Ocean basins - marine sediments and the ocean floor
Earth's relief has 2 dominant levels
0.875 km above sea level = av height continents
3.729 km av deep ocean floor
General topographic features of the oceans - five major topographic divisions.
continental margin further subdivided into
- - shelf
- - slope
rise
trenches
abyssal plains
mid-ocean ridge
seamounts and guyots
Types of sediments
- classified on basis of depth of deposition
littoral = shore-line
shallow water
bathyal - continental slope
abyssal - in deepest parts of ocean
1- terrigenous or land derived. Mainly suppplied by rivers, less by wind and ice
- concentrated near shore lines (which have changed recently due to glacial melting)
- distributed by various currents
- - - along shore - contour currents
- - - outwards - turbidity currents
- coarser near land where material first dropped or where currents are active. Fine dust in deep ocean
2- chemical deposits with or without help from organisms
- often causes not clear - due to unique environments
- high evaporation = evaporites
- changes in temp, salinity, CO2 = carbonate mud
- cementing material for unconsolidated sediments are also chemical deposits
3- organic deposits
- shells or other protective and supporting structures of living organisms - both animal and plant
- near shore = mainly bottom living organisms
- at depth = organisms that float in near surface waters, hard parts sink to bottom and get preserved
relative importance of these different kinds of sediments depends on
abundance of organisms
abundance other types of sediments
tendency of shells (especially carbonate) to dissolve in deep water