Chapter 24: Sedimentary Basins
“Sedimentary basins are regions where sediment accumulates into successions hundreds to
thousands of meters in thickness over areas of thousands to millions of square kilometers. The
underlying control on the formation of sedimentary basins is plate tectonics and hence basins are
normally classified in terms of their position in relation to plate tectonic settings and tectonic
processes. Each basin type has distinctive features, and the characteristics of sedimentation and the
stratigraphic succession that develops in a rift valley can be seen to be distinctly different from those
of an ocean trench. A stratigraphic succession can therefore be interpreted in terms of plate
tectonics and places the study of sedimentary rocks into a larger context. The sedimentary rocks in a
basin provide a record of the tectonic history of the area. They also provide the record of the effects
of other controls on deposition, such as climate, base level and sediment supply.”
24.1 Controls on sediment accumulation
Preservation of deposits that will be part of the sedimentary record is the exception rather then the
rule. The transitory nature of deposition is most obvious in upland areas. Glacial deposits occur in
areas that are undergoing erosion, and will not be preserved in the stratigraphic record. The sediment
we see in rivers today is most likely just passing through. The concept “the present being the key to
the past” is difficult to apply. To create a set of strata at a beach, something has to happen, usually
environment change. Or an abandonment of the river. Larger scale it is tectonic subsidence, local and
regional changes in the vertical position of the crust, that ultimately allows sediment to become
preserved as strata.
24.1.1 Tectonics of sedimentary basins
Without tectonic creating areas that are ‘lows’ on the Earth’s surface, there would be no long-term
accumulation of sediment, no sedimentary rocks and no stratigraphy. Sedimentary basins: places
were sediment accumulates. Range in sizes. They provide a record of depositional environments
through Earth’s history. (geologische benadering). It used to be called geosynclines: broad down-folds
in the crust where successions of strata were first preserved and then subsequently deformed. With
the advent of plate tectonic theory they became known as sedimentary basins.
24.1.2 Climate, sediment supply and base-level controls
Factors that control the volume, type and distribution
of sediment. Climate, tectonics, bedrock geology and
ocean connection/base level all interact within and
around all types of sedimentary basin to govern the
character of the basin-fill succession.
Connection to oceans and sea-level
changes
Shallow marine: sea-level determines, the
accommodation available, and the fluvial deposition
and deep-sea sedimentation.
Do not affect all basins, some have no link or direct exchange of water with oceans. = endorheic
basins. Can form in form in different settings, rifts, foreland basins and strike-dip basins. May be
dominated by lacustrine conditions. More arid climate -> dominate fluvial and aeolian processes.
, Climate effects of weathering, transport and deposition
weathering processes are determined by the availability of water and the temperature. Warm, humid
= clay minerals and ions, cold = more coarse material. Transport of sediment by water, wind or ice is
climate dependent, in terms of water and temperature. Depositional processes are sensitive to the
climate. A clastic lagoon – tropical. Evaporite lagoon – arid
Bedrock and topography controls on sediment supply
Sediment supply important in terms of character and volume. The nature of all facies in all
depositional environments is ultimately determined by the grain size of the sediment available, the
mineralogical and petrological character of the detritus and the chemistry of the water. The volume
of the sediment supply has an impact on the nature of the whole basin fill. Availability is determined
by tectonic control on uplift in the hinterland, and climate and bedrock characteristics play a role. If
sediment supply > tectonic subsidence, the basin fills up (is overfilled) and the facies will be shallow
marine or continental. If sediment supply < tectonic subsidence – the basin is underfilled or starved:
in a marine setting -> mainly deep-water facies. Continental -> end up below sea level.
24.1.3 Tectonic setting classification of sedimentary basins
3 main setting of basin formation can be recognized:
1. Basins associated with regional extension within and between plates.
2. Basins related to convergent plate boundaries.
3. Basins associated with strike-slip plate boundaries.
24.2 Basins related to lithospheric extension
Horizontal stress causes brittle fracture in the surface layers, while the stretching is accommodated by
ductile flow in the lower part of the lithosphere. Extension causes rifts to form, and become
continental sedimentation sites. If stretching continues, the whole lithosphere might rapture, causing
an injection of basaltic magma to start the formation of a new oceanic crust. (rift to drift transition)
this stage is known as the proto-oceanic trough, and is the first stage in the initiation of an oceanic
basin: the remnant flanks of the rift become the passive margins of the ocean basin as it develops.
Continental rift basins may exist very long. So they do not follow the exact same path.
Lithospheric extension happens by “hot spots”: an area of increased heat flow in the crust generated
by thermal plumes in the mantle. Rupture of the continental lithosphere over a plume creates three
branches along which extension occurs, a triple junction.
Not all extensions are related to hot spots and the formation of new ocean basins. Areas of thickened
crust and high heat flow due to asthenosphere upwelling are also regions of widespread rift basin
development as the upper layer of the crust responds to the doming. Arc-trench systems local
tectonic forces lead to the rifting of the crust and the formation of intra-arc and subsequently backarc
basins due to extension.
24.2.1 Rift basins
Extension in continental crust fractures to produce rifts: structural valleys bound by extensional
(normal) fault. Axis of rift lies +/- perpendicular to the direction of stress. Graben: down-faulted
block, horsts: up-faulted area. Bounding faults may be planar or listric. If displacement is larger on
one side -> asymmetric valleys: half-graben. The high heat and structural weakness in the crust may
lead to volcanic activity. Uplift on the flanks of rift due to regional high heat flow and the relative
movement on the rift-bounding faults creates local sediment sources for rift valleys. Controls on
sedimentation: tectonic factors (available material/pathway into the basin), climate (weathering,
available water and facies in the basin), and connection to oceans is important.
“Sedimentary basins are regions where sediment accumulates into successions hundreds to
thousands of meters in thickness over areas of thousands to millions of square kilometers. The
underlying control on the formation of sedimentary basins is plate tectonics and hence basins are
normally classified in terms of their position in relation to plate tectonic settings and tectonic
processes. Each basin type has distinctive features, and the characteristics of sedimentation and the
stratigraphic succession that develops in a rift valley can be seen to be distinctly different from those
of an ocean trench. A stratigraphic succession can therefore be interpreted in terms of plate
tectonics and places the study of sedimentary rocks into a larger context. The sedimentary rocks in a
basin provide a record of the tectonic history of the area. They also provide the record of the effects
of other controls on deposition, such as climate, base level and sediment supply.”
24.1 Controls on sediment accumulation
Preservation of deposits that will be part of the sedimentary record is the exception rather then the
rule. The transitory nature of deposition is most obvious in upland areas. Glacial deposits occur in
areas that are undergoing erosion, and will not be preserved in the stratigraphic record. The sediment
we see in rivers today is most likely just passing through. The concept “the present being the key to
the past” is difficult to apply. To create a set of strata at a beach, something has to happen, usually
environment change. Or an abandonment of the river. Larger scale it is tectonic subsidence, local and
regional changes in the vertical position of the crust, that ultimately allows sediment to become
preserved as strata.
24.1.1 Tectonics of sedimentary basins
Without tectonic creating areas that are ‘lows’ on the Earth’s surface, there would be no long-term
accumulation of sediment, no sedimentary rocks and no stratigraphy. Sedimentary basins: places
were sediment accumulates. Range in sizes. They provide a record of depositional environments
through Earth’s history. (geologische benadering). It used to be called geosynclines: broad down-folds
in the crust where successions of strata were first preserved and then subsequently deformed. With
the advent of plate tectonic theory they became known as sedimentary basins.
24.1.2 Climate, sediment supply and base-level controls
Factors that control the volume, type and distribution
of sediment. Climate, tectonics, bedrock geology and
ocean connection/base level all interact within and
around all types of sedimentary basin to govern the
character of the basin-fill succession.
Connection to oceans and sea-level
changes
Shallow marine: sea-level determines, the
accommodation available, and the fluvial deposition
and deep-sea sedimentation.
Do not affect all basins, some have no link or direct exchange of water with oceans. = endorheic
basins. Can form in form in different settings, rifts, foreland basins and strike-dip basins. May be
dominated by lacustrine conditions. More arid climate -> dominate fluvial and aeolian processes.
, Climate effects of weathering, transport and deposition
weathering processes are determined by the availability of water and the temperature. Warm, humid
= clay minerals and ions, cold = more coarse material. Transport of sediment by water, wind or ice is
climate dependent, in terms of water and temperature. Depositional processes are sensitive to the
climate. A clastic lagoon – tropical. Evaporite lagoon – arid
Bedrock and topography controls on sediment supply
Sediment supply important in terms of character and volume. The nature of all facies in all
depositional environments is ultimately determined by the grain size of the sediment available, the
mineralogical and petrological character of the detritus and the chemistry of the water. The volume
of the sediment supply has an impact on the nature of the whole basin fill. Availability is determined
by tectonic control on uplift in the hinterland, and climate and bedrock characteristics play a role. If
sediment supply > tectonic subsidence, the basin fills up (is overfilled) and the facies will be shallow
marine or continental. If sediment supply < tectonic subsidence – the basin is underfilled or starved:
in a marine setting -> mainly deep-water facies. Continental -> end up below sea level.
24.1.3 Tectonic setting classification of sedimentary basins
3 main setting of basin formation can be recognized:
1. Basins associated with regional extension within and between plates.
2. Basins related to convergent plate boundaries.
3. Basins associated with strike-slip plate boundaries.
24.2 Basins related to lithospheric extension
Horizontal stress causes brittle fracture in the surface layers, while the stretching is accommodated by
ductile flow in the lower part of the lithosphere. Extension causes rifts to form, and become
continental sedimentation sites. If stretching continues, the whole lithosphere might rapture, causing
an injection of basaltic magma to start the formation of a new oceanic crust. (rift to drift transition)
this stage is known as the proto-oceanic trough, and is the first stage in the initiation of an oceanic
basin: the remnant flanks of the rift become the passive margins of the ocean basin as it develops.
Continental rift basins may exist very long. So they do not follow the exact same path.
Lithospheric extension happens by “hot spots”: an area of increased heat flow in the crust generated
by thermal plumes in the mantle. Rupture of the continental lithosphere over a plume creates three
branches along which extension occurs, a triple junction.
Not all extensions are related to hot spots and the formation of new ocean basins. Areas of thickened
crust and high heat flow due to asthenosphere upwelling are also regions of widespread rift basin
development as the upper layer of the crust responds to the doming. Arc-trench systems local
tectonic forces lead to the rifting of the crust and the formation of intra-arc and subsequently backarc
basins due to extension.
24.2.1 Rift basins
Extension in continental crust fractures to produce rifts: structural valleys bound by extensional
(normal) fault. Axis of rift lies +/- perpendicular to the direction of stress. Graben: down-faulted
block, horsts: up-faulted area. Bounding faults may be planar or listric. If displacement is larger on
one side -> asymmetric valleys: half-graben. The high heat and structural weakness in the crust may
lead to volcanic activity. Uplift on the flanks of rift due to regional high heat flow and the relative
movement on the rift-bounding faults creates local sediment sources for rift valleys. Controls on
sedimentation: tectonic factors (available material/pathway into the basin), climate (weathering,
available water and facies in the basin), and connection to oceans is important.
