origin and distribution of marine sediments what’s all that squishy muck at the bottom of the...
TRANSCRIPT
Origin and Distribution of Marine Sediments
Origin and Distribution of Marine Sediments
What’s all that squishy muck at the bottom of the ocean? What can we learn from it?
What’s all that squishy muck at the bottom of the ocean? What can we learn from it?
Marine Sediments are:Marine Sediments are:
Particles of various sizes derived from a variety of sources that are deposited on the ocean floor
A vast “library” recording geologic, oceanographic and climatic conditions
Remarkably complete compared to land
Particles of various sizes derived from a variety of sources that are deposited on the ocean floor
A vast “library” recording geologic, oceanographic and climatic conditions
Remarkably complete compared to land
Where do these come from?Where do these come from?
Inputs are:-- rivers-- atmosphere-- surface waters-- volcanoes (both on land and submarine) -- deep ocean water-- outer space
Inputs are:-- rivers-- atmosphere-- surface waters-- volcanoes (both on land and submarine) -- deep ocean water-- outer space
ClassificationsClassifications
By SizeClay -- Silt -- Sand -- Pebble -- Cobble
0.001 mm 1 mm 100 mm Effects of water velocity on transport:
rivers and near-shore vs open ocean
By SizeClay -- Silt -- Sand -- Pebble -- Cobble
0.001 mm 1 mm 100 mm Effects of water velocity on transport:
rivers and near-shore vs open ocean
Sediment TransportSediment Transport
Fluid velocitydetermines thesize of theparticles thatcan be moved
Fluid velocitydetermines thesize of theparticles thatcan be moved
Size SortingSize Sorting
ClassificationsClassifications
By Origin
Terrigenous -- from landBiogenous -- from life in the oceansHydrogenous -- precipitated from waterCosmogenous -- extraterrestrial
By Origin
Terrigenous -- from landBiogenous -- from life in the oceansHydrogenous -- precipitated from waterCosmogenous -- extraterrestrial
Terrigenous sediments (from land)Terrigenous sediments (from land)
RiversWinds (eolian)Glaciers (ice-rafted debris, IRD)TurbiditesSea level changes
RiversWinds (eolian)Glaciers (ice-rafted debris, IRD)TurbiditesSea level changes
River sediment loads (units 106 tons/yr)
River sediment loads (units 106 tons/yr)
Glacial (Ice-rafted debris)Glacial (Ice-rafted debris)
TurbiditesTurbidites
Rapidly-accumulated terrestrial sediments
Earthquake-triggered submarine avalanches
High velocity (~50 mph!), erosive events Good examples preserved on Mary’s
Peak
Rapidly-accumulated terrestrial sediments
Earthquake-triggered submarine avalanches
High velocity (~50 mph!), erosive events Good examples preserved on Mary’s
Peak
Turbidites (submarine avalanches)
Turbidites (submarine avalanches)
Sea Level ChangesSea Level Changes
Biogenous sediments (from living things)Biogenous sediments (from living things)
Calcareous (CaCO3)Foraminifera -- animalsCoccolithophores -- plants
Siliceous (SiO2)Radiolaria -- animalsDiatoms -- plants
Calcareous (CaCO3)Foraminifera -- animalsCoccolithophores -- plants
Siliceous (SiO2)Radiolaria -- animalsDiatoms -- plants
m = micron = millionth of a meter!
m = micron = millionth of a meter!
m = micron = millionth of a meter!
m = micron = millionth of a meter!
Productivity = skeletons and soft tissueProductivity = skeletons and soft tissue
Accumulation depends on production and preservation
SiO2 is preserved everywhere
CaCO3 is variable, depending on P, T, pH
Accumulation depends on production and preservation
SiO2 is preserved everywhere
CaCO3 is variable, depending on P, T, pH
Carbonate Compensation Depth
Carbonate Compensation Depth
Carbonate Compensation DepthCarbonate Compensation Depth
The depth at which carbonate input from the surface waters is balanced by dissolution in corrosive deep waters
In today’s ocean this depth (CCD) varies between 3 km (polar) and 5 km (tropical)
Thus, accumulation rates vary a lot!
The depth at which carbonate input from the surface waters is balanced by dissolution in corrosive deep waters
In today’s ocean this depth (CCD) varies between 3 km (polar) and 5 km (tropical)
Thus, accumulation rates vary a lot!
Accumulation Rates for Oozes Accumulation Rates for Oozes
Productivityreproduction of planktonic organisms
Preservationsilica dissolves only very slowlycalcium carbonate varies with depth
Rates are variable: <1 to 15mm/1000 yr
Productivityreproduction of planktonic organisms
Preservationsilica dissolves only very slowlycalcium carbonate varies with depth
Rates are variable: <1 to 15mm/1000 yr
Coastal waters are often highly productive, with abundant planktonic organisms thriving in the
surface waters.
Why then are biogenous oozes rarely found nearshore??
Coastal waters are often highly productive, with abundant planktonic organisms thriving in the
surface waters.
Why then are biogenous oozes rarely found nearshore??
the large input of terrigenous sediment to the continental margin overwhelms the biogenous component in the sediment.
the large input of terrigenous sediment to the continental margin overwhelms the biogenous component in the sediment.
Hydrogenous (from sea water)Hydrogenous (from sea water)
Metalliferous sediments at spreading ridges -- “black smokers”
Manganese nodulesEvaporites -- Salt deposits
Metalliferous sediments at spreading ridges -- “black smokers”
Manganese nodulesEvaporites -- Salt deposits
baseball to bowling ball size!
Cosmogenous (from outer space)Cosmogenous (from outer space)
Meteorites and cometsMeteorites and comets
Sediment AccumulationSediment Accumulation
Sediment successionSediment succession
Distribution of Marine SedimentsDistribution of Marine Sediments