The Cretaceous (pronounced /kriːˈteɪʃəs/), Latin Latin is an Italic language originally spoken in Latium and Ancient Rome. With the Roman conquest, Latin was spread to countries around the Mediterranean, including a large part of Europe. Romance languages such as Aragonese, Corsican, Catalan, French, Italian, Portuguese, Romanian, Sardinian, Spanish and others, are descended from Latin, while for "chalky Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under relatively deep marine conditions from the gradual accumulation of minute calcite plates (coccoliths) shed from micro-organisms called coccolithophores. It is common to find chert or flint", usually abbreviated K for its German German (Deutsch, [ˈdɔʏtʃ] ) is a West Germanic language, thus related to and classified alongside English and Dutch. It is one of the world's major languages and the most widely spoken first language in the European Union. Globally, German is spoken by approximately 120 million native speakers and also by about 80 million non-native speakers translation Kreide (chalk), is a geologic period and system The geologic time scale provides a system of chronologic measurement relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth. The table of geologic time spans presented here agrees with the dates from circa 145.5 ± 4 to 65.5 ± 0.3 million years (Ma A year is the orbital period of the Earth moving around the Sun. For an observer on Earth, this corresponds to the period it takes the Sun to complete one course throughout the zodiac along the ecliptic) ago. In the geologic timescale The geologic time scale is a chronologic schema relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth. The table of geologic time spans presented here agrees with the dates and nomenclature, the Cretaceous follows on the Jurassic The Jurassic is a geologic period and system that extends from about 199.6± 0.6 Ma to 145.5± 4 Ma, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the "Age of Reptiles". The start of the period is marked by the major Triassic– Period and is followed by the Paleogene The Paleogene is a geologic period and system that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic Era. Lasting 42 million years, the Paleogene is most notable as being the time in which mammals evolved from relatively small, simple forms into a large group of diverse animals in the wake of Period of the Cenozoic The Cenozoic Era is the most recent of the three classic geological eras and covers the period from 65.5 million years ago to the present. It is marked by the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and the end of the Mesozoic Era. The Cenozoic era is ongoing Era. It is the youngest period of the Mesozoic The Mesozoic Era is a period from about 250 million years ago to about 67 million years ago. It is called the Age of Dinosaurs because most dinosaurs developed, and went extinct, during that time. The Chicxulub impact and other events ended the era when a majority of species on earth went extinct Era An era is a commonly used word for long period of time. When used in science, for example geology, eras denote clearly defined periods of time of arbitrary but well defined length, such as for example the Mesozoic era from 252 Ma–66 Ma, delimited by a start event and an end event. When used in social history, eras may for example denote a period, and at 80 million years long, the longest period of the Phanerozoic The Phanerozoic Eon is the current eon in the geologic timescale, and the one during which abundant animal life has existed. It covers roughly 545 million years and goes back to the time when diverse hard-shelled animals first appeared. Its name is derived from the Greek words φαίνω and ζωή, meaning make life appear, since it was once Eon. The end of the Cretaceous defines the boundary between the Mesozoic and Cenozoic The Cenozoic Era is the most recent of the three classic geological eras and covers the period from 65.5 million years ago to the present. It is marked by the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and the end of the Mesozoic Era. The Cenozoic era is ongoing eras The geologic time scale provides a system of chronologic measurement relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth. The table of geologic time spans presented here agrees with the dates. In many languages this period is known as "chalk period".
The Cretaceous was a period with a relatively warm climate Climates encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elements in a given region over long periods of time. Climate can be contrasted to weather, which is the present condition of these same elements and their variations over periods up to two weeks and high eustatic sea level Mean sea level is a measure of the average height of the ocean's surface (such as the halfway point between the mean high tide and the mean low tide); used as a standard in reckoning land elevation. MSL also plays an extremely important role in aviation, where standard sea level pressure is used as the measurement datum of altitude at flight. The oceans and seas were populated with now extinct In biology and ecology, extinction is the end of an organism or group of taxa. The moment of extinction is generally considered to be the death of the last individual of that species . Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena marine reptiles Marine reptiles are reptiles which have become secondarily adapted for an aquatic or semi-aquatic life in a marine environment, ammonites Ammonites, as they pertain specifically to the order Ammonitida, are an extinct group of marine animals belonging to the cephalopod subclass Ammonoidea. They are excellent index fossils, and it is often possible to link the rock layer in which they are found to specific geological time periods and rudists Rudists are a group of box, tube or ring shaped marine heterodont bivalves that arose during the Jurassic, and became so diverse during the Cretaceous that they were major reef-building organisms in the Tethys Ocean; and the land by dinosaurs Dinosaurs are a diverse group of reptiles. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous period (about 65 million years ago), when the Cretaceous–Tertiary extinction event caused the extinction of most dinosaur species, except for some birds. The fossil. At the same time, new groups of mammals Mammals are a class of vertebrate, air-breathing animals whose females are characterized by the possession of mammary glands while both males and females are characterized by hair and/or fur, three middle ear bones used in hearing, and a neocortex region in the brain. Some mammals have sweat glands, but most do not and birds Birds are winged, bipedal, endothermic (warm-blooded), egg-laying, vertebrate animals. There are around 10,000 living species, making them the most varied of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from the 5 cm (2 in) Bee Hummingbird to the 2.75 m (9 ft) Ostrich as well as flowering plants The flowering plants or angiosperms are the most diverse group of land plants. Angiosperms and the gymnosperms are the only extant groups of seed plants. The flowering plants are distinguished from other seed plants by a series of apomorphies, or derived characteristics appeared. The Cretaceous ended with one of the largest mass extinctions An extinction event is a sharp decrease in the diversity and abundance of macroscopic life. They occur when the rate of extinction increases with respect to the rate of speciation. Because the majority of diversity and biomass on earth is microbial, and thus difficult to measure, mass extinctions have little effect on the total diversity and in Earth history The history of the Earth describes the most important events and fundamental stages in the development of the planet Earth from its formation to the present day during the last 4.6 billion years. Nearly all branches of natural science have contributed to the understanding of the main events of the Earth's past. The Earth is approximately one third, the K-T extinction, when many species, including the dinosaurs, pterosaurs Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period (220 to 65.5 million years ago). Pterosaurs are the earliest vertebrates known to have evolved powered flight. Their wings were formed by a membrane of skin, muscle, and other tissues stretching from the legs, and large marine reptiles, disappeared.
A plate with Nematonotus sp. , Pseudostacus sp., and a partial Dercetis triqueter from Cretaceous found in Hakel, Lebanon
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The Cretaceous world
Paleogeography
During the Cretaceous, the late Paleozoic The Paleozoic or Palaeozoic Era (from the Greek palaios , "old" and zoe (ζωή), "life", meaning "ancient life") is the earliest of three geologic eras of the Phanerozoic Eon. The Paleozoic spanned from roughly 542 to 251 million years ago (ICS, 2004), and is subdivided into six geologic periods; from oldest to – early Mesozoic supercontinent In geology, a supercontinent is a landmass comprising more than one continental core, or craton. The assembly of cratons and accreted terranes that form Eurasia qualifies as a supercontinent today of Pangaea Pangaea, Pangæa, or Pangea was the supercontinent that presumably existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration completed its tectonic Plate tectonics is a scientific theory which describes the large scale motions of Earth's lithosphere. The theory builds on the older concepts of continental drift, developed during the first decades of the 20th century (one of the most famous advocates was Alfred Wegener), and was accepted by the majority of the Geoscientific community when the breakup into present day continents A continent is one of several large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents – they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia, although their positions were substantially different at the time. As the Atlantic Ocean The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about 106,400,000 square kilometres , it covers approximately twenty percent of the Earth's surface and about twenty-six percent of its water surface area. The first part of its name refers to the Atlas of Greek mythology, making the Atlantic the " widened, the convergent-margin orogenies Orogeny refers to forces and events leading to a severe structural deformation of the earth's crust due to the engagement of tectonic plates. Response to such engagement results in the formation of long tracts of highly deformed rock called orogens or orogenic belts. The word "orogeny" comes from the Greek , and it is the primary that had begun during the Jurassic The Jurassic is a geologic period and system that extends from about 199.6± 0.6 Ma to 145.5± 4 Ma, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the "Age of Reptiles". The start of the period is marked by the major Triassic– continued in the North American Cordillera The American Cordillera consists of an essentially continuous sequence of mountain ranges that form the western "backbone" of North America, Central America and South America. From north to south, this sequence of overlapping and parallel ranges begins with the Alaska Range and the Brooks Range in Alaska and run through the Yukon into, as the Nevadan orogeny The Nevadan Orogeny was a major mountain building event that took place along the western edge of ancient North America between the Mid to Late Jurassic . The Nevadan orogeny was the first of three major mountain building episodes to transform Western North America between the Late Mesozoic and Early Cenozoic Eras, the latter two being the Sevier was followed by the Sevier and Laramide orogenies The Laramide orogeny was a period of mountain building in western North America, which started in the Late Cretaceous, 70 to 80 million years ago, and ended 35 to 55 million years ago. The exact duration and ages of beginning and end of the orogeny are in dispute, as is the cause. The Laramide orogeny occurred in a series of pulses, with quiescent.
Geography of the US in the Late Cretaceous PeriodThough Gondwana Gondwana , originally Gondwanaland, is the name given to a southern precursor supercontinent. Its final geological suturing occurred between ca. 570 and 510 million years ago (Ma), joining East Gondwana to West Gondwana. It later separated from Laurasia 180-200 million years ago during the breakup of the Pangaea supercontinent that existed about 50 was still intact in the beginning of the Cretaceous, it broke up as South America South America is the southern continent of America, situated in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. It is bordered on the west by the Pacific Ocean and on the north and east by the Atlantic Ocean; North America and the Caribbean Sea lie to the northwest, Antarctica Antarctica (pronounced /ænˈtɑrktɪkə/ ) is Earth's southernmost continent, underlying the South Pole. It is situated in the Antarctic region of the southern hemisphere, almost entirely south of the Antarctic Circle, and is surrounded by the Southern Ocean. At 14.0 million km2 (5.4 million sq mi), it is the fifth-largest continent in area after and Australia For at least 40,000 years before European settlement in the late 18th century, Australia was inhabited by indigenous Australians, who belonged to one or more of the roughly 250 language groups. After sporadic visits by fishermen from the immediate north and discovery by Dutch explorers in 1606, Australia's eastern half was claimed by Britain in 177 rifted away from Africa Africa is the world's second-largest and second most-populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area. With a billion people (as of 2009, see table) in 61 territories, it accounts for about 14.72% of the world's human population (though India Home to the ancient Indus Valley Civilisation and a region of historic trade routes and vast empires, the Indian subcontinent was identified with its commercial and cultural wealth for much of its long history. Four major religions, Hinduism, Buddhism, Jainism and Sikhism originated here, while Zoroastrianism, Judaism, Christianity and Islam and Madagascar Madagascar, or Republic of Madagascar , is an island nation in the Indian Ocean off the southeastern coast of Africa. The main island, also called Madagascar, is the fourth-largest island in the world remained attached to each other); thus, the South Atlantic and Indian Oceans The Indian Ocean is the third largest of the world's oceanic divisions, covering about 20% of the water on the Earth's surface. It is bounded on the north by the Indian subcontinent; on the west by East Africa; on the east by Indochina, the Sunda Islands, and Australia; and on the south by the Southern Ocean . It is the only ocean to be named were newly formed. Such active rifting lifted great undersea mountain chains along the welts, raising eustatic sea levels Mean sea level is a measure of the average height of the ocean's surface (such as the halfway point between the mean high tide and the mean low tide); used as a standard in reckoning land elevation. MSL also plays an extremely important role in aviation, where standard sea level pressure is used as the measurement datum of altitude at flight worldwide. To the north of Africa the Tethys Sea The Tethys Ocean was an ocean that existed between the continents of Gondwana and Laurasia during the Mesozoic era before the opening of the Indian Ocean continued to narrow. Broad shallow seas advanced across central North America North America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific Ocean; South America lies to the southeast (the Western Interior Seaway The Western Interior Seaway, also called the Cretaceous Seaway, the Niobraran Sea, and the North American Inland Sea, was a huge inland sea that split the continent of North America into two halves during most of the mid and late Cretaceous Period) and Europe, then receded late in the period, leaving thick marine deposits sandwiched between coal beds. At the peak of the Cretaceous transgression, one-third of Earth's present land area was submerged.[4]
The Cretaceous is justly famous for its chalk; indeed, more chalk formed in the Cretaceous than in any other period in the Phanerozoic.[5] 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.[6] 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.
Climate
The Berriasian epoch showed a cooling trend that had been seen in the last epoch of the Jurassic. There is evidence that snowfalls were common in the higher latitudes and the tropics became wetter than during the Triassic and Jurassic.[7] Glaciation was however restricted to alpine glaciers on some high-latitude mountains, though seasonal snow may have existed farther south. Rafting by ice of stones into marine environments occurred during much of the Cretaceous but evidence of deposition directly from glaciers is limited to the Early Cretaxeous of the Eromanga Basin in southern Australia.[8][9]
After the end of the Berriasian, however, temperatures increased again, and these conditions were almost constant until the end of the period.[10] This trend was due to intense volcanic activity which produced large quantities of carbon dioxide. The development of a number of mantle plumes across the widening mid-ocean ridges further pushed sea levels up, so that large areas of the continental crust were covered with shallow seas. The Tethys Sea connecting the tropical oceans east to west also helped in warming the global climate. Warm-adapted plant fossils are known from localities as far north as Alaska and Greenland, while dinosaur fossils have been found within 15 degrees of the Cretaceous south pole.[11]
A very gentle temperature gradient from the equator to the poles meant weaker global winds, contributing to less upwelling and more stagnant oceans than today. This is evidenced by widespread black shale deposition and frequent anoxic events.[12] Sediment cores show that tropical sea surface temperatures may have briefly been as warm as 42 °C (107 °F), 17 °C (31 °F) warmer than at present, and that they averaged around 37 °C (99 °F). Meanwhile deep ocean temperatures were as much as 15 to 20 °C (27 to 36 °F) higher than today's.[13][14]
Further information: Cool tropics paradoxGeology
Key events in the Cretaceous -140 — – -130 — – -120 — – -110 — – -100 — – -90 — – -80 — – -70 — – Maastrichtian Campanian Santonian Coniacian Turonian Cenomanian Albian Aptian Barremian Hauterivian Valanginian Berriasian Jurassic Paleogene C r e t a c e o u s Mesozoic Cenozoic An approximate timescale of key Cretaceous events. Axis scale: millions of years ago.Research history
The Cretaceous as a separate period was first defined by a Belgian geologist Jean d'Omalius d'Halloy in 1822, using strata in the Paris Basin[15] and named for the extensive beds of chalk (calcium carbonate deposited by the shells of marine invertebrates, principally coccoliths), found in the upper Cretaceous of western Europe. The name Cretaceous was derived from Latin creta, meaning chalk.[16] The name of the island Crete has the same origin.
Stratigraphic subdivisions
The Cretaceous is divided into Early and Late Cretaceous epochs or Lower and Upper Cretaceous series. In older literature the Cretaceous is sometimes divided into three series: Neocomian (lower/early), Gallic (middle) and Senonian (upper/late). A subdivision in eleven stages, all origining from European stratigraphy, is now used worldwide. In many parts of the world, alternative local subdivisions are still in use.
As with other older geologic periods, the rock beds of the Cretaceous are well identified but the exact ages of the system's top and base are uncertain by a few million years. No great extinction or burst of diversity separates the Cretaceous from the Jurassic. However, the top of the system is sharply defined, being placed at an iridium-rich layer found worldwide that is believed to be associated with the Chicxulub impact crater in Yucatan and the Gulf of Mexico. This layer has been tightly dated at 65.5 Ma.[17]
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Wed, 25 Aug 2010 00:36:15 GMT+00:00
OCRegister It runs about 90 minutes but covers 200 million years from the Triassic period to the end of the Cretaceous and takes us through the rise, dominance and ... Walking With Dinosaurs in Vancouver Straight.com
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Cretaceous and Paleogene Fossils of North Carolina A Field Guide
Thu, 19 Nov 2009 16:00:00 PST
sauropod dinosaur cretaceous clash of the dinosaurs awesome awesome clash of the dinosaurs cretaceous sauropod sauroposeidon dinosaur awesome ... dsc.discovery.com.
Anthony Martin
Wed, 02 Jun 2010 10:50:00 GM
The Great . Cretaceous. Walk will be an excursion along the coast of Victoria, Australia, east and west of Melbourne, in which I will look for trace fossils burrow, tracks, and other signs of ancient life in the . Cretaceous. rocks of ...
