Sediment What are Marine sediments n n Eroded

Sediment

What are Marine sediments? n n Eroded rock particles and fragments Transported to ocean Deposit by settling through water column Oceanographers decipher Earth history through studying sediments

Two types of Weathering…… Break down of rocks, soils and minerals through direct contact with the planet's atmosphere. 1. Physical Weathering heat, water, ice and pressure….

Physical Weathering Physical breakdown of rock: makes small chunks and surface area

2. Chemical Weathering soil p. H, temperature, precipitation, mineral composition of rock…

CO 2 Respiration H 2 O + CO 2 H 2 CO 3

Chemical Weathering

Chemical Weathering Congruent Weathering--Results in only dissolved ions. Incongruent Weathering--Results in newly made clay minerals and dissolved ions.

Congruent Weathering n Limestone weathering Ca. CO 3 + H 2 O + CO 2 Calcite water carbon dioxide --> Ca 2+ + calcium ion 2 HCO 3 - bicarbonate ion Note: H 2 O + CO 2 --> H 2 CO 3 (called “carbonic acid”)

Florida sinkholes produced by dissolution o limestone by carbonic acid

Incongruent Weathering 2 Na. Al. Si 3 O 8 + 11 H 2 O + 2 CO 2 --> Feldspar 2 Na+ + sodium ion water carbon dioxide 2 HCO 3 - + 4 H 4 Si. O 4 + Al 2 Si 2 O 5(OH)4 bicarbonate ion silica kaolinite (clay)

Wentworth grain-size scale Gravel Diameter of grain Sand Mud

Sediment texture n Grain size n Proportional to energy of transportation and deposition

Why does the deep sea have all this fine grained material?

Why are beaches sandy?

Classification of marine sediments n Classified by origin n Terrigenous or Lithogenous n Biogenous n Hydrogenous n (AKA Authigenic) n Cosmogenous n Volcanogenous

Terrigenous sediments n Most lithogenous sediments at continental margins n Coarser sediments closer to shore n Finer sediments farther from shore. n Mainly mineral quartz (Si. O 2).

Terrigenous sediments n n n Eroded rock fragments from land Reflect composition of rock from which derived Agents of Transport n n Water (e. g. , river-transported sediment) Wind (e. g. , windblown dust) - aolian transport Ice (e. g. , ice-rafted rocks) Gravity (e. g. , turbidity currents)

Water

Wind can be an important agent of erosion Seawifs image showing dust (product of wind erosion) being carried out to sea from California

Relationship of fine-grained quartz and prevailing winds ~ fine grained clay particles from wind can make up about 38% of deep sea sediment

Turbidites Turbidity currents – deposit material further from coast than would be expected “underwater” landslide…. . http: //www. liveleak. com/view? i=c 45_1342620679

Biogenous marine sediments n Hard remains of once-living organisms • Shells, bones, teeth - Macroscopic (large remains) - Microscopic (small remains) Tiny shells or tests settle through water column Biogenic ooze (30% or more tests) Mainly algae and protozoans

Biogenous marine sediments Commonly either calcium carbonate (Ca. CO 3); Calcite n or silica (Si. O 2 or Si. O 2·n. H 2 O) n Usually planktonic (free-floating) n

Silica in biogenic sediments n Diatoms (algae) Photosynthetic n Diatomaceous earth n Radiolarians (protozoans) n Siliceous ooze n If 30% or more of sediment is made up of biogenic material –we call it ooze!

Calcium carbonate in biogenous sediments n Foraminifera (protozoans) n Calcareous ooze

Calcium carbonate in biogenous sediments n Coccolithophores (algae) n n n Photosynthetic Coccoliths (nanoplankton) Rock chalk