Early/Lower Triassic | |||||||||||||||||||||||
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![]() Map of Earth as it appeared 250 million years ago during the Early Triassic, Olenekian stage | |||||||||||||||||||||||
![]() Sandstone from the Lower Triassic Series | |||||||||||||||||||||||
Chronology | |||||||||||||||||||||||
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Etymology | |||||||||||||||||||||||
Chronostratigraphic name | Lower Triassic | ||||||||||||||||||||||
Geochronological name | Early Triassic | ||||||||||||||||||||||
Name formality | Formal | ||||||||||||||||||||||
Usage information | |||||||||||||||||||||||
Celestial body | Earth | ||||||||||||||||||||||
Regional usage | Global (ICS) | ||||||||||||||||||||||
Time scale(s) used | ICS Time Scale | ||||||||||||||||||||||
Definition | |||||||||||||||||||||||
Chronological unit | Epoch | ||||||||||||||||||||||
Stratigraphic unit | Series | ||||||||||||||||||||||
Time span formality | Formal | ||||||||||||||||||||||
Lower boundary definition | FAD of the Conodont Hindeodus parvus | ||||||||||||||||||||||
Lower boundary GSSP | Meishan, Zhejiang, China 31°04′47″N119°42′21″E / 31.0798°N 119.7058°E | ||||||||||||||||||||||
Lower GSSP ratified | 2001 [6] | ||||||||||||||||||||||
Upper boundary definition | Not formally defined | ||||||||||||||||||||||
Upper boundary definition candidates |
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Upper boundary GSSP candidate section(s) |
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The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between 251.9 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 Mesozoic Era. It is preceded by the Lopingian Epoch (late Permian, Paleozoic Era) and followed by the Middle Triassic Epoch. The Early Triassic is divided into the Induan and Olenekian ages. The Induan is subdivided into the Griesbachian and Dienerian subages and the Olenekian is subdivided into the Smithian and 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.[ citation needed ]
The Early Triassic and partly also the Middle Triassic span the interval of biotic recovery from the Permian-Triassic extinction event, the most severe mass extinction event in Earth's history. [8] [9] [10] A second extinction event, 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]
The climate during the Early Triassic Epoch (especially in the interior of the supercontinent Pangaea) was generally arid, rainless and dry and deserts were widespread; however the poles possessed a temperate climate. The pole-to-equator temperature gradient was temporally flat during the Early Triassic and may have allowed tropical species to extend their distribution poleward. This is evidenced by the global distribution of ammonoids. [13] The extremely hot ocean temperatures facilitated extremely powerful hurricanes that frequently hit the coast of North China. [14]
The mostly hot climate of the Early Triassic may have been caused by late volcanic eruptions of the Siberian Traps, [15] [8] which had probably triggered the Permian-Triassic extinction event and accelerated the rate of global warming into the Triassic. [16] Studies suggest that Early Triassic climate was very volatile, punctuated by a number of relatively rapid global temperature changes, marine anoxic events, and carbon cycle disturbances, [17] [18] [19] which led to subsequent extinction events in the aftermath of the Permian-Triassic extinction event. [20] [21] [22] 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. [23]
The Triassic Period opened in the aftermath of the Permian–Triassic extinction event. The massive extinctions that ended the Permian Period (and with that the Paleozoic Era) caused extreme hardships for the surviving species.
The Early Triassic Epoch saw the biotic 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. [24] Many types of corals, brachiopods, molluscs, echinoderms, and other invertebrates had disappeared. The Permian vegetation, which was dominated by Glossopteris in the Southern Hemisphere, ceased to exist. [25] Other groups, such as Actinopterygii, appear to have been less affected by this extinction event [26] and body size was not a selective factor during the extinction event. [27] [28] Animals that were most successful in the Early Triassic were those with high metabolisms. [29] Different patterns of recovery are evident on land and in the sea. Early Triassic faunas lacked biodiversity and were relatively homogeneous due to the effects of the extinction. The ecological recovery on land took 30 million years, well into the Late Triassic. [30] Two Early Triassic lagerstätten stand out due to their exceptionally high biodiversity, the Dienerian aged Guiyang biota [31] and the earliest Spathian aged Paris biota. [32]
The most common land vertebrate was the small herbivorous synapsid Lystrosaurus . Often interpreted as a disaster taxon (although this view was questioned [33] ), Lystrosaurus had a wide range across Pangea. In the southern part of the supercontinent, it co-occurred with the non-mammalian cynodonts Galesaurus and Thrinaxodon , early relatives of mammals. First archosauriforms appeared, such as Erythrosuchus (Olenekian-Ladinian). [34] This group includes the ancestors of crocodiles and dinosaurs (including birds). Fossilized foot prints of dinosauromorphs are known from the Olenekian. [35] The Early Triassic entomofauna is very poorly understood because of the paucity of insect fossils from this epoch. [36]
The flora was gymnosperm-dominated at the onset of the Triassic, but changed rapidly and became lycopod-dominated (e.g. Pleuromeia ) during the Griesbachian-Dienerian ecological crisis. This change coincided with the extinction of the Permian Glossopteris flora. [25] In the Spathian subage, the flora changed back to gymnosperm and pteridophyte dominated. [37] These shifts reflect global changes in precipitation and temperature. [25] [20] Floral diversity was overall very low during the Early Triassic, as plant life had yet to fully recover from the Permian-Triassic extinction. [38]
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. [39] MISS have also been reported from Early Triassic fossil deposits in Arctic Canada. [40] The disappearance of MISS later in the Early Triassic has been interpreted as a signal of increased bioturbation and recovery of terrestrial ecosystems. [39]
In the oceans, the most common Early Triassic hard-shelled marine invertebrates were bivalves, gastropods, ammonoids, echinoids, and a few articulate brachiopods. Conodonts experienced a revival in diversity following a nadir during the Permian. [41] The first oysters ( Liostrea ) appeared in the Early Triassic. They grew on the shells of living ammonoids as epizoans. [42] Microbial reefs were common, possibly due to lack of competition with metazoan reef builders as a result of the extinction. [43] However, transient metazoan reefs reoccurred during the Olenekian wherever permitted by environmental conditions. [44] Ammonoids show blooms followed by extinctions during the Early Triassic. [45]
Aquatic vertebrates diversified after the extinction:
The Permian is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period 298.9 million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the last period of the Paleozoic Era; the following Triassic Period belongs to the Mesozoic Era. The concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the region of Perm in Russia.
Approximately 251.9 million years ago, the Permian–Triassicextinction event forms the boundary between the Permian and Triassic geologic periods, and with them the Paleozoic and Mesozoic eras. It is Earth's most severe known extinction event, with the extinction of 57% of biological families, 83% of genera, 81% of marine species and 70% of terrestrial vertebrate species. It is also the greatest known mass extinction of insects. It is the greatest of the "Big Five" mass extinctions of the Phanerozoic. There is evidence for one to three distinct pulses, or phases, of extinction.
The Triassic is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago (Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is the first and shortest period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events. The Triassic Period is subdivided into three epochs: Early Triassic, Middle Triassic and Late Triassic.
The Triassic–Jurassic (Tr-J) extinction event (TJME), often called the end-Triassic extinction, was a Mesozoic extinction event that marks the boundary between the Triassic and Jurassic periods, 201.4 million years ago, and is one of the top five major extinction events of the Phanerozoic eon, profoundly affecting life on land and in the oceans. In the seas, the entire class of conodonts and 23–34% of marine genera disappeared. On land, all archosauromorphs other than crocodylomorphs, pterosaurs, and non-avian dinosaurs became extinct; some of the groups which died out were previously abundant, such as aetosaurs, phytosaurs, and rauisuchids. Some remaining non-mammalian therapsids and many of the large temnospondyl amphibians had become extinct prior to the Jurassic as well. However, there is still much uncertainty regarding a connection between the Tr-J boundary and terrestrial vertebrates, due to a lack of terrestrial fossils from the Rhaetian (uppermost) stage of the Triassic. Plants, crocodylomorphs, dinosaurs, pterosaurs and mammals were left largely untouched; this allowed the dinosaurs, pterosaurs, and crocodylomorphs to become the dominant land animals for the next 135 million years.
The Late Devonian extinction consisted of several extinction events in the Late Devonian Epoch, which collectively represent one of the five largest mass extinction events in the history of life on Earth. The term primarily refers to a major extinction, the Kellwasser event, also known as the Frasnian-Famennian extinction, which occurred around 372 million years ago, at the boundary between the Frasnian age and the Famennian age, the last age in the Devonian Period. Overall, 19% of all families and 50% of all genera became extinct. A second mass extinction called the Hangenberg event, also known as the end-Devonian extinction, occurred 359 million years ago, bringing an end to the Famennian and Devonian, as the world transitioned into the Carboniferous Period.
The Lopingian is the uppermost series/last epoch of the Permian. It is the last epoch of the Paleozoic. The Lopingian was preceded by the Guadalupian and followed by the Early Triassic.
In the geologic timescale, the Capitanian is an age or stage of the Permian. It is also the uppermost or latest of three subdivisions of the Guadalupian Epoch or Series. The Capitanian lasted between 264.28 and 259.51 million years ago. It was preceded by the Wordian and followed by the Wuchiapingian.
The Carnian is the lowermost stage of the Upper Triassic Series. It lasted from 237 to 227 million years ago (Ma). The Carnian is preceded by the Ladinian and is followed by the Norian. Its boundaries are not characterized by major extinctions or biotic turnovers, but a climatic event occurred during the Carnian and seems to be associated with important extinctions or biotic radiations. Another extinction occurred at the Carnian-Norian boundary, ending the Carnian age.
In the geologic timescale, the Olenekian is an age in the Early Triassic epoch; in chronostratigraphy, it is a stage in the Lower Triassic series. It spans the time between 251.2 Ma and 247.2 Ma. The Olenekian is sometimes divided into the Smithian and the Spathian subages or substages. The Olenekian follows the Induan and is followed by the Anisian.
In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between 247.2 Ma and 237 Ma. It is preceded by the Early Triassic Epoch and followed by the Late Triassic Epoch. The Middle Triassic is divided into the Anisian and Ladinian ages or stages.
The Late Triassic is the third and final epoch of the Triassic Period in the geologic time scale, spanning the time between 237 Ma and 201.4 Ma. It is preceded by the Middle Triassic Epoch and followed by the Early Jurassic Epoch. The corresponding series of rock beds is known as the Upper Triassic. The Late Triassic is divided into the Carnian, Norian and Rhaetian ages.
The Induan is the first age of the Early Triassic epoch in the geologic timescale, or the lowest stage of the Lower Triassic series in chronostratigraphy. It spans the time between 251.9 Ma and 251.2 Ma. The Induan is sometimes divided into the Griesbachian and the Dienerian subages or substages. The Induan is preceded by the Changhsingian and is followed by the Olenekian.
The Lystrosaurus Assemblage Zone is a tetrapod assemblage zone or biozone which correlates to the upper Adelaide and lower Tarkastad Subgroups of the Beaufort Group, a fossiliferous and geologically important geological Group of the Karoo Supergroup in South Africa. This biozone has outcrops in the south central Eastern Cape and in the southern and northeastern Free State. The Lystrosaurus Assemblage Zone is one of eight biozones found in the Beaufort Group, and is considered to be Early Triassic in age.
The Carnian pluvial episode (CPE), often called the Carnian pluvial event, was an interval of major change in global climate that was synchronous with significant changes in Earth's biota both in the sea and on land. It occurred during the latter part of the Carnian Stage, a subdivision of the late Triassic period, and lasted for perhaps 1–2 million years.
The Werfen Formation is a geologic formation in the Southern Limestone Alps and Dinaric Alps of Austria, Bosnia and Herzegovina, and Italy. It preserves fossils dating back to the Triassic period.
Cartorhynchus is an extinct genus of early ichthyosauriform marine reptile that lived during the Early Triassic epoch, about 248 million years ago. The genus contains a single species, Cartorhynchus lenticarpus, named in 2014 by Ryosuke Motani and colleagues from a single nearly-complete skeleton found near Chaohu, Anhui Province, China. Along with its close relative Sclerocormus, Cartorhynchus was part of a diversification of marine reptiles that occurred suddenly during the Spathian substage, soon after the devastating Permian-Triassic extinction event, but they were subsequently driven to extinction by volcanism and sea level changes by the Middle Triassic.
The Lilliput effect is an observed decrease in animal body size in genera that have survived a major extinction. There are several hypotheses as to why these patterns appear in the fossil record, some of which are:
The Capitanian mass extinction event, also known as the end-Guadalupian extinction event, the Guadalupian-Lopingian boundary mass extinction, the pre-Lopingian crisis, or the Middle Permian extinction, was an extinction event that predated the end-Permian extinction event. The mass extinction occurred during a period of decreased species richness and increased extinction rates near the end of the Middle Permian, also known as the Guadalupian epoch. It is often called the end-Guadalupian extinction event because of its initial recognition between the Guadalupian and Lopingian series; however, more refined stratigraphic study suggests that extinction peaks in many taxonomic groups occurred within the Guadalupian, in the latter half of the Capitanian age. The extinction event has been argued to have begun around 262 million years ago with the Late Guadalupian crisis, though its most intense pulse occurred 259 million years ago in what is known as the Guadalupian-Lopingian boundary event.
The Paris biota is an exceptionally diverse Early Triassic fossil assemblage described in 2017 from the Lower Shale Member of the Thaynes Group. It was first discovered in Paris Canyon, west of the town of Paris in Bear Lake County, southeastern Idaho, United States. This biota was later also found in coeval and slightly younger beds in northeastern Nevada and Bear Lake and Caribou counties, southeastern Idaho.
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