Marine sedimentation - 5 Flashcards
How are marine sediments classified?
By size or by origin
What are the size categories for sediment?
Gravel, sand, silt and clay
What are the categories for origin classification of sediment?
- Terrigenous
- Biogenous
- Hydrogenous
- Volcanogenous
- Cosmogenic
What is terrigenous sediment?
Sediment eroded from land (mainly sand and mud)
What is biogenous sediment?
Sediments made from the shells and skeletal rains of organisms
What is hydrogenous sediment?
Chemical and Biogeochemical precipitates the form in place on the sea floor
What is volcangenous sediment?
Volcanic particles ejected during eruptions
What is cosmogenic sediment?
Sediments made form extraterrestrial particles from space
What controls sedimentation?
- particle size
- power or velocity of the eroding/carrying medium
- turbulence at the deposition site
How are terrigenous sediments transported?
Wind, rivers and glaciers
Rapid erosion and short transport time leads to …
Poorly sorted sediment with a heterogeneous mix of grain sizes
What deposition occurs in high energy bottom conditions?
Deposition of larger grains as smaller grains are kept in suspension and transported elsewhere
What deposition occurs in low energy environments?
Deposition of smaller particles, large particles are rare (insufficient transport energy)
What does Hjulstroms diagram show?
Relationship between particle size and energy for erosion, transportation and deposition of a particular grain size
How does particles size change seaward?
Decreases seaward for recent sediments
