23-11-2012, 02:40 PM
Chemical Oceanography
Chemical Oceanography.ppt (Size: 958.5 KB / Downloads: 39)
Marine Bio-geochemistry and Sedimentation
Distribution of Marine Sediments
Carbonate Equilibrium and the CCD
Organic Carbon and Sediments
Bacterial Respiration and Subsurface Redox Zonation
Fe/Mn Nodule Formation
Three Main Sediment Types
Lithogenic – Physically supplied by weathering of sediments from continents, e.g. ice rafted sediment, terrigenous sands and muds, aeolian dust, sediments become finer away from source,
Biogenic – Biological inputs - mineral tests and shells, organic carbon, form oozes
Chemical (Authigenic) – diagenetic alteration of sediments, precipitation and dissolution of different minerals. e.g. dissolution of carbonate
In reality many sediments made up of mix of lithogenic, biogenic and chemical components
Lithogenic sediments
lithogenic particles are produced by weathering of rock and minerals from land
Transported by rivers, glaciers, and wind. Results in thickest seds at continental margins
Transport downslope by gravity-slumps and turbidity currents
Windblown (Aeolian) and volcanic Dust) Components-quartz 2-10 microns-deserts. Important in open ocean.
Ice-rafting- up to 2000km from Antarctica, N Atlantic and Arctic
Dissolution of Carbonate at Depth
Chemical processes modify biological (biogenic) sediments through the dissolution of CaCO3 and opal silica in deep water.
Temperature and pressure play a role in increasing the corrosiveness of deep waters
The other major control on carbonate dissolution is due to the creation of CO2 by the oxidation of organic matter
This creates bicarbonate ions at the expense of carbonate ions thereby driving the dissolution of carbonate tests.