stratigraphic section

{{Short description|Sequence of layers of rocks in the order they were deposited}}

File:Blegny mijn geologisch profiel.svg in Belgium.]]

A stratigraphic section is a sequence of layers of rocks in the order they were deposited. It is based on the principle of original horizontality, which states that layers of sediment are originally deposited horizontally under the action of gravity.{{cite book|last=Levin|first=H.L.|title=The Earth Through Time|url=https://books.google.com/books?id=D0yl7Cqsu78C&q=principle+of+original+horizontality&pg=PA15|access-date=28 November 2010|edition=9|year=2009|publisher=John Wiley and Sons|isbn=978-0-470-38774-0|page=15}}

Biostratigraphers estimate the age of stratigraphic sections by using the faunal assemblages 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.

{{Cite journal

|doi= 10.1016/S0277-3791(98)00077-8

|title= Submerged Late Pleistocene reefs on the tectonically-stable S.E. Florida margin: high-precision geochronology, stratigraphy, resolution of Substage 5a sea-level elevation, and orbital forcing

|year= 1999 |author= Toscano, M |journal= Quaternary Science Reviews

|volume= 18 |pages= 753–767 |last2= Lundberg |first2= Joyce

|issue= 6|bibcode = 1999QSRv...18..753T

}}

Magnetic stratigraphers look for signs of magnetic reversals in igneous rock units within the drill cores. Other scientists perform stable-isotope studies on the rocks to gain information about past climate.{{Cite journal |doi= 10.1029/94PA01838 |title= Magnetostratigraphic, Biostratigraphic, and Stable Isotope Stratigraphy of an Upper Miocene Drill Core from the Salé Briqueterie (Northwestern Morocco): A High-Resolution Chronology for the Messinian Stage |year= 1994 |author= Hodell, David A. |journal= Paleoceanography |volume= 9 |pages= 835–855 |last2= Benson |first2= Richard H. |last3= Kent |first3= Dennis V. |last4= Boersma |first4= Anne |last5= Rakic-El Bied |first5= Kruna |bibcode= 1994PalOc...9..835H |issue= 6}} Stratigraphic sections can also be used to locate areas for water, coal, and hydrocarbon extraction, particularly petroleum and natural gas.

A Global Boundary Stratotype Section and Point (GSSP) is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundaries of stages on the geologic time scale.{{Cite web |title=Global Boundary Stratotype Section and Points |url=https://stratigraphy.org/gssps/ |access-date=2022-04-02 |website=stratigraphy.org |publisher=International Commission on Stratigraphy}} (Recently this has been used to define the base of a system){{Cite journal |last1=Knoll |first1=Andrew |last2=Walter |first2=Malcolm |last3=Narbonne |first3=Guy |last4=Christie-Blick |first4=Nicholas |date=2006 |title=The Ediacaran Period: a new addition to the geologic time scale |url=http://doi.wiley.com/10.1080/00241160500409223 |journal=Lethaia |language=en |volume=39 |issue=1 |pages=13–30 |doi=10.1080/00241160500409223}}