Sedimentology Flashcards
What is sedimentology?
study of modern sediments such as sand, silt, and clay, and the processes that result in their formation, transport, deposition and diagenesis
What is controlling the growth rate of microscopic organisms in surface water and thus their deposition?
narrow ranges in sea-salinity and temperature
What is alluvial deposition?
loose clay, sand, silt or gravel that has been deposited by running water
What is fluvial deposition?
sediments deposited by a moving river of stream
reference: https://www.nps.gov/subjects/geology/fluvial-landforms.htm#:~:text=Fluvial%20deposits%20are%20sediments%20deposited%20by%20the%20flowing%20water%20of%20a%20stream.
What is aoelian deposition?
erosions, transportation and deposition of sediment by wind
Reference: https://www.nps.gov/subjects/geology/aeolian-landforms.htm#:~:text=Aeolian%20processes%20involve%20erosion%2C%20transportation,hot%20deserts%2C%20and%20agricultural%20fields. (paraphrased)
Where does sedimentation occur?
on land and in the seas
What is the name for the collection of processes involved in sedimentology?
Sedimentary systmes
What do the sedimenrary systems need to be like in relation to one another?
always adjacent
What is the general trend with sedimentology?
Sediment will move from land (upland) to oceans via fluxes
What is a flux?
a movement of matter or energy from one store to another
What do narrow environmental conditions control with ocean sedimentology?
where certain sediments can occur
How is an alluvial fan created?
When sediment has flowed down a valley which has stopped reducing constriction and allowing sediment to spread out laterally
What can cause a build up of alluvial sediment?
freeze thaw which weakens rock
What will sediment distribution be like for an alluvial deposit?
thick closer to valley thinner further away as energy available to carry material dissipates
Where can a contrast be seen between grain size in fluvial systems?
in the river
out on the immediate bank
What is the erosive power of a fluvial system?
high erosive power especially on outer bend
What are aeolian systems?
desert systems
What are deserts defined by?
aridity (dryness)
What will grain size distribution be like in an aeolian environment?
uniform
what is the are the processes for grain movement in aeolian environments?
constant blowing wind causing continual material processing
What are interdune areas?
areas of water pooling in-between dunes
How do wind conditions create a homogony of grain sizes?
fine material is blown away as cant handle wind and coarse material is buried
What is the architecture of a sand dune like? (wind blown)
Bed form
Twisty crest
Asymmetrical (steep one side gentle the other)
How will the ice and rock interact in a glacial environment?
The ice will be overlying the bedrock
What general way material is weathered/ broken down in glacial systems?
Physical pressure (dragging)
Pulling (Plucking)
What is sediment distribution rate like for a glacial system?
relatively slow with poorly sorted deposits
What sub-environment for deposition will be present in a glacial system?
glacial meltwater lake which might have seasonal deposition variation (Varves)
What are deltaic areas like?
Low lying
Varying magnitude of rivers cut through
Unconstrained lateral environment
What is the main threat towards deltaic system?
sea level rise
What processes at the interface of a deltaic system help mixing of land and sea systems?
Tides
Waves
How do coasts act as an interface between land and sea sediment systems?
Can be deltaic or non-deltaic
Why is it hard for material to break the energy fence from fluvial to marine?
due to high energy marine processes like waves and tides
What might happen to sediment when it reaches a coastal system?
Rivers become wider form estuary and lose energy leading to deposition (spits and bars)
What can the scale of shelfal sediment systems be?
hundreds of km
What does the vast size of shelfal systems means for the sediment deposited?
highly variable due to changes in conditions which might be broken up by submarine channels
How mobile is the sediment in shelfal sediment systems?
Static only really being disturbed by strong storms
How do reefs affect sediment deposition?
complex rigid structure reduces wave energy
What are some examples of “the giants” for sedimentary systems?
Glacial lake Agassiz
Brahmaputra River Basin
Boreal ocean delta
What was lake Agassiz?
3000-4000 years old
Pleistocene
constrained by glaciers
440,000km*2
What is the general info on Brahmaputra River Basin?
Basin plane encompassing Ganges delta
651,334km*2
9th largest river in world 2900km long
What is the general information on the Boreal ocean delta?
Triassic age
North Pangea
emptied into shallow basin
Growth through 1 million year monsoonal climate
How large was the boreal ocean delta?
1,650,000km*2
1% of earth
Are sediments static?
No they change through time (Wilson cycle/ plate tectonics)
How can sea level change affect the sediment cycles?
change shape and extent of marine to land contact
What are the 3 sea level orders?
1) 100s million years , 100s meters
2) 10s million years , 100s meters
3) 1-10 million years , 10s meters
What can the hierarchy of sea level orders be called?
nested hierarchy
How does sea
