Importance of Sediments Economic Value –Oil, fossil fuels –Salt & Phosphorus deposits Determine shape & structure of Ocean bottom Strongly affect distribution of Benthic Organisms Chronological record of Earth’s history –Tectonic history –Climate history –Evolutionary history
Pteropods (calcareous – all latitudes) http://www.mbari.org/expeditions/
Dissolution Biogenous Particles Silica –Ocean is UNDERSATURATED with silica –Dissolution highest in surface waters Low Pressure High Temperature Accumulation in sediments occurs in: -Areas of very high productivity -Poles and upwelling zones (diatoms) -Tropics (Radiolarians)
Dissolution Biogenous Particles Carbonates Foraminifera (Calcite) – less soluble Pteropods (Aragonite) – More soluble –Dissolution is highest in Deep Waters High pressure Low temperatures Low pH (high C0 2 ) Carbonate Compensation Depth (CCD)
Carbonate Compensation Depth CCD varies with Latitude CCD varies between Oceans North Pacific: 1000m South Pacific: 2500m Atlantic: 4000m
Carbonate Compensation Depth New Deep Waters have low CO 2 conc. Old Deep Waters have high CO 2 conc. –Animal respiration –Decomposer activities Pacific Deep Waters are older than Atlantic Deep Waters
Carbonate Compensation Depth & Greenhouse Effect? CO 2 atmosphere, seawater & sediments are interrelated! Will increase in atmospheric CO 2 cause increase in dissolved seawater CO 2 ? Consequences of a shallow CCD? Release into atmosphere of dissolved carbonate sediments?
Hydrogenous Sediments Lower concentrations than Lithogenous and Biogenous sediments Ocean water usually is UNDERSATURATED, but.. –Hydrothermal Vent Minerals (metal rich sedim.) –Manganese Nodules (areas of low sedimentation) –Carbonate banks - CaCO 3 precipitates at: High Temperature Low Pressure High pH (low CO 2 ) –Caused by high productivity - photosynthesis