Early Jurassic

Last updated
Early/Lower Jurassic
201.3 ± 0.2 – 174.7 ± 0.8 Ma
Chronostratigraphic nameLower Jurassic
Geochronological nameEarly Jurassic
Name formalityFormal
Usage information
Celestial body Earth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Chronological unit Epoch
Stratigraphic unit Series
Time span formalityFormal
Lower boundary definition FAD of the Ammonite Psiloceras spelae tirolicum .
Lower boundary GSSPKuhjoch section, Karwendel mountains, Northern Calcareous Alps, Austria
47°29′02″N11°31′50″E / 47.4839°N 11.5306°E / 47.4839; 11.5306
Lower GSSP ratified2010 [2]
Upper boundary definitionFAD of the Ammonites Leioceras opalinum and Leioceras lineatum
Upper boundary GSSP Fuentelsaz, Spain
41°10′15″N1°50′00″W / 41.1708°N 1.8333°W / 41.1708; -1.8333
Upper GSSP ratified2000 [3]

The Early Jurassic Epoch (in chronostratigraphy corresponding to the Lower Jurassic Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic–Jurassic extinction event, 201.3 Ma (million years ago), and ends at the start of the Middle Jurassic 174.7 ±0.8 Ma.


Certain rocks of marine origin of this age in Europe are called "Lias" and that name was used for the period, as well, in 19th-century geology. [4] In southern Germany rocks of this age are called Black Jurassic.

Origin of the name Lias

There are two possible origins for the name Lias: the first reason is it was taken by a geologist from an English quarryman's dialect pronunciation of the word "layers"; [5] secondly, sloops from north Cornish ports such as Bude would sail across the Bristol Channel to the Vale of Glamorgan to load up with rock from coastal limestone quarries (lias and Carboniferous limestone from South Wales was used throughout North Devon/North Cornwall as it contains calcium carbonate to 'sweeten' (i.e.neutralise) the acidic Devonian and Carboniferous soils of the West Country); the Cornish would pronounce the layers of limestone as 'laiyers' or 'lias'; leac is Gaelic for "flat stone". [5]



Massive cliffs in Zion Canyon consist of Lower Jurassic formations, including (from bottom to top): the Kayenta Formation and the massive Navajo Sandstone The Three Patriarchs in Zion Canyon.jpg
Massive cliffs in Zion Canyon consist of Lower Jurassic formations, including (from bottom to top): the Kayenta Formation and the massive Navajo Sandstone

There has been some debate [6] over the actual base of the Hettangian Stage, and so of the Jurassic System itself. Biostratigraphically, the first appearance of psiloceratid ammonites has been used; but this depends on relatively complete ammonite faunas being present, a problem that makes correlation between sections in different parts of the world difficult. If this biostratigraphical indicator is used, then technically the Lias Group—a lithostratigraphical division—spans the Jurassic / Triassic boundary.

United Kingdom

Lias formations at Lyme Regis, UK, known locally as Blue Lias Blue lias cliffs at Lyme Regis.jpg
Lias formations at Lyme Regis, UK, known locally as Blue Lias

There are extensive Liassic outcrops around the coast of the United Kingdom, in particular in Glamorgan, North Yorkshire and Dorset. The 'Jurassic Coast' of Dorset is often associated with the pioneering work of Mary Anning of Lyme Regis. The facies of the Lower Jurassic in this area are predominantly of clays, thin limestones and siltstones, deposited under fully marine conditions.

Lias Group strata form imposing cliffs on the Vale of Glamorgan coast, in southern Wales. Stretching for around 14 miles (23 km) between Cardiff and Porthcawl, the remarkable layers of these cliffs, situated on the Bristol Channel are a rhythmic decimetre scale repetition of limestone and mudstone formed as a late Triassic desert was inundated by the sea. [7]



During this period, ammonoids, which had almost died out at the end-of-Triassic extinction, radiated out into a huge diversity of new forms with complex suture patterns (the ammonites proper). Ammonites evolved so rapidly, and their shells are so often preserved, that they serve as important zone fossils. There were several distinct waves of ammonite evolution in Europe alone. [8]

Marine reptiles

The Early Jurassic was an important time in the evolution of the marine reptiles. The Hettangian saw the already existing Rhaetian ichthyosaurs and plesiosaurs continuing to flourish, while at the same time a number of new types of these marine reptiles appeared, such as Ichthyosaurus and Temnodontosaurus among the ichthyosaurs, and Eurycleidus , Macroplata , and Rhomaleosaurus among the plesiosaurs (all Rhomaleosauridae, although as currently defined this group is probably paraphyletic). All these plesiosaurs had medium-sized necks and large heads. In the Toarcian, at the end of the Early Jurassic, the thalattosuchians (marine "crocodiles") appeared, as did new genera of ichthyosaurs ( Stenopterygius , Eurhinosaurus , and the persistently primitive Suevoleviathan ) and plesiosaurs (the elasmosaurs (long-necked) Microcleidus and Occitanosaurus , and the pliosaur Hauffiosaurus ).[ citation needed ]

New marine fish appeared, including the fleshy-finned Trachymetopon and Holophagus coelacanths. They very first sharks appeared, although this is still debated. Other cartilaginous fish included the Squaloraja chimaera, and the very first rajiform rays. Tarpon-like elopomorphs also appeared.[ citation needed ]

Terrestrial animals

Terrestrial environment of the Pliensbachian-Toarcian boundary Fennoscandinavia, with flora based on the Sorthat Formation. Dinosaurs are based on material found on various locations of the German realm of the Ciechocinek Formation and on lesser extent, footprints of the Drzewica Formation Ciechocinek Formation Reconstruction.jpg
Terrestrial environment of the Pliensbachian-Toarcian boundary Fennoscandinavia, with flora based on the Sorthat Formation. Dinosaurs are based on material found on various locations of the German realm of the Ciechocinek Formation and on lesser extent, footprints of the Drzewica Formation

On land, a number of new types of dinosaurs—the herbivorous ornithischians (including the armored thyreophorans), dilophosaurs, and averostran theropods—appeared, and joined those groups like the coelophysoids and the saurischian sauropodomorphs (including the sauropods) that had continued over from the Triassic. Accompanying them as small carnivores were new genera of the sphenosuchian and protosuchid crocodylomorphs. In the air, new types of novialoid pterosaurs replaced the eopterosaurian and caviramid pterosaurs that had died out at the end of the Triassic. But in the undergrowth were various types of early mammals, as well as tritylodont synapsids (including the large Bienotherium, the fossorial Tritylodon, and the semi-aquatic Kayentatherium), aquatic tuatara-like pleurosaurids, and early lissamphibians (including the caecilian Eocaecilia, as well as the very first frogs).[ citation needed ]

In bodies of freshwater, eel-like elopomorphs appeared. Holosts included the gar-like lepisosteiforms and the bowfin-like Caturus and Liodesmus. Chondrosts included the coccolepidids, the Saurorhynchus, and the very first paddlefish- and sturgeon-like acipenseriforms. The very first rajiform rays, too, emerged.[ citation needed ]

See also

Related Research Articles

<span class="mw-page-title-main">Jurassic</span> Second period of the Mesozoic Era 201-145 million years ago

The Jurassic is a geologic period and stratigraphic system that spanned from the end of the Triassic Period 201.4 million years ago (Mya) to the beginning of the Cretaceous Period, approximately 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era and is named after the Jura Mountains, where limestone strata from the period were first identified.

The Toarcian is, in the ICS' geologic timescale, an age and stage in the Early or Lower Jurassic. It spans the time between 182.7 Ma and 174.7 ±0.8 Ma. It follows the Pliensbachian and is followed by the Aalenian.

<span class="mw-page-title-main">Aalenian</span> First age of the Middle Jurassic

The Aalenian is a subdivision of the Middle Jurassic Epoch/Series of the geologic timescale that extends from about 174.7 ±0.8 Ma to about 170.9 ±0.8 Ma. It was preceded by the Toarcian and succeeded by the Bajocian.

<span class="mw-page-title-main">Middle Jurassic</span> Second part of the Jurassic geological period, from 174 to 163 million years ago

The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively rare, but geological formations containing land animal fossils include the Forest Marble Formation in England, the Kilmaluag Formation in Scotland, the Calcaire de Caen of France, the Daohugou Beds in China, the Itat Formation in Russia, the Tiouraren Formation of Niger, and the Isalo III Formation of western Madagascar.

The Rhaetian is the latest age of the Triassic Period or the uppermost stage of the Triassic System. It was preceded by the Norian and succeeded by the Hettangian. The base of the Rhaetian lacks a formal GSSP, though candidate sections include Steinbergkogel in Austria and Pignola-Abriola in Italy. The end of the Rhaetian is more well-defined. According to the current ICS system, the Rhaetian ended 201.4 ± 0.2 Ma.

<span class="mw-page-title-main">Anisian</span> Stage of the Triassic

In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from 247.2 million years ago until 242 million years ago. The Anisian Age succeeds the Olenekian Age and precedes the Ladinian Age.

In the geologic timescale, the Bajocian is an age and stage in the Middle Jurassic. It lasted from approximately 170.9 ±0.8 Ma to around 168.2 ±1.2 Ma. The Bajocian Age succeeds the Aalenian Age and precedes the Bathonian Age.

In the geologic timescale the Bathonian is an age and stage of the Middle Jurassic. It lasted from approximately 168.2 ±1.2 Ma to around 165.3 ±1.1 Ma. The Bathonian Age succeeds the Bajocian Age and precedes the Callovian Age.

The Hettangian is the earliest age and lowest stage of the Jurassic Period of the geologic timescale. It spans the time between 201.3 ± 0.2 Ma and 199.3 ± 0.3 Ma. The Hettangian follows the Rhaetian and is followed by the Sinemurian.

<span class="mw-page-title-main">Sinemurian</span> Second age of the Early Jurassic

In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic Epoch or Series. It spans the time between 199.5 ±0.3 Ma and 192.9 ±0.3 Ma. The Sinemurian is preceded by the Hettangian and is followed by the Pliensbachian.

The Pliensbachian is an age of the geologic timescale and stage in the stratigraphic column. It is part of the Early or Lower Jurassic Epoch or Series and spans the time between 192.9 ±0.3 Ma and 184.2 ±0.3 Ma. The Pliensbachian is preceded by the Sinemurian and followed by the Toarcian.

<span class="mw-page-title-main">Ladinian</span> Age in the Middle Triassic

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<i>Temnodontosaurus</i> Extinct genus of reptiles

Temnodontosaurus is an extinct genus of ichthyosaur from the Early Jurassic period. They lived between 200 and 175 million years ago (Hettangian-Toarcian) in what is now Western Europe and possibly Chile. It lived in the deeper areas of the open ocean. University of Bristol paleontologist Jeremy Martin described the genus Temnodontosaurus as "one of the most ecologically disparate genera of ichthyosaurs," although the number of valid Temnodontosaurus species has varied over the years.

<span class="mw-page-title-main">Blue Lias</span> Triassic/Jurassic geological formation in the UK

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<i>Psiloceras</i> Genus of molluscs (fossil)

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<span class="mw-page-title-main">Whitby Mudstone</span> Geological formation in Yorkshire, UK

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<span class="mw-page-title-main">Waterloo Bay</span>

Waterloo Bay is an area of foreshore in Larne on the east coast of County Antrim, Northern Ireland. It is of particular interest to geologists because it provides a clear, complete and accessible example of the sequences from Upper Triassic to Lower Jurassic, when the rock types changed from land to marine.

The Gabbs Formation is a geologic formation in Nevada. It preserves fossils dating back to the Late Triassic and Early Jurassic periods, and is one of the few formations in the United States known to include the Triassic-Jurassic boundary. In 2007, an exposure of the Gabbs Formation at New York Canyon was proposed a candidate GSSP for the Hettangian stage, the first stage of the Jurassic. However, the New York Canyon section was ultimately not selected as Hettangian GSSP, which instead went to the Kuhjoch section of Austria in 2010.

The Kendlbach Formation is a Late Triassic to Early Jurassic (Hettangian) geological formation in Austria and Italy. It contains the Global Boundary Stratotype Section and Point (GSSP) for the Hettangian stage at the Kuhjoch section in the Karwendel Mountains of Austria.


  1. "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy.
  2. Hillebrandt, A.v.; Krystyn, L.; Kürschner, W.M.; Bonis, N.R.; Ruhl, M.; Richoz, S.; Schobben, M. A. N.; Urlichs, M.; Bown, P.R.; Kment, K.; McRoberts, C.A.; Simms, M.; Tomãsových, A (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): 162–198. CiteSeerX . doi:10.18814/epiiugs/2013/v36i3/001. S2CID   128552062.
  3. Cresta, S.; Goy, A.; Arias, C.; Barrón, E.; Bernad, J.; Canales, M.; García-Joral, F.; García-Romero, E; Gialanella, P.; Gómez, J.; González, J.; Herrero, C.; Martínez2, G.; Osete, M.; Perilli, N.; Villalaín, J. (September 2001). "The Global Boundary Stratotype Section and Point (GSSP) of the Toarcian-Aalenian Boundary (Lower-Middle Jurassic)" (PDF). Episodes. 24 (3): 166–175. doi:10.18814/epiiugs/2001/v24i3/003 . Retrieved 13 December 2020.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  4. Rudwick, M.J.S (1992): Scenes from Deep Time: Early Pictorial Representations of the Prehistoric World, University of Chicago Press, 280 pages. Except from Google Books
  5. 1 2 Chisholm, Hugh, ed. (1911). "Lias"  . Encyclopædia Britannica . Vol. 16 (11th ed.). Cambridge University Press. p. 533.
  6. International Subcommission on Jurassic Stratigraphy. Newsletter 35/1, December 2008, Edited by Nicol Morton and Stephen Hesselbo Archived 2015-01-28 at the Wayback Machine
  7. Howe, S., Owen, G. & Sharpe, T. 2005 Walking the Rocks Geologists' Association - South Wales Group
  8. See e.g. Davies, 1920, pp. 173–75