Instruct: Given a question, retrieve passages that can help answer the question.
Query: When was the Cretaceous period?
The Cretaceous 144-66 Ma to Miocene periods deposited clastic sediments from the Cordilleran orogeny. This period saw 40% of the region now called North America below sea level under the Rocky Mountain Seaway which comprised the Western Interior Seaway and the Hudson Seaway, and Labrador Seaway. The Cretaceous period rocks produce medium and heavy gravity oil in the Lloydminster region, and of the western province. The Laramide orogeny episode near the end of the Cretacsous and early Tertiary period caused larger gravels to be deposited from the newly formed Rocky Mountains when the Kula and Farallon Plates subducted below the North American plate. In the Cypress Hills area and southern Saskatchewan, lignite deposits developed from the marshes of these Tertiary rivers. The sea waters have retreated from the areas known as Saskatchewan. The Ravenscrag formation, Cypress Hills, and Wood Mountain Formations were notable gravel deposits from the Tertiary period. The Williston Basin affects this region at the southern edge. Tectonic movements and global changes in the sea level have given rise to a source of oil, natural gas, and coal.
The Paleozoic (or Palaeozoic) Era (; from the Greek "palaios" (παλαιός), "old" and "zoe" (ζωή), "life", meaning "ancient life") is the earliest of three geologic eras of the Phanerozoic Eon. It is the longest of the Phanerozoic eras, lasting from , and is subdivided into six geologic periods (from oldest to youngest): the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. The Paleozoic comes after the Neoproterozoic Era of the Proterozoic Eon and is followed by the Mesozoic Era.
The Phanerozoic Eon is the current eon in the geologic timescale. It covers roughly 541 million years. During this period continents drifted about, eventually collected into a single landmass known as Pangea and then split up into the current continental landmasses.
The Cryptic era is an informal term for the earliest geologic evolution of the Earth and Moon. It is the oldest (informal) era of the Hadean eon, and it is commonly accepted to have begun close to 4533 million (about 4.533 billion) years ago when the Earth and Moon formed. No samples exist to date the transition between the Cryptic era and the following Basin Groups era for the Moon (see also Pre-Nectarian), though sometimes it is stated that this era ended 4150 million years ago for one or both of these bodies. Neither this time period, nor any other Hadean subdivision, has been officially recognized by the International Commission on Stratigraphy.
The team discovered the remains of the largest dinosaur to walk in the southern parts of Africa , namely a 190-million-year-old fossilised egg of a Massospondylus dinosaur. This dinosaur lived in the Late Triassic and Early Jurassic, a period from about 230-million years ago to about 185-million years ago. The Massospondylus wandered about in great herds, migrating back and forth between what would millions of years later become Southern Africa and Russia, when the southern super-continent, Gondwana, was still intact. The rocks that were laid down during this period are called the Stormberg Group of rocks, and it is in rocks of the Stormberg Group that the fossils of Massospondylus and other dinosaurs were found. Massospondylus dinosaurs hatched from eggs not much larger than a hen’s egg, but grew into big creatures 5 to 6 metres long. They had large bodies, long necks and small heads, and long tails.
Pteranodon (; from Greek πτερόν ( pteron, "wing") and ἀνόδων (anodon, "toothless") is a genus of pterosaur that included some of the largest known flying reptiles, with wingspans over 8 meters (26 feet). They lived during the late Cretaceous geological period of North America in present-day Kansas, Alabama, Nebraska, Wyoming, and South Dakota. More fossil specimens of "Pteranodon" have been found than any other pterosaur, with about 1,200 specimens known to science, many of them well preserved with nearly complete skulls and articulated skeletons. It was an important part of the animal community in the Western Interior Seaway.
Mosasaurs (from Latin "Mosa" meaning the 'Meuse river', and Greek σαύρος "sauros" meaning 'lizard') are an extinct group of large marine reptiles containing 38 genera in total. Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. Mosasaurs probably evolved from an extinct group of aquatic lizards known as aigialosaurs in the Early Cretaceous. During the last 20 million years of the Cretaceous period (Turonian-Maastrichtian ages), with the extinction of the ichthyosaurs and pliosaurs, mosasaurs became the dominant marine predators. They became extinct as a result of the K-Pg event at the end of the Cretaceous period, about 66 million years ago.
The Jurassic Period extends from about 201.3 ± 0.2 to 145.0 Ma.
During the early Jurassic, the supercontinent Pangaea broke up into the northern supercontinent Laurasia and the southern supercontinent Gondwana; the Gulf of Mexico opened in the new rift between North America and what is now Mexico's Yucatan Peninsula. The Jurassic North Atlantic Ocean was relatively narrow, while the South Atlantic did not open until the following Cretaceous Period, when Gondwana itself rifted apart.
The Tethys Sea closed, and the Neotethys basin appeared. Climates were warm, with no evidence of glaciation. As in the Triassic, there was apparently no land near either pole, and no extensive ice caps existed. The Jurassic geological record is good in western Europe, where extensive marine sequences indicate a time when much of the continent was submerged under shallow tropical seas; famous locales include the Jurassic Coast World Heritage Site and the renowned late Jurassic "lagerstätten" of Holzmaden and Solnhofen.
In contrast, the North American Jurassic record is the poorest of the Mesozoic, with few outcrops at the surface. Though the epicontinental Sundance Sea left marine deposits in parts of the northern plains of the United States and Canada during the late Jurassic, most exposed sediments from this period are continental, such as the alluvial deposits of the Morrison Formation. The first of several massive batholiths were emplaced in the northern Cordillera beginning in the mid-Jurassic, marking the Nevadan orogeny. Important Jurassic exposures are also found in Russia, India, South America, Japan, Australasia and the United Kingdom.
The Zirconian is the second Era within the Hadean Eon in a proposed revision of the Precambrian time scale. It lasted 373 million years from the end of the Chaotian Era to the beginning of Eoarchean Era . The Zirconian follows the Chaotian Era and its beginning is chronometrically set at 4.404 ± 0.008 Gya. This corresponds to the age of the first occurrence of Hadean zircons in the Jack Hills in Western Australia (Yilgarn craton). The end of the Zirconian Era and the transition to the Acastan Period (the earliest period of the Archean Eon and Eoarchean Era) occurred with the appearance of the oldest rock at 4.031 ± 0.003 Gya.
"Sinosauropteryx" lived in what is now northeastern China during the early Cretaceous period. It was among the first dinosaurs discovered from the Yixian Formation in Liaoning Province, and was a member of the Jehol Biota. Well-preserved fossils of this species illustrate many aspects of its biology, such as its diet and reproduction.
The Precambrian (or Pre-Cambrian, sometimes abbreviated pЄ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic eon, which is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time.
The Hadean () is a geologic eon of the Earth pre-dating the Archean. It began with the formation of the Earth about 4.6 billion years ago and ended, as defined by the ICS, 4 billion years ago. , the ICS describes its status as ""informal"". Geologist Preston Cloud coined the term in 1972, originally to label the period before the earliest-known rocks on Earth. W. Brian Harland later coined an almost synonymous term, the "Priscoan period", from "priscus", the Latin word for "ancient". Other, older texts simply refer to the eon as the Pre-Archean.
Alamosaurus (; meaning "Ojo Alamo lizard") is a genus of titanosaurian sauropod dinosaurs, containing a single known species, Alamosaurus sanjuanensis, from the late Cretaceous Period of what is now southern North America. Isolated vertebrae and limb bones indicate that it reached sizes comparable to "Argentinosaurus" and "Puertasaurus", which would make it the largest dinosaur known from North America. Its fossils have been recovered from a variety of rock formations spanning the Maastrichtian age of the late Cretaceous period. Specimens of a juvenile "Alamosaurus sanjuanensis" have been recovered from only a few meters below the Cretaceous-Paleogene boundary in Texas, making it among the last surviving non-avian dinosaur species.
All specimens of "Catopsbaatar" are known from the Red Beds of Hermiin Tsav formation, except for one molar from the Barun Goyot Formation. The formations are considered coeval (of the same geological age), contain many of the same animals, and probably date to the late Campanian age of the Late Cretaceous Period (about 72 million years ago). The rock facies of the Red Beds of Hermiin Tsav formation consist of orange-coloured, thick-bedded sandstone, with a thin interbedding of light-coloured silt stones and claystones. The rock facies of the Barun Goyot Formation are considered to be the result of an arid or semi-arid environment, with aeolian (deposited by wind) beds.
The Middle Paleolithic (or Middle Palaeolithic) is the second subdivision of the Paleolithic or Old Stone Age as it is understood in Europe, Africa and Asia. The term Middle Stone Age is used as an equivalent or a synonym for the Middle Paleolithic in African archeology. The Middle Paleolithic broadly spanned from 300,000 to 30,000 years ago. There are considerable dating differences between regions. The Middle Paleolithic was succeeded by the Upper Paleolithic subdivision which first began between 50,000 and 40,000 years ago. Pettit and White date the Early Middle Paleolithic in Great Britain to about 325,000 to 180,000 years ago (late Marine Isotope Stage 9 to late Marine Isotope Stage 7), and the Late Middle Paleolithic as about 60,000 to 35,000 years ago.
The Campanian was an age when a worldwide sea level rise drowned many coastal areas. The morphology of some of these areas has been preserved as an unconformity beneath a cover of marine sedimentary rocks.
Dimetrodon ( or , meaning "two measures of teeth") is an extinct genus of synapsids that lived during the Cisuralian (Early Permian), around 295–272 million years ago (Ma). It is a member of the family Sphenacodontidae. The most prominent feature of "Dimetrodon" is the large neural spine sail on its back formed by elongated spines extending from the vertebrae. It walked on four legs and had a tall, curved skull with large teeth of different sizes set along the jaws. Most fossils have been found in the southwestern United States, the majority coming from a geological deposit called the Red Beds of Texas and Oklahoma. More recently, fossils have been found in Germany. Over a dozen species have been named since the genus was first described in 1878.
In fact, recent studies of zircons (in the fall of 2008) found in Australian Hadean rock hold minerals that point to the existence of plate tectonics as early as 4 billion years ago. If this holds true, the previous beliefs about the Hadean period are far from correct. That is, rather than a hot, molten surface and atmosphere full of carbon dioxide, Earth's surface would be very much like it is today. The action of plate tectonics traps vast amounts of carbon dioxide, thereby reducing greenhouse effects, and leading to a much cooler surface temperature, and the formation of solid rock, and possibly even life.
There has been no absolute dating of the Nemegt Formation. It is, however, almost certainly early Maastrichtian c 71-70 Ma. Gradzinski and others considered a Campanian age possible but more recent research indicates otherwise. A Campanian age no longer seems credible, because the Alagteegian (or lower Djadokhtan, at the locality "Chuluut Uul") has been radiometrically dated at about 73.5 Ma or even younger (a more recent K/Ar date is 71.6 +/- 1.6 Ma). The c 73.5 (or perhaps 72) Ma Alagteegian is separated from the Nemegt by the "classic" Djadokhtan (e.g. Bayan Dzag), later Djadohktan (represented by Ukhaa Tolgod) and Barungoyotian (Khulsan). All these intervening horizons almost certainly represent more than the 1.5 million years between the dated Alagteegian level and the onset of Maastrichtian time (72.1 million Ma according to current dating). Ergo the Nemegt is entirely Maastrichtian. See also Shuvalov, Sochava and Martinsson " The Age of Dinosaurs in Russia and Mongolia." The presence of "Saurolophus" further supports an early Maastrichtian age as the same genus occurs in the early Maastrichtian Horseshoe Canyon formation.
This species of wildebeest seems to have evolved around 2.5 million years ago. The black wildebeest is believed to have diverged from the blue wildebeest to become a distinct species around a million years ago, in the mid- to late Pleistocene. Fossil evidence suggests that blue wildebeest were quite common in the Cradle of Humankind in the past. Apart from eastern Africa, fossils are commonly found in Elandsfontein, Cornelia, and Florisbad.
The opening of the Atlantic Ocean coincided with the initial break-up of the supercontinent Pangaea, both of which were initiated by the eruption of the Central Atlantic Magmatic Province (CAMP), one of the most extensive and voluminous large igneous provinces in Earth's history associated with the Triassic–Jurassic extinction event, one of Earth's major extinction events.
Theoliitic dikes, sills, and lava flows from the CAMP eruption at 200 Ma have been found in West Africa, eastern North America, and northern South America. The extent of the volcanism has been estimated to of which covered what is now northern and central Brazil.
The Cretaceous is justly famous for its chalk; indeed, more chalk formed in the Cretaceous than in any other period in the Phanerozoic. Mid-ocean ridge activity—or rather, the circulation of seawater through the enlarged ridges—enriched the oceans in calcium; this made the oceans more saturated, as well as increased the bioavailability of the element for calcareous nanoplankton. These widespread carbonates and other sedimentary deposits make the Cretaceous rock record especially fine. Famous formations from North America include the rich marine fossils of Kansas's Smoky Hill Chalk Member and the terrestrial fauna of the late Cretaceous Hell Creek Formation. Other important Cretaceous exposures occur in Europe (e.g., the Weald) and China (the Yixian Formation). In the area that is now India, massive lava beds called the Deccan Traps were erupted in the very late Cretaceous and early Paleocene.
Cretaceous polar forests were temperate forests that grew at polar latitudes during the final period of the Mesozoic Era, known as the Cretaceous Period 145–66 Ma. During this period, global average temperature was about higher and carbon dioxide (CO) levels were approximately 1000 parts per million (ppm), 2.5 times the current concentration in Earth's atmosphere. The abundance of atmospheric carbon dioxide had a very significant impact on global climate and Earth's natural systems as its concentration is considered one of the main factors in the development of a pronounced greenhouse Earth during the Cretaceous with a very low average global temperature gradient. As a consequence, high paleolatitudes in both hemispheres were much warmer than at present. This temperature gradient was partly responsible for the lack of continental ice sheets in polar regions.
The Cretaceous–Paleogene extinction event was a large-scale mass extinction of animal and plant species in a geologically short period of time, approximately (Ma). It is widely known as the "K–T extinction event" and is associated with a geological signature, usually a thin band dated to that time and found in various parts of the world, known as the Cretaceous–Paleogene boundary (K–T boundary). "K" is the traditional abbreviation for the Cretaceous Period derived from the German name "Kreidezeit", and "T" is the abbreviation for the Tertiary Period (a historical term for the period of time now covered by the Paleogene and Neogene periods). The event marks the end of the Mesozoic Era and the beginning of the Cenozoic Era. "Tertiary" being no longer recognized as a formal time or rock unit by the International Commission on Stratigraphy, the K-T event is now called the Cretaceous—Paleogene (or K-Pg) extinction event by many researchers.
Cretoxyrhina (; meaning 'Cretaceous sharp-nose') is an extinct genus of large mackerel shark that lived about 107 to 70 million years ago during the late Albian to early Maastrichtian of the Late Cretaceous period. The type species, "C. mantelli", is more commonly referred to as the Ginsu shark, first popularized in reference to its theoretical feeding methods being comparable to that of the rapid slicing and dicing when using a Ginsu knife. "Cretoxyrhina" is traditionally classified as the likely sole member of the family Cretoxyrhinidae but other taxonomic placements have been proposed, such as within the Alopiidae and Lamnidae.