GSSP facts for kids

Many GSSPs are marked by golden spikes. This 'golden spike' marks the GSSP for the start of the Ediacaran.

A GSSP stands for Global Boundary Stratotype Section and Point. It's like a special marker in rocks that shows the exact start of a new time period in Earth's history. Think of it as a specific spot on a timeline for our planet.

Scientists use GSSPs to create the geologic time scale. This scale helps us understand when different events happened on Earth. The International Commission on Stratigraphy decides where these important markers should be. This group is part of the International Union of Geological Sciences. As of 2012, they had set up 64 of these markers.

How GSSPs Are Chosen

To pick a GSSP, a rock section must follow strict rules. These rules help scientists agree on the exact start of a geologic time period.

Here are the main rules:

• A GSSP must mark the lower boundary (the beginning) of a geologic time period.
• This boundary needs a main marker. This is usually the first time a specific fossil species appears.
  • There should also be other markers. These can be other fossils, chemical changes, or changes in Earth's magnetic field.
  • The rock layer with the marker should have minerals that can be accurately dated. This means finding its age using scientific methods.
  • The marker must be found in similar rocks around the world. This shows it was a global event.
  • The marker should not depend on the type of rock (its facies).
• The rock section must be thick enough to study well.
• The layers of rock should show steady sedimentation. This means they formed without big changes.
• The rock section should not be too changed by tectonic movements or metamorphism.
• The location must be easy for scientists to reach. It should also be kept in good condition.
  • This means it should be near an airport or good roads. It should ideally be a national reserve. It needs to be large enough for repeated studies. And it must be open to researchers from all countries.

Important GSSP Locations

This table shows some of the chosen GSSPs. It lists the time period, where the GSSP is found, and what marker defines it.

Period	Epoch	Age (mya)	Status	GSSP location	Defining markers	Geographic Coordinates	References
Phanerozoic
Cainozoic
Quaternary
	Holocene	0.117		NGRIP2 ice core, Greenland	End of the Younger Dryas stadial (cold stage)	75°06′00″N 42°19′12″W / 75.1000°N 42.3200°W / 75.1000; -42.3200
	Pleistocene	2.588		Monte San Nicola Section, Sicily, Italy	Base of magnetic polarity chronozone C2r (Matuyama). Extinction of Discoaster pentaradiatus and Discoaster surculus (Calcareous nannofossil).	37°08′49″N 14°12′13″E / 37.1469°N 14.2035°E / 37.1469; 14.2035
Neogene
	Pliocene	5.333		Heraclea Minoa section Heraclea Minoa, Sicily, Italy	Top of magnetic polarity chronozone C3r. First appearance of Ceratolithus acutus and near extinction of Triquetrorhabdulus rugosus (Calcareous nannofossil).	37°23′30″N 13°16′50″E / 37.3917°N 13.2806°E / 37.3917; 13.2806
	Miocene	23.03		Lemme-Carrosio Section, Carrosio, Italy	Base of magnetic polarity chronozone C6Cn.2n. Near first appearance of Paragloborotalia kugleri (Planktonic foraminifera).	44°39′32″N 8°50′11″E / 44.6589°N 8.8364°E / 44.6589; 8.8364
Palaeogene
	Oligocene	33.9		Massignano Section, Massignano, Ancona, Italy	Extinction of Hantkenina and Cribrohantkenina (Planktonic foraminifera).	43°31′58″N 13°36′04″E / 43.5328°N 13.6011°E / 43.5328; 13.6011
	Eocene	56		Dababiya section, Luxor, Egypt	Base of negative Carbon Isotope Excursion (CIE).	25°30′00″N 32°31′52″E / 25.5000°N 32.5311°E / 25.5000; 32.5311
	Palaeocene	66		El Kef Section, El Kef, Tunisia	Iridium enriched layer associated with a major meteorite impact and subsequent extinction event.	36°09′13″N 8°38′55″E / 36.1537°N 8.6486°E / 36.1537; 8.6486
Mesozoic
Cretaceous
	Upper Cretaceous	100.5		Mont Risoux, Hautes-Alpes, France	First appearance of Rotalipora globotruncanoides (Planktonic foraminifera)	44°23′33″N 5°30′43″E / 44.3925°N 5.5119°E / 44.3925; 5.5119
	Lower Cretaceous	145			Candidates: Magnetic—base of Chron M18r Base of Calpionellid zone B
Jurassic
	Upper Jurassic	163.5		Candidate sections: Redcliff Point, Dorset, England Savouron, Provence, France	Horizon of Cardioceras redcliffense (Ammonite).
	Middle Jurassic	174.1		Fuentelsaz, Spain	First appearance of Leioceras opalinum and Leioceras lineatum Biologic: First appearance of genus Leioceras (Ammonite).	41°10′15″N 1°50′00″W / 41.1708°N 1.8333°W / 41.1708; -1.8333
	Lower Jurassic	201.3		Kuhjoch section, Karwendel mountains, Northern Calcareous Alps, Austria	Near first appearance of smooth Psiloceras spela group (Ammonite).	47°29′02″N 11°31′50″E / 47.4839°N 11.5306°E / 47.4839; 11.5306
Triassic
	Upper Triassic	235		Prati di Stuores, Dolomites, Italy	First appearance of Daxatina canadensis (Ammonite). Near first appearance of Metapolygnathus polygnathiformis (Conodont). Above magnetic zone S2n.	46°31′37″N 11°55′49″E / 46.5269°N 11.9303°E / 46.5269; 11.9303
	Middle Triassic	247.2		Candidate sections: Desli Caira, Dobrogea, Romania Guandao, Guizhou, China	First appearance of Chiosella timorensis (Conodont). Magnetic: Base of magnetic zone MT1n.	45°04′27″N 28°48′08″E / 45.0742°N 28.8022°E / 45.0742; 28.8022
	Lower Triassic	252.2		Meishan, Zhejiang, China	First appearance of Hindeodus parvus (Conodont).	31°04′47″N 119°42′21″E / 31.0798°N 119.7058°E / 31.0798; 119.7058
Palaeozoic
Permian		298.9		Aidaralash, Ural Mountains, Kazakhstan	First appearance of Streptognathodus isolatus within the morphotype Streptognathodus wabaunsensis chronocline (Conodont).	50°14′45″N 57°53′29″E / 50.2458°N 57.8914°E / 50.2458; 57.8914
Carboniferous
	Pennsylvanian	323.2		Arrow Canyon, Nevada, USA	First appearance of Declinognathodus nodiliferus (Conodont).	36°44′00″N 114°46′40″W / 36.7333°N 114.7778°W / 36.7333; -114.7778
	Mississippian	358.9		La Serre, Montagne Noire, France	First appearance of Siphonodella sulcata (Conodont). In 2006 it was discovered that this GSSP has biostratigraphic problems.	43°33′20″N 3°21′26″E / 43.5555°N 3.3573°E / 43.5555; 3.3573
Devonian		419.2		Klonk, Prague, Czech Republic	First appearance of Monograptus uniformis (graptolite).	49°51′18″N 13°47′31″E / 49.8550°N 13.7920°E / 49.8550; 13.7920
Silurian		443.4		Dob's Linn, Moffat, U.K.	First appearance of Akidograptus ascensus and Parakidograptus acuminatus (Graptolite). 1.6 m above the base of the Birkhill Shale Formation.	55°26′24″N 3°16′12″W / 55.4400°N 3.2700°W / 55.4400; -3.2700
Ordovician		485.4		Greenpoint section Green Point, Newfoundland, Canada	First appearance of Iapetognathus fluctivagus (Conodont). Planktonic graptolites occur 4.8 m above boundary. Coincides with a peak in carbon isotopes.	49°40′58″N 57°57′55″W / 49.6829°N 57.9653°W / 49.6829; -57.9653
Cambrian		541		Fortune head section, Newfoundland, Canada	First appearance of Treptichnus pedum (trace fossil).	47°04′34″N 55°49′52″W / 47.0762°N 55.8310°W / 47.0762; -55.8310
Era	Period	Precambrian
Proterozoic
Neoproterozoic
	Ediacaran	635		Enorama Creek section Flinders Ranges, South Australia	Worldwide distinct cap carbonates. Beginning of a distinctive pattern of secular changes in carbon isotopes.	31°19′53″S 138°38′00″E / 31.3314°S 138.6334°E / -31.3314; 138.6334
	Cryogenian	850		Defined chronometrically now. GSSP is in progress.
	Tonian	1000		Defined chronometrically
Mesoproterozoic
	Stenian	1200		Defined chronometrically
	Ectasian	1400		Defined chronometrically
	Calymmian	1600		Defined chronometrically
Palaeoproterozoic
	Statherian	1800		Defined chronometrically
	Orosirian	2050		Defined chronometrically
	Rhyacian	2300		Defined chronometrically
	Siderian	2500		Defined chronometrically
Archaean & Hadean
Neoarchaean		2800
Mesoarchaean		3200
Palaeoarchaean		3600
Eoarchaean		4000
Hadean		4567

Global Standard Stratigraphic Ages (GSSAs)

It's hard to find perfect rock sections for very old time periods. This is because older rocks are often changed by Earth's movements. So, for times before about 640 million years ago, scientists use a different method.

These older boundaries are defined by a specific date. They are called "Global Standard Stratigraphic Ages" (GSSAs). The oldest GSSP that marks a physical spot is for the start of the Ediacaran period. This period began 635 million years ago.

Images for kids

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  The 'golden spike' (bronze disk in the lower section of the image) or 'type section' of the Global Boundary Stratotype Section and Point (GSSP) for the base of Ediacaran period (Ediacara, South Australia)

See also

In Spanish: Sección estratotipo y punto de límite global para niños