Marine sediments  Eroded rock particles and fragments  Transported to ocean  Deposit by settling through water column  Oceanographers decipher Earth’s history through studying sediments

Classification of marine sediments  Classified by origin Lithogenous Lithogenous (derived from land) Biogenous Biogenous (derived from organisms) Hydrogenous Hydrogenous (derived from water) ○ Also known as Authigenic Cosmogenous Cosmogenous (derived from outer space)

Lithogenous sediments  Eroded rock fragments from land  Reflect composition of rock from which derived  Transported from land by Water (e.g., river-transported sediment) Wind Ice/glacier Gravity

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

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

Distribution of sediments  Neritic ○ Found on continental shelves and shallow water ○ Generally course grained  Pelagic ○ Found in deep ocean basins ○ Typically fine grained

Distribution of sediments  Neritic Shallow water deposits Close to land Dominantly lithogenous Typically deposited quickly

Distribution of sediments  Pelagic Deeper water deposits Finer-grained sediments Deposited slowly Sources of fine pelagic lithogenous sediments: ○ Volcanic ash (volcanic eruptions) ○ Wind-blown dust ○ Fine-grained material transported by deep ocean currents

Pelagic lithogenous sediments  Abyssal clay (red clay) At least 70% of clay-sized grains from continents Transported by winds and currents Oxidized iron – gives reddish color Abundant if other sediments absent /album/Whittington/16NA241%20G5%20Closeup%20on%20red%20clay%20bleeding% 20into%20lighetr%20soil.jpg

Biogeneous marine sediments  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

Biogeneous marine sediments calcium carbonate silica  Commonly either calcium carbonate (CaCO 3 ) or silica (SiO 2 or SiO 2 ·nH 2 O) planktonic  Usually planktonic (free- floating) ○ When the plankton die, they settle on the bottom

Silica in biogenic sediments  Diatoms  Diatoms (algae) Photosynthetic Where they are abundant, thick deposits accumulate when they die Diatomaceous earth – light white rock  Radiolarians  Radiolarians (protozoans) heterotrophic siliceous ooze  Produces siliceous ooze

Siliceous ooze  Seawater undersaturated with silica so continually dissolves back into water  Therefore, detectable “siliceous ooze” found in the sediments is commonly associated with high biologic productivity in surface ocean because once buried, they don’t dissolve easily

Calcium carbonate in biogeneous sediments  Coccolithophores (algae) Photosynthetic Coccoliths Coccoliths (nano- plankton) Accumulation of dead ones results in Rock chalk

Calcium carbonate in biogeneous sediments  Foraminifera  Foraminifera (protozoans) Heterotrophic Calcareous ooze Fig. 4.8c

Carbonate deposits (CO 3 )  Stromatolites Warm, shallow- ocean, high salinity Cyanobacteria Fig. 4.10a Limestone Limestone Lithified carbonate sediments White Cliffs of Dover, England is hardened coccolithophore ooze CaCO 3

Hydrogenous marine sediments  Minerals precipitate directly from seawater Manganese nodules Manganese nodules Phosphates Phosphates Carbonates Carbonates Metal sulfides Metal sulfides  Small proportion of marine sediments  Distributed in diverse environments Deep sea ferromanganese nodules on the floor of the South Pacific Ocean (individual nodules are 5-10 cm diameter).

Hydrogenous marine sediments  Phosphates Phosphorus-bearing apatite sedimentary rock Occur beneath areas in surface ocean of very high biological productivity  phosphates released into interstitial water by decomposition Economically useful: fertilizer A phosphate mine in Hardee County in central Florida. Seventy-five percent of the phosphate used in the United States comes from the region.

Hydrogenous marine sediments  Carbonates (CaCO 3 ) Aragonite and calcite ○ Calcite found in limestones, marbles, chalks ○ Used in antacids, toothpaste ○ Aragonite (marine shells) is less stable and reverts to calcite crystalline form over time ○ Used in cement, fertilizer Oolites ○ Small, round calcite spheres found in shallow, tropical waters with high carbonate concentrations ○ Small, used in aquariums Calcit e Aragonit e eatSaltLakeSand.jpg/variant/medium Oolitic sand

Hydrogenous marine sediments  Metal sulfides Contain iron, nickel, copper, zinc, silver, and other metals Associated with hydrothermal vents php

Hydrogenous marine sediments  Evaporites Minerals that form when seawater evaporates Restricted open ocean circulation High evaporation rates Halite (common table salt) and gypsum e/GypsumSelenite.JPG

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

Mixtures of marine sediments  Usually mixture of different sediment types For example, biogenic oozes can contain up to 70% non- biogenic components  Typically one sediment type dominates in different areas of sea floor HuZspT7SM/Zou+zou's+mud+2.JPG

Marine sediments often represent ocean surface conditions  preserves record of past Temperature Nutrient supply Abundance of marine life Atmospheric winds Ocean current patterns Volcanic eruptions Major extinction events Changes in climate Movement of tectonic plates

Retrieving sediments  Dredge  Gravity corer  Rotary drilling  Deep Sea Drilling Program  Ocean Drilling Program  Integrated Ocean Drilling Program

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 Ultra-Deep Oil Drilling, capable of drilling in 10,000 feet of water and penetrating 30,000 feet through earth’s crust.

Other reasons to study sediments  Contaminants in water column will sometimes settle in the sediment ○ Conditions that effect toxicity of sediments - Sediment type - Sediment texture (in fine sediment, there is more surface area for toxins to adhere, increasing toxicity) - Dredging and other human activity ○ Sediment Toxicity in Indian River Lagoon

Misconceptions – what have we learned that make these statements false?  Carbon is only produced by trees.  The bioshpere has never caused major changes in the other spheres that make up the Earth system, such as the rocks and air.  Few products we use everyday have anything to do with taking rocks and minerals from the ground.  We will never run out of natural resources such as coal, oil, and other minerals.

Ocean Literacy Principles  1g. - The ocean is connected to major lakes, watersheds and waterways because all major watersheds on Earth drain to the ocean. Rivers and streams transport nutrients, salts, sediments and pollutants from watersheds to estuaries and to the ocean.  1h. - Although the ocean is large, it is finite and resources are limited.