Marine Sediments Marine Sediments Origin, Composition, and DistributionOrigin, Composition, and Distribution

Introductory OceanographyIntroductory OceanographyRay Rector - Instructor

Example of Seafloor SedimentsExample of Seafloor SedimentsExample of Seafloor SedimentsExample of Seafloor Sediments

Shallow Underwater Carbonate Sand Dunes - Bahamas

Ocean Basins are Vast Sinks for SedimentOcean Basins are Vast Sinks for Sediment

Land- and plankton-derived sediments settle on both the continental margins and on the deep ocean seafloor

Two Major Types of Marine Sediment Two Major Types of Marine Sediment

Depositional Environments Depositional Environments Shallow Margin = Littoral and Neritic

Deep Sea = Pelagic

NeriticPelagic

Littoral

Seafloor Sediment ProvincesSeafloor Sediment Provinces

Continental shoreline = Littoral Province

Continental shelf = Neritic Province

Continental slope to rise = Transitional

All deep sea regions = Oceanic or Pelagic

Cross-Section Profile of an Ocean BasinCross-Section Profile of an Ocean Basin

Four Compositional Types Four Compositional Types of Seafloor Sedimentsof Seafloor Sediments

1. TerrigenousTerrigenous

Sources: Erosion of land; volcanic eruptions; wind-blown dust

Material: Gravels, Sands, Silts, and Clays

2. BiogenousBiogenous

Sources: Organic; accumulation of plant and animal hard parts

Material: Calcareous and Siliceous Oozes

3. HydrogenousHydrogenous

Sources: Precipitation of minerals from solution

Material: Carbonates, Metal Oxides and Sulfides

4. CosmogenousCosmogenous

Sources: Extraterrestrial dust and meteorites

Material: Tektite particles, Glassy spheres, Silicate dust

Type and Locality of Marine SedimentsType and Locality of Marine Sediments

Marine Sediment Sampling MethodsMarine Sediment Sampling Methods

Piston Coring

Bucket-Scooping

Submersible

Drilling

Marine Sediment Sampling LocationsMarine Sediment Sampling Locations

Terrigenous Sediments Sources: Erosion of land; volcanic eruptions; wind-blown dust; icebergs

Material Comp: Quartz, Feldspar, Mica, Amphibole, Fe Oxide, & Clays Material Size: Cobbles, Gravels, Sands, Silts, and Clays

Sediment from rivers

Ash from volcanic eruptions

Wind-blown material Sediment-filled glacial ice flows

Biogenous Sediments Sources: Carbonate reefs; Benthic shelled-animals; Plankton

Material Comp: Calcium carbonate and Silica

Material Size: Gravel, Sand, Silt, and Clay

Coral and Sponge Reefs

Microscopic PlanktonBenthic shelled-animals

Type and Locality of Marine SedimentsType and Locality of Marine Sediments

Continental Margins of the WorldContinental Margins of the World

Seafloor that includes shoreline, continental shelf and slope

Submerged continental margins are shown in pale orange color

Continental Margin SettingsContinental Margin Settings

Seafloor that includes shoreline, continental shelf and slope

Key Points

1) Shallow marine sediments that deposit along shorelines and offshore shelf are termed littoral and neritic

2) Coast and shelf sediments are of two types:

Land-derived inorganic rock and mineral fragments of gravel, sand, silt, and clay

Organic carbonate and silica materials of marine life skeletons from reefs and sea bottom habitats

Carbonate, silica and phosphate seawater precipitates

3) Shelf sediments mostly arrive via rivers

4) Coastal sediments may reach deep waters via turbidity currents moving down submarine canyons

Shallow Marine SedimentsShallow Marine SedimentsShallow Marine SedimentsShallow Marine Sediments

Deep Ocean Basins of the World

Deep seafloor excluding the continental shelf and slope

From continental rise to mid-ocean ridge

1) Deep ocean sediments are 1) Deep ocean sediments are termed termed pelagicpelagic

2) Pelagic sediments are 2) Pelagic sediments are predominately very fine-grained predominately very fine-grained

3) Two types of pelagic sediments 3) Two types of pelagic sediments

Inorganic clays – from landInorganic clays – from land

Biogenic oozes – from planktonBiogenic oozes – from plankton

4) Two types of biogenic oozes 4) Two types of biogenic oozes

CalcareousCalcareous

SiliceousSiliceous

5) Abundant benthic organisms 5) Abundant benthic organisms crawl over and burrow through crawl over and burrow through the sediment = the sediment = BioturbationBioturbation

Key PointsKey Points

Deep Marine Deep Marine SedimentsSediments

Calcareous Ooze SedimentsCalcareous Ooze Sediments Accumulation of calcium carbonate hard parts from dead microscopic plankton

Mainly consists of cocolithophores and foraminifera tests

Calcite-shelled plankton abundant in warmer surface waters

Accumulate above the Carbonate Compensation Depth (CCD)

cocolithophoresforaminifera

Distribution of Calcareous Ooze Sediments

1) Calcareous oozes principally deposit in relatively shallow, low- to mid-latitude regions of deep ocean

2) Concentrated on tops and flanks of mid ocean ridges

Silica Ooze Sediments Accumulation of silica hard parts from dead plankton

Mainly consists of diatoms and radiolarian tests

Abundant in deeper, cooler surface waters – high latitude

Silica Ooze Sediments Accumulation of silica hard parts from dead plankton

Mainly consists of diatoms and radiolarian tests

Abundant in cooler surface waters – high latitude

Comparing Silica and Carbonate OozesComparing Silica and Carbonate Oozes

Types of Hydrogenous Sediment Sources:Sources: Precipitation of minerals from solution

Material:Material: Carbonates, Metal Oxides and Sulfides

Manganese Nodules

Black Smoker Chimneys

Types of Cosmogenous Sediment Sources:Sources: Extraterrestrial rock, dust ,and debris

Material:Material: Silicates, glass, and metals

Tektite Strewn Fields

Microtektites

Type and Distribution of Marine Sediments

Percentage Distribution of Pelagic Sediments

1) Calcareous OozesCalcareous Oozes = covers 48% of deep seafloor

2) Abyssal ClaysAbyssal Clays = covers 38% of deep seafloor

3) Siliceous OozesSiliceous Oozes = covers 15% of deep seafloor

Rates of Deposition of Marine SedimentsRates of Deposition of Marine Sediments

Total Sediment Thickness in OceanTotal Sediment Thickness in Ocean

MARINE SEDIMENTSMARINE SEDIMENTSDiscussionDiscussion