(9) Environments of Sedimentary Deposition Flashcards
1
Q
Environments of Sedimentary Deposition
A
- Sediments are formed in many different environments
- Each have characteristic appearance, features that allow them to be recognized in the geologic record
2
Q
Common environments of deposition
A
- Glacier (glacier deposits)
- Alluvial fan
- Lake
- River
3
Q
Glaciers
A
- Alpine and continental
- Deposits sheets of sediments
o Plus ridges on sides and ends - Sediment: till
o Unsorted (has boulders to clay)
o Abraded, rounded
o Chemically unweathered - Plus outwash deposits (rivers carrying meltwater + lost of sediment)
o Characteristics of rivers
4
Q
Alluvial fan
A
- Rivers flow from higher elevation onto flatter plain
o Loses energy with drop in slope, deposits load - Broad, fan-shaped pile of sediment
- Sediment: sand and gravels
o Sorting: depends on the energy
5
Q
River channel and flood plain
A
- Shape is important
- Sinuous, narrow channel
o Channel sediment: gravels and sands - Broad, flat floodplain
o Floodplain sediment: muds - Rounding can occur
- Sorting depends on the energy
6
Q
Lake
A
- Quiet environment
- Sediment: thin-bedded muds
- Material that has been transported the furthest (hard to identify where it came from)
- Evaporate deposits possible
7
Q
Transitional Environments
A
- Beach
- Delta
- Barrier Island
8
Q
Delta
A
- River flows into standing water (lake, sea)
o Loses energy, deposits load - Thick pile of silts and muds
o Some coarser river channel deposits
o May be some peat or coal - Complex environment
o Many influences: river, waves, tides, amount of sediment
9
Q
Beach, Barrier Island, Dune
A
- Built by wave action
- Barrier island: elongate bar, built by wave action
- Sediment: quartz sand (less likely to break down)
- Carbonate sane in tropical places
- Well sorted (except beach action disrupts, wave action helps)
- Well rounded materials
- Influence of wind: dunes
10
Q
Marine Environments
A
- Continental shelf
- Reef
- Abyssal fan
- Deep marine
11
Q
Marine shelf
A
- Broad area, shallow water, near shore
- Sediment: grain size is fine
o Sands -> silts -> muds - Influence of tides: tidal flats (covered and uncovered by tides)
12
Q
Reef
A
- Sediments: limey muds to gravels
- Around islands
- Important to find ancient records of oil
13
Q
Deep marine environment
A
- Quiet environment
- Sediment: muds
14
Q
Sea level is not constant!
A
- Transgressions (sea level rises)
- Regressions (sea level falls)
- Worldwide changes influenced by
o Volume of total water (melting glaciers)
o Change in height of land on the shore
15
Q
Different sediments accumulate next to each other at same time
A
- Each group that has distinctive characteristics reflecting the conditions in a particular environment = sedimentary facies
