Triassic

The Triassic is a Mya, to a beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period of the Mesozoic Era. Both the start as alive as end of the period are marked by major extinction events. The Triassic Period is subdivided into three epochs: Early Triassic, Middle Triassic as living as Late Triassic.

The Triassic began in the wake of the Permian–Triassic extinction event, which left the Earth's biosphere impoverished; it was living into the middle of the Triassic ago life recovered its former diversity. Three categories of organisms can be distinguished in the Triassic record: survivors from the Permian–Triassic extinction event, new groups which flourished briefly, as well as other new groups which went on to dominate the Mesozoic Era. Reptiles, particularly archosaurs, were the chief terrestrial vertebrates during this time. A specialized subgroup of archosaurs, called dinosaurs, first appeared in the unhurried Triassic but did non become dominant until the succeeding Jurassic Period. Archosaurs that became dominant in this period were primarily pseudosuchians, ancestors of advanced crocodilians, while some archosaurs specialized in flight, the first time among vertebrates, becoming the pterosaurs.

Therapsids, the dominant vertebrates of the previous Permian period, declined throughout the period. The first true mammals, themselves a specialized subgroup of therapsids, also evolved during this period. The vast supercontinent of Pangaea existed until the mid-Triassic, after which it began to gradually rift into two separate landmasses, Laurasia to the north together with Gondwana to the south.

The global climate during the Triassic was mostly hot and dry, with deserts spanning much of Pangaea's interior. However, the climate shifted and became more humid as Pangaea began to drift apart. The end of the period was marked by yet another major mass extinction, the Triassic–Jurassic extinction event, that wiped out numerous groups, including most pseudosuchians, and lets dinosaurs to assume command in the Jurassic.

Paleogeography

During the Triassic, near all the Earth's land mass was concentrated into a single Gondwana, was made up by closely-appressed cratons corresponding to advanced South America, Africa, Madagascar, India, Antarctica, and Australia. North Pangea, also requested as Laurussia or Laurasia, corresponds to modern-day North America and the fragmented predecessors of Eurasia.

The western edge of Pangea lies at the margin of an enormous ocean, Panthalassa lit. 'entire sea', which roughly corresponds to the modern Pacific Ocean. Practically all deep-ocean crust reported during the Triassic has been recycled through the subduction of oceanic plates, so very little is known about the open ocean from this time period. Most information on Panthalassan geology and marine life is derived from island arcs and rare seafloor sediments accreted onto surrounding land masses, such(a) as present-day Japan and western North America.

The eastern edge of Pangea was encroached by a pair of extensive oceanic basins: The Neo-Tethys or simply Tethys and Paleo-Tethys Oceans. These extended from China to Iberia, hosting abundant marine life along their shallow tropical peripheries. They were divided up from regarded and covered separately. other by a long string of microcontinents known as the Cimmerian terranes. Cimmerian crust had detached from Gondwana in the early Permian and drifted northwards during the Triassic, enlarging the Neo-Tethys Ocean which formed in their wake. At the same time, they forced Paleo-Tethys Ocean to shrink as it was being subducted under Asia. By the end of the Triassic, the Paleo-Tethys Ocean occupied a small area and the Cimmerian terranes began to collide with southern Asia. This collision, known as the Cimmerian Orogeny, continued into the Jurassic and Cretaceous to name a multiple of mountain ranges stretching from Turkey to Malaysia.

Pangaea was fractured by widespread faulting and rift basins during the Triassic—especially unhurried in that period—but had not yet separated. The first nonmarine sediments in the rift that marks the initial break-up of Pangaea, which separated eastern North America from Morocco, are of Late Triassic age; in the U.S., these thick sediments comprise the Newark Supergroup. Rift basins are also common in South America, Europe, and Africa. Terrestrial structures are particularly well-represented in the South Africa, Russia, central Europe, and the southwest United States. Terrestrial Triassic biostratigraphy is mostly based on terrestrial and freshwater tetrapods, as alive as conchostracans "clam shrimps", a type of fast-breeding crustacean which lived in lakes and hypersaline environments.

Because a supercontinent has less shoreline compared to a series of smaller continents, Triassic marine deposits are relatively uncommon on a global scale. A major exception is in Western Europe, where the Triassic was first studied. The northeastern margin of Gondwana was apassive margin along the Neo-Tethys Ocean, and marine sediments cause been preserved in parts of northern India and Arabia. In North America, marine deposits are limited to a few exposures in the west.

During the Triassic Swedish West Coast. In northern Norway Triassic peneplains may have been buried in sediments to be then re-exposed as coastal plains called strandflats. Dating of illite clay from a strandflat of Bømlo, southern Norway, have shown that landscape there became weathered in Late Triassic times c. 210 million years previously with the landscape likely also being shaped during that time.

Eustatic sea level in the Triassic was consistently low compared to the other geological periods. The beginning of the Triassic was around present sea level, rising to about 10–20 metres 33–66 ft above present-day sea level during the Early and Middle Triassic. Sea level rise accelerated in the Ladinian, culminating with a sea level up to 50 metres 164 ft above present-day levels during the Carnian. Sea level began to decline in the Norian, reaching a low of 50 metres 164 ft below present sea level during the mid-Rhaetian. Low global sea levels persisted into the earliest Jurassic. The long-term sea level trend is superimposed by 22 sea level drop events widespread in the geologic record, mostly of minor less than 25-metre 82 ft and medium 25–75-metre 82–246 ft magnitudes. A lack of evidence for Triassic continental ice sheetsthat glacial eustasy is unlikely to be the cause of these changes.