CHAPTER 4 Marine Sediments Fig CO4 Marine sediments

CHAPTER 4: Marine Sediments Fig. CO-4

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

Sediment Origins Chapter 12 Pages 12 -10 to 12 -13 Types of Sediment n Sediments may be classified by origin based on four categories. n 1. Lithogenous sediments – Come primarily from l_____ e_____ carrying particles into the sea or from v_____ e_____. These are the majority of sediments. n Quartz and clay are the two most common materials along with feldspar. Volcanic islands contribute sediments of basalt and other volcanic materials. n 2. Biogenous sediments – Originate from L_____ O______ and cover a large areaof the seafloor. n S_____ and c_____________ are the materials that come from shells and hard skeletons of planktonic organisms. n 3. Hydrogenous sediments – Result from c_____ r____ within seawater n Minerals come out of solution and form particles that settle on the bottom. n Produces ferromanganese and phosphorite nodules. n Sources of dissolved minerals vary – submerged rock, new crust formation, hydrothermal vent water, river runoff. n 4. Cosmogenous sediments – Come from o____ s_____ consisting of cosmic dust and occasional impacts from asteroids and comets. n 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. 12 - 3

Lithogenous sediments Fig. 4. 5

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

Sediment Sizes n n n Chapter 12 Pages 12 -13 to 12 -15 Types of Sediment n 12 - 6 n n 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.

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

Lithogenous sediments n Sources of material: n V_______ ash (volcanic eruptions) n Eroded M_____ n W____-b_____ dust n Fine-grained material transported by deep ocean currents n Abyssal clay (red clay) n Oxidized iron

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

Biogenous marine sediments n either calcium carbonate (Ca. CO 3) n or silica (Si. O 2 or Si. O 2·n. H 2 O)

Silica in biogenic sediments n Diatoms (algae) n Photosynthetic n Diatomaceous Fig. 4. 7 a earth n Radiolarians (protozoans) n Use external food n Siliceous ooze Fig. 4. 7 b

Siliceous ooze n n Seawater undersaturated with silica Siliceous ooze commonly associated with high biologic productivity in surface ocean Fig. 4. 11

Calcium carbonate in biogenous sediments n Coccolithophores (algae) n n n Photosynthetic Coccoliths (nano-plankton) Rock chalk Fig. 4. 8 a

Calcium carbonate in biogenous sediments n Foraminifera (protozoans) n Use external food n Calcareous ooze Fig. 4. 8 c

Calcareous ooze and the CCD Fig. 4. 13 n n Scarce calcareous ooze below 5000 m in modern ocean Ancient calcareous oozes at greater depths if moved by sea floor spreading

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

Iron-manganese nodules n n n Fist-sized lumps of manganese, iron, and other metals Very slow accumulation rates Why are they on surface sea floor? Fig. 4. 15 a

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

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

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

Marine sediments often represent ocean surface conditions n T_______ n N_____ supply n Abundance of marine life n A_____ winds n Ocean c_____ patterns n V_____ eruptions n Major extinction events n Changes in c______ n Movement of t____ plates

How Scientists Study Sediments Chapter 12 Pages 12 -3 to 12 -6 The Study of Sediments n 12 - 24 Techniques and tools to study ocean sediments include: n Clamshell sampler – n Piston corer – n Drilling vessels – n Seismic tools –

Resources from marine sediments n Energy resources n Petroleum n Mainly n Gas n n from continental shelves hydrates Sand 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. 4 E