Sediments

Sediment thickness of ocean floor Very thin –Mid-Atlantic ridge Very thick –Smooth sea floor

Sediment Texture and color Grain size –Boulders to colloids Color –White or creamy – biological origin –Gray – high in silica –Red clay- iron oxide

Sediment classification by particle size Boulder>256 mm Cobble mm Pebble4 –64 mm Granule2-4 mm Sand0.062 –2mm Silt0.004 –0.062 mm Clay<0.004 mm

Types of sediment Well-sorted sediments –Particles of one size Poorly sorted sediments –A mixture of size

Sediment transport Rivers Glaciers Currents

Classification of Marine sediment by source Terrigenous Sediments Biogenous Sediments Hydrogenous Sediments Cosmogenous Sediments

Terrigenous (lithogenous) Sediments Originates on the continents –derived from igneous rocks Granite - the source of quartz and clay

Biogenous Sediments Made of siliceous and calcareous compounds –near continental margins

Hydrogenous Sediments Minerals that have precipitated directly from sea water Eg manganese nodules Phosphorite nodules

Cosmogenous Sediments Extraterrestrial origin microtektites.

Distribution of Marine Sediments Neritic sediments Pelagic sediments

Average thickness of marine sediments Continental shelves2.5 Km Continental slopes9 km Continental rises8 km Deep ocean floor0.6 km

Sediments of continental margins Terrigenous lithification

Sediment thickness of Deep- Ocean Basin Atlantic and Pacific abyssal plains oceanic ridges

Sediments of Deep Ocean Basin Turbidites Clays Oozes Hydrogenous Materials

Hydrogenous sediments Originate from chemical reaction Evaporites –Eg, calcium carbonate, –Calcium sulfate –Sodium chloride Oolite sand

Studying Sediments clamshell sampler piston corer

stratigraphy

Paleoceanography The study of the Ocean’s past

The Economic Importance of Marine Sediments crude oil natural gas