EON, Era, System, Series, Stages
Age (Ma)
GTS 2004Est.
±MaDerivation of age
Principal correlative events
GSSP and location
Status
Publication
PHANEROZOIC Eon
Cenozoic Era
Neogene System
"Quaternary" is traditionally considered to be the interval of oscillating climatic extremes (glacial and interglacial episodes) that was initiated at about 2.5 Ma, therefore encompasses the Holocene, Pleistocene and uppermost Pliocene. It is not a formal chronostratigraphic unit.
base Holocene
0.0115
0.00
Carbon-14 dating calibration
exactly 10,000 Carbon-14 years (= 11.5 ka calendar years BP) at the end of the Younger Dryas cold spell
Informal working definition
base upper Pleistocene Subseries
0.126
0.00
Astronomical cycles in sediments
base of the Eemian interglacial stage (= base of marine isotope stage 5e) before final glacial episode of Pleistocene
Potentially, within sediment core under the Netherlands (Eemian type area)
Informal working definition
base middle Pleistocene Subseries
0.781
0.00
Astronomical cycles in sediments
Brunhes-Matuyama magnetic reversal
Informal working definition
base Pleistocene Series
1.806
0.00
Astronomical cycles in sediments
Just above top of magnetic polarity chronozone C2n (Olduvai) and the extinction level of calcareous nannofossil Discoaster brouweri (base Zone CN13). Above are lowest occurrence of calcareous nannofossil medium Gephyrocapsa spp. and extinction level of planktonic foraminifer Globigerinoides extremus.
Top of sapropel layer 'e', Vrica section, Calabria, Italy
Ratified 1985
Episodes 8 (2), p.116-120, 1985
base Gelasian Stage
2.588
0.00
Astronomical cycles in sediments
Isotopic stage 103, base of magnetic polarity chronozone C2r (Matuyama). Above are extinction levels of calcareous nannofossil Discoaster pentaradiatus and D. surculus (base Zone CN12c).
Midpoint of sapropelic Nicola Bed ("A5"), Monte San Nicola, Gela, Sicily, Italy
Ratified 1996
Episodes 21 (2), p.82-87, 1998
base Piacenzian Stage
3.600
0.00
Astronomical cycles in sediments
Base of magnetic polarity chronozone C2An (Gauss); extinction levels of planktonic foraminifers Globorotalia margaritae (base Zone PL3) and Pulleniatina primalis.
Base of beige layer of carbonate cycle 77, Punta Piccola, Sicily, Italy
Ratified 1997
Episodes 21 (2), p.88-93, 1998
base Zanclean Stage, base Pliocene Series
5.332
0.00
Astronomical cycles in sediments
Top of magnetic polarity chronozone C3r, ~100 kyr before Thvera normal-polarity subchronozone (C3n.4n). Calcareous nannofossils -- near extinction level of Triquetrorhabdulus rugosus (base Zone CN10b) and the lowest occurrence of Ceratolithus acutus.
Base of Trubi Fm (base of carbonate cycle 1), Eraclea Minoa, Sicily, Italy
Ratified 2000
Episodes 23 (3), p.179-187, 2000
base Messinian Stage
7.246
0.00
Astronomical cycles in sediments
Astrochronology age of 7.251 Ma; middle of magnetic polarity chronozone C3Br.1r; lowest regular occurrence of the Globorotalia conomiozea planktonic foraminifer group.
Base of red layer of carbonate cycle 15, Oued Akrech, Rabat, Morocco
Ratified 2000
Episodes 23 (3), p. 172-178, 2000
base Tortonian Stage
11.608
0.00
Astronomical cycles in sediments
Last Common Occurrences of the calcareous nannofossil Discoaster kugleri and the planktonic foraminifer Globigerinoides subquadratus. Associated with the short normal-polarity subchron C5r.2n.
Midpoint of sapropel 76, Monte dei Corvi beach section, Ancona, Italy
Ratified 2003
Episodes article in preparation
base Serravallian Stage
13.65
0.00
Astronomical cycles in sediments
Near lowest occurrence of nannofossil Sphenolithus heteromorphus, and within magnetic polarity chronozone C5ABr.
GSSP anticipated in 2004
base Langhian Stage
15.97
0.00
Calibrated magnetic anomaly scale
Near first occurrence of planktonic foraminifer Praeorbulina glomerosa and top of magnetic polarity chronozone C5Cn.1n
GSSP anticipated in 2004
base Burdigalian Stage
20.43
0.00
Calibrated magnetic anomaly scale
Near lowest occurrence of planktonic foraminifer Globigerinoides altiaperturus or near top of magnetic polarity chronozone C6An
Guide event is undecided
base Aquitanian Stage, base Miocene Series, base Neogene System
23.03
0.00
Astronomical cycles in sediments
Base of magnetic polarity chronozone C6Cn.2n; lowest occurrence of planktonic foraminifer Paragloborotalia kugleri; near extinction of calcareous nannofossil Reticulofenestra bisecta (base Zone NN1).
35 m from top of Lemme-Carrosio section, Carrosio village, north of Genoa, Italy
Ratified 1996
Episodes 20 (1),p. 23-28, 1997
Paleogene System
base Chattian Stage
28.4
0.1
Calibrated magnetic anomaly scale relative to base-Miocene and C24n. Arbitrary 100 kyr uncertainty assigned.
Planktonic foraminifer, extinction of Chiloguembelina (base Zone P21b)
Probably in Umbria-Marche region of Italy
GSSP anticipated in 2004
base Rupelian Stage, base Oligocene Series
33.9
0.1
Calibrated magnetic anomaly scale relative to base-Miocene and C24n.
Planktonic foraminifer, extinction of Hantkenina
Base of marl bed at 19m above base of Massignano quarry, Ancona, Italy
Ratified 1992
Episodes 16 (3), p.379-382, 1993
base Priabonian Stage
37.2
0.1
Calibrated magnetic anomaly scale relative to base-Miocene and C24n
Near lowest occurrence of calcareous nannofossil Chiasmolithus oamaruensis (base Zone NP18)
Probably in Umbria-Marche region of Italy
base Bartonian Stage
40.4
0.2
Calibrated magnetic anomaly scale relative to base-Miocene and C24n
Near extinction of calcareous nannofossil Reticulofenestra reticulata
base Lutetian Stage
48.6
0.2
Calibrated magnetic anomaly scale relative to base-Miocene and C24n
Planktonic foraminifer, lowest occurrence of Hantkenina
Leading candidate is Fortuna section, Murcia province, Betic Cordilleras, Spain
GSSP anticipated in 2004
base Ypresian Stage, base Eocene Series
55.8
0.2
Astronomical cycles in sediments scaled from base-Paleocene
Base of negative carbon-isotope excursion
Dababiya Section near Luxor, Egypt
Ratified 2003
Episodes article in preparation
base Thanetian Stage
58.7
0.2
Astronomical cycles in sediments scaled from base Paleocene, using base of magnetic polarity chronozone C26n. Arbitrary 0.1 (2 precession cycles, plus the base-Paleogene radiometric) uncertainty assigned to all estimates.
Magnetic polarity chronozone, base of C26n, is a temporary assignment
Leading candidate is Zumaya section, northern Spain
Guide event is undecided
base Selandian Stage
61.7
0.2
Astronomical cycles in sediments scaled from base Paleocene, using magnetic polarity chronozone placement of C27n.9
Boundary task group is considering a higher level -- base of calcareous nannofossil zone NP5 -- which would be ~1 myr younger.
Leading candidate is Zumaya section, northern Spain
Guide event is undecided
base Danian Stage, base Paleogene System, base Cenozoic
65.5
0.3
Ar-Ar and U-Pb age agreement
Iridium geochemical anomaly. Associated with a major extinction horizon (foraminifers, calcareous nannofossils, dinosaurs, etc.);
Base of boundary clay, El Kef, Tunisia (but deterioration may require assigning a replacement section)
Ratified 1991
Mesozoic Era
Cretaceous System
Most Cretaceous substages also have recommended GSSP criteria
base Maastrichtian Stage
70.6
0.6
Estimated placement relative to Ar-Ar calibrated Sr-curve
Mean of 12 biostratigraphic criteria of equal importance. Closely above is lowest occurrence of ammonite Pachydiscus neubergicus. Boreal proxy is lowest occurrence of belemnite Belemnella lanceolata.
115.2 m level in Grande Carrière quarry, Tercis-les-Bains, Landes province, SW France
Ratified 2001
Episodes 24 (4), p.229-238, 2001; Odin (ed.) IUGS Spec. Publ. Series, v.36, Elsevier, 910pp.
base Campanian Stage
83.5
0.7
Spline fit of Ar-Ar ages and ammonite zones.
Crinoid, extinction of Marsupites testudinarius
Leading candidates are in southern England and in Texas
base Santonian Stage
85.8
0.7
Spline fit of Ar-Ar ages and ammonite zones.
Inoceramid bivalve, lowest occurrence of Cladoceramus undulatoplicatus
Leading candidates are in Spain, England and Texas
base Coniacian Stage
89.3
1.0
Spline fit of Ar-Ar ages and ammonite zones.
Inoceramid bivalve, lowest occurrence of Cremnoceramus rotundatus (sensu Tröger non Fiege)
Base of Bed MK47, Salzgitter-Salder Quarry, SW of Hannover, Lower Saxony, northern Germany
GSSP anticipated in 2004
base Turonian Stage
93.5
0.8
Spline fit of Ar-Ar ages and ammonite zones
Ammonite, lowest occurrence of Watinoceras devonense
Base of Bed 120, Rock Canyon Anticline, east of Pueblo, Colorado, west-central USA
Ratified 2003
Episodes article in preparation
base Cenomanian Stage
99.6
0.9
Spline fit of Ar-Ar ages and ammonite zones, plus monitor standard correction. Then cycle stratigraphy to place foraminifer datum relative to ammonite zonation.
Planktonic foraminifer, lowest occurrence of Rotalipora globotruncanoides
36 m below top of Marnes Bleues Formation, Mont Risou, Rosans, Haute-Alpes, SE France
Ratified 2002
Episodes article in preparation
base Albian Stage
112.0
1.0
Estimated placement relative to bases of Cenomanian and Aptian, with large uncertainty due to lack of GSSP criteria. Ar-Ar age of 114.6 +/- 0.7 Ma from Parahoplites nutfieldensis below.
Calcareous nannofossil, lowest occurrence of Praediscosphaera columnata (= P. cretacea of some earlier studies), is one potential marker.
Guide event is undecided
base Aptian Stage
125.0
1.0
Base of M0r, as recomputed from Ar-Ar age from MIT guyot
Magnetic polarity chronozone, base of M0r
Leading candidate is Gorgo a Cerbara, Piobbico, Umbria-Marche, central Italy
base Barremian Stage
130.0
1.5
Pacific spreading model for magnetic anomaly ages (variable rate), using placement at M5n.8.
Ammonite, lowest occurrence of Spitidiscus hugii – Spitidiscus vandeckii group
Leading candidate is Río Argos near Caravaca, Murcia province, Spain
base Hauterivian Stage
136.4
2.0
Pacific spreading model for magnetic anomaly ages (variable rate), using placement at base M11n
Ammonite, lowest occurrence of genus Acanthodiscus (especially A. radiatus)
Leading candidate is La Charce village, Drôme province, southeast France
base Valanginian Stage
140.2
3.0
Pacific spreading model for magnetic anomaly ages (variable rate), using placement at M14r.3 (base T. pertransiens).
Calpionellid, lowest occurrence of Calpionellites darderi (base of Calpionellid Zone E); followed by the lowest occurrence of ammonite “Thurmanniceras” pertransiens
Leading candidate is near Montbrun-les-Bains, Drôme province, southeast France
base Berriasian Stage, base Cretaceous System
145.5
4.0
Pacific spreading model for magnetic anomaly ages (variable rate), assigning to base of Berriasella jacobi zone (M19n.2n.55)
Maybe near lowest occurrence of ammonite Berriasella jacobi
Guide event is undecided
Jurassic System
base Tithonian Stage
150.8
4.0
Pacific spreading model for magnetic anomaly ages (variable rate), assigning to base M22An
Near base of Hybonoticeras hybonotum ammonite zone and lowest occurrence of Gravesia genus, and the base of magnetic polarity chronozone M22An
Guide event is undecided
base Kimmeridgian Stage
155.7
4.0
Pacific spreading model for magnetic anomaly ages (variable rate), assigning to base M26r.2 (Boreal ammonite definition)
Near base of Pictonia baylei ammonite zone of Boreal realm
Leading candidates are In Scotland, SE France and Poland
GSSP anticipated in 2004
base Oxfordian Stage
161.2
4.0
Pacific spreading model for magnetic anomaly ages (variable rate), assigning to base M36An
Ammonite, Brightia thuouxensis Horizon at base of the Cardioceras scarburgense Subzone (Quenstedtoceras mariae Zone)
Leading candidates are in SE France and southern England
GSSP anticipated in 2004
base Callovian Stage
164.7
4.0
Equal subzones scale Bajo-Bath-Callov
Ammonite, lowest occurrence of the genus Kepplerites (Kosmoceratidae) (defines base of Macrocephalites herveyi Zone in sub-Boreal province of Great Britain to southwest Germany)
Leading candidate is Pfeffingen, Swabian Alb, SW Germany
GSSP anticipated in 2004
base Bathonian Stage
167.7
3.5
Equal subzones scale Bajo-Bath-Callov
Ammonite, lowest occurrence of Parkinsonia (G.) convergens (defines base of Zigzagiceras zigzag Zone)
base Bajocian Stage
171.6
3.0
Equal subzones scale Bajo-Bath-Callov
Ammonite, lowest occurrence of the genus Hyperlioceras (defines base of the Hyperlioceras discites Zone)
Base of Bed AB11, 77.8 m above base of Murtinheira section, Cabo Mondego, western Portugal
Ratified 1996
Episodes 20 (1), p.16-22, 1997
base Aalenian Stage
175.6
2.0
Duration of Aalenian-Toarcian from cycle stratigraphy
Ammonite, lowest occurrence of Leioceras genus
base of Bed FZ107, Fuentelsalz, central Spain
Ratified 2000
Episodes 24 (3), p.166-175, 2001
base Toarcian Stage
183.0
1.5
Duration of Aalenian-Toarcian from cycle stratigraphy
Near lowest occurrence of a diversified Eodactylitesammonite fauna; correlates with the NW European Paltus horizon.
Guide event undecided
base Pliensbachian Stage
189.6
1.5
Cycle-scaled linear Sr trend
Ammonite, lowest occurrences of Bifericeras donovani and of genera Apoderoceras and Gleviceras.
Wine Haven section, Robin Hood's Bay, Yorkshire, England, UK
GSSP anticipated in 2003
base Sinemurian Stage
196.5
1.0
Cycle-scaled linear Sr trend
Ammonite, lowest occurrence of arietitid genera Vermiceras and Metophioceras
0.9 m above base of Bed 145, East Quantoxhead, Watchet, West Somerset, SW England, UK
Ratified 2000
Episodes 25 (1), p. 22-26, 2002
base Hettangian Stage, base Jurassic System
199.6
0.6
U-Pb age just below proposed GSSP for base-Jurassic
Near lowest occurrence of smooth Psiloceras planorbis ammonite group
Guide event is undecided
Triassic System
base Rhaetian Stage
203.6
1.5
Magnetostratigraphic correlation to cycle-scaled Newark magnetic polarity pattern
Near lowest occurrence of ammonite Cochlocera, conodonts Misikella spp. and Epigondolella mosheri, and radiolarian Proparvicingula moniliformis
Key sections in Austria, British Columbia (Canada), and Turkey
Guide event is undecided
base Norian Stage
216.5
2.0
Magnetostratigraphic correlation to cycle-scaled Newark magnetic polarity pattern
Base of Klamathites macrolobatus or Stikinoceras kerri ammonoid zones and the Metapolygnathus communisti or M. primitius conodont zones
Leading candidates are in British Columbia (Canada), Sicily (Italy), and possibly Slovakia, Turkey (Antalya Taurus) and Oman.
Guide event is undecided
base Carnian Stage
228.0
2.0
Magnetostratigraphic correlation to cycle-scaled Newark magnetic polarity pattern
Near first occurrence of the ammonoids Daxatina or Trachyceras, and of the conodont Metapolygnathus polygnathiformis
Candidate section at Prati di Stuores, Dolomites, northern Italy. Important reference sections in Spiti (India) and New Pass, Nevada (USA).
Guide event is undecided
base Ladinian Stage
237.0
2.0
U-Pb array by Mundil et al. on levels near Nevadites (= Secedensis) ammonite zone in Dolomites, plus placement relative to magnetostratigraphy corrlations to cycle-scaled Newark magnetic polarity pattern
Alternate levels are near base of Reitzi, Secedensis, or Curionii ammonite zone; near first occurrence of the conodont genus Budurovignathus
Leading candidates are Bagolino (Italy) and Felsoons (Hungary). Important reference sections in the Humboldt Range, Nevada (USA).
Guide event is undecided
base Anisian Stage
245.0
1.5
Proportional subzonal scaling
Ammonite, near lowest occurrences of genera Japonites, Paradanubites, and Paracrochordiceras; and of the conodont Chiosella timorensis
Candidate section probable at Desli Caira, Dobrogea, Romania; significant sections in Guizhou Province (China).
GSSP anticipated in 2004
base Olenekian Stage
249.7
0.7
Composite standard from conodonts scaled to base-Anisian and base-Triassic
Near lowest occurrence of Hedenstroemia or Meekoceras gracilitatis ammonites, and of the conodont Neospathodus waageni
Candidate sections in Siberia (Russia) and probably Chaohu, Anhui Province, China. Important sections also in Spiti.
Guide event is undecided
base Induan Stage, base Triassic System, base Mesozoic
251.0
0.4
U-Pb ages bracket GSSP (Bowring et al., 1998)
Conodont, lowest occurrence of Hindeodus parvus; termination of major negative carbon-isotope excursion. About 1 myr after peak of Late Permian extinctions.
Base of Bed 27c, Meishan, Zhejiang, China
Ratified 2001
Episodes 24 (2), p.102-114, 2001
Paleozoic Era
Permian System
base Changhsingian Stage
253.8
0.7
Permian-Carboniferous time scale is derived from calibrating a master composite section to selected radiometric ages
Near lowest occurrence of conodont Clarkina wangi
Leading candidates are in China
base Wuchiapingian Stage
260.4
0.7
Near lowest occurrence of conodont Clarkina postbitteri
Candidate section is Tieqiao rail-bridge section, Laibin Syncline, Guangxi Province, China
Ratification pending (Jan'04)
base Capitanian Stage
265.8
0.7
Conodont, lowest occurrence of Jinogondolella postserrata
4.5 m above base of Pinery Limestone Member, Nipple Hill, SE Guadalupe Mountains, Texas, USA
Ratified 2001
Episodes article in preparation
base Wordian Stage
268.0
0.7
Conodont, lowest occurrence of Jinogondolella aserrata
7.6 m above base of Getaway Ledge outcrop, Guadalupe Pass, SE Guadalupe Mountains, Texas, USA
Ratified 2001
Episodes article in preparation
base Roadian Stage, base Guadalupian Series
270.6
0.7
Conodont, lowest occurrence of Jinogondolella nanginkensis
42.7 m above base of Cutoff Formation, Stratotype Canyon, southern Guadalupe Mountains, Texas, USA
Ratified 2001
Episodes article in preparation
base Kungurian Stage
275.6
0.7
Near lowest occurrence of conodont Neostreptognathus pnevi - N. exculptus
Leading candidates are in southern Ural Mtns.
base Artinskian Stage
284.4
0.7
Near lowest occurrence of conodont Sweetognathus whitei-Mesogondolella bisselli
Leading candidates are in southern Ural Mtns.
base Sakmarian Stage
294.6
0.8
Near lowest occurrence of conodont Streptognathodus postfusus
Leading candidate is at Kondurovsky, Orenburg Province, Russia.
base Asselian Stage, base Cisuralian Series, base Permian System
299.0
0.8
Conodont, lowest occurrence of Streptognathodus isolatus within the S. "wabaunsensis" conodont chronocline. 6 m higher is lowest fusilinid foraminifer Sphaeroschwagerina
27 m above base of Bed 19, Aidaralash Creek, Aktöbe, southern Ural Mountains, northern Kazakhstan
Ratified, 1996
Episodes 21 (1), p.11-18, 1998
Carboniferous System
Pennsylvanian Subsystem
base Gzhelian Stage
303.9
0.9
Near lowest occurrences of the fusulinids Daixina, Jigulites and Rugosofusulina, or lowest occurrence of Streptognathodus zethu
Guide event is undecided
base Kasimovian Stage
306.5
1.0
Near base of Obsoletes obsoletes and Protriticites pseudomontiparus fusulinid zone, or lowest occurrence of Parashumardites ammonoid
Guide event is undecided
base Moscovian Stage
311.7
1.1
Near lowest occurrences of Declinognathodus donetzianus and/or Idiognathoides postsulcatus conodont species, and fusulinid species Aljutovella aljutovica
Guide event is undecided
base Bashkirian Stage, base Pennsylvanian Subsystem
318.1
1.3
Conodont, lowest occurrence of Declinognathodus nodiliferus s.l.
82.9 m above top of Battleship Wash Fm., Arrow Canyon, southern Nevada, USA
GSSP ratified 1996. Subsystem rank with Mississippian and Pennsylvanian names ratified 2000.
Episodes 22 (4), p.272-283, 1999
Mississippian Subsystem
base Serpukhovian
326.4
1.6
Near lowest occurrence of conodont, Lochriea crusiformis
Guide event is undecided
base Visean
345.3
2.1
Foraminifer, lineage Eoparastaffella simplex morphotype 1/morphotype 2
Leading candidate is Pengchong, south China
base Tournaisian, base Mississippian Subsystem, base Carboniferous System
359.2
2.5
Conodont, above lowest occurrence of Siphonodella sulcata
Base of Bed 89, La Serre, Montagne Noir, Cabrières, southern France
Ratified 1990
Episodes 14 (4), p.331-336, 1991
Devonian System
base Famennian Stage
374.5
2.6
Devonian time scale is a statistical fit of a composite biostratigraphic zonation (based on Figure 8 of Williams et al., 2000) to selected radiometric ages
Just above major extinction horizon (Upper Kellwasser Event), including conodonts Ancyrodella and Ozarkodina and goniatites of Gephuroceratidae and Beloceratidae
base of Bed 32a, upper Coumiac quarry, Cessenon, Montagne Noir, southern France
Ratified 1993
Episodes 16 (4), p.433-441, 1993
base Frasnian Stage
385.3
2.6
Conodont, lowest occurrence of Ancyrodella rotundiloba (defines base of Lower Polygnathus asymmetricus conodont Zone)
Base of Bed 42a', Col du Puech de la Suque section, St. Nazaire-de-Ladarez, SE Montagne Noir, southern France
Ratified 1986
Episodes 10 (2), p.97-101, 1987
base Givetian Stage
391.8
2.7
Conodont, lowest occurrence of Polygnathus hemiansatus, near base of goniatite Maenioceras Stufe
Base of Bed 123, Jebel Mech Irdane ridge, Tafilalt, Morocco
Ratified 1994
Episodes 18 (3), p.107-115, 1995
base Eifelian Stage
397.5
2.7
Conodont, lowest occurrence of Polygnathus costatus partitus; major faunal turnover
Base unit WP30, trench at Wetteldorf Richtschnitt, Schönecken-Wetteldorf, Eifel Hills, western Germany
Ratified 1985
Episodes 8 (2), p.104-109, 1985
base Emsian Stage
407.0
2.8
Conodont, lowest occurrence of Polygnathus kitabicus (= Po. dehiscens)
Base of Bed 9/5, Zinzil'ban Gorge, SE of Samarkand, Uzbekistan
Ratified 1995
Episodes 20 (4), p. 235-240, 1997
base Pragian Stage
411.2
2.8
Conodont, lowest occurrence of Eognathodus sulcatus
Base of Bed 12, Valká Chuchle quarry, southwest part of Prague city, Czech Republic
Ratified 1989
Episodes 12 (2), p.109-113, 1989
base Lochkovian Stage, base Devonian System
416.0
2.8
base-Devonian from scale in Cooper (GTS 2004), which is 1 myr younger than Tucker et al (1998) estimate.
Graptolite, lowest occurrence of Monograptus uniformis
Within Bed 20, Klonk, Barrandian area, southwest of Prague, Czech Republic
Ratified 1972
Martinsson (ed.), The Silurian-Devonian Boundary, IUGS Series A, no.5, 349 pp., 1977
Silurian System [Holland and Bassett (eds), A Global Standard for the Silurian System, Nat. Mus. Wales, Geol. Series No.10, Cardiff, 325 pp., 1989]
base Pridoli Series (not subdivided in stages)
418.7
2.7
Silurian and Ordovician time scales are from calibrating a CONOP composite graptolite zonation to selecte radiometric ages
Graptolite, lowest occurrence of Monograptus parultimus
Within Bed 96, Pozáry section near Reporje, Barrandian area, Prague, Czech Republic
Ratified 1984
Episodes 8 (2), p.101-103, 1985
base Ludfordian Stage
421.3
2.6
Imprecise. May be near base of Saetograptus leintwardinensis graptolite zone.
Base of lithological unit C, Sunnyhill Quarry, Ludlow, Shropshire, southwest England, UK
Ratified 1980
Lethaia 14, p.168, 1981; Episodes 5 (3), p.21-23, 1982
base Gorstian Stage
422.9
2.5
Imprecise. Just below base of local acritarch Leptobrachion longhopense range zone. May be near base of Neodiversograptus nilssoni graptolite zone
Base of lithological unit F, Pitch Coppice quarry, Ludlow, Shropshire, southwest England, UK
Ratified 1980
Lethaia 14, p.168, 1981; Episodes 5 (3), p.21-23, 1982
base Homerian Stage
426.2
2.4
Graptolite, lowest occurrence of Cyrtograptus lundgreni (defines base of C. lundgreni graptolite zone)
Graptolite biozone intersection in stream section in Whitwell Coppice, Homer, Shropshire, southwest England, UK
Ratified 1980
Lethaia 14, p.168, 1981; Episodes 5 (3), p.21-23, 1982
base Sheinwoodian Stage
428.2
2.3
Imprecise. Between the base of acritarch biozone 5 and extinction of conodont Pterospathodus amorphognathoides. May be near base of Cyrtograptus centrifugus graptolite zone.
Base of lithological unit G, Hughley Brook, Apedale, Shropshire, southwest England, UK
Ratified 1980
Lethaia 14, p.168, 1981; Episodes 5 (3), p.21-23, 1982
base Telychian Stage
436.0
1.9
Brachiopods, just above extinction of Eocoelia intermedia and below lowest succeeding species Eocoelia curtisi. Near base of Monograptus turriculatus graptolite zone.
Locality 162 in transect d, Cefn Cerig road, Llandovery area, south-central Wales, UK
Ratified 1984
Episodes 8 (2), p.101-103, 1985
base Aeronian Stage
439.0
1.8
Graptolite, lowest occurrence of Monograptus austerus sequens (defines base of Monograptus triangulatus graptolite zone)
Base of locality 72 in transect h, Trefawr forestry road, north of Cwm-coed-Aeron Farm, Llandovery area, south-central Wales, UK
Ratified 1984
Episodes 8 (2), p.101-103, 1985
base Rhuddanian Stage, base Silurian System
443.7
1.5
Graptolites, lowest occurrences of Parakidograptus acuminatus and Akidograptus ascensus
1.6 m above base of Birkhill Shale Fm., Dob's Linn, Moffat, Scotland, UK
Ratified 1984
Episodes 8 (2), p.98-100, 1985
Ordovician System
base Hirnantian Stage
445.6
1.5
Potentially at base of the Normalograptus extraordinarius - N. ojsuensis graptolite biozone
Candidate section is Wangjiawan, China
base of sixth stage (not yet named)
455.8
1.6
Potentially near first appearance of the graptolite Dicellograptus complanatus and of the conodont Amorphognathus ordovicicus
Guide event is undecided
base of fifth stage (not yet named)
460.9
1.6
Graptolite, lowest occurrence of Nemagraptus gracilis
1.4 m below phosphorite in E14a outcrop, Fågelsång, Scane, southern Sweden
Ratified 2002
Episodes 23 (2), p.102-109, 2000 (proposal; formal GSSP publication in preparation).
base Darriwillian Stage
468.1
1.6
Graptolite, lowest occurrence of Undulograptus austrodentatus
Base of Bed AEP184, 22 m below top of Ningkuo Fm., Huangnitang, Changshan, Zhejiang province, southeast China
Ratified 1987
Episodes 20 (3), p.158-166, 1997
base of third stage (not yet named)
471.8
1.6
Conodont, lowest occurrence of Tripodus laevis
base of second stage (not yet named)
478.6
1.7
Graptolite, lowest occurrence of Tetragraptus approximatus
Just above E bed, Diabasbrottet quarry, Västergötland, southern Sweden
Ratified 2002
Episodes article in preparation
base of Tremadocian stage, base Ordovician System
488.3
1.7
Conodont, lowest occurrence of Iapetognathus fluctivagus;just above base of Cordylodus lindstromi conodont Zone. Just below lowest occurrence of planktonic graptolites. Currently dated around 489 Ma
Within Bed 23 at the 101.8 m level, Green Point, western Newfoundland, Canada
Ratified 2000
Episodes 24 (1), p.19-28,
Cambrian System
Potential GSSP correlation levels include Cordylodus proavus, Glyptagnostus reticulatus, Ptychagnostus punctuosus, Acidusus atavus, and Oryctocephalus indicus. Overview of potential subdivisions in Episodes 23 (3), p. 188-195, 2000.
upper stage(s) in Furongian
Potential GSSP levels in upper Cambrian are based on trilobites and condonts
base Paibian Stage, base Furongian Series
501.0
2.0
Radiometric ages near primary marker level. Estimated age and uncertainty only.
Trilobite, lowest occurrence of agnostoid Glyptagnostus reticulatus. Coincides with base of large positive carbon-isotope excursion
369.06 m above base of Huaqiao Fm, Paibi section, NW Hunan province, south China
Ratified 2003
Episodes article in preparation
513.0
2.0
Radiometric ages near primary marker level. Estimated age and uncertainty only
Potential GSSP levels in Middle Cambrian are based mainly on trilobites
Potential GSSP levels in Lower Cambrian are based on archaeocyatha, small shelly fossils, and to a lesser extent, trilobites
base Cambrian System, base Paleozoic Era, base Phanerozoic Eon
542.0
1.0
U-Pb age from Oman coinciding with the negative carbon excursion
Trace fossil, lowest occurrence of Treptichnus (Phycodes) pedum. Near base of negative carbon-isotope excursion
2.4 m above base of Member 2 of Chapel Island Fm., Fortune Head, Burin Peninsula, southeast Newfoundland, Canada
Ratified 1992
Episodes 17 (1&2), p.95-100, 1994.
PROTEROZOIC Eon
Pre-Cambrian eras and systems below Ediacaran are defined by absolute ages, rather than stratigraphic points.
Neoproterozoic Era
base Ediacaran System
600
Vague estimation from bracketing radiometric ages
Termination of Varanger (or Marinoan) glaciation.
"Base of the Nuccaleena Formation cap carbonate, immediately above the Elatina diamictite in the
Enorama Creek section, Flinders Ranges, South Australia"
Age-definition (650 Ma) ratified in 1990, but ICS now voting on Australian GSSP
Episodes 14 (2), p.139-140, 1991
Cryogenian System
850
Defined chronometrically
Base = 850 Ma
Tonian System
1000
Defined chronometrically
Base = 1000 Ma
Ratified 1990
Episodes 14 (2), p.139-140, 1991
Mesoproterozoic Era
Stenian System
1200
Defined chronometrically
Base = 1200 Ma
Ratified 1990
Episodes 14 (2), p.139-140, 1991
Ectasian System
1400
Defined chronometrically
Base = 1400 Ma
Ratified 1990
Episodes 14 (2), p.139-140, 1991
Calymmian System
1600
Defined chronometrically
Base = 1600 Ma
Ratified 1990
Episodes 14 (2), p.139-140, 1991
Paleoproterozoic Era
Statherian System
1800
Defined chronometrically
Base = 1800 Ma
Ratified 1990
Episodes 14 (2), p.139-140, 1991
Orosirian System
2050
Defined chronometrically
Base = 2050 Ma
Ratified 1990
Episodes 14 (2), p.139-140, 1991
Rhyacian System
2300
Defined chronometrically
Base = 2300 Ma
Ratified 1990
Episodes 14 (2), p.139-140, 1991
Siderian System
2500
Defined chronometrically
Base = 2500 Ma
Ratified 1990
Episodes 14 (2), p.139-140, 1991
ARCHEAN Eon
Neoarchean Era
2800
Defined chronometrically
Base = 2800 Ma
Ratified 1990
Episodes 14 (2), p.139-140, 1991
Mesoarchean Era
3200
Defined chronometrically
Base = 3200 Ma
Ratified 1990
Episodes 14 (2), p.139-140, 1991
Paleoarchean Era
3600
Defined chronometrically
Base = 3600 Ma
Ratified 1990
Episodes 14 (2), p.139-140, 1991
Eoarchean Era
Base is not defined
