A stratigraphic section is a sequence of

layers Layer or layered may refer to: Arts, entertainment, and media * ''Layers'' (Kungs album) * ''Layers'' (Les McCann album) * ''Layers'' (Royce da 5'9" album) *"Layers", the title track of Royce da 5'9"'s sixth studio album * Layer, a female Maveri ...

of rocks in the order they were deposited. It is based on the

principle of original horizontality The principle of original horizontality states that layers of sediment are originally deposited horizontally under the action of gravity. It is a relative dating technique. The principle is important to the analysis of folded and tilted strata. I ...

, which states that layers of

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand ...

are originally deposited horizontally under the action of

gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...

. Biostratigraphers estimate the age of stratigraphic sections by using the

faunal assemblage In archaeology and paleontology a faunal assemblage is a group of associated animal fossils found together in a given stratum. The principle of faunal succession is used in biostratigraphy to determine each biostratigraphic unit, or biozone. T ...

s contained within rock samples from outcrop and drill cores.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictionary of Biology'', 8th ed., Oxford University Press, 2019. Geochronologists precisely date rocks within the stratigraphic section to provide better absolute bounds on the timing and rates of deposition. Magnetic stratigraphers look for signs of magnetic reversals in igneous rock units within the

drill core A modern core drill is a drill specifically designed to remove a cylinder of material, much like a hole saw. The material left inside the drill bit is referred to as the ''core''. Core drills used in metal are called annular cutters. Core dr ...

s. Other scientists perform stable-isotope studies on the rocks to gain information about past climate. Stratigraphic sections can also be used to locate areas for water, coal, and hydrocarbon extraction, particularly

petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...

and

natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbon d ...

. A Global Boundary Stratotype Section and Point A Global Boundary Stratotype Section and Point (GSSP) is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. The effort to define GSSPs is conducted ...
(GSSP) is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundaries of stages on the geologic time scale. (Recently this has been used to define the base of a system)

Gallery

File:OrdOutcropTN.JPG, A stratigraphic section of

Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. T ...

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms w ...

exposed in central

Tennessee Tennessee ( , ), officially the State of Tennessee, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. Tennessee is the List of U.S. states and territories by area, 36th-largest by ...

. File:The most ancient skeletal remains of man 1.png, A stratigraphic section of the site where

Java Man Java Man (''Homo erectus erectus'', formerly also ''Anthropopithecus erectus'', ''Pithecanthropus erectus'') is an early human fossil discovered in 1891 and 1892 on the island of Java (Dutch East Indies, now part of Indonesia). Estimated to be b ...

was found. File:SEUtahStrat.JPG, The

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleo ...

through

Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

stratigraphy of the

Colorado Plateau The Colorado Plateau, also known as the Colorado Plateau Province, is a physiographic and desert region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. This province covers an area o ...

area of southeastern

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to its ...

. Image:Quebrada de Cafayate, Salta (Argentina).jpg,

Strata 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 e ...

in Salta,

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the List of South American countries by area, second-largest ...

. File:Strat section Mesa Verde.png, Stratigraphic section of formations exposed at the surface, Mesa Verde National Park, Colorado (USGS). File:Bouldnor-Formation2.png, Stratigraphic section of the Bouldnor Formation File:Wessex basin lithostratigraphy.png, Lithostratigraphy of the Wessex Basin. File:Stratigraphic section, major tectonic events, and stratigraphic units that make up the Greater Paleozoic, Jurassic, and Cretaceous petroleum systems of the eastern Arabian Peninsula (USGS.gov).png, Stratigraphic section, major tectonic events, and stratigraphic units that make up the Greater Paleozoic, Jurassic, and Cretaceous petroleum systems of the eastern Arabian Peninsula.

References

Geological techniques Stratigraphy {{geology-stub