In the long run eustatic changes in base level are cyclical Do not produce permanent increases in accommodation for longterm sediment storage Base level is also a function of climate energy but it is unlikely that climate changes will lead to substantial ID: 703185
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Slide1
Introduction to Basin AnalysisSlide2
In the long run,
eustatic
changes in base level are cyclicalDo not produce permanent increases in accommodation for long-term sediment storage
Base level is also a function of climate (=energy), but it is unlikely that climate changes will lead to substantial
permanent accommodation
creationSlide3
Yet many sedimentary basins have kilometers (or 10s of km) of sediment fill over 10s-100s of
Myr
How is that much permanent accommodation space created?Slide4
Subsidence
is required for formation of a
sedimentary basin and long-term sediment accumulationSlide5
Physical mechanisms of subsidence:
1.
Isostasy
Pratt
isostasy
Topography is a function of lithospheric density
Airy
isostasy
Topography is a function of lithospheric thicknessSlide6
Physical mechanisms of subsidence:
2.
Flexure (also called regional isostasy)
Earth’s rigid lithosphere acts as an elastic
plate. When
loaded (by a mountain range, sediment column, other tectonic plate), it
flexes.Slide7
Most (but not all) sedimentary basins occur in areas of active plate tectonics
Basins due to
extension
2. Basins
due to
convergence
3. Strike-slip
basinsSlide8
Crustal extension leads to rift basins and ultimately to passive margins
Subsidence driven by crustal thinning and heat flow changes
Primarily isostatic
Basins due to
extensionSlide9
Rift-drift transition marked by “breakup unconformity” that coincides with the onset of seafloor spreading (heat flow from magma production)
Transition to a
passive marginSlide10
Subsidence primarily driven by
flexure
of underlying plate from weight of overriding plateE.g., forearc
basins at continental margins above subduction zones
Basins due to
convergenceSlide11Slide12
Foreland basins are deepest next to the mountain front
Marine or terrestrial sediment fill reflects balance between sedimentation rate and subsidence rate (accommodation space)Slide13
Strike-slip basins
Pull apart or fault overstep basins associated with strike-slip fault
systems
Small size means that heat is lost through walls, leading to rapid fault-controlled subsidenceSlide14
Strike-slip basins often have extremely rapid lateral
facies
variationsMay be sediment-starved (marine or lacustrine) in center