(S9) Shallow Sandy Seas (PARTIAL) Flashcards
What mineral are shallow marine sands dominated by?
Quartz
What is the expected maturity of marine dominated sands?
Mature
What is the expected maturity of marine dominated sands in polar regions?
Less likely to be mature
Where are calcareous shells most likely to be preserved and why?
Mudstones - low energy
What are greensands and when in geological time are they most common?
Glauconite sands - Cretaceous in the N. Hemisphere
What type of organisms are most common in shallow marine sands?
Benthic
Why are benthic organisms most commonly associated with sands as opposed to mud?
The currents required to move sands are also strong enough to provide nutrients
What is left over after groundwater dissolves a carbonate shell?
Casts of the original shells
What controls the supply of clasts to a shallow marine environment?
Relative abundance of wave, storm and tidal
Where are the largest tidal ranges found (2)
Epicontinental seas and restricted parts of shelves
What tidal regieme are open shelves?
Micro to mesotidal
What % of modern shelves are storm-dominated?
80%
What % of modern shelves are tide-dominated?
17%
What is the last 3% of ocean shelves?
Ocean-current dominated
What are the two features of an ocean-current dominated shelf?
Usually narrow, less than 10km, and tend to lie adjacent to strong geostrophic currents
