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 64-256 mm

• Pebble 4 –64 mm

• Granule 2-4 mm

• Sand 0.062 –2mm

• Silt 0.004 –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 sedimentby 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 nodulesPhosphorite nodules

Cosmogenous Sediments

• Extraterrestrial origin

• microtektites.

Distribution of Marine Sediments

• Neritic sediments

• Pelagic sediments

Average thickness of marine sediments

• Continental shelves 2.5 Km

• Continental slopes 9 km

• Continental rises 8 km

• Deep ocean floor 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