Overview of Global Boundary Stratotype Sections and Points (GSSP's)

Status on October 2003, compiled by Jim Ogg (ICS Executive Secretary)

EON, Era, System, Series, Stages Age (Ma)
GTS 2004
Est.
±Ma
Derivation 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.
Holocene Series
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
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Informal working definition
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Pleistocene Series
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
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base middle Pleistocene Subseries 0.781 0.00 Astronomical cycles in sediments Brunhes-Matuyama magnetic reversal
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Informal working definition
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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
Pliocene Series
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
Miocene Series
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.
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GSSP anticipated in 2004
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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
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GSSP anticipated in 2004
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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
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Guide event is undecided
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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
Oligocene Series
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
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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
Eocene Series
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
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base Bartonian Stage 40.4 0.2 Calibrated magnetic anomaly scale relative to base-Miocene and C24n Near extinction of calcareous nannofossil Reticulofenestra reticulata
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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
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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
Paleocene Series
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
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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
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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
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Mesozoic Era
Cretaceous System
Most Cretaceous substages also have recommended GSSP criteria
Upper Cretaceous Series
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 Carri�re 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
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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
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base Coniacian Stage 89.3 1.0 Spline fit of Ar-Ar ages and ammonite zones. Inoceramid bivalve, lowest occurrence of Cremnoceramus rotundatus (sensu Tr�ger non Fiege) Base of Bed MK47, Salzgitter-Salder Quarry, SW of Hannover, Lower Saxony, northern Germany GSSP anticipated in 2004
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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
Lower Cretaceous Series
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.
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Guide event is undecided
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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
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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 R�o Argos near Caravaca, Murcia province, Spain
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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, Dr�me province, southeast France
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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
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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
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Guide event is undecided
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Jurassic System
Upper Jurassic Series
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
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Guide event is undecided
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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
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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
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Middle Jurassic Series
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
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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)
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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
Lower Jurassic Series
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.
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Guide event undecided
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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
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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
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Guide event is undecided
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Triassic System
Upper Triassic Series
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
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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
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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
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Middle Triassic Series
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
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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
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Lower Triassic Series
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
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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
Lopingian Series
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
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base Wuchiapingian Stage 260.4 0.7
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Near lowest occurrence of conodont Clarkina postbitteri Candidate section is Tieqiao rail-bridge section, Laibin Syncline, Guangxi Province, China Ratification pending (Jan'04)
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Guadalupian Series
base Capitanian Stage 265.8 0.7
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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
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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
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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
Cisuralian Series
base Kungurian Stage 275.6 0.7
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Near lowest occurrence of conodont Neostreptognathus pnevi - N. exculptus Leading candidates are in southern Ural Mtns.
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base Artinskian Stage 284.4 0.7
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Near lowest occurrence of conodont Sweetognathus whitei-Mesogondolella bisselli Leading candidates are in southern Ural Mtns.
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base Sakmarian Stage 294.6 0.8
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Near lowest occurrence of conodont Streptognathodus postfusus Leading candidate is at Kondurovsky, Orenburg Province, Russia.
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base Asselian Stage, base Cisuralian Series, base Permian System 299.0 0.8
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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
Upper Pennsylvanian Series
base Gzhelian Stage 303.9 0.9
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Near lowest occurrences of the fusulinids Daixina, Jigulites and Rugosofusulina, or lowest occurrence of Streptognathodus zethu
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Guide event is undecided
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base Kasimovian Stage 306.5 1.0
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Near base of Obsoletes obsoletes and Protriticites pseudomontiparus fusulinid zone, or lowest occurrence of Parashumardites ammonoid
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Guide event is undecided
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Middle Pennsylvanian Series
base Moscovian Stage 311.7 1.1
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Near lowest occurrences of Declinognathodus donetzianus and/or Idiognathoides postsulcatus conodont species, and fusulinid species Aljutovella aljutovica
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Guide event is undecided
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Lower Pennsylvanian Series
base Bashkirian Stage, base Pennsylvanian Subsystem 318.1 1.3
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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
Upper Mississippian Series
base Serpukhovian 326.4 1.6
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Near lowest occurrence of conodont, Lochriea crusiformis
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Guide event is undecided
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Middle Mississippian Series
base Visean 345.3 2.1
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Foraminifer, lineage Eoparastaffella simplex morphotype 1/morphotype 2 Leading candidate is Pengchong, south China
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Lower Mississippian Series
base Tournaisian, base Mississippian Subsystem, base Carboniferous System 359.2 2.5
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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
Upper Devonian Series
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
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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
Middle Devonian Series
base Givetian Stage 391.8 2.7
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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
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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
Lower Devonian Series
base Emsian Stage 407.0 2.8
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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
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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]
Pridoli Series
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
Ludlow Series
base Ludfordian Stage 421.3 2.6
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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
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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
Wenlock Series
base Homerian Stage 426.2 2.4
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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
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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
Llandovery Series
base Telychian Stage 436.0 1.9
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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
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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
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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
Upper Ordovician Series
base Hirnantian Stage 445.6 1.5
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Potentially at base of the Normalograptus extraordinarius - N. ojsuensis graptolite biozone Candidate section is Wangjiawan, China
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base of sixth stage (not yet named) 455.8 1.6
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Potentially near first appearance of the graptolite Dicellograptus complanatus and of the conodont Amorphognathus ordovicicus
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Guide event is undecided
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base of fifth stage (not yet named) 460.9 1.6
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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).
Middle Ordovician Series
base Darriwillian Stage 468.1 1.6
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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
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Conodont, lowest occurrence of Tripodus laevis
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Lower Ordovician Series
base of second stage (not yet named) 478.6 1.7
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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
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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 Cambrian ("Furongian") Series
upper stage(s) in Furongian
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Potential GSSP levels in upper Cambrian are based on trilobites and condonts
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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
Middle Cambrian Series
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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
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Lower Cambrian Series
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
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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
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Defined chronometrically Base = 850 Ma
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Tonian System 1000
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Defined chronometrically Base = 1000 Ma
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Ratified 1990 Episodes 14 (2), p.139-140, 1991
Mesoproterozoic Era
Stenian System 1200
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Defined chronometrically Base = 1200 Ma
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Ratified 1990 Episodes 14 (2), p.139-140, 1991
Ectasian System 1400
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Defined chronometrically Base = 1400 Ma
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Ratified 1990 Episodes 14 (2), p.139-140, 1991
Calymmian System 1600
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Defined chronometrically Base = 1600 Ma
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Ratified 1990 Episodes 14 (2), p.139-140, 1991
Paleoproterozoic Era
Statherian System 1800
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Defined chronometrically Base = 1800 Ma
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Ratified 1990 Episodes 14 (2), p.139-140, 1991
Orosirian System 2050
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Defined chronometrically Base = 2050 Ma
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Ratified 1990 Episodes 14 (2), p.139-140, 1991
Rhyacian System 2300
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Defined chronometrically Base = 2300 Ma
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Ratified 1990 Episodes 14 (2), p.139-140, 1991
Siderian System 2500
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Defined chronometrically Base = 2500 Ma
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Ratified 1990 Episodes 14 (2), p.139-140, 1991
ARCHEAN Eon
Neoarchean Era 2800
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Defined chronometrically Base = 2800 Ma
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Ratified 1990 Episodes 14 (2), p.139-140, 1991
Mesoarchean Era 3200
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Defined chronometrically Base = 3200 Ma
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Ratified 1990 Episodes 14 (2), p.139-140, 1991
Paleoarchean Era 3600
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Defined chronometrically Base = 3600 Ma
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Ratified 1990 Episodes 14 (2), p.139-140, 1991
Eoarchean Era
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Base is not defined
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