I.
How Basins Are Made
- Local: Fault slip over 100s-1000s m sculpting
intermontane basins. Relief persists without isostatic
compensation akin to a rigid granite block.
- Regional: Thermal expansion/contraction and flexural
responses to surface loading shape geometry over
broader areas. Volcanism and mountain building
contribute.
II. Thermal Processes
- Heating induces lithospheric expansion and crustal
uplift. Cooling enables subsidence yet may be incomplete
without erosion.
- Erosion during elevated intervals promotes additional
lowering if crust thins yet thickens elsewhere during
sediment deposition.
III. Flexural Processes
- Loading the lithosphere instigates subsidence through
isostatic accommodation, with flexural rigidity transferring
stresses to adjacent areas.
- Foreland basins exemplify this behavior as thrust
sheets propagate over cratonic crust.
IV. CLASSIFICATION OF SEDIMENTARY BASINS
- Descriptive criteria include fill nature and basin
geometry/paleogeography.
- Genetic categorization utilizes tectonic settings, with
precision lessening for ancient contexts.
V. Assessment of Magnitudes
Thermal limitations: The thermal subsidence mechanisms
alone often fail to account for the true magnitude of
depression observed in many basins. This implies
additional factors are required.
Extensional influences: To remedy the above discrepancy,
it is proposed that in numerous cases lithospheric
extension accompanying heating episodes acts to further
thin and lower the crust beyond thermal effects alone.
This hybrid scenario has been invoked to successfully
explain abundant sedimentary basin geometries.
:Intracratonic Basins .1
Location and tectonic setting: Within stable cratonic
.interiors
Tectonic and sedimentary processes: Formed above slowly
cooling lithosphere via thermal subsidence over hundreds
.of millions of years
Size, shape: Rounded to equidimensional shapes,
.hundreds of kilometers across
Sediment fill: Relatively thin (<1 km) deposits of cratonal
carbonates, shales, and sandstones, thicker than
.surroundings
:Aulacogen Basins .2
Location and tectonic setting: Develop along craton
.margins above failed rift arms
Tectonic and sedimentary processes: Represent failed
.third rift arms where two continued to open ocean basins
Size, shape: Linear and narrow shapes, tens of kilometers
.wide by hundreds of kilometers long
Sediment fill: Very thick sequences (up to 5 km) of coarse-
.fine clastics, often non-marine
:Rift Basins .3
Location and tectonic setting: Above rifting continental
.lithosphere
Tectonic and sedimentary processes: Form due to
lithospheric extension driven by regional subsurface
.heating
Size, shape: Linear shapes, tens of kilometers wide by
.thousands of kilometers long
Sediment fill: Coarse-fine clastics and interbedded basalts,
.frequently lacustrine
:Oceanic Rift Basins .4
.Location and tectonic setting: Within narrow seafloor rifts
Tectonic and sedimentary processes: Represent
.transitional stage as restricted seaways begin to widen
Size, shape: Linear shapes, tens to hundreds of kilometers
.wide by thousands long
Sediment fill: Mafic volcanics and coarse-fine clastics
.filling to marine facies
:Passive Margin Basins .5
Location and tectonic setting: Above subsiding continental
.shelf/slope
Tectonic and sedimentary processes: Infill above cooling,
.extended crust as ocean basin opens
Size, shape: Straight to irregular shapes, hundreds of km
.wide by 1000s of km long
Sediment fill: Thick marine siliciclastics/carbonates
.onlapping older rift sequences
:Trench Basins .6
Location and tectonic setting: Within abyssal seafloor
.trenches
Tectonic and sedimentary processes: Receive subducting
plate sediments and localized trench infill via subduction
.erosion
Size, shape: Linear to arcuate shapes convex to plate,
.tens-hundreds km wide by 1000s km long
Sediment fill: Thin pelagics to thick trench-derived coarse
.clastics and volcaniclastics
:Trench-Slope Basins .7
Location and tectonic setting: Within accretionary wedges
.along subduction interfaces
Tectonic and sedimentary processes: Form between
emergent thrust sheets as the wedge develops under
.tectonic compression
Size, shape: Linear shapes parallel to trench, kilometers
.wide by tens of kilometers long
Sediment fill: Deep marine silts, muds and turbidites
.transported from the upper slope
:Fore-Arc Basins .8
Location and tectonic setting: Between volcanic arcs and
.uplifted subduction complexes
Tectonic and sedimentary processes: Develop as flexural
lowering between elevated terranes in a contracting
.orogenic system
Size, shape: Arcuate shapes, tens-hundreds km wide by
.thousands of km long
Sediment fill: Nonmarine to marine siliciclastics and
.volcanics, thousands of meters thick
:Foreland Basins .9
Location and tectonic setting: Ahead of advancing fold-
.thrust belts
Tectonic and sedimentary processes: Flexural lowering
response to crustal unloading and loading during
.continental collision
Size, shape: Arcuate shapes, tens-hundreds km wide by
.hundreds-thousands km long
Sediment fill: Coarse alluvial facies transitioning to shallow
.marine siliciclastics
:Remnant Basins .10
Location and tectonic setting: Isolated within suture zones
.after collision
Tectonic and sedimentary processes: Preserved as
collisional accommodation ends and suturing resumes
.between consolidated terranes
.Size, shape: Irregular shapes, tens-hundreds km across
Sediment fill: Variable facies from adjacent uplifted
.terrains, fluvial to marine
:Collisional Basins .11
Location and tectonic setting: Within convergent plate
.boundaries during collision
Tectonic and sedimentary processes: Transient pull-apart
structures formed by fault offsets during collisional
.deformation and suturing
Size, shape: Linear and narrow basin shapes developed
.along active fault trends
Sediment fill: Thin and ephemeral sequences reflecting
the brief existence of these basins before final suturing
.and closure
