Transcript Sediments - Cornell College

Sediments
Types of substrates: hard, soft
Types of sediments
Clastics: abiotic
Carbonates: abiotic, biotic
Sediment distribution in the oceans
Importance of sediments to
organisms, ecosystems, and chemistry
Substrate types
Hard bottoms: rocks, hardgrounds, other organisms, and
artifical substrates
Energy: waves, currents
Epibiosis
Substrate types
Soft bottoms: muds, sands, gravels
semi-hard to soupy
Energy determines grain size
Infauna and epifauna
Bioturbation
Oxygenation and anoxia
Sediment properties
Texture = size assortment
Maturity = clay amount, sorting, roundness
Clastic (lithogenous) sediments
The Rock Cycle
metamorphic
rock
recycle
P, T
igneous
rock
recycle
sedimentary
rock
weathering
lithification
sediment
deposition
Pebbles, sand, silt, clay
Abiotic, but can have biotic help in weathering
Weathered rocks (chemical and physical)
Sediment Deposition
Particles into drainage basins then into oceans
Particle size is determined by energy of transport
FW input, storm transport
Exception: ice
Distance from shore: deposition determined by
amount of input, size of particles, energy
Carbonate sediments
Calcium carbonate: CaCO3: formation and dissolution
CaCO3 + H2O + CO2 ↔ Ca2+ + 2HCO3Calcium carbonate + water + carbon dioxide
↔
calcium + bicarbonate
Carbonate sediments
Abiotic precipitation (rare)
Biotic precipitation: shells, etc.
Soft substrates, grain types:
peloids, pellets
Ooid sands
Shell debris
Halimeda
Carbonate sediments
Weathering: algal borings
breakage
dissolution
Role of CO2 and anthropogenic effects
Carbonate sediments
Cambrian explosion: 535 MY
Ocean sediment distribution
Depth
Energy
Proximity to land
Chemistry
Tropics:
Carbonate, clastics on shelf
Polar regions:
Cold carbonates, ice float and boulder drops
Shallow sediments
Variable sed rates
Relict sediments
Turbidites
Glacial deposits
Stromatolites
Reefs
Deep sediments
Low sed rates
Abyssal clay
Oozes
Organic detritus
Dust
Phosphate nodules
Sediments and Organisms
Benthos versus Nekton, Plankton
Soupy to firm bed: different organisms
Sessile versus vagile
Epifauna, infauna
Sediments and Organisms
Organisms modify environment
Bioturbation
Reefs
Sediments and Organisms
Feeding stragegies:
filter feeding,
deposit feeding,
scavenging, predation
Sediments and Organisms
Larvae, adults, and recruitment
Many benthic organisms have planktic larval stage
Settlement and metamorphosis cues
Sediments and Ecosystems
Stratified sediments versus bioturbation
Grain size effects
Energy effects
Sediments and Ecosystems
Microbial loop; detrital food chain and nutrient recycling
Important part of ecosystem in shallow water
Benthic singe-celled algae
Sediments and Ecosystems
Succession
Environmental perturbation
Predictable: seasonality (T, precipitation)
Unpredictable: large storms, anthropogenic effects
Sediments and Chemistry
Nutrient recycling: microbial loop, algae
Nutrient, carbon sink
Sediments buffered from salinity changes
Anoxia at depth
Toxin filter
Pollution trap