Geochronology/Mesozoic

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

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

Notations

Let

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 [...]."

Mesozoic time frames

Sortable table

Name (English)	base/start (Ma)	top/end (Ma)	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	251.0 ± 0.4	246.6	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	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	±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	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	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	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

Cretaceous

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

Late Cretaceous

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.

"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."

“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.”

"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."

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."

"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."

"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)."

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 Cretaceous

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

Photograph is of a fossil ammonite Jeletzkytes spedeni. Credit: Dlloyd..

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

The specimen on the left is Jeletzkytes spedeni from the Maastrichtian (Upper-Cretaceous) Fox Hills Formation, locality - South Dakota, USA. Matrix free specimen is 7.5 cm (3") in diameter, displaying pearly aragonite preservation of the shell.

Early Cretaceous

"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)."

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

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

Jurassic

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

Late Jurassic

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

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

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)." 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 Jurassic

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.

Callovian

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.

Aalenian

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."

"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)."

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."

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 Jurassic

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.

Pliensbachian

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

Pleuroceras spinatum (Bruguière 1789) is of the family Amaltheidae. It is a pyritic specimen. The biozone index is to the end of Pliensbachian.

Hettangian

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)."

"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]."

Another FO is that of "the aragonitic foraminifer Praegubkinella turgescens"

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

Triassic

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."

Late Triassic

"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."

"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."

Upper Triassic

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

Rhaetian

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."

Norian

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.

Sevatian

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

Alaunian

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

Lacian

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

Carnian

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

Tuvalian

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

Julian

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

Cordevolian

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

Middle Triassic

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

Ladinian

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

Longobardian

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

Fassanian

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

Anisian

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.

Illyrian

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

Pelsonian

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

Bithynian

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

Aegean

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 Triassic

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

Early Triassic

"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."

Scythian

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

Olenekian

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

Spathian

The Spathian is sometimes referred to as the Late Olenekian.

Smithian

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.

Brahmanian

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

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."

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

Dienerian

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

Gandarian

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

Gangetian

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).

Locations on Earth

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."

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.

Hypotheses

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 also: Control groups, Proof of concept, and Proof of technology

See also

• Archaeology
• Paleontology

External links

• The Denisens of Cretaceous Mantua
• Global Boundary Stratotype Section and Point (GSSP) of the International Commission on Stratigraphy

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