Triassic period


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See also: Geologic Timescale (table)Geologic Timescale
Era Period Epoch Approximate duration
(millions of years)
Approximate number of years ago
(millions of years)

Cenozoic Quaternary Holocene 10,000 years ago to the present  
Pleistocene 2 .
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Triassic period

(trīăs`ĭk), first period of the Mesozoic eraMesozoic era
[Gr.,=middle life], major division of geologic time (see Geologic Timescale, table) from 65 to 225 million years ago. Great crustal disturbances that marked the close of the Paleozoic and the beginning of the Mesozoic eras brought about drastic changes in the
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 of geologic time (see Geologic TimescaleGeologic Timescale
Era Period Epoch Approximate duration
(millions of years)
Approximate number of years ago
(millions of years)

Cenozoic Quaternary Holocene 10,000 years ago to the present  
Pleistocene 2 .
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, table) from 205 to 250 million years ago.

Throughout the Triassic, E North America, as a result of the mountain-building episode that formed the Appalachians in the late Paleozoic eraPaleozoic era
, a major division (era) of geologic time (see Geologic Timescale, table) occurring between 570 to 240 million years ago. It is subdivided into six periods, the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian (see each listed individually).
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, was elevated above sea level. California and Nevada, however, were submerged. In the Lower Triassic the sea extended E to Idaho, Colorado, and Wyoming; in the Middle Triassic it submerged British Columbia; in the Upper Triassic it extended into Alaska. In Lower and Upper Triassic time the west coast, from Alaska to British Columbia, was disturbed by violent and widespread volcanic activity. The Triassic formations of W North America are chiefly marine shale and limestone, with considerable igneous intrusions.

Near the end of the period, the only Triassic formation of E North America was deposited in downfaulted troughs, parallel to the Appalachians, from Nova Scotia to North Carolina. Composed of shale, conglomerate, and sandstone, this Newark series is comprised of sediments from the Appalachians. It is widely interrupted by so-called traprock—diabase dikes and sills—which forms ridges and cliffs, such as the Palisades of the Hudson near New York City. The end of the Triassic in North America was marked by extensive faulting and tilting of the Newark series, called the Palisade disturbance, and by the emergence of W North America.

The Triassic deposits of Germany form three series. In the Bunter series, the land was emergent, and red sandstone and sandy shale, with some salt and gypsum, were deposited. The Muschelkalk series saw the transgression of the land by the sea and the deposition of marine shale and limestone; the Keuper series saw the land again emergent and shale, sandstone, and gypsum being formed. In England there was no marine phase corresponding to the Muschelkalk; the Triassic of England is commonly called the New Red Sandstone. The Tethys, a great seaway, extended through the Mediterranean region E through the Middle East to the Himalayas and to E India. During the Triassic a subduction complex including an elongate volcanic arc system developed along the N American west coast. N Africa and Europe were still attached to N America as part of the supercontinent Pangaea.

The climate of the Triassic was semiarid to arid. In the plant life, marine algae were abundant, ferns and tree ferns less important than in the Paleozoic, conifers dominant among the trees, and a new group, the cycadscycad
, any plant of the order Cycadales, tropical and subtropical palmlike evergreens. The cycads, ginkgoes, and conifers comprise the three major orders of gymnosperms, or cone-bearing plants (see cone and plant). The cycads first appeared in the Permian period.
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, appeared. Many Paleozoic invertebrates appeared for the last time in the Triassic. The ammonitesammonite
, one of a type of extinct marine cephalopod mollusk, related to the nautilus and resembling it in having an elaborately coiled and chambered shell. Unlike the interiors of nautilus shells, the chambers of ammonite shells display intricately shaped septa and sutures.
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 became very important, then were reduced at the end of the Triassic to one species, but were destined to become numerous again in the succeeding Jurassic period. Amphibians were apparently not as numerous as in the Paleozoic, but some types were more highly developed. The dominant animals of the Triassic were the reptiles; although the Triassic reptiles were less specialized than those of the Jurassic, there were already a number of types of dinosaursdinosaur
[Gr., = terrible lizard], extinct land reptile of the Mesozoic era. The dinosaurs, which were egg-laying animals, ranged in length from 2 1-2 ft (91 cm) to about 127 ft (39 m).
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, pterosaurspterosaur
[Gr., = winged lizard], extinct flying reptile (commonly called pterodactyl [Gr., = wing finger]) of the order Pterosauria, common in the late Triassic and Cretaceous periods, from approximately 228 to 65 million years ago.
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, and marine reptiles. The Triassic rocks also contain the fossils of the earliest known mammals.

References in periodicals archive ?
The work documents more than 500 ammonoid species in 256 genera, spanning the entire Triassic Period. They form the basis of a biochronology of the Triassic that is of not only Canadian but also global significance.
Continents split, volcanoes erupt and the arid desert of the Triassic period gives way to the lush green prairies of the Jurassic age.
There's also a dinosaur-related time line that shows the evolution of plant and animal life as long ago as 250 million years during the Triassic period, when the first dinosaurs began to appear in the form of herds of prosauropods.
The results of these tensions were the faults and dislocations inside the Iberian Microplate which were especially mobile from the end of the Carboniferous until the beginning of the Triassic period (Arthaud and Matte, 1977; Arche and Lopez-Gomez, 1996).
For while the changes leading to major extinctions are caused by planetary catastrophes, such as the intense volcanic activity that took place at the end of the Triassic period, the subtle changes caused by plant activity have often been just as significant.
In Nature for October 19, 2006, the researchers argue that Andromeda's satellite galaxy M32 was involved in a cosmic hit and run a mere 210 million years ago, near the end of the Triassic period on Earth.
Titled, almost embarrassingly, "How I Spent My Summer Vacation; or, Art and Politics in Nevada, Berkeley, San Francisco and Utah (Read about it in Artforum!)" and peppered with pull quotes from Abbie Hoffman, Bob Dylan, Charles Manson, and Smithson ("I'm interested in the politics of the Triassic period"), it recounted a journey that Leider and John Coplans took with Smithson and his wife, Nancy Holt, out to the Spiral Jetty site.
One exploration well, the 3,240 metre SFNE-1, has found pockets of hydrocarbons from a reservoir which dates back to the Triassic period. From the first pocket initial production attempts have resulted in a maximum of 6,490 barrels of oil with an API degree of 39, whilst initial indicators show that the second pocket may offer as much as 14,780 barrels of APIo 42.
Scientists believe turtles appeared on land 210 million years ago in the Triassic Period before diversifying.
Examination of the assumed pattern of continents and oceans during the Triassic Period shows how this ancient seaway must have stretched from southern Europe and northern Africa across India to lands farther east.
But dicynodonts were thought to have died out before the late Triassic period, by which time dinosaurs had become the dominant land creature.
Recently, geologist Dr Benjamin Burger identified a rock layer in Utah that he believed might have formed during the Permian and subsequent Triassic period that could shed light on the cause of the Great Dying.