CHAPTER 4: Marine Sediments Fig. CO-4 S

Marine sediments Eroded rock particles and fragments Eroded rock particles and fragments Transported to or produced in the ocean Transported to or produced in the ocean Deposit by settling through water column Deposit by settling through water column Oceanographers decipher Earth history through studying sediments Oceanographers decipher Earth history through studying sediments S

Classification of marine sediments Classified by origin Classified by origin Lithogenous (derived from land) Lithogenous (derived from land) Biogenous (derived from organisms) Biogenous (derived from organisms) Hydrogenous (derived from water) Hydrogenous (derived from water) Cosmogenous (derived from outer space) Cosmogenous (derived from outer space) P

Lithogenous sediments Eroded rock fragments from land (origin) Eroded rock fragments from land (origin) Transported from land by Transported from land by Water (e.g., river transported sediment) Water (e.g., river transported sediment) Wind (e.g., windblown dust) Wind (e.g., windblown dust) Ice (e.g., ice-rafted rocks) Ice (e.g., ice-rafted rocks) Gravity (e.g., turbidity currents) Gravity (e.g., turbidity currents) P

BY PERCENT Transport Mechanism P

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Lithogenous sediments Fig. 4.5 S

Lithogenous sediments Most lithogenous sediments at continental margins Most lithogenous sediments at continental margins Coarser sediments closer to shore Coarser sediments closer to shore Finer sediments farther from shore WHY? Finer sediments farther from shore WHY? Mainly mineral quartz (SiO 2 ) Mainly mineral quartz (SiO 2 ) P

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distance = rate x time d = rt t = d/r = 4km/ 2.5cm/sec = 4,000m/ 2.5cm/sec =4,000m(100cm.m)/ 2.5cm/sec =400,000cm / 2.5cm/sec =160,000sec/ 24hr/day x 3600sec/hr =160,000sec/ 86,400sec/day =1.85 days S

Clay sinks 10,000 times slower than sank, so 1.8 days x 10,000 (or 10 4 ) = 18,000 days 18,000 days = 49.3 years 365 days/year S

Smaller particles have a larger SA/Vol. ratio, increasing the frictional drag (sinking rates) and making small particles sink more slowly than large particles S

Relationship of fine-grained quartz and prevailing winds Fig. 4.6b S

Brazos River Meets the Gulf of Mexico FLOCCULATION - THE JOINING TOGETHER OF ELECTRICALLY CHARGED CLAY PARTICLES WHICH SETTLE MORE RAPIDLY THAN INDIVIDUAL ONES S

Brazos River S

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Distribution of sediments Neritic Neritic Shallow water deposits Shallow water deposits Close to land Close to land Dominantly lithogenous Dominantly lithogenous Typically deposited quickly Typically deposited quickly Pelagic Pelagic Deeper water deposits Deeper water deposits Finer-grained sediments Finer-grained sediments Deposited slowly Deposited slowly UNDERSTANDING THE PROCESSES WOULD ALLOW YOU TO GENERATE THIS TABLE YOURSELVES S

Neritic lithogenous sediments Beach deposits Beach deposits Mainly wave-deposited quartz-rich sands Mainly wave-deposited quartz-rich sands Continental shelf deposits Continental shelf deposits Relict sediments Relict sediments Turbidite deposits Turbidite deposits Glacial deposits Glacial deposits High latitude continental shelf High latitude continental shelf S

Pelagic lithogenous sediments Sources of fine material: Sources of fine material: Volcanic ash (volcanic eruptions) Volcanic ash (volcanic eruptions) Wind-blown dust Wind-blown dust Fine grained material transported by deep ocean currents Fine grained material transported by deep ocean currents Abyssal clay (red clay) Abyssal clay (red clay) Oxidized iron Oxidized iron Abundant if other sediments absent Abundant if other sediments absent S

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

Biogenous marine sediments Commonly either calcium carbonate (CaCO 3 ) or silica (SiO 2 or SiO 2.nH 2 O) Commonly either calcium carbonate (CaCO 3 ) or silica (SiO 2 or SiO 2.nH 2 O) Usually planktonic (free-floating) Usually planktonic (free-floating) P

Silica in biogenic sediments Diatoms (algae) Diatoms (algae) Photosynthetic Photosynthetic Diatomaceous earth Diatomaceous earth P

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

Calcium carbonate in biogenous sediments Coccolithoph ores (algae) Coccolithoph ores (algae) Photo- synthetic Photo- synthetic Coccoliths (nanno- plankton) Coccoliths (nanno- plankton) P

S White Cliffs of Dover

Calcium carbonate in biogenous sediments Foraminifera (protozoans) Foraminifera (protozoans) Use external food Use external food Calcareous ooze Calcareous ooze P

Living Foraminifera S

Distribution of biogenous sediments Most common as pelagic deposits Most common as pelagic deposits Factors controlling distribution Factors controlling distribution Productivity Productivity Destruction (dissolution) Destruction (dissolution) S

Calcareous ooze and the CCD Warm, shallow ocean saturated with calcium carbonate Warm, shallow ocean saturated with calcium carbonate Cool, deep ocean undersaturated with calcium carbonate Cool, deep ocean undersaturated with calcium carbonate Lysocline--depth at which CaCO 3 begins to dissolve rapidly Lysocline--depth at which CaCO 3 begins to dissolve rapidly Calcite compensation depth CCD--depth where CaCO 3 readily dissolves Calcite compensation depth CCD--depth where CaCO 3 readily dissolves P

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

Distribution of calcareous oozes in surface sediments of modern seafloor S Why in these places?

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

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Iron-Manganese nodules Fist-sized lumps of manganese, iron, and other metals Fist-sized lumps of manganese, iron, and other metals Very slow accumulation rates Very slow accumulation rates Fig. 4.15a S

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Manganese nodules Fig S

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

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Microtektites - extraterrestrial S

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Mixtures of marine sediments Usually mixture of different sediment types Usually mixture of different sediment types For example, biogenic oozes can contain up to 70% non-biogenic components For example, biogenic oozes can contain up to 70% non-biogenic components Typically one sediment type dominates in different areas of the sea floor Typically one sediment type dominates in different areas of the sea floor P

Distribution of neritic and pelagic marine sediments Fig P

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