Get Our Extension

Cretaceous

From Wikipedia, in a visual modern way
Cretaceous
~145.0 – 66.0 Ma
Chronology
Etymology
Name formalityFormal
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Definition
Chronological unitPeriod
Stratigraphic unitSystem
Time span formalityFormal
Lower boundary definitionNot formally defined
Lower boundary definition candidates
Lower boundary GSSP candidate section(s)None
Upper boundary definitionIridium-enriched layer associated with a major meteorite impact and subsequent K-Pg extinction event
Upper boundary GSSPEl Kef Section, El Kef, Tunisia
36°09′13″N 8°38′55″E / 36.1537°N 8.6486°E / 36.1537; 8.6486
Upper GSSP ratified1991

The Cretaceous (IPA: /krɪˈtʃəs/ krih-TAY-shəs)[2] is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, "chalk", which is abundant in the latter half of the period. It is usually abbreviated K, for its German translation Kreide.

The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct marine reptiles, ammonites, and rudists, while dinosaurs continued to dominate on land. The world was ice free, and forests extended to the poles. During this time, new groups of mammals and birds appeared. During the Early Cretaceous, flowering plants appeared and began to rapidly diversify, becoming the dominant group of plants across the Earth by the end of the Cretaceous, coincident with the decline and extinction of previously widespread gymnosperm groups.

The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary (K–Pg boundary), a geologic signature associated with the mass extinction that lies between the Mesozoic and Cenozoic Eras.

Discover more about Cretaceous related topics

International Phonetic Alphabet

International Phonetic Alphabet

The International Phonetic Alphabet (IPA) is an alphabetic system of phonetic notation based primarily on the Latin script. It was devised by the International Phonetic Association in the late 19th century as a standardized representation of speech sounds in written form. The IPA is used by lexicographers, foreign language students and teachers, linguists, speech–language pathologists, singers, actors, constructed language creators, and translators.

Mesozoic

Mesozoic

The Mesozoic Era is the second-to-last era of Earth's geological history, lasting from about 252 to 66 million years ago, comprising the Triassic, Jurassic and Cretaceous Periods. It is characterized by the dominance of archosaurian reptiles, like the dinosaurs; an abundance of conifers and ferns; a hot greenhouse climate; and the tectonic break-up of Pangaea. The Mesozoic is the middle of the three eras since complex life evolved: the Paleozoic, the Mesozoic, and the Cenozoic.

Chalk

Chalk

Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Chalk is common throughout Western Europe, where deposits underlie parts of France, and steep cliffs are often seen where they meet the sea in places such as the Dover cliffs on the Kent coast of the English Channel.

Climate

Climate

Climate is the long-term weather pattern in a region, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorological variables that are commonly measured are temperature, humidity, atmospheric pressure, wind, and precipitation. In a broader sense, climate is the state of the components of the climate system, including the atmosphere, hydrosphere, cryosphere, lithosphere and biosphere and the interactions between them. The climate of a location is affected by its latitude, longitude, terrain, altitude, land use and nearby water bodies and their currents.

Marine reptile

Marine reptile

Marine reptiles are reptiles which have become secondarily adapted for an aquatic or semiaquatic life in a marine environment.

Dinosaur

Dinosaur

Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 245 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is a subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201.3 mya and their dominance continued throughout the Jurassic and Cretaceous periods. The fossil record shows that birds are feathered dinosaurs, having evolved from earlier theropods during the Late Jurassic epoch, and are the only dinosaur lineage known to have survived the Cretaceous–Paleogene extinction event approximately 66 mya. Dinosaurs can therefore be divided into avian dinosaurs—birds—and the extinct non-avian dinosaurs, which are all dinosaurs other than birds.

Mammal

Mammal

A mammal is a vertebrate animal of the class Mammalia. Mammals are characterized by the presence of milk-producing mammary glands for feeding their young, a neocortex region of the brain, fur or hair, and three middle ear bones. These characteristics distinguish them from reptiles and birds, which they diverged from in the Carboniferous Period over 300 million years ago. Around 6,400 extant species of mammals have been described and divided into 29 orders.

Flowering plant

Flowering plant

Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae, commonly called angiosperms. The term "angiosperm" is derived from the Greek words ἀγγεῖον /angeion and σπέρμα / sperma ('seed'), meaning those plants that produce their seeds enclosed within a fruit. They are by far the most diverse group of land plants with 64 orders, 416 families, approximately 13,000 known genera and 300,000 known species. Angiosperms were formerly called Magnoliophyta.

Gymnosperm

Gymnosperm

The gymnosperms are a group of seed-producing plants that includes conifers, cycads, Ginkgo, and gnetophytes, forming the clade Gymnospermae. The term gymnosperm comes from the composite word in Greek: γυμνόσπερμος, literally meaning 'naked seeds'. The name is based on the unenclosed condition of their seeds. The non-encased condition of their seeds contrasts with the seeds and ovules of flowering plants (angiosperms), which are enclosed within an ovary. Gymnosperm seeds develop either on the surface of scales or leaves, which are often modified to form cones, or on their own as in yew, Torreya, Ginkgo. Gymnosperm lifecycles involve alternation of generations. They have a dominant diploid sporophyte phase and a reduced haploid gametophyte phase which is dependent on the sporophytic phase. The term "gymnosperm" is often used in paleobotany to refer to all non-angiosperm seed plants. In that case, to specify the modern monophyletic group of gymnosperms, the term Acrogymnospermae is sometimes used.

Cretaceous–Paleogene extinction event

Cretaceous–Paleogene extinction event

The Cretaceous–Paleogene (K–Pg) extinction event, also known as the Cretaceous–Tertiary (K–T) extinction, was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. The event caused the extinction of all non-avian dinosaurs. Most other tetrapods weighing more than 25 kilograms also became extinct, with the exception of some ectothermic species such as sea turtles and crocodilians. It marked the end of the Cretaceous Period, and with it the Mesozoic era, while heralding the beginning of the Cenozoic era, which continues to this day.

Cretaceous–Paleogene boundary

Cretaceous–Paleogene boundary

The Cretaceous–Paleogene (K–Pg) boundary, formerly known as the Cretaceous–Tertiary (K–T) boundary, is a geological signature, usually a thin band of rock containing much more iridium than other bands. The K–Pg boundary marks the end of the Cretaceous Period, the last period of the Mesozoic Era, and marks the beginning of the Paleogene Period, the first period of the Cenozoic Era. Its age is usually estimated at around 66 million years, with radiometric dating yielding a more precise age of 66.043 ± 0.011 Ma.

Cenozoic

Cenozoic

The Cenozoic is Earth's current geological era, representing the last 66 million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configuration of continents. It is the latest of three geological eras since complex life evolved, preceded by the Mesozoic and Paleozoic. It started with the Cretaceous–Paleogene extinction event, when many species, including the non-avian dinosaurs, became extinct in an event attributed by most experts to the impact of a large asteroid or other celestial body, the Chicxulub impactor.

Etymology and history

The Cretaceous as a separate period was first defined by Belgian geologist Jean d'Omalius d'Halloy in 1822 as the Terrain Crétacé,[3] using strata in the Paris Basin[4] 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.[5] The twofold division of the Cretaceous was implemented by Conybeare and Phillips in 1822. Alcide d'Orbigny in 1840 divided the French Cretaceous into five étages (stages): the Neocomian, Aptian, Albian, Turonian, and Senonian, later adding the Urgonian between Neocomian and Aptian and the Cenomanian between the Albian and Turonian.[6]

Discover more about Etymology and history related topics

Jean Baptiste Julien d'Omalius d'Halloy

Jean Baptiste Julien d'Omalius d'Halloy

Jean Baptiste Julien d'Omalius d'Halloy was a Belgian geologist. He also wrote on races.

Stratum

Stratum

In geology and related fields, a stratum is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as either bedding surfaces or bedding planes. Prior to the publication of the International Stratigraphic Guide, older publications have defined a stratum as either being either equivalent to a single bed or composed of a number of beds; as a layer greater than 1 cm in thickness and constituting a part of a bed; or a general term that includes both bed and lamina.

Paris Basin

Paris Basin

The Paris Basin is one of the major geological regions of France. It developed since the Triassic over remnant uplands of the Variscan orogeny. The sedimentary basin, no longer a single drainage basin, is a large sag in the craton, bordered by the Armorican Massif to the west, the Ardennes-Brabant axis to the north, the Massif des Vosges to the east, and the Massif Central to the south.

Chalk

Chalk

Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Chalk is common throughout Western Europe, where deposits underlie parts of France, and steep cliffs are often seen where they meet the sea in places such as the Dover cliffs on the Kent coast of the English Channel.

Calcium carbonate

Calcium carbonate

Calcium carbonate is a chemical compound with the chemical formula CaCO3. It is a common substance found in rocks as the minerals calcite and aragonite and is the main component of eggshells, gastropod shells, shellfish skeletons and pearls. Things containing much calcium carbonate or resembling it are described as calcareous. Calcium carbonate is the active ingredient in agricultural lime and is created when calcium ions in hard water react with carbonate ions to create limescale. It has medical use as a calcium supplement or as an antacid, but excessive consumption can be hazardous and cause hypercalcemia and digestive issues.

Invertebrate

Invertebrate

Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column, derived from the notochord. This is a grouping including all animals apart from the chordate subphylum Vertebrata. Familiar examples of invertebrates include arthropods, mollusks, annelids, echinoderms and cnidarians.

Western Europe

Western Europe

Western Europe is the western region of Europe. The region's extent varies depending on context.

Latin

Latin

Latin is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area around present-day Rome, but through the power of the Roman Republic it became the dominant language in the Italian region and subsequently throughout the Roman Empire. Even after the fall of Western Rome, Latin remained the common language of international communication, science, scholarship and academia in Europe until well into the 18th century, when other regional vernaculars supplanted it in common academic and political usage. For most of the time it was used, it would be considered a "dead language" in the modern linguistic definition; that is, it lacked native speakers, despite being used extensively and actively.

William Conybeare (geologist)

William Conybeare (geologist)

William Daniel Conybeare FRS, dean of Llandaff, was an English geologist, palaeontologist and clergyman. He is probably best known for his ground-breaking work on fossils and excavation in the 1820s, including important papers for the Geological Society of London on ichthyosaur anatomy and the first published scientific description of a plesiosaur.

Alcide d'Orbigny

Alcide d'Orbigny

Alcide Charles Victor Marie Dessalines d'Orbigny was a French naturalist who made major contributions in many areas, including zoology, palaeontology, geology, archaeology and anthropology.

Neocomian

Neocomian

In geology, Neocomian was a name given to the lowest stage of the Cretaceous system. It is generally considered to encompass the interval now covered by the Berriasian, Valanginian and Hauterivian, from approximately 145 to 130 Ma. It was introduced by Jules Thurmann in 1835 on account of the development of these rocks at Neuchâtel (Neocomum), Switzerland. It has been employed in more than one sense. In the type area the rocks have been divided into two sub-stages, a lower, Valanginian and an upper, Hauterivian ; there is also another local sub-stage, the infra-Valanginian or Berriasian. These three sub-stages constitute the Neocomian in its restricted sense. Adolf von Koenen and other German geologists extend the use of the term to include the whole of the Lower Cretaceous up to the top of the Gault or Albian. Eugène Renevier divided the Lower Cretaceous into the Neocomian division, embracing the three sub-stages mentioned above, and an Urgonian division, including the Barremian, Rhodanian and Aptian sub-stages. Sir A. Geikie regards Neocomian as synonymous with Lower Cretaceous, and he, like Renevier, closes this portion of the system at the top of the Lower Greensand (Aptian). Other British geologists restrict the Neocomian to the marine beds of Speeton and Tealby, and their estuarine equivalents, the Weald Clay and Hastings Sands (Wealden). Much confusion would be avoided by dropping the term Neocomian entirely and employing instead, for the type area, the sub-divisions given above. This becomes the more obvious when it is pointed out that the Berriasian type is limited to Dauphine; the Valanginian has not a much wider range; and the Hauterivian does not extend north of the Paris basin.

Geology

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 into 12 stages, all originating from European stratigraphy, is now used worldwide. In many parts of the world, alternative local subdivisions are still in use.

From youngest to oldest, the subdivisions of the Cretaceous period are:

Subdivisions of the Cretaceous
Epoch Stage Start
(base)
End
(top)
Definition Etymology
(Mya)
Late Cretaceous Maastrichtian 72.1 ± 0.2 66.0 top: iridium anomaly at the Cretaceous–Paleogene boundary
base:first occurrence of Pachydiscus neubergicus
Maastricht Formation, Maastricht, Netherlands
Campanian 83.6 ± 0.2 72.1 ± 0.2 base: last occurrence of Marsupites testudinarius Champagne, France
Santonian 86.3 ± 0.5 83.6 ± 0.2 base: first occurrence of Cladoceramus undulatoplicatus Saintes, France
Coniacian 89.8 ± 0.3 86.3 ± 0.5 base: first occurrence of Cremnoceramus rotundatus Cognac, France
Turonian 93.9 ± 0.8 89.8 ± 0.3 base: first occurrence of Watinoceras devonense Tours, France
Cenomanian 100.5 ± 0.9 93.9 ± 0.8 base: first occurrence of Rotalipora globotruncanoides Cenomanum; Le Mans, France
Early Cretaceous Albian 113.0 ± 1.0 100.5 ± 0.9 base: first occurrence of Praediscosphaera columnata Aube, France
Aptian 125.0 ± 1.0 113.0 ± 1.0 base: magnetic anomaly M0r Apt, France
Barremian 129.4 ± 1.5 125.0 ± 1.0 base: first occurrence of Spitidiscus hugii and S. vandeckii Barrême, France
Hauterivian 132.9 ± 2.0 129.4 ± 1.5 base: first occurrence of Acanthodiscus Hauterive, Switzerland
Valanginian 139.8 ± 3.0 132.9 ± 2.0 base: first occurrence of Calpionellites darderi Valangin, Switzerland
Berriasian 145.0 ± 4.0 139.8 ± 3.0 base: first occurrence of Berriasella jacobi (traditionally);
first occurrence of Calpionella alpina (since 2016)
Berrias, France

Boundaries

The impact of a meteorite or comet is today widely accepted as the main reason for the Cretaceous–Paleogene extinction event.
The impact of a meteorite or comet is today widely accepted as the main reason for the Cretaceous–Paleogene extinction event.

The lower boundary of the Cretaceous is currently undefined, and the Jurassic–Cretaceous boundary is currently the only system boundary to lack a defined Global Boundary Stratotype Section and Point (GSSP). Placing a GSSP for this boundary has been difficult because of the strong regionality of most biostratigraphic markers, and the lack of any chemostratigraphic events, such as isotope excursions (large sudden changes in ratios of isotopes) that could be used to define or correlate a boundary. Calpionellids, an enigmatic group of planktonic protists with urn-shaped calcitic tests briefly abundant during the latest Jurassic to earliest Cretaceous, have been suggested as the most promising candidates for fixing the Jurassic–Cretaceous boundary.[7] In particular, the first appearance Calpionella alpina, coinciding with the base of the eponymous Alpina subzone, has been proposed as the definition of the base of the Cretaceous.[8] The working definition for the boundary has often been placed as the first appearance of the ammonite Strambergella jacobi, formerly placed in the genus Berriasella, but its use as a stratigraphic indicator has been questioned, as its first appearance does not correlate with that of C. alpina.[9] The boundary is officially considered by the International Commission on Stratigraphy to be approximately 145 million years ago,[10] but other estimates have been proposed based on U-Pb geochronology, ranging as young as 140 million years ago.[11][12]

The upper boundary of the Cretaceous is sharply defined, being placed at an iridium-rich layer found worldwide that is believed to be associated with the Chicxulub impact crater, with its boundaries circumscribing parts of the Yucatán Peninsula and extending into the Gulf of Mexico. This layer has been dated at 66.043 Mya.[13]

At the end of the Cretaceous, the impact of a large body with the Earth may have been the punctuation mark at the end of a progressive decline in biodiversity during the Maastrichtian age. The result was the extinction of three-quarters of Earth's plant and animal species. The impact created the sharp break known as the K–Pg boundary (formerly known as the K–T boundary). Earth's biodiversity required substantial time to recover from this event, despite the probable existence of an abundance of vacant ecological niches.[14]

Despite the severity of the K-Pg extinction event, there were significant variations in the rate of extinction between and within different clades. Species that depended on photosynthesis declined or became extinct as atmospheric particles blocked solar energy. As is the case today, photosynthesizing organisms, such as phytoplankton and land plants, formed the primary part of the food chain in the late Cretaceous, and all else that depended on them suffered, as well. Herbivorous animals, which depended on plants and plankton as their food, died out as their food sources became scarce; consequently, the top predators, such as Tyrannosaurus rex, also perished.[15] Yet only three major groups of tetrapods disappeared completely; the nonavian dinosaurs, the plesiosaurs and the pterosaurs. The other Cretaceous groups that did not survive into the Cenozoic Erathe ichthyosaurs, last remaining temnospondyls (Koolasuchus), and nonmammalian cynodonts (Tritylodontidae) were already extinct millions of years before the event occurred.

Coccolithophorids and molluscs, including ammonites, rudists, freshwater snails, and mussels, as well as organisms whose food chain included these shell builders, became extinct or suffered heavy losses. For example, ammonites are thought to have been the principal food of mosasaurs, a group of giant marine lizards related to snakes that became extinct at the boundary.[16]

Omnivores, insectivores, and carrion-eaters survived the extinction event, perhaps because of the increased availability of their food sources. At the end of the Cretaceous, there seem to have been no purely herbivorous or carnivorous mammals. Mammals and birds that survived the extinction fed on insects, larvae, worms, and snails, which in turn fed on dead plant and animal matter. Scientists theorise that these organisms survived the collapse of plant-based food chains because they fed on detritus.[17][14][18]

In stream communities, few groups of animals became extinct. Stream communities rely less on food from living plants and more on detritus that washes in from land. This particular ecological niche buffered them from extinction.[19] Similar, but more complex patterns have been found in the oceans. Extinction was more severe among animals living in the water column than among animals living on or in the seafloor. Animals in the water column are almost entirely dependent on primary production from living phytoplankton, while animals living on or in the ocean floor feed on detritus or can switch to detritus feeding.[14]

The largest air-breathing survivors of the event, crocodilians and champsosaurs, were semiaquatic and had access to detritus. Modern crocodilians can live as scavengers and can survive for months without food and go into hibernation when conditions are unfavorable, and their young are small, grow slowly, and feed largely on invertebrates and dead organisms or fragments of organisms for their first few years. These characteristics have been linked to crocodilian survival at the end of the Cretaceous.[17]

Geologic formations

Drawing of fossil jaws of Mosasaurus hoffmanni, from the Maastrichtian of Dutch Limburg, by Dutch geologist Pieter Harting (1866)
Drawing of fossil jaws of Mosasaurus hoffmanni, from the Maastrichtian of Dutch Limburg, by Dutch geologist Pieter Harting (1866)
Scipionyx, a theropod dinosaur from the Early Cretaceous of Italy
Scipionyx, a theropod dinosaur from the Early Cretaceous of Italy

The high sea level and warm climate of the Cretaceous meant large areas of the continents were covered by warm, shallow seas, providing habitat for many marine organisms. The Cretaceous was named for the extensive chalk deposits of this age in Europe, but in many parts of the world, the deposits from the Cretaceous are of marine limestone, a rock type that is formed under warm, shallow marine conditions. Due to the high sea level, there was extensive space for such sedimentation. Because of the relatively young age and great thickness of the system, Cretaceous rocks are evident in many areas worldwide.

Chalk is a rock type characteristic for (but not restricted to) the Cretaceous. It consists of coccoliths, microscopically small calcite skeletons of coccolithophores, a type of algae that prospered in the Cretaceous seas.

Stagnation of deep sea currents in middle Cretaceous times caused anoxic conditions in the sea water leaving the deposited organic matter undecomposed. Half of the world's petroleum reserves were laid down at this time in the anoxic conditions of what would become the Persian Gulf and the Gulf of Mexico. In many places around the world, dark anoxic shales were formed during this interval,[20] such as the Mancos Shale of western North America.[21] These shales are an important source rock for oil and gas, for example in the subsurface of the North Sea.

Europe

In northwestern Europe, chalk deposits from the Upper Cretaceous are characteristic for the Chalk Group, which forms the white cliffs of Dover on the south coast of England and similar cliffs on the French Normandian coast. The group is found in England, northern France, the low countries, northern Germany, Denmark and in the subsurface of the southern part of the North Sea. Chalk is not easily consolidated and the Chalk Group still consists of loose sediments in many places. The group also has other limestones and arenites. Among the fossils it contains are sea urchins, belemnites, ammonites and sea reptiles such as Mosasaurus.

In southern Europe, the Cretaceous is usually a marine system consisting of competent limestone beds or incompetent marls. Because the Alpine mountain chains did not yet exist in the Cretaceous, these deposits formed on the southern edge of the European continental shelf, at the margin of the Tethys Ocean.

North America

Map of North America During the Late Cretaceous
Map of North America During the Late Cretaceous

During the Cretaceous, the present North American continent was isolated from the other continents. In the Jurassic, the North Atlantic already opened, leaving a proto-ocean between Europe and North America. From north to south across the continent, the Western Interior Seaway started forming. This inland sea separated the elevated areas of Laramidia in the west and Appalachia in the east. Three dinosaur clades found in Laramidia (troodontids, therizinosaurids and oviraptorosaurs) are absent from Appalachia from the Coniacian through the Maastrichtian.[22]

Discover more about Geology related topics

Early Cretaceous

Early Cretaceous

The Early Cretaceous or the Lower Cretaceous, is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma.

Late Cretaceous

Late Cretaceous

The Late Cretaceous is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after creta, the Latin word for the white limestone known as chalk. The chalk of northern France and the white cliffs of south-eastern England date from the Cretaceous Period.

Neocomian

Neocomian

In geology, Neocomian was a name given to the lowest stage of the Cretaceous system. It is generally considered to encompass the interval now covered by the Berriasian, Valanginian and Hauterivian, from approximately 145 to 130 Ma. It was introduced by Jules Thurmann in 1835 on account of the development of these rocks at Neuchâtel (Neocomum), Switzerland. It has been employed in more than one sense. In the type area the rocks have been divided into two sub-stages, a lower, Valanginian and an upper, Hauterivian ; there is also another local sub-stage, the infra-Valanginian or Berriasian. These three sub-stages constitute the Neocomian in its restricted sense. Adolf von Koenen and other German geologists extend the use of the term to include the whole of the Lower Cretaceous up to the top of the Gault or Albian. Eugène Renevier divided the Lower Cretaceous into the Neocomian division, embracing the three sub-stages mentioned above, and an Urgonian division, including the Barremian, Rhodanian and Aptian sub-stages. Sir A. Geikie regards Neocomian as synonymous with Lower Cretaceous, and he, like Renevier, closes this portion of the system at the top of the Lower Greensand (Aptian). Other British geologists restrict the Neocomian to the marine beds of Speeton and Tealby, and their estuarine equivalents, the Weald Clay and Hastings Sands (Wealden). Much confusion would be avoided by dropping the term Neocomian entirely and employing instead, for the type area, the sub-divisions given above. This becomes the more obvious when it is pointed out that the Berriasian type is limited to Dauphine; the Valanginian has not a much wider range; and the Hauterivian does not extend north of the Paris basin.

Gallic epoch

Gallic epoch

The Gallic epoch is an obsolete epoch of the Mesozoic Era's Cretaceous, the latter being a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago (mya) to the beginning of the Paleogene Period 66 mya. The Gallic epoch encompasses the Barremian, Aptian, Albian, Cenomanian and Turonian faunal stages.

Maastrichtian

Maastrichtian

The Maastrichtian is, in the ICS geologic timescale, the latest age of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from 72.1 to 66 million years ago. The Maastrichtian was preceded by the Campanian and succeeded by the Danian.

Cretaceous–Paleogene boundary

Cretaceous–Paleogene boundary

The Cretaceous–Paleogene (K–Pg) boundary, formerly known as the Cretaceous–Tertiary (K–T) boundary, is a geological signature, usually a thin band of rock containing much more iridium than other bands. The K–Pg boundary marks the end of the Cretaceous Period, the last period of the Mesozoic Era, and marks the beginning of the Paleogene Period, the first period of the Cenozoic Era. Its age is usually estimated at around 66 million years, with radiometric dating yielding a more precise age of 66.043 ± 0.011 Ma.

Maastricht Formation

Maastricht Formation

The Maastricht Formation, named after the city of Maastricht in the Netherlands, is a geological formation in the Netherlands and Belgium whose strata date back to the Late Cretaceous, within 500,000 years of the Cretaceous–Paleogene boundary, now dated at 66 million years ago. The formation is part of the Chalk Group and is between 30 and 90 metres thick. It crops out in southern parts of Dutch and Belgian Limburg and adjacent areas in Germany. It can be found in the subsurface of northern Belgium and southeastern Netherlands, especially in the Campine Basin and Roer Valley Graben. Dinosaur remains are among the fossils that have been recovered from the formation.

Maastricht

Maastricht

Maastricht is a city and a municipality in the southeastern Netherlands. It is the capital and largest city of the province of Limburg. Maastricht is located on both sides of the Meuse, at the point where the Jeker joins it. Mount Saint Peter (Sint-Pietersberg) is largely situated within the city's municipal borders. Maastricht is adjacent to the border with Belgium and is part of the Meuse-Rhine Euroregion, an international metropolis with a population of about 3.9 million, which includes the nearby German and Belgian cities of Aachen, Liège and Hasselt.

Campanian

Campanian

The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian spans the time from 83.6 to 72.1 million years ago. It is preceded by the Santonian and it is followed by the Maastrichtian.

Marsupites

Marsupites

Marsupites is an extinct genus of crinoids from the Santonian stage of the Late Cretaceous.

Champagne (province)

Champagne (province)

Champagne was a province in the northeast of the Kingdom of France, now best known as the Champagne wine region for the sparkling white wine that bears its name in modern-day France. The County of Champagne, descended from the early medieval kingdom of Austrasia, passed to the French crown in 1314.

Cladoceramus

Cladoceramus

Cladoceramus is an extinct genus of fossil marine pteriomorphian bivalves that superficially resembled the related winged pearly oysters of the extant genus Pteria. They lived in the Santonian stage of the Late Cretaceous.

Paleogeography

During the Cretaceous, the late-Paleozoic-to-early-Mesozoic supercontinent of Pangaea completed its tectonic breakup into the present-day continents, although their positions were substantially different at the time. As the Atlantic Ocean widened, the convergent-margin mountain building (orogenies) that had begun during the Jurassic continued in the North American Cordillera, as the Nevadan orogeny was followed by the Sevier and Laramide orogenies.

Gondwana had begun to break up during the Jurassic Period, but its fragmentation accelerated during the Cretaceous and was largely complete by the end of the period. South America, Antarctica, and Australia rifted away from Africa (though India and Madagascar remained attached to each other until around 80 million years ago); thus, the South Atlantic and Indian Oceans were newly formed. Such active rifting lifted great undersea mountain chains along the welts, raising eustatic sea levels worldwide. To the north of Africa the Tethys Sea continued to narrow. During the most of the Late Cretaceous, North America would be divided in two by the Western Interior Seaway, a large interior sea, separating Laramidia to the west and Appalachia to the east, then receded late in the period, leaving thick marine deposits sandwiched between coal beds. Bivalve palaeobiogeography also indicates that Africa was split in half by a shallow sea during the Coniacian and Santonian, connecting the Tethys with the South Atlantic by way of the central Sahara and Central Africa, which were then underwater.[23] At the peak of the Cretaceous transgression, one-third of Earth's present land area was submerged.[24]

The Cretaceous is justly famous for its chalk; indeed, more chalk formed in the Cretaceous than in any other period in the Phanerozoic.[25] 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.[26] 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.

Discover more about Paleogeography related topics

Continent

Continent

A continent is any of several large geographical regions. Continents are generally identified by convention rather than any strict criteria. A continent could be a single landmass or a part of a very large landmass, as in the case of Asia or Europe. Due to this, the number of continents varies; up to seven or as few as four geographical regions are commonly regarded as continents. Most English-speaking countries recognize seven regions as continents. In order from largest to smallest in area, these seven regions are Asia, Africa, North America, South America, Antarctica, Europe, and Australia. Different variations with fewer continents merge some of these regions, examples of this are merging North America and South America into America, Asia and Europe into Eurasia, and Africa, Asia, and Europe into Afro-Eurasia.

Atlantic Ocean

Atlantic Ocean

The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about 106,460,000 km2 (41,100,000 sq mi). It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Africa, Europe, and Asia from the "New World" of the Americas in the European perception of the World.

Jurassic

Jurassic

The Jurassic is a geologic period and stratigraphic system that spanned from the end of the Triassic Period 201.4 million years ago (Mya) to the beginning of the Cretaceous Period, approximately 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era and is named after the Jura Mountains, where limestone strata from the period were first identified.

Nevadan orogeny

Nevadan orogeny

The Nevadan orogeny occurred along the western margin of North America during the Middle Jurassic to Early Cretaceous time which is approximately from 155 Ma to 145 Ma. Throughout the duration of this orogeny there were at least two different kinds of orogenic processes occurring. During the early stages of orogenesis an "Andean type" continental magmatic arc developed due to subduction of the Farallon oceanic plate beneath the North American Plate. The latter stages of orogenesis, in contrast, saw multiple oceanic arc terranes accreted onto the western margin of North America in a "Cordilleran type" accretionary orogen. Deformation related to the accretion of these volcanic arc terranes is mostly limited to the western regions of the resulting mountain ranges and is absent from the eastern regions. In addition, the deformation experienced in these mountain ranges is mostly due to the Nevadan orogeny and not other external events such as the more recent Sevier and Laramide Orogenies. It is noted that the Klamath Mountains and the Sierra Nevada share similar stratigraphy indicating that they were both formed by the Nevadan orogeny. In comparison with other orogenic events, it appears that the Nevadan Orogeny occurred rather quickly taking only about 10 million years as compared to hundreds of millions of years for other orogenies around the world.

Laramide orogeny

Laramide orogeny

The Laramide orogeny was a time 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. The Laramide orogeny occurred in a series of pulses, with quiescent phases intervening. The major feature that was created by this orogeny was deep-seated, thick-skinned deformation, with evidence of this orogeny found from Canada to northern Mexico, with the easternmost extent of the mountain-building represented by the Black Hills of South Dakota. The phenomenon is named for the Laramie Mountains of eastern Wyoming. The Laramide orogeny is sometimes confused with the Sevier orogeny, which partially overlapped in time and space.

Gondwana

Gondwana

Gondwana was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic and began to break up during the Jurassic period. The final stages of break-up, involving the separation of Antarctica from South America and Australia, occurred during the Paleogene. Gondwana was not considered a supercontinent by the earliest definition, since the landmasses of Baltica, Laurentia, and Siberia were separated from it. To differentiate it from the Indian region of the same name, it is also commonly called Gondwanaland.

Antarctica

Antarctica

Antarctica is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest continent, being about 40% larger than Europe, and has an area of 14,200,000 km2 (5,500,000 sq mi). Most of Antarctica is covered by the Antarctic ice sheet, with an average thickness of 1.9 km (1.2 mi).

Australia

Australia

Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. Australia is the largest country by area in Oceania and the world's sixth-largest country. Australia is the oldest, flattest, and driest inhabited continent, with the least fertile soils. It is a megadiverse country, and its size gives it a wide variety of landscapes and climates, with deserts in the centre, tropical rainforests in the north-east, and mountain ranges in the south-east.

Africa

Africa

Africa is the world's second-largest and second-most populous continent, after Asia in both aspects. At about 30.3 million km2 including adjacent islands, it covers 20% of Earth's land area and 6% of its total surface area. With 1.4 billion people as of 2021, it accounts for about 18% of the world's human population. Africa's population is the youngest amongst all the continents; the median age in 2012 was 19.7, when the worldwide median age was 30.4. Despite a wide range of natural resources, Africa is the least wealthy continent per capita and second-least wealthy by total wealth, behind Oceania. Scholars have attributed this to different factors including geography, climate, tribalism, colonialism, the Cold War, neocolonialism, lack of democracy, and corruption. Despite this low concentration of wealth, recent economic expansion and the large and young population make Africa an important economic market in the broader global context.

India

India

India, officially the Republic of India, is a country in South Asia. It is the seventh-largest country by area and the second-most populous country. Bounded by the Indian Ocean on the south, the Arabian Sea on the southwest, and the Bay of Bengal on the southeast, it shares land borders with Pakistan to the west; China, Nepal, and Bhutan to the north; and Bangladesh and Myanmar to the east. In the Indian Ocean, India is in the vicinity of Sri Lanka and the Maldives; its Andaman and Nicobar Islands share a maritime border with Thailand, Myanmar, and Indonesia.

Madagascar

Madagascar

Madagascar, officially the Republic of Madagascar is a sovereign island country in the Indian Ocean, approximately 400 kilometres off the coast of East Africa across the Mozambique Channel. At 592,800 square kilometres (228,900 sq mi), it is the world's second-largest island country, after Indonesia. Its capital and largest city is Antananarivo.

Indian Ocean

Indian Ocean

The Indian Ocean is the third-largest of the world's five oceanic divisions, covering 70,560,000 km2 (27,240,000 sq mi) or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by the Southern Ocean or Antarctica, depending on the definition in use. Along its core, the Indian Ocean has some large marginal or regional seas such as the Arabian Sea, Laccadive Sea, Bay of Bengal, and Andaman Sea.

Climate

Palynological evidence indicates the Cretaceous climate had three broad phases: a Berriasian–Barremian warm-dry phase, a Aptian–Santonian warm-wet phase, and a Campanian–Maastrichtian cool-dry phase.[27]

The cooling trend of the last epoch of the Jurassic, the Tithonian, continued into the Berriasian, the first age of the Cretaceous. There is evidence that snowfalls were common in the higher latitudes during this age, and the tropics became wetter than during the Triassic and Jurassic. Glaciation was restricted to high-latitude mountains, though seasonal snow may have existed farther from the poles.[28] After the end of the first age, however, temperatures began to increase again, with a number of thermal excursions, such as the middle Valanginian Weissert Thermal Excursion (WTX), the middle Hauterivian Faraoni Thermal Excursion (FTX), and the early Barremian Hauptblatterton Thermal Event (HTE) occurring. The HTE marked the ultimate end of the Tithonian-early Barremian Cool Interval (TEBCI). The TEBCI was followed by the Barremian-Aptian Warm Interval (BAWI), which itself was followed by the Aptian-Albian Cold Snap (AACS) that began about 118 million years ago.[29] A short, relatively minor ice age may have occurred during this so-called "cold snap", as evidenced by glacial dropstones in the western parts of the Tethys Ocean.[30] The AACS ended around 111 million years ago with the Paquier/Urbino Thermal Maximum, giving way to the Mid-Cretaceous Hothouse (MKH), which lasted from the early Albian until the early Campanian.[29]

The MKH was punctuated by multiple thermal maxima of extreme warmth comparable to and possibly exceeding the better known Palaeocene-Eocene Thermal Maximum in magnitude, including the Amadeus Thermal Maximum around 106 million years ago, the Breistroffer Thermal Maximum around 101 million years ago, the Cenomanian-Turonian Thermal Maximum around 94 million years ago, and the Coniacian Thermal Maximum around 87 million years ago.[29] Such hot temperatures during the MKH resulted in a very gentle temperature gradient from the equator to the poles; the latitudinal temperature gradient during the Cenomanian-Turonian Thermal Maximum was 0.54 °C per ° latitude for the Southern Hemisphere and 0.49 °C per ° latitude for the Northern Hemisphere, in contrast to present day values of 1.07 and 0.69 °C per ° latitude for the Southern and Northern hemispheres, respectively.[31] This meant weaker global winds, which drive the ocean currents, and resulted in less upwelling and more stagnant oceans than today.[32] This is evidenced by widespread black shale deposition and frequent anoxic events.[20] Sediment cores show that tropical sea surface temperatures may have briefly been as warm as 42 °C (108 °F), 17 °C (31 °F) warmer than at present, and that they averaged around 37 °C (99 °F).[33] Meanwhile, deep ocean temperatures were as much as 15 to 20 °C (27 to 36 °F) warmer than today's;[34] one study estimated that deep ocean temperatures were between 12 and 20 °C during the MKH.[35]

Beginning in the Santonian, near the end of the MKH, the global climate began to cool, with this cooling trend continuing across the Campanian.[36] This period of cooling, driven by falling levels of atmospheric carbon dioxide,[35] caused the end of the MKH and the transition into a cooler climatic interval, known formally as the Late Cretaceous-Early Palaeogene Cool Interval (LKEPCI).[29] Deep ocean temperatures declined to 9 to 12 °C,[35] though the shallow temperature gradient between tropical and polar seas remained.[37] Regional conditions in the Western Interior Seaway changed little between the MKH and the LKEPCI.[38] Two upticks in global temperatures are known to have occurred during the Maastrichtian, bucking the trend of overall cooler temperatures during the LKEPCI. Between 70 and 69 Ma and 66–65 Ma, isotopic ratios indicate elevated atmospheric CO2 pressures with levels of 1000–1400 ppmV and mean annual temperatures in west Texas between 21 and 23 °C (70 and 73 °F). Atmospheric CO2 and temperature relations indicate a doubling of pCO2 was accompanied by a ~0.6 °C increase in temperature.[39] The LKEPCI lasted into the Late Palaeocene, when it gave way to another supergreenhouse interval.[29]

A computer-simulated model of surface conditions in Middle Cretaceous, 100 mya, displaying the approximate shoreline and calculated isotherms
A computer-simulated model of surface conditions in Middle Cretaceous, 100 mya, displaying the approximate shoreline and calculated isotherms

The production of large quantities of magma, variously attributed to mantle plumes or to extensional tectonics,[40] 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 to warm 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.[41] It was suggested that there was Antarctic marine glaciation in the Turonian Age, based on isotopic evidence.[42] However, this has subsequently been suggested to be the result of inconsistent isotopic proxies,[43] with evidence of polar rainforests during this time interval at 82° S.[44] 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 Cretaceous of the Eromanga Basin in southern Australia.[45][46]

Discover more about Climate related topics

Cool tropics paradox

Cool tropics paradox

The cool tropics paradox is the apparent difference between modeled estimates of tropical temperatures during warm, ice-free periods of the Cretaceous and Eocene, and the colder temperatures which proxies suggested were present. The long-standing paradox was resolved when novel proxy derived temperatures showed significantly warmer tropics during past greenhouse climates. The low-gradient problem, i.e. the very warm polar regions with respect to present day, is still an issue for state-of-the-art climate models.

Latitude

Latitude

In geography, latitude is a coordinate that specifies the north–south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pole, with 0° at the Equator. Lines of constant latitude, or parallels, run east–west as circles parallel to the equator. Latitude and longitude are used together as a coordinate pair to specify a location on the surface of the Earth.

Hauterivian

Hauterivian

The Hauterivian is, in the geologic timescale, an age in the Early Cretaceous Epoch or a stage in the Lower Cretaceous Series. It spans the time between 132.9 ± 2 Ma and 129.4 ± 1.5 Ma. The Hauterivian is preceded by the Valanginian and succeeded by the Barremian.

Barremian

Barremian

The Barremian is an age in the geologic timescale between 129.4 ± 1.5 Ma and 121.4 ± 1.0 Ma). It is a subdivision of the Early Cretaceous Epoch. It is preceded by the Hauterivian and followed by the Aptian Stage.

Dropstone

Dropstone

Dropstones are isolated fragments of rock found within finer-grained water-deposited sedimentary rocks or pyroclastic beds. They range in size from small pebbles to boulders. The critical distinguishing feature is that there is evidence that they were not transported by normal water currents, but rather dropped in vertically through the air or water column. Such deposition can occur i.e. during a volcanic eruption.

Albian

Albian

The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous Epoch/Series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± 0.9 Ma. The Albian is preceded by the Aptian and followed by the Cenomanian.

Equator

Equator

The equator is a circle of latitude that divides a spheroid, such as Earth, into the northern and southern hemispheres. On Earth, it is an imaginary line located at 0 degrees latitude, about 40,075 km (24,901 mi) in circumference, halfway between the North and South poles. The term can also be used for any other celestial body that is roughly spherical.

Ocean

Ocean

The ocean is the body of salt water that covers approximately 70.8% of the Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the world ocean is conventionally divided. Separate names are used to identify five different areas of the ocean: Pacific, Atlantic, Indian, Southern, and Arctic. Seawater covers approximately 361,000,000 km2 (139,000,000 sq mi) of the planet. The ocean is the principal component of Earth's hydrosphere, and therefore integral to life on Earth. Acting as a huge heat reservoir, the ocean influences climate and weather patterns, the carbon cycle, and the water cycle.

Shale

Shale

Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2Si2O5(OH)4) and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite. Shale is characterized by its tendency to split into thin layers (laminae) less than one centimeter in thickness. This property is called fissility. Shale is the most common sedimentary rock.

Anoxic event

Anoxic event

Oceanic anoxic events or anoxic events (anoxia conditions) describe periods wherein large expanses of Earth's oceans were depleted of dissolved oxygen (O2), creating toxic, euxinic (anoxic and sulfidic) waters. Although anoxic events have not happened for millions of years, the geologic record shows that they happened many times in the past. Anoxic events coincided with several mass extinctions and may have contributed to them. These mass extinctions include some that geobiologists use as time markers in biostratigraphic dating. On the other hand, there are widespread, various black-shale beds from the mid-Cretaceous which indicate anoxic events but are not associated with mass extinctions. Many geologists believe oceanic anoxic events are strongly linked to the slowing of ocean circulation, climatic warming, and elevated levels of greenhouse gases. Researchers have proposed enhanced volcanism (the release of CO2) as the "central external trigger for euxinia."

Sea surface temperature

Sea surface temperature

Sea surface temperature (SST), or ocean surface temperature, is the ocean temperature close to the surface. The exact meaning of surface varies according to the measurement method used, but it is between 1 millimetre (0.04 in) and 20 metres (70 ft) below the sea surface. Air masses in the Earth's atmosphere are highly modified by sea surface temperatures within a short distance of the shore. Localized areas of heavy snow can form in bands downwind of warm water bodies within an otherwise cold air mass. Warm sea surface temperatures are known to be a cause of tropical cyclogenesis over the Earth's oceans. Tropical cyclones can also cause a cool wake, due to turbulent mixing of the upper 30 metres (100 ft) of the ocean. SST changes diurnally, like the air above it, but to a lesser degree. There is less SST variation on breezy days than on calm days. In addition, ocean currents such as the Atlantic Multidecadal Oscillation (AMO), can affect SST's on multi-decadal time scales, a major impact results from the global thermohaline circulation, which affects average SST significantly throughout most of the world's oceans.

Carbon dioxide

Carbon dioxide

Carbon dioxide is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature, and as the source of available carbon in the carbon cycle, atmospheric CO2 is the primary carbon source for life on Earth. In the air, carbon dioxide is transparent to visible light but absorbs infrared radiation, acting as a greenhouse gas. Carbon dioxide is soluble in water and is found in groundwater, lakes, ice caps, and seawater. When carbon dioxide dissolves in water, it forms carbonate and mainly bicarbonate, which causes ocean acidification as atmospheric CO2 levels increase.

Flora

Facsimile of a fossil of Archaefructus from the Yixian Formation, China
Facsimile of a fossil of Archaefructus from the Yixian Formation, China

Flowering plants (angiosperms) make up around 90% of living plant species today. Prior to the rise of angiosperms, during the Jurassic and the Early Cretaceous, the higher flora was dominated by gymnosperm groups, including cycads, conifers, ginkgophytes, gnetophytes and close relatives, as well as the extinct Bennettitales. Other groups of plants included pteridosperms or "seed ferns", a collective term that refers to disparate groups of extinct seed plants with fern-like foliage, including groups such as Corystospermaceae and Caytoniales. The exact origins of angiosperms are uncertain, although molecular evidence suggests that they are not closely related to any living group of gymnosperms.[47]

The earliest widely accepted evidence of flowering plants are monosulcate (single-grooved) pollen grains from the late Valanginian (~ 134 million years ago) found in Israel[48] and Italy,[49] initially at low abundance. Molecular clock estimates conflict with fossil estimates, suggesting the diversification of crown-group angiosperms during the Upper Triassic or Jurassic, but such estimates are difficult to reconcile with the heavily sampled pollen record and the distinctive tricolpate to tricolporoidate (triple grooved) pollen of eudicot angiosperms.[47] Among the oldest records of Angiosperm macrofossils are Montsechia from the Barremian aged Las Hoyas beds of Spain and Archaefructus from the Barremian-Aptian boundary Yixian Formation in China. Tricolpate pollen distinctive of eudicots first appears in the Late Barremian, while the earliest remains of monocots are known from the Aptian.[47] Flowering plants underwent a rapid radiation beginning during the middle Cretaceous, becoming the dominant group of land plants by the end of the period, coincident with the decline of previously dominant groups such as conifers.[50] The oldest known fossils of grasses are from the Albian,[51] with the family having diversified into modern groups by the end of the Cretaceous.[52] The oldest large angiosperm trees are known from the Turonian (c. 90 Mya) of New Jersey, with the trunk having a preserved diameter of 1.8 metres (5.9 ft) and an estimated height of 50 metres (160 ft).[53]

During the Cretaceous, Polypodiales ferns, which make up 80% of living fern species, would also begin to diversify.[54]

Discover more about Flora related topics

Flowering plant

Flowering plant

Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae, commonly called angiosperms. The term "angiosperm" is derived from the Greek words ἀγγεῖον /angeion and σπέρμα / sperma ('seed'), meaning those plants that produce their seeds enclosed within a fruit. They are by far the most diverse group of land plants with 64 orders, 416 families, approximately 13,000 known genera and 300,000 known species. Angiosperms were formerly called Magnoliophyta.

Gymnosperm

Gymnosperm

The gymnosperms are a group of seed-producing plants that includes conifers, cycads, Ginkgo, and gnetophytes, forming the clade Gymnospermae. The term gymnosperm comes from the composite word in Greek: γυμνόσπερμος, literally meaning 'naked seeds'. The name is based on the unenclosed condition of their seeds. The non-encased condition of their seeds contrasts with the seeds and ovules of flowering plants (angiosperms), which are enclosed within an ovary. Gymnosperm seeds develop either on the surface of scales or leaves, which are often modified to form cones, or on their own as in yew, Torreya, Ginkgo. Gymnosperm lifecycles involve alternation of generations. They have a dominant diploid sporophyte phase and a reduced haploid gametophyte phase which is dependent on the sporophytic phase. The term "gymnosperm" is often used in paleobotany to refer to all non-angiosperm seed plants. In that case, to specify the modern monophyletic group of gymnosperms, the term Acrogymnospermae is sometimes used.

Cycad

Cycad

Cycads are seed plants that typically have a stout and woody (ligneous) trunk with a crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants of a species are either male or female. Cycads vary in size from having trunks only a few centimeters to several meters tall. They typically grow very slowly and live very long. Because of their superficial resemblance, they are sometimes mistaken for palms or ferns, but they are not closely related to either group.

Gnetophyta

Gnetophyta

Gnetophyta is a division of plants, grouped within the gymnosperms, that consists of some 70 species across the three relict genera: Gnetum, Welwitschia, and Ephedra. Fossilized pollen attributed to a close relative of Ephedra has been dated as far back as the Early Cretaceous. Though diverse in the Early Cretaceous, only three families, each containing a single genus, are still alive today. The primary difference between gnetophytes and other gymnosperms is the presence of vessel elements, system of small tubes (Xylem) that transport water within the plant, similar to those found in flowering plants. Because of this, gnetophytes were once thought to be the closest gymnosperm relatives to flowering plants, but more recent molecular studies have brought this hypothesis into question.

Bennettitales

Bennettitales

Bennettitales is an extinct order of seed plants that first appeared in the Permian period and became extinct in most areas toward the end of the Cretaceous. Bennettitales were amongst the most common seed plants of the Mesozoic, and had morphologies including shrub and cycad-like forms. The foliage of bennettitaleans is superficially nearly indistinguishable from that of cycads, but they are distinguished from cycads by their more complex flower-like reproductive organs, at least some of which were likely pollinated by insects.

Corystospermaceae

Corystospermaceae

Corystosperms are a group of extinct seed plants belonging to the family Corystospermaceae assigned to the order Corystospermales or Umkomasiales. They were first described based on fossils collected by Hamshaw Thomas from the Burnera Waterfall locality near the Umkomaas River of South Africa. Corystosperms are typified by a group of plants that bore Dicroidium leaves, Umkomasia ovulate structures and Pteruchus pollen organs, that were widespread over Gondwana during the Middle and Late Triassic. Other fossil Mesozoic seed plants with similar reproductive structures have also sometimes been included within the "corystosperm" concept sensu lato, such as the "doyleoids" from the Early Cretaceous of North America and Asia. A potential corystosperm, the leaf fossil Komlopteris cenozoicus, is known from the Eocene of Tasmania, at least 13 million years after the Cretaceous–Paleogene extinction event.

Caytoniales

Caytoniales

The Caytoniales are an extinct order of seed plants known from fossils collected throughout the Mesozoic Era, around 252 to 66 million years ago. They are regarded as seed ferns because they are seed-bearing plants with fern-like leaves. Although at one time considered angiosperms because of their berry-like cupules, that hypothesis was later disproven. Nevertheless, some authorities consider them likely ancestors or close relatives of angiosperms. The origin of angiosperms remains unclear, and they cannot be linked with any known seed plants groups with certainty.

Crown group

Crown group

In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. It is thus a way of defining a clade, a group consisting of a species and all its extant or extinct descendants. For example, Neornithes (birds) can be defined as a crown group, which includes the most recent common ancestor of all modern birds, and all of its extant or extinct descendants.

Eudicots

Eudicots

The eudicots, Eudicotidae, or eudicotyledons are a clade of flowering plants mainly characterized by having two seed leaves upon germination. The term derives from Dicotyledons.

Barremian

Barremian

The Barremian is an age in the geologic timescale between 129.4 ± 1.5 Ma and 121.4 ± 1.0 Ma). It is a subdivision of the Early Cretaceous Epoch. It is preceded by the Hauterivian and followed by the Aptian Stage.

La Huérguina Formation

La Huérguina Formation

The La Huérguina Formation is a geological formation in Spain whose strata date back to the Barremian stage of the Early Cretaceous. Las Hoyas is a Konservat-Lagerstätte within the formation, located near the city of Cuenca, Spain. The site is mostly known for its exquisitely preserved dinosaurs, especially enantiornithines. The lithology of the formation mostly consists of lacustarine limestone deposited in a freshwater wetland environment.

Archaefructus

Archaefructus

Archaefructus is an extinct genus of herbaceous aquatic seed plants with three known species. Fossil material assigned to this genus originates from the Yixian Formation in northeastern China, originally dated as late Jurassic but now thought to be approximately 125 million years old, or early Cretaceous in age. Even with its revised age, Archaefructus has been proposed to be one of the earliest known genera of flowering plants.

Terrestrial fauna

On land, mammals were generally small sized, but a very relevant component of the fauna, with cimolodont multituberculates outnumbering dinosaurs in some sites.[55] Neither true marsupials nor placentals existed until the very end,[56] but a variety of non-marsupial metatherians and non-placental eutherians had already begun to diversify greatly, ranging as carnivores (Deltatheroida), aquatic foragers (Stagodontidae) and herbivores (Schowalteria, Zhelestidae). Various "archaic" groups like eutriconodonts were common in the Early Cretaceous, but by the Late Cretaceous northern mammalian faunas were dominated by multituberculates and therians, with dryolestoids dominating South America.

The apex predators were archosaurian reptiles, especially dinosaurs, which were at their most diverse stage. Avians such as the ancestors of modern-day birds also diversified. They inhabited every continent, and were even found in cold polar latitudes. Pterosaurs were common in the early and middle Cretaceous, but as the Cretaceous proceeded they declined for poorly understood reasons (once thought to be due to competition with early birds, but now it is understood avian adaptive radiation is not consistent with pterosaur decline[57]). By the end of the period only three highly specialized families remained; Pteranodontidae, Nyctosauridae, and Azhdarchidae.[58]

The Liaoning lagerstätte (Yixian Formation) in China is an important site, full of preserved remains of numerous types of small dinosaurs, birds and mammals, that provides a glimpse of life in the Early Cretaceous. The coelurosaur dinosaurs found there represent types of the group Maniraptora, which includes modern birds and their closest non-avian relatives, such as dromaeosaurs, oviraptorosaurs, therizinosaurs, troodontids along with other avialans. Fossils of these dinosaurs from the Liaoning lagerstätte are notable for the presence of hair-like feathers.

Insects diversified during the Cretaceous, and the oldest known ants, termites and some lepidopterans, akin to butterflies and moths, appeared. Aphids, grasshoppers and gall wasps appeared.[59]

Rhynchocephalians

Derasmosaurus pietraroiae, a rhyncocephalian from the late Early Cretaceous of Italy
Derasmosaurus pietraroiae, a rhyncocephalian from the late Early Cretaceous of Italy

Rhynchocephalians (which today only includes the Tuatara) disappeared from North America and Europe after the Early Cretaceous,[60] and were absent from North Africa[61] and northern South America[62] by the early Late Cretaceous. The cause of the decline of Rhynchocephalia remains unclear, but has often been suggested to be due to competition with advanced lizards and mammals.[63] They appear to have remained diverse in high-latitude southern South America during the Late Cretaceous, where lizards remained rare, with their remains outnumbering terrestrial lizards 200:1.[61]

Choristodera

Philydrosaurus, a choristodere from the Early Cretaceous of China
Philydrosaurus, a choristodere from the Early Cretaceous of China

Choristoderes, a group of freshwater aquatic reptiles that first appeared during the preceding Jurassic, underwent a major evolutionary radiation in Asia during the Early Cretaceous, which represents the high point of choristoderan diversity, including long necked forms such as Hyphalosaurus and the first records of the gharial-like Neochoristodera, which appear to have evolved in the regional absence of aquatic neosuchian crocodyliformes. During the Late Cretaceous the neochoristodere Champsosaurus was widely distributed across western North America.[64]

Discover more about Terrestrial fauna related topics

Mammal

Mammal

A mammal is a vertebrate animal of the class Mammalia. Mammals are characterized by the presence of milk-producing mammary glands for feeding their young, a neocortex region of the brain, fur or hair, and three middle ear bones. These characteristics distinguish them from reptiles and birds, which they diverged from in the Carboniferous Period over 300 million years ago. Around 6,400 extant species of mammals have been described and divided into 29 orders.

Marsupial

Marsupial

Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a pouch. Living marsupials include opossums, Tasmanian devils, kangaroos, koalas, wombats, wallabies, and bandicoots among others, while many extinct species, such as the thylacine, are also known.

Metatheria

Metatheria

Metatheria is a mammalian clade that includes all mammals more closely related to marsupials than to placentals. First proposed by Thomas Henry Huxley in 1880, it is a more inclusive group than the marsupials; it contains all marsupials as well as many extinct non-marsupial relatives.

Deltatheroida

Deltatheroida

Deltatheroida is an extinct group of basal metatherians that were distantly related to modern marsupials. The majority of known members of the group lived in the Cretaceous; one species, Gurbanodelta kara, is known from the late Paleocene (Gashatan) of China. Their fossils are restricted to Central Asia and North America. This order can be defined as all metatherians closer to Deltatheridium than to Marsupialia.

Stagodontidae

Stagodontidae

Stagodontidae is an extinct family of carnivorous metatherian mammals that inhabited North America and Europe during the late Cretaceous, and possibly to the Eocene in South America.

Schowalteria

Schowalteria

Schowalteria is a genus of extinct mammal from the Cretaceous of Canada. It is the earliest known representative of Taeniodonta, a specialised lineage of non-placental eutherian mammals otherwise found in Paleocene and Eocene deposits. It is notable for its large size, being among the largest of Mesozoic mammals, as well as its speciation towards herbivory, which in some respects exceeds that of its later relatives.

Theria

Theria

Theria is a subclass of mammals amongst the Theriiformes. Theria includes the eutherians and the metatherians but excludes the egg-laying monotremes and various extinct mammals evolving prior to the common ancestor of placentals and marsupials.

South America

South America

South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southern subregion of a single continent called America.

Archosaur

Archosaur

Archosauria is a clade of diapsids, with birds and crocodilians as the only living representatives. Archosaurs are broadly classified as reptiles, in the cladistic sense of the term, which includes birds. Extinct archosaurs include non-avian dinosaurs, pterosaurs, and extinct relatives of crocodilians. Modern paleontologists define Archosauria as a crown group that includes the most recent common ancestor of living birds and crocodilians, and all of its descendants. The base of Archosauria splits into two clades: Pseudosuchia, which includes crocodilians and their extinct relatives, and Avemetatarsalia, which includes birds and their extinct relatives.

Reptile

Reptile

Reptiles, as most commonly defined, are the animals in the class Reptilia, a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates and rhynchocephalians (tuatara). As of March 2022, the Reptile Database includes about 11,700 species. In the traditional Linnaean classification system, birds are considered a separate class to reptiles. However, crocodilians are more closely related to birds than they are to other living reptiles, and so modern cladistic classification systems include birds within Reptilia, redefining the term as a clade. Other cladistic definitions abandon the term reptile altogether in favor of the clade Sauropsida, which refers to all amniotes more closely related to modern reptiles than to mammals. The study of the traditional reptile orders, customarily in combination with the study of modern amphibians, is called herpetology.

Dinosaur

Dinosaur

Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 245 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is a subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201.3 mya and their dominance continued throughout the Jurassic and Cretaceous periods. The fossil record shows that birds are feathered dinosaurs, having evolved from earlier theropods during the Late Jurassic epoch, and are the only dinosaur lineage known to have survived the Cretaceous–Paleogene extinction event approximately 66 mya. Dinosaurs can therefore be divided into avian dinosaurs—birds—and the extinct non-avian dinosaurs, which are all dinosaurs other than birds.

Pterosaur

Pterosaur

Pterosaurs is an extinct clade of flying reptiles in the order Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous. 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 ankles to a dramatically lengthened fourth finger.

Marine fauna

In the seas, rays, modern sharks and teleosts became common.[65] Marine reptiles included ichthyosaurs in the early and mid-Cretaceous (becoming extinct during the late Cretaceous Cenomanian-Turonian anoxic event), plesiosaurs throughout the entire period, and mosasaurs appearing in the Late Cretaceous. Sea turtles in the form of Cheloniidae and Panchelonioidea lived during the period and survived the extinction event. Panchelonioidea is today represented by a single species; the leatherback sea turtle.

Baculites, an ammonite genus with a straight shell, flourished in the seas along with reef-building rudist clams. The Hesperornithiformes were flightless, marine diving birds that swam like grebes. Globotruncanid Foraminifera and echinoderms such as sea urchins and starfish (sea stars) thrived. Thylacocephala, a class of crustaceans, went extinct in the Late Cretaceous. The first radiation of the diatoms (generally siliceous shelled, rather than calcareous) in the oceans occurred during the Cretaceous; freshwater diatoms did not appear until the Miocene.[59] The Cretaceous was also an important interval in the evolution of bioerosion, the production of borings and scrapings in rocks, hardgrounds and shells.

Discover more about Marine fauna related topics

Batoidea

Batoidea

Batoidea is a superorder of cartilaginous fishes, commonly known as rays. They and their close relatives, the sharks, comprise the subclass Elasmobranchii. Rays are the largest group of cartilaginous fishes, with well over 600 species in 26 families. Rays are distinguished by their flattened bodies, enlarged pectoral fins that are fused to the head, and gill slits that are placed on their ventral surfaces.

Shark

Shark

Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorpha and are the sister group to the Batoidea. Some sources extend the term "shark" as an informal category including extinct members of Chondrichthyes with a shark-like morphology, such as hybodonts and xenacanths. Shark-like chondrichthyans such as Cladoselache and Doliodus first appeared in the Devonian Period, though some fossilized chondrichthyan-like scales are as old as the Late Ordovician. The oldest modern sharks (selachians) are known from the Early Jurassic, about 200 Ma.

Ichthyosaur

Ichthyosaur

Ichthyosaurs are large extinct marine reptiles. Ichthyosaurs belong to the order known as Ichthyosauria or Ichthyopterygia.

Plesiosaur

Plesiosaur

The Plesiosauria or Plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia.

Mosasaur

Mosasaur

Mosasaurs comprise a group of extinct, large marine reptiles from the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. They belong to the order Squamata, which includes lizards and snakes.

Cheloniidae

Cheloniidae

Cheloniidae is a family of typically large marine turtles that are characterised by their common traits such as, having a flat streamlined wide and rounded shell and almost paddle-like flippers for their forelimbs. They are the only sea turtles to have stronger front limbs than back limbs. The six species that make up this family are: the green sea turtle, loggerhead sea turtle, olive ridley sea turtle, hawksbill sea turtle, flatback sea turtle and the Kemp's ridley sea turtle.

Panchelonioidea

Panchelonioidea

Panchelonioidea is a clade of marine turtles that includes the sea turtles and related taxa.

Leatherback sea turtle

Leatherback sea turtle

The leatherback sea turtle, sometimes called the lute turtle or leathery turtle or simply the luth, is the largest of all living turtles and the heaviest non-crocodilian reptile, reaching lengths of up to 1.8 metres and weights of 500 kilograms (1,100 lb). It is the only living species in the genus Dermochelys and family Dermochelyidae. It can easily be differentiated from other modern sea turtles by its lack of a bony shell; instead, its carapace is covered by oily flesh and flexible, leather-like skin, for which it is named.

Baculites

Baculites

Baculites is an extinct genus of cephalopods with a nearly straight shell, included in the heteromorph ammonites. The genus, which lived worldwide throughout most of the Late Cretaceous, and which briefly survived the K-Pg mass extinction event, was named by Lamarck in 1799.

Grebe

Grebe

Grebes are aquatic diving birds in the order Podicipediformes. Grebes are widely distributed freshwater birds, with some species also found in marine habitats during migration and winter. Some flightless species exist as well, most notably in stable lakes. The order contains a single family, the Podicipedidae, which includes 22 species in six extant genera. Although, superficially, they resemble other diving birds such as loons and coots, they are most closely related to flamingos, as supported by morphological, molecular and paleontological data. Many species are monogamous and are known for their courtship displays, with the pair performing synchronized dances across the water's surface. The birds build floating vegetative nests where they lay several eggs. About a third of the world's grebes are listed at various levels of conservation concerns—the biggest threats including habitat loss, the introduction of invasive predatory fish and human poaching. As such, three species have gone extinct.

Foraminifera

Foraminifera

Foraminifera are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly an external shell of diverse forms and materials. Tests of chitin are believed to be the most primitive type. Most foraminifera are marine, the majority of which live on or within the seafloor sediment, while a smaller number float in the water column at various depths, which belong to the suborder Globigerinina. Fewer are known from freshwater or brackish conditions, and some very few (nonaquatic) soil species have been identified through molecular analysis of small subunit ribosomal DNA.

Diatom

Diatom

A diatom is any member of a large group comprising several genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of the Earth's biomass: they generate about 20 to 50 percent of the oxygen produced on the planet each year, take in over 6.7 billion metric tons of silicon each year from the waters in which they live, and constitute nearly half of the organic material found in the oceans. The shells of dead diatoms can reach as much as a half-mile deep on the ocean floor, and the entire Amazon basin is fertilized annually by 27 million tons of diatom shell dust transported by transatlantic winds from the African Sahara, much of it from the Bodélé Depression, which was once made up of a system of fresh-water lakes.

Source: "Cretaceous", Wikipedia, Wikimedia Foundation, (2023, March 27th), https://en.wikipedia.org/wiki/Cretaceous.

Enjoying Wikiz?

Enjoying Wikiz?

Get our FREE extension now!

See also
References

Citations

  1. ^ International Commission on Stratigraphy. "ICS - Chart/Time Scale". www.stratigraphy.org.
  2. ^ "Cretaceous". Dictionary.com Unabridged (Online). n.d.
  3. ^ d’Halloy, d’O., J.-J. (1822). "Observations sur un essai de carte géologique de la France, des Pays-Bas, et des contrées voisines" [Observations on a trial geological map of France, the Low Countries, and neighboring countries]. Annales des Mines. 7: 353–376.{{cite journal}}: CS1 maint: multiple names: authors list (link) From page 373: "La troisième, qui correspond à ce qu'on a déja appelé formation de la craie, sera désigné par le nom de terrain crétacé." (The third, which corresponds to what was already called the "chalk formation", will be designated by the name "chalky terrain".)
  4. ^ Sovetskaya Enciklopediya [Great Soviet Encyclopedia] (in Russian) (3rd ed.). Moscow: Sovetskaya Enciklopediya. 1974. vol. 16, p. 50.
  5. ^ Glossary of Geology (3rd ed.). Washington, D.C.: American Geological Institute. 1972. p. 165.
  6. ^ Ogg, J.G.; Hinnov, L.A.; Huang, C. (2012), "Cretaceous", The Geologic Time Scale, Elsevier, pp. 793–853, doi:10.1016/b978-0-444-59425-9.00027-5, ISBN 978-0-444-59425-9, retrieved 2021-01-08
  7. ^ WIMBLEDON, William A.P. (2017-12-27). "Developments with fixing a Tithonian/Berriasian (J/K) boundary". Volumina Jurassica (1): 0. doi:10.5604/01.3001.0010.7467. ISSN 1731-3708.
  8. ^ Wimbledon, William A.P.; Rehakova, Daniela; Svobodová, Andrea; Schnabl, Petr; Pruner, Petr; Elbra, Tiiu; Šifnerová, Kristýna; Kdýr, Šimon; Frau, Camille; Schnyder, Johann; Galbrun, Bruno (2020-02-11). "Fixing a J/K boundary: A comparative account of key Tithonian–Berriasian profiles in the departments of Drôme and Hautes-Alpes, France". Geologica Carpathica. 71 (1). doi:10.31577/GeolCarp.71.1.3.
  9. ^ Frau, Camille; Bulot, Luc G.; Reháková, Daniela; Wimbledon, William A.P.; Ifrim, Christina (November 2016). "Revision of the ammonite index species Berriasella jacobi Mazenot, 1939 and its consequences for the biostratigraphy of the Berriasian Stage". Cretaceous Research. 66: 94–114. doi:10.1016/j.cretres.2016.05.007.
  10. ^ Cohen, K.M., Finney, S.C., Gibbard, P.L. & Fan, J.-X. (2013; updated) The ICS International Chronostratigraphic Chart. Episodes 36: 199-204.
  11. ^ Lena, Luis; López-Martínez, Rafael; Lescano, Marina; Aguire-Urreta, Beatriz; Concheyro, Andrea; Vennari, Verónica; Naipauer, Maximiliano; Samankassou, Elias; Pimentel, Márcio; Ramos, Victor A.; Schaltegger, Urs (2019-01-08). "High-precision U–Pb ages in the early Tithonian to early Berriasian and implications for the numerical age of the Jurassic–Cretaceous boundary". Solid Earth. 10 (1): 1–14. Bibcode:2019SolE...10....1L. doi:10.5194/se-10-1-2019. ISSN 1869-9529. S2CID 135382485.
  12. ^ Vennari, Verónica V.; Lescano, Marina; Naipauer, Maximiliano; Aguirre-Urreta, Beatriz; Concheyro, Andrea; Schaltegger, Urs; Armstrong, Richard; Pimentel, Marcio; Ramos, Victor A. (2014). "New constraints on the Jurassic–Cretaceous boundary in the High Andes using high-precision U–Pb data". Gondwana Research. 26 (1): 374–385. Bibcode:2014GondR..26..374V. doi:10.1016/j.gr.2013.07.005.
  13. ^ Renne, Paul R.; et al. (2013). "Time scales of critical events around the Cretaceous-Paleogene boundary". Science. 339 (6120): 684–688. Bibcode:2013Sci...339..684R. doi:10.1126/science.1230492. PMID 23393261. S2CID 6112274.
  14. ^ a b c MacLeod, N; Rawson, PF; Forey, PL; Banner, FT; Boudagher-Fadel, MK; Bown, PR; Burnett, JA; et al. (1997). "The Cretaceous–Tertiary biotic transition". Journal of the Geological Society. 154 (2): 265–292. Bibcode:1997JGSoc.154..265M. doi:10.1144/gsjgs.154.2.0265. S2CID 129654916.
  15. ^ Wilf, P; Johnson KR (2004). "Land plant extinction at the end of the Cretaceous: a quantitative analysis of the North Dakota megafloral record". Paleobiology. 30 (3): 347–368. doi:10.1666/0094-8373(2004)0302.0.CO;2. S2CID 33880578.
  16. ^ Kauffman, E (2004). "Mosasaur Predation on Upper Cretaceous Nautiloids and Ammonites from the United States Pacific Coast" (PDF). PALAIOS. 19 (1): 96–100. Bibcode:2004Palai..19...96K. doi:10.1669/0883-1351(2004)0192.0.CO;2. S2CID 130690035.
  17. ^ a b Shehan, P; Hansen, TA (1986). "Detritus feeding as a buffer to extinction at the end of the Cretaceous". Geology. 14 (10): 868–870. Bibcode:1986Geo....14..868S. doi:10.1130/0091-7613(1986)142.0.CO;2.
  18. ^ Aberhan, M; Weidemeyer, S; Kieesling, W; Scasso, RA & Medina, FA (2007). "Faunal evidence for reduced productivity and uncoordinated recovery in Southern Hemisphere Cretaceous–Paleogene boundary sections". Geology. 35 (3): 227–230. Bibcode:2007Geo....35..227A. doi:10.1130/G23197A.1.
  19. ^ Sheehan, PM; Fastovsky, DE (1992). "Major extinctions of land-dwelling vertebrates at the Cretaceous–Paleogene boundary, eastern Montana". Geology. 20 (6): 556–560. Bibcode:1992Geo....20..556S. doi:10.1130/0091-7613(1992)0202.3.CO;2.
  20. ^ a b Stanley 1999, pp. 481–482.
  21. ^ Weimar, R.J. (1960). "Upper Cretaceous Stratigraphy, Rocky Mountain Area". AAPG Bulletin. 44: 1–20. doi:10.1306/0BDA5F6F-16BD-11D7-8645000102C1865D.
  22. ^ Brownstein, Chase D (2018). "The biogeography and ecology of the Cretaceous non-avian dinosaurs of Appalachia". Palaeontologia Electronica. 21: 1–56. doi:10.26879/801.
  23. ^ Moussavou, Benjamin Musavu (25 September 2015). "Bivalves (Mollusca) from the Coniacian-Santonian Anguille Formation from Cap Esterias, Northern Gabon, with notes on paleoecology and paleobiogeography". Geodiversitas. 37 (3): 315–324. doi:10.5252/g2015n3a2. S2CID 128803778. Retrieved 28 December 2022.
  24. ^ Dixon, Dougal; Benton, M J; Kingsley, Ayala; Baker, Julian (2001). Atlas of Life on Earth. New York: Barnes & Noble Books. p. 215. ISBN 9780760719572.
  25. ^ Stanley 1999, p. 280.
  26. ^ Stanley 1999, pp. 279–281.
  27. ^ Wang, Jing-Yu; Li, Xiang-Hui; Li, Li-Qin; Wang, Yong-Dong (September 2022). "Cretaceous climate variations indicated by palynoflora in South China". Palaeoworld. 31 (3): 507–520. doi:10.1016/j.palwor.2021.11.001. S2CID 243963376. Retrieved 11 December 2022.
  28. ^ Kazlev, M.Alan. "Palaeos Mesozoic: Cretaceous: The Berriasian Age". Palaeos.com. Archived from the original on 20 December 2010. Retrieved 18 October 2017.
  29. ^ a b c d e Scotese, Christopher R.; Song, Haijun; Mills, Benjamin J. W.; van der Meer, Douwe G. (April 2021). "Phanerozoic paleotemperatures: The earth's changing climate during the last 540 million years". Earth-Science Reviews. 215: 103503. Bibcode:2021ESRv..21503503S. doi:10.1016/j.earscirev.2021.103503. ISSN 0012-8252. S2CID 233579194. Archived from the original on 8 January 2021. Retrieved 18 March 2023.
  30. ^ Rodríguez-López, Juan Pedro; Liesa, Carlos L.; Pardo, Gonzalo; Meléndez, Nieves; Soria, Ana R.; Skilling, Ian (15 June 2016). "Glacial dropstones in the western Tethys during the late Aptian–early Albian cold snap: Palaeoclimate and palaeogeographic implications for the mid-Cretaceous". Palaeogeography, Palaeoclimatology, Palaeoecology. 452: 11–27. Bibcode:2016PPP...452...11R. doi:10.1016/j.palaeo.2016.04.004. Retrieved 19 March 2023.
  31. ^ Laugié, Marie; Donnadieu, Yannick; Ladant, Jean-Baptiste; Green, J. A. Mattias; Bopp, Laurent; Raisson, François (5 June 2020). "Stripping back the modern to reveal the Cenomanian–Turonian climate and temperature gradient underneath". Climate of the Past. 16 (3): 953–971. Bibcode:2020CliPa..16..953L. doi:10.5194/cp-16-953-2020. S2CID 219918773. Retrieved 19 March 2023.
  32. ^ Pucéat, Emmanuelle; Lécuyer, Christophe; Sheppard, Simon M. F.; Dromart, Gilles; Reboulet, Stéphane; Grandjean, Patricia (3 May 2003). "Thermal evolution of Cretaceous Tethyan marine waters inferred from oxygen isotope composition of fish tooth enamels". Paleoceanography and Paleoclimatology. 18 (2): 1029. Bibcode:2003PalOc..18.1029P. doi:10.1029/2002PA000823. Retrieved 17 March 2023.
  33. ^ "Warmer than a Hot Tub: Atlantic Ocean Temperatures Much Higher in the Past". phys.org. Retrieved 2023-03-27.
  34. ^ Skinner & Porter 1995, p. 557.
  35. ^ a b c Pucéat, Emmanuelle; Lécuyer, Christophe; Donnadieu, Yannick; Naveau, Philippe; Cappetta, Henri; Ramstein, Gilles; Huber, Brian T.; Kriwet, Juergen (1 February 2007). "Fish tooth δ18O revising Late Cretaceous meridional upper ocean water temperature gradients". Geology. 35 (2): 107–110. Bibcode:2007Geo....35..107P. doi:10.1130/G23103A.1. Retrieved 19 March 2023.
  36. ^ Petrizzo, Maria Rose; MacLeod, Kenneth G.; Watkins, David K.; Wolfgring, Erik; Huber, Brian T. (27 December 2021). "Late Cretaceous Paleoceanographic Evolution and the Onset of Cooling in the Santonian at Southern High Latitudes (IODP Site U1513, SE Indian Ocean)". Paleoceanography and Paleoclimatology. 37 (1): e2021PA004353. doi:10.1029/2021PA004353. PMC 9303530. PMID 35910494.
  37. ^ O'Connor, Lauren K.; Robinson, Stuart A.; Naafs, B. David A.; Jenkyns, Hugh C.; Henson, Sam; Clarke, Madeleine; Pancost, Richard D. (27 February 2019). "Late Cretaceous Temperature Evolution of the Southern High Latitudes: A TEX86 Perspective". Paleoceanography and Paleoclimatology. 34 (4): 436–454. Bibcode:2019PaPa...34..436O. doi:10.1029/2018PA003546. S2CID 134095694. Retrieved 19 March 2023.
  38. ^ Wang, Chengshan; Scott, Robert W.; Wan, Xiaoqiao; Graham, Stephan A.; Huang, Yongjian; Wang, Pujun; Wu, Huaichun; Dean, Walter E.; Zhang, Laiming (November 2013). "Late Cretaceous climate changes recorded in Eastern Asian lacustrine deposits and North American Epieric sea strata". Earth-Science Reviews. 126: 275–299. Bibcode:2013ESRv..126..275W. doi:10.1016/j.earscirev.2013.08.016. Retrieved 19 March 2023.
  39. ^ Nordt, Lee; Atchley, Stacy; Dworkin, Steve (December 2003). "Terrestrial Evidence for Two Greenhouse Events in the Latest Cretaceous". GSA Today. Vol. 13, no. 12. p. 4. doi:10.1130/1052-5173(2003)0132.0.CO;2.
  40. ^ Foulger, G.R. (2010). Plates vs. Plumes: A Geological Controversy. Wiley-Blackwell. ISBN 978-1-4051-6148-0.
  41. ^ Stanley 1999, p. 480–482.
  42. ^ Bornemann, Norris RD; Friedrich, O; Beckmann, B; Schouten, S; Damsté, JS; Vogel, J; Hofmann, P; Wagner, T (Jan 2008). "Isotopic evidence for glaciation during the Cretaceous supergreenhouse". Science. 319 (5860): 189–92. Bibcode:2008Sci...319..189B. doi:10.1126/science.1148777. PMID 18187651. S2CID 206509273. Retrieved 18 March 2023.
  43. ^ Huber, Brian T.; MacLeod, Kenneth G.; Watkins, David K.; Coffin, Millard F. (2018-08-01). "The rise and fall of the Cretaceous Hot Greenhouse climate". Global and Planetary Change. 167: 1–23. Bibcode:2018GPC...167....1H. doi:10.1016/j.gloplacha.2018.04.004. hdl:1912/10514. ISSN 0921-8181. S2CID 135295956. Retrieved 18 March 2023.
  44. ^ the Science Team of Expedition PS104; Klages, Johann P.; Salzmann, Ulrich; Bickert, Torsten; Hillenbrand, Claus-Dieter; Gohl, Karsten; Kuhn, Gerhard; Bohaty, Steven M.; Titschack, Jürgen; Müller, Juliane; Frederichs, Thomas (April 2020). "Temperate rainforests near the South Pole during peak Cretaceous warmth". Nature. 580 (7801): 81–86. Bibcode:2020Natur.580...81K. doi:10.1038/s41586-020-2148-5. ISSN 0028-0836. PMID 32238944. S2CID 214736648. Retrieved 18 March 2023.
  45. ^ Alley, N. F.; Frakes, L. A. (2003). "First known Cretaceous glaciation: Livingston Tillite Member of the Cadna‐owie Formation, South Australia". Australian Journal of Earth Sciences. 50 (2): 139–144. Bibcode:2003AuJES..50..139A. doi:10.1046/j.1440-0952.2003.00984.x. S2CID 128739024.
  46. ^ Frakes, L. A.; Francis, J. E. (1988). "A guide to Phanerozoic cold polar climates from high-latitude ice-rafting in the Cretaceous". Nature. 333 (6173): 547–549. Bibcode:1988Natur.333..547F. doi:10.1038/333547a0. S2CID 4344903.
  47. ^ a b c Coiro, Mario; Doyle, James A.; Hilton, Jason (July 2019). "How deep is the conflict between molecular and fossil evidence on the age of angiosperms?". New Phytologist. 223 (1): 83–99. doi:10.1111/nph.15708. ISSN 0028-646X. PMID 30681148.
  48. ^ Brenner, G.J. (1996). "Evidence for the earliest stage of angiosperm pollen evolution: a paleoequatorial section from Israel". In Taylor, D.W.; Hickey, L.J. (eds.). Flowering plant origin, evolution & phylogeny. New York: Chapman & Hall. pp. 91–115. doi:10.1007/978-0-585-23095-5_5. ISBN 978-0-585-23095-5.
  49. ^ Trevisan L. 1988. Angiospermous pollen (monosulcate–trichotomosulcate phase) from the very early Lower Cretaceous of southern Tuscany (Italy): some aspects. 7th International Palynological Congress Abstracts Volume. Brisbane, Australia: University of Queensland, 165.
  50. ^ Condamine, Fabien L.; Silvestro, Daniele; Koppelhus, Eva B.; Antonelli, Alexandre (2020-11-17). "The rise of angiosperms pushed conifers to decline during global cooling". Proceedings of the National Academy of Sciences. 117 (46): 28867–28875. Bibcode:2020PNAS..11728867C. doi:10.1073/pnas.2005571117. ISSN 0027-8424. PMC 7682372. PMID 33139543.
  51. ^ Wu, Yan; You, Hai-Lu; Li, Xiao-Qiang (2018-09-01). "Dinosaur-associated Poaceae epidermis and phytoliths from the Early Cretaceous of China". National Science Review. 5 (5): 721–727. doi:10.1093/nsr/nwx145. ISSN 2095-5138.
  52. ^ Prasad, V.; Strömberg, C. a. E.; Leaché, A. D.; Samant, B.; Patnaik, R.; Tang, L.; Mohabey, D. M.; Ge, S.; Sahni, A. (2011-09-20). "Late Cretaceous origin of the rice tribe provides evidence for early diversification in Poaceae". Nature Communications. 2 (1): 480. Bibcode:2011NatCo...2..480P. doi:10.1038/ncomms1482. ISSN 2041-1723. PMID 21934664.
  53. ^ Jud, Nathan A.; D’Emic, Michael D.; Williams, Scott A.; Mathews, Josh C.; Tremaine, Katie M.; Bhattacharya, Janok (September 2018). "A new fossil assemblage shows that large angiosperm trees grew in North America by the Turonian (Late Cretaceous)". Science Advances. 4 (9): eaar8568. Bibcode:2018SciA....4.8568J. doi:10.1126/sciadv.aar8568. ISSN 2375-2548. PMC 6157959. PMID 30263954.
  54. ^ Regalado, Ledis; Schmidt, Alexander R.; Müller, Patrick; Niedermeier, Lisa; Krings, Michael; Schneider, Harald (July 2019). "Heinrichsia cheilanthoides gen. et sp. nov., a fossil fern in the family Pteridaceae (Polypodiales) from the Cretaceous amber forests of Myanmar". Journal of Systematics and Evolution. 57 (4): 329–338. doi:10.1111/jse.12514. ISSN 1674-4918.
  55. ^ Kielan-Jaworowska, Zofia; Cifelli, Richard L.; Luo, Zhe-Xi (2005). Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure. Columbia University Press. p. 299. ISBN 9780231119184.
  56. ^ Halliday, Thomas John Dixon; Upchurch, Paul; Goswami, Anjali (29 June 2016). "Eutherians experienced elevated evolutionary rates in the immediate aftermath of the Cretaceous–Palaeogene mass extinction". Proc. R. Soc. B. 283 (1833): 20153026. doi:10.1098/rspb.2015.3026. PMC 4936024. PMID 27358361.
  57. ^ Wilton, Mark P. (2013). Pterosaurs: Natural History, Evolution, Anatomy. Princeton University Press. ISBN 978-0691150611.
  58. ^ Longrich, Nicholas R.; Martill, David M.; Andres, Brian (2018-03-13). "Late Maastrichtian pterosaurs from North Africa and mass extinction of Pterosauria at the Cretaceous-Paleogene boundary". PLOS Biology. 16 (3): e2001663. doi:10.1371/journal.pbio.2001663. ISSN 1545-7885. PMC 5849296. PMID 29534059.
  59. ^ a b "Life of the Cretaceous". www.ucmp.Berkeley.edu. Retrieved 18 October 2017.
  60. ^ Cleary TJ, Benson RB, Evans SE, Barrett PM (March 2018). "Lepidosaurian diversity in the Mesozoic-Palaeogene: the potential roles of sampling biases and environmental drivers". Royal Society Open Science. 5 (3): 171830. Bibcode:2018RSOS....571830C. doi:10.1098/rsos.171830. PMC 5882712. PMID 29657788.
  61. ^ a b Apesteguía S, Daza JD, Simões TR, Rage JC (September 2016). "The first iguanian lizard from the Mesozoic of Africa". Royal Society Open Science. 3 (9): 160462. Bibcode:2016RSOS....360462A. doi:10.1098/rsos.160462. PMC 5043327. PMID 27703708.
  62. ^ Simões TR, Wilner E, Caldwell MW, Weinschütz LC, Kellner AW (August 2015). "A stem acrodontan lizard in the Cretaceous of Brazil revises early lizard evolution in Gondwana". Nature Communications. 6 (1): 8149. Bibcode:2015NatCo...6.8149S. doi:10.1038/ncomms9149. PMC 4560825. PMID 26306778.
  63. ^ Jones ME, Tennyson AJ, Worthy JP, Evans SE, Worthy TH (April 2009). "A sphenodontine (Rhynchocephalia) from the Miocene of New Zealand and palaeobiogeography of the tuatara (Sphenodon)". Proceedings. Biological Sciences. 276 (1660): 1385–90. doi:10.1098/rspb.2008.1785. PMC 2660973. PMID 19203920.
  64. ^ Matsumoto R, Evans SE (2010). "Choristoderes and the freshwater assemblages of Laurasia". Journal of Iberian Geology. 36 (2): 253–274. doi:10.5209/rev_jige.2010.v36.n2.11.
  65. ^ "EVOLUTIONARY/GEOLOGICAL TIMELINE v1.0". www.TalkOrigins.org. Retrieved 18 October 2017.

Bibliography

External links

The content of this page is based on the Wikipedia article written by contributors..
The text is available under the Creative Commons Attribution-ShareAlike Licence & the media files are available under their respective licenses; additional terms may apply.
By using this site, you agree to the Terms of Use & Privacy Policy.
Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization & is not affiliated to WikiZ.com.