicious ooze
high productivity areas, diatoms, accumulates past CCD
deep ocean and CaCO3
its undersaturated with CaCO3, not enough calcium to combine with carbonate
calcite compensation depth
depth where CaCO3 dissolves so there’s none on seafloor
carbonate dissolution depends on…
temperature/pressure, rate of carbonate supply, acidity
lysocline
depth where CaCO3 declines rapidly
factors controlling distribution
productivity, dissolution, dilution
ferromanganese nodules
lumps of metal oxides that have precipitated around a nuclei, metals come from weathering of rock
phosphorites
needed for growth of organisms, high productive areas
evaporites
formed when water evaporates, minerals
metal sulfides
iron/nickel, hydrothermal vents
as you approach a continent there’s more…
terrigenous sediment
sources of deep sea sediment
terrigenous/biogenous
bulk emplacement
large amount of sediment transported (not grains), moved due to gravity, sediment build up causes instability/slope failure
slump
sediment piles slides downslope
mud flows (slurries)
mud/sediment mixed with water
turbidity currents
transport sediments to deep sea
pelagic sediment
fine terrigenous/biogenic sediment settled at bottom of ocean
inorganic
red clay
organic
oozes
continental shelf
flat plane of land underwater, where land meets sea
what is shelf sedimentation controlled by
tides/waves/currents
what happens to energy as depth increases
it decreases
what does shoreline turbulence do
prevents small particles from settling
where is calcareous ooze
tropics
where is sand/mud
temperate
subduction zones
squeeze sediment, creates prism
ice rafting
bulk emplacement of terrigenous sediment, large ice fragments broken off glaciers
as seafloor spreads…
ooze accumulates at top of ridge and gets buried/lithified and turns into limestone, as plate spreads it goes past CCD and ooze dissolves, pelagic mud forms and buries limestone protecting older limestone
as continents move apart…
sediments fill gaps as plates move, terrigenous sediment eroded by continent accumulates on shelf causing it to widen, sediment weighs continent down/sinks so sediment can be deposited
Atlantic margins
build up of sediment balances out subsidence, as plate sinks it has enough room for sediment build up
pacific margins
same as subduction zones
