Mesozoic geochronology is the science of applying dates in the past to rocks of the Mesozoic.

Painting of a late Jurassic Scene on one of the large island in the Lower Saxony basin in northern Germany. Credit: Gerhard Boeggemann.



  1. ALMA represent the Asian Land Mammal Age,
  2. b2k represent before AD 2000,
  3. BP represent before present, as the chart is for 2008, this may require an added -8 for b2k,
  4. ELMMZ represent the European Land Mammal Mega Zone,
  5. FAD represent first appearance datum,
  6. FO represent first occurrence,
  7. Ga represent Gegaannum, billion years ago, or -109 b2k,
  8. GICC05 represent Greenland Ice Core Chronology 2005,
  9. GRIP represent Greenland Ice Core Project,
  10. GSSP represent Global Stratotype Section and Point,
  11. HO represent highest occurrence,
  12. ICS represent the International Commission on Stratigraphy,
  13. IUGS represent the International Union of Geological Sciences,
  14. LAD represent last appearance datum,
  15. LO represent lowest occurrence,
  16. Ma represent Megaannum, million years ago, or -106 b2k,
  17. NALMA represent the North American Land Mammal Age,
  18. NGRIP represent North Greenland Ice Core Project, and
  19. SALMA represent South American Land Mammal Age.

"The term b2 k [b2k] refers to the ice-core zero age of AD 2000; note that this is 50 years different from the zero yr for radiocarbon, which is AD 1950 [...]."[1]

Mesozoic time framesEdit

Sortable table
Name (English)[2] base/start (Ma)[3] top/end (Ma)[3] status subdivision of usage named after author, year
Aalenian 175.6 ± 2.0 171.6 ± 3.0 age Jurassic ICS Aalen (Germany)
Aegean 245 ± 1.5 244 age Middle Triassic Europe Aegean Sea
Alaunian 216 211 sub-age Upper Triassic Europe
Albian 112.0 ± 1.0 99.6 ± 0.9 age Cretaceous ICS Albia, Latin name of the river Aube (France) d'Orbigny, 1842
Anisian 245.0 ± 1.5 237.0 ± 2.0? age/Stage Middle Triassic ICS Anisus, Latin name for the river Enns (Austria)
Aptian 125.0 ± 1.0 112.0 ± 1.0 age Cretaceous ICS Apt (France) d'Orbigny, 1840
Aquilan 85.2 82.2 NALMA Cretaceous North America
Arowhanan 95.2 92.1 age Cretaceous New Zealand Arowhana
Austinian age Cretaceous south and east of the US Austin, Texas Murray, 1961
Bajocian 171.6 ± 3.0 167.7 ± 3.5 age Jurassic ICS Bayeux (France) d'Orbigny
Barremian 130.0 ± 1.5 125.0 ± 1.0 age Cretaceous ICS Barrême (France) Coquand, 1873
Bathonian 167.7 ± 3.5 164.7 ± 4.0 age Jurassic ICS Bath (England)
Bedoulian 129.97 125.0 sub-age Cretaceous regional
Berriasian 145.5 ± 4.0 140.2 ± 3.0 age Cretaceous ICS Berrias (France)
Bithynian Substage Middle Triassic Germany
Brahmanian 252.6 251 Stage Lower Triassic India, Germany
Buntsandstein[4] 251.0 ± 0.4 246.6[5] epoch/subperiod Triassic Europe German: bunte Sandstein = coloured sandstone Von Alberti, 1834
Callovian 164.7 ± 4.0 161.2 ± 4.0 age Jurassic ICS Kellaways (England) d'Orbigny
Campanian 83.5 ± 0.7 70.6 ± 0.6 age Cretaceous ICS Champagne (France) Coquand, 1857
Carixian 189.6 ± 1.5 sub-age Jurassic regional
Carnian 228.0 ± 2.0 216.5 ± 2.0 age Late Triassic ICS Carnic Alps (Austria) Mojsisovics, 1869
Cenomanian 99.6 ± 0.9 93.5 ± 0.8 age Cretaceous ICS Latin: Cenomanium = Le Mans (France) d'Orbigny, 1847
Clansayesian 115.0 112.0 sub-age Cretaceous
Coniacian 89.3 ± 1.0 85.8 ± 0.7 age Cretaceous ICS Cognac (France) Coquand, 1857
Cordevolian 237 ~236 sub-age Late Triassic regional
Cretaceous 145.5 ± 4.0 65.5 ± 0.3 period Mesozoic ICS Crete; Latin creta=chalk d'Omalius d'Halloy, 1822
Dienerian 251.6 251 Substage Lower Triassic
Dogger[4] 175.6 ± 2.0 161.2 ± 4.0 epoch Jurassic Northern Europe dogger=ironrich sediment type
Domerian 183.0 ± 1.5 sub-age Jurassic regional
Eaglefordian age Cretaceous Gulf and Atlantic coast of the US Eagle Ford, Dallas, Texas Murray, 1961
Early Triassic Triassic
Edmontonian 80.8 70.7 NALMA Cretaceous North America
Emscherian 89.5 83.5 age Cretaceous Germany
Fassanian 237 ± 2.0? 233? sub-age/substage Middle Triassic Europe
Gallic 130.0 ± 1.5 89.3 ± 1.0 epoch Cretaceous obsolete
Gandarian 251.6 251 Substage Lower Triassic India, Germany
Gangetian 252.6 251.6 Substage Lower Triassic India, Germany
Gargasian 121.0 115.0 sub-age Cretaceous regional
Gaultian sub-age Cretaceous regional
Gulf(-ian) epoch Cretaceous south and east of the US the Mexican Gulf
Haumurian 84 65.5 age Cretaceous New Zealand
Hauterivian 136.4 ± 2.0 130.0 ± 1.5 age Cretaceous ICS Hauterive (Switzerland) Renevier, 1873
Hettangian 199.6 ± 0.6 196.5 ± 1.0 age Jurassic ICS Hettange-Grande (France) Renevier, 1864
Houldjinian 37.2 33.9 ALMA Asia
Illyrian 240 ± 2.0 237 ± 2.0? sub-age/Substage Middle Triassic Europe
Induan 251.0 ± 0.4 249.7 ± 0.7 age Triassic ICS river Indus Kiparisova & Popov, 1956
Judithian 82.2 80.8 NALMA Cretaceous North America
Julian 229.6 ± 2.0 222.5 sub-age Late Triassic Europe
Jurassic 199.6 ± 0.6 145.5 ± 4.0 period Mesozoic ICS Jura mountains Brongniart
Karoo Ice Age ~360 ~260 ice age Phanerozoic Karoo (South Africa)
Kekeamuan 28.4 33.9 ALMA Asia
Keuper[4] ±230 199.6 epoch Triassic Europe Von Alberti, 1834
Kimmeridgian 155.7 ± 4.0 150.8 ± 4.0 age Jurassic ICS Kimmeridge (England) d'Orbigny
Korangan 117.5 108.4 age Cretaceous New Zealand
Lacian 217.4 ± 2.0 211 sub-age Upper Triassic Europe
Ladinian 237.0 ± 2.0 228.0 ± 2.0 age Middle Triassic ICS Ladini, people in northern Italy Bittner, 1892
Lancian 70.7 65.5 NALMA Cretaceous North America
Late Triassic 237 age Triassic Germany
Lias[4] 199.6 ± 0.6 175.6 ± 2.0 epoch Jurassic Northern Europe unclear
Longobardian 233? 229.6 ± 2.0? sub-age/substage Middle Triassic Europe
Lotharingian 193.3 ± 0.7 189.6 ± 0.7 substage Jurassic
Lower Triassic 247 252.6 Triassic Germany
Maastrichtian 70.6 ± 0.6 65.5 ± 0.3 age Cretaceous ICS Maastricht (Netherlands) Dumont, 1849
Malm[4] 161.2 ± 4.0 145.5 ± 4.0 epoch Jurassic Europe Old English: malm = calcareous soil
Mangaotanean 92.1 89.1 age Cretaceous New Zealand
Mesozoic 251.0 ± 0.7 65.5 ± 0.3 era ICS middle life
Middle Triassic 247 237 age Triassic Germany
Motuan 103.3 100.2 age Cretaceous New Zealand
Muschelkalk[4] 243 ± 2 235 ± 2 epoch Triassic Europe German: limestone with mussels Füchsel, 1761
Navarroan age Cretaceous-Paleocene south and east of the US Navarro, Texas Murray, 1961
Neocomian 145.5 125.0/130.0 epoch obsolete Neocomium, Latin name for Neuchâtel
Ngaterian 100.2 95.2 age Cretaceous New Zealand
Norian 216.5 ± 2.0 203.6 ± 1.5 age Upper Triassic ICS Noric Alps (Austria)
Olenekian 249.5 245.9 age Triassic ICS river Olenyok (Siberia)
Oxfordian 161.2 ± 4.0 155.0 ± 4.0 age Jurassic ICS Oxford (England) d’Orbigny
Paleozoic 542.0 ± 1.0 251.0 ± 0.7 era Phanerozoic ICS old life
Pelsonian Substage Middle Triassic Germany
Phanerozoic 542.0 ± 1.0 present eon ICS visible life
Piripauan 86.5 84 age Cretaceous New Zealand
Pliensbachian 189.6 ± 1.5 183.0 ± 1.5 age Jurassic ICS Pliensbach (Germany) Oppel, 1858
Portlandian age Jurassic British Isles Isle of Portland (England)
Puercan 65.5 63.3 age Paleocene-Cretaceous North America
Purbeckian age Cretaceous-Jurassic England (obsolete) Isle of Purbeck (England)
Rhaetian 203.6 ± 1.5 199.6 ± 0.6 age Triassic ICS Rhaetian Alps (Switzerland, Austria, Italy)
Santonian 85.8 ± 0.7 83.5 ± 0.7 age Cretaceous ICS Saintes (France) Coquand, 1873
Scythian 251 ± 0.2 245 ± 1.5 Epoch Early Triassic Europe Scythia
Senonian 89.3 65.5 epoch Cretaceous unofficial Sens (France) d'Orbigny
Sevatian 206 202.3 ± 1.5 sub-age Upper Triassic Europe
Sinemurian 196.5 ± 1.0 189.6 ± 1.5 age Jurassic ICS Semur-en-Auxois (France) d'Orbigny, 1842
Smithian 251 249 Substage Lower Triassic Germany
Spathian 249 247 Substage Lower Triassic Germany
Tayloran age Cretaceous south and west of the US Taylor, Texas Murray, 1961
Teratan 89.1 86.5 age Cretaceous New Zealand
Tithonian 150.8 ± 4.0 145.5 ± 4.0 age Jurassic ICS Tithon (Greek mythology) Oppel, 1865
Toarcian 183.0 ± 1.5 175.6 ± 2.0 age Jurassic ICS Thouars (France) d'Orbigny, 1849
Triassic 251.0 ± 0.4 199.6 ± 0.6 period Mesozoic ICS threefold Von Alberti, 1834
Turonian 93.5 ± 0.8 89.3 ± 1.0 age Cretaceous ICS Tours (France) d'Orbigny, 1842
Tuvalian 222.5 217.4 ± 2.0 sub-age Upper Triassic Europe
Upper Triassic 199.6 age Triassic Germany
Urutawan 108.4 103.3 age Cretaceous New Zealand
Valanginian 140.2 ± 3.0 136.4 ± 2.0 age Cretaceous ICS Valangin (Switzerland) Desor, 1853
Vraconian sub-age Cretaceous regional
Woodbinian age Cretaceous Gulf and Atlantic coast of the US Murray, 1961


The Cretaceous/Cenozoic boundary occurs at 65.0 ± 0.1 Ma (million years ago).[6]

Late CretaceousEdit

The quarry pit in Mantua Township in central New Jersey has been owned by the Inversand Company for nearly a century. Credit: Rowan University.
This is a Catapleura repanda fossil from the Rowan quarry. Credit: Eric Tomenga.
This is a 2.7 cm section of Baculites compressus. Credit: Kevmin.
Fossil is of Baculites ovatus, an extinct mollusc. Credit: Ghedoghedo.
Photograph is of a fossil cast of a Baculites grandis shell taken at the North American Museum of Ancient Life. Credit: Ninjatacoshell.
Plesiacanthoceras wyomingense is from the late Cretaceous in Wyoming, USA. Credit: Ryan Somma.

The aerial image on the right shows the quarry pit in Mantua Township in central New Jersey has been owned by the Inversand Company for nearly a century.[7]

"When an asteroid hit the Earth around 66 million years ago, it wiped out almost 75 percent of the plants and animals on the planet. All dinosaurs, except those that would eventually give rise to modern birds, were killed following the impact. Yet despite such a vast die-off, no bone bed containing a concentration of fossils as a result of this event has been found."[7]

“We don’t know yet [if it dates from the mass extinction], but we are testing this hypothesis by examining the fossils, the sediments and the chemistry.”[8]

"At the end of the Cretaceous, when the dinosaurs met their maker, the region was a shallow tropical sea full of fish, sea turtles, crocodiles, and even mosasaurs. But at some point around 66 million years ago, whether it was due to the asteroid impact or some other cause, many of the inhabitants of the sea died and were preserved in a large bone bed."[7]

On the left is a specimen of Catapleura repanda from the Rowan quarry found in the Cretaceous marl.

"Three Antarctic Ocean K/T boundary sequences from ODP Site 738C on the Kerguelen Plateau, ODP Site, 752B on Broken Ridge and ODP Site 690C on Maud Rise, Weddell Sea, have been analyzed for stratigraphic completeness and faunal turnover based on quantitative planktic foraminiferal studies. Results show that Site 738C, which has a laminated clay layer spanning the K/T boundary, is biostratigraphically complete with the earliest Tertiary Zones P0 and P1a present, but with short intrazonal hiatuses. Site 752B may be biostratigraphically complete and Site 690C has a hiatus at the K/T boundary with Zones P0 and P1a missing."[9]

"The cosmopolitan nature of the dominant fauna began during the last 200,000 to 300,000 years of the Cretaceous and continued at least 300,000 years into the Tertiary. This indicates a long-term environmental crisis that led to gradual elimination of specialized forms and takeover by generalists tolerant of wide ranging temperature, oxygen, salinity and nutrient conditions. A few thousand years before the K/T boundary these generalists gradually declined in abundance and species became generally dwarfed due to increased environmental stress. There is no evidence of a sudden mass killing of the Cretaceous fauna associated with a bolide impact at the K/T boundary. Instead, the already declining Cretaceous taxa gradually disappear in the early Danian and the opportunistic survivor taxa (Ch. waiparaensis and Guembelitria cretacea) increase in relative abundance coincident with the evolution of the first new Tertiary species."[9]

"The Chicxulub impact is commonly believed to have crashed into Yucatan precisely at the KT boundary and caused the mass extinction. However, the stratigraphically oldest impact glass spherule ejecta documented from NE Mexico and Texas predate the mass extinction by 100-150 ky. Elsewhere in the North Atlantic, Caribbean, Belize, Guatemala and southern Mexico, there is a consistent pattern of impact spherules reworked in early Danian sediments and overlying a major KTB unconformity. This indicates that the Chicxulub impact predates the KT boundary and did not cause the mass extinction (Keller et al., 2009, 2013)."[10]

In the top center is a 2.7 cm section of a polished shell with 6 sutures. It is from the extinct cephalopod Baculites compressus; Cretaceous, 100 million years old, Bearpaw Formation, Montana, USA.

The middle center photo is of Baculites ovatus, at the Naturalis Museum, Leiden.

The lower center is a fossil cast of a Baculites grandis shell taken at the North American Museum of Ancient Life.

On the right is an example of Plesiacanthoceras wyomingense from the late Cretaceous in Wyoming, USA. It is exhibited in Smithsonian National Museum of Natural History: Hall of Fossils.

Upper CretaceousEdit

This is an example of Discoscaphites iris an ammonite from the Owl Creek Formation (Upper Cretaceous), Owl Creek, Ripley, Mississippi. Credit: Mark A. Wilson.

Discoscaphites iris on the right is an ammonite from the Owl Creek Formation (Upper Cretaceous), Owl Creek, Ripley, Mississippi USA.


Rendzina soil is on the Maastrichtian Chalk in Kozubów Landscape Park, Poland. Credit: Maciej Szczepańczyk.{{free media}}
Rockground is exposed in the Ripley Formation near Greenville, Alabama. Credit: Wilson44691.{{free media}}

The Maastrichtian, in the International Commission on Stratigraphy geologic timescale, the latest age (uppermost stratigraphy stage) of the Late Cretaceous epoch or Upper Cretaceous stratigraphy series, of the Cretaceous period or system, and of the Mesozoic era or erathem, spanned the interval from 72.1 to 66 million years ago, preceded by the Campanian and succeeded by the Danian (part of the Paleogene and Paleocene).[6]

At the end of this period, there was a mass extinction known as the Cretaceous–Paleogene extinction event, (formerly known as the Cretaceous–Tertiary extinction event).[11]

At this extinction event, many commonly recognized groups such as non-avian dinosaurs, plesiosaurs and mosasaurs, as well as many other lesser-known groups, died out linked to an Chicxulub impactor (asteroid) about 10 to 15 kilometres (6.2 to 9.3 mi) wide[12][13] colliding with Earth at the end of the Cretaceous.

The base of the Maastrichtian stage is at the first appearance of ammonite species Pachydiscus neubergicus, at the original type locality near Maastricht, a reference profile for the base was then appointed in a section along the Ardour river called Grande Carrière, close to the village of Tercis-les-Bains in southwestern France.[14][15]

The Quiriquina Formation, a unit of the Arauco Group of the Late Maastrichtian, is in Chile, where it overlies granitic rocks and underlies the Lebu Group.

The glauconitic sandstones and conglomerates of the formation were deposited in a marine environment.[16]

The Viñita Formation is in Coquimbo, Chile, whose strata date back to the Santonian to Maastrichtian.[17]


Contact (red arrow) is between the underlying marine shales of the Bearpaw Formation and the coastal Horseshoe Canyon Formation. Credit: Anky-man.{{free media}}
Horseshoe Canyon Formation at Horsethief Canyon (Alberta) is near Drumheller. Credit: Anky-man.{{free media}}

The Campanian, in the International Commission on Stratigraphy geologic timescale, the fifth of six ages of the Late Cretaceous epoch (or, the fifth of six stratigraphy stages in the Upper Cretaceous series, spans the time from 83.6 ± 0.7 Ma to 72.1 ± 0.6 Ma and is preceded by the Santonian and followed by the Maastrichtian.[6]

The Bearpaw Formation or Bearpaw Shale is a geologic formation of the Late Cretaceous (Campanian) age that outcrops in the U.S. state of Montana, as well as the Canadian provinces of Alberta and Saskatchewan, and was named for the Bear Paw Mountains in Montana.[18] It includes a wide range of marine fossils, the remains of a few dinosaurs and is known for its fossil ammonites.[19]

The formation was deposited in the Bearpaw Sea, which was part of the Western Interior Seaway that advanced and then retreated across the region during Campanian time.[20] It is composed primarily of dark grey shales, claystones, silty claystones and siltstones, with subordinate silty sandstones, including bedded and nodular concretions (both calcareous and ironstone concretions) and thin beds of bentonite, then as the seaway retreated toward the southwest, the marine sediments of the Bearpaw became covered by the deltaic and coastal plain sediments of the overlying formations.[21][22][23]

Coal beds (black bands) are common in the Horseshoe Canyon Formation and were formed in coastal swamps.

The Horseshoe Canyon Formation is a stratigraphic unit of the Western Canada Sedimentary Basin in southwestern Alberta,[24][22] that takes its name from Horseshoe Canyon, an area of badlands near Drumheller.

The Horseshoe Canyon Formation crops out extensively in the area around Drumheller, as well as farther north along the Red Deer River near Trochu, Alberta and along the North Saskatchewan River in Edmonton.[24] It is overlain by the Battle, Whitemud, and Scollard formations.[22] The Drumheller Coal Zone, located in the lower part of the Horseshoe Canyon Formation, was mined for sub-bituminous coal in the Drumheller area from 1911 to 1979.[25]

The Judith River Formation is a fossil-bearing geologic formation in Montana, part of the Judith River Group, dating to the Late Cretaceous, between 80 and 75 million years ago, corresponding to the "Judithian" land vertebrate age, laid down during the same time period as portions of the Two Medicine Formation of Montana[26] and the Oldman Formation of Alberta.[27]

The Judith River Formation conformably overlies the Claggett Formation and Pakowki Formation, overlain by the Bearpaw Formation, equivalent to the Belly River Formation in the southern Canadian Rockies foothills, the Lea Park Formation in central Albert and the Wapiti Formation in the northwestern plains.[28]


The Santonian, an age in the geologic timescale or a stratigraphy stage, a subdivision of the Late Cretaceous epoch or Upper Cretaceous stratigraphy series, spans the time between 86.3 ± 0.7 mya and 83.6 ± 0.7 mya, and is preceded by the Coniacian and followed by the Campanian.[6]

The base of the Santonian stage is defined by the appearance of the Inoceramidae bivalve Cladoceramus undulatoplicatus and its top (the base of the Campanian stage) is marked by the extinction of the crinoid Marsupites testudinarius.[29]


The Coniacian, an age or stage in the geologic timescale, a subdivision of the Late Cretaceous epoch or Upper Cretaceous stratigraphy series spans the time between 89.8 ± 1 Ma and 86.3 ± 0.7 Ma and is preceded by the Turonian and followed by the Santonian.[6]

Beginning in the Middle Coniacian, an anoxic event (OAE-3) occurred in the Atlantic Ocean, causing large scale deposition of black shales in the Atlantic domain, which lasted till the Middle Santonian (from 87.3 to 84.6 Ma) and is the longest and last such event during the Cretaceous period.[30]


The base of the Turonian stage is defined as the place where the ammonite species Wutinoceras devonense first appears in the stratigraphic column, the GSSP for the base of the Turonian located in the Rock Canyon anticline near Pueblo, Colorado (United States, coordinates: 38° 16' 56" N, 104° 43' 39" W).[31]


The Cenomanian per the International Commission on Stratigraphy is the oldest or earliest age of the Late Cretaceous or the lowest stratigraphic stage of the Upper Cretaceous.[6]

As a unit of geologic time measure, the Cenomanian age spans the time between 100.5 ± 0.9 Ma and 93.9 ± 0.8 Ma, preceded by the Albian and is followed by the Turonian, where the Upper Cenomanian starts approximately at 95 Ma.[32]

The base of the Cenomanian is placed at the first appearance of foram species Rotalipora globotruncanoides in the stratigraphic record, located in an outcrop at the western flank of Mont Risou, near the village of Rosans in the French Alps (département Hautes-Alpes, coordinates: 44°23'33"N, 5°30'43"E), in the reference profile, located 36 meters below the top of the Marnes Bleues Formation.[33]

Early CretaceousEdit

"Paleogeographically, the sub-alpine terrain of southeastern France [...] was located on the proximal part of the South-European Tethys margin. It includes the Vocontian Basin, which experienced relatively high rates of subsidence during Jurassic and Early Cretaceous times, bordered by carbonate platforms limited by a net of extensional or strike–slip faults (Graciansky et al., 1999)."[34]

This phraseology connects "Early Cretaceous" with "times".

Angiosperms (flowering plants) appeared for the first time during the Early Cretaceous.[35] This time also saw the evolution of the first members of the Neornithes (modern birds).[36]

The Jurassic/Cretaceous boundary occurs at 144.2±2.6 Ma (million years ago).[6]


The Albian, the youngest or uppermost subdivision of the Early/Lower Cretaceous, approximate time range of 113.0 ± 1.0 Ma to 100.5 ± 0.9 Ma is preceded by the Aptian and followed by the Cenomanian.[6]

A reference profile for the base of the Albian stage (GSSP) had not yet been established.[37]

The top of the Albian stage (the base of the Cenomanian stage and Upper Cretaceous series) is defined as the place where the foram species Rotalipora globotruncanoides first appears in the stratigraphic column.[38]

The following representatives of the Albian stage are worthy of notice: the phosphorite beds of the Forest of Argonne and Pays de Bray areas in France; the Flammenmergel of northern Germany; the lignites of Utrillas in Spain; the Upper sandstones of Nubia, and the Fredericksburg beds of North America.[39]


The Aptian, a subdivision of the Early or Lower Cretaceous, encompasses the time from 125.0 ± 1.0 Ma to 113.0 ± 1.0 Ma, succeeds the Barremian and precedes the Albian.[6]

The Selli Event, also known as OAE1a, was one of two oceanic Anoxic events, which occurred around 120 Ma and lasted approximately 1 to 1.3 million years.[40][41]

The Aptian extinction was a minor one hypothesized to have occurred around 116 to 117 Ma.[42]


The Barremian, between 129.4 ± 1.5 Ma and 125.0 ± 1.0 Ma is a subdivision of the Early Cretaceous or the Lower Cretaceous preceded by the Hauterivian and followed by the Aptian stage.[43]


The Hauterivian in the Early Cretaceous or in the Lower Cretaceous between 132.9 ± 2 Ma and 129.4 ± 1.5 Ma is preceded by the Valanginian and succeeded by the Barremian.[6]


The Valanginian stage succeeds the Berriasian stage of the Lower Cretaceous and precedes the Hauterivian stage of the Lower Cretaceous.[43]


The Berriasian, the oldest, or lowest, subdivision in the entire Cretaceous, spanned the time between 145.0 ± 4.0 Ma and 139.8 ± 3.0 Ma (million years ago), succeeds the Tithonian (part of the Jurassic) and precedes the Valanginian.[43]


The Jurassic/Cretaceous boundary occurs at 144.2±2.6 Ma (million years ago).[6]

The Jurassic period is a geologic period and system that spanned 56 million years from the end of the Triassic Period 201.3 million years ago (Mya) to the beginning of the Cretaceous Period 145 Mya. A 140 Mya age for the Jurassic-Cretaceous instead of the usually accepted 145 Ma was proposed in 2014 based on a stratigraphic study of Vaca Muerta Formation in Neuquén Basin, Argentina.[44] One of the authors of the study proposing the 140 Ma boundary age, sees the study as a "first step" toward formally changing the age in the International Union of Geological Sciences.[45]

"Si logramos publicar esos nuevos resultados, sería el primer paso para cambiar formalmente la edad del Jurásico-Cretácico. A partir de ahí, la Unión Internacional de la Ciencias Geológicas y la Comisión Internacional de Estratigrafía certificaría o no, depende de los resultados, ese cambio."[45]

The start of the period was marked by the major Triassic–Jurassic extinction event. Two other extinction events occurred during the period: the Pliensbachian-Toarcian extinction in the Early Jurassic, and the Tithonian event at the end;[46] neither event ranks among the "Big Five" mass extinctions, however.

The separation of the term Jurassic into three sections originated with Leopold von Buch.[47] The faunal stages from youngest to oldest are:

Late Jurassic or Upper/Late Jurassic
Tithonian 152.1 ± 4 – 145 ± 4 Mya
Kimmeridgian 157.3 ± 4 – 152.1 ± 4 Mya
Oxfordian 163.5 ± 4 – 157.3 ± 4 Mya
Middle Jurassic
Callovian 166.1 ± 4 – 163.5 ± 4 Mya
Bathonian 168.3 ± 3.5 – 166.1 ± 4 Mya
Bajocian 170.3 ± 3 – 168.3 ± 3.5 Mya
Aalenian 174.1 ± 2 – 170.3 ± 3 Mya
Early Jurassic or Lower/Early Jurassic
Toarcian 182.7 ± 1.5 – 174.1 ± 2 Mya
Pliensbachian 190.8 ± 1.5 – 182.7 ± 1.5 Mya
Sinemurian 199.3 ± 1 – 190.8 ± 1.5 Mya
Hettangian 201.3 ± 0.6 – 199.3 ± 1 Mya

Late JurassicEdit

Kosmoceras cromptoni is from the Late Jurassic. Credit: Daderot.

Paleontologists appear to prefer "Late Jurassic", "Middle Jurassic", and "Early Jurassic".[48]

Time frame references such as "We applied the method of frequency ratios (Huang et al., 1992; Mayer and Appel, 1999) to compare the observed spectral frequencies with orbital frequencies estimated for Late Jurassic time (Berger and Loutre, 1994) (Tables 1A and B)."[34] use "Late Jurassic" as a time frame, but "Upper Jurassic" as a stratigraphic frame.

On the right is an example of Kosmoceras cromptoni from the Late Jurassic, Chippenham, England.

Upper JurassicEdit

The International Commission on Stratigraphy (ICS) uses only "Upper Jurassic", "Middle Jurassic", and "Lower Jurassic" in its Global Boundary Stratotype Section and Point (GSSP) Table for all periods.[49]



Orthosphinctes (Lithacosphinctes) achilles is in the Museum of Toulouse. Credit: Jean Fontayne.

Lithacosphinctes achilles is from the Kimmeridgian.


Middle JurassicEdit


Peltoceras solidum is an ammonite from the Callovian. Credit: Wilson44691.
Kosmoceras medea is from the Callovian. Credit: Hectonichus.
Kosmoceras proniae is sized using 1 PLN coin. Credit: Ag.Ent.

On the right is an image of Peltoceras solidum, an ammonite from the Matmor Formation (Jurassic, Callovian), Makhtesh Gadol, Israel.

On the left is an example of Kosmoceras medea.

Another species of Kosmoceras is on the lower right, specifically Kosmoceras proniae.




This chart shows the magnetic polarity and ammonite zones for the Aalenian. Credit: S. Cresta, A. Goy, S. Ureta, C. Arias, E. Barrón, J. Bernad, M. L. Canales, F. García-Joral, E. García-Romero, P. R. Gialanella, J. J. Gómez, J. A. González, C. Herrero, G. Martínez, M. L. Osete, N. Perilli and J. J. Villalaín.
The image and overlain labels display the type strata for the Jurassic stage Aalenian. Credit: S. Cresta, et al.
Leioceras opalinum, Graphoceratidae; has a diameter: 4.5 cm; Lower Aalenian, Middle Jurassic; between Ohmenhausen and Reutlingen, Germany. Credit: H. Zell.

"The Global Boundary Stratotype Section and Point (GSSP) for the Aalenian Stage, formally defined at the base of bed FZ107 in the Fuentelsaz section, Castilian Branch of the Iberian Range (Spain), has been ratified by the IUGS."[50]

"The position of the boundary coincides with the first occurrence of the ammonite assemblage characterized by Leioceras opalinum and Leioceras lineatum and corresponds with a normal polarity interval correlated with the up-to-date Jurassic magnetic polarity time scale (Gradstein and others, 1994; Ogg, 1995)."[50]

The "first occurrence of the species of the genus Leioceras, evolved from Pleydellia, has been widely accepted as being the biochronological event which best enables the recognition of the basal boundary of the Aalenian Stage."[50]

On the right is a chart which indicates the ammonite zones that serve as geochrons for the Aalenian.

The second image down on the right displays the type strata for the Aalenian.

An example of Leioceras opalinum is shown on the left.

Lower JurassicEdit

Uptonia jamesoni is from the lower Jurassic. Credit: Eduard Solà Vázquez.

Uptonia jamesoni from the lower Jurassic is in the family Polymorphitidae, superfamily Eoderocerataceae, order Ammonitida, subclass Ammonoidea, class Cephalopoda.


The Toarcian, in the International Commission on Stratigraphy (ICS) geologic timescale, an age and stage in the Early or Lower Jurassic, spans the time between 182.7 Ma and 174.1 Ma.[51] It follows the Pliensbachian and is followed by the Aalenian.[52]

The base of the Toarcian is defined as the place in the stratigraphic record where the ammonite genus Eodactylites first appears, a GSSP for the base is located at Peniche, Portugal. The top of the stage is at the first appearance of ammonite genus Leioceras.


Pleuroceras spinatum is from the Pliensbachian. Credit: Didier Descouens.

Pleuroceras spinatum (Bruguière 1789) is of the family Amaltheidae. The Pliensbachian, an age of the geologic timescale and stage in the stratigraphic column, is part of the Early or Lower Jurassic epoch or series and spans the time between 190.8 ± 1.5 Ma and 182.7 ± 1.5 Ma.[51] The Pliensbachian is preceded by the Sinemurian and followed by the Toarcian.[53]

The base of the Pliensbachian is at the first appearances of the ammonite species Bifericeras donovani and genera Apoderoceras and Gleviceras, with The Wine Haven profile near Robin Hood's Bay (Yorkshire, England) has been appointed as global reference profile for the base (GSSP).[54]

It is a pyritic specimen. The biozone index is to the end of Pliensbachian.


The Sinemurian is an age in the Early or Lower Jurassic that spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago).[51]

The Sinemurian is preceded by the Hettangian and is followed by the Pliensbachian.[55]


Psiloceras spelae tirolicum has its first occurrence at the Triassic-Jurassic boundary as geochron for the base of the Jurassic. Credit: Axel von Hillebrandt et al.
Fossil shell of Psiloceras planorbis from Germany, on display at Galerie de paléontologie et d'anatomie comparée in Paris. Credit: Hectonichus.
In this image of the Kuhjoch East section, the "Golden Spike" is at the Triassic-Jurassic boundary. Credit: Axel von Hillebrandt et al.

"Since the 1960’s, the LO (lowest occurrence) of the ammonite Psiloceras (usually the species P. planorbis [first image on the right]) has provided the working definition of the TJB (e.g., Lloyd, 1964; Maubeuge, 1964; Cope et al., 1980; Warrington et al., 1994; Gradstein et al., 2004)."[56]

"The Global Stratotype Section and Point (GSSP) defining the base of the Jurassic System Lower Jurassic Epoch and Hettangian Stage is situated at the Kuhjoch pass, Karwendel Mountains, Northern Calcareous Alps, Austria (47°29'02"N/11°31'50"E). The Triassic-Jurassic (T-J) boundary is exposed at Kuhjoch West and at Kuhjoch East [in the second image on the right], and corresponds to the first occurrence (FO) of the ammonite Psiloceras spelae tirolicum [at the top of this section]."[57]

Another FO is that of "the aragonitic foraminifer Praegubkinella turgescens"[57]

The Triassic/Jurassic boundary occurs at 205.7±4.0 Ma (million years ago).[6]


This is an example of Psiloceras tilmanni from the Jurassic. Credit: Günter Knittel.

"What must underlie discussion of the definition of the TJB is the well accepted concept that global correlateability should be the main emphasis in the selection of a GSSP (e.g., Cowie et al., 1986; Remane et al., 1996; Gradstein et al., 2004; Walsh et al., 2004). As Remane et al. (1996: 79) expressed it, “the boundary definition will normally start from the identification of a level which can be characterised by a marker event of optimal correlation potential.” Thus, our goal here is to evaluate the possible marker events that could be used to define the TJB and to argue that an ammonite-based marker event has optimal correlation potential. This marker event is the LO of Psiloceras tilmanni in the New York Canyon section of Nevada."[56]

Late TriassicEdit

"During the Late Triassic, the Newark rift basin of Eastern North America was in the interior of tropical (2.5–9.5° N) Pangaea. Strikingly cyclical lacustrine rocks comprise most of the 6770 m of continuous core recovered from this basin by the Newark Basin Coring Project."[58]

"A consistent hierarchy in frequencies of the lake level cycles is present throughout the Late Triassic (and earliest Jurassic) portions of the cores, an interval of about 22 m.y.. Calibration of the sediment accumulation rate by a variety of methods shows that these thickness periodicities are consistent with an origin in changes in precipitation governed by celestial mechanics. The full range of precession-related periods of lake level change are present, including the two peaks of the ∼20,000 year cycle of climatic precession, the two peaks of the ∼100,000 year eccentricity cycle, the single peak of the 412,900 year eccentricity cycle, and the ∼2,000,000 year eccentricity cycle."[58]

Upper TriassicEdit

The chart in the Norian section describes the chronology of Upper Triassic time frames.


The "extinction of Conodonta has long been seen as a terminal Triassic event, and the presence/absence of conodonts thus is routinely used to distinguish Triassic from Jurassic strata. Rhaetian conodont assemblages are of low diversity and abundance, and conodonts can be easily reworked. Therefore, the HO of Conodonta is not a reliable criterion for TJB definition. However, it is very useful to know that the presence of autochthonous Conodonta is a pre-Jurassic indicator, and this micropaleontological criterion has been widely used and accepted."[56]


The Norian chart shows the chronological positions of Upper Triassic Stages and Substages. Credit: Heinz W. Kozur & Gerhard H. Bachmann.

The chart above shows the chronological positions of Upper Triassic Stages and Substages, including the Norian.


The chart in the Norian section describes the chronology of Upper Triassic time frames, including the Sevatian.


The chart in the Norian section describes the chronology of Upper Triassic time frames, including the Alaunian.


The chart in the Norian section describes the chronology of Upper Triassic time frames, including the Lacian or Early Norian.


The chart in the Anisian section places the Carnian in the Late, or Upper, Triassic.


The chart in the Norian section describes the chronology of Upper Triassic time frames, including the Tuvalian.


The chart in the Anisian section places the Julian in the Carnian.


The chart in the Anisian section places the Cordevolian in the Carnian.

Middle TriassicEdit

The chart in the Anisian section places the Middle Triassic below the Late Triassic.


The chart in the Anisian section places the Ladinian above the Asinian.


The chart in the Anisian section places the Longobardian above the Fassanian.


The chart in the Anisian section places the Fassanian at the base of the Ladinian.


The chart indicates the time frames at and above the Anisian. Credit: Heinz W. Kozur & Gerhard H. Bachmann.
Ussuriphyllites amurensis (Kiparisova) is from the Lower-most Anisian, Atlasov Cape area. Credit: Alexander M. Popov.

The chart above indicates the time frames at and above the Anisian.

An example of Ussuriphyllites amurensis (Kiparisova) is on the right. It is from the Lower-most Anisian, Atlasov Cape area.[59]


The chart in the Anisian section places the Illyrian at the top of the Anisian.


The chart in the Anisian section places the Pelsonian below the Illyrian.


The chart in the Anisian section places the Bithynian below the Pelsonian.


This chart shows the stratigraphic position of the Aegean in the Middle Triassic. Credit: Heinz W. Kozur & Gerhard H. Bachmann.

The chart above shows the Aegean as the lowest time frame of the Anisian.

The magnetostratigraphy in the farthest right column of the above chart has black as normal polarity, white as reversed polarity, and gray for no reliable data.

Lower TriassicEdit

The chart in the Aegean section shows the Scythian to be equivalent to the Lower Triassic.

Early TriassicEdit

"Global warming is widely regarded to have played a contributing role in numerous past biotic crises. Here, we show that the end-Permian mass extinction coincided with a rapid temperature rise to exceptionally high values in the Early Triassic that were inimical to life in equatorial latitudes and suppressed ecosystem recovery."[60]


The chart in the Aegean section shows the Scythian to be equivalent to the Lower Triassic.


The chart in the Aegean section indicates that the Scythian is divided into the Olenekian above and Induan below.


The Spathian is sometimes referred to as the Late Olenekian.[61]


This diagram is a time-rock north-northwest to south-southeast cross section of the Lower Triassic of Idaho, Wyoming and Utah. Credit: Spencer G. Lucas, Thomas H. Goodspeed and John W. Estep.
This ammonoid fossil is a syntype of Wyomingites aplanatus (White 1879) from the Triassic of S.E. Idaho. Credit: Kevin Bylund.

As indicated in the above stratigraphy, the Sinbad Formation is entirely within the Smithian, or Early Olenekian.

The Smithian is sometimes referred to as the Early Olenekian.[61]


The chart in the Aegean section indicates that the Brahmanian is equivalent to the Induan.


The diagram shows the Permian-Triassic boundary at the base of the Induan. Credit: Yin Hongfu, Zhang Kexin, Tong Jinnan, Yang Zunyi and Wu Shunbao.
Hindeodus parvus is now recognized as the index fossil, occurring in the Zone above the P-T boundary. Credit: Yin Hongfu, Zhang Kexin, Tong Jinnan, Yang Zunyi and Wu Shunbao.

In the diagram on the right, the Permian-Triassic boundary is at the base of the Induan limestone that occurs within the Yinkeng Formation.

"The Global Stratotype Section and Point (GSSP) of the Permian-Triassic boundary [...] is defined at the base of Hindeodus parvus horizon, i.e. the base of Bed 27c of Meishan section D, Changxing County, Zhejiang Province, South China."[62]

"Hindeodus parvus is now recognized as the index fossil" occurring in the Zone above the P-T boundary.[62]


The chart in the Aegean section indicates that the Dienerian is equivalent to the Gandarian.


The chart in the Aegean section indicates that the Gandarian is in the Brahmanian.


The chart in the Aegean section indicates that the Gangetian is in the Brahmanian.

The Permian/Triassic boundary occurs at 248.2 ± 4.8 Ma (million years ago).[6]

Locations on EarthEdit

Paleontologists excavate part of the bone bed that contains thousands of fossils from close to the mass dinosaur extinction. Credit: Rowan University.
The Chicxulub impact crater is outlined. Credit: NASA/JPL-Caltech, modified by David Fuchs.

At the Inversand quarry, imaged on the right, "Located in South Jersey, the cradle of dinosaur paleontology, the quarry in Mantua Township, N.J., contains thousands of fossils dating back 65 million years."[63]

But asteroid impacts, though rare, occur once in a while, over very large areas, at aperiodic intervals such as the Chicxulub crater, diagrammed on the left. Most scientists agree that this impact is the cause of the Cretatious-Tertiary Extinction, 65 million years ago (Ma), that marked the sudden extinction of the dinosaurs and the majority of life then on Earth. This shaded relief image of Mexico's Yucatan Peninsula shows a subtle, but unmistakable, indication of the Chicxulub impact crater.


  1. Each time frame or span of time in geochronology has at least one dating technique.
  2. Late Jurassic and Upper Jurassic are different time frames.

See alsoEdit


  1. Mike Walker, Sigfus Johnsen, Sune Olander Rasmussen, Trevor Popp, Jørgen-Peder Steffensen, Phil Gibbard, Wim Hoek, John Lowe, John Andrews, Svante Björck, Les C. Cwynar, Konrad Hughen, Peter Kershaw, Bernd Kromer, Thomas Litt, David J. Lowe, Takeshi Nakagawa, Rewi Newnham and Jakob Schwander (2009). "Formal definition and dating of the GSSP (Global Stratotype Section and Point) for the base of the Holocene using the Greenland NGRIP ice core, and selected auxiliary records". Journal of Quaternary Science 24 (1): 3-17. doi:10.1002/jqs.1227. Retrieved 2015-01-18. 
  2. Names from local versions of the geologic timescale can often be found in the local language. The English name is usually found by replacing the suffix in the local language for -an or -ian. Examples for "local" suffices are -en (French), -ano (Spanish), -ium (German), -aidd (Welsh) or -aan (Flemish Dutch). The English name "Norian", for example, becomes Noriano in Spanish, Norium in German, Noraidd in Welsh or Norien in French.
  3. 3.0 3.1 Time is given in Megaannum (million years BP, unless other units are given in the table. BP stands for "years before present". For ICS-units the absolute ages are taken from Gradstein et al. (2004).
  4. 4.0 4.1 4.2 4.3 4.4 4.5 This name is often still used in a chronostratigraphic or geochronologic sense, although it is now officially a lithostratigraphic unit.
  5. Menning et al. 2005
  6. 6.00 6.01 6.02 6.03 6.04 6.05 6.06 6.07 6.08 6.09 6.10 6.11 6.12 Felix M. Gradstein, Frits P. Agterberg, James G. Ogg, Jan Hardenbol, Paul Van Veen, Jacques Thierry, and Zehui Huang (1995). A Triassic, Jurassic and Cretaceous Time Scale, In: Geochronology Time Scales and Global Stratigraphic Correlation. SEPM Special Publication No. 54. Society for Sedimentary Geology. doi:1-56576-024-7. Retrieved 2016-10-24. 
  7. 7.0 7.1 7.2 Josh L Davis (12 January 2016). Paleontologists Believe They Have Discovered The First Fossil Bed From The Dinosaur Extinction Event Itself. iflscience. Retrieved 2016-01-16.
  8. Kenneth Lacovara (12 January 2016). Paleontologists Believe They Have Discovered The First Fossil Bed From The Dinosaur Extinction Event Itself. iflscience. Retrieved 2016-01-16.
  9. 9.0 9.1 Gerta Keller (4 January 1993). "The Cretaceous-Tertiary boundary transition in the Antarctic Ocean and its global implications". Marine Micropaleontology 21 (1-3): 1 - 45. doi:10.1016/0377-8398(93)90010-U. Retrieved 2016-10-24. 
  10. Gerta Keller (2014). RESEARCH TOPICS. Princeton, New Jersey USA: Princeton University. Retrieved 2016-10-24.
  11. Ogg, James G.; Gradstein, F. M; Gradstein, Felix M. (2004). A geologic time scale 2004. Cambridge, UK: Cambridge University Press. ISBN 0-521-78142-6.
  12. Sleep, Norman H.; Lowe, Donald R. (9 April 2014). "Scientists reconstruct ancient impact that dwarfs dinosaur-extinction blast". American Geophysical Union. Retrieved 15 March 2018. 
  13. Amos, Jonathan (15 May 2017). Dinosaur asteroid hit 'worst possible place'. Retrieved 16 March 2018.
  14. Odin G.S. (2001). Odin G.S. (ed.). Numerical age calibration of the Campanian-Maastrichtian succession at Tercis-les-Bains (Landes, France) and in the Bottaccione Gorge (Italy), In: Characterisation and correlation from Tercis-les-Bains (Landes, SW France) to Europe and other continents. Elsevier. pp. 775–782.
  15. Odin, G.S. & Lamaurelle, M.A. (2001). "The global Campanian-Maastrichtian stage boundary". Episodes 24 (4): 229–238. 
  16. Cocholgüe village, sea coast at
  17. Pichasca at
  18. Hatcher, J.B. and Stanton, T.W., 1903. The stratigraphic position of the Judith River beds and their correlation with the Belly River beds. Science, no. 5, v. 18, p. 211-212.
  19. Mychaluk, K.A.; Levinson, A.A.; Hall, R.H.. "Ammolite: Iridescent fossil ammonite from southern Alberta, Canada.". Gems & Gemology 37 (1): 4-25. Retrieved 2015-01-11. 
  20. Latest Cretaceous Western Interior Seaway
  21. Glass, D.J. (editor) 1997. Lexicon of Canadian Stratigraphy, vol. 4, Western Canada including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba. Canadian Society of Petroleum Geologists, Calgary, 1423 p. on CD-ROM. ISBN 0-920230-23-7.
  22. 22.0 22.1 22.2 Mossop, G.D. and Shetsen, I., (compilers), Canadian Society of Petroleum Geologists (1994). Upper Cretaceous and Tertiary strata of the Western Canada Sedimentary Basin, In: The Geological Atlas of the Western Canada Sedimentary Basin. Retrieved 2013-08-01.CS1 maint: multiple names: authors list (link)
  23. Wall, J.H., Sweet, A.R. and Hills, L.V. 1971. Paleoecology of the Bearpaw and contiguous Upper Cretaceous formations in the C.P.O.G. Strathmore well, southern Alberta. Bulletin of Canadian Petroleum Geology, vol. 19, no. 3, p. 691-702.
  24. 24.0 24.1 Prior, G. J., Hathaway, B., Glombick, P.M., Pana, D.I., Banks, C.J., Hay, D.C., Schneider, C.L., Grobe, M., Elgr, R., and Weiss, J.A. (2013). Bedrock Geology of Alberta. Alberta Geological Survey, Map 600. Retrieved 2013-08-13.CS1 maint: multiple names: authors list (link)
  25. Mine History. Atlas Coal Mine National Historic Site. Retrieved 9 June 2010.
  26. Sullivan, R.M. and Lucas, S. G. (2006). "The Kirtlandian land-vertebrate "age"–faunal composition, temporal position and biostratigraphic correlation in the nonmarine Upper Cretaceous of western North America." Pp. 7-29 in Lucas, S. G. and Sullivan, R.M. (eds.), Late Cretaceous vertebrates from the Western Interior. New Mexico Museum of Natural History and Science Bulletin 35.
  27. Eberth, David A. (1997). Philip J. Currie; Padian Kevin (eds.) (eds.). Judith River Wedge, In: Encyclopedia of Dinosaurs. San Diego: Academic Press. pp. 379–380. ISBN 0-12-226810-5.CS1 maint: extra text: editors list (link)
  28. Lexicon of Canadian Geological Units. Judith River Formation. Retrieved 2009-02-06.
  29. GeoWhen Database - Barremian. Retrieved 2007-12-02.
  30. Meyers, P.A.; Bernasconi, S.M. & Forster, A. (2006). "Origins and accumulation of organic matter in expanded Albian to Santonian black shale sequences on the Demerara Rise, South American margin". Organic Geochemistry 37: 1816–1830. 
  31. Kennedy, W.J.; Walaszczyk, I. & Cobban, W.A. (2005). "The Global Boundary Stratotype Section and Point for the base of the Turonian Stage of the Cretaceous: Pueblo, Colorado, U.S.A.". Episodes 28 (2): 93–104. 
  32. International Commission on Stratigraphy. International Stratigraphic Chart (PDF). Retrieved 2008-06-17.
  33. Kennedy, W.J.; Gale, A.S.; Lees, J.A. & Caron, M. (2004). "The Global Boundary Stratotype Section and Point (GSSP) for the base of the Cenomanian Stage, Mont Risou, Hautes-Alpes, France". Episodes 27: 21–32. 
  34. 34.0 34.1 Slah Boulila, Bruno Galbrun, Linda A. Hinnov, Pierre-Yves Collin (January 2008). "High-resolution cyclostratigraphic analysis from magnetic susceptibility in a Lower Kimmeridgian (Upper Jurassic) marl–limestone succession (La Méouge, Vocontian Basin, France)". Sedimentary Geology 203 (1-2): 54-63. Retrieved 2015-01-27. 
  35. Sun, G., Q. Ji, D.L. Dilcher, S. Zheng, K.C. Nixon & X. Wang 2002. Archaefructaceae, a New Basal Angiosperm Family. Science 296(5569): 899–904.
  36. Lee, Michael SY; Cau, Andrea; Naish, Darren; Dyke, Gareth J. (May 2014). "Morphological Clocks in Paleontology, and a Mid-Cretaceous Origin of Crown Aves". Systematic Biology (Oxford Journals) 63 (1): 442–449. doi:10.1093/sysbio/syt110. PMID 24449041. 
  37. Kennedy, W.J.; Galeb, A.S.; Huberc, B.T.; Petrizzod, M.R.; Bowne, P.; Barchettad, A.; Jenkyns, H.C. (2014). "Integrated stratigraphy across the Aptian/Albian boundary at Col de Pré-Guittard (southeast France): A candidate Global Boundary Stratotype Section". Cretaceous Research 51: 248–259. doi:10.1016/j.cretres.2014.06.005. 
  38. See Kennedy et al. (2004) for a description of the GSSP for the Cenomanian
  39. Howe, John Allen. Albian. 1. p. 505. 
  40. Li, Yong-Xiang; Bralower, Timothy J.; Montañez, Isabel P.; Osleger, David A.; Arthur, Michael A.; Bice, David M.; Herbert, Timothy D.; Erba, Elisabetta et al. (2008-07-15). "Toward an orbital chronology for the early Aptian Oceanic Anoxic Event (OAE1a, ~ 120 Ma)". Earth and Planetary Science Letters 271 (1–4): 88–100. doi:10.1016/j.epsl.2008.03.055. 
  41. Leckie, R.; Bralower, T.; Cashman, R. (2002). "Oceanic anoxic events and plankton evolution: Biotic response to tectonic forcing during the mid-Cretaceous". Paleoceanography 17 (3): 1–29. doi:10.1029/2001pa000623. 
  42. Archangelsky, Sergio. "The Ticó Flora (Patagonia) and the Aptian Extinction Event." Acta Paleobotanica 41(2), 2001, pp. 115-22.
  43. 43.0 43.1 43.2 F.M. Gradstein, J.G. Ogg, & A.G. Smith (2004). A Geologic Time Scale 2004. Cambridge, England: Cambridge University Press.CS1 maint: multiple names: authors list (link)
  44. Vennari, Verónica V.; Lescano, Marina; Naipauer, Maximiliano; Aguirre-Urreta, Beatriz; Concheyro, Andrea; Schaltegger, Urs; Armstrong, Richard; Pimentel, Marcio et al. (2014). "New constraints on the Jurassic–Cretaceous boundary in the High Andes using high-precision U–Pb data". Gondwana Research 26 (1): 374–385. doi:10.1016/ 
  45. 45.0 45.1 Jaramillo, Jessica (March–April 2014). "Entrevista al Dr. Víctor Alberto Ramos, Premio México Ciencia y Tecnología 2013". Vol. 17 no. 66. Cite magazine requires |magazine= (help)
  46. Hallam, A. (1986). "The Pliensbachian and Tithonian extinction events". Nature 319 (6056): 765–768. doi:10.1038/319765a0. 
  47. "Jurassic". The Geology of Central Europe Mesozoic and Cenozoic: 823–922. (2008). London: Geological Society.
  48. Guillermo W. Rougier, John R. Wible, and James A. Hopson (22 November 1996). "Basicranial Anatomy of Priacodon fruitaensis (Triconodontidae, Mammalia) from the Late Jurassic of Colorado, and a Reappraisal of Mammaliaform Interrelationships". Novitates (3183): 38. Retrieved 2015-01-27. 
  49. International Commission on Stratigraphy (27 January 2015). GSSP Table - All Periods. ICS. Retrieved 2015-01-27.
  50. 50.0 50.1 50.2 S. Cresta, A. Goy, S. Ureta, C. Arias, E. Barrón, J. Bernad, M. L. Canales, F. García-Joral, E. García-Romero, P. R. Gialanella, J. J. Gómez, J. A. González, C. Herrero, G. Martínez, M. L. Osete, N. Perilli and J. J. Villalaín (September 2001). "The Global Boundary Stratotype Section and Point (GSSP) of the Toarcian-Aalenian Boundary (Lower-Middle Jurassic)". Episodes 24 (3): 166-75. Retrieved 2015-01-15. 
  51. 51.0 51.1 51.2 Benton, Michael J. (2012). Prehistoric Life. Edinburgh, Scotland: Dorling Kindersley. pp. 44–45. ISBN 978-0-7566-9910-9.
  52. For a detailed geologic timescale see Gradstein et al. (2004)
  53. See Gradstein et al. (2004) for a detailed geologic timescale
  54. Meister et al. (2006)
  55. F.M. Gradstein, J.G. Ogg, & A.G. Smith (2004). A Geologic Time Scale. Cambridge University Press.CS1 maint: multiple names: authors list (link)
  56. 56.0 56.1 56.2 Spencer G. Lucas, Jean Guex, Lawrence H. Tanner, David Taylor, Wolfram M. Kuerschner Viorel Atudorei and Annachiara Bartolini (April 2005). "Definition of the Triassic-Jurassic boundary". Albertiana 32 (4): 12-35. Retrieved 2015-01-21. 
  57. 57.0 57.1 A V Hillebrandt, L Krystyn, W M Kürschner, N R Bonis, M Ruhl, S Richoz, M A N Schobben, M Urlichs, P R Bown, K Kment, C A McRoberts, M Simms, and A Tomãsových (September 2013). "The Global Stratotype Sections and Point (GSSP) for the base of the Jurassic System at Kuhjoch (Karwendel Mountains, Northern Calcareous Alps, Tyrol, Austria)". Episodes 36 (3): 162-98. Retrieved 2015-01-21. 
  58. 58.0 58.1 Paul E. Olsen, Dennis V. Kent (June 1996). "Milankovitch climate forcing in the tropics of Pangaea during the Late Triassic". Palaeogeography, Palaeoclimatology, Palaeoecology 122 (1-4): 1-26. doi:10.1016/0031-0182(95)00171-9. Retrieved 2016-10-24. 
  59. Yuri D. Zakharov, Alexander M. Popov and Galina I. Buryi (April 2005). "Triassic Ammonoid Succession in South Primorye: 4. Late Olenekian – Early Anisian zones of the Atlasov Cape Section". Albertiana 32: 36-9. Retrieved 2015-01-24. 
  60. Yadong Sun, Michael M. Joachimski, Paul B. Wignall, Chunbo Yan, Yanlong Chen, Haishui Jiang, Lina Wang, Xulong Lai (19 October 2012). "Lethally hot temperatures during the Early Triassic greenhouse". Science 338 (6105): 366-370. doi:10.1126/science.1224126. Retrieved 2016-10-24. 
  61. 61.0 61.1 Heinz W. Kozur & Gerhard H. Bachmann (April 2005). "Correlation of the Germanic Triassic with the international scale". Albertiana 32 (4): 21-35. Retrieved 2015-01-23. 
  62. 62.0 62.1 Yin Hongfu, Zhang Kexin, Tong Jinnan, Yang Zunyi and Wu Shunbao (June 2001). [ "The Global Stratotype Section and Point (GSSP) of the Permian-Triassic Boundary"]. Episodes 24 (2): 102-14. Retrieved 2015-01-20. 
  63. Michelle Bruner (January 2016). The Rowan University Fossil Quarry. Mantua Township, N.J.: Rowan University. Retrieved 2016-01-18.

External linksEdit

{{Archaeology resources}}