Sediments Sediment thickness of ocean floor Very thin

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 Cobble Pebble Granule Sand Silt Clay >256 mm 64 -256 mm 4 – 64 mm 2 -4 mm 0. 062 – 2 mm 0. 004 – 0. 062 mm <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 shelves Continental slopes Continental rises Deep ocean floor 2. 5 Km 9 km 8 km 0. 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