Sedimentary basins Flashcards
what are the types of siliclastics rocks
- quartz
- orthoclase and plagioclase feldspar
- lithics
what results in different sediment compositions
- weathering and erosion of different parent rocks created in different plate tectonic settings
how are sediments categorised
- texture (grain size, sorting, shape)
how are sediments classified
- composition (mineralogical constituents)
- texture (grain things hehe)
full list of sedimentary characteristics
- composition
- texture
- sedimentary structures
- bedding geometry, style and thickness
- nature of bedding contacts
- fossils
- colour
what does the life cycle of a sedimentary rock reflect
- provenance
- transport and deposition
- lithification and diagenesis
sedimentary deposition types
- alluvial fan
- fluvial deposition
- deltaic depositoon
- marine deposition
what is a sedimentary basin
- a sedimentary basin is a low area in the earths crust, of tectonic origin in which sediments accumulate
what shapes can a basin
- doesnt have to be strictly that shape
-can be deposited on gentle/ uniform slope
what is essential to creating sedimentary basins
- tectonic creation of relief
-source of sediment and low place
what is accommodation space
- is the space that is made available within a basin for either marine or non marine sediment to be deposited
what is subsidence
- is the gradual downward sinking of the land surface during sedimentation
why are sedimentary basins important
- hydrocarbons
- carbon sequestration
- water resources
- ore and mineral resources
- earths history
how do sedimentary basins form
- where tectonic activity creates space
different types of sedimentary basins
intracontinental basins- interiors far from the margins
foreland basins- craton side of collisional mountain belt
what controls accomodation space
- is the combined product movement of
- global sea level
- the sea floor
- changes in rate of sediment accumulation
sea level change in response to sedimentary deposition
- shift land/ sea ward in response
- layers of strata and deepening/ shallowing Upward
what is transgression
- flooding due to sea level rise
- sediment belt shifts landward and stata deepen upward
what is an alluvial fan
- is a fan or cone shaped deposit of sediment built up as a river as it decreases in velocity (often associated with a change in slope)
- like a mountain into a valley and deposition
- ## trunk streams cause accumulations of sediment
where is a common place to find alluvial fans
- common in high relief areas (base of a mountain range or below fault scarps)
- sparse vegetation and violet flooding
- humid
what can alluvial fans tell us about the area
- about weathering or uplift of a mountain chain
most important environment of sedimentary deposits in a geological context
- fault- bounded sedimentary basins where periodic fault movements enable subsidence and preservation of fan sediments
composition of alluvial fans
- poorly sorted and gravel dominated
-down fan increase in sediment sorting - decrease in grain size and bed thickness
what is debris flow
- viscous slurry of material that spreads out as a lobe
- when dense water/sediments
what are stream flow dominated fans
- more sheet-like deposits of gravel
- moderately well sorted, cross-bedded, laminated or structureless
- will be confined to channels on the surface
the process of deposition is determined by…….
- availability of water
- amount and type of sediment being carried
- gradient of the fan surface
why are alluvial fans uselful for society
- source of water supply which is important in arid regions
2 main categories of fluvial system
- meandering (single channel)
- braided
controlling factors of fluvial channel morphologies
- grain size
- type of sediment load
- fluid discharge
- discharge regularity
- size of drainage area
- bank stability
- regional slope
- tectonic events
what is a delta
- supply sediments more rapidly than it can be redistributed
- when rivers enter oceans, lakes lagoons ect.
what are deltas importance
- site of substancial fossil fuel resource accumulation
- ## grounds for fisheries
the delta sub environments (3 geomorphological elements)
- delta plain- sub aerial, flat swampy plain
- delta front- shallow submarine platform where most sand accumulates
- pro-delta- most distal water depth 10-15m where bulk suspension settles out
what are the controls on delta environments and facies
- eustatic sea level
what are the different delta types
- river dominated
- tide-dominated
- wave-dominated
