MAST382 Lecture Notes - Lecture 7: Terrigenous Sediment, Coccolithophore, Radiolaria
21 Sep 2016
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Document Summary
170 million years: age of oldest seafloor. Human civilization has altered the steady state of biogeochemical cycles of many elements by: Releasing contaminants that cause acid rain and promote leaching. Releasing that has dissolved in the oceans and made them more acidic. Lithogenous - fragments of rock from terrestrial sources. Biogenous - remains of marine organisms, hard parts. Radiolarians are abundant in tropical areas, they have siliceous hard parts. Phytoplankton- performed in upper 200m of water. Regional variations: at low latitudes many photosynthetic species have no hard parts but coccolithophores may be abundant. They have small calcareous plates that contribute extremely fine particles to the sediment. Siliceous - hard parts of silica in the form of opal which has the same basic composition as glass. Accumulation can be affected by water chem and depth. Rate of dissolution of silica is slow at all depths but decreases even further w depth through the upper 2km.
