Jurassic period


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Related to Jurassic period: Cretaceous period

Jurassic period

Jurassic period (jərăsˈĭk) [from the Jura Mts.], second period of the Mesozoic era of geologic time, lasting from 213 to 144 million years ago. At the start of the Jurassic most of the continents were joined together until the Atlantic began to form and the Americas split off from Africa. Eastern North America was mostly elevated and subject to erosion, which reduced the Appalachian region to a peneplain. Before the end of the period, the Appalachian borderland began to founder as the Atlantic Ocean continued to widen. The Pacific border of North America, from California to Alaska, was submerged for most of the period. In the Early Jurassic, large areas of Arizona, Colorado, and Utah were apparently desert, and the sand was later consolidated into the white and pinkish Glen Canyon and Navajo sandstones, which now enhance the scenic beauty of the district. During the Upper Jurassic, the Logan Sea entered this area from the north. In its various advances and retreats, this body of water covered large areas of Montana, Idaho, Wyoming, Colorado, and Utah, depositing sandstone, shale, limestone, and some gypsum. The retreat of the Logan Sea, toward the end of the period, was followed, probably in the Upper Jurassic but possibly in the Lower Cretaceous Period, by the deposition of the Morrison continental series of clays and sandstones, noted for its richness in fossil dinosaurs. The close of the Jurassic in North America was marked by widespread folding along the western border of the continent, accompanied by the intrusion of lava as the eastern edge of the plate that carries the Pacific Ocean was thrust beneath the westward drifting plate that carries the North American continent. In this disturbance the Sierra Nevada, Klamaths, Cascades, Coast Ranges, and coastal mountains of Canada and Alaska were formed. The history of the European Jurassic is very well known, that system being one of the most complete on the Continent. Studies of oxygen isotopes, the extent of land flora, and marine fossils indicate that climates during Jurassic times were mild—perhaps 15℉ (8℃) warmer than those of today. No glaciers existed during this period. The plant life of the Jurassic was dominated by the cycads, but conifers, ginkgoes, horsetails, and ferns were also abundant. Of the marine invertebrates, the most important were the ammonites. The dominant animals on land, in the sea, and in the air were the reptiles. Dinosaurs, more numerous and more extraordinary than those of the Triassic period, were the chief land animals; crocodiles, ichthyosaurs, and plesiosaurs ruled the sea, while the air was inhabited by the pterosaurs and relatives. Mammals, making their first appearance, were few and small but undoubtedly became well established during the Jurassic period. The Jurassic also saw the appearance of Archaeopteryx. See Geologic Timescale (table).
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References in periodicals archive ?
Paleobiologist Paul Upchurch at University College London, a sauropod expert who was not involved in the study, said it suggests that not all diplodocids succumbed to a mass extinction about 140 million years ago at the end of the Jurassic period.
"It roamed around out West--like in Colorado and Wyoming--during the Jurassic Period."
According to the website of Dinosauria International, the site, located near the village of Ten Sleep, has 'ancient sand and mudstone deposits, dating back to the late Jurassic Period, approximately 150 million years ago'.
The show includes the Tyrannosaurus Rex, the terror of the ancient terrain, as well as the Plateosaurus and Liliensternus from the Triassic period, the Stegosaurus and Allosaurus from the Jurassic period and Torosaurus and Utahraptor from the awesome Cretaceous period and the Brachiosaurus.
The remains were from a long-necked herbivore called Lufengosaurus, a common dinosaur in the Early Jurassic period that measured about eight meters (26 feet) when fully grown.
The stone dates to the Upper Malm Epoch (Late Jurassic Period) and is approximately 160 million years old.
ANSWERS 12.10.11 QUIZ CHALLENGE: 1 Lord Haw-Haw; 2 The Jurassic period; 3 Africa; 4 A catalyst; 5 Snowdon.
Samples from the well in Aldous Major North proved a column of oil of up to 8 m in formations from the Upper Jurassic period, Statoil said.
calocoma is considered a survivor of the Jurassic period which managed to escape extinction for 150 million years.
"After that predators are more complicated to take over then the diversification at the turn of the Triassic to the Jurassic period," said Sues.
A brief prologue explains that millions of years ago aliens collected dinosaurs from Earth's Jurassic period, then beamed them up to a giant preserve on their home planet.
ANSWERS: 1 Lord Haw-Haw; 2 The Jurassic period; 3 Africa; 4 A catalyst; 5 Snowdon; 6 The Jolly Roger; 7 They had a run of 49 unbeaten league football games; 8 Tiramisu; 9 The Matterhorn; 10 Sebastian Coe.