CHAPTER 4: Marine Sediments Fig. CO-4

Marine sediments Eroded rock particles and fragments Oceanographers decipher Earth history through studying sediments

Sediment Origins Sediments may be classified by origin based on four categories. 1. Lithogenous sediments – Come primarily from l_________ e_________ carrying particles into the sea or from v__________ e__________. These are the majority of sediments. Quartz and clay are the two most common materials along with feldspar. Volcanic islands contribute sediments of basalt and other volcanic materials. 2. Biogenous sediments – Originate from L_________ O___________ and cover a large areaof the seafloor. S_________ and c_________c_____________ are the materials that come from shells and hard skeletons of planktonic organisms. 3. Hydrogenous sediments – Result from c_________ r________ within seawater Minerals come out of solution and form particles that settle on the bottom. Produces ferromanganese and phosphorite nodules. Sources of dissolved minerals vary – submerged rock, new crust formation, hydrothermal vent water, river runoff. 4. Cosmogenous sediments – Come from o________ s_________ consisting of cosmic dust and occasional impacts from asteroids and comets. They settle through the air as the others do through water. About 15,000-30,000 metric tons of space dust settle on the Earth each year; least abundant of the sediments. Types of Sediment Chapter 12 Pages 12-10 to 12-13

Lithogenous sediments Fig. 4.5

Lithogenous sediments Most lithogenous sediments at continental margins Coarser sediments closer to shore Finer sediments farther from shore Mainly mineral quartz (SiO2)

Sediment Sizes Sediments are classified on grain size – the diameter of the particle. Most sediments are composed of three sizes 1. Smallest= 2. = 3. = -------- 4. 5. 6. 7. Decomposed organic matter= Grain size and current velocity affect the deposition and erosion of sediment. Types of Sediment Chapter 12 Pages 12-13 to 12-15

Distribution of sediments Neritic Shallow water deposits Close to land Dominantly lithogenous Typically deposited quickly Pelagic Deeper water deposits Finer-grained sediments Deposited slowly

Lithogenous sediments Sources of material: V_______ ash (volcanic eruptions) Eroded M_________ W________-b_________ dust Fine-grained material transported by deep ocean currents Abyssal clay (red clay) Oxidized iron

Biogenous marine sediments Hard remains of once-living organisms S_______, b______, teeth, and diatom _____________ Tiny shells or tests settle through water column Biogenic ooze (30% or more tests) Mainly algae and protozoans

Biogenous marine sediments either calcium carbonate (CaCO3) or silica (SiO2 or SiO2·nH2O)

Silica in biogenic sediments Diatoms (algae) Photosynthetic Diatomaceous earth Radiolarians (protozoans) Use external food Siliceous ooze Fig. 4.7a Fig. 4.7b

Siliceous ooze Seawater undersaturated with silica Siliceous ooze commonly associated with high biologic productivity in surface ocean Fig. 4.11

Calcium carbonate in biogenous sediments Coccolithophores (algae) Photosynthetic Coccoliths (nano-plankton) Rock chalk Fig. 4.8a

Calcium carbonate in biogenous sediments Foraminifera (protozoans) Use external food Calcareous ooze Fig. 4.8c

Calcareous ooze and the CCD Fig. 4.13 Scarce calcareous ooze below 5000 m in modern ocean Ancient calcareous oozes at greater depths if moved by sea floor spreading

Hydrogenous marine sediments Minerals precipitate directly from seawater Manganese nodules Phosphates Carbonates Metal sulfides Small proportion of marine sediments Distributed in diverse environments

Iron-manganese nodules Fist-sized lumps of manganese, iron, and other metals Very slow accumulation rates Why are they on surface sea floor? Fig. 4.15a

Hydrogenous marine sediments Phosphates Phosphorus-bearing Occur beneath areas in surface ocean of very high biological productivity Economically useful: fertilizer Carbonates Aragonite and calcite Oolites

Hydrogenous marine sediments Metal sulfides Contain iron, nickel, copper, zinc, silver, and other metals Associated with hydrothermal vents Evaporites Minerals that form when seawater evaporates Restricted open ocean circulation High evaporation rates Halite (common table salt) and gypsum

Cosmogenous marine sediments Macroscopic meteor debris Microscopic iron-nickel and silicate spherules Tektites Space dust Overall, insignificant proportion of marine sediments

Marine sediments often represent ocean surface conditions N_________ supply Abundance of marine life A__________ winds Ocean c__________ patterns V__________ eruptions Major extinction events Changes in c___________ Movement of t________ plates

How Scientists Study Sediments Techniques and tools to study ocean sediments include: Clamshell sampler – Piston corer – Drilling vessels – Seismic tools – The Study of Sediments Chapter 12 Pages 12-3 to 12-6

Resources from marine sediments Energy resources Petroleum Mainly from continental shelves Gas hydrates Sand and gravel (including tin, gold, and so on) Evaporative salts Phosphorite Manganese nodules and crusts

Salt deposits Fig. 4.26

Manganese nodules Fig. 4.27

End of CHAPTER 4 Marine Sediments Fig. 4E