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Marine Sediments Origin, Composition, and Distribution. Introductory Oceanography. Ray Rector - Instructor. Example of Seafloor Sediments. Shallow Underwater Carbonate Sand Dunes - Bahamas. Ocean Basins are Vast Sinks for Sediment.
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Marine Sediments Origin, Composition, and Distribution Introductory Oceanography Ray Rector - Instructor
Example of Seafloor Sediments Shallow Underwater Carbonate Sand Dunes - Bahamas
Ocean 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 Depositional Environments • Shallow Margin = Littoral and Neritic • Deep Sea = Pelagic Littoral Neritic Pelagic
Seafloor Sediment Provinces Cross-Section Profile of an Ocean Basin • Continental shoreline = Littoral Province • Continental shelf = Neritic Province • Continental slope to rise = Transitional • All deep sea regions = Oceanic or Pelagic
Four Compositional Types of Seafloor Sediments • 1. Terrigenous • Sources:Erosion of land; volcanic eruptions; wind-blown dust • Material:Gravels, Sands, Silts, and Clays 2. Biogenous • Sources:Organic; accumulation of plant and animal hard parts • Material:Calcareous and Siliceous Oozes 3. Hydrogenous • Sources: Precipitation of minerals from solution • Material:Carbonates, Metal Oxides and Sulfides 4. Cosmogenous • Sources:Extraterrestrial dust and meteorites • Material:Tektite particles, Glassy spheres, Silicate dust
Marine Sediment Sampling Methods • Bucket-Scooping • Piston Coring • Submersible • Drilling
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 Ash from volcanic eruptions Sediment from rivers 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 Benthic shelled-animals Microscopic Plankton
Continental Margins of the World Seafloor that includes shoreline, continental shelf and slope Submerged continental margins are shown in pale orange color
Continental Margin Settings Seafloor that includes shoreline, continental shelf and slope
Key Points Shallow Marine Sediments 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
Deep Ocean Basins of the World Deep seafloor excluding the continental shelf and slope From continental rise to mid-ocean ridge
Key Points Deep Marine Sediments 1) Deep ocean sediments are termed pelagic 2) Pelagic sediments are predominately very fine-grained 3) Two types of pelagic sediments • Inorganic clays – from land • Biogenic oozes – from plankton 4) Two types of biogenic oozes • Calcareous • Siliceous 5) Abundant benthic organisms crawl over and burrow through the sediment = Bioturbation
Calcareous 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) cocolithophores foraminifera
Distribution of Calcareous Ooze Sediments • Calcareous oozes principally deposit in relatively shallow, low- to mid-latitude regions of deep ocean • 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
Types of Hydrogenous Sediment • Sources: Precipitation of minerals from solution • Material: Carbonates, Metal Oxides and Sulfides Black Smoker Chimneys Manganese Nodules
Types of Cosmogenous Sediment • Sources: Extraterrestrial rock, dust ,and debris • Material: Silicates, glass, and metals Microtektites Tektite Strewn Fields
Percentage Distribution of Pelagic Sediments 1) Calcareous Oozes = covers 48% of deep seafloor 2) Abyssal Clays = covers 38% of deep seafloor 3) Siliceous Oozes = covers 15% of deep seafloor