Early Triassic

Source: Wikipedia, the free encyclopedia.
Early/Lower Triassic
251.9 – 247.2 Ma
↓
Epoch
Stratigraphic unitSeries
Time span formalityFormal
Lower boundary definitionFAD of the Conodont Hindeodus parvus
Lower boundary GSSPMeishan, Zhejiang, China
31°04′47″N 119°42′21″E / 31.0798°N 119.7058°E / 31.0798; 119.7058
Lower GSSP ratified2001[6]
Upper boundary definitionNot formally defined
Upper boundary definition candidates
Upper boundary GSSP candidate section(s)

The Early Triassic is the first of three

Ma and 247.2 Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which is a unit in chronostratigraphy
.

The Early Triassic is the oldest epoch of the

Spathian subages.[7]

The Lower Triassic series is coeval with the Scythian Stage, which is today not included in the official timescales but can be found in older literature. In Europe, most of the Lower Triassic is composed of Buntsandstein, a lithostratigraphic unit of continental red beds.

The Early Triassic and partly also the

Smithian-Spathian boundary event, occurred during the Olenekian.[11] A third extinction event occurred at the Olenekian-Anisian boundary, marking the end of the Early Triassic epoch.[12]

Early Triassic climate

The Putorana Plateau is composed of basalt rocks of the Siberian Traps.

The climate during the Early Triassic Epoch (especially in the interior of the supercontinent

ammonoids.[13]

The mostly hot climate of the Early Triassic may have been caused by late volcanic eruptions of the

Permian-Triassic extinction event.[19][20][21] On the other hand, an alternative hypothesis proposes these Early Triassic climatic perturbations and biotic upheavals that inhibited the recovery of life following the P-T mass extinction to have been linked to forcing driven by changes in the Earth's obliquity defined by a roughly 32.8 thousand year periodicity with strong 1.2 million year modulations. According to proponents of this hypothesis, radiometric dating indicates that major activity from the Siberian Traps ended very shortly after the end-Permian extinction and did not span the entire Early Triassic epoch, thus not being the primary culprit for the climatic changes throughout this epoch.[22]

Early Triassic life

Fauna and flora

Pleuromeia represented a dominant element of global floras during the Early Triassic

The Triassic Period opened with the Permian–Triassic extinction event. The massive extinctions that ended the Permian Period and Paleozoic Era caused extreme hardships for the surviving species.

The Early Triassic Epoch saw the recovery of life after the biggest mass extinction event of the past, which took millions of years due to the severity of the event and the harsh Early Triassic climate.

Spathian aged Paris biota.[31]

Terrestrial biota

The most common land vertebrate was the small

dinosauromorphs are known from the Olenekian.[34]

The

Spathian subage, the flora changed back to gymnosperm and pteridophyte dominated.[35] These shifts reflect global changes in precipitation and temperature.[24] Floral diversity was overall very low during the Early Triassic, as plant life had yet to fully recover from the Permian-Triassic extinction.[36]

Microbially induced sedimentary structures (MISS) are common in the fossil record of North China in the immediate aftermath of the Permian-Triassic extinction, indicating that microbial mats dominated local terrestrial ecosystems following the Permian-Triassic boundary. The regional prevalence of MISS is attributable to a decrease in bioturbation and grazing pressure as a result of aridification and temperature increase.[37] MISS have also been reported from Early Triassic fossil deposits in Arctic Canada.[38] The disappearance of MISS later in the Early Triassic has been interpreted as a signal of increased bioturbation and recovery of terrestrial ecosystems.[37]

Aquatic biota

In the oceans, the most common Early Triassic hard-shelled marine invertebrates were

Ammonoids show blooms followed by extinctions during the Early Triassic.[43]

Aquatic vertebrates diversified after the extinction.

Fishes: Typical Triassic

Neoselachii, as well as last survivors of Eugeneodontida (Caseodus, Fadenia
).

temnospondyl amphibians, such as Aphaneramma or Wantzosaurus, were geographically widespread during the Induan and Olenekian ages. The fossils of these crocodile-shaped amphibians were found in Greenland, Spitsbergen, Pakistan and Madagascar
.

Reptiles: In the oceans, first marine reptiles appeared during the Early Triassic.

thalattosaurs followed later in the Middle Triassic.[44] The Anisian aged ichthyosaur Thalattoarchon was one of the first marine macropredators capable of eating prey that was similar in size to itself, an ecological role that can be compared to that of modern orcas.[45]

Fossil gallery

See also

References

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Further reading

External links
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