Why should we care about a
bunch of mud anyway?
Marine sediments provide records of marine and
terrestrial events/processes
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Marine Sediments I
Sediment types and sources
Marine microfossils record changes in climate
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Classification of Marine
Sediments – by grain size
Based on diameter of individual grains
Gravel
Sand
Silt
Mud
Clay
Based on source, or origin of formation
(transport) by rivers, wind, glaciers
also known as “siliciclastics
“siliciclastics”” – rich in silica (quartz, SiO2)
– biogenic – produced by organisms
skeletal hard parts (shells) of marine plankton
carbonaceous (carbonate, CaCO3) or siliceous (silica)
Sand
– Mud and sand
are most
common in the
oceans
– Gravel is rare
in the oceans
Mud is fun – just ask kids.
– terrigenous – derived from continents (terra firma)
weathering (chemical and physical breakdown) of land, erosion
Gravel
global ice volume and sea level
ocean temperatures and salinity
ocean stratification (layering) and circulation
even wind patterns!
Classification of Marine
Sediments – by origin
– UddenUdden-Wentworth classification (Wentworth, 1922)
– 4 main
categories:
– volcanogenic – ejected from volcanoes
– authigenic – derived directly from seawater
chemical or biochemical precipitates/evaporites
precipitates/evaporites
salt, iron (Fe) and manganese (Mn
(Mn)) nodules
Silt
volcanic activity
meteorite impacts
changes in ocean chemistry
desiccation of marginal seas
Clay
Note: phi (Φ) = –log2(size in mm)
– extraterrestrial or cosmogenous – micrometeorites
– anthropogenic – derived from human activity
a new part of the sedimentary record
plastics are a main constituent
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Distribution controls on
sedimentation – by origin
Distribution controls on
sedimentation – by grain size
Hjulströ
Hjulström’s Diagram graphs the relationship between particle size
and energy for weathering, transportation and deposition.
Average grain size in
sedimentary deposits is
proportional to velocity
(energy) of bottom
Weathering
currents at time of
deposition.
Following from A to B at
velocity of 100 cm/sec:
rain of organic matter
Continental
Shelf
shelf edge
& pla nkton s he lls
nt
Co
photic zone
aphotic zone
(no light belo w
about 200 m)
Co
n
0
Hydrothermal
Activity
chemical exchange
b etween hot rocks
and cold sea wa ter
Carbonate C ompe nsation De pth
tin
terrigenous sediments
mixed with
calcareous ooze
e nta
lR
ise
(in meters)
Oxyge n Minim um Zone
turbidity
currents
pe
Slo
al
nt
in e
– at A, clay and silt can be
transported but not
weathered – make sense?
– at B, medium sand can be
weathered and
transported
– at C, coarse gravel is
deposited
Water
Depth
oceanic divergence and
upwelling: ab undant nu trients,
high b iomass
calcareous ooze
1000
3000
Seamount
CCD
Spreading Center
CCD
red clay
Abyssal Plains
Fe-Mn nodules
100 note change
500 in scale
2000
siliceous ooze &
calcareous ooze
(CCD)
red clay
dark, organic-rich muds
4000
5000
6000
Fe-Mn nodules
siliceous ooze
& red clay
terrigenous sediments
mixed with
calcareous ooze
& siliceous ooze
terrigenous sediments near continents (source is continental rocks)
red clay carried to deep ocean by winds (as dust) and ocean currents
currents
biogenic calcareous and siliceous sediments in areas of high biological
production and high nutrient supply (near coasts & upwelling regions)
regions)
– calcareous ooze dominates near coasts and on high bathymetric features
features
– siliceous ooze dominates below carbonate compensation depth (CCD)
(CCD)
authigenic sediments (Fe(Fe-Mn nodules) in deep ocean basins
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