Sediments

What to Watch for? You will see the true face of the ocean floor Covered by sediments, gravel, silt and mud Sediment particles from land, from biological activity, and even from space Sediments can help us define what occurred in recent history in the ocean basin Sediment thickest at continental margins Thinnest over active oceanic ridges Sedimentary “memory” of ocean basin is short Think about Movement, transport, how did the sediment arrive, where did it come from, and how can we tell the story of the ocean basin Think about daily contact with marine sediment Building materials, pool filters, toothpaste, oil, natural gas, paint

Sediment Particles of organic or inorganic matter that accumulates in a loose, unconsolidated form.

Major Sediment Input to the Oceans Source Estimated Amount (109 tons/yr) Rivers 18.3 Glaciers and ice sheets 2.0 Wind blown dust 0.6 Coastal erosion 0.25 Volcanic debris 0.15 Groundwater <0.48

What do sediments look like? Depends where you are Atlantic ridge Sponges and corals may be growing over the dusting of sediment Smooth ocean floor Brittle stars feed off surface bacteria and fallen particles of organic sediment May see ripples if the bottom has swift currents Colors differ Biological Often white or cream colored Silica deposits Often gray Clays on the ocean floor Red due to oxidation Chocolate brown

Sediment Classifications Origin Size Gravel - Bigger than 2 mm Sand – .062 – 2 mm, Big in Ocean Terms Silt – .004 - .062 mm, Gritty on Teeth Clay - <.004 mm Use Size to Determine the Energy of the Environment Well sorted sediments Sediments mixture that contains sediments of one size Poorly sorted sediments Sediments mixtures that contains a variety of of sizes

Gravel Sand Mud (silt & clay) Sediment Type Diameter (mm) Boulder >256 Cobble 65-256 Pebble 4-64 Granule 2-4 Sand Very coarse 1-2 Coarse 0.5-1 Medium 0.25-0.5 Fine 0.123-0.25 Very fine 0.0625-0.125 Mud (silt & clay) 0.0002-0.004

Deep Sea Sedimentation The Deep sea has two main sources of sediment: External- terrigenous material transported to oceans via rivers and wind Internal-biogenic and authigenic from the sea.

Origin of the Particles (Genetic) Proposed by Sir John Murray and A.F. Renard while studying sediments during the Challenger expedition Terrigenous/Lithogenous – terra = Earth, generare = to produce From Earth Biogenous – Bio = life, generare = to produce From life Zebra Muscles Diatoms Hydrogenous/ Authigenic – Hydro = life, generare = to produce Precipitates chemically from sea water Iron Stains in Sink in regular water Cosmosgenous – cosmos = universe, generare = to produce Comes from Outer Space Micro meteorites

Origin Classification Terrigenous: Sands and mud produced by weathering and erosion of rocks on land. Biogenic: CaCO3 (calcium carbonate) and SiO2 (silica) muds and oozes composed of hard parts of organisms. Authigenic: formed by precipitation of minerals in seawater (Manganese (Mn) and Phosphorus (P) nodules). Volcanogenic: ejected from volcanoes (ash). Cosmogenous: pieces of meteorites that survive trip thru atmosphere.

Terrigenous Particles Coming from islands or nearby continents Most abundant = Granite Sources of quartz and clay in the oceans Earth’s crust is made of minerals Inorganic crystalline materials that have a specific chemical composition Both particles are small enough that they get transported to deep ocean floor Transportation?? How did they get there what was the Transport Agent… Rivers – Clay  Sand Mississippi River Delta: Birds Foot Trapped Near the Continents

How sediments reach deep ocean Turbidity Currents Density and Gravity pull particles down Slope Causes flatness of the abyssal plains Resistant sandstone - rubble Turbidity current deposit rubble

Terrigenous Particles Wind (Eolian) Covers Long Distances Small Grain Sizes Slow Accumulation

Sediments that wind transports from the Sahara Desert Africa's West Coast: Sediments that wind transports from the Sahara Desert

Terrigenous Particles Transportation Glaciers Deposits of sediment only happens when glaciers reach sea level Iceberg Rafting Rivers and streams Eloation

Biogenous Particles 2nd Most abundant source for sediments Coccolithophorid 2nd Most abundant source for sediments Skeletal Components Sediment Rich in skeletal material “ooze” Sample must contain more than 30% biogenic material Two Major Players CaCO3 Calcium Carbonate: Plants Foraminifera: Animals To make an “ooze” Production ~ Same everywhere Preservation ~ More soluble at high pressure and low temperature As it sinks carbonate needs shallower waters ~ 3500 – 4500 m starts to dissolve When carbonate no longer can be preserved = CCD carbonate compensation depth Little Dilution – Rapid input of Something else Get away from terrigenous areas Foraminifera

Foraminifera (zooplankton with CaCO3 shell)

White Cliffs of Dover

Biogenous Particles Silica Opal – SiO2 . n H2O Radiolarians Zooplankton Diatoms – Plants Radiolarians To make a Siliceous “ooze” Production ~ High Productivity Zones they Do Well Preservation ~ Entire Ocean is Under saturated with Silica Once animal dies it starts to be dissolved Preservation takes place with over whelming the system Make a lot so a Few can Survive Getting to the sediment is the key Micro environment once diatom reaches sediment won’t dissolve because others already have been and water is saturated with silica

Diatoms (phytoplankton with SiO2 shell)

Cleaning agents and toothpaste often contain diatoms because of their sharp surfaces

Biogenous Sediments Soft Tissue Gas Hydrates Near continental Margins A lot of methane stored in sediments Might be a useful source of fuel Possible Problems Limited Stability Range Methane is much greater green house gas = AGGRESSIVE Large Gaseous Emissions!

Hydrogenous/Authigenic Sediments Formed by chemical or biochemical reactions on ocean floor/ formed in the place they now occupy Nodules of ferromanganese (Fe and Mn) or phosphorite (P). Mn found deep sea beds P found continental margins Concentric layers of metal oxides accrete on particles over millions of years (1-4 mm per 106 y). Contain economically important metals Cu, Zn, Co and Pb. (but too expensive to harvest). Origin uncertain (biological?)

Ferromanganese nodules Floor of South Pacific Ocean. Nodule size 1-5 cm diameter

Ferromanganese nodules Cross-section

Hydrogenous Pebble like Manganese Nodules mm per million years, they grow slow Evaporites – Hydrogenous deposit, precipitates out as water evaporates Salts: Evaporates from isolated arms of the ocean Sea salts Red sea Persian Gulf Gypsum Oolite sands – Calcium carbonate precipitates from shell fragments, white and rounded Abundant in many warm, shallow waters Bahamas

Deep Sea Sedimentation Process

Distribution of Sea Sediments Neritic sediments: consist of primary terrigenous material Found normally along continental shelf's

Distribution of Deep Sea Sediments Pelagic sedimentation: Sediments of the slope, rise, and deep-ocean that originate in the ocean Pelagic: Inorganic red or brown clays and silt Fine-grained (0.0002 – 0.0004 mm) Dominate below waters with little planktonic production.

Deep Sea Sedimentation Pelagic: Oozes Deep ocean sediment that has at least 30% of debris from planktonic organisms Named after the dominate remnant organism Calcareous oozes (CaCO3) Shells of foraminifera & pteropods (zooplankton) and coccolithophorids (phytoplankton). Accumulate on seafloor above CCD. Forms hard limestone under pressure Siliceous oozes (SiO2) Shells of radiolaria (zooplankton) and diatoms (phytoplankton). Accumulate on seafloor below CCD. Accumulate below regions of high diatom production (equator, poles, upwelling areas)

Deep Sea Sedimentation Distribution TYPE COMPO-SITION ATLANTIC (%) PACIFIC (%) INDIAN (%) GLOBAL (%) Foram. ooze Carbonate 65 36 54 47 Pteropod ooze 2 0.1 - 0.5 Diatom ooze Silica 7 10 20 12 Radiolarian ooze 5 3 Red clay Aluminum silicate 26 49 25 38

Atlantic Basin Sediments as thick as 1 km (3,300 feet) Small area Great numbers of rivers spilling sediments into ocean

The Atlantic basin contains a “two-layer-cake” stratigraphy–a thick basal layer of carbonate ooze overlain by a layer of mud.

Pacific Basin Less than .5 km in thickness Large area Pacific has many trenches that the sediment gets trapped

Pacific plate moves across latitudes…

The Pacific basin contains a “five-layer-cake” stratigraphy, because unlike the Atlantic its sea floor as it spreads crosses the equator where the CCD is lowered to the ocean bottom.

Continental Margins Rivers and Erosion allow for a lot of the terrigenous sediment transported to the margins Orderly sorting of particles from finest to large grains Large grains stay near shore Small grains get carried into the deep ocean Biogenous Sediments also accumulate in this region Productivity of near shore waters is normally high Some sediments are lithified due to the pressure of overlying sediments.

Exceptions Shelf deposits are subject to erosion as the sea level fluctuates. Ice ages Exposed shelf leads to further erosion

Studying Sediments Clamshell sampler - Shallow sediment sampler

Piston Corer Device capable of punching through as much as 25 m of sediment and returning an intact plug of material

Scientist Sample Sediments

Coring Preserves deep Straitigraphy, or Layering

Stratigraphy Analysis of layered sedimentary deposits in the ocean (or on land) Paleo-oceanogrpahy- Study of the Ocean’s past Interpret ocean and climate history from evidence in deep-sea sediments Started in 1930’s

Andrill

JOIDES: Deep-Sea Drilling Program (DSDP) 1978 Drills into the ocean floor to take core samples 24 a day 50 scientists 65 crew people Statistics

Economic Importance Taken from sedimentary deposits of continental shelves and rises 36% of the world’s crude oil 28% of its natural gas 125 billion dollars Sand and gravel estimated over 480 million dollars

Chapter 5 Vocabulary Silt- Sediment particle between 0.004 and 0.062 mm in diameter Sand- Sediment particle between 0.062 and 2 mm in diameter. Clay- Sediment particle smaller than 0.004 mm in diameter the smallest sediment size category. Well-sorted sediments- A sediment in which particles are of uniform size. Poorly-sorted sediments- A sediment in which particles of many sizes are found. Terrigenous Sediments- Sediment derived form the land and transported to the ocean by wind and flowing water

Biogenous Sediments- Sediment of biological origin Biogenous Sediments- Sediment of biological origin. Organisms can deposit calcareous (calcium-containing) or siliceous (silicon-containing) residue. Hydrogenous Sediments- A sediment formed directly by precipitation from seawater; also called authigenic sediment. Authigenic sediments- Sediment formed directly by precipitiaon from seawater; also called hydrogenous sediment. Cosmogenous sediments- Sediment of extraterrestrial origin. Microtektites- Translucent oblong particles of glass, a component of cosmosgenous sediment. Neritic sediments- Continental shelf sediment consisting primary of terrigenous material. Pelagic sediments- Sediments of the slope, rise, and deep-ocean floor that originate in the ocean.

Turbidites- A terrigenous sediment deposited by a turbidity current; typically, coarse-grained layers of nearshore origin interleaved with finer sediments. Siliceous Ooze- Ooze composed mostly of the hard remains of silica-containing organisms. Calcareous Ooze- Ooze composed mostly of the hard remains of organisms containing calcium carbonate. Foraminifera- One of a group of planktonic amoeba-like animals with a calcareous shell, which contributes to biogenous sediment. Pteropods- A small planktonic mollusk with a calcareous shell, which contributes to biogenous sediments.

Radiolarian- One of a group of usually planktonic amoeba-like animals with a siliceous shell, which contributes to biogenous sediments. Diatoms- Earth’s most abundant, successful, and efficient single celled phytoplankton. Diatoms possess two interlocking valves made primarily of silica. The valves contribute to biogenous sediments. Nodule- Solid mass of hydrogenous sediment, most commonly manganese or ferromanganese nodules and phosphorite nodules. Evaporite- Deposit formed by the evaporation of ocean water. Oolite sands- Hydrogenous sediment formed when calcium carbonate precipitates from warmed seawater as pH rises, forming rounded grains around a shell fragment or other particle.

Piston Corer- A seabed-sampling device capable of punching through up to 25 m (80 feet) of sediment and returning an intact plug of material Stratigraphy- The branch of geology that deals with the definitions and description of natural divisions of rocks; specifically, the analysis of rock strata. Paleoceanography- The study of the ocean’s past. Coccolithophores- A very small planktonic alga carrying discs of calcium carbonate, which contributes to biogenous sediment. Calcium Carbonate Compensation Depth (CCD)- The depth at which rate of accumulation of calcareous sediments equals the rate of dissolution of these sediments. Below this depth, sediment contains little or no calcium carbonate.

Clam shell sampler- A sampling device used to take shallow samples of the ocean bottom. Minerals- A naturally occurring inorganic crystalline material with a specific chemical composition and structure. Lithification- Conversion of sediment into sedimentary rock by pressure or by the introduction of a mineral cement.

Homework with in Chapter 5 - Book Read Chapter 5 take notes Make flashcards of vocab terms Pg. 142 Review Questions – 1, 2, 3 Pg. 142 Critical Thinking Questions – 1, 2