A pinch-out or wedge-out is a point where a

stratum In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ei ...

or other lithologically distinct body of rock thins to a feather edge and disappears, so that the underlying and overlying strata separated by the pinching out stratum come into direct contact. The term also is used in

petroleum geology Petroleum geology is the study of origin, occurrence, movement, accumulation, and exploration of hydrocarbon fuels. It refers to the specific set of geological disciplines that are applied to the search for hydrocarbons (oil exploration). Sedime ...

to describe a

stratigraphic trap In petroleum geology, a trap is a geological structure affecting the reservoir rock and caprock of a petroleum system allowing the accumulation of hydrocarbons in a reservoir. Traps can be of two types: stratigraphic or structural. Structural trap ...

created by a pinch-out. Petroleum migrating through a porous stratum is trapped where the stratum pinches out between impermeable underlying and overlying strata. , at least 20

oil fields A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by the presence ...

containing reserves of 6-7 billion barrels of petroleum are thought to be a result of pinch-out of

turbidite A turbidite is the geologic deposit of a turbidity current, which is a type of amalgamation of fluidal and sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean. Sequencing Turbidites were ...

beds. A pinch-out is distinct from a shale-out, which is a structural trap formed when a porous bed grades laterally into impermeable shale without the bed actually pinching out.

References

{{reflist Structural geology Stratigraphy