Sedimentary structures- Fluvial facies Flashcards
What are the 2 types of fluvial systems?
- Low sinuosity (alluvial fans and braided rivers)
2. High-Sinuosity (Meandering river)
What is sinuosity?
the deviation of a river channel from a straight path
What is the most important geologic agent bringing about a change to Earth’s land surface?
Running water
Running water transports and deposits sediment in or adjacent to?
alluvial fans
braided rivers
meandering streams
Where to alluvial fans occur?
The base of mountains, where a stream flows out onto a level plain
How do braided streams normally transport sediment?
bed load
Rivers and streams are what kind of systems?
DYNAMIC
What is the depositional process of an alluvial fan?
gravity flow and fluid flow
sediments in an alluvial fan are typically ________ sorted and include ________ gravel.
poorly, abundent
does grain size in an alluvial fan increase or decrease down-slope towards the margin of the fan?
DECREASE
What is a Bajadas?
Two or more coalescing alluvial fans
Fluvial depositional systems are the dominant conduit from what regions to what region?
mountains to oceans/basins
How are fluvial depositional systems characterized?
sinuosity(low sinuosity or high sinuosity)
AND
sediment load
(bed load, suspended load or mixed load)
What does aggradation mean?
the process if building up a surface by deposition (eg. alluvial fan)
What are the 3 fluvial systems?
- Alluvial fans
- Low sinuosity braided rivers
- High sinuosity meandering rivers
Define alluvial fan deposits
Coarse grained
poorly sorted
Alluvial fan full fan sequences coarsen upward or downward?
UPWARD (prograde)
What a formation formed by a braided stream complex?
Lower Mcmurray formation
A braided channel has what kind of log response?
Even block with sharp top and base
What kind of log response does a fluvial point bar have?
fining upward and sharp base (retrograding)
What kind of log response does a crevasse splay have?
Coarsening upward and sharp top (prograding)
Give an example of a point bar deposit formation?
Cardium
What is a crevasse splay?
forms when a stream breaks its natural or artificial levees and deposits sediment on a floodplain
what is a levee?
an embankment built to prevent the overflow of a river.
What is an Oxbow lake?
a curved lake formed at a former oxbow where the main stream of the river has cut across the narrow end and no longer flows around the loop of the bend
What are sheet flows?
Sheet flows are turbulent flows with significantly more water and less mud than debris flows.
What is a slow canyon?
A slot canyon is a narrow canyon, formed by the wear of water rushing through rock. A slot canyon is significantly deeper than it is wide
