Sedimentary basin
Region-scale crustal depressions that accumulate thick sedimentary sequences.
Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock. They form when long-term subsidence creates a regional depression that provides accommodation space for accumulation of sediments. Over millions or tens or hundreds of millions of years the deposition of sediment, primarily gravity-driven transportation of water-borne eroded material, acts to fill the depression. As the sediments are buried, they are subject to increasing pressure and begin the processes of compaction and lithification that transform them into sedimentary rock. Sedimentary basins are of great economic importance, containing almost all the world's natural gas and petroleum and all of its coal, and are also scientifically valuable as records of Earth's history.
- number_identified_worldwide
- more than six hundred
- areal_size_range
- tens of square kilometers to well over a million
- sedimentary_fill_thickness_range
- one to almost twenty kilometers
- formation_mechanisms
- lithospheric stretching, lithospheric flexure, thermal subsidence
- economic_importance
- source of almost all natural gas, petroleum, and coal
- preservation_variation
- intracratonic basins have high preservation; basins on oceanic crust likely destroyed by subduction
Lore & Background
Sedimentary basins are created by deformation of Earth's lithosphere in diverse geological settings, usually as a result of plate tectonic activity. Mechanisms of crustal deformation that lead to subsidence and sedimentary basin formation include the thinning of underlying crust; depression of the crust by sedimentary, tectonic or volcanic loading; or changes in the thickness or density of underlying or adjacent lithosphere. Once the process of basin formation has begun, the weight of the sediments being deposited in the basin adds a further load on the underlying crust that accentuates subsidence and thus amplifies basin development as a result of isostasy. The long-term preserved geologic record of a sedimentary basin is a large-scale contiguous three-dimensional package of sedimentary rocks created during a particular period of geologic time, a 'stratigraphic succession', that geologists continue to refer to as a sedimentary basin even if it is no longer a bathymetric or topographic depression. The Williston Basin, Molasse basin and Magallanes Basin are examples of sedimentary basins that are no longer depressions.
Reader's Guide
Sedimentary basins are fundamental to understanding Earth's geological history and economic resources. They form through regional subsidence driven by lithospheric stretching, flexure, or thermal cooling, often in plate tectonic settings. Their classification remains debated, with no single scheme recognized as standard, though common types include those based on plate tectonic setting, nature of underlying crust, geodynamics of formation, and petroleum potential. Basins can evolve over time, such as a rift basin transitioning into a passive margin, with hybrid basins possible. Their preservation varies: intracratonic basins on stable continental interiors have high preservation potential, while those on oceanic crust are likely destroyed by subduction. Continental margins formed during rifting may last hundreds of millions of years but can be partially preserved when ocean basins close. More than six hundred basins have been identified worldwide, ranging from tens of square kilometers to over a million in area, with sedimentary fills up to nearly twenty kilometers thick. Their economic significance is immense, as they host nearly all petroleum, natural gas, and coal, and many metal ores. Scientifically, their sedimentary fill provides a record of Earth's history during active sedimentation.
Did You Know?
- More than six hundred sedimentary basins have been identified worldwide.
- Sedimentary basins range in areal size from tens of square kilometers to well over a million.
- The Williston Basin, Molasse basin, and Magallanes Basin are examples of basins that are no longer depressions.
- Almost all the world's natural gas and petroleum and all of its coal are found in sedimentary rock.
Frequently Asked Questions
What is a Sedimentary basin?
A Sedimentary basin is a region-scale depression in the Earth's crust where long-term sinking has created a hollow that gradually fills with layers of eroded material, which over millions of years compact and lithify into a thick three-dimensional body of sedimentary rock.
How does Sedimentary basin come into existence?
The basin's accommodation space is generated by one or more of three mechanisms: stretching of the lithosphere, bending of the crust under a heavy load (flexure), or the slow cooling and sinking of the lithosphere (thermal subsidence). Once that depression exists, water-borne eroded material is transported in and fills the space over tens to hundreds of millions of years.
What is Sedimentary basin's size and scale?
More than six hundred basins have been identified worldwide, ranging from just tens of square kilometers to well over a million square kilometers in areal extent. Their sedimentary fill can be as thin as roughly one kilometer or as thick as nearly twenty kilometers.
Why is Sedimentary basin important to the real world?
These basins are the geological source of virtually all of the world's natural gas, petroleum, and coal, making them central to global energy supply. They also act as long-term archives of surface processes, with intracratonic basins offering especially well-preserved sedimentary records.
How does Sedimentary basin's story end?
Basins that developed on oceanic crust are ultimately destroyed when their plate is driven into the mantle at a subduction zone, erasing the sedimentary record. In contrast, basins situated on stable continental interiors (intracratonic basins) tend to survive and retain their geological history far more completely.
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