Marine Sediments & Oceanography9

Four Primary Marine Sediment Origins

Terrigenous, biogenous, hydrogenous, and atmospheric/space (aeolian/cosmogenous).

Ooze

Pelagic sediment containing 30% or more plankton debris.

Particle Accelerators in Ocean

Fecal pellets and marine snow that aggregate and sink rapidly (>100 m/day), escaping microbial decay.

Manganese Nodules

Hydrogenous polymetallic lumps containing Mn, Fe, Co, Cu, and Ni found on abyssal plains.

Carbonate Compensation Depth (CCD)

The ocean depth (~4,500-5,000 m) below which calcium carbonate dissolves faster than it accumulates.

Abyssal Clays

Fine terrigenous clays left behind below the CCD, accumulating very slowly (1 cm/1,000 yrs).

Neritic Deposits

Shallow-water deposits near land covering about 1/4 of the seafloor, dominated by coarse lithogenous material.

Gas Hydrates

Ice-like mixtures of methane gas and water trapped under high pressure and cold temperatures on the seafloor.

JOIDES Resolution

The flagship international ocean drilling research ship used to recover sediment cores from deep ocean basins.

K-T Boundary Layer

A distinctive deep-sea sediment horizon containing iridium and soot deposited approximately $65\,Ma$ during a mass extinction event.

Lithogenous (Terrigenous) Sediments

Seafloor mineral deposits formed from the physical and chemical weathering of continental rocks, accounting for approximately $45\%$ of marine sediments.

Biogenous Sediments

Insoluble particulate material derived from the hard skeletal and shell remains of marine organisms, constituting approximately $55\%$ of ocean floor deposits.

Hydrogenous Sediments

Mineral residues that precipitate directly out of seawater via inorganic chemical reactions, representing less than $1\%$ of total marine sediments.

Ooze

Pelagic seafloor sediment consisting of at least $30\%$ microscopic biogenic shell material.

Calcareous Ooze

Deep-sea biogenic mud composed of calcium carbonate ($CaCO_3$) skeletal fragments from organisms like coccolithophores and foraminifera.

Siliceous Ooze

Deep-sea biogenic mud composed of hydrated silica ($SiO_2 \cdot nH_2O$) skeletal remains from organisms like diatoms and radiolarians.

Foraminifera

Single-celled marine protozoans that construct chambered micro-shells from calcium carbonate ($CaCO_3$).

Coccolithophores

Single-celled photosynthetic marine algae encased in microscopic overlapping plates of calcium carbonate ($CaCO_3$).

Diatoms

Single-celled microscopic algae that secrete rigid, ornate pillbox-shaped outer cell walls composed of silica ($SiO_2$).

Radiolarians

Single-celled marine planktonic protozoans that produce delicate, porous spherical skeletons of amorphous silica ($SiO_2$).

Particle Accelerators in Oceanography

Aggregated marine snow and zooplankton fecal pellets that sink faster than $100\,m/day$, transporting biogenic matter to the abyss before microbes consume it.

Carbonate Compensation Depth (CCD)

The oceanic level between $4,500\,m$ and $5,000\,m$ below which cold, acidic deep water dissolves calcium carbonate faster than it accumulates.

Effect of Ocean Acidification on the CCD

Elevated atmospheric carbon dioxide raises carbonic acid concentrations in seawater, causing dissolution thresholds to migrate upward into shallower water depths.

Abyssal Clay

Fine-grained, wind-transported lithogenous dust that blankets vast deep ocean basins below the dissolution limit for carbonate shells, accumulating at about $1\,cm/1,000\,yrs$.

Pelagic Deposits

Open-ocean deep-water sediment accumulations covering roughly $3/4$ of the ocean floor, dominated by fine biogenous oozes and windblown clays.

Manganese Nodules

Dark, concentric hydrogenous concretions containing iron, cobalt, nickel, and copper that form extremely slowly on abyssal plains at about $10\,mm/10^6\,yrs$.

Gas Hydrates

Crystalline solids resembling ice that lock methane molecules inside a cage of water molecules under cold, high-pressure conditions along continental margins.

JOIDES Resolution

A specialized deep-sea research drillship featuring dynamic positioning thrusters, derrick equipment, and sonar re-entry guidance used to recover continuous sediment cores.

Hydrothermal Metal Sulfides

Inorganic minerals enriched in iron, copper, zinc, and silver that precipitate directly from superheated water spewing from mid-ocean ridge vents.

Diatomaceous Earth

A powdery, porous rock formed from uplifted diatomite used commercially in water filters, natural insecticides, abrasives, and chemical stabilization.

Sediment Grain Size vs. Deposition Energy

A sedimentological principle stating that coarse clasts settle out only in high-energy currents, whereas fine silts and clays settle exclusively in quiescent waters.

Rippled Seafloor Bedforms

Microtopographical structures on deep or shallow marine sediments indicating rapid transport driven by energetic bottom currents.

Ocean Crust Age vs. Sediment Thickness

A global depositional trend wherein sediment layers are thinnest along active spreading centers and thicken progressively toward older continental margins.

Quartz Dominance in Beach Sand

A geographic phenomenon caused by silicon dioxide ($SiO_2$) having extreme hardness and chemical durability, resisting weathering while softer minerals disintegrate.

Basaltic Coastal Sand

A dark volcanic sediment found on islands like Iceland that forms from weathered oceanic igneous rock devoid of quartz grains.

Impact Stratigraphy Sequence

A three-part vertical sediment column produced by an extraterrestrial collision, consisting from bottom to top of an ejecta layer, a fireball soot layer, and a post-extinction layer.

Siliceous Ooze Geographic Distribution

Pelagic muds concentrated beneath polar waters and equatorial divergent belts where nutrient upwelling sustains prolific microalgal blooms.

Calcareous Ooze Geographic Distribution

Pelagic muds concentrated along topographic highs like mid-ocean ridges and seamounts that remain elevated above the depth of rapid carbonate dissolution.